1. Nano Electronics Research Laboratories, NEC Corporation, 34 Miyukigaoka, Tsukuba 305-8501, Japan
2. SORST, Japan Science and Technology Agency, c/o NEC Corporation, 34 Miyukigaoka, Tsukuba 305-8501, Japan
3. Meijo University, 1-501 Shiogamaguchi, Nagoya 468-8502, Japan