In a heterogeneous system, ferroelectric materials can exhibit negative capacitance (NC) behavior given that the overall capacitance of the system remains positive. Such NC effects may lead to differential amplification in local potential and can provide an enhanced charge and capacitance response for the whole system compared to their constituents. Such intriguing implications of NC phenomena have

Polar domain walls are currently at the focus of intensive research owing to their unusual and highly localized functional properties, which bear great potential for technological applications. They can present unusual topological features, like swirling polar structures or defect lines. The prediction of possible non-Ising and chiral internal structures of polar domain walls has been a particularly

The combination of organics and metals in a composite film holds promise for combining plasmonic interaction with gain and for the realization of epsilon-near-zero (ENZ) metamaterials. In particular, fluorescent organic dyes can be used to compensate the plasmonic losses of a homogenized metal-organic material. Here, we fabricate such films through thermal co-evaporation of silver and an organic host:guest

A tunable Pr3+:LiYF4 laser using a single birefringent filter (BF) plate under excitation with a frequency doubled optically pumped semiconductor laser was demonstrated to operate at nine different laser wavelengths of 523, 546, 604, 613, 639, 645, 670, 698, and 720 nm. Within these wavelengths, several new wavelengths of 613, 639, 645, and 670 nm were obtained. The total tuning range exceeded 190 nm

At optical frequencies, we design an anisotropic metasurface to realize high-Q perfect absorption in numerical calculation. By establishing the Norton equivalent network model, we first reveal that the root cause of this phenomenon is the coupling excitation of the localized surface plasmon (LSP) mode and the surface plasmon polariton (SPP) mode. This absorber can realize bifunctional switching and

Despite the very different underlying physics of organic photovoltaics (OPVs), inorganic p-n junction’s Shockley’s diode equation is often applied to describe current density–voltage (JV) curves of OPVs. The model parameters, including the diode saturation current, diode ideality factor, series, and parallel resistances, are usually extracted and treated as constants in JV curve analyses. In this work

Scattering-type scanning near-field optical microscopy (s-SNOM) has been widely used to characterize strongly correlated electronic, two dimensional, and plasmonic materials, and it has enormous potential for biological applications. Many of these materials exhibit anisotropic responses that complicate the extraction of dielectric constants from s-SNOM measurements. Here, we generalize our recently

Multi-photon absorption (MPA) and free-carrier (FC) effects, usually considered to be detrimental to microcomb generation by introducing strong nonlinear loss, also offer opportunities to overwhelm the thermal-optic effect by modifying the refractive index. Here, we derive the theoretical expression of solitons expanded with MPA and FC effects, accompanied by numerical simulations to reveal the dynamics

We report results from a study on electrical breakdown in liquid helium using near-uniform-field stainless steel electrodes with a stressed area of ∼ 0.7 cm 2. The distribution of the breakdown field is obtained for temperatures between 1.7 K and 4.0 K, pressures between the saturated vapor pressure and 626 Torr, and with electrodes of different surface polishes. A data-based approach for determining

A retarding potential analyzer was used to characterize the energy distribution of the plume particles from an electrospray source. The electrospray device uses an ionic liquid, operates at bipolar and relatively high voltages from ± 1800 to ± 3500 V, and demonstrated ionic emissions with a relatively high emission density of more than ± 30 μ A per emission tip. Electrostatic simulations were used

The reactions at a plasma–liquid interface often involve species such as the solvated electron or the hydroxyl radical, which initiate the reduction or oxidation of solution-phase reactants (so-called scavengers) or are consumed by their own second-order recombination. Here, the mathematical scaling of the reaction–diffusion equations at the interface is used to obtain a characteristic time that can

One goal that many scientists pursue is the unification of several interesting chemical or physical properties in one system, as only multifunctional materials will meet the challenges of today's technologies. With this background, three novel iron(II) coordination compounds with a Schiff base-like N2O2 coordinating ligand L bearing a sulfur-rich backbone are investigated in this work. Two of the complexes

