1. Center
for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Daejeon 305-701, Republic of Korea
2. Power
Control Device Research Section, Electronics and Telecommunications Researh Institute (ETRI), Daejeon 305-700, Republic of Korea
3. Department
of Materials Science and Engineering and Graduate School of Green
Energy Technology, Chungnam National University, Daejeon 305-764, Republic of Korea