Electronic Materials doi: 10.3390/electronicmat7020009

Authors: Ihor Petrov Ulrich Kunze

This work investigates the performance improvement of a four-probe ballistic rectifier on bilayer graphene (BLG) through the formation of an energy gap under a perpendicular electric field. For this purpose, exfoliated BLG was deposited on oxidized n+-Si and structured into an asymmetric cross junction with 90 nm wide channels. The junction consists of a straight voltage stem (contacts U, L) and slanted current injectors (contacts 1, 2). The differential conductance of the stem, gUL, as a function of back-gate bias, VBG, reveals clear indications of energy gap formation and lateral depletion zones at the edges of the channel. The DC characteristic of the ballistic rectifier, VUL(I12), shows an increase in the output voltage VUL with increasing VBG. We attribute this to reduced diffuse scattering at the rough edges when the lateral depletion zones form smooth barriers.

Electronic Materials doi: 10.3390/electronicmat7020008

Authors: Zhifeng Chen Chengying Chen Yufei Huang

The von Neumann architecture faces a “memory wall” problem due to the physical separation of memory and processor, posing major challenges to energy efficiency and latency in the era of artificial intelligence. To overcome these bottlenecks, artificial synaptic devices inspired by biological systems have emerged as an important research direction. By integrating sensing and computing functions at the device level, these architectures provide a promising approach for the efficient processing of natural physical signals. Supported by advances in functional materials and artificial neural network (ANN) algorithms, artificial synaptic devices are capable of perceiving and processing various external stimuli, showing strong potential for applications in intelligent electronic skins, robotics, and edge computing. This review provides a comprehensive overview of recent advances in artificial synaptic devices, with particular emphasis on tactile and visual sensing applications. We discuss representative device types and operating mechanisms, analyze critical challenges from the perspectives of material engineering and functional integration, and further summarize potential solutions and future trends toward multimodal sensory–memory–computing systems.

Electronic Materials doi: 10.3390/electronicmat7020007

Authors: Zhonghe Zhu Changcun Li Haibo Wang Yvcui Sun Jing Qiao Mingqian Hao Wei Zhao Degang Zhao

With the intensification of the energy crisis and environmental issues, thermoelectric conversion technology has become a research focus due to its ability to directly convert thermal and electrical energy. β-Cu2Se thermoelectric materials have garnered considerable attention owing to their distinctive physical and chemical characteristics. However, their practical implementation is hindered by the inherent imbalance between electrical and thermal transport properties. In this work, β-Cu2Se/SnSe composite thermoelectric materials were successfully synthesized via a facile and scalable in situ compositing strategy by introducing SnSe micro-flakes as the secondary phase. The results demonstrate that the introduced SnSe secondary phase effectively modulates the carrier concentration and enhances the density-of-states effective mass through the energy filtering effect and resonant energy level regulation, thereby significantly optimizing the electrical transport properties. Meanwhile, the abundant heterointerfaces formed between the β-Cu2Se matrix and introduced SnSe secondary phase induce intense phonon scattering, which efficiently suppresses the lattice thermal conductivity of the β-Cu2Se/SnSe composites. Benefiting from the synergistic optimization of electrical and thermal transport behaviors, the β-Cu2Se/5 mol% SnSe composite sample achieves a maximum figure of merit (ZT) value of ~0.51 at 750 K, which represents a 70% enhancement compared with the pristine β-Cu2Se and a 60% improvement compared with the direct composite sample. This study provides a simple and effective in situ composite strategy for designing and synthesizing high-performance thermoelectric materials.

Electronic Materials doi: 10.3390/electronicmat7010006

Authors: Arashdeep Singh Ahsan Mian

Additive Manufacturing (AM) and printing-based fabrication technologies have emerged as powerful enablers for next-generation electronic integration and packaging, addressing the growing limitations of conventional subtractive manufacturing techniques. As electronic systems continue to scale toward higher operating frequencies (10–110 GHz and beyond) and increased functional density (>104 interconnects/cm2), traditional packaging approaches struggle with rigid design constraints, complex processing steps (>15–25 fabrication steps), high tooling costs ($10,000–$100,000 for mask and molds) and limited compatibility with heterogeneous integration. In this review, a comprehensive and critical overview of major additive manufacturing and printing technologies including aerosol jet printing, inkjet printing, vat polymerization, fused filament fabrication (FFF) and nScrypt printing is presented from the perspective of electronic assembly and packaging. The fundamental working mechanisms, material compatibility, resolution limits, scalability, and reliability considerations of each technique are systematically discussed. From a manufacturing standpoint, AM reduces material waste by 50–90% compared to subtractive PCB processing and eliminates tooling costs, enabling low-volume prototyping with per-unit fabrication costs reduced by 30–70% for small batches (<100 units). Production throughput varies widely, from 1 to 20 cm2/min for high-resolution direct write systems to >100 cm2/min for scalable inkjet systems. Moreover, it is discussed how these technologies enable advanced packaging architectures such as printed signal crossovers, three-dimensional interconnects, ramps, and embedded chip assemblies. Recent research efforts and reported demonstrations are analyzed to highlight the advantages and current limitations of additive manufacturing for high-frequency, RF, and system-on-package (SoP) applications. Finally, future directions and remaining challenges are discussed, including advances in materials, custom and on-demand manufacturing, enhanced design freedom, integration of multifunctionality, cost-effectiveness, and smart packaging solutions. This review aims to serve as a reference for researchers and engineers seeking to leverage additive manufacturing for high-performance electronic integration and next-generation electronic packaging solutions.

Electronic Materials doi: 10.3390/electronicmat7010005

Authors: Gunnar Suchaneck Evgenii Artiukh Nikolai Kalanda Marta Yarmolich Gerald Gerlach

In this work, we consider the influence of antisite disorder, e.g., Fe ions on Mo sites, FeMo, and vice versa, MoFe, on the resistivity of strontium ferromolybdate ceramics fabricated by the solid-state reaction method. Strontium ferromolybdate ceramics fabricated via solid-state reactions exhibit a low-temperature minimum resistivity owing to the interplay between the bulk metallic resistivity of the grains, which increases with temperature and becomes dominant at higher temperatures, and an intergrain tunneling mechanism of charge carrier conduction, which leads to a decrease in conductivity with decreasing temperature in the low-temperature region. The parameters of the bulk metallic resistivity and fluctuation-induced intergrain tunneling were determined by fitting the experimental data to these resistivity models. The impact of antisite disorder on the resistivity parameters was considered. It turns out that antisite disorder affects the effective barrier height of intergrain tunneling and the effective values of the barrier width and the barrier area. Disorder increases the effective barrier height for intergrain tunneling, increases its barrier width, and decreases the effective barrier area of nanosized barriers. The results are discussed using experimental data available in the literature.

Electronic Materials doi: 10.3390/electronicmat7010004

Authors: Cecilia Guillén

Heavily doped metal oxide thin films combining high visible transmittance and low electrical resistance are used in a multitude of optoelectronic devices, where their performance is highly dependent on the structural defects and density of electronic states associated with doping. This study explores the structural, optical, and electronic properties of Sn-doped indium oxide (In2O3:Sn) and Al-doped zinc oxide (ZnO:Al) thin films, which were prepared by sputtering on unheated glass substrates and subsequently annealed in N2 at different temperatures between 250 °C and 450 °C. These samples reach free electron densities above 1020 cm−3 due to the presence of extrinsic donors (mainly substitutional defects of SnIn and AlZn) and also intrinsic donors (oxygen vacancies), which change with the annealing temperature due to oxygen desorption and/or cation migration processes. The volume of the crystal lattice expands (up to a maximum of 1.1%) and the band gap widens (up to a maximum of 17.9%) with respect to the undoped material, increasing with electron density. Additional absorption is due to band tail, at an energy ~10% below the undoped band gap, which varies slightly with the carrier concentration. The same general behavior is observed for both materials, with particularities in terms of crystal lattice and electronic states, which can be tuned by the heating temperature.

Electronic Materials doi: 10.3390/electronicmat7010003

Authors: Manar Alenezi Amrit Prasad Kafle Meznh Alsubaie Najwa Albalawi Ian L. Pegg Biprodas Dutta

We present a fresh perspective on the mixed halogen-ion effect (MHE) in lead silicate glasses containing a mixture of halogen ions with a correlative study of optical spectroscopy and halogen ion transport. PbO was partially substituted by either PbCl2 or PbF2 in the ternary glass system: (65 − x) − x(PbF2 or PbCl2)-35SiO2 (where 0 ≤ x ≤ 20 mol%) and by a mixture of PbF2 and PbCl2 in the quaternary glass series: 45PbO − xPbF2 − (20 − x)PbCl2–35SiO2 (where 0 ≤ x ≤ 20 mol%). A suite of improved characterization techniques, including 4-probe van der Pauw resistivity measurements, optical absorption spectroscopy, differential thermal analysis, etc., was employed to correlate composition with physical properties. Replacing PbO with small quantities of PbF2 or PbCl2 in binary 65PbO-35SiO2 glass resulted in a dramatic increase in conductivity by 3–4 orders of magnitude, confirming a shift from Pb2+-mediated to halide ion-mediated conduction and, within the mixed-halogen series, a profound MHE was observed. Contrary to previously reported data, the activation energy for conduction and the resistivity both exhibited maxima at the mixed halogen-ion ratio, MHR = (F/(F + Cl), of 0.5. The glass transition temperature (Tg) exhibited a non-monotonic trend, peaking at 506 °C for the MHR = 0.5 composition. Optical absorption measurements have revealed that the MHR = 0.5 glass has the broadest absorption edge and also exhibits certain features in the near IR region of the Urbach tail, which are suggestive of maximum electronic disorder.

Electronic Materials doi: 10.3390/electronicmat7010002

Authors: Fatemeh Mollaamin Majid Monajjemi

The increasing demand for next-generation rechargeable batteries that offer high energy density, a long lifespan, high safety, and low cost has led to a need for better electrode materials for lithium-ion batteries. This also involves developing alternative storage systems using common resources such as sodium-ion batteries, beryllium-ion batteries, or magnesium-ion batteries. Tin carbide (SnC) is highly promising as an anode material for lithium, sodium, beryllium, and magnesium ion batteries due to its ability to form nanoclusters like Sn(Li2)C, Sn(Na2)C, Sn(Be2)C, and Sn(Mg2)C. A detailed study was done using computational methods, including analysis of charge density differences, total density of states, and electron localization function for these hybrid clusters. This research suggests that SnC could be useful in multivalent-ion batteries using Be2+ ions because its properties can match or even exceed those of monovalent ions. The study also shows that the maximum capacity, stability energy, and ion movement in these materials can be understood by looking at atomic-level properties like the coordination between host atoms and ions. Recent findings on using tin carbide in these types of batteries and methods to improve their performance have been discussed.

Electronic Materials doi: 10.3390/electronicmat7010001

Authors: Alex-Barna Kacsó Ladislau Matekovits Ildiko Peter

Recent studies show that titanium (Ti)-based alloys combine established mechanical strength, corrosion resistance, and biocompatibility with emerging electrical and electrochemical properties relevant to bioelectronics. The main goal of the present manuscript is to give a wide-ranging overview on the use of Ti-alloys in electronics and biomedicine, focusing on a comprehensive analysis and synthesis of the existing literature to identify gaps and future directions. Concurrently, the identification of possible correlations between the effects of the manufacturing process, alloying elements, and other degrees of freedom influencing the material characteristics are put in evidence, aiming to establish a global view on efficient interdisciplinary efforts to realize high-added-value smart devices useful in the field of biomedicine, such as, for example, implantable apparatuses. This review mostly summarizes advances in surface modification approaches—including anodization, conductive coatings, and nanostructuring that improve conductivity while maintaining biological compatibility. Trends in applications demonstrate how these alloys support smart implants, biosensors, and neural interfaces by enabling reliable signal transmission and long-term integration with tissue. Key challenges remain in balancing electrical performance with biological response and in scaling laboratory modifications for clinical use. Perspectives for future work include optimizing alloy composition, refining surface treatments, and developing multifunctional designs that integrate mechanical, biological, and electronic requirements. Together, these directions highlight the potential of titanium alloys to serve as foundational materials for next-generation bioelectronic medical technologies.

Electronic Materials doi: 10.3390/electronicmat6040023

Authors: Yi Cao Yuyan Zhang Zhifeng Chen Dongyi Lin Chengying Chen Liming Chen Jianhua Jiang

To address the issues of insufficient responsivity and low imaging contrast of carbon-based HGFET high-sensitivity short-wave infrared (SWIR) detectors under low-light conditions, this paper proposes a high-sensitivity and high-contrast image enhancement algorithm for low-light detection, with FPGA-based hardware verification. The proposed algorithm establishes a multi-stage cooperative enhancement framework targeting key challenges such as low signal-to-noise ratio (SNR), high dark-state noise, and weak target extraction. Unlike traditional direct enhancement methods, the proposed approach first performs defective row-column correction and background noise separation based on dark-state data, which provides a clean foundation for signal reconstruction. Furthermore, an adaptive gamma correction mechanism based on image maximum value is introduced to avoid unnecessary nonlinear transformations in high-contrast regions. During the contrast enhancement stage, an exposure-constrained adaptive histogram equalization strategy is adopted to effectively suppress noise amplification and saturation in low-light scenes. Finally, an innovative dual-mode threshold selection method based on image variance is proposed, which can dynamically integrate the OTSU algorithm with statistical moment analysis to ensure robust background noise separation across both high- and low-contrast scenarios. Experimental results demonstrate that the proposed algorithm significantly improves target contrast in infrared images while preventing detail loss due to overexposure. Under microwatt-level laser power, background noise is effectively suppressed, and both imaging quality and weak target detection capability are substantially enhanced.

