CN116193976A - Memristor based on flexoelectric effect and preparation method thereof - Google Patents

Abstract

The invention discloses a memristor based on a flexoelectric effect and a preparation method thereof. Firstly, preparing a patterned substrate by using an electron beam lithography technology to obtain an electrode matrix; thinning the indium selenide crystal by mechanically stripping the special blue tape; then, taking the thin slice crystal off the blue adhesive tape by using polydimethylsiloxane and thinning the thin slice crystal again, and selecting a sample under an optical microscope; and transferring the selected sample onto an electrode matrix by means of a two-dimensional material directional transfer auxiliary platform, so as to prepare the memristor. The material used in the invention is safe and environment-friendly, has low cost, simple structure and easy operation in the preparation process, and further expands the application of the two-dimensional material.

Description

A memristor based on the flexoelectric effect and its preparation method

technical field

The invention relates to the related technical field of memristor preparation based on the flexoelectric effect of two-dimensional layered thin films. The EBL technology is used to pattern the substrate, and the suspended and curved indium selenide is used as the channel to induce the flexoelectric effect through the curved structure. , so as to realize the function of high-performance memristor.

Background technique

2D materials have the advantages of tunable bandgap, transition from indirect to direct bandgap with reduced layer number, and strong spin-orbit coupling induced by inversion symmetry breaking. These exceptional properties make 2D materials very promising for optoelectronic and electromechanical applications.

Indium selenide is a two-dimensional material with excellent electrical properties. It has excellent basic characteristics such as ultra-high carrier mobility, interlayer adjustable bandgap, and large elastic deformation capacity. It is one of the two-dimensional layered semiconductor materials. a new star. The layered two-dimensional material InSe monolayer has a band gap of 1.2-1.8 eV, an intrinsic electron mobility as high as 1000 cm ² V ⁻¹ s ⁻¹ and a small effective electron mass, which makes it a low-power device and special switching devices are excellent candidates. Compared with traditional memristor devices, memristors based on suspended and curved indium selenide channels can achieve high switching ratio and large window memristor functions, further enriching the application scenarios of indium selenide devices, and at the same time It also provides a way of thinking for the development of memristors based on two-dimensional materials.

Contents of the invention

The object of the present invention is to provide a memristor based on the flexoelectric effect and a preparation method thereof. The memristor suitable for the preparation method uses suspended and bent indium selenide as a channel. In this method, a pre-designed patterned electrode is prepared on a cleaned silicon/silicon dioxide substrate by means of electron beam lithography and thermal evaporation, and then the mechanically exfoliated few-layer two-dimensional layered material selenium Indium chloride is directional transferred to the patterned electrode by a dry method. By this method, the flexoelectric effect can be induced and generated in the channel region, thereby improving the performance of the memristor device.

The concrete technical scheme that realizes the object of the invention is:

A method for preparing a memristor based on the flexoelectric effect, the method comprising the following specific steps:

Step 1: Preparation of Electrode Matrix

A1: Clean the substrate

Use a diamond knife to cut a P-type heavily doped silicon substrate with 90-300 nm thick silicon dioxide on the surface, cut it into a square with a side length of 1-4 cm, put it in acetone, isopropanol and deionized water in sequence, and ultrasonically Clean for 10-20 min. After the cleaning is completed, use a nitrogen gun to dry the surface for later use, and the cleaning of the substrate is completed so far;

A2: Patterned Substrate

Spin-coat polymethyl methacrylate photoresist with a thickness of 300-350 nm on the cleaned conductive substrate; then perform electron beam exposure according to the pre-designed electrode pattern; after exposure, develop and fix, and the exposed light The resist dissolves in the developer solution, leaving the electrode structure;

A3: Evaporated memristor source and drain electrodes

Fix the patterned substrate to the sample plate on the top of the thermal evaporation coating instrument, put 2-3 gold particles and 2-3 copper particles in the two evaporated tungsten boats, wipe the chamber door with alcohol and close the chamber chamber; then turn on the mechanical pump and molecular pump to evacuate the chamber to a vacuum state; first evaporate a 100-200 nm copper film, and then evaporate a 50-100 nm gold film;

A4: Glue removal

Soak the evaporated patterned substrate in an acetone solution to remove the glue, suck the acetone solution with a rubber dropper to blow off the removed photoresist on the substrate surface, and dry it with a nitrogen gun after the glue removal is completed , an electrode matrix with a pitch of 1-5 microns can be obtained, and the preparation of the electrode matrix is completed so far;

