KR102271060B1 - Layered AlN, manufacturing method thereof and exfoliated AlN nanosheet therefrom - Google Patents

Abstract

The present invention relates to a layered AlN, a method for manufacturing the same, and an AlN nanosheet peeled therefrom, and more particularly, has a two-dimensional crystal structure unlike the conventional bulk AlN, and has excellent peelability and thus peels off in the form of a nanosheet It is easy to perform and relates to a layered AlN having excellent thermal conductivity, a method for manufacturing the same, and AlN nanosheets peeled therefrom.

Description

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

The present invention relates to a layered AlN, a method for manufacturing the same, and an AlN nanosheet peeled therefrom, and more particularly, has a two-dimensional crystal structure unlike the conventional bulk AlN, and has excellent peelability and thus peels off in the form of a nanosheet It is easy to perform, and relates to a layered AlN having excellent thermal conductivity and piezoelectric properties, a manufacturing method thereof, and AlN nanosheets peeled therefrom.

Various ultra-thin two-dimensional (2D) materials including graphene are being actively studied in various fields based on new physical, chemical, mechanical and optical properties. These low-dimensional materials are expected to have innovative new functions that existing bulk materials do not have, and have great potential as a next-generation future material that will replace existing materials.

Research on existing 2D materials is based on the top-down method that separates the van der Waals bond, which has weak interlayer bonding force, by physical and chemical methods, and the bottom-up method that grows a large-area thin film based on the vapor deposition method. is becoming In particular, in the top-down method, since the pristine of the material subject to exfoliation must have a two-dimensional layered crystal structure, graphene without a band gap, layered metal oxide/nitride with low charge mobility, and electron mobility/ There are very limited research subjects such as transition metal chalcogen compounds with low electrical conductivity.

Due to the limitations of conventional research methods, very limited research on 2D materials has been conducted on materials such as graphene or transition metal chalcogen compounds, which intrinsically depends on the type of element to be used depending on whether low-dimensional materials can be developed. It has limitations in that it is limited according to the requirements and is not suitable for the development of low-dimensional future materials of countless 3D bulk materials that are not layered.

On the other hand, aluminum nitride (AlN) has a thermal conductivity (319W/m K) more than 10 times that of alumina, has a relatively lower coefficient of thermal expansion than alumina, and has excellent electrical insulation and mechanical strength. When such AlN is manufactured as a two-dimensional material, the above-described properties can be improved, and thus can be applied to semiconductor substrates or components of high thermal conductivity ceramics.

Republic of Korea Patent No. 10-0954722

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

In order to solve the above problems, the present invention is (1) a mixture containing a Ca precursor or Ca powder, an Al precursor or Al powder, and an N precursor is heat-treated and then cooled so that the space group is 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 contained in the layered compound without changing the crystal structure of the layered compound It provides a method for producing layered AlN, comprising treating the layered compound with a mixed solution containing a salt capable of selectively removing ions and a solvent capable of dissolving the salt.

According to an 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.

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

Also, according to an embodiment of the present invention, the heat treatment in step (1) may be performed at 1000 to 1200° C. for 80 to 200 hours.

Also, according to an embodiment of the present invention, the cooling in step (1) may be performed at a temperature reduction rate of 0.5 to 3° C./hour or 10 to 15° C./hour.

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

According to an embodiment of the present invention, in the X-ray diffraction diagram obtained by powder X-ray diffraction using Cu-Kα ray, the layered AlN having a monoclinic crystal structure in which the space group is C2/2 is 13.54 It has 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, There may be no peaks at 2θ values of 49.48±0.2, 59.02±0.2, 65.54±0.2 and 70.95±0.2.

In addition, according to an embodiment of the present invention, the layered AlN having a monoclinic crystal structure in which the space group is P2/c is obtained by powder X-ray diffraction using Cu-Kα rays in the X-ray diffraction diagram, 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, 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 may not have peaks at 2θ values.

In addition, the present invention provides an AlN nanosheet peeled from the layered AlN according to the present invention and having an amorphous crystal structure.

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

The layered AlN according to the present invention has a two-dimensional crystal structure, unlike the conventional bulk AlN, has excellent peelability, so it is easy to peel in the form of a nanosheet, and has excellent thermal conductivity and piezoelectric properties, so a semiconductor substrate of high thermal conductivity ceramics , can be widely used for thyristor substrates or piezoelectric elements.

1 is a schematic diagram for a layered AlN manufacturing method according to an embodiment of the present invention.
2 is a graph showing the XRD analysis results of the 3D bulk AlN of Comparative Example 1, the layered Ca ₃ Al ₂ N ₄ of the Preparation Example 1, and the layered AlN of Example 1.
Figure 3a is a SEM image of _{the layered Ca 3} Al ₂ N _{4 of Preparation Example 1.}
Figure 3b is a SEM image of _{the layered Ca 3} Al ₂ N _{4 of Preparation Example 1.}
Figure 3c is an SEM image of the layered AlN of Example 1.
4 is a photograph of the layered Ca ₃ Al ₂ N _{4 of Preparation Example 1.}

Hereinafter, with reference to the accompanying drawings, the embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

A method for manufacturing layered AlN according to the present invention will be described.

The method for manufacturing layered AlN according to the present invention can manufacture bulk-type AlN with a conventional 3D structure into a two-dimensional structure, and unlike conventional bulk-type AlN, it is easy to peel and can produce layered AlN with excellent thermal conductivity. .

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

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

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

The mixture may be heat-treated after being sealed 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 high temperatures may be used without limitation.

As shown in FIG. 1, Ca ₃ Al ₂ N ₄ prepared through step (1) has a 2D crystal structure different from AlN of a 3D crystal structure, and in step (2) to be described later, the Ca ₃ Al ₂ N ₄ By selectively removing Ca ions, layered AlN can be prepared without changing the crystal structure of _{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, so unreacted raw materials may remain, and thus there may be problems such as a decrease in the yield of the layered compound produced. have. In addition, when the heat treatment is performed in excess of 1200° C., there may be problems such as destruction of the reaction vessel used during the sintering reaction due to the vaporization of Ca ions, or a decrease in the yield of the layered compound produced.

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

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 10-15 °C/hour or 0.5-3 °C/hour, and when the temperature reduction rate is 10-15 °C/hour, layered Ca ₃ Al ₂ N ₄ can be polycrystallized have. When the temperature reduction rate is 0.5 to 3°C/hour, layered Ca ₃ Al ₂ N ₄ can be single crystallized, and the single crystal size of layered AlN even after removal of Ca ions contained in the layered Ca ₃ Al ₂ N _{4 is} can be maintained As the single crystal size of the layered AlN increases, the grain boundary of the particles may decrease, and the aspect ratio of the InAs nanosheets that are peeled off during the layered InAs peeling may increase.

If the temperature reduction rate is less than 0.5°C/hour, a change in the composition of the prepared material may occur due to the vaporization of Ca ions, and when the temperature reduction rate exceeds 3°C/hour, the prepared layered compound is polycrystallized can be

Next, as step (2), the layered compound prepared in step (1) is mixed with a salt capable of selectively removing Ca ions contained in the layered compound and a solvent capable of dissolving the salt By treatment with a solution, layered AlN is prepared 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 included in the layered compound.

The salt may be represented by the following Chemical Formula 1, and the salt is a cation having an electronegativity value between the alkali metal ion and Al ion, and is composed of M and Cl ion having 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 as long as it 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 3. If the molar ratio of the layered Ca ₃ Al ₂ N ₄ and the salt is less than 1:1, _{the Ca ions of the layered Ca 3} Al ₂ N ₄ may not be removed to a desired level, and if the molar ratio is 1 If it exceeds :3, the salt is not dissolved in the mixed solution, so there may be a problem such as the generation of a precipitate.

In addition, the step (2) may be performed at a temperature at which the Ca ion removal reaction can occur smoothly, and the temperature may vary depending on the composition of the mixed solution, but preferably a temperature of 20 ° C. or higher, more preferably Preferably, it may be carried out at a temperature of 20 to 60 °C. If it is carried out at less than 20 ℃, Ca ions may not be removed to a desired level, and when it is carried out at a temperature exceeding 60 ℃, the layered structure of the _{prepared layered Ca 3} Al ₂ N _{4 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 it is performed at a temperature of 20 to 60° C.

