Tungsten ditelluride / tungsten disulfide heterojunction photoelectric detector and preparation method thereof

Abstract

The invention belongs to the technical field of photoelectric detectors, and discloses a tungsten telluride (WTe2) / tungsten disulfide (WS2) heterojunction photoelectric detector and a preparation method thereof, the structure of the photoelectric detector is an electrode / WTe2 / WS2 heterojunction / electrode, and non-overlapping parts of the electrode and WTe2 and WS2 at two ends of the WTe2 / WS2 heterojunction are in contact with the electrode. A WS2 nanosheet is obtained on a SiO2 / Si substrate by using a mechanical exfoliation method, then a WTe2 nanosheet is obtained by using a PDMS flexible substrate, then the WTe2 nanosheet is transferred to the SiO2 / Si WS2 nanosheet, the overlapped area of the WTe2 nanosheet and the WS2 nanosheet is a heterojunction, and the non-overlapped parts of the WTe2 nanosheet and the WS2 nanosheet at the two ends of the heterojunction are plated with electrodes to prepare the photoelectric detector. The device has good photoelectric response and excellent optical detection performance, and has potential application in solar cells.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photoelectric detectors, and more particularly relates to a photoelectric detector of a tungsten ditelluride (WTe2) / tungsten disulfide (WS2) heterojunction and a preparation method thereof. BACKGROUND

[0002] Photoelectric detectors can convert incident light into electrical signals and are widely used in digital cameras, optical communication, machine vision and industrial detection, and play an indispensable role in today's information technology and people's daily life. Traditional silicon and InGaAs photoelectric detectors have reached a high degree of maturity and dominate the commercial market, but due to their epitaxial growth, bulk and rigidity characteristics, they face challenges in low cost, transparency and flexibility. In recent years, two-dimensional tellurium (Te) has become a promising p-type material compared with other two-dimensional materials (b-P, b-As, Bi, etc.) due to its high mobility, narrow band gap, high light absorption and extraordinary air stability.

[0003] Two-dimensional transition metal dichalcogenides (TMDs) are widely used in various photoelectric detector fields due to their advantages of adjustable interlayer band gap, strong photo-matter interaction, no dangling bonds on the surface and large-scale growth. Among the TMDs family, WS2 has excellent photoelectric properties, mainly in light absorption, light emission and nonlinear optical properties. These characteristics make it have broad application prospects in photoelectric detectors, light-emitting diodes, optical communication and other optoelectronic devices. SUMMARY

[0004] In order to solve the above-mentioned deficiencies and shortcomings of the prior art, the application aims to provide a photoelectric detector of a tungsten ditelluride / tungsten disulfide heterojunction. The photoelectric detector has good photoelectric response, and the response time is 31 ms. The calculated responsivity of the photoelectric detector is about 0.42 A / W, and the specific detectivity is 3x10 11 Jones, which shows superior light detection performance. It is conducive to further development and application of two-dimensional WS2, WTe2 and other two-dimensional materials in the field of light detection.

[0005] Another object of the application is to provide a preparation method of the photoelectric detector of the tungsten ditelluride / tungsten disulfide heterojunction. The method uses a mechanical exfoliation method to obtain single-layer or few-layer WS2 nanosheets on a SiO2 / Si substrate, then uses a PDMS flexible substrate to obtain single-layer or few-layer WTe2 nanosheets, then transfers the obtained WTe2 nanosheets to the WS2 nanosheets on the SiO2 / Si substrate, and the overlapping area of WTe2 and WS2 is the heterojunction. Then, photoetching is performed on the non-overlapping parts of the WS2 nanosheets and the WTe2 nanosheets at both ends of the heterojunction, metal electrodes are plated, and the photoelectric detector is prepared.

[0006] The object of the present application is achieved by the following technical solutions:

[0007] The structure of the photoelectric detector of the tungsten ditelluride / tungsten disulfide heterojunction is electrode / tungsten ditelluride / tungsten disulfide heterojunction / electrode, and the non-overlapping parts of tungsten ditelluride and tungsten disulfide at both ends of the tungsten ditelluride / tungsten disulfide heterojunction are in contact with the electrode.

[0008] Preferably, the thickness of the tungsten disulfide nanosheet in the tungsten ditelluride / tungsten disulfide heterojunction is 1-20 nm, and the thickness of the tungsten ditelluride nanosheet is 1-50 nm; the electrode is Cr and Au, the thickness of Cr is 1-10 nm, and the thickness of Au is 10-50 nm.

