JP2002338228A - Meso-structure thin film and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a meso-structure thin film having orientational tube like fine pores on an optional substrate. SOLUTION: The method for forming the meso-structure thin film by applying a precursor solution containing a surfactant and an inorganic oxide precursor material on the substrate by spin coating includes a process for preparing the precursor solution containing the surfactant and the inorganic oxide precursor material, a process for holding the substrate outside the rotation center of a spin coater and a process for placing the precursor solution on the substrate and applying the solution by spin coating to form the thin film of the meso- structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the application of a porous inorganic oxide used as a catalyst or an adsorbent, and more particularly, to a mesostructured thin film and a method for producing the same, and more particularly, to a mesostructured thin film having a pore structure in a desired direction. And a method for manufacturing the same.

[0002]

2. Description of the Related Art Porous materials are used in various fields such as adsorption and separation. According to IUPAC, the porous body is
Microporous having a pore diameter of 2 nm or less, 2 to 50 nm
And a macroporous of 50 nm or more. Known microporous materials include zeolites such as natural aluminosilicate and synthetic aluminosilicate, and metal phosphates. These are used as selective adsorption using pore size, shape-selective catalytic reaction, and reaction vessels of molecular size.

[0003] In the reported microporous crystal, the maximum pore size is about 1.5 nm.
Synthesis of a solid having a larger diameter is an important issue for performing adsorption and reaction of a bulky compound that cannot be adsorbed on micropores. Silica gel, pillared clay and the like have been known as substances having such large pores, but in these, the distribution of pore diameters is wide, and control of the pore diameter has been a problem.

[0004] Against this background, the synthesis of mesoporous silica having a structure in which tubular mesopores having a uniform diameter are arranged in a honeycomb shape has been developed almost simultaneously by two different methods. One is "Nature" Vol. 359, 71
A substance called MCM-41 synthesized by hydrolyzing an alkoxide of silicon in the presence of a surfactant, as described on page 0, and the other is "Jou
rnal of Chemical Society
FSM-16 synthesized by intercalating alkylammonium between layers of kanemite, which is a kind of layered silicic acid, as described in Chemical Communications, 1993, pp. 680.
It is a substance called.

In both cases, it is considered that the structure of the silica is controlled by using an aggregate of surfactants as a template. These substances are not only very useful materials as catalysts for bulky molecules that do not enter the pores of zeolite, but also are considered to be applied to functional materials such as optical materials and electronic materials.

When a mesoporous material having such a regular pore structure is applied to the field of functional materials other than catalysts, a technique for uniformly holding these materials on a substrate is important. As a method for forming a uniform mesoporous thin film on a substrate, for example, “Chemical Comm.
"Natations", 1996, p. 1149.
359, p. 364, "Nature" 379.
Vol., Page 703, a method of depositing a film on a solid surface.

[0007]

However, these conventional methods for manufacturing a mesostructured thin film have the following problems. That is, in the case of a commonly used spin-coated film, etc., the direction of the centrifugal force applied to the precursor solution on the substrate is not controlled, so that there is no directionality of the mesostructure over the entire film and the pores are oriented. I can't let it.
On the other hand, in the case of a method of depositing a mesostructure on a substrate, the formed film is largely dependent on the substrate, and the formation of a directional film is performed at an atomic level such as a cleavage plane of mica or graphite. Limited to ordered substrates.

For this reason, a technique for forming an inorganic oxide mesostructured thin film having orientation on an arbitrary substrate has been demanded. As a technique for solving this, for example, "N
The method of controlling the pore direction by using a permeation flow of a precursor solution disposed on a substrate, as described in “Ature”, vol. 390, p. 674, and “Langmuir”
Journal, Vol. 15, p. 4544,
A method of holding a substrate in the flow of a solution and controlling the direction of pores has been proposed. However, these methods have a problem that a complicated apparatus must be used and the shape of the thin film is limited.

The present invention has been made in view of the above-mentioned problems of the prior art, and provides a mesostructured thin film having oriented pores on a substrate, and provides a mesostructured thin film on an arbitrary substrate by a simple method. It is an object of the present invention to provide a method for producing a mesostructured thin film having oriented pores.

[0010]

That is, the present invention relates to a mesostructured thin film formed by applying a precursor solution containing a surfactant and an inorganic oxide precursor onto a substrate using centrifugal force. A mesostructured thin film characterized in that the tubular pores in the thin film are oriented substantially parallel to the direction of the centrifugal force applied to the substrate.

The above-mentioned tubular pore may be filled with a surfactant, or may have a hollow structure in which the surfactant is removed from the inside of the tubular pore.

