WO2009031332A1 - Substrate for crystal growth and method for crystal growth using the substrate - Google Patents

Abstract

This invention provides a substrate for crystal growth, which can realize an increase in size of an aligning film and a reduction in cost. The substrate for crystal growth is characterized in that a buffer layer is formed on the surface of the substrate, and the buffer layer is formed of a nanosheet single layer film of two-dimensional crystals.

Description

 Description Crystal growth substrate and crystal growth method using the same Technical Field

 The present invention relates to a crystal growth substrate and a crystal growth method using the same. Background art

High-quality Z obtained by epitaxial growth or orientation growth on single crystal substrates such as S i, sapphire (ct—A l ₂ 0 ₃ ), S r T i O ₃ , MgO, T i Ο ₂ There are light emitting devices, semiconductor elements, dielectric elements, etc. using n O, G a N, B a T i O _{3 and the} like. If a single crystal substrate can be used in this way, it is preferable because a high-quality epitaxial film or alignment film can be obtained. However, these single crystal substrates have problems such as size limit and high cost. In order to solve such problems, a method has been proposed in which crystal growth is controlled by a substrate in which a buffer layer having a crystal structure similar to the crystal to be grown is introduced on the surface. For example, in recent years, an increase in the size of an epitaxial film using a substrate in which a silicon nitride layer is introduced as a buffer layer on the surface of a quartz glass substrate as a substrate for a nitride semiconductor instead of a single crystal substrate has been reported. (For example, see Patent Document 1). On the other hand, there is also a technique for growing an alignment film using an organic template on a glass or plastic substrate as a buffer layer (see, for example, Non-Patent Document 1). According to Patent Document 1, in order to obtain a high-quality buffer layer having high smoothness and crystallinity, it is necessary to irradiate nitrogen plasma using high frequency or electron cyclotron resonance. Such high frequency and electron cyclotron resonance is expensive. This is not only a costly device but also a problem that the work becomes complicated. In addition, when the buffer layer is manufactured, for example, heat treatment at 400 ° C. to 1 200 ° C. is required, and therefore, the buffer layer is limited to a substrate composed of a base material having thermal stability. According to Non-Patent Document 1, although the organic template that is the buffer layer can be easily applied to the substrate by the self-assembled film, the organic template is unstable to heat. Therefore, the technique of Non-Patent Document 1 is not suitable for crystal growth of inorganic materials such as oxides and nitrides that require high temperatures on an organic template. Patent Document 1: JP 2004-55881 A

 Non-Patent Document 1: R. Hiremath, et al., J. Am. Chem. Soc 2005, 127, 18321 Disclosure of the Invention

 Problems to be solved by the invention

 An object of the present invention is to solve the above-described problems of the prior art, and an object of the present invention is to provide a crystal growth substrate that enables an increase in size and cost of a film for crystal growth. Means for solving the problem

 The crystal growth substrate of the invention 1 is a crystal growth substrate having a buffer layer formed on a surface thereof, wherein the buffer layer is composed of a nanosheet monolayer film made of a two-dimensional crystal.

 Invention 2 is characterized in that, in the crystal growth substrate of Invention 1, the nanosheet monolayer film is peeled off from the layered compound.

Invention 3 is the crystal growth substrate according to Invention 2, wherein the layered compound comprises a layered oxide, a layered phosphate, a layered double hydroxide, a layered metal chalcogenite, and a layered It is selected from the group consisting of kaates.

 Invention 4 is the crystal growth substrate according to Invention 3, wherein the layered compound is a layered oxide, and the nanosheet monolayer film is a titanate nanosheet, a layered perovskite nanosheet, a manganate nanosheet, a niobium tantalate nanosheet, titanium Niobic acid nanosheets, ruthenic acid nanosheets, and tungstate nanosheets are selected from the group consisting of single-layer films.

Invention 5 is the crystal growth substrate according to Invention 4, wherein the manganate nanosheet monolayer film is an MnO ₂ nanosheet monolayer film.

Invention 6, in the crystal growth substrate of the invention 4, the layered base mouth Busukai Tonano sheet monolayer film, characterized in that it is a _{C a 2 N b 3 O 1} 0 nanosheet monolayer film. Invention 7 is the crystal growth substrate according to Invention 3, wherein the layered compound is a layered phosphate salt, and the nanosheet monolayer film is a zirconium phosphate nanosheet monolayer film or a vanadium phosphate nanosheet monolayer film Special feature.

 Invention 8 is the crystal growth substrate of Invention 3, wherein the layered compound is a layered double hydroxide, and the nanosheet monolayer film is a hydroxide nanosheet monolayer film.

 Invention 9 is the crystal growth substrate of Invention 3, wherein the layered compound is a layered metal force rucogenite compound, and the nanosheet monolayer film is a metal chalcogenide nanosheet monolayer film.

 Invention 10 is characterized in that in the crystal growth substrate according to Invention 3, the layered compound is a layered silicate, and the nanosheet monolayer film is a smectite nanosheet monolayer film.

 Invention 11 is the crystal growth substrate according to any one of Inventions 1 to 10, wherein the base material provided with the buffer layer is selected from the group consisting of glass, metal, semiconductor single crystal, and plastic A substrate for crystal growth, wherein

Invention 12 is a crystal growth method using the crystal growth substrate according to any one of Inventions 1 to 9, wherein the lattice lengths a and b of the crystal plane of the alignment film on which the crystal is grown on the crystal growth substrate The two-dimensional lattice shape of the nanosheet monolayer film is set as shown in Table A so that the angle 0 formed by the lattice lengths a and b has a desired relationship. It is characterized by.

 (Table A)

Relation of lattice length a b Angle formed by lattice lengths a and b 0 Two-dimensional lattice shape a = b 0 = 9 0 ° Square a ≠ b 0 = 9 0 ° Rectangular a = b 0 = 1 2 0. Hexagon a ≠ b θ ≠ 9 0 ^{ύParallel quadrilateral} Invention 1 3 is a crystal growth method using the crystal growth substrate of Invention 5, wherein the M n 0 ₂ nanosheet monolayer film is formed. It is characterized in that ΖηΟ is oriented and grown on a growth substrate.

Invention 14 is a crystal growth method using the crystal growth substrate of Invention 6, wherein S r T is formed on the crystal growth substrate on which the C a ₂ N b ₃ 0 _{1 0} nanosheet monolayer film is formed. i O ₃ or T i O ₂ is oriented and grown.

 Invention 15 is a crystal growth method using the substrate for crystal growth of Invention 12 from the group consisting of a sol-gel method, a liquid phase epitaxy method, a physical vapor deposition method and a chemical vapor deposition method. The method selected is used. The invention's effect

 A crystal growth substrate according to the present invention includes a substrate and a nanosheet monolayer film positioned on the substrate. The nanosheet monolayer film is a two-dimensional crystal having a submicro to micrometer spread in the horizontal direction of the sheet, and has high crystallinity comparable to that of a single crystal in the plane. As a result, it has become possible to achieve the same crystal growth as when a conventional single crystal substrate is used regardless of the material of the base material.

Furthermore, by using the nanosheet monolayer film peeled from the layered compound, a seed layer (buffer layer) necessary for crystal growth can be produced at room temperature. Such a seed layer has a feature that individual nanosheets are smooth and there is almost no thickness distribution, and therefore a crystal growth substrate having an extremely smooth surface can be provided. Such a seed layer has a strong bond in the in-plane direction of the sheet and a high structural flexibility. Therefore, the seed layer can be applied to a substrate having an arbitrary shape such as a substrate having a curved surface and a substrate having an uneven surface. Can also be applied, which makes it possible to design according to the device, which is advantageous.

 In addition, by selecting a nanosheet monolayer film that matches the crystal structure of the film to be grown and placing it on the substrate, films having various crystal structures can be easily obtained. Furthermore, due to the high structural flexibility described above, the seed layer can be modified to mitigate the lattice mismatch between the crystal structure of the seed layer and the crystal structure of the film to be grown. As a result, since the restriction of lattice mismatch is relaxed compared to the conventional case, various alignment films can be manufactured, and alignment films with high crystallinity can be obtained. In addition, nanosheet monolayer films can easily be made of any material and any shape using the LB method, alternate adsorption method, spin coating method, etc. without employing an expensive physical Z chemical vapor deposition method. Formed on a substrate. As a result, unlike expensive single crystal substrates and seed layers fabricated using complex techniques, it is possible to use large and inexpensive glass substrates, plastic substrates with low thermal stability, etc. as the substrate. This makes it possible to increase the size and cost of the alignment film. Brief Description of Drawings

 FIG. 1 is a schematic view of a crystal growth substrate according to the present invention.

 FIG. 2 is a schematic diagram of an exemplary nanosheet monolayer film 120.

 FIG. 3 is a diagram showing a manufacturing process of a substrate for crystal growth using the L a n g m u i r -B 10 dge t t (L B) method.

 FIG. 4 is a schematic diagram showing matching between an exemplary nanosheet monolayer film and an alignment film.

Figure 5 shows C a ₂ N b ₃ O t. FIG. 4 is a view showing an AFM image of a glass substrate.

Figure 6 shows C a ₂ N b ₃ O i. In the figure showing the UV-visible absorption spectrum of the glass substrate is there.

FIG. 7 is a diagram showing XRD patterns of the SrTiO ₃ films of Example 1 and Comparative Example 1.

FIG. 8 is a diagram showing XRD patterns of the SrTiO ₃ films of Example 2 and Comparative Example 2.

9, Example _{2 S r T i O 3 (} n = 5) ZC a 2 N b 3 O t. It is a figure which shows the SEM image of the surface of Z glass substrate.

FIG. 10 is a view showing an SEM image of the surface of the SrTiO ₃ (n = 5) Z glass substrate of Comparative Example 2.

FIG. 11 is a view showing an SEM image of a cross section of the SrTiO ₃ (η = 5) / Ca ₂ Nb ₃ O ^ ₀ glass substrate of Example 2.

FIG. 12 is a view showing an SEM image of a cross section of the SrTiO ₃ (n = 5) Z glass substrate of Comparative Example 2.

FIG. 13 is a diagram showing XRD patterns of the Ti ₂ O ₂ films of Example 3 and Comparative Example 3.

FIG. 14 is a diagram showing an AFM image of the MnO ₂ glass substrate.

 FIG. 1′5 is a diagram showing XRD patterns of the ZnO films of Example 4 and Comparative Example 4.

FIG. 16 is a view showing XRD patterns of the SrT i 0 ₃ films of Example 5 and Comparative Example 5.

1 7, S r T i Oa / C a 2 Nb 3 Ot was deposited at a substrate temperature of 5 50 ° C in Example 5. It is the TEM image of the cross section of a glass substrate.

 FIG. 18 is a diagram showing XRD patterns of the ZnO films of Example 6 and Comparative Example 6.

 FIG. 19 is a diagram showing XRD patterns of the ZnO films of Example 7 and Comparative Example 7.

FIG. 20 is a view showing an AFM image of the Cs aW O / P ET substrate of Example 8. FIG. 21 shows C a ₂ Nb ₃ Oi of Example 9. A 1 ₂ 0 ₃ AFM image of single crystal substrate (a) and (b), and A 1 ₂ O ₃ single crystal substrate A before C a ₂ N b ₃ O ₁₀ nanosheet application It is a figure which shows FM image (c) and (d). (Explanation of symbols)

 1 0 0 Crystal growth substrate 1 1 0 Base material 1 2 0 Nanosheet monolayer film

1 3 0 Layered compound 2 1 0 Two-dimensional square lattice

 2 2 0 2D rectangular grid 2 3 0 2D hexagonal grid BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, embodiments of the present invention will be described with reference to the drawings. (1: Crystal growth substrate structure)

FIG. 1 is a schematic view of a crystal growth substrate according to the present invention. A crystal growth substrate 100 according to the present invention comprises a base material 110 and a nanosheet monolayer film 120. As the base material 110, any material and any shape can be applied. Specifically, the base material 110 is selected from the group consisting of glass, metal, semiconductor single crystal (for example, Si substrate), and plastic. In particular, glass and plastic are preferable because they are low cost and a large base material can be obtained. Naturally, conventionally applied metals and semiconductor single crystals may also be adopted as the substrate 110. The nanosheet monolayer film 120 is located on the substrate 110. The nanosheet monolayer film 120 is obtained by exfoliating the layered compound 1330 as a single layer (also simply called exfoliation). As schematically shown in FIG. 1, the layered compound 130 is a highly crystalline inorganic compound having a layered structure in which nanosheet monolayer films 120 are stacked on each other. In addition, the interlayer of the nanosheet monolayer film 120 in the layered compound 130 has a weak bond because it is held by electrostatic force or intermolecular force, but in the plane of the nanosheet monolayer film 120 Has strong bond and high structural flexibility. Nanoshi As shown in FIG. 1, the single-layer film 120 is a two-dimensional crystal extending in the horizontal direction (that is, the in-plane direction of the nanosheet single-layer film), and in the plane, it is as high as a single crystal. It is known to have crystallinity (see, for example, the description of Patent 3726 140). Therefore, the nanosheet monolayer film 120 can be regarded as a completely flat single crystal having a molecular thickness. Such a layered compound 130 is selected from the group consisting of a layered oxide, a layered phosphate, a layered double hydroxide, a layered metal chalcogenate, and a layered silicate. Any of these layered compounds is obtained by peeling off a single layer to obtain a nanosheet monolayer film. Each layered compound will be described in detail.

<When layered compound 130 is a layered oxide>

Nanosheet monolayer film 120 consists of titanate nanosheets, layered perovskite nanosheets, manganate nanosheets, niobium Z tantalate nanosheets, titanate niobate nanosheets, ruthenate nanosheets, and tungstate nanosheets. Selected from the group. More specifically, the titanate nanosheet monolayer is composed of T i i- _δ Ο ₂ (0≤ δ≤0.5), T i i-xM 1 xO ₂ (Ml is V, C r, Mn, F e, C o selected, transition metals from the group consisting of N i and Cu is selected at least one from 0 <x <l), the group consisting of _{T i 3 O 7, T i} 4 O 9 and T i ₅ On Is done. The layered belobskite nanosheet monolayer is A ₂ N a. ― ₃ Β _π 〇 _{3η + 1} (Α is at least one selected from the group consisting of alkaline earth metals including C a and S r, B is Nb or _Ta , n = 3 to 5), N a AT a ₃ Oio (A is at least one selected from the group consisting of alkaline earth metals including C a, S r, etc.), L aNb ₂ 0 ₇ , L a ₂ T i ₃ O ₁₀ and W Selected from the group consisting of ₂ O ₇ . Manganate nanosheet monolayer consists of Mn 0 ₂ , Mn i- _y M2 _y O ₂ (M2 is a transition metal selected from the group consisting of Ni, Co and Fe, 0 <y≤ Selected from the group consisting of 0.5) and Mn ₃ O ₇ . Niobium tantalate nanosheet monolayer film is Nb ₆ O ₁₇ , Nb ₃ O ₈ And T a 0 ₃ . The titanium niobate nanosheet monolayer film is selected from the group consisting of T i N b 0 ₅ , T i ₅ Ν b Ο ₁₄ and Τ i ₂ Ν b 0 ₇ . Ruthenate nanosheet monolayer film and the tungsten nanosheets monolayer film, it respectively, is Ru0 ₂ and C s WuOss.

<When layered compound 130 is a layered phosphate>

The nanosheet monolayer film 120 is each monolayer film of zirconium phosphate nanosheet or vanadium phosphate nanosheet. More specifically, the zirconium phosphate nanosheet monolayer _{film, a - Z r (HPO 4} ) is 2 · H ₂ O or _{γ- Z r PO 4 · H 2} ΡΟ 4 · 2Η 2 0. The monolayer film of vanadium phosphate nanosheet is VOPO ₄ '2 Η ₂膜.

<When layered compound 130 is a layered double hydroxide>

The nanosheet monolayer film 120 is a hydroxide nanosheet monolayer film. Hydroxide nanosheet monolayers are [Μ ² ^-zM ^{3 +} _z (OH) 2] ^{z +} , [M ⁺ !-, M ^{3 +} _z (OH) 2] ^(2z — ^{1) +} , and , O ^ + i— zM ^{4 +} _z (OH) 2] selected from the group consisting of ^{2z +} (0≤z≤0.5). Here, M + is a monovalent metal ion, M ^{2 +} is a divalent metal ion, M ^{3 +} is a trivalent metal ion, and M ^{4 +} is a tetravalent metal ion. For example, M + is L i, M ^{2 +} is, Mg, Mn, F e, Co, N i, Cu, selected from the group consisting of Z n and C a, M ^{3 +} is, A l, C r , Mn, Fe, Co, Ni and La, and M4 ⁺ is Ti or Ζr.

<When layered compound 130 is layered metal chalcogenite>

The nanosheet monolayer film 120 is a metal chalcogenite nanosheet monolayer film. Metal chalcogenite nanosheet monolayer film is Mo S ₂ , WS ₂ , Ding & 52 ₂ 1

It is selected from the group consisting of S _2.

