The ever-increasing complexity in the structure and design of functional materials systems and devices necessitates new imaging approaches with 3D characterization capabilities and nanoscale resolution. This Perspective provides a brief review of the tomographic atomic force microscopy technique and its recent applications in the 3D nanocharacterization of energy and electronic materials including

Coding metasurfaces have emerged as a promising venue for terahertz (THz) beam steering and beamforming. In this study, we designed a transmission metasurface with a complementary structure based on Babinet's principle. The beam-steering capability of the coding metasurface is implemented by encoding “0” and “1” elements with different phase responses and by controlling the coding sequences. The deflection

A germanium (Ge) or germanium-on-silicon (Ge-on-Si) substrate is an attractive yet not well-studied platform for developing long-wave infrared photonics devices such as lasers and photodetectors. In this paper, we report a long-wave infrared quantum cascade photodetector grown on the Ge substrate with a submonolayer InAs/GaAs quantum dot as the infrared absorber. At 77 K under zero bias, the detector

Topological insulators (TIs) with unique band structures have wide application prospects in the fields of ultrafast optical and spintronic devices. The dynamics of hot carriers plays a key role in these TI-based devices. In this work, using the time- and angle-resolved photoemission spectroscopy technique, the relaxation process of the hot carriers in Cr-doped Bi2Se3 has been systematically studied

The brain is an especially active metabolic system, requiring a large supply of energy following neuronal activation. However, direct observation of cellular metabolic dynamics associated with neuronal activation is challenging with currently available imaging tools. In this study, an optical imaging approach combining imaging of calcium transients and the metabolic co-enzyme nicotinamide adenine dinucleotide

Metasurfaces are subwavelength-thick constructs, consisting of discrete meta-atoms, providing discretized levels of phase accumulation that collectively approximate a designed optical functionality. The meta-atoms utilizing the Pancharatnam–Berry phase with polarization-converting structures produced encouraging implementations of optical components including metalenses. However, to date, a pending

We report on the demonstration of Al0.85Ga0.15As0.56Sb0.44 (hereafter, AlGaAsSb) avalanche photodiodes (APDs) with a 1000 nm-thick multiplication layer. Such a thick AlGaAsSb device was grown by a digital alloy technique to avoid phase separation. The current-voltage measurements under dark and illumination conditions were performed to determine gain for the AlGaAsSb APDs. The highest gain was ∼ 42

Jumping droplets are interesting because of their applications in energy harvesting, heat transfer, anti-icing surfaces, and displays. Typically, droplets “jump” from a surface when two or more drops coalesce. Here, we demonstrate an approach to get a single droplet of liquid metal (eutectic gallium indium) to jump by using electrochemistry in a solution of 1M NaOH. Applying a positive potential to

Oxygen vacancies (Vo) play significant roles in determining the properties of transition-metal oxides. However, the concentration of Vo cannot be tuned quantitatively by optimizing the preparation conditions, and the precise control of Vo distribution at the atomic scale is even more challenging. Here, by controlling the reversible phase transitions between perovskite LaCoO3 (PV-LCO) and brownmillerite

Titanium-vanadium dioxide or TixV1−xO2 films for 0 ≤ x ≤ 1 were examined using ellipsometry, and their optical constants (n and k) at visible and near-infrared wavelengths were determined at temperatures (T) below, at, and above the semiconductive-to-metallic phase transition (SMT) temperature (TSM). Ellipsometric analysis was performed for each x at each T using a wavelength dispersion model, i.e

The mechanical response of ultralight kagomé structures consisting of hollow nickel (Ni) nanotubes and solid Ni nanorods to compression is studied using molecular dynamics simulations. In both kagomé architectures, 1 6 [ 112 ] Shockley partial dislocations and twin formation are observed under compression. The structure made from solid nanorods shows deformation near both the nodes and beams of the

Effects of the titanium dopant on the physical properties and structure of SbSe thin films were systematically investigated by experiments and first-principles calculations. The amorphous-to-polycrystalline transformation induced by heat was examined by in situ electrical resistance measurements. With the incorporation of titanium atoms, both the crystallization temperature and electrical resistance

