Optothermo-electric graphene terahertz detector and preparation method thereof

Abstract

The present application relates to the technical field of terahertz detectors, and more particularly to a photothermal graphene terahertz detector and a preparation method thereof, the preparation method comprising: S1. performing a patterned etching treatment on a local surface of a substrate layer; S2. preparing a metal electrode at a substrate anchoring area; S3. transferring a graphene film to the surface of the substrate layer, the graphene film covering the substrate etching area and the substrate anchoring area; and S4. performing an annealing treatment. The photothermal graphene terahertz detector comprises a substrate layer, a silicon dioxide substrate layer comprising a substrate etching area and a substrate anchoring area; the silicon dioxide substrate layer is plated with a first electrode and a second electrode, and a graphene film is arranged on the silicon dioxide substrate layer; and the graphene film covers the substrate etching area and the substrate anchoring area. The present application can simultaneously solve the problems of thermal gradient establishment, carrier mobility maintenance and equivalent noise suppression, and realize a self-powered terahertz detector with high sensitivity, fast response and wide frequency band adaptation at room temperature.

Description

Technical Field

[0001] This invention relates to the technical field of terahertz detectors, and more specifically, to a photothermal-electric graphene terahertz detector and its preparation method. Background Technology

[0002] The terahertz band (frequency range 0.1THz-10THz), as a key region in the electromagnetic spectrum connecting microwaves and infrared light, possesses unique advantages such as penetrating nonpolar materials, safety for biological tissues, and abundant spectrum resources. It holds irreplaceable application value in fields such as next-generation high-speed communication (6G), non-destructive testing, biomedical imaging, security inspection, and astronomical detection. Achieving high-sensitivity, fast-response terahertz detection at room temperature is the core bottleneck driving this technology from the laboratory to industrial applications. The photothermoelectric effect (PTE), based on the temperature gradient formed after a material absorbs radiant energy, converts it into an electrical signal through the Seebeck effect, enabling self-powered detection without external bias, making it the preferred technical path for room-temperature terahertz detection. Graphene, as a two-dimensional material, possesses ultra-high carrier mobility, excellent hot electron transport properties, and wide-band absorption capabilities, and is considered an ideal material for constructing high-performance photothermoelectric terahertz detectors. However, the practical application of graphene is limited by the performance degradation caused by the interaction between the device structure and the substrate, making it difficult for traditional devices to simultaneously optimize sensitivity and response speed. Existing photon detectors, such as Schottky diodes and quantum well detectors, while offering fast response times, require extremely low temperatures for noise suppression, resulting in bulky equipment that fails to meet portability requirements. Existing thermal detectors, such as thermopile detectors, calorimeters, and traditional graphene-attached detectors, while capable of operating at room temperature, suffer from inherent performance limitations. Traditional graphene-attached detectors, in particular, exhibit the following problems: 1) Substrate thermal conductivity makes it difficult to establish a temperature gradient: Graphene and dielectric substrate are in direct contact and form strong thermal coupling. The high thermal conductivity of the substrate will quickly dissipate the terahertz energy absorbed by graphene. The heat of charge carriers is lost through the heat sink effect, and an effective in-plane thermal temperature difference cannot be formed, which seriously weakens the photothermal-electric conversion efficiency. Even if a low thermal conductivity substrate is used, it is still difficult to completely suppress thermal diffusion and limit the improvement of detector responsivity. 2) Dielectric loss and phonon scattering reduce carrier mobility: The contact between graphene and the dielectric substrate causes dual performance degradation. On the one hand, the dielectric properties of the substrate generate additional dielectric loss, which consumes terahertz radiation energy. On the other hand, optical phonons on the substrate surface are strongly scattered with the graphene carriers, causing the carrier mobility to deviate significantly from the intrinsic value, reducing charge transport efficiency and affecting the detector response speed and detection sensitivity. 3) Substrate-induced noise leads to high equivalent noise power (NEP): The interfacial interaction between graphene and the substrate introduces additional 1 / f noise and current noise, which, combined with Johnson-Nyquist thermal noise, leads to an increase in the device's equivalent noise power. Existing room-temperature graphene terahertz detectors are difficult to meet the requirements for detecting weak terahertz signals, while low-temperature graphene bilayer detectors rely on cooling systems and cannot be put into practical use at room temperature. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing traditional graphene-attached detectors, such as difficulty in establishing thermal gradients, difficulty in maintaining carrier mobility, and difficulty in suppressing equivalent noise. This invention provides a photothermal-electric graphene terahertz detector and its preparation method, which can simultaneously solve the problems of establishing thermal gradients, maintaining carrier mobility, and suppressing equivalent noise, and achieve self-powered terahertz detection with high sensitivity, fast response, and wide frequency band adaptability at room temperature.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for fabricating a photothermal-electric graphene terahertz detector is provided, comprising the following steps: S1. Select a substrate layer and perform patterned etching on a local surface of the substrate layer, wherein the area subjected to patterned etching forms a substrate etching area, and the area not subjected to patterned etching serves as a substrate anchoring area. S2. Fabricate a metal electrode at the substrate anchoring region; S3. Obtain a graphene film, transfer the graphene film to the surface of the substrate layer, and the graphene film covers the etched area and the anchoring area of ​​the substrate to form a graphene suspended-anchored structure layer; S4. Anneal the sample after step S3 to obtain a photothermal graphene terahertz detector.

