Synthesis of hexagonal boron nitride films on silicon and sapphire substrates by low-pressure chemical vapor deposition

• Hexagonal BN films deposited by chemical vapor deposition on Si and sapphire. • Growth temperature lower than past studies for growth on non-catalytic substrates. • The deposited films have crystallite size of ~ 6 nm and grain size of ~ 80-100 nm. • The films are stoichiometric with the B:N ratio of ~ 1:1. • The measured optical band gaps are 5.48 eV and 5.76 eV. Hexagonal boron nitride (hBN) films are synthesized on silicon (100) and c-sapphire substrates by low-pressure chemical vapor deposition at 1100 °C. Ammonia borane is used as a single-source precursor. hBN films are characterized by Raman, UV-vis, and x-ray photoelectron spectroscopies, and the surface morphology is studied by scanning electron microscopy. This study shows a direct method to synthesize and characterize hBN films on the most extensively used substrates in the semiconductor industry, eliminating the need for a transfer method used when the films are grown on metallic substrates. The synthesized hBN films have an approximate crystallize size of 6.37 nm on silicon and 6.13 nm on sapphire. The B:N ratio is found in agreement with the theoretical stoichiometric values of 1:1 for film growth on both substrates. The deposited films have a granular nature, and films grown on silicon have a high pinhole density. The measured optical band gaps of hBN grown on silicon and sapphire are 4.46 eV and 5.76 eV, respectively.