1. School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore
2. Institute of Microelectronics, A*STAR (Agency for Science, Technology and Research), Singapore 138634, Singapore
3. Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576
4. Applied Materials Inc., Sunnyvale, California 95054-3299, United States
5. Low Energy Electronic Systems (LEES), Singapore-MIT Alliance for Research and Technology (SMART), Singapore 138602