Atomic ordering dependence on growth method in Ge:Si(001) islands: Influence of surface kinetic and thermodynamic interdiffusion mechanisms

Interdiffusion in self-assembled Ge:Si(001) islands has been explained by models based on either thermodynamic and/or surface kinetic considerations. In order to analyze the relevance of bulk and surface diffusion on the final composition state, we performed a set of controlled x-ray diffraction experiments to study both composition and atomic ordering in Ge/Si(001) islands grown by different methods. Surface diffusion strongly enhances the overall interdiffusion during island growth by solid source molecular beam epitaxy while chemical-vapor-deposited islands are closer to thermodynamic model systems. The growth conditions play a crucial role on the appearance of atomic ordering. In particular, a remarkable correlation between atomic ordering and surface diffusion kinetics is found.