JP3604652B2 - Electron emission cathode and method of manufacturing the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electron emission cathode that emits electrons under vacuum and a method for manufacturing the same .
[0002]
[Prior art]
Flat displays, in particular, FEDs (Field Emission Displays), which extract electrons from the cathode by applying an electric field in a vacuum and collide with the phosphor applied to the anode to emit light, are thinner and lighter than conventional CRT displays. Research has been actively conducted because a display device can be realized.
[0003]
[Problems to be solved by the invention]
As an electron emission cathode of this FED, for example, a diamond thin film or a carbon thin film is used. In such a conventional example, the emission start voltage is at most about 5 V / μm, and it is desired to realize a lower emission start voltage. I have.
[0004]
The present invention has been made in view of the above points, and has as its object to provide an electron emission cathode having a low emission start voltage suitable for an FED and a method of manufacturing the same.
[0005]
[Means for Solving the Problems]
The present invention has the following configuration to achieve the above object.
[0006]
That is, the electron emission cathode of the present invention has a composite carbon film formed on a substrate on which ultrafine particles are arranged by controlling the accelerating voltage of carbon ions by a cathodic arc method. A carbon film having sp ³ bonds is laminated on a carbon film having ² bonds.
[0007]
It is preferable that the carbon film having the sp ³ bond is directly laminated on the carbon film having the sp ² bond, but it may be laminated via an intermediate layer in production.
[0008]
According to the present invention, the carbon film having sp ² bonds is graphite-like and shows conductivity, while the carbon film having sp ³ bonds is like diamond and has insulating properties and extremely low electron affinity or negative electron. Indicates affinity. Since these are formed on the substrate on which the ultrafine particles are arranged, that is, projected on the substrate, the electric field is concentrated, and the carbon film having the sp ³ bond, which is a thin film, has a tilted energy band structure. Occurs, and tunneling of electrons from a carbon film having an adjacent sp ² bond becomes possible, so that electrons are injected into a conduction band (conduction band) of the carbon film having an sp ³ bond and are instantaneously released into a vacuum. As a result, the electron emission performance is improved, and the emission start voltage can be reduced.
[0009]
In one embodiment of the present invention, a film structure is formed on a substrate on which ultrafine particles are arranged by controlling an accelerating voltage of carbon ions by a cathodic arc method , and the film structure has an sp ² bond. Is formed by forming carbon having an sp ³ bond on a carbon film having
[0010]
-carbon with sp ³ bonds is preferably laminated directly onto a carbon film having a sp ² bond, manufacturing, it may be laminated via an intermediate layer.
[0011]
According to the present invention, as described above, the electron emission performance is improved, and the emission start voltage can be reduced.
[0012]
In a further preferred embodiment of the present invention, the ultrafine particles are ultrafine diamond particles.
[0013]
According to the present invention, ultrafine diamond particles can be arranged on the substrate at a high density by treating the substrate with a colloid solution of ultrafine diamond particles.
[0014]
In another embodiment of the present invention, the thickness of the carbon film having the sp ³ bond or the size of the carbon having the sp ³ bond is a thickness on the order of nanometers to 10 nanometers.
[0015]
Here, the order of nanometers to ten nanometers refers to a range of 1 nm to 99 nm, and preferably several nm.
[0016]
According to the present invention, since the carbon film or carbon having sp ³ bonds is thin or small, on the order of nanometers to 10 nanometers, tunneling of electrons from the carbon film having sp ² bonds is facilitated and sp ³ bonds are formed. Electrons are injected into the conduction band of the carbon film and are instantaneously released into a vacuum, so that the electron emission performance is improved and the emission start voltage can be reduced.
[0017]
The method for producing an electron emission cathode according to the present invention includes forming a carbon film having an sp ² bond on a substrate on which ultrafine particles are arranged by a cathode arc method, and forming the carbon film on the obtained carbon film by a cathode arc method. By controlling the acceleration voltage of carbon ions, the energy is made higher than that of the carbon film having the sp ² bond to form the carbon film having the sp ³ bond.
[0018]
According to the present invention, an electron emission cathode having a low emission start voltage can be obtained.
[0019]
Further, the method for producing an electron emission cathode of the present invention comprises forming a carbon film having an sp ² bond on a substrate on which ultrafine particles are disposed by a cathode arc method, and forming a cathode arc on the obtained carbon film. By controlling the accelerating voltage of carbon ions by the method, the energy is made higher than the formation of the carbon film having the sp ² bond to form carbon having the sp ³ bond.
[0020]
According to the present invention, an electron emission cathode having a low emission start voltage can be obtained.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0022]
(Embodiment 1)
FIG. 1 is a diagram illustrating a method for manufacturing an electron emission cathode according to one embodiment of the present invention.
