Titanium dioxide (TiO2) thin films were sputtered by radio frequency (RF) magnetron sputtering method and have been employed as the sensing membrane of an extended gate field effect transistor (EGFET) for pH sensing detection application. The TiO2thin films were deposited onto indium tin oxide (ITO) coated glass substrates at room temperature and 200°C, respectively. The effect of deposition temperature on thin film properties and pH detection application was analyzed. The TiO2samples used as the sensing membrane for EGFET pH-sensor and the current-voltage (I-V), hysteresis, and drift characteristics were examined. The sensitivity of TiO2EGFET sensing membrane was obtained from the transfer characteristic (I-V) curves for different substrate heating temperatures. TiO2thin film sputtered at room temperature achieved higher sensitivity of 59.89 mV/pH compared to the one deposited at 200°C indicating lower sensitivity of 37.60 mV/pH. Moreover the hysteresis and the drift of TiO2thin film deposited at room temperature showed lower values compared to the one at 200°C. We have also tested the effect of operating temperature on the performance of the EGFET pH-sensing and found that the temperature effect was very minimal.

Titanium dioxide (TiO2) thin films were fabricated on indium tin oxide (ITO) glass substrates using the spin coating technique and further were implemented as sensing membranes of the extended gate field effect transistor (EGFET) based pH sensor. The as-deposited thin films were annealed at different temperatures from 200 - 600 °C in room ambient for 20 min. The effects of different annealing temperatures on electrical and crystalline properties were analyzed by I-V two point probes measurement and X-ray diffraction respectively. Meanwhile, the surface morphology of thin films was observed by field emission scanning electron microscope (FESEM). We then measured the transfer characteristics (ID-VG) of the TiO2/ITO sensing membrane using a semiconductor parametric device analyzer for sensor characterization. It was found that, TiO2/ITO sensing membrane annealed at 300 °C achieved higher sensitivity and good linearity of 51.48 mV/pH and 0.99415, respectively in the pH buffer solutions of 4, 7, 10, and 12. Thin film annealed at 300 °C gives higher conductivity thin film of 384.62 S/m. We found that the conductivity of TiO2/ITO thin films was proportional with the sensitivity of sensing membrane.

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A highly selective and sensitive EGFET-pH sensor based on composite TiO2–PANI had been developed in this work. A sol-gel titanium dioxide (TiO2) and the composite of TiO2 with semiconducting polyaniline (PANI) were deposited using a simple spin-coating method on an indium tin oxide (ITO) substrate. The films have been explored as a sensing electrode (SE) of extended gate field-effect transistor (EGFET) for pH applications in the range of pH 2 to 12. The pH sensitivities between TiO2, TiO2–PANI bilayer composite, and TiO2–PANI composite thin films were discussed. Among these, the TiO2–PANI composite thin film showed a super-Nernstian behavior with high sensitivity of 66.1 mV/pH and linearity of 0.9931; good repeatability with a standard deviation of 0.49%; a low hysteresis value of 3 mV; and drift rates of 4.96, 5.54, and 3.32 mV/h in pH 4, 7, and 10, respectively, for 6 h. Upon applying the TiO2–PANI composite as the SE for nitrate measurement, low sensitivity of 12.9 mV/dec was obtained, indicating that this film is a highly selective sensing electrode as a pH sensor. The surface morphology and crystallinity of the thin films were also discussed.

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This paper presents an investigation on titanium dioxide (TiO2) thin film, which is used as sensing membrane for Extended-Gate Field Effect Transistor (EGFET) for pH sensing application. TiO2 thin films were deposited using sol-gel spin coating method on indium tin oxide (ITO) substrates. After the deposition, the thin films were annealed at 300 °C for 10 and 15 min, while another sample was annealed at 400 °C for 15 min. The sensitivity measurement was taken using the EGFET setup equipment with constant-current (100 μA) and constant-voltage (0.5 V) biasing interfacing circuit. TiO2 thin film as the pH-sensitive membrane and the working electrode was connected to a commercial metal-oxide semiconductor FET (MOSFET). The MOSFET then was connected to the interfacing circuit. The sensitivity of the TiO2 thin film towards pH buffer solution was measured by dipping the sensing membrane in pH4, pH7 and pH10 buffer solution. For comparison, a sample of bare-ITO was also tested to see its sensitivity. We found that the TiO2 thin film annealed at 400 °C for 15 min gave the highest sensitivity compared to other annealing conditions and also compared to the bare ITO substrate with the value of 44.30 mV/pH. This showed that TiO2 thin film can be used for pH sensing and the post-deposition treatment of the thin film can influence the sensing ability. We also measured the TiO2 thin films’ current – voltage (I-V) characteristics. Relating the I-V characteristic of the thin films and sensitivity, the sensing membrane with higher conductivity gave better sensitivity.

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