Phonon thermal transport in encapsulated copper hybrids

S Tripathi and MM Islam and A Strachan, JOURNAL OF APPLIED PHYSICS, 125, 045106 (2019).

DOI: 10.1063/1.5082191

We use molecular dynamics simulations to characterize the effect of various surface terminations on phonon thermal transport in nanoscale Cu slabs. Specifically, we studied Cu slabs approximately 4 nm in thickness with atomistically flat (111) surfaces, slabs with similar to 30% surface vacancies to mimic atomic-level roughness, and slabs with a surface oxide. Motivated by recent experimental observations, we study the effect of capping these surfaces with single layer graphene. From the thermal conductivity of the various samples as a function of length, we extracted conductivity and phonon mean free paths in the absence of boundary scattering other than that originating from the surfaces under study. As expected, both surface vacancies and an oxide layer reduce thermal conductivity and we characterize the effect in terms of the specularity parameter. While capping the slabs with graphene increases the conductivity, the poor thermal contact between Cu and graphene results in less than ideal performance of the hybrid material. Interestingly, the simulations reveal that the graphene capping layer reduces surface scattering on the Cu slabs, and this effect is significantly more pronounced in the case of a defective surface. The results provide insights into the use of graphene capping to improve transport in nanoscale interconnects for nanoelectronics. Published under license by AIP Publishing.

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