In this work, a UV photodetector was fabricated by constructing a heterojunction between β phase GaOxNy prepared by atomic layer deposition and p-GaN prepared by metal organic chemical vapor deposition. The p-GaN layer shows an extremely sharp absorption characteristic with a cutoff edge of ∼365 nm, while β-GaOxNy shows a broad absorption behavior in the UV region due to its low crystal quality grown

A scanning probe microscope coupled with either femtosecond laser pulses or terahertz pulses holds great promise not only for observing ultrafast phenomena but also for fabricating desirable structures at the nanoscale. In this study, we demonstrate that a few-nanometer-scale phase change can be non-thermally stored on the Ge2Sb2Te5 surface by a laser-driven scanning tunneling microscope (STM). An

Scandium nitride (ScN) is an emerging rock salt indirect bandgap semiconductor and has attracted significant interest in recent years for thermoelectric energy conversion, as a substrate for defect-free GaN growth, as a semiconducting component in single-crystalline metal/semiconductor superlattices for thermionic energy conversion, as well as for Al1−xScxN-based bulk and surface acoustic devices for

The mobility-lifetime ( μ τ) product is an important parameter that determines the performance of electronic and photonic devices. To overcome the previously reported difficulties in measuring the μ τ product at cryogenic temperatures, we implement a time-resolved cyclotron resonance method to determine the carrier lifetime τ. After clarifying the difference between the AC and DC mobilities measured

The structure at the atomic scale and optical properties of GaN-based green light-emitting diodes (LEDs) before and after in situ degradation were investigated by spherical aberration corrected scanning transmission electron microscopy and temperature-dependent micro-photoluminescence. Indium (In) interstitial atoms existed in the degraded sample, due to the small-bond-energy In atoms deviating from

Performing deep level transient spectroscopy (DLTS) on Schottky diodes, we investigated defect levels below the conduction band minima (Ec) in Czochralski-grown unintentionally doped (UID) and vertical gradient freeze-grown Zr-doped β-Ga2O3 crystals. In UID crystals with an electron concentration of 1017 cm−3, we observe levels at 0.18 eV and 0.46 eV in addition to the previously reported 0.86 (E2)

Antiferromagnet (AFM)/ferromagnet (FM) systems such as IrMn/CoFeB/MgO enable spin–orbit-torque- (SOT-) induced switching of perpendicular magnetization in the absence of an external magnetic field. However, the low thermal stability, weak perpendicular magnetic anisotropy (PMA), and indistinctive SOT of these AFM/FM heterostructures pose challenges to the practical application. Here, through the insertion

The spontaneous exchange bias (SEB) effect is a remarkable phenomenon recently observed in some reentrant spin-glass materials. Here, we investigate the SEB in La1.5(Sr0.5−xBax)CoMnO6 double-perovskites, a system with multifarious magnetic phases for which a notable increase in the exchange bias field is observed for intermediate Sr/Ba concentrations. The Ba to Sr substitution leads to the enhancement

We demonstrate a tunable spin–orbit torque (SOT) switching in an antiferromagnetically coupled CoFeB/Ta/CoFeB trilayer through careful design of magnetic anisotropies, where the thicker bottom CoFeB layer has a relatively weak perpendicular magnetic anisotropy (PMA) and PMA of the upper CoFeB layer is robust. The unique anisotropy feature causes a strong sensitivity to the assistant field during SOT

We report on the use of time-resolved scanning transmission x-ray microscopy imaging for the visualization of the dynamical canting of the magnetization induced by field-like spin–orbit torques in a perpendicularly magnetized microwire. In particular, we show how the contributions to the dynamical canting of the magnetization arising from the field-like spin–orbit torque can be separated from the heating-induced

We investigate the noise current in a thermally biased tunnel junction between two superconductors with different zero-temperature gaps. When the Josephson effect is suppressed, this structure can support a nonlinear thermoelectric effect due to the spontaneous breaking of electron–hole symmetry, as we recently theoretically predicted. We discuss the possibly relevant role played by the noise in the

