A vertically oriented graphite-based heterojunction and a method of making the same

Abstract

This invention discloses a vertically oriented graphite-based heterostructure and its preparation method, which is assembled from a three-layer structure of metal nanofilm, vertically oriented graphite film, and semiconductor. It can efficiently absorb X-rays and amplify and confine the photocurrent generated by X-ray irradiation. This detector operates in the low-dose range (0.01n–10 μGy). air s ‑1 It has a value higher than 2×10 at room temperature. 8 C Gy air ‑1 cm ‑2 High sensitivity, below 0.05 nGy air s ‑1 Its extremely low detection limit and ultrafast response speed of less than 50 ns are unique among direct-type detectors. This patent provides a new approach to the design of high-sensitivity, ultrafast X-ray detectors, which is conducive to accelerating the development of medical CT towards a low-dose range that is beneficial to human health.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, and specifically relates to a vertically oriented graphite-based heterostructure and its preparation method. Background Technology

[0002] Ultra-low dose, high-speed X-ray detectors are widely used in medical imaging, security inspection, and industrial testing. However, X-rays cause serious radiation damage to the human body, and reducing the radiation dose is a perpetual pursuit in X-ray applications. Furthermore, due to their high frequency and large information capacity, X-rays can be used for space communication; the high-speed response of devices to X-rays determines the speed of information transmission.

[0003] Currently, the development of ultra-low-dose, high-speed-response X-ray detection devices is slow. The application of novel materials such as graphene, transition metal dihalides, and perovskites in X-ray detection promises to improve detector performance. However, neither can simultaneously achieve ultra-low dose and high-speed response. With the development of microelectronics and artificial intelligence technologies, future X-ray detectors will be more integrated and intelligent, enabling faster, ultra-low-dose detection.

[0004] With the rapid development of new materials, microelectronics, and artificial intelligence technologies, ultra-low-dose, high-speed X-ray detectors are evolving towards integration, intelligence, and high performance. Among these, graphite-based materials, due to their unique physical and chemical properties such as high electron mobility, stability, and carrier gain, hold immense potential for ultra-low-dose X-ray detection. Therefore, the research and development of graphite-based ultra-low-dose X-ray detectors will become a hot topic and key focus of future technological development. Summary of the Invention

[0005] To address the challenges of low sensitivity and slow response speed in current X-ray detector fabrication, this invention provides a high-density vertically oriented graphite-based heterostructure, its fabrication method, and its applications.

[0006] The present invention adopts the following technical solution: a vertically oriented graphite-based heterojunction, comprising a semiconductor layer, a vertically oriented graphite layer, and a reinforcement layer, wherein the reinforcement layer is a metal layer with a thickness of 20–40 nm; the vertically oriented graphite layer has a thickness of 1–50 μm, is composed of graphene sheets with an orientation degree of more than 95%, and has a density of 1.8–2.3 g / cm³. 3 And I D / I GLess than 0.5%; the thickness of the semiconductor layer is 1–200 μm. This invention utilizes a high-density, vertically oriented bulk graphite layer, which offers significant advantages. First, the bulk graphite structure provides sufficient electrons to achieve strong carrier gain. This is due to the weak electron-phonon interaction in graphite, which stabilizes the hot electrons transferred between the metal and semiconductor layers. Furthermore, the strong Coulomb scattering of electrons in the graphite layer further amplifies the number of carriers. Second, the high vertical mobility of graphite enables rapid signal feedback, significantly improving the device's response speed. Third, the low horizontal mobility of the vertically oriented graphite film prevents severe horizontal electron scattering, allowing electrons to be focused for gain and transport. In addition, the metal and semiconductor dual-absorption layer effectively improves X-ray absorption efficiency. High atomic number metal elements have strong high-energy photon absorption, thus promoting the generation of high-energy initial hot electrons. The semiconductor layer also absorbs X-rays; the holes induced by photogenerated electrons generated within it drift into the graphite, correspondingly generating hot electrons in the graphite conduction band.

[0007] Further, the semiconductor layer is one or more of Si, Ge, SiC, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgSe, HgTe, PbS, PbSe, PbTe, perovskite, metal carbide (Mxene), metal composite semiconductor (such as HgCdTe), and metal iodide (such as HgI2).

[0008] Furthermore, the metal element in the reinforcing layer is an inert metal with an atomic number of 20 or higher.

[0009] This invention also provides a method for preparing a vertically oriented graphite-based heterostructure, comprising the following steps:

[0010] (1) Apply a pressure of 10 to 60 MPa to a material composed of oriented pyrolytic graphite, carbon-carbon composite material or graphene in a direction perpendicular to the orientation and keep it at 2000 to 2800 °C for 1 to 12 hours.

[0011] (2) The material obtained in step (1) is sliced ​​along the direction perpendicular to the orientation to obtain vertically oriented graphite slices with controllable thickness. After further surface polishing, it is subjected to high temperature treatment above 2000℃ to restore the surface lattice structure.

[0012] (3) Integrate 1-200 μm semiconductor material on one side surface of the slice obtained in step (2) to obtain a vertically oriented graphite / semiconductor heterojunction;

[0013] (4) A metal layer with a thickness of 20-40 nm is formed on the other side of the graphite in the heterojunction obtained in step (3), and annealed at 600-800℃ for 1-2 h to obtain a metal-vertically oriented graphite / semiconductor three-layer heterojunction.

[0014] Furthermore, materials composed of oriented pyrolytic graphite, carbon-carbon composites, or graphene are membrane materials, fiber materials, and combinations thereof. Materials can be bonded together using resins or similar methods before hot pressing. For example, a thick film with a thickness of 1 cm or more can be formed using resin and then hot-pressed; or a fiber bundle with a diameter of 1 cm or more can be formed using resin and then hot-pressed.

[0015] Furthermore, the slicing method in step (2) includes focused plasma beam cutting, laser cutting, wire cutting, and electrical discharge cutting, and the polishing method is ion polishing, specifically including argon, potassium, hydrogen, and oxygen plasma.

[0016] Further, the semiconductor material mentioned in step (3) is one or more of Si, Ge, SiC, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgSe, HgTe, PbS, PbSe, PbTe, perovskite, metal carbide (Mxene), metal composite semiconductor (such as HgCdTe), and metal iodide (such as HgI2). The integration method includes sol-gel method, hydrothermal synthesis method, precipitation method, vapor deposition method, magnetron sputtering method, evaporation deposition method, high-temperature fusion bonding method, and atomic layer deposition method.

[0017] Furthermore, the metal layer in step (4) is an inert metal with an atomic number of 20 or higher, and the metal layer is generated by vapor deposition, magnetron / ion sputtering, evaporation deposition, high-temperature cladding, laser cladding, or nanoparticle deposition.

[0018] Further, the metal layer in step (4) is one or more of gold, platinum, tungsten, iron, cobalt, nickel, etc.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) The gain efficiency of this device is related to the dose. The lower the dose, the higher the gain ratio. It is especially suitable for ultra-low dose X-ray detection. In the low dose region, the minimum detection dose is reduced by more than two orders of magnitude compared to the most advanced perovskite devices.

[0021] (2) In addition, this device can also be used in many fields such as β-ray detection, water window X-ray detection and X-ray neural network calculation. Attached Figure Description

[0022] Figure 1 This is a schematic cross-sectional view of the vertically oriented graphite / semiconductor heterojunction of Example 1.

[0023] Figure 2 The image shows the microstructure of the vertically oriented graphite / semiconductor heterojunction in Example 1. Detailed Implementation

[0024] The present invention will be specifically described below through embodiments. These embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential changes and adjustments made by those skilled in the art based on the above-described invention shall fall within the scope of protection of the present invention.

[0025] Example 1:

[0026] A vertically oriented graphite-based heterostructure, characterized in that it comprises a semiconductor layer, a vertically oriented graphite layer, and a reinforcement layer, wherein the reinforcement layer is a gold layer with a thickness of 20 nm; the vertically oriented graphite layer has a thickness of 1 μm, is composed of graphene sheets with an orientation degree of more than 95%, and has a density of 1.94 g / cm³. 3 I D / I G The content is 0.3%; the semiconductor layer is Si with a thickness of 1 μm.

