KR102425890B1 - Layered compounds and nanosheets containing aluminum and antimony, and electrical devices using the same - Google Patents

Abstract

An object of the present invention is to provide an aluminum antimonide layered structure compound containing an alkali metal, a nanosheet that can be made therethrough, and an electrical device including the materials. In the present invention, in order to achieve the above object, [Formula 1] M _1-x Al _y Sb _z (M is at least one of group 1 elements, 0 < x ≤ 1.0, 0.75 ≤ y ≤ 1.25, 1.25 ≤ z It is possible to provide a layered structure compound represented by ≤1.75).

Description

Layered compounds and nanosheets containing aluminum and antimony, and electrical devices using the same

The present invention relates to a layered compound and nanosheet containing aluminum and antimony, and an electric device using the same, and more particularly, to a layered compound and nanosheet containing an alkali metal and aluminum and antimony having various electrical properties. And it relates to an electric device using the same.

Layered compounds connected to interlayers through van der Waals bonds can exhibit various properties, and two-dimensional (2D) nanosheets with a thickness of several nanometers to hundreds of nanometers are manufactured by separating them by physical or chemical methods. Research on this is active.

In particular, low-dimensional materials such as nanosheets are expected to have innovative new functions that existing bulk materials do not have, and have great potential as next-generation future materials to replace existing materials.

However, layered structure compounds having a two-dimensional crystal structure have been limited to materials such as graphite or transition metal chalcogen compounds so far, and there is a problem in that they do not develop into materials of various compositions.

On the other hand, aluminum antimonide (Aluminum Antimonide) is a compound semiconductor material and can be used in various electrical devices, but there is no known about aluminum antimonide having a layered structure to date.

The aluminum antimonide compound having a layered structure can not only diversify the application compared to the existing aluminum antimonide compound having a different crystal structure, but also can be expected to be applied to a new area that has not been previously applied.

An object of the present invention is to provide an aluminum antimonide layered structure compound containing an alkali metal, a nanosheet that can be made therethrough, and an electrical device including the materials.

In the present invention to achieve the above object, in the present invention, [Formula 1] M _1-x Al _y Sb _z (M is at least one of group 1 elements, 0<x≤1.0, 0.75≤y≤1.25, 1.25≤z It is possible to provide a layered structure compound represented by ≤1.75).

In the present invention, the composition represented by the [Formula 1] M _1-x Al _y Sb _z (M is at least one of group 1 elements, 0<x≤1.0, 0.75≤y≤1.25, 1.25≤z≤1.75) Including, it is possible to provide a nanosheet made by a physical or chemical peeling method.

In addition, in the present invention, it is possible to provide an electric device including the layered structure compound or nanosheet as described above.

In addition, the electric device may be a memristor.

The layered structure compounds and nanosheets that can be provided through the present invention may have various electrical properties, thereby enabling the development of new electrical devices.

1 is a conceptual diagram of a layered structure compound and a nanosheet made according to the present invention.
2 is a graph showing the XRD diffraction pattern for the layered compound according to the present invention.
3 shows a scanning electron microscope (SEM) image and an energy dispersive spectroscopy (EDS) analysis result for the layered structure compound according to the present invention.
Figure 4 shows a schematic diagram showing the structure of the layered structure compound according to the present invention and STEM (Scanning Transmission Electron Microscope) analysis results.
5 is a graph showing the XRD diffraction pattern for the layered structure compound according to the present invention.
6 is a SEM and TEM (Transmission Electron Microscope) images of the layered structure compound and the nanosheet according to the present invention.
7 shows the SEM image and EDS analysis results for the layered compound according to the present invention.
8 is a schematic diagram showing the structure of the layered compound according to the present invention and shows the results of STEM analysis.
9 shows an atomic force microscopy (AFM) image of a nanosheet according to the present invention and a line profile thereof.
10 is a ferroelectric property evaluation result through PFM (Piezoresponse Force Microscopy) of the nanosheet according to the present invention.
11 shows a TEM image and a diffraction pattern of a nanosheet according to the present invention.

Hereinafter, the configuration and operation of the embodiment of the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related well-known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, when a part 'includes' a certain component, this means that other components may be further included, rather than excluding other components, unless otherwise stated.

The layered structure compound or nanosheet according to the present invention may be represented by the following formula (1).

[Formula 1] M _1-x Al _y Sb _z

(M is at least one type of group 1 element, 0<x≤1.0, 0.75≤y≤1.25, 1.25≤z≤1.75)

In general, as AlSb has a zinc blende crystal structure, a layered structure cannot appear, and therefore it is impossible to make a nanosheet by exfoliating it.

In order to overcome this, the inventors place an additive element between Al _y Sb _z layers by adding a Group 1 element (hereinafter referred to as "additive element") to Al _y Sb _z , resulting in a layered structure compound followed by an Al _y Sb _z layer. was able to make The additive elements positioned between these Al _y Sb _zz layers weakly couple the Al _y Sb _z layers through van der Waals bonds, so that the plane on which these additional elements are positioned forms a cleavage plane that is easily split along this plane.

Accordingly, the layered compound according to the present invention can be easily exfoliated through either or both physical or chemical methods into an Al _y Sb _z layer along this cleavage plane, and this exfoliation becomes easier as additional elements are removed. is done Therefore, Al _y Sb _z nanosheets can be easily made from such a layered compound by a physical or chemical exfoliation method, where some additive elements may remain in the Al _y Sb _z nanosheets.

If the additive element is continuously removed, the Al _y Sb _z interlayer distance in the compound gradually widens, weakening the bonding force between the layers, and eventually the bonding between the layers disappears and cracks may appear between the layers. Therefore, in the layered structure of the layered structure compound described in the present invention, the bonding force between the Al _y Sb _z layers is eliminated as well as when the repeated two-dimensional Al _y Sb _z layer is bonded to each other through van der Waals bonding by an additive element. This includes the case where the distance between the layers becomes wider and cracks appear.

The nanosheet made by exfoliating from such a layered compound may be an Al _y Sb _z single layer, but may be several hundred nm thick because it may be made by overlapping a plurality of layers. In general, nanosheets can exhibit anisotropy according to a two-dimensional shape only when the thickness is below a certain level compared to the width in the transverse direction. For this, the ratio (d/L) of the width (L) to the thickness (d) of the nanosheet is It is preferable that it is 0.1 or less. Since the width of the nanosheet made through the present invention can be 5 μm or more, the thickness of the nanosheet is preferably 500 nm or less. Here, some additive elements may remain in the Al _y Sb _z nanosheet.

As such, the nanosheet according to the present invention refers to a sheet that is peeled off by a physical or chemical method from a layered compound, and includes a case in which the Al _y Sb _z layer is formed of a plurality of layers as well as a single layer.

A conceptual diagram of an example of such a layered compound and nanosheet is shown in FIG. 1 , where M(11), an additive element, is positioned between the Al _y Sb _z layer 10 of MAl _y Sb _z , and the Al _y Sb _z layer ( 10) is _shown to _{maintain a bond between} shows that the Al _y Sb _z nanosheets 20 are made. The nanosheets made in this way may still contain some M(11).

The layered compound before the additive element is removed may be Na ₂ Al ₂ Sb ₃ or K ₂ Al ₂ Sb ₃ having a space group of P2 ₁ /c known in the prior art, and M _1-x that can be made through this Al _y Sb _z The layered structure compound of the formula can be said to be included in the scope of the present invention.

In addition, as a result of prediction through calculation, it can be seen that a layered structure compound according to the MAl _y Sb _z formula is possible using various Group 1 elements such as Li, Na, K, and M _1-x that can be made through this A layered compound or nanosheet of the formula Al _y Sb _z can also be said to be within the scope of the present invention.

A layered structure compound and nanosheets can be made through the layered structure compound and nanosheets using the layered structure compound without completely removing the additive element from the layered structure compound, but the layered structure compound and the nanosheet exhibit various electrical properties be able to

On the other hand, if the additive element is excessively removed when x exceeds 0.95, the crystal structure of MAl _y Sb _z may be changed and an amorphous phase may be exhibited. Even in this case, the surface on which some additional elements remain or are removed still becomes a cleaved surface on which physical exfoliation occurs easily, or the bonding force between the Al _y Sb _z layers is removed and the distance between the layers _widens , resulting in cracks _. By maintaining the layer, the compound has a layered structure, and a nanosheet exfoliated therefrom can be prepared.

Therefore, in the above-mentioned [Formula 1], x is 0.10≤x≤0.95 so that the layered structure compound or nanosheet according to the present invention is easy to peel and maintains the crystal structure before removal of the additive element and at the same time, various electrical properties by the additive element are maintained. , and more preferably 0.3≤x≤0.8.

