1. Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049, P. R. China
2. Department of Chemistry and 4D LABS, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
3. Department of Applied Physics, Donghua University, Ren Min Road 2999, Songjiang District, Shanghai 201620, P. R. China