JPH11319542A - Production ultrathin layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a ultrathin layer on the surface of a solid to be treated such as a substrate by a method in which in semiconductor industries in which the high integration of electronic circuits is aimed, the surface of a hydrogel or an organogel, after being brought into contact with the surface of the solid, is peeled off, and the surface layer part of the gel is transferred to the surface of the solid. SOLUTION: An organic gel, as hydrogel, especially using a polysaccharide or synthetic polymer dispersant can be transferred to the surface of a solid with a high coverage ratio and is preferable for the formation of a thin transfer layer. A known organogel using an organic, solvent as a dispersing medium is adopted. The surface of the hydrogel or the organogel, after being brought into contact with the surface of a solid to be treated, is peeled off in order that the surface layer part of the gel is transferred on the surface of the solid, and a ultrathin layer is produced on the surface of the solid. One layer of the surface layer part of the hydrogel or the organogel is transferred additionally on the surface of the solid on which the ultrathin layer is formed in order to laminate the ultrathin layer precisely.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel method for producing ultra-thin layers on solid surfaces.

[0002]

2. Description of the Related Art The production of ultrathin layers with controlled layer thickness at the nanometer level has been actively studied in many fields due to its wide application and industrial requirements. For example, a technique for thinning a conductive polymer is a very important technical problem in the semiconductor industry which aims at high integration of electronic circuits. In addition, the development of a technology for producing an ultra-thin layer with a controlled layer thickness at the nanometer level on an arbitrary substrate surface includes various separation membranes such as a permeable membrane, a reverse osmosis membrane, and an oxygen-enriched membrane; It is extremely useful for the development of various electronic materials such as gas sensors and optical sensors; medical materials; biocatalyst-immobilized materials.

[0003] In many of these technical fields, a common requirement for ultra-thin layer formation processes is to produce thin layers whose structure is controlled at the nanometer level, at lower cost and under milder conditions. However, it has been difficult to form an ultrathin layer controlled at the nanometer level on an arbitrary carrier surface by a simple method.

[0004] For example, conventionally, the following method has been known as a means for producing an ultra-thin layer. In this method, an ultra-thin polymer layer is formed by a coating drying method or spin coating. However, in this case, it is extremely difficult to form a uniform thin layer having a thickness of 0.1 μm or less.

Further, a solution of a low molecular compound or a polymer is spread on a gas-liquid interface to form a monomolecular film, and these are formed into a cumulative film by a Langmuir-Blodgett (LB) method, or an ionic monolayer. There is also known a method of preparing a polyion complex monomolecular film by adsorbing a polymer electrolyte having an opposite charge to a molecular film from a lower phase aqueous solution, and forming the polyion complex monomolecular film into a cumulative film. But these methods, LB
Due to the high cost of the film forming apparatus and the entire process, it has not been adopted as a practical means for producing an ultra-thin layer.

Further, a technique of adsorbing a charged polyelectrolyte solution onto a substrate having an opposite charge (adsorption method), and further adsorbing a polyelectrolyte having an opposite charge to the polymer electrolyte on the surface thereof, and reapplying the polymer It is also possible to sequentially grow a polymer thin film by using a technique of repeating electrolyte adsorption successively (alternate adsorption method). However, in these adsorption methods, a strong interaction such as electrostatic interaction is indispensable between the substrate to be adsorbed and the polymer, and a similar strong interaction is also observed when thin films are sequentially laminated. Required.

[0007] Further, a method of placing a substrate in a polymer synthesis solution in advance and stacking the polymer on the substrate together with polymerization (polymerization adsorption method), or dissolving and removing the polymer adsorbed by this method, and removing the substrate surface For obtaining polymer monolayers epitaxially grown on GaN (polymerization induced epitaxy)
Is also known. These techniques are suitable because a polymer thin film having a controlled thickness can be obtained on any solid surface.

However, the polymerization adsorption method cannot control the arrangement structure of the polymer chains in a two-dimensional plane, and has a possibility that the polymerization catalyst remains in the polymer film. Further, it is difficult to form a polymer having high solubility by adsorption and lamination on a substrate. On the other hand, in polymerization-induced epitaxy, the substrate for causing the epitaxial growth of the polymer is limited to graphite or the like, and has a problem that it cannot be applied to any solid substrate.

In addition, there is also known a method in which an organic or inorganic compound is vapor-deposited on a solid substrate in a vacuum, or a method in which a polymerizable monomer is vapor-deposited in the same manner and then polymerized on the substrate to form an ultrathin layer. However, since this method is performed in a high vacuum, it is difficult to produce a large-area thin layer, and the cost of the whole production process is high, so that productivity cannot be said to be good.

[0010]

As described above, a method for realizing the production of a general and practical ultra-thin layer capable of controlling the layer thickness at the nanometer level on any solid surface is as follows. , Not found at the moment. Considering the problems of the conventional ultra-thin layer manufacturing method, the conditions required for the new ultra-thin layer manufacturing method are various solids regardless of the presence or absence of the electric charge of the molecule (low molecule, polymer) used. An object of the present invention is to produce an ultrathin layer having a thickness controlled at the nanometer level on the surface with high productivity. Further, a thin-layer structure can be designed so as to be able to meet various demands for thin-layer characteristics at any time.

Against this background, an object of the present invention is to provide a method of manufacturing an ultra-thin layer which is simple, versatile, and capable of precise and structural design.

[0012]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems. As a result, by bringing the surface of the hydrogel and the organogel into contact with the surface of the solid to be treated and then exfoliating, the surface layer of the gel can be transferred to the surface of the solid to be treated with a thickness of nanometer level. An ultra-thin layer having a thickness of a nanometer level is formed on the surface of the solid to be treated, and furthermore, by repeating this transition operation sequentially, it has been found that this ultra-thin layer can be laminated with high thickness accuracy, The present invention has been completed.

That is, the present invention is characterized in that the surface of the hydrogel or organogel is brought into contact with the surface of the solid to be treated and then peeled off, thereby transferring the surface layer of the gel to the surface of the solid to be treated. It is a method of producing an ultra-thin layer on a treated solid surface.

Further, the present invention is characterized in that at least one surface layer of a hydrogel or an organogel is transferred on the surface of the solid to be treated on which the ultrathin layer is formed in the same manner as described above. Also provided is a method of manufacturing an ultra-thin layer.

According to the method of the present invention, an ultra-thin layer having a thickness on the order of nanometers can be formed on the surface of the solid to be processed by the above-described operations. The formation of such an ultra-thin layer is presumed to be based on the following principle. That is, the gel has a packing structure of different constituent molecules in the inside and the surface layer, and unlike the inside of the gel having a three-dimensional crosslinked structure, the surface layer in contact with air has a two-dimensional network structure. I have. This network structure is composed of one to several molecules or molecular aggregates, and therefore, its thickness is almost uniform at the nanometer level. The network structure of this gel surface at the nanometer level is
By directing the hydrophobic part of the molecular aggregate to the outside air side,
It is estimated that the surface free energy tends to be reduced. When the solid surface is brought into contact with the gel surface, the surface layer of the above structure is physically adsorbed by van der Waals interaction with the solid surface. Then, when the solid surface is peeled off from the gel surface, the surface layer having high two-dimensionality is transferred, and an ultra-thin layer is formed on the solid surface.

In the present invention, the surface layer portion of the hydrogel or organogel is further transferred onto the surface of the solid to be treated on which the ultrathin layer has been formed in the same manner as described above. Ultra-thin layers with controlled thickness and structure at the level can also be produced.

In the present invention, known hydrogels are employed without particular limitation. Specifically, polysaccharides such as agarose, alginic acid and carrageenan; proteins such as gelatin and collagen; polyacrylamide;
Examples include organic gels in which synthetic polymers such as polyisopropylacrylamide, polyvinyl alcohol, and poly-L-leucine are dispersed, and inorganic gels such as silica gel, titanium oxide gel, and tungsten oxide gel prepared by a sol-gel method. Among them, an organic gel containing a polysaccharide or a synthetic polymer as a dispersion is particularly preferable because it can be transferred to a solid surface in a state of high coverage and a transfer layer is formed in a thin film shape.

It is preferable that the hydrogel has a viscosity such that it does not flow even when tilted. In order to form a hydrogel having such properties, water as a dispersion medium is selected depending on the type of the dispersion used. The concentration may be adjusted. For example, when the dispersion is a polysaccharide, a protein, or the like, their concentration in water is 10% by weight or less, preferably 0.5 to 3%.
% By weight is preferred. Further, the hydrogel preferably has no cracks or the like formed on the surface.

The preparation of the hydrogel may be appropriately carried out according to a conventional method. Taking agarose gel as an example, pure water or an aqueous solution in which a metal salt such as calcium chloride is dissolved is added to a predetermined amount of agarose, and the mixture is heated and stirred. And allowed to cool.

The present invention is not limited to the hydrogel as described above, and is similarly applicable to an organogel using an organic solvent as a dispersion medium. Known organogels are used without particular limitation. Examples of the organic solvent which is a dispersion medium include alcohols such as methanol and ethanol; aromatic hydrocarbons such as benzene and toluene; chlorinated hydrocarbons such as chloroform and methylene chloride; nitrogen-containing compounds such as dimethylformamide and acetonitrile. Dimethyl sulfoxide and the like;

As the dispersion, compounds capable of gelling these organic solvents can be employed without limitation. Specifically, low molecular weight organic compounds such as hydroxystearic acid, oligopeptides, dibenzylidene sorbitol; N-lauroylglutamic acid dibutylamide;
1-({4- (dodecylamino) -1-[(dodecylamino) carbonyl] -4-oxobutyl} amino) -1
Amino acid derivatives such as 1-oxoundecyl] (2-hydroxyethyl) dimethylammonium bromide; metal alkoxides such as titanium-n-butoxide; metal complexes such as aluminum salts of dialkylphosphoric acid; cross-linked polyethylene glycol; and synthetic polymers such as polystyrene And the like.

These organogels also preferably have a viscosity such that they do not flow when tilted, and the concentration of the organic solvent as a dispersion medium may be adjusted so as to form such a gel.

Next, in the present invention, the solid to be treated which is brought into contact with the surface of the above hydrogel or organogel is limited to the properties and shapes of hydrophilic or hydrophobic materials as long as it can contact these gels. Instead, various things can be adopted. Those having a critical surface tension γ _{c of} not less than 20 Nm ⁻¹ are preferable because a good transition of the surface layer of the gel can be performed. A typical solid to be treated is graphite.
(HOPG); minerals such as mica quartz and quartz; glass; metals such as platinum and gold; and molded articles made of synthetic polymers such as polyethylene terephthalate and polystyrene. It is recommended that the shape has a flat surface such as a plate shape, a film shape, a porous film shape, etc. from the viewpoint of the accuracy of transfer and workability.

Although the surface layer of the gel transferred to the surface of the solid to be treated is well physically adsorbed to the surface of the solid due to van der Waals interaction, in the present invention, the dispersion of the gel used is charged. If the solid to be treated, for example, using a solid whose surface has a charge opposite to the charge of the dispersion, a chemical bond such as ion adsorption is generated, and the surface layer of the gel is formed. It may be more firmly bonded to the surface of the solid to be treated.

At this time, the solid to be treated may be one obtained by modifying the surface of a molded article made of the above-mentioned material by physical adsorption or chemical adsorption to change the surface charge. As a surface modification method by physical adsorption of a solid, for example, a solid having a negative charge such as mica (mica) is immersed in a cationic polyelectrolyte or an aqueous solution of a cationic synthetic lipid, and these are excessively adsorbed. By
There is a method of adding a positive charge. In addition, for the gold deposit, a known thiol compound adsorption method is applied, and a mercurtopropionic acid or the like is adsorbed to generate a negative charge on the surface. A method in which a molecular electrolyte or a cationic synthetic lipid is physically adsorbed to be positively charged can be applied.

As the cationic polymer electrolyte used for the surface modification of the solid to be treated as described above, polyethyleneimine, poly (1,1-dimethyl-3,5-dimethylene-piperidinium) and the like are preferable. Further, as the cationic synthetic lipid, a synthetic lipid having an ammonium hydrophilic group or the like is suitable.

When the solid to be treated is made of a material having a hydroxyl group on the surface, such as glass or quartz, a surface treatment with a silane coupling agent may be performed. As the silane coupling agent, for example, aminobutyltriethoxysilane, aminopropyltriethoxysilane and the like can be used.

