Equilibrium shape of single-layer hexagonal boron nitride islands on iridium

Marin Petrović,Frank-J Meyer Zu Heringdorf,Michael Horn-Von Hoegen

doi:10.1038/s41598-019-56000-1

Marin Petrović, Frank-J Meyer Zu Heringdorf + Show 1 more

Open Access

https://doi.org/10.1038/s41598-019-56000-1

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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.

Highlights

Large, high-quality layers of hexagonal boron nitride are a prerequisite for further advancement in scientific investigation and technological utilization of this exceptional 2D material
low-energy electron microscopy (LEEM) images in Fig. 1(a,b) show isolated hexagonal boron nitride (hBN) islands on the Ir surface, where thin dark lines spanning across the field of view are Ir step edges
When straight steps are present on the Ir surface and sshows minor change across a large area, as in Fig. 1(a,b), one hBN orientation grows exclusively in triangular form, and the other one grows exclusively in the form of trapezoids, as we reported earlier[23]

Summary

Introduction

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 We address this demand by investigating chemical vapor deposition synthesis of hBN on an Ir(111) substrate, and focus on the substrate morphology, mono-atomic steps that are always present on all catalytic surfaces of practical use. Elimination of defects from the production process is essential for scalable, high-throughput synthesis of hBN that holds a great potential for advancements in various fields of technology, such as field effect transistors[4], light-emitting diodes[5] and sensors[6] The method enabling such synthesis is chemical vapor deposition (CVD), which in the case of hBN typically consists of initial nucleation of individual islands on a catalyst metal surface, followed by island growth and coalescence to form a full monolayer[7]. Crystallographic directions noted in the center of the figure apply to all LEEM and μ-LEED images

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