A proportionally optimized rare earth ion co-doped two-dimensional semiconductor material, a preparation method therefor, and applications thereof

Abstract

This invention discloses a rare-earth ion co-doped two-dimensional semiconductor material with optimized ratio, its preparation method, and its application, belonging to the field of two-dimensional materials technology. The material is a transition metal chalcogenide WS2 doped with Er. 3+ and Yb 3+ By adjusting the mass ratio of ErCl3 to YbCl3 in the precursor, the Er:Yb doping molar ratio was optimized to 1:4 while maintaining a constant total doping concentration. This invention employs salt-assisted chemical vapor deposition to grow centimeter-scale, uniformly thick WS2 (Er-Yb) monolayer films on sapphire substrates, achieving an overall rare earth doping concentration as high as 10.7 at%. Experiments confirm that when the Er:Yb doping ratio is optimized to 1:4, the Yb... 3+ As a sensitizer, it can effectively absorb photon energy and efficiently transfer it to Er. 3+ The activator significantly enhances energy transfer efficiency and inhibits concentration quenching, enabling the material to exhibit the best photoelectric properties under 635nm illumination.

Description

Technical Field

[0001] This invention relates to the field of two-dimensional materials technology, and in particular to a rare-earth ion co-doped two-dimensional semiconductor material with optimized ratio, its preparation method, and its application. Background Technology

[0002] With the initial fabrication of graphene, the concept of two-dimensional materials was proposed. Two-dimensional materials refer to materials where one dimension (usually thickness) is limited to a single atomic or molecular layer, while the atomic arrangement and scale are similar in the other two dimensions. Due to their unique monolayer structure, the surface area to volume ratio is significantly increased. Furthermore, electron and heat transport is confined to the plane of the material and cannot diffuse in the vertical direction. Graphene, due to its zero band gap, is difficult to apply in transistors. To address this issue, various two-dimensional semiconductor materials have been continuously explored. Transition metal dichalcogenides (TMDCs) alone number over forty, making them the most numerous, widely studied, and technologically mature class of two-dimensional semiconductor materials after graphene. Two-dimensional layered transition metal dichalcogenides (TMDCs) possess properties similar to graphene. Their general formula can be represented as MX2, where M is a transition metal element of the IVB-VIB group such as W, V, and Mo, and XYb is a chalcogenide element such as YbS, Se, and TeYb. It is an "XMX" sandwich layered structure, with layers stacked by weak van der Waals forces. The atoms in these three layers are arranged in a hexagonal planar array, similar to graphene, belonging to the hexagonal crystal system. The M atom is covalently bonded to the X atom. The structural diversity of these compounds mainly stems from the different coordination modes of the transition metal atoms. The triangular prism structure of the 2H (semiconductor) phase and the octahedral structure of the 1T (semiconductor) phase are the two most common forms. The phase structure of TMDs plays a decisive role in their physicochemical properties. TMDs possess thinness, transparency, and flexibility almost identical to graphene, but with tunable band gaps, high carrier mobility, and high on / off ratios in the visible-near-infrared range. Because most two-dimensional TMDs, unlike graphene, are semiconductor materials, they have potential applications in the fabrication of ultra-small and low-power transistors. TMD-based transistors exhibit higher photoelectric conversion efficiency, lower dark current, and higher on / off ratios than graphene transistors. The optical properties and band gap of two-dimensional TMDs typically change with the number of layers (thickness). A single layer of this material has a direct band gap, exhibiting high luminous efficiency and photoelectric conversion efficiency. Taking tungsten disulfide (WS2) as an example, it possesses excellent nonlinear optical properties, with its two-dimensional structure displaying significant two-photon absorption in the visible and near-infrared bands. WS2 also exhibits strong spin-orbit coupling, leading to band structure splitting, particularly near the valence band apex, generating spin-polarized valley states. These valley states possess both spin and valley degrees of freedom, giving WS2 unique advantages in spintronics and valley electronics. Therefore, WS2 is currently a material of great interest to the scientific community and is expected to become a core material for next-generation electronics and optoelectronic applications.

[0003] However, the preparation of two-dimensional materials still has many defects and shortcomings: The high-quality, highly reproducible preparation of large-area doped two-dimensional materials remains challenging. Currently, chemical vapor deposition (CVD) is considered one of the most promising methods for synthesizing large-scale two-dimensional materials to meet the requirements of large-scale and high-end applications. However, the photoelectric conversion efficiency of pure TMDs thin-film semiconductor materials grown by CVD is relatively low, making it difficult to achieve high-response photoelectric conversion performance. Furthermore, the large-area CVD growth of existing two-dimensional materials is difficult in two main ways: firstly, the controllability of material thickness and uniformity is poor; secondly, the reproducibility of the grown material is poor, hindering industrial application. In summary, the high-quality, highly reproducible preparation of single-layer large-area TMDs materials still presents significant challenges. Many factors influence material growth during the CVD preparation process, such as gas velocity, growth temperature, growth time, precursor quality, and metal ion source quality. CVD-synthesized uniform few-layer or single-layer two-dimensional materials are mostly finite-sized triangles (typically <1000 μm). As the sample size further increases, the two-dimensional material film tends to grow into a non-uniform multilayer film. This is because, under conditions of uneven vapor pressure in the metal ion source, the nucleation sites are random, leading to irregular growth of the two-dimensional material. As the substrate size increases, the vapor pressure distribution of the metal ion source becomes even more uneven, which again results in more uneven thickness of the synthesized two-dimensional material.

[0004] The problem of high-density defects in CVD growth of two-dimensional materials: CVD methods inevitably produce high-density defects. High-density defects typically lead to a sharp decline in crystal quality, resulting in severe degradation of device performance. Furthermore, the atomic-level thickness of 2D materials also implies very limited absorption and material gain. Chemical doping is commonly used to modulate the functionality of semiconductors through doping type and band structure modulation.

[0005] The challenge of controllable co-doping of high-concentration rare-earth (RE) ions in two-dimensional materials: Rare-earth (RE) ions have been proven as structural modifiers in two-dimensional materials due to their abundant excitation energy levels and unique 4f electron transitions. However, due to the limited physical doping space in two-dimensional thin film materials, it is often difficult to obtain sufficiently high rare-earth ion doping concentrations. Furthermore, in two-element doping systems, the ratio of dopant elements also affects the photoelectric properties of two-dimensional materials. Investigating the influence of each element on the band structure of two-dimensional materials in co-doped systems and finding the optimal doping ratio to better improve material properties has become a pressing problem in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a proportionally optimized rare-earth ion co-doped two-dimensional semiconductor material, its preparation method, and its applications. This effectively solves the key challenges in uniformity, repeatability, and controllable high-concentration doping of large-scale rare-earth-doped two-dimensional materials, successfully preparing centimeter-scale, uniformly thick, highly repeatable WS2(Er) semiconductors with significantly increased rare-earth doping concentration. x -Yb y The material was designed to significantly enhance the photogenerated carrier concentration and energy transfer efficiency by adjusting the optimal doping ratio of Er and Yb, thereby achieving excellent optoelectronic properties, including high photoresponsivity, high external quantum efficiency and high specific detectivity.

[0007] To achieve the above objectives, the present invention provides a rare earth ion co-doped two-dimensional semiconductor material with optimized proportions, comprising the following raw materials: sulfur powder, tungsten source, catalyst, and rare earth doping source, wherein the rare earth doping source is ErCl3 and YbCl3, and the molar ratio of Er element to Yb element is 1:4.

[0008] Preferably, the tungsten source is tungstic acid, the catalyst is NaCl, the mass ratio of sulfur powder, tungsten source, catalyst and ErCl3 is 75:35:2:3, and the total content of Er and Yb atoms accounts for 10.7 at% of the sum of Er+Yb+W metal atoms.

[0009] This invention also provides a method for preparing a rare-earth ion co-doped two-dimensional semiconductor material with optimized proportions, comprising the following steps: Step 1: Clean the substrate; Step 2: Place a corundum boat I containing sulfur powder in the upstream temperature zone I of the tube furnace, and place a corundum boat II containing tungsten source, catalyst NaCl, and rare earth doping source ErCl3 and YbCl3 mixed powder in the downstream temperature zone II. Place the cleaned substrate upside down on top of the corundum boat II, seal the quartz tube, and close the inlet and outlet valves. Step 3: Evacuate the quartz tube to a pressure below 1 Pa, then introduce inert gas to atmospheric pressure and keep the gas flowing. Step 4: Control the temperature rise program in the temperature zone and introduce Ar / H2 mixed gas to carry out chemical vapor deposition reaction; Step 5: After the deposition reaction is complete, allow the material to cool naturally to room temperature to obtain a two-dimensional semiconductor material co-doped with rare earth ions.

[0010] Preferably, in step one, the substrate is a sapphire substrate, and the substrate is cleaned as follows: the sapphire substrate is laid flat in a beaker, the beaker is placed in an ultrasonic cleaner, and cleaning agent is added to the beaker in the order of deionized water, acetone, anhydrous ethanol, and deionized water for cleaning. Each cleaning time is 2 minutes. After cleaning, the cleaned substrate is dried with a nitrogen gun.

[0011] Preferably, in step three, the inert gas is argon, and the flow rate is 300 sccm.

[0012] Preferably, in step four, the temperature rise program of the temperature zone is as follows: temperature zone I is kept at room temperature, the temperature rises at 50 min, reaches 200°C at 70 min, the temperature is maintained for 10 min, and then the temperature begins to drop. Temperature zone II is set to start heating at room temperature, reach 950°C after 70 minutes, hold for 10 minutes, and then begin cooling.

[0013] Preferably, in step four, when temperature zone II reaches 150°C during the heating process, the inlet valve and outlet valve are closed, and step three is repeated to perform a vacuuming process until the air pressure is below 1 Pa.

[0014] Preferably, in step four, during the process of heating temperature zone II to 950°C, argon gas is first introduced at a flow rate of 64 sccm. Five minutes before reaching 950°C, the argon gas is replaced with an Ar / H2 mixed gas. In the Ar / H2 mixed gas, argon gas accounts for 90% of the volume percentage of the Ar / H2 mixed gas, hydrogen gas accounts for 10% of the volume percentage of the Ar / H2 mixed gas, and the flow rate of the Ar / H2 mixed gas is 80 sccm for 12 minutes.

[0015] Preferably, in step five, after the reaction is complete, the Ar / H2 mixed gas is replaced with argon gas, and the flow rate of argon gas is 64 sccm.

[0016] The present invention also provides an application of a ratio-optimized rare-earth ion co-doped two-dimensional semiconductor material, which is used in the fabrication of a photodetector.

[0017] Therefore, the present invention, employing the above-mentioned optimized rare-earth ion co-doped two-dimensional semiconductor material, its preparation method, and its application, has the following beneficial effects: (1) It greatly improves the reproducibility of large-scale rare-earth-doped two-dimensional materials and solves the uniformity problem of rare-earth-doped two-dimensional materials to a certain extent. By adjusting the Ar / H2 mixed gas flow rate (dynamic range of 40-100 sccm), a stable laminar flow state is formed in the reaction chamber, and the weight ratio of tungsten source to Er and Yb precursors is controlled to generate a uniform WS2(Er) layer with a thickness of about 1.7 nm on the sapphire substrate. 3+ +Yb 3+ The material thin film was obtained, and the experimental repeatability was as high as 80%. The thickness and performance uniformity of the material were verified by optical microscopy and Raman spectroscopy imaging. (2) By increasing the rare earth doping concentration and adjusting the rare earth ion doping ratio of the two-dimensional material, excellent WS2(Er) was obtained. x -Yb yThe photoelectric properties of two-dimensional semiconductor materials. Using rare-earth Er... 3+ and Yb 3+ Co-doping technology, utilizing rare earth Er 3+ and Yb 3+ For W 4+ The competition effect of site occupancy enables high-concentration in-situ doping of WS2(Er) based on CVD technology. x -Yb y The successful preparation of two-dimensional materials achieved an overall rare-earth ion doping concentration approaching 10.7 at%, far exceeding the previously reported levels of around 1-3 at%. Furthermore, due to the abundant 4f energy levels of rare-earth ions, with 12-14 electrons in each level, and the ease with which these electrons absorb the energy of radiated photons to become free electrons, rare-earth Er... 3+ Yb 3+ The higher the plasma concentration, the higher the concentration of photogenerated electron-hole pairs under illumination, resulting in a larger photocurrent. Secondly, the two-dimensional material WS2 employs a 1:4 Er-Yb doping ratio, with more Yb... 3+ It can provide a larger absorption surface to absorb photon energy, while fully surrounding Er as the activator. 3+ This greatly improves the rate and efficiency of energy transfer from Yb to Er, while avoiding concentration quenching caused by excessively high ion concentrations. These characteristics result in excellent photoelectric properties of the material, specifically manifested in very high photoresponsivity (applicable to weak light detection), high external quantum efficiency (extremely high photoelectric conversion efficiency), and high specific detectivity (extremely high sensitivity). (3) High-performance WS2(Er) was prepared. x -Yb y Photodetector: Based on traditional micro-nano fabrication techniques, WS2 (Er) detectors were successfully fabricated on sapphire substrates. x -Yb y A photodetector was developed and its performance was tested, yielding good results. Comparisons were made between WS2(Er) with different doping ratios. x -Yb y The photodetector prepared by the experiment was found to have an optimal doping ratio of 1:4. The performance of the photodetector at this ratio was significantly better than that of other groups.

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the two-dimensional semiconductor material growth system of the present invention; Figure 2This is a diagram showing the temperature and gas flow rate settings of the equipment system during the CVD growth of two-dimensional semiconductor materials according to the present invention; Figure 3 WS2(Er) grown using the CVD technology of this invention x -Yb y Optical micrographs of two-dimensional semiconductor materials, where (a) is an optical micrograph and (b) is a magnified view of (a); Figure 4 These are atomic force micrographs of the materials prepared in Example 1 and Comparative Examples 1-7 of this invention; Figure 5 These are the EDS and Raman spectra of the materials prepared in Example 1 and Comparative Examples 1-7 of the present invention, wherein (a) is the EDS spectrum of the materials prepared in Example 1 and Comparative Examples 1-7, and (b) is the Raman spectrum of the materials prepared in Example 1 and Comparative Examples 1-7. Figure 6 These are transmission electron microscope (TEM) images and XRD patterns of the materials prepared in Example 1 and Comparative Example 1 of the present invention, wherein (a) is a TEM image of Example 1, (b) is a selected area SAED image of the TEM image of Example 1, and (c) is an XRD pattern of Example 1 and Comparative Example 1. Figure 7 These are the normalized XPS spectra of the materials prepared in Example 1 and Comparative Examples 1-7 of the present invention, wherein (a) is the XPS spectra of Comparative Example 1, (b) is the XPS spectra of Example 1, and (c) is the baseline-corrected and normalized XPS spectra of Er-4d and Yb-4d of the materials prepared in Example 1 and Comparative Examples 1-7. Figure 8 These are the optical fiber diagram and schematic diagram of the photodetector prepared in Example 1 of the present invention, wherein (a) is the optical fiber diagram and (b) is the schematic diagram; Figure 9 These are the IV curves of photodetectors prepared from the materials prepared in Example 1 and Comparative Examples 1-7 of this invention under 635nm radiation light irradiation at different power densities. Among them, (a) is the IV curve of Comparative Example 1, (b) is the IV curve of Comparative Example 1, (c) is the IV curve of Comparative Example 1, (d) is the IV curve of Comparative Example 1, (e) is the IV curve of Comparative Example 1, (f) is the IV curve of Comparative Example 1, (g) is the IV curve of Comparative Example 1, and (h) is the IV curve of Comparative Example 1. Figure 10 It represents the maximum values ​​of various photoelectric characteristic parameters of the photodetector prepared from the materials prepared in Embodiment 1 and Comparative Examples 1-7 of this invention during the photodetector period under 635nm radiation light irradiation. Detailed Implementation

