Radio frequency sputter deposited boron nitride films

Thin films (∼1 μm) of boron nitride were grown on water‐cooled glass, silicon, and sapphire substrates by reactive sputter deposition from a BN target in Ar, Ar/N2, and N2 discharges. The effect of sputtering gas composition on film chemical and optical behavior is reported and discussed in the present paper. The following changes occurred as the gas N2 content was increased: (1) The concentration of excess boron in the films, relative to an external standard, decreased. (2) Absorption of visible and ultraviolet radiation decreased. (3) The energy band gap increased by >2 eV. Smaller band gap values were correlated with excess boron. (4) The average B–N bond strength and the ordering of B and N atoms to form B–N bonds increased. Near stoichiometric (B/N=1.1–1.4), colorless, wide band gap (5.4–5.6 eV) films were grown in gas containing from 25% to 100% N2.