Magnetism breaks the time-reversal symmetry expected to open a Dirac gap in 3D topological insulators that consequently leads to the quantum anomalous Hall effect. The most common approach of inducing a ferromagnetic state is by doping magnetic 3 d elements into the bulk of 3D topological insulators. In Cr 0.15 ( Bi 0.1 Sb 0.9 ) 1.85 Te 3, the material where the quantum anomalous Hall effect was initially

We have developed a new ultra-low field frequency-swept (FS) electrically detected magnetic resonance (EDMR) spectrometer to perform sensitive EDMR measurements of 4H-silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors at sub-millitesla (mT) magnetic fields. The new spectrometer design enables the detection of so-called ultra-strong coupling effects such as multiple-photon transitions

We studied the broadband characteristics of photon–magnon coupling (PMC) between a yuttrium iron garnet (YIG) film and arrays of inverted split-ring resonators (ISRRs). To achieve photon–magnon interaction available in a wide frequency range, we optimized the geometries and dimensions of single ISRRs and their array structure by numerical simulations in order to manipulate the resonance frequencies

A single crystal of Fe (0.3%)-doped BaTiO3 was grown by a top-seeded solution growth method, and the photovoltaic (PV) properties (at 3.1 eV) in a multi-domain state with a 90° domain structure are investigated. We show that the overall behavior can be well understood by an analytical expression of the domain wall (DW)-PV effect superimposed on the bulk-PV effect. The fitting of photocurrents as a

A first-principles study of native point defects in monoclinic, cubic, two different tetragonal, and five different orthorhombic phases of hafnia (HfO2) is presented. They include vacancy of tri-coordinated and tetra-coordinated oxygen, metal vacancy, interstitial metal, and interstitial oxygen. Defect formation energy, trap depth, and relaxation energy upon optical excitation of defects are listed

Bismuth sodium titanate and related compounds are promising lead-free ferroelectric materials potentially useful in a wide range of piezoelectric applications. The domain structure plays an important role in determining the piezoelectric and ferroelectric properties and thereby the performance of electromechanical transducers. In this work, piezoresponse force microscopy (PFM) is used to gain insights

Flexoelectricity in twinned ferroelastic thin films generates polarity inside twin walls. The electrical dipoles are typically aligned parallel to twin walls while out-of-plane dipoles are induced elastically by an atomic force microscopy (AFM) tip or by atomic steps in the substrate. Molecular dynamics modeling shows that the out-of-plane dipoles form polar vortex structures next to the domain walls

We report the band structure of Ba-deficient BaTiO3 as a p-type semiconductor, studied by a combination of light reflectance and photoelectron yield spectroscopy. Two acceptor levels were observed at the tail of a valence band. As the quantity of Ba vacancies increased, the density of state of the two acceptor levels also increased. The levels of the conduction band minimum and the valence band maximum

The bulk photovoltaic (PV) effect exhibited by non-centrosymmetric systems gained research interest due to the observed large open-circuit voltage. Ferroelectric systems exhibiting anomalous photovoltaic effects are mostly crystallized with multi-phase coexistence. Hence, the computational difficulty in building a multi-phase system restricts the detailed photovoltaic studies through phenomenological

We present the numerical tool DeCANT (Diffusion of Excitons in Carbon Nanotubes) that simulates exciton transport in thin films of carbon nanotubes. Through a mesh of nanotubes generated using the Bullet Physics C++ library, excitons move according to an ensemble Monte Carlo algorithm, with the scattering rates that account for tube chirality, orientation, and distance. We calculate the diffusion tensor

Ionizing radiation has the potential to cause operational disruptions and destroy microelectronic devices. This paper introduces and demonstrates a method of hardening microelectronic devices for sustained use in applications where exposure to ionizing radiation exists. By incorporating quantum structures below active regions of devices, gettering of charges created by ionizing radiation becomes possible

The factors limiting channel mobility in AlSiO/p-type GaN-based metal-oxide-semiconductor field-effect transistors (MOSFETs) were systematically investigated. MOSFETs with various thin interfacial layers (ILs) between Al0.78Si0.22Oy films and Mg-doped GaN layers were prepared and found to exhibit different channel mobilities. The maximum effective mobility showed a significant correlation with the

