It has been experimentally observed that Ge will segregate to the surface during Si deposition on Ge/Si(100). We have studied the segregation process by the analytical potential molecular dynamics method. We concentrated on recognizing the segregation mechanism and the time scales involved in the phenomenon. Firstly, we showed that the analytical potential molecular dynamics method can be successfully used to study the processes leading to the segregation. We found that the segregation process is dominated by thermally activated processes at high temperature (1000 K) and that the time scale for the process is fairly short (similar to 1 ns). We describe the observed atom-level segregation mechanisms in detail. (C) 2004 Elsevier B.V. All rights reserved.