1. Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, OH 45433, USA
2. Department of Physics and Center for Two-Dimensional and Layered Materials, The Pennsylvania University, State College, PA, USA
3. Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802, USA
4. Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA