Electronic Structure of Exfoliated and Epitaxial Hexagonal Boron Nitride

TL;DR

This study provides detailed experimental insights into the electronic structure of hexagonal boron nitride (hBN), comparing exfoliated and epitaxial forms, revealing how fabrication methods influence its electronic properties.

Contribution

It presents the first direct measurement of the full valence band structure of exfoliated hBN and compares it with epitaxial hBN, highlighting the impact of growth techniques on electronic properties.

Findings

Exfoliated hBN has a valence band width of 19.4 eV.

Identified {\

}- and {\

Abstract

Hexagonal boron nitride (hBN) is an essential component in van der Waals heterostructures as it provides high quality and weakly interacting interfaces that preserve the electronic properties of adjacent materials. While exfoliated flakes of hBN have been extensively studied using electron transport and optical probes, detailed experimental measurements of the energy- and momentum- dependent electronic excitation spectrum are lacking. Here, we directly determine the full valence band (VB) electronic structure of micron-sized exfoliated flakes of hBN using angle-resolved photoemission spectroscopy with micrometer spatial resolution. We identify the {\pi}- and {\sigma}-band dispersions, the hBN stacking order and determine a total VB bandwidth of 19.4 eV. We compare these results with electronic structure data for epitaxial hBN on graphene on silicon carbide grown in situ using a borazine precursor. The epitaxial growth and electronic properties are investigated using photoe- mission electron microscopy. Our measurements show that the fundamental electronic properties of hBN are highly dependent on the fabrication strategy.