Influences of growth parameters on the film formation of hexagonal boron nitride thin films grown on sapphire substrates by low-pressure chemical vapor deposition

Abstract

Hexagonal boron nitride (h-BN) films were grown on c-plane sapphire substrates by low-pressure chemical vapor deposition with BCl3 and NH3 as the boron and nitrogen sources, respectively, and the influences of growth parameters on the film quality were investigated for samples with a thickness of about 1 µm. The dependence of X-ray diffraction on the growth temperature (T g) indicated that the crystalline quality is most improved in the sample grown at 1200 °C, in which the epitaxial relationship of {100}h-BN ∥ {110}sapphire and {001}h-BN ∥ {001}sapphire was confirmed. This condition enhanced lateral growth, resulting in the formation of grains with flat top surfaces. The T g dependence was discussed in relation to the amorphous AlN formed on the substrate surface and the reaction between BCl3 and NH3 in the vapor phase. The correlation between the structural and luminescent properties, which was found from the T g dependence of CL, was also discussed.

Effects of sapphire nitridation and growth temperature on the epitaxial growth of hexagonal boron nitride on sapphire

“…Other reported CVD growths of sp 2 -BN on sapphire incorporated sapphire nitridation at the growth temperature (1200 o C in Ref. [9] and 1500 o C in Ref. [11]) and those films were of similar crystalline quality to the film in this work grown at 1350 o C with sapphire nitridation at 850 o C (indicated by the similar position and FWHM values of the 26.7 o peak in the corresponding XRD θ-2θ scans).…”

“…tBN shows a broad peak at lower angle than 26.7 o [9]. Depending on the crystalline quality of the AlN formed by the nitridation step, a peak may or may not be seen at 36 o , corresponding to the (002) AlN plane.…”

“…o should be present, corresponding to the (002) hBN plane and the (006) sapphire plane, respectively [9]. tBN shows a broad peak at lower angle than 26.7 o [9].…”

“…Epitaxial sp 2 -BN growth was supported by a thin and amorphous nitridated layer in Ref. [9] and by a thin and strained AlN layer in Ref. [11] (suggested by the (002) AlN peak in the corresponding XRD diffractogram).…”

“…In-plane * Corresponding author: e-mail ahmedk2@rpi.edu, Phone: +15189619314 lattice constants of hBN and sapphire are 2.5 Å and 4.758 Å, respectively, indicating a large lattice mismatch [10]. Some groups [9,12] reduced this lattice mismatch by introducing an AlN buffer layer (in-plane lattice constant of 3.11 Å [10]), grown by a sapphire nitridation step at the growth temperature (TG). In this work, a thin and amorphous buffer layer, formed by a low temperature (850 o C) sapphire nitridation step, is shown to favor epitaxial hBN growth.…”