Engineering the depletion layer of Au-modified ZnO/Ag core-shell films for high-performance acetone gas sensing

Understanding the role of depletion region, charge transport behaviour, and energy band modulations are essential to improve the performance of different sensors including the accurate acetone sensor for the diagnosis of diabetes via the exhaled breath. Herein, we report a new approach to amplify the performance of the acetone gas sensor by engineering the depletion layer. A novel Au decorated ZnO/Ag core-shell films (Au/ZnO/Ag) with different contents of Au, ZnO, and Ag are successfully fabricated via a sequential DC sputtering and post-heat treatment for the detection of acetone in low concentration. The optimum thickness of Ag, ZnO, and Au, to achieve the highest acetone response, are determined to be 11, 13, and 12 nm, respectively. The acetone sensing performance of the Au/ZnO/Ag is four and two times higher than that of ZnO and ZnO/Ag core-shell films. In addition, the Au/ZnO/Ag core-shell sensor exhibits excellent repeatability, high selectivity, and quick response at 150 °C operating temperature. The high performance of the developed sensor is attributed to the formation of a thick depletion layer, and the homogeneous distribution of Au and Ag nanoparticles. The findings demonstrate that the controlled engineering of the depletion layer is an efficacious approach for designing high-performance metal oxide-based gas sensors.