1. Functional Thin Films Group, Organic Nanomaterials Center, National Institute of Materials Science, 1-1 Namiki, Tukuba 305-0044, Japan
2. Tokyo University of Agriculture and Technology, Nakamachi 2-24-16, Koganei-shi, Tokyo 184-8588, Japan
3. Advanced Research Laboratory, Hitachi, Ltd., Hatoyama 350-0395, Japan
4. Department of Physics, Tokyo Institute of Technology, Meguro 152-8550, Japan
5. WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
6. Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5-603 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan