1. Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok 10400, Thailand
2. Metallurgy and Materials Science Research Institute, Chulalongkorn University, Bangkok 10330, Thailand
3. Department of Chemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
4. Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400, Thailand