A method for directly growing a sandwich structure zinc oxide scintillation crystal by a hydrothermal method

Abstract

The application discloses a method for directly growing a sandwich structure zinc oxide scintillation crystal by a hydrothermal method and relates to the technical field of single crystal growth. The method directly obtains a sandwich structure scintillation crystal with complete structure, good interface, excellent performance and excellent double-face response potential by optimizing hydrothermal growth process parameters and using the polar growth characteristics of a ZnO crystal to epitaxially grow a ZnO:Sc scintillation layer on the upper and lower main surfaces (+c surface and -c surface) of a ZnO:Ga c surface seed crystal. The crystal is especially suitable for the field of radiation detection due to the unique structure and double-face response characteristics, and aims at realizing superfast response, high light output and high detection efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of single crystal growth, in particular to a method for directly growing a sandwich structure zinc oxide scintillation crystal by a hydrothermal method. BACKGROUND

[0002] Zinc oxide (ZnO) as a kind of wide band gap semiconductor material, due to its potential high light output, ultrafast decay time and excellent anti-radiation performance, has attracted much attention in the field of scintillation crystal research. Especially in the field of extreme ultraviolet, X-ray, high energy particle detection, it has broad application prospects. The traditional research of ZnO-based scintillation materials is mostly focused on powder, thin film or ceramic forms, but these forms of materials have high self-absorption and defects, and their scintillation performance is difficult to meet the needs of high-level applications.

[0003] Single crystal form of ZnO is considered to be the best way to achieve its ideal scintillation performance. 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 process of growing ZnO crystals, the polar growth characteristic in the c-axis direction is a remarkable feature. When using a c-plane seed crystal, the crystal will grow on the +c plane (Zn plane) and -c plane (O plane) of the seed crystal at the same time, forming a new growth layer. If this characteristic can be effectively controlled and utilized, a "sandwich" structure with the seed crystal as the center layer and the new functional layer on both sides can be directly grown. This symmetrical structure lays the foundation for achieving excellent double-sided response characteristics.

[0004] At present, for ZnO:Ga (gallium-doped zinc oxide) scintillation crystals, although they have excellent fast decay characteristics (such as decay time of tens of picoseconds), the growth of large-size, high-quality single crystals still has bottlenecks, such as the introduction of gallium may lead to decreased crystalline quality and increased defect density, and the polar growth characteristic is difficult to control, resulting in low utilization rate of the crystal. On the other hand, scandium-doped zinc oxide (ZnO:Sc) crystals not only exhibit good scintillation characteristics, but research also shows that the introduction of scandium can significantly improve the growth habit of ZnO crystals, such as increasing the growth rate of -c plane and m plane, making the growth of +c plane and -c plane consistent, thereby improving the crystalline quality, reducing internal defects and improving optical uniformity.

[0005] The combination of ZnO:Ga seed crystal and ZnO:Sc epitaxial layer forms a symmetrical ZnO:Sc / ZnO:Ga / ZnO:Sc sandwich structure, which is expected to combine the ultrafast scintillation core of ZnO:Ga with the excellent growth characteristics, optical characteristics and potential interface synergistic effect of ZnO:Sc, thereby providing a new way for developing new high-performance scintillators. In particular, this structure can support double-sided light collection or have good response to radiation from both sides, thereby possibly significantly improving the light collection efficiency and response uniformity. However, there is currently a lack of a systematic process method for directly and controllably epitaxially growing a ZnO:Sc layer on a ZnO:Ga seed crystal to form a specific sandwich structure scintillation crystal. SUMMARY

[0006] Therefore, the present application provides a method for directly growing a sandwich structure zinc oxide scintillation crystal by a hydrothermal method, which aims to directly obtain a sandwich structure scintillation crystal with complete structure, good interface, excellent performance and excellent potential for double-sided response by epitaxially growing ZnO:Sc scintillation layers on the upper and lower main surfaces (+c surface and -c surface) of a ZnO:Ga c surface seed crystal through optimization of hydrothermal growth process parameters and utilization of the polar growth characteristics of ZnO crystals.

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

[0008] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0009] A method for directly growing a sandwich structure zinc oxide scintillation crystal by a hydrothermal method, comprising the following steps:

[0010] S1 Seed crystal preparation:

[0011] A c surface oriented ZnO:Ga single crystal is selected as a seed crystal (ZnO:Ga), and the seed crystal is subjected to cutting, grinding and polishing treatment; and the surface thereof is ensured to be flat and damage-free. A hole can be punched in the seed crystal for suspension.

