Post-deposition heat treatment effect on pH sensing behavior of chemical bath deposited nanostructured zinc oxide

• Published in: International journal of hydrogen energy 2023-01, Vol.48 (4), p.1636-1648
• Main Authors: Binti Rosli, Aimi Bazilah, Binti Hamid, Nur Hazirah, Bin Zulkefle, Muhammad Alhadi, Binti Shariffudin, Shafinaz Sobihana, Binti Abdullah, Wan Fazlida Hanim, Herman, Sukreen Hana
• Format: Article
• Language: English
• Subjects: CBD; EGFET; pH sensor; Post-deposition heat treatment; ZnO nanostructures
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2022.10.036

The post-deposition heat treatment process was studied to improve zinc oxide (ZnO) ‘s pH sensing performance as the sensing electrode (SE) of extended-gate field effect transistor (EGFET) pH sensor. The low-temperature chemical bath deposited ZnO nanostructured thin film was heated from 200 to 400 °C before being applied as the SE. The heat treatment enhanced the agglomeration of ZnO nanoparticles, and the formation of nanonails was seen at the highest temperature of 400 °C. It was proven by XRD results that the crystallinity of ZnO samples were improved when the ZnO SE was heated at 300 °C and formed different growth orientations at (100), (002) and (101) before turning to (101) growth orientation at 400 °C heat treatment. The heat treatment process also increased the ZnO particle size from 15.47 nm to 260 nm at 300 °C. Further increasing the heat treatment up to 400 °C decreased the particle size to 44.30 nm. The ZnO morphology was correlated with the pH sensor performance. The clustered structure of the untreated ZnO sample exhibited a good pH sensitivity of 52.4 mV/pH with a linearity of 0.93 and a hysteresis value of 46.71 mV. On the other hand, almost similar pH sensitivity was obtained from the sample treated at 300 °C having poly-structure morphology, which was 52.9 mV/pH, but with a significantly improved linearity of 0.99, and hysteresis values of 41.99 mV respectively. The 300 °C heat treatment also improved the stability of ZnO SE performance. The difference in the performance of these two samples can also be related to the crystalline quality of the film. •ZnO nanostructures deposited by the facile CBD method was proposed as an EGFET pH sensor.•Effect of post-deposition heat treatment temperature on the ZnO nanostructures EGFET pH sensor performance was studied.•300 °C post-deposition heat treatment sample showed the highest sensitivity of 52.9 mV/pH with a linearity value of 0.9947