JP2010269372A - Method for preparing self-organized film and planar electron-emitting source using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that an electronic device formed by using an inexpensive sol-gel method allowing nano particles to be self-organized using cohesion of the nano particle is not achieved since a manufacturing method adaptable to the electronic device requires high temperature processing and is not bearable for mass production. <P>SOLUTION: This method for forming a self-organized film includes a step of dispersing nano fine particles by solvent; a step of applying a solution having the nano fine particles dispersed by the solvent on a substrate; and a step of forming a space area where the evaporation of the solvent is more delayed than those of other areas, forming the space area to have a component in a vertical direction to the substrate, and allowing the nano fine particles to grow self-organizingly in the space area. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing nanoparticles in a self-organized manner, and an electronic device using the method for producing a self-assembled film. It is about the source.

  Various methods have been reported as methods for forming fine particle structures in which fine particles are assembled in a self-organized manner and fine particles are regularly and three-dimensionally arranged (see, for example, Non-Patent Documents 1 and 2). )

  One of the methods is a pulling method. In the pulling method, for example, fine particles are dispersed in a solvent to form a fine particle solution, and a substrate having good affinity for the fine particles is vertically inserted therein, and then the substrate is lifted from the fine particle solution. When the substrate is pulled up, an appropriate amount of the fine particle solution is transferred to the substrate surface. Thereafter, in the process of evaporation of the solvent from the transferred fine particle solution, self-organization of the fine particles occurs, and a fine particle structure in which the fine particles are regularly arranged is formed on the substrate (for example, Non-patent documents 3, 4 and 5).

  Another method is a natural sedimentation method. In the natural sedimentation method, a fine particle solution is prepared in the same manner as the pulling method, and then the substrate is allowed to stand under the fine particle solution. The fine particles gradually settle on the substrate due to their own weight, and a fine particle structure in which the fine particles are regularly arranged is formed (for example, see Non-Patent Document 6).

  As a technique for improving these, there is disclosed a fine particle structure in which the mechanical strength and transferability of the fine particle layer are improved and the fine particle layer is prevented from peeling while maintaining the arrangement property of the fine particle layer regularly arranged three-dimensionally. This is proposed in Japanese Patent Laid-Open No. 2006-138980 and Japanese Patent Laid-Open No. 2006-138893.

  In these methods, the fine particles can be fixed while maintaining the alignment of the fine particle layer by forming a plurality of fine particles in which a polymer is applied or sprayed or mixed with a fine particle solution to form a three-dimensionally ordered fine particle. it can. Thereby, the mechanical strength and transferability of the fine particle layer are improved, and the fine particle layer is prevented from peeling off.

  On the other hand, the planar emitters that have been developed include carbon-based substances such as graphite, diamond, and carbon nanotubes, but these tunnels cause electrons to pass through the barrier, and even in low electric fields and low temperatures, It is said that electrons are emitted inside. In particular, a fiber-like material such as a carbon nanotube is expected as a high-efficiency material that can smoothly emit electrons even at a low driving voltage (10 to 50 V). By adopting a novel porous planar electron emission electrode structure in which electron emission protrusions that emit electrons by a spherical recess and an electric field are periodically formed, the electron emission protrusions can be easily and periodically perpendicular to the substrate surface. Japanese Patent Application Laid-Open No. 2007-26790 discloses a technique for forming an electron-emitting emitter by forming them.

JP 2006-138980 A JP 2006-138893 A JP 2007-26790 A

P. J iange te al. , Chem. M at er. (1 9 9 9), 1 1, 2 1 3 2 Y. X ia et al. , A d v. M at er. (2 0 0 0), 1 2 (1 0), 6 9 3 K. N agaya mama, J. et al. S o c. Pow der T ech no nol. J a pan (1 9 95), 3 2, 4 7 6 J. D. Joannopoulos, Nature (20 0 1), 414 (15), 2 5 7 Yong-HongYe et al. , A p p l. Phys. L et t. (2 0 0 1), 7 8 (1), 5 2 H. Migue ze te al. , A d v. M at er. (1 9 9 8), 1 0 (6), 4 8 0

  However, any of the methods described in the above prior art requires expensive materials, precise temperature management and material control. Therefore, high temperature processing is necessary, it is difficult to withstand mass production, and practical application to electronic devices and the like has not been made so much.

  On the other hand, an electronic device that can be self-assembled by using a sol-gel method that can be realized at a relatively low cost, that is, that can withstand practical use by utilizing the cohesive force of nanoparticles has not yet been realized.

  In addition, there was no method for three-dimensional growth using metal nanoparticles. Furthermore, there has been no method for crystal growth by a simple preparation method using the same solvent.

  As the surface electron emission source, a Spindt type surface electron emission source or a CNT (carbon nanotube) type surface electron emission source has been proposed, but the manufacturing method is complicated. Furthermore, since these planar electron emission sources are all formed in a plane, it cannot be said that the three-dimensional space is effectively utilized, and the efficiency of electron emission with respect to the input power is poor.

  The present invention finds a method for three-dimensional crystal growth by self-organizing action by applying and drying a single fine particle or a plurality of particles dissolved in a solvent, and is capable of mass production. The element created by the technique is intended to provide a new electronic device.

  The method for producing a self-assembled film of the present invention includes a step of dispersing nanoparticles in a solvent, a step of applying a solution in which the nanoparticles are dispersed in a solvent, and a method of growing the nanoparticles in a self-organizing manner. It has the process to make it feature. By using such a preparation method, the nanoparticles can be arranged by a simple method, that is, by simply applying the nanoparticles to the substrate by utilizing the closed space, that is, the solvent evaporation delay space. An electron emission device using this production method exhibits good electron emission characteristics and can be applied to an FPD (Flat Panel Display) or the like.

