1. Department of Industrial and Materials Science; Chalmers University of Technology; SE-41296 Gothenburg Sweden
2. Department of Chemistry and Chemical Engineering; Chalmers University of Technology; SE-41296 Gothenburg Sweden
3. Department of Physics; Chalmers University of Technology; SE-41296 Gothenburg Sweden
4. Institute of Applied Physics; Jiangxi Academy of Sciences; Nanchang 330029 P. R. China