WO1998021737A1 - Cathodes contenant du carbone, concues pour une emission electronique accrue - Google Patents

Cathodes contenant du carbone, concues pour une emission electronique accrue Download PDF

Info

Publication number
WO1998021737A1
WO1998021737A1 PCT/US1996/018468 US9618468W WO9821737A1 WO 1998021737 A1 WO1998021737 A1 WO 1998021737A1 US 9618468 W US9618468 W US 9618468W WO 9821737 A1 WO9821737 A1 WO 9821737A1
Authority
WO
WIPO (PCT)
Prior art keywords
cathode
substrate
atoms
carbon
electrons
Prior art date
Application number
PCT/US1996/018468
Other languages
English (en)
Inventor
Renyu Cao
Lawrence Pan
German Vergara
Ciaran Fox
Original Assignee
Board Of Trustees Of The Leland Stanford Junior University
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 Board Of Trustees Of The Leland Stanford Junior University filed Critical Board Of Trustees Of The Leland Stanford Junior University
Priority to PCT/US1996/018468 priority Critical patent/WO1998021737A1/fr
Publication of WO1998021737A1 publication Critical patent/WO1998021737A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J63/00—Cathode-ray or electron-stream lamps
    • H01J63/02—Details, e.g. electrode, gas filling, shape of vessel
    • H01J63/04—Vessels provided with luminescent coatings; Selection of materials for the coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2201/00—Electrodes common to discharge tubes
    • H01J2201/19—Thermionic 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
    • H01J2201/30446—Field emission cathodes characterised by the emitter material
    • H01J2201/30453—Carbon types
    • H01J2201/30457—Diamond
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2201/00—Electrodes common to discharge tubes
    • H01J2201/32—Secondary emission electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2201/00—Electrodes common to discharge tubes
    • H01J2201/34—Photoemissive electrodes

