A WS based on rare earth ion co-doping technology 2 (Er 3+ +Yb 3+ ) / WSe 2 (Er 3+ +Yb 3+ ) Photodetector

Abstract

The present application discloses a WS based on rare earth ion co-doping technology. 2 (Er 3+ +Yb 3+ ) / WSe 2 (Er 3+ +Yb 3+ ) optical detector, involving two-dimensional material rare earth ion co-doping technology and two-dimensional material micro-area fixed-point transfer technology, using the micro-area fixed-point transfer method to transfer WS synthesized by chemical vapor deposition 2 (Er 3+ +Yb 3+ ) layer was successfully transferred to WSe 2 (Er 3+ +Yb 3+ ) surface, and WS 2 (Er+Yb) / WSe 2 (Er+Yb)vdW heterojunction; the surface is successively spin-coated with LOR photoresist and S1805 photoresist, and soft-baked respectively, to obtain sample 1, and laser direct writing is performed on the selected area of ​​the sample 2, and the deteriorated photoresist is removed by developer, and sample 3 is obtained after cleaning, and sample 3 is plated with chromium and gold by magnetron sputtering technology to obtain sample 4, sample 4 is immersed in acetone to dissolve the photoresist, and the excess metal layer is peeled off under a microscope to obtain a van der Waals heterojunction electrode device. Therefore, the present application provides a WS based on rare earth ion co-doping technology 2 (Er 3+ +Yb 3+ ) / WSe 2 (Er 3+ +Yb 3+ ) photodetector, increasing the rare earth doping concentration of the two-dimensional material and obtaining excellent WS 2 (Er 3+ +Yb 3+ ) and WSe 2 (Er 3+ +Yb 3+ ) Photoelectric properties of two-dimensional semiconductor materials.

Description

Technical Field

[0001] The present invention relates to the rare earth ion co-doping technology of two-dimensional materials and the field of two-dimensional material micro-region fixed-point transfer technology, and more particularly to a WS2 (Er2O3) based on the rare earth ion co-doping technology. 3+ +Yb 3+ ) / WSe2(Er 3+ +Yb 3+ ) light detector. Background Art

[0002] With the first preparation of graphene, the concept of two-dimensional materials was formally proposed. However, due to the zero bandgap characteristics of graphene, its application in transistors is limited. In order to solve this problem, various graphene-like semiconductor materials are constantly being explored. Among them, transition metal dichalcogenides (TMDs) have become the most studied, most extensive, and most technologically mature type of two-dimensional semiconductor materials after graphene. TMDs material is a MX2-type monolayer semiconductor material, where M is a transition metal atom in the periodic table, such as Ti, Zr, Hf in the IV subgroup, V, Nb, Ta in the V subgroup, Mo and W in the VI subgroup, Tc and Re in the VII subgroup, Co, Rh, Ir in the IX subgroup, and Ni, Pd, Pt in the X subgroup; X is mostly a VI group element with abundant reserves on the earth, such as S, Se or Te. Typical TMDs materials include MoS2, WS2, MoSe2, etc.

[0003] The crystal structure of TMDs is stabilized by strong covalent bonds between "XMX", forming a sandwich-like structure with chalcogens on the upper and lower layers and transition metal atoms in the middle, and the layers are stacked by weak van der Waals forces. The phase structure of TMDs plays a decisive role in its physical and chemical properties. Currently, the common structural elements are divided into two types: 1H (semiconducting) and 1T (metallic). TMDs have thin layers, transparency and flexibility that are almost similar to graphene, but they have adjustable band gaps, high carrier mobility and high switching ratios. Because most two-dimensional TMDs are semiconductor materials, they have application potential in the preparation of ultra-small and low-power transistors. Compared with graphene transistors, transistors based on TMDs have higher photoelectric conversion efficiency, lower dark current and higher switching ratio.

[0004] However, the performance of a single two-dimensional semiconductor material is too single. In recent years, van der Waals heterojunctions composed of basic monolayer TMDs have attracted extensive research attention due to their unique electronic and optoelectronic properties related to their two-dimensional crystal structure and atomic-level layer thickness. Van der Waals heterojunctions show great potential in light detection applications because they have the advantage of built-in potential and are not restricted by strict lattice matching, which is conducive to higher freedom in material selection. Generally, the optical properties and band gap of two-dimensional TMDs change with the number of layers (thickness). Their single-layer materials have direct band gaps and have high luminescence efficiency and photoelectric conversion efficiency.

[0005] However, TMDs materials still face some challenges and shortcomings in practical applications:

[0006] Difficulty in preparing van der Waals heterojunctions: Currently, the preparation of van der Waals heterojunctions mostly adopts the mechanical exfoliation method, which is to obtain thinner materials by exfoliating bulk materials and then transfer them to make heterojunctions. The thickness is generally tens or even hundreds of nanometers. This is because the mechanical exfoliation method cannot control the thickness and size of the material. Although chemical vapor deposition (CVD) is considered to be one of the most promising methods for synthesizing large-scale two-dimensional materials to meet the requirements of large-scale and high-end applications, the photoelectric conversion efficiency of pure TMDs thin film semiconductor materials grown based on CVD is low, and it is difficult to obtain high-response photoelectric conversion performance. In addition, the preparation of van der Waals heterojunctions involves a complex thin film material transfer process, especially in the transfer of single-atomic layer materials, which is difficult: on the one hand, the transfer process is easy to damage the transferred single-atomic layer material, and on the other hand, it is easy for the transfer medium to remain, affecting the subsequent device effect.

[0007] High-density defect problem during CVD growth of two-dimensional materials: The CVD method inevitably produces high-density defects, which usually lead to a sharp decline in crystal quality and thus serious degradation of device performance. In addition, the atomic-level thickness of two-dimensional materials also means that the absorption rate and material gain are very limited. Chemical doping is often used to adjust the function of semiconductors through doping type and band structure modulation.

[0008] The problem of limited physical doping space of two-dimensional materials: Rare earth (RE) ions have been shown to be useful as structural modifiers in two-dimensional materials due to their rich excitation energy levels and unique 4f electron transition characteristics. However, due to the limited physical doping space of two-dimensional thin film materials, it is often difficult to obtain a sufficiently high rare earth ion doping concentration. Therefore, how to increase the doping concentration of two-dimensional materials is an important problem currently faced. In-situ rare earth doping in two-dimensional van der Waals heterojunctions is still in its early stages. Summary of the invention

[0009] The purpose of this application is to provide a WS2 (Er 3++Yb 3+ ) / WSe2(Er 3+ +Yb 3+ ) photodetector, which solves the technical problems in the prior art of how to increase the rare earth doping concentration of two-dimensional materials and how to dope rare earths in van der Waals heterojunctions.

[0010] The present application discloses a WS2 (Er2O3) based on rare earth ion co-doping technology. 3+ +Yb 3+ ) / WSe2(Er 3+ +Yb 3+ ) Photodetector, characterized in that it comprises the following preparation steps:

[0011] Step 1, using deionized water, acetone, and anhydrous ethanol to ultrasonically clean the SiO2 / Si silicon wafer in sequence, with each cleaning time being 5 minutes, 10 minutes, 10 minutes, and 5 minutes respectively, and finally blowing it dry with nitrogen; using a two-temperature zone tubular furnace to carry out a chemical vapor deposition reaction, placing sulfur powder or selenium powder in temperature zone I, placing tungsten oxide powder, sodium chloride catalyst, erbium chloride, and ytterbium chloride dopant in temperature zone II, and obtaining a single-layer substrate with a WS2 (Er+Yb) layer and a single-layer substrate with a WSe2 (Er+Yb) layer;

[0012] Step 2, prepare PMMA solution and solid PDMS, use micro-area fixed-point transfer method to coat the PMMA solution on a single-layer substrate with a WS2 (Er + Yb) layer grown on it and heat it to obtain a single-layer substrate with a WS2 (Er + Yb) layer grown on it coated with a cured PMMA film, use sodium hydroxide solution to assist in curing the PMMA film and the WS2 (Er + Yb) layer to separate from the substrate to obtain a PMMA film-WS2 (Er + Yb) layer, use a PDMS transfer method to transfer the PMMA film-WS2 (Er + Yb) layer to another single-layer substrate with a WSe2 (Er + Yb) layer grown on it to form a vertical van der Waals heterojunction; then soak and clean the PMMA layer in acetone to leave a bonded WS2 (Er + Yb) / WSe2 (Er + Yb) van der Waals heterojunction.

[0013] Step 3: Prepare a van der Waals heterojunction electrode device.

[0014] Preferably, in step 3, the process of preparing the van der Waals heterojunction electrode device is as follows: the surface of the WS2(Er+Yb) / WS e2(Er+Yb) van der Waals heterojunction is successively spin-coated with LOR photoresist and S1805 photoresist, and soft-baked respectively to obtain sample one after soft-baked photoresist, and then laser direct writing is performed on a selected area of ​​sample one to transfer the electrode pattern to sample one, and the obtained sample two is subjected to developer to remove the deteriorated LOR photoresist and S1805 photoresist, and sample three is obtained after cleaning, and sample three is plated with chromium and gold by magnetron sputtering technology to obtain sample four, sample four is immersed in acetone to dissolve the LOR photoresist and S1805 photoresist, and the excess metal layer is peeled off under a microscope to obtain a van der Waals heterojunction electrode device.

[0015] Preferably, in step 1, the specific steps of performing chemical vapor deposition reaction by means of a two-temperature zone tube furnace to obtain a single-layer substrate with a WS2 (Er+Yb) layer and a single-layer substrate with a WSe2 (Er+Yb) layer are as follows:

[0016] Step 1.1, spread sulfur powder or selenium powder on the bottom of a corundum boat and put it into temperature zone I, spread tungsten oxide powder, sodium chloride catalyst, erbium chloride and ytterbium chloride dopant on the bottom of another corundum boat and put it into temperature zone II, and put the SiO2 / Si silicon wafer after ultrasonic cleaning upside down on the corundum boat in temperature zone II;

[0017] Step 1.2, after the sulfur powder or selenium powder, tungsten oxide powder, sodium chloride catalyst, erbium chloride and ytterbium chloride dopant are placed, the quartz tube is sealed, the air inlet valve and the air outlet valve are closed, and the air pressure in the quartz tube is evacuated to vacuum (<1Pa), and then the air inlet valve is opened to fill the quartz tube to standard atmospheric pressure with argon gas at a flow rate of 300sccm, and then the argon gas flow rate is maintained at 66sccm, and the air outlet valve is opened to maintain normal gas flow in the tube;

[0018] Step 1.3, adjust the temperature of temperature zone I and temperature zone II. When temperature zone II is heated to 950℃, the Ar gas introduced is maintained at a flow rate of 66sccm. Two minutes before reaching 950℃, the Ar gas is replaced with an argon-hydrogen mixture of Ar90% and H210%, and the flow rate is maintained at 66sccm for reaction for 10 minutes. After 10 minutes, a single-layer substrate with a WS2(Er+Yb) layer and a single-layer substrate with a WSe2(Er+Yb) layer are obtained. The argon-hydrogen mixture is replaced with Ar gas. The single-layer substrate with a WS2(Er+Yb) layer and the single-layer substrate with a WSe2(Er+Yb) layer are naturally cooled to room temperature in 66sccm Ar gas. After reaching room temperature, the carrier gas is turned off, and the single-layer substrate with a WS2(Er+Yb) layer and the single-layer substrate with a WSe2(Er+Yb) layer are taken out.

[0019] Preferably, in step 1.3, when preparing a single-layer substrate with a WS2 (Er + Yb) layer grown on it, the specific steps for adjusting the stability of temperature zones I and II are as follows: temperature zone I is maintained at room temperature, and the temperature is increased at 50 minutes, reaching 200°C at 70 minutes, and the temperature is maintained for 10 minutes, and then the temperature is lowered; temperature zone II is set to be heated to 950°C at 70 minutes under room temperature; when temperature zone II is heated to 150°C, the air inlet valve and the air outlet valve are closed, and the air pressure in the quartz tube is evacuated to vacuum (<1Pa), and then the air inlet valve is opened and argon gas is used at a flow rate of 300sccm to inflate the quartz tube to standard atmospheric pressure, and then the argon gas flow rate is maintained at 66sccm, the air outlet valve is opened to maintain normal gas flow in the tube, and the temperature is increased to 950°C and maintained for 10 minutes, and then the temperature is lowered.

