Search Results (355)

The controlled formation of coherent interfaces in lattice-mismatched II–VI semiconductor heterostructures remains challenging. In this work, ZnSe/ZnS laminar nanomaterials were synthesized by an ultrasound-assisted reverse micelle method to determine how ultrasonic power (150 and 200 W) and water-to-surfactant molar ratio (16:1, 32:1, and 48:1) jointly regulate morphology, crystal structure, lattice accommodation, optical response, and photoelectrochemical behavior. Higher ultrasonic power favored more clearly defined laminar morphologies, whereas increasing the water-to-surfactant ratio produced more heterogeneous growth domains. XRD and Raman spectroscopy confirmed the presence of zinc-blende ZnSe and ZnS phases and provided indirect evidence consistent with partial pseudomorphic lattice accommodation, with calculated mismatch values of 1.59–3.07%, compared with the theoretical value of 4.43%. The apparent optical band gap decreased from 3.39 to 3.06 eV at 200 W and from 3.34 to 3.04 eV at 150 W as the water content increased. Photochronoamperometry showed predominantly cathodic responses, whereas P1R1 exhibited an anodic response. These results establish ultrasonic power and micellar composition as coupled synthesis parameters for tuning lamellar growth, interfacial strain, and optoelectronic response in ZnSe/ZnS heterostructures. Full article

Group III-nitride semiconductors (GaN, AlN, InN) serve as foundational materials for modern optoelectronics, high-frequency microelectronics, and next-generation energy harvesting devices. However, traditional high-temperature epitaxy (>700 °C) introduces severe thermal stress, high dislocation densities, and fundamental incompatibility with flexible substrates or CMOS back-end-of-line (BEOL) processes. Plasma-enhanced atomic layer deposition (PEALD) provides a disruptive, ultra-low thermal budget (<300 °C) pathway for atomic-scale precision growth and conformal coating. This review systematically summarizes recent frontiers in PEALD-synthesized Group III-nitrides and 2D/3D polar heterostructures. First, we dissect the microscopic nucleation kinetics, surface bond reconstruction, and impurity suppression mechanisms across diverse substrates, including Si, sapphire, quartz, metals, and flexible polymers. Next, we highlight 2D template-assisted van der Waals epitaxy on graphene and MoS2, and elucidate polarization-driven dipole interactions and band alignment engineering at 2D/3D polar interfaces (e.g., α-In₂Se₃, Janus MoSSe). Furthermore, we comprehensively discuss innovative applications in advanced photovoltaics (as electron transport and passivation layers in perovskite and quantum dot-sensitized solar cells), silicon-based microcavity lasers, high-electron-mobility transistors (HEMTs), and flexible multimodal sensors. Finally, key technological challenges—including the low-thermal-budget paradox, wafer-scale uniformity, and deposition throughput—are addressed alongside future perspectives in area-selective ALD and neuromorphic computing, presenting a cohesive blueprint from underlying physics to macroscopic system integration. Full article

Two-dimensional electron gases (2DEGs) at complex oxide interfaces have emerged as a promising platform for next-generation oxide semiconductor devices, owing to their tunable electronic properties and rich interfacial phenomena. In this work, a LaAlO₃/SrTiO₃/LaTiO₃ (LAO/STO/LTO) trilayer heterostructure is proposed and theoretically investigated using a self-consistent Schrödinger–Poisson framework to examine the effects of multi-interface engineering on quantum confinement and carrier transport. The proposed architecture combines polar-discontinuity-driven electronic reconstruction at the LAO/STO interface with charge-transfer-induced electron accumulation at the STO/LTO interface, forming two coupled 2DEG channels within the SrTiO₃ layer. Compared with conventional single-interface oxide heterostructures, the coupled-interface configuration significantly enhances sheet carrier density and electrical conductivity, with predicted carrier densities approaching 10¹⁴ cm⁻² and gate-tunable conductivities in the range of 10³–10⁴ S cm⁻¹ under idealized operating conditions. The effects of layer thickness, gate bias, temperature, and electrostatic coupling are systematically investigated to establish practical design guidelines for optimizing carrier confinement and transport. A sensitivity analysis incorporating interface trap densities up to 2 × 10¹³ cm⁻² demonstrates that more than 60% of the ideal carrier population is retained under moderate defect concentrations, confirming the robustness of the proposed multi-interface strategy. Although the analytical model represents an upper-bound framework, its predictions are discussed in the context of experimentally relevant limitations, including interface roughness, oxygen vacancies, carrier trapping, and defect-induced scattering. Overall, the proposed LAO/STO/LTO heterostructure provides a predictive framework for engineering high-density, electrically tunable oxide 2DEGs for future nanoelectronic, terahertz, photonic, and energy-related applications. Full article

