Plasma treatment of SnO_2 nanocolumn arrays deposited by liquid injection plasma-enhanced chemical vapor deposition for gas sensors

摘要

SnO_2 nanocolumn arrays have been grown on 4 in. SiO_2/Si substrates by liquid injection plasma-enhanced chemical vapor deposition. The nanocolumns are well-crystallized and aligned without any additional substrate heating and catalysts. Effects of the thermal annealing and O_2 plasma treatment on the sensing response to CO and H_2 gas were comparatively studied. It was found that the sensing response of the SnO_2 nanocolumn arrays was greatly enhanced by O_2 plasma treatment. The oxygen species and the stoichiometry of the as-deposited, annealed and plasma-treated samples were comparatively analyzed by X-ray photoelectron spectroscopy. The average composition ratio [O]_(attice)/[Sn] increased continuously after annealing and O_2 plasma treatment. Plenty of oxygen species were chemisorbed on the surface of the SnO_2 nanocolumns during O_2 plasma treatment, resulting in the shift of binding energy O 1s for the plasma-treated sample to a higher value of 532.3 eV. The improvement in the sensing properties of the O_2 plasma-treated sample is closely related with the chemisorbed oxygen on the surface and obvious aging effects on the sensitivity were also observed on this sample.