1. Applied Physics Program, University of Michigan, Ann Arbor, Michigan 48109, USA
2. Department of Physics, University at Buffalo, Buffalo, New York 14260, USA
3. Department of Electrical and Computer Engineering, Western Michigan University, Kalamazoo, Michigan, 49008-5329, USA
4. Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
5. Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA