Fabrication methods of HfSnS3 single crystals and photodetectors

Abstract

The application discloses a kind of HfSnS3 single crystal and the preparation method of photoelectric detector, the preparation method of HfSnS3 single crystal includes: providing a reaction device, the reaction device includes reaction chamber, the reaction chamber includes the source end and growth end communicated;Source material and iodine are placed in the source end of the reaction chamber;Reaction chamber is heated, and the temperature of source end and growth end is heated to first temperature and second temperature respectively for heat preservation, the first temperature is greater than second temperature, and the second temperature is less than the temperature of Hf metal.The application uses iodine as gas phase transport agent, can effectively reduce the reaction activation energy of HfSnS3, makes gas phase reaction occur at temperature lower than the melting point of Hf metal, inhibits the side reaction of Hf+S→HfS2, compared with the CVT method in the prior art, greatly improve the size and quality of HfSnS3 single crystal, lay the foundation for the development of micro-nano photoelectronic device based on HfSnS3.

Description

Technical Field

[0001] This invention relates to the field of semiconductor materials technology, and in particular to a method for preparing HfSnS3 single crystal and a photodetector. Background Technology

[0002] Compared to two-dimensional materials, one-dimensional van der Waals materials have become an independent research topic. They can be exfoliated into nanoribbons, providing a favorable platform for exploring many low-dimensional physical properties (such as quantum effects) and their applications. Due to the absence of dangling bonds on their surface, their inherent strong anisotropy, and their extremely high aspect ratio, one-dimensional van der Waals materials have significant application value for developing next-generation highly integrated, highly sensitive, and multifunctional optoelectronic devices, including broadband photodetectors, memristors, photosynapses, and integrated sensing-memory-computing devices. However, due to the difficulties in fabricating high-quality single crystals and nanoribbons, only a small number of one-dimensional van der Waals materials and corresponding devices for photodetection have been developed to date.

[0003] Hafnium tin sulfide (HfSnS3) is a ternary compound semiconductor and a one-dimensional van der Waals material. It was first synthesized in 1989 by G.A. Wiegers et al. via chemical vapor transport (CVT) and its crystal structure was determined. However, due to limitations in crystal quality, corresponding semiconductor devices have not yet been developed (GA. Wiegers et al. Solid State Tonics, 1989, 32, 183-191). In 2007, Hersh and Peter A. synthesized HfSnS3 powder samples via a solid-state reaction method and tested the Seebeck coefficients of intrinsic HfSnS3, n-type doped, and p-type doped HfSnS3, indicating that intrinsic HfSnS3 is an environmentally friendly thermoelectric semiconductor material (Hersh, Peter A. Oregon State University, 2007. ISBN: 9780549404255). In 2021, Vincent Mathew et al. calculated the theoretical birefringence of HfSnS3 using density functional theory (DFT) and proved its significant optical anisotropy, demonstrating its potential for developing multifunctional optoelectronic devices (Vincent Mathew et al. Solid State Sciences, 2021, 116, 106608). In the same year, S. Shahab Naghavid et al. calculated the thermoelectric power factor of HfSnS3 along different directions using DFT, indicating significant anisotropy in its thermoelectric properties (S. Shahab Naghavi et al. ACS Appl. Mater. Interfaces, 2021, 13, 14189-14197). However, due to the lack of high-quality single crystals, micro / nano optoelectronic devices based on the one-dimensional van der Waals semiconductor HfSnS3 have not yet been developed.

[0004] The existing method for growing HfSnS3 single crystals is chemical vapor transport, which uses elemental hafnium powder, tin powder, and sulfur powder as reactants for gas-phase reaction. The disadvantage is that the content of HfSnS3 product is low and there is a large amount of byproduct HfS2.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing HfSnS3 single crystals and photodetectors, which can overcome the technical problems of low product content and the presence of by-products in the prior art.

