KR20150006915A - 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 manufacturing a graphene structure for improving the thermal stability of doped graphene, a graphene structure manufactured thereby, a transparent electrode and a light emitting diode including the same. The method for manufacturing a graphene structure according to the present invention forms a first graphene layer on a substrate, dopes the first graphene layer with metallic chloride and laminates at least one second graphene layer on the doped first graphene layer. The graphene structure according to the present invention comprises the first graphene layer and at least second graphene layer laminated on the first graphene layer, wherein the first graphene layer is capable of being doped with metallic chloride. The transparent electrode according to the present invention is capable of including the graphene structure. The light emitting diode according to the present invention is capable of including the transparent electrode.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a graphene structure, a graphene structure produced thereby, and a transparent electrode and a light emitting diode including the same. BACKGROUND ART [0002]

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

Graphene is the most popular new material at present. Recently, graphene has been reported to have better thermal, electrical, and mechanical properties than carbon nanotubes, and application studies are underway in various fields. A graphene is a term made by combining a graphite and a suffix -ene, which means a molecule having a double bond of carbon, which means graphite, and means a two-dimensional allotope of carbon having a hexagonal lattice do. The infinite plane of graphene shows an electron-free energy field where the valence band and the conduction band meet,

Graphene has excellent electrical properties and is suitable as a transparent electrode material because electrical characteristics greatly vary depending on the surface conditions. In particular, due to the two-dimensional nature of graphene, all surfaces of graphene are exposed to the surface adsorbent material, thereby maximizing the electrical properties. Graphene has the property of metal. Therefore, the Johnson noise due to the change of the charge amount due to the extra electrons is very small. In addition, since graphene synthesized by chemical vapor deposition has very few defects on the surface, the effect caused by the thermal change is small. In addition, since the contact with the metal has an ohmic contact property, the contact resistance is very low and measurement using a 4-point probe is possible. Because of this property, graphene of nanostructure can be used as transparent electrode material mainly used in electronic materials.

The transparent electrodes using graphene have excellent stretchability, flexibility and transparency, and are relatively easy to synthesize and pattern. However, the above characteristics do not reach 50% of that in the case of ITO (Indium Tin Oxide), which is a commercially available transparent electrode. Problems when applied to electronic devices based on graphene are as follows.

First, the thickness of the graphene is thinner than that of ITO, which is currently commercially used as a transparent electrode, which affects the electrical properties.

Second, as compared with ITO, graphene has a relatively low transmittance, resulting in a decrease in luminous efficiency as a transparent electrode.

Third, the electron injection barrier is calculated by subtracting the work function of the graphene from the ionization energy of the semiconductor according to the Schottky barrier. In order to minimize the barrier size, . However, according to recent studies, the work function of graphene is known to be 4.2 to 4.5 eV and does not reach the desired work function area. When the graphene is used as a transparent electrode in an electronic device such as a light emitting diode and an organic light emitting diode, low luminous efficiency is shown. To solve this problem, a method of lowering the surface resistance through p-type doping of graphene is being developed.

In order to apply graphene to an electronic device, it is necessary to control the surface resistance and the work function to a low level, and it is reported that the above-mentioned control is possible by forming a silver film on the surface using a gold chloride doping method. That is, graphene can be used as a transparent electrode by doping a graphene surface using a transition metal chloride as a dopant.

However, in the case of doped graphene using such a metal chloride, the conductivity and transmittance of graphene were lowered than those of the original state when a heat treatment process including an electronic device manufacturing process was performed.

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

A problem to be solved by the present invention is to provide a method for manufacturing a graphene structure in which the transmittance is maintained before and after a heat treatment, and a graphene structure produced thereby.

A problem to be solved by the present invention is to provide a method of manufacturing a graphene structure that maintains conductivity before and after a heat treatment, and a graphene structure manufactured thereby.

A problem to be solved by the present invention is to provide a method for producing a graphene structure having little change in work function and sheet resistance before and after a heat treatment, and a graphene structure produced thereby.

