ECS Journal of Solid State Science and Technology

Accelerating interest in silicon nitride thin film material system continues in both academic and industrial communities due to its highly desirable physical, chemical, and electrical properties and the potential to enable new device technologies. As considered here, the silicon nitride material system encompasses both non-hydrogenated (SiN_x) and hydrogenated (SiN_x:H) silicon nitride, as well as silicon nitride-rich films, defined as SiN_x with C inclusion, in both non-hydrogenated (SiN_x(C)) and hydrogenated (SiN_x:H(C)) forms. Due to the extremely high level of interest in these materials, this article is intended as a follow-up to the authors’ earlier publication [A. E. Kaloyeros, F. A. Jové, J. Goff, B. Arkles, Silicon nitride and silicon nitride-rich thin film technologies: trends in deposition techniques and related applications, ECS J. Solid State Sci. Technol., 6, 691 (2017)] that summarized silicon nitride research and development (R&D) trends through the end of 2016. In this survey, emphasis is placed on cutting-edge achievements and innovations from 2017 through 2019 in Si and N source chemistries, vapor phase growth processes, film properties, and emerging applications, particularly in heterodevice areas including sensors, biointerfaces and photonics.

With the advancement of electric vehicle (EV) battery technologies, conventional lithium-ion batteries are approaching their theoretical energy density limits while facing persistent safety concerns. All-solid-state batteries (ASSBs) offer a pathway toward higher energy density and enhanced safety. This review focuses on the fabrication and manufacturing processes of ASSBs, explicitly bridging laboratory-scale research methods with emerging industrial-scale production routes. Emphasis is placed on material systems, scalable processing strategies, manufacturing bottlenecks, and industrial roadmaps.

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Metal oxide thin films are critically important materials for modern technologies, particularly semiconductor thin films in transistors and optoelectronic applications. Many metal oxide thin films attract interest for their electronic bandgap, charge carrier mobility, optical opacity, luminescence, low cost, relative abundance, and environmentally-friendly production. Additionally, these properties are often tuneable via particle size, film density, surface morphology, film deposition, growth method, hetero-interface engineering or ion-doping. The n-type semiconducting zinc oxide (ZnO) is an important material, possessing a variety of useful properties including an intrinsically wide direct bandgap, high electron mobility, relatively high exciton binding energy, high optical transparency, demonstrated metal-ion doping, a range of different particle morphologies and deposition methods, electro/photoluminescence, low cost, and a variety of existing green synthesis methods. Here, these aspects of ZnO and some related compound semiconducting oxides are reviewed, focusing on how the unique properties of these metal oxides make them suitable for a range of different applications from thin film transistors, high mobility oxide interfaces, transparent conductive oxides, photoanodes photodetectors, chemical sensors, photocatalysts, superlattice electronics, and more. The properties and deposition methods and their impact on functionality will be discussed alongside their role in sustainable optoelectronics.

Achieving a void-free bonding interface is an important requirement for the wafer-to-wafer direct bonding process. The two main potential mechanisms for void formation at the interface are (i) void formation induced by gas, such as condensation by-products caused by the bonding process or outgassing of trapped precursors, and (ii) void formation induced by physical obstacles, such as particles. In this work, emphasis is on the latter process. Particles were intentionally deposited on the wafer prior to bonding to study the kinetics of the physical void formation process. Void formations induced by particles deposited on different dielectrics bonding materials were analyzed using scanning acoustic microscopy and image software. The void formation mechanism is then discussed along with the wafer bonding dynamics at room temperature.

This paper reviews how today’s CMP (Chemical Mechanical Polishing) slurries have been innovated and explores ideas for driving further evolution. In early semiconductor polishing, Mechanical Polishing was used, focusing on controlling abrasive particle sizes, leading to the use of alumina abrasives via wet classification. As materials shifted from germanium to silicon and applications transitioned from radios to integrated circuits, research was conducted on the material and size of abrasives to improve polishing accuracy, and silica was finally adopted. Subsequently, in pursuit of higher purity, ultrapure colloidal silica using organic raw materials was introduced in 1985 and became the standard in current semiconductor CMP. The first report on CMP dates back to Schmidt’s 1962 paper. Although the report was based on visual inspection, the approach was validated to be reasonable with today’s inspection technology. CMP achieved further defect reduction by integrating with Clean Technology. Throughout its history, polishing consistently pursued uniform action on surfaces, driving contaminant reduction, and occasionally achieving significant breakthroughs through the combination of diverse technologies. Innovations are born when disparate technologies, evolving independently until a certain point, interact and combine according to market needs.

In recent years, betavoltaic batteries have become an ideal power source for micro electromechanical systems. Betavoltaic battery is a device that converts the decay energy of beta emitting radioisotope sources into electrical energy using transducers. They have the advantages of high energy density, long service life, strong anti-interference ability, small size, light weight, easy miniaturization and integration, thus it has become a research hotspot in the field of micro energy. However, to date, the low energy conversion efficiencies as well as technological limitations of betavoltaic batteries impede their further application. In this review, the theory of betavoltaic energy conversion and recent understanding of the ideal material and structure design of the betavoltaic batteries for efficient exciton production, dissociation and charge transport is described, as well as recent attempts to realize optimum results. This review article concludes by identifying the remaining challenges for the improvement of battery performance and by providing perspectives toward real application of betavoltaic batteries.

Bound to complex perovskite systems, ferroelectric random access memory (FRAM) suffers from limited CMOS-compatibility and faces severe scaling issues in today's and future technology nodes. Nevertheless, compared to its current-driven non-volatile memory contenders, the field-driven FRAM excels in terms of low voltage operation and power consumption and therewith has managed to claim embedded as well as stand-alone niche markets. However, in order to overcome this restricted field of application, a material innovation is needed. With the ability to engineer ferroelectricity in HfO₂, a high-k dielectric well established in memory and logic devices, a new material choice for improved manufacturability and scalability of future 1T and 1T-1C ferroelectric memories has emerged. This paper reviews the recent progress in this emerging field and critically assesses its current and future potential. Suitable memory concepts as well as new applications will be proposed accordingly. Moreover, an empirical description of the ferroelectric stabilization in HfO₂ will be given, from which additional dopants as well as alternative stabilization mechanism for this phenomenon can be derived.

β-Ga₂O₃ is an emerging material and has the potential to revolutionize power electronics due to its ultra-wide-bandgap (UWBG) and lower native substrate cost compared to Silicon Carbide and Gallium Nitride. Since β-Ga₂O₃ technology is still not mature, experimental study of β-Ga₂O₃ is difficult and expensive. Technology-Computer-Aided Design (TCAD) is thus a cost-effective way to study the potentials and limitations of β-Ga₂O₃ devices. In this paper, TCAD parameters calibrated to experiments are presented. They are used to perform the simulations in heterojunction p-NiO/n-Ga₂O₃ diode, Schottky diode, and normally-off Ga₂O₃ vertical FinFET. Besides the current-voltage (I-V) simulations, breakdown, capacitance-voltage (C-V), and short-circuit ruggedness simulations with robust setups are discussed. TCAD Sentaurus is used in the simulations but the methodologies can be applied in other simulators easily. This paves the road to performing a holistic study of β-Ga₂O₃ devices using TCAD.

