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Abstract In an effort to reconcile the various interpretations for the cation components of the 2p3/2observed 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 2p3/2core 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 2p3/2core 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 NixCo1−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.
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This content will become publicly available on February 12, 2026
The surface termination of a Fe (III) spin crossover molecular salt
Abstract From a comparison of the known molecular stoichiometry and x-ray photoemission spectroscopy, it is evident that the Fe(III) spin crossover salt [Fe(qsal)2Ni(dmit)2] has a preferential surface termination with the Ni(dmit)2moiety, where qsal = N(8quinolyl)salicylaldimine, and dmit2−= 1,3-dithiol-2-thione-4,5-dithiolato. This preferential surface termination leads to a significant surface to bulk core level shift for the Ni 2p x-ray photoemission core level, not seen in the corresponding Fe 2p core level spectra. A similar surface to bulk core level shift is seen in Pd 3d in the related [Fe(qsal)2]2Pd(dmit)2. Inverse photoemission spectroscopy, compared with the x-ray absorption spectra at the Ni-L3,2 edge provides some indication of the density of states resulting from the dmit2−= 1,3-dithiol-2-thione-4,5-dithiolato ligand unoccupied molecular orbitals and thus supports the evidence regarding surface termination in the Ni(dmit)2moiety.
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- Award ID(s):
- 2317464
- PAR ID:
- 10615152
- Publisher / Repository:
- Institute of Physics Publishing
- Date Published:
- Journal Name:
- Journal of Physics: Condensed Matter
- Volume:
- 37
- Issue:
- 13
- ISSN:
- 0953-8984
- Page Range / eLocation ID:
- 135001
- Subject(s) / Keyword(s):
- spin crossover molecules, surface to bulk core level shift, surface termination, x-ray absorption spectroscopy
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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