Structures of nanowires with Zn–ZnO:CuO junctions for detecting ethanol vapors

The synthesis of ZnO-ZnO:CuO structures in the form of overlapping layers of nanowires of pure and copper oxide-doped zinc oxide is described. These structures are tested as ethanol vapor sensors. The following two-stage method is used to form ZnO:CuO nanowires. At the first stage, ZnO nanowires are formed by chemical deposition from a solution. At the second stage, arrays of ZnO nanowires are coated with a copper-containing layer. The CuO content on the surface of ZnO nanowires is changed by varying the number of immersions in a Cu(NO$_3$)$_2$ solution. The formed structures are studied by scanning electron microscopy, X-ray diffraction, and energy dispersive X-ray analysis. The interaction of the grown sensor structures with ethanol vapors is analyzed by measuring the potential difference between the layers of pure zinc oxide and copper oxide-modified zinc oxide in the temperature range 190–300$^\circ$C. The response of the sensor is investigated at various ethanol vapor concentrations and detection temperatures.