The ability to achieve near-atomic precision in etching different materials when transferring lithographically defined templates is a requirement of increasing importance for nanoscale structure fabrication in the semiconductor and related industries. The use of ultra-thin gate dielectrics, ultra thin channels, and sub-20 nm film thicknesses in field effect transistors and other devices requires near-atomic scale etching control and selectivity. There is an emerging consensus that as critical dimensions approach the sub-10 nm scale, the need for an etching method corresponding to Atomic Layer Deposition (ALD), i.e. Atomic Layer Etching (ALE), has become essential, and that the more than 30-year quest to complement/replace continuous directional plasma etching (PE) methods for critical applications by a sequence of individual, self-limited surface reaction steps has reached a crucial stage. A key advantage of this approach relative to continuous PE is that it enables optimization of the individual steps with regard to reactant adsorption, self-limited etching, selectivity relative to other materials, and damage of critical surface layers. In this overview we present basic approaches to ALE of materials, discuss similarities/crucial differences relative to thermal and plasma-enhanced ALD, and then review selected results on ALE of materials aimed at pattern transfer. The overview concludes with a discussion of opportunities and challenges ahead.

Gallium Nitride based high electron mobility transistors (HEMTs) are attractive for use in high power and high frequency applications, with higher breakdown voltages and two dimensional electron gas (2DEG) density compared to their GaAs counterparts. Specific applications for nitride HEMTs include air, land and satellite based communications and phased array radar. Highly efficient GaN-based blue light emitting diodes (LEDs) employ AlGaN and InGaN alloys with different compositions integrated into heterojunctions and quantum wells. The realization of these blue LEDs has led to white light sources, in which a blue LED is used to excite a phosphor material; light is then emitted in the yellow spectral range, which, combined with the blue light, appears as white. Alternatively, multiple LEDs of red, green and blue can be used together. Both of these technologies are used in high-efficiency white electroluminescent light sources. These light sources are efficient and long-lived and are therefore replacing incandescent and fluorescent lamps for general lighting purposes. Since lighting represents 20–30% of electrical energy consumption, and because GaN white light LEDs require ten times less energy than ordinary light bulbs, the use of efficient blue LEDs leads to significant energy savings. GaN-based devices are more radiation hard than their Si and GaAs counterparts due to the high bond strength in III-nitride materials. The response of GaN to radiation damage is a function of radiation type, dose and energy, as well as the carrier density, impurity content and dislocation density in the GaN. The latter can act as sinks for created defects and parameters such as the carrier removal rate due to trapping of carriers into radiation-induced defects depends on the crystal growth method used to grow the GaN layers. The growth method has a clear effect on radiation response beyond the carrier type and radiation source. We review data on the radiation resistance of AlGaN/GaN and InAlN/GaN HEMTs and GaN–based LEDs to different types of ionizing radiation, and discuss ion stopping mechanisms. The primary energy levels introduced by different forms of radiation, carrier removal rates and role of existing defects in GaN are discussed. The carrier removal rates are a function of initial carrier concentration and dose but not of dose rate or hydrogen concentration in the nitride material grown by Metal Organic Chemical Vapor Deposition. Proton and electron irradiation damage in HEMTs creates positive threshold voltage shifts due to a decrease in the two dimensional electron gas concentration resulting from electron trapping at defect sites, as well as a decrease in carrier mobility and degradation of drain current and transconductance. State-of-art simulators now provide accurate predictions for the observed changes in radiation-damaged HEMT performance. Neutron irradiation creates more extended damage regions and at high doses leads to Fermi level pinning while ⁶⁰Co γ-ray irradiation leads to much smaller changes in HEMT drain current relative to the other forms of radiation. In InGaN/GaN blue LEDs irradiated with protons at fluences near 10¹⁴ cm⁻² or electrons at fluences near 10¹⁶ cm⁻², both current-voltage and light output-current characteristics are degraded with increasing proton dose. The optical performance of the LEDs is more sensitive to the proton or electron irradiation than that of the corresponding electrical performances.

Polymer blend films of PMMA/PEO, modified with MoS₂ and one of three ammonium iodide salts (TBAI, THAI, or TMAI), were successfully fabricated via the solution casting technique. The structural, optical, fluorescence, and dielectric properties were systematically investigated. The results show that the composites exhibit strong absorption across the UVA, UVB, and UVC ranges, making them effective UV-shielding barriers and promising solar cell absorbers. The direct optical band gap decreased from 5.08 eV (pure blend) to as low as 2.83 eV for the TMAI-containing composite, while the TMAI sample also gave the highest refractive index. Nonlinear optical parameters (χ⁽¹⁾, χ⁽³⁾, n₂) peaked in the visible region, indicating suitability for visible-light optoelectronic devices such as OLEDs. Fluorescence intensity decreased upon doping, and CIE coordinates showed tunable violet-red emission under 320 nm and 380 nm excitation, suggesting potential for LEDs; the decreased fluorescence intensity may indicate charge separation, though photocatalytic activity requires further validation. The THAI-based composite delivered the largest improvements in dielectric constant and AC conductivity, with ε′ > ε″ across the frequency range, indicating good energy storage capability in principle. The alkyl chain length of the ammonium cation (methyl < butyl < hexyl) systematically influenced the properties, demonstrating a clear structure–property relationship. Nyquist plots and equivalent circuit modeling confirmed increased conductivity and reduced electrode polarization upon doping. Overall, the synergistic combination of MoS₂ and iodonium salts transforms PMMA/PEO into a tunable multifunctional material for UV protection, LEDs, solar cells, and high-performance energy storage devices. We emphasize that these conclusions are based on material‑level characterization; actual device performance remains to be verified.

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The structural and electrochemical properties of Li_1+xMn₂O₄ spinel cathode materials were investigated with varying lithium contents by introducing 5%, 10%, and 15% excess Li₂CO₃ precursor relative to what is needed to prepare stoichiometric LiMn₂O₄ composition. Standard material characterizations (SMC) of the samples were performed using X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). Electrochemical tests were performed using electrochemical impedance spectroscopy (EIS) and half-cell galvanostatic cycling, using lithium metal as the counter electrode. The sample with the stoichiometric formulation exhibited only the characteristic Mn³⁺/Mn⁴⁺ redox couple near 4.0 V, whereas the over-lithiated samples showed secondary redox activity in the range of 2.4–3.0 V, which was attributed to the increased rates of Mn²⁺/Mn³⁺ transitions with excess lithium. Alongside the SMC, the evidence reflected from the galvanostatic profiles and impedance response suggests a complex interplay between lithium content, electronic transport, and structural distortion. Specifically, a controlled lithium excess of x $\cong$ 0.08 in Li_1+xMn₂O₄ offers the best compromise between capacity, charge transfer and structural stability. The effects of lithium stoichiometry on the redox mechanisms and structural evolution of these spinel cathodes are addressed in this contribution, with results offering insights into the design of manganese-based cathodes with tailored electrochemical profiles.

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Highlights

• The over-stoichiometric Li_1+xMn₂O₄ compound has been successfully synthesized

• x $\cong$ 0.08 shows the best compromise of capacity, charge transfer, and stability

• The coexistence of two slightly different Li_1+xMn₂O₄ phases has been evidenced

• A higher content of the tetragonal phase contributes to an improved performance

• A simplified, low-cost, and sustainable synthesis technique has been used

This work presents a comprehensive TCAD investigation of p-GaN etching-depth variation in enhancement-mode (E-mode) AlGaN/GaN high electron mobility transistors (HEMTs), calibrated with experimental ICP etching conditions. Three representative scenarios were examined: nominal etch depth, residual p-GaN (under-etch), and over-etch into the AlGaN barrier. In the residual regime, the remaining p-GaN forms a p–i–n-like junction with the underlying heterostructure, altering the electrostatic distribution and partially depleting the two-dimensional electron gas (2DEG). As the residual thickness increases, both the threshold voltage (V_th) and ON resistance (R_ON) exhibit a rapid increase followed by saturation, reflecting the strong sensitivity of channel electrostatics to small residual variations. In contrast, over-etching into the AlGaN barrier reduces the effective barrier thickness and weakens carrier confinement, thereby reducing 2DEG density. This leads to a simultaneous increase in V_th and R_ON due to reduced channel conductivity and altered voltage distribution. A ±0.2 V V_th tolerance was adopted to define a quantitative process window of approximately –0.8 to +1.2 nm relative to the nominal etch depth, within which stable E-mode operation is maintained. These results clarify the electrostatic origins of etch-depth-induced V_th and R_ON variations and provide a predictive guideline for process optimization in p-GaN gate HEMT fabrication.

