Determination of effective tip geometries in Kelvin probe force microscopy on thininsulating films on metals

Abstract

In scanning probe techniques, accurate height measurements on heterogeneous surfaces area major requirement. Different electrostatic potentials of various materials have asignificant influence on the measured force/current and therefore a direct influence on thetip–sample distance. Kelvin probe force microscopy (KPFM) is based on a dynamiccompensation of the electrostatic force while performing non-contact atomic forcemicroscopy measurements. Thus, the influence of the electrostatic potentials can beminimized and accurate height measurements become possible. Here, the study ofultra-thin alkali halide films on Cu(111) investigated by KPFM is presented. This workis focused on the interface between areas of bare Cu(111) and the first layersof salt. The compensation of the electrostatic potential allow us to determinelayer heights with high accuracy. The second objective was to elaborate on thecharacterization of tip geometries across suitable nanostructures. Simulations ofmeasured images are performed with different input parameters, which gives a directestimation of the effective tip radius and geometry used for the measurements.