Indian Journal of Physics最新文献

A new form of the equation of state (EOS) is considered to develop a model for describing the interior of a static, spherically symmetric, compact anisotropic star. The analytic solution is obtained using the Finch and Skea ansatz for the metric potential (g_{rr},) with a distinct geometric interpretation for the related background spacetime. The model parameters are fixed by matching the interior solution to the Schwarzschild exterior metric over the boundary of the star, together with the requirement that the radial pressure vanishes at the boundary. Data available for the pulsar 4U1802030 has been utilized to analyze the physical viability of the developed model. The model is shown to be stable.

In this paper, we present an optimized procedure for depositing SnS thin films using the rapid S-SILAR technique. We also analyze the effects of deposition cycles and post-deposition annealing on various film properties. XRD analysis indicates the presence of orthorhombic and cubic phases in the films. Energy dispersive X-ray analysis confirms near-optimal stoichiometry. SEM images depict the growth of closely spaced spherical granules. High optical absorption is observed in the mid-visible to NIR region, with the absorption edge shifting towards the NIR region after annealing. The bandgap values range from 1.6 eV to 1.9 eV, which is ideal for photovoltaic applications. PL spectra show three clusters of peaks corresponding to red and green emissions. Hall measurements confirm that both the as-deposited and annealed SnS films exhibit p-type conductivity, with a hole concentration on the order of 10¹⁵ cm⁻³.

This study focused on nonlinear ion-acoustic solitary structures (IASS) in a magnetized plasma system that is kappa distributed comprising electrons, positrons, and ions (e–p–i) using a fluid theory approach. A novel nonlinear inverse dispersion relation peculiar to this complex plasma environment was derived. The dispersive properties of ion-acoustic waves in magnetized e–p–i plasma environment were investigated considering the influence of various superthermal of electrons and positrons ((kappa _{e}~textrm{and} ~kappa _{p})), unperturbed positron to ion density ratio, p, electron to ion density ratio, ((delta )), ion to electron temperature ratio, ((sigma )). By numerically analyzing the impact of plasma properties, particularly the nonlinear dispersion characteristics in a magnetized e–p–i plasma. The influence of the external magnetic field (obliqueness) angle, (theta), which alters the frequency value of ((omega ^{2})). It was found that the values of (delta), the frequency (omega ^{2}) of IASS waves decreases with increasing (delta). This result has significant implications for understanding the dynamics of various astrophysical settings, such as the solar wind. However, when (delta > 0), the curves become more nonlinear, indicating the waves become more dispersive. Further, it is discovered that as the value of (theta) for (+~omega ^{2}) solution increases, the shape of the dispersion curve does not significantly change. In contrast, it is observed from the (-~omega ^{2}) solution that for all values of angle (theta), frequency decreases with increasing angle (theta). This is because the ion-acoustic mode is strong at the propagation angle at (theta = 0^{circ }) and weakens as the propagation angle increases, eventually disappearing at (theta = 90^{circ }). Thus, these findings provide an appreciable understanding of the dispersion characteristics of obliquely propagating IASS modes in a magnetized e–p–i plasma. In conclusion, our results provide important and new information on the interaction of plasma parameters in complex astronomical (natural) and laboratory (artificial) settings.