[0020] Preferably, in step 1.3, when preparing a single-layer substrate with a WSe2(Er+Yb) layer grown on it, the specific steps for adjusting the stability of temperature zones I and II are as follows: temperature zone I is maintained at room temperature, and the temperature is increased at 50 minutes, reaching 380°C at 70 minutes, and the temperature is maintained for 10 minutes, and then the temperature is lowered; temperature zone II is set to be heated to 950°C at 70 minutes under room temperature; when temperature zone II is heated to 150°C, the air inlet valve and the air outlet valve are closed, and the air pressure in the quartz tube is evacuated to vacuum (<1Pa), and then the air inlet valve is opened and argon gas with a flow rate of 300sccm is used to inflate the quartz tube to standard atmospheric pressure, and then the argon gas flow rate is maintained at 66sccm, and the air outlet valve is opened to maintain normal gas flow in the tube, and the temperature is increased to 950°C and maintained for 10 minutes, and then the temperature is lowered.

[0021] Preferably, the specific steps of coating the PMMA solution on a single-layer substrate with a WS2(Er+Yb) layer grown thereon and heating to obtain a single-layer substrate with a WS2(Er+Yb) layer grown thereon and coated with a cured PMMA film are as follows: first, use a dropper to evenly spin-coat the prepared PMMA solution on the single-layer substrate with a WS2(Er+Yb) layer grown thereon, and set the rotation speed to 500 rpm for 5 s and 3500 rpm for 35 s; then, transfer the spin-coated single-layer substrate with a WS2(Er+Yb) layer grown thereon to a heating table, heat at 80°C for 10 s to cure the PMMA film layer, and obtain a single-layer substrate with a WS2(Er+Yb) layer grown thereon and coated with a cured PMMA film.

[0022] Preferably, the specific steps of using sodium hydroxide solution to assist the solidification of PMMA film and WS2 (Er + Yb) layer to separate from the substrate to obtain PMMA film-WS2 (Er + Yb) layer are as follows: cut the single-layer substrate coated with a solidified PMMA film and grown with a WS2 (Er + Yb) layer into small pieces, immerse them in a sodium hydroxide solution at 80°C, heat for 10 minutes, assist the solidification of PMMA film and WS2 (Er + Yb) layer to separate from the substrate, and obtain PMMA film-WS2 (Er + Yb) layer; use a clean glass slide to fish out the PMMA film-WS2 (Er + Yb) layer, and soak it in deionized water for 10 minutes to wash away the sodium hydroxide solution.

[0023] Preferably, the PMMA film-WS2(Er+Yb) layer is transferred to another single-layer substrate with a WSe2(Er+Yb) layer grown thereon by a PDMS transfer method to form a vertical van der Waals heterojunction; then the PMMA layer is soaked and cleaned off in acetone to leave the bonded WS2(Er+Yb) / WSe2(Er+Yb) heterojunction. The specific steps are as follows: after cutting the configured solid PDMS, clamp the solid PDMS with tweezers, vertically lower one side of the PMMA film attached to the PMMA film-WS2(Er+Yb) layer, fish it out, and then attach the side with the solid PDMS facing down to a transparent glass slide, which is fixed on a three-dimensional rotating table, and then place another single-layer substrate with a WSe2(Er+Yb) layer grown thereon on the lower transfer rack of the transfer platform, and observe the solid PDMS attached thereto under a microscope. The PMMA film-WS2(Er+Yb) layer with solid PDMS and the single-layer substrate with WSe2(Er+Yb) layer are positioned, and finally the PMMA film-WS2(Er+Yb) layer with solid PDMS on the upper transfer rack is dropped onto the single-layer substrate with WSe2(Er+Yb) layer for bonding using the displacement screw rod in the vertical direction. Then, the solid PD MS on the PMMA film-WS2(Er+Yb) layer with solid PDMS is separated and bonded with the single-layer substrate with WSe2(Er+Yb) layer to form a vertical van der Waals heterojunction. The mixture is then dried at 80°C for 1h, and soaked in acetone for 3-5min to remove the PMMA film to obtain a bonded WS2(Er+Yb) / WSe2(Er+Yb) van der Waals heterojunction.

[0024] Preferably, a selected area of ​​sample one is subjected to laser direct writing to transfer the electrode pattern to sample one, and the obtained sample two is subjected to developer to remove the deteriorated LOR photoresist and S1805 photoresist, and is cleaned to obtain sample three, and sample three is plated with chromium and gold by magnetron sputtering technology to obtain sample four, sample four is immersed in acetone to dissolve the photoresist, and the excess metal layer is peeled off under a microscope to obtain a van der Waals heterojunction electrode device. The specific steps are as follows: laser direct writing is performed on a selected area of ​​sample one, and the electrode channel size is 20μm×30μm, and the properties of the LOR photoresist and the S1805 photoresist are changed after exposure, thereby transferring the electrode pattern to sample one, and the obtained sample two is developed in AZ300 developer for 60S , remove the deteriorated LOR photoresist and S1805 photoresist, rinse with deionized water, remove the residual developer, and finally blow dry with N2 to obtain sample three. Use a sputtering coater for magnetron sputtering. The metal electrodes are chromium and gold with thicknesses of 5nm and 50nm respectively to obtain sample four. Sample four is immersed in acetone for 20-30min, and the LOR photoresist and S1805 photoresist are dissolved to separate the metal layer outside the electrode. The electrode is peeled off under a microscope, and the remaining LOR photoresist and S1805 photoresist are dissolved with AZ400 developer, and then cleaned with anhydrous ethanol, and finally gently rinsed with deionized water, and the surface moisture is blown off with N2 and then dried to obtain a van der Waals heterojunction electrode device.

[0025] Preferably, the surface of the WS2(Er+Yb) / WSe2(Er+Yb) heterojunction is successively spin-coated with LOR photoresist and S1805 photoresist, and soft-baked respectively, and the specific steps of obtaining sample one after soft-baked photoresist are as follows: use a glue spreader to spin-coat a first layer of LOR photoresist, the first stage speed of the glue spreader is 500rmp, and the time is 5S; the second stage speed is 3500rmp, and the time is 35s; then the WS2(Er+Yb) / WSe2(Er+Yb) heterojunction with the first layer of LOR photoresist spin-coated is baked on a drying platform at a temperature of 170°C for 10min to remove excess moisture in the photoresist and increase the adhesion of the photoresist to the substrate; then use a glue spreader to spin-coat a second layer of S1805 photoresist, the first stage of the glue spreader is a speed of 500rmp, and the time is 5S; the second stage is a speed of 2000rmp, and the time is 25s; then it is baked on a drying platform at a temperature of 100°C for 10min.

