EP1424716A1 - Verfahren zur Elektronenemission eines Elektronenemitters - Google Patents

Verfahren zur Elektronenemission eines Elektronenemitters Download PDF

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Publication number
EP1424716A1
EP1424716A1 EP03257240A EP03257240A EP1424716A1 EP 1424716 A1 EP1424716 A1 EP 1424716A1 EP 03257240 A EP03257240 A EP 03257240A EP 03257240 A EP03257240 A EP 03257240A EP 1424716 A1 EP1424716 A1 EP 1424716A1
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Prior art keywords
electrode
emitter section
voltage
emitter
polarization
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EP03257240A
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English (en)
French (fr)
Inventor
Yukihisa Intellectual Property Dept.NGK Takeuchi
Tsutomu Intellectual Property Dept.NGK Nanataki
Iwao Intellectual Property Dept.NGK Ohwada
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NGK Insulators Ltd
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NGK Insulators Ltd
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Publication of EP1424716A1 publication Critical patent/EP1424716A1/de
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    • 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
    • H01J1/30—Cold cathodes, e.g. field-emissive cathode
    • 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
    • H01J1/32—Secondary-electron-emitting electrodes

Definitions

  • the present invention relates to a method of emitting electrons from an electron emitter having a first electrode and a second electrode formed on an emitter section.
  • FEDs field emission displays
  • backlight units a plurality of electron emitters are arranged in a two-dimensional array, and a plurality of fluorescent elements are positioned at predetermined intervals in association with the respective electron emitters.
  • Another object of the present invention is to provide a method of emitting electrons from an electron emitter having an emitter section made of an anti-ferroelectric material in which the electron emitter emits electrons efficiently, and can be utilized easily in displays or light sources.
  • Another object of the present invention is to provide a method of emitting electrons from an electron emitter having an emitter section made of an electrostrictive material in which the electron emitter emits electrons efficiently, and can be utilized easily in displays or light sources.
  • the present invention provides a method of emitting electrons from an electron emitter including an emitter section made of a piezoelectric material, a first electrode in contact with the emitter section, and a second electrode in contact with the emitter section, the method comprising the steps of:
  • an electric field is applied between the first electrode and the second electrode for causing the first electrode to have a potential lower than a potential of the second electrode to reverse polarization of at least a portion of the emitter section.
  • the polarization reversal causes emission of electrons in the vicinity of the first electrode.
  • the polarization reversal generates a locally concentrated electric field on the first electrode and the positive poles of dipole moments in the vicinity the first electrode, emitting primary electrons from the first electrode.
  • the primary electrons emitted from the first electrode impinge upon the emitter section, causing the emitter section to emit secondary electrons.
  • the emitter section, and a vacuum atmosphere define a triple point
  • primary electrons are emitted from a portion of the first electrode in the vicinity of the triple point.
  • the emitted primary electrons impinge upon the emitter section to induce emission of secondary electrons from the emitter section.
  • the secondary electrons herein include electrons emitted from the solid emitter section under an energy that has been generated by a coulomb collision with primary electrons, Auger electrons, and primary electrons which are scattered in the vicinity of the surface of the emitter section (reflected electrons). If the first electrode is very thin, having a thickness of 10 nm or less, electrons are emitted from the interface between the first electrode and the emitter section.
  • the electron emission is stably performed, and the number of emitted electrons would reach 2 billion or more.
  • the electron emitter is advantageously used in the practical applications.
  • the number of emitted electrons is increased substantially proportional to the voltage between the first electrode and the second electrode.
  • the number of the emitted electrons can be controlled easily.
  • the embodiments of the present invention as described later can be advantageously operated in the similar manner.
  • the electric field beyond the level of the coercive field is applied to the emitter section which is polarized in one direction within a certain period. Therefore, the electrons are emitted efficiently, and the electron emitter can be utilized easily in displays or light sources.
  • the electric field for inducing electron emission is beyond the level of the coercive field.
  • the polarization reversal is almost completed.
  • the levels of the electric fields do not change substantially. Therefore, the electron emitter has digital-like electron emission characteristics.
  • the level of the electric field for electron emission depends on the coercive field. When the level of the coercive field is small, the electron emitter can be operated at a low voltage.
  • the polarization of the emitter section in one direction may be performed by applying a first voltage between the first electrode and the second electrode for causing the first electrode to have a potential higher than a potential of the second electrode in a first period
  • the polarization reversal of the emitter section for emitting electrons may be performed by applying a second voltage between the first electrode and the second electrode for causing the first electrode to have a potential lower than a potential of the second electrode in a second period.
  • the level of the second voltage may be controlled so that the electric field beyond the coercive field is applied to the emitter section for emitting electrons within a certain period from the beginning of the second period.
  • the level of the second voltage may be controlled in the following manner. If the second voltage has a pulse waveform having a falling edge (ramp), for example, the maximum amplitude or a transition time (a period from the beginning of the second period until the voltage reaches the maximum amplitude) of the second voltage is controlled, and if the second voltage has a rectangular pulse waveform, only the maximum amplitude is controlled.
  • the certain period should be as small as possible for efficiently emitting electrons. Preferably, the certain period is 1 msec or less, and more preferably, the certain period is 10 ⁇ sec or less.
  • the present invention provides a method of emitting electrons from an electron emitter including an emitter section made of an anti-ferroelectric material, a first electrode in contact with the emitter section, and a second electrode in contact with the emitter section, the method comprising the step of applying an electric field to the emitter section through the first electrode and the second electrode to induce phase transition of the emitter section into a ferroelectric material, and change polarization of the emitter section for emitting electrons.
  • the electric field applied to the emitter section may have a level for inducing phase transition of the emitter section into a ferroelectric material within a certain period, and changing polarization of the emitter section for emitting electrons.
  • an electric field is applied between the first electrode and the second electrode such that the first electrode has a potential lower than a potential of the second the second electrode to change polarization of at least a portion of the emitter section.
  • the polarization change causes emission of electrons in the vicinity of the first electrode.
  • the polarization change generates a locally concentrated electric field on the first electrode and the positive poles of dipole moments in the vicinity the first electrode, emitting primary electrons from the first electrode.
  • the primary electrons emitted from the first electrode impinge upon the emitter section, causing the emitter section to emit secondary electrons. If the first electrode is very thin, having a thickness of 10 nm or less, electrons are emitted from the interface between the first electrode and the emitter section.
  • the electric field is applied to the emitter section rapidly for inducing phase transition of the emitter section into a ferroelectric material and polarization of the emitter section. Therefore, the electrons are emitted efficiently, and the electron emitter can be utilized easily in displays or light sources.
  • the electron emitter In the electric field for inducing electron emission, polarization reversal or polarization change is almost completed. The levels of the electric fields do not change substantially. Therefore, the electron emitter has digital-like electron emission characteristics.
  • the electric field for electron emission depends on the electric field for inducing phase transition of the emitter section into the ferroelectric material. When the level of the electric field for inducing phase transition is small, the electron emitter is operated at a low voltage.