[0007] To achieve the above objectives, embodiments of the present invention provide a method for preparing HfSnS3 single crystals, comprising:

[0008] A reaction apparatus is provided, the reaction apparatus including a reaction chamber, the reaction chamber including a source end and a growth end communicating with each other;

[0009] The source material and iodine are placed at the source end of the reaction chamber;

[0010] The reaction chamber is heated to a first temperature and a second temperature, respectively, and then kept at these temperatures. The first temperature is higher than the second temperature, and the second temperature is lower than the temperature of the Hf metal.

[0011] In one or more embodiments of the present invention, the temperature difference between the first temperature and the second temperature is in the range of 50°C-100°C, and the first temperature is 900°C-1000°C, and the second temperature is 800°C-950°C.

[0012] In one or more embodiments of the present invention, the molar ratio of Hf source, Sn source, and S source in the source material is 0.9–1.1:0.9–1.1:2.9–3.1, preferably 1:1:3.

[0013] The amount of iodine added is 3mg-8mg per cubic centimeter of the reaction chamber volume.

[0014] In one or more embodiments of the present invention, the source material includes Hf particles, Sn powder and S powder, wherein the diameter of the Hf particles ranges from 0.1 mm to 2 mm.

[0015] In one or more embodiments of the present invention, the temperature at the source end is heated to a first temperature at a rate of 0.2°C / min to 1°C / min; and / or

[0016] The temperature of the growth end is heated to the second temperature at a rate of 0.2℃ / min-1℃ / min.

[0017] In one or more embodiments of the present invention, the heat preservation time is 120h-196h.

[0018] To achieve the above objectives, embodiments of the present invention also provide a method for fabricating a photodetector, comprising:

[0019] Provide substrate;

[0020] The HfSnS3 single crystals obtained by the method are prepared into HfSnS3 nanoribbons and transferred to the surface of the substrate;

[0021] Channels were etched at both ends of the HfSnS3 nanoribbon to fabricate electrodes.

[0022] In one or more embodiments of the present invention, HfSnS3 nanoribbons are peeled from HfSnS3 single crystals using adhesive tape and then transferred to the substrate surface.

[0023] In one or more embodiments of the present invention, HfSnS3 single crystals are dispersed in an acetone solution and mixed, and then the mixed solution is dropped onto the surface of the substrate. After drying, HfSnS3 nanoribbons are obtained on the substrate surface.

[0024] In one or more embodiments of the present invention, the electrode is a gold electrode with a thickness greater than or equal to 70 nm and less than or equal to 150 nm.

[0025] Compared with existing technologies, this invention uses iodine as a gas-phase transport agent, which can effectively reduce the activation energy of HfSnS3 reaction, enabling the gas-phase reaction to occur at a temperature below the melting point of Hf metal. This suppresses the side reaction Hf+S→HfS2. Compared with the CVT method in existing technologies, this invention greatly improves the size and quality of HfSnS3 single crystals, laying the foundation for the development of micro-nano optoelectronic devices based on HfSnS3. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a reaction apparatus according to an embodiment of the present invention;

[0027] Figure 2 This is an optical image of the HfSnS3 single crystal obtained according to Embodiment 1 of the present invention;

[0028] Figure 3 This is the X-ray diffraction (XRD) pattern of the HfSnS3 single crystal in Example 1 of the present invention;

[0029] Figure 4 This is an atomic force microscope (AFM) image of HfSnS3 nanoribbons according to Embodiment 1 of the present invention;

[0030] Figure 5 This is a spherical aberration electron microscope (STEM) image of the HfSnS3 nanoribbon

[001] orientation according to Embodiment 1 of the present invention;

[0031] Figure 6 These are elemental distribution mapping images and elemental analysis spectra in Embodiment 1 of the present invention, wherein (a), (b), and (c) are EDS-mapping images of the corresponding Hf, Sn, and S elements, and (d) is the elemental analysis spectrum of the corresponding nanoribbon.

[0032] Figure 7 The image shown is an optical microscope image of the photodetector based on HfSnS3 nanoribbons in Embodiment 1 of the present invention;

[0033] Figure 8 The figure shows the response waveforms and responsivity of the HfSnS3 nanobelt photodetector to various wavelengths of light in Embodiment 1 of the present invention. Among them, (a) is the current-voltage curve of the photodetector under 520nm wavelength laser irradiation at different power densities, (b) is the test of the photodetector's light response time, (c) is the time-current response waveform of the photodetector to different wavelengths of light, and (d) is the responsivity parameter of the photodetector under each wavelength.

[0034] Figure 9 The image shown is a photograph of the product obtained from growth in Comparative Example 1.

[0035] Figure 10 The image shown is a photograph of the product obtained from growth in Comparative Example 2;

[0036] Figure 11 The image shown is a photograph of the product obtained from the growth in Comparative Example 3. Detailed Implementation

[0037] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0038] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0039] This invention discloses a method for preparing HfSnS3 single crystals, including the following steps:

[0040] s11. A reaction apparatus is provided, the reaction apparatus including a reaction chamber, the reaction chamber including a source end and a growth end communicating with each other;

[0041] s12. Place the source material and iodine at the source end of the reaction chamber;

[0042] s13. The reaction chamber is heated to a first temperature and a second temperature, respectively, and the temperatures of the source end and the growth end are kept at these temperatures. The first temperature is greater than the second temperature, and the second temperature is less than the temperature of the Hf metal.

[0043] This embodiment uses iodine as a gas-phase transport agent, which can effectively reduce the activation energy of HfSnS3 reaction, enabling the gas-phase reaction to occur at a temperature below the melting point of Hf metal. This suppresses the side reaction Hf+S→HfS2. Compared with the previous CVT method, this greatly improves the size and quality of HfSnS3 single crystals, laying the foundation for the development of micro-nano optoelectronic devices based on HfSnS3.

[0044] Reference Figure 1 As shown, in one embodiment, the reaction apparatus 10 is a quartz tube, comprising a source end 11 and a growth end 12 which are in communication with each other. Wherein, reaction raw materials are placed at the source end 11 of the quartz tube, the growth end serves as a product growth region, and a growth substrate (not shown in the figure) can be placed thereon. In the absence of a growth substrate, a product can also be directly produced at the growth end 12.

[0045] By way of example, a single-opening quartz tube with a length of 20 cm, a thickness of 1 mm, an outer diameter of 15 mm, and an inner diameter of 14 mm is selected as the gas-phase reaction apparatus. If it is necessary to increase the yield of single crystals, the quartz tube needs to be enlarged correspondingly, that is, a larger gas-phase reaction space is provided, which can be performed according to raw material mass (g): reaction volume (cm 3 ) = 1:24 for proportional scaling.

[0046] It has been found through a large number of experiments that under the same experimental conditions, changes in the inner diameter of the quartz tube will affect the length of the obtained crystal. In one embodiment, the inner diameter of the quartz tube is 13 mm to 17 mm, and the corresponding obtained crystal length ranges from 15 mm to 25 mm.

[0047] The growth substrate comprises any one or a combination of at least two of mica sheets, sapphire, SiO₂ substrates or Si substrates. In one embodiment, the growth substrate comprises a plurality of SiO₂ substrates arranged at intervals one above another.

[0048] After the reaction raw materials are placed, the raw materials are sealed in the reaction apparatus 10 under vacuum to 10 -4 Pa using a hydrogen torch and a molecular pump.

[0049] During heating, the reaction apparatus 10 is placed in a dual-temperature zone tube furnace, the source end 11 is placed in the high-temperature zone, and crystal growth is carried out at the growth end 12 in the low-temperature zone. The two temperature zones of the tube furnace are slowly raised to a set first temperature and a set second temperature at the same time, and heat preservation is performed for a period of time to allow single crystal growth. After single crystal growth is completed, the tube furnace is cooled to room temperature. The quartz tube is taken out and crushed to obtain HfSnS₃ single crystals.

[0050] Preferably, the first temperature is 900°C to 1000°C, for example, it can be 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, etc.

