Single-layer graphene / alpha-In2Se3 / MoS2 ferroelectric tunnel junction and preparation method and application thereof

Abstract

The invention relates to the technical field of ferroelectric tunnel junctions, in particular to a single-layer graphene / alpha-In2Se3 / MoS2 ferroelectric tunnel junction and a preparation method and application thereof. The invention discloses a single-layer graphene / alpha-In2Se3 / MoS2 ferroelectric tunnel junction. The single-layer graphene / alpha-In2Se3 / MoS2 ferroelectric tunnel junction comprises a metal electrode, few layers of MoS2, alpha-In2Se3, single-layer graphene and a target substrate, the single-layer graphene completely covers the surface of the target substrate, the alpha-In2Se3 nanosheet covers the surface of the single-layer graphene, and the few-layer MoS2 completely or partially covers the surface of the alpha-In2Se3 nanosheet; the number of the metal electrodes is two, one metal electrode covers the surface of the single-layer graphene, and the other metal electrode completely or partially covers the few-layer MoS2. The ferroelectric tunnel junction not only can realize a huge on-off ratio of 109, but also is excellent in performance stability, low in cost and simple in manufacturing process, can realize large-scale production, and has a great application value.

Description

Technical Field

[0001] The present invention relates to the technical field of ferroelectric tunnel junction, and in particular to a single-layer graphene / α-In 2 Se 3 / MoS 2 Ferroelectric tunnel junction and its preparation method and application. Background Art

[0002] In today's era, people pay particular attention to the performance of information storage capacity and processing speed. Ferroelectric tunnel junctions have attracted widespread attention in highly sensitive and stable neural network sensor devices due to their advantages such as atomic-level thickness, non-destructive readout, and low power consumption. The working principle of ferroelectric tunnel junctions is to use the polarization state of ferroelectrics to regulate their electron tunneling process, and use the change of their polarization state to realize the readout of the tunnel junction. In ferroelectric materials, the tunneling effect is produced due to the change of their internal electric field. The main problem facing the development of two-dimensional ferroelectric tunnel junctions is that their stability and device performance need to be further improved to meet the needs of practical applications. Therefore, constructing a simple, stable, and high-switching ratio ultra-thin ferroelectric tunnel junction is a technical problem that urgently needs to be solved. Summary of the invention

[0003] The purpose of the present invention is to provide a single-layer graphene / α-In 2 Se 3 / MoS 2 Ferroelectric tunnel junction and its preparation method and application. The present invention utilizes the Dirac band structure unique to single-layer graphene to regulate its barrier height; utilizes MoS 2 The width of the barrier layer can be effectively adjusted to achieve great control over the barrier layer, thereby obtaining a high-performance ferroelectric tunnel junction, thereby achieving high-efficiency and high-stability information storage of the ferroelectric tunnel junction.

[0004] A single-layer graphene / α-In of the present invention 2 Se 3 / MoS 2 Ferroelectric tunnel junction, including metal electrode, few-layer MoS 2 , α-In 2 Se 3 , a single-layer graphene and a target substrate; the single-layer graphene completely covers the surface of the target substrate, the α-In 2 Se 3 Nanosheets are covered on the surface of single-layer graphene, and the few-layer MoS 2 Fully or partially covered in α-In 2 Se 3The number of the metal electrodes is two, one metal electrode covers the surface of the single-layer graphene, and the other metal electrode completely or partially covers the surface of the few-layer MoS 2 superior.

[0005] Furthermore, the α-In 2 Se 3 The thickness of the nanosheets is 5-10 nm.

[0006] Furthermore, the few-layer MoS 2 The thickness is 0.7-40nm.

[0007] Furthermore, the thickness of the single-layer graphene is 1 nm.

[0008] Furthermore, the target substrate is SiO 2 / Si substrate.

[0009] Furthermore, the metal electrode is Au with a thickness of 40 nm.

[0010] A single-layer graphene / α-In 2 Se 3 / MoS 2 A method for preparing a ferroelectric tunnel junction comprises the following steps:

[0011] S1, wet transfer of single-layer graphene on a target substrate;

[0012] S2, using mechanical stripping method to obtain α-In 2 Se 3 Nanosheets;

[0013] S4. Place α-In on the two-dimensional material transfer platform 2 Se 3 The nanosheets are transferred to a target substrate that already has graphene;

[0014] S5. Use the transfer platform to transfer the few-layer MoS 2 Transfer to α-In 2 Se 3 Nanosheets;

[0015] S6. Use the transfer platform to transfer the two metal electrodes to the single-layer graphene and few-layer MoS 2 On top, a single-layer graphene / α-In 2 Se 3 / MoS 2 Ferroelectric tunnel junction.