  • the polarization of the emitter section in one direction may be performed by applying a first voltage between the first electrode and the second electrode for causing the first electrode to have a potential higher than a potential of the second electrode in a first period, and phase transition of the emitter section into a ferroelectric material is induced, and polarization of the emitter section is changed for emitting electrons by applying a second voltage between the first electrode and the second electrode for causing the first electrode to have a potential lower than a potential of the second electrode in a second period.
  • the polarization of the emitter section is reset. Electron emission in the second period can be carried out by the single polarity operation.
  • the driving circuit system is simplified.
  • the electron emitter can be operated by small energy consumption at a low cost with a compact structure.
  • a level of the second voltage may be controlled so that phase transition of the emitter section into a ferroelectric material is induced within a certain period from the beginning of the second period, and polarization of the emitter section is changed.
  • the level of the second voltage may be controlled in the following manner. If the second voltage has a pulse waveform having a falling edge (ramp), for example, the maximum amplitude or a transition time of the second voltage is controlled, and if the second voltage has a rectangular pulse waveform, only the maximum amplitude is controlled.
  • the certain period should be as small as possible for efficiently emitting electrons. Preferably, the certain period is 10 msec or less, and more preferably, the certain period is 10 psec or less.
  • the level of the second voltage applied at the beginning of the second period may be controlled to repeat a series of cycle in which the voltage between the first electrode and the second electrode reaches a level required for electron emission and the voltage between the first electrode and the second electrode drops due to electron emission to a threshold level for resetting polarization of the emitter section.
  • the potential difference between the voltage level for inducing electron emission and the voltage level (threshold level) for resetting polarization is small. Therefore, when electron emission occurs to cause the drop in the voltage between the first electrode and the second electrode, the polarization of the emitter section is reset easily, and the emitter section is brought into a condition as if 0V were applied to the emitter section.
  • the voltage between the first electrode and the second electrode rapidly reaches the voltage level required for electron emission, and the electron emission starts to occur.
  • Electron emission in the second period can be carried out by the single polarity operation.
  • the driving circuit system is simplified.
  • the electron emitter can be operated by small energy consumption at a low cost with a compact structure.
  • the present invention provides a method of emitting electrons from an electron emitter including an emitter section made of an electrostrictive material, a first electrode in contact with the emitter section, and a second electrode in contact with the emitter section, the method comprising the step of applying an electric field to the emitter section to control the amount of polarization of the emitter section for emitting electrons.
  • an electric field is applied between the first electrode and the second electrode such that the first electrode has a potential lower than a potential of the second the second electrode to reverse polarization of at least a portion of the emitter section.
  • the polarization reversal causes emission of electrons in the vicinity of the first electrode.
  • the polarization reversal generates a locally concentrated electric field on the first electrode and the positive poles of dipole moments in the vicinity the first electrode, emitting primary electrons from the first electrode.
  • the primary electrons emitted from the first electrode impinge upon the emitter section, causing the emitter section to emit secondary electrons.
  • the first electrode is very thin, having a thickness of 10 nm or less, electrons are emitted from the interface between the first electrode and the emitter section.
  • the emitter section is polarized gradually according to the change of the electric field.
  • the amount of polarization per unit time is large, the number of emitted electrons is large. Therefore, the electrons are emitted efficiently by controlling the amount of polarization in the emitter section, and the electron emitter can be utilized easily in displays or light sources.
  • the polarization of the emitter section in one direction may be performed by applying a first voltage between the first electrode and the second electrode for causing the first electrode to have a potential higher than a potential of the second electrode in a first period, and polarization of the emitter section-may be changed for emitting electrons by applying a second voltage between the first electrode and the second electrode for causing the first electrode to have a potential lower than a potential of the second electrode in a second period.
  • the polarization of the emitter section is reset. Electron emission in the second period can be carried out by the single polarity operation.
  • the driving circuit system is simplified.
  • the electron emitter can be operated by small energy consumption at a low cost with a compact structure.
  • the level of the second voltage may be controlled so that an amount of polarization in the emitter section within a certain period from the beginning of the second period is controlled, and the number of emitted electrons is controlled.
  • the level of the second voltage may be controlled in the following manner. If the second voltage has a pulse waveform having a falling edge (ramp), for example, the maximum amplitude or a transition time of the second voltage is controlled, and if the second voltage has a rectangular pulse waveform, only the maximum amplitude is controlled.
  • the certain period is 10 msec or less, and more preferably, the certain period is 10 ⁇ sec or less.
  • the level of the second voltage applied at the beginning of the second period may be controlled so that electron emission continues by slight fluctuation of the voltage between the first electrode and the second electrode.
  • the emitter section is polarized gradually according to the change of the electric field.
  • the amount of polarization per unit time is large, the number of emitted electrons is large.
  • the potential difference between the voltage level for inducing electron emission and the voltage level (threshold level) for resetting polarization is small.
  • the polarization in the emitter section is reset easily, and the emitter section is brought into a condition as if 0 V were applied to the emitter section.
  • the second voltage is applied between the first electrode and the second electrode. Therefore, the voltage between the first electrode and the second electrode is increased rapidly. At this time, the change in the polarization progresses rapidly. Thus, electrons are emitted at a voltage lower than the voltage for the first electron emission.
  • the polarization of the emitter section is reset again easily. Thereafter, by continuously applying the second voltage between the first electrode and the second electrode, the voltage between the first electrode and the second electrode is increased again to polarize the emitter section. Again, the change in the polarization progresses rapidly, and the electron emission occurs at a voltage substantially same as the voltage for the second electron emission.
  • the voltage between the first electrode and the second electrode fluctuates slightly.
  • the slight fluctuation keeps the electron emission.
  • Electron emission in the second period can be carried out by the single polarity operation.
  • the driving circuit system is simplified.
  • the electron emitter can be operated by small energy consumption at a low cost with a compact structure.
  • the first electrode may be formed in contact with the emitter section; the second electrode may be formed in contact with the emitter section; and a slit may be formed between the first electrode and the second electrode.
  • the first electrode may be formed on a first surface of the emitter section
  • the second electrode may be formed on a second surface of the emitter section.
  • the voltage Vak between the first electrode and the second electrode is less than a dielectric breakdown voltage of the emitter section.
  • the electron emitters according to embodiments of the present invention can be used in displays, electron beam irradiation apparatus, light sources, alternatives to LEDs, and apparatus for manufacturing electronic parts.
  • Electron beams in electron beam irradiation apparatus have a high energy and a good absorption capability in comparison with ultraviolet rays in ultraviolet ray irradiation apparatus that are presently in widespread use.
  • the electron emitters are used to solidify insulating films in superposing wafers for semiconductor devices, harden printing inks without irregularities for drying prints, and sterilize medical devices while being kept in packages.
  • the electron emitters are also used as high-luminance, high-efficiency light sources such as a projector having a high pressure mercury lamp.
  • the electron emitter according to the present embodiment is suitably used as a light source.
  • the light source using the electron emitter according to the present embodiment is compact, has a long service life, has a fast response speed for light emission.
  • the electron emitter does not use any mercury, and the electron emitter is environmentally friendly.
  • the electron emitters are also used as alternatives to LEDs in indoor lights, automobile lamps, surface light sources for traffic signal devices, chip light sources, and backlight units for traffic signal devices, small-size liquid-crystal display devices for cellular phones.
