Ru Composition Research Articles

Improvement of Copper Diffusion Barrier Properties of Tantalum Nitride Films by Incorporating Ruthenium Using PEALD

Ru-incorporated TaN (Ru–TaN) films were investigated as a Cu diffusion barrier material. Ru–TaN films were prepared by sequential deposition of Ru and TaN using plasma-enhanced atomic layer deposition (PEALD). The film composition was controlled by the number of Ru unit cycles. While the resistivity of Ru–TaN films was increased abruptly at low Ru composition , the resistivity of Ru–TaN films was decreased gradually as the Ru composition increased after that composition. The crystal structures of Ru–TaN films were amorphous at the Ru composition range from 0.19 to 0.52 due to disturbance of grain growth. However, the Ru–TaN films had TaN-like structure below this range and Ru-like structure above this range. The amorphous Ru–TaN films had nanocrystallite embedded structure in an amorphous matrix. This amorphous Ru–TaN barrier showed a better Cu diffusion barrier property than the TaN barrier because the Cu diffusion through the grain boundary was suppressed by the amorphization. In addition, the Ru–TaN barrier exhibited good adhesion to both Cu and .

Influence of Ru segregation on the activity of Ru–Co/γ-Al2O3 during FT synthesis: A comparison with that of Ru–Co/SiO2 catalysts

γ-Al 2 O 3 and SiO 2 supported Co catalysts, with varying amounts of Ru, were prepared and evaluated for Fischer–Tropsch synthesis (FTS). The composition of Ru for optimum activity was found to be support-dependent. The reducible Co 3 O 4 was high in the region of 0–1.64 wt.% of Ru in Co/SiO 2 catalysts. Co/γ-Al 2 O 3 displayed a maximum for reducible Co species at 0.42 wt.% Ru. Segregation of Ru occurred beyond this composition decreasing the extent of reduction. Co/γ-Al 2 O 3 catalysts showed lower activity and olefin selectivity, in spite of higher Co dispersion, than Co/SiO 2 catalysts. The catalytic performance depends on the amount of reducible Co species, which again depends upon the optimum content of Ru.

Carbon/nanostructured Ru composites as electrodes for supercapacitors

Carbon/nano Ru composites were obtained by silica templating of dichlorobis (μ-chloro)bis [(1-3-η: 6-8-η)-2,7- dimethyloctadienediyl] diruthenium(IV), followed by pyrolysis. Carbon/RuO 2·XH 2O composites were obtained by electro-oxidation of carbon/nano Ru composites. It was found that the carbon/Ru composites had homogeneously dispersed Ru nanoparticles in the hierarchical pore structures and carbon matrix. The carbon/RuO 2·XH 2O composites displayed improved capacitive properties (229 F/g at 10 mV/s) as electrodes of supercapacitors in H 2SO 4 electrolyte.

Carbon Electrodes Modified with TiO2/Metal Nanoparticles and Their Application for the Detection of Trinitrotoluene

AbstractThe preparation of modified, catalytically active, functional carbon electrodes and their application to the electrochemical reduction of trinitrotoluene (TNT) is reported. Modification of the electrodes is performed with composites of nanometer‐sized, mesoporous titanium dioxide, which acts as a support containing inserted/deposited nanoparticles of ruthenium, platinum, or gold. These composites are prepared by a novel sonochemical synthesis using simple and low‐cost precursors. Cyclic voltammetry shows that 2,4,6‐trinitrotoluene can be reduced on thus‐modified carbon‐paper electrodes at potentials of around –0.5 V (vs. Ag/AgCl/Cl–) in aqueous solutions. Unexpectedly, carbon‐paper electrodes modified with the TiO2/nano‐Pt composites demonstrate a remarkable electrochemical activity toward the reduction of trinitrotoluene. A significant finding is that the two electrode processes—the reduction of TNT and of oxygen—are quite well separated in potential on the modified carbon‐paper electrodes because of selective electrochemical activity of the TiO2/nano‐Pt and TiO2/nano‐Au composites. TiO2/nano‐Ru composites are found to be much less electrochemically active for the detection of TNT compared to the previous two. It was also established that the titanium dioxide support of TiO2/nano‐Pt composites plays a specific role for facilitating the TNT‐ and oxygen‐reduction processes.

Methanol Oxidation on a Pt ElectrodeModified by Underpotential Deposition of Ru

Underpotential deposition (upd) of ruthenium on a platinum electrode was adopted to obtain a submonolayer of ruthenium on platinum surface. Ru coverage was evaluated according to the change of the hydrogen desorption area in the cyclic voltammograms (CV) of Pt electrodes before and after upd-Ru modification in 0.5 mol·L-1 H2SO4. The effects of the potential for formation of upd-Ru and coverage of upd-Ru adtoms on methanol oxidation were investigated and analyzed. It was shown that Ru adatoms could be underpotentially deposited on a platinum surface. The submonolayer of upd-Ru on the Pt electrode could enhance methanol electrooxidation several times as large as that on the pure Pt electrode. It was also shown that as long as the amount of upd-Ru adatoms was controlled in a proper range, upd-Ru deposits would enhance the methanol oxidation independently of the deposition potential. The catalytic activity of binary Pt-Ru catalysts for methanol electrooxidation was highly associated with the surface composition of Pt and Ru, but was free of whether Pt-Ru deposits appear in a form of alloy, bimetallic compounds, adatoms, or something else.

Direct decomposition of nitrous oxide over Ru/Al2O3 catalysts prepared by deposition–precipitation method

Abstract Alumina-supported ruthenium catalysts were prepared by the deposition–precipitation (DP) and impregnation (IMP) methods. The catalysts were characterized by BET surface area, X-ray diffraction, temperature-programmed reduction (TPR) and diffused reflectance infra-red spectroscopic (DRIFTS) techniques. The DP catalysts showed higher activity than their IMP analogues. The DRIFTS analysis revealed preferential formation of Ru n + species on the surface of DP catalysts. Both Ru n + and Ru 0 species appeared on IMP catalysts, with the composition of Ru 0 increasing with increase in metal loading. The temperatures at which the peak maxima appeared were higher in the TPR patterns of the DP catalysts, indicating greater interaction between Ru and alumina, which explained the formation of the cationic Ru species. The high activity of the catalysts prepared by DP method was related to the formation of electron deficient Ru sites during the preparation of the catalyst.

The influence of acidic and alkaline precursors on Pt [sbnd]Ru/C catalyst performance for a direct methanol fuel cell

This research aims to increase the activity of platinum–ruthenium alloy (Pt Ru/C) catalysts for methanol electrooxidation. The direct methanol fuel cell (DMFC) anodic Pt Ru/C catalysts were prepared from acidic and alkaline Pt(NH 3) 2(NO 2) 2 solutions as Pt precursors, respectively, and with the same acidic Ru compound but without Cl − ion as the Ru precursor by thermal reduction. The phase structures, lattice parameters, particle sizes, alloy composition, distribution, and the morphology of reduced catalysts were determined by means of X-ray diffraction (XRD), energy-dispersive analysis of X-ray (EDAX), and high-resolution transmission electron microscopy (TEM). It was found that the XRD patterns of the two catalysts showed Pt reflections for a face centered cubic (fcc) crystalline alloy structure. The catalyst prepared from the acidic Pt(NH 3) 2(NO 2) 2 as a precursor has a more homogeneous distribution of Pt Ru metal particles on carbon. Its size is relatively small, about 3.7 nm. Its chemical composition is quite similar to theoretical value of 1:1 (Pt:Ru). The catalyst prepared from the alkaline Pt(NH 3) 2(NO 2) 2 as a precursor has an uneven distribution of Pt Ru particles on carbon and its size is relatively large, and the chemical composition of Pt and Ru was 6:4. The performance was tested using a glassy carbon working electrode by cyclic voltammetry (CV) and chronoamperometric curves in a solution of 0.5 mol L −1 CH 3OH and 0.5 mol L −1 H 2SO 4 at 25 °C. The electrocatalytic activity of the Pt Ru/C catalyst prepared from the acidic Pt(NH 3) 2(NO 2) 2 as a precursor was the higher for methanol electrooxidation than that of catalyst from the alkaline source. The peak current density from the CV plot was 11.5 mA cm −2.

