Gas sensing response analysis of p-type porous chromium oxide thin films

Abstract

The ethanol sensing properties of porous Cr₂O₃ thin films deposited by the ultrasonic nebulized spray pyrolysis of an aqueous combustion mixture is reported. The impact of the precursor selection and various deposition parameters on the film crystallinity, surface morphology and stoichiometry are studied using thermo-gravimetric analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and atomic force microscopy techniques. The film morphology exhibits a highly porous nature, as a result of the exothermic combustion reaction during film deposition. The gas sensing properties of these films are investigated in the temperature range of 200–375 °C for ethanol. The films show two different regions of response for ethanol above and below 300 °C. A good relationship between the response and the ethanol concentration is observed, and is modeled using an empirical relation. The possible mechanism and the surface chemical reactions of ethanol over the chromium oxide surface are discussed.