[0027] A method for preparing a vertically oriented graphite-based heterostructure, characterized by comprising the following steps:

[0028] (1) A material composed of oriented pyrolytic graphite was subjected to a pressure of 10 MPa in a direction perpendicular to the orientation and held at 2000 °C for 6 h.

[0029] (2) The material obtained in step (1) is cut by focused plasma beam along the direction perpendicular to the orientation to obtain vertically oriented graphite slices with a thickness of about 2 μm. Then, after further surface polishing with argon ions, it is subjected to high temperature treatment at 2700℃ to restore the surface lattice structure.

[0030] (3) A 1 μm Si layer is integrated on one side surface of the slice obtained in step (2) by vapor deposition to obtain a vertically oriented graphite / semiconductor heterojunction;

[0031] (4) In step (3), a gold layer with a thickness of 20 nm is formed on the other side of the graphite in the heterojunction by magnetron sputtering and annealed at 600 °C for 2 h to obtain a metal-vertically oriented graphite / semiconductor three-layer heterojunction.

[0032] A carbon-based X-ray detector was fabricated by wire bonding with gold wire in a metal-vertically oriented graphite / semiconductor three-layer heterojunction to connect the device and the designed logic circuit. The fabricated device exhibited the following performance under 10 keV high-energy electron irradiation: sensitivity, 5.2 × 10⁻⁶. 8 μC Gyair -1 cm -2 (Bias voltage -1); Detection limit 0.01nGyair s -1 The response time is approximately 20 ns (rising edge).

[0033] Example 2:

[0034] A vertically oriented graphite-based heterostructure, characterized in that it comprises a semiconductor layer, a vertically oriented graphite layer, and a reinforcement layer, wherein the reinforcement layer is a gold layer with a thickness of 40 nm; the vertically oriented graphite layer has a thickness of 1 μm, is composed of graphene sheets with an orientation degree of more than 95%, and has a density of 1.94 g / cm³. 3 I D / I G The content is 0.3%; the semiconductor layer is Si with a thickness of 1 μm.

[0035] A method for preparing a vertically oriented graphite-based heterostructure, characterized in that steps (1) to (3) are the same as in Example 1, and step (4) is:

[0036] (4) In step (3), a gold layer with a thickness of 40 nm is formed on the other side of the graphite in the heterojunction by magnetron sputtering and annealed at 800 °C for 2 h to obtain a metal-vertically oriented graphite / semiconductor three-layer heterojunction.

[0037] A carbon-based X-ray detector was fabricated by wire bonding with gold wires in a metal-vertically oriented graphite / semiconductor three-layer heterojunction to connect the device and the designed logic circuit. The fabricated device exhibited the following performance under 10 keV high-energy electron irradiation: sensitivity, 5.0 × 10⁻⁶. 8 μC Gyair -1 cm -2 (Bias voltage -1); Detection limit 0.01nGyair s -1 The response time is approximately 20 ns (rising edge).

[0038] Example 3:

[0039] A vertically oriented graphite-based heterostructure, characterized in that it comprises a semiconductor layer, a vertically oriented graphite layer, and a reinforcement layer, wherein the reinforcement layer is a gold layer with a thickness of 20 nm; the vertically oriented graphite layer has a thickness of 50 μm, is composed of graphene sheets with an orientation degree of more than 95%, and has a density of 1.94 g / cm³. 3 I D / I G The content is 0.3%; the semiconductor layer is Si with a thickness of 1 μm.

[0040] A method for preparing a vertically oriented graphite-based heterostructure, characterized in that steps (1), (3), and (4) are the same as in Example 1, and step (3) is:

[0041] (2) The material obtained in step (1) is cut by focused plasma beam along the direction perpendicular to the orientation to obtain a vertically oriented graphite slice with a thickness of about 52 μm. Then, after further surface polishing with argon ions, it is subjected to high temperature treatment at 2800℃ to restore the surface lattice structure.

