Controllable preparation method of two-dimensional semiconductor Si2Te3 by chemical vapor phase transport

Abstract

This invention discloses a method for preparing bulk Si2Te3 single crystals using chemical vapor transport (CVT). This method is the first to successfully grow bulk Si2Te3 single crystals using CVT, filling a technological gap in the preparation of single crystals using CVT and overcoming the limitation of traditional processes that can only prepare Si2Te3 thin films. This invention strictly limits the use of silicon wafers as the silicon source, as silicon wafers provide a stable reaction interface. The gas-solid reaction rate is highly matched with the single crystal nucleation and growth pattern, thus avoiding the problems of impurity phase formation and difficulty in single crystal formation from the source.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor functional single crystal material preparation technology, specifically involving a process method for preparing bulk Si2Te3 single crystals using chemical vapor transport method. It is particularly suitable for large-scale preparation scenarios using elemental Te and silicon wafers as core reaction raw materials, elemental iodine as vapor transport agent, and a dual-temperature zone tube furnace for precise temperature control to grow high-crystallinity, large-size, and high-quality bulk Si2Te3 single crystals. Background Technology

[0002] Si2Te3, as a typical IV-VI group layered semiconductor functional single crystal material, possesses excellent photoelectric conversion characteristics, good thermoelectric transport performance, and a unique layered crystal structure. It has irreplaceable application value and broad industrialization prospects in fields such as infrared photoelectric detection, room-temperature thermoelectric power generation, semiconductor optoelectronic devices, and novel layered functional devices. Bulk Si2Te3 single crystals are the core substrate and core functional material for fabricating these high-performance devices. The integrity, size, purity, and internal defect density of the single crystal directly determine the operating efficiency, stability, and lifespan of subsequent devices.

[0003] Currently, most of the research on Si2Te3 preparation focuses on simple preparation processes such as thin film deposition. These processes can only produce Si2Te3 thin film materials and cannot grow bulk Si2Te3 single crystals with complete structure, high crystallinity, and controllable size. This seriously restricts the research and development and industrial application of high-end functional devices based on Si2Te3.

[0004] Chemical vapor transport (CVT) is a commonly used and effective process for preparing high-quality single crystals. It boasts core advantages such as reversible gas-phase reaction transport, low-temperature slow growth, low lattice stress, and superior single crystal quality, making it suitable for preparing various refractory and easily decomposed layered single crystal materials. However, currently, there are no reports or patent publications in the industry regarding the use of CVT to grow bulk Si2Te3 single crystals. Through extensive and repeated orthogonal experiments, the inventors have verified that when using conventional silicon powder as the silicon raw material, regardless of the control of process parameters such as reaction temperature, holding time, and the amount of transport agent added, it is impossible to synthesize and grow bulk Si2Te3 single crystals, thus failing to meet the standards for bulk single crystal use.

[0005] Given the gaps and process defects in existing technologies, there is an urgent need to develop a proprietary preparation method that is stable, easy to operate, and can achieve stable growth of high-quality bulk Si2Te3 single crystals for the first time. This method would fill the technological gap in the industry and meet the substrate requirements for high-end optoelectronic and thermoelectric devices. Summary of the Invention

[0006] The purpose of this invention is to overcome the lack of a mature preparation process for bulk Si2Te3 single crystals in the existing technology, and to provide for the first time a method for preparing bulk Si2Te3 single crystals by chemical vapor transport. By using a silicon wafer as a dedicated silicon source material to replace conventional silicon powder material, and by precisely proportioning Te powder and iodine particles as transport agents, large-size, highly crystalline, low-defect, pure-phase, and impurity-free bulk Si2Te3 single crystals can be prepared.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] Step 1: Precise Weighing and Pre-treatment of Raw Materials: High-purity tellurium powder, single-crystal silicon wafers, and high-purity iodine granules are selected as raw materials. A high-purity quartz tube of suitable specifications is selected as the reaction growth container, and a high-purity quartz column with a size matching the inner diameter of the quartz tube is prepared for use. Among them, the silicon source material is limited to single-crystal silicon wafers. Silicon powder is prohibited from being used as a silicon source, as silicon powder cannot be used to grow Si2Te3 single crystals. According to the stoichiometric ratio of Si2Te3 single crystals and the appropriate ratio of gas phase transport reaction, each raw material is precisely weighed. The weighed tellurium powder, single-crystal silicon wafers, and iodine granules are placed sequentially and orderly in the reaction area at the bottom of one end of the quartz tube. The raw materials are placed in layers and do not mix with each other to avoid premature solid-phase contact reaction and generation of impurity phases.

[0009] Step 2: Argon gas exchange and deoxidation treatment before sealing the quartz tube: Connect the quartz tube filled with raw materials to the vacuum sealing and packaging equipment. First, perform a preliminary vacuum treatment inside the quartz tube to remove most of the air and water vapor impurities inside the tube. Then, insert the matching high-purity quartz column into the opening of the quartz tube, fix the quartz column and the quartz tube at a fixed point, and then repeatedly exchange the gas with high-purity argon gas inside the quartz tube. The number of argon gas exchanges should not be less than 5 times to completely remove residual oxygen, water vapor and air impurities inside the quartz tube, and prevent the oxidation of raw materials and the generation of oxygen defects and impurities during single crystal growth during high-temperature heating. The quartz tube is then subjected to a hot-melt high-temperature vacuum sealing treatment, eliminating the risk of gas leakage.

[0010] Step 3: Quartz tube loading and positioning: Place the sealed quartz tube containing the raw materials stably into the furnace chamber of the dual-temperature zone tube furnace. Precisely adjust the placement of the quartz tube so that the raw material reaction area at the bottom of the quartz tube, which is filled with Te powder and iodine particles, corresponds to the high-temperature heating zone of the dual-temperature zone tube furnace, and the area in the middle of the quartz tube where the silicon wafer is placed corresponds to the low-temperature deposition and growth zone of the dual-temperature zone tube furnace. Ensure that the temperature gradient in the dual-temperature zone is stable and constant, providing a stable temperature field environment for gas phase transport and single crystal directional growth.

[0011] Step 4: Dual-temperature zone segmented temperature-controlled heating growth and cooling unloading: Based on the gas phase transport growth reaction characteristics of Si2Te3 single crystals, preset heating temperatures are set for the high-temperature heating zone and the low-temperature deposition growth zone of the dual-temperature zone tube furnace, respectively. Simultaneously, the stepped heating rate and the isothermal holding time are set. The dual-temperature zone tube furnace is started and heated according to the preset parameters, maintaining the temperature for a duration sufficient for the full progress of the reversible gas phase transport reaction, uniform nucleation of Si2Te3 crystal nuclei, and slow directional growth of the single crystal. After the isothermal growth stage, the dual-temperature zone tube furnace is allowed to cool naturally to room temperature. No rapid cooling intervention is applied during the cooling process to avoid thermal stress cracking and lattice defects in the single crystal. After the furnace body has completely cooled, the quartz tube is removed, and a complete bulk Si2Te3 single crystal is collected from the low-temperature deposition growth zone of the quartz tube after the tube is broken.

[0012] As a preferred embodiment of the present invention, the specific steps for generating high-quality Si2Te3 bulk single crystals are as follows:

[0013] Step 1: Prepare source Te powder, silicon wafer, and iodine particles, place them in a quartz tube, and seal the quartz tube with a quartz column of appropriate size;

[0014] Step 2: When sealing the quartz tube, use argon gas to purify the system;

[0015] Step 3: Place the sealed quartz tube into the dual-zone tube furnace and adjust its position;

[0016] Step 4: Set the required temperature and heating time for the substance.

[0017] In step one, the source is 0.2-0.4 g of Te powder, 2-4 silicon wafers of about 1 cm * 1 cm (0.2-0.4 g of Si powder), and 2-3 iodine particles.

[0018] In step one: the silicon wafers must be cleaned in an ultrasonic cleaner for 5 minutes each with acetone, ethanol and deionized water before use, and then dried with a nitrogen gun.

[0019] In step two, the ventilation step requires fixing the quartz column and quartz tube at fixed points on the quartz column before venting and evacuating the air. This process is repeated five times to ensure that the air in the system is emptied.

