Quantitative XPS surface analysis: Correction for contamination layer

Abstract

The validity of theoretical dependence of the reduced thickness of the contamination layer x on the intensity ratio of C1 s and C KVV lines has been considered. It is shown that the theoretical expression used for the determination of x gives contamination layer thicknesses which significantly exceed the real values. A semiempirical method for a more accurate determination of x, based on the measurement of the intensity ratio r= I C1 s / I C KVV , has been developed. Relative photoionization cross-sections for the 1 s shells of elements with 3≤ Z≤12, 2 s and 2 p shells of elements with 11≤ Z≤20 have been measured with the Al Kα excitation taking into account the presence of the contamination layer. In the case of several sulfates, it is shown that an allowance made for the contamination layer, the thickness of which is determined using the semiempirical method, reduces the systematic error during the quantitative XPS surface analysis.