A layered arrayed TMDC heterojunction, a photodetector and a preparation method thereof

Abstract

The present invention belongs to the technical field of optoelectronic detection of layered materials, and provides a layered arrayed TMDC (few-layer transition metal chalcogenide) heterojunction, an optoelectronic detector and a preparation method thereof. The layered arrayed TMDC heterojunction provided by the present invention includes a first layered TMDC and a second layered TMDC which are stacked; the first layered TMDC has a nanoarray structure. In the heterojunction of the present invention, the array structure of the first layered TMDC improves the optical enhancement effect of the layered TMDC; meanwhile, the optical enhancement effect promotes the generation of photo-generated carriers and the separation of electron-hole pairs, thereby enabling the optoelectronic detector constructed by the layered arrayed TMDC heterostructure to have a high photo-responsivity and a fast response time; in addition, the optical resonances of the nanoarray structure are different under different polarizations, and similarly, when performing optoelectronic detection, the polarization-sensitive detection ability of the optoelectronic detector is enriched.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic detection of layered materials, and particularly to a layered arrayed TMDC heterojunction, an optoelectronic detector and a preparation method thereof. Background Art

[0002] Few-layer transition metal dichalcogenides (TMDCs) have unique physical properties and luminescence characteristics. Van der Waals heterostructures vertically stacked by TMDCs exhibit interesting optoelectronic properties. However, the absorption of atomically layered two-dimensional TMDCs is low, which limits the improvement of the light response performance. In recent years, researchers have found that the combination of TMDCs with metal plasmonic structures or dielectric Mie resonance structures can achieve sub-wavelength light localization and enhance light absorption. However, for such composite structures as TMDC-metal or TMDC-dielectric, the enhancement of the light-matter interaction only occurs at the interface between the nanostructure and the TMDC layer, and it is difficult to affect the photocurrent of the entire layered material, resulting in limited optoelectronic detection performance. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a layered arrayed TMDC heterojunction, an optoelectronic detector and a preparation method thereof. The layered arrayed TMDC heterojunction provided by the present invention can enhance optical absorption and has excellent optoelectronic detection performance.

[0004] To achieve the above invention purpose, the present invention provides the following technical solutions:

[0005] The present invention provides a layered arrayed TMDC heterojunction, which includes a first layered TMDC and a second layered TMDC stacked layer by layer;

[0006] The first layered TMDC has a nanoarray structure;

[0007] The materials of the first layered TMDC and the second layered TMDC are different.

[0008] Preferably, the nanoarray structure includes a nanobar array structure or a nanopore array structure.

[0009] Preferably, the parameters of the nanobar array structure include: the width of the nanobar is 200-400 nm, the depth of the groove is 20-N nm, and the spacing between adjacent nanobars is 200-500 nm; N in the depth of the groove is the thickness of the first layered TMDC.

[0010] Preferably, the parameters of the nanopore array structure include: the diameter of the nanopore is 200-400 nm, the depth of the nanopore is 20-N nm, and the spacing between nanopores is 200-500 nm; N in the depth of the nanopore is the thickness of the first layered TMDC.

[0011] Preferably, the materials of the first-layered TMDC and the second-layered TMDC are independently ReS2, WSe2, WS2, MoSe2, or MoS2.

[0012] Preferably, the thickness of the first-layered TMDC is 20 nm to 150 nm; the thickness of the second-layered TMDC is 5 nm to 100 nm.

[0013] The present invention also provides a photodetector, including a substrate, a layered arrayed TMDC heterojunction, and source and drain electrodes which are stacked;

[0014] The layered arrayed TMDC heterojunction is the layered arrayed TMDC heterojunction described in the above technical solution;

[0015] The first-layered TMDC of the layered arrayed TMDC heterojunction is in contact with the substrate.

[0016] Preferably, the substrate is a Si / SiO2 substrate; the source and drain electrodes are gold films.

[0017] The present invention also provides a preparation method of the photodetector described in the above technical solution, including the following steps:

[0018] Transfer the first-layered TMDC material onto the substrate, and perform etching to obtain the first-layered TMDC;

[0019] Transfer the second-layered TMDC material onto the first-layered TMDC to obtain a layered arrayed TMDC heterojunction;

[0020] Deposit source and drain electrodes on a specific region of the layered arrayed TMDC heterojunction to obtain the photodetector.

[0021] Preferably, the etching is FIB etching; the FIB etching uses a FIB-SEM dual-beam workstation; the etching beam current of the FIB etching is 10 to 50 pA.

