Grazing incidence small angle X-ray scattering investigation of tungsten–carbon films produced by reactive magnetron sputtering

Tungsten–carbon thin films were deposited onto monocrystalline silicon substrates by reactive sputtering in a two-source device. The magnetron discharges operated in an argon+benzene gas mixture at 2 Pa total pressure. The film structure is strongly disordered, presumably due to the incorporation of unbound carbon. The grazing incidence small angle X-ray scattering (GISAXS) technique was applied to investigate the structure of the films. The GISAXS spectra from the samples with lower unbound carbon content (low benzene partial pressure and low substrate temperature) can be successfully interpreted according to distorted wave Born approximation (DWBA). In the case of higher carbon content, grains of amorphous WC are formed, while the carbon is probably concentrated in the grain boundaries. This results in an additional particle-like contribution to the scattering, revealing the sizes of the grains to be in the order of 2.5–3.3 nm.