<When layered compound 1 30 is a layered silicate>

The nanosheet monolayer film 120 is a smectite nanosheet monolayer film. Sume Quetite nanosheet monolayers are (A 1 _2- 'Mg') S i ₄ Oio (OH) ₂ '-(0 <1 2), Mg a (S i- _m A 1 Oio (OH) ₂ ^m — Selected from the group consisting of (0 <m <4) and A 1 (S i 1 Oio (OH) "one (0 <π <4). Figure 2 shows an exemplary nanosheet monolayer 120 Figures 2 (A), (B), and (C) show C a ₂ Nb ₃ O _{1 (} ) (A ₂ N a _n - ₃ in the nanosheet monolayer film 120 described above, respectively. B _n O _{3n + 1} where n = 3, A = C a and B = Nb), Ti is a schematic diagram of aO ₂ and MnO _2. C a ₂ Nb ₃ O ₁₀ (Fig. 2 (A) ), T i ι-δ0 ₂ (Fig. 2 (Β)) and Mn0 ₂ (Fig. 2 (Ο)) have thicknesses of 1.5 nm and 0.71 111 and 0.5 nm, respectively. 2A to 2C, the length in the sheet plane direction is in the range of several hundreds of nanometers to several tens of micrometers, depending on the size of the layered compound. Single layer film 1 Depending on the type of 20 The thickness of the no-sheet monolayer film 120 is uniquely determined by the structure of the base layered compound, and thus has almost no thickness distribution, which produces a seed layer having a uniform thickness distribution. In addition, since the nanosheet monolayer film 120 has a thickness of only about 1 to 2 nm as described above, an extremely thin seed layer can be formed. The nanosheet monolayer film 120 is a two-dimensional crystal that spreads in the horizontal direction and has a two-dimensional lattice, for example, C. a ₂ Nb ₃ O ₁₀ (Fig. 2 (A)), T i,-, 0 ₂ (Fig. 2 (B)) and Mn0 ₂ (Fig. 2 (C)) are two-dimensional square lattices 21 0, 2 Has a two-dimensional rectangular lattice 220 and a two-dimensional hexagonal lattice 230. Table 1 shows various nanosheets The relationship between the single-layer film 120 and the two-dimensional lattice is shown.

 Table 1: Relationship between ¾ nanosheet monolayers and lattices

As shown in Table 1, the nanosheet monolayer film 120 has one of a two-dimensional square lattice, a two-dimensional rectangular lattice, a two-dimensional hexagonal lattice, and a two-dimensional parallelogram lattice. As will be described later, by selecting a nanosheet monolayer film 1 2 0 having a two-dimensional lattice that matches the crystal structure of the alignment film to be grown and placing it on the substrate, alignment films having various crystal structures can be obtained. Can be easily obtained. Shown in Table 1 The lattice constant of the nanosheet monolayer film 120 is one of measured values, literature values, and estimated values.

 The inventors of the present application have found that the use of such a nanosheet monolayer film 120 as a seed layer (buffer layer) results in a crystal growth substrate comparable to the single crystal substrate. That is, the present inventors have found that an alignment film is formed on the nanosheet monolayer film 120 using the crystal structure of the nanosheet monolayer film 120. As described above, the nanosheet monolayer film 120 reflects the crystallinity of the layered compound 130 as the starting material and has extremely high crystallinity, and therefore has a high order of magnitude comparable to that of a single crystal substrate. It has a surface structure. As a result, the alignment film obtained can also be a high-quality film with high crystallinity reflecting the surface structure. The nanosheet monolayer film 120 has various constituent elements, a two-dimensional crystal lattice, and a lattice constant, as described with reference to Table 1, for example. Based on matching with the alignment film to be formed A wide range of material design is possible. The nanosheet monolayer film 120 is on the order of nanometers and has no film thickness distribution. By using such a nanosheet monolayer film 120 as a seed layer, a smooth crystal growth substrate can be obtained. On the other hand, the nanosheet monolayer film 120 reflects the size of the layered compound 130 as a starting material in the in-plane direction of the sheet, and has a spread of submicron to several tens of micrometers. Therefore, the substrate can be coated with the nanosheet monolayer film 120 at a high coverage. This is preferable for increasing the area of the crystal growth substrate. Further, the nanosheet monolayer film 120 is obtained by peeling off the base layered compound 130, and thus has a smooth atomic surface. Since such a nanosheet monolayer film 120 is used as a seed layer, the substrate for crystal growth also has a step-free surface in the nanosheet monolayer film plane, and the alignment film to be formed is of good quality. .

The schematic and exemplary crystal growth substrate 100 according to the present invention has been described above with reference to FIG. In particular, the nanosheet monolayer film 120 has been described as a complete monolayer film over the entire substrate 110, but is not limited thereto. Very good In order to obtain a high-quality alignment film, it is desirable that the nanosheet monolayer film 120 is a complete monolayer film over the entire base material 110, but depending on the crystallinity required for the alignment film to be obtained. Need not be a complete monolayer over the entire substrate. For example, the nanosheet monolayer film 120 is partially overlapped as long as it contributes to the crystallinity of the nanosheet monolayer film 120 described above and the crystallinity of the alignment film in which the two-dimensional crystal lattice should be formed. It may be a film (partially a multilayer film). Next, a method for manufacturing the crystal growth substrate 100 according to the present invention will be described.

(2: Manufacturing method of substrate for crystal growth)

An exemplary method for manufacturing a crystal growth substrate according to the present invention will be described step by step. FIG. 3 is a diagram showing a process for manufacturing a substrate for crystal growth using the Langmuir-Blodgett (LB) method. Step S 3 10: Prepare a colloid solution containing nanosheets. For example, when a layered oxide is selected as the layered compound, the colloid solution is obtained by introducing a bulky guest such as tetra-n-butylammonium hydroxide after a hydrogen ion exchange of the layered oxide. Obtained by exfoliation (see, for example, patent 3726140 by the inventors). In the LB method, a diluted colloid solution is used as a developing solution. The colloid solution is developed in a trough (aquarium), and a part of the nanosheet that has been separated from the single layer floats at the gas-liquid interface. As the layered compound, the layered compound described with reference to FIG. 1 is adopted. Step S320: The base material is immersed in a colloid solution to form a nanosheet monolayer film on the base material. In the LB method, the substrate is immersed in a trough, and then the surface of the developing solution is compressed to a certain surface pressure to form a nanosheet monolayer film at the gas-liquid interface. The nanosheet monolayer film is transferred (formed) onto the substrate by pulling up from the solution. In addition, a specific nanosheet monolayer film using the LB method For example, see Muramatsu et al., Langmuir 2 0 0 5, 5, 1, 6 5 9 0 to 6 5 9 5 for the development of the substrate. Again, the base material described with reference to Fig. 1 is adopted as the base material. The nanosheet monolayer film on the substrate thus obtained has an extremely smooth surface with no grain boundaries or steps in the range of a few micrometers, so that the size of the alignment film can be increased. It is valid. Although FIG. 3 illustrates the case where the LB method is used, the production of the crystal growth substrate according to the present invention is not limited to the LB method. The crystal growth substrate according to the present invention may be manufactured using an alternate adsorption method. Even when the alternate adsorption method is used, the above-described step S is performed except that a step of adding a polymer having a charge opposite to that of the nanosheet monolayer film to be formed on the substrate in advance to the substrate surface is added. Same as 3 1 0 and S 3 2 0. In this case, it is preferable because the adhesion of the nanosheet monolayer film to the substrate is improved by electrostatic interaction.

Further, the crystal growth substrate according to the present invention may be manufactured using a spin coating method. In this case, the nanosheet monolayer film is easily formed on the substrate as compared to the LB method or the alternate adsorption method, but may partially overlap, making it difficult to obtain a good quality nanosheet monolayer film. . However, even such a nanosheet monolayer film can contribute to the improvement of crystallinity of the alignment film to be formed thereon. Therefore, the method for manufacturing the crystal growth substrate may be appropriately selected according to the degree of crystallinity required for the alignment film to be obtained. The crystal growth substrate according to the present invention is obtained by steps S 3 10 and S 3 2 0. Steps S 3 1 0 and S 3 2 0 are both cost effective because they do not require expensive physical Z chemical vapor deposition (MBE, sputtering, PLD, MO CVD, etc.) It is also a green chemical (energy-saving, low environmental load). In addition, the substrate for crystal growth according to the present invention is manufactured at room temperature without heat treatment because the nanosheet monolayer film has high crystallinity. As a result, materials with low thermal stability other than glass (for example, plastic) can also be used as the base material. Such materials are inexpensive and can be made larger. Therefore, it will contribute to the enlargement and cost reduction of the target alignment film. Although FIG. 3 illustrates an example in which a substrate-like flat plate is used as a base material, the base material of the present invention is not limited to this. As described above with reference to FIG. 1, the nanosheet monolayer film has high structural flexibility in addition to strong bonding in the in-plane direction of the sheet. In addition, a nanosheet monolayer film can be formed while maintaining the bonding in the in-plane direction of the sheet (that is, while maintaining the crystal structure). As a matter of course, the characteristics of the nanosheet monolayer film are maintained even on a substrate having a curvature or a substrate having irregularities, so that it can be a single crystal and a step-free seed layer. Thus, since the nanosheet monolayer film according to the present invention can be applied to a substrate having an arbitrary shape, it is advantageous in material design. Next, the relationship between the crystal growth substrate according to the present invention and the alignment film produced thereon will be described.

