Photoelectric detector based on sulfide heterojunction and preparation method thereof

Abstract

The invention provides a sulfide heterojunction-based photoelectric detector and a preparation method thereof, and belongs to the technical field of optoelectronic device preparation, the detector adopts a sandwich layered structure, and a two-dimensional sulfide channel layer, a semimetal platinum diselenide functional layer and a graphene transmission layer are sequentially stacked on a SiO2 / Si substrate. The preparation method combines pulse laser induced synthesis and a dry transfer process, firstly, a two-dimensional sulfide channel is prepared through ultraviolet laser low-temperature conversion of a precursor, then platinum diselenide and the graphene layer are transferred in sequence, and finally, the electrode is formed through photoetching and evaporation. According to the invention, high responsivity and rapid photoelectric detection from visible to near-infrared bands are realized through a heterojunction design matched with an energy band and a full-low-temperature process, and the detector is especially suitable for optical communication bands, and has the advantages of simple preparation process, strong CMOS process compatibility and high stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optoelectronic device preparation, and more particularly relates to a photoelectric detector based on a sulfide heterojunction and a preparation method thereof. BACKGROUND

[0002] The photoelectric detector is a core device for converting optical signals into electrical signals, and is widely used in optical communication, biomedical, environmental monitoring and industrial sensing fields. Among them, the visible light to near-infrared band detector covers the key application window and becomes a current research hotspot. However, the band gap of the traditional Si-based detector limits its near-infrared response, and the high-sensitivity detection requirement is difficult to meet; in a single two-dimensional material detector, MoS2 covers the visible light to short-wave near-infrared but has a slow response speed, PtSe2 has a wide spectrum absorption but a low carrier mobility and a high dark current; the two-dimensional material heterojunction detector is mostly designed as a double component, and has prominent problems such as damage by high-temperature process, poor stability and incompatibility with silicon process. SUMMARY

[0003] In view of the above defects or improvement requirements of the prior art, the present application provides a photoelectric detector based on a sulfide heterojunction and a preparation method thereof, thereby solving the technical problems of low carrier mobility and high dark current of the traditional detector.

[0004] To achieve the above-mentioned purpose, according to one aspect of the present application, a photoelectric detector based on a sulfide heterojunction is provided, which comprises, from bottom to top, a SiO2 / Si composite substrate, a two-dimensional sulfide channel layer, a platinum diselenide functional layer and a graphene transport layer; the two-dimensional sulfide channel layer, the platinum diselenide functional layer and the graphene transport layer are connected by van der Waals force; the surface of the graphene transport layer and the surface of the edge of the two-dimensional sulfide channel layer are respectively provided with electrodes.

[0005] Preferably, the two-dimensional sulfide channel layer is a MoS2 film or a WS2 film; the platinum diselenide functional layer is a semimetal PtSe2 film; the graphene transport layer is 1-3 layers of graphene; the two-dimensional sulfide channel layer, the platinum diselenide functional layer and the graphene transport layer are connected by van der Waals force.

[0006] Preferably, the electrode is a double-layer structure, the lower layer of which is Ti and the upper layer of which is Au.

[0007] Preferably, the thickness of the two-dimensional sulfide channel layer is 6-10 nm; the thickness of the platinum diselenide functional layer is 15-35 nm; the thickness of the electrode is 60-120 nm.

[0008] According to another aspect of the present application, a preparation method of a photoelectric detector based on a sulfide heterojunction is provided, which comprises the following steps: S1, pretreating the SiO2 / Si composite substrate, then spin-coating ammonium tetrathiomolybdate solution or ammonium tetrathiotungstate solution, heat curing to obtain a precursor film, irradiating the precursor film with ultraviolet pulse laser, and forming a two-dimensional sulfide channel layer after cleaning; S2, obtaining a PtSe2 film by mechanical exfoliation, screening a PtSe2 flake with a target thickness, and transferring the PtSe2 flake to the surface of the two-dimensional sulfide channel layer in step S1 by dry transfer to form a platinum diselenide functional layer; S3, obtaining a graphene film by mechanical exfoliation, screening a graphene flake with a target thickness, and transferring the graphene flake to the surface of the platinum diselenide functional layer in step S2 by dry transfer, and performing annealing treatment to form a graphene transport layer, thereby obtaining a target sample; S4, defining an electrode pattern on the surface of the target sample in step S3 by ultraviolet lithography, and then forming an electrode by thermal evaporation or electron beam evaporation of metal, thereby preparing a photodetector.

[0009] Preferably, in step S1, the heat curing temperature of the precursor film is 90-120℃, the heat curing time is 1-2min; the wavelength of the ultraviolet pulse laser is 248nm, the laser energy density is 20-40mJ / cm 2 , the pulse frequency is 5-10Hz, and the number of laser points is 100-2000 pulses.

[0010] Preferably, in step S1, the spin-coating speed is divided into two sections: the first section has a speed of 500-1000rpm for 5-15s, and the second section has a speed of 2000-3000rpm for 30-60s.

[0011] Preferably, in step S2, the thickness of the PtSe2 flake with a target thickness is 15-35nm.

[0012] Preferably, in step S3, the thickness of the graphene flake with a target thickness is 1-3 layers, the vacuum degree of the vacuum annealing is ≤5×10 -3 Pa, the annealing temperature is 180-220℃, and the annealing time is 15-25min.

[0013] According to another aspect of the present application, there is provided an application of a sulfide heterojunction-based photodetector as a visible light to near-infrared waveband photodetector.

[0014] Overall, compared with the prior art, the above technical solutions conceived by the present application can achieve the following beneficial effects: 1. The sulfide heterojunction-based photodetector provided by the present application adopts a synergistic design of a graphene / platinum diselenide / two-dimensional sulfide three-layer heterojunction, and has strong functional complementarity. The 2H phase two-dimensional sulfide (MoS2 / WS2) has high carrier mobility and provides an efficient channel for carrier transport; the semimetal PtSe2 realizes wide-spectrum light absorption from visible light to near-infrared, and can capture more photons to generate photo-generated carriers; the 1-3 layer graphene not only isolates air and water vapor to avoid oxidation of PtSe2 and two-dimensional sulfide, but also accelerates carrier transport due to its high conductivity; the three are tightly combined through van der Waals force, and the interface carrier recombination rate is significantly reduced; and the electrodes are respectively located at the edge of the two-dimensional sulfide and the surface of the graphene, avoiding the leakage current caused by cross overlap, and further improving the signal-to-noise ratio of the device.

[0015] 2. The preparation method of the sulfide heterojunction-based photodetector provided by the present application has precise and controllable process and high compatibility. The two-dimensional sulfide is synthesized at low temperature by ultraviolet pulse laser, without high temperature, and is compatible with the silicon-based CMOS process; the PtSe2 sheet is transferred by the PDMS stamp, which can realize micron-level precise alignment and avoid the positional deviation of traditional transfer.

[0016] 3. The sulfide heterojunction-based photodetector provided by the present application optimizes the electrode structure design of the device, and adopts Ti / Au double-layer electrode to solve the problem of poor adhesion of Au to two-dimensional materials / graphene, and to reduce the contact resistance to ≤10Ω.

[0017] 4. The sulfide heterojunction-based photodetector provided by the present application has comprehensive advantages in device performance. Compared with the existing two-dimensional heterojunction detector, the photodetector of the present application has an improvement of 1-2 orders of magnitude in light responsivity in the visible light to near-infrared band, and the response speed is shortened to within 100μs, while having good long-term stability and low-cost preparation characteristics, and has a wide application prospect in the field of optoelectronic integration. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a structure schematic diagram of a graphene / platinum diselenide / two-dimensional sulfide heterojunction photodetector in an embodiment of the present application.

[0019] Figure 2 is a preparation process flow chart of a graphene / platinum diselenide / two-dimensional sulfide heterojunction photodetector in an embodiment of the present application.

[0020] In all the drawings, the same reference signs are used to represent the same elements or structures, wherein: 1-SiO2 / Si composite substrate; 2-two-dimensional sulfide channel layer; 3-platinum diselenide functional layer; 4-graphene transport layer; 5-electrode. DETAILED DESCRIPTION

[0021] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0022] The present application provides a photoelectric detector based on sulfide heterojunction and a preparation method thereof, which aims to improve the light response and widen the response band. Specifically, as shown in Figure 1 The photoelectric detector based on sulfide heterojunction in the present application comprises, from bottom to top, a silicon substrate, a silicon dioxide layer, a two-dimensional sulfide film, a platinum diselenide film, graphene and a Ti / Au source-drain electrode, the electrode is located at the edge of the two-dimensional sulfide and the surface of the graphene, and the electrodes do not contact each other.

[0023] In an optional embodiment, the two-dimensional sulfide material is selected as MoS2 or WS2, the thickness of the two-dimensional sulfide is 6-10 nm, the thickness of the platinum diselenide layer is 25-35 nm, and the number of layers of the graphene is 1-3 layers.

[0024] In the embodiments of the present application, the method for preparing the above device is as shown in Figure 2 Figure 2 is a preparation process flow chart of the photoelectric detector based on sulfide heterojunction provided by the embodiments of the present application, Figure 2 The serial numbers in the above chart correspond to the following steps: S1, substrate pretreatment, spin-coating precursor, heat curing to form a film; S2, laser-induced synthesis of two-dimensional sulfide; S3, dry transfer of platinum diselenide; S4, dry transfer of graphene, device annealing; S5, photoetching, thermal evaporation or electron beam evaporation of electrode.

[0025] Specifically comprising the following steps: (1) Prepare three single crystal silicon wafers with a thickness of 500 um and an upper surface of 100 nm oxide layer, and clean and dry them. The specific operation is as follows: first, ultrasonic cleaning of the silicon wafer with acetone solution to remove organic dirt, then ultrasonic cleaning of the silicon wafer with anhydrous ethanol to remove acetone, and finally ultrasonic cleaning with deionized water and drying. Denoted as silicon wafer A, silicon wafer B and silicon wafer C respectively. The size of the silicon wafer A, the silicon wafer B and the silicon wafer C is 20mm x 20mm.

[0026] ​(2) In a flask, add 10 mL of deionized water and a magnetic rotor, weigh 80-150 mg of ammonium tetrathiomolybdate or ammonium tetrathiotungstate powder into the flask, place it on a magnetic stirrer in a 40-50 °C water bath, stir at 1000 rpm for 2-3 h, filter to obtain the precursor solution.

[0027] The SiO2 surface of the silicon wafer A is spin-coated with the precursor solution as described above and heat cured into a film in air. As shown in step 1 of Figure 2 .

[0028] (3) The upper surface of the precursor film obtained in step (2) is irradiated with laser to make the reaction source film react to form a two-dimensional sulfide film. As shown in step 2 of Figure 2 , the unreacted precursor film is removed by washing with NMP and deionized water respectively.

[0029] (4) Mechanical peeling is performed with 3M blue tape with viscosity of 12N / 25mm. The tape is attached to the surface of the bulk PtSe2 crystal, 0.08 MPa pressure is applied for 8 s, the tape is slowly peeled off, and the surface PtSe2 is adhered; the tape with PtSe2 is attached to the silicon wafer B, 0.05 MPa pressure is applied and then quickly peeled off, and the process is repeated twice to obtain a thin layer of PtSe2 with uniform thickness; under BX51 optical microscope, the target area is marked according to the color judgment of the thickness.

[0030] Dry transfer is performed using a polydimethylsiloxane / polycarbonate (PDMS / PC) composite stamp. First, the PDMS / PC stamp is fixed on the manipulator arm of the high-precision transfer platform, and the stamp is moved and lowered to make full contact with the marked PtSe2 flake on the silicon wafer B, and the flake is picked up by van der Waals force. The stamp is moved above the two-dimensional sulfide film of step (2) and fine alignment is performed under the microscope. Slowly lower the stamp until the PtSe2 contacts the substrate surface, then heat the sample stage to 60 °C and apply a vertical pressure of 0.2 MPa for 60 seconds to promote the van der Waals force bonding between the layers and the smooth release of the stamp. Finally, the PDMS / PC stamp is lifted vertically and slowly away from the substrate. As shown in step 3 of Figure 2 .

[0031] (5) Single-layer graphene is obtained on silicon wafer C using the same mechanical peeling process as described above, and the graphene is integrated onto the upper surface of the platinum diselenide layer of step (4) using the same dry transfer process as described above. The entire device is then placed in a vacuum annealing furnace and annealed at a vacuum degree of ≤5 × 10 -3 Pa and a temperature of 200 °C for 20 minutes to obtain silicon wafer D, as shown in step 4 of Figure 2 .

[0032] (6) Spin PMMA photoresist on the upper surface of the silicon wafer D, import the pre-drawn electrode layout into the computer connected to the photoetching machine, and expose the silicon wafer D coated with photoresist by electron beam direct writing. After exposure, develop the silicon wafer D with MIBK and isopropyl alcohol.

[0033] Ti / Au source-drain electrodes are prepared on the exposed and developed silicon wafer D by electron beam evaporation. The lower electrode is Ti with a thickness of 5 nm, and the upper electrode is Au with a thickness of 100 nm. The sample after electron beam evaporation is placed in acetone to remove the photoresist and excess Ti / Au, obtaining a silicon wafer E. Figure 2 As shown in step 5 of the method.

