Method for preparing CdZnTe polycrystalline source by using near-space sublimation method

Abstract

The invention provides a method for preparing a CdZnTe polycrystalline source by using a near-space sublimation method, and solves the technical problems that a CdZnTe blocky source for preparing a CdZnTe single crystal at present is expensive and difficult to prepare, and the mass production and large-scale application development of a CdZnTe thin film detector are restricted. According to the method, a CdZnTe polycrystal source is prepared by utilizing a CdZnTe particle source with lower cost and adopting a near-space sublimation method, and then the CdZnTe epitaxial single crystal film is grown by taking the prepared CdZnTe polycrystal source as a growth source and adopting the near-space sublimation method. By adopting the method disclosed by the invention, the preparation cost of the CdZnTe epitaxial single crystal film can be greatly reduced, and large-scale mass production and large-range popularization are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of polycrystalline source preparation, and in particular relates to a method for preparing a CdZnTe polycrystalline source by using a close-space sublimation method. Background Art

[0002] Cadmium zinc telluride (Cd 1-x Zn x CdZnTe (abbreviated as CdZnTe) crystal is a ternary solid solution compound semiconductor room temperature nuclear radiation detector material with excellent performance developed from cadmium telluride (CdTe) crystal, with a zinc blende face-centered cubic structure. CdZnTe has many excellent properties such as low dark current (lower noise), high resistance, good thermal stability, large mobility lifetime product, large bandwidth, and high detection resolution. Detectors made of single crystal CdZnTe can work at room temperature, with a wide operating temperature range (-20℃~40℃), a wide energy detection range (10KeV~6MeV), and high energy resolution for X-rays and gamma rays. It has important uses in X-ray, gamma ray imaging, astrophysical research, industrial detection, safety detection, nuclear radiation detection, nuclear waste monitoring, X-ray fluorescence analysis (XRF), X-ray tomography and nuclear medicine.

[0003] At present, CdZnTe single crystals are mainly prepared using CdZnTe bulk sources by traditional methods such as the vertical Bridgman method and the Czochralski method. However, CdZnTe bulk sources have difficulties such as complex preparation process, long crystal growth time, expensive production equipment, and huge investment. Therefore, the use of expensive and difficult to prepare (i.e., complex process, long crystal growth time, etc.) CdZnTe bulk sources to produce CdZnTe thin films will increase the production cost of CdZnTe thin films, thereby restricting the mass production and large-scale application development of CdZnTe thin film detectors.

[0004] In view of this, it is necessary to explore a solution that can reduce production costs, is easy to prepare, and is conducive to mass production and large-scale application of CdZnTe thin film detectors. Summary of the invention

[0005] The purpose of the present invention is to solve the technical problem that the CdZnTe bulk source for preparing CdZnTe single crystal is expensive and difficult to prepare, which restricts the mass production and large-scale application development of CdZnTe thin film detectors, and to provide a method for preparing CdZnTe polycrystalline source using a close-space sublimation method.

[0006] To achieve the above purpose, the technical solution provided by the present invention is:

[0007] A method for preparing a CdZnTe polycrystalline source by using a close-space sublimation method, which is special in that it comprises the following steps:

[0008] S1. First, place a heat-conducting base plate (such as a graphite plate) on the heating table under the near-space sublimation growth furnace, take a graphite cover and cover it on the heat-conducting base plate, and the two cooperate to form a hollow cylinder (the diameter of the graphite cover is smaller than the diameter of the heat-conducting base plate); then put the CdZnTe particle source into the hollow cylinder; finally, cover the quartz glass mask on the hollow cylinder to form a sealed space;

[0009] The distance between the quartz glass mask and the upper heating stage is 3-7 mm;

[0010] S2. Turn on the mechanical pump and open the ventilation valve clockwise to evacuate the near-space sublimation growth furnace. Generally, the pressure in the near-space sublimation growth furnace chamber is pumped down to below 5 Pa (the limit value that can be reached in most cases) and then water cooling is turned on;

[0011] S3. Preheat the upper and lower heating stages of the near-space sublimation growth furnace to 663-683K and 1023-1043K respectively at a heating rate of 1-3K / S, and keep them warm for at least 2h 30min for pre-evaporation to obtain sufficient CdZnTe polycrystalline sources; after the pre-evaporation is completed, the temperature in the near-space sublimation growth furnace naturally drops to room temperature under the action of water cooling; wherein, the upper heating stage is used to control the substrate temperature, and the lower heating stage is used to control the temperature of the growth source (i.e., the CdZnTe particle source); when the temperature of the lower heating stage is lower than the aforementioned temperature range, the quality of the grown polycrystalline source is poor and the surface is uneven, and when it is higher than the aforementioned temperature range, the reverse evaporation effect is enhanced, resulting in poor crystallization efficiency; and the temperature of the upper heating stage is set within the range of 1023-1043K, which can improve the utilization rate of the growth source. The process parameter program for pre-evaporation can be set in advance;

[0012] S4. Close the ventilation valve, mechanical pump and water cooling in sequence to obtain the prepared CdZnTe polycrystalline source.

[0013] In S1, the distance between the quartz glass mask and the upper heating stage is 5 mm.

[0014] Furthermore, in S3, the heating rate is 1 K / S; the upper heating stage is preheated to 673 K; the lower heating stage is preheated to 1033 K; considering the time cost, the insulation time is 2 h 30 min.

[0015] Furthermore, the CdZnTe particles are sourced from nuclear waste.

[0016] Furthermore, the quartz glass mask needs to be pre-treated before use:

[0017] Add deionized water to the container with the quartz glass mask until it completely covers the quartz glass mask, and place the container in an ultrasonic cleaner for at least 5 minutes, repeatedly until there is no obvious stain when observed with the naked eye;

[0018] Take out the cleaned quartz glass mask and blow dry it evenly with a hair dryer until there is no moisture on the surface observed with the naked eye.

[0019] At the same time, the present invention provides a CdZnTe polycrystalline source prepared by the above method. The cost of preparing the CdZnTe polycrystalline source by the above method is greatly reduced compared with the cost of commercially available CdZnTe polycrystalline sources.

[0020] In addition, the present invention also provides a method for preparing a CdZnTe epitaxial single crystal film, which is special in that it comprises the following steps:

[0021] 1) Clean the growth source

[0022] Ultrasonic cleaning of the CdZnTe polycrystalline source prepared by the above method;

[0023] 2) Growth of epitaxial single crystal film

[0024] The CdZnTe epitaxial single crystal film is grown on the substrate by using the CdZnTe polycrystalline source cleaned in step 1) through a close-space sublimation method.

[0025] Further, step 1) is specifically as follows:

[0026] 1.1) Add deionized water to a container containing a CdZnTe polycrystalline source until the CdZnTe polycrystalline source is completely submerged, and then perform ultrasonic cleaning multiple times, each time for at least 5 minutes;

[0027] 1.2) The cleaned CdZnTe polycrystalline source is evenly blown dry until no moisture is present on the surface when observed with the naked eye.

[0028] Further, step 2) is specifically as follows:

[0029] 2.1) placing the aluminum nitride plate, the graphite mask, the substrate and the quartz glass cover from bottom to top on the lower heating stage of the near-space sublimation growth furnace; and filling the space formed by the aluminum nitride plate, the graphite mask and the substrate with the CdZnTe polycrystalline source cleaned in step 1) as a growth source; wherein the distance between the CdZnTe polycrystalline source and the substrate is 3-7 mm; the upper heating stage is used to control the temperature of the substrate, and the lower heating stage is used to control the temperature of the growth source;

[0030] 2.2) Using a vacuum pump, evacuate the close-space sublimation growth furnace until the vacuum degree in the close-space sublimation growth furnace reaches 5 Pa;

[0031] 2.3) The upper and lower heating stages of the near-space sublimation growth furnace are heated to 663-683K and 893-1093K respectively at a heating rate of 1-3K / S, and the film is grown at the required film thickness. For example, a CdZnTe epitaxial single crystal film of about 100μm can be grown by keeping the temperature for 30 minutes;

[0032] 2.4) After the growth is completed, the temperature is naturally cooled to room temperature to obtain a CdZnTe epitaxial single crystal film on the substrate.

[0033] Furthermore, the substrate is a GaAs substrate.

[0034] At the same time, the present invention also provides a CdZnTe epitaxial single crystal film obtained by the above-mentioned preparation method, and a detector using the CdZnTe epitaxial single crystal film as a detection core material.

[0035] The beneficial effects of the present invention are as follows:

[0036] 1. The present invention takes into account the process and cost issues faced by using CdZnTe bulk sources to prepare CdZnTe single crystals, and therefore attempts to use a low-cost CdZnTe particle source to first prepare a CdZnTe polycrystalline source, and then use the CdZnTe polycrystalline source as a growth source for the growth of CdZnTe epitaxial single crystal films. Compared with CdZnTe bulk sources, the CdZnTe epitaxial single crystal film prepared by the CdZnTe polycrystalline source can maintain substantially unchanged performance in terms of resistivity, sensitivity, and energy spectrum response, and is a good raw material that can be selected to replace the CdZnTe bulk source. However, the price of commercially available CdZnTe polycrystalline sources is expensive. Therefore, the present invention uses a close-space sublimation method to convert the low-cost CdZnTe particle source into a CdZnTe polycrystalline source, so that large-scale, low-cost batch production of CdZnTe epitaxial single crystal films can be achieved, and the polycrystalline source is prepared by the method of the present invention, and the growth of nearly 100μm polycrystalline sources can be achieved in about two hours.

[0037] 2. The CdZnTe polycrystalline source obtained by the method of the present invention is successfully grown into a CdZnTe epitaxial single crystal film by a close-space sublimation method. The surface uniformity, film thickness, single crystal film resistivity, and sensitivity response of the film are significantly improved compared with the CdZnTe polycrystalline film directly prepared by using CdZnTe particles. Moreover, through the conversion of the method of the present invention, the transformation from the epitaxial polycrystalline film of the CdZnTe particle source to the epitaxial single crystal film of the CdZnTe polycrystalline source can be successfully achieved. Compared with the epitaxial single crystal film grown from the CdZnTe bulk source, the resistivity is 10 10In the same order of magnitude, under the same working conditions, the energy resolution capability of the detector is the same and can be replaced; in terms of the light response time of the detector, the CdZnTe epitaxial single crystal film prepared from the CdZnTe polycrystalline source obtained by the method of the present invention has higher sensitivity than the CdZnTe epitaxial single crystal film prepared from the CdZnTe bulk source, and can respond to and collect radiation rays in a shorter time.

[0038] 3. The CdZnTe particles used in the present invention are derived from nuclear waste, and the purchase price is about 5,000 yuan / kg, while the market price of CdZnTe block source is about 16,000 yuan / kg, which greatly reduces the cost of raw materials for production and is beneficial to large-scale production and application. From the perspective of the means of obtaining raw materials, the CdZnTe particle source comes from nuclear waste, which is reused, successfully responding to the national call for energy conservation and environmental protection, turning waste into treasure, while the CdZnTe block source is currently still derived from traditional production methods, such as the Bridgman method, which has a long production cycle and a certain scrap rate. In summary, the use of CdZnTe particle source conversion to prepare CdZnTe epitaxial single crystal film is more than direct preparation of CdZnTe block source, which greatly reduces costs in all aspects, and rapidly promotes the application of CdZnTe thin films in X-ray detectors, Y-ray detectors, etc., and is expected to usher in the peak of CdZnTe industry development in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The process flow of preparing CdZnTe epitaxial single crystal film of the present invention;

