STM studies of the initial stages of growth of Sb on Si(100) surfaces

The Sb:Si(001) surface prepared in situ by evaporation of submonolayer amounts of Sb onto Si(001) at temperatures less than 500 °C has been investigated by scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). We find that antimony displaces silicon in the top layer of atoms of the Si(001) surface at elevated temperatures rather than forming islands on top of the surface. We find a transition temperature range from 180 to 250 °C at which Sb goes from residing on top of the surface to incorporating into the top layer of atoms. The areas of antimony incorporation have the dimer row structure of the pure Si(001) surface but have a high density of ordered defects. Appearance of the defects can be explained by strain relief because of the atomic size difference of silicon and antimony atoms. Antimony clusters and dimers on top of the surface and antimony-rich regions in the top layer of the surface can be distinguished by bias-dependent imaging. I-V scans taken over the antimony rich regions display a more metallic behavior than scans from the non-passivated silicon surface. The displaced silicon atoms form ordered islands in which the dimer rows run perpendicular to those of the substrate.