WO2000010190A2 - Emetteur de champ d'electrons et son procede de fabrication - Google Patents

Emetteur de champ d'electrons et son procede de fabrication Download PDF

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Publication number
WO2000010190A2
WO2000010190A2 PCT/EP1999/005324 EP9905324W WO0010190A2 WO 2000010190 A2 WO2000010190 A2 WO 2000010190A2 EP 9905324 W EP9905324 W EP 9905324W WO 0010190 A2 WO0010190 A2 WO 0010190A2
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Prior art keywords
substrate
carbon film
hydrocarbon
nanomaterial
carbon
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PCT/EP1999/005324
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English (en)
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WO2000010190A3 (fr
Inventor
Sergey Konstantinovich Gordeev
Andrey Ivanovich Kosarev
Aleksandr Nicolaevich Andronov
Andrey Iakovlevich Vinogradov
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Frenton Limited
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Priority to AU54135/99A priority Critical patent/AU5413599A/en
Publication of WO2000010190A2 publication Critical patent/WO2000010190A2/fr
Publication of WO2000010190A3 publication Critical patent/WO2000010190A3/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/022—Manufacture of electrodes or electrode systems of cold cathodes
    • H01J9/025—Manufacture of electrodes or electrode systems of cold cathodes of field emission cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • 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
    • H01J1/304—Field-emissive 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

Definitions

  • the present invention relates to a field emitter of electrons and a method for the manufacturing thereof.
  • Materials with low threshold of field emission can be used in different electronic devices, such as efficient cathodes, e.g. for flat computer and TV displays.
  • Patent appl. WO 9718576 discloses diamond powder field emitters, such as an electron field emitter comprised of diamond powder prepared by shock synthesis. There is also described a field-emitter comprised of diamond powder attached to the surface of a substrate by e.g. pressing it against a conductor or by creating a thin metal layer as a conductor on the substrate.
  • a method for making electron emitters using ultra-fine and larger (5-10000 nm) diamond particles that have been treated to enhance their capability for electron emission under low electric fields is disclosed in U.S. Pat. No. 5,709,577.
  • the diamond particles heat treated by hydrogen plasma allows the production of electron emission current density of at least 0.01 A/cm 2 at very low electric fields (about 0.5-1.5 V/ ⁇ m).
  • the emitters are produced by suspending the diamond particles in an aqueous solution, applying the suspension as a coating onto a conducting substrate such as n-type Si or metal, and then subjecting the coated substrate to a plasma of hydrogen, preferably at temperatures above 300°N, for 30 minutes or longer.
  • the described method provides emitters with low emission threshold but the articles are being of small sizes.
  • US Pat. No. 5.602.439 discloses an emitter comprising diamond and conductive carbon, preferably graphite.
  • the emitter has a graphite-like substrate covered with a diamond or diamond-like carbon coating.
  • the emitter may also be graphite or carbon with embedded diamond.
  • a manner of the production is making a graphite-like substrate by processing carbon fiber with a diamond particle suspension (particle size of 0.25-1.0 ⁇ m) in organic solvent. Then the substrate is dried. Diamond or diamond-like film is deposited on the substrate prepared by plasma or chemical deposition from carbon containing gases.
  • the produced emitter has a substrate with high electrical conductivity and a diamond layer on its surface. The emitter has good emission properties.
  • Producing the known emitter requires rather complex apparatus. Moreover the process does not guarantee uniform deposition of diamond particles onto a rather irregular surface of carbon fibers. This results in irregular thickness of the diamond or diamond-like layer. The irregularity limits the surface area of the emitters. The mentioned drawbacks prevent producing large articles with uniform composition.
  • Another production manner is to mix e.g. graphite and diamond in suitable binder material. After forming and curing of the binder material, the additional diamond surfaces may be exposed by treatment with a suitable etching to remove binder and some graphite from outer diamond surfaces.
  • a suitable etching to remove binder and some graphite from outer diamond surfaces.
  • the drawback of this patent method is the complex and time-consuming technique of diamond deposition, which limits the size of, produced emitters and gives a lower electrical conductivity of the diamond layers, compared with that of the graphite-like carbons. The latter limits the emission current of the emitter.
  • VHF PECVD Very High Frequency Plasma Enhanced Chemical Vapor Deposition
  • a two-stage activation process provided significant improvement of the emission characteristics, and especially reduction of the emission threshold was shown.
