Epitaxial hexagonal boron nitride on Ir(111): A work function template

TL;DR

This study combines experimental STM/STS and DFT calculations to analyze the structure and work function modulation of monolayer hexagonal boron nitride grown on Ir(111), revealing a moiré pattern with significant electronic property variations.

Contribution

The paper provides a detailed experimental and theoretical characterization of h-BN on Ir(111), highlighting the work function modulation and its relation to atomic interactions within the moiré superstructure.

Findings

Moiré superstructure with ~29 Å periodicity and 0.4 Å corrugation observed.

Work function varies by ~0.5 eV within the moiré unit cell.

DFT confirms experimental work function modulation and atomic interaction effects.

Abstract

Hexagonal boron nitride (h-BN) is a prominent member in the growing family of two-dimensional materials with potential applications ranging from being an atomically smooth support for other 2D materials to templating growth of molecular layers. We have studied the structure of monolayer h-BN grown by chemical vapour deposition on Ir(111) by low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS) experiments and state-of-the-art density functional theory (DFT) calculations. The lattice-mismatch between the h-BN and Ir(111) surface results in the formation of a moir\'e superstructure with a periodicity of $\sim$29 \AA\ and a corrugation of $\sim$0.4 \AA. By measuring the field emission resonances above the h-BN layer, we find a modulation of the work function within the moir\'e unit cell of $\sim$0.5 eV. DFT simulations for a 13-on-12 h-BN/Ir(111) unit cell confirm our experimental findings and allow us to relate the change in the work function to the subtle changes in the interaction between boron and nitrogen atoms and the underlying substrate atoms within the moir\'e unit cell. Hexagonal boron nitride on Ir(111) combines weak topographic corrugation with a strong work function modulation over the moir\'e unit cell. This makes h-BN/Ir(111) a potential substrate for electronically modulated thin film and hetero-sandwich structures.