Parameter-free extraction of Thin-Film Dielectric Constants from Scanning Near Field Microwave Microscope Measurements

TL;DR

This paper introduces a parameter-free method to accurately determine the dielectric constants of thin-film materials at microwave frequencies using scanning near field microwave microscopy and finite element electromagnetic simulations.

Contribution

It presents a novel approach that combines finite element modeling with cavity perturbation theory to extract dielectric constants without fitting parameters, especially for thin films.

Findings

Successfully extracts dielectric constants with high spatial resolution.

Applicable to thin-film materials without fitting parameters.

Provides a direct link between measured shifts and material properties.

Abstract

We present a method for extracting high-spatial resolution dielectric constant data at microwave frequencies. A scanning near field microwave microscope probes a sample and acquires data in the form of the frequency and quality factor shifts of a resonant cavity coupled to the sample. The approach reported here is to calculate the electromagnetic fields by the finite element method in both static and time-dependent modes. Cavity perturbation theory connects the measured frequency shifts to changes in the computed energy stored in the electromagnetic field. In this way, the complex permittivity of the sample is found. Of particular interest are thin-film materials, for which a method is reported here to determine the dielectric constant without the need to use any fitting parameters.