Search

Iron will undergo the BCC to HCP transformation under pressure, but the reverse process during the unloading path has not been fully revealed on the atomic scale. This work investigated the unloading dynamics of a HCP single crystal of iron, focusing on the microstructure evolution and related mechanical characteristics. For unloading along the normal direction of the ( 1 ¯ 2 1 ¯ 0) and (10 1 ¯ 0) planes, a mechanism for coupling between twinning and phase transformation was reported. The HCP to BCC transformation with the rod-like structure and twinning was revealed, which was well supported by previous experiments. For unloading along the normal direction of the (0001) plane, the HCP–FCC–BCC transition was observed. Significant shear stress was generated internally, leading to significant dislocations. There are multiple transition paths of the HCP to FCC phase, resulting in the formation of grain boundaries and ultimately leaving the polycrystalline structures. This process was accompanied by coupled development of dislocations, grain mergers, and phase transitions. As the unloading process gradually evolves into the stretching process, detwinning and reconstruction will occur for unloading along the normal direction of the ( 1 ¯ 2 1 ¯ 0) and (10 1 ¯ 0) planes, accompanied by grain rotation. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate a novel strategy to introduce Fe into a Bi 2 Se 3 system through growth of crystals with nominal composition (FeSe) x Bi 2 Se 3. For x < 0.04 , Fe is shown to act mostly as a non-magnetic impurity; it uniformly enters the lattice and monotonically increases the c -lattice parameter, electronic doping level, and Shubnikov–de Haas mobility. The most striking observation is the record high Hall mobility of 8600 cm 2 /V s at 4.2 K for the smallest FeSe content (x = 0.002) that further decreases with x. Elevated mobility is accompanied by a high residual resistance ratio and a rather moderate shift of Shubnikov–de Haas oscillations to a smaller field. These findings indicate that Fe admixture cures the point defects in Bi 2 Se 3 and, thus, opens an effective way to suppress the defect subsystem in Bi 2 Se 3 -based topological insulator materials. [ABSTRACT FROM AUTHOR]

The CsPbBr3 single crystal detector emerges as a highly promising candidate among semiconductor nuclear radiation detectors, which exhibits an extensive potential application across a multitude of critical domains, particularly in nuclear physics, nuclear energy, nuclear medicine, etc. However, the polarization problem has limited the application and development of CsPbBr3 detectors and has even posed a significant hindrance to their practical implementation. In this paper, a pre-designed SnO2/CsPbBr3 hetero-junction was meticulously engineered at the interface of the Ti/CsPbBr3/Ti detector, aiming to solve the polarization problem. This paper investigates the effects of the SnO2/CsPbBr3 hetero-junction on the electrical characteristics, detection performance, and long-term stability of the detector. The final results demonstrated that the SnO2/CsPbBr3 hetero-junction had multiple beneficial effects on the CsPbBr3 detector. On the one hand, the SnO2/CsPbBr3 hetero-junction exhibited superior electron extraction efficiency when compared to the Ti/CsPbBr3 interface. On the other hand, the SnO2 layer played a crucial role in preventing the migration of ions from the CsPbBr3 crystal to the interface, as well as in blocking the permeation of atmospheric and moisture elements from the detector surface to the interface. Consequently, the SnO2/CsPbBr3 hetero-junction detector exhibited superior detection performance and enhanced long-stability when compared to the Ti/CsPbBr3/Ti detector. After the interface enhancement, the SnO2/CsPbBr3 hetero-junction detector achieved an improved energy resolution of 13.59% at an electric field of 6000 V/cm and maintained a stable energy resolution of approximately 24 ± 5% at 3000 V/cm for over 12 h. The study of the SnO2/CsPbBr3 hetero-junction detector in this work provided a new perspective for enhancing the detection performance and ensuring the long-term stability of CsPbBr3-based detectors. [ABSTRACT FROM AUTHOR]

Zinc single crystals have been shocked by planar impact along the [ 10 1 ¯ 0 ] axis as well as in the off-axis direction. The evolution of compression waves has been analyzed from the free surface velocity profiles of zinc single crystal samples. A slip on the primary system is activated by impact loading in directions making angles of θ = 17°–64° with respect to the [ 10 1 ¯ 0 ] axis. The phenomenon of the formation of two plastic compression waves propagating at different velocities is observed in samples oriented at angles of 53° and 64°. The spall fracture of single crystal zinc samples oriented in different directions has been measured. It is shown that the highest value of spall strength is recorded along the highly symmetric axis of the crystal. The experimental results presented are consistent with the data published in the scientific literature on beryllium and magnesium and confirm the important role of crystalline anisotropy in the process of inelastic deformation of single crystals. [ABSTRACT FROM AUTHOR]

In this work, the first fabrication and investigation of normally-off single crystal hydrogen-sterminated diamond MOSFETs with Ga2O3 dielectric has been successfully carried out. 50-nm-thick Ga2O3 was deposited by electron-beam evaporation technique at room temperature. The maximum drain current was −36 mA/mm, which was 164 times larger than previous work. Based on the transfer characteristic curve, the threshold voltage, on/off ratio and extrinsic transconductance were −0.37 V, 2.3 × 107, and 9.8 mS/mm, respectively. The effective mobility of the MOSFET was calculated to be 264.1 cm2/V ⋅s at VGS = − 1 V. This work may significantly promote the application of H-diamond FETs. [ABSTRACT FROM AUTHOR]

