1. NanoLund and Division of Solid State Physics, Lund University, Box 118, Lund 22100, Sweden
2. NanoLund and Division of Synchrotron Radiation Research, Lund University, Box 118, Lund 22100, Sweden
3. Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China