[0040] Figure 2 The results of preparing CdZnTe polycrystalline source by aluminum nitride mask (AIN mask) and quartz glass mask in Example 1 of the present invention are compared; (a) is the CdZnTe polycrystalline source prepared by aluminum nitride mask, and (b) is the CdZnTe polycrystalline source prepared by quartz glass mask;

[0041] Figure 3 The scanning electron microscope images of the CdZnTe epitaxial single crystal film grown from the CdZnTe polycrystalline source prepared by the close-space sublimation method in Example 1 of the present invention, the CdZnTe polycrystalline film directly prepared by the CdZnTe particle source in Comparative Example 1, and the CdZnTe polycrystalline film prepared by the existing CdZnTe bulk source are (a), (b) and (c), respectively;

[0042] Figure 4 The XRD graphs of the CZT epitaxial polycrystalline film grown by using CdZnTe particle source in Comparative Example 1 and the CZT epitaxial single crystal film grown by using CdZnTe polycrystalline source in Example 1 are (a) and (b), respectively;

[0043] Figure 5The IV test curves of the CdZnTe epitaxial single crystal film grown from the CdZnTe polycrystalline source prepared by the close-space sublimation method in Example 1 of the present invention, the IV test curves of the CdZnTe polycrystalline film directly prepared by the CdZnTe particle source in Comparative Example 1, and the IV test curves of the CdZnTe polycrystalline film prepared by the existing CdZnTe bulk source are (a), (b), and (c), respectively;

[0044] Figure 6 The sensitivity fitting curves of the CdZnTe epitaxial single crystal film grown from a CdZnTe polycrystalline source prepared by a close-space sublimation method in Example 1 of the present invention, the sensitivity fitting curves of the CdZnTe polycrystalline film directly prepared by a CdZnTe particle source in Comparative Example 1, and the sensitivity fitting curves of the CdZnTe polycrystalline film prepared by a conventional CdZnTe block source are (a), (b), and (c), respectively. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0046] Example 1

[0047] like Figure 1 As shown, the preparation method of CdZnTe epitaxial single crystal film is generally divided into two steps:

[0048] Step 1: Prepare CdZnTe polycrystalline source using CdZnTe particle source

[0049] 1) Pre-treatment of the quartz glass mask

[0050] Add deionized water to the container with the quartz glass mask until the quartz glass mask is completely submerged, and place the container in an ultrasonic cleaner for cleaning for 5 minutes, repeating three times;

[0051] Take out the cleaned quartz glass mask and blow dry it evenly with a hair dryer until there is no moisture on the surface observed with the naked eye.

[0052] 2) First, place the graphite plate on the lower heating platform of the near-space sublimation growth furnace, take a graphite cover and cover it on the heat-conducting bottom plate, the diameter of the graphite cover is smaller than the diameter of the graphite plate, and the two can cooperate to form a hollow cylinder; then put the CdZnTe particle source into the hollow cylinder; finally, cover the pretreated quartz glass mask on the hollow cylinder to form a sealed space; the distance between the quartz glass mask and the upper heating platform is 5 mm;

[0053] The source of CdZnTe particles comes from nuclear waste or Prepared by vertical Bridgman growth method.

[0054] 3) Turn on the mechanical pump, open the ventilation valve clockwise, evacuate the near-space sublimation growth furnace, and start water cooling after the air pressure in the near-space sublimation growth furnace chamber is pumped to 5 Pa;

[0055] 4) Preheating the upper and lower heating stages of the near-space sublimation growth furnace from room temperature (293K) to 673K ​​and 1033K, respectively, at a heating rate of 1K / S, and pre-evaporating for 2h 30min; after the pre-evaporation is completed, the temperature in the near-space sublimation growth furnace is naturally cooled to room temperature under the action of water cooling; wherein, the upper heating stage is used to control the substrate temperature, and the lower heating stage is used to control the temperature of the growth source (i.e., the CdZnTe particle source); the process parameter program of the pre-evaporation can be set in advance;

[0056] 5) Close the ventilation valve, mechanical pump and water cooling in sequence to obtain the prepared CdZnTe polycrystalline source.

