2D-Conductivity of thin Pd films condensed at low temperatures

Resistance measurements have been made on quenched condensed Pd films with thicknesses between 25 Å and 350Å. The films are prepared under different evaporation conditions by varying the system pressure between 10^?8 and 10^?5 mbar. Resistance minima with a logarithmic increase of the sheet resistance are observed for thick films (d<350Å) condensed under intentionally “bad” (10^?5 mbar) vacuum conditions, as well as for thin films (d<50Å) condensed at pressures around 10^?8 mbar. Structure investigations show that the thick films are granular. For these films the relation of granularity to 2D localization is discussed. The thin films are continuous and the logarithmic resistance increase is in agreement with predictions of 2D-theories.