Auger photoelectron coincidence spectroscopy : simplifying complexity

The use of X-ray photoelectron spectroscopy (XPS) is expanding rapidly with the advent of more convenient, high-resolution laboratory-based instruments. The increase in the numbers and distribution of synchrotrons has also fuelled this burgeoning interest. Powell (C. J. Powell, J. Vac. Sci. Technol. A 21 (S42) 2003) has shown that the number of papers published on or using XPS has doubled in the past 10 years. He reports that there are in excess of 3000 papers published using XPS data each year across a wide range of applications, making it the most important technique for the determination of the composition of nano-scale surface films. Yet XPS and the associated technique of Auger-electron spectroscopy (AES) are not yet developed to the stage where the data and its interpretation are unambiguous. Auger photoelectron coincidence spectroscopy (APECS) provides a means of simplifying spectra, allowing for the decomposition of these into components that have a common origin. The spectra so produced provide a unique opportunity to test theory. In this paper, we will review recent progress in developing better APECS spectrometers and illustrate the power of APECS with new data acquired by these.