Comparison of two parameter choice methods for the extraction of depth profiles by means of a regularized multipoint profile model from ARXPS data obtained on a three-component system

摘要

Polystyrene films were exposed to nitrogen plasmas for periods up to 8 min. Angle-resolved X-ray photoelectron spectroscopy measurements revealed the presence of oxygen and nitrogen in the surface due to the plasma treatment. The depth profiles of these adatoms were determined by fitting a regularized multipoint linear segment model to the data. A regularization parameter chosen such that the chi-square statistic of the fit to the data was equal to the number of independent data points gave a more intuitive result than a parameter chosen according to the L-curve criterion. Although the shape of the nitrogen depth profile was observed to vary as a function of the plasma duration, the oxygen depth profiles were nearly identical.