WO2004103036A2 - Ensembles electrode comportant des couches de metaux modifies, cellules pourvues de tels ensembles et procedes associes - Google Patents

Ensembles electrode comportant des couches de metaux modifies, cellules pourvues de tels ensembles et procedes associes Download PDF

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WO2004103036A2
WO2004103036A2 PCT/US2004/012790 US2004012790W WO2004103036A2 WO 2004103036 A2 WO2004103036 A2 WO 2004103036A2 US 2004012790 W US2004012790 W US 2004012790W WO 2004103036 A2 WO2004103036 A2 WO 2004103036A2
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electrode
metal oxide
layer
metal
layers
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WO2004103036A3 (fr
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Lewis G. Larsen
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Lattice Energy, L.L.C.
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/049—Manufacturing of an active layer by chemical means
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates generally to thin layer devices, for example such devices that may be used in electrical cells, and in one particular aspect to electrical or other reaction cells having components, for instance cathodes, incorporating multiple thin film metal and/or metal oxide layers .
  • electrolytic cells of various designs have been proposed which incorporate multilayer thin films.
  • Miley et al used flat stainless steel plates coated with multilayer thin films as electrodes for an electrolytic cell.
  • Such experiments are described in G. Miley, H. Hora, E. Batyrbekov, and R. Zich, "Electrolytic Cell with Multilayer Thin-Film Electrodes", Trans. Fusion Tech., Vol. 26, No. 4T, Part 2, pp. 313-330 (1994).
  • Still other electrolytic cells have employed coated electrodes of various forms.
  • U. S. Patent No. 4,414,064 entitled “Method For Preparing Low Voltage Hydrogen Cathodes” discusses a co-deposit of a first metal such as nickel, a leachable second metal or metal oxide, such as tungsten, and a nonleachable third metal, such as bismuth.
  • One feature of the present invention involves multilayer thin film devices, including for example electrode devices, incorporating one or more thin layers formed with a metal oxide or metal alloy.
  • metal oxide or metal alloy materials facilitates the creation of devices that present adjacent thin film layers exhibiting high Fermi energy differentials, thermal stability, and good interlayer bonding.
  • layers containing alkali metal oxides or alkaline earth metal oxides can be paired with adjacent layers of metals to provide high Fermi energy level differences between the layers.
  • improved thermal stability may be provided relative to that which would be achieved using corresponding atomic metals, especially in the case of alkali metals.
  • tin alloys can be used instead of pure tin, to provide enhanced thermal stability, structural matching and lower coefficients of thermal expansion, to improve device characteristics. Still other modified metal materials can be used to provide one or more of these advantages, as disclosed herein.
  • a wide variety of layer configurations may be utilized in multilayer thin film devices, with devices incorporating all metal oxide and/or metal alloy layers or combinations of oxide and/or alloy layers and elemental metal layers being contemplated as within the invention.
  • the oxides can be intercalated or sandwiched between pure metals, or vice versa.
  • inventive devices may include a plurality of adjacent metal layers at one level combined with intercalated metal/metal oxide layers at one or more other levels.
  • the present invention provides a multilayer thin-film device, such as an electrode construct useful for an electrical cell.
  • the device includes a substrate and a multilayer thin film structure on the substrate.
  • the multilayer thin film structure includes at least one metal layer and at least one metal oxide layer.
  • the metal oxide layer is relatively thin, for example having a thickness in the range of about 10 to about 500 Angstroms.
  • the metal oxide layer is desirably adhered to the metal layer through metal cations provided at the interface of the metal and metal oxide layers .
  • a metal layer is bonded to the metal oxide layer by a process which involves hydroxylating the metal oxide layer, and then bonding a metal layer to the hydroxylated metal oxide layer via first formation of cations of the metal at the terminal oxide locations, and then the deposition of additional elemental metal overtop the cations.
  • the present invention provides a device, such as an electrode useful for an electrical cell, that includes a substrate and a multilayer structure, e.g. a working electrode, bonded to the substrate.
  • a multilayer structure e.g. a working electrode, bonded to the substrate.
  • the multilayer working electrode or other structure includes at least one layer comprising an alloy of tin.
  • the present invention provides electrical or other reaction cells incorporating devices (e.g. electrodes) as described above.
  • the invention provides methods for preparing electrodes or other similar multilayer devices . These inventive methods comprise the step of providing a metal oxide layer; hydroxylating a surface of the metal oxide layer; and, thereafter applying a metal to the hyrdroxylated metal oxide layer so as to bond a layer of the metal to the metal oxide layer.
  • the invention provides methods for localizing a concentration of atoms (e.g. ions) of hydrogen or its isotopes .
  • the methods include the step of providing cell apparatus as described above, and causing the ions or other atoms to form a localized concentration within the electrode or other multilayer device. This concentration is preferably achieved by electromigration, but other methods of achieving concentrated areas of these atoms are also contemplated as being within the scope of the invention.
  • Figure 1 provides a schematic diagram of a cross-section of a preferred electrode device of the invention.
  • Figure 2 provides a schematic diagram of a cross-section of another preferred electrode device of the invention.
  • Figure 3 provides a schematic diagram of a cross-section of another preferred electrode device of the invention.
  • Figure 4 is a graph showing the relative solubility of hydrogen in various metals.
  • Figure 5 is a graph showing the relative permeability of hydrogen in various metals .
  • the present invention provides electrode constructs and other articles, electric or other reaction cells incorporating such constructs or devices, and methods of operating the cells.
  • thin films of oxide or alloy forms of metals are utilized in order to impart beneficial characteristics to multilayer thin film devices.
  • alkali and alkaline earth metal oxides can be used to provide materials with low Fermi energy levels. These materials can thus be matched with adjacent layers of metals having much higher Fermi energy levels to provide high Fermi energy level differences between the layers while also exhibiting acceptable thermal stability for use at relatively high temperatures, e.g. above about 200°C and often above about 300°C.
  • alloys of tin are used instead of pure tin, to provide enhanced thermal stability, structural matching and lower coefficients of thermal expansion, to improve device characteristics.
  • Electrode or other working structures having a wide variety of geometries.
  • working structures that are substantially planer, convex, concave, convoluted, or combinations of these and/or other geometries can be made in accordance with the invention.
  • the electrode or other working structure can be incorporated into a cell providing communication with a source of hydrogenous atoms (e.g. hydrogen and/or deuterium atoms) .
  • a source of hydrogenous atoms e.g. hydrogen and/or deuterium atoms
  • Such source may, for example, be a liquid, solid, gas or plasma substance that is in contact with the working structure or is otherwise capable of transferring the hydrogenous atoms into the working structure.
  • the electrode or other working structure may include unique layering properties in which metal oxide layers and/or tin alloy layers are combined with other metal layers.
  • These may include structures in which metal oxide or tin alloy layer (s) are intercalated or "sandwiched" between adjacent metal layers, or vice versa.
  • inventive structures may include a plurality of adjacently stacked metal oxide layers, a plurality of adjacently stacked tin alloy layers, or working structures that include one or more regions including a plurality of adjacently stacked metal layers and one or more other regions including one or more layers of metal oxide or tin alloy, e.g. intercalated between metal layers and/or in stacked configuration.
  • a multilayer structure with a single metal oxide layer intercalated between one or more metal layers can be made using the repeating sequence of "metal layer - metal oxide layer - metal layer - metal oxide layer ##; or, with the repeating sequence of "metal layer A - metal layer B - metal oxide layer - metal layer A - metal layer B - metal oxide layer ##.
  • a multilayer structure with more than one sequential layer of a metal oxide could be made using the repeating sequence of "metal layer - metal oxide stack - metal layer - metal oxide stack - metal layer "; or metal layer A - metal layer B - metal oxide stack - metal layer A - metal layer B - metal oxide stack ... " . It will be understood that these are illustrative examples of potential device configurations, and that others are within the spirit and scope of the present invention.
  • electrodes or other working devices incorporate a multilayer working electrode or other similar working structure, wherein at least one of the layers is comprised of a metal oxide.
