1. Department of Materials Science and Engineering, National Dong Hwa University, Hualien 974, Taiwan; Institute of Materials Science & Engineering and Center for Nanoscience & Nanotechnology, National Sun Yat-sen University, Kaohsiung 804, Taiwan; National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan; and Department of Chemical Engineering, National Tsing Hua University, Hsinchu 300, Taiwan