SiO2CuOx films for nitrogen dioxide detection: Correlation between technological conditions and properties

In the paper the SiOxCuOy thin and thick films were deposited from the alcoholic solutions employing the sol-gel technique. Investigations of films structure and surface morphology are represented. The joint X-ray diffraction and X-ray photoelectron spectroscopy studies reveal presence both CuO and Cu2O phases and formation of CuSiO3 phase with crystallites sizes of 35–50 nm. It is shown that surface roughness of the thin films increases in proportion to the increase of copper content in the precursor. Effective band gap energy estimated from the absorption spectra depends on the film thickness and phase composition. The gas sensitivity tests versus 1–25 ppm of NO2 showed the dependence of gas sensing response on the film thickness. The operating temperature was 170 °C and 20 °C for thin and thick film sensors, respectively. Accelerated stability tests of the initial resistance and gas sensor response performed high stability and reproducibility of the thin film sensors.