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Showing papers on "Chemical state published in 2004"


Journal ArticleDOI
TL;DR: In this article, the microstructural and chemical properties of TiO2, obtained by a sol-gel procedure, were investigated by using X-ray diffraction (XRD) and electron spectroscopy for chemical analysis.

464 citations


Journal ArticleDOI
TL;DR: The interpretation of the surface chemical states of amorphous boron carbide films as revealed by X-ray photoelectron spectroscopy (XPS) was investigated in this paper.

157 citations


Journal ArticleDOI
TL;DR: In this paper, the influence of different buffer layers is attributed to a combination of chemical and morphological changes induced in the catalyst due to catalyst-substrate interaction, which can be found in carbon nanotubes grown by chemical vapor deposition.
Abstract: Carbon nanotubes grown by chemical vapor deposition have revealed differences in growth rate and characteristics depending on the underlying buffer layer. As determined by in situ photoelectron spectroscopy, iron catalyst deposited onto Si substrates covered with Al2O3, TiN, or TiO2 underwent different chemical changes during annealing and exposure to C2H2 as function of buffer layer. Formation of thin tubes (2−4 walls) and fast growth rate were associated with conversion of Fe onto FeO particles on Al2O3 layers. On the other hand, thick multiwalled tubes (more than 20 walls) grew from pure Fe particles formed onto TiN and TiO2 layers. The influence of different buffer layers is attributed to a combination of chemical and morphological changes induced in the catalyst due to catalyst-substrate interaction.

156 citations


Journal ArticleDOI
TL;DR: In this paper, the authors studied the morphology and chemical state of the Co-Mo catalysts during their preparation using transmission electron microscopy and X-ray photoelectron spectroscopy.

140 citations


Journal ArticleDOI
TL;DR: In this article, various solgel procedures and post-treatments were applied to modify the distribution of Cu on the surface of Cu/TiO 2 catalysts in order to increase the production of methanol in the photoreduction of CO 2.

139 citations


Journal ArticleDOI
TL;DR: In this paper, a series of manganese-doped copper-based mixed metal oxides under identical conditions by calcination of layered double hydroxides (LDHs) at 773 K for 5h was reported.

130 citations


Journal ArticleDOI
TL;DR: In this paper, the authors revisited the XPS studies of sputter-cleaned β-rhombohedral boron (βr-B), the oxidized surface of β-B, B6O pellet, and polished B2O3, to illustrate the impact and resolution of this scientific issue.
Abstract: Although an increasing volume of x-ray photoemission spectroscopic (XPS) data has been accumulated on boron and boron-rich compounds because of their unusual properties, including a unique three-center, two-electron bonding configuration, their common nonmetallic nature has been overlooked. Typically, the measured energy-state data are not clarified by surface Fermi level positions of these nonmetallic samples, which compromises the scientific contents of the data. In the present study, we revisited the XPS studies of sputter-cleaned β-rhombohedral boron (βr-B), the oxidized surface of βr-B, B6O pellet, and polished B2O3, to illustrate the impact and resolution of this scientific issue. These samples were chosen because βr-B is the most thermodynamically stable polytype of pure boron, B2O3 is its fully oxidized form, and B6O is the best known superhard family member of boron-rich compounds. From our XPS measurements, including those from a sputter-cleaned gold as a metal reference, we deduced that our βr-B had a surface Fermi level located at 0.7±0.1 eV from its valence-band maximum (VBM) (referred as EFL) and a binding energy for its B 1s core level at 187.2 eV from VBM (Eb,VBM). The latter attribute, unlike typical XPS binding energy data that are referenced to a sample-dependent Fermi level (Eb,FL), is immune from any uncertainties and variations arising from sample doping and surface charging. For bulk B2O3, we found an Eb,VBM for its B 1s core level at 190.5 eV and an Eb,FL at 193.6 eV. For our βr-B subjected to a surface oxidation treatment, an overlayer structure of ∼1.2 nm B2O3/∼2 nm B2O/B was found. By comparing the data from this sample and those from βr-B and bulk B2O3, we infer that the oxide overlayer carried some negative fixed charge and this induced on the semiconducting βr-B sample an upward surface band bending of ∼0.6 eV. As for our B6O sample, we found an EFL of ∼1.7 eV and two different chemical states having Eb,VBM of 185.4 and 187.2 eV, with the former belonging to boron with no oxygen neighbor and the latter to boron with an oxygen neighbor. The methodology in this work is universally applicable to all nonmetallic samples.

122 citations


Journal ArticleDOI
01 Jan 2004-Carbon
TL;DR: In this paper, carbon nanotubes (CNTs) have been grown by chemical vapor deposition in a vacuum chamber equipped with in situ photoelectron spectroscopy technique that allows for precise characterization of the chemical state of substrate and catalyst before the CNTs growth.

110 citations


Journal ArticleDOI
TL;DR: In this paper, the chemical states of the HfO2/Si(100) interface were investigated using transmission electron microscopy and high-resolution x-ray photoelectron spectroscopy.
Abstract: The chemical states of the HfO2/Si (100) interface were investigated using transmission electron microscopy and high-resolution x-ray photoelectron spectroscopy. The depth distributions of Hf chemical states showed that the Hf 4f binding energy remains unchanged with the depth and there is no signature of more than one Hf-O state. These facts strongly suggest that the chemical state of the interfacial layer is not Hf-silicate, as previously believed. Instead, the compositions are mainly Si2O3 and SiO2, judging from the deconvolution of Si 2p spectra. The dielectric constant κ=4.8 of the interfacial layer is also consistent with the above conclusions.

109 citations


Journal ArticleDOI
TL;DR: In this article, X-ray absorption spectroscopy was applied to investigate NaAlH4 doped with 5 mol % TiCl3 by ball milling and showed that the Ti atoms are associated only with Ti as next neighbors in the ball-milled state as well as during subsequent desorption and absorption of hydrogen.
Abstract: X-ray absorption spectroscopy is applied to investigate NaAlH4 doped with 5 mol % TiCl3 by ball milling. XANES analysis indicates that after the ball milling Ti species are reduced from Ti (+3) to Ti (0). Release or absorption of hydrogen does not affect the chemical state obtained after ball milling. EXAFS analysis shows that the Ti atoms are associated only with Ti as next neighbors in the ball-milled state as well as during subsequent desorption and absorption of hydrogen. Furthermore, an increase of the particle size and an ordering of the local structure is seen to evolve with the desorption and the absorption of hydrogen.

105 citations


Journal ArticleDOI
TL;DR: Al2O3 incorporated HfO2 films grown by atomic layer deposition were investigated using various measurement tools as discussed by the authors, which showed that the accumulation capacitance of the Al2O 3 incorporated into Hf O 2 film increases as the postannealing temperature increases because of changes in interfacial and upper layer thickness and in inter-layer stoichiometry.
Abstract: Al2O3 incorporated HfO2 films grown by atomic layer deposition were investigated using various measurement tools. The accumulation capacitance of the Al2O3 incorporated into HfO2 film increases as the postannealing temperature increases because of changes in interfacial and upper layer thickness and in interfacial stoichiometry. The core-level energy state of a 15 A thick film shows a shift to higher binding energy, as the result of silicate formation and Al2O3 incorporation. The incorporation of Al2O3 into the HfO2 film has no effect on silicate formation at the interface between the film and Si, while the ionic bonding characteristics and hybridization effects are enhanced compared to a pure HfO2 film. Any dissociated Al2O3 on the film surface is completely removed by a vacuum annealing treatment over 850 °C, while HfO2 contributes to Hf silicide formation on the surface of the film.

Journal ArticleDOI
TL;DR: In this article, an infrared spectroscopy and X-ray diffraction study of hafnium oxide gate dielectric films deposited from Hf tetra- tertbutoxide, Hf(OC(CH3)3)4 is presented.
Abstract: We present an infrared spectroscopy and X-ray diffraction study of hafnium oxide gate dielectric films deposited from hafnium tetra– tertbutoxide, Hf(OC(CH3)3)4. We characterize the crystal phase as a function of thickness and detect the chemical state of impurities in this high-permittivity (high-) material. The HfO2 films are composed of monoclinic crystallites in an amorphous matrix. The crystalline fraction increases with increasing film thickness. Infrared spectroscopy is used to obtain information about impurities, which may help to uncover the nature of electrical defects. We detect and quantify for instance the presence of incorporated hydroxyl groups or water that may be responsible for the deviation from ideal HfO2 stoichiometry. The concentration of residual C–H bonds is low. However, carbon is incorporated in an oxidized form, possibly as carbonate. © 2003 Elsevier B.V. All rights reserved.

Journal ArticleDOI
TL;DR: In this article, the behavior of Pd-based systems supported on alumina and ceria-zirconia and the complex Ceria-Zirconium-supported catalyst was investigated during light-off tests using a stoichiometric C3H6 + CO + NO + O2 mixture.

Journal ArticleDOI
TL;DR: The chemical state of oxygen on the surfaces of mixed electronic-ionic conducting La 0.6 Sr 0.4 Co 1− y Fe y O 3 ceramics was characterized by X-ray photoelectron spectroscopy (XPS).

