Influence of Substrate Temperature on ${\rm H}_{2}{\rm S}$ Gas Sensing Properties of Nanocrystalline Zinc Oxide Thin Films Prepared by Advanced Spray Pyrolysis

In this paper, nanocrystalline zinc oxide (ZnO) films are deposited onto glass substrates by a novel advanced spray pyrolysis technique, using non-aqueous zinc acetate solution. ZnO films are grown at various substrate temperatures in the range of 423-523 K, keeping the reaction chamber temperature constant. The influence of substrate temperature on film crystallinity and surface morphology electrical properties are investigated. The films are found to be polycrystalline with a wurtzite hexagonal structure. Surface morphological studies reveal columnar growth with enhanced crystallinity and lower activation energy at higher substrate temperature. The H₂S gas sensing properties of ZnO films are studied as a function of substrate temperature, operating temperature, and H₂S gas concentration. The film grown at a 523 K substrate temeprature exhibits maximum sensitivity (~22%) to 20-ppm H₂S exposure at a 573-K working temperature and exhibits good selectivity and stability.