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Defects introduced to the surface of Bi(111) break the translational symmetry and modify the surface states locally. We present a theoretical and experimental study of the 2D defects on the surface of Bi(111) and the states that they induce. Bi crystals cleaved in ultrahigh vacuum (UHV) at low temperature (110 K) and the resulting ion-etched surface are investigated by low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy (UPS), and scanning tunneling microscopy (STM) as well as spectroscopy (STS) techniques in combination with density functional theory (DFT) calculations. STS measurements of cleaved Bi(111) reveal that a commonly observed bilayer step edge has a lower density of states (DOS) around the Fermi level as compared to the atomic-flat terrace. Following ion bombardment, the Bi(111) surface reveals anomalous behavior at both 110 and 300 K: Surface periodicity is observed by LEED, and a significant increase in the number of bilayer step edges and energetically unfavorable monolayer steps is observed by STM. It is suggested that the newly exposed monolayer steps and the type A bilayer step edges result in an increase to the surface Fermi density as evidenced by UPS measurements and the Kohn–Sham DOS. These states appear to be thermodynamically stable under UHV conditions.

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Proximity phenomena between superconductors and topological semimetals are at the heart of the search for novel quantum states of matter. Here we show that the epitaxial interface between one-to three-atomic-layer Pb and the Sb(111) substrate has extremely high electronic transparency. As a result, Pb loses its superconducting and even its metallic properties; its electronic spectrum mimics the semimetallic density of states of Sb. Additional states arise from a threefold symmetric potential which develops at the Pb/Sb interface. Our experimental results are supported by DFT simulations which demonstrate that this potential arises from the corrugated structure of the Pb/Sb interface.

International audienceMany metals adopt a face-centered cubic structure in their bulk form, but they often exhibit important structural and morphological deviations when confined to nanoscale or interacting with the environment. In this paper, the growth of lead nanoislands on silicon(111) has been investigated in ultrahigh vacuum for different evaporation conditions: temperature, flux, annealing time, and source or surface condition. Unexpected Pb icosahedral nanoparticles of a very large, up to 100 nm, size have been revealed to grow on Si(111) substrate. The coexistence between these 5-fold twinned Pb pyramids and expected face-centered cubic (fcc) Pb single crystals has been investigated in situ by Scanning Tunneling Microscopy (STM) and ex situ by Scanning Electron Microscopy (SEM). We found that the growth of the Pb icosahedral particles only occurs when very high Pb diffusion conditions are met, with a high quality of the silicon surface and a purified lead source. The icosahedral pyramids have been observed to be more stable upon ripening at room temperature than fcc single crystals