Reduction of oxides of iron, cobalt, titanium and niobium by low-energy ion bombardment

Choudhury, T; Saied, S.O.; Sullivan, J.L.; Abbot, Andrew M.

doi:10.1088/0022-3727/22/8/026

Cited by 390 publications

(237 citation statements)

References 18 publications

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“…The spectrum of Ti(2p3/2 ' 1/2) for a non-sputtered sample shows peaks at 458.5 eV binding energy and 1.7 eV FWHM (Ti2p3/2) and at 464.1 eV binding energy and 2.5 eV FWHM (Ti2p1/2). As shown in Table 3, these peak positions correspond well to the literature data of Ti 4+ [4,21].…”

Section: Xps Results Of Fe-implanted Yszsupporting

confidence: 87%

“…The spectrum of Fe(2p3/2) for a nonsputtered sample shows a peak at 711.2 eV binding energy and 2.5 eV FWHM, after background subtraction. As shown in Table 1, this peak position corresponds to Fe 3 + [21][22][23]. According to previously published CEMS measurements [1][2][3][4][5][6][7][8][9][10][11] all the Fe cations in the Fe depth profile of the oxidized sample are initially present in the trivalent state.…”

Section: I Surface Modificationmentioning

confidence: 77%

“…A deconvolution of the peaks was made using the parameters of Table 3. The new lines were ascribed to suboxides according to literature data [4,21]. A deconvolution of the spectrum with respect to the original components is shown in Fig.…”

Section: Xps Results Of Ti Implantedmentioning

confidence: 99%

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Oxidation state of Fe and Ti ions implanted in yttria-stabilized zirconia studied by XPS

Hassel

Burggraaf

1991

Appl. Phys. A

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Abstract. The oxidation state of Fe and Ti ions implanted in yttria stabilized zirconia (YSZ) was studied by XPS (X-ray photoelectron spectroscopy) in combination with depth profiling using Ar + sputtering. In the "as-implanted" state of the sample Fe was found to be present as Fe 3 +, Fe 2+ and as metallic Fe °. This is in agreement with earlier conversion electron Mrssbauer Spectroscopy measurements. For Ti-implanted YSZ in the "as-implanted" state the majority of the Ti is present as TP +, Ti 3+, and Ti 2+ ions, while a part of the Zr cations is present in the divalent oxidation state (Zr 2 +). After oxidation in air, the Fe and Ti ions are present only in the valence three and four oxidation states, respectively. PACS: 79.60.Eq, 61.70.Tm X-ray photoelectron spectroscopy (XPS) is frequently used to study the chemical nature of surfaces [1]. It gives information on the chemical composition as well as the oxidation state of the elements present in the surface. Ion beams can be used for surface cleaning or depth profiling. Hence in principle it is possible to study the oxidation state of elements in thin films as a function of the depth.During sputtering preferential removal of elements may occur. These effects originate from differences in the surface binding energies and from mass differences [2]. In oxides the lattice oxygen generally is sputtered preferentially with respect to the metal ions [2,3]. The remaining electrons of oxygen cause reduction of cations present in a thin surface layer, with a thickness comparable to the penetration depth of the bombarding ions [4]. It seems, however, not yet to be possible to correct sputtering depth profiles for these preferential sputtering effects.This study, which is part of a larger research effort [5], is intended to give information on the oxidation state of Fe and Ti ions in the "as-implanted" state of YSZ. These results are of importance for the study of the structure [6] and electrochemical properties [7] of these implanted layers. Most information available on the charge state has been obtained with conversion electron Mrssbauer spectroscopy (CEMS) [8][9][10][11]. With CEMS the oxidation state of the implanted ions, in a shallow surface layer of about 100 nm thickness, is analyzed in a non-destructive way. Few elements, however, have suitable isotopes for this technique. The charge state of 57Fe ions [11][12][13][14][15][16][17][18] can be studied very well, but the charge state of Ti cannot.In order to obtain results without any detailed description of the sputtering process at hand, a careful analysis of the evolution of the oxidation states of the cations as a function of the sputtering time is carried out with XPS. The data obtained from the samples in the "as-implanted" state are compared with the data, obtained under similar conditions, from samples with all cations in the highest oxidation state ("oxidized state"). From this analysis conclusions are drawn on the oxidation state of Fe and Ti ions in the "as-implanted" state of the YSZ sample.A disadvant...

