Atomically precise lateral modulation of a two-dimensional electron liquid in anatase TiO2 thin films

TL;DR

This study demonstrates atomic-scale lateral modulation of a two-dimensional electron liquid in anatase TiO2 thin films, revealing precise control over electronic band structure and potential for nanoscale electronic device engineering.

Contribution

We introduce a novel method to achieve atomic-scale lateral modulation of 2DELs in anatase TiO2, enabling tunable electronic properties through surface reconstruction and chemical doping.

Findings

Periodic band backfolding observed due to surface reconstruction

Unidirectional energy gaps opened in the electronic structure

Presence of a saddle point in the density of states near the Fermi level

Abstract

Engineering the electronic band structure of two-dimensional electron liquids (2DELs) confined at the surface or interface of transition metal oxides is key to unlocking their full potential. Here we describe a new approach to tailoring the electronic structure of an oxide surface 2DEL demonstrating the lateral modulation of electronic states with atomic scale precision on an unprecedented length scale comparable to the Fermi wavelength. To this end, we use pulsed laser deposition to grow anatase TiO2 films terminated by a (1 x 4) in-plane surface reconstruction. Employing photo-stimulated chemical surface doping we induce 2DELs with tunable carrier densities that are confined within a few TiO2 layers below the surface. Subsequent in-situ angle resolved photoemission experiments demonstrate that the (1 x 4) surface reconstruction provides a periodic lateral perturbation of the electron liquid. This causes strong backfolding of the electronic bands, opening of unidirectional gaps and a saddle point singularity in the density of states near the chemical potential.