1. Department of Materials Science and Engineering and Center of Nanotechnology, Materials Science, and Microsystem, National Tsing Hua University, Hsinchu, Taiwan, 30043, R. O. C., Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan, 30050 R. O. C., and National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30077, Taiwan, R.O.C.