KR20190132152A - Layered AlN, manufacturing method thereof and exfoliated AlN nanosheet therefrom - Google Patents

Abstract

The present invention relates to a layered AlN, a manufacturing method thereof and an AlN nanosheet exfoliated therefrom and, more specifically, to a layered AlN having a two-dimensional crystalline structure unlike a traditional bulk AlN, having excellent exfoliation properties, being easily exfoliated into a nanosheet form and having excellent thermal conductive properties, a manufacturing method thereof, and an AlN nanosheet exfoliated therefrom.

Description

Layered AlN, manufacturing method thereof, and AlN nanosheet exfoliated therefrom {Layered AlN, manufacturing method according to example and exfoliated AlN nanosheet therefrom}

The present invention relates to a layered AlN, a method for producing the same and an AlN nanosheet peeled from the same, more specifically, unlike a conventional bulk AlN has a two-dimensional crystal structure, and excellent peelability in the form of nanosheets The present invention relates to a layered AlN, a method for preparing the same, and an AlN nanosheet peeled therefrom, which is easy to do, and has excellent thermal conductivity and piezoelectric properties.

Graphene and other ultra-thin two-dimensional (2D) materials are being actively studied in various fields based on new physical, chemical, mechanical and optical properties. This low-dimensional material is expected to be a breakthrough new function that the existing bulk material does not have and is very likely as a next-generation future material to replace the existing material.

Research on existing 2D materials is based on top-down method for separating van der Waals bonds with weak interlayer bondability by physical and chemical methods, and bottom-up method for growing large-area thin films based on vapor deposition. It is becoming. In particular, in the top-down method, since the pristine of the material to be exfoliated must have a two-dimensional layered crystal structure, graphene without band gap, layered metal oxide / nitride with low charge mobility, electron mobility / Research subjects such as transition metal chalcogenides with low electrical conductivity have very limited problems.

Due to the limitations of previous research methods, 2D materials have been very limitedly studied for materials such as graphene and transition metal chalcogenides. It is limited in that it is not suitable for the development of low-dimensional future materials of a myriad of 3D bulk materials that are not layered.

On the other hand, aluminum nitride (AlN) has a thermal conductivity (319 W / m K) or more than 10 times the thermal conductivity of alumina, has a relatively low thermal expansion coefficient than alumina, and has excellent electrical insulation and mechanical strength. When the AlN is manufactured from a two-dimensional material, the above-described characteristics may be improved, and thus, the AlN may be applied to a semiconductor substrate or a component of high thermal conductivity ceramics.

Korea Patent Registration No. 10-0954722

Unlike the conventional bulk AlN, the present invention has a two-dimensional crystal structure, has excellent peelability and is easy to peel in the form of a nanosheet, and has a layered AlN and an AlN nanosheet peeled therefrom having excellent thermal conductivity and piezoelectric properties. The purpose is to provide.

In order to solve the above problems, the present invention is (1) heat treatment and cooling the mixture containing Ca precursor or Ca powder, Al precursor or Al powder, and N precursor, the space group (C2 / 2 or P2) obtaining a layered compound represented by the formula Ca ₃ Al ₂ N ₄ having a monoclinic crystal structure of / c and (2) Ca included in the layered compound without changing the crystal structure of the layered compound It provides a method for producing a layered AlN comprising the step of treating the layered compound with a mixed solution comprising a salt capable of selectively removing ions and a solvent capable of dissolving the salt.

According to one embodiment of the present invention, the salt may be represented by the following formula (1).

<Formula 1>

M _a X _b (1≤a≤2, 1≤b≤3)

In Formula 1, M is any one selected from Al, Mg, and Mn, and X is any one selected from Cl, F, and I.

In addition, according to an embodiment of the present invention, the solvent may be at least one selected from deionized water, tetrahydrofuran and dichloromethane.

In addition, according to an embodiment of the present invention, the heat treatment of step (1) may be performed for 80 to 200 hours at 1000 ~ 1200 ℃.

In addition, according to one embodiment of the present invention, the cooling of the step (1) may be performed at a temperature reduction rate of 0.5 ~ 3 ℃ / hour or 10 ~ 15 ℃ / hour.

The present invention also provides a layered AlN having a monoclinic crystal structure with a space group of C2 / 2 or P2 / c.

According to one embodiment of the present invention, the layered AlN having a monoclinic crystal structure having a space group of C2 / 2 is 13.54 in an X-ray diffractogram obtained by a powder X-ray diffraction method using Cu-Kα rays. Peaks at 2θ values of ± 0.2, 16.68 ± 0.2, 20.79 ± 0.2, 21.25 ± 0.2, 26.85 ± 0.2, 27.43 ± 0.2, 31.46 ± 0.2 and 32.33 ± 0.2, 33.04 ± 0.2, 35.77 ± 0.2, 37.7 ± 0.2, It may not have peaks at 2θ values of 49.48 ± 0.2, 59.02 ± 0.2, 65.54 ± 0.2 and 70.95 ± 0.2.

According to one embodiment of the present invention, the layered AlN having a monoclinic crystal structure in which the space group is P2 / c has an X-ray diffraction diagram obtained by a powder X-ray diffraction method using Cu-Kα rays. It has peaks at 2θ values of 9.94 ± 0.2, 18.24 ± 0.2, 18.73 ± 0.2, 18.95 ± 0.2, 19.96 ± 0.2, 24.24 ± 0.2, 25.21 ± 0.2 and 30.11 ± 0.2, and 33.04 ± 0.2, 35.77 ± 0.2, 37.7 ± 0.2 It may not have peaks at 2θ values of 49.48 ± 0.2, 59.02 ± 0.2, 65.54 ± 0.2 and 70.95 ± 0.2.

The present invention also provides an AlN nanosheet peeled from the layered AlN according to the present invention and having an amorphous crystal structure.

According to one embodiment of the present invention, the thickness of the AlN nanosheets may be 300 nm or less.

Unlike the conventional bulk AlN, the layered AlN according to the present invention has a two-dimensional crystal structure, is excellent in peelability and easily peeled off in the form of a nanosheet, and has a high thermal conductivity and piezoelectric semiconductor substrate. It can be widely used for the substrate of a thyristor and a piezoelectric element.

1 is a schematic diagram of a layered AlN manufacturing method according to an embodiment of the present invention.
FIG. 2 is a graph showing XRD analysis results of 3D bulk AlN of Comparative Example 1, layered Ca ₃ Al ₂ N ₄ of Preparation Example 1, and layered AlN of Example 1. FIG.
3A is an SEM image of the layered Ca ₃ Al ₂ N ₄ of Preparation Example 1. FIG.
3B is an SEM image of the layered Ca ₃ Al ₂ N ₄ of Preparation Example 1. FIG.
3C is an SEM image of the layered AlN of Example 1. FIG.
4 is a photograph of layered Ca ₃ Al ₂ N ₄ of Preparation Example 1. FIG.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

The manufacturing method of layered AlN which concerns on this invention is demonstrated.

The method of manufacturing a layered AlN according to the present invention can produce a bulk AlN of a conventional 3D structure in a two-dimensional structure, and unlike the existing bulk AlN can be easily peeled, it is possible to produce a layered AlN having excellent thermal conductivity properties. .

First, as step (1), the mixture comprising Ca precursor or Ca powder, Al precursor or Al powder, and N precursor is heat-treated and then cooled to give a monoclinic system having a space group of C2 / 2 or P2 / c. monoclinic) to obtain a layered compound having a crystal structure represented by the formula Ca ₃ Al ₂ N ₄ .

The Ca precursor or Ca powder, Al precursor or Al powder, and N precursor may be mixed independently of each other, the N precursor may be included in the mixture with the same material as the Ca precursor or Al precursor.

Specifically, the N precursor may be a compound including N ions, the Ca precursor may be a compound including Ca ions, and the N precursor and the Ca precursor may be the same material as the compound including Ca and N elements. For example, it may be Ca ₃ N ₂ but is not limited thereto. The Al precursor may be a compound including Al ions, for example, may be AlN, but is not limited thereto.

The mixture may be heat treated after being encapsulated in a reaction vessel, and the inside of the reaction vessel may be maintained in an inert gas atmosphere or a vacuum atmosphere.

In addition, the material of the reaction vessel may be, for example, alumina, molybdenum, tungsten or quartz, but any material that does not react with the sample and does not break at a high temperature may be used without limitation in the material.

In the Ca ₃ Al ₂ N ₄ is (2) has an AlN different 2D crystal structure of the 3D crystal structure, which will be described later stage be prepared through the step (1) As shown in Figure 1 of the Ca ₃ Al ₂ N ₄ By selectively removing Ca ions, a layered AlN may be prepared without changing the crystal structure of the Ca ₃ Al ₂ N ₄ .

The heat treatment may be performed at 1000 to 1200 ° C. for 80 to 200 hours.

If the heat treatment is performed at less than 1000 ° C., the sintering reaction of the mixture may not be completed, and thus unreacted raw materials may remain, resulting in a decrease in yield of the layered compound prepared. have. In addition, when the heat treatment is performed in excess of 1200 ℃, there may be a problem such as the reaction vessel used in the sintering reaction by the vaporization of Ca ions, or the yield of the layered compound produced is lowered.

If the heat treatment is performed for less than 80 hours, the sintering reaction of the mixture may not be completed, so that unreacted raw materials may remain, and thus the yield of the layered compound prepared may be deteriorated. have. In addition, when the heat treatment is performed for more than 200 hours, there is a fear that the manufacturing process time unnecessarily increases.

The cooling process after the heat treatment in step (1) is necessary for crystallization of the layered compound, and the single crystal size of the crystal may change according to the cooling rate.

The cooling may be performed at a temperature reduction rate of 10 to 15 ° C./hour or 0.5 to 3 ° C./hour, and when the temperature reduction rate is 10 to 15 ° C./hour, the layered Ca ₃ Al ₂ N ₄ may be polycrystalline. have. The heat-sensing and speed can be purified unity to 0.5 ~ 3 ℃ / hour day when the layered Ca ₃ Al ₂ N _4, a single crystal size of the layered AlN after Ca ion scavenging included in the layered Ca ₃ Al ₂ N ₄ is Can be maintained. As the size of the single crystal of the layered AlN increases, grain boundaries of the particles may decrease, and the aspect ratio of the InAs nanosheets peeled off when the layered InAs is peeled off may increase.

If the temperature reduction rate is less than 0.5 ℃ / hour, a change in the composition of the material can be produced due to the vaporization of Ca ions, if the temperature reduction rate exceeds 3 ℃ / time, the layered compound prepared is polycrystalline Can be.

Next, as step (2), the layered compound prepared in step (1) includes a salt containing a salt capable of selectively removing Ca ions contained in the layered compound and a solvent capable of dissolving the salt. Treated with solution to prepare a layered AlN without changing the crystal structure of the layered compound.

The salt may include an anion having a high electronegativity and a cation having an electronegativity value between the alkali metal ion and the Al ion in order to easily react with the alkali metal ion contained in the layered compound.

The salt may be represented by the following Formula 1, wherein the salt is a cation having an electronegativity value between the alkali metal ion and the Al ion, and is composed of M and Cl ions having a high electronegativity.

<Formula 1>

M _a X _b (1≤a≤2, 1≤b≤3)

In Formula 1, M may be any one selected from Al, Mg, and Mn, and X may be any one selected from Cl, F, and I.

In addition, the solvent may include at least one selected from deionized water, tetrahydrofuran and dichloromethane.

The salt may be included in the mixed solution at a high concentration that can be dissolved in the solvent in order to increase the Ca ion removal efficiency of the layered Ca ₃ Al ₂ N ₄ and prevent the removal of Al ions.

The salt may be used in an amount sufficient to remove Ca ions of the layered Ca ₃ Al ₂ N ₄ , but preferably the layered Ca ₃ Al ₂ N ₄ and the salt in the mixed solution are 1: 1 to 1: It may be included in a molar ratio of three. If the molar ratio of the layered Ca ₃ Al ₂ N ₄ and salt is less than 1: 1, Ca ions of the layered Ca ₃ Al ₂ N ₄ may not be removed to the desired level, if the molar ratio is 1 If it exceeds 3, the salt may not be dissolved in the mixed solution, resulting in a precipitate.

In addition, the step (2) may be carried out at a temperature at which the Ca ion removal reaction may occur smoothly, the temperature may vary depending on the composition of the mixed solution, preferably at least 20 ℃, more preferably Preferably it may be carried out at a temperature of 20 ~ 60 ℃. If carried out below 20 ° C., Ca ions may not be removed to the desired level, and if carried out at temperatures above 60 ° C., the layered structure of the layered Ca ₃ Al ₂ N _{4 produced} may collapse. have. In addition, the alkali metal ion removal rate may be excellent while maintaining the layered structure of the layered Ca ₃ Al ₂ N ₄ prepared when performed at a temperature of 20 ~ 60 ℃.

In addition, the step (2) may be performed a plurality of times depending on the composition of the mixed solution, the removal rate of Ca ions, but is preferably performed once to maintain the layered structure of the layered AlN.

In addition, after performing step (2), a reactant produced by reacting Ca ions with the salt in addition to the layered AlN may be present, for example, calcium chloride, and the powder obtained through step (2) may be removed to remove it. It can be washed with a solvent.

