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2D transition metal chalcogenides (TMCs) and dichalcogenides (TMDCs) are promising candidates for next‐generation electronic devices and sensors. Herein, the fabrication and characterizations of back‐gated Si/SiO2/GaSe‐based (GaSe: gallium selenide) metal–oxide–semiconductor field‐effect transistors (MOSFETs) and top‐gated Gr/h‐BN/GaSe‐based (h‐BN: hexagonal boron nitride) metal–insulator–semiconductor field‐effect transistors (MISFETs) with a common active layer (GaSe) are reported. The morphological, electrical, and optoelectronic properties are investigated, and the device is found to exhibit p‐type behavior with good electrical tunability. At a laser power of 1.147 μW, the device exhibits a photoresponsivity of 90 mA W−1, ION/IOFF ratios exceeding 104, and long decay times. These promising experimental results can promote the application of GaSe‐based MISFETs in multifunctional electronic devices. [ABSTRACT FROM AUTHOR]

Admittance spectroscopy is employed to explain the property differences observe between organic thin film transistors (OTFTs) fabricated with various gate insulator layers based on poly(4‐vinylphenol) (PVP) and poly(methyl methacrylate) (PMMA). The objective is achieved through the development of an equivalent circuit and a compact analytical model of the device core structure, namely, the metal–insulator–semiconductor (MIS) capacitor. The model fitting with experimental data allows to extract a wide range of parameters and, in particular, demonstrates the critical role played by the interface between insulator and semiconductor layers. [ABSTRACT FROM AUTHOR]

It is of pivotal significance to explore robust photocatalysts to promote the photoreduction of CO2 into solar fuels. Herein, an intelligent metal‐insulator‐semiconductor (MIS) nano‐architectural photosystem was constructed by electrostatic self‐assembly between cetyltrimethylammonium bromide (CTAB) insulator‐capped metal Ni nanoparticles (NPs) and covalent triazine‐based frameworks (CTF‐1). The metal‐insulator‐CTF composites unveiled a substantially higher CO evolution rate (1254.15 μmol g−1 h−1) compared with primitive CTF‐1 (1.08 μmol g−1 h−1) and reached considerable selectivity (98.9 %) under visible‐light irradiation. The superior photocatalytic CO2 conversion activity over Ni‐CTAB‐CTF nanoarchitecture could be attributed to the larger surface area, reinforced visible‐light response, and CO2 capture capacity. More importantly, the Ni‐CTAB‐CTF nanoarchitecture endowed the photoexcited electrons on CTF‐1 with the ability to tunnel across the thin CTAB insulating layer, directionally migrating to Ni NPs and thereby leading to the efficient separation of photogenerated electrons and holes in the photosystem. In addition, isotope‐labeled (13CO2) tracer results verified that the reduction products come from CO2 rather than the decomposition of the photocatalysts. This study opens a new avenue for establishing a highly efficient and selective artificial photosystem for CO2 conversion. [ABSTRACT FROM AUTHOR]

Interfacial passivation is an effective strategy to suppress recombination and improve the stability of efficient solar cells. Here, Sb2(S,Se)3, a promising candidate for next‐generation, solution‐processed photovoltaics, is carefully studied focusing on the defect state distribution and recombination mechanism. Ultrathin polymer layers were introduced to the n‐i‐p Sb2(S,Se)3 thin‐film solar cells. The insulating polymers can effectively fill the grain boundaries and pinholes, which physically restrain the leakage channels in the film and reduce the surface roughness. By adding this passivation layer, the device exhibits fewer interface states while spatially separating electron holes localized at the interface. The average fill factor of these optimized devices presents an 8% improvement, compared with the control devices. The maximum efficiency reaches a state‐of‐the‐art efficiency of 8.9%. These results again prove the concept of metal‐insulator‐semiconductor, and revealed the mechanism of polymer passivation enhanced photovoltaic performance. [ABSTRACT FROM AUTHOR]

In this study, we fabricated metal–insulator–semiconductor field-effect transistors (MISFETs) based on nanolayered molybdenum diselenide (MoSe2) using two insulator materials, silicon dioxide (SiO2) and silicon nitride (SiN). We performed morphological and electrical characterizations in which the devices showed good electronic performance, such as high mobility and high Ion/Ioff ratios exceeding 104. The subthreshold swing (ss) was somewhat high in all devices owing to the dimensions of our devices. In addition, the transfer curves showed good controllability as a function of gate voltage. The photogating effect was weakened in MoSe2/SiN/Si, indicating that SiN is a good alternative to silicon oxide as a gate dielectric material. [ABSTRACT FROM AUTHOR]

We investigate the HfO2/Hg0.78Cd0.22Te interface fabricated by plasma-enhanced atomic layer deposition (PEALD) at 120 °C During the deposition of HfO2, no donor-like defects are introduced into mercury cadmium telluride. X-ray photoelectron spectroscopy and ellipsometry were used to establish the optimal process regime at 120 °C and to demonstrate how HfO2 layer composition and growth rate per cycle depend on post-plasma purge time; the optimum is achieved at 6 s. Increasing the post-plasma purge time decreases the carbon and nitrogen impurity concentration in the HfO2 layer. Measurements of the admittance of metal-insulator-semiconductor (MIS) structures over the surface of a sample show that the electro-physical properties are uniform. We discuss the method of measuring the admittance of MIS structures that allows us to minimize the contribution of slow states with trapped charge on shape and shift of the C–V curve. The results demonstrate that the densities of fixed charge, slow states, and fast interfacial traps at the HfO2/MCT interface are greater than that for Al2O3/MCT (also formed by PEALD). The interface trap density is estimated from a normalized parallel conductance map, and the HfO2 film adheres well. [ABSTRACT FROM AUTHOR]

As a transmitter power amplifier (PA), the electrical output characteristics of gallium nitride (GaN) high electron mobility transistors (HEMTs) are closely related to the drain current versus drain voltage (${I}_{d}$ – ${V}_{d}$) characteristics. Any abnormalities in the ${I}_{d}$ – ${V}_{d}$ characteristics will seriously affect device performance. Therefore, many groups have investigated the kink effect of GaN HEMTs. One of the commonly used measurement methods of the kink effect is the ${I}_{d}$ – ${V}_{d}$ forward and reverse sweep. In this study, we used the same method for Al2O3/Si3N4–AlGaN/GaN metal–insulator–semiconductor HEMT (MIS HEMT) devices. We found that not only did the kink effect occurred but ${I}_{d}$ also increased abnormally during the reverse sweep and after a series of electrical measurements. At the end of the forward sweep, impact ionization caused by a high ${V}_{d}$ generated electron–hole pairs and some holes accumulated under the gate region, which caused the negative shift of the threshold voltage (${V}_{\text{Th}}$), leading to an abnormal increase in ${I}_{d}$ during the reverse sweep. [ABSTRACT FROM AUTHOR]

