Patterned two-dimensional VX2, lateral, and vertical VX2 / TMDs heterojunctions, their fabrication and applications
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUNAN UNIV
- Filing Date
- 2024-08-27
- Publication Date
- 2026-05-26
Smart Images
Figure CN119314869B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of two-dimensional material preparation, specifically relating to the controllable preparation of patterned heterostructures of two-dimensional materials. Technical Background
[0002] Two-dimensional (2D) semiconductor heterostructures have attracted attention due to their unique physical properties and potential applications in future electronics, catalysis, sensory processing, optoelectronics, and energy storage. Two-dimensional materials with different crystal structures can form lateral or vertical van der Waals heterostructures, providing a rich platform for exploring carrier and photon transport within atomic-scale interfaces. Chemical vapor deposition (CVD) is one of the most commonly used methods for preparing transition metal chalcogenide (TMD) heterostructures. For example, using a designed Au(111) / W-Re alloy foil substrate, a 100% overlapping ReS2 / WS2 vertical heterostructure was synthesized in one step via CVD. (Ajayan group) 1 A one-step CVD method is reported to selectively prepare transverse or vertical WS2 / MoS2 heterostructures via temperature triggering. A two-step CVD method can also be used to produce various TMD heterostructures, such as WSe2 / MoSe2, SnSe2 / MoS2, and WS2 / MoS2.
[0003] In addition to the widely explored semiconductor heterostructures, the fabrication of metal TMD (m-TMD) and semiconductor TMD (s-TMD) heterostructures is also very important because they have great potential in creating high-quality contacts and improving device performance. For example, Shi et al. 2 Using CVD-grown VTe2 nanosheets as contact metals in monolayer MoS2 devices resulted in a field-effect mobility six times higher than that of traditional Ti / Au electrode contacts. (Ji et al.) 3 Using CVD-grown VS2 as the contact electrode for monolayer MoS2, the resulting contact resistance is approximately one-quarter of that of Ni / Au metal contact resistance. However, the fabrication of the aforementioned heterostructure device requires the transfer of two-dimensional metal nanosheets, a complex process. Furthermore, the channel length is random and difficult to control.
[0004] It is worth mentioning that laser direct writing, as a powerful microfabrication method, plays a crucial role in material synthesis and electronic device fabrication. For example, our team previously developed a laser ablation method to trigger defect formation, thereby allowing the selective growth of single-crystal m-TMDs on s-TMDs, resulting in a series of m-TMD / s-TMD vdWH arrays. 4 Park and others 5 Rapid and selective fabrication of MoS2 and WS2, as well as patterned vertical heterostructures of MoS2 / WS2, were achieved at the wafer scale. (Abbs et al.)6 Selective synthesis of WS2 / MoS2 heterostructures was also achieved using laser printing technology. Compared with traditional photolithography, laser processing has significant advantages such as flexibility, high precision, and no pollution. However, the simple and rapid fabrication of imaged m-TMD / s-TMD heterostructures with controllable channel lengths still faces challenges.
[0005] References
[0006] 1C.Huang,S.Wu,AMSanchez,JJPeters,R.Beanland,JSRoss,P.Rivera,W.Yao,DHCobden,X.Xu,Nat.Mater.2014,13,1096.
[0007] 2. J. Shi, Y. Huan, X. Zhao, P. Yang, M. Hong, C. Xie, S. Pennycook, Y. Zhang, ACSNano 2021, 15, 1858.
[0008] 3. Q.Ji, C.Li, J.Wang, J.Niu, Y.Gong, Z.Zhang, Q.Fang, Y.Zhang, J.Shi, L.Liao, X.Wu, L.Gu, Z.Liu, Y.Zhang, Nano Lett. 2017, 17, 4908.
[0009] 4Z.W.Zhang,ZWHuang,J.Li,D.Wang,Y.Lin,XDYang,H.Liu,S.Liu,YLWang,B.Li,XFDuan,XDDuan,Nat.Nanotechnol.2022,17,493.
[0010] 5.S.Park,A.Lee,KHChoi,SKHyeong,S.Bae,JMHong,TWKim,BHHong,SKLee,ACS Nano 2020,14,8485.
[0011] 6.OAAbbas, AHLewis, N.Aspiotis, C.-C.Huang, I.Zeimpekis, DWHewak, P.Sazio, S.Mailis, Sci.Rep.2021,11,5211. Summary of the Invention
[0012] To fill the gap in the preparation of patterned two-dimensional VX2 nanosheets, the primary objective of this invention is to provide a method for preparing patterned two-dimensional VX2 materials, aiming to obtain clean, undamaged patterned two-dimensional VX2 materials with controllable channel length.
[0013] The second objective of this invention is to provide a patterned two-dimensional VX2 nanosheet prepared by the aforementioned method.
[0014] The third objective of this invention is to provide a method for preparing patterned two-dimensional transverse or vertical VX2 / TMDs heterojunctions.
[0015] The fourth objective of this invention is to provide patterned two-dimensional heterojunctions and devices.
[0016] Two-dimensional materials with different crystal structures can form transverse heterostructures or vertical van der Waals heterostructures (vdWHs), providing a rich material platform for exploring carrier and photon transport within atomic-scale interfaces. However, the fabrication of heterostructure devices relies on a cumbersome two-dimensional metal nanosheet transfer process, and the channel length is random and difficult to control. Laser direct writing, as a powerful microfabrication method, plays a crucial role in material synthesis and electronic device fabrication. Compared with traditional photolithography, laser processing has outstanding advantages such as flexibility, high precision, and no pollution. However, the simple and rapid fabrication of patterned m-TMD / s-TMD heterostructures with controllable channel lengths still faces challenges. To address this problem, this invention provides the following solution:
[0017] A method for preparing patterned two-dimensional VX2 material involves obtaining a two-dimensional VX2 material, then performing patterning etching on it using a laser, followed by treatment with hydrochloric acid solution to obtain the patterned two-dimensional VX2 material; wherein X is S or Se.
