Deconvoluting the Electric-Shielding Effect of Ubiquitous Water in Kelvin Probe Force Microscopy: Finite Element Approach*

An electrostatic Finite Element (FE) model was employed to investigate how the presence of a water meniscus influences the surface potential difference between a simulated tip at a constant electric potential and a flat surface. This numerical approach provided valuable insights into the interplay between a two-dimensional vertical heterostructure material surface and ambient water, which holds importance in the design of functional devices. Kelvin Probe Force Microscopy (KPFM), an experimental technique used to study electronic and topological properties of material surfaces with nanoscale precision, was conducted in varying relative humidity environments. Our numerical methodology and experimental KPFM findings exhibited a close correspondence, revealing an inverse relationship between rising humidity levels and the reduced contrast in surface potential. Based on our results, we posit that this extrinsic effect can be attributed to the electric potential shielding effect of water and therefore subtracted in the experimental KPFM to understand the intrinsic properties of a sample in the presence of ambient water.