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WO1997018576A1 - Emetteurs de champ en poudres de diamant et cathodes d'emission de champ produites a partir de ces poudres - Google Patents

Emetteurs de champ en poudres de diamant et cathodes d'emission de champ produites a partir de ces poudres Download PDF

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Publication number
WO1997018576A1
WO1997018576A1 PCT/US1996/018140 US9618140W WO9718576A1 WO 1997018576 A1 WO1997018576 A1 WO 1997018576A1 US 9618140 W US9618140 W US 9618140W WO 9718576 A1 WO9718576 A1 WO 9718576A1
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WO
WIPO (PCT)
Prior art keywords
diamond powder
field
diamond
cathode
substrate
Prior art date
Application number
PCT/US1996/018140
Other languages
English (en)
Inventor
Graciela Beatriz Blanchet-Fincher
Syed Ismat Ullah Shah
Original Assignee
E.I. Du Pont De Nemours And Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by E.I. Du Pont De Nemours And Company filed Critical E.I. Du Pont De Nemours And Company
Priority to AU77286/96A priority Critical patent/AU7728696A/en
Publication of WO1997018576A1 publication Critical patent/WO1997018576A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/022—Manufacture of electrodes or electrode systems of cold cathodes
    • H01J9/025—Manufacture of electrodes or electrode systems of cold cathodes of field emission cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2201/00—Electrodes common to discharge tubes
    • H01J2201/30—Cold cathodes
    • H01J2201/304—Field emission cathodes
    • H01J2201/30403—Field emission cathodes characterised by the emitter shape
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2201/00—Electrodes common to discharge tubes
    • H01J2201/30—Cold cathodes
    • H01J2201/304—Field emission cathodes
    • H01J2201/30446—Field emission cathodes characterised by the emitter material
    • H01J2201/30453—Carbon types
    • H01J2201/30457—Diamond

