Biosensor based on graphene bilayer gate tunneling field effect transistor

Abstract

The application relates to the field of biosensors, and particularly relates to a biosensor based on a graphene double-material gate tunneling field effect transistor, which comprises a graphene channel, a source electrode, a drain electrode, an insulating medium layer, a silicon substrate, a gate medium layer, a first gate electrode, a second gate electrode, a biological medium layer and a biological nanocavity; the silicon substrate, the insulating medium layer, the graphene channel and the gate medium layer are sequentially stacked from bottom to top; the source electrode and the drain electrode are located on the left and right sides of the graphene channel; the biological medium layer and the second gate electrode are respectively stacked on the left and right end portions of the upper surface of the gate medium layer, and the biological medium layer is hollow to form the biological nanocavity; the first gate electrode is stacked on the upper surface of the biological medium layer; the work functions of the metal materials of the first gate electrode and the second gate electrode are different. The application can comprehensively control the energy band of the graphene channel, can realize energy band tunneling between the graphene without doping the graphene, has a relatively simple manufacturing process, and has high sensitivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of biosensors, in particular to a biosensor based on graphene double-material gate tunneling field effect transistor. BACKGROUND

[0002] As a new two-dimensional material, graphene has great advantages in the field of biosensors. Its high electron mobility and large specific surface area make graphene an ideal material for biosensors. Compared with traditional silicon-based sensors, the introduction of graphene material makes the biosensor exhibit faster response speed and higher sensitivity, and can detect low concentration of biological molecules to a greater extent.

[0003] However, due to its high electron hole concentration and zero band gap characteristics, graphene material exhibits bipolar properties during detection. Therefore, the traditional structure of graphene biosensor often observes the displacement of Dirac point (the lowest point of current in the transfer curve) to judge the type of biological according to the transfer curve, but this method has low detection sensitivity.

[0004] Therefore, biosensors using graphene and other materials as tunnel junctions have gradually developed. By studying the tunneling process, the device has a higher on-off current ratio and higher sensitivity for biological detection, but the interface contact between the two materials is extremely complex, and high doping of the material is generally required to meet the tunneling needs, and the manufacturing process is complex.

[0005] Therefore, it is urgent to solve the problem of biosensors requiring high doping of materials to meet the needs of tunneling, and the manufacturing process is complex. SUMMARY

[0006] The technical problem to be solved by the present application is to overcome the defects of the prior art and provide a biosensor based on graphene double-material gate tunneling field effect transistor. It uses two metal materials with different work functions as the gate to comprehensively regulate the energy band of the graphene channel, so that the energy band tunneling between graphene can be realized without doping the graphene, the manufacturing process is simple, and the sensitivity is high.

[0007] To solve the above technical problems, the technical scheme of the present application is: a biosensor based on graphene double-material gate tunneling field effect transistor, comprising a graphene channel, a source, a drain, an insulating dielectric layer, a silicon substrate, a gate dielectric layer, a first gate, a second gate, a biological medium layer and a biological nanocavity; wherein,

[0008] The silicon substrate, the insulating dielectric layer, the graphene channel and the gate dielectric layer are sequentially stacked from bottom to top;

[0009] The source electrode is located at the left side of the graphene channel, the drain electrode is located at the right side of the graphene channel, and the source electrode and the drain electrode are clamped between the insulating medium layer and the gate medium layer and are in Schottky contact with the graphene channel;

[0010] The biological medium layer is laminated at the left end of the upper surface of the gate medium layer and is hollowed out to form the biological nanocavity;

[0011] The first gate electrode is laminated on the upper surface of the biological medium layer, and the second gate electrode is laminated on the right end of the upper surface of the gate medium layer and has a gap with the biological medium layer.

[0012] The work function of the metal material of the source electrode is greater than the work function of the metal material of the drain electrode, and the work functions of the metal materials of the first gate electrode and the second gate electrode are different.

[0013] Further, the source electrode is made of cobalt metal material, and the drain electrode is made of hafnium metal material.