In the present invention, the contact between the surface of the hydrogel or the organogel and the surface of the solid to be treated is sufficient by contacting the surface of the solid to be treated with the weight of the solid itself. Alternatively, pressure can be applied within a range that does not involve deformation of the gel surface. In addition, the contact time in this case is not particularly limited, but is preferably 30 minutes or more in order to realize good transfer. The temperature of the gel or the solid to be treated at the time of contact is not particularly limited, but the gel transition can be performed better at a relatively low temperature.
It is preferable to carry out in the range of 0 to 30 ° C.

After the above-mentioned contact, when the two are peeled off, the surface layer of the gel is transferred to the surface of the solid to be treated, and an ultrathin layer is formed. This ultrathin layer is a layer in which a highly two-dimensional network structure composed of molecular aggregates of a dispersion constituting a gel is transferred at a high density. Although the layer thickness depends on the kind of the gel dispersion used, it is generally 2 to 100 nm, and particularly preferably 2 to 10 nm. The coating rate of the formed ultra-thin layer on the surface of the solid to be treated is preferably 30% or more, and more preferably 80% or more.

Further, in the present invention, after forming an ultrathin layer on the surface of the solid to be treated as described above, the surface is again brought into contact with the surface of the hydrogel or organogel, and then peeled off. The surface layer of the hydrogel or organogel can be further transferred onto the treated solid surface. By repeating such an operation, any number of surface layers of hydrogel or organogel can be laminated on the surface of the solid to be treated, and an ultrathin layer having a thickness controlled at the nanometer level can be manufactured. . Generally, it is preferable to repeat the lamination operation of the ultra-thin layer about 1 to 5 times to produce an ultra-thin layer having a layer thickness of about 4 to 500 nm. Further, by repeating the operation of laminating the ultra-thin layer in this manner, when the coverage of the ultra-thin layer on the surface of the solid to be treated is low, the coverage can be increased.

When the surface of the solid to be treated on which the ultra-thin layer is formed is brought into contact with the surface of the hydrogel or organogel, it is preferable to dry the surface of the solid to be treated first. Drying may be performed, for example, by blowing an inert gas such as a nitrogen gas. Further, prior to drying, the surface of the solid to be treated may be washed with running water or the like.

The above-mentioned lamination is performed not only by using the same kind of hydrogel or organogel, but also by using two or more kinds of ultra-thin composite layers in which different kinds of ultra-thin layers are laminated. May be formed.

[0033]

The method of the present invention comprises a dispersion which forms a hydrogel or an organogel on the surface of a solid to be treated with a very simple method and without the need for special equipment and equipment, with high productivity. Ultra-thin layers can be produced.

Further, the method of the present invention can laminate the ultra-thin layers with nanometer precision, so that various surface characteristics can be designed. Specifically, it is possible to control the hydrophilicity of the surface of a molded product such as a mineral, a metal, and a synthetic polymer. In addition, forming an ultra-thin layer made of a dispersion of an inorganic gel such as silica gel on a synthetic polymer film imparts anti-blocking properties or gas barrier properties to the film, or controls slipperiness. Can be expected. Further, by forming the ultra-thin layer on the surface of a porous separation membrane, it is expected that the permeability of the separation membrane can be adjusted. As described above, the method of the present invention can be a practical basic technique for surface-modifying various articles.

[0035]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Examples 1 and 2 Agarose was added to water at a concentration of 1% by weight, heated and stirred.
When the solution became uniformly transparent, the solution was transferred to another container and allowed to cool to obtain an agarose hydrogel.

As a transfer substrate, graphite (HOPG)
(Example 1) and cleaved mica plate (Example 2)
These were brought into contact with the agarose hydrogel surface.
The temperature of the agarose hydrogel and substrate during contact is 2
It was 0 ° C. After a lapse of 12 hours, the transfer substrate was separated from the gel surface, and the surface was observed with an atomic force microscope. An atomic force micrograph of the graphite substrate is shown in FIG. The atomic force microscope observation was performed using a silicon nitride cantilever in the air under non-contact mode measurement conditions.

