1. Display Device and Material Laboratory, Samsung Advanced Institute of Technology, P.O. Box 111, Suwon 440-600, Korea, Electronic Chemical Materials Division, Cheil Industries Inc. 332-2 Gocheon-dong, Uiwang-si, Gyeonggi-do, Korea, and AE Center, Samsung Advanced Institute of Technology, P.O. Box 111, Suwon 440-600, Korea