CN102358614A - A kind of processing method of graphene nano pattern - Google Patents

Abstract

The invention relates to a processing method of graphene nano-patterns. The method comprises the following steps of: forming artificial defects on graphene; and carrying out anisotropic etching on the graphene by using hydrogen-containing plasma. According to the method disclosed by the invention, the nano-level graphene structure can be processed in a controllable way, the precision can reach below 10nm, and the graphene nanostructure with an atom-level smooth zigzag edge structure can be obtained.

Description

A kind of processing method of graphene nano pattern

technical field

The invention belongs to the field of micro-nano processing, in particular to a method for processing graphene nano-patterns.

Background technique

Graphite sheets with a nanometer thickness composed of one or a few atomic layers of crystalline graphite are called graphene.

In 2004, British scientists prepared single-layer graphene in the laboratory for the first time (Science 306, 666 (2004)). The electrons in single-layer graphene belong to massless Dirac fermions, so the discovery of this material opens up a new way to use condensed matter materials to study quantum electrodynamics and relativistic effects. The electron mobility in graphene is as high as 200,000 cm ² V ^-1 s ^-1 , which is an ideal material for manufacturing high-speed electronic devices. The electrical properties of graphene nanostructures are affected by both edge structures and quantum confinement effects. The edge structures of graphene nanostructures are divided into armchair (armchair) edge and zigzag (zigzag) edge (see Figure 1). The surface states at the zigzag edge tend to make it more conductive, while the quantum confinement effect tends to make graphene non-conductive with a band gap. In addition, the electrons at the edge of the graphene nanostructure with the zigzag edge structure also exhibit spin polarization, which can be applied to the field of spintronics.

In the prior art, there are some reports on methods for processing graphene nanostructures, mainly including: graphene ultrasonic oscillation method, carbon nanotube stripping method, carbon-based molecular bonding method, electron beam exposure-oxygen plasma etching method. Among them, although the first three methods can process nanoscale graphene structures, their structural patterns are uncontrollable. The last method is a method with good controllability, but its processing accuracy is difficult to reach less than ten nanometers. In addition, none of the above methods can obtain graphene nanostructures with atomically flat zigzag edge structures.

Contents of the invention

Therefore, the object of the present invention is to provide a kind of processing method of graphene nano-pattern, can controllably process out the graphene structure of nanoscale, precision can reach below ten nanometers, and can obtain the zigzag edge structure with atomic level smooth Graphene nanostructures.

The inventors have found through research that by forming artificial defects on graphene and anisotropically etching the graphene with hydrogen-containing plasma, some regular hexagonal holes will appear on the etched graphene instead of the usual plasma The circular hole obtained by bulk etching can obtain the desired zigzag edge structure.

According to above-mentioned finding, the present invention provides a kind of processing method of graphene nano-pattern, comprising:

Formation of artificial defects on graphene;

The graphene is anisotropically etched with hydrogen-containing plasma.

According to the processing method of graphene nano pattern provided by the present invention, wherein the artificial defects include holes.

According to the method for processing graphene nano-patterns provided by the present invention, the artificial defects can be arranged in a lattice pattern.

According to the method for processing graphene nano-patterns provided by the present invention, the lattice pattern may be a triangular lattice or a rectangular lattice.

According to the method for processing graphene nano-patterns provided by the present invention, artificial defects can be formed by photolithography, nano-imprinting, mechanical impact, and laser scanning.

According to the method for processing graphene nano-patterns provided by the present invention, the anisotropic etching of graphene with hydrogen-containing plasma gradually increases artificial defects until a desired pattern is formed.

According to the method for processing graphene nanopatterns provided by the present invention, the parameters of the hydrogen-containing plasma etching are: reaction temperature, room temperature to 520°C; air pressure, less than 1 Torr; plasma power, 30-120W; etching speed , less than 15nm/min.

According to the processing method of the graphene nano-pattern provided by the present invention, it also includes determining the orientation of the graphene lattice, and designing the angle between the orientation of the lattice pattern of the artificial defect and the orientation of the graphene lattice.

According to the processing method of graphene nano-pattern provided by the present invention, wherein the method for determining graphene lattice orientation comprises:

Etching a small hole in the graphene sheet;

The small hole is expanded into a hexagonal macropore by etching with a hydrogen-containing plasma, and the lattice orientation of the graphene is determined according to the orientation of the edges of the hexagonal macropore.

According to the method for processing graphene nano-patterns provided by the present invention, the hydrogen-containing plasma includes plasma generated by hydrogen-containing gases such as hydrogen, methane, ethylene, and water vapor.

The method provided by the invention can obtain various graphene structures of nanometer size, including quantum dots, nanobelts, and superlattice structures, and these graphene nanostructures all have atomic-level flat zigzag edge structures. The method provided by the invention has good controllability, benefiting from the etching and removing effect of the hydrogen-containing plasma on some organic pollutants, the surface of the graphene nanostructure processed by the method is very clean. And the method is compatible with the existing semiconductor processing technology.

In addition, the method can be used for device integration and mass production of graphene nanostructure devices. The processing of various graphene nanopatterns with atomically flat zigzag edge structures not only provides an effective and controllable method for studying the size confinement effect of graphene, but also provides a method for studying the influence of zigzag edge states on the physical properties of devices. Reliable approaches, including single-electron quantum dot devices, field effect transistor devices, spin-polarized quantum devices, ballistic transport devices at room temperature, quantum Hall effect devices, etc.

Description of drawings

Embodiments of the present invention will be further described below with reference to the accompanying drawings, wherein:

Fig. 1 is the schematic diagram of zigzag edge structure and armchair edge structure of graphene;

Fig. 2 is a schematic diagram of the steps of the processing method provided according to embodiment 1;

Fig. 3 is a schematic diagram of graphene lattice structure;

Fig. 4 is a schematic diagram of a square lattice pattern;

Fig. 5 is the atomic force microscopy image of a kind of graphene nanoribbon obtained according to the method for embodiment 1;

Fig. 6 schematic diagram of triangular lattice pattern;

Fig. 7 is the atomic force microscopic image of a kind of graphene superlattice obtained according to the method for embodiment 2;

Fig. 8 is the atomic force microscope image of a kind of graphene quantum dot obtained according to the method for embodiment 2;

Fig. 9 is an atomic force microscopy image of a graphene superlattice obtained according to the method of Example 3.

Detailed ways

Processing method provided by the invention mainly comprises two main steps:

(1) Design and processing of artificial defects;

(2) Hydrogen-containing plasma anisotropic etching.

Hydrogen-containing plasma has an anisotropic etching effect on graphene in the plane, that is, some regular hexagonal holes will appear on the etched graphene, instead of the circular holes usually obtained by plasma etching. The orientation of these hexagonal holes on a sheet of single-crystal graphene is consistent. Because the zigzag edge is the most stable among all the edge structures of graphene, the remaining edge structure after hydrogen-containing plasma etching is zigzag type, and the roughness of the edge is at the atomic level.

The etching effect of hydrogen-containing plasma on graphene comes from the chemical reaction between hydrogen plasma and carbon atoms in graphene to generate gaseous hydrocarbons. This reaction process is relatively mild, and its strength can be precisely controlled by etching conditions. Since the chemical stability of carbon atoms inside and on the edge of the graphene sheet is different, it is possible to control the etching conditions so that the etching only occurs at the defects and edges of the graphene. According to this etching characteristic of hydrogen-containing plasma, artificial defects can be manufactured to control the area where etching occurs, and the desired sample structure can be obtained.

According to the shape of the sample to be processed, artificial defects with certain distribution characteristics are first designed and prepared, and then etched with hydrogen-containing plasma to make these artificial defects grow up and become hexagonal, and gradually etch away those in the graphene sheet. Where it is not desired, the desired graphene nanostructure pattern is finally obtained. Because the orientation of the hexagonal holes on the same graphene is consistent, the final graphene nanostructure pattern mainly depends on the structure of the artificial defect array and the angle between the orientation of the artificial defect array and the graphene crystal orientation. .

For example, artificial defects can be formed using traditional micro-nano processing techniques, for example, holes with a diameter of tens of nanometers are prepared on graphene by standard electron beam exposure combined with oxygen plasma etching as artificial defects. These traditional micro-nanofabrication techniques can precisely control the shape, location and distribution of these artificial defects.

The etching rate of graphene by hydrogen-containing plasma can be adjusted by controlling the etching conditions. The slower etching rate makes it possible to precisely control the sample size at the nanometer scale. The preferred reaction conditions of hydrogen-containing plasma and graphene are reaction temperature: room temperature to 520°C, pressure: less than 1 Torr, plasma power: 30-120W, etching speed: less than 15nm/min.

Several different embodiments are provided below, and in these embodiments, these embodiments are exemplary only, and it is obvious to those skilled in the art that the improvement that the following embodiments are made according to the present invention, therefore also fall into scope of the invention.

Example 1

Referring to Figures 2a to 2d, the present embodiment provides a method for processing graphene nanopatterns, including:

1) As shown in Figure 2a, the graphene sheet 2 is transferred to the silicon substrate 1 (300nm SiO ₂ /Si) with a 300nm oxide layer by mechanical exfoliation, because the edges of graphene sheets obtained by mechanical exfoliation are mostly zigzag edge, so the crystal orientation of graphene can be determined by the edge of graphene, the lattice structure of graphene is as shown in Figure 3, wherein a ₁ and a ₂ can be used to represent the crystal orientation of graphene;

2) Spin-coat a layer of PMMA photoresist 3 on the sample, and form a plurality of circular holes on the photoresist with electron beam exposure and development technology, and the diameter of the circular holes is 50nm, as shown in Figure 2b, the plurality of circular holes Arranged into a square lattice pattern as shown in Figure 4, and make the orientation c ₁ of the square lattice parallel to the graphene crystal direction a ₁ ;

3) Etching with oxygen plasma, transferring the square lattice pattern on the photoresist to graphene (as shown in Figure 2c), and then cleaning the photoresist with acetone;

4) Etching with hydrogen plasma, the etching temperature is 450°C, the gas pressure is 0.3Torr, the hydrogen plasma power is 50W, and the etching speed is 5nm/min, so that multiple round holes are gradually enlarged, forming a shape as shown in Figure 2d multiple hexagonal holes.

Because the zigzag edge is the most stable among all the edge structures of graphene, the remaining edge structures after hydrogen plasma etching are of the zigzag type.

According to this embodiment, step 5) can be carried out on the basis of step 4) to continue etching with hydrogen plasma to further expand the hexagonal hole, thereby forming a pattern as shown in Figure 5, and precisely controlling the etching time. A graphene nanoribbon with a nanoscale width is formed between two adjacent hexagonal holes.

According to this embodiment, step 6) can be further etched with hydrogen plasma on the basis of step 5), and the graphene nanoribbons between two adjacent hexagonal holes are etched away to form isolated graphene quantum A dot array, wherein each quantum dot is a parallelogram.

According to this embodiment, in addition to hydrogen plasma, other hydrogen-containing gases such as methane, ethylene, and water vapor can also be used for etching to form graphene patterns.

Due to the anisotropic etching effect of hydrogen-containing plasma on graphene in the plane, the etched artificial defects will expand into regular hexagonal holes, and the orientation of the regular hexagonal holes is fixed to the lattice orientation of graphene. In Fig. 3, the dotted line 1, the dotted line 2 and the arrow show the expansion direction of the hexagonal hole, and the orientations of all the hexagonal holes in the same graphene are consistent, so the graphene nanostructure pattern obtained at last Mainly depend on the structure of the artificial defect array and the angle between the orientation of the artificial defect array and the graphene crystal direction, other patterns obtained by other structures of the artificial defect array will be introduced below through other embodiments.

Example 2

The present embodiment provides a kind of processing method of graphene nano-pattern, comprising:

1) Transfer the graphene sheet to a silicon wafer substrate (300nm SiO ₂ /Si) with a 300nm oxide layer by mechanical exfoliation, and determine the crystal orientation of the graphene through the edge of the graphene. The crystal orientation of the graphene is shown in Figure 3 shown in a ₁ and a ₂ in;

2) Spin-coat a layer of PMMA photoresist on the sample, and form a plurality of circular holes on the photoresist with electron beam exposure and development technology, the diameter of the circular holes is 50nm, and the multiple circular holes are arranged as shown in Figure 6 triangular lattice pattern, and make the orientation b ₁ of the triangular lattice parallel to the graphene crystal direction a ₁ ;

3) Etching with oxygen plasma, transferring the triangular lattice pattern on the photoresist to the graphene, and then cleaning the photoresist with acetone;

4) Etching is carried out with methane plasma, the etching temperature is 500°C, the pressure is 0.4Torr, the plasma power is 100W, and the etching speed is 8nm/min, so that multiple round holes are gradually enlarged, forming the Multiple hexagonal holes, resulting in a graphene superlattice structure.

According to this embodiment, step 5) can be carried out on the basis of step 4) and continue to be etched with methane plasma to further expand the hexagonal holes so that each hexagonal hole overlaps each other, thereby forming graphite as shown in Figure 8 ene quantum dot array.

Example 3

The present embodiment provides a kind of processing method of graphene nano pattern, and the method that embodiment 2 provides is basically the same, and its difference is that the orientation of lattice in the designed triangular lattice pattern and the angle between graphene crystal direction are different, Make b ₁ and a ₁ form an included angle of 30°, and after etching with methane plasma, a honeycomb graphene superlattice structure as shown in FIG. 9 is formed.

According to this embodiment, after forming the honeycomb graphene superlattice structure as shown in Figure 9, further methane plasma etching can also be carried out, thereby forming graphene between two adjacent hexagonal holes nanobelt.

