Electrical tip-sample contact in scanning conductive torsion mode

We investigated the nature of the mechanical and the electrical tip-sample contact in scanning conductive torsion mode microscopy (SCTMM). Experiments on the soft conducting polymer blend of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) demonstrated that the tip-sample force and thus the danger of tip-induced sample damage can be minimized. Using current-voltage spectroscopy, we found a space-charge limited conduction behavior with no indication of a tunneling barrier. Spectroscopy and imaging experiments showed that SCTMM allows for a gentler tip-sample contact compared to conventional conductive scanning force microscopy. A gentle and well-defined contact is a prerequisite for reproducible scanning probe based conductivity measurements, in particular on soft organic materials. (C) 2013 AIP Publishing LLC [http://dx.doi.org/10.1063/1.4802725]