Distribution of Sn in Strained Ge1-xSnx (001): The Effect of Surface Passivation

The effect of surface passivation on tin distribution in Ge1-xSnx(001)/Ge(001) are studied using first principles calculations. The segregation of Sn atoms towards the surface were suppressed when the clean surface is fully passivated with hydrogen adatoms while changing the passivating species to halogen adatoms resulted in enhancing Sn segregation towards the surface. This effect strengthens when moving down the Group-VII elements from fluorine to iodine. For both hydrogenated and halogenated surfaces, aggregation of sn atoms is not favored.