Torsion angle electrical device under high voltage and preparation method thereof

Abstract

The invention belongs to the technical field of two-dimensional materials, and particularly relates to a torsion angle electrical device under high voltage and a preparation method thereof. A gold film is used for assisting in preparation, an electron beam coating instrument is used for directly evaporating metal on a PDMS polymer, good physical contact between the metal and a two-dimensional material is used for achieving the purposes of atomic level flatness and pollution-free two-dimensional material transfer, and the two-dimensional material transfer efficiency is improved by controlling the temperature and time in each transfer process. By means of the method, smooth and clean transfer of the two-dimensional material can be simply, rapidly and effectively achieved, the electrical device can be prepared on the diamond anvil face, high-voltage electrical testing can be conducted, and the preparation and machining efficiency of the torsion angle electrical device is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of two-dimensional materials, and specifically relates to a twist angle electrical device under high voltage and a preparation method thereof. Background Art

[0002] Since single-layer graphene was first clearly prepared and identified in 2004, two-dimensional materials represented by graphene have attracted extensive attention from scholars in various fields due to their excellent electrical, mechanical, optical, and thermodynamic properties. Superlattice is a periodic structure composed of two or more materials stacked alternately. By controlling the twist angle between two-dimensional material layers to create a new material system, unexpected discoveries can often be made. Taking double-layer twisted graphene as an example, in 2011, Rafi Bistritzer and Alan H. McDonald of the University of Texas studied the electronic structure of the double-layer twisted angle graphene system through theoretical calculations, and first found that for a set of discrete magic twist angles, the Dirac point velocity disappears, the lowest Mohr-Bloch band becomes flat, and the Dirac point electronic state density and reverse current conductivity are strongly enhanced. Until 2018, MIT genius Cao Yuan first verified in experiments the two main characteristics of double-layer magic angle graphene: strongly correlated insulating state and unconventional superconducting state, and revealed the peculiar relationship between the electron strongly correlated state and the carrier filling concentration through theoretical calculations. Since then, the research on constructing new superlattice structures by controlling the interlayer twist angle by "tearing and stacking" various two-dimensional materials has flourished.

[0003] In order to achieve controllable stacking of various two-dimensional materials with rotational arrangement and explore the new electronic states and applications that may appear in these heterostructures, various new two-dimensional material transfer methods have been developed. For example, in 2016, Jin Genghuan et al. reported a technique for tearing and stacking two-dimensional materials using a PPC / PDMS polymer-assisted method. This technique has no restrictions on the size or shape of the material and can achieve precise crystal axis rotation alignment. In 2018, Purdy et al. achieved heterostructure stacking with atomically clean interfaces assisted by PC / PDMS polymers, which can completely remove bubbles caused by contaminants between material layers and effectively improve the various performances of electrical devices. However, to date, most of the widely used two-dimensional material transfer and stacking methods still require the two-dimensional material to be in contact with the polymer, which will inevitably cause certain contamination to the surface of the two-dimensional material, thereby affecting the efficiency of experimental testing. Summary of the invention

[0004] In response to the above-mentioned deficiencies, the present application provides a torsion angle electrical device under high pressure and a method for preparing the same. By utilizing a gold film as an aid, gold is directly evaporated on the PDMS polymer using an electron beam coater, and the good physical contact between gold and the two-dimensional material is utilized to achieve the purpose of atomic-level smooth and pollution-free transfer of two-dimensional materials. By controlling the temperature and time in each transfer process, the smooth and clean transfer of two-dimensional materials can be achieved simply, quickly and effectively. This method can be used to prepare electrical devices on the diamond anvil surface for high-voltage electrical testing.

[0005] To this end, the technical solution of the present application discloses a method for preparing a twist angle electrical device under high voltage, comprising the following steps:

[0006] Ti and Au were sequentially evaporated on the PDMS substrate to obtain a PDMS metal film;

[0007] A silicon wafer with a single layer of two-dimensional material and a silicon wafer with h-BN are prepared using a silicon wafer as a substrate;

[0008] The Au layer of the PDMS metal film is used to lift the h-BN on the h-BN silicon wafer, and then the h-BN layer is used to pick up part of the single-layer two-dimensional material on the single-layer two-dimensional material silicon wafer, and then the film angle is rotated to pick up another part of the single-layer two-dimensional material to obtain a twisted angle double-layer two-dimensional material;

[0009] The obtained twisted-angle double-layer two-dimensional material is released onto the channel electrode, and the entire device preparation process is completed on the diamond anvil surface to obtain a high-voltage twisted-angle electrical device.

[0010] Furthermore, the thickness of the Ti layer is 1-2 nm, and the thickness of the Au layer is 2.5-4 nm.

[0011] Furthermore, the lifting temperature is 100-120°C.

[0012] Furthermore, the picking-up temperature is 90-110°C.

[0013] Furthermore, the release temperature of the twisted double-layer two-dimensional material is 120-140°C.

[0014] Furthermore, the two-dimensional material may be graphene, TMDs material, etc.

[0015] And, a twist angle electrical device prepared according to the above preparation method.

[0016] Beneficial effects: The present invention realizes the preparation of two-dimensional material electrical devices with controllable interlayer twist angles, can selectively prepare two-dimensional material electrical devices with different desired twist angles, and develop new applications with twist angle dependence.

[0017] The present invention adopts a vacuum coating apparatus to deposit a metal film on the surface of a polymer, and can simultaneously and batch-produce films with a specific metal thickness for standby use.

[0018] During the entire operation process of the present invention, the two-dimensional material only contacts the metal film but not any polymer. Therefore, the cleanliness of each interface of the two-dimensional material can be greatly increased, and strict control of the interlayer torsion angle can be achieved. The electrical properties test results show that the torsion angle of the preparation method of the present application differs from the control angle by less than 0.1°. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 (a) is a schematic diagram of evaporating metal film on PDMS and a flow chart of using PDMS with gold film for two-dimensional material transfer stacking;

[0020] Figure 1 (b) Optical photographs of PDMS with evaporated metal film, extracted h-BN material, and extracted twisted-angle graphene material;

[0021] Figure 2 It is an optical photo of a twisted-angle graphene device released on a silicon wafer, a Raman surface scan of the graphene G peak, and a Raman spectrum of the material stacking area;

[0022] Figure 3 This is a high-voltage electrical device made by releasing twisted-angle graphene on a diamond anvil surface using this method, and the electrical IV test curves under normal pressure and high pressure;

[0023] Figure 4 These are the optical photographs of the MoS2-hBN-WSe2 tunnel junction and MoS2-Graphene heterojunction extracted using this method;

[0024] Figure 5 Schematic diagram of the structure of the high-voltage two-dimensional twist angle electrical device prepared by this method. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0026] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0027] Unless otherwise specified, the meanings of the technical terms in this specification are the same as those generally understood by those skilled in the art. However, if there is any conflict, the definitions in this specification shall prevail.

[0028] In this application, “h-BN” refers to hexagonal boron nitride, “PDMS” refers to polydimethylsiloxane, Figure 1 “Graphene” in this article refers to graphene.

[0029] like Figure 1 As shown, the embodiment of the present application discloses a method for preparing a twist angle electrical device under high voltage, comprising the following steps:

[0030] Ti and Au were sequentially evaporated on the PDMS substrate to obtain a PDMS metal film;

[0031] A silicon wafer with a single layer of two-dimensional material and a silicon wafer with h-BN are prepared using a silicon wafer as a substrate;

[0032] The Au layer of the PDMS metal film is used to lift the h-BN on the h-BN silicon wafer, and then the h-BN layer is used to pick up part of the single-layer two-dimensional material on the single-layer two-dimensional material silicon wafer, and then the film angle is rotated to pick up another part of the single-layer two-dimensional material to obtain a twisted angle double-layer two-dimensional material;

[0033] The obtained twisted-angle double-layer two-dimensional material is released onto the channel electrode, and the entire device preparation process is completed on the diamond anvil surface to obtain a high-voltage twisted-angle electrical device.

[0034] In this embodiment, the evaporation is performed by electron beam evaporation using a high vacuum coating apparatus, and the evaporation process uses PDMS as the substrate. Figure 1As shown, Ti and Au are sequentially deposited thereon, wherein Ti is deposited to fix the Au film so that it is not easily damaged during the transfer process; Au is deposited to utilize the weak van der Waals force of gold on two-dimensional materials (such as graphene, MoS2, etc.), so that these materials can adhere to the gold film and maintain their integrity during the transfer process. The thickness of the Ti layer is 1-2nm, and the thickness of the Au layer is 2.5-4nm.

[0035] In this embodiment, if Figure 1 As shown, a silicon wafer is used as a substrate (a silicon wafer with an oxide layer, consisting of a silicon bottom and a silicon dioxide surface), and a single-layer two-dimensional material (such as a single-layer graphene) and h-BN are peeled off from the silicon wafer by mechanical peeling.

[0036] In this embodiment, the lifting control temperature is 100-120°C, and the picking up temperature is 90-110°C.

[0037] In this embodiment, the release temperature of the twisted double-layer two-dimensional material is 120-140°C.

[0038] In this embodiment, h-BN is first extracted using PDMS with Au vapor deposited thereon in order to utilize the weak van der Waals force of the gold film on h-BN to ensure that when h-BN extracts the two-dimensional material, h-BN will not fall on the silicon wafer. During the picking process, the van der Waals force between h-BN and the two-dimensional material can ensure that h-BN tears the two-dimensional material.

[0039] In this embodiment, the two-dimensional material is a two-dimensional material system such as graphene, TMDs, etc.

[0040] In this embodiment, the preparation method of the twist angle electrical device is: first, use photolithography technology, wet transfer method and dry transfer method to stack channel electrode material and gate material on a silicon wafer or diamond anvil surface, and then release the extracted twist angle double-layer two-dimensional material on the channel electrode to complete the device packaging.

[0041] It should be noted that if Figure 5 As shown, a complete electrical device includes from bottom to top: bottom two-dimensional material electrode-h-BN gate-channel electrode-twisted two-dimensional material-h-BN on the top.

[0042] Among them, the h-BN gate and the bottom two-dimensional material are prepared with PDMS as the substrate, and the other materials are prepared with silicon wafer as the substrate; the bottom two-dimensional material electrode and the h-BN gate are stacked by dry transfer method, the channel electrode is stacked by photolithography technology and wet transfer method, and the twisted angle two-dimensional material and the top h-BN are stacked by the method described in this application.

[0043] Hereinafter, graphene will be used as a two-dimensional material, and the preparation method and technical effects of the present application will be specifically disclosed in combination with the implementation mode of the present application.

[0044] Example 1 Preparation of twist angle electrical device

[0045] S1 uses mechanical stripping and dry transfer to prepare single-layer graphene, few-layer graphene (used as channel electrodes), and h-BN materials on silicon substrates; h-BN materials (used as gate materials) and few-layer graphene electrodes (used as bottom electrodes) are prepared on PDMS substrates: First, use a scalpel to remove a graphite crystal sheet with a flat surface and metallic luster from bulk graphite, and use tweezers to place the graphite crystal sheet on the white tape purchased from 3M. Fold the white tape in half and tear it open repeatedly, and ensure that the graphite sheets do not overlap until the graphite sheets cover most of the tape area. After that, stick the prepared PDMS (the recommended PDMS thickness is 1mm) on the torn white tape, and then quickly peel it off to achieve the purpose of peeling the graphene onto the PDMS substrate. At the same time, stick the tape on the cleaned silicon substrate, heat it on a heating table at 100°C for five minutes, and slowly peel it off to achieve the purpose of peeling the graphene onto the silicon substrate (the silicon substrate is cleaned using acetone, deionized water, and isopropanol in turn for 5 minutes, and then blown dry with a nitrogen gun). In particular, there is no special requirement for the silicon substrate, and the thickness of the oxide layer is selected according to the specific situation. The mechanical peeling of the h-BN crystal is the same as above.

[0046] S2. Preparation of polymer with gold film: Cut the sample-free, clean PDMS into squares of about 5mm*5mm, and use a high vacuum coating apparatus to evaporate a 1nm thick Ti film and a 2.5nm thick Au film on the small PDMS piece by electron beam evaporation.

