Atomic structure of an impurity-stabilized Si{111} surface: Refinement using a combined-layer method

Abstract

A low-energy electron diffraction (LEED) structure analysis of a Te-stabilized unreconstructed Si{111} 1 × 1 surface is described. The intensity calculations were carried out with a computer program that treats multiple scattering in a unit made up of closely spaced surface or bulk layers in a spherical-wave expansion mode and then combines these units using a beam basis. Some details of an improved method of structure-constant evaluation employed in this program are described. The observed LEED intensities were compared with intensities calculated for several values of both the interlayer spacing and the inner potential. Quantitative comparison was made by the systematic use of the reliability factor of Zanazzi and Jona to yield both expectation values and confidence intervals. We find the separation of the first and second atomic layers to be $d_{12}=0.62\mathrm{}\pm 0.03$ Å (bulk value 0.78 Å) and the inner potential, assumed to be energy independent, to be $V_0=11.7\mathrm{}\pm 0.9$ eV. The separation of the second and third layers is unchanged from the bulk value within about 1.5%.