1. Electronic Materials Research Laboratory, School of Electronics and Information Engineering, Xi'an Jiaotong University, Xi'an 710049, China
2. State Key Laboratory for Strength and Vibration of Mechanical Structures, International Center for Applied Mechanics and School of Aerospace, Xi'an Jiaotong University, Xi'an 710049, China
3. School of Engineering and Applied Sciences, Kavli Institute of Bionano Science and Technology, Harvard University, Cambridge, Massachusetts 02138, USA