KR101586792B1 - A method for manufacturing a nanowire structure using a graphene and a nanowire structure manufactured by the same - Google Patents

Abstract

A method of manufacturing a nanowire according to an embodiment of the present invention includes the steps of: (a) providing a substrate; (b) forming a graphene layer on the substrate; And (c) growing nanowires on the graphene layer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a nanowire structure using graphene and a nanowire structure manufactured thereby,

The present invention relates to a method of manufacturing a nanowire structure using graphene and a nanowire structure manufactured thereby. More particularly, the present invention relates to a method of obtaining a nanowire structure by growing nanowires on a graphene layer, To a nanowire structure fabricated therefrom.

Development of light emitting diodes and laser diodes having a wavelength range of blue light to ultraviolet light region has been demanded in connection with improvement of multi-coloring and data density required for light emitting devices and optoelectronic devices.

Gallium nitride (GaN) is a direct bandgap semiconductor, and its band gap is relatively large at about 3.45 eV, so it is widely used to develop blue and ultraviolet light emitting devices. However, since the conventional GaN light emitting device based on a thin film has a size of more than a micrometer, it is limited to be applied to a light emitting device which becomes finer and smaller.

Particularly, in the case of a thin-film device, a stress is generated due to a difference in lattice constant between the substrate and the GaN film during fabrication, and defects such as dislocation occur to mitigate the stress, have.

Nanowires are collectively referred to as nanostructures with a diameter of several hundreds of nanometers or less and a length of several micrometers or more. These nanowires remain standing without contact with the substrate and have a large surface area, so they can be used as a basic unit for constructing various devices. Particularly, the GaN nanowire can be used as a material of a new next-generation nano light emitting device which overcomes the disadvantages of the conventional thin film light emitting device.

However, when the GaN nanowires are grown while directly supplying a precursor of gallium and a precursor of nitrogen on the Si substrate, the formation density of the nanowires is low and the growth length is short.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a nanowire structure superior in terms of formation density and growth length by forming a graphene layer on a substrate and then growing GaN nanowire thereon And to provide a high-quality nanowire structure manufactured by such a method.

It is to be understood, however, that the technical scope of the present invention is not limited to the above-mentioned problems, and other matters not mentioned may be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a method of manufacturing a nanowire structure, including: (a) providing a substrate; (b) forming a graphene layer on the substrate; And (c) growing nanowires on the graphene layer.

The step (b) may include: synthesizing graphene by reacting the catalyst layer with a metal catalyst, a gas containing methane and hydrogen, and cooling the catalyst layer; Removing the synthesized metal catalyst portion under the graphene; And layering a graphene layer obtained by removing the metal catalyst portion on the substrate.

(B) forming a metal catalyst layer on the substrate; And forming the graphene layer by reacting the catalyst layer with a gas containing methane and hydrogen and cooling the catalyst layer.

The step (b) may be a step of synthesizing graphene by chemical vapor deposition (CVD).

The step (c) may be a step of growing the nanowire by metal organic chemical vapor deposition (MOCVD).

The nanowire may be a GaN nanowire.

(C) growing the first-type GaN nanowire on the graphene layer; And (c2) growing a second type GaN nanowire of a different type on the grown first type GaN nanowire.

The first type nanowire may be an n-type nanowire, and the second type nanowire may be a p-type nanowire.

In the step (c1), the substrate on which the graphene layer is formed is charged into the MOCVD reactor. Performing heat treatment on the graphene layer of the loaded substrate together with supply of hydrogen gas; Growing a nanowire while supplying a precursor gas of gallium and a precursor gas of gallium at a first temperature; And allowing the n-type nanowires to grow by supplying an n-type doping material while the nanowires are growing.

The precursor gas of gallium is trimethyl gallium (TMG), and the precursor gas of nitrogen may be non-ammonia.

The n- type doping materials, can be a SiH ₄ gas.

The step (c2) may include supplying a P-type doping material at a second temperature to form a p-type nanowire on the n-type nanowire.

The p-type doping material may be Cp ₂ Mg.

The second temperature may be lower than the first temperature.

Meanwhile, the nanowire structure according to one embodiment of the present invention manufactured according to this manufacturing method includes a substrate; A graphene layer formed on the substrate; And nanowires grown on the graphene layer.

The nanowire may be a GaN nanowire.

The nanowire layer comprising: a first type nanowire layer formed on the graphene layer; And a second-type nanowire layer formed on the first-type nanowire layer.

The first type nanowire layer may be an n-type nanowire layer, and the second type nanowire layer may be a p-type nanowire layer.

According to the present invention, it is possible to obtain a high-quality nanowire structure having excellent properties in terms of formation density, growth length, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description of the invention given below, serve to further the understanding of the technical idea of the invention. And should not be construed as limiting.
1 is a flowchart illustrating a method of manufacturing a nanowire structure according to an embodiment of the present invention.
2 is a view illustrating a substrate constituting a nanowire structure according to an embodiment of the present invention.
3 is a view showing a state where a graphene layer is formed on a substrate.
4 is a graph showing a temperature change with time in growing the graphene layer.
5 is a view showing a state in which first-type nanowires are grown on a graphene layer.
6 is a view showing a state in which a second-type nanowire is grown on the grown first-type nanowire.
7 is a photomicrograph of a comparative example showing nanowires grown directly on a Si substrate.
Figures 8 and 9 are a micrograph and an enlarged view of an embodiment showing nanowires grown on a graphene layer formed on a Si substrate.
10 is a graph showing the Raman spectra for the graphene layer.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be interpreted in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only some of the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

1 is a flowchart illustrating a method of manufacturing a nanowire structure according to an embodiment of the present invention.

Referring to FIG. 1, a method of manufacturing a nanowire structure according to an exemplary embodiment of the present invention includes the steps of (a) providing a substrate, (b) forming a graphene layer on the substrate, and (c) And growing nanowires on the pinned layer.

First, the step (a) will be described with reference to FIG.

2 is a view illustrating a substrate constituting a nanowire structure according to an embodiment of the present invention.

The substrate 1 is a (111) -oriented Si substrate, which is prepared through a cleaning process of moving at least once.

Next, the step (b) will be described with reference to FIG. 3 and FIG.

FIG. 3 is a view showing a state where a graphene layer is formed on a substrate, and FIG. 4 is a graph showing a temperature change with time in growing the graphene layer.

Referring to FIGS. 3 and 4, the graphene layer 2 may be synthesized by chemical vapor deposition (CVD) using a metal such as nickel, copper, or platinum as a catalyst layer.

That is, the graphene layer 2 is formed by reacting a substrate 1 on which a catalyst layer is deposited with a thickness of several nanometers to several tens of nanometers at a high temperature with a mixed gas of methane and hydrogen so that an appropriate amount of carbon is dissolved in the catalyst layer Or adsorbed, and then cooled to room temperature.

When the substrate 1 is reacted with a mixed gas of methane and hydrogen at a high temperature and then cooled to room temperature, the carbon atoms contained in the catalyst layer are crystallized on the surface to determine the graphene crystal structure.

On the other hand, the graphene layer 2 may be formed directly on the substrate 1 according to the above-described method, but the graphene layer 2 may be formed directly on the substrate 1 by reacting a separate catalytic metal foil with a methane- And may be obtained by removing the catalyst layer under the fin.

As described above, when graphene is synthesized using a metal foil, the synthesized graphene layer 2 can be layered on the substrate 1 by a separate process.

Next, steps (c) will be described with reference to Figs. 5 and 6. Fig.

FIG. 5 is a view showing a state in which first-type nanowires are grown on a graphene layer, and FIG. 6 is a view showing a state in which second-type nanowires are grown on grown first-type nanowires.

5 and 6, the nanowire 3 is grown and formed on the graphene layer 2, but includes the first-type nanowire 3a and the second-type nanowire 3b.

That is, the nanowire growth step may include growing nanowires on the graphene layer 2 by growing a first type nanowire 3a by implanting a first type doping material during growth, Type nanowire 3b on the first-type nanowire 3a by implanting a second-type doping material in the first-type nanowire 3a.

The nanowire 3a may be formed, for example, by metal organic chemical vapor deposition (MOCVD), and may correspond to a GaN nanowire. Further, the first type nanowire 3a may be, for example, an n-type nanowire, and the second type nanowire 3b may correspond to a p-type nanowire.

Referring to FIG. 5, the first type nanowire 3a is formed by filling a substrate 1 having a graphene layer 2 thereon into a MOCVD reactor to perform heat treatment together with supply of hydrogen gas, Lt; RTI ID = 0.0 > 1 < / RTI > while supplying the precursor gas of gallium and the precursor gas of nitrogen at a temperature of about < RTI ID =

6, the grown nanowires are continuously grown at a second temperature lower than the first temperature, and the second-type nanowires 3a are formed on the previously formed first-type nanowires 3a by supplying the second- (3b) can be grown.

As described above, when growing a nanowire on a substrate, it is possible to obtain a vertically-grown nanowire without a metal catalyst when the nanowire is grown on the graphene layer after the graphene layer is formed on the substrate first, It is possible to minimize the defects that can be caused by the metal catalyst and to have improved thermal characteristics and excellent electrical characteristics when used as a device.

In addition, the nanowires grown by the above-described method using graphene have excellent quality in terms of formation density and growth length compared with the nanowires grown directly on the Si substrate.

Hereinafter, in the case of growing the nanowire using the graphene as described above (Embodiment) and directly growing it without forming the graphene layer or the metal catalyst layer on the substrate (Comparative Example ) Will be described.

Example

(Preparation of Substrate) The Si (111) substrate was immersed in an acetone solution and then cleaned with an ultrasonic cleaner for about 5 minutes. Subsequently, the substrate taken out of the acetone solution was immersed in a methanol solution and cleaned with an ultrasonic cleaner for about 5 minutes. Subsequently, the substrate taken out from the methanol solution was immersed in a solution prepared by mixing distilled water, hydrogen peroxide and sulfuric acid in a ratio of 1: 1: 3 for about 5 minutes, and then the substrate was taken out and washed in distilled water for about 5 minutes. The washed substrate was immersed in a 2% HF solution for about 5 minutes, the substrate taken out of the hydrofluoric acid solution was immersed in an iso-propanol solution, the substrate was taken out from the iso-propanol solution and dried with N ₂ gas.

( Formation of Graphene Layer ) A substrate on which a catalyst layer made of copper (applicable to various metals such as nickel and platinum) with a thickness of several nanometers to several tens of nanometers was deposited was inserted in the center of the horizontal electric furnace of the CVD system, And then reacted with a methane / hydrogen mixed gas at a high temperature to allow an appropriate amount of carbon to be dissolved or adsorbed in the catalyst layer. The amount of hydrogen gas was about 2 ~ 5 sccm, the amount of methane gas was about 30 ~ 50 sccm, and the growth pressure was about 300 ~ 600 mTorr. After cooling to room temperature at a rate of about 100 to 250 ° C / min, the carbon atoms contained in the catalyst layer crystallized on the surface to form a graphene structure.

( Growth of Nanowire ) A substrate is charged into an MOCVD reactor to grow n-type GaN nanowires on graphene, and the substrate is stabilized at a high temperature for a certain period of time. Thereafter, hydrogen gas is flowed, Deg.] C for about 30 seconds to 5 minutes. Trimethylgallium (TMG), which is a precursor of Ga, and ammonia gas, which is a precursor of nitrogen, are used as the fuel gas to be supplied to the inside of the reactor, and substrate temperature, pressure and growth time are respectively 850 to 1000 ° C, 400 to 600 Torr, 60 Lt; / RTI > for 90 minutes. At this time, the amount of TMG is about 0.2 to 1.0 sccm, and the flow rate of ammonia gas is 1 to 3 slpm. SiH ₄ gas was supplied as an n-type doping material during the growth of the nanowires to produce n-type GaN for LED applications, the amount of which was about 10 to 20 sccm.

In this way, n-type nanowires are grown, and TMG and ammonia gas are applied as a fuel gas to the inside of the reactor in the same manner as the growth of n-type nanowires. In the growth process, Cp ₂ Mg The p-type nanowire was grown for about 15 to 45 minutes by injecting about 5 to 15 sccm of gas. At this time, the growth conditions were a temperature of 650 to 800 ° C and a pressure of 400 to 600 Torr. The grown p-type nanowire has a constant thickness and a uniformly grown shape along the n-type nanowire, and the length of the GaN nanowire is increased in proportion to the growth time so that it has a length of several nanometers to several tens of nanometers By obtaining nanowires, we were able to apply them to various devices.

Comparative Example

All conditions were equally applied to grow the nanowires, except that a graphene layer was formed on the substrate and the nanowires were grown directly on the substrate without growing the nanowires thereon.

Referring to FIGS. 7 to 9, the nanowires grown according to the embodiment of the present invention and the nanowires obtained according to the comparative example can be compared.

7 is a micrograph of a comparative example showing nanowires grown directly on a Si substrate and FIGS. 8 and 9 are micrographs of an embodiment showing nanowires grown on a graphene layer formed on a Si substrate And an enlarged photograph thereof.

Referring to FIGS. 7-9, nanowires grown using nanowires grown according to an embodiment of the present invention (see FIGS. 8 and 9), i.e., graphene layers, It can be seen that nanowires, that is, nanowires grown directly on a substrate without a graphene layer, show many differences in their formation density and growth length.

Also, referring to FIG. 10, which shows a graph of Raman spectra for the graphene layer 2, it can be seen that the peak for graphene is clearly visible in the nanowire structure, It can be seen that the nanowires were directly grown on the graphene layer.

On the other hand, this method gives better results than the method of growing nanowires directly on a substrate, as well as the method of growing nanowires using a metal catalyst. That is, when nanowires are grown on graphenes, defects due to metal impurities and scattering of electrons can be reduced as compared with the nanowire growth method using a metal catalyst.

In addition, when the nanowire structure manufactured by this method is applied to a device, carrier mobility due to graphene can be improved and a light emitting diode device having excellent thermal characteristics can be developed.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not to be limited to the details thereof and that various changes and modifications will be apparent to those skilled in the art. And various modifications and variations are possible within the scope of the appended claims.

1: substrate 2: graphene layer
3: nanowire 3a: type 1 nanowire
3b: Type 2 nanowire

Claims (18)

(a) providing a Si substrate;
(b) forming a graphene layer on the Si substrate; And
(c) growing a GaN nanowire on the graphene layer by metal organic chemical vapor deposition (MOCVD), wherein the nanowire is grown without a metal catalyst for growth of the nanowire. The method according to claim 1,
The step (b)
Reacting the catalyst layer with a metal catalyst with a gas containing methane and hydrogen and cooling the catalyst layer to synthesize graphene;
Removing the synthesized metal catalyst portion under the graphene; And
And layering a graphene layer obtained by removing the metal catalyst portion on the substrate. The method according to claim 1,
The step (b)
Forming a metal catalyst layer on the substrate; And
And forming a graphene layer by reacting the catalyst layer with a gas containing methane and hydrogen and cooling the catalyst layer. The method according to claim 1,
The step (b)
Wherein the step of synthesizing graphene is a step of synthesizing graphene by chemical vapor deposition (CVD). delete delete The method according to claim 1,
The step (c)
(c1) growing a first type GaN nanowire on the graphene layer; And
(c2) growing second type GaN nanowires of different types on the grown first type GaN nanowires. 8. The method of claim 7,
The first type nanowire is an n-type nanowire,
Wherein the second type nanowire is a p-type nanowire. 8. The method of claim 7,
The step (c1)
Charging the substrate on which the graphene layer is formed into an MOCVD reactor;
Performing heat treatment on the graphene layer of the loaded substrate together with supply of hydrogen gas;
Growing a nanowire while supplying a precursor gas of gallium and a precursor gas of gallium at a first temperature; And
Type doping material so that the n-type nanowire is grown by supplying an n-type doping material while the nanowire is grown. 10. The method of claim 9,
The precursor gas of gallium is trimethyl gallium (TMG)
Wherein the nitrogen precursor gas is ammonia. ≪ RTI ID = 0.0 > 8. < / RTI > 10. The method of claim 9,
Type doping material,
SiH < / _RTI > gas. 10. The method of claim 9,
The step (c2)
Type doped material at a second temperature to grow a p-type nanowire on the n-type nanowire. ≪ Desc / Clms Page number 20 > 13. The method of claim 12,
The p-type doping material may include,
Cp < / _RTI > _{2 <} RTI ID = 0.0 > Mg. ≪ / _RTI > 13. The method of claim 12,
Wherein the second temperature is less than the first temperature. delete delete delete delete

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