Definitions

  • the invention generally relates to the use of diamond powders prepared by shock synthesis as electron field emitters and more particularly to the use of said diamond powders in field emitter cathodes
  • Field emission electron sources often referred to as field emission materials or field emitters, can be used in a variety of electromc applications, e g , vacuum electronic devices, flat panel computer and television displays, emission gate amplifiers, klystrons and lighting devices
  • Display screens are used in a wide variety of applications such as home and commercial televisions, laptop and desktop computers and indoor and outdoor advertising and information presentations
  • Flat panel displays are typically only a few inches thick in contrast to the deep cathode ray tube monitors found on most televisions and desktop computers
  • Flat panel displays are a necessity for laptop computers, but also provide advantages rn weight and size for many of the other applications
  • laptop computer flat panel displays use liquid crystals which can be switched from a transparent state to an opaque state by the application of small elect ⁇ cal signals It is difficult to reliably produce these displays in sizes larger than that suitable for laptop computers
  • Plasma displays have been proposed as an alternative to liquid crystal displays
  • a plasma display uses tiny pixel cells of electrically charged gases to produce an image and requires relatively large electrical power to operate
  • Flat panel displays having a cathode using a field emission electron source, 1 e , a field emission material or field emitter, and a phosphor capable of emitting light upon bombardment by electrons emitted by the field emitter have been proposed
  • Such displays have the potenual for providing the visual display advantages of the conventional cathode ray tube and the depth, weight and power consumption advantages of the other flat panel displays
  • U S Patents 4,857,799 and 5,015,912 disclose matrix-addressed flat panel displays using micro-tip cathodes constructed of tungsten, molvbdenum or silicon WO 94-15352.
  • WO 94-15350 and WO 94-28571 disclose flat panel displays wherein the cathodes have relatively flat emission surfaces
  • field emitters and field emitter cathodes are useful in vacuum electronic devices, flat panel computer and television displays, emission gate amplifiers, klystrons and lighting devices
  • panel displays can be planar or curved DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • the mvention provides a novel electron field emitter comprised of diamond powder prepared by shock synthesis and a novel electron field emitter cathode made therefrom
  • diamond powder means diamond in a fmely divided state, l e , particulate diamond, with a particle size less than about 20 ⁇ m
  • the diamond powder used in this mvention preferably has a particle size less than about 10 ⁇ m
  • the diamond powder may be "nanoparticulate" meanmg that the particulate diamond powder has a particle size in the nanometer range (I e , less than 1 micron)
  • shock synthesis means a synthesis in which a shock wave, l e , a compressional or detonation wave, is used to provide the pressure necessary for synthesis
  • a shock wave l e
  • detonation wave a shock wave that is used to provide the pressure
  • the synthesis can occur withm mate ⁇ al which is subjected to the pressure or withm the explosive mate ⁇ al itself
  • Diamond powder can be prepared bv shock synthesis
  • carbon, e g graphite
  • driver a steel tube which turn is placed concentrically in a larger, heavier (driver) tube
  • This system is su ⁇ ounded by several thousand pounds of high-velocity explosive confmed mside a cylmdrical culvert Detonation is instigated at one end of the charge of explosive and propagates along the cymd ⁇ cal charge of explosive to the other end
  • the explosive detonates it progressively collapses the driver tube onto the product tube, subjecting the graphite to very high pressure
  • This pressure can be as high as 7 x IO 6 lb/in 2 (5 x 10 10 Pa)
  • These crystallites bond together m random structures and.
  • the resultmg particles can be up to 100 ⁇ m in size
  • the heat generated must be controlled by incorporating a heat-sink material so that the temperature does not rise to the level sufficient to reconvert the diamond to carbon.
  • Polycrystalline diamond powders made by this method are the commercially available Mypolex® diamond powders (E. I. du Pont de Nemours and Company. Wilmington, DE). V. L. Kuznetsov et al., Carbon 32 (5), 873 ( 1994), the contents of which are incorporated herein, describe another method for making polycrystalline diamond powder by shock synthesis.
  • Soot resulting from the detonation of explosives in hermetic tanks filled with a gas that is inert toward elemental carbon contains diamond particles 2- 1 nm in size.
