Quantitative X-ray photoelectron spectroscopy explained for specialists and non-experts

Across fields, X-ray photoelectron spectroscopy (XPS) has practical applications in the identification of chemical species. XPS spectra also have lesser-known additional uses, which Alex Shard highlights in a tutorial which teaches readers how to comprehend and utilize XPS data to its fullest.

“I attempted to set out the most important issues to be aware of when trying to perform XPS measurements,” said Shard. “This is my attempt at summarizing a vast effort undertaken by others over many years that has resulted in XPS becoming a standard analytical tool in industry and academia.”

Divided into sections based on the instrument, information, data and reporting, the tutorial breaks down the process of gathering XPS measurements. In response to an increased interest in reproducibility, Shard hopes to make the technique accessible to non-experts as XPS becomes more mainstream. Specifically, Shard focuses on how to use XPS in a quantitative manner, where multiple intensities in XPS spectra are compared to ascertain the amount of material at the surface of a sample.

The tutorial highlights significant sources of error commonly encountered during XPS experimentation and goes into detail on how to avoid them. For instance, by testing the performance of the device on a weekly basis and getting to know how long it takes to equilibrate, researchers can maintain consistency and repeatability of data.

“I am excited to see the current drive from manufacturers to use higher energy X-ray sources to look deeper into materials. This should reveal more information about the depth distribution of chemicals,” said Shard. “I hope that the lessons that have already been learned in ‘standard’ XPS can be translated to make these newer instruments reliable, comparable and accurate.”

Source: “Practical guides for x-ray photoelectron spectroscopy: Quantitative XPS,” by Alexander G. Shard, Journal of Vacuum Science & Technology A (2020). The article can be accessed at https://doi.org/10.1116/1.5141395 .