Thin films of cubic boron nitride (c-BN) and B4C/BCN/c-BN multilayers, were deposited by r.f. (13.56 MHz) multi-target magnetron
sputtering from high-purity (99.99%) h-BN and a (99.5%) B4C targets, in an Ar (90%)/N2 (10%) gas mixture. Films were deposited onto silicon
substrates with (100) orientations at 300 -C, with r.f. power density near 7 W/cm2. In order to obtain the highest fraction of the c-BN phase, an r.f.
substrate bias voltage between 100 and 300 V was applied during the initial nucleation process and 50 to 100 V during the film growth.
Additionally, B4C and BCN films were deposited and analyzed individually. For their deposition, we varied the bias voltage of the B4C films
between 50 and 250 V, and for the BCN coatings, the nitrogen gas flow from 3% to 12%. A 300-nm-thick TiN buffer layer was first deposited
to improve the adhesion of all samples. X-ray diffraction patterns revealed the presence of c-BN (111) and h-BN phases. FTIR spectroscopy
measurements indicate the presence of a peak at 780 cm1 referred to as ‘‘out-of-plane’’ h-BN vibration mode; another peak at 1100 cm1
corresponds to the c-BN TO mode and the ‘‘in-plane’’ vibration mode of the h-BN at 1400 cm1. BN films deposited at 300 -C at a pressure of 4.0
Pa and under 150 Vof nucleation r.f. bias, applied for 35 min, presented the highest c-BN fraction, near 85%. By using 32 layers, it was possible
to deposit a 4.6-Am-thick c-BN film with adequate mechanical properties and good adhesion to the substrate.
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