Evaluation of take‐off‐angle‐dependent XPS for determining the thickness of passivation layers on aluminium and silicon

Abstract

Investigating the effect of a cleaner (used to remove lubrication oil residues) on the surface composition of rolled aluminium foils, we applied angledependent XPS to determine the thickness of the passivation layer on these foils. We found the simple uniform overlayer model, which bas frequently been applied to translate XPS intensity ratios into a value for the overlayer thickness, to be inapplicable on these aluminium foils. However, data obtained from an Si(100) singlecrystal surface were in rather good agreement with the model. SEM images from the aluminium foils show that their surface is rough on the (sub)micron scale. We believe this roughness to be the reason for the inapplicability of the uniform overlayer model. Simulations of XPS intensity ratios for model rough surfaces support this point of view. Both experiment and simulations make it clear that one should not base XPS thickness determinations on one measurement only, because in that case the applicability of the uniform overlayer model cannot be checked.

Preparation of a rhodium catalyst from rhodium trichloride on a flat, conducting alumina support studied with static secondary ion mass spectrometry and monochromatic X-ray photoelectron spectroscopy

“…We note, however, that the assumption of a flat surface is a particularly critical one. Surface roughness may cause the actual average layer thickness to deviate as much as 1 nm from the calculated value [9].…”

Interfacial Reactivity of Au, Pd, and Pt on BiI3 (001): Implications for Electrode Selection

“…A decrease in relative peak intensity with the increasing takeoff angle is typically observed for subsurface species as a result of the decreased sampling depth for this geometry. 22,23 As discussed above, the appearance of metallic Bi, PdI 2 and I 2 is attributed to an interfacial reaction. The angle dependent results provide additional evidence of this interfacial reactivity and indicate that the reaction products are primarily located at the surface.…”

The Thickogram: a method for easy film thickness measurement in XPS

“…Thin oxide layers on Al and Si are of great technological importance 3,4 and are ideal for Eqn (1). Chemical shifts and peak fitting allow the intensities of overlayer and substrate peaks to be measured, 5 but these chemical shifts are sufficiently small that the signal electrons from oxide and substrate have very nearly the same energy and therefore almost identical attenuation lengths in the oxide.…”