Perturbative phenomena affecting the quality of local measurements of electrical quantities at nanoscale

This contribution aims at making an inventory of the sources of errors which impinge current and capacitance measurements operated with an atomic force microscope, especially in contact mode and in air. Parasitic capacitances and resistances, electrical and mechanical properties of the tip and atmosphere of measurement are the main parameters which strongly influence the reproducibility, repeatability and even the reliability of the results. In particular, the presence of a water layer covering the surface when the measurements are operated in air is responsible for electrochemical perturbative phenomena which alter the interpretation of e.g. electrical measurements. An example will be provided where this layer is responsible for a premature degradation of a very thin oxide during current measurements.