A molybdenum disulfide-based asymmetric structure schottky diode

Abstract

The application belongs to the technical field of diode structure design and preparation, and specifically provides a non-symmetrical structure Schottky diode based on molybdenum disulfide, which is used to solve the problems of poor unidirectional conductivity of the existing molybdenum disulfide Schottky diode under the same metal electrode structure and complex preparation process under the different metal electrode structure. The application creatively proposes a continuous layered step structure molybdenum disulfide film in the design of the Schottky diode, different thickness regions of which have different work functions, the thickest region of the molybdenum disulfide film forms an ohmic contact with the metal film, and the thinnest region of the molybdenum disulfide film forms a Schottky contact with the metal film, so that only one kind of metal and one kind of semiconductor material are used to construct the Schottky contact and the ohmic contact at the same time, the goal of simplifying the diode device structure and the preparation process is achieved, and the unidirectional conductivity of the diode device is effectively improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of diode structure design and preparation, and relates to a Schottky diode, and particularly provides a non-symmetrical structure Schottky diode based on molybdenum disulfide. BACKGROUND

[0002] With the rapid development of semiconductor technology, the Schottky diode based on the metal-semiconductor structure is increasingly important in the fields of renewable energy, electronic components and detection sensors. For common semiconductor materials such as metal oxide materials and silicon-based materials, based on the characteristics of the work function, the energy level matching conditions with the metal and the characteristics of the semiconductor process technology, the commonly used Schottky diode basically uses two metals with different work functions as electrodes to contact the semiconductor material, respectively forming a Schottky contact and an ohmic contact, which has certain limitations on the structure and process of the Schottky diode.

[0003] Molybdenum disulfide has high carrier mobility and ideal energy band structure due to its two-dimensional structure, and has been widely used in the semiconductor field. Among them, the Schottky diode constructed by molybdenum disulfide and metal materials has been widely studied. For example, a heterojunction diode based on molybdenum disulfide is disclosed in Chinese Patent No. CN 202310176490.X, which adopts a symmetrical semiconductor-metal heterojunction structure, and uses the same metal film as the two electrodes of the diode to form a Schottky contact with the molybdenum disulfide film. However, the device working state is not good due to the mutual breakdown of the Schottky junction. For example, Chinese Patent No. CN 202310797064.8 uses different metal materials as metal electrodes to form different types of contacts with the molybdenum disulfide film, uses a plating process to reduce surface impurity adsorption and defects, and constructs a device with excellent performance to achieve good rectification characteristics. However, since different metals are used as electrodes, the device structure and preparation process are relatively complex, and the molybdenum disulfide film morphology is poor under the deposition process, which has unstable working current. As can be seen, the common molybdenum disulfide diode is divided into the same metal electrode structure and the different metal electrode structure, and the molybdenum disulfide Schottky diode under the two structures all has many problems, therefore, it is extremely necessary to design a Schottky heterojunction diode with a simpler structure and a more simplified preparation process. SUMMARY

[0004] The present application aims to provide a non-symmetrical structure Schottky diode based on molybdenum disulfide, to solve the problems of poor unidirectional conductivity of the existing molybdenum disulfide Schottky diode under the same metal electrode structure and complex preparation process under different metal electrode structures; by using the characteristics that the work function of two-dimensional molybdenum disulfide material is affected by its thickness, the present application proposes a Schottky diode based on a continuous layered step structure molybdenum disulfide film, which uses the relationship between the work function of the molybdenum disulfide film and the work function of the metal, forms a Schottky contact and an Ohmic contact based on a kind of metal and a kind of semiconductor material, and achieves the goal of simplifying the structure and preparation process of the diode device.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is:

[0006] A non-symmetrical structure Schottky diode based on molybdenum disulfide, comprising: a silicon wafer substrate 1, a molybdenum disulfide film 2, a first metal thin film electrode 3-1 and a second metal thin film electrode 3-2; characterized in that the molybdenum disulfide film adopts a continuous layered step structure, and its thickness decreases in a stepwise manner from one side to the other side; the molybdenum disulfide film is arranged on the silicon wafer substrate, and the first metal thin film electrode and the second metal thin film electrode are arranged on the silicon wafer substrate and located on both sides of the molybdenum disulfide film, the first metal thin film electrode covers the side with the maximum thickness of the molybdenum disulfide film and forms an Ohmic contact at the contact surface, and the second metal thin film electrode covers the side with the minimum thickness of the molybdenum disulfide film and forms a Schottky contact at the contact surface.

[0007] Further, the maximum thickness of the molybdenum disulfide film is 15-30 nm, and the minimum thickness is 0.5-10 nm, and the molybdenum disulfide film has different work functions in different thickness regions, for realizing an asymmetric heterojunction.

[0008] Further, the thickness of the first metal thin film electrode and the second metal thin film electrode is 30-50 nm.

[0009] Further, the first metal thin film electrode and the second metal thin film electrode adopt the same material, and the work function range is 4.85-5.25 eV.

[0010] Further, the molybdenum disulfide film is prepared by a mechanical exfoliation process and is arranged on the surface of the silicon wafer substrate by a transfer process.

[0011] Further, the metal thin film is deposited on the surface of the molybdenum disulfide film and the silicon wafer substrate by a magnetron sputtering process.

[0012] From the working principle:

[0013] The continuous layered step structure molybdenum disulfide film has a non-uniform thickness, the continuous layered step structure molybdenum disulfide film material has different work functions in different thickness regions, the work function of the maximum thickness region of the continuous layered step structure molybdenum disulfide film is greater than the work function of the metal film, and the molybdenum disulfide film and the metal film form an ohmic contact at the position; the work function of the minimum thickness region of the continuous layered step structure molybdenum disulfide film is less than the work function of the metal film, and the molybdenum disulfide film and the metal film form a Schottky contact at the position; thus, the Schottky contact and the ohmic contact are simultaneously constructed by using only one kind of metal and one kind of semiconductor material, and the goal of simplifying the structure and the preparation process of the diode device is achieved.

[0014] In summary, the application has the following advantages:

[0015] The application provides a molybdenum disulfide-based asymmetric structure Schottky diode, a continuous layered step structure molybdenum disulfide film is obtained by a combination of mechanical peeling and transfer processes; based on the continuous layered step structure molybdenum disulfide film, an ohmic contact is formed at the maximum thickness region of the continuous layered step structure molybdenum disulfide film and a metal film, and a Schottky contact is formed at the minimum thickness region of the continuous layered step structure molybdenum disulfide film and the metal film, different types of contacts are constructed by using different thickness regions of the molybdenum disulfide film and the metal, a Schottky diode is prepared by using only one kind of metal and one kind of semiconductor material, the goal of simplifying the structure and the preparation process of the diode device is achieved, the unidirectional conductivity of the diode device is effectively improved, and the Schottky diode can be widely applied to the preparation field of the Schottky diode. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a structure schematic diagram of the Schottky diode in the embodiment of the application, wherein 1 is a silicon wafer substrate, 2 is a molybdenum disulfide film, 3-1 is a first metal film electrode, and 3-2 is a second metal film electrode.

[0017] Figure 2 It is a structure schematic diagram of the Schottky diode in the comparative example of the application.

[0018] Figure 3 It is an AFM scanning diagram of a heterojunction of the Schottky diode in the embodiment and the comparative example of the application, wherein (a) is the embodiment, and (b) is the comparative example.

[0019] Figure 4 It is an AFM thickness scanning diagram of a heterojunction of the Schottky diode in the embodiment and the comparative example of the application.

[0020] Figure 5 It is a current-voltage characteristic curve diagram of the Schottky diode in the embodiment and the comparative example of the application.

[0021] Figure 6 It is a logarithmic current-voltage characteristic curve diagram of the Schottky diode in the embodiment and the comparative example of the application. DETAILED DESCRIPTION

[0022] In order to make the purposes, technical solutions and beneficial effects of the present application clearer, the present application is further explained in detail below in combination with the drawings, examples and comparative examples.

