1. Materials Laboratories, Sony Corporation, 4-16-1 Okata, Atsugi, Kanagawa 243-0021, Japan, Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan, and Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan