A wide-band photodetector based on a novel two-dimensional semimetal material and a preparation method thereof

Abstract

The application discloses a wide-band photodetector based on a novel two-dimensional semi-metal material and a preparation method thereof, and relates to the technical field of photodetector preparation. The method comprises the following steps: mixing 3d magnetic transition metal powder, Ta powder and Te powder, grinding, and preparing mixed raw materials; putting the mixed raw materials into a quartz tube, adding iodine, vacuumizing and sealing, heating, simultaneously establishing a temperature difference, maintaining for one week, cooling to room temperature, then selecting a crystal material obtained in a low-temperature zone, and obtaining a pure-phase target single crystal sample; adopting a mechanical stripping method to dissociate to a thin layer, transferring to a substrate, then adhering and fixing with a mask plate engraved with an electrode pattern, then evaporating Cr / Au electrodes, and preparing the wide-band photodetector based on the novel two-dimensional semi-metal material. The photodetection range is expected to be expanded to a far-infrared light zone or even a terahertz wave band.

Description

Technical Field

[0001] This invention relates to the field of photodetector fabrication technology, specifically to a broadband photodetector based on a novel two-dimensional semi-metallic material and its fabrication method. Background Technology

[0002] As an important optical information sensing device, photodetectors can convert optical signals into electrical signals and are a crucial component of optoelectronic systems, with wide applications in modern military and civilian fields. However, due to the bandgap limitations of materials, photodetectors based on traditional semiconductor materials often only cover a certain wavelength range, and there have always been many technical barriers in some special bands, especially the mid-infrared band. With the gradual expansion of photodetector applications, the demand for high-performance photodetectors (especially ultra-wideband photodetectors capable of covering multiple band responses) is increasing.

[0003] In recent years, researchers have explored using semi-metallic materials to replace narrow-bandgap semiconductors for mid- to long-wavelength photodetectors. These materials have demonstrated unparalleled advantages over semiconductors in terms of low energy consumption, wide spectral density, and high-speed response, attracting widespread attention from researchers both domestically and internationally. Two-dimensional materials possess excellent flexibility, atomic-level thickness, and naturally passivated surfaces (achieving atomic-level flatness, which facilitates multifunctional integration), promising to drive the development of next-generation high-density, low-power memory, high-efficiency photovoltaics, ultra-short channel devices, and spintronic devices. Furthermore, the interaction between two-dimensional materials and light exhibits many fascinating properties, leading to their widespread application in photodetectors, polarization-response detectors, and neural network image sensors. Therefore, the fabrication of novel two-dimensional semi-metallic materials with novel electronic structures and the development of wide-band photodetectors hold significant practical importance. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a wideband photodetector based on a novel two-dimensional semi-metallic material and its fabrication method, thereby solving the problem of low performance of existing photodetectors.

[0005] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for fabricating a broadband photodetector based on a novel two-dimensional semi-metallic material is provided, comprising the following steps:

[0006] (1) Mix 3d magnetic transition metal powder, Ta powder and Te powder, grind them to obtain mixed raw materials;

[0007] (2) The mixed raw material obtained in step (1) is put into a quartz tube, iodine is added, vacuum is applied and sealed, and heated to 700-800 / 600-700℃ within 8-12h, while establishing a temperature difference of 90-110℃, and maintained for one week. Then, the sample is cooled to room temperature and selected from the crystal materials obtained in the low temperature region to obtain the target single crystal sample of the pure phase.

[0008] (3) The target single crystal sample obtained in step (2) is dissected into a thin layer by mechanical peeling and transferred to the substrate. Then, the mask with the electrode pattern is attached and fixed to the target single crystal sample. Then, Cr / Au electrodes are deposited on the surface of the target single crystal sample to obtain a broadband photodetector based on a novel two-dimensional semi-metallic material.

[0009] Based on the above technical solution, the present invention can be further improved as follows:

[0010] Furthermore, in step (1), the 3d magnetic transition metal is Ni or Co.

