1. Dept. of Electronic Materials Engineering, Kwangwoon University, 447-1, Wolgye-Dong, Nowon-Gu, Seoul, 139-701, South Korea
2. Dept. of Electronic Engineering, Yeojoo Institute of Technology, 454-5, Cyo-Ri, Yeoju-Eup, Yeoju-Gun, Gyeonggi-Do, 469-705, South Korea