TWI571437B - Method for growing graphene by chemical vapor deposition - Google Patents

Description

Method for growing graphene by chemical vapor deposition

The present invention relates to a method of growing graphene, and more particularly to a method of growing graphene by chemical vapor deposition.

Graphene includes a two-dimensional structure of a tight honeycomb lattice formed by covalent bonding of a single layer of carbon atoms with sp ² . Graphene has a variety of special properties, especially high carrier mobility, hardness, thermal conductivity, current carrying capacity and extremely large surface-to-volume ratio, while there are many biomedical, electronic and optoelectronic components for graphene in the next generation. Research in the application.

One of the methods of preparing graphene is to use chemical vapor deposition (CVD). Graphene has been successfully grown on the surface of various transition metals by chemical vapor deposition. In this growth process, the carbon-containing gas is decomposed by the catalysis of the transition metal at a high temperature. Depending on the catalytic effect of the various transition metals on the hydrocarbon molecules and their corresponding carbon solubility, the decomposed carbon atoms will produce varying degrees of deposition, dissolution, and precipitation on the surface of the transition metal.

For copper foil (a typical metal substrate for growing graphene), when a carbon atom covering a metal surface forms a continuous graphene film, it becomes a protective shield, so the metal surface loses catalytic decomposition and is subsequently introduced. The ability of hydrocarbon molecules. This self-limiting growth mechanism will limit the single layer coverage of graphene grown on copper surfaces to only 90%.

In addition, in order to electrically isolate the graphene film, the metal substrate of the grown graphene film is removed by wet (acid) etching, and the graphene film is transferred to have a thin polymer scaffold (polymer scaffold) ) an insulating substrate. However, in addition to the strong acid-destroying structure in the wet etching process, the residual metal particles are inevitably left on the surface of the graphene to scatter electrons, thereby reducing the electron mobility of the graphene. Further, the aforementioned thin polymer scaffold is usually composed of long-chain hydrocarbon molecules, making it difficult to thoroughly remove by using any conventional organic solvent.

The present invention provides a novel method of growing graphene by chemical vapor deposition, which can directly grow a low-defect graphene film on a surface of a substrate (particularly an insulating surface).

The method for growing graphene by chemical vapor deposition according to the present invention comprises: loading at least one substrate into a furnace tube; introducing a reaction gas containing an oxygen-containing carbon source into the furnace tube; heating the reaction gas, And irradiating the reaction gas with ultraviolet light using an ultraviolet (UV) source to decompose the oxygen-containing carbon source; and depositing the graphene film on the surface of the at least one substrate by carbon atoms released by decomposition of the carbon source.

The at least one substrate may include at least one insulating substrate (particularly at least one insulating surface) or at least one metal substrate.

In an embodiment of the invention, the above method of growing graphene by chemical vapor deposition further comprises using a plasma source to promote decomposition of the oxygen-containing carbon source.

In another embodiment of the present invention, the above method of growing graphene by chemical vapor deposition further comprises providing metal vapor as a catalyst into the furnace tube. The method of providing metal vapor is, for example, placing a solid metal into a furnace tube or supplying an organometallic compound to a furnace tube, wherein the solid metal comprises copper, nickel, zinc or a combination thereof.

The reaction gas may further include a carbon-free oxygen-containing compound (for example, H ₂ O). The reaction gas may further include hydrogen gas and an inert gas as a diluent gas.

Since the carbon source is decomposed by irradiating ultraviolet light at a high temperature, not by surface decomposition of the metal, a single layer coverage of nearly 100% can be achieved, and wet (acid) etching of the metal substrate can be avoided, and it is not necessary The use of a polymer scaffold to transfer the graphene film prevents the above-mentioned disadvantages caused by wet (acid) etching and polymer scaffolding. The multilayer graphene film can be grown on the surface of the substrate (especially on the surface of the insulating substrate) by the extended controlled growth time.

The above described features and advantages of the invention will be apparent from the following description.

The invention is further illustrated by the following examples and the accompanying drawings, which are not intended to limit the scope of the invention. For example, although the ultraviolet light for decomposing the carbon source in the following embodiments starts to act on the reaction gas in the pipeline and is also introduced into the furnace tube through the pipeline, it may be modified to be formed on the furnace tube. The window introduces ultraviolet light and acts on the reaction gas. More specifically, the ultraviolet light source may be located upstream of the reactant gas stream, and the ultraviolet light may be irradiated to the inner space of the furnace tube through the transparent window in a direction substantially parallel to the planar direction of the at least one insulating substrate.

1 is a diagram showing an apparatus for a method of growing graphene by chemical vapor deposition according to a first embodiment of the present invention.

Referring to FIG. 1, at least one substrate 10 is loaded into the furnace tube 100. The substrate 10 may be a wafer, and the wafer may be loaded in the furnace tube 100 in a state of being placed in the wafer holder. The surface of the substrate 10 may be an insulating surface or a metal surface. The above-described insulating surface may include a material selected from the group consisting of ruthenium, osmium, iridium oxide, tantalum nitride, tantalum carbide, quartz, sapphire, glass, and combinations thereof. The surface of the above metal may include a material selected from the group consisting of copper (Cu), nickel (Ni), ruthenium (Ru), cobalt (Co), and combinations thereof. The surface of the substrate 10 may be treated with oxygen plasma or hydrogen plasma prior to loading the substrate 10 into the furnace tube 100. Oxygen plasma can be used to remove organic materials from the surface of the substrate 10. Hydrogen plasma can be used to reduce the native oxide layer on the metal surface of substrate 10, or can be used to clean carbonaceous polymer residues or soil on substrate 10. A patterned carbon-containing seed may be deposited on the surface of the substrate 10 prior to loading the substrate 10 into the furnace tube 100.

Then, a gas 110 containing carbon and oxygen is introduced into the furnace tube 100, and hydrogen gas 112 as a catalyst gas and an inert gas 114 as a diluent gas are usually introduced together into the furnace tube 100 to form a reaction gas. Gas 110 essentially contains an oxygen-containing carbon source. The gas 110 may further include a carbon-free oxygen-containing compound (for example, H ₂ O) to promote graphitization of carbon atoms on the surface of the insulating substrate 10. Three flow meters 120, 122, 124 are used to measure the flow of gas 110, hydrogen 112, and inert gas 114, respectively. Gas 110, hydrogen 112, and inert gas 114 may be mixed prior to introduction to furnace tube 100 prior to line 135. In this embodiment, the ultraviolet light source 130 is disposed at the end of the line 135 such that ultraviolet light emitted by the ultraviolet light source 130 can be introduced into the line 135 and can be introduced into the furnace tube 100 through the line 135.

When the reaction gas is introduced into the furnace tube 100, the pressure in the furnace tube 100 is lowered to a predetermined value by the vacuum pump 140, the furnace tube 100 is heated to a predetermined temperature, and ultraviolet light is supplied from the ultraviolet light source 130 to illuminate the line 135. The reaction gas in the furnace tube 100. Due to the effect of ultraviolet light and heating, the oxygen-containing carbon source contained in the reaction gas is decomposed, and carbon atoms released by the above decomposition are deposited on the surface of each of the substrates 10 to form a graphene film. The deposited graphene film may comprise a single layer of graphene or a plurality of layers of graphene, depending on process conditions and reaction time.

The oxygen-containing carbon source may be selected from the group consisting of carbon monoxide, carbon dioxide, ketones, ethers, esters, alcohols, aldehydes, phenols, organic acids, and combinations thereof. The oxygen contained in the oxygen-containing carbon source has the effect of providing a reaction path with a low activation energy, and the carbon atoms can thereby be graphitized on the surface of the insulating substrate. The inert gas 114 can be selected from the group consisting of argon and helium. Depending on the size of the reaction chamber, the flow rate of the gas 110 containing carbon and oxygen may be in the range of 5 to 600 sccm, the flow rate of the hydrogen 112 may be in the range of 5 to 200 sccm, and the flow rate of the inert gas 114 may be 60. Within the range of ~800 sccm. The pressure in the furnace tube 100 is measured by a vacuum gauge 145, and the pressure can be reduced to several tens of torr. The furnace tube 100 can be heated to a temperature in the range of 600 ° C to 1100 ° C. The ultraviolet light provided by the ultraviolet light source 130 can have a wavelength in the range of 160 nm to 400 nm.