[0034] The graphene / platinum diselenide / two-dimensional sulfide heterojunction photodetector is prepared.

[0035] The technical solutions of the present application are further illustrated by specific examples as follows: Example 1 (1) Take three p-type silicon substrates with a 100 nm silicon dioxide layer on the surface, and ultrasonically clean them with acetone, isopropyl alcohol and deionized water in sequence and dry them with nitrogen. Label them as silicon wafer A, silicon wafer B and silicon wafer C.

[0036] (2) Weigh 100 mg of ammonium tetrathiomolybdate and dissolve it in 10 mL of deionized water. Stir it at 1000 rpm under a 45℃ water bath for 2.5 hours, and filter it through a filter membrane to obtain a precursor solution. Place the silicon wafer A on a spin coater, spin it at 500 rpm for 5 seconds, then spin it at 2000 rpm for 30 seconds, and then solidify it on a 100℃ hot plate for 90 seconds to form a precursor film.

[0037] (3) Use a KrF excimer laser with a wavelength of 248 nm to irradiate 2000 pulses under the conditions of energy density 30 mJ / cm 2 , pulse frequency 7 Hz, to induce the precursor to convert into a MoS2 film with a thickness of about 6 nm.

[0038] (4) Integrate a semimetal PtSe2 flake with a thickness of about 15 nm to the MoS2 surface of the silicon wafer A by mechanical exfoliation and dry transfer process: first, adhere the bulk PtSe2 crystal to the silicon wafer A with a 12N / 25mm adhesive 3M blue film, apply a pressure of 0.08MPa for 8 seconds, then slowly exfoliate, and then adhere and exfoliate twice at a pressure of 0.05MPa to achieve thickness uniformization; then, complete the van der Waals integration by using a PDMS / PC stamp at 60℃ and 0.2MPa for 60 seconds.

[0039] (5) Stack the single-layer graphene prepared by mechanical exfoliation on the PtSe2 layer by the same dry transfer process. The overall device is placed in a vacuum degree less than or equal to 5×10 -3Pa, 200℃ for 20 minutes to optimize the interface contact.

[0040] (6) The electrode was prepared by using ultraviolet lithography and electron beam evaporation process: first, the photoresist was spin-coated on the surface of the sample and defined the electrode pattern through exposure and development, then 5 nm titanium layer and 55 nm gold layer were deposited in turn, and finally the asymmetric source-drain electrode structure was formed by acetone stripping to complete the device preparation.

[0041] Example 2 (1) Three SiO2 / Si substrates were cleaned in the same way and marked as silicon wafer A, silicon wafer B and silicon wafer C.

[0042] (2) 120 mg of ammonium tetrathiotungstate was weighed to prepare a precursor solution, spin-coated at 800 rpm for 10 seconds, then spin-coated at 2500 rpm for 40 seconds, and cured at 110℃ for 2 minutes to form a uniform thin film.

[0043] (3) The 248 nm pulsed laser was used to irradiate 100 pulses under the conditions of energy density 35 mJ / cm 2 , pulse frequency 9 Hz to prepare a WS2 channel layer with a thickness of about 9 nm.

[0044] (4) PtSe2 flakes with a thickness of about 28 nm were obtained on silicon wafer B by mechanical exfoliation method, and the PDMS / PC stamp was used to align and stack them on the surface of WS2 on the precision transfer platform, and the transfer parameters were 60℃, 0.2 MPa and 60 seconds.

[0045] (5) The double-layer graphene prepared by mechanical exfoliation method was transferred to the upper surface of the PtSe2 layer. The overall device was transferred to the vacuum chamber of the probe station under the condition of vacuum degree ≤5×10 -3 Pa, 200℃ for 20 minutes to optimize the interface contact.

[0046] (6) The electrode was prepared by using ultraviolet lithography and thermal evaporation process: first, the photoresist was spin-coated on the surface of the sample and defined the electrode pattern through exposure and development, then 10 nm titanium layer and 110 nm gold layer were deposited in turn, and finally the asymmetric source-drain electrode structure was formed by acetone stripping to complete the device preparation.

[0047] Since the steps of preparing the heterojunction are the same, the difference between the various embodiments is only the difference of the parameters, and the above examples only give the parameters in individual embodiments; the specific examples are shown in Table 1 below, and Table 1 shows the preparation method of the graphene / platinum diselenide / two-dimensional sulfide heterojunction photodetector.

