Two-dimensional material line contact heterojunction and array preparation method thereof

Abstract

The application discloses a two-dimensional material line contact heterojunction and an array type preparation method thereof, and belongs to the field of nanomaterials, and comprises the following steps: transferring a first material layer on a substrate, and etching a plurality of first material units; preparing an isolation protection layer covering the first material units, etching a plurality of isolation protection units respectively covering the first material units, and at least one side of the first material units protruding the boundary of the isolation protection units; etching the first material units again to obtain a lap joint side where the isolation protection units and the first material units are flush; transferring a second material layer on the substrate, etching the second material layer into a plurality of second material units, one end of the second material units being lap jointed with the isolation protection units, the other end of the second material units being attached to the substrate on one side of the lap joint side, and the middle part of the second material units being lap jointed with the boundary of the first material units on the lap joint side. The method can realize array type preparation of the two-dimensional material line contact heterojunction, improve the preparation efficiency, and reduce the preparation cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of nanomaterials, and particularly relates to a two-dimensional material line contact heterojunction and an array type preparation method thereof. BACKGROUND

[0002] In the field of nanomaterials, two-dimensional materials can be freely combined without the restriction of lattice matching due to the characteristic of no dangling bonds on the surface, and seamless connection along a specific direction is realized through direct growth or precise patterning technology, which provides new possibilities for the construction of high-performance electronic devices and the research of new physical phenomena. Among them, various heterojunctions based on two-dimensional materials have been widely studied in recent years, and the unique layered structure of two-dimensional materials makes them have different physical, chemical, optical and electromagnetic properties from bulk materials, which has shown broad application prospects in many fields.

[0003] However, due to the nanoscale thickness of two-dimensional materials, and the small size of the prepared two-dimensional material heterojunctions, the preparation of two-dimensional material heterojunctions is usually difficult, especially batch high-precision preparation. Moreover, for different forms of two-dimensional material heterojunctions, the preparation methods may also differ, and they are difficult to be used together. Among them, for two-dimensional material line contact heterojunctions, different two-dimensional materials are matched in a line contact manner, and the contact area between two-dimensional materials is extremely small, which further increases the difficulty of heterojunction preparation, and greatly restricts the research and application of two-dimensional material line contact heterojunctions. SUMMARY

[0004] In view of one or more of the above defects or improvement needs of the prior art, the application provides a two-dimensional material line contact heterojunction and an array type preparation method thereof, which can realize array type preparation of two-dimensional material line contact heterojunctions, ensure the preparation precision of two-dimensional material line contact heterojunctions, and improve the preparation efficiency of two-dimensional material heterojunctions.

[0005] To achieve the above-mentioned purpose, in one aspect of the application, an array type preparation method of a two-dimensional material line contact heterojunction is provided, which comprises the following steps:

[0006] (1) transferring a first material layer onto a substrate, wherein the first material layer is a two-dimensional material;

[0007] (2) etching the first material layer into a plurality of first material units arranged in an array on the substrate;

[0008] (3) preparing an isolation protection layer covering all the first material units on the surface of the substrate, wherein the isolation protection layer is an insulating layer;

[0009] (4) etching the isolation protection layer into a plurality of isolation protection units in an array distribution; wherein the isolation protection units correspond to the first material units one by one, and each of the isolation protection units is respectively covered on the corresponding first material unit, and at least one side edge of each of the first material units protrudes the boundary of the isolation protection unit;

[0010] (5) performing re-etching on each of the first material units to remove the part of the first material unit protruding the boundary of the isolation protection unit, and obtaining at least one boundary flush lapping side of the two units in the corresponding layer;

[0011] (6) transferring a second material layer covering all the isolation protection units on the substrate; wherein the second material layer is a two-dimensional material;

[0012] (7) etching a plurality of arrayed second material units on the second material layer; one end of each of the second material units is lapped on the isolation protection unit, the other end is lapped on the surface of the substrate, and the middle part of the second material unit is in contact with the edge line of the first material unit on the lapping side, so as to obtain a two-dimensional material line contact heterojunction in an array distribution.

[0013] As a further improvement of the application, the substrate is made of an insulating material, and the substrate is any one of glass, aluminum oxide, silicon oxide, silicon nitride, silicon carbide, polyethylene terephthalate, polymethyl methacrylate and polyimide.

[0014] As a further improvement of the application, the first material layer and / or the second material layer is a transition metal sulfide, selenide, antimonide, graphene, black phosphorus, MXenes or h-BN.

[0015] As a further improvement of the application, the isolation protection layer is an oxide layer, a nitride layer, a silicon compound layer or an organic thin film layer.

[0016] As a further improvement of the application, the isolation protection layer is an aluminum oxide layer, a silicon oxide layer or a hafnium oxide layer; or, the isolation protection layer is a silicon carbide layer or a silicon oxynitride layer; or, the isolation protection layer is a PMMA layer or a PDMS layer.

