Ruthenium Layer Research Articles

High-Brightness and Low-Voltage Light-Emitting Devices Based on Trischelated Ruthenium(II) and Tris(2,2‘-bipyridine)osmium(II) Emitter Layers and Low Melting Point Alloy Cathode Contacts

Solid-state light-emitting devices (LEDs) were fabricated based on an amorphous film of Ru(bpy)3(ClO4)2 (bpy = 2,2‘-bipyridine) about 100 nm thick on indium−tin oxide (ITO) with printed low melting point alloys, such as Ga:In, Ga:Sn, and Bi:In:Pb:Sn, as cathodic contacts. A device with the structure of ITO (≤10 Ω/square)/Ru(bpy)3(ClO4)2/Ga:Sn produces a bright red emission (3500 cd/m2 at 4.0 V) centered at 660 nm. This new method of making contacts significantly simplifies the fabrication of an electroluminescence cell and has potential application in the production of LEDs by inkjet or microcontact printing. LEDs based on C12−Ru(bpy)3(ClO4)2, Ru(phenanthroline)3(ClO4)2, and Os(bpy)3(PF6)2 were also studied. Low melting point alloy contacts were also used with cells based on tris(8-hydroxyquinoline)aluminum.

Growth of ruthenium islands on Pt( hkl) electrodes obtained via repetitive spontaneous deposition

We have examined the ruthenium island growth on Pt(111), Pt(100), and Pt(110) surfaces resulting from repeated spontaneous depositions of ruthenium from a 1 mM RuCl 3 in 0.1 M HClO 4 solution. Scanning tunneling microscopy and cyclic voltammetry were used to characterize the multiple depositions. We found that the details of the island growth were strongly single-crystal substrate dependent. On Pt(111), after four depositions, approximately 30–35% of the surface is covered with large (2–12 nm) ruthenium islands of varying heights. About 65% of the islands surface is a monolayer high, while 25% consists of two ruthenium layers and 10% consists of three monolayers or higher. However, it was revealed via STM imaging, that on Pt(100) and Pt(110), the two and three dimensional growth of the islands is much lower. It was possible to obtain 40% coverage of ruthenium on Pt(100) with 92% of the island area a monolayer high, while the island size ranged from 0.5–4 nm. On Pt(110), the tendency to grow in three dimensions is even less, as 98% of the islands peppering the surface are a monolayer high. These results are discussed as they pertain to possible use of additive island-covered nanoparticles in methanol oxidation fuel cell catalysis.

Electrochemical and X-ray scattering study of well defined RuO 2 single crystal surfaces

Electrochemical and synchrotron surface-X-ray scattering measurements were performed on two low index faces, (110) and (100), of RuO 2 single crystal electrodes in a variety of solutions. The two crystal faces displayed uniquely different cyclic voltammograms and the structural changes associated with cyclic voltammograms were investigated with synchrotron surface-X-ray scattering measurements. In sulfuric acid solution, the cyclic voltammogram of the (100) surface exhibits a reduction signature near the hydrogen evolution potential. The reduction feature was found to be associated with an expansion of the top ruthenium layer approximately along the (110) direction. The same reduction feature was seen much less clearly at the (110) surface. However, the associated displacement of ruthenium atoms is very similar to that of the (100) surface, leading to the conclusion that the oxygen bonds on the surface are elongated by a chemical reaction of the oxygen atoms with hydronium molecules in solution. In NaOH solution, the cyclic voltammogram of the (110) surface indicates two clearly identifiable oxidation features near the oxygen evolution potential. We find that the oxidation features are associated with the clearly identifiable surface-structure changes and these structure models are presented. The structure models and corresponding charge-transfer amounts were consistent with the pH-dependent cyclic voltammograms and the super-nernstian behavior measured by adding phosphoric acid to the solution.

