Effect of the boron-to-nitrogen ratio on leakage current characteristics of boron nitride films prepared by surface-wave plasma enhanced chemical vapor deposition

Sp²-bonded boron nitride (BN) films with different B-to-N ratios are deposited on Si and Ni substrates at an ion impact energy of around 50 eV by surface-wave plasma enhanced chemical vapor deposition. The overall crystallinity and order of sp² bonding structure are almost retained with increasing BF₃/N₂ gas flow ratio in the plasma, while the B-to-N ratio in the film is varied from 0.89 to 0.96. The electrical resistivity of the films measured at room temperature for Ni-BN-Ni structures shows a large increase up to the order of 10¹⁰ Ω cm when the B-to-N ratio in the film is increased closer to the stoichiometry due to a lower density of defect states related to the boron vacancy. The characteristics of leakage current vs. applied bias voltage show Ohmic behavior at low fields and non-Ohmic behavior governed by the thermionic emission mechanism at high fields for any B-to-N ratio.