Physics of the Solid State最新文献

The theoretical investigation of the temperature dependence in hybrid one-dimensional photonic crystals with a metal defect involved simultaneously considering thermal expansion effect and thermal-optical effect. Firstly, we study the effect of the number of iterations in the H(LH)^NH(LH)^N and H(LH)^NSH(LH)^N systems, where H (GaAs) and L (Bi₄Ge₃O₁₂ “BGO”) are two different materials with constant refractive index nH (n_GaAs = 3.3) and nL (n_BGO = 2.31), respectively. S is a metal chosen as the Ag. The presence of metal S enhances noticeably the sensitivity for the temperature. It has been shown that when N increases the transmission peak λ_peak shifts to higher wavelengths for the structure H(LH)^NH(LH)^N. We show that the proposed device H(LH)^NSH(LH)^N can be used as a temperature sensor. Indeed, the sensitivity changes from the value 4.5 pm K^–1 in the absence of the metal layer to the value 17 pm K^–1 in its presence. Enhancing the sensitivity of the H (LH)^NSH(LH)^N component, we proceeded to a deformation of the system by the application of a law of the type y = x^1 + k, where y denotes the deformation coordinate of the structure H(LH)^NSH(LH)^N and x the coordinate before deformation. The degree of deformation is defined by the coefficient k. The value of N is chosen equal to 4. This value corresponds to the minimum of layers of the system leading to its satisfactory performance. We show in this case that the sensitivity increases by increasing the positive value of k.

As the demand for sustainable energy solutions rises, the development of energy-efficient technologies becomes imperative. Smart windows, incorporating thermochromic materials, emerge as promising contributors to reducing building energy consumption. Vanadium dioxide (VO₂), known for its thermochromic properties, faces challenges in commercial application due to its limited visible light transmittance. This study addresses these challenges by utilizing quartz as a substrate and depositing VO₂ thin films using radio frequency sputtering. To enhance optical performance, a bilayer structure was created by integrating this single-layer film with SnO₂. Room-temperature X-ray diffraction confirmed the single-phase growth of VO₂ on quartz, and XRD validated the proper fabrication of films. Ultraviolet-visible spectroscopy at room temperature substantiated the improved transmittance of the SnO₂/VO₂ bilayer, marking a significant advancement toward more efficient and commercially viable smart windows. This research highlights the potential of SnO₂-based thin films in mitigating the visible light transmittance limitations of VO₂, thus opening avenues for advanced smart window applications with enhanced energy-saving capabilities. Additionally, Atomic Force Microscopy (AFM) was employed to compare the roughness of the films, and the impact of reduced roughness on optical transmittance was evaluated. The results contribute to the optimization of smart window technologies for broader sustainable energy applications.

This study focuses on the synthesis and characterization of calcium–zinc Ca_1–xZn_xFe₂O₄ (x = 0, 0.25, 0.50, 0.75, 1.0) (Ca–Zn) ferrite nanoparticles by the solution combustion synthesis (SCS), exploring their potential applications in various technological fields. The characterization involved a comprehensive analysis of their structural, magnetic, and morphological features using various techniques such as X-ray diffraction, transport properties, biological studies and magnetic measurements. Understanding the synthesis process and the resulting nanoparticle properties is crucial for harnessing their unique attributes in diverse fields like biomedical engineering, magnetic storage.

BaFe_12–2xNi_xZr_xO₁₉ (x = 0–1) ferrites were successfully synthesized by hydrothermal method based on metal chloride. The synergistic effects of Ni²⁺–Zr⁴⁺ ions doping and heat treatment on microstructure and ions distribution to tailoring the magnetic properties were studied. Without calcination the traces of BaCO₃ appears in all samples where the Fe₂O₃ phase appears at x > 0.6. It exhibits very good hexagonal crystals with doping content x < 0.8, but deviate from hexagonal flakes for x = 1. With low temperature 950°C calcination, the pure phase and the uniform distribution of particle size were obtained. XPS characterization show that the concentrations of non-lattice oxygen decrease, where Fe²⁺ contents slightly increase and then decrease with increasing Ni²⁺–Zr⁴⁺ ions. The comprehensive magnetic properties, especially the saturation magnetization, of doped ferrites prepared by hydrothermal method decrease sharply when x > 0.6. The anisotropy field also decreases to the lowest at x = 0.6. By comparing the magnetic properties under heat treatment conditions, the optimum annealing temperature is 1000°C, where the saturation magnetization (Ms) increases up to 59.54 emu/g at x = 0.8. Thus, the as-synthesized Ni²⁺–Zr⁴⁺ doping strontium barium hexaferrite will be useful for the applications in security switching, microwave absorption and recording media.

