A COMPARISON OF CONDUCTANCE BEHAVIOR BETWEEN SNO2 AND CDS GAS-SENSITIVE FILMS

The conductance behaviours of SnO2 and CdS semiconducting films as a f unction of temperature and after rapid changes in temperature and in o xygen partial pressure are compared. Experimental results are given at different partial pressure of oxygen in dry mixtures with nitrogen in the temperature ranges 350-850 K for SnO2 and 300-550 K for CdS. In t he case of conductance response to rapid changes in oxygen partial pre ssure, results are given for both an increase and a decrease of the pa rtial pressure. Some results are also given for SnO2 films doped with aluminium and antimony. SnO2 samples are in the form of thick films, w hich together with gold electrodes are screen printed on an alumina su bstrate. Spray pyrolysis is used for the deposition of CdS thin films from CdCl2 and (NH2)(2)CS solutions on glass substrates. A similar sig moidal variation of conductance during heating is found for both SnO2 and CdS films with a shift of 200 K and more in the temperature scale for this variation between the two films. The results are discussed in the light of conduction models where the surface barriers at intergra nular contacts dominate the him resistance.