JP2000235830A - Field emission tip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable emission of much electron even when the applying voltage is low while optimizing the atom structure of a tip part by obliquely cutting a tip of a carbon nano tube in relation to a vertical axis. SOLUTION: A tip of a carbon nano tube is obliquely cut in relation to the axis thereof on purpose so as to obtain the zigzag chain-shaped structure of carbon atom to be exposed at the tip. The same structure with the arrangement structure of the carbon atom to be generated in the periphery of a (n, 0) nano tube ((n) means an integer) is thereby obtained. In the case of multiple carbon nano tubes, tips thereof are obliquely cut. In this case, even if carbon for communicating adjacent layers with each other is adhered to the tip, the same effect is obtained and when electric field is applied, potential energy at the tip of the nano tube is raised, and the work function is lowered. consequently, energy barrier is lowered, and electron emitting probability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a field emission chip for various devices including a display device.
More particularly, the present invention relates to a carbon nanotube used as a chip for emitting electrons in various devices.

[0002]

2. Description of the Related Art A field emission display device (FED; Field Em
has been proposed in 1986. At present, various displays such as television screens use a conventional cathode ray tube (CRT) or a thin film transistor liquid crystal device (TF) which has recently been in the limelight.
T-LCD) has been continuously researched and developed as a new display element of the next generation.

In such a field emission display device,
The most important component is a field emission chip (or field emitter) which replaces the conventional CRT electron gun.
Or an electron emission tip), but until now, as a field emission tip,
Metals, semiconductors or diamonds have been used. 19
Since the proposal to use carbon nanotubes as field emission chips was made around 1995, research on this has been ongoing and interim results have been reported one after another.

When a carbon nanotube is used as a chip, its size is much smaller than that of a conventional chip,
The advantage is that there are so many chips, that the redundancy is high and the stability is high.

The following have been proposed as techniques for producing carbon nanotubes.

[0006] First, by using a plasma enhanced chemical vapor deposition (PECVD) method to add hydrocarbons, and sometimes hydrocarbons and ammonia gas, onto a glass substrate coated with a catalyst such as nickel. A technique for vertically growing carbon nanotubes on a substrate has been proposed.

Second, a technique has been proposed in which hydrocarbons are passed through a structure in which micropores are formed in the anode aluminum oxide film to form a large number of parallel carbon nanotube aggregates.

Third, carbon nanotubes are produced by a conventional arc discharge or laser cutting method,
Then, a technique of aligning using another adhesive or electric force was proposed.

In addition, many similar techniques have been proposed. Despite such research and development efforts on carbon nanotubes, the exact atomic structure of the ends of carbon nanotubes from which electrons are actually emitted under an applied electric field is not yet known. Also, little is known about what structure the electron emission is optimized when. Therefore, it is far from the known research results reports to derive various parameters appropriate for actual use, such as current density and threshold voltage required for operating the FED.

Since carbon nanotubes used as field emission chips must be conductive metals, so-called (n, n) nanotubes are mainly used (where n is an integer indicating the size). is there). However, since it was not well known what form the tip structure of the carbon nanotube had, it was used without particular consideration.

In most cases, the tip is dome shaped (FIG. 1a).
And FIG. 1b) or a shape in which the cross section of the tip is cut perpendicular to the nanotube axis (FIGS. 2a and 2b).
See). Here, the case where the nanotubes are single-wall nanotubes is shown in the drawings, but the same applies to the case where the nanotubes are multi-wall nanotubes.

[0012]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to optimize the atomic structure of the tip of a carbon nanotube tip so that many electrons are emitted even at a low applied voltage, thereby reducing the number of electrons. An object of the present invention is to provide a field emission chip capable of manufacturing a field emission device having a high voltage and a high current.

[0013]

The use of carbon nanotubes as a field emission chip of a display device to achieve the object of the present invention is the same as in the prior art. A feature of the present invention is that, as already mentioned in the description of the prior art, the carbon nanotubes are arranged by the first method of making many carbon nanotubes by a technique of vertically growing the nanotubes on a glass substrate or other methods. Later, the tip of the carbon nanotube is cut not obliquely but perpendicularly to the axis of the carbon nanotube for use as a field emission chip.

[0014]

Hereinafter, a field emission chip of a display device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3A is a side view showing an embodiment of the field emission chip according to the present invention, and FIG. 3B is a plan view of FIG. 3A. Although many such chips are gathered in an actual element, only one is shown here, and the same applies to other drawings.

