A method for transferring a two-dimensional film from a mica substrate and a pretreatment method

Abstract

The present invention belongs to the technical field of thin film transfer, and particularly relates to a method for transferring a two-dimensional thin film from a mica substrate and a pretreatment method. The present invention successively treats the mica substrate with an acidic solution and an alkali metal chloride solution, which can weaken the binding force of the mica substrate to the two-dimensional thin film without damaging the two-dimensional thin film, significantly improve the quality of the two-dimensional thin film transfer, reduce the material defects and lattice distortion introduced by the transfer, and achieve the purpose of conveniently and efficiently transferring a high-quality two-dimensional thin film. The pretreatment method provided by the present invention is applicable to the transfer processes of different types of two-dimensional thin films, and has a high transfer success rate, small sample damage, low cost and fast efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of thin film transfer, and in particular relates to a method for transferring a two-dimensional thin film from a mica substrate and a pre-treatment method. Background Art

[0002] With the advancement of material growth and synthesis technology, two-dimensional thin film materials have broad application prospects and important significance in scientific research and industrial production due to their excellent physical and chemical properties such as electrical conductivity, thermal conductivity, mechanical toughness and catalysis.

[0003] Before discussing the performance of devices containing two-dimensional thin film materials, how to transfer high-quality two-dimensional thin films to the target substrate becomes a key issue. During the synthesis of two-dimensional thin films, there are a large number of dangling bonds on the surface of the mica substrate used, which makes the mica and the two-dimensional thin film have a very strong bonding force, greatly increasing the difficulty of the transfer process. The adhesion force between the adhesive layer material used in traditional wet transfer and dry transfer techniques and the two-dimensional thin film is much smaller than the bonding force between the mica substrate and the two-dimensional thin film. This causes the two-dimensional thin film to be damaged during the transfer process due to the excessive bonding force of the bottom layer, which seriously limits the quality of the two-dimensional thin film. Summary of the invention

[0004] The purpose of the present invention is to provide a method and a pretreatment method for transferring a two-dimensional film from a mica substrate. The pretreatment method provided by the present invention can reduce the bonding force between the two-dimensional film and the mica substrate, and significantly improve the quality of the two-dimensional film transfer.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a pre-treatment method for transferring a two-dimensional film from a mica substrate, comprising:

[0007] The mica substrate on which the two-dimensional film is grown is first immersed in an acidic solution and then immersed in an alkali metal chloride solution for a second time; the acidic solution does not react with the two-dimensional film.

[0008] Preferably, the acidic solution comprises a hydrofluoric acid solution or a hydrochloric acid solution; and the mass concentration of the acidic solution is 0.5-2%.

[0009] Preferably, the temperature of the first immersion is room temperature, and the time is 1 to 3 minutes.

[0010] Preferably, the alkali metal chloride solution includes sodium chloride solution or potassium chloride solution; the concentration of the alkali metal chloride solution is 0.5-2 mol / L.

[0011] Preferably, the second immersion is carried out under heating and ultrasonic conditions; the heating temperature is 50-70° C., the ultrasonic power is 40-60 W, and the time is 3-5 min.

[0012] Preferably, the two-dimensional film comprises Bi 2 O 2 Se film, Bi 2 Se 3 Thin film, MoS 2 Thin film or WSe 2 film.

[0013] The present invention also provides a method for transferring a two-dimensional film from a mica substrate, comprising the following steps:

[0014] The pre-treatment method described in the above technical solution is used for pre-treatment to obtain a treated mica substrate;

[0015] Coating a polymer solution on the side of the treated mica substrate where the two-dimensional film is grown to obtain a mica substrate with a polymer attached thereto;

[0016] placing the mica substrate with the polymer attached thereto in water for peeling, thereby obtaining a polymer carrying a two-dimensional film;

[0017] After removing impurities from the polymer carrying the two-dimensional film, the polymer is attached to the surface of a target substrate so that the side carrying the two-dimensional film contacts the target substrate. After removing the polymer, the transfer of the two-dimensional film is completed.

[0018] Preferably, the polymer solution includes a polypropylene carbonate solution and a polymethyl methacrylate solution.

[0019] Preferably, the impurity removal method is to immerse the polymer carrying the two-dimensional film in an inorganic alkaline solution; the inorganic alkaline solution includes a sodium hydroxide solution or a potassium hydroxide solution; the concentration of the inorganic alkaline solution is 0.5-2 mol / L.