Electronic Materials doi: 10.3390/electronicmat6040022

Authors: Junjie Tang Huafei Wang Maoqiu Pu Penghui Luo Min Yu Zhiyuan Zhu

In this study, we explore the integration of a cost-effective triboelectric nanogenerator (TENG) with an large silicon PIN detector (diameter: 12 mm) for intelligent wireless recognition applications. Wireless communication eliminates the need for physical connections, enabling greater flexibility and scalability in deployment. It allows for seamless integration of AI systems into a wide range of environments without the constraints of wiring, reducing installation complexity and enhancing mobility. Additionally, we demonstrate the TENG’s functionality as an autonomous communication unit. The TENG is employed to convert various environmentally triggered signals into digital formats and to autonomously power optoelectronic devices, thus eliminating the need for an external power supply. By integrating optoelectronic components within the self-powered sensing system, the TENG can identify specific trigger information and reduce extraneous noise, thereby improving the accuracy of information transmission. Moreover wireless technology facilitates real-time data transmission and processing. This setup not only enhances the overall efficiency and adaptability of the system but also supports continuous operation in diverse and dynamic settings. This paper introduces a novel convolutional neural network-long short-term memory (CNN-LSTM) fusion neural network model. Utilizing the sensing system in combination with the CNN-LSTM neural network enables the collection and identification of variations in the flicker frequency and luminosity of optoelectronic devices. This capability allows for the recognition of environmental trigger signals generated by the TENG. The classification and recognition results of human body trigger signals indicate a recognition accuracy of 92.94%.

Electronic Materials doi: 10.3390/electronicmat6040021

Authors: Pratheeksha Suresh Bhaskar Awadhiya Vikash Mishra Pramod Martha Sampath Kumar Yashwanth Nanjappa

This work examines a cylindrical FE-DE heterostructure and compares its performance with that of a cylindrical FE-FE-DE heterostructure. It aims to maximize voltage amplification, increase capacitance, and attain a constant negative capacitance. First, the existence of negative capacitance is shown by analyzing isolated cylindrical ferroelectric capacitors. A cylindrical dielectric capacitor and a cylindrical ferroelectric capacitor are integrated in series to stabilize negative capacitance. Our results indicate that the capacitance of the FE-FE-DE stack, consisting of Si:HfO2 and Zr:HfO2, closely aligns with the dielectric capacitance. Consequently, enhanced performance is anticipated in comparison with the FE-DE arrangement. Additionally, the dynamic response of two distinct configurations was analyzed, yielding a comprehensive understanding of these heterostructures’ behavior.

Electronic Materials doi: 10.3390/electronicmat6040020

Authors: Pham Xuan Thao Ngo Thu Huong Tran Quang Dat Nguyen Thi Sa Luu Thi Nhan Dao Son Lam

Multiferroic composites of xNi0.8Zn0.2Fe2O4/(1 − x)BaTiO3 (x = 0, 0.1, 0.3, 0.5, labeled NZFO/BTO) with ~100 nm particle size were synthesized via high-energy ball milling and thermal annealing. The X-ray diffraction shows a co-existence of the ferromagnetic phase of NZFO and the ferroelectric phase of BTO. Our observations indicate that saturation, remanence, and coercivity progressively increase with increasing NFO content, specifically from x = 0 to x = 0.5. At x = 0.1, the maximum electric polarization, remanent electric polarization, coercivity and electric power loss density reach their maximum values of ~0.057 µC/cm2, 0.018 µC/cm2, 3.25 kV/cm and 0.222 mJ/cm3, respectively, for an applied electric field less than 10 kV/cm. These multiferroic composites demonstrate excellent electromagnetic wave absorption capabilities from 2 to 18 GHz. With BTNF1 (x = 0.1) sample thickness of 2.5–3.5 mm, a minimum reflection loss of −41.51, −37, −28.72 dB corresponds to frequencies of 12.52 GHz, 11 GHz and 9.32 GHz. The effective absorption bandwidth for this sample is 11.5–16 GHz, indicating optimal impedance and attenuation matching and effective absorption of electromagnetic waves throughout the Ku bands. These outcomes reveal the capability for wideband absorption uses in radar invisibility technology and electromagnetic insulation.

Electronic Materials doi: 10.3390/electronicmat6040019

Authors: Hongjie Luo Bin Liu Wenbin Dou Xinzhan Zhou Xiao Jia Lin Chen

The rapid development of electronic devices has led to increasing requirements for higher-performance thermal interface materials (TIMs). Based on the finite element method, this study investigates the heat transfer enhancement mechanism of polymer-based TIMs reinforced by carbon fiber and boron nitride fillers. An ordered aggregation algorithm and a collision detection algorithm were developed to construct representative volume element models, enabling filler volume fractions exceeding 50 vol% in the simulation. A predictive thermal resistance model was developed and validated, demonstrating good agreement with experimental results. Then, the effects of filler ratio, orientation angle, and size on thermal conductivity were systematically analyzed. Results demonstrate that a high CF/BN ratio can construct more efficient thermal conduction pathways and the optimal ratio is 4 (13.72 W/m∙K). The thermal conductivity exhibits extreme sensitivity to filler orientation, showing an increase of 17.68 times when the angle decreases from 45° to 0°. Meanwhile, the BN particle diameters have less impact on heat transfer; thermal conductivity only increased by 19.9% when DBN rose from 10 μm to 45 μm. The predictive model based on thermal resistance theory was developed, and the average prediction error was only 5.18%. These findings provide quantitative design principles for developing high-efficiency thermal interface materials through rational filler selection and structural optimization.

Electronic Materials doi: 10.3390/electronicmat6040018

Authors: Haohan Guo Shubhra Bansal

A new and transformative era in semiconductor packaging is underway, wherein, there is a shift from transistor scaling to system scaling and integration through advanced packaging. For advanced packaging, interconnect scaling is a key driver, with interconnect density requirements for chip-to-substrate microbump pitch below 5 μm and half-line pitch below 1 μm for Cu redistribution layer (RDL). Here, we present a comprehensive theoretical comparison of thermal cycling behavior in accordance with JESD22-A104D standard, intermetallic thickness evolution, and steady-state thermal analysis of Cu-microbump assembly for different bonding materials and substrates. Bonding materials studied include solder caps such as SAC105 (Sn98.5Ag1.0Cu0.5), eutectic Sn-Pb (Sn63Pb37), eutectic Sn-Bi (Sn42Bi58), Pb95Sn5, Indium, and Cu-Cu TCB structure. Effect of substrates including Si, glass and FR-4 is evaluated for various microbump structures with varying pitches (85 µm, 40 µm, 10 µm, and 5 µm) on their fatigue life. Results indicate that for Cu-microbump assemblies at an 85 µm pitch. The Pb95Sn5 exhibits the longest predicted fatigue life (3267 cycles by Engelmaier and 452 cycles by Darveaux), while SAC105 shows the shortest (320 and 103 cycles). Additionally, the Cu-Cu TCB structure achieves an estimated lifetime of approximately 7800 cycles, which is significantly higher than all solder-based Cu-microbump assemblies. The findings contribute to advanced packaging applications by providing valuable theoretical references for optimizing solder materials and structural configurations.

Electronic Materials doi: 10.3390/electronicmat6040017

Authors: Weiyi Zheng Yuyan Zhang Zhifeng Chen Qiaoying Gan Xuefang Xiao Ying Gao Jianhua Jiang Chengying Chen

In the post-Moore era, carbon nanotube field-effect transistors (CNTFETs) are a promising alternative to complementary metal-oxide-semiconductor (CMOS) technology at and below the 5 nm node. Compact models bridge circuit design and device physics, yet the electrostatic discharge (ESD) behavior of CNTFETs remains insufficiently captured. Focusing on the local bottom-gate (LBG) CNTFET structure, which offers enhanced gate control due to its bottom-gate configuration, this paper investigates three dominant ESD-triggering mechanisms—thermionic current, tunneling leakage current, and thermal failure breakdown. Then, a hybrid compact–behavioral ESD model for CNTFETs is established. After theoretical derivation and comparison with test results, the model parameters are optimized through fitting. The simulation results exhibit excellent agreement with CNTFET measurements, particularly capturing the Human Body Model (HBM) pre-charge threshold phenomenon at 72 V and accurately predicting the subsequent voltage collapse behavior. This validates the accuracy and effectiveness of the model, laying a theoretical and experimental foundation for further construction of carbon-based standard-cell and I/O libraries.

Electronic Materials doi: 10.3390/electronicmat6040016

Authors: Chang Peng Yuetong Lin Zhenyu Jiang Yiping Liu Licheng Zhou Zejia Liu Liqun Tang Bao Yang

Triboelectric materials can convert irregular mechanical stimuli from human motion or environmental sources into high surface charge densities and instantaneous electrical outputs. Their intrinsic properties, such as flexibility, stretchability, chemical tunability, and compatibility with diverse substrates, play a critical role in determining the efficiency and reliability of triboelectric devices. In the context of active health, triboelectric materials not only serve as the core functional layers for self-powered sensing but also enable real-time physiological monitoring, motion tracking, and human–machine interaction by directly transducing biomechanical signals into electrical information. Soft triboelectric sensors exhibit high sensitivity, wide operational ranges, excellent biocompatibility, and wearability, making them highly promising for active health monitoring applications. Despite these advantages, challenges remain in enhancing surface charge density, achieving effective signal multiplexing, and ensuring long-term stability. This review provides a comprehensive overview of triboelectric mechanisms, working modes, influencing factors, performance enhancement strategies, and wearable health applications. Finally, it systematically summarizes the key improvement approaches and future development directions of triboelectric materials for active health, offering valuable guidance for advancing wearable self-powered biosensors.

Electronic Materials doi: 10.3390/electronicmat6040015

Authors: Masayuki Okoshi

In metal nanoparticles, localized surface plasmon resonance occurs due to the interaction between electrons on the surface and light. Among them, aluminum (Al) nanoparticles are known to have a resonant absorption wavelength in the ultraviolet light region. In this paper, I found a new phenomenon in which nanoswelling structures are formed on the silicone rubber surface by distributing Al nanoparticles on the surface and irradiating them uniformly with an ArF excimer laser at a wavelength of 193 nm. The formation of the nanoswelling structure was not observed when gold nanoparticles were distributed. Thus, the mechanism of nanoswelling structure formation is considered as follows: localized surface plasmon resonance is induced in the Al nanoparticles by the interaction between the Al nanoparticles and the ArF excimer laser, which causes photodissociation of the Si-O-Si bonds of the silicone rubber underneath, volume expansion due to molecular weight reduction, and swelling to nanometer sizes. The present study provides a new biomimetic method for ensuring the mechano-bactericidal functions of a silicone rubber surface to develop highly functional plastic windows for automobiles.

Electronic Materials doi: 10.3390/electronicmat6040014

Authors: Marcello Cioni Giacomo Cappellini Giovanni Giorgino Alessandro Chini Antonino Parisi Cristina Miccoli Maria Eloisa Castagna Aurore Constant Ferdinando Iucolano

In this paper, the impact of SiN passivation on dynamic-RON degradation of AlGaN/GaN HEMTs devices is put in evidence. To this end, samples showing different SiN passivation stoichiometry are considered, labeled as Sample A and Sample B. For dynamic-RON tests, two different experimental setups are employed to investigate the RON-drift showing up during conventional switch mode operation by driving the DUTs under both (i) resistive load and (ii) soft-switching trajectory. This allows to discern the impact of hot carriers and off-state drain voltage stress on the RON parameter drift. Measurements performed with both switching loci shows similar dynamic-RON response, indicating that hot carriers are not involved in the degradation of tested devices. Nevertheless, a significant difference was observed between Sample A and Sample B, with the former showing an additional RON-degradation mechanism, not present on the latter. This additional drift is totally ascribed to the SiN passivation layer and is confirmed by the different leakage current measured across the two SiN types. The mechanism is explained by the injection of negative charges from the Source Field-Plate towards the AlGaN surface that are captured by surface/dielectric states and partially depletes the 2DEG underneath.

Electronic Materials doi: 10.3390/electronicmat6040013

Authors: Hiryu Hayashi Yuna Hachikubo Mano Ando Misaki Oshima Mayu Morita Satoshi Takei

Water-developable photoresist was synthesized by introducing methacrylate groups into hydroxypropyl cellulose (HPC), a cellulose derivative, via substitution of hydroxyl groups. The material enabled micropatterning through ultraviolet (UV) exposure at a wavelength of 365 nm with an exposure dose of 450 mJ/cm2. Line and dot micropatterns were formed on polypropylene substrates applying underlayer, achieving resolutions of 4.5 µm and 5.0 µm, respectively. The photoresist demonstrated superior etching resistance under CF4 plasma compared to another water-soluble photo resist. Unlike conventional photoresists that require hazardous organic solvents, this water-developable photoresist offers an environmentally friendly alternative, reducing health risks and environmental impact in the electronics industry.

Electronic Materials doi: 10.3390/electronicmat6030012

Authors: Zeyu Zhang Lingdong Wang Lili Xie Feifei Qin Xu Wang

The combination of polypyrrole (PPy) with graphene has attracted extensive attention as a nonlinear optical material with various optoelectronic applications. Here, we describe the development of PPy nanoplates prepared using a simple spin-coating method. The appropriate volume of the dropped PPy solution was determined to be 50 drops by comparing the surface morphologies, chain structures, elementary compositions, and optical properties of PPy saturable absorbers (SAs). The hybrid PPy/graphene heterostructure SA was obtained using the wet transfer process of a graphene layer. This approach led to significant improvements in optical properties, including a ~7.2% increase in linear optical absorption, a 2.5-fold increase in modulation depth, and a third decrease in saturable intensity at 1550 nm due to the additional optical absorption and the π-π interaction between PPy nanoplates and the graphene layer. By inserting the PPy/graphene heterostructure SA into the passively mode-locked fiber laser cavity, 1559 nm ultrashort laser pulses were generated, with an average output power of 1.24 mW, a 815 fs pulse width, and a repetition frequency of 3.26 MHz. Our experimental results demonstrate that the prepared PPy SA has excellent nonlinear optical characteristics, providing a new opportunity for the generation of ultrashort laser pulses.

Electronic Materials doi: 10.3390/electronicmat6030011

Authors: Archana Chamarahalli Manjunatha Pratheeksha Suresh Akshatha Bhat Vikash Mishra Yashwanth Nanjappa Bhaskar Awadhiya Sachin Agrawal

This paper explores ferroelectric–dielectric heterostructures comprising a ferroelectric oxide (Lead Zirconium Titanate (PbZr1−xTix O3)) with a varying mole fraction and a fixed dielectric oxide (Silicon dioxide (SiO2)). The study aims to enhance capacitance, optimize voltage amplification, and achieve stable negative capacitance. An isolated ferroelectric capacitor is examined by varying mole fractions of ferroelectric oxide. The negative capacitance in isolated ferroelectric capacitor is highly unstable in nature. The instability problem is fixed and the overall capacitance of the heterostructure is raised while the negative capacitance is stabilized by connecting a dielectric oxide in series with the ferroelectric capacitor. PbZr1−xTix O3 is utilized as the ferroelectric oxide, with mole fractions x=0,0.2,0.4,0.6,0.8,1.0. Among the investigated mole fractions, ferroelectric oxide with x=0.6 offers the maximum voltage amplification and improved capacitance because its capacitance closely matches the dielectric capacitance. Also, dynamic response and temperature analysis of heterostructure are studied further.

