Effects of MeV ion irradiation of thin cubic boron nitride films

Adherent boron nitride thin films with a high cubic phase content (up to about 90%) were synthesized over large areas by means of ion assisted evaporation. Besides the well known superior properties of cubic boron nitride (c-BN) nearly nothing is known about the behavior of c-BN under MeV ion irradiation where the ions penetrate through the thin film and come to rest far away in the substrate. Therefore, exploratory MeV ion implantation experiments into as-deposited c-BN rich films were conducted at room temperature. Ions with different masses were chosen to study the effect of the nuclear and electronic stopping processes on the highly cubic BN films. Furthermore the influence of various ion doses (3.5×1013–2.0×1017 ions/cm2) on the cubic structure was investigated. To get an insight into the effects of the different post-deposition treatments, the as-deposited and ion implanted films were analyzed by Fourier transformed infrared spectroscopy, Rutherford backscattering, x-ray diffraction, and Auger electron spectroscopy. Depending on the ion dose, the heavy Xe ion implantation results in four different regimes for the resulting material. The implantation induced the total number of displacements per unit volume as an essential measure of the effect of the postdeposition treatment. Depending on the total number of displacements per unit volume the cubic BN structure can be transformed into a hexagonal BN dominated network.