[0011] Furthermore, in step (1), the molar ratio of the 3d magnetic transition metal, Ta, and Te is 1.5-2.5:1:1.5-2.5.

[0012] Furthermore, in step (1), the molar ratio of the 3d magnetic transition metal, Ta, and Te is 2:1:2.

[0013] Furthermore, in step (2), the mass ratio of the mixed raw materials to iodine is 400-600:40-60.

[0014] Furthermore, in step (2), the mass ratio of the mixed raw materials to iodine is 500:50.

[0015] Furthermore, in step (2), a pure phase target single crystal sample is selected from the crystal material obtained in the low-temperature region using XRD.

[0016] Furthermore, in step (2), the diameter of the quartz tube is 1-1.5cm and the length is 25-30cm.

[0017] Furthermore, in step (2), the diameter of the quartz tube is 1.3cm and the length is 27cm.

[0018] Furthermore, in step (2), after vacuum sealing, the furnace is heated in a dual-temperature zone tubular furnace to establish a temperature difference.

[0019] Furthermore, in step (2), after the pure phase target single crystal sample is tested for physical properties, step (3) is then performed.

[0020] Furthermore, in step (2), the target single crystal sample is TaM′2Te2, where M′ = Co or Ni.

[0021] Furthermore, in step (2), the temperature is heated to 750 / 650°C while establishing a temperature difference of 100°C.

[0022] Furthermore, in step (3), the substrate is a SiO2 / Si substrate.

[0023] Furthermore, in step (3), the mask with the electrode pattern is fixed on the three-dimensional displacement stage to complete the bonding and fixing process.

[0024] Furthermore, in step (3), the substrate containing the target single crystal sample is placed on the sample stage, and the sample to be transferred is found under an optical microscope. Then, the mask with the electrode pattern is fixed on a precise three-dimensional displacement stage using vacuum technology. By manipulating the X and Y axes of the three-dimensional displacement stage, the electrode pattern is aligned with the target single crystal sample. By manipulating the Z axis of the three-dimensional displacement stage, the mask with the electrode pattern is attached and fixed to the target single crystal sample.

[0025] Furthermore, in step (3), Cr / Au electrodes are deposited on the surface of the target single crystal sample by electron beam evaporation.

[0026] Furthermore, in step (3), the thickness of Cr in the Cr / Au electrode is 5-10 nm, and the thickness of Au is 35-45 nm.

[0027] Furthermore, in step (3), the thickness of Cr in the Cr / Au electrode is 8 nm, and the thickness of Au is 40 nm.

[0028] Furthermore, in step (3), after bonding and fixing, Cr / Au electrodes are vapor-deposited in the vacuum chamber.

[0029] The present invention also provides a broadband photodetector based on a novel two-dimensional semi-metallic material prepared by the above method.

[0030] The present invention has the following beneficial effects:

[0031] 1. The fields of condensed matter physics and optoelectronics are investing heavily in finding material platforms that can achieve better performance and circumvent technological bottlenecks. Two-dimensional semi-metallic materials hold promise for exhibiting interesting physical phenomena and have potential applications in broadband optoelectronic detection.

[0032] 2. This invention utilizes 3d magnetic transition metal (M′=Co, Ni) atoms to reduce metallic transition metal tellurium compounds (TaTe2) to prepare TaM′2Te2, which exhibits typical half-metal properties. Its crystal structure contains a Te square network, which readily produces Peierls distortion and exhibits unusual physical phenomena, potentially advancing the development of condensed matter physics. High-quality TaCo2Te2 single-crystal samples at low temperature (2.5K) exhibit large, unsaturated, anisotropic positive magnetoresistance (2682%, at a magnetic field of 9T) and high carrier mobility (1.309 × 10⁻⁶). 4 cm 2 V -1 s -1 Due to incompletely compensated hole and electron concentrations and multiple scattering mechanisms, the field dependence curve of TaCo2Te2 magnetoresistance deviates significantly from H. 2 Field dependence;

[0033] 3. In self-powered mode, the TaCo2Te2 photodetector exhibits a fast response time (18.99μs) and a wide-band response. When the laser beam moves away from the metal electrode-TaCo2Te2 contact area, a robust edge photocurrent response is generated. This is because the crystal field at the low symmetry boundary provides a robust charge separation mechanism, which promotes the effective separation of photogenerated electron-hole pairs.

