1. State Key Laboratory of Electronic Thin Films and Integrated Devices and the School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, China
2. School of Information Science and Technology, Southwest Jiaotong University, Chengdu, China
3. Department of Electrical, Computer and Biomedical Engineering, University of Pavia, Pavia, Italy
4. Electronics and Nanoscale Engineering Division and the School of Engineering, University of Glasgow, Glasgow, U.K.