1. Center for Condensed Matter Sciences National Taiwan University No. 1, Sec. 4, Roosevelt Rd. Taipei 10617 Taiwan
2. Department of Physics National Taiwan University No. 1, Sec. 4, Roosevelt Rd. Taipei 10617 Taiwan
3. Materials Science Division and Center for Molecular Engineering Argonne National Laboratory Lemont IL 60439 USA
4. Department of Material Science and Engineering National Taiwan University No. 1, Sec. 4, Roosevelt Rd. Taipei 10617 Taiwan
5. Center for Integrated Nanotechnologies, Materials Physics and Application Division Los Alamos National Laboratory Los Alamos NM 87545 USA
6. Pritzker School of Molecular Engineering University of Chicago Chicago IL 60637 USA
7. Department of Material Science and Engineering National United University 1, Lienda Miaoli 36003 Taiwan
8. Institute of Polymer Science and Engineering National Taiwan University No. 1, Sec. 4, Roosevelt Rd. Taipei 10617 Taiwan