Deposited Indium-Zinc-Oxide Thin Film by RF Sputtering for pH-Sensing Application

In this study, the indium-zinc-oxide(IZO) thin mms were deposited on silicon substrates by r.f. sputtering. The IZO/Si sensing structure was used as a disposable sensor head and connected to the gate terminal of MOSFET. The IZO extended-gate field-effect transistor (EGFET) sensing structure and the Ag/AgCl reference electrode were immersed into the different buffer solutions (pH=1,3,5,7,9,11). Afterward, the current-voltage (I-V) characteristics curves and the pH sensitivity were measured and analyzed. According to the experimental results, the pH sensitivity of the IZO EGFET was obtained at approximately 52 mV/pH, and the pH-sensing response is linear (~1). The superior sensing properties of IZO pH-EGFET can be applied to detecting the $H^{+}-$ion concentrations.