1. Department of Electrical and Computer Engineering, Herbert Wertheim College of Engineering, University of Florida, Gainesville, Florida 32611, USA
2. Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio 43210, USA
3. Department of Materials Science and Engineering, Ohio State University, Columbus, Ohio 43210, USA
4. State Key Laboratory of Crystal Materials, Shandong University, Jinan, Shandong 250100, China