Graphene flexible terahertz wave detector and preparation method thereof

Abstract

The invention discloses a graphene flexible terahertz wave detector and a preparation method thereof. The detector comprises a substrate layer and a graphene layer, the substrate layer is of a flexible insulation structure, the graphene layer is located above the substrate layer, the graphene layer is a single-layer graphene film, and the two ends of the graphene layer are connected with a source metal electrode and a drain metal electrode of asymmetric electrodes in a covering mode respectively. The graphene flexible terahertz wave detector provided by the invention has good flexibility and stability, supports recognizable and repeatable terahertz response, and can expand the response wavelength range to ultraviolet to millimeter wave frequency bands. And under conformal attachment with a flexible curved surface, high-resolution terahertz wave imaging of a composite material object and a hidden object is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible wearable terahertz wave detection and imaging, and particularly to a graphene flexible terahertz wave detector and a preparation method thereof. Background Art

[0002] Terahertz waves (0.1 THz–10 THz), as the transition band between microwaves and infrared in the electromagnetic spectrum, have characteristics such as low photon energy, high penetrability, high bandwidth, and molecular fingerprint spectra, and have important application prospects in fields such as wireless communication, radar imaging, and medical detection. As the core functional component of the terahertz technology system, a terahertz detector can convert terahertz wave signals into electrical signals to achieve target object detection and two-dimensional image reconstruction. Among them, miniaturized and flexible terahertz wave detectors can improve the device integration, resolution, and applicability, providing a technical basis for the development of high-spatial-resolution and wearable imaging systems. However, commercial terahertz detectors (such as Golay cells, bolometers, Schottky diodes, etc.) still face core challenges in miniaturization, high-resolution detection, and imaging. Due to the low terahertz absorption efficiency of traditional materials and the need to rely on antennas to achieve terahertz focusing, the system volume is large and the detection efficiency is limited. In addition, most actual objects have three-dimensional curvatures, and traditional rigid terahertz detectors cannot accurately measure them. For example, in current technologies, terahertz images for human body security inspection are obtained by rotating a terahertz detector 360°, which results in a very bulky terahertz imaging system. Although several types of terahertz tomography technologies have been reported, they still require complex systems and cannot be moved, which is not conducive to the miniaturization and high integration of detection and imaging systems.

[0003] Therefore, how to design a flexible terahertz wave detector to improve the integration, curved surface imaging ability, and application range of terahertz wave detection and imaging systems has become a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0004] The present invention provides a graphene flexible terahertz wave detector and a preparation method thereof to solve the technical problem of how to design a flexible terahertz wave detector to improve the integration and application range of terahertz wave detection and imaging systems, and to improve the detection efficiency and curved surface imaging ability of the terahertz wave detector.

[0005] On the one hand, the present invention provides a graphene flexible terahertz wave detector, including a substrate layer and a graphene layer; the substrate layer is a flexible insulating structure, the graphene layer is located above the substrate layer, the graphene layer is a single-layer graphene film, and source and drain metal electrodes of an asymmetric electrode are respectively covered and connected at both ends of the graphene layer.

[0006] In the technical solution of this application, the graphene flexible terahertz wave detector includes a flexible insulating substrate layer, a single-layer graphene layer, a source metal electrode, and a drain metal electrode, which has good flexibility and stability and supports recognizable and repeatable terahertz responses. The source metal electrode and the drain metal electrode are composed of asymmetric electrodes and have a broadband optoelectrothermal effect in the ultraviolet to millimeter-wave frequency band. The single-layer graphene layer has broadband absorption in the ultraviolet to millimeter-wave frequency band, and the response wavelength range can be extended to the ultraviolet to millimeter-wave frequency band. Since the substrate layer is a flexible insulating structure, the graphene flexible terahertz wave detector can achieve high-resolution terahertz wave imaging of composite material objects and hidden objects under conformal attachment to a flexible curved surface.

[0007] Further, the graphene layer is a rectangular structure.

[0008] Further, the dimension range of the length of the rectangular structure is 2 μm to 3000 μm, and the dimension range of the width of the rectangular structure is 2 μm to 3000 μm. Further, the source metal electrode and / or the drain metal electrode is circular.

[0009] Further, the diameter range of the circle is 10 μm to 1000 μm.

[0010] Further, the source metal electrode and / or the drain metal electrode is a regular polygon.

[0011] Further, the side length range of the regular polygon is 10 μm to 1000 μm.

[0012] Further, the source metal electrode is any one of Al, Ag, Au, Bi, Cr, Ti, and Ni, the drain metal electrode is any one of Al, Ag, Au, Bi, Cr, Ti, and Ni, and the materials of the source metal electrode and the drain metal electrode are different.

[0013] Further, the substrate layer is a single material of any one of mica, polyethylene terephthalate, polydimethylsiloxane, polymethyl methacrylate, polystyrene, and polyvinyl alcohol.

[0014] On the other hand, the present invention provides a preparation method of a graphene flexible terahertz wave detector, and the preparation method includes: Performing plasma etching treatment on one surface of the obtained substrate layer to form a hydrophilic surface; Transferring the graphene layer on the hydrophilized side of the substrate layer and performing patterning treatment on the graphene layer to obtain a single-layer graphene thin film; Lithography, sputtering, deposition, or evaporation coating processes are carried out at both ends of the graphene layer to form a source metal electrode and a drain metal electrode of an asymmetric pole, so as to obtain the graphene flexible terahertz wave detector.

[0015] This application provides a graphene flexible terahertz wave detector and a preparation method thereof. Compared with the prior art, the beneficial effects of the present invention are as follows: The graphene flexible terahertz wave detector of this application is composed of an asymmetric source metal electrode and drain metal electrode, and has a broadband optoelectrothermal effect in the ultraviolet to millimeter wave frequency band. The single-layer graphene layer has broadband absorption in the ultraviolet to millimeter wave frequency band, and the response wavelength range can be extended to the ultraviolet to millimeter wave frequency band. Since the substrate layer is a flexible insulating structure, the graphene flexible terahertz wave detector can achieve high-resolution terahertz wave imaging of composite material objects and concealed objects when conformally attached to a flexible curved surface. Description of the Drawings

[0016] Figure 1 is the front view structural schematic diagram of the graphene flexible terahertz wave detector provided in Embodiment 1 of the present invention; Figure 2 is the top view structural schematic diagram of the graphene flexible terahertz wave detector provided in Embodiment 1 of the present invention; Figure 3 is the schematic diagram of the optoelectronic response magnitude at different laser powers when the graphene flexible terahertz wave detector in Embodiment 1 of the present invention is irradiated with a 2.52 THz laser; Figure 4 is the schematic diagram of the optoelectronic response magnitude when the graphene flexible terahertz wave detector in Embodiment 1 of the present invention is irradiated with lasers of different wavelengths in the ultraviolet to millimeter wave frequency band; Figure 5 is the schematic diagram of the optoelectronic response magnitude at different laser powers when the graphene flexible terahertz wave detector in Embodiment 2 of the present invention is irradiated with a 2.52 THz laser; Figure 6 is the schematic diagram of the optoelectronic response magnitude at different laser powers when the graphene flexible terahertz wave detector in Embodiment 3 of the present invention is irradiated with a 2.52 THz laser; Figure 7 is the schematic diagram of the optoelectronic response magnitude at different laser powers when the graphene flexible terahertz wave detector in Embodiment 4 of the present invention is irradiated with a 2.52 THz laser; Figure 8 is the schematic diagram of the optoelectronic response magnitude at different bending angles when the graphene flexible terahertz wave detector of the present invention is irradiated with a 2.52 THz laser; Figure 9It is a schematic diagram of the light response magnitude of the graphene flexible terahertz wave detector of the present invention under the irradiation of a 2.52 THz laser and at a bending angle of 60° with different bending times; Figure 10 It is a schematic diagram of the conformal attachment of the graphene flexible terahertz wave detector of the present invention to a curved surface; Figure 11 It is a schematic diagram of terahertz wave imaging of a composite material object when the graphene flexible terahertz wave detector of the present invention is conformally attached to a curved surface under the irradiation of a 2.52 THz laser; Figure 12 It is a flow chart of the preparation method of the graphene flexible terahertz wave detector of the present invention.

[0017] Reference numerals: 1 - Source metal electrode; 2 - Graphene layer; 3 - Drain metal electrode; 4 - Substrate layer. Detailed implementation manners

[0018] The following specifically illustrates the implementation manners of the present invention in conjunction with the drawings. The given examples are only for illustrative purposes and should not be construed as limitations on the present invention. The included drawings are for reference and illustration only and do not constitute a limitation on the scope of protection of the present invention. Based on the examples in the present invention, all other examples obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. In the description of the present invention, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", "third", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "plurality" is two or more.

