JPH11246300A - Titanium nano fine wire, production of titanium nano fine wire, structural body, and electron-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a titanium nano fine wire having a uniform wire diameter by forming a structural body provided with a layer having fine pores on a base body having a surface containing titanium and in which the pores extend to the surface and then, heat-treating the structural body to form fine wires containing titanium in the pores. SOLUTION: A base body 10 is obtd. by forming a layer 11 which constitutes a surface containing titanium on the surface of a substrate 16 such as quartz glass and Si. Then, a film 12 essentially comprising Al is formed on the layer 11 of the base body 10 and is subjected to anodic oxidation to form a porous body 13 comprising anodically oxidized alumina having pores extending to the surface on the base body 10. The structural body forming the porous body 13 on the base body 10 provided with the surface containing titanium is heat- treated in an atmosphere containing >=1 Pa water vapor at 500 to 1,000 deg.C to allow the titanium in the pore bottoms to react with the atmosphere to form titanium nano fine wires 15 having <=300 nm diametert essentially comprising titanium in the pores of the porous body 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nanowire composed mainly of titanium, a method for producing the same, a nanostructure, and an electron-emitting device. As a photoelectric conversion element that can be used in a wide range, especially as a functional material,
The present invention relates to a nanowire usable as a photocatalyst element, an electron-emitting material, a fine wire for a micromachine, a thin wire for a quantum effect element, a method for manufacturing the same, a nanostructure provided with the nanowire, and an electron-emitting device using the same.

[0002]

2. Description of the Related Art Conventionally, titanium and its alloys have been widely used as structural materials for aircraft, automobiles, chemical machines, and the like because of their characteristics of being light, strong, and resistant to corrosion. Titanium and its alloys are harmless to the human body and are therefore used in medical equipment.

Recently, the optical semiconductor properties of titanium oxide,
As applications of photocatalysis and the like, researches on photovoltaic cells, decomposition of harmful substances, antibacterial and the like have been actively conducted. In addition, the application range of the titanium material covers various fields such as a vacuum getter material, an electron emission material, a hydrogen storage alloy, and electrodes of various electronic devices.

On the other hand, thin films, thin wires, dots, and the like of metals and semiconductors exhibit unique electrical, optical, and chemical properties by confining the movement of electrons in a size smaller than a certain characteristic length. There is. From such a viewpoint, a material (nanostructure) having a structure finer than 100 nm is increasing as a functional material.

As an example of a method for manufacturing a nanostructure, for example, there is a method using a semiconductor processing technique including a fine pattern drawing technique such as photolithography, electron beam exposure, and X-ray diffraction exposure.

[0006] In addition to such a production method, there is an attempt to realize a novel nanostructure based on a regular structure formed naturally, that is, a structure formed self-organizingly. Many studies have begun on these methods because there is a possibility that finer and special structures than conventional methods can be produced depending on the microstructure used as a base.

An example of a unique structure formed in a self-organizing manner is an Al anodized film (for example, R.A.
C. Furneaux, W.C. R. Rigby & A. P.
Davidson "NATURE" Vol. 337, P
147 (1989)).

This is a porous oxide film formed by anodizing an Al plate in an acidic electrolyte. As shown in FIG. 6, the porous oxide film has a very small diameter of several nm to several hundred nm. Cylindrical pores (nano holes) 14
It has a specific geometric structure of being arranged in parallel at an interval of ~ several hundred nm. This cylindrical pore 14
Has a high aspect ratio, is excellent in linearity, and is also excellent in uniformity in cross-sectional diameter.

Various applications have been attempted using such a specific geometric structure of anodized alumina as a base. Comment by Masuda (Masuda: "Solid State Physics" 31,
493, 1996), a technique of filling a metal or a semiconductor in a pore or a technique of taking a replica is typical.
Various applications such as coloring, magnetic recording media, EL light emitting elements, electrochromic elements, optical elements, solar cells, gas sensors and the like have been attempted.

[0010] Further, application to various fields such as quantum wire, quantum effect devices such as MTM (metal-insulator-metal tunnel) elements, molecular sensors using nanoholes as a chemical reaction field, etc. are expected.

When such a nanostructure can be realized by a highly functional titanium material, it can be used as a functional material or a structural material of an electronic device or a microdevice.
Wide application is expected.

On the other hand, as an example of forming a nanostructure by controlling the size and shape using titanium as a main material, as described above, photolithography, electron beam exposure, X-ray diffraction exposure, etc. Patterning of a Ti material thin film by a semiconductor processing technique such as a fine pattern drawing technique.

However, these methods have problems such as a low yield and a high cost of the apparatus. Therefore, a method that can be created with a simple method with high reproducibility is desired. Compared with such semiconductor processing techniques, the method using self-organizing phenomena, particularly the method using anodized alumina as a base, enables nanostructures to be formed easily, with good control, and over a large area. It is preferred because of its advantages.

As an example of applying such a method to form a nanostructure mainly composed of titanium, there is an example in which a replica of anodic oxide alumina is formed by titanium oxide to form porous TiO ₂ by Masuda et al. ("J
pn. J. Appl. Phys. "31 (1992) L
1775-Ll777, "J. of Material
s Sci. Lett. "15 (1996) 1228-
1230).

However, this method has problems to be solved, such as the necessity of going through many complicated steps in the process of taking a replica and the poor crystallinity of TiO ₂ formed by electrodeposition.

On the other hand, metal,
A method of forming a nanostructure by filling a semiconductor is often performed. For example, a method of filling Ni, Fe, Co, Cd or the like by an electrochemical method (D. Al-
Malawi et. al. “J. Mater. Re
s. "9, 1014 (1994), Masuda et al." Surface technology "
Vol. 43, 798 (1992)), In, S
Method for melting and introducing n, Se, Te, etc. (CA Hub
er et. al. SCIENCE 263,800
(1994)).

However, since the electrodeposition of Ti is not common and the Ti material generally has a high melting point, filling with a material containing Ti as a main component has not been reported in any of the methods.

On the other hand, as an application to fiber reinforced plastic, fiber reinforced metal, and fiber reinforced ceramic, a submicron-sized potassium titanate whisker (0.2 to
1. Om diameter, 5-60 m length) has been developed ("Journal of the Japan Institute of Metals" 58 (1994) 69-77).
However, these are powders, and the technology of controlling and arranging the positions on the substrate is not known at present. Further, in order to expect unique electrical, optical, and chemical properties as nanostructures, there is a need for further miniaturization in terms of size.

[0019]

SUMMARY OF THE INVENTION The present invention has been made in view of the demands for the various technologies as described above, and has been made in view of the above. A method for producing a nanowire composed mainly of titanium (titanium nanowire), particularly on a substrate. It is an object of the present invention to provide a method for producing titanium nanowires.

[0020] Further, the substrate has a specific direction on the substrate,
An object of the present invention is to realize a nanostructure in which titanium nanowires having a uniform fine wire diameter are arranged at equal intervals. Another object of the present invention is to provide a high-performance electron-emitting device having a large electron emission amount.

[0021]

According to one embodiment of the present invention, there is provided a method for producing a titanium nanowire, comprising: forming a structure having a layer having pores extending on the surface on a substrate having a surface containing titanium. The method is characterized by comprising a first step of preparing and a second step of heat-treating the structure to form a fine wire containing titanium in the pores.

Further, the structure according to one embodiment of the present invention is characterized in that the surface of the substrate having a surface containing titanium has a fine line mainly composed of titanium and extending substantially perpendicularly to the surface. Is what you do.

The nanowire according to one embodiment of the present invention is a first step of preparing a structure having a porous body having pores extending on the surface of a substrate having a surface containing, for example, titanium. And a method for producing a nanowire having a second step of heat-treating the structure to form a fine wire containing titanium in the pores.

The electron-emitting device according to one embodiment of the present invention includes a porous body having pores extending on the surface of a substrate having a surface containing titanium, wherein titanium is mainly contained in the pores. It is characterized by comprising a structure having a thin wire as a component, a counter electrode disposed to face the surface, and means for applying a potential between the surface and the counter electrode.

According to the above embodiments of the present invention, it is possible to realize a nanowire having titanium as a main material and a nanostructure having titanium as a main material and having a nanometer-scale structure.

