JPH11200090A - Nanostructural body and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an anodically oxidized film having uniform fine pores and to produce a nanostructural body applicable to a high function device by anodically oxidizing a film contg. Al formed on the electrically conductive surface contg. Ti, Nb or the like of a substrate till it reaches the electrically conductive film. SOLUTION: On the surface of a substrate 10 such as quartz glass, an electrically conductive film 11 essentially consisting of any of Ti, Zr, Nb, Ta, Mo, Cu, Zn, Au, Pt, Pd, Ni, Fe, Co and W and excellent in heat resistance is formed to a thickness of about 10 nm to 100 μm by vapor deposition. On the surface, a film 12 essentially consisting of Al is formed by plating or the like. This sample 41 is arranged in an electrolyte, and voltage is applied to the space between an Al film 12 and the cathode as the counter electrode to anodically oxidize the Al film 12. At this time, after the change of the anodic oxidation current showing the arrival of the anodic-oxidation at the electrically conductive surface is detected, the anodic-oxidation is stopped. In this way, An Al anodically oxidized film 13 having parallel, many fine pores 14 of nanoholes at almost equal intervals is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nanostructure having pores (nanoholes) formed by using an anodizing method of Al, and the structure includes a functional device such as an electronic device or a microdevice, or a structural material. As such, it can be used in a wide range. Furthermore, it can also be used as a wear-resistant material and an insulating material as an anodized film.

[0002]

2. Description of the Related Art Metal and semiconductor thin films, fine lines, dots, and the like are required to have a size smaller than a certain characteristic length.
When the movement of electrons is confined, it may exhibit unique electrical, optical, and chemical properties. From such a viewpoint, as a functional material, 100 nanometers (nm)
Interest in materials having finer structures (nanostructures) is increasing.

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

[0004] In addition to such a production method, attempts have been made to realize a novel nanostructure based on a regular structure formed naturally, that is, a structure formed self-organizingly. is there. Many studies have begun on these techniques because, depending on the microstructure used as a base, there is a possibility that a finer and special structure can be created that exceeds conventional methods.

An example of a unique structure formed in a self-organizing manner is an Al anodic oxide film (for example, R.A.
C. Furneaux, W.C. R. Rigby & A.
P. Davidson "NATURE" Vol. 3
37 P147 (1989) and the like). When the Al plate is anodized in an acidic electrolyte, a porous oxide film is formed.

The feature of this porous oxide film is shown in FIG.
As shown in the figure, there is a specific geometric structure in which extremely fine cylindrical pores (nano holes) 14 having a diameter of several nm to several hundred nm are arranged in parallel at intervals of several nm to several hundred nm. It is in. The columnar pores 14 have a high aspect ratio and are excellent in uniformity of cross-sectional diameter. The diameter and interval of the pores 14 are determined by the current during anodization,
Some control is possible by adjusting the voltage.

Various applications have been attempted, focusing on the specific geometric structure of the Al anodic oxide film. The explanation by Masuda is detailed, but the application column is listed below. For example, there is an application as a film utilizing the wear resistance and insulation resistance of the anodic oxide film, and an application to a filter by peeling the film. Furthermore, by using a technique of filling a nanohole with a metal or a semiconductor or a replica technique of the nanohole, coloring, a magnetic recording medium, an EL light emitting element, an electrochromic element, an optical element, a solar cell, a gas sensor,
And various other applications have been attempted. Furthermore, quantum effect devices such as quantum wires and MIM elements,
It is expected to be applied to various fields such as molecular sensors using nanoholes as a chemical reaction field (Masuda Solid State Physics
31, 493 (1996)).

[0008] The above-described production of nanostructures by the semiconductor processing technique has problems such as poor yield and high equipment cost, and a technique that can be produced with a simple technique and high reproducibility is desired.

From such a viewpoint, the self-assembly method, particularly the Al anodic oxidation method has an advantage that a nanostructure can be easily and controlledly formed. In addition, this technique can generally produce a large-area nanostructure.

For example, Japanese Patent Application Laid-Open No. 63-187415 discloses that a base layer having conductivity and electrochemical stability is provided on a substrate, and an anodic oxide film of aluminum or an aluminum alloy is laminated on the base layer. There is disclosed a magnetic recording medium in which a magnetic material is filled in micropores formed in an anodized film. Here, Rh, Nb, Ta, A
u, Ir, Pt, Ti, Cr, Pd, Ru, Os, G
The use of materials such as a, Zr, Ag, Sn, Cu, Hf and Be has the effect that the depth of the micropores formed in the anodic oxide film at the time of anodic oxidation of aluminum or aluminum alloy becomes uniform. Is described.

In Japanese Patent Publication No. 1-237927, an anodic oxide film of a metal other than aluminum or an aluminum alloy is provided between a nonmagnetic substrate and an aluminum or aluminum alloy anodic oxide film to form an anodic oxide film. Eliminate the barrier layer at the bottom of the micropore,
There is disclosed a magnetic recording medium in which the plating efficiency for fine holes is improved.

[0012]

By the way, in order to form a high-performance device by utilizing fine holes formed in an anodic oxide film of aluminum, the state of a large number of fine holes existing in the anodic oxide film (for example, fine holes) It is preferable to make the depth of the holes and the conductivity at the bottom of the micropores as uniform as possible. Until now, anodic oxidation was mainly controlled by the anodic oxidation time. However, according to the study of the present inventors, the state of the fine pores of the anodic oxide film is largely dependent on the material of the underlying layer of the anodic oxide film. It was found that it was difficult to make the state of the micropores highly uniform when the anodic oxidation was controlled only by the anodic oxidation time.

