1. School
of Semiconductor and Chemical Engineering, Semiconductor Physics Research
Center, Chonbuk National University, Jeonju, Chonbuk 561-756, Korea
2. Department
of Nano-Optical Engineering, Korea Polytechnic University, Siheung 429-793, Korea
3. Division
of Materials Science, Korea Basic Science Institute, Daejeon 305-333, Korea
4. Analysis
Center for Research Advancement, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea