Figure 5: Mechanism of the Au hcp islands formation after annealing the sample at temperatures exceeding the Au/Ge eutectic temperature (above ~634 K).

(a) deposited Au aggregation due to the surface diffusion and formation of Au/Ge liquid droplet. Germanium substrate etching and formation of truncated inverted pyramidal pits; (b) cooling the sample–Au recrystallization from the liquid into the fcc phase with simultaneous Ge enhancement in the remaining liquid; (c) formation of βAuGe hcp alloy; (d) formation of Au hcp phase and Ge rim from the βAuGe hcp alloy decay at sample temperature of ~463 K. (e) Experimentally derived Au/Ge phase diagram for self-assembled Au nanostructures on a Ge(001) surface, sample cooling rate as a function of sample annealing temperature and germanium content in Au/Ge liquid The relative sizes of Auhcp(red), intergrowth domain(green) and Aufcc(blue) regions of the island after recrystallization of the liquid are marked. When changing the sample annealing temperature and sample cooling rate, the Auhcp relative sizes change.