34 results on '"Kateřina, Veltruská"'
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2. The Impact of Pt-Ir Nanoparticle Catalyst Structure on Oxygen Evolution and Reduction Activity
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Lucinda Blanco-Redondo, Yevheniia Lobko, Kateřina Veltruská, Jaroslava Nováková, Michal Mazur, Tomáš Hrbek, Milan Dopita, Iva Matolínová, and Vladimír Matolín
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- 2023
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3. Influence of thermal treatment on the structure and electrical conductivity of thermally expanded graphite
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Alina Madalina Darabut, Yevheniia Lobko, Yurii Yakovlev, Miquel Gamón Rodríguez, Kateřina Veltruská, Břetislav Šmíd, Peter Kúš, Jaroslava Nováková, Milan Dopita, Maryna Vorokhta, Vladimír Kopecký, Marek Procházka, Iva Matolínová, and Vladimír Matolín
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Mechanics of Materials ,General Chemical Engineering - Published
- 2022
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4. Struvite-K crystal growth inhibition by citric acid: Formation of complexes in solution and surface adsorption effects
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Alberto Viani, Lucie Zárybnická, Radek Ševčík, Petra Mácová, Jana Machotová, and Kateřina Veltruská
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Inorganic Chemistry ,Materials Chemistry ,Condensed Matter Physics - Published
- 2022
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5. Tailoring of highly porous SnO2 and SnO2-Pd thin films
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Kateřina Veltruská, Ivan Khalakhan, Peter Kúš, Valérie Potin, Nataliya Tsud, Tomáš Duchoň, Arnaud Cacucci, Mykhailo Chundak, and Vladimír Matolín
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Materials science ,business.industry ,Annealing (metallurgy) ,chemistry.chemical_element ,02 engineering and technology ,Sputter deposition ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Tin oxide ,01 natural sciences ,0104 chemical sciences ,chemistry ,X-ray photoelectron spectroscopy ,Optoelectronics ,General Materials Science ,Nanorod ,Thin film ,0210 nano-technology ,High-resolution transmission electron microscopy ,Tin ,business - Abstract
Tin oxide is a material that attracts attention due to variety of technological applications. The main parameters that influence its properties are morphology, crystalline structure and stoichiometry. Researchers try to develop nanostructured thin films with tunable parameters that would conform its technological applications. Herein, we report on the preparation and characterization of highly porous SnO2 and Pd-doped SnO2 thin films. These films were deposited in the form of nanorods with controllable geometry. Such morphology was achieved by utilizing glancing angle deposition (GLAD) with assisted magnetron sputtering. This arrangement allowed preparation of slanted pillars, zig-zag structure, vertically standing posts, spiral posts and “bush”-like structures. We calculated that slanted pillars feature the highest surface area among the listed. Then, sets of slanted pillars were deposited and studied in more details. Tin oxide films were thoroughly characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and synchrotron radiation photoelectron spectroscopy (SRPES). The influence of substrate annealing during the deposition and Pd doping on the morphology, crystalline structure and stoichiometry of the films are discussed. GLAD with assisted magnetron sputtering allowed us to deposit broad range of SnO2 nanostructures while annealing of the substrate during deposition affected the films crystallinity. Also, we found out that doping of the SnO2 films with Pd leads to alloy phase formation. These findings can be applied in variety of applications including gas sensing, catalysis, optics and electronics.
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- 2019
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6. On the growth mechanisms of polar (100) surfaces of ceria on copper (100)
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Slavomír Nemšák, Stefan Cramm, Claus M. Schneider, Daniel M. Gottlob, Tomáš Duchoň, Johanna Hackl, Vladimír Matolín, and Kateřina Veltruská
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Materials science ,Absorption spectroscopy ,Nucleation ,chemistry.chemical_element ,Substrate (chemistry) ,02 engineering and technology ,Surfaces and Interfaces ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Epitaxy ,01 natural sciences ,Copper ,0104 chemical sciences ,Surfaces, Coatings and Films ,Low-energy electron microscopy ,Photoemission electron microscopy ,Chemical state ,chemistry ,Chemical physics ,Materials Chemistry ,0210 nano-technology - Abstract
We present a study of temperature dependent growth of nano-sized ceria islands on a Cu (100) substrate. Low-energy electron microscopy, micro-electron diffraction, X-ray absorption spectroscopy, and photoemission electron microscopy are used to determine the morphology, shape, chemical state, and crystal structure of the grown islands. Utilizing real-time observation capabilities, we reveal a three-way interaction between the ceria, substrate, and local oxygen chemical potential. The interaction manifests in the reorientation of terrace boundaries on the Cu (100) substrate, characteristic of the transition between oxidized and metallic surface. The reorientation is initiated at nucleation sites of ceria islands, whose growth direction is influenced by the proximity of the terrace boundaries. The grown ceria islands were identified as fully stoichiometric CeO2 (100) surfaces with a (2 × 2) reconstruction.
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- 2018
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7. Multifunctional MoOx and MoOxNy films with 2.5 < x < 3.0 and y < 0.2 prepared using controlled reactive deep oscillation magnetron sputtering
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Stanislav Haviar, Jaroslav Vlček, M. Procházka, Jiri Houska, Radomír Čerstvý, and Kateřina Veltruská
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Reactive gas ,Materials science ,Kontrolované reaktivní magnetronové naprašování s hlubokými oscilacemi ,Tunable composition ,02 engineering and technology ,01 natural sciences ,0103 physical sciences ,Electrical conductivity ,Materials Chemistry ,Optické vlastnosti ,Redukované trioxidy molybdenu ,010302 applied physics ,Optical properties ,business.industry ,Oxynitridy molybdenu ,Metals and Alloys ,Surfaces and Interfaces ,Plasma ,Sputter deposition ,021001 nanoscience & nanotechnology ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Flow control (fluid) ,Elektrická vodivost ,Controlled reactive deep oscillation magnetron sputtering ,Molybdenum oxynitrides ,Řiditelné složení ,Optoelectronics ,Reduced molybdenum trioxides ,0210 nano-technology ,business - Abstract
Reaktivní magnetronové naprašování s hlubokými oscilacemi, pulzní kontrolou toku reaktivního plynu a vstupem reaktivního plynu, orientovaným k substrátu a umístěným v zóně hustého plazmatu před Mo terčem, bylo použito pro nízkoteplotní (< 120 °C) přípravu vrstev MoOx a MoOxNy s 2,5 < x < 3,0 a y < 0,2. Vysvětlujeme výhody použité depoziční techniky umožňující hladkou a reprodukovatelnou kontrolu složení vrstev a tím i jejich struktury a vlastností. Speciální pozornost věnujeme silnému dopadu malého snížení x ve vrstvách MoOx a malého zvýšení y ve vrstvách MoOxNy na jejich optické a elektrické vlastnosti, které přímo souvisí s proměnnou elektronovou strukturou těchto vrstev. Diskutujeme možné aplikace těchto vrstev v oblasti solárních článků, organické elektroniky a lithium-iontových baterií. Reactive deep oscillation magnetron sputtering with a pulsed reactive gas flow control and to-substrate reactive gas injection into the high-density plasma in front of the sputtered Mo target was used for a low-temperature (< 120 °C) preparation of MoOx and MoOxNy films with 2.5 < x < 3.0 and y < 0.2. We explain the advantages of this deposition technique, allowing us to control smoothly and reproducibly the film composition and thus the film structure and properties. Special attention is paid to the strong effect of slightly decreasing x in MoOx films and slightly increasing y in MoOxNy films on their optical and electrical properties which are directly related to varying electronic structure of the films. We discuss possible applications of these films in the field of solar cells, organic electronic devices and lithium-ion batteries.
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- 2021
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8. Reversible laser-assisted structural modification of the surface of As-rich nanolayers for active photonics media
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Kevin C. Prince, Vladimír Matolín, V.M. Mitsa, Roman Holomb, Tomáš Duchoň, Miklós Veres, V. Takáts, N. Tsud, Martin Vondráček, O. Kondrat, Attila Csik, Alexander Mitsa, and Kateřina Veltruská
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In situ ,Materials science ,business.industry ,Annealing (metallurgy) ,Binding energy ,General Physics and Astronomy ,Chalcogenide glass ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,Thermal treatment ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Photochemistry ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Full width at half maximum ,Optical medium ,Photonics ,0210 nano-technology ,business - Abstract
Reversible structural changes of As-rich As–Se nanolayers occurring during in situ thermal annealing and above-bandgap laser illumination were studied by synchrotron radiation photoelectron spectroscopy. It was found that the first thermal annealing of As56Se44 nanolayers led to a decrease of the concentration of As that can be connected with evaporation of more volatile As-rich fractions from the surface. This process is accompanied by structural rearrangements in the nanolayers. In situ green laser illumination of annealed samples causes an increase in the concentration of homopolar As–As bonds associated with As-Se2As s.u., while the opposite effect was detected during further thermal treatment. These processes appeared to be reversible for three sequences of annealing and illumination. The observed effect of the reversible photoinduced structural modification is discussed in detail, and possible applications as an active optical medium for photonics are proposed.
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- 2020
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9. Role of nitrogenated carbon in tuning Pt-CeOx based anode catalysts for higher performance of hydrogen-powered fuel cells
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Tomáš Duchoň, Roman Fiala, Š. Fuka, Viktor Johánek, Valérie Potin, Jaroslava Nováková, Vladimír Matolín, Iva Matolínová, Martin Dubau, and Kateřina Veltruská
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Materials science ,Scanning electron microscope ,Catalyst support ,Electron energy loss spectroscopy ,Energy-dispersive X-ray spectroscopy ,General Physics and Astronomy ,Proton exchange membrane fuel cell ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Catalysis ,Anode ,Chemical engineering ,X-ray photoelectron spectroscopy ,0210 nano-technology - Abstract
Due to promising catalytic properties of cerium oxide, such based materials have been recognized as a suitable candidate for catalysts at the anode side of fuel cells. In order to achieve the largest active surface area, a commercially available gas diffusion layer used as Pt-CeOx catalyst support has been enhanced by the application of a CNx interlayer. Herein, the surface morphology modification, into the form of individual needles, observed by Scanning Electron Microscopy and Transmission Electron Microscopy, is presented. Furthermore, spectroscopy techniques, namely X-ray Photoelectron Spectroscopy, Electron Energy Loss Spectroscopy, and Energy Dispersive X-ray Spectroscopy reveal important role of nitrogen incorporated in the CNx interlayer that enables formation of very porous surface structures. In addition, it is demonstrated that tuning of catalyst film morphology provides a viable strategy towards higher performance in the PEMFC tests, complemented by better corrosion resistance of CNx interlayers under the start-up conditions of fuel cells.
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- 2020
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10. Compositionally tuned magnetron co-sputtered PtxNi100-x alloy as a cathode catalyst for proton exchange membrane fuel cells
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Kateřina Veltruská, Milan Dopita, Daniel J. S. Sandbeck, Yurii Yakovlev, Lukáš Supik, Mykhailo Vorokhta, Iva Matolínová, Serhiy Cherevko, and Ivan Khalakhan
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Materials science ,Scanning electron microscope ,Alloy ,General Physics and Astronomy ,Proton exchange membrane fuel cell ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,Sputter deposition ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,X-ray reflectivity ,X-ray photoelectron spectroscopy ,Chemical engineering ,Cavity magnetron ,engineering ,Thin film ,0210 nano-technology - Abstract
In this study, PtxNi100-x (0 ≤ x ≤ 100) alloy catalysts were prepared using magnetron co-sputtering in order to reveal the correlation between their composition and catalytic properties as a cathode in proton exchange membrane fuel cells (PEMFCs). Fine power adjustment on magnetrons allowed to deposit alloys with precise composition and at the same time with identical thickness of 10 nm and similar morphologies. The powerful surface characterization techniques such as atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray reflectivity (XRR) and X-ray photoelectron spectroscopy (XPS) were applied to thoroughly investigate the catalytic layers. The desired composition of the films was confirmed by EDX and XRD results. All deposited layers showed similar morphologies with vertical and horizontal roughness of ~0.35 nm and ~6 nm, respectively. XRD confirmed the alloy nature of the films with one crystalline phase of the fcc PtNi. The PtxNi100-x alloys showed significant enhancement of specific power (SP) comparing to the pure Pt in PEMFC. Particularly, the Pt25Ni75 sample exhibited the highest SP of 24 kW/g(Pt). This catalyst showed a 2- and almost 10-fold improvement in SP with respect to the Pt film and commercial nanopowder Pt catalyst, respectively.
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- 2020
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11. A photoemission study of the ceria and Au-doped ceria/Cu(111) interfaces
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Iva Matolínová, M. Cabala, M. Škoda, Vladimír Matolín, Kateřina Veltruská, and Tomáš Skála
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Cerium oxide ,Materials science ,X-ray photoelectron spectroscopy ,Doping ,Analytical chemistry ,Resonance ,Ionic bonding ,Thin film ,Condensed Matter Physics ,Instrumentation ,Deposition (law) ,Spectral line ,Surfaces, Coatings and Films - Abstract
The photoelectron spectroscopy (PES) study compares electronic states in three different ceria thin film surfaces prepared on a Cu(111) single-crystal surface by vapour deposition under different conditions: at 250 °C, at room temperature and finally Au-doped ceria film obtained by simultaneous deposition of Au and CeO 2 at room temperature (RT). Electronic properties of the layers and interaction of gold with CeO 2 were investigated using synchrotron-radiation-excited PES and resonant photoemission (Ce 4d → 4f transitions). We observed partial Ce 4+ → Ce 3+ reduction induced by the decrease of deposition temperature to RT instead of 250 °C and also by doping ceria with gold, accompanied by a 4f resonance enhancement of the Ce 3+ species. In the case of the Au-doped sample the surface reduction degree is stronger and can be explained by the possible creation of a new ionic Au + state observed in the Au 4f spectra.
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- 2009
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12. Photoelectron spectroscopy and secondary ion mass spectrometry characterization of diamond-like carbon films
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Karel Mašek, Iva Matolínová, Kateřina Veltruská, and Vladimír Matolín
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Photoemission spectroscopy ,Chemistry ,Metals and Alloys ,Analytical chemistry ,Surfaces and Interfaces ,Electron spectroscopy ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Secondary ion mass spectrometry ,Condensed Matter::Materials Science ,Carbon film ,Amorphous carbon ,X-ray photoelectron spectroscopy ,Physics::Atomic and Molecular Clusters ,Materials Chemistry ,Spectroscopy ,Ultraviolet photoelectron spectroscopy - Abstract
Photoelectron spectroscopy at different photon energies was used to optimize the photoexcitation cross section for valence band study of diamond-like hydrogenated carbon films. The electronic states of diamond-like carbon (DLC) were studied by synchrotron radiation photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. The valence band spectra measured at different excitation energies show the gradual emergence of the p–π band in relation to the sample annealing and ion bombardment amorphization. The p–π band of the annealed DLC was characterized by localized pz states whilst the formation of the amorphous carbon surface was accompanied by appearance of the delocalized pz states in the gap. Secondary ion mass spectrometry and thermal desorption spectroscopy showed that sample annealing was accompanied by hydrogen content decrease.
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- 2007
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13. Photoelectron-spectroscopic and reactivity investigation of thin Pd–Sn films prepared by magnetron sputtering
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Vladimír Matolín, Iva Matolínová, Tomáš Skála, Kateřina Veltruská, Karel Mašek, and L. Sedláček
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Annealing (metallurgy) ,Analytical chemistry ,General Physics and Astronomy ,chemistry.chemical_element ,Surfaces and Interfaces ,General Chemistry ,Sputter deposition ,Condensed Matter Physics ,Electron spectroscopy ,Surfaces, Coatings and Films ,chemistry ,X-ray photoelectron spectroscopy ,Sputtering ,Cavity magnetron ,Thin film ,Tin - Abstract
We have studied Pd–Sn layers with different composition prepared by magnetron sputtering. Layers were sputtered onto Al 2 O 3 and SiO 2 substrates and studied by X-ray photoelectron spectroscopy (XPS). Spectra confirmed that after vacuum annealing residual oxygen and carbon have been removed and bimetallic bonds have been created. The shift of Pd 3d 5/2 core level to higher binding energy followed by the peak narrowing in dependence on the composition was observed, accompanied by the shift of the Pd 4d in the valence band region, induced by hybridization of Pd-d and Sn-s,p states. Experiments carried out on a gas-flow reactor indicate increasing temperature of the CO oxidation with tin ratio in the alloy.
