Method for preparing In2Se3 semiconductor crystal

Abstract

The invention belongs to the technical field of semiconductor crystal growth, and particularly discloses a method for preparing an In2Se3 semiconductor crystal. According to the invention, a rocking furnace process and a vertical crucible descent method system are combined and applied to In2Se3 large single crystal growth, so that the bottleneck of size and component uniformity is broken through; the low-defect In2Se3 crystal is prepared by optimizing parameters such as raw material ratio, temperature gradient, growth rate, annealing process and the like. According to the method, crystal growth equipment is simple, the cost is low, the process repeatability is high, the prepared crystal is large in size, element distribution is uniform, the method is very suitable for batch production, the problems that existing CVD and MBE methods for preparing In2Se3 crystals are expensive in equipment, small in crystal size, non-uniform in component and multiple in defect are solved, and the method is suitable for industrial production. And a reliable material basis is provided for the application of the In2Se3 crystal in the fields of photoelectricity, thermoelectricity and storage.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor crystal growth, and in particular to a method for preparing In2Se3 semiconductor crystals. Background Art

[0002] In2Se3 is an important layered III-VI compound semiconductor material. Its crystal structure consists of five stacked layers: Se-In-Se-In-Se, held together by van der Waals forces. This unique structure allows for easy exfoliation into two-dimensional materials, which exhibit excellent optoelectronic and ferroelectric properties. In2Se3 has a high optical absorption coefficient in the visible and near-infrared bands, making it an ideal material for high-efficiency solar cells and photodetectors. Furthermore, In2Se3 exhibits a high thermoelectric figure of merit (ZT), promising promising applications in thermoelectric conversion. At present, the main methods for growing In2Se3 crystals are chemical vapor deposition (CVD, such as references Inorg.Chem.2018, 57, 18, 11775-11781; Nano Lett.2013, 13, 8, 3501-3505) and molecular beam epitaxy (MBE, such as references Journal of crystal growth 175 (1997): 1045-1050; Nano letters, 18 (10), 6340-6346).

[0003] The process of growing In2Se3 crystals by CVD has extremely strict requirements on reaction conditions. The chemical composition of In2Se3 is complex, involving two elements, indium (In) and selenium (Se), and their chemical properties are quite different. Indium has a low vapor pressure, while selenium has a high vapor pressure. Therefore, in the CVD process, how to accurately control the gas phase ratio of these two elements is a huge challenge. Even a slight deviation in the ratio of the reaction gases may lead to uneven crystal composition and even generate non-target products, such as InSe or In2Se. 3-x Etc. This compositional inhomogeneity can seriously affect the electrical, optical and thermal properties of the crystal.

[0004] While the MBE method offers significant advantages in precisely controlling crystal growth at the atomic level, it also presents several significant drawbacks when growing In2Se3 crystals. First, MBE equipment is expensive, requiring operation in an ultra-high vacuum environment and requiring extremely high-purity source materials, which increases the economic burden of the process. Second, MBE growth rates are slow, typically only a few to a few hundred nanometers per hour, resulting in low production efficiency and difficulty meeting the demands of large-scale production. Furthermore, In2Se3 exhibits complex phase transition behavior and is extremely sensitive to temperature and stoichiometry. Minor parameter fluctuations during the MBE process can lead to the formation of non-target phases, compromising crystal quality. Furthermore, when growing on large substrates, the MBE method suffers from uneven molecular beam distribution, which can easily lead to local variations in crystal thickness and composition, limiting its application in large-scale devices. Finally, the MBE process requires high operator skill, and any operational errors can compromise crystal growth quality. These shortcomings present numerous challenges for the MBE method in growing In2Se3 crystals. Summary of the Invention

[0005] In view of the shortcomings of the current CVD and MBE methods for preparing In2Se3 crystals, such as expensive equipment, complex processes and low crystal quality, the present invention develops a low-cost technology for growing high-quality, large-sized In2Se3 crystals, which has important practical significance.