[0020] This invention provides a rare earth ion co-doped two-dimensional semiconductor material with optimized ratio, comprising the following raw materials: sulfur powder, tungsten source, catalyst, and rare earth doping source, wherein the rare earth doping source is ErCl3 and YbCl3, and the molar ratio of Er element to Yb element is 1:4.

[0021] In this invention, the tungsten source is tungstic acid, the catalyst is NaCl, the mass ratio of sulfur powder, tungsten source, catalyst and ErCl3 is 75:35:2:3, and the total content of Er and Yb atoms accounts for 10.7 at% of the sum of Er+Yb+W metal atoms.

[0022] This invention also provides a method for preparing a rare-earth ion co-doped two-dimensional semiconductor material with optimized proportions, comprising the following steps: Step 1: Clean the substrate; Step 2: Place a corundum boat I containing sulfur powder in the upstream temperature zone I of the tube furnace, and place a corundum boat II containing tungsten source, catalyst NaCl, and rare earth doping source ErCl3 and YbCl3 mixed powder in the downstream temperature zone II. Place the cleaned substrate upside down on top of the corundum boat II, seal the quartz tube, and close the inlet and outlet valves. Step 3: Evacuate the quartz tube to a pressure below 1 Pa, then introduce inert gas to atmospheric pressure and keep the gas flowing. Step 4: Control the temperature rise program in the temperature zone and introduce Ar / H2 mixed gas to carry out chemical vapor deposition reaction; Step 5: After the deposition reaction is complete, allow the material to cool naturally to room temperature to obtain a two-dimensional semiconductor material co-doped with rare earth ions.

[0023] In this invention, in step one, the substrate is a sapphire substrate. The substrate is cleaned as follows: the sapphire substrate is laid flat in a beaker, the beaker is placed in an ultrasonic cleaner, and cleaning agent is added to the beaker in the order of deionized water, acetone, anhydrous ethanol, and deionized water for cleaning. Each cleaning time is 2 minutes. After cleaning, the cleaned substrate is dried with a nitrogen gun.

[0024] In this invention, in step three, the inert gas is argon, and the flow rate is 300 sccm.

[0025] In this invention, in step four, the temperature rise program of the temperature zone is as follows: temperature zone I is kept at room temperature, the temperature rises at 50 min, reaches 200°C at 70 min, the temperature is maintained for 10 min, and then the temperature is lowered. Temperature zone II is set to start heating at room temperature, reach 950°C after 70 minutes, hold for 10 minutes, and then begin cooling.

[0026] In this invention, in step four, when temperature zone II reaches 150°C during the heating process, the inlet valve and outlet valve are closed, and step three is repeated to perform a vacuuming process until the air pressure is below 1 Pa.

[0027] In this invention, in step four, during the process of raising the temperature in zone II to 950°C, argon gas is first introduced at a flow rate of 64 sccm. Five minutes before reaching 950°C, the argon gas is replaced with an Ar / H2 mixed gas. In the Ar / H2 mixed gas, argon gas accounts for 90% of the volume percentage of the Ar / H2 mixed gas, and hydrogen gas accounts for 10% of the volume percentage of the Ar / H2 mixed gas. The flow rate of the Ar / H2 mixed gas is 80 sccm, and the reaction lasts for 12 minutes.

[0028] In this invention, in step five, after the reaction is complete, the Ar / H2 mixed gas is replaced with argon gas, and the flow rate of argon gas is 64 sccm.

[0029] The present invention also provides an application of a ratio-optimized rare-earth ion co-doped two-dimensional semiconductor material, which is used in the fabrication of a photodetector.

[0030] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims and are all within the protection scope of the present invention.

[0031] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0032] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0033] In this invention, unless otherwise specified, all other test materials and instruments are conventional test materials in the field and can be purchased through commercial channels.

