We have used liquid-gating to investigate the sensitivity of nanowire (NW)-based biosensors for application in the field of ultrasensitive biodetection. We developed an equivalent capacitance model of the biosensor system to explore the dependence of the sensitivity on the liquid-gate voltage (V(lg)), which was influenced by capacitive competition between the NW capacitance and the thin oxide capacitance. NW biosensors with highest sensitivity were obtained when we operated the device in the subthreshold regime while applying an appropriate value of V(lg); the influence of leakage paths through the ionic solutions led, however, to significant sensitivity degradation and narrowed the operating window in the subthreshold regime.

An unprecedented high sensitive sensing of neurotransmitter dopamine at fM level was demonstrated using a poly-crystalline silicon nanowire field-effect transistor (poly-SiNW FET) fabricated by employing a simple and low-cost poly-Si sidewall spacer technique, which was compatible with current commercial semiconductor processes for large-scale standard manufacture.

Defects present in the grain boundaries of polycrystalline materials are known to impede carrier transport inside the materials, and the electronic device performance having such materials as active channels will be adversely affected. In this work, dramatic improvement in device performance was observed as field-effect transistors with polycrystalline silicon nanowire (poly-SiNW) channels were exposed to a wet environment. Passivation of defects in the poly-SiNW by H+ and/or OH− contained in the aqueous solution is proposed to explain the phenomenon.