Crystal field effects on the photoemission spectra in Cr2O3 thin films: from multiplet splitting features to the local structure

Pamella Vasconcelos (1) , Alain Chartier (1) , Jean-Baptiste Moussy (2) , Denis Menut (3) , Frédéric Miserque (4)

1 LM2T - Laboratoire de Modélisation, Thermodynamique et Thermochimie
2 SPEC - UMR3680 - Service de physique de l'état condensé
3 SSOLEIL - Synchrotron SOLEIL
4 SCCME - Service de la Corrosion et du Comportement des Matériaux dans leur Environnement

Changes in the shape of X-ray photoemission (XPS) spectra can be related to changes in the local structure of a transi-tion metal. By combining Crystal Field Multiplet calculations and well-controlled molecular beam epitaxy growth of alpha-Cr2O3(0001) thin films on alpha-Al2O3(0001) substrates, we prove that it possible to link the features of Cr 2p XPS spectra with local distortions of CrO6 octahedra and d-orbitals reorganization. Hence, we show that the splitting of the Cr 2p3/2 envelope is related to the degeneracy of the t2g orbital triplet, which corresponds to a fully relaxed structure. Conversely, the broad unstructured Cr 2p3/2 envelope relies on splitting of t2g orbitals and it is the fingerprint of large trigonal distor-tions of CrO6 octahedra. Then, using the Cr 2p XPS as a structural tool for -Cr2O3, we show that the Cr2O3 protective layer formed by oxidation of polycrystalline Ni30Cr alloy exhibits in-plane strains at early oxidation stages and grows preferentially along the c-axis.

Domaines: Physique [physics]

Pamella Vasconcelos, Alain Chartier, Jean-Baptiste Moussy, Denis Menut, Frédéric Miserque. Crystal field effects on the photoemission spectra in Cr2O3 thin films: from multiplet splitting features to the local structure. Materialia, 2020, 12, pp.100753. ⟨10.1016/j.mtla.2020.100753⟩. ⟨cea-03265613⟩