Here, the crystal structure of the layered compound or nanosheet may maintain the space group of P2 ₁ /c, which is the crystal structure before removing the additive element.

A strong acid such as nitric acid or hydrochloric acid can be used to remove the additive element. As the additive element is removed through such a strong acid, hydrogen ions contained in the strong acid are replaced with the site from which the additive element has been removed and combined with a layered structure compound containing hydrogen. Through this, it is also possible to provide a nanosheet.

The above-described layered compound or nanosheet exhibits various properties as a result of analysis, and these properties will be described below. The layered structure compound or nanosheet described herein includes both cases with and without additional elements.

In XRD measurement using CuKα ray, the above-described layered compound or nanosheet may have a space group of P2 ₁ /c.

In addition, depending on the residual amount of the added element, the layered structure compound may include an amorphous phase.

On the other hand, the above-described layered structure compound or nanosheet, in XRD measurement using CuKα ray, 2θ = 25.1 ° ± 0.50 °, 29.1 ° ± 0.50 °, 41.6 ° ± 0.50 °, 49.2 ° ± 0.50 ° 51.6 ° ± 0.50 ° It may be a layered compound or nanosheet in which a peak does not appear at the position. The peak may mean a peak having an intensity of 5% or more compared to a peak having the greatest intensity.

In general, the naturally occurring AlSb compound has a three-dimensional zinc blend structure and shows a diffraction pattern at 25.1°, 29.1°, 41.6°, 49.2°, and 51.6°, but the layered structure compound or nanosheet according to the present invention has a zinc blend structure Since it is not, the diffraction pattern does not appear at these angles.

The layered structure compound or nanosheet as described above can exhibit various electrical properties due to its inherent layered structure and residual additive elements.

First, the layered compound or nanosheet according to the present invention exhibits ferroelectric-like properties.

The ferroelectric characteristic is generally a characteristic of an oxide having an asymmetric structure such as a perovskite structure BaTiO ₃ , and the ferroelectric characteristic appears according to a change in the position of Ba located at the center.

However, the layered compound or nanosheet according to the present invention does not have such an asymmetric structure, but nevertheless exhibits ferroelectric-like properties. The reason why it exhibits ferroelectric-like properties even though it is not an asymmetric structure is thought to be that the positions of the remaining additive elements move according to the external electric field.

Through the ferroelectric-like properties of the layered structure compound or nanosheet according to the present invention, it can be applied to various electrical devices.

In addition, the layered compound or nanosheet according to the present invention exhibits resistance switching properties.

If a material has resistance switching characteristics, the current does not increase linearly according to the voltage applied to the material, but when an initial voltage is applied, the material maintains a high resistance state and the increase in current is insignificant and reaches a certain critical point. As it changes to a low-resistance state, the current rapidly increases.

This resistance switching characteristic is a characteristic generally found in oxides. Recently, the development of memory devices such as memristors that can store information such as flash memories using these characteristics is active, and the layered structure compound of the present invention and the Nanosheets can be actively used in the development of memory devices such as memristors by utilizing resistance switching characteristics.

[Example]

1) Synthesis of layered Na ₂ Al ₂ Sb ₃

Na, Al, and Sb metal pieces were weighed according to the molar ratio, mixed, and then put into an alumina crucible. After that, it was placed in a quartz tube and double-sealed to block outside air. This process was carried out in a glove box in an argon atmosphere. Thereafter, the temperature was raised to 750° C. for 3 hours in a box furnace and maintained for 40 hours. Then, it was slowly cooled to room temperature for 200 hours for recrystallization and crystal growth to obtain a Na ₂ Al ₂ Sb ₃ sample.

2) Removal of Na

After dissolving AlCl ₃ to a concentration of 0.05M in acetonitrile and adding 2ml of ethanol-based HCl to prepare a solution, the solution was reacted by time to remove Na from the layered Na ₂ Al ₂ Sb ₃ . The results are shown in the table below. Residual Na in Table 1 shows the results obtained through EDS analysis.

sample name reaction time Residual Na (at%) sample A - 28.5 sample B 0.5 hours 13.9 sample C 2 hours 8.8 sample D 4 hours 4.1 sample E 12 hours 0.25

3) Nanosheeting process

After irradiating ultrasonic waves in ethanol with respect to the samples prepared as shown in Table 2, peeled nanosheets were prepared using a tape.

