Emissivity as a method of surfaces and thin films analysis

Abstract

Limited to the field of pyrometry, the observation of thermal radiation has never been really used as a source of information for the characterization of material surface. An IR spectrometry technique which is briefly described has been conceived in order to study the influence of surface physico-chemical parameters on the directional and spectral emissivity (ελθ) of materials. One of these apparatus has been set up on a conventional UHV system equipped with AES and SIMS. The variation (Δϵϵ)λθ is recorded in situ during the evolution of a surface parameter. The examples shown are platinum deposit on graphite by vapour condensation, growth of an oxide film on metal, growth of homogeneous or inhomogeneous films, influence of the crystalline phase transition of a deposit, etc. For each case, an optical theoretical description has been carried out. From the comparison with other observations (electron microscopy. X-ray diffraction, AES and kinetic measurements), it is shown how the observation of (Δϵ)λθ enables us to obtain information on parameters such as the number, the shape or the orientation of islands in granular deposits, the crystal structure, the porosity of a film or the failure critical thickness of a coating.