1. Department
of Electronic Engineering, Dong-A University, Busan 604-714, Korea
2. School of Chemical and Biological Engineering, Seoul National University, Seoul 151-744, Korea
3. Department of Electrical and Computer Engineering, Inter-university
Semiconductor Research Center (ISRC), Seoul National University, Seoul 151-744, Korea
4. Department
of Chemistry, Seoul National University, Seoul 151-747, Korea