[0017] As a further improvement of the application, the transfer process of the first material layer and / or the transfer process of the second material layer is performed by the following method:

[0018] (1.1) growing two-dimensional materials on the selected bottom layer material;

[0019] (1.2) solidifying a thin film layer on the surface of the two-dimensional material, and removing the bottom layer material to obtain the two-dimensional material after solidification of the thin film layer;

[0020] (1.3) transferring the two-dimensional material after the thin film layer is solidified to a target substrate, and after the two-dimensional material is tightly attached to the target substrate, removing the thin film layer on the surface of the two-dimensional material to complete the transfer of the two-dimensional material on the target substrate.

[0021] As a further improvement of the present application, in step (4), neither side boundary of the isolation protection unit protrudes from the edge of the first material unit, so that the projection area size and position of the first material unit after step (5) are the same as those of the isolation protection unit.

[0022] As a further improvement of the present application, between step (2) and step (3), an electrode is also made for each first material unit, and the manufacturing process is as follows:

[0023] A first electrode and a second electrode are respectively arranged on the surface of the substrate for each first material unit; wherein one end of the first electrode is a lap joint end and the other end is a protruding end, the lap joint end is lap jointed on the first material unit, and the protruding end protrudes out of the first material unit; at least one side of the first material unit is a line contact side which is not in contact with the first electrode, the second electrode is arranged on the substrate on one side of the first material unit and is spaced apart from the first electrode; and

[0024] Each isolation protection unit formed in step (4) does not cover the line contact side on the corresponding first material unit, and forms a lap joint side for the line contact of two two-dimensional materials between the first electrode and the second electrode.

[0025] As a further improvement of the present application, the electrode is prepared by a stripping process, and the preparation process is as follows:

[0026] Using a photolithography process, spin a layer of photoresist on the substrate on which the arrayed first material units have been prepared and pre-bake and cure; cover a mask on the substrate, and expose and develop under a UV photolithography machine; thereafter, sputter electrodes on the substrate by magnetron sputtering to prepare arrayed first electrodes and second electrodes; finally, use acetone to strip the photoresist, and finally prepare the required metal electrode array.

[0027] In another aspect of the present application, a two-dimensional material line contact heterojunction is provided, which is prepared by using the arrayed preparation method of the two-dimensional material line contact heterojunction,

[0028] The two-dimensional material line contact heterojunction comprises a first material unit, a second material unit and an isolation protection unit;

[0029] The first material unit and the isolation protection unit are arranged in layers, and one side of the two units arranged in layers is flush with each other to form a lap joint side;

[0030] One end of the second material unit overlaps the side of the isolation and protection unit away from the first material unit, and the other end extends along the side away from the overlap side. The middle part of the second material unit is bent and closely attached to the overlap side, so that the first material unit is only connected to the middle part of the second material unit through the edge on the overlap side.

[0031] The aforementioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0032] In summary, the beneficial effects of the above-described technical solutions conceived by this invention compared with the prior art include:

[0033] The array-based fabrication method for two-dimensional material line contact heterojunctions in this invention is simple in steps, highly controllable, and can realize the array-based fabrication of two-dimensional material line contact heterojunctions. It improves the fabrication efficiency of two-dimensional material line contact heterojunctions, ensures the fabrication accuracy of two-dimensional material line contact heterojunctions, reduces the fabrication cost of two-dimensional material heterojunctions, and promotes the effective transformation of two-dimensional material line contact heterojunctions from laboratory research to practical applications, thus having broad application prospects. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic flowchart of the array-type fabrication method of two-dimensional material line contact heterojunction in an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the cross-sectional form of a two-dimensional material line contact heterojunction in an embodiment of the present invention;

[0037] Figure 3 This is a cross-sectional schematic diagram of a two-dimensional material line contact heterojunction with electrodes in an embodiment of the present invention.

[0038] Figure 4 These are actual photographs of the graphene / molybdenum disulfide line contact array prepared using the method described in the embodiments of this invention.

[0039] Figure 5 This is a transmission electron microscope image of the cross-section of a single graphene / molybdenum disulfide heterojunction in an embodiment of the present invention.

[0040] In all the accompanying drawings, the same reference numerals denote the same technical features, specifically:

[0041] 1. substrate; 2. first material unit; 3. second material unit; 4. isolation protection unit; 5. first electrode; 6. second electrode. DETAILED DESCRIPTION

[0042] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0043] In the description of the present application, it should be understood that, unless otherwise explicitly specified and limited, the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the purpose of facilitating the description of the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0044] In addition, unless otherwise explicitly limited, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise explicitly specified and limited.

[0045] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0046] In the present application, unless otherwise explicitly specified and limited, a first feature is "on" or "under" a second feature can mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature is "over", "above" and "on top of" the second feature can mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. The first feature is "under", "below" and "underneath" the second feature can mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is horizontally lower than the second feature.

[0047] In the following, reference is made to Figures 1-5 A method for array preparation of a line-contact heterojunction of two-dimensional materials according to a preferred embodiment of the present application is described.

[0048] It should be noted that the line-contact heterojunction of two-dimensional materials (which can also be referred to as "line-contact two-dimensional material van der Waals heterojunction") prepared in the preferred embodiment of the present application, as shown in Figure 2 , includes a first material unit 2, a separation protection unit 4 and a second material unit 3. Among them, the first material unit 2 is arranged flush with at least one side edge of the separation protection unit 4, and forms a lap side between the second material unit 3 and the first material unit 2. At the same time, the middle part of the second material unit 3 is tightly attached to the lap side, and one end of the second material unit 3 is lapped on the separation protection unit 4, and the other end extends to the side away from the first material unit 2. In this way, the first material unit 2 and the second material unit 3 are only in contact at the lap side, forming a line-contact area as shown in Figure 2 .

[0049] The array preparation method in the preferred embodiment of the present application is just for the array preparation of the aforementioned line-contact heterojunction of two-dimensional materials.

[0050] In addition, the two-dimensional material in the present application refers to a material composed of a single layer or a few layers of atoms or molecular layers, which are connected by strong covalent bonds or ionic bonds within the layer, and are combined by weak van der Waals forces between layers. At the same time, the thickness of the two-dimensional material is usually at the atomic or molecular level (for example, 1-100 nm).

[0051] For the array preparation method of the line-contact heterojunction of two-dimensional materials in the present application, it preferably includes the following steps:

[0052] (1) transferring a first material layer onto a substrate 1, wherein the first material layer is a two-dimensional material;

[0053] In the preferred embodiment, the substrate 1 is preferably made of an insulating material, including but not limited to any one of glass, aluminum oxide, silicon oxide, silicon nitride, silicon carbide, polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), and polyimide (PI).

[0054] Meanwhile, for the transfer of the two-dimensional material on the substrate 1, the preferred embodiment preferably includes the following processes:

[0055] (1.1) Select a bottom layer material for growing the two-dimensional material, and grow the two-dimensional material on the bottom layer material;

[0056] In the preferred embodiment, the method of growing the two-dimensional material on the bottom layer material includes but is not limited to any one of CVD (Chemical Vapor Deposition), ALD (Atomic Layer Deposition), sputtering, evaporation, or IBD (Ion Beam Deposition).

[0057] (1.2) Solidify a thin film layer on the surface of the obtained two-dimensional material, and remove the bottom layer material to obtain the two-dimensional material after solidification of the thin film layer;

[0058] (1.3) Transfer the two-dimensional material after solidification of the thin film layer to a target substrate, and after the two-dimensional material is tightly attached to the target substrate, remove the thin film layer on the surface of the two-dimensional material, and finally realize the transfer of the two-dimensional material on the target substrate.

[0059] It can be understood that the selection of the above-mentioned bottom layer material and thin film layer material can be optimized according to the characteristics of the two-dimensional material, so as to ensure that the two-dimensional material and the thin film layer are not affected when the bottom layer material is removed, and the target substrate and the two-dimensional material are not affected when the thin film layer is removed.

[0060] As follows, the transfer of graphene grown on a copper foil by CVD is taken as an example to further illustrate the foregoing transfer process. The graphene is transferred by a PMMA-assisted wet transfer method, and the specific process is as follows:

[0061] First, grow the graphene material on the copper foil by CVD.

[0062] Secondly, a PMMA (Poly methylmethacrylate) solution with a mass fraction of 2% to 4% is sprayed on the surface of the graphene material, and a PMMA film is solidified on the surface of the graphene material by baking on a hot plate at 120°C for 3 minutes. Thereafter, the copper foil layer is placed in an ammonium persulfate solution with a mass fraction of 5% for etching for 3 hours to remove the copper foil layer on the back side. Finally, the graphene material on the back side is rinsed with deionized water multiple times to remove the residual ammonium persulfate, and a two-dimensional material (graphene two-dimensional material) solidified by the PMMA film is obtained.

[0063] Further, the two-dimensional material is lifted using a target substrate, so that the graphene two-dimensional material contacts the surface of the target substrate on the side away from the PMMA film. The target substrate is kept vertical, and the residual water is allowed to drip in one direction and is left to dry naturally for a period of time (e.g., one day). Thereafter, the sample after natural drying is heated on a hot plate at 110°C for a period of time (e.g., 1 hour) to make the graphene and the target substrate closely adhere to each other. After the sample cools down, the sample is placed in an acetone solution to remove the PMMA film, and the process is repeated 3 times, each time for 10 minutes, until the PMMA film is removed.

[0064] Through the above process, the transfer of the graphene two-dimensional material on the target substrate is finally completed.

[0065] (2) The first material layer is etched to form a plurality of first material units 2 arranged in an array on the substrate 1;

[0066] It can be understood that, when the first etching is performed, the etching process does not damage the substrate 1.

