Experimental verification of the surface termination in the topological insulator TlBiSe$_{2}$ using core-level photoelectron spectroscopy and scanning tunneling microscopy

TL;DR

This study combines scanning tunneling microscopy and core-level photoelectron spectroscopy to analyze the surface termination of TlBiSe₂, revealing residual atom islands and a broken bonding surface structure, crucial for understanding its topological properties.

Contribution

It provides the first detailed surface morphology and chemical analysis of TlBiSe₂, clarifying the surface termination and bonding structure after cleaving.

Findings

Residual atom islands observed on cleaved surface

Thallium core-level spectra show surface-specific deformation

Broken Tl-Se bonds inferred from spectroscopic data

Abstract

The surface termination of the promising topological insulator TlBiSe$_{2}$ has been studied by surface and bulk sensitive probes. Our scanning tunneling microscopy has unmasked for the first time the unusual surface morphology of TlBiSe$_{2}$ obtained by cleaving, where islands are formed by residual atoms on the cleaved plane. The chemical condition of these islands was identified using core-level spectroscopy. We observed thallium core-level spectra that are strongly deformed by a surface component in sharp contrast to the other elements. We propose a simple explanation for this behavior by assuming that the sample cleaving breaks the bonding between thallium and selenium atoms, leaving the thallium layer partially covering the selenium layer. These findings will assist the interpretation of future experimental and theoretical studies on this surface.