[0005] The present invention discloses a method for fabricating a photothermal graphene terahertz detector. By performing patterned etching on a local surface of a substrate layer to obtain an etched area and an anchored area, and then covering it with a graphene film, a graphene suspended-anchored structure layer is formed. This method can eliminate the adverse effects of the substrate layer on the graphene, maximize the potential of the interaction between graphene and terahertz waves, and achieve a self-powered terahertz detector with high sensitivity, fast response, and wide frequency band adaptability at room temperature. At the same time, it takes into account the thermal stability and performance balance of the device, and can also reduce power consumption to meet the needs of practical applications.

[0006] Further, step S1 includes the following steps: S11. Select a high thermal resistance silicon oxide wafer as the substrate layer, clean and dry the substrate layer, and then modify the dried substrate layer. S12. Coat the surface of the substrate with photoresist, perform local maskless patterning photolithography, develop, and then use reactive ion etching process to etch the silicon dioxide substrate layer of the substrate to form the substrate etching area.

[0007] Furthermore, the substrate etching region includes an array of circular hole groove structures.

[0008] Furthermore, the groove depth of the circular hole groove structure is 0.1~1μm.

[0009] Further, step S2 includes the following steps: S21. Coating photoresist on the surface of the substrate anchoring area, positioning overlay, and developing to complete the positioning photolithography patterning of the electrode area; S22. A Cr / Au composite metal layer is deposited in the electrode area with a positioning photolithography pattern using a thermal evaporation process. Then, the composite metal layer outside the electrode area is peeled off to obtain the first electrode and the second electrode.

[0010] Furthermore, the first electrode and the second electrode are arranged along a first direction in the substrate anchoring region, and the width of the graphene suspended-anchoring structure layer in the second direction is smaller than the width of the first electrode and / or the second electrode in the second direction, wherein the first direction is perpendicular to the second direction.

[0011] Further, step S3 includes the following steps: S31. Obtain a graphene film, and use a PMMA support layer to transfer the graphene film to the surface of the substrate layer, wherein the graphene film covers the etched area and the anchoring area of ​​the substrate; S32. Coating the surface of the graphene film with photoresist, overlaying, and plasma etching to form the graphene suspended-anchored structure layer.

[0012] Furthermore, the coverage area of ​​the graphene suspended-anchored structure layer is smaller than the surface area of ​​the substrate layer.

[0013] The present invention also provides a photothermal-electric graphene terahertz detector, comprising a substrate layer, the substrate layer comprising a silicon-based substrate layer and a silicon dioxide substrate layer stacked thereon, the silicon dioxide substrate layer comprising a substrate etching region and a substrate anchoring region, wherein the substrate etching region comprises an array of circular hole groove structures; the silicon dioxide substrate layer is coated with a first electrode and a second electrode, the substrate etching region being located between the first electrode and the second electrode; a graphene film is covered on the silicon dioxide substrate layer, and the graphene film is in contact with both the first electrode and the second electrode; the graphene film covers the substrate etching region and the substrate anchoring region, forming a graphene suspended-anchored structure layer.