[0067] In a specific preferred embodiment, the etching of the first material layer is performed by using a photolithography process, and a layer of photoresist is provided on the surface of the first material layer before the photolithography to protect the first material units 2 during the etching. At this time, the first etching is preferably performed as follows:

[0068] A layer of photoresist is spin-coated on the surface of the first material layer and is pre-baked and cured; a mask is placed on the surface of the first material layer after the photoresist is coated; thereafter, photolithography is performed under a UV lamp and development is performed. After the photolithography is completed, the device after the photolithography is used to etch the first material layer by using oxygen ions to form a plurality of first material units 2 arranged in an array and coated with photoresist on the surface. Thereafter, the photoresist on the surface of each first material unit is removed by using acetone to obtain the first material units 2 arranged in an array.

[0069] More preferably, the type of the photoresist is preferably AZ12XT-20PL-5, and the mask is preferably a chromium metal mask.

[0070] (3) A protective layer is prepared on the surface of the substrate 1, covering all the first material units 2, and the protective layer is an insulating layer.

[0071] In the preferred embodiment, the protective layer prepared on the surface of the substrate 1 is preferably an oxide layer, a nitride layer, a silicon compound layer or an organic thin film layer prepared by CVD, ALD, sputtering, evaporation or IBD.

[0072] More specifically, the protective layer is an aluminum oxide layer, a silicon oxide layer or a hafnium oxide layer; or the protective layer is a silicon carbide layer or a silicon oxynitride layer; or the protective layer is a PMMA (Poly methyl methacrylate) layer or a PDMS (Polydimethylsiloxane) layer.

[0073] In addition, the thickness of the protective layer in the preferred embodiment is also preferably in the order of nanometers, and further preferably 1-100 times the thickness of the first material layer.

[0074] (4) The second etching is performed to etch the protective layer into a plurality of arrayed protective units 4, each corresponding to a first material unit 2; each protective unit 4 covers part of the first material unit 2, and at least one side edge of the first material unit 2 protrudes beyond the boundary of the protective unit 4.

[0075] As a feasible example, in one specific embodiment, any side of the protective unit 4 does not protrude beyond the edge of the first material unit 2, and at this time, the projected area of the protective unit 4 on the substrate 1 is smaller than the projected area of the first material unit 2 on the substrate 1.

[0076] In actual operation, the protective unit 4 preferably covers more than 50% of the first material unit 2. At the same time, one side edge of the first material unit 2 protrudes beyond the protective unit 4.

[0077] It can be understood that the second etching only etches the protective layer without affecting the first material unit 2 covered by the protective layer.

[0078] In one specific preferred embodiment, the material of the protective layer is aluminum oxide, and at this time, the aforementioned second etching is preferably achieved by using a photolithography process, and the specific process is as follows:

[0079] A photoresist is spin-coated on the isolation protection layer and pre-baked to solidify; a mask is then placed on the coated isolation protection layer; after that, the photoresist is exposed to UV light and developed, and the developed area corresponds to the formation area of each isolation protection unit 4. In the preferred embodiment, the photoresist is preferably of type NR9-3000PY, and the mask is preferably a chromium metal mask. The developed device is etched using an alkaline etching solution, and a plurality of arrayed isolation protection units 4 are etched on the isolation protection layer corresponding to each first material unit 2; after that, the photoresist on the surface of the isolation protection units 4 is removed using acetone, and the arrayed isolation protection units 4 are completed. In this embodiment, the alkaline etching solution for etching the isolation protection layer is preferably RD6 developer.

[0080] Obviously, the etching processes for the first material layer and the isolation protection layer can use the same or similar processes, except that specific materials and / or process conditions need to be selected for each process. With the determination of the above process content, it is ensured that different etching processes only target specific parts of specific material layers, without affecting other materials on the substrate 1. This can be achieved in combination with mature processes in the prior art, and will not be described in detail here.

[0081] (5) The isolation protection units 4 are used as a protection layer, and each first material unit 2 on the substrate 1 is etched again to remove the first material layer protruding beyond the boundary of the isolation protection unit 4, and at least one boundary flush lap side is obtained corresponding to the two units arranged in layers.

[0082] In more detail, for the case where the outer peripheral boundary of each isolation protection unit 4 does not protrude beyond the edge of the first material unit 2, after the aforementioned process (5) is performed, a nanosheet unit composed of first material units 2 and isolation protection units 4 with the same projection area size and position can be obtained. At this time, the nanosheet units on the substrate 1 are arrayed, and each side edge of the first material unit 2 can form a lap side vertically aligned with the boundary of the isolation protection unit 4.

[0083] (6) A second material layer is transferred to the surface of the substrate 1, and the second material layer covers all the isolation protection units 4; wherein the second material layer is a two-dimensional material.

[0084] For the transfer of the second material layer, it can also refer to the methods in the aforementioned (1.1)~(1.3) in actual operation, for example, using a PMMA-assisted wet transfer method. Of course, in addition to the above-mentioned method, it can also use other methods to transfer, for example, using a dry transfer method to transfer the second material layer, or using other transfer methods in the prior art, as long as the two-dimensional material can be transferred to the target substrate, which will not be described in detail here.

[0085] In addition, since the second material layer is a two-dimensional material, the thickness thereof is extremely thin, and the length-thickness ratio (the ratio of the length of the second material layer to the outer diameter to the thickness) can even reach 100000:1. In addition, the thickness of the isolation protection layer and the first material layer is extremely small (usually in nanometer level), so after covering the second material layer, the second material layer outside the boundary of each isolation protection unit 4 will naturally collapse to the surface of the substrate 1. At this time, the second material layer will be in close contact with each lap side, thereby realizing the line contact between the second material layer and the edge of each first material unit 2.

[0086] (7) Perform fourth etching to etch a plurality of arrayed second material units 3 on the second material layer; one end of each second material unit 3 is lapped on the isolation protection unit 4, the other end is lapped on the surface of the substrate 1, and the middle part of the second material unit 3 is in close contact with the edge of the first material unit 2 on the lap side, thereby obtaining an arrayed two-dimensional material line contact heterojunction.

[0087] In actual operation, the etching of the second material layer can also use a similar photoetching process as preferred in the foregoing step (2), which will not be repeated here.

[0088] As a specific example, when etching the second material layer, one lap side is selected as the line contact position of the second material unit 3 and the first material unit 2. At this time, the etching boundary of the second material unit 3 corresponding to the lap side is preferably not protruding to the lateral sides of the lap side.

[0089] When actually etching the second material unit 3, the projection of the etching boundary of one end of the second material unit 3 lapped on the isolation protection unit 4 is preferably located within the boundary of the isolation protection unit 4, so that one end of the second material unit 3 is only lapped on the isolation protection unit 4, and will not cross the isolation protection unit 4 to connect and conduct with the first material unit 2.

[0090] The selection of the foregoing arrangement form of the second material unit 3 and the first material unit 2 makes the two two-dimensional materials only communicate in the form of "line contact" at the lap side, and the isolation protection unit 4 can fully ensure the accurate separation between the two two-dimensional materials.

[0091] For the two-dimensional material line contact heterojunction in the preferred embodiment, since the contact position between the two two-dimensional materials is only one nm-level "contact line", the heterojunction can exhibit special performance different from conventional heterojunctions, meeting the application requirements in various new sensors.

[0092] Further, in actual preparation, there is a need to test the prepared two-dimensional material line contact heterojunction, at which time, electrodes need to be arranged for the two two-dimensional materials, i.e., a first electrode 5 in communication with the first material unit 2 and a second electrode 6 in communication with the second material unit 3, as shown in Figure 3as shown in FIG. 2.

[0093] At this time, between process (2) and process (3), a preparation process of the electrode is further provided:

[0094] (2.5) The first electrode 5 and the second electrode 6 are respectively provided for each first material unit 2; one end of the first electrode 5 is a lapping end, and the other end is a protruding end, the lapping end is lapped on the first material unit 2, and the protruding end protrudes out of the first material unit 2; at least one side of the first material unit 2 is a line contact side which does not contact the first electrode 5, and the second electrode 6 is provided on the substrate 1 on one side of the first material unit 2 and is spaced apart from the first electrode 5.

[0095] Correspondingly, each isolation protection unit 4 formed in step (4) does not cover the line contact side on the corresponding first material unit 2, and forms a lapping side for two-dimensional material line contact between the first electrode and the second electrode.

[0096] After the first electrode 5 and the second electrode 6 are provided, the production of the isolation protection unit 4, the secondary etching of the first material unit 2 and the production of the second material unit 3 are continued, so that one end of the second material unit 3 is lapped on the isolation protection unit 4, the other end is lapped on one end of the second electrode 6, and the middle part of the second material unit 3 is closely lapped on the lapping side formed by the first material unit 2 and the isolation protection unit 4, forming a two-dimensional material line contact heterojunction with electrode as shown in FIG. 2. Figure 3

[0097] More specifically, in the preferred embodiment, the stripping process is preferably used to prepare the electrode, and the preparation process is preferably as follows:

[0098] A layer of photoresist is spin-coated and pre-baked on the substrate 1 on which the arrayed first material units 2 have been prepared, using a photolithography process; a mask plate is covered on the substrate 1, and is exposed and developed under a UV photolithography machine. Thereafter, the electrodes are sputtered on the substrate 1 by means of a magnetron sputtering, to prepare the arrayed first electrode 5 and the second electrode 6. Finally, the photoresist is stripped using acetone, and the required metal electrode array is finally prepared. Here, the electrode adopts 5 nanometer titanium and 25 nanometer palladium.

[0099] In the preferred embodiment, the photoresist is preferably Nr9-3000py, and the mask plate is preferably a chromium metal mask plate.