[0034] Example 1 This invention provides a rare-earth ion co-doped two-dimensional semiconductor material with optimized proportions. The total content of Er and Yb atoms in the rare-earth ion co-doped two-dimensional semiconductor material accounts for 10.7 at% of the sum of Er, Yb, and W atoms. The preparation method specifically includes the following steps: Step 1: Clean the substrate. The substrate is a sapphire substrate, 2cm long and 1cm wide. The substrate is cleaned as follows: the sapphire substrate is laid flat in a beaker and the beaker is placed in an ultrasonic cleaner. The cleaning agent is added to the beaker in the following order: deionized water, acetone, anhydrous ethanol, and deionized water. Each cleaning time is 2 minutes. After cleaning, the cleaned substrate is dried with a nitrogen gun.

[0035] Step 2: Place a corundum boat I containing sulfur powder in the upstream temperature zone I of the tube furnace, and place a corundum boat II containing tungsten source, catalyst NaCl, and rare earth doping source ErCl3 and YbCl3 mixed powder in the downstream temperature zone II. Place the cleaned substrate upside down on top of the corundum boat II, seal the quartz tube, and close the inlet and outlet valves. The composition of the furnace includes 150 mg of sulfur powder, 70 mg of tungsten acid (the tungsten source), 4 mg of NaCl, 6 mg of ErCl3, and 24 mg of YbCl3. The molar ratio of Er to Yb is 1:4. The purity of the sulfur powder and tungsten acid is >99.5%, and the purity of NaCl, ErCl3, and YbCl3 is >99.9%. The tube furnace uses... Figure 1 The image shows a tube furnace with two temperature zones using 2-inch diameter quartz tubes.

[0036] Step 3: Evacuate the quartz tube to a pressure below 1 Pa, then introduce an inert gas to atmospheric pressure and keep the gas flowing; the inert gas is argon, and the flow rate is 300 sccm.

[0037] Step 4: Control the temperature rise program in the temperature zone and introduce Ar / H2 mixed gas to carry out chemical vapor deposition reaction; The temperature rise curve of the temperature zone heating program is as follows: Figure 2 As shown, the specific settings are as follows: Temperature zone I maintains room temperature, starts to rise after 50 minutes, reaches 200°C after 70 minutes, maintains this temperature for 10 minutes, and then starts to cool down; Temperature zone II is set to start heating at room temperature, reach 950°C after 70 minutes, hold for 10 minutes, and then begin cooling.

[0038] During the heating process in zone II, when the temperature reaches 150°C, close the inlet and outlet valves and repeat step three to perform a vacuuming process until the pressure is below 1 Pa.

[0039] During the process of heating in temperature zone II to 950℃, argon gas is first introduced at a flow rate of 64 sccm. Five minutes before reaching 950℃, the argon gas is replaced with an Ar / H2 mixture. In the Ar / H2 mixture, argon accounts for 90% of the volume percentage and hydrogen accounts for 10% of the volume percentage. The flow rate of the Ar / H2 mixture is 80 sccm, and the reaction lasts for 12 minutes.

[0040] Step 5: After the deposition reaction is complete, allow the material to cool naturally to room temperature to obtain a rare earth ion co-doped two-dimensional semiconductor material, denoted as WS2(Er1-Yb4). After the reaction, the Ar / H2 mixed gas is replaced with argon gas at a flow rate of 64 sccm.

[0041] Comparative Example 1 The only difference between this comparative example and Example 1 is that ErCl3 and YbCl3 are not added; all other conditions are the same, and the product is denoted as WS2.

[0042] Comparative Example 2 The only difference between this comparative example and Example 1 is that the molar ratio of ErCl3 to YbCl3 is 2:1, while all other conditions are the same. The product is denoted as WS2(Er2-Yb1).

[0043] Comparative Example 3 The only difference between this comparative example and Example 1 is that the molar ratio of ErCl3 to YbCl3 is 1:1, while all other conditions are the same. The product is denoted as WS2(Er1-Yb1).

[0044] Comparative Example 4 The only difference between this comparative example and Example 1 is that the molar ratio of ErCl3 to YbCl3 is 1:2, while all other conditions are the same. The product is denoted as WS2(Er1-Yb2).

[0045] Comparative Example 5 The only difference between this comparative example and Example 1 is that the molar ratio of ErCl3 to YbCl3 is 1:3, while all other conditions are the same. The product is denoted as WS2(Er1-Yb3).

[0046] Comparative Example 6 The only difference between this comparative example and Example 1 is that the molar ratio of ErCl3 to YbCl3 is 1:5, while all other conditions are the same. The product is denoted as WS2(Er1-Yb5).

[0047] Comparative Example 7 The only difference between this comparative example and Example 1 is that the molar ratio of ErCl3 to YbCl3 is 1:6, while all other conditions are the same. The product is denoted as WS2(Er1-Yb6).

[0048] Typical optical microscope images of the rare-earth co-doped two-dimensional semiconductor material finally prepared in Example 1 are shown below. Figure 3 As shown, by Figure 3 It can be seen that the material is a continuous and uniform thin film, which shows the uniformity of the material.

