KR20190063045A - Tansparent electrode using graphene and nanowire and method for fabricating the same - Google Patents

Abstract

Disclosed are a transparent electrode using graphene and a nanowire, and a manufacturing method thereof. According to an embodiment of the present invention, the method of manufacturing a transparent electrode using graphene and a nanowire comprises: a first step of forming a nanowire layer on a substrate; a second step of forming an etch mask pattern on the nanowire layer; a third step of etching the nanowire layer by using the etch mask pattern to form a nanowire grid; and a fourth step of transferring graphene onto the surface of the nanowire grid to form a transparent electrode having a structure in which the graphene is bonded on the nanowire grid. According to the present invention, the transparent electrode having high electrical conductivity and high transmittance can be manufactured.

Description

TECHNICAL FIELD [0001] The present invention relates to a transparent electrode using graphene and a nanowire, and a method of fabricating the transparent electrode using graphene and nanowire,

The present invention relates to a transparent electrode using graphene and nanowire and a method of manufacturing the same. More particularly, the present invention relates to a method of manufacturing a transparent electrode using graphene and nanowire, which can be used for various photoelectric devices having a high electrical conductivity and high transparency, And a method of manufacturing the transparent electrode.

Nanotechnology is a technology that physically or chemically controls materials at the atomic and molecular levels to produce useful structures and functions, which can implement devices with completely different principles and become a core field of science and technology in the future. And is growing much more rapidly in terms of infrastructure and speed than other technologies.

Nanotechnology is a field that deals with nanomaterials. It has a diameter of less than 100 nm, such as macromolecule, zero-dimensional nanoparticles such as quantum dot, nanowire, nanorod, nanoribbon, Dimensional structure of nanostructures and nanostructures and other nanostructures of 100 nm or less. The possibility that the two-dimensional structures of nanostructures can become the basic building blocks of new electronic devices is proven.

One-dimensional nanostructures with large aspect ratios such as nanorods, nanowires, and nanofibers can have large surface area, small dislocation density, high crystallinity, physical properties such as quantum size effect by nanoscale, It exhibits excellent electrical, optical, mechanical and thermal properties. Such one-dimensional nanostructures can be applied not only to electronic devices, semiconductor light emitting devices, and optical devices but also to environment related materials. In particular, semiconductor nanostructures can be applied not only to single electron transistor devices but also to new optical device materials Do.

 Among these nanostructures, nanowires are known to have good reactivity and flexibility because of their wide surface area. The formation of nanowires is most often achieved by a Vapor-Liquid-Solid (VLS) method using a catalyst such as a transition metal, and the diameter is controlled by a catalyst or a pattern. The growth direction can also be controlled by using the surface index of the semiconductor substrate. These nanowires have the disadvantage that their electrical properties are limited in high transparency when used alone.

On the other hand, graphene has a structure in which a layer of carbon atoms is two-dimensionally spread in an extremely thin honeycomb shape. In case of monatomic layer graphene, it absorbs only 2.3% of light in the 550 nm wavelength band. It is a promising material. It also has electrical conductivity about 100 times higher than copper per unit area, and the thermal conductivity is more than twice as high as diamond, which is known to be the best.

In addition, graphene has an elastic modulus of 1.02 Tpa, which is very high in mechanical strength, and is highly attracted to electronic materials because it can be stretched to a maximum of 20% or maintain its electric conductivity even when fully folded. In addition, since graphene can provide both flexibility and mechanical strength required for flexible devices as well as gas / moisture barrier properties, It can be very usefully used in a light emitting diode (OLED) display or a flexible display device.

Graphene can be manufactured to a reliable level in the following way. (1) mechanical peeling from high quality graphite, (2) production of a graphene film by selective sublimation of Si from a SiC wafer, (3) production of a graphene film by chemical oxidation / reduction reaction of graphite, (4) And graphene film synthesis using chemical vapor deposition (CVD). A possible method for commercial large-area graphene fabrication for applications in the field of electronic materials is chemical vapor deposition (CVD). The chemical vapor deposition method is advantageous not only in manufacturing large-area graphene but also in transferring or transferring.

Since such nanowires and graphenes can be used for various purposes, the utilization of nanowires and graphenes is increasing.

Korean Registered Patent No. 10-1618974 (Apr. 29, 2016)

Disclosure of Invention Technical Problem [8] The present invention is directed to a transparent electrode using graphene and nanowires that can overcome the above-described problems, and a method of manufacturing the same.

Another object of the present invention is to provide a transparent electrode using graphene and nanowires that can improve electrical characteristics and transmittance through the combination of a nanowire grid and a single layer graphene, and a method of manufacturing the same.

The objects of the present invention are not limited to those described above, and other objects not mentioned may be clearly understood by those skilled in the art from the following description.

According to another aspect of the present invention, there is provided a method of fabricating a transparent electrode using graphene and a nanowire, comprising: forming a nanowire layer on a substrate; A second step of forming an etch mask pattern on the nanowire layer; A third step of etching the nanowire layer using the etch mask pattern to form a nanowire grid; And a fourth step of transferring graphene onto the surface of the nanowire grid to form a transparent electrode having the graphene-bound structure on the nanowire grid.

The substrate may be a glass substrate, and the nanowires may be silver (Ag) nanowires.

The substrate is thermally stable to 200 < 0 > C, and the substrate may serve as an etch stop layer during the etching of the nanowire layer in the third step.

In the first step, the nanowire layer is formed by applying nanowires to the substrate using a spin coating technique; And performing a heat treatment in a vacuum state with respect to the applied nanowire layer.

The nanowire forming the nanowire layer may have a diameter of 20 to 50 nm and a length of 5 to 40 μm.

In the second step, the etch mask pattern may be formed through a photo lithography process.

The third step may include: a first etching step of etching the nanowire layer on which the etching mask pattern is formed, using a solution of ferric chloride at room temperature for 40 to 60 seconds; And a second etching step of performing ultrasonic etching for 5 to 15 seconds in an ultrasonic bath where ultrasonic waves are generated.

The nanowire grid may have a channel width of 15 to 25 μm and a channel length of 25 to 65 μm.

The nanowire grid may have a fill factor of 0.5 or 0.4 to 0.6.

The channel width and the channel length of the nanowire grid may be adjusted so that the fill factor has a value of 0.4 to 0.6.

The nanowire grid may have rounded corners.

And removing the etch mask pattern between the third step and the fourth step.

The graphene may be graphene deposited on a copper substrate using a chemical vapor deposition (CVD) process.

The graphene comprises the steps of charging a copper substrate into a growth chamber in a chemical vapor deposition equipment; Heat treating the copper substrate while supplying hydrogen gas for 40 minutes while the growth chamber is set at a temperature of 1000 ° C and a vacuum of 0.1 mTorr; 15 sccm of hydrogen gas, 30 sccm of methane gas, and depositing graphene on the copper substrate for 30 minutes while maintaining the pressure at 0.5 mTorr.

The transparent electrode may have a transparency of 90 to 98% at a wavelength of 550 nm.

According to another embodiment of the present invention, a transparent electrode is manufactured by the manufacturing method described above.

According to another aspect of the present invention, there is provided a transparent electrode comprising: a glass substrate; A silver (Ag) nanowire grid formed on the glass substrate; And a graphene that is transferred onto the surface of the silver (Ag) nanowire grid and bonded to the nanowire grid.

According to the present invention, it is possible to provide a more improved electrical characteristic under a high transmittance condition than in the case of a transparent electrode having a general nanowire structure. Accordingly, it is possible to use it for future LED display, future optical optoelectronic devices such as optical window or optical filter. In addition, it is possible to manufacture a transparent electrode exhibiting a low surface resistance in a high transmittance region, to be stable, to exhibit an electrically high conductivity and a high transmittance, and to have a transparent electrode having a high performance.

The effects of the present invention are not limited to those described above, and other effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 is a process flow diagram illustrating a method of fabricating a transparent electrode using graphene and nanowires according to an embodiment of the present invention.
2 is a graph showing the transparency and surface resistance of the nanowire layer.
Figure 3 shows the shape of the nanowire grid.
4 is a photograph of a surface of a silver nanowire grid and a transparent electrode of a graphene bonding structure manufactured according to the present invention.
FIG. 5 is a graph showing electrical characteristics and transmittance of a silver nanowire grid and a silver nanowire layer. FIG.
FIG. 6 is a current-voltage graph showing changes in voltage with respect to transparent electrodes having various structures of 95% transparency and observing changes in current.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

In addition, in the various embodiments, elements having the same configuration are denoted by the same reference numerals and only representative embodiments will be described. In other embodiments, only the configurations other than the representative embodiments will be described.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "indirectly connected" between other parts. Also, when a component is referred to as "comprising ", it may mean that it does not exclude other components as well as other components, unless specifically stated otherwise.

1 is a process flow diagram illustrating a method of fabricating a transparent electrode using graphene and nanowires according to an embodiment of the present invention.

In general, nanowires have a disadvantage in that their electrical characteristics are limited in a high transparency state, and they have been a limiting factor in manufacturing transparent electrodes having high transmittance using nanowires. In the present invention, graphene is used to overcome these limitations to produce transparent electrodes having high electrical conductivity and high transmittance.

As shown in FIG. 1, the fabrication of a transparent electrode using graphene and nanowires according to an embodiment of the present invention includes a first step (S112) of forming a nanowire layer on a substrate, A second step S114 of forming an etch mask pattern on the layer, a third step S116 of etching the nanowire layer using the etch mask pattern to form a nanowire grid, And a fourth step (S118) of transferring a graphene onto the surface of the wire grid to form a transparent electrode having the graphene-bound structure on the nanowire grid.

The first step S112 may include forming a nanowire layer on the substrate, the substrate may be a glass substrate, and the nanowire may be silver or silver nanowire. The substrate may include a substrate that is thermally stable up to 200 ° C including a glass substrate and may include an acid-resistant substrate so as to function as an etch stop layer during the etching of the nanowire layer in the third step .

The nanowire layer is formed by applying silver nanowires to the substrate using a spin coating method (at about 500 rpm for 30 seconds) and then applying a vacuum in a vacuum of 200 DEG C for about 1 hour And may be formed by heat treatment. The heat treatment is performed to keep the nano-wire resistance constant.

Here, the transparency and the surface resistance of the nanowire layer are determined according to the application degree. 2 is a graph showing the relationship between the transparency of the nanowire layer and the surface resistance. As shown in FIG. 2, the more the application, the thicker the nanowire layer, the lower the surface resistance but the lower the transparency, while the higher the transparency but the greater the surface resistance.

Accordingly, the degree of application of the nanowire for forming the nanowire layer is preferably adjusted as necessary to determine the thickness of the nanowire layer.

Also, the conductivity of the nanowire layer is determined by the length / thickness ratio of the nanowire, the contact resistance between the nanowire and the nanowire, and the contact density of the nanowire. In this case, the ratio of the length / thickness of the nanowire is kept constant, and therefore, it is not a variable, and the resistance between the nanowire and the nanowire can be kept constant through the above-described heat treatment.

The nanowire forming the nanowire layer may have a diameter of 20 to 50 nm and a length of 5 to 40 μm.

In the second step S114, an etch mask pattern is formed on the nanowire layer, and the etch mask pattern is formed through a photo lithography process. For example, a photosensitive material such as a photoresist is used to form an etch mask pattern having a desired pattern.

In the third step S116, the nanowire layer is etched using the etch mask pattern to form a nanowire grid.

The etching method for forming the nanowire grid is performed through a two-step etching process. For example, the first etching step of etching the nanowire layer on which the etching mask pattern is formed using a solution of ferric chloride at room temperature for 40 to 60 seconds, and a second etching step of etching the nanowire layer using an ultrasound bath The nanowire grid may be formed through a second etch step that performs ultrasonic etching for 5 to 15 seconds.

Here, the second etching step may be performed while the first etching step is maintained. That is, ultrasonic etching can be performed in a state where the nanowire layer having the etched mask pattern is immersed in a solution of ferric chloride.

The first etching step is an etching step for forming a nanowire grid on the nanowire layer immersed in the etching solution, and the second etching step is a step for complete completion of the partially incomplete nanowire grid and for removing etch residues will be. If ultrasonic waves are generated in the ultrasonic bath and etching is performed, it is possible to precisely etch and remove etching residues.

Thereafter, the etching mask pattern is removed by using a removal solution such as an acetone solution, and the cleaning process is performed using a cleaning solution such as distilled water. After that, a drying process by nitrogen spraying may be performed. So that the nanowire grid on the substrate has a structure formed as shown in FIG.

Figure 3 shows the shape of the nanowire grid. As shown in FIG. 3, the nanowire grid may have a channel width (A) of 15 to 25 μm and a channel length (B) of 25 to 65 μm, and a fill factor of 0.5 And can have a value of 0.4 to 0.6 close thereto. Accordingly, the channel width and the channel length of the nanowire grid can be adjusted so that the fill factor has a value of 0.4 to 0.6. The channel width and channel length of the nanowire grid may be enabled by adjusting the size of the etch mask pattern when forming the etch mask pattern. Further, the nanowire grid may have rounded corners.

The fourth step S118 is a step of transferring a graphene on the surface of the nanowire grid to form a transparent electrode having a structure in which the graphene is bonded on the nanowire grid.