[0019] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components. The terms "vertical", "horizontal", "left", "right", "up", "down" and similar expressions used herein are only for illustrative purposes and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation on the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0020] In the description of the present invention, it should be noted that unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which this technology belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0021] Van der Waals two-dimensional atomic crystals refer to materials in which electrons can only move freely (planar motion) in two non-nano scales (1–100 nm). They have unique weak interlayer interactions, tunable electronic band structures, and mechanical stretching properties, and are regarded as potential flexible detector materials. It has been reported that two-terminal devices with simple structures are fabricated on flexible substrates using two-dimensional semiconductors such as transition metal dichalcogenides (TMDCs) and black phosphorus. They have excellent responsivity, specific detectivity, and response time, up to 1.28 × 10 3 A / W, 3.02 × 10 11 Jones and on the order of milliseconds. However, two-dimensional semiconductors have relatively wide bandgaps, which enable them to operate only in the ultraviolet to near-infrared bands. In contrast, two-dimensional semimetals (such as graphene, WTe2, PtTe2, PdTe2, NiTe2, and T d -MoTe2) have zero-bandgap structures. In particular, the second type of semimetals (such as WTe2, Cd3As2, and T d -MoTe2) have inclined linear electron dispersion relations and exhibit fast optoelectronic responses in a wide spectral range from ultraviolet to terahertz under the drive of optically excited hot carriers. However, most of the reported two-dimensional semimetal optoelectronic detectors are fabricated on rigid substrates. Even on flexible substrates, additional antenna integration or long channels are required to achieve long-wave detection, resulting in large device areas, slow response speeds, and complex fabrication processes, which limit the detection and imaging applications of detectors in miniaturized, flexible, and wearable devices.

[0022] The photothermoelectric effect is a physical phenomenon in which a temperature difference is formed at both ends of a material under light induction, which promotes the diffusion of carriers and then generates a photocurrent. It is a representative optoelectronic response mechanism in graphene optoelectronic detectors. Since the energy of terahertz waves is 0.414 meV–41.4 meV, which is much smaller than the energy of the interband transition of graphene carriers (the energy of the interband transition is 2E f), the incident light mainly generates hot carriers through intra-band excitation in the graphene layer, thereby increasing the carrier temperature in the single-layer graphene. The metal electrodes of the asymmetric electrodes at both ends act as heat sinks, resulting in an uneven temperature distribution along the channel. At the same time, the work function difference of the metal electrodes of the asymmetric electrodes at both ends will cause different degrees of metal-induced doping at both ends of the graphene, resulting in a non-uniform local Fermi level distribution in the channel region. The asymmetric Fermi level and temperature distributions further lead to a position-dependent Seebeck coefficient distribution. The presence of a temperature gradient and an asymmetric Seebeck coefficient will induce a local potential gradient, which is beneficial to the diffusion of hot carriers, and thus generate a photocurrent response. Therefore, introducing a single-layer graphene and asymmetric electrode metal electrodes on a flexible substrate is expected to achieve efficient detection in the ultraviolet to millimeter-wave frequency bands including terahertz waves, while reducing the detection area of the device, which is beneficial to the miniaturization and integration of flexible electronic devices.

[0023] In view of this, as Figure 1 , Figure 2 shown, in Embodiment 1 of the present invention, a graphene flexible terahertz wave detector includes a substrate layer 4 and a graphene layer 2; the substrate layer 4 is a flexible insulating structure, the graphene layer 2 is located above the substrate layer 4, the graphene layer 2 is a single-layer graphene film, and the source metal electrode 1 and the drain metal electrode 3 with asymmetric electrodes are respectively covered and connected at both ends of the graphene layer 2. It should be noted that the "source metal electrode 1 and drain metal electrode 3 with asymmetric electrodes" means that the source metal electrode 1 and the drain metal electrode 3 are composed of metals of two different materials.

