Preparation and Characterization of Nanostructured SnO2 Thick Films on Flexible Polyimide Substrates for CO Gas Sensor Application

Pure nano-sized SnO2 metal oxide powder has been prepared by two kinds of modified hydrothermal methods using oxalic acid and hydrazine, respectively. Then nanostructured SnO2 thick films have been deposited on polyimide flexible substrate by ink synthesis and dropping. Especially, the SnO2 thick films fabricated by hydrazine method exhibited pure tetragonal phase, a small grain size of 30 nm, and a BET specific surface area of 56.19 m(2)/g. Plasma surface treatment has been introduced prior to ink dropping in order to compensate the poor adhesion strength due to low temperature annealing. The Ar-plasma-activated surface was maintained up to three days in spite of a mild RF power of 25 W and adhesive SnO2 thick films could be obtained to patterned Pt electrodes on flexible substrate. Finally fabricated SnO2 flexible sensors without any addition of catalysis showed a gas sensitivity of 6%, a response speed of 159 sec, and a recovery speed of 85 sec at a CO gas concentration of 1,000 ppm at a temperature of 300 degrees C.