1. State Key Laboratory of Electronic Thin Films and Integrated Devices University of Electronic Science and Technology of China Chengdu 610054 P. R. China
2. Institute of Microelectronics of Chinese Academy of Sciences Beijing 100029 P. R. China
3. State Key Laboratory of Material Processing and Die & Mould Technology School of Materials Science and Engineering Huazhong University of Science and Technology Wuhan 430074 P. R. China
4. Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing 100081 P. R. China
5. Hunan Provincial Key Laboratory of Thin Film Materials and Devices School of Materials Science and Engineering Xiangtan University Xiangtan 411105 P. R. China