Step 2: Preparation of InSe channel layer

B1: Preparation of indium selenide channel layer

Use alcohol to wipe clean the tweezers, blades and glass slides of the laboratory equipment, cut the blue film tape to 2 cm x 5 cm, and use the tweezers to pick up a 2 mm x 2 mm indium selenide block and place it in the center of the blue film tape. Repeatedly fold in half to make the indium selenide block into few layers; select 1 cm × 1 cm PDMS and paste it on a clean glass slide, and then paste the blue film tape containing few layers of indium selenide material on the flat PDMS, After a few light pressures, lift up slowly to separate the blue film tape from PDMS; turn on the optical microscope and adjust its sensitivity, and place the glass slide with the indium selenide material under the optical microscope to find out the uniform texture, thickness and 30 The indium selenide layer of micron × 30 micron is used as the target material; then the PDMS is cut to 5 mm × 5 mm with a blade as the target glass slide;

Step 3: Transfer of InSe thin film material

C1: Transfer InSe thin film material

Turn on the control switch of the transfer table and the microscope screen, and then turn on the nitrogen cylinder to make the air bearing table in a horizontal state; check the horizontal state of the transfer table with the help of a spirit level, if it is not in a horizontal state, adjust it to be in a horizontal state; put the prepared in step 1 Place the substrate on the stage, focus on the substrate surface by adjusting the zoom ring and the coarse/fine focus screw, and place the target substrate in the center of the microscope field of view by adjusting the X/Y axis of the stage movement axis, and then open The mechanical pump makes the substrate adsorb on the stage; fix one end of the target glass slide prepared in step B1 on the fixture stage and move it to the field of view of the microscope, and look for the target slide prepared in step B1 under a low magnification. Target indium selenide and focus the microscope to the surface of the target indium selenide material by adjusting the coarse/fine focus helix; slowly lower the target slide to a position 1-2 cm away from the substrate by controlling the Z-axis knob of the fixture table, adjust The magnification of the microscope makes it possible to mark the contour of the target indium selenide material and the position of the target substrate at the maximum magnification. By adjusting the X/Y axis of the stage and the fixture stage to make the two positions correspond, and then control the fixture stage Z The axis is lowered to close to the surface of the substrate while adjusting the focal length so that it can always focus on the PDMS on the glass slide and the target substrate; when the microscope screen sees the ripples, press down quickly to make the target indium selenide material and the substrate fit, and wait After they are completely overlapped, slowly move up the Z-axis until the PDMS is completely separated from the target indium selenide material. At this point, the transfer of the indium selenide layer is completed, and the substrate after the transfer of the indium selenide layer is taken out to obtain the flexoelectric effect-based the memristor.

A memristor based on the flexoelectric effect prepared by the above method.

Compared with the prior art, the present invention has the biggest advantages: the operation process of the present invention is simpler and the cost is lower; on the basis of the traditional two-dimensional material memristor, the suspended and curved indium selenide is introduced as the channel, and the channel The flexoelectric effect induced by the track region can significantly improve the performance of the device.

Description of drawings

Fig. 1 is the schematic diagram of the cross-sectional structure of the indium selenide memristor prepared by the method of the present invention;

2 is a schematic cross-sectional structure diagram of an indium selenide memristor prepared in a comparative example;

Fig. 3 is the typical current-voltage curve of the threshold switch under the quasi-DC voltage scanning of the indium selenide memristor of the present invention;

FIG. 4 is a typical current-voltage curve of the threshold switch of the indium selenide memristor of the comparative example under the quasi-DC voltage sweep.

Implementation

The present invention will be further described below in conjunction with the accompanying drawings, examples and comparative examples.

Referring to Fig. 1, the indium selenide transistor based on the flexoelectric effect according to the embodiment of the present invention includes a gate electrode 4, a dielectric layer 3, a copper/gold electrode 2 and an indium selenide channel layer 1; wherein, the The gate electrode 4 is a P-type heavily doped silicon substrate; the dielectric layer 3 is a silicon dioxide layer; the electrode 2 is a copper/gold electrode prepared by a thermal evaporation evaporation apparatus; the channel layer 1 is made by The obtained indium selenide layer was transferred by mechanical exfoliation.

