Tungsten disulfide homojunction, preparation method and application
By controlling the temperature and airflow direction of WS2 and sulfur powder in a dual-temperature-zone tube furnace, a single-layer WS2 homojunction with excellent photoelectric properties and high crystallinity was prepared, which solved the small size of WS2 homojunction in the prior art. , the problem of poor crystallinity has achieved an efficient and low-cost preparation process.
Patent Information
- Application Number
- CN202411760569.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-03
- Publication Date
- 2025-02-18
AI Technical Summary
In the preparation of the homojunction of tungsten disulfide (WS2) tungsten disulfide (WS2) in the prior art, the size is small, the crystallinity is poor and the optical performance is poor. The preparation process is low and the cost is high. The samples are easily contaminated, which affects the photoelectric performance.
The preparation of WS2 homojunction is carried out by using a dual-temperature zone tube furnace. By controlling the temperature and airflow direction of WS2 and sulfur powder respectively in the heating zones A and B, the high-temperature deposition of WS2 and sulfur rich atmosphere growth is achieved, and a high-temperature deposition of WS2 and sulfur rich atmosphere is achieved. Single-layer WS2 homojunction with excellent photoelectric performance.
A single-layer WS2 homogenous junction with a size greater than 400 microns was successfully prepared, with high crystallinity and excellent optical properties, overcoming the problems of small size and poor crystallinity of WS2 in traditional methods, and improving the preparation efficiency and product performance.
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Figure CN119465038A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of inorganic two-dimensional materials, and specifically relates to a tungsten disulfide homojunction, a preparation method and an application. Background Art
[0002] Two-dimensional transition metal chalcogenides (TMDs) have excellent physical and chemical properties due to their special layered structure. Two-dimensional transition metal chalcogenides are excellent materials for the preparation of electronic and optoelectronic devices. Their excellent properties such as atomically thin layered structure, weak coupling force between layers and adjustable band gap have broad application prospects in the fields of electronics and optics.
[0003] Tungsten disulfide (WS2) is a typical TMDs material. This type of material has the characteristics of low lattice symmetry and weak interlayer coupling, and has great research value. The weak van der Waals force between the two-dimensional WS2 layered structure provides great flexibility for the assembly of layered materials, and can realize structural assembly such as corner, stacking, and slip. The band gap of WS2 changes from an indirect band gap of ~1.3 eV to a direct band gap of ~2.0 eV as the number of layers decreases - from multilayer to single layer, so the single-layer WS2 has excellent optical properties. The structure of the single-layer WS2 can be controlled by applying an external field to control strain, phase, doping, and defects to improve performance. When the single-layer WS2 is used for device fabrication and application testing, the single-layer WS2 is used as the top electrode and bottom electrode of the vertical field effect transistor to form a homojunction, maintain the intrinsic characteristics of the vertical channel, and optimize the VFET performance and scalability.
[0004] Among the existing methods for preparing WS2, bottom-up CVD (chemical vapor deposition), PVD (physical vapor deposition), MBE (molecular beam epitaxy) and top-down mechanical stripping are the main methods. Mechanical stripping can obtain WS2 with high-quality single layers, but the WS2 produced by this method is small in size, and the sample is easily contaminated, and the efficiency of preparing materials is not high. The equipment required for MBE to prepare a single layer of WS2 is relatively expensive, and the preparation time is too long, the efficiency is low, and the preparation cost is high. The process of preparing a single layer of WS2 by CVD is affected by many factors. Since the metal oxide of tungsten and sulfur powder are more likely to form nuclei on the substrate under a high-temperature inert gas atmosphere, the number of single-layer WS2 is reduced and the size of WS2 is limited. When a single layer of WS2 grown by mechanical stripping or CVD is transferred by dry or wet method to construct a WS2 homojunction, the sample is easily contaminated during the transfer process, which greatly reduces the photoelectric performance. Summary of the invention
[0005] The technical problem to be solved by the present invention is to provide a tungsten disulfide homojunction, a preparation method and an application. The prepared tungsten disulfide homojunction has a larger size, high crystallinity and optical properties, and excellent product performance.