We present a computational study that demonstrates the concept of a microwave excited plasma flow sensor. The geometric configuration consists of an array of circularly arranged “receiver” (ground) electrodes that surround a central “transmitter” (excited) electrode that is flush mounted on a surface exposed to incident flow. Microwave excitation is used to strike a low-temperature plasma between the

The sign of quantum interference (constructive or destructive) based on cavity optomechanics is crucial for observing quantum phenomena and designing high-sensitivity sensors with an integrable structure. Here, we propose an efficient scheme to generate constructive interference and optomechanically induced absorption (OMIA) in a hybrid atom–cavity optomechanical system. Using experimentally achievable

The ability to tune the performance of acoustic metamaterials without structural modifications or complex active control circuits is a remarkable challenge. In this work, we present a square piezoelectric side-branch (PSB) pipe-type structure that consists of the piezoelectric composite sheets (PCSs) on its sidewall and propose the corresponding equivalent electroacoustic circuit model. Compared with

Plasma-activated water (PAW) is gaining significant attention these days due to its potential use as a disinfectant, pesticide, food preservative, cancer cell treatment, fertilizer, etc. These applications of PAW depend on its reactivity (oxidizing-potential) and electrical conductivity (EC). In the present work, we have studied the effect of process parameters, viz., air flow rate, water stirrer speed

Lentil seeds have been packed in a dielectric barrier device and exposed for several minutes to a cold atmospheric plasma generated in helium with/without a reactive gas (nitrogen or oxygen). While no impact is evidenced on germination rates (caping nearly at 100% with/without plasma exposure), seeds’ vigor is clearly improved with a median germination time decreasing from 1850 min (31 h) to 1500 min

We introduce a model system composed of elastically coupled one-dimensional chains of elastic rotators. The chains of rotators are analogous to elastic Su-Schrieffer–Heeger models. The coupled chain system is shown analytically and numerically to support an unusual number of topological properties such as Dirac degeneracies, band inversion and topological transition as a function of the strength of

We present a combined experimental and numerical investigation of phonon transport in multiphase nanostructured silicon. The sample was synthesized by high-pressure torsion with a nominal pressure of 24 GPa. Based on the x-ray diffraction measurement, we have identified the existence of three phases of silicon in the sample: Si-I, Si-III, and Si-XII, with volume fractions of 66%, 25%, and 9% and average

Tuning thermal transport in semiconductor nanostructures is of great significance for thermal management in information and power electronics. With excellent transport properties, such as ballistic transport, immunity to point defects and disorders, and forbidden backscattering, topological phonon surface states show remarkable potential in addressing this issue. Herein, topological phonon analyses

Bi 2 Se 3, a layered three-dimensional (3D) material, exhibits topological insulating properties due to the presence of surface states and a bandgap of 0.3 eV in the bulk. We study the effect of hydrostatic pressure P and doping with rare earth elements on the topological aspect of this material in bulk from a first principles perspective. Our study shows that under a moderate pressure of P > 7.9 GPa

This work determines the phase stabilities and point defect energetics of TiSi2 and TiGe2 allotropes using density functional theory. The primary focus is on the C49 and C54 allotropes, which compete during TiSi2 phase formation. It is found that the ground state structure for TiGe2 is the C54 allotrope, desirable for its low sheet resistance, while the less desirable, higher resistance C49 allotrope

We propose a model for the thermal conductivity of 2D-samples when the mean free paths due to the phonon–phonon interactions exceed the sample dimensions. The physical mechanisms that ensure the stationary heat flux and the stationary nonequilibrium temperature distribution are examined. A recursive equation is derived to quantify the contribution of phonon scattering to the net heat flux in the pure

Spin-transition materials, including the families of spin-crossover and charge-transfer systems, and more generally molecular-based materials exhibiting electronic and/or structural bistability, may undergo various types of phase transitions. The change of electronic state is stabilized by molecular reorganizations and both phenomena, which are usually non-symmetry breaking, can be described through

