The effect of patch potentials in Casimir force measurements determined by heterodyne Kelvin probe force microscopy

TL;DR

This study uses advanced Kelvin probe force microscopy to analyze how surface potential variations on gold surfaces affect precise Casimir force measurements, revealing that surface preparation influences patch potentials and force calculations.

Contribution

It demonstrates that heterodyne Kelvin probe force microscopy enhances spatial resolution and shows how patch potentials vary with surface treatment, impacting Casimir force measurements.

Findings

HAM-KPFM improves spatial resolution over AM-KPFM

Patch potentials depend on surface preparation methods

Calculated electrostatic pressures can match differences in Casimir models

Abstract

Measurements of the Casimir force require the elimination of electrostatic interactions between the surfaces. However, due to electrostatic patch potentials, the voltage required to minimize the total force may not be sufficient to completely nullify the electrostatic interaction. Thus, these surface potential variations cause an additional force, which can obscure the Casimir force signal. In this paper, we inspect the spatially varying surface potential (SP) of e-beamed, sputtered, sputtered and annealed, and template stripped gold surfaces with Heterodyne Amplitude Modulated Kelvin Probe Force Microscopy (HAM-KPFM). It is demonstrated that HAM-KPFM improves the spatial resolution of surface potential measurements compared to Amplitude Modulated Kelvin Probe Force Microscopy (AM-KPFM). We find that patch potentials vary depending on sample preparation, and that the calculated pressure can be similar to the pressure difference between Casimir force calculations employing the plasma and Drude models.