In this article, a novel p-type trapezoidal gate (PTG) lateral double-diffused MOSFET (LDMOS) is proposed and investigated by the 3-D TCAD simulation. The results reveal that the PTG LDMOS boasts a reduced gate-to-drain charge (${Q}_{\text {GD}}$) while maintaining an acceptable breakdown voltage (BV) and specific ON-resistance (${R}_{ \text{ON},\text {sp}}$). Compared with conventional LDMOS, a better tradeoff between the static figure of merit (FOMS, FOM $_{\text {S}}\,\,=$ BV2/ ${R}_{ \text{ON},\text {sp}}$) and the dynamic figure of merit (FOMD, FOM $_{\text {D}} = {R}_{ \text{ON},\text {sp}} \cdot {Q}_{\text {GD}}$) is realized. In the ON-state, the p-type polysilicon gate embedded in the drift region induces multiple plane majority-carrier accumulation layers, leading to a decrease in ${R}_{ \text{ON},\text {sp}}$. In the OFF-state, the metal–insulator–semiconductor (MIS) capacitor, which is composed of extended trench gate, gradual trapezoidal oxide, and N-drift. assists in depleting the drift region. Therefore, the doping concentration of drift region can be significantly lifted, and the BV is increased. Besides, the p-n junction capacitor composed of p-type and n-type polysilicon isolates the field coupling between gate and drain, and the gate-to-drain capacitor (${C}_{\text {GD}}$) is thus reduced. Compared with multiple-plane electron accumulation layer LDMOS (MAL LDMOS) and split triple-gate LDMOS (STG-LDMOS), ${Q}_{\text {GD}}$ and ${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}}$ of our proposed PTG LDMOS are shrunk by 34.3% and 54.4%, respectively. In general, the proposed PTG LDMOS achieves a better tradeoff between the static and switching characteristics. [ABSTRACT FROM AUTHOR]

To employ graphene's rapid conduction in 2D devices, a heterostructure with a broad bandgap dielectric that is free of traps is required. Within this paradigm, h-BN is a good candidate because of its graphene-like structure and ultrawide bandgap. We show how to make such a heterostructure by irradiating alternating layers of a-C and a-BN film with a nanosecond excimer laser, melting and zone-refining constituent layers in the process. With Raman spectroscopy and ToF-SIMS analyses, we demonstrate this localized zone-refining into phase-pure h-BN and rGO films with distinct Raman vibrational modes and SIMS profile flattening after laser irradiation. Furthermore, in comparing laser-irradiated rGO-Si MS and rGO/h-BN/Si MIS diodes, the MIS diodes exhibit an increased turn-on voltage (4.4 V) and low leakage current. The MIS diode I-V characteristics reveal direct tunneling conduction under low bias and Fowler-Nordheim tunneling in the high-voltage regime, turning the MIS diode ON with improved rectification and current flow. This study sheds light on the nonequilibrium approaches to engineering h-BN and graphene heterostructures for ultrathin field effect transistor device development. [ABSTRACT FROM AUTHOR]

One of the most promising techniques for manufacturing low-cost solar cells is a solution processing method. In this study, it is proposed that solution-grown ZnO nanorods (NRs) are used as antireflection coatings on metal-insulator-semiconductor (MIS) solar cells with sol-gel SiO2. Except Al electrodes prepared by thermal evaporation, no other vacuum process was utilized during fabrication. The ZnO NRs were produced with a hydrothermal method and suppressed Fresnel reflection. With the solution-grown ZnO NRs, it was observed the average reflectance of the MIS solar cell decreased from 38.7% to 15.8%, and the short circuit density (JSC) increased from 5.22 mA/cm2 to 6.71 mA/cm2 (28.4% enhancement). Meanwhile, the open circuit voltage (VOC) was improved from 0.39 V to 0.47 V owing to a passivation effect. The MIS solar cell with the ZnO NRs exhibited a 35.5% efficiency enhancement compared to that without ZnO NRs. The performance improvement in MIS solar cells with ZnO NRs could be due to multiple reflections of an incident light between the vertically arranged NRs, and then light coupling into the cell. The results show a potential application of ZnO NRs for the performance enhancement of MIS solar cells. [ABSTRACT FROM AUTHOR]

Metal-insulator-metal (MIM) tunnel junctions with the aluminum Oxide tunnel barriers confined between cobalt electrodes exhibit less resistance drift over time than junctions that utilize a thick, unconfined aluminum electrode. The improved long time stability is attributed to better initial Oxide quality achieved through confinement (use of a potential energy well for the Oxygen) and plasma Oxidation. In this work, Co/AlOx/Co and Co/Al/AlOx/Co tunnel junction aging is compared over a period of apprOximately 9 months using transport measurements and Wentzel-Kramers-Brillouin (WKB) based modelling. The Co/AlOx/Co (confined) tunnel junction resistance increased by (32?±?6) % over 5400?h, while Co/Al/AlOx/Co (unconfined) tunnel junction resistance increased by (85?±?23) % over 5200?h. Fit parameters for the tunnel barrier width and potential energy barriers were extracted using WKB transport modelling. These values change only a small amount in the confined Co/AlOx/Co tunnel junction but show a significant drift in the unconfined Co/AlOx/Co tunnel junction. [ABSTRACT FROM AUTHOR]

Charge carrier transport in organic semiconductor devices is thermally activated with characteristic activation energies in the range of 0.2–0.6 eV, leading to strongly temperature-dependent behaviour. For designing efficient organic semiconductor materials and devices, it is therefore indispensable to understand the origin of these activation energies. We propose that in bilayer organic light-emitting diodes (OLEDs) employing a polar electron transport layer, as well as in metal-insulator-semiconductor (MIS) devices, the hole injection barrier Einj and the hole mobility activation energy Eμ can be decoupled from each other if temperature-dependent capacitancefrequency (C-f-T) and MIS-CELIV (charge extraction by linearly increasing voltage) experiments are combined. While the C-f-T signal contains information of both injection and transport, the CELIV current is expected to be insensitive to the electrode injection properties. We employ numerical drift-diffusion simulations to investigate the accuracy of this analytical parameter extraction approach and to develop criteria for its validity. We show that the implicit assumption of constant charge density and field profiles leads to systematic errors in determining the activation energies. Thus, one should be aware of the intrinsic limitations of the analytical Arrhenius fit, and for more accurate parameter determination a full drift-diffusion modelling is advised. Applying the analytical method to a standard bilayer OLED, we find that the total activation energy of 0.5 eV for the hole current can be split into contributions of ≈0.25 eV each for injection barrier and mobility. Finally, we also discuss the broader applicability of this method for other device stacks and material combinations. [ABSTRACT FROM AUTHOR]

