1. Electronic Materials Research Laboratory, Xi'an Jiaotong University, Xi'an 710049, P. R. China
2. International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049, P. R. China
3. National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, CAEP, Mianyang 621900, P. R. China