1. Department of Physics, Faculty of Science; Khon Kaen University; 40002 Khon Kaen Thailand
2. Integrated Nanotechnology Research Center; Khon Kaen University; 40002 Khon Kaen Thailand
3. Nanotec-KKU Center of Excellence on Advanced Nanomaterials for Energy Production and Storage; 40002 Khon Kaen Thailand
4. Condensed Matter Theory Group, Department of Physics and Astronomy; Uppsala University; Box 516 SE-751 20 Uppsala Sweden
5. Applied Materials Physics, Department of Materials and Engineering; Royal Institute of Technology (KTH); SE-100 44 Stockholm Sweden