A silicon-based schottky diode with switchable anode and cathode and a preparation method thereof

Abstract

The application relates to the technical field of two-dimensional semiconductor nanomaterials, and discloses a silicon-based Schottky diode capable of switching positive and negative electrodes, which comprises a few-layer hexagonal boron nitride, gamma-indium selenide nanosheet, few-layer graphene, a gold electrode layer, a titanium adhesion layer, a silicon dioxide insulation layer and a silicon-based substrate, the silicon dioxide insulation layer is arranged on the silicon-based substrate, the titanium adhesion layer is arranged on the silicon dioxide insulation layer, the outer surface of the titanium adhesion layer is provided with the gold electrode layer, one end of the gamma-indium selenide nanosheet is arranged on the gold electrode layer, and the other end is arranged on the surface of the silicon dioxide insulation layer; one end of the few-layer graphene is arranged on the gamma-indium selenide nanosheet, and the other end is arranged on the gold electrode layer; and the few-layer hexagonal boron nitride covers the gamma-indium selenide nanosheet and the few-layer graphene.

Description

Technical Field

[0001] This invention relates to the field of two-dimensional semiconductor nanomaterials technology, specifically to a silicon-based Schottky diode with switchable positive and negative electrodes and its fabrication method. Background Technology

[0002] Ferroelectric materials are widely used in modern electronic devices due to their reversible and non-volatile polarization, such as ferroelectric capacitors, non-volatile ferroelectric memories, ferroelectric diodes, and ferroelectric transistors. With the discovery of two-dimensional layered ferroelectric materials, the development of two-dimensional ferroelectric prototype electronic devices based on van der Waals materials will keep pace with the ever-miniaturizing demands of modern electronics, thereby enabling the application of ferroelectric devices within the atomic layer thickness limit.

[0003] A diode made using the rectifying contact characteristics of a metal-semiconductor junction is called a Schottky barrier diode. Similar to a pn junction diode, they both exhibit unidirectional conductivity. Schottky barrier diodes are majority carrier devices and have better high-frequency characteristics than pn junction diodes. Furthermore, Schottky barrier diodes have a lower forward voltage. Based on these characteristics, Schottky barrier diodes have many important applications in fields such as high-speed integrated circuits and microwave technology.

[0004] For example, Chinese patent CN109037317B describes a ferroelectric memory device comprising: a substrate; and a ferroelectric layer, a variable resistance memory layer, and a gate electrode sequentially stacked on the surface of the substrate. The ferroelectric layer has any one of a plurality of different residual polarization values ​​depending on the resistance state of the variable resistance memory layer.

[0005] However, the aforementioned patents and existing technologies have poor fatigue resistance, are difficult to miniaturize, and are difficult to apply to the field of scalable devices. Therefore, we propose a silicon-based Schottky diode with switchable positive and negative electrodes and its fabrication method. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the shortcomings of existing technologies, this invention provides a silicon-based Schottky diode with switchable positive and negative electrodes and its fabrication method. Two-dimensional ferroelectric material γ-indium selenide nanosheets exhibit out-of-plane ferroelectric polarization. When two-dimensional ferroelectric γ-indium selenide is combined with few-layer graphene to form a multilayer van der Waals heterojunction, the properties of the entire heterojunction are modulated by the ferroelectric polarization. By reversing the ferroelectric polarization using an applied electric field, the properties of the ferroelectric heterojunction can be transformed, such as from "semiconductor" to "metallic." The Schottky barrier formed at the ferroelectric / metal interface is also affected by the direction of ferroelectric polarization. Polarization reversal induces different barrier heights, thereby changing the diode's on / off ratio, resulting in a silicon-based Schottky diode with switchable positive and negative electrodes.

[0008] (II) Technical Solution

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution: a silicon-based Schottky diode with switchable positive and negative electrodes, comprising a few-layer hexagonal boron nitride, indium γ-selenide nanosheets, a few-layer graphene, a gold electrode layer, a titanium adhesion layer, a silicon dioxide insulating layer, and a silicon substrate. The silicon dioxide insulating layer is disposed on the silicon substrate, and the titanium adhesion layer is disposed on the silicon dioxide insulating layer. The gold electrode layer is disposed on the outer surface of the titanium adhesion layer. One end of the indium γ-selenide nanosheet is placed on the gold electrode layer, and the other end is placed on the surface of the silicon dioxide insulating layer. One end of the few-layer graphene is placed on the indium γ-selenide nanosheets, and the other end is placed on the gold electrode layer. The few-layer hexagonal boron nitride covers the indium γ-selenide nanosheets and the few-layer graphene.