[0006] The embodiment of the present invention provides a method for preparing a tungsten disulfide homojunction, wherein tungsten disulfide is placed in the central area of a heating zone A of a double-temperature zone tubular furnace, sulfur powder is placed at the edge of a heating zone B of the double-temperature zone tubular furnace, and a substrate is placed in a deposition area of the double-temperature zone tubular furnace; an inert gas is introduced from the substrate into the heating zone to remove impurity gases in the double-temperature zone tubular furnace; the temperature is increased, and after the temperature of the heating zone A reaches 1180-1200°C and the temperature of the heating zone B reaches 240-260°C, the gas flow direction of the inert gas is changed, tungsten disulfide begins to be deposited, and after a period of deposition, the sulfur powder is pushed into the central area of the heating zone B, and the deposition is continued to obtain a tungsten disulfide homojunction.
[0007] Preferably, after the temperature of the heating zone A reaches 1190° C. and the temperature of the heating zone B reaches 250° C., the gas flow direction of the inert gas is changed.
[0008] Preferably, the weight ratio of tungsten disulfide to sulfur powder is 15:2.
[0009] Preferably, the heating rate of the heating zone A is 26.4°C·min -1 The heating rate of the heating zone A is 5.5°C·min -1 .
[0010] Preferably, tungsten disulfide begins to deposit, and after 45 seconds of deposition, sulfur powder is pushed into the central area of the temperature rising zone B and the deposition continues for 80 seconds.
[0011] Preferably, the inert gas is argon.
[0012] Preferably, the method for pushing the sulfur powder into the central area of the temperature rising zone B is that the sulfur powder is placed on a quartz boat, the quartz boat is connected to a quartz hook with a magnet, and the sulfur powder can be moved by moving the magnet with a magnetic device.
[0013] Preferably, an inert gas is introduced from the substrate to the heating zone to remove impurity gases in the dual-temperature zone tubular furnace at a gas flow rate of 1200 sccm. After removing the impurity gases in the dual-temperature zone tubular furnace, the gas is continuously introduced at a gas flow rate of 100 sccm.
[0014] The embodiment of the present invention provides a tungsten disulfide homojunction, which is obtained by using the preparation method.
[0015] An embodiment of the present invention provides an application of the tungsten disulfide homojunction, wherein the tungsten disulfide homojunction is used to prepare transistors, photodetectors or devices in the field of torsional electronics.
[0016] The beneficial effect of the present invention is that the present invention improves the growth mode of PVD-grown WS2 homojunction, and can obtain a single-layer WS2 homojunction with excellent photoelectric performance and a thickness of more than 400 microns.
[0017] The present invention provides a preparation method of PVD-grown WS2 homojunction under sulfur-rich conditions, which adopts WS2 and S powder as precursors and is prepared by a high-temperature tube furnace. The size of the prepared single-layer WS2 homojunction can reach more than 400 microns, and the prepared WS2 homojunction has excellent optical properties, and the material exhibits high crystallinity. The present invention overcomes the problems of small size of mechanically peeled single-layer WS2 and a large number of nucleation and formation defects caused by high vapor pressure and unstable supply ratio of precursor elements in the process of preparing single-layer WS2 using WO3 and S powder as raw materials in traditional CVD. The prepared single-layer WS2 lateral homojunction has high crystallinity and optical properties and is large in size.
[0018] The present invention regulates the S / W ratio of precursor elements during the growth process through dual temperature zones. Compared with the traditional CVD growth method, a "magnet" device is used to supplement the S element midway, providing an S-rich atmosphere for the growth of the WS2 homojunction, thereby providing an adequate supply of S atoms and successfully preparing WS2 homojunctions with a variety of configurations. Compared with the commonly used mechanical stripping combined with dry transfer, the single-layer WS2 lateral homojunction prepared by this method has high crystallinity and optical properties, and is larger in size, simpler and more convenient to operate, which is conducive to the in-depth application of single-layer WS2 lateral homojunction in photoelectric detection.
