SKM 2023 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 3: Development of Computational Methods: Evaporation, Growth and Oxidation – Density Functional, Tight Binding

MM 3.6: Vortrag

Montag, 27. März 2023, 11:45–12:00, SCH A 251

Role of an adsorbed gas layer in field ion microscopy contrast — •Shalini Bhatt, Felipe F.Morgado, Shyam Katnagallu, Christoph Freysoldt, and Jörg Neugebauer — Max Planck Institut für Eisenforschung GmbH Düsseldorf Germany

The imaging contrast in field ion microscopy (FIM) is associated with the ionization probability of gas atoms near a surface under 10-100 V/nm electric fields. To better understand contrast variations among atoms observed in FIM, we employ density functional theory (DFT) in combination with the Tersoff-Hamann approximation that links electron tunneling from the gas atom to the surface with the surface's local density of states at the position of the gas atom 3-6 Å away from the surface. Based on our new EXTRA approach (extrapolated tail via reverse algorithm) that eliminates numerical noise in the tails of the wavefunctions, we demonstrate a chemical brightness contrast for Ta in Ni (012) surface. However, we find that the simulated imaging contrast for Ni alone is much lower than in experiment. We therefore explore the role of an adsorbed gas layer as an essential ingredient to explain FIM's unexpectedly large spatial resolution.