2014, Vol.24, No.3

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

In this study, effects of the V/III ratio on a-plane GaN epitaxial on r-plane grown by HVPE have beeninvestigated. According to increasing of V/III ratio, the value of FWHM of a-plane (11-20) GaN and the value of surfaceroughness (Ra) were decreased. Growth rate of a-plane GaN epitaxial layer were increased until V/III ratio = 7 as theincreasing of V/III ratio, but it was reduced at V/III ratio = 10. At V/III ratio = 10, the FWHM of a-plane (11-20) GaN RCand the surface roughness (Ra) were 829 arcsec and 1.58 nm, respectively, as the lowest value in this study. Also for V/IIIratio = 10, cracks under surface or voids were observed the lowest values in images of optical microscope. An M-shapedazimuthal dependence over 360oangle range was observed for all samples. At V/III ratio = 10, the difference of FWHM ofa-plane GaN between 0oand 90owas 439 arcsec revealed as the lowest value in the 4 samples.

LiCoO2 thin film has received diverse attention as cathodes material of thin-film micro-batteries. In this study,LiCoO2 thin films were synthesized on Au substrates by sol-gel spin coating method and an annealing process. Theirstructures were studied using X-ray diffraction and Raman Spectroscopy. The particle morphologies of these thin films wereobserved by Scaning electron microscope. From the results of X-ray diffractometry and Raman Spectroscopy analyses, itwas found that as-grown films had the structure of spinel (LT-LiCoO2) and layered-Rock-salt (HT-LiCoO2) at 550oC and750oC respectively. The annealed films at 650oC were presumed to be the mixed state of these two types. Throlugh thescanning electron microscope, It was estimated that the particle size in as-grown films at 750oC, were larger crystillineparticle than in those at the other lower temperature and well distributed in the film.

LiCoO2 thin film have received attention as cathodes of thin-film microbatteries. In this study, LiCoO2 thin filmswere synthesized on Au substrates by sol-gel spin coating method and electrochemical properties were investigated underannealing temperature and time. The phycochemical properties of LiCoO2 thin film were investigated by X-ray diffraction,scaning electron microscopy and atomic force microscopy. The electrochemical properties were characterized usinggalvanostatic charging/discharging cycling tests. From X-ray diffraction, as-grown films annealed at 550oC and 750oC arepresumed to be spinel structure and a single phase of the layered-rock-salt, respectively. The RMS roughness and grain sizeof the films which annealed at 750oC has similar values for annealing time 10 and 30 min, while for annealing time120 min surface roughness, grain size increase and pore appearance were observed. The first discharge capacity of LiCoO2thin films annealed at 750oC for 10, 30 and 120 min is about 54.5, 56.8 and 51.87 μAh/cm2μm, respectively. Correspondingcapacity retention at 50th cycle is 97.25, 76.69, 77.19%.