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Transistor Technology plays a crucial role in human life. The aim is to increase the number of applications and increase speed in a single Integrated Circuit (IC) of Transistor Technology. This paper reviews the conventional transistor devices (Planar MOSFET, MESFET, DGMOSFET, DGMOSFET with Dual Material, and DGMOSFET with High-k Materials), modern transistor devices (FinFET and SOI FinFET), and advanced transistor devices (GAAFET (Gate All Around Nanosheet FET, Gate All around Nanowire FET and Tree FET). Different aspects, such as Drain Induced Barrier Leakage (DIBL), Leakage Current, Short Channel Effects (SCE), and Subthreshold Swing (SS), influence the performance of FETs. A comparison study shows that the Nanosheet Field Effect Transistor (NSFET) is the best transistor device in the semiconductor industry due to its low power performance, and also provides low parasitic capacitance, low temperature sensitivity, better electrostatic control, higher switching capacity, and good considerable scaling. The review also explores the development of next-generation transistor architectures such as Forksheet FETs, Complementary FETs, Vertical Transport FETs, Quantum Dot Transistors, Single-Electron Transistors, and Qubit Devices, which are among the most promising candidates under active research and are being considered as potential replacements for nanosheet FETs.

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Highlights

• This paper reviews the conventional transistor devices (Planar MOSFET, DGMOSFET, etc), modern transistor devices (FinFET and SOI FinFET), and advanced transistor devices (GAAFET (Gate All Around Nanosheet FET, Gate All around Nanowire FET and Tree FET).

• A comparison study shows that the Nanosheet Field Effect Transistor (NSFET) is the best transistor device in the semiconductor industry due to its low power performance, and also provides low parasitic capacitance, better electrostatic control, and good considerable scaling.

• The review also explores the development of next-generation transistor architectures such as Forksheet FETs, Complementary FETs, Vertical Transport FETs, Quantum Dot Transistors, Single-Electron Transistors, and Qubit Devices, which are among the most promising candidates under active research and are being considered as potential replacements for nanosheet FETs.

Ferrite nanostructures of the type MFe₂O₄ (M = Co and Mg) were synthesized using the sol–gel auto-combustion method and subsequently annealed at 500 °C and 800 °C to examine the effect of thermal treatment on their physical and functional properties. Structural analysis performed using X-ray diffraction and Rietveld refinement confirmed the formation of a single-phase spinel structure for all samples. The crystallite size, estimated using the Debye–Scherrer and Williamson-Hall methods, was found to increase with annealing temperature, which was further supported by field-emission scanning electron microscopy observations showing grain growth. Optical studies based on UV–Visible absorption spectra revealed an increase in the optical band gap with increasing annealing temperature. Magnetic measurements carried out at room temperature showed enhanced magnetic properties for cobalt ferrites, whereas magnesium ferrites exhibited a reduction in magnetic behavior upon annealing. In addition, antibacterial activity tests against both Gram-positive and Gram-negative bacterial strains demonstrated that thermal treatment significantly influences the antimicrobial performance of the ferrite nanostructures. Overall, the results highlight the critical role of annealing temperature in tailoring the structural, optical, magnetic, and antibacterial properties of ferrite materials for potential multifunctional applications.

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Transistor Technology plays a crucial role in human life. The aim is to increase the number of applications and increase speed in a single Integrated Circuit (IC) of Transistor Technology. This paper reviews the conventional transistor devices (Planar MOSFET, MESFET, DGMOSFET, DGMOSFET with Dual Material, and DGMOSFET with High-k Materials), modern transistor devices (FinFET and SOI FinFET), and advanced transistor devices (GAAFET (Gate All Around Nanosheet FET, Gate All around Nanowire FET and Tree FET). Different aspects, such as Drain Induced Barrier Leakage (DIBL), Leakage Current, Short Channel Effects (SCE), and Subthreshold Swing (SS), influence the performance of FETs. A comparison study shows that the Nanosheet Field Effect Transistor (NSFET) is the best transistor device in the semiconductor industry due to its low power performance, and also provides low parasitic capacitance, low temperature sensitivity, better electrostatic control, higher switching capacity, and good considerable scaling. The review also explores the development of next-generation transistor architectures such as Forksheet FETs, Complementary FETs, Vertical Transport FETs, Quantum Dot Transistors, Single-Electron Transistors, and Qubit Devices, which are among the most promising candidates under active research and are being considered as potential replacements for nanosheet FETs.

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Highlights

• This paper reviews the conventional transistor devices (Planar MOSFET, DGMOSFET, etc), modern transistor devices (FinFET and SOI FinFET), and advanced transistor devices (GAAFET (Gate All Around Nanosheet FET, Gate All around Nanowire FET and Tree FET).

• A comparison study shows that the Nanosheet Field Effect Transistor (NSFET) is the best transistor device in the semiconductor industry due to its low power performance, and also provides low parasitic capacitance, better electrostatic control, and good considerable scaling.

• The review also explores the development of next-generation transistor architectures such as Forksheet FETs, Complementary FETs, Vertical Transport FETs, Quantum Dot Transistors, Single-Electron Transistors, and Qubit Devices, which are among the most promising candidates under active research and are being considered as potential replacements for nanosheet FETs.

With the advancement of electric vehicle (EV) battery technologies, conventional lithium-ion batteries are approaching their theoretical energy density limits while facing persistent safety concerns. All-solid-state batteries (ASSBs) offer a pathway toward higher energy density and enhanced safety. This review focuses on the fabrication and manufacturing processes of ASSBs, explicitly bridging laboratory-scale research methods with emerging industrial-scale production routes. Emphasis is placed on material systems, scalable processing strategies, manufacturing bottlenecks, and industrial roadmaps.

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Biomedical procedures needed to be upgraded with time through various innovative techniques in order to enhance its efficacy. Graphene’s transformative potential in biomedicine owing to its unique physicochemical properties provides innovative platform in this regard. The current review begins with highlights on key attributes of graphene such as biocompatibility, surface functionalization potential, mechanical strength, and electrical/thermal conductivity. Further emphasis has been given to the graphene’s diverse roles, including nanocarriers for drug delivery, stimuli-responsive and targeted therapeutic strategies, biosensors for biomarker detection and their integration into wearable devices, and significant contributions to tissue engineering as well as regenerative medicine through scaffolds. Besides, its applications in bioimaging (MRI, fluorescence) and photothermal/photodynamic therapies are also discussed. Later part of review involves in vitro/in vivo biocompatibility and dose-dependent toxicity of graphene. Conclusively, the major challenges obstructing graphene-derivatives in biomedical applications are highlighted along with possible measures. Integration with emerging trends like AI and ML- empowered devices can underscore graphene’s promising role in next-generation biomedical platforms.

