Growth of Single Crystals of (KNa)NbO by the Self-Flux Method and Characterization of Their Phase Transitions.

In this study, single crystals of (KNa)NbO are grown by the self-flux crystal growth method and their phase transitions are studied using a combination of Raman scattering and impedance spectroscopy. X-ray diffraction shows that single crystals have a perovskite structure with monoclinic symmetry. Single crystal X-ray diffraction shows that single crystals have monoclinic symmetry at room temperature with space group P121.

Atomistic Simulation of HF Etching Process of Amorphous SiN Using Machine Learning Potential.

An atomistic understanding of dry-etching processes with reactive molecules is crucial for achieving geometric integrity in highly scaled semiconductor devices. Molecular dynamics (MD) simulations are instrumental, but the lack of reliable force fields hinders the widespread use of MD in etching simulations. In this work, we develop an accurate neural network potential (NNP) for simulating the etching process of amorphous SiN with HF molecules.

The Effect of Cesium Incorporation on the Vibrational and Elastic Properties of Methylammonium Lead Chloride Perovskite Single Crystals.

Hybrid organic-inorganic lead halide perovskites (LHPs) have emerged as a highly significant class of materials due to their tunable and adaptable properties, which make them suitable for a wide range of applications. One of the strategies for tuning and optimizing LHP-based devices is the substitution of cations and/or anions in LHPs. The impact of Cs substitution at the A site on the structural, vibrational, and elastic properties of MACsPbCl-mixed single crystals was investigated using X-ray diffraction (XRD) and Raman and Brillouin light scattering techniques.

Color Rendering Index over 95 Achieved by Using Light Recycling Process Based on Hybrid Remote-Type Red Quantum-Dot Components Applied to Conventional LED Lighting Devices.

Red color conversion materials have often been used in conventional white LEDs (light-emitting diodes) to enhance the insufficient deep-red component and thus improve the color-rendering property. Quantum dots (QDs) are one of the candidates for this due to their flexibility in controlling the emission wavelength, which is attributed to the quantum confinement effect. Two types of remote QD components, i.

Influence of Halides on Elastic and Vibrational Properties of Mixed-Halide Perovskite Systems Studied by Brillouin and Raman Scattering.

The relationship between halogen content and the elastic/vibrational properties of MAPbBrCl mixed crystals ( = 1.5, 2, 2.5, and 3) with MA = CHNH has been studied using Brillouin and Raman spectroscopy at room temperature.

Quasielastic Light Scattering in the Broadband Brillouin Spectra of Relaxor Ferroelectric PbMgNbO.

In this paper, the behavior of quasielastic light scattering (QELS) in a PbMgNbO (PMN) crystal under broadband Brillouin light scattering in a temperature range from 750 K to 80 K was studied. It was shown that QELS consists of two components: narrow (0.9 GHz to 11 GHz) and wide (80 GHz to 600 GHz).

Structural Phase Transitions and Thermal Degradation Process of MAPbCl Single Crystals Studied by Raman and Brillouin Scattering.

Raman spectroscopy was applied to MAPbCl single crystals in a wide frequency range from 10 to 3500 cm over a broad temperature range from -196 °C to 200 °C including both two structural phase transitions and a thermal degradation range. Low-frequency lattice modes of MAPbCl were revealed for the first time, which showed discontinuous anomalies along with the change in the number of Raman modes at the transition points of -114 °C and -110 °C. Several Raman modes related to the C-N stretching and MA rocking modes in addition to the lattice modes displayed temperature dependences similar to those of MAPbBr in both Raman shifts and half widths, indicating that the MA cation arrangement and H-halide bond interactions behave similarly in both systems during the phase transition.

Reversibly Controlled Ternary Polar States and Ferroelectric Bias Promoted by Boosting Square-Tensile-Strain.

