Mathias Schwendt’s research while affiliated with University of Graz and other places

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Publications (2)


Figure 1. Chemical structures of the O-doped perylenes investigated in this study: 5,5′,8,8′,11,11′-hexa-tert-butyl-[3,3′-biperylene]-2,2′-diol (BPOL), 2,5,8,14,17,20-hexa-tert-butyldiperyleno[2,3-b:3′,2′-d]furan (BPF), and 2,5,9,12,15,19-hexa-tert-butylbenzo[5′,10′]anthra-[9′,1′,2′:7,8,1]isochromeno[5,4,3-cde]benzo[5,10]anthra[9,1,2-hij]-isochromene (BPPP). 23
Figure 2. Results from (a) Pawley fitting and (b) final Rietveld refinement of the powder XRD data (background subtracted) for BPPP (red "+" marks, experimental data; green line, calculated data; purple tick marks, peak positions; the green line at the bottom shows the difference between the experimental and calculated powder XRD data). In each case, the inset shows an expanded region of the powder XRD data in the range of 2θ = 7.5−30°. Excluded regions correspond to the positions of two impurity peaks, as discussed in the text.
Figure 3. Crystal structure of BPPP viewed along (a) a-axis and (b) baxis.
Figure 6. Molecular domains for BPPP/Cu(111). (a) Molecular ordering in the vicinity of the substrate's steps is compromised, while extended molecular networks are formed a few nm away from the terrace edges. (b) Evidence of coexisting domains with opposite surface chirality. The superimposed molecular cartoonic pictures (red and green for the two surface enantiomers) help in the pattern visualization. From the combined analysis of the measured STM micrographs and LEED patterns, an angle of 20° between the two chiral partners is confirmed.
Figure 7. BPF arrangement on Cu(111). Low-resolution (a) and highresolution (b) STM micrographs show the herringbone configuration for the square-like molecular pattern with no evidence of chiral domains.

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Orbital Mapping of Semiconducting Perylenes on Cu(111)
  • Article
  • Full-text available

October 2021

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185 Reads

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2 Citations

The Journal of Physical Chemistry C

Giovanni Di Santo

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Mathias Schwendt

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Semiconducting O-doped polycyclic aromatic hydrocarbons constitute a class of molecules whose optoelectronic properties can be tailored by acting on the π-extension of the carbon-based frameworks and on the oxygen linkages. Although much is known about their photophysical and electrochemical properties in solution, their self-assembly interfacial behavior on solid substrates has remained unexplored so far. In this paper, we have focused our attention on the on-surface self-assembly of O-doped bi-perylene derivatives. Their ability to assemble in ordered networks on Cu(111) single-crystalline surfaces allowed a combination of structural, morphological, and spectroscopic studies. In particular, the exploitation of the orbital mapping methodology based on angle-resolved photoemission spectroscopy, with the support of scanning tunneling microscopy and low-energy electron diffraction, allowed the identification of both the electronic structure of the adsorbates and their geometric arrangement. Our multi-technique experimental investigation includes the structure determination from powder X-ray diffraction data for a specific compound and demonstrates that the electronic structure of such large molecular self-assembled networks can be studied using the reconstruction methods of molecular orbitals from photoemission data even in the presence of segregated chiral domains.

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Plane-wave final state for photoemission from nonplanar molecules at a metal-organic interface

April 2020

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53 Reads

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13 Citations

In recent years, the method of orbital tomography has been a useful tool for the analysis of a variety of molecular systems. However, the underlying plane-wave final state has been largely expected to be applicable to planar molecules only. Here, we demonstrate on photoemission data from the molecule C60 adsorbed on Ag(110) that it can indeed be a valid approximation for truly three-dimensional molecules at a metal-organic interface. A comparison of the experimental data supported by density functional theory (DFT) calculations of the full interface and simulations of the photoemission process with a more exact final state enables the determination of the adsorption geometry and orientation of the C60 molecules in a monolayer on the Ag(110) surface. Additionally, charge transfer into the molecules is used to confirm the lifting in degeneracy of the t1u molecular orbitals as predicted by DFT calculations.

Citations (1)


... Photoelectron momentum microscopy is a technique in which a light pulse ionizes a probe, leading to the detachment of a photoelectron. The momentum distribution of the detached photoelectron encodes information about the shape of an orbital or a bond in the real space from which the electron was detached [1][2][3][4][5][6][7][8][9][10][11][12]. This connection is facilitated by the Fourier transform, which links real and momentum space. ...

Reference:

Attosecond imaging of photoinduced dynamics in molecules using time-resolved photoelectron momentum microscopy
Plane-wave final state for photoemission from nonplanar molecules at a metal-organic interface
  • Citing Article
  • April 2020