Herein, the electronic, thermoelectric, and optical properties of semimetallic HPX6 (X = C, Si, Ge, Sn) monolayers are systematically studied under the influence of external electric field in the framework of density functional theory. A band tuning has been achieved in these structures by the application of an external electric field of appropriate strength. It is predicted that Dirac cone splitting is nearly proportional to the external electric field strength. The modulation of electric properties induced by external field can alter the position of chemical potential in the band diagram and brings significant improvement in thermoelectric responses. The application of an external electric field significantly modulates the optical properties. The electric field-induced HPX6 system provides better thermoelectric and optical response for nanodevice applications.

Herein, the comprehensive study of different properties of undoped MoS2, MoS2 lattice with sulfur (S) and, molybdenum (Mo) vacancy, and MoS2 with substitutional doping of niobium (Nb), vanadium (V), and zinc (Zn) atoms is done. The density functional theory (DFT) is used and the electronic properties like density of states, band structure, electron density, and optical properties like dielectric function, optical conductivity, and refractive index are studied. It is observed that undoped MoS2 monolayer shows direct bandgap semiconductor characteristics with a bandgap of around 1.79 eV. P-type characteristics are observed for Nb-, V-, and Zn-doped MoS2 lattices. The real part and imaginary parts of all optical parameters along x and z directions for different MoS2 supercells are found to be anisotropic in nature up to a photon energy of almost 11 eV and thereafter they show nearly isotropic nature. Finally, it is found that the obtained properties of MoS2 monolayer as per literature are suitable for next-generation MOSFET application.

Optical, magnetoresistance, and thermoelectric of La1-xKxMnO3 (x= 0.05, 0.15 and 0.25 at%) compounds have been investigated. The crystallography demonstrated that the samples × = 0.05 and 0.15 are a single-phase rhombohedral ( R 3 ¯ C $R \bar{3} C$ ) structure, while x= 0.25 is near to a single rhombohedral phase with a minor amount of Mn3O4 (with a ratio of ∽ 2%). The optical properties manifested that the reflectivity decreases slightly with increasing x-doping, where the sample of x=0.05 has the lowest reflection value, making it a promising material for photovoltaic applications. Electrical resistivity measurements show that the samples have a metal-semiconductor transition, and the transition temperature Tms decreases with the K content. The thermoelectric data shows a remarkable coincidence behavior of the ρ-T relationship, which has a peak at a transition temperature (TS). Magnetic susceptibility data show that the samples undergo Ferro- paramagnetic transition at a certain temperature (Curie temperature).

Cu-doped TiO2 is a dilute magnetic semiconductor with excellent electrical, magnetic and optical properties. In this study, we employed first-principles methods to investigate its electronic structure, magnetic properties, and optical behavior. The results demonstrate that Cu-doped TiO2 exhibits intrinsic ferromagnetism. The presence of O vacancies facilitates the ferromagnetic exchange between Cu ions by forming bound magnetic polarons (BMPs). This finding validates the BMPs model and provides an explanation for the decrease in magnetic properties during annealing under O2 conditions. As the concentration of Cu increases, the system undergoes a transition from a semiconductor to a metal. Cu ions exhibit a preference for a compact configuration and display either paramagnetism or antiferromagnetism. The spin polarization can be effectively controlled from 0 to 100% by adjusting the concentration and site of Cu. Additionally, Cu doping leads to a reduction in the bandgap and an extension of the absorption range into the infrared region. The absorption intensity is positively correlated with the concentration. The presence of a spin-polarized intermediate band indicates a correlation between the spin of the excited electron and the energy of the absorbed photon. Overall, Cu-doped TiO2 shows significant potential for applications in spintronics and spin-related optics, including photospintronics and spin photocatalysis.

A series of Gd7O6(BO3)(PO4)2:xDy3+ phosphors are synthesized using high-temperature solid-phase method. The phase and spectral characteristics of phosphors are analyzed using X-ray diffraction and spectrometer. It is found that the ratio of the light intensity corresponding to the electric dipole and magnetic dipole can regulate the color of the photoluminescence, and the optimal concentration x = 0.05 reaches 1.0834, which is very close to white light. This phenomenon is related to the symmetry of the lattice. Simultaneously, it is observed that the fluorescence decay lifetime decreases with increasing concentration. The Commission Internationale de l'Eclairage coordinates obtained from the measured color of the sample are also very close to the standard white light coordinates (0.3333, 0.3333). The results presented above suggest that Gd7O6(BO3)(PO4)2:xDy3+ is a promising candidate for the next generation of white light-emitting diodes.

