Abstract
The experimental detection of capacitance variations with a resolution as low as few zeptoFarads (10−21F) is presented. This is achieved by means of a CMOS ultra-low-noise and wide-bandwidth current sensing circuit, coupled to a lock-in amplifier to perform capacitance and conductance measurements in a frequency range from DC to 1MHz. The adoption of an integrated implementation, based on an original circuital topology, provides miniaturization and performance improvement. The mm-sized chip can be easily integrated in extremely compact sensing setups. Resolution limits are analyzed in detail and experimentally investigated by means of a mechanical fixture that converts micrometric linear displacement into sub-aF capacitance steps. The experimental results match the theoretical expectation down to a resolution of 5zFrms (6V at 100kHz, with a 100ms time constant). The achieved current resolution of 15fArms (at ∼ms time scale) and the tracking of 40zF capacitance steps demonstrate how the proposed read-out circuit can serve as a versatile tool for the development of nanosensors.
Published Version
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