Effects of Surface Roughness and Electron-Phonon Interaction on Electron Transport of Ultrathin Epitaxial Copper Films

We report effects of surface roughness and electron-phonon interaction on transport properties of electrons in ultrathin epitaxial copper films of thickness ranging from 5 nm to 500 nm grown on Si(100) substrates. The transport of electrons in the film was examined by measuring the temperature dependent resistivity in the temperature range of 5 K to 300 K. We demonstrate that the temperature independent component of resistivity can be described by the root-mean-square-surface roughness and lateral correlation length with no adjustable parameter, using a recent quasi-classical model developed by Chatterjee and Meyerovich [1]. However, the temperature dependent component of the resistivity can be described using the Bloch-Gr\"{u}neisen formula with a thickness dependent electron-phonon coupling constant and a thickness dependent Debye temperature. We show that the increase of the electron-phonon coupling constant with the decrease of film thickness gives rise to an enhancement of the temperature dependent component of the resistivity.\\[4pt] [1] Chatterjee S and Meyerovich A E 2010 Interference between bulk and boundary scattering in high quality films \textit{Phys. Rev. B} \textbf{81} 245409--10