Dresden 2017 – wissenschaftliches Programm
MM 30: Topical session: Interface-Controlled Microstructures: Mechanical Properties and Mechano-Chemical Coupling - Structure and Deformation II
MM 30.1: Vortrag
Dienstag, 21. März 2017, 11:45–12:00, BAR 205
Low angle grain boundaries induced buckling in nanoscale copper films — •Xiaopu Zhang1, Jian Han2, David Srolovitz2, and John Boland1 — 1CRANN, Trinity College Dublin, Dublin 2, Ireland — 2Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut St., Philadelphia, PA 19104 USA
Scanning tunneling microscopy is used to study the grain boundaries that emerge at the surface of nearly coplanar copper nanocrystalline films with (111) surface orientations. At symmetric low angle grain boundaries the film is found to buckle so as to form valleys comprised of dissociated edge dislocations and ridges where dislocations have recombined. Geometry analysis shows that buckling is induced by the out-of-plane grain rotation driven by the favorable energy of dislocation-dissociation, and confirmed by simulations. Due to the symmetry of the FCC slab, both the type of emergent grain boundaries (dissociated or recombined) and the film buckling sense are forced to toggle whenever grain boundaries shift direction by 60o, producing a novel buckling pattern. These results indicate that it is impossible to form perfectly flat two dimensional nanoscale films of copper and indeed other metals that exhibit low dislocation-dissociation energies.