Accordingly, an object of the present invention is to provide a nanostructure in which the state of micropores in the anodic oxide film is extremely uniform and which can be applied to a further highly functional device, and a method for producing the same. .

[0014]

The above object can be attained by the following constitution and manufacturing method of the present invention. The method for producing a nanostructure according to one embodiment of the present invention includes an anodized film having pores on the conductive surface of a substrate having a conductive surface, and the bottom of the pores and the conductive material. A nanostructure having an oxide layer between the surface and the oxide layer, connecting the bottom of the pores to the conductive surface, and having a path including a material contained in the conductive surface; 1) a step of forming a film containing aluminum on the conductive surface of a substrate having a conductive surface containing at least one element selected from Ti, Zr, Nb, Ta and Mo;
And 2) applying a voltage between the film containing aluminum and the counter electrode to anodize the film containing aluminum. Forming an anodic oxide film having pores, wherein the step 2) performs anodic oxidation while detecting an anodic oxidation current, and indicates that the anodic oxidation has reached the conductive surface. The method includes a step of stopping anodization after detecting a change in current.

According to this aspect, the bottom of the pores of the anodic oxide film and the conductive surface are connected by a path containing an element constituting the conductive surface, and as a result, the pores having excellent conductivity at the bottom are formed. A nanostructure having uniformity can be obtained.

After the anodic oxidation is stopped, the nanostructure is subjected to heat treatment or heat treatment in a reducing atmosphere, whereby the conductivity at the bottom of the pores can be further improved.

According to another embodiment of the present invention, there is provided a method of manufacturing a nanostructure, comprising: Cu, Zn, Au, Pt, Pd, Ni,
A substrate provided with a conductive surface containing at least one element selected from Fe, Co and W, comprising an anodized film having pores on a conductive surface thereof, wherein the pores reach the conductive surface; 1) Cu, Zn, Au, Pt, Pd, Ni, Fe, Co
Forming a film containing aluminum on a conductive surface of a substrate having a conductive surface containing at least one element selected from W and W; and 2) applying a voltage between the film containing aluminum and the counter electrode. Forming an anodic oxide film having fine pores, and in the step 2), current limiting is performed on the anodic oxidation voltage output.

According to this aspect, a nanostructure having pores reaching the conductive surface can be formed stably.

A nanostructure according to one embodiment of the present invention comprises a substrate having a conductive surface, an anodized film having pores on the conductive surface, and a bottom portion of the pores and the conductive film. An oxide layer between the conductive surface and the bottom surface of the pores, the oxide layer having a path including a material contained in the conductive surface. And According to this aspect, a nanostructure having uniform conductivity at the bottom of the pores can be obtained.

The nanostructure according to another embodiment of the present invention includes: 1) a conductive surface of a substrate having a conductive surface containing at least one element selected from Ti, Zr, Nb, Ta and Mo. Forming a film containing aluminum in the
And 2) a step of applying a voltage between the film containing aluminum and the counter electrode to anodize the film containing aluminum to form an anodic oxide film having pores, wherein the step 2) comprises: A method for producing a nanostructure, comprising the steps of performing anodization while detecting an anodization current, and stopping the anodization after detecting a change in the anodization current indicating that the anodization has reached the conductive surface. It is characterized by being manufactured by.

The nanostructure according to another embodiment of the present invention includes: 1) Cu, Zn, Au, Pt, Pd, Ni, Fe, Co
Forming a film containing aluminum on a conductive surface of a substrate having a conductive surface containing at least one element selected from W and W; and 2) applying a voltage between the film containing aluminum and the counter electrode. And forming an anodized film having pores by performing anodizing, wherein in the step 2), it is manufactured by the method for manufacturing a nanostructure for limiting current to the anodized voltage output. Features.

According to these embodiments, the nanostructure is more uniform in the state of the pores and is suitable for application to high-performance devices. In the present invention, by selecting a material for the conductive film, there is an effect that an Al anodic oxide film can be formed on an arbitrary substrate.

According to the present invention, an Al anodic oxide film is formed by using a quantum wire,
MIM element, molecular sensor, coloring, magnetic recording medium, EL
It can be applied in various forms including light-emitting elements, electrochromic elements, optical elements, solar cells, gas sensors, abrasion-resistant, insulating-resistant films, filters, etc. Has the effect of spreading.

In the manufacturing method of the present invention, a nanostructure having an Al anodic oxide film formed on a conductive film can be realized. Further, the nanostructure of the present invention has excellent heat resistance, and has effects such as good electrical connection between the filling material in the pores and the conductive film.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. FIG. 1 schematically shows a conceptual diagram of the nanostructure of the present invention. FIG. 1A is a plan view, and FIG. 1B is a sectional view taken along the line AA.

In FIG. 1, reference numeral 10 denotes a substrate, 11 denotes a conductive film, 13 denotes an Al anodic oxide film, and 14 denotes pores (nano holes).
It is. Further, the pores can be filled with any material such as a metal and a semiconductor by an electrochemical method or the like.

As the material of the base 10, any material can be used, and examples thereof include insulating materials such as quartz glass, semiconductor materials such as Si, and various metal materials.