Large area (up to 4 squared inches) epitaxial VO2 films, with a uniform thickness and exhibiting an abrupt metal-insulator transition with a resistivity ratio as high as 2.85 × 104, have been grown on (001)-oriented sapphire substrates by electron beam evaporation. The lattice distortions (mosaicity) and the level of strain in the films have been assessed by X-ray diffraction. It is demonstrated that the films grow in a domain-matching mode where the distortions are confined close to the interface which allows growth of high-quality materials despite the high film-substrate lattice mismatch. It is further shown that a post-deposition high-temperature oxygen annealing step is crucial to ensure the correct film stoichiometry and provide the best structural and electrical properties. Alternatively, it is possible to obtain high quality films with a RF discharge during deposition, which hence do not require the additional annealing step. Such films exhibit similar electrical properties and only slightly degraded structural properties. [ABSTRACT FROM AUTHOR]

Monocrystalline Germanium quantum dots (Ge QDs), grown by molecular beam epitaxy (MBE), are intricately embedded within a SiO 2 oxide layer of a metal-insulator-semiconductor (MIS) structure, catering to optoelectronic applications. These monocrystalline Ge QDs exhibit high density (D ∼ 5 x 1012 cm−2), possess a spherical morphology, and an average size of 6 nm with narrow size distribution. A comprehensive investigation into the influence of these quantum dots on the electrical transport and dielectric properties of the metal-insulator-semiconductor (MIS) structure was conducted through current-voltage (I–V) spectroscopy and impedance spectroscopy. Notably, I–V measurements demonstrate that Ge QDs enhance conduction phenomena, thereby improving electrical transport within the MIS structure. Furthermore, the capacitance-voltage (C–V) and conductance-voltage (G-V) measurements, spanning the inversion and accumulation regions, demonstrate a memory effect induced by Ge QDs within the MOS structure. Extensive analysis of dielectric parameters, including permittivity (ε′), dielectric loss (ε"), dissipation factor (tan δ ), as well as electrical modulus (M' and M"), across a broad frequency range and under varying bias voltages, reveals no anomalous electrical or dielectric behavior attributable to the presence of Ge QDs in MIS structure. Consequently, these findings affirm the viability of the novel MIS structures with Ge QDs for the development of optoelectronic devices such as photodetectors or solar cells. [ABSTRACT FROM AUTHOR]

An electro-thermal coupling simulator for GaN devices based on electron Monte Carlo (e-MC) simulations is established. Taking GaN Metal Insulator Semiconductor High Electron Mobility Transistor (MISHEMT) as example, the non-equilibrium thermal transport processes of self-heating effect in the channel layer are studied. This simulator is mainly coupled by e-MC and the phonon Boltzmann transport equation (pBTE), physical property parameters and electric field parameters are provided by first-principles and Technology Computer Aided Design (TCAD), respectively. We first verify the e-MC program by calculating the electron transport properties of GaN materials, verify the feasibility of the established GaN MISHEMT model by using TCAD and obtained its operating characteristics. Further, the simulator is used to evaluate the non-equilibrium processes inside the channel layer in detail, the results show that there is significant consistency in the peak positions of electric field strength, heat generation and diffusion temperature, the diffusion temperature peak occurs at the secondary peak of heat generation. The frequency distribution of phonon emission under different drain-source bias voltages is revealed by phonon emission spectrum analysis. The strength of the non-equilibrium effect is measured by effective temperature. Increasing the drain-source bias voltage will significantly increase the peak temperature of hotspot and further enhance the non-equilibrium effect. Our study reports an efficient scheme for electro-thermal simulations of GaN MISHEMT, which provides insights for thermal management of GaN-based transistor devices. • A self-consistent electrothermal coupling simulation process is established. • The electronic transport properties of GaN materials are verified in detail by the e-MC program. • A new improvement scheme is proposed to solve the problem of complex dispersion curves and multiple scattering types. • The non-equilibrium thermal transport and phonon emission spectrum based on selective excitation are studied. [ABSTRACT FROM AUTHOR]

A metal–insulator–semiconductor high‐electron‐mobility transistor (MIS‐HEMT) with Al2O3/SiNx (SiNx next to semiconductor) double insulators is proposed to obtain lower gate leakage and lower current collapse simultaneously and is comparatively studied in this article. SiNx directly next to the (Al)GaN induces fewer interface traps and provides better passivation, and Al2O3 can greatly reduce gate leakage. The Schottky gate HEMT and MIS‐HEMTs with single SiNx and Al2O3 layer are also fabricated for comparison. The proposed structure shows the lowest gate leakage and the lowest current collapse as well as better output, transfer, breakdown performance. Besides, this proposed structure shows low requirements on fabrication techniques and induces fewer interface traps. Moreover, to further explore the reason behind those superior performances, the gate leakage mechanisms under reverse and forward bias conditions are studied and the interface traps are compared through capacitance–voltage (C–V) measurements in those four kinds of devices. The experimental results demonstrate that the MIS‐HEMT with Al2O3/SiNx double insulators is a superior candidate for nitrides‐based MIS‐HEMT devices. [ABSTRACT FROM AUTHOR]

Photoinduced electrochemiluminescence (PECL) allows the electrochemically assisted conversion of low‐energy photons into high‐energy photons at an electrode surface. This concept is expected to have important implications, however, it is dramatically limited by the stability of the surface, impeding future developments. Here, a series of metal‐insulator‐semiconductor (MIS) junctions, using photoactive n‐type Si (n‐Si) as a light absorber covered by a few‐nanometer‐thick protective SiOx/metal (SiOx/M, with M=Ru, Pt, and Ir) overlayers are investigated for upconversion PECL of the model co‐reactant system involving the simultaneous oxidation of tris(bipyridine)ruthenium(II) and tri‐n‐propylamine. We show that n‐Si/SiOx/Pt and n‐Si/SiOx/Ir exhibit high photovoltages and record stabilities in operation (35 h for n‐Si/SiOx/Ir) for the generation of intense PECL with an anti‐Stokes shift of 218 nm. We also demonstrate that these surfaces can be employed for spatially localized PECL. These unprecedented performances are extremely promising for future applications of PECL. [ABSTRACT FROM AUTHOR]