[0018] The power intensity of the laser is less than 3.5 × 10⁻⁶. 5 W / cm 2 .
[0019] This invention innovatively uses a laser of the aforementioned power intensity to etch two-dimensional VX2 materials, and further combines this with hydrochloric acid treatment. This allows for the simple patterning of two-dimensional VX2 materials, resulting in clean, undamaged patterned two-dimensional VX2 materials with controllable channel lengths.
[0020] In this invention, VX2 material can be obtained based on known methods. For example, as an example, the VX2 material can be obtained by volatilizing VCl3 and X powder and performing CVD deposition in carrier gas a.
[0021] The purity of VCl3 and X powder raw materials is greater than 99%.
[0022] In this invention, the substrate for CVD deposition can be a conventional substrate, such as a 280nm thick SiO2 / Si substrate.
[0023] Preferably, the volatilization temperature of VCl3 is 550–650°C, and more preferably 590–620°C.
[0024] Preferably, X powder is S powder, with a volatilization temperature of 180–250°C. X powder is Se powder, with a volatilization temperature of 380±20°C.
[0025] Preferably, the weight ratio of VCl3 to X powder is 1:2 to 5.
[0026] Preferably, the carrier gas a includes a protective gas and hydrogen; preferably, the protective gas includes an inert gas.
[0027] Preferably, in carrier gas a, the flow rate of the protective gas is 50-100 sccm, more preferably 60-80 sccm, and the flow rate of hydrogen is 1-5 sccm, more preferably 1-3 sccm.
[0028] In this invention, the CVD deposition temperature is 550–650°C, and can be further 590–620°C.
[0029] Preferably, the CVD deposition time is 5 to 15 minutes, and more preferably 9 to 11 minutes.
[0030] In this invention, the power intensity of the laser and the subsequent hydrochloric acid-alcohol treatment are key to the synergistic induction of clean and non-destructive patterning of two-dimensional VX2 materials.
[0031] Preferably, the power intensity of the laser is 1.0 to 3.5 × 10⁻⁶. 5 W / cm 2 Further, it can be 1.5–3.2 × 10⁻⁶. 5 W / cm 2 Furthermore, it is 1.7–1.9 × 10⁻⁶. 5 W / cm 2 .
[0032] In this invention, the size of the laser spot and the duration of laser action on the sample have little impact on the patterning behavior. Therefore, the length of the etched channel can be changed by altering the size of the laser spot, thereby achieving controllable channel length.
[0033] In this invention, the laser processing time can be less than 2 seconds, and more specifically, it can be 0.01 to 2 seconds.
[0034] In this invention, by combining the control of the laser and its power, the physicochemical transformation of the laser-irradiated area can be unexpectedly induced with high selectivity. This, combined with subsequent hydrochloric acid treatment in solution, enables the acquisition of highly crystalline and non-destructive patterns.
[0035] Preferably, the solute concentration in the hydrochloric acid solution can be adjusted as needed. For example, considering the effect and efficiency, it can be above 5M, further to 10-12M, and even further to 11.6-12.0M.
[0036] Preferably, the temperature during the hydrochloric acid solution treatment stage is room temperature.
[0037] Preferably, the hydrochloric acid solution treatment time is more than 1 minute, more preferably 1 to 10 minutes, and considering the treatment efficiency, it can be further 2 to 4 minutes.
[0038] In this invention, after hydrochloric acid treatment, further alcohol solution treatment can be performed. The purpose of the alcohol treatment in this invention is to accelerate the drying process.
[0039] Preferably, the alcohol solution is at least one of C1-C4 monools, diols, and polyols.
[0040] The present invention also includes patterned two-dimensional VX2 materials prepared by the aforementioned preparation method.
[0041] The present invention also provides a method for preparing a patterned two-dimensional lateral VX2 / TMDs heterojunction, wherein the raw materials for synthesizing TMDs are deposited on the surface of the patterned two-dimensional VX2 material deposition substrate to obtain a patterned two-dimensional lateral VX2 / TMDs heterojunction.
[0042] The present invention unexpectedly demonstrates that using the patterned two-dimensional lateral VX2 obtained by the method described in this invention as a deposition substrate for TMDs can unexpectedly promote the growth of TMDs along the lateral direction of VX2, allowing the TMDs to fill the pattern gaps and obtain a patterned two-dimensional lateral VX2 / TMDs heterojunction.
[0043] In this invention, TMDs can be grown on the surface of a patterned two-dimensional transverse VX2 substrate based on conventional principles and methods.
[0044] For example, as an optional solution, the deposition method is CVD deposition;
[0045] For example, the raw materials of the TMDs include a metal element source and a chalcogen element source, wherein the metal element source is at least one of an oxide or chloride of a metal element; wherein the metal element includes at least one of W and Mo; and the chalcogen element source is at least one of elemental sulfur and elemental selenium.
[0046] In one embodiment of the present invention, the TMDs are MoS2, and the synthesized patterned two-dimensional lateral VX2 / MoS2 heterojunction can be MoO3 as the metal source. The oxalic element source is elemental sulfur. The conditions for CVD deposition of MoS2 are as follows: the volatilization temperature of the sulfur powder is 150–250°C, preferably 190–210°C; the volatilization temperature of MoO3 is 550°C–580°C, further preferably 560±10°C; the carrier gas in the CVD stage is an inert gas, such as Ar; the flow rate of the carrier gas is 50–150 sccm; the temperature of the CVD deposition stage is 550°C–580°C, further preferably 560±10°C. 0.1–0.2% by weight of potassium chloride is also mixed into the MoO3 raw material. The CVD deposition time is 5–15 min. An alternative approach is to obtain WSe2 by conventional CVD and PVD methods when the TMDs are WSe2. For example, when using the PVD method, the volatilization temperature of WSe2 can be 1160±40℃; the carrier gas in the PVD stage can be an inert gas with a flow rate of 50 to 100 sccm; and the PVD deposition time can be 1 to 10 min.
