A method for low-temperature growth of a scintillation crystal, a large-area thick-film scintillation crystal and application

Abstract

The present application relates to a kind of scintillation crystal low-temperature growth method, large-area thick film scintillation crystal and application, it relates to scintillation crystal growth technical field, the scintillation crystal low-temperature growth method uses low-temperature seeding, floating face evaporation process, combine high-precision temperature regulation system, including S1: substrate pretreatment, S2: low-temperature seeding, S3: floating face evaporation growth, S4: crystal column regulation and S5: post-processing five steps;Scintillation crystal uniform growth is realized on large-area substrate, growth temperature is reduced by 300-500 DEG C, energy consumption is low;The prepared thick film scintillation crystal crystal column diameter is 3-5 μm, growth direction and substrate angle ≥88 DEG, quantum detection efficiency reaches more than 80%, can be applied to digital X-ray photoelectric detector, large-area imaging system and other fields, is suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of scintillation crystal growth, and more specifically, relates to a low-temperature growth method for a scintillation crystal, a large-area thick-film scintillation crystal, and applications thereof. Background Art

[0002] Existing large-area thick-film scintillation crystals have high growth temperatures, high energy consumption, non-uniform crystal column growth, large dimensional deviations, and high industrialization difficulty.

[0003] Chinese Patent Document CN104762657A, published on 2025.07.08, discloses a thallium-doped cesium iodide scintillator and an application thereof. The thallium-doped cesium iodide scintillator is thallium and ytterbium co-doped cesium iodide, which has the following general composition formula: (Cs 1-x- y Tl x Yb y )(I 1-y M 2y ) or (Cs 1-x-y Tl x Yb y )(I 1-y M 3y ), wherein: M=I, Br, Cl or F; 0<x≤0.05, 0<y≤0.05; The thallium-doped cesium iodide thin films and single crystal fibers prepared by using the thallium-doped cesium iodide scintillator of the present invention both have excellent properties of high scintillation efficiency and low afterglow, and can be widely applied in the field of X-ray radiation imaging. However, in this technical solution, a high-temperature annealing treatment is required after depositing the thin film;

[0004] Chinese Patent Document CN107201500A, published on 2017.09.26, discloses a moisture-resistant thallium-doped cesium iodide thin film and a preparation method thereof, belonging to the technical field of scintillator detectors; in the present invention, a vacuum thermal evaporation method is preferably used to deposit a thallium-doped cesium iodide thin film on a substrate, and then a plasma-enhanced chemical vapor deposition method is used to prepare a nano-sized silicon dioxide thin film on the surface of the thallium-doped cesium iodide thin film. The dense silicon dioxide thin film can effectively prevent water molecules in the air from entering the thallium-doped cesium iodide thin film, can overcome the defect that the thallium-doped cesium iodide thin film is prone to deliquescence, avoid the influence of deliquescence on performance indicators such as the light conversion efficiency and spatial resolution of the thallium-doped cesium iodide thin film, and improve the moisture resistance and service life of the thin film. However, in this technical solution, a rotational evaporation method is used to prepare the cesium iodide thick film, and the problem of poor uniformity of crystal column arrangement easily occurs under conventional low-temperature evaporation conditions.

[0005] The foregoing description is provided to provide general background information and does not necessarily constitute prior art. Contents of the Invention

[0006] The purpose of this invention is to provide a low-temperature growth method for scintillation crystals and its application. This low-temperature growth method solves the technical problems of existing large-area thick-film scintillation crystals, such as high growth temperature, uneven crystal column growth, difficulty in controlling size, high preparation cost, and difficulty in industrialization.

[0007] This invention provides a method for low-temperature growth of scintillation crystals, comprising the following steps:

[0008] S1: Substrate pretreatment: Select borosilicate glass or... Ceramic substrate, size 17×17 inches and above, thickness 1-2 mm, surface flatness ≤0.005 mm; immerse the substrate in cleaning solution for ultrasonic cleaning for 20-30 minutes, rinse with deionized water 3 times, 5 minutes each time; 80℃, vacuum degree The substrate was dried for 2 hours under the specified conditions, and the moisture content on the substrate surface after drying was ≤0.01%. A 50-100 nm thick lead layer was coated on the substrate surface using vacuum evaporation.

