Electrical characterization of a thin film tin oxide sensor array for VOCs detection

A tin oxide sensor array has been fabricated using the r.f. reactive sputtering technique. Some elements of the array have been doped with Pt, Pd and Al by sputtering. Sensors have been characterized by DC electrical measurements for different volatile organic compounds (VOCs) such as benzene, toluene, chloroform, propanal, methyl-ethyl-ketone (MEK) and octane, in a concentration range from 50 to 500 ppm in dry air at 300 degrees C. The best response has been obtained by Pt and Pd doped sensors for the oxygenated compounds, but for all gases good sensitivities are shown. The impedance spectra were obtained by AC variable-frequency measurements for all the sensors in air, in benzene and in propanal atmospheres at 300 degrees C. The VOCs peak frequencies changed with regard to air peak frequencies for all the sensors. The roles of dopants and doping level are discussed. (C) 1998 Elsevier Science S.A.