1. Samsung
Advanced Institute of Technology, Samsung Electronics Co., Ltd., Mt. 14-1, Nongseo-Dong,
Giheung-Gu, Yongin-Si, Gyeonggi-Do 446-712, Korea
2. Electronic
Materials Research Center, Korea Institute of Science and Technology (KIST), Seoul 136-791, Republic of Korea
3. Center
for Artificial Low Dimensional Electronic Systems, Institute for Basic Science, Pohang 790-784, Korea
4. Department
of Materials Science and Engineering, Hanbat National University, 125 Dongseo-daero,
Yuseong-Gu, Daejeon 305-719, Korea