| AVS 62nd International Symposium & Exhibition | |
| Surface Science | Monday Sessions |
| Session SS+AS+EN-MoM |
| Session: | Synthesis, Structure and Characterization of Oxides |
| Presenter: | Joel Langford, University of California, Irvine |
| Authors: | J.M. Langford, University of California, Irvine F. Rosner, Technical University of Munich, Germany J. Kwon, University of California, Irvine J.C. Hemminger, University of California, Irvine |
| Correspondent: | Click to Email |
We are using High Resolution Electron Energy Loss Spectroscopy (HREELS) and Auger Electron Spectroscopy (AES) to investigate nanoclusters and films of iron oxide supported on highly oriented pyrolytic graphite (HOPG). For the films, two AES oxidation profiles were generated by annealing in oxygen. One profile was at a constant sample temperature of 500 K with varying exposure, the other by varying sample temperature while keeping exposure at a constant 1000 L. Both oxidation profiles saturate at an AES O/Fe ratio of 1.2. This ratio is below the O/Fe ratio of magnetite (Fe3O4), and hematite (Fe2O3) indicating incomplete oxidation of the film. Additional evidence for incomplete film oxidation comes from the absence of Fuchs-Kliewer phonons in the HREEL spectra. For the nanoclusters we are investigating two systems; polydispersed iron oxide nanoclusters on HOPG, and platinum nanoclusters supported on iron oxide nanoclusters. The polydispersed nanoclusters are more susceptible to oxidation than the film as evident by the higher AES O/Fe ratio and the presence of Fuchs-Kliewer phonons in the HREEL spectra. The platinum nanoclusters are synthesized on the iron oxide nanoparticles by an ex-situ photodeposition technique and therefore adventitious carbon is adsorbed prior to transfer into the UHV chamber. To remove the adventitious carbon we annealed in oxygen at a sample temperature of 1000 K. HREEL spectra show that the annealing procedure removes adventitious carbon because of the absence and appearance of a CO resonance before and after cleaning, respectively. HREEL spectra after low temperature CO adsorption and as a function of subsequent anneal temperature will be presented.