1. Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 440-746, Republic of Korea
2. Department of Energy Science, Department
of Physics, Sungkyunkwan University, Suwon 440-746, Republic of Korea
3. Device Lab, Samsung Advanced Institute of Technology, Suwon 443-803, Republic of Korea
4. AE Group, Platform Technology Laboratory, Samsung Advanced Institute of Technology, Suwon 443-803, Republic of Korea