Structural analysis of FeO(1 1 1)/Ag(0 0 1): undulation of hexagonal oxide monolayers due to square lattice metal substrates

• Published in: Journal of physics. Condensed matter Vol. 26; no. 31; p. 315001
• Main Authors: Bruns, D, Kiesel, I, Jentsch, S, Lindemann, S, Otte, C, Schemme, T, Kuschel, T, Wollschläger, J
• Format: Journal Article
• Language: English
• Published: England IOP Publishing 06.08.2014
• Subjects: Brackets; Condensed matter; Deposition; FeO monolayer; Lattices; Molecular structure; Monolayers; Scanning tunneling microscopy; Spectra; spot profile analysis low energy electron diffraction; unudulated monolayer
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/26/31/315001

Iron oxide monolayers are grown on Ag(0 0 1) via reactive molecular beam epitaxy (metal deposition in oxygen atmosphere). The monolayer shows FeO stoichiometry as concluded from x-ray photoemission spectra. Both low energy electron diffraction as well as scanning tunneling microscopy demonstrate that the FeO layer has a quasi-hexagonal (1 1 1) structure although deposited on a surface with square symmetry. Compared to bulk values, the FeO(1 1 1) monolayer is unidirectionally expanded by 3.4% in directions while bulk values are maintained in directions. In directions, this lattice mismatch between FeO(1 1 1) monolayer and Ag(0 0 1) causes a commensurate undulation of the FeO monolayer where 18 atomic rows of the FeO(1 1 1) monolayer match 17 atomic rows of the Ag(0 0 1) substrate. In directions, however, the FeO(1 1 1) monolayer has an incommensurate structure.