[0026] Therefore, the present application adopts the above-mentioned WS2 (Er 3+ +Yb 3+ ) / WSe2(Er 3+ +Yb 3+ ) light detector, has the following beneficial effects:

[0027] (1) Using rare earth Er 3+ and Yb3+ Ion co-doping technology, using rare earth Er 3+ and Yb 3+ Ion pair W 4+ The competitive effect of ion position occupation enables high-concentration in-situ doping of WS2 (Er) based on CVD technology. 3+ +Yb 3+ ) and WSe2(Er 3+ +Yb 3+ ) The two-dimensional material was successfully prepared, and the overall rare earth ion doping concentration reached a level close to 20at%, which is much higher than the level of about 1-3at% reported in previous academic reports.

[0028] (2) By increasing the rare earth doping concentration of the two-dimensional material, excellent WS2 (Er 3+ +Yb 3+ ) and WSe2(Er 3+ +Yb 3+ ) Photoelectric properties of two-dimensional semiconductor materials. Since rare earth ions have very rich 4f energy levels, the number of electrons in their 4f energy levels reaches 12-14, and these electrons can easily become free electrons by absorbing the energy of radiation photons, rare earth Er 3+ , Yb 3 + The higher the concentration of plasma, the higher the concentration of photogenerated electron-hole pairs generated under illumination conditions, and thus the greater the photocurrent. Secondly, the two-dimensional materials WS2 and WSe2 in this application are single crystal film materials with high crystal quality, very short electron transit time, and long hole transit time, combined with high concentration of electron density, resulting in high gain of the material, that is, the external quantum efficiency of the material far exceeds 100%. These characteristics lead to excellent optoelectronic properties of the material, which are specifically manifested in the very high light responsiveness of the material (can be applied to weak light detection), high external quantum efficiency (extremely high photoelectric conversion efficiency), and high specific detection rate (extremely high sensitivity).

[0029] (3) Using the micro-area fixed-point transfer method, WS2 (Er 3+ +Yb 3+ ) layer was successfully transferred to WSe2(Er 3+ +Yb 3+ ) surface layer, and prepared WS2(Er 3+ +Yb 3+ ) / WSe2(Er 3+ +Yb 3+ ) van der Waals heterojunction composite materials; then based on the traditional micro-nano processing technology, silicon-based WS2 (Er 3+ +Yb 3+ ) / WSe2(Er 3+ +Yb3 + )Vertical van der Waals heterojunction photodetector, and tested to obtain good detector performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A two-temperature zone quartz tube in the preparation process of a single-layer substrate with a WS2 (Er+Yb) layer and a single-layer substrate with a WSe2 (Er+Yb) layer;

[0031] Figure 2 The temperature and gas flow rate setting diagram of the equipment system during the preparation process of a single-layer substrate with a WS2 (Er + Yb) layer and a single-layer substrate with a WSe2 (Er + Yb) layer;

[0032] Figure 3 Optical micrographs and corresponding atomic force micrographs of the prepared WS2(Er+Yb) layer and WSe2(Er+Yb) layer; wherein a is an optical micrograph of the WS2(Er+Yb) two-dimensional single crystal material, b is an optical micrograph of the WSe2(Er+Yb) two-dimensional single crystal material, c is an atomic force micrograph of the WS2(Er+Yb) two-dimensional single crystal material, and d is an atomic force micrograph of the WSe2(Er+Yb) two-dimensional single crystal material;

[0033] Figure 4 EDS spectra and element atomic distribution diagrams of WS2(Er+Yb) and WSe2(Er+Yb) two-dimensional single crystal thin film materials; wherein, a is the EDS spectrum and element atomic distribution diagram of WS2(Er+Yb) two-dimensional single crystal thin film material; b is the EDS spectrum and element atomic distribution diagram of WSe2(Er+Yb) two-dimensional single crystal thin film material;

[0034] Figure 5 It is a technical flow chart of the micro-area fixed-point transfer method;

[0035] Figure 6 This is an optical micrograph of the WS2(Er+Yb) / WSe2(Er+Yb) heterojunction prepared by the micro-area fixed-point transfer method;

[0036] Figure 7 Raman spectra obtained from experimental tests of different regions of the WS2(Er+Yb) / WSe2(Er+Yb) heterojunction;

[0037] Figure 8 Optical micrograph of WS2(Er+Yb) / WSe2(Er+Yb) heterojunction device.

[0038] Fig. 9The IV curves of WS2(Er+Yb) / WSe2(Er+Yb) heterojunction detectors under 635nm radiation light of different power densities;

[0039] Fig.10 This is the light power density dependence of the device photocurrent of the WS2(Er+Yb) / WSe2(Er+Yb) heterojunction detector under 635nm radiation light. DETAILED DESCRIPTION

[0040] Example 1

[0041] In the first stage, the preparation of a single-layer substrate with a WS2 (Er + Yb) layer and a single-layer substrate with a WSe2 (Er + Yb) layer is as follows:

[0042] Step 1, cleaning of substrate: put a beaker in the ultrasonic cleaning machine, lay the cut silicon wafer in the beaker, the size of the silicon wafer is 2cm long, 1cm wide, the oxide layer thickness is 300nm, and the pure silicon thickness is 500μm. Add cleaning agent to the beaker, and clean the substrate in the order of deionized water → acetone → anhydrous ethanol → deionized water. The cleaning time is set to 5min, 10min, 10min, 5min respectively. Finally, use a nitrogen gun to blow dry the cleaned substrate.

[0043] Step 2, use Figure 1 The tubular furnace with two temperature zones and a 2-inch diameter quartz tube as shown is used for chemical vapor deposition reaction to prepare a single-layer two-dimensional transition metal chalcogenide co-doped with erbium and ytterbium ions: the precursor sulfur (S) powder (120 mg, purity>99.5%) or selenium (Se) powder (110 mg, purity>99.5%) is evenly spread on the bottom of a corundum boat and placed at the center of temperature zone I at the upstream inlet of the tubular furnace, tungsten oxide (WO3) powder (60 mg, purity>99.5%), catalyst sodium chloride (NaCl) powder (4 mg, purity>99.99%) and dopant erbium chloride (ErCl3) and ytterbium chloride (YbCl3) powder (6 mg:6 mg, purity>99.9%) are evenly mixed and spread on the bottom of another corundum boat, the substrate washed and dried in step one is turned upside down on the corundum boat in temperature zone II, and the corundum boat is pushed into the center of temperature zone II at the downstream outlet of the tubular furnace;

[0044] Step 3: After the reactants are placed, the quartz tube is sealed, the inlet valve and the outlet valve are closed, and the air pressure in the quartz tube is evacuated to vacuum (<1Pa). Then, the inlet valve is opened and argon (Ar) with a flow rate of 300 sccm is used to fill the quartz tube to standard atmospheric pressure. The argon flow rate is then maintained at 66 sccm, and the outlet valve is opened to maintain normal gas flow in the tube.

