Dispersing and semi-flat bands in the wide band gap two-dimensional semiconductor bilayer silicon oxide

TL;DR

This study reveals the electronic band structure of epitaxial bilayer silicon oxide, showing dispersing and semi-flat bands, with implications for deep UV optoelectronics and heterostructure applications.

Contribution

It provides the first detailed experimental and theoretical analysis of the band structure of bilayer silicon oxide, including the discovery of dispersing and semi-flat bands.

Findings

Dispersing bands related to electronic delocalisation within planes.

Semi-flat bands from chemical bridges between planes.

Band gap estimated at 5 eV experimentally, 7.36 eV theoretically.

Abstract

Epitaxial bilayer silicon oxide is a transferable two-dimensional material predicted to be a wide band gap semiconductor, with potential applications for deep UV optoelectronics, or as a building block of van der Waals heterostructures. The prerequisite to any sort of such applications is the knowledge of the electronic band structure, which we unveil using angle-resolved photoemission spectroscopy and rationalise with the help of density functional theory calculations. We discover dispersing bands related to electronic delocalisation within the top and bottom planes of the material, with two linear crossings reminiscent of those predicted in bilayer AA-stacked graphene, and semi-flat bands stemming from the chemical bridges between the two planes. This band structure is robust against exposure to air, and can be controled by exposure to oxygen. We provide an experimental lower-estimate of the band gap size of 5 eV and predict a full gap of 7.36 eV using density functional theory calculations.