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- 2007
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14. Structure and electronic properties of gold adsorbed on Ti(0 0 0 1)
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Vladimír Matolín, Nataliya Tsud, František Šutara, Vladimír Cháb, Kevin C. Prince, V. Dudr, Iva Matolínová, and Kateřina Veltruská
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Valence (chemistry) ,Low-energy electron diffraction ,Chemistry ,Photoemission spectroscopy ,Alloy ,Analytical chemistry ,Intermetallic ,General Physics and Astronomy ,Surfaces and Interfaces ,General Chemistry ,engineering.material ,Condensed Matter Physics ,Electron spectroscopy ,Surfaces, Coatings and Films ,Crystallography ,Electron diffraction ,X-ray photoelectron spectroscopy ,engineering - Abstract
The Au/Ti(0 0 0 1) adsorption system was studied by low energy electron diffraction (LEED) and photoemission spectroscopy with synchrotron radiation after step-wise Au evaporation onto the Ti(0 0 0 1) surface. For adsorption of Au at 300 K, no additional superstructures were observed and the (1 × 1) pattern of the clean surface simply became diffuse. Annealing of gold layers more than 1 ML thick resulted in the formation of an ordered Au–Ti surface alloy. Depending on the temperature and annealing time, three surface reconstructions were observed by LEED: (√3 × √3) R30°, (2 × 2) and a one-dimensional incommensurate (√3 × √3) rectangular pattern. The Au 4f core level and valence band photoemission spectra provided evidence of a strong chemical interaction between gold and titanium. The data indicated formation of an intermetallic interface and associated valence orbital hybridization, together with diffusion of gold into the bulk. Au core-level shifts were found to be dependent on the surface alloy stoichiometry.
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- 2006
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15. Electronic properties of Sn/Pd intermetallic compounds on Pd(1 1 0)
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Vladimír Matolín, N. Tsud, Kevin C. Prince, Vladimír Cháb, V. Dudr, Kateřina Veltruská, Tomáš Skála, František Šutara, S. Fabík, and L. Sedláček
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Low-energy electron diffraction ,Analytical chemistry ,Intermetallic ,chemistry.chemical_element ,Surfaces and Interfaces ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Adsorption ,chemistry ,Electron diffraction ,X-ray photoelectron spectroscopy ,Transition metal ,Materials Chemistry ,Tin ,Palladium - Abstract
We have studied the Sn/Pd(1 1 0) adsorption system by synchrotron radiation photoelectron spectroscopy and low-energy electron diffraction (LEED). For room temperature evaporation, two surface reconstructions were observed: c(2 × 2) and (3 × 1), corresponding to about 0.5 ML and 0.75 ML of Sn adlayer coverage. The Pd 3d and Sn 4d core levels as well as valence band spectra indicate a strong chemical interaction between Sn and Pd, and the formation of an intermetallic interface. Structural models are proposed for both of these phases based on the photoemission and CO adsorption results. We show that at coverage higher than 0.7 ML, tin is alloyed with the Pd crystal forming a subsurface layer of Pd–Sn intermetallic compound of stoichiometry which varies with tin coverage. CO adsorption occurs only at low temperature (120 K) and depends on the Sn coverage and reconstruction of the Pd(1 1 0) surface. We estimate the CO adsorption energy for the c(2 × 2)- and (3 × 1)-Sn/Pd(1 1 0) surfaces to be reduced by 40% compared to the clean palladium (1 1 0) surface.
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- 2005
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16. XPS, TDS and static SIMS studies of binary Pd/Al system properties: correlation between Pd–Al bimetallic interaction and CO adsorption
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Kateřina Veltruská, Iva Matolínová, Viktor Johánek, Vladimír Matolín, and Tomáš Skála
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Static secondary-ion mass spectrometry ,Thermal desorption spectroscopy ,Chemistry ,Analytical chemistry ,General Physics and Astronomy ,Surfaces and Interfaces ,General Chemistry ,Condensed Matter Physics ,Electron spectroscopy ,Surfaces, Coatings and Films ,Adsorption ,Chemical bond ,X-ray photoelectron spectroscopy ,Chemisorption ,Desorption - Abstract
Carbon monoxide (CO) adsorption properties of Pd/Al systems have been studied using X-ray photoelectron spectroscopy (XPS), thermal desorption spectroscopy (TDS) and static secondary ion mass spectroscopy (SSIMS) under UHV conditions. Measured XPS and TDS spectra were compared to that of clean bulk metals (Pd, Al). Pd adlayers, prepared by vacuum evaporation onto a pure polycrystalline Al surface, exhibited a strong interaction with Al atoms resulting in formation of a Pd–Al alloy of a noble metal-like electronic structure. The shifts of the Pd 3d core levels and the Pd 4d-band centroid toward higher binding energies due to bimetallic bond formation were observed. The CO TDS spectra consisted of two desorption peaks, both lying lower than the one typical for a Pd foil, indicating distinct weakening of the Pd–CO chemisorption bond. Partial CO dissociation on the Pd/Al surface during adsorption/desorption cycles, accompanied by CO 2 and H 2 O production, was observed. CO dissociation caused creation of Pd–C and Al–O chemical bonds on the Pd/Al surface resulted in weakening of the Pd–Al bimetallic bond.
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- 2005
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17. Activation of binary Zr–V non-evaporable getters: synchrotron radiation photoemission study
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S. Fabík, Tomáš Skála, Kevin C. Prince, František Šutara, Karel Mašek, Kateřina Veltruská, V. Dudr, Nataliya Tsud, Vladimír Cháb, Iva Matolínová, and Vladimír Matolín
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Zirconium ,Materials science ,Zirconium alloy ,Analytical chemistry ,General Physics and Astronomy ,Synchrotron radiation ,chemistry.chemical_element ,Surfaces and Interfaces ,General Chemistry ,Sputter deposition ,Condensed Matter Physics ,Electron spectroscopy ,Surfaces, Coatings and Films ,Secondary ion mass spectrometry ,X-ray photoelectron spectroscopy ,chemistry ,Getter - Abstract
Zr–V alloy getter films were prepared on stainless steel substrates by magnetron sputtering. The thermal activation behavior of these getters was investigated by synchrotron radiation photoelectron spectroscopy using photon excitation energies of 600, 250 and 73 eV. Depth resolved results were compared to the results of the SIMS profiling. The measurements confirmed the disappearance of the superficial oxide layer covering the air-exposed Zr–V surfaces via its progressive reduction during the thermal activation. The depth sensitive results showed that the activated getter surface is covered by a residual zirconium sub-oxide.
