Relaxation mechanism of Ge islands/Si(001) at low temperature

Strained layers generally relax by dislocation glide. Here, using UHV‐TEM, we study growth of Ge islands on Si(001) at ≲350 °C. We find that, although conventional relaxation (i.e., via glide of 60° dislocations) is suppressed, the islands grow relaxed from the outset, by direct incorporation of sessile 90° dislocations into the edge of the growing island. Paradoxically, the low‐temperature islands are more fully relaxed than those grown at higher temperature.