KR102071033B1 - A method for manufacturing graphene structure, graphene structure by the same and transparent electrode and light emitting diode comprising the same - Google Patents

Abstract

The present invention relates to a method for producing a graphene structure for improving the thermal stability of the doped graphene, a graphene structure prepared by the same, and a transparent electrode and a light emitting diode including the same. In the graphene structure manufacturing method according to the present invention, a first graphene layer is formed on a substrate, the first graphene layer is doped with a metal chloride, and at least one second graphene layer is laminated on the doped first graphene layer. It may include doing. The graphene structure according to the present invention may include a first graphene layer and at least one second graphene layer stacked on the first graphene layer, wherein the first graphene layer may be doped with a metal chloride. The transparent electrode according to the present invention may include the graphene structure. The light emitting diode according to the present invention may include the transparent electrode.

Description

A method for manufacturing a graphene structure, a graphene structure manufactured by the same, and a transparent electrode and a light emitting diode including the same.

The present invention relates to a graphene structure manufacturing method, a graphene structure produced by the same, and a transparent electrode and a light emitting diode including the same. More specifically, the present invention relates to a graphene structure manufacturing method for improving the thermal stability of the doped graphene, a graphene structure prepared by the same and a transparent electrode and a light emitting diode comprising the same.

Graphene is the new material that is currently attracting the most attention. Recently, graphene is reported to have better thermal, electrical, and mechanical properties than carbon nanotubes, and application research is being conducted in various fields. Graphene is a term made by combining the suffix -ene, which means a molecule having a double bond of graphite, which means graphite, and a two-dimensional allotrope of carbon, which has hexagonal lattice. do. The infinite plane of graphene shows an energy-free region of electrons where the valence and conduction bands meet,

Graphene is suitable as a transparent electrode material because it has excellent electrical properties and greatly changes its electrical properties depending on surface conditions. In particular, due to the two-dimensional characteristics of graphene, since all surfaces of graphene are exposed to surface adsorbents, electrical characteristics may be maximized. Graphene is a metal. Thus, there is very little Johnson noise due to the change in the main charge amount due to the extra electrons. In addition, graphene synthesized by Chemical Vapor Deposition has very few defects on the surface, so the effect caused by thermal change is less. In addition, since the contact with the metal has the property of ohmic contact, the contact resistance is very low, and measurement using the 4-point-probe is possible. Due to these properties, graphene of nanostructures can be utilized as a transparent electrode material, which is mainly used in electronic materials.

Graphene transparent electrodes have excellent elasticity, flexibility and transparency, and are relatively simple to synthesize and pattern. However, the above characteristics are less than 50% of using ITO (Indium Tin Oxide), which is a commercial transparent electrode. Problems when applied to electronic devices based on graphene are as follows.

First, compared with ITO, which is currently used as a transparent electrode, graphene has a thin thickness, which affects electrical properties.

Second, compared with ITO, graphene has a relatively low transmittance, so that luminous efficiency as a transparent electrode is inferior.

Third, the hole injection barrier in the electronic device is calculated by subtracting the graphene work function from the ionization energy of the semiconductor according to the Schottky barrier theory, where the work function of graphene is minimized to minimize the size of the barrier. Should be large. However, according to a recent study, the work function of graphene is known to be 4.2 to 4.5 eV, which falls short of the desired work function region. When graphene is used as a transparent electrode in an electronic device such as a light emitting diode and an organic light emitting diode, the light emitting efficiency is low. To solve this problem, a method of lowering sheet resistance through graphene doping of p-type has been developed.

In order to apply graphene to electronic devices, low surface resistance and high work function need to be controlled, and it is reported that the above adjustment is possible by forming a thin film on the surface by using gold chloride doping method. That is, graphene may be used as a transparent electrode by doping the graphene surface using a transition metal chloride as a dopant.

However, in the case of graphene doped with such a metal chloride, it was observed that the conductivity and permeability of graphene are lowered than the original state when the heat treatment process included in the electronic device manufacturing process is performed.

The problem to be solved by the present invention is to provide a graphene structure manufacturing method having a thermal stability and the graphene structure produced by it.

The problem to be solved by the present invention is to provide a graphene structure manufacturing method and a graphene structure prepared by the before and after heat treatment, the transmittance is maintained.

The problem to be solved by the present invention is to provide a graphene structure manufacturing method and a graphene structure prepared by the conductivity is maintained before and after heat treatment.

The problem to be solved by the present invention is to provide a graphene structure manufacturing method and a graphene structure produced by the change in the work function and the sheet resistance less before and after heat treatment.

The problem to be solved by the present invention is to provide a graphene structure manufacturing method and a graphene structure prepared by the before and after heat treatment, the vaporization of chlorine atoms is prevented.

The problem to be solved by the present invention is to provide a transparent electrode including a graphene structure having the above characteristics and a light emitting diode comprising the transparent electrode.

The problem to be solved by the present invention is to provide a light emitting diode comprising a transparent electrode formed of a graphene structure with improved luminous efficiency.

