Enhanced Humidity Sensing Properties of Sn-Doped ZnO Nanostructures on AZO/PET Substrates via Sol-Gel Immersion Method

This work reports the structural and humidity-sensing properties of Tin (Sn)-doped Zinc Oxide (ZnO) nanostructures deposited on Aluminum-doped Zinc Oxide/Polyethylene Terephthalate (AZO/PET) substrates via the sol-gel immersion method. Accordingly, X-ray Diffraction (XRD) and FESEM analyses confirmed that low-level Sn incorporation (1 at.%) enhanced the (002) orientation and crystallinity, while higher doping introduced lattice distortion and defects. Meanwhile, humidity sensing measurements revealed that undoped ZnO exhibited the highest sensitivity (178.5), though it recorded a very slow response (231 s) and recovery (648 s). In contrast, 1 at.% Sn-doped ZnO achieved a balanced performance, combining high sensitivity (144.4) with much faster response (121 s) and recovery (411 s). These results demonstrate that controlled Sn doping optimizes ZnO nanostructures for flexible humidity-sensing applications. Overall, the findings provide valuable insight for developing real-time environmental and wearable sensing devices, with future work focusing on stability testing and mechanical flexibility evaluation.