Tensile properties of ultrathin copper films and their temperature dependence

• Published in: Computational materials science 2010-12, Vol.50 (2), p.319-330
• Main Authors: Guo, Qiao-Neng, Yue, Xue-Dong, Yang, Shi-E, Huo, Yu-Ping
• Format: Article
• Language: English
• Subjects: ACTIVATION; ACTIVATION ENERGY; COMPUTER SIMULATION; Condensed matter: structure, mechanical and thermal properties; Copper; DEFORMATION; Dislocation; Dislocation pinning; DISLOCATIONS; Exact sciences and technology; Mechanical and acoustical properties; Molecular dynamics; Physical properties of thin films, nonelectronic; Physics; PINNING; STRESS; Stresses; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Temperature dependence; Temperature effect; Tensile deformation; TENSILE PROPERTIES; Tension; Thermal activation; THIN FILMS
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2010.08.021

The molecular dynamics simulations are performed with single-crystal copper thin films under uniaxial tensile loading to investigate temperature effects on the mechanical responses. We found that with increasing sample temperatures, both the maximum stress and the Young’s modulus decrease, but the maximal potential energy increases. So, we identified the critical temperature for the transition of deformation mechanism. Then, the deformation was analyzed by examining the variation of the atomic structure of the emerging dislocation. Finally, activation volume and activation free energy of tensile deformation at the maximum stress point of thin Cu film have been calculated for the first time in a temperature range from 293 to 460 K. Thus, the mechanisms of the strange temperature dependence of tensile deformation have been explained. It is found that there exist three temperature regions, which correspond to different thermal activation mechanisms of dislocation motion. When the temperature is above 370 K, the rate-controlling mechanism is dislocation climbing; when below 370 K, the mechanism is mainly characterized by the overcoming of Peierls–Nabarro barrier and a few localized pinnings; and when about 370 K, the mechanism is pipe diffusion.