Surface topography effects on glow discharge depth profiling analysis

Glow discharge optical emission spectroscopy (GD-OES) has been shown to be of immense value in elemental depth profiling of thin or thick films on conductive or non-conductive substrates. For aluminium, GD-OES has been employed to examine locations of markers and tracers in anodic films, thereby assisting understanding of transport phenomena. In order to investigate the influence of surface topography on depth profiling analysis, anodic aluminium oxide films of various thicknesses, with incorporated electrolyte species, were produced on superpure aluminium substrates of controlled roughnesses. The distributions of incorporated species in the films were subsequently probed. Surface topography modifications and consequent depth resolution degradation were examined during depth profiling analysis performed by GD-OES. The results reveal that the sputtering process leads to the roughening or smoothing of the surface topography of the specimen for a ratio of the film thickness to the amplitude of the substrate texture less, or greater, than 1 respectively. As a consequence of the surface topography dependence of the ion bombardment, analysis of thin films over rough surfaces suffers from depth resolution limitations due to sputtering-induced topography changes, thereby limiting quantification of the resultant spectra. Copyright (C) 2010 John Wiley & Sons, Ltd.