The structure having nanowires mainly composed of titanium, which is one of the embodiments according to the present invention, includes a photoelectric conversion element, a photocatalyst, a quantum wire, an MIM element, an electron emission element,
It can be applied in a wide range as a functional material such as a vacuum getter material, various electronic devices and micro devices, and a structural material. Further, the titanium nanowire, which is one of the embodiments according to the present invention, can be used as a reinforcing material such as plastic.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be specifically described below. First, the configuration of a titanium nanowire and a nanostructure to which the titanium nanowire is applied will be described.

The titanium nanowires of the present invention and the nanostructures to which the nanowires are applied can be obtained by forming a porous body having pores on a substrate having a titanium element on the surface, and further performing a heat treatment in a specific atmosphere. It is created by forming titanium nanowires in the pores.

FIG. 1 is a schematic view showing the shape of a titanium nanowire of the present invention. (A) in FIG. 1 is a string-like shape, (b)
Shows a columnar shape, (c) shows a columnar shape with a stepwise change in thickness, and (d) shows a shape in which a plurality of columnar bodies are united.

FIG. 3 is a schematic view of a nanostructure having a titanium nanowire. FIG. 3A shows a layer 11 constituting a surface containing Ti formed on a substrate 10 and a specific direction (almost perpendicular direction) on the surface of the layer 11 with respect to the surface. 5 shows a nanostructure composed of arranged titanium nanowires 15.

FIG. 3B shows the state of the Ti formed on the base 10.
A porous body (anodic oxidized alumina) 13 having pores 14 extending in a direction perpendicular to the surface, provided on the surface of the layer 11 constituting the surface containing titanium, and a titanium nanowire 15 disposed in the pores 14 1 shows a nanostructure composed of:

In the nanostructure shown in FIG.
Although the titanium nanowires 15 protrude from the surface of the pores, it is also possible to stop the growth inside the pores and use the nanostructures as in the nanostructure shown in FIG.

Further, in FIGS. 3B and 3C, the titanium nanowires are described as being thinner than the pore diameter.
As shown in FIG. 3 (d), it can be composed of a titanium nanowire having the same thickness as the pore diameter.

The titanium nanowires 15 are a metal, a semiconductor, and an insulator containing titanium as a main component, for example, titanium, titanium alloys such as titanium-iron and titanium-aluminum, titanium oxide, titanium hydride, titanium nitride, Any titanium compound such as titanium carbide. The fine wire diameter (thickness) of the titanium nano fine wire 15 is 1 nm to 2 μm and the length is 10 nm.
The range is from nm to 100 μm. Also, titanium nanowires are
Since the shape of the pores of the porous body is reflected to some extent, the diameter of the titanium nanowires can be controlled to a certain extent by controlling the shape of the pore diameter, spacing, etc. of the porous body, and the direction of the fine wires is also perpendicular to the base, for example. It can be.

Under special conditions, titanium nanowires can be whisker crystals. This condition will be described later.

In the structure shown in FIG. 3B, the porous body 13 formed on the layer 11 constituting the surface containing Ti
For example, anodized alumina, zeolite, porous silicon, a mask formed by photolithography, or the like can be used. In particular, since anodized alumina has linear pores at equal intervals, it is possible to create titanium nanowires having excellent linearity at equal intervals, and furthermore, it is possible to form titanium nanowires in a specific direction (for example, on a substrate). This is desirable because the nanostructures can be arranged at substantially equal intervals (substantially perpendicular to the surface).

FIG. 6 shows the structure of anodized alumina. The anodized alumina 13 has Al and O as main components, and has a large number of columnar linear pores 14 arranged almost perpendicular to the membrane (plate) surface, and the pores are parallel and substantially equal to each other. They are arranged at intervals. In addition, the pores tend to be arranged in a triangular lattice as shown in FIG. The pore diameter 2r is 5 nm
５００500 nm, the interval 2R is about 10 nm５００500 nm, and the concentration and temperature of the electrolytic solution used for anodic oxidation, and
Depending on the application method of the anodic oxidation voltage, the voltage value, the time, and the process conditions such as the subsequent pore wide processing conditions,
Can be controlled to some extent. That is, by controlling the pore diameter and the interval, the fine wire diameter (thickness) and interval of the titanium nanowire can be controlled to some extent in the above range, for example, the fine wire diameter to 300 nm or less.

