Halide perovskite single crystal and surface polishing method thereof

Abstract

The application discloses a surface polishing method of a halide perovskite single crystal. The method first cuts the prepared halide perovskite single crystal, and then performs step-by-step polishing treatment on the halide perovskite single crystal by using a polishing liquid formed by mixing polishing powder and a non-aqueous inert lubricating medium, so that a high-quality single crystal surface is obtained. Thus, the problems of low hardness and easy deliquescence of the halide perovskite single crystal such as CsPbBr 3(1‑x) Cl 3x (x=0-1) are solved. In the traditional water-based polishing, single-stage polishing and sandpaper polishing process, deliquescence corrosion is prone to occur, and defects such as scratches, subsurface cracks, polycrystalline damage layers and halogen vacancies are generated, thereby causing the sample surface defect density to be significantly increased, the bulk resistivity to be greatly decreased, the leakage current to be increased, and finally the radiation detection performance to be deteriorated. The polishing method can efficiently and lowly damagely realize surface processing of the halide perovskite single crystal, so that the halide perovskite single crystal with better surface quality and more excellent electrical and radiation detection performance is obtained.

Description

Technical Field

[0001] This invention pertains to the field of precision machining of perovskite single crystals, and is particularly suitable for the precision machining of soft-lattice, deliquescent single crystals. It relates to a method for improving the precision machining of halide perovskite single crystals such as CsPbBr. 3(1-x) Cl 3x (x=0-1) Surface polishing method for single crystal electrical properties. Background Technology

[0002] Halide perovskite single crystals (such as CsPbBr3 and CsPbCl3) have broad application prospects in fields such as radiation detection due to their excellent properties, including high absorption coefficients, long carrier diffusion lengths, and low defect densities. However, these single crystals typically exhibit low hardness and deliquescence, making them prone to defects such as polycrystalline layers, scratches, and cracks during surface processing. These surface-damaging defects significantly affect the electrical properties of the single crystals, such as reducing bulk resistivity, increasing leakage current, and weakening electrical stability, ultimately impairing their radiation detection performance.

[0003] The existing surface polishing methods for halide perovskite single crystals mainly include: (1) water-based polishing fluid system (such as CN1858087A, CN101463227A, etc.). The presence of water molecules in this method can easily cause crystal deliquescence, corrosion and surface crystallization, which seriously damages the integrity of the crystal structure; (2) mechanical polishing with sandpaper (such as CN117261002A, CN117794341A, CN120287116A, etc.). The rigid contact of sandpaper can easily introduce deep scratches, large-area subsurface damage layer, secondary contamination of debris and lattice distortion. It is especially unsuitable for perovskite single crystals with low hardness and easy deliquescence; (3) single-stage or few-stage polishing process (such as CN109746771B, etc.). This method is difficult to balance material removal efficiency and damage control. It can easily lead to residual cutting damage layer or the introduction of new defects, resulting in poor surface quality and high defect density, which seriously weakens the electrical properties of the single crystal.

[0004] In summary, existing technologies struggle to achieve efficient, low-damage surface mirror-finishing while preserving the integrity of the single-crystal structure. Therefore, there is an urgent need to develop a highly efficient, repeatable, and low-damage surface polishing method for halide perovskite single crystals. Summary of the Invention

[0005] For low-hardness and deliquescent halide perovskite single crystals such as CsPbBr 3(1-x) Cl 3x(x=0-1), etc., in traditional water-based polishing, single-stage polishing, and sandpaper grinding processes, defects such as deliquescence corrosion, scratches, subsurface cracks, polycrystalline damage layers, and halogen vacancies are easily generated, leading to problems such as significantly increased surface defect density, a substantial decrease in bulk resistivity, increased leakage current, and deterioration of radiation detection performance. The purpose of this invention is to provide a high-efficiency, low-damage halide perovskite single crystal surface polishing method.

[0006] To achieve the above objectives, this invention provides a surface polishing method for halide perovskite single crystals. The technical solution adopted by this invention is as follows: A surface polishing method for halide perovskite single crystals, wherein the method first cuts the prepared halide perovskite single crystal, and then mixes polishing powder with a non-aqueous inert lubricating medium to prepare polishing liquids with different compositions, which are then applied to the surface of the halide perovskite single crystal in stages during the polishing process to perform step-by-step polishing treatment on the surface of the halide perovskite single crystal.

[0007] In some implementations, the method includes the following steps: 1) Cutting: Cut the grown halide perovskite single crystal into samples to be polished; 2) Rough polishing: A flexible polishing carrier is selected, and the polishing pressure and main rotation speed of the polishing disc are set. The polishing process is carried out under the condition of continuous replenishment of the first polishing liquid. 3) Precision polishing: Maintain the same or similar pressure and speed as the rough polishing stage, and further reduce the residual processing traces after rough polishing by continuously supplying the second polishing fluid and the flexible polishing carrier. 4) Ultra-precision polishing: Maintain the same or similar pressure and speed as the rough polishing stage, and use a third polishing fluid and a flexible polishing carrier to perform final ultra-precision polishing to obtain a high-quality single crystal surface.

[0008] In some embodiments, the polishing pressure is 2 kPa to 20 kPa; the main rotation speed of the polishing disc is set to 40 r / min to 200 r / min.

[0009] In some embodiments, the volume ratio of the polishing powder to the non-aqueous inert lubricating medium in the first polishing liquid, the second polishing liquid, and the third polishing liquid is controlled to be from 1:1 to 1:9, and the ratio at different stages is one or more of the above ratios.

[0010] In some embodiments, each polishing slurry uses oxide abrasive particles as polishing powder; the oxide abrasive particles are selected from any one or more combinations of cerium oxide, silicon oxide, zirconium oxide, and aluminum oxide.

[0011] In some embodiments, the non-aqueous inert lubricating medium is selected from one or more combinations of aviation kerosene, mineral oil, isoalkanes, paraffin oil, and perfluorinated liquids.

[0012] In some embodiments, the oxide abrasive particles in the first, second, and third polishing slurries decrease in a gradient between 6 μm and 10 nm.

[0013] In some embodiments, the oxide abrasive particles used in the first polishing slurry have a particle size of 1-6 μm; the oxide abrasive particles in the second polishing slurry have a particle size of 100-1000 nm; and the oxide abrasive particles in the third polishing slurry have a particle size of 10-100 nm.

[0014] In some implementations, the polishing time for each stage is 2-20 minutes.

[0015] In some embodiments, the flexible polishing carrier is any one or more of velvet polishing cloth, polyurethane polishing pad, non-woven polishing pad, or microfiber polishing cloth.

[0016] The second objective of this invention is to provide a halide perovskite single crystal, prepared according to the method described above, with a roughness of less than 5 nm.

[0017] In some embodiments, the halide perovskite single crystal has the structural formula CsPbBr 3(1-x) Cl 3x x = 0-1, or Cs2ZnCl4 or Cs3ZnCl5. Of course, it can be extended to more halide perovskite single crystal structures according to different application requirements.

[0018] Compared with traditional single-stage polishing, water-based polishing fluid methods, and sandpaper grinding processes, the advantages of this invention are: 1) The surface polishing method for halide perovskite single crystals of the present invention firstly eliminates the sandpaper grinding process, fundamentally avoiding the mechanical crushing, deep scratches, large-area subsurface damage layer, and lattice distortion caused by the rigid abrasive grains of sandpaper on the surface of low-hardness perovskite single crystals. At the same time, it avoids secondary pollution to the single crystal surface caused by sandpaper debris residue, effectively protecting the crystal structure integrity of the perovskite single crystal. Secondly, it uses a chemically stable non-aqueous inert lubricating medium as the polishing fluid carrier, avoiding the deliquescent corrosion and chemical erosion of the easily deliquescent halide perovskite single crystal by water-based systems. On this basis, a three-level abrasive gradient system of "coarse polishing - precision polishing - ultra-precision polishing" is adopted. By gradually reducing the abrasive grain size and using a flexible polishing carrier, the processing damage can be reduced layer by layer while ensuring material removal efficiency, promoting the single crystal surface to gradually transition to a high-quality state, thereby significantly reducing surface roughness and the risk of mechanical damage.

[0019] 2) In the coarse polishing stage, this invention uses larger-diameter abrasive grains to quickly remove the cutting damage layer; in the precision polishing stage, the grain size is reduced to further smooth the surface and reduce subsurface damage; in the ultra-precision polishing stage, the smallest-diameter abrasive grains are used to achieve a mirror effect. Atomic force microscopy analysis shows that the surface roughness Ra is reduced to approximately 2 nm, achieving high-precision polishing. This step-by-step strategy effectively reduces the surface damage layer, thereby improving bulk resistivity, reducing leakage current, enhancing electrical stability, and improving radiation detection performance.

[0020] 3) The core innovations of this invention are non-aqueous inert medium carrier, gradient abrasive polishing, and abandoning sandpaper polishing, which realizes efficient and low-damage polishing of halide perovskite single crystals. This strategy combines excellent surface smoothness and consistency, good process versatility and repeatability, and significantly improved processing efficiency: the microscopic and macroscopic surface roughness test results of the polished samples in different regions are highly consistent, and the Ra measured by AFM and optical profilometry are all stable at the nanometer level (~3nm), indicating that the crystal surface morphology is uniform and the overall smoothness is excellent. At the same time, this process is applicable to a variety of low-hardness, deliquescent single crystal materials, effectively removing surface processing damage without introducing structural destruction, and maintaining the integrity of the single crystal structure. By introducing a non-aqueous inert lubricating medium that does not chemically react with halide single crystals, chemical erosion and surface degradation caused by water-based systems are avoided, making the polishing process more stable and reliable. The surface roughness Ra of multiple batches of samples is less than 5 nm, demonstrating good repeatability and reliability. In addition, this process supports parallel polishing of multiple samples, and the double-sided polishing time does not exceed 1 hour, significantly improving the overall processing efficiency while ensuring low surface roughness and low damage characteristics.

[0021] 4) This invention can significantly improve various properties of perovskite single crystals. Taking CsPbBr3 as an example, after mirror polishing according to this invention, the crystal exhibits a systematic improvement in both electrical and radiation detection performance: compared with the control sample in the precision polishing stage, the bulk resistivity of the ultra-precision polished sample is increased by about an order of magnitude (see...). Figure 6 This indicates that surface and near-surface defects and leakage channels are effectively suppressed; within the same voltage scanning range, the leakage current under high-voltage conditions is reduced by approximately 60-73% compared to the precision-polished sample (see...). Figure 6 This significantly reduces dark current and background noise levels. Benefiting from the effective reduction in leakage current and improved electrical stability, under the same 200 V bias condition... 241 When performing energy resolution testing with Am (59.5 keV) gamma rays, the energy resolution of the single crystal after ultra-precision polishing decreased from 25.2% to 15.1%, a relative improvement of over 40% (see...). Figure 7The above results fully demonstrate that the surface polishing method proposed in this invention can simultaneously improve the electrical properties and radiation response characteristics of CsPbBr3 single crystals, thereby significantly enhancing their overall performance and application potential in radiation detection applications. Attached Figure Description

[0022] Figure 1 These are physical comparison images of different polishing stages of CsPbBr3 inorganic perovskite single crystals in Example 1 of the method of the present invention.

[0023] Figure 2 This is a comparison chart of the transmittance of CsPbBr3 inorganic perovskite single crystal at different polishing stages in Example 1 of the method of the present invention.

[0024] Figure 3 This is a diagram showing the microscopic surface roughness height of different regions on the surface of the CsPbBr3 inorganic perovskite single crystal after polishing in Example 1 of the method of the present invention.

[0025] Figure 4 The image shows the macroscopic surface roughness curve and calculation results obtained by an optical profilometer after polishing of CsPbBr3 inorganic perovskite single crystal in Example 1 of the method of the present invention.

[0026] Figure 5 This is a scanning electron microscope (SEM) image of the surface morphology of CsPbBr3 inorganic perovskite single crystal after polishing in Example 1 of the method of the present invention.

[0027] Figure 6 This is a comparison of IV curves of CsPbBr3 single crystals obtained by precision polishing and ultra-precision polishing in Example 1 of the method of the present invention.