[0042] A carbon-based X-ray detector was fabricated by wire bonding with gold wires in a metal-vertically oriented graphite / semiconductor three-layer heterojunction to connect the device and the designed logic circuit. The fabricated device exhibited the following performance under 10 keV high-energy electron irradiation: sensitivity, 5.5 × 10⁻⁶. 8 μC Gyair -1 cm -2 (Bias voltage -1); Detection limit 0.01nGyair s -1 The response time is approximately 26 ns (rising edge).

[0043] Example 4:

[0044] A vertically oriented graphite-based heterostructure, characterized in that it comprises a semiconductor layer, a vertically oriented graphite layer, and a reinforcement layer, wherein the reinforcement layer is a platinum layer with a thickness of 20 nm; the vertically oriented graphite layer has a thickness of 10 μm, is composed of graphene sheets with an orientation degree of more than 95%, and has a density of 2.3 g / cm³. 3 I D / I G The content is 0.1%; the semiconductor layer is HgI2 with a thickness of 200 μm.

[0045] A method for preparing a vertically oriented graphite-based heterostructure, characterized by comprising the following steps:

[0046] (1) A material composed of oriented pyrolytic graphite was subjected to a pressure of 60 MPa in a direction perpendicular to the orientation and held at 2800 °C for 12 h.

[0047] (2) The material obtained in step (1) is cut by focused plasma beam along the direction perpendicular to the orientation to obtain vertically oriented graphite slices with a thickness of about 11 μm. Then, after further argon ion surface polishing, it is subjected to high temperature treatment at 2500℃ to restore the surface lattice structure.

[0048] (3) A 200 μm HgI2 layer is integrated on one side surface of the slice obtained in step (2) by vapor deposition to obtain a vertically oriented graphite / semiconductor heterojunction;

[0049] (4) In step (3), a platinum layer with a thickness of 20 nm is formed on the other side of the graphite in the heterojunction by magnetron sputtering and annealed at 800 °C for 1 h to obtain a metal-vertically oriented graphite / semiconductor three-layer heterojunction.

[0050] A carbon-based X-ray detector was fabricated by wire bonding with gold wires in a metal-vertically oriented graphite / semiconductor three-layer heterojunction to connect the device and the designed logic circuit. The fabricated device exhibited the following performance under 10 keV high-energy electron irradiation: sensitivity, 6.1 × 10⁻⁶. 8 μC Gyair -1 cm -2 (Bias voltage -1); Detection limit 0.01nGyair s -1 The response time is approximately 30 ns (rising edge).

[0051] Example 5:

[0052] A vertically oriented graphite-based heterostructure, characterized in that it comprises a semiconductor layer, a vertically oriented graphite layer, and a reinforcement layer, wherein the reinforcement layer is a nickel layer with a thickness of 15 nm; the vertically oriented graphite layer has a thickness of 5 μm, is composed of graphene sheets with an orientation degree of more than 95%, and has a density of 1.8 g / cm³. 3 I D / I G The content is 0.45%; the semiconductor layer is perovskite with a thickness of 20 μm.

[0053] A method for preparing a vertically oriented graphite-based heterostructure, characterized by comprising the following steps:

[0054] (1) A material composed of oriented pyrolytic graphite was subjected to a pressure of 10 MPa in a direction perpendicular to the orientation and held at 2200 °C for 1 h.

[0055] (2) The material obtained in step (1) is laser-cut along the direction perpendicular to the orientation to obtain a vertically oriented graphite slice with a thickness of about 6 μm. Then, after further surface polishing with hydrogen ions, it is subjected to high temperature treatment at 2500℃ to restore the surface lattice structure.

[0056] (3) A 200 μm perovskite layer is integrated on one side of the slice obtained in step (2) by sol-gel method to obtain a vertically oriented graphite / semiconductor heterojunction;

[0057] (4) In step (3), a nickel layer with a thickness of 20 nm is formed on the other side of the graphite in the heterojunction by laser cladding, and annealed at 600 °C for 2 h to obtain a metal-vertically oriented graphite / semiconductor three-layer heterojunction.

[0058] A carbon-based X-ray detector was fabricated by wire bonding with gold wires in a metal-vertically oriented graphite / semiconductor three-layer heterojunction to connect the device and the designed logic circuit. The fabricated device exhibited the following performance under 10 keV high-energy electron irradiation: sensitivity, 5.4 × 10⁻⁶. 8 μC Gyair -1 cm -2 (Bias voltage -1); Detection limit 0.01nGyair s -1 The response time is approximately 20 ns (rising edge).