[0023]
First, as shown in FIG. 1A, ultrafine diamond particles 2 are arranged and formed on a substrate, for example, on an n ⁺ silicon substrate 1 having high electron conductivity in this embodiment. The ultrafine diamond particles 2 are obtained, for example, by the method for producing hydrophilic diamond fine particles disclosed in Japanese Patent No. 2691884.
[0024]
That is, ultrafine diamond particles having a specific size in the range of nanometer order to 100 nanometer order, for example, an average particle diameter of several tens nm, for example, 30 nm, are selected and washed, and the ultrafine diamond particles after purification are removed. The suspension is dispersed in purified water, the dispersion is centrifuged, and the total volume is adjusted by adding alcohol to the supernatant colloid solution. Further, 0.2% of hydrogen fluoride is added and centrifuged, and the supernatant is used as a treatment liquid that is a fine particle diamond colloid solution.
[0025]
The silicon substrate 1 shown in FIG. 1A is immersed in the treatment liquid 3 for several minutes as shown in FIG. 2A and dried as shown in FIG. Ultrafine diamond particles 2 having a self-shaped surface or a cleavage surface of a selected particle size of several tens nm are arranged and formed thereon.
[0026]
In addition, as another embodiment of the present invention, the processing liquid 3 may be dropped by rotating the silicon substrate 1 or the processing liquid 3 may be sprayed on the silicon substrate 1.
[0027]
The colloid solution of the hydrophilic diamond fine particles of the above-mentioned Japanese Patent No. 2691884, that is, the treatment liquid 3, is such that ultrafine diamond particles are dispersed and suspended in the liquid without being aggregated in the form of substantially single particles. By treating the silicon substrate 1 with the treatment liquid 3, single diamond particles can be formed at a high density. That is, ultrafine diamond particles 2 having a size of several tens nm can be arranged and formed at intervals of several tens nm.
[0028]
Next, as shown in FIG. 1B, the composite carbon film 4 is formed by, for example, a cathode arc method.
[0029]
The composite carbon film 4 has a two-layer structure in which the carbon film 6 having a sp ³ bonds on charcoal Motomaku 5 that have a sp ² bonds are stacked, the cathode arc method, the carbon ions It is formed by controlling the acceleration voltage. That is, when the energy is decreased, the carbon film 5 having the sp ² bond is formed, and when the energy is increased, the carbon film 6 having the sp ³ bond is formed. As described above, in the cathode arc method, the composite carbon film 4 can be formed only by changing the conditions, which is advantageous in the process.
[0030]
The lower carbon film 5 having sp ² bonds is graphite-like and exhibits electron conductivity, and the upper carbon film 6 having sp ³ bonds is diamond-like and exhibits insulating properties and is low or high. It shows a negative electron affinity.
[0031]
The carbon film 5 having sp ² bonds is formed to a thickness of, for example, about 10 nm to several microns, and the carbon film 6 having sp ³ bonds is, for example, several nm in order to enable tunneling as described later. It is formed thin to a thickness of about.
[0032]
The carbon film 6 having the sp ³ bond assists in the electric field concentration and the direction of the emitted electrons, that is, the emission of the emitted electrons in the vertical direction. Further, since the thickness is extremely small, tunneling of electrons from the carbon film 5 having sp ² bonds easily occurs, and this is promoted by the above-described electric field concentration. Further, the carbon film 6 having sp ³ bonds has a negative affinity or a very small (close to 0) positive affinity because of inheriting the properties of crystalline diamond. , And easily jump into a vacuum.
[0033]
The composite carbon film 4 has a low work function that facilitates electron emission, as described later, and improves electron emission performance.
[0034]
The electron emission cathode having the composite carbon film 4 is disposed as a cold cathode of the FED in a vacuum (about 10 ⁻⁷ Torr) so as to face the anode coated with the phosphor, and is applied with a voltage to be in a vacuum. Electrons are extracted, accelerated, collide with the phosphor, and emit light by excitation.
[0035]
Next, the improvement of the electron emission performance by the composite carbon film 4 will be described.
[0036]
As described above, the carbon film 5 having the sp ² bond is graphite-like and shows conductivity, while the carbon film 6 having the sp ³ bond is diamond-like and has insulating and low or negative electron affinity. Is shown.
[0037]
Since the composite carbon film 4 on the ultrafine diamond particles 2 having a size of several tens of nanometers protrudes from the silicon substrate 1, the electric field is concentrated, and the sp ² bonds closely contact the silicon substrate 1 having high electron conductivity. While the electrons are about to flow into the carbon film 5 having the carbon film 5, the carbon film 6 having the sp ³ bond, which is a thin film of about several nm, has a gradient in the energy band structure due to the applied electric field, and the adjacent sp ² bond Tunneling of electrons from the carbon film 5 having the above-mentioned structure can be performed, and electrons are injected into the conduction band of the carbon film 6 having the sp ³ bond and are instantaneously released into a vacuum. The performance is improved, and the emission start voltage can be reduced.
