KR100556746B1 - Field emission device - Google Patents

Abstract

According to the present invention, in an undergate structure using carbon nanotubes as field emission emitters, a focusing electrode is formed on one or left and right coplanar surfaces of a cathode to prevent crosstalk, and to reduce the amount of electrons accumulated in an insulating layer, thereby causing abnormal light emission. The present invention relates to a field emission device capable of preventing the emission voltage and lowering the emission voltage, and includes a gate electrode and an insulation layer sequentially formed on a lower substrate (glass substrate), and an upper portion of the insulation layer and a carbon nanotube in a portion of the region. Is formed on the same plane as the cathode electrode, and a focusing electrode configured to focus electrons emitted from the carbon nanotubes, thereby converging electron beams emitted from the carbon nanotubes to prevent crosstalk. Can reduce the amount of electrons accumulated in the insulating layer to prevent abnormal light emission phenomenon and lower the emission voltage It can be effective.

Description

Field emission device {FIELD EMISSION DEVICE}

1 is a cross-sectional view showing an example of the bottom plate structure of a three-electrode field emission device using a conventional carbon nanotube.

Figure 2 is a plan view and a cross-sectional view showing a bottom plate structure for the field emission device of the undergate structure using a conventional carbon nanotube.

3 is a plan view and a sectional view showing a bottom plate structure of the field emission device of the undergate structure of the present invention;

4 is a plan view and a cross-sectional view showing a bottom plate structure of another embodiment of the field emission device of the present invention undergate structure.

** Description of the symbols for the main parts of the drawings **

20: glass substrate 21: gate electrode

22: insulating layer 23: cathode electrode

24: carbon nanotube 25: focused electrode

The present invention relates to a field emission device, and in particular, in an undergate structure using carbon nanotubes as a field emission emitter, a focusing electrode is formed on one side or left and right coplanar surfaces of a cathode electrode to prevent crosstalk. The present invention relates to a field emission device capable of preventing abnormal light emission by reducing the amount of accumulated electrons and lowering an emission voltage.

Due to the rapid development of information and communication technology and the demand for the visualization of diversified information, the demand for electronic displays is increasing and the required display appearance is also diversified. For example, in an environment where mobility is emphasized such as a portable information device, a display having a small weight, volume, and power consumption is required, and when used as an information transmission medium for the public, display characteristics of a large viewing angle are required.

In addition, in order to satisfy such demands, electronic displays require conditions such as large size, low price, high performance, high definition, thinness, and light weight, so that light and thin that can replace the existing CRT are required to satisfy these requirements. There is an urgent need for the development of flat panel display devices.

Recently, as the needs of various display devices have been applied to display fields, devices using field emission have been actively developed for thin film displays that can provide high resolution while reducing size and power consumption.

The field emission device is attracting attention as a next-generation information communication flat panel display that overcomes all the disadvantages of flat panel displays (LCD, PDP, VFD, etc.) currently being developed or produced. The field emission device has a simple electrode structure, high-speed operation using the same principle as the CRT, and has the advantages of display such as infinite color, infinite gray scale, high luminance, and high video rate. .

Field emission devices utilize quantum mechanical tunneling which causes electrons to exit the vacuum from the metal or conductor when a high field is applied on the metal or conductor surface (emitter) in the vacuum. At this time, the device exhibits the current-voltage characteristic according to the Fowler-Nordheim law. The field emission device is composed of an anode portion which emits an electron emission source and the emitted electrons collide with each other to emit light, a spacer supporting the upper and lower plates, and a sealing portion for maintaining a vacuum tightness.

Recently, the importance of the field emission device using the carbon nanotubes (CNT) because of the mechanically strong, chemically stable and excellent electron emission characteristics at a relatively low vacuum degree has been recognized. Since such carbon nanotubes have a small diameter (about 1.0 to several tens of nanometers), the field enhancement factor is considerably superior to the conventional microtip type spin emission field emission tips, and thus the emission threshold is low. Since it can be made in a turn-on field (about 1 to 5 [V / μm]), there is an advantage of reducing power loss and production cost.

