THIN-FILM CHARACTERIZATION OF DIAMOND-LIKE CARBON-FILMS PREPARED BY RF PLASMA CHEMICAL-VAPOR-DEPOSITION

Using atomic force microscopy and infrared spectroscopy, diamond-like carbon films deposited by r.f. plasma discharge were investigated. Har dness and roughness of the films strongly depend on the bias voltage o f the substrates and thus the pressure in the deposition chamber. At h igher pressures, the surface roughness of the films increases with the ir thickness. For films deposited at medium pressures, the roughness i s almost constant regardless of the film thickness. At pressures below 53 Pa decreasing roughness is observed and hard films are obtained. T hese findings can be explained by the predominance of different specie s in the plasma. At low pressure, ionic species an accelerated towards sharp tips on the film surface leading to sputter removal of weakly b ond material in these regions. At higher pressure neutral species in t he plasma dominate. Thus, the balancing effect of sputtering is not ob served. Hydrogen content and sp(3)/sp(2) ratios obtained from IR spect ra revealed that the lower hardness of the rough surfaces can be expla ined by a higher content of sp(2) species in the films deposited at hi gh pressure. Whereas the intensity ratio of sp(3)/sp(2) is almost cons tant for the films at higher pressure preferred sputter removal of sp( 2) species leads to a significant increase of that ratio at low pressu re. (C) 1997 Elsevier Science S.A.