Thickness Dependent Carrier Density at the Surface of SrTiO3 (111) Slabs

TL;DR

This study uses density functional theory to explore how the surface electronic structure and stability of SrTiO3 (111) slabs depend on thickness, revealing conditions for 2DEG formation and potential for device applications.

Contribution

It demonstrates the thickness-dependent formation of 2DEG on Ti-terminated SrTiO3 (111) surfaces and analyzes stability conditions for experimental realization.

Findings

Ti-terminated slabs can host a 2DEG.

Carrier density varies strongly with thickness.

Surface stability favors Ti termination with oxygen atoms.

Abstract

We investigate the surface electronic structure and thermodynamic stability of the SrTiO3 (111) slabs using density functional theory. We observe that, for Ti-terminated slabs it is indeed possible to create a two-dimensional electron gas (2DEG). However, the carrier density of the 2DEG displays a strong thickness dependence due to the competition between electronic reconstruction and polar distortions. As expected, having a surface oxygen atom at the Ti termination can stabilize the system, eliminating any electronic reconstruction, thereby making the system insulating. An analysis of the surface thermodynamic stability suggests that the Ti terminated (111) surface should be experimentally realizable. This surface may be useful for exploring the behavior of electrons in oxide (111) interfaces and may have implications for modern device applications.