The interaction between the itinerant carriers, lattice dynamics, and defects is a problem of long-standing fundamental interest for developing quantum theory of transport. Here, we study this interaction in the compositionally and strain-graded AlGaN heterostructures grown on AlN substrates. The results provide direct evidence that a dimensional crossover (2D–3D) occurs with increasing temperature

We report on the electrical detection of electron nuclear double resonance (EDENDOR) through spin-dependent tunneling transport in an amorphous hydrogenated silicon thin film. EDENDOR offers a many orders of magnitude improvement over classical ENDOR and is exclusively sensitive to paramagnetic defects involved in electronic transport. We observe hyperfine interactions with 1H nuclei very close to

Isotropic spin analysis is a key step in spintronics and could be useful in quantum information, which usually requires light as an essential component. It has not yet been realized in a solid-state device. Here, we propose an isotropic all electrical spin analyzer designed from a quantum ring with spin–orbit couplings by analytically and numerically modeling how the charge transmission rate depends

Skyrmions in synthetic antiferromagnets (SAFs) could be immune to the skyrmion Hall effect and are, thus, promising in spintronics applications. We introduce breathing modes that can be realized by changing the magnetocrystalline anisotropy periodically in time to generate spin waves around a deformed SAF skyrmion. The net momentum transferred from the magnon spin currents results in a motion of the

A shape-anisotropy magnetic tunnel junction (MTJ) holds promise for its scaling into single-digit nanometers while possessing high data-retention capability. Understanding magnetization reversal mode is crucial to quantify the thermal stability factor Δ for data retention with high accuracy. Here, we study magnetization reversal mode in the shape-anisotropy MTJ with a 15-nm-thick CoFeB layer by evaluating

Electron vortex beams generated by a transmission electron microscope (TEM) are employed to study magnetic properties of an impurity often embedded in materials. Compared to the optical wave, a higher spatial resolving power of electron waves enables the detection of impurities on the nanoscale. Here, we investigate theoretically the interaction of the twisted electrons and the magnetic impurity in

By a combination of magnetization M(T), M(H) and strain ΔL/L700K, ΔL/L0Oe, the positive magnetostrictions up to ∼5000 ppm originating from the rearrangement of tetragonal domains were observed in spinel Mn0.85Mg0.15V2O4, which exhibits two successive magnetic transitions at TC ∼ 42 K and T* ∼ 28 K. An anomalous magnetic hysteresis loop under a high field occurs below T*, caused by the rearrangement

For ferroelectric random access memory (FRAM) with HfO 2-based materials, the wake-up effect and the imprint have to be limited. Here, the electrical behavior of different samples is investigated during retention tests on woken-up samples at room temperature. Retention properties are compared during tests with or without alternations of voltage pulses with opposite signs. First, during retention tests

Crystallographic characterization and the ferroelectric properties of 50 nm-thick sputter-deposited Al0.78Sc0.22N films deposited at room temperature (RT) and 400 °C are investigated. c-axis oriented growths were confirmed by x-ray diffraction patterns with rocking curve measurements for both samples. Al0.78Sc0.22N films were found to grow in the c-axis direction and showed poling-free ferroelectric

In the context of growing interest in strain engineering, we present a theoretical protocol for the reconstruction of extrinsic and intrinsic strain tensors in single-crystals attached to a template, with an arbitrary oriented coordinate system. Input data for the protocol are extrinsic deformations of lattice planes, i.e., measured with reference to a template. By combining the protocol with elasticity

The natural intrinsic magnetic topological insulator MnBi2Te4(Bi2Te3)n is a platform for studying intriguing transport phenomena and provides an essential chance for the fundamental understanding of the combination of magnetism and topology. Here, we fabricated MnBi4Te7 thin film devices and carried out the transport measurement. It shows the unconventional anomalous Hall effect in the devices with

