[1] Beijing Inst Technol, Sch Integrated Circuits & Elect, Beijing 100081, Peoples R China
[2] Zhengzhou Univ, Sch Phys & Microelect, Key Lab Mat Phys, Minist Educ, Daxue Rd 75, Zhengzhou 450052, Peoples R China
[3] Henan Univ Sci & Technol, Sch Phys & Engn, Luoyang 471023, Peoples R China
[4] Soochow Univ, Inst Theoret & Appl Phys, Sch Phys Sci & Technol, Jiangsu Key Lab Thin Films, Suzhou 215006, Peoples R China