[0045] Step 4: When preparing a single-layer substrate with a WS2 (Er+Yb) layer, set the temperature parameters of the tube furnace: the heating curve is as follows: Figure 2 , temperature zone I is kept at room temperature, starts to heat up at 50 minutes, reaches 200℃ at 70 minutes, maintains this temperature for 10 minutes, and then starts to cool down. Temperature zone II is set to heat up to 950℃ at room temperature at 70 minutes, maintains 10 minutes, and then starts to cool down. During this period, when the temperature zone II heats up to 150℃, the air inlet valve and the air outlet valve are closed, and step three is repeated to perform a vacuum (<1Pa) to remove water vapor and impurities generated by heating in the quartz tube.

[0046] Step 5: When preparing a single-layer substrate with a WSe2(Er+Yb) layer, set the temperature parameters of the tube furnace: the heating curve is as follows: Figure 2 . Temperature zone I is kept at room temperature, and the temperature is raised at 50 minutes. At 70 minutes, the temperature is 380℃, maintained for 10 minutes, and then the temperature is lowered, and it is lowered to room temperature at 95 minutes. Temperature zone II is set to rise to 950℃ at room temperature in 70 minutes, maintained for 10 minutes, and then lowered to room temperature. During this period, when the temperature zone II rises to 150℃, the air inlet valve and the air outlet valve are closed, and step 3 is repeated to perform a vacuum (<1Pa) to remove water vapor and impurities generated by heating in the quartz tube.

[0047] Step 6: When the temperature in temperature zone II is raised to the maximum reaction temperature of 950°C, the Ar gas is introduced at a flow rate of 66 sccm. Two minutes before reaching 950°C, the Ar gas is replaced with an argon-hydrogen mixed gas (Ar 90%, H2 10%) at about 900°C. The reaction is maintained at a flow rate of 66 sccm for 10 minutes.

[0048] Step 7, after keeping the temperature in zone II at 950℃ for 10 minutes, replace the argon-hydrogen mixed gas with Ar gas, and cool the single-layer substrate with WS2(Er+Yb) layer and the single-layer substrate with WSe2(Er+Yb) layer to room temperature in 66sccm Ar gas naturally. After reaching room temperature, turn off the carrier gas, take out the single-layer substrate with WS2(Er+Yb) layer and the single-layer substrate with WSe2(Er+Yb) layer. Typical optical microscope pictures of the synthesized materials and the corresponding atomic force microscope pictures of the materials are shown in Figure 1. Figure 3 As shown in the figure. The optical micrograph shows that the material has a regular triangular or hexagonal morphology, showing the single crystal characteristics of the material; the atomic force micrograph reflects the single atomic layer thickness characteristics of the thin film material. X-ray energy dispersive spectrometry (EDS) was further used to test the element type, content, and micro-area distribution of the material. The results are shown in the figure. Figure 4 The EDS spectrum shows that the total content of Er and Y atoms is about 20 at% of the sum of the three metal element atoms Er+Yb+W, reflecting an extremely high doping concentration.

[0049] The second stage is the preparation of WS2(Er+Yb) / WSe2(Er+Yb) heterojunction. The preparation diagram is shown in Figure 5 shown.

[0050] Step 1, prepare PMMA solution: 9.4 g of ethyl lactate and 0.6 g of polymethyl methacrylate are placed in the center of a magnetic stirrer, the speed is set to 600 rpm, and the mixture is rotated and stirred for 72 h until the particles are dissolved to obtain a PMMA solution with a concentration of 6%.

[0051] Step 2, prepare solid PDMS: 10 ml of 184-silicone rubber main agent (A), 4 ml of 184-silicone rubber curing agent (B), stir evenly and pour into a container, put it into a vacuum tank and repeatedly evacuate 3-5 times until the bubbles in the mixed liquid disappear. Then heat at 120°C for 30 minutes until the PDMS solidifies.

[0052] Step 3, the preparation of WS2(Er+Yb) / WSe2(Er+Yb) heterojunction adopts micro-area fixed-point transfer method: first, use a dropper to evenly spin-coat the PMMA solution on the single-layer substrate with the WS2(Er+Yb) layer grown, and set the rotation speed to 500 rpm for 5 s and 3500 rpm for 35 s. Then, the single-layer substrate with the WS2(Er+Yb) layer grown after spin coating is transferred to a heating table, and heated at 80°C for 10 s to solidify the PMMA film layer, thereby obtaining a single-layer substrate with the WS2(Er+Yb) layer grown and coated with a cured PMMA film;

[0053] Step 4, use a knife to divide the solidified PMMA film layer into small cubes of 4mm×4mm in size, soak them in 80°C sodium hydroxide solution (100ml of deionized water, 8g of sodium hydroxide particles), heat them at 80°C for 10min, and the sodium hydroxide solution assists in solidifying the PMMA film and the WS2(Er+Yb) layer to separate from the substrate and float on the water surface to obtain the PMMA film-WS2(Er+Yb) layer. Use a clean glass slide to fish out the PMMA film-WS2(Er+Yb) layer, and soak it in deionized water for 10min to wash away the sodium hydroxide solution.