Example

Fabrication of indium selenide memristor based on flexoelectric effect:

(1) Use a diamond knife to cut a P-type heavily doped silicon substrate with 280 nm thick silicon dioxide on the surface, cut it into a square with a side length of 1 cm, put it into acetone, isopropanol and deionized water in sequence, and ultrasonically After cleaning for 15 min, use a nitrogen gun to dry the surface for later use; spin-coat polymethyl methacrylate photoresist with a thickness of 330 nm on the cleaned conductive substrate; then perform electron beam exposure according to the pre-designed electrode pattern ; After exposure, develop and fix, the photoresist after exposure is dissolved in the developer, leaving the electrode structure; the patterned substrate is fixed to the sample plate on the top of the thermal evaporation coating instrument, and the two evaporated tungsten boats Put 3 gold particles and 2 copper particles respectively, wipe the chamber door with alcohol and close the chamber, then turn on the mechanical pump and molecular pump to pump the chamber to a vacuum state, first evaporate a 150 nm copper film, and then evaporate 100 nm gold film; immerse the vapor-deposited patterned substrate in acetone solution to remove the glue, suck the acetone solution with a rubber dropper to blow off the removed photoresist on the surface of the substrate, after the glue removal is completed , blowing dry with a nitrogen gun, an electrode matrix with a pitch of 2 microns×2 microns can be obtained, and thus the preparation of the electrode matrix is completed.

(2) Use alcohol to wipe clean the experimental equipment, such as: tweezers, blades, glass slides, etc. Cut the blue film tape to a size of 2 cm x 5 cm, use tweezers to pick up a 2 mm x 2 mm indium selenide block and place it in the center of the blue film tape, and fold it repeatedly to make the indium selenide block into a few layers. Select a 1 cm × 1 cm PDMS and paste it on a clean glass slide, then paste the blue film tape containing a few layers of indium selenide material on the flat PDMS, press lightly for a few times and slowly lift it up to make the blue film tape and PDMS isolation. Turn on the optical microscope and adjust its sensitivity, put the glass slide with the indium selenide material under the optical microscope for observation, look for the indium selenide layer with uniform texture, thickness and 30 microns × 30 microns as the target material; then use the blade Cut the PDMS to 5 mm × 5 mm as a target slide for the next step.

(3) Turn on the control switch of the transfer table and the microscope screen, and then turn on the nitrogen cylinder to make the air flotation table level; check the level of the transfer table with the help of a spirit level, if it is not in a horizontal state, adjust it to be in a horizontal state. Place the substrate prepared in step (1) on the stage, focus on the substrate surface by adjusting the zoom ring and the coarse/fine focus screw, and adjust the X/Y axis of the stage moving axis to make the target substrate Place it in the center of the field of view of the microscope, and then turn on the mechanical pump to make the substrate adsorb on the stage; fix one end of the target slide prepared in step (2) on the fixture stage and move it to the field of view of the microscope. Look for the target indium selenide prepared in step (2) under a low magnification microscope and focus the microscope on the surface of the target indium selenide material by adjusting the coarse/fine focus helix. Slowly lower the target glass slide to a position 1 cm away from the substrate by controlling the Z-axis knob of the fixture table, adjust the magnification of the microscope to mark the outline of the target indium selenide material and the position of the target substrate at the maximum magnification, and pass Adjust the X/Y axis of the stage and the fixture table to make the two positions correspond, and then control the Z-axis of the fixture table to descend close to the substrate surface and adjust the focal length so that it can always focus on the PDMS on the slide glass and the target substrate ; When the microscope screen sees the ripples, quickly press down to make the target InSe material and the substrate fit together, and then slowly move up the Z axis until the PDMS is completely separated from the target InSe material, and the InSe memory is completed. The preparation of the resistor, its structure is shown in Figure 1.

Indium Selenide Transistor Fabrication

(1) Select a P-type heavily doped silicon substrate with a silicon dioxide layer thickness of 280 nm, use a diamond knife to cut it into a square with a side length of 1 cm and perform ultrasonic cleaning, and place it in a drying oven to evaporate the excess Moisture yields a silicon/silicon dioxide wafer with a clean surface.

(2) Cut the blue ink tape to a size of 2 cm × 5 cm, place the bulk indium selenide material in the center of the blue film tape, and repeatedly fold the blue film tape in half to obtain a blue film tape containing a few layers of indium selenide material; PDMS was cut to a size of 1 cm × 1 cm and pasted on a clean glass slide, and then the blue film tape with a few layers of indium selenide material was pasted on the PDMS, and the blue film tape was peeled off with light pressure by hand to complete the second transfer the dimensional material to PDMS, and then observe the PDMS with the indium selenide material under an optical microscope to find a target sample with uniform texture, size and thickness; finally, use a knife to cut off the excess PDMS for later use, and the selenization is completed Preparation of the indium layer.

