Identification of Fe3+–Li+ complexes in ZnO by means of high-frequency EPR/ENDOR spectroscopy

[Display omitted] •Li was identified as the charge compensator in Fe-related complexes by ENDOR.•EPR spectra of the charge-compensated Fe3+ centers in ZnO were recorded at W-band.•Hyperfine interaction constants of 7Li within the Fe3+–Li+ complexes were obtained.•Quadrupole interactions of the 7Li n...

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Bibliographic Details
Published in:Journal of magnetic resonance (1997) 2013-12, Vol.237, p.110-114
Main Authors: Kutin, Yu.S., Mamin, G.V., Orlinskii, S.B.
Format: Article
Language:English
Subjects:
Charge-compensated centers
Complex
ENDOR
High-frequency EPR
Iron
Lithium
Quadrupole interaction
W-band
ZnO
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Summary:[Display omitted] •Li was identified as the charge compensator in Fe-related complexes by ENDOR.•EPR spectra of the charge-compensated Fe3+ centers in ZnO were recorded at W-band.•Hyperfine interaction constants of 7Li within the Fe3+–Li+ complexes were obtained.•Quadrupole interactions of the 7Li nuclei within the complexes were measured. Theoretical prediction of a high Curie temperature in ZnO doped with Mn, Fe, and other transition metals has stimulated the investigation of these materials by many research groups. Although charge-compensated Fe3+ centers in ZnO:Fe have been observed by means of EPR and have been known for decades, conclusions on the chemical nature of these defects are still contradictory. Originally, these centers were treated as Fe3+–Li+ complexes with both ions occupying adjacent cationic sites. Recently, however, the centers were interpreted as a substitutional Fe3+ ion with a vacancy at an adjacent zinc or oxygen site (Fe-VZn or Fe-VO). In order to determine the chemical nature of the impurity associated with Fe3+, electron-nuclear double resonance (ENDOR) spectroscopy was used. ENDOR measurements reveal NMR transitions corresponding to nuclei with g-factor gN=2.171 and spin I=3/2. This unambiguously shows presence of Li as a charge compensator and also resolves contradictions with the theoretical prediction of the Fe-VO formation energy. The electric field gradients at the 7Li nuclei (within the Fe3+–Li+ complexes) were estimated to be significantly lower than the gradient at undistorted Zn sites.
ISSN:1090-7807
1096-0856
DOI:10.1016/j.jmr.2013.09.014