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Recent developments in nano-materials have re-architected the frontiers of solid-state sensor design, enabling high sensitivity, selectivity, and sustainability across a broad spectrum of real-world applications. This review summarises the advances in nanomaterial-engineered sensors, including the connection between material structure and functional mechanisms, as well as the device’s performance. Doped metal-oxide semiconductors (SnO₂ or ZnO, or WO₃) or polyoxometalates or MXenes exhibit an improved speed of charge transfer, low temperatures, and selectivity. Hydrophilic polymers, biocomposites and MXene hybrid sensors based on impedance and ionic humidity are flexible, fast-reactive and self-powered. Piezoelectric and photoacoustic transduction, based on ferroelectric ceramics, PVDF, and bio-based polymers such as PLA, chitosan, and cellulose, provides a platform for sustainable and energy-harvesting wearable devices and implants. The combination of electrochemical materials and biodegradable materials also enhances environmentally friendly sensor technologies. Multimodal sensing is adopting new architectures developed using adaptive calibration and intelligent data interpretation based on new artificial intelligence. As observed in the review, the compositional tuning, heterostructuring, and nanoscale morphology are used to control the science of bridge materials and the engineering of functional devices. The vision for this area is to develop fully autonomous, power-driven, and recyclable sensor ecosystems that can seamlessly integrate into Internet of Things (IoT) networks, enabling continuous monitoring of the environment, health, and industrial status with minimal human intervention and environmental impact. Lastly, the existing challenges, such as interference from humidity, signal drift, and the possibility of large-scale manufacturability, are not only documented but also addressed through the opportunities presented by multifunctional sensor systems, autonomous sensor systems, and recyclable sensor systems of the future. Future developmental trends include the integration of machine learning algorithms with multimodal sensor arrays to provide real-time adaptive analytics, the development of biodegradable and bioresorbable platforms for transient implantable diagnostics, and the development of flexible, skin-conformal architectures for precision medicine and personalized wearable health monitoring. This comprehensive evaluation offers a unique perspective on how nanomaterial-engineered solid-state sensors can be utilized to support the development of next-generation, sustainable, and intelligent technologies.

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Resistive gas sensors are widely utilized to detect a variety of gases including poisonous, explosive, biomarker, and even non-toxic gases because of their exceptional performance. Zinc stannate (Zn₂SnO₄) is a ternary metal oxide with exceptional stability and distinctive electrical characteristics. In a variety of morphologies and along with other materials, it has been utilized to realize resistive gas sensors. Here, we thoroughly explain the gas sensing characteristics of Zn₂SnO₄ gas sensors in pristine, doped, and composite forms. Also, we have emphasized in sensing mechanism to further understand the gas sensing principle of Zn₂SnO₄ gas sensors.

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The properties of orthorhombic κ-Ga₂O₃ films grown by Epitaxial Lateral Overgrowth (ELOG) were studied by Scanning Transmission Electron Microscopy (STEM), X-ray diffraction, capacitance-voltage profiling, Microcathodoluminescence (MCL) spectroscopy and imaging. ELOG mask was formed by deposition of SiO₂ stripes on TiO₂ buffer prepared on basal plane sapphire, with the stripes going along the [11$\mathop{2}\limits^{\unicode{x00305}}$0] direction of sapphire. κ-Ga₂O₃ ELOG growth was performed using Halide Vapor Phase Epitaxy (HVPE), with ELOG wing of the structure formed by lateral overgrowth over the 20 μm-wide SiO₂ stripes, while growth in between the stripes proceeded initially by vertical growth in the 5-μm-wide windows. TEM analysis showed that the material in the windows comprised 120^o rotational nanodomains typical of κ-Ga₂O₃, while, in the wing regions, the material was single-domain monocrystalline. The films were conducting, with the net donor density close to 10¹³ cm⁻³. The data suggested the material in the windows have much higher resistance than in the wings. MCL spectra and imaging revealed much higher density of nonradiative recombination centers in the windows than in the wings.

WS₂ is an emerging semiconductor with potential applications in next-generation device architecture owing to its excellent electrical and physical properties. However, the presence of inevitable surface contaminants and oxide layers limits the performance of WS₂-based field-effect transistors (FETs); therefore, novel methods are required to restore the pristine WS₂ surface. In this study, the thickness of a WS₂ layer was adjusted and its surface was restored to a pristine state by fabricating a recessed-channel structure through a combination of self-limiting remote plasma oxidation and KOH solution etching processes. The reaction between the KOH solution and WO_X enabled layer-by-layer thickness control as the topmost oxide layer was selectively removed during the wet-etching process. The thickness of the WS₂ layer decreased linearly with the number of recess cycles, and the vertical etch rate was estimated to be approximately 0.65 nm cycle⁻¹. Micro-Raman spectroscopy and high-resolution transmission electron microscopy revealed that the layer-by-layer etching process had a nominal effect on the crystallinity of the underlying WS₂ channel. Finally, the pristine state was recovered by removing ambient molecules and oxide layers from the surface of the WS₂ channel, which resulted in a high-performance FET with a current on/off ratio greater than 10⁶. This method, which provides a facile approach to restoring the pristine surfaces of transition-metal dichalcogenide (TMDC) semiconductors with precise thickness control, has potential applications in various fields such as TMDC-based (opto)electronic and sensor devices.

Novel metal oxide materials such as InGaZnO (IGZO), ZnO, SnO, and In₂O₃ and improved fabrication processes dramatically enhanced the achieved and projected thin film transistor (TFT) performance. The record values of the effective field-effect mobility of Metal Oxide TFT (MOTFT) materials have approached 150 cm²/Vs. We report on an improved compact TFT model based on three models: the RPI TFT model, the unified charge control model (UCCM), and the multi-segment TFT compact model. This improved model accounts for a non-exponential slope in the subthreshold regime by introducing a varying subthreshold slope and accounts for non-trivial capacitance dependence on the gate bias, and parasitic impedances. The analysis of the TFT response using this model and the analytical calculations showed that TFTs could have a significant response to impinging THz and sub-THz radiation. Using a complementary inverter and the phase-matched THz signal feeding significantly improves the detection sensitivity.

The ion implantation of H⁺ and D⁺ into Ga₂O₃ produces several O–H and O–D centers that have been investigated by vibrational spectroscopy. These defects include the dominant V_Ga(1)-2H and V_Ga(1)-2D centers studied previously along with additional defects that can be converted into this structure by thermal annealing. The polarization dependence of the spectra has also been analyzed to determine the directions of the transition moments of the defects and to provide information about defect structure. Our experimental results show that the implantation of H⁺ (or D⁺) into Ga₂O₃ produces two classes of defects with different polarization properties. Theory finds that these O–H (or O–D) centers are based on two shifted configurations of a Ga(1) vacancy that trap H (or D) atom(s). The interaction of V_Ga(1)-nD centers with other defects in the implanted samples has also been investigated to help explain the number of O–D lines seen and their reactions upon annealing. Hydrogenated divacancy V_Ga(1)-V_O centers have been considered as an example.

This paper describes a theoretical investigation of the phase composition of oxide precipitates and the corresponding emission of self-interstitials at the minimum of the free energy and their evolution with increasing number of oxygen atoms in the precipitates. The results can explain the compositional evolution of oxide precipitates and the role of self-interstitials therein. The formation of suboxides at the edges of SiO₂ precipitates after reaching a critical size can explain several phenomena like gettering of Cu by segregation to the suboxide region and lifetime reduction by recombination of minority carriers in the suboxide. It provides an alternative explanation, based on minimized free energy, to the theory of strained and unstrained plates. A second emphasis was payed to the evolution of the morphology of oxide precipitates. Based on the comparison with results from scanning transmission electron microscopy the sequence of morphology evolution of oxide precipitates was deduced. It turned out that it is opposite to the sequence assumed until now.

