Boron carbide thin films deposited by tuned-substrate RF magnetron sputtering

Boron carbide thin films were deposited in a tuned RF magnetron sputtering system from a target of B4C with Ar as the processing gas. The ion bombardm ent during film growth was controlled by the substrate-tuning technique, wh ich allows the setting up of a variable DC bias even for insulant materials . The substrate bias was varied from -80 to +15 V. The RF power was fixed a t 300 W. X-ray photoelectron spectroscop (XPS) and secondary ion mass spect rometry (SIMS) analyses indicate that the films are stoichiometric B4C and homogeneous. The vibrational properties were studied by Fourier transform i nfrared spectroscopy (FTIR). The X-ray diffraction results indicated the am orphous or nanocrystalline character of these films. The optical properties were calculated from transmission measurements, and bandgap values from 2. 52 to 2.38 eV were obtained. These films present good mechanical properties , such as moderate internal stress (4.5 GPa), high microhardness (19.5-25 G Pa) and good adhesion to the substrate. (C) 1999 Elsevier Science S.A. All rights reserved.