(3) Transfer the indium selenide prepared in step (2) to a clean substrate by means of a transfer table. Turn on the control switch of the transfer table and the microscope screen, and then turn on the nitrogen cylinder to make the air bearing table in a horizontal state; check the horizontal state of the transfer table with the help of a spirit level, if it is not in a horizontal state, adjust it to be in a horizontal state. Place the substrate prepared in step (1) on the stage, focus on the substrate surface by adjusting the zoom ring and the coarse/fine focus screw, and adjust the X/Y axis of the stage moving axis to make the target substrate Place it in the center of the field of view of the microscope, and then turn on the mechanical pump to make the substrate adsorb on the stage; fix one end of the target slide prepared in step (2) on the fixture stage and move it to the field of view of the microscope. Look for the target indium selenide prepared in step (2) under a low magnification microscope and focus the microscope on the surface of the target indium selenide material by adjusting the coarse/fine focus helix. Slowly lower the target glass slide to a position 1 cm away from the substrate by controlling the Z-axis knob of the fixture table, adjust the magnification of the microscope to mark the outline of the target indium selenide material and the position of the target substrate at the maximum magnification, and pass Adjust the X/Y axis of the stage and the fixture table to make the two positions correspond, and then control the Z-axis of the fixture table to descend close to the substrate surface and adjust the focal length so that it can always focus on the PDMS on the slide glass and the target substrate ;When the microscope screen sees the ripples, press down quickly to make the target indium selenide material and the substrate fit together, and then slowly move up the Z axis until the PDMS is completely separated from the target indium selenide material, and the indium selenide layer is completed. transfer.

(4) Paste a suitable length of high-temperature tape around the mask plate as a spare. Turn on the control switch of the transfer stage and the microscope screen, and use a spirit level to adjust the X/Y axis of the transfer stage to be in a horizontal state. The substrate containing the indium selenide layer is placed in the substrate and fixed on the stage, and the mask plate is fixed on the fixture stage. Focus the microscope on the substrate surface by adjusting the zoom ring of the microscope and the coarse/fine focus screw, adjust the X/Y axis of the stage to place the target sample in the center of the microscope field of view; control the Z axis of the fixture table to slowly descend until the mask The template touches the surface of the substrate, and the relative position of the mask and the sample on the substrate is fine-tuned; after the adjustment, the mask and the substrate are completely attached and the fixture table is slowly lifted to gradually separate the fixture table from the mask. So far, the patterning process of the sample is completed. Put the sample into the thermal evaporation coating apparatus, put 3 gold particles and 2 copper particles in the two evaporated tungsten boats respectively, wipe the chamber door with alcohol and close the chamber, turn on the mechanical pump and the molecular pump chamber pumping chamber in turn. To vacuum, slowly increase the current to control the melting and evaporation rate of copper and gold particles, first evaporate a 150 nm copper film, and then evaporate a 100 nm gold film to complete the preparation of the electrode, and thus complete the entire preparation of the indium selenide transistor. Its structure is shown in Figure 2.

The comparison of the electrical parameters of the memristor based on the suspended and curved indium selenide as the channel prepared in the example and the transistor with the tiled indium selenide as the channel prepared in the comparative example is as follows:

Figure 3 is the typical current-voltage curve of the threshold switch under the quasi-DC voltage sweep of the memristor with the suspended and curved InSe as the channel; Figure 4 is the quasi-DC curve of the transistor with the tiled InSe as the channel Typical current-voltage curves for threshold switching under DC voltage sweep.

From Figure 3 and Figure 4, it can be seen that the typical current-voltage curve of the threshold switch under the quasi-DC voltage sweep of the transistor with tiled indium selenide as the channel does not show an obvious window, no memristor performance, and the floating And the curve of the memristor with curved indium selenide as the channel shows obvious memristive performance, the on-off ratio is as high as 10 ⁶ , and the window is about 10 ⁴ . Compared with the traditional InSe transistor, the flexoelectric effect can be effectively induced by using the suspended and curved InSe as the channel, which can effectively improve the performance of the memristor. Therefore, the memristor based on the flexoelectric effect prepared by the present invention has a simple and easy-to-operate manufacturing process and optimizes the structure of the traditional two-dimensional transistor, which is of great significance for the further application of two-dimensional materials.