[0014] Furthermore, the first electrode is any one or more of Al, Ag, Au, Bi, Cr, Pt, Ti, and Ni, and the second electrode is any one or more of Al, Ag, Au, Bi, Cr, Pt, Ti, and Ni, and the first electrode and the second electrode are made of the same electrode material.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention discloses a photothermal-electric graphene terahertz detector and its fabrication method. By patterning and etching a local surface of a substrate layer to obtain an etched area and an anchoring area, and then covering it with a graphene film, a graphene suspended-anchored structure layer is formed. This eliminates the adverse effects of the substrate layer on the graphene, maximizes the potential for interaction between graphene and terahertz waves, and achieves high sensitivity, fast response, and wide-band adaptability self-powered terahertz detection at room temperature. It also balances the thermal stability and performance of the photothermal-electric graphene terahertz detector, and reduces power consumption to meet practical application requirements. Attached Figure Description

[0016] Figure 1 This is a flowchart of a method for fabricating a photothermal-electric graphene terahertz detector according to the present invention; Figure 2 This is a schematic diagram of the device structure formed after step S1 in the preparation method of the present invention; Figure 3 This is a schematic diagram of the device structure formed after step S2 in the preparation method of the present invention; Figure 4 This is a schematic diagram of the device structure formed after step S3 in the preparation method of the present invention; Figure 5 This is a schematic diagram of the structure of a photothermal-electric graphene terahertz detector according to the present invention; Figure 6 This is a three-dimensional structural schematic diagram of a photothermal-electric graphene terahertz detector according to the present invention. Figure 7 The figure shows the numerical simulation results of the photovoltage and channel thermal distribution of the photothermal graphene terahertz detector of this invention. Figure 8 The multi-dimensional characterization of the photothermal-electric graphene terahertz detector of this invention is obtained through optical microscopy, SEM, and Raman spectroscopy. Figure 9 This is an AFM morphology characterization image of the substrate etching region of the photothermal graphene terahertz detector of the present invention before and after graphene transfer. Figure 10 The graph shows the switching characteristics of the photothermal-electric graphene terahertz detector of this invention and the comparative device.

[0017] In the attached figures: 110, silicon substrate layer; 120, silicon dioxide substrate layer; 121, substrate etched area; 122, substrate anchoring area; 200, first electrode; 300, second electrode; 400, graphene suspended-anchoring structure layer; 410, graphene suspended area; 420, graphene anchoring area. Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments. The accompanying drawings are for illustrative purposes only, representing schematic diagrams rather than actual physical objects, and should not be construed as limiting the scope of this patent. To better illustrate the embodiments of the present invention, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0019] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0020] Example 1 like Figures 1 to 6 The first embodiment of the method for fabricating a photothermal-electric graphene terahertz detector according to the present invention is shown, which includes the following steps: S1. Select a substrate layer and perform patterned etching on a local surface of the substrate layer. The area where the patterned etching is performed forms the substrate etching area 121, and the area where the patterned etching is not performed is the substrate anchoring area 122. S2. Fabricate a metal electrode at the substrate anchoring region 122; S3. Obtain a graphene film, transfer the graphene film to the surface of the substrate layer, and cover the substrate etched area 121 and the substrate anchoring area 122 with the graphene film to form a graphene suspended-anchoring structure layer 400. S4. Anneal the sample after step S3 to obtain a photothermal graphene terahertz detector.

[0021] This invention obtains a substrate etched region 121 and a substrate anchoring region 122 by patterning a local surface of the substrate layer, and then covers it with a graphene film to obtain a graphene suspended-anchoring structure layer 400. This can eliminate the adverse effects of the substrate layer on the graphene, release the potential of graphene and terahertz wave interaction to a greater extent, realize a self-powered terahertz detection with high sensitivity, fast response and wide frequency band adaptability at room temperature, while taking into account the thermal stability and performance balance of the device, and can also reduce power consumption to meet the needs of practical applications.

[0022] In this embodiment, step S1 includes the following steps: S11. Select a high thermal resistance silicon oxide wafer as the substrate layer, clean and dry the substrate layer, and then modify the dried substrate layer; specifically: The high thermal resistance silicon oxide wafer is a high-resistivity silicon wafer with a 300 nm thick SiO2 layer grown by thermal oxidation (resistivity > 20,000 Ω·cm). After cleaning and drying the substrate layer, it is treated in hexamethyldisilazane (HMDS) vapor (120℃, 5 min) for modification, which can improve the adhesion between the photoresist and the substrate layer when using photoresist, and ensure the accuracy of subsequent photolithography processes. S12. Coat the surface of the substrate with photoresist, perform local maskless patterning photolithography, develop, and then use reactive ion etching to etch the silicon dioxide substrate 120 to form the substrate etching region 121; specifically: Photoresist is spin-coated onto the surface of the substrate layer, and then local maskless patterning photolithography is completed using a maskless photolithography machine according to preset exposure parameters. The exposed sample is then immersed in a developing solution for development. Then, reactive ion etching is used to etch the silicon dioxide substrate area that is not protected by photoresist to form substrate etched area 121. After removing the photoresist, a substrate layer containing substrate etched area 121 and substrate anchoring area 122 is obtained.

[0023] like Figure 5 and Figure 6 As shown, the high thermal resistance silicon dioxide wafer includes a silicon substrate layer 110 and a silicon dioxide substrate layer 120 stacked from bottom to top. The thickness of the silicon substrate layer 110 in the Z-axis direction is ≤1000μm, and the thickness of the silicon dioxide substrate layer 120 in the Z-axis direction is 0.1~1μm. The substrate etching region 121 includes an array of circular hole trench structures, the trench depth of which is 0.1~1μm. Figure 2As shown, a submicron-level suspended gap of 0.1~1μm is formed between the graphene suspended region 410 of the graphene suspended-anchored structure layer 400 and the circular hole groove structure of the substrate etched region 121 in the Z-axis direction. The graphene anchored region 420 of the graphene suspended-anchored structure layer 400 is tightly bonded to the silicon dioxide film of the substrate anchored region 122.

[0024] It should be noted that the photothermoelectric effect is the core physical mechanism by which the photothermoelectric graphene terahertz detector prepared by the method of this invention achieves room-temperature self-powered terahertz detection. For example... Figure 6 As shown, when a terahertz wave is incident perpendicularly onto the graphene suspended-anchored structure layer 400, the photon energy is absorbed by the charge carriers and converted into Joule heat, resulting in a localized temperature increase. In the graphene suspended-anchored structure layer 400, the graphene suspended region 410, lacking substrate thermal coupling, cannot rapidly dissipate the absorbed terahertz energy, forming a hot end. The graphene anchored region 420 is tightly bonded to the high thermal resistance silicon oxide wafer, allowing heat to dissipate rapidly through the substrate layer, forming a cold end. This establishes a stable temperature gradient within the graphene film surface. .

[0025] Based on the Seebeck effect, the temperature gradient drives the directional diffusion of charge carriers from the graphene suspended region 410 (hot end) to the graphene anchored region 420 (cold end), resulting in charge separation and generating an open-circuit thermal voltage at both ends of the graphene. (1-1) In the formula, This represents the Seebeck open-circuit thermal voltage (V). The Seebeck coefficient (V / K) represents the graphene, and its value is determined by the position of the Fermi level and the carrier concentration. A typical value is 80–100 μV / K (intrinsic monolayer graphene). Indicates the hot end temperature T sus With cold end temperature T anchor steady-state temperature difference (K); The temperature gradient-induced thermocurrent density can be described by the generalized Ohm's law: (1-2) In the formula, This represents the thermal current density (A / m²). This indicates the electrical conductivity of graphene (S / m). The formula represents the in-plane temperature gradient (K / m). This formula reveals the microscopic mechanism of photothermal-electric conversion: the temperature gradient induces thermal diffusion of charge carriers, forming a detectable electrical signal, such as... Figure 6 The e shown -The direction it points to; The responsivity of a photothermal-electric graphene terahertz detector characterizes its ability to convert incident terahertz radiation into an electrical signal; voltage responsivity. Defined as the ratio of output open-circuit voltage to incident terahertz power: (1-3) In the formula, Let W represent the incident terahertz power. Substituting equation (1-1) into equation (1-3) and combining it with the heat transfer theory, we can establish the relationship between responsivity and device physical parameters.

[0026] Example 2 This embodiment is a second embodiment of a method for fabricating a photothermal-electric graphene terahertz detector. This embodiment is similar to Embodiment 1, such as... Figures 3 to 10 As shown, step S2 includes the following steps: S21. Coating photoresist, positioning and overlaying, and developing are performed on the surface of the substrate anchoring area 122 to complete the positioning photolithographic patterning of the electrode area; specifically: Photoresist is spin-coated on the surface of the substrate anchoring area 122. The positioning and overlay are completed using a maskless lithography machine according to the preset exposure parameters. Then, the electrode area is immersed in the developer solution to complete the positioning photolithography patterning. S22. A Cr / Au composite metal layer is deposited in the electrode area patterned by photolithography using a thermal evaporation process. Then, the composite metal layer outside the electrode area is peeled off to obtain the first electrode 200 and the second electrode 300; specifically: A Cr / Au composite metal layer is deposited in the electrode area with a positioning photolithography pattern using a thermal evaporation process, and then immersed in an acetone solution until the composite metal layer outside the electrode area is peeled off, resulting in the first electrode 200 and the second electrode 300.

[0027] In this embodiment, step S3 includes the following steps: S31. Obtain a graphene film, use a PMMA support layer and transfer the graphene film to the surface of the substrate layer by dry transfer, so that the graphene film covers the substrate etching area 121 and the substrate anchoring area 122. S32. Photoresist is spin-coated, overlaid, and plasma-etched on the surface of the graphene film to form a graphene suspended-anchored structure layer 400; specifically, the graphene suspended-anchored structure layer 400 can be configured as a rectangular structure, and the coverage area of ​​the graphene suspended-anchored structure layer 400 is smaller than the surface area of ​​the substrate layer.

[0028] like Figure 3 , Figure 4 and Figure 6As shown, the first electrode 200 and the second electrode 300 have the same width in the Y-axis direction; the first electrode 200 and the second electrode 300 are arranged in the substrate anchoring region 122 along the X-axis direction, and the width of the graphene suspended-anchoring structure layer 400 in the Y-axis direction is smaller than the width of the first electrode 200 in the Y-axis direction. This arrangement can better collect the photovoltage generated at both ends of the photothermal graphene terahertz detector.

[0029] In step S4, the sample processed in step S3 is inverted, and a channel is constructed below it. The sample is then slowly cleaned with acetone for 30 min to remove the residual PMMA support layer and photoresist on the sample surface. After cleaning with C4F9OCH3 electronic fluorination solution, the sample is prevented from being damaged by rapid drying of the graphene due to acetone. The sample is then placed in a single-temperature zone tube furnace and annealed at 220°C under negative pressure for 120 min in an argon atmosphere to achieve ohmic contact between the graphene and the metal electrode, thus obtaining a photothermal graphene terahertz detector.

[0030] like Figure 7 The figure shows the simulation results of a typical device structure, in which, Figure 7 (a) Temperature distribution of a graphene terahertz detector without substrate etching region 121 under horizontal polarization terahertz wave excitation. Figure 7 (b) shows the temperature distribution of the photothermal graphene terahertz detector of the present invention under horizontally polarized terahertz wave excitation; Figure 7 (c) Figure 7 (d) respectively correspond to Figure 7 (a) with Figure 7 (b) The potential distribution. Among them, such as Figure 7 (a) shows a device that, due to its close contact with the substrate, rapidly dissipates photogenerated heat into SiO2, resulting in a uniform channel temperature distribution. <0.01K), almost no potential difference is generated, such as Figure 7 As shown in (c). In contrast, as Figure 7 In the device shown in (b), the substrate etching region 121 eliminates the substrate thermal channel, causing heat accumulation and raising the local temperature to 293.37 K. The substrate anchoring region 122 effectively dissipates heat through the substrate, maintaining a temperature of 293.30 K, thus forming a stable in-plane temperature gradient of 0.07 K. Based on the Seebeck effect, this temperature gradient drives carrier diffusion from the high-temperature region to the low-temperature region, generating an open-circuit photovoltage of approximately 3 μV, such as... Figure 7 As shown in (d), it is in high agreement with the theoretical estimate. Figure 7 The simulation results can quantitatively verify the physical mechanism by which the substrate etched region 121 establishes a temperature gradient through thermal asymmetry, thereby enhancing the photothermal-electric conversion efficiency. At the same time, it shows that the heat sink effect of the substrate anchoring region 122 is beneficial to maintaining the stability of the electrical signal output.

[0031] In this embodiment, the implemented device represents a photothermal-electric graphene terahertz detector prepared by the preparation method of the present invention, and the comparative device is a graphene terahertz detector without the substrate etching region 121. That is, the difference between the comparative device and the implemented device is that the silicon dioxide substrate layer 120 does not have the substrate etching region 121. Figure 8 middle, Figure 8 (a) An optical display for implementing the device. Figure 8 (b) is the optical display of the comparison device. Figure 8 (c) Raman spectra at 420 nm in the graphene anchoring region of the implemented device. Figure 8 (d) shows the Raman spectrum results at the graphene suspension region 410 of the implemented device, obtained through... Figure 8 (c) and Figure 8 The Raman spectroscopy results in (d) reveal the difference in strain state between the graphene suspended region 410 and the graphene anchored region 420, providing experimental basis for subsequent device performance optimization.

[0032] To verify whether the graphene suspended-anchored structure layer 400 was successfully formed, such as... Figure 9 As shown, AFM characterization was performed on the etched region 121 of the substrate: Figure 9 (a) shows the morphological features of the substrate etched region 121, with a clear step outline. Further measurement shows that the depth of the circular hole groove structure in the substrate etched region 121 is 300 nm ± 5 nm, which is consistent with the thickness of the silicon dioxide substrate layer 120. This indicates that a clear height difference is formed between the substrate etched region 121 and the substrate anchoring region 122, indicating that the substrate etched region 121 has been successfully constructed. Figure 9 (b) is an AFM image of the graphene suspended region 410, for comparison. Figure 9 (a) A height difference of 0.05~0.3μm between graphene and the substrate can be observed, which can verify the suspension characteristics of the graphene suspension region 410 and observe the continuously distributed wrinkled structure. The wrinkles mainly come from the stress release process of graphene after losing the support below, which is a common morphological feature of suspended two-dimensional films. At the same time, this also shows that the graphene suspension region 410 still remains continuous and intact without obvious cracking. The graphene suspension-anchoring structure layer 400 was successfully formed, which can prove the successful fabrication of the photothermal graphene terahertz detector.

[0033] like Figure 10As shown, the photocurrent switching response curves of the comparative device and the implementation device under 2.52 THz irradiation are presented. Both devices exhibit good repeatability and stability in multiple switching cycles, with no significant attenuation or baseline drift in the photocurrent signal, indicating that both devices have good operational stability. However, at a uniformly normalized incident power of 80 mW, the photocurrent output by the implementation device is approximately 8-10 times that of the comparative device. These results demonstrate that the implementation device, namely the photothermoelectric graphene terahertz detector of this invention, can significantly improve the terahertz photothermoelectric response of the device.