  • the metal oxide is desirably provided as a thin film, having a thickness not exceeding about 500 Angstroms, for example ranging from about 10 to about 500 Angstroms.
  • Such thin films commonly possess properties that differ from those of a bulk oxide material.
  • such thin films exhibit dynamic structural rearrangements and re-constructions that occur at the surface of the interface between the thin film and an adjacent layer, or the thin film and an exposed environment (e.g. as an outermost layer exposed to a liquid, solid, gas, or plasma source of hydrogenous atoms) .
  • these reconstructed surfaces expose atoms of metals included in the oxide, for example alkali or alkaline earth metals, to an immediately adjacent thin film layer, for example a thin film metal layer.
  • metals included in the oxide for example alkali or alkaline earth metals
  • an immediately adjacent thin film layer for example a thin film metal layer.
  • the chemical and electronic environment at the interface in the immediate neighborhood of the exposed metal of the oxide layer approximates that of two pure or atomic metals in contact with each other across the interface (even though one side of the interface is actually an oxide) .
  • the local atoms can effectively experience very large differences in Fermi energies across the interface.
  • metal oxide layers are expected to provide effective access to a range of additional metal combinations exhibiting very large differences in Fermi levels between thin films (additional and beyond that currently available using two pure (elemental) metal layers) .
  • Oxides of metals such as alkaline metals and alkaline earth metals have, on average, much lower Fermi energies than other pure metals located "to the right" of those columns in the Periodic Table of elements.
  • a wide variety of alkali metal oxide and alkaline earth metal oxide materials as well as other metal oxide materials such as oxides of cadmium, cerium, cobalt, dysprosium, iron, hafnium, mercury, manganese, lead, thorium, and uranium, may be used to advantage in the present invention.
  • Appendices 1-4 provide several Tables noting changes in key physical and structural properties of desirable metals, such as those noted above, in going from the pure elemental form to the corresponding oxide form.
  • Appendix 5 provides a number of Tables showing preferred combinations of oxides with metals, respective lattice mismatches, and differences in Fermi energies. It will be understood that these Tables and the combinations shown are illustrative and not necessarily limiting of the present invention. In each case, the materials provide significant differences in Fermi energy levels while also contributing beneficial structural and beneficial attributes to working structures in which they are incorporated.
  • deposition techniques are used that permit fabrication of thin film multilayer structures in laminar growth modes that exhibit strong bonding at interfaces and thermal stability at likely operational temperatures, wherein the thin film multilayer structures incorporate layers of metal oxides, e.g. alkali metal oxides and/or alkaline earth metal oxides, optionally intercalated between thin film layers of pure or atomic metals.
  • Preferred deposition techniques will involve depositing metals atop a hydroxylated surface of a metal oxide layer. During this deposition the metal desirably reacts at the surface and forms metal cations with the terminal oxide positions on the surface of the metal oxide layer. These metal cations bind strongly to the underlying metal oxide layer, and provide strong binding to metallic atoms deposited above. In one specific preparative process, the following steps are undertaken:
  • a metal oxide surface that is capable of hyroxylation is polished and cleaned; desirably, the metal oxide surface has not been ion sputtered; (2) the polished/cleaned surface of the oxide layer or substrate is exposed to water to fully terminate the surface with hydroxyl groups, typically with the water being exposed at greater than 1 Torr; (3) surface impurities are removed from the hydroxylated surface by oxygen plasma cleaning (this will not removed the surface hydroxyl groups) ;
  • a metal is deposited on top of the hydroxylated urface in a vacuum and desirably at room temperature using magnetron sputtering equipment, wherein the metal reacts at the surface and forms metal cations within the terminal oxide layer; metal cations are thereby deposited at the surface which are strongly bound to the lower metal oxide layer; such deposition processes are desirably conducted under ultra high vacuum conditions, for example at pressures of lO-- ⁇ to lO-- ⁇ Torr.
  • steps 1-6 may be repeated as many times as desired.
  • processing used in these techniques reference can be made for example to "Laminar Growth of Ultrathin Metal Films on Metal Oxides : Co on Hydroxylated (X-AI2O3 (0001) " S.A. Chambers, T.
  • the invention provides thin film metal oxide layers deposited and interleaved or intercalated with pure metals such as palladium, titanium, nickel, or other metals that are typically selected for their capacity for loading with hydrogen or its isotopes, including deuterium.
  • pure metals such as palladium, titanium, nickel, or other metals that are typically selected for their capacity for loading with hydrogen or its isotopes, including deuterium.
  • Other criteria which are used for selecting metals include those discussed in the passages below, for example possession of appropriate structural (e.g. lattice constants, space group, etc.), physical (e.g. melting point, coefficient thermal expansion) , and chemical (valance electron properties and bonding orbitals) characteristics.
  • melting points such that thin film structures containing them may not be structurally stable at elevated temperatures as required in many applications.
  • oxides of alkali and alkaline earth metals have substantially higher melting points than pure metals of the same elements .
  • an ultra thin oxide buffer layer may be created by surface oxidation of a metal layer.
  • the oxidation of the metal layer to create an oxide buffer layer is preferably conducted so as to form an oxide layer that is extremely thin, for example having from about 1 atomic layer to about 25 atomic layers.
  • This oxidation step can be conducted for example by annealing the metal layer in an oxygen-containing environment such as air or an argon-oxygen mixture, under pressure, temperature and other conditions, and for a duration, necessary to create the desired oxidized buffer layer.
  • a layer of the desired metal oxide can be deposited.
  • surface hydroxylation and reaction with metal may be utilized, as discussed above.
  • a metal oxide layer can be deposited directly on top of an underlying metal layer by appropriate techniques such as pulsed laser deposition (PLD) or molecular beam epitaxy (MBE) .
  • PLD pulsed laser deposition
  • MBE molecular beam epitaxy
  • successive layers of metal oxides will be deposited within an electrode structure. This may be accomplished, for example, by depositions techniques such as PLD or MBE, as discussed above. For additional information as to these techniques, reference can be made for example to "Epitaxial oxide thin films by pulsed laser deposition: Retrospect and prospect", Hedge, M.S., Proc . Indian Acad. Sci . (Chem . Sci . ) , Vol. 113, Nos.
  • a "Group I" combination of a preferred metal oxide with a preferred metal is defined as a combination that possesses the following four characteristics:
  • the lattice mismatch between the lattice constant of the Preferred Metal (in the appropriate planar orientation relative to the thin film oxide layer) and the lattice constant of the metal oxide structure is less than 11.0%
  • the lattice constant of the 0-0 sublattice represents the average distance between the oxygen atoms in the growth plane of the metal oxide, such as 001 for example, oriented parallel relative to the underlying thin film of metal on which the metal oxide is deposited;
  • the structure of the metal oxide is an Anti-Fluorite, Fluorite, NaCl structure, or pervoskite structure
  • the thin film of the metal oxide has a thickness of between 2 and 100 monolayers or from about 10 Angstroms to about 500 Angstroms;
  • the difference in Fermi Energys between the selected metal layer and "target" metal in the selected metal oxide layer is greater than or equal to about 0.50 eV.
  • the electronic structure of metals is such that the allowed electron energy states within the metallic atoms are occupied up to a maximum energy called the Fermi energy, EF.
  • EF Fermi energy
  • the energy difference between the Fermi level and zero potential energy is the work function, phi.
  • the Fermi level and work function of a given material are highly correlated with each other, and the selection of two materials to maximize Fermi energy differentials will likewise be generally expected to maximize work function differentials.
  • the use of relatively thin metal oxide layers takes advantage of structural rearrangements and relaxations, as noted above.
  • relatively thin metal oxide layers intercalated with comparatively thicker metal layers can help reduce the effects on the stability of the heterostructure arising from differences in the coefficients of thermal expansion (CTE) of the layers.
  • metal/metal oxide combinations when considering metal/metal oxide combinations, the following considerations may be taken into account : A. Given the lattice constant of a thin film layer of particular metal, select a metal oxide that forms a Group I combination with that metal on which the thin film oxide layer is to be deposited (See Tables in Appendix 1 for lists preferred metals form Group I combinations with selected preferred oxides) .