(3: Relationship between crystal growth substrate and alignment film)

By using the crystal growth substrate according to the present invention, an alignment film can be obtained without using a conventional expensive single crystal substrate. Oriented growth is realized under the condition that the crystal structure consistency between the nanosheet monolayer film of the crystal growth substrate and the target oriented film is high. It is known that when a predetermined material is oriented and grown on a substrate, a lattice mismatch between the substrate and the predetermined material contributes. Usually, in the field of thin film growth, it is desirable that the crystal structure of the substrate and the predetermined material be the same, and the absolute value of the lattice mismatch be small. A specific example will be described. FIG. 4 is a schematic diagram showing matching between an exemplary nanosheet monolayer film and an alignment film. Figure 4 (A) shows that the nanosheet monolayer film is ○ & ₂ 1> ₃ 0 _{1 0} , and the alignment film is S r T a case of i O _3, FIG. 4 (B) is a Ca ₂ Nb ₃ O ₁₀ is nanosheet monolayer film, the case alignment film of anatase T i 0 _2, FIG. 4 (C) nanosheet This is the case when the single layer film is MnO _z and the alignment film is Z ηθ. Figure 4 (D) shows the case where the nanosheet monolayer film is C s AWUO and the alignment film is ZnO. C a zNbaOi as described with reference to Figure 2 (A). Has a structure related to the perovskite structure and has a two-dimensional square lattice. As shown in Fig. 4 (A), the lattice length of the two-dimensional square lattice is a = b = 3.86 A (0.386 nm). On the other hand, SrTiO _{3, which} is known as a dielectric material, has a cubic system of buzzite structure and its (100) plane has a square lattice. The lattice length of the square lattice of S r T i Oa (100) is a = b = 3.9A (0. 390 η m). (Of course, the angle Θ between a and b is 90 °. is there). Nanosheet monolayer film C a ₂ Nb ₃ Oi. The surface and S r T i 0 ₃ (100) have the same crystal structure, and their lattice lengths are very close. The lattice mismatch calculated from the lattice length is 1% or less, and this value is the nanosheet monolayer film C a ₂ N b ₃ Ο. This suggests that S r T i O ₃ (100) is oriented and grown. Similarly, as shown in Fig. 4 (Β), the (001) plane of anatase T i O ₂ known as a photocatalytic material also has a square lattice. The lattice length of the square lattice of T i O ₂ (001) is a = b = 3. 79 A (0. 379 nm) (Of course, the angle 0 between a and b is 90 ° ). Nanosheet monolayer C a ₂ Nb SOL. The surface and T i 0 ₂ (00 1) have similar crystal structures and their lattice lengths are very close. The mismatch calculated from the lattice length is about 1.8%, which is the nanosheet monolayer C a ₂ Nb ₃ Oi. This suggests that Ti O ₂ (001) grows on the surface. As explained with reference to Fig. 2 (C), MnO ₂ has a two-dimensional hexagonal lattice. The lattice length of the two-dimensional hexagonal lattice is a = b = 2. 87 A (0. 287 nm), and the angle Θ between a and b is 120 °. On the other hand, known as a semiconductor material Z nO has a Wurtzite type (hexagonal) structure, and its (001) plane has a hexagonal lattice. The lattice length of the hexagonal lattice of Z nO (00 1) is a = b = 3.25 A (0. 3 25 nm), and the angle 0 between a and b is 120 °. As shown in FIG. 4 (C), and the nanosheet monolayer film Mn_〇 ₂ and ZnO (001), has the same hexagon grid and the lattice length is relatively close. The mismatch calculated from the lattice length is about 13%. This value is relatively large, but suggests that ZnO (001) may grow on the nanosheet monolayer MnO ₂ by orientation. To do. Similarly, as shown in Figure 4 (D), CS

Has a two-dimensional hexagonal lattice. The lattice length of the two-dimensional hexagonal lattice is a = b = 7.3 A (0.73 nm), and the angle Θ between a and b is 120 °. As described above, the lattice length of ηηθ is a = b = 3.25 A (0. 325 nm), and C s ₄ W i O ₃₆ and Z n O seem to be lattice mismatch. However, when four unit lattices of the alignment film are included in one unit lattice of the nanosheet monolayer film, the lattice mismatch is about 12%. As a result, C s AWHO and Z nO are lattice matched. Although FIG. 4 exemplarily described the relationship between the crystal growth substrate according to the present application and the alignment film oriented thereon, the present invention is not limited to this. The general relationship between the nanosheet monolayer film of the crystal growth substrate according to the present invention and the alignment film oriented thereon is the lattice length a and b of the alignment surface of the alignment film, and the angle formed by the a and b. Using Θ, the following can be summarized as 1) 4).

1) When a = b and 0 = 90 °, the nanosheet monolayer has a two-dimensional square lattice. This corresponds to the case of Fig. 4 (A) and (B).

 2) When a ≠ b and θ = 90 °, the nanosheet monolayer has a two-dimensional rectangular lattice.

 3) When a = b and θ = 120 °, the nanosheet monolayer has a two-dimensional hexagonal lattice. This corresponds to the cases of Fig. 4 (C) and (D).

4) When a ≠ b and 0 ≠ 90 °, the nanosheet monolayer has a two-dimensional parallelogram lattice. In addition, as described above, the absolute value of the lattice mismatch between the lattice length of the two-dimensional crystal lattice of the nanosheet monolayer film and the lattice length of the alignment plane of the alignment film to be manufactured thereon should be small. Is desirable. However, as described above, since the nanosheet monolayer film has high structural flexibility, the lattice mismatch can be mitigated by the deformation of the nanosheet monolayer film. As a result, since the strain for relaxing the lattice mismatch can be suppressed in the alignment film, a high-quality alignment film having high crystallinity can be obtained. As described above, the crystal growth substrate of the present invention is advantageous in the production of the alignment film because the lattice mismatch limit is smaller than in the case of using the conventional rigid buffer layer. Table 2 shows exemplary alignment films and their structural characteristics. Table 2 also shows the crystal lattice of the alignment layer for reference.

Table 2: Example iWJl Self-directed Moon fc and Sokyo Professor For example, if one skilled in the art refers to Table 1 and Table 2, the nanosheet monolayer film that is the seed layer of the substrate for crystal growth and the matching orientation A combination of membranes can be appropriately selected. Thus, the crystal growth substrate of the present invention is advantageous for material design because the selection range of the nanosheet monolayer film is extremely wide. The crystal growth substrate according to the present invention is not limited to the alignment film shown in Table 2 above, and any material that matches the nanosheet monolayer film can be obtained as the alignment film. Please understand that you can.

 When an alignment film is produced using the crystal growth substrate of the present invention, a liquid phase epitaxial growth method such as a sol-gel method such as a spin coating method, a dip coating method, or a spray coating method, a gradient method, or a sliding boat method, Physical vapor deposition methods such as pulsed laser deposition (PLD), molecular beam epitaxy (MBE), sputtering, resistance heating deposition, electron beam deposition, and thermal CVD, photo CVD, plasma CVD, Chemical vapor deposition methods such as organometallic CVD can be used.

 In particular, when the substrate for crystal growth according to the present invention is combined with a dry process (eg, PLD, MBE, sputtering, plasma CVD, etc.) among the above methods, the alignment film is formed at a low temperature and further at a room temperature. It becomes possible to form. As a result, an inexpensive plastic substrate with low thermal stability and a large size can be used as the base material for the crystal growth substrate, so that cost reduction is achieved. Next, examples will be described, but it should be noted that the present invention is not limited to the examples.

(Example 1)

As a layered compound, KC a ₂ Nb ₃ O ₁₀ was exfoliated according to the procedure described in Ebina et al., Solid State Ionics 2002, 1 51, 1 77, and C a ₂ Nb SOL. A colloid solution containing nanosheets was obtained. More specifically, K ₂ CO ₃ , C a O and Nb ₂ 0 ₅ are mixed and calcined at 1 200 ^ for 12 hours, and KCazNbaOt. Was synthesized. Next, KC a ₂ Nb _{3 10} was ion-exchanged with HN0 ₃ (5M) to obtain HC a zNbaO ^ * 1.5H ₂ O. HC a ₂ Nb ₃ O ₁₀ '1.5H ₂ O was reacted with an aqueous solution containing tetra-n-butylammonium hydroxide and separated into a single layer to obtain a colloid solution (step S 31 above). Hi). In this way, the ability to perform single-layer exfoliation of nanosheets using a soft chemical method is also advantageous for energy saving in the process. The colloid solution was diluted with ultrapure water (eg, C azNbaOi. In the case of nanosheets, it was about 0.08 g cm– ³ ) and placed on the trough. In the present specification, it is a layered compound that has been peeled off in a single layer, It should be noted that a material that does not exist is simply referred to as a “nanosheet”, and a material that intentionally forms a “nanosheet” is referred to as a “nanosheet monolayer film”. As the base material, a # 1 737 non-strengthening re-borosilicate glass substrate (obtained from Corning Co. L t d., Hereinafter simply referred to as a glass substrate) was used. The glass substrate was washed by immersing it in HC lZCHaOH solution and then in concentrated H ₂ SO ₄ solution for 30 minutes each. CazNbaOi using the LB method on the cleaned glass substrate. Nano sheet colloid solution. From the solution C a ₂ Nb ₃ Oi. A nanosheet monolayer film was formed. Specifically, the cleaned glass substrate was immersed in a trough that maintained the above conditions, and the surface was compressed at a speed of 0.5 mm * s_— ¹ . Next, the glass substrate was pulled up at a vertical pulling rate of lmm · min ¹ while maintaining a constant surface pressure (step S 320 described above). Ca ₂ Nb ₃ Oi. The nanosheet monolayer film was formed on the glass substrate with a surface pressure of 8.5 mN * ni- ¹ . The best C a ₂ N b ₃ O when the surface pressure is 8. SmN'm- ¹ . It was confirmed that a nanosheet monolayer film was obtained. In this way, a crystal growth substrate was obtained. The obtained substrate for crystal growth, the C a ₂ Nb ₃ O ₁₀ Z glass substrate, was observed using an atomic force microscope AFM (SP A400, Seiko Instrume nts Inc., Japan) . The AFM observation was performed in a tapping mode using a silicon chip cantilever. The observation results are shown in Fig. 5 and described later. The ultraviolet-visible light absorption spectrum of the Ca ₂ Nb ₃ 0 ₁₀ glass substrate was measured using a spectrophotometer (U-4 100, Hitachi). The results are shown in Fig. 6 and described later.

