KR101753590B1

KR101753590B1 - Method for doping graphene using substrate of improved surface and graphine structure having the same

Info

Publication number: KR101753590B1
Application number: KR1020150052901A
Authority: KR
Inventors: 문진산; 조인수; 박원배; 박수범; 홍병희
Original assignee: 엘지전자 주식회사; 서울대학교산학협력단
Priority date: 2015-04-15
Filing date: 2015-04-15
Publication date: 2017-07-04
Also published as: KR20160122976A

Abstract

The present invention relates to graphene, and more particularly, to a graphene doping method using substrate surface modification and a graphene structure including the same. The present invention provides a doping method of graphene using substrate surface modification, comprising: forming a precursor polymer layer for doping on a substrate; And positioning the graphene on the substrate having the precursor polymer layer formed thereon.

Description

TECHNICAL FIELD [0001] The present invention relates to a graphene doping method using a substrate surface modification, and a graphene structure including the graphene doped graphene substrate.

The present invention relates to graphene, and more particularly, to a graphene doping method using substrate surface modification and a graphene structure including the same.

As materials composed of carbon atoms, fullerene, carbon nanotube, graphene, graphite and the like exist. Among them, graphene is a structure in which carbon atoms are composed of one layer on a two-dimensional plane.

In particular, graphene is not only very stable and excellent in electrical, mechanical and chemical properties, but it is also a good conductive material that can move electrons much faster than silicon and can carry much larger currents than copper, It has been proved through experiments that a method of separation has been discovered.

Such graphene can be formed in a large area and has electrical, mechanical and chemical stability as well as excellent conductivity, and thus is attracting attention as a basic material for electronic circuits.

In addition, since graphenes generally have electrical characteristics that vary depending on the crystal orientation of graphene of a given thickness, the user can express the electrical characteristics in the selected direction and thus design the device easily. Therefore, graphene can be effectively used for carbon-based electric or electromagnetic devices.

Recently, we have used a form that is applied as a silicon oxide dielectric to analyze the device characteristics of graphene. In the conventional case, p-type doping is exhibited due to the doping effect of the substrate, and further doping is performed through heat treatment or self-assembled monolayer coating.

On the other hand, in a substrate other than the silicon oxide, heat treatment can not be performed or a self-assembled monolayer film is not formed, so that a general surface modification method can not be realized. Therefore, the effect of doping of graphene was limited.

SUMMARY OF THE INVENTION The present invention provides a graphene doping method using surface modification of a substrate and a graphene structure including the graphene doping method.

Also, a graphene doping method using a substrate surface modification capable of maximizing a graphene doping effect and a graphen structure including the graphene doping method are provided.

According to a first aspect of the present invention, there is provided a doping method of graphene using a substrate surface modification, comprising: forming a precursor polymer layer for doping on a substrate; And positioning the graphene on the substrate having the precursor polymer layer formed thereon.

Here, the precursor polymer layer may include a precursor having a methyl group.

At this time, the precursor polymer layer may include a precursor having the methyl group as a terminal group.

The precursor having a methyl group may be a precursor of a cyclohexane series.

The precursor of the cyclohexane series may be at least one of cyclohexane, methylcyclohexane, and ethylcyclohexane. The precursor of the cyclohexane series may be at least one of cyclohexane, methylcyclohexane, and ethylcyclohexane.

Here, the substrate may be a polymer substrate.

At this time, the polymer substrate may include at least one of polyethyleneterephthalate (PET), triacetyl cellulose (TAC), and polycarbonate (PC).

Here, the step of forming the precursor may be performed using a plasma enhanced chemical vapor deposition method.

The method may further include doping the graphene further.

According to a second aspect of the present invention, there is provided a semiconductor device comprising: a substrate; A precursor layer having a methyl group positioned on the substrate; And graphenes located on the precursor layer.

Here, the precursor having the methyl group may be at least one of cyclohexane, methylcyclohexane, and ethylcyclohexane.

Here, the substrate may be a polymer substrate including at least one of polyethyleneterephthalate (PET), triacetyl cellulose (TAC), and polycarbonate (PC).

The present invention has the following effects.

The graphenes positioned on the surface-modified substrate can have improved electrical characteristics. Further, graphene may exhibit the characteristics of n-type doping or p-type doping.

Such a doping process can compensate for the reduction in conductivity due to graphene crystal defects (defects due to a grane boundary or the like between the crystal faces of the metal) formed on the catalyst metal.

Further, by modifying the surface of the substrate through the polymer layer, it is possible to provide a state in which the effect of this doping can be maximized when additional doping is performed.

As a result, the surface of various types of substrates can be modified quickly and inexpensively using a polymer layer comprising an organic precursor.

Such graphenes are advantageous in that they can be applied to flexible devices because they can be deposited as flexible insulator materials that replace conventional silicon oxides that can not be applied to flexible devices.

Further, a graphene structure having high transmittance can be manufactured, and can be applied to an optical element, a display, and the like.

1 is a flowchart showing an example of a doping method of graphene using a substrate surface modification.
2 is a schematic diagram showing a precursor having a methyl group as a terminal group.
FIGS. 3 and 4 are schematic cross-sectional views showing examples of a doping method of graphene using substrate surface modification.
5 to 7 are schematic cross-sectional views showing examples of a graphene structure using substrate surface modification.
8 is a graph showing the current characteristics of graphene in relation to doping characteristics.
9 is a schematic diagram of PECVD in which a process of substrate surface modification is performed.
FIGS. 10 and 11 are schematic views for explaining the principle of polymerization using plasma.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. Rather, the intention is not to limit the invention to the particular forms disclosed, but rather, the invention includes all modifications, equivalents and substitutions that are consistent with the spirit of the invention as defined by the claims.

It will be appreciated that when an element such as a layer, region or substrate is referred to as being present on another element "on," it may be directly on the other element or there may be an intermediate element in between .

Although the terms first, second, etc. may be used to describe various elements, components, regions, layers and / or regions, such elements, components, regions, layers and / And should not be limited by these terms.

1 is a flowchart showing an example of a doping method of graphene using a substrate surface modification.

As shown in FIG. 1, a step (S10) of forming a precursor polymer layer for doping on a substrate and a step (S20) of placing graphene on the substrate on which such precursor polymer layer is formed .

Here, the precursor polymer layer may include a precursor having a methyl group (CH ₃ ).

At this time, the precursor polymer layer may include a precursor having a methyl group as a terminal group. The precursor having such a methyl group as an end group can provide a condition for allowing the methyl group to interact with the graphene itself to improve the conductivity of the graphene or to allow the graphene to be doped in an optimal state. This will be described in detail later.

The precursor having such a methyl group may be a precursor of the cyclohexane series. That is, the precursor having a methyl group may be at least one of cyclohexane, methylcyclohexane, and ethylcyclohexane.

Table 1 below shows the structures of these cyclohexane-based precursors.

Here, the substrate may be a polymer substrate.

Such a polymer substrate may include at least one of PET (polyethyleneterephthalate), TAC (triacetyl cellulose), and PC (poly carbonate).

Hereinafter, each manufacturing step will be described with reference to FIG. 1 and the drawings.

FIG. 2 is a schematic view showing a precursor having a methyl group as a terminal group, and FIGS. 3 and 4 are schematic cross-sectional views showing an example of doping method of graphene using substrate surface modification.

The precursor polymer layer 20 can be formed on the substrate 10 as shown in FIG. 3 by using a precursor having a methyl group (CH ₃ ) as shown in FIG.

Here, the polymer layer 20 may be formed using plasma enhanced chemical vapor deposition (PECVD).

Polymers such as cyclohexane have a ring shape, but they can be opened by plasma treatment, such as plasma enhanced chemical vapor deposition, to form radical molecules. Thus, the methyl group may be exposed at the terminal.

As described above, the surface of the substrate 10 can be improved (modified) by the polymer layer 20 having a methyl group at its end.

This graphene 30 may be formed on a catalyst metal (not shown) and transferred onto the substrate 10 on which the polymer layer 20 is formed.

Metals such as Ni, Co, Fe, Pt, Au, Al, Cr, Cu, Mg, Mn, Mo, Rh, Si, Ta, Ti, W, U, V, Zr, Or at least two of these alloys.

The graphene 30 may be formed by a method such as thermal-chemical vapor deposition (CVD), inductively coupled plasma chemical vapor deposition (ICP-CVD), plasma chemical vapor deposition (PE-CVD) Chemical vapor deposition may be used. In addition, various methods such as rapid thermal annealing (RTA), atomic layer deposition (ALD), and physical vapor deposition (PVD) may be used.

As an example, the chemical vapor deposition method is a method of growing graphene 30 by placing a catalyst metal in a chamber (not shown), introducing a carbon source, and providing suitable growth conditions.

Examples of the carbon source include a gas such as methane (CH ₄ ), acetylene (C ₂ H ₂ ), etc., and a solid form such as powder or polymer and a liquid such as bubbling alcohol It is possible.

In addition, various carbon sources such as ethane, ethylene, ethanol, acetylene, propane, butane, butadiene, pentane, pentene, cyclopentadiene, hexane, cyclohexane, benzene, toluene,

Instead of transferring the graphene 30 onto the substrate 10, the graphene 30 may be directly transferred onto the substrate 10 if the substrate 10 is made of a material that is not deformed even at a high temperature, .

As mentioned above, the substrate 10 may comprise a polymer comprising at least one of PET (polyethylen terephthalate), TAC (triacetyl cellulose), and PC (poly carbonate). For example, the substrate 10 may be formed of any one of PEC, TAC, and PC.

The graphene 30 may be positioned on the substrate 10 on which the polymer layer 20 is formed, as shown in Fig.

That is, the substrate 10 can use a flexible substrate, and the graphen 30 positioned on such a flexible substrate can be used as an electrode of a flexible device.

When the graphenes 30 are positioned on the surface-modified substrate 10, the graphene 30 may be doped with a methyl group to improve electrical characteristics.

In addition, this doping effect can exhibit the characteristics of n-type doping or p-type doping.

5 to 7 are schematic cross-sectional views showing examples of a graphene structure using substrate surface modification.

That is, as shown in FIG. 5, the graphenes 30 are positioned on the substrate 10, which has been surface-modified through the polymer layer 20 exposed at the end of the methyl group, so that the electrical characteristics are improved, A graphene structure can be fabricated.

Further, as shown in FIG. 6, a separate doping layer 40 may be further formed on the graphene structure having the structure shown in FIG.

That is, the graphene 30 positioned on the surface-modified substrate 10 can be improved in electric characteristics through an additional doping process. Also, as noted above, graphene 30 may exhibit the characteristics of n-type doping or p-type doping.

Such a doping process can compensate for a decrease in conductivity due to graphene crystal defects (defects due to a boundary between the crystal grains and the like) formed on the catalyst metal.

That is, a carrier may be generated by substituting the dopant material included in the doping layer 40 and the material of the graphene 30, thereby increasing the carrier density.

The dopant for such doping may include an organic dopant, an inorganic dopant, or a combination thereof. As an example, a vapor or a solution of a substance containing nitric acid and nitric acid can be used. In particular, it may be more advantageous to perform vapor doping using steam.

The dopant may be selected from the group consisting of NO ₂ BF ₄ , NOBF ₄ , NO ₂ SbF ₆ , HCl, H ₂ PO ₄ , CH ₃ COOH, H ₂ SO ₄ , HNO ₃ , PVDF, Nafion, , AuCl ₃ , SOCl ₂ , Br ₂ , CH ₃ NO ₂ , dichlorodicyanoquinone, oxone, di-myristoyl phosphatidyl inositol, and trifluoromethanesulfonimide.

On the other hand, as shown in Fig. 7, the surface modification of the substrate 10 can be performed on both side surfaces of the substrate 10. Fig. That is, the precursor polymer layer 20 may be formed on both sides of the substrate 10, and the graphenes 30 may be placed on the polymer layer 20.

As described above, the electrical characteristics of the graphen 30 positioned on the substrate 10 improved in surface characteristics by the polymer layer 20 can be greatly improved as described above.

8 is a graph showing the current characteristics of graphene in relation to doping characteristics. 9 is a schematic diagram of PECVD in which a substrate surface modification process is performed, and FIGS. 10 and 11 are schematic views for explaining the principle of polymerization using plasma by PECVD.

Hereinafter, the process of modifying the substrate surface will be described with reference to FIGS. 8 to 11. FIG.

As described above, the surface modification process of the substrate 10 can be performed by PECVD.

PECVD includes a chamber 100, a magnetic coil 120 for generating a plasma in the chamber 100, and an RF power source 130, as shown in FIG. 9, and a chuck (not shown) Plasma can be formed on the substrate 110.

A backside cooling helium is supplied to the lower side of the chamber 100 to lower the temperature of the substrate.

Process gases are supplied through the upper side of Fig. 9, and by-products after the reaction can be exhausted through the lower side through a pump (not shown).

According to this PECVD method, the reaction gas is adsorbed on the surface of the substrate 10 whose temperature is lowered by the cooling back helium, and the reaction gases activated by the plasma are deactivated The polymer layer can be formed by the reaction between the reaction gases.

Here, the principle that can be deposited on the substrate 10 can be considered as the adsorption of the process gases by the directionality of the plasma and the low temperature of the surface of the substrate 10

Hereinafter, the principle of reaction in which such a polymer layer is formed will be described.

In Fig. 10, M _i denotes a polymer formed by collecting M molecules. The bases therefore indicate that the polymer has an arbitrary number of molecules (e.g., k, j).

Also, the meaning of a dot means that it has a radical form.

One dot means one radical, and two dots means there are two radicals.

Radicals are highly reactive and can react with other molecules or radical molecules to form bonds.

Here, the meaning of "+" means to react between two substances. The product from the reaction between the two substances is located in the head direction of the arrow, and when they react, it shows that the bonding occurs.

Also, the meaning of "-" means that an intermolecular bond has been formed.

By such a process, the polymer layer 20 by plasma can be formed.

Referring to Fig. 11, in the case of ring-shaped cyclohexane, the radicals can be opened to form radical molecules in a manner similar to the principle described above in Fig. 10 by plasma treatment in a hydrogen atmosphere.

The various types of radical molecules thus formed are increased in molecular weight as the reaction proceeds as described with reference to FIG.

By this process, the precursor polymer layer 20 having a methyl group as a terminal group on the substrate 10 is uniformly formed, and the characteristics of the substrate 10 can be greatly improved by the polymer layer 20 have.

FIG. 8 shows the characteristics of graphene when a polymer layer 20 having a chain-like precursor such as a methyl group is used, and it is known that the effect of doping is maximized when the lowest point of the current curve is located near 0 V .

As shown in Fig. 8, it can be seen that the lowest point of the current curve is located near 0V. When the graphene 30 is placed on the polymer layer 20, the electrical characteristics of the graphene 30 can be improved by bonding with the polymer layer 20.

Further, by modifying the surface of the substrate 10 through the polymer layer 20, it is possible to provide a state where the effect of the doping can be maximized when additional doping is performed.

In this embodiment, the use of the polymer layer 20 with respect to the characteristics of doping including the property of improving the conductivity has been described, but various characteristics may be improved depending on the type of the polymer.

For example, the functional groups may vary depending on the purpose, and depending on the functional groups used, other properties of the graphene may be improved.

It should be noted that the embodiments of the present invention disclosed in the present specification and drawings are only illustrative of specific examples for the purpose of understanding and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

10: substrate 20: polymer layer
30: graphene 40: doped layer

Claims

In a graphene doping method using a substrate surface modification,
Forming a precursor polymer layer on the substrate, the precursor polymer layer comprising a precursor having a methyl group for doping; And
Positioning the graphene on a substrate having the precursor polymer layer formed thereon,
Wherein the precursor having a methyl group is a precursor of a cyclohexane series.

delete

The doping method of graphene according to claim 1, wherein the precursor polymer layer comprises a precursor having the methyl group as a terminal group.

delete

The method of claim 1, wherein the precursor of the cyclohexane series is at least one of plasma-treated cyclohexane, methylcyclohexane, and ethylcyclohexane. Doping method using graphene.

The doping method of graphene according to claim 1, wherein the substrate is a polymer substrate.

7. The doping method of graphene according to claim 6, wherein the polymer substrate comprises at least one of polyethylene terephthalate (PET), triacetyl cellulose (TAC), and polycarbonate (PC) .

2. The method of claim 1, wherein the step of forming the precursor polymer layer is performed using a plasma enhanced chemical vapor deposition process.

2. The method of claim 1, further comprising doping the graphene further.

Board;
A precursor polymer layer located on the substrate and comprising a precursor having a methyl group; And
And graphenes located on the precursor polymer layer,
Wherein the precursor having the methyl group is at least one of plasma-treated cyclohexane, methylcyclohexane, and ethylcyclohexane.

delete

The graphene structure according to claim 10, wherein the substrate is a polymer substrate comprising at least one of PET (polyethylene terephthalate), TAC (triacetyl cellulose), and PC (polycarbonate).