1. Applied Physics Program, University of Michigan-Ann Arbor, 450 Church St., 1425 Randall Laboratory, Ann Arbor, Michigan 48109, USA
2. Electrical and Computer Engineering Department, University of Michigan-Ann Arbor, 1301 Beal Avenue, Ann Arbor, Michigan 48109, USA
3. Materials Science and Engineering Department, University of Michigan-Ann Arbor, 2300 Hayward St., Ann Arbor, Michigan 48109, USA