1. Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division; King Abdullah University of Science and Technology (KAUST); Thuwal 23955-6900 Kingdom of Saudi Arabia
2. Department of Electrophysics; National Chiao Tung University; Hsinchu 30010 Taiwan Republic of China
3. Department of Materials Science and Engineering; National Chiao Tung University; Hsinchu 30010 Taiwan Republic of China
4. Physical Sciences and Engineering (PSE) Division; King Abdullah University of Science and Technology (KAUST); Thuwal 23955-6900 Kingdom of Saudi Arabia
5. Department of Electrical and Computer Engineering; Purdue University; West Lafayette IN 47907 USA
6. Department of Chemical and Biological Engineering; Iowa State University; Ames IA 50011 USA