Next, a method for manufacturing a titanium nanowire and a nanostructure using the titanium nanowire will be described.
Nanostructures using nanowires and titanium nanowires are:
Preparing a structure having a porous body having pores on a substrate having at least a titanium element on the surface (step 1);
It is preferable to manufacture the structure using a method having a step (step 2) of forming titanium nanowires in pores by performing a heat treatment.

Hereinafter, a method for manufacturing a titanium nanowire and a nanostructure to which the titanium nanowire is applied will be sequentially described with reference to FIG. In FIG. 2, reference numeral 10 denotes a base, and 15 denotes a titanium nanowire. Reference numeral 11 denotes a layer constituting a surface containing Ti, 12 denotes a film containing Al as a main component, 13 denotes a porous body (anodized alumina), 14 denotes pores (nanoholes), and 15 denotes a titanium nanowire.

(Step 1: Preparation of Structure Having a Porous Body Having Pores on Base 10) The base 10 having a titanium element on its surface is not limited except that it contains a titanium element. For example, a plate of titanium and its alloy, FIG.
As shown in (a), various substrates 16 made of quartz glass, Si, etc.
There is a base having a structure in which a layer 11 constituting a surface containing Ti as a main component is formed thereon.

Here, the layer 11 constituting the surface containing Ti is used.
Are prepared by resistance heating evaporation, EB evaporation, sputtering, C
Any film forming method including VD and plating can be applied. The porous body is preferably anodized alumina which can be formed by an easy manufacturing method, has linear pores, and has a high aspect ratio. Hereinafter, a method for forming positive alumina oxide as a porous body will be described.

(Step la: forming a film 12 containing Al as a main component on the substrate.) As shown in FIG. 2B, the film containing Al as a main component is formed by resistance heating evaporation, EB evaporation, sputtering, or the like.
Any film forming method including CVD and plating can be applied.

(Step lb: anodizing step)
The porous body 13 made of anodized alumina is formed on the substrate by performing anodization of the film 12 mainly composed of (see FIG. 2C). FIG. 5 shows an outline of an anodizing apparatus that can be used in this step.

In FIG. 5, reference numeral 50 denotes a constant temperature bath;
Is a reaction vessel, 52 is a sample in which a film 12 containing Al as a main component is formed on a substrate 10 having a surface containing Ti, 53 is a Pt cathode, 54 is an electrolytic solution, 56 is a power supply for applying an anodizing voltage, Reference numeral 55 denotes an ammeter for measuring an anodic oxidation current. In addition, a computer (not shown) for automatically controlling and measuring voltage and current is incorporated. The sample 52 and the cathode 53 are placed in an electrolytic solution whose temperature is kept constant by a constant temperature water bath, and anodization is performed by applying a voltage between the sample and the cathode from a power supply.

Examples of the electrolytic solution used for the anodic oxidation include oxalic acid, phosphoric acid, sulfuric acid, and chromic acid solution. Various conditions such as anodizing voltage and temperature can be appropriately set according to the nanostructure to be formed.

In the anodic oxidation step, the film 12 mainly composed of Al is oxidized over the entire thickness. Anodizing is Al
When the anodic oxidation current progresses from the surface and reaches the substrate surface, a change is observed in the anodic oxidation current. This can be detected to determine the end of anodic oxidation.

For example, when a substrate having a Ti film disposed on an arbitrary substrate is used, it is possible to judge that the application of the anodic oxidation voltage is to be terminated based on a decrease in the anodic oxidation current. Further, the pore diameter can be appropriately increased by a pore widening process of dipping in an acid solution (for example, a phosphoric acid solution) after the anodizing process. The pore size can be controlled by the concentration, processing time, and temperature.

