On the choice of the residual norm function in the interpretation of ARXPS data by regularized fitting

Angle‐resolved X‐ray photoelectron spectroscopy (ARXPS) data taken on a polystyrene film exposed to a nitrogen plasma are interpreted by the fitting of regularized depth profiles. Three ways of measuring the goodness of fit are compared—the χ² statistic with variances drawn from the raw spectra, the χ² statistic with variances drawn from the concentration figures obtained from the data analysis, and a simple sum of the squared differences (ssd) that does not require variances to be calculated. It is shown that for these data, the depth profiles obtained using an objective method for the choice of the regularization parameter are essentially identical irrespective of whether or how the variances are introduced into the calculation. Copyright © 2010 John Wiley & Sons, Ltd.