1. Department of Physics and Memory and Catalyst Research Center, Hankuk University of Foreign Studies, Yongin 449-791, Republic of Korea
2. Institute of Physics, Bhubaneswar 751005, India
3. Silicon Austria Laboratories GmbH, Sandgasse 34, A-8010 Graz, Austria
4. Department of Physics and Center for Lattice Defectronics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
5. Department of Physics Education, Seoul National University, Seoul 08826, Republic of Korea
6. Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea