1. Department of Electrical Engineering, University of California, Los Angeles, Los Angeles, California 90095, USA
2. Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
3. State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
4. Univerisité de Saint-Etienne, Université de Lyon, LT2C, 25 rue du Docteur Rémy Annino, 42000 Saint-Etienne, France