Effects of nanoscale surface roughness on the resistivity of ultrathin epitaxial copper films

Abstract

The knowledge on the influence of surface roughness and the electron–phonon (el–ph) interaction on electrical transport properties of nanoscale metal films is important from both fundamental and technological points of view. Here we report a study of the temperature dependent electron transport properties of nanoscale copper films by measuring temperature dependent electrical resistivity with thickness ranging from 4 to 500 nm. We show that the residual resistivity, which is temperature independent, can be described quantitatively using both measured vertical surface root-mean-square roughness and lateral correlation length in the nanoscale, with no adjustable parameter, by a recent quasi-classical model developed by Chatterjee and Meyerovich (2010 Phys. Rev. B 81 245409–10). We also demonstrate that the temperature dependent component of the resistivity can be described using the Bloch–Grüneisen equation with a thickness dependent el–ph coupling constant and a thickness dependent Debye temperature. We show that the increase of the el–ph coupling constant with the decrease of film thickness gives rise to an enhancement of the temperature dependent component of the resistivity.