1. Department of Physics, Faculty of Science; Khon Kaen University; Khon Kaen 40002 Thailand
2. Integrated Nanotechnology Research Center; Khon Kaen University; Khon Kaen 40002 Thailand
3. Materials Science and Nanotechnology Program; Faculty of Science; Khon Kaen University; Khon Kaen 40002 Thailand
4. School of Physics, Institute of Science; Suranaree University of Technology; Nakhon Ratchasima Thailand
5. Synchrotron Light Research Institute (Public Organization); Nakhon Ratchasima; Thailand
6. Graduate School of Engineering; Osaka University; Suita 565-0871 Japan