A Two-Step Chemical Vapor Deposition Process for the Synthesis of an Ir(111)/Borophene/2D-Hexagonal Boron Nitride Heterostructure by Intrinsic Segregation

TL;DR

This paper presents a novel two-step chemical vapor deposition method for synthesizing a vertical heterostructure of Ir(111), borophene, and hexagonal boron nitride, leveraging intrinsic segregation for scalable 2D material growth.

Contribution

It introduces an intrinsic segregation-assisted growth process for high-quality, scalable 2D heterostructures using a single precursor in ultrahigh vacuum conditions.

Findings

Successful synthesis of a micron-sized, homogeneous Ir(111)/borophene/hBN heterostructure.

Use of complementary microscopy techniques to characterize the heterostructure.

Demonstration of a scalable growth route for 2D material heterostructures.

Abstract

We report on a two-step ultrahigh vacuum chemical vapor deposition synthesis of a vertical Ir(111)/borophene/hexagonal boron nitride heterostructure, using borazine as a single-source precursor. The process takes advantage of the finite solubility of boron in Ir: low precursor pressure at high temperature first establishes a boron reservoir in the near-surface region of the substrate, whereas subsequent growth at higher precursor pressure promotes the formation of a closed hexagonal boron nitride monolayer. During cooldown, the reduced boron solubility drives segregation to the surface, resulting in the formation of a borophene monolayer beneath the hexagonal boron nitride overlayer. The heterostructure, with micron sized grains, homogeneously covers the entire Ir substrate. The study is performed by complementary spot profile analysis low-energy electron diffraction, low-energy electron microscopy, and scanning tunneling microscopy measurements. This intrinsic segregation-assisted growth concept provides a promising route toward scalable synthesis of high-quality, vertical heterostructures of two-dimensional materials.