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- 2005
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18. XPS and SSIMS studies of Pd/SnO system: reduction and oxidation in hydrogen containing air
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Tomáš Skála, M. Moroseac, Iva Matolínová, Vladimír Matolín, and Kateřina Veltruská
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Static secondary-ion mass spectrometry ,Hydrogen ,Inorganic chemistry ,chemistry.chemical_element ,Surfaces and Interfaces ,Thermal treatment ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Chemical state ,chemistry ,X-ray photoelectron spectroscopy ,Transition metal ,Materials Chemistry ,Pyrolysis ,Palladium - Abstract
In this work the study of a redox process on Pd/SnOx system by means of X-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectrometry (SSIMS) is presented. SnOx substrates were prepared by spray pyrolysis onto Si(1 1 1). Palladium ultra-thin films were evaporated in UHV chamber and then stabilised in air at 720 K for 2 h. Results obtained after thermal treatment in 1% H2 containing air and in pure air showed the reversible change in palladium chemical state.
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- 2004
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19. Redox process of Pd–SnO2 system
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Tomáš Skála, Kateřina Veltruská, Albert Cirera, Vladimír Matolín, Iva Matolínová, and Mihail Moroseac
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Work (thermodynamics) ,Hydrogen ,Inorganic chemistry ,chemistry.chemical_element ,Surfaces and Interfaces ,Condensed Matter Physics ,Redox ,Surfaces, Coatings and Films ,Chemical state ,X-ray photoelectron spectroscopy ,chemistry ,Transition metal ,Materials Chemistry ,Microwave ,Palladium - Abstract
SnO 2 system is known to be very universal in gas sensing applications. Sensing properties can be improved by adding of a small amount of transition metals. The exact mechanism of this enhancement is not known yet. In this work we used X-ray photoelectron spectroscopy to study the chemical state changes during heating in usual and hydrogen containing atmosphere on Pd-doped SnO 2 powder prepared by microwave irradiation wet method. Reversible oxidation and reduction of Pd additive during the treatment were observed. We found out a dependence of the redox process on heating temperature and gas mixture proportion.
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- 2004
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20. CO interaction with Ni3Al alloy: XPS, LEIS and TPD study
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Iva Matolínová, Vladimír Matolín, František Šutara, and Kateřina Veltruská
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Chemistry ,Thermal desorption spectroscopy ,technology, industry, and agriculture ,Analytical chemistry ,Thermal desorption ,chemistry.chemical_element ,Surfaces and Interfaces ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Nickel ,chemistry.chemical_compound ,Low-energy ion scattering ,X-ray photoelectron spectroscopy ,Chemisorption ,Desorption ,Materials Chemistry ,Carbon monoxide - Abstract
Polycrystalline Ni 3 Al alloy surface was investigated during CO adsorption–desorption experiments by means of X-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS) and temperature programmed desorption (TPD). It was shown that CO partially dissociates giving nickel bonded carbon and carbon monoxide species and aluminum bonded oxygen. Thermal desorption was characterized by both low temperature CO desorption peaks typical for Ni–Al alloy, and high temperature one of highly reactive sites with lower CO dissociative barrier.
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- 2004
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21. Activation of binary Zr–V non-evaporable getters: a soft X-ray photoemission study of carbide formation
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Kevin C. Prince, Karel Mašek, Kateřina Veltruská, S. Fabík, František Šutara, V. Dudr, Martin Vondráček, Nataliya Tsud, Vladimír Matolín, and Vladimír Cháb
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Zirconium ,Materials science ,Alloy ,Analytical chemistry ,chemistry.chemical_element ,Surfaces and Interfaces ,engineering.material ,Sputter deposition ,Condensed Matter Physics ,Synchrotron ,Surfaces, Coatings and Films ,law.invention ,Carbide ,chemistry ,X-ray photoelectron spectroscopy ,Getter ,law ,Cavity magnetron ,Materials Chemistry ,engineering - Abstract
Zr–V alloy getter films were prepared on stainless steel substrates by magnetron sputtering. The thermal activation behavior of these getters was investigated by photoelectron spectroscopy using two photon excitation energies of 600 eV (synchrotron light) and 1253.6 eV (Mg Kα laboratory source). During the activation by heating from 120 to 320 °C, the adsorbed carbon was transformed to metal carbides and diffused to the subsurface region.
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- 2004
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22. Study of Pd–Al interactions on Pd/AlO /Al systems during CO adsorption and desorption cycles: XPS and LEIS
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Iva Matolínová, L. Sedláček, Vladimír Matolín, and Kateřina Veltruská
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Chemistry ,Analytical chemistry ,Surfaces and Interfaces ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Adsorption ,Transition metal ,Low-energy ion scattering ,X-ray photoelectron spectroscopy ,Desorption ,Materials Chemistry ,Physical chemistry ,Thin film ,Bimetallic strip ,Stoichiometry - Abstract
The metal–substrate and metal–metal interactions (MSI, MMI) represent important effects which can determine properties of supported catalysts. We investigated Pd–Al bimetallic interactions of Pd thin films vapor deposited onto non-stoichiometric aluminum oxide surfaces by means of X-ray photoelectron spectroscopy (XPS) and low energy ion scattering (LEIS). The formation of a Pd–Al surface alloy phase exhibiting noble metal-like electronic structure was observed. Changes of the Pd 3d and Pd 4d photoemission features and a modification of surface stoichiometry as a function of degree of aluminum surface oxidation as well as during CO adsorption–desorption cycles are discussed.
