Physics of the Solid State最新文献

This study provides a comprehensive investigation into the structural, optoelectronic, and elastic properties of inorganic metal halide perovskites FrBX₃ (B = Pb, Zr; X = Br, Cl) using first-principles calculations based on density functional theory (DFT). Structural analysis confirms the stability of these perovskite phases through optimized lattice parameters and positive formation energies. Electronic band structure calculations reveal that FrZnX₃ compounds exhibit direct band gaps, while FrPbX₃ compounds possess indirect band gaps. Using the GGA-PBE functional, the band gaps are found to decrease in the order: FrPbCl₃ (2.237 eV), FrPbBr₃ (1.795 eV), FrZnCl₃ (1.185 eV), and FrZnBr₃ (0.057 eV), highlighting their potential for photovoltaic applications, particularly in solar energy harvesting. The optical properties, evaluated via dielectric functions, absorption coefficients, and refractive indices, demonstrate strong absorption in the visible region, suggesting their suitability as efficient light-absorbing materials. Furthermore, the elastic properties, including elastic constants, bulk modulus, shear modulus, and Poisson’s ratio, confirm the mechanical stability and ductility of all studied compounds, as they satisfy the Born stability criteria. Moreover, the calculated elastic anisotropy indicates that these materials exhibit moderate directional dependence in their mechanical response, which is advantageous for thin-film fabrication processes. Overall, the combination of favorable electronic, optical, and mechanical properties makes these Fr-based perovskites promising candidates for use in next-generation photovoltaic devices and other optoelectronic applications.

A novel approach for sintering In₂O₃ ceramics using chemical vapor transport based on chlorine as a transport agent has been developed. Thermodynamic analysis has shown that this transport agent is the most promising among halogens for low-temperature sintering. The vapor phase composition of In₂O₃−MeO₂−Cl₂ (Me = Si, Ti, V, Ge, Zr, Sn, Ce, Hf) CVT systems has been calculated, and it has been shown that Cl₂ should promote a fast dissolution rate of SnO₂ and GeO₂ dopants in ceramics. It has been experimentally demonstrated that in the case of using Cl₂, a dense gaseous medium of In- and Sn-containing species is formed, which contributes to high uniformity of indium-tin oxide ceramics. The advantages of the proposed sintering method consists in: low sintering temperature of 800°C, increase in density by 20–30%, possibility of a decrease in resistivity by a factor of 10², higher thermal stability of CVT ceramics, as well as higher structural perfection of thin films deposited by high-power magnetron sputtering.

This study investigates the temperature-dependent behavior of the step-channel dual-metal double-gate tunnel field-effect transistor (SCP-DG-TFET) incorporating an InGaSb pocket, within the range of 250 to 450 K, highlighting its thermal reliability and operational robustness. The InGaSb pocket, characterized by a low bandgap and minimal lattice mismatch with GaSb, significantly enhances carrier injection efficiency and strengthens electrostatic control within the device. The SCP-DG-TFET exhibits remarkable switching characteristics, achieving a high I_on/I_off ratio of 2.65 × 10¹³, alongside an improved subthreshold swing (SS) of 25.94 mV/dec, indicating efficient suppression of leakage currents. The device achieves a transconductance (g_m) of 4.98 mS, which aids in maintaining a stable threshold voltage (V_th) of 0.384 V. Furthermore, it delivers an ON-state current (I_on) of 1.10 mA/µm and an OFF-state leakage current (I_off) of 5.83 × 10⁻¹⁷ A/µm. These findings highlight the device’s capability for efficient switching, making it a promising candidate for future low-power and high-frequency electronic applications.

Photoluminescence (PL) spectra of CdSe single crystals grown by Bridgman technique are investigated in the wavelength range from 640 (1.938 eV) to 760 nm (1.632 eV) at temperatures between 15 and 200 K. PL spectra consist of a series of narrow bands of short-wavelength exciton emission and wider bands of impurity emission, the energy position and intensity of which are determined by the sample temperature. It is shown that the total exciton energy, including its kinetic energy, weakly depends on temperature and is equal to 29–30 meV for temperatures below 70 K, and then increases linearly to the value of 38 meV at 200 K. At low temperatures, the impurity PL band with phonon replica with the energy of LO-phonon equal to (25.6 ± 0.8) meV is attributed to donor–acceptor (D–A) pairs and is of self-activated nature. With increasing temperature, as shallow donors are ionized, this band is attributed to recombination of free electrons with the holes localized at acceptor level with the energy depth of 0.117 eV. In the short-wavelength range of PL spectra for CdSe samples annealed in the melt of Cd and CrCl₃ salt, a new PL band is observed at 649 nm (1.9106 eV), with localization energy exceeding the band gap energy. This band is supposed to be caused by intracenter transitions within the background impurity ions, probably, of manganese. The possible structure of the radiative center is discussed.

We investigate a hybrid quantum system consisting of two coupled optical cavities, each containing an ensemble of coherently pumped artificial or real two-level atoms. The system is modelled within the dressed-state formalism, accounting for coherent driving and dissipative interactions with independent electromagnetic reservoirs. Focusing on the regime where the Rabi frequency greatly exceeds the collective spontaneous emission and cavity decay rates, respectively, we derive the equations of motion characterizing the system and analyse its steady-state behaviours. Special attention is given to the scenario in which only one cavity contains a pumped multi-atom ensemble, and as a consequence, coherent excitation transfer to the second cavity occurs via cavity–cavity coupling. In this case, the mean photon number in the second cavity mode scales proportional to the squared number of atoms, i.e., N² from the first cavity. The proposed model offers insight into light–matter interaction in composite systems and suggests viable mechanisms for engineering collective interactions and non-local excitation transport in quantum optical platforms.

The structural, electronic, thermodynamic, and thermoelectric properties of GaNi_1–xTa_xSb alloys (x = 0.125–0.875) have been investigated using the FP-LAPW method within the framework of the generalized gradient approximation (GGA) and the modified Becke–Johnson (mBJ) potential for electronic properties. The results predict that these alloys exhibit ferromagnetic behavior. The calculated band structures and Density of states reveal an overlap between the valence and conduction bands, indicating a metallic character for all compositions considered. Furthermore, the quasi-harmonic Debye model has been employed to evaluate the thermodynamic properties of the alloys over the temperature range of 0–1800 K at ambient pressure (P = 0 GPa). The thermoelectric performance was assessed through electrical conductivity, thermal conductivity, Seebeck coefficient, and power factor. Among the studied compositions, GaNi_0.25Ta_0.75Sb and GaNi_0.75Ta_0.25Sb exhibit the highest power factors, suggesting their potential for high-temperature thermoelectric applications.

Cadmium oxide (CdO) has been recognized as a promising diluted magnetic semiconductors (DMSs) for its various applications in spintronics, high sensitivity gas sensors and electrochemical sensors, etc. The present work reports the synthesis, structural, magnetic and dielectric properties of pure CdO and Mn-doped CdO nanoparticles with Mn-content (x = 7%) which were synthesized using simple co-precipitation method. Structural analysis via X-ray diffraction patterns revealed a cubic crystal structure in all materials, with no discernible impurity phases. FESEM images indicated a reduction in the grain size of CdO after doping of Mn-content. Magnetic measurements revealed a superparamagnetic behavior in CdO with magnetization (0.05 emu/g) at 5 K temperature and this superparamagnetic ordering was notably augmented through Mn-doping with magnetization (0.5 emu/g). In M(T) curves, blocking temperature (T_b) showed the transition from ferromagnetic to super paramagnetic behavior, also confirmed the presence of superparamagnetic behavior at low temperature in these nanoparticles. The dielectric constant is 25 × 10² and electrical conductivity is 5 × 10^–5 Ω^–1 cm^–1 of CdO. Both are found to increase (dielectric constant 22 × 10³ and electrical conductivity 15 × 10^–5 Ω^–1 cm^–1) after doping of Mn-content, may be due to increase in free charge carriers.

We present the first experimental report of the complete elastic tensor of incipient ferroelectric KTaO₃ between 9.6 and 307 K, using resonant ultrasound spectroscopy (RUS). The elastic constants C₁₁ and C₄₄, as well as the bulk and shear moduli increase roughly linearly upon cooling. Deviations from such dependence are a result of impurities. Zener anisotropy factor is 0.697 at room temperature and decreases to 0.627 at 9.6 K, indicating increasing elastic anisotropy. The temperature dependence of C₁₂ is anomalous with no stiffening on cooling, which could be a result of different defect species influencing C₁₂ but not the other constants, possibly due to defect anisotropy. The values of elastic constants and anisotropy are compared at room temperature and below 10 K with the literature reporting experimental results and density functional theory calculations.

This study explores the structural, morphological, optical and photoluminescent properties of pure CdO, CdO/La₂O₃, and CdO/La₂O₃/PVP nanocomposites synthesized via the microwave irradiation method. XRD analysis confirms the face—centered cubic phase of CdO and the successful incorporation of La₂O₃ and PVP, evidenced by changes in lattice parameters and reduced crystallite sizes. Fourier transformed infrared spectroscopy (FTIR) analysis detects functional groups associated with La₂O₃ and PVP, confirming their integration into the CdO matrix. TEM reveals smaller particle sizes, improved dispersion and enhanced crystallinity in the composites. UV-Vis spectroscopy shows a bandgap increase from 3.4 eV (CdO) to 4.2 eV (CdO/La₂O₃/PVP), attributed to the Burstein–Moss effect and structural changes. PL studies indicate enhanced multi-band emissions and defect related transitions, suggesting improved charge separation and reduced recombination. Under UV irradiation, CdO/La₂O₃/PVP exhibits the highest photocatalytic degradation efficiency for MB dye (65.77% in 120 min), outperforming CdO/La₂O₃ (48%) and pure CdO (22%) due to smaller particle size, more active sites, and better charge carrier separation. These results demonstrate the potential of CdO-based nanocomposites in photocatalysis, optoelectronics and energy harvesting applications.

This study investigates the electrical and magnetic characteristics of chromium phosphide (CrP) through the introduction of transition metal (TM) atomssuch as Mn and Fe, as dopants. The FP-LAPW method has been employed under the density functional theory (DFT) framework, utilizing the WIEN2k software. The GGA approximation was utilized as the exchange-correlation potential to determine the solution of the Kohn–Sham equation. To study the band structure, the full potential linearized augmented plane wave (FP-LAPW) method has been utilized. The stable atomic structure of chromium phosphide has been derived from the zinc blende (ZnB) configuration. Furthermore, Cr_1–xTM_xP demonstrates a zinc-blende phase when doped with x = 0.125 and 0.25 concentrations. The phenomenon of half-metallic behavior is exhibited in CrP when the atomic constants are greater than or equal to 4.48 Å, and the muffin-tin radii (RMT) of Cr and P are set at 2.28 and 2.01, respectively. Analysis of Cr_1–xTM_xP (TM = Mn and Fe) at different doping concentrations (x) reveals that the material retains its half-metallic characteristics at low doping levels, but this feature declines as the doping levels increase. The magnetic moments of Cr_0.75Fe_0.25P are greater than those of Cr_0.75Mn_0.25P because of the interaction between the hybridized 3d-orbitals of the host Cr and the dopant Mn/Fe. These findings indicate that Cr_1–xTM_xP (TM = Mn and Fe) at low concentrations have great potential as materials for spintronic applications.