TUNGSTEN TRIOXIDE (WO3) SPUTTERED THIN-FILMS FOR A NOX GAS SENSOR

WO3 thin films have been deposited by reactive rf sputtering onto low- cost glass substrates as gas sensitive coatings. The properties of the grown films have been investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIM S) in order to characterize their structure, composition, surface chem istry. The d.c. electrical response to different gases of the WO3 thin films has been measured in the temperature range from 100 to 400 degr ees C showing an increase of electrical resistance with a good sensiti vity towards NOx gas at 250 degrees C. WO3 thin films oppositely detec t also NH3, H-2, H2S, SO2 gases by decreasing the electrical resistanc e and are practically insensitive to interfering gases like CO, CH4 in the same temperature range. The sensing characteristics of the NOx ga s detector based on tungsten trioxide (WO3) thin films are reported. ( C) 1998 Elsevier Science S.A. All rights reserved.