Determine the microscopic identity and energetic alignment of hBN defect states

Determine the dominant impurity types in hexagonal boron nitride, their positions within the hBN bandgap, and their energetic alignment relative to the graphene charge-neutrality point, in order to resolve the competing interpretations of displacement-field-induced charge transfer and defect ionization.

Background

The paper attributes the observed displacement-field-induced electron doping and increased disorder in graphene to the ionization of defect states in the surrounding hBN. The applied field tilts the hBN bands and can bring donor- or acceptor-like in-gap states into energetic resonance with graphene, enabling charge transfer and producing charged impurities.

However, the discussion identifies unresolved disagreement in the literature concerning which microscopic defects dominate, where their energy levels lie within the hBN bandgap, and how those levels align with graphene’s charge-neutrality point. Experimental measurements and density-functional-theory calculations provide differing estimates, particularly for donor-like states. Resolving these quantities is therefore necessary for a microscopic interpretation of defect charging and for predicting the electronic response of hBN-encapsulated van der Waals heterostructures.