Solid-state electrical conductivity and alcohol sensing properties of radio frequency sputtered thin films of Ti4+ doped eskolaite Cr2O3 derived from citrate combustion technique

Fine powder of Cr1.8Ti0.2O3 (CTO) was prepared by citrate combustion technique followed by compacting into discs of 40 nun diameter. Discs were used as radio frequency sputtering targets and coated on a hollow ceramic tube of 4 turn length comprising two Au-electrodes with 4-probe contact and on Al2O3 slices with interdigitated gold electrodes. The films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and atomic force microscopy techniques. The resistance of the film derived from alternate current impedance measurement in ambient air was found to decrease with increasing temperature. The activation energy was found to be 0.39 eV. These films were exposed to various concentrations of alcohols followed by determination of sensor response, reversibility, potential stability and reproducibility. The sensor response was attributed to the surface catalytic reaction of R-OH with O-(ads)(-) to form adsorbed R-CHO. (c) 2007 Elsevier B.V. All rights reserved.