[0006] In order to achieve the above object, the specific technical solutions adopted by the present invention are as follows:

[0007] A method for preparing an In2Se3 semiconductor crystal comprises the following steps:

[0008] (1) Raw material preparation: Indium (In) and selenium (Se) are used as raw materials, weighed according to the stoichiometric ratio, and placed in a quartz crucible. After evacuation, the crucible is sealed with a hydrogen-oxygen flame (the flame is aimed at the connection between the opening of the quartz crucible and the lid to seal the crucible);

[0009] (2) Raw material synthesis: Place the quartz crucible filled with raw materials into a rocking furnace, and control the rocking furnace temperature to 900-1000°C; after the raw materials are melted and kept warm in the rocking furnace, turn on the rocking system to allow In and Se to react chemically to generate In2Se3 compounds;

[0010] (3) Selection of crystal growth furnace: A vertical crucible descending furnace is used to grow In2Se3 crystals. The furnace body is divided into a high-temperature zone and a low-temperature zone. The temperature of the high-temperature zone is 900-1000°C, and the temperature of the low-temperature zone is 600-800°C. The high-temperature zone is above the low-temperature zone and the temperature decreases gradually between the high-temperature zone and the low-temperature zone, forming a stable temperature gradient.

[0011] (4) Crystal growth: Place the crucible containing the In2Se3 compound in a high temperature zone and heat it to 900-1000°C to completely melt the In2Se3 compound. Then slowly lower the crucible, and the In2Se3 melt gradually crystallizes from the bottom.

[0012] (5) Annealing: After the growth is completed, the crystal is annealed in a vertical crucible descending furnace.

[0013] Preferably, in step (1), In and Se with a purity of ≥99.99% are used as raw materials; and the purity of the quartz crucible is ≥99.99%, ensuring that the raw material synthesis under high temperature conditions is not contaminated by residual metal ions in the quartz crucible.

[0014] Preferably, in step (1), the quartz crucible is evacuated to 10 -3 -10 -4 Pa level, to prevent oxidation of raw materials.

[0015] Preferably, in step (1), the bottom of the crucible is designed to be conical with a cone angle of 30-90° to eliminate the number of spontaneously nucleated crystal particles and promote the growth of large-sized single crystals. The cone angle refers to the size of the cone top angle.

[0016] Preferably, in step (2), the raw materials are kept warm in the rocking furnace for 1-2 hours.

[0017] Preferably, in step (2), the rotation speed of the rocking system is 20-50 revolutions per minute, and the rocking time is 0.5-2 hours, to ensure that In and Se react fully and the elements are evenly distributed.

[0018] Preferably, in step (3), the temperature gradient is 15-30°C / cm, which provides a sufficiently large thermodynamic driving force for the crystallization of the In2Se3 solution.

[0019] Preferably, in step (4), the crucible descends at a speed of 0.5-2 mm / h, so that the In2Se3 solution crystallizes slowly, avoiding the formation of severe thermal stress inside the crystal material due to too fast a descent.

[0020] Preferably, in step (5), the annealing temperature is 650-750° C. and the annealing time is 24-48 hours, so as to fully release the thermal stress in the In 2 Se 3 crystal material and avoid cracking of the crystallized material.

[0021] The present invention has the following beneficial effects:

[0022] This invention provides a method for growing high-quality, large-sized In2Se3 semiconductor crystals using a vertical crucible descent method. This method combines a rocking furnace process with a vertical crucible descent system for the growth of large In2Se3 single crystals, overcoming bottlenecks in size and composition uniformity. By optimizing parameters such as the raw material ratio, temperature gradient, growth rate, and annealing process, it overcomes existing issues such as small crystal size and uneven composition. This method offers the advantages of simplicity, low cost, and suitability for large-scale production, providing a reliable material foundation for the application of In2Se3 crystals in optoelectronics, thermoelectrics, and storage applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is an In2Se3 polycrystalline raw material synthesized using a rocking furnace.

[0024] Figure 2 This is the X-ray diffraction pattern of In2Se3 polycrystalline raw material.