[0009] S2: Low-Temperature Die-Picking: Place the pretreated substrate into the growth furnace and fix it on the stage, ensuring the substrate surface is level; evacuate to... Introduce argon or nitrogen gas and continue purging for 20 minutes; then raise the temperature to 400-600℃ at a rate of 5℃ / min and hold for 1-2 hours to fully activate the seed layer and increase the density of crystal nuclei. ;

[0010] S3: Floating surface evaporation growth: Place CsI:Tl, CsI:Na, or NaI:Tl raw materials into a tungsten boat or tantalum boat evaporation source and heat to 800-900℃ to melt the raw materials; control the evaporation rate to 0.1-0.5nm / s, with fluctuations ≤±0.05nm / s; control the temperature gradient inside the furnace to 2-5℃ / cm, and adjust the stage height to form a uniform liquid film of 5-10μm thick on the substrate surface of the molten raw materials, guiding the crystal pillar to grow vertically;

[0011] S4: Crystal pillar control: The furnace temperature is monitored by a high-precision temperature control system to control the crystal pillar growth rate to 1-3 μm / h and the growth time to 2-5h; the crystal pillar diameter is controlled to 3-5 μm, and the angle between the growth direction and the substrate surface is ≥88°; the inert gas flow rate is kept stable during the growth process.

[0012] S5: Post-processing: After growth, the substrate is cooled to room temperature in stages; the substrate is removed and chemical mechanical polishing is performed at a pressure of 0.05-0.1 MPa, a rotation speed of 100 r / min, and a time of 1-2 h; after polishing, performance testing is performed to obtain a large-area thick film scintillation crystal with a thickness of 5-20 μm.

[0013] Further, the cleaning solution in step S1 is acetone, anhydrous ethanol and deionized water; wherein the volume ratio of acetone, anhydrous ethanol and deionized water is 1:1:2, and the ultrasonic cleaning power in the cleaning solution is 400W and the time is 25min.

[0014] Furthermore, the pilot layer in step S1 is a CsI or TlI thin film, and the purity of the pilot layer is ≥99.99%, the evaporation rate is 0.2 nm / s, and the vacuum degree is... The thickness of the lead crystal layer is 70-80 nm.

[0015] Furthermore, step S1 also includes detecting the surface roughness Ra≤0.2nm after the substrate pretreatment is completed.

[0016] Further, in step S2, the flow rate of argon or nitrogen gas is 150 mL / min; the temperature is increased to 500-550℃ at 5℃ / min and held for 1.5 h.

[0017] Furthermore, in step S3, the evaporation rate is controlled at 0.2-0.3 nm / s, and the temperature gradient inside the furnace is controlled at 3-4 °C / cm.

[0018] Furthermore, after growth is completed in step S5, the temperature is reduced to room temperature in stages: the temperature reduction rate is 3℃ / h from 600℃ to 300℃ and the temperature reduction rate is 5℃ / h from 300℃ to room temperature; the polishing solution in the chemical mechanical polishing method is colloidal silica and anhydrous ethanol, wherein the volume ratio of colloidal silica to anhydrous ethanol is 1:2.

[0019] Furthermore, step S5 also includes a surface roughness Ra≤0.3nm for the polished thick film, a quantum detection efficiency of over 80%, a light output ≥22000ph / MeV, and a decay time ≤80ns.

[0020] The present invention also provides a large-area thick-film scintillation crystal, which is fabricated by the above-described low-temperature growth method for scintillation crystals.

[0021] The present invention also provides an application of a large-area thick-film scintillation crystal prepared by the above-mentioned low-temperature growth method in a digital X-ray photodetector and a large-area imaging system.

[0022] The present invention provides a low-temperature growth method for scintillation crystals, employing low-temperature crystal introduction and floating surface evaporation processes combined with a high-precision temperature control system. The method comprises five steps: substrate pretreatment, low-temperature crystal introduction, floating surface evaporation growth, crystal pillar control, and post-treatment. This method achieves uniform growth of scintillation crystals on large-area substrates, reducing the growth temperature by 300-500℃ and resulting in low energy consumption. The prepared thick-film scintillation crystals have a crystal pillar diameter of 3-5μm, a growth direction angle ≥88° with the substrate, and a quantum detection efficiency exceeding 80%. These crystals can be applied to fields such as digital X-ray photodetectors and large-area imaging systems, and are suitable for large-scale industrial production. The present invention reduces the growth temperature by 300-500℃, significantly reduces energy consumption, produces uniform crystal pillar growth with controllable dimensions, and features a simple and highly controllable fabrication process, making it suitable for large-scale industrial production and overcoming the industrialization bottlenecks of existing technologies. Attached Figure Description