  • An activation of a silicon surface was performed in hydrogen plasma, in a very high frequency capacity discharge at a temperature of 220°C.
  • the second stage was carried out in a gas mixture of hexane and hydrogen at the same temperature. In both cases the discharge frequency was 56 MHz. Excluding either the first or the second step resulted in deterioration of the emission properties (e.g. threshold field and emission cunent).
  • VHF CVD Very High Frequency Chemical Vapor Deposition
  • the inventors of the present invention have developed a new field electron emitter comprising several carbon materials, having a substrate made of a nanomaterial coated by a carbon film layer prepared by VHF PECVD technique
  • the object of the presented invention is to provide a field emitter combining low threshold of emission with high electrical conductivity, uniform surface properties and stable properties in the same time, and easy in producing.
  • a further object of the invention is to provide a process for producing a field electron emitter, simple in realization, which makes it possible to form large articles having desired shapes and controllable surfaces (in respect to desired structure and properties of the surface) to obtain significant increase of the emission at certain conditions compared to earlier known emitters.
  • the object of the invention is obtained by a field emitter of electrons comprising a substrate with a deposited layer on it, characterized in that the substrate is made of nanomaterial, i.e. a porous carbon material having skeleton structure, with an open porosity of 35-70% and in that the deposited layer is a carbon film obtained from of mixture of hydrocarbon or hydrocarbons and hydrogen using a very high frequency plasma enhanced chemical vapor deposition (VHF PECVD) technique.
  • VHF PECVD very high frequency plasma enhanced chemical vapor deposition
  • the thickness of the carbon film is 0.2 - 1.5 ⁇ m.
  • the substrate consists of a porous carbon material, including diamond particles of a size less than 10 nm bonded together by a pyrocarbon matrix, the mass proportion of the pyrocarbon matrix to the diamond particles is 0.08-0.50.
  • the substrate is made of porous carbon material comprising nanopores in the size range of 0.6-2.5 nm, the volumetric content of the pores being 20- 50% vol. In both alternatives the carbon film is made under conditions of capacitance discharge.
  • the present invention relates also to a method for producing a field electron emitter, comprising a step of depositing a layer on a substrate, c h a c t e r i s e d by forming a substrate in the form of a nanomaterial, i.e. a porous carbon material having skeleton structure, and by depositing a carbon film thereon.
  • the substrate is formed by the following steps: molding a blank from diamond particles, having size below 10 nm; heat treating the blank in a medium of at least one hydrocarbon at a temperature above the decomposition temperature of the hydrocarbon or hydrocarbons.
  • the substrate is formed by the following steps: molding a blank from covalent or metal-like carbide particles of sizes from 0.1 to 60 ⁇ m; heat treating the blank in a medium of at least one hydrocarbon at a temperature above the decomposition temperature of the hydrocarbon or hydrocarbons; heat treating the blank in a medium of at least one gaseous halogen at a temperature of 350-1200°C, preferably the heat treating of the blank is made in a medium of chlorine at a temperature of 500-1000°C.
  • the carbon film is formed by very high frequency plasma enhanced chemical vapor deposition technique in a gaseous mixture of at least one hydrocarbon and hydrogen, and the carbon film is deposited under conditions of capacitance discharge at a temperature of 200-400°C and a discharge frequency of 10-100 MHz.
  • the substrate is preferably treated before forming the carbon film by the following steps: treating in hydrogen plasma under conditions of capacitance very high frequency plasma discharge; and treating under conditions of very high frequency plasma enhanced chemical vapor deposition technique in a gas medium of hydrocarbon or hydrocarbons and hydrogen at a deposition rate of the carbon film being less than 1 nm/hour.
  • Fig.l shows a cross section of the field emitter and circuitry for the observation of emitted electrons on a phosphor screen.
  • Fig.2 shows an experimental set up for the measurements of field emission characteristics.
  • Fig.3 shows the electron emission current density versus the electric field.
  • Fig.4 shows an Auger spectra for diamond, graphite and VHF PECVD carbon film
  • nanomaterial in the present invention refers to carbon materials comprising a carbon skeleton having pores of a size less than 20 nm.
