Method for identifying polar surface of tellurium-cadmium compound crystal (111)

Abstract

The invention belongs to the technical field of semiconductor material detection, and particularly relates to a method for identifying a polar surface of a tellurium-cadmium compound crystal (111). The method comprises the steps that S1, cutting is conducted along the face of a tellurium-cadmium compound crystal ingot (111), and the cut face is ground and polished to be flat; s2, cleaning the surface of the sample; s3, putting the cleaned sample into a KOH aqueous solution for treatment, then taking out the sample, and washing off KOH residual liquid; s4, the sample washed in the step S3 is put into a 10%-15% H2O2-NH4F solution to stand for 5-10 min, and then residual liquid is washed away; d5, the color of the surface of the sample washed in the step S4 is observed, and if it is observed that the surface of the sample is black, it is judged that the surface is the (111) A face of the cadmium telluride or cadmium zinc telluride sample; and if the surface of the sample is observed to be colored, judging that the surface is a (111) B surface of the cadmium telluride or cadmium zinc telluride sample. According to the method disclosed by the invention, the (111) A surface and the B surface of the tellurium-cadmium compound crystal can be distinguished in a relatively short time, and are easy to observe.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor material detection, and in particular relates to a method for identifying the polarity plane of a cadmium telluride crystal (111). Background Art

[0002] Cadmium telluride crystals, especially cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe), have been widely used in radiation detectors, solar cells, infrared detectors and other fields due to their excellent optoelectronic properties. CdZnTe crystals have the advantages of wide bandgap, high atomic number, high resistivity, etc., and are an excellent room temperature X-ray and gamma-ray detector material. These characteristics make CdZnTe crystals have broad application prospects in medical imaging, nuclear safety, environmental monitoring, astrophysics and other fields.

[0003] In these applications, the polarity of the crystal has a significant impact on the performance of the device. When the CdZnTe wafer is cut along the (111) plane, two different stable atomic planes appear, namely the Cd plane (called the A plane) and the Te plane (called the B plane). These two planes have significant differences in chemical reactivity, surface state density, charge transfer characteristics, etc., which directly affect the photoelectric conversion efficiency, response speed and stability of the device. For example, the work function of the Cd plane (A plane) is higher, and Cd compounds are easily formed on the surface, which easily leads to high surface state density and affects the contact performance of the electrode; the work function of the Te plane (B plane) is lower, and Te compounds are easily formed on the surface, which may reduce the electrical performance and electrode adhesion of the CdZnTe detector. Therefore, the ability to quickly and accurately identify the polarity plane of the cadmium telluride crystal is of great significance for optimizing device design and improving product quality.

[0004] Currently, the public methods for identifying the polar planes of cadmium telluride crystals mainly rely on equipment such as X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM). Although these physical methods are feasible, they require expensive equipment support and have high technical requirements for operators. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for identifying the polar plane of a cadmium telluride crystal (111), with the aim of providing a fast, low-cost, safe and reliable identification solution.

[0006] The method for identifying the polar surface of a cadmium telluride crystal (111) provided by the present invention comprises the following steps: Step S1: cutting along the (111) surface of the cadmium telluride ingot and grinding and polishing the cut surface to make it smooth; Step S2: Clean the sample surface; Step S3: placing the cleaned sample in a KOH aqueous solution for treatment, then taking out the sample and washing away the KOH residual liquid; Step S4: Place the sample rinsed in step S3 into a 10%-15% H2O2-NH4F solution and let it stand for 5-10 minutes, then wash away the residual liquid; Step D5: Observe the color of the sample surface after rinsing in step S4. If the sample surface is observed to be black, it is determined that the surface is the (111) A surface of the cadmium telluride or cadmium zinc telluride sample; if the sample surface is observed to be colored, it is determined that the surface is the (111) B surface of the cadmium telluride or cadmium zinc telluride sample.

[0007] As a further optimization scheme of the method for identifying the (111) polar plane of the cadmium telluride crystal, the cadmium telluride crystal is a cadmium telluride crystal or a cadmium zinc telluride crystal.

