Physics of the Solid State最新文献

Currently, phytochemical approaches to metal oxide nanoparticles (NPs) are regarded as the most effective and environmentally benign option due to the varied roles in the formation of nanostructures. This study focused on synthesizing zinc oxide nanoparticles from Citron leaf extract. The synthesized samples were evaluated by XRD, FTIR, XPS, PL, UV-Vis, SEM with EDX, and HRTEM with EDX, respectively. As the leaf extract increases, the structure analysis shows that the ZnO NPs have the average size of the crystallites which decreases from 16.4 to 12.7 nm. The FT-IR study provides assurance about the contribution of various biomolecules to the sample surface and the formation of Zn–O bonding. SEM and HRTEM investigations revealed nanorod-shaped morphology with high particle homogeneity from the 20 mL ZnO NPs. Furthermore, surface chemical state analyses by XPS verified the accommodation of different oxygen-coordinated molecular species. The dye degradation rates of methylene orange and methylene violet organic dyes were found to be 99% and 98%, respectively. These outcomes were attained by using a bio nano-rod catalyst for 60 min under sun light irradiation. According to the findings, the photodegradation of MO dye solution by ZnO nanoparticles via an ecologically benign approach under favorable conditions was effective. Based on the present study, the application of bio-mediated ZnO NPs is suitable for aquatic environmental purification.

In this work, thin films of hafnium oxide HfO_x obtained by electron beam deposition were crystallized by thermal annealing in air atmosphere. The relationship between the structural changes occurring as a result of annealing and the electrical properties of the films was determined. It was found that the formation of nanocrystals with a monoclinic structure in the studied films, occurring at annealing temperatures of 500°C and higher, is accompanied by a decrease in their specific conductivity by more than 6 times, which can be associated with a decrease in the number of oxygen vacancies as a result of structure ordering. It was also shown that the specific conductivity of all HfO_x films (pristine and annealed at different temperatures) has a strong dependence on temperature, described by the activation law with an activation energy from 0.86 to 0.93 eV. The obtained data can be used to improve the characteristics of memristive systems and other electronic devices based on hafnium oxide layers.

The Sr-doped bismuth ferrite nanoparticles with chemical formula Bi_1–xSr_xFeO₃ (x = 0.1, 0.2, 0.3, 0.4, and 0.5) were prepared via facile sol–gel method. A detailed investigation was conducted into the effects of substituting divalent Sr²⁺ at the Bi³⁺ site on the structural, morphological, magnetic, and electrical characteristics. The XRD study revealed the occurrence of structural transformation in the samples upon doping. The reduction in crystallite size can be attributed to the creation of oxygen vacancies. The morphological analysis carried out using field emission scanning electron microscopy (FESEM) further validated this theory. The increasingly greater lattice distortion with doping is in line with the increasing value of microstrain for increasing doping concentrations. The improving stability of the structure with increasing doping concentration was confirmed by the increasing value of the tolerance (T) factor. The FESEM micrographs reveal the change in morphology of the particles upon doping. The EDS results confirm the expected presence of the constituent elements Sr, Bi, Fe, and O in permissible proportions. The M–H curve reported at 3 K and at ambient temperature both confirmed the appreciable increase in magnetization with increasing doping concentration. The investigation of the dielectric properties of the samples was performed using an LCR meter operating in the frequency range of 10 Hz–8 MHz. The results showed a marked increase in the value of the dielectric constant with an increase in doping concentration. The increasing resistivity of the doped BFO samples is confirmed by the significant values of grain resistance as indicated by the Cole-Cole plots. The good ferroelectric properties of the samples are revealed by the P–E loops and may find potential applications in spintronic devices and microwave devices. The P–E loops reveal the good ferroelectric nature of the samples and can have potential applications in spintronic devices and microwave devices.

This study focuses on the electronic band structure, lattice dynamics, density of states, and mechanical properties of molybdenum (Mo), using first-principle calculations. The results obtained show that Mo exhibits metallic behavior with high electrical conductivity. The bands gap at the Fermi level (around 0 eV) are overlapping, which is characteristic of metals and indicates high electrical conductivity. As the temperature increases, the vibrational energy of Mo rises, while its vibrational free energy decreases. Furthermore, the entropy and heat capacity of Mo also increase with temperature. These findings have important implications for the use of Mo in various applications, as they can help optimize its current uses and potentially lead to the development of new technologies.

In this work, titanium dioxide (TiO₂) was deposited on a microscopic glass substrate by means of the spray pyrolysis method. The precursor was made of one molar solution of titanium(III) chloride propanol and glacial acetic acid thoroughly mixed. The deposited thin films were annealed at 450 and 600°C, respectively. The optical and structural properties of the as-grown and the annealed thin films were studied using a spectrophotometer, X-ray power diffractometer, and scanning electron microscopy. The result obtained revealed that TiO₂ absorbs, reflects, and transmits light in the wavelength range of 200–1000 nm. The TiO₂ thin films have good optical properties in the ultraviolet region of the electromagnetic spectrum. The as-grown and annealed TiO₂ thin films have bandgap energy varying from 1.6–2.2 eV depending on the annealing temperature. The X-ray diffraction study reveals that the peak positions do not change due to the annealing. Still, the annealed sample has a high intensity that seems to depend on the annealing temperature. Annealing of TiO₂ causes the surface to be more uniform, devoid-free, and with improved surface structure.

