1. Key Laboratory of Graphene Technologies and Applications Ningbo Institute of Materials Technology and Engineering (NIMTE) Chinese Academy of Sciences (CAS); Ningbo 315201 P.R. China
2. Department of Physics Govt. College University Faisalabad; Allama Iqbal Road 38000 Faisalabad Pakistan
3. International School University of Chinese Academy of Sciences; Beijing 100049 P.R. China
4. Department of Microelectronic Science and Engineering Faculty of Science Ningbo University; Ningbo 315211 P.R. China
5. Key Laboratory of Semiconductor Materials Science Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices Institute of Semiconductors Chinese Academy of Sciences; Beijing 100083 P.R. China