Apparent topographic height variations measured by noncontact atomic force microscopy

Abstract

The topographic height measurement on a sample consisting of domains of different materials in noncontact atomic force microscopy (NC-AFM) is typically incorrect owing to the variation in electrostatic force between a tip and a sample. The tip-sample electrostatic force is owing to the difference in effective contact potential between a tip and a sample. This study demonstrates that the error in height strongly depends on the bias applied between the tip and the sample, the radius of the tip apex. the work function difference, and the frequency shift. Experimental results are well explained by integrated model calculations and by including the van der Waals and electrostatic forces between the tip and the sample in the analysis. When the simultaneous compensation of contact potentials during imaging is not performed, the errors occurring in the height measurement can be estimated from the tip-sample distance vs the bias curves obtained in situ.