Abstract
The Ge segregation mechanism in the Si/Ge system has been studied by medium-energy ion scattering (MEIS). One monolayer of Ge was grown on Si(001) at 450oC and annealed at 780oC. We find that the Ge redistributes during the very early stages of the annealing process and remains constant even after annealing at longer periods of time. Therefore, we conclude that the top few layers attain thermal equilibrium in a short period of time (less than 1 min). In addition, we find that the activation energy for the site exchange process occurring at the subsurface region is lower than the previously reported value when Si overlayer is grown on the Ge thin film. The exchange between the second and third layers occurs readily during the growth, even though these layers are buried, and are not expected to reduce the surface free energy. The contribution of the second layer to Ge segregation is similar to that of the topmost layer.
