The process of depositing Me⧹C : H composite films in an argon⧹n-hexane gas mixture using a DC unbalanced magnetron was analysed by energy selective mass spectrometry and microgravimetric techniques. With only argon as the working gas the ion mass spectra show contributions typically expected from the process gas and sputtered metal. The plasma composition changes with n-hexane admixture, resulting in densely packed ion mass spectra from C XH Y + fragments and oligomer ions of higher molecular mass than the parent molecule. Poisoning of the nickel target is revealed by the time dependent ion current signals. The ion energy distribution is dominated by two groups of ions : a low energy peak generated by thermalised plasma ions gaining an energy of several eV during transit across a small plasma sheath in front of the grounded discharge anode, and high energy ions produced either by direct ionisation of high energy neutrals from the sputter process, by elastic collisions with the high energy neutrals, or by backscattering of neutralised primary ions. The collisional processes require ions with a sufficiently high elastic collision cross-section and low dissociation probability. As a result of the influence of the discharge parameters on the ion energy distribution, the grounded substrate is bombarded mainly by positive CH + 3 , Ar + and Ni + ions with a mean energy of between 2 and 10 eV.