The sensitivity behavior of TiO₂ thin films-based extended-gate field effect transistor pH sensor

To present highly sensitive and precise pH sensor, fabrication of metal oxide based EGFET sensor is needed. The used of TiO₂ thin films as sensing electrode for pH sensor is widely known for its best sensitive in pH measurement. The films were prepared by depositing the films onto ITO glass substrate using sol-gel spin coating method. The sensitivity and linearity of TiO₂ EGFET sensing electrode for various spin speeds (1000 to 5000 rpm) were obtained from transfer characteristic (IDS -VREF) and output characteristics (IDS -VDS) analysis. The effect of different immersion time (25, 50, and 75 s) and repeatability measurement for each sample were also investigated in this study. Among of all samples, the sensing electrode prepared at 5000 rpm spin speed with 75 s immersion time achieved the highest sensitivity of 52.20 mV/pH and good linearity of 99.64 %. Meanwhile, the sensing electrode prepared at spin speed 3000 rpm produced good repeatability and small standard deviation. The performance EGFET sensor has also been tested at different pH values (pH4, pH7, and pH10) and found TiO₂ sensing electrode showed more precise results in an alkaline (pH10).