Synthesis and microstructural properties of tetrahedral amorphous carbon films

Tetrahedral amorphous carbon (ta-C) films have been prepared using a magnet ic field filtered plasma stream system. The optical and microstructural pro perties of these films as a function of the substrate bias voltage, Vb, hav e been studied using optical absorption spectroscopy, Raman spectroscopy an d atomic force microscopy. The results show that ta-C films with larger fra ction of sp(3) bonding were formed when the substrate bias voltage was in t he range from -10 to - 50V. The optical band gap is about 3.0 eV. The sp(3) fraction in these films was estimated to be >80% by a fitting of the Raman spectra with a single skewed Lorentzian lineshape. The surface of such ta- C films was found to be smooth and uniform from the images of atomic force microscopy. The variations of the microstructural properties and surface mo rphology with V-b have been discussed in relation to evolution of the D and G Raman bands and root-mean-square surface roughness. (C) 1999 Published b y Elsevier Science B.V. All rights reserved.