Search Results (1,300)

Highly integrable silicon carbide (SiC) has emerged as a promising platform for photonic integrated circuits (PICs), offering a comprehensive set of material and optical properties that are ideal for the integration of nonlinear devices and solid-state quantum defects. However, despite significant progress in nanofabrication technology, the development of SiC on an insulator (SiCOI)-based photonics faces challenges due to fabrication-induced material optical losses and complex processing steps. An alternative approach to mitigate these fabrication challenges is the direct deposition of amorphous SiC on an insulator (a-SiCOI). However, there is a lack of systematic studies aimed at producing high optical quality a-SiC thin films, and correspondingly, on evaluating and determining their optical properties in the telecom range. To this end, we have studied a single-source precursor, 1,3,5-trisilacyclohexane (TSCH, C₃H₁₂Si₃), and chemical vapor deposition (CVD) processes for the deposition of SiC thin films in a low-temperature range (650–800 °C) on a multitude of different substrates. We have successfully demonstrated the fabrication of smooth, uniform, and stoichiometric a-SiCOI thin films of 20 nm to 600 nm with a highly controlled growth rate of ~0.5 Å/s and minimal surface roughness of ~5 Å. Spectroscopic ellipsometry and resonant micro-photoluminescence excitation spectroscopy and mapping reveal a high index of refraction (~2.7) and a minimal absorption coefficient (<200 cm⁻¹) in the telecom C-band, demonstrating the high optical quality of the films. These findings establish a strong foundation for scalable production of high-quality a-SiCOI thin films, enabling their application in advanced chip-scale telecom PIC technologies. Full article

Memristors with resistive switching capabilities are vital for information storage and brain-inspired computing, making them a key focus in current research. This study demonstrates non-volatile analog resistive switching behavior in Al/TiO_x/TiN/Si(n⁺⁺)/Al memristive devices. Analog resistive switching offers gradual, controllable conductance changes, which are essential for mimicking brain-like synaptic behavior, unlike digital/abrupt switching. The amorphous titanium oxide (TiO_x) active layer was deposited using the pulsed-DC reactive magnetron sputtering technique. The impact of increasing the oxide thickness on the electrical performance of the memristors was investigated. Electrical characterizations revealed stable, forming-free analog resistive switching, achieving endurance beyond 300 DC cycles. The charge conduction mechanisms underlying the current–voltage (I–V) characteristics are analyzed in detail, revealing the presence of ohmic behavior, Schottky emission, and space-charge-limited conduction (SCLC). Experimental results indicate that increasing the TiO_x film thickness from 31 to 44 nm leads to a notable change in the current conduction mechanism. The results confirm that the memristors have good stability (>1500 s) and are capable of exhibiting excellent long-term potentiation (LTP) and long-term depression (LTD) properties. The analog switching driven by oxygen vacancy-induced barrier modulation in the TiO_x/TiN interface is explained in detail, supported by a proposed model. The remarkable switching characteristics exhibited by the TiO_x-based memristive devices make them highly suitable for artificial synapse applications in neuromorphic computing systems. Full article

Multilayer thin films composed of cobalt (Co), carbon (C), and chromium (Cr) possess promising electromagnetic properties, yet the combined Co–C–Cr system remains underexplored, particularly regarding its performance as a microwave absorber. Existing research has primarily focused on binary Co–C or Co–Cr compositions, leaving a critical knowledge gap in understanding how ternary multilayer architectures influence electromagnetic behavior. This study addresses this gap by investigating the structure, phase composition, and microwave absorption performance of Co–C–Cr multilayer coatings fabricated via magnetron sputtering onto porous silicon substrates. This study compares four-layer and eight-layer configurations to assess how multilayer architecture affects impedance matching, reflection coefficients, and absorption characteristics within the 8.2–12.4 GHz frequency range. Structural analyses using X-ray diffraction and transmission electron microscopy confirm the coexistence of amorphous and nanocrystalline phases, which enhance absorption through dielectric and magnetic loss mechanisms. Both experimental and simulated results show that increasing the number of layers improves impedance gradients and broadens the operational bandwidth. The eight-layer coatings demonstrate a more uniform absorption response, while four-layer structures exhibit sharper resonant minima. These findings advance the understanding of ternary multilayer systems and contribute to the development of frequency-selective surfaces and broadband microwave shielding materials. Full article

