Two-dimensional graphene and preparation method thereof, and photoelectric detector

Abstract

The application provides two-dimensional graphene and a preparation method and a photoelectric detector thereof, and comprises the following steps: preparing a nickel layer on a substrate layer by using electron beam evaporation, so as to form a growth gap between the substrate layer and the nickel layer; injecting carbon ions into the nickel layer; preparing a copper layer on the side of the nickel layer away from the substrate layer; and heating the nickel layer and the copper layer, so that the carbon ions in the nickel layer move into the growth gap, and two-dimensional graphene is directly formed on the substrate layer.

Description

Technical Field

[0001] This invention relates to the field of two-dimensional graphene preparation methods, and in particular to a two-dimensional graphene and its preparation method, as well as a photodetector. Background Technology

[0002] In the prior art, such as Chinese patent CN103265021B, carbon ions are implanted into the Ni layer to achieve the purpose of growing two-dimensional graphene. The number of layers of two-dimensional graphene can be adjusted by controlling the amount of carbon ions implanted.

[0003] The aforementioned two-dimensional graphene is grown on a nickel layer. If it is to be used as a device, it needs to be transferred to another substrate first. This transfer process disrupts the structure of the two-dimensional graphene, compromising its film integrity. Furthermore, when growing multilayer two-dimensional graphene, the heating temperature needs to be lower than when growing single-layer graphene; otherwise, the uniformity of graphene growth will decrease, leading to a corresponding decrease in the growth rate of multilayer graphene and affecting its growth efficiency. Summary of the Invention

[0004] Therefore, it is necessary to address the issues of insufficient efficiency during the multilayer growth of two-dimensional graphene and the need for transfer after growth, by providing a two-dimensional graphene, its preparation method, and a photodetector.

[0005] The technical solution provided by this invention is as follows:

[0006] A method for preparing two-dimensional graphene includes the following steps:

[0007] A nickel layer is prepared on a substrate by electron beam evaporation to create growth gaps between the substrate and the nickel layer.

[0008] Carbon ions are injected into the nickel layer;

[0009] A copper layer is prepared on the side of the nickel layer that faces away from the substrate.

[0010] The nickel and copper layers are heated to allow carbon ions in the nickel layer to move into the growth voids and form two-dimensional graphene directly on the substrate.

[0011] The thickness of the nickel layer described in this invention is no greater than 200 nm, and the carbon ion implantation amount in the nickel layer is 4n × 10⁻⁶. 15 ions / cm 2 , where n is a positive integer.

[0012] The thickness of the nickel layer described in this invention is 100 nm, and n = 1 or 2.

[0013] The thickness of the copper layer described in this invention is 150 nm.

[0014] The present invention also includes: after the two-dimensional graphene is grown, the nickel layer and the copper layer are removed by using thermally peelable tape.

[0015] The substrate layer described in this invention is made of Si, SiO2, glass, or sapphire.

[0016] The copper layer described in this invention is prepared by magnetron sputtering.

[0017] The nickel and copper layers of this invention are at 10°C during the heating process. -5 Under mbar conditions, the heating temperature is 1000℃.

[0018] A two-dimensional graphene is obtained by a preparation method in which the two-dimensional graphene is directly grown on a substrate.

[0019] A photodetector includes a substrate and two-dimensional graphene.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. Two-dimensional graphene is grown directly on the substrate, eliminating the need for a subsequent transfer process and ensuring the integrity of the two-dimensional graphene film.

[0022] 2. The nickel layer is prepared by electron beam evaporation, which ensures that sufficient growth gaps are formed between the substrate and the nickel layer, thereby allowing a complete and continuous two-dimensional graphene film to grow on the substrate.

[0023] 3. By changing the thickness of the nickel layer, the size of the growth gap can be adjusted. While allowing for the growth of complete and continuous two-dimensional graphene, the growth gap can also limit the number of two-dimensional graphene growth layers, improve the uniformity of two-dimensional graphene growth, increase the control over the number of two-dimensional graphene growth layers, and provide a control method for controlling the number of two-dimensional graphene growth layers in addition to the ion implantation amount.

[0024] 4. Based on the advantages mentioned above, a higher temperature can be used to heat the nickel layer, thereby increasing the growth rate of two-dimensional graphene without worrying about the impact of the higher temperature on the growth quality of two-dimensional graphene.

[0025] 5. During the growth process, two-dimensional graphene is protected by a nickel layer and a substrate layer on both sides. If the growth process of two-dimensional graphene is in a non-vacuum environment, the oxidation of two-dimensional graphene can be effectively suppressed. Attached Figure Description

[0026] Figure 1 This is a diagram showing the structural changes corresponding to the preparation method of two-dimensional graphene in Example 1 of the present invention;

[0027] Figure 2 The images show the Raman spectra of the two-dimensional graphene in Examples 1-8 of this invention.