Interaction between dipoles often emerges intriguing physical phenomena, such as exchange bias in the magnetic heterostructures and magnetoelectric effect in multiferroics, which lead to advances in multifunctional heterostructures. However, the defect-dipole tends to be considered the undesired to deteriorate the electronic functionality. Here, deterministic switching between the ferroelectric and the pinched states by exploiting a new substrate of cubic perovskite, BaZrO is reported, which boosts the square-tensile-strain to BaTiO and promotes four-variants in-plane spontaneous polarization with oxygen vacancy creation.

Structural Optimization of Vertically-Stacked White LEDs with a Yellow Phosphor Plate and a Red Quantum-Dot Film.

A remote-type white light-emitting diode (LED) consisting of a red quantum-dot (QD) film and a yellow phosphor plate was studied by both experiment and optical simulation. The sequence of the two color-conversion films had a substantial effect on the color-rendering properties of the vertically-stacked white LED, and the optimized configuration exhibited a high color rendering index of more than 90 thanks to the enhanced red component via the QD film. For the design of high-power white LED devices of a remote type, it was necessary to locate the color-conversion films below the diffuser plate to remove the substantial color dispersion depending on the viewing angle.

Long-Term Isothermal Phase Transformation in Lead Zirconate.

Lead zirconate PbZrO has been the subject of research interest for several dozen years. Recently, even its antiferroelectric properties have started to be questioned, and many researchers still deal with the so-called intermediate phase below Curie temperature (T), whose existence is not fully understood. It turns out that PbZrO doped with Nb exhibits below T phases with complex domain structures.

Acoustic Anomalies and the Critical Slowing-Down Behavior of MAPbCl Single Crystals Studied by Brillouin Light Scattering.

Inelastic light scattering spectra of organic-inorganic halide perovskite MAPbCl single crystals were investigated by using Brillouin spectroscopy. Sound velocities and acoustic absorption coefficients of longitudinal and transverse acoustic modes propagating along the cubic [100] direction were determined in a wide temperature range. The sound velocities exhibited softening upon cooling in the cubic phase, which was accompanied by the increasing acoustic damping.

Substantial Improvement of Color-Rendering Properties of Conventional White LEDs Using Remote-Type Red Quantum-Dot Caps.

A new type of remote red quantum-dot (QD) component was designed and fabricated to improve the color-rendering properties of conventional white LED (light-emitting diode) lightings. Based on an optical simulation, the rectangular cavity-type QD cap was designed with an opening window on the top surface. Red QD caps were fabricated using a typical injection molding technique and CdSe/ZnS QDs with a core/shell structure whose average size was ~6 nm.

Elastic Properties of Taurine Single Crystals Studied by Brillouin Spectroscopy.

The inelastic interaction between the incident photons and acoustic phonons in the taurine single crystal was investigated by using Brillouin spectroscopy. Three acoustic phonons propagating along the crystallographic -axis were investigated over a temperature range of -185 to 175 °C. The temperature dependences of the sound velocity, the acoustic absorption coefficient, and the elastic constants were determined for the first time.

Formation kinetics of SrBaNbO and LiBO crystals from 0.25SrO-0.75BaO-NbO-LiO-2BO glass.

We have investigated the transition kinetics of SrBaNbO (SBN) and LiBO (LBO) crystals from 0.25SrO-0.75BaO-NbO-LiO-2BO (SBNLBO) glass under isothermal and non-isothermal processes.

Precursor Phenomena of Barium Titanate Single Crystals Grown Using a Solid-State Single Crystal Growth Method Studied with Inelastic Brillouin Light Scattering and Birefringence Measurements.

The nature of precursor phenomena in the paraelectric phase of ferroelectrics is one of the main questions to be resolved from a fundamental point of view. Barium titanate (BaTiO₃) is one of the most representative perovskite-structured ferroelectrics intensively studied until now. The pretransitional behavior of BaTiO₃ single crystal grown using a solid-state crystal growth (SSCG) method was investigated for the first time and compared to previous results.

Finite-Difference Time-Domain Simulation of Fractal-Like Microlens Arrays for High Outcoupling Efficiency of Organic Light-Emitting Diodes.