The solvent for removing the reactant may be used without limitation as long as it is a solvent having solubility in calcium chloride and may be at least one selected from water, deionized water and ethanol.

Next, the layered AlN of the present invention will be described.

Layered AlN according to the present invention has a monoclinic (monoclinic) crystal structure of the space group (space group) of C2 / 2 or P2 / c, which is different from the existing 3D bulk AlN as a nanocrystalline sheet with excellent peelability It is easy to peel off in the form of, and may have excellent thermal conductivity characteristics.

In the X-ray diffractogram obtained by the powder X-ray diffraction method using Cu-Kα rays, the layered AlN having a monoclinic crystal structure in which the space group is C2 / 2 is 13.54 ± 0.2, 16.68 ± 0.2, 20.79 ±. It has peaks at 2θ values of 0.2, 21.25 ± 0.2, 26.85 ± 0.2, 27.43 ± 0.2, 31.46 ± 0.2 and 32.33 ± 0.2, 33.04 ± 0.2, 35.77 ± 0.2, 37.7 ± 0.2, 49.48 ± 0.2, 59.02 ± 0.2, 65.54 It may not have peaks at 2θ values of ± 0.2 and 70.95 ± 0.2. In addition, the layered AlN having a monoclinic crystal structure of the space group P2 / c is 9.94 ± 0.2, 18.24 ± 0.2, 18.73 ± 0.2, 18.95 ± 0.2, 19.96 ± 0.2, 24.24 ± 0.2, 25.21 ± 0.2 and 30.11 ± It may have peaks at 2θ values of 0.2 and may not have peaks at 2θ values of 33.04 ± 0.2, 35.77 ± 0.2, 37.7 ± 0.2, 49.48 ± 0.2, 59.02 ± 0.2, 65.54 ± 0.2 and 70.95 ± 0.2.

Next, the AlN nanosheet of this invention is demonstrated.

The AlN nanosheets according to the present invention can be obtained by peeling from the layered AlN according to the present invention and have an amorphous crystal structure.

According to an embodiment of the present invention, the AlN nanosheets may have a thickness of 300 nm or less, and if the thickness exceeds 300 nm, the surface area of the AlN nanosheets may be lowered to lower thermal conductivity and piezoelectric properties, or the AlN nanosheets. Lamination of sheets can be difficult.

As the peeling method of the layered AlN, a peeling method of a layered material known in the art may be used, and for example, a peeling method using energy by ultrasonic waves, a peeling method by invasion of a solvent, a peeling method using a tape, and adhesion Any of the stripping methods using a substance having a surface may be used.

Meanwhile, since the layered AlN and AlN nanosheets according to the present invention have excellent thermal conductivity and piezoelectric properties, they may be used for semiconductor substrates of high thermal conductivity ceramics, substrates of thyristors, or piezoelectric elements.

When the layered AlN and AlN nanosheets according to the present invention are utilized in piezoelectric elements, the layered AlN or AlN nanosheets according to the present invention may be included as piezoelectric elements included in the piezoelectric elements, thereby providing excellent piezoelectric properties. The configuration other than the piezoelectric element included in the piezoelectric element may adopt a configuration known in the art, and thus the detailed description thereof will be omitted.

In addition, since the layered AlN and AlN nanosheets according to the present invention have excellent thermal conductivity, when used in a semiconductor substrate or a substrate of a high thermal conductivity ceramic, the thermal conductivity may be excellent. The configuration other than the substrate may employ a configuration known in the art, and thus the detailed description thereof will be omitted.

Although one embodiment of the present invention has been described above, the spirit of the present invention is not limited to the embodiments set forth herein, and those skilled in the art who understand the spirit of the present invention may add components within the same scope. Other embodiments may be easily proposed by changing, deleting, adding, and the like, but this will also fall within the spirit of the present invention.

Preparation Example 1 Layered Ca ₃ Al ₂ N ₄  Produce

In order to synthesize the layered Ca ₃ Al ₂ N ₄ , Ca ₃ N ₂ powder and Al powder were mixed and encapsulated in a quartz tube in a vacuum atmosphere. The quartz tube containing the sample was heat-treated at 1050 ° C. for 100 hours. Thereafter, cooling was performed at a temperature reduction rate of 2 ° C./hour for recrystallization to obtain a high purity layered Ca ₃ Al ₂ N ₄ single crystal.

Example 1 Manufacture of Layered AlN

The layered Ca ₃ Al ₂ N ₄ prepared in Preparation Example 1 was mixed with deionized water, tetrahydrofuran and AlCl ₃ to remove Ca ions from the Ca ₃ Al ₂ N ₄ , through which a layered AlN was prepared.

