Microfabricated, silicon devices with nanowells and nanogap electrodes: a platform for dielectric spectroscopy with silane-tunable response

Combining the advantages of nanogap devices and impedance spectroscopy can potentially provide a platform for dielectric spectroscopy with widely ranging applications—from fundamental studies at the nanoscale and surfaces to label free and selective sensors. The present study characterizes the impedance response of a microfabricated, silicon-based device with a large array of nanowells surrounded by annular, nanogap detection regions. Device impedance is measured versus frequency over 5 orders in a variety of organic solvents with dielectric constants ranging over 2 orders. The study finds two key results. First, an equivalent R/C circuit model is found to compare favorably with device impedance response over these wide ranges of parameters. Importantly, the model correlates with structure of the nanogap device, which suggests that such a structure-impedance response approach can help guide modeling of other devices geometries. Second, the model points to—and data confirm—correlation between nanogap device response and dielectric constant of materials in the nanogaps, particularly at low frequencies. In addition, the correlation is significantly modified by robust, silane functionalization of the devices due to a large surface-to-volume ratio of the nanogaps. These results demonstrate that nanogap impedance spectroscopy using microfabricated/silanized silicon devices is a robust and versatile platform for dielectric spectroscopy of materials on the nanoscale and on surfaces.