Method for directly growing zinc oxide scintillation crystal with sandwich structure by hydrothermal method

Abstract

The invention discloses a method for directly growing a zinc oxide scintillation crystal with a sandwich structure by a hydrothermal method, and relates to the technical field of single crystal growth. By optimizing hydrothermal growth process parameters and utilizing the polarity growth characteristics of ZnO crystals, scandium-doped zinc oxide (ZnO: Sc) scintillation layers are epitaxially grown on the upper main surface and the lower main surface (+ c surface and-c surface) of gallium-doped zinc oxide (ZnO: Ga) c-surface seed crystals, so that the scintillation crystal with the sandwich structure, which is complete in structure, good in interface, excellent in performance and excellent in double-surface response potential, is directly obtained. The crystal is especially suitable for the field of radiation detection due to a unique structure and a double-sided response characteristic, and aims to realize ultrafast response, high light output and high detection efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of single crystal growth, and more particularly to a method for directly growing sandwich-structured zinc oxide scintillation crystals using a hydrothermal method. Background Art

[0002] Zinc oxide (ZnO), a wide-bandgap semiconductor material, has attracted significant attention in the field of scintillation crystal research due to its potential for high light output, ultrafast decay time, and excellent radiation resistance. It holds particular promise for applications in extreme ultraviolet (EUV), X-ray, and high-energy particle detection. Traditional research on ZnO-based scintillating materials has focused on powder, thin film, or ceramic forms. However, these materials suffer from high self-absorption and defects, making their scintillation performance insufficient for advanced applications.

[0003] ZnO in single crystal form is considered to be the best way to achieve its ideal scintillation performance. The hydrothermal method, as a technology that can grow high-quality large-size single crystals under relatively mild conditions, has been successfully applied to the growth of ZnO and its doped crystals. In the growth process of ZnO crystals, the polar growth characteristic in the c-axis direction is a significant feature. When using a c-face seed crystal, the crystal will grow simultaneously on the +c face (Zn face) and -c face (O face) of the seed crystal to form a new growth layer. If this characteristic can be effectively controlled and utilized, a "sandwich" structure with the seed crystal as the central layer and new functional layers on both sides can be directly grown. This symmetrical structure lays the foundation for achieving excellent double-sided response characteristics.

[0004] Currently, despite the excellent fast decay characteristics of ZnO:Ga (gallium-doped zinc oxide) scintillating crystals (e.g., decay times of up to tens of picoseconds), the growth of large-scale, high-quality single crystals remains a bottleneck. For example, the introduction of gallium can lead to a decrease in crystal quality and an increase in defect density, and its polar growth characteristics are difficult to control, resulting in low crystal utilization. On the other hand, scandium-doped zinc oxide (ZnO:Sc) crystals not only exhibit excellent scintillation properties, but research has also shown that the introduction of scandium can significantly improve the growth habits of ZnO crystals, for example, increasing the growth rates of the -c and m planes, making the +c and -c planes grow more uniformly, thereby improving crystal quality, reducing internal defects, and enhancing optical uniformity.

[0005] Combining a ZnO:Ga seed crystal with a ZnO:Sc epitaxial layer to form a symmetrical ZnO:Sc / ZnO:Ga / ZnO:Sc sandwich structure is expected to combine the ultrafast scintillation core of ZnO:Ga with the excellent growth characteristics, optical properties, and potential interfacial synergistic effects of ZnO:Sc, providing a new approach for the development of new high-performance scintillators. In particular, this structure can support double-sided light collection or respond well to radiation from both sides, which may significantly improve light collection efficiency and response uniformity. However, there is currently a lack of a systematic process method specifically for directly and controllably growing a scandium-doped zinc oxide layer on a gallium-doped zinc oxide seed crystal to form a specific sandwich structure scintillator crystal. Summary of the Invention

[0006] In view of this, the present invention provides a method for directly growing a sandwich-structured zinc oxide scintillator crystal by a hydrothermal method. The method aims to optimize the hydrothermal growth process parameters, utilize the polar growth characteristics of ZnO crystals, and epitaxially grow a scandium-doped zinc oxide (ZnO:Sc) scintillator layer on the upper and lower main surfaces (+c surface and -c surface) of a gallium-doped zinc oxide (ZnO:Ga) c-plane seed crystal, thereby directly obtaining a sandwich-structured scintillator crystal with a complete structure, a good interface, excellent performance, and excellent double-sided response potential.

[0007] Due to its unique structure and double-sided response characteristics, this crystal is particularly suitable for the field of radiation detection, aiming to achieve ultrafast response, high light output and high detection efficiency.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for directly growing sandwich-structured zinc oxide scintillation crystals using a hydrothermal method comprises the following steps:

[0010] S1 seed crystal preparation:

[0011] Select a c-plane oriented gallium-doped zinc oxide single crystal as the seed crystal (ZnO:Ga). Cut, grind, and polish the seed crystal to ensure its surface is flat and undamaged. Holes can be drilled in the seed crystal to facilitate hanging.

[0012] Preparation of S2 raw materials and mineralizers:

[0013] Weigh high-purity ZnO powder as a zinc source for growing the ZnO:Sc layer;

[0014] According to the target sandwich epitaxial layer composition, Sc2O3 is weighed as a scandium source to form a ZnO:Sc scintillating layer;

[0015] Mixing KOH solution and LiOH solution to obtain a composite mineralizer solution;

[0016] S3 Autoclave filling and sealing:

[0017] The prepared ZnO powder and Sc2O3 precursor were placed in the dissolution zone of the autoclave liner;

[0018] In the growth area of ​​the lining, a processed c-plane oriented gallium-doped zinc oxide single crystal is suspended by a seed crystal rack;

[0019] A baffle is set between the dissolution zone and the growth zone to regulate solute transport;

[0020] Add the prepared composite mineralizer solution to the lining and set the filling degree;

[0021] The inner liner is welded to ensure tightness, placed in the autoclave body, and filled externally (for suspended liners) to balance the pressure;

[0022] S4 hydrothermal growth:

[0023] The filled autoclave is placed in a heating furnace. The heating program is set to slowly heat the autoclave to the preset growth temperature, with a temperature difference of 20°C between adjacent zones. Continuous growth is carried out under the set temperature, temperature difference, and pressure conditions. The growth cycle is determined by the target thickness and is typically 30-60 days. During this process, the raw materials in the dissolution zone are dissolved under high temperature and pressure and transported to the growth zone through convection driven by the temperature difference. In the lower temperature growth zone, the +c and -c planes of the ZnO:Ga seed crystals supersaturate and crystallize, forming a new epitaxial growth layer (ZnO:Sc).

[0024] S5 cooling and sampling:

[0025] After the growth cycle, the temperature is slowly lowered to room temperature according to a preset program. The autoclave is opened, the lining is removed, and then the crystal grown inside is removed. The collected crystal is a symmetrical sandwich structure crystal with the original c-plane ZnO:Ga seed crystal as the middle layer and new scandium-doped zinc oxide (ZnO:Sc) material layers grown on its +c and -c surfaces respectively.

[0026] S6 post-processing:

[0027] The grown crystals are cleaned and dried.

[0028] Preferably, the Ga content in the gallium-doped zinc oxide single crystal in step S1 is 0.05 wt%.

[0029] Preferably, the mass ratio of ZnO to Sc2O3 in step S2 is 400:1;

[0030] Preferably, in step S2, the amount of Sc2O3 added is optimized according to the target scintillation performance and the need to improve the crystal growth habit;

[0031] The volume ratio of the LiOH solution to the KOH solution is 1:1;

[0032] The concentration of the LiOH solution is 4 mol / L, and the concentration of the KOH solution is 1 mol / L.

[0033] Preferably, the autoclave in step S3 is a variable-caliber autoclave with a precious metal lining inside;

[0034] The filling degree is 75%.

[0035] Preferably, it is characterized in that the heating furnace in step S4 is a double-temperature zone or three-temperature zone pit-type resistance furnace; the heating program is to heat the temperature from room temperature to the target temperature at a rate of 50°C / h.

[0036] Preferably, the heating furnace is a dual-temperature zone pit-type resistance furnace, the temperature of the dissolving zone T1 = 380°C, and the temperature of the growth zone T2 = 360°C.

