1. Department
of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
2. Center
for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
3. Institute
for Functional Imaging of Materials, Oak Ridge National Laboratory, Oak
Ridge, Tennessee 37831, United States
4. Department
of Photonics, National Cheng Kung University, 70101 Tainan, Taiwan, ROC