[0034] 4. In traditional mode, the TaCo2Te2 photodetector exhibits a fast response time (753 μs) and high responsivity (3.13 AW). -1 It exhibits a wide-band photoelectric response of up to 10.6 μm. Due to the gapless electronic structure of TaCo(Ni)2Te2, its photoelectric detection range is expected to be extended to the far-infrared region and even the terahertz band. Attached Figure Description

[0035] Figure 1 The crystal structure diagram of TaCo2Te2 obtained in Example 1 is shown.

[0036] Figure 2 The crystal structure diagram of TaNi2Te2 obtained in Example 2 is shown.

[0037] Figure 3 The XRD pattern of TaCo2Te2 obtained in Example 1;

[0038] Figure 4 The XRD pattern of TaNi2Te2 obtained in Example 2;

[0039] Figure 5 Temperature dependence curves of normalized resistance for TaCo2Te2 prepared in Example 1 and TaNi2Te2 prepared in Example 2;

[0040] Figure 6 The temperature dependence curve of resistivity of TaCo2Te2 obtained in Example 1;

[0041] Figure 7 The field dependence curve of the TaCo2Te2 magnetoresistive material obtained in Example 1 is shown.

[0042] Figure 8 Kohler plot analysis of the magnetoresistance of TaCo2Te2 prepared in Example 1;

[0043] Figure 9 The field dependence curves of the magnetoresistance and Hall resistance of TaNi2Te2 obtained in Example 2 are shown.

[0044] Figure 10 Kohler plot analysis of the magnetoresistance of TaNi2Te2 prepared in Example 2;

[0045] Figure 11 The photocurrent time-resolved curve of the photodetector prepared in Example 1;

[0046] Figure 12 The scanning photocurrent of the photodetector prepared in Example 1;

[0047] Figure 13 The optical power dependence curve of the photocurrent of the photodetector obtained in Example 1;

[0048] Figure 14 The photocurrent response of the photodetector prepared in Example 1 is related to the chopping frequency.

[0049] Figure 15 I is the photodetector prepared in Example 1 ph -V ds curve;

[0050] Figure 16 The photocurrent time-resolved curve amplified within one cycle of the photodetector prepared in Example 1;

[0051] Figure 17 The photocurrent distribution of the photodetector prepared in Example 1 is related to the entire channel position.

[0052] Figure 18 The power density dependence curves of the responsivity and detectivity of the photodetector obtained in Example 1 are shown.

[0053] Figure 19 The time-resolved curve of the photodetector prepared in Example 1 at 532 nm photocurrent;

[0054] Figure 20The time-resolved curve of the photodetector prepared in Example 1 at 980 nm photocurrent;

[0055] Figure 21 Time-resolved curve of photodetector at 10.6 μm photocurrent obtained in Example 1. Detailed Implementation

[0056] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0057] Example 1:

[0058] A broadband photodetector based on a novel two-dimensional semi-metallic material is fabricated using the following steps:

[0059] (1) In a glove box, 3d magnetic transition metal Co powder, Ta powder and Te powder are mixed in a molar ratio of 2:1:2 and ground in an agate mortar to obtain 500mg of mixed raw material.

[0060] (2) The mixed raw materials obtained in step (1) are put into a quartz tube (1.3 cm in diameter and 27 cm in length), and 50 mg of iodine is added as a transport agent. The quartz tube is vacuum sealed and placed in a dual-temperature zone tube furnace. It is heated to 750 / 650℃ within 10 hours, while a temperature difference of 100℃ is established and maintained for one week. After the reaction is completed, the quartz tube is taken out of the tube furnace and quickly cooled to room temperature. The quartz tube is transferred to a fume hood and the quartz tube is opened with a tube breaking tool. Then, XRD is used to select from the crystal materials obtained in the low-temperature zone to obtain the target single crystal sample of pure phase.

