[1] Shaanxi Normal Univ, Coll Phys & Informat Technol, Xian 710119, Shaanxi, Peoples R China
[2] Xian Univ Posts & Telecommun, Elect Engn Inst Xian, Xian 710121, Shaanxi, Peoples R China
[3] Minist Educ & Guangdong Prov, Key Lab Optoelect Devices & Syst, Collaborat Innovat Ctr Optoelect Sci & Technol, Shenzhen Key Lab Two Dimens Mat & Devices,Shenzhe, Shenzhen 518060, Guangdong, Peoples R China