[0057] Step 2: Prepare CdZnTe epitaxial single crystal film using the CdZnTe polycrystalline source prepared above

[0058] 1) Cleaning the growth source, that is, ultrasonically cleaning the CdZnTe polycrystalline source obtained by the above method:

[0059] Add deionized water to the container containing the CdZnTe polycrystalline source until the CdZnTe polycrystalline source is completely covered, and place the container in an ultrasonic cleaning machine for cleaning for 5 minutes, and repeat three times;

[0060] The cleaned CdZnTe polycrystalline source is blown dry evenly until no moisture is present on the surface as observed with the naked eye.

[0061] 2) Using the close-space sublimation method, the CdZnTe polycrystalline source cleaned in step 1) is used to grow a CdZnTe epitaxial single crystal film on the substrate:

[0062] 2.1) The aluminum nitride plate, the graphite mask, the GaAs substrate and the quartz glass cover are placed from bottom to top on the lower heating stage of the near-space sublimation growth furnace; and the cleaned CdZnTe polycrystalline source is filled in the space formed by the aluminum nitride plate, the graphite mask and the GaAs substrate as the growth source; wherein the distance between the CdZnTe polycrystalline source and the substrate is 3 mm; the upper heating stage is used to control the temperature of the substrate, and the lower heating stage is used to control the temperature of the growth source;

[0063] 2.2) Using a vacuum pump, evacuate the close-space sublimation growth furnace until the vacuum degree in the close-space sublimation growth furnace is 5 Pa;

[0064] 2.3) The upper and lower heating stages of the near-space sublimation growth furnace were heated to 673 K and 993 K respectively at a heating rate of 1 K / S, and kept at these temperatures for 30 min for growth;

[0065] 2.4) After the growth is completed, the temperature is naturally cooled to room temperature to obtain a CdZnTe epitaxial single crystal film on the GaAs substrate.

[0066] In order to select a suitable mask, this application also explored the selection of mask in the early stage. The specific process is as follows:

[0067] When growing a CdZnTe polycrystalline source, an aluminum nitride mask and a quartz glass mask are used to perform a long source operation, and a scanning electron microscope and other instruments are used to observe and analyze the composition and surface morphology of the obtained CdZnTe polycrystalline source. Subsequently, the peeling ease of the CdZnTe polycrystalline source grown by the aluminum nitride mask and the quartz glass mask is compared to facilitate the subsequent separation of the mask and the CdZnTe polycrystalline source and to perform the operation of growing a CdZnTe epitaxial single crystal film.

[0068] from Figure 2 It can be seen that (a) is a CdZnTe polycrystalline source prepared by an aluminum nitride mask, and (b) is a CdZnTe polycrystalline source prepared by a quartz glass mask. In the experimental operation process and combined with the analysis of the scanning electron microscope results, when the mask is aluminum nitride (AIN), the CdZnTe polycrystalline source is in close contact with AIN and is not easy to peel off, which affects the growth of the subsequent epitaxial single crystal film, and the composition is uneven, and the quality and performance of the grown CdZnTe film are poor; when the mask is quartz glass, the CdZnTe polycrystalline source is easy to peel off from the quartz glass, and randomly selects points on the surface and interface, the composition is uniform, and the grown CdZnTe film is of high quality and good performance, and can be applied to the subsequent. Therefore, the selection of a quartz glass mask in each embodiment is more conducive to subsequent applications.

