In situ TEM observation of dislocation motion in thermally strained Al nanowires

Abstract Al thin films deposited epitaxially on (0001) α-Al2O3 substrates, have been thinned cross-sectionally to form Al nanowires. The Al wires, consisting of two Σ3 twin variants, have been strained in situ by differential thermal expansion between the Al wires and the Al2O3 substrate during transmission electron microscopy heating. Dynamical observations show that maximum dislocation activity occurs in the first heating cycle up to 400°C, with decreasing activity during further cycles. The {111} Al || (0001) α-Al2O3 interface acts as a source of dislocation half-loops. The motion of threading dislocations along the wires generates long trailing dislocation segments parallel to, and offset from, the {111} Al || (0001) α-Al2O3 interface. Dislocation multiplication occurs by the reaction of half-loops and extended threading dislocation segments at the wire boundaries and substrate interface. The Σ3 twin grains bisecting the wires are observed to be stable during thermal cycling to 400°C, and their { 2 11 } boundaries are weak pinning sites.