Properties of amorphous carbon-silicon alloys deposited by a high plasma density source

The addition of silicon to hydrogenated amorphous carbon can have the advan tageous effect of lowering the compressive stress, improving the thermal st ability of its hydrogen, and maintaining a low friction coefficient up to h igh humidity. Most experiments to date have been on hydrogenated amorphous carbon-silicon alloys (a-C1-xSix:H) deposited by rf plasma enhanced chemica l vapor deposition. This method gives alloys with sizeable hydrogen content and only moderate hardness. Here we use a high plasma density source known as the electron cyclotron wave resonance source to prepare films with high er sp(3) content and lower hydrogen content. The composition and bonding in the alloys is determined by x-ray photoelectron spectroscopy, Rutherford b ackscattering, elastic recoil detection analysis, visible and ultraviolet ( UV) Raman spectroscopy, infrared spectroscopy, and x-ray reflectivity. We f ind that it is possible to produce relatively hard, low stress, low frictio n, almost humidity insensitive a-C1-xSix:H alloys with a good optical trans parency and a band gap well over 2.5 eV. The friction behavior and friction mechanism of these alloys are studied and compared with that of a-C:H, ta- C:H, and ta-C. We show how UV Raman spectroscopy allows the direct detectio n of Si-C, Si-H-x, and C-H-x vibrations, not seen in visible Raman spectra. (C) 2001 American Institute of Physics.