  • the electron emitters are also used in apparatus for manufacturing electronic parts, including electron beam sources for film growing apparatus such as electron beam evaporation apparatus, electron sources for generating a plasma (to activate a gas or the like) in plasma CVD apparatus, and electron sources for decomposing gases.
  • the electron emitters are also used as vacuum micro devices such as high speed switching devices operated at a frequency on the order of Tera-Hz, and large current outputting devices.
  • the electron emitter are used suitably as parts of printers, such as light emitting devices for emitting light to a photosensitive drum, and electron sources for charging a dielectric material.
  • the electron emitters are also used as electronic circuit devices including digital devices such as switches, relays, and diodes, and analog devices such as operational amplifiers.
  • the electron emitters are used for realizing a large current output, and a high amplification ratio.
  • an electron emitter 10A As shown in FIG. 1, an electron emitter 10A according to a first embodiment-of the present-invention has an emitter section 14 formed on a substrate 12, a first electrode (cathode electrode) 16 and a second electrode (anode electrode) 20 formed on one surface of the emitter section 14. A slit 18 is formed between the cathode electrode 16 and the anode electrode 20. A drive voltage Va from a pulse generation source 22 is applied between the cathode electrode 16 and the anode electrode 20 through a resistor R1. In an example shown in FIG. 1, the anode electrode 20 is connected to GND (ground) and hence set to a zero potential. However, the anode electrode 20 may be set to a potential other than the zero potential.
  • a third electrode (collector electrode) 24 is provided above the emitter section 14 at a position facing the slit 18, and the collector electrode 24 is coated with a fluorescent layer 28.
  • the collector electrode 24 is connected to a bias voltage source 102 (bias voltage Vc) through a resistor R3.
  • the electron emitter 10A according to the first embodiment of the present invention is placed in a vacuum space. As shown in FIG. 1, the electron emitter 10A has electric field concentration points A and B.
  • the point A can be defined as a triple point where the cathode electrode 16, the emitter section 14, and the vacuum are present at one point.
  • the point B can be defined as a triple point where the anode electrode 20, the emitter section 14, and the vacuum are present at one point.
  • the vacuum level in the atmosphere is preferably in the range from 10 2 to 10 -6 Pa and more preferably in the range from 10 -3 to 10 -5 Pa.
  • the range of the vacuum level is determined for the following reason. In a lower vacuum, (1) many gas molecules would be present in the space, and a plasma can easily be generated and, if the plasma were generated excessively, many positive ions would impinge upon the cathode electrode 16 and damage the cathode electrode 16, and (2) emitted electrons would impinge upon gas molecules prior to arrival at the collector electrode 24, failing to sufficiently excite the fluorescent layer 28 with electrons that are sufficiently accelerated by the collector potential (Vc).
  • the emitter section 14 is made of a dielectric material.
  • the dielectric material should preferably have a high relative dielectric constant (relative permittivity), e.g., a dielectric constant of 1000 or higher.
  • Dielectric materials of such a nature may be ceramics including barium titanate, lead zirconate, lead magnesium niobate, lead nickel niobate, lead zinc niobate, lead manganese niobate, lead magnesium tantalate, lead nickel tantalate, lead antimony stannate, lead titanate, lead magnesium tungstenate, lead cobalt niobate, etc.
  • nPMN-mPT nPMN-mPT
  • PT lead titanate
  • MPB morphotropic phase boundary
  • a dielectric material may be mixed with 20 weight % of platinum.
  • the emitter section 14 may be formed of a piezoelectric/electrostrictive layer or an anti-ferroelectric layer. If the emitter section 14 is a piezoelectric/electrostrictive layer, then it may be made of ceramics such as lead zirconate, lead magnesium niobate, lead nickel niobate, lead zinc niobate, lead manganese niobate, lead magnesium tantalate, lead nickel tantalate, lead antimony stannate, lead titanate, barium titanate, lead magnesium tungstenate, lead cobalt niobate, or the like, or a combination of any of these materials.
  • ceramics such as lead zirconate, lead magnesium niobate, lead nickel niobate, lead zinc niobate, lead manganese niobate, lead magnesium tantalate, lead nickel tantalate, lead antimony stannate, lead titanate, barium titanate, lead magnesium tungstenate,
  • the emitter section 14 may be made of chief components including 50 weight % or more of any of the above compounds. Of the above ceramics, the ceramics including lead zirconate is most frequently used as a constituent of the piezoelectric/electrostrictive layer of the emitter section 14.
  • the piezoelectric/electrostrictive layer is made of ceramics, then oxides of lanthanum, calcium, strontium, molybdenum, tungsten, barium, niobium, zinc, nickel, manganese, or the like, or a combination of these materials, or any of other compounds may be added to the ceramics.
  • the piezoelectric/electrostrictive layer should preferably be made of ceramics including as chief components lead magnesium niobate, lead zirconate, and lead titanate, and also including lanthanum and strontium.
  • the piezoelectric/electrostrictive layer may be dense or porous. If the piezoelectric/electrostrictive layer is porous, then it should preferably have a porosity of 40 % or less.
  • the anti-ferroelectric layer may be made of lead zirconate as a chief component, lead zirconate and lead stannate as chief components, lead zirconate with lanthanum oxide added thereto, or lead zirconate and lead stannate as components with lead zirconate and lead niobate added thereto.
  • the anti-ferroelectric layer may be porous. If the anti-ferroelectric layer is porous, then it should preferably have a porosity of 30 % or less.
  • Strontium bismuthate tantalate is used suitably for the emitter section 14.
  • the emitter section 14 made of strontium bismuthate tantalate is not damaged by the polarization reversal easily.
  • lamellar ferroelectric compounds represented by a general formula (BiO 2 ) 2+ (A m-1 B m O 3m+1 ) 2 are used.
  • the ionized metal A includes Ca 2+ , Sr 2+ , Ba 2+ , Pb 2+ , Bi 3+ , La 3+
  • Piezoelectric/electrostrictive/anti-ferroelectric ceramics is mixed with glass components such as lead borosilicate glass or other compounds having a low melting point such as bismuth oxide to lower the firing temperature.
  • the emitter section 14 may be made of a material which does not contain any lead, i.e., made of a material having a high melting temperature, or a high evaporation temperature. Thus, the emitter section 14 is not damaged easily when electrons or ions impinge upon the emitter section 14.
  • the emitter section 14 may be formed on the substrate 12 by any of various thick-film forming processes including screen printing, dipping, coating, electrophoresis, etc., or any of various thin-film forming processes including an ion beam process, sputtering, vacuum evaporation, ion plating, chemical vapor deposition (CVD), plating, etc.
  • various thick-film forming processes including screen printing, dipping, coating, electrophoresis, etc.
  • various thin-film forming processes including an ion beam process, sputtering, vacuum evaporation, ion plating, chemical vapor deposition (CVD), plating, etc.
  • the emitter section 14 is formed on the substrate 12 suitably by any of various thick-film forming processes including screen printing, dipping, coating, electrophoresis, etc.
