Fabrication of shrub-like CuO porous films by a top-down method for high-performance ethanol gas sensor

The shrub-like CuO porous films were prepared by a top-down chemical etching method, where Cu2OAl2O3 film precursor was firstly deposited on the SiO2/Si substrate by sputtering in air, then the part of Al2O3 was selectively etched in diluted HCl solution, and finally the etched film was annealed in air. The structural and morphological characterizations of prepared samples were measured by XRD, FESEM, and TEM, respectively. The results showed that the shrub-like CuO porous films can be obtained with monoclinic tenorite phase. Etching time and annealed temperature were important parameters in the preparation of shrub-like CuO porous films. Gas sensing properties demonstrated the response of gas sensor based on the CuO porous films to ethanol gas was consistent with the power-law relationship. The maximum sensor response to ethanol gas was obtained at an operating temperature of 250 °C with fast response and recovery speeds. By comparing with the sensing performances based on various CuO microstructures to ethanol gas in the literature, the shrub-like CuO porous films exhibited excellent overall sensing performance. The growth mechanism and sensing mechanism of CuO porous films to ethanol gas were proposed and discussed.