CVD preparation and characterization of tin dioxide films for electrochemical applications

SnO2 films have been succesfully prepared by chemical vapour deposition (CVD) by reaction of SnCl2 with O-2 and a value of the activation energy of 58 kJ mol(-1) has been measured. The temperature range 450-500 degrees C has been found to be the optimum for the reaction with resistivities of the films of 9 x 10(-4) Omega cm on silicon and 6 x 10(-4) Omega cm on Pyrex. These two values are the lowest reported so far for SnO2 films which have not been deliberately doped. For their use as transparent conducting films, a figure of merit of 9.87 x 10(-3) square Omega(-1) was found for a 0.8 mu m thick film; this is also the highest reported so far. Characterization of the films by XRD showed a preferred [200] orientation and the grain size obtained from the XRD and SEM micrographs was in excess of 0.4 mu m. The SnO2 films, when tested in an eletrochemical cell, were unstable. A surface electrochemical process has been suggested for the disintegration.