CLACSA 2003 - Characterization of thin Pd films grown on noble metal substrates by AFM and XPS
Characterization of thin Pd films grown on noble metal substrates by AFM and XPS
S.S. Maluf, A.L. Gobbi, P.I. Paulin-Filho, P.A.P. Nascente
Presented at Congreso Latinoamericano de Ciencias de Superficies y sus Aplicaciones (CLACSA 2003), Pucón, Chile, 7-12, Diciembre 2003
Abstract
The understanding of the physical and chemical properties of the outer atomic layers of materials is important in several technological processes, including heterogeneous catalysis, magnetic devices, and sensors. Palladium is one of the most important metals in catalysis due to its high activity in several chemical reactions. Alloying the noble metals with palladium enhances the catalytic performance in several reactions. In this work, thin films (100 Å) of palladium were grown on polycrystalline copper, silver, and gold substrates by DC sputtering. The morphology of the films was investigated by atomic force microscopy (AFM). X-ray photoelectron spectroscopy (XPS) was employed to investigate the surface composition and electronic structure of the films. The AFM images of the three substrates show that the Au morphology is flat and with no detectable grains, but the surfaces of Ag and Cu are covered by small grains, being more pronounced on the Cu surface. The deposition of Pd on all three substrates produced flat films, which morphology was similar to the pure palladium one. The Cu and Ag signals were detected before the Ar sputtering for Pd/Cu and Pd/Ag. The Pd 3d5/2 binding energies for all three Pd films, both before and after Ar sputtering, are higher than the value for pure Pd. The Cu 2p3/2 and Ag 3d5/2 peaks taken before the Ar sputtering have smaller energies than the values of pure Cu (932.7 eV) and Ag (368.3 eV). The findings obtained by XPS indicate the possibility of alloy formation for both Pd/Cu and Pd/Ag systems. However, this does not seem to occur for Pd/Au.
CLACSA 2003 - Characterization of thin Pd films grown on noble metal substrates by AFM and XPS
