Probing Electronic Properties of CVD Monolayer Hexagonal Boron Nitride by an Atomic Force Microscope

Shiyu Deng,Xi Wan,Shijia Xu,Kun Chen,Yanyun Gu,Mingliang Gao,Huanjun Chen

doi:10.3389/fmats.2021.735344

Shiyu Deng, Xi Wan + Show 5 more

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Ultrathin hexagonal boron nitride (h-BN) has recently attracted a lot of attention due to its excellent properties. With the rapid development of chemical vapor deposition (CVD) technology to synthesize wafer-scale single-crystal h-BN, the properties of h-BN have been widely investigated with a variety of material characterization techniques. However, the electronic properties of monolayer h-BN have rarely been quantitatively determined due to its atomically thin thickness and high sensitivity to the surrounding environment. In this work, by the combined use of AFM (atomic force microscope) PeakForce Tunneling (PF-TUNA) mode and Kevin probe force microscopy (KPFM) model, both the electrical resistivity (529 MΩ cm) and the inherent Fermi level (∼4.95 eV) of the as-grown monolayer h-BN flakes on the copper substrate have been quantitatively analyzed. Moreover, direct visualization of the high-temperature oxidation-resistance effect of h-BN nanoflakes has been presented. Our work demonstrates a direct estimation of the electronic properties for 2D materials on the initial growth substrate without transfer, avoiding any unwanted contaminations introduced during the transfer process. The quantitative analysis by state-of-the-art atomic force microscope techniques implies that monolayer h-BN can be employed as an atomically thin and high-quality insulator for 2D electronics, as well as a high-temperature antioxidation layer for electronic device applications.

Highlights

Ultrathin hexagonal boron nitride (h-BN) has recently attracted more and more attention because of its similarity to graphene in structure, as well as its demonstrated excellent properties (Dean et al, 2010; Liu et al, 2013a; Wang et al, 2019; Chen et al, 2020)
Monolayer h-BN nanoflakes with regular shapes have been synthesized on the copper foil and the electronic properties including the electrical resistivity (529 MΩ cm) and the inherent Fermi level (∼4.95 eV) of the chemical vapor deposition (CVD) monolayer h-BN on the initial growth substrate have been quantitatively analyzed by the combined use of AFM PeakForce Tunneling (PF-TUNA) mode and Kevin probe force microscopy (KPFM) model, demonstrating that monolayer h-BN can be used as an atomically thin and highquality insulator as well as an antioxidation layer
If the growth time was less than 15 min, the nucleation sites of h-BN with random shapes were distributed along the polished lines (Supplementary Figure S2A and Supplementary Section S2) on the copper surface, in good agreement with the previous result (Kim et al, 2012b)

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Introduction

Ultrathin hexagonal boron nitride (h-BN) has recently attracted more and more attention because of its similarity to graphene in structure, as well as its demonstrated excellent properties (Dean et al, 2010; Liu et al, 2013a; Wang et al, 2019; Chen et al, 2020). Monolayer h-BN nanoflakes with regular shapes have been synthesized on the copper foil and the electronic properties including the electrical resistivity (529 MΩ cm) and the inherent Fermi level (∼4.95 eV) of the CVD monolayer h-BN on the initial growth substrate have been quantitatively analyzed by the combined use of AFM PeakForce Tunneling (PF-TUNA) mode and Kevin probe force microscopy (KPFM) model, demonstrating that monolayer h-BN can be used as an atomically thin and highquality insulator as well as an antioxidation layer.

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