Ni content and grain size dependency of perovskite structure La0.8Sr0.2Co1-xNixO3-delta thin films for CO gas sensor

La0.8Sr0.2Co1-xNixO3-delta perovskite films prepared by the radio frequency sputtering technique in a wide range of Ni content (x less than or equal t o 0.6) were studied. The microstructure of the films determined by scanning electron microscopy showed the changing of grain size after heat treatment at different temperature for 5 h. The effect of Ni doping on the sensitivi ty to CO was studied. The La0.8Sr0.2Co0.6Ni0.4O3-delta film treated at 700 degrees C for 5 h shows the best improvement of sensitivity to CO. The CO-O -2 reaction on the surface of film can be indirectly probed by electron spe ctroscopy for chemical analysis. The sensitivity dependence affected by gra in size is also investigated. The combination of binding energy to the adso rbed oxygen and the connecting condition of the adjacent grains would domin ate the sensing property. The results, show the La0.8Sr0.2Co0.6Ni0.4O3-delt a film treated at 700 degrees C for 5 h yields the maximum sensitivity of 1 0.1% in 50 ppm of CO. (C) 1999 American Vacuum Society. [S0734-2101(99)0170 2-9].