Preparation method for enhancing performance of TMDCs heterojunction photoelectric detector with Cu-coated CuO core-shell structure

Abstract

The invention designs a 0D / 2D Cu-coated CuO / MoS2 heterojunction of a Cu-coated CuO core-shell structure enhanced TMDCs system, and the 0D / 2D Cu-coated CuO / MoS2 heterojunction can realize efficient photoelectric conversion and is applied to a high-sensitivity photoelectric detector. According to the invention, a core-shell plasma structure is obtained through a metal surface thermal oxidation technology, and a type-II 0D / 2D Cu-coated CuO / MoS2 heterojunction is constructed. On one hand, a built-in electric field is formed by a plasma shell layer material CuO and MoS2, so that separation of photo-induced electron-hole pairs can be promoted, hot electrons of LSPR (Local Surface Plasma Resonance) can be injected into a MoS2 layer in cooperation, the photoelectric conversion efficiency of a heterojunction system is improved, the contradiction between light absorption and carrier separation of a traditional heterojunction system is solved, and the photoelectric conversion efficiency of the heterojunction system is improved. And the response speed of the device is improved. And on the other hand, the shell layer material CuO can reduce interface damage caused by metal / semiconductor contact, so that the problem of high dark current accompanied by the plasma type photoelectric detector under high light response is solved. Compared with a traditional plasma type device only paying attention to light absorption, the plasma / TMDCs system heterojunction photoelectric detector designed by the invention effectively solves the problem of low response speed and shows excellent photoelectric conversion efficiency. The method is of great significance to development of low-dimensional hybrid heterojunction photoelectric detectors.

Description

[0001] The present invention belongs to the field of low-dimensional hybrid heterojunction optoelectronic devices, and in particular relates to a method for preparing a plasma-type 0D / 2D heterojunction photodetector with high-efficiency photoelectric conversion. Background Art

[0002] Zero-dimensional / two-dimensional (0D / 2D) low-dimensional hybrid heterostructure systems have attracted widespread attention in the fields of photodetectors, biosensors, and solar cells due to their efficient light absorption and light transmission. Among them, 0D metal nanoparticles (NPs) with a large specific surface area can be used as a light absorption layer to enhance the responsiveness of the device. 2D transition metal dichalcogenides (TMDCs) with high electron mobility, tunable band gap, and strong light-matter interaction can be used as carrier transport layers to improve the response speed of the device. However, defects are inevitably introduced during the integration of metal NPs onto the surface of TMDCs. Carriers are captured by defect states, which prolongs the carrier lifetime and increases their transmission time, ultimately resulting in the device response speed remaining in the millisecond range. Therefore, it is particularly important to develop a plasmon-enhanced 0D / 2D heterojunction photodetector with both high responsiveness and fast response speed.

[0003] The heterojunction interface is a key region for the separation of photogenerated electrons and holes, and has a crucial impact on the response speed of optoelectronic devices. Existing interface engineering technologies mainly promote the separation of photogenerated carriers by increasing the interface contact area, adjusting the energy band matching, and suppressing interface defects. 2D / 2D heterojunctions with face-to-face contact can provide more areas for the separation of photogenerated carriers, thereby improving the photoelectric conversion efficiency of photodetectors. The gradient strain method is used to adjust the type-II energy band matching and enhance the built-in electric field, thereby improving the carrier separation efficiency. During the material growth process, oxygen plasma treatment and post-annealing are used to fill oxygen / sulfur atoms into vacancy defects to achieve surface passivation of the material, improve the quality of the heterojunction interface, and accelerate the separation of photogenerated carriers at the interface. The above-mentioned interface regulation methods can significantly improve the carrier separation efficiency of TMDCs-based heterojunctions, thereby realizing photodetectors with high response speeds. However, the plasma / TMDCs heterojunction designed in the present invention is different from the traditional heterojunction system and can simultaneously achieve efficient light absorption and photogenerated carrier separation efficiency, balancing the dilemma of plasma-type devices that are difficult to achieve both high response and fast response speed.

