Influence of System Performance on Layer Thickness Determination Using Terahertz Time-Domain Spectroscopy

The quality of coatings in industrial applications and scientific research with thicknesses in the micrometer range is an important criterion for quality management. Therefore, thickness determination devices are of high interest. Terahertz time-domain spectroscopy systems have demonstrated the capability to address thickness determination of dielectric single- and multilayer coatings on different substrates. However, due to the large range of different samples, there are different performance requirements to ensure a high-quality determination result. In this paper, we investigate the influence of system parameters-bandwidth and dynamic range-on thickness determination performance for a single-layer coating on metal substrates with thicknesses from 0.5 to 100 pm, based on measurements and numerical calculations within dynamic ranges from 10 to 90 dB and bandwidths from 1.5 to 10 THz.