  In addition, a spatial region in which the evaporation of the solvent is delayed from other spatial regions is formed, and the spatial region is formed so as to have a component in a direction perpendicular to the substrate. According to this production method, in addition to the above effects, the nanoparticles can be arranged three-dimensionally at a desired position.

  In addition, the space region is formed of a particle larger than the nano fine particles and a substrate. According to this production method, a closed space can be easily configured by using fine particles, and when an electronic device is produced with this configuration, an element with high electron emission efficiency can be formed.

  Further, the space region is characterized in that a wedge shape is created by etching. According to this method, a closed space can be easily configured, and when an electronic device is created, a light emission position can be determined more accurately, and thus a device with higher light emission efficiency can be obtained.

  Further, the space region where the evaporation of the solvent is delayed is a space region formed by a substrate and a member arranged to form an angle of 90 degrees or less with respect to the substrate. According to this creation method, in addition to the above effects, it becomes possible to set an optimal evaporation amount for self-organization, so that a more efficient device can be obtained when used in a device.

  The planar electron emission source of the present invention has a first dielectric member arranged in a substantially parallel direction with respect to the conductive member, and a substantially vertical direction component with respect to the conductive substrate between the first dielectric members. Nanoparticle covered with the second dielectric member arranged in such a manner, the nanoparticle covered with the second dielectric member is carried on the first dielectric member Yes. According to this configuration, since the insulating coating nanoparticles are repeatedly arranged in the direction perpendicular to the conductive substrate, ballistic electrons can be emitted with a simple configuration and manufacturing method.

  Further, the nanoparticles covered with the supported second dielectric member are arranged in a substantially wedge-shaped region formed by the first dielectric member and the conductive member, and the crystal is grown in a self-organized manner. It is characterized by that. According to this configuration, since the dielectric coating nanoparticle is arranged in a self-organizing manner, it can be crystallized with minimum energy. Therefore, the nano-particles essential for ballistic electron emission can be repeatedly arranged, so that a surface electron emission source can be created at a low manufacturing cost.

  In the planar electron emission source of the present invention, in addition to the above-described configuration, the conductor forming the nanoparticles may include at least one of gold, silver, platinum, palladium, and nickel. As described above, since the conductor that forms the nanoparticles includes at least one of gold, silver, platinum, palladium, and nickel, elements such as oxidation of the nanoparticles by oxygen in the atmosphere are included. Deterioration can be prevented more effectively. Therefore, the lifetime of the surface electron emission source can be extended more effectively.

  In the surface electron emission source of the present invention, in addition to the above configuration, the average diameter of the nanoparticles must be smaller than the size of the insulating member because it is necessary to control conductivity, and is 3 to 20 nm. Is preferred. Thus, by setting the average diameter of the nanoparticles to be smaller than the particle diameter of the insulating member, preferably 3 to 20 nm, a conductive path by the nanoparticles is not formed in the electron acceleration layer, and the electrons Dielectric breakdown is less likely to occur in the acceleration layer. Although there are many unclear points in principle, electrons are efficiently generated by using nanoparticles having a particle diameter in the above range.

  Furthermore, in detail, it has the following characteristics.

In the surface electron emission source of the present invention, in addition to the above configuration, the insulating member may include at least one of SiO ₂ , Al ₂ O ₃ , and TiO ₂ . Or it may contain an organic polymer. When the insulating member contains at least one of SiO ₂ , Al ₂ O ₃ , and TiO ₂ , or contains an organic polymer, the insulating property of these substances is high, and thus the electron acceleration layer It is possible to adjust the resistance value to an arbitrary range. In particular, when an oxide (SiO ₂ , Al ₂ O ₃ , and TiO ₂ ) is used as an insulating member, and a conductor having high anti-oxidation power is used as a nanoparticle, device deterioration due to oxidation by oxygen in the atmosphere Therefore, the effect of stably operating even at atmospheric pressure can be more remarkably exhibited.

  Here, the insulating member may be fine particles, and the average diameter is preferably 10 to 1000 nm, and more preferably 12 to 110 nm. In this case, the dispersion state of the particle diameter may be broad with respect to the average particle diameter. For example, fine particles having an average particle diameter of 50 nm may have a particle diameter distribution in the region of 20 to 100 nm. By making the average diameter of the insulating member, which is the fine particle, preferably 10 to 1000 nm, more preferably 12 to 110 nm, heat conduction can be efficiently conducted from the inside of the nanoparticles smaller than the size of the insulating member to the outside. Thus, Joule heat generated when current flows in the device can be efficiently released, and the surface electron emission source can be prevented from being destroyed by heat. Furthermore, the resistance value in the electron acceleration layer can be easily adjusted.

  In the surface electron emission source of the present invention, in addition to the above configuration, the ratio of the insulating member to the insulating coating metal fine particles in the electron acceleration layer is preferably 4: 1 to 19: 1 by weight. When the weight ratio is within the above range, the resistance value in the electron acceleration layer can be increased moderately, and the planar electron emission source can be prevented from being destroyed by a large amount of electrons flowing at once.