[0020] Preferably, the method for removing the polymer is to dissolve it in an organic solvent, and the organic solvent includes one or more of acetone, isopropanol and toluene.

[0021] The invention provides a pretreatment method for transferring a two-dimensional film from a mica substrate, comprising: first immersing the mica substrate on which the two-dimensional film is grown in an acidic solution, and then immersing it in an alkali metal chloride solution for a second time; the acidic solution does not react with the two-dimensional film.

[0022] The present invention uses an acid solution and an alkali metal chloride solution to treat the mica substrate in sequence, which can weaken the binding force of the mica substrate to the two-dimensional film without damaging the two-dimensional film, significantly improve the quality of the two-dimensional film transfer, reduce material defects and lattice distortion introduced by the transfer, and achieve the purpose of conveniently and efficiently transferring high-quality two-dimensional films. The pre-treatment method provided by the present invention is suitable for the transfer process of different types of two-dimensional films, and has a high transfer success rate, little sample damage, low cost, and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the transfer method provided by the present invention;

[0024] Figure 2 The conventional transfer method and the transfer method provided in Examples 1 to 3 transfer Bi 2 O 2 Physical picture of Se film;

[0025] Figure 3 Bi obtained by the conventional transfer method and the transfer method provided in Examples 1 to 3 2 O 2 Comparison of photocurrent response and device noise of Se thin film devices. DETAILED DESCRIPTION

[0026] The present invention provides a pre-treatment method for transferring a two-dimensional film from a mica substrate, comprising:

[0027] The mica substrate on which the two-dimensional film is grown is first immersed in an acidic solution and then immersed in an alkali metal chloride solution for a second time; the acidic solution does not react with the two-dimensional film.

[0028] In the present invention, the two-dimensional film preferably comprises Bi 2 O 2 Se film, Bi 2 Se 3 Thin film, MoS 2 Thin film or WSe 2 Film. In the present invention, the size of the mica substrate is preferably 1*1 cm, and the thickness is preferably 200 μm. In the present invention, the size of the two-dimensional film is preferably 50*50 μm, and the thickness is preferably 10 nm.

[0029] In the present invention, the acidic solution includes a hydrofluoric acid solution or a hydrochloric acid solution; the mass concentration of the acidic solution is 0.5-2%, specifically 0.5%, 1%, 1.5%, 2%. In the present invention, when the two-dimensional film is Bi 2 O 2When the Se film is formed, the acidic solution is preferably a hydrofluoric acid solution. In the present invention, the temperature of the first immersion is preferably room temperature, and the time is preferably 1 to 3 minutes. After the first immersion, the present invention also preferably includes cleaning the immersed substrate with deionized water and drying it with a nitrogen gun for standby use.

[0030] In the present invention, since the acidic solution has a corrosive effect on the mica substrate but no corrosive effect on the two-dimensional film, the dangling molecular bonds on the mica surface are destroyed, and the two-dimensional film is more easily peeled off from the mica substrate.

[0031] In the present invention, the alkali metal chloride solution preferably includes a sodium chloride solution or a potassium chloride solution; the concentration of the alkali metal chloride solution is preferably 0.5~2mol / L, specifically 0.5mol / L, 1mol / L, 1.5mol / L, 2mol / L. In the present invention, the second impregnation is preferably carried out under heating and ultrasonic conditions; the heating temperature is preferably 50~70°C, specifically 50°C, 60°C, 70°C, the ultrasonic power is preferably 40~60W, specifically 40W, 50W, 60W, and the time is preferably 3~5min. After the second impregnation, the present invention also preferably includes blowing the impregnated substrate dry with a nitrogen gun for standby use. In the present invention, the Cl in the alkali metal chloride solution - Ions and alkali metal cations can combine with unpaired chemical bonds on the surface of the substrate due to lattice termination to form stable chemical bonds. This process neutralizes the unpaired electrons of the dangling bonds, reducing the binding force of the substrate to the organic film. At the same time, since there are no dangling bonds on the surface of the two-dimensional film material, it is not easy to combine with the ions of the alkali metal chloride solution, and can form a strong contact with the organic film, further promoting the separation of the two-dimensional film from the mica substrate; at the same time, a layer of alkali metal chloride grain film is formed on the surface of the non-two-dimensional film area of ​​the mica substrate. In the present invention, the alkali metal chloride grain film protects the mica surface and avoids dissociation caused by the strong adsorption force of the organic film during the transfer process; at the same time, the alkali metal chloride grain film also increases the hydrophilicity of the mica surface and improves the stripping efficiency.