The aim of this study is to obtain the most reliable zero-phonon line (ZPL) energies and related Racah parameters for Mn⁴⁺ ions activated in Al₂O₃, Ga₂O₃, and (Al_1-xGa_x)₂O₃. The Franck-Condon analysis with the configurational-coordinate model is used for this purpose. The Racah parameters, B and C, in conjunction with the Tanabe-Sugano energy-level diagram, known as plots of the energies for the electronic states of each electron configuration as a function of the crystal-field strength parameter Dq, are successfully determined by properly assuming the Racah parameter ratio of r=C/B for such Mn⁴⁺-activated phosphors. Here, an assumption of r makes possible to determine the reliable Racah and related parameters, B, C, and Dq, only from relatively easily and accurately determinable “two” ZPL energies E(²E_g)_ZPL and E(⁴T_2g)_ZPL, without introducing any E(⁴T_1g,a)_ZPL value that is known to be very difficult to exactly determine from optical spectra. Results suggest that an assumption of r = 8.0 successfully explains the luminescence properties of these Mn⁴⁺-activated phosphors. Of particular interest for the (Al_1-xGa_x)₂O₃:Mn⁴⁺ quasibinary phosphor system is its alloy composition dependence of the excited-state ZPL energies and Racah parameters. Key properties of this practically important oxide phosphor system is also discussed.

Tunnel Field-Effect Transistors (TFETs) have emerged as strong candidates for next-generation ultra-low-power electronics due to their ability to achieve sub-60 mV/dec subthreshold swing and suppressed leakage characteristics. This work presents a unified analytical framework and performance enhancement strategy for Tri-Material Gate-All-Around (TM-GAA) Silicon Nanowire TFETs, integrating advancements from subthreshold analysis, transconductance-to-drain current ratio evaluation, and potential distribution modeling. A compact 2-D analytical model is developed by solving the Poisson equation using the parabolic approximation, enabling accurate estimation of minimum surface potential, subthreshold current, and transconductance efficiency across varying design parameters. The model captures gate material engineering effects, electrostatic control, oxide thickness impact, and silicon nanowire diameter dependence with high fidelity. Simulation results show that the proposed TM-GAA nanowire TFET architecture achieves a significantly improved transconductance-to-drain current ratio (up to 40 V⁻¹), reduced subthreshold swing (< 35 mV/dec), and lower leakage compared with conventional double-material and MOSFET structures. Variations in thickness, channel length, and silicon diameter are analyzed to determine optimal operating regions for analog and digital applications. TCAD simulations validate the proposed mathematical model, demonstrating excellent correlation with the analytical predictions. These findings highlight the strong potential of TM-GAA nanowire TFETs for energy-efficient integrated circuits and high-sensitivity analog front-ends.

Copper (Cu) interconnects are extensively employed in the manufacturing of integrated circuits. During the chemical mechanical polishing (CMP) process of these interconnects, precise control over the material removal selectivity between copper and barrier layers, such as tantalum/tantalum nitride (Ta/TaN), cobalt (Co), and ruthenium (Ru), is essential. As a critical component in CMP slurries, complexing agents play a direct role in regulating this selectivity by forming coordination bonds with copper and barrier-layer metals. This paper provides a systematic review of the mechanisms of commonly used complexing agents in CMP, classifying them into five categories: carboxylic acids, amines, organic acids, inorganic salts, and macromolecular polymer complexing agents. It focuses on elucidating their respective action mechanisms and current limitations in the removal of copper and barrier-layer metals. The review aims to offer valuable insights for future research and technological advances in related fields, as well as a theoretical foundation for achieving more efficient and controllable CMP processes.

This study aims to tailor the dielectric and electrical properties of PMMA/LiTFSI-based solid polymer electrolytes for energy storage applications by incorporating indium-doped ZnWO4 nanofillers. Polymer nanocomposite films with ZnW1-xInxO4 (x = 0, 0.05, 0.1) were synthesized via solution casting. XRD confirmed a biphasic system with a monoclinic ZnWO4 phase dispersed in an amorphous PMMA matrix, while FTIR revealed Li⁺ coordination with carbonyl groups and polymer-filler interactions modulated by indium doping. Dielectric analysis showed that the undoped composite (x=0) exhibited the highest dielectric constant (56.17 at 363 K, 1 kHz) due to Maxwell-Wagner-Sillars interfacial polarization, but indium doping systematically reduced dielectric loss from 1.59 to 1.36 by introducing charge-trapping defects. Although all composites showed lower energy density than pure PMMA, the x=0.05 sample achieved the highest among composites (0.01921 J/m³). AC conductivity revealed non-monotonic frequency behavior that persisted at high temperatures only for x=0.1, attributed to indium-induced structural distortions. Impedance and electric modulus analyses highlighted contrasting temperature dependencies and distinct relaxation mechanisms. Nyquist plots at 363 K demonstrated that moderate indium doping (x=0.05) optimally balances enhanced charge transport and reduced trap states. Thus, indium doping offers a systematic route to tune dielectric/electrical performance, with x=0.05 identified as optimal for high-conductivity, moderate-dielectric-constant applications.

Reactive-ion sputter deposition of Al_1-xSc_xN has shown great promise in the fabrication of next generation piezoelectric, ferroelectric, and optoelectronic applications. Due to the nature of sputtering, post-deposition, high temperature thermal processing is encouraged to improve the film crystalline quality and subsequently improve the overall device performance. However, a complete analysis on the thermal stability of high Sc content Al_1-xSc_xN remains as a gap that needs to be filled. In this work, reactive-ion sputtered Al_0.70Sc_0.30N was annealed using a face-to-face configuration at temperatures between 1100 °C and 1300 °C, and for durations between 60 and 180 mins to study the thermal impact on structural and optical properties. Annealing at 1100 °C for 60 mins under this configuration improved the thin film crystalline quality while maintaining phase purity and structural stability. Annealing at higher temperatures and durations lead to ScN segregation, as well as Sc₂O₃ formation at the highest temperature regime. Optically, it was found that annealing can eliminate vacancy-oxygen complex defects and improve transmission in the deposited thin film.

A paste-press packing (PPP) method is proposed for loading pastes and suspensions into micro- and nano-sized through-holes in thin membranes. First, the effectiveness of the PPP method was evaluated by electrochemiluminescence (ECL) imaging and scanning electron microscopy (SEM) using carbon paste (CP)-packed track-etched membranes. Uniform and dense packing of CP into 8 μm-diameter through-holes was achieved by the PPP method, enabling the membranes to function as closed bipolar electrode arrays suitable for bipolar electrochemical microscopy. Next, the versatility of the PPP method was demonstrated by successfully packing silver paste and an alumina suspension into micro-sized through-holes, despite their different compositions and rheological properties. Finally, Au micro- and nano-rods with diameters ranging from 12 to 0.6 μm were fabricated from Au paste-packed track-etched membranes by removing the membranes either by dissolution in organic solvents or by calcination. These results demonstrate that the PPP method provides a simple and versatile approach for uniformly packing various functional materials into membrane through-holes and for fabricating micro- and nano-rod structures, offering a broadly applicable platform for microfabrication.

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We previously reported a powerful method to improve dielectric/GaN interface properties: the dummy SiO₂ process [Y. Irokawa et al., ECS J. Solid State Sci. Technol. 13, 085003 (2024)]. Here, GaN metal-oxide-semiconductor (MOS) interfaces prepared with this process were investigated using a sub-bandgap photo-assisted capacitance–voltage technique. GaN MOS interfaces were previously revealed to have deep states, and the dummy process was expected to reduce the number of deep states through its interface modification process. However, the deep state densities in Al₂O₃/GaN MOS interfaces after the dummy process did not substantially change compared with those in devices fabricated without the dummy process. Meanwhile, we recently observed oxygen atoms in positions proximate to nitrogen sites in MOS interface regions, with the GaN crystal maintaining the same structure [J. Uzuhashi et al. ECS J. Solid State Sci. Technol. 14, 085001 (2025)]. We therefore performed first-principles calculations and found that, under certain circumstances, a pair of oxygen atoms replacing nitrogen atoms in GaN created deep states in the bandgap, with slight displacements, similar to DX centers; this substitution could be one of the origins of deep states in GaN MOS interfaces.

