Preparation of nanostructured SnO₂ thick films onto patterned Pt electrodes by ink dropping and plasma surface treatment for CO gas sensor

Nanostructured SnO₂ thick films with pure tetragonal phases onto patterned Pt electrodes have been prepared by ink dropping and plasma surface treatment for CO gas sensors. Fine SnO₂ powder with a diameter of 30 nm was synthesized by modified hydrazine method and the ink solution was fabricated by mixing water, glycerol, bicine, and the SnO₂ powder. Crack-free films without agglomeration could be obtained by controlling the SnO₂ powder content in the ink and heating rate during final sintering. The region of formed SnO₂ thick films by the ink dropping was able to successfully fill the 10-μm gap of patterned Pt electrodes. Additionally, plasma surface treatment was introduced prior to ink dropping in order to improve the adhesion strength and electrical connectivity between the SnO₂ thick films and patterned Pt electrodes. The prepared nanostructured SnO₂ thick films exhibited a gas sensitivity of 43%, a response time of 8.5 sec, and a recovery time of 34.2 sec at a CO gas concentration of 500 ppm and a temperature of 300°C without any addition of catalyst.