---
abstract: 'In this paper we investigate the influence of ultra thin water layer ($\sim 1-1.5\; nm$) on the van der Waals/Casimir force between gold surfaces. Adsorbed water is inevitably present on gold surfaces at ambient conditions as jump-up-to contact during adhesion experiments demonstrate. Calculations based on the Lifshitz theory give very good agreement with the experiment in absence of any water layer for surface separations $d\gtrsim 10\; nm$. However, a layer of thickness $h\lesssim 1.5\; nm$ is allowed by the error margin in force measurements. At shorter separations, $d\lesssim 10\; nm$, the water layer can have a strong influence as calculations show for flat surfaces. Nonetheless, in reality the influence of surface roughness must also be considered, and it can overshadow any water layer influence at separations comparable to the total sphere-plate rms roughness $w_{shp}+w$.'
author:
- 'G. Palasantzas'
- 'V. B. Svetovoy'
- 'P. J. van Zwol'
title: 'Influence of water adsorbed on gold on van der Waals/Casimir forces'
---

Introduction {#Sec1}
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When material objects such as electrodes in micro/nanoelectromechanical system are separated by distances of $100\;nm$ or less forces of quantum origin become operative [@Ser97; @Cle03; @Cha01]. These are the van der Waals (vdW) and Casimir 