[0025] Figure 3 It is an In2Se3 crystal grown using the vertical crucible descent technique.

[0026] Figure 4 This is the X-ray diffraction pattern of In2Se3 single crystal.

[0027] Figure 5 This is the EDS composition distribution diagram of In2Se3 crystal. DETAILED DESCRIPTION

[0028] In order to overcome the problems of expensive equipment, small crystal size, uneven composition and many defects in the existing CVD and MBE methods for preparing In2Se3 crystals, the present invention first uses a rocking furnace to synthesize In2Se3 polycrystals with a standard physical structure, and then uses a vertical crucible descent process to gradually crystallize the melt to obtain In2Se3 single crystals. The existing CVD and MBE methods mainly use the vapor phase method to prepare In2Se3 crystals, and the technical solution of the present invention is to grow In2Se3 crystals by the melt method. The significant effects of this technical solution are fast speed, simple crystal growth equipment, low cost and high process repeatability, large size of the prepared crystals (the size of In2Se3 obtained by the prior art is micron-level, as reported in Adv.Mater.2020,32,1907244, and the crystal size of the present invention can reach 50mm in diameter), uniform element distribution, and very suitable for mass production.

[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0030] Example 1

[0031] In and Se elements with a total weight of 50 g and a purity of 99.99% were prepared according to the stoichiometric ratio of In:Se = 2:3 and placed in a quartz crucible with an inner diameter of 20 mm and a bottom taper angle of 30°. The crucible was evacuated to 1.0×10 -3 After the Pa is reached, the material is sealed with an oxyhydrogen flame. The quartz crucible is placed in a rocking furnace controlled at 900°C. After the raw materials are melted and held for 1 hour, the rocking system is activated at a rotation speed of 20 revolutions per minute for 0.5 hours, allowing a chemical reaction between In and Se to form the In2Se3 compound. In2Se3 crystals are grown in a vertical crucible-down furnace, with a high-temperature zone temperature of 900°C and a low-temperature zone temperature of 600°C. The crystal growth temperature gradient is 15°C / cm, and the crucible descends at a rate of 0.5 mm / h. After crystal growth, the In2Se3 crystals are annealed at 650°C for 24 hours to release thermal stress within the material.

[0032] Example 2

[0033] In and Se elements with a total weight of 200 g and a purity of 99.99% were prepared according to the stoichiometric ratio of In:Se = 2:3 and placed in a quartz crucible with an inner diameter of 30 mm and a bottom taper angle of 60°. The crucible was evacuated to 1.0×10 -4 After the Pa is reached, the material is sealed with an oxyhydrogen flame. The quartz crucible is placed in a rocking furnace controlled at 950°C. After the raw materials are melted and held for one hour, the rocking system is activated at a rotation speed of 30 revolutions per minute for one hour, allowing a chemical reaction between In and Se to form the In2Se3 compound. In2Se3 crystals are grown in a vertical crucible-down furnace, with a high-temperature zone temperature of 950°C and a low-temperature zone temperature of 650°C. The crystal growth temperature gradient is 20°C / cm, and the crucible descends at a rate of 1 mm / h. After crystal growth, the In2Se3 crystals are annealed at 700°C for 36 hours to release thermal stress within the material.

[0034] Example 3

[0035] In and Se elements with a total weight of 500 g and a purity of 99.999% were prepared according to the stoichiometric ratio of In:Se = 2:3, placed in a quartz crucible with an inner diameter of 50 mm and a bottom taper angle of 90°, and evacuated to 2.0×10 -4After the Pa is reached, the material is sealed with an oxyhydrogen flame. The quartz crucible is placed in a rocking furnace controlled at 1000°C. After the raw materials are melted and held for two hours, the rocking system is activated at a rotation speed of 50 revolutions per minute for two hours, allowing a chemical reaction between In and Se to form the In2Se3 compound. In2Se3 crystals are grown in a vertical crucible-down furnace, with a high-temperature zone temperature of 1000°C and a low-temperature zone temperature of 800°C. The crystal growth temperature gradient is 30°C / cm, and the crucible descends at a rate of 2 mm / h. After crystal growth, the In2Se3 crystals are annealed at 750°C for 48 hours to release thermal stress within the material.

