Self-powered lithium tantalate film photoelectric detector and preparation method thereof

Abstract

The invention discloses a self-powered lithium tantalate film photoelectric detector and a preparation method thereof. The self-powered lithium tantalate film photoelectric detector sequentially comprises a silicon substrate, a silicon dioxide insulating layer, an intrinsic lithium tantalate film layer, an ion implantation lithium tantalate film layer and a metal electrode layer from bottom to top, the preparation method specifically comprises the following steps: (1) cleaning the lithium tantalate film, and polishing the surface of the lithium tantalate film; (2) ion implantation; (3) annealing treatment; (4) spin-coating photoresist, and preparing a mask plate pattern; and (5) depositing a metal electrode. Compared with a traditional self-powered photoelectric detector, the self-powered lithium tantalate film photoelectric detector is a miniature integratable photoelectric detector, the integration level is greatly improved, and the self-powered lithium tantalate film photoelectric detector has a wider application prospect.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor optoelectronic technology, and more specifically to a self-powered lithium tantalate thin film photoelectric detector and a preparation method thereof. Background Art

[0002] Lithium niobate on insulator (LNOI) is a material obtained by bonding lithium niobate film to a wafer slice. Due to its excellent light confinement effect and good inherent properties of bulk materials, it has become an important optical platform for building chip integrated devices. As ferroelectric crystals with similar structures, lithium tantalate and lithium niobate both have rich optical properties, such as pyroelectric effect, photorefractive effect, nonlinear optical effect and bulk photovoltaic effect. Lithium tantalate on insulator (LTOI) is a material obtained by bonding lithium tantalate film to a wafer slice. Compared with LNOI, LTOI has a lower Curie temperature, a higher light damage threshold and a lower preparation cost, which is suitable for low-cost large-scale manufacturing, and therefore shows important potential in photonic chip applications.

[0003] In a full-function photonic chip, optical signals need to be detected after they are generated and modulated. On-chip photodetectors are used to convert optical signals (light energy) into electrical signals (electrical energy) and are key components of photonic circuits. Self-powered photodetectors are devices that can work without an external energy supply and are particularly suitable for unattended environmental monitoring and target detection in special environments. Although lithium tantalate has a wide optical transparency window, its light absorption capacity in the visible and infrared bands is weak, resulting in low photoelectric conversion efficiency. In addition, the high insulation and low conductivity of lithium tantalate limit the ability to collect photogenerated current, thereby affecting the response speed and sensitivity of the self-powered photodetector.

[0004] The most common method for preparing lithium tantalate thin film photodetectors is to heterogeneously integrate lithium tantalate thin films with photosensitive materials such as wide bandgap semiconductors (such as AlN, GaN), silicon, III-V semiconductors, and two-dimensional materials. However, this type of heterogeneous integration device has a complex structure, high cost, high loss, and a narrow response band. At the same time, lattice mismatch problems may occur, which is not conducive to further integration of the device.

[0005] Therefore, in order to develop high-performance on-chip self-powered photodetectors, it is urgent to find a method that can simultaneously improve the conductivity of lithium tantalate and enhance the photoelectric conversion capability to achieve efficient photodetection in the LTOI platform. Summary of the invention

[0006] In view of this, an object of the present invention is to provide a self-powered lithium tantalate thin film photodetector and a preparation method thereof to address the deficiencies in the prior art.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A self-powered lithium tantalate thin film photodetector comprises, from bottom to top, a silicon substrate, a silicon dioxide insulating layer, an intrinsic lithium tantalate thin film layer (not ion-implanted), an ion-implanted lithium tantalate thin film layer and a metal electrode layer.

[0009] Furthermore, the thickness of the silicon substrate is 0.5-0.6 mm.

[0010] Furthermore, the thickness of the silicon dioxide insulating layer is 2 μm.

[0011] Furthermore, the thickness of the intrinsic lithium tantalate thin film layer is 750-800 nm.

[0012] Furthermore, the thickness of the ion-implanted lithium tantalate thin film layer is 100-150 nm.

[0013] Furthermore, the metal electrode layer is in the shape of parallel electrodes or interdigitated electrodes, is made of at least one of nickel, chromium and gold, and has a thickness of less than 100 nm.

[0014] Furthermore, the thickness of the parallel electrodes is 50 nm, the electrode spacing is 50-70 μm, and the electrode width is 30-50 μm.

[0015] Furthermore, the thickness of the interdigital electrodes is 35 nm, and the distance between the electrodes is 40 to 70 μm.

[0016] A method for preparing the self-powered lithium tantalate thin film photodetector comprises the following steps:

[0017] (1) cleaning the lithium tantalate film and polishing the surface to obtain a pretreated lithium tantalate film;

[0018] (2) the silicon substrate of the pretreated lithium tantalate film is adhered to a silicon wafer target plate by means of a conductive adhesive and placed in an ion implantation vacuum chamber, and ions are implanted into the surface (film surface) of the pretreated lithium tantalate film to obtain an ion-implanted lithium tantalate film;

[0019] (3) placing the ion-implanted lithium tantalate film in an annealing furnace for annealing to obtain an annealed lithium tantalate film;

[0020] (4) spin coating a photoresist on the annealed lithium tantalate film, and using a photolithography technique to prepare a mask pattern on the annealed lithium tantalate film to obtain a photolithographic lithium tantalate film;

[0021] (5) Electron beam evaporation or magnetron sputtering is used to deposit metal electrodes on the photolithographic lithium tantalate film to obtain a self-powered lithium tantalate thin film photodetector.

[0022] Furthermore, in the above step (2), the ion implantation adopts low-energy metal ion implantation, the implantation condition is vacuum, the implantation angle is normal incidence, and the angle with the normal line is less than 5°, the implanted metal ions are not screened for valence state, contain multiple valence states, and the beam density during the implantation process is less than 10nA / cm 2 After the injection is completed, it is left to stand for 24 hours to avoid radiation hazards, and an embedded plasmon nanoparticle structure is obtained in the near-surface area; the size of the nanoparticles is 2 to 20 nm, and the distance from the near-surface is within 150 nm.

[0023] Furthermore, in the above step (2), the ion implantation is performed by gold ion implantation, the implantation energy is 120-160 keV, preferably 150 keV, and the implantation dose is (2×10 16 )~(8×10 16 )ions / cm 2 , preferably 2×10 16 ions / cm 2 .

[0024] Furthermore, in the above step (2), the ion implantation is performed by silver ion implantation, the implantation energy is 120 to 200 keV, preferably 200 keV, and the implantation dose is (5×10 16 )~(1×10 17 )ions / cm 2 , preferably 1×10 17 ions / cm 2 .

[0025] Furthermore, in the above step (3), the annealing treatment is carried out in a nitrogen or vacuum atmosphere, at a temperature of 100 to 150° C., for a time of 0.5 to 1 hour. It should be noted that when silver ion implantation is used, annealing treatment may not be performed.

[0026] Furthermore, in the above step (5), metal nickel is deposited on the photolithographic lithium tantalate film to form parallel electrodes.

[0027] Furthermore, in the above step (5), a layer of metal chromium with a thickness of 5 nm is first deposited on the photolithographic lithium tantalate film, and then a layer of gold with a thickness of 30 nm is deposited to form a chromium / gold interdigital electrode.

[0028] It can be seen from the above technical solution that compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. The method of the present invention uses lithium tantalate film on a silicon substrate as a functional material, and uses ion implantation technology to bombard the surface of the lithium tantalate film with metal ions of specific energy and specific dose, forming embedded metal nanoparticles near the surface of the lithium tantalate film, and then uses electron beam evaporation or magnetron sputtering to evaporate metal electrodes of specific patterns on the pre-masked ion-implanted lithium tantalate film to prepare a self-powered lithium tantalate film photodetector. Due to the localized surface plasmon resonance effect of the nanoparticles, the interaction between light and matter inside the lithium tantalate is enhanced, and a higher photocurrent can be obtained.

[0030] 2. The present invention prepares a self-powered lithium tantalate thin film photodetector based on the ion implantation method. Under the conditions of precise control of the implantation energy and the implantation dose, the distribution of plasmon nanoparticles in the lithium tantalate thin film and the damage to the lithium tantalate lattice structure can be controlled, thereby improving the conductivity of lithium tantalate and broadening the light response bandwidth. It has extremely strong controllability and finally realizes the preparation of a wide-band self-powered lithium tantalate thin film photodetector from ultraviolet to near-infrared band at room temperature.

[0031] 3. Compared with the method of preparing lithium tantalate thin film photodetectors by heterogeneous integration, the preparation method of the present invention is simple, efficient, low-cost, and highly repeatable, and dozens of self-powered lithium tantalate thin film photodetectors with similar performance can be prepared at one time.

[0032] 4. Compared with the traditional self-powered photodetector, the self-powered lithium tantalate thin film photodetector of the present invention is a miniature integrable photodetector with greatly improved integration and broader application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the ion implantation and structure of the self-powered lithium tantalate thin film photodetector of the present invention; wherein, a is a schematic diagram of the ion implantation of the self-powered lithium tantalate thin film of the present invention, b is a schematic diagram of the structure of the self-powered lithium tantalate thin film photodetector of the present invention, 1-silicon substrate, 2-silicon dioxide insulating layer, 3-intrinsic lithium tantalate thin film layer, 4-ion implantation, 5-ion implanted lithium tantalate thin film layer, 6-nanoparticles, 7-metal electrode layer;

[0034] Figure 2 The distribution diagram of ion concentration with implantation depth simulated by SRIM software;

[0035] Figure 3 This is a current-voltage curve of the self-powered lithium tantalate thin film photodetector in Example 1 under light-free conditions and at 532 nm;

[0036] Figure 4 This is a current-time curve of the self-powered lithium tantalate thin film photodetector of Example 1 excited at a wavelength of 532 nm;

[0037] Figure 5 This is a current-time curve diagram of the self-powered lithium tantalate thin film photodetector of Example 1 excited at a wavelength of 980nm;

[0038] Figure 6 This is a current-time curve of the self-powered lithium tantalate thin film photodetector of Example 1 excited at a wavelength of 1310 nm;

[0039] Figure 7 This is the current-time curve of the self-powered lithium tantalate thin film photodetector of Example 2 under zero bias and 473nm light excitation. The laser power density is 3.19mW / cm 2 .

[0040] Figure 8 This is the current-time curve of the self-powered lithium tantalate thin film photodetector of Example 2 under zero bias and 473nm light excitation. The laser power density is 3.98mW / cm 2 . DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Example 1

[0043] Self-powered lithium tantalate thin film photodetectors, such as Figure 1 As shown, from bottom to top, there are a silicon substrate 1 with a thickness of 0.5 mm, a silicon dioxide insulating layer 2 with a thickness of 2 μm, an intrinsic lithium tantalate thin film layer 3 with a thickness of 750 nm, an ion-implanted lithium tantalate thin film layer 5 with a thickness of 150 nm, and a parallel metal nickel electrode layer 7 with a thickness of 50 nm, an electrode spacing of 50 μm, and an electrode width of 50 μm;

[0044] The method for preparing the self-powered lithium tantalate thin film photodetector specifically comprises the following steps:

[0045] (1) cleaning a lithium tantalate film on an insulator with a thickness of 900 nm and a size of 5 mm×5 mm×0.5 mm, and polishing the surface to obtain a pretreated lithium tantalate film;

[0046] (2) The silicon substrate 1 with the pre-treated lithium tantalate film was adhered to the silicon wafer target plate by conductive adhesive and placed in an ion implantation vacuum chamber. Gold ions were implanted into the surface of the pre-treated lithium tantalate film under vacuum conditions. The implantation energy was 150 keV and the implantation dose was 2×10 16ions / cm 2 The beam density during the injection process is 8nA / cm 2 , an embedded plasmon nanoparticle structure is obtained in the near-surface region, the size of the nanoparticle 6 is 2 to 10 nm, and the distance from the near-surface is 150 nm. After the injection is completed, the film is left to stand for 24 hours to obtain a gold ion-implanted lithium tantalate film;

[0047] (3) placing the gold ion-implanted lithium tantalate film in an annealing furnace, and annealing the film in a vacuum environment at a temperature of 150° C. for 0.5 h to obtain an annealed lithium tantalate film;

[0048] (4) spin coating a photoresist on the annealed lithium tantalate film, and using a photolithography technique to prepare a mask pattern on the annealed lithium tantalate film to cover the area other than the electrode, thereby obtaining a photolithographic lithium tantalate film;

[0049] (5) Electron beam evaporation is used to deposit metallic nickel on the photolithographic lithium tantalate film, the photoresist is removed by cleaning in acetone, and the remaining liquid is blown dry with a nitrogen gun to prepare the source and drain electrodes, thereby obtaining a self-powered lithium tantalate thin film photodetector.