Aluminum nitride (AlN) thin films were deposited on SiO₂ substrates by RF-magnetron sputtering at varying powers (110–140 W) and subsequently subjected to thermal annealing at 450 °C under nitrogen atmosphere. A comprehensive multi-technique investigation—including X-ray reflectometry (XRR), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), optical profilometry, spectroscopic ellipsometry (SE), and electrical measurements—was performed to explore the physical structure, morphology, and optical and electrical properties of the films. The analysis of the film structure by XRR revealed that increasing sputtering power resulted in thicker, denser AlN layers, while thermal treatment promoted densification by reducing density gradients but also induced surface roughening and the formation of island-like morphologies. Optical studies confirmed excellent transparency (>80% transmittance in the near-infrared region) and demonstrated the tunability of the refractive index with sputtering power, critical for optoelectronic applications. The electrical characterization of Au/AlN/Al sandwich structures revealed a transition from Ohmic to trap-controlled space charge limited current (SCLC) behavior under forward bias—a transport mechanism frequently present in a material with very low mobility, such as AlN—while Schottky conduction dominated under reverse bias. The systematic correlation between deposition parameters, thermal treatment, and the resulting physical properties offers valuable pathways to engineer AlN thin films for next-generation optoelectronic and high-frequency device applications. Full article

Nitrile rubber (NBR) is prone to adhesion and hysteresis deformation when in contact with hard materials, leading to wear failure. To mitigate this issue, the deposition of diamond-like carbon (DLC) films onto the rubber surface is a commonly employed method. By utilizing pulsed arc ion plating technology and adjusting the arc voltage of the pulsed arc ion source, tetrahedral amorphous carbon (ta-C) films with varying sp³ content were prepared on the surface of NBR. The effects of arc voltage on the structural composition and friction performance of NBR/ta-C materials were examined. A scanning electron microscopy analysis revealed that the ta-C film applied to the surface of NBR was uniform and dense, exhibiting typical network crack characteristics. The results of Raman spectroscopy and X-ray photoelectron spectroscopy indicated that as the arc voltage increased, the sp³ content in the film initially rose before declining, reaching a maximum of 72.28% at 300 V. Mechanical tests demonstrated that the bonding strength and friction performance of the film are primarily influenced by the percentage of sp³ content. Notably, the ta-C film with lower sp³ content demonstrates enhanced wear resistance. At 200 V, the sp³ content of the film is 58.16%, resulting in optimal friction performance characterized by a stable friction coefficient of 0.38 and minimal wear weight loss. This performance is attributed to the protective qualities of the ta-C film and the formation of a graphitized transfer film. These results provide valuable insights for the design and development of wear-resistant rubber materials. Full article

Incorporating probiotics into edible films offers an effective strategy for delivering viable microorganisms to the body. This study aimed to develop edible films based on three types of pregelatinized cassava starch—pregelatinized native starch (PNS), hydroxypropyl distarch phosphate (HDP), and hydroxypropyl starch (HS)—as carriers for Bacillus coagulans (BC). The interactions between probiotic powder and the polymer matrix, as well as the viability of B. coagulans during film drying and subsequent storage, were evaluated to assess the effectiveness of the films as protective delivery systems at room temperature (25 °C). The addition of BC altered the amorphous-to-ordered structure of the starch matrices. Surface morphology analysis showed BC aggregates on PNS films, whereas HDP and HS films retained smooth surfaces. Incorporation of BC increased the tensile strength and Young’s modulus of PNS films but reduced their elongation at break. Additionally, BC decreased both the light transmittance and water contact angle in PNS films, while 1% BC increased the contact angle in HDP and HS films. BC had no significant effect on the solubility of PNS films but enhanced the solubility of HDP and HS films. Notably, B. coagulans maintained viability around 8 log CFU/g after 90 days of storage at room temperature, supporting the potential of pregelatinized starch-based films as effective probiotic carriers. Full article

Hydrogenated amorphous carbon (a-C:H) films are widely valued for their excellent mechanical strength and low friction, but their performance significantly degrades at elevated temperatures, limiting practical applications in aerospace environments. In this work, we aimed to enhance the high-temperature tribological behavior of a-C:H films through controlled silicon (Si) doping. A series of a-C:H:Si films with varying Si contents were fabricated via direct current magnetron sputtering, and their microstructure, mechanical properties, and friction behavior were systematically evaluated from room temperature up to 400 °C. Results show that moderate Si doping (8.3 at.%) substantially enhances hardness and wear resistance, while enabling ultralow friction (as low as 0.0034) at 400 °C. This superior performance is attributed to the synergistic effects of transfer layer formation, preferential Si oxidation, and tribo-induced graphitization. This study provides new insights into the high-temperature lubrication mechanisms of Si-doped a-C:H films and demonstrates the critical role of Si content optimization, highlighting a viable strategy for extending the thermal stability and lifespan of solid-lubricating films. Full article