Tunnel field effect transistor (TFET) is replacing other similar devices, because of it’s extremely lower value of sub-threshold swing (SS) and leakage current. Due to the limitations of ambipolar effect and relatively lower value of ON-current, researches are trying to enhance the performance of it by modification in the structure and choice of appropriate materials. To increase the ON-current, a highly dense thin layer source pocket (SP) is used and reduction of the ambipolar current is done by using hetero dielectric as a gate. Hence, various characteristics/properties and parameters of source pocket hetero dielectric double gate TFET (SP-HD-DG-TFET) are studied by varying the width of the SP by 4, 6, and 8 nm. By using the Silvaco TCAD, it is found that the current ratio decreases and SS increases with increase in the width of the SP. Hence, the lower value of the width of the SP is considered to be suitable for low power and high speed application.

Thin ZnTe:Cu films are prepared by pulse laser deposition. ZnTe films were doped with Cu to increase the p type carrier concentration and to state the influence of the Cu concentration on their structural, optical, and electrical properties and also to consider their potential applications in electronic devices. X-ray diffraction studies, studies of X-ray photoelectron spectroscopy, UV-visible spectroscopy, and the Hall effect of ZnTe:Cu films are performed.

Doping at various positions of BaFe₂As₂, providing stable chemical pressure and adjusting carriers, has always been a popular research topic. In the work, we conducted a comprehensive theoretical study on the isovalent Mg-substituting-Ba for BaFe₂As₂ by using the density functional theory (DFT) method. All DFT calculations were performed with the set of GTH-PBE/DZVP-MOLOPT-SR-GTH. By exhaustively post-processing the DFT-calculated wavefunction, the electronic properties such as HOCO, ELF, BO, charge population, LOL-π, IRI, etc., were reported. Up to now, the investigations of electronic properties for novel Mg-doped BaFe₂As₂ based on the generated wavefunction are barely, thus it is well expected that our results with the corresponding method will benefit the research of the Fe-based superconductors family.

The perovskite type compounds of BaCe_0.6–xZr_0.3Sm_xPr_0.1O_3–δ (x = 0.1, 0.2, 0.3, and 0.4; named as BCZSP1, BCZSP2, BCZSP3, and BCZSP4, respectively) were synthesized by the dry chemistry reaction method. The structure, phase, microstructure, impedance spectroscopy and chemical stability of the synthesized compounds were investigated by different techniques. The XRD data of the materials showed the cubic crystal symmetry within the Pm–3m space group. The Chekcell and WinXPow software were used to index the crystal symmetry and space group of the XRD data and the FullProf suite software was utilized to carry out the Rietveld refinements of the acquired XRD data. The scanning electron microscopy (SEM) was used to examine the grain morphology and grain growth of the materials, and the SEM results indicate that all of the materials had densities more than 97% of the theoretical density. The thermogravimetric analysis (TGA) of the materials in the CO₂ gas atmosphere exhibited superior stability. The protonic conductivity was found the highest in the wet 5% H₂ in argon (Ar) gas environment for the BCZSP1 (x = 0.10) material and were ~1.19 × 10^–2 and ~1.03 × 10^–2 S cm^–1 at 650 and 700°C, respectively. The highest stability was for BCZSP4 in the CO₂ gas environment for the four samples of the BCZSP series. At intermediate temperatures (500–700°C), the materials show potential electrolyte behavior for applications in solid oxide fuel cell that transport protons.

In this study, we have established a careful analysis on the effect of Pt substitution at Ni sites on the electronic structure and magnetic properties of the Ni₂MnGa system in both cubic and tetragonal phases using FP-LAPW+lo method based on density functional theory. Two Pt concentrations were investigated x = 0.125 and 0.250 in Ni_2–xPt_xMnGa Heusler alloys using the supercell model. GGA+U calculations show that Ni_2–xPt_xMnGa alloys (x = 0, 0.125, 0.250) are stable in the cubic structure and the lattice parameters increase linearly with increasing platinum concentration. Band structure calculations show overlapping bands at the Fermi level indicating that these alloys are metallic. The atomic and total magnetic moments increase with increasing Pt concentration, which is responsible to the strengthening of ferromagnetism in these alloys. The anisotropy energy calculations predict that [100] and [010] axis are the easy and hard one respectively in our cubic ferromagnetic Pt doped Heusler. Our Pt doped Ni₂MnGa alloys could be synthesized to obtained novel shape memory alloys.