The outcoupling efficiencies (OCEs) of organic light-emitting diodes (OLEDs) were studied for a fractal-like two-dimensional structure consisting of three layers of semicircular microlens on a glass substrate using a finite-difference time-domain (FDTD) method. The OCE with only one semicircular microlens layer was 29.5%, 1.

Acoustic Anomalies and Phase Transition Behaviors of Lead-Free Piezoelectric (NaBi)TiO₃-BaTiO₃ Single Crystals as Revealed by Brillouin Light Scattering.

The elastic properties of unpoled and prepoled (NaBi)TiO₃-BaTiO₃ (NBT-BT) single crystals near the morphotropic phase boundary were investigated as a function of temperature using Brillouin light scattering. The acoustic mode frequency and the related acoustic damping of unpoled NBT-BT showed very broad minimum and maximum, respectively, consistent with typical relaxor behaviors. The frequency softening of the longitudinal acoustic mode together with the increase in acoustic damping was largest along the <100> direction, indicating that polarization fluctuations were most substantial along this crystallographic direction.

Highly Ordered Microscale-Pyramidal-Structure-Arrayed Silicon Membranes for Filter Applications.

Microscale-pyramidal-structure-arrayed patterned silicon membranes are manufactured using semiconductor processes and potassium hydroxide (KOH) etching techniques for filter applications. The silicon nitride on silicon on the insulator wafer functions as a masking layer, and the roughness of the silicon (100) plane strongly depends on the etching temperature and KOH concentration. To fabricate the membrane filter, a series of dry and wet etching using 45 wt% KOH solutions at the constant temperature of 70 °C was performed.

Hole Mobility Characteristics with Surface Roughness on Silicon-on-Insulator Substrate.

Hole mobility characteristics were investigated with surface roughness and silicon-on-insulator (SOI) thickness variations to investigate the influence of surface roughness to mobility. The root mean square roughness varied between 0.16, 0.

>1000-Fold Lifetime Extension of a Nickel Electromechanical Contact Device via Graphene.

Micro-/nano-electromechanical (M/NEM) switches have received significant attention as promising switching devices for a wide range of applications such as computing, radio frequency communication, and power gating devices. However, M/NEM switches still suffer from unacceptably low reliability because of irreversible degradation at the contacting interfaces, hindering adoption in practical applications and further development. Here, we evaluate and verify graphene as a contact material for reliability-enhanced M/NEM switching devices.

Acoustic Anomalies and Fast Relaxation Dynamics of Amorphous Progesterone as Revealed by Brillouin Light Scattering.

The amorphous state of pharmaceuticals has attracted much attention due to its high bioavailability and other advantages. The stability of the amorphous state in relation with the local molecular mobility is important from both fundamental and practical points of view. The acoustic properties of amorphous progesterone, one of the representative steroid hormones, were investigated by using a Brillouin inelastic light scattering technique.

Author Correction: Two-magnon scattering in the 5d all-in-all-out pyrochlore magnet CdOsO.

A correction to this article has been published and is linked from the HTML version of this article.

The Effect of Thickness and Chemical Reduction of Graphene Oxide on Nanoscale Friction.

The tribological properties of two-dimensional (2D) atomic layers are quite different from three-dimensional continuum materials because of the unique mechanical responses of 2D layers. It is known that friction on graphene shows a remarkable decreasing behavior as the number of layers increases, which is caused by the puckering effect. On other graphene derivatives, such as graphene oxide (GO) or reduced graphene oxide (rGO), the thickness dependence of friction is important because of the possibilities for technical applications.

Two-magnon scattering in the 5d all-in-all-out pyrochlore magnet CdOsO.

5d pyrochlore oxides with all-in-all-out magnetic order are prime candidates for realizing strongly correlated, topological phases of matter. Despite significant effort, a full understanding of all-in-all-out magnetism remains elusive as the associated magnetic excitations have proven difficult to access with conventional techniques. Here we report a Raman spectroscopy study of spin dynamics in the all-in-all-out magnetic state of the 5d pyrochlore CdOsO.