Surfactant-stabilized PtRu colloidal catalysts with good control of composition and size for methanol oxidation

Well-dispersed PtRu/C catalysts were prepared by supporting surfactant-stabilized PtRu hydrosol on carbon followed by a heat-treatment at elevated temperature. The effect of the synthesis conditions and the heat-treatment on the composition and electrcatalytic properties of PtRu/C towards methanol oxidation was systematically investigated. It was found that the pH environment and the reaction temperature could greatly affect the final compositions of Pt and Ru in the PtRu catalysts. Moreover, after a post-heat-treatment process, the electrocatalytic activity of PtRu colloidal catalysts can be much improved, the enhancement of which can be largely explained by the improved alloying formation and the removal of surfactant from catalyst demonstrated by the XRD and XPS analyses, respectively.

Plasma-Enhanced Atomic Layer Deposition of Ru–TiN Thin Films for Copper Diffusion Barrier Metals

Ruthenium-titanium nitride (Ru–TiN) thin films were grown by plasma-enhanced atomic layer deposition (PEALD) at a growth temperature of . For the Ru–TiN PEALD, Ru and TiN were sequentially deposited to intermix TiN with Ru. The composition of Ru–TiN films was controlled by changing the number of deposition cycles allocated to Ru, while the number of deposition cycles for TiN was fixed to one cycle. The microstructures of Ru–TiN films changed from polycrystalline to amorphous, as the intermixing ratio of Ru increased in the deposited Ru–TiN films. The resistivity of the Ru–TiN film was abruptly increased by adding Ru at the first stage, but after showing a peak resistivity, it decreased with the intermixing ratio of Ru in the films. Especially, the film of showed an electrical resistivity of . As a Cu diffusion barrier layer, amorphous Ru–TiN films showed a superior copper diffusion barrier property to TiN or Ru itself, which had a polycrystalline structure. Moreover, Ru–TiN films showed a good adhesion to both chemical vapor deposition copper and an underlayer of .

Formation of a series of chimney–ladder compounds in the Ru–Re–Si system

Rhenium-alloyed ruthenium sesquisilicide alloys have been prepared over the wide composition range Ru 1− δ Re δ Si 1.5, 0 ⩽ δ ⩽ 0.85. The phase relationships of these alloys have been investigated using X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. Alloys with δ ⩾ 0.03 are multi-phase, composed of a series of (Ru,Re)Si y chimney–ladder phases with compositions of Ru 1− x Re x Si 1.5386+0.1783 x (0.14 ⩽ x ⩽ 0.76) and B20-type monosilicide (Ru,Re)Si as a secondary phase. These chimney–ladder structures are considered to form to stabilize the high-temperature Ru 2Si 3 chimney–ladder phase through the substitution of Ru with Re. The solubility limit of Re in a series of chimney–ladder phases is as large as 76% Re ( x = 0.76) and the Si/(Ru + Re) ratio of the chimney–ladder phases increases with increasing Re content. The observed deviation of the chimney–ladder structure from the idealized composition and the possibility of adjusting the semiconducting properties of these chimney–ladder structures are discussed in terms of the valence electron concentration per metal atom.

Double MITs and magnetoresistance: an intrinsic feature of Ru substitutedLa0.67Ca0.33MnO3

In this paper, we examine the possible influence of extrinsic factors on the electrical and magnetotransportof La0.67Ca0.33Mn1−xRuxO3 (x≤0.10). Ru substitution results in double metal–insulator transitions (MITs) atTMI1 and TMI2, both exhibiting magnetoresistance (MR). No additional magneticsignal corresponding to a second low-temperature maximum (LTM) atTMI2 could be observed, either in ac susceptibility(χ′) or in specificheat (Cp). Typicalgrain sizes of ∼18 000–20 000 nm, as estimated from the scanning electron microscope (SEM) micrographs, are notso small as to warrant an LTM. The absence of additional peaks in the highstatistics powder x-ray diffraction (XRD), a linear systematic increase of theunit cell parameters, close matching of the transition temperatures in resistivity,χ′ andCp and their linearsystematic decrease with x, and an homogeneous distribution of Mn, Ru and O at arbitrarily selected regions withinand across the grains exclude chemical inhomogeneity in the samples. The insensitivity ofgrain boundary MR at 5 K to Ru composition indicates that the grain boundary is notaltered to result in an LTM. Oxygen stoichiometry of all the compounds is close to thenominal value of 3. These results not only exclude the extrinsic factors, but alsoestablish that double MITs, both exhibiting MR, are intrinsic to Ru substitutedLa0.67Ca0.33MnO3.

