ORGANICALLY MODIFIED SIO2 AND AL2O3 FILMS AS SELECTIVE COMPONENTS FORGAS SENSORS

Pure SiO2 and Al2O3 films and organically modified SiO2 layers are dep osited by three different CVD techniques on SnO2 thin-film gas detecto rs. Ion-beam-assisted deposition (IBAD) of TEOS and ph-TEOS under bomb ardment with argon or oxygen ions is found to be suitable for the prep aration of organically modified SiO2 membranes at room temperature. Th e intended selective function of the membranes for gas detection is pr oved. A size selective mechanism is found to be dominant, primarily co ntrolled by the thickness of the films independent of the type of the membrane. The thickness is the most important parameter to design a me mbrane of specific selectivity. Smaller effects are induced by the che mistry of the membranes which nevertheless may be suitable to distingu ish between molecules of comparable size. Although the organic modific ations are not stable at the operation temperature of the sensors, the initial incorporation seems to be capable to tailor ceramic membranes with different properties.