Synthesis of adhesive c-BN films in pure nitrogen radio-frequency plasma

Cubic boron nitride (c-BN) thin films were prepared at 600 °C by radio-frequency (rf) plasma pulsed laser deposition. All c-BN films prepared in Ar-rich plasma have poor adhesion on Si(100) substrates, but those prepared in pure N₂ plasma can be maintained for more than 5 months without degradation. However, an increase of ion flux at an ion energy similar to that of pure N₂ plasma results in the peeling of c-BN films. Thus, application of pure N₂ plasma with suppressed ion flux can improve c-BN film adhesion. Under such conditions, an extended sp²-bonded interlayer is suspected, with the onset of the c-BN phase being delayed. Suppression of radiative damage in reduced nitrogen ion flux on both the c-BN and h-BN/t-BN phases are important for the adhesive of c-BN films.