Physics of the Solid State最新文献

Two series of Mn_0.5Zn_0.5Fe_2–xO₄R_x (where R = Ce, Y, and x = 0.00 to 0.15) spinel nanoferrites were synthesized via a co-precipitation approach. Methods including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), and scanning electron microscopy (SEM) were utilized to examine the samples’ structural, morphological, optical, and magnetic features. XRD confirmed a cubic spinel structure, with crystalline sizes lies between 16 and 24 nm for Ce³⁺ added and 15 and 19 nm for Y³⁺ added ferrite NPs. XRD analysis showed that Ce³⁺ and Y³⁺ ions were successfully incorporated into the Mn–Zn spinel structure. FTIR spectra validated the presence of tetrahedral (A) and octahedral (B) sites in all compositions of Mn_0.5Zn_0.5Fe_2–xO₄R_x nanoparticles, indicative of spinel ferrites exhibiting a face-centered cubic (FCC) structure. SEM studies revealed agglomerated nanoparticles with spherical morphology. Energy dispersive X-ray spectroscopy (EDS) verified that all elements are present in the composition. The TEM micrograph shows the existence of slightly agglomerated nanoparticles. Magnetic properties, including saturation magnetization and coercivity, were analyzed using M–H hysteresis curves, showing dependence on rare earth substitution and A–B exchange interactions. The lower value of coercivity (H_c) indicatied of soft nature of NPs. The multidomain nature of the nanoferrites indicates their potential for electronics applications.

An uncomplicated and cost-effective sol–gel method was employed to effectively synthesize nickel oxide nanoparticles at various pH levels. A range of analytical instruments is utilized to define the material’s structural, morphological, optical, dielectric, magnetic, and electrochemical characteristics. The tools comprise X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy, photoluminescence spectroscopy (PL), LCZ measurements, and the vibrating sample magnetometer (VSM). Analysis of the powder XRD pattern enabled us to ascertain the crystallite size of the synthesized powder, revealing that the crystallite dimensions increase with elevated pH levels. An elevation in pH level influences the enhancement of the strain value, as demonstrated in the W–H plot. The influence of pH levels on morphological alterations was confirmed by scanning electron micrographs. As pH levels increase, blue shift absorption peaks are observed in the UV-visible spectra. Estimates of the bandgap value were obtained utilizing the Mott and Davis connection, which demonstrates that the bandgap value escalates with rising pH levels. The correlation between temperature and both the dielectric constant and dielectric loss is analyzed within the frequency spectrum of 50 Hz to 5 MHz. The grain effect, as indicated by the Cole–Cole plot, has been eclipsed by the influences at the grain boundary and the interfacial effects in all synthetic materials. Nickel oxide nanoparticles exhibited ferromagnetic properties over a range of pH values. For the NiO sample, the values of squareness and magnetization are enhanced when the pH is set at 8.0 during synthesis. The el-ectrochemical study validated that the NiO sample generated at pH level 8.0 had an improved conductivity property.

In this work, we report the frequency dependent ac conductivity properties and dielectric behavior of lead sulphide (PbS) thin films. Effect of nickel doping on particle size, optical band gap and electrical conductivity is presented. Pure and Ni doped PbS films (3, 6, and 9% doping) were prepared by chemical bath deposition (CBD) process on biological glass slides. X-ray diffraction (XRD) pattern confirms that cubic mono-phase PbS is formed. Particle size was found to decrease and band gap was found to increase with increasing doping level up to 6%. Complex impedance spectroscopy was utilized to investigate the e-lectrical conductivity and dielectric property. Highest value of electrical conductivity is obtained for 6% doped film.

Zinc oxide (ZnO) nanoparticles were substituted with Al in the ratio of 0 to 0.1 and synthesized using co-precipitation. Nanoparticles were characterized by X-ray diffraction and UV-visible spectroscopy. The synthesized nanoparticles of ZnO have shown a wurtzite structure. The crystallite sizes of pure and ZnO nanoparticles substituted with Al were calculated with the help of Debye–Scherrer’s equation. With the rise in Al concentration doping, there is a reduction in the nanoparticles average crystallite size. It was observed that the DC conductivity increases as temperature and Al concentration rise. The dielectric constant ε, and dielectric loss, tan δ rise with temperature rise. Complex impedance analysis distinguishes the grain and grain boundary contribution to the material. The UV-Vis spectrum has shown that as the Al doping concentration increased, Urbach energy increased, and optical conductivity was highest when 0.03 of Al was doped in ZnO (ZA03).