Journal ArticleDOI
TL;DR: In this article, a Mg Auger parameter defined as the difference between the kinetic energy (KE) of the Mg K L L L Auger peak and the KE of Mg 1s peak was used to distinguish magnesium nitride from magnesium oxide.
Abstract: Metallic, oxide and hydroxide environments of magnesium are clearly identified by X-ray photoelectron spectroscopy from chemical shift of Mg 1s and Mg 2p photopeaks. Unfortunately, Mg3N2 cannot be distinguished from MgO through these two peaks. In this work, we give evidence that it is possible to unambiguously identify magnesium nitride from magnesium oxide thanks to a Mg Auger parameter defined as the difference between the kinetic energy (KE) of the Mg K L L Auger peak and the KE of the Mg 1s peak. The value obtained for Mg3N2 (1000.0 eV) is quite different from the one observed for MgO (998.6 eV). Values obtained for metallic Mg and for Mg(OH)2 are, respectively, equal to 1004.2 and 997.5 eV. This parameter is then used in order to characterize the modification of the Mg chemical environment in the Al-5083 aluminum alloy (containing 4.5 at.% Mg) nitrided by a distributed electron cyclotron resonance nitrogen plasma.

Journal ArticleDOI
TL;DR: In this article, Synchrotron-based high-resolution x-ray photoemission spectroscopy has been used to characterize the sulfur chemical states at the SAM/gold interface.
Abstract: L-cysteine self-assembled monolayers (SAMs) have been deposited on gold from the liquid and vapour phase. Synchrotron based high resolution x-ray photoemission spectroscopy has been used to characterize the sulfur chemical states at the SAM/gold interface. Results obtained from pristine and x-ray irradiated samples, prepared with both as-received and purified L-cysteine, are reported. Pristine samples prepared with purified cysteine are characterized by an intense, largely dominant S 2p state at a binding energy around 162 eV (2p3/2 level) assigned to thiolates. A second doublet around 161 eV develops during irradiation. By comparison with the literature, this doublet is assigned to atomic sulfur present either as impurity or generated by S–C bond scission. Comparative measurements performed, under similar experimental conditions, on pristine 3-mercaptopropionic acid [HS(CH2)2COOH] layers deposited from the liquid phase are also presented and discussed.

Journal ArticleDOI
TL;DR: In this paper, the absolute energies of the S-Kα 1,2 lines were measured with a crystal spectrometer in Johansson geometry, which enables energy resolution below the natural linewidth of the measured Kα line.
Abstract: The proton induced Kα X-ray emission spectra of pure and some compound targets of sulfur were measured with a crystal spectrometer in Johansson geometry, which enables energy resolution below the natural linewidth of the measured Kα line. From these measurements the absolute energies of the S-Kα 1,2 lines were experimentally determined. In addition, the energies of the KαL 1 X-ray satellite lines, appearing in these spectra as a result of the radiative decay of atomic states with one hole in the K shell and one in the L subshells, were also measured. The measured Kα diagram and satellite line energies depend crucially on the S chemical state. The measured diagram line energies, as well as their relative intensity ratios obtained from the X-ray spectra of different S compounds, allow the deconvolution of X-ray spectra of mixed targets containing two different S compounds and the accurate determination of their mass ratio. Finally, the proton induced S-Kα X-ray spectrum from an aerosol sample was collected and the measured energies of the Kα 1,2 lines were used to specify the chemical state of S in the aerosol as a sulfate ([SO 4 ] 2− ). In conclusion, the results of the present paper demonstrate that the S-Kα 1,2 emission energies depend on the S chemical state and, therefore, their determination allows the chemical state speciation of S in a given sample.

Journal ArticleDOI
TL;DR: In this article, a peak decomposition of the main Cu 2p 3/2 signal is used to determine the chemical state of copper in differently prepared catalysts, and a molecular picture is formulated to describe a possible mechanism for copper reduction occurring during the catalyst preparation route at the zeolite surface.
Abstract: A procedure to determine the chemical state of copper in differently prepared catalysts is proposed. It is based on a peak decomposition of the main Cu 2p 3/2 signal only, which involves both Cu(II) and Cu(I) contributions. The presence of the closest shake-up satellite is related to the Cu(II) contribution only, in fact a linear dependence of the satellite area versus the Cu(II) area has been found. This method has been applied to characterize variously prepared catalysts and to quantify the different copper states at the surface. A molecular picture is formulated to describe a possible mechanism for copper reduction occurring during the catalyst preparation route at the zeolite surface.

Journal ArticleDOI
Geonja Lim1, Jong-Ho Lee, Joosun Kim, Hae-Weon Lee, Sang-Hoon Hyun1 
01 Nov 2004-Wear
TL;DR: In this paper, the effects of oxidants on tungsten chemical mechanical planarization (CMP) process were investigated using two different oxidants, hydrogen peroxide and ferric nitrate.

Journal ArticleDOI
TL;DR: In this article, the effects of metalworking fluids on the processes of machining and grinding are discussed, including the chemical interactions which occur between the various participating surfaces, and the impact of the resulting chemical state of the surface produced is addressed.