  • a second, third, fourth, or fifth successive layer of a metal oxide is to be deposited on top of a first layer of a metal oxide (that is in turn deposited on top of a metal) , then one may for example use the "oxide sandwich" methods taught hereinafter.
  • metal oxides including those not only of alkali and alkaline earth metals but also others, may be advantageous in several respects.
  • oxides of metals can have melting points higher than those of the corresponding metals.
  • the metal oxides can offer greater structural compatibility with thin film layers that are adjacent, including for example other pure atomic metal layers.
  • the lattice constant for a given metal oxide may present a more desirable combination than that of the corresponding metal, in respect of an adjacent metal or metal oxide layer.
  • pure ccp Ca with a lattice constant of 558.84 pm is transformed to CaO which has a NaCl ccp structure with a lattice constant of 416.84 pm.
  • This latter value is a closer match to a large number of metals that may be used in electrodes of the invention.
  • Use of the oxide form of a metal may also change a crystalline structure from a hep or orthorhombic structure to a ccp NaCl or ccp Fluorite structure that is more compatible and less strained when combined in thin film heterostructures with bcc or ccp structure typical of many metals (e.g. Cd with an hep structure is transformed to CdO which has a ccp NaCl structure) .
  • Complex oxides may also be used in the invention, and can be sandwiched between other oxide layers in a given electrode structure.
  • complex oxides such as PbTi ⁇ 3 , HgB»2CaCu20g+6, Dy2C>3 , or DyBa2CaCu2U _ x can be incorporated in thin film heterostructures by layering them in sandwiches using SrTi ⁇ 3 deposited between a given complex oxide and a selected structurally compatible metal.
  • Figures 2 and 3 illustrate two types of three-layer and five-layer sandwiches that can be fabricated to incorporate layers of complex oxides in thin film heterostructures combining metals and oxides.
  • Figure 2 illustrates a working device 10A, potentially an electrode, that incorporates a sandwich of three layers of intercalated oxides .
  • Certain components of the device 10A of Figure 2 can correspond to those discussed in connection with Figure 1 herein, and are similarly numbered. These include a substrate 11, adhesion layer or structure 12 (which may include a plurality of layer components 12a-12d) , working structure 13, and optional barrier layers 14a, 14b, and 14c and thermoelectric element 15. For the sake of brevity, the relevant discussions of these components will not be repeated here.
  • Device 10A also includes a metal layer 16 atop the adhesion structure 12, followed by three sequential layers of metal oxide.
  • layers 17a and 17b in the illustrated embodiment are SrTi ⁇ 3
  • layer 18 sandwiched therebetween is a metal oxide material selected from PbTi ⁇ 3 , HgB «2CaCu20 ⁇ + g and Dy2 ⁇ 3 _
  • Additional metal layers 19 and 20 can optionally be provided atop SrTi0 3 layer 17b.
  • FIG 3 illustrates a working device 10B, potentially an electrode, that incorporates a sandwich of five layers of intercalated oxides.
  • a metal layer 16 again is bonded to the adhesion structure 12, followed by a region having five sequential layers of metal oxides.
  • a layer 21a of SrTi0 3 is positioned atop metal layer 16, followed by a layer 22a of Dy 2 0 3 .
  • a layer of DyBa 2 CaCu 2 0 7 _ x 23 is centrally located in the metal oxide stack, followed by another layer 22b of Dy 2 0 3 and then another layer 21b of SrTi0 3 .
  • metal layers may optionally then follow, including for example metal layers 24 and 25.
  • Tin alloys to be used in the invention are desirably those that have melting points higher than that of Tin itself (232°C) .
  • Preferred alloys also grow in isometric structures (cubic variance) that are compatible with larger numbers of metals and oxides as discussed elsewhere herein as compared to tetragonal structures .
  • These alloys will also be capable of deposition in thin films on tope of metals and/or oxides as discussed herein using suitable techniques such as sputtering.
  • preferred alloys of Tin will have coefficients of thermal expansion that are significantly less than that of pure Tin, which is about 30.
  • Atokite (Pd,Pt) 3 Sn ; composition is Pd (47.47%); Pt (29.00%); Sn (23.53%)
  • Tin alloys with metals or oxides will be referred to herein as Group II combinations. These combinations will generally possess the following characteristics .
  • the lattice mismatch between the lattice constant of the Tin alloy and the lattice constant of the of the metal or metal oxide (in the appropriate growth orientation relative to the Tin alloy) should preferably be less than 11.0%.
  • the lattice constant of the 0 - 0 sublattice represents the average distance between the oxygen atoms in the preferred growth plane of the metal oxide
  • the structure of the metal, and/or metal oxide should preferably be some type of isometric (cubic variant) structure, as is the Tin alloy;
  • the oxide should have a thickness of between 2 and 100 monolayers or roughly from 10 Angstroms to 500
  • the metal combination should preferably not be a member of the elemental composition of the alloy.
  • thin film layers of Pd or Pt should not be included in combinations with Atokite or Rustenburgite because those Tin alloys contain Pd and Pt as an integral part of their composition. This restriction is imposed because sharp interfaces between adjacent layers of thin films are desirable. Permitting some of the same elements on both sides of a interface between thin films would likely allow too much interdiffusion and further alloying to occur across the interface at typical operating temperatures in the contemplated applications, which would conflict with the preference for sharp interfaces .
  • any suitable technique can be utilized to deposit thin films of Tin alloys.
  • PVD magnetron sputtering can be used to deposit alloy films containing Tin. This strategy can be used to modify the effective lattice constant of the thin film to reduce mismatches in lattice constants as compared to pure materials, and/or to create thin film layers in a complex multilayer heterostructure with special physical properties.
  • the equation expressing Vegard's Law uses simple linear interpolation to yield a more complex form that is described along with supporting references in Herman, M.A. , "Silicon-Based Heterostructures: Strained-Layer Growth by Molecular Beam Epitaxy", Cryst. Res. Technol . , 34, 1999, 5-6, 583 - 595. In many cases, deviations of predicted effective lattice constants from the law are not large, i.e. on the order of 3%.
  • Tin alloys will desirably be provided in layers having a thickness from about 10 Angstroms to about 10,000 Angstroms.
  • CTE and melting point were estimated through the computation of a simple weighted average based upon the atomic weight percent of the reported composition of the alloy. It is understood that these values are therefor only approximate; however, such approximate values are sufficient to guide selection of appropriate materials in accordance with the invention. Lattice constants were estimated in some cases using Vegard's law, as well.
  • Device 10 includes a substrate 11 made of a suitable material.
  • the substrate 11 is preferably electrically non-conductive, for example constructed of non-conductive materials such as crosslinked polymers, ceramics, or glass.
  • Substrate 11 is preferably made of a silicon-containing material. Other suitable substrate materials may also be used within the scope of the present invention as will be understood by the skilled practitioner.
  • Device 10 includes an adhesive coating 12 which may be formed from a single layer of material or multiple layers of material, e.g. 12a-12d as illustrated.
  • Adhesive coating 12 serves to more stably bond a working electrode structure 13 ultimately to the electrode substrate 11.
  • Working device 13 may be composed of a single thin film metal or metal oxide layer, but preferably includes multiple thin film layers, in many cases including at least one conductive (metal or metal oxide) layer and optionally also including one or more non- conductive layers.
  • the working electrode 13 may include layers 13a-13c as shown in Figure 1. In this regard, it will be understood that the working electrode or other device 13 may contain even more thin film layers . In many applications of the invention, it is expected that the working device will include from about 2 to about 50 thin film layers.
  • the device 10 also optionally includes barrier layers 14a-14c covering the top and sides of the device.
  • the device 10 will also include a heat-to- electricity converter such as a thermoelectric or thermoionic element 15 in heat transfer relationship with the multilayer working structure.
  • adhesive coatings as discussed above and elsewhere herein may not be used.
  • a metal layer may be deposited directly atop the oxide using techniques as described herein to deposit a metal layer directly atop a hydroxylated surface of a metal oxide layer, e.g. using steps 1-6 as outlined above.
  • metal oxide-metal oxide combinations may be incorporated into multilayer working electrode structures as an alternative to, above, below, or in between, the metals and metal combinations set forth in such patent application and below.
  • electrode or other mutlilayer working devices will include an adhesive component including copper layer on top of a tantalum nitride/ ⁇ -tantalum combination adhered to a substrate.
  • the electrode will comprise the silicon- containing substrate (11) , a silicon dioxide layer (12a) , a tantalum nitride layer (12b) , an -tantalum layer (12c) , a copper layer (12d) , and the working electrode and barrier layers 13 and 14.
  • metals other than copper are bonded to such an underlying structure.
  • Preferred materials for these purposes will be metals or metal oxides that are amenable to deposition as thin films, and which have melting points greater than 150°C.
  • substitutes for copper in this combination preferably minimize the differences between the types of crystalline lattice structures (for example bcc on hep vs. bcc on bcc), and minimize the differences in the lattice constants, as for example expressed in terms of percent mismatch, with the underlying tantalum layer (desirably ⁇ -tantalum) .
  • Materials to be deposited atop the tantalum layer will also preferably exhibit thermal expansion characteristics such that the difference in the coefficient of thermal expansion (CTE) between the tantalum layer and the selected metal is no greater than that exhibited by the ⁇ -tantalum/copper combination.
  • metals having an ability to form nitrides or which possess other characteristics indicating electronic and/or chemical compatibility with ⁇ -tantalum.
  • the material will be selected for its ability to either absorb hydrogen or deuterium in solution and/or to form hydrides, or in some cases to serve as a diffusion barrier to hydrogen and/or deuterium.
  • a first group of preferred materials to deposit on top of ⁇ -tantalum includes certain metals presenting a lattice constant mismatch less than 11% relative to ⁇ -tantalum. Included in this group (Group 1 Copper Substitutes) are the following metals:
  • Another set of preferred metals for deposition atop of ⁇ - tantalum present a lattice constant mismatch from 11 to 21% relative to ⁇ -tantalum. These preferred metals are either normally in bcc/ccp structure or wherein a bcc/fcc/ccp/bct allotrope is known. Additionally, these metals are known to form nitrides.
  • This group of metals (Group 2 Copper Substitutes) includes the following:
  • Electrode or other structures having metal interlayers from about 10 Angstroms to several thousand Angstroms thick, composed of TaN/ ⁇ -Ta/M, where M is a metal other than copper.
  • M is a metal other than copper.
  • preferred structures will exhibit thermodynamic stability within the temperature ranges for operation, and will strongly adhere to silicon-based substrates.
  • preferred structures will possess diffusion barrier properties to prevent poisoning of the substrate by the metal deposited atop the ⁇ -tantalum.
  • one practiced in the area can first select one of these preferred materials, and then use thin film deposition techniques and conditions appropriate to manipulate film growth conditions to deposit a bcc, fee, ccp or other closely-matched psuedomorphic structure atop the ⁇ -tantalum.
  • These and other design strategies can be used to minimize effective lattice mismatches, create sharp interfaces between metal layers, and achieve desired stability in the finished construct.
  • Multilayer electrodes of the invention can be of any suitable shape.
  • they may include planar or curvilinear structures, provided oh a single, monolithic structure or on multiple structures such as pellets or beads of spherical or other shapes .
  • the electrodes are created by depositing multiple sequential thin film layers of selected materials on top of insulating, preferably silicon-containing substrates. In use, these electrodes will be subjected to substantial heat and thermal cycling stresses, for example as a result of ohmic heating from the passage of current through the electrode materials and/or exothermic reactions.
  • thin film electrodes of the invention will be expected to operate at temperatures ranging from about 100°C to about 300°C when using aqueous electrolytes, and from about 300°C to about 1,000°C or more for other systems such as gas-phase systems, molten salt electrolytes, or "dry” electrolytes using solid metal hydrides .
  • Preferred electrodes of the invention will also be constructed so as to avoid substantial interdiffusion of materials between thin film interfaces.
  • preferred electrodes will be designed to avoid prolonged operation at temperatures higher than about 2/3 of the melting point of the material with the lowest melting point in the thin film structure.
  • preferred metals for incorporation in thin films of electrodes of the invention will have melting points greater than about 150°C. This design feature is illustrated in the following table, which suggests subsets of materials for multi-layer thin film electrodes that are desirable for use in applications sustaining a given maximum operating temperature . Table 1
  • ⁇ Selecting correctly from a variety of different deposition, alternative triggered growth modes, and processing techniques (e.g. choosing between conventional sputtering versus molecular beam epitaxy for deposition, or vacuum annealing versus annealing under a gas between steps) to choose the right technique for a particular combination of electrode materials and specific application requirements that can achieve the desired results. For example, use of known surfactants during surface film growth can improve epitaxy and resulting adhesion. ⁇ Selecting combinations of thin film materials in order to incorporate other particular desired properties and/or requirements such as: melting point, Fermi Energy differences, solubility of hydrogen and/or deuterium, conductivity, coefficient of thermal expansion, ferromagnetic or antiferromagnetic layers, in a given electrode design.
  • ultra-thin interlayers also called “buffer layers”; these may have a thickness ranging from several monolayers up to approximately 30 atomic monolayers of a material) as a "work around” technique, where necessary, to promote abrupt interfaces between specific thicker interlayers of other thin film materials (ranging from approximately 100 Angstroms up to several thousand Angstroms in thickness) that would otherwise be less compatible when in direct contact with each other.
  • structural strain can be reduced by creating a multilayer structure that incorporates an ultra-thin, compatible interlayer with a lattice constant that is intermediate between two other materials .
  • Chemical Vapor deposition includes Low Pressure CVD, Plasma Enhanced CVD, Metalorganic CVD (MOCVD) , Ultrahigh Vacuum CVD (UHV CVD), and metalorganic atomic layer deposition (MOALD)
  • MBE Molecular Beam Epitaxy
  • VPE Vapor Phase Epitaxy
  • MBE is particularly attractive for metals such as Cu and the Cu substitutes noted above, because MBE can provide hetero-epitaxy at temperatures close to room temperature, thus virtually eliminating the problem of interdiffusion at thin film interfaces during electrode fabrication.
  • One other advantage is that many epitaxial techniques can achieve very high growth rates of material.
  • Electroplating or Electrodeposition ED is known to be a particularly good technique for copper, gold, and nickel and other noble metals . It is known that copper can be electroplated on top of a PVD copper seed layer.
  • Electroless Plating Deposition plating of metals on metals via an aqueous, autocatalytic chemical reduction reaction that does not require external applied current like electroplating. Working temperatures are 30° to 80°C; coverage is not sensitive to substrate geometry; and the process deposits dense thin films having little or no stress. Known to be especially good for depositing metals such as Cu, Ni , Pd, Ni on Al, Cu on Ni on Ti, Au, Rh, Ag, Co, and Fe.
  • ⁇ Displacement Plating Deposition after deposition of a sufficiently thick layer of a first metal (e.g. copper) on an electrode, it is immersed in a bath containing dissolved ions of a metal more noble than the deposited metal (copper) such as Ag, Au, Pt, Pd,
  • Pulsed Laser Deposition Pulsed Laser Deposition (PLD) : is an efficient, cost-effective method to deposit high-quality thin films by utilizing a technique called laser ablation. In this deposition method, a high-power pulsed laser vaporizes a small amount of material on the surface of a selected target, creating a plume of material in the form of a plasma that is ejected from the surface of the target.
  • Evaporated material from the resulting vapor plume (comprised of neutral atoms, positive and negative ions, etc) is then guided and deposited onto the surface of a selected substrate placed in the pulsed laser deposition chamber.
  • the amount of vaporized material is a function of the laser pulse parameters employed; as a result, the thickness and coverage area of the PLD film can be very accurately controlled.
  • PLD is very flexible and can be used to deposit a wide range of materials from polymers to metals, it is especially preferred for stochiometric deposition of either simple oxides or complex, multi-component oxides.
