Self-driven heterostructure X-ray detector based on liquid medium photo-induced polarization and preparation method thereof

Abstract

The application discloses a self-driven heterostructure X-ray detector based on liquid medium photo-induced polarization and a preparation method thereof. The detector main body is two semiconductor structures with different Fermi energy levels (one of the semiconductor structures can also be graphene / metal) and a polar liquid containing an absorbent or a scintillator sandwiched therebetween. X-rays are irradiated on the structure, which can generate electrons or fluorescence in the liquid. The electrons are transported to the semiconductor under the action of the built-in electric field, thereby generating X-ray photocurrent. The fluorescence can excite electron-hole pairs in the semiconductor, which further interact with molecules in the liquid, thereby generating X-ray photocurrent. Compared with a traditional X-ray detector, the novel photodetector directly solves the problem of lattice matching difficulty of the traditional solid-phase device. The design is simple and easy to prepare. The self-driven working mode does not require an external power supply and can be applied to harsh working environments, and is a novel, efficient and low-cost solution.

Description

Technical Field

[0001] This invention belongs to the field of photodetectors and relates to a self-driven heterostructure X-ray detector based on photopolarization in a liquid medium and its fabrication method. Background Technology

[0002] X-ray detection has important applications in daily life, but traditional X-ray detectors are generally made of solid materials, with liquid materials rarely used. This invention presents an innovative solution for a liquid-phase X-ray detector based on photopolarization of a polar liquid. This solution achieves successful fabrication of a liquid-phase X-ray detector by adding an X-ray absorber or scintillator to a polar liquid, breaking free from the framework of solid-state photoelectric detection and greatly expanding the design and application boundaries of X-ray detectors. Moreover, the device performance of this photopolarized liquid-phase X-ray detector is already at a leading level in the field of X-ray semiconductor self-actuated devices. This innovative device driving method based on photopolarization of a polar liquid and the innovative thinking of solution-controlled absorption will open up entirely new paths for X-ray detection technology, highlighting its originality and broad application prospects. Summary of the Invention

[0003] The main objective of this invention is to overcome the shortcomings and limitations of existing solid-state light-absorbing photodetectors and provide a self-driven heterostructure X-ray detector based on photopolarization in a liquid medium and its fabrication method. This X-ray detector is self-driven, overcomes process limitations, and its absorption wavelength can be flexibly designed according to the liquid, showing broad application prospects.

[0004] The technical solution adopted in this invention is:

[0005] A self-driven heterostructure X-ray detector with photopolarization in a liquid medium is mainly composed of two semiconductor structures (one of which can be graphene / metal) with different Fermi levels and a polar liquid containing an absorber or a scintillator sandwiched between them. 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 a scintillator, the second structural layer is graphene, a metal, or a semiconductor material, and the first and second structural layers have different Fermi levels; the polar liquid is in direct contact with both the first and second structural layers, forming an electrical heterostructure.

[0006] In addition, electrodes are provided on both the first structural layer and the second structural layer. These electrodes can be one or more materials selected independently from gold, aluminum, copper, iron, and tin, and their thickness can generally be controlled between 300 μm and 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 zinc cadmium 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] A polar liquid is a key element, located between two structural layers. This polar liquid can be any polar solution, including but not limited to water, ethylene glycol, ethanol, acetone, glycerol, and propylene glycol. Its presence, under external light irradiation, induces a dynamic polarization-depolarization process at the semiconductor (or graphene / metal) / polar liquid interface, thereby causing the accumulation and separation of surface charges and forming a response current.

[0009] Furthermore, polar liquids also contain solutes, i.e., absorbers or scintillators, which can selectively absorb or enhance the wavelength. These include, but are not limited to, one or more of sodium iodide, barium sulfate, and polystyrene. Their presence enhances the absorption of X-rays by the polar liquid, improving the overall device response. When X-rays irradiate this structure, electrons (when the solute is an absorber) or fluorescence (when the solute is a scintillator) can be generated in the liquid. Electrons are transported to the semiconductor under the influence of the built-in electric field formed by semiconductors with different Fermi levels, thereby generating an X-ray photocurrent. Fluorescence excites electron-hole pairs in the semiconductor, which further interact with molecules in the liquid, thus generating an X-ray photocurrent.

[0010] The preparation method includes: fabricating electrodes on the surface of the first or 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; finally covering the surface of the polar liquid with the blank surface of the other structural layer, so that both the first and second structural layers are in direct contact with the polar liquid, forming an electrical heterostructure. In the actual preparation process, electrodes are first formed on the clean first and second structural layers. Then, a window is fabricated in the blank area of ​​one of the structural layers (as a substrate) using a transparent insulating material, and the window needs to be sealed to the substrate. Next, the polar liquid containing the absorbent or scintillator is injected into the window until it is completely filled. Finally, another structural layer is placed over the window so that the polar liquid can fully contact the two structural layers.