2 is a graph showing the XRD diffraction peak, the diffraction peak of a non-layered AlSb having a general zinc blend structure (3D AlSb), a reference diffraction peak of a Na ₂ Al ₂ Sb ₃ single crystal (Na ₂ Al ₂ Sb ₃ Ref), and the method described above. shows the diffraction peak for Na ₂ Al ₂ Sb ₃ (Sample A) made of

Comparing the AlSb diffraction peaks (3D AlSb) of the zinc blend structure with Sample A, it was found that in Sample A, the diffraction peaks at 25.1°, 29.1°, 41.6°, 49.2°, and 51.6° did not appear in the zinc blend structure. .

On the other hand, when comparing the reference diffraction peak (Na ₂ Al ₂ Sb ₃ Ref) of the Na ₂ Al ₂ Sb ₃ single crystal with the diffraction peak of Sample A, the intensity at the main peak is slightly different, but the angle at which the main peak appears is the same. could Therefore, it can be seen that the sample A synthesized through the above-described synthesis process is Na ₂ Al ₂ Sb ₃ having a layered structure.

In addition, it was confirmed that sample A synthesized through XRD analysis had a monoclinic crystal structure of the space group P2 ₁ /c.

3 shows a scanning electron microscope (SEM) image and an energy dispersive spectroscopy (EDS) result of the synthesized sample A. FIG. The layered structure of Sample A was confirmed on the SEM image, and as a result of EDS analysis, the molar ratio of Na:Al:Sb was close to the theoretical composition ratio of 2:2:3.

4 shows Na₂Al₂Sb₃A schematic diagram showing the structure of , the results of STEM (Scanning Transmission Electron Microscope) analysis in the [110] direction for Sample A, and Selected Area Diffraction (SAED) patterns are shown. As a result of analyzing the SAED pattern, the interplanar distance of the measured (002) plane pattern was 7.76 Å, and the measured (11-3) plane The interplanar distance of the pattern was 4.01 Å.

Theoretically, since the interplanar distances of the (200) plane and the (002) plane were 7.776 Å and 4.05 Å, respectively, the measured value was close to the theoretical value. However, these measured values are values that cannot be obtained from AlSb having a non-layered zinc blend structure. The measured pattern is a pattern that appears only in the P2 ₁ /c space group. In the SAED pattern, the zone-axis can be obtained through the cross product from the surface measured by the pattern, and the vector obtained through the cross product of the (002) and (11-3) surfaces is [1-10]. Therefore, it could be confirmed that the zone-axis is [1-10], and comparing the lattice structure in the actually measured STEM image seen from the [1-10] zone and the theoretically obtained atomic structure model exactly matched. It was confirmed that the synthesized sample was Na ₂ Al ₂ Sb ₃ having a P2 ₁ /c space group.

As such, it was confirmed through XRD, SEM, EDS, and STEM results that sample A was Na ₂ Al ₂ Sb ₃ having a layered P2 ₁ /c space group.

5 shows the diffraction peak of non-layered AlSb (3D AlSb) having a typical zinc blend structure, the diffraction peak of Sample A (Sample A), and the diffraction peak of Sample C from which Na is partially removed. The XRD diffraction pattern of sample C showed a main peak in the same angular range as compared to sample A according to the removal of Na, so it was judged that the monoclinic crystal structure of P2 ₁ /c of sample A was still maintained.

6 shows a nanosheet made by removing Na from Sample A to become Sample C, which is then peeled off using a tape. In Sample A, a cleavage plane between the layers was observed, but in Sample C, as Na was removed, not only the cleavage plane but also the interlayer gap was widened and cracks were formed.

7 shows scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) results of samples C and D. FIG. Samples C and D showed a layered structure with cleavage planes or cracks on the SEM image, and as a result of EDS analysis, the Na content was found to be 8.84 at% and 4.1 at%, respectively.

