1. Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, People’s Republic of China
2. Department of Mechanical and Aerospace Engineering, University of California, Los Angeles (UCLA), Los Angeles, California 90095, USA
3. Department of Mechanical Engineering, University of California, Riverside (UCR), Riverside, California 92521, USA