1. Department of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20, Hayashi-cho, Takamatsu, Kagawa 761-0396, Japan
2. Advanced Technology Research Laboratories, Panasonic Corporation, 3-4 Hikaridai, Seika-cho, Souraku-gun, Kyoto 619-0237, Japan
3. Department of Electronics and Informatics, Faculty of Science and Technology, Ryukoku University, 1-5 Yokotani, Oe-cho, Seta, Ohtsu city, Siga 520-2194, Japan