Growth of Cubic Boron Nitride Thin Film on Diamond Surface

High-power electronics demand high-speed, highly integrated electrical circuits with excellent heat dissipation. Owing to their ultrawide-bandgap, high thermal stability and chemical inertness, the heterostructure of cubic boron nitride (c-BN) and diamond are predicted as promising power-efficient materials for next-generation electronics. Therefore, extensive efforts are ongoing to develop epitaxial c-BN thin films on diamond with an atomically smooth interface, however with limited success due to the metastable nature of c-BN. Here, c-BN thin films are grown on (001) single crystal diamond substrates. Exhaustive spectroscopic and microscopic characterizations reveal a near-epitaxial growth of ultrathin (≈2 nm) c-BN films on nitrogen functionalized diamond surfaces. However, the top surface of the films shows amorphous nature, possibly due to lattice relaxations as it is more energetically favorable than the cubic phase. Further, observed strain mediated epitaxy of few-layer c-BN film has been corroborated with the first principle density functional theory (DFT) calculations, confirming that the modified diamond surface increases stability by reducing the energy barriers associated with c-BN growth and favors the near-interface epitaxy. The observations may offer valuable insights for fully epitaxial c-BN films on diamond, important for high-power electronics.