Abstract
We investigate the effects of native Si adatoms on structural and electronic properties of the Si(111)5 × 2-Au surface, a representative one-dimensional metal-chain system, by means of scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. High-resolution STM images of relatively long adatom-free chain segments evidence directly the inherent ×2 reconstruction, which is the essential part of a recently proposed structural model based on a renewed Au coverage of 0.7 monolayer. On the other hand, STM images for chain segments of different lengths reveal that the structural distortion induced by Si adatoms is confined in neighboring unit cells, in good agreement with DFT calculations based on that model. Si adatoms greatly affect the metallic bands of Au chains, one of which becomes fully occupied and represents a tightly confined electronic state to the distortion around Si adatoms, potentially forming short insulating segments within metallic chains. This finding provides an atomic-scale understanding of the observed gradual metal-insulator transition and atomic-scale phase separation induced by Si adatoms.
Highlights
One-dimensional (1D) metal atomic chain systems on semiconductor surfaces have attracted substantial attention because of their intriguing electronic properties and potential applications in atomic scale devices
Within the KK model, the characteristic ×2 reconstruction of the atomic chains is realized by the intrinsic ×2 arrangement of Au atoms in clear contrast to the previous model, which resorts to the global doping effect of Si adatoms[25]
We investigate the effects of Si adatoms on the Si(111)5 × 2-Au surface by examining local atomic and electronic structures around the Si adatoms with the use of scanning tunneling microscopy (STM) measurements and density functional theory (DFT) calculations
Summary
One-dimensional (1D) metal atomic chain systems on semiconductor surfaces have attracted substantial attention because of their intriguing electronic properties and potential applications in atomic scale devices. Atomic chain structures on flat and vicinal Si (or Ge) surfaces induced by In or Au adsorbates are the most actively discussed, and the Si(111)5 × 2-Au surface has been the model system for the latter cases[7,8,9,10,11] This surface has been extensively investigated by both experimental[7,11,12,13,14,15,16,17,18,19,20,21,22] and density functional theory (DFT) studies[23,24,25,26] since 1980’s. Greatly affect the metallic bands of the Au chains; one of the metallic bands becomes fully occupied just below the Fermi energy and represents a tightly confined electronic state around the Si adatom This possibly accounts for the intriguing metal-insulator transition and atomic-scale phase separation observed with the increase of Si adatoms[11,28]
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