The material of the conductive film 11 of the present invention depends on the purpose of use, but as shown in the examples described later, Ti, Zr, N
b, Ta, Mo, Cu, Zn, Au, Pt, Pd, N
It can be a conductive film containing i, Fe, Co, W, or the like as a main component.

By selecting a conductive film, a nanostructure having excellent heat resistance can be obtained. In the conventional configuration in which the A1 plate is anodized (FIG. 3A) or the configuration in which the Al film is partially anodized (FIG. 3B), the melting point of Al is limited in terms of heat resistance. If the temperature is equal to or lower than the melting point and the temperature is equal to or higher than 300 ° C., the Al anodic oxide film may be damaged such as a film crack. On the other hand, heat resistance can be improved by disposing an Al anodic oxide film on a conductive film as in the present invention. For example, Nb is preferable as the conductive film, and at least 11
It can withstand heat treatment at temperatures up to 00 ° C. This enables a high-temperature process and widens the range of choices in applications such as material filling into nanoholes. Further, the chemical stability of the nanoholes can be improved by heat treatment.

Further, as the underlying conductive film, T
When i, Zr, Nb, Ta, Mo, or the like is used, an oxide of the material forming the conductive film may be formed at the bottom of the pores. In such a case, reduction of hydrogen or the like is performed. By performing heat treatment in a neutral atmosphere, reduction is performed, and the conductivity at the bottom of the pores can be improved.

Further, the present invention provides a method for manufacturing a substrate comprising Ti, Z
r, Nb, Ta, Mo, Cu, Zn, Au, Pt, P
When a material containing any of d, Ni, Fe, Co, and W as a main component is used, a conductive film is not necessarily required. In the present invention, a conductive film can be laminated, and Ti /
A laminated film of Ni or the like may be used.

In the present invention, the thickness of the conductive film depends on the purpose of use, but is set in consideration of the following. When the substrate has conductivity, the thickness of the conductive film disposed on the substrate may be sufficient if it can sufficiently cover the substrate.
It can be set in the range of 0 nm to 100 μm.

When the conductivity of the substrate is insufficient, the conductive film plays the role of an electrode in the anodic oxidation step. That is, when anodizing a film containing Al as a main component over the entire thickness, the film containing Al as a main component oxidizes and increases in resistance as the anodic oxidation progresses. And may cause a voltage drop. From this viewpoint, it is desirable that the conductive film has sufficient conductivity, that is, the conductive film is thick as long as a good and flat film quality is selected. The preferred range of the film thickness cannot be specified unconditionally because it is set based on the conductivity ρ of the conductive film material, the area, and the like, but is generally in the range of 10 nm to 100 μm, and more preferably 50 nm to
The range is 1 μm.

The Al anodic oxide film 13 is formed by anodizing a film containing Al as a main component. This Al
The anodic oxide film 13 contains Al and O (oxygen) as main components, and has a large number of columnar pores (nanoholes) as shown in FIG.

In the Al anodic oxide film 13, a large number of cylindrical nanoholes 14 are arranged almost perpendicular to the film (plate) surface.
The nanoholes are arranged in parallel with each other and at substantially equal intervals. Each nanohole is shown in Fig. 1.
As shown in a), they tend to be arranged in a triangular lattice.

The diameter 2r of the nanohole is several nm to several hundred n.
m, the interval 2R is about several nm to several hundred nm, and the depth is 10 nm.
１００100 μm.

The interval and diameter of the nanoholes are controlled to some extent by various process conditions such as the concentration and temperature of the electrolytic solution used for anodic oxidation, the method of applying the anodic oxidation voltage, the voltage value, the time, and the subsequent pore-wide processing conditions. can do.

In the structure of the present invention, the film containing Al as a main component is oxidized over the entire thickness from the surface to the conductive film by the anodic oxidation step. That is, it has a feature that the bottom of the nanohole faces the conductive film. Hereinafter, such a configuration is referred to as a nanohole on a conductive film. For example, when Ti is used as the conductive film, it is called a nanohole on Ti.

In particular, Ti, Z
When r, Nb, Ta, Mo, etc. are used, FIG.
As shown in the figure, the bottom of the pore has an oxide layer 17 made of a mixture of a material constituting the conductive film and Al and O, and the oxide layer 17 connects the bottom of the pore and the conductive film. And a path (hereinafter referred to as a path) 16 having a large amount of elements constituting the conductive film 11. This path is thought to be formed by the diffusion of the material constituting the conductive film toward the bottom of the pores when the anodic oxidation is continued even after the barrier layer at the bottom of the pores reaches the underlying conductive film. It is. With this route, when metal or semiconductor is continuously electrodeposited in the pores, the electrodeposition can be controlled with a lower voltage and better than the conventional anodized alumina with a barrier layer at the bottom of the pores. And Also, since this path has conductivity, good electrical connection can be realized between the filling in the pores and the conductive film.

Further, by subjecting the nanostructure having such paths formed thereon to a heat treatment in a hydrogen gas or inert gas atmosphere, the conductivity of the paths can be further improved. Thus, uniform deposition with a small variation in the amount of electrodeposition can be realized. It is considered that the reason for the improvement in conductivity is that the paths are reduced.

On the other hand, Cu, Z
In the case of using n, Au, Pt, Pd, Ni, Fe, Co, W, etc., as shown in FIG. 6B), the bottom of the pores penetrates without aluminum oxide (barrier layer). Become.

