Physics of the Solid State最新文献

The full potential linearized augmented plane wave (FP-LAPW) method, employing density functional theory (DFT) within the generalized gradient approximation (GGA), is utilized to investigate the structural, electronic and magnetic characteristics of the rare earth element based Pr₂CoX (X = Al, Ga, In) full Heusler compounds. The results indicate that, at the equilibrium volume, the Hg₂CuTi-type structure is energetically more stable than the Cu₂MnAl-type structure for Pr₂CoX (X = Al, Ga, In). The electronic band structure of Pr₂CoX (X = Al, Ga, In) reveals an indirect band gap with the minority spin, suggesting half-metallic behavior. The calculations of magnetic properties affirm the half-metallic nature of these compounds, with total magnetic moment of 3.99 μB.

In this paper, we delved into the intricacies of In_0.17Al_0.83N/GaN high-electron-mobility transistors (HEMTs) using a comprehensive simulation model and by Leveraging the capabilities of Nextnano simulation software. We extensively explored how different thicknesses of the AlN buffer layer impact electronic and electrical properties. Our study was centered on scrutinizing the density and mobility of the two-dimensional electron gas (2-DEG) within the In_0.17Al_0.83N/GaN HEMT structure. Aiming to understand how different AlN buffer layer thicknesses impact device performance. Our findings unveil a crucial relationship between AlN buffer layer thickness and critical performance metrics. Specifically, we observed significant trends in output current and transconductance, shedding light on the direct influence of AlN thickness on device behavior. Our simulations identified an optimal AlN thickness of 350 nm, demonstrating the highest output current and surpassing a transconductance peak of 510 mS/mm. Importantly, our computational predictions closely align with experimental observations, validating the reliability and accuracy of our simulation model. Through this meticulous analysis, we contribute valuable insights that can guide the design and optimization of In_0.17Al_0.83N/GaN HEMT, paving the way for improved device performance and functionality across various electronic applications. Our study underscores the importance of considering AlN buffer layer thickness in designing and engineering high-performance HEMTs, highlighting avenues for future research and development in semiconductor device technology.

Triple perovskite La₃Mn₂FeO₉ powder was synthesized via the sol gel method. The microstructural, morphological and magnetic features of the prepared perovskite sample were examined by means of X‑ray diffraction (XRD), filed-emission scanning electron microscopy (FE-SEM), and vibrating sample magnetometry (VSM). The XRD pattern was refined using the MAUD software based on the Rietveld program. The results confirmed that the sample crystallized in a trigonal structure, with a crystallite size measuring approximately 257 ± 5 nm and a microstrain of about 0.16%. The FE-SEM image revealed spherical like-particles with an average grain size in the vicinity of 514 nm. The VSM curve revealed that the prepared La₃Mn₂FeO₉ powder exhibited a ferromagnetic behavior, and subsequent fitting using the law of approach to saturation revealed a saturation magnetization of 1.156438 ± 0.00384 emu/g.

In this study, Zn_{1 – x}Fe_xS thin films were synthesized using the chemical spray pyrolysis technique at a substrate temperature of 450°C and with varying Fe concentrations. The spraying solution was prepared by combining distilled water with 0.05 M zinc chloride (ZnCl₂), 0.05 M iron chloride (FeCl₃⋅6H₂O), and 0.2 M thiourea ((NH₂)₂CS). The initial solution was atomized onto heated glass substrates using an ultrasonic nebulizer operating at a frequency of 1.63 MHz and dry air. The morphology of the films was examined by scanning electron microscopy (SEM). The crystal structures were determined by X-ray diffraction analysis (XRD). The optical properties of the films were analyzed using a UV spectrometer. The energy band gap of the films was defined using the absorption spectrum.

