Round Robin Test for the Quantification and Standardization of Sample Damage during XPS Measurements

To evaluate sample degradation during XPS measurement, a round-robin test involving five laboratories was carried out with four kinds of samples such as cellulose nitrate (NC), polyvinyl chloride (PVC), silicon wafer modified with chloropropyltriethoxysilane (CPTES-Si) and gold substrate modified with 1H, 1H, 2H, 2H-perfluorodecanethiol (PFDT-Au) as model samples. In each sample, the degradation behavior followed first-order kinetics with respect to the relative dose provided by the peak intensity of either Ag 3d5/2 or Au 4f derived from Ag or Au substrates, respectively, as an index of X-ray dose. The result shows that the rank order of the damaging factors of samples was almost the same in each apparatus, but the obtained values were different among the apparatuses. On the other hand, from comparison of Au and Ag substrates for calculating relative X-ray dose, it can be seen that the damaging factors using those two metal substrates are almost equivalent. Considering the convenience in handling and the sputtering process, we concluded that Au substrate is more suitable for an index material to estimate relative X-ray dose. Furthermore, the relative damaging factor RDF, i.e. the damaging factor of each material divided by that of PFDT-Au as a reference material, did not depend on the difference of the apparatuses, and indicated close value for each sample, suggesting that the RDF should have universality and provide an useful information for evaluating sample degradation. Thus, the construction of that database would allow the prediction of the sample degradation by measuring degradation behavior of PFDT-Au as a reference material.