[0004] Therefore, the Cu@CuO / MoS2 core-shell plasma heterojunction photodetector designed in the present invention achieves high responsiveness and fast response speed thanks to type-II band alignment and heterojunction-assisted hot electron injection. On the one hand, the plasma shell material CuO and MoS2 form a built-in electric field, which not only promotes the separation of photogenerated electron-hole pairs, but also can cooperate with the LSPR hot electron injection into the MoS2 layer, improving the photoelectric conversion efficiency of the heterojunction system, solving the contradiction between light absorption and carrier separation in traditional heterojunction systems, and improving the response speed of the device. On the other hand, the shell material CuO can reduce the interface damage caused by metal / semiconductor contact, thereby solving the problem of high dark current associated with high light response of plasma-type photodetectors. Summary of the Invention

[0005] The purpose of the present invention is to design a 0D / 2D Cu@CuO / MoS2 heterojunction of a Cu@CuO core-shell structure-enhanced TMDCs system to resolve the contradiction between light absorption and carrier separation in traditional heterojunction systems. The 0D / 2D low-dimensional hybrid heterojunction constructed by the present invention can achieve type-II band alignment and heterojunction-assisted hot electron injection. On the one hand, the plasma shell material CuO and MoS2 construct a heterojunction interface electric field, which can not only promote the separation of photogenerated electron-hole pairs, but also can cooperate with the LSPR hot electron injection into the MoS2 layer, thereby improving the photoelectric conversion efficiency of the heterojunction system and resolving the contradiction between light absorption and carrier separation in traditional heterojunction systems. On the other hand, the shell material CuO can reduce the metal free electron transfer and the interface damage caused by the uneven plane in the contact interface between Cu NPs and MoS2, thereby avoiding the problems of slow device light response speed and high dark current caused by the extension of carrier lifetime. In addition, the 0D / 2D Cu@CuO / MoS2 heterojunction was constructed by spin coating, which is simple to operate and easy to integrate, and finally a highly sensitive photodetector was obtained.

[0006] The Cu@CuO / MoS2 heterojunction photodetector of the present invention comprises, from bottom to top, a Si / SiO2 substrate layer, a gold interdigitated electrode, a MoS2 layer, and a Cu@CuO core-shell plasma structure.

[0007] The preparation process of the above-mentioned Cu@CuO / MoS2 heterojunction photodetector includes the following steps:

[0008] Gold interdigital electrodes were fabricated on clean Si / SiO2 substrates using UV lithography. The interdigital electrodes were made of gold, with a finger gap of 3 μm, a finger width of 5 μm, and a finger length of 1400 μm.

[0009] Use 3M tape to peel off a small amount of MoS2 from the MoS2 bulk material, fold the tape in half several times, press and unfold it, and repeat this process several times to break the van der Waals force between the layers to obtain a few-layer MoS2 material;

[0010] The tape with the MoS2 film was attached to the gold interdigital electrode and heated at 80°C for 10 minutes to enhance the adsorption between the MoS2 film and the gold electrode, thus obtaining a MoS2 photodetector.

[0011] The Cu NPs were thermally oxidized in a tube furnace. The temperature was raised to 300°C over 30 minutes and then maintained at this temperature for 10 minutes to obtain a Cu@CuO core-shell plasma structure.

[0012] Prepare 10 mL of anhydrous ethanol and weigh 2.54 mg of Cu nanoparticles on a balance. Pour the mixture into a test tube and sonicate for 20 minutes to obtain a 0.004 mol / L Cu solution. Use the same method to prepare a 0.004 mol / L Cu@CuO solution.

[0013] Take 0.004 mol / L Cu solution and Cu@CuO solution respectively, and use a pipette to drop them onto the center of the surface of two MoS2-based photodetectors prepared in advance. Adjust the relevant parameters of the spin coater to control the thickness of the formed film. First, spin coat at 1000 rpm / min for 10 s, and then spin coat at 3000 rpm / min for 20 s.

[0014] By drying and removing the remaining solvent, Cu / MoS2 and Cu@CuO / MoS2 plasmon-enhanced photodetectors were successfully prepared;

[0015] Compared with traditional plasma-type devices that only focus on light absorption, the plasma / TMDCs system heterojunction photodetector designed in the present invention effectively solves the problem of slow response speed and can achieve efficient photoelectric conversion. Experiments have shown that the plasma shell CuO and MoS2 construct a built-in electric field, which can not only promote the separation of photogenerated electron-hole pairs, but also cooperate with the LSPR hot electron injection into the MoS2 layer to improve the photoelectric conversion efficiency of the heterojunction system and solve the contradiction between light absorption and carrier separation in traditional heterojunction systems. In addition, the CuO layer can suppress the increase in dark current caused by direct contact between Cu NPs and MoS2 without affecting the plasma resonance intensity. The present invention is simple to operate and provides a research idea for the preparation of highly sensitive plasma-type heterojunction photodetectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Flow chart for the preparation of 0D / 2D Cu@CuO / MoS2 plasmonic heterojunction photodetectors;

[0017] Figure 2 X-ray diffraction (XRD) characterization diagram of Cu@CuO structure;

[0018] Figure 3 Comparison of Raman spectra of MoS2, Cu / MoS2 and Cu@CuO / MoS2 photodetectors;

[0019] Figure 4 Comparison of photoluminescence spectra of MoS2, Cu / MoS2 and Cu@CuO / MoS2 photodetectors;

[0020] Figure 5 (a) is a comparison of the dark current and photocurrent of MoS2 and the integrated Cu nanoparticles, (b) is a comparison of the dark current and photocurrent of MoS2 and the integrated Cu@CuO nanoparticles;

[0021] Figure 6 Comparison of (a) photocurrent, (b) dark current, (c) responsivity, and (d) detectivity of MoS2 and integrated Cu nanoparticles and Cu@CuO core-shell nanoparticles plasmonic devices, respectively.

[0022] Figure 7 (a) Response time diagram of Cu@CuO / MoS2 heterojunction photodetector. Figure 7 (b) Figure 7 (a) Extracted photoresponse period of one femtosecond pulse. DETAILED DESCRIPTION

[0023] The following is a further detailed description of the specific embodiments of the present invention with reference to the accompanying drawings:

[0024] Example 1:

[0025] 1. Preparation of interdigitated electrodes: Gold interdigitated electrodes were prepared on a clean Si / SiO2 substrate using UV photolithography. The interdigitated electrodes were made of gold, with a gap of 3 μm, a width of 5 μm, and a length of 1400 μm.

[0026] 2. Preparation of MoS2 thin film: Use 3M tape to peel off a small amount of MoS2 from the MoS2 bulk material. Cut the tape to an appropriate length with scissors. Use tweezers to place the thin layer of MoS2 material flat on the tape. Fold the tape in half several times, press and unfold it, and repeat several times to destroy the van der Waals force between the layers to obtain a few-layer MoS2 thin film.

[0027] 3. Preparation of MoS2 Photodetectors: The mechanically exfoliated two-dimensional few-layer MoS2 film was transferred to pre-prepared gold interdigital electrodes and heat-treated at 80°C for approximately 10 minutes using a DB-1 stainless steel hot plate to strengthen the adhesion between the outermost layer of the MoS2 material and the interdigital electrodes. This was used to prepare the MoS2 photodetector.

[0028] 4. Preparation of Cu solution: Prepare 10 mL of anhydrous ethanol solution, weigh 2.54 mg of Cu nanoparticles using a balance, pour both into a test tube, and sonicate for 20 min to obtain a 0.004 mol / L Cu solution.

[0029] 5. Place the previously prepared MoS2-based photodetector on a glue spreader at room temperature and evacuate it to ensure it does not fall off.

[0030] 6. Preparation of Cu / MoS2 plasmonic heterojunction photodetectors: A 0.004 mol / L Cu solution was pipetted onto the center of a pre-prepared MoS2-based photodetector. The solution was first spin-coated at 1000 rpm / min for 10 s and then at 3000 rpm / min for 20 s. The remaining solvent was removed by drying on a DB-1 stainless steel hot plate at 80°C for 5 min. This successfully prepared a Cu / MoS2 plasmonic photodetector.

[0031] Example 2:

[0032] 1. Preparation of interdigitated electrodes: Gold interdigitated electrodes were prepared on a clean Si / SiO2 substrate using UV photolithography. The interdigitated electrodes were made of gold, with a gap of 3 μm, a width of 5 μm, and a length of 1400 μm.

[0033] 2. Preparation of MoS2 thin film: Use 3M tape to peel off a small amount of MoS2 from the MoS2 bulk material. Cut the tape to an appropriate length with scissors. Use tweezers to place the thin layer of MoS2 material flat on the tape. Fold the tape in half several times, press and unfold it, and repeat several times to destroy the van der Waals force between the layers to obtain a few-layer MoS2 thin film.

[0034] 3. Preparation of MoS2 Photodetectors: Mechanically exfoliated two-dimensional few-layer MoS2 films were transferred to pre-prepared gold interdigital electrodes and heat-treated at 80°C for approximately 10 minutes using a DB-1 stainless steel hot plate to strengthen the adhesion between the outermost layer of the MoS2 material and the interdigital electrodes. This resulted in the fabrication of MoS2 photodetectors.

[0035] 4. Thermal Oxidation of Cu Nanoparticles: A LAKTL1700-1400 dual-temperature tube furnace was used to thermally oxidize the Cu nanoparticles. The furnace parameters were set. The temperature was raised to 300°C over 30 minutes, followed by air annealing at this temperature for 10 minutes to accelerate oxidation and obtain a Cu@CuO core-shell plasma structure.

[0036] Preparation of Cu@CuO solution: Prepare 10 mL of anhydrous ethanol solution and weigh 2.54 mg of Cu@CuO nanoparticles on a balance. Pour both into a test tube and ultrasonicate for 20 min to obtain a 0.004 mol / L Cu@CuO solution.

[0037] 6. Place the previously prepared MoS2-based photodetector on a glue spreader at room temperature and evacuate it to ensure it does not fall off.

[0038] 7. Preparation of Cu@CuO / MoS2 core-shell plasmonic heterojunction photodetectors: A 0.004 mol / L Cu@CuO solution was pipetted onto the center of the surface of a pre-prepared MoS2-based photodetector. The solution was first spin-coated at 1000 rpm / min for 10 s and then at 3000 rpm / min for 20 s. The remaining solvent was removed by drying on a DB-1 stainless steel hot plate at 80°C for 5 min. This successfully prepared a Cu@CuO / MoS2 core-shell plasmonic heterojunction photodetector.

[0039] Figure 3 Comparison of Raman spectra of MoS2, Cu / MoS2 and Cu@CuO / MoS2 photodetectors. Peak and A 1g The peaks correspond to the in-plane and out-of-plane vibration modes of the MoS2 film, respectively. Compared with the Raman peak of the original MoS2 photodetector, the Raman peak of the Cu / MoS2 photodetector is significantly increased. This can be attributed to the local field enhancement characteristics of the LSPR induced by Cu metal nanoparticles. The intensity of the Raman vibration peak remains basically unchanged after oxidation treatment, indicating that the presence of CuO cannot reduce the LSPR effect. In order to better analyze the Raman peak, we fitted a Gaussian curve, as shown in Figure 3 (b) As shown. In the Raman spectrum, A 1g The peak is more sensitive to electrons. After the electrons move, A 1g The movement range is larger, such as Figure 3As shown in (c), the two characteristic Raman peaks of both the Cu / MoS2 and Cu@CuO / MoS2 heterojunction photodetectors exhibit a red shift, with the shift being more pronounced in the Cu@CuO / MoS2 device. This is attributed to the formation of the Cu@CuO / MoS2 heterojunction, where photogenerated electrons from CuO are transferred to MoS2. Furthermore, hot electrons from Cu are also injected into MoS2. This demonstrates that the heterojunction can assist in hot electron injection.

[0040] Figure 4 (a) is a comparison of the PL spectra of MoS2, Cu / MoS2 and Cu@CuO / MoS2 photodetectors. Compared with the luminescence peak of the original MoS2 photodetector, the luminescence peak of the Cu / MoS2 photodetector shows an enhanced phenomenon, which is attributed to the LSPR effect of Cu NPs enhancing the light absorption of MoS2. Compared with the Cu / MoS2 photodetector, the PL spectrum of the Cu@CuO / MoS2 photodetector shows obvious quenching, proving that interlayer charge transfer occurs in the heterojunction. In order to further analyze the changes in the PL spectrum, Figure 4 (b) is the fitted Gaussian curve, corresponding to the charged exciton (X - ) and neutral excitons (X 0 ), X - and X 0 represent the concentrations of charged excitons and neutral excitons in MoS2, respectively. Figure 4 (c) X in pristine MoS2, Cu / MoS2, and Cu@CuO / MoS2 heterojunction photodetectors 0 and X - After the heterojunction is formed, X - The proportion of X increases 0 The decrease in the ratio of CuO QDs is attributed to the transfer of photogenerated electrons in CuO QDs to MoS2.

[0041] Figure 5 (a) and Figure 5 (b) Comparison of IV curves of MoS2-based photodetectors before and after integration of Cu nanoparticles and Cu@CuO core-shell structure nanoparticles. Figure 5 (a) Dark state current and photocurrent of MoS2 and integrated Cu nanoparticles, Figure 5(b) Dark-state current and photocurrent of MoS2 and integrated Cu@CuO core-shell nanoparticles. Compared with the Cu / MoS2 photodetector, the Cu@CuO / MoS2 heterojunction photodetector exhibits a stronger photocurrent enhancement while suppressing dark current. This is attributed to the strong built-in electric field formed at the interface. The Fermi level of MoS2 is higher than that of CuO, allowing electrons to flow from MoS2 to CuO, suppressing the dark current of the Cu@CuO / MoS2 photodetector.

