1. College of Science Institute of Materials Physics and Chemistry Nanjing Forestry University Nanjing Nanjing 210037 P. R. China
2. Theoretical Physics and Applied Mathematics Department Ural Federal University Mira Street 19 Ekaterinburg 620002 Russia
3. Department of Physical and Chemical Sciences University of L'Aquila L'Aquila 67100 Italy
4. Consiglio Nazionale delle Ricerche (CNR)-Istituto Officina dei Materiali (IOM) Laboratorio TASC in Area Science Park S.S. 14 km 163.5 Trieste 34149 Italy
5. CNR-SPIN Uos Via Vetoio 10 L'Aquila 67100 Italy
6. CNR-IMM Istituto per la Microelettronica e Microsistemi VIII strada 5 Catania 9512 Italy