The Study of Ultrathin Tantalum Oxide Films before and after Annealing   with X-Ray Photoelectron Spectroscopy

Muto, Akiko; Yano, Fumiko; Sugawara, Yasuhiro; Iijima, S.

doi:10.1143/jjap.33.2699

Cited by 36 publications

(19 citation statements)

References 6 publications

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“…The XP spectrum for O1s 1/2 contains a component for the XP transition O Ta-O 1s(Ta 2 O 5 ) at E b = 531.3 eV, which is in accord with the spectral data given in previous work [9][10][11]. All the O1s 1/2 XP spectra for samples studied before and after catalysis show a component at E b = 530.2 eV, corresponding to surface OH groups [14], whose presence facilitates the migration of metal species (Pt/Pd) over the support surface.…”

supporting

confidence: 90%

“…The proposed assignment is based on the results of a combined analysis of the XP spectra of some tantalum oxides (Ta 2 O, Ta 2 O 5 , TaO x ) given by Atanassova [10] and Muto [11] and the XP spectra of samples studied in the present work. The values of E b obtained from XPS data indicate the existence of oxygen-deficient oxides derived from Ta 2 O 5-x on the catalyst surface layer (samples prior to catalysis).…”

mentioning

confidence: 99%

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Oxidation of hydrogen on previously reduced Ta2O5 with Pt and Pd additives

et al. 2008

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X-ray photoelectron spectroscopy (XPS) was used to establish that the surface layer of catalysts obtained by the reduction of Ta 2 O 5 with added Pt and Pd by hydrogen contains nonstoichiometric oxides TaO x , which enhance the activity of the catalyst. A study of the hydrogen oxidation kinetics showed that the kinetic relationships are described satisfactorily by the Eley-Riedel mechanism, according to which the reaction occurs by an interaction of hydrogen from the gas phase with adsorbed oxygen.Ta 2 O 5 , which is stable in various chemical media, is a k-dielectric material with a broad Fermi level. Ta 2 O 5 modified with a platinum metal is found in the sensitive layer of many sensors, permitting us to determine the concentration of H 2 , D 2 , H 2 S, C 2 H 5 SH, and NH 3 in atmospheric gas mixtures [1, 2] and used as a component of cathodic materials of hydrogen fuel cells [3].A composite catalyst derived from tantalum pentoxide reduced by H 2 in the presence of Pt or Pd holds promise. Structural defects and TaO x phases are formed within the surface layer and bulk of this catalyst [4,5], which provide for a high rate of diffusion of adsorbed oxygen in the surface layer and an increased rate of catalytic redox reactions on the surface [4,6,7].In previous work [8], we showed that catalysts obtained upon the hydrogen reduction of Ta 2 O 5 with added Pt and Pd display high catalytic activity in the oxidation of H 2 . The results of an X-ray phase analysis and electron microscopy study indicated the formation of oxygen-deficient tantalum oxides in the reduction of Ta 2 O 5 , which lead to high catalyst activity. The catalytic reaction is accompanied by amorphization of the oxide phase, leading to disordering of its regular structure, i.e., formation of an active surface with TaO x clusters, extended defects, and dislocations.In the present work, we studied the characteristics of the surface layer of these catalysts and the kinetics of the oxidation of hydrogen on the given samples. The catalysts were prepared by the impregnation of samples of Ta 2 O 5 , obtained from Alfa-Aesar with 99.995 mass % purity, with solutions of H 2 PtCl 6 and PdCl 2 according to moisture capacity taking 0.1 and 0.5 mass % deposited platinum metal in the sample. The samples obtained were dried for 1 h at 393 K and reduced with 10 vol.% H 2 in argon at 673 K. The specific surface of the samples (S sp ) was determined by a method involving the low-temperature adsorption of argon. The values for S sp for the samples containing 0.1 mass % Pt or Pd were 3.6 and 3.4 m 2 /g, while these values for samples containing 0.5 mass % Pt or Pd were 5.8 and 5.6 m 2 /g, respectively.The charge state of the elements and composition of the surface layer of the 0.5 mass % Pt/Ta 2 O 5 and 0.5 mass % Pd/Ta 2 O 5 catalysts was studied by X-ray photoelectron spectroscopy (XPS) using Kratos XPS 800 and Axis-165 X-ray photoelectron spectrometers using AlK a = 1486.6 eV and Au4f 1/2 = 83.8 eV as standards. The spectra were analyzed by integration using the Loren...

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confidence: 90%

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confidence: 99%

Oxidation of hydrogen on previously reduced Ta2O5 with Pt and Pd additives

et al. 2008

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“…The small peak at 532.1 eV was attributed to surface contamination [12]. The lower binding energy at 530.7 eV was attributed to the bonding of Ta-O [13]. Compared to deposition conditions of the film, the Ta 4f and O 1s states of the films fabricated by other conditions of PH 2 /(PAr + PO 2 + PH 2 ) were similar to the above results.…”

Section: Characterizationsupporting

confidence: 79%

Electrochromic switchable mirror foil with tantalum oxide thin film prepared by reactive DC magnetron sputtering in hydrogen-containing gas

Tajima

Hotta

Yamada

et al. 2011

Surface and Coatings Technology

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“…The lower binding energy component at 530.8 eV is from Ta-O binding. 10,11 Using only the O contents from the Ta-O binding, the O/Ta ratio is calculated to be 2.45, which is about the same O/Ta ratio for a stoichiometric Ta 2 O 5 film. The high-resolution XPS spectrum for the Ta 4 f peak is shown in Fig.…”

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confidence: 91%

X-ray photoelectron spectroscopy study of Al/Ta2O5 and Ta2O5/Al buried interfaces

Chen

Yang

Nielsen

et al. 1997

Applied Physics Letters

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Buried interfaces of thin Al/Ta2O5 and Ta2O5/Al films were studied using the x-ray photoelectron spectroscopy technique. The peak decomposition technique was employed to identify the composition and chemical states at the interface region. It was observed that there is an “intermixing layer” at the Al/Ta2O5 interface, where Ta2O5 has been reduced to lower binding energy states due to the reaction of Al with Ta2O5 during deposition. On the other hand, the Ta2O5/Al interface is relatively stable, consisting of Ta2O5 and Al2O3 interfacial layers. Based on a uniform multilayer structure model, the thickness of the interfacial layers was estimated by using the relative photoelectron intensities.

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The Study of Ultrathin Tantalum Oxide Films before and after Annealing with X-Ray Photoelectron Spectroscopy

Cited by 36 publications

References 6 publications

Oxidation of hydrogen on previously reduced Ta2O5 with Pt and Pd additives

Oxidation of hydrogen on previously reduced Ta2O5 with Pt and Pd additives

Electrochromic switchable mirror foil with tantalum oxide thin film prepared by reactive DC magnetron sputtering in hydrogen-containing gas

X-ray photoelectron spectroscopy study of Al/Ta2O5 and Ta2O5/Al buried interfaces

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