1. Department of Materials Science and Engineering, Chungnam National University, Daejeon 34134, Republic of Korea
2. School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
3. National Nano Fab Center, Daejeon 34141, Republic of Korea
4. Semiconductor Process Laboratory, WONIK IPS, Gyeonggi-do 17709, Republic of Korea
5. Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea