Gas Sensing Properties of Indium Oxide Thin Film on Silicon Substrate Prepared by Spin-Coating Method

Abstract

Thin films of indium oxide were prepared on a silicon substrate by a spin-coating method using a coating solution dissolving In(OH)₃, acetic acid and ammonium carboxymethyl cellulose. The films consisted of a dense stack of fairly uniform grains, adhering well to the substrate, as observed with atomic force microscopy (AFM) and scanning electron microscopy (SEM). The film thickness was well controlled by repeating the spin-coating. The sensing properties of the In₂O₃ film to CO, H₂ and C₃H₈ depended on the film thickness and temperature, fairly good sensing performance to CO being achieved with a 140-nm-thick film at 350°C. The contact between platinum electrode and In₂O₃ in these devices was found to be slightly non-Ohmic, unlike that in the sintered block type device.