[0032] The present invention also provides a method for transferring a two-dimensional film from a mica substrate, comprising the following steps:

[0033] The pre-treatment method described in the above technical solution is used for pre-treatment to obtain a treated mica substrate;

[0034] Coating a polymer solution on the side of the treated mica substrate where the two-dimensional film is grown to obtain a mica substrate with a polymer attached thereto;

[0035] placing the mica substrate with the polymer attached thereto in water for peeling, thereby obtaining a polymer carrying a two-dimensional film;

[0036] The polymer carrying the two-dimensional film is immersed in an inorganic alkali solution and then attached to the surface of a target substrate. The transfer of the two-dimensional film is completed after the polymer is removed.

[0037] The present invention adopts the pretreatment method described in the above technical solution to perform pretreatment to obtain a treated mica substrate. In the present invention, the pretreatment process preferably refers to the steps of the pretreatment method described in the above technical solution, which will not be repeated here.

[0038] After obtaining the treated mica substrate, the present invention coats a polymer solution on the side of the treated mica substrate where the two-dimensional film is grown, to obtain a mica substrate with a polymer attached.

[0039] In the present invention, the polymer solution preferably includes polymethyl methacrylate solution (PMMA) and polypropylene carbonate solution (PPC).

[0040] In the present invention, the coating polymer solution is preferably a sequential coating of a polymethyl methacrylate solution and a polypropylene carbonate solution. In the present invention, the coating method is preferably spin coating.

[0041] In the present invention, the process of coating the polymethyl methacrylate solution is preferably: dripping the polymethyl methacrylate solution on the side of the treated mica substrate where the two-dimensional film is grown, first spin coating at 500 rpm for 5 seconds, then spin coating at 3000 rpm for 30 seconds, after the spin coating is completed, placing it on a 150°C hot plate for baking for 5 minutes to obtain a polymethyl methacrylate layer. In the present invention, the mass concentration of the polymethyl methacrylate solution is preferably 6-10%, and the solvent is preferably anisole. In the present invention, the thickness of the polymethyl methacrylate layer is preferably 400 nm, and the size of the polymethyl methacrylate layer is preferably the same as that of the mica substrate.

[0042] In the present invention, the process of coating the polypropylene carbonate solution is preferably: dripping the polypropylene carbonate solution on the surface of the polymethyl methacrylate layer, first spin coating at 500rpm for 5s, then spin coating at 3000rpm for 30s, after the spin coating is completed, placing it on a 120°C hot plate for baking for 3min to form a polypropylene carbonate layer. In the present invention, the mass concentration of the polypropylene carbonate solution is preferably 15%, and the solvent is preferably anisole. In the present invention, the thickness of the polypropylene carbonate layer is preferably 600nm, and the size of the polypropylene carbonate layer is preferably the same as the size of the mica substrate.

[0043] After obtaining the mica substrate with the polymer attached, the present invention places the mica substrate with the polymer attached in water for peeling to obtain the polymer carrying the two-dimensional film.

[0044] In the present invention, the water is preferably deionized water, and the peeling time is preferably 30 minutes. After the peeling, the present invention also preferably includes peeling the polymer carrying the two-dimensional film from the surface of the mica substrate with tweezers. In the present invention, due to the existence of the surface tension of the material, the polymer carrying the two-dimensional film will be evenly spread on the surface of the deionized water.

[0045] After obtaining the polymer carrying the two-dimensional film, the present invention removes impurities from the polymer carrying the two-dimensional film and then attaches it to the surface of the target substrate so that the side carrying the two-dimensional film contacts the target substrate, and completes the transfer of the two-dimensional film after removing the polymer.

[0046] In the present invention, the impurity removal method is preferably to immerse the polymer carrying the two-dimensional film in an inorganic alkali solution; the inorganic alkali solution preferably includes a sodium hydroxide solution or a potassium hydroxide solution; the concentration of the inorganic alkali solution is preferably 0.5-2 mol / L, specifically 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L. In the present invention, by immersing in an inorganic alkali solution, the alkali chloride on the surface of the polymer will dissolve in the solution due to the high solubility of the alkali chloride crystals; the mica fragments will react with the inorganic alkali solution and dissolve in the solution, thereby removing the alkali chloride and mica fragments on the polymer to achieve impurity removal.

[0047] The present invention has no special limitation on the type of target substrate, and any substrate known to those skilled in the art can be used. In the present invention, the attachment process is preferably as follows: the impregnated polymer carrying the two-dimensional film is evenly spread on the surface of deionized water, with the side carrying the two-dimensional film facing upward, the target substrate is clamped with tweezers and inserted into the deionized water, and the target substrate is slowly brought close to the polymer film on the surface of the deionized water until the film is completely attached to the surface of the target substrate.

[0048] In the present invention, the method for removing the polymer is preferably to dissolve using an organic solvent, and the organic solvent preferably includes one or more of acetone, isopropanol and toluene; the acetone is preferably anhydrous acetone. The present invention has no particular limitation on the time of dissolution, as long as the polymer can be completely dissolved. After the dissolution, the present invention also preferably includes blowing the target substrate dry with nitrogen to complete the transfer.

[0049] The process schematic diagram of the transfer method provided by the present invention is as follows Figure 1 shown.

[0050] Unless otherwise specified, the materials and equipment used in the present invention are all commercially available products in the art.

[0051] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Example 1

[0053] Step 1: Prepare hydrogen fluoride solution: Take 5g of 15% industrial hydrogen fluoride solution in a polyethylene (PP) bottle filled with 70g of deionized water, shake it thoroughly to mix the solution completely, and obtain a 1% hydrogen fluoride solution;

[0054] Step 2: Prepare sodium chloride solution: take 2.925 g of sodium chloride crystals into a polyethylene (PP) bottle filled with 50 mL of deionized water, shake it thoroughly to mix the solution completely, and obtain a sodium chloride solution with a molar mass fraction of 1 mol / L;

[0055] Step 3: Prepare PPC solution: dissolve 3g of PPC in 17g of anisole, place on a magnetic stirrer and stir at 90°C for 2h to obtain a PPC solution; the PMMA solution is industrial A5 PMMA model, and its ratio is a PMMA / anisole solution with a mass concentration of 6%;

[0056] Step 4: Prepare sodium hydroxide solution. Take 2g of sodium hydroxide in a polyethylene (PP) bottle filled with 50mL of deionized water, shake it thoroughly to mix the solution completely, and obtain a sodium hydroxide solution with a molar mass fraction of 1mol / L;

[0057] Step 5: Prepare the Bi- 2 O 2 The mica substrate of the Se film was placed in a 1% hydrogen fluoride solution, left to soak for 3 minutes at room temperature, then taken out, cleaned with deionized water, and dried with a nitrogen gun for later use;

[0058] Step 6: Place the mica substrate obtained in step 5 into a 1 mol / L sodium chloride solution, heat it in a water bath at 60°C and perform ultrasound at 50W for 5 minutes, then take the mica substrate out of the sodium chloride solution, blow dry it with a nitrogen gun and set it aside to obtain a treated mica substrate;

[0059] Step 7: Place the treated mica substrate on the rotary vacuum table of the glue spreader, vacuum adsorb the substrate, drip PMMA solution on the surface, spin coat at 500 rpm for 5 seconds, then spin coat at 3000 rpm for 30 seconds, remove the substrate, place it on a 150°C hot plate and bake for 5 minutes to obtain a PMMA layer with a thickness of 400 nm; place the mica substrate on the rotary vacuum table of the glue spreader again, vacuum adsorb the substrate, drip PPC solution on the surface of the PMMA layer, spin coat at 500 rpm for 5 seconds, then spin coat at 3000 rpm for 30 seconds, remove the substrate, place it on a 120°C hot plate and bake for 3 minutes to complete the preparation of PMMA / PPC polymer;

[0060] Step 8: Place the mica substrate obtained in step 7 in deionized water and soak for 30 minutes. Then, use tweezers to remove the Bi 2 O 2 The PMMA / PPC polymer of Se film was peeled off from the mica surface to obtain Bi 2 O 2 The PMMA / PPC polymer of the Se film was evenly spread on the surface of deionized water;

[0061] Step 9: The Bi-loaded 2 O 2 The PMMA / PPC polymer of the Se film was spread evenly on the surface of 1 mol / L sodium hydroxide solution, and the sodium chloride grains and mica fragments on it were removed;

[0062] Step 10: Spread the PMMA / PPC polymer processed in step 9 evenly on the surface of deionized water, hold the target substrate with tweezers and insert it into the deionized water, and slowly bring the target substrate close to the PMMA / PPC film on the surface of the deionized water until the film is completely attached to the surface of the target substrate;

[0063] Step 11: Place the target substrate obtained in step 10 in a glass container and add acetone to soak for 10 minutes. The PMMA / PPC film will be dissolved and Bi 2 O 2 The Se film adheres to the target substrate and is transferred after being gently dried with a nitrogen gun.

