Deposition Of Ru Research Articles

Directed assembly of Ru nanoclusters on Ru(0001)-supported graphene: STM studies and atomistic modeling

Directed assembly of an array of Ru nanoclusters (NCs) is achieved by deposition of Ru at around room temperature on a single layer of graphene supported on Ru(0001). In this system, directed assembly is guided by the periodic moire structure of the buckled graphene sheet. Behavior is analyzed utilizing both scanning tunneling microscopy and atomistic lattice-gas modeling together with kinetic Monte Carlo simulation. We elucidate the kinetics of NC nucleation and growth, specifically assessing the coverage dependence of the NC density and height distribution. In addition, we provide a detailed characterization of the development of short-range spatial order within the NC array, identifying a tendency for row formation.

Structural Characterization of Ru-Modified Carbon-Supported Pt Nanoparticles Using Spontaneous Deposition with CO Oxidation Activity

The modification of carbon-supported Pt nanoparticles, high performance (HP) 20% Pt on Vulcan XC-72 carbon black (Pt/C electrocatalyst), by spontaneous deposition of Ru species is examined employing electrochemical and structural techniques. Thin-layer electrodes were prepared by applying aqueous catalyst inks of Pt/C on glassy carbon (GC) disks. Ru deposition was carried out by immersion of the prepared electrode in deaerated RuCl3/HClO4 solutions. The subsequent cyclic voltammetry experiments of the modified electrocatalysts (Ru(Pt)/C) were performed in 0.5 M H2SO4 to determine the Ru coverage and the electroactive surface. CO stripping voltammetry showed the promotional effect of Ru(Pt)/C for the CO oxidation compared to Pt/C. The structural characterization of the modified electrocatalysts was performed by transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analyses, fast Fourier transform (FFT), selected-area electron diffraction (SAED), X-ray diffraction (XRD), and X-ray photoelect...

A comparison of direct methanol fuel cell degradation under different modes of operation

The degradation test of direct methanol fuel cells (DMFCs) under on–off operation with variable load profile, known as a variable load on-off operation (VLOO) mode, was compared to continuous operation with a constant load, known as a constant load continuous operation (CLCO) mode. It was found that the performance loss in the VLOO mode was higher than that under the CLCO mode in terms of open circuit voltage drop (3.6 times higher) and the maximum power density reduction rate (1.23 times greater). Under both operation modes, the anode catalyst was deteriorated by Ru dissolution. However, the faster decay of cell performance under VLOO mode was mainly caused by the increase of cathode polarization due to higher methanol crossover and the decrease of Pt activity to the oxygen reduction reaction induced by Ru deposition.

Templating of arrays of Ru nanoclusters by monolayer graphene/Ru Moirés with different periodicities

We have studied the formation of Ru nanocluster arrays on several monolayer graphene/Ru Moiré structures with different relative orientations of the graphene and Ru lattices. Experiments and ab initio calculations clearly show that the presence of a graphene/Ru Moiré does not guarantee the ordered adsorption of Ru nanoclusters. The simultaneous deposition of Ru onto coexisting Moirés demonstrates that a structure with aligned graphene and Ru lattices templates the formation of arrays of small Ru clusters with narrow size spread and adsorption exclusively in a single site (the ‘low fcc’ site). The other Moirés considered here gave rise to substantially larger clusters with broader size distribution and without detectable site selectivity. Calculations explain these findings via the density of states (DOS) at different sites of the graphene/Ru Moiré. The ordered nucleation of many small clusters instead of incorporation of metal atoms into larger ones requires one Moiré site with a large DOS at the Fermi level, so that the binding of metal adatoms to this site is stronger than to competing sites in the Moiré and to existing metal clusters.

Platinum group element abundances in the upper continental crust revisited – New constraints from analyses of Chinese loess

Platinum group element (PGE) abundances in the upper continental crust (UCC) are poorly constrained with published values varying by up to an order of magnitude. We evaluated the validity of using loess to estimate PGE abundances in the UCC by measuring these elements in seven Chinese loess samples using a precise method that combines NiS fire assay with isotope dilution. Major and trace elements of the Chinese loess show a typical upper crustal composition and PGE abundances are consistent with literature data on Chinese loess, except for Ru, which is a factor of 10 lowe than published values. We suggest that the high Ru data and RuN/IrN values of Chinese loess reported by Peucker-Ehrenbrink and Jahn (2001) (Geochem. Geophys. Geosys.2, 2001GC000172) are an analytical artifact, rather than a true geochemical characteristic of loess because likely sources of loess are not significantly enriched in Ru and transport and deposition processes cannot preferentially enrich Ru in loess. The effect of eolian fractionation on PGE abundances in loess appears to be limited because Chinese loess from different locations shows similar PGE patterns and concentrations. This conclusion is supported by strong positive correlations between the PGE (except for Pt) and other compatible elements such as Fe2O3, Ni, Cr, Co. Using a compilation of PGE data for loess from China, Argentina and Europe, including our data but excluding one sample with an anomalously high Pt content, we propose average PGE abundances for global loess of Ir=0.022ppb (ng/g), Ru=0.030ppb, Rh=0.018ppb, Pt=0.599ppb, and Pd=0.526ppb, and suggest that these are the best current estimates for the PGE abundances of the UCC.

