Self-driven heterostructure X-ray detector based on liquid medium light-induced polarization and preparation method of self-driven heterostructure X-ray detector

Abstract

The invention discloses a liquid medium light-induced polarization-based self-driven heterostructure X-ray detector and a preparation method thereof. A detector main body comprises two semiconductor structures with different Fermi levels (one of the semiconductors can be graphene / metal) and polar liquid which is sandwiched between the two semiconductor structures and contains an absorbent or a scintillator; x-rays irradiate on the structure, electrons or fluorescence can be generated in liquid, the electrons can be conveyed to a semiconductor under the action of a built-in electric field so as to generate X-ray light current, and the fluorescence can excite electron-hole pairs in the semiconductor to further act with molecules in the liquid so as to generate the X-ray light current. Compared with a traditional X-ray detector, the novel photoelectric detector directly solves the problem that lattice matching of a traditional solid-phase device is difficult. The design is simple, the preparation is easy, the self-driven working mode does not need an external power supply, and the self-driven self-driven LED lamp can be suitable for a severe working environment, and is a brand-new, efficient and low-cost novel solution.

Description

Technical Field

[0001] The invention belongs to the field of photoelectric detectors and relates to a self-driven heterostructure X-ray detector based on liquid medium photoinduced polarization and a preparation method thereof. Background Art

[0002] X-ray detection has important applications in people's lives, but the main materials of traditional X-ray detection are generally solid, and liquid materials are rarely used to detect X-rays. The present invention brings an innovative solution for liquid-phase X-ray detectors based on polar liquid photopolarization. This solution achieves the successful preparation of liquid-phase X-ray detectors by adding X-ray absorbers or scintillators to polar liquids, breaking out of the framework of solid-state photoelectric detection, thereby greatly broadening the design and application boundaries of X-ray detectors. Moreover, the device performance of this liquid-phase X-ray detector based on polar liquid photopolarization is already at the top level in the field of X-ray semiconductor self-driven devices. This innovative thinking of polar liquid photopolarization device driving method and solution-regulated absorption will open up a new path for X-ray detection technology, highlighting the originality and broad prospects for application. Summary of the invention

[0003] The main purpose of the present invention is to overcome the shortcomings and limitations of the photoelectric detectors based on solid light absorption in the prior art, and to provide a self-driven heterostructure X-ray detector based on liquid medium photopolarization and a preparation method thereof. The X-ray detector can be self-driven, breaking through the process limitations, and its absorption wavelength can be flexibly designed according to the liquid, which has broad application prospects.

[0004] The technical solution adopted by the present invention is:

[0005] A liquid medium photo-polarized self-driven heterostructure X-ray detector, the main components of which are two semiconductor structures with different Fermi levels (one of the semiconductors may also be graphene / metal) and a polar liquid containing an absorber or scintillator sandwiched therebetween. Specifically, the detector includes: a first structural layer, a polar liquid, and a second structural layer; the first structural layer is a semiconductor material, the polar liquid contains an absorber or scintillator, the second structural layer is a graphene, metal or semiconductor material, and the first structural layer and the second structural layer have different Fermi levels; the polar liquid is in direct contact with both the first structural layer and the second structural layer to form an electrical heterostructure.

[0006] In addition, electrodes are provided on the first structural layer and the second structural layer, which can be independently selected from one or more of gold, aluminum, copper, iron, and tin, and their thickness can generally be controlled within 300 μm-10 nm.

[0007] The semiconductor material of the first structural layer includes but is not limited to one of silicon, germanium, diamond, silicon carbide, gallium nitride, gallium arsenide, cadmium telluride, and cadmium zinc telluride. The semiconductor material of the second structural layer includes but is not limited to one of zinc oxide, indium tin oxide, and polymer semiconductor materials.

[0008] Polar liquid is a key element, which is located between the two structural layers. This polar liquid can be any polar solution, including but not limited to water, ethylene glycol, ethanol, acetone, glycerol, propylene glycol, etc. Its presence can cause a dynamic polarization-depolarization process at the semiconductor (or graphene / metal) / polar liquid interface under the irradiation of an external light source, thereby causing the accumulation and separation of surface charges and forming a response current.