[0047] This invention also provides a method for preparing a patterned two-dimensional vertical VX2 / TMDs heterojunction. The method involves first preparing a two-dimensional TMDs material and depositing VX2 on its surface to obtain a VX2 / TMDs heterojunction. Then, the method described in this invention is used to perform laser patterning, hydrochloric acid treatment, and alcohol treatment on the VX2 surface of the VX2 / TMDs heterojunction to obtain the patterned vertical VX2 / TMDs heterojunction.
[0048] In this invention, the VX2 / TMDs heterojunction can be grown using known methods.
[0049] In this invention, as an optional solution, the patterned two-dimensional vertical VX2 / TMDs heterojunction can be a patterned two-dimensional vertical VS2 / MoS2 heterojunction or a patterned two-dimensional vertical VSe2 / WSe2 heterojunction.
[0050] The present invention also provides a patterned two-dimensional heterojunction, which is the patterned two-dimensional transverse VX2 / TMDs heterojunction obtained by the present invention, or the patterned two-dimensional vertical VX2 / TMDs heterojunction.
[0051] The present invention also provides a device comprising the patterned two-dimensional heterojunction, or fabricated by means of the patterned two-dimensional heterojunction using known methods.
[0052] For example, the optional device fabrication steps of the present invention are as follows:
[0053] A field-effect transistor was fabricated by exposing and marking a patterned vertical VX2 / MoS2 metal / semiconductor heterostructure using electron beam lithography, followed by depositing metal onto the sample using electron beam evaporation.
[0054] The metal deposited by electron beam evaporation is Au.
[0055] Beneficial effects
[0056] 1. This invention demonstrates that, through innovative combined control of the laser and its power, the physicochemical characteristics of the material in the laser region can be selectively controlled. Further combined with hydrochloric acid treatment, this synergistic approach yields highly crystallinity and non-destructive patterns. Furthermore, the patterned material obtained by this method, as a substrate, can induce the lateral growth of other two-dimensional materials, resulting in lateral heterojunctions. Moreover, the patterning method described in this invention has good universality and can also pattern the appearance of heterojunctions, obtaining patterned vertical heterojunctions.
[0057] This invention demonstrates, through Raman, EDS, and TEM characterization, that VX2 nanosheets irradiated by laser can be cleanly etched and have a clear interface after acid treatment, thus providing a guarantee for the subsequent growth of heterostructures.
[0058] 2. This invention benefits from the laser radiation etching method described herein, making it possible to pattern vertical VX2 / TMDs metal / semiconductor heterostructures. Thanks to the selective etching of VX2, the TMDs in the vertical heterostructure are not damaged, resulting in VX2 contact TMDs transistors with relatively short channel lengths (~400nm). Attached Figure Description
[0059] Figure 1 An atmospheric pressure chemical vapor deposition apparatus for preparing VS2 two-dimensional materials;
[0060] Figure 2 This is a schematic diagram of the experimental process of laser-irradiated nanosheets in Example 1-1, which were soaked in concentrated hydrochloric acid and then cleaned with ethanol, as well as the morphology and thickness diagram of the patterned VS2 nanosheets.
[0061] Figure 3 EDS elemental analysis diagram of patterned VS2 nanosheets in Example 1-1;
[0062] Figure 4 The laser power density used in Examples 1-2 was 2.23 × 10⁻⁶. 5 W / cm 2 The topography of VS2 after patterning;
[0063] Figure 5 The laser power density used in Examples 1-2 was 3.11 × 10⁻⁶. 5 W / cm2 The topography of VS2 after patterning;
[0064] Figure 6 The graph shows the variation of sample thickness with laser power density in Examples 1-2.
[0065] Figure 7 The blue area represents the thickness of VS2 before and after etching using different laser power densities in Examples 1-2, with the blue area being less than 3.5 × 10⁻⁶. 5 W / cm 2 The red area is greater than 3.5 × 10 5 W / cm 2 ;
[0066] Figure 8 The images show the EDS spectra of VS2 nanosheets etched with different laser power densities in Examples 1-2, where the blue curves show laser power densities less than 3.5 × 10⁻⁶. 5 W / cm 2 The red curve uses a laser power density greater than 3.5 × 10⁻⁶. 5 W / cm 2 ;
[0067] Figure 9 The images show the energy spectrum of VS2 nanosheets under laser irradiation at different laser power densities in Examples 1-2; where... Figure 9 The laser power density used in AD is less than 3.5 × 10⁻⁶. 5 W / cm 2 , Figure 9 The laser power density used in EF is greater than 3.5 × 10⁻⁶. 5 W / cm 2 ;
[0068] Figure 10 These are morphology images of VS2 nanosheets after acid treatment under laser irradiation at different laser power densities in Examples 1-2. Figure 10 b is the morphology of the complete dissolution of the VS2 nanogap under low laser power density laser irradiation; Figure 10 c is the morphology of VS2 transformed into acid-insoluble nanoparticles under high laser power density laser irradiation;
[0069] Figure 11 The images and morphological images of experimental group A treated with 5M hydrochloric acid in Examples 1-3 are shown.
[0070] Figure 12 These are optical images of the samples in Experimental Group B after being fumigated with hydrochloric acid vapor at different times in Examples 1-3.
[0071] Figure 13Examples 1-4 show optical images and topographic thickness maps of VSe2 patterned under different laser power density irradiation; wherein... Figure 13 ad represents the result under high power density radiation; Figure 13 eh represents the result under low power density radiation;
[0072] Figure 14 Optical images of VS2 nanosheets etched using HF treatment in Comparative Example 1-1;
[0073] Figure 15 The experimental setup for synthesizing the transverse VS2-MoS2 metal / semiconductor heterostructure in Example 2-1 is shown in (15a), the structural schematic diagram of the synthesized transverse heterostructure is shown in (15b), and the optical image is shown in (15c).