  • These thick-film forming processes are capable of providing good piezoelectric operating characteristics as the emitter section 14 can be formed using a paste, a slurry, a suspension, an emulsion, a sol, or the like which is chiefly made of piezoelectric ceramic particles having an average particle diameter ranging from 0.01 to 5 ⁇ m, preferably from 0.05 to 3 ⁇ m.
  • electrophoresis is capable of forming a film at a high density with high shape accuracy, and has features described in technical documents such as "Electrochemistry Vol. 53. No. 1 (1985), p. 63 - 68, written by Kazuo Anzai", and "The 1 st Meeting on Finely Controlled Forming of Ceramics Using Electrophoretic Deposition Method, Proceedings (1998), p. 5 - 6, p. 23 - 24".
  • the piezoelectric/electrostrictive/anti-ferroelectric material may be formed into a sheet, or laminated sheets. Alternatively, the laminated sheets of the piezoelectric/electrostrictive/anti-ferroelectric material may be laminated on, or attached to another supporting substrate. Any of the above processes may be chosen in view of the required accuracy and reliability.
  • the dielectric breakdown voltage of the emitter section 14 is at least 10kV/mm or higher.
  • the width d of the slit 18 is 70 ⁇ m, even if the drive voltage of -100V is applied between the cathode electrode 16 and the anode electrode 20, the portion of the emitter section 14 which is exposed through the slit 18 does not break down dielectrically.
  • the cathode electrode 16 is made of materials described below.
  • the cathode electrode 16 should preferably be made of a conductor having a small sputtering yield and a high evaporation temperature in vacuum.
  • materials having a sputtering yield of 2.0 or less at 600 V in Ar + and an evaporation temperature of 1800 k or higher at an evaporation pressure of 1.3 ⁇ 10 -3 Pa are preferable.
  • Such materials include platinum, molybdenum, tungsten, etc.
  • the cathode electrode 16 is made of a conductor which is resistant to a high-temperature oxidizing atmosphere, e.g., a metal, an alloy, a mixture of insulative ceramics and a metal, or a mixture of insulative ceramics and an alloy.
  • the cathode electrode 16 should be composed chiefly of a precious metal having a high melting point, e.g., platinum, iridium, palladium, rhodium, molybdenum, or the like, or an alloy of silver and palladium, silver and platinum, platinum and palladium, or the like, or a cermet of platinum and ceramics.
  • the cathode electrode 16 should be made of platinum only or a material composed chiefly of a platinum-base alloy.
  • the electrode should preferably be made of carbon or a graphite-base material, e.g., diamond thin film, diamond-like carbon, or carbon nanotube. Ceramics to be added to the electrode material should preferably have a proportion ranging from 5 to 30 volume %.
  • oxide electrode is used.
  • the oxide electrode is made by mixing any of these materials with platinum resinate paste, for example.
  • the cathode electrode 16 may be made of any of the above materials by an ordinary film forming process which may be any of various thick-film forming processes including screen printing, spray coating, dipping, coating, electrophoresis, etc., or any of various thin-film forming processes including sputtering, an ion beam process, vacuum evaporation, ion plating, CVD, plating, etc.
  • the cathode electrode 16 is made by any of the above thick-film forming processes. Dimensions of the cathode electrode 16 will be described with reference to FIG. 2.
  • the cathode electrode 16 has a width W1 of 2 mm, and a length L1 of 5 mm.
  • the cathode electrode 16 has a thickness of 20 ⁇ m or less, or more preferably 5 ⁇ m or less.
  • the anode electrode 20 is-made of the same material by the same process as the cathode electrode 16.
  • the anode electrode 20 is made by any of the above thick-film forming processes.
  • the anode electrode 20 has a thickness of 20 ⁇ m or less, or more preferably 5 ⁇ m or less.
  • the anode electrode 20 has a width W2 of 2 mm, and a length L2 of 5 mm as with the cathode electrode 16.
  • the width d of the slit 18 between the cathode electrode 16 and the anode electrode 20 is 70 ⁇ m.
  • the substrate 12 should preferably be made of an electrically insulative material in order to electrically isolate the line electrically connected to the cathode electrode 16 and the line electrically connected to the anode electrode 20 from each other.
  • the substrate 12 may be made of a highly heat-resistant metal or a metal material such as an enameled metal whose surface is coated with a ceramic material such as glass or the like.
  • the substrate 12 should preferably be made of ceramics.
  • Ceramics which the substrate 12 is made of include stabilized zirconium oxide, aluminum oxide, magnesium oxide, titanium oxide, spinel, mullite, aluminum nitride, silicon nitride, glass, or a mixture thereof.
  • aluminum oxide or stabilized zirconium oxide is preferable from the standpoint of strength and rigidity.
  • Stabilized zirconium oxide is particularly preferable because its mechanical strength is relatively high, its tenacity is relatively high, and its chemical reaction with the cathode electrode 16 and the anode electrode 20 is relatively small.
  • Stabilized zirconium oxide includes stabilized zirconium oxide and partially stabilized zirconium oxide. Stabilized zirconium oxide does not develop a phase transition as it has a crystalline structure such as a cubic system.
  • Zirconium oxide develops a phase transition between a monoclinic system and a tetragonal system at about 1000°C and is liable to suffer cracking upon such a phase transition.
  • Stabilized zirconium oxide contains 1 to 30 mol % of a stabilizer such as calcium oxide, magnesium oxide, yttrium oxide, scandium oxide, ytterbium oxide, cerium oxide, or an oxide of a rare earth metal.
  • the stabilizer should preferably contain yttrium oxide.
  • the stabilizer should preferably contain 1.5 to 6 mol % of yttrium oxide, or more preferably 2 to 4 mol % of yttrium oxide, and furthermore should preferably contain 0.1 to 5 mol % of aluminum oxide.
  • the crystalline phase may be a mixed phase of a cubic system and a monoclinic system, a mixed phase of a tetragonal system and a monoclinic system, a mixed phase of a cubic system, a tetragonal system, and a monoclinic system, or the like.
  • the main crystalline phase which is a tetragonal system or a mixed phase of a tetragonal system and a cubic system is optimum from the standpoints of strength, tenacity, and durability.
  • the substrate 12 is made of ceramics, then the substrate 12 is made up of a relatively large number of crystalline particles.
  • the crystalline particles should preferably have an average particle diameter ranging from 0.05 to 2 ⁇ m, or more preferably from 0.1 to 1 ⁇ m.
  • the assembly is heated (sintered) into a structure integral with the substrate 12.
  • the cathode electrode 16, and the anode electrode 20 are formed, they may simultaneously be sintered so that they may simultaneously be integrally coupled to the substrate 12.
  • they may not be heated (sintered) so as to be integrally combined with the substrate 12.
  • the sintering process for integrally combining the substrate 12, the emitter section 14, the cathode electrode 16, and the anode electrode 20 may be carried out at a temperature ranging from 500 to 1400°c, preferably from 1000 to 1400°C.
  • the emitter section 14 For heating the emitter section 14 which is in the form of a film, the emitter section 14 should be sintered together with its evaporation source while their atmosphere is being controlled.
  • the emitter section 14 may be covered with an appropriate member for preventing the surface thereof from being directly exposed to the sintering atmosphere when the emitter section 14 is sintered.
