Effects of electric field on XPS measurements.

Abstract

X-ray Photoelectron Spectroscopy is a widely used technique in analyzing the chemical state of a material. However, the presence of a potential difference in the material often complicates analysis. This can lead to erroneous attribution of peak binding energy that results in wrong analysis of the photoemission data. The field effect present causes changes in the lineshape and the binding energy and in this work this will be carefully examined. We introduce simulations of XPS core-level peaks through modeling peak shape changes by varying parameters such as the original line width of the element, mean free path and different field effects. We found that the mean free path and initial FWHM are crucial starting parameters for lineshape changes with the effects of potential. We also found that although potential, film thickness and field are related, interplay between them means that a simple relationship is not possible. Instead, the relationship between the film thickness and mean free path affects the effective field that can change the lineshape. Finally, we tested our model against experimental data. We found that we can predict not only surface potential that is present, but also on initial lineshapes that will be useful in the future to understand broadening relationship. We also suitably explain phenomenon of asymmetric peaks towards lower binding energies that previously has been difficult.