[0009] In addition, the polar liquid also contains a solute, namely an absorber or a scintillator, which can play a role in absorption wavelength selection or enhancement, including but not limited to one or more of sodium iodide, barium sulfate, and polystyrene. Its presence can enhance the absorption of X-rays by the polar liquid and improve the response of the overall device. When X-rays are shone on the structure, electrons (when the solute is an absorber) or fluorescence (when the solute is a scintillator) can be generated in the liquid, where the electrons are transported to the semiconductor under the action of the built-in electric field formed by semiconductors with different Fermi levels, thereby generating X-ray photocurrent, and the fluorescence can excite electron-hole pairs in the semiconductor, which further interact with molecules in the liquid, thereby generating X-ray photocurrent.

[0010] The preparation method includes: making electrodes on the surface of the first structural layer or the second structural layer, then directly applying a polar liquid containing an absorbent or a scintillator to the blank surface of one of the structural layers, and finally covering the blank surface of the other structural layer on the surface of the polar liquid, so that the first structural layer and the second structural layer are in direct contact with the polar liquid to form an electrical heterogeneous structure; in the actual preparation process, it is first necessary to form electrodes on the clean first structural layer and the second structural layer, and then use a transparent insulating material to make a window in the blank area of ​​one of the structural layers (which is the substrate), and the window and the substrate need to be sealed. Then, the polar liquid containing an absorbent or a scintillator is injected into the window until the entire window is filled, and another structural layer is covered on the window so that the polar liquid can fully contact the structural layers on both sides.

[0011] It is worth noting that when the detector is exposed to periodic light input, it can generate three types of currents, namely transient photoinduced polarization current, steady-state photoinduced polarization current and depolarization current. This is mainly due to the photoinduced polarization of the polar liquid under the incident light, which causes a large number of carriers to accumulate at the semiconductor / polar liquid interface, thereby generating a current signal in the external circuit. When the light source is turned off, the carriers accumulated at the polar liquid / semiconductor interface will be cleared to form a depolarization current. This unique working mechanism gives the detector a strong response sensitivity and a wide response spectrum range.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] The present invention provides a disruptive perspective on the basis of traditional X-ray detection technology. It introduces polar liquids and realizes X-ray detection based on the dynamic photopolarization of polar liquids for the first time. It also introduces solutes through polar liquids to enhance X-ray absorption, greatly improving the flexibility of photodetector design, and ultimately achieving high current response intensity and high sensitivity to X-rays. Compared with the design of traditional devices that rely on solid light absorption, the present invention directly eliminates the impact of inherent process problems such as lattice matching on device performance, and reduces the high requirements of traditional X-ray detectors for solid materials. By introducing solutes that can enhance the absorption of X-rays, the absorption capacity of X-rays is improved and enhanced, and the overall photoelectric conversion efficiency of the device is improved. In particular: In Example 1, the experimental group to which a sodium iodide solution with a concentration of 0.02 mol / L was added produced 1.149 μA cm under an X-ray dose of 5.18 mGy / s. -2 The peak response of the device is 152μC Gy by changing the incident X-ray dose. -1 cm -2 The experimental group in Example 2 that added 25 mg / mL of polystyrene scintillator solution produced 1.126 μA cm -2 The peak response of the device is 149.4μC Gy by changing the incident X-ray dose. -1 cm -2 This is already at the top level in the field of X-ray semiconductor self-driven devices. In addition, the self-driven characteristics of the present invention ensure stable operation without an external power supply and open up a new way to use liquid media in the field of photoelectric conversion. In general, the present invention provides a new solution for the field of X-ray detection technology, further enriching the application potential in this field. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1The schematic diagram of the structure of the polarization photocurrent response photodetector based on semiconductor / polar liquid / graphene heterogeneous device;

[0015] Figure 2 Schematic diagram of the static equilibrium energy band of semiconductor / polar liquid / graphene heterogeneous devices after contact.

[0016] Figure 3 It is a time-current curve of the silicon / sodium iodide solution / graphene heterogeneous device under X-ray irradiation with a radiation dose of 5.18mGy / s;

[0017] Figure 4 The dose-current relationship diagram of the silicon / sodium iodide solution / graphene heterogeneous device under X-ray irradiation with a radiation dose of 1.39-5.18 mGy / s;

[0018] Figure 5 It is a time-current curve of the diamond / scintillator solution / graphene heterogeneous device under X-ray irradiation with a radiation dose of 5.18mGy / s;

[0019] Figure 6 The dose current curve of the diamond / scintillator solution / graphene heterogeneous device under X-ray irradiation with a radiation dose of 1.39-5.18 mGy / s; DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the first structural layer and the second structural layer in the present invention are only used to distinguish the two structural layers, and are not used to limit their relative positions with the polar liquid, and their positions can be interchanged.