[0028] Figure 3 These are SAED images of two-dimensional graphene from Examples 1, 5, and 9-14 of this invention;

[0029] Figure 4 These are snapshots of C and Ni atoms in the XY plane during the heating process in Reference Examples 1 and 2 of the present invention;

[0030] Figure 5 This is a concentration distribution diagram of C atoms in the Z direction during the heating process in Reference Examples 1 and 2 of the present invention;

[0031] Figure 6 This is a diagram illustrating the growth process of two-dimensional graphene in Example 2 of the present invention;

[0032] Figure 7 The transmission spectra of two-dimensional graphene in Examples 1 and 5 of this invention are shown.

[0033] Figure 8 The two-dimensional graphene I in Example 1 of this invention 2D / I G Planar distribution map;

[0034] Figure 9 The two-dimensional graphene I in Example 5 of this invention 2D / I G Planar distribution map;

[0035] Figure 10 Two-dimensional graphene I in Comparative Example 1 of the present invention 2D / I G Planar distribution map;

[0036] Figure 11 This is an operational demonstration diagram of step 106 in Embodiment 1 of the present invention;

[0037] Figure 12 This is a three-dimensional structural diagram of the photodetector in Embodiment 15 of the present invention;

[0038] Figure 13 This is the IV curve of the photodetector in Embodiment 15 of the present invention;

[0039] Figure 14 This is the photocurrent of the photodetector in Embodiment 15 of the present invention as a function of light intensity. Detailed Implementation

[0040] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0041] This invention improves upon the prior art CN103265021B, and the prior art thereafter specifically refers to this application.

[0042] Example 1:

[0043] See Figure 1 This embodiment provides a method for preparing two-dimensional graphene, which includes the following steps:

[0044] Step 101: Electron beam evaporation is used to prepare a 100nm thick nickel layer on the substrate. The substrate and the nickel layer are not in dense contact, but rather growth gaps are formed. The substrate material is Si, SiO2, glass or sapphire, and the type is not limited. In this embodiment, it is SiO2.

[0045] Step 102: Implant carbon ions into the nickel layer at room temperature, with an implantation energy of 70 keV and an implantation depth of 4 × 10⁻⁶. 15 ions / cm 2 ;

[0046] Step 103: Prepare a copper layer with a thickness of 150 nm on the side of the nickel layer away from the substrate by magnetron sputtering at room temperature;

[0047] Step 104: The sandwich structure formed by the substrate layer, nickel layer, and copper layer is subjected to 10... -5 Heating to 1000℃ under mbar conditions for 10 minutes causes carbon ions in the nickel layer to be gradually squeezed out into the aforementioned growth voids, forming two-dimensional graphene.

[0048] Step 105: In 10 -5 Cooled to room temperature under mbar conditions;

[0049] Step 106: During the heating process, the copper layer dissolves in the nickel layer to form an alloy. Therefore, the nickel and copper layers can be removed simultaneously by using a thermal peeling tape to obtain two-dimensional graphene grown directly on the substrate. In this embodiment, a single-layer two-dimensional graphene is obtained.

[0050] Example 2:

[0051] The difference between this embodiment and Embodiment 1 is that the heating temperature in step 104 is 940°C.

[0052] Example 3:

[0053] The difference between this embodiment and Embodiment 1 is that the heating temperature in step 104 is 960°C.

[0054] Example 4:

[0055] The difference between this embodiment and Embodiment 1 is that the heating temperature in step 104 is 980℃.

[0056] Example 5:

[0057] The difference between this embodiment and Embodiment 1 is that the carbon ion implantation amount in step 102 is 8 × 10⁻⁶. 15 ions / cm 2 Therefore, the bilayer two-dimensional graphene obtained in this embodiment is a graphene.

[0058] Example 6:

[0059] The difference between this embodiment and embodiment 5 is that the heating temperature in step 104 is 940°C.

[0060] Example 7:

[0061] The difference between this embodiment and embodiment 5 is that the heating temperature in step 104 is 960°C.

[0062] Example 8:

[0063] The difference between this embodiment and embodiment 5 is that the heating temperature in step 104 is 980°C.

[0064] Example 9:

[0065] The difference between this embodiment and Embodiment 1 is that the heating time in step 104 is 4 minutes.

[0066] Example 10:

[0067] The difference between this embodiment and Embodiment 1 is that the heating time in step 104 is 6 minutes.

[0068] Example 11:

[0069] The difference between this embodiment and Embodiment 1 is that the heating time in step 104 is 8 minutes.

[0070] Example 12:

[0071] The difference between this embodiment and embodiment 5 is that the heating time in step 104 is 4 minutes.

[0072] Example 13:

[0073] The difference between this embodiment and embodiment 5 is that the heating time in step 104 is 6 minutes.

[0074] Example 14:

[0075] The difference between this embodiment and embodiment 5 is that the heating time in step 104 is 8 minutes.

[0076] Comparative Example 1:

[0077] The difference between this comparative example and Example 1 is that the nickel layer in step 101 is prepared by magnetron sputtering.

[0078] Refer to Example 1:

[0079] In this reference embodiment, two-dimensional graphene was prepared using the method described in Example 1, wherein the ratio of C atoms to Ni atoms was 75:25, and the heating process was increased from 300K to 1800K.

[0080] Refer to Example 2:

[0081] In this reference embodiment, two-dimensional graphene was prepared using the method described in Example 1, wherein the ratio of C atoms to Ni atoms was 85:15, and the heating process was increased from 300K to 1800K.

[0082] See Figure 7 In Example 1, the transmittance of the two-dimensional graphene under 550nm light was 97.3%, and in Example 5, the transmittance of the two-dimensional graphene under 550nm light was 95.1%. This proves that the two-dimensional graphene in Example 1 has one layer, and the two-dimensional graphene in Example 5 has two layers.

[0083] See Figure 2 The intensity of the D peak is positively correlated with the defect intensity of the two-dimensional graphene. For the monolayer two-dimensional graphene in Examples 1-4, the D peak intensity gradually decreases with increasing heating temperature, thus demonstrating that the crystallinity of the two-dimensional graphene is actually improved. A similar situation occurs in the bilayer two-dimensional graphene in Examples 5-8. In Examples 1 and 5, the D peak completely disappears.

[0084] The effect of heating temperature on the quality of two-dimensional graphene is the opposite of that in existing technologies. The most likely mechanism for this anomaly is that in existing technologies, there is no substrate layer on the surface of the nickel layer, so the growth of two-dimensional graphene on the nickel layer surface is completely unrestricted, and increasing the temperature intensifies the disordered growth of two-dimensional graphene. In contrast, in Examples 1-8, the growth gaps formed by the substrate layer and the nickel layer spatially restrict the growth process of two-dimensional graphene, inhibiting its disordered growth. The growth gaps, in fact, guide the growth of two-dimensional graphene.

[0085] See Figure 3 SAED (Selected Area Electron Diffraction) observations revealed that with increasing heating time, the patterns in both single-layer and double-layer two-dimensional graphene gradually transformed from ring-like to dot-like patterns. Both single-layer and double-layer two-dimensional graphene formed clear dot-like patterns after 10 minutes of heating, indicating that both reached a relatively perfect crystalline state at this time. Combined with the foregoing analysis, it can be seen that the method of this invention for preparing two-dimensional graphene, regardless of the number of layers prepared, can maintain a fixed heating time and temperature of 10 minutes and 1000℃, without needing to adjust for the required number of layers. This characteristic is completely different from existing technologies, demonstrating that the method of this invention significantly improves process stability and controllability compared to existing technologies.

[0086] See Figure 4 Referring to Examples 1 and 2, changing the C atom content did not affect the growth positions of the two-dimensional graphene. See also Figure 5 The First curve represents the initial state, the Last curve represents the final state, and the Heat curve represents the state at one point in time as the C atom content increases. It can be seen that although the increase in C atom content increases the final height of the two-dimensional graphene, its growth rate also increases. This also reflects why the heating temperature and time do not need to be changed when the number of layers in the preparation of the aforementioned two-dimensional graphene changes.

[0087] See Figure 6 In Example 2, the growth process of two-dimensional graphene is roughly as follows: First, carbon atoms appear randomly. Between 0 and 150 ps, ​​the carbon atoms gradually form carbon chains. Then, the slender carbon chains gradually combine to form carbon rings. The carbon rings, as the core, gradually connect with the surrounding free carbon chains and free carbon atoms. At 160 ps, ​​the core carbon rings form small sheet-like graphene. At 500 ps, ​​the small sheet-like two-dimensional graphene connects to form large sheets of two-dimensional graphene. Between 500 ps and 1650 ps, ​​the size of the two-dimensional graphene hardly changes anymore, but gradually reduces defects and forms a more regular shape.

[0088] Using existing methods, the Raman intensity of the two-dimensional graphene in the 30 μm × 30 μm range in Examples 1 and 5 was detected to calculate I. 2D / I G How the numerical value changes within a plane. See also Figure 8 and Figure 9 For single-layer two-dimensional graphene, I0 is present in more than 90% of the area. 2D / I G The values ​​all exceed 1.8, which is significant for bilayer two-dimensional graphene. 2D / I G There were no numerical points exceeding 1.3, indicating no single-layer two-dimensional graphene signal, and I values ​​above 1.3 were found in over 90% of the region. 2D / I G The values ​​are all around 0.5. This fully demonstrates that the single-layer two-dimensional graphene in Example 1 and the double-layer two-dimensional graphene in Example 5 have high structural integrity and are very continuous, forming a relatively complete two-dimensional graphene film, and the number of two-dimensional graphene layers is controlled relatively precisely.

[0089] On the contrary Figure 10 Compared with Example 1, I 2D / I G The numerical values ​​change drastically in the plane, which proves that if the nickel layer is prepared by magnetron sputtering, a growth gap of suitable shape and size cannot be formed between the nickel layer and the substrate. This results in the inability to grow two-dimensional graphene continuously or to guide the growth process of two-dimensional graphene, thus failing to achieve the goal of controllable growth layer number of two-dimensional graphene.

[0090] Furthermore, increasing the thickness of the nickel layer leads to a reduction in the growth gap between it and the substrate. Therefore, by changing the thickness of the nickel layer, the size of the growth gap can be adjusted. In some embodiments, this can be used to further guide and restrict the growth process of two-dimensional graphene, thereby further improving parameters such as the controllability of the number of two-dimensional graphene layers, crystal quality, and film continuity. Of course, to ensure that at least a single continuous two-dimensional graphene film can be grown, in all embodiments, the thickness of the nickel layer generally needs to be no greater than 200 nm.

[0091] The thickness of the copper layer should match the thickness of the nickel layer to ensure that carbon ions in the nickel layer are fully squeezed out. However, compared with the prior art, the thickness of the copper layer in this invention can be reduced. This is because heating can be performed at higher temperatures in Examples 1 and 5. Furthermore, due to the limiting effect of growth gaps on the growth of two-dimensional graphene, there is no need to worry about the above heating method adversely affecting the integrity and continuity of the growth of two-dimensional graphene, and it will not cause the problem of intermittent growth of two-dimensional graphene. This also means that even with a small amount of copper layer, the high-temperature heating conditions can be used to increase the intensity of copper atom movement in the nickel layer, thereby fully squeezing out carbon ions in the nickel layer.

[0092] Example 15:

[0093] The difference between this embodiment and Embodiment 1 is that the substrate is a Si substrate. Thus, a Schottky junction is formed between the monolayer two-dimensional graphene and the substrate. Based on this, a 200nm silver electrode is formed by electron beam evaporation, thus fabricating a structure as shown in the figure. Figure 12 The photodetector shown is a prior art structure and will not be described in detail in this embodiment.

[0094] Irradiation was achieved using light rays at 532nm, 980nm, and 1550nm, with a light power density of 30mW / cm². 2 The obtained IV curve is as follows Figure 13 As shown, this demonstrates that the two-dimensional graphene prepared using the methods in Examples 1 and 5 can be directly used to fabricate photodetectors without additional processing of the two-dimensional graphene and the substrate. After preparation, the two-dimensional graphene already generates a sufficient built-in electric field with the substrate.

[0095] See Figure 14 The light power density of the aforementioned photodetector is from 5 mW / cm². 2 Increased to 30mW / cm 2 Then reduce by 5mW / cm 2 There is a good correlation between the magnitude of the photocurrent and the illumination power density, which proves that the above photodetector has good stability.

[0096] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0097] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing two-dimensional graphene, characterized in that, Includes the following steps: A nickel layer is prepared on a substrate by electron beam evaporation to create growth gaps between the substrate and the nickel layer. The thickness of the nickel layer is 100 nm. Carbon ions are implanted into the nickel layer, wherein the amount of carbon ions implanted in the nickel layer is 4n × 10. 15 ions / cm 2 n = 1 or 2; A copper layer is prepared on the side of the nickel layer that faces away from the substrate. The nickel and copper layers are heated to allow carbon ions in the nickel layer to move into the growth voids and form two-dimensional graphene directly on the substrate. The thickness of the copper layer is 150 nm; The nickel and copper layers are at 10 during the heating process. -5 Under mbar conditions, the heating temperature is 1000℃ and the heating time is 10min.

2. The method for preparing two-dimensional graphene according to claim 1, characterized in that, Also includes: After the two-dimensional graphene is grown, the nickel and copper layers are removed using thermally peelable tape.

3. The method for preparing two-dimensional graphene according to claim 1, characterized in that, The substrate is made of Si, SiO2, glass, or sapphire.

4. The method for preparing two-dimensional graphene according to claim 1, characterized in that, The copper layer was prepared by magnetron sputtering.

5. A two-dimensional graphene, characterized in that, The two-dimensional graphene is obtained by the preparation method described in any one of claims 1-4, so that the graphene is directly grown on the substrate.

6. A photodetector, characterized in that, It includes a substrate layer and the two-dimensional graphene as described in claim 5.

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