Photoelectron diffraction study on the structure of a vanadium ultrathin film deposited at the TiO2(110) surface

Sambi, Mauro; Pin, Erica; Sangiovanni, Guido; Zaratin, Laura; Granozzi, Gaetano; Parmigiani, F.

doi:10.1016/0039-6028(95)01339-3

Cited by 49 publications

(23 citation statements)

References 13 publications

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“…Traditionally, oxide/oxide interfaces have not been studied so extensively as metal/oxide interfaces, apparently because the latter are less complex and experimentally less difficult to be studied. [2][3][4][5] However, surface investigations of metal oxides 6,7 and ultrathin oxide films supported on oxide substrates [8][9][10][11][12] have intensified in the past few years for the purpose of both understanding fundamental properties of interfaces in oxide systems and developing novel layered oxide structures. 13 The aim of this paper is to obtain information about the chemical composition and electronic structure of the TiO 2 / SiO 2 interface.…”

Section: Introductionmentioning

confidence: 99%

Synchrotron Photoemission Characterization of TiO₂ Supported on SiO₂

Espinós¹,

Lassaletta²,

Caballero³

et al. 1998

Langmuir

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The system formed by TiO2 deposited on SiO2 has been studied by photoemission and X-ray absorption spectroscopies with synchrotron radiation. TiO2 spreads on the surface of SiO2 where it forms a layer (1-2 ML thick) prior to thickening. Extended X-ray absorption fine structure/X-ray absorption near-edge spectroscopy (EXAFS/XANES) analysis at the TiK edge shows that, whatever the coverage, the TiO2 films are amorphous with titanium ions in a 6-fold coordination of oxygen ions. Photoemission with photons of 140 eV shows that for low coverages, the Ti3p binding energy increases by 0.5 eV with respect to the value in bulk TiO2. Under these conditions, a new feature appears in the O2s peak in the form of an extra shoulder around 24 eV. This new form of oxygen is attributed to oxygen ions at the interface acting as a bridge between TiO2 and SiO2 (i.e., formation of Si-O-Ti cross-linking bonds). The shift in the Ti3p peak is accompanied by a shift to higher binding energies in the valence band edge of the spectra at low TiO2 coverage. This shift would indicate that the band gap of the titanium oxide increases for low coverages of TiO2. A detailed analysis of the valence band region was carried out with photons of 35 < hν < 70 eV. The valence band spectra of TiO2 are narrower (3.6 eV fwhm) and less defined than that of bulk TiO2 (3.9 eV fwhm). Resonance photoemission of the valence band of a thin layer of TiO2 reproduces the pattern reported in the literature for bulk TiO2 characterized by a maximum enhancement of the intensity of the valence band spectrum for hν ) 47 eV.

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Section: Introductionmentioning

confidence: 99%

Synchrotron Photoemission Characterization of TiO₂ Supported on SiO₂

Espinós¹,

Lassaletta²,

Caballero³

et al. 1998

Langmuir

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“…11 In the last period, we have devoted our efforts to elucidating the structural properties of the vanadium-titania interface, mainly by means of angle-scanned x-ray photoelectron diffraction ͑XPD͒. 12 We have shown that a few ML of vanadium deposited at the TiO 2 ͑110͒ surface grow, forming islands of the metal with a bcc structure, with the ͓100͔ direction normal to the substrate surface. In addition, the ͓001͔ azimuth of the overlayer is aligned with the ͓110͔ direction of the substrate and with a well-developed shortrange order, although the long-range coherence between the two lattices is lacking, as demonstrated by the absence of a low-energy electron-diffraction ͑LEED͒ pattern.…”

Section: Introductionmentioning

confidence: 99%

Growth and the structure of epitaxialVO2at theTiO2(110) surface

Sambi¹,

Sangiovanni²,

Granozzi³

et al. 1997

Phys. Rev. B

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Epitaxial VO 2 layers have been grown on the TiO 2 ͑110͒ rutile surface up to thicknesses of 5 ML. These ultrathin films have been characterized by means of x-ray photoelectron spectroscopy ͑XPS͒, x-ray photoelectron diffraction ͑XPD͒, low-energy electron diffraction ͑LEED͒, and ultraviolet photoelectron spectroscopy ͑UPS͒ measurements. LEED and XPD structural data demonstrate that the layer is both short-and long-range ordered, and that it has a rutile structure. The success in preparation of a single-crystalline epitaxial VO 2 layer opens possibilities for studying the properties and the surface chemistry of this interesting oxide, so far complicated by the difficulties in growing macroscopic crystals. From the He I spectra it turns out that the shape, position, and width of the 3d band closely resemble the UPS data of the bulk monoclinic semiconductive phase. The reported results could add new clues to a better understanding of the metal-to-semiconductor phase-transition phenomenon in VO 2 .

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“…They were used as received without further purifiplications, such as thin film technology, electronic devices cation. All the other chemicals used in the experiments were and heterogeneous catalysis (1). Much work has been caranalytical grade reagents, and double distilled deionized waried out on the phenomenon of the so-called strong metalter was used for solution preparation.…”

Section: Introductionmentioning

confidence: 99%

“…The photoreduction was carried out in a home-made photochemical reactor. A 300 W high-pressure mercury lamp (l ú 330 1 To whom correspondence should be addressed. nm) was used as a light source which was cooled by cold 2 ples for TEM and EDS were prepared by dropping colloidal samples onto amorphous carbon overlayers on a copper grid.…”

Section: Introductionmentioning

confidence: 99%