It is to be noted that a new nanostructure can be prepared by embedding a metal, a semiconductor, or the like in the anodized nanoholes of the nanostructure of the present invention or by forming a replica thereof.

Hereinafter, the method for producing a nanostructure of the present invention will be described in more detail with reference to FIG. Figure 2a)-
e) will be described in order, but the following steps a) to e) will be described.
Corresponds to a) to e) in FIG.

A) Forming the conductive film 11 on the substrate 10 The conductive film 11 can be formed by resistance heating evaporation, EB evaporation,
Any film forming method including sputtering, CVD, and plating can be applied.

B) A sample 41 is formed by forming a film 12 containing Al as a main component on the conductive film 11. As a method for forming a film containing Al as a main component, any film forming method including resistance heating evaporation, EB evaporation, sputtering, CVD, and plating can be applied.

C) Anodizing Step Anodizing the sample 41 to form the nanostructure of the present invention. Specifically, the anodizing step of the present invention is a step in which a material having a film mainly composed of Al is disposed in an electrolytic solution, and an anodizing voltage is applied between the material and the cathode. Further, in this step, the film mainly containing Al is oxidized over its entire thickness, that is, until the bottom of the formed nanohole reaches the conductive film. FIG. 4 schematically shows an anodizing apparatus used in this step.

In FIG. 4, 40 is a thermostat, 41 is a sample,
43 is an electrolytic solution, 44 is a reaction vessel, 42 is a cathode of a Pt plate, 45 is a power supply for applying an anodizing voltage, and 46 is an ammeter for measuring an anodizing current. Although not shown in the figure, a computer for automatically controlling and measuring the voltage and current is incorporated. The sample 41 and the cathode 42 are arranged in an electrolytic solution maintained at a constant temperature by a constant temperature water bath, and anodization is performed by applying a voltage between the sample and the cathode from a power supply.

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

The anodic oxidation step is as follows. It is preferable to perform the process while continuously detecting the anodic oxidation current. For example, Ti, Z
The anodizing current when the layer containing aluminum formed on the conductive surface containing at least one element selected from r, Nb, Ta and Mo is anodized changes as shown in FIG. That is, when the anodic oxidation of the aluminum-containing layer reaches its entire thickness, the anodic oxidation current starts to decrease and thereafter converges to a substantially constant value. When the current decreases and the anodic oxidation is stopped when the current reaches a substantially constant value, the bottom of the pore formed in the anodic oxide film and the bottom of the pore as shown in FIG. Although an anodic oxide film is interposed between the fine pores and most of the pores, a path including an element constituting the conductive surface is formed between the bottom and the conductive surface. As a result of performing electrodeposition on the bottom of the pore using a DC power supply, an electrodeposited film was stably deposited on the bottom of most pores. This indicates that the state of the pores is highly uniform.

On the other hand, when the conductive surface contains Zn or Cu, the anodic oxidation current once increased and then decreased as shown in FIG. 5B. When the anodic oxidation current increases once, and once increases and then decreases, the anodic oxidation is stopped. Observing the nanostructure obtained by FE-SEM, the anodic oxide film is partially damaged like a crater. Is recognized,
There were portions where pores had disappeared.

Au, Pt, Pd, N
The anodic oxidation current when at least one element selected from i, Fe, Co and W was included increased sharply as shown in FIG. The anodic oxidation was stopped after the anodic oxidation current was rapidly increased, and the resulting nanostructure was observed in the same manner. As a result, most of the pores had disappeared. And Cu, Zn, A
The anodizing current of the film containing aluminum formed on the conductive surface of the substrate having the conductive surface containing at least one element selected from u, Pt, Pd, Ni, Fe, Co, and W changes. When the operation was stopped immediately after the operation, the pores were hardly damaged, and the state of the pores was uniform.

The reason why such a result is obtained is not clear, but the following is a presumption. Anodization proceeds gradually from the surface of the film containing aluminum to reach the conductive surface. At this time, the conductive surface is, for example, Ti, Zr, Nb,
In the case of a conductive surface containing at least one element selected from Ta and Mo, the anodic oxide film at the bottom of the pore is not removed, and the material constituting the conductive surface passes through the anodic oxide film to form the pore. It is conceivable that a path containing the elements that diffuse toward the bottom and constitute the conductive surface is formed.

The reason why the conductivity of the bottom of the pores is further improved when such a nanostructure is heated or heat-treated in a reducing atmosphere is considered to be because the material constituting the pathway is reduced. . It is considered that the reason why it is preferable to stop the anodization after the current value converges to a constant value in the anodization current profile shown in FIG. 5A is that the path is formed at almost all the bottoms of the pores. .

In this embodiment, the anodic oxidation current is 1 mA
It is preferable to stop the anodic oxidation at the time when the pressure falls to / cm ² or less.

On the other hand, Au, Pt, Pd, N
In the case of a conductive surface containing at least one element selected from i, Fe, Co, and W, the anodic oxidation gradually proceeds from the surface of the film containing aluminum to reach the conductive surface, and the electrolytic solution At the time of contact with the conductive surface, the electrolysis of the electrolyte on the conductive surface and the dissolution of the conductive surface occur,
As a result, it is considered that a large current flows, which is presumed to be the cause of the disappearance of the pores. Also, even when the conductive surface is a conductive surface containing Cu or Zn, when the electrolytic solution comes into contact, some electrolysis or dissolution occurs, a relatively large current flows, thereby causing pores to disappear. Conceivable. In this embodiment, the anodic oxidation is stopped immediately after the anodizing current has changed, so that the disappearance of the pores can be prevented very effectively. Other methods include, for example, current limiting the anodic oxidation voltage output and anodic oxidation with a series resistor. In particular, when the current is limited, the current limit value is 50 mA /
cm ² or less.

