To obtain wide linear pH sensing range, the tantalum doped zinc oxide (ZnO:Ta) thin film was deposited as the sensing membrane of extended-gate field-effect-transistor (EGFET) pH sensors using the vapor cooling condensation system. Compared with the ZnO EGFET pH sensors, the experimental results exhibited that the linear sensing pH range of the ZnO:Ta EGFET pH sensors was extended from the pH range of 4-12 to the pH range of 1.3-12. Furthermore, the ZnO:Ta pH sensors was stable in the whole extended pH range and showed favorable sensing sensitivity of 41.56 mV/pH. The AFM images of the ZnO:Ta sensing membrane after the measurement in strong acidic solution showed no observable surface damage, which further verified the high corrosion resistance of the ZnO:Ta sensing membrane.
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