1. Lab for Nanoelectronics and NanoDevices, Department of Electronics Science and Technology, Hangzhou Dianzi University, Hangzhou 310018, China
2. School of Physics, Southeast University, Nanjing 211189, China
3. College of Physics and Hebei Advanced Thin Film Laboratory, Hebei Normal University, Shijiazhuang 050024, China
4. Institute of Materials Physics, Hangzhou Dianzi University, Hangzhou 310018, China