Electronic Materials doi: 10.3390/electronicmat6030010

Authors: Jacob E. Daniel Evan Watkins Mitchel S. Jensen Allen Benton Apparao Rao Sriparna Bhattacharya Mary E. Anderson

Famatinite (Cu3SbS4) is an earth-abundant, nontoxic material with potential for thermoelectric energy generation applications. Herein, rapid, energy-efficient, and facile one-pot modified polyol synthesis was utilized to produce gram-scale quantities of phase-pure famatinite (Cu2.7M0.3SbS4, M = Cu, Zn, Mn) nanoparticles (diameter 20–30 nm) with controllable and stoichiometric incorporation of transition metal dopants on the Cu-site. To produce pellets for thermoelectric characterization, the densification process by spark plasma sintering was optimized for individual samples based on thermal stability determined using differential scanning calorimetry and thermogravimetric analysis. Electronic transport properties of undoped and doped famatinite nanoparticles were studied from 225–575 K, and the thermoelectric power factor was calculated. This is the first time electronic transport properties of famatinite doped with Zn or Mn have been studied. All famatinite samples had similar resistivities (>0.8 mΩ·m) in the measured temperature range. However, the Mn-doped famatinite nanomaterials exhibited a thermoelectric power factor of 10.3 mW·m−1·K−1 at 575 K, which represented a significant increase relative to the undoped nanomaterials and Zn-doped nanomaterials engendered by an elevated Seebeck coefficient of ~220 µV·K−1 at 575 K. Future investigations into optimizing the thermoelectric properties of Mn-doped famatinite nanomaterials are promising avenues of research for producing low-cost, environmentally friendly, high-performing thermoelectric materials.

Electronic Materials doi: 10.3390/electronicmat6030009

Authors: János Hegedüs Péter Gábor Szabó László Pohl Gusztáv Hantos Gyula Lipák Andrea Reolon Ferenc Ender

In this article, thermal investigation methods for electrically insulating and thermally conductive substrate materials will be presented. The investigations were performed in their real-world application environment, i.e., in the form of IGBT (insulated gate bipolar transistor) module substrate plates. First, the overall thermal resistance and thermal structure function of the system in a multivariable parameter space were revealed using CFD (computational fluid dynamics) simulations. Afterwards, thermal transient testing was performed on real samples, with the help of which the thermal resistance values of the modules were determined using the thermal dual interface test method. The presented tests are not intended to determine material parameters, but to rank different substrate materials based on their thermal performance.

Electronic Materials doi: 10.3390/electronicmat6020008

Authors: Christina Veneti Lykourgos Magafas Panagiota Papadopoulou

In the present work a-SiC:H thin films were prepared using magnetron sputtering technique for different substrate temperatures from 100 °C to 290 °C. Their optical properties were studied using the ellipsometry technique. The experimental results show that the optical band gap of the films varies from 2.00 eV to 2.18 eV for the hydrogenated films, whereas the Eg is equal to 1.29 eV when the film does not contain hydrogen atoms and for Ts = 100 °C. The refractive index has been observed to remain stable in the region of 100 °C–220 °C, whereas it drops significantly when the temperature of 290 °C is reached. Additionally, the refractive index exhibits an inverse relationship with Eg as a function of Ts. Notably, these thin films were deposited 12 years ago, and their optical properties have remained stable since then.

Electronic Materials doi: 10.3390/electronicmat6020007

Authors: Juan C. Rubio Martin Bolduc

Printed electronics employ established printing methods to create low-cost, mechanically flexible devices including batteries, supercapacitors, sensors, antennas and RFID tags on plastic, paper and textile substrates. This review focuses on the specific contribution of screen printing to that landscape, examining how ink viscosity, mesh selection and squeegee dynamics govern film uniformity, pattern resolution and ultimately device performance. Recent progress in advanced ink systems is surveyed, highlighting carbon allotropes (graphene, carbon nano-onions, carbon nanotubes, graphite), silver and copper nanostructures, MXene and functional oxides that collectively enhance mechanical robustness, electrical conductivity and radio-frequency behavior. Parallel improvements in substrate engineering such as polyimide, PET, TPU, cellulose and elastomers demonstrate the technique’s capacity to accommodate complex geometries for wearable, medical and industrial applications while supporting environmentally responsible material choices such as water-borne binders and bio-based solvents. By mapping two decades of developments across energy-storage layers and functional electronics, the article identifies the key process elements, recurring challenges and emerging sustainable practices that will guide future optimization of screen-printing materials and protocols for high-performance, customizable and eco-friendly flexible devices.

Electronic Materials doi: 10.3390/electronicmat6020006

Authors: Nisarg Hirens Purabiarao Kumar Vivek Gaurav Shubham Sharma Yoshito Ando Shyam Sudhir Pandey

Optimizing charge transport in organic semiconductors is crucial for advancing next-generation optoelectronic devices. The performance of organic field-effect transistors (OFETs) is significantly influenced by the alignment of films in the channel direction and the quality of the dielectric surface, which should be uniform, smooth, and free of charge-trapping defects. Our study reports the enhancement of OFET performance using large-area, uniform, and oriented thin films of regioregular poly[3-hexylthiophene] (RR-P3HT), prepared via the Floating Film Transfer Method (FTM) on octadecyltrichlorosilane (OTS) passivated SiO2 surfaces. SiO2 surfaces inherently possess dangling bonds that act as charge traps, but these can be effectively passivated through optimized surface treatments. OTS treatment has improved the optical anisotropy of thin films and the surface wettability of SiO2. Notably, using octadecene as a solvent during OTS passivation, as opposed to toluene, resulted in a significant enhancement of charge carrier transport. Specifically, passivation with OTS-F (10 mM OTS in octadecene at 100 °C for 48 h) led to a >150 times increase in mobility and a reduction in threshold voltage compared to OTS-A (5 mM OTS in toluene for 12 h at room temperature). Under optimal conditions, these FTM-processed RR-P3HT films achieved the best device performance, with a saturated mobility (μsat) of 0.18 cm2V−1s−1.

Electronic Materials doi: 10.3390/electronicmat6020005

Authors: Hamza Mabchour Yassine Essakali Mounir El Hassan Samir Elouaham Boujemaa Nassiri Said Dlimi Abdelhamid El Kaaouachi

In this study, we investigate the magnetoconductivity behavior in a 2D p-Si/SiGe/Si system. To achieve this, we develop a theoretical model that incorporates three key contributions, the weak localization effect, electron–electron interaction effects, and the Zeeman effect, which is considered only in the presence of a magnetic field. We then compare our theoretical predictions with experimental magnetoconductivity data, analyzing both the consistencies and discrepancies between the model and the measurements. Through this comparison, we aim to provide a deeper physical understanding of the factors influencing magnetoconductivity in this system.

Electronic Materials doi: 10.3390/electronicmat6010004

Authors: Dandan Feng Xiaojing Wang Xueying Han Zhiqiang Yu Jialun Feng Hefei Wang

Al2O3 ceramics are widely used in vacuum electronic devices. However, surface flashover in a vacuum during the application of high voltage significantly influences their reliability and restricts the development of vacuum electronic devices. The secondary electron emission yield (SEY) and surface resistivity of ceramics are the main factors affecting the vacuum withstand voltage of ceramic materials. In this study, the bulk density, microstructure, and surface properties—including SEY and surface resistivity—of Al2O3 ceramics were tested. The relationship between these properties and the vacuum withstand voltage of the ceramics was investigated. The influence of the addition ratio of Cr2O3 to MnO2 and the sintering temperature was investigated. The results show Cr/Mn-doped Al2O3 ceramics, with appropriate amounts of Cr2O3 and MnO2 and sintered at suitable temperatures, exhibit low SEY, high withstand voltage, and excellent stability in vacuum.

Electronic Materials doi: 10.3390/electronicmat6010003

Authors: Cecilia Guillén

This research is on the structural, optical, and electrical properties of SnO2 and ZnO thin films, which are increasingly used in many electronic devices, including gas sensors, light-emitting diodes, and solar cells. For the various applications, it is essential to accurately determine the band gap energy, as it controls the optical and electrical behavior of the material. However, there is no single method for its determination; rather, different approximations depend on the crystalline quality and the doping level because these modify the energy band structure of the semiconductor. With the aim of analyzing the various approaches, SnO2 and ZnO films were prepared by sputtering on unheated glass substrates and subsequently annealed in N2 at various temperatures between 250 °C and 450 °C. These samples showed different crystallite sizes, absorption coefficients, and free carrier concentrations depending on the material and the annealing temperature. Analysis of the results shows that the expression developed for amorphous materials underestimates the band gap value, and the so-called unified method tends to overestimate it, while the equations for perfect or heavily doped crystals give band gap energies more consistent with the doping level, regardless of the crystalline quality of the films.

Electronic Materials doi: 10.3390/electronicmat6010002

Authors: Jiaxin Liu Shan Huang Zhenyuan Xiao Ning Li Jaekyun Kim Jidong Jin Jiawei Zhang

Amorphous oxide semiconductor transistors with a high current density output are highly desirable for large-area electronics. In this study, wrapping amorphous indium-gallium-zinc-oxide (a-IGZO) transistors are proposed to enhance the current density output relative to a-IGZO source-gated transistors (SGTs). Device performances are analyzed using technology computer-aided design (TCAD) simulations. The TCAD simulation results reveal that, with an optimized device structure, the current density of the wrapping a-IGZO transistor can reach 7.34 μA/μm, representing an approximate two-fold enhancement compared to that of the a-IGZO SGT. Furthermore, the optimized wrapping a-IGZO transistor exhibits clear flat saturation and pinch-off behavior. The proposed wrapping a-IGZO transistors show significant potential for applications in large-area electronics.

Electronic Materials doi: 10.3390/electronicmat6010001

Authors: Michelle Yap Catherine Yap Yasa Sampurno Glenn Whitener Jason Keleher Len Borucki Ara Philipossian

We investigated the tribological, thermal, kinetic, and surface microtextural characteristics of chemical mechanical polishing (CMP) of 300 mm p-type <100> prime silicon wafers (and their native oxide) at various pressures, sliding velocities, and starting platen temperatures. Results showed the dominant tribological mechanism for both native oxide and silicon polishing to be boundary lubrication. Using frictional data, we pinpointed the exact time that corresponded to the total removal of the native oxide and the onset of silicon polishing. This allowed us to separately characterize removal rates of each layer. For native oxide, while the rate depended on temperature, the presence of a temperature-independent shear force threshold and the low observed rates suggested that its removal by the slurry was dominantly mechanical. In contrast, for silicon polish, the absence of a distinctive shear force threshold and the fact that, for the same set of consumables, rates were more than 200 times larger for silicon than for native oxide suggested a dominantly chemical process with an average apparent activation energy of 0.34 eV. It was further confirmed that rate selectivity between native oxide and PE-TEOS based SiO2 control wafers was around 1 to 7, which underscored the importance of being able to directly measure native oxide removal rates. In all cases, we achieved excellent post-polish surfaces with Sa and Sq values of below 1 nm. Due to thermal softening of the thermoplastic pad at elevated temperatures, which we confirmed via dynamic mechanical analysis, overall process vibrations were significantly higher when platen heating was employed.

Electronic Materials doi: 10.3390/electronicmat5040020

Authors: Te-Kuang Chiang

Based on the minimum conduction band edge caused by the minimum channel potential resulting from the quasi-3D scaling theory and the 3D density of state (DOS) accompanied by the Fermi–Dirac distribution function on the source and drain sides, a unified semiconductor-device-physics-based ballistic model is developed for the threshold voltage of modern multiple-gate (MG) transistors, including FinFET, Ω-gate MOSFET, and nanosheet (NS) MOSFET. It is shown that the thin silicon, thin gate oxide, and high work function will alleviate ballistic effects and resist threshold voltage degradation. In addition, as the device dimension is further reduced to give rise to the 2D/1D DOS, the lowest conduction band edge is increased to resist threshold voltage degradation. The nanosheet MOSFET exhibits the largest threshold voltage among the three transistors due to the smallest minimum conduction band edge caused by the quasi-3D minimum channel potential. When the n-type MOSFET (N-FET) is compared to the P-type MOSFET (P-FET), the P-FET shows more threshold voltage because the hole has a more effective mass than the electron.

Electronic Materials doi: 10.3390/electronicmat5040019

Authors: Lingling Liu Li Li Shixian Zhang Wenhan Xu Qing Wang

Polyimide (PI) has received great attention for high-temperature capacitive energy storage materials due to its remarkable thermal stability, relatively high breakdown strength, strong mechanical properties, and ease of synthesis and modification. In this review, several key parameters for evaluating capacitive energy storage performance are introduced. Subsequently, the properties of the commercially available PIs are presented. Then, the recent development of designing and tailoring all-organic PI-based polymers is discussed in detail, focusing on molecular composition and spatial configuration to enhance dielectric constant, breakdown strength, discharged energy density, and charge-discharge efficiency. Finally, we outline the current challenges and future development directions of PI-based high-temperature energy storage dielectric materials.

Electronic Materials doi: 10.3390/electronicmat5040018

Authors: Vladimir Bruevich Leila Kasaei Leonard C. Feldman Vitaly Podzorov

A helium ion microscope (HIM) with a focused He+-ion beam of variable flux and energy can be used as a tool for local nanoscale surface modification. In this work, we demonstrate a simple but versatile use of the HIM focused He ion beam to fabricate conducting metallic nano- and microstructures on arbitrary substrates of varied types and shapes by directly patterning pre-deposited initially discontinuous and highly insulating (>10 TΩ/sq.) ultrathin metal films. Gold or silver films, measuring 3 nm in thickness, thermally evaporated on solid substrates have a discontinuous nanocluster morphology. Such highly resistive films can be made locally conductive using moderate doses (2 × 1016–1017 cm−2) of low-energy (30 KeV) ion bombardment. We show that an HIM can be used to directly “draw” Au and Ag conductive lines and other patterns with a variable sheet resistance as low as 10 kΩ/sq. without the use of additional precursors. This relatively straightforward, high-definition technique of direct writing with an ion beam, free from complex in vacuo catalytic or precursor chemistries, opens up new opportunities for directly fabricating elements of conformal metallic nanocircuits (interconnects, resistors, and contacts) on arbitrary organic or inorganic substrates, including those with highly curved surfaces.