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This study reports an integrated hydrometallurgical and hydrothermal route that converts NMC-type black mass from spent Li-ion batteries into a mixed cobalt-nickel-manganese sulfide (CNMS) and demonstrates its application as a high-performance positive electrode for asymmetric supercapacitor (ASC). Black mass is leached in 3 M H₂SO₄ with 10% v/v H₂O₂ (S/L = 1:50) at room temperature. The dissolved Co, Ni and Mn are co-precipitated as a mixed hydroxide (CNMOH) by pH adjustment and subsequently sulfidized to produce CNMS via thioacetamide-assisted ion exchange in a hydrothermal reactor (180 °C, 12 h). Electrochemical characterization in a three-electrode cell yields an areal capacitance of 1262 mF.cm⁻² (CV, 5 mV.s⁻¹) and 1103 mF.cm⁻² (GCD, 5 mA.cm⁻²). An ASC (CNMS//graphite, 6 M KOH) delivers an areal capacitance of 88.3 mF.cm⁻² (5 mV.s⁻¹), respectively. This ASC device shows the energy and power density values of 11.06 μWh.cm⁻² and 367 μW.cm⁻² and retains 80.6% capacitance after 5000 cycles. The combined recovery-to-device approach highlights the feasibility of upcycling the battery black mass into ternary transition metal sulfide. This work provides a practical pathway to couple critical materials recovery with advanced electrochemical energy storage.

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Reactive-ion sputter deposition of Al_1-xSc_xN has shown great promise in the fabrication of next generation piezoelectric, ferroelectric, and optoelectronic applications. Due to the nature of sputtering, post-deposition, high temperature thermal processing is encouraged to improve the film crystalline quality and subsequently improve the overall device performance. However, a complete analysis on the thermal stability of high Sc content Al_1-xSc_xN remains as a gap that needs to be filled. In this work, reactive-ion sputtered Al_0.70Sc_0.30N was annealed using a face-to-face configuration at temperatures between 1100 °C and 1300 °C, and for durations between 60 and 180 mins to study the thermal impact on structural and optical properties. Annealing at 1100 °C for 60 mins under this configuration improved the thin film crystalline quality while maintaining phase purity and structural stability. Annealing at higher temperatures and durations lead to ScN segregation, as well as Sc₂O₃ formation at the highest temperature regime. Optically, it was found that annealing can eliminate vacancy-oxygen complex defects and improve transmission in the deposited thin film.

The growing need for environmentally responsible, safe, and resource–efficient energy storage materials has driven interest in biodegradable polymer electrolytes. This work reports the design and evaluation of an eco–friendly solid polymer electrolyte (SPE) derived from iota carrageenan (IC) doped with sodium acetate (NA). Films were prepared using a cost–efficient solution–casting method. FTIR analysis verified successful polymer–salt complexation, as evidenced by notable shifts in characteristic functional group bands. XRD patterns revealed a gradual reduction in crystallinity with increasing salt content, thereby enhancing the amorphous phase and supporting efficient ion mobility. Electrochemical Impedance Spectroscopy confirmed that the film containing 30 wt% NA achieved the highest ionic conductivity of 1.93 × 10^–5 S cm^–1 at ambient temperature. The electrolyte also exhibited a broad electrochemical stability window of 3.6 V. A primary sodium–ion cell assembled with the optimized SPE delivered a stable open–circuit voltage of ∼2.9 V, highlighting its promise for clean, resilient, and sustainable energy technologies.

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With the advancement of electric vehicle (EV) battery technologies, conventional lithium-ion batteries are approaching their theoretical energy density limits while facing persistent safety concerns. All-solid-state batteries (ASSBs) offer a pathway toward higher energy density and enhanced safety. This review focuses on the fabrication and manufacturing processes of ASSBs, explicitly bridging laboratory-scale research methods with emerging industrial-scale production routes. Emphasis is placed on material systems, scalable processing strategies, manufacturing bottlenecks, and industrial roadmaps.

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Europium doped silicon (oxy)carbonitride (Si(O)CN) thin films were fabricated using an integrated electron cyclotron resonance plasma-enhanced chemical vapor deposition system combined with in situ magnetron sputtering. Post-deposition annealing was performed from 800 °C to 1200 °C to investigate europium activation within the Si(O)CN matrix. Room-temperature photoluminescence revealed visible bright red emission attributed to the intra 4 f transition of Eu³⁺ ions, prominently observed in films annealed at 1100 °C and 1200 °C. A detailed compositional analysis was performed with a combination of Rutherford backscattering spectrometry and elastic recoil detection analysis showing nearly 7 at% of europium in the luminescent film. The presence of crystalline phases from the high temperature annealed samples was confirmed by X-ray diffraction analysis. These investigations were conducted to assess the feasibility of amorphous Si(O)CN as a thermally and chemically stable, silicon-compatible host for rare-Earth doping. Europium doped Si(O)CN can offer promising potential for visible light emission in next generation integrated photonic and optoelectronic devices.

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Bifacial photovoltaic (PV) cells present a promising solution for enhanced energy harvesting in diverse environments, particularly for powering the proliferating network of low-energy Internet of Things (IoT) devices. This work details the numerical optimization of a novel bifacial cell based on a tunable CZT_1−xG_xSe absorber for dual indoor-outdoor applications. Using SCAPS-1D and RCWA simulations, the cell structure was systematically optimized by tuning key parameters, including germanium content, buffer layer, back contact, absorber properties, and an anti-reflection coating. The buffer layer material was selected to ensure optimal band alignment with the absorber, thereby minimizing non-radiative recombination. Meanwhile, the absorber thickness was optimized to balance photon absorption against the increase in series resistance. The cell’s performance was evaluated under 36 indoor wall colors and various outdoor ground albedos. Under indoor illumination, the optimized cell delivers an output power of 58.93 mW·cm⁻² (halogen) and 297 μW·cm⁻² (LED), sufficient to power a range of IoT sensors. Under outdoor AM1.5 G illumination, the output power ranges from 75.69 mW·cm⁻² (snow albedo) to 35.51 mW·cm⁻² (soil albedo). This study establishes a robust design framework for a versatile, high-efficiency PV cell, paving the way for sustainable power sources in smart buildings and embedded electronics.

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The radiation tolerance of single-crystal diamond devices was investigated under 10 MeV proton irradiation. Schottky barrier diodes (SBDs) and ITO/diamond heterojunction diodes were fabricated on boron-doped diamond substrates with a 10 μm lightly doped drift layer and exposed to proton fluences from 1.0 × 10¹³ to 1.6 × 10¹⁴ cm⁻². Irradiation induced increased on-resistance, reduced saturation current, and enhanced reverse leakage, with heterojunction devices showing greater degradation due to the vulnerability of the ITO layer and interface. Capacitance–voltage measurements revealed carrier removal rates of 171, 65, and 43 cm⁻¹ for fluences of 1.0 × 10¹³, 6.0 × 10¹³, and 1.6 × 10¹⁴ cm⁻², respectively, confirming diamond’s superior radiation hardness compared to Si, GaN, and Ga₂O₃. This resilience is attributed to diamond’s high atomic displacement energy, which limits lattice damage. These results demonstrate the potential of single-crystal diamond devices for radiation-hard power electronics and high-radiation environments.

