1. Nanoengineering, Joint School of Nanoscience and Nanoengineering, North Carolina A&T State University, Greensboro, North Carolina 27411, United States
2. Department of Electrical and Computer Engineering, North Carolina A&T State University, Greensboro, North Carolina 27411, United States
3. Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
4. Analytical Instrumentation Facility, North Carolina State University, Raleigh, North Carolina 27695, United States