The degradation of organic pollutants through photocatalysis is currently a major research focus. Core–shell heterostructures of metal semiconductors have been widely recognized as an effective strategy for enhancing photocatalytic performance, particularly when alloy nanoparticles are incorporated due to their unique electronic and catalytic properties. However, conventional synthetic approaches typically rely on high-temperature and high-pressure conditions, which often induce undesirable particle overgrowth and aggregation. Herein, AuPt bimetallic alloy nanoparticles were successfully fabricated via two successive in situ redox processes under room-temperature and ambient-pressure conditions, which were in situ integrated with Cu₂O to form multilevel core–shell composite particles. Structurally, an octahedral Cu₂O crystal serves as the inner core (denoted as Cu₂O_(O)), sequentially coated with a Cu₂O nanoparticle (denoted as Cu₂O_(P)) interlayer and a AuPt alloy nanoparticle shell. Functionally, the enhanced photocatalytic activity of Cu₂O_(O)@Cu₂O_(P)@AuPt was proven to be attributed to a dual function of AuPt, which includes an adsorption-induced polarized interface and an efficient charge-transfer mediator with the ohmic contact. This work demonstrates a mild and versatile synthetic strategy for constructing semiconductor–alloy heterostructures, offering valuable insights into the rational design of highly efficient and stable photocatalysts. Full article

The synthesis of metal-free heterostructures is useful for the generation of sustainable green hydrogen production and is becoming more relevant in the last years. Among emerging materials, carbon nitride (CN) decorated with carbon dots (CDs) offers a suitable alternative to traditional semiconductors due to its low cost and tuneable optical properties. In this paper, the interaction between carbon dots (CDs) and carbon nitride (CN) is studied to evaluate how the degree of purification affects the efficiency of photocatalytic water-splitting reactions. The CDs were synthetized via a hydrothermal carbonization process at 180 °C for 8 h from citric acid and ethylenediamine (EDA) as precursors and then they are subjected to purification through dialysis (0–72 h). This synthesis generates a complex mixture of CDs, unreacted precursors and molecular fluorophores. The purification degree presents a direct impact on the HER values, increasing them 1.7 times compared to the initial value of the pristine CN (1941 μmol/h·g. The analysis of the CN/CD properties and the CDs characterization reveals that the surrounded matrix around the CDs and the functional groups attached to them are essential for avoiding the recombination of photogenerated electron/hole pairs, raising the charge density on the system and reducing the transfer barrier. Full article

MXenes, a rapidly expanding family of two-dimensional transition-metal carbides and nitrides, are increasingly viewed as strong candidates for defense-oriented multifunctional systems because they combine metallic conductivity, surface tunability, mechanical flexibility, and solution processability within a lightweight platform. Unlike conventional metals, ceramics, and semiconductors, which usually optimize one or two parameters at the expense of density, brittleness, or integration compatibility, MXenes offer a rare opportunity to coordinate electromagnetic, mechanical, thermal, and sensing functions within one material family. Different from existing reviews that focus on laboratory-level record performance or single-function optimization, this review presents an innovative deployment-oriented perspective and fills the research gap of systematic military-oriented evaluation for MXenes. In this review, we examine MXenes from a deployment-oriented perspective rather than through isolated record values. We first summarize their formation chemistry and major synthesis routes, including HF and in-situ HF etching, bifluoride and alkaline methods, molten-salt strategies, electrochemical approaches, and precursor-free chemical vapor deposition. We then discuss the principal levers of property regulation, focusing on composition design, surface-termination control, and heterostructure engineering, and show how these strategies shape the performance envelopes relevant to shielding, stealth, impact response, energy storage, and sensing. This review constructs a full-chain analytical framework from synthesis, property regulation to military application and deployment challenges for the first time. Finally, we identify the main barriers to translation, especially manufacturing inconsistency, termination heterogeneity, oxidation and interfacial degradation, and limited application-level validation, and outline the most realistic paths toward deployable defense technologies. Full article

Passively mode-locked lasers, as essential tools for generating ultrashort pulses, have found widespread applications in industrial manufacturing, optical communications, biomedical imaging, and fundamental scientific research. Saturable absorbers serve as the key components governing the performance of such laser systems. Conventional saturable absorber materials, including semiconductor saturable absorber mirrors, carbon nanotubes, and graphene, however, suffer from inherent limitations in operational wavelength range, damage threshold, and environmental stability. In recent years, two-dimensional transition metal carbides and nitrides, known as MXenes, have emerged as a promising class of materials to address these challenges. Their unique metallic conductivity, broadband saturable absorption, ultrafast carrier dynamics, excellent thermal management capability, and versatile chemical tunability offer unprecedented opportunities for advanced saturable absorber applications. This review systematically summarizes the recent progress of MXene-based saturable absorbers, with an emphasis on their distinctive advantages in extending the mode-locked wavelength range, enhancing output pulse stability, and increasing the optical damage threshold. Furthermore, strategies for performance optimization through surface terminal group engineering, defect modulation, and heterostructure design are discussed in depth. Finally, the future prospects and key challenges toward industrial implementation of MXenes in ultrafast photonics are outlined, aiming to stimulate further advancements in high-performance ultrafast laser technology. Full article

The oscillator strengths of absorptive transitions from the ground to the resonant excited impurity states for the impurity positioned in and near the GaAs/AlGaAs rectangular quantum well are studied. Due to the resonant nature of the final states, the absorption peaks are broadened. The shape of the peaks is reproduced numerically as a function of impurity position with respect to the well and the well width. Peak parameters, such as maximum, broadening, and integral absorption, are analyzed numerically; the Fano parameter is considered qualitatively. Full article

As a representative wide-bandgap semiconductor material, gallium nitride (GaN) has attracted increasing attention because of its superior material properties (e.g., high electron mobility, high electron saturation velocity, and critical electric field). For power electronics applications, and to take full advantage of the superiorities of the GaN material, the normally off operation is required based on an AlGaN/GaN heterostructure. For a commercial approach, GaN HEMTs with a p-GaN gate have become a research hotspot. The characteristics of p-GaN gate HEMTs have a significant relationship with gate structure, especially the contact type on the p-GaN layer. In this review, the necessity of normally off operation and the advantages of adopting a p-GaN gate are elaborated, followed by the theory of achieving normally off operation by p-GaN and critical fabrication processes. The various gate structures are discussed, including metal gate, junction gate and hybrid gate structures on the p-GaN layer, to improve threshold voltage. Meanwhile, the methods required to optimize breakdown voltage and monolithically integrated technologies are also demonstrated. This review outlines the development and future trends of p-GaN gate HEMTs for power systems. Full article

To overcome the inherent limitations of 2D MXenes in photocatalysis, namely severe nanosheet restacking and rapid charge recombination, this study reports a synergistic dual-modification strategy. By integrating microwave-assisted in situ growth of carbon nanotubes (CNTs) with the hydrothermal incorporation of multivalent cobalt (Co) species, a 3D hierarchical Co-Ti₃C₂/CNT composite was successfully fabricated. Structural characterization reveals that the in situ grown CNTs act as robust spatial spacers and conductive highways, effectively preventing Ti₃C₂ agglomeration while providing a continuous electron-transfer network. The introduction of Co significantly enriches the surface with redox-active sites and facilitates the formation of an interfacial Schottky junction. Under visible-light irradiation, the optimized Co_10%-Ti₃C₂/CNT composite achieved a superior methylene blue degradation efficiency of 90.3% within 120 min. Mechanistic insights, supported by EPR and electrochemical analyses, confirm that the Schottky barrier at the semiconductor-metal interface acts as a potent electron trap, significantly suppressing e⁻/h⁺ recombination and accelerating surface-mediated radical generation (•OH, •O₂⁻). This work provides a sophisticated template for designing high-performance, dimensionally stable MXene-based heterostructures for advanced environmental remediation. Full article

Organic dye-, pharmaceutical-, and heavy metal-contaminated water are emerging environmental issues, and thus there is a requirement for the development of efficient and sustainable purification methods. Semiconductor (SmC) material-based photocatalysis using TiO₂ and Fe₂O₃ nanostructures is considered a promising field for pollutant degradation due to its chemical stability, nontoxicity, and ability to perform photocatalytic degradation using light irradiation. Understanding the thermal, optical, and charge transport properties governing their photocatalytic activity requires advanced characterisation methods. In this context, photothermal (PT) techniques provide powerful tools for probing non-radiative processes and energy transport in photocatalytic materials. The photocatalytic activity of these materials strongly depends on their structural, optical, thermal, and electronic properties. These properties can be enhanced through several modification strategies, including metal and non-metal doping (e.g., C, N, Cu, Ag, Au), surface modification, forming a complex with SiO₂, and the formation of Fe₂O₃–TiO₂ heterostructure nanocomposites. In this review, a comprehensive overview is provided of TiO₂ and Fe₂O₃-based nanocomposites with a specific focus on characterisation techniques for photothermal characterisation techniques, including thermal lens spectroscopy (TLS), beam deflection spectrometry (BDS), and photoacoustic spectroscopy (PAS), for determining thermal diffusivity, thermal conductivity, bandgap energy, carrier lifetime, surface roughness, porosity, etc., which are related to photocatalytic activity. The properties of these nanocomposites are correlated with photocatalytic activity for pollutant degradation using these nanocomposites. The challenges faced while using these nanocomposites for pollutant degradation are also discussed, along with future prospects for designing efficient photocatalysts for water purification applications. Full article

