1. College of Science, Institute of Materials Physics and Chemistry, Nanjing Forestry University, Nanjing 210037, P. R. China
2. Institute of Physics and Technology, Ural Federal University, Mira Str. 19, 620002 Yekaterinburg, Russia
3. Department of Physical and Chemical Sciences, University of L’Aquila, via Vetoio, 67100 L’Aquila (AQ), Italy
4. Consiglio Nazionale delle Ricerche (CNR), Istituto Officina dei Materiali (IOM), Laboratorio TASC, Area Science Park S.S. 14 km 163.5, 34149 Trieste, Italy
5. Department of Physics, National Cheng Kung University, 1 Ta-Hsueh Road, 70101 Tainan, Taiwan
6. Department of Information Engineering, Infrastructures and Sustainable Energy (DIIES), University “Mediterranea” of Reggio Calabria, Loc. Feo di Vito, 89122 Reggio Calabria, Italy
7. Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016, India