[0028] Figure 7 Example 1 of the method of the present invention describes the precision polishing and ultra-precision polishing of CsPbBr3 single crystal under a bias voltage of 200 V. 241 Energy resolution comparison of gamma-ray detection from Am (59.5 KeV) source. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0030] Throughout the invention, when a composition is described as having, containing, or including specific ingredients, or a method is described as having, containing, or including specific process steps, it should be understood that the compositions of the invention are also substantially composed of or consisting of the mentioned ingredients, and the methods of the invention are also substantially composed of or consisting of the mentioned process steps.

[0031] In this invention, when an element or component is referred to as being included in and / or selected from the list of mentioned elements or components, it should be understood that the element or component may be any one of the mentioned elements or components, or the element or component may be selected from the group consisting of two or more mentioned elements or components. Furthermore, it should be understood that the elements or features of the compositions, apparatus, or methods described herein, whether expressly or implicitly stated, can be combined in any manner without departing from the subject matter and scope of the invention.

[0032] It should be understood that the order of steps or the sequence of actions is not important as long as the teachings of this invention are operable. Furthermore, two or more steps or actions can be performed simultaneously.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the subject matter described herein belongs.

[0034] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0035] In one aspect of the invention, a non-aqueous, multi-level gradient polishing method is developed specifically for low-hardness, deliquescent halide perovskite single crystals. This method aims to obtain a mirror-like surface with roughness (Ra) down to the nm level, high uniformity, and excellent flatness, while significantly reducing the surface damage layer, increasing bulk resistivity, reducing leakage current, enhancing electrical stability, and improving radiation detection performance. The method involves cutting the halide perovskite single crystal and using a mixed polishing powder and a non-aqueous inert lubricating medium as the polishing slurry. Different compositions of polishing slurries adapted to the surface of the halide perovskite single crystal are used in stages to polish the surface progressively. By adapting the polishing slurry to the single crystal surface in stages for progressive polishing, this method can obtain a high-quality mirror-like surface with extremely low roughness, excellent uniformity, and flatness while ensuring the integrity of the single crystal structure.

[0036] This can be done through the following steps: 1) Sample cutting: The grown halide perovskite single crystal is cut into samples to be polished; wherein, the cutting method can be wire cutting or other mechanical cutting methods that can obtain a basically flat surface; in this step, a mechanical damage layer and micro scratches of a certain thickness will inevitably be generated on the surface of the sample after cutting, which need to be removed by subsequent polishing process. 2) Coarse polishing: A flexible polishing carrier is selected, and the polishing pressure and main speed of the polishing disc are set. The sample is rotated in a planetary manner to improve the polishing uniformity. The polishing process is carried out under the condition of continuous replenishment of the first polishing liquid. It should be noted that coarse polishing is carried out on a conventional commercially available polishing device that allows the sample to rotate in a planetary manner on the grinding disc to ensure stable abrasive distribution and effective chip removal, so as to achieve rapid material removal. 3) Precision polishing: Maintain the same or similar pressure and speed as the rough polishing stage, and further reduce the residual processing traces after rough polishing by continuously supplying the second polishing fluid and the flexible polishing carrier. 4) Ultra-precision polishing: Maintain the same or similar pressure and speed as the rough polishing stage, and use a third polishing fluid and flexible polishing carrier to perform final ultra-precision polishing, so as to further reduce the surface defects and obtain a high-quality single crystal surface that meets the requirements of optical or electrical applications.

[0037] Specifically, the coarse polishing stage uses a specific polishing slurry to quickly remove the cutting damage layer from the single crystal surface; the precision polishing stage further smooths the surface and reduces subsurface damage; and the ultra-precision polishing stage achieves the final mirror finish. Combined with the experimental verification described later, atomic force microscopy showed that the surface roughness Ra after polishing reached approximately 2 nm, successfully achieving low-surface-damage polishing. This step-by-step polishing strategy effectively reduces the surface damage layer, thereby increasing bulk resistivity, reducing leakage current, and enhancing electrical stability. It should be noted that this embodiment offers significant advantages through three-stage polishing. The three polishing stages are interconnected: coarse polishing aims to eliminate macroscopic unevenness and surface saw marks introduced during cutting while ensuring efficiency, achieving initial surface leveling; precision polishing aims to eliminate subsurface scratches remaining from coarse polishing, while significantly reducing the thickness of the mechanical damage layer, providing a uniform, low-damage surface foundation for subsequent ultra-precision polishing; and ultra-precision polishing aims to achieve nanoscale flatness and surface consistency. The three stages are interconnected and mutually compatible, ultimately achieving a high-precision polishing effect. However, in practical applications, the polishing level can be adjusted to level two or four according to the required specific roughness.

