Distinct 2D <i>p</i>(2 × 2) Sn/Cu(111) Superstructure at Low Temperature: Experimental Characterization and DFT Calculations of Its Geometry and Electronic Structure.

Abstract

Atomically precise control of metal adatoms on metal surfaces is critical for designing novel low-dimensional materials, and the Sn-Cu(111) system is of particular interest due to the potential of stanene in topological physics. However, conflicting reports on Sn-induced superstructures on Cu(111) highlight the need for clarifying their geometric and electronic properties at low temperatures. We employed scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), angle-resolved photoemission spectroscopy (ARPES), and density functional theory (DFT) to investigate submonolayer (<0.25 ML) Sn adsorption on Cu(111) at 100 K. We confirmed a <i>p</i>(2 × 2) Sn/Cu(111) superstructure with one Sn atom per unit cell and found that Sn preferentially occupies three-fold <i>hcp</i> sites. ARPES measurements of the band structure-including a ~0.3 eV local gap between two specific bands at the Γ¯2 point in a metallic overall electronic structure-were in good agreement with the DFT results. Notably, the STM-observed <i>p</i>(2 × 2) morphology differs from the honeycomb-like or buckled stanene structures reported on Cu(111), which highlights the intricate interactions between adatoms and the substrate.