2013, Vol.23, No.5

Journal of the Korean Crystal Growth and Crystal Technology 2023 KCI Impact Factor : 0.19

pISSN : 1225-1429 / eISSN : 2234-5078
https://journal.kci.go.kr/jkcgct

The GaN layer was typical III-V nitride semiconductor and was grown on the sapphire substrate which cheap and convenient. However, sapphire substrate is non-conductivity, low thermal conductivity and has large lattice mismatch with the GaN layer. In this paper, the poly GaN epilayer was grown by HVPE on the metallic compound graphite substrate with good heat dissipation, high thermal and electrical conductivity. We tried to observe the growth mechanism of the GaN epilayer grown on the amorphous metallic compound graphite substrate. The HCl and NH3 gas were flowed to grow the GaN epilayer. The temperature of source zone and growth zone in the HVPE system was set at 850oC and 1090oC, respectively. The GaN epilayer grown on the metallic compound graphite substrate was observed by SEM, EDS, XRD measurement.

In this study, the reflectivity characteristics of Ag nano-coating grown by electroless plating were investigated in order to use as the reflecting plate of BLU (Back Light Unit) in the LCD (Liquid Crystal Display) or LED (Light Emitting Diode) display equipment. The microstructure of Ag nano-coating was polycrystalline nano-structure that consisted of Ag nano-crystals to be reduced and precipitated, and the size of reduced nano-crystals increased as the thickness of nano-coating increased. The reflectivity of Ag nano-coating in the visible light decreased as the thickness of nano-coating increased and the reduction of reflectivity was more severe in the short wavelength region of visible light. The decrease of reflectivity was closely related to the size of Ag nano-crystal and was thought to be due to the larger surface roughness of larger nano-coating thickness. Therefore, the finer Ag nano-crystals and thinner nano-coating thickness could be favorable for the higher reflectivity of Ag nano-coating grown by electroless plating.

Vanadium oxide thin films were deposited on c-Al2O3 (001) substrate by in-situ RF magnetron sputtering. Oxygen partial pressure was adjusted to prepare thermochromic VO2 phase. X-ray diffraction patterns and scanning electron microscopy convincingly showed that plate-like V2O5 grains were changed into round-shape VO2 grains as oxygen partial pressure decreased. After the optimized deposition conditions were fixed, the effect of substrate temperature and orientation on the optical properties of VO2 thin films was analyzed.