[0020] In step three, when placing the silicon wafer into the dual-temperature zone furnace, it is necessary to ensure that the Te powder is placed in the first temperature zone, the silicon wafer is placed in the second temperature zone, and the temperature difference between the first and second temperature zones is maintained at 100 °C.

[0021] In step four, the optimal temperature is set as follows: 850 ℃ in the first temperature zone, 750 ℃ ​​in the second temperature zone, and the growth time is 480 min.

[0022] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0023] 1. This invention is the first to successfully prepare bulk Si2Te3 single crystals using the chemical vapor transport method, filling the technological gap in the preparation of single crystals using the chemical vapor transport method at home and abroad, breaking through the technical limitation of traditional processes that can only prepare Si2Te3 thin films, and realizing the stable preparation of high-quality bulk single crystals.

[0024] 2. The core of this invention is to limit the use of silicon source materials specifically for silicon wafers, strictly excluding the use of silicon powder. Extensive testing has verified that when silicon powder is used as a silicon source, the reaction activity is out of control and the reaction rate is too fast, making it impossible to form a regular single crystal lattice. In contrast, the reaction interface of silicon wafer raw materials is stable and the solid-phase and gas-phase reaction rates are matched, which can precisely match the nucleation and growth law of Si2Te3 single crystals. This solves the core problems of single crystals being unable to form and excessive impurities from the source of raw materials. Detailed Implementation

[0025] This invention proposes a preparation method for two-dimensional Si2Te3 by chemical vapor phase transport. In order to make the advantages and technical solutions of this invention clearer and more explicit, the invention will be described in detail below with reference to specific embodiments.

[0026] All the raw materials required for this invention can be purchased through commercial channels.

[0027] Example 1:

[0028] Two-dimensional Si2Te3 was prepared in a horizontal tube furnace with dual heating zones using a chemical vapor transport method.

[0029] Step 1: Place the silicon wafer in a weighing bottle, add acetone solution until it covers the wafer, and sonicate in an ultrasonic machine for 5 minutes. After sonication, pour out the acetone solution into a waste container. Add ethanol solution and repeat the above steps. Finally, add deionized water, sonicate for 5 minutes, and then remove the weighing bottle.

[0030] Step 2: Remove the silicon wafer with tweezers and dry it with nitrogen gas.

[0031] Step 3: Weigh 0.4g of Te powder and place it at the bottom of the quartz tube, add 3 iodine granules, and place 4 prepared silicon wafers in the middle of the quartz tube;

[0032] Step 4: Prepare a quartz column that matches the size of the quartz tube, evacuate the system, then use a spray gun to apply high temperature to the point, and use argon to replace the air in the system. Repeat this process 5 times to ensure that the air in the system is completely removed.

[0033] Step 5: Place the fired quartz tube into a dual-temperature zone furnace and set the heating program so that the temperature of the first temperature zone rises from room temperature to 1050 ℃ and the temperature of the second temperature zone rises from room temperature to 950 ℃, and is held at these temperatures for 480 min. After the process is complete, allow the tube furnace to cool naturally to room temperature to obtain a two-dimensional Si2Te3 bulk single crystal.

[0034] Example 2:

[0035] Two-dimensional Si2Te3 was prepared in a horizontal tube furnace with dual heating zones using a chemical vapor transport method.

[0036] Step 1: Place the silicon wafer in a weighing bottle, add acetone solution until it covers the wafer, and sonicate in an ultrasonic machine for 5 minutes. After sonication, pour out the acetone solution into a waste container. Add ethanol solution and repeat the above steps. Finally, add deionized water, sonicate for 5 minutes, and then remove the weighing bottle.

[0037] Step 2: Remove the silicon wafer with tweezers and dry it with nitrogen gas.

[0038] Step 3: Weigh 0.4g of Te powder and place it at the bottom of the quartz tube, add 3 iodine granules, and place 4 prepared silicon wafers in the middle of the quartz tube;

[0039] Step 4: Prepare a quartz column that matches the size of the quartz tube, evacuate the system, then use a spray gun to apply high temperature to the point, and use argon to replace the air in the system. Repeat this process 5 times to ensure that the air in the system is completely removed.