[0042] like Figure 6 (ad) are shown. The three devices were calculated and compared at -6V voltage, 178 mW / cm 2 The photocurrent, dark current, responsivity and detectivity under power density showed that the responsivity and detectivity of the Cu@CuO / MoS2 device increased by 12.6 times and 4.8 times respectively compared with the basic MoS2 device. In comparison, the responsivity and detectivity of the Cu / MoS2 device only increased by 3.2 times and 0.5 times compared with the basic MoS2 device. In addition, when Cu nanoparticles are in direct contact with the MoS2 surface, the dark current of the device will increase, and the dark current will increase by 6.6 times. By comparison, it was found that after the MoS2-based photodetector integrated Cu@CuO core-shell nanoparticles, the dark current only increased by 4.5 times, further confirming that the Cu@CuO / MoS2 heterojunction photodetector has better photoresponse characteristics.

[0043] Figure 7 (a) Time-dependent photoresponse characteristics of a Cu@CuO / MoS2 heterojunction photodetector under femtosecond pulse laser irradiation. Response speed is an important parameter for measuring photodetector performance. To evaluate the response speed of the Cu@CuO / MoS2 heterojunction photodetector, pulsed photoresponse measurements were performed. Figure 7 (b) The Cu@CuO / MoS2 photodetector accurately responds to every pulse signal under femtosecond pulse laser irradiation, with an ultrafast response speed (30 ns). This ultrafast response time is attributed to the proposed metal core-shell plasmon-enhanced 0D / 2D heterojunction structure, which enables type-II band alignment and heterojunction-assisted hot electron injection, improving the separation and transport efficiency of photogenerated carriers.

[0044] This patent describes the design of a metal core-shell plasmon-enhanced 0D / 2D heterojunction that achieves type-II band alignment and heterojunction-assisted hot electron injection. The material has a wide range of applications. The plasmon / TMDCs heterojunction photodetector designed in this invention effectively addresses the issue of slow response speed, exhibiting excellent photoelectric conversion efficiency. The experimental operation is simple, meeting current demands for the rapid construction of high-quality, low-dimensional hybrid heterojunctions.

[0045] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for fabricating a Cu@CuO core-shell structure-enhanced TMDCs 0D / 2D Cu@CuO / MoS2 heterojunction photodetector. From bottom to top, there is a Si / SiO2 substrate layer, interdigitated electrodes, a MoS2 layer, and a Cu@CuO core-shell structure.

2. According to the Cu@CuO / MoS2 heterojunction photodetector described in claim 1, gold interdigital electrodes are photolithographically prepared on a clean Si / SiO2 substrate by ultraviolet photolithography technology, the material of the interdigital electrodes is gold, the finger gap is 3 μm, the finger width is 5 μm, and the finger length is 1400 μm.

3. Use 3M tape to peel off a small amount of MoS2 from the MoS2 bulk material, fold the tape in half several times, press and unfold it, and repeat several times to destroy the van der Waals force between the layers to obtain a few-layer MoS2 material. This method is also applicable to other two-dimensional materials transition metal dichalcogenides (TMDCs) such as MoS2, WS2, WSe2, MoSe2, etc.

4. Preparation of Cu@CuO / MoS2 heterojunction photodetector, characterized by the following steps: (1) A tape with a MoS2 film was attached to a gold interdigital electrode and heated at 80 °C for 10 min to enhance the adsorption between the MoS2 film and the gold electrode, thereby obtaining a MoS2-based photodetector. (2) The Cu nanoparticles were placed in a tube furnace for thermal oxidation treatment. The temperature was raised to 300 °C for 30 min and then kept constant for 10 min to obtain a Cu@CuO nanoparticle core-shell structure. (3) Prepare 10 mL of anhydrous ethanol and weigh out 2.54 mg of Cu@CuO solution nanoparticles using a pipette. Pour the two into a test tube and sonicate for 20 min to obtain a 0.004 mol / L Cu@CuO solution. (4) Use a pipette to drop the Cu@CuO solution onto the center of the pre-prepared MoS2-based photodetector surface. Adjust the relevant parameters of the spin coater to control the required thickness. First, spin coat at 1000 rpm / min for 10 s, then spin coat at 3000 rpm / min for 20 s. (5) The remaining solvent was removed by drying, and a core-shell plasmonic Cu@CuO / MoS2 heterojunction photodetector was successfully prepared.

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