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This paper proposes a gap-type metal-semiconductor-metal (MSM) phototransistor architecture based on lead sulfide quantum dots (PbS QDs) for room-temperature infrared (IR) thermal sensing applications. Owing to their tunable bandgap, strong IR absorption, and simple fabrication, PbS QDs are promising candidates for low-cost photodetection. The devices with PbS QDs exhibiting peak absorptions at 940 and 1600 nm were fabricated and compared. The 1600 nm device demonstrated a lower detectable temperature threshold and a linear photocurrent–temperature response above 150 °C, whereas the 940 nm device required over 300 °C. The enhanced performance of the 1600 nm device arises from its narrower bandgap, enabling stronger IR absorption and higher responsivity. However, the larger QD size and higher defect density result in a slower total response time (13.21 s) compared with the 940 nm device (157 μs). Consequently, the 940 nm device is suitable for real-time monitoring of high-temperature objects, while the 1600 nm device is preferable for static or slowly varying thermal radiation. These findings highlight the potential of PbS QD–based gap-type MSM photodetectors to achieve extended room-temperature IR sensing without external cooling, providing a feasible approach for low-cost and uncooled thermal imaging applications.

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The β-polytype of Ga₂O₃ has a bandgap of ∼4.8 eV, can be grown in bulk form from melt sources, has a high breakdown field of ∼8 MV.cm⁻¹ and is promising for power electronics and solar blind UV detectors, as well as extreme environment electronics (high temperature, high radiation, and high voltage (low power) switching. High quality bulk Ga₂O₃ is now commercially available from several sources and n-type epi structures are also coming onto the market. There are also significant efforts worldwide to grow more complex epi structures, including β-(Al_xGa_1x)₂O₃/Ga₂O₃ and β-(In_xGa_1−x)₂O₃/Ga₂O₃ heterostructures, and thus this materials system is poised to make rapid advances in devices. To fully exploit these advantages, advances in bulk and epitaxial crystal growth, device design and processing are needed. This article provides some perspectives on these needs.

ZnO has several potential applications into its credit. This review article focuses on the influence of processing parameters involved during the synthesis of ZnO nanoparticles by sol-gel method. During the sol-gel synthesis technique, the processing parameters/experimental conditions can affect the properties of the synthesized material. Processing parameters are the operating conditions that are to be kept under consideration during the synthesis process of nanoparticles so that various properties exhibited by the resulting nanoparticles can be tailored according to the desired applications. Effect of parameters like pH of the sol, additives used (like capping agent, surfactant), the effect of annealing temperature and calcination on the morphology and the optical properties of ZnO nanoparticles prepared via sol-gel technique is analyzed in this study. In this study, we tried to brief the experimental investigations done by various researchers to analyze the influence of processing parameters on ZnO nanoparticles. This study will provide a platform to understand and establish a correlation between the experimental conditions and properties of ZnO nanoparticles prepared through sol-gel route which will be helpful in meeting the desired needs in various application areas.

Gallium Nitride based high electron mobility transistors (HEMTs) are attractive for use in high power and high frequency applications, with higher breakdown voltages and two dimensional electron gas (2DEG) density compared to their GaAs counterparts. Specific applications for nitride HEMTs include air, land and satellite based communications and phased array radar. Highly efficient GaN-based blue light emitting diodes (LEDs) employ AlGaN and InGaN alloys with different compositions integrated into heterojunctions and quantum wells. The realization of these blue LEDs has led to white light sources, in which a blue LED is used to excite a phosphor material; light is then emitted in the yellow spectral range, which, combined with the blue light, appears as white. Alternatively, multiple LEDs of red, green and blue can be used together. Both of these technologies are used in high-efficiency white electroluminescent light sources. These light sources are efficient and long-lived and are therefore replacing incandescent and fluorescent lamps for general lighting purposes. Since lighting represents 20–30% of electrical energy consumption, and because GaN white light LEDs require ten times less energy than ordinary light bulbs, the use of efficient blue LEDs leads to significant energy savings. GaN-based devices are more radiation hard than their Si and GaAs counterparts due to the high bond strength in III-nitride materials. The response of GaN to radiation damage is a function of radiation type, dose and energy, as well as the carrier density, impurity content and dislocation density in the GaN. The latter can act as sinks for created defects and parameters such as the carrier removal rate due to trapping of carriers into radiation-induced defects depends on the crystal growth method used to grow the GaN layers. The growth method has a clear effect on radiation response beyond the carrier type and radiation source. We review data on the radiation resistance of AlGaN/GaN and InAlN/GaN HEMTs and GaN–based LEDs to different types of ionizing radiation, and discuss ion stopping mechanisms. The primary energy levels introduced by different forms of radiation, carrier removal rates and role of existing defects in GaN are discussed. The carrier removal rates are a function of initial carrier concentration and dose but not of dose rate or hydrogen concentration in the nitride material grown by Metal Organic Chemical Vapor Deposition. Proton and electron irradiation damage in HEMTs creates positive threshold voltage shifts due to a decrease in the two dimensional electron gas concentration resulting from electron trapping at defect sites, as well as a decrease in carrier mobility and degradation of drain current and transconductance. State-of-art simulators now provide accurate predictions for the observed changes in radiation-damaged HEMT performance. Neutron irradiation creates more extended damage regions and at high doses leads to Fermi level pinning while ⁶⁰Co γ-ray irradiation leads to much smaller changes in HEMT drain current relative to the other forms of radiation. In InGaN/GaN blue LEDs irradiated with protons at fluences near 10¹⁴ cm⁻² or electrons at fluences near 10¹⁶ cm⁻², both current-voltage and light output-current characteristics are degraded with increasing proton dose. The optical performance of the LEDs is more sensitive to the proton or electron irradiation than that of the corresponding electrical performances.

Using a conventional casting method, flexible polymeric film nanocomposites composed of PMMA (polymethyl methacrylate), PS (polystyrene), PVC (polyvinyl chloride) and ZnO nanoparticles were synthesized. Fourier transform infrared (FTIR) spectroscopy identified distinct peaks corresponding to vibrational groups in the prepared samples. Upon doping the PVC/PMMA/PS blend with varying concentrations of ZnO NPs (2.5–10 wt%), most absorption intensities tend to diminish progressively as the ZnO contents have been increased to 5 wt%. Changes in FTIR vibrational bands indicated interactions between the PVC/PMMA/PS/ZnO nanocomposite constituents. The XRD patterns of the ZnO NPs-based composites have exhibited the same peaks of the pure blend; however, there is a notable increase in broadness and a significant reduction in intensity as the weight percentage of ZnO NPs rises from 2.5 to 10. This observation indicates the development of interactions between the polymer and nanoparticles. The redshift seen in the absorption edge of the samples filled with ZnO provided strong evidence that charge transfer complexes had formed inside the polymeric matrix. The indirect and direct energy gaps for allowable transitions decreased with increasing ZnO NP concentrations, ranging from 3.88 eV and 4.87 eV in the pure blend to 3.31 eV and 4.67 eV, respectively. The σ_AC value at 100 Hz was 8.41 × 10⁻¹³ S·cm⁻¹ and increased with frequency, reaching 5.12 × 10⁻⁹ S·cm⁻¹ at 10⁶ Hz. Also, a modest improvement in σ_AC values is observed with the increase of ZnO NPs loading. The increase in conductivity can be ascribed to the improved amorphous nature of the synthesized nanocomposite facilitated by the incorporation of ZnO NPs. Dielectric studies showed that the best improvement was attained for the PVC/PMMA/PS/5 wt% of ZnO nanocomposite sample. Further, its imaginary part (ε″) exhibited a constructive decrease in its value with the increase in the ZnO loadings. These findings recommend these nanocomposites for potential applications in optoelectronics and energy storage devices.