[0023] The present embodiment provides a kind of asymmetric structure schottky diode based on molybdenum disulfide, its structure is as shown in Figure 1 The present embodiment provides a kind of asymmetric structure schottky diode based on molybdenum disulfide, its structure is as shown inFigure 1, including: silicon wafer substrate 1, molybdenum disulfide film 2, first metal thin film electrode 3-1 and second metal thin film electrode 3-2;Wherein, molybdenum disulfide film 2 adopts continuous layered step structure, its thickness decreases in ladder from one side to the other side, i.e. molybdenum disulfide film 2 has non-uniform thickness;The molybdenum disulfide film 2 is arranged on the silicon wafer substrate 1, and the first metal thin film electrode 3-1 and the second metal thin film electrode 3-2 are arranged on the silicon wafer substrate 1 and located on both sides of the molybdenum disulfide film 2, the first metal thin film electrode 3-1 covers the thickest side of the molybdenum disulfide film 2, and forms ohmic contact at the contact surface, and the second metal thin film electrode 3-2 covers the thinnest side of the molybdenum disulfide film 2, and forms schottky contact at the contact surface;In the asymmetric structure schottky diode, the thickness-work function relationship of the continuous layered step structure molybdenum disulfide controls the contact type of the contact constructed by the molybdenum disulfide film and the metal thin film, the thickest part of the molybdenum disulfide film forms ohmic contact with the metal thin film, i.e. the heterojunction constructed by the metal thin film electrode 3-1 and the molybdenum disulfide film 2, the thinnest part of the molybdenum disulfide film forms schottky contact with the metal thin film, i.e. the heterojunction constructed by the metal thin film electrode 3-2 and the molybdenum disulfide film 2, only one kind of metal and one kind of semiconductor material realize schottky diode, simplify diode device structure and preparation process, improve diode device unidirectional conductivity.

[0024] Further, in the present embodiment, first, 1cm×1cm silicon wafer with insulating oxide layer is used as substrate, after being immersed in chemical drugs acetone, ethanol and deionized water in turn and ultrasonic drying, it is ready for use;Second, based on stripping transfer process, continuous layered step structure molybdenum disulfide film is configured on the surface of silicon wafer substrate, wherein, the thickest part of the molybdenum disulfide film is about 15-30nm, and the thinnest part of the molybdenum disulfide is about 0.5-10nm;Finally, through magnetron sputtering process, 50nm thick palladium metal film is deposited on the surface of molybdenum disulfide film and part of the surface of silicon wafer substrate to form asymmetric schottky diode.

[0025] Further, in the embodiment, the molybdenum disulfide film is prepared by a mechanical exfoliation process and is configured on the surface of a silicon substrate by a transfer process. The mechanical exfoliation process is as follows: a bulk molybdenum disulfide material is placed on the surface of a tape adhesive and fixed, the material is repeatedly pasted by using the tape, and the process is repeated 4-5 times to obtain a molybdenum disulfide film material. The molybdenum disulfide film material is lightly pasted by using PDMS, the PDMS is placed on the surface of a glass slide, the color of the molybdenum disulfide material adhered to the surface of the PDMS is observed by using an optical microscope, and part of the complete molybdenum disulfide material with blue and yellow colors is selected to obtain a continuous layered step structure molybdenum disulfide film. The transfer process is as follows: the glass slide with the PDMS in the previous step is inverted on a transfer table clamp and fixed, a silicon substrate is placed on a silicon substrate stage and adsorbed and fixed, the glass slide is slowly approached to the silicon substrate by rotating a knob, until the PDMS is completely in contact with the silicon substrate, the adhesion of the molybdenum disulfide film to the surface of the silicon substrate is confirmed by using an observation device, the silicon substrate is heated to 110°C by starting a heating device and kept for 15-20 min, the molybdenum disulfide film on the surface of the PDMS is released to the surface of the silicon substrate, and finally the PDMS and the silicon substrate are separated by rotating the knob to obtain a silicon substrate with the continuous layered step structure molybdenum disulfide film adhered thereto.

[0026] The beneficial effects of the present application are described in detail below in combination with tests. In order to more directly illustrate the beneficial effects of the present application, a comparative example is provided. In the comparative example, the molybdenum disulfide Schottky diode is as shown in Figure 2 , which is different from the embodiment in that a symmetric structure is adopted, i.e., the molybdenum disulfide film adopts a uniform thickness structure, and the metal film on both sides forms a Schottky contact with the molybdenum disulfide film.

[0027] The AFM atomic force microscope scanning characterization of the embodiment and the comparative example is performed, as shown in Figure 3 , the metal film on the molybdenum disulfide film in the embodiment and the comparative example is effectively covered, and a heterojunction is constructed.

[0028] The AFM atomic force microscope scanning of the molybdenum disulfide film-metal film overlap (as shown by the dashed line in Figure 3 ) of the embodiment and the comparative example is performed, and the thickness of the molybdenum disulfide film in each heterojunction region is obtained, as shown in Figure 4 , the thinnest part (about 8.5 nm) and the thickest part (about 17 nm) of the continuous layered step structure molybdenum disulfide film in the embodiment are involved in constructing a Schottky heterojunction and an Ohmic heterojunction, respectively, and the uniform thickness molybdenum disulfide film (about 8 nm) in the comparative example is involved in constructing a Schottky heterojunction.

[0029] The current-voltage test of the embodiment and the comparative example is performed, and the results are as shown in Figure 5As shown, the I-V curve of the embodiment shows obvious unidirectional conductivity, and the opening voltage is about -2V, indicating that the device in the embodiment has only one end of Schottky contact and the other end of Ohmic contact; the I-V curve of the comparative example shows a symmetrical structure in the positive and negative voltage range, and the opening voltage is about ±10V, indicating that its structure is a double Schottky heterojunction, and the current is opened by mutual breakdown.

[0030] The current-voltage test was performed on the embodiment and the comparative example, and the current-voltage logarithmic curve was obtained, as shown in Figure 6 As shown, the current level of the embodiment in the negative voltage range is much higher than that in the positive voltage range, and the current level of the comparative example shows an approximate symmetrical structure, and the results show that one side of the metal-molybdenum disulfide contact in the embodiment belongs to Schottky contact, and the other side of the metal-molybdenum disulfide contact belongs to Ohmic contact, which has obvious unidirectional conductivity, indicating that the embodiment belongs to a Schottky diode.

[0031] In summary, the present application provides a kind of asymmetric structure Schottky diode based on molybdenum disulfide, by the thickness-power function modulation of molybdenum disulfide film, utilize the Ohmic contact and Schottky contact of different thickness area of molybdenum disulfide film and metal structure, effectively simplify the device structure and preparation process, and optimize the unidirectional conductivity of device.

[0032] The above is only a specific embodiment of the present application, any feature disclosed in the specification can be replaced by other equivalent or similar purpose alternative features unless specifically described; all features disclosed, or steps in all methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A molybdenum disulfide-based asymmetric-structure Schottky diode comprising: The silicon wafer substrate (1), the molybdenum disulfide film (2), the first metal thin film electrode (3-1) and the second metal thin film electrode (3-2); characterized in that the molybdenum disulfide film adopts a continuous layered step structure, and the thickness thereof decreases in a step manner from one side to the other side; the molybdenum disulfide film is arranged on the silicon wafer substrate, and the first metal thin film electrode and the second metal thin film electrode are arranged on the silicon wafer substrate and located on both sides of the molybdenum disulfide film, the first metal thin film electrode covers the side with the largest thickness of the molybdenum disulfide film and forms an ohmic contact on the contact surface, and the second metal thin film electrode covers the side with the smallest thickness of the molybdenum disulfide film and forms a Schottky contact on the contact surface.

2. The non-symmetric structure Schottky diode based on molybdenum disulfide according to claim 1, characterized in that, The maximum thickness of the molybdenum disulfide film is 15-30 nm, and the minimum thickness is 0.5-10 nm.

3. The MoS2-based asymmetric structure Schottky diode according to claim 1, wherein, The thickness of the first metal thin film electrode and the second metal thin film electrode is 30-50 nm.

4. The non-symmetric MoS2-based Schottky diode according to claim 1, wherein, The first metal thin film electrode and the second metal thin film electrode adopt the same material, and the work function ranges from 4.85 eV to 5.25 eV.

5. The non-symmetric MoS2-based Schottky diode according to claim 1, wherein, The molybdenum disulfide film is prepared by a mechanical peeling process and is arranged on the surface of the silicon wafer substrate by a transfer process.

6. The non-symmetric MoS2-based Schottky diode according to claim 1, wherein, The metal thin film is deposited on the surface of the molybdenum disulfide film and the silicon wafer substrate by a magnetron sputtering process.

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