Physics of the Solid State最新文献

GaN/AlGaN multiple quantum well light-emitting diodes (MQW-LEDs) are high-performance electroluminescent sources with broad applications in solid-state lighting, medical diagnostics, and industrial processing. This study systematically investigates the ultraviolet (UV) emission mechanisms and wavelength-tuning strategies of GaN/AlGaN MQWs through Technology Computer-Aided Design (TCAD) simulations. Unlike conventional GaN heterojunction LEDs, the emission characteristics of the MQW-LEDs are governed by quantum confinement effects (QCE) and polarization field engineering. By optimizing structural parameters, we achieve tunable UV emission across 335–366 nm, with optimized electroluminescence (EL) centered at 342.6–348.7 nm. Deconvolution analysis of EL spectra reveals that the emission blue shift originates from enhanced QCE due to reduced well thickness-an effect that not only increases carrier wavefunction overlap and radiative recombination efficiency by also suppress non-radiative recombination losses by minimizing lattice relaxation and interfacial strain accumulation. These findings establish critical design guidelines for bandgap engineering in nitride-based MQWs and provide theoretical foundations for developing high-efficiency UV LEDs.

The bromobenzene (BrB) based single electron transistor (SET) has been investigated as a toxic gas sensor using the density functional theory based ab-initio approach. The adsorption behaviour of the considered toxic gas molecules (NH₃, AsH₃, HCN, and COCl₂) and bromobenzene has been assessed through the adsorption energy and distance, density of states profiles, and Bader charge transfer analysis. The sensing behaviour is further analyzed by the charge stability diagram of SET and horizontal and vertical line scans over it, which were further treated as a unique fingerprint of toxic gases for detection. It has been observed that the modelled bromomobenzene based SET offers a better sensing ability, adsorption strength, and recovery time in comparison to its counterparts, making it a suitable candidate for toxic gas detection.

Gold (Au) catalyzed zinc oxide (ZnO) nanowires (NWs) were synthesized onto silicon (Si) substrates using a thermal evaporation technique. The effect of different Au film thicknesses (1, 3, 5, and 7 nm) on the physical features of ZnO NWs is studied in detail. The surface morphology, elemental composition, crystalline structure, optical behavior, and crystallographic information of the grown samples are evaluated using field emission scanning electron microscope (FESEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffractometer (XRD), photoluminescence (PL) spectroscopy, and high-resolution transmission electron microscope (HRTEM). FESEM images shown that the thickness of the Au film is a critical factor in forming Au nanoparticles (NPs) for growing ZnO NWs with different diameters (ranging from ~31 to ~83 nm) and lengths (ranging from ~318 to ~2923 nm). Based on microscopic analysis, the growth of NWs could be controlled by the vapor-liquid-solid (VLS) nucleation mechanism. EDX spectra showed the expected elements (O, Zn, and Au) in the synthesized NWs structure. XRD analysis disclosed that the grown samples are polycrystalline in nature and had a hexagonal wurtzite structure, with the (002) plane as the dominant preferred direction. PL characterization demonstrated that the concentration of surface oxygen vacancies (V_ο) in smaller NWs is higher than in larger NWs. HRTEM images indicated that the ZnO NWs had a high crystallinity and grew along the [0001] direction.

The paper provides a theoretical analysis of the scattering process within a ferromagnet-strain/Kekulé-Y/superconductor graphene heterostructure. Equal-valley pair correlations in the vicinity of the ferromagnet-Kekulé-Y interface have been calculated, revealing a direct relationship between valley-related anomalous Andreev reflection, which is caused by the proximity effect in the presence of Kekulé-Y‑shaped graphene. The results show that the action of magnetic vector, strain and Kekulé-Y graphene caenhance the anomalous Andreev reflection. Moreover, by calculating the charge conductance and valley polarization conductance, our results reveal that the valley polarization conductance can be enhanced by Kekulé-Y shaped, strain and magnetic vector. These findings may provide a tool for detecting the entanglement of the equal valley superconducting pair correlations in hybrid structures.