Here, we have investigated the impact of heat treatment on structural, morphological, optical and magneto-dielectric properties of Co_0.5Cu_0.5Fe₂O₄ spinel nanoferrites prepared by sol–gel auto-combustion method. The prepared samples were sintered at 700, 800, and 900 °C and then characterized by XRD, FTIR, SEM, UV–Vis spectroscopy, VSM and impedance analyser techniques. The obtained XRD patterns were refined with Full Prof Suite Software which confirmed the cubic spinel structure of the prepared sample and it was observed that crystallite size increases from 38 to 44 m with increase in sintering temperature and the same is confirmed by W–H plot also. The SEM micro graphs represent the morphological features of the prepared samples and average particle size was calculated by using the imageJ software, which ranges 47–126 nm with increase in temperature. The FTIR spectra confirmed the presence of tetrahedral and octahedral sites in the prepared samples. Various optical parameters were recorded using UV–Vis spectroscopy and it was found that optical band gap energy decreased from 3.976 to 3.832 eV, whereas refractive index increased from 2.262 to 2.283, and high frequency dielectric constant varied from 5.114 to 5.210 with rise in temperature which was due to decrease in grain boundary area and porosity. The magnetic studies were carried out at room temperature using VSM and it was found that magnetic parameters get improved with increase in sintering temperature. Dielectric measurements were made by impedance analyser in a frequency range of 20 Hz to 10 MHz which were in consonance with Maxwell–Wagner polarization and Koop’s theory.

The structural and optical properties of copper doped cadmium sulfide (Cu:CdS) thin films on flexible polyethylene terepthalate substrates have been presented. The hexagonal crystallite structure of as-deposited thin films was characterized by the X-ray diffraction technique. X-ray photoelectron spectroscopy has been used to study the chemical binding energy and compositional analysis of the deposited thin films. The surface morphology of the deposited thin films has been analysed by an atomic force microscope image. The optical and photoluminescence properties of deposited films have been studied by UV–Vis–NIR spectrophotometer and fluorimeter respectively. A linear shrinkage of lattice parameters has been observed in the CdS thin films with Cu doping because of the smaller ionic radius of Cu than that of Cd. The optical band gap energy of CdS thin films decreased initially with Cu doping due to s, p–d exchange interactions and then increased due to the reduction in crystallite size. The photoluminescence property of the Cu:CdS thin films has been studied at room temperature (30 °C). Photoluminescence spectra showed two emission peaks around 545 nm and 580 nm, respectively, the exact positions of which are dependent on the Cu at% in the thin films. The former is due to the band-band transition of CdS, and the second is due to sulphur vacancy.

This work deals with theoretical analysis of performance of a formamidinium tin iodide (FASnI₃) based perovskite solar cell. The advantages of using FASnI₃ over other perovskites include its low toxicity and environmental friendliness. While FASnI₃ has slightly lower thermal and moisture stability compared to the inorganic CsSnI₃, it offers better tunability of properties and higher power conversion efficiency (CE) potential. In PVSCs not only the surface defect but also the high concentration of Sn⁴⁺ creates huge bulk defect density inside the FASnI₃ and limits the CE. The bulk defect is of two types (1) fixed ionic defects due to Sn⁴⁺ and (2) mobile ionic defects due to Sn interstitial and halide vacancy. With a goal to overcome the impact of fixed defect, we used a technique to gradient distribution of Sn⁴⁺ mediated bulk defects inside the absorber. The PVSC: ITO/PEDOT: PSS/FASnI₃/C60/Au is simulated in OghmaNano where uniform distribution versus gradient distribution of defect inside FASnI₃ are analyzed. The ~ 10 to 13% rise in CE is observed for the gradient distribution of defect and is attributed to the enhancement in electric field inside the device. Moreover, the impact of mobile ions on the performance of both uniform and gradient PVSCs is comprehensively analyzed and reported in this work. The analysis indicates that an ion density up to the order of 10²² m⁻³ has no significant impact on the performance of the PVSC. In addition, considering the pivotal role of charge transport layers, seven different materials such as MoO₃, PEDOT: PSS, TCTA, V₂O₅, Li_0.05Ni_0.95O, SrCu₂O₂, and CuI are assessed for eligibility as HTAL in the proposed PVSC. Amongst those the CuI and C60 as HTAL and ETAL results in highest CE, FF, J_SC and V_OC of 20.64%, 69.09%, 1.14 V and 26.16 mA cm⁻² respectively. The reported photovoltaic device with high CE is environment friendly and may be a potential candidate for solar energy harvesting.