Pd–Ru electrodeposits with high hydrogen absorption capacity

Thin Pd–Ru deposits with 90–100% Pd in the bulk were obtained electrochemically from the mixtures of PdCl2 and RuCl3 aqueous solutions. Hydrogen absorption in Pd–Ru deposits was performed using cyclic voltammetry and chronoamperometry from 0.5 H2SO4 solutions at room temperature. Pd–Ru electrodeposits with a high Pd bulk content (above 97%) can absorb more hydrogen than pure Pd, with the hydrogen-to-metal atomic ratio up to 0.85 (as compared with 0.74 for Pd). The absorption capacity of Pd–Ru electrodes containing less than 97% Pd gradually decreases and the H/M ratio drops to ca. 0.50 for electrodes with 90% Pd. With increasing Ru content the potential corresponding to the α- and β-phase transition is shifted negatively with respect to that for pure Pd. Hydrogen absorption properties of Pd–Ru electrodes may be explained taking into account changes in electronic structure probably resulting from alloy formation between Pd and Ru.

Nanotubules-supported Ru nanoparticles for preferential CO oxidation in H2-rich stream

CO present in H2 provided as fuel for polymer electrolyte membrane fuel cells (PEMFC) can degrade the electrochemical performance and needs efficient removal, which can be accomplished by CO preferential oxidation (PROX). PROX catalytic activities in a H2-rich stream were tested and compared using ruthenium (Ru) nanoparticles supported on two different nanotubularly structured materials, carbon nanotubes (CNTs) and halloysite nanotubes (HNTs). In both of the support materials the morphology remains unchanged after Ru deposition and reduction, demonstrating that their tubular structure is thermally-stable. The catalytic results show that the Ru/HNTs perform better than Ru/CNTs at temperatures below about 110°C, owing to the easier reducibility of Ru particles over the former than the latter. However, Ru/HNTs can only reach a maximum CO conversion of 55%, with an O2 selectivity of around 27% applying an O2/CO mole ratio=1 at 123°C, which is insufficient for PROX applications. CNTs, on the other hand, provide larger surface area and have functional groups with stronger interaction with Ru nanoparticles, presenting a better Ru dispersion, which accounts for the superior catalytic activity at higher reaction temperature. Ru/CNTs catalyst exhibits a CO conversion over 90% and O2 selectivity of around 50% applying the same O2/CO mole ratio at temperatures above 120°C.

Effects of Ar plasma treatment for deposition of ruthenium film by remote plasma atomic layer deposition

Ruthenium thin films were deposited on argon plasma-treated SiO2 and untreated SiO2 substrates by remote plasma atomic layer deposition using bis(ethylcyclopentadienyl)ruthenium [Ru(EtCp)2] as a Ru precursor and ammonia plasma as a reactant. The results of in situ Auger electron spectroscopy (AES) analysis indicate that the initial transient region of Ru deposition was decreased by Ar plasma treatment at 400 °C, but did not change significantly at 300 °C. The deposition rate exhibited linearity after continuous film formation and the deposition rates were about 1.7 Å/cycle and 0.4 Å/cycle at 400 °C and 300 °C, respectively. Changes of surface energy and polar and dispersive components were measured by the sessile drop test. The quantity of surface amine groups was measured from the surface nitrogen concentration with AES. Furthermore, the Ar plasma-treated SiO2 contained more amine groups and less hydroxyl groups on the surface than on untreated SiO2. Auger spectra exhibited chemical shifts by Ru-O bonding, and larger shifts were observed on untreated substrates due to the strong adhesion of Ru films.