[0061] (3) The target single crystal sample (TaCo2Te2) obtained in step (2) is dissected into a thin layer by mechanical exfoliation and transferred to a SiO2 / Si substrate. The substrate containing the target single crystal sample is placed on the sample stage, and the sample to be transferred is found under an optical microscope. Then, the mask with the electrode pattern is fixed on a precise three-dimensional displacement stage by vacuum technology. By manipulating the X and Y axes of the three-dimensional displacement stage, the electrode pattern is aligned with the target single crystal sample. By manipulating the Z axis of the three-dimensional displacement stage, the mask with the electrode pattern is attached and fixed to the target single crystal sample. The sample is transferred into a vacuum cavity, and electron beam evaporation is used to deposit Cr / Au (8 / 40nm) electrodes on the surface of the target single crystal sample to obtain a broadband photodetector based on a novel two-dimensional semi-metallic material.

[0062] Example 2:

[0063] A broadband photodetector based on a novel two-dimensional semi-metallic material is fabricated using the following steps:

[0064] (1) In a glove box, 3d magnetic transition metal Ni powder, Ta powder and Te powder were mixed in a molar ratio of 1.5:1:1.5 and ground in an agate mortar to obtain 400mg of mixed raw material;

[0065] (2) The mixed raw materials obtained in step (1) are put into a quartz tube (1.3 cm in diameter and 27 cm in length), and 40 mg of iodine is added as a transport agent. The quartz tube is vacuum sealed and placed in a dual-temperature zone tube furnace. It is heated to 700 / 610℃ within 10 hours, while a temperature difference of 90℃ is established and maintained for one week. After the reaction is completed, the quartz tube is taken out of the tube furnace and quickly cooled to room temperature. The quartz tube is transferred to a fume hood and the quartz tube is opened with a tube breaking tool. Then, XRD is used to select from the crystal materials obtained in the low-temperature zone to obtain the target single crystal sample of pure phase.

[0066] (3) The target single crystal sample (TaNi2Te2) obtained in step (2) is dissected into a thin layer by mechanical exfoliation and transferred to a SiO2 / Si substrate. The substrate containing the target single crystal sample is placed on the sample stage, and the sample to be transferred is found under an optical microscope. Then, the mask with the electrode pattern is fixed on a precise three-dimensional displacement stage by vacuum technology. By manipulating the X and Y axes of the three-dimensional displacement stage, the electrode pattern is aligned with the target single crystal sample. By manipulating the Z axis of the three-dimensional displacement stage, the mask with the electrode pattern is attached and fixed to the target single crystal sample. The sample is transferred into a vacuum cavity, and electron beam evaporation is used to deposit Cr / Au (5 / 35nm) electrodes on the surface of the target single crystal sample to obtain a broadband photodetector based on a novel two-dimensional semi-metallic material.

[0067] Example 3:

[0068] A broadband photodetector based on a novel two-dimensional semi-metallic material is fabricated using the following steps:

[0069] (1) In a glove box, 3d magnetic transition metal Co powder, Ta powder and Te powder were mixed in a molar ratio of 2.5:1:2.5 and ground in an agate mortar to obtain 600mg of mixed raw material;

[0070] (2) The mixed raw materials obtained in step (1) are put into a quartz tube (1.3 cm in diameter and 27 cm in length), and 60 mg of iodine is added as a transport agent. The quartz tube is vacuum sealed and placed in a dual-temperature zone tube furnace. It is heated to 800 / 690℃ within 8 hours, while establishing a temperature difference of 110℃. It is maintained for one week. After the reaction is completed, the quartz tube is taken out of the tube furnace and quickly cooled to room temperature. The quartz tube is transferred to a fume hood and the quartz tube is opened with a tube breaking tool. Then, XRD is used to select from the crystal materials obtained in the low-temperature zone to obtain the target single crystal sample of pure phase.

