The conductivity of thin metallic films according to the electron theory of metals

TLDR

The observed drop in conductivity of thin alkali‑metal films is attributed to reduced electron mean free paths caused by boundary collisions. The paper aims to derive a more accurate conductivity formula for thin alkali‑metal films and compare it with experiment to deduce surface characteristics. The study compares measured conductivity of thin films with a theoretical formula derived from boundary‑collision limited mean free paths. Measurements show that as alkali‑metal films thin to a few atomic layers, their conductivity falls below bulk values.

Abstract

The conductivity of thin films of the alkali metals has recently been measured in the H. W. Wills Physical Laboratory, Bristol*. It was found that as the thickness of the film is decreased to that of a few atomic layers the conductivity drops below that of the bulk metal. In the papers quoted the hypothesis was put forward that this effect is due to the shortening of the mean free paths of the conduction electrons of the metal by collisions with the boundaries of the film. The experimental results were compared with a formula derived on the basis of this hypothesis. This formula was, however, obtained subject to a number of simplifying assumptions, and it is the first purpose of this paper to obtain a more accurate formula. I also compare this formula with experiment, and make certain deductions about the surfaces of thin films.