Preparation method of deformed graphene field effect sensor

Abstract

The invention discloses a preparation method of a deformed graphene field effect sensor, and the method comprises the following steps: S1, graphene growth: employing a CVD method, and preparing high-quality single-layer graphene through the pretreatment of a copper foil and the optimization of growth parameters; s2, graphene transfer: cleaning the silicon wafer by using a Piranha solution (the ratio of H2SO4 to H2O2 solution is 7: 3), dropwise adding AuNPs with the particle size of 10nm on the surface of the silicon wafer, and dissolving the copper foil in combination with a PMMA support structure and a FeCl3 solution to realize efficient transfer of graphene; s3, covering and etching the template for the first time; and S4, covering the evaporation electrode with the template for the second time. The finally prepared deformed graphene field effect sensor has remarkable advantages in an electrical property test, the drain current is increased to 2.73 [mu] A from 230nA of conventional graphene, the current is discharged by about 10 times, and the deformed graphene field effect sensor has excellent field effect characteristics and sensitivity. The method is high in repeatability, and the prepared sensor is excellent in performance and suitable for the fields of high-sensitivity gas detection, biosensing, environment monitoring and the like.

Description

Technical Field

[0001] The present invention relates to the field of preparation of biosensors, and more specifically to a method for preparing a deformed graphene field-effect sensor. Background Art

[0002] The deformed graphene field-effect biosensor is a cutting-edge biosensing technology based on graphene materials. In recent years, with the rapid development of biodietection technology, the demand for high sensitivity, high specificity, and real-time detection capabilities has been increasing day by day. Graphene has become a research hotspot in the field of biosensors due to its unique physical and chemical properties.

[0003] Graphene is a two-dimensional material composed of carbon atoms arranged in a hexagonal honeycomb lattice, with an extremely high specific surface area, excellent charge transport ability, and outstanding mechanical strength. These properties make graphene very suitable for the detection of biomolecules. In addition, the electronic structure of graphene is adjustable, and high-sensitivity detection of biomolecules can be achieved through means such as surface functionalization or doping. The self-doping property and low electrical noise property of graphene further enhance its potential in biosensing applications.

[0004] The deformed graphene field-effect biosensor usually grows graphene by chemical vapor deposition (CVD) and transfers it to an insulating substrate such as sapphire or flexible polyethylene terephthalate (PET). This process can endow the sensor with a certain degree of flexibility while reducing production costs. The design of the sensor usually combines biorecognition elements (such as antibodies, nucleic acid aptamers, etc.) to achieve the recognition and detection of specific biomolecules, showing high sensitivity and specificity. Its main applications include the detection of inflammatory markers, viral RNA / DNA, etc., and can be widely used in the fields of biomedical detection, disease diagnosis, and public health monitoring.

[0005] Although the deformed graphene field-effect biosensor has shown great potential in the field of biodietection, its practical application still faces some challenges. For example, how to control the quality and uniformity of graphene in large-scale production, how to reduce production costs, and how to improve the long-term stability of the sensor are all problems that need to be solved urgently at present. Therefore, further developing a reliable, economical, and high-performance method for preparing a deformed graphene field-effect biosensor is of great significance for promoting the technological progress in this field. Summary of the Invention

[0006] To solve the problems existing in the prior art, the present invention provides a preparation method of a deformed graphene field effect sensor, and the specific scheme is as follows:

[0007] A preparation method of a deformed graphene field effect sensor, the preparation method comprising the following steps:

[0008] S1. Growth of graphene:

[0009] S101. Pretreatment of copper foil: Cut the copper foil to a size smaller than the quartz boat to avoid wrinkles and bends;

[0010] S102: Immerse in acetic acid solution to remove oxides and flatten the surface of the copper foil;

[0011] S103. Grow graphene in a tube furnace;

[0012] S2. Transfer of graphene:

[0013] S201: Clean the silicon wafer with Piranha solution;

[0014] S202. Pretreatment of silicon wafer: Drop about 150 μL of AuNPs solution on the surface of the silicon wafer and let it dry naturally;

[0015] S203. Transfer graphene;

[0016] S3. First template covering and etching: Remove excess graphene and impurities by reactive ion etching under the action of O 2 plasma to form a graphene strip structure;

[0017] S4. Second template covering and electrode evaporation: Evaporate Cr and Au electrodes and perform resistance evaporation coating at the positions fixed by the mask plate.

