SKM 2023 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 68: Poster: Oxide and Insulator Surfaces

O 68.1: Poster

Mittwoch, 29. März 2023, 18:00–20:00, P2/EG

Sub-nanometer depth profiling of native transition metal oxide layers within single XPS spectra — •Martin Wortmann, Dominik Graulich, Natalie Frese, and Timo Kuschel — Bielefeld University, Bielefeld, Germany

Many transition metals form a thin oxide layer of only few nanometers upon exposure to the atmosphere, which affects their interfacial properties. Such native oxide layers are commonly analyzed using photoemission spectroscopy (PES) and X-ray photoelectron spectroscopy (XPS) in particular. The most common method to obtain compositional depth profiles in PES is based on gradual surface ablation by ion sputtering. However, it is known to affect the microstructure of the surface, compromising depth-resolution and compositional accuracy. Other methods such as angular-resolved, energy-resolved, or hard X-ray PES are associated with considerable experimental effort or demands on sample texture. Here we propose a simple and accessible approach for sub-nanometer depth profiling of native metal oxide layers within single lab-XPS spectra. Heavy transition metals usually have multiple orbital energies within the energy range of a lab-XPS giving rise to peak regions at various binding energies. The signal contributions of oxidized and elemental metals can be distinguished by peak deconvolution. The kinetic energy of the photoelectron determines its inelastic mean free path (IMFP) length, which is a measure for the depth from which information is obtained. Different binding energies can thus be assigned to different values for IMFP, so that an oxide concentration profile can be inferred from a single XPS spectrum.