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- 2004
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23. XPS and SIMS study of the ageing mechanism of Zr–V non-evaporable getter films
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Iva Matolínová, Vladimír Matolín, Karel Mašek, Tomáš Skála, and Kateřina Veltruská
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chemistry.chemical_classification ,Zirconium ,Materials science ,Inorganic chemistry ,technology, industry, and agriculture ,Analytical chemistry ,General Physics and Astronomy ,chemistry.chemical_element ,Vanadium ,Non-Evaporable Getter ,Surfaces and Interfaces ,General Chemistry ,Condensed Matter Physics ,Electron spectroscopy ,Surfaces, Coatings and Films ,chemistry ,X-ray photoelectron spectroscopy ,Sputtering ,Getter ,Compounds of carbon - Abstract
Thin films of the Zr–V getter alloy were prepared on stainless steel substrates using magnetron sputtering. The getter surface chemical composition was investigated by X-ray photoelectron spectroscopy (XPS) for four air exposure/activation cycles. The experimental results show the decrease of the activation capacity after several oxidation/activation cycles. The adsorbed carbon is transformed simultaneously to zirconium and vanadium carbides, which are inactive for both oxidation and reduction processes. Higher affinity of V to carbon atoms was confirmed by secondary ion mass spectroscopy (SIMS) study of CO adsorption.
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- 2004
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24. Influence of Pd–Co bimetallic interaction on CO adsorption properties of Pd Co1 alloys: XPS, TPD and static SIMS studies
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S. Fabík, Kateřina Veltruská, Iva Matolínová, L. Sedláček, Karel Mašek, Tomáš Skála, and Vladimír Matolín
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Secondary ion mass spectrometry ,Static secondary-ion mass spectrometry ,Adsorption ,X-ray photoelectron spectroscopy ,Thermal desorption spectroscopy ,Chemistry ,Desorption ,Analytical chemistry ,Condensed Matter Physics ,Instrumentation ,Bimetallic strip ,Stoichiometry ,Surfaces, Coatings and Films - Abstract
Pd x Co 1− x thin layers with different stoichiometry, prepared by DC magnetron sputtering on α -Al 2 O 3 (sapphire) substrates, were investigated by X-ray photoelectron spectroscopy (XPS), static secondary ion mass spectroscopy (SSIMS) and temperature programmed desorption (TPD). The shifts of Pd 3d, XPS Auger Pd-MNN and the valence-band centre toward higher binding energies due to the formation of a bimetallic bond were observed. CO adsorption properties of the alloys were strongly dependent on alloy stoichiometry. The common property was the lowering of the CO desorption temperature with respect to the desorption from pure metals. The SSIMS study showed that CO partially dissociated on Co–Pd alloy surfaces.
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- 2003
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25. Study of Pd–In interaction during Pd deposition on pyrolytically prepared In2O3
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Tomáš Skála, M. Moroseac, Vladimír Matolín, Kateřina Veltruská, Ghennadii S. Korotchenkov, and Iva Matolínová
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Hydrogen ,Chemistry ,Alloy ,Analytical chemistry ,General Physics and Astronomy ,chemistry.chemical_element ,Surfaces and Interfaces ,General Chemistry ,engineering.material ,Condensed Matter Physics ,Evaporation (deposition) ,Electron spectroscopy ,Surfaces, Coatings and Films ,X-ray photoelectron spectroscopy ,Transition metal ,engineering ,Spectroscopy ,Stoichiometry - Abstract
In2O3 belongs to the group of metal oxides used successfully for gas detection, with sensitivity for CO and H2 comparable with that of SnO2 and excellent for O3. The sensing properties of these sensors could be greatly improved by adding small amount of transition metals such as Pd, Pt, Au, etc. In this work, we used X-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS) to study the growth of Pd particles on In2O3 substrates prepared by spray pyrolysis method. Surface stoichiometry and its changes during Ar+ ion bombardment used for surface cleaning were checked with XPS and ISS. The Pd growth was studied stepwise in situ using the micro-electron beam evaporation source (MEBES) with controlled evaporation rate. XPS and ISS measurements were carried out with special attention to metal–substrate interaction (MSI), which was observed for Pd–In and resulted in the formation of Pd–In alloy with noble metal-like electronic structure. Further, we studied reduction of these samples after oxidation in air. A lower reduction temperature than with bulk PdO was observed. The results are compared with the experiment of Pd deposition performed on a pure In foil.
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- 2003
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26. Pd/Al2O3 interaction: the influence of ionicity character of different alumina surfaces
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Kateřina Veltruská, Vladimír Matolín, and Nataliya Tsud
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Chemistry ,Alloy ,Analytical chemistry ,Oxide ,Surfaces and Interfaces ,engineering.material ,Condensed Matter Physics ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,X-ray photoelectron spectroscopy ,Transition metal ,Chemisorption ,Materials Chemistry ,engineering ,Crystallite ,Spectroscopy ,Stoichiometry - Abstract
The nature of the bonding between Pd atoms and alumina surfaces was investigated by analysing the oxygen photoelectron induced Auger KLL transitions. The activity of oxide surfaces was analysed in terms of the surface ability for electronic exchange with the metal adlayer. The comparative study of the metal–substrate interaction on different types of Pd supports (α-Al 2 O 3 , γ-Al 2 O 3 and thin alumina layers on polycrystalline Al foil) is presented in this paper. The surface atomic composition of all substrates after cleaned bombardment procedure was determined by ion scattering spectroscopy. The ionicity of the oxygen sites was observed to be a function of the oxide thickness and stoichiometry. It was found that the reduction of the oxide surfaces caused the increase of the I (KL 23 L 23 )/ I (KL 1 L 23 ) intensity ratio, i.e. the increase of the ionicity. The opposite tendency for this ratio was observed during Pd deposition on thin alumina oxide. The possible explanations of such behaviour (charge transfer to Pd particle and/or creation of the Al–Pd alloy) are discussed.
