Copper tungstate thin-films for nitric oxide sensing

CuWO4 thin-films prepared by the pulsed laser deposition technique were studied for monitoring nitric oxide (NO) in the concentration range of 10 < [NO] < 400 ppm under synthetic air. The thin-film films were characterized by X-ray diffraction (XRD), depth-profilometry and electron transport measurements. The CuWO4 thin-film response to O2 confirmed an n-type conductivity. Monitoring the thin-film conductometric response to NO at both 300 and 500 °C revealed the operation of a temperature-dependent mechanism for detection. At 300 °C, increasing [NO] produced a consistent increment in thin-film resistance, while at 500 °C the thin-film resistance decreased with [NO]. At 500 °C, a transient response was systematically observed. The chemical origin of the transient is discussed. The estimation of response factors to NO exposure in the presence of high [O2] indicates a significantly higher selectivity to NO. Extensive conductometric measurements show that the thin-films feature good electronic and thermal stability over time.