[0074] Figure 16 Raman characterization of the synthesized transverse VS2-MoS2 metal / semiconductor heterostructure in Example 2-1;
[0075] Figure 17 Optical images and Raman characterization of the vertical VS2 / MoS2 metal / semiconductor heterostructure synthesized in Example 2-2;
[0076] Figure 18 The images show the morphology of MoS2 under different laser power density irradiation in Example 2-2.
[0077] Figure 19 Optical images of the synthesized vertical VSe2 / WSe2 metal / semiconductor heterostructures in Examples 2-3;
[0078] Figure 20 Optical images and transfer characteristic curves of the lateral VS2-MoS2 metal / semiconductor heterostructure field-effect transistor prepared in Example 3-1.
[0079] Figure 21 Optical images (small images), output characteristic curves, and transfer characteristic curves of the vertical VS2 / MoS2 metal / semiconductor heterostructure field-effect transistors prepared in Examples 3-2 are shown.
[0080] Figure 22 Optical images (small images), output characteristic curves, and transfer characteristic curves of the vertical VSe2 / WSe2 metal / semiconductor heterostructure field-effect transistors prepared in Examples 3-3 are shown. Detailed implementation method:
[0081] The present invention will be further illustrated by the following implementation examples, but the content of the present invention is not limited to the following content.
[0082] An optional embodiment of the present invention (Embodiment A) provides a method for preparing two-dimensional VX2 nanosheets based on known methods. For example, the optional method provides the following synthesis conditions for the two-dimensional VX2 nanosheets:
[0083] 1T phase VX2 was grown at ambient pressure on a 280 nm SiO2 / Si substrate using VCl3 (AlfaAssar, ≥99%) and sulfur (AlfaAssar, ≥99.5%) as sources. The X source (e.g., sulfur or selenium) was placed in magnetic boat A upstream of the carrier gas; VCl3 and the substrate were placed in magnetic boat B downstream of the carrier gas. The X source temperature (temperature of magnetic boat A) and the substrate temperature (temperature of magnetic boat B) were controlled at T1 (200±20℃ when the X source was sulfur; 380±20℃ when the X source was elemental selenium) and 605±20℃, respectively. Deposition was carried out for 5–15 min at a mixed flow rate of hydrogen (1–5 sccm) and argon (50–100 sccm), followed by natural cooling to ~300℃, and then rapid cooling by opening the furnace.
[0084] In this invention, VX2 two-dimensional materials obtained by conventional methods can be patterned and etched using a laser, followed by treatment with hydrochloric acid solution to obtain patterned two-dimensional VX2 materials; the power intensity of the laser is less than 3.5 × 10⁻⁶. 5 W / cm 2 .
[0085] This invention provides an optional lateral heterojunction scheme (Scheme B), which uses patterned two-dimensional VX2 nanosheets as the deposition substrate for TMDs. This invention takes MoS2 as an example of TMDs and VS2 nanosheets as an example of patterned two-dimensional VX2 nanosheets. An optional patterned lateral VS2 / MoS2 metal / semiconductor heterostructure is prepared as follows: A magnetic boat C containing sulfur powder is placed upstream of a deposition furnace with a single heating device. Molybdenum oxide powder (5 mg 99.99% Alfa) is mixed with a trace amount of potassium chloride (0.1-0.2% by weight of molybdenum oxide) and placed in the middle of a ceramic boat D, which is then placed downstream of the deposition furnace. A 280 nm SiO2 / Si substrate with patterned two-dimensional VS2 nanosheets is placed face down in the middle of the ceramic boat D containing molybdenum oxide powder. The temperature of magnetic boat C is controlled at 200±20℃ and the temperature of magnetic boat D is controlled at 560℃±20℃. The materials are deposited in an inert atmosphere with a carrier gas flow rate of 100±50 sccm for 10 to 20 minutes, and then allowed to cool naturally to obtain the final product.
[0086] The present invention provides an optional vertical heterojunction scheme (Scheme C), which involves patterning two-dimensional VX2 nanosheets to synthesize a vertical VX2 / MoS2 metal / semiconductor heterostructure. The steps are as follows: using the above-mentioned MoS2 process (Scheme B), MoS2 is deposited on a substrate (which can be a 280nm SiO2 / Si substrate). Then, using the VX2 deposition process of Scheme A, VX2 is deposited on the MoS2 to obtain a VX2 / MoS2 heterojunction. Subsequently, based on the patterning scheme of Scheme A, the patterned vertical VX2 / MoS2 metal / semiconductor heterostructure is obtained.
[0087] This invention provides an optional vertical heterojunction scheme (Scheme C), which involves patterning two-dimensional VX2 nanosheets to synthesize a vertical VX2 / TMD metal / semiconductor heterostructure. Scheme C1 involves patterning two-dimensional VS2 nanosheets to synthesize a vertical VS2 / MoS2 metal / semiconductor heterostructure. The steps are as follows: using the aforementioned MoS2 process (Scheme B), MoS2 is deposited on a substrate (which can be a 280nm SiO2 / Si substrate). Subsequently, using the VX2 deposition process of Scheme A, VS2 is deposited on the MoS2 to obtain a VS2 / MoS2 heterojunction. Then, based on the patterning scheme of Scheme A, the patterned vertical VS2 / MoS2 metal / semiconductor heterostructure is obtained. Scheme C2 involves synthesizing a vertical VSe2 / WSe2 metal / semiconductor heterostructure using patterned two-dimensional VSe2 nanosheets. The steps include: using an optional scheme where the TMDs are WSe2, which can be obtained through conventional CVD and PVD methods. For example, when using PVD, the volatilization temperature of WSe2 can be 1160±40℃; the carrier gas in the PVD stage can be an inert gas with a flow rate of 50–100 sccm; and the PVD deposition time can be 1–10 min. Subsequently, VSe2 is deposited on WSe2 using the VX2 deposition process of Scheme A described above, forming a VSe2 / WSe2 heterojunction. Then, based on the patterning scheme of Scheme A, the patterned vertical VSe2 / WSe2 metal / semiconductor heterostructure is obtained.
[0088] In one embodiment of the present invention, the vertical VX2 / TMD metal / semiconductor heterostructure has a selected TMD greater than 50 μm, and more preferably greater than 100 μm.
[0089] In this invention, the deposition process can be implemented using existing equipment, as long as the temperature control method described above is met.
[0090] In this invention, the materials described herein can be used to prepare devices using known methods.
[0091] 1. Preparation method of patterned VX2 (X = S, Se) two-dimensional material
[0092] Example 1-1
[0093] Step (1):
[0094] Experimental setup for synthesizing VS2 two-dimensional materials, such as Figure 1 As shown, sulfur powder is placed in magnetic boat A upstream of the carrier gas, and VCl3 (sulfur powder and VCl3 weight ratio of 5:1) is placed in magnetic boat B downstream of the carrier gas. The substrate (SiO2 / Si substrate) is placed flat on magnetic boat B with its deposition surface facing upward. Carrier gas (hydrogen flow rate of 2 sccm and Ar flow rate of 70 sccm) is introduced into the deposition tube, and the temperature of magnetic boat A and magnetic boat B is controlled to make the temperature of magnetic boat A 200℃ and the temperature of magnetic boat B 605℃. The deposition is carried out at this temperature and under the carrier gas for 10 min to obtain VS2 two-dimensional material.
[0095] Step (2):
[0096] The VS2 two-dimensional material obtained in step (1) is patterned using a 488nm wavelength laser (intensity 1.88×10⁻⁶). 5 W / cm 2 The VS2 two-dimensional material was laser-treated for 0.01s, then immersed in 12M hydrochloric acid solution for 2 minutes, then treated with ethanol, and dried to obtain the patterned VS2 two-dimensional material.
[0097] Figure 2 a is an experimental flowchart of patterning VS2 and post-treatment of acid-alcohol solution. Figure 2 b and Figure 2 c represents a schematic diagram of the material structure after laser etching and hydrochloric acid solution treatment. Figure 2 de shows the optical image of VS2 after laser etching and its AFM morphology and thickness diagram. Figure 2 fg is an optical image and its AFM morphology and thickness map of the sample obtained after soaking in 12M hydrochloric acid for 2 minutes and washing with ethanol.
[0098] Figure 3 TEM characterization images of patterned VS2 two-dimensional materials prepared after acid treatment and ethanol cleaning show that the prepared material has good crystallinity and compositional uniformity. The laser-etched part was completely cleaned by hydrochloric acid and ethanol treatment, and no V or S elements were found, proving that the two processes of laser etching and solution treatment can obtain a clean two-dimensional material patterned structure.
[0099] Examples 1-2
[0100] Compared with Example 1-1, the only difference is that the laser power density is changed, and the experimental groups are as follows:
[0101] Group A: Laser density is 2.23 × 10⁻⁶ 5 ;
[0102] Group B: Laser density is 3.11 × 10⁻⁶ 5 ;
[0103] Comparative group A: Laser power density is 4.23 × 10⁻⁶ 5 W / cm 2 .
[0104] Other operations and parameters are the same as in Example 1-1.
[0105] Figure 4 The blue area represents experimental group A with a power density of 2.23 × 10⁻⁶. 5 The sample obtained after laser etching, soaking in 12M concentrated hydrochloric acid for 2 minutes, and then cleaning with ethanol. Figure 4 b. Material morphology images confirm the obtained two-dimensional patterned material structure with a clean interface.
[0106] Figure 5 The blue area represents experimental group B with a power density of 3.11 × 10⁻⁶. 5 The sample obtained after laser etching, soaking in 12M concentrated hydrochloric acid for 2 minutes, and then cleaning with ethanol. Figure 5 b. Material morphology images confirm the obtained two-dimensional patterned material structure with a clean interface.
[0107] Figure 6 The statistical variation of VS2 nanosheet thickness under different confocal laser power densities is shown. When the power intensity is approximately 3.5 × 10⁻⁶, the variation is statistically significant. 5 W / cm 2 The thickness of the irradiated area changes drastically. When the power intensity is below the laser power threshold, the thickness of the irradiated area decreases, and vice versa.
[0108] Figure 7 These are optical images of the materials after laser etching in Examples 1-1 and 1-2, wherein... Figure 7 b represents the use of low power density (1.88 × 10⁻⁶) in Example 1-1. 5 W / cm 2 The laser-irradiated area (blue frame area) produces a certain thinning effect, and the thickness of the laser-irradiated area is 1.2nm thinner than the original thickness (7.5nm). Figure 7 The laser etching power used in the red-framed area in Example a is the same as that used in Comparative Group A of Examples 1-2. Figure 7 a and Figure 7 b. Comparison revealed that the higher power density (4.23 × 10⁻⁶) 5 W / cm 2This resulted in a 2.3 nm increase in thickness, and a large number of aggregated nanoparticles were observed in the irradiated area. Once the laser power threshold (3.5 × 10⁻⁶) was exceeded... 5 W / cm 2 The full oxidation reaction of VS2 nanosheets leads to amorphous vanadium oxide (VO₂O₃). z Particle formation.
[0109] Figure 8 Chemical composition analysis of products irradiated with lasers of different power densities was performed using transmission electron microscopy. At relatively weak laser powers (less than 3.5 × 10⁻⁶), the analysis focused on... 5 W / cm 2 Under these conditions, the photothermal oxidation process of VS2 is incomplete, resulting in only partial oxygen doping and the formation of a ternary compound (VS2) composed of V, S, and O. x O y ()( Figure 8 The blue line represents the detection results of the laser-treated material in Example 1-1. Once the laser power threshold (3.5 × 10⁻⁶) is exceeded... 5 W / cm 2 The full oxidation reaction of VS2 nanosheets leads to amorphous vanadium oxide (VO₂O₃). z Particle formation Figure 8 The red line in the figure represents the test results of the material after laser treatment in Comparative Group A in Examples 1-2.