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Section: Xps Results Of Fe-implanted Yszsupporting

confidence: 87%

Section: I Surface Modificationmentioning

confidence: 77%

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Oxidation state of Fe and Ti ions implanted in yttria-stabilized zirconia studied by XPS

Hassel

Burggraaf

1991

Appl. Phys. A

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“…4e presents three types of O. The fitting peak for O1 at the binding energy of 529.2 eV is a typical of metal-oxygen bonds (M-O-M) [44], including Ni-O, Co-O and Ir-O. The fitting peak of O2 at 531.1 eV indicates defects, contaminants, and a number of surface species [45].…”

Section: Resultsmentioning

confidence: 99%

IrNi nanoparticle-decorated flower-shaped NiCo2O4 nanostructures: controllable synthesis and enhanced electrochemical activity for oxygen evolution reaction

et al. 2016

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In this work, we demonstrated the enhanced oxygen evolution reaction (OER) activity of flower-shaped cobalt-nickel oxide (NiCo2O4) decorated with iridium-nickel bimetal as an electrode material. The samples were prepared by carefully depositing pre-synthesized IrNi nanoparticles on the surfaces of the NiCo2O4 nano-flowers. Compared with bare NiCo2O4, IrNi, and IrNi/Co3O4, the IrNi/NiCo2O4 exhibited significantly enhanced electrocatalytic activity in the OER, including a lower overpotential of 210 mV and a higher current density at an overpotential of 540 mV. We found that the IrNi/NiCo2O4 showed more efficient electron transport behavior and reduced polarization because of its bimetal IrNi modification by analyzing its Tafel slope and turnover frequency. Furthermore, the electrocatalytic mechanism of IrNi/NiCo2O4 in the OER was studied, and it was found that the combined active sites of the composite effectively improved the rate determining step. The synergic effect of the bimetal and metal oxide plays an important role in this reaction, enhancing the transmission efficiency of electrons and providing more active sites for the OER. The results reveal that IrNi/NiCo2O4 is an excellent electrocatalyst for OER.

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“…The preferential sputtering of oxygen in iron oxides is a well reported phenomenon. 22 Magnetite probably nucleates when the concentration of oxygen vacancies is too high to be accommodated in the hematite structure. But magnetite also undergoes oxygen loss once it is formed.…”

mentioning

confidence: 99%

Formation of a magnetite/hematite epitaxial bilayer generated with low energy ion bombardment

Ruiz-Gómez

Serrano

Carabias

et al. 2017

Applied Physics Letters

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We have used a low-energy ion bombardment to fabricate an epitaxial single-crystalline magnetite/hematite bilayer grown on Au(111). This non-conventional fabrication method involves the transformation of the upper layers of a single-crystalline hematite thin film to single-crystalline magnetite, a process driven by the preferential sputtering of oxygen atoms and favoured by the good structural matching of both phases. We show the reversibility of the transformation between hematite and magnetite, always keeping the epitaxial and single-crystalline character of the films. The magnetic characterization of the bilayer grown using this method shows that the magnetic response is mainly determined by the magnetite thin film, exhibiting a high coercivity.

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Reduction of oxides of iron, cobalt, titanium and niobium by low-energy ion bombardment

Cited by 390 publications

References 18 publications

Oxidation state of Fe and Ti ions implanted in yttria-stabilized zirconia studied by XPS

Oxidation state of Fe and Ti ions implanted in yttria-stabilized zirconia studied by XPS

IrNi nanoparticle-decorated flower-shaped NiCo2O4 nanostructures: controllable synthesis and enhanced electrochemical activity for oxygen evolution reaction

Formation of a magnetite/hematite epitaxial bilayer generated with low energy ion bombardment

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