Each of the substrate surfaces formed an ultrathin layer in which agarose was well transferred to the substrate. When graphite was used as the transfer substrate, the network structure of the agarose was transferred to the substrate surface with a thickness of about 3 nm, and the coverage on the substrate surface was about 80%, which was covered in a film form. Similarly, when the mica plate was used as the transfer substrate, the mica substrate was coated in a film form from the ultrathin agarose layer at a coverage of about 80%.

When these transfer substrates were immersed in pure water and subjected to ultrasonic treatment for 5 minutes for cleaning, the ultrathin agarose layer was stably held on any of the substrate surfaces and did not peel off. Was.

Example 3 In Example 1, an agarose gel was sequentially transferred using a quartz oscillator covered with a gold electrode as a transfer substrate. The crystal oscillator is known as a microbalance, and is a device that can measure the weight of a thin layer formed on the surface thereof with a change in frequency with an accuracy of 10 ⁻⁹ g.

After the above-mentioned gold-deposited crystal oscillator was subjected to a surface treatment by the following operation, the agarose gel was successively transferred.
Beforehand, concentrated sulfuric acid and a 31% by weight aqueous solution of hydrogen peroxide were mixed at a volume
The solution was mixed in a ratio of one to one, and the solution was applied to the gold electrode portion of the crystal oscillator, and then thoroughly washed with water. After this operation was repeated twice, nitrogen gas was sprayed to sufficiently dry and then used for transfer.

Next, the above quartz oscillator was brought into contact with the same agarose hydrogel as that used in Example 1. The temperature of the agarose hydrogel and the substrate during the contact was 20 ° C. After 30 minutes of contact, the oscillator was peeled off from the gel surface, washed with running water and dried with nitrogen gas, and the frequency of the crystal oscillator was recorded. This transition-
A series of operations consisting of washing and drying was further repeated five times, and an ultrathin agarose layer was sequentially laminated on the crystal oscillator.

Table 1 shows the change in the frequency of the crystal oscillator associated with the above-described transition operation. With each transition operation of the ultra-thin agarose layer, the crystal oscillator showed frequency change. The frequency change due to the first transition is 46 Hz, which corresponds to a transition weight of about 41 ng. 34 Hz after the second transition
[31 ng], 24 Hz [22 ng], 15 Hz [1
4ng], 23Hz [21ng], 19Hz [17n
g) of the agarose ultrathin layer was transferred, and the transfer was performed with good reproducibility.

[0044]

[Table 1]

Example 4 An ultrathin polyacrylamide layer was formed on a polyacrylamide gel by the same procedure as in Example 1 by contacting and peeling off the graphite surface.

The preparation of polyacrylamide gel was carried out by the following method. 4.43 ml of a 30% by weight aqueous solution of acrylamide (containing acrylamide monomer and N, N'-methylenebisacrylamide monomer in a weight ratio of 29 to 1)
Then, a 10% by weight aqueous solution of ammonium persulfate was added thereto, and pure water was added thereto to adjust the total amount to 30 ml. After the aqueous solution was sufficiently deoxygenated, the aqueous solution was poured into a petri dish and left under a nitrogen stream for 20 minutes. Thereafter, 15 μl of N, N, N ′, N′-tetramethyl-ethylenediamine was injected, and the mixture was allowed to stand under a nitrogen stream for 60 minutes. Thus, a 4% by weight polyacrylamide gel was prepared.

As a transfer substrate, graphite (HOPG) was used, which was brought into contact with the surface of the above-mentioned polyacrylamide gel. The temperature of the polyacrylamide gel and the substrate during the contact was 20 ° C. After 12 hours, the substrate was peeled off from the gel surface, and the surface was observed with an atomic force microscope.
The atomic force micrograph is shown in FIG.

In FIG. 2, a polyacrylamide ultra-thin layer is transferred onto a graphite substrate, and has a diameter of about 100 nm to 2 nm.
It had a structure in which 00 nm spherical domains were two-dimensionally integrated. The height of the surface irregularities was about 0 to 6 nm, the coverage of the transferred ultrathin layer on the substrate surface was about 95%, and the film was covered in a film form.

Further, when this transfer substrate was immersed in pure water and subjected to ultrasonic treatment for 5 minutes for washing, the polyacrylamide ultrathin layer was stably held and did not peel off.

