Text and Data Mining valid from 2016-10-24
Received: 13 January 2016
Accepted: 23 August 2016
First Online: 24 October 2016
: R.H. is a co-founder of Neaspec GmbH, a company producing scattering-type scanning near-field optical microscope systems such as the one used in this study. All other authors declare no competing financial interests.