In this study, the effect of annealing temperature on the extended gate field effect transistor (EGFET) for pH sensors of CuO thin film was investigated. The CuO thin films were deposited on an indium tin oxide (ITO) substrate using the sol-gel spin-coating method. The thin films were then annealed in air ambient at 200 to 500 ᵒC for 30 minutes. The sensitivity and linearity of the sensing electrodes were determined in a pH range from pH 2, 4, 7, 10 and 12. The sensing electrode annealed at 400 ᵒC showed the highest pH sensitivity of 47.3 mV/pH. It showed that the post-annealing process improved the sensing performance of the device. The morphology characteristic was characterized by field emission scanning electron microscopy (FESEM) and showed a porous structure as the annealing temperature increased, indicating that the porous film could be the sensing electrode of an EGFET pH sensor. The hysteresis of the sensing electrode was measured in buffer solutions prepared at pH 7, pH 4, pH 7, pH 10, and pH 7 to find its pH response delay. These findings indicated that sol-gel spin-coated CuO thin film can be considered a promising candidate for applications as an EGFET-pH sensor.