  • the diamond powders prepared by shock synthesis are prepared under severe conditions and it is not surprising that the diamond product typically contains metal impurities. These impurities depend upon the apparatus used for the preparation and the particular explosive when soot from the explosive is the source of the diamond.
  • the more prevalent impurities in diamond powders prepared by shock synthesis are copper, iron, silicon, chromium, titanium, aluminum, calcium and manganese.
  • Measurement Unit I Field emission tests on samples of diamond powder were carried out using a flat-plate emission measurement unit comprised of two electrodes, one serving as the anode or collector and the other serving as the cathode. This will be referred to in the Examples as Measurement Unit I.
  • the thickness of the insulators determines the distance or gap between the electrodes and spacers of thicknesses from about 0.055 cm to about 1.0 cm were available. Electrical contacts with the electrodes were made with screws at the backs of the electrodes.
  • the diamond powder was attached to an electrically conducting substrate and the substrate was placed on the copper plate serving as the cathode.
  • Another emission measurement unit (referred to in the Examples as Measurement Unit II) was used when wires or fibers were employed as the substrate. Electron emission from wires having attached diamond powder particles was measured in a cylindrical test fixture.
  • the conducting wire to be tested was mounted in the center of a cylinder (anode).
  • This anode cylinder typically consisted of a fine mesh cylindrical metal screen coated with a phosphor. Both the cathode and anode were held in place by an aluminum block with a semi-cylindrical hole cut therein.
  • the conducting wire was held in place by two 1/16 inch-diameter stainless steel tubes, one at each end These tubes were cut open at each end, forming an open trough in the shape of a half cylinder of length 1/2 inch and diameter 1/16 mch, and the wire was placed in the open trough that results and held in place with silver paste.
  • the connecting tubes were held in place within the aluminum block by tight fitting polytetrafluoroethylene (PTFE) spacers, which served to electrically separate the anode and cathode.
  • PTFE polytetrafluoroethylene
  • the total length of exposed wire was generally set at 1 0 cm, although shorter or longer lengths could be studied by controlling the placement of the holder tubes T e cylmd ⁇ cal screen mesh cathode was placed m the semi-cylindrical trough in the aluminum block and held m place with copper tape The cathode was m elect ⁇ cal contact with the aluminum block.
  • Elect ⁇ cal leads were connected to both the anode and cathode
  • the anode was maintained at ground potential (0 V) and the voltage of the cathode was controlled with a 0-10 kV power supply
  • Electrical cu ⁇ ent emitted by the cathode was collected at the anode and measured with an electrometer
  • the electrometer was protected from damagmg current spikes by an rn-senes 1 M ⁇ resistor and in-parallel diodes which allowed high current spikes to bypass the electrometer to ground.
  • Samples for measurement of length about 2 cm were cut from longer lengths of processed wires With the flexible stainless steel screen with phosphor removed, they were inserted into the cylindrical troughs of the two holder arms Silver paste was applied to hold them in paste The silver paste was allowed to dry and the phosphor screen was reattached and held in place with copper tape at the two ends.
  • the test apparatus was inserted mto a vacuum system, and the system was evacuated to a base pressure below 3 x IO "6 ton.
  • Emission cu ⁇ ent was measured as a function of applied voltage Electrons emitted from the cathode create light when they stroke the phosphor on the anode. The distribution and intensity of electron emission sites on the coated wire were observed by the pattem of light created on the phosphor/wire mesh screen.
  • the diamond powder is attached to the surface of a substrate to form a field emitter cathode
  • the substrate may be of any shape, e g , a plane, a fiber, a metal wire, etc. Suitable metal wires include nickel, copper and tungsten.
  • the means of attachment must withstand and maintain its integrity under the conditions of manufacturing, in the apparatus into which the field emitter cathode is placed, and under the conditions surrounding its use. e.g., typically vacuum conditions and temperaures up to about 450°C.
  • organic materials are not generally applicable for attaching the particles to the substrate and the poor adhesion of many inorganic materials to carbon further limits the choice of materials that can be used.
  • One method of attaching the diamond powder to a substrate is by pressing it against a conductor, e.g., a silver foil, with sufficient pressure to embed the diamond powder in the conductor.
  • the diamond powder can be attached to a substrate by creating a thin metal, layer of a conductive metal, such as gold or silver, on the substrate with the diamond powder embedded in the thin metal layer.
  • the thin metal layer anchors the diamond powder to the substrate.
  • the cathode surface should be comprised of the surfaces of an array of diamond powder particles with the metal filling the interstices between the diamond powder particles,
  • the quantity of diamond particles and the thickness of the metal layer must be chosen to promote the formation of such a surface.
  • the conducting metal layer also provides means to apply a voltage to the diamond powder particles.
  • One process for creating a thin metal layer of a conductive metal, such as gold or silver, on a substrate with the diamond powder embedded in the thin metal layer comprises depositing a mixture of diamond powder and a conductive paste or composition of the type used in the electronics industry in producing printed circuit boards.
  • An example of such a paste is 5007 Silver Conductor composition commercially available from E. I. du Pont de Nemours and Company, Wilmington. DE.
  • Another process for creating a thin metal layer of a conductive metal, such as gold or silver, on a substrate with the diamond powder embedded in the thin metal layer comprises depositing a solution of a metal compound in a solvent and the diamond powder onto the surface of the substrate.
  • the solution can be applied to the surface first and the diamond particles then deposited, or the diamond particles can be dispersed in the solution which is then applied to the surface.
  • the metal compound is one which is readily reduced to the metal, e.g..
  • the product is a substrate coated with a thin layer of the metal with the diamond powder (e g , Mypolex® polycrystallme diamond powder) embedded therem and anchored to the substrate
  • the diamond powder e g , Mypolex® polycrystallme diamond powder
  • EXAMPLE 1 A 1 g portion of Mypolex® polycrystallme diamond powder (commercially available from E I du Pont de Nemours and Company, Wilmington, DE) with 6 ⁇ m particle size was evenly dispersed on a st ⁇ p of silver foil and a second silver foil was placed on top of the diamond powder The two silver foils were 0 2 cm thick and 1 1 cm wide The two silver foils with the Mypolex® polycrystallme diamond powder between them were manually pressed together usmg a pestle The pestle was rubbed on the foils untd essentially all the diamond powder was embedded in the fods as determined by pulling apart the foils and tapping them to determme if there was any unembedded diamond powder The foils were then blown with compressed air to remove any unembedded diamond particles 1 cm x 1 cm pieces were cut from each foil for emission testing Each 1 cm x 1 cm piece of silver foil with diamond powder embedded in it was placed on the cathode of the flat-plate emission measurement unit described above as Measurement Unit
  • the mixture was deposited m the form of two lmes 1/8 in (0.32 cm) wide, 1/16 in (0.16 cm) thick and 3/4 ( 1.9 cm) long
  • the substrate, with these lmes, was heated to 1 0°C and mamtamed at that temperature for 20 mmutes and then cooled in the furnace to ambient temperature, about 20°C, before it was removed from the furnace
  • the substrate was placed on the cathode of the flat- plate emission measurement unit described first above and held there with conducting Cu tape Two additional pieces of conducting Cu tape were used to hold the cathode Cu plate Electrical connection to each of the prmted silver lines containing the embedded diamond powder was made by a screen-prmtable thick film silver conductor composition.
  • This example illustrates a method for attaching 6 ⁇ m diamond powder particles (Mypolex® polycrystalline diamond powder from E. I. du Pont de Nemours and Company) onto a metal wire (2 mil nickel wire commercially available from Goodfellow Co ⁇ oration, Berwyn. PA) by using gold compound (commercially available from Aesar 12943, Ward Hill, MA) that was brushed onto the support wire following the manufacturer's suggestions.
  • gold compound commercially available from Aesar 12943, Ward Hill, MA
  • the wire was immersed into the diamond powder.
  • the nickel wire covered with gold compound and diamond particles was then placed in a furnace for firing in an air atmosphere.
  • the wire was heated to 540°C at a 25°C/minute heating rate in an air atmosphere for 30 minutes to bum off all organic materials.
  • the wire was then cooled to room temperature.
  • the fired samples comprised a thin gold metal layer that anchored the diamond particles onto the nickel wire.
  • the emission was measured using Measurement Unit II previously described. Emission data is shown in Table HI below where the same sample was used but 20 cu ⁇ ent readings for each voltage were taken to provide an average emission cu ⁇ ent.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Cold Cathode And The Manufacture (AREA)

