Interpretation of the Shirley background in x-ray photoelectron spectroscopy analysis

This brief review sets out the facts concerning the intrinsic nature of the asymmetric background step associated with most peaks in an x-ray photoelectron spectroscopy spectrum. This step is most clearly seen if the extrinsic background is first subtracted by the methods suggested and developed by Tougaard. Recent work using synchrotron radiation has confirmed that the intrinsic loss tail is generated as a one-step process during photoemission and thus corresponds to a shakeup excitation to a continuum of final states. The background is useful in identifying compound formation and in some cases, can point to hybridization of the p and d orbitals. The review illustrates how the use of predetermined backgrounds gives advantages in curve fitting and concludes with a discussion of the impact of intrinsic losses on quantification. (C) 2001 American Vacuum Society.