[0009] The preparation method of the photoelectric detector of the tungsten ditelluride / tungsten disulfide heterojunction comprises the following specific steps:

[0010] S1. Using a mechanical peeling method, the cut PDMS is peeled off the soft film layer and laid on the adhesive tape full of tungsten disulfide nanosheets, and tungsten disulfide nanosheets with a thickness of 1-20 nm and flatness are selected;

[0011] S2. Using a transfer platform, the tungsten disulfide nanosheets are transferred to the center position of the cleaned SiO2 / Si substrate, the heating temperature is 30-50℃, the transfer is completed, and the tungsten disulfide nanosheets are prepared on the SiO2 / Si substrate;

[0012] S3. Using a mechanical peeling method, the soft layer is pasted on the adhesive tape full of tungsten ditelluride nanosheets after the PDMS is peeled off the soft film layer, and tungsten ditelluride nanosheets with a thickness of 1-50 nm and flatness are selected;

[0013] S4. Using a transfer platform, the tungsten ditelluride nanosheets are transferred to the tungsten disulfide nanosheets on the SiO2 / Si substrate, the heating temperature is 30-50℃, the transfer is completed, and the tungsten disulfide / tungsten ditelluride heterojunction is prepared on the SiO2 / Si substrate;

[0014] S5. The tungsten ditelluride / tungsten disulfide heterojunction / SiO2 / Si substrate is placed in a uniform glue machine, and photoresist is uniformly dropped on the surface of the silicon wafer, the non-overlapping parts of tungsten ditelluride and tungsten disulfide at both ends of the tungsten ditelluride / tungsten disulfide heterojunction are photoetched as source and drain electrodes, the SiO2 / Si substrate and the tungsten disulfide / tungsten ditelluride heterojunction / SiO2 / Si substrate are placed in a developing solution for immersion, the silicon wafer after development is subjected to electron beam evaporation, after immersion and rinsing, the tungsten disulfide / tungsten ditelluride heterojunction / SiO2 / Si substrate is heated at 100-200℃, and the photoelectric detector of the tungsten ditelluride / tungsten disulfide heterojunction is prepared.

[0015] Preferably, the soaking time in the developing solution in step 5 is 10-15s.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] 1. The present application obtains single-layer or multi-layer WS2 nanosheets and WTe2 nanosheets by mechanical exfoliation, and the prepared two-dimensional material has the advantages of few defects, smooth surface, high mobility and the like. The open-circuit voltage of the photodetector is 0.16V, and the short-circuit current is 6.43nA, and the photoelectric conversion performance is better than that of a general photodetector.

[0018] 2. The photodetector of the present application has an extremely fast light response time, and the response time under 635nm laser irradiation is 31ms. Under 635nm laser, a high responsivity of 0.42A / W and a response speed of about 3x10 11 Jones' s detection rate, showing fast light detection performance on visible light. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a structure schematic diagram of the photodetector of the tungsten ditelluride (WTe2) / tungsten disulfide (WS2) heterojunction of Example 1.

[0020] Figure 2 It is an optical image of the photodetector of Example 1.

[0021] Figure 3 It is a schematic diagram of the dark current of the photodetector of Example 1 under no light irradiation and the I-V relationship of the photodetector of Example 1 under different light power densities of 635nm laser irradiation. ds

[0022] Figure 4 It is a schematic diagram of the light response time change of the photodetector of Example 1 under 635nm laser irradiation. DETAILED DESCRIPTION

[0023] The content of the present application will be further described below in combination with specific embodiments, but should not be understood as a limitation of the present application. If not specifically indicated, the technical means used in the embodiments are conventional means familiar to those skilled in the art. Unless specifically indicated, the reagents, methods and equipment used in the present application are conventional reagents, methods and equipment in the technical field.

[0024] Example 1

[0025] 1. The SiO2 / Si substrate is rinsed with anhydrous ethanol, and then immersed and rinsed with distilled water, so as to ensure that the surface of the substrate is free of dust and other impurities.

[0026] ​2. Cut the PDMS flexible material with an area of 0.5 cm*0.5 cm, and use the mechanical peeling method to tear off the soft film layer. Then, place the cut PDMS on the adhesive tape coated with tungsten disulfide (WS2) and let it stand for 15 s. Use an optical microscope to observe and select the few-layer tungsten disulfide nanosheets with a thickness of 1-20 nm and a relatively flat surface.

