Spinel formation at the interface: a structural study by X-ray photoelectron diffraction

Galeotti, Monica; Torrini, Marco; Bardi, Ugo; Santucci, A.; Ghisletti, Danila

doi:10.1016/s0039-6028(96)01222-8

Cited by 11 publications

(5 citation statements)

References 14 publications

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“…[7] In general, the deposited metal is oxidized and coordinated with oxygen to form an oxide while the metal ion of the substrate is reduced. In our investigations Fe 2p spectra recorded at low iron coverage were used for determination of the oxidation state of iron.…”

Section: Interface Formationmentioning

confidence: 99%

Study of formation and thermal stability of the Fe/ZnO(000‐1) interface

Demund¹,

Wett²,

Szargan³

2008

Surface & Interface Analysis

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Formation and thermal stability of the Fe/ZnO(000-1) interface have been studied by means of X-ray photoelectron spectroscopy and low energy electron diffraction. The results indicated a pseudo 2D growth mode for iron on ZnO. In addition, it could be shown that under ultra high vacuum conditions deposited Fe 0 on a ZnO(000-1) single crystal was partially oxidized by a small fraction of residual -OH-groups and ZnO to FeO. A strong temperature dependence of the interface reactivity was found upon annealing at temperatures up to 600• C. Starting from 200• C iron was first oxidized to bivalent iron oxide. After complete oxidation of Fe 0 to Fe 2+ at 375• C, Fe 2+ reacted to Fe 3+ . Above temperatures of 500 • C the deposited metallic iron was completely oxidized to trivalent iron. Further experiments with FeO on ZnO showed the oxidation state and the oxide film thickness of the deposited iron to be mainly dependent on the annealing temperature.

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Section: Interface Formationmentioning

confidence: 99%

Study of formation and thermal stability of the Fe/ZnO(000‐1) interface

Demund¹,

Wett²,

Szargan³

2008

Surface & Interface Analysis

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“…Annealing-induced interdiffusion at the interface of metal oxides is a recurrent mechanism for spinel formation, but the phenomenon is generally studied only at microscopic level [59][60][61] . The spinel phase has been previously hypothesized on sputter-deposited ZnO/Ti/ZnO coatings annealed at 900 K 13,37 as well as at the Cr/O-ZnO interface and at the Fe/Zn-ZnO interface upon annealing at 830 K 34,35 and 820-870 K 36 ,respectively. Interestingly, a thin zinc oxide layer above metallic chromium is observed at room temperature for Cr/O-ZnO, in analogy to our results 34,35 .…”

Section: Annealing Ti/zno Interfacesmentioning

confidence: 81%

“…The spinel phase has been previously hypothesized on sputter-deposited ZnO/Ti/ZnO coatings annealed at 900 K 13,37 as well as at the Cr/O-ZnO interface and at the Fe/Zn-ZnO interface upon annealing at 830 K 34,35 and 820-870 K 36 ,respectively. Interestingly, a thin zinc oxide layer above metallic chromium is observed at room temperature for Cr/O-ZnO, in analogy to our results 34,35 . Finally, the activation temperature for the Ti oxidation dramatically differs for the two polar surfaces.…”

Section: Annealing Ti/zno Interfacesmentioning

confidence: 81%

“…Most studies involving the polar ZnO(0001) and ZnO(000 1 ) surfaces have focused either on noble metals or on the end of the transition series: Pt [18][19][20][21][22] , Pd 23 , Cu [24][25][26][27][28][29][30] , Ag 23,31,32 , Au 33 . But dramatic transformations can occur with metals from the beginning and middle of the transition series, as illustrated by the formation of spinels upon annealing Cr/ZnO(000 1 ) 34,35 and Fe/ZnO(0001) 36 films and ZnO/Ti/ZnO coatings 13 (ZnCr2O4, ZnFe2O4 and Zn2TiO4, respectively). Regarding Ti, the chemical reactions at the interface of sputter-deposited ZnO-Ti multilayers have been explored by hard x-ray photoelectron spectroscopy, revealing the oxidation of Ti and the reduction of ZnO 13,37 .…”

Section: Introductionmentioning

confidence: 99%

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Orientation-dependent chemistry and band-bending of Ti on polar ZnO surfaces

Borghetti

Mouchaal

Dai

et al. 2017

Phys. Chem. Chem. Phys.