Technological application of semiconductors depends critically on their defect properties. Recently, it has been experimentally observed that monolayer (ML) black phosphorus (BP) and black arsenic (BAs) are intrinsic p-type semiconductors, which conflict with the theoretical predictions previously acknowledged that there are no shallow defects in two-dimensional semiconductors. In this paper, we have

van der Waals p–n heterojunctions using both 2D–2D and mixed-dimensional systems have shown anti-ambipolar behavior. Gate tunability in anti-ambipolar characteristics is obtained in special heterojunction geometries, such as self-aligned black phosphorus/MoS2 p–n heterojunctions. Although the device physics of anti-ambipolar characteristics has been investigated using finite-element or semi-classical

For the development of photonic integrated circuits, it is mandatory to implement light sources on a Si-on-insulator (SOI) platform. However, point defects in the Si matrix and, e.g., at the Si/SiO2 interface act as nonradiative recombination channels, drastically limiting the performance of Si-based light emitters. In this Letter, we study how these defects can be healed by applying an advanced hydrogenation

In this Letter, we demonstrate coupled double-quantum dot (DQD)-like transport in an ∼ 30 nm-wide controllably doped graphene nanoribbon (GNR). Controlled doping is introduced from hydrogen silsesquioxane by changing its electron exposure dose. The proximity effect, which brings in additional dose accumulation, is utilized to introduce two charge puddles with stronger p-doping at the two ends of the

Pairing two-dimensional semiconductors with ferroelectric films may allow for the development of hybrid electronic devices that would not only exhibit a combination of the functional properties of both material groups but would also reveal unusual characteristics emerging from coupling between these properties. Here, we report the observation of a considerable (up to 103 at 0.8 V read bias) polarization-mediated

The diffusion coefficient (D) of charge carriers in pentacene has been determined independently using current–voltage and capacitance–frequency characteristics of asymmetric metal/pentacene/metal structures. The values of D measured using these two methods are found to be in excellent agreement. D has been estimated using first principles calculations and compared with experimental values. The applicability

Quasi-2D perovskite semiconductors can be created by introducing organic interlayer cations into 3D perovskites and possess large binding energy, superior stability, high luminance efficiency, and tunable bandgap, holding promising applications in blue-light emitting devices. Compared with mixed halide perovskites, quasi-2D bromide perovskites emit blue light with high color stability. However, multiple-phases

We have obtained an excitation of longitudinal bulk acoustic waves in a diamond-based High overtone Bulk Acoustic Resonator (HBAR) at microwave and enhanced frequency bands as EHF up to 40 GHz. As an effective piezoelectric transducer, an aluminum-scandium nitride film is employed. The frequency response of acoustic overtones excited in the HBARs with a different aperture in the 1.0 up to 40 GHz range

Resistive Random Access Memories (ReRAMs) are promising future candidates for nonvolatile memory. The underlying mechanism involves resistive switching in high-k dielectric layers, and changes in resistance due to different mechanisms are caused by the evolution of defective structures triggered by electrical and thermal effects. For the memory purpose of the ReRAM, the electrical field can be used

Exposed to the nanosecond pulsed electric field (nsPEF), biological cells can be stretched in the direction parallel to the electric field direction. A multiphysics model to investigate electrodeformation of a spherical cell with double-layered plasma membrane accounting for both electroporation and dielectric relaxation of the membrane is proposed. Transmembrane potential, Maxwell stress tensor, total

An updated thermionic converter was established through the introduction of a graphene anode and an optical reflector, significantly decreasing the irreversible losses inside the device and enhancing the device performances. At 1940 K, the maximum efficiency and power output density of the converter reached 76.6 % and 95.1   W   c m − 2. The optimum performances of the proposed model were obviously

We present an analytical model for calculating the entropy at melt of monatomic liquids. The model is motivated by the concept of a rough potential energy surface. It offers a simple, physical explanation for Richard's melting rule and provides a material-dependent correction to Trouton's vaporization rule. Without employing any adjustable parameters, the model agrees closely with experimental entropy

Machine learning is a powerful tool in finding hidden data patterns for quantum information processing. Here, we introduce this method into the optical readout of electron-spin states in diamond via single-photon collection and demonstrate improved readout precision at room temperature. The traditional method of summing photon counts in a time gate loses all the timing information crudely. We find

