A model for determining the composition of layer structured samples using XPS electron take‐off angle experiments

A model is presented for interpreting the results of electron take‐off‐angle(ETOA) experiments in x‐ray photoelectron spectroscopy (XPS). The surface region of a solid is treated as a multilayer structure where each layer is of homogeneous but different composition. The model is used to derive the true composition of a solid from the apparent compositions obtained by quantification of the spectra taken at each take‐off‐angle. All the species present are treated simultaneously to yield the physical structure of the surface region, within a maximum sampling depth of ∼5–10 nm, with no loss of chemical information. The validity of the model is demonstrated using ETOA data from a single layer of oxidised single crystal silicon. The derived layer stoichiometry and thickness agrees with the results which can be obtained using intensity ratio calculations which are restricted to the single layer case. As an example of the potential use of the model the structure of a Langmuir–Blodgett (L–B) film of cadmium stearate deposited on the oxidised silicon surface is investigated.