Influence of an inert background gas on bimetallic cross-beam pulsed laser deposition

A cross-beam pulsed laser deposition (CBPLD) system operated at variable pressure in an inert (He) background atmosphere was used to deposit films from two dissimilar targets (Pt–Ru and Pt–Au). Using this setup, we showed that films with mixed Pt–Au and Pt–Ru composition can be prepared over the whole compositional range, from [Pt] = 0 to 100at.%. Films deposited at He pressure higher than 1.6Torr are fairly homogeneous and the standard deviation of the Pt concentration over the whole area of the deposit is less than 1at.%. Using a diaphragm located at the interaction zone between the two plasmas, a drastic reduction of the normalized droplet density was observed, from about 700×102cm−2nm−1 in conventional PLD to 6×102cm−2nm−1 in CBPLD. The deposition rate increases as the pressure is increased from vacuum to an optimal He pressure. The deposition rate decreases again for higher He pressure. The optimal operating conditions are P(He)=2Torr for Pt–Ru and P(He)=4Torr for Pt–Au. In these conditions, the deposition rates are, respectively, ∼32% and ∼22% of what they would be in conventional PLD. The behavior of the deposition rate with the He pressure is consistent with what can be concluded from a visual observation of the interaction of the plasma plumes at various pressures. A simple model considering the quadratic dependence of the velocity on the flow resistance of heavy particles in the rarefied light ambient particles is developed to understand the role of the background gas in the deposition rate. This model succeeds in predicting a maximum in the deposition rate versus He pressure curve, allowing us to get a better physical understanding of what is going on during the interaction between the two plasma plumes.

Development of PtRu-CeO 2/C anode electrocatalyst for direct methanol fuel cells

Ceria (CeO 2)-modified PtRu/C catalysts with different compositions of Ru and CeO 2, viz. PtRu 0.9(CeO 2) 0.1/C, PtRu 0.7(CeO 2) 0.3/C and PtRu 0.5(CeO 2) 0.5/C and unmodified PtRu/C catalyst were synthesized by the sodium borohydride reduction method. Transmission electron microscopic results indicated that the lower concentrated CeO 2-modified PtRu/C catalysts had almost a similar morphological structure (well-dispersed particles with size around 2.3–2.5 nm) with that of the unmodified PtRu/C catalyst. X-ray diffraction and X-ray photoelectron spectroscopy analyses indicated the formation of PtRu alloy and presence of CeO 2 in an amorphous form with a mixed oxidation states (Ce 3+–Ce 4+). Electro-catalytic activity of these catalysts for methanol oxidation was investigated by linear sweep voltammetry and chronoamperometry and it was found that the PtRu 0.7(CeO 2) 0.3/C catalyst yielded the higher methanol oxidation current than did the unmodified PtRu/C catalysts.

Binding sites of [Ru(bpy)2(H2O)2](BF4)2 with sulfur‐ and histidine‐containing peptides studied by electrospray ionization mass spectrometry and tandem mass spectrometry

The composition and binding sites of cis-[Ru(II)(bpy)2]2+-bound sulfur-containing peptides of Met-Arg-Phe-Ala, glutathione and oxidized glutathione, and also histidine-containing peptide of oxidized insulin B chain, were investigated by electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS). The composition of Ru(II)-containing peptides was precisely determined by ESI-MS, zoom scan and simulation of isotope distribution patterns. MS/MS analysis shows that, in sulfur-containing peptides, the Ru(II) complex prefers to anchor to a carboxyl group, although some other potential binding sites of thiol, thioether and N-terminal amino groups present in these peptides, and in oxidized insulin B chain, Ru(II) first anchors to His10, then either to the hydroxyl group of Thr27 or to the carboxyl group of Ala30. Its secondary structure and microenvironment surrounding the potential binding sites may affect the binding ability of cis-[Ru(II)(bpy)2]2+ to oxidized insulin B chain.