[0021] Reference Figure 1 According to a specific embodiment of the present invention, a photoinduced liquid polarization X-ray detector based on a semiconductor / polar liquid / graphene structure is provided. Figure 1 As shown. From top to bottom, the structure includes graphene 1, a transparent insulating window filled with a polar liquid 2 containing an absorber or scintillator, and a semiconductor 3. When testing the light response performance, the X-ray light source irradiates from the side of the device. In all examples, the area of ​​the insulating window remains the same. The photoinduced liquid polarization X-ray detector uses the surface tension of the polar liquid to tightly bond with the semiconductor and graphene. Due to the difference in Fermi levels between the semiconductor and graphene, the polar liquid in the interlayer will be polarized, such as Figure 2As shown. Under the excitation of X-rays, due to the presence of absorbers or scintillators in the liquid, electrons or fluorescence can be generated in the liquid, where electrons are transported to the semiconductor under the action of the built-in electric field, thereby generating X-ray photocurrent, while fluorescence can excite electron-hole pairs in the semiconductor, further interacting with molecules in the liquid, thereby generating X-ray photocurrent, a large number of electrons will drift to the semiconductor / polar liquid interface, and a large number of holes will drift to the graphene / polar liquid interface, generating instantaneous photopolarized current. After the light is stable, the photopolarized current will tend to be stable. When the light source is turned off, a depolarized current will be generated.

[0022] Embodiment 1:

[0023] 1) Select a graphene sheet and introduce a silver electrode thereon;

[0024] 2) Select a clean silicon wafer;

[0025] 3) Use transparent insulating tape to delineate a window working area on the silicon wafer and ensure that its edge is tightly sealed with the silicon wafer;

[0026] 4) Fill the silicon window working area with 10 μL of 0.02 mol / mL sodium iodide solution;

[0027] 5) The blank area of ​​the graphene sheet is transferred to the window working area so that it is in close contact with water, while preventing the silver electrode on the graphene side from contacting water. The four sides of the window working area are fixed and sealed with UV glue to prevent deionized water from leaking, thereby forming a stable silicon / sodium iodide solution / graphene X-ray detector.

[0028] Taking the obtained X-ray detector based on silicon / sodium iodide solution / graphene as an example, its photoelectric response results are as follows Figure 3 As shown. At a radiation dose of 5.18mGy*s -1 Under the irradiation of X-ray source, the specific values ​​of transient photopolarization current, steady-state photopolarization current and depolarization current were measured according to the experimental equipment and conditions. The peak value of transient photopolarization current reached 1.149μAcm -2. Due to the difference in Fermi levels between semiconductors and graphene, the water molecules in the interlayer are polarized. In this process, negatively charged oxygen atoms move closer to graphene and induce positively charged holes, while positively charged hydrogen atoms move closer to silicon and induce negatively charged electrons. Under light, a large number of electrons drift to the silicon / water interface, and a large number of holes drift to the water / graphene interface, generating a transient photopolarized current. During this process, the iodine ions in the solution absorb part of the X-rays and release electrons, which strengthens the transient photopolarized current. Under continuous light conditions, due to the continuous accumulation of non-equilibrium carriers in the two-phase interface, the polarization current will tend to stabilize, and at the same time, more water molecules will be polarized in an orderly manner. When the light source is turned off, a negative polarization current will be generated, which is a depolarization process. The photoexcited carriers will relax and recombine inside the graphene, and the water molecules will return to a disordered state.

[0029] The device performance was further tested by changing the incident X-ray dose to obtain a relationship diagram between the incident X-ray dose and the peak value of the response current, such as Figure 4 As shown in Figure 2, the X-ray response sensitivity of the device is 152μCGy obtained by linear fitting. -1 cm -2 .

[0030] Embodiment 2:

[0031] 1) Select a graphene sheet and introduce a silver electrode thereon;

[0032] 2) Select a cleaned B-doped diamond sheet;

[0033] 3) Use transparent insulating tape to delineate a window working area on the diamond sheet and ensure that its edge is tightly sealed with the silicon sheet;

[0034] 4) Fill the diamond window working area with 10 μL of 25 mg / mL polystyrene scintillator solution;

[0035] 5) The blank area of ​​the graphene sheet is transferred to the window working area so that it is in close contact with the solution, while preventing the silver electrode on the graphene side from contacting the solution. The four sides of the window working area are fixed and sealed with UV glue to prevent solution leakage, thereby forming a stable diamond / scintillator solution / graphene X-ray detector.