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- 2002
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27. XPS, ISS and TDS study of bimetallic interaction between Pd and Al: CO interaction with supported Pd/alumina catalysts
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Viktor Johánek, Kateřina Veltruská, Vladimír Matolín, Nataliya Tsud, and I. Stará
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Chemistry ,Thermal desorption spectroscopy ,Inorganic chemistry ,Intermetallic ,Surfaces and Interfaces ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Catalysis ,Transition metal ,X-ray photoelectron spectroscopy ,Chemisorption ,Materials Chemistry ,Physical chemistry ,Spectroscopy ,Bimetallic strip - Abstract
The metal–substrate interaction (MSI) represents an important effect determining the properties of supported heterogeneous catalysts. We investigated the MSI effects by X-ray photoelectron spectroscopy, ion scattering spectroscopy and thermal desorption spectroscopy in the case of Pd films vapor deposited on non-stoichiometric aluminum oxide substrates. We compared the obtained results with these of bulk Pd and Pd/Al reference alloy. The observed MSI is explained by the formation of an intermetallic interface exhibiting a strong bimetallic transition-metal (Pd)/s, p-metal (Al) interaction. The fundamental studies of Pd/Al bimetallic alloys are of an importance due to the role that they play in the modification of chemisorption and catalytic properties of real Pd/Al-oxide systems as well as in the realization of novel Pd-alloy catalysts. The reported behavior represents a new way in explanation of former unexpected CO adsorption properties of alumina supported Pd particles.
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- 2002
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28. Optical characterization of diamond-like carbon films using multi-sample modification of variable angle spectroscopic ellipsometry
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Ivan Ohlídal, Lenka Zajíčková, Daniel Franta, Kateřina Veltruská, and Jan Janča
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010302 applied physics ,Materials science ,Silicon ,Diamond-like carbon ,Band gap ,Mechanical Engineering ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Electronic, Optical and Magnetic Materials ,Characterization (materials science) ,chemistry ,Plasma-enhanced chemical vapor deposition ,0103 physical sciences ,Dispersion (optics) ,Materials Chemistry ,Energy level ,Electrical and Electronic Engineering ,0210 nano-technology ,Single crystal - Abstract
In the first part, thicknesses and spectral dependences of the optical constants of the diamond like carbon (DLC) films were determined without any parameterization in the range 240–830 nm by multi-sample modification of variable angle spectroscopic ellipsometry (VASE). DLC films were prepared by plasma enhanced chemical vapor deposition (PECVD) onto silicon single crystal substrates. It was shown that the influence of some defects of the DLC films on the optical constants is suppressed by applying the method of multi-sample modification of VASE. In the second part, the spectral dependences of the determined optical constants were interpreted using a recently developed model of dispersion based on the modified Lorentz oscillator. Two modified Lorentz oscillators corresponding to both π→π* and σ→σ* interband transitions were taken into account. Within this model of dispersion of the optical constants, the concept of the band gap and the existence of localized energy states within the band gap were taken into account as well.
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- 2002
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29. Pd Interaction with Reduced Thin-Film Alumina: XPS and ISS Study
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Vladimír Matolín, Kateřina Veltruská, and Nataliya Tsud
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Alloy ,Analytical chemistry ,Oxide ,Intermetallic ,Substrate (electronics) ,engineering.material ,Catalysis ,Overlayer ,chemistry.chemical_compound ,chemistry ,X-ray photoelectron spectroscopy ,Sputtering ,engineering ,Physical and Theoretical Chemistry ,Thin film - Abstract
X-ray photoelectron spectroscopy and ion-scattering spectroscopy (ISS) were used to investigate the interaction of palladium with reduced thin-film alumina. The substrate was prepared by Ar+ ion bombardment thinning of the natural oxide layer on polycrystalline aluminum foil. It was found that the constitution of a surface equilibrium is determined by the energy of sputtering ions. Therefore, after the sputtering, the aluminum oxide surface is covered by more or less Al0-rich overlayer. During the first stage of the Pd deposition, the IAl/IO ratio decreases because of Pd atom deposition onto the Al sites, keeping the anionic oxygen sites unaffected. With increasing Pd, the PdAl intermetallic compound is formed. The alloy forms three-dimensional clusters and a bare alumina surface appears, giving the ISS intensity ratio IAl/IO characteristic for γ-Al2O3. At a high amount of deposited Pd, the Pd bulk-like phase is formed, gradually burying the PdAl alloy clusters. To interpret catalytic behavior of Pd/Al2O3 systems, the presence of the PdAl alloy caused by strong metal–substrate interaction should be considered.
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- 2001
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30. XPS, ISS and TPD study of Pd–Sn interactions on Pd–SnO systems
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Vladimír Matolín, N. Tsud, Viktor Johánek, I. Stará, and Kateřina Veltruská
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Chemistry ,Doping ,Metals and Alloys ,Analytical chemistry ,Thermal desorption ,Surfaces and Interfaces ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Metal ,Transition metal ,X-ray photoelectron spectroscopy ,visual_art ,Desorption ,Materials Chemistry ,visual_art.visual_art_medium ,Spectroscopy ,Bimetallic strip - Abstract
The sensitivity and selectivity of SnO2 based gas sensors could be improved by doping of small amount of transition metals. In this work we used X-ray photoelectron spectroscopy, ion scattering spectroscopy, and thermal desorption techniques to investigate Pd evaporated on SnOx thin layer substrate, prepared by spray pyrolysis. The evolution of Pd/SnOx layer morphology with increasing amount of Pd deposits was studied using the XPS inelastic background shape analysis. The observations are compared to the results obtained from natural SnO2 crystal and metallic Sn substrates. A strong Pd–Sn bimetallic interaction was observed, resulting in the formation of PdSn alloy of noble metal-like electronic structure. This feature also corresponds to the presence of two CO desorption states with low energy peaks at approximately 390 K. The relation of our results with the operation mechanism of gas detection are discussed.
