WO3 sensing properties enhanced by UV illumination: An evidence of surface effect

The behaviour of the conductance of a nanostructured WO3-based chemioresistive gas sensor under UV illumination was investigated in a synthetic air and in a pure nitrogen environment. The observed increase in conductance under illumination is expected to depend on interband electronic transitions, being the bandgap of the material smaller than the energy of the incident photons. In the present work we show an evidence that an important contribution to this increase is given by surface barrier modulation rather than interband transitions. Indeed, the conductance variation from the dark to the light was interpreted in terms of a direct effect of the light on the adsorbed oxygen ions.