Cardiovascular diseases are responsible for a large number of severe disability cases and deaths worldwide. Strong research in this field has been extensively carried out, in particular for the associated complications, such as the occlusion of small-diameter (<6 mm) vessels. Accordingly, in the present research, two random copolyesters of poly(butylene 2,5-furandicarboxylate) (PBF) and poly(butylene isophthalate) (PBI), were successfully synthesized via two-step melt polycondensation and were thoroughly characterized from molecular, thermal, and mechanical perspectives. The copolymeric films displayed a peculiar thermal behavior, being easily processable in the form of films, although amorphous, with T_g close to room temperature. Their thermal stability was high in all cases, and from the mechanical point of view, the materials exhibited a high ultimate strength, together with values of elastic moduli tunable with the chemical composition. The long-term stability of these materials under physiological conditions was also demonstrated. Cytotoxicity was assessed using a direct contact assay with human umbilical vein endothelial cells (HUVECs). In addition, hemocompatibility was tested by evaluating the adhesion of blood components (such as the adsorption of human platelets and fibrinogen). As a result, a proper chemical design and, in turn, both the solid-state and functional properties, are pivotal in regulating cell behavior and opening new frontiers in the tissue engineering of soft tissues, including vascular tissues. Full article

Laser-induced periodic surface structures (LIPSSs) produced via ultrafast laser-induced oxidation offer a promising route for high-quality nanostructuring, with reduced thermal damage compared to conventional ablation-based methods. However, the influence of laser repetition frequency on the formation and morphology of oxidized LIPSSs remains insufficiently explored. In this study, we systematically investigate the effects of varying the femtosecond laser repetition frequency from 1 kHz to 100 kHz while keeping the total pulse number constant on the oxidation-induced LIPSSs formed on amorphous silicon films. Scanning electron microscopy and Fourier analysis reveal a transition between two morphological regimes with increasing repetition frequency: at low frequencies, the long inter-pulse intervals result in irregular, disordered oxidation patterns; at high frequencies, closely spaced pulses promote the formation of highly ordered, periodic surface structures. Statistical measurements show that the laser-modified area decreases with frequency, while the LIPSS period remains relatively stable and the ridge width exhibits a peak at 10 kHz. Finite-difference time-domain (FDTD) and finite-element simulations suggest that the observed patterns result from a dynamic balance between light-field modulation and oxidation kinetics, rather than thermal accumulation. These findings advance the understanding of oxidation-driven LIPSS formation dynamics and provide guidance for optimizing femtosecond laser parameters for precise surface nanopatterning. Full article

The article suggests a simple one-step sol–gel method for synthesizing nanostructured zinc oxide films co-doped with copper and aluminum. It shows the possibility of forming hierarchical ZnO:Al:Cu nanostructures combining branches of different sizes and ranks and quasi-spherical fractal aggregates. It demonstrates the use of the synthesized samples as highly efficient photocatalysts providing the decomposition of toxic dyes (methyl orange) under the action of both ultraviolet radiation and visible light. It establishes the contribution of the average crystallite size, the proportion of zinc atoms in the crystalline phase, their nanostructure, as well as X-ray amorphous phases of copper and aluminum to the efficiency of the photocatalysis process. Full article

Gallium oxide (Ga₂O₃), as a wide-bandgap semiconductor material, is highly expected to find extensive applications in optoelectronic devices, high-power electronics, gas sensors, etc. However, the photoelectric properties of Ga₂O₃ still need to be improved before its devices become commercially viable. As is well known, doping is an effective method to modulate the various properties of semiconductor materials. In this study, Zn–N co-doped Ga₂O₃ films with various doping concentrations were grown in situ on sapphire substrates by atomic layer deposition (ALD) at 250 °C, followed by post-annealing at 900 °C. The post-annealed undoped Ga₂O₃ film showed a highly preferential orientation, whereas with the increase in Zn doping concentration, the preferential orientation of Ga₂O₃ films was deteriorated, turning it into an amorphous state. The surface roughness of the Ga₂O₃ thin films is largely affected by doping. As a result of post-annealing, the bandgaps of the Ga₂O₃ films can be modulated from 4.69 eV to 5.41 eV by controlling the Zn–N co-doping concentrations. When deposited under optimum conditions, high-quality Zn–N co-doped Ga₂O₃ films showed higher transmittance, a larger bandgap, and fewer defects compared with undoped ones. Full article