  • Several unique characteristics of PLD are the deposited particles high kinetic energy (up to -100 eV) and the wide deposition temperature range (0 - 1000° C) . Key properties of thin-films made via PLD are very controllable; films can be deposited as extremely smooth and amorphous layers, or as highly crystalline near-epitaxial structures, depending on specific choices of various deposition parameters.
  • Thermal Growth or Oxidation oxidation of substrate surface in oxygen-rich atmosphere
  • Annealing modification of film surface structural properties via heating, recrystallization, and cooling under various levels of vacuum and/or under specific gases and air at various partial pressures and elevated temperatures to reduce lattice strain, control grain size, control statistical distribution of grain sizes, and modify properties of grain boundaries .
  • the equation expressing Vegard's Law uses simple linear interpolation to yield a more complex form that is described along with supporting references in Herman, M.A. , "Silicon-Based Heterostructures: Strained-Layer Growth by Molecular Beam Epitaxy" , Cryst. Res .
  • spin valve structures can be incorporated in "upper" layers of electrodes of the invention, such structures being comprised by pairs of ferromagnetic layers (e.g. Co) separated by a nonmagnetic conducting film such as Cu or Pd, creating an intermediate Co/Cu/Co/Cu... or Co/Pd/Co/Pd.... structure in "upper" layers of an electrode taught by the Invention.
  • ferromagnetic layers e.g. Co
  • nonmagnetic conducting film such as Cu or Pd
  • spin valve structures can be incorporated in an electrode using the methods disclosed herein relating to materials selection, deposition, and processing.
  • Spin valve or any other layered structures with special properties may comprise some or all of the "upper” layers of an electrode taught by the Invention.
  • Ion implantation and/or rapid solidification can also be used to create unusual alloys that contain "...nanosized inclusions of elements that are [normally] insoluble in the matrix.”
  • This strategy can be used to fabricate electrodes using metals that form relatively few compatible pairs with other metals.
  • metals include: Be, Ce, Mg, Th, and Tl .
  • thallium can be implanted into aluminum (Al) as sub-10 nm inclusions that adopt the fee structure of the aluminum matrix (see: Johnson, E., “Multiphase and Multicomponent Nanoscale Inclusions in Aluminum” , Philosophical Magazine Letters, 1993, 68, 131 - 135).
  • this electrode thin film fabrication strategy involves deliberate triggering of strained and/or psuedomorphic growth during deposition.
  • epitaxial growth of B on top of A can create a strained and/or psuedomorphic regime in which B adopts the in-plane lattice spacing of A.
  • Elastic energy is accumulated up to a critical thickness for which plastic relaxation takes place, which is typically accompanied by a change in the growth mode.
  • strained or psuedomorphic structural transitions include hep to bcc in Zr, bcc to hep in Nb, fee to hep in Al, and hep to fee in Ti .
  • fee Ti can be grown successfully on top of fee Al(100) surfaces in films up to 5 monolayers thick, in spite of a 22% lattice mismatch "on paper" (see: Smith, R.J. et al,
  • this technique uses a third atomic species (that is not being deposited on, or being incorporated in, a surface) to mediate the growth of a metal B being deposited on top of another metal A.
  • Properly selected surfactants encourage surface "wetting" and orderly 3D layer-by-layer growth rather than the formation of 2D and 3D "islands" (Volmer-Weber growth) of the metal that is being deposited on the surface of A. It is desirable to avoid islanding during deposition and surface growth if possible, because it can lead to strain-enhanced diffusion (which reduces the "sharpness" of the interface between A and B) and/or create defects and dislocations that can weaken structural integrity and adhesion at the interface. Surfactants achieve their effect by lowering the surface energies of both A and
  • Electrode constructs including a copper layer, optionally itself atop a tantalum nitride/ ⁇ -tantalum combination, also including at least one and preferably several metal layers and/or metal oxide layers deposited on top the copper layer. Similar to the selection of copper substitutes as disclosed above, those skilled in the art may consider the following factors when selecting a material for deposition on top of copper :
  • ⁇ Preferred materials will allow deposition as thin films through some known deposition technique and method, and ⁇ Candidate materials will preferably have melting points greater than 150° C, and ⁇ Candidate materials will be chosen where possible to minimize the differences between types of crystalline lattice structures (e.g. bcc on hep versus bcc on bcc), and relative values of lattice constants expressed in terms of % mismatch, in comparison to those of copper, and ⁇ Candidate materials for deposition on top of copper will preferably not have differences in coefficients of thermal expansion ("CTE") in comparison to copper that are larger than the difference in CTE between ⁇ -tantalum and copper, and
  • CTE coefficients of thermal expansion
  • ⁇ Preferred materials will have the ability to form nitrides, indicating some chemical compatibility with copper, and ⁇
  • a candidate material desirably have the ability to either absorb hydrogen/deuterium in solution and/or form hydrides, or serve as a diffusion barrier to hydrogen/deuterium.
  • the following metals constitute a preferred group for deposition on top of copper, presenting a lattice constant mismatch of less than 11%.
  • the metal is either normally in bcc/ccp structure or a bcc/fcc/ccp/bct allotrope is known, and the metals are known to form nitrides.
  • Group III the percent lattice mismatch and the Fermi energy difference are given in relation to copper.
  • the working electrode will preferably includes a plurality of thin metal and/or metal oxide films, including at least two different types of metals and/or metal oxides.
  • These multi-layer working electrodes can be relatively simple or comparatively complex, and advantageously will be characterized by a- specific sequence of thin metal and/or metal oxide layers.
  • the particular set or sequence of thin metal and/or metal oxide layers selected for the working electrode will depend upon several factors including, for example, the overall physical, electrochemical, and electronic characteristics desired for a particular electrode application.
  • Parameters that may be considered in this regard include the need to survive particular sustained operating temperatures, the need to maximize hydrogen or deuterium loading rates or levels, resistance to hydrogen embrittlement, the incorporation of intermediate ferromagnetic or anti- ferromagnetic layered structures, the incorporation of intermediate heavy electron structures, and the like.
  • the following table sets forth metal-metal combinations which are expected to be preferred.
  • the left column of the table shows a given metal material
  • the center column shows a first group of combinations with that metal material wherein the percent lattice constant mismatch among the two metals is less than 11%
  • the right column shows a second group of metals wherein the lattice constant mismatch among the two metals is between 11% and 21%.
  • neodymium forms more Group 3 combinations (lattice constant mismatch less than 11%) than any other of the identified metals.
  • Copper and erbium both form the second-largest number of Group 3 combinations, underscoring copper's advantageous use as a layer, including an underlying base layer, in thin film structures.
  • neodymium is preferred, followed by copper, with the next tier including niobium, ⁇ -tantalum, and ⁇ -titanium.
  • the next tier including niobium, ⁇ -tantalum, and ⁇ -titanium.
  • niobium is preferred, followed by copper, with the next tier including niobium, ⁇ -tantalum, and ⁇ -titanium.
  • Group IV combinations There is also a large cluster of fourteen elements that form six Group IV combinations .
  • the selected metals identified cluster into two broad assemblages separated by a relatively wide gap (from 6 to 10 total combinations) .
  • those metals identified in Table 3 above occurring in the first assemblage, having nine or more total combinations (Group 3 + Group 4) form an additional preferred set of materials for use in the invention.
  • electrodes of the invention will be loaded with hydrogen isotopes such as hydrogen, deuterium or tritium, when used in electrochemical cells or otherwise.
  • hydrogen isotopes such as hydrogen, deuterium or tritium
  • Hydrogen loading will commonly involve the dissociation of hydrogen or deuterium molecules at the surface of the metals, after which hydrogen or deuterium atoms dissolve exothermally or endothermally, and diffuse into interstitial sites within the metal lattice as a solid solution.
  • lattice constants tend to increase (e.g. roughly linearly) and parallel with high hydrogen or deuterium loading ratios.
  • the values of the lattice constant for a given metal can change relatively abruptly, for instance, at the onset of hydride formation.