[0038] In one embodiment, the polishing pressure parameters and polishing disc rotation speed can be adjusted according to the characteristics of the single crystal material. Here, the polishing pressure is 2 kPa to 20 kPa; the main rotation speed of the polishing disc is set to 40 r / min to 200 r / min. Specifically, the pressure fluctuation range used in the precision polishing and ultra-precision polishing stages is within ±10% of that used in the rough polishing stages; the rotation speed fluctuation range is within ±5%. Furthermore, the duration of each polishing stage can be adjusted according to the single crystal size, material properties, and target surface quality; typically, the polishing time for each stage is several minutes to tens of minutes, such as 2-20 minutes.

[0039] In another embodiment, the volume ratio of the polishing powder to the non-aqueous inert lubricating medium in the first, second, and third polishing slurries is controlled to be from 1:1 to 1:9. Each polishing slurry uses oxide abrasive particles as the polishing powder; the oxide abrasive particles are selected from any one or any combination of cerium oxide, silicon oxide, zirconium oxide, and alumina. The non-aqueous inert lubricating medium is selected from any one or any combination of aviation kerosene, mineral oil, isoalkanes, paraffin oil, and perfluorinated liquids. Thus, this embodiment effectively avoids the chemical corrosion and surface degradation problems caused by water-based systems on low-hardness, deliquescent single crystals by using a non-aqueous inert lubricating medium that does not chemically react with halide single crystals as the dispersion and cooling carrier of the polishing slurry. Simultaneously, the non-aqueous inert lubricating medium in each polishing slurry also has a chemical passivation effect, maintaining excellent lubrication, heat dissipation, and chip removal capabilities, making the polishing process more stable and reliable, and exhibiting excellent repeatability in surface polishing treatment.

[0040] In another embodiment, the oxide abrasive particles in the first, second, and third polishing slurries decrease in size from 6 μm to 10 nm in the coarse polishing stage. This stage uses larger-diameter abrasive particles to quickly remove the very rough, deep, and numerous cutting damage layers from the single crystal surface. This stage is suitable for coarse processing with relatively large-diameter abrasive particles, balancing efficiency and low damage. In the precision polishing stage, the particle size is reduced to further smooth the relatively rough and shallowly scratched single crystal surface formed after coarse polishing, while also reducing subsurface damage. The ultra-precision polishing stage uses the smallest particle size abrasive particles, adapted to the shallower scratches and less roughness of the single crystal surface to achieve a mirror effect, completing low-damage surface polishing. Thus, the polishing slurries at different stages are respectively adapted to the single crystal surface at their respective polishing stages, achieving excellent grinding compatibility and eliminating the need for sandpaper. Specifically, the oxide abrasive particles used in the first polishing slurry have a particle size of 1-6 μm; the oxide abrasive particles in the second polishing slurry have a particle size of 100-1000 nm; and the oxide abrasive particles in the third polishing slurry have a particle size of 10-100 nm. Thus, this gradient abrasive step-by-step polishing strategy effectively reduced the surface damage layer, increased the bulk resistivity, reduced the leakage current, and improved the electrical stability and radiation detection performance.

[0041] It is understandable that, in practical applications, the flexible polishing carrier can be made of velvet polishing cloth, polyurethane polishing pad, non-woven polishing pad, or microfiber polishing cloth, etc., to obtain a stable polishing effect at each stage.

[0042] In another aspect of all embodiments of the present invention, high-quality halide perovskite single crystals can be obtained by using the above-described step-by-step polishing process to perform surface polishing treatment on halide perovskite single crystals, typically such as single crystal CsPbBr. 3(1-x) Cl 3x By using x=0-1, a halide perovskite single crystal can be obtained. The surface roughness of the single crystal after polishing by this process can reach the nanometer level and can be precisely controlled to within 5 nm.

