Non-monotonic boundary resistivity for electron transport in metal nanowires

Boundary scattering is the most widely encountered size effect in nanoscale transport phenomena, and the scattering rate is usually regarded as a constant that is proportional to the ratio of carrier velocity to the characteristic size. Here, through combined experimental measurements and numerical modeling, we show non-monotonic variations of the boundary scattering rate for free electrons in metal nanowires as temperature escalates. This observation is attributed to the change in the electron-phonon (e-ph) scattering angle as temperature reduces, which alters the surface scattering rate. In particular, at low temperatures, electrons traveling along the wire axis have to be first relaxed by e-ph scattering before they collide with the nanowire surface. Theoretical analysis indicates a transition temperature of 0.29 times Debye temperature. A theoretical model considering the effects of the scattering angle is proposed that can fit the measured experimental data for both copper and silver nanowires over a wide temperature range.