Person:

Martinez, R

X-ray standing-wave measurements and tunneling microscopy have been combined to solve the atomic geometry of the √3×√3R30° honeycomb phase of Bi on Si(111). The standing-wave measurements utilize three different diffracting planes to triangulate the surface position of Bi atoms. The unoccupied surface sites required to completely determine the structure can be deduced from Rutherford-backscattering coverage and low-energy electron-diffraction symmetry arguments. These arguments are completely confirmed by a tunneling-microscope study, which is free of the ambiguities of previous studies. The final result is a 2/3-ML √3×√3R30° structure with Bi atoms in the T1 sites directly above first-layer Si atoms.

We resolve the atomic structure of the one-monolayer incommensurate (IC) reconstruction of Pb on Si(111) using a tunneling microscope. The local structure of this surface consists of two types of Pb trimers and a quasi-1×1 region, while on larger (>10 Å) scales the trimers are assembled into alternating domains discommensurate with the substrate. One feature of this surface is the sensitivity of the domain morphology to surface-stress inhomogeneities. This sensitivity dramatically alters the temperature at which the IC phase transforms locally to a 1×1 phase.

High quality homoepitaxialgrowth of Si on Si(111) through an overlayer of Au is shown to occur at 450–500 °C, far below the temperature required for growth of Si of similar quality on bare Si(111). Films of unlimited thickness can be obtained with excellent crystalline quality, as revealed by Rutherford backscattering spectrometry ion channeling measurements (χmin=2.2%). A distinct range of Au coverage (0.4–1.0 monolayer) results in the best quality epitaxy, with no measurable amount of Au trapped at either the interface or within the grownfilms. Cross‐sectional transmission electron microscopy reveals that in filmsgrown with Au coverages below and above the optimum range, the predominant defects are twins on (111) planes and Auinclusions, respectively.