The present invention also relates to a method of forming a mesostructured thin film by applying a precursor solution containing a surfactant and an inorganic oxide precursor on a substrate by spin coating. Adjusting the precursor solution containing the precursor, holding the substrate outside the center of rotation of the spin coating apparatus, placing the precursor solution on the substrate and applying by spin coating to form a mesostructured thin film And forming a mesostructured thin film.

Further, the present invention provides a method for forming a mesostructured thin film by applying a precursor solution containing a surfactant and an inorganic oxide precursor on a substrate by spin coating. Adjusting the precursor solution containing the precursor, holding the substrate outside the center of rotation of the spin coating apparatus, placing the precursor solution on the substrate and applying by spin coating to form a mesostructured thin film A method for producing a mesostructured thin film, comprising a step of forming and a step of removing a surfactant from a tubular pore in the formed mesostructured thin film to form a hollow structure.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
FIG. 1 is a schematic view showing an example of the mesostructured thin film of the present invention, wherein FIG. 1A is a schematic plan view, and FIG. 1B is a schematic cross-sectional view taken along line AA. The mesostructured thin film of the present invention is a thin film formed by applying a precursor solution containing a surfactant and an inorganic oxide precursor onto a substrate using centrifugal force, and a tube in the thin film 2 is formed. The major axis direction of the fine pores 3 is oriented substantially parallel to the direction 4 of the centrifugal force applied to the substrate 1.

Further, the method for producing a mesostructured thin film of the present invention is directed to a method for forming a mesostructured thin film by applying a precursor solution containing a surfactant and an inorganic oxide precursor onto a substrate by spin coating. Adjusting the precursor solution, holding the substrate outside the center of rotation of the spin coating apparatus, and placing the precursor solution on the substrate and applying the solution by spin coating to form a thin film of the mesostructure. And a step.

FIG. 2 is a schematic view showing an example of holding a substrate in the present invention. In the spin coating apparatus used in the present invention, as shown in FIG. 2, a substrate 12 for forming a mesostructured thin film is placed outside a rotation center 13 of the spin coating apparatus. In the ordinary spin coating, since the substrate is placed on the center of rotation 13, the substrate receives a centrifugal force in all directions radially from the center of the substrate due to rotation. A one-way centrifugal force indicated by an arrow is generated.

It is known that when a precursor solution flows when a mesostructured thin film is formed, the tubular pores in the mesostructure are oriented in the flow direction.
As described in “Ture”, Vol. 390, p. 674, a method for forming an oriented mesostructured thin film utilizing this fact is being studied.

In the case of ordinary spin coating, since the precursor solution on the substrate flows in the radial direction, the tubular pores tend to be oriented radially from the center. However, the centrifugal force F is the angular velocity ω, the distance r from the center and

[0019]

(Equation 1)

Since the centrifugal force is weaker near the center of rotation and theoretically becomes zero at the center of the substrate,
At the center, the orientation is random, so that a clear radial orientation is difficult to achieve over the entire substrate.

In the case of the present invention, since the substrate is placed outside the center of rotation of the spin coating apparatus, a one-way force acts on the precursor solution on the substrate, and the resulting flow is reduced by a thin tube. The holes are oriented in the direction of centrifugal force.

FIG. 3 is a schematic view showing an example of the substrate holder used in the present invention, and FIG. 4 is a sectional view taken along the line BB of the substrate holder of FIG.

The method for fixing the substrate to the substrate holder 11 shown in FIG. 2 is not particularly limited, but the rotary shaft of the spin coating apparatus is hollow and connected to a vacuum pump, and the substrate holder having the structure shown in FIG. Generally, a method of performing vacuum chucking using 11 is used. The manner in which the substrate 12 is fixed to the substrate holder 11 will be described with reference to the cross-sectional view of FIG. FIG.
In the above, the space between the substrate 12 and the groove 22 provided on the substrate holder 11 is evacuated by a vacuum pump through a cavity 24 connecting a hole 23 formed at the center of the groove and the rotating shaft 21 of the spin coater. Then, the substrate 12 is fixed to the substrate holder 11.

A precursor solution containing a surfactant and an inorganic oxide precursor is dropped onto a substrate fixed to a substrate holder. The precursor solution used for forming the mesostructured thin film of the present invention is at least a solution obtained by adding a catalyst to a solvent containing a surfactant, and comprises a compound that generates an inorganic oxide by any method such as hydrolysis polycondensation. It is a mixture of inorganic oxide precursors, and the precursor solution may be a known one.