A homogenization field lateral double diffused metal oxide semiconductor based on the trench-stopped depletion (TS-HOF LDMOS) is proposed and experimentally realized in this article. By solving the 3-D Poisson equation, the curvature factor ${k}$ is introduced to give the quantitative relationship between the maximum field ${E}_{\text {max}}$ and parameters of the 3-D bulk curvature effect. Based on the theory, the trench-stop concept and the TS-HOF structure were proposed to reduce ${E}_{\text {max}}$. In the new structure, the depletion of the last discrete metal insulator semiconductor (MIS) array is stopped by process compatible drain trenches for suppressing the serious 3-D bulk curvature effect especially at high voltage, which is a special technology for improving breakdown voltage ${V}_{\text {B}}$ of the complementary homogenization field (C-HOF) LDMOS. It was demonstrated by experiments that ${V}_{\text {B}}$ of the TS-HOF LDMOS is more than 15% higher than that of the C-HOF device while maintaining the same specific ON-resistance ${R} _{\text {on,sp}}$. The TS-HOF LDMOS achieved a measured ${V}_{\text {B}}$ of 675 V and a ${R} _{\text {on,sp}}$ of 49.1 $\text{m}\Omega \,\cdot $ cm2, which represents a reduction of 43.2% when compared with the theoretical value of the triple reduced surface field (RESURF) technology. [ABSTRACT FROM AUTHOR]

Herein, a novel technique to monitor the quality and reliability of thin nano‐scale dielectric films is suggested. The method is based on the modification of the current stress technique (J‐Ramp) described in the corresponding JEDEC standard. The proposed technique, in addition to the J‐ramp tests, allows monitoring a change of charge state of the gate dielectric during all the tests. To implement this, in the suggested method before each transition to a higher current level, the current level is switched to the injection mode by a measurement current level and the change of voltage across the metal–insulator–semiconductor (MIS) structure is measured. A density of the measurement current level is chosen based on the condition that under this current level, a considerable charge degradation of the dielectric should not be observed, and the switches to the measurement current level should not considerably influence the studied sample. In addition to the monitoring of the charge injected until the dielectric breakdown, the proposed method allows to monitor the value of the injected charge at which the unacceptable degradation of MIS device characteristics takes place and, accordingly, to estimate the reliability of the dielectric film based on statistical measurements of these values. [ABSTRACT FROM AUTHOR]

Coupling phenomenon between two Al/SiO2/Si(p) metal–insulator–semiconductor (MIS) tunneling diodes (TD) with various thin oxide thicknesses was studied in detail. When the bias voltage at one MIS TD is positive enough, the saturation currents of the two neighboring MIS TDs with concentric gate structures would be approximately the same due to saturation current coupling effect though the areas of these two devices are different. With thinner oxide, the saturation current coupling effect occurs earlier. This result indicates an enhancement of coupling sensitivity between two neighboring MIS TDs with thinner oxide. A physical mechanism of lateral minority carrier flow attracted by the fringing field was given to explain this phenomenon. Moreover, this oxide thickness dependent phenomenon of coupling effect was confirmed by capacitance–voltage (C–V) characteristics, and the fringing field extension and strengthening were clarified by 2D TCAD simulation. [ABSTRACT FROM AUTHOR]

In this study, the spectral control of near-field radiation transfer between a metal-insulator-metal (MIM)-structured emitter and a metal-semiconductor-metal (MSM)-structured cell was studied for advanced nanogap thermophotovoltaic (TPV) power generation systems using the finite-difference time-domain method. Moreover, the mechanism of spectral control was investigated by the visualization of magnetic condition through the emitter/vacuum gap/cell. For the emitter side, an MIM emitter consisting of nickel and silicon dioxide was used for the spectral enhancement of near-field radiation. For the cell side, an MSM cell consisting of gold, as the electrode, and gallium antimonide, for the photovoltaic semiconductor, was proposed considering a thin-layered TPV cell. The simulation results demonstrated that by the adjustment of the size of the MIM and MSM structures, the near-field radiation can be transferred selectively aiming the target wavelength for the bandgap of GaSb, and those effects can be shown based on the comparison to the blackbody radiation transfer at the same temperatures of the emitter (1000 K). In addition, a unique magnetic resonance condition was appeared when sharper radiation spectral control with enhanced near-field radiation flux can be obtained by optimizing the surface electrode structure of the cell (300 K). Furthermore, the evaluation results show that the spectral efficiency and power ratio increase when the structured emitter and cell was applied. Consequently, using a thin semiconductor layer cell with a p-n junction, similar to conventional cells, an energy conversion system with higher power density can be developed through spectral-controlled radiation transfer between the MIM emitter and MSM cell. These results provide greater flexibility for the control and design of the emitter and cell for nano-gap TPV generation systems. [ABSTRACT FROM AUTHOR]

This work reports a unique gate bias dependence of dynamic ON-resistance in metal–insulator–semiconductor (MIS)-gated AlGaN/GaN high-electron-mobility transistors (HEMTs). The absence of such dependence in Schottky HEMTs confirms that the phenomenon is unique to MISHEMTs. Based on the observations, the weakening of gate control over GaN channel by the insertion of the gate insulator is proposed as the phenomenon responsible for the observed behavior. The proposal is verified by incorporating high- $\kappa $ (25) $\text {Al}_{{0.5}}\text {Ti}_{{0.5}}\text {O}_{y}$ as the gate oxide, which successfully mitigated the gate bias dependence of dynamic ON-resistance by improving the gate control. [ABSTRACT FROM AUTHOR]

A numerical model that describes the transport of mobile ionic species in metal–insulator–semiconductor (MIS) and photovoltaic (PV) devices subject to temperature and voltage stress is presented. The finite element method (FEM) is used to solve the Nernst–Planck equation while imposing Poisson's equation self‐consistently as a restriction for the electrostatic potential. This allows the contribution of the ionic species to the potential to be taken into account. Using a variational formulation eases the implementation of diverse boundary conditions, including the incorporation of segregation kinetics at the device interfaces. Segregation across the dielectric–semiconductor interface is relevant to modeling the electronic device degradation in systems where contamination reaches the semiconductor. The model in closed systems with no‐flux boundary conditions is validated first. In the limiting case of low contamination levels with respect to the gate bias, the FEM solution matches analytically derived approximations. Then, the implementation is broadened to include an open boundary at the dielectric–semiconductor interface to account for leakage of ions. The predicted time dependence of the flatband voltage in Na‐contaminated MIS test structures agrees well with measurements. The model successfully captures the role of long‐range ion transport at concentrations of relevance to electronic and PV device instability and neuromorphic computing. [ABSTRACT FROM AUTHOR]

Discovery of wideband gap semiconductor materials has boosted the field of power electronics. Fabrication of HEMT has overcome the drawback of lower mobility and ON‐state current of wide bandgap materials. However, due to lower ON‐state current earlier proposed devices suffer from poor ON‐state resistance; hence, in this work dual gate technique has been proposed. To further switch the device characteristics from Normally‐ON to Normally‐OFF state, recessed gate technique is used. Device physics, analog parameters of Normally‐OFF dual‐recessed gate metal insulator semiconductor AlGaN/GaN HEMT (DRG‐MIS‐HEMT) are analyzed and compared with conventional DG‐MIS‐HEMT. To solidify the analysis, width of recessed gate has been varied from 2 nm to 28 nm. At recessed gate width (=28 nm), proposed device resulted RON = 1.98 Ω‐cm2, threshold voltage 1.25 V, IDS of 1100 mA/mm, ION/IOFF = 1014 and ft = 10 GHz. Proposed device also resulted in improved linearity characteristics over single gate structure. In future, the proposed device can be used for RF applications. [ABSTRACT FROM AUTHOR]