[0064] Example 2

[0065] Step 1: Prepare hydrogen fluoride solution: Take 5g of 15% industrial hydrogen fluoride solution in a polyethylene (PP) bottle filled with 145g deionized water, shake it thoroughly to mix the solution completely, and obtain a 0.5% hydrogen fluoride solution;

[0066] Step 2: Prepare sodium chloride solution: take 2.925 g of sodium chloride crystals into a polyethylene (PP) bottle filled with 100 mL of deionized water, shake it thoroughly to mix the solution completely, and obtain a sodium chloride solution with a molar mass fraction of 0.5 mol / L;

[0067] Step 3: Prepare PPC solution: dissolve 3g of PPC in 17g of anisole, place on a magnetic stirrer and stir at 90°C for 2h to obtain a PPC solution; the PMMA solution is industrial A5 PMMA model, and its ratio is a PMMA / anisole solution with a mass concentration of 6%;

[0068] Step 4: Prepare sodium hydroxide solution. Take 2g of sodium hydroxide and put it into a polyethylene (PP) bottle filled with 100mL of deionized water. Shake it thoroughly to mix the solution completely, and obtain a sodium hydroxide solution with a molar mass fraction of 0.5mol / L.

[0069] Step 5: Prepare the Bi- 2 O 2 The mica substrate of the Se film was placed in a 0.5% by mass hydrogen fluoride solution, left to soak for 3 min at room temperature, then taken out, cleaned with deionized water, and dried with a nitrogen gun for later use;

[0070] Step 6: Place the mica substrate obtained in step 5 into a 0.5 mol / L sodium chloride solution, heat it in a water bath at 50°C and perform ultrasound at 40W for 5 minutes, then take the mica substrate out of the sodium chloride solution, blow dry it with a nitrogen gun and set it aside to obtain a treated mica substrate;

[0071] Step 7: Place the treated mica substrate on the rotary vacuum table of the glue spreader, vacuum adsorb the substrate, drip PMMA solution on the surface, spin coat at 500 rpm for 5 seconds, then spin coat at 3000 rpm for 30 seconds, remove the substrate, place it on a 150°C hot plate and bake for 5 minutes to obtain a PMMA layer with a thickness of 400 nm; place the mica substrate on the rotary vacuum table of the glue spreader again, vacuum adsorb the substrate, drip PPC solution on the surface of the PMMA layer, spin coat at 500 rpm for 5 seconds, then spin coat at 3000 rpm for 30 seconds, remove the substrate, place it on a 120°C hot plate and bake for 3 minutes to complete the preparation of PMMA / PPC polymer;

[0072] Step 8: Place the mica substrate obtained in step 7 in deionized water and soak for 30 minutes. Then, use tweezers to remove the Bi 2 O 2 The PMMA / PPC polymer of Se film was peeled off from the mica surface to obtain Bi 2 O 2The PMMA / PPC polymer of the Se film was evenly spread on the surface of deionized water;

[0073] Step 9: The Bi-loaded 2 O 2 The PMMA / PPC polymer of the Se film was spread evenly on the surface of 0.5 mol / L sodium hydroxide solution, and the sodium chloride grains and mica fragments on it were removed;

[0074] Step 10: Spread the PMMA / PPC polymer processed in step 9 evenly on the surface of deionized water, hold the target substrate with tweezers and insert it into the deionized water, and slowly bring the target substrate close to the PMMA / PPC film on the surface of the deionized water until the film is completely attached to the surface of the target substrate;

[0075] Step 11: Place the target substrate obtained in step 10 in a glass container and add acetone to soak for 10 minutes. The PMMA / PPC film will be dissolved and Bi 2 O 2 The Se film adheres to the target substrate and is transferred after being gently dried with a nitrogen gun.