The present invention provides a method for producing a graphene structure laminated on the graphene doped with thermally and chemically stable graphene to solve the degradation of the doped graphene due to heat treatment. Through the structure, it is stable to heat treatment and maintains electrical characteristics. If the graphene structure layer prepared by the above manufacturing method is used as an electrode, the characteristics of the graphene may be maximized even in an element process requiring heat treatment.

According to an embodiment of the present invention, a method of manufacturing a graphene structure may include forming a first graphene layer on a substrate, doping the first graphene layer with a metal chloride, and forming at least one agent on the doped first graphene layer. It may include laminating two graphene layers.

The at least one second graphene layer may include at least one graphene layer doped with a metal chloride.

The metal chloride may include at least one metal chloride selected from the group consisting of AuCl ₃ , IrCl ₃ , MoCl ₃ , OsCl ₃ , PdCl ₂ and RhCl ₃ .

The substrate may include a metal oxide substrate, a silica substrate, or a plastic substrate.

The substrate may be any one of SiO ₂ , ZrO ₂ , TiO ₂ , Al ₂ O ₃ , glass, quartz, HfO ₂ , MgO, and BeO.

Forming the first graphene layer may include transferring the first graphene layer onto a substrate.

Graphene structure according to an embodiment of the present invention includes a first graphene layer, at least one second graphene layer stacked on the first graphene layer, the first graphene layer may be doped with a metal chloride. .

The at least one second graphene layer may include at least one graphene layer doped with a metal chloride.

The metal chloride may include at least one metal chloride selected from the group consisting of AuCl ₃ , IrCl ₃ , MoCl ₃ , OsCl ₃ , PdCl ₂ and RhCl ₃ .

The transparent electrode according to an embodiment of the present invention may include the graphene structure.

The light emitting diode according to the embodiment of the present invention may include the transparent electrode.

The method for producing a graphene structure according to the present invention and the graphene structure produced by it may have a high thermal stability.

The method for producing a graphene structure according to the present invention and the graphene structure prepared by the same may have a small change in conductivity and transmittance before and after heat treatment.

The method for producing a graphene structure according to the present invention and the graphene structure produced by the same have little change in work function and sheet resistance before and after heat treatment.

The method for producing a graphene structure according to the present invention and the graphene structure prepared thereby can prevent vaporization of the doped metal chloride.

The light emitting diode including the transparent electrode using the graphene structure according to the present invention has high thermal stability and luminous efficiency.

1 is a schematic view showing a method of manufacturing a graphene structure according to an embodiment of the present invention.
Figure 2 is a schematic diagram showing the manufacturing method of the graphene structures according to the comparative example for comparing with the graphene structure according to an embodiment of the present invention.
3 are graphs showing changes in transmittance according to wavelengths of graphene structures and graphs showing changes in sheet resistance according to the number of layers according to one embodiment and comparative embodiments of the present invention.
FIG. 4 is a graph illustrating changes in transmittance and sheet resistance according to annealing temperatures of graphene structures according to an exemplary embodiment and comparative examples. FIG.
5 is a field emission scanning electron microscope (FE-SEM) photograph before and after heat treatment of graphene structures according to an embodiment of the present invention and comparative embodiments.
FIG. 6 is a graph showing Raman Spectroscopy results before and after heat treatment of graphene structures according to an embodiment of the present invention and comparative examples. FIG.
FIG. 7 is a graph illustrating an analysis result of an photoelectron spectrometer (XPS) for metal atoms included in graphene structures according to an embodiment of the present invention and a comparative example.
FIG. 8 is a graph illustrating an analysis result of a chlorine atom photoelectron spectrometer (XPS) included in graphene structures according to an embodiment and a comparative example of the present invention.
9 is a schematic diagram of a phenomenon occurring during the heat treatment of the graphene structures according to an embodiment of the present invention and a comparative embodiment.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals have the same reference numerals as much as possible even if displayed on different drawings. In addition, in describing the present invention, if it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, preferred embodiments of the present invention will be described below, but the technical spirit of the present invention is not limited thereto, but may be variously modified and modified by those skilled in the art.

1 is a schematic view showing a method of manufacturing a graphene structure according to an embodiment of the present invention.

Referring to FIG. 1, the first graphene layer 12 is transferred onto the substrate 11, and the second graphene layer 13 is formed by doping the transferred first graphene layer 12 with metal chloride. Step, stacking another first graphene layer 12 on the second graphene layer 13 to form a graphene structure (14). The first graphene layer may be an undoped graphene layer. The second graphene layer may be a graphene layer doped with a metal chloride.