Electrochemical quartz crystal microbalance study of electrodeposited ruthenium

Voltammetric and electrochemical quartz crystal microbalance measurements have been used in the characterisation of surface electrochemical processes of electrodeposited ruthenium under the conditions of repetitive potential cycling in 0.5 M sulphuric acid solution. The stability of the electrodeposited ruthenium layer and the pseudocapacity of surface electrochemical reactions were measured as a function of potential window and number of cycles. Six different stages of oxide formation and reduction in cyclic voltammogram and cyclic voltmassogram of the first potentiodynamic cycle have been found and discussed. Mass losses or gains were detected depending on whether water from the layer or water from the bulk solution was consumed. Complex voltammetric and mass change behaviour was found when the potential was continuously cycled. Several types of non-stoichiometric surface reactions which include various ruthenium oxyhydroxide species and water are presented. The stability of the electrodeposited layer depends on whether ruthenium is reduced to the metallic state or only the Ru(III)/Ru(IV) transition is involved in the electrochemical process. In the Ru/RuO2 transition 26 ng of electrodeposited ruthenium was dissolved per one cycle. The stability was significantly enhanced when the potential range between 0 and 1.0 V was used. In that case only 18 ng of deposited ruthenium was dissolved after 5400 cycles at 0.5 Hz.

Photoelectrochemical decomposition of water using modified monolithic tandem cells

Photovoltaic tandem cells, consisting of a gallium indium phosphide (GaInP 2) homojunction grown epitaxially on a gallium arsenide (GaAs) homojunction with a Ga Astunnel diode interconnect, were modified with an additional top p-layer of GaInP 2. These cells were used as electrodes to photoelectrochemically decompose water into hydrogen and oxygen in 1M, 5M and 11M KOH electrolyte solutions. The hydrogen reaction was catalyzed at the semiconductor surface with a photoelectrochemically deposited thin layer of platinum and ruthenium. Gas chromatography and electrochemical experiments demonstrate that the modified tandem cells produce hydrogen and oxygen with a light-to-hydrogen conversion efficiency of up to 6%. Both the efficiency and the stability of these cells are discussed. © 1999 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.

Proton capture cross sections of the ruthenium isotopes

The proton capture cross sections of the stable ruthenium isotopes 96, 98, 99, and 104 have been measured by means of the activation method in the proton energy range between 1.5 and 3 MeV. Thin layers of natural ruthenium were irradiated at the Karlsruhe 3.75 MV Van de Graaff accelerator with proton beams of 20--50 \ensuremath{\mu}A. The activity induced by $(p,\ensuremath{\gamma})$ reactions was measured with a calibrated HPGe detector. In this way, six $(p,\ensuremath{\gamma})$ cross sections for populating ground states and isomers in four different Rh isotopes could be determined simultaneously with systematic uncertainties of typically 4--5 %. The fact that experimental data are almost completely missing in the $A>70$ region illustrates the need of checking and complementing the statistical model calculations which are so far the only data used in $p$ process studies.

Vacuum annealing characteristics of electron beam evaporated ruthenium contacts to n-GaAs grown by organometallic vapour phase epitaxy

High quality ruthenium Schottky barrier diodes were fabricated on organometallic vapour phase epitaxially grown n-GaAs, with a carrier density of 1 x 10 16 cm −3, by electron beam evaporation of ruthenium at a rate of 1 Å s −1. The annealing studies were carried out in vacuum over the temperature range from 225 °C to 600 °C. The electrical characteristics of the Schottky contacts were evaluated by standard current-voltage I–V and capacitance-voltage C–V measurements. The effective barrier height ϕ e I–V and the flat band barrier height ϕ b C–V of the as-deposited R u-n-GaAs Schottky contacts were 0.865 eV and 0.916 eV respectively. These barrier heights reached their respective maximum values of 0.925 eV and 0.955 eV after annealing at 450 °C. Auger electron spectroscopy results indicated that ruthenium forms structurally a very stable contact to GaAs, with no evidence of any chemical reactions between ruthenium and GaAs up to 500 °C. Very limited diffusion of arsenic through the ruthenium layer was observed after annealing at 400 °C. Diffusion of arsenic increased sharply after annealing at temperatures above 500 °C.

