A promising technique capable of performing localized resistance measurements over a surface is presented using a modified commercial atomic force microscope with a conducting probe. Its overall purpose is to obtain simultaneous cartographies of surface roughness and local resistance within a given microscopic area of a sample with nanometer scale resolution. Although an elaboration of suitable probes remains an ongoing problem, convincing images of some metal surfaces that reveal occasionally surprising features have already been obtained. Calculations performed from measurements have allowed us to clarify the mechanical nature of the tip/surface nanocontact and hence to determine the most probable transport process according to the range of resistance considered.

LGEP 2014 ID = 1519International audienceWe demonstrate the high potential of GaN nanowires (NWs) to convert mechanical energy into electric energy. Using an atomic force microscope equipped with a Resiscope module, an average output voltage of –74 mV and a maximum of –443 mV ± 2% per NW were measured. This latter value is the highest reported so far for GaN NWs. By considering these output signals, we have estimated an average and a maximum power density generated by one layer of GaN NWs of the order of 5.9 mW/cm2 and 130 mW/cm2, respectively. These results offer promising prospects for the use of GaN NWs for high-efficiency ultracompact piezogenerators