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

• Published in: International Journal of Hydrogen Energy
• Main Author: Binti Rosli A.B.; Binti Hamid N.H.; Bin Zulkefle M.A.; Binti Shariffudin S.S.; Binti Abdullah W.F.H.; Herman S.H.
• Format: Article
• Language: English
• Published: Elsevier Ltd 2023
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85140954196&doi=10.1016%2fj.ijhydene.2022.10.036&partnerID=40&md5=350cf06db6f3de30e7ee76bc01ceb192

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. © 2022 Hydrogen Energy Publications LLC