NCAFM2023 Programme Booklet

Tuesday 1700 - 1720

Nc-AFM CHARACTERIZATION OF METAL OXIDE SURFACES WITH AN O TERMINATED COPPER TIP

Philipp Wiesener, 1 Saeed Amirjalayer, 1 Bertram Schulze Lammers, 1 Harald Fuchs, 1 Harry Mönig 1 *

1 Physikalisches Institut, Universität Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany *Email: harry.moenig@uni-muenster.de

Previously we investigated the performance of various tip terminations, namely Cu-, Xe-, CO-, and O-terminated Cu-tips (CuOx-tips [1]), on the Cu(110)O(2x1) surface with non-contact AFM [2]. A direct comparison of the imaging and force-spectroscopy capabilities by these different tip terminations shows, that only for the CuOx-tip a significantly selective force interaction between metal and oxygen atoms can be observed (Figure a and b ). In this work we want to generalize the idea of chemical selective imaging by analyzing a broad spectrum of metal oxide systems with CuOx-tips. We perform constant-height measurements over an extended range of tip sample distances and analyze surfaces that possess varying relative heights of metal and oxygen atoms to probe possible effects on the chemical selectivity. In a next step we investigate various defects of the metal oxide surfaces and complement our site-selective microscopy with force-spectroscopy measurements on the observed metal and oxygen atoms. Figure b and c show our measurements for the magnetite Fe 3 O 4 (100) [3] surface, which we investigated as a model system to demonstrate the outstanding ability of CuOx-tips for the characterization of metal oxide surfaces and predominant defects. To further consolidate our findings, we perform experiments on a variety of metal oxide systems with a high degree of complexity and disorder to explore the possibilities and limits of our approach. To extend our methodology even beyond metal oxides we also investigate the chemical selective contrast for metal nitride systems. By employing DFT simulations, we can also provide insight into the physics behind the contrast formation of the CuOx-tips, where the strongly electronegative tip termination plays a crucial role.

Fig. a Cu(110)O(2x1) reconstruction imaged with a CuOx-tip. b Force spectroscopy curves for metal and oxygen sites marked in a. c Magnetite Fe3O4(100) [3] surface imaged with a CuOx-tip. d Force spectroscopy curves for metal and oxygen sites marked in c. The underlaying DFT structure emphasize the chemical selective contrast for oxygen (red) and metal (blue) sites.

References [1] H. Mönig et. al., Nat. Nanotechnol., 13 , 371-375 (2018). [2] B. Schulze Lammers et. al., Nanoscale 13 , 13617–13623 (2021). [3] R. Bliem et. al., Science 346, 1215–1218 (2014).

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