Electronic Materials doi: 10.3390/electronicmat5040017

Authors: Usman Ghani Muhammad Anas Wazir Kareem Akhtar Mohsin Wajib Shahmir Shaukat

An efficient cooling system is necessary for the reliability and safety of modern microchips for a longer life. As microchips become smaller and more powerful, the heat flux generated by these chips per unit area also rises sharply. Traditional cooling techniques are inadequate to meet the recent cooling requirements of microchips. To meet the current cooling demand of microelectromechanical systems (MEMS) devices and microchips, microchannel heat sink (MCHS) technology is the latest invention, one that can dissipate a significant amount of heat because of its high surface area to volume ratio. This study provides a concise summary of the design, material selection, and performance parameters of the MCHSs that have been developed over the last few decades. The limitations and challenges associated with the different techniques employed by researchers over time to enhance the thermal efficiency of microchannel heat sinks are discussed. The effects on the thermal enhancement factor, Nusselt number, and pressure drop at different Reynold numbers in passive techniques (flow obstruction) i.e., ribs, grooves, dimples, and cavities change in the curvature of MCHSs, are discussed. This study also discusses the increase in heat transfer using nanofluids and how a change in coolant type also significantly affects the thermal performance of MCHSs by obstructing flow. This study provides trends and useful guidelines for researchers to design more effective MCHSs to keep up with the cooling demands of power electronics.

Electronic Materials doi: 10.3390/electronicmat5040016

Authors: Minho Yoon

In this study, we investigated the density of states extraction method for atomic-deposited ZnO thin-film transistors (TFTs) by analyzing gate-dependent field-effect mobility. The atomic layer deposition (ALD) method offers ultra-thin and smooth ZnO films, but these films suffer from interface and semiconductor defects, which lead to disordered localized electronic structures. Hence, to investigate the unstable localized structure of ZnO TFTs, we tried to derive the electronic state relationship by assuming field-effect mobility can be expressed as a gate-dependent Arrhenius relation, and the activation energy in the relation is the required energy for hopping. Following this derived relationship, the DOS of the atomic-deposited ZnO transistor was extracted and found to be consistent with those using temperature-dependent measurements. Moreover, to ensure the proposed method is reliable, we applied methods for the extraction of DOSs of doped ZnO transistors, which show enhanced mobilities with shifted threshold voltages, and the results show that the extraction method is reliable. Thus, we can state that the mobility-based DOS extraction method offers practical benefits for estimating the density of states of disordered transistors using a single transfer characteristic of these devices.

Electronic Materials doi: 10.3390/electronicmat5040015

Authors: Diyi Jin Min Zhao Haochen Zhu Guangming Li Wenzhi He

Waste printed circuit boards (WPCBs) hold great recycling value, but improper recycling can lead to environmental issues. This study combines pyrolysis and microwave technologies, leveraging the unique phenomenon where metal materials tend to “spark” in a microwave field, to develop a microwave pyrolysis process for WPCBs that incorporates metal fillers. The research analyzes the effects of microwave power, metal filler addition, and pyrolysis time on the efficiency of microwave pyrolysis. It explores the mechanisms of microwave pyrolysis and the pathways of pyrolysis product formation, and the kinetics of the pyrolysis reaction of WPCBs. The results indicate that microwave-assisted pyrolysis greatly improves efficiency. Within the experimental range, the optimal conditions are found to be a microwave power of 1600–1800 W, a metal filler addition of 10%, and a pyrolysis time of 10 min. Under these conditions, the yield of pyrolysis liquid was 12.8%, with approximately 5–12 different components, while the yield of pyrolysis gas was 12.7–13.4%, with about 9–11 different components. Compared to conventional pyrolysis products, the liquid products from microwave pyrolysis are simpler and more advantageous for resource utilization. Theoretical calculations show that the average activation energy for the microwave pyrolysis process is 81.05 kJ/mol, with an average reaction order of 0.93, which is greatly better than the 147.75 kJ/mol of the conventional pyrolysis process.

Electronic Materials doi: 10.3390/electronicmat5040014

Authors: Rabih Khazaka Rachelle Hanna Yvan Avenas Stephane Azzopardi

Power modules can occasionally be exposed to brief power peaks, causing overheating and premature failure of the power semiconductor devices. In order to overcome this issue without oversizing the module or its cooling system, this study aims to design a new class of power modules with integrated Phase Change Material (PCM) in a container serving as a top device interconnection. Simulations and experiments are performed with two organic PCMs, and the interest in adding copper foam is discussed. Under various test conditions, the results show that the simulations agree well with the experiments. Hence, virtual prototyping can be very useful for sizing containers based on a specific mission profile. For a constant selected PCM volume (around 1 cm3/device) and with a convection heat transfer coefficient value of 800 W.m−2.K−1, the solution allows achieving a junction temperature reduction of about 35 °C (erythritol and 90% porosity copper foam) compared to a wire-bonded conventional technique. Repetitive power cycles can be achieved with both materials, but the selection of the PCM should be conducted cautiously based on the mission profile. The two selected organic PCMs show degradation of their latent heat of fusion and mass loss during high-temperature isothermal aging in air above 130 °C. By assuming as endpoint criterion the reduction of energy storage by 50% compared to the initial state, the lifetime of erythritol and RT100 is evaluated to be about 100 and 340 h, respectively, during aging at 150 °C.

Electronic Materials doi: 10.3390/electronicmat5040013

Authors: Ahmad Adlie Shamsuri Siti Nurul Ain Md. Jamil Mohd Zuhri Mohamed Yusoff Khalina Abdan

Polymer composites are engineered materials that combine polymers with diverse fillers to enhance their physicochemical properties. The electrical conductivity of polymer composites is a vital characteristic that significantly broadens their use, particularly in electronic applications. The addition of ionic liquids into polymer composites represents a new method to enhance their functional properties, particularly in terms of electrical conductivity. In this brief review, several polymer matrices, conductive fillers, and ionic liquids utilized in polymer composites are categorized. Additionally, the effect of ionic liquids on the electrical conductivity of polymer composites is concisely explained. This review gives brief information that increases the understanding of electrical conductivity in polymer composites containing ionic liquids. In summary, most studies show that adding ionic liquids enhances the electrical conductivity of polymer composites regardless of the polymer matrix or conductive filler type. This enhancement is due to ionic liquids improving filler dispersion and promoting the creation of effective three-dimensional conductive networks within the matrix, thus boosting electron transport and mobility throughout the structure. This review provides new insights into the behavior of ionic liquids in composite systems, highlighting their role in improving properties for advanced applications. It encourages innovation in next-generation conductive materials and assists future research and development of more efficient materials for electronics.

Electronic Materials doi: 10.3390/electronicmat5030012

Authors: Amrit P. Kafle David McKeown Winnie Wong-Ng Meznh Alsubaie Manar Alenezi Ian L. Pegg Biprodas Dutta

We have investigated the influence of the relative proportions of glass formers in a series of lithium alumino-borosilicate glasses with respect to electrical conductivity (σ) and glass transition temperature (Tg) as functions of glass structure, as determined using Raman spectroscopy. The ternary lithium alumino-borate glass exhibits the highest σ and lowest Tg among all the compositions of the glass series, 30Li2O•3Al2O3• (67−x) B2O3•xSiO2. However, as B2O3 is replaced by SiO2, a shallow minimum in σ, as well as a shallow maximum in Tg, are observed near x = 27, where the Raman spectra indicate that isolated diborate/tetraborate/orthoborate groups are being progressively replaced by danburite/reedmergnerite-like borosilicate network units. Overall, as the glasses become silica-rich, σ is minimized, while Tg is maximized. In general, these findings show correlations among Tg (sensitive to network polymerization), σ (proportional to ionic mobility), and the different borate and silicate glass structural units as determined using Raman spectroscopy.

Electronic Materials doi: 10.3390/electronicmat5030011

Authors: Huiwen Bai Richard M. Voyles Robert A. Nawrocki

In this work, a gate insulator poly (4-vinylphenol) (PVP) of an organic field effect transistor (OFET) was deposited using an inkjet printing technique, realized via a high printing resolution. Various parameters, including the molecular weight of PVP, printing direction, printing voltage, and drop frequency, were investigated to optimize OFET performance. Consequently, PVP with a smaller molecular weight of 11 k and a printing direction parallel to the channel, a printing voltage of 18 V, and a drop frequency of 10 kHz showed the best OFET performance. With a direct ink writing-printed organic semiconductor, this work paves the way for fully inkjet-printed OFETs.

Electronic Materials doi: 10.3390/electronicmat5030010

Authors: Jobair Al Rafi Md. Ariful Islam Sayed Mahmud Mitsuhiro Honda Yo Ichikawa Muhammad Athar Uddin

This work presents a copper zinc tin sulfide (CZTS)-based solar cell structure (AI/ITO/C60/CZTS/SnS/Pt) with C60 as a buffer layer, developed using the SCAPS-1D simulator by optimizing each parameter to calculate the output. Optimizing the parameters, the acceptor concentration and thickness were altered from 6.0 × 1015 cm−3 to 6.0 × 1018 cm−3 and 1500 nm to 3000 nm, respectively. Although, in this simulator, we can tune the value for the acceptor concentration to 6.0 × 1022, higher doping might present an issue regarding adjustment in the physical experiment. Thus, tunable parameters need to be chosen according to the reliability of the experimental work. The defect density varied from 1.0 × 1014 cm−3 to 1.0 × 1017 cm−3 and the auger hole/electron capture coefficient was determined to be 1.0 × 10−26 cm6 s−1 for the maintenance of the minorities in theoretical to quasi-proper experimental measurements. Although the temperature was intended to be kept near room temperature, this parameter was varied from 290 K to 475 K to investigate the effects of the temperature on this cell. The optimization of the proposed structure resulted in a final acceptor concentration of 6.0 × 1018 cm−3 and a thickness of 3000 nm at a defect density of 1.0 × 1015 cm−3, which will help to satisfy the desired experimental performance. Satisfactory outcomes (VOC = 1.24 V, JSC = 27.03 mA/cm2, FF = 89.96%, η = 30.18%) were found compared to the previous analysis.

Electronic Materials doi: 10.3390/electronicmat5030009

Authors: Marcello Cioni Giovanni Giorgino Alessandro Chini Antonino Parisi Giacomo Cappellini Cristina Miccoli Maria Eloisa Castagna Cristina Tringali Ferdinando Iucolano

In this paper, a new method for evaluating hot-electron degradation in p-GaN gate AlGaN/GaN power HEMTs is proposed. The method exploits a commercial parameter analyzer to study VTH and RON drifts induced by on-state stress at VDS = 50 V. The results show that VTH drift and part of the RON degradation induced by the on-state stress are recoverable and likely due to the ionization of C-related acceptors in the buffer. This was confirmed by a preliminary characterization of C-related buffer traps. Conversely, the remaining part of RON degradation (not recovered in 1000 s) was strongly affected by the surface treatment. The current level set during on-state stress affected the amount of non-recoverable degradation, confirming the involvement of hot electrons. Thanks to the monitoring of the parameters’ recovery, the proposed method provides important insights into the physical mechanisms governing the parameters’ degradation. This extends the capabilities of state-of-the art systems, without the need for custom setup development.

Electronic Materials doi: 10.3390/electronicmat5030008

Authors: Jingyu Wang Bao Yang Zhenyu Jiang Yiping Liu Licheng Zhou Zejia Liu Liqun Tang

Conductive hydrogels combine the properties of both hydrogels and conductors, making them soft, flexible, and biocompatible. These properties enable them to conform to irregular surfaces, stretch and bend without losing their electrical conductivity, and interface with biological systems. Conductive hydrogels can be utilized as conductive traces, electrodes, or as a matrix for flexible electronics. Exciting applications in sensors, tissue engineering, and human-machine interaction have been demonstrated worldwide. This review comprehensively covers the progress in this field, focusing on several main aspects: functional materials, performance improvement strategies, and wearable applications in human-related areas. Furthermore, the major approaches and challenges for improving their mechanical properties, conductivity, and long-term stability are systematically summarized.

Electronic Materials doi: 10.3390/electronicmat5020007

Authors: Xu Gao Qiang Jia Yishu Wang Hongqiang Zhang Limin Ma Guisheng Zou Fu Guo

The rising demand for increased integration and higher power outputs poses a hidden risk to the long-term reliable operation of third-generation semiconductors. Thus, the power cycling test (PCT) is widely regarded as the utmost critical test for assessing the packaging reliability of power devices. In this work, low-thermal-resistance packaging design structures of SiC devices are introduced, encompassing planar packaging with dual heat dissipation, press-pack packaging, three-dimensional (3D) packaging, and hybrid packaging. PCT methods and their control strategies are summarized and discussed. Direct-current PCT is the focus of this review. The failure mechanisms of SiC devices under PCT are pointed out. The electrical and temperature-sensitive parameters adopted to monitor the aging of SiC devices are organized. The existing international standards for PCT are evaluated. Due to the lack of authoritative statements for SiC devices, it is difficult to achieve comparison research results without consistent preconditions. Furthermore, the lifetimes of the various packaging designs of the tested SiC devices under PCTs are statistically analyzed. Additionally, problems related to parameter monitoring and test equipment are also summarized. This review explores the broader landscape by delving into the current challenges and main trends in PCTs for SiC devices.

Electronic Materials doi: 10.3390/electronicmat5020006

Authors: So-Yeon Kwon Woon-San Ko Jun-Ho Byun Do-Yeon Lee Hi-Deok Lee Ga-Won Lee

In this study, the bipolar switching behaviors in ZnO/HfO2 bilayer resistive random-access memory (RRAM), depending on different metal top electrodes (TE), are analyzed. For this purpose, devices with two types of TE–TiN/Ti and Pd, which have varying oxygen affinities, are fabricated. X-ray diffraction (XRD) analysis shows that ZnO has a hexagonal wurtzite structure, and HfO2 exhibits both monoclinic and orthorhombic phases. The average grain sizes are 10.9 nm for ZnO and 1.55 nm for HfO2. In regards to the electrical characteristics, the I–V curve, cycling test, and voltage stress are measured. The measurement results indicate that devices with TiN/Ti TE exhibit lower set and higher reset voltage and stable bipolar switching behavior. However, a device with Pd TE demonstrates higher set and lower reset voltage. This phenomenon can be explained by the Gibbs free energy of formation (∆Gf°). Additionally, the Pd TE device shows unstable bipolar switching characteristics, where unipolar switching occurs simultaneously during the cycling test. This instability in devices with Pd TE could potentially lead to soft errors in operation. For guaranteeing stable bipolar switching, the oxygen affinity of material for TE should be considered in regards to ZnO/HfO2 bilayer RRAM.