In the transferring of the first graphene layer 12 onto the substrate 11, the first graphene layer 12 is formed of graphene. Graphene is a sheet-like material having a planar hexagonal lattice structure composed of carbon atoms bonded to each other with sp ² . The graphene may be single layer graphene that is not stacked, or multilayer graphene in which a plurality of layers of single layer graphene are stacked. In the present embodiment, the graphene is not limited to the above, but single-layer graphene is suitable from the viewpoint of light transmittance of the graphene structure 14 and the fact that no delamination occurs. The substrate 11 is a support substrate of the graphene structure 14. The substrate 11 may be a metal oxide substrate, a silica substrate, or a plastic substrate. The substrate 11 may be any one or more of SiO ₂ , ZrO ₂ , TiO ₂ , Al ₂ O ₃ , glass, quartz, HfO ₂ , MgO, and BeO. The material of the substrate 11 is not particularly limited. When light transmittance is required for the graphene structure 14, the substrate 11 may be made of a material having light transmittance.

A method of transferring the first graphene layer 12 on the substrate 11 may be as follows.

First, graphene is deposited on a catalyst substrate to provide a graphene layer. The film formation may be formed by thermal CVD (Chemical Vapor Deposition), plasma CVD, or the like. In the thermal CVD method, graphene is formed by heating a carbon source material (a material containing a carbon material) supplied to the surface of a catalyst substrate. In the plasma CVD method, graphene is formed by plasmalizing a carbon source material. In addition to the CVD method, it is also possible to use graphene released from the solution or graphene physically released. However, it should be noted that the CVD method is appropriate in view of control of the number of layers (transparency), crystallinity (conductivity), and the area which can be formed as a uniform film.

Although the material of a catalyst substrate is not specifically limited, Nickel, iron, copper, etc. can be used as a material. Since single-layer graphene with high adhesion is formed, it is appropriate to use copper as a material of the catalyst substrate. Graphene can be formed on the surface of the catalyst substrate by supplying a substance (methane, etc.), which is a carbon source, to the surface of the catalyst substrate and heating the catalyst substrate above the graphene formation temperature. Specifically, graphene can be grown by heating the catalyst substrate at 960 ° C. for 10 minutes in an atmosphere of a mixed gas containing methane and hydrogen (methane: hydrogen = 100cc: 5cc for reducing the catalyst substrate). have.

Subsequently, graphene grown on the catalyst substrate is transferred onto the substrate. The substrate may be selected according to the purpose, and may be a quartz substrate when transparency is required. The transfer method is not particularly limited, but may be as follows, for example. A 4% PMMA (Poly (methyl methacrylate)) solution was applied on the graphene grown on the catalyst substrate by spin coating (2000 rpm, 40 seconds) and baked at 130 ° C. for 5 minutes. Through this, a resin layer containing PMMA is formed on the graphene. Next, the catalyst substrate is etched using a 1 M iron chloride solution.

After the graphene including the resin layer and the catalyst substrate is removed, the graphene is washed with ultrapure water, and then the graphene is transferred to a substrate (such as a quartz substrate) to naturally dry. After drying, the mixture is heated (annealed) to 400 ° C in a hydrogen atmosphere to decompose PMMA. Through the above-described process, the graphene layer 12 may be transferred onto the substrate 11.

In the step of forming the second graphene layer 13 by doping the transferred first graphene layer 12 with a metal chloride, the metal chloride is AuCl ₃ , IrCl ₃ , MoCl ₃ , OsCl ₃ , PdCl ₂ , and RhCl ₃ may be included. A method of forming the second graphene layer 13 by doping the first graphene layer 12 with metal chloride may be as follows. If the dopant is gold chloride (AuCl ₃ ), the gold chloride is vacuum dried at room temperature for 4 hours. It is dissolved in a solvent (dehydrated nitromethane, etc.) to obtain a 10 mM solution (hereinafter, referred to as a dopant solution). The dopant solution is applied on the first graphene layer 12 by spin coating (2000 rpm, 40 seconds) and dried in vacuo. Since the dopant solution is dried to form a layer on the first graphene layer 12, and the layer contacts the first graphene layer 12, the dopant (gold chloride, etc.) located near the interface has a first graphene layer. It is chemically adsorbed and doped by the graphene of (12). According to the above process, the second graphene layer 13 doped with gold chloride may be formed.

In addition, the concentration of the dopant in the dopant solution can be appropriately selected, but if the concentration is too high, the light transmittance of the doped second graphene layer 13 is lowered, and if the concentration is too low, resistance deterioration is likely to occur after doping.

In the step of forming the graphene structure 14 by stacking the first graphene layer 12 on the second graphene layer 13, the lamination method may include the transfer method described above.

According to each step described above, it is possible to manufacture the graphene structure 14 according to an embodiment of the present invention. Since the graphene structure 14 has a structure in which an undoped graphene layer is laminated on the graphene layer doped with metal chloride, the metal chloride including the doped graphene layer is vaporized in a process requiring heat treatment. The laminated graphene layer can be prevented. Therefore, the work function and sheet resistance of the graphene structure can be kept constant.

