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O: Fachverband Oberflächenphysik

O 87: Focus Session: Molecular Nanostructures on Surfaces: On-Surface Synthesis and Single-Molecule Manipulation III

O 87.6: Vortrag

Donnerstag, 21. März 2024, 16:30–16:45, HE 101

Distance-Dependence of Orbital Density Mapping Using a CO-Functionalized STM Tip — •Fabian Paschke, Leonard-Alexander Lieske, Florian Albrecht, and Leo Gross — IBM Research Europe - Zurich, 8803 Rueschlikon, Switzerland

Knowledge over the tip apex in scanning probe techniques is indispensable to reliably identify the structure and electronic properties of surfaces and adsorbed molecules [1]. In particular, CO-terminated tips are widely used to achieve atomic resolution in atomic force microscopy [2]. In scanning tunneling microscopy (STM) the defined states of a CO tip apex enable high-resolution mapping of ionic resonances, and resulting orbital density images reflect a mix of s- and p-wave symmetries of the CO tip states [3-5].

In this work we study the appearance of frontier molecular orbitals of pentacene on a bilayer of NaCl grown on Cu(111) as a function of the tip-sample distance. STM constant-height imaging reveals a transition from p- to s-wave dominated tunneling. The findings provide an additional control knob to identify molecular electronic and spin states, which often requires STM imaging of orbital densities and careful assignment to calculated molecular orbitals [6].

[1] P. Hapala et al., Phys. Rev. B 90, 085421 (2014). [2] L. Gross et al., Science 325, 1110 (2009). [3] L. Gross et al., Phys. Rev. Lett. 107, 086101 (2011). [4] N. Pavlicek et al., Phys. Rev. Lett. 110, 136101 (2013). [5] A. Gustafsson et al., Phys. Rev. B 93, 115434 (2016). [6] S. Mishra et al., ACS Nano 16, 3264 (2022).

Keywords: CO tip; Orbital density mapping; p-wave imaging; Scanning tunneling microscopy; On-surface synthesis