[0014] Further, the graphene channel is made of undoped intrinsic graphene material, with a length of 100 nm and a thickness of 5-10 nm.

[0015] Further, the material of the gate medium layer is hafnium dioxide.

[0016] Further, the first gate electrode and the second gate electrode have a horizontal spacing of 1-10 nm.

[0017] Further, the first gate electrode is made of copper metal material, and the second gate electrode is made of titanium metal material.

[0018] Further, the first gate electrode voltage range is set to -0.1V to 0.1V.

[0019] The application also relates to a preparation method of a graphene double-material gate tunneling field effect transistor-based biosensor.

[0020] Step S1: taking a silicon wafer as a silicon substrate, growing a uniform-thickness silicon dioxide film on the surface of the silicon substrate by a thermal oxidation method, adjusting the temperature to 800-1100 DEG C after growth, and performing annealing treatment on the silicon dioxide substrate under nitrogen protection for 30 minutes to obtain an insulating medium layer.

[0021] Step S2: taking a copper foil as a substrate, cracking methane at a high temperature of 1000 DEG C to make carbon atoms deposited on the copper foil, and determining the deposition time according to the thickness of graphene.

[0022] Step S3, the graphene surface on the copper foil is coated with a PMMA film to adhere the graphene deposited on the copper foil, and the copper foil is removed by wet etching, at which time the graphene is still adhered to the PMMA surface.

[0023] Step S4, the PMMA film and the graphene thereon are transferred to an insulating medium layer, and the PMMA film is removed by using an acetone solution;

[0024] Step S5, the source and drain electrode patterns are defined at both ends of the graphene by using a photolithography technology, the metal material of the source and drain electrodes is deposited by using an electron beam evaporation technology, and finally, annealing treatment is performed under nitrogen protection, at a temperature of 300-400℃ for 30 minutes, to improve the contact performance between the metal and the graphene;

[0025] Step S6, the gate dielectric layer and the biological medium layer are sequentially deposited on the graphene surface;

[0026] Step S7, the gate pattern is defined by using a photolithography technology, the first gate electrode is deposited above the biological medium layer by using an electron beam evaporation technology, and annealing treatment is performed.

[0027] Step S8, the nanobiological cavity is etched in the biological medium layer by using dry etching, the pattern is defined on the biological medium layer by using a photolithography technology, the photoresist is used to protect the area that does not need to be etched, and the area is etched by using hydrogen fluoride gas, and after completion, the photoresist is removed by using an acetone solution;

[0028] Step S9, the second gate electrode is deposited above the gate dielectric layer beside the nanobiological cavity;

[0029] Step S10, the whole device is cleaned, and the residual photoresist and contaminants are removed, and finally, annealing is performed under nitrogen environment, at a temperature of 200℃ for 30 minutes, to improve the electrical performance and stability of the graphene field effect transistor.

[0030] By adopting the above technical solution, this invention uses intrinsic graphene as the conductive channel. Without doping the graphene, it incorporates a source metal with a high work function and a drain metal with a low work function to introduce P-regions and N-regions into the source and drain regions of the graphene, respectively, creating the PIN conditions required for tunneling. Two different metal materials are used as gates. By adjusting the graphene channel with these two gate metals of different work functions, the graphene channel achieves tunneling conditions. Compared to traditional single-gate graphene field-effect transistors, this structure eliminates the need to observe minute changes in the Dirac point of the transfer curve to distinguish biological types; only the saturation current output by the sensor needs to be compared. Furthermore, this structure has a lower turn-off current and a higher on / off current ratio, overcoming the limitation of graphene's on / off current ratio of only a few hundred, resulting in higher sensitivity for biological detection. In addition, compared to traditional silicon-graphene heterojunction tunneling field-effect transistors, the biosensor of this invention does not require consideration of doping and interface state issues, thus simplifying the fabrication process. Because it uses an all-graphene channel, it exhibits a lower subthreshold swing. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the biosensor structure based on a graphene dual-material gate tunneling field-effect transistor according to the present invention.

[0032] Figure 2 This is a band structure diagram of the channel of the biosensor of the present invention under different biological conditions;

[0033] Figure 3 This is a graph showing the tunneling distance and tunneling rate of electrons in the tunneling region of the biosensor of the present invention under different biological conditions;

[0034] Figure 4 This is a transfer curve diagram of the biosensor in Embodiment 1 of the present invention under different biological conditions;

[0035] Figure 5 This is a transfer curve diagram of the biosensor in Embodiment 2 of the present invention under different biological conditions;

[0036] Figure 6 This is a comparison of the tunneling transfer curves of the biosensor in Example 1 and the conventional silicon-graphene heterojunction in Comparative Example 1 at a biological dielectric constant k = 6.

[0037] Figure 1 In the diagram: 1. Graphene channel; 2. Source; 3. Drain; 4. Insulating dielectric layer; 5. Silicon substrate; 6. Gate dielectric layer; 7. First gate; 8. Second gate; 9. Bio-medium layer; 10. Bio-nano cavity. Detailed Implementation

[0038] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0039] like Figure 1 As shown, a biosensor based on a graphene dual-material gate tunneling field-effect transistor includes a graphene channel 1, a source 2, a drain 3, an insulating dielectric layer 4, a silicon substrate 5, a gate dielectric layer 6, a first gate 7, a second gate 8, a bio-medium layer 9, and a bio-nano cavity 10; wherein,

[0040] The silicon substrate 5, the insulating dielectric layer 4, the graphene channel 1, and the gate dielectric layer 6 are stacked sequentially from bottom to top;

[0041] Source 2 is located on the left side of graphene channel 1, and drain 3 is located on the right side of graphene channel 1. Both source 2 and drain 3 are sandwiched between insulating dielectric layer 4 and gate dielectric layer 6, and both are in Schottky contact with graphene channel 1.

[0042] The biological medium layer 9 is stacked on the left end of the upper surface of the gate medium layer 6 and hollowed out to form a biological nano cavity 10. The biological nano cavity 10 is used to contain the detection of organisms. Different organisms are assigned different dielectric constants k, and the categories of organisms are distinguished by the dielectric constant k.

[0043] A first gate 7 is stacked on the upper surface of the biological medium layer 9, and a second gate 8 is stacked on the right end of the upper surface of the gate dielectric layer 6, with a gap between them. The first gate 7 and the second gate 8 can have a horizontal spacing of 1-10 nm.

[0044] In this embodiment, to create the electron-hole concentration required for tunneling, the work function of the metal material of source 2 is greater than that of the metal material of drain 3. Source 2 can be made of cobalt metal (Co) with a work function of 5 eV to create a P-region in the source region, and drain 3 can be made of hafnium metal (Hf) with a work function of 3.9 eV to create an N-region in the drain region. To ensure uniform carrier distribution in the channel, the source and drain metals are of the same size, with dimensions of 10 nm × 5 nm.

[0045] In this embodiment, intrinsic graphene is used as the conductive channel. Without doping the graphene, in order to enable the graphene channel 1 to tunnel, the work functions of the metal materials of the first gate 7 and the second gate 8 are different. The first gate 7 can be made of copper (Cu) with a work function of 4.65 eV, and the second gate 8 can be made of titanium (Ti) with a work function of 4.33 eV. The voltage range of the first gate 7 should be set from -0.1V to 0.1V.

[0046] In this embodiment, the graphene channel 1 is made of undoped intrinsic graphene material, 100 nm long and 5-10 nm thick.

[0047] In this embodiment, the gate dielectric layer 6 is closely attached to the graphene 1 and covers the source and drain metals, and is made of an insulating material with high dielectric constant, such as hafnium dioxide (HfO2), 1-3 nm thick.

