Ultra sensitive low temperature metal oxide gas sensors

InO/sub x/ films, in the thickness range of 10-725 nm, were grown by dc magnetron sputtering. Their structural, electrical, and O/sub 3/ and NO/sub 2/ sensing properties were analyzed at various temperatures. Structural investigations carried out by XRD and AFM showed a strong correlation between crystallinity, surface topology and gas sensitivity. Moreover, the electrical conductivity exhibited a change of over six orders of magnitude during the processes of photoreduction and oxidation. The films have shown sensitivities towards O/sub 3/ of <50 ppb and NO/sub 2/ of <100 ppb, at temperatures from RT to 100/spl deg/C.