Next, an SrTiO ₃ film was aligned on a C azNbsOwZ glass substrate by spin coating. Specifically, SrTiO ₃ coating solution (precursor sol or simply called sol) was prepared using strontium acetate and titanium isopropoxide (TTIP). Acetic acid was used as the solvent, and 2,4-pentanedione (acetylacetone: A c A c) was used as the stabilizer. Mix TT IP with Ac Ac at a mixing ratio of 1: 1 and add to the acetic acid solution in which strontium acetate is dissolved. did. The resulting clear solution was stirred continuously for 12 hours in a closed flask. Then, methanol was added to the clear solution to obtain a S r T i O ₃ Kotin grayed solution 0. 3M. S r T i O ₃ coating solution is spin-coated with C a 2 Nb 3 O. It was applied on a glass substrate and then dried on a hot plate heated to 120 ° C. for 1 minute. The spin coat rotation speed was 2500 rpm. Next, the Ca ₂ Nb ₃ 0 ₁₀ glass substrate to which the SrTiO ₃ coating solution was applied was used in an atmosphere at 500 ° C, 550 ° C, 600 ° C and 650 ° C using an electric furnace. Baked for 1 hour each. The crystal planes and crystal orientation of the samples fired at each firing temperature were examined by powder X-ray diffraction (XRD). A powder X-ray diffractometer (R int 2200, Rigaku) was used for the measurement. The measurement conditions were a monochromated CuKa line, an acceleration voltage of 40 kV, and an applied current of 4 OmA. The results are shown in Fig. 7 and described later.

(Comparative Example 1)

In Example 1, C a zN b aO t on a cleaned glass substrate. Since it is the same as Example 1 except that the SrTiO ₃ coating solution is directly applied by spin coating without forming the nanosheet monolayer film, the description is omitted. In the same manner as in Example 1, the crystal plane and crystal orientation of the sample fired at each firing temperature were examined using XRD. The results are shown in Fig. 7 and described later.

(Example 2)

In Example 1, grant of S r T i O ₃ coating solution by spin coating, drying on a hot plate, and the operation of firing at 550 ° C, was repeated until either et 5 times once Other than this, the description is omitted because it is similar to the first embodiment. The crystal plane and crystal orientation of each application (coating) sample were examined using XRD. The results are shown in Fig. 8 and described later. The surface and cross-section of the sample with 5 application times were observed using a scanning electron microscope SEM (S-4200, Hitachi). The results are shown in Figure 9 and This is shown in Figure 11 and will be described later. (Comparative Example 2)

In Comparative Example 1, grant of S r T i 0 ₃ coating solution by spin coating, drying on a hot plate, and the operation of firing at 550 ° C, was repeated until either et 5 times once Other than this, the description is omitted because it is the same as Comparative Example 1. The crystal plane and crystal orientation of the sample with each application number were examined using XRD. The results are shown in Fig. 8 and described later. The surface and cross section of the sample with 5 application times were each observed using SEM. The results are shown in Fig. 10 and Fig. 12 and will be described later.

(Example 3)

In the same manner as in Example 1 to obtained a substrate for crystal growth, to align the T i 0 ₂ film C a ₂ Nb ₃ O ₁₀ Z glass base plate. In particular, the T I_〇 ₂ coating solution, a coating solution is based on a commercially available titanium I Seo propoxide (NDH- 510 C;.. N ippon S oda C o L t d, To kyo, J apan force ^¾ et obtain ) Was used. The TiO ₂ coating solution was applied onto a Ca ₂ Nb ₃ Oio / glass substrate by spin coating, and then dried on a hot plate heated to 120 ° C. for 1 minute. The rotation speed of the spin coat was 1 500 rpm. Then C a sNbaOi provided with T i O ₂ coating solution. / The glass substrate was baked at 500 ° C for 1 hour in the air using an electric furnace. The crystal plane and crystal orientation of the fired sample were examined by XRD. The results are shown in Fig. 13 and will be described later.

(Comparative Example-3)

In Example 3, since a glass substrate is used instead of the crystal growth substrate and the TiO ₂ coating solution is directly applied by a spin coating method, the description is omitted because it is the same as Example 3. As in Example 3, the crystal plane and crystal orientation of the fired sample were examined by XRD. The results are shown in Fig. 13 and will be described later. (Example 4)

Ko. ₄₅ Mn 0 ₂ to Om omo et a layered compound, according to the procedure described in J. Am. C he m. S oc. 2003, 1 25, 3568, and peeling single layer of MnO ₂ nanosheet monolayer film A colloid solution was obtained (step S 3 10 above). In the same manner as in Example 1, the colloid solution was diluted with ultrapure water (c a. 0.08 gcm ³ ) and developed on a trough. In the same manner as in Example 1, the glass substrate was washed, and an MnO ₂ nanosheet monolayer film was formed using the LB method (step S 320 described above). The MnO ₂ nanosheet monolayer film was formed on the glass substrate at a surface pressure of 8. OmN · m- ¹ . In this way, a crystal growth substrate was obtained. The obtained crystal growth substrate, MnO ₂ Z glass substrate, was observed using AFM. The observation results are shown in FIG. Next, the Z Itashita film was oriented growth by spin coating Mn0 ₂ / glass substrate. Specifically, zinc acetate (dihydrate) [Z n (CHaCOO) ₂ · 2Η ₂₀ ] is dissolved in an isopropanol solution with a predetermined amount of diethanolamine (molar ratio 1: 1) as a chelating ligand. A 0.2 Ζ ηθ coating solution was prepared. Zeta Itaomikuron coating solution was applied to Myuitaomikuron ₂ glass substrate by a spin encoding method, and dried on a hot plate heated to 1 20 ° C 1 min. The spin coat rotation speed was 2500 rpm. Then, the Mn0 ₂ Z glass substrate Z nO Koti packaging solution has been applied, using an electric furnace in the atmosphere, and baked for 1 hour at 40 0 ° C. This operation was repeated 1 to 5 times. The crystal plane and crystal orientation of the sample with each application number were examined using XRD. The results are shown in Fig. 15 and described later.

(Comparative Example 4)

In Example 4, a glass substrate is used instead of the crystal growth substrate, and the Z ηθ coating solution is directly applied by a spin coating method. In the same manner as in Example 4, the crystals of the samples each given number of times The orientation of the plane and crystal was examined by XRD. The results are shown in Figure 15 and described later. The experimental conditions of Examples 1 to 4 and Comparative Examples 1 to 4 are summarized in Table 3.

 Table 3: Live cattle in examples 1-4 and tandem 1-4

(Example 5)

C a ₂ Nb ₃ Oi produced in Example 1. / Sr T i 0 ₃ films were grown on glass substrates by pulsed laser deposition. Specifically, K r F excimer monodentate (wavelength 248 nm, C omp exl 02) as a laser was used _{S r T i O 3 (100} ) plane of the single crystal, respectively as a target. The laser was introduced into the chamber through a quartz glass window installed in the vacuum chamber. The film forming conditions are shown below. Laser intensity: approx. 3 J cm ²

 Distance between target and substrate: 50mm

Substrate: C a ₂ N b sOt. Glass substrate

 Oxygen partial pressure: 0.12 Pa

 Substrate temperature: 500 ° C and 550 ° C

Deposition time: 60 minutes The crystal planes and crystal orientations of the samples obtained at substrate temperatures of 500 ° C. and 550 ° C. were examined by powder X-ray diffraction (XRD) in the same manner as in Example 1. The measurement conditions were an acceleration voltage of 40 kV, an applied current of 40 mA, a diverging slit (DS) and a scattering slit (SS) of 12 °, and a receiving slit (RS) of 0.3 mm. The measurement results are shown in FIG.

 The cross section of the sample obtained at a substrate temperature of 550 ° C was observed using a high-resolution transmission electron microscope (HR TEM, JEM-2010, JEOL). The sample for HRTEM was prepared by Ar ion milling. The observation results are shown in Fig. 17 and will be described later.

(Comparative Example 5)

Example 5 is the same as Example 5 except that a glass substrate was used instead of the crystal growth substrate and the SrTiO ₃ film was directly grown by the pulse laser method, so the description was omitted. To do. In the same manner as in Example 5, the crystal planes and crystal orientations of the samples obtained at the substrate temperatures of 500 ° C. and 550 ° C. were examined by XRD. The results are shown in Fig. 16 and described later.