Figure 2 is a schematic diagram showing the manufacturing method of the graphene structures according to the comparative example for comparing with the graphene structure according to an embodiment of the present invention. 2A is a schematic diagram illustrating a method of manufacturing the A-type graphene structure 15 having a structure in which undoped graphene layers are stacked. Figure 2 (b) is a schematic diagram showing a method for manufacturing a B-type graphene structure 16 having a structure in which the doped graphene layers are stacked.

Method of manufacturing the A-type graphene structure 15 is the step of transferring the first graphene layer 12 on the substrate 11, another first graphene layer 12 on the transferred first graphene layer 12 Laminating). The first graphene layer 12 may be a graphene layer that is not doped. The specific manufacturing method of each step is similar to the manufacturing method of the graphene structure of FIG.

In the manufacturing method of the B-type graphene structure 16, the step of transferring the first graphene layer 12 on the substrate 11, the second graphene by doping the transferred first graphene layer 12 with a metal chloride Forming (13), and laminating another second graphene 13 on the second graphene (13). The first graphene layer 12 may be a graphene layer that is not doped. The second graphene layer 13 may be a graphene layer doped with a metal chloride. The specific manufacturing method of each step is similar to the manufacturing method of the graphene structure of FIG.

2 (a) and 2 (b), compared to the graphene structure 14 according to an embodiment of the present invention of Figure 1, in the case of the A-type graphene structure 15 doped graphene The pinned layer does not include the second graphene layer 13. In the case of the B-type graphene structure 16, the first graphene layer 12, which is an undoped graphene layer, is not included.

Experiment and analysis of the graphene structure 14, the A-type graphene structure 15 and the B-type graphene structure 16 which is a comparative example according to the embodiment of the present invention described above. In order to compare the A and B type graphene structures 15 and 16 which are comparative embodiments, the graphene structure 14 according to an embodiment of the present invention may be represented as a C type graphene structure.

3 are graphs showing changes in transmittance according to wavelengths of graphene structures and graphs showing changes in sheet resistance according to the number of layers according to one embodiment and comparative embodiments of the present invention. 3 (a) is a graph showing a change in transmittance according to the wavelength of the graphene structures according to an embodiment and a comparative embodiment of the present invention. 3 (b) are graphs showing a change in sheet resistance according to the number of layers of graphene structures according to an embodiment and a comparative example of the present invention.

Referring to FIG. 3 (a), FIG. 3 (a) (1) is a graph of a type A graphene structure 15 as a comparative example, and FIG. 3 (a) (2) is a type B graphene as a comparative example. 3A is a graph of the structure 16, and FIGS. 3A and 3 are graphs of the C-type graphene structure 14 according to an embodiment of the present invention. Through this, it can be seen that the transmittance decreases as the number of layers in which all of the A-type, B-type, and C-type graphene structures are stacked.

Referring to FIG. 3 (a) (1), the line 1L shows a case where the first graphene layer is one layer, the line 2L shows a case where the first graphene layer is two layers, and the line 3L shows a case where the first graphene layer is three layers. , Line 4L represents a case where the first graphene layer is four layers, line 5L represents a case where the first graphene layer is five layers, and the first graphene layer is an undoped graphene layer. As the graphene structure of A type increases as the number of layers increases, the slope of the graph also increases.

Referring to FIG. 3 (a) (2), the line 1L shows a case where the second graphene layer is one layer, the line 2L shows a case where the second graphene layer is two layers, and the line 3L shows a case where the second graphene layer is three layers. , Line 4L represents a case where the second graphene layer is four layers, line 5L represents a case where the second graphene layer is five layers, and the second graphene layer is a graphene layer doped with a metal chloride. As the B-type graphene structure increases in number of layers, the slope of the graph also increases.

Referring to FIG. 3 (a) (3), the line PG is a case where the first graphene layer is one layer, the line Doped is a case where the second graphene layer is one layer, and the line 1BL is on one layer of the second graphene layer. In the case where one layer of the first graphene layer is stacked, the line 2BL is the case where two layers of the first graphene layer are stacked on the one layer of the second graphene layer, and the line 3BL is on the second layer of graphene layer. The first graphene layer of three layers is stacked, the first graphene layer is an undoped graphene layer, the second graphene layer is a graphene layer doped with a metal chloride. The C graphene structure is compared with the A and B graphene structures, it can be seen that the slope of the graph is smooth.

Therefore, the graphene structure according to the embodiment of the present invention may exhibit a relatively uniform transmittance in a wide wavelength region as compared with the graphene structure according to the comparative example.

Referring to FIG. 3 (b), FIG. 3 (b) (1) is a graph of a graphene structure of Comparative Example A, and FIG. 3 (b) (2) is of a graphene structure B of Comparative Example. 3 (b) and (3) are graphs of the C-type graphene structure according to the embodiment of the present invention. Through this, it can be seen that the sheet resistance decreases as the number of layers in which all of the A-type, B-type, and C-type graphene structures are stacked. However, the B-type and C-type graphene structures have the same sheet resistance as the number of layers increases, but unlike the A-type graphene structure, the slope of the graph changes smoothly as the number of layers increases. That is, the B-type and C-type graphene structures have a relatively rapid decrease in sheet resistance when the initial layer number is changed, but then smoothly decreases in sheet resistance. In addition, it can be seen that the C-type graphene structure has the smoothest sheet resistance when the number of layers is 1BL or more.

