Formation and characterization of metal atom nanostructures on Si(112) facet surfaces

Abstract

Auger electron spectroscopy (AES) and reflectance anisotropy (RA) have been used to study the formation of Ga or Al chains and nanowires on the Si(112) surface. The Ga or Al chains form on the step ledges by a self-limiting process at higher temperatures (>350 °C), while at lower temperatures, Ga or Al nanowires form on the terraces in addition to the chains on the ledges. The process has been tracked in real time from the rapid change of the (2×1) Si(112) reconstruction under subcritical coverage to chain formation leading to a 5×1 reconstruction followed by a 6×1 reconstruction. During sequential deposition of Ga and Al, we observe (in RA and AES) that Ga atoms forming the chains can be replaced by Al. This indicates that the Al–Si bond is stronger than the Ga–Si bond and confirms the chemical sensitivity of the light scattering in RA. Low temperature depositions (in the 300 °C range) are shown to lead to the formation of Ga or Al metallic wires on the Si(111) terraces. Continued deposition of less than 10 monolayers at T below 250 °C leads to a very anisotropic but patterned Al or Ga structure in registry with the substrate which retains an unexpectedly large polarizability for coverages as thick as 40 monolayers.