1 is a cross-sectional view showing an example of the bottom plate structure of a three-electrode field emission device using a conventional carbon nanotube. As shown, the resistive layer 12, the insulating layer 14, and the gate electrode 15 are sequentially formed on the silicon substrate 11, and the gate electrode 15 and the insulating layer 14 are formed by photolithography. After etching a portion to form a hole, the catalyst transition metal layer 13 is formed on the resistive layer 12 at the bottom of the hole through evaporation, and the entire silicon substrate 11 is about 600-900 [deg.] C. The carbon nanotubes 16 are selectively formed only on the catalyst transition metal layer 13 through a thermal chemical vapor deposition method using a hydrocarbon gas or a plasma chemical vapor deposition method by heating to a temperature range. .

In this case, since the carbon nanotubes 16 are selectively formed only on the catalyst transition metal layer 13, the larger the area of the catalyst transition metal layer 13, the larger the area of the carbon nanotubes 16. As such, when the area of the carbon nanotubes 16 increases, the electric field applied through the gate electrode 15 is not concentrated, so that the beam of the emitted electrons is spread and the electron emission region is not even. Only the electron emission is likely to occur locally, and due to an asymmetric electric field distribution, the leakage current to the gate electrode 15 has many problems.

In order to solve the above problems, the structure of the carbon nanotube field emission device having the gate electrode positioned at a lower position than the cathode electrode has been proposed.

FIG. 2 shows a plan view and a cross-sectional view (A-A 'of the plan view) of an example of a bottom plate structure in a field emission device having an under gate structure using a conventional carbon nanotube. As shown, the gate electrode 21 and the cathode electrode 23 on the glass substrate 20 have a matrix structure that is orthogonal to each other with the insulating layer 22 interposed therebetween. The method is applied to the gate electrode 21 under the tube 24.

Referring to the manufacturing process of the bottom plate structure for the field emission device of the undergate structure as follows.

First, an Indium-Tin-Oxide (ITO) transparent electrode is deposited on the glass substrate 20 to a thickness of about 120 nm, and the gate electrode 21 is formed by using a photolithography method. (21) The dielectric powder in the form of a paste is coated on the top by screen printing, and fired at about 580 [deg.] C to form the insulating layer 22.

A conductive metal such as aluminum (Al) or chromium (Cr) is deposited on the insulating layer 22 to a predetermined thickness, and then vertically intersects with the gate electrode 21 using a photolithography method to form the cathode electrode 23. The carbon nanotubes 24 are formed at the edges of the cathode electrode 23.

However, as shown in FIG. 2, the field emission device having the three-pole undergate structure has a large spread of the electron beam emitted from the carbon nanotubes, so that crosstalk may occur, and the emitted electrons may be formed on the insulating layer. It may accumulate and cause abnormal light emission.

As described above, the field emission device having the three-pole undergate structure using the carbon nanotube has a problem that crosstalk may occur because the electron beam emitted from the carbon nanotube is large.

In addition, the prior art has a problem that electrons emitted from the carbon nanotubes are accumulated on the insulating layer may cause abnormal light emission phenomenon.

Accordingly, the present invention in consideration of such a problem comprises a focusing electrode to which an electric field of the same polarity as that of the cathode electrode formed on one side or left and right coplanar surfaces of the cathode electrode formed on the insulating layer in the undergate electrode structure is applied, The purpose of the present invention is to provide a field emission device capable of focusing electron beams emitted from carbon nanotubes to prevent crosstalk, reducing the amount of electrons accumulated in an insulating layer, preventing abnormal light emission, and lowering an emission voltage. .

The present invention for achieving the above object comprises a gate electrode and an insulating layer formed sequentially on the lower substrate (glass substrate); A cathode formed on the insulating layer and having carbon nanotubes formed in a portion of the insulating layer; And a focusing electrode formed on the same plane as the cathode and focusing electrons emitted from the carbon nanotubes.

In addition, the polarity of the electric field applied to the focusing electrode is the same as the polarity of the electric field applied to the cathode electrode.

In addition, the carbon nanotubes are characterized by being biased toward the focusing electrode formed to be spaced apart from the cathode electrode.

In addition, the carbon nanotubes and the focusing electrode may be formed symmetrically about the cathode electrode.

With reference to the accompanying drawings, a preferred embodiment of the field emission device of the present invention having the above characteristics will be described.