Definitions

  • the present invention relates to electron-emitting devices, and in particular to a cathode comprising a carbon-containing substrate and electropositive metal atoms chemically bonded to the substrate.
  • An emissive cathode emits electrons during processes such as field emission, thermionic emission, and photoemission.
  • a key parameter governing electron emission from a cathode is the work function of its emitting surface.
  • a low work function is desirable since it generally corresponds to a high emission current. It is also desirable that cathode performance not degrade substantially upon normal operation, or following exposure to air and/or high temperatures.
  • the emissive cathode consists of a semiconductor substrate coated with an electropositive metallic layer.
  • cathodes having a GaAs substrate coated with composite Cs-0 films see the article by Rougeot et al . in Adv. Electronics and Electron Phys . , 48: 1- 36 (1979) .
  • a cathode having a Cs-0- coated Si substrate see the article by Levine in Surf . Sci . 1973, p. 90-107.
  • Diamond and diamond- like carbon have been proposed as potential substrate materials for semiconductor emissive cathodes.
  • the deposition of a durable layer of electropositive metal on carbon-containing or diamond substrates has proven difficult, however. This difficulty stems from the fragility of the attachment of metal atoms to the substrate.
  • heating a conventional Cs-coated diamond substrate to a moderate temperature (-200 °C) reverses the cathode performance to that of untreated diamond (see Fig. 5 of Geis et al . ) .
  • An emissive cathode of the present invention comprises a carbon-containing substrate having an electron-emissive surface, and a layer (preferably monolayer) of electropositive metal atoms chemically bonded to the substrate along the emissive surface.
  • the metal atoms facilitate the emission of electrons from the substrate surface.
  • the cathode has a negative electron affinity. The chemical bonds between the metal and the substrate prevent the easy removal of the metallic layer from the substrate.
  • the atomic fraction of C in the substrate is at lease 50% along the surface.
  • the substrate consists substantially of a synthetic diamond film.
  • the substrate comprises a diamond like material.
  • a substantial fraction (e.g. >25%) of the carbon atoms of the substrate are tetrahedrally bonded (i.e. hybridized sp- .
  • the electropositive metal atoms are bonded to carbon atoms along the surface.
  • the atomic fraction of the electropositive metal in the metallic layer is at least 50% along the surface.
  • the metal is preferably Cs .
  • Other suitable metals include Ba, K, Na, Sr, Li, Rb, Sc , Y, and La.
  • a display comprises a plurality of cathodes of the present invention, and a plurality of display elements such as phosphors situated opposite the cathodes, such that electrons emitted from the cathodes are incident on corresponding display elements.
  • a cathode corresponds to independently addressable display elements of different colors (red, green and blue) .
  • the display may be a flat panel display, or a part of an imaging system having electron multiplication stages.
  • a detector comprises an end cathode of the present invention, and an anode for detecting electrons emitted by the end cathode.
  • a detection cathode absorbs particles (such as photons or electrons), and emits electrons, thereby inducing an emission of electrons in the end cathode.
  • An electron multiplier comprises a plurality of multiplier cathodes.
  • First and second multiplier cathodes are situated in an opposite relation, such that electrons emitted by the first multiplier cathode are incident on the second multiplier cathode.
  • the multiplier cathodes are connected to corresponding voltages, where the voltage of the first cathode is less than the voltage of the second cathode.
  • Fig. 1-A shows schematically a prior art metal-coated cathode comprising electronegative atoms bonded to a carbon- containing substrate.
  • Fig. 1-B shows schematically a prior art metal-coated hydrogen-terminated carbon-containing cathode.
  • Fig. 2 shows a cathode of the present invention.
  • Fig. 3 is a flowchart illustrating possible approaches to making a cathode of the present invention.
  • Fig. 4-A shows a hydrogen-terminated substrate.
  • Fig. 4-B shows a bare substrate.
  • Fig. 4-B' shows a halide-terminated substrate.
  • Fig. 4-C shows a cathode similar to that shown in Fig. 2, according to the present invention.
  • Fig. 5-A shows an electron multiplier in a reflection geometry, according to the present invention.
  • Fig. 5-B shows an electron multiplier in a transmission geometry, according to present invention.
  • Fig. 6-A shows a part of a monochrome flat panel display of the present invention.
  • Fig. 6-B shows a part of a color flat panel display of the present invention.
  • Fig. 7 shows an imaging system of the present invention.
  • Fig. 8-A is a schematic energy diagram of a positive electron affinity cathode.
  • Fig. 8-B is a schematic energy diagram of a negative electron affinity cathode of the present invention.
  • Fig. 9 shows photoemitted electron counts and energy distributions for several cathodes comprising Cs-coated diamond substrates, according to the present invention.
  • Fig. 10 illustrates the durability of a cathode of the present invention.
  • Fig. 11 shows a comparison of a cathode of the present invention with a cathode having a GaAs substrate.
  • Fig. 12 shows photoemission data illustrating the restoration of the performance of a cathode of the present invention by annealing, following exposure to air.
  • Fig. 13 shows field emission data illustrating the lowering of the field emission threshold voltage by annealing.
  • Fig. 1-A shows a prior art cathode described m the above- incorporated U.S. Patent No. 5, 463, 271 (Geis et al . ) .
  • a cathode is mounted on an electrically conductive supporting piece 20.
  • the cathode comprises a carbon-containing substrate 22 having carbon atoms 24 on its emitting surface(s).
  • Electronegative atoms 26 (such as oxygen) are chemically bonded to atoms 24, while electropositive atoms 30