Mid- and long-wave infrared nBn structures based on HgCdTe grown by molecular beam epitaxy (MBE) on GaAs (013) substrates were fabricated. For mid-wave nBn structures, the composition in the absorbing layer was 0.29, and for long-wave nBn structures, this composition was 0.21. The composition in the MBE HgCdTe barrier layers ranged from 0.61 to 0.67. Based on the fabricated HgCdTe nBn structures, test metal–insulator–semiconductor (MIS) devices were created by applying a dielectric Al2O3 film with the thickness of about 90 nm. The admittance of test MIS devices was investigated over a wide range of frequencies and temperatures. An equivalent circuit of MIS device based on MBE HgCdTe nBn structure is proposed, which includes the dielectric capacitance, the capacitance and resistance of the barrier layer, and the series resistance of the absorbing layer bulk. It is shown that the values of the equivalent circuit elements are easy to determine from the experimental frequency dependences of admittance in accumulation mode. Comparison of element values for MIS devices based on mid-wave and long-wave nBn structures is carried out. [ABSTRACT FROM AUTHOR]

The ever-growing exploration of negative capacitance field effect transistors (NCFETs) for low-power digital application and recent integration in the advanced technology node calls for an investigation of NCFET technology in radio-frequency (RF) applications featuring metal ferroelectric insulator semiconductor (MFIS) configuration. In this article, through TCAD simulation study, we investigate the RF/ac performance of NCFETs by well-known performance metrics such as short-circuit unity current gain frequency or cutoff frequency ${f}_{T} $ , transconductance generation factor ${g}_{m}/{I}_{d}$ , and transconductance frequency product ${g}_{m} {f}_{T}/{I}_{d}$ , a measure of RF performance per dc power consumption, where ${g}_{m}$ and ${I}_{d}$ are transconductance and drive current, respectively. It is found that MFIS NCFET fares better when compared to the 14-nm fully-depleted silicon-on-insulator (FDSOI) field effect transistor (FET) as a baseline device, in terms of improved performance in ${g}_{m}/{I}_{d}$ and ${g}_{m} {f}_{T}/{I}_{d}$. A performance parity in cutoff frequency ${f}_{T}$ is observed. Additionally, the intermodulation distortion $\text {IMD}_{{3}}$ and transistor-level linearity are studied. When a qualitative analysis of the behavior of the key linearity metrics such as higher-order harmonics (${g}_{m{2}}, {g}_{m{3}} $), second- and third-order voltage intercept points ($\text {VIP}_{{2}}, \text {VIP}_{{3}} $), third-order power-intercept point ($\text {IIP}_{{3}} $) is carried out, NCFETs fared comparatively better in linearity. Our conclusions would provide a better insight into adopting NCFET technology for RF applications. [ABSTRACT FROM AUTHOR]

We investigate the doping-driven metal–insulator transition of the (2+1)-dimensional Hubbard model in the path-integral formalism with the tensor renormalization group method. We calculate the electron density 〈 n 〉 as a function of the chemical potential μ, choosing three values of the Coulomb potential with U = 80, 8, and 2 as representative cases of the strong, intermediate, and weak couplings. We determine the critical chemical potential at each U , where the Hubbard model undergoes the metal–insulator transition from the half-filling plateau with 〈 n 〉 = 1 to the metallic state with 〈 n 〉 > 1. Our results indicate that the model exhibits the metal–insulator transition over a vast region of the finite coupling U. [ABSTRACT FROM AUTHOR]

In this study we analysed halide perovskite films deposited directly on crystalline silicon by means of two set-ups using different operating modes of the surface photovoltage (SPV) methods, i.e., the Kelvin probe force microscopy (KPFM) and the metal-insulator-semiconductor (MIS) technique. The KPFM allowed to visualize surface potential distribution on a microscale while MIS technique allowed to study SPV spectral dependence. We studied wavelength dependent SPV of these samples, which allowed us to effectively vary the probe depth in the sample and discern the contribution from each interface to the overall effect measured under white light illumination. Depending on where the photocarriers are generated, different SPV signals are observed: at the perovskite/Si interface, the signal depends on Si doping type, while at the surface the SPV is always negative indicating downward surface band bending. This is confirmed by analysing SPV phase measured in the AC MIS mode. In addition, distinction between slow and fast processes contributing to measured SPV was possible. It has been observed, that with decreasing the illumination wavelength, the processes causing SPV become slower, which can indicate that high energy photons not only generate electronic photocarriers but can also induce chemical changes with creation of defects or ionic species that also modify the measured SPV. [ABSTRACT FROM AUTHOR]

The Metal Wrap Through+ (HIP-MWT+) solar cell is based on the PERC concept but features two additional electrical contacts, namely the Schottky contact between p-type Si bulk and Ag n-contact and the metal-insulator-semiconductor (MIS) contact on the rear side of the cell below the n-contact pads. To prevent thermal hotspots under reverse bias, both contacts shall either restrict current flow or allow a homogenous current flow at low voltage. In this work we present both options. First the stable reverse bias characteristics up to −15 V with a MIS contact using industrially manufactured SiON passivation and second, an integrated by-pass diode using AlOX as insulator in the passivation stack allowing current flows at approximately Vrev = –3.5 V depending on the chosen screen-print paste. The examined Schottky contacts break down at around Vrev = –2.5 V. Reverse bias testing of the cells reveals a solid performance of the cells under reverse bias and an average conversion efficiency of η = 21.2% (AlOX) and η = 20.7% (SiON), respectively. [ABSTRACT FROM AUTHOR]

In this work, we study the possibility of realizing two distinct mechanisms of metal-insulator transitions in hole-doped cuprates induced by the localization of charge carriers near the small-radius impurities and in a deformable lattice (i.e. in the absence of impurities). The purpose of this research is to determine the criteria (i.e. conditions) for the existence of the localized states of hole carriers and solve the problem of metal-insulator transitions in La-based cuprates. The advantage of La-based cuprate versus other types of cuprates is that two distinct metal-insulator transitions in La-based cuprates driven by the strong carrier-impurity-phonon and carrier-phonon interactions occur simultaneously in a wider doping range from the lightly doped to heavily doping regime. We show that at very low doping, the separate levels of hole carriers localized near impurities and in a deformable lattice are formed in the charge-transfer gap of the cuprates. As the doping level increases towards underdoped region, the energy levels of such charge carriers start to form energy bands which gradually broaden with increasing doping. We propose a new two-carrier cuprate superconductor model for studying two distinct metal-insulator transitions occurring simultaneously in hole-doped La-based cuprate compounds. We demonstrate that when hole carriers reside in impurity and polaron bands, these metal-insulator transitions in La-based superconductors with small-radius dopants occur accordingly in a wide doping range and relatively lower doping levels. [ABSTRACT FROM AUTHOR]

