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In this work, the impact of Al doping and Mg alloying on the conduction band misalignment (Δ E C) between ZnO and (100) Si with a SiO x interlayer was studied by combining capacitance vs voltage, Hall and x-ray diffraction measurements, energy-dispersive x-ray spectroscopy, secondary mass spectrometry, and high-resolution scanning transmission electron microscopy. To decouple the effect of the high carrier density in the ZnO-based layers due to the Al introduction, the measured Δ E C was corrected for the conduction band lowering effect taking into account the conduction band non-parabolicity of ZnO. Then, from the Mg content dependence, using the interface-induced gap states approach, branch point energies referred to the valence band maximum equal to (2.7 ± 0.2) and (3.6 ± 0.4) eV were extracted for ZnO and MgO, respectively. These branch point energies were obtained under the assumption of a linear variation between the respective values of the corresponding two binary compound semiconductors, ZnO and MgO, and taking into account the presence of the SiO x interlayer. Furthermore, in the case of the undoped Zn 0.96 Mg 0.04 O layers, a ∼ 0.27 eV reduced Δ E C was found, with the difference with respect to Zn 0.94 Mg 0.06 O:Al attributed to the presence of a downward band bending toward the interface with SiO x. Full 1 × 1 cm test solar cells based on Zn 0.8 Mg 0.2 O:Al layers exhibited short circuit currents, open circuit voltages, fill factors, and efficiencies that varied in the (28 ± 1) mA / cm 2 , (430 ± 20) mV, (61 ± 2) %, and (7.2 ± 0.3) % ranges with the residual Δ E C ∼ 0.6 eV being among the main causes of the reduced device performances. [ABSTRACT FROM AUTHOR]

Antiferromagnetic (AFM) materials exhibit great potential for next-generation spintronic applications because they have some unique characteristics compared to ferromagnetic (FM) materials. For example, the successful electrical manipulation and detection of the Néel vector at room temperature was recently realized for AFM CuMnAs in its tetragonal phase. The Néel temperature (TN) for tetragonal CuMnAs is about 480 K. In contrast, cubic half-Heusler CuMnSb, despite it is isovalent to CuMnAs, exhibits a notably lower TN of about 50 K, limiting its applicability in spintronic devices. The physical origin behind the stark difference in TN between the two compounds remains unclear. In this study, we investigate both CuMnAs and CuMnSb in both tetragonal and cubic phases. We find that the band crossing between the valence band and conduction band is more pronounced in CuMnSb compared to CuMnAs. This disparity arises from the higher energy level of the Sb 5p orbital relative to the As 4p orbital, resulting in a greater abundance of carriers in CuMnSb than in CuMnAs. Utilizing the effective band coupling model, we establish a relationship between carrier concentration and magnetic stability and confirm that the elevated carrier concentration is the origin of the weakened antiferromagnetism observed in both phases of CuMnSb. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS2) is a promising electrocatalyst for the hydrogen evolution reaction (HER) due to excellent stability and low cost. However, the utilization in electrocatalytic hydrogen evolution is constrained by inherent shortcomings, including fewer edge active sites, poor dispersion, and electrical conductivity. In this work, MoS2 was compounded with carbon nanotubes (CNTs), which are known for their high specific surface area and excellent electrical conductivity. These CNTs, laden with oxygen-containing functional groups, provided nucleation sites that facilitated the rapid assembly of MoS2 nanoflowers under hydrothermal conditions within 3 h. Due to their diminutive size (∼300 nm), these nanoflowers possess a large specific surface area and numerous active sites at their edges. Furthermore, MoS2 nanoflowers exhibited a high concentration of intrinsic S-vacancies. This heterojunction material exhibited superior HER properties. In addition, density functional theory simulation further confirmed that the MoS2 with S vacancy and CNT heterojunction electrocatalysts (VS-M/C) provided a fast charge transfer pathway for water electrolysis, and analysis showed that the conduction band minimum and valence band maximum were mainly contributed by the d orbits of Mo and the p orbits of C. This study proffered a novel approach for the engineering of high-performance MoS2-based HER electrocatalysts. [ABSTRACT FROM AUTHOR]

We present a comprehensive theoretical analysis of intrinsic high-field transport in cuprous halides: CuCl, CuBr, and CuI. Ensemble Monte Carlo transport simulations were performed based on analytical approximations of the multi-valley and three-band electronic structure model. The deformation potentials, extracted from carrier–phonon interaction matrix elements calculated via the Wannier function approach, were employed to determine scattering rates. Our detailed analysis uncovers intriguing transport characteristics based on the complex valence band structures, resulting from spin–orbit coupling and band inversion. Remarkably, the hole mobility in CuI was exceptionally high, reaching up to 193 cm2/V s, while CuCl exhibited unusual temperature dependencies in hole transport. Additionally, the electron mobility in CuI was found to be 254 cm2/V s, indicating a minimal disparity between carrier mobilities, which is advantageous for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Two-dimensional ferroelectric materials are beneficial for power-efficient memory devices and transistor applications. Here, we predict out-of-plane ferroelectricity in a new family of buckled metal oxide (MO; M: Ge, Sn, Pb) monolayers with significant spontaneous polarization. Additionally, these monolayers have a narrow valence band, which is energetically separated from the rest of the low-lying valence bands. Such a unique band structure limits the long thermal tail of the hot carriers, mitigating subthreshold thermionic leakage and allowing field-effect transistors (FETs) to function beyond the bounds imposed on conventional FETs by thermodynamics. Our quantum transport simulations reveal that the FETs based on these MO monolayers exhibit a large ON/OFF ratio with an average subthreshold swing of less than 60 mV/decade at room temperature, even for short gate lengths. Our work motivates further exploration of the MO monolayers for developing advanced, high-performance memory and logic devices. [ABSTRACT FROM AUTHOR]

Broadband blue emission in zero-dimensional perovskites has received considerable attention, which is very important for the realization of stable blue-light emitters; however, the underlying formation mechanism remains unclear. Based on first-principles calculations, we have systematically studied the self-trapped excitons (STEs) behavior and luminescence properties in 0D-(DMA)4PbI6 perovskite. Our calculations show that there is a significant difference between the intrinsic STE luminescence mechanism (∼2.51 eV) and experimental observations (∼2.70 eV). In contrast, we found that the iodine vacancy (VI) is energetically accessible and exhibits a shallow charge transition level at ∼2.69 eV (0/+1) above the valence band maximum, which provides the initial local well for the STEs formation. Moreover, the low electronic dimension synergistic Jahn–Teller distortion facilitates the formation of extrinsic excitons self-trapping. Further excited state electronic structure analysis and configuration coordinate diagram calculations confirmed that the broadband blue emission in 0D-(DMA)4PbI6 is the origin of VI-induced extrinsic STEs instead of intrinsic STEs. Therefore, our simulation results rationalize the experimental phenomena and provide important insights into the formation mechanism of STEs in low-dimensional perovskite systems. [ABSTRACT FROM AUTHOR]

The valence and core photoelectron spectra of three substituted disulfide systems, α-lipoic acid, trans-4,5-dihydroxy-1,2-dithiane, and di-Boc-cystamine, are presented alongside detailed theoretical analysis based on equation-of-motion coupled-cluster singles doubles for ionization potentials and the nuclear ensemble approach. A comparison of the linear and five- and six-membered ring cyclic structures reveals that the energetic separation of the non-bonding sulfur orbitals can be used to calculate a reliable estimate of the C–S–S–C dihedral angle, even for substituted disulfides, and that the sulfur 2p, oxygen 1s, and valence band photoelectron spectra are a useful site-specific probe of hydrogen bonding. [ABSTRACT FROM AUTHOR]

A series of Mg doped p-type multi-layered hBN films were prepared by atmospheric pressure chemical vapor deposition. Temperature dependent conductivity measurements were performed from 0.1 Hz to 10 MHz to analyze the characteristics of tail states close to the valence band edge. Jonscher's power law (A ω s ) is successfully applied to understand charge carrier transport through these states. In this work, exponent S increases from 0.6 → 0.8, 0.8 → 0.995, and 1.4 → 1.6 for samples B (precursor temperature, 750 °C), D (850 °C), and E (900 °C), indicating that non-overlapping small polaron tunneling dominates to 548 K. Polaron binding energies of 0.2–0.40 eV and tunneling distances <4.9 Å are calculated, confirming transport through localized states. The density of states near the Fermi level N(EF) was extracted from a fit to the AC conductivity data, yielding values of 10 15 and 10 17 e V − 1 c m − 3 as the precursor temperature increases. Singular Mg acceptor levels of 74, 30, and 17 meV are identified for each sample. A hole concentration from 6.5 × 1017 to 1 × 1018 cm−3 and carrier mobility from 18 to 25 cm2/V s is measured at 300 K. From RC fitting, carrier recombination lifetimes of 1.2, 0.4, and 0.35 μs are determined. Fermi's golden rule is used to determine an optical joint density of states of 1.1 × 1021 eV−1 cm−3 at a band edge. Overall, we show that AC conductivity is an effective method to evaluate midgap states in 2D (two-dimensional) materials at EF and p-type hBN possesses sufficient electrical properties to be integrated into a wide range of semiconductor applications. [ABSTRACT FROM AUTHOR]

Deep levels in the whole bandgap of 4H-SiC generated by reactive ion etching (RIE) are investigated with both n- and p-type SiC Schottky barrier diodes by deep-level transient spectroscopy (DLTS). Depth profiles of the observed deep levels were analyzed using the DLTS peak intensities at various bias voltages and numerical calculations. The major electron traps detected after RIE and subsequent annealing at 1300 ° C include the Z 1 / 2 (E C − 0.66 eV), ON1 (E C − 0.88 eV), ON2 (E C − 0.95 eV), and EH 6 / 7 (E C − 1.50 eV) centers, and the major hole traps include the UK1 (E V + 0.51 eV), UK2 (E V + 0.72 eV), HK0 (E V + 0.77 eV), HK2 (E V + 0.79 eV), and HK3 (E V + 1.31 eV) centers, where E C and E V denote the conduction and valence band edges, respectively. Most of the traps were localized near the surface (<0.5 μ m) with a maximum density of about 1 × 10 15 cm − 3 , but several traps such as the ON1 and HK0 centers penetrate deep into the bulk region (>2 μ m). By annealing at 1400 ° C, most of the hole traps were eliminated, but several electron traps remained. From these results, the origins of these defects are discussed. [ABSTRACT FROM AUTHOR]

With density functional theory (DFT), it is possible to calculate the formation energy of charged point defects and in turn to predict a range of experimentally relevant quantities, such as defect concentrations, charge transition levels, or recombination rates. While prior efforts have led to marked improvements in the accuracy of such calculations, comparatively modest effort has been directed at quantifying their uncertainties. However, in the broader DFT research space, the development of Bayesian Error Estimation Functionals (BEEF) has enabled uncertainty quantification (UQ) for other properties. In this paper, we investigate the utility of BEEF as a tool for UQ of defect formation energies. We build a pipeline for propagating BEEF energies through a formation-energy calculation and test it on intrinsic defects in several materials systems spanning a variety of chemistries, bandgaps, and crystal structures, comparing to prior published results where available. We also assess the impact of aligning to a deep-level transition rather than to the VBM (valence band maximum). We observe negligible dependence of the estimated uncertainty upon a supercell size, though the relationship may be obfuscated by the fact that finite-size corrections cannot be computed separately for each member of the BEEF ensemble. Additionally, we find an increase in estimated uncertainty with respect to the absolute charge of a defect and the relaxation around the defect site without deep-level alignment, but this trend is absent when the alignment is applied. While further investigation is warranted, our results suggest that BEEF could be a useful method for UQ in defect calculations. [ABSTRACT FROM AUTHOR]

Band-tail states, i.e., charge-carrier energy states located in the bandgap at the valence and conduction band edges of amorphous materials, even though not delocalized, exhibit nonzero mobility; thus, they are expected to contribute to the charge-conduction process. A microscopic model based on hydrodynamic transport equations for unipolar conduction, including trap, band-tail, and band states, and coupled to the Poisson equation is presented here. The equations are self-consistently solved by means of a numerical procedure, and the results provide qualitative and quantitative estimates of the influence of band-tail states (namely, of their energy distribution, density, and mobility) on the carrier heating, precursor of the Ovonic threshold switch. [ABSTRACT FROM AUTHOR]

β-LiGaO2 with a wurtzite-like crystal structure is a direct ultra-wide bandgap semiconductor. Similar to many wide bandgap oxides, the valence band of LiGaO2 is predominantly composed of O-2p orbital, leading to a low valence band position, drastically limiting its applications. In this work, we employ first-principles calculations to demonstrate that adding a small amount of Bi into LiGaO2 to form the highly mismatched Li(Ga1−xBix)O2 alloys can dramatically modulate the valence band compositions. Compared to LiGaO2, the valence band maximum of the alloys is significantly elevated, and a fully occupied intermediate valence band appears, further raising the valence band positions. Despite the appearance of intermediate valence bands that significantly reduce the alloys' bandgap, the bandgap remains over 3.10 eV, ensuring visible light transparency. With increasing Bi composition in the alloys, the bulk modulus increases while the shear modulus gradually decreases, which improves the ductility. Moreover, the compliant elastic constants of the alloys indicate mechanical stability. These findings suggest that Li(Ga1−xBix)O2 alloys are promising flexible transparent conductive oxides, offering valuable insights for future applications. [ABSTRACT FROM AUTHOR]

This study investigates the impact of biaxial strain on monolayer black phosphorus (BP) through first-principles calculations, confirming its stability and subsequently modifying its photocatalytic performance. Under biaxial strain, BP exhibits a direct bandgap suitable for photocatalytic hydrogen production during water splitting, albeit with limitations due to its valence band maximum edge. A distinctive GaN/BP heterojunction is proposed, featuring a direct bandgap and advantageous band edge positions conducive to efficient photocatalytic overall water splitting. Under the influence of biaxial strain, the heterojunction type undergoes a transition from direct type-I to direct type-II and Z, augmenting the separation of photoexcited electrons and holes and markedly enhancing the efficiency of photocatalytic hydrogen production. Furthermore, the heterojunction exhibits commendable capabilities in absorbing visible light. This research provides a promising avenue to surmount the constraints associated with monolayer BP in photocatalysis, offering valuable insights for the development of efficient photocatalytic materials. [ABSTRACT FROM AUTHOR]

