Regensburg 2022 – scientific programme

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O: Fachverband Oberflächenphysik

O 17: Poster Monday: Organic Molecules at Surfaces 1

O 17.13: Poster

Monday, September 5, 2022, 18:00–20:00, P4

Measuring the change in reactivity of a molecular species: Does the bottom affect the top? — •Jack Henry, Philip Blowey, and Adam Sweetman — University Of Leeds, Woodhouse, Leeds, England, LS2 9JT

Decades of surface science studies on adsorbed molecules have shown the surface a molecule is adsorbed on can affect the molecule's electronic and geometric structure [1]. However, the change in reactivity of a single molecule induced by the presence of a surface has not been rigorously investigated. The influence of molecule-substrate bonding on the interactions experienced by a scanning probe microscope (SPM) tip was investigated by studying C60 molecules adsorbed on the Cu(111) surface, using simultaneous non-contact atomic force microscopy (NC-AFM) and scanning tunnelling microscopy (STM). C60 can form distinctly different structures when adsorbed on the Cu(111) surface [2][3], two of which were utilized in this work. In the first structure, the Cu(111) surface remains relatively unperturbed. In the second, the presence of the C60 induces a reconstruction of the underlying Cu(111) surface, with the C60 molecules occupying a 7 atom vacancy. Despite this, both configurations adopt a (4x4) periodicity. This provides an ideal system to probe the effect the molecule-substrate bonding has on the physico-chemical properties of the molecule. As the molecules adsorb in the same orientation in both structures, any difference in the interaction between the SPM tip and the C60 molecules can be attributed to differences in the molecule-substrate bonding [2][4][5][6].

In this work, the physico-chemical properties of C60 molecules (in different adsorption structures) were investigated using NC-AFM force spectroscopy, through comparing the minima in collected force spectra. Complementary ab initio simulations of the spectra were also performed in DFT to gain a deeper understanding of the experimental results.

[1] L. Gross, F. Mohn, N. Moll, P. Liljeroth, and G. Meyer, Science 325, 1110 (2009).

[2] W. W. Pai, H. T. Jeng, C.-M. Cheng, C.-H. Lin, X. Xiao, A. Zhao, X. Zhang, G. Xu, X. Q. Shi, M. A. Van Hove, C.-S. Hsue, and K.-D. Tsuei, Physical Review Letters 104, (2010).

[3] L. Forcieri, S. Taylor, P. Moriarty, and S. P. Jarvis, Physical Review B 104, (2021).

[4] A. Tamai, A. P. Seitsonen, F. Baumberger, M. Hengsberger, Z.-X. Shen, T. Greber, and J. Osterwalder, Physical Review B 77, (2008).

[5] L.-L. Wang and H.-P. Cheng, Physical Review B 69, (2004).

[6] A. Ogawa, M. Tachibana, M. Kondo, K. Yoshizawa, H. Fujimoto, and R. Hoffmann, The Journal of Physical Chemistry B 107, 12672 (2003).