Extraction of material parameters of a bi-layer structure using Terahertz time-domain spectroscopy

For a bi-layer structure consisting of a film deposited on a substrate, a new extraction method is proposed using which we can extract both the material parameters of the film and the thickness of the substrate from the measured Terahertz transmission through it, so long as the complex refractive index of the substrate is known beforehand. This method is applicable to a range of refractive indices of the film less than the refractive index of the substrate and a very wide range of layer thicknesses from 20 mu m to at least 200 mu m. It is very useful in some cases where the thickness of the substrate cannot be determined using conventional methods such as a Vernier caliper or micrometer screw.