Physica B-condensed Matter最新文献

A and B-site doping has been viewed as a very effective approach to stabilise the desired perovskite cube phase of pure and doped hetero-structure CsPbI₃-Pb_1-xMg_xSe and the simple system CsPb_1-xMgxI₃. In this analysis, the effect of (Mg²⁺) on the crystal structure, electronic, mechanical, and optical responses of hetero-structure CsPbI₃-Pb_1-xMg_xSe and CsPb_1-xMgxI₃ were thoroughly investigated, by employing first-principles computations. A theoretical study of target responses of the metal-halide CsPbI₃ is presented with a plane wave ultra-soft pseudopotential approach as personified in the CASTP code. The computed results show that the band gap of CsPbI₃-Pb_1-xMg_xSe can be changed from '1.809eV' to '1.75eV' when the concentration range (x = 0 to 0.25) is changed. A valuable band gap of '0.48eV' and '1.28eV' of doped CsPbI₃-Pb_1-xMg_xSe can be achieved under concentrations changed from (x = 0.25 to '0.75eV') and as shown in direct (Γ - Γ) nature and become optically active. The density of states shows that Cs-6p, I-4p, and Pb-6p states contribute to the valence band maximum, whereas the main involvement conduction band minimum by Mg-5p and Cs-6p states in the CsPbI₃-Pb_1-xMg_xSe system. Elastic properties designate the flexibility and softness of target materials. The computed elastic parameters further indicate that this hetero-structure material is stable under the doping concentration condition. Replacing the Pb²⁺ site with Mg²⁺ has red-shifted the maximum absorption edges and changed the optical characteristics to be anisotropic. Their ability of these two materials with their Mg²⁺ based mixed halide perovskite nature for optoelectronic applications.

This paper presents a study of the dielectric properties of ZnNb₂O₆ (ZNO) with added CaTiO₃ (CTO) in the microwave (MW) region. An X-ray diffraction analysis is performed, and a reaction between ZNO and CTO is demonstrated that results in the formation of other crystalline phases. The dielectric properties in the MW region show no significant change in permittivity (ε'_r), whereas the addition of CTO results in an increase in the dielectric loss (tan δ). The thermal stability is also measured, and the temperature coefficient of resonant frequency (τ_f) is varied from −88.95 to −8.16 ppm °C⁻¹. Numerical simulations are carried out to evaluate these materials for use as a dielectric resonator antenna, and the results show a reflection coefficient (|S₁₁|) of below −10 dB, a radiation efficiency above 96 %, a bandwidth ranging from 100 to 170 MHz, and a gain of above 4.50 dBi. The values obtained here show that these materials could be employed in electronic devices acting in the C- and S-bands.

In this study, the effect of Mn doping on the photovoltaic properties of ZnO films deposited on a p-Si substrate via spray pyrolysis has been evaluated. The Mn concentration was varied at 0, 1, and 3 wt%. The spray was carried out at 400 °C for 10 min. As a result, the X-ray diffraction pattern shows that the crystallite size decreases linearly with increasing Mn doping, from 44 nm (0% Mn) to 31 nm (3% Mn). Scanning electron microscopy images show that the increase in Mn concentration causes the nanostructure size to be smaller, from 325 nm (0% Mn) to 112.3 nm (3% Mn). Interestingly, the best photosensitivity and response time are found in the doped sample (3% Mn) at a bias voltage of 0 V rather than 1 V and 5 V, indicating the photovoltaic effect. This result is important to develop future self-powered devices.

Gadolinium-substituted NiO crystal structures with excellent stability were utilized for the first time to degrade antibiotic and organic dye pollutants. The present study investigated the effect of Gd³⁺ substitution on the NiO crystal structure and its increased photocatalytic degradation activities. A simple one-step hydrothermal technique procedure was used to synthesize different concentrations of Gd³⁺ substituted NiO, and the catalysts were thoroughly characterized using sophisticated techniques to explore the influence of Gd³⁺ on the crystal structure and optical characteristics of NiO. p-XRD, UV–Vis DRS, PL, HR-TEM, and HR-XPS techniques. The 1.5 % Gd³⁺ substituted NiO showed outstanding photocatalytic activity on against tetracycline and direct yellow degradation, with percentages of 90.72 and 95.5 %, respectively. The improvement of photocatalytic degradation efficiency is primarily due to the suppression of photoinduced electron and hole recombination via the creation of Gd³⁺ as the inner energy band state below the conduction band. The recycling experiments revealed that the catalyst is more stable, with no indication of loss after ten cycles. Scavenging investigations also demonstrated that superoxide and holes were responsible for the efficient degradation of pollutants.

