1. Key Laboratory of Intelligent Computing and Signal Processing of Ministry of Education, School of Electronics and Information Engineering, Anhui University, 111 Jiulong Road, Hefei, Anhui 230601, P. R. China
2. School of Optical and Electronic Information, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074, P. R. China
3. Department of Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, Alabama 35487, United States
4. Key Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, P. R. China