[0022] The present invention provides a layered arrayed TMDC heterojunction, which includes a first-layered TMDC and a second-layered TMDC arranged in a stacked manner; the first-layered TMDC has a nanoarray structure; the materials of the first-layered TMDC and the second-layered TMDC are different. In the heterojunction of the present invention, the array structure of the first-layered TMDC improves the optical enhancement effect of the layered TMDC; at the same time, the optical enhancement effect promotes the generation of photo-generated carriers and the separation of electron-hole pairs, thereby enabling the photodetector constructed by the layered arrayed TMDC heterostructure to have a high photosensitivity and a fast response time; in addition, the optical resonance of the nanoarray structure has differences under different polarizations, and similarly, when performing photoelectric detection, it enriches the polarization-sensitive detection ability of the photodetector.

[0023] The present invention also provides a photodetector, which includes a substrate, a layered arrayed TMDC heterojunction, and source and drain electrodes arranged in a stacked manner; the layered arrayed TMDC heterojunction is the layered arrayed TMDC heterojunction described in the above technical solution; the first-layered TMDC of the layered arrayed TMDC heterojunction is in contact with the substrate. The photodetector of the present invention uses a layered arrayed TMDC heterojunction, and the first-layered TMDC of the layered arrayed TMDC heterojunction has a nanoarray structure, so that the photodetector has a high photosensitivity and a fast response time; at the same time, the optical resonance of the nanoarray structure has differences under different polarizations, and similarly, when performing photoelectric detection, it enriches the polarization-sensitive detection ability of the photodetector.

[0024] The present invention also provides a preparation method of the photodetector described in the above technical solution, which includes the following steps: transferring the first-layered TMDC material onto the substrate and performing etching to obtain the first-layered TMDC; transferring the second-layered TMDC material onto the first-layered TMDC to obtain a layered arrayed TMDC heterojunction; depositing source and drain electrodes on a specific area of the layered arrayed TMDC heterojunction to obtain the photodetector. The preparation method provided by the present invention is simple, fast, safe and environmentally friendly. Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the operation of FIB etching;

[0026] Figure 2 It is a schematic diagram of the structure of the photodetector obtained in Example 1;

[0027] Figure 3 It is an atomic force microscope thickness measurement diagram of layered ReS2;

[0028] Figure 4 It is a scanning electron microscope diagram of the ReS2 nanoarray structure;

[0029] Figure 5 Bright-field and dark-field images of the ReS2 nanoarray structure;

[0030] Figure 6 Atomic force microscope thickness measurement image of layered WSe2;

[0031] Figure 7 Bright-field and dark-field images of the ReS2-WSe2 layered heterojunction under an optical microscope;

[0032] Figure 8 Photoluminescence spectra of the unetched ReS2-WSe2 layered heterojunction region, etched ReS2-WSe2 layered heterojunction region, and pure WSe2 region;

[0033] Figure 9 Photocurrent curves of the ReS2-WSe2 layered heterojunction region under forward and reverse biases of an excitation wavelength of 405 nm and 1 V;

[0034] Figure 10 For the ReS2-WSe2 layered heterojunction region at an excitation wavelength of 405 nm and a laser power of 305.31 mw / cm 2 、Photocurrent-time relationship curve under a 3 V bias;

[0035] Figure 11 Map of the area labels for the photodetection performance test;

[0036] Figure 12 Comparison map of the local photocurrent performance of the photodetector in different regions. Detailed implementation mode

[0037] The present invention provides a layered arrayed TMDC heterojunction, including a first-layered TMDC and a second-layered TMDC stacked;

[0038] The first-layered TMDC has a nanoarray structure;

[0039] The materials of the first-layered TMDC and the second-layered TMDC are different.

[0040] In the present invention, unless otherwise specified, the raw materials used in the present invention are preferably commercially available products.

[0041] The layered arrayed TMDC heterojunction provided by the present invention includes a first-layered TMDC. In the present invention, the first-layered TMDC has a nanoarray structure; the nanoarray structure preferably includes a nanobar array structure or a nanopore array structure.

[0042] In the present invention, the parameters of the nanobar array structure include: the width of the nanobar is preferably 200 - 400 nm; the depth of the groove is preferably 20 - N nm, where N in the depth of the groove is the thickness of the first-layered TMDC; the spacing between adjacent nanobars is preferably 200 - 500 nm.

[0043] In the present invention, the parameters of the nanopore array structure include: the aperture of the nanopore is preferably 200 - 400 nm; the depth of the nanopore is preferably 20 - N nm, where N in the depth of the nanopore is the thickness of the first-layered TMDC; the spacing between nanopores is preferably 200 - 500 nm.

[0044] In the present invention, the material of the first-layered TMDC is preferably ReS2, WSe2, WS2, MoSe2 or MoS2, and more preferably ReS2. In the present invention, the thickness of the first-layered TMDC is preferably 20 nm - 150 nm. In the present invention, the thickness of the first-layered TMDC is set to 20 nm - 150 nm, which not only ensures the generation of optical resonance but also guarantees the construction of the second-layered TMDC.