[0069] Comparative Example 1:

[0070] In order to demonstrate the effect of epitaxial single crystal film further prepared by CdZnTe polycrystalline source prepared by close space sublimation method in the present invention, this comparative example is specially prepared for comparison with Example 1. Comparative Example 1 is to set the same sublimation procedure as that of the present invention in a close space sublimation growth furnace by close space sublimation method, and directly obtain CdZnTe polycrystalline film by epitaxy from CdZnTe particle source, and the specific steps are as follows:

[0071] S1. A close-space sublimation growth furnace is used, and the upper heating stage of the close-space sublimation growth furnace is used to control the temperature of the substrate, and the lower heating stage of the close-space sublimation growth furnace is used to control the temperature of the CdZnTe growth source; an aluminum nitride plate, a graphite mask, a GaAs substrate and a quartz glass cover are placed from bottom to top on the lower heating stage of the close-space sublimation growth furnace, and a CdZnTe particle source is filled in the space formed by the aluminum nitride plate, the graphite mask and the GaAs substrate as a growth source;

[0072] S2. Use a vacuum pump to evacuate the close-space sublimation growth furnace until the vacuum degree in the close-space sublimation growth furnace reaches 5 Pa;

[0073] S3, heating the upper and lower heating stages of the near-space sublimation growth furnace to 673K ​​and 993K respectively at a heating rate of 1K / S, and keeping them warm for 30 minutes for growth;

[0074] S4. After the growth is completed, the temperature is naturally cooled to room temperature to obtain a CdZnTe polycrystalline film on the GaAs substrate.

[0075] In order to compare the performance of the epitaxial films grown by the two methods, the present invention also conducted the following experiments:

[0076] like Figure 3 As shown, (a) is a scanning electron microscope image of the CdZnTe epitaxial single crystal film prepared in Example 1, (b) is a scanning electron microscope image of the CdZnTe polycrystalline film directly prepared by the CdZnTe particle source in Comparative Example 1, and (c) is a scanning electron microscope image of the CdZnTe polycrystalline film prepared by the existing CdZnTe block source. It can be seen intuitively from the scanning electron microscope images that the surface of the CdZnTe polycrystalline film prepared by the CdZnTe particle source is very uneven and bumpy; and the roughness of the film surface directly affects the photoelectric properties of the film; the surface of the CdZnTe epitaxial film obtained by the CdZnTe polycrystalline source prepared by the close-space sublimation method is very smooth, which is equivalent to the CdZnTe polycrystalline film prepared by the existing CdZnTe block source, and the single crystal rate can reach more than 95%, and this effect can also be reflected in the photoelectric properties of the epitaxial film.

[0077] like Figure 4 The X-ray diffraction patterns of CZT epitaxial films prepared using CZT particle sources and CZT polycrystalline sources are shown in the figure. It can be seen from the figure that the CZT epitaxial film directly grown from the CZT particle source is a polycrystalline film, and the CZT epitaxial film grown from the CZT polycrystalline source is a single crystal film. There are many grain boundaries in the epitaxial polycrystalline film, forming a large number of recombination and capture centers, which lead to the annihilation of carriers, thereby making the transport performance and counting performance of the prepared detector worse, so the detector uses a single crystal film.

[0078] like Figure 5As shown, resistivity is an important indicator for evaluating whether the photoelectric performance of CdZnTe film can reach the detector level, because the noise generated by leakage current will reduce the energy resolution of the detector. According to the calculation formula of the volume resistivity of the crystal:

[0079] ρ=RL / S=VL / (IS)

[0080] Where ρ is the volume resistivity, R is the volume resistance, V is the test voltage, I is the test current, L is the film thickness, and S is the electrode contact area.

[0081] It can be clearly seen that the volume resistivity of the epitaxial single crystal film of CdZnTe polycrystalline source prepared by close-space sublimation method is about 2.72×10 10 Ω·cm, while the bulk resistivity of the polycrystalline film of CdZnTe particle source is about 7.169×10 9 Ω·cm, the bulk resistivity of the polycrystalline film of CdZnTe bulk source is about 3.69×10 10 Ω·cm. The resistivity of the epitaxial single crystal film of CdZnTe polycrystalline source and the resistivity of the epitaxial single crystal film of CdZnTe bulk source are both 10 10 It is about one order of magnitude higher than the resistivity of the polycrystalline film prepared by CdZnTe particle source, which means that under the same working conditions, the noise caused by leakage current when the detector is working will be less and the energy resolution will be higher.

