Subthreshold operation of Schottky barrier silicon nanowire FET for highly sensitive pH sensing

Presented is the notion that the sensitivity of Schottky barrier silicon nanowire field-effect transistors (SB-SiNWFETs) to hydrogen ions is strongly modulated by back-gate voltage. The sensitivity is evaluated by measuring the current variation ratios compared at various back-gate voltages and electrolyte potentials. The characteristics are complemented by monitoring the conductance response to exchange of pH level in the time domain. The response shows that the differential current increases with back-gate voltage, whereas the current variation ratio converges to unity. The conductance response to exchange of pH level reveals that the operation in the subthreshold regime gives rise to 30% enhancement in the sensitivity for the detection of hydrogen ions.