Thin and thick palladium overlayers were deposited onto clean and oxid
ized niobium surfaces, Thermally programmed desorption of carbon monox
ide, chemisorbed at room temperature on these Layers has been investig
ated. Qualitatively similar results, i.e., weak interaction of CO with
thin Pd overlayers and a stronger one with thick overlayers both for
Pd/Nb and for Pd/NbOx/Nb systems have been obtained.