(Step 2: forming titanium nanowires in pores by heat treatment) The above-described structure in which a porous body is formed on a substrate having a surface having a titanium element is placed in a reaction vessel and specified. By performing heat treatment in the atmosphere, the titanium at the bottom of the pores reacts with the atmosphere, and titanium nanowires 15 mainly containing titanium, which is a reaction product of titanium and the atmosphere, are formed in the pores of the porous body (FIG. 2 (d)).

Here, a reactor for performing the above heat treatment will be described with reference to FIG. In FIG. 4, reference numeral 41 denotes a reaction vessel, reference numeral 42 denotes a sample (substrate), reference numeral 43 denotes an infrared absorbing plate, which also serves as a sample holder. Reference numeral 44 denotes a gas introduction pipe for introducing a gas such as hydrogen or oxygen, and is preferably arranged so that the concentration of the source gas near the substrate is uniform. Reference numeral 46 denotes a gas exhaust line, which is connected to a turbo molecular pump or a rotary pump. Reference numeral 47 denotes an infrared lamp for heating the substrate, and reference numeral 48 denotes a condenser mirror for efficiently collecting infrared rays on the infrared absorbing plate.

Although not shown in the figure, a vacuum gauge for monitoring the pressure in the container, a thermocouple for measuring the temperature of the substrate, and the like are also incorporated. Of course, not only the device described here, but also an electric furnace type device that heats the whole from the outside does not pose a problem.

The atmosphere and temperature at which the heat treatment is performed are appropriately set depending on the material and shape of the titanium nanowire to be formed. For example, nano-wires of titanium hydride, titanium oxide, titanium nitride, and carbonized titanium can be formed by including hydrogen, oxygen, nitrogen, hydrocarbon, and the like as the atmosphere, respectively.

In addition, SiH ₄ , B ₂ H ₆ , PH ₃ , A
Materials used in the chemical vapor deposition method such as l (C ₂ H ₅ ) ₃ and Fe (CO) ₅ can be used, and titanium silicide, titanium boride, titanium phosphide, aluminum titanium alloy, It is also possible to create nanowires containing titanium compounds such as iron-aluminum alloys.

In particular, when nanowires made of titanium oxide are prepared, whisker fine wires can be formed by performing a heat treatment at a temperature of 500 ° C. or more and 900 ° C. or less in an atmosphere containing water vapor of 1 Pa (Pascal) or more. it can. At this time, it is preferable to mix hydrogen in the atmosphere because the growth is promoted.

In general, whiskers are crystals having a small number of needle-like transitions, and are known to precipitate from a solution or decompose a compound, for example, a method of reducing a halide with hydrogen. It is presumed that the production method of titanium whiskers grows by oxidation reaction of titanium surface with water vapor and reduction reaction with hydrogen (or heat).
Such a titanium oxide fine wire having excellent crystallinity can be expected to have good electric characteristics and electron emission characteristics as a semiconductor.

The method shown in FIG.
A titanium nanowire is a porous body having pores extending perpendicular to the surface containing Ti, and a nanostructure existing in the pores is formed. Then, by removing the layer (porous body) 13 having pores around the nanowires of this structure by etching, a layer containing Ti as shown in FIG.
A nanostructure having nanowires extending perpendicular to the surface is obtained.

Further, by separating only the nano-fine wires from the nano-structures shown in FIGS. 3A and 3B, it is possible to obtain nano-fine wires having a very small thickness and a uniform thickness and excellent linearity. be able to.

Further, in the nanostructure obtained as described above, the counter electrode 701 is arranged so as to face the surface containing Ti as shown in FIG.
An electron-emitting device can be obtained by configuring so that a potential can be applied between the first electrode 701 and the counter electrode 701. In the nanostructure used here, since most of the nanowires extend almost perpendicular to the surface, efficient and stable emission of electrons is expected.

[0058]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the embodiments and drawings, but the present invention is not limited to these embodiments.

Example 1 This example is an example in which a titanium oxide nanowire and a nanostructure provided with the titanium oxide nanowire are prepared. Hereinafter, with reference to FIGS. 2A to 2D, a method for manufacturing a nanostructure to which the nanowires of the present invention and the titanium nanowires are applied will be sequentially described.