[0008] As a further optimization scheme for the method of identifying the (111) polar plane of the cadmium telluride crystal, in step S2, the sample obtained in step S1 is cleaned with an organic solvent.

[0009] As a further optimization scheme of the method for identifying the (111) polar plane of the cadmium telluride crystal, in step S2, the sample is ultrasonically cleaned with acetone at 40° C. for 15 min, and then rinsed with water to remove the acetone residue.

[0010] As a further optimization scheme for the method of identifying the (111) polar face of the cadmium telluride crystal, in step S3, the cleaned sample is placed in a 10%-15% KOH solution and allowed to stand for 5-10 minutes, then the sample is taken out and rinsed with deionized water to remove the KOH residue.

[0011] As a further optimization scheme for the method of identifying the (111) polar plane of the cadmium telluride crystal, in step S3, the cleaned sample is placed in a 15% KOH solution and allowed to stand for 10 minutes, then the sample is taken out and rinsed with deionized water to remove the KOH residue.

[0012] As a further optimization scheme of the method for identifying the (111) polar face of the cadmium telluride crystal, in step S4, the sample is placed in a 10% H2O2-NH4F solution and allowed to stand for 10 minutes, and then the residual liquid is washed away with deionized water.

[0013] As a further optimization scheme for the method of identifying the (111) polar face of cadmium telluride crystals, a 10% H2O2-NH4F solution was prepared by the following method: NH4F solid was dissolved in deionized water, and then the diluted H2O2 aqueous solution was slowly added to control the mass ratio of H2O2, NH4F, and deionized water in the mixed solution to be 1:1:8.

[0014] As a further optimization scheme of the method for identifying the polar plane (111) of the cadmium telluride crystal, in step S1, the grinding and polishing process includes first polishing for 15 minutes using Al2O3 powder with a particle size of 3 μm, and then continuing to polish for 30 minutes using SiO2 powder with a particle size of 100 nm.

[0015] As a further optimization solution of the method for identifying the polar plane of the cadmium telluride crystal (111), in step S1, a dicing machine is used to slice and cut the cadmium telluride crystal ingot (111) surface.

[0016] Beneficial Effects The present invention provides a method for quickly, cheaply, safely and reliably identifying the polarity of the (111) surface of cadmium telluride or cadmium zinc telluride. By treating the sample with a KOH solution and an H2O2-NH4F solution, the (111) surface A and surface B of the cadmium telluride crystal can be distinguished in a relatively short time, wherein the surface A is black and the surface B is colorful, and the color difference is significant and easy to observe. The method of the present invention has excellent reliability, repeatability and stability, and avoids the use of high-risk chemicals, reduces the risk of experimental operation, and also reduces potential harm to the environment.

[0017] In addition, the method of the present invention further verifies the different reaction mechanisms of surface A and surface B during the passivation process by accurately measuring the thickness of the oxide layer on the surface of the treated sample, thereby verifying the reliability of the method at the mechanism level. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the flow chart of the identification method of the present invention.

[0019] Figure 2 This is a diagram of the surface state of one side of the sample in Example 1 after treatment.

[0020] Figure 3 This is a surface state diagram of the other side of the sample after treatment in Example 1.

[0021] Figure 4 This is a scanning electron microscope image of the surface of one side of the sample after treatment in Example 1.

[0022] Figure 5 This is a scanning electron microscope image of the other side surface of the sample after treatment in Example 1. DETAILED DESCRIPTION

[0023] The present invention is further illustrated by specific examples below. These examples are exemplary and are intended to illustrate the problem and explain the present invention, but are not intended to be limiting.