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

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

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

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

The layered AlN according to the present invention has a monoclinic crystal structure in which a space group is C2/2 or P2/c, which has a different crystal structure from the existing 3D bulk-type AlN, and has excellent peelability, resulting in nanosheet It is easy to peel in the form of a, and may have excellent thermal conductivity.

In the X-ray diffraction diagram obtained by powder X-ray diffraction 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 There may be no peaks at 2θ values of ±0.2 and 70.95 ±0.2. In addition, the layered AlN having a monoclinic crystal structure in which the space group is 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 the present invention will be described.

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

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

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

On the other hand, since the layered AlN and AlN nanosheets according to the present invention described above have excellent thermal conductivity and piezoelectric properties, they can 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 used in a piezoelectric element, the layered AlN or AlN nanosheets according to the present invention are included as a piezoelectric body included in the piezoelectric element, so that the piezoelectric properties may be excellent. Configurations other than the piezoelectric element included in the piezoelectric element may employ a configuration known in the art, so a detailed description thereof will be omitted in the present invention.

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

Although one embodiment of the present invention has been described above, the spirit of the present invention is not limited to the embodiments presented herein, and those skilled in the art who understand the spirit of the present invention can add components within the scope of the same spirit. , changes, deletions, additions, etc. will be able to easily suggest other embodiments, but this will also fall within the scope of the present invention.

(Preparation Example 1) Layered Ca ₃ Al ₂ N ₄ Produce

For the synthesis of layered Ca ₃ Al ₂ N _{4 , Ca 3} N ₂ powder and Al powder were mixed and then sealed in a quartz tube in a vacuum atmosphere. The quartz tube containing the sample was heat-treated at 1050° C. for 100 hours. Thereafter, it was cooled at a temperature reduction rate of 2° C./hour for recrystallization to obtain a layered Ca ₃ Al ₂ N ₄ single crystal of high purity.

(Example 1) Preparation 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 , thereby preparing layered AlN.

(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 product, 3D bulk type AlN (Sigma-Aldrich) was prepared.

(Experimental Example 1) XRD analysis

3D AlN of Comparative Example 1, the layered Ca ₃ Al ₂ N ₄ of Preparation Example 1, and the layered AlN of Example 1 were subjected to XRD analysis, 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 in which space groups are C2/2 and P2/c.

In addition, _{it can be confirmed that the layered AlN (Example 1) in which Ca ions are removed from the layered Ca 3} Al ₂ N ₄ has a monoclinic crystal structure in which the space groups are C2/2 and P2/c, which is a bulk type of 3D structure. It has a different crystal structure from AlN.

(Experimental Example 2) SEM analysis

SEM images were taken for 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.

Referring to FIGS. 3A and 3C , _{it can be seen that the layered Ca 3} Al ₂ N ₄ AlN prepared after removing Ca ions has a layered structure.

Claims (10)

(1) Ca ₃ N _{2 , and the formula Ca 3} Al ₂ having a monoclinic crystal structure in which a space group is C2/2 or P2/c by heat-treating a mixture containing Al powder and cooling it obtaining a layered compound represented by N _{4 ;} and
_{(2) A mixed solution containing an AlCl 3} salt capable of selectively removing Ca ions contained in the layered compound without changing the crystal structure of the layered compound and a solvent capable of dissolving the salt, the layered compound processing;
A method for producing a layered AlN comprising a.
delete According to claim 1,
The solvent is at least one selected from deionized water, tetrahydrofuran and dichloromethane.
According to claim 1,
The heat treatment of step (1) is a method for producing a layered AlN is performed for 80 to 200 hours at 1000 ~ 1200 ℃.
According to claim 1,
The cooling in step (1) is a method for producing a layered AlN is carried out at a temperature reduction rate of 0.5 ~ 3 ℃ / hour or 10 ~ 15 ℃ / hour.
delete delete delete delete delete

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