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 SnO 2 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 SnO 2 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.