1. National Nano Device Laboratories (NDL); National Applied Research Laboratories; Hsinchu 30078 Taiwan
2. Department of Electrical Engineering; University of California at Los Angeles; Los Angeles CA 90095 USA
3. Physical Sciences and Engineering Division; King Abdullah University of Science and Technology (KAUST); Thuwal 23955-6900 Kingdom of Saudi Arabia
4. Research Center for Applied Sciences; Academia Sinica; Taipei 10617 Taiwan
5. Department of Electrical Engineering; National University of Kaohsiung; Kaohsiung 811 Taiwan