We report a strong negative capacitance effect in back to back combination of a metal-insulatorsemiconductor (MIS) structure and a metal-semiconductor junction, which is fabricated on an n type Silicon-on-Insulator substrate. The MIS capacitor comprises a SiO2-HfO2 insulator stack with embedded Pt nanoparticles. The capacitor undergoes a voltage stress process and thereby turns into a varactor and a photodetector. The negative capacitance is observed only under illumination in structures that employ a Schottky back contact. A symmetric double or an asymmetric single negative capacitance peak is observed depending on the nature of illumination. The phenomenon is attributed to the modulation of the semiconductor conductance due to photo generated carriers and their incorporation in trapping/de-trapping processes on interfacial and post filamentation induced defects in the insulator stack. The frequency range of the observed effect is limited to 100 kHz. Large ratios of light to dark and maximum to minimum of negative capacitances as well as of the obtained sensitivity to the applied voltage are, respectively, 105, more than 100, and 10-15. These were measured at 10 kHz under illumination at 365 nm with a power of 2.5×10-6 W. [ABSTRACT FROM AUTHOR]

The evolution of oxidation/reduction states of vanadium oxide thin film was monitored in situ as a function of oxygen pressure and temperature via ambient pressure X-ray photoemission spectroscopy. Spectra analysis showed that VO2 can be grown at a relatively low temperature, T∼523 K, and that V2O5 oxide develops rapidly at elevated oxygen pressure. Raman spectroscopy was applied to confirm the formation of VO2 oxide inside of the film. In addition, the temperaturedependent resistivity measurement on the grown thin film, e.g., 20 nm exhibited a desirable metalinsulator transition of VO2 with a resistivity change of ∼1.5×10³ times at 349.3 K, displaying typical characteristics of thick VO2 film, e.g., 100 nm thick. Our results not only provide important spectroscopic information for the fabrication of vanadium oxides, but also show that high quality VO2 films can be formed at relatively low temperature, which is highly critical for engineering oxide film for heat-sensitive electronic devices. [ABSTRACT FROM AUTHOR]

The original Fano response induced by the interference between the localized plasmons and interface-reflected surface plasmon polaritons in a single metal-insulator-metal waveguide with two parallel separated metal strips is predicted theoretically through the coupled mode theory combined with the Fano function. The prominent asymmetric line shape resulting from the coupling between the discrete dipole resonance formed between metal strips and an interface-reflected-induced continuum is confirmed by the performed numerical simulations. The novel Fano spectrum is tuned easily by varying the length and coupling distance of metal strips. By introducing another separated metal strip, the outstanding double Fano behavior is obtained, and the corresponding underlying physics is illustrated. In particular, based on the performed refractive index sensing spectra, the high sensitivity of 855nm/RIU and figure of merit up to 30 are achieved via the double Fano resonance. Undoubtedly, such ingenious structure may benefit the fabrications of nano-integrated plasmonic devices for optical switching and sensing. [ABSTRACT FROM AUTHOR]

Using aluminum titanium oxide (AlTiO, an alloy of Al2O3 and TiO2) as a high-k gate insulator, we fabricated and investigated AlTiO/AlGaN/GaN metal-insulator-semiconductor heterojunction field-effect transistors. From current low-frequency noise (LFN) characterization, we find Lorentzian spectra near the threshold voltage, in addition to 1/f spectra for the well-above-threshold regime. The Lorentzian spectra are attributed to electron trapping/detrapping with two specific time constants, ~25 ms and ~3ms, which are independent of the gate length and the gate voltage, corresponding to two trap level depths of 0.5-0.7 eV with a 0.06 eV difference in the AlTiO insulator. In addition, gate leakage currents are analyzed and attributed to the Poole-Frenkel mechanism due to traps in the AlTiO insulator, where the extracted trap level depth is consistent with the Lorentzian LFN. [ABSTRACT FROM AUTHOR]

Metal-insulator-metal metamaterial thermal emitters or absorbers have been widely investigated, and the fundamental and higher-order modes are generally excited in these metamaterial resonators. In this paper, we propose a methodology to widen the frequency interval between the fundamental and the second-order modes by enhancing coupling between resonators in close-proximity. At the second-order mode, antiparallel magnetic fields are excited in the insulating layer of rectangular resonators. A diagonal arrangement of rectangles allows destructive interaction between neighboring resonators, resulting in higher second-order frequency. The maximum frequency interval between the two modes is achieved when resonators are shifted by half a period. Furthermore, we suggest a possibility to split the second-order mode by adjusting the arrangement of rectangles. Measured reflection spectra of fabricated metamaterial absorbers agree well with numerical simulations. [ABSTRACT FROM AUTHOR]

A lateral power device with complementary homogenization field structure (C-HOF) is proposed and experimentally proved in this letter. The C-HOF is formed by introducing a P-type metal insulator semiconductor (P-MIS) on the N-MIS. The complementary P/N-MIS and the PN junction between them ensure the homogenized field ${E}_{\text {hof}}$ distributions and the high breakdown voltage ${V}_{\text {B}}$ in higher doping. Based on the C-HOF mechanism, experiments were performed, which demonstrated that a significantly increased N-drift doping dose up to 6.8 $\times \,\,10^{{12}}$ cm−2 can be realized in the C-HOF device. A measured low specific on-resistance ${R}_{ {{\scriptscriptstyle \text{ ON}}},\text {sp}}$ of 19.7 $\text{m}\Omega \cdot $ cm2 was observed in the C-HOF device under a ${V}_{\text {B}}$ of 426 V, realizing a high figure of merit $FOM = {V}_{\text {B}}^{{2}}/{R}_{ {{\scriptscriptstyle \text{ON}}},\text {sp}}$ of 9.21 MW/cm2 and a reduction of 42.8% when compared with the theoretical value of the triple RESURF technology under the same ${V}_{\text {B}}$. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of a series of closely related Y(III) compounds comprising the formamidinate ligands (RNCHNR) (R = alkyl) is reported, with the scope of using them as prospective precursors for atomic layer deposition (ALD) of yttrium oxide (Y2O3) thin films. The influence of the side chain variation on the thermal properties of the resulting complexes is studied and benchmarked by thermal analysis and vapor pressure measurements. Density functional theory (DFT) studies give theoretical insights into the reactivity of the compounds towards water, which was targeted as a co-reactant for the deposition of Y2O3via thermal ALD in the next step. Among the four complexes analyzed, tris(N,N′-di-tert-butyl-formamidinato)yttrium(III) [Y(tBu2-famd)3] 1 was found to possess enhanced thermal stability and was selected for Y2O3 ALD process development. A broad ALD window ranging from 200 °C to 325 °C was obtained, yielding films of high compositional quality. Furthermore, with a film density of (4.95 ± 0.05) g cm−1 close to the bulk value, polycrystalline fcc Y2O3 layers with a smooth topography resulted in promising dielectric properties when implemented in metal insulator semiconductor (MIS) capacitor structures. [ABSTRACT FROM AUTHOR]

