H2S gas sensitive Sn-doped ZnO thin films: Synthesis and characterization

• Sn doped ZnO films were grown at low temperature by advanced spray pyrolysis.
• Influence of Sn doping concentration on the H2S sensing properties was studied.
• All the films are polycrystalline with a hexagonal wurtzite crystal structure.
• Highest sensitivity to 20 ppm of H2S was achieved for 4SZO film at 473 K.
• Pd sensitized film demonstrates adequately stable H2S sensing performance.

Tin doped zinc oxide thin films were synthesized at low substrate temperature (473 K) by advanced spray pyrolysis technique for H2S gas sensing application. Equimolar solution of zinc acetate and tin chloride were used to grow Sn doped ZnO thin films. The effects of tin doping concentration on the structural, morphological, and gas sensing properties of Sn doped ZnO films were investigated. It is revealed that all films exhibit wurtzite structure and the average crystallite size reduce with increasing Sn doping concentration. With an increase in Sn doping, the peak position of the (0 0 2) plane was shifted to the low 2θ values indicating the lattice distortion incorporated into the film due to Sn doping. The results obtained from TEM and FESEM characterizations confirmed the XRD observations. Further, the as-characterized Sn doped ZnO films were profoundly studied for their H2S sensing performance. The H2S gas sensing characteristics that are mainly governed by an operating temperature were found to be optimum at 473 K. A maximum response of ∼31% to 30 ppm H2S was obtained at 473 K with reasonably fast response and recovery. Particularly, the 4 wt.% Sn doped ZnO sample exhibits selective behavior towards H2S on account of its surface morphological features. The H2S detection properties of the 4 wt.% Sn doped ZnO film were improved significantly on palladium (Pd) sensitization and the film demonstrated adequately stable sensing performance.