Affiliation: | 1. Department of Materials Science and Engineering, Yonsei University, 262 Seongsanno Seodaemun‐gu, Seoul, 120‐749 (Korea), Fax: (+82)?2‐312‐5375;2. Current address: Department of Materials Science and Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208‐3113 (USA) |