CN109987597B - Preparation method of heterogeneously stacked graphene - Google Patents

Abstract

The invention discloses a method for preparing anisotropic stacked graphene, comprising the steps of: preparing an insulating or semiconductor substrate; preparing a layered nickel layer and a doped carbon source layer on the surface of the substrate, and making the nickel layer and the The doped carbon source layer is in direct contact; the doped carbon source layer is heated, so that carbon is incorporated into the nickel layer, and then the temperature is lowered, so that one side of the nickel layer grows doped graphene, and the other side grows pure graphene; annealing The nickel layer is evaporated so that the doped graphene and the pure graphene are distributed in layers and in contact with each other. Growth of layered doped and pure graphene on insulating or semiconducting substrates avoids subsequent transfer steps and thus avoids damage to doped and pure graphene.

Description

A kind of preparation method of anisotropic stacked graphene

【Technical field】

The invention relates to a preparation method of anisotropic stacked graphene, belonging to the field of graphene production.

【Background technique】

In 2004, two scientists from the University of Manchester in the United Kingdom discovered graphene using the method of micromechanical exfoliation, and won the Nobel Prize in Physics in 2010. Graphene is a new two-dimensional honeycomb carbonaceous material in which carbon atoms are closely arranged in a regular hexagon by sp ² hybridization, and the thickness of the single layer is only 0.335nm. Theoretically, graphene exhibits excellent electronic stability, thermal conductivity, optical properties, mechanical properties, etc. Since the discovery of graphene, due to its excellent properties and huge market application prospects, it has triggered a research upsurge in the fields of physics and materials science. Graphene is currently the thinnest and hardest nanomaterial. It also has the properties of good light transmittance, high thermal conductivity, high electron mobility, low resistivity, and high mechanical strength that many ordinary materials do not have. It is expected to be used in electrodes, batteries in the future. , transistors, touch screens, solar energy, sensors, ultra-light materials, medical, seawater desalination and many other fields are widely used, is one of the most promising advanced new materials.

The preparation methods of graphene include chemical vapor deposition method, redox method, liquid phase exfoliation method and mechanical exfoliation method, etc., but these methods have complex processes, difficult to control process conditions, high requirements for substrates, poor repeatability, and pollution. Such shortcomings are not conducive to the industrial production of graphene. Chemical vapor deposition is one of the most common methods of use. This traditional preparation method is inevitably followed by transfer. Impurity defects and pollution will inevitably be introduced during the transfer process, resulting in damage and fracture, reducing the stability of graphene. , electrical properties, etc., thus affecting the subsequent application and preparation of devices; at the same time, there is a lack of precise control over the number of graphene layers and stacking methods, especially the control over the doping of foreign heteroatoms into the lattice structure of graphene. its difficult. The application of graphene in semiconductor devices requires the preparation technology of graphene to be compatible with the semiconductor process, and doping can improve the performance of graphene, which requires more stringent preparation technology for doping.

Therefore, there is an urgent need for a preparation method that is compatible with semiconductor technology, has no transfer, and has a controllable number of doping and layers, so as to realize the industrial application of graphene and provide material and technical support for my country's microelectronics technology to enter the non-silicon CMOS era. .

[Content of the invention]

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for preparing anisotropic stacked graphene with a controllable number of layers.

To solve the above-mentioned technical problems, the present invention adopts the following technical solutions:

A preparation method of anisotropic stacked graphene, comprising the steps:

Step ①: Prepare an insulating or semiconductor substrate;

Step ②: preparing a layered nickel layer and a doped carbon source layer on the surface of the substrate, and making the nickel layer and the doped carbon source layer in direct contact;

Step 3: heating and annealing the doped carbon source layer, so that carbon is incorporated into the nickel layer, and then cooling down, so that one side of the nickel layer grows doped graphene, and the other side grows pure graphene;

Step ④: annealing and evaporating the nickel layer, so that the doped graphene and the pure graphene are distributed in layers and are in contact with each other.

The beneficial effects of the present invention are: growing layered doped graphene and pure graphene on an insulating or semiconductor substrate, avoiding subsequent transfer steps, and also avoiding damage to doped graphene and pure graphene. At the same time, the penetration effect of the nickel layer on carbon atoms and the blocking effect on other non-metallic doping elements are used, so that some carbon atoms in the doped carbon source layer pass through the nickel layer and reach the other side of the nickel layer, with the nickel layer as the In the subsequent growth process, the doped graphene and the pure graphene grow independently without mutual interference, so as to avoid mutual interference between the two and improve the process compatibility.