  • the nanomaterial can consist solely of a carbon skeleton with nanoporosity or a carbon skelton containing within it nanodiamonds being bonded to a pyrocarbon (deposited pyrolytic carbon) matrix.
  • nanomonds refers to diamonds, also known as ultra-dispersed diamonds with sizes less than 10 nm.
  • skeleton means a continuous network structure.
  • VHF PECVD Very High Frequency Plasma Enhanced Chemical Vapor Deposition
  • the emitter has a nanomaterial substrate comprising nanodiamond particles with size less than 10 nm bonded by a pyrocarbon skeleton and having pores of a size less than 20 nm.
  • nanomaterial is obtained by the treatment of a blank molded of nanodiamonds in a medium of hydrocarbon (or a mixture of hydrocarbons) at a temperature above their decomposition temperature. The method is described in European patent application WO 97/11923.
  • the mass proportion of the pyrocarbon matrix and the diamond particles should be in the range of 0.08-0.50. Materials with a higher mass proportion are complicated to manufacture, while those with a lower mass proportion do not possess sufficient conductance for use in emitters.
  • the nanomaterial substrate is coated by a carbon film layer prepared by Very High Frequency Plasma Enhanced Chemical Vapor Deposition (VHF PECVD) technique.
  • VHF PECVD Very High Frequency Plasma Enhanced Chemical Vapor Deposition
  • the emitter has a nanomaterial substrate being a carbon skeleton with nanoporosity.
  • the material is made by treating a formed blank comprising of one or more carbides with particle size 0.1-60 ⁇ m with two thermochemical treatments.
  • the first treatment is in a medium of at least one hydrocarbon at a temperature above its decomposition temperature.
  • the second treatment is in a medium of gaseous halogens, such as chlorine, at elevated temperatures of 350-1200°C.
  • the nanopores are formed owing to the chemical reaction of the gaseous halogen and covalent or metal-like carbides, where the metal or non-metal (i.e. the carbide forming element) forms gaseous halogenides.
  • the treatment of blanks containing carbide of a certain element e.g. silicon carbide, boron carbide, titanium carbide, molybdenum carbide etc., may for example be treated in a medium of chlorine at 500-1000°C.
  • the manufacture of such materials can be carried out e.g. as described in WO 98/54111 or WO 97/20333, and the blank may comprise one or several different carbides.
  • the size of the nanopores is rigidly connected with the composition of the initial raw material.
  • the nanomaterial of skeleton structure comprises nanopores with a size (or several sizes) between about 0.6 to 2.5 nm, with a volumetric content of the pores being 20 to 50 %. Nanomaterials having pores of different size ranges can of course also be used in the present invention.
  • the manufacture of the materials with a volume content of nanopores outside the range 20-50% offers some technological difficulties.
  • the substrate made of the nanomaterial is a carbon conductive material.
  • the nanomaterial substrate is coated by a carbon film layer prepared by VHF PECVD technique in the same way as in the prefened embodiment.
  • the carbon film layer of the emitter in both embodiments is formed by means of VHF PE CVD technique from a mixture of gaseous hydrocarbon (or hydrocarbons) and hydrogen using capacitance discharge.
  • the capacitance discharge is carried out e.g. at temperatures of 200-400°C and with a discharge frequency of 10-100 MHz.
  • the surface treatment consists of two stages: The first stage is a treatment by hydrogen plasma, and the second stage is carried out in a gas mixture of hydrocarbon(s) and hydrogen plasma at the same temperature, and at a rate avoiding carbon film deposition (less than 1 nm hour). In both cases the discharge frequency of 10-100 MHz is used. Then the deposition of the carbon film layer is performed onto the previously treated surface of the substrate at the same temperature, in a medium of a mixture of hydrocarbon (or hydrocarbons) and hydrogen.
  • the pretreatment of the nanomaterial before the carbon film layer deposition is of high importance. Because of the formation of an interface between the surface of the nanomaterial substrate and the deposited carbon film layer, an improved injection of electrons from the nanomaterial substrate into the carbon layer is achieved, and thereby an effective escaping of electrons into vacuum.
  • This interface results from the two- stage pretreatment and the carbon film deposition, where the two-stage pretreatment changes the microstructure and the morphology of the nanomaterial surface, and also chemically passivates it by hydrogen (preventing it from being contaminated).