[0024] In this embodiment, the graphene flexible terahertz wave detector includes a substrate layer 4 with a flexible insulating structure, a single-layer graphene layer 2, a source metal electrode 1 and a drain metal electrode 3, and has good flexibility and stability, supporting recognizable and repeatable terahertz responses. Since the source metal electrode 1 and the drain metal electrode 3 are asymmetric electrodes with different work functions, there are differences in the carrier concentrations in the contact regions between the graphene layer 2 and the source metal electrode 1 and the drain metal electrode 3, which promotes the diffusion of hot carriers and can effectively improve the detection performance of the graphene flexible terahertz wave detector.

[0025] In this embodiment, the substrate layer 4 is Polythylene terephthalate (PET), the source metal electrode 1 and the drain metal electrode 3 are Ti and Bi respectively. The source metal electrode 1 and the drain metal electrode 3 have a broadband optoelectrothermal effect in the ultraviolet to millimeter-wave frequency band, and the single-layer graphene layer 2 has a broadband absorption in the ultraviolet to millimeter-wave frequency band, and the response wavelength range can be extended to the ultraviolet to millimeter-wave frequency band. Since the substrate layer 4 is a flexible insulating structure, the graphene flexible terahertz wave detector can achieve high-resolution terahertz wave imaging of composite material objects and hidden objects when conformally attached to a flexible curved surface.

[0026] In the embodiment of the present application, during the terahertz wave detection process of the graphene flexible terahertz wave detector, the bias voltage V ds = 0. The terahertz wave irradiates on the graphene layer 2, and a current signal or a voltage signal is obtained at the source metal electrode 1 and the drain metal electrode 3. Due to the asymmetry of the metal materials of the source metal electrode 1 and the drain metal electrode 3, the work function difference of the two asymmetric electrode metals will cause different degrees of metal-induced doping at both ends of the graphene, resulting in a non-uniform local Fermi level distribution in the channel region of the graphene layer 2, leading to a temperature gradient on both sides, thus generating an optoelectrothermal effect. By changing parameters such as the size of the graphene channel and the materials of the source metal electrode 1 and the drain metal electrode 3, recognizable and stable room-temperature terahertz wave detection can be achieved. As Figure 3 shown is a schematic diagram of the optoresponse magnitude of the graphene flexible terahertz wave detector based on a PET substrate under 2.52 THz laser irradiation at different excitation powers. As the power increases, the photocurrent increases linearly.

[0027] In the preferred embodiment of the present application, due to the broadband optoelectrothermal effect of the asymmetric electrode in the ultraviolet to millimeter-wave frequency band, the response wavelength range of the graphene flexible detector can be extended to the ultraviolet to millimeter-wave frequency band. As Figure 4 shown is a schematic diagram of the optoresponse magnitude of the graphene flexible terahertz wave detector under laser irradiation at different wavelengths in the ultraviolet to millimeter-wave frequency band. As the excitation wavelength changes, the optoresponse shows an obvious response in the ultraviolet to millimeter-wave frequency band, and as the excitation wavelength increases, the optoresponse gradually increases, indicating that the graphene flexible terahertz wave detector has a broadband response covering the ultraviolet to millimeter-wave frequency band including terahertz waves, and it has the widest response spectrum among the currently reported flexible two-dimensional detectors.

[0028] Among them, the graphene layer 2 is a rectangular structure.

[0029] In addition, the dimension range of the length of the rectangular structure is 2 μm to 3000 μm, and the dimension range of the width of the rectangular structure is 2 μm to 3000 μm. Among them, the source metal electrode 1 and / or the drain metal electrode 3 are circular. Since the source metal electrode 1 and / or the drain metal electrode 3 are circular, sampling this symmetric structure can enhance the local electric field, improve graphene absorption, and thus enhance the device response. It should be noted that the thickness of the source metal electrode 1 and the drain metal electrode 3 is greater than the thickness of the graphene layer 2.

[0030] In addition, the diameter range of the circle is 10 μm to 1000 μm.

[0031] Among them, the source metal electrode 1 and / or the drain metal electrode 3 are regular polygons. Since the source metal electrode 1 and / or the drain metal electrode 3 are regular polygons, sampling this symmetric structure can enhance the local electric field, improve graphene absorption, and thus enhance the device response In addition, the side length range of the regular polygon is 10 μm to 1000 μm.

[0032] Embodiment 2 The difference from Embodiment 1 is that the substrate layer 4 is polydimethylsiloxane (PDMS), the graphene layer 2 is located above the substrate layer 4, the graphene layer 2 is a single-layer graphene film, and the source metal electrode 1 and the drain metal electrode 3 covered and connected with asymmetric electrodes are respectively located at both ends of the graphene layer 2. The source metal electrode 1 and the drain metal electrode 3 are Ti and Bi respectively.