[0051] In the present invention, if the first temperature is too low, for example, lower than 900°C, the gas-phase reaction cannot occur; if the temperature is too high, for example, higher than 1000°C, the by-product HfS₂ is easily produced.

[0052] Preferably, the second temperature is 800℃~950℃, for example, it can be 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, 940℃, 950℃, etc.

[0053] In this invention, if the second temperature is too low, such as below 800°C, the gas phase reaction will not occur; if the temperature is too high, such as above 950°C, the byproduct HfS2 will easily be generated.

[0054] In addition, the temperature difference between the first temperature and the second temperature is controlled within the range of 50℃-100℃. Preferably, when the first temperature is 950℃, the second temperature is 900℃; when the first temperature is 900℃, the second temperature is 800℃.

[0055] During the heating process, the heating rate of the source end 11 and the growth end 12 is controlled at 0.2℃ / min to 1℃ / min, for example, it can be 0.2℃ / min, 0.3℃ / min, 0.4℃ / min, 0.5℃ / min, 0.6℃ / min, 0.7℃ / min, 0.8℃ / min, 0.9℃ / min, 1℃ / min, etc.

[0056] Maintaining a low heating rate is beneficial for achieving a steady state of gas-phase transport and improving crystallization quality. In this invention, excessively high heating rates, such as greater than 2°C / min, will cause the transport agent's transport rate to exceed the crystallization rate, resulting in a mismatch that leads to low crystallization quality.

[0057] It should be noted that, in the gas-phase reaction process of this invention, a carrier gas is not required to be introduced into the reaction apparatus, but it is necessary to maintain a temperature of 10°C. -4 High vacuum below Pa.

[0058] Preferably, the heat preservation time is 120h-196h. For example, it can be 120h, 144h, 168h, 172h, 196h, etc.

[0059] In this invention, if the heat preservation time is too short, such as less than 120 hours, the reaction will be incomplete.

[0060] In the raw material, the molar ratio of Hf source, Sn source, and S source is 0.9–1.1:0.9–1.1:2.9–3.1. The amount of iodine added is 3 mg–8 mg per cubic centimeter of reaction chamber volume. In a preferred embodiment, the molar ratio of Hf source, Sn source, and S source is 1:1:3, and the amount of iodine added to the raw material is 5 mg / cm³. -3Extensive experimental comparisons revealed that altering the ratio of Hf, Sn, and S sources could lead to incomplete reactions or excessive waste of raw materials. Conversely, excessive iodine addition would reduce the quality of the obtained crystals, while insufficient iodine addition would affect the gas phase transport rate.

[0061] In some embodiments, the source material includes Hf particles, Sn powder, and S powder, wherein the diameter of the Hf particles ranges from 0.1 mm to 2 mm.

[0062] In this invention, if the Hf particles are too large, they may have internal pores, which can easily cause them to burst during the heating process.

[0063] In some embodiments, the source material may include Hf particles and SnS compounds; in other embodiments, the source material may also include Hf particles and SnS2 compounds.

[0064] This invention also discloses a method for fabricating a photodetector, comprising:

[0065] s21, Provide a substrate;

[0066] s22. The HfSnS3 single crystal obtained by the method described in step s13 is prepared into HfSnS3 nanoribbons and transferred to the surface of the substrate;

[0067] s23. Etch channels at both ends of the HfSnS3 nanoribbon and fabricate electrodes.

[0068] In one embodiment, the substrate may be SiO2 / Si, wherein the SiO2 layer has a thickness of 285 nm and the Si layer has a thickness of 500 μm. In other embodiments, the substrate may also be a flexible PET substrate.

[0069] In step s22, HfSnS3 nanoribbons can be peeled off from the HfSnS3 single crystal using adhesive tape and then transferred to the substrate surface; alternatively, the HfSnS3 single crystal can be dispersed in an acetone solution for mixing, and then the mixed solution can be dropped onto the substrate surface and dried to obtain HfSnS3 nanoribbons on the substrate surface.

[0070] Gold is the preferred material for the electrodes.

[0071] The thickness of the electrode is preferably greater than or equal to 70nm, such as 70nm, 80nm, 90nm, 120nm, 130nm, 140nm, 150nm, etc.

[0072] In this invention, the electrode thickness must not be less than 70 nm, otherwise there will be a large contact resistance.

[0073] Example 1

[0074] Hafnium granules, tin powder, sulfur powder, and iodine granules were selected as raw materials. A single-opening quartz tube with a length of 20 cm, a thickness of 1 mm, an outer diameter of 15 mm, and an inner diameter of 14 mm was selected as the gas-phase reaction apparatus. Figure 1 As stated above.

[0075] Hafnium granules, tin powder, sulfur powder, and iodine granules were mixed in a ratio of 0.454g:0.302g:0.244g:0.12g and then loaded into a quartz tube. A quartz plunger was inserted 12cm from the raw materials, and the tube was sealed by evacuating the vacuum and melting the plunger with a hydrogen gun. The sealed quartz tube was then heated in a dual-temperature zone tube furnace. The high-temperature zone was set to 950℃, and the low-temperature zone was set to 900℃, with a heating rate of 1℃ / min. After reaching the set temperature, it was held for 7 days, and then cooled to room temperature in the furnace. The quartz tube was removed, broken, and HfSnS3 single crystals were obtained.

[0076] HfSnS3 single crystals were placed on adhesive tape and peeled off. After repeating this process 6 to 7 times, the tape with nanowires was pasted onto a SiO2 / Si substrate. The tape was then removed, and nanowires were obtained on the substrate.

[0077] HfSnS3 single crystals were peeled off into nanoribbons using adhesive tape and transferred onto a SiO2 / Si substrate (285 nm / 500 μm thick). Source and drain electrode channels for a photodetector were fabricated at a distance of 10 μm between the two ends of the nanoribbons using electron beam lithography. Gold electrodes with a thickness of 70 nm were then deposited using electron beam evaporation, resulting in a photodetector based on HfSnS3 nanoribbons.

[0078] Figure 2 The image shows a single HfSnS3 crystal grown by the CVT method in this embodiment. It has a needle-like morphology, a metallic luster, and a length of about 2 cm.

[0079] Figure 3 The experimental XRD (x-ray diffraction) pattern and theoretical diffraction peaks of the HfSnS3 single crystal in this embodiment are shown. The two are in good agreement, indicating the accuracy of the grown HfSnS3 single crystal phase.

[0080] Figure 4 The image shows the nanoribbons obtained after peeling off the HfSnS3 single crystal with tape in this embodiment. The nanoribbons have a thickness of 8.62 nm and a width of 540 nm.

[0081] Figure 5 The image shown is a dark-field STEM (scanning transmission electron microscopy) image of a single HfSnS3 nanoribbon in this embodiment. The cell parameters of the a-axis and b-axis of a unit cell in the crystal can be measured, which are 9.31 Å and 3.73 Å, respectively.

[0082] Figure 6Images (a)-(c) in the middle are the corresponding EDS (energy-dispersive X-ray spectroscopy)-mapping images of Hf, Sn, and S elements, respectively. Figure 6 The middle (d) image shows the elemental analysis spectrum of the corresponding nanoribbon, which proves the crystal structure and high crystallinity of HfSnS3.

[0083] Figure 7 The image shows the photodetectors at both ends based on HfSnS3 nanoribbons in this embodiment.

[0084] Figure 8 Figure a shows the current-voltage curves of the photodetector in this embodiment under 520nm wavelength laser irradiation at different power densities. As can be seen from the figure, the HfSnS3 nanoribbons can form a good ohmic contact with the Au electrode at room temperature, resulting in a relatively low interface resistance.

[0085] Figure 8 Figure b shows the test results of the device's photoresponse time in this embodiment. As can be seen from the figure, under the conditions of applied illumination and removal of illumination with a bias voltage of 10V, the measured response times of the detector are 0.355 ms and 0.356 ms, respectively, demonstrating an ultrafast response time.

[0086] Figure 8 Figure c shows the time-current response waveforms of the detector in this embodiment to different wavelengths of light. As can be seen from the figure, the detection wavelength range covers ultraviolet light (275nm) to near-infrared light (808nm), and the detector generates a significant and repeatable photocurrent plateau in each wavelength range, demonstrating the stability of the photodetector based on HfSnS3 nanoribbons at room temperature.

[0087] Figure 8 Figure d shows the responsivity parameters of the photodetector calculated for each wavelength band in this embodiment. It demonstrates the device's effective detection capability from ultraviolet to near-infrared light.

[0088] Example 2

[0089] Hafnium granules, tin powder, sulfur powder, and iodine granules were selected as raw materials. A single-opening quartz tube with a length of 20 cm, a thickness of 1 mm, an outer diameter of 15 mm, and an inner diameter of 14 mm was selected as the gas-phase reaction apparatus. Figure 1 As stated above.

[0090] Hafnium granules, tin powder, sulfur powder, and iodine granules were mixed in a ratio of 0.545g:0.362g:0.293g:0.144g and then loaded into a quartz tube. A quartz plunger was inserted 12cm from the raw materials, and the tube was sealed by evacuating the vacuum and melting the plunger with a hydrogen gun. The sealed quartz tube was then heated in a dual-temperature zone tube furnace. The high-temperature zone was set to 930℃, and the low-temperature zone was set to 880℃, with a heating rate of 1℃ / min. After reaching the set temperature, it was held for 168 hours, and then cooled to room temperature in the furnace. The quartz tube was removed, broken, and HfSnS3 single crystals were obtained.

[0091] The obtained HfSnS3 single crystals have a needle-like morphology, a metallic luster, and a length of approximately 1.8 cm. The yield of HfSnS3 single crystals is approximately 0.5 g, with no byproduct HfS2.

[0092] HfSnS3 single crystals were placed on adhesive tape and peeled off. After repeating this process 6 to 7 times, the tape with nanowires was pasted onto a SiO2 / Si substrate. The tape was then removed, and nanowires were obtained on the substrate.

[0093] HfSnS3 single crystals were peeled off into nanoribbons using adhesive tape and transferred onto a SiO2 / Si substrate (285 nm / 500 μm thick). Source and drain electrode channels for a photodetector were fabricated at a distance of 10 μm between the two ends of the nanoribbons using electron beam lithography. Gold electrodes with a thickness of 70 nm were then deposited using electron beam evaporation, resulting in a photodetector based on HfSnS3 nanoribbons.

[0094] Example 3

[0095] Hafnium granules, tin powder, sulfur powder, and iodine granules were selected as raw materials. A single-opening quartz tube with a length of 20 cm, a thickness of 1 mm, an outer diameter of 15 mm, and an inner diameter of 14 mm was selected as the gas-phase reaction apparatus. Figure 1 As stated above.

[0096] Hafnium granules, tin powder, sulfur powder, and iodine granules were mixed in a ratio of 0.363g:0.242g:0.195g:0.096g and then loaded into a quartz tube. A quartz plunger was inserted 12cm from the raw materials, and the tube was sealed by evacuating the vacuum and melting the plunger with a hydrogen gun. The sealed quartz tube was then heated in a dual-temperature zone tube furnace. The high-temperature zone was set to 970℃, and the low-temperature zone was set to 900℃, with a heating rate of 1℃ / min. After reaching the set temperature, it was held for 168 hours, and then cooled to room temperature in the furnace. The quartz tube was removed, broken, and HfSnS3 single crystals were obtained.

[0097] The obtained HfSnS3 single crystals have a needle-like morphology, a metallic luster, and a length of approximately 1.5 cm. The yield of HfSnS3 single crystals is approximately 0.6 g, with no byproduct HfS2.

[0098] HfSnS3 single crystals were placed on adhesive tape and peeled off. After repeating this process 6 to 7 times, the tape with nanowires was pasted onto a SiO2 / Si substrate. The tape was then removed, and nanowires were obtained on the substrate.

[0099] HfSnS3 single crystals were peeled off into nanoribbons using adhesive tape and transferred onto a SiO2 / Si substrate (285 nm / 500 μm thick). Source and drain electrode channels for a photodetector were fabricated at a distance of 10 μm between the two ends of the nanoribbons using electron beam lithography. Gold electrodes with a thickness of 70 nm were then deposited using electron beam evaporation, resulting in a photodetector based on HfSnS3 nanoribbons.

[0100] Example 4

[0101] Hafnium granules, tin powder, sulfur powder, and iodine granules were selected as raw materials. A single-opening quartz tube with a length of 20 cm, a thickness of 1 mm, an outer diameter of 15 mm, and an inner diameter of 14 mm was selected as the gas-phase reaction apparatus. Figure 1 As stated above.

[0102] Hafnium granules, tin powder, sulfur powder, and iodine granules were mixed in a ratio of 0.363g:0.242g:0.195g:0.096g and then loaded into a quartz tube. A quartz plunger was inserted 12cm from the raw materials, and the tube was sealed by evacuating the vacuum and melting the plunger with a hydrogen gun. The sealed quartz tube was then heated in a dual-temperature zone tube furnace. The high-temperature zone was set to 950℃, and the low-temperature zone was set to 900℃, with a heating rate of 1℃ / min. After reaching the set temperature, it was held for 168 hours, and then cooled to room temperature in the furnace. The quartz tube was removed, broken, and HfSnS3 single crystals were obtained.

[0103] The obtained HfSnS3 single crystals have a needle-like morphology, a metallic luster, and a length of approximately 1.2 cm. The yield of HfSnS3 single crystals is approximately 0.4 g, with no byproduct HfS2.

[0104] HfSnS3 single crystals were placed on adhesive tape and peeled off. After repeating this process 6 to 7 times, the tape with nanowires was pasted onto a SiO2 / Si substrate. The tape was then removed, and nanowires were obtained on the substrate.

[0105] HfSnS3 single crystals were peeled off into nanoribbons using adhesive tape and transferred onto a SiO2 / Si substrate (285 nm / 500 μm thick). Source and drain electrode channels for a photodetector were fabricated at a distance of 10 μm between the two ends of the nanoribbons using electron beam lithography. Gold electrodes with a thickness of 70 nm were then deposited using electron beam evaporation, resulting in a photodetector based on HfSnS3 nanoribbons.

[0106] Comparative Example 1

[0107] Hafnium granules, tin powder, sulfur powder, and iodine granules were selected as raw materials, and a single-opening quartz tube with a length of 20cm, a thickness of 1mm, and an outer diameter of 15mm was selected as the gas phase reaction vessel.

[0108] Hafnium granules, tin powder, sulfur powder, and iodine granules were mixed in a ratio of 0.454g:0.302g:0.244g:0.12g and then loaded into a quartz tube. A quartz plunger was inserted 12cm away from the raw materials, and the tube was sealed by melting the plunger with a hydrogen gun after evacuating the vacuum.

[0109] The sealed quartz tube was placed in a dual-temperature zone tube furnace and heated. The raw material end was set to 900°C, and the other end to 950°C, for reverse temperature gradient growth at a heating rate of 1°C / min. After reaching the set temperature, it was held for 168 hours, and then cooled to room temperature in the furnace. The quartz tube was then removed and broken. The product consisted only of HfS2 single crystals. Figure 9 As shown.

[0110] Comparative Example 2

[0111] Hafnium granules, tin powder, and sulfur powder were selected as raw materials, without the addition of transport agents. A single-opening quartz tube with a length of 20 cm, a thickness of 1 mm, an outer diameter of 15 mm, and an inner diameter of 14 mm was selected as the gas-phase reaction vessel.

[0112] Hafnium granules, tin powder, and sulfur powder were mixed in a ratio of 0.454g:0.302g:0.244g and then loaded into a quartz tube. A quartz plunger was inserted 12cm from the raw material, and the tube was sealed by evacuating the vacuum and melting the plunger with a hydrogen gun. The sealed quartz tube was then placed in a dual-temperature tube furnace for heating. The raw material end was set to 950℃, and the other end to 900℃, with a heating rate of 1℃ / min. After reaching the set temperature, it was held for 168 hours, and then cooled to room temperature in the furnace. The product consisted only of HfS2 single crystals. Figure 10 As shown.

[0113] Comparative Example 3

[0114] Hafnium granules, tin powder, and sulfur powder were selected as raw materials, and TeCl4 was used as the transport agent. A single-opening quartz tube with a length of 20 cm, a thickness of 1 mm, and an outer diameter of 15 mm was selected as the gas-phase reaction vessel.

[0115] Hafnium granules, tin powder, sulfur powder, and TeCl4 raw materials were mixed in a ratio of 0.454g:0.302g:0.244g:0.12g and then loaded into a quartz tube. A quartz plunger was inserted 12cm from the raw materials, and the tube was sealed by evacuating the vacuum and melting the plunger with a hydrogen gun. The sealed quartz tube was then placed in a dual-temperature tube furnace for heating. The raw material end was set to 950℃, and the other end to 900℃, with a heating rate of 1℃ / min. After reaching the set temperature, it was held for 168 hours, and then cooled to room temperature in the furnace. The product consisted only of HfS2 single crystals. Figure 11 As shown.

[0116] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing HfSnS3 single crystal, characterized in that, include: A reaction apparatus is provided, the reaction apparatus including a reaction chamber, the reaction chamber including a source end and a growth end communicating with each other; The source material and iodine are placed at the source end of the reaction chamber; The reaction chamber is heated to a first temperature and a second temperature, respectively, and held at these temperatures. The first temperature is higher than the second temperature, and the second temperature is lower than the melting point of Hf metal. The temperature difference between the first and second temperatures is within 50℃-100℃. The first temperature is 900℃-1000℃, and the second temperature is 800℃-950℃. The holding time is 120h-196h. In the source material, the molar ratio of Hf source, Sn source, and S source is 0.9–1.1:0.9–1.1:2.9–3.1, or 1:1:

3. The amount of iodine added is 3mg-8mg per cubic centimeter of the reaction chamber volume.

2. The method for preparing HfSnS3 single crystal as described in claim 1, characterized in that, In the source material, the molar ratio of Hf source, Sn source and S source is 1:1:

3.

3. The method for preparing HfSnS3 single crystal as described in claim 1, characterized in that, The source material includes Hf particles, Sn powder and S powder, and the diameter of the Hf particles ranges from 0.1 mm to 2 mm.

4. The method for preparing HfSnS3 single crystal as described in claim 1, characterized in that, The source end temperature is heated to the first temperature at a rate of 0.2℃ / min -1℃ / min; and / or The temperature of the growth end is heated to the second temperature at a rate of 0.2℃ / min-1℃ / min.

5. A method for fabricating a photodetector, characterized in that, include: Provide substrate; The HfSnS3 single crystal obtained by any one of the methods described in claims 1 to 4 is prepared into HfSnS3 nanoribbons and transferred to the surface of the substrate; Channels were etched at both ends of the HfSnS3 nanoribbon to fabricate electrodes.

6. The method for fabricating a photodetector as described in claim 5, characterized in that, HfSnS3 nanoribbons were peeled from the HfSnS3 single crystal using adhesive tape and then transferred to the substrate surface.

7. The method for fabricating a photodetector as described in claim 5, characterized in that, HfSnS3 single crystals were dispersed in an acetone solution and mixed. The mixed solution was then dropped onto the substrate surface and dried to obtain HfSnS3 nanoribbons on the substrate surface.

8. The method for fabricating a photodetector as described in claim 5, characterized in that, The electrode is a gold electrode with a thickness greater than or equal to 70 nm and less than or equal to 150 nm.

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