Hierarchy of defect ensembles on the surface of loaded copper

The evolution of the distribution of nanodefects formed on the surface of polished copper foils under tensile stresses is investigated. It is found that nanodefects form four ensembles. The energies of formation and the mean sizes of nanodefects in two consecutive ensembles differ, respectively, by a factor of three. When the concentration of nanodefects in a particular ensemble reaches a thermodynamically optimum value (≈5%), some of these nanodefects annihilate and the other nanodefects transform to nanodefects of the following ensemble. The load applied to the sample continuously generates nanodefects comprising the first ensemble, which leads to periodic oscillations of the nanodefect concentration in all four ensembles.