[0048] In this embodiment, the biological medium layer 9 is a general oxide, which can be silicon dioxide, aluminum oxide, hafnium dioxide, etc., and the biological nanocavity 10 is the detection position of biological molecules, filled with air when not detected, with a size of 35 nm x 10 nm.

[0049] The biosensor in this embodiment can detect the concentration of a single biological molecule according to the dielectric constant of the single biological molecule after being filled in the biological nanocavity 10, and can also distinguish different single biological molecules according to the dielectric constant.

[0050] The preparation method of the graphene-based double-material gate tunneling field effect transistor biosensor according to the above embodiment comprises:

[0051] Step S1: A silicon wafer with a smooth surface and high resistivity is used as the silicon substrate 5, and a uniform thickness of silicon dioxide film is grown on the surface of the silicon substrate 5 by thermal oxidation method. After growth is completed, the temperature is adjusted to 800-1100℃, and the silicon dioxide substrate 5 is annealed under nitrogen protection for 30 minutes to obtain the insulating medium layer 4.

[0052] Step S2, select copper foil as the substrate, crack methane at a high temperature of 1000℃, and make carbon atoms deposit on the copper foil. The deposition time is determined according to the thickness of graphene.

[0053] Step S3, apply a polymethyl methacrylate (PMMA) film on the surface of graphene on the copper foil to adhere the graphene deposited on the copper foil, and remove the copper foil by wet etching. At this time, the graphene is still adhered to the surface of the PMMA.

[0054] Step S4, transfer the PMMA film and the graphene on it to the insulating medium layer 4, and remove the PMMA film with acetone solution.

[0055] Step S5, define the source and drain 3 pattern at both ends of the graphene by using photolithography technology, and deposit metal electrode material by electron beam evaporation technology. The source 2 is deposited with cobalt metal, and the drain 3 is deposited with hafnium metal, with a length of 10 nm and a thickness of 5 nm. Finally, annealing treatment is performed under nitrogen protection, with a temperature of 300-400℃ and a duration of 30 minutes, to improve the contact performance between the metal and the graphene.

[0056] Step S6, sequentially depositing gate dielectric layer 6 and biological dielectric layer 9 on the graphene surface by atomic layer deposition (ALD), the thickness of gate dielectric layer 6 is 1-3 nm, and the length of biological dielectric layer 9 is 40-48 nm and the thickness is 10 nm

[0057] Step S7: using photolithography technology to define the gate pattern, using electron beam evaporation technology to deposit the material copper of the first gate 7 above the biological dielectric layer 9, and performing annealing treatment.

[0058] Step S8, using dry etching to etch a nano-biological cavity 10 with a length of 30-38 nm and a thickness of 10 nm in the biological dielectric layer 9, using photolithography technology to define a pattern on the biological dielectric layer 9, using photoresist to protect the area that does not need to be etched, and using hydrogen fluoride gas to etch it, and after completion, using acetone solution to remove the photoresist;

[0059] Step S9, depositing the material titanium of the second gate 8 above the gate dielectric layer 6 beside the nano-biological cavity 10;

[0060] Step S10, cleaning the whole device and removing the residual photoresist and contaminants, and finally annealing in a nitrogen environment, with a temperature setting of 200°C for 30 minutes, to improve the electrical performance and stability of the graphene field effect transistor.

[0061] The working principle of the graphene-based double-material gate tunneling field effect transistor biosensor involved in the above embodiment is as follows:

[0062] The intrinsic graphene is used as the conductive channel, without doping the graphene, high work function source metal and low work function drain metal are used to introduce P region and N region in the source region and the drain region of the graphene respectively, and the P-I-N condition for tunneling is created; then two kinds of metal materials are used as the gate, under the modulation of different work functions of the gate metal, the energy band of the graphene channel 1 presents different degrees of bending, so that the structure better meets the tunneling condition; by introducing the biological nano-cavity 10 under the first gate 7, under the different dielectric constants of the biological, the degree of bending of the graphene energy band under the influence of the first gate 7 is different, which leads to different tunneling distances of electrons in the channel when detecting different biological, and then affects the size of the tunneling current; by comparing the saturation current of the sensor when detecting the biological, the category of the biological can be further distinguished, and because the tunneling distance of the electrons is different, the saturation current of the sensor for each biological is greatly different, so the sensor has higher sensitivity for biological detection.

