Physical vapour deposition (PVD) is considered to deposit a-C:Au thin. films for electrochemical applications. The relevant point in this context is the ability to generate structures where Au nanoparticles are embedded in a-C in a stable way. Such a configuration would in fact enable one to increase the catalytic activity of Au by decreasing the Au cluster size. Investigation of the deposited. films is performed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The two techniques consistently show that nanosized Au clusters, with a broad size distribution, are indeed formed within the a-C matrix. The cluster size depends on the Au concentration, and falls in the nanometer range for Au concentrations below the percolation threshold. (C) 2008 Elsevier B. V. All rights reserved.