ZnO/Silicon Nanowire Hybrids Extended-Gate Field-Effect Transistors as pH Sensors

Abstract

A new type of zinc oxide/silicon nanowire (ZnO/SiNW) hybrid is developed for use in an extended-gate field-effect transistor (EGFET) for pH sensors. SiNWs are first formed using the Ag-assisted electroless etching technique and are then covered with ZnO nanostructures through a combination of sol-gel and hydrothermal processes. The ZnO nanostructures were synthesized at 90°C for 3 h using precursor solutions with molar concentrations of 10 mM and 25 mM. The ZnO nanostructures provide a larger surface area than the pristine SiNWs for adsorbing additional H+ and OH− ions, along with increased oxygen-related binding to effectively sense H+ ions in the acid solution region. The 25 mM ZnO/SiNW sensors exhibited higher sensitivity (66 mV/pH) than pristine SiNW sensors (52 mV/pH). This simple and low-cost sensing device can be applied in disposable biosensors.