JPH04332424A - Field electron emitter - Google Patents

Abstract

PURPOSE:To eliminate instability of electron emission and reduce noise by applying an electric field to a cathode electrode through a gate electrode, irradiating light onto the cathode electrode so as to accelerate emitted electrons. CONSTITUTION:A field electron emitting element substrate is provided with a flat quartz substrate 1 and an insulating layer 2 formed on the substrate 1. A cathode electrode 3 is formed on the insulating layer 2, and a electrons are 64 emitted from a projection 4 of the cathode electrode 3. A gate electrode 5 is disposed nearly right under the projection 4, and an anode electrode 6 is formed on the side opposite to the electrode 3 with the electrode 5 formed on the substrate 1 held therebetween. The electrode 3 is adapted to emit an electron by an electric field effect so that an electric field is applied by the electrode 5. The electrons are accelerated by the electric field to be collected in the electrode 6. An irradiating means irradiates light onto the electrode 3, to thus generate a electrons. Accordingly, noise of the discharged current and instability such as a aging are eliminated, thereby obtaining a stable electric discharge current having a large S/N ratio and high reliability.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field emission device that emits electrons by a field effect, and more particularly to a field emission device in which the emission current of a cathode electrode is stabilized.

0002

[Prior Art] Gray (
H. F. Gray) et al. at the International Electronic Devices Conference (IED)
M86), p. 776 (1986), in which electrons are emitted from a flat substrate in a generally vertical direction, and the vertical type, in which electrons are emitted from a flat substrate in a generally vertical direction, and the vertical type, as published by Ito in Applied Physics, Vol. 59, No. 2, p. 164
(1990), in which electrons are emitted in a direction generally parallel to a flat substrate, is well known. Such conventional field electron emission devices do not have any special means for irradiating light to the cathode electrode, and are usually operated at around room temperature.

0003

[Problems to be Solved by the Invention] However, conventional field electron emission devices have had several problems as described below. In other words, the amount of electrons emitted from the cathode electrode is greatly affected by the surface condition of the cathode electrode, and if the surface condition changes during driving, the amount of emitted electrons changes greatly over time, which is a problem of instability in the cathode emission current. was there. In addition, burst noise occurs during electron emission, resulting in a poor signal-to-noise ratio (S/N ratio). Furthermore, in order to increase the emission current, a method is taken to simultaneously emit electrons from multiple cathode electrodes, but due to the non-uniformity of the emission threshold voltage of each cathode electrode and changes over time, the emission current is more uniform than that of all cathode electrodes. There was a problem in that it was not possible to obtain

[0004] In order to improve the above-mentioned noise and instability, the inventor conducted detailed research and discovered that the electron emitting region of the cathode electrode is irradiated with light immediately before or during electron emission of the field emission device. It has been found that this significantly reduces noise and instability and stabilizes the emission current. This is because the surface of the cathode electrode is stabilized by the heating effect or light action caused by light irradiation, and contamination of the cathode electrode surface due to degassing from surrounding constituent materials is prevented.

The present invention overcomes the problems of the prior art by introducing such a light irradiation means into a conventional field electron emission device, and its purpose is to eliminate electrons from the cathode electrode. It is an object of the present invention to provide a field electron emission device that reduces emission instability and noise, increases reliability and S/N ratio, reduces emission threshold voltage, and increases emission current density.

[0006]

[Means for Solving the Problems] The field electron emission device of the present invention includes a protrusion-shaped cathode electrode that emits electrons by a field effect, a gate electrode that applies an electric field to the cathode electrode, and a field electron emission device that emits electrons from the cathode electrode. A field electron emission device comprising at least an anode electrode for accelerating and collecting the emitted electrons, and further comprising a light irradiation means for irradiating the cathode electrode with light, and the light irradiation means includes a light source. and a condensing optical system, and further,
The light irradiation means is characterized in that the light source is light emitted from an electron/light conversion function body formed on the anode electrode.

[0007]

【Example】

(Embodiment 1) FIG. 1 is for explaining a first embodiment of the present invention, and is a schematic cross-sectional view of a horizontal field electron emission device equipped with a light source and a condensing optical system. This field electron emission device consists of a field electron emission device substrate, a vacuum panel, and a light source system as a light irradiation means.

