1. a Department of Physics and Materials Science, Faculty of Science , Chiang Mai University , Chiang Mai , 50200 , Thailand
2. b School of Physics , Institute of Science, Suranaree University of Technology and NANOTECH-SUT Center of Excellence on Advanced Functional Nanomaterials , Nakorn Ratchasima , 30000 , Thailand
3. c Department of Electrical and Computer Engineering, College of Engineering , University of Texas at San Antonio (UTSA) , San Antonio , TX , 78249 , USA