  • the covering member should preferably be made of the same material as the substrate 12.
  • the drive voltage Va outputted from the pulse generation source 22 has repeated steps each including a period in which a first voltage Va1 is outputted (preparatory period T1) and a period in which a second voltage Va2 is outputted (electron emission period T2).
  • the first voltage Va1 is such a voltage that the potential of the cathode electrode 16 is higher than the potential of the anode electrode 20
  • the second voltage Va2 is such a voltage that the potential of the cathode electrode 16 is lower than the potential of the anode electrode 20.
  • the drive voltage Va has a rectangular pulse waveform including the first voltage Va1 in the preparatory period T1, and the second voltage Va2 in the electron emission period T2.
  • the preparatory period T1 is a period in which the first voltage Va1 is applied between the cathode electrode 16 and the anode electrode 20 to polarize the emitter section 14, as shown in FIG. 4.
  • the first voltage Va1 may be a DC voltage, as shown in FIG. 3, but may be a single pulse voltage or a succession of pulse voltages.
  • the preparatory period T1 should preferably be longer than the electron emission period T2 for sufficient polarization.
  • the preparatory period T1 should preferably be 100 ⁇ sec. or longer. This is because the absolute value of the first voltage Va1 for polarizing the emitter section 14 is smaller than the absolute value of the second voltage Va2 to reduce the power consumption at the time of applying the first voltage Va1, and to prevent the damage of the cathode electrode 16.
  • the voltage levels of the first voltage Va1 and the second voltage Va2 are determined so that the polarization to the positive polarity and the negative polarity can be performed reliably.
  • the dielectric material of the emitter section 14 has a coercive voltage
  • the absolute values of the first voltage Va1 and the second voltage Va2 are the coercive voltage or higher.
  • the electron emission period T2 is a period in which the second voltage Va2 is applied between the cathode electrode 16 and the anode electrode 20.
  • the triple point A is defined by the cathode electrode 16, the emitter section 14, and the vacuum.
  • the primary electrons are emitted from the cathode electrode 16 near the triple point A, and the primary electrons thus emitted from the triple point A impinge upon the emitter section 14, causing the emitter section 14 to emit secondary electrons. If the thickness of the cathode electrode 16 is very small (up to 10 nm), then electrons are emitted from the interface between the cathode electrode 16 and the emitter section 14.
  • the electron emission is stably performed, and the number of emitted electrons would reach 2 billion or more.
  • the electron emitter is advantageously used in the practical applications.
  • the number of emitted electrons is increased substantially proportional to the amplitude Vin of the drive voltage Va applied between the cathode electrode 16 and the anode electrode 20.
  • the number of the emitted electrons can be controlled easily.
  • a distribution of emitted secondary electrons will be described below.
  • most of the secondary electrons have an energy level near zero.
  • the secondary electrons are emitted from the surface of the emitter section 14 into the vacuum, they move according to only an ambient electric field distribution. Specifically, the secondary electrons are accelerated from an initial speed of about 0 (m/sec) according to the ambient electric field distribution. Therefore, as shown in FIG. 5B, if an electric field Ea is generated between the emitter section 14 and the collector electrode 24, the secondary electrons has their emission path determined along the electric field Ea. Therefore, the electron emitter 10A can serve as a highly straight electron source.
  • the secondary electrons which have a low initial speed are electrons which are emitted from the solid emitter section 14 under an energy that has been generated by a coulomb collision with primary electrons.
  • the pattern or the potential of the collector electrode 24 may be changed suitably depending on the application. If a control electrode (not shown) or the like is provided between the emitter section 14 and the collector electrode 24 for arbitrarily setting the electric field distribution between the emitter section 14 and the collector electrode 24, the emission path of the emitted secondary electrons can be controlled easily. Thus, it is possible to change the size of the electron beam by converging and expanding the electron beam, and to change the shape of the electron beam easily.
  • the electron source emitting a straight electron beam is produced, and the emission path of emitted secondary electrons is controlled easily. Therefore, the electron emitter 10A according to the first embodiment can be utilized advantageously as a pixel of a display with an aim to decrease the pitch between the pixels.
  • secondary electrons having an energy level which corresponds to the energy E 0 of primary electrons are emitted. These secondary electrons are primary electrons that are emitted from the cathode electrode 16 and scattered in the vicinity of the surface of the emitter section 14 (reflected electrons).
  • the secondary electrons-referred herein include both the reflected electrons and Auger electrons.
  • the thickness of the cathode electrode 16 is very small (up to 10 nm), then primary electrons emitted from the cathode electrode 16 are reflected by the interface between the cathode electrode 16 and the emitter section 14, and directed toward the collector electrode 24.
  • An electron emitter 10Aa according to a first specific example has substantially the same structure as the electron emitter 10A according to the first embodiment described above, but differs from the electron emitter 10A in that the emitter section 14 is made of a piezoelectric material.
  • FIG. 7 shows a polarization-electric field characteristic curve of the piezoelectric material of the emitter section 14.
  • the hysteresis loop from a point p1, a point p2, to a point p3 will be described.
  • a positive electric field is applied to the piezoelectric material at the point p1
  • the piezoelectric material is polarized substantially in one direction.
  • the electric field is negatively increased to a level of a coercive field (about - 700V/mm) at the point p2, polarization reversal starts to occur.
  • polarization reversal is carried out completely.
  • a first voltage Va1 is applied between the cathode electrode 16 and the anode electrode 20, and a positive electric field (about 1000V/mm) is applied to the emitter section 14 in the preparatory period T1.
  • a positive electric field about 1000V/mm
  • the emitter section 14 is polarized in one direction.
  • the second voltage Va2 is applied between the cathode electrode 16 and the anode electrode 20, for causing emission of the secondary electrons from the emitter section 14 or from the interface between the cathode electrode 16 and the emitter section 14.
  • the voltage Vak between the cathode electrode 16 and the anode electrode 20 is increased again by the second voltage Va2 applied to the cathode electrode 16.
  • the voltage drop at the time of the electron emission is small (about 20V)
  • the electron emission does not occur after the first electron emission.
  • the electric field beyond the level of the coercive field is rapidly applied to the emitter section 14 which is polarized in one direction. Therefore, the electrons are emitted efficiently, and the electron emitter 10Aa can be utilized easily in displays or light sources.
  • the electric field for inducing electron emission (the electric field at the point p4) is beyond the level of the coercive field. In the electric field for electron emission, the polarization reversal is almost completed. The levels of the electric fields do not change substantially. Therefore, the electron emitter 10Aa has digital-like electron emission characteristics. The level of the electric field for electron emission depends on the coercive field. When the level of the coercive field is small, the electron emitter can be operated at a low voltage.
  • the level of the second voltage Va2 applied between the cathode electrode 16 and the anode electrode 20 is controlled for applying an electric field beyond the level of the coercive field to the emitter section 14 within a certain period tc1 (e.g., 10 psec or less) from the beginning of the electron emission period T2.
  • tc1 e.g. 10 psec or less
  • a drive voltage Va having an alternating waveform including positive and negative pulses can be used for carrying out the successive electron emissions easily.
