1. State Key Laboratory of Electronic Thin Films and Integrated Devices; University of Electronic Science and Technology of China (UESTC); 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