[0034] Example 3 like Figures 4 to 6 The illustration shows an embodiment of a photothermal-electric graphene terahertz detector according to the present invention. It includes a substrate layer comprising a silicon-based substrate layer 110 and a silicon dioxide substrate layer 120 stacked together. The silicon dioxide substrate layer 120 includes a substrate etching region 121 and a substrate anchoring region 122. The substrate etching region 121 includes an array of circular hole groove structures. A first electrode 200 and a second electrode 300 are deposited on the silicon dioxide substrate layer 120, with the substrate etching region 121 located between the first electrode 200 and the second electrode 300. A graphene film is covered on the silicon dioxide substrate layer 120, and the graphene film is in contact with both the first electrode 200 and the second electrode 300. The graphene film covers the substrate etching region 121 and the substrate anchoring region 122, forming a graphene suspended-anchored structure layer 400. This photothermal-electric graphene terahertz detector can be prepared by the preparation method described in Embodiment 1 or Embodiment 2.

[0035] Specifically, the first electrode 200 is any one or more of Al, Ag, Au, Bi, Cr, Pt, Ti, and Ni, and the second electrode 300 is any one or more of Al, Ag, Au, Bi, Cr, Pt, Ti, and Ni, and the first electrode 200 and the second electrode 300 are made of the same electrode material. Preferably, both the first electrode 200 and the second electrode 300 are Cr / Au composite electrodes.

[0036] The present invention discloses a photothermal graphene terahertz detector that can effectively establish a stable temperature gradient and improve the photothermal-electric conversion efficiency. The graphene suspended region 410 can get rid of the thermal coupling effect of the substrate layer and avoid the rapid loss of terahertz energy. Combined with the thermal conductivity difference between the substrate etched region 121 and the substrate anchoring region 122, a stable and effective in-plane thermal temperature difference is formed on the graphene suspended-anchoring structure layer 400, which greatly improves the photothermal-electric conversion efficiency and solves the problem that it is difficult to establish a temperature gradient in traditional structures. The present invention can also eliminate the adverse effects of the substrate layer on charge carriers and improve mobility and response speed: the graphene suspended region 410 can avoid direct contact with the silicon dioxide substrate 120, eliminate the scattering effect of optical phonons and charge carriers in the substrate layer, and at the same time reduce dielectric loss, so that the charge carrier mobility of graphene is close to the intrinsic value, improve charge transport efficiency, and significantly improve the response speed and detection sensitivity of the detector. This invention can also reduce substrate-induced noise and reduce equivalent noise power (NEP): the interface interaction between the graphene suspended-anchored structure layer 400 and the substrate layer is greatly reduced, effectively suppressing the generation of 1 / f noise and current noise. Combined with the removal of residual impurities brought about by process optimization, the overall noise level of the detector is significantly reduced, and the equivalent noise power (NEP) is greatly reduced, enabling high-sensitivity detection of weak terahertz signals at room temperature. This invention also enables wideband adaptation and fully self-powered operation, meeting the requirements for portability: the graphene suspended-anchored structure layer 400 can maintain the wideband absorption characteristics of graphene, enabling the detector to still have excellent detection performance in the mid-to-high frequency band above 2THz; the detector achieves complete self-powering based on the photothermoelectric effect, without the need for external bias voltage, which can reduce system complexity and power consumption, meeting the requirements of portable and low-power application scenarios; This invention also achieves a synergistic balance of multiple performance characteristics, improving the stability and practicality of the detector: The photothermal-electric graphene terahertz detector of this invention can combine the anchoring contact between graphene and the substrate layer, which can not only avoid the degradation of graphene performance by the substrate layer, but also provide an effective heat sink through the substrate anchoring region 122, solving the problems of poor thermal stability and slow response speed of completely suspended settings; at the same time, strategies such as thickness optimization and heterojunction integration can improve light absorption efficiency without destroying the temperature gradient, achieving a synergistic balance of multiple performance characteristics such as thermal gradient establishment, carrier mobility maintenance, noise suppression, and thermal stability.

[0037] In the specific implementation of the above embodiments, the technical features can be combined in any non-contradictory way. For the sake of brevity, not all possible combinations of the above technical features are described. However, as long as the combination of these technical features is not contradictory, it should be considered to be within the scope of this specification.

