1. School of Nano-Tech and Nano-Bionics University of Science and Technology of China Hefei 230027 P. R. China
2. i-Lab & Printable Electronics Research Center Suzhou Institute of Nano-Tech and Nano-Bionics Chinese Academy of Sciences (CAS) Suzhou 215123 P. R. China
3. Department of Electro-Physics National Yang Ming Chiao Tung University Hsinchu 300 Taiwan
4. Beijing National Laboratory for Molecular Sciences CAS Key Laboratory of Organic Solids Institute of Chemistry Chinese Academy of Sciences, Beijing 100190 P. R. China
5. Vacuum Interconnected Nanotech Workstation (Nano-X) Suzhou Institute of Nano-Tech and Nano-Bionics Chinese Academy of Sciences (CAS) Suzhou 215123 P. R. China
6. Department of Physics National Taiwan Normal University Taipei 106 Taiwan
7. Department of Photonics National Yang Ming Chiao Tung University Hsinchu 300 Taiwan
8. Institute of Physics National Yang Ming Chiao Tung University Hsinchu 300 Taiwan