MAGNETRON-SPUTTERED SUPERHARD MATERIALS

Superhard materials such as nanocrystalline cubic boron nitride (c-BN) and beta-silicon carbide (beta-SIC) as well as amorphous boron carbid e (B4C) and highly tetrahedral amorphous carbon (ta-C) are produced by radio frequency (RF) unbalanced magnetron sputtering in combination w ith intense ion plating in a pure argon discharge. As a result of ener gy and mass analysis the film-forming fluxes Phi(n) consist of sputter ed atomic target components and the plating flux Phi(Ar+) of argon ion s. Subplantation, ion-plating-induced increase of surface mobility and substrate-temperature-induced crystallisation are the three main para meters affecting the formation of superhard phases with strong covalen t bonding. Knock-on subplantation allows the formation of B4C with har dness up to 72 GPa at a flux ratio Phi(Ar+)/Phi(n) of 3 for a plating energy of 75 eV. Also c-BN and ta-C can be produced with similar param eters. In the case of SiC, densification is diminished by preferential sputtering of Si and consequently stochiometry and hardness are adver sely affected. However, intense ion plating with a low ion energy of 2 5 eV and small film-forming fluxes shift the temperature of the phase transition from amorphous to nanocrystalline beta-SIC from the usual v alue of > 900 degrees C to about 420 degrees C. Furthermore, investiga tions of the formation of superhard materials in the ternary system bo ron-carbon-nitrogen are reported. (C) 1997 Elsevier Science S.A.