Catalytic materials are central to the advancement of hydrogen generation technologies, playing a pivotal role in enabling sustainable, carbon-neutral energy systems. Hydrogen can be produced via electrochemical water splitting, thermochemical reforming, or photocatalysis—each imposing unique performance requirements on catalysts in terms of activity, selectivity, stability, and efficiency. While traditional noble metals (e.g., platinum, ruthenium, iridium) provide benchmark catalytic activity, their widespread use is hindered by scarcity, high cost, and limited long-term durability. Consequently, researchers have increasingly focused on earth-abundant alternatives such as transition metals (Ni, Co, Fe, Mo), alloys, metal oxides, carbides, sulfides, nitrides, and carbon-based systems. Among these, two-dimensional materials, particularly the MXene family, have attracted significant attention due to their metallic conductivity, layered structure, and tunable surface chemistry. These features enable rapid charge transfer and abundant active sites, making MXenes and related nanostructured catalysts promising for both the Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER) across a wide range of electrochemical conditions. Parallel efforts have integrated novel semiconductors, plasmonic nanomaterials, and hybrid heterostructures to improve the efficiency of solar-to-hydrogen energy conversion. This paper reviews the main types of catalytic materials used in hydrogen production, explains their design strategies and structure–performance relationships, and discusses key engineering challenges such as integrating renewable energy sources, scaling up manufacturing, and ensuring long-term durability in real-world systems. Future research goals are also highlighted, including the development of affordable non-noble catalysts, enhancing catalyst stability through surface and defect engineering, and coupling hydrogen production with circular economy principles, all of which are essential to making hydrogen generation more efficient, scalable, and cost-effective as the world transitions to clean and sustainable energy. Full article

Multijunction laser power converters are demonstrated for the first time with high efficiencies for average optical irradiances exceeding 150 W/cm². The GaAs-based photovoltaic power converting III-V heterostructures are designed with six GaAs subcells having an area of 0.14 cm², receiving up to 22 W of input power at ~811 nm, delivering over 14 W of output power. The maximum efficiencies are obtained in the range of 30 to 75 W/cm², and efficiencies > 64% are still obtained at 160 W/cm². The efficiency reduction for higher irradiance values originates predominantly from residual heat generated in the active layers. For example, in 100% duty factor measurements, the bandgap voltage offset saturates to W_oc ~ 170 mV. However, in pulsed mode, W_oc values as low as 150 mV have been obtained for a device base temperature of 20 °C. For smaller 0.029 cm² devices, W_oc values around 137 mV are obtained at 240 W/cm². Full article

In this study, we have investigated heterostructural TiO₂/BiVO₄ anodes to determine the effect of the amount and form of BiVO₄ nanoparticles on TiO₂ on the response of photoanodes under UV and visible illumination. BiVO₄ nanopowders were prepared and annealed at temperatures ranging from 200 to 500 °C. Structural and optical characterization indicates that as the annealing temperature is increased, a phase transition from a weakly ordered to a dominant monoclinic BiVO₄ phase is observed, which is accompanied by an increase in visible light absorption. Subsequently, the most crystalline powder was utilized to deposit BiVO₄ on nanostructured TiO₂ either as a compact overlayer (drop-casting) or as a progressively grown nanoparticle (TiO₂@S series) in the successive ionic layer adsorption and reaction process (SILAR). Photoelectrochemical measurements were performed, revealing a morphology-dependent photocurrent response under UV and visible illumination. A further increase in the number of cycles systematically increases the photocurrent in the visible light range while limiting the response to UV radiation. The TiO₂@d photoanode demonstrates the highest relative activity within the visible range; however, it also generates the lowest absolute photocurrent, indicating the presence of significant transport and recombination losses within the thick BiVO₄ layer. The results demonstrate that the presence of BiVO₄ nanoparticles on TiO₂ exerts a substantial influence on the separation of charge between semiconductors and the synergistic utilization of photons from the UV and visible ranges. This research yielded a proposed scheme of mutual band arrangement and charge carrier transfer mechanism in TiO₂@BiVO₄ heterostructures. Full article

Silicon carbide (SiC) has emerged as a robust and tunable semiconductor for advanced photocatalytic applications. This review provides a comprehensive overview of recent progress in the development of SiC-based materials for environmental remediation and solar-driven hydrogen production. Key aspects discussed include morphological engineering, heterostructure design, doping strategies, and plasmonic enhancement. Emphasis is placed on structure–activity relationships, insights from density functional theory (DFT) and machine learning (ML) models, and synergistic effects in composite systems. This review concludes with a critical analysis of current challenges and future research directions, highlighting the potential of SiC implementation as a sustainable platform for next-generation photocatalytic technologies. Full article