THE SYNTHESIS, CHARACTERIZATION, AND MECHANICAL-PROPERTIES OF THICK, ULTRAHARD CUBIC BORON-NITRIDE FILMS DEPOSITED BY ION-ASSISTED SPUTTERING

Significant ion irradiation is needed during growth to synthesize cubi c boron nitride (cBN) films. This results in large film stresses, whic h have limited cBN film thicknesses to only a few hundred nm and repre sents a significant barrier in the development of cBN film technology. Using a new hybrid deposition technique, we have synthesized cubic BN films up to 700 nm (0.7 mu m) thick. A compositional and structural a nalysis of the films using several standard characterization technique s confirms that relatively thick polycrystalline films with a high cBN content were synthesized, Thicker cBN films enable hardness measureme nts to be undertaken without major substrate effects. Nanoindentation measurements yield hardness values for the cubic BN films up to 60-70 GPa, which are greater than values measured for bulk cBN. The measured elastic modulus was observed to be lower than the bulk, and this can be accounted for by an elastic deformation of the silicon substrate. T he mechanical properties of the cubic BN films are discussed with refe rence to other ultrahard thin films such as diamond and diamondlike ca rbon. (C) 1997 American Institute of Physics.