[0071] (3) The target single crystal sample (TaCo2Te2) obtained in step (2) is dissected into a thin layer by mechanical exfoliation and transferred to a SiO2 / Si substrate. The substrate containing the target single crystal sample is placed on the sample stage, and the sample to be transferred is found under an optical microscope. Then, the mask with the electrode pattern is fixed on a precise three-dimensional displacement stage by vacuum technology. By manipulating the X and Y axes of the three-dimensional displacement stage, the electrode pattern is aligned with the target single crystal sample. By manipulating the Z axis of the three-dimensional displacement stage, the mask with the electrode pattern is attached and fixed to the target single crystal sample. The sample is transferred into a vacuum cavity, and electron beam evaporation is used to deposit Cr / Au (10 / 45nm) electrodes on the surface of the target single crystal sample to obtain a broadband photodetector based on a novel two-dimensional semi-metallic material.

[0072] Example 4:

[0073] A broadband photodetector based on a novel two-dimensional semi-metallic material is fabricated using the following steps:

[0074] In step (2), the temperature is heated to 800 / 700°C within 12 hours, and the rest is the same as in Example 1.

[0075] Test case

[0076] I. The novel two-dimensional crystal material TaM′2Te2 (M′ = Co or Ni) prepared in Examples 1-2 was subjected to crystal structure and XRD analysis. The XRD test was performed on the prepared single crystal sample, with only the ab crystal plane exposed to X-rays. The results are shown in [Figure 1]. Figure 1-4 . ( Figure 3-4 (The inset is a photograph of the prepared single-crystal sample)

[0077] Depend on Figure 1-2It is known that the TaCo2Te2 and TaNi2Te2 crystals prepared in this invention are typical layered materials, belonging to the orthorhombic Pmcn (No. 62) space group. TaM′2Te2 (M′ = Co or Ni) is formed by stacking five layers of Te-M′-Ta-M′-Te along the c-axis with weak van der Waals interactions, and the Ta atoms in the central layer exhibit a wrinkled square network structure. Alternating M′-M′ dimers support the two sides of the Ta atom square network, forming a serrated long chain. The Te atom layer sandwiches the above structure in the middle on the outermost side, occupying the space between M′ and Ta atoms. In the projection of the TaNi2Te2 crystal structure onto the (001) plane, the serrated chain formed by Ni-Ni dimers is perpendicular to the middle Ta square network layer. In the TaCo2Te2 crystal structure, the serrated long chain formed by Co-Co dimers is alternately tilted to the Ta square network layer. Therefore, the crystal structure of TaCo2Te2 can be considered as the structure formed by the Pearce distortion of the TaNi2Te2 crystal structure driven by electrons.

[0078] Depend on Figure 3-4 It can be seen that all diffraction peaks belong to the ab crystal plane and can be labeled as (00l), consistent with the standard diffraction peaks calculated from the crystal structure in the ICSD database. The XRD pattern shows sharp diffraction peaks, and no impurity diffraction peaks were observed, indicating that the prepared crystal has high purity and crystallinity. To further confirm the composition of the prepared material, the composition of the crystal was analyzed in detail by EDS and EPMA, respectively. The atomic ratio of Ta:Co(Ni):Te is almost close to 1:2:2, with an uncertainty of less than 2%, which is consistent with the results of crystal structure and XRD analysis.

[0079] II. The temperature dependence curves of the conductivity of the TaCo2Te2 single crystal samples prepared in Example 1 and the TaNi2Te2 single crystal samples prepared in Example 2 were detected. The results are shown in […]. Figure 5-6 . ( Figure 5 The normalized resistance is R T / R T0 R T0 (Resistance at 300K)

[0080] Depend on Figure 5 It is known that the room temperature resistivity of the TaCo2Te2 and TaNi2Te2 crystal materials prepared in this invention is 137 mΩcm and 210 mΩcm, respectively. Their resistivity both show a significant decreasing trend with decreasing temperature, exhibiting typical metallic behavior. The residual resistivity (RRR) of TaCo2Te2 and TaNi2Te2 crystals is defined as... xx (300K) / xxThe resistivity (at 2.5K) values ​​are 62 and 82, respectively, indicating higher crystal quality. The temperature dependence curves of the normalized resistivity show significant differences, which may be attributed to the Peierls distortion of the TaCo2Te2 crystal (although there is no indication of the formation of charge density waves), and imply different electron transport properties.