This paper considers the uniaxial orientation effect on the structure and piezoelectric properties of vinylidene fluoride-tetrafluoroethylene copolymer ferroelectric films. The films were exposed to uniaxial orientation stretching in a temperature range from 20 °C to 60 °C; then, they were contact polarized under normal conditions. The temperature dependence of the electric strength was determined. The longitudinal piezoelectric coefficient d₃₃ values were measured by the quasi-static Berlincourt method. The piezoresponse force microscopy (PFM) method was used to investigate the film domain structure before and after polarization, and the local piezoelectric coefficient values were also calculated. Phase composition was studied using differential scanning calorimetry and infrared spectroscopy with the Fourier transform. It was found that uniaxial orientation stretching contributed to an increase in the piezoelectric coefficient d₃₃ from 5 pC/N to 16–20 pC/N. The results obtained indicate the importance of the amorphous phase contribution to the formation of the piezoelectric properties in polymeric materials. Full article

A flexible and highly sensitive piezoresistive strain sensor was fabricated through the application of CO₂ laser ablation on a composite film composed of multi-walled carbon nanotubes, carbon black, and polydimethylsiloxane (MWCNT/CB/PDMS). The results of scanning electron microscopy (SEM) surface analysis shows that the “bush-like” conductive structure on the PDMS-based composite material membrane post-laser ablation is formed. Transmission electron microscopy (TEM) images and X-ray diffraction (XRD) spectra of the ablation products indicated the formation of an amorphous carbon layer on the surface of carbon nanomaterials due to laser ablation. Experimental findings revealed that the sensitivity (GF) value of the sensor based on CNT0.6CB1.0-P3.0 is up to 584.7 at 5% strain, which is approximately 14% higher than the sensitivity 513 of the sensor previously prepared by the author using CO₂ laser ablation of MWCNT/PDMS composite films. The addition of a very small volume fraction of CB particles significantly enhances the piezoresistive sensitivity of the sensor samples. Combined with the qualitative analysis of microscopic morphology characterization, CB and MWCNT synergistically promote the deposition of amorphous carbon. This phenomenon increases the probability of tunnel effect occurrence in the strain response region of the sensor, which indirectly confirms the synergistic enhancement effect of the combined action of CB and MWCNT on the piezoresistive sensitivity of the sensor. Full article

In this work, we present the development and validation of an automated system for the Successive Ionic Layer Adsorption and Reaction (SILAR) method, aimed at depositing Cu₂ZnSnS₄ (CZTS) thin films. The system is based on a Raspberry Pi Pico microcontroller programmed in Micro-Python (Thonny 4.0.2), allowing precise control over immersion sequences, timing intervals, and substrate positioning along two degrees of freedom. Automation enhances reproducibility, safety, and reduces human error compared with manual operation. CZTS films were deposited on borosilicate glass and optically and structurally characterized. A gradual darkening of the films with increasing deposition cycles indicates controlled material accumulation. X-ray diffraction (XRD) and Raman spectroscopy confirmed the presence of CZTS phases, although with a partially amorphous structure. The estimated optical bandgap of ~1.34 eV is consistent with photovoltaic applications. These results validate the functionality of the automated SILAR platform for repeatable and scalable thin-film fabrication, offering a low-cost alternative for producing semiconductor absorber layers in solar energy technologies. Full article

Thin amorphous oxide films (a-SiO₂, a-Al₂O₃, a-MgO) were prepared by magnetron sputtering deposition. Their response to high-energy heavy ion beams (23 MeV I, 18 MeV Cu, 2.5 MeV Cu) and gamma-ray (1.25 MeV) irradiation was studied by elastic recoil detection analysis and infrared spectroscopy. It was established that their high radiation hardness is due to a high level of disorder, already present in as-prepared samples, so the high-energy heavy ion irradiation cannot change their structure much. In the case of a-SiO₂, this resulted in a completely different response to high-energy heavy ion irradiation found previously in thermally grown a-SiO₂. In the case of a-MgO, only gamma-ray irradiation was found to induce significant changes. Full article