1. Department of Electrical and Computer Engineering, University of California, Riverside, California92521, United States
2. Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova ScotiaB3H 4R2, Canada
3. Department of Chemistry, University of California, Riverside, California92521, United States
4. Central Facility for Advanced Microscopy and Microanalysis, Research and Economic Development, University of California, Riverside, California92521, United States