X-ray photoelectron spectroscopy: towards reliable binding energy referencing

Publication date: Available online 30 July 2019Source: Progress in Materials ScienceAuthor(s): G. Greczynski, L. HultmanAbstractWith more than 9000 papers published annually, X-ray photoelectron spectroscopy (XPS) is an indispensable technique in modern surface and materials science for the determination of chemical bonding. The accuracy of chemical-state determination relies, however, on a trustworthy calibration of the binding energy (BE) scale, which is a nontrivial task due to the lack of an internal BE reference. One approach, proposed in the early days of XPS, employs the C 1s spectra of an adventitious carbon layer, which is present on all surfaces exposed to air. Despite accumulating criticism, pointing to the unknown origin and composition of the adventitious carbon, this is by far the most commonly used method today for all types of samples, not necessarily electrically insulating. Alarmingly, as revealed by our survey of recent XPS literature, the calibration procedure based on the C 1s peak of adventitious carbon is highly arbitrary, which results in incorrect spectral interpretation, contradictory results, and generates a large spread in reported BE values for elements even present in the same chemical state. The purpose of this review is to critically evaluate the status quo of XPS with a historical perspective, provide the technique’s operating principles, resolve myths associated with C 1s referencing, and offer a comprehensive account of recent findings. Ow...
Source: Progress in Materials Science - Category: Materials Science Source Type: research