[0019] The present invention first deposits WS2 normally. After the growth of a single layer of WS2 is completed, S powder is pushed in to make it grow secondary in an atmosphere rich in S. The present invention does not use S as a precursor reactant. During the preparation process, S powder is not used as a raw material for preparing WS2, but as a precursor for adjusting the S / W ratio when WS2 is homoepitaxially grown. The quartz hook with a magnet is connected to a quartz boat containing S powder, so that the S powder is placed outside the heating zone. When the WS2 powder temperature zone reaches about 1190 ° C, the air flow direction is changed, and WS2 is physically deposited. After growing for a period of time, preferably 45 seconds, the S powder is pushed to a position where it reaches 250 ° C, and continues to grow for a period of time, preferably 1 minute and 20 seconds, and then stops heating and heat preservation, and naturally cools to room temperature. During the two growth processes, the S atmosphere has a significant difference, thereby generating a single-layer WS2 homojunction with a center-edge difference. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 Schematic diagram of the experimental equipment for growing WS2 homojunction using WS2 and S powder as raw materials.
[0021] Figure 2This is a schematic diagram of a quartz hook with a magnet device connected to a quartz boat filled with S powder. The length of the quartz hook is 10 cm.
[0022] Figure 3 This is an optical photograph of a single-layer lateral WS2 homojunction grown using WS2 and S powder as raw materials.
[0023] Figure 4 This is a photoluminescence scan of a single-layer lateral WS2 homojunction grown using WS2 and S powder as raw materials.
[0024] Figure 5 This is the Raman scan image of a single-layer lateral WS2 homojunction grown using WS2 and S powder as raw materials.
[0025] Figure 6 These are the atomic force microscopy test results of a single-layer lateral WS2 homojunction grown using WS2 and S powder as raw materials.
[0026] Figure 7 This is the Raman single spectrum of a single-layer lateral WS2 homojunction grown using WS2 and S powder as raw materials.
[0027] Figure 8 This is a single spectrum comparison diagram of the photoluminescence from the center to the edge of a single-layer lateral WS2 homojunction grown using WS2 and S powder as raw materials.
[0028] Fig. 9 This is a single spectrum comparison diagram of the photoluminescence from the center to the edge of a single layer of WS2 grown using WS2 as the raw material without pushing in S powder.
[0029] Fig.10 This is an optical photograph of WS2 prepared in Comparative Example 2.
[0030] Fig.11 This is an optical photograph of WS2 prepared in comparative example 3. DETAILED DESCRIPTION
[0031] The present invention is further described in detail below by specific examples, wherein the raw materials are all industrial products. The examples are only used to explain the present invention and cannot be construed as limiting the present invention. Changes or modifications to the equivalent forms of the present invention by those skilled in the art also fall within the scope defined by the appended claims of the present application.
[0032] Example 1 The present invention provides a method for preparing a WS2 homojunction. Experiments of two-dimensional WS2 homojunctions of various morphologies are carried out in a dual-temperature zone tube furnace. The experimental apparatus is as follows: Figure 1-2 shown.
[0033] The double-temperature-zone tubular furnace comprises a deposition area 1, a heating zone A2 and a heating zone B3 which are connected in sequence. Quartz boats are placed in the deposition area 1, the heating zone A2 and the heating zone B3. A substrate 4 is placed in the quartz boat of the deposition area 1, WS221 is placed in the quartz boat of the heating zone A2, and sulfur powder 31 is placed in the quartz boat of the heating zone B3, wherein the sulfur powder 31 is initially arranged at the edge of the heating zone B3 rather than in the central area.
[0034] The quartz boat in the heating zone B3 is connected to a magnet 5 via a quartz hook 6 (the magnet 5 can be fixed to the end of the quartz hook 6 via a raw tape). The magnet 5 is driven to move by the external magnet 7, so the quartz boat in the heating zone B3 can be easily moved.
[0035] Other supporting equipment include argon tanks, tee pipes, flanges, switches, quartz boats, quartz tubes and silicon wafers, etc., which are all known supporting equipment for the dual-temperature zone tubular furnace.
[0036] The specific steps include: 1) The substrate used for preparing the WS2 homojunction is a SiO2 / Si silicon wafer with a 300 nm oxide layer. The silicon wafer is cut into 1.75 × 4.0 cm in size using a silicon wafer cutter, and the dust on the surface of the silicon wafer is blown away with a nitrogen air gun; 2) Weigh 1.5 g of precursor WS2 powder and 0.2 g of S powder, and spread them evenly on the bottom of a quartz boat (the quartz boat container is 11 cm long and 1.5 cm wide); place the quartz boat containing WS2 in the center of one heating zone, and connect one end of the quartz boat containing S powder to a quartz hook with a magnet device and place it at the edge of another heating zone. Both ends of the double temperature zones are sealed with asbestos furnace plugs.
[0037] 3) Place the mica with the precursor in the middle of the heating zone of the tube furnace, and place the cut silicon wafers on the same quartz boat into the deposition area of the quartz tube with a diameter of 25 mm; 4) Wrap the quartz tube with the asbestos furnace plugs at both ends of the double temperature zone and assemble the flange parts at both ends; 5) Turn on the argon flowmeter gas purge switch. At this time, argon gas blown from the silicon wafer to the precursor is introduced into the tube. High-purity argon gas is sent into the quartz tube at a flow rate of 1200 sccm to discharge the impurity gas in the tube. Continue for 5 minutes; 6) After the purge is completed, the argon gas flow is set to 100 sccm, and the temperature is raised and kept in the tube furnace until the growth is completed and then naturally cooled to room temperature, and the gas flow is maintained at 100 sccm; 7) Set the heating parameters of the dual temperature zones. The heating rate of the WS2 temperature zone is 26.4℃·min -1 The heating rate of the S powder temperature zone is 4.4℃·min -1When the WS2 temperature zone reaches 1190 °C and the S temperature zone reaches 250 °C, the temperature is kept constant and the airflow direction is changed. Argon gas is blown from the precursor to the silicon wafer. After 45 seconds of positive airflow growth, the quartz boat containing S powder is pushed into the S temperature zone at a temperature of 250 °C by a quartz hook with a magnet device. Growth continues for 1 minute and 20 seconds. The growth argon gas flow size is 100 sccm. The quartz hook with a magnet device is: a quartz hook with a length of 10 cm, the end of which is fixed with a high-temperature resistant raw tape and a strong magnet with a size of 15 mm*10 mm*5 mm. Another magnet is used outside the quartz tube to control the quartz hook to drive the quartz tube containing S powder to move inside the tube.
[0038] 8) After the reaction is completed and the mixture is naturally cooled to room temperature, the growth substrate is taken out to complete the preparation, and WS2 homojunctions with various morphologies can be obtained.
[0039] The performance of the WS2 homojunction obtained in Example 1 was tested and the following results were obtained: Figure 3-8 Performance table shown.
[0040] Figure 3 Optical photograph of the prepared single-layer WS2 homojunction.
[0041] Figure 4 This is the photoluminescence scan of the single-layer WS2 homojunction. Figure 4 It can be shown that the Raman response of the single-layer WS2 gradually increases from the edge to the center, and the layer number-dependent second-order Mode enhancement.
[0042] Figure 5 This is the Raman scan of the single-layer WS2 homojunction. Figure 5 It can be seen that the PL response is enhanced from the edge to the center, the luminescence is enhanced, and the optoelectronic performance is significantly improved.
[0043] Figure 6 This is the AFM scan of the single-layer WS2 homojunction. Figure 6 It can be seen that the sample is a uniform single layer WS2 with a thickness of about 0.75 nm.
[0044] Figure 7 This is the Raman spectrum test image of the single-layer WS2 homojunction. The Raman peaks from the edge to the center are basically consistent with the Raman peaks of the single-layer two-dimensional tungsten sulfide. and Located at 350 cm -1 and 418 cm -1 .
[0045] Figure 8This is the PL single spectrum test diagram of the single-layer WS2 homojunction. The PL peak from the edge to the center is around 628 nm, which is consistent with the PL peak of the single-layer WS2, and gradually increases from the edge to the center.
[0046] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that sulfur powder is not added into the temperature rising zone B3, and the other conditions are the same as those of Example 1.
[0047] The single spectrum of photoluminescence from the edge to the center of the monolayer WS2 is measured, and the results are as follows Fig. 9 As shown. Fig. 9 It can be seen that the strength of the single layer prepared without adding S powder is basically the same from the edge to the center, and no enhancement occurs.
[0048] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that sulfur powder is added to the temperature rising zone B3, but in step 7), the temperature of the S powder temperature zone is set to 300 degrees Celsius, and the rest is the same as Example 1.
