EFFECT OF NOBLE-GAS IONS ON THE SYNTHESIS OF C-BN BY ION-BEAM-ASSISTED DEPOSITION

BN films were deposited by using a mixture of nitrogen and argon ions for assistance during growth. On condition that the nitrogen-to-boron flux ratio should be high enough to synthesize stoichiometric material, tetrahedral bonds in BN films are formed when the argon-to-boron flux ratio and accelerating voltage exceed interdependent threshold values, which depend slightly on incident angle of the beam, but not on the substrate temperature above 200-degrees-C. The fraction of cubic phase in films is maximized for energies less than 300 eV and Ar-to-B flux ratios higher than one. Computer simulations of the deposition process seem to indicate that threshold conditions are connected with a threshold number of displacements per deposited atom and that collisions which transfer recoil energies lying in the range 0-50 eV are favorable to the formation of sp3 bonding, while those leading to higher energy values are detrimental. This explains why the very surface of a growing film remains in the trigonal form for beam energies greater than 200 eV.