[0018] Further, S103 further comprises the following sub-steps: First, place the copper foil in a quartz boat and send it into the tube furnace, evacuate to 3 - 4 Pa; then introduce hydrogen with a flow rate of 10 sccm, heat the furnace to 1000 °C; after preheating for 15 minutes, introduce CH 4 gas with a flow rate of 4 sccm, adjust the flow rate of H 2 gas to 8 sccm, maintain this proportional flow rate for 35 minutes; finally, after introducing CH 4 gas for 20 minutes, stop the supply of CH 4 gas, introduce 10 sccm of hydrogen, and cool to room temperature for 2 - 3 hours under this condition, then take out the copper foil with graphene grown on its surface for use.

[0019] Further, S201 further comprises the following sub-steps:

[0020] S201a Prepare the solution: The volume ratio of the solution is concentrated H 2 SO 4 :H 2 O 2 solution is 7:3. First, put the concentrated H 2 SO 4 in the petri dish, and then use a dropper to slowly drop the H 2 O 2 solution onto the concentrated H 2 SO 4 slowly along the wall;

[0021] S201b: Slowly put the cut silicon wafers into the solution in the petri dish one by one, shake the petri dish to immerse all the silicon wafers in the cleaning solution, and pay attention to avoid overlapping between the silicon wafers as much as possible;

[0022] S201c: Adjust the temperature of the hot plate to between 85 - 95 °C, soak for about 2 h at this temperature. The sign that the silicon wafers are cleaned is that there are no more bubbles on the surface;

[0023] S201d: After cooling the cleaning solution to room temperature, pour it into the waste liquid bucket, add ultrapure water to the petri dish, and wash it repeatedly 3 times, about 10 min each time until the cleaning is completed;

[0024] S201e: Dry the cleaned silicon wafers with nitrogen, put them into the petri dish, seal and store them for later use.

[0025] Furthermore, the particle size of AuNPs in S202 is 10 nm.

[0026] Furthermore, S203 also includes the following sub - steps:

[0027] S203a: Cut the copper sheet with grown graphene into a shape slightly larger than the silicon wafer and coat the silicon wafer;

[0028] S203b, Glue coating: Place the coated silicon wafer on the middle suction hole of the tabletop spin coater, and drop 0.1 - 0.15 mL of PMMA with a molecular weight of 495000 and a concentration of A6 on the surface of the copper sheet;

[0029] S203c: Adjust the rotation speed to 4000 r / min and the time to 45 s, start the spin coater to rotate, and then bake at 180 °C for 2 min;

[0030] S203d, Tape sticking: Wipe the special glass table clean, stick the special tape, cut it according to the coated graphene - silicon wafer as a standard; use a cutter to draw a glue frame, align one side of the glue frame with the lower edge of the copper foil, stick it in one go, and cut off the excess copper sheet or glue frame;

[0031] S203e: Slowly move the graphene with the glue frame to the prepared FeCl 3In the solution, seal it and let it corrode for about one day, and the copper foil will be completely dissolved;

[0032] S203f: After the copper corrosion is completed, wash it with ultrapure water;

[0033] S203g: Take out the sample from the ultrapure water, carefully stick it to the silicon wafer with AuNPs attached to the surface, and place it on a hot plate at 45 °C until the water between the silicon wafer and the sample is dried;

[0034] S203h: Carefully cut off the glue frame with a blade, then use tweezers to remove the glue frame, leaving the transferred deformed graphene; Immerse the transferred deformed graphene in acetone solution for more than one day to remove the PMMA on the surface of the deformed graphene, observe the degumming effect under a microscope, and seal it for standby.

[0035] Furthermore, in S4, the thickness of Cr is 80 nm, the evaporation current is 200 A, and the evaporation time is 8 - 9 minutes; the thickness of Au is 600 nm, the evaporation current is 150 A, and the evaporation time is until the film thickness is completed.

[0036] Furthermore, when preparing the FeCl 3 solution in S203e, an appropriate amount of HCl solution should be added to prevent Fe 3+ hydrolysis.

[0037] Furthermore, in S203b, the volume of PMMA is 0.1 - 0.15 mL, the molecular weight is 495000, and the concentration is A6.

[0038] Beneficial effects:

[0039] The present invention provides a preparation method of a deformed graphene field effect sensor, having the following beneficial effects:

[0040] (1) In electrical tests, compared with conventional graphene, the current of deformed graphene has increased significantly from about 230 nA to about 2.73 μA, nearly 10 times. This indicates that deformed graphene regulates the carrier mobility through deformation, thereby greatly improving its field effect transmission characteristics. This significant improvement makes deformed graphene have more extensive application potential in the field of high-sensitivity sensing.

