1. Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
2. Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210, USA
3. Columbus School for Girls, Columbus, Ohio 43209, USA
4. Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106, USA
5. Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210, USA