Example 3 Preparation of AlN Nanosheets

The layered AlN prepared in Example 1 was peeled off with a tape to prepare an AlN nanosheet.

Comparative Example 1 3D Bulk AlN

A commercial 3D bulk AlN (Sigma Aldrich) was prepared.

Experimental Example 1 XRD Analysis

XRD analysis was performed on 3D AlN of Comparative Example 1, layered Ca ₃ Al ₂ N ₄ of Preparation Example 1, and layered AlN of Example 1, and the results are shown in FIG. 2.

Referring to FIG. 2, it can be seen that the layered Ca ₃ Al ₂ N ₄ (preparation example 1) has a monoclinic crystal structure of space groups C2 / 2 and P2 / c.

In addition, it can be seen that the layered AlN (Example 1) from which Ca ions were removed from the layered Ca ₃ Al ₂ N ₄ has a monoclinic crystal structure of C2 / 2 and P2 / c, which is a bulk of 3D structure. It is a crystal structure different from AlN.

Experimental Example 2 SEM Analysis

SEM images were taken of the layered Ca ₃ Al ₂ N ₄ of Preparation Example 1 and the layered AlN of Example 1, and the results are shown in FIGS. 3A and 3C.

3A and 3C, it can be seen that AlN prepared after removing Ca ions of the layered Ca ₃ Al ₂ N ₄ has a layered structure.

Claims (10)

(1) A monoclinic crystal structure in which a space group is C2 / 2 or P2 / c by cooling after heat-treating a mixture containing Ca precursor or Ca powder, Al precursor or Al powder, and N precursor. Obtaining a layered compound represented by the formula Ca ₃ Al ₂ N ₄ ; And
(2) treating the layered compound with a mixed solution containing a salt capable of selectively removing Ca ions contained in the layered compound and a solvent capable of dissolving the salt, without changing the crystal structure of the layered compound. Making;
Method of producing a layered AlN comprising a.
The method of claim 1,
The salt is a method for producing a layered AlN represented by the following formula (1):
<Formula 1>
M _a X _b (1≤a≤2, 1≤b≤3)
In Formula 1, M is any one selected from Al, Mg, and Mn, and X is any one selected from Cl, F, and I.
The method of claim 1,
The solvent is a method of producing a layered AlN is at least one selected from deionized water, tetrahydrofuran and dichloromethane.
The method of claim 1,
The heat treatment of step (1) is a method of producing a layered AlN is carried out for 80 to 200 hours at 1000 ~ 1200 ℃.
The method of claim 1,
The cooling of step (1) is a method of producing a layered AlN is carried out at a temperature reduction rate of 0.5 ~ 3 ℃ / hour or 10 ~ 15 ℃ / hour.
Layered AlN having a monoclinic crystal structure with a space group of C2 / 2 or P2 / c.
The method of claim 6,
In the X-ray diffractogram obtained by the powder X-ray diffraction method using Cu-Kα rays, the layered AlN having a monoclinic crystal structure of the space group C2 / 2 was 13.54 ± 0.2, 16.68 ± 0.2, 20.79 ±. It has peaks at 2θ values of 0.2, 21.25 ± 0.2, 26.85 ± 0.2, 27.43 ± 0.2, 31.46 ± 0.2 and 32.33 ± 0.2, and has 33.04 ± 0.2, 35.77 ± 0.2, 37.7 ± 0.2, 49.48 ± 0.2, 59.02 ± 0.2, 65.54 Layered AlN without peaks at 2θ values of ± 0.2 and 70.95 ± 0.2.
The method of claim 6,
In the X-ray diffractogram obtained by the powder X-ray diffraction method using Cu-Kα rays, the layered AlN having a monoclinic crystal structure having the space group of P2 / c is 9.94 ± 0.2, 18.24 ± 0.2, 18.73 ±. It has peaks at 2θ values of 0.2, 18.95 ± 0.2, 19.96 ± 0.2, 24.24 ± 0.2, 25.21 ± 0.2 and 30.11 ± 0.2 and has 33.04 ± 0.2, 35.77 ± 0.2, 37.7 ± 0.2, 49.48 ± 0.2, 59.02 ± 0.2, 65.54 Layered AlN without peaks at 2θ values of ± 0.2 and 70.95 ± 0.2.
An AlN nanosheet exfoliated from the layered AlN according to claim 6 and having an amorphous crystal structure.
The method of claim 9,
AlN nanosheets having a thickness of 300 nm or less.

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