[0027] 3. Use the transfer platform to transfer the tungsten disulfide nanosheets to the SiO2 / Si substrate, ensuring that they are in the center of the substrate. Then, press the tungsten disulfide nanosheets against the SiO2 / Si substrate and adjust the temperature of the heating stage to 50℃. After 1 min, the transfer is complete, and the tungsten disulfide nanosheets are prepared on the SiO2 / Si substrate.

[0028] 4. Cut the PDMS flexible material with an area of 0.5 cm*0.5 cm, and tear off the soft film layer. Then, place the soft layer on the adhesive tape coated with tungsten ditelluride (WTe2) and press for 15 s. Take out the PDMS and place the side coated with tungsten ditelluride on a clean glass slide. Observe the soft layer of the PDMS under an optical microscope and find the tungsten ditelluride nanosheets with a thickness of 1-50 nm and a relatively flat surface.

[0029] 5. Use the transfer platform to transfer the tungsten ditelluride nanosheets to the tungsten disulfide nanosheets on the SiO2 / Si substrate. Press the tungsten ditelluride nanosheets against the tungsten disulfide nanosheets and adjust the temperature of the heating stage to 50℃. After 1 min, the transfer is complete, and the tungsten ditelluride / tungsten disulfide heterojunction is prepared on the SiO2 / Si substrate.

[0030] 6. Place the tungsten ditelluride / tungsten disulfide heterojunction in the spin coater and use the rubber dropper to evenly drop the photoresist on the surface of the silicon wafer. Set the spin coater running steps and, after the spin coating is complete, place the silicon wafer on the heating stage for baking. Set the temperature to 100℃ and heat for 4 min. Use an opaque cover to cover the silicon wafer during the process to avoid light exposure.

[0031] After baking, place the silicon wafer in the photoetching machine and select the two ends of the non-overlapping WTe2 nanosheets and WS2 nanosheets outside the tungsten ditelluride / tungsten disulfide heterojunction as the source electrode and the drain electrode. After photoetching, develop the silicon wafer in the developing solution (developing solution AR 300-26). When black spots appear on the silicon wafer, quickly remove it from the developing solution and place it in deionized water for 5 s. Then, use a nitrogen gun to blow off the residual deionized water on the surface. Perform electron beam evaporation on the developed silicon wafer. After evaporation, immerse the tungsten ditelluride / tungsten disulfide heterojunction / SiO2 / Si substrate in acetone solution. Use the rubber dropper to rinse off the gold on the silicon wafer. Then, immediately rinse it with distilled water and blow off the residual distilled water on the surface with a gas gun.

[0032] 7. Measure the length and width of the electrodes under an optical microscope and estimate the area of ​​the heterojunction. Place the tungsten ditelluride / tungsten disulfide heterojunction / SiO2 / Si substrate on a heating stage inside a glove box, set the temperature to 150℃ for 20 minutes, and obtain a photodetector of the tungsten ditelluride (WTe2) / tungsten disulfide (WS2) heterojunction.

[0033] Figure 1 This is a schematic diagram of the photodetector in Example 1. From... Figure 1 It can be seen that the structure of the photodetector is an electrode / tungsten ditelluride / tungsten disulfide heterojunction / electrode, wherein the tungsten ditelluride nanosheets in the tungsten ditelluride / tungsten disulfide heterojunction are built on tungsten disulfide nanosheets. Figure 2 The optical image of the photodetector in Example 1 is from... Figure 2 As can be seen, the photolithographically plated gold electrodes Cr / Au have a thickness of 1-10 nm and an Au thickness of 10-50 nm. The overlapping shaded area is the constructed tungsten ditelluride / tungsten disulfide heterojunction. Figure 3 The dark current of the photodetector in Example 1 under no light and under 635nm laser irradiation with different optical power densities is shown below. ds Diagram illustrating the relationship of change. From Figure 3 As can be seen, the dark current of this photodetector is in the pA range, the turn-on voltage is 0.16V, and the optical power density at a wavelength of 635nm is 147.5mW / cm². 2 The short-circuit current under laser irradiation is 6.43 nA. The photocurrent of this photodetector increases with increasing optical power density. This indicates that the photoelectric conversion performance of this photodetector is superior to that of a general photodetector. Figure 4 This is a schematic diagram illustrating the photoresponse time variation of the heterojunction photodetector in Example 1 under 635nm laser irradiation. Figure 4 It is known that the response time of this photodetector is 31 ms, and both the rise time and fall time are 31 ms. This photodetector achieves a high responsivity of 0.42 A / W under 635 nm laser light, indicating that it has good photoelectric response at a wavelength of 635 nm. The photodetector can achieve a responsivity of approximately 3 × 10⁻⁶ A / W under 635 nm laser light. 11 Jones's detectivity indicates that it has good optical detection performance. Among them, responsivity R and detectivity D... * The calculation formula is shown below.