[0054] Step 5, cut the configured solid PDMS into 1cm×1cm size, clamp the solid PDMS with tweezers, vertically lower the side of the PMMA film attached to the PMMA film-WS2(Er+Yb) layer, fish it out, and then attach the side with the solid PDMS facing down to a transparent slide, fix the transparent slide on a three-dimensional rotating table, and then place another single-layer substrate with a WSe2(Er+Yb) layer on the lower transfer rack of the transfer platform, and use a microscope to observe the PMMA film-WS2(Er+Yb) layer attached to the solid PDMS and the PMMA film-WS2(Er+Yb) layer with the WSe2(Er +Yb) layer, and finally use the displacement screw rod in the vertical direction to drop the PMMA film-WS2(Er+Yb) layer with solid PDMS on the upper transfer rack to the single-layer substrate with WSe2(Er+Yb) layer for bonding, and then heat it to 75°C. After 10-25 minutes, carefully and slowly lift the upper transfer rack to lift the transparent slide. At this time, the solid PDMS on the PMMA film-WS2(Er+Yb) layer with solid PDMS is separated and bonded to the single-layer substrate with WSe2(Er+Yb) layer to form a vertical van der Waals heterojunction;

[0055] Step 6, after the vertical van der Waals heterojunction is left overnight, it is dried at 80°C for 1 hour, and then soaked in acetone for 3-5 minutes to remove the PMMA film, thereby obtaining a bonded WS2(Er+Yb) / WSe2(Er+Yb)vdW heterojunction. The prepared WS2(Er+Yb) / WSe2(Er+Yb)vdW heterojunction is as follows Figure 6 As shown, the thick bottom is characterized by atomic force microscopy, all of which are single-layer TMDs materials. Figure 7 The Raman spectra of WS2(Er+Yb) monolayer, WSe2(Er+Yb) monolayer, and WS2(Er+Yb) / WSe2(Er+Yb) heterojunction stack were characterized at selected points at different positions of the heterojunction material to further prove the successful preparation of the van der Waals heterojunction.

[0056] The third stage is the preparation of WS2(Er) / WSe2(Er) van der Waals heterojunction photodetector.

[0057] Step 1, spin coating: Use a spin coating machine to spin coat the first layer of LOR photoresist. The speed of the spin coating machine in the first stage is 500 rpm and the time is 5 s; the speed of the second stage is 3500 rpm and the time is 35 s.

[0058] Step 2, soft baking: The sample is baked on a drying platform at a temperature of 170°C for 10 minutes to remove excess moisture in the LOR photoresist and increase the adhesion of the LOR photoresist to the substrate.

[0059] Step 3, spin coating again: use a spin coating machine to spin coat a second layer of S1805 photoresist. The first stage of the spin coating machine has a rotation speed of 500 rpm and a time of 5 seconds; the second stage has a rotation speed of 2000 rpm and a time of 25 seconds.

[0060] Step 4, soft baking again: the sample is baked on a drying platform at a temperature of 100°C for 10 minutes, which has the same effect as the first soft baking.

[0061] Step 5, laser direct writing: Use the designed electrode pattern to write directly on the selected area of ​​the sample by laser, and the electrode channel size is 20μm×30μm. LOR photoresist and S1805 photoresist are organic substances whose properties change after exposure, so that the electrode pattern is transferred to the WS2(Er+Yb) / WSe2(Er+Yb) van der Waals heterojunction to obtain sample 2.

[0062] Step 6, development and fixing: Sample 2 was developed in AZ300 developer for 60 seconds. The developer can remove the deteriorated LOR photoresist and S1805 photoresist in the exposed part. Then, it was rinsed with deionized water to remove the residual developer. Finally, it was blown dry with high-purity N2 to obtain Sample 3.

[0063] Step 7, coating: Sample 3 is subjected to magnetron sputtering by a sputtering coating machine to obtain sample 4. In this experiment, the sputtered metal electrodes are chromium (Cr) and gold (Au), with thicknesses of 5 nm and 50 nm respectively.

[0064] Step 8, stripping and degumming: Soak sample 4 in acetone for 20-30 minutes. Acetone can dissolve the LOR photoresist and S1805 photoresist to separate the Au outside the electrode from the substrate. Stripping is performed under a microscope until the electrode is successfully stripped, and the remaining LOR photoresist and S1805 photoresist are dissolved with AZ400 developer (30S), then cleaned with anhydrous ethanol, and finally gently rinsed with deionized water, and the surface moisture of the sample is blown off with high-purity N2 and then baked to obtain a van der Waals heterojunction electrode device such as Figure 8 The device heterojunction position is irradiated with 635nm laser of different powers, and the photocurrent generated by the illumination is measured under a certain bias voltage, as shown in FIG. Figure 9-10 shown.

[0065] Therefore, the present application provides a WS2 (Er2O3) based on rare earth ion co-doping technology. 3+ +Yb 3+ ) / WSe2(Er 3+ +Yb 3+) photodetector, based on the CVD method, synthesized high-concentration erbium (Er) and ytterbium (Yb) co-doped WSe2 and WS2 single-layer materials, with a doping concentration of 20at%, thereby greatly reducing the defect density in the material synthesis process and greatly increasing the carrier concentration in the material. The micro-area fixed-point transfer technology was chosen to use the new idea of ​​building a CVD-grown single-layer rare earth co-doped two-dimensional transition metal chalcogenide on another single-layer rare earth co-doped two-dimensional transition metal chalcogenide, and successfully prepared a thin-layer van der Waals heterojunction. The photodetector device prepared based on this van der Waals heterojunction has extremely excellent photodetection performance, providing a new preparation method for the preparation of high-performance heterojunction photodetectors.

[0066] In the description of this specification, the description with reference to the terms "an experimental example", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the experimental example or example are included in at least one experimental example or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same experimental example or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more experimental examples or examples in a suitable manner.

[0067] Finally, it should be noted that the above experimental examples are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred experimental examples, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A WS2(Er2O3) based on rare earth ion co-doping technology 3+ +Yb 3+ ) / WSe2(Er 3+ +Yb 3+ ) a light detector, characterized in that The method comprises the following preparation steps: Step 1, using deionized water, acetone, and anhydrous ethanol to ultrasonically clean the SiO2 / Si silicon wafer in sequence, with each cleaning time being 5 minutes, 10 minutes, 10 minutes, and 5 minutes respectively, and finally blowing it dry with nitrogen; using a two-temperature zone tubular furnace to perform a chemical vapor deposition reaction to obtain a single-layer substrate with a WS2 (Er+Yb) layer grown thereon and a single-layer substrate with a WSe2 (Er+Yb) layer grown thereon; Step 2, prepare PMMA solution and solid PDMS, use micro-area fixed-point transfer method to coat the PMMA solution on a single-layer substrate with a WS2(Er+Yb) layer and heat to obtain a single-layer substrate with a WS2(Er+Yb) layer coated with a cured PMMA film, use sodium hydroxide solution to assist in curing the PMMA film and the WS2(Er+Yb) layer to separate from the substrate to obtain a PMMA film-WS2(Er+Yb) layer, use a PDMS transfer method to transfer the PMMA film-WS2(Er+Yb) layer to another single-layer substrate with a WSe2(Er+Yb) layer to form a vertical van der Waals heterojunction; then soak and clean the PMMA layer in acetone to leave a bonded WS2(Er+Yb) / WSe2(Er+Yb) van der Waals heterojunction; Step 3: Prepare a van der Waals heterojunction electrode device.

