Gdig-assisted dual-heterojunction flexible photodetector, preparation and application
By introducing a GdIG-assisted double heterojunction structure and a gadolinium iron garnet thin film interlayer into a flexible photodetector, the problems of dark current and spectral response were solved, achieving high-performance broadband detection and mechanical stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XI AN JIAOTONG UNIV
- Filing Date
- 2023-02-20
- Publication Date
- 2026-06-02
AI Technical Summary
Existing flexible photodetectors suffer from large dark currents due to their low-dimensional material construction, which affects their ability to detect weak signals and makes it difficult to achieve a wide spectral response.
A GdIG-assisted double heterojunction structure was adopted, and a gadolinium iron garnet film was used as an intermediate layer to optimize the heterojunction interface. By constructing a double van der Waals heterojunction of molybdenum disulfide, graphene and single-walled carbon nanotubes, carrier separation and photoresponse were enhanced.
The device's responsivity and specific detectivity were improved, achieving a broad spectral response from visible light to near-infrared, reducing dark current, and the device exhibited good mechanical stability.
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Figure CN116528635B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the fields of materials science, optoelectronic devices, semiconductor devices and micro-nano fabrication technology, specifically relating to a GdIG-assisted double heterojunction flexible photodetector, its fabrication method and its application. Background Technology
[0002] In recent years, the demand for developing next-generation electronic application devices has been increasing, such as bio-integrated sensors and flexible wearable devices. These applications place new demands on semiconductor materials, requiring them to possess unique mechanical, optical, and electrical properties. Flexible photodetectors are fundamental components for developing flexible wearable systems and can be widely used in health monitoring, environmental monitoring, human-computer interaction, and flexible displays. By fabricating van der Waals heterostructures, two-dimensional materials can be stacked and combined arbitrarily, much like making sandwiches, without considering lattice mismatch issues. The wide variety of two-dimensional materials provides a broad material basis for fabricating two-dimensional van der Waals heterostructures. However, since most flexible photodetectors built from low-dimensional materials are based on the photovoltaic effect, and the doping of low-dimensional materials is difficult to stably adjust and control, large dark currents are generated, affecting the device's ability to detect weak signals. Therefore, finding suitable materials and structures is of profound significance for constructing high-performance flexible photodetectors. Summary of the Invention
[0003] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide a GdIG-assisted double heterojunction flexible photodetector and its fabrication method. This detector accelerates carrier separation and improves device responsivity by constructing a double van der Waals heterojunction; it achieves a broad spectral response from the visible to near-infrared bands through the combination of different metal materials. A gadolinium-iron garnet thin film with excellent uniformity and continuity is used as an intermediate layer to optimize the double heterojunction interface, increase the barrier height between heterojunctions, block majority carrier dark current, and enhance the device's ability to detect weak signals, thus meeting the significant demand for high-performance flexible photodetectors.
[0004] The present invention is achieved through the following technical solution.
[0005] In one aspect, this invention provides a method for fabricating a GdIG-assisted double heterojunction flexible photodetector, comprising the following steps:
[0006] 1) Take the PET substrate and clean it thoroughly;
[0007] 2) Deposit a layer of metallic Al on a PET substrate to form an aluminum mask, and define a square window on the surface of the metallic Al;
[0008] 3) Spin-coat a molybdenum disulfide dispersion uniformly onto the window, and dry it to form a molybdenum disulfide film;
[0009] 4) Control the conditions of magnetron sputtering to sputter a gadolinium iron garnet film onto the surface of a molybdenum disulfide film in the formed window to obtain a gadolinium iron garnet intercalation layer;
[0010] 5) Remove the aluminum shield to obtain a molybdenum disulfide film and an upper gadolinium iron garnet intercalated film;
[0011] 6) Prepare graphene films and transfer them onto PET substrates to completely cover the gadolinium iron garnet intercalation and molybdenum disulfide film surfaces;
[0012] 7) The edges of the graphene film are etched using photolithography and plasma processes to obtain the graphene film;
[0013] 8) A layer of metallic Al is deposited on the graphene film using ultraviolet lithography and electron beam deposition techniques, and a square window is defined on the surface of the metallic Al.
[0014] 9) Control the conditions of magnetron sputtering to sputter gadolinium iron garnet film onto the surface of graphene film in the formed window to form gadolinium iron garnet intercalation;
[0015] 10) A single-walled carbon nanotube dispersion is uniformly spin-coated onto the formed gadolinium iron garnet intercalation layer and dried to form a single-walled carbon nanotube film.
[0016] 11) Remove metallic Al to obtain a single-walled carbon nanotube film and a gadolinium-iron garnet intercalation layer underneath;
[0017] 12) Metal electrodes for the detector are fabricated at both ends of the obtained graphene film and at both ends of the single-walled carbon nanotube film to obtain a flexible photodetector based on GdIG-assisted double heterojunction.
[0018] A further improvement of the present invention is that, in step 3), a layer of molybdenum disulfide dispersion is spin-coated at a speed of 2000-5000 rpm using a spin coater, the spin coating time is 30-60 seconds, and the spin-coated sample is placed on a baking table at 100°C and baked for 10-20 minutes.
[0019] A further improvement of the present invention is that, in steps 4) and 9), the back vacuum of the magnetron sputtering machine is controlled to be 2 × 10⁻⁶. -5 The sputtering pressure was 1 Pa, the volume ratio of oxygen and argon was 1:1, and the gas flow rate was 20 sccm. The sputtering power was set to 60 W, the magnetron sputtering time was 20 s, and the gadolinium iron garnet intercalation thickness was 2-5 nm.
[0020] A further improvement of the present invention is that, in step 6), a PMMA wet transfer method is used to transfer the graphene film onto the PET substrate.
[0021] A further improvement of the present invention is that, in step 8), a 100-200 nm layer of metallic Al is deposited on the graphene film.
[0022] A further improvement of the present invention is that, in step 12), metal Cr electrodes with a thickness of 10-30 nm and metal Au electrodes with a thickness of 60-90 nm are prepared on the left and right sides of the graphene film and the single-walled carbon nanotube film.
[0023] In another aspect, this invention provides a GdIG-assisted flexible photodetector based on the method described above, comprising a PET substrate, a molybdenum disulfide film, a gadolinium iron garnet intercalation layer, a graphene film, a single-walled carbon nanotube film, and metal electrodes. The molybdenum disulfide film is located on the surface of the PET substrate. The gadolinium iron garnet intercalation layer covers the molybdenum disulfide film. The graphene film covers both the gadolinium iron garnet intercalation layer and the PET substrate surface, with a gadolinium iron garnet intercalation layer covering the graphene film. The single-walled carbon nanotube film covers the gadolinium iron garnet intercalation layer and is positioned above the graphene film, forming a cross-shaped pattern with the graphene film, and is also separated from it by gadolinium iron garnet intercalation layers. The metal electrodes are located on the graphene film covering the PET substrate and on both sides corresponding to the square window.
[0024] Preferably, the graphene film covers the upper surface of the molybdenum disulfide film and gadolinium iron garnet intercalation layer of the square window on the PET substrate, as well as the rectangular graphene film on the PET substrate on both sides of the square window.
[0025] In another aspect, the present invention provides the application of a GdIG-assisted double heterojunction flexible photodetector in intelligent medical detection.
[0026] The present invention adopts the above technical solution and has the following beneficial effects:
[0027] 1. This invention provides a detector constructed by molybdenum disulfide and graphene, and graphene and single-walled carbon nanotubes to form a double van der Waals heterojunction. The asymmetry of the two heterojunctions brings a larger built-in electric field, which accelerates the separation of charge carriers, generates a larger photoresponse, and greatly improves the responsivity of the device. Furthermore, by combining different materials, the response spectrum range of the device is broadened, and a wide spectrum response from visible light to near-infrared bands can be achieved.
[0028] 2. By using a gadolinium iron garnet film with excellent uniformity and continuity as an intermediate layer to optimize the double heterojunction interface, the potential barrier height between heterojunctions is increased, blocking the majority carrier dark current and improving the device's ability to detect weak signals.
[0029] When a gadolinium iron garnet film is inserted as an interlayer, single-walled carbon nanotubes and graphene, as well as graphene and molybdenum disulfide, are spatially separated, generating a potential along the gadolinium iron garnet film, thereby significantly improving the heterojunction barrier and built-in electric field. In the absence of light, due to insufficient energy, thermally generated charge carriers attempting to cross the barrier are blocked, thus suppressing the majority carrier dark current generated by the built-in electric field. Furthermore, under illumination, the larger built-in electric field accelerates charge tunneling, rendering the 2-5 nm thin gadolinium iron garnet layer ineffective. More holes flow to the single-walled carbon nanotubes and graphene through tunneling, resulting in a higher photocurrent and enhancing the device's specific detectivity.
[0030] By using a gadolinium iron garnet thin film with excellent uniformity and continuity as an interlayer to optimize the double heterojunction interface, the dark current of majority carriers is blocked, enabling the detector to exhibit excellent photoresponse capability in a broad spectral band from visible to near-infrared. The combination of the double heterojunction and gadolinium iron garnet as the interlayer material gives the device the characteristics of broad spectrum, high responsivity, and weak light detection, achieving technological innovation.
[0031] 3. The devices are made of flexible materials, which gives them good mechanical stability.
