1. CAS Key Laboratory of Standardization and Measurement for Nanotechnology & CAS Center for Excellence in Nanoscience, National Centre for Nanoscience and Technology, No. 11, Zhongguancun Beiyitiao, Beijing 100190, P. R. China
2. University of Chinese Academy of Science, No. 19A Yuquan Road, Beijing 100049, P. R. China
3. Key Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029, P. R. China
4. SDU NanoSYD, Mads Clausen Institute, University of Southern Denmark, Sønderborg DK-6400, Denmark