Au nanoparticles supported on HOPG: an XPS characterization

Gold nanoparticles were deposited on HOPG by rf sputtering in Ar plasmas. All experiments were carried out at a substrate temperature as low as 60 °C, in order to minimize the contribution of thermal effects with respect to plasma-dependent phenomena. The system structure and composition were studied by x-ray photoelectron spectroscopy (XPS) and glancing incidence x-ray diffraction (GIXRD). This work is dedicated to the XPS characterization of a representative Au/HOPG sample (rf power = 5 W, total pressure = 0.38 mbar, deposition time = 10 min). Detailed scans for the C 1s, O 1s, N 1s, and Au 4f peaks are presented and discussed. The obtained results pointed out to the presence of metallic gold on HOPG. In particular, high-resolution Au 4f spectra evidenced the presence of a core-level shift, typical of nano-sized gold particles.