[0012] S2 Preparation of raw materials and mineralizer:

[0013] High-purity ZnO powder is weighed as a zinc source for growing a ZnO:Sc layer;

[0014] According to the composition of the target sandwich epitaxial layer, Sc2O3 is weighed as a scandium source for forming a ZnO:Sc scintillation layer;

[0015] A KOH solution and a LiOH solution are mixed to obtain a composite mineralizer solution;

[0016] S3 Filling and sealing of an autoclave:

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

[0018] The prepared c-plane oriented gallium-doped zinc oxide single crystal is hung by a seed crystal holder in the growth zone of the inner liner;

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

[0020] The prepared complex mineralizer solution is added to the inner liner, and the filling degree is set;

[0021] The inner liner tube is welded and sealed to ensure the sealing, and is placed in the main body of the autoclave, and is externally filled (for a suspended liner) to balance the pressure;

[0022] S4 hydrothermal growth:

[0023] The filled autoclave is placed in a heating furnace, a heating program is set, the autoclave is slowly heated to a preset growth temperature, and the temperature difference between adjacent zones is 20°C; under the conditions of the set temperature, temperature difference and pressure, continuous growth is carried out; the growth period is determined according to the target thickness, and is usually 30-60 days. During the process, the raw materials in the dissolution zone are dissolved under high temperature and high pressure, and are transported to the growth zone by the convection driven by the temperature difference. In the growth zone with lower temperature, the +c plane and the -c plane of the ZnO:Ga seed crystal are supersaturated and crystallized to form a new epitaxial growth layer (ZnO:Sc);

[0024] S5 cooling and sampling:

[0025] After the growth period ends, the autoclave is opened, the inner liner is taken out, and then the internally grown crystal is taken out; the collected crystal is a symmetric sandwich structure crystal in which a new layer of scandium-doped zinc oxide (ZnO:Sc) material is grown on the +c plane and the -c plane of the original c-plane ZnO:Ga seed crystal as an intermediate layer;

[0026] S6 post-processing:

[0027] The grown crystal is washed and dried.

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

[0029] Preferably, the mass ratio of the ZnO to the 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-diameter autoclave equipped with a noble metal lining inside.

[0034] The filling degree is 75%.

[0035] Preferably, in step S4, the heating furnace is a double-temperature-zone or a triple-temperature-zone shaft resistance furnace, and the heating procedure is to increase the temperature from room temperature to the target temperature at a rate of 50℃ / h.

[0036] Preferably, the heating furnace is a double-temperature-zone shaft resistance furnace, the temperature of the dissolving zone T1 is 380℃, and the temperature of the growth zone T2 is 360℃.

[0037] Preferably, the heating furnace is a triple-temperature-zone shaft resistance furnace, the temperature of the growth zone T1 is 340℃, the temperature of the transition zone T2 is 360℃, and the temperature of the dissolving zone T3 is 380℃.

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

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

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

[0041] Preferably, the drying is drying in a 60℃ oven for 24h.

[0042] According to the above technical solution, compared with the prior art, the present application has the following beneficial effects:

[0043] 1. Direct preparation of a sandwich structure with specific functions: The present method can obtain a symmetrical sandwich structure of "ZnO:Sc / ZnO:Ga / ZnO:Sc" in one time by directly epitaxially growing a ZnO:Sc layer on a ZnO:Ga seed crystal. The structure is expected to combine the ultrafast bulk scintillation characteristics of ZnO:Ga with the excellent crystal quality, growth habit and unique luminescence characteristics of the ZnO:Sc layer, and lays a material foundation for realizing efficient double-sided response detection.

[0044] 2. Improved crystal utilization and growth efficiency: By simultaneously growing effective ZnO:Sc layers on both the +c and -c faces of the ZnO:Ga seed crystal, the utilization and growth efficiency of the crystal material is improved, which is beneficial for obtaining larger size and volume of usable composite crystals.

[0045] 3. Substantially optimized scintillation performance and device adaptability: Improved light collection and output: The symmetric ZnO:Sc epitaxial layer structure is beneficial for realizing double-sided light collection, significantly improving the scintillation light collection efficiency and total light output, which can improve the energy resolution. Improved response uniformity: For particles incident from both sides or interactions occurring at different depths in the crystal, double-sided response can provide more uniform detection signals. Enhanced device adaptability: The central ZnO:Ga layer ensures fast time response, while the ZnO:Sc layers on both sides not only contribute to scintillation, but also improve the optical uniformity of the entire scintillator, surface treatment characteristics, and can serve as a protective layer to improve the stability and environmental adaptability of the device.

