Sensitive Gas-Sensing by Creating Adsorption Active Sites: Coating an SnO2 Layer on Triangle Arrays

It is a widely used strategy to enhance gas sensor sensitivity by improving its surface area, but this process, including bonding the sensing block into a device substrate, needs complex manipulations. This work shows a concept of creating adsorption active sites, in which an SnO2 layer (6.85 nm thin) is directly coated on a triangle array substrate to be of an ensemble of triangular convex adsorption active sites (TCAASs). The resultant SnO2 gas sensors, with TCAAS periods ranging from 289 to 1154 nm, exhibit an adsorption-active-site-dependent sensitivity and present a low detection limit of around 6 ppm ethanol gas at room temperature. By characterizations of Kelvin force microscopy, a large surface potential variation exists on these adsorption active sites after introducing ethanol gas, distinctly showing a local adsorption enhancement. These results confirm that the creation of adsorption active sites can efficiently increase surface adsorption of a sensor to realize its sensitive gas-sensing.