Differential charging in XPS. Part III. A comparison of charging in thin polymer overlayers on conducting and non-conducting substrates

Abstract

Previous work has used small-area and imaging XPS to show that differential charging in bulk insulators develops as a result of non-uniform x-ray flux across the surface, causing lateral differential charging. Charging in heterogeneous samples can be further affected by the local sample environment and sample mounting. The current work extends these studies through an analysis of differential charging effects in thin overlayers on conducting and insulating substrates. The charging observed in PnBMA overlayers on indium tin oxide, glass, Ag and Al is discussed as a function of substrate conductivity and photoelectron cross-sections. Substrate conductivity is the most significant factor in determining the magnitude of the overlayer charging observed when no charge compensation is utilized. Differential charging in the PnBMA overlayer was used to image a patterned substrate containing insulating and conducting areas. © 1997 John Wiley & Sons, Ltd.