Growth and Decay of Germanium Islands on Silicon Studied by High Temperature Stm

We use a scanning tunneling microscope (STM) capable of imaging the growing layer at high temperature during molecular beam epitaxy (MBE) to study the epitaxial growth of Germanium on Silicon and the decay of Ge islands. The periodicity of the (2×N) reconstruction of two-dimensional Ge layers on Si (001) is measured as function of the Ge coverage. Strain energy drives the formation of the (2×N) reconstruction and Si/Ge intermixing. A comparison to total energy calculations predicting the periodicity of the (2×N) reconstruction is used to estimate the amount of Si-Ge intermixing near the surface. The evolution of the size and shape of individual “hut clusters” is measured and explained by kinetically self-limiting growth. The relaxation of kinetically a determined morphology towards equilibrium is followed for a Ge layer on Si(111). Strained two-dimensional as well as partially relaxed three-dimensional islands dissolve and are soaked up by larger three-dimensional islands which are dislocated and therefore fully relaxed.