Structural and electronic properties of Tl films on Ag(111): From ($\sqrt3 3$) surface alloy to moiré superstructure
Phys. Rev. B, 107 (20):
205144 (May 23, 2023)DOI: 10.1103/PhysRevB.107.205144
Abstract
We present a detailed study of the growth behavior and the electronic properties of thin Tl films epitaxially grown on Ag(111). We combine experimental results obtained by Auger electron spectroscopy, low-energy electron diffraction, scanning tunneling microscopy, scanning tunneling spectroscopy (STS), and inverse photoemission (IPE). The electronic properties identified by STS and IPE are substantiated via density functional theory (DFT) calculations. For a Tl coverage of 0.33 atomic layers (AL), our experimental results show the formation of small patches with a (√3×√3) reconstruction. With STS and IPE, we observe two dominant empty-state electronic features at E−EF≈1.6 and 3.5 eV, which are attributed to downward dispersing s,pz-derived states and to states with pz orbital symmetry, respectively. On the basis of band structure and charge distribution calculations, we discuss the variation of the binding energies of the respective electronic features observed by STS and IPE. Above 0.5 AL, a moiré superstructure evolves due to the rather large lattice mismatch between the Tl adlayer and Ag(111) which exhibits a sharp spectroscopic feature at around E−EF≈3.1 eV in STS and IPE. The comparison with DFT calculations suggests that it originates from a predominantly pz-like surface state. For even larger film thicknesses up to 4 AL, we find a rotation of the Tl layer with respect to the Ag(111) substrate of α=±(2.50±0.20)∘.
Description
Phys. Rev. B 107, 205144 (2023) - Structural and electronic properties of Tl films on Ag(111): From $(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})$ surface alloy to moir\'e superstructure