[0037] Preferably, the heating furnace is a three-temperature-zone pit-type resistance furnace, with the temperature of the growth zone T1 = 340°C, the temperature of the transition zone T2 = 360°C, and the temperature of the dissolution zone T3 = 380°C.

[0038] Preferably, the pressure in step S4 is 120 MPa.

[0039] Preferably, in step 4, the thickness, uniformity and scandium concentration distribution of the ZnO:Sc new layer are regulated by precisely controlling parameters such as temperature (temperature control accuracy ±0.1° C.), temperature difference, pressure and mineralizer concentration.

[0040] Preferably, the step S5 of slowly cooling to room temperature according to a preset program is to first cool to 100° C. at a rate of 10° C. / h, and then naturally cool to room temperature.

[0041] Preferably, the drying is carried out in an oven at 60° C. for 24 hours.

[0042] It can be seen from the above technical solutions that compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. Direct preparation of sandwich structures with specific functions: This method can obtain a symmetrical "ZnO:Sc / ZnO:Ga / ZnO:Sc" sandwich structure in one go by directly epitaxially growing a ZnO:Sc layer on a ZnO:Ga seed crystal. This structure not only has the potential to combine the ultrafast bulk scintillation properties of ZnO:Ga with the excellent crystal quality, growth habits, and unique luminescence properties of the ZnO:Sc layer, but also lays the material foundation for achieving efficient double-sided response detection.

[0044] 2. Improve crystal utilization and growth efficiency: By simultaneously performing effective ZnO:Sc outgrowth on the +c and -c surfaces of the ZnO:Ga seed crystal, the utilization and growth efficiency of the crystal material are improved, which is conducive to obtaining usable composite crystals of larger size and volume.

[0045] 3. Significantly optimize scintillation performance and device adaptability: Improve light collection and output: The symmetrical ZnO:Sc epitaxial layer structure is conducive to double-sided light collection, significantly improving the scintillation light collection efficiency and total light output, thereby potentially improving energy resolution. Improve response uniformity: For particles incident from both sides or interactions occurring at different depths in the crystal, double-sided response can provide a more uniform detection signal. Enhance device adaptability: The central ZnO:Ga layer ensures a fast temporal response, while the ZnO:Sc layers on both sides may not only contribute to scintillation, but also improve the optical uniformity and surface treatment characteristics of the entire scintillator, and may serve as a protective layer to improve the stability and environmental adaptability of the device.

[0046] 4. Improve crystal quality: The introduction of scandium helps to improve the growth behavior of ZnO and reduce defects, thereby improving the crystallization quality of the epitaxial ZnO:Sc layer and helping to form a high-quality heteroepitaxial interface on the ZnO:Ga seed crystal, thereby improving the performance and stability of the entire sandwich structure device.

[0047] 5. Process controllability and repeatability: The present invention provides a set of systematic process parameters and operating procedures, which helps to achieve the controllability and repeatability of the hydrothermal growth of sandwich-structured zinc oxide scintillating crystals with specific components and structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0049] Figure 1 The following are photos and schematic diagrams of sandwich-structured zinc oxide scintillation crystals grown by the method of the present invention.

[0050] Figure 2 The X-ray excitation spectrum (left) and scintillation time behavior spectrum (right) measured for the sandwich structure zinc oxide scintillation crystal grown by the method of the present invention.

[0051] Figure 3 The decay time behavior spectrum (left) and slit luminescence diagram (right) of the sandwich structure zinc oxide scintillating crystal grown by the method of the present invention under electron beam bombardment.

[0052] Figure 4 Photos of the gallium-doped zinc oxide crystal grown in Comparative Example 1, +c plane (left); -c plane (right). DETAILED DESCRIPTION

[0053] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0054] Example 1: Direct growth of ZnO:Sc / ZnO:Ga / ZnO:Sc sandwich structure scintillating crystals by hydrothermal method

[0055] 1. Seed crystal preparation:

[0056] A high-quality, c-plane (0001) oriented, gallium-doped zinc oxide (ZnO:Ga) single crystal (Ga content 0.05 wt%), approximately 30 mm × 10 mm × 1 mm, was selected as the seed crystal. Double-sided chemical mechanical polishing was performed. A hole was laser-drilled along the edge of the seed crystal, which was then secured with a gold wire.