[0032] Because the device is fabricated using two-dimensional materials and flexible substrates to construct the photodetector, the two-dimensional semiconductor material has a strong resistance to deformation, and the atomic-layer thickness of the two-dimensional material ensures the transparency and flexibility of the device, overcoming the problem of traditional detectors being unable to bend and deform. Attached Figure Description
[0033] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, do not constitute an undue limitation of the invention. In the drawings:
[0034] Figure 1 This is a schematic cross-sectional view of a dual heterojunction flexible photodetector according to an embodiment of the present invention;
[0035] Figure 2 a-2l is a schematic diagram of the fabrication process of the double heterojunction flexible photodetector in an embodiment of the present invention.
[0036] Explanation of reference numerals in the attached figures:
[0037] 1. PET substrate (polyethylene terephthalate substrate), 2. molybdenum disulfide film, 3. gadolinium iron garnet intercalation, 4. graphene film, 5. single-walled carbon nanotube film, 6. metal electrode, 7. aluminum mask. Detailed Implementation
[0038] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.
[0039] like Figure 1 The diagram shows a cross-sectional view of a GdIG-assisted double heterojunction flexible photodetector provided by the present invention, comprising a PET substrate 1, a molybdenum disulfide film 2, a gadolinium iron garnet intercalation layer 3, a graphene film 4, a single-walled carbon nanotube film 5, and a metal electrode 6. The molybdenum disulfide film 2 is located on the surface of the PET substrate 1. The gadolinium iron garnet intercalation layer 3 covers the molybdenum disulfide film 2. The graphene film 4 covers the gadolinium iron garnet intercalation layer 3, and another gadolinium iron garnet intercalation layer 3 covers the graphene film 4. The single-walled carbon nanotube film 5 covers the gadolinium iron garnet intercalation layer 3. The metal electrode 6 is located on both sides of the graphene film 4 and on both sides of the single-walled carbon nanotube film 5. The metal electrode forms an ohmic contact with the graphene film and the single-walled carbon nanotube film.
[0040] A molybdenum disulfide film 2 is placed on top of a PET substrate and completely covered by a graphene film 4. The molybdenum disulfide film 2 and the graphene film 4 are separated by gadolinium iron garnet intercalation layers 3. A single-walled carbon nanotube film 5 is placed above the graphene film 4, forming a cross-structure pattern with it, and they are also separated by gadolinium iron garnet intercalation layers 3. The graphene film 4 covers the upper surface of the square window on the PET substrate 1 where the molybdenum disulfide film 2 and the gadolinium iron garnet intercalation layers 3 are superimposed, and also covers the rectangular graphene films 4 on the PET substrates on both sides of the square window.
[0041] To achieve flexible detector fabrication, reduce dark current, and improve device performance, this invention is based on gadolinium-iron garnet intercalation and double heterojunction theory. The working principle is as follows:
[0042] In the device, single-walled carbon nanotubes form a PP heterojunction with graphene to absorb near-infrared wavelengths and generate a hole accumulation layer, and also serve as a transparent electrode to transport hole carriers; graphene forms a PN junction with molybdenum disulfide to absorb visible light, and graphene also serves as a transparent electrode to transport electron carriers, thus achieving a light response range from visible to near-infrared.
[0043] When a gadolinium iron garnet film is inserted as an interlayer, single-walled carbon nanotubes and graphene, as well as graphene and molybdenum disulfide, are spatially separated, generating a potential along the gadolinium iron garnet film, thereby significantly improving the heterojunction barrier and built-in electric field. In the absence of light, due to insufficient energy, thermally generated charge carriers attempting to cross the barrier are blocked, thus suppressing the majority carrier dark current generated by the built-in electric field. Furthermore, under illumination, the larger built-in electric field accelerates charge tunneling, rendering the 2-5 nm thin gadolinium iron garnet layer ineffective. More holes flow to the single-walled carbon nanotubes and graphene through tunneling, resulting in a higher photocurrent and enhancing the device's specific detectivity.
[0044] Among them, single-walled carbon nanotubes form a PP heterojunction with graphene to absorb near-infrared wavelengths and generate a hole accumulation layer, and also serve as a transparent electrode to transport hole carriers; graphene forms a PN junction with molybdenum disulfide to absorb visible light, and graphene also serves as a transparent electrode to transport electron carriers, thus achieving a light response range from visible to near-infrared.
[0045] The molybdenum disulfide film, graphene film, and single-walled carbon nanotube film used are all two-dimensional materials. The gadolinium iron garnet intercalation layer in the middle is only 2-5 nm thick. Their surfaces have no dangling bonds. The layers are bonded to form heterojunctions through van der Waals forces and have good mechanical bending properties.
[0046] By employing a 2-5 nm thick gadolinium garnet intercalation layer as an intermediate layer, single-walled carbon nanotube films and graphene films, as well as graphene films and molybdenum disulfide films, are spatially separated, generating an electric potential along the gadolinium garnet film, thereby improving the heterojunction barrier and built-in electric field.
