Chemical vapor deposition of sp(2)-boron nitride films on Al2O3 (0001), (11 2 over bar 0), (1 1 over bar 02), and (10 1 over bar 0) substrates

Thin films of boron nitride in its sp(2)-hybridized form (sp(2)-BN) have potential uses in UV devices and dielectrics. Here, we explore chemical vapor deposition (CVD) of sp(2)-BN on various cuts of sapphire: Al2O3 ( 11 2 over bar 0 ), Al2O3 ( 1 1 over bar 02 ), Al2O3 ( 10 1 over bar 0 ), and Al2O3 (0001) using two CVD processes with two different boron precursors triethylborane and trimethylborane. Fourier transform infrared spectroscopy shows that sp(2)-BN grows on all the sapphire substrates; using x-ray diffraction, 2 theta/omega diffractogram shows that only Al2O3 ( 11 2 over bar 0 ) and Al2O3 (0001) rendered crystalline films: and using phi(phi)-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 ( 11 2 over bar 0 ) substrate, which is determined using omega(omega)-scans. Our study suggests that Al2O3 ( 11 2 over bar 0 ) is the most favorable sapphire substrate to realize the envisioned applications of r-BN films.Funding Agencies|Swedish Research Council [2017-04164]; Swedish Foundation for Strategic Research (SSF) [IS14-0027]; Carl Tryggers Foundation for Scientific Research [CTS 14:189]; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Swedish Research Council VR-RFI [2019-00191]; Swedish Foundation for Strategic Research [RIF14-0053]