[0049] The optical microscope image of WS2 obtained by measurement is as follows Fig.10 As shown. Fig.10 It can be seen that the second layer of WS2 is not completely uniformly grown on the single layer of WS2. Since the temperature of the S powder temperature zone is too high, the evaporation rate of the S source is increased, and the flow speed in the deposition area is too fast, which is not conducive to the stable preparation of the WS2 homojunction. Therefore, an incomplete WS2 homojunction is prepared, which is not conducive to the preparation of optoelectronic and electronic devices.
[0050] Comparative Example 3 Compared with Example 1, Comparative Example 3 has the following differences: In step 7), when the WS2 temperature zone reaches 1190°C and the S temperature zone reaches 250°C, the air flow direction is changed. At this time, the quartz boat containing S powder is pushed into the S temperature zone with a temperature of 250°C through a quartz hook with a magnet device. The WS2 temperature zone and the S temperature zone evaporate at the same time. After growing for 2 minutes, the insulation is stopped and the tube furnace is naturally cooled to room temperature. The rest is the same as in Example 1.
[0051] The optical microscope image of WS2 obtained by measurement is as follows Fig.11 As shown. Fig.11 It can be seen that under the comparative example conditions, the number of WS2 nuclei prepared increases, the edge deposition of the sample is too thick, and after the WS2 precursor and the S precursor evaporate, they are simultaneously transferred to the deposition area by argon gas in the tube. Under high temperature and high pressure, the high concentration of precursors causes the sample deposition to be too thick, which is not conducive to the preparation of the WS2 homojunction.
[0052] A person skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of protection of the present application is limited to these examples. In line with the concept of the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.
[0053] One or more embodiments of the present application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the present application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present application should be included in the protection scope of the present application.
Claims
1. A method for preparing a tungsten disulfide homojunction, characterized in that: Tungsten disulfide is placed in the central area of the heating zone A of the double-zone tubular furnace, sulfur powder is placed at the edge of the heating zone B of the double-zone tubular furnace, and the substrate is placed in the deposition area of the double-zone tubular furnace; inert gas is introduced from the substrate to the heating zone to remove the impurity gas in the double-zone tubular furnace; the temperature is increased, and after the temperature of the heating zone A reaches 1180-1200 ℃ and the temperature of the heating zone B reaches 240-260 ℃, the airflow direction of the inert gas is changed, and tungsten disulfide begins to be deposited. After a period of deposition, the sulfur powder is pushed into the central area of the heating zone B and the deposition continues to obtain a tungsten disulfide homojunction.
2. The preparation method according to claim 1, characterized in that: After the temperature of the heating zone A reaches 1190°C and the temperature of the heating zone B reaches 250°C, the gas flow direction of the inert gas is changed.
3. The preparation method according to claim 1, characterized in that: The weight ratio of the tungsten disulfide to the sulfur powder is 15:
2.
4. The preparation method according to claim 1, characterized in that: The heating rate of the heating zone A is 26.4°C·min -1 The heating rate of the heating zone A is 5.5°C·min -1 .
5. The preparation method according to claim 1, characterized in that: Tungsten disulfide begins to deposit. After 45 seconds, sulfur powder is pushed into the central area of the heating zone B and continues to deposit for 80 seconds.
6. The preparation method according to claim 1, characterized in that: The inert gas is argon.
7. The preparation method according to claim 1, characterized in that: The method for pushing the sulfur powder into the central area of the temperature rising zone B is that the sulfur powder is placed on a quartz boat, the quartz boat is connected to a quartz hook with a magnet, and the sulfur powder can be moved by moving the magnet with a magnetic device.
8. The preparation method according to claim 1, characterized in that: Inert gas is introduced from the substrate to the heating zone, and the gas flow rate for removing impurity gas in the dual-temperature zone tubular furnace is 1200 sccm. After the impurity gas in the dual-temperature zone tubular furnace is removed, gas is continuously introduced at a gas flow rate of 100 sccm.
9. A tungsten disulfide homojunction, characterized in that: The method is adopted as claimed in any one of claims 1 to 8.
10. An application of the tungsten disulfide homojunction as claimed in claim 9, characterized in that: The tungsten disulfide homojunction is used to prepare transistors, photodetectors or devices in the field of torsional electronics.