(Step 1) A quartz substrate is used as the substrate 16 of the present embodiment, and after sufficiently washed with an organic solvent and pure water,
A base film 10 was formed by forming a 1 μm-thick Ti film 11 by a sputtering method (see FIG. 2A).

(Step la) Further, as the film 12 containing Al as a main component, a film having a thickness of 1 μm was formed on the substrate by sputtering.
An Al film having a thickness of m was formed (see FIG. 2B).

(Step lb) Subsequently, the Al film 12 is anodized using the anodizing apparatus shown in FIG. 5 (FIG. 2C).
See). The electrolytic solution was a 0.3 M oxalic acid aqueous solution, and the solution was kept at 17 ° C. in a thermostatic water bath. The anodic oxidation voltage is DC 40 V, and the anodic oxidation time is 10 min.
And During the anodic oxidation step, anodic oxidation reached the surface of the base (Ti film) after about 8 minutes, and a reduction in anodic oxidation current was observed.

Further, as a pore wide treatment, phosphoric acid 5
The pore size was adjusted by immersion in a wt% solution for 45 minutes. After the treatment, cleaning with pure water and isopropyl alcohol was performed.

(Step 2: Heat treatment step) Subsequently, the structure obtained by forming anodized alumina on the substrate by the following method is subjected to a heat treatment in a mixed atmosphere of steam, hydrogen and helium, thereby oxidizing the structure. A titanium nanowire was formed.

That is, the structure was placed in the reactor shown in FIG.
The pure water held in the reactor is bubbled and introduced at a flow rate of 50 sccm from the gas introduction pipe 44, and the pressure in the reaction vessel is set to 1000 P
a. Then, the infrared lamp was turned on to perform a heat treatment at a structure temperature of 700 ° C. for 1 hr. Then, the infrared lamp was turned off, the temperature of the substrate was lowered to room temperature, the gas supply was cut off, and the sample was taken out into the atmosphere.

The surface and the cross section of the sample taken out were FE-
SEM (Field Emission-Scanni)
ng Electron Microscope (field emission scanning electron microscope).

As a result, as shown in FIG. 3 (b), the diameter is about 60 nm, the thin layers are arranged in parallel and at substantially equal intervals at an interval of about 100 nm, and extend perpendicular to the surface of the Ti-containing film 11. A large number of nanowires were grown in the pored anodized alumina and in and out of the pores. The shape of the titanium nanowire reflects the shape of the pore, and the diameter of the wire is about 40 to 60 nm, and the length is several hundred nanometers.
m to several μm, it was grown almost vertically from the substrate surface.

Further, it was confirmed by EDAX (non-dispersive X-ray diffraction analyzer) that the nanowires mainly consisted of titanium. X-ray diffraction showed the presence of rutile titanium oxide.

Further, when the titanium nanowires formed in the pores are separated from the substrate and observed at a high magnification using a microscope, the titanium nanowires shown in FIG. As shown in FIG. 1 (c), a columnar member having a columnar shape, a columnar member having a stepwise changing thickness as shown in FIG. 1 (c), and a columnar member having a plurality of columnar members as shown in FIG. FIG.
Some of (b), (c) and (d) have an edge shape indicating a plane orientation, and are considered to be crystal-grown, that is, whisker-grown.

Example 2 This example is an example in which the control of the fine diameter of titanium nanowires was attempted by controlling the pore diameter of anodized alumina. The voltage of the anodic oxidation was set to 50 V, and the time of the pore widening treatment was set to 0, 15 min, 30 min, 45 min.
The same treatment as in Example 1 was conducted except that the heat treatment time was set to 60 minutes, and a structure was prepared in which the pore diameters of the anodized alumina were different from each other.

The standard pore size of each structure is 10n
m, 25 nm, 40 nm, 60 nm and 80 nm. Next, these structures were subjected to a heat treatment. The heat treatment step was the same as in Example 1.

As a result, the fine wire diameter of the titanium nanowires formed in the pores of each structure reflected the pore diameter, and the sample having a large pore diameter tended to have a large fine wire diameter. That is, the titanium nanowires grew reflecting the shape of the pores. Specifically, the diameter of the average titanium nanowire is
8nm, 20nm, 30nm, 50nm and 70n respectively
m.

