Physics of the Solid State最新文献

In this paper, we have synthesized zinc oxide (ZnO) nanoparticles using the sol–gel method. Zinc acetate dihydrate ({text{Zn(C}}{{{text{H}}}_{3}}{text{C}}{{{text{O}}}_{2}}{{{text{)}}}_{2}}cdot2{{{text{H}}}_{2}}{text{O}}), sodium hydroxide (NaOH) were used as a basic precursors for the synthesis. The synthesized crystalline powder was characterized by X-ray diffraction (XRD). The XRD studies explain that zinc oxide nanoparticles have a single phase with a wurtzite hexagonal structure. The theoretically calculated lattice parameters have obtained using the famous Scherrer equation and agree well accordance with the standard JCPDS card number. Various relevant physical parameters such as micro-strain, stress, energy density, and crystalline size have calculated by using the modified Williamson–Hall (W–H) assuming uniform deformation (UD) model, uniform stress deformation (USD) model and uniform deformation energy density (UDED) model. The root mean square (rms) lattice strain (leftlangle {{{varepsilon }_{{{text{rms}}}}}} rightrangle ) theoretically calculated from the interplanar spacing and strain estimated obtained the USD and UDED models are different due to consideration of anisotropic crystal nature. The obtained results shows that the average particle size of zinc oxide nanoparticles from Scherrer’s formula and the W–H method are the best intercorrelated. All the calculated physical parameters from the Willamson–Hall plot are tabulated, compared, and found to match well the value of bulk zinc oxide. Similarly for the synthesized ZnO nanoparticles, the optical properties were analyzed by UV-vis spectroscopy which confirmed the bandgap energy.

We present a theoretical design for a photonic structure based on one-dimensional inhomogeneous p-erfect and defect loop waveguide network. The structure is composed of a segment of length d₁ (where d₁ = (d_{1}^{'} + d_{1}^{{''}})) connected to a loop of lengths d₂ and d₃ (where d₂ = (d_{2}^{'} + d_{2}^{{''}}) and d₃ = (d_{3}^{'} + d_{3}^{{''}})) and the permittivity of each piece of length d_i (i = 1, 2, 3) is different. We calculate the dispersion relation and transmission coefficient using the Green function method based on the interface response theory. The perfect loop waveguide generates photonic bandgaps depending on the number of cells and the structure parameters. The insertion of a defect in the structure generates defect modes inside the gaps. These defect modes can be precisely controlled in terms of frequency and transmission rate by tuning the length and permittivity of the defective segment. The proposed structure offers promising potential for the development of advanced photonic filters and other photonic devices.

The effect of deprotonation of the hydrazine-based ditopic isomeric terpyridine-like ligand on the spin crossover behavior of the Fe(II) complex is studied. The deprotonation is modelled by the appearance of a negative charge on the nitrogen ions from the first coordination sphere of the iron ion. It is demonstrated that depending on the distribution of this negative charge on the nitrogen ions, deprotonation can either prevent or facilitate spin conversion.

Perovskite BaZrO₃ possesses higher phase stability from room temperature up to its melting point, yet pressure can induce phase transitions. However, detailed theoretical reports on pressure-induced transformations are scarce. We investigated the pressure-induced phase transition, elastic and electronic properties of BaZrO₃ under high pressure using first-principles calculations. The findings reveal that BaZrO₃ undergoes a series of structural transitions with increasing pressure, shifting from a cubic perovskite structure ((Pmbar {3}m)) to an orthorhombic structure (Cmcm), and subsequently to a tetragonal structure ((I4{text{/}}mcm)). These transitions occur at pressures of 3.5 and 20 GPa, respectively. The calculated transition pressure from Cmcm to (I4{text{/}}mcm) structure is consistent well with experimental values, and the predicted Cmcm structure should be further testified by future experimental study. At zero pressure, the mechanical stability of perovskite BaZrO₃ is assessed through elastic constants. Additionally, all stable polymorphs of BaZrO₃ remain insulating nature under high hydrostatic pressure. This investigation provides insight into the complex pressure-induced phase transformations in BaZrO₃ and offers guidance for future experimental investigations and potential applications.

Ba_0.85Ca_0.15Zr_0.9Ti_0.1O₃ (BCZT) ceramics possess exceptional dielectric, ferroelectric, and piezoelectric properties, making them a compelling choice for manufacturing microelectronic devices. The BCZT ceramic materials were replaced with Ba_0.85Ca_0.15–xSr_xZr_0.9Ti_0.1O₃. The samples were calcinated at 1150°C for 4 h in a conventional high-temperature muffle furnace. The powders were then sintered in a microwave furnace at 1450°. The cubic structure of the material at room temperature was confirmed using Rietveld X-ray diffraction. Dielectric studies, which were temperature and frequency dependent, showed that the dielectric constant and dielectric loss increased with SrO substitution upto x = 0.10. Relaxor behavior was observed in all Sr-substituted samples. The degree of diffuseness was calculated using the modified Curie–Weiss law.

