Measurement of dispersive forces between evaporated metal surfaces in the range below 100 nm

TL;DR

This study measures dispersive forces between gold surfaces at separations below 100 nm using atomic force microscopy, showing good agreement with theoretical predictions when accounting for optical properties and surface roughness.

Contribution

It provides precise measurements of van der Waals/Casimir forces at nanometer scales and compares them with theory including real material properties.

Findings

Force measurements agree with theory within 10%

Surface roughness and optical properties are crucial for accurate predictions

Dispersive forces are significant below 100 nm

Abstract

In this work we describe dispersion force (van der Waals/Casimir) measurements between gold surfaces at separations as close as 12 nm. The force measurements were performed in the plane-sphere configuration by Atomic Force Microscopy at distances ranging between 12 and 200 nm. This was accomplished by using evaporated smooth metal surfaces for both sphere and plane, and stiff cantilevers to minimize jump-to-contact problems. Finally, it is shown that below separations of 100 nm experiment and theory are found in agreement within 10 % by including in the theory the measured optical properties of gold and contribution from surface roughness.