Christine Creagh

The use of Auger photoelectron coincidence spectroscopy to deconvolute the M45N45N45 AES of Palladium

Palladium (Pd) has a complex Auger spectrum. It is difficult to fully describe the M45N45N45 Auger spectra of its surface atoms because of the many possible cascade processes placing intensity in this energy region. Weightman et al. described this Auger peak from a multiplet-splitting point of view and we used this model as a starting point. The model was compared to Auger photoelectron coincidence spectroscopy (APECS) data of the same peak and intensity was found in the M4N45N45 APECS spectra that could not be accounted for by Weightmans model. Thus new model curves for each component of the Auger peak were created by applying the Cini-Sawatzky Theory to the convoluted one-electron density of states. Experimental APECS data was used to verify the model curves and the final composite picture was compared to a high resolution AES spectrum. There was a good fit between the final model, the APECS data and high resolution AES data. The model also provided evidence for an M4-M5N45-N45N45(N45) Coster-Kronig process.

More Auger photoelectron coincidence spectra from copper

We have recently re-built our Auger photoelectron coincidence spectroscopy (APECS) system at Murdoch University. The new instrument counts at much higher rates and with greater energy resolution. With this we have looked again at the APECS spectra from Cu. We have been able to see more clearly the L2–L3V–VV(V) Coster–Kronig satellite and, in a reverse experiment, to find out which parts of the photoelectron spectrum are responsible for the satellite. The data also show the importance of shake-up/off processes in the background of the L3–VV line. We will present information on the changes we have made to the apparatus as well as the implications of the data we have collected with it.

Investigating the structure of the Tin M45N45N45 auger spectrum using auger photoelectron coincidence spectroscopy

Auger photoelectron coincidence spectroscopy (APECS) data were collected for the M45N45N45 Auger peak in coincidence with the 3p3/2, 3d3/2 and 3d5/2 photoelectron lines of Tin. Model spectra were created to fit the APECS data from sets of Gaussian curves defined by Parry-Jones et al., J. Phys. C: Solid State Physics, 12 (1979) 1587. These models were then combined using information about the relative intensities of the peaks from the aforementioned paper to produce a model of the Auger peak which proved a good comparison to high resolution AES spectra. The APECS data revealed satelite structure in the M5N45N45 peak in coincidence with the 3d5/2 photoelectron line (M5N45N45:3d5/2) due to the Mg Kα3 line of the X-ray source. There was evidence of a small Coster–Kronig component in the M4N45N45:3d3/2 data and the M45N45N45:3p3/2 data showed intensity in the M4N45N45 and M5N45N45 regions also arising from Coster–Kronig processes. The contribution of the M4N45N45 plasmon was included in each of the APECS models and was reflected in the high resolution AES spectra. Slight oxidation of the surface of the sample during each 24-h period produced a 0.7 eV shift of the singles Auger peak to lower kinetic energies. The shift was not reflected in the coincidence peak which produced a spectrum of a clean surface due to the nature of the coincidence experiment.

Auger photoelectron coincidence spectroscopy of the 2p1/2 line in coincidence with the L3-M45M45 peak of copper

As new surface analytical equipment becomes available, it is increasingly important to understand the physics behind the small satellites and features in electron spectra. Auger photoelectron coincidence spectroscopy (APECS) has been used to study the 2p1/2 photoelectron line (electrons from the L2 level) of copper in coincidence with the L3-M4,5M4,5Auger peak. The intensity in coincidence in the L3-M4,5M4,5 peak is due to a Coster–Kronig transition, L2-L3-M4,5M4,5(M4,5). We have found that there is a shift in the position of the photoelectron line when the Auger analyser is fixed at different positions in the low kinetic energy tail of the Auger peak. This is an unusual effect, which we attribute to an electrostatic interaction between the outgoing electrons, in a form of post-collisional interaction.