JPH11204022A - Cold cathode and element using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow an application to a display or the like by forming a cold electron emission part without using a micro machining technology for reducing the production cost, sufficiently increasing the density and homogeneity of a cold electron emission point for improving quality, preventing deterioration due to impurities, eliminating tip evaporation of a material and increasing a heat releasing function for improving durability, and lowering operating voltage and power consumption. SOLUTION: A film (first layer 1 and second layer 2) made of carbon material such as carbon, graphite, amorphous carbon, DLC(diamond-like carbon) or diamond is formed on a substrate 3, thereby forming a projected cold electron emission part 2. In this case, cold electrons 4 are emitted from the tip 2c of the projected cold electron emission part 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold cathode in which a cold electron emitting portion is formed in a convex shape with respect to a substrate and cold electrons are emitted from the convex cold electron emitting portion. It relates to elements such as used devices and sensors.

[0002]

2. Description of the Related Art In contrast to a hot cathode which emits electrons by heating a cathode, there is a cathode called a cold cathode which emits (cold) electrons without heating.

The principle of electron emission of a cold cathode will be briefly described with reference to an energy level E shown in FIG. 6. In order to emit cold electrons from a material into a vacuum, the potential peak is likely to be exceeded by a tunnel effect. It is necessary to apply a voltage between the anode and the cold cathode to be able to do so.

In manufacturing a cold cathode, it is important that a cold electron emitting portion has a shape in which an electric field concentration easily occurs in order to easily emit cold electrons.

In the prior art, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent Publication No. 300558, single-crystal silicon is finely processed by anisotropic etching to form a cone-shaped cold electron emission portion with a sharp tip on a substrate.

Further, Mo, Si, Ga, As or the like is vapor-deposited in a fine hole formed by using a fine processing technique to form a cone-shaped cold electron emission portion having a sharp tip. .

[0007]

However, according to the above-mentioned prior art, since the cold electron emission portion is formed by using a fine processing technique such as etching, it is very difficult to form a cold cathode. There is a problem that a complicated process is required and a manufacturing cost is required.

In addition, the larger the number of cold electron emission points (cold electron emission portions) per unit area of the substrate (cold electron emission point density), the more current can flow. Since the point density depends on the level of the fine processing technology, the cold electron emission point density cannot be increased to a certain level or more.

Although it is desirable to form cold electron emission points uniformly on a substrate, it is not always possible to form cold electron emission points uniformly at the current level of microfabrication technology.

For this reason, when a cold cathode is used for a display, the density and uniformity of cold electron emission points are not sufficient, so that the quality of an image has been impaired.

In addition, materials such as Si, Mo, Ga, and As are used as a material of the cold cathode (cold electron emission portion), and these materials become impurities such as H2 which becomes impurities in a vacuum which is an operating environment. , O2 and the like.

Further, these materials such as Si, Mo, Ga and As are not necessarily high melting point materials when used as a material for a cold cathode.

That is, in the cold cathode, the current is concentrated and heat is generated at the tip of the sharp cone-shaped cold electron emitting portion. For example, Si (silicon) having a melting point of about 1200 ° C. evaporates, and the cold cathode evaporates. It may not work as a cathode. In addition, the heat conductivity is low and the heat dissipation is not good, so that there is also a problem in durability.

Further, materials such as Si, Mo, Ga, and As require high electric field strength and high voltage in order to emit cold electrons from the material into a vacuum.

For this reason, when the cold cathode is used as an element of a display or the like, the operating voltage is high, and the power consumption is accordingly high, so that the cold cathode is used for various displays such as LCD, plasma display, and EL. Was an obstacle.

The present invention has been made in view of the above circumstances, and allows a cold electron emitting portion to be formed without using a fine processing technique, thereby reducing manufacturing costs and reducing the density of cold electron emitting points. Enhance uniformity sufficiently, improve quality, prevent deterioration due to impurities, eliminate evaporation of materials, improve heat dissipation, improve durability, operating voltage, power consumption It is an object of the present invention to achieve practical use for a display or the like by lowering.