[0040] Step 5: Place the fired quartz tube into a dual-temperature zone furnace and set the heating program so that the temperature of the first temperature zone rises from room temperature to 950 ℃ and the temperature of the second temperature zone rises from room temperature to 850 ℃, and is held at these temperatures for 480 min. After the process is complete, allow the tube furnace to cool naturally to room temperature to obtain a two-dimensional Si2Te3 bulk single crystal.

[0041] Example 3:

[0042] Two-dimensional Si2Te3 was prepared in a horizontal tube furnace with dual heating zones using a chemical vapor transport method.

[0043] Step 1: Place the silicon wafer in a weighing bottle, add acetone solution until it covers the wafer, and sonicate in an ultrasonic machine for 5 minutes. After sonication, pour out the acetone solution into a waste container. Add ethanol solution and repeat the above steps. Finally, add deionized water, sonicate for 5 minutes, and then remove the weighing bottle.

[0044] Step 2: Remove the silicon wafer with tweezers and dry it with nitrogen gas.

[0045] Step 3: Weigh 0.4g of Te powder and place it at the bottom of the quartz tube, add 3 iodine granules, and place 4 prepared silicon wafers in the middle of the quartz tube;

[0046] Step 4: Prepare a quartz column that matches the size of the quartz tube, evacuate the system, then use a spray gun to apply high temperature to the point, and use argon to replace the air in the system. Repeat this process 5 times to ensure that the air in the system is completely removed.

[0047] Step 5: Place the fired quartz tube into a dual-temperature zone furnace and set the heating program so that the temperature of the first temperature zone rises from room temperature to 850 ℃ and the temperature of the second temperature zone rises from room temperature to 750 ℃, and is held at these temperatures for 480 min. After the process is complete, allow the tube furnace to cool naturally to room temperature to obtain a two-dimensional Si2Te3 bulk single crystal.

[0048] Example 4:

[0049] Two-dimensional Si2Te3 was prepared in a horizontal tube furnace with dual heating zones using a chemical vapor transport method.

[0050] Step 1: Place the silicon wafer in a weighing bottle, add acetone solution until it covers the wafer, and sonicate in an ultrasonic machine for 5 minutes. After sonication, pour out the acetone solution into a waste container. Add ethanol solution and repeat the above steps. Finally, add deionized water, sonicate for 5 minutes, and then remove the weighing bottle.

[0051] Step 2: Remove the silicon wafer with tweezers and dry it with nitrogen gas.

[0052] Step 3: Weigh 0.4g of Te powder and place it at the bottom of the quartz tube, add 3 iodine granules, and place 4 prepared silicon wafers in the middle of the quartz tube;

[0053] Step 4: Prepare a quartz column that matches the size of the quartz tube, evacuate the system, then use a spray gun to apply high temperature to the point, and use argon to replace the air in the system. Repeat this process 5 times to ensure that the air in the system is completely removed.

[0054] Step 5: Place the fired quartz tube into a dual-temperature zone furnace and set the heating program so that the temperature of the first temperature zone rises from room temperature to 750 ℃ ​​and the temperature of the second temperature zone rises from room temperature to 650 ℃, and is held at these temperatures for 480 min. After the process is complete, allow the tube furnace to cool naturally to room temperature to obtain a two-dimensional Si2Te3 bulk single crystal.

[0055] Example 5:

[0056] Two-dimensional Si2Te3 was prepared in a horizontal tube furnace with dual heating zones using a chemical vapor transport method.

[0057] Step 1: Place the silicon wafer in a weighing bottle, add acetone solution until it covers the wafer, and sonicate in an ultrasonic machine for 5 minutes. After sonication, pour out the acetone solution into a waste container. Add ethanol solution and repeat the above steps. Finally, add deionized water, sonicate for 5 minutes, and then remove the weighing bottle.

[0058] Step 2: Remove the silicon wafer with tweezers and dry it with nitrogen gas.

[0059] Step 3: Weigh 0.4g of Te powder and place it at the bottom of the quartz tube, add 3 iodine granules, and place 4 prepared silicon wafers in the middle of the quartz tube;

[0060] Step 4: Prepare a quartz column that matches the size of the quartz tube, evacuate the system, then use a spray gun to apply high temperature to the point, and use argon to replace the air in the system. Repeat this process 5 times to ensure that the air in the system is completely removed.