The properties of Ru films deposited by remote plasma atomic layer deposition on Ar plasma‐treated SiO2

AbstractBy using remote plasma atomic layer deposition (ALD), ruthenium thin films were deposited on SiO2 using bis(ethylcyclopentadienyl)ruthenium [Ru(EtCp)2] as a Ru precursor and an ammonia plasma as a reactant. Different plasma treatments were applied, and the best results were obtained with the Ar plasma‐treated SiO2 surface. The initial transition region usually observed with Ru deposition before continuous film formation was present, and the number of ALD cycles required to obtain a continuous film was reduced to about 35 cycles on the Ar plasma‐treated SiO2 substrates. The transition region of Ru cluster growth on Ar plasma‐treated SiO2 was investigated with transmission electron microscopy (TEM). Most of the Ru clusters were larger and better crystallized on the Ar plasma‐treated SiO2 than on untreated SiO2. Also, Ru films deposited on the treated SiO2 exhibited a (002) preferred orientated structure with a film resistivity of about 10.26 µΩ‐cm. The growth rates of Ru after passing the transition region were similar on both the treated and untreated SiO2 at about 1.7 Å/cycles. From the Auger electron spectroscopy (AES) spectrum, a very low content of oxygen was observed in the Ru films. About 9% carbon was detected by a rutherford backscattering spectrometer (RBS).

Comparison of radiation detector performance for different metal contacts on CdZnTe deposited by electroless deposition method

AbstractA comparative study of four different metals gold (Au), platinum (Pt), ruthenium (Ru) and rhodium (Rh) deposited on CdZnTe(CZT) by the electroless deposition method has been carried out. Two of these materials, Ru and Rh, have been deposited for the first time by this method. In contrast to the Pt deposition, the deposition of Ru and Rh were not carried out under the optimal conditions. The metals deposited on the samples were identified by Total reflection X‐ray Fluorescence (TXRF). Rutherford Backscattering Spectrometry (RBS) analyses show that Au forms the thickest layer (∼160 nm) for the experimental conditions of this work. Current‐voltage measurements show that Pt forms a more linear ohmic contact with the lowest leakage current. A 57Co gamma ray spectrum gave a better detector performance with a FWHM 11 keV at 122 keV. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Anomalous codeposition of cobalt and ruthenium from chloride–sulfate baths

Codeposition of Ru and Co was studied at room temperature and at 50 °C with various Ru3+ and Co2+ concentrations in the electrolyte. The codeposition of Co and Ru proved to be anomalous since no pure Ru could be obtained in the presence of Co2+ in the electrolyte, but a significant Co incorporation into the deposit was detected at potentials where the deposition of pure Co was not possible. The composition of the deposits varied monotonously with the change of the concentration ratio of Co2+ and Ru3+. The deposition of Ru was much hindered, and the current efficiency was a few percent only when the molar fraction of Co in the deposit was low. Continuous deposits could be obtained only when the molar fraction of Co in the deposit was at least 40 at.%. The deposit morphology was related to the molar fraction of Co in the deposit. The X-ray diffractograms are in conformity with a hexagonal close-packed alloy and indicate the formation of nanocrystalline deposits. Two-pulse plating did not lead to a multilayer but to a Co-rich alloy. Magnetoresistance of the samples decreased with increasing Ru content.

Oblique-incidence sputtering of Ru intermediate layer for decoupling of intergranular exchange in perpendicular recording media

During the Ru deposition process for granular type perpendicular magnetic recording media, both a reduction in the Ru intermediate layer thickness and lowering of sputtering gas pressure were successfully achieved by focusing on a self-shadowing effect. Oblique-incidence sputtering with a 60° incident angle under an Ar gas pressure of 0.6 Pa yielded (1) columnar Ru grains with a growth direction of 30° from the film normal, (2) c-plane sheet texture by epitaxial growth on the Pt underlayer, and (3) a flat envelope of the surface and a deep gap at grain boundaries. This change in the Ru structure significantly contributes to reducing exchange coupling among magnetic grains, especially in the initial growth region in an overlying granular medium.

ALD Ru and its Application in DRAM MIM-Capacitors and Interconnect

Ruthenium is proposed as electrode for next generation DRAM metal-insulator-metal capacitors and interconnect barrier/seed. This study compares different ALD processes to deposit Ru and RuO2 films. ALD with oxygen results in the deposition of either Ru or RuO2, depending on deposition conditions. We also report the growth and scalability of Ru films by plasma-enhanced ALD (PEALD) with ammonia. The inorganic precursor RuO4 was studied as an alternative chemical pathway, of which the characteristics and film properties were studied at temperature range 100-250ºC using various process conditions. The quality of films deposited with thermal ALD and PEALD is compared with respect to the targeted applications. In particular, the investigation of the thermal stability of the different Ru and RuO2 films under typical DRAM anneal conditions is presented.