In summary, the present invention has the following advantages:

1. The transfer-free preparation is realized without destroying the excellent properties of graphene, and graphene can be directly applied to related fields;

2. Controllable preparation of doped and undoped graphene is achieved at the same time;

3. The preparation technology is compatible with the existing mature semiconductor process, which helps to realize the industrial application of graphene materials;

4. Through the continuous superposition of configurations, it is expected to realize the multi-layer controllable preparation of continuous alternating between doped and undoped graphene;

5. The preparation method is green and pollution-free, with low cost and high efficiency.

Step 2, step 3 and step 4 are repeated after step 4 of the present invention is completed.

In step ② of the present invention, the doped carbon source layer includes a carbon source layer and a doped layer, and the carbon source layer is located between the doped layer and the nickel layer.

In step 2 of the present invention, the surface of the substrate is first spin-coated with a doping liquid to form a doping layer, then spin-coated with a carbon source liquid to form a carbon source layer, and finally Ni is evaporated on the surface of the carbon source layer by electron beam evaporation to form a nickel layer to form the substrate, Layered distribution structure of doped layer, carbon source layer and nickel layer.

In step 2 of the present invention, electron beam evaporation is performed on the surface of the substrate to form a nickel layer, and then chemical vapor deposition is performed on the gaseous carbon source and the gaseous doping source, so that the doped carbon source layer is formed on the surface of the nickel layer.

In step ② of the present invention, the doping liquid and the carbon source liquid are mixed and spin-coated onto the surface of the nickel layer to form a doped carbon source layer.

The doping element in the doped carbon source layer of the present invention is one or more of N, S, P and B.

In step ③ of the present invention, the heating temperature of the doped carbon source layer is 800-900° C., and the temperature is kept at 800-900° C. for 2-15 minutes, and the cooling rate is 25-30° C./min.

The carbon source liquid of the present invention is PMMA.

Other features and advantages of the present invention will be disclosed in detail in the following detailed description and accompanying drawings.

【Description of drawings】

The present invention will be further described below in conjunction with the accompanying drawings:

Fig. 1 is the working steps diagram of the preparation method of anisotropic stacked graphene in the embodiment of the present invention 1;

Fig. 2 is a photo of a sample of the embodiment of the present invention 1 anisotropic stacked graphene;

Fig. 3 is the sample 2 photo of anisotropic stacked graphene in the embodiment of the present invention 1;

Fig. 4 is the sample three photos of the anisotropic stacked graphene in Example 1 of the present invention;

5 is the Raman spectra of samples one, two and three of anisotropically stacked graphene in Example 1 of the present invention.

【Detailed ways】

The technical solutions of the embodiments of the present invention will be explained and described below with reference to the accompanying drawings of the embodiments of the present invention, but the following embodiments are only preferred embodiments of the present invention, not all. Based on the examples in the implementation manner, other examples obtained by those skilled in the art without creative work shall fall within the protection scope of the present invention.

In the following description, the appearance of terms such as "inner", "outer", "upper", "lower", "left", "right" etc. to indicate orientation or positional relationship is only for the convenience of describing the embodiment and simplifying the description, rather than An indication or implication that the referred device or element must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as a limitation of the invention.

Example 1:

Referring to FIG. 1, this embodiment shows a preparation method of anisotropic stacked graphene, including the following steps:

Step ①: Prepare an insulating or semiconductor substrate.

Step ②: Prepare a layered nickel layer and a doped carbon source layer on the surface of the substrate, and make the nickel layer and the doped carbon source layer in direct contact.

In this embodiment, the doped carbon source layer includes a carbon source layer and a doped layer, and the carbon source layer is located between the doped layer and the nickel layer.

The specific preparation method of the nickel layer and the doped carbon source layer is as follows: the surface of the substrate is first spin-coated with a doping liquid to form a doped layer, then spin-coated with a carbon source liquid to form a carbon source layer, and finally Ni is evaporated on the surface of the carbon source layer by electron beam. A nickel layer is formed to form a layered distribution structure of the substrate, the doping layer, the carbon source layer and the nickel layer.

In this embodiment, the carbon source liquid is PMMA.

The doping element in the doped carbon source layer is one or more of N, S, P and B. For example, the doping liquid can be selected as nitrogen-sulfur co-doped graphene quantum dots.

Step ③: under the gas atmosphere of Ar:H ₂ =290:10 (sccm), heat the doped carbon source layer to 800-900°C, and keep the temperature for 2-15min, so that the carbon is incorporated into the nickel layer, and then the temperature is 25- The temperature is lowered at a rate of 30 °C/min, so that one side of the nickel layer grows doped graphene, and the other side grows pure graphene.

The heating temperature should not be too high. Too high heating temperature will make the growth rate of the doped carbon source layer to grow too fast, resulting in a growth rate much higher than the rate at which carbon is incorporated into the nickel layer, resulting in the subsequent segregation growth process. The content of pure graphene is too small to form layered pure graphene with effective structure. In addition, the heating temperature should not be too low. Too low heating temperature makes it difficult for carbon to enter the nickel layer, and it is also difficult for PMMA to grow into graphene. Therefore, in this embodiment, it is necessary to ensure that the carbon can be incorporated into the nickel layer at a temperature as low as possible and a long holding time to suppress the early growth of graphene as much as possible, so that enough carbon can be Incorporated into the nickel layer, there is enough carbon to form pure graphene in the subsequent cooling process. In addition, the cooling rate should not be too large nor too small. Too fast cooling rate is difficult to provide enough time for the precipitation of carbon in the nickel layer, and also destroys the mechanical strength of doped graphene and pure graphene. The too slow cooling rate leads to the rapid growth of pure graphene on the surface of the nickel layer in the early stage, which inhibits the precipitation of carbon in the subsequent nickel layer.

Step ④: annealing and evaporating the nickel layer, so that the doped graphene and the pure graphene are distributed in layers and are in contact with each other.

In this embodiment, due to the barrier of the nickel layer, the doping element in the doped layer cannot pass over the nickel layer, and due to the dissolution effect of the nickel layer on the carbon element, the carbon element in the carbon source layer will gradually move during the heating and heat preservation process into the nickel layer, and then during the cooling process, the carbon element in the nickel layer gradually seeps out to the side of the nickel layer away from the doped layer for segregation growth. At the same time, because the carbon source layer is in direct contact with the nickel layer, the carbon source layer is less hindered by the doping layer during the process of integrating into the nickel layer, and the carbon source layer is also hindered between the doping layer and the nickel layer. During the process, the doped layer and the adjacent residual carbon source layer grow into doped graphene, and the growth on the other side becomes pure graphene. The pure graphene and doped graphene are separated on both sides of the nickel layer to achieve anisotropic growth. the goal of. After that, the nickel layer is evaporated at high temperature to realize the preparation of layered components of doped graphene and pure graphene. During the evaporation of the nickel layer, the pure graphene will physically settle on the doped graphene. The thickness of the graphene is relatively thin, so the pure graphene will not separate after it settles on the doped graphene, forming a physical layered stack structure, so as to avoid the formation of chemical bonds between the pure graphene and the doped graphene, resulting in Unnecessary interfacial effects, thus affecting the respective physicochemical properties of pure graphene and doped graphene. In addition, in the process of nickel evaporation, the carbon that does not segregate and grow in the nickel layer can re-grow through the space left by the evaporated nickel to form pure graphene, which is combined with the segregated graphene.

Referring to 2-5, in order to confirm that the layered structure of doped graphene and pure graphene can be prepared in this example, sample 1 with a heating temperature of 800°C, sample 2 with a heating temperature of 850°C, and a heating temperature of 850°C were prepared respectively. The temperature of sample three is 900 °C, and the Raman spectra of the three groups of samples are measured to form characteristic peak positions at 1350 cm ^-1 , 1575 cm ^-1 and 2700 cm ^-1 , indicating the effective formation of graphene.

Example 2:

The present embodiment shows a method for preparing anisotropic stacked graphene, comprising the following steps:

Step ①: Prepare an insulating or semiconductor substrate.

Step ②: Prepare a layered nickel layer and a doped carbon source layer on the surface of the substrate, and make the nickel layer and the doped carbon source layer in direct contact.

The specific preparation method of the nickel layer and the doped carbon source layer is as follows: electron beam evaporation is performed on the surface of the substrate to form the nickel layer. The doping liquid and the carbon source liquid are mixed and spin-coated onto the surface of the nickel layer to form a doped carbon source layer.