Therefore, in the graphene structure according to the exemplary embodiment of the present invention, when more than one undoped graphene layer serving as a protective layer is stacked, it can be seen that the sheet resistance change according to the increase in the number of layers is small.

FIG. 4 is a graph illustrating changes in transmittance and sheet resistance according to annealing temperatures of graphene structures according to an exemplary embodiment and comparative examples. FIG. Figure 4 (a) is a graph showing a change in transmittance according to the annealing temperature of the graphene structures according to an embodiment and a comparative embodiment of the present invention. 4 (b) are graphs showing changes in sheet resistance according to annealing temperatures of graphene structures according to an embodiment and a comparative example of the present invention.

4 (a), FIG. 4 (a) (1) is a graph of a type A graphene structure according to a comparative example, and FIG. 4 (a) (2) is a type B graphene according to a comparative example. Figure 4 (a) (3) is a graph of the structure of the graphene graphene structure according to an embodiment of the present invention.

Referring to FIG. 4 (a) (1), the line 1L shows a case where the first graphene layer is one layer, the line 3L shows a case where the first graphene layer is three layers, and the line 5L shows a case where the first graphene layer is five layers. The first graphene layer is an undoped graphene layer. It can be seen that the A-type graphene structure has a constant transmittance regardless of the annealing temperature when the number of layers is the same. This is because the A-type graphene structure has a lamination structure of an undoped graphene layer and thus has high thermal stability.

Referring to FIG. 4 (a) (2), the line 1L shows a case where the second graphene layer is one layer, the line 3L shows a case where the second graphene layer is three layers, and the line 5L shows a case where the second graphene layer is five layers. The second graphene layer is a graphene layer doped with a metal chloride. It can be seen that the type B graphene structure has a decrease in transmittance according to the annealing temperature when the number of layers is the same. The type B graphene structure is because all of the graphene structures forming the graphene structure are doped with metal chloride, and as the annealing temperature increases, the metal nanoparticles on the surface of the graphene structure aggregate together.

Referring to FIG. 4 (a) (3), the line doped is a case where the second graphene layer is one layer, and the line 1BL is a case where one layer of the first graphene layer is laminated on one layer of the second graphene layer. Line 2BL indicates a case where two first graphene layers are stacked on a second layer of graphene, and line 3BL indicates a case where three first graphene layers are stacked on a second layer of graphene. The first graphene layer represents a graphene layer that is not doped, and the second graphene layer represents a graphene layer doped with metal chloride. The C-type graphene structure has a structure covering the second graphene layer with the first graphene layers. Therefore, since the second graphene layer contains a metal chloride, the drop in transmittance according to the change in the annealing temperature is the same as that of the B-type graphene structure. However, since the first graphene layers covering the second graphene layer do not include metal chlorides, the degree of permeability decrease with increasing annealing temperature is smaller than that of the B-type graphene structure.

In the graphene structure according to the exemplary embodiment of the present invention, since only one layer of the graphene layers forming the graphene structure includes a metal chloride, the degree of decrease in transmittance with increasing annealing temperature is relatively small.

4 (b), FIG. 4 (b) (1) is a graph of the A-type graphene structure according to the comparative example, and FIG. 4 (b) (2) is the B-type graphene according to the comparative example. Figure 4 (b) (3) is a graph of the structure of the graphene graphene structure according to an embodiment of the present invention.

Referring to Figure 4 (b) (1), it can be seen that the annealing temperature does not affect the sheet resistance of the A-type graphene structure formed of the first graphene layer which is an undoped graphene layer.

Referring to FIG. 4 (b) (2), the B-type graphene structure formed of the second graphene layer, which is a graphene layer doped with a dopant (AuCl ₃ ), exhibits an increase in sheet resistance according to the annealing temperature. When the graphene structure is formed of lines 3L) and 5 layers (line 5L), it can be seen that the increase in sheet resistance according to the annealing temperature is small compared with the case of forming a single layer (line 1L).

Referring to Figure 4 (b) (3), the C-type graphene structure shows a surface resistance is increased according to the annealing temperature, but when three first graphene layers are stacked on one second graphene layer (line) It can be seen that 3BL) effectively maintains sheet resistance.

That is, the graphitic structure according to the embodiment of the present invention may maintain the sheet resistance at a low state regardless of the annealing temperature by stacking an undoped graphene layer on the doped graphene layer.

