STUDIES OF THE FORMATION OF GA AND AL NANOWIRES ON SI(112) FACET SURFACES

摘要

Reflectance anisotropy (RA), low energy electron diffraction (LEED) and AFM have been used to study the formation of Ga or Al chains and nanowires on the Si(112) surface. At T > 350℃, the Ga or Al chains form at the step edges by a self-limiting process, 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 (2x1) Si(112) reconstruction under sub-critical coverage to chain formation leading to a 5x1 reconstruction followed by a 6x1 reconstruction (1). During sequential deposition of Ga and Al, we observe (in RA and AES) that Ga atoms forming the chains can be replaced by Al, indicating a stronger Al-Si bond strength and confirming the chemical sensitivity of the light scattering in RA. Low temperature depositions (in the 300℃ range) are shown to lead to the formation of Al (or Ga) metallic wires on the Si(111) terraces. Continued deposition of less than 10 monolayers at T below 250℃ 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 ml.