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The recent claimed room-temperature superconductivity in Cu-doped lead apatite at ambient pressure is under debate. To identify its physical origin, we conducted a detailed analysis of the crystal structure, band structure, lattice dynamics and magnetic properties of the parent Pb${}_{10}$(PO₄)₆O compound and the two different phases of Pb₉Cu(PO₄)₆O (LK-99) compound. Our results show that the parent Pb${}_{10}$(PO₄)₆O compound is an indirect band gap semiconductor, where Cu doping at the 4f site of Pb leads to a semiconducting to half-metallic transition. Two half-filled flat bands spanning the Fermi energy levels are present in the 4f phase of LK-99, which are mainly formed by hybridization of the d orbitals of Cu with the 2p orbitals of O. In addition, 6h phase of LK-99 always has spin polarization at the bottom of the conduction band and at the top of the valence band, making the material a magnetic semiconductor. Our theoretical research reveals recent experimental reports on the different transport properties of LK-99.

Scanning nuclear microprobes using Rutherford backscattering (RBS) and particle-induced X-ray emission (PIXE) with light ions have been formed using variable objective slits and a magnetic quadrupole doublet. Beam optics, focusing techniques, factors limiting the minimum beam-spot size, and data acquisition systems are discussed. Two- and three-dimensional RBS mapping and channeling contrast mapping of processed semiconductor layers such as multilayered wiring and focused ion-implanted layers are demonstrated. Problems with microbeam analysis such as radiation damages due to the probe beams are discussed.

Material characterization is challenged by continuously decreasing device dimensions placing significant demands on characterization instruments and measurement interpretation. Numerous techniques exist and a few are highlighted here. Some of these have existed for a long time, while others have only emerged from the laboratory recently. Generally they are more user-friendly and have reasonable turn-around times. The trend in many techniques is clearly toward characterization of smaller dimensions. Among the myriad of characterization techniques in use today, I will discuss recent advances in transmission electron microscopy (TEM), electron holography, magnetic exchange force microscopy (MExFM), atom probe ion field ion microscopy, and X-ray tomography. They have made significant advances in the last few years and in some cases have produced very impressive results. For example, TEM is now able to generate images with 0.05 nm resolution, allowing display of individual atoms. MExFM in conjunction with magnetic fields has demonstrated vertical resolution of 0.0015 nm. Helium ion microscopy is also highlighted because it contributes a new application of ion beams, which had been largely the domain of Rutherford backscattering. Progress in developing further advances in nm dimensional characterization will, no doubt, continue to satisfy the demand for such measurements in the future.

Power semiconductor devices are important for numerous applications with power conversion being an important one. Wide energy gap semiconductors SiC and GaN have properties that make them attractive for such applications. Among these properties are high thermal conductivity, high breakdown electric field, wide energy gap, low intrinsic carrier concentration, high thermal stability, high saturation velocity and chemical inertness. These lead to low on-resistance, high breakdown voltage, high frequencies, small volume, and small passive inductors and capacitors. These desirable properties are offset by the higher material costs and higher defect densities. Although wide energy gap devices have been in development for many years, only recently have they become available commercially. Their main competition is silicon power devices with breakdown voltages up to 8000 V and very high surge current capacity. However, silicon power devices are approaching their material limits and wide energy gap devices are beginning to have an impact in the power electronics space. SiC has the advantage of substrates with diameters approaching 150 mm and the ability to grow thermal SiO₂. GaN has the heterojunction advantage, but no viable substrate technology. In fact, a large portion of SiC production is used for GaN substrates. GaN material development has also benefited significantly from the development of optical devices, e.g., light-emitting diodes and lasers.

First-principles calculations were carried out to study the stability and electronic properties of native vacancy defects in the semiconducting ZnIn₂Te₄ (ZIT) and CdIn₂Te₄ (CIT). The Zn/Cd and In vacancies are acceptor defects, while the Te vacancy is donor defect. However, the In and Te vacancies dominate in the $n$-type and $p$-type semiconducting environments, respectively. The Te vacancy is not excited, so it could not compensate the majority of free carriers. The In vacancy prefers to be excited, which generates free hole carriers to compensate the majority of electron carriers. The Zn vacancy is rare in a typical semiconducting environment. Furthermore, all the vacancies induce localized defect states which may be trap centers for the free carriers. Accordingly, these native vacancy defects are destructive for the development of solar cells based on ZIT and CIT, so they should be avoided as much as possible during the growth process.

We present a detailed theoretical study of the influence of linearly polarized intense terahertz (THz) laser radiation on energy states of hydrogen-like impurities in semiconductors. The dependence of the binding energy for ground (1s) and first excited (2s) states, E_1s and E_2s, on the intensity and the frequency of the THz radiation has been examined for a GaAs-based system. It is found that E_1s, E_2s and E_2s-E_1s decrease with increasing radiation intensity or with decreasing radiation frequency, which implies that an intense THz field can enhance ionization of dopants in semiconductors. Our analytical and numerical results show that one of the most important results obtained by A. L. A. Fonseca et al. [Phys. Stat. Sol. (b)186, K57 (1994)] is incorrect.

The near band-edge polarized optical optical absortion spectra of EuTe at low temperatures and high magnetic fields were investigated. The samples were grown by MBE on BaF₂ substrates, and the thickness varied in the 0.18-2.0 μm range. At high magnetic fields, the well-known 4f⁷→4f⁶5d(t_2g) optical transition splits into two well resolved lines at σ⁺ and two lines for σ^-. These lines can be described by localized transitions tunable by the d-f exchange interaction, with a quadratic dependence on the intensity of the external magnetic field. Comparative measurements of the magnetization and the optical absorption as a function temperature provides a further test of the model of a localized excitation extending over a few lattice sites.

Doped superlattices of GaAs/Al_0.21Ga_0.79As composition, with a carrier concentration of n=1.4×10¹²cm^-2 and n=1.7×10¹²cm^-2 per superlattice period, where studied by photoluminescence in high magnetic fields. The photoluminescence intensity at fixed photon energies showed weak oscillations. From the oscillatory photoluminescence the superlattice miniband energy width and the renormalized bandgap were deduced.

ZnO nanorods and bamboo-like structures were fabricated by carbothermal evaporation in Ar gas and air atmosphere on Au-coated silicon wafers. Deposition in air atmosphere led to the fabrication of nanostructured ZnO. Investigation of substrate distance from the source material revealed that thinner nanorods are grown at shorter distances.

In recent years, electrical spin injection and detection has grown into a lively area of research in the field of spintronics. Spin injection into a paramagnetic material is usually achieved by means of a ferromagnetic source, whereas the induced spin accumulation or associated spin currents are detected by means of a second ferromagnet or the reciprocal spin Hall effect, respectively. This article reviews the current status of this subject, describing both recent progress and well-established results. The emphasis is on experimental techniques and accomplishments that brought about important advances in spin phenomena and possible technological applications. These advances include, amongst others, the characterization of spin diffusion and precession in a variety of materials, such as metals, semiconductors and graphene, the determination of the spin polarization of tunneling electrons as a function of the bias voltage, and the implementation of magnetization reversal in nanoscale ferromagnetic particles with pure spin currents.

Laser ablation has attracted special interest for the formation of thin films compared with other formation technique. A distinctive feature of laser ablation is that it allows high quality and stoichiometry of films of even very complex element material. In this presentation, laser ablation of AgInSe₂ chalcopyrite semiconductor will be discussed in which it is difficult to maintain stoichiometry by conventional method. High Quality AgInSe₂ (AIS) films were grown on Glass substrates by the ultra-high-vacuum pulsed laser deposition technique from the AIS target synthesized from high-purity materials. The X-ray diffraction studies of the films show that films are textured in (112) direction. The substrate temperature appears to influence the properties of films. Increase in substrate temperature results in a more ordered structure. Compositional analysis has been carried out by EDAX. It is observed that compositional stoichiometry is maintained to a greater extent by PLD technique than other traditional methods like thermal evaporation. The optical studies of the films show that the optical band gap is about 1.20 eV.