  In the surface electron emission source of the present invention, in addition to the above configuration, the thickness of the electron acceleration layer is preferably 12 to 6000 nm, and more preferably 300 to 6000 nm. By making the layer thickness of the electron acceleration layer preferably 12 to 6000 nm, more preferably 300 to 6000 nm, the electron acceleration layer can be made uniform, and the resistance of the electron acceleration layer can be adjusted in the layer thickness direction. It becomes possible. As a result, electrons can be uniformly emitted from the entire surface of the surface electron emission source surface, and electrons can be efficiently emitted outside the device.

  In the surface electron emission source of the present invention, in addition to the above configuration, the thin film electrode may include at least one of gold, silver, carbon, tungsten, titanium, aluminum, and palladium. By containing at least one of gold, silver, carbon, tungsten, titanium, aluminum, and palladium in the thin film electrode, electrons generated in the electron acceleration layer are efficiently tunneled due to the low work function of these materials. Thus, more high-energy electrons can be emitted outside the surface electron emission source.

  In addition to the above structure, the insulating film of the insulating film nanoparticles of the planar electron emission source of the present invention is characterized in that it has a thickness capable of tunneling electrons. This is because electrons cannot be emitted from the conductor to the outside unless the thickness allows electrons to tunnel, and a basic function as a planar electron emission source cannot be realized.

  In the surface electron emission source of the present invention, in addition to the above-described structure, the insulating coating of the insulating coating nanoparticles includes at least one of alkane, alcohol, fatty acid, alkanethiol, hydrocarbon-based silane compound, and organic surfactant. May be. An insulating film made of such an organic material contributes to improving the dispersibility of the nanoparticles in the dispersion during device creation. Therefore, abnormal path formation of current based on the aggregates of nanoparticles is formed. In addition to making it difficult to occur, the composition of the particles due to oxidation of the nanoparticles present around the insulating member itself does not change, so that the electron emission characteristics are not affected. Therefore, the lifetime of the surface electron emission source can be extended more effectively.

  As described above, according to the surface electron emission source of the present invention, a surface electron emission source can be easily created by simply applying an electron acceleration layer between electrodes and drying at room temperature, and the electron emission efficiency is remarkably high. A device with a large area can be provided easily.

  The method for producing a self-assembled film of the present invention includes a step of dispersing nanoparticles in a solvent, a step of applying a solution in which the nanoparticles are dispersed in a solvent, and evaporation of the solvent from other space regions. It is characterized by having a step of forming a delayed spatial region and growing in a self-organized manner in the spatial region. By using such a preparation method, the nanoparticles can be arranged by a simple method, that is, by simply applying the nanoparticles to the substrate by utilizing the closed space, that is, the solvent evaporation delay space. An electron emission device using this production method exhibits good electron emission characteristics and can be applied to an FPD (Flat Panel Display) or the like.

  A first dielectric member arranged in a substantially parallel direction with respect to the conductive member; and a second dielectric member arranged so as to have a substantially vertical direction component with respect to the conductive substrate between the first dielectric members. Nanoparticle covered with the dielectric member, and the nanoparticle covered with the second dielectric member is carried on the first dielectric member. According to this configuration, since the insulating coating nanoparticles are repeatedly arranged in the direction perpendicular to the conductive substrate, ballistic electrons can be emitted with a simple configuration and manufacturing method. The planar electron emission source configured as described above is efficient in the amount of electron emission with respect to input power, and can be reduced in power consumption when used for a display or a light source. In addition, since a conductor having high anti-oxidation power is used as the metal fine particles, it is difficult to cause element degradation due to oxidation by oxygen in the atmosphere, and therefore it can be stably operated even under atmospheric pressure.

  In addition, since the first dielectric member and the insulating coating nanoparticles can adjust the resistance value and the amount of electrons generated in the electron acceleration layer, the current value flowing through the electron acceleration layer and the amount of electron emission can be controlled. And Furthermore, since the first dielectric member can also have a role of efficiently releasing Joule heat generated by the current flowing through the electron acceleration layer, the surface electron emission source can be prevented from being destroyed by heat.

  In addition, since no discharge occurs even when operated not only in a vacuum but also at atmospheric pressure, no harmful substances such as ozone and NOx are generated, and the surface electron emission source is not oxidized and deteriorated. Therefore, the surface electron emission source of the present invention has a long lifetime and can be operated continuously for a long time even in the atmosphere. Therefore, according to the present invention, it is possible to provide a surface electron emission source that can stably emit electrons not only in a vacuum but also in an atmospheric pressure and suppress generation of harmful substances such as ozone and NOx.

It is explanatory drawing explaining the process of forming an insulating film nanoparticle in an insulating member. FIG. 2 is a schematic view of a cross section in the vicinity of a substrate of a fine particle layer in the electron-emitting device of FIG. 1. It is a schematic diagram which shows the structure of the electron-emitting element of one Embodiment of this invention. FIG. 2 is a schematic view of a cross section in the vicinity of a fine particle layer in the electron-emitting device of FIG. 1. It is a figure which shows the energy band of the fine particle layer in the electron emission element of this embodiment. It is a figure which shows the measurement system of an electron emission experiment. It is a figure showing the graph which shows the electron emission current in a vacuum. It is a figure showing the graph which shows the electric current in an element at the time of the electron emission in a vacuum. It is a figure showing the graph which shows the electron emission current and the element internal current in air | atmosphere. It is a figure which shows the time-dependent change of the electron emission current in air | atmosphere, and the element internal current. It is an enlarged view of the section near the electron acceleration layer of the electron-emitting device as a comparative example.

