Revisiting contact potential difference in electrostatic force microscopy

Abstract

Understanding the tip-substrate interaction in Electrostatic Force Microscopy (EFM) is essential for the quantitative analysis of experimental data. In this work, the role of the contact potential difference (VCPD) between tip and substrate, both experimentally and theoretically, is investigated. Over the past decades, several models have been proposed to describe the tip-substrate interaction, commonly assuming an equipotential surface on the tip. A common feature of these models is the treatment of VCPD as an additional voltage, which is added to the externally applied voltage VDC. In EFM a non-zero vertex of the voltage parabola is reported in several publications which cannot be explained by theory so far. We investigate experimentally if a model with different contributions for cone and apex better explains experimental data.