CHARACTERIZATION OF ION-BEAM-DEPOSITED DIAMOND-LIKE CARBON-FILMS

Diamond-like carbon (DLC) films are excellent prospects for a wide ran ge of high-technology applications but their precise structure and pro perties are not well understood, The purpose of the present work was t o use several complementary techniques to characterize the nature, str ucture and microstructure of DLC films. Thin DLC films were deposited on various substrates in the presence of a Si interlayer (500 Angstrom thick) using CH4 ion-beam deposition at an acceleration energy of 750 eV and a current density of about 2.5 mA cm(-2). The Si interlayer wa s deposited by either e-beam evaporation or Si evaporation enhanced by Ar+ beam bombardment (1 keV). The produced DLC films were featureless , very smooth and of high hardness (2900-3300 kg mm(-2)). Auger electr on spectroscopy and electron diffraction showed that the films were ma inly amorphous. Their microstructure was characterized by a three-dime nsional network structure with a medium-range order of about 25 nm. Fo urier transform infrared and Raman spectroscopies showed that the film s were mainly composed of sp(3) and sp(2) carbon-bonded hydrogen. The sp(3)/sp(2) ratio varied from 3.2 to 4.1 and was found to depend on th e nature of the Si bond layer. The results showed that the nucleation of the diamondlike structure was promoted on the Si interlayer that wa s deposited under Ar+ beam bombardment. This effect can be explained b y the higher surface roughness produced in this interlayer as suggeste d by the reflectivity measurements. Spectroscopic ellipsometry reveale d that the films had an optical band gap between 1.56-1.64 eV. The pre sent results are consistent with previous proposals suggesting that th e DLC structure is composed of small graphitelike clusters (involving fused six-fold rings) that are interconnected by sp(3)-bonded carbon.