Auger Photoelectron Coincidence Spectroscopy

Abstract

Auger photoelectron coincidence spectroscopy (APECS) involves measuring an Auger line in coincidence with the corresponding photoelectron line of an X ray excited spectrum. Such spectra are free of many of the complicating features of conventional data and display the correlations that exist between the lines. APECS has been used to study a number of fundamental aspects of Auger spectroscopy, such as the removal of complicating effects due to Coster-Kronig transitions in the LZ.3 VV spectra of Cu. We have been able to show similar behaviour in the Auger spectra of Co. In principle, APECS can also be used to make measurements of surface core level shifts, to examine the process of electron scattering in solids, and it holds some promise as a technique for the routine examination of materials. The coincidence technique discriminates against secondary electrons in the background, the Auger and photoelectron peaks appear on a flatter background, and this helps to make the interpretation of Auger data collected in coincidence more straightforward. A number of successful APECS experiments have been constructed, using either X ray tubes or synchrotrons as sources. When an X ray tube is used as a source, the principal problem has been with the length of time needed to acquire a sufficient number of counts. We have recently completed construction of a novel spectrometer that goes someway towards overcoming this problem, however the challenge still remains to produce an instrument that will permit routine measurement of these features.