Abstract

We report an investigation of the electronic band structure of the ${\mathrm{Si}}_{x}{\mathrm{Sn}}_{(1\ensuremath{-}x)}/\mathrm{Si}(111)\ensuremath{-}(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})R30\ifmmode^\circ\else\textdegree\fi{}$ solid solution using angle-resolved photoemission. This reconstruction was studied in the coverage range between 0.15 and 0.40 monolayers at room and low temperature, with special emphasis on the analysis of the symmetry and morphology of the surface states and the metallic character as a function of temperature and coverage. While there is no indication of a $(3\ifmmode\times\else\texttimes\fi{}3)$ pattern at low temperature with structural techniques, strikingly clear features of this phase are found in the valence band analysis for a coverage of 0.33 ML. We present also an analysis of the influence of the Si intermixing in the surface-state behavior and metallic character.

Highlights

  • No Fermi surface nesting was found in photoemission,[11] and an analysis of the electronic band structures and of the Sn 4d core level at RT and LT did not reveal any significant difference.[12,13]

  • The surface band crossing the Fermi energy is split in two different surface state bands, and the Sn 4d core level exhibits two components in both phases

  • The electronic band structure of the Sn/Si111͒ interface was determined at RT and LT170 Kalong the ⌫K and ⌫M

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Summary

INTRODUCTION

The properties of ordered metal overlayers on semiconducting substrates have been investigated for many years, due to both their fundamental interest and their many implications in several technologically relevant fields.[1,2,3] One of the most common adsorbate-induced surface reconstructions is the (ͱ3ϫͱ3)R30° ͑in the following ͱ3), which is found on the111͒ surfaces of Si and Ge for many different metals. An interesting feature of Sn/Si111͒ with respect to the Sn/Ge111͒ case is that no phase transition has been found so far with structural techniques like low-energy electron diffractionLEEDor STM,[25–27] besides the formation of local (3ϫ3) patches around defect sites. A recent ab initio study[30] has predicted even more drastic features for these surfaces: besides a semiconducting character for the mosaic phase, decoupled surface bands associated either with Si or Sn atoms should be observed, with a strong coverage dependence in the range of the solid solution (0.16 MLϽ⌰Ͻ0.33 ML). In the quoted values of the coverage.[11,12] The surface was annealed to 650 °C to favor the formation of the ͱ3 structure This annealing temperature gives rise to the lowest defect density at the surface, around 3%.22. The sample temperature during the measurements was RT and 170 K

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