[1] Shandong Normal Univ, Sch Phys & Elect, Jinan 250014, Peoples R China
[2] Univ Jinan, Sch Phys & Technol, 336 West Rd Nan Xinzhuang, Jinan 250022, Shandong, Peoples R China
[3] Qilu Univ Technol, Sch Sci, Jinan 250353, Peoples R China
[4] Harbin Normal Univ, Minist Educ, Key Lab Photon & Elect Bandgap Mat, Harbin 150025, Peoples R China