We describe experimental and related theoretical work on the measurement of the Casimir force using semiconductor test bodies. This field of research started in 2005 and several important and interesting results have already been obtained. Specifically, the Casimir force or its gradient was measured in the configuration of an Au-coated sphere and different semiconductor surfaces. It was found that the force magnitude depends significantly on the replacement of the metal with a semiconductor and on the concentration of charge carriers in the semiconductor material. Special attention is paid to the experiment on the optical modulation of the Casimir force. In this experiment the difference in Casimir force between an Au-coated sphere and a Si plate in the presence and in the absence of laser light was measured. Possible applications of this experiment are discussed, specifically, for the realization of the pulsating Casimir force in three-layer systems. Theoretical problems arising from the comparison of the experimental data for the difference in Casimir force with the Lifshitz theory are analyzed. We consider the possibility to control the magnitude of the Casimir force in phase transitions of semiconductor materials. Experiments on measuring the Casimir force gradient between an Au-coated sphere and a Si plate covered with rectangular corrugations of different characters are also described. Here, we discuss the interplay between the material properties and nontrivial geometry and the applicability of the proximity force approximation. The review contains comparison between different experiments and analysis of their advantages and disadvantages.

Anomalous (non-Gaussian) kinetics is often observed in various disordered materials, such as amorphous semiconductors, porous solids, polycrystalline films, liquid-crystalline materials, polymers, etc. Recently the anomalous relaxation-diffusion processes have been observed in nanoscale systems: nanoporous silicon, glasses doped by quantum dots, quasi-one-dimensional (1D) systems, arrays of colloidal quantum dots, and some others. The paper presents a review of new approach, based on fractional kinetic equations. We give a physical basis for some fractional equations deriving them from their classical counterparts by means of averaging over statistical ensemble of disordered media. We consider self-similarity as the main feature of these processes, and explain memory phenomena in frameworks of hidden variables conception.

The quest for novel low-dimensional materials has led to the discovery of graphene and thereafter, a tremendous attention has been paved in designing of its fascinating properties aiming in fabricating electronic devices. Using first-principles calculations, we study the structure, energetic and electronic as well as magnetic properties of graphene induced by the interactions in presence of both external and internal foreign agents in detail. We find that a variety of tunable electronic states, e.g., semiconductor-to-half-metal-to-metal and magnetic behaviors can be achieved under such hierarchical interactions and their influence. We also find that the nature and compositions of foreign substances play a key role in governing the electro-magnetic characteristics of these nanomaterials. In this review, we suggest a few routes for engineering the tunable graphene properties suitable for future electronic device applications.

A novel temperature-independent superconducting device that employs a doped semiconductor is presented in this study. The underlying theory of this superconductivity is confirmed by experimental results. Specifically, superconductivity generates a negative electric field with characteristics of both electrostatic and current-induced fields. This type of electric field creates a new paired interaction between two electrons and implies the existence of a new force. The negative electric field also exhibits the Meissner effect. Moreover, magnetic flux quanta are produced in the semiconductor. The Aharonov–Bohm effect is exhibited to create a superconducting current along the electric circuit of the superconducting system. Therefore, a load introduced to the circuit will also become superconductive. This finding has strong potential for practical applications. To solve the problem of critical current, a static magnetic field is applied. This field combines with the new electric field to yield cyclotron motion, which increases superconducting current.

The elastic, electronic, and optical properties of ${\mathrm{\text{Cu}}}_{3}M{\mathrm{\text{Te}}}_4$$(M=\mathrm{\text{Nb}}$, $\mathrm{\text{Ta}})$ are investigated for the first time using the density-functional formalism. The optimized crystal structure is obtained and the lattice parameters are compared with available experimental data. Different elastic moduli are calculated. The Born criteria for mechanical stability are found to be fulfilled from the estimated values of the elastic moduli, $C_{ij}$. The band structure and the electronic energy density of states (EDOS) are also determined. The band structure calculations show semiconducting behavior for both the compounds. The theoretically calculated values of the band gaps are found to be strongly dependent on the nature of the functional representing the exchange correlations. Technologically significant optical parameters (e.g., dielectric function, refractive index, absorption coefficient, optical conductivity, reflectivity, and loss function) have been determined. Important conclusions are drawn based on the theoretical findings.