[0046] 4. Improved crystal quality: The introduction of scandium helps to improve the growth behavior of ZnO, reduce defects, thereby improving the crystalline quality of the epitaxial ZnO:Sc layer, and helps 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 application provides a set of systematic process parameters and operation procedures, which helps to realize the controllability and repeatability of the hydrothermal method growth of sandwich structure zinc oxide scintillation crystals with specific components and structures. BRIEF DESCRIPTION OF DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of the provided drawings.

[0049] Figure 1 A photograph and schematic diagram of the sandwich structure zinc oxide scintillation crystal grown by the method of the present application.

[0050] Figure 2 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 application.

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

[0052] Figure 4 The photo of the gallium-doped zinc oxide crystal obtained by growing the comparative example 1, +c surface (left); -c surface (right). DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0054] Example 1: Hydrothermal method for directly growing ZnO:Sc / ZnO:Ga / ZnO:Sc sandwich structure scintillation crystal

[0055] 1. Seed crystal preparation

[0056] A high-quality c-plane (0001) oriented gallium-doped zinc oxide (ZnO:Ga) single crystal wafer with a size of about 30 mm x 10 mm x 1 mm was selected as the seed crystal (Ga content of 0.05 wt%). The seed crystal was subjected to double-side chemical mechanical polishing. The edge of the seed wafer was perforated by laser, and then fixed by gold wire.

[0057] 2. Preparation of raw materials and mineralizer

[0058] High-purity ZnO powder (purity 99.99%) 20 g was weighed as zinc source and nutrient material (for growing ZnO:Sc layer).

[0059] Sc2O3 powder (purity 99.99%) 0.05 g was weighed as scandium source, which was used to form the ZnO:Sc epitaxial scintillation layer.

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

[0061] 3. Filling and sealing of autoclave

[0062] A Φ22 mm type autoclave with a volume of about 100 ml was used, which was equipped with a suspended gold lining tube (Φ22 mm).

[0063] After the ZnO powder and Sc2O3 powder were uniformly mixed, they were filled into the bottom dissolution zone of the gold lining of the autoclave.

[0064] In the upper growth zone of the gold lining, the treated ZnO:Ga seed wafer was hung by the gold seed crystal holder, ensuring that the c-plane of the seed crystal was perpendicular to the main solute transport direction.

[0065] A gold baffle with a specific opening rate is placed between the dissolving zone and the growth zone.

[0066] Slowly inject the prepared KOH-LiOH complex mineralizer solution into the gold liner until the filling degree reaches about 75%.

[0067] Seal the open end of the gold liner tube using argon arc welding.

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

[0069] 4. Hydrothermal growth:

[0070] Place the autoclave vertically into the three-zone well-type resistance furnace. Use the Xiamen Yudian AI-719 industrial program regulator and AI-3170Y cloud penetration recording monitoring system for external temperature control.

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

[0072] Set the growth zone (where the seed crystal is located, corresponding to the middle part of the furnace body) temperature T1 to 340°C, the transition zone (lower part of the furnace body) temperature T2 to 360°C, and the dissolving zone (where the raw materials are located, corresponding to the lower part of the furnace body) temperature T3 to 380°C. Ensure that the dissolving zone has the highest temperature, the growth zone has the lowest temperature, the temperature difference ΔT (T3-T1) is 40°C, and the temperature difference between adjacent temperature zones is 20°C. The temperature control accuracy is ±0.1°C.

[0073] Under the conditions of this temperature and an autogenous pressure of about 120 MPa, conduct hydrothermal growth, and the growth period is 45 days.

[0074] 5. Cooling and sampling:

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

[0076] Slowly release the pressure of the autoclave, safely open the autoclave, and take out the gold liner tube.

[0077] Carefully cut open the gold liner tube and take out the internally grown crystals. At this time, the original ZnO:Ga seed crystal wafer has served as an intermediate layer, and a certain thickness of transparent ZnO:Sc single crystal layer has been grown on both the upper and lower c-planes (+c-plane and -c-plane), 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 hours.

[0080] Observations show that the interface between the original ZnO:Ga seed crystal (intermediate layer) and the newly formed ZnO:Sc layer (outer layer) is clear, the thickness of the epitaxial layers on both sides is uniform, and the transparency of the newly formed layer is high. Figure 1 ).

