Identification of O-rich structures on platinum(111)-supported ultrathin iron oxide films

• Published in: Surface science Vol. 652; no. C; pp. 261 - 268
• Main Authors: Merte, Lindsay R., Bai, Yunhai, Zeuthen, Helene, Peng, Guowen, Lammich, Lutz, Besenbacher, Flemming, Mavrikakis, Manos, Wendt, Stefan
• Format: Journal Article
• Language: English
• Published: United States Elsevier B.V 01.10.2016; Elsevier
• Subjects: Catalysis; Density functional theory (DFT); FeO2 − x islands; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Iron oxide; MATERIALS SCIENCE; O adatom dislocations; Scanning tunneling microscopy (STM); Iron oxide; Catalysis; O adatom dislocations; FeO2−x islands; Density functional theory (DFT); Scanning tunneling microscopy (STM)
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2015.12.031

Using high-resolution scanning tunneling microscopy (STM) we have studied the oxidation of ultrathin FeO films grown on Pt(111). At the initial stage of the FeO film oxidation by atomic oxygen exposure, we identified three distinct types of line defects, all of which form boundaries between FeO domains of opposite orientation. Two types of line defects appearing bright (type-i) and dark (type-ii) in the STM images at typical scanning parameters are “metallic”, whereas the third line defect exhibits nonmetallic behavior (type-iii). Atomic-scale structure models of these line defects are proposed, with type-i defects exhibiting 4-fold coordinated Fe atoms, type-ii exhibiting 2-fold coordinated O atoms, and type-iii exhibiting tetrahedrally-coordinated Fe atoms. In addition, FeO2 trilayer islands are formed upon oxidation, which appear at FCC-type domains of the moiré structure. At high scanning bias, distinct protrusions on the trilayer islands are observed over surface O ions, which are assigned to H adatoms. The experimental data are supported by density functional theory (DFT) calculations, in which bare and hydroxylated FeO2 trilayer islands are compared. Finally, we compare the formation of O-rich features on continuous FeO films using atomic oxygen with the oxidation of Pt(111)-supported FeO islands accomplished by O2 exposure. [Display omitted] •Oxidation of 2-D Iron oxide (FeO) on Pt(111) with atomic oxygen leads to 3 different types of line defects.•FeO2 trilayer islands at FCC domains at oxygen-rich conditions were characterized by high-resolution STM and DFT+U.•√3×√3R30° arrangement of H adatoms on the FeO2 trilayer islands explains bright protrusions on the FeO2 trilayer islands.•The FeO–FeO2 interface is an inherent feature of oxidized FeO / Pt(111).