Hereinafter, a method for producing a self-assembled film and a surface electron emission source according to the present invention will be specifically described with reference to FIGS. Note that the embodiments and examples described below are merely specific examples of the present invention, and the present invention is not limited thereto.
(How to create a self-assembled film)
FIG. 1 is a schematic diagram showing a configuration of an embodiment of a method for producing a self-assembled film of the present invention. The creation flow of the self-assembled film of the present embodiment can be realized by applying the method of creating the fine particle layer 4 shown in FIG. 1 on the substrate (conductive member) 2. That is, the two types of fine particles of the second dielectric member and the first dielectric member are used and dispersed with an appropriate solvent. It is formed by applying it on the substrate 2 and allowing it to naturally dry at room temperature to develop a self-organizing action. Here, it is better that the degree of dispersion of the plurality of fine particles in the solution is larger. It is desirable to perform ultrasonic cleaning to increase the degree of dispersion. If not properly dispersed, a self-organizing action does not occur and a three-dimensional structure cannot be formed.

  Here, FIG. 2 shows an explanation using a principle model for forming a three-dimensional structure. When the dispersion state of the solution is large, the second dielectric member is (1) a second dielectric member floating in the solution (2) a second dielectric member attached to the first dielectric member Broadly divided. Next, the second dielectric member dispersed in the solution (1) is dispersed alone or in an aggregate in the solvent. Since the solvent is evaporated in a short time in the open space, the aggregation of fine particles is difficult to form. However, in the closed space, the solvent evaporates slowly over a long time. In this closed space, a self-organizing action occurs, so that the fine particles aggregate. Therefore, a self-assembled film in which the particles are regularly aggregated is completed. With this principle, a three-dimensional bottom-up structure can be formed.

  In the above description of the principle model, a method for forming a three-dimensional structure using a solution in which two kinds of fine particles are mixed has been described. First, a first dielectric member having a large particle diameter is disposed on a substrate. Then, a three-dimensional structure can also be obtained by applying the dispersed solution of the second dielectric member using a method such as an ink jet method. Further, it is needless to say that a three-dimensional structure can be obtained by arranging an insulator so as to have an acute angle (inverted triangular shape) with respect to the substrate, and then applying a solution of metal particles coated with insulating coating similarly dispersed. .

  In short, it is preferable to have a structure that provides a difference in evaporation speed of the solvent. A self-assembled film is formed in the region where the evaporation rate is delayed. For example, by adopting the specific structure described above, the evaporation rate is delayed by making the small space (closed space) wedged or by using an etching technique to make the closed taper type, that is, the closed space acute-angled. And a self-assembled film can be formed in the region.

Using such a self-organizing action, an attempt was made to create a surface electron emission source using metal nanoparticles instead of the second dielectric member described above. The configuration of the surface electron emission source and the device characteristics will be described below.
(Configuration of area electron emission source)
First, the configuration of the surface electron emission source will be described using the self-assembled film of the present invention.

  As shown in FIG. 3, the surface electron emission source 1 includes an insulator 5, insulating coating metal fine particles 6 (hereinafter referred to as an electron emission layer 4) on the first conductive member 2, and a first conductive member 2. A second conductive member 3 is provided so as to face each other, and a power source 7 and a counter electrode 8 are arranged.

  The electron emission layer 4 is sandwiched between the first conductive member 2 and the second conductive member 3. The power source 7 applies a voltage between the first conductive member 2 and the second conductive member 3. As will be described later, the electron emission layer 4 has at least a plurality of aggregates of fine metal particles coated with an insulating film. The surface electron emission source 4 is configured such that a voltage is applied between the first conductive member 2 and the second conductive member 3 so that the first conductive member 2 and the second conductive member 3 The electrons are accelerated during the interval (that is, the electron emission layer 4), and the electrons are emitted from the second conductive member 3 toward the counter electrode 8.