  • the electronic properties of the interface layer depend on the nanomaterial, the pretreatment and the carbon film deposition parameters. This interface is of high importance for the resulting emission current.
  • the carbon film layer has a frontal surface facing towards the vacuum whereto the electrons will escape. This frontal surface forms an energy barrier for the electrons before their emission.
  • hydrogen is implanted ("terminated by hydrogen"), (there are carbon-hydrogen bonds), which promotes the electron emission due to the formation of local electric fields by the dipoles of the C-H bonds on the surface.
  • the essence of the present invention consists in that the electron emitter is comprised of a carbon film layer deposited on a nanomaterial substrate, where the carbon layer and the substrate are being different by their physico-chemical and electrophysical properties, this difference giving a desirable technical effect.
  • the substrate a carbon conductive material, assures strength of the emitter composite material owing to its skeleton structure and uniform transfer of electrons into the emission zone owing to its high conductance.
  • the heterogeneous structure of the substrate comprises of a skeleton of diamond particles and pyrocarbon, or a skeleton carbon, both with nanopores.
  • Nanopores are herewithin considered to be an independent phase.
  • the nanopores and the nanodiamonds assures a high content of phase boundaries, which causes significant improvement of electron injection from the nanomaterial substrate into the carbon film and consequently in electron emission current.
  • the structure of the nanomaterial having a surface with a high content of open pores, gives a very high surface area being much larger (by many orders) than its geometrical area.
  • the carbon film is a polymer-like carbon material, with a structure and properties closer to polymers (e.g. polyethylene) rather than to diamond or to graphite.
  • the polymer-like carbon material is containing about 10 atomic % of chemically bonded hydrogen (the concentration of C-H links being about 10 22 cm "3 ), with a wide band gap (being more than 3 eV), having a low conductivity (below 10 " S/cm) and a conductance activation energy of 1.5-1.7 eV
  • the carbon film layer of the emitter is formed from a gaseous phase on the surface of highly porous materials with heterogeneous structure, and it is evident that the structure of such a deposited layer depends considerably on the structure of the nanomaterial substrate.
  • the thickness of the carbon film should be in the range of 0.2-1.5 ⁇ m. For thinner layers the electric field needed in the carbon layer will not be sufficient, and the electrons from the nanomaterial will not be influenced by the carbon film layer. For thicker layers problems with transport of the injected electrons will arise and the electrons will not reach the frontal surface to escape into the vacuum. Therefore there exists an optimal thickness and its value depends on the specific properties of the carbon layer and consequently of the deposition conditions of this layer.
  • the formation of an interface layer between the material substrate and the carbon layer is achieved by the pretreatment of the substrate and by the deposition of the carbon film layer onto the treated surface.
  • the prepared unique interface provides effective injection of electrons from the nanomaterial into the carbon layer.
  • the surface of the substrate Prior to the deposition of the carbon film layer the surface of the substrate is treated by a two-stage processing including surface treatment with hydrogen plasma (first stage) and the following treatment in hydrogen plasma with low content of hydrocarbon (second stage).
  • the second stage is usually earned out with a positive potential (e.g. 50-100 V) applied to the powered electrode.
  • the conditions of the treatment in the second stage are selected in such a way that there is no indication of film growth, only nuclei are appearing, in other words the deposition rate is below 1 nm/hour.
  • a desirable interface between the carbon film layer and the nanomaterial substrate is formed.
  • the manufacturing process for the claimed emitter is substantially simplified owing to the possibility of obtaining a substrate coated by a carbon film with predetermined dimensions and shape. There are no technical limitations for scaling up the area of the proposed emitter of either the nanomaterial production technology or the carbon deposition process involving plasma treatment, in contrast to emitters based on crystalline materials.
  • Nanomaterial in the form of a blank 20 mm in diameter and 1 mm thick is prepared from diamond powder with size of particles below 10 nm.
  • the molding is carried out without using any binders, in a steel mold, and a force of 50 kN is used.
  • the obtained blank is treated at 740°C in an atmosphere of natural gas until the mass proportion of the pyrocarbon synthesized at the treatment and the diamond reaches 0.30.
  • the open porosity of the material is 56 vol.% (determined by water absorption after boiling of the sample in water during 1 hour).
