1. Department of Physics and Astronomy University of Georgia Athens GA 30602 USA
2. Department of Chemistry University of Utah Salt Lake City UT 84112 USA
3. Faculty of Materials Science and Engineering Phenikaa University Ha Dong Hanoi 10000 Vietnam
4. Institute of Engineering Physics Hanoi University of Science and Technology 1 Dai Co Viet Road Hanoi 10000 Vietnam
5. School of Materials Science and Engineering Georgia Institute of Technology 771 Ferst Drive NW Atlanta GA 30332 USA