1. Institute of Material Science and Engineering, Ocean University of China, Qingdao, Shangdong 266100, China, Centre of Super-Diamond and Advanced Films (COSDAF) & Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, China, and Institute of Materials Engineering, University of Siegen, Paul-Bonatz-Str. 9-11, 57076 Siegen, Germany