The Anomalous Temperature Effect on the Ductility of Nanocrystalline Cu Films Adhered to Flexible Substrates

The effect of temperature, T, on the ductility of nanocrystalline (NC) Cu films of different thicknesses on flexible substrates is studied by uniaxial tension. It is found that the NC Cu films will fracture more easily with increasing T, exhibiting the anomalous T effect compared with that of bulk NC metals and freestanding films. Moreover, the T dependence of ductility becomes stronger for thinner films due to the larger decrement of the interfacial strength in thinner films. T-induced softening of the stretchable substrate reduces the interface constraint ability for suppressing strain localization, leading to the anomalous T effect.