[0041] (2) The present invention uses chemical vapor deposition method (growing high-quality single-layer graphene on copper foil, and by strictly controlling the flow ratio of CH 4 and H 2 to 1:2 and the growth time of 20 minutes, effectively improving the uniformity and monolayer property of the graphene film, and avoiding the formation of multi-layer graphene or defective graphene. By pre-treating the copper foil with acetic acid, the oxide layer is effectively removed and the surface of the copper foil is flattened, improving the quality of graphene growth.

[0042] (3) During the transfer process of graphene, by using AuNPs (particle size 10 nm) to modify the surface of the silicon wafer, the binding force between graphene and the substrate is enhanced, significantly reducing the breakage and slippage phenomena during the graphene transfer process. Through PMMA support and glue frame design, the mechanical support ability of graphene is enhanced. Combining with the method of using FeCl 3 solution and appropriate amount of HCl to dissolve the copper foil, the transfer quality of graphene is further optimized, avoiding the fracture and residual pollution of graphene.

[0043] (4) During the transfer and etching process of graphene, using the reactive ion etching (RIE) process, under the action of O 2 plasma, the excess graphene and impurities can be accurately removed to form a high-quality graphene strip structure, laying a good foundation for subsequent electrode evaporation. During the electrode evaporation process, by evaporating Cr (80 nm) and Au (600 nm) step by step and strictly controlling the current and evaporation time, the high conductivity and adhesion of the electrode are ensured, thereby improving the overall performance and stability of the device.

[0044] (5) Adopting the method of combining FeCl 3 solution with a small amount of HCl to dissolve the copper foil, avoiding the dependence on strong corrosive reagents in the traditional transfer method. At the same time, by washing with ultrapure water for a long time, the surface impurities are reduced, ensuring the cleanliness and environmental friendliness of the sample. The PMMA coating technology used in the preparation process can effectively protect graphene. Subsequently, the PMMA residue is dissolved by acetone, ensuring the cleanliness of the graphene surface, not affecting the electrical properties, and at the same time reducing material waste. Description of the Drawings

[0045] Figure 1 is a diagram showing the measurement of the electrical properties of conventional graphene.

[0046] Figure 2 is a diagram showing the measurement of the electrical properties of deformed graphene. Detailed Embodiments

[0047] To deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with embodiments. These embodiments are only used to explain the present invention and do not limit the protection scope of the present invention.

[0048] Embodiment:

[0049] A preparation method of a deformed graphene field effect sensor includes the following steps:

[0050] S1. Growth of graphene:

[0051] S101. Pretreatment of the copper foil: Cut the copper foil to a size smaller than the quartz boat to avoid wrinkles and bends;

[0052] S102: Immerse in an acetic acid solution to remove oxides and flatten the surface of the copper foil;

[0053] S103. Grow graphene in a tube furnace:

[0054] First, place the copper foil in a quartz boat and send it into the tube furnace, evacuate to 3 - 4 Pa; then introduce hydrogen with a flow rate of 10 sccm, heat the furnace to 1000 °C; after preheating for 15 minutes, introduce CH 4 gas with a flow rate of 4 sccm, adjust the flow rate of H 2 gas to 8 sccm, maintain this proportional flow rate for 35 minutes; finally, after introducing CH 4 gas for 20 minutes, stop the supply of CH 4 gas, introduce 10 sccm of hydrogen, cool to room temperature under this condition for 2 - 3 hours, and take out the copper foil with graphene grown on its surface for standby.

[0055] S2. Transfer of graphene:

[0056] S201: Clean the silicon wafer with Piranha solution:

[0057] S201a Prepare the solution: The volume ratio of the solution is concentrated H 2 SO 4 : H 2 O 2 solution is 7:3. First, put concentrated H 2 SO 4 in a petri dish, and then use a dropper to slowly drip H 2 O 2 solution slowly along the wall of the dish into concentrated H 2 SO 4 ;

[0058] S201b: Slowly place the cut silicon wafers into the solution in the petri dish one by one, shake the petri dish to immerse all the silicon wafers in the cleaning solution, and pay attention to avoid overlapping between the silicon wafers as much as possible;

[0059] S201c: Adjust the temperature of the hot plate to between 85 - 95 °C, soak for about 2 h at this temperature. The sign that the silicon wafer is cleaned is that there are no more bubbles on the surface;

[0060] S201d: After cooling the cleaning solution to room temperature, pour it into the waste liquid bucket, add ultrapure water to the petri dish, and wash it repeatedly 3 times, about 10 minutes each time until the cleaning is completed;

[0061] S201e: Dry the cleaned silicon wafers with nitrogen, put them into a petri dish, seal and store for standby.

[0062] S202. Wafer pretreatment: Drop approximately 150 μL of AuNPs solution onto the wafer surface and let it dry naturally;

[0063] S203. Transfer graphene:

[0064] S203a: Cut the copper sheet with grown graphene into a shape slightly larger than the wafer and coat the wafer;

[0065] S203b. Glue coating: Place the coated wafer on the middle suction hole of a tabletop spin coater, and drop 0.1 - 0.15 mL of PMMA with a molecular weight of 495000 and a concentration of A6 onto the surface of the copper sheet;

[0066] S203c: Adjust the rotation speed to 4000 r / min and the time to 45 s, start the spin coater to rotate, and then bake at 180 °C for 2 min;

[0067] S203d. Tape sticking: Wipe the special glass table clean, stick the special tape, and cut it according to the wafer coated with graphene as a standard; Use a cutter to draw a glue frame, align one side of the glue frame with the lower edge of the copper foil, stick it in one go, and cut off the excess copper sheet or glue frame;

[0068] S203e: Slowly move the graphene with the glue frame to the prepared FeCl 3 solution (when preparing the FeCl 3 solution, an appropriate amount of HCl solution should be added to prevent Fe 3+ hydrolysis), seal it, and let it corrode for about one day until the copper foil is completely dissolved;

[0069] S203f: After the copper etching is completed, wash it with ultrapure water;

[0070] S203g: Take out the sample from the ultrapure water, carefully stick it to the wafer with AuNPs attached to the surface, and place it on a hot plate at 45 °C until the water between the wafer and the sample is dried;

[0071] S203h: Carefully cut off the glue frame with a blade, then use tweezers to remove the glue frame, leaving the transferred deformed graphene; Soak the transferred deformed graphene in acetone solution for more than one day to remove the PMMA on the surface of the deformed graphene, observe the degumming effect under a microscope, and seal it for standby.

[0072] S3. First template covering and etching: Through reactive ion etching, remove the excess graphene and impurities under the action of O 2 plasma to form a graphene strip structure;

[0073] S4. Second template-overlay evaporation deposition of electrodes: Evaporate deposit Cr and Au electrodes, and conduct resistance evaporation coating at the positions fixed by the mask plate. The thickness of Cr is 80 nm, the evaporation current is 200 A, and the evaporation time is 8 - 9 minutes; the thickness of Au is 600 nm, the evaporation current is 150 A, and the evaporation time is until the film layer thickness is completed.

[0074] Among them, the particle size of AuNPs in S202 is 10 nm.

[0075] Optimizing the particle size of AuNPs to 10 nm can not only provide sufficient surface energy to enhance the bonding force between graphene and the silicon wafer substrate, but also prevent surface roughness or uneven distribution due to overly large particles. This significantly improves the stability and adhesion performance after graphene transfer. The uniform distribution of 10-nm AuNPs on the silicon wafer can effectively promote the electron transfer efficiency at the interface, thereby enhancing the sensitivity and signal output stability of the graphene field-effect sensor.

[0076] Among them, when preparing the FeCl 3 solution in S203e, an appropriate amount of HCl solution should be added to prevent Fe 3+ hydrolysis.

[0077] Among them, the volume of PMMA in S203b is 0.1 - 0.15 mL, the molecular weight is 495000, and the concentration is A6.

[0078] Conduct electrical property measurement

[0079] For the prepared deformed graphene molecular device, measure the basic properties of the device through a semiconductor parameter analyzer on the probe station: source (S), gate (G), drain (D). The gate voltage is selected as -10 - 10 V, and the source-drain voltage is selected as 50 mV. At V S-D of 50 mV, the measured current value may range from a few microamperes to more than ten microamperes. Figure 1 For the measurement of the electrical properties of conventional graphene, it is about 230 nA or so, Figure 2 while for the measurement of the electrical properties of deformed graphene, it is about 2.73 μA, and the current effect is amplified by about 10 times.

[0080] As a further improvement, the above is only the preferred embodiment of the present invention and is not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a deformable graphene field effect sensor, characterized in that: The preparation method comprises the following steps: S1. Growth of graphene: S101, pre-treating the copper foil: cutting the copper foil to a size smaller than the quartz boat to avoid wrinkles and bends; S102: Soak in acetic acid solution to remove oxides and smooth the surface of the copper foil; S103, growing graphene in a tube furnace; S2. Transfer of graphene: S201: Clean the silicon wafer using Piranha solution; S202, silicon wafer pretreatment: about 150 μL of AuNPs solution is added to the surface of the silicon wafer and dried naturally; S203, transferring graphene; S3, first template covering etching: using reactive ion etching to remove excess graphene and impurities under the action of O2 plasma to form a graphene strip structure; S4, the second template covers the evaporated electrode: evaporate Cr and Au electrodes, and perform resistance evaporation coating at the fixed position of the mask plate.

2. The method for preparing a deformable graphene field effect sensor according to claim 1, characterized in that: S103 also includes the following sub-steps: first, placing the copper foil in a quartz boat and sending it into a tubular furnace, evacuating to 3-4Pa; then introducing hydrogen with a flow rate of 10sccm, and raising the temperature in the furnace to 1000°C; after preheating for 15 minutes, introducing CH4 gas with a flow rate of 4sccm, adjusting the H2 gas flow rate to 8sccm, and maintaining this proportional flow rate for 35 minutes; finally, after introducing CH4 gas for 20 minutes, stop the CH4 gas supply, introduce 10sccm of hydrogen, cool to room temperature for 2-3 hours under this condition, and take out the copper foil with graphene grown on the surface for standby use.

3. The method for preparing a deformable graphene field effect sensor according to claim 1, characterized in that: S201 also includes the following sub-steps: S201a solution preparation: The volume ratio of the solution is 7:3 for concentrated H2SO4:H2O2 solution. First, put the concentrated H2SO4 into the culture dish, then use a dropper to suck up the H2O2 solution and slowly drip it onto the concentrated H2SO4. S201b: Slowly place the cut silicon wafers into the culture dish solution one by one, shake the culture dish to make all the silicon wafers immersed in the cleaning solution, and pay attention to avoid overlapping between the silicon wafers as much as possible; S201c: Adjust the temperature of the heating plate to between 85-95℃ and soak at this temperature for about 2 hours. The sign that the silicon wafer is clean is that there are no more bubbles on the surface. S201d: After the cleaning solution is cooled to room temperature, pour it into a waste liquid bucket, add ultrapure water to the culture dish, and repeat the cleaning three times, each time for about 10 minutes until the cleaning is completed; S201e: Blow dry the cleaned silicon wafer with nitrogen, place it in a petri dish, seal it and keep it for later use.

4. The method for preparing a deformable graphene field effect sensor according to claim 1, characterized in that: The particle size of AuNPs in S202 is 10 nm.

5. The method for preparing a deformable graphene field effect sensor according to claim 1, characterized in that: S203 also includes the following steps: S203a: cutting the copper sheet on which graphene has been grown into a shape slightly larger than the silicon sheet, and coating the silicon sheet; S203b, glue coating: place the coated silicon wafer on the middle suction hole of a desktop glue spreader, and drip 0.1-0.15 mL of PMMA with a molecular weight of 495000 and a concentration of A6 on the surface of the copper sheet; S203c: Adjust the speed to 4000r / min, the time to 45s, start the glue spreader to rotate, and then bake at 180℃ for 2min; S203d, tape application: clean the dedicated glass table, apply dedicated tape, and cut the silicon wafer coated with graphene as the standard; use a carving knife to mark out the tape frame, align one side of the tape frame with the lower edge of the copper foil, and cut off the excess copper sheet or tape frame after applying; S203e: Slowly move the graphene with the glue frame into the prepared FeCl3 solution, seal it, and dissolve it for about a day until the copper foil is completely dissolved; S203f: After copper etching is completed, use ultrapure water for cleaning; S203g: Take the sample out of the ultrapure water, carefully stick it on the silicon wafer with AuNPs attached to the surface, and place it on a heating plate at 45°C until the moisture between the silicon wafer and the sample is dried; S203h: Carefully scrape the glue frame with a blade, and then use tweezers to remove the glue frame, leaving the transferred deformed graphene; soak the transferred deformed graphene in an acetone solution for more than one day to remove the PMMA on the surface of the deformed graphene, observe the glue removal effect under a microscope, and seal it for later use.

6. The method for preparing a deformable graphene field effect sensor according to claim 1, characterized in that: The thickness of Cr in S4 is 80nm, the evaporation current is 200A, and the evaporation time is 8-9 minutes; the thickness of Au is 600nm, the evaporation current is 150A, and the evaporation time is until the film thickness is completed.

7. The method for preparing a deformable graphene field effect sensor according to claim 5, characterized in that: When preparing FeCl3 solution in S203e, HCl solution is added to prevent Fe 3+ hydrolysis.

8. The method for preparing a deformable graphene field effect sensor according to claim 1, characterized in that: The volume of PMMA in S203b is 0.1-0.15 mL, the molecular weight is 495000, and the concentration is A6.

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