Imperfection-sensitive ductility of aluminium thin films

Ductility, defined as the strain at the onset of necking, has been characterized in thin Al films using an on-chip, internal stress actuated, microtensile testing setup. In the smallest specimens, the ductility is equal to 0.08 and 0.27 for 200 and 375 nm thick films, respectively, while the average strain-hardening exponents are, respectively, equal to 0.11 and 0.23. In addition to the thickness effect, ductility decreases with increasing specimen size due to imperfection sensitivity, involving a size-dependent statistical behaviour.