The surfactant is appropriately selected from quaternary alkylammoniums and nonionic surfactants containing polyethylene oxide as a hydrophilic group. The length of the surfactant molecule used is determined according to the pore size of the target mesostructure. Further, an additive such as mesitylene may be added to increase the diameter of the surfactant micelle.

Examples of the catalyst include an acid such as hydrochloric acid and a base such as sodium hydroxide, and more preferably hydrochloric acid. The solvent used is not particularly limited as long as it can dissolve a surfactant, a catalyst, and a compound that forms an inorganic oxide, but more preferably includes water and alcohol.

As the oxide precursor for forming the inorganic oxide, halides, alkoxides and the like can be mentioned.
The oxide to be formed is not limited, but includes silicon oxide, titanium oxide, tin oxide, zirconium oxide, gallium oxide,
Aluminum oxide, vanadium oxide, or the like is preferably applied, and a composite oxide of two or more elements may be used.

There is no particular limitation on the material of the substrate on which the precursor solution is applied, and a wide range of materials can be applied. For example, glass, ceramics, resin and the like can be used. However, it is necessary to select one that does not react with the precursor solution.

As the substrate, a substrate whose surface has been subjected to an orientation treatment in some form may be used. The orientation treatment is the same as the method used for the orientation of the liquid crystal, and a known method such as rubbing treatment or oblique vapor deposition can be used. In this case, it is necessary to make the orientation direction by the orientation treatment coincide with the direction of the centrifugal force during spin coating.

When the substrate is fixed to the substrate holder as described above and the spin coating apparatus is rotated after the precursor solution is dropped, the solution moves on the substrate in the circumferential direction under centrifugal force. By using the generated flow, it is possible in the present invention to control the micelle direction, that is, to control the orientation of the pore structure. The number of rotations is set according to the film thickness, and the higher the number of rotations, the higher the uniaxial orientation of the pores and the thinner the film.

Since it is preferable that the centrifugal force acts on the substrate holder, it is advantageous that the radius is large. The fixing position of the substrate is preferably as far as possible outside the substrate holder.
It is desirable to design and use an optimal substrate holder within an acceptable range based on the size of the spin coating apparatus used. The orientation of the pores of the mesostructure is affected not only by the centrifugal force, but also by the viscosity of the solution and the surfactant species used, oxide precursor species, solvent species, substrate, temperature, humidity, etc.
Even if you hold the board at the same distance from the center of rotation,
The same orientation cannot always be obtained.

The material of the substrate holder is not particularly limited as long as it has resistance to chemicals, particularly acids, and materials such as stainless steel, polypropylene and Teflon (registered trademark) can be used. Although FIG. 3 shows a substrate holder having a configuration in which four substrates can be fixed, more substrates may be held as long as they are symmetrical with respect to the center along the circumference and at the same position.

It is preferable that the entire spin coating apparatus be installed in a space where the temperature and humidity are adjusted. The temperature and humidity are controlled so as to be optimal according to the target oxide, surfactant type, solvent and the like. By drying the film formed on the substrate in this way, an oxide mesostructured thin film having a surfactant retained in the pores is obtained.

By removing the surfactant micelle of the template from the mesostructure, a hollow mesostructure thin film can be formed. Removal of the surfactant is carried out by baking,
It is selected from extraction with a solvent, extraction with a fluid in a supercritical state, irradiation with ultraviolet light and decomposition with ozone generated at that time, decomposition with an ozone aqueous solution, and the like. For example, in the case of a silica mesostructured thin film, the surfactant can be completely removed from the mesostructured thin film with almost no destruction of the mesostructure by baking in air at 550 ° C. for 10 hours. In addition, when means such as solvent extraction is used, 10
Although it is difficult to remove 0% of the surfactant, it is possible to form a mesoporous thin film on a substrate made of a material that cannot withstand firing.

[0035]

The present invention will be described in more detail with reference to the following examples.

Example 1 The surface was cleaned with acetone, isopropyl alcohol and pure water, and the surface was cleaned in an ozone generator.
An m (1.5 inch) square non-alkali glass (7059, manufactured by Corning Incorporated) was used as a substrate.

6.0 g of polyethylene oxide 10 cetyl ether (manufactured by Aldrich) was added to 6
After dissolving in 2 ml of water, 8.2 ml of tetramethyl orthosilicate (manufactured by Kishida Chemical Co., Ltd.) was added, and the mixture was heated to 80 ° C. and stirred to form a homogeneous solution. 0.5 ml of concentrated hydrochloric acid (about 35%, manufactured by Kishida Chemical Co., Ltd.) was added thereto, and
It stirred at 500 degreeC and 500 mmHg for 30 minutes, and was set as the precursor solution.