Here, a so-called (5,5) nanotube is shown as an example, but the result is the same even with other metallic nanotubes having different sizes. As shown in the drawing, the tip of the carbon nanotube is intentionally cut in a direction oblique to its axis. Therefore, the structure of the carbon atoms exposed at the tip becomes a zigzag chain shape. This is the same as the arrangement structure of carbon atoms generated around the (n, 0) nanotube (n is an integer) in a technical term.

The basic structure of the carbon nanotube body is also called chirality, but (n,
n) Even if it is not the structure, if the arrangement structure of the tip portion has a zigzag chain shape, the effect shown in FIG.

In the case where the carbon nanotubes are multi-wall nanotubes, similarly, as shown in FIG. 3, the shape of the tip is cut obliquely. In this case, even if carbon which connects adjacent layers is attached to the tip, the result is not so different.

In the present invention, it is possible to process the tip of the carbon nanotube obliquely by a relatively simple process.

That is, when the tube is cut by a non-isotropic method, that is, an anisotropic method in the process of cutting into a tube having an open end having a uniform height, an obliquely cut chip structure can be obtained. Specifically, when a chemical substance for etching or a highly reactive gas is applied in one direction, or in the case of a thin and bendable nanotube, a force is applied to one of the nanotubes, whereby the nanotube is cut obliquely.

In a carbon nanotube having such a structure, when an electric field is applied, electrons are better collected at the tip of the nanotube, and as a result, the potential energy at the tip is increased and the work function is reduced. Therefore, that is, the energy barrier decreases, and the electron emission probability increases.

Such a result was confirmed by calculation using a precise quantum mechanical method. That is, the change in the electronic structure due to the electric field in each case (FIGS. 1, 2 and 3) is calculated by the first principle pseudo-potential (ab initio pseudopotential) method well known in solid-state physical structure calculation. At this time, the electric field (electric field) is blocked (screenin
g) It was confirmed that the potential increase due to the accumulated electrons was determined. Compared with the case of FIGS. 1 and 2, in the case of FIG. 3, the result that the potential was increased by 0.8 V and 1.1 V, respectively, was obtained.

Localization at the tip of the carbon nanotube (loca
According to the above calculation, the lized) electrons move by about 0.5 electron volts (eV) even in a relatively low electric field (electric field), are subjected to a so-called Fermi level, and are charged at room temperature or lower. This directly contributes to electron emission by the field (electric field). Due to the characteristics of such an electron, the number of overlap integrals of the electron with the wave function on the anode side when compared with the so-called pi (π) wave function, which is delocalized, is small. Times, resulting in a large increase in current density.

As clearly shown in FIG. 3A, the radius of curvature at the tip of the carbon nanotube is small, and the electric field strength at that portion increases due to the lightning rod effect, thereby contributing to an increase in the probability that electrons flow through by tunneling. Will be.

FIG. 4 is a side view showing another embodiment of the field emission chip according to the present invention. As shown in the figure, the tip of the carbon nanotube is cut so as to have two or more inclined surfaces. In this case, the same effect as that of the carbon nanotube shown in FIGS. 3A and 3B is expected. . FIG.
The inclined cross-sectional structure shown in the figure is a multi-wall
nanotube). In this case, the effect is not different from that of the single-wall nanotube. The result is basically the same when hydrogen and oxygen are attached to the tip of the chip.

Although the embodiments of the present invention have been described, the technical terms used are for explanation, not for limiting the present invention. It should be understood that many modifications and variations of the present invention are possible in light of the above teachings, and thus, within the scope of the appended claims, the present invention may be practiced other than in the embodiments described above.

[0027]

As described above, in the field emission chip of various devices according to the present invention, electrons are emitted even at a low applied voltage by cutting the tip of the carbon nanotube chip obliquely with respect to its axis. This increases the effect of producing a low-voltage, high-current display element.

[Brief description of the drawings]

FIG. 1a is a side view of a conventional field emission chip. FIG. 1b is a plan view of FIG. 1a.

FIG. 2a is a side view showing another example of a conventional field emission chip. FIG. 2b is a plan view of FIG. 2a.

FIG. 3a is a side view showing one embodiment of a field emission chip according to the present invention. FIG. 3b is a plan view of FIG. 3a.

FIG. 4 is a side view showing another embodiment of the field emission chip according to the present invention.

Claims (3)

[Claims] 1. A field emission chip for various devices, wherein a tip of a carbon nanotube is cut obliquely to a vertical axis. 2. The field emission chip according to claim 1, wherein the tip portion of the carbon nanotube has a plurality of surfaces crossing each other. 3. The field emission chips of various devices are manufactured so that a zigzag chain structure appears at the tip of the carbon nanotube, and have the same atomic arrangement structure as the structure of the tip of the carbon nanotube of claim 1. A field emission chip characterized in that: