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Indium oxide (InOx) films with a thickness of 10–1100 nm were deposited onto Corning 7059 glass and silica substrates at various substrate temperatures. An unusual decrease of the lateral grain size with increasing substrate temperature during deposition was found. The changes in the conductivity of the films after exposure to ultraviolet light in vacuum and subsequent oxidation in ozone atmosphere were analyzed and related to their structural and morphological properties. It is suggested that the photoreduction and oxidation treatments affect only a thin layer less than 10 nm at the surface of the film, while the minimum bulk conductivity is mainly determined by the structural and morphological properties.

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The room temperature ozone sensing properties of polycrystalline indium oxide (InO x ) thin films have been investigated. Films with thicknesses of 10 to 1100 nm were sputtered in a dc-magnetron system onto Corning 7059 glass at various substrate temperatures and sputtering atmospheres. Initially, as-grown films were brought to a high conducting state through a photoreduction process by UV light exposure and subsequently they were exposed to a controlled ozone atmosphere. By this treatment the sensitivity of the films could be monitored. The films exhibit resistivity changes of more than five orders of magnitude. The sensitivity was studied for different ozone concentrations and at different temperatures. The response of the films increased linearly with the ozone concentration and the highest sensitivity was achieved when the measurements were carried out at room temperature. Best results were achieved with very thin InO x films (< 100 nm) deposited at room temperature in a pure oxygen atmosphere.