Processing method of patterned two-dimensional layered material with dangling bond-free closed edge

Abstract

The invention discloses a method for processing a patterned two-dimensional layered material with a dangling bond-free closed edge, which comprises the following steps of: cutting a double-layer two-dimensional layered material by using a tip of a scanning tunneling microscope under the conditions of ultrahigh vacuum and low temperature, and realizing atomic precision energy injection by controlling the magnitude and duration of applied pulse voltage. And performing atomic-scale local processing along the specific atomic chain direction of the material to obtain two layers of flat and aligned fresh edges, and re-bonding to form a dangling bond-free closed edge. According to the method, atomic-scale precise controllable cutting of the two-dimensional layered material is achieved, the effects of high cutting precision and low processing power consumption are achieved, and the problems of edge pollution and stray electronic states caused by the fact that edge dangling bonds randomly adsorb environmental molecules after patterning processing are solved.

Description

Technical Field

[0001] This invention belongs to the field of two-dimensional layered material cutting and edge patterning processing, and relates to an atomic-level precision processing method for patterned two-dimensional layered materials with dangling bond-free closed edges. Background Technology

[0002] Two-dimensional layered materials have been extensively studied for their unique physical properties, leading to the development of various electronic and spintronic devices. The material properties are modulated by factors such as the number of layers and stacking, with the edges being a crucial factor influencing the transport properties of these materials. By fabricating nanopatterns with atomically precise edges, integrated devices based on two-dimensional layered materials can be realized.

[0003] Existing methods for patterning two-dimensional layered materials mainly focus on thermally driven nanoparticle cutting, ion beam etching, laser etching, and atomic force microscopy (AFM) anodizing. While these techniques can achieve patterning of two-dimensional layered materials, they have drawbacks. Thermally driven nanoparticle cutting in a liquid environment faces sample contamination issues; ion beam etching is highly destructive, leading to edge defects and insufficient cutting precision; laser etching consumes a lot of power, resulting in higher processing costs; and AFM anodizing offers high precision but faces challenges such as edge passivation (the binding of dangling bonds to specific atoms, such as hydrogen and oxygen) or edge reconstruction (forming pentagonal or heptagonal rings) to form complete chemical bonds between edge atoms, thereby eliminating dangling bonds and achieving a stable state. Therefore, these methods do not simultaneously solve the problems of low cutting precision, high processing power, and the impact of edge contamination and stray electronic states on device performance in the patterning of two-dimensional layered materials. Summary of the Invention

[0004] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide a method for processing patterned two-dimensional layered materials with dangling-bond-free closed edges. Based on scanning tunneling microscopy (STM) micromachining technology, energy is precisely injected atomically with pulsed voltage applied by a needle tip, allowing for atomic-level precise cutting along specific surface atomic chain directions of the two-dimensional layered material. This achieves high cutting accuracy and low processing power consumption. Furthermore, the resulting two layers of flat, aligned fresh edges are rebonded under ultra-high vacuum and low temperature conditions, forming dangling-bond-free closed edges. This avoids edge contamination and stray electronic states caused by the random adsorption of environmental molecules by dangling bonds after patterning.

[0005] The present invention is achieved through the following technical solution.

[0006] One aspect of the present invention provides a method for processing a patterned two-dimensional layered material having a dangling-bond-free closed edge, comprising: A double-layer two-dimensional layered material is selected, which has a layered stacking structure; Under ultra-high vacuum conditions, the surface morphology of the sample is obtained by scanning the sample with a scanning tunneling microscope. Identify the orientation of atomic chains on the surface of a two-dimensional layered material based on its surface morphology. The scanning tunneling microscope tip is placed above a double-layered two-dimensional material, and the line width of the cut is controlled by adjusting the magnitude of the pulse voltage applied to the tip. The scanning tunneling microscope tip is moved along the atomic chain direction of a specific surface of a bilayer two-dimensional layered material, and the magnitude and duration of the pulse voltage applied to the tip are controlled to perform atomic-level precision cutting. By controlling the position of the needle tip when applying pulse voltage, the pre-set cutting shape of the double-layer two-dimensional layered material is cut with atomic-level precision, thereby achieving patterned processing of the double-layer two-dimensional layered material with dangling bond-free closed edges.

[0007] According to an exemplary embodiment of the present invention, the two-dimensional layered material includes graphene or hexagonal boron nitride.

[0008] According to an exemplary embodiment of the present invention, the two-dimensional layered graphene is AB stacked, where the upper carbon atom is above the center of the lower six-membered ring.

[0009] According to an exemplary embodiment of the present invention, the two-dimensional layered hexagonal boron nitride sample is an AA' stack, wherein the AA' stack is such that the upper nitrogen atoms are above the lower boron atoms, and the upper boron atoms are above the lower nitrogen atoms.

[0010] According to an exemplary embodiment of the present invention, the specific surface atomic chain orientation of atomically precise cutting refers to the serrated edges and armchair edges of graphene or hexagonal boron nitride; graphene is composed of carbon atoms arranged in sp... 2 Hybridization forms a honeycomb lattice with serrated or armchair-shaped edges; hexagonal boron nitride consists of nitrogen and boron atoms arranged in sp... 2 Hybridization forms a honeycomb lattice with serrated or armchair-shaped edges.

[0011] According to an exemplary embodiment of the present invention, the ultra-high vacuum pressure is no higher than 10. -7 Pa; temperature not exceeding 4.5 K.

[0012] According to an exemplary embodiment of the present invention, a pulse voltage of -7 V to -15 V is applied to the tip of the scanning tunneling microscope for a duration of 0.1 to 0.2 s.

[0013] According to an exemplary embodiment of the present invention, the minimum line width formed during cutting is 5 nm to 20 nm.

[0014] According to an exemplary embodiment of the present invention, the dangling bond-free closed edge refers to the field evaporation of the two-dimensional layered material after a pulse voltage is applied to the tip of a scanning tunneling microscope, resulting in two flat and aligned fresh edges. The two fresh edges will then rebond to form a closed edge.

[0015] According to an exemplary embodiment of the present invention, the carbon atoms at the fresh edges of the upper and lower layers of graphene are rebonded, and the nitrogen or boron atoms at the fresh edges of hexagonal boron nitride are rebonded to the upper and lower layers of boron or nitrogen atoms.

[0016] The present invention, by adopting the above technical solution, has the following beneficial effects: This invention provides a method for processing patterned two-dimensional layered materials with dangling-bond-free closed edges, effectively solving the problems of low cutting accuracy, high power consumption, and edge contamination in existing patterned processing methods. Specifically: 1. This invention is based on scanning tunneling microscope micromachining technology. By controlling the magnitude and duration of the pulse voltage applied to the tip, it achieves atomic-precision energy injection and atomic-level precise cutting along the atomic chain direction of a specific surface of a two-dimensional layered material, thereby effectively solving the problems of low precision and high power consumption in patterned cutting.

[0017] 2. The fresh edges of the upper and lower layers that are flat and aligned after cutting are rebonded under ultra-high vacuum and low temperature conditions to form a closed edge without dangling bonds, which solves the problems of edge contamination and stray electronic states after patterning. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, do not constitute an undue limitation of the invention. In the drawings: Figures 1(a)-(d) show the manufacturing process flow of patterned two-dimensional layered materials with dangling key-free closed edges; Figure 2 To apply a pulse voltage to realize the change of tunneling current detected by the needle tip over time during the cutting process; Figure 3 To achieve a scanning tunneling microscope morphology image of graphene with a serrated edge direction and no dangling bond closed edge; Figure 4 To achieve a scanning tunneling microscope morphology image of graphene with a closed edge without dangling bonds along the edge direction of an armchair; Figure 5 Scanning tunneling microscope morphology of patterned graphene with dangling bond-free closed edges. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0020] This invention provides a method for processing patterned two-dimensional layered materials with dangling-bond-free closed edges, the specific steps of which are as follows: Step 1: Select a bilayer two-dimensional layered material, including graphene or hexagonal boron nitride. The graphene sample is AB stacked, and the hexagonal boron nitride substrate is AA' stacked.

[0021] In this embodiment, the graphene AB stack is configured such that the upper carbon atom is above the center of the lower six-membered ring. The hexagonal boron nitride AA' stack is configured such that the upper nitrogen atom is above the lower boron atom, and the upper boron atom is above the lower nitrogen atom.

[0022] Step 2: Scan the sample using a scanning tunneling microscope (STM). The STM and its tip operate in an ultra-high vacuum environment with a pressure not exceeding 10 kJ / m². -7 Pa; temperature not exceeding 4.5 K. Surface morphology images were obtained, and the orientation of atomic chains on the surface of the bilayer two-dimensional layered material was identified based on the surface morphology images, as shown in Figure 1(a).

[0023] The specific atomic chain orientation in bilayer two-dimensional layered materials refers to the serrated edges and armrest edges of graphene or hexagonal boron nitride. Graphene is composed of carbon atoms arranged in sp... 2 Hybridization forms a honeycomb lattice with serrated or armchair-shaped edges. Hexagonal boron nitride consists of nitrogen and boron atoms arranged in sp... 2 Hybridization forms a honeycomb lattice with serrated or armchair-shaped edges.

[0024] Boundary regions formed by lattice arrangement or processing in the two-dimensional layered edge monolayer or few-layer structures of graphene or hexagonal boron nitride possess unique physical and chemical properties. Physical properties include the potential introduction of edge states by their serrated edges, enhancing local conductivity and exhibiting phenomena such as the quantum Hall effect. Chemical properties include the susceptibility of edge dangling bonds to reactions with the external environment, such as oxidation or bonding with other molecules, affecting material stability.

[0025] Step 3: Place the scanning tunneling microscope tip above the double-layered two-dimensional material, and control the linewidth of the cut by adjusting the magnitude of the applied pulse voltage. The applied pulse voltage is -7 V to -15 V, the duration is 0.1 to 0.2 s, and the minimum linewidth formed during cutting is 5 nm to 20 nm.

[0026] Step 4: Move the scanning tunneling microscope tip along the direction of the atomic chains on a specific surface of the bilayer two-dimensional layered material to perform atomic-level precision cutting of the bilayer two-dimensional layered material. The cut bilayer two-dimensional layered material will undergo field evaporation to produce two layers of flat and aligned fresh edges, as shown in Figure 1(b). Since the cut upper and lower fresh edges will not be passivated or reconstructed under ultra-high vacuum and low temperature conditions, the two layers of edges will rebond and spontaneously close to form dangling bond-free edges.

[0027] After the scanning tunneling microscope tip performs atomic-level precision cutting along the specific surface atomic chain direction of the bilayer two-dimensional layered material in 0.1 to 0.2 s, a controllable field evaporation is carried out between the tip and the bilayer two-dimensional layered material. The field evaporation can reach the depth of several surface layers, generating fresh bilayer edges on the surface of the two-dimensional layered material. The fresh bilayer material edges are aligned, and there is a spontaneous bonding mechanism, which enables the two-dimensional layered material to bond and form closed edges along the serrated or armchair direction.

[0028] Specifically, in the serrated edges of the AB-stacked bilayer graphene, the carbon atoms in the upper and lower layers re-bond. In the armchair-shaped edges of the AB-stacked bilayer graphene, the upper graphene layer experiences a bond length shift along the armchair edge direction, allowing the carbon atoms in the upper and lower layers to re-bond.

[0029] After trimming, the serrated edges of the AA' stacked double-layer hexagonal boron nitride show that the upper nitrogen (boron) atoms and the lower boron (nitrogen) atoms re-bond. The armchair edges of the AA' stacked double-layer hexagonal boron nitride show a bond length slip along the armchair edge direction, with the upper nitrogen (boron) atoms and the lower boron (nitrogen) atoms re-bonding.

[0030] In this embodiment, a scanning tunneling microscope is used to apply pulsed voltage, causing the two-dimensional layered material to undergo field evaporation in ionic form. Transient free radicals are formed along the cut edges, due to the pressure not exceeding 10... -7 Under conditions where the temperature does not exceed 4.5 K, free radicals will not adsorb functional groups or molecules in the environment.

[0031] The fresh edges of the upper and lower layers spontaneously close to form dangling bond-free closed edges, as shown in Figure 1(c). The carbon atoms at the fresh edges of the upper and lower layers of graphene rebond, and the nitrogen (boron) atoms in the upper layer and the boron (nitrogen) atoms in the lower layer of the fresh edges of boron nitride rebond.

[0032] Step 5: By controlling the needle tip to apply pulse voltage and move its position, repeat steps 2-4 multiple times to perform atomic-level precision cutting of the preset cutting shape of the double-layer two-dimensional layered material, thereby achieving patterned processing with dangling bond-free closed edges, as shown in Figure 1(d).

[0033] The following embodiments further illustrate the processing of patterned two-dimensional layered materials with dangling key-free closed edges according to the present invention.

[0034] Example 1 S1, select graphene, a two-dimensional layered material, and the graphene sample is AB stacked.

[0035] S2. The sample is scanned using a scanning tunneling microscope (STM). The STM and its tip operate in an ultra-high vacuum environment with a pressure not exceeding 10 kJ / m². -7 Pa, temperature not exceeding 4.5 K. Obtain surface morphology images and identify the orientation of atomic chains on the surface of graphene materials based on the surface morphology images.

[0036] S3. The scanning tunneling microscope tip is placed above the bilayer two-dimensional layered material graphene, and a pulsed voltage of -7 V is applied. The minimum linewidth formed during cutting is 5 nm.

[0037] S4, the scanning tunneling microscope tip is moved along a specific surface atomic chain direction, including serrated edges and armchair edges, to perform atomic-level precision trimming of the bilayer graphene material along this direction. The trimming time is controlled to 0.2 s. The trimmed bilayer graphene material undergoes field evaporation, producing two layers of smooth, aligned fresh edges. The tip detects the trend of tunneling current change. Figure 2 An increase in the absolute value of the tunneling current indicates that field evaporation has occurred.

[0038] The fresh edges of the top and bottom layers spontaneously close to form dangling bond-free closed edges, and the carbon atoms at the fresh edges of the top and bottom layers of graphene re-bond. (See...) Figure 3-4 .

[0039] S5, repeating steps S2-S4 multiple times, by controlling the position of the needle tip to apply pulse voltage, the preset cutting shape of the double-layer two-dimensional layered material is cut with atomic-level precision, achieving patterned processing with dangling bond-free closed edges, see... Figure 5 .

[0040] Example 2 S1, select a two-dimensional layered material, hexagonal boron nitride, and the hexagonal boron nitride sample is AA' stacked.

[0041] S2. The sample is scanned using a scanning tunneling microscope (STM). The STM and its tip operate in an ultra-high vacuum environment with a pressure not exceeding 10 kJ / m². -7 Pa, temperature not exceeding 4.5 K. Obtain surface morphology images and identify the atomic chain orientation on the surface of the hexagonal boron nitride material based on the surface morphology images.

[0042] S3. The scanning tunneling microscope tip is placed above the double-layered two-dimensional layered material hexagonal boron nitride, and a pulsed voltage of -12 V is applied. The minimum linewidth formed during the cutting is 10 nm.

[0043] S4, the scanning tunneling microscope tip is moved along a specific surface atomic chain direction, including serrated edges and armchair edges, to perform atomic-level precision trimming of the bilayer hexagonal boron nitride material along this direction. The trimming time is controlled to 0.15 s. The trimmed bilayer hexagonal boron nitride material undergoes field evaporation, producing two layers of smooth, aligned, fresh edges.