[0110] Figure 9 ad refers to the use of low power density (1.88 × 10⁻⁶) in Example 1-1. 5 W / cm 2 The EDS analysis diagram of the laser irradiation product clearly shows the distribution of the three elements V, O, and S. Figure 9 eh represents the value higher than 3.5 × 10 in control group A of Examples 1-2. 5 W / cm 2 EDS analysis of the product after laser irradiation showed that only V and O elements were visible in the etched area, further confirming the influence of laser power on VS2 nanosheets.
[0111] Figure 10 a is Figure 5 The sample was soaked in 12M concentrated hydrochloric acid for 2 minutes, and then washed with ethanol to obtain the AFM morphology and thickness map of the product. The results showed that the low power density (1.88 × 10⁻⁶) used in Examples 1-1 was effective. 5 W / cm 2 The laser-irradiated product can dissolve in acid, forming a clean interface; while in Examples 1-2, control group A had a concentration higher than 3.5 × 10⁻⁶. 5 W / cm 2 The product after laser irradiation is insoluble in acid, making it impossible to proceed with the next step of heterojunction synthesis.
[0112] Examples 1-3
[0113] Compared to Example 1-1, the only difference is that the concentration of hydrochloric acid was changed, and the experimental groups were as follows:
[0114] Group A: The concentration of hydrochloric acid is 5M;
[0115] Compared to Group A: The laser-etched VS2 nanosheets were placed upside down on a 12M hydrochloric acid solution (without contact with the hydrochloric acid), and then fumigated with HCl vapor at 60°C. The actual concentration of hydrochloric acid acting on the VS2 was higher than that of 12M.
[0116] Group A: Hydrochloric acid concentration of 5M, treatment time of 5min; power density of 1.88×10 5 W / cm 2 After laser etching of VS2 nanosheets, soaking them in approximately 5M hydrochloric acid for 5 minutes still completely removed the etched portion. Figure 11 a shows an optical image of the VS2 after etching. Figure 11 b shows a VS2 optical image after soaking in 5M hydrochloric acid for 5 minutes. Figure 11 c is the AFM topography diagram.
[0117] Compared to Group A: the hydrochloric acid concentration was HCl vapor, but the actual hydrochloric acid concentration acting on VS2 was higher than 12M. Figure 12 Image a is the original optical image from VS2. Figure 12 b is a VS2 optical image taken at 30 seconds. Figure 12 c is the VS2 optical image after 5 minutes of fumigation. This method results in material adsorption in the etched channels, which is detrimental to the subsequent synthesis of heterojunctions.
[0118] A comparison with Examples 1-1 shows that using the hydrochloric acid solution method with a hydrochloric acid concentration of 10M or higher can achieve better non-destructive patterning and crystallinity.
[0119] Examples 1-4
[0120] Example 1-1 describes the preparation of patterned two-dimensional material VS2, and Examples 1-4 describe the preparation of patterned two-dimensional material VSe2. The preparation method is the same as in Example 1-1, except that sulfur powder is replaced with selenium powder, and the volatilization temperature of the selenium powder region (the temperature of magnetic boat A is controlled in the region of 380±5℃) is controlled. In addition, the patterning treatment method and conditions of step 2 in Example 1-1 are used to pattern the material. Other operations and parameters are the same as in Example 1-1.
[0121] (1.88×10 5 W / cm 2 VSe2 nanosheets irradiated by laser ( Figure 13e, f) After immersion in 12M concentrated hydrochloric acid solution for 2 minutes and cleaning with ethanol, the AFM morphology and thickness were measured as follows. Figure 13 As shown in h, the etched portion has been completely etched, forming a relatively clean interface. Similar to control group A in Examples 1-2, the power density used in control group A of Examples 1-2 is 4.23 × 10⁻⁶. 5 W / cm 2 When VSe2 is irradiated with a high-power laser, the thickness of the irradiated region increases, and it becomes insoluble in acid. Figure 13 ad).
[0122] Comparative Example 1-1
[0123] Compared with Example 1-1, the only difference is that HF is used instead of HCl, while other operations and parameters are the same as in Example 1-1.
[0124] Figure 14 a is an optical image of VS2 after etching in Example 1-1. Figure 14 b is an optical image of VS2 after immersion in HF solution for 1 minute. It can be seen that the surface of VS2 nanosheets is damaged after treatment with HF solution, which is not conducive to subsequent growth.
[0125] 2. Fabrication method of patterned two-dimensional transverse and vertical VX2 / MX2 (X = S, Se, M = Mo, W) metal / semiconductor heterostructures
[0126] Example 2-1 - Preparation of Patterned Lateral VS2 / MoS2 Heterojunction
[0127] The preparation steps are as follows: A magnetic boat C containing sulfur powder is placed upstream of a deposition furnace with a single heating device. Molybdenum oxide powder (5 mg 99.99% Alfa) is mixed with a trace amount of potassium chloride (0.1-0.5% by weight of molybdenum oxide) and placed in the middle of a ceramic boat D, which is then placed downstream of the deposition furnace. A 280 nm SiO2 / Si substrate with patterned two-dimensional VS2 nanosheets (prepared in Example 1-1) is placed face down in the middle of the ceramic boat D containing molybdenum oxide powder. The temperature of the magnetic boat C is controlled at 200 °C, and the temperature of the magnetic boat D is controlled at 560 °C. Deposition is carried out for 15 min under an inert atmosphere carrier gas (flow rate of 100 sccm), followed by natural cooling to obtain the final product. Figure 15 Figure a shows a schematic diagram of the experimental setup for growing a transverse VS2 / MoS2 metal / semiconductor heterostructure. When pre-patterned VS2 is used as a growth template for subsequent epitaxial growth, MoS2 tends to nucleate at the edges and gradually fill the nano-intervals of VS2. This is thermodynamically advantageous due to the abundant dangling bonds at the edges. Therefore, a patterned VS2-MoS2 transverse heterostructure was fabricated, where the pink region represents MoS2 and the blue region represents VS2 (…). Figure 15 c).