Example 4

This embodiment provides another method for processing graphene nanopatterns. The difference from the above-mentioned embodiments lies in the way of determining the crystal orientation of graphene. In the above-mentioned embodiments, the crystal orientation of graphene is determined by the edge of graphene. The graphene crystal orientation determined by the method is generally rough, and this embodiment provides a new method, which can more precisely control the angle between the orientation of the artificial defect array and the graphene crystal orientation.

The processing method of the graphene nano-pattern provided in this embodiment includes:

1) transfer the graphene sheet to a silicon substrate with a 300nm oxide layer (300nm SiO ₂ /Si) by mechanical exfoliation;

2) Etching a small hole on the graphene sheet;

3) with hydrogen plasma etching, the small hole is expanded into a hexagonal macropore, and the lattice orientation of graphene is determined according to the orientation of the edge of the hexagonal macropore;

4) Spin-coat a layer of PMMA photoresist on the sample, and form a plurality of circular holes on the photoresist with electron beam exposure and development technology, the diameter of the circular holes is 50nm, and the multiple circular holes are arranged as shown in Figure 4 square lattice pattern, and make the orientation c ₁ of the square lattice parallel to the graphene crystal direction a ₁ ;

5) Etching with oxygen plasma, transferring the square lattice pattern on the photoresist to the graphene, and then cleaning the photoresist with acetone;

6) Etching with hydrogen plasma, the etching temperature is 400°C, the gas pressure is 0.35Torr, the hydrogen plasma power is 50W, and the etching speed is 4nm/min, so that multiple round holes are gradually enlarged, forming the shape shown in Figure 2d multiple hexagonal holes.

In this embodiment, the structure of the artificial defect lattice can also be designed as the triangular lattice in Embodiment 2 and 3, and the angle obtained in Embodiment 2 or 3 can also be obtained by adjusting the angle between the lattice orientation and the graphene orientation. picture of.

According to an embodiment of the present invention, wherein the graphene sheet can also be transferred to the substrate by means other than the mechanical method, the substrate is not limited to a silicon wafer with a 300nm oxide layer, and other materials can be selected according to practical applications base.

According to an embodiment of the present invention, the lattice patterns of artificial defects are not limited to triangular lattices and rectangular lattices, and the angle between the arrangement direction of lattices and the graphene crystal orientation is not limited to the angles described in the above-mentioned embodiments, Those skilled in the art can easily design a suitable lattice pattern and a suitable angle according to the desired graphene pattern.

According to an embodiment of the present invention, the manufacturing method of artificial defects is not limited to photolithography, and other methods can also be used, such as nanoimprinting, mechanical impact, laser scanning, etc. The shape of the artificial defect is not limited to a round hole, and may also be a square hole, a tapered hole, or the like.

According to an embodiment of the present invention, the size of the artificial defect is tens to hundreds of nanometers.

According to an embodiment of the present invention, the etching temperature of the hydrogen-containing plasma is preferably from room temperature to 520° C., the pressure is preferably less than 1 Torr, the power of the hydrogen-containing plasma is preferably 30-120 W, and the etching rate is preferably below 15 nm/min.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than limit them. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent replacements to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all of them should be included in the scope of the present invention. within the scope of the claims.

Claims (10)

1. the processing method of a graphene nano pattern comprises:

On Graphene, form artificial defect;

With containing hydrogen plasma this Graphene is carried out anisotropic etching.

2. method according to claim 1, wherein said artificial defect comprises the hole.

3. method according to claim 1, wherein said artificial defect can be arranged in the dot matrix pattern.

4. method according to claim 3, wherein said dot matrix pattern can be triangle dot matrix or rectangular lattice.

5. method according to claim 1, wherein artificial defect can form through photoetching, nano impression, mechanical shock, laser scanning.

6. method according to claim 1 wherein with containing the anisotropic etching of hydrogen plasma to Graphene, increases artificial defect gradually, till forming required pattern.

7. method according to claim 1, the parameter of wherein said hydrogeneous plasma etching is: reaction temperature, room temperature to 520 ℃; Air pressure is less than 1Torr; Plasma power, 30-120W; Etching speed was less than 15nm/ minute.

8. method according to claim 3 also comprises and confirms the Graphene crystal lattice orientation, and designs orientation and the angle between the Graphene crystal lattice orientation of the dot matrix pattern of said artificial defect.

9. method according to claim 8, confirm that wherein the method for Graphene crystal lattice orientation comprises:

On graphene film, etch an aperture;

Use hydrogeneous plasma etching, this aperture is extended to the hexagon macropore, confirm the crystal lattice orientation of Graphene according to the orientation at the edge of this hexagon macropore.

10. according to claim 1,6,7 or 9 described methods, wherein contain the plasma that hydrogen plasma comprises that hydrogen, methane, ethene, steam generate.

Images