1. State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, People's Republic of China
2. Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA
3. ExxonMobil Chemical Company, Baytown Technology and Engineering Complex, Baytown, Texas 77520, USA
4. College of Materials and Chemical Engineering, Hainan University, Haikou, Hainan 570228, People's Republic of China