[0050] Example 2

[0051] Self-powered lithium tantalate thin film photodetectors, such as Figure 1 As shown, from bottom to top, there are a silicon substrate 1 with a thickness of 0.5 mm, a silicon dioxide insulating layer 2 with a thickness of 2 μm, an intrinsic lithium tantalate thin film layer 3 with a thickness of 800 nm, an ion-implanted lithium tantalate thin film layer 5 with a thickness of 100 nm, and a parallel metal nickel electrode layer 7 with a thickness of 50 nm, an electrode spacing of 70 μm, and an electrode width of 50 μm;

[0052] The method for preparing the self-powered lithium tantalate thin film photodetector specifically comprises the following steps:

[0053] (1) cleaning a lithium tantalate film on an insulator with a thickness of 900 nm and a size of 5 mm×5 mm×0.5 mm, and polishing the surface to obtain a pretreated lithium tantalate film;

[0054] (2) The silicon substrate 1 with the pre-treated lithium tantalate film was adhered to the silicon wafer target plate by conductive adhesive and placed in an ion implantation vacuum chamber. Silver ions were implanted into the surface of the pre-treated lithium tantalate film under vacuum conditions. The implantation energy was 200 keV and the implantation dose was 1×10 17 ions / cm 2 The beam density during the injection process is 8nA / cm 2, an embedded plasmon nanoparticle structure is obtained in the near-surface region, the size of the nanoparticle 6 is 2 to 20 nm, and the distance from the near-surface is 100 nm. After the injection is completed, the silver ion-implanted lithium tantalate film is obtained by standing for 24 hours;

[0055] (3) placing the silver ion-implanted lithium tantalate film in an annealing furnace, and annealing the film in a vacuum environment at a temperature of 150° C. for 0.5 h to obtain an annealed lithium tantalate film;

[0056] (4) spin coating a photoresist on the annealed lithium tantalate film, and using a photolithography technique to prepare a mask pattern on the annealed lithium tantalate film to cover the area other than the electrode, thereby obtaining a photolithographic lithium tantalate film;

[0057] (5) Electron beam evaporation is used to deposit metallic nickel on the photolithographic lithium tantalate film, the photoresist is removed by cleaning in acetone, and the remaining liquid is blown dry with a nitrogen gun to prepare the source and drain electrodes, thereby obtaining a self-powered lithium tantalate thin film photodetector.

[0058] Performance Testing

[0059] 1. Example 1 SRIM simulation test of self-powered lithium tantalate thin film photodetector

[0060] During the ion implantation process, when the metal ions in the lithium tantalate film exceed the solid solubility of lithium tantalate, the metal ions agglomerate and spontaneously precipitate to form nanoparticles; when the metal ions in the lithium tantalate film are lower than the solid solubility of lithium tantalate, the metal ions exist in the lithium tantalate film in the form of ions.

[0061] The distribution of ion concentration with implantation depth simulated by SRIM software is shown in the figure below: Figure 2 shown.

[0062] Depend on Figure 2 It can be seen that the concentration distribution of metal ions shows a Gaussian distribution characteristic with the injection depth. Therefore, after ion implantation, metal nanoparticles with a diameter of about 2 to 10 nm can be formed near the surface of the lithium tantalate film, and some metal ions can be doped into the lithium tantalate film. On the one hand, metal nanoparticles produce a strong near-field enhancement effect under the action of the localized surface plasmon effect, which can promote the interaction between light and matter in the lithium tantalate film and improve the light absorption capacity of lithium tantalate, thereby generating more photocarriers in the lithium tantalate film; on the other hand, metal ion doping will increase the number of free carriers in lithium tantalate, while forming oxygen vacancies, changing the energy band structure of lithium tantalate, and improving the carrier mobility, thereby enhancing the conductivity of the lithium tantalate film.

[0063] By measuring the linear absorption spectrum and electron transmission microscopy of the ion-implanted lithium tantalate film, the distribution of metal nanoparticles inside the lithium tantalate film and the change of the lithium tantalate absorption peak are determined. Combined with the test results, the ion implantation parameters are optimized to broaden the absorption bandwidth of the lithium tantalate film and improve the absorbance.