[0033] In the embodiments of the present application, during the terahertz wave detection process of the graphene flexible terahertz wave detector, the bias voltage V ds = 0, the terahertz wave irradiates on the graphene layer 2, and current signals or voltage signals are obtained at the source metal electrode 1 and the drain metal electrode 3. Since the metal materials of the source metal electrode 1 and the drain metal electrode 3 are asymmetric, the work function difference of the asymmetric electrode metals at both ends will cause different degrees of metal-induced doping at both ends of the graphene, resulting in a non-uniform local Fermi level distribution in the channel region of the graphene layer 2, resulting in a temperature gradient on both sides, and thus generating a photothermal electric effect. The photothermal electric effect drives the hot carriers to move in the channel, thereby realizing recognizable and stable room-temperature terahertz wave detection. As Figure 5 shown in the schematic diagram of the optical response magnitude of the graphene flexible terahertz wave detector based on the PDMS substrate under the irradiation of a 2.52 THz laser at different excitation powers. As the power increases, the photocurrent increases linearly.

[0034] Embodiment 3 The difference from Example 1 is that the source metal electrode 1 and the drain metal electrode 3 are composed of Ti and Cr respectively. The substrate layer 4 is polyethylene terephthalate (PET). The graphene layer 2 is located above the substrate layer 4. The graphene layer 2 is a single-layer graphene film. The two ends of the graphene layer 2 are respectively covered and connected with the source metal electrode 1 and the drain metal electrode 3 with asymmetric electrodes.

[0035] In the embodiment of the present application, during the process of detecting terahertz waves by the graphene flexible terahertz wave detector, the bias voltage V ds = 0. When the terahertz wave irradiates on the graphene layer 2, a current signal or a voltage signal is obtained at the source metal electrode 1 and the drain metal electrode 3. Since the source metal electrode 1 and the drain metal electrode 3 are made of asymmetric metal materials, the difference in the work functions of the metals of the asymmetric electrodes at both ends will cause different degrees of metal-induced doping at both ends of the graphene, thereby generating a non-uniform local Fermi level distribution in the channel region of the graphene layer 2, resulting in a temperature gradient on both sides, and thus generating a photothermoelectric effect. The photothermoelectric effect drives the hot carriers to move in the channel, thereby realizing recognizable and stable room-temperature terahertz wave detection. As Figure 6 Shown is a schematic diagram of the optical response magnitude of the graphene flexible terahertz wave detector based on Ti and Cr asymmetric electrodes under different excitation powers when irradiated by a 2.52 THz laser. As the power increases, the photocurrent increases linearly.

[0036] Example 4 The difference from Example 2 is that the source metal electrode 1 and the drain metal electrode 3 are composed of Ti and Cr respectively. The substrate layer 4 is polydimethylsiloxane (PDMS). The graphene layer 2 is located above the substrate layer 4. The graphene layer 2 is a single-layer graphene film. The two ends of the graphene layer 2 are respectively covered and connected with the source metal electrode 1 and the drain metal electrode 3 with asymmetric electrodes. In the embodiment of the present application, during the process of detecting terahertz waves by the graphene flexible terahertz wave detector, the bias voltage V ds = 0. When the terahertz wave irradiates on the graphene layer 2, a current signal or a voltage signal is obtained at the source metal electrode 1 and the drain metal electrode 3. Since the source metal electrode 1 and the drain metal electrode 3 are made of asymmetric metal materials, the difference in the work functions of the metals of the asymmetric electrodes at both ends will cause different degrees of metal-induced doping at both ends of the graphene, thereby generating a non-uniform local Fermi level distribution in the channel region of the graphene layer 2, resulting in a temperature gradient on both sides, and thus generating a photothermoelectric effect. The photothermoelectric effect drives the hot carriers to move in the channel, thereby realizing recognizable and stable room-temperature terahertz wave detection. As Figure 7The figure shows a schematic diagram of the light response magnitude of a graphene flexible terahertz wave detector based on a PDMS substrate and Ti and Cr asymmetric electrodes under 2.52 THz laser irradiation at different excitation powers. As the power increases, the photocurrent increases linearly.

[0037] It should be noted that in the above Embodiment 1 to Embodiment 4, the substrate layer 4 can also be a single material of any one of mica, polyethylene terephthalate, polydimethylsiloxane, polymethyl methacrylate, polystyrene, and polyvinyl alcohol. When the material of the substrate layer 4 remains unchanged, the source metal electrode 1 is any one of Al, Ag, Au, Bi, Cr, Ti, and Ni, and the drain metal electrode 3 is any one of Al, Ag, Au, Bi, Cr, Ti, and Ni, and the materials of the source metal electrode 1 and the drain metal electrode 3 are different. Under 2.52 THz laser irradiation, as the power increases, the photocurrent of the graphene flexible terahertz wave detector increases linearly. When the materials of the source metal electrode 1 and the drain metal electrode 3 are different, the photocurrent will fluctuate within the range of 0.2 nA to 10 nA. Exchanging the materials of the source metal electrode 1 and the drain metal electrode 3 will not affect the photocurrent.

[0038] It should also be noted that the substrate layer 4 is a single material of any one of mica, polymethyl methacrylate, polystyrene, and polyvinyl alcohol, and the source metal electrode 1 and the drain metal electrode 3 are respectively any two different materials of Al, Ag, Au, Bi, Cr, Ti, and Ni. The thickness of the substrate layer 4 is 80 μm to 500 μm. Both the substrate layer 4 and the graphene layer 2 have good mechanical flexibility and can have excellent flexibility and repeatable terahertz wave response at different bending angles and bending times. As Figure 8 The figure shows a schematic diagram of the light response magnitude of the graphene flexible terahertz wave detector under 2.52 THz laser irradiation at different bending angles. As the bending angle increases, the photocurrent intensity slightly decreases (~ 8%), presumably due to the weakening of the plasmon resonance intensity caused by the deformation of the graphene rectangular patterned structure array. As Figure 9 The figure shows a schematic diagram of the light response magnitude of the graphene flexible terahertz wave detector under 2.52 THz laser irradiation and a 60° bending angle at different bending times. After bending 100 times, the photocurrent only decays by 0.3%, indicating that the device can continue to be bent multiple times. The slight fluctuation of the photocurrent intensity during the bending process may be caused by a slight change in the laser irradiation position. This result demonstrates that the device has good flexibility and stable photocurrent to adapt to terahertz wave detection and imaging during three-dimensional curved surface conformal attachment, and has important application potential in wearable intelligent electronic devices.

[0039] As Figure 10The figure shows a schematic diagram of conformal attachment of a graphene flexible terahertz wave detector to a curved surface. The graphene flexible terahertz wave detector can perform non-invasive imaging on objects in a curved state. The device is fixed on the curved surface of the human wrist, and a terahertz dual-focus imaging system is used to study the terahertz wave imaging ability of the device for composite material objects and concealed objects. As Figure 11 The figure shows a schematic diagram of terahertz wave imaging of a composite material object when the graphene flexible terahertz wave detector is conformally attached to a curved surface under the irradiation of a 2.52 THz laser; the plastic "T" is difficult to be detected when pasted on the paper due to being nearly transparent; while in the terahertz image, the morphologies of the metal "T" and the plastic "T" can be easily observed, and there are different contrasts between the two, which are very easy to distinguish. The graphene flexible terahertz wave detector can also achieve terahertz wave imaging of concealed objects when conformally attached to a curved surface under the irradiation of a 2.52 THz laser; the anti-counterfeiting watermark of the RMB cannot be distinguished by the naked eye, while under the irradiation of 2.52 THz terahertz waves, the anti-counterfeiting watermark has different terahertz wave transmittances from the surrounding paper. By performing two-dimensional grating scanning imaging on the area within the red dashed box, a terahertz photocurrent image of the anti-counterfeiting watermark "orchid" with a pixel of 63 × 53 can be obtained. It shows that the graphene flexible terahertz wave detector plays a crucial role in wearable imaging electronic devices.

[0040] Example 5 As Figure 12 As shown, a preparation method of a graphene flexible terahertz wave detector includes: S1. Perform plasma etching treatment on one surface of the obtained substrate layer 4 to form a hydrophilic surface; S2. Transfer the graphene layer 2 to the hydrophilically treated side of the substrate layer 4, and perform patterning treatment on the graphene layer 2 to obtain a single-layer graphene film; S3. Perform photolithography, sputtering, deposition or evaporation treatment at both ends of the graphene layer 2 to form a source metal electrode 1 and a drain metal electrode 3 with asymmetric poles, so as to obtain a graphene flexible terahertz wave detector.