[0100] More preferably, the electrode in the preferred embodiment is a Ti / Au electrode or a Ti / Pd electrode. For example, a combination of 5 nm Ti and 25 nm Pd is adopted, the bottom of the electrode is Ti, and the upper part is Pd.

[0101] ​In the foregoing steps (1)-(7), the material selection of the isolation protective layer and the selection of the four-time etching form can be determined according to the selection of the two two-dimensional materials, as long as the etching of the corresponding material does not affect other materials. The specific etching method can be selected from the prior art in combination with the selection of various materials, which will not be described here.

[0102] More specifically, at least one of the foregoing etching processes adopts plasma etching, laser etching or chemical etching.

[0103] Through the above steps (1)-(7), the array-type preparation of the two-dimensional material line contact heterojunction can be accurately realized based on the introduction of the isolation protective layer and the design of the multiple etching processes, and the array-type two-dimensional material line contact heterojunction after preparation can ensure a good product state.

[0104] In addition, for the first material layer and the second material layer in the preferred embodiment, the material selection includes but is not limited to transition metal sulfides (such as MoS2, WS2, MoSe2), selenides, antimonides, graphene, black phosphorus, MXenes or h-BN.

[0105] Based on the design of the array-type preparation method of the two-dimensional material line contact heterojunction, the preparation of the two-dimensional material line contact heterojunction can be efficiently carried out, and the two-dimensional material line contact heterojunction as shown in Figure 2 can be prepared.

[0106] As another aspect of the present application, a two-dimensional material line contact heterojunction as shown in the foregoing is also provided, which includes a first material unit 2, a second material unit 3 and an isolation protective unit 4.

[0107] The first material unit 2 and the isolation protective unit 4 are arranged in layers, and one side of the two units arranged in layers is flush with each other, forming a lap side. In actual arrangement, the first material unit 2 and the isolation protective unit 4 can have the same size, i.e., the four sides of the first material unit 2 are flush with the four sides of the isolation protective unit 4, and at this time, the four sides of the first material unit 2 can form the lap side.

[0108] At the same time, one end of the second material unit 3 is lapped on the side end face of the isolation protective unit 4 away from the first material unit 2, i.e., the top surface as shown in Figure 2 , the middle part of the second material unit 3 is bent and closely attached to one lap side, and the other end of the second material unit 3 extends away from the lap side, and at this time, the first material unit 2 is only connected to the middle part of the second material unit 3 through the edge on the lap side in line contact.

[0109] In order to better illustrate the technical solutions in the preferred embodiments of the present application, the array type preparation method of the two-dimensional material line contact heterojunction in the foregoing preferred embodiments is further illustrated through several specific embodiments.

[0110] Embodiment 1:

[0111] In this embodiment, the first material layer is a single layer of graphene.

[0112] At this time, the technical solution of the first etching is preferably a gas etching process or a liquid etching process; for the former, a 200w, 200ccm oxygen ion bombardment is used on the first material layer after photolithography development, and the bombardment time is preferably 1 min; for the latter, a hydrogen peroxide and nitric acid mixed solution is preferably used to etch the first material layer after photolithography development at a temperature of 140°C, and the etching time is preferably 1 min.

[0113] Meanwhile, in the preferred embodiments, electrodes are respectively arranged for the first material unit 2 and the second material unit 3, and at this time, the manufacturing process of the two electrodes preferably adopts a stripping process based on magnetron sputtering. The specific method is as follows:

[0114] A layer of Nr9-3000py photoresist is spin-coated on the substrate 1 and pre-baked and cured, a chromium metal mask is arranged on the surface after the photoresist is cured, and is exposed and developed under a ultraviolet photolithography machine. Thereafter, the electrode after photolithography is sputtered using a magnetron sputtering table, and after the two electrodes are sputtered, the photoresist is stripped using acetone, and finally the required metal electrode array is prepared. In this embodiment, the two metal electrodes are both composed of 5nm of lower titanium and 25nm of upper palladium.

[0115] Further, the isolation protection layer in this embodiment is preferably a 20nm silicon oxide layer.

[0116] At this time, the etching scheme (second etching) of the isolation protection layer is preferably that: a hydrofluoric acid-based etching liquid or a phosphoric acid-based etching liquid is used to etch the isolation protection layer after photolithography development, and the etching time is preferably 1 min, and finally the array distributed silicon oxide isolation protection unit 4 is obtained.

[0117] In addition, for the re-etching of the first material unit 2 after the isolation protection unit 4 is arranged, the same process as the first etching can be used, or a different process from the first etching can be used. For example, the first etching of the first material layer uses a liquid etching process, and the re-etching of the first material unit 2 uses a gas etching process.

[0118] Meanwhile, the third material layer is a single layer of molybdenum disulfide.

[0119] At this time, the third etching scheme for the third material layer can select the gas etching process selected in the first etching, that is, 200w, 200ccm oxygen ion bombardment is adopted for the third material layer after photoetch development, and the bombardment time is 1min. Alternatively, the following liquid etching process is selected: using hydrogen peroxide solution to etch the second material layer after photoetch development at a temperature of 140°C, and the etching time is preferably 1min.

[0120] In addition, for the transfer mode of the third material layer, the PMMA assisted wet transfer mode is adopted in the preferred embodiment.

[0121] In the above four etching schemes, the etching scheme for the isolation protection layer will not affect the first material unit 2; the second etching scheme for the first material unit 2 will not affect the isolation protection unit 4; and the fourth etching scheme for the second material layer will not affect the isolation protection unit 4. At the same time, based on the setting of the isolation protection unit 4, on the one hand, it can avoid the large-area lapping of the second material unit 3 and the first material unit 2, and on the other hand, it can also avoid the influence of the fourth etching on the first material unit 2.

[0122] In addition, when two electrodes are provided on the substrate 1 for two-dimensional materials, since the metal electrode has high stability and the thickness is often large (relative to the two-dimensional material), the metal electrode will not be affected during the above etching process.

[0123] Through the determination of the above etching scheme, combined with steps (1)-(7) in the preferred embodiment, an array type two-dimensional material line contact heterojunction can be finally formed on the substrate 1, as shown in Figure 4 The transmission electron microscope photo of the cross section of a single two-dimensional material line contact heterojunction is shown in Figure 5 .

[0124] For each two-dimensional material line contact heterojunction, it is connected in a line contact manner by a single-layer graphene unit and a single-layer molybdenum disulfide unit, a silicon oxide unit is arranged above the single-layer graphene unit, and the vertical edge of the single-layer graphene unit and the single-layer molybdenum disulfide unit in line contact is vertically flush with the edge of the silicon oxide unit.

[0125] Embodiment 2:

[0126] In this embodiment, the first material layer is a multi-layer h-BN (hexagonal boron nitride).

[0127] At this time, the first etching scheme is preferably a gas etching process or a liquid etching process; for the former, 200w, 200ccm oxygen ion bombardment is used to etch the first material layer after photolithography development, and the bombardment time is preferably 1min; for the latter, a mixed solution of hydrogen peroxide and phosphoric acid is preferably used to etch the first material layer after photolithography development at a temperature of 140 DEG C, and the etching time is preferably 1min. By using the first etching, a plurality of arrayed multilayer h-BN units on the substrate 1 are finally obtained.

[0128] At the same time, the isolation protection layer is preferably 30nm of aluminum oxide.

[0129] At this time, the etching scheme of the isolation protection layer (second etching) is preferably a gas etching process, that is, 50w, 20ccm hydrogen fluoride is used to etch the isolation protection layer after photolithography development, and the etching time is preferably 10min, and finally a plurality of arrayed aluminum oxide units are obtained.

[0130] After that, the second etching of the first material unit 2 (multilayer h-BN unit) arranged after the isolation protection unit 4 (aluminum oxide unit) can use the same process as the first etching, or a different process from the first etching. For example, the first etching of the first material layer uses a liquid etching process, and the second etching of the first material unit 2 uses a gas etching process.

[0131] Further, the third material layer is a single layer of tungsten diselenide.

[0132] At this time, the third etching scheme for the third material layer can select the gas etching process selected in the first etching, that is, 200w, 200ccm oxygen ion bombardment is used to etch the third material layer after photolithography development, and the bombardment time is 1min. Alternatively, the following liquid etching process is used: etching with ammonia water for 1min.

[0133] Through the determination of the above etching scheme, combined with steps (1)-(7) in the preferred embodiment, an arrayed two-dimensional material line contact heterojunction can be finally formed on the substrate 1. Each two-dimensional material heterojunction is formed by line contact lapping of the multilayer h-BN unit and the single layer tungsten diselenide unit, and the multilayer h-BN unit and the single layer tungsten diselenide unit are separated by the aluminum oxide unit.

[0134] The arrayed two-dimensional material line contact heterojunction preparation method in the application has simple steps, strong controllability, can realize the arrayed preparation of the two-dimensional material line contact heterojunction, improve the preparation efficiency of the two-dimensional material line contact heterojunction, ensure the manufacturing precision of the two-dimensional material line contact heterojunction, reduce the preparation cost of the two-dimensional material heterojunction, promote the effective transformation of the two-dimensional material line contact heterojunction from laboratory research to practical application, and has wide application prospect.

