1. Department of Applied Physics; The Hong Kong Polytechnic University; Hong Kong China
2. Texas Materials Institute and Materials Science and Engineering Program; The University of Texas at Austin; Austin TX 78712 USA
3. Department of Mechanical Engineering; The Hong Kong Polytechnic University; Hong Kong China
4. Centre for Advanced Materials Technology (CAMT), School of Aerospace, Mechanical and Mechatronics Engineering J07; The University of Sydney; NSW 2006 Australia