Here, the graphene is deposited on a separate substrate through a separate process and transferred onto the nanowire grid.

The graphene is deposited using chemical vapor deposition (CVD) equipment. First, the copper substrate is charged into the growth chamber in the chemical vapor deposition apparatus. Thereafter, the growth chamber temperature is raised to 1000 ° C., and the copper substrate is heat-treated while hydrogen gas is supplied for 40 minutes in a state where the growth chamber is set at a temperature of 1000 ° C. and a vacuum of 0.1 mTorr. Next, graphene is deposited on the copper substrate for approximately 30 minutes, while hydrogen gas is supplied at 15 sccm, methane gas is supplied at 30 sccm, and the pressure is increased to 0.5 mTorr. If necessary, it is possible to change the deposition thickness or the deposition characteristics by changing the deposition conditions (time, pressure, etc.).

The graphene deposited on the copper substrate is transferred and bonded onto the surface of the nanowire grid to complete a transparent electrode having a structure in which a nanowire grid and graphene are bonded. Well known methods can be used. The graphene may have a continuous graphene film structure with monolayer graphene.

FIG. 4 is a photograph of the surface of a silver nano wire grid fabricated according to the present invention and a transparent electrode having a graphene structure. Referring to FIG. 4, a silver nanowire, It can be seen that a graphene-bonded structure is shown thereon.

The transparent electrode may have a transparency (or transmittance) of 90 to 98% at a wavelength of 550 nm. More preferably 95 to 98% transparency (or transparency).

5 is a graph showing the electrical characteristics of the silver nano wire grid formed through the third step and the silver nano wire layer not subjected to the third step and not being etched and the transmittance at a wavelength of 550 nm ) And electron micrographs (Figs. 5 (b) and 5 (c)).

As shown in FIG. 5 (a), it can be seen that the silver nanowire grid (B) has improved electrical properties over the silver wire layer (A) at a transmittance of 90% or more. That is, it can be seen that the surface resistance of the silver nanowire grid (B) is smaller than that of the silver wire layer (A) by 90% or more. Therefore, in the case of a transparent electrode having a high transmittance of 90% or more, it can be seen that having a nanowire grid structure is advantageous in terms of electrical characteristics as compared with a silver nano wire layer in a case where a grid is not formed.

FIG. 5 (b) shows the nano-wire contact density of the silver nanowire grid showing the transparency of 98%, and FIG. 5 (c) shows the nanowire contact density of the nanowire layer at the same transparency as FIG. As shown in FIGS. 5 (b) and 5 (c), the contact density between the nanowires is the same as in the case of the silver nanowire grid formed through the etching process in the third step described above. It can be seen that it is improved than the case of the silver nano wire layer which is not used.

This indicates that the improvement of the electrical characteristics of the silver wire grid at high transparency is due to the improvement of the nanowire contact density.

FIG. 6 is a graph of a current-voltage obtained by observing a change in voltage with respect to transparent electrodes having transparency of 95% at 550 nm with various structures. And exhibits a lower resistance and superior electrical characteristics when the inclination is large.

As shown in Fig. 6, a transparent electrode g1 having a silver nano wire grid single-layer structure without graphene bonding, a transparent electrode g2 having a silver nano wire grid and a graphene bonding structure manufactured according to the present invention, A graph of a current-voltage characteristic of a transparent electrode g3 having a silver nano wire single layer structure not having a grid formed thereon and a transparent electrode g4 having a silver nano wire single layer and a graphene bonding structure having no grid formed will be described. In the graph of the current-voltage characteristic of the transparent electrode (g3) of the silver nanowire single-layer structure and the graph of the current-voltage characteristic of the transparent electrode (g4) of the silver nanowire single- Showed a low slope. That is, the resistance is the highest.

In addition, the transparent electrode (g1) having a single-layered structure of silver nanowire grid has the highest slope and shows the best electrical characteristics. That is, in the region of transparency of 95% or less, it can be seen that the transparent electrode (g1) having a single layer structure of silver nanowire grid has the best electrical characteristics. However, nanowires have a disadvantage in that their electrical characteristics are limited in a state of high transparency.

 At a transparency of 97%, the surface resistance of the transparent electrode of the silver nano wire grid single layer structure was measured at about 200? / Sq. As shown in Fig. 5 (a), and the silver nano wire grid The transparent electrode of the graphene bonding structure was measured at 31.95? / Sq. Therefore, it can be seen that the transparent electrode of the silver nano wire grid-graphene bonding structure according to the present invention has the best electrical characteristics in the transparency region of 95% or more (more preferably 97% or more of the transparency region).

As shown in FIG. 4, the transparent electrode manufactured according to the above-described manufacturing method includes a glass substrate, a silver (Ag) nanowire grid formed on the glass substrate, and a silver And has a structure including a graphene transferred onto the surface and bonded to the nanowire grid.

The transparent electrode manufactured according to the above-described manufacturing method can provide more improved electrical characteristics under the high transmittance condition than the transparent electrode having the general nanowire structure. Accordingly, it is possible to use it for future LED display, future optical optoelectronic devices such as optical window or optical filter.

The foregoing description of the embodiments is merely illustrative of the present invention with reference to the drawings for a more thorough understanding of the present invention, and thus should not be construed as limiting the present invention. It will be apparent to those skilled in the art that various changes and modifications may be made without departing from the basic principles of the present invention.

Claims (17)

Forming a nanowire layer on a substrate;
A second step of forming an etch mask pattern on the nanowire layer;
A third step of etching the nanowire layer using the etch mask pattern to form a nanowire grid;
And a fourth step of transferring a graphene onto the surface of the nanowire grid to form a transparent electrode having a structure in which the graphene is bonded on the nanowire grid. Wherein the transparent electrode is formed of a transparent electrode.
The method according to claim 1,
Wherein the substrate is a glass substrate and the nanowire is a silver (Ag) nanowire.
The method according to claim 1,
Wherein the substrate is thermally stable to 200 ° C. and the substrate functions as an etch stop layer during the etching of the nanowire layer in the third step. The method of manufacturing a transparent electrode using graphene and a nanowire .
The method of claim 2,
In the first step, the nanowire layer is formed,
Applying nanowires to the substrate using a spin coating technique;
And performing heat treatment in a vacuum state with respect to the coated nanowire layer.
The method according to claim 1,
Wherein the nanowire forming the nanowire layer has a diameter of 20 to 50 nm and a length of 5 to 40 占 퐉.
The method according to claim 1,
Wherein the etch mask pattern is formed through a photolithography process in the second step. The method of claim 1, wherein the etch mask pattern is formed by a photolithography process.
The method according to claim 1,
In the third step,
A first etching step of etching the nanowire layer on which the etching mask pattern is formed by using a solution of ferric chloride at room temperature for 40 to 60 seconds;
And a second etching step of performing ultrasonic etching in an ultrasonic bath in which ultrasonic waves are generated for 5 to 15 seconds. The method of manufacturing a transparent electrode using graphene and nanowires.
The method of claim 7,
Wherein the nanowire grid has a channel width of 15 to 25 mu m and a channel length of 25 to 65 mu m.
The method of claim 7,
Wherein the nanowire grid has a fill factor of 0.5 or 0.4 to 0.6. 2. The method of claim 1, wherein the nanowire grid has a fill factor of 0.5 or 0.4 to 0.6.
The method of claim 7,
Wherein the nanowire grid has a channel width and a channel length so that the fill factor has a value of 0.4 to 0.6.
The method of claim 7,
Wherein the nanowire grid is formed with rounded corners. 2. The method of claim 1, wherein the nanowire grid has a rounded corners.
The method according to claim 1,
And removing the etching mask pattern between the third step and the fourth step. The method of manufacturing a transparent electrode using graphene and a nanowire according to claim 1,
The method according to claim 1,
Wherein the graphene is a graphene deposited on a copper substrate using a chemical vapor deposition (CVD) process.
14. The method of claim 13,
The graphene
Charging a copper substrate into a growth chamber in a chemical vapor deposition equipment;
Heat treating the copper substrate while supplying hydrogen gas for 40 minutes while the growth chamber is set at a temperature of 1000 ° C and a vacuum of 0.1 mTorr;
A hydrogen gas of 15 sccm, and a methane gas of 30 sccm are supplied, and the graphene is deposited on the copper substrate for 30 minutes while the pressure is maintained at 0.5 mTorr. The method of manufacturing a transparent electrode using graphene and a nanowire .
The method according to claim 1,
Wherein the transparent electrode has a transparency of 90 to 98% at a wavelength of 550 nm.
A transparent electrode using graphene and nanowires produced by a manufacturing method according to any one of claims 1 to 15.
A glass substrate;
A silver (Ag) nanowire grid formed on the glass substrate;
Wherein the silver nanoparticles are transferred onto a surface of the silver (Ag) nanowire grid and include a graphene bonded with the nanowire grid.

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