  • the electron emitter 10Ab according to the second specific example has substantially the same structure as the electron emitter 10A according to the first embodiment described above, but differs from the electron emitter 10A in that the emitter section 14 is made of an anti-ferroelectric material.
  • the polarization of the anti-ferroelectric material is induced proportionally to the voltage in a small electric field.
  • the anti-ferroelectric material functions as a ferroelectric material (electric field induced phase transition).
  • Hysteresis loops are shown in the positive electric field and the negative electric field.
  • the anti-ferroelectric material functions as a dielectric material (polarization is reset).
  • the hysteresis loop in the positive electric field from a point p11, a point p12, to a point p13 will be described.
  • the anti-ferroelectric material is polarized almost in one direction when the positive electric field is applied at the point p11. Then, the intensity of the electric field is decreased. From the point 12 to point 13, the amount of polarization decrease significantly.
  • the anti-ferroelectric material functions as a dielectric material at the point p13 where the electric field is zero, and the polarization is reset. Then, when the negative electric field is applied, a phase transition occurs in the emitter section 14, and the emitter section 14 functions as a ferroelectric material.
  • the electric field is negatively increased beyond a level of about -2300V/mm at the point p14, polarization reversal of the emitter section 14 is started. At the point p15, the emitter section 14 is polarized in the opposite direction.
  • the first voltage Va1 is applied between the cathode electrode 16 and the anode electrode 20 for applying the positive electric field (about 3000V/nm) to the emitter section 14.
  • the emitter section 14 is polarized in one direction.
  • the first voltage va1 applied between the cathode electrode 16 and the anode electrode 20 in the preparatory period T1 may be a reference voltage (0v). In this case, no electric field is applied to the emitter section 14. At this time, as shown in the polarization-electric field characteristic curve, the polarization of the emitter section 14 is reset.
  • a second voltage Va2 is applied between the cathode electrode 16 and the anode electrode 20 for rapidly applying an electric field (e.g., about -3000V/mm) to the emitter section 14 to change the polarization of the emitter section 14.
  • an electric field e.g., about -3000V/mm
  • the difference between the electric field for inducing electron emission (the electric field at the point p16) and the electric field for resetting polarization (the electric field at the point p17) is small. Therefore, when electron emission occurs to cause the drop in the voltage between the cathode electrode 16 and the anode electrode 20, the polarization in the emitter section 14 is reset easily, and the emitter section 14 is brought into a condition as if a reference voltage 0V were applied.
  • the electric field is applied to the emitter section 14 rapidly for causing phase transition in the emitter section 14 into a ferroelectric material and changing polarization of the emitter section 14. Therefore, the electrons are emitted efficiently, and the electron emitter 10Ab can be utilized easily in displays or light sources.
  • the electron emitter 10Ab has digital-like electron emission characteristics.
  • the electric field for electron emission depends on the electric field for inducing phase transition of the emitter section 14 into the ferroelectric material. When the level of the electric field for inducing phase transition is small, the electron emitter is operated at a low voltage.
  • Electron emission in the electron emission period T2 can be carried out by the single polarity operation (negative polarity).
  • the driving circuit system is simplified.
  • the electron emitter can be operated by small energy consumption at a low cost with a compact structure.
  • the level (the maximum amplitude or phase transition period ta) of the second voltage Va2 applied between the cathode electrode 16 and the anode electrode 20 is controlled for applying an electric field to induce the phase transition of the emitter section 14 within a certain period tc2 (e.g., 10 ⁇ sec or less) from the beginning of the electron emission period T2, and polarize the emitter section 14.
  • tc2 e.g. 10 ⁇ sec or less
  • the electron emitter 10Ac according to the third specific example has substantially the same structure as the electron emitter 10A according to the first embodiment described above, but differs from the electron emitter 10A in that the emitter section 14 is made of an electrostrictive material.
  • a method of emitting electrons from the electron emitter 10Ac according to the third specific example will be described.
  • the polarization of the electrostrictive material is induced substantially proportionally to the electric field.
  • the rate of change in the polarization is large in a small electric field in comparison with a large electric field.
  • the polarization occurs gradually according to the change of the electric field. When no electric field is applied, the polarization is reset.
  • the characteristics curve from a point p21 to a point p23 will be described.
  • the electrostrictive material of the emitter section 14 is polarized almost in one direction. Then, as the intensity of the electric field is decreased from the point p21 to the point 22, the amount of the polarization is decreased corresponding to the intensity of the positive electric field.
  • the electrostrictive material functions as a dielectric material. Thereafter, as the intensity of the negative electric field is increased from the point p22 to the point p23, the polarization is reversed gradually into the opposite direction. At the point p23, the emitter section 13 is almost polarized in the opposite direction. The amount of the polarization in the emitter section 14 is proportional to the intensity of the applied electric field.
  • a first voltage Va1 is applied between the cathode electrode 16 and the anode electrode 20 for applying the positive electric field (about 2000V/nm) to the emitter section.
  • the emitter section 14 is polarized in one direction.
  • the first voltage va1 applied between the cathode electrode 16 and the anode electrode 20 in the preparatory period T1 may be a reference voltage (0v). In this case, no electric field is applied to the emitter section 14. At this time, as shown in the polarization-electric field characteristic curve, the polarization of the emitter section 14 is reset.
  • a second voltage Va2 is applied between the cathode electrode 16 and the anode electrode 20 for rapidly applying an electric field (e.g., about -2000V/mm) to the emitter section 14 to change the polarization of the emitter section 14.
  • an electric field e.g., about -2000V/mm
  • electron emission starts to occur.
  • tc3 10 ⁇ sec or less in this example
  • the emitter section 14 is polarized gradually according to the change of the electric field.
  • the amount of polarization per unit time is large, the number of emitted electrons is large. Therefore, the electron emitter 10Ac has analog-like electron emission characteristics.
  • the potential difference between the electric field for inducing electron emission (the electric field at the point p23) and the electric field for resetting polarization (the electric field at the point p22) is small. Therefore, when electron emission occurs to cause the drop in the voltage between the cathode electrode 16 and the anode electrode 20, the polarization in the emitter section 14 is reset easily, and the emitter section 14 is brought into a condition as if the reference voltage 0V were applied.
  • the second voltage Va2 is applied between the cathode electrode 16 and the anode electrode 20. Therefore, the voltage Vak between the cathode electrode 16 and the anode electrode 20 is increased rapidly. At this time, the change in the polarization progresses rapidly. Thus, the electrons are emitted at a voltage lower than the voltage for the first electron emission.
  • the polarization of the emitter section 14 is reset again easily. Thereafter, by continuously applying the second voltage Va2 between the cathode electrode 16 and the anode electrode 20, the voltage Vak between the cathode electrode 16 and the anode electrode 20 is increased again to polarize the emitter section 14. Again, the change in the polarization progresses rapidly, and the electron emission occurs at a voltage substantially same as the voltage for the second electron emission.
  • the voltage Vak between the cathode electrode 16 and the anode electrode 20 fluctuates slightly. The slight fluctuation keeps the electron emission. By controlling the level of the second voltage Va2, it is possible to control the duration of the electron emission.
