Auger photoelectron coincidence spectroscopy: simplifying complexity

Abstract

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.

Direct and core-resonant double photoemission from Cu(001)

“…In previous APECS experiments the energy of one fixed analyser scanned [8][9][10][11][12][13], which imposes a constraint on the uncertainty of one electron and consequently on the other electron of the correlated pair. By detecting correlated pairs over a wide energy range without imposing any restriction on the energy of either electron we reveal that the energy of both electrons is not strictly limited to the lifetime-broadened lines that are observed when each electron is detected individually by single-electron (noncoincidence) spectroscopy.…”

“…A second electron may be excited to the continuum by an Auger (autoionization) transition in which the core-hole is annihilated, leaving two holes in the valence band. Auger photoelectron coincidence spectroscopy (APECS) has been developed to study this process, motivated also by the ability to yield information not directly accessible by single-electron spectroscopy [8][9][10][11][12][13][14][15][16].…”

Detection systems for mass spectrometry imaging: A perspective on novel developments with a focus on active pixel detectors

“…Currently, MCPs in combination with crossed‐delay line detectors or cross‐strip anodes are used for imaging atom probe, COLTRIMS, MSI experiments, X‐ray photoelectron spectroscopy (XPS), and Auger photoelectron spectroscopy for surface chemistry. The MCP, phosphor screen, CCD camera combination is used for microprobe mode MSI and velocity map imaging experiments .…”

Auger photoelectron coincidence spectroscopy of molecules adsorbed on a gold wire surface

“…The significance of this technique was recognized with the Nobel Prize in 1981, awarded to Kai Siegbahn for his work on electron spectroscopy for chemical analysis [1]. Moreover, it has been long acknowledged [2,3] that detecting Auger electrons in coincidence with associated photoelectrons-known as Auger photoelectron coincidence spectroscopy (APECS)can significantly enhance the interpretation of Auger spectra, which may otherwise be complex or/and congested. Although * Author to whom any correspondence should be addressed.…”