1. School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, United States
2. Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan
3. Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division, King Abdullah University of Science & Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
4. Institute of Biomedical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
5. Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, China