5 is a field emission scanning electron microscope (FE-SEM) photograph before and after heat treatment of graphene structures according to an embodiment of the present invention and comparative embodiments. Figure 5 (a) is a field emission type before heat treatment (Fig. 5 (a) (1)) and after heat treatment (Fig. 5 (a) (2) when the first graphene layer of the A-type graphene structure is one layer Scanning electron microscope (Filed Emission Scanning Electron Microscope). Figure 5 (b) is the field emission type before heat treatment (Fig. 5 (b) (1)) and after heat treatment (Fig. 5 (b) (2)) when the second graphene layer of the B-type graphene structure is one layer Scanning electron micrograph. Figure 5 (c) is a field emission type before the heat treatment (Fig. 5 (c) (1)) and after the heat treatment (Fig. 5 (c) (2) when the second graphene layer of the B-type graphene structure is five layers Scanning electron micrograph. Figure 5 (d) is before the heat treatment (Fig. 5 (d) (1)) and after the heat treatment when the first graphene layer covering the second graphene layer of one layer of the C-type graphene structure (three layers) (Fig. 5 (d) Field emission scanning electron micrograph of (1)). The first graphene layer is an undoped graphene layer, and the second graphene layer is a graphene layer doped with a metal chloride.

Referring to Figure 5 (a), it can be seen that the surface of the A-type graphene structure is constant regardless of the heat treatment. 5 (b), 5 (c) and 5 (d), it can be seen that the type B graphene structure and the type C graphene structure increase in number and size of metal nanoparticles on the surface before and after heat treatment. have. but. It can be seen that the C-type graphene structure has a relatively small number and size of increased metal nanoparticles compared to the B-type graphene structure.

FIG. 6 is a graph showing Raman Spectroscopy results before and after heat treatment of graphene structures according to an embodiment of the present invention and comparative examples. FIG. 6 (a) shows Raman spectroscopy results of graphene structures before heat treatment, and FIG. 6 (b) shows Raman spectroscopy results of graphene structures after heat treatment. 6 (c) is a graph showing variation of G peaks of respective graphene structures before and after heat treatment. In each of the graphs, 3BL C type means a C type graphene structure having a structure in which three first graphene layers are stacked on a second layer of graphene, and 5L B shows five layers of a second graphene layer. Mean B-type graphene structure having a stacked structure. 1L type B means a type B graphene structure having a structure in which one layer of the second graphene layer is stacked. The first graphene layer is an undoped graphene layer, and the second graphene layer is a graphene layer doped with a metal chloride.

So it is the most noticeable in the Raman spectrum of the pin it is a 2D peak of G peak (peak) and the vicinity of 2700cm ^-1 in the vicinity of 1580cm ^-1. The G peak is a peak commonly found in graphite-based materials and is called G mode or G peak after 'g' of graphite. The G peak of the Raman spectrum shows the doping state due to the foreign matter of graphene.

Specifically, when the electronic state of the graphene is changed due to an external material, it means n-type doping when the G peak is shifted to a low wavelength, and p-type doping when the G peak is shifted to a high wavelength.

Referring to FIG. 6 (a), the G peaks of the graphene structures before the heat treatment are all located on the right, which is a high wavelength at 1580 cm ⁻¹ . This means that it is doped with p-type. Referring to FIG. 6 (b), the first layer (see line 1L type B) and the fifth layer (see line 5L type B) of the type B graphene structure are found again at 1580 cm ⁻¹ after heat treatment. This means that after the heat treatment, it is returned to the state before the doping.

However, in the case of the graphene structure C-type graphene structure according to an embodiment of the present invention (see line 3BL C-type) it can be seen that the G peak is still located in the 1580cm ^-1 right region even after the heat treatment. That is, in the case of the C-type graphene structure having a structure covering the doped graphene with graphene, the doped graphene layer because the undoped graphene layer serves as a barrier layer to protect the doped graphene layer The doped state of the pin can be effectively maintained before and after the heat treatment.

Referring to FIG. 6 (c), the white circle represents the variation of the G peak in the state before the heat treatment in which the graphene structures are doped with the dopant, and the black circle is the heat treatment of the graphene structures doped with the dopant. The variation of the G peak after 1 h is shown. AuCl ₃ , IrCl ₃ , MoCl ₃ , OsCl _3, PdCl ₂ and RhCl ₃ are used as dopants in order from top to bottom of the graph.

In the case of the 1L type B, the variation of the G peak before the heat treatment was approximately 10 ¹ cm ^−1, but the variation of the G peak was 10 ⁰ cm ⁻¹ regardless of the type of dopant after the heat treatment. This means that the graphene layer is returned to the state before the doping due to the heat treatment. In the case of the 5L B type, the difference in the variation of the G peak before and after the heat treatment is smaller than that of the 1L B type. This is because the upper doped graphene layers serve to protect the lower doped graphene layers.

In the case of 3BL type C, it can be seen that the variation of the G peak before and after the heat treatment is constant regardless of the type of dopant. That is, in the case of the C-type graphene structure, since the graphene layers stacked on the doped graphene layer serve as a barrier layer to protect the dopant, the doped state of the doped graphene layer is maintained regardless of the heat treatment. do.