SrxBi2Se3 is a candidate topological superconductor, but its superconductivity requires the intercalation of Sr into the van der Waals gaps of Bi2Se3. We report the synthesis of SrxBi2Se3 thin films by molecular beam epitaxy, and we characterize their structural, vibrational, and electrical properties. X-ray diffraction and Raman spectroscopy show evidence of substitutional Sr alloying into the structure

Pressure and temperature dependences of the unit cell volumes of Y2O3’s three polymorphs (cubic, monoclinic, and hexagonal) have been measured by synchrotron energy dispersive x-ray diffraction in conjunction with a cubic anvil technique to pressures and temperatures up to 7.5 GPa and 1073 K, respectively. The measured pressure–volume–temperature (P–V–T) data were used to obtain thermoelastic parameters

When a metallic specimen is plastically deformed, its underlying crystal structure must often rotate in order to comply with its macroscopic boundary conditions. There is growing interest within the dynamic-compression community in exploiting x-ray diffraction measurements of lattice rotation to infer which combinations of plasticity mechanisms are operative in uniaxially shock- or ramp-compressed

Anisotropic ɛ-near-zero effective medium multilayer structures for omnidirectional bending light to the normal are theoretically studied. A finite element method is presented, using a unit cell with Floquet port master and slave boundaries, for examining metal–dielectric multilayer structures to form the permittivity tensor. Ellipsometry measurements of CdO films are reported, and it is found that

Trench-fin MOSFETs, with their near-surface heat generation and the higher-surface area afforded by their geometry for thermal management, represent a promising solution to the thermal problems frequently encountered in lateral β-Ga2O3 devices. Here, we investigate potential thermal-management strategies for a vertical β-Ga2O3 trench-fin MOSFET through parametric analysis, offering recommendations

Some mechanisms of creep, especially those involving dislocations for many crystalline materials, can be verified by direct microstructural examination. However, metallic glass thin films (MGTFs) are disordered materials lacking the long-range order of crystals. Even today, the creep mechanisms for amorphous alloys are far from being fully understood. The physical factors governing localization and

In this work, we report on three new extremely sharp emission lines in zinc oxide (ZnO) related to iron–lithium complexes. The identification is based on a comparison of hydrothermally grown ZnO with high lithium concentration and a lithium-free sample grown by methane based chemical vapor deposition, which both were implanted with iron. After annealing in a mixed oxygen/argon atmosphere at 800 ° C

Electron paramagnetic resonance (EPR) is used to monitor photoinduced changes in the charge states of sulfur vacancies and Cu ions in tin hypothiodiphosphate. A Sn2P2S6 crystal containing Cu+ (3d10) ions at Sn2+ sites was grown by the chemical vapor transport method. Doubly ionized sulfur vacancies ( V S 2 +) are also present in the as-grown crystal (where they serve as charge compensators for the

Fe acts as an electron trap in gallium oxide (Ga2O3), thereby producing a semi-insulating material that can be used in device fabrication. However, such trapping can lead to negative effects when Fe is unintentionally incorporated into bulk crystals or thin films. In this work, photoinduced electron paramagnetic resonance (photo-EPR) is used to investigate carrier capture at Fe in β-Ga2O3. Two crystals

Ultrafast experiments using sub-picosecond pulses of light are poised to play an important role in the study and use of topological materials and, particularly, of the three-dimensional Dirac and Weyl semimetals. Many of these materials’ characteristic properties—their linear band dispersion, Berry curvature, near-vanishing density of states at the Fermi energy, and sensitivity to crystalline and time-reversal

Polymer gels are unique materials, which consist of a polymer network swollen in a solvent. The modulus and the overall state of the gel depend on thermodynamic parameters, such as strand length, structure, and chemical compatibility of the solvent. Scattering techniques have been used to study the gel structure and osmotic pressure and are discussed in this Tutorial pedagogically. These techniques