3 is a plan view and a cross-sectional view (B-B 'of the plan view) of the bottom plate structure of the field emission device of the undergate structure using the carbon nanotube of the present invention. As shown, a structure in which a focusing electrode 25 is added on the same plane as the cathode electrode 23 in the bottom plate structure of a field emission device having a conventional undergate structure, is formed on the glass substrate 20. 21, an insulating layer 22 formed on the gate electrode 21, a cathode electrode 23 formed on the insulating layer 22, and having carbon nanotubes 24 formed on a portion of the gate electrode 21, and One side of the cathode electrode 23 is composed of a focusing electrode 25 formed on the same plane.

Figure 4 shows a plan view and a cross-sectional view (C-C 'of the plan view) of another embodiment of the present invention, unlike shown in Figure 3 carbon nanotubes are formed on the upper left and right sides of the cathode electrode, It is formed on the same plane on the left and right sides of the cathode electrode to perform the function of focusing the electrons (e) emitted from the carbon nanotubes, and the effect of more emission current than expected if there is only one focusing electrode (Fig. 3) Can be.

The cathode electrode 23 and the focusing electrode 25 are formed using the same process, and when the electric field having the same polarity as that of the cathode electrode 23 is applied to the focusing electrode 25, the electron beam emitted from the carbon nanotube 24 is emitted. And the emission voltage can be lowered when an electric field of opposite polarity is applied.

Then, the manufacturing process for the present invention having such a configuration will be described.

First, an Indium-Tin-Oxide (ITO) transparent electrode is deposited on the glass substrate 20 to a thickness of about 120 nm, and the gate electrode 21 is formed using a photolithography method.

The paste-type dielectric powder is coated on the gate electrode 21 by screen printing, and baked at about 580 [deg.] C to form an insulating layer 22 having a thickness of about 10 [[mu] m].

A conductive metal such as aluminum (Al) or chromium (Cr) is deposited on the insulating layer 22 to a thickness of about 300 [nm], and then vertically intersects with the gate electrode 21 using a photolithography method to form a cathode. A focusing electrode 25 is formed on one side or left and right sides of the electrode 23 and the cathode electrode 23, and a carbon nanotube 24 is formed at one side or left and right edge positions of the upper portion of the cathode electrode 23.

In this case, the carbon nanotubes 24 formed at the edges of the cathode electrode 23 may form the carbon nanotubes in the form of a paste by a printing method, or may be accurately drawn using a lift-off method. It is also possible to form an island).

The focusing electrode 25 of the field emission device thus formed may be formed on the same layer using the same mask as the cathode electrode 23, and may be formed as an independent electrode or a common electrode. The focusing electrode 25 performs the function of focusing the electron beam emitted from the carbon nanotubes 24 or lowers the emission voltage. For example, when a positive electric field is applied to the gate electrode 21 and a zero or negative electric field is applied to the cathode electrode 23, electrons are emitted from the carbon nanotubes 24. When a negative electric field is applied to the focusing electrode 25, the emitted electrons e are focused as shown in FIG. 3 or 4 and attracted to the anode electrode (not shown).

In addition, applying a positive electric field instead of a negative electric field to the focusing electrode may lower the threshold voltage (emission voltage) of the emitted electrons.

As described in detail above, the present invention includes a focusing electrode to which an electric field of the same polarity is applied as the cathode electrode formed on one side or the left and right coplanar surfaces of the cathode electrode formed on the insulating layer in the undergate electrode structure, thereby providing carbon The electron beam emitted from the nanotubes can be focused to prevent crosstalk, and the amount of electrons accumulated in the insulating layer can be reduced to prevent abnormal light emission and to lower the emission voltage.

Claims (4)

A gate electrode and an insulating layer sequentially formed on the lower substrate (glass substrate); A cathode formed on the insulating layer and having carbon nanotubes formed in a portion of the insulating layer; And a focusing electrode formed on the same plane as the cathode and focusing electrons emitted from the carbon nanotubes. The field emission device of claim 1, wherein the polarity of the electric field applied to the focusing electrode is the same as the polarity of the electric field applied to the cathode electrode. The field emission device of claim 1, wherein the carbon nanotubes are formed to be biased toward a focusing electrode formed to be spaced apart from the cathode electrode. The field emission device according to claim 1, wherein the carbon nanotubes and the focusing electrode are symmetrically formed around the cathode electrode.

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