Midgap states and band gap modification in defective graphene/h-BN heterostructures

TL;DR

This study investigates how various defects in graphene/h-BN heterostructures influence electronic properties, revealing midgap states from certain defects and band gap modifications from oxygen defects, using ab initio and model calculations.

Contribution

It demonstrates the impact of specific defects on electronic states in graphene/h-BN heterostructures and introduces a simple tight-binding model to reproduce these effects.

Findings

Defects in h-BN induce midgap states in graphene.

Oxygen defects significantly alter the graphene band gap.

Hybridization varies depending on defect type.

Abstract

The role of defects in van der Waals heterostructures made of graphene and hexagonal boron nitride (h-BN) is studied by a combination of ab initio and model calculations. Despite the weak van der Waals interaction between layers, defects residing in h-BN, such as carbon impurities and antisite defects, reveal a hybridization with graphene p$_{\rm z}$ states, leading to midgap state formation. The induced midgap states modify the transport properties of graphene and can be reproduced by means of a simple effective tight-binding model. In contrast to carbon defects, it is found that oxygen defects do not strongly hybridize with graphene's low-energy states. Instead, oxygen drastically modifies the band gap of graphene, which emerges in a commensurate stacking on h-BN lattices.