Electronic structure and magnetism of hexagonal iron layers

Using a tight-binding model, the recursion method and a self-consistent Stoner criterion to calculate the magnetic moments, we have investigated the magnetism of 6 hexagonal layers of Fe between ruthenium layers. In the ferromagnetic and antiferromagnetic states, we obtain a magnetic moment of about 2μ B per atom in the 4 inner iron layers and one dead magnetic iron layer at the interface. But in a ferrimagnetic state, a magnetic moment of 1.7μ B is obtained for the interface layer. Total energy has been computed and found lower than the paramagnetic state for all the three magnetic states. These are very close in energy, the most stable one being the antiferromagnetic state. To investigate the origin of the two dead layers, found experimentally, a study of the interface defects has been made, using a virtual crystal model.

Electronic structure of hexagonal iron layers

Using a tight-binding Hamiltonian, the recursion method and a self-consistent Stoner criterion to calculate the magnetic moments we have investigated the magnetism of 6 hexagonal layers of Fe between ruthenium layers on each sides. With ferromagnetic spin-polarization we obtain a magnetic moment of about 2μ B per atom in the 4 inner iron layers and one dead magnetic iron layer at the interface, but the densities of states of this layer shows an antiferromagnetic tendency. Allowing a reverse polarization of the interface layer, a magnetic moment of 1.7μ B is obtained for this layer. The two dead layers found experimentally by M. Maurer et al. and C. Liu and S.D. Bader may be related to interface defects such as substitutional Ru atoms or steps.

Oxygen evolution on an electrodeposited ruthenium electrode in acid solution —the effect of thermal treatment

The ruthenium layer galvanostatically electrodeposited on a titanium substrate is unstable and dissolves during anodic polarization at the potentials of the oxygen evolution reaction in 0.5 mol dm −3 sulfuric acid. Thermal treatment of the electrodeposited layer at temperatures between 450°C and 600°C in air stabilizes the electrode surface. The decrease of oxygen evolution current is attributed to the decrease in electrode area and to the loss in the electrochemical activity. The latter conclusion is supported by the increase of the Tafel slope from 30 to 50 mV dec −1 after thermal treatment.

Calalytic hydrogen evolution on ruthenium and platinum nuclei

It is shown that thin layers of platinum and ruthenium on mercury behave differently from nuclei of the same metals grown on a carbon substrate. The mechanism of hydrogen evolution is controlled by the direct discharge of H + in the case of platinum and ruthenium on mercury, the relative current densities into edge and top of the two dimensional layers being about 100:1. In contrast, the hydrogen evolution reaction on platinum is controlled under all conditions by diffusion of molecular hydrogen. The reaction on ruthenium, at which the coverage by H is lower than platinum, appears to be controlled by H · + H + + e → H 2

Electron beam decomposition of carbonyls on silicon

For pattern generation in the submicron range electron beam induced deposition of desired materials is expected to be a promising technique (1). Our investigations revealed carbonlys to be appropriate for this procedure. In the present study we demonstrate results on the growth of ruthenium and osmium layers formed by electron induced dissociation of ruthenium carbonyl Ru 3 (CO) 12 and osmium carbonyl Os 3 (CO) 12. A simple phenomenological model of surface interaction gives guidance for determination of the process parameters.

The deposition of thick ruthenium layers by ion plating

The deposition of thick ruthenium layers by ion plating

Catalytic hydrogen evolution on ruthenium and platinum nuclei

It is shown that thin layers of platinum and ruthenium on mercury behave differently from nuclei of the same metals grown on a carbon substrate. The mechanism of hydrogen evolution is controlled by the direct discharge of H+ in the case of platinum and ruthenium on mercury, the relative current densities into edge and top of the two dimensional layers being about 100:1. In contrast, the hydrogen evolution reaction on platinum is controlled under all conditions by diffusion of molecular hydrogen. The reaction on ruthenium, at which the coverage by H is lower than platinum, appears to be controlled by H·+H++e→H2