Accessing the interface properties with photoemission electron microscopy
Ass.-Prof. Dr. Giovanni Zamborlini
Karl-Franzens-Universität Graz, Institut für Physik, NAWI Graz, 8010 Graz, Austria
16:15 - 17:15 Tuesday 04 March 2025 Photoemission electron microscopes (PEEMs) are incredibly versatile tools for investigating the chemical and physical properties of surfaces. Thanks to their electron lens system, they can capture both spatial and angular information of the photoemitted electrons. This feature makes them suitable to measure electron momenta (and thus the material’s band structure) from selected areas (usually few µm wide) of the surface. They can also be coupled with pulsed light sources, such as high harmonic generation or UV-pulsed sources, in a pump-probe scheme that allows for performing time-resolved experiments with femtosecond resolution. Moreover, by inserting an electron mirror within the optical path, it is possible to simultaneously probe both the electron momenta and their spin character.
The aim of this talk is to showcase examples where the PEEM capabilities can be fully exploited to unravel the physical properties of completely different systems, from single crystal surfaces, molecular overlayers, to 2D materials. At first, we will discuss how the oxygen passivation of the iron surface (O-Fe) strongly modifies the surface electronic properties, enhancing electron correlation. This enhancement results in a non-trivial spin texture, which can be accessed by spin-resolved PEEM measurements [1]. Then, we will show how the very same surface can also be used for supporting molecular adsorbates. In the case of self-assembled porphyrin films, we will illustrate how angle-resolved photoemission measurements benefit from the full-field acquisition scheme offered by PEEM for probing the molecular conformation with extreme precision [2]. As last example, we will show the ability of the PEEM set-ups to perform time and angle-resolved photoemission spectroscopy in a pump-probe configuration (with pump pulses in a very broad photon energy range, while almost preserving the state-of-the-art resolution in momentum space. We benchmark our set-up through a series of time-resolved experiments on a bismuth selenide (Bi2Se3) and tungsten disulfide (WS2) crystals [3,4].
Finally, we will present a brief outlook introducing of a novel class heterointerfaces based on 2D dimensional metal-organic frameworks (employing different coordination schemes) grown atop WS2 single layers.
[1] D. M. Janas et. al. Advanced Materials 35, 2205698 (2023).
[2] D. M. Janas et. al. Inorganica Chimica Acta 557, 121705 (2023).
[3] S. Ponzoni et al. Advanced Physics Research 2, 2200016 (2023).
[4] K. Schiller et al. Scientific Reports (2025), DOI: 10.1038/s41598-025-
86660-1.
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