(Example 6)

A ZnO film was grown on the MnO ₂ / glass substrate prepared in Example 4 by pulsed laser deposition. Specifically, a KrF excimer laser (wavelength: 248 nm, Camp exl 02) was used as the laser, and a polycrystalline ZnO pellet was used as the target. The film forming conditions are shown below.

Laser intensity: approx. 1.7 J / cm ²

Distance between target and substrate: 50mm

Substrate: MnO ₂ / Glass substrate

Oxygen partial pressure: 0.12 Pa

Substrate temperature: room temperature (no heating)

Deposition time: 180 minutes

The crystal plane and crystal orientation of the obtained sample were measured by XRD as in Example 5. I investigated. The measurement results are shown in Fig. 18 and will be described later.

(Comparative Example 6)

 Example 6 is the same as Example 6 except that a glass substrate is used instead of the crystal growth substrate and the Z ηθ film is directly grown by the pulse laser method, and thus the description thereof is omitted. As in Example 6, the crystal plane and crystal orientation of the obtained sample were examined by XRD. The results are shown in Fig. 18 and described later. '

(Example 7)

The CS 6. ₃₁ WnO ₃₆ as layered compound releases Tanso剥intercalation method. Specifically, ion exchange was performed by treating C s 6. ₃₁ WnO ₃₆ with an acid (here, 12N hydrochloric acid was used and reacted for 24 hours × 2 times). This

We obtained a hydrogen ion exchanger in which hydrogen ions or oxonium ions were introduced between CS 6. ₃₁ Wn0 ₃₆ host layers. Next, a hydrogen ion exchanger and a cationic exfoliation promoter (here, tetraammonium ion TBA +) was mixed and shaken at room temperature. As a result, a colloid solution of CS 4W 036 nanosheet monolayer film was obtained (step S 310 described above). In the same manner as in Example 1, the colloid solution was diluted with ultrapure water (ca. 0.08 g cm- ³ ) and developed on a trough. In the same manner as in Example 1, the glass substrate was washed, and a C s AWUO nanosheet monolayer film was formed using the LB method (step S 320 described above). CS

The nanosheet monolayer film was formed on a glass substrate by spreading the colloid solution in a trough and letting the glass substrate stand for 30 minutes after immersion. Next, after compressing to a surface pressure of 1 8. OmN · m− ¹ , the glass substrate was pulled up vertically. In this way, a crystal growth substrate made of CS 4WHO36 / glass substrate was obtained.

Next, a ZnO film was grown on a C s ₄ WnO ₃₆ / glass substrate by pulsed laser deposition. Specifically, a KrF excimer laser (wavelength 248 ηm, Camp exl 02) was used as the laser, and a polycrystalline ZnO pellet was used as the target. The film forming conditions are shown below. Laser intensity: approx. 1.7 J / cm ²

 Distance between target and substrate: 5 Omm

Board: C s

Board

 Oxygen partial pressure: 0.1 2 Pa and 1.7 Pa

 Substrate temperature: room temperature (no heating) and 100 ° C

 Deposition time: 1 80 minutes

 The crystal plane and crystal orientation of each sample obtained at different oxygen partial pressures and substrate temperatures were examined by XRD as in Example 5. The measurement results are shown in Fig. 19 and described later.

(Comparative Example 7)

 Example 7 is the same as Example 7 except that a glass substrate is used instead of the crystal growth substrate and the Z ηθ film is directly grown by the pulse laser method, and thus the description is omitted. As in Example 5, the crystal plane and crystal orientation of the obtained sample were examined by XRD. The results are shown in Fig. 19 and described later. Table 4 summarizes the experimental conditions of Examples 5-7 and Comparative Examples 5-7.

Table 4: Cattle in rows 5-7 and J: country 5-7 (Example 8)

In Example 7, a crystal growth substrate was produced using a polyethylene terephthalate substrate (hereinafter simply referred to as a PET substrate) instead of the glass substrate. The surface of the PET substrate was cleaned by UVZO ₃ treatment for 1 hour. As a result, the surface of the PET substrate was in a hydrophilic state, and water wettability was improved. For the pretreatment of the PET substrate, any means for improving the wettability of the surface of the PET substrate to water can be used. For example, plasma treatment may be performed instead of uv / o ₃ treatment. . A CS 4WHO36 nanosheet monolayer film was formed on the PET substrate thus treated using the LB method in the same manner as in Example 7, and C s ₄ \ ^ ₁₁ 0 ₃₆ A crystal growth substrate consisting of a £ 10 substrate was obtained. The surface of the obtained crystal growth substrate was observed using AFM as in Example 1. The observation results are shown in Fig. 20 and will be described later.

(Example 9)

In Example 1, a step structure appears on the surface instead of the glass substrate. Α 1 ₂ Ο ₃ (000 1) Single crystal substrate (hereinafter simply referred to as A 1 ₂ 0 ₃ single crystal substrate) The substrate for crystal growth was produced using it. The A 1 ₂ O ₃ single crystal substrate was treated with UVZ03 for 30 minutes to clean the surface. On the treated A 1 ₂ O ₃ single crystal substrate, a C a ₂ Nb ₃ O ₁₀ nanosheet monolayer film was formed using the LB method in the same manner as in Example 1, and C a ₂ Nb sOio / A 1 ₂ Ο _A crystal growth substrate composed of _three single crystal substrates was obtained. The surface of the obtained crystal growth substrate was observed using AFM as in Example 1. The observation results are shown in Fig. 21 and will be described later. Figure 2 shows C a zNbsOt. An AFM image of the surface of the A 1 ₂ O ₃ single crystal substrate before the nanosheet monolayer is also shown. Hereinafter, the results of Examples 1 to 9 and Comparative Examples 1 to 7 will be described in detail. FIG. 5 is a diagram showing an AFM image of the C a ₂ N b ₃ 0 _{1 (} ) Z glass substrate. According to Figure 5, very flat C a ₂ Nb ₃ Ot on a glass substrate. It can be seen that the nanosheet monolayer film was formed. Such a surface is extremely small between nanosheets It is comparable to a flat single crystal at the atomic level, except for the overlap and gaps. The surface roughness (R a) was calculated to be 0.6 1 nm. The film thickness of the nanosheet monolayer film was 1.5 to 1.6 nm. This value is C a ₂ N b. This agrees with the crystallographic thickness of the nanosheet monolayer film (see Fig. 2 (A)), suggesting that a monolayer film was formed on the glass substrate. At a surface pressure of 8.5 mN · m- ¹ , the Ca ₂ N b ₃ 0 ₁₀ nanosheet monolayer was applied to 95% of the area of the glass substrate, indicating that there was the least overlap between nanosheets. Figure 6 shows C a ₂ Nb sOi. It is a figure which shows the ultraviolet visible absorption spectrum of a glass substrate. From FIG. 6, the broad absorption edge below 300 nm is due to the nanosheet monolayer film, and the absorbance at 200 nm was about 0.1. According to the molar extinction coefficient of the nanosheet monolayer film (ε = 4. 3 9 X 1 0 ⁴ m ο 1 ^_1 · dm ³ · cm '@ 20 0 nm), this value is It was found to be comparable to the theoretical value (absorbance = 0.0.94) when. This suggests that the Ca ₂ Nb ₃ O ₁₀ nanosheet formed by the LB method is a single layer film. FIG. 7 is a diagram showing XRD patterns of the SrTi 0 ₃ films of Example 1 and Comparative Example 1. The upper part of FIG. 7 is an XRD pattern according to Example 1, and the lower part of FIG. 7 is an XRD pattern according to Comparative Example 1. From the upper part of FIG. 7, all the samples fired at 550¾ or more showed clear peaks near 23 ° and 46 °. These peaks coincide with the 100 and 200 diffraction peaks of S r T i 0 ₃ . In addition, other diffraction peaks such as 1 1 0, 1 1 1 or 2 1 0 were not observed. From this, by firing at 5500 ° C or higher, the S r T iO ₃ film is formed on the C a ₂ Nb ₃ O ₁₀ / glass substrate (ie, on the C a ₂ Nb ₃ O ₁₀ nanosheet monolayer film). ) To (1 0 0) Orientation growth was found in the direction. Incidentally, the sample was calcined at 500 ° C in the range of § Amorphous, since the firing temperature is low, because the S r T i 0 ₃ sol was not crystallized. On the other hand, in the lower part of Fig. 7, no clear peak was observed except that a weak 1 10 diffraction peak of S r T i Oa was observed at around 32 ° after firing at 600 ° C or higher. 1 10 diffraction peak of the S r T i O ₃ is the strongest peak of S r T i O 3 shown in JC PD S pattern, La in S r T i O 3 thin film is calcined above 600 ° C randomly This suggests that the crystal is oriented and crystallized. From the above, it was shown that a cubic SrTi 0 ₃ film grows in a (1 00) orientation on a Ca ₂ Nb ₃ 0 _{1 (} ) / glass substrate. Further, it was found that the crystallization temperature is preferably 550 ° C. or higher when the above precursor sol is used. FIG. 8 is a diagram showing 10 patterns of the SrTi 0 ₃ films of Example 2 and Comparative Example 2. The upper part of FIG. 8 is an XRD pattern according to Example 2, and the lower part of FIG. 8 is an XRD pattern according to Comparative Example 2. From the upper part of FIG. 8, only the 100 and 200 diffraction peaks of S r T i 0 ₃ were shown for all coating times 1 to 5. The peak intensity increased as the number of coatings increased. This suggests that an SrTiO ₃ film oriented and grown in the (100) direction can be obtained even when the film thickness is increased.

