Photoluminescence properties of ZnO microstructures are investigated for potential scintillator applications. Samples are successfully prepared by the carbothermal reduction method. A single free-standing ZnO microribbon exhibits UV and visible emissions which behave differently along the microstructure.Fast UV emission lifetimes of 40 and 150 ps have been observed for the microstructures compared to 440 ps and 2 ns for a bulk crystal. With waveguided emissions and fast lifetimes, the ZnO microstructures have promising applications as future XFEL scintillators.

Some fluctuations in composition are commonly observed in epitaxial-grown III-V multinary alloys. These fluctuations are attributed to compositional pulling effects, and an insight into their atomistic origin is necessary to improve current epitaxial growth techniques. In addition, the crystallinity of III-V multinary alloys varies widely depending on the constituent atoms. Using first-principles calculations, we then investigated different geometric configurations of gallium nitride (GaN)-based ternary alloy, X 0.125 Ga 0.875 N where X is the minority atom which is boron (B), aluminum (Al), or indium (In). The minority atoms are presented as two atoms in the simulation cell, and the energetics of five geometric configurations are analyzed to estimate the most stable configuration. For the B 0.125 Ga 0.875 N alloy, the most stable configuration is the one where the minority atoms occupy gallium (Ga) sites in a collinear orientation along the c-axis. On the contrary, the configurations along the in-plane direction result in a higher energy state. In 0.125 Ga 0.875 N and Al 0.125 Ga 0.875 N also show the same trend with a small relative energy difference. These preferential sites of minority atoms are consistent with composition pulling effects in wurtzite nitride phases. Moreover, the degree of crystallinity for wurtzite nitride alloys can be well described by the order of calculated relative energy.

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Homoepitaxial film and semi-insulating bulk β-Ga2O3 with (001) orientation were studied using terahertz time-domain spectroscopy (THz-TDS) in the frequency region from 0.2 to 3.0 THz parallel to the [100] and [010] directions. The static permittivity of the bulk was determined to be 10.0 and 10.4 along the a-axis and b-axis, respectively, and the refractive index values at 0.2 THz are 3.17 and 3.23 for each axis. The electrical resistivity of the epilayer was extracted with good accuracy by employing the Drude–Lorentz model and without the use of electrical contacts. This noninvasive and contact-free material evaluation through THz-TDS proves to be a powerful tool for probing and obtaining various types of information about β-Ga2O3 materials such as bulk and thin films for the development of β-Ga2O3-based device applications.

Under 266-nm (deep ultraviolet, DUV) laser irradiation, an SrB4O7 (SBO) single crystal has been found to exhibit a surface laser-induced damage threshold (LIDT) of ∼ 16.4 J/cm2, which is higher than those of a synthetic silica glass (4.8 J/cm2) and a calcium fluoride (CaF2) crystal (11.4 J/cm2). By catalyst-referred etching (CARE), the LIDT of an SBO crystal can also be improved to around 24.1 J/cm2, which is 1.4 and 6.0 times higher compared to an unetched crystal and a silica glass, respectively. With high surface LIDTs, SBO single crystals can then be used as optical window materials for high-power DUV laser systems.