Large lateral contact stiffness on Si nanopillar surfaces

We studied the lateral contact stiffness ([Formula: see text]) between the tip of a frictional force microscope and a pillar surface to identify the sliding behavior of the tip at the submicrometer scale. The [Formula: see text] and mean lateral force (⟨ F⟩) were systematically measured as functions of pillar diameter φ. We found that the [Formula: see text] on a single Si pillar surface increased whereas the ⟨ F⟩ rapidly decreased as φ decreased from the micrometer to the nanometer scale. This contradiction could be explained by the change in tip behavior from dynamic sliding to static sticking.