Os and Pd modified tin oxide films for sensors by the sol gel process

Pure, Pd and Os modified SnO2 films were prepared by the sol gel process an d used as active materials in gas sensing devices. The films have been prep ared starting from tin tetrachloride in alcoholic solution hydrolysed with water. The modifier was added to the sol as inorganic salt. Pd acetate and Os chloride were the Pd and Os precursors respectively. A structural and mo rphological study was carried out by means of Atomic Force Microscope (AFM) , Secondary Ion Mass Spectrometer (SIMS) and x-ray Diffraction (XRD). The e lectrical resistance variations as a function of various gaseous atmosphere s and temperature were measured to evaluate the sensing properties of the f ilms. CO, CH4, CH3OH and C2H5OH gases were used for the tests. Following re sults were obtained: Pd is present in the form of PdO nanoclusters in the p olycrystalline SnO2 matrix as evidenced by XRD spectra whereas Os is a cati onic modifier uniformly dispersed as evidenced in SIMS studies. Optimum sen sing temperature and the sensitivity variations, with respect to the undope d films, differ according to the gaseous species. It looks therefore promis ing to use inexpensive, sol-gel derived, array of films in smart gas sensin g devices that are able to recognise gas species and concentration.