[0043] Example 1 1) Sample cutting: The grown CsPbBr3 single crystal ingot was mechanically cut into sheet-like samples with a thickness of 2 mm. After cutting, a certain thickness of mechanical damage layer and micro-scratches will inevitably be generated on the sample surface, which need to be removed by subsequent polishing process.

[0044] 2) Rough polishing: The sheet sample is fixed on the sample stage of a commercially available polishing device. Velvet cloth is selected as a flexible polishing carrier to ensure that the polishing carrier and the sample surface are fully in contact during the polishing process, thereby reducing the adverse effects of local stress concentration on the single crystal surface.

[0045] In the rough polishing stage, a non-aqueous, inert first polishing slurry, formed by mixing cerium oxide (CeO2) polishing powder with a particle size of 1 μm and aviation kerosene in a predetermined ratio of 1:3, was continuously dripped onto the surface of the polishing carrier. The polishing pressure was set to 8 kPa, the polishing table speed to 90 r / min, and the first polishing slurry was continuously replenished. The sample underwent rough polishing for 5 minutes to achieve rapid removal of the surface damage layer formed during the cutting process and macroscopic smoothing.

[0046] 3) Precision Polishing: After rough polishing, the polishing carrier is cleaned and the polishing slurry is replaced. In the precision polishing stage, a second polishing slurry is prepared by mixing 100 nm silica (SiO2) polishing powder with aviation kerosene at a predetermined ratio of 1:3. Under the same polishing pressure and rotation speed, the sample is subjected to precision polishing for 5 minutes to further reduce residual scratches and machining marks on the surface, reduce surface roughness, and obtain a semi-finished polished sample.

[0047] 4) Ultra-precision polishing: The ultra-precision polishing stage then begins. Under low polishing load conditions, a third polishing solution is prepared by mixing 10nm silica polishing powder with aviation kerosene in a predetermined ratio of 1:3. The polishing carrier is replaced, and the sample undergoes ultra-precision polishing for 3 minutes. This further refines submicron-scale defects on the surface, achieving a mirror-like surface.

[0048] After polishing, the ultra-precision polished sample is removed from the polishing device, and the sample surface is gently cleaned with a dry, lint-free cloth, ultimately obtaining the desired result. Figure 1 The CsPbBr3 single crystal sample shown has a mirror-like surface, no visible scratches, and high transparency. Further performance tests were performed on the sample obtained in Example 1, and the results are as follows: like Figure 2 As shown, the transmittance of the ultra-precision polished sample increases sequentially after three polishing stages. This multi-stage surface polishing strategy successfully replaces traditional sandpaper polishing, achieving a gradual increase in light transmittance.

[0049] like Figure 3 As shown, the microscopic surface morphology height map and corresponding surface roughness Ra value of the ultra-precision polished sample were obtained by atomic force microscopy (AFM), with a scanning area of ​​30 μm × 30 μm. The test areas were selected at four positions: the upper left corner, the upper right corner, the lower left corner, and the lower right corner of the same crystal. The results show that the surface roughness of different regions of the same sample is stable at around 3 nm. The local roughness of each region measured by AFM is highly consistent, indicating that the crystal surface has excellent flatness and uniform morphology after polishing, and no obvious regional differences are observed.

[0050] like Figure 4 As shown, the ultra-precision polished sample underwent large-area surface morphology testing and Ra calculation using an optical profilometer. The scanning area was 500 μm, and the surface roughness Ra reached 2-3 nm. This result is highly consistent with the roughness values ​​measured locally at the four corners of the crystal by AFM. This good agreement between macroscopic and microscopic scales further indicates that the crystal surface morphology is highly uniform after ultra-precision polishing, and the overall flatness is significantly improved.

[0051] like Figure 5 As shown, the surface roughness of the single crystal decreases step by step after three-stage polishing. After coarse polishing and fine polishing, the surface smoothness is improved, but there are still many scratches on the single crystal surface; after ultra-precision polishing, the scratches on the single crystal surface are significantly reduced, and it has better smoothness and surface consistency.

[0052] like Figure 6As shown, compared with the control sample in the precision polishing stage, the volume resistivity of the ultra-precision polished sample is increased by an order of magnitude. Within a certain voltage scanning range, the leakage current of the ultra-precision polished sample is reduced by 60-73% compared with that of the precision polished sample, and the high-voltage leakage current is significantly reduced.

