1. Condensed
Matter Physics and Materials Sciences Department, Building 480, Brookhaven National Laboratory, Upton, New York 11973, United States
2. Department
of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400, United States
3. Materials
Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20889, United States