Step 3: heating the doped carbon source layer so that carbon is incorporated into the nickel layer, and then cooling down, so that one side of the nickel layer grows doped graphene, and the other side grows pure graphene.

Step ④: annealing and evaporating the nickel layer, so that the doped graphene and the pure graphene are distributed in layers and are in contact with each other.

The difference between this embodiment and Embodiment 1 is that since the doping liquid and the carbon source liquid are in uniform contact with the nickel layer, although the doping element has a certain hindering effect on carbon during the process of carbon infiltration into the nickel layer, the carbon A low distance is still maintained between it and the nickel layer, so it does not have an excessive effect on the carbon penetration rate. At the same time, it is more conducive to the contact between the doping element and the nickel layer, and the subsequent growth of doped graphene is also more favorable.

Example 3:

The difference between this embodiment and Embodiment 1 is that step ②, step ③ and step ④ are repeated after step ④ is completed. In this way, periodic layered structures of substrate, doped graphene, pure graphene, doped graphene, and pure graphene are formed.

Example 4:

The present embodiment shows a method for preparing anisotropic stacked graphene, comprising the following steps:

Step ①: Prepare an insulating or semiconductor substrate.

Step ②: Prepare a layered nickel layer and a doped carbon source layer on the surface of the substrate, and make the nickel layer and the doped carbon source layer in direct contact.

The specific preparation method of the nickel layer and the doped carbon source layer is as follows: electron beam evaporation is performed on the surface of the substrate to form a nickel layer, and then chemical vapor deposition is performed on the gaseous carbon source and the gaseous doping source, so that the doped carbon source layer is formed on the surface of the substrate. Nickel layer surface. Meanwhile, nickel can catalyze the growth of graphene during chemical vapor deposition.

In addition, since the substrate is an insulating or semiconductor material, if vapor deposition is performed on the surface of the substrate first, it cannot ensure the formation of graphene on the surface of the nickel layer, and the result is uncontrollable if the nickel layer is prepared later. The nickel layer can be prepared first.

Step 3: heating the doped carbon source layer so that carbon is incorporated into the nickel layer, and then cooling down, so that one side of the nickel layer grows doped graphene, and the other side grows pure graphene.

Step ④: annealing and evaporating the nickel layer, so that the doped graphene and the pure graphene are distributed in layers and are in contact with each other.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes but is not limited to the drawings and the descriptions in the above specific embodiments. content. Any modifications that do not depart from the functional and structural principles of the present invention are intended to be included within the scope of the claims.

Claims (4)

1. A preparation method of heterosexual stacked graphene is characterized by comprising the following steps: the method comprises the following steps:

the method comprises the following steps: preparing an insulating or semiconductor substrate;

step two: preparing a nickel layer and a doped carbon source layer which are distributed in a layered manner on the surface of a substrate, and enabling the nickel layer to be in direct contact with the doped carbon source layer;

step three: heating and annealing the doped carbon source layer to enable carbon to be fused into the nickel layer, and then cooling to enable doped graphene to grow on one side of the nickel layer and pure graphene to grow on the other side of the nickel layer;

step IV: annealing and evaporating the nickel layer to ensure that the doped graphene and the pure graphene are distributed in a layered manner and are mutually contacted;

in the third step, the heating temperature of the doped carbon source layer is 800-900 ℃, and the temperature is kept at 800-900 ℃ for 2-15min, and the cooling rate is 25-30 ℃/min;

in the second step, the doped carbon source layer comprises a carbon source layer and a doping layer, and the carbon source layer is positioned between the doping layer and the nickel layer;

and secondly, spin-coating doping liquid on the surface of the substrate to form a doping layer, spin-coating carbon source liquid to form a carbon source layer, and finally performing electron beam evaporation on Ni on the surface of the carbon source layer to form a nickel layer so as to form a layered distribution structure of the substrate, the doping layer, the carbon source layer and the nickel layer.

2. The method for preparing stacked anisotropic graphene according to claim 1, wherein: and fourthly, repeating the third step, the fourth step and the fourth step after the fourth step is finished.

3. The method for preparing stacked anisotropic graphene according to claim 1, wherein: the doping element in the doped carbon source layer is one or more of N, S, P and B.

4. The method for preparing stacked anisotropic graphene according to claim 1, wherein: the carbon source liquid is PMMA.

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