On the other hand, in the lower part of Fig. 8, in the thick film with more than 4 coatings, in addition to the 110 diffraction peak of Sr T i 0 ₃ confirmed in Comparative Example 1, multiple peaks were observed. It was. These corresponded to the diffraction peaks of 1 1 1, 210, 200 and 2 11, respectively. From this, it can be seen that the SrTiOa film does not grow in 100 orientation directly on the glass substrate, but the randomly oriented SrTiO3 polycrystalline film grows. I got it. Looking at the 200 diffraction peaks in the XRD pattern with 5 coatings in Example 2 and Comparative Example 2, their half-widths (FWHM) were 0.23 ° and 0.33 °, respectively. It was. This is because the _{C a 2 N b 3 O 10} Z glass S r T i O 3 film on the substrate, and indicates that higher crystallinity than S r T i 0 ₃ film directly on a glass substrate . This suggests that the C a ₂ N b ₃ O ₁₀ nanosheet monolayer film has a function of promoting crystal growth. From Fig. 7 and Fig. 8, C a ₂ N b ₃ Ot. The glass substrate was found to be suitable for obtaining a 100-oriented SrTiO3 film. FIG. 9 is a view showing a SEM image of the surface of the SrTiO ₃ (n = 5) / Ca ₂ Nb ₃ O ₁₀ glass substrate of Example 2. FIG. FIG. 10 is a view showing an SEM image of the surface of SrTiO ₃ (n = 5) / glass substrate of Comparative Example 2. n indicates the number of coatings. The surface shapes of FIGS. 9 and 10 both show the surface structure of a typical sol-gel film in which fine particles are aggregated. The particle size is in the range of about 30 nm to 40 nm, indicating that the coating film is polycrystalline. FIG. 11 is a diagram showing a SEM image of a cross section of SrT i Oa (n = 5) / C a ₂ N b ₃ O _{1 (} > Z glass substrate of Example 2. FIG. Comparative example 2 of _{S r T i O 3 (n} = 5) is a diagram showing the S EM image of a cross-section of the Z glass substrate. FIG. 1 1 Oyopi Figure 1 2, the film thickness, both, about 4 0 0 nm. There Assuming proportional to coating times, S r T i O ₃ film having a thickness of about 80 nm by a single coating is obtained. FIG. 13 is a diagram showing XRD patterns of the Ti ₂ O ₂ films of Example 3 and Comparative Example 3. The XRD pattern of Comparative Example 3 showed peaks at about 25.5 ° and 38 °. Which corresponded to 101 diffraction peak Contact Yopi 004 diffraction peak of T i 0 ₂ ANATA one zero phase. On the other hand, the XRD pattern of Example 3 only showed a sharp and high intensity peak of about 38 °. This indicates that tetragonal anatase T i O ₂ grows in the c-axis direction on a C a ₂ Nb ₃ O ₁₀ Z glass substrate. FIG. 14 is a view showing an AFM image of the MnO ₂ glass substrate. According to FIG. 14, it can be seen that a very flat MnO ₂ nanosheet monolayer film was formed on the glass substrate. Similar to Fig. 5, such a surface is comparable to a flat single crystal at the atomic level, except for extremely small overlaps and gaps between nanosheet monolayers. The surface roughness (Ra) was 0.27 nm. The film thickness of the nanosheet monolayer film was 0.5 to 0.9 nm, which was nano level. This value is comparable to the crystallographic thickness of the MnO ₂ nanosheet monolayer (see Fig. 2 (C)), suggesting that the monolayer was formed on the glass substrate. At a surface pressure of 8. OmN 'rn- ¹ , it was found that the Mn O ₂ nanosheet monolayer film was formed in about 90% of the area of the glass substrate, and the overlap of the nanosheet monolayer film was the smallest. FIG. 15 is a diagram showing XRD patterns of the Z ηθ films of Example 4 and Comparative Example 4. The upper part (A) of FIG. 15 is an XRD pattern according to Example 4, and the lower part (B) of FIG. 15 is an XRD pattern according to Comparative Example 4. From the top (A) of Fig. 5 In all cases where the number of coatings was 1 to 5, a clear peak was observed around 35 °. This peak coincided with the 002 diffraction peak of ZnO. The peak intensity increased as the number of coatings increased, as in Example 2. This suggests that a ZnO film oriented and grown in the (001) direction can be obtained even when the film thickness is increased. On the other hand, in the lower part (B) of Fig. 15, multiple peaks were observed in the thick film with 3 or more coatings. These peaks corresponded to the 100, 002 and 101 diffraction peaks of ZnO, respectively. This indicates that the ZnO film is not (001) oriented, that is, randomly oriented Ζ, ηΟ polycrystals grow on the glass substrate even if it is a thick film with many coatings. . FIG. 16 is a diagram showing XRD patterns of the SrTiOa films of Example 5 and Comparative Example 5. The lower part of Fig. 16 shows the XRD pattern of the sample formed at a substrate temperature of 500 ° C, and the upper part of Fig. 16 shows the XRD pattern of the sample formed at a substrate temperature of 550 ° C. 1 6 forces, et al, XRD patterns of _{C s 4 WuO 36 S r T} i O 3 film formed on a glass substrate are all showed a clear peak in the vicinity of 23 ° and near 46 °. These peaks coincide with the 100 and 200 diffraction peaks of S r T i 0 ₃ . In addition, other diffraction peaks such as 1 10, 1 1 1 or 2 10 were not observed. Note that the peak intensity of the sample deposited at the substrate temperature of 550 ° C is higher than the peak intensity of the sample deposited at the substrate temperature of 500 ° C. This indicates that the crystallization of the SrT i 0 ₃ film was promoted by increasing the substrate temperature.

Meanwhile, XRD pattern of the sample which was deposited directly on the glass substrate are both not show diffraction peaks, S r T i 0 ₃ film formed was an amorphous state. Figure 17 shows the Sr T i Oa / C a ₂ Nb ₃ film formed at the substrate temperature of 550 ° C in Example 5. O t. A TEM image of the cross section of the glass substrate, Figure 17 shows that the Ca ₂ Nb ₃ O ₁₀ nanosheet monolayer remains between the glass substrate and the Sr T i O ₃ film . Further, it can be seen that S r T i O ₃ film having uniform crystal axis C a ₂ Nb ₃ O ₁₀ nanosheet monolayer film directly is growing well. Note that the film thickness of the SrTiO 3 film was about 120 nm. From the above, C azNbaOi. In addition to being effective as a buffer layer for S r T i O ₃ films, nanosheet monolayer films can be obtained on a Ca ₂ Nb ₃ 0 ₁₀ glass substrate by physical vapor deposition (here, pulsed laser deposition). It was found that the SrT i 0 ₃ film can be oriented and grown well in the (100) direction (that is, on the Ca ₂ Nb ₃ O ₁₀ nanosheet monolayer film). FIG. 18 is a diagram showing XRD patterns of the Z ηθ films of Example 6 and Comparative Example 6. According to the XRD pattern of the sample of Example 6 in FIG. 8, a clear peak was observed at around 35 °. This peak coincided with the 002 diffraction peak of Z ηθ. On the other hand, the XRD pattern of the sample of Comparative Example 6 in Fig. 18 also showed a peak near 35 °, but its intensity was very small. This is, on Myuitaomikuron ₂ nanosheet monolayer film, it is accelerated crystal growth Zeta Itashita, in order to grow uniform crystal orientation. In addition to the fact that 単 η の₂ nanosheet monolayer film is effective as a buffer layer for ηηθ film, it is possible to heat the substrate by physical vapor deposition (here, pulsed laser deposition method). no, that is, even at room temperature, ΜηΟ ₂ / on glass substrates (ie, Myuitaomikuron ₂ nanosheet monolayer film) of the Zeta Itaomikuron membrane (001) that can be favorably oriented growth direction I understood. FIG. 19 is a diagram showing XRD patterns of ηηθ films of Example 7 and Comparative Example 7. The lower part of Fig. 19 shows the XRD pattern of the sample deposited without substrate heating (room temperature), and the upper part of Fig. 19 shows the XRD pattern of the sample deposited at the substrate temperature of 100 ° C. According to the XRD pattern of the sample of Example 7 in the lower part of Fig. 9, a clear peak was observed around 35 °. This peak coincided with the 002 diffraction peak of Z ηθ. On the other hand, the XRD pattern of the sample of Comparative Example 7 in the lower part of Fig. 19 also showed a peak near 35 °, but its intensity was extremely small. This is C s

If the Noshito monolayer film, like the Mn0 ₂ nanosheet monolayer film, the crystal growth of Z nO is promoting, in order to grow uniform crystal orientation. From this, the physical vapor phase growth method (here, pulsed laser deposition) can be used on a C s ₄ WHO ₃₆ glass substrate (ie, C s) without heating the substrate, that is, even at room temperature. It was found that a ZnO film can be grown in the (001) direction on a ₄ WnO ₃₆ nanosheet monolayer film. The peak intensity of the XRD pattern of the sample of Example 7 in the upper part of FIG. 19 was larger than that of the sample of Example 7 in the lower part of FIG. This is because the crystallinity was improved by raising the substrate temperature from room temperature to 100 ° C. It was also found that the Cs WuO nanosheet monolayer film functions stably as a buffer layer for the alignment film (here, ZnO) even at 100 ° C heating. In addition, as explained with reference to Fig. 4 (D), the relationship between the unit cell of C s AW O and the unit cell of Z ηθ is an integer even in a combination that seems to be lattice mismatch at first glance. If it is doubled, it is found that lattice alignment is achieved and an alignment film can be manufactured. Figure 20 shows the C s of Example 8.

