Intrinsic Resistivity and Electron Mean Free Path in Aluminum Films

Abstract

Measurements of the electrical resistivity at 296° and 4.2°K in aluminum films, evaporated both in an ion‐pumped ultrahigh‐vacuum system and in conventional oil‐pumped systems onto unheated glass substrates, are presented and used to calculate the intrinsic mean free path and intrinsic electrical resistivity at 4.2°K. It is shown that the UHV films are characterized by a maximum mean free path of the order of 1 μ and by smaller residual resistances than other films. While the mean free path so obtained is still several orders of magnitude smaller than the published value for high‐purity foils of bulk aluminum, it is nevertheless not small enough to appreciably influence the resistivity at 296°K which is measured to be ≈60% higher than the bulk value. This discrepancy, which may be due to structural effects, emphasizes the view that the sample artifact of adding the bulk thermal resistivity to a residual resistivity can be misleading in the case of thin films, even when surface scattering is accounted for.