[0017]

Therefore, according to a first aspect of the present invention, a cold electron emitting portion is formed in a convex shape with respect to a substrate, and the cold electron emitting portion emits cold electrons from the convex cold electron emitting portion. In such a cold cathode, a carbon-based material is formed on a substrate to form the convex cold electron emitting portion.

According to the first invention, as shown in FIG. 1, a carbon-based material such as carbon, graphite, amorphous carbon, DLC (diamond-like carbon: diamond-like carbon), or diamond is formed on a substrate 3. By forming the first layer 1 and the second layer 2, a cold electron emission portion 2 having a convex shape is formed. Then, the cold electrons 4 are emitted from the tip 2c of the convex cold electron emitting portion 2.

As described above, only by performing the process of forming a film of the carbon-based material on the substrate 3, the carbon-based material grows in a convex shape with respect to the substrate. Uniformly formed with density. This is due to the unique three-dimensional microstructure of the carbon-based material.

For this reason, since it is not necessary to form the cold electron emitting portion by using a fine processing technique such as etching, the process can be simplified and the manufacturing cost can be reduced.

Also, regardless of the level of the fine processing technology,
Since the density and uniformity of the cold electron emission points can be sufficiently increased, the quality as a cold cathode can be improved.

The carbon-based material is Si, Mo, Ga, As.
Compared with such materials, the degree of deterioration by H2, O2, etc., which are impurities in a vacuum as an operating environment, is extremely small. For this reason, the durability against deterioration due to impurities can be dramatically increased.

Further, carbon-based materials include conventional Si, Mo, G
It has a higher melting point than materials such as a and As. For example,
The melting point of Si (silicon) is 1200 ° C., whereas the melting point of a carbon-based material is about 3000 ° C. to 4000 ° C. (particularly, diamond has a high melting point).

For this reason, even if the current is concentrated on the tip 2c of the cold electron emitting portion 2 and heat is generated, the melting point is 3000 ° C. or more.
Since the temperature is as high as about 4000 ° C., it does not evaporate, and it is possible to prevent a situation in which it does not operate as a cold cathode. In addition, since the thermal conductivity is high and the heat radiation property is good, the durability against heat can be enhanced, and the overall durability can be drastically improved in combination with the durability against the deterioration due to the impurities.

Also, compared to materials such as Si, Mo, Ga, and As, carbon-based materials do not require so high electric field strength and voltage to discharge cold electrons from the material into a vacuum.

For this reason, when the cold cathode is used as an element of a display or the like, the operating voltage can be reduced, and the power consumption can be reduced accordingly. Therefore, LC
Various displays such as D, plasma display, and EL can be put to practical use.

According to a second aspect, in the first aspect,
The convex cold electron emitting portions 2 a are formed continuously as viewed from the upper surface of the substrate 3.

According to the second aspect of the present invention, by forming the cold electron emitting portions 2a continuously, it is possible to further increase the density of cold electron emission points and to allow a larger current to flow.

According to a third aspect, in the first aspect,
The convex cold electron emitting portions 2a are formed discretely when viewed from the upper surface of the substrate 3.

According to the third aspect of the present invention, since the cold electron emitting portions 2a are discretely formed, the electric field can be more easily concentrated on the cold electron emitting portions 2a. For this reason, the operating voltage can be further reduced, and accordingly, the power consumption can be further reduced.

In the fourth invention, as shown in FIG. 7, for example, the supersonic nozzle 7 is used to accelerate a gas plasma (CH 4) of a carbon-based material to a flow velocity larger than the sonic velocity, and The convex cold electron emission part 2 is formed by guiding upward and forming a convex thin film.

In the fifth invention, as shown in FIG.
The cold cathode 20 of the first invention is used for an element having an anode 21.

[0033]

Embodiments of the present invention will be described below with reference to the drawings.

In the present embodiment, a graphite thin film is assumed as the thin film formed on the substrate 3.

FIG. 7 shows a configuration of a manufacturing apparatus of the embodiment for manufacturing the cold cathode 20.