[0081] Depend on Figure 6 It can be seen that when a sufficiently large magnetic field is applied, the resistivity of TaCo2Te2 first decreases and then increases with decreasing temperature. The temperature point where the resistivity is lowest is called the threshold temperature (T*), and the threshold temperature tends to move to higher temperatures with increasing magnetic field (e.g., ...). Figure 6 (As shown in the illustration), this phenomenon implies a complex scattering mechanism.

[0082] III. To further describe the electrical transport properties of the material, the changes in transverse resistivity and Hall resistivity with magnetic field at different temperatures were tested. The results are shown in [Figure number missing]. Figure 7-10 .

[0083] Depend on Figure 7 It can be seen that the magnetoresistance of TaCo2Te2 (RRR value 62) seems to show H over the entire tested magnetic field range. 2 The field dependence corresponds to a carrier-compensated half-metallic material (where the concentrations of holes and electrons are the same, i.e., n). e =n h The expected result. For the dual-carrier model, the magnetoresistance of the material can be described by the following equation:

[0084]

[0085] In the formula n h and μ h n represents the hole concentration and mobility, respectively. e and μ e These represent the electron concentration and mobility, ρ, respectively. xx (H) is the transverse resistivity of the sample under an applied magnetic field strength H, ρ xx (0) represents the transverse resistivity of the sample without an external magnetic field.

[0086] Analysis of the magnetic reluctance equation reveals that, for a fully compensated semi-metallic material, the H value in the denominator increases across the entire tested magnetic field range. 2 The phase can be ignored. Because Therefore, the magnetic resistance of a material can be approximated as:

[0087] MR=μ e μ h H 2

[0088] This hypothesis is also consistent with the anomalous behavior of Hall resistivity: it is dominated by H under low magnetic fields and by H under high fields. 3 Dominant. H and H 3 The contribution coefficient and its sign are both sensitively dependent on n. h n e The small changes in these physical quantities, μe and μh, will lead to a large change in the Hall resistivity field dependence.

[0089] Depend on Figure 8 It can be seen that the magnetoresistance of TaCo2Te2 deviates significantly from H. 2 Field dependence (on the x-axis at 10) 18 At that time, the straight lines in the diagram from bottom to top are H. 1.5 and H 2 Furthermore, the field dependence at low temperatures exhibits a change from H to H with increasing magnetic field. 1.6 Field dependence to H 1.5 The change in field dependence is mainly attributed to the following reasons:

[0090] (1) The charge carriers are not fully compensated (that is, the concentration of holes and the concentration of electrons deviate significantly), and the H in the denominator 2 The contribution of magnetoresistance cannot be ignored. The magnetoresistance increases nonlinearly with the increase of magnetic field (Köhler plot), which is consistent with the carrier concentration information obtained from the fitting.

[0091] (2) Multiple scattering mechanisms. For example, the time reversal symmetry in Dirac halfmetals can prevent backscattering of charge carriers, thereby extending the transport lifetime. These scattering mechanisms are not yet clear and require further investigation.

[0092] Depend on Figure 9-10 It can be seen that although the prepared TaNi2Te2 single crystal sample (RRR value of 82) also exhibits similar H to TaCo2Te2, 1.55 Field correlation ( Figure 10 The middle is at the x-axis of 10 18 At that time, the straight lines in the diagram from bottom to top are H. 1.55 and H 2 However, due to the low carrier mobility, it did not exhibit the expected magnetoresistance effect, and no evidence of dual carrier transport was observed.

[0093] IV. The prepared TaCo2Te2 material exhibits the aforementioned excellent electron transport properties (high carrier mobility) and typical half-metallic characteristics, showing potential research value in wide-wavelength photodetectors. A TaCo2Te2 two-electrode photodetector was fabricated in conjunction with Example 1, and its output performance in self-powered mode was tested using a lock-in amplifier and a chopper at a chopping frequency of 232 Hz. The results are shown in [Figure 1]. Figure 11-14 .

