# Controlled fabrication of BN/C one-dimensional van der Waals heterostructures by atomic layer deposition

A. Hossain, Hanako Okuno, Catherine Journet, Catherine Marichy

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A. Hossain, Hanako Okuno, Catherine Journet, Catherine Marichy. Controlled fabrication of BN/C one-dimensional van der Waals heterostructures by atomic layer deposition. Rafald 2022, Nov 2022, Caen, France. hal-04871244

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Submitted on 8 Jan 2025

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# Controlled fabrication of BN/C one-dimensional van der Waals heterostructures by atomic layer deposition

Ali Hossain¹,², Hanako Okuno², Catherine Journet¹, Catherine Marichy¹

1. Laboratoire des Multimatériaux et Interfaces, UMR CNRS 5615, Univ Lyon, Université Claude Bernard Lyon 1, F-69622 Villeurbanne, France

2. IRIG/MEM/LEMMA, CEA-Grenoble, 17 Avenue des Martyrs, 38054 Grenoble Cedex 09, France

ali.hossain@univ-lyon1.fr

Graphene's isolation has led to a strong interest in van der Waals (VdW) heterostructures. Owing to their intrinsic structure, VdW heterostructures show strong in-plane covalent bonding and weak out-of-plane van der Waals (VdW) interactions. In particular, the one-dimensional (1D) VdW heterostructures consist of coaxially stacked two or more distinct materials that can improve the physical and chemical properties of the final material compared to the initial one due to the confinement of electrons into two dimensions. Hexagonal Boron Nitride (hBN) attracts attention as it is isostructural to graphene with a large bandgap, excellent thermal stability and photoluminescence intensity; thus, coaxial stacking of hBN onto carbon nanotubes (CNTs) can enrich optoelectronic properties of BN/C heterostructures.¹ The growth of 1D VdW heterostructures requires a synthesis approach able to control the deposition onto a support at the atomic scale. Thanks to its simplicity, versatility and ability to control thickness at the angstrom level, Atomic Layer Deposition (ALD) appears as one of the most suited techniques to fabricate VdW heterostructures with atomic-scale precision.

Herein, the two-step ALD process of hBN developed at LMI is optimized towards controlled fabrication of 1D VdW heterostructures.² Briefly, single-wall and multi-wall CNTs are successfully coated with a layer of polyborazine within the first ALD step and then annealed at high temperature (1000-1500 °C) in order to convert the polyborazine into crystalline hBN. The obtained BN-coated CNTs are characterized by means of advanced analytic Transmission Electron Microscopy (TEM) and Electron Energy Loss Spectroscopy (EELS). A uniform coating of BN is observed onto multi-wall CNTs as revealed by EELS mapping (Fig. 1). The influence of the ALD parameters and post-annealing treatment on BN growth and structure (amorphous, turbostratic, hexagonal phase) will be discussed, as well as the impact of the starting carbon material on the final heterostructures in terms of morphology and crystallinity.

<figure><img src="image_2.png" /><figcaption>**Fig. 1.** Scanning TEM image of BN coated multi-wall CNT and its corresponding C (red), B (yellow) and N (green) elemental EELS mapping.</figcaption></figure>

<footnote>(1) Xiang, R. et al. One-Dimensional van Der Waals Heterostructures. *Science* **2020**, *367* (6477), 537–542.</footnote>

<footnote>(2) Hao, W. et al. A Novel Two-Step Ammonia-Free Atomic Layer Deposition Approach for Boron Nitride. *ChemNanoMat* **2017**, *3* (9), 656–663.</footnote>