Scanning electrochemical microscope characterization of thin film combinatorial libraries for fuel cell electrode applications

Pt–Ru combinatorial libraries of potential fuel cell anode catalysts are formed by sequential sputter deposition through masks onto Si wafers. Scanning electrochemical microscopy (SECM) is employed for characterization of electrocatalytic activity. Aspects of using a scanning electrochemical microscope for characterization of an array of thin film fuel cell electrode materials are discussed. It is shown that in applying SECM to library characterization, careful attention must be paid to thin film annealing, specimen topography and tip degradation in order to realize meaningful results. Results from a Pt–Ru thin film library reveal the most active members near the 50 Pt/50 Ru composition.

Characteristics of adsorbed CO and CH 3OH oxidation reactions for complex Pt/Ru catalyst systems

Pt/Ru powder catalysts of the same nominal Pt to Ru composition were prepared using a range of methods resulting in different catalyst properties. Two PtRu alloy catalysts were prepared, one of which has essentially the same surface and bulk Pt to Ru composition, while the second catalyst is surface enriched with Ru. Two powders consisting of non-alloyed Pt phases and surfaces enriched with Ru were also prepared. The oxidation state of the surface Ru of the latter two catalysts is mainly metallic Ru or Ru-oxides. The catalyst consisting of Ru-oxides was formed at 500 °C. Part of this catalyst was then reduced in a H 2 atmosphere under “mild” conditions, thus catalyst properties such as particle size are not changed, as they are locked in during previous high temperature treatment. The oxidation kinetics of adsorbed CO (CO ads) and solution CH 3OH were studied and compared to the Ru ad-metal state and Pt to Ru site distribution of the as-prepared catalysts. The kinetics of the CO ads oxidation reaction were observed to be slower for the catalyst containing Ru-oxides as opposed to mainly Ru metal. The CH 3OH oxidation activities measured per Pt surface area, i.e., the catalytic activities are better (by ca. seven times) for the alloy catalysts than the non-alloyed Pt/Ru catalysts. The latter two catalysts showed essentially the same catalytic CH 3OH oxidation activities, i.e., independent of the Ru ad-metal oxidation state of the as-prepared catalysts. Furthermore, it is shown that CO ads oxidation experiments can be used to extract characteristics that allow the comparison of catalytic activities for the CO ads oxidation reaction and Pt to Ru site distribution for complex catalyst systems.

High-temperature stability of nano-grained B2-structured RuAl-based intermetallics by mechanical alloying

A series of nano-grained B2-structured RuAl-based intermetallics and corresponding composites are synthesized by mechanical alloying. These RuAl-based materials include stoichiometric RuAl, B2-structured ternary (Ru,Ni)Al and (Ru,Ir)Al, eutectic RuAl–Ru and particle reinforced RuAl–ZrO 2 composite. The accumulation of impurities, mainly Fe, in grain boundaries and the structural evolution during grain growth are found to be the controlling factors for the grain growth stagnation in nano-grained B2-structured binary RuAl and ternary (Ru,Ni)Al and (Ru,Ir)Al intermetallics. Ternary alloying element forming iso-structured pseudo-binary compounds, eutectic in situ and ceramic particle reinforced composites are explored to be the effective routes to enhance the stability of single-phase RuAl. The thermal stability of microstructure in various RuAl-based materials are found to decrease in a sequence from pseudo-binary RuAl–IrAl, RuAl–NiAl, eutectic RuAl–Ru composites, ceramic particle reinforced RuAl–ZrO 2 composites to binary stoichiometric RuAl.

