1. Key Laboratory of Advanced Technologies of Materials (Ministry of Education), School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, China
2. State Key Laboratory of Electronic Thin films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
3. University of Electronic Science and Technology of China, Chengdu 610054, China c Department of Material Science, Sichuan University, Chengdu, China