Nature - USA (2020-06-25)

512 | Nature | Vol 582 | 25 June 2020

Article

boron nitride (a-BN) have been investigated as potential low-κ die-
lectrics, showing promising results^5. However, recent reports on BN
dielectrics show films with turbostratic structure or high dielectric
constants that indicate crystalline structure^15 ,^16. In this study, we

utilized low-temperature remote inductively coupled plasma–chemical

vapour deposition (ICP-CVD; see Methods) to obtain 3-nm-thick BN

layers on Si substrates (see Extended Data Fig. 1 for growth on Cu and

SiO 2 substrates). The transmission electron microscopy imaging and

b

cd

e

5 nm

2 nm

a

500 nm

Fig. 1 | Atomic structure of a-BN. a, Low-magnification TEM image of a-BN. b,
Selected-area electron diffraction image showing a diffuse pattern with no
discernible crystalline rings. c, High-resolution TEM image. d, Magnification of

the area indicated by the red box in c, showing a disordered atomic arrangement.

e, Fast Fourier transform results for the area depicted in d, demonstrating a

diffuse diffraction pattern that is typical of an amorphous film.

1,700 1,600 1,500 1,400 1,300

–0.0 1

0.00

0.01

0.02

0.03

0.04

1,260 1,400 1,540 1,680

0

600

1,200

1,800

Raman shift (cm–1)

a-BN

SiO 2 /Si

196192 188184

0

3

6

9

12

15

18

Binding energy (eV)

Intensity (a.u.

)

Boron 1 s Nitrogen 1 s

d

abc

e

190 195 200 205 210

0

2

4

6

8

10

2

4

6

8 30 °

55 °

70 °

S*

V*

402400398396394

0

20

40

60

Binding energy (eV)

Ab

sorption

(a.u.)

Intensity (a.u.

)

Inte

nsity (a.u.)

Wavenumber (cm–1) Energy (eV)

Trilayer hBN

E1u (LO) E1u (TO)

Fig. 2 | Chemical structure of a-BN. a, b, XPS profiles for the B 1s (a) and N 1s (b)
peaks. c, Raman spectra of a-BN and epitaxially grown trilayer hBN (used as a
reference) on a SiO 2 (300 nm)/Si substrate. The Raman spectrum of the SiO 2
substrate is identical to that of a-BN, suggesting that no distinct crystalline hBN
modes are present in a-BN. d, FTIR spectrum measured using s-polarized

radiation at an incident angle of 60°. The absorption peaks near 1,370 cm−1 and

1,570 cm−1 are attributed to transverse optical (TO) and longitudinal optical

(LO) modes of BN, respectively. e, PEY-NEXAFS spectra for the B K edge of a-BN,

measured at incident angles of 30°, 55° and 70°, showing no dependence on

orientation. a.u., arbitrary units.