ZnO extended-gate field-effect transistors as pH sensors

The objective of this work is the study and characterization of zinc oxide (ZnO) as pH sensor. We used an extended-gate field-effect transistor (EGFET) to obtain the response of ZnO as a function of pH. Sol-gel was used for the production of ZnO films because this is a low cost and easy fabrication procedure. The ZnO powder was obtained at different temperatures of calcination, from 150 up to 500°C. The samples were investigated by x-ray diffraction, infrared spectroscopy, thermogravimetric analysis and differential thermal analysis. The films were investigated as pH sensors (range 2–12) and the ZnO EGFET shows a sensitivity of 38mV∕pH.