[0094] Depend on Figure 11 It can be seen that, due to the bandgap-free band structure of TaCo2Te2 and the greatly reduced transient lifetime of photoexcited carriers, the photodetector exhibits a significant short-circuit photocurrent response at different excitation photon energies ranging from 0.12 to 2.33 eV.

[0095] Depend on Figure 12 Significant extreme photocurrents were observed at the interface between the TaCo2Te2 sheet and the metal electrode. This is attributed to the effective charge separation induced at the interface by the interaction of the built-in electric field and the photothermoelectric effect. The lattice temperature difference induced by laser irradiation on the device surface generates a thermoelectric driving force due to the photothermoelectric effect, causing charge carriers to move from the high-temperature region to the low-temperature region, thus generating a directional photocurrent. When the laser beam moves away from the interface between the TaCo2Te2 sheet and the metal electrode, the generated photocurrent becomes very weak or even negligible due to the absence of the main charge separation mechanisms (e.g., built-in electric field, photo-Dember effect). A robust photocurrent response was observed at the edge of the channel material inside the interface region of the TaCo2Te2 sheet and the metal electrode, which was completely unexpected. This is because the lattice breaks along the low-symmetry boundary under stress during material peeling. The crystal field at the low-symmetry boundary provides a robust charge separation mechanism, promoting the effective separation of photogenerated electron-hole pairs and generating a significant edge photocurrent response.

[0096] Depend on Figure 13 It can be seen that the photocurrent power dependence curve of the TaCo2Te2 photodetector in self-powered mode shows good linear correlation, and its responsivity is approximately 35 μA W. -1 .

[0097] Depend on Figure 14 It can be seen that the TaCo2Te2 detector exhibits a relatively fast photoelectric response time (18.99μs) related to the chopping frequency under 532nm laser.

[0098] The TaCo2Te2 photodetector fabricated in this invention exhibits a fast response time (18.99 μs) and a wide wavelength range response in self-powered mode. A robust edge photocurrent response is generated when the laser beam moves away from the metal electrode-TaCo2Te2 contact region. This is because the low-symmetry boundary crystal field provides a robust charge separation mechanism, promoting the efficient separation of photogenerated electron-hole pairs. This edge current response provides a robust charge separation mechanism for photoelectric response and energy harvesting over a wide wavelength range.

[0099] V. The photoelectric performance of the TaCo2Te2 two-electrode photodetector prepared in Example 1 was tested in conventional mode using a semiconductor analyzer. The results are shown in [Figure 1]. Figure 15-18 .

[0100] Depend on Figure 15 It can be seen that the TaCo2Te2 photodetector exhibits a significant negative photocurrent response across the entire voltage testing range, and the photocurrent shows a good linear correlation with the external bias voltage. As the laser intensity gradually increases, the generated negative photocurrent shows a significant increasing trend.

[0101] Depend on Figure 16 It is known that the negative photocurrent of the TaCo2Te2 photodetector originates from the entire channel of the photodetector, which is a negative photoconductivity phenomenon caused by the thermal effect of light irradiation or air adsorption. Considering the following facts, the effect of air adsorption is basically ruled out: 1) The prepared TaCo2Te2 material is a typical half-metal material with a relatively small absorption coefficient; 2) The TaCo2Te2 photodetector exhibits good light absorption under high vacuum and in the mid-infrared region (10.6 μm, such as...). Figure 21 As shown, the TaCo2Te2 photodetector still exhibits a large negative photocurrent response. Based on the previous analysis, the negative photocurrent response of the TaCo2Te2 photodetector is attributed to the photothermal effect. That is, when light shines on the surface of the photodetector, the photothermal effect increases the detector's temperature, deteriorates its conductivity, and thus reduces its current when an external voltage is applied, resulting in a negative photocurrent response.

[0102] Depend on Figure 17 It is known that the TaCo2Te2 photodetector exhibits an ultrafast response speed (defined as the time taken for the maximum photocurrent to change between 10% and 90%): a fall time of 852 μs and a rise time of 753 μs.

[0103] Depend on Figure 18 It can be seen that, with an external bias voltage of 2.0V, the TaCo2Te2 photodetector achieves a maximum responsivity of 3.03AW at room temperature. -1 Its output performance is no weaker than that of detectors based on narrow bandgap semiconductors.

[0104] VI. The time-resolved photocurrent curves of the TaCo2Te2 two-electrode photodetector prepared in Example 1 at different laser wavelengths were detected, and the results are shown in [the table below]. Figure 19-21 . ( Figure 19 532nm@0.14W cm -2 ; Figure 20 980nm@0.39W cm -2 ; Figure 21 10.6μm@0.23W cm -2 )

[0105] Depend on Figure 19-21It is evident that, due to the zero-bandgap electronic structure and negative photoelectric response dominated by the photothermal effect of TaCo2Te2 crystal, TaCo2Te2 photodetectors exhibit excellent performance in the infrared and even far-infrared regions. Even at photon energies as low as 0.12 eV, the TaCo2Te2 photodetector still displays a good photoelectric response. Due to the photothermal effect in the infrared band and the influence of the large spot size (3 mm), the photocurrent change of the photodetector at 10.6 μm is relatively slow. The photoresponsivity of the photocurrent generated under continuous illumination for 2.5 min can reach 6.34 AW. -1 It has shown great potential in the field of low photon energy detection. Considering the advantages of the bandgap-free band structure of TaCo2Te2, its photoelectric detection range is expected to be extended to the far-infrared and even terahertz bands.

[0106] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating a broadband photodetector based on a novel two-dimensional semi-metallic material, characterized in that, Includes the following steps: (1) Mix 3d magnetic transition metal powder, Ta powder and Te powder, grind them to obtain mixed raw materials; (2) The mixed raw materials obtained in step (1) are put into a quartz tube, iodine is added, vacuum is applied and sealed, and heated to 700-800 / 600-700℃ within 8-12h, while establishing a temperature difference of 90-110℃, and maintained for one week. Then, the mixture is cooled to room temperature, and the pure phase target single crystal sample is obtained from the crystal materials obtained in the low temperature region. (3) The target single crystal sample obtained in step (2) is dissected into a thin layer by mechanical peeling and transferred to the substrate. Then, the mask with the electrode pattern is attached and fixed to the target single crystal sample. Then, Cr / Au electrodes are deposited on the surface of the target single crystal sample to obtain a wide-band photodetector based on a novel two-dimensional semi-metallic material. In step (1), the 3d magnetic transition metal is Ni or Co; In step (1), the molar ratio of the 3d magnetic transition metal, Ta, and Te is 2:1:2; In step (2), the mass ratio of the mixed raw materials to iodine is 400-600:40-60.

2. The method for fabricating a broadband photodetector based on a novel two-dimensional semi-metallic material according to claim 1, characterized in that, In step (2), XRD is used to select the target single crystal sample of pure phase from the crystal material obtained in the low temperature region.

3. The method for fabricating a broadband photodetector based on a novel two-dimensional semi-metallic material according to claim 1, characterized in that, In step (3), the substrate is a SiO2 / Si substrate.

4. The method for fabricating a broadband photodetector based on a novel two-dimensional semi-metallic material according to claim 1, characterized in that, In step (3), the mask with the electrode pattern is fixed on the three-dimensional displacement stage to complete the bonding and fixing process.

5. The method for fabricating a broadband photodetector based on a novel two-dimensional semi-metallic material according to claim 1, characterized in that, In step (3), Cr / Au electrodes are deposited on the surface of the target single crystal sample by electron beam evaporation.

6. A broadband photodetector based on a novel two-dimensional semi-metallic material, prepared by the method of fabricating a broadband photodetector based on a novel two-dimensional semi-metallic material according to any one of claims 1-5.

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