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

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

[0083] Example 2: The effect of changing the growth temperature difference

[0084] This embodiment 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 scintillation crystals.

[0085] 1. Seed crystal preparation: Same as in Example 1.

[0086] 2. Preparation of raw materials and mineralizing agents: Same as in 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 into the three-temperature-zone well-type resistance furnace. The external temperature control was the same as in Example 1.

[0090] Setting the heating program: Same as in Example 1.

[0091] The temperature T1 of the growth zone (where the seed crystal is located, corresponding to the middle of the furnace) is set at 345℃, the temperature T2 of the transition zone (lower middle part of the furnace) is set at 360℃, and the temperature T3 of the dissolution zone (where the raw materials are located, corresponding to the lower part of the furnace) is set at 375℃. This ensures that the temperature in the dissolution zone is the highest and the temperature in the growth zone is the lowest. At this point, the temperature difference ΔT(T3-T1) = 30℃ (a decrease compared to 40℃ in Example 1), and the temperature differences between adjacent zones are 15℃ and 15℃ respectively. The temperature control accuracy is ±0.1℃.

[0092] Hydrothermal growth was carried out at this temperature and autogenous pressure of about 120 MPa, with a growth period of 45 days.

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

[0094] 6. Post-treatment and characterization:

[0095] Same as Example 1.

[0096] The growth rate, crystal integrity, and surface morphology of the newly grown ZnO:Sc layer were observed and recorded. The effects of smaller temperature difference on crystal growth kinetics, defect control, and final scintillation performance were evaluated.

[0097] This example aims to explore the optimization of ZnO:Sc epitaxial layer growth quality and uniformity by adjusting the temperature difference, in order to obtain a sandwich structure scintillation crystal with 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 scintillation crystal.

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

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

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

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

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

[0105] 3. Autoclave filling and sealing: same as 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-treatment and characterization:

[0109] Same as Example 1.

[0110] The growth rate of the new ZnO:Sc layer, the doping efficiency of Sc element, and the optical transparency of the crystal are observed and recorded. The influence of higher mineralizer concentration on the solubility of raw materials, solute transport rate, crystal growth habit, and final scintillation performance is evaluated.

[0111] This example aims to study the influence of mineralizer concentration on the growth process and performance of ZnO:Sc epitaxial layer, in order to find the mineralizer conditions that optimize 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 aims to compare with Example 1 of the present application, to illustrate the growth of ZnO:Ga layer on pure ZnO seed crystal, and the advantages of using ZnO:Ga seed crystal and epitaxially growing ZnO:Sc layer in the present application.

[0114] 1. Seed crystal preparation:

[0115] A high-quality c-plane (0001) oriented pure zinc oxide (ZnO) single crystal wafer with a size of about 20 mm x 10 mm x 1 mm is selected as the seed crystal. The seed crystal is double-side chemically and mechanically polished. A hole is punched on the edge of the seed wafer with a laser, and a gold wire is passed through to fix it.

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

[0117] High-purity ZnO powder (purity 99.99%) 20 g is weighed as the zinc source and nutrient material (for growing ZnO:Ga layer).

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

[0119] Prepare the mineralizer: same as Example 1 (4 mol / L LiOH solution and 1 mol / L KOH solution mixed at a volume ratio of 1:1).

[0120] 3. Filling and sealing of autoclave:

[0121] A Φ22 mm type autoclave with a volume of about 100 ml is used, which is equipped with a suspended gold lining tube (Φ22 mm).

[0122] After the ZnO powder and Ga2O3 powder are mixed uniformly, they are filled into the bottom dissolution zone of the gold lining of the autoclave.

[0123] In the middle and upper growth zone of the gold lining, the treated pure ZnO seed wafer is hung up through the gold seed crystal holder.

[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 45 days).

[0126] 5. Cooling and sampling:

[0127] After the growth, the cooling and sampling are performed as in Example 1.

[0128] The gold inner liner tube is carefully cut open, and the crystal grown inside is taken out. At this point, the original pure ZnO seed piece has served as an intermediate layer, and a certain thickness of ZnO:Ga single crystal layer has been grown on both of its upper and lower c-planes (+c-plane and -c-plane), forming a sandwich structure of “ZnO:Ga / pure ZnO seed / ZnO:Ga”.

[0129] 6. Post-treatment and characterization:

[0130] The grown sandwich structure crystal is repeatedly cleaned with deionized water and ethanol, and then dried in a 60°C oven for 24 hours.