  • Fig. 1-B shows another prior art cathode having a substrate similar to that in Fig. 1-A.
  • Hydrogen atoms 32 are chemically bonded to carbon atoms 24.
  • Electropositive atoms 34 adhere, but are not chemically bonded, to hydrogen atoms 32.
  • the relative fragility of the attachment of electropositive atoms 34 to substrate 22 results in facile degradation of cathode performance during cathode operation, or upon exposure of the cathode to moderate temperatures (-100 °C) and/or air.
  • Fig. 2 shows a part of a cathode 40 of the present invention. The electrical contacts to cathode 40 are not shown for simplicity.
  • Cathode 40 is mounted on an electrically conductive support (not shown) .
  • a carbon-containing substrate 50 has atoms 52 along an electron-emissive surface 53. At least 50% of atoms 52 are carbon atoms, i.e. an atomic fraction of C in substrate 50 is at least 50% along surface 53.
  • Substrate 50 preferably consists substantially of a synthetic diamond film. Amorphic diamond, silicon-diamond mixtures, diamond-like carbon, and other carbon-containing compounds are also suitable for use in substrate 50.
  • a substantial fraction (e.g. at least 25%) of the carbon atoms in a substrate of the present invention be tetrahedrally (sp3) bonded, such that the substrate is diamond-like.
  • the properties (bandgap, etc.) of a diamond-like substrate are similar to those of diamond, and dissimilar to those of graphite or metals.
  • An electropositive metallic layer comprises electropositive metallic atoms 54 chemically bonded to substrate 50 along surface 53.
  • the metallic layer is substantially a monolayer, although thicker layers are also suitable in a cathode of the present invention.
  • Atoms 54 are chemically bonded to atoms 52.
  • the electron affinity (electronegativity) of atoms 54 is preferably less than 0.65.
  • atoms 54 comprise Cs atoms.
  • atoms 54 comprise Ba, K or Na atoms.
  • Other electropositive metals such as Li, Rb, Sc , Sr, Y and La can also be used in a cathode of the present invention.
  • Substrate 50 is electrically conductive, at least along surface 53.
  • Methods for generating electrically conducting diamond, including doping methods, are known in the art.
  • Doping affects the position of the Fermi level in diamond, and thus the type of doping (n or p) is chosen according to the application for which the cathode is used. Nitrogen impurities are typically used to generate n-type diamond, while boron impurities are commonly used for p-type diamond.
  • Fig. 3 is a flowchart outlining the major steps in making a diamond cathode of the present invention, while Figs. 4-A through 4-C illustrate the intermediary structures generated during the making of the cathode.
  • a hydrogen plasma treatment is used to clean the surface of the substrate. Hydrogen plasma treatments are well known in the art. For example, a hydrogen plasma treatment is performed for 3 hours at 15 torr and 750 W in a microwave plasma system from Aztecs. The temperature of the substrate stays under -600 °C during the treatment, as estimated from the absence of glowing in the chamber. A clean hydrogen-terminated surface can also be obtained by oil-polishing the diamond surface.
  • Fig. 4-A shows a hydrogen-terminated substrate 60 having an emissive surface 61. A monolayer of hydrogen atoms 64 is chemically bonded to carbon atoms 62 along surface 61.
  • Hydrogen atoms 64 prevent the chemical bonding of electropositive atoms to atoms 62.
  • Depositing an electropositive metal on a hydrogen-terminated surface results in weak adhesion between the metal and the carbon atoms within the substrate. Consequently, a typical cathode having an electropositive metal deposited on a hydrogen-terminated substrate surface is susceptible to exposure to air and/or high temperatures.
  • Several methods are available for the removal of hydrogen atoms 64.
  • hydrogen atoms 64 are removed by annealing substrate 60 to >800 °C.
  • Substrate 60 is heated to 950 °C (in general 800-1200 °C) for about 10 minutes (in general from a few minutes to hours) under vacuum (IO -7 torr or lower) .
  • Overheating may lead to transformation of diamond into graphite at surface 61.
  • the heating desorbs any adsorbates on surface 61, and removes hydrogen atoms 64.
  • the article by Pate "The Diamond Surface: Atomic and Electronic Structure” in Surf . Sci . 162: 83 (1986), herein incorporated by reference, contains a description of an annealing method for removing the hydrogen monolayer from an as-polished diamond surface.
  • the Pate article also contains a discussion of the consequences of annealing, including surface structural changes.
  • the resulting substrate is shown schematically in Fig. 4-B.
  • surface 61 is bombarded by energetic particles such as electrons, ions, or molecules. A majority (ideally, substantially all) of hydrogen atoms 64 are removed from surface 61. Bombardment methods suitable for removing hydrogen atoms 64 are known in the art. Care should be taken so that the bombardment does not physically damage substrate 60.
  • electropositive metal atoms 80 are deposited on surface 61, yielding the cathode of Fig. 4-C.
  • Techniques, such as vapor deposition, for depositing electropositive metals on diamond are well known in the art.
  • the deposition is preferably done under good vacuum (pressures of 10 ⁇ 9 torr or lower) , using either a pure metal source or a metal compound source. Suitable metal sources are available commercially. Suitable deposition temperatures, evaporation rates and treatment durations can be readily determined by the skilled artisan, depending on the source used and the geometry of the deposition chamber.
  • Atoms 80 form chemical bonds with atoms 62.
  • the dipole moments of the metal-carbon bonds act to reduce the work function of the cathode.
  • atoms 80 form a monolayer. If a thicker layer of atoms 80 is originally deposited on surface 61, substrate 60 is heated to a moderate temperature for a period of time sufficient to allow the evaporation of the metal atoms not chemically bonded to surface 61.
  • Fig. 4-B' illustrates a preferred approach for removing hydrogen atoms 64.
