Room-temperature oxidation of Fe(100), Fe(100)-3.5 wt.% MoN and segregated MoN: a mathematical analysis

The room-temperature oxidation of Fe(100), Fe(100)–3.5 wt.% MoN and a segregated MoN layer were compared with each other by using Auger electron spectroscopy. The linear least-squares method was applied successfully to the low-energy Fe AES peaks to obtain the fraction of metal and oxide as a function of oxygen exposure time. The backscattering term is, however, a function of the oxide coverage and an illogical decrease in the oxide thickness at higher exposures were measured. The high-energy Auger peak-to-peak heights of Fe were also used to calculated the oxide thickness at different exposure times and these oxide thickness values were used to calculate the backscattering term for the different oxides as a function of exposure time. The backscattering term for the segregated MoN layer on the Fe(100)–3.5 wt.%MoN specimen is a combination of the backscattering from MoN, the iron oxide and the substrate. The profile indicates how important the change in the backscattering term may be for accurate surface concentration calculations. The backscattering terms for the Fe(100) and Fe(100)−3.5 wt.% MoN decrease exponentially with an increase in the oxygen exposure, which is in direct correlation with the logarithmic growth law of the oxides on the samples. Copyright © 2002 John Wiley & Sons, Ltd.