Sensor array on structured PET substrates for detection of thin dielectric layers at terahertz frequencies

A method to increase the sensitivity for detection of thin dielectric materials with low thickness below 10 μm is presented. By structuring a Polyethylene terephthalate (PET) substrate and introducing a floating electrode in a resonant Jerusalem cross unit cell, the sensing electric field can be confined in the thin material under test (MUT) yielding an increased sensitivity compared to strictly planar resonant structures. Analysis of the achievable sensitivity in terms of resonance frequency shift is performed for MUT thicknesses below 10 μm at 0.5 THz. Measurements demonstrate the detection of a dielectric layer with a relative permittivity of 2.4 and thickness of 3.3 μm.