We have successfully synthesized vertically aligned ZnO nanotube arrays by metalorganic chemical vapor deposition. Since no metal catalysts are used in this work, the growth process of ZnO nanotube arrays does not follow a vapor-liquid-solid mechanism but a self-catalyzed growth mechanism. X-ray diffraction results show that the nanotubes have ZnO hexagonal wurizite structures and only the ZnO (0002) peak can be seen. The rocking curve also shows a full width at half-maximum value of similar to 1625 arc second. A 6-fold symmetry in phi-scan data is also observed, indicating in-plane alignment of ZnO nanotube arrays. Room temperature photoluminescence results present a high optical quality and nearly defect-free crystal structure of ZnO nanotube at-rays. Moreover, the high near-band edge emission to deep level emission intensity ratio (I(NBE)/I(DLE)) of 2050 is obtained

This study evaluates the effect of crystallinity and point defects on time-dependent photoresponsivity and the cathodoluminescence (CL) properties of β-Ga₂O₃ epilayers. A synchrotron high-resolution X-ray technique was used to understand the crystalline structure of samples. Rutherford backscattering spectroscopy was used to determine the net chemical composition of the samples to examine the type and ratio of their possible point defects. The results show that in functional time-dependent photoresponsivity of photodetectors based on β-Ga₂O₃ epilayers, point defects contribution overcomes the contribution of crystallinity. However, the crystalline structure affects the intensities and emission regions of CL spectra more than point defects.

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We verified that nanocrystalline SixNy with a size ranging from 4 to 6 nm appeared on the pit sidewall and preferred to reside at the pit.

In this study, indium-tin oxide (ITO)/Al-doped zinc oxide (AZO) composite films were fabricated by pulsed laser deposition and used as transparent contact layers (TCLs) in GaN-based blue light emitting diodes (LEDs). The ITO/AZO TCLs were composed of the thin ITO (50 nm) films and AZO films with various thicknesses from 200 to 1000 nm. Conventional LED with ITO (200 nm) TCL prepared by E-beam evaporation was fabricated and characterized for comparison. From the transmittance spectra, the ITO/AZO films exhibited high transparency above 90% at wavelength of 465 nm. The sheet resistance of ITO/AZO TCL decreased as the AZO thickness increased, which could be attributed to the increase in a carrier concentration, leading to a decrease in the forward bias of LED. The LEDs with ITO/AZO composite TCLs showed better light extraction as compared to LED with ITO TCL in compliance with simulation. When an injection current of 20 mA was applied, the output power for LEDs fabricated with ITO/AZO TCLs had 45%, 63%, and 71% enhancement as compared with those fabricated using ITO (200 nm) TCL for the AZO thicknesses of 200, 460, and 1000 nm, respectively.