[0135] It is to be understood that the above description is intended to be illustrative and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. The scope of the application should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. An array-type fabrication method for two-dimensional material line-contact heterojunctions, characterized in that, Includes the following steps: (1) Transfer a first material layer onto the substrate, wherein the first material layer is a two-dimensional material; (2) The first material layer is etched into multiple first material units distributed in an array on the substrate; (3) An isolation protective layer covering all the first material units is prepared on the surface of the substrate, wherein the isolation protective layer is an insulating layer; (4) The isolation protection layer is etched into a plurality of isolation protection units distributed in an array; wherein, the isolation protection unit corresponds one-to-one with the first material unit, and each isolation protection unit covers the corresponding first material unit, and at least one edge of each first material unit protrudes from the boundary of the isolation protection unit. (5) Etch each first material unit again to remove the part of the first material unit that protrudes from the boundary of the isolation protection unit, so that the two stacked units have at least one overlapping side with flush boundary. (6) Transfer a second material layer covering all isolation protection units onto the substrate; wherein the second material layer is a two-dimensional material; (7) Multiple array-type second material units are etched on the second material layer; one end of each second material unit is connected to the isolation protection unit, and the other end is connected to the surface of the substrate, and the middle part of the second material unit is in contact with the edge line of the first material unit on the connecting side, thereby obtaining an array-type distributed two-dimensional material line contact heterojunction.

2. The array-type fabrication method of two-dimensional material line-contact heterojunction according to claim 1, characterized in that, The substrate is made of an insulating material, and the substrate is any one of glass, alumina, silicon oxide, silicon nitride, silicon carbide, polyethylene terephthalate, polymethyl methacrylate, and polyimide.

3. The array-type fabrication method of two-dimensional material line-contact heterojunction according to claim 1, characterized in that, The first material layer and / or the second material layer are transition metal sulfides, selenides, antimonides, graphene, black phosphorus, MXenes, or h-BN.

4. The array-type fabrication method of two-dimensional material line contact heterojunction according to claim 1, characterized in that, The isolation and protective layer is an oxide layer, a nitride layer, a silicon compound layer, or an organic thin film layer.

5. The array-type fabrication method of two-dimensional material line-contact heterojunction according to claim 4, characterized in that, The isolation and protective layer is an aluminum oxide layer, a silicon oxide layer, or a hafnium oxide layer; or, the isolation and protective layer is a silicon carbide layer or a silicon oxynitride layer; or, the isolation and protective layer is a PMMA layer or a PDMS layer.

6. The array-type fabrication method of two-dimensional material line-contact heterojunctions according to any one of claims 1 to 5, characterized in that, The transfer process of the first material layer and / or the transfer process of the second material layer are performed using the following method: (1.1) Growth of two-dimensional materials on the selected substrate material; (1.2) A thin film layer is cured on the surface of a two-dimensional material, and the underlying material is removed to obtain a two-dimensional material cured by the thin film layer; (1.3) Transfer the two-dimensional material after the film layer is cured to the target substrate. After the two-dimensional material is in close contact with the target substrate, remove the film layer on the surface of the two-dimensional material to complete the transfer of the two-dimensional material to the target substrate.

7. The array-type fabrication method of two-dimensional material line-contact heterojunctions according to any one of claims 1 to 5, characterized in that, In step (4), neither side boundary of the isolation protection unit protrudes beyond the edge of the first material unit, so that the first material unit after step (5) has the same projected area size and position as the isolation protection unit.

8. The array-type fabrication method of two-dimensional material line-contact heterojunctions according to any one of claims 1 to 5, characterized in that, Between step (2) and step (3), electrodes are fabricated for each first material unit. The fabrication process is as follows: A first electrode and a second electrode are respectively disposed on the surface of the substrate for each first material unit; wherein, one end of the first electrode is an overlapping end and the other end is a protruding end, the overlapping end overlapping the first material unit, and the protruding end protruding from the first material unit; at least one side of the first material unit is a line contact side that does not contact the first electrode, and the second electrode is disposed on the substrate on one side of the first material unit and is spaced apart from the first electrode; and Each of the isolation protection units formed in step (4) does not cover the line contact side on the corresponding first material unit, and forms an overlap side between the first electrode and the second electrode for line contact between the two two-dimensional materials.

9. The array-type fabrication method of two-dimensional material line-contact heterojunction according to claim 8, characterized in that, The electrode is prepared using a stripping process, the preparation process of which is as follows: Using photolithography, a layer of photoresist is spin-coated onto the substrate of the prepared array of first material units and then pre-baked and cured. A photomask is placed on the substrate and exposed and developed under ultraviolet lithography. Subsequently, electrodes were sputtered onto the substrate using magnetron sputtering to fabricate an array of first and second electrodes; finally, the photoresist was stripped with acetone to ultimately fabricate the desired metal electrode array.

10. A two-dimensional material line-contact heterojunction, fabricated using the array-type fabrication method of the two-dimensional material line-contact heterojunction according to any one of claims 1 to 9, characterized in that, The two-dimensional material line contact heterojunction includes a first material unit, a second material unit, and an isolation and protection unit; The first material unit and the isolation and protection unit are stacked on top of each other, and one side of the two stacked units is flush with each other to form an overlapping side; One end of the second material unit overlaps the side of the isolation and protection unit away from the first material unit, and the other end extends along the side away from the overlap side. The middle part of the second material unit is bent and closely attached to the overlap side, so that the first material unit is only connected to the middle part of the second material unit through the edge on the overlap side.

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