Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 17: Scanning Probe Techniques: Method Development II

O 17.1: Vortrag

Montag, 20. März 2017, 15:45–16:00, TRE Phy

Imaging adatoms, rest atoms and defects on Si(111)-7x7 with a CO terminated metal tip — •Daniel Meuer and Franz Josef Giessibl — University of Regensburg, D-93055 Regensburg, Germany

The surface of Si(111)-7x7 exposes adatoms at the top surface layer and rest atoms that are approximately 100 pm below the adatom layer [1]. We show that a CO tip of an AFM resolves both adatoms and rest atoms as roughly Gaussian protrusions, which is in agreement with charge density calculations using Slater-type-orbitals. Both the experimental and calculated data do not show apparent artifacts. In this contribution we also present that we can resolve the atomic structure inside surface defects. This is possible due to the fact that the CO molecule at the metal tip apex is a very sharp probe with a thin apex compared to metal cluster tips.

The previous work was done in a force regime, where CO bending artifacts do not occur. For distance regimes with CO bending one would expect a non-Gaussian shape of the adatoms. In 2014 Sweetman et al showed data, where they observe a non-Gaussian shape of the adatoms with a unknown tip termination. They relate this subatomic features of the adatoms of the Si(111)-7x7 surface to the back bonding of the surface atoms [2]. We show data with a CO terminated tip, which clearly show CO bending in preferred directions.

References:

[1] K. D. Brommer et al - Jpn. J. Appl. Phys. 32, 1360 (1993)

[2] A. Sweetman et al.- Nano Lett. 14, 2265-2270 (2014)