[0034] R = I ph / (P λ S)

[0035]

[0036] Among them, I phThe net photocurrent, i.e. the same V ds The value of I light The value of I dark The value of I light The current measured under light conditions, I dark The current measured in the dark, P λ The incident light power density, S is the area of the heterojunction of the device, e is the basic charge amount, and its value is 1.6 x 10 19 C.

[0037] The photoelectric detector based on the WTe2 / WS2 heterojunction has been proved to have good photoelectric response performance and can realize potential application in solar cells.

[0038] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are all included in the protection scope of the present application.

Claims

1. A photodetector with a tungsten ditelluride / tungsten disulfide heterojunction, characterized in that, The photodetector has the structure of an electrode / tungsten ditelluride / tungsten disulfide heterojunction / electrode, with the non-overlapping portions of tungsten ditelluride and tungsten disulfide at both ends of the electrode and the tungsten ditelluride / tungsten disulfide heterojunction in contact with the electrode.

2. The photodetector of the tungsten ditelluride / tungsten disulfide heterojunction according to claim 1, characterized in that, The thickness of the tungsten disulfide nanosheets in the tungsten ditelluride / tungsten disulfide heterojunction is 1-20 nm, and the thickness of the tungsten ditelluride nanosheets is 1-50 nm; the electrodes are Cr and Au, with the thickness of Cr being 1-10 nm and the thickness of Au being 10-50 nm.

3. The method for fabricating a photodetector with a tungsten ditelluride / tungsten disulfide heterojunction according to claim 1 or 2, characterized in that, The specific steps include the following: S1. Using the mechanical peeling method, after peeling off the thin film layer of the cut PDMS, lay it flat on the tape covered with tungsten disulfide nanosheets and let it stand. Select tungsten disulfide nanosheets with a thickness of 1-20nm and flatness. S2. Using a transfer platform, tungsten disulfide nanosheets are transferred to the center of a cleaned SiO2 / Si substrate. The heating temperature is 30-50℃ to complete the transfer, and tungsten disulfide nanosheets are prepared on the SiO2 / Si substrate. S3. Using a mechanical peeling method, after peeling off the soft film from PDMS, the soft layer is attached to an adhesive tape covered with tungsten ditelluride nanosheets. The tungsten ditelluride nanosheets with a thickness of 1-50 nm and a flat surface are selected. S4. Using a transfer platform, tungsten ditelluride nanosheets are transferred to tungsten disulfide nanosheets on a SiO2 / Si substrate. The heating temperature is 30-50℃ to complete the transfer, and a tungsten disulfide / tungsten ditelluride heterojunction is prepared on the SiO2 / Si substrate. S5. Place the tungsten ditelluride / tungsten disulfide heterojunction / SiO2 / Si substrate in a spin coater, uniformly drop photoresist onto the silicon wafer surface, and use photolithographic electrodes on the non-overlapping portions of tungsten ditelluride and tungsten disulfide at both ends of the tungsten ditelluride / tungsten disulfide heterojunction as source and drain electrodes, respectively. Immerse the SiO2 / Si substrate and the tungsten disulfide / tungsten ditelluride heterojunction / SiO2 / Si substrate in a developing solution, perform electron beam evaporation on the developed silicon wafer, and after immersion and rinsing, heat the tungsten disulfide / tungsten ditelluride heterojunction / SiO2 / Si substrate at 100-200℃ to obtain the tungsten ditelluride / tungsten disulfide heterojunction photodetector.

4. The method for fabricating a tungsten ditelluride / tungsten disulfide heterojunction photodetector according to claim 3, characterized in that, The soaking time in the developing solution in step 5 is 10-15 seconds.

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