1. Graduate Program for Nanotechnology Department of Materials Science and Engineering, National Chiao-Tung University, Hsinchu 30010, Taiwan
2. Department of Electronics Engineering and the Institute of Electronics, National Chiao Tung University, Hsinchu 30010, Taiwan
3. Department of Electronics Engineering, National United University, No. 2, Lienda, Nan Shih Li, Miaoli City, Taiwan 36003, R.O.C.
4. National Nano Device Laboratories, Hsinchu 30078, Taiwan