[0082] like Figure 6 The sensitivity curve under 10V bias voltage fitted by It curve is shown in Figure 1. The sensitivity of the epitaxial single crystal film of CdZnTe polycrystalline source prepared by close-space sublimation method is about 141.68μC Gy -1 cm -2 , epitaxial single crystal film of CdZnTe bulk source, with a sensitivity of about 95.79μC Gy -1 cm -2 , while the sensitivity of the polycrystalline film of CdZnTe particle source is about 35.82μC Gy -1 cm -2 It is known that the sensitivity of the light response is improved, and the excitation of the photocurrent can be completed in a shorter time. In other words, the response time of the detector made of the epitaxial single crystal film of the CdZnTe polycrystalline source prepared by the near-space sublimation method is shorter than that of the detector made of the polycrystalline film obtained by particle growth and the epitaxial single crystal film obtained by bulk source growth, and it has a better response and collection of radiation rays.

[0083] Example 2

[0084] The difference from Example 1 is:

[0085] In step one:

[0086] 4) Preheat the temperature of the heating stage on the near-space sublimation growth furnace to 663K.

[0087] Observation under a microscope shows that the surface morphology of the CZT polycrystalline source prepared using the CZT particle source is not much different from that of the CZT polycrystalline source prepared in Example 1; although the resistivity, sensitivity and other film parameters of the CZT epitaxial single crystal film prepared using the CZT polycrystalline source fluctuate, the fluctuation range is small and can still meet the performance requirements.

[0088] Example 3

[0089] The difference from Example 1 is:

[0090] In step one:

[0091] 4) Preheat the temperature of the heating stage on the near-space sublimation growth furnace to 683K.

[0092] Observed under a microscope, the surface morphology of the CZT polycrystalline source prepared using the CZT particle source is not much different from that of the CZT polycrystalline source prepared in the aforementioned embodiment; although the resistivity, sensitivity and other film parameters of the CZT epitaxial single crystal film prepared by the CZT polycrystalline source fluctuate, the fluctuation range is small and can still meet the product performance requirements.

[0093] Example 4

[0094] The difference from Example 1 is:

[0095] 4) Preheat the temperature of the heating platform under the near-space sublimation growth furnace to 1023K.

[0096] Observation under a microscope shows that the surface morphology of the CZT polycrystalline source prepared using the CZT particle source is not much different from that of the CZT polycrystalline source prepared in the aforementioned embodiment, and the uniformity is consistent; the resistivity, sensitivity and other film parameters of the CZT epitaxial single crystal film prepared thereby also fluctuate within a small range and can still meet the product performance requirements.

[0097] Example 5

[0098] The difference from Example 1 is:

[0099] 4) Preheat the temperature of the heating platform under the near-space sublimation growth furnace to 1043K.

[0100] Observation under a microscope shows that the surface morphology of the CZT polycrystalline source prepared using the CZT particle source is not much different from that of the CZT polycrystalline source prepared in the aforementioned embodiment, and the uniformity is consistent; the resistivity, sensitivity and other film parameters of the CZT epitaxial single crystal film prepared thereby also fluctuate within a small range and can still meet the product performance requirements.

[0101] In summary, the method of the present invention not only has low production cost and simple preparation process, but also can prepare epitaxial single crystal films with better performance than the existing technology, and can achieve large-scale mass production and wide-range promotion for the preparation of detectors.

[0102] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be included in the protection scope of the present invention.

