EFFECT OF SURFACE ENERGY ON THE GROWTH OF DIAMOND-LIKE CARBON/AMORPHOUS SILICON FILMS ON VARIOUS SUBSTRATES

Abstract

Diamond-like carbon/amorphous silicon bilayer films were deposited on SiO2, Ge, and Ta2O5 substrates using a pulsed filtered cathodic arc (PFCA) system. Amorphous silicon (a-Si) layer was firstly deposited on three substrates using DC magnetron sputtering, then diamond-like carbon (DLC) film was deposited on a-Si layer via pulsed filtered cathodic arc. The thicknesses of a-Si layer and DLC film as monitored by in-situ ellipsometry during the film deposition were 7 and 10 nm, respectively. The surface energy of SiO2, Ge, and Ta2O5 substrates was determined by measuring the contact angle of water on these substrates. It was found that the contact angles of water on SiO2, Ge, and Ta2O5 substrates were 53°, 63°, and 75°, respectively. This result indicates that SiO2 has the highest surface energy while Ta2O5 has the lowest surface energy. The thickness of the a-Si layer and DLC film was determined from the cross-section transmission electron microscopy (TEM) images. The thinnest a-Si layer of 5.64 nm was obtained from SiO2 substrate which has the highest surface energy. The thickest a-Si layer of 6.97 nm was obtained from Ta2O5 corresponding to the lowest surface energy. This study shows that the thickness of the growth film strongly depends on the surface energy of the substrate. However, the DLC films deposited on each a-Si layer of three substrates have the same thickness approximately of 9.9 nm, because all of them were deposited on a-Si layers having the same surface energy.