  • the nanomaterial surface is then treated and the carbon film deposited in a plasma deposition system, which consists of two chambers: a load-lock chamber that is opened to atmosphere and used for loading the samples, and a plasma reactor that conventionally is not opened to atmosphere because it must be pure (for the plasma deposition and treatment).
  • a plasma deposition system which consists of two chambers: a load-lock chamber that is opened to atmosphere and used for loading the samples, and a plasma reactor that conventionally is not opened to atmosphere because it must be pure (for the plasma deposition and treatment).
  • the plasma deposition system is not shown in the figures.
  • the nanomaterial is loaded into a load-lock chamber that is connected with a reactor (not shown in the figures) within a vacuum chamber.
  • the load lock chamber is closed and preheated to lead away the air and to provide a leakage rate being not more than 0.08 seem (standard cubic centimeters per minute).
  • the nanomaterial After pumping of the load lock chamber to at least 10 "5 Ton, the nanomaterial is transported into the plasma reactor.
  • the nanomaterial sample in the reactor is baked at a temperature higher than the deposition temperature (e.g. at 350°C) to remove gases from the sample.
  • the system is pumped until steady state minimal out-gassing rate is reached. Thereafter the temperature is decreased down to the deposition temperature.
  • a shutter closes (covers) the deposition area, and a power of very high frequency (VHF) and a DC bias are switched on. After a few minutes, about 2-5 minutes, when having reached steady state discharge parameters, the shutter is opened and the first stage of the deposition pretreatment begins.
  • VHF very high frequency
  • the first stage is conducted in a hydrogen plasma at the following parameters: Excitation frequency 56 MHz, substrate temperature 225°C, loaded power density 0.2 W/cm 2 , pressure 30 mTon, gas flow 27 seem, bias DC voltage 16 V.
  • the duration of the first stage is 10 min. The shutter is closed to stop the process and the VHF power together with DC are turned off.
  • the second stage is conducted in a highly hydrogen diluted carbon containing gas mixture of the composition 12% C6H14 and 89 % H2 at the following parameters: Excitation frequency 56 MHz, substrate temperature 250°C, loaded power density 0.2 W/cm 2 , pressure 30 mTon, gas flow 27 seem, bias DC voltage is 10 V. The shutter is closed to stop the process and the VHF power is turned off. The duration of the second stage is 30 min.
  • the carbon film deposition is performed in a gas mixture containing source of carbon gas and hydrogen, 5% C6H14 and 95% H2, at the following deposition conditions: Excitation frequency 56 MHz, substrate temperature 250°C, loaded power density 0.2 W/cm 2 , pressure 50 mTon, gas flow 40 seem, bias DC voltage 10 V. The shutter is closed to stop the process and the VHF power is turned off. The duration of this step is 2.5 hours (for the deposition of a film of thickness 0.7 ⁇ m).
  • the emitter, sample 1, produced according to Example 1 is a nanomaterial substrate coated by a carbon film layer where the substrate is made of a porous carbon material comprising diamond particles of a size below 10 nm bonded together to skeleton structure by a pyrocarbon matrix.
  • the mass proportion of the pyrocarbon matrix and the diamond particles is 0.30; the open porosity is 56 % vol.
  • the carbon film, having a thickness of 0.7 ⁇ m, is produced by the VHF PECVD technique.
  • the emission characteristics of sample 1 are presented in Table 1.
  • Example 2 A blank with diameter 20 mm, and thickness 1 mm, is prepared from silicon carbide particle mixture. The particle sizes are 0.1- 60 ⁇ m.
  • the blank is moulded using 2 wt.-% of a phenol formaldehyde resin (being a 25% alcoholic solution). After hardening of the resin the blank is treated in an atmosphere of natural gas at 850°C until the mass increases by 10%. The blank is treated in chlorine at 1000°C until the mass change has ceased. In such a way a carbon material of skeleton structure is obtained having an open porosity of 68 vol. - %.
  • the material has in its structure nanopores with an average size of 0.82 nm (when measured by gas porosity analysis by Nitrogen adsorption), their volumetric content being 35%. Thereafter the surface of the skeleton nanomaterial is pretreated and a carbon film is deposited onto it according to the same conditions as in Example 1.
  • the emitter, sample 2, produced according to Example 2 is a nanomaterial substrate coated by a carbon film layer where the substrate is made of a porous carbon material comprising nanopores of an average size of 0.82 nm with a volumetric content of 35%, the open porosity being 68 % vol.
