Scientific Reports 4: Article number: 6433; ; published online: 22 September 2014; updated: 25 June 2015

In the original version of this Article, the affiliations for Bin Li were incorrectly listed as ‘College of Science, Nanjing University of Posts and Telecommunications, Nanjing 210023, China’, ‘National Laboratory of Solid State Microstructures and School of Physics, Nanjing University, Nanjing 210093, China’ and ‘Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China’; and the affiliations for Zhongwen Xing were incorrectly listed as ‘Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China’ and ‘Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China’. These errors have now been corrected in both the HTML and PDF versions of the Article.