Large-scale nanotwins in Cu films/Cu nanowires via stress engineering by a high-energy ion beam bombardment process: growth and characterization

Dense nanoscale twins were introduced into Cu films and nanowires through bombardment with highenergy Ar+ ions at low temperatures. Both the twin boundary density and indentation hardness of the ion-irradiated Cu films increased with decreases in the bombardment temperature. The improved mechanical strength in the ion-irradiated Cu films is attributed to twin boundary-dislocation and dislocation-dislocation interactions. The strengthened region is several hundreds of nanometers beneath the surface of the bombarded nanowires and thin strips. A mechanism based on irradiation-induced thermal spike cascades is proposed to explain the influence of the energy of the Ar+ ions and bombardment temperature on nanoscale twinning in crystalline Cu. This study provides a route to developing advanced interconnection technology for micro- and nanoelectronic devices.