Both A- and B-site-substituted BaTiO3 ceramics are promising alternative relaxor materials to replace lead zirconium titanate as an actuator. With a motivation to improve electromechanical properties, a lead-free Ba0.95Ca0.05Sn0.09Ti0.91O3 (BCST) ceramic close to the polymorphic phase boundary composition is synthesized by solid-state reaction. X-ray diffraction and Raman spectroscopy confirm the coexistence

The utilization of ferroelectric ceramics in electrical energy storage has become a hot topic due to the urgent need for advanced pulsed power and high power energy storage applications. Much attention has been paid to achieving nanograined ferroelectric ceramics but little to the effect of grain size uniformity, which is critical for dielectric breakdown and reliability. We first investigated this

Space charge accumulation is the main factor in accelerating the degradation of polymeric insulation in high-voltage direct current (HVDC) cables. It is essential for the development of HVDC cables to suppress the space charge in the insulating layer. In this paper, an approach is presented to decrease carrier injection from the inner semiconductive layer to the insulating layer, using a magnetic semiconductive

CeO2–HfO2 solid solution thin films, Hf1−xCexO2, are fabricated on n+-Si(100) substrates by the chemical solution deposition method. The effects of the CeO2 content and annealing temperature on the structure and ferroelectric properties of Hf1−xCexO2 are studied. The structural properties are investigated by glancing incidence x-ray diffraction and high resolution transmission electron microscopy,

The reliability of Hf0.5Zr0.5O2 (HZO) metal–ferroelectric–semiconductor capacitors grown by plasma-assisted atomic oxygen deposition on Ge substrates is investigated with an emphasis on the influence of crystallization annealing. The capacitors show very weak wake-up and imprint effects, allowing reliable operation in excess of 10 years, which is attributed partly to the clean, oxide-free Ge/HZO bottom

We have employed a variable stripe length method in order to measure the optical gain of GaAs/AlGaAs quantum rings. Although the large lateral diameter of quantum rings ( ∼ 50 nm) with a few nm size distribution is expected to cause a small spectral inhomogeneity ( ∼ 1 %), a broad gain width ( ∼ 300 meV) was observed. This result was attributed to a variation of the vertical heights and variations

We study the validity of implementing MoS2 multilevel memories in future neuromorphic networks. Such a validity is determined by the number of available states per memory and their retention characteristics within the nominal computing duration. Our work shows that MoS2 memories have at least 3-bit and 4.7-bit resolvable states suitable for hour-scale and minute-scale computing processes, respectively

Observation at low voltage using scanning electron microscopes (SEMs) enables the characterization of surface details on specimens on a nanometer scale and is widely used in science and industry. However, the energy width of the electron source restricts the spatial resolution of SEMs at low voltage, but it can be narrowed by lowering the work function of the emitter material. Here, we developed a

A chemical vapor deposition (CVD) growth model is presented for a technique resulting in naturally formed 2D transition metal dichalcogenide (TMD)-based metal-oxide-semiconductor structures. The process is based on a standard CVD reaction involving a chalcogen and transition metal oxide-based precursor. Here however, a thin metal oxide layer formed on lithographically defined contacts composed of pure

We have compared the magnetic properties of well-controlled ultra-short (≤50 nm) atomic iron (Fe) chains embedded in Fe-phthalocyanine films with those in Fe–hydrogen (H2) phthalocyanine superlattices. Surprisingly, we found that the coercivity of the atomic chains with free boundary conditions is independent of the chain length, whereas the one subject to hybridization of the chain ends exhibits an

While a linear growth behavior is one of the fingerprints of textbook atomic layer deposition processes, the growth often deviates from that behavior in the initial regime, i.e., the first few cycles of a process. To properly understand the growth behavior in the initial regime is particularly important for applications that rely on the exact thickness of very thin films. The determination of the thicknesses

We use micro-focused Brillouin light scattering spectroscopy (BLS) to investigate surface acoustic waves (SAWs) in a GaN layer on a Si substrate at GHz frequencies. Furthermore, we discuss the concept of BLS for SAWs and show that the crucial parameters of SAW excitation and propagation can be measured. We investigate a broad range of excitation parameters and observe that Rayleigh and Sezawa waves