Based on the basic configuration as described above, each member and the electron emission principle will be described in detail with reference to FIG. 4 showing a state in which the inside of the electron emission layer 4 in FIG. 1 is modeled.
(First conductive member)
The board | substrate 2 used as a 1st electroconductive member plays the role of the support body of a surface electron emission source. Therefore, any material can be used without particular limitation as long as it has a certain degree of strength, has good adhesion to a directly contacting substance, and has appropriate conductivity. Examples thereof include metal substrates such as SUS, Ti, and Cu, semiconductor substrates such as Si, Ge, and GaAs, insulator substrates such as glass substrates, and plastic substrates. For example, if an insulating substrate such as a glass substrate is used, a conductive material such as a metal is attached to the interface with the electron emission layer 4 as an electrode, and used as the substrate 2 that becomes the first conductive member. be able to. The conductive material is not particularly limited as long as a noble metal material excellent in conductivity can be formed into a thin film using magnetron sputtering or the like. An ITO thin film widely used for transparent electrodes is also useful as an oxide conductive material. In addition, for example, a metal thin film in which a Ti film is formed to 200 nm on a glass substrate surface and a Cu film is further formed to a 1000 nm thickness may be used in that a tough thin film can be formed. Never happen.
(Second conductive member)
The second conductive member 3 applies a voltage in the electron emission layer 4. Therefore, any material that can be applied with voltage can be used without particular limitation. However, from the viewpoint of transmitting electrons emitted in the electron emission layer 4 and having high energy through as much energy loss as possible, the material is lower if it has a low work function and can form a thin film. The effect can be expected. Examples of such a material include gold, silver, carbon, tungsten, titanium, aluminum, palladium, and the like whose work function corresponds to 4 to 5 eV. In particular, assuming operation at atmospheric pressure, gold without oxide and sulfide formation reaction is the best material. In addition, silver, palladium, tungsten, and the like, which have a relatively small oxide formation reaction, are materials that can withstand actual use without problems. The film thickness of the second conductive member 3 is important as a condition for efficiently emitting electrons from the surface electron emission source 1 to the outside, and is preferably in the range of 10 to 55 nm. The minimum film thickness for causing the second conductive member 3 to function as a planar electrode is 10 nm. If the film thickness is less than this, electrical conduction cannot be ensured. On the other hand, the maximum film thickness for emitting electrons from the surface electron emission source 1 to the outside is about 100 nm. As a result, a large amount of recapture occurs, and the device cannot be driven with low power consumption.
(Metal fine particles)
Any metal species can be used as the metal species of the metal fine particles 6 on the principle of operation of generating electrons. However, for the purpose of avoiding oxidative degradation when operated at atmospheric pressure, it is necessary to be a metal with high antioxidation power, and a noble metal is preferable, and examples thereof include materials such as gold, silver, platinum, palladium, and nickel. Such metal fine particles 6 can be prepared by using a known fine particle production technique such as sputtering or spray heating, and commercially available metal fine particle powders such as silver metal fine particles manufactured and sold by Applied Nano Laboratory are also used. Is possible.
(Insulator)
The insulating fine particles 5 can be used without particular limitation as long as the material has insulating properties. However, the weight ratio of the insulating fine particles 5 to the whole fine particles constituting the fine particle layer 4 is preferably 80 to 95%, that is, the ratio to the metal fine particles is preferably 4: 1 to 19: 1 as will be described later in the experimental results. The size is preferably larger than the diameter of the metal fine particle 6 in order to obtain a heat dissipation effect superior to that of the metal fine particle 6, and the diameter (average diameter) of the fine particle 5 of the insulator is 10 to 1000 nm. Is preferable, and 12 to 110 nm is more preferable. Therefore, the material of the insulating fine particles 5 is practically SiO ₂ , Al ₂ O ₃ , or TiO ₂ . However, using small-sized silica particles with surface treatment increases the surface area of the silica particles in the solvent and increases the solution viscosity compared to using spherical silica particles with a larger particle diameter. Therefore, the film thickness of the fine particle layer 4 tends to increase slightly. The material of the insulating fine particles 5 may be fine particles made of an organic polymer. For example, highly crosslinked fine particles (SX8743) made of styrene / divinylbenzene manufactured and sold by JSR Corporation, or made by Nippon Paint Co., Ltd. The fine sphere series of styrene / acrylic fine particles manufactured and sold can be used. Here, two or more different types of particles may be used as the insulating fine particles 5, particles having different particle size peaks may be used, or a single particle having a broad particle size distribution. A thing may be used.

Further, since the role of the insulator does not depend on the shape of the fine particles, a sheet substrate made of an organic polymer may be used for the insulating member, or an insulating layer formed by applying an insulating member by any method. However, the sheet-like substrate or the insulator layer needs to have a plurality of fine holes penetrating in the thickness direction. As a sheet-like substrate material satisfying such requirements, for example, a membrane filter new clipper (made of polycarbonate) manufactured and sold by Whatman Japan Co., Ltd. is useful.
(Electron emission layer)
The electron emission layer 4 includes the insulator 5 and the metal fine particles 6. Electrons can be accelerated by applying a low voltage as a thinner electric field is applied, but the thickness of the electron-emitting layer can be made uniform, and the resistance of the electron-emitting layer in the layer thickness direction can be adjusted. The layer thickness of the fine particle layer 4 is 100 to 1000 nm, more preferably 300 to 6000 nm. If the thickness is less than 100 nm, contact between the electrodes or dielectric breakdown due to application of a high voltage may occur. If the thickness is 6000 nm or more, a high electric field necessary for electron emission cannot be applied. Become.

  As shown in FIG. 4, the surface electron emission source using the self-organized film as described above has metal fine particles 6 with insulating coatings in contact with each other to some extent in the fine particle layer 4. The conductor is alternately agglomerated and exists. When a voltage is applied here, the energy level in the electron emission direction of each particle is as shown in FIG.

FIG. 5 shows a state where the particles are aggregated. The solid line is the energy level in the electron emission direction when the electric field is large, and the broken line is the energy level of the electron in the electron emission direction when the electric field is small. When an electric field is applied between the electrode substrate 2 and the thin film electrode 3, electrons tend to flow to the thin film electrode due to the electric field applied to the electrode substrate 2. Since the central portion of the MIM electrode structure is literally composed of an insulator, a strong electric field is applied to the electrode substrate 2 by field emission, and energy is imparted to the electrons. Then, the electrons move to the nearest particle. In this case, if the distance between the substrate and the nanoparticles is larger than the mean free path of the surrounding atmosphere (atmospheric pressure or in vacuum), the electrons move toward the thin film electrode due to scattering before reaching the nanoparticles. Acceleration is reduced and scattered in multiple directions. On the other hand, if the distance between the substrate and the nanoparticles is smaller than the mean free path and has enough energy to tunnel through the insulating coating provided on the nanoparticles, the insulating coating is tunneled and the nanoparticles inside the metal 6 storm in. Here, free electrons in the metal have acceleration due to an electric field, but energy in the electron emission direction is reduced due to scattering by atoms. In this way, the electrons are given new energy enough to tunnel through the insulating film, and the electrons are accelerated. By repeating this state between the particles, electrons reach a thin film electrode formed at a distance that does not cause dielectric breakdown with the electrode substrate. Finally, if the electrons have enough energy to tunnel through the thin film electrode, the thin film electrode is tunneled and emitted out of the device. According to such a principle, electrons can be emitted from the fine particle layer.
(Metal fine particles with insulating coating)
Here, as the metal species of the metal fine particles coated with an insulating film, any metal species can be used on the operation principle that the metal fine particles are aggregated by self-organization to generate ballistic electrons. However, for the purpose of avoiding oxidative degradation when operated at atmospheric pressure, a metal that is difficult to oxidize is preferable, and examples thereof include materials such as gold, silver, platinum, nickel, and palladium. In addition, any insulating coating can be used as the insulating coating of the metal fine particles 12 with an insulating coating on the principle of operation of generating ballistic electrons. The average diameter of the metal fine particles 6 must be smaller than the size of the insulating fine particles 5 described below, and is more preferably 3 to 50 nm, because it is necessary to control the conductivity. Thus, by setting the average diameter of the metal fine particles 6 to be smaller than the particle diameter of the insulating fine particles 5, preferably 5 to 20 nm, no conductive path is formed by the metal fine particles 6 in the fine particle layer 4. Insulation breakdown in the fine particle layer 4 hardly occurs and electrons are generated efficiently.

