Atomic Scale Surface Structure and Morphology of InAs Nanowire Crystal Superlattices: The Effect of Epitaxial Overgrowth

While shell growth engineering to the atomic scale is important for tailoring semiconductor nanowires with superior properties, a precise knowledge of-the surface structure and morphology at different stages of this type of overgrowth has been lacking. We present a systematic scanning tunneling microscopy (STM) study of homoepitaxial Shell growth of twinned superlattices in zinc blende InAs nanowires that transforms {11I}A/B-type facets to the nonpolar {110}type. STM imaging along the nanowires provides information on different stages of the shell growth revealing distinct differences in growth dynamics of the crystal facets and surface structures not found in the bulk. While growth of a new surface layer is initiated simultaneously (at the twin plane interface) on the {111}A and {111}B nanofacets, the step flow growth proceeds much faster on {111}A compared to {111}B leading to significant differences in roughness. Further, we observe that the atomic scale structures on the {111}B facet is different from its bulk counterpart and that shell growth on this facet occurs via steps perpendicular to the (112)B-type directions