Principal component analysis with integral Auger electron spectroscopy spectra

Abstract

In this study, N(E) Auger electron spectroscopy (AES) depth profiles were obtained in the same determination for both the M2,3VV and LMM regions of Cu ion implanted in a 50–50 Co/Ni alloy. Principal component analysis (PCA) calculations on the M2,3 VV depth profile spectra suggested the presence of an additional component. The amount of Cu was estimated at about the detection limit in the M2,3VV depth profile when an averaged Co-Ni standard was used from the end of profile. This depth profile was similar to that obtained in an earlier study with derivative AES spectra. Simulated M2,3VV spectra (with added noise) for the ion implanted alloy indicated that Cu should be detected at a relative amount of 2 at. %. The number of components indicated by PCA in the integral LMM depth profile was the same as the number of standards employed. Again, the depth profile from the integral LMM spectra was similar to that obtained from the derivative spectra; in both cases the relative atomic amount of Cu was about three times that determined in the M2,3VV spectral region. Thus, preferential sputtering of Cu seems to be present and PCA could detect this effect. In addition, Co appeared to be preferentially sputtered compared to Ni. PCA analysis was not successful when loss features were removed (which cannot be done easily with derivative AES spectra) from both the M2,3VV and LMM spectra.