Non-destructive in-depth composition profile of oxy-hydroxide nanolayers on iron surfaces from ARXPS measurements

In this work the maximum entropy method (MEM) is applied, for the first time, to angle-resolved X-ray photoelectron spectroscopy (ARXPS) data from oxy-hydroxide films on iron surfaces. This nondestructively derives information on the in-depth distribution of the composition and chemical state. An MEM algorithm was created and first tested on the simulated data. The reconstructed composition depth profiles agreed very well with the theoretical ones up to 5% Gaussian noise added to the data. The same algorithm was then applied to ARXPS data from iron samples to investigate the in-depth variations in the composition and chemical state of the nanosized oxy-hydroxide film naturally grown on the iron surface. The resulting surface film presents a complex multilayer structure with concentration gradients. The effect of air exposure on the structure was also investigated. Copyright (C) 2006 John Wiley & Sons, Ltd.