Fractal Nature of Nanocomposite Thin Films with Co NPs in a-C:H Matrix

The aim of the present article is to investigate experimentally the fractal nature of the 3-D surface morphology of nanocomposite thin films consisting of partially oxidized cobalt nanoparticles with a face-centered-cubic (fcc) structure embedded in a hydrogenated amorphous carbon matrix. The samples were prepared by reactive magnetron sputtering using acetylene gas under gas pressures varying from 2.1 to 2.9 Pa. The characterization of the films surfaces was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM), and the obtained AFM images were analyzed dividing them into motifs of significant peaks and pits using a segmentation algorithm. This analysis revealed that these nanocomposite thin films are well described as monofractal structures presenting only one scaling exponent whose value was found within the range from 2.4 to 2.7 for the different samples.