KR102425891B1 - Layered compounds and nanosheets containing gallium and antimony, and electrical devices using the same - Google Patents

Abstract

An object of the present invention is to provide a gallium 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 Ga _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 ≤2.25).

Description

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

The present invention relates to a layered compound and nanosheet containing gallium and antimony, and an electric device using the same, and more particularly, to a layered compound and nanosheet containing an alkali metal and gallium 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, gallium antimonide (Gallium Antimonide) is a compound semiconductor material and can be used in various electrical devices, but there is no known about gallium antimonide having a layered structure to date.

The antimony antimonide compound composed of a layered structure can not only diversify the application than the existing gallium antimonide compound having a different crystal structure, but can also be expected to be applied to a new area that has not been applied before.

An object of the present invention is to provide a gallium 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 Ga _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 ≤2.25).

In addition, in the present invention, the composition represented by the [Formula 1] M _1-x Ga _y Sb _z (M is at least one of group 1 elements, 0<x≤1.0, 0.75≤y≤1.25, 1.25≤z≤2.25) 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 Ga _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≤2.25)

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

In order to overcome this, the inventors place an additive element between Ga _y Sb _z layers by adding a Group 1 element (hereinafter referred to as "additive element") to Ga _y Sb _z , resulting in a layered structure compound followed by a Ga _y Sb _z layer. was able to make The additive elements positioned between these Ga _y Sb _z layers weakly couple the Ga _y Sb _z layers through van der Waals bonds, so that the surface 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 a Ga _y Sb _z layer along this cleavage plane, and this exfoliation becomes easier as the additive element is removed is done Therefore, Ga _y Sb _z nanosheets can be easily made from such a layered compound by a physical or chemical exfoliation method, where some of the additive elements may remain in the Ga _y Sb _z nanosheets.

If the additive element is continuously removed, the Ga _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 Ga _y Sb _z layers is eliminated as well as when the repeated two-dimensional Ga _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 a Ga _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 of the additive elements may remain in the Ga _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 Ga _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 Ga _y Sb _z layer 10 of MGa _y Sb _z , and the Ga _y Sb _z layer ( ₁₀ ) _indicates that _{the bond} is _maintained between It shows that the Ga _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 KGaSb ₂ having a space group of Cmca or K ₂ Ga ₂ Sb ₃ having a space group of P2 ₁ /c known in the prior art, and M ₁ that can be made through this _-x Ga _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 MGa _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 It can be said that the layered structure compound or nanosheet of the Ga _y Sb _z formula also falls 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 MGa _y Sb _z may be changed and an amorphous phase may be exhibited. Even in this case, the surface on which some additional elements are left or removed still becomes a cleaved surface where physical exfoliation occurs easily, or the bonding force between the Ga _y Sb _z layers is removed, so that the distance between the layers increases and cracks appear. Accordingly, the Ga _y Sb _z layer becomes two-dimensional. 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 Cmca, 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, the hydrogen ion contained in the strong acid is replaced with a 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 Cmca.

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, 2θ = 25.3 ° ± 0.50 °, 29.3 ° ± 0.50 °, 41.9 ° ± 0.50 °, 49.6 ° ± 0.50 °, 52.0 ° ± 0.50 ° in XRD measurement using CuKα ray It may be a layered compound or nanosheet in which a peak does not appear at the position of The peak may mean a peak having an intensity of 3% or more compared to a peak having the greatest intensity.

In general, the naturally occurring GaSb compound has a three-dimensional zinc blend structure, and diffraction patterns appear at 25.3°, 29.3°, 41.9°, 49.6°, and 52°, 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 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) Layered KGaSb ₂ Synthesis

K, Ga, 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 15 hours. After slowly cooling to 500° C. for 100 hours for recrystallization and crystal growth, it was maintained for 100 hours again and cooled to room temperature to obtain a final KGaSb ₂ sample.

2) removal of K

GaCl ₃ was dissolved in acetonitrile (acetonitrile) and 2 ml of ethanol-based HCl was added to prepare a solution, and then reacted in this solution for time to remove K from the layered KGaSb ₂ . The results are shown in the table below. Residual K in Table 1 shows the results obtained through EDS analysis.

sample name reaction time Residual K (at%) sample A - 29.9 sample B 0.5 hours 17.5 sample C 2 hours 15 sample D 4 hours 6.6 sample E 8 hours 4.9 sample F 12 hours 0.29

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.

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

Comparing the GaSb diffraction peaks (3D GaSb) of the zinc blend structure with Sample A, it was found that in Sample A, the diffraction peaks at 25.3°, 29.3°, 41.9°, 49.6°, and 52° did not appear in the zinc blend structure. .

On the other hand, when the reference diffraction peak of the KGaSb ₂ single crystal (KGaSb ₂ Ref) and the diffraction peak of Sample A were compared, the intensity at the main peak was slightly different, but the angle at which the main peak appeared was the same. Therefore, it was found that the sample A synthesized through the above-described synthesis process was KGaSb ₂ having a layered structure.

