Variation of carbon concentration, ion energy, and ion current density of magnetron-sputtered boron carbonitride films

Diamond, cubic boron nitride and also ternary materials consisting of boron, carbon and nitrogen exhibit an extraordinary combination of extreme mechanical and physical properties due to their bonding characteristics and crystal structure. This results in a high application potential in protective and functional layers. Taking into account the special properties of these phases, the compositions inside the B-C-N concentration triangle are of particular interest, as novel superhard phases are expected to occur. In this work, boron carbonitride films of variable compositions were produced by means of reactive radio frequency (r.f.) magnetron sputtering in combination with ion bombardment. Examination up to now has revealed carbon concentrations between 16 and 27 at.% and a boron/nitrogen ratio varying between 1.08 and 1.26. For a carbon concentration of 12 at.%, the ion energy was varied between 125 and 300 eV at a constant ratio of ions to film-forming particles, Phi(ion)/Phi(BCN). Peak analyses of the differentiated Auger spectra gave no indication of any generation of B-C bonds. The contents of the h-BN phase and c-BN phase as well as the threshold conditions and optimum conditions for c-BN formation were investigated for 8 energy variations at 18 values of Phi(ion)/Phi(BCN) between 0.1 and 0.5. IR spectroscopy showed that the maximum fraction of sp(3)-hybrid BN bonds reached approximately 61% at an ion energy of 200 eV and an ion current density of 0.5 mA cm(-2). The film properties can be strongly influenced by the flux ratio of ions to film-forming particles, Phi(ion)/Phi(BCN), and by the ion energy. Generally, the effect on the film properties by increasing the flux ratio Phi(ion)/Phi(BCN) or by decreasing the ion energy is often the same. This statement is discussed theoretically. (C) 1999 Published by Elsevier Science S.A. All rights reserved.