Surface composition of the phases formed by solid state reaction at the interface studied by low energy ion scattering and X-ray photoelectron spectroscopy

Spolveri, I.; Atrei, A.; Cortigiani, Brunetto; Bardi, Ugo; Santucci, A.; Ghisletti, Danila

doi:10.1016/s0039-6028(98)00497-x

Cited by 12 publications

(9 citation statements)

References 19 publications

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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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Section: Annealing Ti/zno Interfacesmentioning

confidence: 81%

Section: Annealing Ti/zno Interfacesmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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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“…The determination of the fraction of vanadium surface covered by metallic tin is prevented by the difficulties in quantifying LEIS data when different matrixes are involved. 25 The oxygen LEIS signal visible also for the thicker vanadium films may be attributed to oxygen chemisorbed on the vanadium surface. This oxygen appears to be the product of both the dissociative adsorption of carbon monoxide from the gas phase (a carbon signal was observed in the XPS spectra measured for the deposited films) and of the diffusion of oxygen atoms from the substrate.…”

Section: Resultsmentioning

confidence: 95%

Growth, Composition, and Structure of Ultrathin Vanadium Films Deposited on the SnO₂(110) Surface

Atrei¹,

Bardi²,

Tarducci³

et al. 2000

J. Phys. Chem. B

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The growth mechanism of vanadium films deposited on the SnO2(110) surface at room temperature and the structure of the phases formed after annealing at 800 K were studied using X-ray photoelectron spectroscopy (XPS), low-energy ion-scattering (LEIS), low-energy electron diffraction (LEED), and X-ray photoelectron diffraction (XPD). The vanadium films were deposited by thermal evaporation in ultrahigh vacuum (UHV) conditions on an oxygen-deficient SnO2 surface prepared by cycles of sputtering and annealing. In the initial stages of vanadium deposition a redox reaction occurs at the metal−oxide interface leading to the formation of vanadium oxide and metallic tin. Upon increasing the amount of deposited vanadium, we observed the growth of islands of metallic vanadium. XPS and LEIS data show that the surface of the vanadium film is partially covered by metallic tin diffusing from the interface. When the deposited vanadium films are heated to 800 K, the reoxidation of metallic tin and the oxidation of all metallic vanadium take place, with no detectable diffusion of vanadium into the SnO2 bulk. The XPD results rule out the formation of a V−Sn mixed oxide. The simulation of the experimental XPD curves by means of single-scattering cluster (SSC) calculations performed for various structural models indicate that the product of the oxidation is an oxide of formula VO x ≈ 2 with a structure close to that of the rutile VO2(110) surface. The vanadium oxide phase is covered by layers of disordered tin oxide.

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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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Surface composition of the phases formed by solid state reaction at the interface studied by low energy ion scattering and X-ray photoelectron spectroscopy

Cited by 12 publications

References 19 publications

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

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

Growth, Composition, and Structure of Ultrathin Vanadium Films Deposited on the SnO₂(110) Surface

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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Surface composition of the phases formed by solid state reaction at the interface studied by low energy ion scattering and X-ray photoelectron spectroscopy

Cited by 12 publications

References 19 publications

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

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

Growth, Composition, and Structure of Ultrathin Vanadium Films Deposited on the SnO2(110) Surface

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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Growth, Composition, and Structure of Ultrathin Vanadium Films Deposited on the SnO₂(110) Surface

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