Misfit Accommodation During Heteroepitaxial Growth

Abstract

For heteroepitaxial growth the misfit has to be accommodated during growth. For different systems the processes are quite different. For metals on metals (like Pb on Cu(111)) the film is more or less floating where only the orientation is provided by the substrate. For some materials the growing film accommodates coherently to the substrate and overgrows defects like atomic steps by elastic deformation of the film. For semiconductors a one-to-one correspondence of film atoms to substrate atoms requires a clear transition from pseudomorphic to relaxed growth of the film. This process is studied for the growth of Ge on Si(111) with Sb as surfactant by SPA-LEED (spot profile analysis of LEED). A detailed analysis shows after the pseudomorphic film a rough surface with pyramids showing three slopes of 113 type. Filling the trenches between the pyramids gives rise to the dislocation network formation, which is needed to form a smooth relaxed film. The dislocation network is well analysed by LEED due to the elastic corrugation, which the dislocation produce even for film thicknesses of more than 50 monolayers