Modern electronic and optoelectronic devices rely on the development of the complementary pair of n-type and p-type semiconductors. However, it is often seen that n-type semiconductors are easier to realize and offer superior performances than their p-type counterparts, with p-type semiconductors showing much lower hole mobility and inefficient carrier doping. Here, by using first-principles studies, we demonstrate that lattice strain engineering can be a universal approach to enhance the hole mobility and dopability in p-type semiconductors. A broad class of p-type semiconductors, including anion p orbital derived valence band compounds (nitrides, oxides, halides, and chalcogenides), s orbital based post-transition metal oxides (e.g., SnO), and d-orbital based transition metal oxides (e.g., NiO), have been applied on strain to demonstrate their valence band modulation ability for the purpose of increasing the hole mobility and p-type dopability. We show that compressive lattice strain generally results in an upshifted valence band edge and reduced effective hole mass, leading to enhanced p-type dopability and increased hole mobility. Our work highlights strain engineering as a universal and effective approach for achieving better performed p-type compound semiconductors. [ABSTRACT FROM AUTHOR]

Four types of barrier detectors based on a type II InAs/InAsSb superlattice with a wide-gap barrier made of a solid AlInAsSb lattice matched to the GaSb buffer were compared. The tested detectors differed in the type of doping of the active layer and the level and type of doping of the contact layer at the barrier. The epitaxial layers were deposited on GaAs (100) substrates using the molecular beam epitaxy method. The spectral and current–voltage characteristics of the analyzed detectors were compared. The highest current responsivities were observed in the structure with a p-type absorber (p+BpN+). Detectors with an n-type absorber (p+Bnn+, n+Bnn+, and nBnn+) show an increase in the current responsivity with an increase in the reverse bias voltage due to the reduction in the undesirable barrier in the valence band. Arrhenius characteristics for the dark current show that only in nBnn+ detectors, it was possible to limit the generation–recombination current. These detectors at 150 K were characterized by the highest normalized detectivity of approximately 3 × 1011 cm · Hz1/2/W. The obtained results were compared with literature data, showing that the parameters of type II superlattice photodetectors are close to those of HgCdTe photodiodes according to the "Rule 07" and "Rule 22" principles. [ABSTRACT FROM AUTHOR]

The valence and conduction band offsets at the interfaces between NiO/AlN, SiO2/AlN, Al2O3/AlN, and ITO/AlN heterointerfaces were determined via x-ray photoelectron spectroscopy using the standard Kraut technique. These represent systems that potentially would be used for p-n junctions, gate dielectrics, and improved Ohmic contacts to AlN, respectively. The band alignments at NiO/AlN interfaces are nested, type-I heterojunctions with a conduction band offset of −0.38 eV and a valence band offset of −1.89 eV. The SiO2/AlN interfaces are also nested gap, type-I alignment with a conduction band offset of 1.50 eV and a valence band offset of 0.63 eV. The Al2O3/AlN interfaces are type-II (staggered) heterojunctions with a conduction band offset of −0.47 eV and a valence band offset of 0.6 eV. Finally, the ITO/AlN interfaces are type-II (staggered) heterojunctions with conduction band offsets of −2.73 eV and valence band offsets of 0.06 eV. The use of a thin layer of ITO between a metal and the AlN is a potential approach for reducing contact resistance on power electronic devices, while SiO2 is an attractive candidate for surface passivation or gate dielectric formation on AlN. Given the band alignment of the Al2O3, it would only be useful as a passivation layer. Similarly, the use of NiO as a p-type layer to AlN does not have a favorable band alignment for efficient injection of holes into the AlN. [ABSTRACT FROM AUTHOR]

Crystal structure, bandgap, and the changes in the charge conduction mechanisms in ceramics are interrelated, and the underlying physics unifies all these different phenomena. The experimental and theoretical evaluation of the electronic properties of the solid solution of (1 − x)BaTiO3–(x)LaFeO3 (x = 0, 0.015, 0.031, 0.062) is attempted in this work. Bandgap was observed to be tunable with La/Fe doping from 3.2 eV (x = 0) to 2.6 eV (x = 0.06), while the lattice disorder was found to increase. A theoretical assessment confirms a considerable shift of valence band maxima and conduction band minima with an introduction of additional defect states within the bandgap. Electron localization was also confirmed theoretically with doping. Such changes in the electronic properties were experimentally confirmed from dielectric/AC - conductivity/impedance spectroscopy studies. From different transportation models, hopping is a preferred mechanism in the less distorted BaTiO3. However, a large polaron tunneling process can be justified for the doped samples at lower temperatures. Only at higher temperatures, a small polaron tunneling can be justified for the doped samples. The transportation is affected by the grain boundaries as much as the grains themselves. A complete analysis using Nyquist plots reveals the competing contributions of these regions to the transportation mechanism and is correlated to the disorder/distortions in the lattice in terms of the formation of oxygen vacancies. [ABSTRACT FROM AUTHOR]

The chemical flexibility of metal-organic frameworks (MOFs) offers an ideal platform to tune structure and composition for specific applications, from gas sensing to catalysis and from photoelectric conversion to energy storage. This variability gives rise to a large configurational space that can be efficiently explored using high-throughput computational methods. In this work, we investigate from first principles the structural and electronic properties of MOF-5 variants obtained by replacing Zn with Be, Mg, Cd, Ca, Sr, and Ba and by functionalizing the originally H-passivated linkers with CH3, NO2, Cl, Br, NH2, OH, and COOH groups. To build and analyze the resulting 56 structures, we employ density-functional theory calculations embedded in an in-house developed library for automatized calculations. Our findings reveal that structural properties are mainly defined by metal atoms and large functional groups, which distort the lattice and modify coordination. The formation energy is largely influenced by functionalization and enhanced by COOH and OH groups, which promote the formation of hydrogen bonds. The charge distribution within the linker is especially influenced by functional groups with electron-withdrawing properties, while the metal nodes play a minor role. Likewise, the bandgap size is crucially determined by ligand functionalization. The smallest gaps are found with NH2 and OH groups, which introduce localized orbitals at the top of the valence band. This characteristic makes these functionalizations particularly promising for the design of MOF-5 variants with enhanced gas uptake and sensing properties. [ABSTRACT FROM AUTHOR]

The spontaneous formation of a Ga-oxide (GaO x ) intermediate layer at the GaN/SiO 2 interface has been reported during the SiO 2 deposition on the GaN substrate. In this study, we have performed first-principles calculations and unveiled atomic and electronic structures of the GaN/SiO 2 interface with 1-nm thick GaO x intermediate layer. Our calculations show that the top-layer Ga atoms on the GaN side are terminated with the O atoms on the GaO x side, leading to the clean GaN/GaO x interface and the absence of the electronic state in the midgap region. However, strongly localized states, which are originated from O atoms lone-pair orbitals in the –GaOSi– local structures, emerge in the gap near the valence-band maximum of GaN. These in-gap states become hole traps in GaN MOS devices, leading to a degradation in device controllability and operational speed. [ABSTRACT FROM AUTHOR]