Polyoxymethylene (POM) is a high-performance semi-crystalline thermoplastic widely used for its excellent mechanical strength, wear resistance, and dimensional stability. This study investigates the mechanical and thermal behavior of POM under large deformations through tensile testing and thermal analysis. The results indicate that POM exhibits linear elastic behavior at low strains, transitioning to nonlinear viscoelastic and plastic behavior at higher deformations. Stress whitening and microvoid formation significantly influence failure mechanisms. Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) confirm POM’s high crystallinity (~40%) and thermal stability, with a melting temperature of 166°C. Scanning Electron Microscopy (SEM) reveals cavitation and fibrillation as dominant damage mechanisms. The findings highlight the challenges of substituting POM due to its unique property balance. Further research should focus on predictive plasticity models to optimize POM’s industrial applications.

The performance of Dual Material Heterodielectric Graphene Nanoribbon channel tunnel FET (DM-H-GNR-TFET) and TFETs based on Silicon (DM-H-Si-TFET and DM-Si-TFET) are compared in this work. The narrow bandgap, higher carrier mobility, and fast saturation velocity of the two-dimensional material GNR have led to its proposal as a channel material to improve device performance. This analysis of the proposed structure’s DC, RF, performance and thermal stability has been conducted. The GNR-based channel TFET demonstrates a higher current ratio of the order of 10¹⁴, in contrast to the Si-based TFET (~10¹¹) with improved subthreshold swing. This investigation encompasses the influence of temperature on the DC parameters, in addition to the analog/RF figures of merit for the proposed structure. Moreover, the results are compared with existing literature on TFETs, revealing that DM-H-GNR-TFET excels Si-based TFETs and other variants.

Triglycine sulfate crystals doped with P-Chlorophenzophenone (TGS P-CPP) were grown and characterized using various techniques. Single-crystal X-ray diffraction analysis revealed the crystal structure and lattice parameters. Powder XRD confirmed the crystalline nature of the material. Fourier transform infrared spectroscopy (FTIR) identified the functional groups present in the crystal. UV-Vis spectroscopy showed a wide transparency range, making it suitable for nonlinear optical applications. The crystal exhibited a second harmonic generation efficiency of 0.96 times that of KDP. Thermal analysis revealed a melting point of 236°C and a decomposition point of 347.6°C. Dielectric studies showed a high dielectric constant and low dielectric loss, indicating potential applications in nonlinear optical devices. Impedance spectroscopy revealed a negative temperature coefficient of resistance behavior and a Debye-type relaxation process. The results of this comprehensive characterization study demonstrate the potential of TGS P-CPP single crystals for nonlinear optical applications.

In this work, the surface of commercially pure titanium grade VT1-0 was strengthened by electron beam treatment, which significantly increased the fatigue life of the material. The structural and phase states and defect substructure of titanium subjected to cyclic fatigue tests were studied using scanning and transmission electron diffraction microscopy. It was shown that the surface layer formed as a result of electron beam irradiation contains micropores oriented parallel to the sample surface. Irradiation of commercially pure titanium VT1-0 with a high-intensity pulsed electron beam under the conditions (16 keV, 25 J/cm², 150 µs, 3 pulses, 0.3 s^–1) leads to grain refinement and the formation of an intragranular substructure, i.e., to the development of additional structural levels in the submicron and nanometer range in the surface layer.

The electronic and optical properties of AlAs_1–xP_x under the influence of phosphorous concentration at various values of temperature have been studied. The optical lattice vibration frequencies in zinc-blende AlAs_1–xP_x have been investigated based on a pseudopotential method (EPM) under the virtual crystal approximation (VCA). It is demonstrated that the composition dependency of energy bandgaps is non-linear. It is discovered that the AlAs_1–xP_x is an indirect semiconductor alloy in the range x = 0–1. Overall, our results demonstrated an acceptably high degree of agreement with published data. The findings collected in this study could be useful for photonic technological uses.

Optical quenching of photocurrent, the dependence of the quenching magnitude on the wavelength of the additional quenching light, and temperature were studied in stoichiometric, nonstoichiometric, and copper-doped CdIn₂S₄ samples. It was shown that a deficiency of cadmium and indium in CdIn₂S₄ does not change the energy distance of slow recombination centers from the valence band top ((E_{{{text{vr}}}}^{{text{0}}}) = 0.73 eV for both undoped samples and those with cadmium and indium deficiency), whereas doping the crystals with copper leads to a slight increase in this energy distance ((E_{{{text{vr}}}}^{{text{0}}}) = 0.86 eV).