Surfactant-mediated growth of ultrathin Ge and Si films and their interfaces: Interference-enhanced Raman study

We report on the growth and interfaces of ultrathin polycrystalline Ge and Si films when they are grown on each other using ion beam sputter depositio n with and without surfactant at different growth temperatures, studied usi ng interference enhanced Raman spectroscopy. Ge films grown on Si without s urfactant show Ge segregation at the interfaces forming an alloy of GexSi1- x as indicated by the Ge-Si Raman mode. However, use of Sb as surfactant st rongly suppresses the intermixing. Also Si films grown on Ge have been obse rved to crystallize at low-substrate temperatures in the presence of the su rfactant. In contrast to the growth of Ge on Si, the intermixing in the gro wth of Si on Ge is observed to be negligibly small even without the surfact ant layer.