Recently, LiGa 5 O 8 was claimed to be a p -type dopable ultrawide-bandgap oxide, based on measurements of undoped material. Here, the electronic properties of potential acceptor dopant impurities in LiGa 5 O 8 are calculated using hybrid density functional theory to evaluate their potential for causing p -type conductivity. As with the related compound LiGaO 2 , the heavy oxygen-derived valence bands lead to stable self-trapped holes in LiGa 5 O 8. Acceptor defects and dopants also bind trapped holes (or small polarons), which lead to large acceptor ionization energies. The calculations here indicate that neither native acceptor defects (such as cation vacancies or antisites) nor impurity dopants can give rise to p -type conductivity in LiGa 5 O 8. Optical transitions associated with these defects are also calculated, in order to allow for possible experimental verification of their behavior. [ABSTRACT FROM AUTHOR]

Mexican-hat-shaped quartic dispersion manifests itself in certain families of single-layer two-dimensional hexagonal crystals such as compounds of groups III–VI and groups IV–V as well as elemental crystals of group V. A quartic band forms the valence band edge in various of these structures, and some of the experimentally confirmed structures are GaS, GaSe, InSe, SnSb, and blue phosphorene. Here, we numerically investigate strictly one-dimensional and quasi-one dimensional (Q1D) systems with quartic dispersion and systematically study the effects of Anderson disorder on their transport properties with the help of a minimal tight-binding model and Landauer formalism. We compare the analytical expression for the scaling function with simulation data to distinguish the domains of diffusion and localization regimes. In one dimension, it is shown that conductance drops dramatically at the quartic band edge compared to the quadratic case. As for the Q1D nanoribbons, a set of singularities emerge close to the band edge, suppressing conductance and leading to short mean-free-paths and localization lengths. Interestingly, wider nanoribbons can have shorter mean-free-paths because of denser singularities. However, the localization lengths sometimes follow different trends. Our results display the peculiar effects of quartic dispersion on transport in disordered systems. [ABSTRACT FROM AUTHOR]

Recently, LiGa 5 O 8 was claimed to be a p -type dopable ultrawide-bandgap oxide, based on measurements of undoped material. Here, the electronic properties of potential acceptor dopant impurities in LiGa 5 O 8 are calculated using hybrid density functional theory to evaluate their potential for causing p -type conductivity. As with the related compound LiGaO 2 , the heavy oxygen-derived valence bands lead to stable self-trapped holes in LiGa 5 O 8. Acceptor defects and dopants also bind trapped holes (or small polarons), which lead to large acceptor ionization energies. The calculations here indicate that neither native acceptor defects (such as cation vacancies or antisites) nor impurity dopants can give rise to p -type conductivity in LiGa 5 O 8. Optical transitions associated with these defects are also calculated, in order to allow for possible experimental verification of their behavior. [ABSTRACT FROM AUTHOR]

We used photoluminescence (PL) spectroscopy and first-principles calculations to investigate GaN doped with Mg, Be, and implanted with Ca. The PL spectra revealed distinct red emission bands (RLA, where A = Be, Mg, and Ca) with maxima between 1.68 and 1.82 eV, each associated with a specific impurity. These bands consistently appeared alongside the green GL2 PL band at 2.33 eV, attributed to nitrogen vacancy (VN). Our calculations suggest that these bands result from recombination via defect complexes of group-II acceptors substituting for Ga with VN (AGaVN, A = Be, Mg, and Ca). The experimental + / 0 transition levels for these complexes were estimated to be 0.6, 0.8, and 1.0 eV above the valence band maximum for Mg-, Be-, and Ca-containing complexes, respectively. The radiative recombination is facilitated by excited donor states located close to the conduction band minimum. Furthermore, our theory predicts that ZnGaVN and CdGaVN are stable and possess similar properties, although, no PL was detected from these defect complexes. The presented findings shed light on the identity of compensating donor complexes that impede the efficiency of p -type doping in GaN. [ABSTRACT FROM AUTHOR]

The electron–phonon scattering plays a crucial role in determining the electronic, transport, optical, and thermal properties of materials. Here, we employ a non-Markovian stochastic Schrödinger equation (NMSSE) in momentum space, together with ab initio calculations for energy bands and electron–phonon interactions, to reveal the phonon-mediated ultrafast hole relaxation dynamics in the valence bands of monolayer black phosphorus. Our numerical simulations show that the hole can initially remain in the high-energy valence bands for more than 100 fs due to the weak interband scatterings, and its energy relaxation follows single-exponential decay toward the valence band maximum after scattering into low-energy valence bands. The total relaxation time of holes is much longer than that of electrons in the conduction band. This suggests that harnessing the excess energy of holes may be more effective than that of electrons. Compared to the semiclassical Boltzmann equation based on a hopping model, the NMSSE highlights the persistence of quantum coherence for a long time, which significantly impacts the relaxation dynamics. These findings complement the understanding of hot carrier relaxation dynamics in two-dimensional materials and may offer novel insights into harnessing hole energy in photocatalysis. [ABSTRACT FROM AUTHOR]

Rare-earth titanate oxides are believed to be prospective functional materials for photocatalytic and photoluminescent applications because of their excellent optical properties and thermal stability of their physical properties. However, the relationships between optical properties and photoelectron trapping mechanisms are unclear. Herein, the structure, electronic, and optical properties of pyrochlore-structure Re2Ti2O7 (Re = Sm and Eu) were investigated using the first-principles approach with the Hubbard parameter U (GGA + U). The calculated bandgap is 2.5 eV for Sm2Ti2O7 and 2.4 eV for Eu2Ti2O7, which is in good agreement with the experimental observation. The results indicate that the strongly localized f states at the top of valence band are charge-trapping sites for photoexcitation of Re2Ti2O7, where electrons can absorb photon energy and transfer from the valence band to the conduction band, resulting in the photocatalytic and/or fluorescent effects in the visible and early UV regions. The important optical parameters, dielectric function ε (ω) , refractive index n (ω) , extinction coefficient k (ω) , reflectivity R (ω) , absorption coefficient I (ω) , optical conductivity σ (ω) , and electron energy-loss L (ω) were studied in detail, indicating that these optical parameters of Sm2Ti2O7 and Eu2Ti2O7 are insensitive to the ultra-violet (UV) radiation, but both Sm2Ti2O7 and Eu2Ti2O7 exhibit excellent optical properties in the visible and early UV regions. This work provides a clear understanding on the photoelectron trapping mechanism of pyrochlore-structure Re2Ti2O7, which will help to improve the photocatalytic and photoluminescent performance of Re2Ti2O7 and broaden their applications. [ABSTRACT FROM AUTHOR]

This Tutorial focuses on the physics of layered compounds under high pressure. We have chosen h-BN and III–VI layered materials as representative materials. h-BN layers are strictly two-dimensional. Layers in III–VI compounds are more complex, and subtle details in their structural behavior play an important role in the evolution of high pressure properties. They are also interesting because they contain a different number of layers in their primitive unit cell and/or have a different ionic character. We begin describing the structural evolution. We discuss the experimental challenges encountered as well as the main findings related to intra- and interlayer compressibility, polytype influence, and geometrical modifications induced by pressure inside the layers. We then describe lattice vibrations. The origin of the modes is reviewed, paying attention to the relationships between atom motions in different layers. We discuss the convenience of redefining the Grüneisen parameter and describe the behavior of rigid layer modes, soft modes, and Davidov pairs. The last section is devoted to the electronic properties. We show that the changes observed when passing from a single layer to a three-dimensional BN are qualitatively similar to those induced by high pressure. The pressure behavior of electronic transitions in III–VI layered compounds is very rich, revealing the subtle balance between intra- and inter-layer interactions. Finally, we take advantage of high pressure studies to explain the formation of the Mexican hat type of valence band at ambient conditions in single layers of InSe and GaSe, but not in three-dimensional compounds. [ABSTRACT FROM AUTHOR]

Hole mobility anisotropy in 4H-SiC was investigated based on both experimental and theoretical approaches. First, the authors established a complete database of the anisotropic hole mobility along both directions parallel and perpendicular to the c -axis in 4H-SiC over the wide acceptor density and temperature ranges by preparing Hall bar structures on p-type SiC(11 2 ¯ 0) epitaxial layers. Empirical equations for the mobility along each direction vs the acceptor density and temperature were determined, which should be useful for the simulation and designing of any SiC devices. In addition to that, the anisotropy in the hole mobility was extracted from the experimental results, and its origin was discussed focusing on that in the effective mass (m ∗) of holes. The obtained mobility ratio was far from the m ∗ ratio at the valence band maximum, and an averaged m ∗ along each direction was determined by theoretical calculation taking into account the energy distribution of holes. Consequently, the authors revealed that the anisotropic hole mobility is explained quantitatively by the anisotropic m ∗ considering the E – k dispersion over the entire first Brillouin zone. [ABSTRACT FROM AUTHOR]

Mixed thorium/uranium dioxide, (Th,U)O2, is under consideration for advanced nuclear fuel applications. Investigating the point defect structure and energy in this oxide is important for predicting its behavior as fuel. In this work, we use first-principles calculations based on the generalized gradient approximation (GGA)+Hubbard U approach to investigate the internal energy and entropy of the formation of point defects in Th1−xUxO2 at various compositions below x ≤ 0.5. Point defects including O vacancies, O interstitials, Th vacancies, Th interstitials, U vacancies, and U interstitials have all been considered with their charges ranging from neutral to the maximum nominal values. The observed trends have been explained in terms of electronic density of states. The valence band maxima of crystals that contain defects play a crucial role and exhibit variations depending on the U content and the applied charge. The temperature dependence of internal energy and entropy of formation of defects have also been examined. The internal energy of formation of defects was found to exhibit slowly varying or constant values with respect to changes in the U content, except at low values of x and low temperatures. The entropy of formation of defects was observed to decrease with increasing U content. It was additionally observed that the entropy of formation of vacancies increases with temperature, while that of interstitials decreases. This investigation further revealed that at 0 K, the cation vacancies and anion interstitials become increasingly favorable with increasing U content, while cation interstitials and anion vacancies become less favorable. [ABSTRACT FROM AUTHOR]

The evolution of the valence band, charge states of atoms, and optical and vibrational spectra in compounds Ca10−xMx(PO4)xY2, M = Fe, Ni, Cu, Mg; Y = OH, Cl, F was studied by using XPS, infrared, and optical spectroscopy, with the addition of quantum mechanics calculations. The changes in the bandgap in these compounds were analyzed. Isomorphic substitution of calcium ions in the cationic sublattice of calcium hydroxyapatite by metal ions changes the shape of the curve that represents the occupied part of the valence band only slightly. It retains a pronounced gapped character with different lengths of individual subbands—the upper and lower parts of the valence band. It is shown that the predominant position of rare earth and uranium atoms in the apatite structure is the Ca(2)-position. Isomorphic substitution of calcium atoms by metal atoms (Fe, Ni, Cu, Mg) in the apatite structure in the range of 1%–2% of atoms leads to the narrowing of the energy gap. The most significant narrowing is observed when calcium is substituted by nickel and copper. The theoretically calculated bandgap width in calcium apatites can be well described in terms of the generalized gradient approximation. The design of the structure of calcium apatites via the method of isomorphic substitutions in the cation sublattice makes it possible to control the bandgap width, thus expanding the field of practical application of these compounds. [ABSTRACT FROM AUTHOR]

MoS2 has generated significant attention due to its unique electronic properties and versatile applications. Being a van der Waals material, MoS2 is expected to exhibit an inert surface due to lack of dangling bond. However, our photoemission study finds MoS2 to be highly sensitive toward residual gases. The position of the valence band maximum (VBM) shifts even in a vacuum of 10−10 Torr. We find this to be due to CO adsorption causing unintentional electron doping. The time evolution of the position of VBM is exponential, and it reaches two different saturation points, depending on whether the sample is exposed to ultraviolet (UV) radiation or not. Our XPS (x-ray photoemission spectroscopy) study shows no time-dependent escape of sulfur, which was in a previous study attributed to a VBM shift. The VBM shift can be reversed by annealing, sputtering, and UV light, which desorb CO gases. The study shows that the MoS2 surface is easily doped, which offers the possibility of using it as a sensor but in many other applications could diminish device performance and needs to be considered. [ABSTRACT FROM AUTHOR]

MoS2 has generated significant attention due to its unique electronic properties and versatile applications. Being a van der Waals material, MoS2 is expected to exhibit an inert surface due to lack of dangling bond. However, our photoemission study finds MoS2 to be highly sensitive toward residual gases. The position of the valence band maximum (VBM) shifts even in a vacuum of 10−10 Torr. We find this to be due to CO adsorption causing unintentional electron doping. The time evolution of the position of VBM is exponential, and it reaches two different saturation points, depending on whether the sample is exposed to ultraviolet (UV) radiation or not. Our XPS (x-ray photoemission spectroscopy) study shows no time-dependent escape of sulfur, which was in a previous study attributed to a VBM shift. The VBM shift can be reversed by annealing, sputtering, and UV light, which desorb CO gases. The study shows that the MoS2 surface is easily doped, which offers the possibility of using it as a sensor but in many other applications could diminish device performance and needs to be considered. [ABSTRACT FROM AUTHOR]

