Quantitative measurements of dielectric spectra using microdielectric fringe-effect sensors

Microdielectric fringe-effect sensors are miniature planar interdigitated structures, which can be used in situ and in real time to measure electrical properties of materials, such as dielectric loss and storage, at the interface between the sensor and the sample. However, interpretation of the fringe-effect (FE) measurements is difficult due to the complexity of the excitation electrical field created by the FE sensor and the contribution of the sensor substrate and stray elements to the measured properties. In this paper, we present the basic theory, which relates the broadband impedance measurements obtained with the fringe-effect sensors and the actual electrical properties of the materials under test (MUT), and develop the calibration procedure which allows us to separate the contribution of the MUT sample and the sensor substrate from the overall measurements. Using the result of calibration as an initial guess, we then develop a compensation method, which allows us to remove the contribution of unknown properties of the FE sensor and other stray elements from instrumental measurements.