Substrate modification during chemical vapor deposition of hBN on sapphire

Anushka Bansal, Maria Hilse, Benjamin Huet, Ke Wang, Azimkhan Kozhakhmetov, Ji Hyun Kim, Saiphaneendra Bachu, Nasim Alem, Ramon Collazo, Joshua A. Robinson, Roman Engel-Herbert, Joan M. Redwing

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

A comparison of hexagonal boron nitride (hBN) layers grown by chemical vapor deposition on C-plane (0001) versus A-plane (112¯ 0) sapphire (α-Al2O3) substrate is reported. The high deposition temperature (>1200 °C) and hydrogen ambient used for hBN deposition on sapphire substantially alters the C-plane sapphire surface chemistry and leaves the top layer(s) oxygen deficient. The resulting surface morphology due to H2 etching of C-plane sapphire is inhomogeneous with increased surface roughness which causes non-uniform residual stress in the deposited hBN film. In contrast to C-plane, the A-plane of sapphire does not alter substantially under a similar high temperature H2 environment, thus providing a more stable alternative substrate for high quality hBN growth. The E2g Raman mode full width at half-maximum (FWHM) for hBN deposited on C-plane sapphire is 24.5 ± 2.1 cm-1 while for hBN on A-plane sapphire is 24.5 ± 0.7 cm-1. The lesser FWHM standard deviation on A-plane sapphire indicates uniform stress distribution across the film due to reduced undulations on the surface. The photoluminescence spectra of the hBN films at 300 and 3 K, obtained on C-plane and A-plane sapphire exhibit similar characteristics with peaks at 4.1 and 5.3 eV reported to be signature peaks associated with defects for hBN films deposited under lower V/III ratios. The dielectric breakdown field of hBN deposited on A-plane sapphire was measured to be 5 MV cm-1, agreeing well with reports on mechanically exfoliated hBN flakes. Thus, under the typical growth conditions required for high crystalline quality hBN growth, A-plane sapphire provides a more chemically stable substrate.

Original languageEnglish (US)
Pages (from-to)54516-54526
Number of pages11
JournalACS Applied Materials and Interfaces
Volume13
Issue number45
DOIs
StatePublished - Nov 17 2021

All Science Journal Classification (ASJC) codes

  • Materials Science(all)

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