[0063] Figure 2This is a band structure diagram of the channel of this biosensor under different biological conditions (using the same color to represent the conduction band and valence band, with the conduction band above the valence band, assuming the same biological dielectric constant). The source 2 voltage is 0V, the drain 3 voltage is 0.1V, the first gate 7 voltage is 0V, and the second gate 8 voltage starts at 0V with a step size of 0.01V, eventually set to 0.5V. When tunneling occurs, electrons tunnel from the valence band near the source region to the conduction band to the right, with the main tunneling occurring at the x-axis position of 0.04nm. Figure 2 It can be seen that the sensor has a shorter tunneling distance at this location under high-k biological conditions. It can also be seen that the degree of graphene band bending controlled by the first gate 7 varies under different biological conditions. This is due to the different dielectric constant k of the biological nanocavity 10, according to the effective capacitance formula:

[0064]

[0065] Among them, C be The effective capacitance of the biological nanocavity is 10, where k is the dielectric constant of the organism to be tested, and t is the effective capacitance of the biological nanocavity. b The thickness of the bio-nano cavity 10 is shown.

[0066] It can also be seen that with a high dielectric constant k, the effective capacitance of the bio-nano cavity is larger. In this case, the first gate 7 has a more obvious control over the channel energy band, and the degree of bending is greater. Since the gate dielectric layer 6 uses an oxide layer with a higher dielectric constant, when a voltage is applied to the second gate 8, the control force on the energy band in the channel is much greater than the control force of the first gate 7 on the channel. Therefore, the energy band under the influence of the second gate 8 is a horizontal line and does not bend.

[0067] The region between the first gate 7 and the second gate 8 in the graphene channel 1 is the main area for electron tunneling. The electron tunneling distance and tunneling rate are as follows: Figure 3 As shown, for organisms with a dielectric constant k = 12, the electron tunneling distance is shortened from 17.5 nm to 8.5 nm, and the tunneling velocity is reduced from 2.18 × 10⁻⁶. 26 / (cm 2 ·s) increased to 1.37×10 30 / (cm 2 The tunneling distance was shortened by 9 nm, but the electron tunneling rate increased by 4 orders of magnitude.

[0068] The above-mentioned biosensor will be described in detail below through specific embodiments and simulation processes.

[0069] In the computer simulation software, we use different dielectric constant k to distinguish different biomolecules, where the dielectric constant k = 1 represents that there is no biological to be detected in the biological nanocavity, but air; k = 1.5, 2.6, 6, 12 represents that the biological nanocavity contains the same kind of biological with the dielectric constant. The formula for calculating the sensitivity of the biosensor is the ratio of the saturation current of the sensor with biological to the saturation current without biological to be detected.

[0070] Example one

[0071] A biosensor based on graphene double-material gate tunneling field effect transistor, wherein the length of the biological nanocavity 10 is 35 nm, the horizontal distance between the first gate 7 and the second gate 8 is 5 nm, the voltage of the first gate 8 is set to 0V, and the thickness of the gate dielectric layer 6 is 1 nm.

[0072] In the modeling simulation of computer software, we simulate the biosensor under different biological conditions, focusing on the analysis of its transfer curve, and the simulation results are shown in Figure 4 . The biosensor has only a turn-off current of 10 -13 A / μm when it is turned off. And under the biological conditions of air k = 1 and dielectric constant k = 12, it respectively presents a saturation current of 8.58×10 -11 A / μm and 1.15×10 -6 A / μm, with a sensitivity as high as 1.34×10 4 .