2. A WS2 (Er2O3) based on rare earth ion co-doping technology according to claim 1 3+ +Yb 3+ ) / WSe2(Er 3+ +Yb 3+ ) a light detector, characterized in that In step 3, the process of preparing the van der Waals heterojunction electrode device is as follows: the surface of the WS2(Er+Yb) / WSe2(Er+Yb) van der Waals heterojunction is successively spin-coated with LOR photoresist and S1805 photoresist, and soft-baked respectively to obtain sample one after soft-baked photoresist, and then laser direct writing is performed on a selected area of ​​sample one to transfer the electrode pattern to sample one, and the obtained sample two is subjected to developer to remove the deteriorated LOR photoresist and S1805 photoresist, and sample three is obtained after cleaning, and sample three is plated with chromium and gold by magnetron sputtering technology to obtain sample four, sample four is immersed in acetone to dissolve the LOR photoresist and S1805 photoresist, and the excess metal layer is peeled off under a microscope to obtain a van der Waals heterojunction electrode device.

3. A WS2 (Er2O3) based on rare earth ion co-doping technology according to claim 1 3+ +Yb 3+ ) / WSe2(Er 3+ +Yb 3+ ) a light detector, characterized in that In step 1, the specific steps of performing chemical vapor deposition reaction with the aid of a two-temperature zone tube furnace to obtain a single-layer substrate with a WS2 (Er+Yb) layer and a single-layer substrate with a WSe2 (Er+Yb) layer are as follows: Step 1.1, spread sulfur powder or selenium powder on the bottom of a corundum boat and put it into temperature zone I, spread tungsten oxide powder, sodium chloride catalyst, erbium chloride and ytterbium chloride dopant on the bottom of another corundum boat and put it into temperature zone II, and put the SiO2 / Si silicon wafer after ultrasonic cleaning upside down on the corundum boat in temperature zone II; Step 1.2, after the sulfur powder or selenium powder, tungsten oxide powder, sodium chloride catalyst, erbium chloride and ytterbium chloride dopant are placed, the quartz tube is sealed, the air inlet valve and the air outlet valve are closed, and the air pressure in the quartz tube is evacuated to vacuum (<1Pa), and then the air inlet valve is opened to fill the quartz tube to standard atmospheric pressure with argon gas at a flow rate of 300sccm, and then the argon gas flow rate is maintained at 66sccm, and the air outlet valve is opened to maintain normal gas flow in the tube; Step 1.3, adjust the temperature of temperature zone I and temperature zone II. When temperature zone II is heated to 950℃, the Ar gas introduced is maintained at a flow rate of 66sccm. Two minutes before reaching 950℃, the Ar gas is replaced with an argon-hydrogen mixture of Ar90% and H210%, and the flow rate is maintained at 66sccm for reaction for 10 minutes. After 10 minutes, a single-layer substrate with a WS2(Er+Yb) layer and a single-layer substrate with a WSe2(Er+Yb) layer are obtained. The argon-hydrogen mixture is replaced with Ar gas. The single-layer substrate with a WS2(Er+Yb) layer and the single-layer substrate with a WSe2(Er+Yb) layer are naturally cooled to room temperature in 66sccm Ar gas. After reaching room temperature, the carrier gas is turned off, and the single-layer substrate with a WS2(Er+Yb) layer and the single-layer substrate with a WSe2(Er+Yb) layer are taken out.

4. A WS2 (Er2O3) based on rare earth ion co-doping technology according to claim 3 3+ +Yb 3+ ) / WSe2(Er 3+ +Yb 3+ ) a light detector, characterized in that In step 1.3, when preparing a single-layer substrate with a WS2 (Er+Yb) layer grown on it, the specific steps for adjusting the stability of temperature zones I and II are as follows: temperature zone I is maintained at room temperature, and the temperature is increased at 50 minutes, reaching 200°C at 70 minutes, and the temperature is maintained for 10 minutes, and then the temperature is reduced. Temperature zone II is set to increase the temperature to 950°C at 70 minutes under room temperature. When temperature zone II is heated to 150°C, the inlet valve and the outlet valve are closed, and the air pressure in the quartz tube is evacuated to vacuum (<1Pa), and then the inlet valve is opened and argon gas with a flow rate of 300sccm is used to inflate the quartz tube to standard atmospheric pressure, and then the argon gas flow rate is maintained at 66sccm, and the outlet valve is opened to maintain normal gas flow in the tube. After the temperature is increased to 950°C, it is maintained for 10 minutes, and then the temperature is reduced.

5. The WS2 (Er2O3) based on rare earth ion co-doping technology according to claim 3 3+ +Yb 3+ ) / WSe2(Er 3+ +Yb 3+ ) a light detector, characterized in that In step 1.3, when preparing a single-layer substrate with a WSe2(Er+Yb) layer grown on it, the specific steps for adjusting the stability of temperature zones I and II are as follows: temperature zone I is maintained at room temperature, and the temperature is increased at 50 minutes, reaching 380°C at 70 minutes, and the temperature is maintained for 10 minutes, and then the temperature is lowered; temperature zone II is set to be heated to 950°C at 70 minutes under room temperature; when temperature zone II is heated to 150°C, the inlet valve and the outlet valve are closed, and the air pressure in the quartz tube is evacuated to vacuum (<1Pa), and then the inlet valve is opened and argon gas is used at a flow rate of 300sccm to inflate the quartz tube to standard atmospheric pressure, and then the argon gas flow rate is maintained at 66sccm, and the outlet valve is opened to maintain normal gas flow in the tube, and the temperature is increased to 950°C and maintained for 10 minutes, and then the temperature is lowered.