In addition, it was confirmed through XRD analysis that the synthesized sample A had an orthorhombic crystal structure of the space group Cmca.

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 K:Ga:Sb was close to the theoretical composition ratio of 1:1:2.

4 is a schematic diagram showing the structure of KGaSb ₂ , a Scanning Transmission Electron Microscope (STEM) analysis result in the [110] direction for Sample A, and a Selected Area Diffraction (SAED) pattern. As a result of analyzing the SAED pattern, the interplanar distance of the measured (004) plane pattern was 7.404 Å, and the measured (114) plane pattern was The interplanar distance of the pattern was 5.12 Å. Theoretically, since the interplanar distances of the (004) plane and the (114) plane were 7.408 Å and 5.10 Å, respectively, the measured values almost coincided with the theoretical values. However, such a measured value is a value that cannot be obtained from GaSb having a non-layered zinc blend structure. The measured pattern is a pattern that appears only in the Cmca 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 (004) and (114) surfaces is [1-10]. Therefore, it was confirmed that the zone-axis was [1-10], and the lattice structure in the STEM image actually measured from the [1-10] zone was compared with the theoretically obtained atomic structure model. exactly matched. It was confirmed that the synthesized sample was KGaSb ₂ having a Cmca space group.

As such, it was confirmed through XRD, SEM, EDS, and STEM results that sample A was KGaSb ₂ having a layered structure and a Cmca space group.

5 shows the diffraction peak (3D GaSb) of non-layered GaSb having a general zinc blend structure, the diffraction peak of sample A, and the diffraction peak of sample C from which K is partially removed. The XRD diffraction pattern of sample C showed major peaks in the same angular range as compared to sample A according to the removal of K, so it was judged that the orthorhombic crystal structure of sample A, Cmca, was still maintained.

6 shows a nanosheet made by removing K 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 K was removed, not only the cleavage plane but also the layer gap was widened and cracks were formed.

7 shows a scanning electron microscope (SEM) image of sample E and an energy dispersive spectroscopy (EDS) result. A layered structure with cleavage planes or cracks was confirmed on the SEM image, and the K content was found to be 4.9 at% as a result of EDS analysis.

8 is a schematic diagram of the layered K _1-x GaSb _two -atom structure after K is selectively removed, and a STEM image and SAED pattern image for sample D in the [010] direction. The atomic ratio of the remaining K ions was 6.59 at%. As a result of SAED analysis, the interplanar distance of the diffraction pattern of the (004) plane was 7.465 Å, and that of the diffraction pattern of the (114) plane was 5.07 Å. Compared with the theoretical (004) plane and (114) plane interplanar distances of 7.408 Å and 5.10 Å, respectively, it can be seen that the measured value is the same as the theoretical value. These measurements cannot be obtained from GaSb having a non-layered zinc blend structure. In addition, although the K ratio of the matrix structure KGaSb ₂ was 25%, the measured Na ratio of K _1-x GaSb ₂ was 6.59%, so it was confirmed that some K was removed, and the measured pattern was a pattern that appeared only in the Cmca 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 (004) and (114) surfaces is [1-10]. Therefore, it was confirmed that the zone-axis was [1-10], and the lattice structure in the STEM image actually measured from the [1-10] zone was compared with the theoretically obtained atomic structure model. exactly matched. Through this, it was confirmed that the material from which K was removed also maintained the Cmca space group of the parent material KGaSb ₂ 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 10 nm.

In addition, ferroelectric properties were measured through PFM (Piezoresponse Force Microscopy) for a nanosheet of sample C from which K was removed, 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 K 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 Ga _y Sb _z (M is at least one group 1 element, 0.3≤x≤0.8, 0.75≤y≤1.25, 1.25≤z≤2.25) delete delete The method of claim 1,
Wherein M is K, the 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 Cmca, a layered structure compound. delete The method of claim 1,
The layered compound has a peak at the positions of 2θ = 25.3°±0.50°, 29.3°±0.50°, 41.9°±0.50°, 49.6°±0.50°, 52.0°±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, made by a physical or chemical exfoliation method, and having ferroelectric-like properties.
[Formula 1] M _1-x Ga _y Sb _z (M is at least one group 1 element, 0.3≤x≤0.8, 0.75≤y≤1.25, 1.25≤z≤2.25) delete delete 13. The method of claim 12,
Wherein M is K, nanosheet. 13. The method of claim 12,
The composition further comprises H, nanosheets. delete 13. The method of claim 12,
The crystal structure of the composition represents a space group of Cmca, nanosheets. delete 13. The method of claim 12,
The composition does not show a peak at the positions of 2θ = 25.3 ° ± 0.50 °, 29.3 ° ± 0.50 °, 41.9 ° ± 0.50 °, 49.6 ° ± 0.50 °, 52.0 ° ± 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. delete 13. The method of claim 12,
The composition exhibits resistance switching properties, nanosheets. 13. The method of claim 12,
The thickness of the nanosheet is 500 nm or less, nanosheet.
delete delete delete

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