A problem to be solved by the present invention is to provide a method for manufacturing a graphene structure in which vaporization of chlorine atoms is prevented before and after a heat treatment, and a graphene structure produced thereby.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a transparent electrode including a graphene structure having the above-described characteristics and a light emitting diode including the transparent electrode.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a light emitting diode including a transparent electrode formed of a graphene structure having improved light emitting efficiency.

The present invention proposes a method for producing a graphene structure by laminating graphene doped with thermally and chemically stable graphene in order to solve the degradation of the properties of doped graphene due to heat treatment. Through this structure, it is stable to heat treatment and can maintain electric characteristics. If the graphene structure layer produced by the above manufacturing method is used as an electrode, the characteristics of graphene can be maximized even in an element process requiring a heat treatment process.

A method of fabricating a graphene structure according to an embodiment of the present invention includes forming a first graphene layer on a substrate, doping the first graphene layer with a metal chloride, 2 < / RTI > graphene layer.

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 based substrate, a silica based 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.

The forming of the first graphene layer may include transferring the first graphene layer onto the substrate.

A 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, wherein the first graphene layer is 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 exemplary embodiment of the present invention may include the graphene structure.

The light emitting diode according to an 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 thereby can have high thermal stability.

The method for manufacturing a graphene structure according to the present invention and the graphene structure produced therefrom may have less change in conductivity and transmittance before and after the heat treatment.

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

The method of manufacturing a graphene structure according to the present invention and the graphene structure produced 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 high luminous efficiency.

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

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same or similar components throughout the drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. In addition, the preferred embodiments of the present invention will be described below, but it is needless to say that the technical idea of the present invention is not limited thereto and can be variously 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, there is shown a method of fabricating a semiconductor device including the steps of transferring a first graphene layer 12 onto a substrate 11, doping the transferred first graphene layer 12 with a metal chloride to form a second graphene layer 13 , And laminating another first graphene layer (12) on the second graphene layer (13) to form the 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 step of transferring 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 sp ² bonded to each other. The graphene may be a single-layer graphene that is not laminated, or a multi-layer graphene in which a plurality of single-layer graphenes are laminated. In this embodiment, the graphene is not limited to the above, but a single-layer graphene is suitable in view of the light transmittance of the graphen structure 14 and no delamination. The substrate 11 is a support substrate of the graphene structure 14. The substrate 11 may be a metal oxide based substrate, a silica based 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 onto the substrate 11 may be as follows.

First, a graphene film is formed on a catalyst substrate, and a graphene layer is provided. The film formation may be performed using a thermal CVD (Chemical Vapor Deposition) method, a plasma CVD method, or the like. In the thermal CVD method, the carbon source material (material containing carbon material) supplied to the surface of the catalyst substrate is heated to form graphene. In the plasma CVD method, the carbon source material is converted into plasma to form graphene. In addition to the CVD method, it is also possible to use released graphene in solution or physically peeled graphene. However, it should be noted that the CVD method is suitable from the viewpoints of control of the number of layers (transparency), crystallinity (conductivity), an area that can be formed as a uniform film, and the like.

The material of the catalyst substrate is not particularly limited, but nickel, iron, copper and the like can be used as the material. Since single-layer graphene with high adhesiveness is formed, it is appropriate to use copper as a material for the catalyst substrate. Graphene can be deposited on the surface of the catalyst substrate by supplying a carbon source material (such as methane) to the surface of the catalyst substrate and heating the catalyst substrate above the graphenization temperature. Specifically, graphene can be grown by heating the catalyst substrate at 960 ° C. for 10 minutes in a mixed gas containing methane and hydrogen (for reducing the catalyst substrate, methane: hydrogen = 100 cc: 5 cc) have.

Then, the 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 an example is as follows. 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 캜 for 5 minutes. Through this, a resin layer containing PMMA is formed on the graphene. Then, the catalyst substrate is etched using a 1M solution of iron chloride.

After the graphene containing the resin layer and having the catalyst substrate removed is washed with ultrapure water, the graphene is transferred to a substrate (quartz substrate or the like) and air-dried. After drying, the PMMA is decomposed by heating (annealing) at 400 DEG C in a hydrogen atmosphere. Through the above-described process, the graphene layer 12 can be transferred onto the substrate 11.

Wherein the metal chloride is selected from the group consisting of AuCl ₃ , IrCl ₃ , MoCl ₃ , OsCl ₃ , PdCl ₂ , and AuCl ₃ , and the second graphene layer 13 is formed by doping the transferred first graphene layer 12 with a metal chloride. It may include RhCl _3. A method of forming the second graphene layer 13 by doping the first graphene layer 12 with a metal chloride may be as follows. If the dopant is yeomhwageum (AuCl _3), and dried in vacuo for 4 hours at room temperature yeomhwageum. And dissolved in a solvent (dehydrated nitromethane or the like) to obtain a 10 mM solution (hereinafter referred to as a dopant solution). The dopant solution was applied on the first graphene layer 12 by spin coating (2000 rpm, 40 seconds) and vacuum dried. The dopant solution is dried to form a layer on the first graphene layer 12 and the layer is in contact with the first graphene layer 12 so that a dopant (such as chloride) Is chemically adsorbed and doped by the graphene of the first electrode 12. A second graphene layer 13 doped with chlorine may be formed according to the above-described process.

Also, the concentration of the dopant in the dopant solution can be appropriately selected. However, if the concentration is too high, the light transmittance of the doped second graphene layer 13 lowers. If the concentration is too low, resistance deterioration easily occurs after doping.

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

According to each of the above-described steps, the graphene structure 14 according to an embodiment of the present invention can be manufactured. Since the graphene structure 14 has a structure in which a graphene layer that is not doped is laminated on a graphene layer doped with a metal chloride, the metal chloride contained in the doped graphene layer is vaporized during a process requiring heat treatment It can be prevented by using a stacked graphene layer. Therefore, the work function and sheet resistance of the graphene structure can be kept constant.

FIG. 2 is a schematic view illustrating methods of manufacturing graphene structures according to a comparative example for comparison with a graphene structure according to an embodiment of the present invention. Referring to FIG. 2 (a) is a schematic view showing a method for producing an A-type graphene structure 15 having a structure in which undoped graphene layers are laminated. 2 (b) is a schematic view showing a method of manufacturing a B-type graphene structure 16 having a structure in which doped graphene layers are laminated.

A method of manufacturing an A-type graphene structure 15 includes the steps of transferring a first graphene layer 12 onto a substrate 11, forming another first graphene layer 12 on the transferred first graphene layer 12 ). ≪ / RTI > The first graphene layer 12 may be a non-doped graphene layer. A specific manufacturing method of each step is similar to the above-described method of manufacturing the graphene structure of Fig.

A method for manufacturing a B-type graphene structure 16 includes the steps of transferring a first graphene layer 12 onto a substrate 11, doping the transferred first graphene layer 12 with a metal chloride, (13), and laminating another second graphene (13) on the second graphene (13). The first graphene layer 12 may be a non-doped graphene layer. The second graphene layer 13 may be a graphene layer doped with a metal chloride. A specific manufacturing method of each step is similar to the above-described method of manufacturing the graphene structure of Fig.

Referring to FIGS. 2 (a) and 2 (b), in comparison with the graphene structure 14 according to the embodiment of the present invention shown in FIG. 1, in the case of the A-type graphene structure 15, And does not include the second graphene layer 13 which is a pin layer. But does not include the first graphene layer 12 which is a non-doped graphene layer in the case of the B-type graphene structure 16.

Experiments and analyzes are performed on the graphene structure 14, the A-type graphene structure 15 and the B-type graphene structure 16 according to an embodiment of the present invention. A graphene structure 14 according to an embodiment of the present invention can be represented by a C-type graphene structure for comparison with the A-type and B-type graphene structures 15 and 16 of the comparative example.

