Supplementary Information

a Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Fukuoka 816-

8580, Japan

b CNT Application Research Center, AIST, Tsukuba 305-8565, Japan

c Nanomaterials Institute, AIST, Tsukuba 305-8565, Japan

d Global Innovation Center (GIC), Kyushu University, Fukuoka 816-8580, Japan

e School of Science and Technology, Kwansei Gakuin University, Hyogo 669-1337, Japan

Synthesis of sub-millimeter single-crystal grains of

aligned hexagonal boron nitride on epitaxial Ni film

Alexandre Budiman Taslim,a Hideaki Nakajima,b Yung-Chang Lin,c Yuki Uchida,a

Kenji Kawahara,d Toshiya Okazaki,b Kazu Suenaga,c Hiroki Hibino,e and Hiroki Ago*a,d

- 1 -

Electronic Supplementary Material (ESI) for Nanoscale.This journal is © The Royal Society of Chemistry 2019

(a) Cu/sapphire (b) Cu-Ni/sapphire

[Cu]/([Cu]+[Ni]) = 52%

Gas flow(c)

[Cu]/([Cu]+[Ni]) = 38%[Cu]/([Cu]+[Ni]) = 9%

Cu-Ni

a-Al2O3 (0001)

10 mm10 mm10 mm

50 mm200 mm

Figure S1. (a) Optical micrograph of the Cu(111) surface after the CVD at 1050 ºC. Severe evaporation

of Cu makes rough surface with many pits reaching to the underlying sapphire substrate. (b) SEM image

of the Cu-Ni(111) surface after the CVD at 1050 ºC. A number of very small h-BN grains were observed.

(c) Schematic of the Cu-Ni surface after the CVD and the SEM images taken at the marked positions. The

initial Cu concentration, i.e. [Cu]/([Cu]+[Ni]), of the alloy film is ~80%. The concentration of Cu was

strongly dependent on the substrate position, indicating the significant evaporation of Cu from the alloy

film during the CVD process. The spatial distribution of Cu concentration suggests that the Cu evaporation

is enhanced by the borazine vapor. (d) Optical micrograph of the Ni(111) surface after the CVD at 1100 ºC,

which shows clean and flat surface.- 2 -

(d) Ni/sapphire

200 µm

Figure S2. Atomic model of aligned h-BN grains on the Ni(111) surface.

- 3 -

0°- 180°0°- 0°

Figure S3. Comparison of the grain size of monolayer h-BN grown by thermal CVD method.

- 4 -

500

300

100

La

tera

l s

ize

(µ

m)

1 32

Reference no.

4 5 6 This

work

4 Q. Wu et al., Sci. Rep. 5,16159 (2015)5 S. Caneva et al., Nano Lett. 15, 1867 (2015)6 Y. Ji et al., ACS Nano 11, 12057 (2017)

1 S. Caneva et al., Nano Lett. 16, 1250 (2016)2 J. Yin et al., Small 11, 4497 (2015)3 G. Lu et al., Nat. Commun. 6, 6160 (2015)

400

200

Figure S4. (a) BF-LEEM and (b) PEEM images of the same h-BN grain shown in Figure 3a. Due to

large grain size, both images are composed of multiple view images. The LEEM images at the central

area of (a) are omitted. Fields-of-view are 40 mm and 100 mm for BF-LEEM and PEEM images,

respectively.

- 5 -

(a) (b)

Figure S5. (a) BF-LEEM image and corresponding diffraction patterns. The h-BN grain is different

from that shown in Figure 3a. (b) Electron reflectivity curves taken at h-BN and Ni surfaces of the

grain shown in (a).

- 6 -

(a)

2

2

1

1

33

4

4

5

5

Ni h-BN

1 µm

(b)

Energy (eV)

Inte

nsity (

arb

. u

nit)

20 mm

200 300 400 500 600

C

ou

nts

Energy loss (eV)

Figure S6. EELS spectrum collected from the sample shown in Figure 4d.

B K edge

N K edge

- 7 -

100 µm

(a) (b)

100 µm

(c)

100 µm

Figure S7. Influence of N2 gas added during the h-BN growth. The concentration of N2 gas: (a) 0 vol%,

(b) 10 vol%, and (c) 25 vol%.

- 8 -

Figure S8. AFM images of Ni(111) surface after annealing H2 gas at 1000 Pa (a) and 30 Pa (b). The

Ni annealed at 30 Pa shows rougher surface than that annealed at 1000 Pa, strongly suggesting Ni

evaporation at the low pressure (30 Pa). The RMS value was measured for the whole scanned area. (c)

SEM image of the Ni(111) surface after the CVD performed at 30 Pa. As the rough Ni surface

increased the nucleation density, the Ni surface was fully covered with h-BN after the CVD under the

standard condition (10 min at 1100 ºC).

(b)

100 mm

(c)

(a)

- 9 -

0 nm

3 nm

2 µm 0 nm

3 nm

2 µm

RMS = 0.57 nm RMS = 0.69 nm