1. Nanofabrication Laboratory CAS Key Laboratory for Nanophotonic Materials and Devices CAS Key Laboratory for Hierarchical Fabrication and Systems National Center for Nanoscience and Technology Beijing 100190 P. R. China
2. Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing 100049 P. R. China
3. Institute of Earth Sciences China University of Geosciences Beijing 100083 P. R. China