Silicon-based nanoelectronic field-effect pH sensor with local gate control

The authors demonstrate the operation of a nanoscale field-effect pH sensor engineered from a functionalized silicon nanowire. With this nanofabricated pH sensor, the change in the hydrogen ion concentration or the pH value of a solution can be detected by the corresponding change in the nanowire differential conductance with a resolution of +/- 5nS/pH. Fabrication of selective side gates on the nanowire sensor allows field-effect control of the surface charge on the nanowire by controlling the accumulation of charge carriers with the side-gate voltage. A simple physical model is used to analyze the observed data and to quantify the dependence of the conductance on pH. The development of a nanoscale sensor with physically engineered gates offers the possibility of highly parallel labeling and detection of chemical and biological molecules with selective control of individual array elements.