Claims

1. A method for preparing a CdZnTe polycrystalline source using a close-space sublimation method, characterized in that: The following steps are involved: S1. First, place the heat-conducting base plate on the heating table under the near-space sublimation growth furnace, take the graphite cover and cover it on the heat-conducting base plate, and the two cooperate to form a hollow cylinder; then place the CdZnTe particle source into the hollow cylinder; finally, cover the quartz glass mask on the hollow cylinder to form a sealed space; The distance between the quartz glass mask and the heating platform of the close-space sublimation growth furnace is 3-7 mm; S2. Turn on the mechanical pump and the vent valve to evacuate the near-space sublimation growth furnace, and then turn on the water cooling; S3. Preheat the upper and lower heating stages of the near-space sublimation growth furnace to 663-683K and 1023-1043K, respectively, at a heating rate of 1-3K / S, and keep them warm for at least 2h 30min for pre-evaporation; after the pre-evaporation is completed, the temperature in the near-space sublimation growth furnace is naturally cooled to room temperature under the action of water cooling; S4. Close the ventilation valve, mechanical pump and water cooling in sequence to obtain the prepared CdZnTe polycrystalline source.

2. The method for preparing CdZnTe polycrystalline source by close space sublimation method according to claim 1, characterized in that: In S1, the distance between the quartz glass mask and the upper heating stage is 5 mm.

3. The method for preparing CdZnTe polycrystalline source by close space sublimation method according to claim 1, characterized in that: In S3, the heating rate is 1K / S; the upper heating stage is preheated to 673K; the lower heating stage is preheated to 1033K; and the temperature is kept at this temperature for 2h 30min.

4. The method for preparing CdZnTe polycrystalline source by close space sublimation method according to any one of claims 1 to 3, characterized in that: The CdZnTe particles are sourced from nuclear waste.

5. A CdZnTe polycrystalline source, characterized in that: The method is prepared by any one of claims 1 to 4.

6. A method for preparing a CdZnTe epitaxial single crystal film, characterized in that: The following steps are involved: 1) Clean the growth source Ultrasonic cleaning of the CdZnTe polycrystalline source obtained by the method of any one of claims 1 to 4; 2) Growth of epitaxial single crystal film The CdZnTe epitaxial single crystal film is grown on the substrate by using the CdZnTe polycrystalline source cleaned in step 1) through a close-space sublimation method.

7. The method for preparing a CdZnTe epitaxial single crystal film according to claim 6, characterized in that: Step 1) is specifically as follows: 1.1) Add deionized water to a container containing a CdZnTe polycrystalline source until the CdZnTe polycrystalline source is completely submerged, and then perform ultrasonic cleaning multiple times, each time for at least 5 minutes; 1.2) The cleaned CdZnTe polycrystalline source is evenly blown dry until no moisture is present on the surface when observed with the naked eye.

8. The method for preparing a CdZnTe epitaxial single crystal film according to claim 7, characterized in that: Step 2) is specifically as follows: 2.1) placing the aluminum nitride plate, the graphite mask, the substrate and the quartz glass cover from bottom to top on the lower heating table of the near-space sublimation growth furnace; and filling the space formed by the aluminum nitride plate, the graphite mask and the substrate with the CdZnTe polycrystalline source cleaned in step 1); wherein the distance between the CdZnTe polycrystalline source and the substrate is 3-7 mm; 2.2) Using a vacuum pump to evacuate the near-space sublimation growth furnace; 2.3) The upper and lower heating stages of the near-space sublimation growth furnace are heated to 663-683K and 893-1093K respectively at a heating rate of 1-3K / S, and the growth is carried out according to the required film thickness by heat preservation; 2.4) After the growth is completed, the temperature is naturally cooled to room temperature to obtain a CdZnTe epitaxial single crystal film on the substrate.

9. A CdZnTe epitaxial single crystal film, characterized in that: The method is prepared by any one of claims 6 to 8.

10. A detector, characterized in that: The CdZnTe epitaxial single crystal film prepared by any preparation method described in claims 6-8 is used as the detection core material.

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