  However, if the insulating film is covered with an oxide film of fine metal particles, the thickness of the oxide film may increase beyond the desired thickness due to oxidative degradation in the atmosphere. In order to avoid oxidative degradation, an insulating film made of an organic material is preferable. For example, it preferably contains at least one of alkane, alcohol, fatty acid, alkanethiol, hydrocarbon-based silane compound, and organic surfactant. An insulating film made of such an organic material contributes to improving the dispersibility of the metal fine particles in the dispersion at the time of element creation. In addition to making it difficult to occur, the composition of the particles due to oxidation of the metal fine particles existing around the insulating member does not change, so that the electron emission characteristics are not affected. Therefore, the lifetime of the surface electron emission source can be extended more effectively.

It is important that the diameter of the metal fine particles 12 with the insulating coating is about 10 nm, and it can be said that the thinner the insulating coating, the more advantageous.
(Electron emission principle)
The principle of electron emission will be described with reference to FIG. 4 in which the electron acceleration layer 4 is modeled. The colloidally crystallized metal fine particle group 6 having an insulating film is formed by self-organization. The principle is shown below.

  Immediately after the insulating coated metal fine particles are dissolved in the solvent, the insulating coated metal fine particles are in an amorphous state in which the finely spaced metal particles are spaced apart from each other. Is distributed to put.

  Then, the particles are rearranged by Brownian rocking force and electrostatic repulsive force, colloidal crystallization proceeds to minimize the internal energy of the system, and a group of metal particles with an insulating film is formed. In this order, a colloidal crystal of insulating coating metal fine particles is formed by self-organization. Through such a process, a plurality of colloidally crystallized metal particles having an insulating film formed between the first conductive member and the second conductive member are formed.

  Here, as explained in the method for producing the self-assembled film, the metal particles coated with the insulating film are (1) the second dielectric member dispersed in the solution, and (2) the first dielectric member. The second dielectric member is roughly classified. When the first dielectric member and the second dielectric member are mixed in a solvent, the second dielectric member is aggregated on the first dielectric member having a large particle diameter if dispersed well. There are cases where it exists, and cases where it exists alone. The second dielectric member floating in the solution settles when the solvent evaporates, and finally, the second dielectric member is a closed space where the evaporation of the solvent described above finally occurs. Aggregate to form a self-assembled film. In this case, the self-assembled film has a three-dimensional structure in which particles are three-dimensionally aggregated on the first dielectric, and ballistic electrons are emitted from the tip portion.

  That is, although the insulating coating metal fine particles aggregated in the vicinity of the first conductive member are randomly formed in the space, the insulating coating metal fine particles are formed by an aggregate of one-dimensional structure in which the insulating coating metal fine particles are connected in series. Electrons in the formed metal particles are confined and random movement is prohibited, but when a voltage is applied from the outside, a strong electric field is generated at the contact portion between the insulating coating metal particles, and the electrons are adjacent with high probability. It tunnels to the metal particles coated with insulation. Since the tunnel is limited to the portion where the fine metal particles coated with the insulating film are in contact with each other, only electrons having high energy traveling straight through can continuously conduct in the layer. The high energy electrons are emitted to the outside as ballistic electrons.

  Specifically, first, the fine particle layer 4 is formed on the substrate 2 by applying a dispersion solution in which the insulating fine particles 5 and the metal fine particles 6 are dispersed using a spin coating method. Here, the solvent used in the dispersion solution can be used without particular limitation as long as the insulating fine particles 5 and the metal fine particles 6 can be dispersed and dried after coating. For example, toluene, benzene, xylene, hexane, Tetradecane or the like can be used.

  In particular, in order to disperse the insulating coating metal fine particles, a nonpolar solvent (a solvent having a small relative dielectric constant, such as hexane) is preferred. However, water and the like are typical polar solvents, but can be used because they have cost merit. The reason for using the nonpolar solvent is that it is better to shield the charge of the metal fine particles in order to avoid attracting the charge of the metal fine particles in the solvent. Also, the viscosity of the solvent affects the ease of movement of the metal fine particles, and therefore affects the dispersibility. In particular, a solvent having a relative dielectric constant of 5 or less (hexane 1.9, toluene 2.3, xylene 2.3) is preferable.