In this study, we obtain an expression to calculate the probability of electron transmission in a linear chain of N quantum dots with fluctuations of the potential levels on the Fermi seas of each point. Here, the transmission probability model is based on concepts of Probability Theory. From this expression, we determine the transmission in the chain under these fluctuations. Besides, Anderson localization and other transport properties were studied using numerical simulations. Results show the impact of fluctuations on transmission efficiency and aid in comprehensively understanding electron transport in quantum dot systems.

In this research, a mesoporous Mn/Fe/N-doped ZnO nanocomposite was developed via solvothermal synthesis, focusing on its optical and magnetic potentials for dye degradation. FTIR spectroscopy identified unique functional groups, while EDX analysis confirmed its elemental composition. BET analysis showcased an expanded surface area due to mesoporosity, evidenced by a type IV isotherm. UV-Visible spectroscopy revealed a red shift and optical band gap reduction from 3.13 to 2.68 eV, indicating improved light absorption. SEM provided insights into distinctive morphologies, and PL studies showed reduced electron-hole recombination in highly doped samples. SQUID measurements verified the nanocomposite’s ferromagnetic characteristics. These properties collectively enhance its photocatalytic efficacy against Congo red and Methylene blue dyes, presenting a viable solution for environmental clean-up.

Janus In₂Ge₂Te₆ bilayer exhibit the potential for low thermal conductivity due to their complex geometry and large atomic mass contrast. The results demonstrate that the intersection of the low-frequency optical branch and the longitudinal acoustic phonon branch (LA) within the Janus In₂Ge₂Te₆ bilayer structure, combined with a larger average atomic mass, leads to a smaller phonon group velocity, a higher phonon scattering rate, a lower phonon relaxation time, and a stronger anharmonicity. These factors contribute to the lower thermal conductivity of the Janus In₂Ge₂Te₆ bilayer. The Janus In₂Ge₂Te₆ bilayer structure exhibits a maximum and minimum lattice thermal conductivity of about 0.35 and 0.1 W/(m K) at 300 and 1000 K, respectively.

The mechanisms of hardening surface layers of carbon steel 45 after combined treatment including electroexplosive boroaluminizing, aluminizing with silicon carbide, and electron beam processing (EBP) are revealed. The combined processing leads to an increase in the hardening depth. After the electroexplosive boroaluminizing and EBP, the microhardeness is 16 GPa and the hardening depth is 90 μm; after the electroexplosive aluminizing combined with silicon carbide and EBP, the microhardness is 12.5 GPa and the hardening depth is 50 μm. In the initial state, the microhardness is 2 GPa. In the conditions of dry sliding friction, the wear resistance increases by a factor of 43 after electroexplosive boroaluminizing and EBP, and by a factor of 12 after electroexplosive aluminizing with silicon carbide. The surface hardening is achieved as a result of the formation of fine-disperse nonequilibrium structure containing strengthening phases. The models developed in this work allow one to explain the results by the peculiarities of the thermal and diffusion processes during EBP.

Using the method of compiling an expression invariant with respect to the operations of inversion of time and coordinates for the energy of a magnetic structure under the influence of some external effective field which is considered an independent vector parameter of the problem, a system of differential equations generalized the Landau–Lifshitz and Hilbert results is obtained. When obtaining these equations, the explicit expression for the dissipative function are obtained taking into account the pseudovector the nature of the magnetic field strength. The analysis of the obtained equations for the case of strong magnetic fields is carried out and the possibility of the existence of practically continuous oscillations of the magnetization at a frequency (bar {omega }) = (xi {{gamma }_{e}}{{M}_{0}}) (where coefficient ξ is greater than unity) is predicted.

Structure and composition of spray pyrolized thin films in ZnO–In₂O₃ system with a relative atomic zinc content (Zn/In) in the range of 0.125–2 is investigated using X-ray diffraction analysis. These nanostructured films constitute of 1 to 5 In- and Zn-based oxide nanocrystalline phases including In₂O₃(ZnO)₃ with superlattice structure and ZnO with rather unexpected rocksalt structure. The octahedral coordination of Zn atoms and practically the same Zn–O distances as in the case of In₂O₃ facilitate a growth of ZnO rock salt on the surface of In₂O₃ nanocrystals. The modified Williamson-Hall method is applied to determine the crystallite size and micro-strain in the predominant In₂O₃ phase. The monotonous crystallite fineness of this phase with increase of Zn content and monotonous increase of In–Zn-based oxide crystallites is established. A mutual doping of In₂O₃ and ZnO nanocrystallites, leading to the formation of n–n⁺ contacts at their boundaries, has been revealed. Model representations about the influence of the nanocomposite structure of films on their electrical properties are proposed.