Claims

1. A vertically oriented graphite-based heterostructure for X-ray detection, characterized in that, It includes a semiconductor layer, a vertically oriented graphite layer, and a reinforcement layer, wherein the reinforcement layer and the semiconductor layer are respectively disposed on both sides of the vertically oriented graphite layer; The reinforcing layer is a metal layer with a thickness of 20–40 nm, and the metal in the metal layer is one or more of gold, platinum, tungsten, iron, cobalt, or nickel; The vertically oriented graphite layer is a high-density vertically oriented bulk graphite layer with a thickness of 1–50 μm, composed of graphene sheets with an orientation degree of over 95%, and a density of 1.8–2.3 g / cm³. 3 Furthermore, the ID / IG ratio in the Raman spectrum is less than 0.5%; The thickness of the semiconductor layer is 1–200 μm; The enhancement layer and the semiconductor layer are used to absorb X-rays, and the enhancement layer is used to promote the generation of high-energy initial hot electrons; the vertically oriented graphite layer is used to stabilize and gain the carriers transferred by the enhancement layer and the semiconductor layer, and to rapidly transport the carriers along the vertical orientation direction and suppress the scattering of the carriers in the horizontal direction.

2. The vertically oriented graphite-based heterojunction according to claim 1, characterized in that, The semiconductor layer is one or more of the following: Si, Ge, SiC, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgSe, HgTe, PbS, PbSe, PbTe, perovskite, metal carbide MXene, metal composite semiconductor HgCdTe, or metal iodide HgI2.

3. A method for preparing a vertically oriented graphite-based heterojunction for X-ray detection as described in any one of claims 1 to 2, characterized in that, Includes the following steps: (1) Apply a pressure of 10 to 60 MPa to a material composed of oriented pyrolytic graphite, carbon-carbon composite material or graphene in a direction perpendicular to the orientation and keep it at 2000 to 2800 °C for 1 to 12 h. (2) The material obtained in step (1) is sliced ​​along the direction perpendicular to the orientation to obtain vertically oriented graphite slices with controllable thickness. After surface polishing of the vertically oriented graphite slices, they are subjected to high-temperature treatment at 2000℃ or above to restore the surface lattice structure. (3) Integrate a semiconductor material with a thickness of 1 to 200 μm on one side surface of the vertically oriented graphite slice obtained in step (2) to obtain a vertically oriented graphite / semiconductor heterojunction; (4) A metal layer with a thickness of 20 to 40 nm is formed on the other side of the vertically oriented graphite / semiconductor heterojunction obtained in step (3), and annealed at 600 to 800 °C for 1 to 2 h to obtain a metal-vertically oriented graphite / semiconductor three-layer heterojunction.

4. The preparation method according to claim 3, characterized in that, The material composed of oriented pyrolytic graphite, carbon-carbon composite material, or graphene is a membrane material, a fiber material, or a combination thereof.

5. The preparation method according to claim 3, characterized in that, The slicing method in step (2) includes focused plasma beam cutting, laser cutting, wire cutting or electrical discharge cutting; the polishing method is ion polishing, which uses argon plasma, potassium plasma, hydrogen plasma or oxygen plasma.

6. The preparation method according to claim 3, characterized in that, The semiconductor material mentioned in step (3) is one or more of the following: Si, Ge, SiC, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgSe, HgTe, PbS, PbSe, PbTe, perovskite, metal carbide MXene, metal composite semiconductor HgCdTe, or metal iodide HgI2; The integration methods for semiconductor materials include sol-gel method, hydrothermal synthesis method, precipitation method, vapor deposition method, magnetron sputtering method, evaporation deposition method, high-temperature fusion bonding method, or atomic layer deposition method.

7. The preparation method according to claim 3, characterized in that, The metal layer is formed by vapor deposition, magnetron sputtering, ion sputtering, evaporation deposition, high-temperature cladding, laser cladding, or nanoparticle deposition.

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