TiO2-based extended gate FET pH-sensor: Effect of annealing temperature on its sensitivity, hysteresis and stability

In this study, titanium dioxide (TiO₂) thin films have been investigated as a sensing membrane of the extended gate field effect transistor (EGFET) for pH detection application. The sol-gel TiO₂ has been prepared and spin coated onto the indium tin oxide (ITO) coated glass as a substrate. Then the TiO₂/ITO test structures thin films were annealed for 15 min at different temperatures; 300 °C and 400 °C under ambient atmosphere. The pH sensing characterizations of TiO₂ thin films were measured by Semiconductor Parametric Device Analyzer in different pH buffer solutions of pH 4, 7, 10 and 12. The sensitivity of TiO₂ thin film annealed at 400 °C exhibited a higher sensitivity that is 51 mV/pH compared to the thin film annealed at 300 °C gave slightly lower sensitivity of 49 mV/pH. The hysteresis and drift effect for TiO₂ thin films also being investigated in this study. TiO₂ thin films annealed at 400 °C obtain better hysteresis and drift value compared to the TiO₂ thin films annealed at 300 °C.