A mesostructured thin film was prepared by using a spin coater installed in a constant temperature / humidity chamber at a temperature of 25 ° C. and a humidity of 60%. The substrate holder used has the same configuration as that shown in FIG. 3 and can hold four substrates by vacuum chucking. A circular substrate holder having a radius of 17 cm is provided between the edge of the substrate and the center of rotation. The coating liquid was dropped on the glass substrate adhered to a position separated by 160 mm, and rotated at 2000 rpm for 30 seconds. Thereafter, the film was dried in air at room temperature for 12 hours to form a transparent silica mesostructured thin film.

The substrate on which the silica mesostructured thin film was formed was analyzed by X-ray diffraction analysis. As a result, the surface spacing was 4.3.
A strong diffraction peak at 7 nm attributed to the (100) plane of the hexagonal structure was confirmed, confirming that this thin film had a hexagonal pore structure. Since no diffraction peak was observed in the wide-angle region, it was found that the silica constituting the wall was amorphous.

In order to quantitatively evaluate the uniaxial orientation of the mesochannel in the silica mesostructured thin film, evaluation was performed by in-plane X-ray diffraction analysis. This method is described in "Chem
issue of Materials ", 11th edition
Vol., P. 1609, to measure the in-plane rotation dependence of X-ray diffraction intensity due to the (110) plane perpendicular to the substrate, and to examine the orientation direction and distribution of mesochannels. Can be. FIG. 5 shows the in-plane rotation angle dependence of the (110) plane diffraction intensity measured for the silica mesostructured thin film produced in this example. In this measurement, the direction of the centrifugal force acting on the substrate was set to 0 °. This figure 5
As shown in Table 2, a Gaussian profile centered on 0 ° was obtained. Thus, in the silica mesostructured thin film produced in this example, the mesochannels are oriented in a direction parallel to the direction in which the centrifugal force acts during spin coating, and the distribution of the orientation direction has a half-value width. It was shown to be about 46 °.

The substrate on which the thin film of the silica mesostructure was formed was placed in a muffle furnace and heated at 500 ° C. at a rate of 1 ° C./min.
And fired in air for 10 hours. No significant difference was observed in the shape of the substrate surface after firing compared to before the firing. Further, as a result of X-ray diffraction analysis of the fired thin film, a hexagonal structure (10
A strong diffraction peak attributed to the 0) plane was observed, confirming that the hexagonal pore structure was maintained. Even after firing, no diffraction peak was observed in the wide-angle region, and it was confirmed that the silica on the wall remained amorphous. In addition, the analysis of the infrared absorption spectrum and the like confirmed that the sample after the calcination did not contain any organic components derived from the surfactant.

The fired sample was also subjected to in-plane X-ray diffraction analysis to examine the orientation of the pores. Also in this case, the in-plane rotation angle dependence of the (110) plane diffraction intensity was measured. As a result, almost the same profile as that measured for the mesostructured thin film before firing was obtained, and it was confirmed that the orientation of the pores was completely maintained.

The thin film before and after firing was cut perpendicularly to the direction of the centrifugal force, and the cross section was observed with a transmission electron microscope. As a result, pores having a hexagonal structure were confirmed in the cross section of both thin films. It was confirmed that the channel was oriented in the direction of centrifugal force.

COMPARATIVE EXAMPLE 1 As a comparative example, a silica mesostructured thin film was prepared in the same manner as in Example 1 except that a normal spin coating method was used, in which the center of gravity of the substrate was brought into close contact with the rotation axis of a spin coater. It was created.

The substrate on which the silica mesostructured thin film was formed was measured by X-ray diffraction analysis.
m, a strong diffraction peak attributed to the (100) plane of the hexagonal structure was confirmed, confirming that this thin film had a hexagonal pore structure. Since no diffraction peak was observed in the wide-angle region, it was found that the silica constituting the wall was amorphous.

The thin film sample was subjected to in-plane X-ray diffraction analysis in order to examine the orientation direction of the tubular pores.
As in Example 1, the in-plane rotation angle dependence of the (110) plane diffraction intensity perpendicular to the film surface was measured. In this case, the position of 0 ° can be set in any direction. In this case, the observed profile is substantially flat with respect to the rotation angle, indicating that there is almost no structural anisotropy in the in-plane direction.

According to this comparative example, it was shown that when spin-coating was performed with the center of the substrate aligned with the rotation axis, formation of a mesostructure having the orientation of the tubular pores could not be achieved.