Electronic Materials doi: 10.3390/electronicmat5020005

Authors: Tamiru Kebede Mulualem Abebe Dhakshnamoorthy Mani Aparna Thankappan Sabu Thomas Jung Yong Kim

All-inorganic perovskite semiconductors have received significant interest for their potential stability over heat and humidity. However, the typical CsPbI3 displays phase instability despite its desirable bandgap of ~1.73 eV. Herein, we studied the mixed halide perovskite CsPbI2Br by varying the silver doping concentration. For this purpose, we examined its bandgap tunability as a function of the silver doping by using density functional theory. Then, we studied the effect of silver on the structural and optical properties of CsPbI2Br. Resultantly, we found that ‘silver doping’ allowed for partial bandgap tunability from 1.91 eV to 2.05 eV, increasing the photoluminescence (PL) lifetime from 0.990 ns to 1.187 ns, and, finally, contributing to the structural stability when examining the aging effect via X-ray diffraction. Then, through the analysis of the intermolecular interactions based on the solubility parameter, we explain the solvent engineering process in relation to the solvent trapping phenomena in CsPbI2Br thin films. However, silver doping may induce a defect morphology (e.g., a pinhole) during the formation of the thin films.

Electronic Materials doi: 10.3390/electronicmat5020004

Authors: Sonia Ceron David Barba Miguel A. Dominguez

The functionalization of conductive inks has been carried out through the decomposition of hydrogen peroxide (H2O2) onto the surface of silver nanoparticles (AgNPs). The ink prepared using this eco-friendly chemical reagent has been characterized structurally, chemically, and morphologically, showing the presence of stable AgNPs with suitable properties as well as the absence of residual contamination. The electrical conductivity of such a solution-processable ink is evidenced for patterns designed on flexible photographic paper substrates, using a refillable fountain pen that is implemented as a printing mechanism for the fabrication of simple printed circuit boards (PCBs). The functionality and durability of the tested systems are demonstrated under various mechanical constraints, aiming to basically reproduce the normal operation conditions of flexible electronic devices. The obtained results indicate that the implementation of these AgNP-based inks is relevant for direct applications in inkjet printing technology, thus paving the way for the use of greener chemicals in ink preparation.

Electronic Materials doi: 10.3390/electronicmat5010003

Authors: Gayan K. L. Sankalpa Gayan R. K. K. G. R. Kumarasinghe Buddhika S. Dassanayake Gayan W. C. Kumarage

The impact of N2 purging in the CdS deposition bath and subsequent N2 annealing is examined and contrasted with conventional CdS films, which were deposited without purging and annealed in ambient air. All films were fabricated using the chemical bath deposition method at a temperature of 80 °C on fluorine-doped tin oxide glass slides (FTO). N2 purged films were deposited by introducing nitrogen gas into the deposition bath throughout the CdS deposition process. Subsequently, both N2 purged and un-purged films underwent annealing at temperatures ranging from 100 to 500 °C for one hour, either in a nitrogen or ambient air environment. Photoelectrochemical (PEC) cell studies reveal that films subjected to both N2 purging and N2 annealing exhibit a notable enhancement of 37.5% and 27% in ISC (short-circuit current) and VOC (open-circuit voltage) values, accompanied by a 5% improvement in optical transmittance compared to conventional CdS thin films. The films annealed at 300 °C demonstrate the highest ISC, VOC, and VFB values, 55 μA, 0.475 V, and −675 mV, respectively. The improved optoelectrical properties in both N2-purged and N2-annealed films are attributed to their well-packed structure, enhanced interconnectivity, and a higher sulfur to cadmium ratio of 0.76 in the films.

Electronic Materials doi: 10.3390/electronicmat5010002

Authors: Mahmoud Darwish László Pohl

This article investigates resistive random access memory (ReRAM) crossbar memory arrays, which is a notable development in non-volatile memory technology. We highlight ReRAM’s competitive edge over NAND, NOR Flash, and phase-change memory (PCM), particularly in terms of endurance, speed, and energy efficiency. This paper focuses on the architecture of crossbar arrays, where memristive devices are positioned at intersecting metal wires. We emphasize the unique resistive switching mechanisms of memristors and the challenges of sneak path currents and delve into the roles and configurations of selectors, particularly focusing on the one-selector one-resistor (1S1R) architecture with an insulator–metal transition (IMT) based selector. We use SPICE simulations based on defined models to examine a 3 × 3 1S1R ReRAM array with vanadium dioxide selectors and titanium dioxide film memristors, assessing the impact of ambient temperature and critical IMT temperatures on array performance. We highlight the operational regions of low resistive state (LRS) and high resistive state (HRS), providing insights into the electrical behavior of these components under various conditions. Lastly, we demonstrate the impact of selector presence on sneak path currents. This research contributes to the overall understanding of ReRAM crossbar arrays integrated with IMT material-based selectors.

Electronic Materials doi: 10.3390/electronicmat5010001

Authors: Gunnar Suchaneck Evgenii Artiukh Nikolay Kalanda Marta Yarmolich Gerald Gerlach

In this work, we demonstrate the preparation of easy-to-fabricate nanogranular strontium ferromolybdate/strontium molybdate core-shell ceramics and examine their properties, including tunnel magnetoresistance, magnetic field sensitivity, and temperature coefficient of the tunnel magnetoresistance. The tunnel magnetoresistance of nanogranular strontium ferromolybdate/strontium molybdate core-shell ceramics was modeled, yielding values suitable for magnetoresistive sensor applications. Such structures possess a narrow peak of magnetic flux sensibility located at about 80 mT. For magnetic flux measurement, single-domain granules with superparamagnetic behavior should be applied. The predicted TMR magnetic flux sensitivities for granules with superparamagnetic behavior amount to about 7.7% T−1 and 1.5% T−1 for granule sizes of 3 nm and 5 nm, respectively. A drawback of the tunnel magnetoresistance of such nanogranular core-shell ceramics is the unacceptably large value of the temperature coefficient. Acceptable values, lower than 2% K−1, are obtained only at low temperatures (less than 100 K) or large magnetic flux densities (exceeding 6 T). Therefore, a Wheatstone bridge configuration should be adopted for magnetoresistive sensor design to compensate for the effect of temperature.

Electronic Materials doi: 10.3390/electronicmat4040014

Authors: Julia Isidora Salas Diego de Leon Sk Shamim Hasan Abir M. Jasim Uddin Karen Lozano

A triboelectric nanogenerator (TENG) is one of the most significantly innovative microdevices for built-in energy harvesting with wearable and portable electronics. In this study, the forcespinning technology was used to synthesize a nanofiber (NF) mat-based TENG. Polyvinylidene fluoride (PVDF) membrane was used as the negative triboelectric electrode/pole, and chemically designed and functionalized thermoplastic polyurethane (TPU) was used as the positive electrode/pole for the TENG. The electronic interference, sensitivity, and gate voltage of the synthesized microdevices were investigated using chemically modified bridging of multi-walled carbon nanotubes (MWCNT) with a TPU polymer repeating unit and bare TPU-based positive electrodes. The chemical functionality of TPU NF was integrated during the NF preparation step. The morphological features and the chemical structure of the nanofibers were characterized using a field emission scanning electron microscope and Fourier-transform infrared spectroscopy. The electrical output of the fabricated MWCNT-TPU/PVDF TENG yielded a maximum of 212 V in open circuit and 70 µA in short circuit at 240 beats per minute, which proved to be 79% and 15% higher than the TPU/PDVF triboelectric nanogenerator with an electronic contact area of 3.8 × 3.8 cm2, which indicates that MWCNT enhanced the electron transportation facility, which results in significantly enhanced performance of the TENG. This device was further tested for its charging capacity and sensory performance by taking data from different body parts, e.g., the chest, arms, feet, hands, etc. These results show an impending prospect and versatility of the chemically functionalized materials for next-generation applications in sensing and everyday energy harvesting technology.

Electronic Materials doi: 10.3390/electronicmat4040013

Authors: Masaya Ichimura

GaOOH, having a bandgap of 4.7–4.9 eV, can be regarded as one of several ultrawide-bandgap (UWBG) semiconductors, although it has so far mainly been used as a precursor material of Ga2O3. To examine the possibility of valence control and application in electronics, impurity levels in GaOOH are investigated using the first-principles density-functional theory calculation. The density values of the states of a supercell including an impurity atom are calculated. According to the results, among the group 14 elements, Si is expected to introduce a shallow donor level, i.e., a free electron is introduced. On the other hand, Ge and Sn introduce a localized state about 0.7 eV below the conduction band edge, and thus cannot act as an effective donor. While Mg and Ca can introduce a free hole and act as a shallow acceptor, Zn and Cd introduce acceptor levels away from the valence band. The transition metal elements (Fe, Co, Ni, Cu) are also considered, but none of them are expected to act as a shallow dopant. Thus, the results suggest that the carrier concentration can be controlled if Si is used for n-type doping, and Mg and Ca for p-type doping. Since GaOOH can be easily deposited using various chemical techniques at low temperatures, GaOOH will potentially be useful for transparent electronic devices.

Electronic Materials doi: 10.3390/electronicmat4040012

Authors: Ju-Seong Kim Jonghyun Choi Won Kook Choi

In this work, we report the first attempt to investigate the dependence of thioacetamide (TAA) on the size of ZnO nanoparticles (NPs) in forming ZnS nanostructures from ZnO. Size-controlled B(blue)_, G(green)_, and Y(yellow)_ZnO quantum dots (QDs) and NC (nanocrystalline)_ZnO NPs were synthesized using a sol–gel process and a hydrothermal method, respectively, and then reacted with an ethanolic TAA solution as a sulfur source. ZnO QDs/NPs began to decompose into ZnS QDs through a reaction with TAA for 5~10 min, so rather than forming a composite of ZnO/ZnS, ZnO QDs and ZnS QDs were separated and remained in a mixed state. At last, ZnO QDs/NPs were completely decomposed into ZnS QDs after a reaction with TAA for 1 h irrespective of the size of ZnO QDs up to ~50 nm. All results indicate that ZnS formation is due to direct crystal growth and/or the chemical conversion of ZnO to ZnS.

Electronic Materials doi: 10.3390/electronicmat4030011

Authors: Wojciech Pisula

Inorganic semiconductors have a wide range of applications in various fields, including electronics, optoelectronics, photovoltaics, and even catalysis [...]

Electronic Materials doi: 10.3390/electronicmat4030010

Authors: Jeffrie Fina Navdeep Kaur Chen-Yu Chang Cheng-Yu Lai Daniela R. Radu

Dye-sensitized solar cells (DSSCs) hold unique promise in solar photovoltaics owing to their low-cost fabrication and high efficiency in ambient conditions. However, to improve their commercial viability, effective, and low-cost methods must be employed to enhance their light harvesting capabilities, and hence photovoltaic (PV) performance. Improving the absorption of incoming light is a critical strategy for maximizing solar cell efficiency while overcoming material limitations. Mesoporous silica nanoparticles (MSNs) were employed herein as a reflective layer on the back of transparent counter electrodes. Chemically synthesized MSNs were applied to DSSCs via bar coating as a facile fabrication step compatible with roll-to-roll manufacturing. The MSNs diffusely scatter the unused incident light transmitted through the DSSCs back into the photoactive layers, increasing the absorption of light by N719 dye molecules. This resulted in a 20% increase in power conversion efficiency (PCE), from 5.57% in a standard cell to 6.68% with the addition of MSNs. The improved performance is attributed to an increase in photon absorption which led to the generation of a higher number of charge carriers, thus increasing the current density in DSSCs. These results were corroborated with electrochemical impedance spectroscopy (EIS), which showed improved charge transport kinetics. The use of MSNs as reflectors proved to be an effective practical method for enhancing the performance of thin film solar cells. Due to silica’s abundance and biocompatibility, MSNs are an attractive material for meeting the low-cost and non-toxic requirements for commercially viable integrated PVs.

Electronic Materials doi: 10.3390/electronicmat4030009

Authors: Mario Moreno Arturo Torres-Sánchez Pedro Rosales Alfredo Morales Alfonso Torres Javier Flores Luis Hernández Carlos Zúñiga Carlos Ascencio Alba Arenas

In this work, we report on the deposition of microcrystalline silicon (µc-Si:H) films produced from silane (SiH4), hydrogen (H2), and argon (Ar) mixtures using the plasma-enhanced chemical vapor deposition (PECVD) technique at 200 °C. Particularly, we studied the effect of RF power on the crystalline fraction (XC) of the deposited films, and we have correlated the XC with their optical, electrical, and structural characteristics. Different types of characterization were performed in the µc-Si:H film series. We used several techniques, such as Raman scattering spectroscopy, Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM), among others. Our results show that RF power had a strong effect on the XC of the films, and there is an optimal value for producing films with the largest XC.

Electronic Materials doi: 10.3390/electronicmat4020008

Authors: Joseph Oluwadamilola Bodunrin Duke Ateyh Oeba Sabata Jonas Moloi

The effects of Fe-implantation on the electrical characteristics of Au/p-Si Schottky barrier diodes (SBDs) were studied using current–voltage (I–V) and capacitance–voltage (C–V) techniques. The Rutherford Backscattering Spectrometry (RBS) and Energy Dispersive Spectroscopy (EDS) results showed that Fe ions are well implanted and present in the Fe-implanted Si material. The acquired results from I–V and C–V analysis showed that the diodes were well fabricated, and Fe-implantation changed the normal diode’s I–V behaviour from typical exponential to ohmic. The ohmic behaviour was described in terms of the defect levels induced by Fe in the middle of the band gap of Si. The conduction mechanism for both forward and reverse currents was presented, and the effect of Fe-implantation on the conduction mechanisms was investigated. The C–V results show that Fe generates a high density of minority carriers in p-Si, which agreed with the increase in reverse current observed in the I–V results. The diode parameters in terms of saturation current, ideality factor, Schottky barrier height, doping density, and space charge region (SCR) width were used to investigate the effect of Fe in p-Si based diode. Owing to the observed changes, which were analogous to those induced by dopants that improve the radiation hardness of silicon, it was safe to say that Fe can also assist in the quest to improve the radiation hardness of silicon using the defect-engineering method.