Depending on the use of the nanostructure, the following processes d) and e) may be performed. d) Pore widening treatment By this treatment of immersing the nanostructure c) that has undergone the above steps in an acid solution (for example, a phosphoric acid solution), the diameter of the nanoholes can be appropriately increased. The nanohole diameter can be controlled by the concentration, the processing time, and the temperature.

E) Filling the nanoholes with metal and semiconductor Metals and semiconductors are filled in the nanoholes 14 of each of the structures c) and d).
Semiconductors can be filled. At this time, filling of Ni, Fe, Co, Cd, etc. by an electrochemical method (D. Al
-Malawwi et. al. J. . Mater.
Res. , 9, 1014 (1994), Masuda et al. Surface Technology Vol 43, 798 (1992)), introduction of molten metal (CA Huber et. Al. SCIENC).
E 263,800 (1994)) and the like, and various material filling techniques can be used. For example, as an example of the method of electrochemically filling Fe, Ni, and Co, electrolytic deposition using an aqueous solution of FeSO4, NiSO4, and CoSO4, respectively, may be mentioned. In FIG. 2E), the filler 15 completely covers the Al anodic oxide film 13, but it is also possible to fill the nanohole 14 partway and use it.

As described above, the present invention provides a
When using a material containing any one of Ti, Zr, Nb, Ta, Mo, Cu, and Zn as a main component, a conductive film is not necessarily required. In that case, in the above manufacturing process, step a) Is omitted, and b ′) a film 12 containing Al as a main component is formed on the substrate 10 to obtain a sample 41, and the following c) to e)
Step may be performed.

[0059]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples and can be appropriately modified within the scope of the present invention.

Example 1 Five quartz substrates having a width of 40 mm and a length of 15 mm were prepared, sufficiently washed with an organic solvent and pure water, and then the surface of each quartz substrate was coated with Ti, Z by vacuum evaporation or sputtering.
r, Nb, Ta and Mo were formed to a thickness of 100 nm.
Except for Ti, in order to improve the adhesion to glass, a film of Ti was previously formed to a thickness of 20 nm and then formed to obtain a quartz substrate having a conductive surface. Next, an aluminum film was formed to a thickness of 1 μm on each conductive surface by a sputtering method.

The aluminum film was anodized by using the anodizing apparatus shown in FIG. A 0.3 M oxalic acid aqueous solution was used as the electrolytic solution, the electrolytic solution was kept at 17 ° C. in a thermostatic water bath, and anodizing was performed while anodizing current was detected at an anodizing voltage of 40 V DC. The results as shown in A of Figure 5 from the start anodized after 8 minutes began to drop anodic oxidation current, after 10 minutes to stop the anodic oxidation because became LMA / cm ² or less. Next, as a pore-wide treatment, the substrate was immersed in a 5 wt% phosphoric acid solution for 30 minutes, and then washed with pure water and isopropyl alcohol to obtain a nanostructure.

The surface of the nanostructure was observed with a field emission scanning electron microscope (FE-SEM), and the cross section was observed with a transmission electron microscope (TEM). As a result, the structure at the bottom of most of the pores is a path as shown in FIG.
Had 16. The pores 14 were extremely fine and uniform cylindrical pores having a diameter of about 50 nm, and a large number of pores were arranged at intervals of about 100 nm in parallel with each other and at substantially equal intervals. The aluminum film was oxidized over the entire thickness.

The path (path) was confirmed by elemental analysis to contain each metal constituting the conductive surface. This is because the anodic oxidation gradually progresses from the aluminum film surface, and the anodic oxidation continues after reaching the conductive surface, so that the material constituting the conductive surface passes through the anodic oxide film at the bottom of the pores. This is probably due to diffusion toward the bottom of the pores. Especially when the conductive surface is T
In the case of i or Nb, the decrease in the anodic oxidation current profile is sharp, and it seems that more uniform pores are formed.

Comparative Example 1 In Example 1, the metal layer constituting the conductive surface was replaced with W, F
Example 1 except that e, Ni, Pd, Pt and Au were replaced
In the same manner as in the above, a substrate having an aluminum film on the conductive surface was produced. Next, anodization was performed on the aluminum film under the same conditions as in Example 1, and anodization was stopped 10 minutes after the anodization current rapidly increased as shown in FIG. 5C.

Thereafter, as in the case of the first embodiment, the processing of the pore width is performed.
After washing, the state of the pores was observed by FE-SEM and TEM. As a result, moderate to severe damage was observed in the pores in the anodic oxide film. Here, moderate damage means loss of a part of the pores, and severe damage means loss of most of the pores.

Comparative Example 2 A substrate having an aluminum film on the conductive surface was prepared in the same manner as in Example 1 except that the conductive metal layer was changed to Zn and Cu. Next, anodization was performed on the aluminum film under the same conditions as in Example 1, and the anodization was stopped 10 minutes after the anodization current once increased and then decreased as shown in FIG. 5B.

Thereafter, in the same manner as in the first embodiment,
After washing, the state of the pores was observed by FE-SEM and TEM. As a result, slight damage was observed in the pores in the anodic oxide film. Here, the slight damage refers to a case where a crater-shaped hole having a diameter of several μm is partially observed.

