Characterization and Capacitive Modeling of Target Concentration-Dependent Subthreshold Swing in Silicon Nanoribbon Biosensors

The effect of streptavidin concentration as a target molecule on the subthreshold swing (SS) of biotin-functionalized silicon nanoribbon sensors was investigated for a configuration of field effect transistors. The increasing concentration of conjugated target molecules was modeled as a degradation of the coupling capacitance between the electrolyte and the sensor surface. A binding factor for the ratio of conjugation between targets and receptors was modeled as a coupled capacitance and experimentally determined to be from 0.65 (streptavidin at 1 pM) to 1 (1 nM). This result suggests that SS is potentially a good indicator of the target concentration.