Determination of the dielectric constant of non-planar nanostructures and single nanoparticles by electrostatic force microscopy

Abstract

Electrostatic Force Microscopy has been proven to be a precise and versatile tool to perform quantitative measurements of the dielectric constant of thin film domains in the nanometer range. However, it is difficult to measure non-planar nanostructures because topographic crosstalk significantly contributes to the measured signal. This topographic crosstalk due to distance changes between tip and substrate measuring non-planar surface structures is still an ongoing issue in literature and falsifies measurements of the dielectric constant of nanostructures and nanoparticles. Tip and substrate form a capacitor based on the contact potential difference between the tip and substrate material. An increase of the distance between tip and substrate causes a repulsive force while a decrease causes an attractive force. Thus, measuring in the so-called lift mode scanning the surface in a second scan following the topography determined by a first scan leads to a mirroring of the non-planar surface structure in the electrostatic signal superimposing the signal from dielectric contrast. In this work we demonstrate that the topographic crosstalk can be avoided by using the linear mode instead of the lift mode. The use of the linear mode now allows the determination of the dielectric constant of single nanoparticles.