Electronic sensitization of CuO thin films by Cr-doping for enhanced gas sensor response at low detection limit

In this paper we investigate the effect of Cr-doping on the electronic structure of CuO and Cr-doped CuO thin films, which are deposited by DC-pulsed magnetron sputtering at 100 degrees C. Density Functional Theory calculations explain the effect of Cr dopant, which is introduction of the shallow donor band that decreases the charge carrier concentration. The Cr dopant is shown to be responsible for enhanced sensor response and selectivity towards acetone in ideal (dry air) and in realistic conditions (high relative humidity environment). The chemical and phase compositions are investigated by means of Energy Dispersive x-ray spectroscopy, x-ray Photoelectron Spectroscopy and Grazing Incidence x-ray Diffraction. The surface topography and microstructure are analysed by Scanning Electron Microscopy and Atomic Force Microscopy. The high level of control of the whole fabrication process of Cr-doped CuO thin films in one step and its feasibility for industrial up-scaling, open up a way for the commercial application of this material in gas sensing, catalysis, photovoltaics, using this cost-effective technology.