Towards a reliable characterisation of oxide layers on pure aluminium using high energy resolution FE‐AES

Abstract

AbstractAl2O3 on metallic aluminium is a widely used material of high technological importance. For the local chemical characterisation of these substrates, field‐emission Auger electron spectroscopy (FE‐AES) bears potential thanks to its high lateral resolution. In this study, the O KLL and Al KLL Auger electron spectral lines are recorded with high energy resolution from pure aluminium, thin Al2O3 and thick Al2O3 layers on metallic aluminium. The behaviour of these aluminium oxide layers under electron beam irradiation is investigated.It is demonstrated that, thanks to the high energy resolution used, it is possible to discriminate between the metallic and oxidised aluminium on the basis of the Al0 KL2, 3L2, 3 and Al3+ KL2, 3L2, 3 Auger electron peaks recorded within one and the same spectrum. Oxygen electron‐stimulated desorption is observed for both aluminium oxides. The estimation of the effective cross‐section for the oxygen desorption shows that the thin oxide layer is less stable against this phenomenon than the thick oxide layer. It is shown that when an Al2O3 layer is irradiated with an electron beam, surface charging occurs. These phenomena remain limited thanks to the presence of the underlying metallic aluminium substrate. Finally, it is shown that non‐homogeneities at the surface of the analysed oxides result in significant chemical shifts of the O KLL and Al KLL Auger electron transitions. Copyright © 2010 John Wiley & Sons, Ltd.