Electronic Materials doi: 10.3390/electronicmat4020007

Authors: Sébastien Pecqueur Dominique Vuillaume Željko Crljen Ivor Lončarić Vinko Zlatić

Extracting relevant data from real-world experiments is often challenging with intrinsic materials and device property dispersion, such as in organic electronics. However, multivariate data analysis can often be a mean to circumvent this and to extract more information when larger datasets are used with learning algorithms instead of physical models. Here, we report on identifying relevant information descriptors for organic electrochemical transistors (OECTs) to classify aqueous electrolytes by ionic composition. Applying periodical gate pulses at different voltage magnitudes, we extracted a reduced number of nonredundant descriptors from the rich drain-current dynamics, which provide enough information to cluster electrochemical data by principal component analysis between Ca2+-, K+-, and Na+-rich electrolytes. With six current values obtained at the appropriate time domain of the device charge/discharge transient, one can identify the cationic identity of a locally probed transient current with only a single micrometric device. Applied to OECT-based neural sensors, this analysis demonstrates the capability for a single nonselective device to retrieve the rich ionic identity of neural activity at the scale of each neuron individually when learning algorithms are applied to the device physics.

Electronic Materials doi: 10.3390/electronicmat4020006

Authors: Lutendo Muremi Pitshou N. Bokoro Wesley Doorsamy

In this study, commercially low-voltage MOVs are exposed to switching surges to analyse and model the relationship between the number of surges and the MOV grain barrier height response. Repeated slow-front overvoltage transients are used to degrade the protective qualities of metal oxide surge arrester devices, affecting their reliability and stability. A total of 360 MOVs with similar specifications from three different manufacturers are degraded under switching surges at a constant temperature of 60 °C. The reference voltage and C-V characteristics of MOVs are measured before and after the degradation process to analyse the MOVs’ conditions. Grain barrier heights are determined from the C-V characteristics curve. An F-statistical analysis is then applied to analyse the effects of number of surges on the grain barrier height. The T-test is used to assess the statistical difference between the tested groups. Linear regression analysis is then applied to model the relationship between the number of surges and MOV grain barrier height. The results obtained show that the number of surges has a significant impact on grain barrier height. MOV grain barrier height is found to decrease as the number of surges applied increases. Regression models obtained for the tested MOV groups across all three manufacturers agree and indicate that the reduction in grain barrier height results from an increased number of surges. Regression coefficients of a developed model indicate that for one surge applied, the MOV grain barrier height decreases by 0.024, 0.055, and 0.033 eV/cm for manufacturers X, Y, and Z, respectively. Therefore, there is a linear relationship between grain barrier height and the number of applied switching surges.

Electronic Materials doi: 10.3390/electronicmat4020005

Authors: Jinwei Fan Zhuoqun Wang Haoge Cheng Dingguan Wang Andrew Thye Shen Wee

Covalent organic framework nanosheets (COF nanosheets) are two-dimensional crystalline porous polymers with in-plane covalent bonds and out-of-plane Van der Waals forces. Owing to the customizable structure, chemical modification, and ultra-high porosity, COF nanosheets show many fascinating properties unique to traditional two-dimensional materials, and have shown potential applications in gas separation, sensors, electronic, and optoelectronic devices. This minireview aims to illustrate recent progress on two-dimensional covalent organic framework nanosheets, from two aspects of on-surface synthesis and potential applications. We first review the synthesis of COF nanosheets at the gas–solid interface. On-surface synthesis under ultrahigh vacuum and on-surface synthesis under vapor are highlighted. In addition, we also review the liquid–solid interface synthesis of COF nanosheets at various substrates, i.e., both crystalline and amorphous substrates. Beyond the synthesis, we highlight state-of-the-art applications of the COF nanosheets, particularly in charge transport, chemical sensors, and gas separation.

Electronic Materials doi: 10.3390/electronicmat4010004

Authors: Yin-Pai Lin Dmitry Bocharov Inta Isakoviča Vladimir Pankratov Aleksandr A. Popov Anatoli I. Popov Sergei Piskunov

Chloride is one of the most abundant ions in sea water, which is more available than fresh water. Due to lack of H2O adsorbate states near the valence band maximum (VBM) edge, the difficulty of water dissociation incidents has been reported on the rutile TiO2 surface as the excitation energy is around the band gap energy of TiO2. It is interesting whether the extra chloride can be a benefit to the water dissociation or not. In this study, the models of chlorine adatoms placed on the rutile TiO2 (110)/water interface are constructed using ab initio methods. The time-dependent spatial charges, bond-lengths of water molecules, and Hirshfeld charges are calculated by real-time time-dependent density functional theory and the Ehrenfest dynamics theory for investigating the excited state nonadiabatic dynamics of water dissociation. This study presents two photoinduced water-splitting pathways related to chlorine and analyzes the photogenerated hole along the reactions. The first step of water dissociation relies on the localized competition of oxygen charges between the dissociated water and the bridge site of TiO2 for transforming the water into hydroxyl and hydrogen by photoinduced driving force.

Electronic Materials doi: 10.3390/electronicmat4010003

Authors: Yaxuan He Haibo Li

Owing to the 3D open framework, excellent structural stability, and high ionic conductivity, NASICON-type compounds are extensively employed as promising cathode materials for sodium-ion batteries (SIBs). Being one of the representative NASICON-type compounds, the Na3V2(PO4)3 delivers high theoretical capacity with an operating voltage exceeding 3.3 V, enabling it to be a good candidate for SIBs. Unfortunately, the Na3V2(PO4)3 suffers from low electronic conductivity. In this work, we briefly review the recent research progress on novel carbon engineering strategies to enhance the electronic conductivity of Na3V2(PO4)3. Moreover, we will point out the issues relating to the development of NASICON cathode materials and put forward some suggestions.

Electronic Materials doi: 10.3390/electronicmat4010002

Authors: Electronic Materials Editorial Office Electronic Materials Editorial Office

High-quality academic publishing is built on rigorous peer review [...]

Electronic Materials doi: 10.3390/electronicmat4010001

Authors: Darpan Dubey Rohit Kumar Abhishek Dwivedi Awadhesh Kumar Rai

Laser-induced Breakdown Spectroscopy (LIBS) is primarily an atomic emission spectroscopic method based on analyzing the spectral lines of elements in the laser-induced plasma. However, when the plasma cools down after its ignition, i.e., when one collects the emissions from the plasma after a certain interval of time/gate delay (~1 micro-second), the signature of the electronic bands of diatomic molecules is also observed along with ionic/atomic emission lines. The present manuscript reports the evaluation of toxicity/pollutants in green crackers based on the intensity of the electronic bands of the Aluminum Oxide (AlO), calcium oxide (CaO), and strontium oxide (SrO) molecules observed in the laser-induced plasma of the firecrackers. LIBS spectra of the green crackers show the presence of spectral lines of the heavy/toxic elements such as Al, Ca, Sr, Cr, Cu, and Ba, along with the electronic bands of the AlO, CaO, and SrO. Fourier Transform Infra-Red Spectroscopy (FTIR) has been used to validate the LIBS results and confirm the molecules in these crackers. The concentration of toxic elements in green crackers such as Aluminum (Al), Copper (Cu), and Chromium (Cr) has also been estimated using the Partial Least Square Regression method (PLSR) to evaluate and compare the extent of the toxicity of green crackers.

Electronic Materials doi: 10.3390/electronicmat3040029

Authors: Pargam Vashishtha Pukhraj Prajapat Lalit Goswami Aditya Yadav Akhilesh Pandey Govind Gupta

Epitaxial GaN nanostructures are developed, and the influence of the AlN buffer layer (temperature modulation) on material characteristics and optoelectronic device application is assessed. The AlN buffer layer was grown on a Si (111) substrate at varying temperatures (770–830 °C), followed by GaN growth using plasma-assisted molecular beam epitaxy. The investigation revealed that the comparatively lower temperature AlN buffer layer was responsible for stress and lattice strain relaxation and was realized as the GaN nano-obelisk structures. Contrarily, the increased temperature of the AlN growth led to the formation of GaN nanopyramidal and nanowax/wane structures. These grown GaN/AlN/Si heterostructures were utilized to develop photodetectors in a metal–semiconductor–metal geometry format. The performance of these fabricated optoelectronic devices was examined under ultraviolet illumination (UVA), where the GaN nano-obelisks-based device attained the highest responsivity of 118 AW−1. Under UVA (325 nm) illumination, the designed device exhibited a high detectivity of 1 × 1010 Jones, noise equivalent power of 1 × 10−12 WHz−1/2, and external quantum efficiency of 45,000%. The analysis revealed that the quality of the AlN buffer layer significantly improved the optoelectronic performance of the device.

Electronic Materials doi: 10.3390/electronicmat3040028

Authors: Georgia A. Boni Lucian D. Filip Cristian Radu Cristina Chirila Iuliana Pasuk Mihaela Botea Ioana Pintilie Lucian Pintilie

Electrocaloric effect is the adiabatic temperature change in a dielectric material when an electric field is applied or removed, and it can be considered as an alternative refrigeration method. Materials with ferroelectric order exhibit large temperature variations in the vicinity of a phase transition, while antiferroelectrics and relaxors may exhibit a negative electrocaloric effect. In this study, the temperature variation in polarization was investigated for epitaxial ferroelectric thin film structures based on PbZrTiO3 materials in simple or complex multilayered structures. We propose the intriguing possibility of a giant negative electrocaloric effect (ΔT = −3.7 K at room temperature and ΔT = −5.5 K at 370 K) in a simple epitaxial Pb(ZrTi)O3 capacitor. Furthermore, it was shown that abnormal temperature variation in polarization is dependent on the non-FE component introduced in a multilayered structure. No significant variation in polarization with temperature was obtained for PZT/STON multilayered structures around room temperature. However, for PZT/BST or PZT/Nb2O5 multilayers, an abnormal temperature variation in polarization was revealed, which was similar to a simple PZT layer. The giant and negative ∆T values were attributed to internal fields and defects formed due to the large depolarization fields when the high polarization of the FE component was not fully compensated either by the electrodes or by the interface with an insulator layer. The presented results make Pb(ZrTi)O3-based structures promising for cooling applications operating near room temperature.

Electronic Materials doi: 10.3390/electronicmat3040027

Authors: May Zin Toe Wai Kian Tan Hiroyuki Muto Go Kawamura Atsunori Matsuda Khatijah Aisha Binti Yaacob Swee-Yong Pung

Aerosol deposition (AD) is a simple, dry raw-powder deposition process in which the targeted film is formed by direct bombardment of accelerated starting powder onto the substrate surface at room temperature. Despite the increased interest in AD film formation, no work has been completed to systematically investigate the formation of dense zinc oxide (ZnO) films using the AD method and their optical properties. Therefore, this study was carried out to investigate the effect of AD gas flow rate on the formation of AD films and the optical properties of aerosol-deposited ZnO films. ZnO films with nanosized (<40 nm) crystallites were successfully deposited on FTO substrates at room temperature. A dense and uniform layer of aerosol-deposited ZnO films with a roughened surface was obtained without subsequent heat treatment. With the increase in the AD gas flow rate, the crystal size and the AD film’s thickness were reduced. The Raman spectroscopy verified that the thin film was of a ZnO wurtzite structure. The room temperature photoluminescence of the ZnO thin film produced strong visible emissions. The findings of this work demonstrated that AD can be an alternative technique for the rapid deposition of dense and thick ZnO films for optoelectronic applications.

Electronic Materials doi: 10.3390/electronicmat3040026

Authors: Yusuke Yamada

Wireless energy harvesting, a technique to generate direct current (DC) electricity from ambient wireless signals, has recently been featured as a potential solution to reduce the battery size, extend the battery life, or replace batteries altogether for wearable electronics. Unlike other energy harvesting techniques, wireless energy harvesting has a prominent advantage of ceaseless availability of ambient signals, but the common form of technology involves a major challenge of limited output power because of a relatively low ambient energy density. Moreover, the archetypal wireless energy harvesters are made of printed circuit boards (PCBs), which are rigid, bulky, and heavy, and hence they are not eminently suitable for body-worn applications from both aesthetic and comfort points of view. In order to overcome these limitations, textile-based wireless energy harvesting architectures have been proposed in the past decade. Being made of textile materials, this new class of harvesters can be seamlessly integrated into clothing in inherently aesthetic and comfortable forms. In addition, since clothing offers a large surface area, multiple harvesting units can be deployed to enhance the output power. In view of these unique and irreplaceable benefits, this paper reviews key recent progress in textile-based wireless energy harvesting strategies for powering body-worn electronics. Comparisons with other power harvesting technologies, historical development, fundamental principles of operation and techniques for fabricating textile-based wireless power harvesters are first recapitulated, followed by a review on the principal advantages, challenges, and opportunities. It is one of the purposes of this paper to peruse the current state-of-the-art and build a scientific knowledge base to aid further advancement of power solutions for wearable electronics.

Electronic Materials doi: 10.3390/electronicmat3040025

Authors: Wael Hourani Christophe Rousselot Kouamé Boko Joël-Igor N’Djoré Alain Billard Mohammad Arab Pour Yazdi Younes Makoudi

Lanthanum manganite (LMO) thin films were deposited by co-sputtering La and Mn targets in an Ar and O2 gas mixture. The films were synthesized on silicon and fused silica substrates. The influences of thermal annealing on the structure, optical and electrical properties of LMO films were investigated. The results exhibited a correlation between these properties. In the amorphous state, an increase in annealing temperature improved the optical transmission and decreased the electrical capacitance. The beginning of crystallization at 600 °C was manifested by a strong increase in the capacitance and a decrease in the optical transmission. At higher annealing temperature, polycrystalline films were obtained with different optical and electrical characteristics. On the other hand, the annealed LMO films showed a photocurrent effect during exposure to a weak LED light.

