Tl on the Si(111)- surface: Density Functional Theory

ABSTRACT

The atomic geometry and electronic structure of a single and double-layer of Thallium (Tl) on the Si(111)-($\sqrt{7}\times \sqrt{3}$) surface have been studied using density functional theory. For Tl layer, we considered three cases: (i) Tl single layer as H${}_3$ (Tl is directly above a fourth-layer Si atom) and T${}_4$ (Tl is directly above a second-layer Si atom) sites, (ii) Tl double layer as H${}_3$–T${}_4$ (the first Tl layer at H${}_3$ site while the second layer at the T${}_4$ site) and T${}_4$–H${}_3$ (the first Tl layer at T${}_4$ site while the second layer at the H${}_3$ site) sites, and (iii) Tl double layer as rectangular (rect) and hexagonal (hex) sites. We have calculated the electronic band structures and the electronic charge densities of the energetically favourable cases. While the Tl single-layer makes the Si(111) surface semiconductor character, the double-layer Tl makes electronically the Si(111) surface metallic which agrees with the recent experimental measurements.

KEYWORDS:

• Ab initio
• surfaces
• electronic structure
• atomic structure

Acknowledgments

Our calculations were performed with high-performance computing centre (HPCC) at Gazi University. The authors thank Dr B.S. Kandemir for the valuable contribution.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work also was financially supported by the Ministry of Development of TR under project no. 2016K121220.