Yb, Eu, and (Yb + Eu)-stabilized 3 × 1 and 3 × 2 reconstructions on Si(1 1 1)

The atomic arrangement of Si(1 1 1)3 × 1 and 3 × 2 surfaces stabilized by adsorption of divalent rare-earth metals (RE=ytterbium (Yb) and europium (Eu)) in the range of 0.1–0.33 monolayer (ML) has been studied by low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). The 3 × 2 surface is shown to have the metal coverage of 1/6 ML and possess the atomic arrangement which is independent on the nature of adsorbed RE atoms. Based on the analysis of empty and filled-state STM images, the honeycomb-chain-channel structure is proposed for Yb and Eu-induced 3 × 2 reconstructions, with the adsorption sites of metal atoms being strongly shifted from T4 or H3. A poor ordering of RE atoms in this structure results in 1/2-order LEED streaks in narrow energy range (60–80 eV). The origin of 3 × 1 reconstruction is discussed in terms of present results as well as previously published data.