[0011] It is noteworthy that when the detector is exposed to periodic light input, it generates three types of currents: transient photopolarization current, steady-state photopolarization current, and depolarization current. This is primarily due to the photopolarization of the polar liquid under incident light, which causes a large number of charge 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 charge carriers accumulated at the polar liquid / semiconductor interface are cleared, forming a depolarization current. This unique working mechanism gives the detector strong response sensitivity and a wide response spectrum range.

[0012] Compared with the prior art, the beneficial effects of the present invention are:

[0013] This invention offers a disruptive perspective on traditional X-ray detection technology by introducing polar liquids and, for the first time, achieving X-ray detection based on the dynamic photopolarization of polar liquids. Furthermore, by introducing solutes into the polar liquids to enhance X-ray absorption, it significantly improves the flexibility of photodetector design, ultimately achieving high current response intensity and high sensitivity to X-rays. Compared to traditional devices that rely on solid-state light absorption, this invention directly eliminates the impact of inherent process issues such as lattice matching on device performance, reducing the high requirements of traditional X-ray detectors on solid materials. By introducing a solute component that enhances X-ray absorption, the absorption capacity for X-rays is improved and enhanced, increasing the overall photoelectric conversion efficiency of the device. Specifically, in Example 1, the experimental group with a concentration of 0.02 mol / L sodium iodide solution produced 1.149 μA cm⁻¹ under X-ray dose radiation of 5.18 mGy / s. -2 The peak response was obtained by changing the incident X-ray dose, and the device sensitivity was 152 μC Gy. -1 cm -2 In Example 2, the experimental group containing a polystyrene scintillator solution at a concentration of 25 mg / mL produced 1.126 μA cm⁻¹ under X-ray radiation at a dose of 5.18 mGy / s. -2 The peak response was obtained by changing the incident X-ray dose, and the device sensitivity was 149.4 μC Gy. -1 cm -2 This is already at the forefront of the field of X-ray semiconductor self-actuated devices. Furthermore, the self-actuated nature of this invention ensures stable operation even without an external power source and opens up new avenues for using liquid media in photoelectric conversion. In summary, this invention provides a completely new solution for the field of X-ray detection technology, further enriching its application potential. Attached Figure Description

[0014] Figure 1This is a schematic diagram of a polarized photocurrent-responsive photodetector based on a semiconductor / polar liquid / graphene heterostructure.

[0015] Figure 2 This is a schematic diagram of the static equilibrium energy band of a semiconductor / polar liquid / graphene heterostructure after contact.

[0016] Figure 3 The time-current curves of the silicon / sodium iodide solution / graphene heterostructure under X-ray irradiation with a radiation dose of 5.18 mGy / s are shown.

[0017] Figure 4 The dose-current relationship is shown in the figure for silicon / sodium iodide solution / graphene heterostructure devices under X-ray irradiation with a radiation dose of 1.39-5.18 mGy / s.

[0018] Figure 5 The time-current curves of the diamond / scintillator solution / graphene heterostructure device under X-ray irradiation with a radiation dose of 5.18 mGy / s are shown.

[0019] Figure 6 The dose-current curves of diamond / scintillator solution / graphene heterostructure devices under X-ray irradiation with radiation doses ranging from 1.39 to 5.18 mGy / s are shown. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Furthermore, the first structural layer and the second structural layer in this invention are only used to distinguish between the two structural layers and are not used to limit their relative positions with the polar liquid; their positions can be interchanged.

[0021] Reference Figure 1 According to a specific example of the present invention, a photo-induced liquid polarization X-ray detector based on a semiconductor / polar liquid / graphene structure is provided, such as... Figure 1 As shown. From top to bottom, the structure comprises graphene 1, a transparent insulating window filled with a polar liquid 2 containing an absorber or scintillator, and a semiconductor 3. During photoresponse performance testing, an X-ray source is used to illuminate the device from the side. In all examples, the area of ​​the insulating window remains consistent. This photo-liquid-polarized X-ray detector utilizes the surface tension of the polar liquid to tightly bond with the semiconductor and graphene. Due to the Fermi level difference between the semiconductor and graphene, the polar liquid in the interlayer is polarized, such as... Figure 2As shown. Under X-ray excitation, the presence of absorbers or scintillators in the liquid can generate electrons or fluorescence. Electrons are transported to the semiconductor under the influence of a built-in electric field, generating an X-ray photocurrent. Fluorescence excites electron-hole pairs in the semiconductor, which further interact with molecules in the liquid, producing an X-ray photocurrent. A large number of electrons drift to the semiconductor / polar liquid interface, while a large number of holes drift to the graphene / polar liquid interface, generating a momentary photopolarized current. After the illumination stabilizes, the photopolarized current tends to level off. When the light source is turned off, a depolarization current is generated.