[0010] Preferably, the γ-indium selenide nanosheets have 10 or more layers and a thickness of 10-20 nm, the few-layer graphene has 5 or more layers and a thickness of 5-10 nm, and the few-layer hexagonal boron nitride has 10 or more layers and a thickness of 20-30 nm.

[0011] Preferably, the γ-indium selenide nanosheets have a thickness of 15 nm and a size of 30 μm * 50 μm, the few-layer graphene has a thickness of 5 nm and a size of 15 μm * 40 μm, and the few-layer hexagonal boron nitride has a thickness of 23 nm and a size of 40 μm * 60 μm.

[0012] A method for fabricating a silicon-based Schottky diode with switchable positive and negative electrodes includes the following steps:

[0013] Step 1: Clean the target substrate, which consists of a silicon dioxide insulating layer and a silicon substrate, with acetone, ethanol, and deionized water. Finally, dry it with an air can and heat it on a hot table at 120°C for ten minutes to obtain a clean and uncontaminated target substrate.

[0014] Step 2: Place a copper mesh as a mask for the electrode array, fix it on the target substrate with silver paste, and sputter a titanium adhesion layer and a gold electrode layer using magnetron sputtering to complete the fabrication of the electrode array on the target substrate.

[0015] Step 3: According to the requirements of electrode array spacing and coverage, prepare γ-indium selenide nanosheets, few-layer graphene and few-layer hexagonal boron nitride respectively. Place the corresponding bulk materials on blue adhesive, tear the adhesive tape to obtain a thinner material, and then use PDMS adhesive to tear it multiple times until a semi-transparent γ-indium selenide nanosheet, few-layer graphene and few-layer hexagonal boron nitride are obtained.

[0016] Step 4: Under a microscope, align the PDMS adhesive containing γ-indium selenide nanosheets, few-layer graphene, and few-layer hexagonal boron nitride with the target position of the electrode on the target substrate. Then, adjust the knob up and down until the PDMS adhesive is in close contact with the designated position on the target substrate. Heat to 60°C and wait for 5 minutes. After the material and the target substrate are in full contact, slowly rotate the knob to move the PDMS adhesive upwards. The target material will then fall completely onto the target substrate, resulting in a γ-indium selenide nanosheet / few-layer graphene / few-layer hexagonal boron nitride Schottky diode.

[0017] Step 5: Anneal the obtained γ-indium selenide nanosheet / few-layer graphene / few-layer hexagonal boron nitride Schottky diode to finally obtain a silicon-based Schottky diode with switchable positive and negative electrodes.

[0018] Preferably, the sputtering conditions in the second step are: power 50W, background vacuum 2*10 -5 mbar, argon pressure is 1.05*10 -2 mbar, sputtering distance of 25-30cm;

[0019] The titanium adhesive layer was sputtered at a rate of 0.04 nm / s, for a time of 260 s, and with a thickness of approximately 10 nm.

[0020] The sputtering rate of the gold electrode layer was 0.33 nm / s, the sputtering time was 150 s, and the thickness was approximately 50 nm.

[0021] Preferably, the annealing in step five is carried out under a vacuum of 2*10 -4 mbar performs rapid annealing of the device at 200°C for 5-10 minutes to remove air bubbles and residual adhesive on the sample surface to achieve better contact.

[0022] (III) Beneficial Effects

[0023] Compared with the prior art, the present invention provides a silicon-based Schottky diode with switchable positive and negative electrodes and its fabrication method, which has the following beneficial effects:

[0024] 1. The silicon-based Schottky diode with switchable positive and negative electrodes and its fabrication method are disclosed. The heterojunction device has obvious polarization reversal characteristics, thereby changing the rectification direction of the device. Compared with the existing switchable positive and negative electrodes Schottky diodes, the fabrication method of the device involved in this invention is simple, non-toxic, and low in cost. It also has advantages such as a large on / off ratio, polarity-controllable rectification effect, good repeatability, and fatigue resistance. It can be widely used in the field of two-dimensional semiconductor nanomaterials technology. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a silicon-based Schottky diode with switchable positive and negative electrodes based on indium γ-selenide;

[0026] Figure 2 This is a schematic diagram of the out-of-plane ferroelectric amplitude of γ-indium selenide nanosheets;

[0027] Figure 3 This is a schematic diagram showing the relationship between the phase of γ-indium selenide nanosheets and the applied external electric field;

[0028] Figure 4 This is a schematic diagram of the current-voltage IV curve of the present invention;

[0029] Figure 5 This is a schematic diagram of the hyperbolic logarithmic processing of the IV curve of the present invention;

[0030] Figure 6 This is the Raman spectrum measured from γ-indium selenide nanosheets;

[0031] Figure 7 These are the IV curves of the present invention in the unpolarized original state, with 7V polarization upward and -7V polarization downward.