We report depth-resolved photoluminescence measurements of nitrogen-vacancy (NV−) centers formed along the tracks of swift heavy ions (SHIs) in type Ib synthetic single crystal diamonds that had been doped with 100 ppm nitrogen during crystal growth. Analysis of the spectra shows that NV− centers are formed preferentially within regions where electronic stopping processes dominate and not at the end

We report the influence of static mechanical deformation on the zero-field spin splitting of silicon vacancies in silicon carbide at room temperature. We use AlN/6H-SiC heterostructures deformed by growth conditions and monitor the stress distribution as a function of distance from the heterointerface with spatially resolved confocal Raman spectroscopy. The zero-field spin splitting of the V1/V3 and

Magnetic particles (MPs), a group of engineered particles in the nanometer and microscale, are valuable tools for separation of chemical or biological substance in environmental research, for target delivery of antibodies or proteins in biomedical applications, and for quantification of cells or biomolecules in biological systems. Despite the estimation of the amount of magnetic nanoparticles that

An anisotropic unit cell based on glide symmetry is proposed for tailoring a metasurface that engineers an optically transformed Luneburg lens. Thanks to the optical transformation, the size of the lens is reduced by 25%. The proposed lens is ultrawideband, and it covers multi-octave frequency bands. The required constitutive materials are achieved in an air gap bounded by top and bottom glide-symmetric

In this work, a design for a mid-infrared quantum cascade laser frequency comb source that enhances the high frequency response and the comb characteristics of the device is presented. A state-of-the-art active region, grown on a heavily n-doped InP:Si substrate, was processed into a buried heterostructure with a microstrip-like line waveguide. As a result, the repetition rate frequency frep, around

Chiral edge modes in photonic topological insulators host great potential to realize slow-light waveguides with topological protection. Increasing the winding of the chiral edge mode around the Brillouin zone can lead to broadband topological slow light with ultra-low group velocity. However, this effect usually requires careful modifications on a relatively large area around the lattice edge. Here

Cesium lead halide perovskites have shown great potential applications in photoelectric devices because of their high quantum efficiency, good stability, and tunable bandgap. Herein, we prepared CsPbBr3 microwires with a high crystal quality, smooth surface, and rectangular cross section via the solution method. The as-prepared microwires presented a high quality whispering gallery mode lasing with

Phase gradient metasurfaces have revolutionized modern optical components by significantly reducing the path length of bulk optics while maintaining high performance. However, their geometric design makes dynamic modulation challenging, with devices facing a trade-off between the modulation range and efficiency. Here, we introduce Silicon-on-Lithium Niobate (LNO) high-Quality-factor (high-Q) metasurfaces

Efficient mid-infrared light output has been obtained by incorporating a W-superlattice into a cascaded mid-infrared LED structure and by thinning and roughening of the emission side of the structure. At cryogenic temperatures, a radiance of ∼13.4 W/cm2-sr is achieved. Compared to the best published InAs/GaSb mid-IR LED, the maximum radiance is improved by ∼2.0×, while the wallplug efficiency improvement

Supercontinuum generation is an extensively studied and arguably the most important and all-encompassing nonlinear phenomenon. Yet, we do not have a good control over all the signals generated in this process. Usually, a large part of an octave spanning spectrum has an orders of magnitude weaker signal than the peak to be useful for any application. In this work, we show strong signal generation within

We demonstrate a 1-kHz, single-shot, dynamic, and sensitive flame temperature measurement using hybrid femtosecond/picosecond vibrational coherent anti-Stokes Raman scattering. This benefits from a 7-cm−1, 240-μJ, and sideband-free picosecond pulse out of a broadband 35-fs pulse through a quasi-common-path second harmonic bandwidth compressor system. Measurements around optimal time delay exhibit superior

Recently, it has been shown that hot-electron photoemission in waveguide-integrated graphene can occur at peak optical power densities many orders of magnitude lower than multiphoton and strong field emission. In this work, we study how the deposition of low-work function lanthanum hexaboride nanoparticles can alter the behavior of hot-electron emission from graphene and thin gold waveguide-integrated

Photoreduction of graphene oxide (GO) holds great potential for developing graphene-based electrodes for high-performance supercapacitors (SCs). However, the insufficient micro-nanostructure on photoreduced GO (PRGO) restricts its electrochemical performance. Here, a hierarchically structured PRGO-based planar SC is reported by combining two-beam-laser-interference with the masking technique. The hierarchical