Abstract

Des poudres de diamant préparées par synthèse par chocs sont utiles comme émetteurs de champ d'électrons. Des cathodes d'émission de champ, constituées de ces poudres de diamant, fixées à la surface d'un substrat sont également décrites. Ces émetteurs de champ et ces cathodes d'émission de champ sont utiles dans des dispositifs électroniques sous vide, dans des écrans de télévisions et d'ordinateurs à panneaux plats, dans des amplificateurs à portes d'émission, dans des klystrons et dans des dispositifs d'éclairage.
PCT/US1996/018140 1995-11-15 1996-11-13 Emetteurs de champ en poudres de diamant et cathodes d'emission de champ produites a partir de ces poudres WO1997018576A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU77286/96A AU7728696A (en) 1995-11-15 1996-11-13 Diamond powder field emitters and field emitter cathodes made therefrom

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US674895P 1995-11-15 1995-11-15
US60/006,748 1995-11-15

Publications (1)

Publication Number Publication Date
WO1997018576A1 true WO1997018576A1 (fr) 1997-05-22

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1996/018140 WO1997018576A1 (fr) 1995-11-15 1996-11-13 Emetteurs de champ en poudres de diamant et cathodes d'emission de champ produites a partir de ces poudres

Country Status (2)

Country Link
AU (1) AU7728696A (fr)
WO (1) WO1997018576A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999031701A1 (fr) * 1997-12-15 1999-06-24 E.I. Du Pont De Nemours And Company Emetteurs electroniques de graphite a fil revetu bombardes par un faisceau ionique
WO1999034385A1 (fr) * 1997-12-23 1999-07-08 Alfar International Ltd. Dispositif d'emission electronique a effet de champ et son procede de production
US5948465A (en) * 1995-11-15 1999-09-07 E. I. Du Pont De Nemours And Company Process for making a field emitter cathode using a particulate field emitter material
US6409567B1 (en) 1997-12-15 2002-06-25 E.I. Du Pont De Nemours And Company Past-deposited carbon electron emitters

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4273561A (en) * 1975-08-27 1981-06-16 Fernandez Moran Villalobos Hum Ultrasharp polycrystalline diamond edges, points, and improved diamond composites, and methods of making and irradiating same
WO1994028571A1 (fr) * 1993-06-02 1994-12-08 Microelectronics And Computer Technology Corporation Cathode plate a emission de champ pourvue d'une pellicule de diamant amorphe
WO1995022169A1 (fr) * 1994-02-14 1995-08-17 E.I. Du Pont De Nemours And Company Emetteurs de champ en fibres de diamant
EP0712146A1 (fr) * 1994-11-08 1996-05-15 Commissariat A L'energie Atomique Source d'électrons à effet de champ et procédé de fabrication de cette source, application aux dispositifs de visualisation par cathodoluminescence
EP0725415A2 (fr) * 1995-01-31 1996-08-07 AT&T Corp. Dispositifs à émission de champ utilisant des particules de diamant activées émettrices et procédés de fabrication

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4273561A (en) * 1975-08-27 1981-06-16 Fernandez Moran Villalobos Hum Ultrasharp polycrystalline diamond edges, points, and improved diamond composites, and methods of making and irradiating same
WO1994028571A1 (fr) * 1993-06-02 1994-12-08 Microelectronics And Computer Technology Corporation Cathode plate a emission de champ pourvue d'une pellicule de diamant amorphe
WO1995022169A1 (fr) * 1994-02-14 1995-08-17 E.I. Du Pont De Nemours And Company Emetteurs de champ en fibres de diamant
EP0712146A1 (fr) * 1994-11-08 1996-05-15 Commissariat A L'energie Atomique Source d'électrons à effet de champ et procédé de fabrication de cette source, application aux dispositifs de visualisation par cathodoluminescence
EP0725415A2 (fr) * 1995-01-31 1996-08-07 AT&T Corp. Dispositifs à émission de champ utilisant des particules de diamant activées émettrices et procédés de fabrication

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5948465A (en) * 1995-11-15 1999-09-07 E. I. Du Pont De Nemours And Company Process for making a field emitter cathode using a particulate field emitter material
WO1999031701A1 (fr) * 1997-12-15 1999-06-24 E.I. Du Pont De Nemours And Company Emetteurs electroniques de graphite a fil revetu bombardes par un faisceau ionique
US6409567B1 (en) 1997-12-15 2002-06-25 E.I. Du Pont De Nemours And Company Past-deposited carbon electron emitters
WO1999034385A1 (fr) * 1997-12-23 1999-07-08 Alfar International Ltd. Dispositif d'emission electronique a effet de champ et son procede de production

Also Published As

Publication number Publication date
AU7728696A (en) 1997-06-05

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