抄録
Cubic boron nitride (cBN) has many excellent properties, such as the highest hardness next to diamond, high electrical insulation and high thermal conductivity. cBN films were deposited by IVD (Ion-beam-assisted vapor deposition) method. Effects of the ion current density, the composition of the supplied gas into the ion source and pressure in the vacuum chamber on cBN formation were investigated. At a constant B deposition rate, cBN was formed in a certain range of an ion current density. XPS analyses showed that the cBN film has a stoichiometric composition of BN, and the diffraction patterns from cBN (111), (220) and (311) were observed by transmission electron diffraction. Under the constant ion acceleration voltage and the B deposition rate (0.5 kV, 0.13 nm s−1), cBN was formed when an Ar-based gas containing N2 of 20 to 80% was supplied to the ion source. The deposition rate of cBN films was as high as about 5×10−2 nm s−1 and the range of the cBN formation conditions was wide when the Ar-based gas contained N2 of 36 to 50%. With increase of the pressure in the vacuum chamber, cBN formations were observed at lower ion current densities. We consider that this is due to the charge exchange and not only ions but accelerated fast neutrals also contribute to the cBN formation. Based on the above results, we propose a map of the cBN formation conditions as functions of fast N2 flux and fast Ar flux.