Acoustic orbital angular momentum (OAM) has emerged as a new multiplexing degree of freedom in acoustic communication and shows application prospect in particle manipulation. The separation and detection of acoustic vortices carrying different OAM are significant in OAM-based signal de-multiplexing. In this work, we theoretically proposed and experimentally demonstrated an OAM prism for efficient and

We have investigated the anomalous Hall effect (AHE) of a ferrimagnetic GdFeCo film with perpendicular magnetic anisotropy. In the vicinity of magnetization compensation temperature TM, the peak structure or triple loop of the Hall resistance loops is mainly caused by the opposite magnetic moments of the two sublattices of Gd and FeCo, and that can be explained by the mechanism of the two-channel AHE

According to the Equivalence Principle, any distribution of electromagnetic fields can be generated within a closed region by suitable electric and magnetic sources lying on its bounding surface. In electromagnetic theory, these sources have been used as fictitious analytical tools. However, this has changed in recent years with the development of “Huygens's metasurfaces,” which are subwavelength thin

We report a lightweight tunable acoustic metamaterial with deep subwavelength thickness (e.g., λ / 300) and strong load-bearing capability for underwater low-frequency and ultra-broadband acoustic perfect absorption. The metamaterial is constructed by introducing a rubber coating and an embedded metallic neck into a metallic hexagonal honeycomb Helmholtz resonator. Physically, the quasi-Helmholtz resonance

Effective governance of thermal conductivity and other properties is of significant interest for science, including the fields of thermal barrier coatings, thermoelectric materials, and limit alloys. In this study, we investigated the impact of entropy engineering on properties of fluorite RE3NbO7, and limit thermal conductivity and strengthened mechanical properties are achieved. The solution strengthening

We report the characteristics of heavily Si-doped GaN prepared by pulsed sputtering deposition (PSD) and its application as tunneling junction (TJ) contacts for nitride-based light-emitting diodes (LEDs). We determined that the use of PSD allows us to grow extremely heavily Si-doped wurtzite GaN epitaxial layers with [Si] = 1.0 × 1021 cm−3 on commercially available UV-A LED wafers. Then, we processed

AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MISHEMTs) were fabricated on Si substrates with a 10 nm boron nitride (BN) layer as a gate dielectric deposited by electron cyclotron resonance microwave plasma chemical vapor deposition. The material characterization of the BN/GaN interface was investigated by X-ray photoelectric spectroscopy (XPS) and UV photoelectron spectroscopy

The leakage current caused by the Si pileup at the regrowth interface of AlGaN/GaN high electron mobility transistors (HEMTs) is significantly suppressed by the semi-insulating Mg-doped GaN layer. Mg is unintentionally doped and can be originated from the graphite susceptor of metal organic vapor phase epitaxy. Before regrowth of the AlGaN/GaN heterostructure, the GaN template is treated with hydrochloric

We report a positron annihilation study using state-of-the-art experimental and theoretical methods in n-type and semi-insulating β - Ga 2 O 3. We utilize the recently discovered unusually strong Doppler broadening signal anisotropy of β - Ga 2 O 3 in orientation-dependent Doppler broadening measurements, complemented by temperature-dependent positron lifetime experiments and first principles calculations

By combining temperature-dependent resistivity and Hall effect measurements, we investigate donor state energy in Si-doped β-Ga2O3 films grown using metal-organic vapor phase epitaxy. High-magnetic field (H) Hall effect measurements (–90 kOe ≤ H ≤ +90 kOe) showed non-linear Hall resistance for T < 150 K, revealing two-band conduction. Further analyses revealed carrier freeze out characteristics in

Efficient p-type doping of III-nitride materials is notoriously difficult due to their large bandgaps, intrinsic n-type doping, and the large ionization energy of acceptors. Specifically, aluminum-containing nitrides such as AlN and AlGaN have demonstrated low p-type conductivity, which increases device resistances and reduces carrier injection in optoelectronic applications. Dilute-anion III-nitride