  • structural problems can arise at metal interfaces. For example, problems may occur when otherwise acceptably matched lattice constants for two different metals at a thin film interface change at radically different rates during the loading process. This may eventually result in a lattice constant mismatch that is unacceptably high, which in turn may compromise adhesion and stability of thin film interfaces when a desired, steady-state hydrogen/metal ratio and temperature are reached.
  • Table 4 sets forth calculated percent changes in the total volume of a metal as a result of increases in the lattice constant for a hypothetical cubic lattice structure. These values may be used as a guide by those skilled in the art when evaluating metals for incorporation into working thin film electrodes of the invention. Table 4
  • hydrogen loading can also cause significant alteration of a metal's structural space group and/or lattice packing arrangement. These changes may significantly impact adhesion and stability of thin film interfaces.
  • Loading of hydrogen isotopes and metals may also in some cases cause embrittlement, which involves a significant reduction in the structural integrity of specific metals, sometimes manifested by the development of macroscopic stress-related cracks, avoid formation, blistering, or fracturing along grain boundaries . Loss of mechanical strength and structural failure may result.
  • the change in lattice constant experienced for a given level of hydrogen isotope loading may be measured empirically or estimated based upon data for other similar metals. For most metals, it is expected that the percent increase in lattice constant of simpler hydrides of the form in M y H x may not substantially exceed values of about 4% to 7% for loading ratios that finally saturate at values well below 1.5.
  • This range includes the likely maximum hydrogen isotope/metal ratios for a number of preferred metals herein including palladium (which at maximal loading has a hydrogen/metal ratio of approximately 1) , titanium, and 7 out of the 8 phases of Niobium. Niobium's and Zirconium's ⁇ -phases maximize at a hydrogen/metal ratio of nearly 2.
  • lattice constants may increase non-linearly above hydrogen isotope/metal loading ratios above about 1.2, for example, in the case of certain hydrides of the form Ml y M2 z H x , where Ml and M2 are metals .
  • FIGS. 4 and 5 and Table 5 below set forth hydrogen solubility and hydrogen permeability for selected preferred materials for use in working electrode layers of the invention, and are illustrative of the types of data utilizable by those skilled in the art in preparing multilayer thin film electrodes of the present invention.
  • copper has a comparatively low affinity for dissolving hydrogen and deuterium and for forming hydrides , and a comparatively high coefficient of thermal expansion (17.5) .
  • metals directly on top of copper that will load hydrogen or deuterium to a comparatively higher hydrogen/deuterium to metal ratio than copper, that possess smaller lattice constants than copper prior to loading, and that have lower coefficients of thermal expansion than copper.
  • preferred metals for deposition on top of copper include niobium, nickel, tantalum, titanium, vanadium, and zirconium.
  • tantalum will be incorporated in adhesion or base layers . Tantalum is known to be susceptible to embrittlement when loaded with Hydrogen isotopes . In accordance with another aspect of the invention, such tantalum-containing layers will be protected against hydrogen embrittlement by overlying layers that are resistant to hydrogen isotope diffusion.
  • the tantalum-containing layer is protected by a layer of oxygen-free copper, also known as electronic grade or magnetron grade oxygen-free copper. Suitable sources of such copper include, for example, Mitibishi Materials Corporation under the brand descriptions of "MOF for Magnetron" and "MOF for super conductivity" .
  • Oxydative-free Copper is sold as a Zirconium-oxygen-free- Copper alloy developed by Thatcher Alloys, Ltd., United Kingdom, known as "Outokunpu Zirconium Copper Zrk015" (Zirconium content of 0.15%).
  • metals from the above-disclosed copper substitutes may be selected according to their relative solubility, permeability, affinity and embrittlement with respect to hydrogen. For preferred metals, these values will not be significantly higher than, and ideally less than, those of copper.
  • molybdenum and tungsten are preferred metals for forming barrier layers protecting tantalum against hydrogen embrittlement, as well as having lattice-constant mismatches with ⁇ -tantalum less than 11%.
  • Iridium, osmium, platinum, rhenium, and rhodium constitute a second preferred group of metals for forming such a protective layer, while having a lattice-constant mismatch of 11% to 21% relative to ⁇ -tantalum.
  • the hydrogen-embrittlement-protecting material can be applied to ⁇ -tantalum using displacement plating deposition.
  • an ultra thin layer of copper may first be deposited on top of ⁇ -tantalum using techniques such as PVD, CVD, MVE, or VPE. This ultra thin layer of copper can then be removed and replaced with the selected metal by displacement plating deposition. The resulting ultra thin layer of metal would serve as a seed layer for the deposition of addition atomic mono-layers of the selected metal through techniques such as PVD, CVD, MVE, VPE, electroless plating, or electro-plating thin film deposition methods . The remainder of the electrode structure can then be prepared as described herein.
  • two or more layer of the same or different protective metals can be deposited over the top of the tantalum-containing layer.
  • a hydrogen-diffusion/permeation- resistant metals selected from those disclosed above for deposition on top of copper, can be used.
  • iridium, platinum, and rhodium are relatively resistant to hydrogen permeation/diffusion, and have a lattice-constant mismatch of less than 11% relative to copper.
  • gold, molybdenum, silver, and tungsten exhibit lattice-constant mismatches of 11% to 21% relative to copper, and are relatively resistant to hydrogen permeation/diffusion.
  • additional factors in the metal selection may include maximization of Fermi energy differences between film layers (preferably presenting a Fermi energy difference of greater than about 0.5, more preferably greater than about 1), minimizing inter-diffusion, and other factors as taught herein.
  • Another feature of the invention involves mitigation against deleterious electromigration affects that can occur within multi-layer thin film electrodes. Such mitigation will help to maximize the robustness, stability, and longevity of electrode devices operated under normal conditions .
  • the invention protects against diffusion of copper or copper substitutes, as discussed above, into the insulating substrate, where it can react with and poison the insulating substrate.
  • this electrodiffusion can be ameliorated utilizing the tantalum nitride/ ⁇ -tantalum layers bonded to the silicon-based substrate. These tantalum-containing layers are resistant to diffusion of copper.
  • electromigration results from current-induced, physical transport of conductive material within an electrodes ' thin film layers as a result of direct forces on ions from the voltage gradient, and/or momentum transferred directly between moving electrons and atoms/ions.
  • This unwanted net physical flux of material can cause materials in thin film layers to be depleted "upwind” and accumulated “downwind”, forming empty voids in thin films upwind and hillocks downwind.
  • mass transport associated with electromigration occurs primarily along the metallic grain boundaries, up to approximately 50% of the melting point of any given material .
  • both types of forces are expected to be present, with protons or deuterons comprising the migrating ionic species .
  • electrolytic electromigration In the case of multi-layer thin film electrodes operating in wet electrochemical cells, there will be an additional electromigration affect, known as electrolytic electromigration, in addition to the solid state electromigration effects described above.
  • Operating conditions for electrodes of the invention are expected to present the opportunity for the development of deleterious effects from electromigration.
  • Preferred operations will involve minimum current densities of from about 10 2 to about 10 5 A/cm 2 .
  • Typical operating temperatures will be a minimum of 100 2 C, and may range up to 1,000 2 C or more. In certain applications, operating temperatures will be in the range of about 100 a C to about 500 e C, more typically 100 a C to 300 2 C.
  • Preferred multi-layer thin film electrodes of the invention will also be expected to have useful operating lifetimes ranging from 5,000 to 100,000 hours.
  • thin film layers can be incorporated which posses a relative large average grain size in relation to the layer thickness.
  • Utilization of such large grain sizes relative to layer thickness can create a cross- sectional grain pattern known as a bamboo or bamboo-like structure.
  • a bamboo or bamboo-like structure Preferably, such bamboo grain structures will have a mean grain size having a dimension at least as thick as the layer in which the structure is incorporated.
  • Such bamboo grain patterns are expected to maximize the stability, functional integrity, and operating lifetime of multi-layer thin film electrodes of the invention. Specifically, such grain patterns will provide the following benefits:
  • each thin film layer in the working electrode an ordinarily skilled practitioner will control the total thickness of each such thin film layer (in terms of the number of atomic monolayers comprising it) in conjunction with deposition and annealing techniques so that the layer's mean grain size will possess physical dimensions necessary to insure the creation of bamboo grain patterns in that layer.
