Cubic BN(c‐BN) films were deposited on cubic SiC (&bgr;‐SiC) films on Si(100) by ion‐assisted pulsed laser deposition. The films were nearly phase pure, withc‐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 &bgr;‐SiC, followed by hexagonal/turbostratic BN (h‐BN/t‐BN), and then polycrystallinec‐BN, as commonly observed on Si substrates. However, there are alsoc‐BN crystals that extend to within 10 A˚ of the SiC interface,withnointerveningh‐BN/t‐BNlayer. A sharp falloff inc‐BN content was observed for substrate temperatures <150 °C, and below 100 °Cc‐BN did not form for any ratio of the ion current flux to the deposition flux. At a different ion‐to‐substrate angle (20° closer to glancing incidence) the falloff inc‐BN content forT<150 °C was less sharp. The existence of a critical temperature forc‐BN formation does not result from a nitrogen deficiency at low temperature since film stoichiometry did not change with temperature. ©1995 American Institute of Physics.