[1] Hong Kong Polytech Univ, Dept Appl Phys, Hong Kong, Hong Kong, Peoples R China
[2] Hong Kong Polytech Univ, Mat Res Ctr, Hong Kong, Hong Kong, Peoples R China
[3] Hong Kong Univ Sci & Technol, Dept Chem & Biomol Engn, Hong Kong, Hong Kong, Peoples R China