  • the carbon film, with a film thickness 0.7 ⁇ m, is produced by the VHF PECVD technique.
  • the emission characteristics of sample 2 are presented in Table 1.
  • a carbon film was deposited onto a backing comprising of single-crystal silicon according to the conditions in Example 1.
  • the emission characteristics of sample 3 are presented in Table 1.
  • a sample comprising a diamond nanomaterial is produced according to the same conditions as in Example 1, except that there was no pretreatment of its surface and no carbon film deposited onto it.
  • the emitter, sample 4, produced according to Example 4 is a nanomaterial sample.
  • the sample is made of a porous carbon material comprising diamond particles of a size below 10 nm bonded together to skeleton structure by a pyrocarbon matrix. The mass proportion of the pyrocarbon matrix and the diamond particles is 0.30; the open porosity is 56 % vol.
  • the emission characteristics of sample 4 are presented in Table 1.
  • a sample comprising a skeleton carbon nanomaterial with nanoporosity is produced according to the conditions in Example 2, except that there was no pretreatment of its surface and no carbon film deposited onto it.
  • the sample is made of a porous carbon material comprising nanopores of 0.82 nm with a volumetric content of 35%, the open porosity being 68 % vol.
  • the emission characteristics of sample 5 are presented in Table 1.
  • Fig. 1 shows a cross section of the field emitter (produced according to examples 1 and 2) and the circuitry in which it has been installed.
  • a metal electrode 1 is in contact with the nanomaterial substrate 2.
  • the metal electrode may be coated onto the nanomaterial substrate.
  • the other surface of the nanomaterial 2 is subjected to a two-step plasma treatment as described above. Thereafter the carbon film layer 3 is deposited by VHF PE CVD onto the pretreated nanomaterial 2 surface.
  • the assembly of these three layers serves as a cathode.
  • the anode consists of a phosphor surface 6 on a conductive electrode 7, e.g. made of indium - tin - oxide 3 located on a substrate 8 of e.g. glass.
  • the distance (d) between the cathode and the anode is determined as the distance between the frontal surface of the carbon film layer 3 (or the nanomaterial when the materials produced according to Examples 4 and 5 are used) and the phosphor surface 6.
  • the cathode and the anode are placed into a vacuum chamber 4 and connected to a voltage supply 10 and ammeter 11.
  • the emitted electrons are denoted as 5 in Fig.l. Being accelerated these electrons interact with the phosphor layer 6 and causes light emission. This process is well known for cathode ray tubes (CRT).
  • the emission characteristics of the emitters made according to the examples 1-5 were measured in the experimental installation shown in Fig.2, a diode configuration.
  • the distance (d) between the cathode and the anode was 45 ⁇ m.
  • the samples were used as cathodes and studied under an applied DC voltage.
  • the anode was being either a metal or a transparent conductive layer on a glass substrate (e.g. layer of indium-tin-oxide (ITO) on glass) or a phosphor screen on a conductive substrate.
  • ITO indium-tin-oxide
  • the scheme of such installation as shown in fig.2 includes a cathode 12 comprising the nanomaterial substrate coated by the carbon film layer, an anode 13, a vacuum chamber for measurements 14, an optical window 15, a flange 16, a voltage supply and an ammeter- 17, high voltage connectors 18, vacuum pumping system 19, a video camera 20, and a computer 21.
  • the distance between the cathode and the anode is usually in the range of 45-200 ⁇ m. Spacers of calibrated thickness made of quartz or other isolators can be used to provide a necessary cathode to anode distance.
  • the cathode 12 During the measurements of the emission characteristics, there are possibilities to move the cathode 12, to adjust the cathode to anode distance (d). Both the cathode 12 and the anode 13 are placed into the vacuum chamber for measurement 14, supplied with optical window 15 on flange 16.
  • the video camera 20 is used for registration of emission nuclei on the phosphor screen.
  • the computer 21 collects and processes data from the video camera 20 and the voltage supply 17.
  • the emission cunent density as a function of the applied field - J(E) - is one of the most important characteristics of a field emitter: It is conventionally measured in an experimental installation similar to that described in Fig.2 [e.g. see in "A.A. Blyabin, A.V. Kandidov, A.A. Piletkiy, A.T. Rakimov, V.A. Samorodov, B.N. Seleznev, ⁇ N. Suetin, and M.A. Timofeev, 11 th Int. Vac. Microelectronics Conf., 1998, ⁇ C, USA, Abstract, p. 234.].