[0044] The two fresh edges of the upper and lower layers spontaneously close to form a closed edge without dangling bonds, and the upper nitrogen (boron) atoms and the lower boron (nitrogen) atoms of hexagonal boron nitride rebond.

[0045] S5. Repeat steps S2-S4 multiple times. By controlling the position of the needle tip to apply pulse voltage, the preset cutting shape of the double-layer two-dimensional layered material hexagonal boron nitride is cut with atomic precision, so as to achieve patterned processing with dangling bond-free closed edges.

[0046] Example 3 S1, select graphene, a two-dimensional layered material, as the AB stack.

[0047] S2. The sample is scanned using a scanning tunneling microscope (STM). The STM and its tip operate in an ultra-high vacuum environment with a pressure not exceeding 10 kJ / m². -7 Pa, temperature not exceeding 4.5 K. Obtain surface morphology images and identify the orientation of atomic chains on the surface of graphene materials based on the surface morphology images.

[0048] S3. The scanning tunneling microscope tip is placed above the bilayer two-dimensional layered material graphene, and a pulsed voltage of -12 V is applied. The minimum linewidth formed during cutting is 15 nm.

[0049] S4. The scanning tunneling microscope tip is moved along a specific surface atomic chain direction, including serrated edges and armchair edges, to perform atomic-level precision trimming of the bilayer graphene material along this direction. The trimming time is controlled to 0.1 s. The trimmed bilayer graphene material undergoes field evaporation, producing two layers of smooth, aligned, fresh edges.

[0050] The fresh edges of the upper and lower layers spontaneously close to form dangling bond-free closed edges, and the carbon atoms of the fresh edges of the upper and lower layers of graphene re-bond.

[0051] S5. Repeat steps S2-S4 multiple times. By controlling the position of the needle tip to apply pulse voltage, the preset cutting shape of the double-layer two-dimensional layered material graphene is cut with atomic precision, so as to achieve patterned processing with dangling bond-free closed edges.

[0052] Example 4 S1, select a two-dimensional layered material, hexagonal boron nitride, and the hexagonal boron nitride sample is AA' stacked.

[0053] S2. The sample is scanned using a scanning tunneling microscope (STM). The STM and its tip operate in an ultra-high vacuum environment with a pressure not exceeding 10 kJ / m². -7 Pa, temperature not exceeding 4.5 K. Obtain surface morphology images and identify the atomic chain orientation on the surface of the hexagonal boron nitride material based on the surface morphology images.

[0054] S3. The scanning tunneling microscope tip is placed above the double-layered two-dimensional layered material hexagonal boron nitride, and a pulsed voltage of -15 V is applied. The minimum linewidth formed during the cutting is 20 nm.

[0055] S4, the scanning tunneling microscope tip is moved along a specific surface atomic chain direction, including serrated edges and armchair edges, to perform atomic-level precision trimming of the bilayer hexagonal boron nitride material along this direction. The trimming duration of the scanning tunneling microscope tip is controlled to 0.2 s. The trimmed bilayer hexagonal boron nitride material undergoes field evaporation, producing two layers of smooth, aligned, fresh edges.

[0056] The two fresh edges of the upper and lower layers spontaneously close to form a closed edge without dangling bonds, and the upper nitrogen (boron) atoms and the lower boron (nitrogen) atoms of hexagonal boron nitride rebond.

[0057] S5. Repeat steps S2-S4 multiple times. By controlling the position of the needle tip to apply pulse voltage, the preset cutting shape of the double-layer two-dimensional layered material hexagonal boron nitride is cut with atomic precision, so as to achieve patterned processing with dangling bond-free closed edges.

[0058] As can be seen from the above embodiments, the method of the present invention uses the tip of a scanning tunneling microscope to cut two-dimensional layered materials. By applying pulsed voltage and injecting energy with atomic precision, atomic-level cutting is achieved along the direction of atomic chains on a specific surface. By operating under ultra-high vacuum and low temperature conditions, the fresh edges of the upper and lower layers after cutting will not be passivated or reconstructed. The edges of the upper and lower layers will rebond, forming closed edges without dangling bonds. Since closed edges without dangling bonds are formed after cutting, and the operation achieves atomic-level precision and low processing power consumption, the problem of contamination and stray electronic states caused by random adsorption of environmental molecules by dangling bonds at the edges after patterning is solved. This provides a good solution to the problem of open edge contamination in nanoscale two-dimensional layered material devices.

[0059] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A method for processing a patterned two-dimensional layered material with a dangling-bond-free closed edge, characterized in that, include: A double-layer two-dimensional layered material is selected, which has a layered stacking structure; Under ultra-high vacuum conditions, the surface morphology of the sample is obtained by scanning the sample with a scanning tunneling microscope. Identify the orientation of atomic chains on the surface of a two-dimensional layered material based on its surface morphology. The scanning tunneling microscope tip is placed above a double-layered two-dimensional material, and the line width of the cut is controlled by adjusting the magnitude of the pulse voltage applied to the tip. The scanning tunneling microscope tip is moved along the atomic chain direction of a specific surface of a bilayer two-dimensional layered material, and the magnitude and duration of the pulse voltage applied to the tip are controlled to perform atomic-level precision cutting. By controlling the position of the needle tip when applying pulse voltage, the pre-set cutting shape of the double-layer two-dimensional layered material is cut with atomic-level precision, thereby achieving patterned processing of the double-layer two-dimensional layered material with dangling bond-free closed edges.

2. The processing method for patterned two-dimensional layered materials with dangling key-free closed edges according to claim 1, characterized in that, Two-dimensional layered materials include graphene or hexagonal boron nitride.

3. The processing method for patterned two-dimensional layered materials with dangling key-free closed edges according to claim 2, characterized in that, Two-dimensional layered graphene is an AB stack, where the upper carbon atom is above the center of the lower six-membered ring.

4. The processing method for patterned two-dimensional layered materials with dangling key-free closed edges according to claim 2, characterized in that, Two-dimensional layered hexagonal boron nitride is AA' stacked, where the upper nitrogen atom is above the lower boron atom, and the upper boron atom is above the lower nitrogen atom.

5. The method for processing patterned two-dimensional layered materials with dangling key-free closed edges according to claim 1, characterized in that, The specific surface atomic chain orientation of atomically precise cutting refers to the serrated edges and armrest edges of graphene or hexagonal boron nitride; graphene is composed of carbon atoms arranged in sp... 2 Hybridization forms a honeycomb lattice with serrated or armchair-shaped edges; hexagonal boron nitride consists of nitrogen and boron atoms arranged in sp... 2 Hybridization forms a honeycomb lattice with serrated or armchair-shaped edges.

6. The method for processing a patterned two-dimensional layered material with a dangling-bond-free closed edge according to claim 1, characterized in that, Ultra-high vacuum pressure not exceeding 10 -7 Pa; temperature not exceeding 4.5 K.

7. The method for processing patterned two-dimensional layered materials with dangling key-free closed edges according to claim 1, characterized in that, The scanning tunneling microscope tip is applied with a pulse voltage of -7 V to -15 V for a duration of 0.1 to 0.2 s.

8. The method for processing a patterned two-dimensional layered material with a dangling key-free closed edge according to claim 1, characterized in that, The minimum line width formed during cutting is 5 nm to 20 nm.

9. The method for processing a patterned two-dimensional layered material with a dangling key-free closed edge according to claim 1, characterized in that, The dangling bond-free closed edge refers to the field evaporation of a two-dimensional layered material after a pulse voltage is applied to the tip of a scanning tunneling microscope, resulting in two flat and aligned fresh edges. These two fresh edges then re-bond to form a closed edge.

10. The method for processing a patterned two-dimensional layered material with a dangling key-free closed edge according to claim 9, characterized in that, The carbon atoms at the fresh edges of the top and bottom layers of graphene rebond, and the nitrogen or boron atoms at the fresh edges of hexagonal boron nitride rebond.

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