[0049] Atomic force micrographs of the materials prepared in Example 1 and Comparative Examples 1-7 are shown below. Figure 4 As shown. Performance comparisons are only meaningful when the thicknesses are similar. The consistent thickness measured for the eight samples was 1.7 ± 0.05 nm. This is attributed to the fact that all samples were grown under the same CVD process parameters, with only the weight ratio of ErCl3 and YbCl3 adjusted. This consistency in thickness effectively eliminates interference that could arise from variations in thickness when comparing sample performance.

[0050] The materials prepared in Example 1 and Comparative Examples 1-7 were characterized structurally. Specifically, eight materials were placed in a laser confocal Raman spectrometer. When the laser irradiated the sample, most photons underwent elastic scattering, while a minority of photons underwent inelastic scattering (Raman scattering). The energy of the Raman-scattered photons changed compared to the incident photons; this energy change corresponded to transitions in molecular vibrational or rotational energy levels. By detecting the frequency changes of the scattered light, molecular vibrational information of the sample could be obtained, thereby inferring its chemical bonds, molecular symmetry, and crystal structure. The results are shown below. Figure 5 As shown.

[0051] Depend on Figure 5 (a) As can be seen, energy-dispersive X-ray spectroscopy (EDS) measurements further confirmed the doping ratio. Besides the original WS2 film, the other seven Er... 3+ With Yb 3+ The average total doping concentration of the doped samples was 10.46 at%, with an average deviation of 0.41%. Furthermore, all eight samples maintained a S / W atomic ratio close to stoichiometry 2. The EDS and XPS measurements for this group of samples were consistent.

[0052] Depend on Figure 5 (b) It can be seen that using a 532nm laser as the excitation source, undoped WS2 and WS2(Er) were demonstrated. x -Yb y Raman spectra of undoped WS2 and WS2(Er). x -Yb y All samples showed four Raman peaks, located at approximately 296 cm⁻¹. -1(2E 2 g ), approximately 323cm -1 (E 2 2g ), approximately 350cm -1 (E 2g ) and approximately 420cm -1 (A 1g ).

[0053] XRD and TEM testing: Used for characterizing WS2 doping. Transmission electron microscopy (TEM) and X-ray diffraction (TEM) are used to test whether rare earth elements are doped into the two-dimensional material and to test the effect of doping on the material's lattice. By irradiating TMDCs with X-rays, the crystal type of the material can be determined, the number of layers in layered two-dimensional materials can be distinguished, and atomic defects and doping status can be detected. TEM is used to characterize key structural features of WS2 thin films, such as atomic arrangement, interlayer stacking, and lattice distortion caused by rare earth doping. Results are as follows: Figure 6 As shown, by Figure 6 It can be seen that, through transmission electron microscopy (TEM), WS2(Er) x -Yb y The crystal structure of WS2(Er) was characterized, and no obvious lattice distortion was observed in the figure. x -Yb y The interplanar spacing of WS2(Er1-Yb4) is 0.279 nm, and the contrast difference of metal ions in WS2(Er1-Yb4) is not significant, indicating that the lattice distortion caused by Er-Yb co-doping is small. The selected area electron diffraction (SAED) pattern, shown in 4d, displays six-fold symmetric diffraction spots, confirming the hexagonal crystal structure of the material. This indicates that even under high concentrations of erbium and ytterbium ion doping, WS2(Er1-Yb4) exhibits a relatively small lattice distortion due to Er-Yb co-doping. x -Yb y The crystal symmetry remains good.

[0054] Elemental composition analysis of materials: XPS, as an important surface analysis technique, is based on the photoelectric effect and is mainly used to analyze the surface chemical composition and chemical states of elements in materials. When a beam of monochromatic X-rays is focused onto the sample surface, the energy it carries excites and releases electrons from the inner layers of the sample atoms; these released electrons are called photoelectrons. By accurately measuring the kinetic energy of the photoelectrons, their binding energy can be further calculated, and the binding energy is closely related to the type of element and its chemical environment. XPS spectra can provide rich information, covering key aspects such as the type, content distribution, and chemical states of elements on the sample surface. In this experiment, for the in-situ substitution doping of TMDCs, XPS is crucial for identifying the dopant elements and characterizing their content. The results... Figure 7 As shown.

[0055] Depend on Figure 7It can be seen that X-ray photoelectron spectroscopy (XPS) measurement is used to confirm WS2 (Er x -Yb y The elemental concentrations in the thin film are shown, with the C1s peak as a reference. The integrated intensity of each characteristic peak reflects the content of the corresponding element in the material, including sulfur, tungsten, erbium, and ytterbium. High-resolution W-4f and S-2p spectra show characteristic peaks appearing at specific binding energies: S-2p 1 / 2 Located at 164.21 eV, S-2p 3 / 2 Located at 162.97 eV, W5p 3 / 2 Located at 38.18 eV, W-4f 5 / 2 Located at 35.56 eV, W-4f 7 / 2 Located at 33.29 eV. In the corrected and normalized Er / Yb-4d spectrum, it is clear that as the Er:Yb ratio changes from 2:1 to 1:6, the peak intensity and integrated intensity at 172.4 eV (corresponding to Er-4d) and 190.8 eV (corresponding to Yb-4d) exhibit a regular change. Seven WS2(Er x -Yb y The average total co-doping concentration of Er and Yb ions in the thin film samples was 11.03 at, with an average deviation of 6.87%.

