Adsorbate induced enhancement of electrostatic non-contact friction

TL;DR

This paper presents a theoretical study showing that adsorbates supporting acoustic vibrations can significantly enhance non-contact friction between an AFM tip and a metal surface, aligning with recent experimental observations.

Contribution

It introduces a model explaining how adsorbate layers amplify electrostatic non-contact friction via acoustic vibrations, matching experimental data.

Findings

Adsorbate layers can increase friction by orders of magnitude.

Even isolated adsorbates can produce measurable friction.

The theory agrees with recent experimental results.

Abstract

We study the non-contact friction between an atomic force microscope tip and a metal substrate in the presence of bias voltage. The friction is due to energy losses in the sample created by the electromagnetic field from the oscillating charges induced on the tip surface by the bias voltage. We show that the friction can be enhanced by many orders of magnitude if the ads orbate layer can support acoustic vibrations. The theory predicts the magnitude and the distance dependence of friction in a good agreement with recent puzzling non-contact friction experiment \cite{Stipe}. We demonstrate that even an isolated adsorbate can produce high enough friction to be measured experimentally.