1. School
of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, United States
2. Laboratory
of Nanophotonic Functional Materials and Devices, Institute of Optoelectronic
Materials and Technology, South China Normal University, Guangzhou, China 510631
3. Beijing
Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, China 100083