[0076] Example 3

[0077] Step 1: Prepare hydrogen fluoride solution: Take 5g of 15% industrial hydrogen fluoride solution in a polyethylene (PP) bottle filled with 32.5g deionized water, shake it thoroughly to mix the solution completely, and obtain a 2% hydrogen fluoride solution;

[0078] Step 2: Prepare sodium chloride solution: Take 2.925 g of sodium chloride crystals into a polyethylene (PP) bottle filled with 25 mL of deionized water, shake it thoroughly to mix the solution completely, and obtain a sodium chloride solution with a molar mass fraction of 2 mol / L;

[0079] Step 3: Prepare PPC solution: dissolve 3g of PPC in 17g of anisole, place on a magnetic stirrer and stir at 90°C for 2h to obtain a PPC solution; the PMMA solution is industrial A5 PMMA model, and its ratio is a PMMA / anisole solution with a mass concentration of 6%;

[0080] Step 4: Prepare sodium hydroxide solution. Take 2g of sodium hydroxide in a polyethylene (PP) bottle filled with 25mL of deionized water, shake it thoroughly to mix the solution completely, and obtain a sodium hydroxide solution with a molar mass fraction of 2mol / L;

[0081] Step 5: Prepare the Bi- 2 O 2The mica substrate of the Se film was placed in a 2% by mass hydrogen fluoride solution, left to soak for 3 minutes at room temperature, then taken out, cleaned with deionized water, and dried with a nitrogen gun for later use;

[0082] Step 6: Place the mica substrate obtained in step 5 into a 2 mol / L sodium chloride solution, heat it in a water bath at 70°C and perform ultrasound at 60W for 5 minutes, then take the mica substrate out of the sodium chloride solution, blow dry it with a nitrogen gun and set it aside to obtain a treated mica substrate;

[0083] Step 7: Place the treated mica substrate on the rotary vacuum table of the glue spreader, vacuum adsorb the substrate, drip PMMA solution on the surface, spin coat at 500 rpm for 5 seconds, then spin coat at 3000 rpm for 30 seconds, remove the substrate, place it on a 150°C hot plate and bake for 5 minutes to obtain a PMMA layer with a thickness of 400 nm; place the mica substrate on the rotary vacuum table of the glue spreader again, vacuum adsorb the substrate, drip PPC solution on the surface of the PMMA layer, spin coat at 500 rpm for 5 seconds, then spin coat at 3000 rpm for 30 seconds, remove the substrate, place it on a 120°C hot plate and bake for 3 minutes to complete the preparation of PMMA / PPC polymer;

[0084] Step 8: Place the mica substrate obtained in step 7 in deionized water and soak for 30 minutes. Then, use tweezers to remove the Bi 2 O 2 The PMMA / PPC polymer of Se film was peeled off from the mica surface to obtain Bi 2 O 2 The PMMA / PPC polymer of the Se film was evenly spread on the surface of deionized water;

[0085] Step 9: The Bi-loaded 2 O 2 The PMMA / PPC polymer of the Se film was spread evenly on the surface of 2 mol / L sodium hydroxide solution, and the sodium chloride grains and mica fragments on it were removed;

[0086] Step 10: Spread the PMMA / PPC polymer processed in step 9 evenly on the surface of deionized water, hold the target substrate with tweezers and insert it into the deionized water, and slowly bring the target substrate close to the PMMA / PPC film on the surface of the deionized water until the film is completely attached to the surface of the target substrate;

[0087] Step 11: Place the target substrate obtained in step 10 in a glass container and add acetone to soak for 10 minutes. The PMMA / PPC film will be dissolved and Bi 2 O 2 The Se film adheres to the target substrate and is transferred after being gently dried with a nitrogen gun.

[0088] Performance Testing

[0089] Test Example 1

[0090] Figure 2 The Bi obtained by the conventional thin film transfer method (i.e., the transfer method without pre-treatment step) and the transfer method of Examples 1 to 3 is 2 O 2 Physical picture of Se film, where Figure 2 (1) is the traditional thin film transfer method. Figure 2 (2) is Example 1, Figure 2 (3) is Example 2, Figure 2 (4) is Example 3; it can be seen that the transfer method provided by the present invention can greatly reduce the mica surface to the target Bi 2 O 2 The binding force of Se film greatly improves the transfer efficiency and avoids the damage of film material caused during the transfer process.