Example 2 In the anodizing step, a nanostructure was formed in the same manner as in Comparative Examples 1 and 2, except that a current limiter was applied to an anodizing power supply.

That is, after 5 minutes from the anodic oxidation, Al
When the current profile of the membrane was restored (arrow X in FIG. 5), the DC power supply current limiter was activated. The value of the current limit was set as 1.2 times the anodic oxidation current value after 5 minutes. Other conditions were in accordance with Comparative Examples 1 and 2.

As a result of FE-SEM observation, Comparative Examples 1 and 2
It was found that the damage of the nanoholes was significantly reduced as compared with the nanostructure of the above. Looking at the cross section,
It was found that most of the pores reached the conductive surface as shown in FIG. 6b). Further, in the case of Cu, a part thereof formed an oxide at the bottom of the pore.

Next, for each nanostructure, 0.14M
Immersed in an electrolytic solution consisting of NiSO ₄ and 0.5M H ₃ BO _3, and N was applied to the bottom of the pores using a carbon counter electrode.
When i was electrodeposited, -1V with respect to the calomel standard electrode
At a voltage as low as -1.5V, Ni
Could be filled. Further, when the electric conductivity between Ni filled in the pores and the conductive surface was examined, the electrical connection between the conductive surface and Ni filled in the pores was good.

Example 3 This example describes an anodic oxidation current monitor in the production of a nanostructure using a metal substrate.

In this example, the following samples were used. Example 3-1: Mo was formed as a conductive film to a thickness of 1 μm on a Ni plate substrate having a thickness of 0.5 mm by EB vapor deposition. Example 3-2: A Mo plate having a thickness of 0.5 mm was used as a base, and no conductive film was formed.

An Al film was formed to a thickness of 1.5 μm on the Mo thin film of each sample or on the Mo substrate by EB evaporation. Further, on the surface on which the Al film was not formed, a portion that was in contact with the electrolytic solution was covered with epoxy. The anodic oxidation step was in accordance with Example 1. However, the end of the anodic oxidation, during the treatment, always monitor the current profile of the anodic oxidation, after the current decrease indicating that the anodic oxidation has reached the conductive film surface,
Further, it was determined that the current was stabilized (arrow Y in FIG. 5), and the application of the voltage was stopped, and this step was completed.

When the sample of this example was observed by FE-SEM observation, the Al sample shown in FIG.
Anodized nanoholes were formed on each of the metal substrates, and the depth of the nanoholes in this example was uniform.

Comparative Example 3 An aluminum plate was anodized under the same conditions as in Example 3 for 10 minutes to obtain a nanostructure having the structure shown in FIG. As a result of observing this structure by FE-SEM in the same manner as in Example 3, variation was observed in the depth of the pores.

From Example 3 and Comparative Example 3, it was found that by arranging the conductive film of the material shown in Example 1 as an undercoat, Al anodized nanoholes could be formed on any substrate. Further, in the present embodiment, Al
The thickness of the anodized nanoholes and the depth of the nanoholes are Al
Since they are defined by the film thickness, they can be made uniform over a wide area.

Further, as in this embodiment, by monitoring the anodizing current and judging the end of the anodizing based on the current profile, it is possible to form a path with good reproducibility and to avoid unnecessary anodizing. Was completed.

Embodiment 4 In this embodiment, a 2-inch diameter n-Si
Using a substrate, a 200 nm-thick Ti
(Example 4-1) and an Nb film (Examples 4-2 and 3) were used. The thickness of the Al film was 500 nm. In addition, as Comparative Example 4, a sample having the configuration shown in FIG. 3B) in which an Al film was anodized halfway without a conductive film was used.

The procedures of c) anodization and d) pore-wide treatment were the same as in Example 1. In Example 4-3,
After the anodic oxidation, a heat treatment was performed at 500 ° C. for 1 hr in a reducing atmosphere of 2% H ₂ and 98% He.

E) Filling of pores The sample completed up to the pore widening treatment was
M NiSO _4, in 0.5M H ₃ BO ₃ electrolytic solution consisting, to precipitate Ni in nanoholes bottom by electrodeposition is immersed together with the counter electrode of carbon.

In Comparative Example 4, a voltage of -15 V or more was required for electrodeposition, and the deposition was poor in reproducibility. However, in Examples 4-1 and 4-2, compared to Comparative Example 4, As a result, the calomel electrode was uniformly filled with Ni over the entire surface of the sample at a voltage as low as -1 to -1.5 V. The FE-SEM observation result had the form shown in FIG. The columnar pores having a diameter of about 50 nm were filled with Ni, and a large number of these Ni-filled pores were arranged at intervals of about 100 nm and arranged at substantially regular intervals. In particular, in Example 4-3 in which the amount of electrodeposition was controlled and Ni was deposited halfway through the nanoholes as shown in FIG. 7B, the variation in the amount of filler between the pores was small.

Considering the reason, in electrodeposition into the nanohole, it is important that the deposition reaction proceeds rapidly at the bottom of the nanohole. In the comparative example, the barrier layer at the bottom of the nanohole shown in FIG. On the other hand, in the present example, as shown in FIG. 6 a), by having the path 16 at the bottom of the pore, the path became a conductive path, and the Ni precipitation reaction at the bottom of the hole proceeded smoothly. It seems to be due to.

