SIMPLE METHOD OF DEPTH PROFILING (STRATIFYING) CONTAMINATION LAYERS, ILLUSTRATED BY STUDIES ON STAINLESS-STEEL

Stainless-steel artefacts are used as reference masses for the calibra tion of balances and instruments involving force. The surfaces of thes e masses react with the environment, leading to changes in the chemist ry of the steel surface, accretion of surface contamination layers and a dynamic absorption of moisture in those contamination layers. In or der to understand these layers, to stabilize or correct for the concom itant mass changes, it is important to define what chemical states are developing and their stratification at the surface. Four chemical sta tes are identified in the oxygen XPS peak and four in the carbon peak. In the project a very large number of samples are studied and so a ra pid, simple stratifying method has been developed requiring measuremen ts at only two angles of emission. The method, which involves a simple ratio of the peak intensities either after separation of the states o r by using the peak envelope, or just by ratioing the whole spectra at the two angles enables the stratification and other parameters to be readily determined for all eight peaks.