[0091] Figure 3 Bi obtained by the conventional thin film transfer method without pre-treatment scheme and the transfer method of Examples 1 to 3 2 O 2 Comparison of photocurrent responses of Se thin film devices ( Figure 3 (1)) and device noise comparison chart ( Figure 3 (2)).

[0092] Photocurrent test method: The thin film device was irradiated with a THORLABS PL520 laser with a light power of 5 microwatts, and the photocurrent value of the device was recorded using a Keithley 2400 source meter.

[0093] Noise current test method: In dark conditions, use the DSA800 spectrum analyzer to record the device noise current value. The detection rate is calculated using the formula: Where A is the photosensitive area of ​​the device, which is 2.5×10 - 5 cm 2 , R is the device responsivity (unit: A / W) defined as the ratio of photocurrent to incident light power, is the device noise.

[0094] in Figure 3 In (1), the black curve is the photocurrent response of the thin film device after Example 1, the red curve is the photocurrent response of the thin film device after Example 2, the blue curve is the photocurrent response of the thin film device after Example 3, and the purple line is the photocurrent response of the thin film device of the traditional transfer scheme. Figure 3In (2), the green dotted line is the noise current level of the thin film device after Example 1, the purple dotted line is the noise current level of the thin film device after Example 2, the red dotted line is the noise current level of the thin film device after Example 3, and the blue dotted line is the noise current level of the thin film device of the traditional transfer scheme; the specific test results are shown in Table 1;

[0095] Table 1 Performance test results of thin film devices obtained by transfer in Example

[0096]

[0097] It can be seen that the transfer method provided by the present invention can greatly improve the target Bi 2 O 2 The film quality of Se film is improved, the light response capability is improved, and the noise caused by factors such as recombination is reduced.

[0098] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A pre-treatment method for transferring a two-dimensional thin film from a mica substrate, characterized in that: include: The mica substrate on which the two-dimensional film is grown is first immersed in an acid solution, and then immersed in an alkali metal chloride solution for a second time; The acidic solution does not react with the two-dimensional film.

2. The pre-treatment method according to claim 1, characterized in that: The acidic solution includes a hydrofluoric acid solution or a hydrochloric acid solution; the mass concentration of the acidic solution is 0.5-2%.

3. The pre-treatment method according to claim 1 or 2, characterized in that: The temperature of the first dipping is room temperature, and the time is 1 to 3 minutes.

4. The pre-treatment method according to claim 1, characterized in that: The alkali metal chloride solution includes a sodium chloride solution or a potassium chloride solution; the concentration of the alkali metal chloride solution is 0.5-2 mol / L.

5. The pre-treatment method according to claim 1 or 4, characterized in that: The second immersion is carried out under heating and ultrasonic conditions; the heating temperature is 50-70° C., the ultrasonic power is 40-60 W, and the time is 3-5 min.

6. The pre-treatment method according to claim 1, characterized in that: The two-dimensional film includes a Bi2O2Se film, a Bi2Se3 film, a MoS2 film or a WSe2 film.

7. A method for transferring a two-dimensional film from a mica substrate, characterized in that: The following steps are involved: Pre-treating by the pre-treatment method according to any one of claims 1 to 6 to obtain a treated mica substrate; Coating a polymer solution on the side of the treated mica substrate where the two-dimensional film is grown to obtain a mica substrate with a polymer attached thereto; placing the mica substrate with the polymer attached thereto in water for peeling, thereby obtaining a polymer carrying a two-dimensional film; After removing impurities from the polymer carrying the two-dimensional film, the polymer is attached to the surface of a target substrate so that the side carrying the two-dimensional film contacts the target substrate. After removing the polymer, the transfer of the two-dimensional film is completed.

8. The method according to claim 7, characterized in that The polymer solution includes a polypropylene carbonate solution and a polymethyl methacrylate solution.

9. The method according to claim 7, characterized in that: The impurity removal method is to immerse the polymer carrying the two-dimensional film in an inorganic alkali solution; the inorganic alkali solution includes a sodium hydroxide solution or a potassium hydroxide solution; the concentration of the inorganic alkali solution is 0.5-2 mol / L.

10. The method according to claim 7, characterized in that The method for removing the polymer is to dissolve it with an organic solvent, and the organic solvent includes one or more of acetone, isopropanol and toluene.

Images