[0036] The appearance of the In2Se3 polycrystalline raw material synthesized by the swing furnace of the present invention is as follows Figure 1 As shown, the surface is smooth and has not reacted with the quartz tube. The X-ray diffraction pattern of In2Se3 polycrystalline raw material is as follows Figure 2 The appearance of the In2Se3 single crystal grown by vertical crucible descent technique is shown in Figure 3, which is consistent with the standard PDF#34-0455 card. Figure 3 As shown in Figure 1, the cleavage surface is smooth and has typical mirror features. The X-ray diffraction pattern of the In2Se3 single crystal is shown in Figure 1. Figure 4 As shown in Figure 2, only the {001} diffraction peak exists, indicating that a typical single crystal material has been obtained. The EDS composition distribution of the In2Se3 single crystal is shown in Figure 2. Figure 5 As shown, the In and Se elements are evenly distributed.

[0037] This specific implementation is merely an explanation of the present invention and is not a limitation of the present invention. Any changes made by those skilled in the art after reading the specification of the present invention will be protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for preparing an In2Se3 semiconductor crystal, characterized in that: The following steps are involved: (1) Raw material preparation: In and Se are used as raw materials, placed in a quartz crucible according to the stoichiometric ratio, and then vacuumed and sealed with a hydrogen-oxygen flame; (2) Raw material synthesis: Place the quartz crucible filled with raw materials into a rocking furnace, and control the rocking furnace temperature to 900-1000°C; after the raw materials are melted and kept warm in the rocking furnace, turn on the rocking system to allow In and Se to react chemically to generate In2Se3 compounds; (3) Selection of crystal growth furnace: A vertical crucible descending furnace is used to grow In2Se3 crystals. The furnace body is divided into a high-temperature zone and a low-temperature zone. The temperature of the high-temperature zone is 900-1000°C, and the temperature of the low-temperature zone is 600-800°C. The high-temperature zone is above the low-temperature zone and the temperature decreases gradually between the high-temperature zone and the low-temperature zone, forming a stable temperature gradient. (4) Crystal growth: Place the crucible containing the In2Se3 compound in a high temperature zone and heat it to 900-1000°C to completely melt the In2Se3 compound. Then slowly lower the crucible, and the In2Se3 melt gradually crystallizes from the bottom. (5) Annealing: After the growth is completed, the crystal is annealed in a vertical crucible descending furnace.

2. The method for preparing an In2Se3 semiconductor crystal according to claim 1, characterized in that: In step (1), the purity of In, Se and the quartz crucible is ≥99.99%.

3. The method for preparing an In2Se3 semiconductor crystal according to claim 1, wherein: In step (1), the quartz crucible is evacuated to 10 -3 -10 -4 Pa level.

4. The method for preparing an In2Se3 semiconductor crystal according to claim 1, characterized in that: In step (1), the bottom of the crucible is designed to be conical, and the cone angle is 30-90°.

5. The method for preparing an In2Se3 semiconductor crystal according to claim 1, characterized in that: In step (2), the raw materials are kept warm in the rocking furnace for 1-2 hours.

6. The method for preparing an In2Se3 semiconductor crystal according to claim 1, characterized in that: In step (2), the rocking system rotates at a speed of 20-50 revolutions per minute, and the rocking time is 0.5-2 hours.

7. The method for preparing an In2Se3 semiconductor crystal according to claim 1, characterized in that: In step (3), the temperature gradient is 15-30°C / cm.

8. The method for preparing an In2Se3 semiconductor crystal according to claim 1, wherein: In step (4), the crucible descends at a speed of 0.5-2 mm / h.

9. The method for preparing an In2Se3 semiconductor crystal according to claim 1, wherein: In step (5), the annealing temperature is 650-750° C., and the annealing time is 24-48 hours.

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