In this work, ZnO and Cd doped ZnO nanorods (NRs) were synthesized using a hydrazine-assisted sol–gel method, followed by two annealing at temperatures (300 and 500°C). X-ray diffraction (XRD) analysis confirmed that the samples possess a hexagonal wurtzite crystalline structure. Transmission electron microscopy (TEM) revealed that the Cd doped ZnO nanoparticles are rod-shaped. X-ray photoelectron spectroscopy (XPS) indicated that Cd²⁺ ions successfully substituted into the Zn lattice. Photoluminescence (PL) analysis showed intense UV-region luminescence at 500°C due to Zn and oxygen vacancies and defects. These results suggest that Cd doped ZnO NRs annealed at 500°C could be promising candidates for next generation UV detectors. Furthermore, the antibacterial tests demonstrated that Cd²⁺ incorporation significantly enhanced that antibacterial effects of ZnO NRs, particularly against S. aureus (15 ± 0.85 mm) and E. coil (14 ± 0.71 mm) under light exposure. Thus, Cd-doped ZnO NRs offer great potential as an alternative antibacterial materials, especially in biomedical applications.

The Raman scattering intensity of oriented polyvinyl alcohol (PVA) films doped with cadmium sulfide and iodine is found to depend on the position of the sample with respect to the direction of the exciting radiation polarization. This dependence agrees with the supposed polymer structure of the inorganic component of the complex and the Raman scattering mechanism with its participating similar to the surface-enhanced Raman spectroscopy (SERS). The spectra are found to contain bands similar to the G- and D‑bands of carbon materials in the Raman shift range 1000–2000 cm^–1. The origin of these bands is discussed.

Ni_0.5Zn_0.5−xCu_xFe₂O₄ (x  =  0, 0.05, 0.1, 0.15, 0.2, 0.25) spinel ferrite nanoparticles were synthesized via the sol-gel auto-combustion method and sintered at 700°C for 5 h. Thermogravimetric and differential thermal analysis (TG-DTA) revealed the thermal decomposition behaviour. Single phase ferrite with Fd‑3m space group was confirmed by the Rietveld refinement of X-ray diffraction data. The distribution of cation among octahedral B and tetrahedral A-site was estimated by the computational method. With increasing copper substitution, the lattice parameter decreased while X-ray density increased. Crystallite sizes ranged from 22 to 24 nm, consistent with the Williamson–Hall method, and strain decreased. Fourier-transform infrared (FTIR) spectroscopy confirmed the spinel structure. High-resolution transmission electron microscopy (HR-TEM) and field emission scanning electron microscopy (FE-SEM) showed grain sizes between 70 and 130 nm. Energy dispersive X-ray (EDAX) analysis confirmed chemical purity. Magnetic studies showed an increase in saturation magnetization and coercivity (42 to 57 Oe) with copper substitution, while dielectric behaviour followed the Maxwell–Wagner model.

In this work, we present the theory of quantum capacitance in two-dimensional buckled germanene. Germanene is a material with a natural bandgap and strong spin–orbit interaction, offering significant advantages over graphene. The results of this study reveal the behavior of the quantum capacitance in response to variations in the spin–orbit interaction and electric field. The capacitance in each valley can be adjusted with the electric field, shifting from a minimum to a maximum as the external gate voltage is applied. The total capacitance, derived from both the K and K ′ valleys, shows a tunable band gap at ({{E}_{{text{F}}}} = 0). When the electric field energy ({{Delta }_{z}} = 2{{{{lambda }}}_{{{text{so}}}}}), the capacitance is zero at ({{E}_{{text{F}}}} = 0), whereas the electric field energy ({{Delta }_{z}} = {{{{lambda }}}_{{{text{so}}}}}), the capacitance reaches maximum with a single peak at ({{E}_{{text{F}}}} = 0) and electron–hole symmetric spectrum. As the electric field affects the band structure, the spin-up states retain their energy gap, whereas the spin-down states converge. Shubnikov–de Haas oscillations in quantum capacitance are also observed, showing a be-ating pattern at low magnetic fields that disappears as the electric field dominates. At higher magnetic fields, the splitting of the oscillations becomes evident. The disappearance of beating pattern and subsequent oscillation splitting are attributed to the interplay between the spin–orbit interaction, electric field, and magnetic field.

Thin films of nanocrystalline zinc oxide (nc-ZnO) have been deposited onto silicon substrates through a sol–gel route followed by annealing at 900°C, and subsequently develop a zinc–silicate layer at the ZnO–Si interface. The above interlayer was removed successfully after irradiation with 120 MeV Ag ions at different fluences of 5 × 10¹², 1 × 10¹³, and 3 × 10¹³ ions/cm². Glancing angle X-ray diffraction (GAXRD) confirmed increased crystallinity, especially the stronger (002) peak at higher fluences. Fourier transform infrared (FTIR) spectra gave an indication of the disappearance of the Si–O–Zn vibration and zinc silicate phase after irradiation, thus confirming a successful removal of the unwanted interlayer through ion treatment.