1. School of Physical and Mathematical Sciences; Nanyang Technological University; 637371 Singapore
2. National Institute of Education; Nanyang Technological University; 637616 Singapore
3. College of Optical and Electronic Technology; China Jiliang University; Hangzhou 310038 P. R. China
4. Singapore Institute of Manufacturing Technology; 2 Fusionopolis Way 138634 Singapore
5. State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering; Zhejiang University; Hangzhou 310027 P. R. China