Effects of annealing on structure of GaAs(001) nanoindentations

We have studied the changes generated by a post-annealing treatment of a nanoindentation structure realized on GaAs(001). The nanoindentations were made under a large range of loads (between 0.5 and 10 mN) at room temperature and were subsequently annealed at 500° C for 1 h. Transmission electron microscopy was used to observe the nanoindentation structures before and after annealing. The size of the dense plastic zone generated around the indent site decreased by about 20% after annealing and rosette arms propagated along the ⟨110⟩ directions parallel to the indented surface. Not only were the lengths of the rosette arms multiplied by a factor of three after the annealing process but also the arrangement and structure of the dislocations drastically changed. The hairpin dislocations starting from the side of the indents observed before annealing transformed into alignments of half-loop dislocations. Furthermore, no partial dislocations were observed after the annealing whereas some of the e could be detected before annealing.