Sensors, Vol. 19, Pages 4118: A Sensitive and Versatile Thickness Determination Method Based on Non-Inflection Terahertz Property Fitting

Sensors, Vol. 19, Pages 4118: A Sensitive and Versatile Thickness Determination Method Based on Non-Inflection Terahertz Property Fitting
Sensors doi: 10.3390/s19194118
Authors:
Xuequan Chen
Emma Pickwell-MacPherson

The accuracy of thin-film characterization in terahertz spectroscopy is mainly set by the thickness uncertainty. Physical thickness measurement has limited accuracy for thin-film samples thinner than a few hundreds of micrometers and is sometimes even impossible. The temporal resolution of time-domain terahertz spectrometers is not sufficient to resolve such thin films. Previously reported numerical methods mainly only work for materials with low dispersion and absorption. Here, we propose a novel method for thickness determination by fitting a non-inflection offset exponential function to the material optical properties. Theoretical analysis predicts the best fitting to only be achieved when the correct thickness is given. Transmission measurements on a thin-film polymer, water, and a lactose pallet verify the theory and show the accurate thickness determination and property characterization on materials which are either achromatic or dispersive, transparent or absorptive, featureless or resonant. The measurements demonstrate the best versatility and sensitivity compared to the state-of-art. The method could be widely adapted to various types of research and industrial applications.

Source: Sensors - September 22, 2019 Category: Biotechnology Authors: Xuequan Chen Emma Pickwell-MacPherson Tags: Article Source Type: research