Example 3 This example is an example in which the length of titanium nanowires was controlled by controlling the heat treatment. Five structures having anodized alumina formed on a substrate were prepared in the same manner as in Example 1 except that the pore widening treatment was performed for 45 minutes.

These structures were subjected to heat treatment at 600 ° C., 650 ° C., 700 ° C., 750 ° C. and 800 ° C., respectively.
The heat treatment was performed in the same manner as in Example 1 except that the temperature was changed to.
The nanostructure thus obtained was observed in the same manner as in Example 1. As a result, according to the FE-SEM observation, in the sample at the heat treatment temperature of 600 ° C., as shown in FIG. 3C, the growth of most of the titanium nanowires stopped in the middle of the pores.

As the heat treatment temperature is increased, the length of the titanium nanowire tends to be longer.
As shown in (b), many titanium nanowires protruding above the fine pores were observed. At 800 ° C,
As shown in FIG. 3D, the thickness of the titanium nanowire is about 6
0 nm, which was equivalent to the pore diameter.

Embodiment 4 This embodiment is an example in which the nanostructure shown in FIG. 3A is formed. In the present embodiment, similar to the first embodiment, FIG.
After the formation of the nanostructure shown in (b), the anodized alumina 13 was etched with phosphoric acid.

As shown in FIG. 3A, in the nanostructure of the present example, titanium nanowires having a diameter of about 40 to 60 nm were grown in a direction substantially perpendicular to the surface of the substrate at intervals of about 100 nm.

Embodiment 5 This embodiment is an example in which a titanium oxide nanowire and a nanostructure provided with the titanium oxide nanowire are prepared. In this example, the procedure was the same as in Example 1 except for Step 2.

In step 2 of this embodiment, oxygen gas was introduced into the reaction vessel at a flow rate of 10 sccm, the pressure in the reaction vessel was set to 100 Pa, the substrate temperature was set to 500 ° C., and lhr was applied.
Heat treatment. A nanowire and a nanostructure as shown in FIG. 3B were confirmed by FE-SEM. Further, the presence of anatase type titanium oxide was confirmed by X-ray diffraction.

When the nanostructure of this example was placed in an aqueous methanol solution (methanol: water = 1: 6) and subjected to all-light irradiation with a high-pressure mercury lamp, hydrogen was confirmed. Was confirmed to have photocatalytic activity.

Example 6 This example is an example in which a titanium carbide nanowire and a nanostructure having the titanium carbide nanowire are formed. In this example, the procedure was the same as in Example 1 except for Step 2.

In step 2 of this embodiment, ethylene gas was introduced into the reaction vessel at a flow rate of 50 sccm, the pressure in the reaction vessel was set to 1000 Pa, the substrate temperature was set to 900 ° C.,
lhr heat treatment. Fig. 3 by FE-SEM
Nanowires and nanostructures as shown in (b) were confirmed. Further, the presence of titanium carbide was confirmed by X-ray diffraction.

The nanostructure of the present example was placed in a vacuum device facing the anode having the phosphor at an interval of 1 mm,
When 1 KV was applied to the substrate and the anode, the electron emission current was confirmed with the fluorescence of the phosphor. Thus, it was confirmed that the nanostructure of the present example could function as a good electron emitter.

[0084]

As described above, according to each embodiment of the present invention, for example, the following effects can be obtained. (1) A titanium nanowire having a diameter of several tens to several hundreds of nm can be easily formed. (2) Titanium nanowires having excellent linearity can be produced. In particular, a titanium oxide whisker excellent in crystallinity is obtained. (3) A nanostructure mainly composed of titanium is obtained. (4) A nanostructure in which titanium nanowires having a specific direction and having a uniform fine wire diameter are arranged at equal intervals on a substrate is obtained. (5) A high-performance electron-emitting device with a large amount of electron emission can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the shape of a titanium nanowire of the present invention.

