1. Department of Applied
Chemistry, Kyung Hee University, Yongin, Gyeonggi 17104, Korea
2. Department
of Physics, Michigan Technological University, Houghton, Michigan 49931, United States
3. Technology Development Division, Korea Advanced Nanofab Center (KANC), Suwon, Gyeonggi 16229, Korea
4. Department
of Electrical Engineering, Chungnam National University, Daejeon 34134, Korea