摘要：Scientific Reports 3 , Article number: 2481 10.1038/srep02481 ( 2013 ); Published: 3 October 2013 ; Updated: 1 November 2013 The incorrect version of the Supplementary Information file was inadvertently published with this Article. This version contained typographical errors and an additional section ‘Charge carrier concentration estimate’ not relevant to this article.
