1. Department of Electrical and Computer Engineering, Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
2. Department of Electrical and Computer Engineering, Microelectronics Research Center, University of Texas, Austin, Texas 78758, USA
3. Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210, USA
4. Air Force Research Laboratory, Sensors Directorate, WPAFB, Ohio 45433, USA
5. Department of Materials Science and Engineering, The Ohio State University, Columbus Ohio 43210, USA