  • the amount of polarization in the emitter section 14 is controlled for efficiently emitting the electrons.
  • the electron emitter 10Ac can be utilized easily in displays or light sources.
  • the electron emitter can be operated at a low voltage.
  • Electron emission in the electron emission period T2 can be carried out by the single polarity operation (negative polarity).
  • the driving circuit system is simplified.
  • the electron emitter can be operated by small energy consumption at a low cost with a compact structure.
  • the level (the maximum amplitude or phase transition period ta) of the second voltage Va2 applied between the cathode electrode 16 and the anode electrode 20 is controlled for controlling the amount of polarization in the emitter section 14 within a certain period tc3 (e.g., 10 ⁇ sec or less) from the beginning of the electron emission period T2 and controlling the number of emitted electrons.
  • a certain period tc3 e.g. 10 ⁇ sec or less
  • the electron emitter 10B according to the second embodiment has substantially the same structure as the electron emitter 10A according to the first embodiment described above, but differs from the electron emitter 10A in that the cathode electrode 16 is formed on a front surface of the emitter section 14 having a plate shape, and the anode electrode 20 is formed on a back surface of the emitter section 14.
  • the drive voltage Va is applied between the cathode electrode 16 and the anode electrode 20 through a lead electrode 17 extending from the cathode electrode 16 and a lead electrode 21 extending from the anode electrode 20, for example.
  • a collector electrode 24 is positioned above the cathode electrode 16, and the collector electrode 24 is coated with a fluorescent layer 28.
  • Vak is a voltage - between the cathode electrode 16 and the anode electrode 20.
  • the dielectric breakdown voltage of the emitter section 14 is at least 10kV/mm or higher. In the embodiment, when the thickness h of the emitter section 14 is 20 ⁇ m, even if the drive voltage of -100V is applied between the cathode electrode 16 and the anode electrode 20, the emitter section 14 does not break down dielectrically.
  • the cathode electrode 16 may have an oval shape as shown in a plan view of FIG. 16, or a ring shape like an electron emitter 10Ba of a first modification as shown in a plan view of FIG. 15.
  • the cathode electrode 16 may have a comb teeth shape like an electron emitter 10Bb of a second modification as shown in FIG. 17.
  • the cathode electrode 16 having a ring shape or a comb teeth shape in a plan view When the cathode electrode 16 having a ring shape or a comb teeth shape in a plan view is used, the number of triple points (electric field concentration points A) of the cathode electrode 16, the emitter section 14, and the vacuum is increased, and the efficiency of electron emission is improved.
  • the cathode electrode 16 has a thickness tc (see FIG. 14) of 20 ⁇ m or less, or more preferably 5 ⁇ m or less.
  • the cathode electrode 16 may have a thickness tc of 100 nm or less.
  • the cathode electrode 16 of an electron emitter 10Bc of a third modification shown in FIG. 18 is very thin, having a thickness tc of 10 nm or less. In this case, electrons are emitted from the interface between the cathode electrode 16 and the emitter section 14, and thus, the efficiency of electron emission is further improved.
  • the anode electrode 20 is made of the same material by the same process as the cathode electrode 16.
  • the anode electrode 20 is made by any of the above thick-film forming processes.
  • the anode electrode 20 has a thickness tc of 20 ⁇ m or less, or more preferably 5 ⁇ m or less.
  • the drive voltage Va outputted from the pulse generation source 22 has repeated steps each including a period in which a first voltage Va1 is outputted (preparatory period T1) and a period in which a second voltage Va2 is outputted (electron emission period T2).
  • the preparatory period T1 is a period in which the first voltage Va1 is applied between the cathode electrode 16 and the anode electrode 20 to polarize the emitter section 14 in one direction, as shown in FIG. 20.
  • the first voltage Va1 may be a DC voltage, as shown in FIG. 19, but may be a single pulse voltage or a succession of pulse voltages.
  • the preparatory period T1 should preferably be longer than the electron emission period T2 for sufficient polarization. For example, the preparatory period T1 should preferably be 100 ⁇ sec. or longer.
  • the electron emission period T2 is a period in which the second voltage Va2 is applied between the cathode electrode 16 and the anode electrode 20.
  • the second voltage Va2 is applied between the cathode electrode 16 and the anode electrode 20, as shown in FIG. 21, the polarization of at least a part of the emitter section 14 is reversed or changed. Specifically, the polarization reversal or the polarization change occurs at a portion of the emitter section 14 which is underneath the cathode electrode 16, and a portion of the emitter section 14 which is exposed near the cathode electrode 16. The polarization likely to changes at the exposed portion near the cathode electrode 16.
  • the electron emitter 10B of the second embodiment having the triple point A where the cathode electrode 16, the emitter section 14, and the vacuum are present at one point, primary electrons are emitted from the cathode electrode 16 near the triple point A, and the primary electrons thus emitted from the triple point A impinge upon the emitter section 14, causing the emitter section 14 to emit secondary electrons. If the thickness of the cathode electrode 16 is very small (up to 10 nm), then electrons are emitted from the interface between the cathode electrode 16 and the emitter section 14.
  • a local cathode is formed in the cathode electrode 16 in the vicinity of the interface between the cathode electrode 16 and the emitter section 14, and positive poles of the dipole moments charged in the area of the emitter section 14 near the cathode electrode 16 serve as a local anode which causes the emission of electrons from the cathode electrode 16.
  • Some of the emitted electrons are guided to the collector electrode 24 (see FIG. 14) to excite the fluorescent layer 28 to emit fluorescent light from the fluorescent layer 28 to the outside. Further, some of the emitted electrons impinge upon the emitter section 14 to cause the emitter section 14 to emit secondary electrons. The secondary electrons are guided to the collector electrode 24 to excite the fluorescent layer 28.
  • the electron emitter 10B In the electron emitter 10B according to the second embodiment, distribution of the emitted electrons are same as the distribution of the second electrons described with reference to FIG. 10. Most of the secondary electrons have an energy level near zero.
  • the secondary electrons When the secondary electrons are emitted from the surface of the emitter section 14 into the vacuum, they move according to only an ambient electric field distribution. Specifically, the secondary electrons are accelerated from an initial speed of about 0 (m/sec) according to the ambient electric field distribution. Therefore, as shown in FIG. 14, if an electric field Ea is generated between the emitter section 14 and the collector electrode 24, the secondary electrons has their emission path determined along the electric field Ea. Therefore, the electron emitter 10B can serve as a highly straight electron source.
  • the secondary electrons which have a low initial speed are electrons which are emitted from the solid emitter section 14 under an energy that has been generated by a coulomb collision with primary electrons.
  • Secondary electrons having an energy level which corresponds to the energy E 0 of primary electrons are emitted. These secondary electrons are primary electrons that are emitted from the cathode electrode 16 and scattered in the vicinity of the surface of the emitter section 14 (reflected electrons).
  • the secondary electrons referred herein include the electrons which have a low initial speed are electrons which are emitted from the solid emitter section 14 under an energy that has been generated by a coulomb collision with primary electrons, the reflected electrons and Auger electrons.