We investigate electron transport between circular graphene quantum dots (CGQDs) and ZnO nanowires (ZnO NWs). This structure can be used as donor and acceptor in hybrid solar cells. We consider circular quantum dots (QDs) and use analytical calculation in order to estimate wavefunctions of GQD and ZnO NWs. After calculating the wavefunctions overlap, we use Marcus relation in order to calculate electron transfer rate. Also, we calculate this transfer rate for CdSe QDs–ZnO NWs system. Results from analytical calculation show that the transfer rate is limited to 10${}^{13}$ s${}^{-1}$. This result is in agreement with experimental results which are reported earlier. Such systems could be suitable for solar cells.

The spectroscopic study of La₂O₃ thin films deposited over Si and SiC at low RF power of 25 W by using indigenously developed plasma-enhanced atomic layer deposition (IDPEALD) system has been investigated. The tris (cyclopentadienyl) lanthanum (III) and O₂ plasma were used as a source precursor of lanthanum and oxygen, respectively. The $\sim$1.2 nm thick La₂O₃ over SiC and Si has been formed based on our recipe confirmed by means of cross-sectional transmission electron microscopy. The structural characterization of deposited films was performed by means of X-ray photoelectron Spectroscopy (XPS) and X-ray Diffraction (XRD). The XPS result confirms the formation of 3${}^{+}$ oxidation state of the lanthania. The XRD results reveals that, deposited La₂O₃ films deposited on SiC are amorphous in nature compare to that of films on Si. The AFM micrograph shows the lowest roughness of 0.26 nm for 30 cycles of La₂O₃ thin films.

This paper introduces a device performance optimization approach for the FinFET through optimization of the gate length. As a result of reducing the gate length, the leakage current (I${}_{\mathrm{\text{off}}}$) increases, and consequently, the stress along the channel enhances which leads to an increase in the drive current (I${}_{\mathrm{\text{sat}}}$) of the PMOS. In order to sustain I${}_{\mathrm{\text{off}}}$, work function is adjusted to offset the effect of the increased stress. Changing the gate length of the transistor yields different drive currents when the leakage current is fixed by adjusting the work function. For a given device, an optimal gate length is found to provide the highest drive current. As an example, for a standard performance device with I${}_{\mathrm{\text{off}}}$ = 1 nA/um, the best performance I${}_{\mathrm{\text{sat}}}$ = 856 uA/um is at L = 34 nm for 14 nm FinFET and I${}_{\mathrm{\text{sat}}}$ = 1130 uA/um at L = 21 nm for 7 nm FinFET. A 7 nm FinFET will exhibit performance boost of 32% comparing with 14 nm FinFET. However, applying the same method to a 5 nm FinFET, the performance boosting is out of expectance comparing to the 7 nm FinFET, which is due to the severe short-channel-effect and the exhausted channel stress in the FinFET.

With the help of temperature dependence, Raman scattering anharmonic effect of various modes of layered semiconductor InSe over temperature range of 20–650 K has been studied. It was found that with an increase in temperature, anharmonicity will increase. Two and three phonons coupling with optical phonon, are used to describe temperature-induced anharmonicity in the linewidth of Raman modes. It was found that the temperature variation of the phonon parameter can be accounted for well by the cubic term in anharmonic model. To describe line-center shift of Raman modes, a model not considering independently cubic and quartic anharmonicity was used. A similar study has been done for InSe doped with different concentration of GaS dopant. The result of temperature study of InSe doped with GaS revealed that in this case anharmonicity increases with an increase in dopant and an increase in temperature.