1. Micro-Electronics Research Institute and College of Electronics and Information, Hangzhou Dianzi University, Hangzhou 310018, PR China
2. National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nano Technology, Nanjing University, Nanjing 210093, PR China
3. College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211100, PR China
4. School of Physics Science and Technology, Yangzhou University, Yangzhou 225002, PR China