Al thin films deposited epitaxially on (0001) α-Al_2O_3 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 Al_2O_3 substrate during transmission electron microscopy heating. Dynamical observations show that maximum dislocation activity occurs in the first heating cycle up to 400 ℃, with decreasing activity during further cycles. The {111} Al ‖ (0001) α-Al_2O_3 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-Al_2O_3 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 ℃, and their {2((11)-bar)} boundaries are weak pinning sites.
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机译：外延沉积在（0001）α-Al_2O_3衬底上的Al薄膜在横截面上变薄，形成Al纳米线。在透射电子显微镜加热过程中，由两个 Σ3 孪晶变体组成的 Al 线在原位被 Al 线和Al_2O_3基板之间的热膨胀差异拉紧。动力学观测表明，在高达400°C的第一个加热循环中，位错活性最大，在后续循环中活性降低。{111} Al ‖ （0001） α-Al_2O_3 接口充当位错半环的源。沿导线的螺纹位错运动产生平行于{111} Al ‖ （0001） α-Al_2O_3界面并偏移的长尾随位错段。位错倍增是通过半环和扩展螺纹位错段在导线边界和基板界面处的反应而发生的。观察到将导线一分为二的Σ3双晶粒在400 °C的热循环过程中是稳定的，它们的{2（（11）-bar）}边界是弱钉扎位点。
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