Radio-frequency magnetron sputtering using a Cu target was used to deposit cuprous oxide and cupric oxide thin films on silicon wafer. The substrate bias voltage and the O-2 flow ratio were varied during the deposition. The deposited thin films were characterized using scanning electron microscope. We found that the spherical and pyramid shapes structure of copper oxide thin films were deposited at critical O-2 flow ratio between 7 and 14%. The influence of substrate bias voltage was small and negligible. The deposited thin films were used for sensing characterization using ethanol vapor. Experimental results reveal that the pyramid shape of copper oxide thin film contribute to high respond rate when exposed to ethanol vapor. The respond and recovery rates which were measured at room temperature were very fast. This work had successfully demonstrated the formation of optimized copper oxide thin films and their usage for gas sensing application. (C) 2016 The Authors. Published by Elsevier B.V.

Cuprous oxide and cupric oxide thin films were deposited on silicon wafer with additional substrate bias voltage using radio-frequency magnetron sputtering of a Cu target with Ar+O-2 discharge plasma. Optical emission spectroscopy was employed to monitor the intensity of atomic Cu and O emission lines at various substrate bias voltages and oxygen flow ratios. Thin film transition from cuprous oxide to cupric oxide phase was observed by X-ray diffraction analysis when the oxygen flow ratio increased. This transition was not influenced by the substrate bias voltage. Optical emission spectroscopy showed a real time monitoring results of the transition from cuprous to cupric oxide thin films The transition was observed at a critical O-2 flow ratio of 7%. The results proposed a tightly control of reactive Cu sputtering through a closed loop and real-time monitoring system for precise copper oxide thin films deposition. (C) 2016 The Authors. Published by Elsevier B.V.