Understanding grain boundary electrical resistivity in Cu: the effect of boundary structure

TL;DR

This study systematically investigates how grain boundary structure in copper influences electrical resistivity, revealing that low-angle boundaries and curvature significantly increase resistivity, with atomistic structure playing a key role.

Contribution

The paper provides a detailed correlation between grain boundary structure, excess volume, and resistivity in copper, combining experimental measurements with molecular dynamics simulations.

Findings

Low-angle grain boundaries have twice the resistivity of high-angle boundaries.

Grain boundary curvature increases resistivity by about 80%.

Resistivity correlates with grain boundary excess volume.

Abstract

Grain boundaries (GBs) in metals usually increase electrical resistivity due to their distinct atomic arrangement compared to the grain interior. While the GB structure has a crucial influence on the electrical properties, its relationship with resistivity is poorly understood. Here, we perform a systematic study on the resistivity and structure relationship in Cu tilt GBs, employing high resolution in-situ electrical measurements coupled with atomic structure analysis of the GBs. Excess volume and energies of selected GBs are calculated using molecular dynamics simulations. We find a consistent relation between the coincidence site lattice (CSL) type of the GB and its resistivity. The most resistive GBs are high range of low-angle GBs (misorientation 14 to 18 degrees) with twice the resistivity of high angle tilt GBs, due to the high dislocation density and corresponding strain fields. Regarding the atomistic structure, GB resistivity approximately correlates with the GB excess volume. Moreover, we show that GB curvature increases resistivity by about 80%, while phase variations and defects within the same CSL type do not considerably change it.