CO sensitivity of undoped-ZnO, Cr-ZnO and Cu-ZnO thin films obtained by spray pyrolysis

摘要

In this work, we present the gas–sensing properties of chemically sprayed undoped (ZnO), copper–doped (Cu–ZnO), and chromium–doped ZnO thin films (Cr–ZnO), in an atmosphere of carbon monoxide, CO. Films were deposited at 400°C, using zinc acetylacetonate as zinc precursor. Three different atomic concentration ratios of the dopant were tested. A maximum sensitivity of the order of four orders of magnitude was obtained at measurement temperatures of 200 and 300°C in an atmosphere containing 100 ppm of CO. It was found that chromium doping favors a higher sensitivity at lower measurement temperatures (200°C), whereas the best sensitivity appears in copper–doped ZnO films at higher measurement temperatures (300° C). The thinnest films exhibited higher sensitivities.