  • the J(E) characteristics of the samples produced in the examples above were measured in the above-described installation.
  • the sample was positioned as a cathode and a titanium electrode on glass located at a distance of 45 ⁇ m was used as an anode.
  • the emission measurements were carried out in vacuum of about 10 "5 tolO "10 Ton.
  • the measured area was 10mm 2 .
  • the nanomaterial emitters with a deposited carbon film according to the present invention demonstrated an improvement compared to both nanomaterials without the carbon coating and to the silicon substrate with a carbon film.
  • Fig. 4 shows the Auger spectra of the carbon film (curve no. 27) used in the present invention, in comparison with that for diamond (curve no. 28) and graphite (curve no. 29). This and other experimental data bear evidence for the polymer-like structure of the carbon film. Curves no. 28 and 29 are from "Ivanov V.Sh. Handbook of Auger spectra for chemical elements and their compounds // MCh TI of Mendeleev, Moscow, 1986".
  • the main idea of the proposed invention is the improvement of the emission properties in the nanomaterial-carbon film structures with an interface between the nanomaterial and the carbon film. This is illustrated by Table 1 and the curves in Fig.3.
  • emission threshold field as determined above E th
  • maximal electric field E max an cunent density
  • J max determined as maximum values in Fig.3 for the samples
  • transconductance ⁇ determined as (related to the slope of the curves).
  • the emitter according to the present invention demonstrated an improvement of the emission characteristics - low voltage and high cunent density - when compared to carbon film on crystalline silicon (sample 3) and to nanomaterials without carbon films (samples 4 and 5).
  • the threshold field Eth as reduced up to 10 times when comparing to samples 2 and 5, and the transconductance ⁇ was improved by factor of 2.
  • the nanomaterial samples with carbon films, samples 1 and 2 showed lower E max values (in other words high cunent density could be reached at lower fields) compared with samples 4 and 5.
  • sample 6 refers to sharp silicon tips measured in the same system as the other samples 1-5.
  • the threshold field is reduced by a factor of 4.5, the maximal field by a factor of 2.5 and the transconductance is increased by a factor of 2.
  • the present invention will provide an emitter which possesses a low emission threshold and a high transconductance and assures the possibility of manufacturing planar emitters of a large area. This is achieved by the production technology of the nanomaterial substrates and carbon film deposition technique.
  • the emitter can be manufactured by a simplified technology owing to the formation of layers having predetermined shape and dimensions, and deposition of the upper layer at lower temperatures, compared to temperatures used for diamond and graphite films deposition.
  • Cold cathodes based on field emission from nanomaterial-carbon film structures according to the present invention are expected to be widely used as electron sources in various devices: displays, electron guns, x-ray tubes, magnetrons and other microwave tubes, light sources etc.
  • One important advantage of the present invention is the possibility to scale-up the size of the emitter (there are no principal limitations for the emitter area) and low cost production

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical Vapour Deposition (AREA)
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Abstract

L'invention concerne un émetteur de champ d'électrons composé d'un substrat sur lequel est déposée une couche. D'après l'invention, ce substrat est fabriqué en nanomatériau, à savoir un matériau de carbone poreux possédant une structure de squelette dont la porosité ouverte est de 35-70 % et la couche déposée consiste en une couche mince de carbone obtenue à partir d'un mélange d'un ou de plusieurs hydrocarbures et d'hydrogène au moyen d'une technique de dépôt chimique en phase vapeur augmentée au plasma à très haute fréquence (VHF PECVD).