[0038]
That is, the composite carbon film 4 has a substantially very low work function and promotes electron emission.
[0039]
Further, according to the cathode arc method, the kinetic energy is given to the ultrafine particles 2 from the carbon ions by the impact of the carbon ions hitting the ultrafine diamond particles 2, and as a result, as shown in FIG. The bottoms of the fine particles 2 slightly enter into the silicon substrate 1 to obtain physical stability (adhesion) and also ensure electrical contact.
[0040]
This effect can be obtained not only by the cathode arc method but also by laser ablation or ion plating.
[0041]
The electron emission cathode of this embodiment can reduce the emission start voltage to, for example, about 1 V to 1.5 V / μm, and increase the emission current density to, for example, about 50 mA / cm ² or more. Can be.
[0042]
Further, in the electron emission cathode of this embodiment, the electric field is concentrated on the composite carbon film 4 on the ultrafine diamond particles 2 having a size of several tens of nanometers, so that the electron emission site becomes an electron emission site and emits electrons. The density is, for example, 10 ⁶ to 10 ⁷ / cm ² , and a uniform and high electron emission site density can be obtained as compared with a conventional example having an electron emission site density of 10 ^{2 to 5} / cm ² or less.
[0043]
In addition, since the electric field concentrates on another electron emission site when the emission current from one electron emission site decreases due to the shielding effect, the number of sites acting as electron emission sources is extremely large, Long life is guaranteed.
[0044]
Note that between the carbon film 5 having an sp ² bond and the carbon film 6 having an sp ³ bond, an extremely thin one or two atomic layer is present in the production, but this intermediate layer is not present. Is preferred.
[0045]
The presence of the carbon film 6 having sp ³ bonds in this embodiment can be confirmed by EELS (Electron Energy Loss spectroscopy), Raman spectroscopy, or the like.
[0046]
In this embodiment, ultrafine diamond particles 2 having an average particle diameter of approximately several tens of nm are used, but as another embodiment of the present invention, a diamond having an average particle diameter of, for example, several nm is used. Among the ultrafine particles, ultrafine diamond particles having a large size, for example, ultrafine diamond particles having an average particle diameter of several tens to several hundreds of nm may be used in a designed manner. That is, as the processing liquid which is the diamond colloid solution of the ultrafine particles shown in FIG. 2 described above, the ultrafine diamond particles 2 having an average particle size of several nm have a large size, for example, an average particle size of several tens nm to A solution in which ultrafine diamond particles of several hundred nm are mixed at a mixing ratio according to the design is used.
[0047]
Thus, ultrafine diamond particles including ultrafine ultrafine particles can be arranged and formed on the substrate. Then, the composite carbon film 4 on the ultra-fine diamond particles having a large size becomes protruding higher than the other portions, and the electric field is concentrated so that electrons can be designed and emitted.
[0048]
The number and spacing of the portions where the electric field is concentrated can be designed and defined by the mixing ratio of ultrafine diamond particles of different sizes.
[0049]
Note that the size relationship between the particles to be mixed is wide, and the determination depends on the design policy.
[0050]
Depending on the conditions of the cathode arc method, instead of the composite carbon film 4 described above, as shown in FIG. 3, a carbon film in which clusters (collections, lumps) 10 of carbon particles having sp ² bonds are continuous. A structure in which carbon particles 11 having sp ³ bonds are formed thereon may be used. The carbon 11 having the sp ³ bond does not need to be in the form of a continuous film, and may be scattered in the form of ultrafine particles. The diameter of the cluster 10, that is, the thickness of the carbon film is, for example, about 10 nm to several microns as described above, and the size of the carbon 11 having the sp ³ bond is, for example, as described above. It is about several nm.
[0051]
(Embodiment 2)
FIG. 4 is a diagram showing an electron emission cathode according to another embodiment of the present invention, and portions corresponding to the above-described embodiment are denoted by the same reference numerals.
[0052]
In the above-described embodiment, the composite carbon film 4 is formed by arranging the ultrafine diamond particles 2 on the silicon substrate 1, but in this embodiment, a known chemical treatment is performed on the silicon substrate 1. Accordingly, for example, ultrafine particles 7 of gold are adhered and formed, and a carbon film 6 having sp ³ bonds is laminated on a carbon film 5 having sp ² bonds thereon similarly to the above-described embodiment. This is one in which a carbon film 4 is formed. The particle size of the ultrafine gold particles 7 is several tens nm to several hundreds nm, for example, about 50 nm to 200 nm.
[0053]
Note that, instead of gold, ultrafine particles such as silica, alumina, titanium oxide, nickel, and palladium may be used.
[0054]
Further, as shown in FIG. 5, instead of the composite carbon film 4 described above, carbon 11 having sp ³ bonds is formed on a carbon film in which clusters 10 of carbon particles having sp ² bonds are continuous. It may have a structure.