6. The WS2 (Er2O3) based on rare earth ion co-doping technology according to claim 1 3+ +Yb 3+ ) / WSe2(Er 3+ +Yb 3+ ) a light detector, characterized in that Using the micro-area fixed-point transfer method, the PMMA solution is coated on a single-layer substrate with a WS2(Er+Yb) layer grown thereon and heated to obtain a single-layer substrate with a WS2(Er+Yb) layer grown thereon and coated with a cured PMMA film. The specific steps are as follows: first, use a dropper to evenly spin-coat the prepared PMMA solution on the single-layer substrate with a WS2(Er+Yb) layer grown thereon, and the rotation speed is set to 500 rpm for 5 s and 3500 rpm for 35 s. Subsequently, the single-layer substrate with a WS2(Er+Yb) layer grown thereon after spin coating is transferred to a heating table, and heated at 80°C for 10 s to cure the PMMA film layer, thereby obtaining a single-layer substrate with a WS2(Er+Yb) layer grown thereon and coated with a cured PMMA film.

7. The WS2 (Er2O3) based on rare earth ion co-doping technology according to claim 1 3+ +Yb 3+ ) / WSe2(Er 3+ +Yb 3+ ) a light detector, characterized in that The specific steps of using sodium hydroxide solution to assist in solidifying the PMMA film and separating the WS2 (Er + Yb) layer from the substrate to obtain the PMMA film-WS2 (Er + Yb) layer are as follows: cut the single-layer substrate coated with the solidified PMMA film and grown with the WS2 (Er + Yb) layer into small pieces, immerse them in a sodium hydroxide solution at 80°C, heat for 10 minutes, assist in solidifying the PMMA film and WS2 (Er + Yb) layer from the substrate to obtain the PMMA film-WS2 (Er + Yb) layer, and use a clean glass slide to fish out the PMMA film-WS2 (Er + Yb) layer, and immerse it in deionized water for 10 minutes to wash away the sodium hydroxide solution.

8. The WS2 (Er2O3) based on rare earth ion co-doping technology according to claim 1 3+ +Yb 3+) / WSe2(Er 3+ +Yb 3 + ) a light detector, characterized in that The PMMA film-WS2(Er+Yb) layer is transferred to another single-layer substrate with a WSe2(Er+Yb) layer by using the PDMS transfer method to form a vertical van der Waals heterojunction; then the PMMA layer is soaked and cleaned in acetone to leave the bonded WS2(Er+Yb) / WSe2(Er+Yb) heterojunction. The specific steps are as follows: after cutting the configured solid PDMS, clamp the solid PDMS with tweezers, vertically lower the side of the PMMA film attached to the PMMA film-WS2(Er+Yb) layer, and after taking it out, stick the side with the solid PDMS facing down on a transparent glass slide, fix the transparent glass slide on a three-dimensional rotating stage, and then place another single-layer substrate with a WSe2(Er+Yb) layer on the lower transfer rack of the transfer platform, and observe the solid PDMS attached to the substrate under a microscope. The PMMA film-WS2(Er+Yb) layer of S and the single-layer substrate with WSe2(Er+Yb) layer are positioned, and finally the PMMA film-WS2(Er+Yb) layer with solid PDMS on the upper transfer rack is dropped onto the single-layer substrate with WSe2(Er+Yb) layer for bonding using the displacement screw rod in the vertical direction. Then the PMMA film-WS2(Er+Yb) layer with solid PDMS is heated to 75°C. After 10-25min, the solid PDMS on the PMMA film-WS2(Er+Yb) layer with solid PDMS is separated and bonded with the single-layer substrate with WSe2(Er+Yb) layer to form a vertical van der Waals heterojunction. The mixture is then dried at 80°C for 1h, and soaked in acetone for 3-5min to remove the PMMA film to obtain a bonded WS2(Er+Yb) / WSe2(Er+Yb) van der Waals heterojunction.

9. The WS2 (Er2O3) based on rare earth ion co-doping technology according to claim 2 3+ +Yb 3+ ) / WSe2(Er 3+ +Yb 3+ ) a light detector, characterized in that The selected area of ​​sample one is laser-written to transfer the electrode pattern to sample one. The obtained sample two is used to remove the deteriorated LOR photoresist and S1805 photoresist with a developer, and then cleaned to obtain sample three. Sample three is plated with chromium and gold by magnetron sputtering technology to obtain sample four. Sample four is immersed in acetone to dissolve the photoresist, and the excess metal layer is peeled off under a microscope to obtain a van der Waals heterojunction electrode device. The specific steps are as follows: laser direct writing is performed on the selected area of ​​sample one, and the electrode channel size is 20μm×30μm. The properties of LOR photoresist and S1805 photoresist change after exposure, thereby transferring the electrode pattern to sample one. The obtained sample two is developed in AZ300 developer for 60S to remove The deteriorated LOR photoresist and S1805 photoresist were removed, rinsed with deionized water, the residual developer was removed, and finally dried with N2 to obtain sample three. Magnetron sputtering was performed using a sputtering coating machine. The metal electrodes were chromium and gold with thicknesses of 5nm and 50nm respectively to obtain sample four. Sample four was immersed in acetone for 20-30min, the LOR photoresist and S1805 photoresist were dissolved to separate the metal layer outside the electrode, and the electrode was peeled off under a microscope. The remaining LOR photoresist and S1805 photoresist were dissolved with AZ400 developer, and then cleaned with anhydrous ethanol, and finally gently rinsed with deionized water, and the surface moisture was blown off with N2 and then dried to obtain a van der Waals heterojunction electrode device.

10. The WS2 (Er2O3) based on rare earth ion co-doping technology according to claim 2 3+ +Yb 3+ ) / WSe2(Er 3+ +Yb 3+ ) a light detector, characterized in that The surface of the WS2(Er+Yb) / WSe2(Er+Yb) heterojunction is successively spin-coated with LOR photoresist and S1805 photoresist, and soft-baked respectively. The specific steps of obtaining sample 1 after soft-baked photoresist are as follows: a first layer of LOR photoresist is spin-coated using a glue spreader, the first stage speed of the glue spreader is 500 rpm, the time is 5 s; the second stage speed is 3500 rpm, the time is 35 s, and then the WS2(Er+Yb) / WSe2(Er+Yb) heterojunction with the first layer of LOR photoresist spin-coated is baked on a drying platform at a temperature of 170°C for 10 min to remove excess moisture in the photoresist and increase the adhesion of the photoresist to the substrate, and then a second layer of S1805 photoresist is spin-coated using a glue spreader, the first stage of the glue spreader is a speed of 500 rpm, the time is 5 s; the second stage is a speed of 2000 rpm, the time is 25 s, and then it is baked on a drying platform at a temperature of 100°C for 10 min.

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