[0032] In the figure: 1. Few-layer hexagonal boron nitride; 2. γ-indium selenide nanosheets; 3. Few-layer graphene; 4. Gold electrode layer; 5. Titanium adhesion layer; 6. Silicon dioxide insulating layer; 7. Silicon substrate. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] See Figure 1 A silicon-based Schottky diode with switchable positive and negative electrodes includes a few-layer hexagonal boron nitride 1, an indium γ-selenide nanosheet 2, a few-layer graphene 3, a gold electrode layer 4, a titanium adhesion layer 5, a silicon dioxide insulating layer 6, and a silicon substrate 7. The silicon dioxide insulating layer 6 is disposed on the silicon substrate 7, and the titanium adhesion layer 5 is disposed on the silicon dioxide insulating layer 6. The gold electrode layer 4 is disposed on the outer surface of the titanium adhesion layer 5. One end of the indium γ-selenide nanosheet 2 is placed on the gold electrode layer 4, and the other end is placed on the surface of the silicon dioxide insulating layer 6. One end of the few-layer graphene 3 is placed on the indium γ-selenide nanosheet 2, and the other end is placed on the gold electrode layer 4. The few-layer hexagonal boron nitride 1 covers the indium γ-selenide nanosheet 2 and the few-layer graphene 3 as a protective encapsulation, but some electrodes need to be left uncovered for testing.

[0035] The γ-indium selenide nanosheets 2 have 10 or more layers and a thickness of 10–20 nm, the few-layer graphene 3 has 5 or more layers and a thickness of 5–10 nm, and the few-layer hexagonal boron nitride 1 has 10 or more layers and a thickness of 20–30 nm.

[0036] The γ-indium selenide nanosheet 2 has a thickness of approximately 15 nm and a size of 30 μm * 50 μm, the few-layer graphene 3 has a thickness of approximately 5 nm and a size of 15 μm * 40 μm, and the few-layer hexagonal boron nitride 1 has a thickness of approximately 23 nm and a size of 40 μm * 60 μm.

[0037] A silicon-based Schottky diode with switchable positive and negative electrodes and its fabrication method, comprising the following steps:

[0038] Step 1: Fabrication of the electrode array:

[0039] First, using the principle of "like dissolves like," organic impurities on the surface of silicon substrate 7 (a silicon substrate with a 280nm silicon dioxide insulating layer on the surface, collectively referred to as silicon substrate 7) are removed with acetone solution. Then, silicon substrate 7 is carefully removed with tweezers and placed back into the organic ethanol solution. Ultrasonic operation can also be performed if necessary. Next, silicon substrate 7 is removed with tweezers and placed in pure deionized water for cleaning. Finally, it is dried with an air can and heated on a hot table at 120°C for ten minutes to ensure that the substrate is clean and free of contamination.

[0040] The silicon substrate 7 was cleaned with acetone, ethanol, and deionized water, and then dried using a gas cylinder and heated on a hot stage at 120°C for ten minutes to ensure it was clean and free of contaminants. Next, a 100-mesh copper mesh with 45μm rib width and 200μm aperture was placed on the silicon substrate 7 as a mask, and silver paste was used to tightly adhere the copper mesh to the substrate. 10nm titanium and 50nm gold were sputtered onto the target silicon substrate 7 using magnetron sputtering to obtain a titanium adhesion layer 5 and a gold electrode layer 4; the sputtering conditions were: power 50W, base vacuum 2*10⁻⁶. -5 mbar, argon pressure is 1.05*10 -2 The sputtering speed was mbar, the sputtering distance was 25-30 cm, the sputtering speed of titanium adhesion layer 5 was 0.04 nm / s, and the sputtering time was 260 s; the sputtering speed of gold electrode layer 4 was 0.33 nm / s, and the sputtering time was 150 s; after sputtering, the copper mesh was removed with tweezers to obtain a square electrode array with a size of 200 μm * 200 μm and a spacing of 45 μm.

