SURFACE-ROUGHNESS OF METALLIC-FILMS PROBED BY RESISTIVITY MEASUREMENTS

The resistance of thin cobalt (Co) and niobium (Nb) films was monitore d during their exposure to hydrogen or carbon monoxide for 1000 s, at a fixed pressure, and also during the removal of the gas from the surf ace. In an adsorption-desorption cycle the resistivity changed in a '' saw-tooth'' fashion, similar to the changes observed in traditional gr avimetric studies. The resistivity increase caused by the adsorbed gas seems to be directly related to weakly adsorbed states and the roughn ess of the film surface. The surface roughness decreases the magnitude of the adsorption-driven resistivity change in such a way that rough- thin Co films show a similar resistance change to that for smooth-thic k Nb films. The roughness of the films depends on the deposition techn ique used, and it was determined by low-angle X-ray diffraction and sc anning tunneling microscopy.