The wet chemical precipitation technique was used to synthesize CuO, Nd:CuO and Ni-Nd:CuO nanoparticles efficiently. The produced substance was tested using X-ray diffraction (XRD) for confirming the crystallite structure, and scanning electron microscopy (SEM) was used to examine the morphological properties of the produced materials. Crystal defects and optical properties of the synthesized samples were analyzed through luminescence (PL) investigations and UV–Vis spectroscopy. EIS spectrum was utilized to study the electrochemical behavior of the prepared material. Vibrating Sample Magnetometer (VSM) was employed to examine the magnetic properties influencing from the doping of Ni²⁺ and Nd³⁺ ions into CuO, attributed to their substantial magnetic moment and ferromagnetic traits. Photovoltaic efficiency of the prepared material was studied by J-V characteristics and photon-to-electron converting efficacy (IPCE) studies. Photocatalytic properties were studied by degrading MB and RhB dyes. The enhancement in the photocatalytic performance of the Ni-Nd:CuO was a result of suppression of photogenerated electron-hole pair recombination and accelerated separation and migration of photogenerated charges.

The quantum correlations of a system of two quantum dots with Föster interaction ($\Gamma$) in a microcavity with strongly coupled dissipation and a single mode of the electromagnetic field and driven by a laser pulse were studied theoretically, using the formalism of the master equation in Lindbland form. The energy eigenvalues of the system were studied as a function of detuning for the first and second excitation varieties. Concurrence ($C$), formation entanglement ($EoF$), mutual information ($I$) and quantum discord ($Q$) are studied as a function of time considering different values of Föster coupling, varying the pump times of the simulated laser pulse and pulse intensity. We found a discrepancy between $EoF$ and $C$ as entanglement quantifiers, noting that concurrence reaches much higher values than $EoF$; so concurrence can indicate results that are well above the $EoF$. The presence of the Föster interaction favors that the quantum discord is the dominant correlation in the system, which indicates that the system maintains quantum correlations even when the entanglement of the system has disappeared, but that it is affected by the increase in the laser pump time.

Electronic structure and magneto-elastic characteristics of lanthanide nitrides Ln₃NIn (Ln = Nd-Tb) are explored by DFT. The structural reported data are reliable with the experimental outcomes and the observed structural characteristics drop from Nd to Tb due to the small atomic radii of Tb compare to Nd. Electrical resistivity and electronic characteristics demonstrate that all the investigated compounds are metallic. The resistivity at 300 K emphasizes that they are effective conductors. These compounds are ideal for situation where large acting load are expected such as implants that bear a disproportionate amount of weight as endoprostheses for hip, knee and as screw, nails and plates, especially when structural materials need to have sufficient bending fatigue strength for skeletal reconstruction. These compounds are antiferromagnetic and their Neel temperatures are 18, 15, 39, 45, 27, and 33 K, respectively. These compounds might be therefore feasible for magnetic cloaking and storage technologies.

This study investigates the electron transport properties of two-terminal disordered graphene nanoribbons (GNRs), considering the presence of randomly distributed “5-5-8” line defects (LDs). Although the presence of random LDs causes significant localization and suppression in conductance, attributed to Anderson localization, several robust conductance peaks, including a quantized peak, can be observed in the transmission spectra of disordered GNRs regardless of sizes and LD concentrations. Furthermore, the study demonstrates that the width, particularly the edge configuration of disordered GNRs, significantly affects these peaks. For symmetric edge configurations, the number of peaks remains constant, but their positions shift as the width increases. In contrast, for asymmetric edge configurations, the number and positions of the peaks change with width. Notably, a quantized conductance peak regardless of various configurations is observed. The study offers valuable insights for the design GNR devices based on LDs and edge symmetry.

This study proposed a performance enhancement scheme for GaAs thin-film solar cell (TFSC) based on Ti plasma enhancement. It aims to enhance the light absorption ability of the cell by using surface plasmon excitations of metal nanoparticles, and to predict and optimize the performance of the TFSC using the FDTD method. By introducing Ti nanosphere and pyramid structures on the upper and lower surfaces of the cell, the reflection and transmission losses of light are effectively reduced. This increases the interaction between the cell materials and light, and significantly improves the cell's ability to absorb light. It is shown that Ti nanosphere and pyramid structures can localize the electric field near the metal surface, which greatly enhances the absorption of light on the upper and lower surfaces of the cell. In the wavelength range of 380–1200 nm, the absorption of all bands reaches more than 93 %, with an average absorption rate as high as 97.60 %, and is close to perfect absorption in the wavelength range of 700–900 nm. Meanwhile, the photoelectric conversion efficiency (PCE) of the cell reaches 32.72 %, which significantly improves the overall performance of the cell and provides a compelling design solution for the innovation and development of GaAs TFSC technology.