[0056] Application examples The materials prepared in Example 1 and Comparative Examples 1-7 were used to prepare van der Waals heterojunction photodetectors. Example 1 was used as the sample for preparation, and the preparation method was as follows: Step 1: Spin-coating photoresist: The sample prepared in Example 1 was cleaned with high-purity N2, placed in the center of a spin coater, and fixed with a vacuum pump. A layer of LOR photoresist was spin-coated using the spin coater. The spin coater speed / time was set as follows: first stage speed 500 rpm, spin coat time 5 s; second stage speed 3500 rpm, spin coat time 35 s.

[0057] Step 2, soft baking: Place the spin-coated photoresist sample on a drying platform and bake at 170°C for 10 minutes to remove excess moisture from the photoresist and ensure that the substrate and photoresist adhere firmly.

[0058] Step 3, Second coating: Spin coat the second layer of S1805 photoresist using a spin coater. The spin coater speed / time settings are as follows: First stage: speed 500 rpm, spin coat time 5s; Second stage: speed 2000 rpm, spin coat time 25s.

[0059] Step 4, Second Soft Bake: Bake the sample at 100℃ for 10 minutes on the drying platform. The effect is the same as the first soft bake.

[0060] Step 5, Laser Direct Writing: Design the electrode pattern in AutoCAD, using symmetrical rectangular electrodes with an electrode channel size of 20μm × 20μm. Apply the designed electrode pattern to a selected area of ​​the sample using laser direct writing, and use laser irradiation to denature the photoresist at the electrode location.

[0061] Step Six: Development and Fixing: Immerse the sample in AZ300 developer for 60 seconds to fully dissolve the photoresist in the exposed areas. Rinse the sample with deionized water to remove any residual developer. Finally, dry with high-purity N2.

[0062] Step 7: Sputtering Electrodes: The sample is sputtered using a sputtering coating machine. The sputtered metal electrodes are chromium (Cr) and gold (Au), with thicknesses of 5 nm and 50 nm respectively. Chromium is used to enhance electrode stability and ensure its stability. Gold, with its lower work function, is the preferred electrode material.

[0063] Step 8: Photoresist Removal: Immerse the entire sputtered sample in acetone for 5-10 minutes, then place it in an ultrasonic cleaner and vibrate for 1 minute to fully peel the photoresist from the sample. Observe the peeling results under a microscope until the electrode is successfully peeled off. Next, immerse the sample in AZ400 developer for 30 seconds to dissolve the remaining LOR photoresist. Remove the remaining developer with anhydrous ethanol, then gently rinse the sample with deionized water. Finally, blow away the surface moisture with high-purity N2. The resulting electrode device is shown below. Figure 8 As shown.

[0064] Comparative Examples 1-7 were prepared using the same steps as above. The photodetectors prepared in Example 1 and Comparative Examples 1-7 were subjected to photoelectric performance testing, and the test results are as follows: Figure 9 and Figure 10 As shown.

[0065] Depend on Figure 9 As can be seen, all samples exhibit linear IV curves, indicating a good ohmic contact at the interface between the electrode and the tungsten disulfide film. The pristine tungsten disulfide photodetector shows the lowest photocurrent under the same bias and illumination power, compared to the erbium-yttrium co-doped samples. With the erbium to ytterbium ratio decreasing from 2:1 to 1, 1:2, 1:3, and 1:4, at a bias of 5V and 72.77mW / cm², the photocurrent remains relatively constant. 2 Under illumination, the photocurrent continuously increased from 41 nA to 59 nA, 153 nA, 372 nA, and 753 nA. However, when the Er:Yb ratio was further reduced to 1:5 and 1:6, the photocurrent decreased to 529 nA and 180 nA, respectively, under the same bias voltage and illumination conditions. Clearly, similar to the photoluminescence intensity, the WS2 (Er1-Yb4) sample exhibited the highest photocurrent across all incident power densities, approximately 40 times that of the original WS2 device.

[0066] Depend on Figure 10 As can be seen from the 3D plot, under the condition of constant total doping concentration, as the ratio of Er and Yb decreases, WS2(Er) x -Yb y The changes in the photoresponsivity, external quantum efficiency, and specific detectivity of the photodetector when a 5V bias voltage and 0.39mW / cm² are applied. 2 Under illumination, the original WS2 photodetector exhibits the highest R... λ , and EQE The values ​​are 1.02 A·W. -1 1.48×10 11 Jones and 200.7%, while the WS2 (Er1-Yb4) photoelectric sensor exhibits significantly higher performance parameters, at 22.66 A·W. -1 3.27×10 12 Jones and 4433.5%.

[0067] Therefore, this invention employs a rare-earth ion co-doped two-dimensional semiconductor material with optimized proportions, its preparation method, and its application, effectively solving the key challenges in uniformity, repeatability, and controllable high-concentration doping of large-scale rare-earth-doped two-dimensional materials. It successfully prepares centimeter-scale, uniformly thick, highly repeatable WS2(Er) semiconductors with a significantly increased rare-earth doping concentration (approximately 10.7 at%). x -Yb y The material was developed by adjusting the optimal doping ratio of Er to Yb (1:4), which significantly enhanced the photogenerated carrier concentration and energy transfer efficiency, thereby achieving excellent optoelectronic properties, including high photoresponsivity, high external quantum efficiency (up to 4433.5%) and high specific detectivity.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A rare-earth ion co-doped two-dimensional semiconductor material with optimized ratio, characterized in that: Including the following raw materials: Sulfur powder, tungsten source, catalyst, rare earth doping source, the rare earth doping source is ErCl3 and YbCl3, wherein the molar ratio of Er element to Yb element is 1:

4.

2. The rare-earth ion co-doped two-dimensional semiconductor material with optimized proportions according to claim 1, characterized in that: The tungsten source is tungstic acid, the catalyst is NaCl, and the mass ratio of sulfur powder, tungsten source, catalyst and ErCl3 is 75:35:2:

3. The total content of Er and Yb atoms accounts for 10.7 at% of the total content of Er+Yb+W metal atoms.

3. The method for preparing a rare-earth ion co-doped two-dimensional semiconductor material with optimized proportions as described in any one of claims 1-2, characterized in that: Includes the following steps: Step 1: Clean the substrate; Step 2: Place a corundum boat I containing sulfur powder in the upstream temperature zone I of the tube furnace, and place a corundum boat II containing tungsten source, catalyst NaCl, and rare earth doping source ErCl3 and YbCl3 mixed powder in the downstream temperature zone II. Place the cleaned substrate upside down on top of the corundum boat II, seal the quartz tube, and close the inlet and outlet valves. Step 3: Evacuate the quartz tube to a pressure below 1 Pa, then introduce inert gas to atmospheric pressure and keep the gas flowing. Step 4: Control the temperature rise program in the temperature zone and introduce Ar / H2 mixed gas to carry out chemical vapor deposition reaction; Step 5: After the deposition reaction is complete, allow the material to cool naturally to room temperature to obtain a two-dimensional semiconductor material co-doped with rare earth ions.

4. The method for preparing a rare-earth ion co-doped two-dimensional semiconductor material with optimized proportions according to claim 3, characterized in that: In step one, the substrate is a sapphire substrate. The substrate is cleaned as follows: the sapphire substrate is laid flat in a beaker, the beaker is placed in an ultrasonic cleaner, and the cleaning agent is added to the beaker in the order of deionized water, acetone, anhydrous ethanol, and deionized water for cleaning. Each cleaning time is 2 minutes. After cleaning, the cleaned substrate is dried with a nitrogen gun.

5. The method for preparing a rare-earth ion co-doped two-dimensional semiconductor material with optimized proportions according to claim 3, characterized in that: In step three, the inert gas is argon, and the flow rate is 300 sccm.

6. The method for preparing a rare-earth ion co-doped two-dimensional semiconductor material with optimized proportions according to claim 3, characterized in that: In step four, the temperature rise program for the temperature zone is as follows: Temperature zone I is kept at room temperature, and the temperature rises at 50 minutes, reaching 200°C at 70 minutes. This temperature is maintained for 10 minutes, and then the temperature begins to drop. Temperature zone II is set to start heating at room temperature, reach 950°C after 70 minutes, hold for 10 minutes, and then begin cooling.

7. The method for preparing a rare-earth ion co-doped two-dimensional semiconductor material with optimized proportions according to claim 6, characterized in that: In step four, during the heating process of temperature zone II, when the temperature reaches 150°C, the inlet valve and outlet valve are closed, and step three is repeated to perform a vacuuming process until the air pressure is below 1 Pa.

8. The method for preparing a rare-earth ion co-doped two-dimensional semiconductor material with optimized proportions according to claim 6, characterized in that: In step four, during the process of raising the temperature in zone II to 950℃, argon gas is first introduced at a flow rate of 64 sccm. Five minutes before reaching 950℃, the argon gas is replaced with an Ar / H2 mixture. In the Ar / H2 mixture, argon accounts for 90% of the volume percentage and hydrogen accounts for 10% of the volume percentage. The flow rate of the Ar / H2 mixture is 80 sccm, and the reaction lasts for 12 minutes.

9. The method for preparing a rare-earth ion co-doped two-dimensional semiconductor material with optimized proportions according to claim 3, characterized in that: In step five, after the reaction is complete, the Ar / H2 mixed gas is replaced with argon gas at a flow rate of 64 sccm.

10. An application of a rare-earth ion co-doped two-dimensional semiconductor material with optimized ratio, characterized in that: The rare-earth ion co-doped two-dimensional semiconductor material according to any one of claims 1-2 is used in the fabrication of a photodetector.

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