The significance of reduced thicknesses determined by XPS using the variable take‐off angle technique

The results of quantitative XPS analysis show a systematic change when the sample surface is covered by an overlayer. An accurate knowledge of the reduced thickness ( x ) of the total overlayer (e.g. oxide plus contamination) allows the quantification of such changes. The total reduced thickness ( x ) can be determined from the photoelectron signals of the substrate measured for different take‐off angles. It is found that this method can be applied for reduced thicknesses up to x = 3 with an error Δ x estimated at less than 10%.