[0055]
(Another Embodiment of that)
In each of the above embodiments, the silicon substrate is used as the substrate, but the substrate is not limited to the silicon substrate, and a substrate having high electron conductivity, for example, a metal or graphite substrate may be used to supply the field emission electrons. It can be. Further, a glass substrate to which an electron conductive film such as metal or ITO is attached may be used.
[0056]
The substrate may have grooves or irregularities of an appropriate size introduced by appropriate patterning or molding such as position in design. These shapings can support selective electric field concentration.
[0057]
The composite carbon film 6 in which the carbon film 6 having the sp ³ bond is laminated on the carbon film 5 having the sp ² bond is formed on the emitter film of the existing electron emission cathode to improve the electron emission ability. Alternatively, it may be formed instead of the emitter film.
[0058]
As another embodiment of the present invention, a carbon film or an amorphous carbon film (DLC film) may be formed on the substrate 1 and the ultrafine particles 2 and 7 may be disposed thereon.
[0059]
As another embodiment of the present invention, hydrogen, fluorine, or the like may be attached to lower the electron affinity of the carbon film having an sp ³ bond so that the carbon film has a low or negative electron affinity. Alternatively, the conductivity of the carbon film having sp ² bonds may be increased by doping or mixing an appropriate amount of ultrafine metal particles.
[0060]
【The invention's effect】
As described above, according to the present invention, since a carbon film having an sp ³ bond or a film structure in which carbon is formed on a carbon film having an sp ² bond is formed so as to protrude above the substrate, electron emission The performance is improved and the emission start voltage can be reduced.
[0061]
Further, a carbon film having an sp ³ bond or a film structure in which carbon is formed on a carbon film having an sp ² bond can improve electron emission performance by being formed on an emitter film of an existing electron emission cathode. The emission start voltage can be reduced.
[0062]
Further, by using ultrafine particles such as diamond, an electron emission cathode having a long lifetime and a high electron emission site density can be realized. Moreover, according to the cathode arc method, kinetic energy is given to the ultrafine particles from the carbon ions by the impact of the carbon ions hitting the ultrafine particles arranged on the substrate, whereby the bottom of the ultrafine particles is slightly applied to the substrate. It is possible to obtain the immersion and physical stability (adhesion) and also to guarantee the electrical contact.
[Brief description of the drawings]
FIG. 1 is a diagram showing a manufacturing method according to one embodiment of the present invention.
FIG. 2 is a diagram illustrating a method of forming ultrafine diamond particles on the silicon substrate of FIG. 1;
FIG. 3 is a diagram showing a structure of another embodiment of the present invention.
FIG. 4 is a diagram showing a structure of still another embodiment of the present invention.
FIG. 5 is a diagram showing a structure of another embodiment of the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 glass substrate 2 ultrafine diamond particles 3 treatment liquid 4 composite carbon film 5 carbon film having sp ² bond 6 carbon film having sp ³ bond

Claims (7)

A composite carbon film is formed on a substrate on which ultrafine particles are arranged by controlling the acceleration voltage of carbon ions by a cathode arc method , and the composite carbon film is formed on a carbon film having sp ² bonds by sp ³ An electron emission cathode comprising a carbon film having a bond laminated thereon. A film structure is formed on the substrate on which the ultrafine particles are arranged by controlling the acceleration voltage of carbon ions by a cathode arc method , and the film structure forms sp ³ bonds on a carbon film having sp ² bonds. An electron emission cathode comprising carbon having carbon. 3. The electron emission cathode according to claim 1, wherein the ultrafine particles are ultrafine diamond particles. 4. The electron emission cathode according to claim 1, wherein the thickness of the carbon film having the sp ³ bond or the size of the carbon having the sp ³ bond is in the order of nanometer to 10 nanometer. . A carbon film having sp ² bonds is formed by a cathode arc method on a substrate on which ultrafine particles are arranged, and an acceleration voltage of carbon ions is controlled on the obtained carbon film by a cathode arc method. A method for producing an electron emission cathode, comprising forming a carbon film having an sp ³ bond at a higher energy than forming a carbon film having an sp ² bond . A carbon film having an sp ² bond is formed by a cathode arc method on a substrate on which ultrafine particles are arranged, and an acceleration voltage of carbon ions is controlled on the obtained carbon film by a cathode arc method to form the sp. ^A method for producing an electron emission cathode, comprising forming carbon having an sp ³ bond at a higher energy than forming a carbon film having ² bonds . Wherein an ultrafine particles of the ultrafine diamond, size of carbon having a thickness or the sp ³ bonds of the carbon film having the sp ³ bonds, claim 5 is the thickness of tens of nanometer order from the order of nanometers Or a method for producing an electron emission cathode according to item 6.

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