1. Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China
2. Key Laboratory of Optoelectronics Technology, Ministry of Education, Faculty of Information Technology, Beijing University of Technology, Beijing 100124, China
3. School of Electrical and Electronic Engineering, Beijing-Dublin International College (BDIC), University College Dublin, Ireland
4. National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan