1. Department of Materials Science and Engineering and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
2. Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080, United States
3. Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
4. Department of Electrical Engineering, The Pennsylvania State University, State College, University Park, Pennsylvania 16802, United States