Relevance of Colorimetric Interferometry for Thin Surface Film Contaminants

Publisher Summary In the field of surface contamination and its removal, colorimetric interferometry constitutes a powerful tool to characterize the thickness of the contaminant layers. A broad spectrum of potential applications appears open to exploitation. The spatial and time resolution can be adapted to suit particular conditions, as can the environment of the surface at the time of its characterization. The optical instrumentation that can be employed offers a broad spectrum of possibilities from this point of view. The optical character of this technique confers the advantage of it being able to be coupled with other apparatus, in particular with those using the broad range of visible light, and so is likely to provide complementary information on the chemical or physical nature of the layers under investigation. Currently, the main constraint seems to be the need for a precise calibration that needs to be carried out under conditions as close as possible to those used during measurements. The practical difficulty is to constitute a starting point for this calibration, that is, to form defined layers of a known thickness. For this purpose, one has to fabricate thin-layers using a controlled process, even if the film formation process is different from that responsible for the surface contamination. In all cases, one does not avoid the need to know the properties of the medium under evaluation. Finally, constant attention needs to be given to the instrumentation, both from the optical aspects, and from those concerning picture digitalization and extraction of colorimetric information.