1. Department of Materials Science and Engineering, Korea Advanced Institute of Science and Tehcnology (KAIST), Daejeon 305-701, Republic of Korea
2. Power Control Device Research Section, Electronics and Telecommunications Research Institute (ETRI), Daejeon 305-700, Republic of Korea
3. Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Daejeon 305-701, Republic of Korea
4. School of Mechanical and Advanced Materials Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea
5. Interdisciplinary School of Green Energy, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea