Preferential sputtering of oxides: A comparison of model predictions with experimental data

Malherbe, J.B.; Hofmann, S.; Sanz, J. M.

doi:10.1016/0169-4332(86)90139-x

Cited by 243 publications

(83 citation statements)

References 17 publications

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“…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: 81%

mentioning

confidence: 99%

“…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].…”

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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: I Surface Modificationmentioning

confidence: 81%

mentioning

confidence: 99%

mentioning

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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“…Using these values, the modification of the surface composition by ion bombardment is calculated and compared with experimental values. Results typical for this kind of study, including a model for the surface binding energy, are published by Malherbe et al [21]. Some simulation codes, e.g.…”

Section: ( )mentioning

confidence: 99%

Sputter Deposition Processes

Depla

Mahieu

Greene

2010

Handbook of Deposition Technologies for Films and Coatings

126

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Sputter deposition is a widely used technique to deposit thin films on substrates. The technique is based upon ion bombardment of a source material, the target. Ion bombardment results in a vapor due to a purely physical process, i.e. the sputtering of the target material. Hence, this technique is part of the class of physical vapor deposition techniques, which includes, for example, thermal evaporation and pulsed laser deposition. The most common approach for growing thin films by sputter deposition is the use of a magnetron source in which positive ions present in the plasma of a magnetically enhanced glow discharge bombard the target. This popular technique forms the focus of this chapter. The target can be powered in different ways, ranging from dc for conductive targets, to rf for nonconductive targets, to a variety of different ways of applying current and/or voltage pulses to the target. Since sputtering is a purely physical process, adding chemistry to, for example, deposit a compound layer must be done ad hoc through the addition of a reactive gas to the plasma, i.e. reactive sputtering. The undesirable reaction of the reactive gas with the target material results in a non-linear behavior of the deposition parameters as a function of the reactive gas flow. To model this behavior, the fluxes of the various species towards the target must be determined. However, equally important are the fluxes of species incident at the substrate because they not only influence the reactive sputter deposition process, but also control the growth of the desired film. Indeed, the microstructure of magnetron sputter deposited films is defined by the identity of the particles arriving at the substrate, their fluxes and the energy per particle.

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“…In addition to X-rays, electron, ion, and other energetic particle exposures, which are frequently encountered for cleaning and/or depthprofiling, also cause reduction of certain metal ions to their lower oxidation states [29][30][31][32][33][34]. The extent of reduction varies drastically from one metal ion to another and extensive efforts had been devoted to correlate this with certain chemical/ physical properties of them [24][25][26][27][28][29][30][31][32][33][34]. In one of our earlier work, we had claimed that the extent of X-ray induced reduction could be related with the electrochemical reduction potential of the metal ion [35,36].…”

Section: Introductionmentioning

confidence: 99%

X-ray induced reduction of Au and Pt ions on silicon substrates

Ozkaraoglu

Tunç

Süzer

2007

Surface and Coatings Technology

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Prolonged exposure to X-rays of HAuCl 4 , PtCl 4 and their mixtures, deposited from an aqueous solution onto a silicon substrate, causes chemical reduction of the metal ions to their metallic states. The corresponding oxidation reaction is the conversion of chloride ions to chlorine. The resultant metal atoms aggregate to form metallic/bimetallic nanoclusters as evidenced from their XPS chemical shifts. Hence, X-rays are usable for in-situ nanoparticle production or for direct-writing applications on silicon substrates.

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Preferential sputtering of oxides: A comparison of model predictions with experimental data

Cited by 243 publications

References 17 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

Sputter Deposition Processes

X-ray induced reduction of Au and Pt ions on silicon substrates

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