Achieving total mode conversion from longitudinal to shear waves for a broad incident angle has been a big scientific challenge in elastic fields, which was impossible to be achieved in classical elastic wave theory. In this paper, we propose and realize a refractive transmodal elastic metasurface that can convert an incident longitudinal wave to a shear wave for a broad incident angle. Here, the total

Current human body cooling technologies aggravate the energy crisis and cause environmental issues, and an efficient and energy-saving personal comfort cooling technology is critical. Many recent smart cooling textiles involve complex and time-consuming fabrication processes and fail to achieve both comfort drying and cooling functions. Herein, a hydrophobic/superhydrophilic Janus fabric was fabricated

Directed cell migration following the gradients of extracellular matrix stiffness, termed durotaxis, plays an essential role in development, wound healing, and cancer invasion. Here, we develop a cytoskeleton-based mechanical model to study the migration modes of both isolated cells and cell clusters on gradient substrates. We find that collective cell durotaxis is attributed to the geometrical restriction

Electronic contribution to thermal conductivity ( κ e) is proportional to electrical conductivity ( σ) as given by the Wiedemann–Franz law ( κ e = L σ T). The Lorenz number ( L) scales the thermal current associated with the electrical current and implies the electrons' capability of carrying heat. By experimental transport measurements and first-principles calculations, we show that electron transport

Quantum imaging based on entangled light, laser light, and thermal light has been extensively studied. However, single-photon quantum imaging is still in its infancy. In this paper, we perform quantum imaging using heralded single-photon sources and achieve single-photon illumination computational ghost imaging and single-photon illumination single-pixel camera imaging.

We have demonstrated a technique for remote magnetometry using fluorescence measurements in a sodium cell. This technique utilizes two-photon resonance instead of single-photon resonance to generate magnetic resonances with synchronous modulation of two laser fields. A strong magnetic resonance with its dip matching the Larmor frequency, ΩL, is produced when a magnetic field perpendicular to the laser

To describe the state of polarization (SOP) of light, the Stokes parameters are obtained using intensity measurements made at different component polarization states. Using these Stokes parameters, complex field distributions called Stokes fields can be synthesized, and the phase singularities present in these Stokes fields are called Stokes vortices. The SOP of a Stokes vortex can be either linear

We report on the development of a highly sensitive imaging polarimeter that allows for the investigation of polarization changing properties of materials in the x-ray regime. By combining a microfocus rotating anode, collimating multilayer mirrors, and two germanium polarizer crystals, we achieved a polarization purity of the two orthogonal linear polarization states of 8 × 10−8. This enables the detection

We report on a detailed study of terahertz (THz) photoresistivity in a strained HgTe three-dimensional topological insulator (3D TI) for all Fermi level positions: inside the conduction and valence bands and in the bulk gap. In the presence of a magnetic field, we detect a resonance corresponding to the cyclotron resonance (CR) in the top surface Dirac fermions (DFs) and examine the nontrivial dependence

A diamond (111) substrate cleaned with an NH3/H2O2 mixture could form low-temperature direct bonding under atmospheric conditions. When the diamond surface was bonded with a plasma activated SiO2 surface at 200 °C, the bonding strength was sufficiently high so that cleavage within diamond occurred in a shear test. Moreover, the diamond and Si substrates treated with the NH3/H2O2 mixture could form

Diamond is a promising electronic semiconductor candidate that has recently attracted intense interest in the implementation of its superior physical properties in electronic devices. In particular, attention has been focused on the surface transfer doping of diamond, in which the hydrogen-terminated diamond (diamond:H) benefices of a unique conductive two-dimensional hole gas (2DHG) layer at the diamond's

One-inch free-standing (001) diamond layers on a (11 2 ¯0) (a-plane) sapphire substrate with an Ir buffer layer (Kenzan Diamond®) were grown. The full-width at half maximum values of (004) and (311) x-ray rocking curves were 113.4 and 234.0 arc sec, respectively. The dislocation density of the substrates was 1.4 × 107 cm−2, determined by plan-view transmission electron microscopy observation. These

Localization of carriers in a self-organized quantum dot is a problem of quantum mechanics to be solved with the localizing potential for electrons and holes determined by the geometry, chemical composition, and built-in mechanical stress–strain field. We show that changes in the aspect ratio of a buried pyramidal quantum dot result in a substantial redistribution of the mechanical field components