PCT/EP1999/005324 1998-08-12 1999-07-26 Emetteur de champ d'electrons et son procede de fabrication WO2000010190A2 (fr)

Priority Applications (1)

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AU54135/99A AU5413599A (en) 1998-08-12 1999-07-26 A field electron emitter and a method for producing the field electron emitter

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US6359378B1 (en) 1998-10-12 2002-03-19 Extreme Devices, Inc. Amplifier having multilayer carbon-based field emission cathode
WO2002029844A1 (fr) * 2000-10-04 2002-04-11 Extreme Devices Incorporated Dispositif d'emission electronique par champ electrique a base de carbone multicouche utilise avec des applications a densite de courant eleve
WO2002029843A1 (fr) * 2000-10-04 2002-04-11 Extreme Devices Incorporated Dispositif d'emission electronique par champ electrique a base de carbone utilise avec des applications a densite de courant elevee
US6624578B2 (en) 2001-06-04 2003-09-23 Extreme Devices Incorporated Cathode ray tube having multiple field emission cathodes
EP1487004A2 (fr) * 2003-06-11 2004-12-15 Canon Kabushiki Kaisha Dispositif d'émission d'électrons, source d'électrons et afficheur d'image à couche dipolaire
WO2006127326A2 (fr) * 2005-05-19 2006-11-30 Texas Instruments Incorporated Emetteur de champ avec reglage de la separation de la cathode et de l'anode
US7583016B2 (en) 2004-12-10 2009-09-01 Canon Kabushiki Kaisha Producing method for electron-emitting device and electron source, and image display apparatus utilizing producing method for electron-emitting device
US7811625B2 (en) 2002-06-13 2010-10-12 Canon Kabushiki Kaisha Method for manufacturing electron-emitting device

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US6710534B2 (en) 1998-10-12 2004-03-23 Extreme Devices, Inc. Traveling wave tube having multilayer carbon-based emitter
US6359378B1 (en) 1998-10-12 2002-03-19 Extreme Devices, Inc. Amplifier having multilayer carbon-based field emission cathode
WO2002029844A1 (fr) * 2000-10-04 2002-04-11 Extreme Devices Incorporated Dispositif d'emission electronique par champ electrique a base de carbone multicouche utilise avec des applications a densite de courant eleve
WO2002029843A1 (fr) * 2000-10-04 2002-04-11 Extreme Devices Incorporated Dispositif d'emission electronique par champ electrique a base de carbone utilise avec des applications a densite de courant elevee
US6903519B2 (en) 2001-06-04 2005-06-07 Trepton Research Group, Inc. Multi-element field emission cathode
US6906470B2 (en) 2001-06-04 2005-06-14 Trepton Research Group, Inc. Method and system for controlling electron beams from field emission cathodes
US6833679B2 (en) 2001-06-04 2004-12-21 Trepton Research Group, Inc. Method for forming an image on a screen of a cathode ray tube
US6624578B2 (en) 2001-06-04 2003-09-23 Extreme Devices Incorporated Cathode ray tube having multiple field emission cathodes
US7811625B2 (en) 2002-06-13 2010-10-12 Canon Kabushiki Kaisha Method for manufacturing electron-emitting device
CN100428393C (zh) * 2003-06-11 2008-10-22 佳能株式会社 电子发射器件、电子源和图像显示器
US7109663B2 (en) 2003-06-11 2006-09-19 Canon Kabushiki Kaisha Electron emission device, electron source, and image display having dipole layer
US7259520B2 (en) 2003-06-11 2007-08-21 Canon Kabushiki Kaisha Electron emission device, electron source, and image display having dipole layer
EP1487004A2 (fr) * 2003-06-11 2004-12-15 Canon Kabushiki Kaisha Dispositif d'émission d'électrons, source d'électrons et afficheur d'image à couche dipolaire
US7682213B2 (en) 2003-06-11 2010-03-23 Canon Kabushiki Kaisha Method of manufacturing an electron emitting device by terminating a surface of a carbon film with hydrogen
EP1487004A3 (fr) * 2003-06-11 2005-02-09 Canon Kabushiki Kaisha Dispositif d'émission d'électrons, source d'électrons et afficheur d'image à couche dipolaire
US7583016B2 (en) 2004-12-10 2009-09-01 Canon Kabushiki Kaisha Producing method for electron-emitting device and electron source, and image display apparatus utilizing producing method for electron-emitting device
WO2006127326A2 (fr) * 2005-05-19 2006-11-30 Texas Instruments Incorporated Emetteur de champ avec reglage de la separation de la cathode et de l'anode
WO2006127326A3 (fr) * 2005-05-19 2007-05-31 Texas Instruments Inc Emetteur de champ avec reglage de la separation de la cathode et de l'anode
US7786662B2 (en) 2005-05-19 2010-08-31 Texas Instruments Incorporated Display using a movable electron field emitter and method of manufacture thereof

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