1. Department of Applied Physics, National Defense Academy, 1-10-20 Hashirimizu, Yokosuka 239-8686, Japan
2. Research & Development Group, Hitachi, Ltd., 832-2, Horiguchi, Hitachinaka, Ibaraki 312-0034, Japan
3. Advanced Technology Research & Development Center, Hitachi Chemical Co. Ltd., 48 Wadai, Tsukuba, Ibaraki 300-4247, Japan