CaMnO3 is a promising starting point for the search of perovskites which are suitable as electrode materials for the hydrogen evolution reaction (HER). In a previous theoretical study [Phys. Status Solidi B 2022, 260, 2200427], it was established that the global hybrid functional PW1PW is well suited to obtain structural, energetic, and electronic bulk properties. Herein, the focus is extended to surface properties of CaMnO3. All symmetry-inequivalent low-index surfaces of CaMnO3 are investigated with PW1PW. Based on the experience with polar surfaces, it is decided to employ stoichiometric and symmetric models, in some cases with Schottky defects. From the calculated surface energies, the crystal morphologies are predicted based on the Gibbs–Wulff theorem. The (101), (100), (011), (001), and (010) surfaces (space group no. 62) and the (010), (110), (011), and (101) surfaces (space group no. 20) dominate the surfaces of respective single crystals and should be considered in future theoretical calculations of the HER. Furthermore, it is found that the modification with space group no. 20 is significantly more stable than space group no. 62 for nanoparticles with a diameter below 10 nm.

InGaAs infrared photodetectors subjected to irradiation environments undergo microstructural modifications and concomitant degradation, yet the underlying microscopic mechanism has not been fully studied. Herein, the influence of γ irradiation (total dose of 20 krad(Si)) on an In0.53Ga0.47 As/InP p–i–n focal plane array is studied by spatially resolved and temperature-dependent (3–290 K) photoluminescence (PL) measurements. By comparative PL studies of pre-irradiation and post-irradiation, the spatially resolved PL results of irradiation indicate that the in-plane uniformity of all PL features presents bigger fluctuations, meanwhile, the results of temperature-dependence PL demonstrate that the PL integral intensity related to impurities and interface-bound states is significantly weakened after irradiation. This can be attributed to the enhanced migration and reaction of defects caused by γ irradiation. Some mobile defects tend to migrate to lower energy regions, such as interfaces, and form defect complexes. In addition, some impurities combine with mobile defects and form inactive impurity–defect complexes. The findings reveal the effects of low-dose γ irradiation on InGaAs devices and may provide useful information for enhancing radiation resistance.

The multi-quantum-barrier electron blocking layer (EBL) is reported to significantly improve efficiency by nearly 3 times over a single barrier in deep-UV AlGaN light-emitting diodes to deal with electron leakage. The improvement is usually attributed to the enhanced effective barrier height, and this article aims to explore the benefits of the tunneling effect by calculating the tunneling currents of electrons and holes through an Al0.6Ga0.4N/AlyGa1−yN double-barrier EBL under external bias from opposite directions. The results show that the tunneling current for holes Jh is several orders of magnitude higher than that of the electrons Je as the barriers are with Al mole fraction y greater than 0.75 and thickness larger than 2 nm, which promises effective hole injection by tunneling without much electron leakage. Tunneling mechanism works better in EBL with higher and thicker barriers because the tunneling coefficients of light hole drop much slower than electrons due to its small effective mass. A proper distance between the barriers is needed to avoid electron leakage while holes tunnel through the EBL. Built-in electric fields tilt the band to enlarge the peak-to-valley ratio. This work indicates that the tunneling effect substantially facilitates a multibarrier EBL to enhance carrier-injection efficiency.

For heat-treatable aluminum alloys, solid solute elements play key role in material strengthening. Al–Mg–Si alloy is a typical heat-treatable alloy; Cu and Si atoms are its main solid solution atoms. To reveal the strengthening mechanism, the interaction between the edge dislocations and the Cu and Si solute atoms of different concentration in aluminum matrix is investigated by molecular dynamics (MD) simulation. Results indicate that Cu atoms provide a more effective strengthening due to the stronger pinning effect. The increment of critical resolved shear stress (ΔCRSS) is a function of concentration of solid solute atoms. When more than two types of solid solution atoms coexist in matrix, the final increment of the ΔCRSS is determined by the interactive effects of the atoms instead of the direct sum of all items. The pinning of Cu solid solute atoms can lead to two Shockley partial dislocations merging to an edge dislocation.

The consequences of an elaborated computational survey of electronic structure and optical spectra for A2BCl6 (A= Cs; B= Se, Sn, Te, Ti, Zr) and (A=K; B=Pd, Pt, Sn) materials have been conducted utilizing Vanderbilt Ultra Soft Pseudo Potential (US-PP) process. The obtained structural properties of the materials of interest are in wonderful accordance with the obtainable theoretical input. From the electronic band-structure results, the Cs2BCl6 (B=Se, Sn, Te, Ti, Zr) and K2BCl6 (B= Pd, Pt, Sn) have been established to be within an energy band-gap that varies between 1.131 - 3.731 eV. The metallic behavior of the materials for Cs2BCl6 (B=Ta, W) and K2BCl6 (B=Ta, W, Mn, Mo, Os, Re, Ru, Ta, Tc) has been confirmed showing the attendance of conducting lineaments. The dielectric function is wide close to the ultraviolet districts (3.10-4.13 eV). They be least in the middle (4.13-6.20 eV) and far in the ultraviolet (6.20-12.4 eV) regions. The extinction coefficient of the A2BCl6 has the ability to worn for implements like Bragg’s reflectors, optical and optoelectronic equipments. The optical parameters of A2BCl6 disclose that our working constructions have an elevated dielectric constant, with a greatest absorption in the visible range holding out over 26.6 ​× ​104 ​cm−1. The present work confirms that, bromine and chlorine founded double perovskites are extremely attractive for photovoltaic and optoelectronic appliances.

The Hall resistivity of natural single crystals of pyrrhotite Fe7S8 exhibits oscillations with the inverse external magnetic field 1/B at temperature 77 K and B up to 0.73 Tesla. This resembles phenomena due to Landau quantization of the carriers demanding very pure samples, temperatures near 4 K and magnetic fields of several Tesla. However, none of these requirements is met in the experiments. The oscillations appear only when there is orientation of the elementary magnetic moments of Fe atoms, which happens when B is parallel to the c-plane at 77 K. At room temperature with the orientation destroyed by the thermal agitation and for B parallel to the c-axis along which the alignment of the Fe magnetic moments is negligible, the oscillations disappear. According to the s–d model proposed for heavily doped magnetic semiconductors, defects and impurities produce large local fluctuations of carrier concentrations. These through the strong s–d exchange interaction between the carriers and the lattice magnetic moments of Fe establish variations of local magnetization. These constitute scattering centers which are enforced for certain values of B, though for others weaken giving the oscillatory behavior of the Hall resistivity.

Sodium zinc phosphate glasses modified by Tl2O addition of composition Na2−xTlxZnP2O7 (x = 0, 0.005, 0.01, and 0.015) are synthesized following the melt quenching technique. The structure of the glass samples is analyzed by the Fourier transform infrared absorption spectroscopy. The results suggest that the phosphate network is polymerized by the addition of Tl+ ions. The electrical conductivity, electric modulus, and dielectric constant characteristics of the glasses are measured over a wide continuous frequency range of 10−2 Hz–1 MHz and in the temperature range 293–473 K by the impedance spectroscopic method. The ac conductivity data are analyzed following the power law exponent (S) and the proposed correlated barrier hopping mechanism (CBH) is the most suitable conduction mechanism in the studied compositions. The electrical modulus formalism is applied to analyze the electric data to study their dielectric relaxation. Non-Debye type relaxation is obtained. From the obtained results, the present glass can be used as a high-energy capacitor.

Material´s patterned modifications are crucial for device fabrication, and their evolution from the micro- to the nanoscale depends on the development of modification and characterization techniques. Herein, a graphene sample cut by a He-ion beam is characterized using Raman spectroscopy. What can be obtained from micro-Raman spectroscopy as compared to nano-Raman spectroscopy is analyzed, the latter implemented in the tip-enhanced Raman spectroscopy (TERS) configuration. Local sputtering, inhomogeneous distributions of defects, strain and doping are only observed in the higher-resolution nano-Raman-mode characterization.

The macroscopic physical properties of materials are determined by their crystal and electronic structures. Iridates have anomalous electronic structures because of the competition of comparable energies between the Coulomb repulsion of electrons and spin–orbit coupling. The polycrystalline Sr4Ir3O10 sample is successfully synthesized, which owns a trilayered perovskite structure using the high-pressure and high-temperature technique. The transmission electron microscopy studies give the structural evidence of Sr4Ir3O10 in real space experimentally. It is proved that tetragonal and orthorhombic structures with I4/mmm and Pbca space groups coexist in the polycrystalline Sr4Ir3O10 sample.

First-principles calculations are employed to explore the elastic anisotropy and thermal properties of Mg–Ti–O compounds (MgTiO3, MgTi2O5, and Mg2TiO4). The structure parameters used in this work are in good agreement with other theoretical and experimental results. The mechanical stability and ductile nature are demonstrated. The elastic anisotropy is characterized by different anisotropy indexes, three-dimensional (3D) surface constructions, and two-dimensional (2D) projections of Young's modulus. Besides, the sound velocities, Debye temperature, and minimum thermal conductivity are also investigated from the elastic modulus. The obtained results can provide references for future experimental investigations and engineering applications of these Mg–Ti–O compounds.

The aim of this research is to obtain and to compare the electrical conductivity and the transmittance of two heterostructures: Gr/WS2 and Gr/MoS2 on quartz. Raman spectroscopy is used to analyse the quality of the samples before and after the measurements. Terahertz time domain spectroscopy (THz-TDS) in transmission mode is used as a non-destructive technique to obtain the surface conductivity and the transmittance in the frequency range [0.2, 1.6] THz. The transmittance values obtained for both samples are similar, whereas the surface conductivity of Gr/WS2 is higher than the one of Gr/MoS2 and both are higher than the conductivity values obtained for individual homogeneous layers. FT-IR and UV-Vis spectroscopies are used to obtain the optical transmittance and to evaluate the behaviour of each layer in the frequency ranges [90, 180] THz and [300, 1200] THz, respectively. In the IR range, the transmittance of the heterostructures is similar to that of the individual materials, although in the visible range the transmittance is totally dominated by the WS2 and MoS2 layers. These characteristics make these heterostructures good candidates to be used for optoelectronics sensors.

In order to enhance the load-bearing capacity and energy absorption capacity of the honeycomb, star-rhombus honeycombs (SRHs) are proposed by adding rhombic parts to the traditional star-shaped honeycomb (TSH). Three kinds of SRHs named SRH-A, SRH-B, and SRH-C are designed. The quasi-static crushing responses of SRHs, including deformation mechanism, crushing stress, specific energy absorption (SEA), and Poisson’s ratio, are studied based on the finite element (FE) method. The FE results show that the introduction of rhombic parts increased the number of plastic hinges on the SRHs, resulting in significantly higher crushing stress and SEA of the SRHs than that of the TSH. Among the SRHs, SRH-A has the largest energy absorption, and the SEA value of SRH-A is 98.2% higher than TSH. Then, parametric studies including wall thickness, cell-wall angle, and spacing length between the vertices of the star-shaped part and the rhombic part are carried out. The wall thickness and cell-wall angle have the greatest influence on the crushing response of the SRHs. Crushing stress and Poisson’s ratio of SRHs can be adjusted by changing the wall thickness of the rhombic part. The configurations and geometric parameters of the rhombic part determine the Poisson’s ratio of SRHs. This study provides effective guidance for designing star-shaped honeycombs with enhanced load-bearing capacity and energy absorption capacity.

A method for modulating transverse magnetic intrinsic graphene plasmons by temperature is proposed. In contrast to existing 2D or 3D infinite graphene structures, an intrinsic graphene 3D finite structure with periodicity in all three directions is designed. At the matching point, where the dispersion curve of the intrinsic graphene plasmons intersects with that of electromagnetic radiation, the intrinsic graphene plasmons and electromagnetic radiation can be excited by each other; in other words, the plasmon can be excited by light without additional mechanisms. Furthermore, the influence of environment temperature on the matching point is shown. The study reveals that the plasmon modulation is adaptive to the temperature. These results are beneficial for the design of compact graphene-based optoelectronic devices.

Ultrasensitive gas sensors have been fabricated depending on novel 2D materials. The adsorption behavior of diatomic molecules (H2, HF, N2, CO, O2, and NO) on the 2D-SnP3 monolayer is investigated by utilizing first-principle calculations for seeking the applications of sensing and detecting gases. H2 molecule displays weak adsorption effects on the SnP3 monolayer, while N2, CO, HF, and O2 show a moderate adsorption effect. NO molecule tends to chemisorb, resulting in a significant change transition for the electrical conductivity of the SnP3 monolayer. The calculation results of adsorption energies, charge transfers, and work function indicate that the SnP3 monolayer can be a promising candidate as a room-temperature NO gas sensing 2D material due to its high selectivity, conspicuous sensitivity, and short recovery time. This study can guide the feasibility of using SnP3 monolayer as a NO gas sensor in further experimental applications.

Herein, the biaxial strain effect is investigated on the structural, electronic, and optical properties of 1T and 1H phases of Janus CaFBr monolayer in the framework of density functional theory. It is found that both phases of the Janus CaFBr monolayer are direct semiconductors at equilibrium, with bandgaps of 3.90 and 3.55 eV for 1T and 1H phases, respectively. The thermodynamic stability is examined via cohesive energy and phonon dispersion. The bandgap decreases linearly and is nearly parabolic for 1T and 1H phases, respectively, when switching from the tensile to compressive strain with a drastic shift from direct to indirect bandgap at −10% of compressive strains. The calculated dielectric function and optical properties such as reflectivity, refractive index, extinction, and absorption coefficients enhance under biaxial with an improvement of the absorption coefficient especially in the visible and ultraviolet (UV) regions for 1H and 1T phases, respectively, which is in line with the dielectric constant. The results suggest that the Janus CaFBr monolayer might be a potential candidate for optoelectronic applications in visible/UV detection and absorption.