Berlin 2018 – scientific programme
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DS: Fachverband Dünne Schichten
DS 7: Thin Film Properties: Structure, Morphology and Composition (XRD, TEM, XPS, SIMS, RBS, AFM, ...): Session I
DS 7.5: Talk
Monday, March 12, 2018, 16:00–16:15, H 2032
Revealing the actual structure of the oxygen-rich surface of α-Fe2O3(0001) — •Jesús Redondo1, Petr Lazar2, Benjamín Mallada1, Aleš Cahlik1, Pavel Procházka3, Martin Vondráček1, Jan Čechal3, Pavel Jelínek1, and Martin Švec1 — 1Institute of Physics, Czech Academy of Sciences, Praha, Czech Republic — 2Regional Center for Advanced Materials and Technologies, Olomouc, Czech Republic — 3Central European Institute of Technology, Brno, Czech Republic
The surface of metal oxides reconstructs in many ways depending on the crystallographic planes and preparation procedures. In the case of iron oxides, the surface reconstruction of α-Fe2O3(0001) is still controversial. Under oxidizing conditions, it partially reconstructs in the so-called "biphase" structure, which traditionally has been explained by the coexistence of small islands of FeO and Fe2O3(0001). Furthermore, other phases are present, and there is no recipe to obtain large domains of single phases on the surface, which hinders an unambiguous interpretation of spectroscopic and microscopy data.
In this work, we present a procedure to obtain micrometer-sized domains of single stoichiometry under reducing and oxidative conditions. This has allowed us to thoroughly characterize the two main phases of the α-Fe2O3(0001) by means of STM, AFM, LEEM, µLEED, XPS, and NEXAFS. Moreover, we have solid evidence that that the "biphase" structure may, in fact, be a novel 2D material rather than a truncated bulk. Complementary DFT calculations support the model of an O-Fe-O trilayer (FeO2) on the surface.