As shown in FIG. 7, the apparatus of this embodiment is
Generally, a chamber 8 in which the substrate 3 is disposed, a compound gas containing methane (CH4), which is an element constituting graphite, and a gas obtained by adding hydrogen gas (H2) to the chamber 8 are turned into a plasma state. And this is the surface 3 of the substrate 3
and a Laval nozzle (supersonic nozzle) 7 to be supplied toward a. Substrate 3 is made of a material different from graphite (C), for example, n-type silicon single crystal (Si).

More specifically, in the chamber 8, which is a reaction chamber, a table 15 on which the substrate 3 is mounted and a table 15
In order to increase the temperature of the substrate 3 mounted thereon, a heater 9 built in a table 15 is provided.

The vacuum pump 10 evacuates the chamber 3 to a low pressure (for example, 0.1 torr).

The substrate 3 is controlled by the heater 9 so as to be kept at, for example, 800 ° C. in order to increase the growth rate of the film.

That is, the temperature of the substrate 3 is detected by the temperature sensor 14 such as a thermocouple, and the detected temperature is input to the temperature controller 13 as a feedback signal.

The temperature control unit 13 outputs a power adjustment signal to the power adjustment unit 12 so that the difference between the fed-back current temperature and the target temperature (800 ° C.) becomes zero. The power adjusting unit 12 adjusts the current flowing through the heater 9 via the DC power supply 11 by changing the variable resistance value, and maintains the temperature of the substrate 3 at the target temperature (800 ° C.).

The nozzle 7 has, for example, a flow rate of 500 (sc)
c / min) of hydrogen gas and, for example, a flow rate of 50 (scc / min) of methane gas.

Here, methane gas is used to form a graphite film, but other compound gases may be used as long as they are compounds containing carbon C. Further, a liquid containing carbon such as alcohol may be used.

The reason why hydrogen gas (H 2) is supplied at the same time is to remove “soot” generated during the reaction.

Further, in order to easily perform plasma conversion, Ar is used.
A rare gas such as a gas may be supplied at the same time.

These gases supplied to the substrate 3 in the chamber 8 are turned into plasma by induction heating.

That is, for example, a high-frequency (RF) power supply 6 of 13.56 MHz causes a high-frequency current to flow through the high-frequency coil 5 wound around the throat portion of the Laval nozzle 7 to supply methane gas or the like to the substrate 3 in the chamber 8. Is heated to a plasma state. In this case, the supplied high frequency power is, for example, 1 kW.

The methane gas or the like, which has been turned into plasma, is supplied to the surface 3 a of the substrate 3 in the chamber 8 through the Laval nozzle 7, and a film having a graphite structure is formed on the substrate 3. The film formation is performed, for example, for one hour.

It should be noted that a nozzle other than a Laval nozzle may be used as the nozzle 7 as long as it can be turned into plasma.

FIG. 1 conceptually shows the structure of a cold cathode 20 manufactured using the manufacturing apparatus of FIG.

That is, as shown in FIG. 1, a first continuous film having a dense graphite structure is formed on a substrate 3.
Layer 1 is deposited. Further, a convex (flake-shaped) cold electron emitting portion 2 having a side wall 2b and an edge 2a which is a top portion is formed so as to stand substantially perpendicularly to the surface of the first layer 1. Thus, the second layer 2 having a graphite structure is formed. Note that the height of the first layer 1 is about 0.3 to 0.4 μm, and the height of the second layer 2 is about 0.3 μm.

Thus, the cold cathode 20 including the substrate 3, the first layer 1, and the second layer 2 is formed. And this cold cathode 2
0, a required voltage is applied to the tip 2 of the cold electron emission portion 2.
Electric field concentration occurs at c, and the cold electrons 4 are emitted from the tip 2c of the cold electron emitting portion 2.

As described above, the gas plasma (CH 4) of the carbon-based material is accelerated using the supersonic nozzle 7 so as to have a flow velocity larger than the sonic velocity, and is guided onto the substrate 3, whereby the convex thin film is formed. Is generated, and the cold electron emission portion 2 having a convex shape is formed.

Although the first layer 1 and the second layer 2 have a graphite structure, they do not necessarily have to have a graphite structure.

In this embodiment, a graphite film is assumed, but other than this, a carbon-based material such as carbon, diamond, amorphous carbon, DLC (diamond-like carbon: diamond-like carbon), etc. may be formed. Thus, the convex second layer 2 can be formed.

The electric conductivity may be increased by doping B, P or the like into the carbon-based material.

As described above, when a process of forming a carbon-based material on the substrate 3 using the manufacturing apparatus of the present embodiment is performed,
The carbon-based material grows in a convex shape with respect to the substrate 3, and the cold electron emitting portions 2 having a convex shape are formed densely. This is due to the unique three-dimensional microstructure of the carbon-based material. The projecting cold electron emitting portions 2, that is, the cold electron emitting points, are formed with high density and uniformity.

Therefore, unlike the prior art, it is not necessary to form the cold electron emission portion using a fine processing technique such as etching, so that the process can be simplified and the manufacturing cost can be reduced. Can be.

Further, regardless of the level of the fine processing technology,
Since the density and uniformity of the cold electron emission points can be sufficiently increased, the quality as a cold cathode can be improved.

In the case of the present embodiment, the density of cold electron emission points (electron generation sources) is 2.0 × 10 ⁹ (pieces / cm 2).
Was measured. On the other hand, in the case of the prior art in which the convex portion of silicon is formed by etching, 1.3 is used.
The density can be increased only to about × 10 ⁷ pieces / cm 2.

As described above, according to the present embodiment, it can be seen that the electron source density is dramatically increased, and that a much larger amount of current can flow.

The carbon-based materials include Si, Mo, Ga, and As.
Compared with such materials, the degree of deterioration by H2, O2, etc., which are impurities in a vacuum as an operating environment, is extremely small. For this reason, the durability against deterioration due to impurities can be dramatically increased.

The carbon-based materials include conventional Si, Mo, G
It has a higher melting point than materials such as a and As. For example,
The melting point of Si (silicon) at 1200 ° C. is about 3000 ° C. to 4000 ° C. for the carbon-based material.

Therefore, even if the current is concentrated on the tip 2c of the cold electron emitting portion 2 to generate heat, the melting point is 3000 ° C.
Since the temperature is as high as about 4000 ° C., it does not evaporate, and it is possible to prevent a situation where the cathode does not operate as a cold cathode. In addition, since the thermal conductivity is high and the heat radiation property is good, the durability against heat can be enhanced, and the overall durability can be drastically improved in combination with the durability against the deterioration due to the impurities.

Further, compared with materials such as Si, Mo, Ga, and As, carbon-based materials do not require so high electric field strength and voltage to emit cold electrons from the material into vacuum.

In particular, in diamond, as shown by the broken line in FIG. 6, the energy level in the material may be higher than that in vacuum, and the cold electrons 4 are emitted even when the electric field is considerably low. You.

For this reason, when the cold cathode is used as an element of a display or the like, the operating voltage can be reduced, and the power consumption can be reduced accordingly. Therefore, LC
A flat panel display that can replace conventional various flat displays such as D, plasma display, and EL can be put to practical use.

Incidentally, FIG. 4 shows: • Substrate: n-type silicon single crystal • H2 flow rate: 500 (scc / min) • CH4 flow rate: 50 (scc / min) • Input high frequency power: 1 kW • Substrate temperature: 800 ° C. A state of a film formation surface when a film is formed under the above-described film formation condition of “film formation time: 1 hour” is shown. FIG. 4 (a) shows an electron microscope x
FIG. 4B shows the film formation surface when observed at a magnification of 10 k, and FIG. 4B shows the film formation surface when observed with an electron microscope at a magnification of × 30 k.

FIG. 2 conceptually shows the state of the film forming surface in FIG.

As can be seen from FIGS. 2 and 4, the projecting cold electron emitting portions 2, that is, the edges 2 a are formed in a continuous mesh shape when viewed from the upper surface of the substrate 3.