[0048] Table 1

[0049] In the structure of the graphene / platinum diselenide / two-dimensional sulfide heterojunction photodetector disclosed in the application, photo-generated carriers can be effectively separated at the interface of platinum diselenide and sulfide, platinum diselenide can effectively absorb near-infrared photons, light absorption is improved, and electrons can be quickly transmitted in the two-dimensional sulfide, which can greatly improve the light response; the graphene transmission layer is introduced at the top to realize efficient carrier collection, enhance the conductivity, and also greatly increase the photocurrent. The photodetector not only has excellent response characteristics, but also can be self-driven, and has very good application prospect in the field of photoelectricity.

[0050] Those skilled in the art will easily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A photodetector based on a sulfide heterojunction, characterized in that, The photodetector comprises, from bottom to top, a SiO2 / Si composite substrate (1), a two-dimensional sulfide channel layer (2), a platinum diselenide functional layer (3), and a graphene transport layer (4); the two-dimensional sulfide channel layer (2), the platinum diselenide functional layer (3), and the graphene transport layer (4) are all connected by van der Waals forces; electrodes (5) are respectively provided on the surface of the graphene transport layer (4) and the surface of the edge of the two-dimensional sulfide channel layer (2).

2. A photodetector based on a sulfide heterojunction according to claim 1, characterized in that, The two-dimensional sulfide channel layer (2) is a MoS2 film or a WS2 film; the platinum diselenide functional layer (3) is a half-metal PtSe2 film; and the graphene transport layer (4) is 1 to 3 layers of graphene.

3. The photodetector based on a sulfide heterojunction according to claim 1, wherein the electrode (5) has a double-layer structure, with the lower layer being Ti and the upper layer being Au.

4. A photodetector based on a sulfide heterojunction according to claim 1, characterized in that, The thickness of the two-dimensional sulfide channel layer (2) is 6-10 nm; the thickness of the platinum diselenide functional layer (3) is 15-35 nm; and the thickness of the electrode (5) is 60-120 nm.

5. A method for fabricating a photodetector based on a sulfide heterojunction as described in any one of claims 1-4, characterized in that, The preparation method includes the following steps: S1. The SiO2 / Si composite substrate is pretreated, and then spin-coated with ammonium tetrathiomolybdate solution or ammonium tetrathiotungstate solution. The precursor film is then thermally cured to obtain a precursor film. The precursor film is then irradiated with ultraviolet pulsed laser and cleaned to form a two-dimensional sulfide channel layer. S2, PtSe2 film is obtained by mechanical exfoliation, PtSe2 sheet of target thickness is screened, and dry transfer is applied to the surface of the two-dimensional sulfide channel layer described in step S1 to form a platinum diselenide functional layer. S3. Obtain graphene film by mechanical exfoliation, screen graphene sheets of target thickness, transfer them to the surface of platinum diselenide functional layer described in step S2 by dry method, and perform annealing treatment to form graphene transport layer and obtain target sample. S4. In step S3, the electrode pattern is defined on the surface of the target sample by ultraviolet lithography, and then the metal is formed by thermal evaporation or electron beam deposition to prepare the photodetector.

6. The preparation method according to claim 5, characterized in that, In step S1, the thermosetting temperature of the precursor film is 90–120°C, and the thermosetting time is 1–2 min; the wavelength of the ultraviolet pulsed laser is 248 nm, and the laser energy density is 20–40 mJ / cm². 2 The pulse frequency is 5-10Hz, and the number of laser points is 100-2000 pulses.

7. The preparation method according to claim 6, characterized in that, In step S1, the spin coating speed is divided into two segments: the first segment has a speed of 500-1000 rpm and a time of 5-15 s; the second segment has a speed of 2000-3000 rpm and a time of 30-60 s.

8. The preparation method according to claim 5, characterized in that, In step S2, the thickness of the PtSe2 sheet with the target thickness is 15-35 nm.

9. The preparation method according to claim 5, characterized in that, In step S3, the thickness of the graphene sheet with the target thickness is 1 to 3 layers, and the vacuum degree of the vacuum annealing is ≤5×10⁻⁶. -3 Pa, annealing temperature is 180~220℃, annealing time is 15~25min.

10. The application of a sulfide heterojunction-based photodetector as described in any one of claims 1-4 as a photodetector in the visible to near-infrared band.

Images