The surface chemistry of InAlN ultra-thin layers, having undergone an oxidation procedure usually running through the HEMT fabrication process (850°C, O₂ and O₂+Ar) is studied by XPS. The suitability of XPS analysis to operate as a retro-engineering tool for added value microelectronic devices fabrication is shown. A precise examination of the Al2p, In3d_5/2, N1s, and O1s peaks directly informs about spatial and atomic arrangement. The formation of a covering 3 nm surface oxide is evidenced after O₂ annealing. Once annealed, two specific additional N1s contributions are shown, at higher (404.0 eV) and lower binding energies (397.4 eV) compared to the InAlN matrix one (396.5 eV). To our knowledge, such fingerprint is rather unusual for ternary III-V materials. It reveals the formation of a nitrogen deficient interlayer, situated between the oxide overlayer and the undisturbed matrix, and the presence of interstitial N₂ molecules trapped at the interface. After Ar annealing, both oxide and interface layers are partially reorganized. InAlN reactivity toward higher annealing temperature (950°C) and its stability over time is finally discussed. N₂ molecules are unstable and progressively eliminated in time although nitrogen deficient interlayer still remains. Thermal treatments below 850°C are recommended to preserve the barrier chemical integrity.

The Cr³⁺-activated phosphor properties are discussed in detail from an aspect of spectroscopic point of view. The host materials considered here are a various kind of oxide compounds. The photoluminescence (PL) and PL excitation spectra of the Cr³⁺-activated oxide phosphors are analyzed based on Franck−Condon analysis within the configurational-coordinate model. A new method is proposed for obtaining reliable crystal-field (Dq) and Racah parameters (B and C) based on a general ligand field theory with paying an attention to difficulty in the exact estimation of such important ligand field parameters. The intra-d-shell Cr³⁺ states, such as ²E_g (²G), ⁴T_2g (⁴F), and ⁴T_1g (⁴F), in various oxide hosts are determined and plotted against Dq in the Tanabe−Sugano energy-level diagram. The results obtained are summarized in graphical and tabular forms. A comparative discussion of Cr³⁺ ion as an efficient activator in oxide and fluoride hosts is also given. The present analysis method can be used to predict an energy of Cr³⁺ emission and/or to check a validity of the Racah parameter values for a variety of Cr³⁺-activated phosphors and related optical and optoelectronic device applications.

Gallium oxide (β-Ga₂O₃) is an emerging semiconductor with relevant properties for power electronics, solar-blind photodetectors, and some sensor applications due to its ultra-wide bandgap and developing technology base for high quality, melt-based substrate growth and thick, low-doped homoepitaxial layers. Of critical importance for the commercialization of this potentially important material is understanding of doping mechanisms in the monoclinic lattice, where two types of Ga sites and three types of O sites have been identified. A critical literature review of doping and defects of the monoclinic β-phase of gallium oxide is provided in this work. Theoretical fundamentals of both donor and acceptor doping in Ga₂O₃ are reviewed. Advances in doping of epitaxial Ga₂O₃ with a focus on molecular beam epitaxy and ion implantation are critically examined. As doping is fundamentally related to defects, particularly in this material, a review of defect characterization by optical and electrical spectroscopic methods is provided as well. P-type doping, one of the fundamental challenges for Ga₂O₃, is discussed in terms of first-principles calculations and ion implantation of known acceptors such as Mg and N.

The ability to achieve near-atomic precision in etching different materials when transferring lithographically defined templates is a requirement of increasing importance for nanoscale structure fabrication in the semiconductor and related industries. The use of ultra-thin gate dielectrics, ultra thin channels, and sub-20 nm film thicknesses in field effect transistors and other devices requires near-atomic scale etching control and selectivity. There is an emerging consensus that as critical dimensions approach the sub-10 nm scale, the need for an etching method corresponding to Atomic Layer Deposition (ALD), i.e. Atomic Layer Etching (ALE), has become essential, and that the more than 30-year quest to complement/replace continuous directional plasma etching (PE) methods for critical applications by a sequence of individual, self-limited surface reaction steps has reached a crucial stage. A key advantage of this approach relative to continuous PE is that it enables optimization of the individual steps with regard to reactant adsorption, self-limited etching, selectivity relative to other materials, and damage of critical surface layers. In this overview we present basic approaches to ALE of materials, discuss similarities/crucial differences relative to thermal and plasma-enhanced ALD, and then review selected results on ALE of materials aimed at pattern transfer. The overview concludes with a discussion of opportunities and challenges ahead.

Nanocomposites composed of polyethylene oxide (PEO) and sodium alginate (SA), containing varying contents of lithium titanium oxide nanoparticles (Li₄Ti₅O₁₂NPs), were synthesized by solution casting technique. Li₄Ti₅O₁₂ was incorporated into PEO/SA blend and is a valuable biopolymer for its biocompatibility, solubility and eco-friendliness. Structural analysis via X-ray diffraction spectroscopy revealed a decrease in the crystallinity of PEO/SA matrix with increasing nanoparticle content. Complementary Fourier transform infrared analysis verified the presence of strong molecular interactions between Li₄Ti₅O₁₂ and the blend chains. Scanning electron microscopy verified a uniform dispersion of Li₄Ti₅O₁₂ within PEO/SA blend, contributing to the improved properties of the electrolytes, while optical analysis showed a decrease in the bandgap energy, indicating enhanced light absorption and improved suitability for applications in nanodielectric devices. The thermal stability of PEO/SA/Li₄Ti₅O₁₂ electrolyte samples was improved as shown by thermogravimetric analysis. Furthermore, a significant improvement in the ionic conductivity of the filled samples was observed, attributed to the reduced bulk resistance and improved charge transport pathways. Dielectric studies further showed improved dielectric permittivity and reduced dielectric losses for filled samples, enhancing the material’s charge storage capability. These findings highlight the potential of PEO/SA/Li₄Ti₅O₁₂ biopolymer electrolytes for advanced applications in nanodielectric devices and lithium-ions batteries.

Vertical heterojunction NiO/β n-Ga₂O/n⁺ Ga₂O₃ rectifiers with 100 μm diameter fabricated on ∼17–18 μm thick drift layers with carrier concentration 8.8 × 10¹⁵ cm⁻³ and employing simple dual-layer PECVD SiNx/SiO₂ edge termination demonstrate breakdown voltages (V_B) up to 13.5 kV, on-voltage (V_ON) of ∼2.2 V and on-state resistance R_ON of 11.1–12 mΩ.cm². Without edge termination, the maximum V_B was 7.9 kV. The average critical breakdown field in heterojunctions was ∼7.4–9.4 MV. cm⁻¹, within the reported theoretical value range from 8–15 MV.cm⁻¹ for β-Ga₂O_3. For large area (1 mm diameter) heterojunction deives, the maximum V_B was 7.2 kV with optimized edge termination and 3.9 kV without edge termination. The associated maximum power figure-of-merit, V_B²/R_ON is 15.2 GW·cm⁻² for small area devices and 0.65 GW.cm⁻² for large area devices. By sharp contrast, small area Schottky rectifiers concurrently fabricated on the same drift layers had maximum V_B of 3.6 kV with edge termination and 2.7 kV without edge termination, but lower V_ON of 0.71–0.75 V. The average critical breakdown field in these devices was in the range 1.9–2.7 MV. cm⁻¹, showing the importance of both the heterojunction and edge termination. Transmission electron microscopy showed an absence of lattice damage between the PECVD and sputtered films within the device and the underlying epitaxial Ga₂O₃. The key advances are thicker, lower doped drift layers and optimization of edge termination design and deposition processes.