  • the thin film layers will form a working electrode having an geometric form shaped either like flat, quasi-two-dimensional sheets, or like more complicated, quasi- two-dimensional sheets having various areas of positive and/or negative curvatures .
  • the preferred bamboo-type grain patterns are preferably deposited and oriented so that they are as close as possible to being perpendicular (or at a high inclination) to the major flow of current and/or ions through the working thin film layers .
  • control over mean grain size, inclinations of grain boundaries, and tightness of distribution of grain sizes around the mean for each working layer can be achieved in a number of ways, including for example by the selection of appropriate deposition methods.
  • electroplating and electroless plating depositions will be preferred as compared to various sputtering methods . This is because for certain metals, electroplating or electroless plating are known to produce significantly larger grain sizes than can be deposited with sputtering techniques. Starting with larger grain sizes during the initial deposition step will eliminate or reduce the amount of annealing required to achieve desired final mean grain sizes and tight size distributions. Further, subsequent annealing and patterning steps can be used to control grain size and grain size distributions. Annealing temperature, holding time at a specified temperature (“soaking"), and cooling rate are specific process parameters that will be uniquely determined for a given metal .
  • Damage from electromigration can also be controlled by maximizing heat dissipation out of the working layers of the thin film electrode.
  • This in turn, can be accomplished by a combination of: (a) controlling the total thickness of working layers of the thin film multilayer electrodes, (b) selecting substrates that can help conduct heat through the "Base Layers" of the electrodes, (c) selecting barrier layer materials that have physical properties that help facilitate heat conduction out of the thin film working layers, and (d) using macroscopic electrode and electrochemical cell geometries that maximize heat transfer out of thin film working layers into the electrolyte and/or another heat sink integrated with the cell .
  • Si0 2 is not as thermally conductive as pure Si at the operating temperatures likely to be experienced by multilayer thin film electrodes.
  • any Si0 2 layer present will advantageously be kept as thin as possible.
  • underlying electrode substrate will desirably bond strongly with Si0 2 , have good electrical insulating characteristics, have sufficient mechanical strength to support the attached thin film Layers, and have a high thermal conductivity (under typical electrode operating conditions and temperatures.
  • suitable substrate materials meeting these criteria include, for example, pure Si; crystalline Si0 2 (quartz) ; amorphous Si0 2 (quartz) , amorphous diamond-like carbon, or other types of doped glasses or optical fibers, or ceramic materials containing substantial amounts of Si or N, such as Al 6 Si 2 0 13 , Si 3 N, or BN
  • electrode structures of the invention will include multilayer, thin film working electrodes, desirably formed of two or more different metal and/or metal oxide layers .
  • a number of configurations or patterns for such working electrodes are contemplated. Some include repeating sequences of differing layers. Each such sequence may be comprised, for example, of two to ten or more different thin film layers.
  • these working electrodes will be deposited on top of a base or adhesion layer applied to a substrate as disclosed above, for example a silicon based substrate coated with Si02/TaN/ ⁇ -Ta/Cu or with a substitute for Cu as discussed above.
  • Ml, M2 , M3 , M4 , M5, M6, M7 , M8 , M9, and M10 are potential metals or metal oxides for use in the working electrode.
  • S Substrate
  • Bl optional barrier layer
  • M6 CePd3 being an example of a heavy electron compound.
  • NiFe being an example of a ferromagnetic compound
  • M6 ZrV2 being an example of a compound that absorbs Hydrogen up to ZrV2H5.2
  • Electrode devices of the invention will also optionally include one or more barrier layers (e.g. 14a-14c, Figure 1) covering the electrode structure.
  • this may include a top barrier 14a and side barriers 14b and 14c.
  • these barrier layers will desirably possess some or all of the following mechanical, electrical, and chemical characteristics:
  • Comparatively low deposition temperatures (preferably signi icantly less than 200 a C) .
  • barrier layers will be provided that are made from amorphous carbon coatings, for example amorphous diamond-like coatings .
  • amorphous carbon coatings for example amorphous diamond-like coatings .
  • Suitable such coating materials are available commercially under the brand name of "Dylyn” , produced and sold by Bekaert Advanced Coating Technologies, Amherst, New York, USA
  • Dylyn When Dylyn is used as an upper and side barrier Layer (with one end of the electrode having "open" exposed edges or surfaces of working layers where electrons and hydrogen/deuterium can enter the electrode, as taught by Miley in WO0163010) , the preferred thickness for such barrier layers is 2 to 3 microns .
  • Dylyn When Dylyn is used as an upper barrier layer, it is preferably deposited on top of a carbide-forming metal or other material such as Pt, Pd, Rh and a number of other carbide-forming metals such as Ti, Zr, V, Nb, Ta, Cr, Mo, W, Fe, Co, Ni, Al, and certain other carbide-forming rare earth metals .
  • Dylyn is used as a side barrier layer (14b and 14c in Figure 1), because Dylyn' s amorphous structure and enormous mechanical strength should allow it to "span" occasional layers of metals that adhere only poorly to Dylan e.g. certain noble metals such as Ag, Au, Cu.
  • an amorphous carbon layer such as Dylyn may be used within the electrode structure.
  • the amorphous carbon layer may be used in between a substrate and an Si0 2 layer.
  • the amorphous carbon layer preferably about 2 to about 20 microns thick, may serve as a heat transfer buffer layer that is used to transfer heat from layers above to the substrate which may include alumina ceramics, heat sinks composed of certain compatible metals such as extruded Al, and compatible physical materials that are used to further transfer heat directly to the operationally hot side of thermoelectric and thermionic devices .
  • a layer of amorphous carbon in the thin film multilayer structure has the effect of encasing the adhesion coating or base layers as well as a large percentage of working layers of a thin film multilayer electrode with an amorphous carbon coating. This helps improve heat transfer out of working electrode layers and contributes to overall stability of the entire multilayer structure because Dylyn (or similar amorphous carbon coatings) possesses an advantageous combination of properties that include: ability to function as an excellent hydrogen/deuterium/proton barrier layer, high dielectric strength, extreme thermal conductivity, and exceptional mechanical strength.
  • Another aspect of the invention involves the use of a graphite layer as a heat transfer buffer layer within thin film electrodes or other working devices of the invention.
  • a suitable graphite for this purpose is described, for example, in U.S. Patent No. 6,037,032 assigned to Oak Ridge National Laboratory. It is produced and marketed commercially under the brand name of "PocoFoam Graphite" by Poco Graphite, Inc., of Decatur, Texas, U.S.A.
  • PocoFoam is a specially prepared form of amorphous carbon that has excellent thermal conductivity and heat transfer capabilities relative to its weight.
  • PocoFoam has a "foamed" cellular structure consisting of mostly empty, interconnected spherical voids in which the structure exhibits distinctive, highly graphitic aligned ligaments within the foam's cell walls. Due to its porosity (typically 73% to 82%), PocoFoam does not provide preferred properties for use as a diffusion barrier for hydrogen, deuterium, and/or protons.
  • PocoFoam graphite carbon foam can be utilized with advantage as an optional heat transfer buffer layer within the substrate layers of the thin film electrodes of the invention.
  • PocoFoam or other similar graphite substances in electrodes of the invention may involve the use of a thin Pocofoam layer bonded directly to the substrate (i.e. used as layer 12a in Figure 1). All layers occurring above layer 12a can occur as described otherwise herein, including the use of additional layers in an adhesion coating, such as a tantalum nitride layer bonded to the graphite layer, a tantalum (especially ⁇ -tantalum) layer bonded to the tantalum nitride layer, a copper or copper-substitute layer bonded to the tantalum nitride layer, and working electrode layers bonded to the copper or copper-substitute layer, etc. It should also be noted in this regard that the use of the Pocofoam or other graphite material as layer 12a can provide an alternative to the use of silicon-dioxide as layer 12a in embodiments of the invention
  • the present invention also provides electrical or other reaction cells incorporating electrodes or other similar thin film working structures of the invention. These may, for example, be dry or wet electrical or other reaction cells.