Example 5 An ultra-thin layer was formed on an organogel by a contact / peeling operation with the graphite surface in the same manner as in Example 1.

As a dispersion, a cationic amphiphilic compound ([11- (タ 4-
(Dodecylamino) -1-[(dodecylamino) carbonyl] -4-oxobutyl {amino) -11-oxoundecyl] (2-hydroxyethyl) dimethylammonium bromide) was used. Using chloroform as an organic solvent, a chloroform solution prepared by heating (concentration 5
(0 mM) was rapidly cooled to 4 ° C. to obtain an organogel. After leaving this gel at 4 ° C. for several hours, a graphite (HOPG) substrate was brought into contact with its surface. The temperature of the organogel and the substrate during the contact was 4 ° C. After standing for 12 hours, the substrate was peeled off, and the surface was observed with an atomic force microscope. The atomic force micrograph is shown in FIG.

In FIG. 3, a nanostructure having a width of about 170 nm and a thickness of about 23 nm was observed on the graphite substrate. In addition, a spiral structure was observed, and its thickness was about 8
It was 0 nm. With these transitions, the graphite substrate was almost completely covered. The following experiment confirmed that this transition product had a surface layer structure of the organogel formed from an amphiphilic compound and was not formed by drying chloroform as a dispersion medium. That is, the sample obtained by dropping the chloroform solution (concentration: 50 mM) used for preparing the organogel on graphite and drying was subjected to an atomic force microscope, and as a result, the ultrathin layer as described above was not formed.

Further, these transfer substrates are immersed in pure water,
Ultrasonic treatment was performed for 5 minutes for cleaning, and as a result, the ultra-thin layer was stably held and did not peel off.

Example 6 An ultra-thin layer was formed on silica gel by the same procedure as in Example 1 by contacting and peeling off the graphite surface.

The preparation of silica gel was performed by the following method. 8.3 g of tetramethoxysilane is dissolved in 5 g of dimethylformamide, and this solution is added to a solution containing 10 g of water, 3.8 g of methanol, and 0.001 g of ammonia.
It was dripped slowly with stirring. The solution was then added to 3
By leaving it to stand at 5 ° C for 5 hours, a flexible silica gel was obtained.

As a transfer substrate, graphite (HOPG) was used, which was brought into contact with the silica gel surface. The temperature of the silica gel and the substrate during the contact was 20 ° C. 1
After 2 hours, the substrate was separated from the gel surface, and the surface was observed with an atomic force microscope. This atomic force micrograph is shown in FIG.

In FIG. 5, the silica particles were transferred onto the graphite substrate, and had a structure in which spherical domains having a diameter of about 8 to 400 nm were scattered or connected linearly. The height of these domains was about 2-6 nm and the coverage of the transferred ultrathin layer on the substrate surface was about 40%.

Further, these transfer substrates are immersed in pure water,
Ultrasonic treatment was performed for 5 minutes for cleaning, and as a result, the ultra-thin silica particle layer was stably held and did not peel off.

[Brief description of the drawings]

FIG. 1 is an atomic force micrograph showing the surface state of an ultra-thin layer obtained by transferring an agarose gel to a graphite substrate in Example 1.

FIG. 2 is an atomic force micrograph showing the surface state of an ultra-thin layer obtained by transferring a polyacrylamide gel to a graphite substrate in Example 4.

FIG. 3 is an atomic force microscope photograph showing a surface state of an ultra-thin layer obtained by transferring an organogel to a graphite substrate in Example 5.

FIG. 4 is an atomic force microscope photograph showing the surface state of an ultra-thin layer obtained by transferring silica gel to a graphite substrate in Example 6.

Claims (2)

[Claims] 1. The method according to claim 1, wherein the surface of the hydrogel or organogel is brought into contact with the surface of the solid to be treated and then peeled off.
A method for producing an ultra-thin layer on a surface of a solid to be treated, wherein the surface layer of the gel is transferred to the surface of the solid to be treated. 2. The method according to claim 1, wherein at least one surface layer of a hydrogel or an organogel is further transferred onto the surface of the solid to be treated on which the ultra-thin layer has been formed by the method according to claim 1. A method for producing an ultra-thin layer.