  In addition, for the purpose of improving the dispersibility of the metal fine particles 6, an alcoholate treatment may be performed as a pretreatment. A predetermined film thickness can be obtained by repeating film formation and drying by a spin coating method a plurality of times. The fine particle layer 4 can be formed by a method such as a dropping method or a spray coating method in addition to the spin coating method. Any of these methods can form a space where evaporation last occurs, that is, a closed space. Then, the thin film electrode 3 is formed on the electron acceleration layer 4. For forming the thin film electrode 3, for example, a magnetron sputtering method may be used.

  That is, the insulator and the insulating coating metal fine particles are dissolved in a solvent, the metal fine particles are dispersed by an ultrasonic cleaner, and coating is performed on the first conductive member. Then, it is left at room temperature and the solvent is slowly removed. With the simple process as described above, an electron acceleration layer can be formed without the need for high-temperature treatment.

  Further, in order to easily cause electric field concentration in the vicinity of the first conductive member, it is better to moderately roughen the substrate. This is because electric field concentration occurs, so that a low-voltage element can be created.

  The embodiments of the present invention will be described below based on the principle of electron emission described above.

  As an example, an electron emission experiment using the surface electron emission source according to the present invention will be described with reference to FIGS. In addition, this experiment is an example of implementation and does not limit the content of the present invention.

In this example, five types of surface electron emission sources 1 were produced in which the ratio of the insulating fine particles 5 to the insulating coated metal fine particles 6 in the fine particle layer 4 was changed. Specifically, a 30 mm square SUS substrate was used as the substrate 2, and the fine particle layer 4 was deposited on the substrate 2 by spin coating. The solution used for spin coating is as follows. Toluene is used as the solvent, silver nanoparticles (average diameter 10 nm, of which the insulating coating alcoholate is 1 nm thick) as the insulating coated metal fine particles 6, and silica particles (average diameter 100 nm) as the insulating fine particles 5. The silica particles were mixed and dispersed at a ratio of 70, 80, 90, 95, and 99 w% of silica particles to (silver nanoparticles and silica particles). The spin coat was deposited in three layers at 500 RPM · 5 sec + 3000 RPM · 10 sec, and was naturally dried at room temperature without firing. The film thickness was about 500 nm. Gold was used for the upper electrode 3 and deposited on the fine particle layer 4 by magnetron sputtering to a layer thickness of 12 nm. Electrode area was 0.28 cm ^2.

With respect to the surface electron emission source manufactured as described above, an electron emission experiment was performed using a measurement system as shown in FIG. In the experimental system of FIG. 6, the counter electrode 8 is disposed on the upper electrode 3 side of the surface electron emission source 1 with the insulator spacer 9 interposed therebetween. The surface electron emission source 1 and the counter electrode 8 are each connected to a power source 7, and a voltage V1 is applied to the surface electron emission source 1 and a voltage V2 is applied to the counter electrode 8. An electron emission experiment was conducted by placing such an experimental system in a vacuum of 1 × 10 ⁻⁸ ATM, and an electron emission experiment was conducted by placing such an experimental system in the atmosphere. The results of these experiments are shown in FIGS.

FIG. 7 is a graph showing a result of measuring an electron emission current when an electron emission experiment is performed in a vacuum. Here, V1 = 1 to 10V and V2 = 50V. As shown in FIG. 7, in a vacuum of 1 × 10 ⁻⁸ ATM, electron emission is not observed when the ratio of silica particles is 70, 99 w%, whereas current due to electron emission is observed at 80, 90, 95 w%. It was done. The value was about 10 ⁻⁷ A when a voltage of 10 V was applied.

  FIG. 8 is a graph showing the result of measuring the current in the device when the electron emission experiment was performed in a vacuum as described above. Also here, V1 = 1 to 10V and V2 = 50V as described above. From FIG. 8, it can be said that when the ratio of the silica particles is 70 w% (the ratio of the silver nanoparticles is 30 w%), the aggregates are too large, and the dielectric breakdown occurs due to insufficient resistance. Moreover, when the ratio of silica particles is 99 w% (the ratio of silver nanoparticles is 1%), it can be said that an appropriate aggregate is not formed because the resistance value is too large. TEM observation was performed in the vicinity of the substrate having a silica ratio of 90 w% and about 99%. As a result, it was found that there were many aggregates in the vicinity of the substrate and there were not many aggregates. That is, as explained in the embodiment in terms of the principle of creating a self-assembled film, it is presumed that the electron emission efficiency is good when moderate aggregates are formed near the substrate.

  FIG. 9 shows the measurement of electron emission current and in-device current when an electron emission experiment is performed in the atmosphere with V1 = 1 to 15 V and V2 = 200 V using a surface electron emission source having a silica particle ratio of 90 w%. It is a graph which shows the result.

As shown in FIG. 9, a current of about 10 ⁻¹⁰ A was observed in the atmosphere when a voltage of V1 = 15 V was applied.

Further, FIG. 10 uses a planar electron emission source ratio of 90 w% similar silica particles 9, this Kodewa, V1 = 15V, V2 = the time obtained by continuous driving at a voltage application of 200V, the electron emission It is a graph which shows the result of having measured the electric current and the electric current in an element. As shown in FIG. 10, the current was stably released even after 6 hours.
(Comparative example)
FIG. 11 is a schematic diagram enlarging a cross section in the vicinity of the electron acceleration layer 4 ′ of the surface electron emission source 1 ′ which is another example of the configuration of the surface electron emission source according to the present invention. In this comparative example, the second dielectric material 5 ′ is laminated on the substrate 2 in a sheet shape and has a shape having a plurality of openings 51 penetrating in the lamination direction.