That is, the field electron emission device substrate includes a planar quartz substrate 1, an insulating layer 2 formed on the surface of the quartz substrate 1, and a protrusion 4 formed on the surface of the insulating layer 2 with a thickness of 5 μm for electron emission. There are 20 cathode electrodes 3 at a pitch, a gate electrode 5 formed on the surface of the quartz substrate 1 and placed directly under the protrusion 4, and a cathode electrode 3 formed on the surface of the quartz substrate 1 with the gate electrode 5 in between. The main component is an anode electrode 6 arranged on the opposite side. The insulating layer 2 is made of a silicon dioxide thin film with a thickness of 4000 Å, the cathode electrode 2 is made of a molybdenum thin film with a thickness of 2000 Å, and the gate electrode 5 and the anode electrode 6 are made of a molybdenum thin film with a thickness of 1000 Å. The protrusion 4 of the cathode electrode 3 is manufactured by an over-etching method, and the radius of curvature of its tip in a plane is about 300 Å. The gate electrode 5 was manufactured in self-alignment with the protrusion 4 by a directional particle deposition method such as a vapor deposition method. The distance between the protrusion 4 and the gate electrode 5 is about 3000 Å.

The vacuum panel consists of a quartz substrate 1, a planar transparent substrate 7 placed opposite to the quartz substrate 1, and a low melting point glass sandwiching body 8 formed around these two substrates and bonded to each other. It consists of a vacuum layer 9 surrounded by a substrate and a sandwiching body 8. A field emission device consisting of the cathode electrode 3, gate electrode 5, and anode electrode 6 described above is arranged inside the vacuum layer 9. The vacuum degree of vacuum layer 9 is 1×1
A high vacuum of 0-7 Torr or less is maintained.

The light source system includes a light source 10 consisting of a halogen lamp.
The light source 10 and the condensing optical system are designed to condense light around the protrusion 4, with a condensing optical system consisting of a first condensing lens 11 and a second condensing lens 12 as constituent elements. For example, the focal length of the first condensing lens 11 is F1=60mm.
, assuming that the second condensing lens 12 has F2=80 mm, the shortest distance of the optical path 13 from the light source 10 to the protrusion 4 is approximately 200 m.
It is m.

The light of the halogen lamp passes through the lens and the transparent substrate 7 well and has good light collection efficiency. Furthermore, since the cathode electrode 4 is made of metal, it absorbs light well and is heated, and the quartz substrate 1 has a low thermal conductivity. The heating efficiency of the field electron emission device is good because it is small and prevents heat emission. Rating is 100V, 300W
When a voltage of 60 V was applied to the halogen lamp and the cathode electrode 3 was irradiated with light, the temperature of the cathode electrode 3 rose to about 300°C. Further, when an applied voltage of 100V was applied, the temperature rose to about 600°C.

The emission current was measured while the cathode electrode 3 and projection 4 were heated to about 300° C. by light irradiation. When the anode voltage was 200 V and the gate voltage was 120 V, the average cathode current was 50 μA and the fluctuation (noise) component was within 2%. Further, in continuous measurement for 30 minutes, the change (instability) in the average value of the cathode current was within 5%. If no light is irradiated, the noise is 30
%, and the instability was 20%, indicating that the effect of light irradiation on stability was very good. Although a halogen lamp is used as a light source, the present invention is not limited to this, and high-pressure or low-pressure mercury lamps, metal halide lamps, laser light, etc. can also be used. When irradiating ultraviolet rays using a mercury lamp or laser, a lens or transparent substrate that transmits ultraviolet rays, such as a fused silica material, may be used.

(Embodiment 2) FIG. 2 is a partial cross-sectional view of a field emission device having a fluorescent layer on an anode electrode, for explaining a second embodiment of the present invention. This field electron emission device utilizes light emission from a fluorescent layer as an electron/light conversion function body as a light irradiation means.

This field electron emission device includes a single crystal silicon substrate 21, a cathode electrode 22 formed on the surface of the silicon substrate 21, and an insulating layer 23 formed on the surface of the silicon substrate 21 and having an opening near the cathode electrode 22. , a gate electrode 24 formed on the surface of the insulating layer 23 and opened near the cathode electrode 22 , a glass substrate 25 disposed opposite to the silicon substrate 21 , and an anode electrode formed on the surface of the glass substrate 25 26, a fluorescent layer 27 formed on the surface of the anode electrode 26, and a vacuum layer 28 in the area sandwiched between these two substrates are the main components.

The silicon substrate 21 has a carrier concentration of 2×1.
015 cm-3 and has a (100) plane orientation. The cathode electrode 22 is a conical protrusion with a height of 1.2 μm and an apex angle of 90 degrees, which is manufactured by anisotropically etching the surface of the silicon substrate 21 . The insulating layer 23 is made of a silicon dioxide thin film with a thickness of 5000 Å, and the gate electrode 24 has a thickness of 2000 Å.
It consists of tantalum thin film. Glass substrate 25 is #7740
(manufactured by Corning Inc.), and the anode electrode 26 is an ITO (indium tin oxide) thin film with a film thickness of 2000 Å. The phosphor layer 27 is made of ZnO:Zn phosphor with a particle size of 3 μm, and its film thickness is about 10 μm. Fluorescent layer 27
The distance between the cathode electrode 22 and the vacuum layer 28 is approximately the same as the thickness of the vacuum layer 28, which is approximately 50 μm.