[0047] S3. Align PDMS with h-BN on the transfer table, heat at 120℃ for 5 minutes after bonding, and transfer h-BN to the metal film; heat PDMS at 100℃ for 1 minute, align h-BN with graphene on the transfer table, hold for 5 seconds after bonding, and tear the graphene; after rotating the transfer table to a specific angle, align h-BN with another part of graphene, hold for 5 seconds after bonding, and lift the graphene; align the sample with the channel electrode on the transfer table, heat at 130℃ for 5 minutes after bonding, and transfer the sample to the silicon wafer or diamond anvil surface.

[0048] like Figure 1 Shown is a schematic diagram of evaporating metal film on PDMS and a flow chart of two-dimensional material transfer stacking using PDMS with a gold film; Figure 1 (b) Optical photographs of PDMS with evaporated metal film, extracted h-BN material, and extracted twisted-angle graphene material, respectively.

[0049] like Figure 2The optical photo of the twisted double-layer graphene device released on the silicon wafer, the graphene G peak Raman surface scan and the Raman spectrum of the material stacking area are shown. It can be seen that the Raman spectrum and surface scan results successfully scanned the graphene overlapping area, proving that this method can effectively tear and stack graphene materials. From the optical picture, the two-dimensional material extracted by this method is flat and wrinkle-free, with high flatness. This reflects the flatness of the two-dimensional material extracted by this method. Figure 3 The figure shows a high-voltage electrical device made by releasing twisted-angle bilayer graphene onto a diamond anvil surface using this method, as well as a normal-pressure (1×10 5 Pa) and high pressure (1×10 9 Electrical IV test curve under 1000 Pa: Figure 3 The electrical test results are consistent with the previous literature on the measurement of the resistance value of twisted-angle graphene, and it can be seen that its electrical properties are regulated by high voltage. The double-layer twisted-angle graphene system can exhibit rich electrical properties under high pressure and can increase the cleanliness of each interface of the two-dimensional material: This is because most of the current transfer methods involve the use of polymers, such as PMMA / PPC, which are difficult to clean after transfer. In our process, the two-dimensional material has no contact with the polymer and only with the gold film, so it will have a very high degree of cleanliness.

[0050] like Figure 4 According to the preparation method of Example 1, in step S3, the Au film PDMS was evaporated to form the tunnel junction formed by MoS2-h-BN-WSe2 (left) and the optical photographs of the heterojunction formed by MoS2-Graphene (right) were extracted respectively. Figure 4 It can be seen that the preparation method of the present application can effectively tear and stack two-dimensional materials and ensure good flatness.

[0051] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a twist angle electrical device under high voltage, characterized in that: The steps include: Ti and Au were sequentially evaporated on the PDMS substrate to obtain a PDMS metal film; Using silicon wafer as substrate, a silicon wafer with a single layer of two-dimensional material and a silicon wafer with h-BN were prepared by peeling off. The Au layer of the PDMS metal film is used to lift the h-BN on the h-BN silicon wafer, and then the h-BN layer is used to pick up part of the single-layer two-dimensional material on the single-layer two-dimensional material silicon wafer, and then the film angle is rotated to pick up another part of the single-layer two-dimensional material to obtain a twisted angle double-layer two-dimensional material; The obtained twisted-angle double-layer two-dimensional material is released onto the channel electrode, and the entire device preparation process is completed on the diamond anvil surface to obtain a high-voltage twisted-angle electrical device.

2. The preparation method according to claim 1, characterized in that: The thickness of the Ti layer is 1-2 nm, and the thickness of the Au layer is 2.5-4 nm.

3. The preparation method according to claim 1, characterized in that: The lifting temperature is 100-120°C.

4. The preparation method according to claim 1, characterized in that: The pick-up temperature is 90-110°C.

5. The preparation method according to claim 1, characterized in that: The release temperature of twisted double-layer two-dimensional materials is 120-140℃.

6. The preparation method according to claim 1, characterized in that: The two-dimensional material may be graphene, TMDs material, etc.

7. A high voltage twist angle electrical device prepared according to any one of the preparation methods of claims 1-6.

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