Nanoclusters of Noble Metals in Amorphous Hydrogenated Carbon

Nanocomposite thin films of amorphous hydrogenated carbon (a-C:H) doped with noble transition metals of 1B group (gold, silver and copper) are studied. Composite materials are obtained by combined magnetron sputtering of a metal target by argon, and plasma-assisted chemical vapor deposition of methane under vacuum conditions. In low metal-content samples, the metallic inclusions have a form of isolated nanoclusters. The objective was to reveal surface cluster arrangement, i.e. to see whether topmost metallic nanoclusters are covered with a layer of a-C:H or are bald on the surface and hence exposed to the surrounding environment. The differences encountered between samples deposited onto substrates kept on the ground potential and on the negative dc bias voltage offer a possible answer to this question. From the applicative point of view, the principle mechanism that may be employed to tailor the coverage/exposure of the topmost metallic clusters embedded in the a-C:H matrix is described.