Excess minority carriers create boron-related recombination centers that degrade the efficiency of the non-particle-irradiated silicon solar cells. However, the carrier-induced reactions among the radiation-induced defects are poorly understood for devices exposed to particle radiation. This study investigates the structure, electronic properties, formation and annihilation mechanisms, and diffusion dynamics of the carrier-induced defects in particle-irradiated boron-doped silicon using density-functional modeling and junction spectroscopy. By revisiting the ground-state structures of the boron-di-interstitial clusters (B I 2), we find that the calculated acceptor and donor levels of such defects agree well quantitatively with the carrier-induced deep-level transient spectroscopy (DLTS) hole emission signatures at 0.43 and 0.53 eV above the valence band edge (E v), respectively. We also find that the formation of B I 2 is thermally activated by an energy of 0.50 eV, which we explain theoretically by the reduction of the migration barrier of mono-interstitials to 0.53 eV in the presence of excess minority carriers. Moreover, we discover that the B I 2 are potentially mobile with a migration barrier of 1.18 eV, contrary to the present understanding. [ABSTRACT FROM AUTHOR]

Terminal solid solutions in the Zn O 1 − x S e x system (0 ≤ x ≤ 0.15 , 0.95 ≤ x ≤ 1) exhibit extreme bandgap reduction attributable to band anti-crossing (BAC). In this work, we perform a theoretical investigation of alloying in this system (0 ≤ x ≤ 1). The temperature-composition phase diagram of Zn O 1 − x S e x is obtained via first principles and cluster expansion-based Monte–Carlo simulations. For 0 ≤ x ≤ 0.05 , a solid solution in the wurtzite structure and for 0.5 ≤ x ≤ 1 , a solid solution in the sphalerite structure is obtained. The alloy system exhibits a miscibility gap in the range of 0.05 ≤ x ≤ 0.5. Only the solid solutions are seen to obey bandgap reduction predicted by BAC. The bandgap of the alloys, calculated using the Δ -sol method, shows a bowing behavior as predicted by the BAC model. Difference in the electronegativities of O and Se atoms in the lattice leads to hybridization of O-2p and Se-4p electronic states. Interaction between these electronic states also leads to a split in the valence band edge at the O-rich end and a split in the conduction band edge at the Se-rich end. The effective mass, estimated from the density of states, of holes at the O-rich end and that of electrons at the Se-rich end, increases with alloying. These fundamental insights should help in choosing suitable alloy compositions for optimal photocurrent density when these materials are used as photoanodes. [ABSTRACT FROM AUTHOR]

This Tutorial provides a comprehensive overview of various k ⋅ p models used to describe the electronic band structures of semiconductors with cubic diamond and zinc blende symmetries. Our primary focus is on III–V semiconductors, with a particular emphasis on highly mismatched alloys. We begin our exploration with the six-band k ⋅ p model, which effectively captures interactions within the highest valence bands. Following that, we delve into the intricacies of the eight-band k ⋅ p model, which takes into account strain effects and modifications to energy dispersion. The Tutorial also introduces the band anticrossing model and its corresponding ten-band k ⋅ p models, specifically tailored for dilute nitride semiconductors. Furthermore, we extend our discussion to the valence band anticrossing model and its application to the 14-band k ⋅ p model in the context of dilute bismide materials. Additionally, we emphasize the significance of more comprehensive models, exemplified by the 30-band k ⋅ p model, for faithfully representing the entire Brillouin zone. [ABSTRACT FROM AUTHOR]

Interband recombination in bulk indium-rich InGaN is studied via both spontaneous and stimulated emissions. Based on the low-temperature luminescence and absorption data, the magnitude of the edge tails in conduction and valence bands is determined, and the non-thermal energy distribution of excess holes localized in the fluctuating band potential is revealed. We show that the combination of carrier localization effects and Auger-determined interband rates fully accounts for the experimentally observed stimulated emission thresholds and gain values (∼20–30 kW/cm2 and >100 cm−1, respectively) at low temperatures (T < 100 K). It is suggested that exploiting structural disorder to keep injected holes below the mobility edge, thus suppressing defect-related recombination, is a prerequisite for high-temperature infrared lasing from degenerate InGaN with relatively temperature-stable threshold intensities of some 100 kW/cm2. [ABSTRACT FROM AUTHOR]

Nickel-doped β-Ga2O3 crystals were investigated by optical absorption and photoconductivity, revealing Ni-related deep levels. The photoconductivity spectra were fitted using the phenomenological Kopylov and Pikhtin model to identify the energy of the zero-phonon transition (thermal ionization), Franck–Condon shift, and effective phonon energy. The resulting values are compared with the predicted ones by first-principle calculations based on the density functional theory (DFT). An acceptor level (0/−) of 1.9 eV and a donor level (+/0) of 1.1 eV above the valence band minimum are consistently determined for NiGa, which preferentially incorporates on the octahedrally coordinated Ga site. Temperature-dependent resistivity measurements yield a thermal activation energy of ∼2.0 eV that agrees well with the determined Ni acceptor level. Conclusively, Ni is an eminently suitable candidate for compensation doping for producing semi-insulating β-Ga2O3 substrates due to the position of the acceptor level (below and close to the mid-bandgap). [ABSTRACT FROM AUTHOR]

The luminescence efficiency of AlxGa1−xN quantum dots (QDs) and quantum wells (QWs), buried in AlN cladding layers and emitting in the ultraviolet range between 234 and 310 nm, has been investigated. The growth and optical properties have been done using similar aluminum composition (varying from 0.4 to 0.75) for both QDs and QWs. In order to compare as much as possible the optical properties, the QWs were fabricated with a growth time tuned such that the QW width is similar to the average height of the QDs. The photoluminescence (PL) showed emission ranging from 4 to 5.4 eV, putting into evidence differences in terms of full width at half maximum, PL intensity, and asymmetry of the line shape between QDs and QWs. The results show shorter wavelengths and a slightly narrower PL linewidth for QWs. To determine the light emission dependence with the electric field direction in the crystal, the evolutions of the emission diagrams for all samples were recorded along two orthogonal directions, namely, the "in-plane" (growth) and the "on-side" directions, from which the light emission was collected. For the whole QDs and QWs samples' series, the shapes of the emission diagram indicate emission in both in-plane and on-side directions, as evidenced by intra-valence band mixings caused by strain effects combined with the anisotropic Coulomb interactions that are particularly contributing to the polarization at wavelengths below 260 nm. Furthermore, the degree of polarization, determined for each sample, showed good agreement with results from the literature. [ABSTRACT FROM AUTHOR]

The polarization-induced quantum confined Stark effect has been recognized as a significant factor contributing to the Internal Quantum Efficiency (IQE) droop in light-emitting diodes (LEDs). This study focuses on the design of LEDs by investigating the InAlN/AlGaN interface. By incorporating InAlN quantum wells, a polarization-matched (PM) multi-quantum well (MQW) LED architecture was developed. While the flat conduction and valence bands on PM MQWs indicate an improved recombination rate, it is crucial to examine the impact on IQE, considering carrier confinement and injection efficiency influenced by the band offsets. This paper presents a numerical analysis comparing two LEDs emitting at 245 and 275 nm, respectively. The results demonstrate that the PM LED operating at 275 nm exhibits enhanced performance, benefiting from high probability density overlap. Conversely, the PM LED emitting at 245 nm demonstrates poor confinement, resulting in an overall low performance, regardless of polarization matching. [ABSTRACT FROM AUTHOR]

