A study of the electromagnetic fluctuation induced forces on thin metallic films

TL;DR

This paper investigates electromagnetic fluctuation forces on thin metallic films using a plasma model, revealing how these forces depend on film size, plasma frequency, and substrate interactions, including force sign changes.

Contribution

It provides a detailed analysis of fluctuation-induced forces on metallic films, highlighting the impact of substrate properties and film thickness on force magnitude and direction.

Findings

Force is attractive and peaks at specific plasma frequencies.

Force can switch from attraction to repulsion by changing substrate plasma frequency.

Force magnitude on film boundaries and substrate are comparable for 50-100 nm films.

Abstract

Using the plasma model for the metal dielectric function we have calculated the electromagnetic fluctuation induced forces on a free standing metallic film in vacuum as a function of the film size and the plasma frequency. The force for unit area is attractive and for a given film thickness it shows an intensity maximum at a specific plasma value, which cannot be predicted on the basis of a non retarded description of the electromagnetic interaction. If the film is deposited on a substrate or interacts with a plate, both the sign and the value of the force are modified. It is shown that the force can change sign from attraction to repulsion upon changing the substrate plasma frequency. A detailed comparison between the force on the film boundaries and the force between film and substrate indicates that, for 50-100 nm thick films, they are comparable when film-substrate distance is of the order of the film thickness.