Investigation of CoPd alloys by XPS and EPES using the pattern recognition method

The electrons elastically backscattered from a solid surface are visualised in the elastic peak electron spectroscopy (EPES) spectra, which intensity recorded at certain geometry and energy of primary electrons, is a measure of electron backscattering probability. The theoretical description of electron interaction with a solid surface reflected in the EPES spectrum and its vicinity is of a complex character.In the present work the EPES method was applied for quantification of the in-depth composition in sputter-cleaned CoPd alloys and annealed Co50Pd50 at different measurement geometries and electron energies. The present approach applies the pattern recognition method called the fuzzy k-nearest neighbour (fkNN) rule to the line shape analysis of the EPES spectra recorded at Co, Pd and CoPd alloys. The proposed method was successful for distinguishing qualitatively the effect of the surface roughness, the texture and the grain size, and for identifying quantitatively the surface composition. Discrepancies between the results are discussed, within the limitations and sensitivity of the applied method, and the accuracy of the electron elastic cross-sections.