1. Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA
2. Nano-Device Laboratory (NDL) and Phonon Optimized Engineered Materials (POEM) Center, Department of Electrical and Computer Engineering, University of California–Riverside, Riverside, California 92521, USA
3. Central Facility for Advanced Microscopy and Microanalysis, University of California–Riverside, Riverside, California 92521, USA