[0128] Figure 16 Raman spectroscopy further confirmed the successful formation of the transverse heterostructure, and Raman characteristic peaks of VS2 (red line) and MoS2 (green and blue lines) could be detected in the heterostructure. Located at 121 cm⁻¹ -1 165cm -1 and 300cm -1 The Raman peak belongs to the 1T-VS2 category, and is located at 384cm. -1 and 404cm -1 The characteristic peaks are consistent with those of MoS2. Raman mapping studies further confirmed the formation of the VS2 / MoS2 transverse heterostructure. Figure 16 b,c).
[0129] Example 2-2 - Patterned Vertical VS2 / MoS2 Heterogeneous Structure
[0130] Compared to Example 2-1, the only difference is that Example 2-2 uses MoS2 as a growth template to grow VS2 nanosheets, and then performs patterned etching on the VS2 nanosheets to prepare a patterned two-dimensional vertical VS2 / MoS2 heterostructure. The specific operation is the same as in Example 1-1. The steps include:
[0131] Step (a): Preparation of MoS2 nanosheets
[0132] The synthesis method and conditions of MoS2 are the same as in Example 2-1. For example, a magnetic boat C containing sulfur powder is placed upstream of a deposition furnace with a single heating device. Molybdenum oxide powder (5 mg 99.99% Alfa) is mixed with a trace amount of potassium chloride (0.1-0.5% by weight of molybdenum oxide) and placed in the middle of a ceramic boat D, which is placed downstream of the deposition furnace. A 280 nm SiO2 / Si substrate is placed face down in the middle of the ceramic boat D containing molybdenum oxide powder. The temperature of the magnetic boat C is controlled at 200 °C, and the temperature of the magnetic boat D is controlled at 560 °C. Deposition is carried out for 15 min under an inert atmosphere carrier gas (flow rate of 100 sccm), followed by natural cooling to grow MoS2 nanosheets on the substrate.
[0133] Step (b): Preparation of VS2 / MoS2 heterostructure
[0134] The method for growing VS2 nanosheets on MoS2 nanosheets can refer to the preparation of VS2 nanosheets in Example 1, and the steps are as follows:
[0135] S powder is placed in magnetic boat A upstream of the carrier gas, and VCl3 is placed in magnetic boat B downstream of the carrier gas. The substrate (the SiO2 / Si substrate for growing MoS2 nanosheets in step a) is placed flat on magnetic boat B. The carrier gas (hydrogen flow rate of 2 sccm and Ar flow rate of 70 sccm) is introduced into the deposition tube, and the temperature of magnetic boat A and magnetic boat B is controlled to make the temperature of magnetic boat A 200℃ and the temperature of magnetic boat B 605℃. The deposition is carried out at this temperature and under the carrier gas for 10 min to obtain the VS2 / MoS2 heterostructure.
[0136] Step (c): Patterning
[0137] The VS2 on the surface of the VS2 / MoS2 heterostructure was patterned and treated with hydrochloric acid under the conditions of Example 1-1. The steps were as follows:
[0138] The VS2 / MoS2 heterostructure obtained in step (2) was patterned using a 488nm wavelength laser (intensity 1.88×10⁻⁶). 5 W / cm 2 The VS2 / MoS2 heterostructure was laser-treated for 0.1 s, then immersed in 12 M hydrochloric acid solution for 2 min, treated with ethanol, and dried to obtain the patterned VS2 / MoS2 heterostructure.
[0139] Figure 17 To pattern vertical vdW VS2 / MoS2 heterostructures. By changing the growth order of VS2 and MoS2, i.e., using MoS2 as a template for VS2 epitaxial growth, vertical vdW VS2 / MoS2 heterostructures can be grown. Similar to the method in Example 1-1, using a power intensity less than 3.5 × 10⁻⁶. 5 W / cm 2 Laser etching of a vertical vdW VS2 / MoS2 heterostructure, as seen in optical images ( Figure 17 a) It can be seen that etching only occurs in the upper VS2 layer, resulting in a patterned vertical vdW VS2 / MoS2 heterostructure. Figure 17 bc. Raman characterization confirmed the formation of the patterned vertical VdW VS2 / MoS2 heterojunction. Raman mapping showed no Raman peaks for VS2 in the channel region, while the Raman peaks for MoS2 were consistent with the original surface. This provides strong evidence for selective etching of VS2 without damaging the underlying MoS2.
[0140] Figure 18 The images show the morphology of MoS2 etched with different laser powers. The laser power intensities for lines 1 to 6 are 1.88 × 10⁻⁶. 5 W / cm 2 9.92×10 4W / cm 2 1.40×0 5 W / cm 2 4.23×0 5 W / cm 2 4.23×0 5 W / cm 2 2.23×0 5 W / cm 2 As can be seen from the AFM plot, the laser power threshold for pure MoS2 oxidation is slightly lower than that for VS2 radiation, ensuring that MoS2 oxidation does not occur during post-processing.
[0141] Example 2-3 Patterned Vertical VSe2 / WSe2 Heterojunction
[0142] Compared to Example 2-2, the only difference is that step (a) grows WSe2. The preparation steps for WSe2 are as follows: 100 mg of WSe2 powder is weighed and placed in a quartz boat, which is then placed in the center of the tube furnace temperature zone. The SiO2 / Si substrate is placed in the downstream transition temperature zone. The reaction chamber is purged with 1000 sccm of high-purity argon for 10 min to remove residual oxygen and moisture. Then, with argon gas at 80 sccm, the temperature of the central temperature zone is raised to 1160°C using a reverse gas flow (gas flowing from the substrate to the raw material). The gas flow is then switched, and the temperature is maintained at a forward gas flow for 5 min. Natural cooling yields the WSe2 substrate.
[0143] In step b, VSe2 nanosheets are grown, that is, the sulfur powder in step b is replaced with selenium powder, and the temperature of the region where the selenium powder is located is 380±5℃; thus, a VSe2 / WSe2 heterojunction is obtained.
[0144] In step c, VSe2 is patterned using the methods described in Examples 1-3.
[0145] All other operations and parameters are the same as in Example 2-2.
[0146] Then, patterned etching was performed on the VSe2 nanosheets to prepare a patterned two-dimensional vertical VSe2 / WSe2 heterostructure. Figure 19 ).
[0147] 3. Fabrication of patterned vertical VS2 / MoS2 metal / semiconductor heterostructure field-effect transistors
[0148] The fabrication steps of a field-effect transistor are as follows:
[0149] Electron beam lithography was used to expose the desired electrodes on the metal material in the patterned heterostructures of Examples 2-1, 2-2, and 2-3. Then, 60 nm Au was deposited by electron beam evaporation, and the excess metal was stripped off to obtain a vertical VS2 / MoS2 metal / semiconductor heterostructure field-effect transistor.
[0150] Example 3-1
[0151] Figure 20 Optical images and transfer characteristic curves of the patterned lateral VS2 / MoS2 metal / semiconductor heterostructure field-effect transistor synthesized in Example 2-1.
[0152] Example 3-2
[0153] Figure 21 The figures show the output and transfer characteristic curves of the patterned vertical VS2 / MoS2 metal / semiconductor heterostructure field-effect transistor synthesized in Example 2-2. Based on the patterned VS2 / MoS2 vdW heterostructure, VS2 contact MoS2 transistors with relatively short channel lengths (~400 nm) can be easily fabricated, such as... Figure 17 As shown in small figure a, the obtained monolayer MoS2 transistor with vdW contacts exhibits linear IT. ds -V ds The contact is ohmic. The on-state current of the device is ~4.01 μA / μm. -1 The on / off ratio is ~2.89×10 6 The field-effect mobility is ~3.56 cm⁻¹. 2 s -1 V -1 .
[0154] Example 3-3
[0155] Figure 22 The output and transfer characteristic curves of the patterned vertical VSe2 / WSe2 metal / semiconductor heterostructure field-effect transistors synthesized in Examples 2-3 are shown. The VSe2 contact device exhibits a satisfactory near-linear relationship, generating a conduction current of 10 μA / μm. -1 ( Figure 18 a) The corresponding WSe2 transistor exhibits typical p-type transistor behavior in its transfer characteristics, with an on / off current ratio close to 5 × 10⁻⁶. 5 .
Claims
1. A method for preparing patterned two-dimensional VX2 material, characterized in that: Two-dimensional VX2 material was obtained, and then patterned and etched using a laser. After treatment with hydrochloric acid solution, the patterned two-dimensional VX2 material was obtained. X is S or Se. The solute concentration in the hydrochloric acid solution is 10~12M. The temperature of the hydrochloric acid solution treatment stage is room temperature. The hydrochloric acid solution treatment time is 1~10 minutes. The power intensity of the laser is less than 3.5 × 10⁻⁶. 5 W / cm 2 .
2. The method for preparing patterned two-dimensional VX2 material as described in claim 1, characterized in that: The VX2 material was obtained by volatilizing VCl3 and S powder and performing CVD deposition in carrier gas a; The volatilization temperature of VCl3 is 550~650℃; The volatilization temperature of S powder is 180~250℃; The weight ratio of VCl3 to S powder is 1:4~5; Carrier gas a includes a protective gas and hydrogen; the protective gas is an inert gas. In carrier gas a, the flow rate of the protective gas is 50~100 sccm, and the flow rate of hydrogen is 1~5 sccm; The CVD deposition time is 5~15 minutes.
3. The method for preparing patterned two-dimensional VX2 material as described in claim 1, characterized in that: The power intensity of the laser is 1.0 ~ 3.5 × 10⁻⁶. 5 W / cm 2 .
4. The method for preparing patterned two-dimensional VX2 material as described in claim 1, characterized in that: The treatment time with hydrochloric acid solution is 2 to 4 minutes.
5. The method for preparing patterned two-dimensional VX2 material as described in claim 1, characterized in that: After hydrochloric acid treatment, further alcohol solution treatment is carried out; The alcohol solution is at least one of C1-C4 monools, diols, and polyols.
6. A patterned two-dimensional VX2 material prepared by the preparation method according to any one of claims 1 to 5.
7. A method for preparing a patterned two-dimensional transverse VX2 / TMDs heterojunction, characterized in that, The raw materials for synthesizing TMDs are deposited on the surface of the patterned two-dimensional VX2 material deposition substrate as described in claim 6 to obtain a patterned two-dimensional transverse VX2 / TMDs heterojunction.
8. The method for preparing patterned two-dimensional transverse VX2 / TMDs heterojunctions as described in claim 7, characterized in that, The deposition method described is CVD deposition.
9. The method for preparing a patterned two-dimensional transverse VX2 / TMDs heterojunction as described in claim 8, characterized in that, The raw materials for the TMDs include a metal element source and a chalcogen element source, wherein the metal element source is at least one of an oxide or chloride of a metal element; wherein the metal element includes at least one of W and Mo; and the chalcogen element source is at least one of elemental sulfur and elemental selenium.
10. A method for preparing a patterned two-dimensional longitudinal VX2 / TMDs heterojunction, characterized in that, A two-dimensional TMDs material is prepared in advance, and VX2 is deposited on its surface to obtain a VX2 / TMDs heterojunction. Then, the VX2 surface in the VX2 / TMDs heterojunction is subjected to laser patterning, hydrochloric acid treatment and alcohol treatment using the preparation method described in claim 5 to obtain the patterned two-dimensional longitudinal VX2 / TMDs heterojunction.
11. A patterned two-dimensional heterostructure, characterized in that, The patterned two-dimensional transverse VX2 / TMDs heterojunction prepared by any one of the methods of claims 7 to 9, or the patterned two-dimensional longitudinal VX2 / TMDs heterojunction prepared by the method of claim 10.
12. A device, characterized in that, It includes the patterned two-dimensional heterojunction as described in claim 11, or is prepared by the patterned two-dimensional heterojunction described above.
13. The device as claimed in claim 12, characterized in that, The device in question is a field-effect transistor (FET).