[0057] 2. Preparation of raw materials and mineralizers:

[0058] Weigh 20 g of high-purity ZnO powder (purity 99.99%) as a zinc source and nutrient (for growing the ZnO:Sc layer).

[0059] 0.05 g of Sc2O3 powder (purity 99.99%) was weighed as a scandium source for forming a ZnO:Sc epitaxial scintillating layer.

[0060] Preparation of mineralizer: 4 mol / L LiOH solution and 1 mol / L KOH solution were mixed in a volume ratio of 1:1 to obtain a composite mineralizer solution.

[0061] 3. Filling and sealing of autoclave:

[0062] A Φ22mm autoclave with a volume of approximately 100ml was used, equipped with a suspended gold bushing tube (Φ22mm).

[0063] After the ZnO powder and Sc2O3 powder are mixed evenly, they are filled into the bottom dissolution area of ​​the gold liner of the autoclave.

[0064] In the middle and upper growth zone of the gold liner, the processed ZnO:Ga seed crystals are suspended by a gold seed crystal rack to ensure that the c-face of the seed crystal is perpendicular to the main solute transport direction.

[0065] A gold baffle with a specific porosity is placed between the dissolution zone and the growth zone.

[0066] The prepared KOH-LiOH composite mineralizer solution was slowly injected into the gold lining to achieve a filling degree of about 75%.

[0067] The open end of the gold lined tube was sealed using argon arc welding.

[0068] Place the sealed gold liner tube into the autoclave body, fill the space between the autoclave body and the liner tube with an appropriate amount of deionized water as a pressure balancing medium (external filling degree is about 75%), and finally seal the autoclave.

[0069] 4. Hydrothermal growth:

[0070] The autoclave was placed vertically in a three-temperature-zone pit-type resistance furnace. External temperature control was performed using a Xiamen Yudian AI-719 industrial program controller and an AI-3170Y cloud-penetrating recording and monitoring system.

[0071] Set the temperature program: increase from room temperature to the target temperature at a rate of 50°C / h.

[0072] Set the temperature T1 in the growth zone (where the seed crystal resides, corresponding to the middle of the furnace) to 340°C, the temperature T2 in the transition zone (the lower middle section of the furnace) to 360°C, and the temperature T3 in the dissolution zone (where the raw materials reside, corresponding to the lower section of the furnace) to 380°C. Ensure that the dissolution zone has the highest temperature and the growth zone has the lowest temperature, with a temperature difference ΔT(T3-T1) of 40°C and a 20°C difference between adjacent zones. Temperature control accuracy is ±0.1°C.

[0073] At this temperature and autogenous pressure of about 120 MPa, hydrothermal growth is carried out with a growth period of 45 days.

[0074] 5. Cooling and sampling:

[0075] After the growth was completed, the temperature was programmed to decrease to 100°C at a rate of 10°C / h, and then the heating power was turned off to allow the autoclave to cool naturally to room temperature.

[0076] Slowly release the pressure in the autoclave, safely open the autoclave, and remove the gold-lined tube.

[0077] The gold-lined tube was carefully cut open to remove the crystal grown inside. At this point, the original ZnO:Ga seed crystal served as an intermediate layer, with both its upper and lower c-planes (+c and -c) already growing a certain thickness of transparent scandium-doped zinc oxide (ZnO:Sc) single crystal layers, forming a "ZnO:Sc / ZnO:Ga seed crystal / ZnO:Sc" sandwich structure.

[0078] 6. Post-processing and characterization:

[0079] The grown sandwich structure crystals were repeatedly washed with deionized water and ethanol and then dried in an oven at 60 °C for 24 h.

[0080] It can be seen from the observation that the interface between the original ZnO:Ga seed crystal (middle layer) and the newly formed ZnO:Sc layer (outer layer) is clear, the thickness of the epitaxial layer on both sides is uniform, and the transparency of the newly formed layer is high ( Figure 1 ).

