Aerosol assisted chemical vapour deposition of MoO3 and MoO2 thin films on glass from molybdenum polyoxometallate precursors; thermophoresis and gas phase nanoparticle formation

Ashraf, Sobia, Blackman, Christopher S., Hyett, Geoffrey and Parkin, Ivan P. (2006) Aerosol assisted chemical vapour deposition of MoO3 and MoO2 thin films on glass from molybdenum polyoxometallate precursors; thermophoresis and gas phase nanoparticle formation. Journal of Materials Chemistry, 16 (35), 3575-3582. (doi:10.1039/b607335b).

Abstract

Aerosol assisted chemical vapour deposition (AACVD) of molybdenum polyoxometallates dissolved in acetonitrile or water yielded adhesive thin films of molybdenum oxides on glass. At substrate temperatures of 300 - 350 degrees C single phase MoO(3) was obtained, from 350 - 500 degrees C mixed phases of MoO(3) - MoO(2) were formed and at 500 - 550 degrees C single phase MoO(2) was observed. The morphology of the as-deposited molybdenum oxide films was found to be dependent upon a number of factors including the nature of the precursor used, the deposition temperature and position of the film within the reactor. Needles, spheres, agglomerates and platelets formed depending on the conditions. The films with a needle-like microstructure displayed enhanced hydrophobicity to water droplets (125 degrees contact angle). X-Ray diffraction showed that the MoO(3) films had typical cell constants of a = 3.96, b = 13.85, c = 3.69 angstrom and the MoO(2) films had typical cell constants of a = 5.62, b = 4.84, c = 5.56 angstrom, beta = 119.32 degrees. The MoO(2) films were readily converted to MoO(3) by annealing in air for 30 minutes at 600 degrees C. The MoO(3) films functioned as gas sensors showing a linear change in electrical resistance upon exposure to trace amounts of ethanol vapour in air.

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Contributors

Author: Geoffrey Hyett

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