This field electron emission device emits electrons from the tip of the protrusion of the cathode electrode 22 by applying a gate voltage, and the emitted electrons 29 are accelerated by the anode voltage and excite the fluorescent layer 27 to emit light. This is the action of flowing into. The phosphor 27 serves as a light source, and its emitted light 30 irradiates the surface of the silicon substrate 21, particularly the surface of the cathode electrode 22. Irradiation intensity is controlled by gate voltage or anode voltage. The density of the cathode electrode 22 is 106
particles/cm2, the average electron emission amount of the cathode electrode 22 is 10 nA/piece, the anode voltage is 400 V, the luminous efficiency of the fluorescent layer 27 is 5 lm/W, and the irradiation efficiency is 30%, then the average irradiation intensity to the cathode electrode 22 is 6 lm/cm2. To increase the irradiation intensity, increase the gate voltage,
All you have to do is increase the amount of electron emission. The average electron emission amount is 1μA/
When the number of particles is reduced, the irradiation intensity is approximately 0.
5 W/cm2, which is an effective value for stabilizing the emission current of the cathode electrode 22. Note that as long as the irradiation intensity is at least a certain value, even if the irradiation intensity fluctuates, the stabilizing effect of the emission current will not be affected.

Emission current was observed while irradiating a field emission device having a total of 1000 cathode electrodes with a light energy of 0.5 W/cm 2 . At this time, the average cathode current was 1 mA, its noise component was 0.5%, and the fluctuation in the average value of the cathode current for 30 minutes was within 1%. These values are about one order of magnitude better than those of the field emission device without the fluorescent layer 27, indicating that the emission current is stabilized. By using the cathode electrode 22 made of single crystal silicon, the threshold voltage for electron emission can be lowered by changing the energy state of the semiconductor due to light irradiation. This is equivalent to an increase in emission current with the same gate voltage. In the field electron emission device of this example, the threshold voltage was lowered by about 20 V under the above-mentioned irradiation conditions, and an emission current that was about one order of magnitude larger could be obtained at the same gate voltage.

Note that it is also effective to irradiate light with a shorter wavelength emission spectrum and higher photon energy for stabilizing the emission current. ZnS in the fluorescent layer 27:
By using or mixing a zinc sulfide-based phosphor material such as Zn, it is possible to irradiate light including near-ultraviolet light. Further, it is also effective to use an electron/light conversion functional body such as an organic EL material or a compound semiconductor material.

The field electron emission device described in this embodiment can be used as a vacuum transistor in a switching device or an amplifier. It is also suitable for application to displays.

[0020]

As explained above, the field electron emission device of the present invention has the effects of the invention as listed below.

That is, instability such as noise and aging of the emission current is improved, and a stable emission current with a high S/N ratio and high reliability can be obtained.

Furthermore, since the threshold voltage for electron emission is lowered by light irradiation, an emission current that is about one order of magnitude larger can be obtained at the same gate voltage.

Furthermore, since molecules adsorbed on the surface of the cathode electrode are removed by light irradiation, plasma damage to the cathode electrode can be prevented.

Furthermore, since the fluorescent layer formed on the anode electrode emits light using the energy obtained from the anode voltage,
There is no waste of energy consumed by the light source, and energy loss in the entire device can be suppressed.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a horizontal field emission device including a light source and a condensing optical system, for explaining a first embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of a field emission device including a fluorescent layer on an anode electrode, for explaining a second embodiment of the present invention.

[Explanation of symbols]

1 Quartz substrate 2 Insulating layer 3 Cathode electrode 4.Protrusion 5 Gate electrode 6 Anode electrode 7 Transparent substrate 8 Holding body 9 Vacuum layer 10 Light source 11 First condenser lens 12 Second condensing lens 13. Light path 21 Silicon substrate 22 Cathode electrode 23 Insulating layer 24 Gate electrode 25 Glass substrate 26 Anode electrode 27 Fluorescent layer 28 Vacuum layer 29 Emitted electron 30 Luminescence

Claims (3)

[Claims] 1. A protruding cathode electrode that emits electrons by a field effect, a gate electrode that applies an electric field to the cathode electrode, and an anode electrode that accelerates and collects electrons emitted from the cathode electrode. What is claimed is: 1. A field electron emission device comprising: a light irradiation means for irradiating light onto the cathode electrode. 2. A field electron emission device according to claim 1, wherein the light irradiation means comprises a light source and a condensing optical system. 3. A field electron emission device according to claim 1, wherein the light irradiation means uses light emission from an electron/light conversion function body formed on the anode electrode as a light source.