  • Atoms 64 are replaced by electronegative atoms 66 by exposing substrate 60 to a plasma of electronegative atoms 66.
  • Atoms 66 are halogen atoms (F, Cl, Br or I) .
  • Halogen plasma treatment methods are known in the art.
  • a SFg plasma is used in a RF plasma system (reactive ion etcher) from Ion and Plasma Equipment, Inc., for 5 minutes at 50 W and under 20 mtorr pressure.
  • the temperature of substrate 60 during the halogen plasma treatment is less than 200 °C .
  • another method of fluorinating diamond see for example the article by Ando et al .
  • the halogen-coated substrate is exposed to an excess of electropositive metal, and moderately heated to a temperature (as low as 150 °C) sufficient to remove the resulting metal halide molecules from surface 66. Suitable heating temperatures and heating durations can readily be determined by the skilled artisan.
  • the excess electropositive metal bonds chemically to atoms 62, yielding the cathode of Fig. 4- C.
  • a cathode of the present invention is preferably protected from exposure to air or oxygen, and is electrically connected to a power supply (not shown) . Electron emission from the cathode is induced thermally (thermionic emission), optically (photoemission), or electrically (field emission). The type of electron emission chosen depends on the application of the cathode . Particularly useful applications of a cathode of the present invention include detectors, electron multipliers, and displays. In a display, a cathode of the present invention generates electrons which are absorbed by display element (s), which in turn emit photons. In a detector, the cathode absorbs photons, electrons, or other energetic particles (e.g. ⁇ - or ⁇ -rays), and in turn emits electrons. In an electron multiplier, the cathode absorbs a number electrons and, in turn, emits a larger number of electrons.
  • a cathode of the present invention is suitable for use as a photocathode .
  • Photons incident on the cathode induce the emission of electrons from the cathode.
  • the electrons are detected at an anode.
  • semiconductor negative-electron-affinity (NEA) photocathodes see for example Chapter 57 of Complete Guide to Semiconductor Devices by Ng, McGraw-Hill, 1995.
  • a cathode of the present invention is also suitable for use in an electron multiplier. Electron multipliers are known in the art, and will be described here only briefly.
  • Fig. 5-A illustrates schematically an electron multiplier 120 comprising a plurality of cathodes (or dynodes ) arranged in a reflection geometry. Adjacent cathodes 122, 124, and 126 are held at corresponding voltages V[n-1] ⁇ V[n] ⁇ V[n+1] , and are situated in an opposite relation such that electrons emitted by cathode 122 are incident on cathode 124, and electrons emitted by cathode 124 are incident on cathode 126.
  • Cathode 124 absorbs and emits electrons from the same surface 128.
  • An anode 130 at a voltage V collects electrons emitted by a last cathode 132.
  • Other cathode arrangements for reflection-mode electron multipliers are known in the art.
  • Fig. 5-B illustrates an electron multiplier 150 comprising a plurality of cathodes (or dynodes) arranged in a transmission geometry. Adjacent cathodes 152, 154, and 156 are held at corresponding voltages V[n-1] ⁇ V[n] ⁇ V[n+1], and are separated by electrically insulating spacers 158 . Electrons emi t ted by cathode 152 are inc ident on an absorpt ion surf ac e 160 of cathode 154 , and generate an emission of elec trons from the subs trate of cathode 154 , through an emissive surface 162 of cathode 154 .
  • Emissive surface 162 is opposite absorption surface 160 . Electropositive metal atoms are chemical ly bonded to the subs trate of cathode 154 along emissive surface 162 . An anode 164 at a voltage V collects electrons emitted by a last cathode 166 .
  • Fig . 6-A shows schematically a pixel of a black-and-white flat panel display .
  • a cathode 180 is mounted on an electrically conductive substrate 182 .
  • a display element 184 is mounted on a transparent glass faceplate 186 opposite cathode 180 , such that elec trons generated by cathode 180 are absorbed by display element 184 .
  • Field emission is used to extract electrons from cathode 180 .
  • Display element 184 comprises a phosphor capable of emitting photons through faceplate 186 upon absorption of electrons from cathode 180 .
  • Fig. 6-B shows schematically a part of a color flat panel display.
  • First, second, and third display elements 188, 190, and 192 comprise red, green and blue phosphors, respectively, and can be accessed selectively by electrons emitted from cathode 180.
  • a flat panel display using cathodes of the present invention can approach the performance of a cathode ray tube display, while being more compact and consuming less power.
  • a flat panel display using cathodes of the present invention is not subject to some of the disadvantages of other display technologies such as liquid crystal displays (limited size and viewing angles), electroluminescence (inferior addressability), or LED (complexity of design) .
  • Fig. 7 shows an imaging system 200 comprising a plurality of cathodes arranged in a transmission geometry.
  • the cathode arrangement is similar to that shown in Fig. 5-B.
  • Barriers 202 focus the emission of electrons through apertures 204.
  • a phosphor layer 206 attached to a glass plate 208 emits photons upon absorption of electrons.
  • a system such as system 200 is suitable for medical imaging applications.
  • An imaging system using a cathode of the present invention allows a wider dynamic range, higher operation speeds, a larger display area, lower operating temperatures, a simpler design, and higher resolutions than currently available imaging systems .
  • Figs. 8-A and 8-B show energy diagrams for simple (uncoated) semiconductor cathodes having positive and negative electron affinities, respectively.
  • the horizontal axis denotes position, while the vertical axis denotes energy.
  • the figures also illustrate photoemission from the two cathodes. In photoemission, electrons are excited inside the cathode by incident light, migrate to an emissive surface of the cathode, and exit the cathode through the emissive surface.