In 4-3, it is considered that the conductivity at the bottom of the pores was further improved by reducing the path at the bottom of the pores by heat treatment in a reducing atmosphere (hydrogen). Further, when the electric conductivity between the Ni filler and the conductive film was examined, in Examples 4-1, 4-2, and 4-3, the electrical connection between the conductive film and the filler was good. Was.

Example 5 In this example, a quartz glass substrate was used, and a 1 μm thick Nb film (Example 5-1) and a Ti film were used as conductive films.
A film (Example 5-2), a Cu film (Example 5-3), a Pt film (Example 5-4), and a Co film (Example 5-5) were used.
The thickness of the Al film was 1 μm. The anodic oxidation method was based on Example 1 for Nb and Ti, and Example 2 for Cu, Pt and Co.

As Comparative Example 5, a sample having the structure shown in FIG. 3A in which an Al plate was anodized for 5 minutes was prepared. As Comparative Example 6, a sample having the configuration shown in FIG. 3B in which an Al film on quartz glass was anodized partway without a conductive film was prepared. The thickness of Al is 1 μm and the anodic oxidation time is 5 min.
It is.

Subsequently, the Nb-subtracted nanoholes of this example were subjected to a heat treatment at 200 ° C. to 1100 ° C. for 1 hour in a He atmosphere, and the morphological changes were observed by FE-SEM. The rate of temperature rise and fall was 5 ° C./min.

FIG. 3A and FIG.
The nanoholes on Al in (b) show the melting point of Al (630 ° C).
In view of the above, the range was set to 200 to 500 ° C. Comparative Examples 5 and 6 had the forms of FIGS. 3a) and b) before the heat treatment, respectively. However, the samples that had been subjected to the heat treatment at about 300 ° C. or more suffered from anodic oxide film (Al anodized nanoholes). Had occurred.

On the other hand, in the structure of this embodiment in which the conductive film is undercoated, the structure shown in FIG. 1 is obtained up to the high temperature shown below, and the shape and change by the heat treatment are not observed. . For example, the pores were uniform columnar pores having a diameter of about 50 nm, and a large number of fine lines were arranged at intervals of about 100 nm in parallel and at substantially equal intervals.

Table 1 below shows the temperature range in which no damage was caused by the heat treatment.

[0091]

[Table 1]

As a result, it was found that the nanostructure having the nanohole structure on the conductive film of the present invention, among which the nanohole on Nb, had excellent heat resistance. As a result, nanoholes capable of withstanding a high-temperature process could be formed.

Further, the TEM observation shows that the Al
Aluminum oxide constituting the anodized nanoholes was excellent in crystallinity. Furthermore, when the acid resistance of Al anodized nanoholes before and after the treatment was compared, it was found that the chemical stability was improved by the heat treatment.

Example 6 A nanostructure having a conductive surface of Nb and Pt was prepared in the same manner as in Example 5. C. in the pores of these structures.
A. Metals and semiconductor materials were introduced in a manner similar to Huber et al. That is, the material to be introduced is arranged in a thin metal ampoule together with each nanostructure, and the inside of the ampoule is filled with an inert atmosphere. In addition, the ampoules were finally crushed and crushed. Here, Huber et al. Performed heat treatment up to 800 ° C., but heat treatment up to 1100 ° C. was possible by using the nanostructure of the present invention.

Thus, low melting point metal In, Sn, A
l, semiconductors (Se, Te, GaSb, Bi ₂ Te ₃ ), etc., as well as higher melting point metals such as Ag, Au, Cu, etc.
A semiconductor such as Ge could be introduced. Further, in the present invention, since the nanoholes are arranged on the conductive material, the nanoholes can be electrically connected to the conductive film (Nb or Pt).

[0096]

As described above, the present invention has the following effects. 1) A having very uniform pores on any substrate
1 An anodic oxide film can be formed. 2) An Al anodic oxide film having pores in a very uniform state can be formed on the conductive material. Further, in the configuration in which the metal or the semiconductor is filled in the nanohole, the conductive material and the metal or the semiconductor can be electrically connected. 3) An Al anodic oxide film having a uniform nanohole depth over a large area can be formed. 4) A nanostructure excellent in high temperature resistance can be formed. Also,
By the heat treatment, an Al anodic oxide film having excellent crystallinity can be formed.

These allow the Al anodic oxide film to be applied in various forms and greatly expand the range of application. The nanostructure of the present invention,
Although it can be used as a functional material by itself, it can also be used as a base material, a template, and the like for further novel nanostructures.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing the structure of a nanostructure according to the present invention, wherein FIG. 1 (a) is a plan view and FIG. 1 (b) is a sectional view taken along line AA of FIG.

FIG. 2 is a schematic cross-sectional view illustrating a manufacturing process of a nanostructure of the present invention, in which a) shows a case where a conductive film is formed on a substrate, and b) shows a case where A1 is a main component on the conductive film. When the film was formed, c) when the A1 film was anodized to form nanoholes, d) when the nanohole diameter was increased by pore widening treatment, and e) when the metal or semiconductor was filled in the nanoholes. Show.

FIG. 3 is a schematic view showing the structure of a conventional A1 anodic oxide film on an A1 plate (film). FIG. 3A is a cross-sectional view when the A1 plate is anodized. It is a sectional view at the time of oxidation, c) It is a perspective view of nanohole formed in A1 board (film).

FIG. 4 is a schematic diagram for explaining an anodizing apparatus.