Claims (2)

1. The preparation method of the memristor based on the flexoelectric effect is characterized by comprising the following specific steps:

step 1: preparation of electrode matrix

A1: cleaning a substrate

Cutting a P-type heavily doped silicon substrate with 90-300-nm thick silicon dioxide on the surface by using a diamond knife, cutting the P-type heavily doped silicon substrate into squares with the side length of 1-4cm, sequentially placing the squares into acetone, isopropanol and deionized water, ultrasonically cleaning for 10-20 min, and drying the surface for later use by using a nitrogen gun after cleaning is finished, thereby finishing the cleaning of the substrate;

a2: patterned substrate

Spin-coating a polymethyl methacrylate photoresist with a thickness of 300-350-nm on the cleaned substrate; then carrying out electron beam exposure according to a pre-designed electrode pattern; after exposure, developing and fixing are carried out, and the photoresist after exposure is dissolved in a developing solution to leave an electrode structure;

a3: evaporation memristor source and drain electrode

Fixing the patterned substrate on a sample plate at the top of a thermal evaporation coating instrument, respectively placing 2-3 gold particles and 2-3 copper particles in two evaporated tungsten boats, and closing the chamber after alcohol wipes the chamber door; then the mechanical pump and the molecular pump are started to pump the chamber to a vacuum state; firstly, evaporating a copper film of 100-200 nm, and then evaporating a gold film of 50-100 nm;

a4: adhesive removing

Immersing the evaporated patterned substrate in acetone solution for removing photoresist, sucking the acetone solution by using a rubber head dropper, blowing off the photoresist removed from the surface of the substrate, and drying by using a nitrogen gun after the photoresist removal is completed, so as to obtain an electrode matrix with a 1-5-micrometer spacing, thereby completing the preparation of the electrode matrix;

step 2: preparation of indium selenide channel layer

B1: preparation of indium selenide channel layer

Wiping the forceps, the blade and the glass slide of the experimental appliance clean by using alcohol, cutting the blue film adhesive tape to 2 cm multiplied by 5 cm, clamping the indium selenide bulk material with the thickness of 2 mm multiplied by 2 mm by using the forceps, placing the indium selenide bulk material in the center of the blue film adhesive tape, and repeatedly folding the indium selenide bulk material in half to change the indium selenide bulk material into a few layers; selecting 1 cm multiplied by 1 cm PDMS, adhering the PDMS on a clean glass slide, adhering a blue film adhesive tape containing a small layer of indium selenide material on the smooth PDMS, and slowly lifting the PDMS after slightly pressing the PDMS to separate the blue film adhesive tape from the PDMS; opening an optical microscope and adjusting the sensitivity of the optical microscope, and placing a glass slide adhered with an indium selenide material under the optical microscope for observation to find an indium selenide layer with uniform texture and thickness and 30 micrometers multiplied by 30 micrometers as a target material; PDMS was then cut with a blade to 5 mm x 5 mm as a target slide;

step 3: transfer of indium selenide thin film materials

C1: transfer indium selenide thin film material

Opening a control switch of the transfer table and a microscope screen, and then opening a nitrogen cylinder to enable the air floatation table to be in a horizontal state; checking the horizontal state of the transfer table by means of a level gauge, and if the transfer table is not in the horizontal state, adjusting the transfer table to be in the horizontal state; placing the substrate prepared in the step 1 on an objective table, focusing on the surface of the substrate by adjusting a zoom ring and a coarse/fine focusing screw, enabling a target substrate to be placed in the center of a microscope visual field by adjusting an X/Y axis of a moving axis of the objective table, and then starting a mechanical pump to enable the substrate to be adsorbed on the objective table; fixing one end of the target glass slide prepared in the step B1 on a fixture table and moving the end of the target glass slide to the view range of a microscope, searching the target indium selenide prepared in the step B1 under a low-power mirror, and focusing the microscope on the surface of the target indium selenide material by adjusting a coarse/fine focusing screw; slowly lowering a target glass slide to a position which is 1-2 cm away from a substrate by controlling a Z-axis knob of a clamp table, adjusting the magnification of a microscope to mark the outline of a target indium selenide material and the position of the target substrate under the maximum magnification, enabling the positions of an objective table and the X/Y axis of the clamp table to correspond to each other, and then controlling the Z-axis of the clamp table to be close to the surface of the substrate while adjusting the focal length so that the Z-axis of the clamp table can be focused on PDMS on the glass slide and the target substrate all the time; and rapidly pressing down when the screen of the microscope sees the corrugation to enable the indium selenide material on the PDMS to be attached to the substrate, slowly moving upwards the Z axis until the PDMS is completely separated from the target indium selenide material after the indium selenide material is completely overlapped, so that the transfer of the indium selenide layer is completed, and taking out the substrate with the transferred indium selenide layer, thereby preparing the memristor based on the flexoelectric effect.

2. A memristor based on the flexoelectric effect made by the method of claim 1.

Images