Example 2 This example is an example in which a tin oxide mesostructured thin film in which tubular pores are oriented in one direction by the spin coating method of the present invention. 2 g of polyethylene oxide 10 stearyl ether (manufactured by Aldrich) was dissolved in 20 g of ethanol (manufactured by Kishida Chemical Co., Ltd.), and after complete dissolution, 5.2 g of tin chloride (SnCl ₄ ) was added.
After stirring this mixed solution for 30 minutes, 1 g of pure water was added and used as a precursor solution.

The same temperature used at 25 ° C. as used in Example 1
Using a spin coating apparatus installed in a constant temperature / humidity chamber at a humidity of 60% and the same substrate holder, the same glass substrate as in Example 1 was rotated at 2000 rpm for 30 seconds to form a film. This is left to dry at room temperature for 72 hours,
A tin oxide mesostructured thin film was prepared.

When this thin film was analyzed by X-ray diffraction analysis, it was found that the hexagonal structure (10
A strong diffraction peak attributed to the 0) plane was confirmed, confirming that this thin film had a hexagonal pore structure.

When this thin film was measured by in-plane X-ray diffraction analysis, a diffraction peak attributed to the (110) plane perpendicular to the film surface was observed. The in-plane angle dependence of the diffraction intensity of this peak was measured. Also in this case, the direction of the centrifugal force on the substrate was set to 0 °. As a result, also in the case of the tin oxide mesostructured thin film prepared in this example, as observed in Example 1, a Gaussian-type profile centered at 0 ° was observed, and a tubular pore was formed. It was found that the particles were oriented in the direction of centrifugal force. In addition, from the half width, it was confirmed that the orientation distribution of the mesochannel had a half width of about 52 °.

According to this embodiment, the method of the present invention
It was shown that a tin oxide mesostructured thin film having uniaxially oriented tubular pores could be formed.

[0053]

As described above, according to the present invention,
At the time of spin coating, the substrate is held outside the rotation axis of the spin coating apparatus, and a unidirectional centrifugal force is applied to the precursor solution on the substrate to form an oriented tubular pore on any substrate. A mesostructured thin film and a mesoporous thin film having the same can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one example of a mesostructured thin film of the present invention.

FIG. 2 is a schematic view showing an example of holding a substrate in the present invention.

FIG. 3 is a schematic view showing an example of a substrate holder used in the present invention.

FIG. 4 is a sectional view taken along the line BB of the substrate holder of FIG. 3;

FIG. 5 shows (11) in the in-plane X-ray diffraction analysis observed for the silica mesostructure produced in Example 1 of the present invention.
It is a figure which shows the profile which shows the rotation angle dependence in a plane of a sample of the 0) plane.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Thin film 3 Pores 4 Direction of centrifugal force 11 Substrate holder 12 Substrate 13 Center of rotation 21 Hollow rotation axis 22 Groove 23 Hole formed in the center of groove 24 Cavity

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G072 AA25 BB09 BB13 BB15 GG01 HH30 KK17 NN21 RR12 UU11 UU15

Claims (5)

[Claims] 1. A mesostructured thin film formed by applying a precursor solution containing a surfactant and an inorganic oxide precursor onto a substrate using centrifugal force, wherein the thin film has a tubular shape. A mesostructured thin film, wherein the holes are oriented substantially parallel to the direction of the centrifugal force applied to the substrate. 2. The mesostructured thin film according to claim 1, wherein the tubular pores are filled with a surfactant. 3. The mesostructured thin film according to claim 1, wherein the thin film has a hollow structure in which a surfactant is removed from inside the tubular pores. 4. A method for forming a mesostructured thin film by applying a precursor solution containing a surfactant and an inorganic oxide precursor on a substrate by spin coating, comprising a surfactant and an inorganic oxide precursor. A step of adjusting the precursor solution, a step of holding the substrate outside the center of rotation of the spin coating apparatus, and a step of placing the precursor solution on the substrate and applying by spin coating to form a mesostructured thin film; A method for producing a mesostructured thin film, comprising: 5. A method for forming a mesostructured thin film by applying a precursor solution containing a surfactant and an inorganic oxide precursor on a substrate by spin coating, wherein the surfactant and the inorganic oxide precursor are contained. A step of adjusting the precursor solution, a step of holding the substrate outside the center of rotation of the spin coating apparatus, and a step of placing the precursor solution on the substrate and applying by spin coating to form a mesostructured thin film; And removing the surfactant from the tubular pores in the prepared mesostructured thin film to form a hollow structure.