  We extend quantum models of nanowire surface scattering to incorporate bulk
resistivity and extract an expression for the increased resistivity due to
surface roughness. To learn how to improve conductivity, we calculate
conductivity degradation from individual wavelengths of surface roughness, and
show how these can be convolved to give resistivity for arbitrary surfaces. We
review measurements from Cu films and conclude that roughness at short
wavelengths (less than 100 nm) dominates scattering, and that primarily
specular scattering should be achievable for RMS roughness below about 0.7 nm.
