Shape evolution of Ge/Si(001) islands induced by strain-driven alloying

The shape evolution of Ge/Si(001) islands grown by ultrahigh vacuum chemica l vapor deposition were investigated by atomic force microscopy at differen t deposition rates. We find that, at low deposition rates, the evolution of islands follows the conventional pathway by which the islands form the pyr amid islands, evolve into dome islands, and dislocate at a superdome shape with increasing coverage. While at a high deposition rate of 3 monolayers p er minute, the dome islands evolve towards the pyramids by a reduction of t he contact angle. The presence of the atomic intermixing between the Ge isl ands and Si substrate at high deposition rate is responsible for the revers e evolution. (C) 2001 American Institute of Physics.