1. School of Information Science and Engineering, Lanzhou University, Lanzhou, Gansu, China
2. School of Physical Science and Engineering, Lanzhou University, Lanzhou, Gansu, Chian
3. Institute of Microelectronics Chinese, Academy of Sciences, Beijing, China
4. Department of microelectronics and nanoelectronics, Institute of Microelectronics Tsinghua University, Beijing National Research Center for Information Science and Technology, Beijing, China