Berlin 2015 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 117: Graphene: Intercalation (jointly with O, HL)
TT 117.5: Vortrag
Freitag, 20. März 2015, 11:30–11:45, MA 041
Oxygen orders differently under graphene: new superstructures on Ir(111) — •Antonio J. Martínez-Galera1, Felix Huttmann1, Ulrike Schröder1, Fabian Craes1, Carsten Busse1, Vasile Caciuc2, Nicolae Atodiresei2, Stefan Blügel2, and Thomas Michely1 — 1Universität zu Köln, II. Physikalisches Institut, Germany — 2Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich, Germany
Modifying the properties of graphene (Gr) by intercalation of atoms or molecules at the Gr/substrate interface has been proven to be a straightforward and versatile concept. However, the effect of the Gr layer on the ordering of the intercalated material remains much less studied. We present evidence that indeed the Gr cover has a substantial influence on the resulting superstructures of oxygen chemisorbed on Ir(111). As a function of exposure to molecular oxygen and temperature the oxygen adsorbate superstructures on Ir(111) are identified by scanning tunneling microscopy (STM). They are compared to the ones formed by intercalation in between graphene and Ir(111). For bare Ir(111) we observe O-(2x2) and O-(2x1) structures, thereby clarifying a long-standing debate on the existence of these structures and the role of defects for their stability. For Gr/O/Ir(111) with increasing exposure O-(2x2), O-(R3xR3)-R30, O-(2x1) and O-(2R3x2R3)-R30 superstructures referred to Ir(111) are observed. The (R3xR3)-R30 and (2R3x2R3)-R30 structures were not yet reported and they exist only under Gr. Based on density functional theory (DFT) we discuss the origin of the new adsorbate superstructures under graphene.