[0053] like Figure 7 As shown, thanks to the effective reduction in leakage current, the background noise during radiation detection is significantly suppressed. Under a bias voltage of 200 V, the sample's... 241 Am (59.5 KeV) gamma-ray energy resolution test results show that the energy resolution of the single crystal decreased from 25.2% to 15.1% after polishing optimization, representing a relative improvement of over 40%. These results demonstrate that the polishing process proposed in this invention can significantly improve the radiation detection performance of single-crystal materials, which is beneficial for performance optimization in radiation detection applications.

[0054] Comparative Example 1 The same method as in Example 1 was used to process single-crystal CsPbBr3 as in CN120287116A: the single crystal to be polished was heat-mounted; the perovskite single crystal sample was fixed on a polishing table and coarsely polished with sandpaper; subsequently, the coarsely polished perovskite single crystal sample was finely polished to obtain a polished perovskite single crystal sample. The fine polishing process included: using artificial leather polishing cloth and anhydrous ethanol as the polishing solution for the first droplet addition treatment; after a preset time interval in the first droplet addition treatment, the anhydrous ethanol was replaced with a suspension of dimethyl sulfoxide and anhydrous ethanol for the second droplet addition treatment. Although a nanoscale roughness surface was ultimately obtained, the low hardness and hygroscopicity of single-crystal CsPbBr3 led to various defects during the polishing process, such as deliquescent corrosion, scratches, subsurface cracks, polycrystalline damage layers, and halogen vacancies. These defects directly resulted in a significant increase in the surface defect density of the sample, and caused problems such as a significant decrease in bulk resistivity, an increase in leakage current, and deterioration of radiation detection performance.

[0055] Comparative Example 2 The same method as in Example 1 was used to process single-crystal CsPbBr3 as in CN117794341A: the perovskite single-crystal sample to be polished was fixed on a polishing table, and coarse polishing was performed on the perovskite single-crystal sample using sandpaper and the first polishing slurry; and fine polishing was performed on the perovskite single-crystal sample after the first polishing treatment using a wool pad and the second polishing slurry to obtain a polished perovskite single-crystal sample. The coarse polishing process included: using 1000-grit sandpaper and dimethyl silicone oil as the polishing slurry for surface leveling; after the perovskite single-crystal surface was leveled, the sandpaper was replaced with a wool pad, and a second polishing powder of appropriate concentration was prepared using silicon oxide powder and dimethyl silicone oil for fine polishing. Although a nanoscale roughness surface was ultimately obtained, due to the low hardness of single-crystal CsPbBr3, the use of sandpaper for polishing caused breakage during the coarse polishing process, which could not guarantee the integrity of the crystal. This directly led to a significant increase in surface defect density, resulting in a significant decrease in bulk resistivity, an increase in leakage current, and a deterioration in radiation detection performance.

[0056] Examples 2-18 and Comparative Example 19 The overall process flow of each example is consistent with that of Example 1, except that the single crystal composition, the particle size of the oxide abrasive used as polishing powder in each polishing stage, and the processing time are adjusted accordingly based on the conditions listed in Table 1 below according to the example number. Among them, as the Cl doping content increases, the polishing pressure and rotation speed parameters are moderately increased to accommodate the slight changes in the hardness of the single crystal material.

[0057]

[0058]

[0059] Notes: 1. When the volume ratio of polishing powder to lubricating medium in the table is a single value, it indicates that the volume ratio of polishing powder to non-aqueous inert lubricating medium in the polishing liquid used for coarse polishing, precision polishing, and ultra-precision polishing is always the same. When there are multiple values ​​(such as in Example 16), it indicates that the volume mixing ratio of polishing powder to non-aqueous inert lubricating medium is different in coarse polishing, precision polishing, and ultra-precision polishing (from 1:3 to 1:4 to 1:5 respectively); 2. The surface states involved in the table are compared in terms of surface consistency as follows: mirror finish, high transparency > mirror finish, excellent gloss > mirror finish, uniform gloss > smooth as a mirror > high transparency > extremely high gloss > smooth and bright > low transmittance.

