XPS analysis of gallium oxides

Carli, R.; Bianchi, Claudia L.

doi:10.1016/0169-4332(94)90104-x

Cited by 165 publications

(85 citation statements)

References 10 publications

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“…3 shows the Ga 3d binding energy region recorded on Pd/Ga 2 O 3 during preoxidation (a) and during reduction at 448 (b), 523 (c), and 623 K (d). The main signal at 20.55 eV remained unchanged, irrespective of the atmosphere and temperature, and can unambiguously be assigned to Ga 3+ from the Ga 2 O 3 support [39]. A broad O 2s signal also originating from the Ga 2 O 3 support was additionally observed at around 23 eV and proved to be independent of atmosphere and temperature.…”

Section: In Situ Xps During H2 Reductionmentioning

confidence: 60%

“…toelectron peak was observed at 18.35 ± 0.10 eV. Since the observed chemical shift of 2.2 eV between Ga 3+ and the low-energy Ga species is in the range reported in the literature for oxidic and metallic Ga [39,40], and in accordance with in situ XRD, we assign this species to zero-valent Ga within the intermetallic compound Pd 2 Ga. XPS studies of bulk, metallurgically prepared PdGa (1:1 composition) additionally support our peak assignment [23]. The lower onset-temperature of intermetallic formation compared with XRD can be explained by the surface sensitivity of XPS, which in contrast to XRD does not rely on the presence of three-dimensional crystalline intermetallic particles of a certain size.…”

Section: In Situ Xps During H2 Reductionmentioning

confidence: 81%

“…A signal at binding energies of 19.2 ± 0.1 eV (ΔBE = -1.35 ± 0.10 eV relative to Ga 3+ ) was observed on the Pd catalyst, both under oxidative and under reductive conditions (see Fig. 3), and is assigned to Ga in an intermediate oxidation state (Ga δ+ , δ < 2) [33,39]. On supported Ga/SiO 2 and GaPd/SiO 2 catalysts, a signal at the same relative position (ΔBE = -1.2 to-1.4 eV compared with Ga 3+ ) was observed only upon high-temperature reduction and interpreted as incompletely reduced Ga at the surface [33].…”

Section: In Situ Xps During H2 Reductionmentioning

confidence: 99%

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In situ study of the formation and stability of supported Pd2Ga methanol steam reforming catalysts

Haghöfer

Föttinger

Girgsdies

et al. 2012

Journal of Catalysis

106

138

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Pd/Ga2O3 methanol steam reforming (MSR) catalysts were characterized in detail by utilizing a range of in situ techniques of varying surface sensitivity. Correlating the nature of the intermetallic Pd-Ga compound (IMC; formed upon reduction) with the corresponding activity/selectivity revealed pronounced differences. Generally, a dynamic response of the catalyst surface to the surrounding gas environment was observed. Special attention was paid to the bulk and surface stability of the Pd-Ga IMCs. Whereas the bulk was stable in O2, decomposition of the surface occurred resulting in a partial coverage by GaxOy islands. In addition, we focused on the formation mechanism of undesired CO and were able to identify the reasons limiting the selectivity to MSR. We observed a detrimental effect of CO on the selective Pd-Ga intermetallic compound, causing partial decomposition of the IMC to metallic Pd at the surface. Consequently, patches of Pd metal are present under reaction conditions, catalyzing the unwanted parallel methanol decomposition reaction.

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Section: In Situ Xps During H2 Reductionmentioning

confidence: 60%

Section: In Situ Xps During H2 Reductionmentioning

confidence: 81%

Section: In Situ Xps During H2 Reductionmentioning

confidence: 99%

See 1 more Smart Citation

In situ study of the formation and stability of supported Pd2Ga methanol steam reforming catalysts

Haghöfer

Föttinger

Girgsdies

et al. 2012

Journal of Catalysis

106

138

View full text Add to dashboard Cite

show abstract

“…Two main peaks can be differentiated for the as-grown sample. The lower binding energy peak is centered at 18.7 eV and it is due to the emission of electrons from the Ga atoms in a metallic environment 25 . This 3d peak can be resolved in a doublet thanks to the fine energy step used (0.025 eV).…”

Section: Resultsmentioning

confidence: 99%

The role of the oxide shell in the chemical functionalization of plasmonic gallium nanoparticles

Catalán‐Gómez

Briones

Redondo-Cubero

et al. 2017

Optical Sensors 2017

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Plasmonic Ga nanoparticles (NPs) were thermally oxidized at low temperature in order to increase the native Ga 2 O 3 shell thickness and to improve their stability during the chemical functionalization. The optical, structural and chemical properties of the oxidized NPs have been studied by spectroscopic ellipsometry, scanning electron microscopy, grazing incidence X-ray diffraction and X-ray photoelectron spectroscopy. A clear redshift of the peak wavelength is observed with the increasing annealing time due to the Ga 2 O 3 thickness increase, and barely affecting the intensity of the plasmon resonance. This oxide layer enhances the stability of the NPs upon immersion in ethanol or water. The surface sensitivity properties of the as-grown and oxidized NPs were investigated by linking a thiol group from 6-Mercapto-1-hexanol through immersion. Ellipsometric spectra at the reversal polarization handedness (RPH) condition are in agreement with the Langmuir absorption model, indicating the formation of a thiol monolayer on the NPs.

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“…3b) clearly differentiate between the HRS film within the TE mark area (bright) and the pristine surface area (grey), thus indicating Figure 3c shows the m-XPS spectra collected on the pristine and polarized film surfaces, respectively. The pristine film exhibits three different Ga valence states; a strong peak at 20.7 eV (P 1 ) is assigned to the oxide (Ga 3 þ ) 39 state, a peak at around 19.6 eV (P 2 ) to the suboxide (Ga þ ) 39,40 state and a pair of small peaks at 18.7 (P 3 ) and 18.2 eV (P 4 ) can be assigned to the metal (Ga 0 ) state (by comparing with a GaCo alloy reference sample, Supplementary Fig. 5).…”

Section: Resultsmentioning

confidence: 99%

Bulk mixed ion electron conduction in amorphous gallium oxide causes memristive behaviour

et al. 2014

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In thin films of mixed ionic electronic conductors sandwiched by two ion-blocking electrodes, the homogeneous migration of ions and their polarization will modify the electronic carrier distribution across the conductor, thereby enabling homogeneous resistive switching. Here we report non-filamentary memristive switching based on the bulk oxide ion conductivity of amorphous GaO x (xB1.1) thin films. We directly observe reversible enrichment and depletion of oxygen ions at the blocking electrodes responding to the bias polarity by using photoemission and transmission electron microscopies, thus proving that oxygen ion mobility at room temperature causes memristive behaviour. The shape of the hysteresis I-V curves is tunable by the bias history, ranging from narrow counter figure-eight loops to wide hysteresis, triangle loops as found in the mathematically derived memristor model. This dynamical behaviour can be attributed to the coupled ion drift and diffusion motion and the oxygen concentration profile acting as a state function of the memristor.

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XPS analysis of gallium oxides

Cited by 165 publications

References 10 publications

In situ study of the formation and stability of supported Pd2Ga methanol steam reforming catalysts

In situ study of the formation and stability of supported Pd2Ga methanol steam reforming catalysts

The role of the oxide shell in the chemical functionalization of plasmonic gallium nanoparticles

Bulk mixed ion electron conduction in amorphous gallium oxide causes memristive behaviour

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