Post-growth enhancement of CVD-grown hexagonal boron nitride films on sapphire

This study explores the effect of post-growth annealing on hexagonal boron nitride (hBN) films grown on c-sapphire substrates by chemical vapor deposition as post-growth annealing proves to overcome the equipment limitations of commercial thermal CVD systems and offers a simplistic way to enhance the properties of the as-grown hBN films useful for multiple-wafer scalability, thereby making it a practical approach for industrial manufacturing of high-quality hBN films. hBN films are grown at 1100 °C by CVD process and are annealed up to 1300 °C under nitrogen atmosphere in an annealing furnace system. It is observed that the annealed hBN films are continuous and have a pronounced granular structure as compared to the as-grown hBN films. The annealed BN films retain the 1:1 B:N stoichiometry and the hexagonal phase as observed in the as-grown hBN films. The optical bandgap of the annealed hBN films is augmented from 5.70 eV to 5.82 eV as a result of the annealing treatment, indicating enhanced optical properties.