1. Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, Xi’an Jiaotong University, Xi’an 710049, China
2. Shaanxi Engineering Research Center of Advanced Energy Materials & Devices, Xi’an Jiaotong University, Xi’an 710049, China
3. Institut für Chemie, AG Elektrochemie, Technische Universität Chemnitz, 09111 Chemnitz, Germany
4. Institut für Physik, Technische Universität Chemnitz, 09111 Chemnitz, Germany