[0016] Furthermore, the metal electrode is prepared by a mechanical stripping method.

[0017] A single-layer graphene / α-In as described above2 Se 3 / MoS 2 Application of ferroelectric tunnel junction devices in microelectronic devices

[0018] The main principle of the present invention is: two-dimensional ferroelectric material α-In 2 Se 3 Ferroelectric polarization with out-of-plane direction can modulate α-In 2 Se 3 Compared with single-layer graphene and MoS 2 The tunneling barrier will flip the direction of the ferroelectric polarization under the action of an external electric field. The flipped ferroelectric polarization will modulate the tunneling barrier in the opposite way, causing a huge change in the tunneling barrier, thereby realizing the high and low changes in the device resistance, thereby realizing the non-volatile storage function.

[0019] A single-layer graphene / α-In with a vertical structure was designed and constructed by mechanical exfoliation. 2 Se 3 / MoS 2 Van der Waals ferroelectric tunnel junction, electrode, α-In 2 Se 3 、MoS 2 , In the same vertical structure of single-layer graphene, electrons can not only flow horizontally, but also tunnel directly between the two materials, ensuring that the tunnel resistance of the ferroelectric tunnel junction is larger and the storage effect is better. In addition, compared with multilayer graphene, the uniqueness of single-layer graphene is that single-layer graphene has zero band gap, which can effectively control the barrier height, which is impossible for multilayer graphene. α-In can be flipped by changing the direction of the applied electric field 2 Se 3 The ferroelectric polarization direction of α-In 2 Se 3 With MoS 2 The width and height of the tunneling barrier between the graphene layer and the single-layer graphene ensure that the device achieves a huge tunneling electroresistance. Therefore, this fully two-dimensional van der Waals heterostructure ferroelectric tunnel junction can not only achieve 10 9 It has a huge on-off ratio, excellent performance stability, low cost and simple manufacturing process, can be mass-produced, and has great application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is based on single-layer graphene / α-In 2 Se 3 / MoS 2 Schematic diagram of the structure of a ferroelectric tunnel junction;

[0021] 1. α-In 2 Se3 , 2. MoS 2 , 3. Metal electrode, 4. Single-layer graphene, 5. Target substrate;

[0022] Figure 2 To investigate the effect of single-layer graphene / α-In on the polarization voltage 2 Se 3 / MoS 2 Current-voltage curve of a ferroelectric tunnel junction;

[0023] Figure 3 is the surface potential difference measured under KPFM test;

[0024] Figure 4 The current values ​​and switching ratios of the ferroelectric tunnel junctions prepared in Examples 3 to 6 in high and low resistance states;

[0025] Figure 5 For single-layer graphene / α-In 2 Se 3 / MoS 2 Data retention of a ferroelectric tunnel junction measured at room temperature. DETAILED DESCRIPTION

[0026] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0027] Example 1

[0028] A single-layer graphene / α-In 2 Se 3 / MoS 2 The preparation method of the ferroelectric tunnel junction is specifically as follows:

[0029] (1) Wet transfer of graphene onto a target substrate;

[0030] (2) The layered two-dimensional In was prepared by mechanical stripping and repeated bonding with transparent tape. 2 Se 3 With MoS 2 Material;

[0031] (3) Put the two-dimensional layered In 2 Se 3 Paste it on PDMS, try to paste it several times to make more In 2 Se 3 Can be adhered to PDMS, making it easy to observe and find In with the right size and thickness under a microscope 2 Se 3 sample;

[0032] (4) Place In on the two-dimensional material transfer platform 2 Se 3 Transfer to a target substrate that already has graphene;

[0033] (5) Put the two-dimensional layered MoS on the tape 2 Paste it onto PDMS and select 2 Se 3 For samples with suitable size and thickness, a heterojunction is constructed using a transfer platform;

[0034] (6) In the single-layer graphene / α-In 2 Se 3 / MoS 2 The Au metal electrode is transferred to the surface of the van der Waals ferroelectric tunnel junction to obtain the α-In 2 Se 3 The two-dimensional van der Waals ferroelectric tunnel junction, such as Figure 1 shown.

[0035] Among them, α-In 2 Se 3 The thickness is 5nm, MoS 2 The thickness is 20nm, the thickness of the single-layer graphene is 1nm, the thickness of the Au metal electrode (made by mechanical stripping) is 40nm, and the target substrate is an insulating SiO 2 / Si substrate thickness is 300nm.

[0036] Example 2

[0037] A single-layer graphene / α-In 2 Se 3 / MoS 2 The preparation method of the ferroelectric tunnel junction is specifically as follows:

[0038] (1) Wet transfer of graphene onto a target substrate;

[0039] (2) The layered two-dimensional In was prepared by mechanical stripping and repeated bonding with transparent tape. 2 Se 3 With MoS 2 Material;

[0040] (3) Put the two-dimensional layered In 2 Se 3 Paste it on PDMS, try to paste it several times to make more In 2 Se 3 Can be adhered to PDMS, making it easy to observe and find In with the right size and thickness under a microscope 2 Se 3 sample;

[0041] (4) Place In on the two-dimensional material transfer platform 2 Se 3 Transfer to a target substrate that already has graphene;

[0042] (5) Put the two-dimensional layered MoS on the tape 2 Paste it onto PDMS and select 2 Se 3 For samples with suitable size and thickness, a heterojunction is constructed using a transfer platform;

[0043] (6) In the single-layer graphene / α-In 2 Se 3 / MoS 2 The Au metal electrode is transferred to the surface of the van der Waals ferroelectric tunnel junction to obtain the α-In 2 Se 3 Two-dimensional van der Waals ferroelectric tunnel junction;

[0044] α-In 2 Se 3 The thickness is 8nm, MoS 2 The thickness is 25nm, the thickness of the single-layer graphene is 1nm, the thickness of the Au metal electrode is 40nm, and the target substrate is an insulating SiO 2 / Si substrate thickness is 300nm.

[0045] Example 3

[0046] A single-layer graphene / α-In 2 Se 3 / MoS 2 The preparation method of the ferroelectric tunnel junction is specifically as follows:

[0047] (1) Wet transfer of graphene onto a target substrate;

[0048] (2) The layered two-dimensional In was prepared by mechanical stripping and repeated bonding with transparent tape. 2 Se 3 With MoS 2 Material;

[0049] (3) Put the two-dimensional layered In 2 Se 3 Paste it on PDMS, try to paste it several times to make more In 2 Se 3 Can be adhered to PDMS, making it easy to observe and find In with the right size and thickness under a microscope 2 Se 3 sample;

[0050] (4) Place In on the two-dimensional material transfer platform 2 Se3 Transfer to a target substrate that already has graphene;

[0051] (5) Put the two-dimensional layered MoS on the tape 2 Paste it onto PDMS and select 2 Se 3 For samples with suitable size and thickness, a heterojunction is constructed using a transfer platform;

[0052] (6) In the single-layer graphene / α-In 2 Se 3 / MoS 2 The Au metal electrode is transferred to the surface of the van der Waals ferroelectric tunnel junction to obtain the α-In 2 Se 3 Two-dimensional van der Waals ferroelectric tunnel junction;

[0053] α-In 2 Se 3 The thickness is 10nm, MoS 2 The thickness is 30nm, the thickness of the single-layer graphene is 1nm, the thickness of the Au metal electrode is 40nm, and the target substrate is an insulating SiO 2 / Si substrate thickness is 300nm.

[0054] Example 4

[0055] In addition to MoS 2 The thickness is 100 nm, and the rest is the same as in Example 3.

[0056] Example 5

[0057] In addition to MoS 2 The thickness is 40 nm, and the rest is the same as in Example 3.

[0058] Example 6

[0059] In addition to MoS 2 The thickness is 5 nm, and the rest is the same as in Example 3.

[0060] Figure 2 To investigate the effect of single-layer graphene / α-In on the polarization voltage 2 Se 3 / MoS 2 The current-voltage curve of a ferroelectric tunnel junction; Figure 2 It can be seen that when the polarization voltage of +5V and -5V is applied, the device shows two resistance states, namely high resistance state (HRS) and low resistance state (LRS), and there is a large order of magnitude between them. The ratio of low resistance state to high resistance state can be used to obtain the switching ratio, and the ratio of on-state current to off-state current is 10 9 , indicating that based on single-layer graphene / α-In2 Se 3 / MoS 2 Ferroelectric tunnel junctions enable data storage.

[0061] From experience, we know that the current density is closely related to the barrier height and width. Based on this, the device was tested with KPFM to measure the surface potential difference of the material, and it was found that the barrier height was modulated by about 1.05eV, such as Figure 3 As shown. When the device is in the on state, the tunneling barrier is approximately equal to the thickness of the ferroelectric layer. When the device is in the off state, the ferroelectric electric field forms a low-width depletion region inside the semiconductor. At this time, the thinner the semiconductor layer, the stronger the internal Schottky barrier, resulting in a huge difference in current between the on and off states. Compared with the effect of barrier thickness on device performance, the modulation of barrier width is more important. That means understanding MoS 2 The role it plays in the device.

[0062] Figure 4 The current values ​​and switching ratios of the ferroelectric tunnel junctions prepared in Examples 3 to 6 in high and low resistance states; Figure 4 Showing four In 2 Se 3 With the same thickness, MoS 2 The thickness of the ferroelectric tunnel junction is 100nm, 40nm, 30nm, and 5nm. 2 When the thickness is reduced from 100nm to 5nm, the switching ratio of the device is improved by 3 orders of magnitude.

[0063] Based on single-layer graphene / α-In 2 Se 3 / MoS 2 The data retention of the ferroelectric tunnel junction measured at room temperature is as follows Figure 5 As shown, it shows excellent retention within 8000s. The data retention performance shows that TER is greater than 10 9 It can be maintained for more than 10 years, showing the great potential of this device in achieving long-term data retention.

[0064] For matters not mentioned above, the prior art applies.

[0065] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art to which the present invention belongs may make various modifications or supplements to the specific embodiments described or replace them in a similar manner, but they will not deviate from the direction of the present invention or exceed the scope defined by the attached claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A single-layer graphene / α-In2Se3 / MoS2 ferroelectric tunnel junction, characterized in that: It includes a metal electrode, a few-layer MoS2, α-In2Se3, a single-layer graphene and a target substrate; the single-layer graphene completely covers the surface of the target substrate, the α-In2Se3 nanosheets cover the surface of the single-layer graphene, and the few-layer MoS2 completely or partially covers the surface of the α-In2Se3 nanosheets; there are two metal electrodes, one metal electrode covers the surface of the single-layer graphene, and the other metal electrode completely or partially covers the few-layer MoS2.

2. The single-layer graphene / α-In2Se3 / MoS2 ferroelectric tunnel junction according to claim 1, characterized in that: The thickness of the α-In2Se3 nanosheet is 5-10 nm.

3. The single-layer graphene / α-In2Se3 / MoS2 ferroelectric tunnel junction according to claim 1, characterized in that: The thickness of the few-layer MoS2 is 0.7-40nm.

4. The single-layer graphene / α-In2Se3 / MoS2 ferroelectric tunnel junction according to claim 1, characterized in that: The thickness of the single-layer graphene is 1 nm.

5. The single-layer graphene / α-In2Se3 / MoS2 ferroelectric tunnel junction according to claim 1, characterized in that: The target substrate is a SiO2 / Si substrate.

6. The single-layer graphene / α-In2Se3 / MoS2 ferroelectric tunnel junction according to claim 1, characterized in that: The metal electrode is Au with a thickness of 40 nm.

7. A method for preparing a single-layer graphene / α-In2Se3 / MoS2 ferroelectric tunnel junction as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: S1, wet transfer of single-layer graphene on a target substrate; S2, using mechanical exfoliation method to prepare α-In2Se3 nanosheets; S4, transferring the α-In2Se3 nanosheets to the target substrate with graphene on the two-dimensional material transfer platform; S5, transferring the few-layer MoS2 to α-In2Se3 nanosheets using a transfer platform; S6. Use a transfer platform to transfer the two metal electrodes to the single-layer graphene and the few-layer MoS2 respectively, so as to obtain a single-layer graphene / α-In2Se3 / MoS2 ferroelectric tunnel junction.

8. The method for preparing a single-layer graphene / α-In2Se3 / MoS2 ferroelectric tunnel junction according to claim 7, characterized in that: The metal electrodes were prepared by mechanical stripping.

9. Application of the single-layer graphene / α-In2Se3 / MoS2 ferroelectric tunnel junction device as claimed in any one of claims 1 to 6 in a microelectronic device.

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