FIG. 2 is a conceptual cross-sectional view showing one embodiment of a method for manufacturing a nanostructure of the present invention. (A) is a diagram in which a film mainly composed of Ti is formed on a substrate to form a base, (b) is a diagram in which a film mainly composed of Al is formed, (C) is an anodized Al film,
(Figure showing anodized alumina formed, (d) shows a figure with titanium nanowires formed in the pores)

FIG. 3 is a schematic view showing one embodiment of a nanostructure to which a titanium nanowire according to the present invention is applied. ((A) shows a nanostructure in which titanium nanowires are arranged in a direction substantially perpendicular to the substrate, and (b) to (d) show nanostructures in which titanium nanowires are arranged in pores of anodized alumina.)

FIG. 4 is a schematic view showing an outline of a heat treatment reaction apparatus when producing a titanium nanowire.

FIG. 5 is a schematic view showing an outline of an anodizing apparatus.

FIG. 6 is a schematic view showing anodized alumina.

FIG. 7 is a schematic sectional view showing one embodiment of the electron-emitting device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Substrate 11 Layer which comprises the surface containing Ti 12 Film containing Al as a main component 13 Porous body (anodic oxidized alumina) 14 Pores 15 Titanium nanowire 16 Substrate 41 Reaction vessel 42 Sample 43 Infrared absorbing plate 44 Gas introduction pipe 46 Exhaust Line 47 Infrared lamp 48 Light collecting mirror 50 Thermostat 51 Reaction vessel 52 Sample 53 Pt cathode 54 Electrolyte 55 Ammeter 56 Power supply 701 Counter electrode

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // B22F 9/02 B22F 9/02 Z 9/12 9/12 Z 9/14 9/14 Z

Claims (18)

[Claims] 1. A first step of preparing a structure having a layer having pores extending on the surface on a substrate having a surface containing titanium, and heat treating the structure to form a structure in the pores. A method for producing a titanium nanowire, comprising: a second step of forming a titanium-containing fine wire. 2. The method according to claim 1, wherein said first step includes a step of forming a film containing aluminum as a main component on said substrate and a step of anodizing said film containing aluminum as a main component. Method. 3. The method according to claim 1, wherein the second step includes a step of heat-treating the structure at a temperature of 500 ° C. to 900 ° C. in an atmosphere containing steam of 1 Pa or more. 4. The method according to claim 1, wherein the second step is performed by heating the structure at 500 ° C. to 9 ° C. in an atmosphere containing steam and hydrogen gas of 1 Pa or more.
The method according to claim 1, further comprising a step of performing a heat treatment at a temperature of 00 ° C. or less. 5. A nanostructure comprising a substrate having a titanium-containing surface and a fine wire comprising titanium as a main component and extending substantially perpendicular to the surface. 6. The nanostructure according to claim 5, wherein the fine wire is in the pores of a porous body provided on the surface and having pores extending in a direction perpendicular to the surface. 7. The nanostructure according to claim 6, wherein the diameter of the fine wire is 300 nm or less. 8. The method according to claim 1, wherein the fine wire is at least one selected from titanium hydride, titanium oxide, titanium nitride and carbonized titanium.
7. The nanostructure according to claim 6, comprising: 9. The nanostructure according to claim 6, wherein the fine wire contains at least one selected from titanium silicide, titanium boride, titanium phosphide, aluminum titanium alloy, and iron titanium alloy. 10. The nanostructure according to claim 6, wherein said porous body is an anodic oxide film. 11. The nanostructure according to claim 10, wherein said porous body is an anodic oxide film of a film containing aluminum. 12. The nanostructure according to claim 6, wherein the fine wire is a titanium oxide whisker. 13. A nanowire produced by the method according to claim 1. 14. The nanowire according to claim 13, wherein the diameter of the nanowire is 300 nm or less. 15. The nanowire according to claim 13, wherein the nanowire contains titanium oxide as a main component. 16. The nanowire according to claim 13, wherein the nanowire is a whisker crystal. 17. A structure having, on a substrate having a surface containing titanium, a porous body having pores extending in a direction perpendicular to the surface, and having a fine wire containing titanium as a main component in the pores. A counter electrode arranged opposite to the surface,
And an means for applying a potential between the surface and the counter electrode. 18. The electron-emitting device according to claim 17, wherein the fine wire containing titanium as a main component is a titanium nano-fine wire manufactured by the method according to claim 1.