Towards Absolute Energy Referencing in XPS

Abstract

An inherent difficulty in X-ray photoelectron spectroscopy (XPS) regards the frequent emergence of spectral shifts due to probe-induced surface charging. Various energy-scale correction methods were already proposed, yet it is generally agreed that no fundamental answer to this problem has been demonstrated so far. Here, a method is proposed that can, in principle, address this issue and lead to a transformative improvement in XPS analyses. The method is based on extrapolation to the “zero exposure state” of the sample, based on a reference measurable at nearly zero charging conditions. Temporal changes in the surface potential can thus be monitored at high accuracy and subsequently be implemented to get the desired energy-scale calibration. This methodology demonstrates remarkable improvements in reliability and applicability of both the chemical and electrical XPS-based analyses.