  • electrodes of the invention can be incorporated as cathode elements in electrochemical cells as described by Miley in WO9807898 entitled FLAKE-RESISTANT MULTILAYER THIN- FILM ELECTRODES AND ELECTROLYTIC CELLS INCORPORATING SAME, published February 26, 1998, and in U.S. Patent No. 6,599,404, each of which is hereby incorporated herein by reference in its entirety.
  • such cells may include a packed bed of cathodic electrode pellets arranged in a flowing electrolytic cell.
  • the packed bed of pellets allows flow area, and the packing fraction may be fairly large, leading to a large electrode surface area, which is desirable to provide a high reaction rate per unit volume.
  • the packed bed of pellets provides a small pressure drop at the modest flow rates .
  • Electrodes of the invention may also be arranged as described by Miley in WO0163010 entitled ELECTRICAL CELLS, COMPONENTS AND METHODS, published August 30, 2001, which is hereby incorporated herein by reference in its entirety, and/or incorporated into electrical cell devices as disclosed therein.
  • electrodes of the invention can included in an electrode device having a substrate and an anode and cathode provided in discreet locations on the substrate and thus having a gap therebetween.
  • the multilayer thin film electrodes of the invention are preferably provided as the cathode. Operation of such an electrode device in the presence of an electrolyte (e. g.
  • an aqueous electrolyte, optionally including heavy water) filling the gap and contacting the electrode surfaces results in the electro-migration of the ions (e. g. protons or deuterons) within the cathode and the creation of a region in the cathode enriched in these ions .
  • the ions e. g. protons or deuterons
  • Electrodes of the invention can also be included in solid-state cell arrangements as described in the above-cited WO0163010, which include anodic and cathodic connections to the electrode provided as a conductive element .
  • a solid-state source of the ions is provided and arranged to feed the ions into the conductive element.
  • a solid-state source can include a metal hydride or a corresponding deuteride for release of hydrogen or deuterium in gaseous form, and a catalyst for splitting the gaseous hydrogen or deuterium so as to provide protons or deuterons.
  • the catalyst may be layered onto the conductive element, and the metal hydride may be layered onto the catalyst. In this fashion, gas released by the metal hydride (e. g.
  • Electrodes or deuterons which can then migrate into and along the working layers of the electrode of the invention (conductive element) when a voltage drop is applied across the electrode.
  • Preferred arrangements include a barrier layer, as discussed above, along at least a portion of the conductive element that resists permeation by the protons or deuterons .
  • Cell arrangements of this embodiment may advantageously be incorporated into various geometric devices such as the cylindrical cell devices as described in connection with Figures 5-8 of WO0163010.
  • Working electrodes or other working structures of the invention may also be incorporated into electrical or other reaction cells including a neutral gas or charged plasma that provides the source of hydrogenous atoms to the working structure.
  • cells incorporating electrodes or other working devices of the invention may also include one or more thermoelectric or thermionic converter elements thermally coupled to the thin films of the working device (see, e.g. thermoelectric or thermionic element 15 shown in phantom in Figure 1) .
  • thermoelectric or thermionic element 15 shown in phantom in Figure 1
  • the thermoelectric and/or thermionic element (s) and electrode (s) or other working device (s) can be bonded to one another in a back-to-back fashion or otherwise thermally coupled in a fashion facilitating heat transfer from the working device (s) to the converter element (s).
  • the thermoelectric element (s) may serve as the substrate (s) for the electrode (s) of the invention as described above including a substrate and an anode and cathode thereon in discrete locations.
  • a plurality of such combined structures can be arranged in a cell leaving spaces for electrolyte flow and spaces for coolant flow through the cell (see WO0163010, Figure 4) .
  • Spaces for electrolyte flow occur on the electrode sides of the combined electrode/thermoelectric structures, providing the electrolyte for the operation of the devices .
  • Spaces for coolant occur on the thermoelectric element side of the combined structures. In this fashion, as the cell is operated, a temperature differential can be created across the thermoelectric converter elements, thus promoting the generation of electric energy.
  • Cell devices of the invention can be used for example in the electrolysis of electrolytes such as water, forming hydrogen and oxygen gases, and may also be used in energy conversion devices or cells which include the generation of heat and optionally conversion of the heat to electrical energy, and/or in causing transmutation reactions.
  • Devices of the invention may also be used to provide densified regions of atoms (e.g. ions) of hydrogen or its isotopes, increasing the probability of and facilitating the further study of ion-ion or other atom-atom reactions or ion-metal or atom-metal reactions, including exploring fusion and related reactions.
  • atoms e.g. ions
  • such densified regions or localized concentrations of hydrogen or its isotopes, including deuterium can be caused by any suitable means including for example electromigration or other similar means involving the application of electrical current, physical pressure diffusion gradients, electrolysis or other electrolytic processing, or any other means capable of achieving a localized ion or other atom concentration.
  • electromigration or other similar means involving the application of electrical current, physical pressure diffusion gradients, electrolysis or other electrolytic processing, or any other means capable of achieving a localized ion or other atom concentration.
  • Oxide Layer is Preferably Utilized in Thin Film Heterostructure primarily because Oxide Structure offers Greater Compatibility with Pure Metals

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Abstract

L'invention concerne des électrodes pour cellules électriques et d'autres dispositifs similaires multicouches, notamment à couches minces, lesdits ensembles électrodes comprenant un substrat auquel est collée une structure de travail multicouche. Dans un mode de réalisation, la structure de travail multicouche comprend au moins une couche métallique et au moins une couche d'oxyde métallique. Dans un autre mode de réalisation, la structure de travail comprend au moins une couche comprenant un alliage d'étain. L'invention concerne également des appareils associés et des procédés faisant appel à ces ensembles.
PCT/US2004/012790 2003-04-25 2004-04-26 Ensembles electrode comportant des couches de metaux modifies, cellules pourvues de tels ensembles et procedes associes WO2004103036A2 (fr)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017127800A1 (fr) * 2016-01-21 2017-07-27 Ih Ip Holdings Limited Procédés d'amélioration de rapport de charge de gaz d'hydrogène
WO2018102165A3 (fr) * 2016-11-30 2018-07-26 Saint-Gobain Performance Plastics Corporation Électrode et procédé de fabrication d'électrode
TWI822844B (zh) * 2018-10-02 2023-11-21 國立研究開發法人科學技術振興機構 異質磊晶結構體及其製作方法， 以及包含異質磊晶結構之金屬堆疊體及其製作方法、奈米縫隙電極及奈米縫隙電極之製作方法

Citations (1)

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Publication number Priority date Publication date Assignee Title
WO1998007898A1 (fr) * 1996-08-19 1998-02-26 Miley George H Electrodes a couches minces, multicouches et resistantes a l'ecaillage et cellules electrolytiques les comportant

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998007898A1 (fr) * 1996-08-19 1998-02-26 Miley George H Electrodes a couches minces, multicouches et resistantes a l'ecaillage et cellules electrolytiques les comportant
US6599404B1 (en) * 1996-08-19 2003-07-29 Lattice Energy Llc Flake-resistant multilayer thin-film electrodes and electrolytic cells incorporating same

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017127800A1 (fr) * 2016-01-21 2017-07-27 Ih Ip Holdings Limited Procédés d'amélioration de rapport de charge de gaz d'hydrogène
RU2721009C2 (ru) * 2016-01-21 2020-05-15 Их Ип Холдингз Лимитед Способы улучшения коэффициента загрузки газообразного водорода
WO2018102165A3 (fr) * 2016-11-30 2018-07-26 Saint-Gobain Performance Plastics Corporation Électrode et procédé de fabrication d'électrode
CN110291386A (zh) * 2016-11-30 2019-09-27 美国圣戈班性能塑料公司 电极和用于制造电极的方法
TWI822844B (zh) * 2018-10-02 2023-11-21 國立研究開發法人科學技術振興機構 異質磊晶結構體及其製作方法， 以及包含異質磊晶結構之金屬堆疊體及其製作方法、奈米縫隙電極及奈米縫隙電極之製作方法

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