A 30 mm square SUS substrate was used as the substrate 2, and a polycarbonate sheet having a thickness of 6 μm was laminated thereon as the second dielectric material 5 ′. The polycarbonate sheet has six openings (holes) 51 having a diameter of 50 nm per 1 μm ² , and the opening ratio is about 1.2%. The opening 51 penetrates in the sheet stacking direction.

Next, gold nanoparticles (average particle diameter: 10 nm, of which the insulating film water-soluble polymer was 1 nm) were dispersed in water as a solvent at a concentration of 2.5 mmol / L as the metal fine particles 6 coated with the insulating film. An appropriate amount of this solution was dropped onto the polycarbonate sheet, allowed to permeate the opening 51, and then naturally dried. Gold was used for the upper electrode 3 and deposited on a polycarbonate sheet (electron acceleration layer 4 ′) in which gold nanoparticles were buried in the opening 51 with a layer thickness of 12 nm by magnetron sputtering. The electrode area was 0.28 cm ² .

The surface electron emission source 1 ′ produced as described above was subjected to an electron emission experiment using a measurement system as shown in FIG. 6, and a current due to electron emission of about 10 ⁻⁹ A was confirmed when a voltage of 10 V was applied. It was done.

  Here, the result of having compared the surface electron emission source in which the ratio of the silica particle of an Example is 90 w% and the surface electron emission source in a comparative example (FIG. 11) is considered.

  In the electron acceleration layer of the surface electron emission source in which the proportion of the silica particles of the example is 90%, the silica particles as the insulator are substantially spherical, and the boundary with the substrate has a wedge shape. However, an opening of 50 nm is formed in the polycarbonate sheet of the comparative example, and metal fine particles are deposited there, and the angle with respect to the substrate is formed substantially perpendicularly. Here, considering the evaporation rate of the solvent, it can be said that the wedge shape is more suitable for self-organization because the evaporation rate is slower because the wedge shape is a closed space (see explanation of principle). Further, the evaporation rate varies depending on the ambient environment, for example, the ambient wind velocity and its distribution, the atmospheric humidity, etc. In this embodiment, the spin coating rotation speed is set in order to apply with an optimum film thickness. However, it is better to set appropriately according to the situation.

  Also, in order to create a closed space, the wedge-shaped space is configured using silica particles in the embodiment, but the wedge-shaped space is configured and used by etching the insulating sheet into a tapered shape. It is also possible to do.

  The present invention relates to a method for obtaining a fine particle structure three-dimensionally by using the self-organizing action of particles. By using this method, a display such as a field emission display (FED) or an electron beam irradiation apparatus is provided. The present invention is applied to a planar electron emission source that can be applied as an electron beam source in various devices using an electron beam, such as a light source, an electronic component manufacturing apparatus, and an electronic circuit component.

1,1'-plane electron emission source 2 First conductive member (electrode substrate)
3 Second conductive member (thin film electrode)
4,4 'fine particle layer (electron acceleration layer)
5,5 'Insulator fine particles (dielectric material)
6 Metal fine particles (insulating coating nano-particles)
6 'Insulating coating of metal particles 7 Power supply (power supply section)
8 Counter electrode 9 Insulator spacer 10 Open space 11 Closed space

Claims (10)

  Self-organization comprising a step of dispersing nanoparticles in a solvent, a step of applying a solution in which the nanoparticles are dispersed in a solvent, and a step of growing the nanoparticles in a direction perpendicular to the substrate in a self-organized manner How to make a film.   The step of growing the nano-particles in a self-organized manner forms a spatial region in which the evaporation of the solvent is delayed from other spatial regions, and the spatial region is formed to have a component perpendicular to the substrate, 2. The method for producing a self-assembled film according to claim 1, wherein the nano-particles are grown in a self-organized manner in the space region.   3. The method for producing a self-assembled film according to claim 2, wherein the space region is formed of a particle larger than the nano fine particle and a substrate.   The method for producing a self-assembled film according to claim 2, wherein the space region is created by etching.   The space region where the evaporation of the solvent is delayed is a space region formed by a substrate and a member arranged to form an angle of 90 degrees or less with respect to the substrate. A method for producing a self-assembled film as described in 1. In the surface electron emission source in which the first conductive member and the second conductive member are formed substantially in parallel, and a voltage is applied between the conductive members to emit electrons.
A first dielectric member arranged in a substantially parallel direction with respect to the conductive member, and a second dielectric member arranged so as to have a substantially vertical direction component with respect to the conductive member between the first dielectric members. A planar electron emission source comprising: a nanoparticle covered with a dielectric member, wherein the nanoparticle covered with a second dielectric member is supported on the first dielectric member.   7. The nanoparticle covered with the supported second dielectric member is crystal-grown in a self-organized manner in a substantially wedge-shaped region formed by the first dielectric member and a conductive member. Planar electron emission source.   8. The surface electron emission source according to claim 6, wherein an average diameter of the nano fine particles covered with the second dielectric member is 3 to 20 nm.   The first dielectric member is a fine particle, and the ratio of the nano fine particles covered with the first dielectric member and the second dielectric member in the surface electron emission source is 4: 1 to 19 by weight ratio. The planar electron emission source according to claim 6, wherein the surface electron emission source is one.   10. The surface electron emission source according to claim 6, wherein the second dielectric member has a thickness capable of tunneling electrons.