Force on a Conducting Tip near a Metallic Surface Coated with a Polarizable Dielectric Layer: Theory and Experiment

Abstract

In the present study, we have derived a formula for the electrostatic force between the conducting tip and a metallic sample coated with a thin layer of polarizable dielectric of known dielectric constant by exploiting the fact that the tip-sample configuration in scanning probe microscopes can be represented as confocal hyperboloid surfaces of revolution in a prolate spheroidal coordinate system. The general behavior of the dependence of the force on tip-sample separation and the thickness of the dielectric film has been experimentally verified using a conducting atomic force microscope. The results are in better agreement with prolate spheroidal coordinate system over a wide range of tip-sample distances than the results obtained by the widely used sphere-on-plane approximation. [DOI: 10.1380/ejssnt.2011.206]