Growth of cubic BN films on β-SiC by ion-assisted pulsed laser deposition

Cubic BN(c-BN) films were deposited on cubic SiC (β-SiC) films on Si(100) by ion-assisted pulsed laser deposition. The films were nearly phase pure, with c-BN fractions of up to ∼90% as determined by infrared spectroscopy. Cross-sectional transmission electron microscopy showed that much of the film/substrate interface had a thin amorphous layer next to the β-SiC, followed by hexagonal/turbostratic BN (h-BN/t-BN), and then polycrystalline c-BN, as commonly observed on Si substrates. However, there are also c-BN crystals that extend to within 10 A of the SiC interface, with no intervening h-BN/t-BN layer. A sharp falloff in c-BN content was observed for substrate temperatures <150 degree C, and below 100 degree C c-BN did not form for any ratio of the ion current flux to the deposition flux. At a different ion-to-substrate angle (20 degree closer to glancing incidence) the falloff in c-BN content for T<150 degree C was less sharp. The existence of a critical temperature for c-BN formation does not result from a nitrogen deficiency at low temperature since film stoichiometry did not change with temperature