Abstract
The Tl/Si(111)1 × 1 surface is a representative of a 2D layer with Rashba-type spin-split electronic bands. To utilize the spin polarization, doping of the system should be understood on atomic level. We present a study of two types of atomic defects predicted to dope the considered electronic system – Si-induced vacancies and defects associated with the presence of extra Tl atoms. Structural calculations based on density functional theory (DFT) confirm the stability of the proposed defect structure consisting of an extra Si atom and missing seven Tl atoms as proposed in an earlier experimental study. The calculated spatial charge distributions indicate an enhancement of the charge around the extra Si atom, which correctly reproduces topographies of the corresponding scanning tunneling microscopy images while the calculated local densities of states of this system explain obtained scanning tunneling spectra. The DFT structural calculations let us determine the atomic structure of the defect caused by the presence of an extra Tl atom. The calculated spatial charge distributions show a ring-like feature around the extra Tl atom. The obtained results indicate a charge transfer from the central extra Tl atom to its vicinity in the agreement with earlier photoemission measurements.
Highlights
The Tl/Si(111)1 × 1 surface is a representative of a 2D layer with Rashba-type spin-split electronic bands
We presented a combined theoretical and experimental study of the Tl/Si(111) adsorption system with Si-induced vacancies and defects implied by the presence of extra Tl adatoms
We considered a Tl/Si(111) system defected by an extra Si atom and missing seven Tl atoms, structure of which is based on a model proposed in the earlier scanning tunneling microscopy (STM) study[31]
Summary
The Tl/Si(111)1 × 1 surface is a representative of a 2D layer with Rashba-type spin-split electronic bands. Electronic structures of Bi/Si(111) and Tl/Si(111) have been modified by the formation of 2D alloys with other elements[17,18], or by sandwiching a Sn monolayer between Si(111) and the heavy element layer[19]. This resulted in metallic spin-split bands instead of the otherwise semiconducting bands formed by Bi or Tl on Si(111). The complex spin texture of the spin-polarized states has been studied in detail[5,8,9,10] and the spin-split bands have been shown to be robust against exposure to H2 (100 L) and O2 (500 L)[10]
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