[0081] The sandwich structure crystal can be cut and polished to prepare scintillator samples of specific size, and its X-ray excitation spectrum and scintillation time behavior spectrum ( Figure 2 ) and the decay time behavior spectrum and slit luminescence diagram under electron beam bombardment ( Figure 3 ), and evaluate its performance as a scintillator.

[0082] The sandwich-structured ZnO:Sc / ZnO:Ga / ZnO:Sc scintillating crystal obtained in this example is expected to combine the fast response of ZnO:Ga with the good crystal quality and luminescence properties of ZnO:Sc, and exhibits excellent double-sided response potential, verifying the feasibility and effectiveness of the method of the present invention.

[0083] Example 2: Effects of Changing Growth Temperature Difference

[0084] This example aims to study the effect of different growth temperature differences (temperature difference between the dissolution zone and the growth zone) on the growth of ZnO:Sc / ZnO:Ga / ZnO:Sc sandwich structure scintillating crystals.

[0085] 1. Seed crystal preparation: same as Example 1.

[0086] 2. Preparation of raw materials and mineralizers: Same as Example 1 (Sc2O3 powder is still 0.05g).

[0087] 3. Filling and sealing of the autoclave: same as in Example 1.

[0088] 4. Hydrothermal growth:

[0089] The autoclave was placed vertically in a three-temperature-zone pit-type resistance furnace. External temperature control was the same as in Example 1.

[0090] Set the heating program: same as Example 1.

[0091] The temperature of the growth zone (where the seed crystals are located, corresponding to the middle of the furnace) was set to 345°C (T1), the transition zone (where the raw materials are located, corresponding to the lower part of the furnace) to 360°C (T2), and the dissolution zone (where the raw materials are located, corresponding to the lower part of the furnace) to 375°C (T3). The dissolution zone was kept at the highest temperature and the growth zone at the lowest. The temperature difference ΔT(T3-T1) was 30°C (reduced from 40°C in Example 1), and the temperature differences between adjacent zones were 15°C and 15°C, respectively. The temperature control accuracy was ±0.1°C.

[0092] At this temperature and autogenous pressure of about 120 MPa, hydrothermal growth is carried out with a growth period of 45 days.

[0093] 5. Cooling and sampling: Same as Example 1.

[0094] 6. Post-processing and characterization:

[0095] Same as Example 1.

[0096] Observe and record the growth rate, crystal integrity, and surface morphology of the newly formed ZnO:Sc layer. Evaluate the effects of small temperature differences on crystal growth dynamics, defect control, and ultimate scintillation performance.

[0097] This embodiment aims to explore the optimization effect of adjusting the temperature difference on the growth quality and uniformity of the ZnO:Sc epitaxial layer, in order to obtain a sandwich structure scintillating crystal with a lower defect density.

[0098] Example 3: Effect of Changing Mineralizer Concentration

[0099] This example aims to study the effect of different mineralizer concentrations on the growth of ZnO:Sc / ZnO:Ga / ZnO:Sc sandwich structure scintillating crystals.

[0100] 1. Seed crystal preparation: same as Example 1.

[0101] 2. Preparation of raw materials and mineralizers:

[0102] Weigh 20 g of high-purity ZnO powder (purity 99.99%) as a zinc source and nutrient.

[0103] Weigh 0.05 g of Sc2O3 powder (purity 99.99%) as a scandium source.

[0104] Preparation of mineralizer: 5 mol / L LiOH solution and 1 mol / L KOH solution were mixed in a volume ratio of 1:1 to obtain a composite mineralizer solution (compared to the 4 mol / L LiOH in Example 1, the LiOH concentration here is increased).

[0105] 3. Filling and sealing of the autoclave: same as in Example 1.

[0106] 4. Hydrothermal growth: Same as Example 1 (growth zone temperature T1 = 340°C, transition zone temperature T2 = 360°C, dissolution zone temperature T3 = 380°C; growth period is 45 days).

[0107] 5. Cooling and sampling: Same as Example 1.

[0108] 6. Post-processing and characterization:

[0109] Same as Example 1.

