Proceedings of International Forum for Green Asia 2017
Special issue of Evergreen - Joint Journal of Novel Carbon Resource Sciences & Green Asia Strategy

P-13

Epitaxial chemical vapor deposition growth of boron nitride atomic sheet overCu(111)/sapphire substrate
Yuki Uchida1, Tasuku Iwaizako1, Seigi Mizuno1, Masaharu Tsuji2 and Hiroki Ago1,312Interdisciplinary Graduate School of Engineering, Kyushu University
Research and Education Center of Carbon Resources, Kyushu University
3
Global Innovation Center (GIC), Kyushu University
6-1 Kasugakouen, Kasuga, Fukuoka 816-8580, JapanAbstract
Hexagonal boron nitride (h-BN), an insulating two-dimensional (2D) material, is an ideal
substrate to bring out properties of other 2D materials, such as graphene, transition metal
dichalcogenides and black phosphorus. Here, we demonstrate chemical vapor deposition(CVD) growth of high-quality, large-area monolayer h-BN on Cu(111) thin film deposited onc-plane sapphire using BH3NH3 as a feedstock. Highly oriented triangular h-BN grains growon the Cu(111). Low-energy diffraction (LEED) mesurement indicate the hexagonal lattice ofthe monolayer h-BN is well oriented along the underlaying Cu(111) lattice, implying epitaxial
growth of the h-BN.
deposition growth of h-BN atomic sheet
using thin Cu(111) film deposited on c-planesapphire substrate by sputtering. Prepared Cu
film consists of (111) plane, which produce
highly oriented h-BN sheet. We observed that
triangular h-BN grains are oriented in two
define directions with respect to the Cu(111)thin film. The controlled orientation of thehexagonal lattice in large-area was confirmed
by low-energy electron diffraction (LEED)
measurement.

1. Introduction
Two dimensional (2D) materials such asgraphene, transition metal dichalcogenides
and black phosphorus have been gaining
interest due to the excellent physicalproperties.1-3 However, they are sensitive tosurroundings owing to their extremely thin
2D structure. Hexagonal boron nitride (hBN), a layered material with a hexagonal
network of boron and nitrogen atoms, is anideal insulating substrate for bringing out theintrinsic properties of 2D materials.4
Chemical vapor deposition (CVD) using
catalytic substrate has been widely reported
as a promising method to grow large-area hBN films in recent year.5-7 Most researchers
have used polycrystalline catalytic substrate,
mainly Cu foil,5 Ni foil6 and Pt foil,7 whichhave rough surface with different orientationsof grains. Consequently, h-BN film grown on
polycrystalline metal substrate consists of anumber of h-BN grains with different
orientations and even different thickness,
resulting in polycrystalline h-BN films
composed of poorly connected small h-BN
grains. Therefore, the control of crystallinityof the metal substrate is essential for thegrowth of high-quality h-BN films. Here, wedemonstrate epitaxial chemical vapor

2. ExperimentalCu(111) prepared by sputtering wasused for catalytic substrate. CVD growth ofh-BN was performed using ammonia borane
as a feedstock. To investigate morphologies
of grown h-BN and surface conditions
surface, SEM and AFM measurements wereperformed. LEED was measured fordemonstrating epitaxial growth of h-BN film.
3 Results and discussion
3.1 SEM observation of grown h-BN
Figure 1 show a SEM images of h-BNgrains grown on Cu(111) by CVD. After ashort CVD process with 5 min reaction,triangular h-BN grains were observed on theCu(111) surface. It is considered that the edgeof triangular h-BN grains have zigzag edges

38Proceedings of International Forum for Green Asia 2017
Special issue of Evergreen - Joint Journal of Novel Carbon Resource Sciences & Green Asia Strategy

P-13
and a previous theoretical study suggested
that edge structures of h-BN with terminating
nitrogen atoms are more stable in triangulargrains.8 Therefore, it is likely that obtained hBN grains have zigzag edges withterminating nitrogen atoms (Inset of Fig. 1a).
As can be seen in Fig. 1a, most of the h-BN
grains are oriented in two specific directions.
The existence of these two preferredorientations indicates an epitaxial growth of
the h-BN on the Cu(111) surface. By
extending the CVD growing time, the lateralsize of h-BN grains increase, after longenough growing periods grains completely
coalesce, and a uniform h-BN sheet covering
the entire Cu surface can be obtained. This
resultsuggests
thath-BN
grows
preferentially on a Cu catalyst compared withthe surface of h-BN.

Fig. 2. (a) LEED pattern measured for the fully
covered h-BN sheet. (b) Magnified image of oneof the diffraction spots. (c) Atomic model oftriangular grains of h-BN on Cu(111).

4 Conclusion
Monolayer h-BN was epitaxially grownby CVD on Cu(111) thin film deposited on cplane sapphire substrates.
The use ofsapphire substrate realizes a large-scale
synthesis of transferrable h-BN.
Weobserved that the orientations of triangular hBN grains are highly controlled by theCu(111) lattcice, pointing to two main
directions. Further, we obtained a wellaligned monolayer h-BN sheet by extending
the growth time, which also presents theepitaxy of the monolayer h-BN on Cu(111).
Our work is expected to develop an insulating
layer for future flexible and transparent 2Ddevices.

Figure 1. SEM images of h-BN grown onCu(111)/sapphire substrate at different
reaction time of 5 min (a) and 15 min (b).
Inset illustrates atomic model of triangulargrain of h-BN Scale bar is 20 m.

3.2 LEED measurement for investigatingorientation of h-BN
An orientation of as-grown h-BN on aCu(111) film was measured by LEED.
Because a beam size of LEED we used isabout 1mm, it is possible to investigate amacroscopic orientation of h-BN on Cu(111).
Fig. 2a and b show LEED pattern measured
with 100 eV and the six clear spots which arederived from both h-BN and Cu(111) lattices
were measured. Therefore, the diffraction
pattern obtained by LEED measurement
support a epitaxial growth of h-BN on theCu(111) suggested by SEM observation. Fig.
2c illustrates the atomic model of triangularh-BN grains oriented in two directions withrespect to the Cu(111) lattice determined byour SEM and LEED observations.

Acknowledgements
This work was supported by thePRESTO-JST and JSPS KAKENHI. Y.U.
acknowledges the recipt of scholarship from
Advanced Graduate Program in Global
Strategy for Green Asia.
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