Structure, composition, mechanical, and tribological properties of BCN films deposited by plasma enhanced chemical vapor deposition

In this work thin BCN films were deposited by plasma enhanced chemical vapor deposition (PECVD) using chloridic precursors. Through adjusting the BCl3 content in the inlet gas mixture the chemical composition of the deposited films was changed from carbon rich to boron rich. Based on optical emission spectroscopy (OES) measurements, a correlation between film composition and precursor species concentration in the plasma was established. The films were amorphous as detected by grazing incidence X-ray diffraction (GIXRD). The hardness and the elastic modulus have maximal values of 25.5 +/- 1.2 and 191 +/- 6 GPa, respectively, for the films with a boron concentration of 45.2 at.%. GIXRD data suggest that a depletion in boron content may initiate the formation of graphitic domains in the amorphous matrix. The observed degradation of the mechanical properties is associated with the graphitization. The tribological behavior was studied with a tribometer operated in pin-on-plate configuration at the temperatures 25 and 400 degrees C. The wear mechanisms were discussed with respect to the formation of a boric acid surface layer which was detected by reflection electron energy loss spectroscopy (REELS) analysis.