  • the energy Eg is the difference between the valence and conduction band energies, while ⁇ (the electron affinity) is the potential difference between the vacuum level and the bottom of the conduction band.
  • ⁇ the electron affinity
  • a positive-electron-affinity photocathode In a positive-electron-affinity photocathode, photoexcited electrons that are not close (relative to the mean free path) to the emissive surface scatter down to the bottom of the conduction band (Ec) , and thus become less energetic than the vacuum level before reaching the surface, as illustrated in Fig. 8-A.
  • the electrons eventually emitted by a positive- electron-affinity photocathode are originally excited relatively close to the surface, and are above the vacuum level upon migration to the cathode surface.
  • the energy distribution of electrons generated by such a cathode is in general relatively wide.
  • a negative-electron-affinity (NEA) photocathode In a negative-electron-affinity (NEA) photocathode, electrons resting at E migrate to the cathode surface upon the application of a suitable electric field. The energy distribution of the electrons generated by a NEA photocathode is relatively narrow.
  • a key parameter controlling electron emission is the energy difference ⁇ between the vacuum level and the highest occupied electron states.
  • ⁇ is the energy difference between the vacuum level and the top of the valence band
  • ⁇ B is the difference between the vacuum level and the dopant level.
  • I AT 2 e " ⁇ B /kT , [ 2 ]
  • V is the applied voltage
  • T is the cathode temperature
  • k is the Boltzmann constant
  • A, A' , C and D are structural constants of the cathode.
  • the vacuum level, and consequently the value of ⁇ , of a cathode can be reduced by generating strong dipoles pointing toward the cathode substrate.
  • Such dipoles are generated in the present invention by treating the cathode substrate with an electropositive metal.
  • the difference in energies ⁇ of untreated and metal-treated cathodes is given by
  • N is the dipole density and Pi is the dipole moment of the substrate-metal bond.
  • Pi is the dipole moment of the substrate-metal bond.
  • Some hydrogen-terminated uncoated diamond cathodes have been shown to have low barriers ⁇ . The maximum currents generated by such cathodes have been generally very low, however. Cs- coated hydrogen-terminated diamond cathodes have lower barriers ⁇ than uncoated cathodes, but are sensitive to high temperatures and/or exposure to air.
  • a cathode of the present invention comprising electropositive metal atoms chemically bonded to a carbon-containing substrate, is relatively robust. In one embodiment, the cathode also displays a negative electron affinity. Although the NEA condition is desirable in a cathode of the present invention, the NEA condition is not absolutely required.
  • n-type substrate may be desirable for some applications, however, even though such a substrate may not allow NEA.
  • field emission from a cathode can be enhanced geometrically, i.e. by defining sharp features on the cathode surface .
  • Such sharp features enhance locally the electric field at the cathode surface, for a given potential applied to the cathode.
  • Ways of defining sharp geometric features on surfaces of various materials are known in the art .
  • Fig. 9 shows the energy distributions of photoexcited electrons emitted by three (100) type II-B diamond cathodes: a hydrogen- terminated as-installed cathode, a hydrogen- terminated cathode following annealing to 600 °C, and a cathode of the present invention having Cs atoms directly bonded to C atoms of the substrate.
  • the large energy absolute values are due to the acceleration of the electrons through a potential following emission.
  • the hydrogen-terminated as- installed diamond displays low emission current and a broad peak.
  • the Cs-treated cathode shows a high emission current and a very narrow peak corresponding to electrons emitted from the conduction band minimum Ec (see Fig. 8-B) .
  • the narrow peak is indicative of negative electron affinity.
  • the narrow energy distribution allows easy focusing of the electrons, which is critical in some applications.
  • Fig. 10 shows electron energy distributions for a fresh cathode and a cathode after >15 hours of operation in vacuum. The two curves are vertically displaced for clarity of presentation.
  • Fig. 10 illustrates the excellent durability of a cathode of the present invention. The performance of the cathode does not degrade substantially following 15 hours of operation in vacuum.
  • Fig. 11 shows electron energy distributions for a diamond cathode of the present invention and a Cs-coated GaAs cathode.
  • the actual counts for the GaAs cathode are 20 times lower than those displayed.
  • the counts and energy distribution of electrons emitted by the diamond cathode are superior to those of electrons emitted by the GaAs cathode.
  • the lifetime of a cathode depends strongly on its operating environment. Electronegative contaminants from its environment adsorb onto the cathode surface, and weaken the surface dipole strength (see Eq. [4]). The contaminants can be removed without causing damage to the cathode.
  • Fig. 12 shows the number of electrons emitted by a diamond cathode of the present invention under several conditions: fresh, after exposure to air, and following subsequent annealing for restoring the damage caused by the exposure to air.
  • annealing to 550 °C causes a partial restoration of the cathode performance.
  • the performance of a cathode of the present invention can also be restored, following exposure to oxygen, by an appropriate electron beam treatment, or by the deposition of additional Cs on the cathode (data not shown).
  • Fig. 13 shows schematically the results of field emission measurements performed on a diamond cathode of the present invention, following exposure to oxygen and subsequent annealing for restoring the cathode performance.
  • the threshold voltage for emission is significantly lowered following annealing.

Landscapes

  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)

Abstract

Une cathode comporte des atomes électropositifs (80) directement liés à un substrat (60) contenant du carbone. Le substrat comporte, de préférence, du carbone diamant ou du type diamant (sp3), et les atomes électropositifs sont Cs. La cathode présente une efficacité et une durabilité supérieures. Dans un mode de réalisation, la cathode présente une affinité pour les électrons négatifs (NEA). La cathode peut être utilisée pour l'émission de champ, l'émission thermoionique ou la photoémission. Lorsqu'elle est exposée à l'air ou à l'oxygène, les performances de la cathode peuvent être rétablies par recuit ou autre. Lesdites cathodes peuvent être utilisées dans des détecteurs, des multiplicateurs d'électrons, des capteurs, des systèmes d'imagerie et des affichages, plus particulièrement des affichages à écran plat.
PCT/US1996/018468 1996-11-13 1996-11-13 Cathodes contenant du carbone, concues pour une emission electronique accrue WO1998021737A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/US1996/018468 WO1998021737A1 (fr) 1996-11-13 1996-11-13 Cathodes contenant du carbone, concues pour une emission electronique accrue

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1996/018468 WO1998021737A1 (fr) 1996-11-13 1996-11-13 Cathodes contenant du carbone, concues pour une emission electronique accrue

