Surface roughness and conductivity of thin Ag films

Abstract

The diffuse scattering of conduction electrons at a rough surface has a considerable contribution to the resistivity of thin films, which is well known as the classical size effect. We have separated this contribution from other scattering mechanisms such as the phonon and bulk defect scattering by the following procedure: Silver was deposited at low temperatures (\ensuremath{\approxeq}130 K) onto a well-annealed relatively thick silver base layer (\ensuremath{\approxeq}24 nm), which has been deposited onto a Si(111)-7\ifmmode\times\else\texttimes\fi{}7 substrate. During deposition the resistivity of the thin film was measured in situ, and afterwards the surface roughness was determined quantitatively with profile analysis of low-energy electron diffraction. An increase of both resistivity and surface roughness was observed. Such an increase of the measured resistivity must be due to the increase of surface roughness because there was no change in temperature or concentration of bulk defects. With the measured surface roughness we are able to evaluate the additional resistivity without any free parameters. The experiment reveals excellent agreement with the theoretical predictions.