Therefore, the graphene structure according to the embodiment of the present invention has excellent thermal stability before and after heat treatment.

FIG. 7 is a graph illustrating an analysis result of an photoelectron spectrometer (XPS) of metal atoms included in graphene structures according to an embodiment and a comparative example of the present invention. FIG. 7 (a) shows an analysis result of XPS (X-ray photoelectron spectroscopy) of core level Au 4f in a doped state before heat treatment. FIG. 7 (b) shows the results of X-ray photoelectron spectroscopy (XPS) analysis of the core level Au 4f in the state after heat treatment. Figure 7 (c) is a result of comparing the intensity of the metal particles and the ionic state after the heat treatment of the graphene structures. In each of the graphs, 3BL C type means a C type graphene structure having a structure in which three first graphene layers are stacked on a second layer of graphene, and 5L B shows five layers of a second graphene layer. Mean B-type graphene structure having a stacked structure. 1L type B means a type B graphene structure having a structure in which one layer of the second graphene layer is stacked. The first graphene layer is an undoped graphene layer, and the second graphene layer is a graphene layer doped with a metal chloride.

7 (a) and 7 (b), the dotted line a represents the intensity at the cabinet level Au ³⁺ 4f _5/2 in the ion particle state, and the dotted line b represents the cabinet level Au in the metal particle state. The intensity at 4f _5/2 is shown, the dotted line c represents the strength at the cabinet level Au ³⁺ 4f _7/2 in the ion particle state, and the dotted line d is the strength at the cabinet level Au 4f _7/2 in the metal particle state. Indicates.

In FIG. 7 (a) showing the state before the heat treatment, the intensity of each graphene layer appears on the dotted line a and the dotted line b, which are the inner states of the ionic state. Regardless of the type of graphene layer, the intensity does not appear. Since the intensities on the dotted line a and the dotted line b appear when the metal atoms are in the ion particle state, the invisible intensity means that the metal (Au) atoms return to the metal particle state after the heat treatment in the ion particle state before the heat treatment. That is, due to the heat treatment process, the metal atoms in the ion particle state existing on the doped graphene surface are changed to the metal particle state.

Referring to FIG. 7 (c), the dopant is AuCl ₃ , in order from the top of the graph to the bottom of the graph. The case of IrCl ₃ , MoCl ₃ , OsCl ₃ , PdCl ₂ , and RhCl ₃ is shown. The white circle represents the ratio of the strength of the metal particles to the strength of the ion particles in the doped state before the heat treatment, and the black circles represent the strength of the metal particles and the strength of the ion particles in the annealed state. Indicates a ratio. It can be seen that the heat treatment of all the graphene structure samples increases the strength of the metal particles and decreases the strength of the ion particles. That is, when the graphene layer doped with the metal chloride is heat treated, the metals of the metal chlorides as dopants are separated and aggregated together. As a result, the transmittance is reduced.

FIG. 8 is a graph illustrating an analysis result of a chlorine atom photoelectron spectrometer (XPS) included in graphene structures according to an embodiment and a comparative example of the present invention. FIG. 8 (a) shows an analysis result of XPS (X-ray photoelectron spectroscopy) of core level Cl 2p in the graphene-doped state before heat treatment. FIG. 8 (b) shows the results of X-ray photoelectron spectroscopy (XPS) of the cabinet level Cl 2p in the graphene state after heat treatment. FIG. 8 (c) is a graph showing changes in peak intensity of the internal level Cl 2p of the graphene layer before and after heat treatment. In each of the graphs, 3BL C type means a C type graphene structure having a structure in which three first graphene layers are stacked on a second layer of graphene, and 5L B shows five layers of a second graphene layer. Mean B-type graphene structure having a stacked structure. 1L type B means a type B graphene structure having a structure in which one layer of the second graphene layer is stacked. The first graphene layer is an undoped graphene layer, and the second graphene layer is a graphene layer doped with a metal chloride.

Referring to FIGS. 8A and 8B, a dotted line a indicates a case where the cabinet level is Cl 2p _1/2 and a dotted line b indicates a case where the cabinet level is Cl 2p _3/2 . Before the heat treatment (Fig. 8 (a)) and after the heat treatment (Fig. 8 (b)), the dotted line a and the dotted line b has a change in binding energy of -0.7eV, the average intensity of the peaks after the heat treatment is 3BL C type In this case, 1.27 times, 5L type B, 3.56 times, and 1L type B should be 8.15 times to reach the average intensity level before the heat treatment. This can be interpreted that the heat treatment vaporizes the chlorine atom on the surface of the graphene layer, and thus, the conductivity of the graphene structure tends to be lowered.

Therefore, in the case of 1L B-type graphene structure that does not include a graphene layer that serves to prevent chlorine vaporization, the amount of chlorine change before and after heat treatment is relatively large, but in the case of 3BL C-type graphene structure, chlorine vaporization Since it contains a graphene layer to prevent the, the amount of change of chlorine before and after heat treatment is relatively small.

