A selective methane gas sensor based on SnO2 utilizing a reactive and porous substrate

• A novel structure was proposed to enhance selectivity of MOS gas sensors. • The process of gas diffusion and reaction were modulated by a porous substrate. • Numerical calculations were performed for gas diffusion and reaction behavior. Generally, selective response of MOS gas sensors is dominated by the process of gas diffusion and reactions through the sensing layers. The microstructure and surface chemical activities of MOS thin films simultaneously control the diffusion reaction process and modulate electronic conduction. Thus, it is very difficult to modulate the diffusion-reaction process just using sensing layers because gas diffusion and reaction process cannot be separated from the sensing films. Hence, the selective response of the MOS gas sensors is barely satisfactory. In this study, a novel sensor structure was proposed. The MOS sensing layer was printed on a porous ceramic substrate with a well-defined pore structure. The gas molecules must diffuse through the porous substrate before contacting the sensing layer of the MOS. Therefore, the diffusion reaction and sensing processes are separated from each other and are performed by two different parts of the sensor devices. Consequently, the selective response was significantly improved by the proposed sensor structure.