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 deposition with and without surfactant at different growth temperatures, studied using interference enhanced Raman spectroscopy.  Ge films grown on Si without surfactant show Ge segregation at the interfaces forming an alloy of ${\mathrm{Ge}}_x{\mathrm{Si}}_{1-x}$ as indicated by the Ge-Si Raman mode. However, use of Sb as surfactant strongly suppresses the intermixing. Also Si films grown on Ge have been observed to crystallize at low-substrate temperatures in the presence of the surfactant. In contrast to the growth of Ge on Si, the intermixing in the growth of Si on Ge is observed to be negligibly small even without the surfactant layer.