Since the cold electron emitting portions 2 (edges 2 a) are formed in a continuous mesh like this, it can be seen that the density of the cold electron 4 emitting points is increased.

That is, the cold electron emitting portions 2 are formed in a continuous mesh.
If the (edge 2a) can be formed, a large amount of current can flow.

On the other hand, FIG. 5 shows: • Substrate: n-type silicon single crystal • H2 flow rate: 500 (scc / min) • CH4 flow rate: 25 (scc / min) • Input high frequency power: 1 kW • Substrate temperature: 800 ° C. The film formation time is shown under the condition that the film formation time is 1 hour. FIG. 5A shows the surface of the film formed when the electron microscope was observed at a magnification of × 10 k, and FIG.
Shows the film-forming surface when observed with an electron microscope at a magnification of × 30 k.

FIG. 3 conceptually shows the state of the film formation surface in FIG.

As can be seen from FIGS. 3 and 5, the cold electron emitting portions 2 having a convex shape, that is, the edges 2 a are formed so as to be discrete when viewed from the upper surface of the substrate 3.

As described above, since the cold electron emission portions 2 (edges 2a) are discretely formed, the emission points 2 of the cold electrons 4
It can be seen that the electric field is easily concentrated on a.

That is, the cold electron emission portions 2 are discretely
If the (edge 2a) can be formed, the operating voltage can be reduced, and accordingly, the power consumption can be reduced.

The cold cathode 20 of this embodiment can be used for any device having an anode.

That is, it can be used for various devices and sensors.

FIG. 8 shows the structure of a cathode of an LCD backlight.
The case where the cold cathode 20 is used is illustrated. The anode is shown at 21.

FIG. 9 shows an example in which a cold cathode 20 is used in a simple matrix drive type flat display.

That is, the cold cathode 2 as the cathode electrode
Electrons 4 are emitted from 0 toward the phosphor 21 on the anode electrode side.

[Brief description of the drawings]

FIG. 1 is a structural view conceptually showing the structure of a cold cathode according to the present invention.

FIG. 2 is a diagram conceptually showing a shape of a cold electron emission portion when the substrate is viewed from above.

FIG. 3 is a diagram corresponding to FIG. 2 when film forming conditions are changed.

4 (a) and 4 (b) are diagrams (photographs) showing the results of observing the film-formed surface with an electron microscope, and correspond to FIG. 2 (photographs).

5 (a) and 5 (b) are diagrams (photographs) showing the results of observation of the film formation surface with an electron microscope, and are diagrams (photographs) corresponding to FIG.

FIG. 6 is a diagram used to explain the principle of cold electron emission.

FIG. 7 is a diagram showing a configuration of a film forming apparatus for manufacturing a cold cathode.

FIG. 8 is a diagram showing a case where the cold cathode of the embodiment is used as a cathode of an LCD backlight.

FIG. 9 is a diagram showing a case where the cold cathode of the embodiment is used as a cathode of a simple matrix drive type flat display.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 1st layer 2 ... 2nd layer (cold electron emission part) 3 ... Substrate

Claims (5)

[Claims] 1. A cold cathode in which a cold electron emitting portion is formed in a convex shape with respect to a substrate and a cold electron is emitted from the convex cold electron emitting portion. A cold cathode in which the convex cold electron emitting portions are formed by forming a film. 2. The cold cathode according to claim 1, wherein the projecting cold electron emitting portions are formed continuously as viewed from the upper surface of the substrate. 3. The cold cathode according to claim 1, wherein the projecting cold electron emitting portions are formed discretely when viewed from the upper surface of the substrate. 4. A cold cathode in which a cold electron emitting portion is formed in a convex shape with respect to a substrate, and a cold electron is emitted from the convex cold electron emitting portion. A cold cathode in which the convex cold electron emission portion is formed by accelerating so as to have a large flow velocity and guiding it onto a substrate to form a convex thin film. 5. An element comprising the cold cathode according to claim 1 and an anode.