MAXIMUM-ENTROPY - A NEW APPROACH TO NONDESTRUCTIVE DECONVOLUTION OF DEPTH PROFILES FROM ANGLE-DEPENDENT XPS

The application of the maximum entropy method to non-destructive depth profiling by angle-dependent XPS is described. The algorithm gives the set of depth profiles that has maximum Skilling-Jaynes entropy, subject to the condition that the calculated data agree with the measured data within the experimental precision. The method does not require an inverse transform, is robust to experimental noise and is not restricted to small numbers of components. The programme can determine which of a set of prior estimates for the depth profiles is most probable; however, the reconstruction near the surface is virtually independent of this choice. Further, the method also estimates the accuracy of the reconstruction from a single data set. It is illustrated using model data and by a re-analysis of angle-resolved XPS data sets available in the literature