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[en] Effect of resistive switching in gallium oxide structure was studied. It was shown, that gallium oxide structure, formed by local anodic oxidation, demonstrated resistive switching from high-state resistance (HRS) to low-state resistance (LRS) at +4 V, and from LRS to HRS at -6V. RHRS, RLRS, RHRS/RLRS were equaled 11.7±1.6 GΩ, 2.3±0.8 GΩ and 5, respectively. Homogeneity test showed, that RHRS and RLRS were equaled 10.6±2.8 GΩ and 2.5±1.7 GΩ, respectively. It was shown, that confidence interval of resistive switching effect of endurance test for HRS is less on 42% and for LRS is less on 53%, than for homogeneity test So, it was shown that the obtained gallium oxide structure has a uniform effect of resistive switching within 15 measurements. The results can be useful for based on gallium oxide neuromorphic system manufacturing. (paper)
[en] Highlights: • Polarizable force field PHB was applied to fold a hybrid protein FSD-EY. • The effect of reducing the polarization effect integrated into the force field by the PHB model was also examined. • Precise folding of the β-sheet of FSD-EY was further achieved by relaxing the REMD structure in explicit water. We conducted an all-atom ab initio folding of FSD-EY, a protein with a ββα configuration using non-polarizable (AMBER) and polarizable force fields (PHB designed by Gao et al.) in implicit solvent. The effect of reducing the polarization effect integrated into the force field by the PHB model, termed the PHB0.7 was also examined in the folding of FSD-EY. This model incorporates into the force field 70% of the original polarization effect to minimize the likelihood of over-stabilizing the backbone hydrogen bonds. Precise folding of the β-sheet of FSD-EY was further achieved by relaxing the REMD structure obtained in explicit water.
[en] We systematically study the dissociation of H2 molecules on the β-Ga2O3 (100)B surface, with the influences of surface oxygen vacancy being considered. After introducing the surface oxygen vacancy, the nearest topmost O(I) atom becomes very active, and hydrogen molecules become much easier to dissociate.
[en] A flux composed of lithium and rare earth molybdates has been found to be an effective transfer medium for the preparation of yttrium and rare earth iron gallium and aluminum garnets. Magnetic bubble domain properties of epitaxial iron garnet films grown from the molybdate flux are easily controlled by virtue of the transfer process including dimensional control for submicron thick films. The properties of these films compare well to those grown from the PbO . B2O3 flux, but the films are contaminant free. This is particularly important for the growth of Nd-doped YAG laser films. Stability region of the garnet phase in the Li2MoO4-Y2O3-MoO3 pseudo-ternary system and solubility are discussed as related to crystal and film growth
[en] Low temperature atomic layer deposition was used to deposit α-Ga2O3 films, which were subsequently annealed at various temperatures and atmospheres. The α-Ga2O3 phase is stable up to 400 °C, which is also the temperature that yields the most intense and sharpest reflection by x-ray diffraction. Upon annealing at 450 °C and above, the material gradually turns into the more thermodynamically stable ε or β phase. The suitability of the materials for solar-blind photodetector applications has been demonstrated with the best responsivity achieved being 1.2 A W−1 under 240 nm illumination and 10 V bias, for the sample annealed at 400 °C in argon. It is worth noting however that the device performance strongly depends on the annealing conditions, with the device annealed in forming gas behaving poorly. Given that the tested devices have similar microstructure, the discrepancies in device performance are attributed to hydrogen impurities. (paper)
[en] The indentation size effect (ISE) is studied for spherical and pyramidal indentations on a Ni poly-crystal. The indentation experiments were conducted using a Berkovich geometry as well as different spherical indenters with radii of 0.38, 3.8 and 51.0 μm. A strong ISE is observed for the material yielding a higher hardness at smaller depths or smaller sphere radii. The transition from elastic to plastic behaviour is associated with a pop-in in the load-displacement curve, in contrast to the conventional elastic-plastic transition as discussed by Tabor. The indentation response is modelled using Tabor's approach in conjunction with the uniaxial macroscopic stress-strain behaviour for calculating the statistically stored dislocation density for a given indenter geometry. The geometrically necessary dislocation (GND) density is calculated using a modified Nix/Gao approach, whereas the storage volume for GNDs is used as a parameter for the measured depth dependence of hardness. It will be shown that the ISE for both pyramidal and spherical indentations is related and can be understood within the same given framework. The indentation response of metallic materials can thus be modelled from pop-in to macroscopic hardness
[en] Mg/Au stacks were introduced to prepare ohmic contact at different annealing temperatures on Sn lightly doped β-Ga2O3. Linear current–voltage characteristics were realized when the annealing temperatures were 300, 400 and 500 °C. The transmission line measurements were used to extract the specific contact resistance (ρc) of the annealed samples. The ρc decreased as annealing temperature increased and a minimum ρc of 2.1 × 10−5 Ω cm2 was obtained for the sample annealed at 500 °C. However, the contact electrodes with the ρc of 1.3 × 10−4 Ω cm2 after annealing at 400 °C had better surface profile and stability. The ohmic contact mechanism and stability of electrodes were discussed in details.
[en] Highlights: • Epilayers of ε-Ga2O3 are employed for the first time as UV photodetectors. • Fabricated photoresistors are sensitive to UV (270 nm), stable and reliable. • Their properties compare well with those of the β polytype of Ga2O3. • Bandgap and deep levels are investigated by optical absorption/cathodoluminescence.
[en] This paper reports on the ZnCa2O4 phosphor investigated for its application to vacuum fluorescent displays (VFDs) utilizing low-voltage cathodoluminescence. It is expected that this oxide phosphor does not cause damage to filaments in VFD's, while it is a serious problem for conventional sulfide phosphors. This phosphor shows blue luminescence with a spectral peak at with 470 nm and a chromaticity at X = 0.170 and Y = 0.130. A luminous efficiency of 0.7 lm/W has been obtained, when the VFD with this phosphor is operated at 30 V dc. The results of high-temperature operating life test have proven the excellent stability of VFDs utilizing this phosphor