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 exi sting 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) abl ation of graphite in high vacuum (p = 1.5 x 10(-7) Pa) and in a nitrogen at mosphere (p=13 Pa). The composition (N/C ratio), the structural and electro nic properties and the surface morphology of the deposited films were inves tigated as a function of laser fluence (1-12 J/cm(2)). The highest N/C rati o 0.40 was obtained with a laser fluence of 12 J/cm(2); for this nitrogen c oncentration 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 sp(2) 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 al so reveals a gradient in the chemical nature of the films through the thick ness. Atomic force microscopy analysis shows that the root-mean-squared rou ghness of the DLC samples is about 3 Angstrom over the laser fluence range investigated. (C) 2000 Elsevier Science S.A. All rights reserved.