The aim of this study is to optimize the conditions for producing thin VO2 films for their use in SAW devices. We used the pulsed laser deposition (PLD) method to produce VO2 films. We used a metallic vanadium target. The dependence of the oxygen pressure during PLD on the resistive metal–insulator transition (MIT) on substrates of c -sapphire and LiNbO3 YX/128 ∘ was studied. The resulting films had sharp metal–insulator temperature transitions on c -Al2O3. The most high-quality films showed resistance change by four orders of magnitude. At the lower point of the hysteresis, the resistance of these samples was in the range of 50–100 Ω. The synthesized VO2 films had a sharp temperature transition and a relatively small width of thermal hysteresis. The SAW damping during its passage through a VO2/ZnO/LiNbO3 YX/128 ∘ film at the metal–insulator phase transition temperature was studied. Attenuation SAW decreases with increasing temperature from 52 dB/cm to 0 dB/cm. [ABSTRACT FROM AUTHOR]

We report a series of metal insulator semiconductor devices with embedded Pt nano particles (NPs) fabricated using a low temperature atomic layer deposition process. Optically sensitive nonvolatile memory cells as well as optical sensors: (i) varactors, whose capacitance-voltage characteristics, non-linearity, and peak capacitance are strongly dependent on illumination intensity; (ii) highly linear photo detectors whose responsivity is enhanced due to the Pt NPs. Both single devices and back to back pairs of diodes were used. The different configurations enable a variety of functionalities with many potential applications in biomedical sensing, environmental surveying, simple imagers for consumer electronics and military uses. The simplicity and planar configuration of the proposed devices makes them suitable for standard CMOS fabrication technology. [ABSTRACT FROM AUTHOR]

In this work, we present the terrace etching technique to obtain excessive thickness series of atomic layer deposition (ALD) grown Al2O3 and HfO2 on GaN-cap/AlGaN/GaN heterostructures allowing for the detailed study of oxide charge distribution and its impact of the metal-insulator-semiconductor high electron mobility transistor (MISHEMT) threshold voltage. By modeling the experimental plot of threshold voltage versus oxide thickness on the basis of experimentally determined two-dimensional electron gas charge density in AlGaN/GaN MISHEMTs, we separated the interface and bulk charge components and determined the oxide-metal barrier height for the investigated gate dielectrics. In both Al2O3 and HfO2 gate dielectrics, the oxide charges are mainly located at the oxide/GaN interface. Determining the interface trap charges from comparison of the pulsed capacitance-voltage (CV) technique with very fast voltage sweep to the modulation type CV method with slow DC voltage ramp, we extracted positive fixed charges of NOx = 2.7 × 1012 cm–2 for Al2O3 and NOx = 7.8 × 1012 cm–2 for HfO2. We found a strong Vth shift of opposite direction for both high-k materials, corresponding to negatively charged up trap states at the HfO2/GaN interface and positively charged up trap states at the Al2O3/GaN interface. The evaluation of the metal-oxide barrier height in dependence of the metal work function followed the trend of the Schottky model, whereas HfO2 showed less Fermi level pinning compared to Al2O3 indicating the presence of an increased number of interface states in Al2O3 on GaN. [ABSTRACT FROM AUTHOR]

Motivated by significant interest in metal-semiconductor and metal-insulator interfaces and superlattices for energy conversion applications, we developed a molecular dynamics-based model that captures the thermal transport role of conduction electrons in metals and heat transport across these types of interface. Key features of our model, denoted eleDID (electronic version of dynamics with implicit degrees of freedom), are the natural description of interfaces and free surfaces and the ability to control the spatial extent of electron-phonon (e-ph) coupling. Non-local e-ph coupling enables the energy of conduction electrons to be transferred directly to the semiconductor/insulator phonons (as opposed to having to first couple to the phonons in the metal). We characterize the effect of the spatial e-ph coupling range on interface resistance by simulating heat transport through a metal-semiconductor interface to mimic the conditions of ultrafast laser heating experiments. Direct energy transfer from the conduction electrons to the semiconductor phonons not only decreases interfacial resistance but also increases the ballistic transport behavior in the semiconductor layer. These results provide new insight for experiments designed to characterize e-ph coupling and thermal transport at the metal-semiconductor/insulator interfaces. [ABSTRACT FROM AUTHOR]

We investigated the nature of transport and magnetic properties in SrIr0.5Ru0.5O3 (SIRO), which has characteristics intermediate between a correlated non-Fermi liquid state and an itinerant Fermi liquid state, by growing perovskite thin films on various substrates (e.g., SrTiO3 (001), (LaAlO3)0.3(Sr2TaAlO6)0.7 (001), and LaAlO3 (001)). We observed systematic variation of underlying substrate dependent metal-to-insulator transition temperatures (TMIT ~ 80K on SrTiO3, ~90K on (LaAlO3)0.3(Sr2TaAlO6)0.7, and ~ 100K on LaAlO3) in resistivity. At temperature 300K⩾T⩾TMIT, SIRO is metallic and its resistivity follows a T3/2 power law, whereas insulating nature at T25 K, with negative MR ∼ B1/2 and positive MR ∼ B2; consistent with the localized-to-normal transport crossover dynamics. Furthermore, observed spin glass like behavior of SIRO on SrTiO3 (001) at T<25K in the localized regime validates the hypothesis that (Anderson) localization favors glassy ordering. These remarkable features provide a promising approach for future applications and of fundamental interest in oxide thin films. [ABSTRACT FROM AUTHOR]

We provide theoretical and simulation analysis of the small signal response of SiO2/AlGaN/GaN metal insulator semiconductor (MIS) capacitors from depletion to spill over region, where the AlGaN/SiO2 interface is accumulated with free electrons. A lumped element model of the gate stack, including the response of traps at the III-N/dielectric interface, is proposed and represented in terms of equivalent parallel capacitance, Cp, and conductance, Gp, . Cp, -voltage and Gp, -voltage dependences are modelled taking into account bias dependent AlGaN barrier dynamic resistance Rbr, and the effective channel resistance. In particular, in the spill-over region, the drop of Cp, with the frequency increase can be explained even without taking into account the response of interface traps, solely by considering the intrinsic response of the gate stack (i.e., no trap effects) and the decrease of Rbr, with the applied forward bias. Furthermore, we show the limitations of the conductance method for the evaluation of the density of interface traps, Dit, from the Gp,/ω vs. angular frequency ω curves. A peak in Gp/ω vs. ω occurs even without traps, merely due to the intrinsic frequency response of gate stack. Moreover, the amplitude of the Gp/ vs. ω peak saturates at high Dit, which can lead to underestimation of Dit. Understanding the complex interplay between the intrinsic gate stack response and the effect of interface traps is relevant for the development of normally on and normally off MIS high electron mobility transistors with stable threshold voltage. [ABSTRACT FROM AUTHOR]

