Transport of Secondary Electrons Through a Film of Condensed Water; Implications for Imaging Wet Samples

Abstract

We have performed a theoretical and experimental study of the the effect that a surface layer of condensed water has on the emission of secondary electrons from the surface. This is an issue of considerable interest to users of the Environmental SEM (ESEM) when imaging wet samples. Previous work has been performed to investigate the effect of a layer of water on back scattered electrons (BSE), but secondary electron (SE) imaging is more commonly used in ESEM, so an understanding of the interactions of SE with water is important. The aim of this work is to quantify the thickness of water through which imaging is possible, by considering both the interactions of secondary electrons with the water, and the interactions of the water layer with the sample, which may affect the secondary electron emission coefficient, δ.The effects that a surface layer of water may have on electron emission from a sample surface can be split into three regimes.