A comparison of the gas sensing properties of solid state metal oxide semiconductor gas sensors produced by atmospheric pressure chemical vapour deposition and screen printing

The reaction of metal chloride, MCln ( where M = Ga, Sb or Sn) and ethyl acetate under atmospheric pressure chemical vapour deposition (APCVD) conditions leads to the production of metal oxide thin films on a variety of gas sensor substrates. Scanning electron microscopy indicated that an island growth mechanism predominated. X-ray photoelectron spectroscopy revealed binding energy shifts similar to previous literature values. Energy dispersive x-ray analysis, wavelength dispersive x-ray analysis and electron probe microanalysis gave coherent elemental compositions indicating that single-phase materials were made, with negligible impurity levels. The films showed little optical reflectance (similar to 10%) and 65 - 75% total transmission from 400 - 800 nm. Gas sensing experiments indicated that the APCVD produced films responded best to a reducing gas at 450 degrees C, whereas the corresponding screen-printed metal oxide sensors were generally more responsive and responded best to a reducing gas at 500 degrees C.