[0041] Step 2: Mechanically peel off the target material:

[0042] Using clean tweezers, a small piece of two-dimensional material was placed onto PDMS. By repeatedly applying adhesive tape, the two-dimensional material was peeled and thinned, finally yielding an ultrathin two-dimensional material. The thickness of γ-indium selenide nanosheet 2 was 15 nm, the thickness of few-layer graphene 3 was 5 nm, and the thickness of few-layer hexagonal boron nitride 1 was 23 nm.

[0043] Step 3: Precise dry transfer of the target material onto the silicon substrate 7:

[0044] The back side of PDMS with few-layer two-dimensional material is adhered to a glass slide with good light transmittance. Care is taken not to obstruct the middle part during fixation to avoid affecting transparency and hindering observation under a microscope. A silicon substrate 7 with pre-fabricated electrodes is placed on a stationary stage, and the glass slide with PDMS is placed on a movable stage, with the PDMS sheet below. Under a microscope, the silicon substrate 7 and the required material are rotated into the display area by adjusting the knobs. The knobs are then adjusted left and right to move the material of suitable size and thickness to the appropriate position on the silicon substrate 7 with pre-fabricated electrodes in the display. The knobs are then adjusted up and down until the PDMS is in close contact with the target substrate. The mixture is heated to 60°C and left for 5 minutes. After the material and silicon substrate 7 are in full contact, the knobs are slowly rotated to move the PDMS adhesive upwards, allowing the target material to fall completely onto the silicon substrate 7. This yields a γ-indium selenide nanosheet / few-layer graphene / few-layer hexagonal boron nitride Schottky diode. Finally, the diode is processed under a vacuum of approximately 2*10⁻⁶. -4 mbar performs rapid annealing of the device at 200°C for 5-10 minutes to remove air bubbles and residual adhesive on the sample surface to achieve better contact.

[0045] See Figure 2 as well as Figure 3 The study employed piezoelectric microscopy (PFM) for single-point testing. PFM is a powerful tool for studying ferroelectricity; under external electric field stimulation, ferroelectric materials undergo minute deformations that can be detected by a probe cantilever. We grounded the target substrate and applied a voltage to the conductive probe using PFM to obtain an external electric field that altered the local polarization direction. The results showed that... Figure 2 A clear hysteresis loop can be observed in it. Figure 3 The 180° inversion of the mid-phase signal confirms the existence of switchable ferroelectric polarization in γ-indium selenide nanosheets 2. Figure 2 as well as Figure 3 It was demonstrated that γ-indium selenide nanosheets 2 are ferroelectric materials with ferroelectric properties.

[0046] See Figure 4 as well as Figure 5The IV curve test voltage scanned from +7V to -7V and then back to +7V, showing obvious hysteresis behavior, indicating that the resistor can switch back and forth. Under high DC bias, the device is in a "conducting" state due to the change in the Schottky barrier. We found that the on / off ratio of the ferroelectric diode is approximately ~10. 7 Furthermore, after dozens of scanning voltage tests, the ferroelectric diode still maintained its hysteresis IV characteristic, indicating excellent repeatability and fatigue resistance.

[0047] Figure 6 This is the Raman spectrum measured by indium γ-selenide in Example 1 of this invention. It has three main characteristic peaks, representing three main vibrational modes: A 1 1g The pattern is at 116cm -1 E 1 2g The pattern is at 117cm -1 A 2 1g The pattern is at 227cm -1 .

[0048] See Figure 7 The measured voltage range was ±1V. For three different conditions, the initial state was unpolarized, polarization-up was achieved by polarizing for 200ms under a 7V square pulse, and polarization-down was achieved by polarizing for 200ms under a -7V square pulse. The results show that for the initial state, the current is very small and increases linearly with voltage under both positive and negative biases; however, for the polarization-up state, the current increases exponentially with positive voltage but increases slowly with negative voltage, indicating forward diode behavior; however, for the polarization-down state, the current exhibits reverse diode behavior. This result confirms that the behavior of the switchable diode is observable and is controlled by ferroelectric polarization. These characteristics suggest that this thin-film device can be used to develop switchable Schottky diodes.

