The growth of epitaxial iron oxides on platinum (111) as studied by X-ray photoelectron diffraction, scanning tunneling microscopy, and low energy electron diffraction
- Univ. of California, Berkeley, CA (United States)
Three complementary surface structure probes, x-ray photoelectron diffraction (XPD), scanning tunneling microscopy (STM), and low-energy electron diffraction (LEED) have been combined in a single instrument. This experimental system has been utilized to study the structure and growth mechanisms of iron oxide films on Pt(111); these films were formed by first depositing a single overlayer of Fe with a certain coverage in monolayers (ML`s), and then thermally oxidizing it in an oxygen atmosphere. For films up to ~1 ML in thickness, a bilayer of Fe and O similar to those in FeO(111) is found to form. In agreement with prior studies, STM and LEED show this to be an incommensurate oxide film forming a lateral superlattice with short- and long-range periodicities of ~3.1 Å and ~26.0 Å. XPD in addition shows a topmost oxygen layer to be relaxed inward by -0.6 Å compared to bulk FeO(111), and these are new structural conclusions. The oxygen stacking in the FeO(111) bilayer is dominated by one of two possible binding sites. For thicker iron oxide films from 1.25 ML to 3.0 ML, the growth mode is essentially Stranski-Krastanov: iron oxide islands form on top of the FeO(111) bilayer mentioned above. For iron oxide films of 3.0 ML thickness, x-ray photoelectron spectroscopy (XPS) yields an Fe 2p3/2 binding energy and an Fe:O stoichiometry consistent with the presence of Fe3O4. Our XPD data further prove this overlayer to be Fe3O4(111)-magnetite in two almost equally populated domains with a 180° rotation between them. The structural parameters for this Fe3O4 overlayer generally agree with those of a previous LEED study, except that we find a significant difference in the first Fe-O interplanar spacing. This work demonstrates the considerable benefits to be derived by using this set of complementary surface structure probes in such epitaxial growth studies.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE; Department of Defense; National Energy Research Supercomputer Center)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 109505
- Report Number(s):
- LBL-37449; ON: DE96000113; CNN: Office of Naval Research Contract N00014-90-5-1457; Office of Naval Research Contract N00014-94-1-0162; TRN: 95:007067
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: May 1995
- Country of Publication:
- United States
- Language:
- English
Similar Records
Nucleation and growth of Fe and FeO nanoparticles and films on Au(111)
Nucleation and growth of Fe and FeO nanoparticles and films on Au(1 1 1)