Properties of ion-assisted pulsed laser deposited H-BNrC-BN layer systems

Boron nitride films were prepared by pulsed laser ablation from a boron nitride target using a KrF-excimer laser, where the growing films were deposited in nitrogen atmosphere or bombarded by a nitrogenrargon ion beam. Films deposited at ion-to-arriving-target-atom IrA.ratios at the substrate below 0.5 l-BN.are hexagonal. Nucleation of the cubic phase c-BN.takes place exclusively with ion bombardment at IrA ratios above 1.0, which may be reduced down to 0.6 after the completion of the nucleation process. The adhesion of c-BN films is improved significantly using l-BN films as intermediate layers. Up to 400-nm thick c-BN films have been investigated by cross-section transmission electron microscopy TEM.. The l-BN layers show a strong preferred orientation with the c-axis parallel to the substrate surface. The crystallites of the nearly phase pure c-BN layers show strong 110:preferred orientation. The Vickers microhardness of l-BN films is in the range of 25–5 GPa and the compressive stresses in the range of 2–16 GPa. The compressive stresses of 400-nm thick c-BN films were in the range of 4–6 GPa. q2000 Elsevier Science B.V. All rights reserved