Determinação estrutural de Pd(111) e Fe3O4/Pd(111) via difração de fotoelétrons

Abstract

In this work we have determined the surface structure of Pd(111) and of an ultra-thin lm of Fe3O4 (111) on Pd (111) by means of photoelectron diraction (PED). The lm was grown and characterized in ultra-high vacuum (UHV) environment in the Brazilian Synchrotron Light Laboratory (LNLS). The growth of Fe3O4 (111) / Pd (111) was accomplished by evaporation of ultra pure iron on the substrate in an oxygen atmosphere (PO2 = 9106 mbar). We used synchrotron light source (h = 300 eV) and conventional X-ray (AlK ) in the PED experiments. Chemical analysis was done by XPS (X-ray Photoelectron Spectroscopy) and by LEED (Low Energy Electron Diraction) the surface crystallography of our samples were veried. For Pd (111) we found a reliability factor (ra) of 0.23, while for Fe3O4 (111)/Pd (111) the values were 0.275, 0.30 and 0.28 for the Fe2p, Fe3p and O1s lines, respectively. Our results for the magnetite lm indicate that this surface is terminated with 1 4 of monolayer of iron in tetrahedral site. We also found important relaxations for the rst Fe3O4(111) surface layers. These results are consistent with LEED studies of Fe3O4(111) thin lms.