The influence of Cu on dislocation motion in Si

Intrinsic silicon specimens are compressed along the (2 11 1) axis and cooled under a high stress. Transmission electron microscopy (TEM) examinations show that the specimens contain hexagonal dislocation loops and very large stacking faults which are often formed by the trailing partial dislocation being pinned by a sessile jog. An in-situ TEM video recording of a 90° trailing partial moving by double kink nucleation leads to the evaluation of the kink migration energy at 1.2 eV. Hexagonal dislocation loops are found to relax to curved segments at 260 °C in specimens containing Cu compared to 350 °C for intrinsic Si specimens. The interstitial Cu atoms enhance glide motion by reducing the energy barrier heights which the kinks must surmount. The mechanism of reducing bond strength is similar to that proposed for the doping effect and is that which is responsible for low temperature formation of intermetallic compounds. Sessile jogs are found to be present in the specimens containing Cu heat treated at 260 °C, even though the hexagonal loops relaxed. The activation energy for a dislocation containing a sessile jog is higher because it involves motion of dislocation segments in the cross slip planes.