  • the thickness of the cathode electrode 16 is very small (up to 10 nm), then primary electrons emitted from the cathode electrode 16 are reflected by the interface between the cathode electrode 16 and the emitter section 14, and directed toward the collector electrode 24.
  • the electron emission from the cathode electrode 16 progresses, floating atoms of the emitter section 14 which are evaporated due to the Joule heat are ionized into positive ions and electrons by the emitted electrons.
  • the electrons generated by the ionization ionize the atoms of the emitter section 14. Therefore, the electrons are increased exponentially to generate a local plasma in which the electrons and the positive ions are neutrally present.
  • the secondary electrons may also ionize the atoms of the emitter section 14.
  • the positive ions generated by the ionization may impinge upon the cathode electrode 16, possibly damaging the cathode electrode 16.
  • the electrons emitted from the cathode electrode 16 are attracted to the positive poles, which are present as the local anode, of the dipole elements in the emitter section 14, negatively charging the surface of the emitter section 14 near the cathode electrode 16.
  • the factor for accelerating the electrons (the local potential difference) is lessened, and any potential for emitting secondary electrons is eliminated, further progressively negatively charging the surface of the emitter section 14.
  • the positive polarity of the local anode provided by the dipole moments is weakened, and the intensity E A of the electric field between the local anode and the local cathode is reduced (the small intensity E A of the electric field is indicated by the broken-line arrow in FIG. 22).
  • the electron emission is stopped.
  • the drive voltage Va applied between the cathode electrode 16 and the anode electrode 20 has a positive voltage Va1 of 50 V, and a negative voltage va2 of -100V.
  • the change ⁇ Vak of the voltage between the cathode electrode 16 and the anode electrode 20 at the time P1 (peak) the electrons are emitted is 20V or less (about 10 V in the example of FIG. 23B), and very small. Consequently, almost no positive ions are generated, thus preventing the cathode electrode 16 from being damaged by positive ions. This arrangement is thus effective to increase the service life of the electron emitter 10B.
  • the emitter section 14 is likely to be damaged when electrons emitted from the emitter section 14 impinge upon the emitter section 14 again or when ionization occurs near the surface of the emitter section 14. Due to the damages to the crystallization, the mechanical strength and the durability of the emitter section 14 are likely to be lowered.
  • the emitter section 14 is made of a dielectric material having a high evaporation temperature in vacuum.
  • the emitter section 14 may be made of BaTiO 3 which does not include Pb.
  • the emitter section 14 is not evaporated into floating atoms easily due to the Joule heat, and the ionization by the emitted electrons is prevented. Therefore, the surface of the emitter section 14 is effectively protected.
  • the electron emitter 10C according to the third embodiment has substantially the same structure as the electron emitter 10A according to the first embodiment, but differs from the electron emitter 10A in that the electron emitter 10C includes one substrate 12, an anode electrode 20 is formed on the substrate 12, the emitter section 14 is formed on the substrate 12 to cover the anode electrode 20, and the cathode electrode 16 is formed on the emitter section 14.
  • the electron emitter 10C can prevent the damages of the cathode electrode 16 by the positive ions, and has a long service life.
  • the emitter section 14 is made of a piezoelectric material, an anti-ferroelectric material, or an electrostrictive material.
  • the electron emitters 10B, 10C In the electron emitters 10B, 10C according to the second and third embodiments, only the positive poles or the negative poles of the dipole moments are oriented to the cathode electrode 16. Therefore, the local electric field generated at the cathode electrode 16 is large. In the first and second embodiments, when polarization of the emitter section 14 is reversed or changed, only the positive poles are oriented to the cathode electrode 16 having the negative polarity. Thus, the primary electrons are efficiently emitted from the cathode electrode 16.
  • one electron emitter 10B or 10C includes one emitter section 14, and one cathode electrode 16 and one anode electrode 20 formed on the emitter section 14.
  • a plurality of electron emitters 10(1), 10(2), 10(3) may be formed using one emitter section 14 as shown in FIG. 25, for example.
  • a plurality of cathode electrodes 16a, 16b, 16c are formed independently on a front surface of one emitter section 14, and a plurality anode electrodes 20a, 20b, 20c are formed on a back surface of the emitter section 14 to form the plurality of electron emitters 10(1), 10(2), 10(3).
  • the anode electrodes 20a, 20b, 20c are provided under the corresponding cathode electrodes 16a, 16b, 16c.
  • the emitter section 14 is interposed between the anode electrodes 20a, 20b, 20c and the cathode electrodes 16a, 16b, 16c.
  • a plurality of cathode electrodes 16a, 16b, 16c are formed independently on a front surface of one emitter section 14, and one anode electrode 20 (common anode electrode) is formed on a back surface of the emitter section 14 to form a plurality of electron emitters 10(1), 10(2), 10(3).
  • one very thin (up to 10nm) cathode electrode 16 (common cathode electrode) is formed on a front surface of one emitter section 14, and a plurality of anode electrodes 20a, 20b, 20c are formed independently on a back surface of the emitter section 14 to form a plurality of electron emitter 10(1), 10(2), 10(3).
  • a plurality of anode electrodes 20a, 20b, 20c are formed independently on a substrate 12
  • one emitter section 14 is formed to cover these anode electrodes 20a, 20b, 20c
  • a plurality of cathode electrodes 16a, 16b, 16c are formed independently on the emitter section 14 to form a plurality of electron emitter 10(1), 10(2), 10(3).
  • the cathode electrodes 16a, 16b, 16c are provided above the corresponding anode electrodes 20a, 20b, 20c.
  • the emitter section 14 is interposed between the anode electrodes 20a, 20b, 20c and the cathode electrodes 16a, 16b, 16c.
  • one anode electrode 20 is formed on a substrate 12, and one emitter section 14 is formed to cover the anode electrode 20, and a plurality of cathode electrodes 16a, 16b, 16c are formed independently on the emitter section 14 to form a plurality of electron emitters 10(1), 10(2), 10(3).
  • a plurality of anode electrodes 20a, 20b, 20c are formed independently on a substrate 12, one emitter section 14 is formed to cover these anode electrodes 20a, 20b, 20c, and one very thin cathode electrode 16 is formed on the emitter section 14 to form a plurality of electron emitters 10(1), 10(2), 10(3).
  • a plurality of electron emitters 10(1), 10(2), 10(3) are formed using one emitter section 14. As described later, the electron emitters 10(1), 10(2), 10(3) are suitably used as pixels of a display.
  • the collector electrode 24 is coated with a fluorescent layer 28 to for use as a pixel of a display as shown in FIG. 1.
  • the displays of the electron emitters 10A through 10C offer the following advantages:
  • the displays can be used in a variety of applications described below.
  • the electron emitters can be used as a variety of light sources described below.

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JP4678832B2 (ja) 2004-07-27 2011-04-27 日本碍子株式会社 光源
US20060132052A1 (en) * 2004-10-14 2006-06-22 Ngk Insulators, Ltd. Electron-emitting apparatus and method for emitting electrons
CN1856857A (zh) * 2004-12-28 2006-11-01 日本碍子株式会社 光源
JP5053524B2 (ja) * 2005-06-23 2012-10-17 日本碍子株式会社 電子放出素子

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