[0110] Observe and record the growth rate of the newly formed ZnO:Sc layer, the efficiency of Sc incorporation, and the optical transparency of the crystal. Evaluate the effect of higher mineralizer concentrations on the solubility of the raw materials, the solute transport rate, the crystal growth habit, and the final scintillation properties.

[0111] This example aims to study the effect of adjusting the mineralizer concentration on the growth process and performance of the ZnO:Sc epitaxial layer, in order to find the mineralizer conditions that optimize the crystal quality and growth efficiency.

[0112] Comparative Example 1: Hydrothermal growth of gallium-doped zinc oxide crystal layer on pure zinc oxide seed crystal

[0113] This comparative example is intended to be compared with Example 1 of the present invention to illustrate the advantages of growing a ZnO:Ga layer on a pure ZnO seed crystal and using a ZnO:Ga seed crystal and epitaxially growing a ZnO:Sc layer in the present invention.

[0114] 1. Seed crystal preparation:

[0115] A high-quality, c-plane (0001) oriented, pure zinc oxide (ZnO) single crystal was selected as the seed crystal. The crystal was approximately 20 mm × 10 mm × 1 mm in size. Double-sided chemical mechanical polishing was performed. A hole was laser-drilled along the edge of the seed crystal, which was then secured with a gold wire.

[0116] 2. Preparation of raw materials and mineralizers:

[0117] Weigh 20 g of high-purity ZnO powder (purity 99.99%) as a zinc source and nutrient (for growing a ZnO:Ga layer).

[0118] 0.05 g of Ga2O3 powder (purity 99.99%) was weighed as a gallium source (this amount was used to compare the amount of Sc2O3 added in Example 1, aiming to form a certain concentration of Ga doping in the crystal).

[0119] Preparation of mineralizer: Same as Example 1 (4 mol / L LiOH solution and 1 mol / L KOH solution were mixed in a volume ratio of 1:1).

[0120] 3. Filling and sealing of autoclave:

[0121] A Φ22mm autoclave with a volume of approximately 100ml was used, equipped with a suspended gold bushing tube (Φ22mm).

[0122] After the ZnO powder and Ga2O3 powder are mixed evenly, they are filled into the bottom dissolution area of ​​the gold liner of the autoclave.

[0123] In the upper and middle growth area of ​​the gold lining, the processed pure ZnO seed crystals are suspended by a gold seed crystal rack.

[0124] The remaining filling and sealing steps are the same as in Example 1.

[0125] 4. Hydrothermal growth: Same as Example 1 (growth zone temperature T1 = 340°C, transition zone temperature T2 = 360°C, dissolution zone temperature T3 = 380°C; growth period is 45 days).

[0126] 5. Cooling and sampling:

[0127] After the growth is completed, the temperature is lowered and sampling is performed in the same manner as in Example 1.

[0128] The gold-lined tube was carefully cut open to remove the crystal grown inside. At this point, the original pure ZnO seed crystal served as an intermediate layer, with a certain thickness of gallium-doped zinc oxide (ZnO:Ga) single crystal layers growing on both its upper and lower c-planes (+c-plane and -c-plane), forming a "ZnO:Ga / pure ZnO seed crystal / ZnO:Ga" sandwich structure.

[0129] 6. Post-processing and characterization:

[0130] The as-grown sandwich structure crystals were repeatedly washed with deionized water and ethanol and then dried in an oven at 60 °C for 24 h.

[0131] Observe the crystal appearance, especially the transparency, uniformity and presence of obvious defects of the newly formed ZnO:Ga layer ( Figure 4 ).

[0132] It is expected that compared with Example 1 (ZnO:Sc / ZnO:Ga / ZnO:Sc), the ZnO:Ga epitaxial layer grown in this comparative example is more likely to have problems such as decreased crystal quality, increased defect density or uneven growth (such as the possible negative effects of Ga introduction as described in the background technology, and the possible lattice mismatch problem between the pure ZnO seed crystal and the ZnO:Ga layer), thereby highlighting the advantages of the present invention in improving crystal quality, growth habits and final scintillation performance by combining ZnO:Ga seed crystals with ZnO:Sc epitaxial layers.

