1. Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand
2. Institute of Nanomaterials Research and Innovation for Energy (IN-RIE), Khon Kaen University, Khon Kaen 40002, Thailand
3. Department of Physics, Faculty of Science, Mahasarakham University, Maha Sarakham 44150, Thailand