Fluorescence EXAFS Study on Local Structures around Mn and Fe Atoms Doped in ZnO

Ofuchi, Hironori; Jin, Zheng Wu; Fukumura, Tomoteru; Kawasaki, Masashi; Matsumoto, Yuji; Hasegawa, Tetsuya; Fujioka, Hiroshi; Oshima, Masaharu; Koinuma, Hideomi

doi:10.1238/physica.topical.115a00614

Cited by 7 publications

(6 citation statements)

References 6 publications

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“…The pressure at which this transition occurs strongly depends on the Al 3+ content and according to our calculations increases from 76 GPa for Al-free to 134 GPa for Al-bearing perovskites. This explains previous experimental results [e.g., 7,8], which were thought to contradict each other. These findings have important geophysical implications [9].…”

supporting

confidence: 72%

Investigation of Mn site configuration in wurtzite and rock-salt Zn_1−xMn_xO by means of XAS experiments under pressure

Polian¹,

Pellicer‐Porres²,

Sans³

et al. 2006

Acta Cryst Sect A

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Earth's lower mantle is believed to contain ∼75 vol.% (Mg,Fe)SiO 3 perovskite, 20 vol.% (Mg,Fe)O ferropericlase, 5 vol.% CaSiO 3 perovskite. In the lowermost ∼200 km of the mantle, (Mg,Fe)SiO 3 adopts the post-perovskite structure [1,2]. While the properties and behaviour of pure MgSiO 3 phases are well understood (see e.g. ref.[2-5]), the effects of impuritiesmost importantly iron and aluminium, are poorly known and the existing experimental studies are contradictory. Here, we perform ab initio simulations that address the valence and spin states of iron impurities in MgSiO 3 polymorphs. In agreement with [6] we find a valence disproportionation reaction: 3Fe 2+ →2Fe 3+ +Fe 0 metal . This highly exothermic (and somewhat counterintuitive) reaction results in the predominance of Fe 3+ impurities in lower mantle silicates and produces free metallic iron. It occurs both in perovskite and post-perovskite, Al-free and Al-rich, at all lower mantle pressures. In presence of Al 3+ , iron forms Fe 3+ -Al 3+ coupled substitutions in perovskite, but separate Fe 3+ -Fe 3+ and Al 3+ -Al 3+ substitutions in post-perovskite. Only the high-spin state is found for Fe 2+ impurities at all mantle pressures, while Fe 3+ impurities on the Si-site are low-spin at all pressures in both phases. Fe 3+ impurities on the Mg-site are in the high-spin state in post-perovskite at all mantle pressures, but in perovskite we predict a high-spin -low-spin transition. The pressure at which this transition occurs strongly depends on the Al 3+ content and according to our calculations increases from 76 GPa for Al-free to 134 GPa for Al-bearing perovskites. This explains previous experimental results [e.g., 7,8], which were thought to contradict each other. These findings have important geophysical implications [9].

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supporting

confidence: 72%

Investigation of Mn site configuration in wurtzite and rock-salt Zn_1−xMn_xO by means of XAS experiments under pressure

Polian¹,

Pellicer‐Porres²,

Sans³

et al. 2006

Acta Cryst Sect A

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“…Previous XAS experiments, realized at ambient conditions, focused either on the x-ray absorption near edge spectroscopy 8 ͑XANES͒ or on the extended x-ray absorption fine structure ͑EXAFS͒ regions, 4,9 failing to give a full analysis of the absorption spectra. For concentrations higher than 10 at.…”

mentioning

confidence: 99%

Local environment of a diluted element under high pressure: Zn1−xMnxO probed by fluorescence x-ray absorption spectroscopy

Pellicer‐Porres

Segura

Sánchez-Royo

et al. 2006

Applied Physics Letters

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The authors report on x-ray absorption measurements performed on Zn1-xMnxO x=0.05, 0.25 at the Mn K edge 6539 eV under high pressure. Mn is found to substitute for Zn both in the low pressure wurtzite phase and in the high pressure rocksalt phase. The Mn–O bond length is determined to be 2.02±0.01 Å at ambient conditions, with a compressibility similar to that of Zn–O in pure ZnO, being dictated by the ZnO crystalline environment. The phase transition is reversible in Zn0.95Mn0.05O, but not in Zn0.75Mn0.25O. The authors demonstrate that fluorescence detected x-ray absorption under high pressure can be used to characterize structural changes around minority elements

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“…Refs. [2][3][4][5][6]8) An important consequence of the previous paragraph is that O-substitution can thus explain the observed 4+ charge state of minority fractions of Mn impurities in ZnO thin films. 4,14,15 Moreover, the fact that for those studies the impurities were not incorporated by ion implantation but during growth, indicates that minority anion substitution may be a general phenomenon in transition metal doped ZnO.…”

Section: Resultsmentioning

confidence: 92%

“…2-4 for Co and Refs. 5-7 for Mn, incorporated either during growth [2][3][4][5][6]8 or by ion implantation. 7,9 When secondary phase segregation is avoided, all 3d TMs, including Co and Mn, were always found to substitute Zn, independently of the growth method, 10 as expected from the chemical similarities between the impurities and the host elements.…”

Section: Introductionmentioning

confidence: 99%

Mixed Zn and O substitution of Co and Mn in ZnO

et al. 2011

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The physical properties of an impurity atom in a semiconductor are primarily determined by the lattice site it occupies. In general, this occupancy can be correctly predicted based on chemical intuition, but not always. We report on one such exception in the dilute magnetic semiconductors (DMS) Co-and Mn-doped ZnO, experimentally determining the lattice location of Co and Mn using β − emission channeling from the decay of radioactive 61 Co and 56 Mn implanted at the ISOLDE facility at CERN. Surprisingly, in addition to the majority substituting for Zn, we find up to 18% (27%) of the Co (Mn) atoms in O sites, which is virtually unaffected by thermal annealing up to 900 • C. We discuss how this anion site configuration, which had never been considered before for any transition metal in any metal oxide material, may in fact have a low formation energy. This suggests a change in paradigm regarding transition metal incorporation in ZnO and possibly other oxides and wide-gap semiconductors.

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Fluorescence EXAFS Study on Local Structures around Mn and Fe Atoms Doped in ZnO

Cited by 7 publications

References 6 publications

Investigation of Mn site configuration in wurtzite and rock-salt Zn_1−xMn_xO by means of XAS experiments under pressure

Investigation of Mn site configuration in wurtzite and rock-salt Zn_1−xMn_xO by means of XAS experiments under pressure

Local environment of a diluted element under high pressure: Zn1−xMnxO probed by fluorescence x-ray absorption spectroscopy

Mixed Zn and O substitution of Co and Mn in ZnO

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Fluorescence EXAFS Study on Local Structures around Mn and Fe Atoms Doped in ZnO

Cited by 7 publications

References 6 publications

Investigation of Mn site configuration in wurtzite and rock-salt Zn1−xMnxO by means of XAS experiments under pressure

Investigation of Mn site configuration in wurtzite and rock-salt Zn1−xMnxO by means of XAS experiments under pressure

Local environment of a diluted element under high pressure: Zn1−xMnxO probed by fluorescence x-ray absorption spectroscopy

Mixed Zn and O substitution of Co and Mn in ZnO

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Investigation of Mn site configuration in wurtzite and rock-salt Zn_1−xMn_xO by means of XAS experiments under pressure

Investigation of Mn site configuration in wurtzite and rock-salt Zn_1−xMn_xO by means of XAS experiments under pressure