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

3 (a) is a graph for an A-type graphene structure 15 as a comparative example, and Figs. 3 (a) and 2 (2) 3 (a) and 3 (b) are graphs for a C-type graphene structure 14 according to an embodiment of the present invention. As a result, it can be seen that the transmittance decreases as the number of layers of the A, B, and C graphene structures increases.

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

3 (a) and 2 (b), the line 1L represents the case where one layer of the second graphene layer is provided, the line 2L represents the case where the second graphene layer has two layers, and the line 3L represents the case where the second graphene layer has three layers Line 4L represents the case where the second graphene layer has four layers, line 5L represents the case where the second graphene layer has five layers, and the second graphene layer is the graphene layer doped with the metal chloride. It can be seen that as the number of layers increases, the slope of the graph also increases.

3 (a) and 3 (b), line PG shows a case where one layer of the first graphene layer is formed, line Doped shows a case where one layer of the second graphene layer is provided, Line 2BL represents the case where two layers of the first graphene layer are laminated on one layer of the second graphene layer and line 3BL represents the case where the one layer of the first graphene layer is laminated on the one layer of the second graphene layer The first graphene layer is a non-doped graphene layer, and the second graphene layer is a graphene layer doped with a metal chloride. It can be seen that the C-type graphene structure is smooth compared to the A- and B-type graphene structures.

Accordingly, the graphene structure according to an exemplary embodiment of the present invention can exhibit a relatively uniform transmittance over a wide wavelength range as compared with the graphene structure according to the comparative example.

Referring to FIG. 3 (b), FIG. 3 (b) (1) is a graph of an A-type graphene structure as a comparative example, 3 (b) and 3 (3) are graphs for a C-type graphene structure according to an embodiment of the present invention. As a result, it can be seen that the sheet resistance decreases as the number of layers in which the A-type, B-type and C-type graphene structures are all stacked increases. However, the B-type and C-type graphene structures have the same sheet resistance as the number of layers is increased. However, unlike the A-type graphene structure, the slope of the graph changes smoothly as the number of layers increases. That is, the B and C graphene structures decrease in sheet resistance relatively rapidly when the number of initial layers is changed, but then the sheet resistance drops smoothly. Also, it can be seen that the sheet resistance decreases most smoothly when the number of layers of the C-type graphene structure is 1BL or more.

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

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

4A is a graph of an A-type graphene structure according to a comparative example, and FIGS. 4A and 2B are graphs of a B-type graphene And FIGS. 4 (a) and (3) are graphs of a C-type graphene structure according to an embodiment of the present invention.

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

Referring to FIG. 4A and FIG. 4B, a line 1L indicates a case where one layer of the second graphene layer is provided, a line 3L indicates a case where the second graphene layer has three layers, and a line 5L indicates a case where the second graphene layer has five layers And the second graphene layer is a graphene layer doped with a metal chloride. It can be seen that the permeability of the B-type graphene structure decreases with annealing temperature when the number of layers is the same. The B-type graphene structure is because all of the graphene structures forming the graphene structure are doped with metal chloride, and the metal nanoparticles on the graphene structure surface aggregate as the annealing temperature increases.

4 (a) and 3 (b), the line Doped shows a case in which the second graphene layer is one layer, the line 1BL shows a case in which one layer of the first graphene layer is laminated on one layer, Line 2BL represents the case where two layers of the first graphene layer are laminated on one layer of the second graphene layer and line 3BL represents the case where three layers of the first graphene layer are laminated on the one layer of the second graphene layer , The first graphene layer represents an undoped graphene layer, and the second graphene layer represents a graphene layer doped with a metal chloride. The C-type graphene structure has a structure in which the second graphene layer is covered with the first graphene layers. Therefore, since the second graphene layer contains a metal chloride, it is the same as the B-type graphene structure that the transmittance decreases with the change of the annealing temperature. However, since the first graphene layers covering the second graphene layer do not contain a metal chloride, the degree of decrease in transmittance is small as the annealing temperature increases as compared with the B-type graphene structure.

Since the graphene structure according to an embodiment of the present invention includes only one of the graphene layers forming the graphene structure, the degree of decrease in the transmittance is relatively small as the annealing temperature increases.

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

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

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 ), shows a rise in sheet resistance according to the annealing temperature, (Line 3L) and the fifth layer (line 5L), the increase in sheet resistance according to the annealing temperature is smaller than that in the case where the graphen structure is formed as a single layer (line 1L).

Referring to FIGS. 4 (b) and 3 (c), the C-type graphene structure shows a rise in sheet resistance according to the annealing temperature, but when three first graphene layers are stacked on one second graphene layer 3BL), the sheet resistance is effectively maintained.

That is, the graphene layer according to an exemplary embodiment of the present invention can stack a non-doped graphene layer on the doped graphene layer to keep the sheet resistance low relative to the annealing temperature.

FIG. 5 is a field emission scanning electron microscope (FE-SEM) photograph of graphene structures according to one embodiment of the present invention and comparative examples before and after heat treatment. FIG. 5A is a graph showing the relationship between the field emission type (FIG. 5A) before annealing (FIG. 5A) and annealing after annealing (FIG. (Filed Emission Scanning Electron Microscope). FIG. 5 (b) is a graph showing the relationship between the field emission type (FIG. 5 (b)) of the B-type graphene structure before the heat treatment It is a scanning electron microscope photograph. Fig. 5 (c) is a graph showing the relationship between the electric field emission type of the B-type graphene structure before the heat treatment (Fig. 5 (c) (1)) and the heat treatment after the second graphene layer It is a scanning electron microscope photograph. 5 (d) is a graph showing the relationship between the thickness of the first graphene layer before the heat treatment (FIG. 5 (d) (1)) and the heat treatment after the first graphene layer covering three layers of the second graphene layer ) (1)). ≪ / RTI > 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 FIG. 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 number and size of metal nanoparticles on the surface of the B-type graphene structure and the C-type graphene structure increase before and after the heat treatment have. but. The C-type graphene structure has a relatively smaller number and size of increased metal nanoparticles than the B-type graphene structure.

FIG. 6 is a graph showing Raman spectroscopy results of graphene structures before and after heat treatment according to one embodiment of the present invention and comparative examples. FIG. FIG. 6 (a) is a Raman spectroscopic analysis result of the graphene structures before the heat treatment, and FIG. 6 (b) is a Raman spectroscopic analysis result of the graphene structures after the heat treatment. 6 (c) is a graph showing the variation of the G peak of each graphene structure after the heat treatment. In each of the graphs, the 3BL C type means a C-type graphene structure having a structure in which three first graphene layers are laminated on a second graphene layer in one layer, Means a type B graphene structure having a laminated structure. 1L type B refers to a type B graphene structure having a structure in which one layer of a second graphene layer is laminated. 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 is a 2D peak of G peak (peak) and the vicinity of 2700cm ^-1 in the vicinity of 1580cm ^-1. The G peak is commonly found in graphite materials and is called the G mode or G peak after the 'g' of graphite. Through the G peak of Raman spectrum, the doping state due to the external material of graphene can be known.

Specifically, when the electron state of graphene changes due to an external substance, the G peak means n-type doping if the peak is shifted to a lower wavelength, and p-type doping when the G peak is shifted to a higher wavelength.

Referring to FIG. 6 (a), the G peaks of the graphene structures before the heat treatment are all located on the right side at a high wavelength of 1580 cm ^-1 . This means that it is doped to 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 B type graphene structure are found to have a G peak at 1580 cm ^-1 after the heat treatment. This means that after the heat treatment, it returns to the state before the doping.

However, in the case of the C-type graphene structure (see line 3BL C type) according to one embodiment of the present invention, it can be seen that the G peak is still located in the right region at 1580 cm ^-1 after the heat treatment. That is, in the case of a C-type graphene structure having a structure in which doped graphene is covered with graphene, since a non-doped graphene layer functions as a barrier layer for protecting a doped graphene layer, The doped state of the fin 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 graphen structures are doped with the dopant, and the black circle represents the annealing of the graphene structures doped with the dopant ) ≪ / RTI > In each case, AuCl ₃ , IrCl ₃ , MoCl ₃ , OsCl _3, PdCl ₂ and RhCl ₃ are used as dopants in order from the top to the 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 after the heat treatment, the variation of the G peak was 10 ⁰ cm ^-1 regardless of the kind of the dopant. This means that the graphene layer is returned to the state before doping due to heat treatment. It can be seen that the difference of the G peak before and after the heat treatment is smaller than that of the 1L B type in the case of the 5L B type. This is because the upper doped graphene layers serve to protect the underlying doped graphene layers.

In the case of 3BL C type, it can be seen that the variation of the G peak before and after the heat treatment is constant irrespective of the kind of the 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 for protecting the dopant, the doping state of the doped graphene layer is maintained regardless of the heat treatment do.

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

FIG. 7 is a graph showing an analysis result of a photoelectron spectroscopy (XPS) for a metal atom included in graphene structures according to an embodiment and a comparative example of the present invention. FIG. 7 (a) shows the X-ray photoelectron spectroscopy (XPS) analysis result of the core level Au 4f in the doped state before the heat treatment. FIG. 7 (b) shows the X-ray photoelectron spectroscopy (XPS) analysis results of the core level Au 4f in the state after the heat treatment. FIG. 7 (c) is a result of comparing the intensities of the metal particles and the ion states after the heat treatment of the graphen structures. In each of the graphs, the 3BL C type means a C-type graphene structure having a structure in which three first graphene layers are laminated on a second graphene layer in one layer, Means a type B graphene structure having a laminated structure. 1L type B refers to a type B graphene structure having a structure in which one layer of a second graphene layer is laminated. 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 internal level Au ³⁺ 4f _5/2 of the ion particle state, and the dotted line b represents the internal state of the metal particle Au 4f _5/2 , the dotted line c represents the intensity at the internal level Au ³⁺ 4f _7/2 of the ionic particle state, and the dotted line d represents the intensity at the internal level Au 4f _7/2 of the metal particle state .

7 (a) showing the state before the heat treatment shows the intensities of the graphene layers on the dotted line a and the dotted line b, which are the inner angle levels of the ionic state, but in FIG. 7 (b) Century does not appear regardless of the type of graphene layer. Since the intensity on the dashed line a and the dashed line b appears when the metal atom is in the ion particle state, the absence of the 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 state of ionic particles existing on the surface of the doped graphene are changed into the metal particles state.

Referring to FIG. 7 (c), the dopant is sequentially deposited from the top to the bottom of the graph in the order of AuCl ₃ , IrCl ₃ , MoCl ₃ , OsCl ₃ , PdCl ₂ , and RhCl ₃ . The white circles represent the ratio of the intensity of the metal particles to the intensity of the metal particles in the doped state before the heat treatment and the black circle represents the intensity of the metal particles and the intensity of the ion particles in the annealed state Lt; / RTI > It can be seen that heat treatment in all samples of the graphene structure weakens the intensity of the metal particles and 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 chloride as the dopant are separated and aggregated together. As a result, the transmittance is lowered.

FIG. 8 is a graph showing an analysis result of a chlorine atom photoelectron spectroscopy (XPS) including graphene structures according to an embodiment and a comparative example of the present invention. FIG. 8 (a) is a result of XPS (X-ray photoelectron spectroscopy) analysis of a core level Cl 2p in a state where graphene is doped before heat treatment. FIG. 8 (b) shows the X-ray photoelectron spectroscopy (XPS) analysis results of the internal level Cl 2p in the graphene state after the heat treatment. FIG. 8 (c) is a graph showing changes in the peak intensity of the inner-level Cl 2p of the graphene layer before and after the heat treatment. In each of the graphs, the 3BL C type means a C-type graphene structure having a structure in which three first graphene layers are laminated on a second graphene layer in one layer, Means a type B graphene structure having a laminated structure. 1L type B refers to a type B graphene structure having a structure in which one layer of a second graphene layer is laminated. 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. 8 (a) and 8 (b), the dotted line a represents the case where the inner-level level is Cl 2p _1/2 , and the dotted line b represents the case where the inner-level level is Cl 2p _3/2 . The bonding energy of the dotted line a and the dotted line b was changed by -0.7 eV before the heat treatment (FIG. 8 (a)) and after the heat treatment (FIG. 8 (b)), and the average intensity of the peaks after the heat treatment was 3BL C type , The peak intensity before the heat treatment reaches the average intensity level by 1.27 times, 3.56 times in the case of the 5L type B, and 8.15 times in the case of the 1L type B. It can be interpreted that the heat treatment vaporizes the chlorine atoms on the surface of the graphene layer, which tends to lower the conductivity of the graphene structure.