We report simultaneous Raman scattering and photoluminescence (PL) mapping results to study the strain and doping effects of chemical treatment with bis(trifluoromethane) sulfonimide (TFSI) on the optical phonon, exciton, and trion characteristics of a vertically stacked monolayer–bilayer (1L–2L) MoS2 structure. Correlation analysis between the E ′ and A 1 ′ phonon energies revealed that tensile strain

The weakest mode of the infrared active folded phonons in 4H–SiC, folded transverse acoustic (FTA) mode, has been experimentally studied. The lifetime of the FTA phonons has been determined. The lifetime is 58 ± 4 ps at room temperature and increases to 140 ± 7 ps when the temperature is decreased to 5 K. These results were obtained by the experimental study of far-infrared transmission of the SiC

Although many studies have been continuously conducted to reduce the power consumption of a resistive random access memory (RRAM) cross-point array with the current-compliance effect, it has been difficult yet to realize intrinsic self-compliance effects in an RRAM device itself. In this study, a simple oxygen-rich TiOy layer is inserted into the Al2O3/TiOx-based RRAM stack as a current suppression

We study the thermal conductivity distribution of hypothetical graphene-like materials composed of carbon and heavy carbon atoms. These materials are representative of alloys and disordered materials, which are relatively unexplored for thermal properties owing to their large configuration spaces. Since the full thermal conductivity calculations using the Boltzmann transport equation based solutions

The magnetic skyrmionium can be seen as a coalition of two magnetic skyrmions with opposite topological charges and has potential applications in next-generation spintronic devices. Here, we report the current-driven dynamics of a skyrmionium in a ferromagnetic nanotrack with the voltage-controlled magnetic anisotropy. The pinning and depinning of a skyrmionium controlled by the voltage gate are investigated

The anomalous Hall effect (AHE) has been extensively studied in terms of its diverse and profound physics, but the AHE behavior under spatially rotated external fields has not been well understood yet. Here, we selected a traditional CoFeB-based multilayer film as the platform, and by continuously tuning its magnetic anisotropy, we have observed the progressively evolved angular-dependence of the AHE

Multilevel nonvolatile regulation (MNR) is demonstrated in a heterostructure composed of an amorphous hard magnetic SmCo thin film and a (011)-oriented ferroelectric 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) substrate. Two alternative ways of obtaining MNR are employed: the quasi-unipolar method and the quasi-minor-loop method, both of which utilize the transition from the rhombohedral (R) to monoclinic

We investigate spin-wave resonance in nanoscale CoFeB/MgO magnetic tunnel junctions (MTJs) with a perpendicular easy axis and various free-layer sizes. Two types of MTJs are fabricated by different process conditions, and the spin-wave resonance is measured with homodyne-detected ferromagnetic resonance. We focus on the distance between resonance frequencies of the uniform and spin-wave modes as a

In this work, we study the effects of mobile oxygen ions in a synthetic antiferromagnet structure gated by a sputtered SiO2 dielectric layer for memory and logic applications. Our devices utilize electrochemical reactions between dielectric reactive species and magnetic elements to create irreversible changes in magnetization. We analyzed the dependence of ion velocity on the gate dielectric properties

The electrocaloric effect represents an adiabatic temperature change or isothermal entropy change upon the application or removal of an external electric field. However, the effect of the repetitive bipolar/unipolar electric field on the electrocaloric effect in ferroelectrics is not well understood. In this work, the electrocaloric effect after both bipolar and unipolar electrical cycling in Pb0.92La0

HfO2 nanodots and epitaxial HfO2 thin films with ferroelectric properties were grown on yttria-stabilized zirconia substrates with indium tin oxide bottom electrodes via a pulsed laser deposition (PLD) method. The crystallinity and ferroelectric properties of the epitaxial HfO2 thin films were analyzed to compare ferroelectric properties resulting from crystallinity and the strained structure of HfO2

Spin–orbit coupling (SOC) offers an alternative technique for generating pure spin currents in non-magnetic materials and controlling spin precessions for spin-field effect transistors. In addition, introducing SOC into graphene causes pristine graphene to evolve into a new condensed matter phase, such as the topological insulator state (quantum spin Hall state). Thus, the control of SOC in graphene