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Orientation-dependent reactivity and band-bending are evidenced upon Ti deposition (1-10 Å) on polar ZnO(0001)-Zn and ZnO(0001[combining macron])-O surfaces. At the onset of the Ti deposition, a downward band-bending was observed on ZnO(0001[combining macron])-O while no change occurred on ZnO(0001)-Zn. Combining this with the photoemission analysis of the Ti 2p core level and Zn L(L)MM Auger transition, it is established that the Ti/ZnO reaction is of the form Ti + 2ZnO → TiO + 2Zn on ZnO(0001)-Zn and Ti + yZnO → TiZnO + (y - x)Zn on ZnO(0001[combining macron])-O. Consistently, upon annealing thicker Ti adlayers, the metallic zinc is removed to leave ZnO(0001)-Zn surfaces covered with a TiO-like phase and ZnO(0001[combining macron])-O surfaces covered with a defined (Ti, Zn, O) compound. Finally, a difference in the activation temperature between the O-terminated (500 K) and Zn-terminated (700 K) surfaces is observed, which is tentatively explained by different electric fields in the space charge layer at ZnO surfaces.

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“…51,52 Therefore, the growth temperature is limited by the onset of Cr/Zn interdiffusion and the resulting formation of zinc chromate.…”

Section: A Evolution Of Cr 2 O 3 Film Structurementioning

confidence: 99%

Growth, structure, and electronic properties of nonpolar thin films on a polar substrate:Cr2O3on ZnO (0001) and ZnO (0001¯
Zhu
¹
,
Morales-Acosta
²
,
Shen
³

et al. 2015
Phys. Rev. B
10
0
3
0
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The growth and geometric and electronic structures of Cr 2 O 3 layers on the polar ZnO surfaces were characterized to determine how polar substrates can influence the properties of non-polar films. Photoelectron spectroscopy (XPS and UPS), high resolution transmission electron microscopy (HRTEM), electron diffraction (RHEED and LEED), and x-ray diffraction and reflectivity (XRD and XRR) were employed to characterize the growth mode, film quality and interfacial electronic properties. Chromium oxide growth on ZnO 0001 and 0001 followed the same trends: two dimensional growth with initial disorder followed by the formation of epitaxial Cr 2 O 3 0001 . Despite the initial disorder, HRTEM and XRD/XRR measurements on thicker films revealed an abrupt interface with the Cr 2 O 3 lattice extending all the way to the interface. This indicates that above a critical thickness of 10 -15 Cr-O 3 -Cr repeat units the entire film reorganizes into an ordered structure. It is postulated that the oxygen remained ordered throughout the growth but that the chromium initially filled interstices randomly in the oxygen sublattice which allowed the film to eventually grow with a well-defined epitaxial relationship with the substrate. The polar interfaces showed a small band offset that decayed with increasing film thickness, suggesting that the compensating charges at the interface 2 may partially migrate to the film surface. No evidence of formal changes in the Cr oxidation state at the interfaces was seen. On the other hand, statistical analyses of UPS valence band spectra revealed an enhanced density of states near the valence band edge for Cr 2 O 3 on ZnO 0001 , consistent with stabilization of the positive interface by filling surface electronic states.In contrast, no significant valence band differences were observed between bulk Cr 2 O 3 and thin Cr 2 O 3 layers on ZnO 0001 suggesting a different charge compensation mechanism on the negative surface. The potential impact of these findings on the surface properties of chromium oxide thin films is discussed. PACS number(s): 68.47.Gh,

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Spinel formation at the interface: a structural study by X-ray photoelectron diffraction

Cited by 11 publications

References 14 publications

Study of formation and thermal stability of the Fe/ZnO(000‐1) interface

Study of formation and thermal stability of the Fe/ZnO(000‐1) interface

Orientation-dependent chemistry and band-bending of Ti on polar ZnO surfaces

Growth, structure, and electronic properties of nonpolar thin films on a polar substrate:Cr2O3on ZnO (0001) and ZnO (0001¯
Zhu
¹
,
Morales-Acosta
²
,
Shen
³

et al. 2015
Phys. Rev. B
10
0
3
0
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Spinel formation at the interface: a structural study by X-ray photoelectron diffraction

Cited by 11 publications

References 14 publications

Study of formation and thermal stability of the Fe/ZnO(000‐1) interface

Study of formation and thermal stability of the Fe/ZnO(000‐1) interface

Orientation-dependent chemistry and band-bending of Ti on polar ZnO surfaces

Growth, structure, and electronic properties of nonpolar thin films on a polar substrate:Cr2O3on ZnO (0001) and ZnO (0001¯Zhu1, Morales-Acosta2, Shen3 et al. 2015Phys. Rev. B10030View full textAdd to dashboardCite

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Product

Resources

About

Growth, structure, and electronic properties of nonpolar thin films on a polar substrate:Cr2O3on ZnO (0001) and ZnO (0001¯
Zhu
¹
,
Morales-Acosta
²
,
Shen
³

et al. 2015
Phys. Rev. B
10
0
3
0
View full text Add to dashboard Cite