1. Department
of Electrical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
2. Department
of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
3. Condensed
Matter Physics and Materials Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, United States
4. Department
of Physics, University of Michigan, Ann Arbor, Michigan 48109, United States
5. Department
of Electrical Engineering, National Changhua University of Education, Changhua
City 500, Taiwan
6. National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
7. Department
of Mathematics, University of Michigan, Ann Arbor, Michigan 48109, United States