Equilibrium shape of single-layer hexagonal boron nitride islands on low-index metal substrates

TL;DR

This study investigates how the shape of hexagonal boron nitride islands grown on metal substrates is influenced by substrate step edges, combining microscopy data with theoretical modeling to understand equilibrium shapes and interactions.

Contribution

It introduces an extended Wulff construction scheme to analyze the equilibrium shapes of hBN islands considering substrate step interactions, advancing understanding of 2D material growth.

Findings

Substrate step edges significantly influence hBN island shapes.

Intrinsic edge energies and substrate interactions are quantitatively characterized.

The substrate morphology affects the overall quality of 2D hBN layers.

Abstract

Large, high-quality layers of hexagonal boron nitride (hBN) are a prerequisite for further advancement in scientific investigation and technological utilization of this exceptional 2D material. Here we address this demand by investigating chemical vapor deposition synthesis of hBN on an Ir(111) substrate, and focus on the substrate morphology, more specifically mono-atomic steps that are always present on all catalytic surfaces of practical use. From low-energy electron microscopy and atomic force microscopy data, we are able to set up an extended Wulff construction scheme and provide a clear elaboration of different interactions governing the equilibrium shapes of the growing hBN islands that deviate from the idealistic triangular form. Most importantly, intrinsic hBN edge energy and interaction with the iridium step edges are examined separately, revealing in such way the importance of substrate step morphology for the island structure and the overall quality of 2D materials.