Characterization and Ethanol Sensing Performance of Sol–Gel Derived Pure and Doped Zinc Oxide Thin Films

Abstract

ZnO, ZnO:Fe and ZnO:Co thin films have been deposited on glass substrates by a sol–gel dip coating method at different concentrations (i.e., 5 wt.% and 10 wt.%). The physical properties of the samples were investigated. X-ray diffraction, field emission scanning electron microscopy and Fourier transform infrared spectroscopy were applied to study the structural and morphological features. Pure and doped zinc oxide thin films have been placed in an electric circuit for the evaluation of gas sensing properties toward ethanol injection. The results showed a response to ethanol, and it was verified that gas response was affected by the doping. The optimal operating temperature, dynamic response and sensitivity of the samples have been determined. According to our results, in pure zinc oxide, an uncommon p-type sensing method is observed, but in doped ones a usual n-type method can be seen. The sample with 10% cobalt doped had a comparable response/recovery times compared with pure zinc oxide.