FIG. 5 is a graph showing the classification of current profiles during anodization.

FIG. 6 is a schematic view showing the form of the bottom of the pores of the nanostructures of Example 1 and Example 3 of the present invention.

FIGS. 7A and 7B are schematic diagrams showing the form of the bottom of the pores of the nanostructure of Example 4 of the present invention. FIG. 7A shows a form in which pores are completely filled, and FIG. The form is shown.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Substrate 11 Conductive film formation 12 Film mainly composed of A1 13 A1 anodic oxide film 14 Pores 15 Filler 16 Path 17 Oxide layer 31 A1 plate 32 Barrier layer 40 Thermostatic layer 41 Sample 42 Cathode 43 Electrolyte 44 Reaction vessel 45 Power supply 46 Ammeter

[Procedure amendment]

[Submission date] November 13, 1998

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

FIG. 2

FIG. 4

FIG. 5

FIG. 3

FIG. 6

FIG. 7

Claims (24)

[Claims] 1. A substrate having a conductive surface, comprising: an anodic oxide film having pores on the conductive surface; and an oxide layer between the bottom of the pores and the conductive surface. A method for producing a nanostructure, comprising: connecting the bottom of the pores to the conductive surface with the oxide layer; and having a path including a material contained in the conductive surface, wherein 1) Ti, Forming a film containing aluminum on the conductive surface of a substrate having a conductive surface containing at least one element selected from Zr, Nb, Ta and Mo;
And 2) a step of applying a voltage between the film containing aluminum and the counter electrode to anodize the film containing aluminum to form an anodic oxide film having pores, wherein the step 2) comprises: Anodizing while detecting the anodizing current, and stopping the anodizing after detecting a change in the anodizing current indicating that the anodizing has reached the conductive surface. The method of manufacturing the structure. 2. The method according to claim 1, wherein the anodic oxidation is stopped after the anodic oxidation current has dropped to 1 mA / cm ² or less. 3. The method according to claim 1, further comprising a step of performing a heat treatment after the step 2). 4. The method according to claim 3, wherein said heat treatment is performed in a reducing atmosphere. 5. The method according to claim 3, wherein said heat treatment includes a step of heating to 300 ° C. or higher. 6. The method according to claim 1, wherein the element contained in the conductive surface is Nb or T.
The method according to claim 1, wherein i is i. 7. The method according to claim 1, further comprising a step of filling at least one of a metal and a semiconductor into the pores after the step 2). 8. The manufacturing method according to claim 4, further comprising, after the step of heat-treating the nanostructure, a step of filling at least one of a metal and a semiconductor in the pores. 9. The step of filling at least one of a metal and a semiconductor in the pores comprises contacting the nanostructure with the metal, the semiconductor or a melt of the metal and the semiconductor to be filled. 9. The production method according to claim 7, comprising: 10. The method according to claim 9, wherein the contacting step is performed under pressure. 11. The method according to claim 11, wherein the metal and the semiconductor are In, Sn, A
l, Se, Te, The process according to any one of claims 7 to 10 is at least one member selected from the GaSb and _Bi 2 Te _3. 12. The metal and the semiconductor are made of Ag, Au, Cu.
And at least one selected from Ge and Ge.
10. The production method according to any one of the above items 10. 13. Cu, Zn, Au, Pt, Pd, N
an anodic oxide film having pores on a conductive surface of a substrate having a conductive surface containing at least one element selected from i, Fe, Co and W, wherein the pores reach the conductive surface; 1) Cu, Zn, Au, Pt, Pd, Ni, Fe, Co
Forming a film containing aluminum on a conductive surface of a substrate having a conductive surface containing at least one element selected from W and W; and 2) applying a voltage between the film containing aluminum and the counter electrode. A process of forming an anodic oxide film having pores by performing anodic oxidation to form an anodic oxide film having pores, wherein in the step (2), a current is applied to the anodic oxidation voltage output. 14. The method according to claim 13, wherein the current limit value is smaller than 50 mA / cm ² . 15. The method according to claim 13, further comprising a step of filling at least one of a metal and a semiconductor into the pores after the step 2). 16. The step of filling at least one of a metal and a semiconductor in the pores includes a step of bringing the pores into contact with the metal, the semiconductor, or a melt of the metal and the semiconductor to be filled. The method according to claim 15. 17. The method according to claim 16, wherein the contacting step is performed under pressure. 18. The method according to claim 18, wherein the metal and the semiconductor are In, Sn, A
l, Se, Te, The process according to any one of claims 15 to 17 is at least one member selected from the GaSb and _Bi 2 Te _3. 19. The method according to claim 19, wherein the metal and the semiconductor are Ag, Au, Cu
And at least one selected from Ge and Ge.
18. The manufacturing method according to any one of Items 17 to 17. 20. A substrate having a conductive surface, comprising: an anodic oxide film having pores on the conductive surface; and an oxide layer between the bottom of the pores and the conductive surface. A nanostructure, wherein the oxide layer connects a bottom of the pore and the conductive surface and has a path including a material contained in the conductive surface. 21. The conductive surface is made of Ti, Zr, Nb, T
The nanostructure according to claim 20, comprising at least one element selected from a and Mo. 22. The nanostructure according to claim 21, wherein the element contained in the conductive surface is Ti or Nb. 23. A nanostructure manufactured by the method according to claim 1. 24. A nanostructure manufactured by the method according to claim 13.