We report the spontaneous adsorption of ions on graphene at the interface with electrolytes through an investigation based on the electrolyte-gated field effect transistor configuration. It is found that the gate voltage at which the minimum conductivity occurs in these devices is highly sensitive to the type of ions and their concentrations in the electrolytes; yet the experimental results exhibit

We present an extensive investigation of the charge-trapping processes in vertical GaN nanowire FETs with a gate-all-around structure. Two sets of devices were investigated: Gen1 samples have unipolar (n-type) epitaxy, whereas Gen2 samples have a p-doped channel and an n-p-n gate stack. From experimental results, we demonstrate the superior performance of the transistor structure with a p-GaN channel/Al2O3

Very high temperature operation β-Ga2O3 Schottky contacts were fabricated on moderately doped 2 ¯ 01 β-Ga2O3 single crystal substrates using four different types of intentionally oxidized platinum group metal (PGM) Schottky contacts (SCs), i.e., PtOx, IrOx, PdOx, and RuOx (x ∼ 2.0, 2.2, 1.1, and 2.4, respectively) formed by reactive rf sputtering of plain-metal targets in an oxidizing plasma. All four

We have investigated how the beam geometry affects the thermal responsivity of doubly clamped GaAs microelectromechanical systems (MEMS) beam resonator structures. When the MEMS beam is heated, a thermal strain is generated and shifts the resonance frequency. MEMS beams with larger l/h ratios (l and h are the length and the thickness of the MEMS beam, respectively) have lower thermal conductances and

Ferroelectric Si-doped HfO2 is a promising candidate for future generation memory devices. However, such devices are vulnerable to significant threshold voltage shifts resulting from charge trapping in oxide defects. We use complementary characterization and modeling techniques to reveal significant electron trapping/de-trapping behavior, together with a strong temperature dependence of the electron

We investigate the transport properties in nodal-line Weyl semimetal resonant tunneling junction. Double reflections and double transmissions appear, which are specular reflection, retroreflection, normal transmission, and specular transmission. The incident angle dependence transmissions and reflections are studied with different incident energies and different quantum well widths. The retroreflection

The output power of modern 975 nm GaAs-based broad area diode lasers is limited by increasing carrier and photon losses at high bias. We use experiment and one-dimensional calculations on these devices to reveal that higher current densities (and hence higher local recombination rates and higher losses) arise near the front facet due to spatial hole burning and that the non-uniformity is strongly affected

Melanin, with its high refractive index (RI) and broadband absorption, is an important biomaterial responsible for many of the vibrant structural colors observed in nature and for UV protection. Even though the RI plays an important role in the function of melanin, there is an ambiguity in its reported complex RI and a lack of understanding of whether and how the UV radiation, these materials are likely

In this report, we discuss the 22% efficiency improvement of solar cells based on the MAPbI3 perovskite film extracted with a mixed anti-solvent. The film quality of MAPbI3 extracted from the mixed anti-solvent of ether and isopropanol is improved greatly. The average grain size of the film may be enlarged twice. We argue that some solvents residing in the precursor may effectively promote the crystallization

The coherent interaction of Rydberg helium atoms with microwave fields in a λ / 4 superconducting coplanar waveguide resonator has been exploited to probe the spectral characteristics of an individual resonator mode. This was achieved by preparing the atoms in the 1s55s 3S1 Rydberg level by resonance enhanced two-color two-photon excitation from the metastable 1s2s 3S1 level. The atoms then traveled

Magnetometers based on nitrogen-vacancy center ensembles in diamond have received considerable attention in recent years. However, their sensitivities are limited by low fluorescence collection efficiencies. With the introduction of some schemes, collection efficiencies of NV ensembles have been improved, but further improvement is still needed. In this Letter, we propose and demonstrate a fluorescence

We verify the similarity law (SL) and show a violation of frequency scaling (f-scaling) in low-pressure capacitive radio frequency (rf) plasmas via fully kinetic particle-in-cell simulations. The SL scaling relations for electron density and electron power absorption are first confirmed in similar rf discharges. Based on these results, with only the driving frequency varied, the f-scaling for electron