[0061] Step 5: Place the fired quartz tube into a dual-temperature zone furnace and set the heating program so that the temperature of the first temperature zone rises from room temperature to 850 ℃ and the temperature of the second temperature zone rises from room temperature to 750 ℃, and is held at these temperatures for 360 min. After the process is complete, allow the tube furnace to cool naturally to room temperature to obtain a two-dimensional Si2Te3 bulk single crystal.

[0062] Example 6:

[0063] Two-dimensional Si2Te3 was prepared in a horizontal tube furnace with dual heating zones using a chemical vapor transport method.

[0064] Step 1: Place the silicon wafer in a weighing bottle, add acetone solution until it covers the wafer, and sonicate in an ultrasonic machine for 5 minutes. After sonication, pour out the acetone solution into a waste container. Add ethanol solution and repeat the above steps. Finally, add deionized water, sonicate for 5 minutes, and then remove the weighing bottle.

[0065] Step 2: Remove the silicon wafer with tweezers and dry it with nitrogen gas.

[0066] Step 3: Weigh 0.4g of Te powder and place it at the bottom of the quartz tube, add 3 iodine granules, and place 4 prepared silicon wafers in the middle of the quartz tube;

[0067] Step 4: Prepare a quartz column that matches the size of the quartz tube, evacuate the system, then use a spray gun to apply high temperature to the point, and use argon to replace the air in the system. Repeat this process 5 times to ensure that the air in the system is completely removed.

[0068] Step 5: Place the fired quartz tube into a dual-temperature zone furnace and set the heating program so that the temperature of the first temperature zone rises from room temperature to 850 ℃ and the temperature of the second temperature zone rises from room temperature to 750 ℃, and is held at these temperatures for 240 min. After the process is complete, allow the tube furnace to cool naturally to room temperature to obtain a two-dimensional Si2Te3 bulk single crystal.

[0069] Example 7:

[0070] Two-dimensional Si2Te3 was prepared in a horizontal tube furnace with dual heating zones using a chemical vapor transport method.

[0071] Step 1: Place the silicon wafer in a weighing bottle, add acetone solution until it covers the wafer, and sonicate in an ultrasonic machine for 5 minutes. After sonication, pour out the acetone solution into a waste container. Add ethanol solution and repeat the above steps. Finally, add deionized water, sonicate for 5 minutes, and then remove the weighing bottle.

[0072] Step 2: Remove the silicon wafer with tweezers and dry it with nitrogen gas.

[0073] Step 3: Weigh 0.4g of Te powder and place it at the bottom of the quartz tube, add 3 iodine granules, and place 4 prepared silicon wafers in the middle of the quartz tube;

[0074] Step 4: Prepare a quartz column that matches the size of the quartz tube, evacuate the system, then use a spray gun to apply high temperature to the point, and use argon to replace the air in the system. Repeat this process 5 times to ensure that the air in the system is completely removed.

[0075] Step 5: Place the fired quartz tube into a dual-temperature zone furnace and set the heating program so that the temperature of the first temperature zone rises from room temperature to 850 ℃ and the temperature of the second temperature zone rises from room temperature to 750 ℃, and holds at these temperatures for 120 min. After the process is complete, allow the tube furnace to cool naturally to room temperature to obtain a two-dimensional Si2Te3 bulk single crystal.

[0076] Example 8:

[0077] Two-dimensional Si2Te3 was prepared in a horizontal tube furnace with dual heating zones using a chemical vapor transport method.

[0078] Step 1: Place the silicon wafer in a weighing bottle, add acetone solution until it covers the wafer, and sonicate in an ultrasonic machine for 5 minutes. After sonication, pour out the acetone solution into a waste container. Add ethanol solution and repeat the above steps. Finally, add deionized water, sonicate for 5 minutes, and then remove the weighing bottle.

[0079] Step 2: Remove the silicon wafer with tweezers and dry it with nitrogen gas.

