1. Department of Physics and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education and Hubei Nuclear Solid Physics Key Laboratory, Wuhan University, Wuhan 430072, People's Republic of China
2. Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
3. Laboratory of Functional Nanomaterials and Printed Electronics, School of Printing and Packaging, Wuhan University, Wuhan 430072, People's Republic of China
4. Key Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, People's Republic of China
5. Su Zhou Institute of Wuhan University, Suzhou 215123, People's Republic of China