[0038] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a photothermal tellurium graphene terahertz detector, characterized in that, Includes the following steps: S1. Select a substrate layer and perform patterned etching on a local surface of the substrate layer, wherein the area where the patterned etching is performed forms a substrate etching area (121), and the area where the patterned etching is not performed is a substrate anchoring area (122). S2. A metal electrode is fabricated at the substrate anchoring region (122); S3. Obtain a graphene film and transfer the graphene film to the surface of the substrate layer. The graphene film covers the substrate etched area (121) and the substrate anchoring area (122) to form a graphene suspended-anchored structure layer (400). S4. Anneal the sample after step S3 to obtain a photothermal graphene terahertz detector.

2. The method of claim 1, wherein the method further comprises: Step S1 includes the following steps: S11. Select a high thermal resistance silicon oxide wafer as the substrate layer, clean and dry the substrate layer, and then modify the dried substrate layer. S12. Coat the surface of the substrate layer with photoresist, perform local maskless patterning photolithography, develop, and then use reactive ion etching process to etch the silicon dioxide substrate layer (120) of the substrate layer to form the substrate etched area (121).

3. The method of claim 1 or 2, wherein the method further comprises: The substrate etching region (121) includes an array of circular hole groove structures.

4. The method for fabricating the photothermal-electric graphene terahertz detector according to claim 3, characterized in that, The groove depth of the circular hole groove structure is 0.1~1μm.

5. The method for fabricating the photothermal-electric graphene terahertz detector according to claim 1, characterized in that, Step S2 includes the following steps: S21. Photoresist is coated, positioning and overlaying are performed, and development is carried out on the surface of the substrate anchoring area (122) to complete the positioning photolithography patterning of the electrode area; S22. A Cr / Au composite metal layer is deposited in the electrode area with a positioning photolithography pattern using a thermal evaporation process. Then, the composite metal layer outside the electrode area is peeled off to obtain the first electrode (200) and the second electrode (300).

6. The method for fabricating the photothermal-electric graphene terahertz detector according to claim 5, characterized in that, The first electrode (200) and the second electrode (300) are arranged in the substrate anchoring region (122) along a first direction, and the width of the graphene suspended-anchoring structure layer (400) in the second direction is smaller than the width of the first electrode (200) and / or the second electrode (300) in the second direction, and the first direction is perpendicular to the second direction.

7. The method for fabricating the photothermal-electric graphene terahertz detector according to claim 1, characterized in that, Step S3 includes the following steps: S31. Obtain a graphene film and transfer the graphene film to the surface of the substrate layer using a PMMA support layer. The graphene film covers the substrate etched area (121) and the substrate anchoring area (122). S32. Photoresist is coated on the surface of the graphene film, overlay is performed, and plasma etching is performed to form the graphene suspended-anchored structure layer (400).

8. The method for fabricating the photothermal-electric graphene terahertz detector according to claim 1 or 7, characterized in that, The coverage area of ​​the graphene suspended-anchored structure layer (400) is smaller than the surface area of ​​the substrate layer.

9. A photothermal-electric graphene terahertz detector, characterized in that, The system includes a substrate layer comprising a silicon-based substrate layer (110) and a silicon dioxide substrate layer (120) stacked together. The silicon dioxide substrate layer (120) includes a substrate etching region (121) and a substrate anchoring region (122). The substrate etching region (121) includes an array of circular hole groove structures. The silicon dioxide substrate layer (120) is coated with a first electrode (200) and a second electrode (300). The substrate etching region (121) is located between the first electrode (200) and the second electrode (300). A graphene film is covered on the silicon dioxide substrate layer (120), and the graphene film is in contact with both the first electrode (200) and the second electrode (300). The graphene film covers the substrate etching region (121) and the substrate anchoring region (122) to form a graphene suspended-anchoring structure layer (400).

10. The photothermal-electric graphene terahertz detector according to claim 9, characterized in that, The first electrode (200) is any one or more of Al, Ag, Au, Bi, Cr, Pt, Ti, and Ni, and the second electrode (300) is any one or more of Al, Ag, Au, Bi, Cr, Pt, Ti, and Ni, and the first electrode (200) and the second electrode (300) are made of the same electrode material.

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