Electronic Materials doi: 10.3390/electronicmat3040024

Authors: Nicolò Lago Marco Buonomo Federico Prescimone Stefano Toffanin Michele Muccini Andrea Cester

Among the plethora of soluble and easy processable organic semiconductors, 6,13-Bis(triisopropylsilylethynyl)pentacene (TIPS-P5) is one of the most promising materials for next-generation flexible electronics. However, based on the information reported in the literature, it is difficult to exploit in field-effect transistors the high-performance characteristics of this material. This article correlates the HMDS functionalization of the silicon substrate with the electrical characteristics of TIPS-P5-based bottom gate organic field-effect transistors (OFETs) and electrolyte-gated organic field-effect transistors (EGOFETs) fabricated over the same platform. TIPS-P5 transistors with a double-gate architecture were fabricated by simple drop-casting on Si/SiO2 substrates, and the substrates were either functionalized with hexamethyldisilazane (HMDS) or left untreated. The same devices were characterized both as standard bottom-gate transistors and as (top-gate) electrolyte-gated transistors, and the results with and without HMDS treatment were compared. It is shown that the functionalization of the silicon substrate negatively influences EGOFETs performance, while it is beneficial for bottom-gate OFETs. Different device architectures (e.g., bottom-gate vs. top-gate) require specific evaluation of the fabrication protocols starting from the effect of the HMDS functionalization to maximize the electrical characteristics of TIPS-P5-based devices.

Electronic Materials doi: 10.3390/electronicmat3040023

Authors: Bruna Cruz Philipp Eschlwech Michael Hani Erwin Biebl

The use of nonmetallic conductor materials in RF applications has recently become a highlighted issue when it comes to sustainability in the electronics industry, mainly because of the waste problems associated with heavy metals and the necessity of reducing and managing them. The replacement of metal in functional applications such as in electronics is therefore very important. Among these new materials, organic conductors are of great interest since they are, in general, biocompatible and biodegradable, allowing for the disposal of electronic devices, which reduces the negative environment impact caused by electronics waste. In this work, PEDOT:PSS and Carbon are investigated. Since these materials are available as conducting pastes or inks, the production of conducting patterns by printing techniques such as screen printing is possible, which can make the process less harmful to the environment, since it permits the use of organic substrates such as paper. In order to investigate the feasibility of these materials for RF signal transmission, screen printed PEDOT:PSS and Carbon transmission lines have been designed, fabricated and characterized. Results regarding conductivity, thickness, electric permittivity and S21 parameter are presented and will serve as a foundation for the development of further reaching applications utilizing organic materials.

Electronic Materials doi: 10.3390/electronicmat3030022

Authors: Wojciech Pisula

Electronic materials are of great interest due to their potential to be applied in a broad range of important electronic devices including transistors, sensors, solar cells and others [...]

Electronic Materials doi: 10.3390/electronicmat3030021

Authors: Jong-Keun Choi Young-Gyun Kim Kwan-Young Han

Currently, as the next-generation of display progresses—with high performance and high integration—the surface mounting technology of components is very important. In particular, in the case of flexible displays, such as rollable and bendable displays, ACF that connects wires to any curvature is essential. However, the conductive ball used inside the ACF has had problems with particle size and non-uniform metal coating. It was confirmed that the presence of solvent and oxygen, which are used in polymer synthesis, affects the sphere formation of polymer beads. By optimizing the factors affecting the polymer beads, a perfect spherical polymer bead was manufactured. In addition, the conductive ball manufacturing process was optimized by confirming the factors affecting the metal coating. The metal coating on the surface of the polymer bead was applied with a uniform thickness by considering the specific surface area and concentration of the conductive balls, and, through this optimized process, conductive balls for anisotropic conductive films with uniform size and metal thickness were obtained.

Electronic Materials doi: 10.3390/electronicmat3030020

Authors: Samiul Hasan Iftikhar Ahmad

This article will briefly review the progress of h-BN based solid-state metal semiconductor metal (MSM) neutron detectors. In the last decade, several groups have been working on hexagonal boron nitride (h-BN)-based solid-state neutron detectors. Recently, the detection efficiency of 59% has been reported. Efficient, low-cost neutron detectors made from readily available materials are essential for various applications. Neutron detectors are widely used to detect fissile materials and nuclear power plants for security applications. The most common and widely used neutron detectors are 3He based, which are sometimes bulky, difficult to transport, have high absorption length, need relatively high bias voltage (>1000 V), and have low Q-value (0.764 MeV). In addition, 3He is not a readily available material. Thus, there is a strong need to find an alternative detection material. The 10B isotope has a high neutron absorption cross-section, and it has been tested as a coating on the semiconducting materials. Due to the two-step process, neutron capture through 10B and then electron–hole pair generation in a typical semiconducting material, the efficiency of these devices is not up to the mark. The progress in h-BN based detectors requires a review to envision the further improvement in this technology.

Electronic Materials doi: 10.3390/electronicmat3030019

Authors: Gunnar Suchaneck

This work presents an examination and unification of fragmented data on spin polarization in half-metallic, ferrimagnetic oxides. It also includes well understood ferromagnetic metals for comparison. The temperature and disorder dependencies of the spin polarization are evaluated. Both the temperature dependence of the tunnel magnetoresistance and, for the very first time, its temperature coefficient are calculated based on the simplified Julliére model. The tunnel magnetoresistance in the magnetic tunnel junctions deteriorates due to the temperature dependence of the spin polarization the lower the Curie temperature is. As a result, magnetic tunnel junctions—consisting of ferromagnetic oxides with a Curie temperature not far above room temperature—are not promising for room temperature applications. Additionally, ferrimagnetic oxides possessing a Curie temperature below 650 K are not suitable for room temperature applications because of an unacceptable temperature coefficient exceeding −2%.

Electronic Materials doi: 10.3390/electronicmat3030018

Authors: Lucas Florêncio Jéssica Luzardo Marcelo Pojucan Victor Cunha Alexander Silva Rogério Valaski Joyce Araujo

In this work, the electrical properties of graphene papers were investigated with the aim of developing pressure sensor prototypes for measuring pressures up to 2 kPa. In order to determine which graphene paper would be the most suitable, three different types of graphene papers, synthesized by different routes, were prepared and electrically characterized. The results of electrical characterizations, in terms of electrical conductivity and sheet resistance of graphene papers, are presented and discussed. Prototypes of pressure sensors are proposed, using graphene papers obtained by chemical oxidation (graphene oxide and reduced graphene oxide) and by electrochemical exfoliation. The prototypes were tested in static compression/decompression tests in the working range of 0 kPa to 1.998 kPa. The compression/decompression sensitivity values observed in these prototype sensors ranged from 20.8% ΔR/kPa for graphene sensors obtained by electrochemical exfoliation to 110.7% ΔR/kPa for those prepared from graphene oxide obtained by chemical oxidation. More expressive sensitivity values were observed for the sensors fabricated from GO, intermediate values for those made of rGO, while prototypes made of EG showed lower sensitivity.

Electronic Materials doi: 10.3390/electronicmat3020017

Authors: Ashwin Gaonkar Homero Valladares Andres Tovar Likun Zhu Hazim El-Mounayri

The development of lithium-ion batteries (LIBs) based on current practice allows an energy density increase estimated at 10% per year. However, the required power for portable electronic devices is predicted to increase at a much faster rate, namely 20% per year. Similarly, the global electric vehicle battery capacity is expected to increase from around 170 GWh per year today to 1.5 TWh per year in 2030—this is an increase of 125% per year. Without a breakthrough in battery design technology, it will be difficult to keep up with their increasing energy demand. The objective of this investigation is to develop a design methodology to accelerate the LIB development through the integration of electro-chemical numerical simulations and machine learning algorithms. In this work, the Gaussian process (GP) regression model is used as a fast approximation of numerical simulation (conducted using Simcenter Battery Design Studio®). The GP regression models are systematically updated through a multi-objective Bayesian optimization algorithm, which enables the exploration of innovative designs as well as the determination of optimal configurations. The results reported in this work include optimal thickness and porosities of LIB electrodes for several practical charge–discharge scenarios which maximize energy density and minimize capacity fade.

Electronic Materials doi: 10.3390/electronicmat3020016

Authors: Tomah Sogabe Kodai Shiba Katsuyoshi Sakamoto

The hot-carrier effect and hot-carrier dynamics in GaAs solar cell device performance were investigated. Hot-carrier solar cells based on the conventional operation principle were simulated based on the detailed balance thermodynamic model and the hydrodynamic energy transportation model. A quasi-equivalence between these two models was demonstrated for the first time. In the simulation, a specially designed GaAs solar cell was used, and an increase in the open-circuit voltage was observed by increasing the hot-carrier energy relaxation time. A detailed analysis was presented regarding the spatial distribution of hot-carrier temperature and its interplay with the electric field and three hot-carrier recombination processes: Auger, Shockley–Read–Hall, and radiative recombinations.

Electronic Materials doi: 10.3390/electronicmat3020015

Authors: Mihaela Botea Cristina Chirila Georgia Andra Boni Iuliana Pasuk Lucian Trupina Ioana Pintilie Luminiţa Mirela Hrib Becherescu Nicu Lucian Pintilie

The ferroelectric and pyroelectric properties of bismuth ferrite (BFO) epitaxial thin film have been investigated. The ferroelectric epitaxial thin layer has been deposited on strontium titanate (STO) (001) substrate by pulsed laser deposition, in a capacitor geometry using as top and bottom electrode a conductive oxide of strontium ruthenate (SRO). The structural characterizations performed by X-ray diffraction and atomic force microscopy demonstrate the epitaxial character of the ferroelectric thin film. The macroscopic ferroelectric characterization of BFO revealed a rectangular shape of a polarization-voltage loop with a remnant polarization of 30 μC/c m2 and a coercive electric field of 633 KV/cm at room temperature. Due to low leakage current, the BFO capacitor structure could be totally pooled despite large coercive fields. A strong variation of polarization is obtained in 80–400 K range which determines a large pyroelectric coefficient of about 10−4 C/m2 K deduced both by an indirect and also by a direct method.

Electronic Materials doi: 10.3390/electronicmat3020014

Authors: Nekane Azkona Alvaro Llaria Octavian Curea Federico Recart

In this work, a defective commercial module with a rounded IV characteristic is analyzed in detail to identify the sources of its malfunction. The analysis of the module includes thermography images taken under diverse conditions, the IV response of the module obtained without any shadow, and shadowing one cell at a time, as recommended by the IEC 61215 Standard. Additionally, a direct measurement of the IV characteristic and resistance of single cells in the panel has been conducted to verify the isolation between the p and n areas. In parallel, theoretical cell and module behaviors are presented. In this frame, simulations show how cell mismatch can be the explanation to the rounded IV output of the solar panel under study. From the thermal images of the module, several localized hot spots related to failing cells have been revealed. During the present study, thermal breakdown is seen before avalanche breakdown in one of the cells, evidencing a hot spot. Not many papers have dealt with this problem, whereas we believe it is important to analyze the relationship between thermal breakdown and hot spotting in order to prevent it in the future, since hot spots are the main defects related to degradation of modern modules.

Electronic Materials doi: 10.3390/electronicmat3010013

Authors: Volodymyr Dzhagan Oleksandr Selyshchev Serhiy Kondratenko Nazar Mazur Yevhenii Havryliuk Oleksandra Raievska Oleksandr Stroyuk Dietrich R. T. Zahn

Thin films of colloidal CZTS nanocrystals (NCs) synthesized using a “green” approach in water with a variation of the copper-to-tin ratio are investigated by Raman scattering, mid-infrared (molecular vibrations) and near-infrared (free carrier) absorption, X-ray photoemission spectroscopy (XPS), electrical conductivity, and conductive atomic force microscopy (cAFM). We determined the effect of the actual Cu content on the phonon spectra, electrical conductivity, and spectral parameters of the plasmon band. An increase in the electrical conductivity of the NC films upon annealing at 220 °C is explained by three factors: formation of a CuxS nanophase at the CZTS NC surface, partial removal of ligands, and improved structural perfection. The presence of the CuxS phase is concluded to be the determinant factor for the CZTS NC film conductivity. CuxS can be reliably detected based on the analysis of the modified Auger parameter of copper, derived from XPS data and corroborated by Raman spectroscopy data. Partial removal of the ligand is concluded from the agreement of the core-level XPS and vibrational IR spectra. The degree of lattice perfection can be conveniently assessed from the Raman data as well. Further important information derived from a combination of photoelectron and optical data is the work function, ionization potential, and electron affinity of the NC films.

Electronic Materials doi: 10.3390/electronicmat3010012

Authors: Madjid Arab Véronique Madigou Virginie Chevallier Christian Turquat Christine Leroux

This study aims to discuss the combined theoretical and experimental results of elastic properties of tungsten trioxide films supported on Quartz (YX)/45°/10° resonator to form surface acoustic wave (SAW) devices. The SAW systems with different thicknesses of WO3 thin films were imaged and structurally characterized by X-ray diffraction, atomic force, and transmission electron microscopy. The deposited WO3 films (100, 200, and 300 nm of thickness) crystallized in a single monoclinic phase. The acoustoelectric properties of the SAW system were obtained by combining theoretical simulations with experimental measurements. The modeling of the SAW devices has been performed by the finite element and boundary element methods (FEM/BEM). The elastic constants of the films at room temperature were assessed via electrical admittances experiments in light of theoretical calculations. The gravimetric effect of the deposited layers is observed by a shift of the resonance frequency to lower values as the thickness of the films increases. Moreover, the acoustic losses are affected by the dielectric losses of the WO3 films while the resonant frequency decreases almost linearly. SAW devices revealed strong displacement fields with low acoustic losses as a function of WO3 thicknesses. For all the deposited layers, the measured Young’s moduli and Poisson’s ratios are 8 GPa and 0.5, respectively.

Electronic Materials doi: 10.3390/electronicmat3010011

Authors: Ivana Capan Tomislav Brodar

In this review, we provide an overview of the most common majority and minority charge carrier traps in n-type 4H-SiC materials. We focus on the results obtained by different applications of junction spectroscopy techniques. The basic principles behind the most common junction spectroscopy techniques are given. These techniques, namely, deep-level transient spectroscopy (DLTS), Laplace DLTS (L-DLTS), and minority carrier transient spectroscopy (MCTS), have led to recent progress in identifying and better understanding the charge carrier traps in n-type 4H-SiC materials.