[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A silicon-based Schottky diode with switchable positive and negative electrodes, comprising a few-layer hexagonal boron nitride (1), γ-indium selenide nanosheets (2), a few-layer graphene (3), a gold electrode layer (4), a titanium adhesion layer (5), a silicon dioxide insulating layer (6), and a silicon substrate (7), characterized in that, A silicon dioxide insulating layer (6) is disposed on a silicon substrate (7). A titanium adhesion layer (5) is disposed on the silicon dioxide insulating layer (6). A gold electrode layer (4) is disposed on the outer surface of the titanium adhesion layer (5). One end of the γ-indium selenide nanosheet (2) is placed on the gold electrode layer (4), and the other end is placed on the surface of the silicon dioxide insulating layer (6). One end of the few-layer graphene (3) is placed on the γ-indium selenide nanosheet (2), and the other end is placed on the gold electrode layer (4). A few-layer hexagonal boron nitride (1) covers the γ-indium selenide nanosheet (2) and the few-layer graphene (3).

2. A silicon-based Schottky diode with switchable positive and negative terminals according to claim 1, characterized in that: The γ-indium selenide nanosheets (2) have 10 or more layers and a thickness of 10-20 nm. The few-layer graphene (3) has more than 5 layers and a thickness of 5-10 nm. The few-layer hexagonal boron nitride (1) has more than 10 layers and a thickness of 20-30 nm.

3. A silicon-based Schottky diode with switchable positive and negative terminals according to claim 1, characterized in that: The γ-indium selenide nanosheets (2) have a thickness of 15 nm and a size of 30 μm * 50 μm, the few-layer graphene (3) has a thickness of 5 nm and a size of 15 μm * 40 μm, and the few-layer hexagonal boron nitride (1) has a thickness of 23 nm and a size of 40 μm * 60 μm.

4. A method for fabricating a silicon-based Schottky diode with switchable positive and negative electrodes as described in claim 1, characterized in that, Includes the following steps: Step 1: Clean the target substrate consisting of a silicon dioxide insulating layer (6) and a silicon substrate (7) with acetone, ethanol and deionized water. Finally, dry it with an air can and heat it on a hot table at 120°C for ten minutes to obtain a clean and uncontaminated target substrate. Step 2: Place a copper mesh as a mask for the electrode array, fix it on the target substrate with silver paste, and sputter a titanium adhesion layer (5) and a gold electrode layer (4) using magnetron sputtering, thus completing the preparation of the electrode array on the target substrate; Step 3: According to the requirements of electrode array spacing and coverage, prepare γ-indium selenide nanosheets (2), few-layer graphene (3) and few-layer hexagonal boron nitride (1) respectively. Place the corresponding bulk materials on the blue adhesive, tear the adhesive tape to obtain a thinner material, and then use PDMS adhesive to tear it multiple times until a semi-transparent γ-indium selenide nanosheets (2), few-layer graphene (3) and few-layer hexagonal boron nitride (1) are obtained. Step 4: Under a microscope, align the PDMS adhesive with γ-indium selenide nanosheets (2), few-layer graphene (3), and few-layer hexagonal boron nitride (1) with the target position of the electrode on the target substrate. Then, adjust the knob up and down until the PDMS adhesive is in close contact with the designated position on the target substrate. Heat to 60°C and wait for 5 minutes. After the material and the target substrate are in full contact, slowly rotate the knob to move the PDMS adhesive upward. The target material will fall completely onto the target substrate to obtain a γ-indium selenide nanosheet / few-layer graphene / few-layer hexagonal boron nitride Schottky diode. Step 5: Anneal the obtained γ-indium selenide nanosheet / few-layer graphene / few-layer hexagonal boron nitride Schottky diode to finally obtain a silicon-based Schottky diode with switchable positive and negative electrodes.

5. The method for fabricating a silicon-based Schottky diode with switchable positive and negative electrodes according to claim 4, characterized in that: The sputtering conditions in the second step are: power 50W, background vacuum 2*10 -5 mbar, argon pressure is 1.05*10 - 2 mbar, sputtering distance is 25~30cm; The sputtering rate of the titanium adhesive layer (5) is 0.04 nm / s, the sputtering time is 260 s, and the thickness is about 10 nm. The sputtering rate of the gold electrode layer (4) is 0.33 nm / s, the sputtering time is 150 s, and the thickness is about 50 nm.

6. The method for fabricating a silicon-based Schottky diode with switchable positive and negative electrodes according to claim 4, characterized in that: The annealing in the fifth step is carried out under a vacuum of 2*10. -4 The device is rapidly annealed at 200°C for 5-10 minutes using mbar.

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