Si(001) and SiGe(001) surfaces as a multiscale problem

The need of a multiscale approach to understand properties of semiconductor surfaces is illustrated by the examples of Si and SiGe(001) surfaces. Driving forces for several processes occur at the atomic level, and should be treated by ab inito methods. These include the structure of surfaces, diffusion of adatoms, as well as mechanisms of surface segregation. On the other hand, the presence of strain fields or the formation of quantum dots occurs at the mesoscopic length scale. These effects involve thousands of atoms, thus necessitating the use of simple atomistic models or the theory of continuous media.