8 is a schematic diagram of the layered Na _2-x Al ₂ Sb ₃ atom structure after selectively removing Na, a STEM image in the [010] direction, and a SAED pattern image for sample B. FIG. As a result of SAED analysis, the interplanar distance of the diffraction pattern of the (002) plane was 7.79 Å, and that of the diffraction pattern of the (020) plane was 3.63 Å. Compared to the theoretical (002) plane and (020) plane interplanar distances of 7.776 Å and 3.61 Å, respectively, it can be seen that the measured value is the same as the theoretical value. These measured values cannot be obtained from AlSb having a non-layered zinc blend structure. In addition, although the Na ratio of the matrix structure Na ₂ Al ₂ Sb ₃ is 28.5%, the Na ratio of Na _2-x Al ₂ Sb ₃ measured is 13.9%, so it can be confirmed that some Na is removed. Also, the measured pattern is a pattern that appears only in the P2 ₁ /c space group. In the SAED pattern, the zone-axis can be obtained through the cross product from the surface measured by the pattern, and the vector obtained through the cross product of the (002) and (020) surfaces is [100]. Therefore, it can be confirmed that the zone-axis is [100], and when the lattice structure in the actually measured STEM image seen from the [100] zone is compared with the theoretically obtained atomic structure model, it is exactly the same. Through this, it was confirmed that the material from which Na was removed also maintained the P2 ₁ /c space group of the parent material Na ₂ Al ₂ Sb ₃ as it is.

9 shows an AFM (Atomic Force Microscopy) image of the exfoliated nanosheet in Sample C and the resulting line profile. It was confirmed that the nanosheet was peeled off with a thickness of 20 nm or less.

In addition, ferroelectric properties were measured through PFM (Piezoresponse Force Microscopy) for nanosheets from which Na was removed from sample C, and the results are shown in FIG. 10 . Through this, it was possible to observe that ferroelectric-like characteristics appeared.

It was found that by using such ferroelectric-like characteristics, it can be applied to various electrical devices and can be applied to memristor devices, which are being actively developed as neuromorphic memory devices in recent years.

Meanwhile, TEM analysis was performed on sample E from which Na was excessively removed, and the results are shown in FIG. 11 . TEM analysis showed that the nanosheet from sample D was an amorphous phase.

Claims (26)

A layered structure compound represented by the following Chemical Formula 1 and having ferroelectric-like properties.
[Formula 1] M _1-x Al _y Sb _z
(M is at least one of group 1 elements, 0.3≤x≤0.8, 0.75≤y≤1.25, 1.25≤z≤1.75) delete delete The method of claim 1,
Wherein M is Na, a layered structure compound. The method of claim 1,
The layered structure compound further comprises H, the layered structure compound. delete The method of claim 1,
The crystal structure of the layered structure compound represents a space group of P2 ₁ /c, a layered structure compound. delete The method of claim 1,
The layered compound has a peak at the positions of 2θ = 25.1°±0.50°, 29.1°±0.50°, 41.6°±0.50°, 49.2°±0.50°, and 51.6°±0.50° in XRD measurement using CuKα ray. Without, the peak means a peak having an intensity of 3% or more compared to the peak having the greatest intensity, a layered structure compound. delete The method of claim 1,
The layered structure compound exhibits resistance switching properties, a layered structure compound. A nanosheet comprising a composition represented by the following Chemical Formula 1 and made by a physical or chemical peeling method.
[Formula 1] M _1-x Al _y Sb _z
(M is at least one of group 1 elements, 0<x<1.0, 0.75≤y≤1.25, 1.25≤z≤1.75) 13. The method of claim 12,
Wherein x is 0.10≤x≤0.95, nanosheets. 13. The method of claim 12,
Wherein x is 0.3≤x≤0.8, the nanosheet. 13. The method of claim 12,
Wherein M is Na, nanosheets. 13. The method of claim 12,
The composition further comprises H, nanosheets. 13. The method of claim 12,
Wherein x is 0.95<x, nanosheets. 17. The method according to any one of claims 12 to 16,
The crystal structure of the composition represents a space group of P2 ₁ /c, nanosheets. 18. The method of claim 17,
The composition comprises an amorphous phase, nanosheets. 18. The method according to any one of claims 12 to 17,
The composition does not show a peak at the positions of 2θ = 25.1 ° ± 0.50 °, 29.1 ° ± 0.50 °, 41.6 ° ± 0.50 °, 49.2 ° ± 0.50 °, 51.6 ° ± 0.50 ° in XRD measurement using CuKα rays, The peak means a peak having an intensity of 3% or more compared to the peak having the greatest intensity, nanosheet. 18. The method according to any one of claims 12 to 17,
wherein the composition exhibits ferroelectric-like properties. 18. The method according to any one of claims 12 to 17,
The composition exhibits resistance switching properties, nanosheets. 18. The method according to any one of claims 12 to 17,
The thickness of the nanosheet is 500 nm or less, nanosheet. delete delete delete

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