[0047] When there is no light, due to insufficient energy, thermally generated charge carriers attempting to pass through the potential barrier are blocked by the gadolinium iron garnet intercalation layer. This suppresses the dark current of majority carriers generated by the built-in electric field. When there is light, the larger built-in electric field accelerates charge tunneling. The 2-5 nm thin gadolinium iron garnet intercalation layer becomes ineffective, and holes flow to the single-walled carbon nanotube film through the tunneling effect, while electrons flow to the molybdenum disulfide film through the tunneling effect, resulting in a higher photocurrent.
[0048] To achieve a simple and efficient fabrication of the aforementioned double heterojunction flexible photodetector, this invention provides a GdIG-assisted fabrication method for a double heterojunction flexible photodetector, such as... Figure 2 As shown in a-2l, the following steps are included:
[0049] 1) First, prepare a clean PET substrate 1, and clean it thoroughly with acetone, ethanol, and clean deionized water. Figure 2 As shown in a; the method for cleaning the PET substrate is a well-known and commonly used method in the art, and will not be described in detail here.
[0050] 2) A 100-200 nm layer of metallic Al was deposited on a PET substrate using ultraviolet lithography and electron beam deposition techniques to form an aluminum mask 7. A 0.1 × 0.1 mm square window was defined on the surface of the metallic Al, such as... Figure 2 As shown in b.
[0051] Ultraviolet lithography involves first preparing a photoresist mask layer using photolithography, then depositing a 100-200 nm thick layer of metallic Al on the photoresist mask layer using electron beam deposition, and finally removing the photoresist mask layer with acetone to obtain the desired aluminum mask layer.
[0052] 3) Uniformly spin-coat the molybdenum disulfide dispersion onto the window formed in step 2), and dry it to form a molybdenum disulfide film 2, as shown. Figure 2 As shown in c. A layer of molybdenum disulfide dispersion was spin-coated onto the device at a speed of 2000-5000 rpm for 30-60 seconds using a spin coater. The spin-coated sample was then placed on a baking table at 100°C and baked for 10-20 minutes until the dispersion solvent was completely evaporated, resulting in a uniform molybdenum disulfide film as required.
[0053] 4) Sputter a gadolinium-iron garnet film onto the surface of the molybdenum disulfide film 2 in the window formed in step 3), such as Figure 2 As shown in d. Using a gadolinium-iron garnet target, a magnetron sputtering machine was used, with the background vacuum of the magnetron sputtering machine controlled at 2 × 10⁻⁶. -5 The sputtering pressure was 1 Pa, the volume ratio of oxygen and argon was 1:1, and the gas flow rate was 20 sccm. The sputtering power was set to 60 W, and the magnetron sputtering time was 10-20 s. This yielded a 2-5 nm thick gadolinium-iron garnet intercalation layer.
[0054] 5) Then, the aluminum shield 7 is removed using an aluminum etching solution to obtain a 0.1 × 0.1 mm molybdenum disulfide film 2 and an upper gadolinium iron garnet intercalation film 3, as shown. Figure 2 As shown in e.
[0055] 6) The graphene film 4 was transferred onto the PET substrate 1 using a PMMA wet transfer method, completely covering the surface of the gadolinium iron garnet intercalation layer 3 and the molybdenum disulfide film 2, as shown. Figure 2 As shown in f;
[0056] 7) The edges of the graphene film from step 6) are etched using photolithography and plasma processing to obtain a graphene film 4 with a size of 0.4 × 0.1 mm, as shown. Figure 2As shown in g, graphene is patterned using photolithography and plasma etching processes: First, a photoresist mask layer is prepared on the graphene surface by photolithography to obtain the mask layer of the desired pattern. At the same time, part of the graphene to be etched is exposed, forming an etching window. At the etching window, the exposed graphene part is etched by plasma. After removing the photoresist, the desired pattern is obtained.
[0057] 8) A 100-200 nm layer of metallic Al was deposited on the graphene film using ultraviolet lithography and electron beam deposition techniques, and a 0.1 × 0.4 mm square window was defined on the surface of the metallic Al, such as... Figure 2 As shown in h; the aluminum shield preparation method is the same as step 2), and will not be repeated here.
[0058] 9) Sputter a gadolinium-iron garnet film onto the surface of the graphene film in the window formed in step 8) to form a gadolinium-iron garnet intercalation 3, as shown. Figure 2 As shown in i; the preparation method of gadolinium-iron garnet intercalation is the same as in step 4), and will not be repeated here.
[0059] 10) A single-walled carbon nanotube dispersion is uniformly spin-coated onto the gadolinium-iron garnet formed in step 9), and then dried to form a single-walled carbon nanotube film 5, as shown. Figure 2 As shown in j; the preparation method of single-walled carbon nanotube thin film is the same as in step 3), except that the material is replaced with single-walled carbon nanotube dispersion, which will not be described in detail here.