Journal ArticleDOI
TL;DR: In this article, a two-phase CrN and CrO0.5N 0.1N0.9 films were produced by r.f.f.-sputtering and both compositions showed CrN (Fm-3m) structure in XRD.

Journal ArticleDOI
TL;DR: In this paper, metal-carbon composite targets were used for X-ray photoelectron spectroscopy (XPS) to analyze the composition and chemical state of the films.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the oxidation state and localization of the Mn cations in the corundum lattice for Mn-doped α-alumina pigments prepared in the absence and the presence of fluxes.
Abstract: We have investigated the oxidation state and localization of the Mn cations in the corundum lattice for Mn-doped α-alumina pigments prepared in the absence and the presence of fluxes by mainly using XPS, XANES and EXAFS techniques. It was found that irrespective of the preparation method, the pink colour of the pigments is mainly due to Mn(III) species dissolved in the corundum lattice, in which they form cluster containing ∼2 Mn cations. The more intense colour presented by the sample prepared in the presence of fluxes is due to the incorporation of a higher amount of Mn to the alumina lattice as a consequence of the presence of liquid phase which favours the diffusion process involved in the solid solution formation.

Journal ArticleDOI
TL;DR: In this paper, XANES experiments were carried out on fresh UO2 pellets implanted with Mo ions and the measurements performed at the oxygen K and molybdenum LIII edges showed a correlation between the chemical state of moly bdenum and the O/U ratio of the UO 2 matrix.

Journal ArticleDOI
TL;DR: In this paper, amorphous electrodeposited nickel-phosphorus alloys were analyzed in the amorphous and re-crystallized state by EDXD and XPS surface analysis.
Abstract: Amorphous electrodeposited nickel-phosphorus alloys with 22 at. % of phosphorus (Ni22P) have been analyzed in the amorphous and re-crystallized state by EDXD and XPS surface analysis. The re-crystallization kinetics have been determined following in situ structural changes by EDXD. Distinct diffraction patterns indicating the presence of Ni 3 P confirm alloy re-crystallization at 645 °C. The XPS results show that all the core level binding energies of nickel such as Ni2p 3/2 and Ni2p 1/2 and phosphorus (P2p, P2s) remained constant after the change from X-ray amorphous to crystalline structure of the NiP alloy. Differences observed were as follows: (a) the binding energy difference between the Ni2p main lines and the satellite, (b) the fine structure of the NiLMM Auger lines, and (c) the density of states in the valence band in the region of the Ni3d electrons. On the basis of these results from EDXD and XPS, it can be concluded that the change in alloy structure from X-ray amorphous to crystalline influences the electronic structure of the NiP alloy but not the chemical state of phosphorus. An explanation based on the screening model proposed in the literature is discussed.

Journal ArticleDOI
TL;DR: In this paper, a single high nitrogen face-centered-cubic phase (γN) was formed on the plasma source ion nitrided 1Cr18Ni9Ti (18-8 type) austenitic stainless steel.
Abstract: A single high nitrogen face-centered-cubic phase (γN) was formed on the plasma source ion nitrided 1Cr18Ni9Ti (18-8 type) austenitic stainless steel. Auger electron spectroscopy and x-ray photoelectron spectroscopy, in conjuction with ion beam sputtering, were used to determine the chemical composition and bonding of nitrogen in the γN phase. The chemical composition of the γN phase was shown as a formula with atomic fraction (Fe0.60,Cr0.22,Ni0.18)2N. The γN phase possessed weaker Cr–N ionic-type bonds and stronger Fe–N ionic-type bonds, compared with the stoichiometric nitrides. The Cr2p3∕2 binding energy was 1.1eV lower than that of CrN and Cr2N phases (at 575.5eV). The chemical shift of the Fe–N bonding compared with the Fe–Fe bonding was nearly 2.1eV. The N1s binding energies showed that the nitrogen was in the chemical state with iron (at 396.6eV) and chromium (at 397.7eV). All the chromium appeared to be in the Cr–N bond. A part of iron was also observed in the nitride state, and all the nickel was ...

Journal ArticleDOI
TL;DR: In this article, the doping effect by NO2 molecules of copper phthalocyanine (CuPc) thin films has been studied by means of X-ray photoemission spectroscopy (XPS).

Journal ArticleDOI
TL;DR: In this article, the authors 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.

Journal ArticleDOI
TL;DR: In this paper, the interfacial reaction between deposited molybdenum and three different TiO2(1.1.0) substrates was investigated by means of X-ray photoelectron spectroscopy (XPS) and x-ray absorption near edge spectrography (XANES) using a new model based on thermodynamical considerations including entropic effect.

Journal ArticleDOI
TL;DR: The impact of primary ion bombardment conditions on SIMS depth profiles through HfO 2 high-k films was investigated in this article, showing that the apparent presence of Hf throughout the film, as well as tailing of the Hf signal into the substrate, is inconsistent with simple ion beam-induced mixing.