Molecular Dynamics Study on the Coupled Effects of Size and Pre-Existing Oxide Layer on the Compressive Mechanical Properties of Copper Nanowires

Abstract

Copper nanowires generally exhibit a native oxide shell layer, which can significantly impact their performance and reliability, especially in nanoelectronics applications. Using molecular dynamics simulations with the variable charge ReaxFF potential, we systematically examine the effects of pre-existing oxide layers on the mechanical properties and deformation mechanisms of [001]-oriented Cu nanowires with varying diameters at room temperature. Our findings reveal a size-dependent influence of the native oxide layer on the mechanical behavior. Specifically, the formation of an oxide shell (CuxOy) around the Cu core reduces the activation barrier for defect nucleation, reducing yield properties and, thereby, weakening the nanowires. This effect is more pronounced in smaller samples due to the intensified interaction between the metallic core and the oxide shell. Additionally, while the strength, elastic modulus, and yield stress increase with the diameter of pristine and oxidized specimens, pristine nanowires consistently exhibit superior mechanical properties when compared to their oxidized counterparts. The degradation in mechanical performance primarily stems from the early onset of plasticity initiated at the oxidized surface. These findings emphasize the detrimental impact of native oxide layers on the mechanical behavior of Cu nanowires and highlight the critical role played by size upon the mechanical properties of nano-oxidized metal samples. This work provides valuable insights into tailoring the mechanical properties of Cu nanowires, contributing to the optimization of their performance in both nanoelectronics and mechanical applications.