X-ray phase-contrast microtomography based on speckle tracking is an attractive method for non-destructive three-dimensional imaging owing to its simple setup and ability to yield absorption, refractive, and scattering images simultaneously. However, the edge-enhancement effect usually results in image artifacts or inaccurate phase retrieval, limiting the extensive application of this method in biomedical

We report an effective antireflective surface structure fabricated by a sequential process comprising colloidal lithography, maskless plasma etching, and inverted nanoimprinting replication. The hierarchical inverse micro–nano structure is composed of randomly positioned microholes of 3–5 μm in diameter and numerous nanoprotrusions of 60–80 nm diameter located at the bottom surface of the microholes

We present experimental and theoretical results of the molecular sensing performance of a novel platform based on magnetic modulation of surface-enhanced infrared absorption spectroscopy. For this, we study the effect that molecular infrared vibrations of a PMMA layer have on the optical and magneto-refractive response of spintronic antennas. Specifically, a periodic array of rods is fabricated from

Carrier localization effects in III-N heterostructures are often studied in the frame of modified continuum-based models utilizing a single-band effective mass approximation. However, there exists no comparison between the results of a modified continuum model and atomistic calculations on the same underlying disordered energy landscape. We present a theoretical framework that establishes a connection

Wire X-pinches (WXPs) have been studied comprehensively as fast ( ∼ 1 ns pulse width), small ( ∼ 1  μm) x-ray sources, created by twisting two or more fine wires into an “X” to produce a localized region of extreme magnetic pressure at the cross-point. Recently, two alternatives to the traditional WXP have arisen: the hybrid X-pinch (HXP), composed of two conical electrodes bridged by a thin wire or

Helium is frequently used as a working medium for the generation of plasmas and is capable of energetic photon emissions. These energetic photon emissions are often attributed to the formation of helium excimer and subsequent photon emission. When the plasma device is exposed to another gas, such as nitrogen, this energetic photon emission can cause photoionization and further ionization wave penetration

Fully coupled randomly disordered recurrent superconducting networks with additional open-ended channels for inputs and outputs are considered the basis to introduce a new architecture to neuromorphic computing in this work. Various building blocks of such a network are designed around disordered array synaptic networks using superconducting devices and circuits as an example, while emphasizing that

We report the dielectric properties of improper ferroelectric hexagonal (h-)ErMnO3. From the bulk characterization, we observe a temperature and frequency range with two distinct relaxation-like features, leading to high and even “colossal” values for the dielectric permittivity. One feature trivially originates from the formation of a Schottky barrier at the electrode–sample interface, whereas the

We have investigated the role of pseudospin polarization in electron wave packet dynamics in pristine graphene and in a graphene antidot lattice subject to an external magnetic field. By employing Green’s function formalism, we show that the electron dynamics can be controlled by tuning pseudospin polarization. We find that in Landau quantized pristine graphene, both the propagation of an electron

Experimental realization of a new class of active Nonreciprocal Gyroscopic Meta-Material (NGMM) is presented. The proposed active NGMM system consists of a one-dimensional acoustic cavity provided with piezoelectric boundaries that act as sensors and actuators. These active boundaries are integrated with linear dynamic control capabilities that virtually synthesize a gyroscopic control action in order

Characterization of a newly developed class of passive nonreciprocal acoustic metamaterials is presented in an attempt to quantify their ability of controlling the flow and distribution of acoustic energy in acoustic cavities and systems. The proposed nonreciprocal acoustic metamaterial (NAMM) cell consists of a one-dimensional acoustic cavity provided with piezoelectric flexible boundaries connected

Owing to the additional usage of sub-bandgap photons, the intermediate-band solar cell has been regarded as a promising device design to exceed the conversion limits of conventional photovoltaic devices. An output-voltage preservation is theoretically possible in this kind of device in the case of independent quasi-Fermi levels. This phenomenon manifests experimentally in a voltage recovery induced

Valley pseudo-spin and its associated interface wave transport in sonic crystals has attracted increasing attention from researchers for the potential manipulation of acoustic waves. The topological interface state, projected from a specific valley, is valley-locked, and, thus, renders robust reflection immunity against defects. In this work, we report on the experimental observation of the different