[0060] Surface morphology and roughness tests showed that the final surface roughness (Ra) of the samples in Examples 1-17 was controlled within 5 nm, and a high-quality single-crystal surface with a mirror finish and no visible processing marks was consistently obtained. Based on the treatment of the high-quality single-crystal surface, a stable improvement in electrical performance was achieved.

[0061] Based on the above embodiments, this invention focuses on non-aqueous inert media carriers, gradient abrasive polishing, and eliminating the need for sandpaper polishing as its core innovations, achieving highly efficient and low-damage polishing of halide perovskite single crystals. This strategy combines excellent repeatability with broad composition applicability. It not only achieves high-quality mirror-like surfaces with nanoscale roughness Ra, excellent uniformity and flatness while ensuring the integrity of the single crystal structure, but also effectively reduces the surface damage layer, significantly improves the bulk resistivity of the material, reduces leakage current, and enhances electrical stability, providing a better surface foundation for subsequent optical and electrical performance testing and the fabrication of high-performance devices. Furthermore, this process is effective for CsPbBr... 3(1-x) Cl 3x The full-component series and other low-hardness, hygroscopic crystals all exhibit good versatility, providing a reliable, high-quality surface basis for subsequent performance testing and device fabrication of this type of single crystal.

[0062] Based on the above-described preferred embodiments of the present invention, those skilled in the art can make various changes and modifications without departing from the inventive concept, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for surface polishing of halide perovskite single crystals, characterized in that, The method first cuts the prepared halide perovskite single crystal, and then mixes polishing powder with a non-aqueous inert lubricating medium to prepare polishing liquids with different compositions. During the polishing process, the liquids are applied to the surface of the halide perovskite single crystal in stages to perform step-by-step polishing treatment on the surface of the halide perovskite single crystal.

2. The method according to claim 1, characterized in that, Includes the following steps: 1) Sample cutting: Cut the halide perovskite single crystal into samples to be polished; 2) Rough polishing: A flexible polishing carrier is selected, and the polishing pressure and main rotation speed of the polishing disc are set. The polishing process is carried out under the condition of continuous replenishment of the first polishing liquid. 3) Precision polishing: Maintain the same or similar pressure and speed as the rough polishing stage, and further reduce the residual processing traces after rough polishing by continuously supplying the second polishing fluid and the flexible polishing carrier. 4) Ultra-precision polishing: Maintain the same or similar pressure and speed as the rough polishing stage, and use a third polishing fluid and a flexible polishing carrier to perform the final mirror polishing.

3. The method according to claim 1, characterized in that: The polishing pressure is 2 kPa to 20 kPa; the main rotation speed of the polishing disc is set to 40 r / min to 200 r / min.

4. The method according to claim 2, characterized in that: The volume ratio of the polishing powder to the non-aqueous inert lubricating medium in the first polishing liquid, the second polishing liquid, and the third polishing liquid is controlled to be from 1:1 to 1:

9.

5. The method according to claim 2, characterized in that: All polishing fluids use oxide abrasive particles as polishing powder; the oxide abrasive particles are selected from any one or a combination of cerium oxide, silicon oxide, zirconium oxide, and aluminum oxide; the non-aqueous inert lubricating medium is selected from any one or a combination of aviation kerosene, mineral oil, isoparaffin oil, paraffin oil, and perfluorinated liquid.

6. The method according to claim 2, characterized in that: The oxide abrasive particles in the first, second, and third polishing slurries decrease in a gradient between 6 μm and 10 nm.

7. The method according to claim 7, characterized in that: The oxide abrasive particles used in the first polishing liquid have a particle size of 1-6 μm; the oxide abrasive particles in the second polishing liquid have a particle size of 100-1000 nm; and the oxide abrasive particles in the third polishing liquid have a particle size of 10-100 nm.

8. The method according to claim 2, characterized in that: The polishing time for each stage is 2-20 minutes.

9. The method according to claim 2, characterized in that: The flexible polishing carrier is any one or more of the following: velvet polishing cloth, polyurethane polishing pad, non-woven polishing pad, or microfiber polishing cloth.

10. A halide perovskite single crystal, prepared according to the method of any one of claims 1-9, characterized in that, The roughness of the obtained single crystal does not exceed 5 nm.

Images