Arrays of Ru nanoclusters with narrow size distribution templated by monolayer graphene on Ru

Ru nanoclusters self-assemble over macroscopic sample areas during vapor deposition of Ru on monolayer graphene (MLG) on Ru(0001). The Ru nanoclusters form arrays with a mean lateral cluster diameter of ~ 20 Å, cluster heights of 1 or 2 ML, and a size distribution that remains nearly constant with increasing coverage. Combined scanning tunneling microscopy and density functional theory (DFT) show that the clusters are templated by the MLG/Ru(0001) moiré unit cell and identify the preferred binding site of the clusters as the low fcc region of the moiré. Cross-sectional transmission electron microscopy (TEM) and high-resolution TEM contrast simulations experimentally demonstrate that the interaction of the Ru clusters with the underlying MLG/Ru(0001) leads to a local lifting of the graphene layer of the template. DFT calculations confirm this mechanism of interaction of the Ru clusters with the strongly coupled MLG/Ru(0001). Weakening of the graphene-support coupling via oxygen intercalation is shown to have a major effect on the assembly of Ru nanocluster arrays. With a preferred binding site lacking on decoupled graphene, the Ru nanoclusters grow significantly larger, and clusters with 1 to 4 ML height can coexist.

Performance and reliability analysis of p-type metal-oxide-semiconductor field effect transistors with various combinations of Ru and Al gate metal

Device performance and reliability characteristics of various types of Ru–Al-based metal gates on HfSiO gate dielectrics were investigated for p-type metal-oxide-semiconductor field effect transistor (pMOSFET) applications. Using the high work function of Ru and a dipole formed by Al atoms in a gate dielectric, the threshold voltage of the pMOSFET could be controlled successfully. However, the excessive diffusion of Al atoms generated more interface states and bulk trapping in the high-k dielectric layer and degraded the device performances and reliability characteristics. It was also found that the carefully tailored sequence of deposition and composition of Ru and Al metals can be used to prevent the excessive diffusion of Al atoms.

The Deposition of Ru and RuO2 Films for DRAM Electrode

Ru and RuO2 films were deposited from Torus, a blend of RuO4. At low hydrogen dose RuO2 films were deposited at 200ºC. With sufficient dosing of hydrogen, Ru films were obtained; either a high enough hydrogen pressure or plasma was used. Process temperatures between 100ºC and 250ºC were explored. At 100ºC the process behaves like ALD, while at 200ºC thermal decomposition is dominating. Above 200ºC the decomposition of RuO4 increases rapidly. The deposited films are smooth and with low impurities.

Study of core–shell platinum-based catalyst for methanol and ethylene glycol oxidation

A Ru core–Pt shell, XC72-supported catalyst was synthesized in a two-step process: first, by deposition of Ru on XC72 by the polyol process and then by deposition of Pt on the XC72-supported Ru, with NaBH 4 as reducing agent. The structure and composition of this core–shell catalyst were determined by EDS, XPS, TEM and XRD. Electrochemical characterization was determined with the use of cyclic voltammetry and chronoamperometry. The methanol and ethylene glycol oxidation activities of the core–shell catalyst were studied at 80 °C and compared to those of a commercial catalyst. It was found to be significantly better (in terms of A g −1 of Pt) in the case of methanol oxidation and worse in the case of ethylene glycol oxidation. Possible reasons for the lower ethylene glycol oxidation activity of the core–shell catalyst are discussed.

Deposition of Ru and RuO2 Films for DRAM Electrode

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Influence of Ru/Ru–SiO 2 underlayers on the microstructure and magnetic properties of CoPt–SiO 2 perpendicular recording media

SiO 2 was doped into Ru underlayer to reduce the grain size of CoPt–SiO 2 perpendicular media. The effects of SiO 2 volume fraction and sputtering deposition pressure of Ru–SiO 2 underlayer on the microstructure and magnetic properties of CoPt–SiO 2 media were studied. Increasing SiO 2 volume fraction in Ru–SiO 2 layer decreased the grain sizes of Ru and CoPt. Adding 5% SiO 2 to Ru–SiO 2 layer increased the coercivity and enhanced the exchange decoupling and thermal stability of CoPt–SiO 2 layer. A further increase in SiO 2 volume fraction caused the deterioration of magnetic properties of CoPt–SiO 2 layer. Deposition of Ru–SiO 2 layer at 1.3 Pa resulted in a smaller activation volume and higher thermal stability of the CoPt–SiO 2 media than that deposited at 0.4 Pa.

Mechanism, Products, and Growth Rate of Atomic Layer Deposition of Noble Metals

We present mechanisms for atomic layer deposition of Ru, Rh, Pd, Os, Ir, or Pt metal from homoleptic precursors and oxygen. The novel mechanistic feature is that combustion of ligands produces transient hydroxyl groups on the surface, which can undergo Brønsted-type elimination of a further ligand or water from the surface. Each ligand therefore releases one electron for reduction of the metal. The growth reaction may be described as oxide-catalyzed redox decomposition of the precursor. To validate the mechanism against experiment, we derive analytical expressions for product ratios and the growth rate in terms of saturating coverages.