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- 2001
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31. XPS and ellipsometric study of DLC/silicon interface
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Daniel Franta, Lenka Zajíčková, Nataliya Tsud, and Kateřina Veltruská
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010302 applied physics ,Amorphous silicon ,Materials science ,Silicon ,Silicon dioxide ,Nanocrystalline silicon ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,Substrate (electronics) ,Chemical vapor deposition ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,chemistry ,Sputtering ,0103 physical sciences ,0210 nano-technology ,Instrumentation ,Layer (electronics) - Abstract
Diamond-like carbon (DLC) films were prepared by plasma-enhanced chemical vapour deposition from the mixture of methane and argon on silicon substrates. Films were characterised by multi-sample modification of variable angle spectroscopic ellipsometry. Ellipsometry showed that there is a transition interlayer between the DLC film and the silicon substrate that cannot be attributed to a thin silicon dioxide layer but rather to amorphous silicon and/or a modified oxide layer. TRIM calculations revealed that argon or carbon ions could not produce a significant layer of amorphous silicon because the depth of target atom displacements is below the thickness of a native oxide layer. The chemical composition of a DLC film profile including a DLC/silicon interface was studied by X-ray photoelectron spectroscopy (XPS) coupled with argon sputtering of the 34 nm thick DLC film. The DLC/silicon interface composed of less than 6% of oxygen and a gradually decreasing and increasing carbon and silicon percentage, respectively.
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- 2001
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32. XPS and TPD study of CO interaction with Pd–Al and Pd–Al2O3 systems
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Vladimír Matolín, Nataliya Tsud, I. Stará, Viktor Johánek, and Kateřina Veltruská
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Radiation ,Chemistry ,Thermal desorption spectroscopy ,Binding energy ,Analytical chemistry ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Dissociation (chemistry) ,Electronic, Optical and Magnetic Materials ,Auger ,Catalysis ,Adsorption ,X-ray photoelectron spectroscopy ,Desorption ,Physical chemistry ,Physical and Theoretical Chemistry ,Spectroscopy - Abstract
The metal–substrate and metal–metal interactions represent important effects determining the properties of supported catalysts. We investigate the CO adsorption mechanism on Pd particles supported on Al 2 O 3 and Al by X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). CO–metal interaction is investigated by TP desorption of CO and by XPS of C 1s intensities that exhibit three CO-related components. The dissociation activity is monitored as a rise of C 1s signal at 285 eV while the molecularly adsorbed CO exhibits the intensity at 287 eV. Pd–substrate interaction is determined from the Pd core- and valence-level binding energy variations. The influence of the Pd–Al alloying process on the Pd MNN Auger transition is shown. The studies show that the metal–substrate and metal–metal interactions play an important role in CO–Pd adsorption process.
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- 2001
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33. CO adsorption on palladium model catalysts: XPS Pd–Al2O3 interaction study
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Viktor Johánek, Nataliya Tsud, Vladimír Matolín, I. Stará, and Kateřina Veltruská
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Binding energy ,Inorganic chemistry ,chemistry.chemical_element ,Surfaces and Interfaces ,Condensed Matter Physics ,Dissociation (chemistry) ,Surfaces, Coatings and Films ,Catalysis ,Electron transfer ,Adsorption ,chemistry ,Transition metal ,X-ray photoelectron spectroscopy ,Materials Chemistry ,Palladium - Abstract
The metal–substrate interaction (MSI) represents one of the most important effects determining the properties of supported catalysts. It is expected to be one of the driving forces of the size effect in catalysis. In this work we investigated the MSI by X-ray photoelectron spectroscopy (XPS) in the case of small Pd particles deposited on γ- and α-alumina substrates. We compared the binding energy and initial state variations as a function of Pd coverage. The initial state has been found to be shifted to higher positive values for a more strongly interacting substrate (γ-Al2O3), whilst for the inert-like sapphire substrate the MSI was less important. The initial state shift value was associated with the electron transfer in the substrate clusters direction. It was shown that the substrate–metal charge transfer could be responsible for partial CO dissociation on γ-Al2O3 supported Pd particles.
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- 2000
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34. CO adsorption on Al2O3-supported Pd clusters: XPS study
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I. Stará, Nataliya Tsud, Vladimír Matolín, Viktor Johánek, and Kateřina Veltruská
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chemistry.chemical_classification ,Inorganic chemistry ,technology, industry, and agriculture ,Oxide ,General Physics and Astronomy ,Surfaces and Interfaces ,General Chemistry ,Condensed Matter Physics ,Dissociation (chemistry) ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,Adsorption ,chemistry ,Transition metal ,X-ray photoelectron spectroscopy ,Physical chemistry ,Particle size ,Inorganic compound ,Carbon monoxide - Abstract
The adsorption of carbon monoxide on small alumina-supported Pd particles have been studied by X-ray photoelectron spectroscopy (XPS). The results showed clearly different surface properties of bulk metal and supported clusters. The effect of partial CO dissociation was observed on Pd deposited on γ-alumina and on clean aluminium, but not on small Pd particles prepared on thin amorphous oxide film on Al substrate. CO–Pd interaction was determined from C 1s photoelectron spectra that exhibited two CO-related components. The dissociation activity was monitored as a rise of C 1s signal at 285 eV, while the molecularly adsorbed CO exhibited the intensity at 287 eV. The study showed that beside the particle size, the metal–substrate interaction (MSI) plays an important role in CO–Pd adsorption process.
- Published
- 2000
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