Characterization of the reaction film formed by zinc dialkyldithiophosphate using two different ellipsometric analyses

Two functionally different ellipsometry, spectroscopic ellipsometry (SE) and color-imaging ellipsometry (CIE) were employed to measure the thickness of film formed by zinc dialkyldithiophosphate on a steel surface during a friction test. In SE, the optical constants of the film were parameterized by one Lorentz oscillator, and the film thickness was then determined to be approximately 110 nm by regression-fitting of the data generated by the oscillator model to the experimental data. In CIE, the intensity of the reflected light from the film was converted to the distribution of the film thickness. Quantification of distribution of thickness provided much information regarding the morphology and topography of the film.