1. Department of Electrical and Electronic Engineering Graduate School of Engineering Kobe University Rokkodai Nada Kobe 657–8501 Japan
2. Department of Materials Science and Engineering Northwestern University Evanston IL 60208 USA
3. Department of Electrical and Computer Engineering Northwestern University Evanston IL 60208 USA
4. International Institute for Nanotechnology (IIN) Northwestern University Evanston IL 60208 USA
5. Northwestern University Atomic and Nanoscale Characterization Experimental (NUANCE) Center Northwestern University Evanston IL 60208 USA