Therefore, in the case of a 1L type B graphene structure that does not contain a graphene layer that prevents the vaporization of chlorine, the amount of chlorine change before and after the heat treatment is relatively large. In the case of the 3BL type C graphene structure, The amount of change of chlorine before and after the heat treatment is relatively small.

Referring to FIG. 8 (c), the bar graph 1 shows the case where the dopant is AuCl ₃ , the bar graph 2 shows the case where the dopant is IrCl ₃ , the bar graph 3 shows the case where the dopant is MoCl ₃ , It is the case of OsCl _3, 5 is a bar graph shows the peak (peak) intensity variation in the cabinet level Cl 2p when the dopant is in the case of PdCl _3, 6 is a bar graph dopant RhCl _3. It can be seen from the bar graph that the change of the peak is small in the case of the C-type graphene structure before and after the most 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.

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

Referring to FIG. 9 (a), 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. 9 (b), since the B-type graphene structure is a laminated structure of doped graphenes, chlorine atoms are vaporized in the graphene layer of the uppermost layer.

Referring to FIG. 9 (c), since the C-type graphene structure has a structure in which a doped graphene layer is laminated on a doped graphene layer, the surface stability of the undoped graphene layer Not found. However, aggregation of metal atoms contained 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 existing on the surface of the graphene layer is small by the XPS analysis described above. Thus, it can be seen that the stacked undoped graphene layers act effectively as a gas barrier. Therefore, when a 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 an embodiment of the present invention can be utilized in various fields such as a transparent electrode and an intermediate layer of a semiconductor device.

It will be apparent to those skilled in the art that various modifications, substitutions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. will be. Therefore, the embodiments disclosed in the present invention and the accompanying drawings are intended to illustrate and not to limit the technical spirit of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments and the accompanying drawings . The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

11: substrate.
12: First graphene layer.
13: Second graphene layer.
14: Grain structure (C-type graphen structure).
15: Type A graphene structure.
16: Type B graphene structure.

Claims (11)

Forming a first graphene layer on the substrate,
The first graphene layer is doped with a metal chloride,
And laminating at least one second graphene layer on the doped first graphene layer. The method according to claim 1,
Wherein the at least one second graphene layer comprises at least one graphene layer doped with a metal chloride. The method according to claim 1 or 2,
Wherein the metal chloride comprises 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,
Wherein the substrate comprises a metal oxide based substrate, a silica based substrate, or a plastic substrate. The method according to claim 1,
Wherein the substrate is 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,
Wherein forming the first graphene layer comprises transferring a first graphene layer onto a substrate. A first graphene layer;
And at least one second graphene layer stacked on the first graphene layer, wherein the first graphene layer is doped with a metal chloride. The method of claim 7,
Wherein the at least one second graphene layer comprises at least one graphene layer doped with a metal chloride. The method according to claim 7 or 8,
Wherein the metal chloride comprises at least one metal chloride selected from the group consisting of AuCl ₃ , IrCl ₃ , MoCl ₃ , OsCl ₃ , PdCl ₂ and RhCl ₃ . A transparent electrode comprising a graphene structure according to claim 7 or 8. A light emitting diode comprising a transparent electrode according to claim 10.

Images