Optical analysis of coatings by variable angle spectrophotometry

Variable angle spectrophotometry (VAS) involves measurement of transmittance and reflectance as a function of the angle of incidence, wavelength and polarisation. This provides a means for analysis that yields the thickness and optical constants of the individual layers in multi-layer coatings, as well as other parameters that can be related to optical material properties. In the past decade, VAS has evolved into an accurate tool for optical characterisation of coatings, with many advantages over ellipsometry.The paper describes the tools for measurement and analysis developed by the author for the UV/Vis/NIR and IR wavelength ranges. Examples are given for single- and multilayer stacks with materials like ZnO, Cr, ITO and SiO2.