Chromium and Ruthenium-Doped Zinc Oxide Thin Films for Propane Sensing Applications

Chromium and ruthenium-doped zinc oxide (ZnO:Cr) and (ZnO:Ru) thin solidfilms were deposited on soda-lime glass substrates by the sol-gel dip-coating method.A 0.6 M solution of zinc acetate dihydrate dissolved in 2-methoxyethanol andmonoethanolamine was used as basic solution. Chromium (III) acetylacetonate andRuthenium (III) trichloride were used as doping sources. The Ru incorporation and itsdistribution profile into the films were proved by the SIMS technique. The morphologyand structure of the films were studied by SEM microscopy and X-ray diffractionmeasurements, respectively. The SEM images show porous surfaces covered by small grains with different grain size, depending on the doping element, and the immersionsnumber into the doping solutions. The sensing properties of ZnO:Cr and ZnO:Ru films in apropane (C3H8) atmosphere, as a function of the immersions number in the dopingsolution, have been studied in the present work. The highest sensitivity values wereobtained for films doped from five immersions, 5.8 and 900, for ZnO:Cr and ZnO:Rufilms, respectively. In order to evidence the catalytic effect of the chromium (Cr) andruthenium (Ru), the sensing characteristics of undoped ZnO films are reported as well.