Further, when a plurality of substrates 10 including a plurality of wafers are loaded into the furnace tube 100, the wafers are preferably arranged in parallel with each other and substantially in parallel with the ultraviolet light irradiation direction 118 of the ultraviolet light source 130. Hydrogen 112 and inert gas 114 may also be provided during the temperature rise phase prior to deposition to clean the surface such that graphene may then be uniformly deposited thereon. The flow rate of the hydrogen gas 112 may be in the range of 50 to 600 sccm in the temperature rising phase. The flow rate of the inert gas 114 may be in the range of 60 to 800 sccm in the temperature rising phase.

Although in the above embodiment, the carbon source is decomposed only by ultraviolet light and heating, at least one of the plasma source and the metal vapor may be further provided to promote decomposition of the carbon source.

2 is a second embodiment of the above modified embodiment, in which a plasma source 150 is attached to the furnace tube 100 to induce plasma in the reaction gas contained in the furnace tube 100, and has a solid. Metal 160 is placed in furnace tube 100 to produce metal vapor that is capable of catalyzing the decomposition of the carbon source. Solid metal 160 can comprise copper, nickel, zinc, or a combination thereof. Additionally, it is also feasible to provide only one of the plasma source 150 and the solid metal 160.

In the second embodiment, in the case where the solid metal 160 is provided, a stage in which only the hydrogen gas 112 and the inert gas 114 are supplied may be inserted between the temperature rising phase and the deposition phase to reduce the oxide on the surface of the solid metal 160. The required temperature of the furnace tube 100 may be reduced by the help of the plasma source 150 and/or catalytic metal vapor generated from the solid metal 160, possibly down to the range of 400 °C to 1100 °C.

3 illustrates the other embodiment of the modified embodiment described above as a third embodiment of the present invention in which the source of the metal vapor is the organometallic compound 116 introduced into the furnace tube 100 instead of the solid metal placed in the furnace tube 100. 160. The organometallic compound 116 can be decomposed by pyrolysis in the furnace tube 100 to form a metal vapor capable of catalyzing the decomposition of the carbon source. As shown in FIG. 3, the organometallic compound 116 can be introduced into the furnace tube 100 in a state of being mixed with the gas 110, the hydrogen gas 112, and the inert gas 114, and the flow rate of the organometallic compound 116 can be measured by the flow meter 126. The organometallic compound 116 may include a metal selected from the group consisting of copper, nickel, platinum, and rhodium.

In the above embodiment, since the carbon source is decomposed at a high temperature by ultraviolet light (and catalysis by plasma and/or metal vapor), instead of being decomposed by the surface of the metal, a single layer coverage of nearly 100% can be achieved. Moreover, the wet (acid) etching of the metal substrate can be avoided, and the polymer scaffold is not required to transfer the graphene film, thereby preventing the above-mentioned disadvantages caused by the wet (acid) etching and the polymer scaffold.

In order to further illustrate the invention, the following Examples 1 to 3 are provided, however, such examples are not intended to limit the scope of the invention.

In Example 1, a single layer of graphene was grown directly on the surface of sapphire at 1000 ° C using the apparatus illustrated in FIG. The deposition settings specifically include an ultraviolet source that provides a continuous wavelength of 160 to 400 nm. The ultraviolet light source is located upstream of the reaction gas stream, and the ultraviolet light is irradiated to the inner space of the reaction chamber through the transparent window in a direction substantially parallel to the planar direction of the substrate. The oxygen-containing carbon source uses ethyl methyl ether, which has a fixed flow rate of 30 sccm throughout the growth phase. Hydrogen was also introduced as a catalytic gas having a flow rate of 120 sccm. The argon gas used as the diluent gas has a flow rate of 200 sccm.

4A shows the Raman spectrum of the obtained single-layer graphene, FIG. 4B shows the X-ray photoelectron spectroscopy spectrum of the obtained single-layer graphene, and FIG. 5 shows the electron microscopy of the single-layer graphene directly grown on the sapphire substrate. Sectional view.

The narrow half-height of the G peak and the 2D peak can be clearly seen from Fig. 4A, which shows high crystallinity of the formed graphene layer. Fig. 4B shows that a metal residue having a traceable amount was found in the graphene film which was not grown directly on the insulating substrate. It can be clearly seen from Figure 5 that the formed graphene layer conforms to the surface of the substrate.

In Examples 2 and 3, the multilayer graphene was directly grown on the tantalum nitride substrate and the tantalum oxide substrate, respectively, using the same apparatus as in Example 1. The deposition settings include an ultraviolet source that provides a continuous wavelength of 160 to 400 nm. The ultraviolet light source is located upstream of the reaction gas stream, and the ultraviolet light is irradiated to the inner space of the reaction chamber through the transparent window in a direction substantially parallel to the planar direction of the substrate. The oxygen-containing carbon source uses ethyl methyl ether, which has a fixed flow rate of 60 sccm throughout the growth phase. Hydrogen was also introduced as a catalytic gas having a flow rate of 120 sccm. The argon gas used as the diluent gas has a flow rate of 200 sccm. The plasma is ignited a short time before the start of the growth and continues to ignite during growth.

Figure 6A shows an electron micrograph of a multilayer graphene grown directly on a tantalum nitride substrate in Example 2. 6B shows an electron micrograph of a multilayer graphene grown directly on a ruthenium oxide substrate in Example 3.

It can be clearly seen from FIGS. 6A and 6B that graphene can be grown on an insulating substrate and stacked layer by layer. A multilayer graphene stack parallel to the surface of the substrate can be obtained using the techniques disclosed herein, which differ from the graphene petal and other non-parallel graphene layers described in the previous section.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

10‧‧‧Substrate
100‧‧‧ furnace tube
110‧‧‧ gas
112‧‧‧ Hydrogen
114‧‧‧Inert gas
116‧‧‧Organic Metal Compounds
118‧‧‧UV direction
120, 122, 124, 126‧‧ ‧ flowmeter
130‧‧‧UV light source
135‧‧‧ pipeline

140‧‧‧vacuum pump

145‧‧‧ vacuum gauge

150‧‧‧ Plasma source

160‧‧‧solid metal

1 is a diagram showing an apparatus for a method of growing graphene by chemical vapor deposition according to a first embodiment of the present invention. 2 illustrates an apparatus for a method of growing graphene by chemical vapor deposition in accordance with a second embodiment of the present invention. 3 illustrates an apparatus for a method of growing graphene by chemical vapor deposition in accordance with a second embodiment of the present invention. 4A shows a Raman spectrum of a single-layer graphene grown on a sapphire substrate in Example 1 of the present invention. 4B shows an X-ray photoelectron spectroscopic spectrum of a single-layer graphene grown on a sapphire substrate in Example 1 of the present invention. Fig. 5 shows an electron microscopic sectional view of a single-layer graphene directly grown on a sapphire substrate in Example 1 of the present invention. Fig. 6A shows an electron microscopic sectional view of a multilayer graphene directly grown on a tantalum nitride substrate in Example 2 of the present invention. Fig. 6B shows an electron microscopic sectional view of a multilayer graphene directly grown on a cerium oxide substrate in Example 3 of the present invention.

10‧‧‧Substrate

100‧‧‧ furnace tube

110‧‧‧ gas

112‧‧‧ Hydrogen

114‧‧‧Inert gas

118‧‧‧UV direction

120, 122, 124‧‧‧ flowmeter

130‧‧‧UV light source

135‧‧‧ pipeline

140‧‧‧vacuum pump

145‧‧‧ vacuum gauge

Claims (19)

A method for growing graphene by chemical vapor deposition, comprising: loading at least one insulating substrate into a furnace tube; introducing a reaction gas containing an oxygen-containing carbon source into the furnace tube; heating the reaction gas, and using ultraviolet light The light source irradiates the reaction gas with ultraviolet light to decompose the oxygen-containing carbon source, wherein the ultraviolet light source is located upstream of the flow of the reaction gas, and the ultraviolet light is substantially opposite to the at least one insulating substrate The plane direction is parallel, and is irradiated to the inner space of the furnace tube through the transparent window; and a graphene film is deposited on the surface of the at least one insulating substrate. A method of growing graphene by chemical vapor deposition as described in claim 1, wherein the method further comprises using a plasma source to promote decomposition of the oxygen-containing carbon source. The method of growing graphene by chemical vapor deposition according to claim 1, wherein the method further comprises supplying metal vapor as a catalyst into the furnace tube. A method for growing graphene by chemical vapor deposition according to claim 3, wherein a solid metal is placed in the furnace tube to provide the metal vapor, the solid metal comprising copper, nickel, zinc Or a combination thereof. A method of growing graphene by chemical vapor deposition as described in claim 3, wherein an organometallic compound is supplied to the furnace tube to provide the metal vapor. A method of growing graphene by chemical vapor deposition as described in claim 5, wherein the organometallic compound comprises a metal selected from the group consisting of copper, nickel, platinum, and rhodium. The method of growing graphene by chemical vapor deposition according to claim 1, wherein the surface of the at least one insulating substrate comprises a layer selected from the group consisting of ruthenium, osmium, iridium oxide, tantalum nitride, tantalum carbide, A group of materials consisting of quartz, sapphire, glass, and combinations thereof. The method for growing graphene by chemical vapor deposition according to claim 1, wherein the oxygen-containing carbon source is selected from the group consisting of carbon monoxide, carbon dioxide, ketones, ethers, esters, alcohols, aldehydes, phenols, organic acids, and A group consisting of its combinations. A method of growing graphene by chemical vapor deposition as described in claim 1, wherein the reaction gas further comprises a carbon-free oxygen-containing compound. A method of growing graphene by chemical vapor deposition as described in claim 9, wherein the carbon-free oxygen-containing compound comprises H ₂ O. The method for growing graphene by chemical vapor deposition as described in claim 1, wherein the reaction gas further comprises hydrogen gas and an inert gas. The method of growing graphene by chemical vapor deposition according to claim 1, wherein a plurality of insulating substrates including a plurality of wafers are loaded into the furnace tubes, the wafers are arranged in parallel with each other and It is substantially parallel to the ultraviolet light irradiation direction of the ultraviolet light source. A method of growing graphene by chemical vapor deposition as described in claim 1, wherein the reaction gas is heated to a temperature in a range of from 400 ° C to 1100 ° C. A method of growing graphene by chemical vapor deposition as described in claim 1, wherein the ultraviolet light source provides ultraviolet light having a wavelength ranging from 160 nm to 400 nm. A method of growing graphene by chemical vapor deposition as described in claim 1, wherein the graphene film deposited comprises a single layer of graphene or a plurality of layers of graphene. The method for growing graphene by chemical vapor deposition according to claim 1, further comprising: using oxygen plasma before depositing the graphene film on the surface of the at least one insulating substrate Or treating the surface of the at least one insulating substrate with hydrogen plasma. The method for growing graphene by chemical vapor deposition according to claim 1, further comprising: depositing a patterned layer before depositing the graphene film on the surface of the at least one insulating substrate A carbon-containing seed crystal is on the surface of the at least one insulating substrate. A method for growing graphene by chemical vapor deposition, comprising: loading at least one metal substrate into a furnace tube; introducing a reaction gas containing an oxygen-containing carbon source into the furnace tube; heating the reaction gas, and using ultraviolet light The light source irradiates the reaction gas with ultraviolet light to decompose the oxygen-containing carbon source, wherein the ultraviolet light source is located in the reaction gas Upstream of the flow of the body, and the ultraviolet light is irradiated to the inner space of the furnace tube in a direction substantially parallel to the planar direction of the at least one metal substrate, and through the transparent window; and depositing the graphene film On the surface of the at least one metal substrate. The method of growing graphene by chemical vapor deposition according to claim 18, wherein the at least one metal substrate comprises a material selected from the group consisting of copper, nickel, ruthenium, cobalt, and combinations thereof.