[Display omitted] In the field of photocatalytic treatment of dye wastewater, zinc oxide (ZnO) is a typical semiconductor photocatalyst, but it has some disadvantages such as wide band gap, low carrier yield and easy recombination. In this study, Cr-ZnO/N-CQDs catalyst was synthesised using the strategy of p-type doping and construction of Z-scheme heterojunction. The results showed that the removal rate of Cr-ZnO/N-CQDs for MB dye was 97.42 %, which was 70.56 % higher than that of ZnO, and was still 92.16 % after 5 cycles, and the TOC removal rate of methylene blue wastewater was 88.60 %. The reason for the enhanced photocatalytic activity of Cr-ZnO/N-CQDs is that the π* electron (e−) in the N-CQDs interact with the 3d orbitals of Cr-ZnO, so that e− is more easily transferred from the valence band of Cr-ZnO to the conduction band of N-CQDs. The band gap of p-type Cr-ZnO is narrowed, which makes its photogenerated carrier yield increase, hole concentration raise, and the adsorption capacity of H 2 O molecules reduce by 1.04 eV. The density functional theory calculation shows that the maximum Gibbs free energy of Cr-ZnO for the production of hydroxyl radical is 0.05 eV lower than that of ZnO. This study lays theoretical and practical foundation for the photocatalytic treatment of dye wastewater with ZnO. [ABSTRACT FROM AUTHOR]

The effect of biaxial tensile deformation on the optoelectronic properties of Al-doped monolayers SnS2 is explored using density functional theory. We found that the pure SnS2 monolayer is an indirect bandgap semiconductor, and with Al doping it changes to a p-type semiconductor with a lowered bandgap value. After applying biaxial tensile deformation to the doped system, i.e., with the increase of tensile strain, bandgap value decreases. Analyzing the density of states, it is found that the conduction band in a doped system is primarily made of the Sn-5s orbital and the S-3p orbital, and the valence band is primarily made of Sn-5p orbital and S-3p orbital, with the majority of S-3p orbital. The conduction and valence bands change with the rise in tensile strain, and hence the gap in the density of states close to the Fermi energy level shrinks. It is also noticed that the absorption coefficient peaks and reflection peaks of the SnS2 doped system subjected to biaxial tensile strain are blueshifted. The absorption coefficient and reflectance peaks of the doped system show a tendency to increase and then decrease with the increase of tensile strain. [ABSTRACT FROM AUTHOR]

The effect of biaxial tensile deformation on the optoelectronic properties of Al-doped monolayers SnS2 is explored using density functional theory. We found that the pure SnS2 monolayer is an indirect bandgap semiconductor, and with Al doping it changes to a p-type semiconductor with a lowered bandgap value. After applying biaxial tensile deformation to the doped system, i.e., with the increase of tensile strain, bandgap value decreases. Analyzing the density of states, it is found that the conduction band in a doped system is primarily made of the Sn-5s orbital and the S-3p orbital, and the valence band is primarily made of Sn-5p orbital and S-3p orbital, with the majority of S-3p orbital. The conduction and valence bands change with the rise in tensile strain, and hence the gap in the density of states close to the Fermi energy level shrinks. It is also noticed that the absorption coefficient peaks and reflection peaks of the SnS2 doped system subjected to biaxial tensile strain are blueshifted. The absorption coefficient and reflectance peaks of the doped system show a tendency to increase and then decrease with the increase of tensile strain. [ABSTRACT FROM AUTHOR]

Thermoelectrics have been limited by the scarcity of their constituent elements, especially telluride. The earth-abundant, wide-bandgap (Eg ≈ 46 kBT) tin sulfide (SnS) has shown promising performance in its crystal form. We improved the thermoelectric efficiency in SnS crystals by promoting the convergence of energy and momentum of four valance bands, termed quadruple-band synglisis. We introduced more Sn vacancies to activate quadruple-band synglisis and facilitate carrier transport by inducing SnS2 in selenium (Se)-alloyed SnS, leading to a high dimensionless figure of merit (ZT) of ~1.0 at 300 kelvin and an average ZT of ~1.3 at 300 to 773 kelvin in p-type SnS crystals. We further obtained an experimental efficiency of ~6.5%, and our fabricated cooler demonstrated a maximum cooling temperature difference of ~48.4 kelvin at 353 kelvin. Our observations should draw interest to earth-abundant SnS crystals for applications of waste-heat recovery and thermoelectric cooling. [ABSTRACT FROM AUTHOR]

When annealing a 4H silicon carbide (SiC) crystal, a sequence of optically active defect centers occurs among which the TS center is a prominent example. Here, we present low-temperature photoluminescence analyses on the single defect level. They reveal that the three occurring spectral signatures TS1, TS2 and TS3 originate from one single defect. Their polarization dependences expose three different crystallographic orientations in the basal plane, which relate to the projections of the nearest neighbor directions. Accordingly, we find a three-fold level-splitting in ensemble studies, when applying mechanical strain. This dependency is quantitatively calibrated. A complementary electrical measurement, deep level transient spectroscopy, reveals a charge transition level of the TS defect at 0.6 eV above the valence band. For a future identification, this accurate characterization of its optical and electronic properties along with their response to mechanical strain is a milestone. [ABSTRACT FROM AUTHOR]

The inverse spin Hall effect is a critical method for detecting spin Hall conductivity. Unearthing the physical relationship between electronic structure and spin Hall conductivity is conducive to establishing an intrinsic link between microstructure and macroscopic phenomena. Here, we report MnBi2Te4 as an ideal candidate: a stable, inversion symmetry-broken magnetic topological insulator for investigating the intrinsic correlation between spin Hall conductivity signal reversal and electronic structure. The valence band exhibits a significant Rashba spin splitting, with a magnitude reaching up to 4.61 eV/Å. We identify robust topological properties independent of Rashba and Lifshitz spin-splitting types. Moreover, transitioning the spin-splitting type not only widens the bulk band gap, enhancing the spin Hall conductivity plateau, but also triples the intrinsic spin Hall conductivity value. We propose the inverse spin Hall effect that is tunable by spin-splitting types, thereby advancing the research on the microscopic electronic mechanisms of spin current detection. The spin Hall effect facilitates the generation and detection of spin currents and is expected to play an important role in future spintronic devices. Here, the authors theoretically investigate the presence of Rashba spin splitting for MnBi2Te4 and the relationship with an inverse spin Hall effect also present in the system. [ABSTRACT FROM AUTHOR]

Promising 2D materials suitable for low‐temperature processing are crucial for advancing beyond Moore's law. While p‐type performance is as essential as n‐type in CMOS technology, the development of high‐performance p‐type 2D materials has lagged behind their n‐type counterparts. Here, high‐performance p‐type tellurium (Te) field‐effect transistors (TeFETs) that undergo plasma treatment at low temperatures to enhance their electrical and optoelectrical properties are presented. Ar plasma‐treated Te shows significantly improved crystallinity compared to untreated counterparts, confirmed by various characterization techniques. Plasma treatment shifts the Fermi level toward the valence band and induces subgap states near the valence band in the Te film. A valence band offset of 0.2 eV and 30.6% surface flattening are confirmed in plasma‐treated TeFETs. The electrical performance of plasma‐treated TeFETs exhibits a 20‐fold increase in the Ion/Ioff ratio, from 1.2 × 104 to 2.7 × 104, and a 51% reduction in subthreshold swing, from 19.1 to 9.4 V per decade, compared to pristine devices. Stability and bias stress tests show resilience to degradation after plasma treatment. Notably, optoelectrical performance improves due to the trap‐assisted photogating effect. These findings provide a promising pathway for improving p‐type materials at low temperatures, facilitating their use in various next‐generation electronic platforms. [ABSTRACT FROM AUTHOR]

