Ag nanoparticles on highly ordered pyrolytic graphite (HOPG) surfaces studied using STM and XPS

Ag nanoparticles grown on low- and high-defect HOPG surfaces were characterized using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Much stronger interactions between Ag and highly defective HOPG surfaces were found compared to those of low-defect HOPG surfaces. We demonstrate that Ag nanoparticles can be prepared on HOPG with relatively narrow size distributions, allowing investigations on size-dependent changes of electronic and chemical properties of nanoparticles. XPS studies reveal that the Ag 3d states converge to the bulk properties at a much larger particles size range (above 6 nm in diameter in 5 nm in height) compared to other previous results obtained from different substrates, which can be attributed to either inefficient final state screening and/or different particle geometry. Stronger Ag-W-oxide interactions were observed for Ag nanoparticles compared to Ag bulk crystals using XPS.