[0133] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0134] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for directly growing sandwich-structured zinc oxide scintillation crystals using a hydrothermal method, characterized in that: The following steps are involved: S1 seed crystal preparation: Selecting a c-plane oriented gallium-doped zinc oxide single crystal as a seed crystal, and cutting, grinding, and polishing the seed crystal; Preparation of S2 raw materials and mineralizers: Weigh high-purity ZnO powder as a zinc source for growing the ZnO:Sc layer; According to the target sandwich epitaxial layer composition, Sc2O3 is weighed as a scandium source to form a ZnO:Sc scintillating layer; Mixing KOH solution and LiOH solution to obtain a composite mineralizer solution; S3 Autoclave filling and sealing: The prepared ZnO powder and Sc2O3 precursor were placed in the dissolution zone of the autoclave liner; In the growth area of ​​the lining, a processed c-plane oriented gallium-doped zinc oxide single crystal is suspended by a seed crystal rack; A baffle is set between the dissolution zone and the growth zone to regulate solute transport; Add the prepared composite mineralizer solution to the lining and set the filling degree; The liner tube is welded to ensure tightness, placed in the autoclave body, and filled externally to balance the pressure; S4 hydrothermal growth: Place the filled autoclave in a heating furnace; set the heating program and slowly heat the autoclave to the preset growth temperature, with a temperature difference of 20°C between adjacent zones; continue growth under the set temperature, temperature difference, and pressure conditions; the growth cycle is determined based on the target thickness; S5 cooling and sampling: After the growth cycle is completed, the temperature is slowly lowered to room temperature according to the preset program; the autoclave is opened, the lining is removed, and then the crystal grown inside is taken out; S6 post-processing: The grown crystals are cleaned and dried.

2. The method for directly growing sandwich-structured zinc oxide scintillation crystals by hydrothermal method according to claim 1, characterized in that: The Ga content in the gallium-doped zinc oxide single crystal in step S1 is 0.05 wt%.

3. The method for directly growing sandwich-structured zinc oxide scintillation crystals by hydrothermal method according to claim 1, characterized in that: The mass ratio of ZnO to Sc2O3 in step S2 is 400:1; The volume ratio of the LiOH solution to the KOH solution is 1:1; The concentration of the LiOH solution is 4 mol / L, and the concentration of the KOH solution is 1 mol / L.

4. The method for directly growing sandwich-structured zinc oxide scintillation crystals by hydrothermal method according to claim 1, characterized in that: The autoclave in step S3 is a variable-caliber autoclave with a precious metal lining inside; The filling degree is 75%.

5. The method for directly growing sandwich-structured zinc oxide scintillation crystals by hydrothermal method according to claim 1, characterized in that: The heating furnace in step S4 is a two-temperature zone or three-temperature zone pit-type resistance furnace; the heating program is to heat the temperature from room temperature to the target temperature at a rate of 50°C / h.

6. The method for directly growing sandwich-structured zinc oxide scintillating crystals by hydrothermal method according to claim 5, characterized in that: The heating furnace is a dual-temperature zone well-type resistance furnace, with the temperature of the dissolving zone T1 = 380°C and the temperature of the growing zone T2 = 360°C.

7. The method for directly growing sandwich-structured zinc oxide scintillation crystals by hydrothermal method according to claim 5, characterized in that: The heating furnace is a three-temperature-zone well-type resistance furnace, with a growth zone temperature T1 = 340°C, a transition zone temperature T2 = 360°C, and a dissolution zone temperature T3 = 380°C.

8. The method for directly growing sandwich-structured zinc oxide scintillation crystals by hydrothermal method according to claim 1, characterized in that: The pressure in step S4 is 120 MPa.

9. The method for directly growing sandwich-structured zinc oxide scintillation crystals by hydrothermal method according to claim 1, characterized in that: In step S5, the temperature is slowly lowered to room temperature according to a preset program, which is to first lower the temperature to 100° C. at a rate of 10° C. / h, and then naturally lower the temperature to room temperature.

10. The method for directly growing sandwich-structured zinc oxide scintillation crystals using a hydrothermal method according to claim 1, characterized in that: The drying step is to dry the mixture in an oven at 60° C. for 24 hours.

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