Wide-bandgap two-dimensional (2D) β -TeO2 has been reported as a high-mobility p -type transparent semiconductor [ Nat. Electron. 4 277 (2021)], attracting significant attention. This "breakthrough" not only challenges the conventional characterization of TeO2 as an insulator but also conflicts with the anticipated difficulty in hole doping of TeO2 by established chemical trends. Notably, the reported Fermi level of 0.9 eV above the valence band maximum actually suggests that the material is an insulator, contradicting the high hole density obtained by Hall effect measurement. Furthermore, the detected residual Se and the possible reduced elemental Te in the 2D β -TeO2 samples introduces complexity, considering that elemental Se, Te, and Te1− x Se x themselves are high-mobility p -type semiconductors. Therefore, doubts regarding the true cause of the p -type conductivity observed in the 2D β -TeO2 samples arise. In this Letter, we employ density functional theory calculations to illustrate that TeO2, whether in its bulk forms of α -, β -, or γ -TeO2, or in the 2D β -TeO2 nanosheets, inherently exhibits insulating properties and poses challenges in carrier doping due to its shallow conduction band minimum and deep valence band maximum. Our findings shed light on the insulating properties and doping difficulty of TeO2, contrasting with the claimed p -type conductivity in the 2D β -TeO2 samples, prompting inquiries into the true origin of the p -type conductivity. [ABSTRACT FROM AUTHOR]

The inverse spin Hall effect is a critical method for detecting spin Hall conductivity. Unearthing the physical relationship between electronic structure and spin Hall conductivity is conducive to establishing an intrinsic link between microstructure and macroscopic phenomena. Here, we report MnBi2Te4 as an ideal candidate: a stable, inversion symmetry-broken magnetic topological insulator for investigating the intrinsic correlation between spin Hall conductivity signal reversal and electronic structure. The valence band exhibits a significant Rashba spin splitting, with a magnitude reaching up to 4.61 eV/Å. We identify robust topological properties independent of Rashba and Lifshitz spin-splitting types. Moreover, transitioning the spin-splitting type not only widens the bulk band gap, enhancing the spin Hall conductivity plateau, but also triples the intrinsic spin Hall conductivity value. We propose the inverse spin Hall effect that is tunable by spin-splitting types, thereby advancing the research on the microscopic electronic mechanisms of spin current detection. The spin Hall effect facilitates the generation and detection of spin currents and is expected to play an important role in future spintronic devices. Here, the authors theoretically investigate the presence of Rashba spin splitting for MnBi2Te4 and the relationship with an inverse spin Hall effect also present in the system. [ABSTRACT FROM AUTHOR]

In this study, bilayer MoS2 was synthesized on graphene film using chemical vapor deposition (CVD) to get a hetero‐film photo‐catalyst for the photo‐assisted charging of Li‐oxygen battery. The synthesized hetero‐film exhibited an optical band gap of 1.8 eV and a valence band edge potential of −1.23 VAg/AgCl (2.04 VLi+/Li). Fast‐responding photocurrents in the microampere range were achieved through on‐off cycles under visible‐light irradiation. The anodic nature of the photocurrents indicated that the synthesized semiconductor film was n‐type. Photo‐assisted testing demonstrated that the MoS2/graphene hetero‐film photo‐catalyst significantly reduced the charging potential and increased the discharging potential at a current density of 0.1 mA cm−2, thereby greatly enhancing the cyclic performance of the Li‐oxygen battery. [ABSTRACT FROM AUTHOR]

Using ab initio calculations, the structural and photoelectric properties of γ-GeSe with B, C, and N adsorption were systematically investigated. The atomic structure relaxations show that B, C, and N are preferentially located on the lower hexagonal hollow, upper hexagonal hollow, and on top of Se, respectively. The adsorption with B, C, and N can induce defective bands between the energy region n of the valence bands and the conduction bands, and all the systems with adatoms are magnetic, with 1 μB, 2 μB, and 1 μB magnetic moments, respectively, which are mainly caused by the hybridization between adatoms and the adjacent Ge and Se atoms. Based on the spin-polarized band structure, we find that C-adsorbed γ-GeSe is metallic, while γ-GeSe with B and N adatoms is half-metallic, with 100% spin polarization at the Fermi level. Furthermore, owing to the electronic structural differences between spin-up and spin-down sections of B- and N-adsorbed γ-GeSe, the light in the low-energy region (< 1.0 eV) can only cause electronic excitations in one spin channel, giving rise to interesting spin-polarized photoelectric properties. Our results suggest that γ-GeSe with B, C, and N adsorption is a promising candidate for spintronic photoelectric device applications. [ABSTRACT FROM AUTHOR]

The topological features of a heavy‐mass hole (HH) confined in a 2D Si quantum well system via Bloch sphere (BS) representation and logic gate analysis are studied. Strong anisotropy‐and‐nonparabolicity in the semiconductor valence band causes the re‐degeneracy between HHs having opposite spins. The newly yielded degenerate states function as topological singularities. By employing the semiclassical equation of cyclotron motion, the time‐evolved (TE) Schrödinger equation as a rate equation is rewritten, and then the numerically solved TE wave function on the BS by determining the zenith θB$\left(\theta\right)_{\text{B}}$ and azimuthal ϕB$\left(\phi\right)_{\text{B}}$ angles is represented. The two‐state rotating‐wave (TSRW) approximation introduced reveals that the slope of θB$\left(\theta\right)_{\text{B}}$ against quantum state (time) evolution includes the information of the non‐Abelian Berry connection. The TSRW further demonstrates that the slope of ϕB$\left(\phi\right)_{\text{B}}$ contains the information of the Abelian connection. The TE operator is expressed by the three rotation logic gates ℝx(χ2)$&amp;amp;amp;amp;amp;reals;_{x} \left(\right. \left(\chi\right)_{2} \left.\right)$ around the x‐axis by an angle χ2$\left(\chi\right)_{2}$, which is sandwiched by the two rotations ℝz(χ3)$&amp;amp;amp;amp;amp;reals;_{z} \left(\right. \left(\chi\right)_{3} \left.\right)$ and ℝz(χ1)$&amp;amp;amp;amp;amp;reals;_{z} \left(\right. \left(\chi\right)_{1} \left.\right)$ around the BS pole axis (z). The TSRW approach enables us to decompose ℝz$&amp;amp;amp;amp;amp;reals;_{z}$ into two partial rotations around the z‐axis, with Abelian and non‐Abelian Berry connections. [ABSTRACT FROM AUTHOR]