Efficient methane detection by Co doping of ZnO thin films

• Co doped ZnO films reveal fibrous roots and grains morphology all over the surface.
• The presence of fibrous roots on the surface assures a high surface to volume ratio.
• Co doped films are more sensitive to methane that ammonia and ethanol.
• The sensor devices show long-term stability and reproducibility of the measurements.

Here, we report on the Co-doping of ZnO thin films and on its role on detection of methane. The complementary investigations have been conducted in order to understand, explain and confirm the influence of the Co on the surface morphology and on the gas sensitivity exhibit at relatively low gas concentrations. The X-ray diffraction patterns indicate that the studied films present a single-phase wurtzite structure of ZnO and the X-ray Photoelectron Spectroscopy investigation confirms the successful incorporation of Co2+ ions into the ZnO lattice. The plane-view Scanning Electron Microscopy images reveal the increase of surface to volume ratio with the increase of the dopant concentration. We investigated, the sensitivity of the sensor-devices tailored using the Co-doped and undoped ZnO thin films respectively. The maximum sensitivity, to 600 ppm methane, was obtained at an operating temperature of 170 °C. After repeated sensing measurements, the obtained results show long-term sensors stability.