[0073] Example two

[0074] A biosensor based on graphene double-material gate tunneling field effect transistor, wherein the length of the biological nanocavity 10 is 35 nm, the horizontal distance between the first gate 7 and the second gate 8 is 5 nm, the voltage of the first gate 8 is set to 0V, and the thickness of the gate dielectric layer 6 is 1 nm.

[0075] In the modeling simulation of computer software, we simulate the biosensor under different biological conditions, focusing on the analysis of its transfer curve, and the simulation results are shown in Figure 5 . The biosensor has only a turn-off current of 10 -13 A / μm when it is turned off. And under the biological conditions of air k = 1 and dielectric constant k = 12, it respectively presents a saturation current of 8.58×10 -10 A / μm and 1.15×10 -6 A / μm, with a sensitivity as high as 1.34×10 4 .

[0076] Comparative example one

[0077] A biosensor, a traditional silicon-graphene heterojunction tunneling structure, which requires 1x10 20 cm -3 of heavy P doping to the source region and 5x10 18 cm -3 of N doping to the drain region, in addition, the interface state doping problem needs to be considered, the manufacturing process is complex.

[0078] Figure 6 A comparison chart of the transfer curve of the biosensor in Example 1 and Comparative Example 1 at a biological dielectric constant k = 6. It can be seen from the comparison that the biosensor in Example 1 and Comparative Example 1 have the same off current, but the biosensor in Example 1 only needs an increment of 0.2V of the gate voltage to make the device reach the saturation current, and has a smaller sub-threshold swing (the sub-threshold swing refers to the change in the gate voltage when the current of the device increases by one order of magnitude from off to full on). When the device has a smaller sub-threshold swing, it can respond quickly under a smaller change in the gate voltage, which means that even a slight change in the biological molecules can cause a significant change in the current, thereby making the sensor more sensitive to slight changes in the biological sample.

[0079] Comparative Example 2

[0080] A traditional single-gate graphene field effect transistor, the transfer curve is in the shape of a "V", the displacement of the Dirac point is observed to analyze the biological, and the overall current is large, the saturation current can reach 10 -6 A / μm, and the off current is also 10 -8 A / μm, and the on-off current ratio of only a few hundred limits its application in detection and sensitivity, and the sensitivity is much lower than that of the tunneling structure in Comparative Example 1.

[0081] Compared with Comparative Example 2, Example 1 and Example 2 overcome the problem of large overall current of the traditional single-gate graphene field effect transistor, and also overcome the problem of on-off current ratio of only a few hundred, have a higher on-off current ratio, and the sensor does not need to observe the slight change of the Dirac point in the transfer curve to analyze the biological category, while the change of the Dirac point is often very subtle, which may be affected by environmental noise and other factors, resulting in low sensitivity. In comparison, Examples 1 and 2 instead use the saturation current of the device to detect the biological, which can more directly reflect the existence and concentration change of the biological molecules, avoiding the non-obviousness of the Dirac point movement and the difficulty of detection, and thus have higher sensitivity for biological detection.

[0082] With the above ideal embodiments according to the present application as the inspiration, through the above description, relevant staff can make various changes and modifications without deviating from the technical idea of the present application. The technical scope of the present application is not limited to the content of the specification, and must be determined according to the scope of the claims.

Claims

1.A biosensor based on graphene double-material gate tunneling field effect transistor, characterized in that, comprising a graphene channel (1), a source electrode (2), a drain electrode (3), an insulating dielectric layer (4), a silicon substrate (5), a gate dielectric layer (6), a first gate electrode (7), a second gate electrode (8), a biological medium layer (9) and a biological nanocavity (10), wherein, the silicon substrate (5), the insulating dielectric layer (4), the graphene channel (1) and the gate dielectric layer (6) are sequentially stacked from bottom to top; the source electrode (2) is located on the left side of the graphene channel (1), the drain electrode (3) is located on the right side of the graphene channel (1), the source electrode (2) and the drain electrode (3) are clamped between the insulating dielectric layer (4) and the gate dielectric layer (6), and both are in Schottky contact with the graphene channel (1) ; the biological medium layer (9) is stacked on the left end of the upper surface of the gate dielectric layer (6) and is hollowed out to form the biological nanocavity (10) ; the first gate electrode (7) is stacked on the upper surface of the biological medium layer (9), and the second gate electrode (8) is stacked on the right end of the upper surface of the gate dielectric layer (6), leaving a gap between the biological medium layer (9) ; the work function of the metal material of the source electrode (2) is greater than the work function of the metal material of the drain electrode (3), and the work functions of the metal materials of the first gate electrode (7) and the second gate electrode (8) are different. 2.The biosensor based on graphene double-material gate tunneling field effect transistor according to claim 1, characterized in that, the source electrode (2) is made of cobalt metal material, and the drain electrode (3) is made of hafnium metal material. 3.The biosensor based on graphene double-material gate tunneling field effect transistor according to claim 1, characterized in that, the graphene channel (1) is made of undoped intrinsic graphene material, 100nm long and 5-10nm thick. 4.The biosensor based on graphene double-material gate tunneling field effect transistor according to claim 1, characterized in that, the material of the gate dielectric layer (6) is hafnium dioxide. 5.The biosensor based on graphene double-material gate tunneling field effect transistor according to claim 1, characterized in that, the first gate electrode (7) and the second gate electrode (8) have a horizontal spacing of 1-10nm. 6.The biosensor based on graphene double-material gate tunneling field effect transistor according to claim 1, characterized in that, the first gate electrode (7) is made of copper metal material, and the second gate electrode (8) is made of titanium metal material. 7.The biosensor based on graphene double-material gate tunneling field effect transistor according to claim 1, characterized in that, the voltage range of the first gate electrode (7) is set to-0.1V to 0.1V. 8.A method for preparing the biosensor based on graphene double-material gate tunneling field effect transistor according to any one of claims 1-7, characterized in that, comprising: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Step S1: using a silicon wafer as a silicon substrate (5), a uniform thickness of silicon dioxide film is grown on the surface of the silicon substrate (5) by thermal oxidation method, after the growth is completed, the temperature is adjusted to 800-1100°C, and the annealing treatment is carried out on the silicon dioxide substrate (5) under the protection of nitrogen for 30 minutes, and the insulating medium layer (4) is obtained; Step S2, select copper foil as the substrate, crack methane at high temperature of 1000°C, make carbon atoms deposit on the copper foil, and determine the deposition time according to the thickness of graphene; Step S3, smearing PMMA film on the surface of graphene on the copper foil to adhere the graphene deposited on the copper foil, and removing the copper foil by wet etching, at this time, the graphene is still adhered to the surface of PMMA; Step S4, transfer the PMMA film and the graphene on it to the insulating medium layer (4), and remove the PMMA film by using acetone solution; Step S5, define the source and drain (3) pattern on both ends of the graphene by using photolithography technology, deposit the metal material of the source (2) and the drain (3) by using electron beam evaporation technology, and finally perform annealing treatment under the protection of nitrogen, the temperature is 300-400°C, and the duration is 30 minutes, to improve the contact performance between the metal and the graphene; Step S6, deposit the gate dielectric layer (6) and the biological medium layer (9) on the surface of graphene in sequence; Step S7: define the gate pattern by using photolithography technology, deposit the first gate (7) on the biological medium layer (9) by using electron beam evaporation technology, and perform annealing treatment; Step S8, etch the nanobio cavity in the biological medium layer (9) by using dry etching, define the pattern on the biological medium layer (9) by using photolithography technology, protect the area that does not need to be etched by using photoresist, select hydrogen fluoride gas for etching, after completion, remove the photoresist by using acetone solution; Step S9, deposit the second gate (8) on the gate dielectric layer (6) beside the biological nanocavity (10); Step S10, clean the whole device, remove the residual photoresist and contaminants, and finally anneal under the protection of nitrogen, the temperature is set to 200°C, and the duration is 30 minutes, to improve the electrical performance and stability of the graphene field effect transistor.

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