[0060] 11) Then, metallic Al is removed using an aluminum etching solution to obtain a 0.1 × 0.4 mm single-walled carbon nanotube film 5 and a lower gadolinium-iron garnet intercalation layer 3, as shown. Figure 2 As shown in k;
[0061] 12) Metal electrodes 6 for the detector are fabricated at both ends of the graphene film 4 obtained in step 7) and the single-walled carbon nanotube film 5 obtained in step 11), resulting in a GdIG-assisted double heterojunction flexible photodetector. Figure 2 As shown in l.
[0062] A photoresist mask layer was prepared by spin coating, pre-baking, exposure, development, and post-baking. Combined with metal deposition and lift-off micro / nano fabrication processes, 10-30 nm thick Cr and 60-90 nm thick Au electrodes were prepared on the left and right sides of the graphene film and single-walled carbon nanotube film. Cr served as a buffer material, while Au, with its excellent conductivity, served as the electrode material, increasing the adhesion between Au and the two-dimensional material.
[0063] The fabrication process of the detector of the present invention will be further illustrated below through specific embodiments.
[0064] Example 1
[0065] 1) First, prepare a clean PET substrate by cleaning it with acetone, ethanol and clean deionized water.
[0066] 2) A 160nm layer of metallic Al was deposited on a PET substrate using ultraviolet lithography and electron beam deposition. First, a photoresist mask layer was prepared by photolithography. Then, a 100nm thick layer of metallic Al was deposited on the photoresist mask layer using electron beam deposition. Finally, the photoresist mask layer was removed with acetone to form an aluminum mask wall, and a 0.1×0.1mm square window was defined on the surface of the metallic Al.
[0067] 3) Spin-coat a uniform molybdenum disulfide dispersion onto the window formed in step 2), and dry it to form a molybdenum disulfide film. Spin-coat a layer of molybdenum disulfide dispersion onto the device at a speed of 3000 rpm for 40 seconds using a spin coater. Then place the spin-coated sample on a baking table at 100°C and bake for 15 minutes until the dispersion solvent has completely evaporated to obtain a uniform molybdenum disulfide film as required.
[0068] 4) Sputter a gadolinium-iron garnet film onto the surface of the molybdenum disulfide film in the window formed in step 3). The gadolinium-iron garnet target is used in a magnetron sputtering machine, with the background vacuum of the magnetron sputtering machine controlled at 2 × 10⁻⁶. -5 With a sputtering pressure of 1 Pa, an oxygen and argon gas with a volume ratio of 1:1 and a flow rate of 20 sccm, a sputtering power of 60 W, and a magnetron sputtering time of 10 s, a 2 nm thick gadolinium iron garnet intercalation layer can be obtained.
[0069] 5) Then, the aluminum shield 7 is removed by aluminum etching solution to obtain a molybdenum disulfide film of size 0.1×0.1mm and an upper gadolinium iron garnet intercalation film;
[0070] 6) Prepare graphene films and transfer them onto PET substrates to completely cover the gadolinium iron garnet intercalation and molybdenum disulfide film surfaces;
[0071] 7) The edges of the graphene film obtained in step 6) are etched by photolithography and plasma processes to obtain a graphene film with a size of 0.4 × 0.1 mm;
[0072] 8) A 150nm layer of metallic Al was deposited on the graphene film using ultraviolet lithography and electron beam deposition, and a 0.1×0.4mm square window was defined on the surface of the metallic Al; the aluminum mask was prepared using the same method as in step 2).
[0073] 9) Sputter a gadolinium iron garnet film onto the surface of the graphene film in the window formed in step 8) to form a gadolinium iron garnet intercalation. The gadolinium iron garnet intercalation preparation method is the same as in step 4).
[0074] 10) A single-walled carbon nanotube dispersion is uniformly spin-coated onto the gadolinium iron garnet film formed in step 9), and then dried to form a single-walled carbon nanotube film; the preparation method of the single-walled carbon nanotube film is the same as in step 3).
[0075] 11) Metallic Al was removed by aluminum etching solution to obtain a single-walled carbon nanotube film with a size of 0.1×0.4mm and a gadolinium iron garnet intercalation layer underneath;
[0076] 12) Metal electrodes for the detector are fabricated at both ends of the graphene film obtained in step 7) and the single-walled carbon nanotube film 5 obtained in step 11). A photoresist mask layer is prepared by spin-coating, pre-baking, exposure, development, and post-baking. Combined with metal deposition and lift-off micro / nano fabrication processes, 20 nm thick Cr and 80 nm thick Au electrodes are fabricated on the left and right sides of the graphene film and the single-walled carbon nanotube film, respectively. Cr serves as a buffer material, and Au serves as the electrode material. This yields a GdIG-assisted double heterojunction flexible photodetector.
[0077] Example 2
[0078] 1) First, prepare a clean PET substrate 1, and clean it with acetone, ethanol and clean deionized water.
[0079] 2) A 100nm layer of metallic Al was deposited on a PET substrate using ultraviolet lithography and electron beam deposition. First, a photoresist mask layer was prepared by photolithography. Then, a 120nm thick layer of metallic Al was deposited on the photoresist mask layer using electron beam deposition. Finally, the photoresist mask layer was removed with acetone to form an aluminum mask wall, and a 0.1×0.1mm square window was defined on the surface of the metallic Al.
[0080] 3) Spin-coat a uniform molybdenum disulfide dispersion onto the window formed in step 2), and dry it to form a molybdenum disulfide film. Spin-coat a layer of molybdenum disulfide dispersion onto the device at a speed of 5000 rpm for 30 seconds using a spin coater. Then place the spin-coated sample on a baking table at 100°C and bake for 10 minutes until the dispersion solvent has completely evaporated to obtain a uniform molybdenum disulfide film as required.
[0081] 4) Sputter a gadolinium-iron garnet film onto the surface of the molybdenum disulfide film in the window formed in step 3). The gadolinium-iron garnet target is used in a magnetron sputtering machine, with the background vacuum of the magnetron sputtering machine controlled at 2 × 10⁻⁶. -5 With a sputtering pressure of 1 Pa, an oxygen and argon gas with a volume ratio of 1:1 and a flow rate of 20 sccm, a sputtering power of 60 W, and a magnetron sputtering time of 20 s, a 5 nm thick gadolinium iron garnet intercalation layer can be obtained.
[0082] 5) Then, the aluminum mask is removed by aluminum etching solution to obtain a 0.1×0.1 mm molybdenum disulfide film and an upper gadolinium iron garnet intercalation film;
[0083] 6) Prepare graphene films and transfer them onto PET substrates to completely cover the gadolinium iron garnet intercalation and molybdenum disulfide film surfaces;
[0084] 7) The edges of the graphene film obtained in step 6) are etched by photolithography and plasma processes to obtain a graphene film with a size of 0.4 × 0.1 mm;
[0085] 8) A 100nm layer of metallic Al was deposited on the graphene film using ultraviolet lithography and electron beam deposition, and a 0.1×0.4mm square window was defined on the surface of the metallic Al; the aluminum mask was prepared using the same method as in step 2).
[0086] 9) Sputter a gadolinium iron garnet film onto the surface of the graphene film in the window formed in step 8) to form a gadolinium iron garnet intercalation. The gadolinium iron garnet intercalation preparation method is the same as in step 4).
[0087] 10) A single-walled carbon nanotube dispersion is uniformly spin-coated onto the gadolinium iron garnet film formed in step 9), and then dried to form a single-walled carbon nanotube film; the preparation method of the single-walled carbon nanotube film is the same as in step 3).
[0088] 11) Metallic Al was removed by aluminum etching solution to obtain a single-walled carbon nanotube film with a size of 0.1×0.4mm and a gadolinium iron garnet intercalation layer underneath;
[0089] 12) Metal electrodes for the detector are fabricated at both ends of the graphene film obtained in step 7) and the single-walled carbon nanotube film obtained in step 11). A photoresist mask layer is prepared by spin-coating, pre-baking, exposure, development, and post-baking. Combined with metal deposition and lift-off micro / nano fabrication processes, 10 nm thick Cr and 90 nm thick Au electrodes are fabricated on the left and right sides of the graphene film and the single-walled carbon nanotube film, respectively. Cr serves as a buffer material, and Au serves as the electrode material. This yields a GdIG-assisted double heterojunction flexible photodetector.
[0090] Example 3
[0091] 1) First, prepare a clean PET substrate by cleaning it with acetone, ethanol and clean deionized water.
[0092] 2) A 200nm layer of metal Al was deposited on a PET substrate using ultraviolet lithography and electron beam deposition. First, a photoresist mask layer was prepared by photolithography. Then, an 80nm thick layer of metal Al was deposited on the photoresist mask layer using electron beam deposition. Finally, the photoresist mask layer was removed with acetone to form an aluminum mask wall, and a 0.1×0.1mm square window was defined on the surface of the metal Al.
[0093] 3) Spin-coat a uniform molybdenum disulfide dispersion onto the window formed in step 2), and dry it to form a molybdenum disulfide film. Use a spin coater to spin-coat a layer of molybdenum disulfide dispersion onto the device at a speed of 2000 rpm for 60 seconds. Then place the spin-coated sample on a baking table at 100°C and bake for 20 minutes until the dispersion solvent evaporates completely to obtain a uniform molybdenum disulfide film as required.
[0094] 4) Sputter a gadolinium-iron garnet film onto the surface of the molybdenum disulfide film in the window formed in step 3). The gadolinium-iron garnet target is used in a magnetron sputtering machine, with the background vacuum of the magnetron sputtering machine controlled at 2 × 10⁻⁶. -5 With a sputtering pressure of 1 Pa, oxygen and argon gas with a volume ratio of 1:1 and a flow rate of 20 sccm, sputtering power of 60 W, and magnetron sputtering time of 10 s, a 3 nm thick gadolinium iron garnet intercalation layer can be obtained.
[0095] 5) Then, the aluminum mask is removed by aluminum etching solution to obtain a 0.1×0.1 mm molybdenum disulfide film and an upper gadolinium iron garnet intercalation film;
[0096] 6) Prepare graphene films and transfer them onto PET substrates to completely cover the gadolinium iron garnet intercalation and molybdenum disulfide film surfaces;
[0097] 7) The edges of the graphene film obtained in step 6) are etched by photolithography and plasma processes to obtain a graphene film with a size of 0.4 × 0.1 mm;
[0098] 8) A 200nm layer of metallic Al was deposited on the graphene film using ultraviolet lithography and electron beam deposition, and a 0.1×0.4mm square window was defined on the surface of the metallic Al; the aluminum mask was prepared using the same method as in step 2).
[0099] 9) Sputter a gadolinium iron garnet film onto the surface of the graphene film in the window formed in step 8) to form a gadolinium iron garnet intercalation. The gadolinium iron garnet intercalation preparation method is the same as in step 4).
[0100] 10) A single-walled carbon nanotube dispersion is uniformly spin-coated onto the gadolinium iron garnet film formed in step 9), and then dried to form a single-walled carbon nanotube film; the preparation method of the single-walled carbon nanotube film is the same as in step 3).
[0101] 11) Metallic Al was removed by aluminum etching solution to obtain a single-walled carbon nanotube film with a size of 0.1×0.4mm and a gadolinium iron garnet intercalation layer underneath;
[0102] 12) Metal electrodes for the detector are prepared at both ends of the graphene film obtained in step 7) and the single-walled carbon nanotube film 5 obtained in step 11). A photoresist mask layer is prepared by spin-coating, pre-baking, exposure, development and post-baking. Combined with metal deposition and lift-off micro-nano manufacturing processes, 30nm thick metal Cr and 60nm thick metal Au electrodes are prepared on the left and right sides of the graphene film and the single-walled carbon nanotube film. Cr is used as a buffer material and Au is used as an electrode material, thus obtaining a GdIG-assisted double heterojunction flexible photodetector.
[0103] This invention proposes and prepares a gadolinium-iron garnet film with excellent uniformity and continuity as an intermediate layer to optimize the interface of a dual heterojunction, thereby increasing the barrier height between heterojunctions and blocking majority carrier dark current. At a 3V bias, dark current is suppressed by a factor of 10, responsivity is improved by a factor of 21, and specific detectivity is improved by two orders of magnitude. At a wavelength of 450nm, the responsivity is 47.375 A / W, and the specific detectivity is 1.952 × 10⁻⁶. 12 Jones exhibits a responsivity of 109.311 A / W and a specific detectivity of 4.504 × 10⁻⁶ at a wavelength of 1080 nm. 12 Jones demonstrated that molybdenum disulfide (MoD) films and single-walled carbon nanotube (SHU) films, acting as the primary light-absorbing layers, enable the detector to exhibit excellent photoresponse across a broad spectral band from the visible to the near-infrared. Furthermore, bending tests at different radii of curvature showcased the good mechanical stability of this flexible photodetector. This research demonstrates the potential of combining a double heterojunction with GdIG as the intermediate layer material for applications involving broad spectral coverage and weak light detection, providing a novel solution for high-performance flexible photodetectors.
[0104] In the field of intelligent medical monitoring, photodetectors can achieve non-destructive monitoring of vital signs of living organisms through photoplethysmography, enabling real-time and rapid medical monitoring services. Optical vital sign monitoring typically involves irradiating specific wavelengths of light onto human tissue and analyzing the light signals applied to the body to obtain personal physiological information. It can be used to measure heart rate, blood oxygen saturation, blood pressure, blood volume, and other personal health indicators. The flexible photodetector of this invention achieves effective matching between the detector and human tissue through flexibility, overcoming the problem of traditional detectors being inflexible and deformable, thereby improving data accuracy and providing a new platform for monitoring methods in intelligent medicine. Furthermore, the broad-spectrum absorption of this flexible photodetector covers most of the wavelength range (600–1300 nm) of human physiological information, enabling multi-functional detection purposes, such as simultaneously monitoring blood oxygen concentration and blood glucose concentration, for tracking the blood oxygen concentration of infants at risk of respiratory failure or breath-holding underwater athletes, and real-time blood glucose levels of diabetic patients, allowing for timely treatment and life-saving measures in case of problems.
[0105] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.
Claims
1. A method for fabricating a GdIG-assisted double heterojunction flexible photodetector, characterized in that, Includes the following steps: 1) Take the PET substrate and clean it thoroughly; 2) Deposit a layer of metallic Al on a PET substrate to form an aluminum mask, and define a square window on the surface of the metallic Al; 3) Spin-coat a molybdenum disulfide dispersion uniformly onto the window, and dry it to form a molybdenum disulfide film; 4) Control the conditions of magnetron sputtering to sputter a gadolinium iron garnet film onto the surface of a molybdenum disulfide film in the formed window to obtain a gadolinium iron garnet intercalation layer; 5) Remove the aluminum shield to obtain a molybdenum disulfide film and an upper gadolinium iron garnet intercalated film; 6) Prepare graphene films and transfer them onto PET substrates to completely cover the gadolinium iron garnet intercalation and molybdenum disulfide film surfaces; 7) The edges of the graphene film are etched using photolithography and plasma processes to obtain the graphene film; 8) A layer of metallic Al is deposited on the graphene film using ultraviolet lithography and electron beam deposition techniques, and a square window is defined on the surface of the metallic Al. 9) Control the conditions of magnetron sputtering to sputter gadolinium iron garnet film onto the surface of graphene film in the formed window to form gadolinium iron garnet intercalation; 10) A single-walled carbon nanotube dispersion is uniformly spin-coated onto the formed gadolinium iron garnet intercalation layer and dried to form a single-walled carbon nanotube film. 11) Remove metallic Al to obtain a single-walled carbon nanotube film and a gadolinium-iron garnet intercalation layer underneath; 12) Metal electrodes for the detector are fabricated at both ends of the obtained graphene film and at both ends of the single-walled carbon nanotube film to obtain a flexible photodetector based on GdIG-assisted double heterojunction.
2. The fabrication method of the GdIG-assisted double heterojunction flexible photodetector according to claim 1, characterized in that, In step 3), a layer of molybdenum disulfide dispersion is spin-coated at a speed of 2000-5000 rpm using a spin coater for 30-60 seconds. The spin-coated sample is then placed on a baking table at 100℃ and baked for 10-20 minutes.
3. The fabrication method of the GdIG-assisted double heterojunction flexible photodetector according to claim 1, characterized in that, In steps 4) and 9), the back vacuum of the magnetron sputtering machine is controlled to be 2 × 10⁻⁶. -5 The sputtering pressure was 1 Pa, the volume ratio of oxygen and argon was 1:1, and the gas flow rate was 20 sccm. The sputtering power was set to 60 W, and the magnetron sputtering time was 10-20 s.
4. The fabrication method of the GdIG-assisted double heterojunction flexible photodetector according to claim 3, characterized in that, The thickness of the gadolinium-iron garnet intercalation layer is 2-5 nm.
5. The method for fabricating a GdIG-assisted double heterojunction flexible photodetector according to claim 1, characterized in that, In step 6), the PMMA wet transfer method is used to transfer the graphene film onto the PET substrate.
6. The method for fabricating a GdIG-assisted double heterojunction flexible photodetector according to claim 1, characterized in that, In step 8), a 100-200 nm layer of metallic Al is deposited on the graphene film.
7. The method for fabricating a GdIG-assisted double heterojunction flexible photodetector according to claim 1, characterized in that, In step 12), 10-30 nm thick metal Cr and 60-90 nm thick metal Au electrodes are prepared on the left and right sides of the graphene film and the single-walled carbon nanotube film.
8. A flexible photodetector based on GdIG-assisted double heterojunction prepared by the method according to any one of claims 1-7, characterized in that, It includes a PET substrate, a molybdenum disulfide film, a gadolinium iron garnet intercalation layer, a graphene film, a single-walled carbon nanotube film, and a metal electrode. The molybdenum disulfide film is located on the surface of the PET substrate, the gadolinium iron garnet intercalation layer covers the molybdenum disulfide film, the graphene film covers the gadolinium iron garnet intercalation layer and the surface of the PET substrate, a gadolinium iron garnet intercalation layer is covered on top of the graphene film, the single-walled carbon nanotube film covers the gadolinium iron garnet intercalation layer, and the metal electrode is located on the graphene film covering the PET substrate and on both sides corresponding to the square window.
9. The GdIG-assisted double heterojunction flexible photodetector according to claim 8, characterized in that, The metal electrode uses 10nm-30nm Cr metal as a transition layer and 60-90nm Au metal as the electrode. The electrode forms an ohmic contact with the graphene film and the single-walled carbon nanotube film.
10. The application of the GdIG-assisted double heterojunction flexible photodetector according to claim 9 in intelligent medical detection.