1. State
Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
2. School
of Microelectronics and Solid-State Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China
3. Department
of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, Hong Kong