[0023] Figure 1 This is a schematic flowchart of the low-temperature growth method for scintillation crystals provided in Embodiment 1 of the present invention. Detailed Implementation

[0024] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0025] The terms "first," "second," "third," "fourth," etc., used in the specification and claims of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0026] Example 1

[0027] Figure 1 This is a schematic flowchart of the low-temperature growth method for scintillation crystals provided in Embodiment 1 of the present invention. Please refer to... Figure 1 The low-temperature growth method for scintillation crystals provided in this embodiment of the invention includes the following steps:

[0028] S1: Substrate pretreatment: Select borosilicate glass or... Ceramic substrate, size 17×17 inches and above, thickness 1-2 mm, surface flatness ≤0.005 mm; immerse the substrate in cleaning solution for ultrasonic cleaning for 20-30 minutes, rinse with deionized water 3 times, 5 minutes each time; 80℃, vacuum degree The substrate was dried for 2 hours under the specified conditions, and the moisture content on the substrate surface after drying was ≤0.01%. A 50-100 nm thick lead layer was coated on the substrate surface using vacuum evaporation.

[0029] Specifically, the cleaning solution in step S1 of the present invention is acetone, anhydrous ethanol and deionized water; wherein, the volume ratio of acetone, anhydrous ethanol and deionized water is 1:1:2, and the ultrasonic cleaning power in the cleaning solution is 400W and the time is 25min.

[0030] Furthermore, the pilot layer in step S1 is a CsI or TlI thin film, wherein the purity of the pilot layer is ≥99.99%, the evaporation rate is 0.2 nm / s, and the vacuum degree is... The thickness of the lead layer is 70-80 nm;

[0031] In addition, step S1 of the present invention also includes detecting the surface roughness Ra≤0.2nm after the substrate pretreatment is completed.

[0032] S2: Low-Temperature Die-Picking: Place the pretreated substrate into the growth furnace and fix it on the stage, ensuring the substrate surface is level (levelness ≤ 0.001 mm / m); evacuate to... Introduce argon or nitrogen gas (flow rate 100-200 mL / min) and continue inhaling for 20 min; then raise the temperature to 400-600℃ at a rate of 5℃ / min and hold for 1-2 h to fully activate the seed layer and increase the density of crystal nuclei. ;

[0033] Specifically, in step S2 of the present invention, the flow rate of argon or nitrogen gas introduced is 150 mL / min; the temperature is increased to 500-550°C at 5°C / min and held for 1.5 h.

[0034] S3: Floating surface evaporation growth: CsI:Tl, CsI:Na, or NaI:Tl raw materials (purity ≥99.999%, particle size ≤1mm) are placed in a tungsten boat or tantalum boat evaporation source (purity 99.95%) and heated to 800-900℃ to melt the raw materials; the evaporation rate is controlled at 0.1-0.5nm / s, with fluctuation ≤±0.05nm / s; the temperature gradient inside the furnace is controlled at 2-5℃ / cm, and the stage height is adjusted to form a 5-10μm thick uniform liquid film (uniformity ≤±0.5μm) on the substrate surface, guiding the crystal pillar to grow vertically;

[0035] Specifically, in step S3 of the present invention, the evaporation rate is controlled at 0.2-0.3 nm / s, and the temperature gradient inside the furnace is controlled at 3-4 °C / cm.

[0036] S4: Crystal pillar control: The furnace temperature is monitored by a high-precision temperature control system (temperature control accuracy ±0.5℃), the crystal pillar growth rate is controlled at 1-3μm / h, and the growth time is 2-5h; the crystal pillar diameter is controlled at 3-5μm (deviation ≤±0.5μm), and the angle between the growth direction and the substrate surface is ≥88° (deviation ≤±1°); the inert gas flow rate is kept stable during the growth process.

[0037] S5: Post-processing: After growth is completed, the substrate is cooled to room temperature in stages; the substrate is removed and chemical mechanical polishing is performed at a pressure of 0.05-0.1 MPa, a rotation speed of 100 r / min, and a time of 1-2 h; after polishing, the performance is tested to obtain a large-area thick film scintillation crystal with a thickness of 5-20 μm (uniformity ≤ ±0.5 μm).

