Surfactant induced reversible changes of surface morphology

Abstract

We have investigated the influence of a surfactant on the equilibrium surface morphology in the pseudomorphic regime of heteroepitaxial growth. At 700 \ifmmode^\circ\else\textdegree\fi{}C, 8 monolayers of Ge on Si(001) using Sb as surfactant form strained islands with a size of \ensuremath{\sim}300 \AA{}, allowing partial elastic relaxation. The surface morphology depends strongly on the Sb coverage and changes from islands with [117] facets at high Sb coverage via round, flat cones with an inclination angle of 12\ifmmode^\circ\else\textdegree\fi{} to islands rotated by 45\ifmmode^\circ\else\textdegree\fi{} with [105] facets formed during growth at low Sb coverage. The equilibrium conditions are verified by the reversible transition from [117] facets to 12\ifmmode^\circ\else\textdegree\fi{} cones initiated by a change of the surfactant coverage.