ZrTi alloys have potential applications in critical parts of spacecraft. As lightweight design is a fundamental requirement for spacecraft, incorporating light elements into ZrTi alloys is a feasible approach. In this paper, we investigated the tensile deformation behavior of ZrTi doped with light element by using the plane-wave pseudopotential density functional method. Covalent Ti–Zr bonds accommodate deformation by softening and breaking at large tensions, and structural stability of ZrTi and ZrTiX (X = B, Al, Ga, and V) is determined by the strength of these Ti–Zr bonds under tension. The results show that the lower doped concentrations of light element decrease the tensile strengths. However, there is no obvious difference in tensile strengths along [11(bar {2})0] direction between ZrTi and ZrTi_0.875Al_0.125. The results of Mulliken overlap populations indicate that different tensile strengths of ZrTiX should be resulted from different strengths of covalent Ti–Zr bonds. The incorporation of light element dopants does not strengthen all chemical bonds and weakens strengths of covalent Ti–Zr bonds, indicating that experimental strengthening mechanism of ternary ZrTiX alloys could be ascribed to Hall–Petch effect.

The temperature and pressure dependences of low-frequency Raman scattering were studied on structural phase transformations of Sr₂Ta₂O₇ ceramics. The Raman spectrum was measured over a temperature range from 0 to –185°C. The temperature dependence of the Raman shift of a low-lying mode of the B_1g symmetry shows at T = –110°C. This anomaly of Sr₂Ta₂O₇ is related to a ferroelectric phase transition. During cooling, the peak width of the B_1g mode shows a change at 150°C, and the temperature dependence of Raman shifts of B_3g, and B_1g modes becomes abnormal. Under high pressure, we discovered a phase transition between 4 and 5.5 GPa. Angle-dispersive X-ray diffraction data suggest the phase transition from incommensurate to commensurate states.

In this work, we present first-principles DFT calculations to predict the structural and electronic properties of HgX (X = S, Se, and Te) compounds. First-principles methods using the local density approximation (LDA) and generalized gradient approximation (GGA) lead to an underestimation of the band gap energy. The objective of this work is to use various exchange and correlation potentials (LDA, GGA-PBE, EVGGA, MBJGGA, MBJLDA, etc.) to determine the band gap energy and electronic properties. We show that the use of the modified Becke–Johnson (mBJ) approximation leads to very good agreement with the experimental band gap energies for mercury chalcogenides.

In this work, we studied by simulation the performance of a cancer sensor based on 1D symmetrical photonic crystal. The proposal 1D photonic crystal structure is (AB)⁵C(BA)⁵ where A = TiO₂ with high refractive index, B = SiO₂ with low refractive index and layer C is a blood cell. The study was conducted using the Transfer Matrix method (TMM) method. So, the transmissions spectra, the sensitivity as well as the quality factor of the sensor for different blood cell samples including normal blood cells and various cancerous blood cells: Jurkat, HeLa, PC-12, MDA-MB-231, and MCF-7 were obtained. The obtained results have shown the improvement in the performance of the proposal 1D photonic crystal sensors, namely sensitivity and quality factor, as a function of the thickness of the sample layer C and the angle of incidence in case of the two polarization mode.

The electron mobility characteristics of a ZnMgO/ZnO heterostructure are systematically investigated by an ensemble Monte Carlo method. Screening effects are included in all electron scattering mechanisms. The mobilities are calculated for a temperature range of 4 to 300 K and Mg contents ranging from 8.5 to 44%. In this range, dislocation scattering (DS) and interface roughness scattering (IFR) are highly effective for low and high values of Mg compositions, respectively. Screening effects must be considered in scattering mechanisms to achieve a reasonable agreement with existing experimental results. Our findings could be significant for the design and optimization of ZnO-based devices.

This study investigates the impact of spin torque diode (STD) effect in a composite spin valve pillar, comprising distinct magnetic and non-magnetic layers arranged as AF/F0/NM1/F1/NM2/F2. Our investigation delves into the foundational mechanisms governing the STD effect within this magnetic multilayer system. Through the utilization of the composite spin valve pillar as a dynamic platform, we unravel the intricate interplay between spin-dependent charge transport and magnetic fields. Our inquiry is to understand diverse structural parameters, allowing us to unveil its operational capabilities and optimize its functionality across varied operating conditions. Furthermore, our exploration encompasses the quantification of detection sensitivity, scrutinizing the relationship between output voltage and applied input power. In our study, we have done an analysis of crucial parameters such as current, resistance, and sensitivity in the STD system. Our findings showcase the manifestation of the spin diode effect in low-dimensional magnetic structure. This finding indicates the feasibility of fabricating a spin diode device with diverse potential applications.