Plasma-Modified SnO2 Nanowires for Enhanced Gas Sensing

Tin oxide (SnO2) nanowires grown by chemical vapor deposition were modified by Ar/O2 plasma treatment through preferential etching of the lattice oxygen atoms, which produced nonstoichiometric surface compositions that imparted a manyfold higher sensitivity toward gas absorption on such surfaces. Microstructures of as-grown and plasma-treated SnO2 nanowires confirmed the gradual change in the chemical composition and morphologies. Surficial disorder caused by the bombardment of argon and oxygen ions present in the plasma was visible as a disordered overlayer in high-resolution TEM micrographs, when compared to single crystalline as-grown SnO2 nanowires. Gas-sensing experiments on modified SnO2 nanostructures showed higher sensitivity for ethanol gas at lower operating temperatures and exhibited an improved transduction response toward changing gas atmospheres, attributed to the increased concentration of oxygen vacancies on the surface of SnO2 nanowires. Modulation of surface chemistry was also supported by photoluminescence and X-ray photoemission spectroscopy studies.