Ellipsometric studies are generally carried out in reflection mode rather than in transmission mode, requiring invariably opaque substrates or substrates in which the back reflection is minimized or suppressed by different methods. In the present work, we have used a transmission and reflection photo-ellipsometry method to study electrochromic materials and their multilayer systems deposited on thick substrates. The role of the substrate is examined carefully and the contributions from multiple reflections in the substrate are taken into account in the theoretical treatment. This procedure not only allows the study of thin films deposited on quasi-transparent substrates but carried out in conjunction with reflection measurements improves greatly the accuracy in the determination of the optical constants. Optical measurements have been carried out on an automatic reflection-transmission spectrophoto- ellipsometer. Solid state ionics materials used in electrochromic systems such as indium-tin oxide, tungsten oxide, and their multilayer structures deposited on glass substrates are used as examples. A software based on the above theory, OPTIKAN, has been developed to model and analyze such systems. It is demonstrated that the photo-ellipsometry method proposed is especially suited to analyze in a non-destructive way electrochromic materials and transmitting devices.
|