High NOx sensitivity of oxide thin films prepared by RF sputtering

SnO2- and In2O3-based thin films were prepared by magnetron sputtering onto alumina ceramic substrates, and their sensitivities to NO, and NO were inv estigated. The deposition of oxide thin films varied, depending on the subs trate temperature, sputtering rate, and oxygen partial pressure, When the S nO2 sensor doped with Nb2O5 and TiO2 and prepared under optimal conditions was kept at 300 degreesC, its sensitivity (RgRair) reached a value of 2 or more in an atmosphere including 0.4 ppm NO2. The In2O3-based thin film sens or including appropriate amounts of additives showed a much higher sensitiv ity, which was satisfactory to detect 0.04 to 0.06 ppm NOx, as required by the Ambient Environmental Quality Standard. The detecting mechanism is disc ussed based on a previously reported theory. (C) 2001 Elsevier Science Ltd. All rights reserved.