1. College of Science
2. Institute of Materials Physics and Chemistry
3. Nanjing Forestry University
4. Nanjing 210037
5. P. R. China
6. Department of Industrial and Information Engineering and Economics
7. Via G. Gronchi 18
8. 7 University of L’Aquila
9. I-67100 L’Aquila
10. Italy
11. Department of Physical and Chemical Sciences
12. University of L’Aquila
13. 67100 L’Aquila
14. CNR-IMM Istituto per la Microelettronica e Microsistemi