High-frequency electrochemical impedance measurements of self-assembled monolayer formation using CMOS-based nanocapacitor arrays

Electrochemical impedance spectroscopy is mostly sensitive to the state of the electrode surface at low frequencies, where the electrical properties of the surrounding electrolyte do not yet dominate the response. The available frequency range increases linearly with the inverse electrode size, such that miniaturized electrodes offer the ability to probe the surface at higher frequencies. Measuring the AC response of miniaturized electrodes is however highly challenging due to the parasitic capacitance of the interconnects. Here we employ nanoelectrodes integrated with readout circuitry on the same complementary metal-oxide-semiconductor (CMOS) chip to conduct measurements over a frequency range from 1.6 MHz to 50 MHz. We report the ability to probe the formation of self-assembled monolayers at frequency above 10 MHz in phosphate-buffered saline solution.