[0024] like Figure 1FIG. 1 is a flow chart of a method for identifying the polarity plane of cadmium telluride or cadmium zinc telluride (111) according to an embodiment of the present invention. The identification method comprises the following steps: Step S1: cutting and slicing the cadmium telluride or cadmium zinc telluride ingot (111) surface, and then grinding and polishing the wafer; Step S2: washing the sample obtained in step S1 with an organic solvent; Step S3: Place the cleaned sample in a 10%-15% KOH solution for 5-10 minutes, and then rinse with deionized water; Step S4: Place the sample rinsed in step S3 into a 10%-15% H2O2-NH4F solution and let it stand for 5-10 minutes, then rinse; Step D5: Observe the color of the sample surface after rinsing in step S4. If the sample surface is observed to be black, it is determined that the surface is the (111) A surface of the cadmium telluride or cadmium zinc telluride sample; if the sample surface is observed to be colored, it is determined that the surface is the (111) B surface of the cadmium telluride or cadmium zinc telluride sample.

[0025] Example 1 Sample cutting A CdZnTe ingot was taken and cut into samples of 10×10×2 mm along the (111) plane of the ingot using a dicing machine.

[0026] Sample polishing The cut samples were initially polished, first using Al2O3 powder with a particle size of 3 μm for double-sided polishing for 15 minutes to remove the rough marks produced during cutting. Then, SiO2 powder with a particle size of 100 nm was used to continue double-sided polishing for 30 minutes to further improve the smoothness of the sample surface.

[0027] Ultrasonic cleaning After polishing, the sample was placed in an acetone solution at 40°C and cleaned with an ultrasonic cleaner for 15 minutes to remove polishing powder and other attachments remaining on the sample surface. After ultrasonic cleaning, the sample surface was rinsed with deionized water to remove the acetone residue.

[0028] Passivation solution preparation Accurately weigh H2O2 (hydrogen peroxide), NH4F (ammonium fluoride) and deionized water, mix them in a mass ratio of 1:1:8, and prepare a passivation solution of 10% H2O2-10% NH4F.

[0029] Passivation treatment Soak the cleaned sample in 15% KOH solution for 10 minutes, take out the sample, rinse it with deionized water to remove the residual KOH solution on the surface. Then immerse the sample in 10% H2O2-10% NH4F passivation solution for 10 minutes. After the treatment, rinse the sample again with deionized water to remove the residual passivation solution on the surface.

[0030] Observation and analysis After the above treatment, one side of the CdZnTe sample was observed to be Figure 2 The black color shown, the other side is as Figure 3 The black surface corresponds to the (111) A surface of the CdZnTe sample, and the colored surface corresponds to the (111) B surface of the CdZnTe sample.

[0031] The cross section near the surface of the treated CdZnTe sample was observed using a scanning electron microscope. Figure 4 The image of the (111) A surface of the CdZnTe sample is shown. Figure 5 The image of the (111) B surface of the CdZnTe sample is shown. After measurement, the thickness of the oxide layer of the CdZnTe (111) A surface is about 175±20nm, while the thickness of the oxide layer of the B surface is 217±44nm. It can be seen that the thickness of the oxide layer formed on the B surface during the passivation process is significantly more uneven than that on the A surface. Due to this unevenness, the light produces obvious interference, which makes the CdZnTe (111) B surface present a unique color appearance. Therefore, this feature can be used as a reliable basis for judging the polarity of the CdZnTe (111) surface.

[0032] In Example 2 and Example 3, the sample was placed in a 12% H2O2-NH4F solution and allowed to stand for 8 minutes, and the sample was placed in a 15% H2O2-NH4F solution and allowed to stand for 5 minutes, respectively. The other operating steps were consistent with Example 1, and it can also be observed that the A side is black and the B side is colorful.

[0033] In summary, the method of the present invention can accurately and reliably distinguish the (111) A face and B face of CdZnTe crystal in a short time and at a low cost. Moreover, the method of the present invention significantly reduces the risk compared to the currently possible use of high concentrations of nitric acid and hydrofluoric acid.

[0034] Hydrofluoric acid is a strong acid that is also highly corrosive and toxic. It can corrode materials such as glass and metal, and is also extremely destructive to biological tissues. Even a small amount of hydrofluoric acid in contact with the skin can cause severe burns, and once its vapor or liquid is inhaled or absorbed through the skin, it will cause damage that is difficult to heal. In contrast, although ammonium fluoride may also release hydrogen fluoride gas under certain conditions, as a salt, its physical properties are more stable and not easy to volatilize, so the safety hazards it creates during the handling process are far less than hydrofluoric acid.

[0035] In addition, potassium hydroxide is significantly less dangerous than concentrated nitric acid. Concentrated nitric acid is a strong acid and strong oxidant, which is highly corrosive and toxic. It can react violently with a variety of substances, generating a large amount of heat and toxic gases, posing a great threat to the environment and human health. Potassium hydroxide is mainly alkaline, and compared with acidic substances, it is relatively less harmful to human skin and mucous membranes. Potassium hydroxide waste liquid is also easier to handle and has less operational risks.

[0036] The above embodiments are exemplary, and their purpose is to illustrate the technical concept and features of the present invention so that people familiar with the technology in this field can understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for identifying the polarity plane of a cadmium telluride crystal (111), characterized in that: The following steps are involved: Step S1: cutting along the (111) surface of the cadmium telluride ingot and grinding and polishing the cut surface to make it smooth; Step S2: Clean the sample surface; Step S3: placing the cleaned sample in a KOH aqueous solution for treatment, then taking out the sample and washing away the KOH residual liquid; Step S4: Place the sample rinsed in step S3 into a 10%-15% H2O2-NH4F solution and let it stand for 5-10 minutes, then wash away the residual liquid; Step D5: Observe the color of the sample surface after rinsing in step S4. If the sample surface is observed to be black, it is determined that the surface is the (111) A surface of the cadmium telluride or cadmium zinc telluride sample; if the sample surface is observed to be colored, it is determined that the surface is the (111) B surface of the cadmium telluride or cadmium zinc telluride sample.

2. The method for identifying the polarity plane of a cadmium telluride crystal (111) according to claim 1, characterized in that: The cadmium telluride crystal is a cadmium telluride crystal or a cadmium zinc telluride crystal.

3. The method for identifying the polarity plane of a cadmium telluride crystal (111) according to claim 1, characterized in that: In step S2, the sample obtained in step S1 is cleaned using an organic solvent.

4. The method for identifying the polarity plane of a cadmium telluride crystal (111) according to claim 3, characterized in that: In step S2, the sample is ultrasonically cleaned with acetone at 40°C for 15 minutes, and then rinsed with water to remove residual acetone.

5. The method for identifying the polarity plane of a cadmium telluride crystal (111) according to claim 1, characterized in that: In step S3, the cleaned sample is placed in a 10%-15% KOH solution and allowed to stand for 5-10 minutes, then the sample is taken out and rinsed with deionized water to remove the KOH residue.

6. The method for identifying the polarity plane of a cadmium telluride crystal (111) according to claim 1, characterized in that: In step S3, the cleaned sample is placed in a 15% KOH solution and allowed to stand for 10 minutes, then the sample is taken out and rinsed with deionized water to remove the KOH residue.

7. The method for identifying the polarity plane of a cadmium telluride crystal (111) according to claim 1, characterized in that: In step S4, the sample is placed in a 10% H2O2-NH4F solution and allowed to stand for 10 min, and then the residual liquid is washed away with deionized water.

8. The method for identifying the polarity plane of a cadmium telluride crystal (111) according to claim 7, characterized in that: 10% H2O2-NH4F solution was prepared by the following method: NH4F solid was dissolved in deionized water, and then diluted H2O2 aqueous solution was slowly added to control the mass ratio of H2O2, NH4F and deionized water in the mixed solution to be 1:1:

8.

9. The method for identifying the polarity plane of a cadmium telluride crystal (111) according to claim 1, characterized in that: In step S1, the grinding and polishing process includes first polishing with Al2O3 powder having a particle size of 3 μm for 15 minutes, and then polishing with SiO2 powder having a particle size of 100 nm for another 30 minutes.

10. The method for identifying the polarity plane of a cadmium telluride crystal (111) according to claim 1, characterized in that: In step S1, a dicing machine is used to slice and cut the surface of the cadmium telluride ingot (111).

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