Publications (1)

Publication Number Publication Date
WO1998021737A1 true WO1998021737A1 (fr) 1998-05-22

Family

ID=22256154

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1996/018468 WO1998021737A1 (fr) 1996-11-13 1996-11-13 Cathodes contenant du carbone, concues pour une emission electronique accrue

Country Status (1)

Country Link
WO (1) WO1998021737A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8507785B2 (en) 2007-11-06 2013-08-13 Pacific Integrated Energy, Inc. Photo induced enhanced field electron emission collector
US9348078B2 (en) 2010-06-08 2016-05-24 Pacific Integrated Energy, Inc. Optical antennas with enhanced fields and electron emission

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3678325A (en) * 1969-03-14 1972-07-18 Matsushita Electric Ind Co Ltd High-field emission cathodes and methods for preparing the cathodes
US5123039A (en) * 1988-01-06 1992-06-16 Jupiter Toy Company Energy conversion using high charge density
US5341063A (en) * 1991-11-07 1994-08-23 Microelectronics And Computer Technology Corporation Field emitter with diamond emission tips

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3678325A (en) * 1969-03-14 1972-07-18 Matsushita Electric Ind Co Ltd High-field emission cathodes and methods for preparing the cathodes
US5123039A (en) * 1988-01-06 1992-06-16 Jupiter Toy Company Energy conversion using high charge density
US5341063A (en) * 1991-11-07 1994-08-23 Microelectronics And Computer Technology Corporation Field emitter with diamond emission tips

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8507785B2 (en) 2007-11-06 2013-08-13 Pacific Integrated Energy, Inc. Photo induced enhanced field electron emission collector
US8969710B2 (en) 2007-11-06 2015-03-03 Pacific Integrated Energy, Inc. Photon induced enhanced field electron emission collector
US9348078B2 (en) 2010-06-08 2016-05-24 Pacific Integrated Energy, Inc. Optical antennas with enhanced fields and electron emission

Similar Documents

Publication Publication Date Title
US6091186A (en) Carbon-containing cathodes for enhanced electron emission
US5729094A (en) Energetic-electron emitters
US6147456A (en) Field emission display with amplification layer
US7629736B2 (en) Method and device for preventing junction leakage in field emission devices
US6853129B1 (en) Protected substrate structure for a field emission display device
US5268612A (en) Feedback limited microchannel plate
KR20130114137A (ko) 나노 다이아몬드층을 가지는 전자 증배기 장치
Fehrs et al. Contact-potential measurements of the adsorption of Cs, O2 and H2 on (110) Ta
US4639638A (en) Photomultiplier dynode coating materials and process
US6215243B1 (en) Radioactive cathode emitter for use in field emission display devices
US20060261719A1 (en) Field emitter device
Siegmund et al. Gallium nitride photocathodes for imaging photon counters
WO1998021737A1 (fr) Cathodes contenant du carbone, concues pour une emission electronique accrue
Dinh et al. Synthesis and characterization of Si/Cs/O nanocluster thin films with negative electron affinity
US3830717A (en) Semiconductor camera tube target
US3721848A (en) Camera tube having photoconductive lead monoxide layer on silicon carbide signal plate
US6455987B1 (en) Electron multiplier and method of making same
JPH08321256A (ja) 電子放出陰極、それを用いた電子放出素子、フラットディスプレイ、及び熱電冷却装置、ならびに電子放出陰極の製造方法
US5619091A (en) Diamond films treated with alkali-halides
US7750548B2 (en) Image display device
EP1318538A2 (fr) Cathode froide et ecran plat
JP3768658B2 (ja) 二次電子放出装置、製造方法及びそれを用いた電子管
Geis et al. Fabrication and theory of diamond emitters
US3723278A (en) Method of depositing hafnium-tantalum nitride layer by reactive sputtering
Giunji et al. Micro capillary glass plates as a gaseous detector of photons and particles

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): JP

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FI FR GB GR IE IT LU MC NL PT SE

121 Ep: the epo has been informed by wipo that ep was designated in this application
NENP Non-entry into the national phase

Ref country code: JP

Ref document number: 1998522504

Format of ref document f/p: F

122 Ep: pct application non-entry in european phase