Platinum nanoclusters encapsulated in amorphous carbon

Films of a nanocomposite based on Pt and amorphous carbon (a-C), including hydrogenated carbon (a-C:H), are studied. The nanocomposite was synthesized by encapsulation of Pt nanoclusters in amorphous carbon films via dc magnetron co-sputtering of graphite and platinum targets in an argon-hydrogen plasma. The content of platinum in the films was determined by the methods of Rutherford backscattering and instantaneous nuclear reactions. The morphology of nanocomposite films and separate Pt clusters was examined by transmission electron microscopy. It was shown that nanoclusters ∼3 nm in size are crystals with well-formed low-defect crystal structure and that their shape in the plane is approximated well with an ellipse. Distribution functions for the eccentricity and average size were constructed for a set of 100 of the best discernible clusters. It was found that introduction of hydrogen into the plasma leads to a decrease in the average size of Pt nanoclusters for a constant ratio between the carbon and platinum concentrations in the nanocomposite