[0022] Example 1:

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

[0024] 2) Select cleaned silicon wafers;

[0025] 3) Mark out a window working area on the silicon wafer with transparent insulating tape, and ensure that its edges are tightly sealed to the silicon wafer;

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

[0027] 5) Transfer the blank area of ​​the graphene sheet to the window working area, so that it is in close contact with water, while avoiding contact between the silver electrode on the graphene side and the water. Fix and seal the perimeter of the window working area with UV glue to prevent deionized water leakage, 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. The radiation dose is 5.18 mGy*s. -1 Under X-ray irradiation, 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 the transient photopolarization current reached 1.149 μA / cm. -2Due to the Fermi level difference between the semiconductor and graphene, water molecules in the interlayer become polarized. During this process, negatively charged oxygen atoms approach the graphene and induce positively charged holes, while positively charged hydrogen atoms approach the silicon and induce negatively charged electrons. Under illumination, 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 photopolarization current. Simultaneously, iodide ions in the solution absorb some X-rays and release electrons, reinforcing the transient photopolarization current. Under continuous illumination, the polarization current tends to stabilize due to the continuous accumulation of non-equilibrium charge carriers at the two-phase interface, while more water molecules become orderly polarized. When the light source is turned off, a negative polarization current is generated, which is the depolarization process. The photoexcited charge carriers relax and recombine inside the graphene, while the water molecules return to a disordered state.

[0029] Further testing of the device performance was conducted by varying the incident X-ray dose, resulting in a graph showing the relationship between the incident X-ray dose and the peak response current. Figure 4 As shown, the X-ray response sensitivity of the device was determined to be 152 μCy through linear fitting. -1 cm -2 .

[0030] Example 2:

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

[0032] 2) Select cleaned boron-doped diamond wafers;

[0033] 3) Mark a working window area on the diamond wafer with transparent insulating tape, and ensure that its edges are tightly sealed to the silicon wafer;

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

[0035] 5) Transfer the blank area of ​​the graphene sheet to the window working area to make it in close contact with the solution, while avoiding contact between the silver electrode on the graphene side and the solution. Fix and seal the perimeter of the window working area 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. The radiation dose is 5.18 mGy*s. -1 Under X-ray irradiation, 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 the transient photopolarization current reached 1.126 μA / cm.-2 .

[0037] The Fermi level difference between the semiconductor and graphene causes water molecules in the interlayer to become polarized. During this process, negatively charged oxygen atoms approach the graphene and induce positively charged holes, while positively charged hydrogen atoms approach the silicon and induce negatively charged electrons. Under illumination, 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 photopolarization current. Simultaneously, the polystyrene scintillator in the solution absorbs some X-rays and emits fluorescence. This fluorescence excites electron-hole pairs in the semiconductor, causing the semiconductor to generate more photogenerated carriers and enhancing the transient photopolarization current. Under continuous illumination, the polarization current tends to stabilize due to the continuous accumulation of non-equilibrium carriers at the two-phase interface, while more water molecules become orderly polarized. When the light source is turned off, a negative polarization current is generated, which is the depolarization process. The photo-excited carriers relax and recombine within the graphene, while the water molecules return to a disordered state.

[0038] Further testing of the device performance was conducted by varying the incident X-ray dose, resulting in a graph showing the relationship between the incident X-ray dose and the peak response current. Figure 6 As shown, the X-ray response sensitivity of the device was determined to be 149.4 μC Gy through linear fitting. -1 cm -2 .

[0039] It is obvious that this invention is not limited to the specific embodiments described above. Those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of this invention. The exemplary embodiments were chosen and described to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various exemplary embodiments of the invention, as well as various choices and modifications. The scope of this invention is intended to be defined by the claims and their equivalents.

Claims

1. A self-driven heterostructure X-ray detector based on photopolarization in a liquid medium, characterized in that, The detector comprises: a first structural layer, a polar liquid, and a second structural layer; the first structural layer is a semiconductor material, the polar liquid is water containing an absorber or a scintillator, the second structural layer is graphene, and the Fermi levels of the first and second structural layers are different; the polar liquid is in direct contact with both the first and second structural layers, forming an electrical heterostructure.

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

3. The self-driven heterostructure X-ray detector based on photopolarization in a liquid medium as described in claim 1, characterized in that, The semiconductor material of the first structural layer is selected from one of silicon, germanium, diamond, silicon carbide, gallium nitride, gallium arsenide, cadmium telluride, and zinc cadmium telluride.

4. The self-driven heterostructure X-ray detector based on photopolarization in a liquid medium as described in claim 1, characterized in that, The absorbent or scintillator is selected from one or more of sodium iodide and polystyrene.

5. A method for preparing a self-driven heterostructure X-ray detector based on photopolarization in a liquid medium as described in any one of claims 1-4, characterized in that, The method includes: fabricating 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 surface of the polar liquid with the blank surface of the other structural layer, so that both the first and second structural layers are in direct contact with the polar liquid to form an electrical heterostructure.

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