Hard BCxNy thin films grown by dual ion beam sputtering

Boron carbonitride thin films were deposited by sputtering of a B₄C target with Ar-N₂ ion assistance. BC_xN_y films were grown onto Si (001) at room temperature. The chemical composition and the type of bonding were determined by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The hardness of the films was measured with a nanoindenter. The chemical analysis of the samples indicates the formation of two different compounds, a ternary BC_xN_y and a binary carbonitride CN_x. All the films showed high hardness, in the range 16-33 GPa, which clearly increases as the BC_xN_y content in the sample increases. In this study the highest hardness (i.e. 33 GPa) was obtained when the BC_xN_y content in the sample was 50%. The average composition of this BC_xN_y was estimated by XPS as 20 at.% carbon and 12 at.% nitrogen.