Phonon thermal transport in copper: The effect of size, crystal orientation, and grain boundaries

Abstract

In electronic devices at the micro- and nanoscale, thermal management is vital. At such small sizes, crystal orientation, grain boundaries, and even the size itself can play an important role in the thermal transport and need to be taken into careful consideration when devices are designed. In this article, we perform computational experiments using non-equilibrium molecular dynamics simulations to evaluate the effect of size, orientation, and grain boundaries on the phonon thermal transport of copper. In addition, we compare the results obtained from the rescale and Langevin thermostat procedures. We find that the contribution of phonons to the total thermal conductivity in copper increases as the size decreases. Furthermore, the Σ5(210)[001] twist grain boundary is found to have a significant effect on the thermal transport of a bi-crystalline copper system when the grains are 15 nm. No such effect is found for the Σ3(112)[110] twin boundary. The effect of crystal orientation on the thermal conductivity is also studied, and no discerned effect can be observed. It is found that the Langevin thermostat leads to an over-estimation of the thermal conductivities at smaller scales and should be used with caution.