Electronic Materials doi: 10.3390/electronicmat3010010

Authors: Andrzej Molak Anna Z. Szeremeta Janusz Koperski

This work shows a correlation between light reflectance, absorption, and morphologies of series of bismuth manganate–lead titanate, (1 − x) BM–x PT, (x = 0.00, 0.02, 0.04, 0.08, 0.12, 0.16, 0.24, 1.00) ceramics composite. Low reflectance in the Vis-NIR range corresponds to ‘black mirror’ features. The modified Kubelka-Munk function applied to measured visible-near infrared (Vis-NIR) diffuse reflectance enabled the estimation of the energy gaps magnitude of the order of 1.0–1.2 eV for BM-PT. Histograms of grains, obtained using a scanning electron microscope, enabled finding the correlation between grains size, reflectance magnitude, and PT content. The magnitude of energy gaps was attributed to electronic structure bands modified by crystal lattice disorder and oxygen vacancies.

Electronic Materials doi: 10.3390/electronicmat3010009

Authors: Hongxu Huang Lijing Li Yuxuan Ma Mingjie Sun

Computational ghost imaging, as an alternative photoelectric imaging technology, uses a single-pixel detector with no spatial resolution to capture information and reconstruct the image of a scene. Due to its essentially temporal measurement manner, improving the image frame rate is always a major concern in the research of computational ghost imaging technology. By taking advantage of the fast switching time of LED, an LED array was developed to provide a structured illumination light source in our work, which significantly improves the structured illumination rate in the computational ghost imaging system. The design of the LED array driver circuit presented in this work makes full use of the LED switching time and achieves a pattern displaying rate of 12.5 MHz. Continuous images with 32 × 32 pixel resolution are reconstructed at a frame rate of 25,000 fps, which is approximately 500 times faster than what a universally used digital micromirror device can achieve. The LED array presented in this work can potentially be applied to other techniques requiring high-speed structured illumination, such as fringe 3D profiling and array-based LIFI.

Electronic Materials doi: 10.3390/electronicmat3010008

Authors: Gunnar Suchaneck Nikolai Kalanda Marta Yarmolich Evgenii Artiukh Gerald Gerlach Nikolai A. Sobolev

In this work, we describe the magnetization of nanosized SFMO particles with a narrow size distribution around ca. 70 nm fabricated by the citrate-gel technique. The single-phase composition and superstructure ordering degree were proved by X-ray diffraction, the superparamagnetic behavior by magnetization measurements using zero-field cooled and field-cooled protocols, as well as by electron magnetic resonance. Different contributions to the magnetic anisotropy constant and the temperature dependence of the magnetocrystalline anisotropy are discussed.

Electronic Materials doi: 10.3390/electronicmat3010007

Authors: Amir Dayan Yi Huang Alex Schuchinsky

Passive intermodulation (PIM) is a niggling phenomenon that debilitates the performance of modern communications and navigation systems. PIM products interfere with information signals and cause their nonlinear distortion. The sources and basic mechanisms of PIM have been studied in the literature but PIM remains a serious problem of signal integrity. In this paper, the main sources and mechanisms of PIM generation by joints of good conductors are discussed. It is shown that the passive electrical, thermal and mechanical nonlinearities are intrinsically linked despite their distinctively different time scales. The roughness of the contact surfaces plays an important role in PIM generation by conductor joints. A review of the PIM phenomenology at the contacts of the good conductors suggests that novel multiphysics models are necessary for the analysis and reliable prediction of PIM products generated by several concurrent nonlinearities of a diverse physical nature.

Electronic Materials doi: 10.3390/electronicmat3010006

Authors: Electronic Materials Editorial Office Electronic Materials Editorial Office

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Electronic Materials doi: 10.3390/electronicmat3010005

Authors: Hari Chandra Nayak Shivendra Singh Parmar Rajendra Prasad Kumhar Shailendra Rajput

In this article, the dielectric properties of poly (9-vinylcarbazole) (PVK) and ferrocene-doped PVK thin films are studied. The thin films were grown by the isothermal solution casting technique. Dielectric properties of grown films were studied as function of ferrocene concentration, frequency, and temperature. The relative permittivity (ε′) is increased with increasing ferrocene percentage (~1%) due to the free charge carriers. The relative permittivity decreases for higher ferrocene percentage (~2%). However, the relative permittivity of PVK and ferrocene-doped PVK samples remains almost constant for studied temperature range (313–413 K). The frequency dependence of tan δ for all samples is studied. The frequency dependence of dielectric parameter exhibits frequency dispersion behavior, which suggests all types of polarization present in the lower frequency range. The loss tangent (tanδ) values are larger at higher temperatures in the low frequency region. However, the tan δ values at different temperatures are almost similar in the high frequency region. It is observed that the relative permittivity is maximum, dielectric loss is minimum, and AC conductivity is minimum for 1% ferrocene doped PVK as compared to pure PVK and 2% ferrocene doped PVK samples.

Electronic Materials doi: 10.3390/electronicmat3010004

Authors: Michael Vogl Martin Valldor Roman Boy Piening Dmitri V. Efremov Bernd Büchner Saicharan Aswartham

We present the synthesis and characterization of the iridium-based sulfide Ca1−xIr4S6(S2). Quality and phase analysis were conducted by means of energy-dispersive X-ray spectroscopy (EDXS) and powder X-ray diffraction (XRD) techniques. Structure analysis reveals a monoclinic symmetry with the space group C 1 2/m 1 (No. 12), with the lattice constants a = 15.030 (3) Å, b = 3.5747 (5) Å and c = 10.4572 (18) Å. Both X-ray diffraction and EDXS suggest an off-stoichiometry of calcium, leading to the empirical composition Ca1−xIr4.0S6(S2) [x = 0.23–0.33]. Transport measurements show metallic behavior of the compound in the whole range of measured temperatures. Magnetic measurements down to 1.8 K show no long range order, and Curie–Weiss analysis yields θCW = −31.4 K, suggesting that the compound undergoes a magnetic state with short range magnetic correlations. We supplement our study with calculations of the band structure in the framework of the density functional theory.

Electronic Materials doi: 10.3390/electronicmat3010003

Authors: Alain E. Kaloyeros Jonathan Goff Barry Arkles

Stoichiometric silicon carbide (SiC) thin films were grown using thermal chemical vapor deposition (TCVD) from the single source precursor 1,3,5-trisilacyclohexane (TSCH) on c-Si (100) substrates within an optimized substrate temperature window ranging from 650 to 850 °C. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analyses revealed that the as-deposited films consisted of a Si-C matrix with a Si:C ratio of ~1:1. FTIR and photoluminescence (PL) spectrometry studies showed that films deposited ≥ 750 °C were defect- and H-free within the detection limit of the techniques used, while ellipsometry measurements yielded an as-grown SiC average refractive index of ~2.7, consistent with the reference value for the 3C-SiC phase. The exceptional quality of the films appears sufficient to overcome limitations associated with structural defects ranging from failure in high voltage, high temperature electronics to 2-D film growth. TSCH, a liquid at room temperature with good structural stability during transport and handling as well as high vapor pressure (~10 torr at 25 °C), provides a viable single source precursor for the growth of stoichiometric SiC without the need for post-deposition thermal treatment.

Electronic Materials doi: 10.3390/electronicmat3010002

Authors: Argyris Tilemachou Matthew Zervos Andreas Othonos Theodoros Pavloudis Joseph Kioseoglou

Cu3N with a cubic crystal structure is obtained in this paper by the sputtering of Cu under N2 followed by annealing under NH3: H2 at 400 °C, after which it was doped with iodine at room temperature resulting into p-type Cu3N with hole densities between 1016 and 1017 cm−3. The Cu3N exhibited distinct maxima in differential transmission at ~2.01 eV and 1.87 eV as shown by ultrafast pump-probe spectroscopy, corresponding to the M and R direct energy band gaps in excellent agreement with density functional theory calculations, suggesting that the band gap is clean and free of mid-gap states. The Cu3N was gradually converted into optically transparent γ-CuI that had a hole density of 4 × 1017 cm−3, mobility of 12 cm2/Vs and room temperature photoluminescence at 3.1 eV corresponding to its direct energy band gap. We describe the fabrication and properties of γ-CuI/TiO2/Cu3N and γ-CuI/Cu3N p-n heterojunctions that exhibited rectifying current-voltage characteristics, but no photogenerated current attributed to indirect recombination via shallow states in Cu3N and/or deep states in the γ-CuI consistent with the short (ps) lifetimes of the photoexcited electrons-holes determined from transient absorption–transmission spectroscopy.

Electronic Materials doi: 10.3390/electronicmat3010001

Authors: Rasmus Tranås Ole Martin Løvvik Kristian Berland

Low thermal conductivity is an important materials property for thermoelectricity. The lattice thermal conductivity (LTC) can be reduced by introducing sublattice disorder through partial isovalent substitution. Yet, large-scale screening of materials has seldom taken this opportunity into account. The present study aims to investigate the effect of partial sublattice substitution on the LTC. The study relies on the temperature-dependent effective potential method based on forces obtained from density functional theory. Solid solutions are simulated within a virtual crystal approximation, and the effect of grain-boundary scattering is also included. This is done to systematically probe the effect of sublattice substitution on the LTC of 122 half-Heusler compounds. It is found that substitution on the three different crystallographic sites leads to a reduction of the LTC that varies significantly both between the sites and between the different compounds. Nevertheless, some common criteria are identified as most efficient for reduction of the LTC: The mass contrast should be large within the parent compound, and substitution should be performed on the heaviest atoms. It is also found that the combined effect of sublattice substitution and grain-boundary scattering can lead to a drastic reduction of the LTC. The lowest LTC of the current set of half-Heusler compounds is around 2 W/Km at 300 K for two of the parent compounds. Four additional compounds can reach similarly low LTC with the combined effect of sublattice disorder and grain boundaries. Two of these four compounds have an intrinsic LTC above ∼15 W/Km, underlining that materials with high intrinsic LTC could still be viable for thermoelectric applications.

Electronic Materials doi: 10.3390/electronicmat2040039

Authors: Yujian Sun Yongcao Zhang Yuxin Li Yilin Li

Luminescent solar concentrators (LSCs) are considered promising in their application as building-integrated photovoltaics (BIPVs). However, they suffer from low performance, especially in large-area devices. One of the key issues is the self-absorption of the luminophores. In this report, we focus on the study of self-absorption in perovskite-based LSCs. Perovskite nanocrystals (NCs) are emerging luminophores for LSCs. Studying the self-absorption of perovskite NCs is beneficial to understanding fundamental photon transport properties in perovskite-based LSCs. We analyzed and quantified self-absorption properties of perovskite NCs in an LSC with the dimensions of 6 in × 6 in × 1/4 in (152.4 mm × 152.4 mm × 6.35 mm) using three approaches (i.e., limited illumination, laser excitation, and regional measurements). The results showed that a significant number of self-absorption events occurred within a distance of 2 in (50.8 mm), and the photo surface escape due to the repeated self-absorption was the dominant energy loss mechanism.

Electronic Materials doi: 10.3390/electronicmat2040038

Authors: Atsushi Nitta Naohiko Chosa Kazuhiro Takeda

Recently, active research has been conducted on the development of flexible electronic devices. Hence, the transparent conductive film (TCF), an essential component of the device, must also be flexible. However, the commonly used indium tin oxide (ITO) TCF lacks flexibility and contains rare metal, making resource depletion an issue. Therefore, we focused on poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS), which has high flexibility and conductivity. Flexible TCFs have been fabricated by coating PEDOT:PSS on polyethylene naphthalate substrates using an inkjet printer. However, the current issue in such fabrication is the effect of the interface state on the transparency and conductivity of the thin film. In this study, we investigated the effect of surfactant in addition to polar solvents on the properties of thin films fabricated with PEDOT:PSS ink. Although the electrical conductivity was reduced, the transmittance remained above 90%. Thus, these results are comparable to those of ITO TCFs for practical use in terms of optical properties.

Electronic Materials doi: 10.3390/electronicmat2040037

Authors: Peter Andersson Ersman Jessica Åhlin David Westerberg Anurak Sawatdee Patrik Arvén Mikael Ludvigsson

Batteryless hybrid printed electronic systems manufactured on glass substrates are reported. The electronic system contains a sensor capable of detecting water, an electrochromic display, conductors, a silicon chip providing the power supply through energy harvesting of electromagnetic radiation, and a silicon-based microcontroller responsible for monitoring the sensor status and the subsequent update of the corresponding display segment. The silicon-based components were assembled on the glass substrate by using a pick and place equipment, while the remainder of the system was manufactured by screen printing. Many printed electronic components, often relying on organic materials, are sensitive to variations in environmental conditions, and the reported system paves the way for the creation of electronic sensor platforms on glass substrates for utilization in see-through applications in harsh conditions. Additionally, this generic hybrid printed electronic sensor system also demonstrates the ability to enable autonomous operation through energy harvesting in future smart window applications.

Electronic Materials doi: 10.3390/electronicmat2040036

Authors: Nikolay Sidorenko Yaakov Unigovski Zinovi Dashevsky Roni Shneck

A unique method was developed to significantly improve the strength of Bi(1−x)Sbx single crystals, the most effective thermoelectric (TE) materials in the temperature range from 100 to 200 K due to their plastic deformation by extrusion. After plastic deformation at room temperature under all-round hydrostatic compression in a liquid medium, n-type Bi–Sb polycrystalline solid solutions show a significant increase in mechanical strength compared to Bi–Sb single crystals in the temperature range from 300 to 80 K. The significantly higher strength of extruded alloys in comparison with Bi–Sb single crystals is associated with the development of numerous grains with a high boundary surface as well as structural defects, such as dislocations, that accumulate at grain boundaries. Significant stability of the structure of extruded samples is achieved due to the uniformity of crystal plastic deformation under all-round hydrostatic compression and the formation of the polycrystalline structure consisting of grains with the orientation of the main crystallographic directions close to the original single crystal. The strengthening of Bi–Sb single crystals after plastic deformation allows for the first time to create workable TE devices that cannot be created on the basis of single crystals that have excellent TE properties, but low strength.

Electronic Materials doi: 10.3390/electronicmat2040035

Authors: Daniel Fritsch

The p-type semiconductors Cu2O and ZnRh2O4 have been under investigation for potential applications as transparent conducting oxides. Here, we re-evaluate their structural, electronic, and optical properties by means of first-principles calculations employing density functional theory and a recently introduced self-consistent hybrid functional approach. Therein, the predefined fraction α of Hartree–Fock exact exchange is determined self-consistently via the inverse of the dielectric constant ε∞. The structural, electronic, and optical properties will be discussed alongside experimental results, with a focus on possible technological applications.