Transport characteristics of ultrathin SrRuO3 films, deposited epitaxially on TiO2-terminated SrTiO3 (001) single-crystal substrates, were studied as a function of film thickness. Evolution from a metallic to an insulating behavior is observed as the film thickness decreases from 20 to 4 unit cells. In films thicker than 4 unit cells, the transport behavior obeys the Drude low temperature conductivity with quantum corrections, which can be attributed to weak localization. Fitting the data with 2-dimensional localization model indicates that electron-phonon collisions are the main inelastic relaxation mechanism. In the film of 4 unit cells in thickness, the transport behavior follows variable range hopping model, indicating a strongly localized state. Magnetoresistance measurements reveal a likely magnetic anisotropy with the magnetic easy axis along the out-of-plane direction. [ABSTRACT FROM AUTHOR]

Herein, the Kubo–Greenwood formula is utilized to project the electronic conductivity into real space, and a Hermitian positive semidefinite matrix Γ is discussed, which is called the conduction matrix, that reduces the computation of spatial conduction activity to a diagonalization. It is shown that for low‐density amorphous carbon, connected sp2 rings and sp chains are conduction‐active sites in the network. In amorphous silicon, transport involves hopping through tail states mediated by the defects near the Fermi level. It is found that for liquid silicon, thermal fluctuations induce spatial and temporal conductivity fluctuations in the material. The frequency‐dependent absorption of light as a function of wavelength in an amorphous silicon suboxide (a‐SiO1.3) is also studied. It is shown that the absorption is strongly frequency dependent and selects out different oxygen vacancy subnetworks depending on the frequency. Γ is diagonalized to obtain conduction eigenvalues and eigenvectors, and it is shown that the density of states of the eigenvalues for FCC aluminum has an extended spectral tail that distinguishes metals from insulators and semiconductors. The method is easy to implement with any electronic structure code, providing suitable estimates for single‐particle electronic states and energies. [ABSTRACT FROM AUTHOR]

We fabricated and characterized metal insulator semiconductor (MIS) structures by applying amorphous AlN thin layers as a dielectric in gate recessed AlGaN/GaN heterostructure field effect transistors (HFETs). Micro photoluminescence measurements performed on MISHFET devices reveal a local non-uniform distribution of strain in the source—gate recess—drain region. Furthermore, a reduction of compressive stress up to 0.3 GPa in GaN after gate recessing was experimentally determined. The local stress increases by ∼0.1 GPa and ∼0.2 GPa after the deposition of 4 and 6 nm thin AlN layers in the gate recessed structures, respectively. Additionally, an increase in sheet charge density in the devices under investigation from ∼ to ∼ was evaluated by capacitance–voltage measurements. Therefore, strain engineering by applying amorphous AlN layers in gate recessed MISHFETs can significantly improve their device characteristics. [ABSTRACT FROM AUTHOR]

Superconductivity frequently appears by doping compounds that show a collective phase transition. So far, however, this has not been observed in topological materials. Here we report the discovery of superconductivity induced by Ga doping in orthorhombic Re3Ge7, which undergoes a second-order metal–insulator-like transition at ~58 K and is predicted to have a nontrivial band topology. It is found that the substitution of Ga for Ge leads to hole doping in Re3Ge7−xGax. As a consequence, the phase transition is gradually suppressed and disappears above x = 0.2. At this x value, superconductivity emerges and Tc exhibits a dome-like doping dependence with a maximum value of 3.37 K at x = 0.25. First principles calculations suggest that the phase transition in Re3Ge7 is associated with an electronic instability driven by Fermi-surface nesting and the nontrival band topology is preserved after Ga doping. Our results indicate that Ga-doped Re3Ge7 provides a rare opportunity to study the interplay between superconductivity and competing electronic states in a topologically nontrivial system. [ABSTRACT FROM AUTHOR]

Heavily oxygen-deficient NdNiO3 (NNO) films, which are insulating due to electron localization, contain pristine regions that undergo a hidden metal-insulator transition. Increasing oxygen content increases the connectivity of the metallic regions and the metal-insulator transition is first revealed, upon reaching the percolation threshold, by the presence of hysteresis. Only upon further oxygenation is the global metallic state (with a change in the resistivity slope) eventually achieved. It is shown that sufficient oxygenation leads to linear temperature dependence of resistivity in the metallic state, with a scattering rate directly proportional to temperature. Despite the known difficulties to establish the proportionality constant, the experiments are consistent with a relationship 1/τ = αkBT/ℏ, with α not far from unity. These results could provide experimental support for recent theoretical predictions of disorder in a two-fluid model as a possible origin of Planckian dissipation. [ABSTRACT FROM AUTHOR]

A simple chemical oxidation process is introduced to grow SiO x to form p-Si based MIS photocathode with high-quality insulating layer for efficient PEC hydrogen production. [Display omitted] • A simple chemical oxidation process was introduced to grow high quality SiO x for the passivation of p-Si. • The carrier flux, barrier height and interfacial resistance of p-Si MIS junction can be tuned by controlling the thickness and quality of SiO x. • AFM and XPS analysis proved that the chemically oxidized SiO x is more uniform, with a higher Si4+/Si3+ ratio. • Up to 6% of applied bias photon-to-current efficiency (ABPE) was obtained with p-Si/SiO x /Ti/Pt photocathode. Photoelectrochemical (PEC) water splitting provides a potential method to produce renewable hydrogen energy, but there is still plenty of room for improving the efficiency and stability of photoelectrodes. In this paper, we present a metal–insulator-semiconductor (MIS) structure based on p-Si that enables stable and efficient water splitting by engineering the interfacial insulating layer. The silicon oxide (SiO x) film with appropriate thickness and low defects is regrown by a chemical oxidation process, which provides a high-quality insulating layer to passivate the p-Si. The carrier flux, barrier height and interfacial resistance of p-Si based MIS junction can be systematically tuned by controlling the thickness and quality of SiO x layer. Under AM 1.5G illumination, the optimized p-Si/SiO x /Ti/Pt photoelectrode shows an onset potential of 0.5 V vs. RHE, a maximum photocurrent of 28 mA/cm2 and a high applied bias photon-to-current efficiency (ABPE) of 6 %. These results have significant implications for constructing MIS photoelectrodes towards effective water splitting. [ABSTRACT FROM AUTHOR]