Referring to FIG. 8C, bar graph 1 shows a case where the dopant is AuCl ₃ , bar graph 2 shows the case where the dopant is IrCl ₃ , bar graph 3 shows the case where the dopant is MoCl ₃ , and bar graph 4 shows the dopant. In the case of OsCl ₃ , the bar graph 5 represents the case where the dopant is PdCl ₃ , and the bar graph 6 represents the change of the peak intensity at the internal level Cl 2p when the dopant is RhCl ₃ . It can be seen from the bar graph that the change in the peak of the C-type graphene structure is the most before and after the heat treatment. Therefore, in the case of the graphene structure according to an embodiment of the present invention, the conductivity of the graphene structure can be maintained before and after the heat treatment.

9 is a schematic diagram of a phenomenon occurring during the heat treatment of the graphene structures according to an embodiment and a comparative embodiment of the present invention. Figure 9 (a) is a schematic diagram of a comparative example A-type graphene structure having a laminated structure of undoped graphene layers, Figure 9 (b) is a comparative example B type graphene having a laminated structure of the doped graphene layers 9 (c) is a schematic diagram of an example C-type graphene structure of the present invention having a structure in which undoped graphene layers are stacked on a doped graphene layer. Each of the graphene structures was annealed in an atmosphere of nitrogen gas (N ₂ Gas).

Referring to FIG. 9A, since the A-type graphene structure is not doped with a dopant, there is no change due to the thermal stability of the graphene layers.

Referring to FIG. 9B, since the B-type graphene structure is a stacked structure of doped graphenes, chlorine atoms are vaporized in the graphene layer on the top layer.

Referring to FIG. 9 (c), since the C-type graphene structure is a structure in which an undoped graphene layer is stacked on the doped graphene layer, the surface change is due to the thermal stability of the undoped graphene layer stacked thereon. Not found However, agglomeration of metal atoms included in the doped graphene layer was found.

In the case of the graphene structure according to an embodiment of the present invention, it can be confirmed that the change of chlorine present on the surface of the graphene layer is small through the above-described XPS analysis. Therefore, it can be seen that the stacked undoped graphene layers effectively serve as a gas barrier. Therefore, when the graphene structure according to an embodiment of the present invention is introduced into a device process including a heat treatment process, the device including the graphene structure may have high thermal stability. That is, the graphene structure according to the embodiment of the present invention may be utilized in various fields such as a transparent electrode and an intermediate layer of a semiconductor device.

The above description is merely illustrative of the technical idea of the present invention, and various modifications, changes, and substitutions may be made by those skilled in the art without departing from the essential characteristics of the present invention. will be. Accordingly, the embodiments disclosed in the present invention and the accompanying drawings are not intended to limit the technical spirit of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by the embodiments and the accompanying drawings. . The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

11: substrate.
12: first graphene layer.
13: second graphene layer.
14: graphene structure (type C graphene structure).
15: Type A graphene structure.
16: Type B graphene structure.

Claims (11)

In the manufacturing method of the graphene structure comprising a multilayer graphene layer,
Forming a first graphene layer on the substrate,
Doping the first graphene layer with a metal chloride,
Including laminating a second graphene layer, which is the last layer of the graphene structure, on the doped first graphene layer,
The second graphene layer is a method for producing a graphene structure remaining on the first graphene layer without metal chloride doping. The method according to claim 1,
The graphene layer of the other multilayers other than the second graphene layer is a method for producing a graphene structure all doped with a metal chloride. The method according to claim 1 or 2,
The metal chloride is a method of producing a graphene structure comprising at least one metal chloride selected from the group consisting of AuCl ₃ , IrCl ₃ , MoCl ₃ , OsCl ₃ , PdCl ₂ and RhCl ₃ . The method according to claim 1,
The substrate is a method of manufacturing a graphene structure comprising a metal oxide substrate, a silica substrate, or a plastic substrate. The method according to claim 1,
The substrate is a method for producing a graphene structure of any one of SiO ₂ , ZrO ₂ , TiO ₂ , Al ₂ O ₃ , glass, quartz, HfO ₂ , MgO and BeO. The method according to claim 1,
Forming the first graphene layer, the method of manufacturing a graphene structure comprising transferring the first graphene layer on the substrate. First graphene layer;
A second graphene layer stacked on the first graphene layer, wherein the first graphene layer is doped with a metal chloride,
And the second graphene layer remains on the first graphene layer without metal chloride doping. The method according to claim 7,
A graphene structure comprising a plurality of graphene layers doped with a metal chloride, wherein the second graphene layer is located on the plurality of graphene layers. The method according to claim 7 or 8,
The metal chloride is a graphene structure comprising at least one metal chloride selected from the group consisting of AuCl ₃ , IrCl ₃ , MoCl ₃ , OsCl ₃ , PdCl ₂ and RhCl ₃ . Transparent electrode comprising a graphene structure according to claim 7 or 8. A light emitting diode comprising the transparent electrode according to claim 10.

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