Theoretical study of the atomic-force-microscopy imaging process on the NaCl(001) surface

Based on a fully relaxed molecular-mechanics approach, we present a complete series of atomic force microscopy images of the NaCl(001) surface. For a given atomic structure of a diamond probe-tip [111] oriented, we analyze the results obtained from the two usual imaging modes either based on the monitoring of lateral or vertical forces. By accounting for the atomic relaxation of the whole system for any tip-sample configuration, we were able to get new insights about the achievement of atomic resolution on such substrates. Depending on the tip-sample distance range, the scanning of the NaCl(001) surface results in completely different behaviors associated with these two imaging modes. At very short distance we observed an increase of the apparent corrugation when working with the lateral force mode. The perturbations generated in the images by the presence of localized defects (vacancy and monoatomic step) are also analyzed within this model. These last calculations clearly indicate the fundamental role played by the relaxation phenomena on the observed topography when the tip scans the surface defects.