1. Materials Science and Engineering Department; Stanford University; 496 Lomita Mall Stanford CA 94305-4034 USA
2. Chemical Engineering Department; Stanford University; 443 Via Ortega Stanford CA 94305 USA
3. Materials Physics and Chemistry; University of Science and Technology, Beijing; Haidian Beijing 100083 P. R. China
4. Electrical Engineering Department; Stanford University; 350 Serra Mall Stanford CA 94305 USA
5. Department of Physics; National Taiwan University; Taipei 10617 Taiwan P. R. China
6. Department of Chemistry; Chung-Ang University; 221 Heukseok-dong, Dongjak-gu Seoul 156-756 South Korea
7. Samsung Advanced Institute of Technology; Yeongtong-gu, Suwon-si Gyeonggi-do 443-803 South Korea