[0036] Taking the obtained X-ray detector based on diamond / scintillator solution / graphene as an example, its photoelectric response results are as follows Figure 5 As shown. At a radiation dose of 5.18mGy*s -1 Under the irradiation of X-ray source, the specific values ​​of transient photopolarization current, steady-state photopolarization current and depolarization current are measured according to the experimental equipment and conditions. The peak value of transient photopolarization current reaches 1.126μAcm-2 .

[0037] Due to the difference in Fermi levels between semiconductors and graphene, water molecules in the interlayer are polarized. In this process, negatively charged oxygen atoms move closer to graphene and induce positively charged holes, while positively charged hydrogen atoms move closer to silicon and induce negatively charged electrons. Under light, a large number of electrons drift to the diamond / water interface, and a large number of holes drift to the water / graphene interface, generating a transient photopolarized current. During this process, the polystyrene scintillator in the solution absorbs part of the X-rays and releases fluorescence, which stimulates electron-hole pairs in the semiconductor, causing the semiconductor to generate more photogenerated carriers and strengthen the transient photopolarized current. Under continuous light conditions, due to the continuous accumulation of non-equilibrium carriers in the two-phase interface, the polarization current will tend to stabilize, and at the same time, more water molecules will be polarized in an orderly manner. When the light source is turned off, a negative polarization current will be generated, which is a depolarization process. The photoexcited carriers will relax and recombine inside the graphene, and the water molecules will return to a disordered state.

[0038] The device performance was further tested by changing the incident X-ray dose to obtain a relationship diagram between the incident X-ray dose and the peak value of the response current, such as Figure 6 As shown in Figure 2, the X-ray response sensitivity of the device is 149.4 μC Gy obtained by linear fitting. -1 cm -2 .

[0039] Obviously, the present invention is not limited to the above-mentioned specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different options and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A self-driven heterostructure X-ray detector based on liquid medium photopolarization, characterized in that: The detector comprises: a first structural layer (1), a polar liquid (2), and a second structural layer (3); the first structural layer (1) is a semiconductor material, the polar liquid (2) contains an absorber or a scintillator, the second structural layer (3) is graphene, a metal or a semiconductor material, and the first structural layer and the second structural layer have different Fermi levels; the polar liquid (2) is in direct contact with both the first structural layer (1) and the second structural layer (3) to form an electrical heterostructure.

2. The self-driven heterostructure X-ray detector based on liquid medium photopolarization according to claim 1, characterized in that: Electrodes are provided on the first structural layer (1) and the second structural layer (3), and the electrodes are independently selected from one or more of gold, aluminum, copper, iron, and tin, and have a thickness of 300 μm-10 nm.

3. The self-driven heterostructure X-ray detector based on liquid medium photopolarization according to claim 1, characterized in that: The semiconductor material of the first structural layer (1) is selected from one of silicon, germanium, diamond, silicon carbide, gallium nitride, gallium arsenide, cadmium telluride, and cadmium zinc telluride, and the semiconductor material of the second structural layer (3) is selected from one of zinc oxide, indium tin oxide, and polymer semiconductor materials.

4. The self-driven heterostructure X-ray detector based on liquid medium photopolarization according to claim 1, characterized in that: The polar liquid (2) is any polar liquid.

5. The self-driven heterostructure X-ray detector based on liquid medium photopolarization according to claim 1, characterized in that: The absorbent or scintillator is selected from one or more of sodium iodide, barium sulfate and polystyrene.

6. A method for preparing a self-driven heterostructure X-ray detector based on liquid medium photopolarization according to any one of claims 1 to 5, characterized in that: The method comprises: making an electrode on the surface of the first structural layer (1) or the second structural layer (3), then directly applying a polar liquid containing an absorbent or a scintillator to a blank surface of one of the structural layers, and finally covering the blank surface of the other structural layer on the surface of the polar liquid, so that the first structural layer (1) and the second structural layer (3) are in direct contact with the polar liquid, thereby forming an electrical heterogeneous structure.

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