1. School
of Materials Science and Engineering, Hubei University, Wuhan 430062, China
2. Department
of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China
3. Lehrstuhl
für Funktionelle Materialien, Physik-Department, Technische Universität München, 85748 Garching, Germany
4. School
of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798