Chemical vapor deposition of sp2-boron nitride films on Al2O3 (0001), (112¯), (11¯02), and (101¯) substrates

Thin films of boron nitride in its sp2-hybridized form (sp2-BN) have potential uses in UV devices and dielectrics. Here, we explore chemical vapor deposition (CVD) of sp2-BN on various cuts of sapphire: Al2O3 (112¯0), Al2O3 (11¯02), Al2O3 (101¯0), and Al2O3 (0001) using two CVD processes with two different boron precursors triethylborane and trimethylborane. Fourier transform infrared spectroscopy shows that sp2-BN grows on all the sapphire substrates; using x-ray diffraction, 2θ/ω diffractogram shows that only Al2O3 (112¯0) and Al2O3 (0001) rendered crystalline films: and using phi(ϕ)-scans, growth of the rhombohedral polytype (r-BN) films on these substrates is confirmed. These films were found to be epitaxially grown on an AlN interlayer with comparatively higher crystalline quality for the films grown on the Al2O3 (112¯0) substrate, which is determined using omega(ω)-scans. Our study suggests that Al2O3 (112¯0) is the most favorable sapphire substrate to realize the envisioned applications of r-BN films.