It is a figure which shows the AFM image of an ET board | substrate. Figures 20 (a) and (b) show AFM images at different magnifications. According to FIG. 20, it was confirmed that the surface of the C s WnOae / PET substrate showed the same morphology as the AFM image (not shown) of the C a ₂ N b ₃ O o Z glass substrate of Example 7. . From this, a flat C s AW O nanosheet monolayer film is formed on a PET substrate. It can be seen that it was formed. Except for extremely small overlaps or gaps between nanosheets, nanosheet monolayers can be formed even on plastic substrates with low thermal stability, such as PET substrates, which are comparable to atomically flat single crystals. This was shown. FIG. 21 shows C a zNbsOi of Example 9. A 1 ₂ O ₃ AFM images of a single crystal substrate (a) and (b) and, C a ₂ Nb ₃ O ₁₀ nanosheet applied before the A 1 ₂ O ₃ single crystal substrate A FM image (c) and (d) FIG. Figures 21 (a) and (c), and (b) and (d) show A FM images with different magnifications. Figures 21 (c) and (d) show a step with a period of about 200 nm, confirming that the surface of the A 12 O ₃ single crystal substrate has atomic irregularities. On the other hand, the surface of the substrate for crystal growth consisting of C a ₂ Nb ₃ O ₁₀ ZA 1 ₂ Oa single crystal substrate is C a ₂ Nb ₃ O ₁₀ as shown in Fig. 2 (a) and (b). The nanosheet monolayer film is deformed at the atomic level so as to follow the steps shown in Fig. 21 (c) and (d), and the unevenness of the original A 1 ₂ O ₃ single crystal substrate is It can be seen that it is directly reflected in the formed Ca ₂ Nb ₃ O ₁₀ nanosheet monolayer film. From this, it was shown that the nanosheet monolayer film can be provided even on a substrate having irregularities due to the structural flexibility of the nanosheet monolayer film obtained by peeling from the layered compound. As described above, according to Examples 1 to 4, by using a material having a two-dimensional square lattice (for example, CazNbaOLo) as a nanosheet monolayer film and adopting a sol-gel method, cubic and tetragonal systems can be obtained. alignment film material is obtained, the material (e.g., Mn0 ₂₎ having a two-dimensional hexagonal lattice as a nanosheet monolayer film using, by adopting a sol-gel method, to obtain an alignment film material of hexagonal I was able to do that.

Further, according to Examples 5 to 7, a material having a two-dimensional square lattice (for example, C a zNbaO ^) is used as the nanosheet monolayer film as the nanosheet monolayer film. By adopting the phase growth method, alignment films of cubic and tetragonal materials can be obtained, and materials with a two-dimensional hexagonal lattice as a nanosheet monolayer film (for example, M n O ₂ and C s AW UO It has been found that an alignment film of a hexagonal material can be obtained even at room temperature by using a physical vapor deposition method.

 Furthermore, according to Examples 8 and 9, it was shown that a plastic substrate with low thermal stability can be used as a base material, and that a base material having unevenness can be used. The above Examples 1 to 9 are exemplifications, and the configuration of the substrate for crystal growth of the present invention (combination of a base material and a nanosheet monolayer film) and an alignment film formed thereon are included in this. It is not limited. Industrial applicability

 The substrate for crystal growth according to the present invention comprises a base material and a nanosheet monolayer film located on the base material and peeled from the layered compound. In such a crystal growth substrate, an alignment film matching the nanosheet monolayer film appropriately selected can be formed. Such a substrate for crystal growth can be used for a light emitting element, a semiconductor element, a ferroelectric device, a dielectric device, a magnetic device, etc., depending on the material of the alignment film. In addition, since the nanosheet monolayer film of the crystal growth substrate according to the present invention is easily formed at room temperature, it is also applied to a plastic substrate with low thermal stability. As a result, an inexpensive and large area crystal growth substrate can be provided. The crystal growth substrate according to the present invention can also be used as a stable intermediate layer (for example, an intermediate layer of a photocatalyst) that separates the base material and the alignment film.

Claims

The scope of the claims

1. A crystal growth substrate having a buffer layer formed on its surface,

 The crystal growth substrate, wherein the buffer layer is composed of a nanosheet monolayer film composed of a two-dimensional crystal.

2. The crystal growth substrate according to claim 1, wherein the nanosheet monolayer film is peeled off from the layered compound.

3. The substrate for crystal growth according to claim 2, wherein the layered compound is composed of a layered oxide, a layered phosphate, a layered double hydroxide, a layered metal chalcogenite, and a layered cate salt. A crystal growth substrate selected from the group consisting of:

4. In the crystal growth substrate according to claim 3,

 The layered compound is a layered oxide,

 The nanosheet monolayer film is composed of a monolayer film of a titanate nanosheet, a layered berovskite nanosheet, a manganate nanosheet, a niobium Z tantalate nanosheet, a titanium niobate nanosheet, a ruthenate nanosheet, and a tungstate nanosheet. A substrate for crystal growth, which is selected.

5. The crystal growth substrate according to claim 4, wherein the manganate nanosheet monolayer film is an MnO ₂ nanosheet monolayer film.

6. The crystal growth substrate according to claim 4, wherein the layered perovsk force nanosheet monolayer film is a Ca ₂ Nb ₃ O ₁₀ nanosheet monolayer film. Growth substrate.

7. In the crystal growth substrate according to claim 3,

 The layered compound is a layered phosphate;

 The substrate for crystal growth, wherein the nanosheet monolayer film is a zirconium phosphate nanosheet monolayer film or a vanadium phosphate nanosheet monolayer film.

8. In the crystal growth substrate according to claim 3,

 The layered compound is a layered double hydroxide,

 The substrate for crystal growth, wherein the nanosheet monolayer film is a hydroxide nanosheet monolayer film. .

9. In the crystal growth substrate according to claim 3,

 The layered compound is a layered metal chalcogenite compound,

 The substrate for crystal growth, wherein the nanosheet monolayer film is a metal chalcogenide nanosheet monolayer film.

1 0. In the crystal growth substrate according to claim 3,

 The layered compound is a layered silicate;

 The substrate for crystal growth, wherein the nanosheet monolayer film is a smectite nanosheet monolayer film.

1 1. The substrate for crystal growth according to claim 1, wherein the base material provided with the buffer layer is selected from the group consisting of glass, metal, semiconductor single crystal, and plastic. A crystal growth substrate.

12. A crystal growth method using the crystal growth substrate according to any one of claims 1 to 11, wherein the crystal of the alignment film grows on the crystal growth substrate. The two-dimensional lattice shape of the nanosheet monolayer film is set as shown in the following table A so that the lattice lengths a and b of the surface and the angle Θ formed by the lattice lengths a and b have a desired relationship. A crystal growth method using a crystal growth substrate characterized by the above. (Table A)

Relation between lattice length a b Angle formed by lattice lengths a and b 0 Two-dimensional lattice shape a = b 0 = 90 ° Square a ≠ b 0 = 9 Ο ^β rectangle a = b 0 = 120. Hexagon a ≠ b θ ≠ = 90 ° Parallelogram

1 3. shall apply in the crystal growth method using the crystal growth substrate according to claim 5, causing the Myuitaomikuron ₂ nanosheet monolayer film oriented growth of Zeta Itashita to become formed crystal growth substrate A crystal growth method using the crystal growth substrate.

14. shall apply in claims 6 crystal growth method using the crystal growth substrate according to Section the _{C a 2 N b 3 Ο 10} S in nanosheet monolayer film is formed crystal growth substrate A crystal growth method using a crystal growth substrate, characterized by orientation-growing r T i 0 ₃ or T i O ₂ .

1 5. Crystal growth method using the crystal growth substrate according to claim 1 'From sol-gel method, liquid phase epitaxy method, physical vapor deposition method and chemical vapor deposition method A crystal growth method, characterized in that a method selected from the group consisting of: