Structural and Gas Sensing Characteristics of CuO-Doped ZnO Thin Films Papered by Pulsed-Laser Deposition

Abstract

In this work, pulsed-laser deposition was used to prepare zinc oxide (ZnO) thin films on glass and porous silicon substrates. These films were doped with different contents of copper oxide (CuO). The x-ray diffraction patterns showed peaks belonging to hexagonal ZnO structure only for the samples with CuO contents of 10, 30 and 50%, while the peaks belonging to cubic CuO structure were observed in the samples with partial CuO contents of 70 and 90%. As the CuO content was increased, the average roughness of the prepared surfaces was accordingly increased. The electrical measurements showed that all prepared samples were of n-type conductivity and the charge carrier concentration was decreasing with increasing partial content of CuO. The CuO-doped ZnO films deposited on porous silicon substrates were tested as gas sensors. The maximum sensitivity of 49% for NO2 gas was recorded at constant current of 15 mA and exposure time of 30 min for the sample of 10% CuO content at operation temperature of 200 °C.