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=1.5×10−7 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. on 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.