1. Department
of Mechanical Engineering, University of California Merced, 5200
North Lake Road, Merced, California 95343, United States
2. Department
of Mechanical and Manufacturing Engineering, University of Calgary, 40 Research Place NW, Calgary, Alberta T2L 1Y6, Canada
3. Physics
Division, Center for Integrated Nanostructure Physics, Sungkyunkwan University, Suwon 440-746, South Korea