BCN thin films near the B4C composition deposited by radio frequency magnetron sputtering

Materials with composition within the system B-C-N are very interesting because they are expected to combine some of the excellent properties of BN, B4C and C3N4. In this work our interest is focused on the region around B4C in the B-C-N composition diagram. Films were deposited by radio frequency magnetron sputtering using a target of sintered B4C. A mixture of Ar and N-2 was used as the plasma gas at a constant working pressure of 2 x 10(-3) mbar, and with variable N-2/Ar composition. The substrate was heated to 500 degrees C. Film composition, structure, and mechanical properties are presented. As the N-2/Ar content in the plasma gas is varied from 0 to 10%, both secondary ion mass spectroscopy and X-ray photoelectron spectroscopy analyses show a continuous increase in the nitrogen incorporated into the film. From the Fourier transform IR spectra, a structure evolution from B4C towards h-BN can be deduced. Film growth rate increased from 0.5 mu m/h to 1 mu m/h, whereas film stress decreased from 5 GPa to 2 GPa, and him hardness also decreased from 26 GPa to 12 GPa. From these results, a suitable value of the N-2/Ar plasma gas composition can be selected in order to deposit films with a satisfactory low stress while keeping a sufficiently high hardness, as required in hard coating applications. (C) 2000 Elsevier Science S.A. All rights reserved.