An interpretation for the components of 2 p3/2core level x-ray photoelectron spectra of the cations in some inverse spinel oxides

Arjun Subedi; Detian Yang; Wai Kiat Chin; Binny Tamang; Sushrisangita Sahoo; Paul Yancey; Rifat Mahbub; Jeffrey Shield; Rebecca Y Lai; Xiaoshan Xu; Peter A Dowben; Vijaya Rangari

doi:10.1088/1361-648X/ad3271

An interpretation for the components of 2 p_3/2core level x-ray photoelectron spectra of the cations in some inverse spinel oxides

J Phys Condens Matter. 2024 Apr 12;36(28). doi: 10.1088/1361-648X/ad3271.

Authors

Affiliations

¹ Department of Physics and Astronomy, Theodore Jorgensen Hall, University of Nebraska-Lincoln, 855 North 16th Street, Lincoln, NE 68588-0299, United States of America.
² Department of Chemistry, Hamilton Hall, University of Nebraska-Lincoln, Lincoln, NE 68588-0304, United States of America.
³ Department of Material Science and Engineering, Tuskegee University, Tuskegee, AL 36088, United States of America.
⁴ Department of Mechanical Engineering, Materials Processing Laboratory, Tuskegee University, Tuskegee, AL 36088, United States of America.
⁵ Department of Mechanical and Materials Engineering, 339 Nebraska Hall, University of Nebraska, Lincoln, NE 68588-0526, United States of America.

PMID: 38467066
DOI: 10.1088/1361-648X/ad3271

Abstract

In an effort to reconcile the various interpretations for the cation components of the 2p_3/2observed in x-ray photoelectron spectroscopy (XPS) of several spinel oxide materials, the XPS spectra of both spinel alloy nanoparticles and crystalline thin films are compared. We observed that different components of the 2p_3/2core level XPS spectra, of these inverse spinel thin films, are distinctly surface and bulk weighted, indicating surface-to-bulk core level shifts in the binding energies. Surface-to-bulk core level shifts in binding energies of Ni and Fe 2p_3/2core levels of NiFe₂O₄thin film are observed in angle-resolved XPS. The ratio between surface-weighted components and bulk-weighted components of the Ni and Fe core levels shows appreciable dependency on photoemission angle, with respect to surface normal. XPS showed that the ferrite nanoparticles Ni_xCo_1-xFe₂O₄(x= 0.2, 0.5, 0.8, 1) resemble the surface of the NiFe₂O₄thin film. Surface-to-bulk core level shifts are also observed in CoFe₂O₄and NiCo₂O₄thin films but not as significantly as in NiFe₂O₄thin film. Estimates of surface stoichiometry of some spinel oxide nanoparticles and thin films suggested that the apportionment between cationic species present could be farther from expectations for thin films as compared to what is seen with nanoparticles.

Keywords: spinel oxides; surface-to-bulk core level shift; x-ray photoelectron spectroscopy.

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