This study presents systematic investigations into the growth and physical properties of EuAl3Si single crystals, encompassing magnetic, transport, and thermodynamic analyses. EuAl3Si undergoes a ferromagnetic transition at TC = 15 K. A significant reversible magnetocaloric effect was observed around TC. Strikingly, with a small change of magnetic field 2 T, the maximum values of magnetic entropy change (13.4 J/kg K), refrigerant capacity (166 J/kg), and adiabatic temperature change (7.2 K) are found. These parameters, respectively, are 60%, 148%, and 64% larger than those of the parent compound EuAl4 and suggest EuAl3Si as an excellent candidate for magnetic-refrigeration applications near the temperature of liquid hydrogen. The possible mechanism for this enhancement is also discussed. [ABSTRACT FROM AUTHOR]

In this work, the first fabrication and investigation of normally-off single crystal hydrogen-sterminated diamond MOSFETs with Ga2O3 dielectric has been successfully carried out. 50-nm-thick Ga2O3 was deposited by electron-beam evaporation technique at room temperature. The maximum drain current was −36 mA/mm, which was 164 times larger than previous work. Based on the transfer characteristic curve, the threshold voltage, on/off ratio and extrinsic transconductance were −0.37 V, 2.3 × 107, and 9.8 mS/mm, respectively. The effective mobility of the MOSFET was calculated to be 264.1 cm2/V ⋅s at VGS = − 1 V. This work may significantly promote the application of H-diamond FETs. [ABSTRACT FROM AUTHOR]

The search for and fabrication of materials for the near-infrared range of the spectrum, including telecommunication windows, is an extremely important task in modern technology. This work presents the results of studies on the photoluminescence of CsPbCl3 single crystals with varying contents of ytterbium and erbium impurities, grown using the Bridgman method. The existence of electrically neutral Yb3+–VPb–Er3+ complexes within the crystal structure was confirmed. Resonant absorption of excitation radiation λ = 980 nm by Yb3+ ions reveals a three-step energy transfer channel from Yb3+ to Er3+ ions within a single complex. The estimated quantum yield of up-conversion luminescence at λ = 524 nm (0.02%) associated with erbium ions indicates the presence of electronic transitions to higher energy levels, with the possibility of subsequent emission within the third telecommunication window. [ABSTRACT FROM AUTHOR]

High-performance relaxor ferroelectric single crystals, such as Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT), play a crucial role in the applications of medical ultrasonic imaging due to their high piezoelectric properties. In this study, we successfully grew a 2-in. Eu-doped PMN–PT single crystal whose composition variation and electrical properties were systematically investigated. It was found that the PT content of the crystal boule increased gradually along the growth direction, while the change of Eu3+ content was opposite. The property results show that Eu-doped PMN–PT single crystals exhibit a remarkable piezoelectric coefficient of 3300 pC N−1 at DC-poling while maintaining the rhombohedral phase to a tetragonal phase transition temperature (TRT) at 88 °C and the coercive field (EC) at 2.7 kV cm−1, higher to the undoped single crystals. Through the study of the local structure of Eu-PMN–PT, it illustrated that the introduction of Eu3+ increased the standard deviation of an A sublattice from 3.0% to 4.8%. The dopant simultaneously enhanced a tetragonal phase ratio and local structural heterogeneity, resulting in improved piezoelectric properties and temperature stability of the crystal. We further treated the doped crystals with AC-poling to obtain ultrahigh piezoelectric performance (d33 > 4000 pC N−1) and high transparency. This work provides a new approach to achieve a relaxor ferroelectric single crystal with high performance and transparency with good temperature stability, which could be the material of choice for optoelectronic devices in the future. [ABSTRACT FROM AUTHOR]

Metallic nanolaminates are promising materials for nuclear applications due to their ability to withstand extreme radiation environments by trapping irradiation-induced defects. However, the effects of irradiation-induced voids on confined layer slips (CLS) in nanolaminates remain largely unexplored. In this study, molecular dynamics simulations are employed to investigate how void size and location impact CLS in two types of Ag/Cu nanolaminates. Nanolaminated Ag and Ag single crystals are also studied as references. The results show that voids act as obstacles, significantly increasing the critical stress for dislocation glide. The void location plays a role in the critical stress but in different ways for different slip planes. The void-induced hardening is stronger on planes with lower intrinsic critical stress; as a result, adding a void homogenizes the resistance to CLS across different slip planes. Ag/Cu type II nanolaminates, where the two crystals have a "cube-on-cube" crystallographic orientation, demonstrate reduced void-induced hardening compared to type I, where two adjacent layers possess differing crystallographic orientations. In addition, some void-containing nanolaminated Ag show lower critical stress than their single-crystal line counterparts. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) and strontium titanate (SrTiO3) are widely used photocatalytic materials in photoelectrochemical (PEC) water-splitting processes. Recent advancements have aimed at improving energy conversion efficiency by loading cobalt oxide (CoOx) cocatalysts onto these materials' surfaces to enhance O2 evolution and capture photogenerated holes. Charge carrier recombination plays a crucial role in PEC reactions. This investigation explores the impact of CoOx loading on various crystal faces on the charge carrier recombination dynamics in TiO2 and SrTiO3 single crystals using the microwave photoconductivity decay (μ-PCD) technique. The results indicate that CoOx loading increases the charge carrier recombination for both TiO2 and SrTiO3 across all crystal faces, as observed from the decay curves. Additionally, different tendencies of the injected photon density and temperature dependence of the carrier lifetime, derived from μ-PCD curves, reveal that CoOx loading on TiO2 surfaces introduces the new surface recombination center that dominates the charge carrier recombination. In contrast, for SrTiO3, the surface recombination center remains unchanged across all crystal faces. Consequently, these findings suggest that while CoOx loading on SrTiO3 surfaces does not affect the charge carrier dynamics and remains effective for water splitting, it poses a risk of enhancing carrier recombination and reducing efficiency in TiO2. [ABSTRACT FROM AUTHOR]