Pulsed laser deposition of cubic boron nitride films at high growth rates

Abstract

Cubic boron nitride films were prepared by ion-assisted pulsed laser deposition. High c-BN growth rates of 50 nm/min were achieved using a high laser fluence of more than 30 J/cm 2 at an ion beam energy of 600–700 eV and an ion-current density of 450–570 μA/cm 2. The ratio of ions from the ion beam to the ablated atoms and ions necessary for cubic film growth can be reduced to 0.14 at high laser fluences, since the ablated boron and nitrogen species themselves have a high mean kinetic energy of 130–180 eV. The films deposited at high growth rates show relatively high compressive stress in the range of 10–12 GPa, which is governed by the energy of the ablated species. The stress can be lowered to 5.6 GPa by annealing the films after deposition. However, relatively high temperatures above 650°C are required for this. Using pulsed laser-deposited h-BN adhesion layers, 300–350-nm-thick c-BN films with good adhesion were prepared on Si and WC substrates. The Vickers microhardness of these films was up to 42 GPa and the Young's modulus up to 590 GPa.