Regensburg 2025 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 14: 2D Materials Beyond Graphene: Growth, Structure and Substrate Interaction (joint session O/HL)

O 14.1: Vortrag

Montag, 17. März 2025, 15:00–15:15, H11

Hexagonal structures of europium oxides on Pd(111) studied with LEED and STM — •Muriel Wegner, Stefan Förster, and Wolf Widdra — Martin-Luther-Universität Halle-Wittenberg, Germany

With an increasing interest in technological applications of oxide materials, also two-dimensional (2D) oxides came into focus. The large flexibility in the variation of the cationic species, including even a combination of different cations, promises a rich variety of properties [1,2]. So far, the center of attention has been on transition metal sesquioxides M₂O₃ of corundum structure.

Here, we expand this field towards lanthanides. We present a combined scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) study of the growth of submonolayer coverages of europium oxide on a Pd(111) surface. Upon annealing the as deposited Eu in oxygen containing environments at temperatures above 800 K, long-range ordered multilayer islands of Eu₂O₃ are obtained. From LEED a ( 8/34/3
−4/34/3 ) superstructure on Pd(111) is derived, which corresponds to a hexagonal lattice with a lattice parameter of 6.35 Å. This structure exhibits a large stability range. Only upon annealing to 1175 K in UHV an additional (2×2) superstructure evolves, which is seen as a hexagonal array of pores at a distance of 12.70 Å in STM.
By addition of small amounts of Ti atoms, the transformation into planar two-dimensional films is achieved. These mixed-metal oxides form a honeycomb lattice with a lattice parameter of 7.2 Å. In contrast to pristine Eu₂O₃, the Ti containing honeycomb can easily be resolved in STM.
[1] M. Van den Bossche, J. Goniakowski, and C. Noguera, Nanoscale 13, 19500 (2021)
[2] P. I. Wemhoff, N. Nilius, C. Noguera, and J. Goniakowski, J. Phys. Chem. C 126 (10), 5070 (2022)

Keywords: 2D systems; two dimensional oxides; sesquioxides; lanthanides; honeycomb structures