1. School of Integrated Circuit, Huazhong University of Science and Technology, Wuhan 430074, PR China
2. Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Kowloon, Hong Kong 999077, PR China
3. College of Mechanical Engineering, University of South China, Hengyang 421001, PR China
4. Hubei Yangtze Memory Laboratories, Wuhan 430205, China