1. CAS Key Laboratory of Nanophotonic Materials and Devices, CAS Key Laboratory of Standardization and Measurement for Nano-technology National Center for Nanoscience and Technology Beijing 100190 P.R. China
2. Physikalisches Institut Westfälische Wilhelms-Universität Wilhelm-Klemm-Straße 10 48149 Münster Germany
3. Center for Nanotechnology Heisenbergstraße 11 48149 Münster Germany
4. Organisch-Chemisches Institut Westfälische Wilhelms-Universität Corrensstraße 40 48149 Münster Germany
5. Institute of Physics and University of Chinese Academy of Sciences, Chinese Academy of Sciences Beijing 100190 P.R. China
6. Songshan Lake Materials Laboratory Dongguan, Guangdong 523808 P.R. China
7. Herbert Gleiter Institute of Nanoscience Nanjing University of Science and Technology Nanjing 210094 P.R. China