[0131] The crystal appearance is observed, especially the transparency, uniformity and presence or absence of obvious defects of the newly grown 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 prone to problems such as reduced crystal quality, increased defect density, or uneven growth (as described in the background art, the negative effects that Ga introduction may bring, and the lattice mismatch problem that may exist between the pure ZnO seed and the ZnO:Ga layer), thus highlighting the advantages of the present application in improving crystal quality, growth habit and final scintillation performance through the combination of ZnO:Ga seed and ZnO:Sc epitaxial layer.

[0133] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other. For the device disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method part.

[0134] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for directly growing a sandwich structure of a ZnO scintillation crystal by a hydrothermal method, characterized in that, The method comprises the following steps: S1 seed preparation: selecting a c-plane oriented gallium-doped zinc oxide single crystal as a seed crystal, and performing cutting, grinding and polishing treatment on the seed crystal; S2 preparation of raw materials and mineralizer: weighing high-purity ZnO powder as a zinc source for growing a ZnO:Sc layer; according to the composition of a target sandwich epitaxial layer, weighing Sc2O3 as a scandium source for forming a ZnO:Sc scintillation layer; mixing KOH solution and LiOH solution to obtain a composite mineralizer solution; S3 autoclave filling and sealing: placing the prepared ZnO powder and Sc2O3 precursor into a dissolution zone of an inner liner of the autoclave; suspending the treated c-plane oriented gallium-doped zinc oxide single crystal through a seed crystal holder in a growth zone of the inner liner; setting a flow baffle between the dissolution zone and the growth zone to regulate solute transport; adding the prepared composite mineralizer solution to the inner liner, and setting a filling degree; welding and sealing the inner liner tube to ensure the sealing, placing it into a main body of the autoclave, and performing outer filling to balance the pressure; S4 hydrothermal growth: placing the filled autoclave into a heating furnace; setting a heating program, slowly heating the autoclave to a preset growth temperature, and making the temperature difference between adjacent zones 20 DEG C; under the set temperature, temperature difference and pressure conditions, continuously growing; the growth period is determined according to the target thickness; S5 cooling and sampling: after the growth period ends, slowly cooling to room temperature according to the preset program; opening the autoclave, taking out the inner liner, and then taking out the internally grown crystal; S6 post-treatment: cleaning and drying the grown crystal.

2. The method for directly growing sandwich structure ZnO scintillation crystal 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 0.05wt%.

3. The method for directly growing sandwich structure ZnO scintillation crystal by hydrothermal method according to claim 1, characterized in that, The mass ratio of the ZnO to the 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 4mol / L, and the concentration of the KOH solution is 1mol / L.

4. The method for directly growing sandwich structure ZnO scintillation crystal by hydrothermal method according to claim 1, characterized in that, The autoclave in step S3 is a variable-diameter autoclave, which is internally provided with a noble metal inner liner; The filling degree is 75%.

5. The method for directly growing sandwich structure ZnO scintillation crystal by hydrothermal method according to claim 1, characterized in that, The heating furnace in step S4 is a double-temperature-zone or a triple-temperature-zone well-type resistance furnace; and the heating program is to increase the temperature from room temperature to a target temperature at a rate of 50 DEG C / h.

6. The method for directly growing sandwich structure ZnO scintillation crystal by hydrothermal method according to claim 5, characterized in that, The heating furnace is a double-temperature-zone well-type resistance furnace, the temperature T1 of the dissolution zone is 380 DEG C, and the temperature T2 of the growth zone is 360 DEG C.

7. The method for directly growing sandwich structure ZnO scintillation crystal by hydrothermal method according to claim 5, characterized in that, The heating furnace is a triple-temperature-zone well-type resistance furnace, the temperature T1 of the growth zone is 340 DEG C, the temperature T2 of the transition zone is 360 DEG C, and the temperature T3 of the dissolution zone is 380 DEG C.

8. The method for directly growing sandwich structure ZnO scintillation crystal by hydrothermal method according to claim 1, characterized in that, The pressure in step S4 is 120MPa.

9. The method for directly growing sandwich structure ZnO scintillation crystal by hydrothermal method according to claim 1, characterized in that, In step S5, the slow cooling to room temperature according to the preset program is to program the temperature to decrease to 100 DEG C at a rate of 10 DEG C / h, and then naturally cool to room temperature.

10. The method for directly growing sandwich structure ZnO scintillation crystal by hydrothermal method according to claim 1, characterized in that, The drying is drying in a 60 DEG C oven for 24h.

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