[0064] 2. Photoelectric performance test of self-powered lithium tantalate thin film photodetector in Example 1

[0065] The laser output by the optical fiber coupling is focused onto the upper surface of the lithium tantalate film through a microscope objective lens, and a wire is led out from the nickel electrode to connect to a digital source meter, and the photoelectric performance of the self-powered lithium tantalate film photodetector prepared in Example 1 is tested.

[0066] The excitation wavelength was selected as 532 nm and the laser power density was set to 150 mW / cm 2 The current-voltage characteristic relationship diagrams measured under no light conditions and light conditions are shown in the figure below. Figure 3 As shown, it is proved that the device can work without external bias and realize self-power supply. This is because the lithium tantalate film after ion implantation has a strong photovoltaic effect, which can generate a strong built-in electric field under light excitation, thus realizing self-powered photoelectric detection.

[0067] Figure 4 The current-time curve under this excitation condition was recorded, and the laser frequency was set to 0.2Hz. It can be seen that the self-powered lithium tantalate thin film photodetector generated a stable steady-state photocurrent signal under 532nm wavelength excitation.

[0068] Change the excitation wavelength, select a 980nm continuous wave laser as the light source, and set the laser power density to 200mW / cm 2 , the laser modulation frequency is 0.2Hz, the test time is 30s, Figure 5 is the measured current-time curve.

[0069] In order to further explore the light response characteristics of the self-powered lithium tantalate thin film photodetector in the infrared band, a wavelength of 1310nm was selected for excitation, and the test method was the same as above. 2 、150mW / cm 2 , 200mW / cm 2 、250mW / cm 2 、300mW / cm 2 Photocurrent changes under power density excitation, Figure 6 The current-time curves at different powers were recorded.

[0070] Depend on Figure 3-6It can be seen that the self-powered lithium tantalate thin film photodetector of Example 1 has the characteristic of wide-band response, and can realize self-powered photodetection from visible light to infrared light.

[0071] 3. Photoelectric performance test of self-powered lithium tantalate thin film photodetector in Example 2

[0072] The semiconductor laser with a central wavelength of 473nm coupled to the fiber is focused on the upper surface of the lithium tantalate film through a microscope objective lens, and the laser power density is 3.19mW / cm 2 , the focused spot diameter is about 80 μm. The laser is externally modulated by a signal generator, the frequency is set to 0.2 Hz, and the laser switching and light-off time are 2.5 s respectively. Lead wires are connected to a digital source meter on the nickel electrode, and the photoelectric performance of the self-powered lithium tantalate thin film photodetector prepared in Example 2 is tested.

[0073] Figure 7 The current was recorded as a function of time. The laser power density was 3.19 mW / cm 2 . Under zero bias, the on / off ratio is >1000, the responsivity is 35μA / W, and the detection rate is 1.86×10 4 Jones. Applying a 1V bias to the device increases the responsivity to 50mA / W. This proves that the device can generate photocurrent without applying an external bias, thus achieving self-powered photodetection.

[0074] Increase the laser power density to 3.98mW / cm 2 , Figure 8 is the current-time curve under this power density. After increasing the power, the photocurrent signal still appears as a pyroelectric current signal. This is because under low power density excitation, the number of photogenerated carriers generated is small and the steady-state photocurrent is low. Therefore, the pyroelectric signal occupies a dominant position.

[0075] 4. Comparative description of Example 1 and Example 2

[0076] The structures and preparation methods of the self-powered lithium tantalate thin film photodetectors of Example 1 and Example 2 are similar, except that the parameters (type, energy, and dosage) of ion implantation are different, resulting in different damage to the lithium tantalate lattice after ion implantation and different distribution of nanoparticles. Figure 2-7 It can be seen that ion implantation parameters will affect the device performance of self-powered lithium tantalate thin film photodetector.

[0077] The above experiments show that the present invention abandons the commonly used heterogeneous integration method, and innovatively uses ion implantation technology to directly modify the material inside the lithium tantalate film, directly using the lithium tantalate film as a new optoelectronic material, without the need to integrate with other semiconductor materials, to achieve a wide-band self-powered photodetector. The preparation method of the present invention has a simple process and low cost, and can be mass-produced on a large scale. The present invention has a simple structure and is easy to integrate with other optoelectronic devices or photonic devices, thereby realizing a multifunctional on-chip photonic system in the lithium tantalate film. Moreover, by adjusting the parameters of ion implantation (such as the type of implanted ions, implantation energy, implantation dose, implantation method and other parameters), the size and distribution of the nanoparticles can be optimized, thereby further regulating the light absorption characteristics of the lithium tantalate film and enhancing the photoelectric conversion capability.

[0078] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A self-powered lithium tantalate thin film photodetector, characterized in that: From bottom to top, they are silicon substrate, silicon dioxide insulating layer, intrinsic lithium tantalate thin film layer, ion-implanted lithium tantalate thin film layer and metal electrode layer.

2. A self-powered lithium tantalate thin film photodetector according to claim 1, characterized in that: The thickness of the silicon substrate is 0.5-0.6 mm; the thickness of the silicon dioxide insulating layer is 2 μm; the thickness of the intrinsic lithium tantalate thin film layer is 750-800 nm; the thickness of the ion-implanted lithium tantalate thin film layer is 100-150 nm; the shape of the metal electrode layer is parallel electrodes or interdigitated electrodes, and the material is at least one of nickel, chromium and gold, and the thickness is less than 100 nm.

3. A self-powered lithium tantalate thin film photodetector according to claim 2, characterized in that: The thickness of the parallel electrodes is 50 nm, the electrode spacing is 50-70 μm, and the electrode width is 30-50 μm; the thickness of the interdigital electrodes is 35 nm, and the electrode spacing is 40-70 μm.

4. A method for preparing a self-powered lithium tantalate thin film photodetector as claimed in claim 1, characterized in that: The specific steps include: (1) cleaning the lithium tantalate film and polishing the surface to obtain a pretreated lithium tantalate film; (2) pasting the silicon substrate of the pretreated lithium tantalate film on a silicon wafer target plate by means of a conductive adhesive and placing the silicon substrate on an ion implantation vacuum chamber, and implanting ions into the surface of the pretreated lithium tantalate film to obtain an ion-implanted lithium tantalate film; (3) placing the ion-implanted lithium tantalate film in an annealing furnace for annealing to obtain an annealed lithium tantalate film; (4) spin coating a photoresist on the annealed lithium tantalate film, and using a photolithography technique to prepare a mask pattern on the annealed lithium tantalate film to obtain a photolithographic lithium tantalate film; (5) A metal electrode is deposited on the photolithographic lithium tantalate film by electron beam evaporation or magnetron sputtering to obtain the self-powered lithium tantalate film photodetector.

5. The method for preparing a self-powered lithium tantalate thin film photodetector according to claim 4, characterized in that: In step (2), the ion implantation adopts low-energy metal ion implantation, the implantation condition is vacuum, the implantation angle is normal incidence, and the angle with the normal line is less than 5°, the implanted metal ions contain multiple valence states, and the beam density during the implantation process is less than 10nA / cm 2 After the injection is completed, the mixture is allowed to stand for 24 hours to obtain an embedded plasmon nanoparticle structure in the near-surface area; the size of the nanoparticles is 2 to 20 nm and is within 150 nm from the near-surface area.

6. The method for preparing a self-powered lithium tantalate thin film photodetector according to claim 5, characterized in that: In step (2), the ion implantation is performed by gold ion implantation, the implantation energy is 120-160 keV, and the implantation dose is (2×10 16 )~(8×10 16 )ions / cm 2 .

7. The method for preparing a self-powered lithium tantalate thin film photodetector according to claim 5, characterized in that: In step (2), the ion implantation is carried out by silver ion implantation, the implantation energy is 120-200 keV, and the implantation dose is (5×10 16 )~(1×10 17 )ions / cm 2 .

8. The method for preparing a self-powered lithium tantalate thin film photodetector according to claim 4, characterized in that: In step (3), the annealing treatment is carried out in an atmosphere of nitrogen or vacuum, at a temperature of 100 to 150° C., for a time of 0.5 to 1 h.

9. The method for preparing a self-powered lithium tantalate thin film photodetector according to claim 4, characterized in that: In step (5), metallic nickel is deposited on the photolithographic lithium tantalate film to form parallel electrodes.

10. The method for preparing a self-powered lithium tantalate thin film photodetector according to claim 4, characterized in that: In step (5), a layer of metal chromium with a thickness of 5 nm is first deposited on the photolithographic lithium tantalate film, and then a layer of gold with a thickness of 30 nm is deposited to form a chromium / gold interdigital electrode.

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