[0041] For the specific limitations on the preparation method of the graphene flexible terahertz wave detector, reference can be made to the above limitations on the graphene flexible terahertz wave detector, which will not be elaborated here. Those skilled in the art can use different methods for each specific application to achieve the described functions, but such implementation should not be considered to exceed the scope of the present invention.

[0042] The graphene flexible terahertz wave detector and its preparation method provided in this embodiment are used to solve the technical problem of how to design a flexible terahertz wave detector to improve the integration, detection dimension and application range of terahertz wave detection and imaging systems, and improve the detection performance and curved surface imaging ability of terahertz wave detectors. The flexible terahertz wave detector provided in this application has good flexibility and stability, supports broadband detection covering the ultraviolet to millimeter wave frequency bands including terahertz waves, and realizes high-resolution terahertz wave imaging of composite material objects and hidden objects under conformal attachment to flexible curved surfaces, and has good application prospects.

[0043] Each embodiment in this specification is described in a progressive manner. For parts that are the same or similar in each embodiment, reference can be made to each other. The key point of each embodiment is to illustrate the differences from other embodiments. In particular, for method embodiments, since they are basically similar to device embodiments, the description is relatively simple, and reference can be made to the relevant parts of the device embodiments for the relevant parts. It should be noted that the above technical features of the embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the above technical features in the embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0044] The above embodiments only represent several preferred embodiments of the present invention, and the description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and replacements can be made, and these improvements and replacements should also be regarded as the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the protection scope of the claims.

Claims

1. A graphene flexible terahertz wave detector, characterized in that, It includes a substrate layer (4) and a graphene layer (2); the substrate layer (4) is a flexible insulating structure, the graphene layer (2) is located above the substrate layer (4), the graphene layer (2) is a single-layer graphene film, and source metal electrodes (1) and drain metal electrodes (3) of asymmetric electrodes are respectively covered and connected at both ends of the graphene layer (2).

2. The graphene flexible terahertz wave detector according to claim 1, wherein The graphene layer (2) is a rectangular structure.

3. The graphene flexible terahertz wave detector according to claim 2, wherein The dimension range of the length of the rectangular structure is 2 μm to 3000 μm, and the dimension range of the width of the rectangular structure is 2 μm to 3000 μm.

4. The graphene flexible terahertz wave detector according to claim 1, wherein The source metal electrode (1) and / or the drain metal electrode (3) is circular.

5. The graphene flexible terahertz wave detector according to claim 4, wherein The diameter range of the circle is 10 μm to 1000 μm.

6. The graphene flexible terahertz wave detector according to claim 1, characterized in that The source metal electrode (1) and / or the drain metal electrode (3) is a regular polygon.

7. The graphene flexible terahertz wave detector according to claim 6, wherein The side length range of the regular polygon is 10 μm to 1000 μm.

8. The graphene flexible terahertz wave detector according to claim 1, wherein The source metal electrode (1) is any one of Al, Ag, Au, Bi, Cr, Ti, Ni, the drain metal electrode (3) is any one of Al, Ag, Au, Bi, Cr, Ti, Ni, and the source metal electrode (1) and the drain metal electrode (3) are made of different materials.

9. The graphene flexible terahertz wave detector according to claim 1, wherein The substrate layer (4) is a single material of any one of mica, polyethylene terephthalate, polydimethylsiloxane, polymethyl methacrylate, polystyrene, and polyvinyl alcohol.

10. A preparation method of a graphene flexible terahertz wave detector for preparing the graphene flexible terahertz wave detector according to any one of claims 1-9, characterized in that, The preparation method includes: Performing plasma etching treatment on one surface of the obtained substrate layer (4) to form a hydrophilic surface; Transferring the graphene layer (2) to the hydrophilically treated side of the substrate layer (4) and performing patterning treatment on the graphene layer (2) to obtain a single-layer graphene film; Performing photolithography, sputtering, deposition or evaporation on both ends of the graphene layer (2) to form source metal electrodes (1) and drain metal electrodes (3) of an asymmetric pole, so as to obtain the graphene flexible terahertz wave detector.

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