ZnO extended-gate field-effect transistors as pH sensors

The objective of this work is the study and characterization of zinc oxide (ZnO) as $p\mathrm{H}$ sensor. We used an extended-gate field-effect transistor (EGFET) to obtain the response of ZnO as a function of $p\mathrm{H}$ . 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 $500°\mathrm{C}$ . The samples were investigated by x-ray diffraction, infrared spectroscopy, thermogravimetric analysis and differential thermal analysis. The films were investigated as $p\mathrm{H}$ sensors (range 2–12) and the ZnO EGFET shows a sensitivity of $38\mathrm{mV}∕p\mathrm{H}$ .