1. Department of Electrical and Computer Engineering; National University of Singapore; Singapore 117576 Singapore
2. NUS Graduate School for Integrative Sciences and Engineering; Singapore 117456 Singapore
3. Institute of Microelectronics, A* STAR (Agency for Science Technology and Research); Singapore 11 Science Park 2 Singapore 117685 Singapore
4. SAINT (SKKU Advanced Institute of Nanotechnology); 300 Cheoncheon-Dong, Jangan-Gu Suwon Gyeonggi-Do 440-746 South Korea