[0038] Specifically, in step S5 of the present invention, after growth is completed, the temperature is cooled to room temperature in stages: the cooling rate from 600°C to 300°C is 3°C / h, and the cooling rate from 300°C to room temperature is 5°C / h; the polishing liquid in the chemical mechanical polishing method is colloidal silica and anhydrous ethanol, wherein the volume ratio of colloidal silica to anhydrous ethanol is 1:2.

[0039] In addition, step S5 of the present invention also includes a surface roughness Ra≤0.3nm of the thick film after polishing, a quantum detection efficiency of over 80%, a light output ≥22000ph / MeV, and a decay time ≤80ns.

[0040] It should be noted that the scintillation crystal low-temperature growth method provided by this invention employs low-temperature crystal introduction and floating surface evaporation processes, combined with a high-precision temperature control system. It includes five steps: substrate pretreatment, low-temperature crystal introduction, floating surface evaporation growth, crystal pillar control, and post-processing. This method achieves uniform growth of scintillation crystals on large-area substrates, reducing the growth temperature by 300-500℃ and resulting in low energy consumption. The prepared thick-film scintillation crystal pillars have a diameter of 3-5μm, an angle ≥88° between the growth direction and the substrate, and a quantum detection efficiency of over 80%. It can be applied to fields such as digital X-ray photodetectors and large-area imaging systems, and is suitable for large-scale industrial production. This invention reduces the growth temperature by 300-500℃, significantly reduces energy consumption, produces uniform crystal pillar growth with controllable dimensions, and features a simple and highly controllable fabrication process, making it suitable for large-scale industrial production and solving the industrialization bottlenecks of existing technologies.

[0041] Example 2

[0042] This embodiment provides a large-area thick-film scintillation crystal, which is fabricated using the low-temperature growth method for scintillation crystals described in Example 1.

[0043] Example 3

[0044] This embodiment provides an application of a large-area thick-film scintillation crystal fabricated using the low-temperature growth method of Embodiment 1 in a digital X-ray photodetector and a large-area imaging system.

[0045] Example 4

[0046] In this embodiment, a 17×17-inch borosilicate glass substrate with a thickness of 1.5 mm and a surface flatness of 0.004 mm was selected; the cleaning solution volume ratio was 1:1:2; ultrasonic cleaning was performed for 25 min; vacuum drying was carried out at 80℃ for 2 h; and the water content was 0.008%; a 75 nm thick CsI seed layer was deposited by vapor deposition at a deposition rate of 0.2 nm / s.

[0047] During low-temperature crystal development, argon gas was introduced at a rate of 150 mL / min, the temperature was raised to 520 °C, and held for 1.5 hours. The crystal nucleus formation density was then determined. ;

[0048] The raw material used was CsI:Tl, with a melting temperature of 850℃, an evaporation rate of 0.25nm / s, and a liquid film thickness of 8μm.

[0049] The crystal column growth rate was 2 μm / h, the growth time was 3 h, the crystal column diameter was 4 μm, and the included angle was 89°.

[0050] After polishing, the film thickness is 12μm, the uniformity is ±0.4μm, the surface Ra=0.25nm, and the quantum detection efficiency is 82%.

[0051] As can be seen from the above description, the advantages of this invention are:

[0052] The present invention provides a low-temperature growth method for scintillation crystals, employing low-temperature crystal introduction and floating surface evaporation processes combined with a high-precision temperature control system. The method comprises five steps: substrate pretreatment, low-temperature crystal introduction, floating surface evaporation growth, crystal pillar control, and post-treatment. This method achieves uniform growth of scintillation crystals on large-area substrates, reducing the growth temperature by 300-500℃ and resulting in low energy consumption. The prepared thick-film scintillation crystals have a crystal pillar diameter of 3-5μm, a growth direction angle ≥88° with the substrate, and a quantum detection efficiency exceeding 80%. These crystals can be applied to fields such as digital X-ray photodetectors and large-area imaging systems, and are suitable for large-scale industrial production. The present invention reduces the growth temperature by 300-500℃, significantly reduces energy consumption, produces uniform crystal pillar growth with controllable dimensions, and features a simple and highly controllable fabrication process, making it suitable for large-scale industrial production and overcoming the industrialization bottlenecks of existing technologies.

