Effect of de-twinning on tensile strength of nano-twinned cu films

Chia Hung Lee, Erh Ju Lin, Jyun Yang Wang, Yi Xuan Lin, Chen Yu Wu, Chung Yu Chiu, Ching Yu Yeh, Bo Rong Huang, Kuan Lin Fu, Cheng Yi Liu

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1 Scopus citations


Tensile tests were carried on the electroplated Cu films with various densities of twin grain boundary. With TEM images and a selected area diffraction pattern, nano-twinned structure can be observed and defined in the electroplated Cu films. The density of the nano-twin grain structure can be manipulated with the concentration of gelatin in the Cu-sulfate electrolyte solution. We found that the strength of the Cu films is highly related to the twin-boundary density. The Cu film with a greater twin-boundary density has a larger fracture strength than the Cu film with a lesser twin-boundary density. After tensile tests, necking phenomenon (about 20 µm) occurred in the fractured Cu films. Moreover, by focused ion beam (FIB) cross-sectional analysis, the de-twinning can be observed in the region where necking begins. Thus, we believe that the de-twinning of the nano-twinned structure initiates the plastic deformation of the nano-twinned Cu films. Furthermore, with the analysis of the TEM images on the nano-twinned structure in the necking region of the fractured Cu films, the de-twinning mechanism attributes to two processes: (1) the ledge formation by the engagement of the dislocations with the twin boundaries and (2) the collapse of the ledges with the opposite twin-boundaries. In conclusion, the plastic deformation of nano-twinned Cu films is governed by the de-twinning of the nano-twinned structure. Moreover, the fracture strength of the nano-twinned Cu films is proportional to the twin-boundaries density.

Original languageEnglish
Article number1630
Issue number7
StatePublished - Jul 2021


  • De-twinning
  • Nano-twinned Cu
  • Tensile strength


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