[0080] Step 3: Weigh 0.4g of Te powder and place it at the bottom of the quartz tube, add 3 iodine granules, and place 4 prepared silicon wafers in the middle of the quartz tube;

[0081] Step 4: Prepare a quartz column that matches the size of the quartz tube, evacuate the system, then use a spray gun to apply high temperature to the point, and use argon to replace the air in the system. Repeat this process 5 times to ensure that the air in the system is completely removed.

[0082] Step 5: Place the fired quartz tube into a dual-temperature zone furnace and set the heating program so that the temperature of the first temperature zone rises from room temperature to 850 ℃ and the temperature of the second temperature zone rises from room temperature to 750 ℃, and hold at these temperatures for 60 min. After the process is complete, allow the tube furnace to cool naturally to room temperature to obtain a two-dimensional Si2Te3 bulk single crystal.

[0083] Example 9:

[0084] A control experiment was set up to verify whether bulk single crystals of Si2Te3 could be grown from Te powder and Si powder.

[0085] Step 1: Weigh 0.4 g of Te powder and 0.4 g of Si powder and place them at the bottom of a quartz tube, then add 3 iodine granules;

[0086] Step 2: Prepare a quartz column that matches the size of the quartz tube, evacuate the system, then use a spray gun to apply high temperature to the point, and use argon to replace the air in the system, repeating 5 times to ensure that the air in the system is completely removed.

[0087] Step 3: Place the fired quartz tube into a dual-temperature zone furnace and set the heating program so that the temperature of the first zone rises from room temperature to 850 ℃ and the temperature of the second zone rises from room temperature to 750 ℃, and is held at these temperatures for 480 min. After the process is complete, allow the tube furnace to cool naturally to room temperature.

[0088] It should be noted that any equivalent or obvious modifications made by those skilled in the art under the guidance of this specification should be within the scope of protection of this invention. Attached Figure Description

[0089] Figure 1 An optical microscope image of a Si2Te3 single crystal from an embodiment.

[0090] Figure 2 XRD pattern of Si2Te3 single crystal in the example

[0091] Figure 3 Raman diagram of Si2Te3 single crystal in the example

[0092] Figure 4 XPS image of Si2Te3 single crystal as an example.

Claims

1. A controllable preparation method for two-dimensional semiconductor Si2Te3 via chemical vapor phase transport, characterized in that: The method steps are as follows: Step 1: Prepare source Te powder and silicon wafers, place the transport agent iodine particles in a quartz tube, and seal the quartz tube with a quartz column of appropriate size; Step 2: When sealing the quartz tube, use argon gas to purify the system; Step 3: Place the sealed quartz tube into the dual-zone tube furnace and adjust its position; Step 4: Set the required temperature and heating time for the substance.

2. The controllable preparation method of two-dimensional semiconductor Si2Te3 by chemical vapor transport according to claim 1, characterized in that: In step one, the source is 0.2-0.4 g of Te powder, about 2-4 silicon wafers of 1 cm * 1 cm, and 2-3 iodine particles.

3. The controllable preparation method of two-dimensional semiconductor Si2Te3 by chemical vapor phase transport according to claim 1, characterized in that: In step one, the silicon wafer substrate must be facing upwards.

4. The controllable preparation method of two-dimensional semiconductor Si2Te3 by chemical vapor phase transport according to claim 1, characterized in that: In step two, the ventilation step requires fixing the quartz column and quartz tube at a fixed point on the quartz column, and then performing ventilation-extraction five times to ensure that the air in the system is emptied.

5. The controllable preparation method of two-dimensional semiconductor Si2Te3 by chemical vapor phase transport according to claim 1, characterized in that: In step three, when placing the silicon wafer into the dual-temperature zone furnace, it is necessary to ensure that the source Te powder is in the first temperature zone, the silicon wafer is in the second temperature zone, and the temperature difference between the first and second temperature zones is maintained at 100 °C.

6. The controllable preparation method of two-dimensional semiconductor Si2Te3 by chemical vapor phase transport according to claim 1, characterized in that: In step four, the optimal temperature is set to 850 ℃ in the first temperature zone and 750 ℃ ​​in the second temperature zone, with a growth time of 480 min.

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