[0053] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for low-temperature growth of scintillation crystals, characterized in that, Includes the following steps: S1: Substrate pretreatment: Select borosilicate glass or... Ceramic substrate, size 17×17 inches and above, thickness 1-2mm, surface flatness ≤0.005mm; immerse the substrate in cleaning solution for ultrasonic cleaning for 20-30 minutes, rinse with deionized water 3 times, 5 minutes each time; 80℃, vacuum degree The substrate was dried for 2 hours under the specified conditions, and the moisture content on the substrate surface after drying was ≤0.01%. A 50-100 nm thick lead layer was coated on the substrate surface using vacuum evaporation. S2: Low-Temperature Die-Picking: Place the pretreated substrate into the growth furnace and fix it on the stage, ensuring the substrate surface is level; evacuate to... Introduce argon or nitrogen gas and continue ventilating for 20 minutes. Increase the temperature to 400-600℃ at a rate of 5℃ / min and hold for 1-2 hours to fully activate the seed layer and increase the density of crystal nuclei. ; S3: Floating surface evaporation growth: Place CsI:Tl, CsI:Na, or NaI:Tl raw materials into a tungsten boat or tantalum boat evaporation source and heat to 800-900℃ to melt the raw materials; control the evaporation rate to 0.1-0.5nm / s, with fluctuations ≤±0.05nm / s; control the temperature gradient inside the furnace to 2-5℃ / cm, and adjust the stage height to form a uniform liquid film of 5-10μm thick on the substrate surface of the molten raw materials, guiding the crystal pillar to grow vertically; S4: Crystal pillar control: The furnace temperature is monitored by a high-precision temperature control system to control the crystal pillar growth rate to 1-3 μm / h and the growth time to 2-5h; the crystal pillar diameter is controlled to 3-5 μm, and the angle between the growth direction and the substrate surface is ≥88°; the inert gas flow rate is kept stable during the growth process. S5: Post-processing: After growth, the substrate is cooled to room temperature in stages; the substrate is removed and chemical mechanical polishing is performed at a pressure of 0.05-0.1 MPa, a rotation speed of 100 r / min, and a time of 1-2 h; after polishing, performance testing is performed to obtain a large-area thick film scintillation crystal with a thickness of 5-20 μm.

2. The method for low-temperature growth of scintillation crystals according to claim 1, characterized in that, The cleaning solution in step S1 is acetone, anhydrous ethanol and deionized water; wherein the volume ratio of acetone, anhydrous ethanol and deionized water is 1:1:2, and the ultrasonic cleaning power in the cleaning solution is 400W and the time is 25min.

3. The method for low-temperature growth of scintillation crystals according to claim 1, characterized in that, The pilot layer in step S1 is a CsI or TlI thin film, and the purity of the pilot layer is ≥99.99%, the evaporation rate is 0.2 nm / s, and the vacuum degree is... The thickness of the lead crystal layer is 70-80 nm.

4. The method for low-temperature growth of scintillation crystals according to claim 1, characterized in that, Step S1 further includes detecting the surface roughness Ra≤0.2nm after the substrate pretreatment is completed.

5. The method for low-temperature growth of scintillation crystals according to claim 1, characterized in that, In step S2, the flow rate of argon or nitrogen gas is 150 mL / min; the temperature is increased to 500-550℃ at a rate of 5℃ / min, and held for 1.5 h.

6. The method for low-temperature growth of scintillation crystals according to claim 1, characterized in that, In step S3, the evaporation rate is controlled at 0.2-0.3 nm / s, and the temperature gradient inside the furnace is controlled at 3-4 °C / cm.

7. The method for low-temperature growth of scintillation crystals according to claim 1, characterized in that, After growth is completed in step S5, the temperature is reduced to room temperature in stages: the temperature is reduced from 600℃ to 300℃ at a rate of 3℃ / h, and the temperature is reduced from 300℃ to room temperature at a rate of 5℃ / h. The polishing solution in the chemical mechanical polishing method is colloidal silica and anhydrous ethanol, wherein the volume ratio of colloidal silica to anhydrous ethanol is 1:

2.

8. The method for low-temperature growth of scintillation crystals according to claim 1, characterized in that, Step S5 further includes a thick film surface roughness Ra≤0.3nm after polishing, a quantum detection efficiency of over 80%, a light output ≥22000ph / MeV, and a decay time ≤80ns.

9. A large-area thick-film scintillation crystal, characterized in that, The large-area thick-film scintillation crystal is fabricated using the scintillation crystal low-temperature growth method described in any one of claims 1-8.

10. The application of a large-area thick-film scintillation crystal fabricated by the low-temperature growth method according to any one of claims 1-8 in a digital X-ray photodetector and a large-area imaging system.

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