Structural properties and surface morphology of laser-deposited amorphous carbon and carbon nitride films

A study of the relationship between structure and growth parameters for existing and candidate carbon-based protective coatings has been carried out. In particular, diamond-like carbon (DLC) and carbon nitride thin films were deposited on silicon wafers by pulsed Nd:YAG laser (wavelength 532 nm) ablation of graphite in high vacuum (p = 1.5 x 10^-7 Pa) and in a nitrogen atmosphere (p = 13 Pa). The composition (N/C ratio), the structural and electronic properties and the surface morphology of the deposited films were investigated as a function of laser fluence (1-12 J/cm²). The highest N/C ratio 0.40 was obtained with a laser fluence of 12 J/cm²; for this nitrogen concentration X-ray photoelectron spectroscopy (XPS) reveals an increase of C-N bonds instead of C=N bonds with respect to lower concentrations. Electron energy loss spectroscopy (EELS) and XPS show an increase of sp² carbon bonded sites in the DLC films deposited with lower laser fluences in agreement with the theory of the so-called sub-implantation model. EELS also reveals a gradient in the chemical nature of the films through the thickness. Atomic force microscopy analysis shows that the root-mean-squared roughness of the DLC samples is about 3 Å over the laser fluence range investigated. (C) 2000 Elsevier Science S.A. All rights reserved.