Dependence of CH 3 OH Oxidation Activity for a Wide Range of PtRu Alloys: Detailed Analysis and New Views

Unsupported PtRu alloy powders of a wide range of compositions were prepared at low temperatures by carefully adjusting the preparation procedure. PtRu alloys of essentially the same surface, nominal and bulk composition, were formed up to ca. 46 atom % Ru content. Adsorbed CO stripping voltammetry and oxidation characteristics, namely, i-V curves and pseudo-steady-state current density values recorded at constant potentials, were the same as reported for corresponding bulk alloys, suggesting that the electrocatalytic activities of the powders can be compared to bulk alloys. oxidation activities obtained for PtRu alloy, Pt, and Ru powders showed the PtRu alloy of 70:30 atom % Pt:Ru composition to exhibit the highest activity independent of the temperature and potential tested (0.3 and 0.4 V vs. a reversible hydrogen electrode). The experimental pseudo-steady-state current density values for the oxidation reaction were found to show the same dependence on Ru content as theoretical values calculated assuming that an assembly of three neighboring Pt and one Ru site are involved in the oxidation of a molecule. © 2004 The Electrochemical Society. All rights reserved.

Osmium isotope constraints on contrasting sources and prolonged melting in the Proterozoic upper mantle: evidence from ophiolitic Ru–Os sulfides and Ru–Os–Ir alloys

This study presents the first extensive data set of Os isotopic compositions of primary Ru–Os–Ir alloys and Ru–Os sulfides derived from two Neoproterozoic ophiolite-type ultramafic massifs (Kunar in Northern Taimyr, Russia, and Kraubath in Eastern Alps, Austria). The study employed a multi-technique approach and utilized a number of analytical techniques, including hydroseparation, electron microprobe analysis, negative thermal ionization mass-spectrometry (N-TIMS) and laser ablation attached to multiple collector-inductively coupled plasma-mass spectrometry (LA MC-ICP-MS). The results identify two different Os isotope sources (subchondritic and suprachondritic) for bedrock Ru–Os sulfides at Kraubath, whereas detrital Ru–Os–Ir alloys at Kunar are characterized by ‘unradiogenic’ 187Os/ 188Os values, indicative of a chondritic or subchondritic mantle source of platinum-group elements (PGE). The ‘unradiogenic’ 187Os/ 188Os values yield a very wide range of 187Os/ 188Os (0.1094±0.0003 to 0.1241±0.0004, n=19, N-TIMS data), which is almost identical to the Os isotope composition of bedrock laurite, (Ru,Os)S 2, in podiform chromitite within an ophiolitic mantle section at Kraubath (0.11249±0.00062 to 0.12437±0.00051, n=17, N-TIMS and LA MC-ICP-MS data). These results are consistent with a model in which a prolonged history of melting events of parent ultramafic source rocks took place in the oceanic upper mantle. In contrast, erlichmanite and laurite from banded chromitite within the transition zone at Kraubath show high 187Os/ 188Os (0.13080 to 0.13212) values, indicative of a suprachondritic source of PGE. This signature might be interpreted as either evidence of an enriched mantle source or an indication of a ‘radiogenic’ crustal component, which was introduced during a subduction-related event. The Os isotope results obtained support the conclusion that the Re–Os system, represented by PGM, has remained unchanged from the time of formation of the PGM until now, despite later thermal events, which occurred in the vicinity of ophiolite-type complexes.

NMOS 소자에 대한 Ru1Zr1합금 게이트 전극의 특성

This paper describes the characteristics of Ru-Zr alloy gate electrodes deposited by co-sputtering. The various atomic composition was made possible by controlling sputtering power of Ru and Zr. Thermal stability was examined through 600 and 700 <TEX>$^{\circ}C$</TEX> RTA annealing. Variation of oxide thickness and X-ray diffraction(XRD) pattern after annealing were employed to determine the reaction at interface. Low and relatively stable sheet resistances were observed for Ru-Zr alloy after annealing. Electrical properties of alloy film were measured from MOS capacitor and specific atomic composition of Zr and Ru was found to yield compatible work function for nMOS. Ru-Zr alloy was stable up to <TEX>$700^{\circ}C$</TEX> while maintaining appropriate work function and oxide thickness.