The electrical properties of the sample RFeO₃ (R = Nd,Gd) were investigated by the study of complex impedance, electric modulus, conductivity, and density of states synthesized through the conventional solid-state reaction technique. The orthorhombic crystal structure was confirmed. The electrical conductivity of RFeO₃ is found to be low at lower frequencies due to space charge polarization and increased gradually, indicating the presence of local charge carriers. The complex impedance study reveals the presence of grain and grain boundary contributions, which are modeled using (RQC) and a combination of (RQC) (RC) electrical circuits. At low temperatures, the grain effect was explained by the quantum tunneling (QTM) model for NdFeO₃ and the correlated barrier hopping (CBH) model for GdFeO₃. At high temperatures, the grain boundary effect was explained by the CBH model for NdFeO₃ and the Non-overlapping small polaron tunneling (NSPT) model for GdFeO₃. The shifting of the peaks (imaginary part of the electric modulus) towards the higher frequency with the increase of temperature was explained by the heat-activated mobile ions speeding up the relaxation process.

The spectral dependences of the optical conductivity and reflection coefficients of TlFeS₂ and TlFeSe₂ crystals were studied experimentally using spectral ellipsometry and theoretically from first principles using density functional theory (DFT). Based on ellipsometric data in the energy range of 0.7–6.5 eV, the widths of the indirect band gap E_g, reflection coefficients R, Urbach energy E_U, skin depth, and other parameters were determined. Analysis of the refractive index spectrum using the single-effective-oscillator model yielded estimates of the single oscillator energy E_so and the dispersion energy E_d. The experimental data were also used to determine the plasma frequency and the ratio of the charge carrier concentration to the effective mass. Furthermore, the nonlinear refractive indices and the first- and third-order nonlinear susceptibilities were calculated.

This study presents investigation of the photoluminescence (PL) properties of ZnIn₂S₄ single crystals. The PL emission characteristics were performed across a temperature spectrum spanning from 5 to 300 K. The PL emission maxima were observed in the infrared region at a wavelength of 725 nm (1.71 eV). At lower temperatures, this peak undergoes a blue shift, moving towards higher energies. At 5 K, the peak shifted by 40 nm, being observed at 685 nm (1.81 eV). At ambient temperature, the photoluminescence excitation (PLE) analysis of ZnIn₂S₄ revealed distinct spectral maxima at 2.75 eV (450 nm) and 2.33 eV (530 nm), corresponding to electronic transitions from the valence band to the conduction band, and from defect states to the conduction band, respectively.

This review article is focused to present an outline of the advancement in the research area of graphene nanostructures such as graphene nanoribbons, graphene nanodisks, graphene nanomesh, graphene nanoplatelets, graphene quantum dots, etc., and their properties in terahertz (THz) region. The density functional theory (DFT) study of graphene nanostructures has also been focused along with their applications in the THz fields such as security, life sciences, analytical sciences, molecular spectroscopy and solid-state physics. The reported study about the graphene nanostructures and their applications have opened up the new gate of opportunities for the fabrication of futuristic graphene based nano-devices. Although a lot of research work has already been reported on the synthesis and the experimental investigation of graphene nanostructures in the literature survey, their computational study using THz spectroscopy is still less explored. That is why in the present article, the theoretical study of graphene nanostructures using DFT in the THz region has mainly been reviewed.

Zn-doped NiFe₂O₄ was synthesized by using sol–gel citrate technique, and its phase homogeneity, surface morphology, optical, magnetic, and electrochemical performance were analyzed. X-ray diffraction (XRD) confirmed a cubic spinel structure with Fd3m space group symmetry. Field emission scanning electron microscopy (FE-SEM) revealed increasing agglomeration with Zn doping. Magnetic characterization via vibrating sample magnetometer (VSM) showed an increase in saturation magnetization with Zn content, specifying its soft magnetic behavior. UV-visible spectroscopy revealed an increase in bandgap energy from 1.7 to 3.89 eV with Zn doping. Current–voltage characteristics and voltage–time cycling data showed best conductivity for Zn composition x = 0.1. Impedance spectroscopy further indicated that charge transfer resistance was lowest for x = 0.1, measuring 50.23 Ω.

Ga₂O₃ polycrystalline thin films were deposited by spray pyrolysis method. The films were post-annealed at 700, 900, and 1100°C for 2 h, then the crystal structure, surface morphology and optical properties of the films were studied. As the post-annealing temperature increases, the average crystallite size of the film increased from approximately 6 to 21 nm, and the FWHM of rocking curve for the (400) plane of the β‑Ga₂O₃ decreased from 1.29° to 0.38°. The increase of post-annealing temperature controls phase formation in the films. When post-annealed at 700°C, the Ga₂O₃ film is not completely transformed into β phase. While post-annealed at temperatures ≥900°C, the Ga₂O₃ in the films is all β-Ga₂O₃. Additionally, the increase in post-annealing temperature induced changes in the micro-strains of Ga₂O₃ films, which resulted in a reduction of the bandgap. These findings highlight the critical role of post-annealing temperature in controlling the structural and optical properties of Ga₂O₃ thin films, making it a key parameter for improving the quality of β-Ga₂O₃ films.