[0045] The layered arrayed TMDC heterojunction provided by the present invention includes a second-layered TMDC. In the present invention, the thickness of the second-layered TMDC is preferably 5 nm - 100 nm. In the present invention, the material of the second-layered TMDC is preferably ReS2, WSe2, WS2, MoSe2 or MoS2, and more preferably WSe2.

[0046] In the present invention, the preparation method of the layered arrayed TMDC heterojunction is preferably introduced in the preparation of the photodetector.

[0047] The present invention also provides a photodetector, which includes a substrate, a layered arrayed TMDC heterojunction, and source and drain electrodes that are stacked;

[0048] The layered arrayed TMDC heterojunction is the layered arrayed TMDC heterojunction described in the above technical solution;

[0049] The first-layered TMDC of the layered arrayed TMDC heterojunction is in contact with the substrate.

[0050] The photodetector provided by the present invention includes a substrate, and the substrate is preferably a Si / SiO2 substrate. In the present invention, the Si / SiO2 substrate preferably includes a bottom single-crystalline silicon and a silicon dioxide oxide layer; the thickness of the bottom single-crystalline silicon is preferably 500 μm; the thickness of the silicon dioxide oxide layer is preferably 300 nm.

[0051] The photodetector provided by the present invention includes a layered arrayed TMDC heterojunction, and the layered arrayed TMDC heterojunction is the layered arrayed TMDC heterojunction described in the above technical solution. In the present invention, the first-layered TMDC of the layered arrayed TMDC heterojunction is in contact with the substrate.

[0052] The photodetector provided by the present invention includes source and drain electrodes, and the source and drain electrodes are preferably gold films. In the present invention, the thickness of the gold film is preferably 50-100 nm.

[0053] The present invention also provides a preparation method of the photodetector described in the above technical solution, including the following steps:

[0054] Transfer the first-layered TMDC material onto the substrate, and perform etching to obtain the first-layered TMDC;

[0055] Transfer the second-layered TMDC material onto the first-layered TMDC to obtain a layered arrayed TMDC heterojunction;

[0056] Deposit source and drain electrodes on a specific region of the layered arrayed TMDC heterojunction to obtain the photodetector.

[0057] In the present invention, the layered TMDC is transferred onto the substrate and etched to obtain the first-layered TMDC.

[0058] In the present invention, the preparation method of the first-layered TMDC material preferably includes the following steps: obtaining the first-layered TMDC material from a first TMDC single crystal material by mechanical exfoliation. In the present invention, the mechanical exfoliation preferably includes the following steps: placing the first TMDC single crystal material on a blue tape, performing repeated sticking and peeling so that the first TMDC single crystal material becomes a layered thin sheet, transferring the layered thin sheet on the blue tape above a PDMS substrate, and repeatedly pressing with a cotton swab. After standing, slowly peel off the blue tape to obtain the first-layered TMDC material attached to the PDMS substrate.

[0059] In the present invention, the size of the PDMS substrate is preferably 1.5 cm × 1.5 cm.

[0060] In the present invention, the first TMDC single crystal material is preferably sheet-shaped.

[0061] In the present invention, the transfer preferably includes the following steps: placing the PDMS substrate with the first-layered TMDC material attached thereto upside down on a moving platform, and transferring the first-layered TMDC material above the substrate through the moving stage. Slowly press down and then slowly lift it to fix the first-layered TMDC material at a specific position on the substrate.

[0062] In the present invention, the etching is preferably FIB etching; the FIB etching preferably uses a FIB-SEM dual-beam workstation; the etching beam current of the FIB etching is preferably 10-50 pA. In the present invention, the length of the etched area is preferably 10 μm to 50 μm, and the width is preferably 5 μm to 20 μm. In the present invention, the operation schematic diagram of the FIB etching is as shown in Figure 1 shown.

[0063] After obtaining the first-layer TMDC, the present invention transfers the second-layer TMDC material onto the first-layer TMDC to obtain a layered arrayed TMDC heterojunction.

[0064] In the present invention, the preparation method of the second-layer TMDC material preferably includes the following steps: obtaining the second-layer TMDC material by mechanical exfoliation from the second TMDC single crystal material. In the present invention, the steps of the mechanical exfoliation are preferably the same as those of the above technical solution and will not be elaborated herein.

[0065] In the present invention, the transfer preferably includes the following steps: inverting the PDMS substrate attached with the second-layer TMDC material onto the moving platform, aligning the second-layer TMDC material with the first-layer TMDC through the moving stage, slowly pressing down and then slowly lifting.

[0066] In the present invention, when the second-layer TMDC material is transferred onto the first-layer TMDC, a second-layer TMDC will be formed, and the first-layer TMDC and the second-layer TMDC constitute a layered arrayed TMDC heterojunction.

[0067] After obtaining the layered arrayed TMDC heterojunction, the present invention deposits source and drain electrodes on specific regions of the layered arrayed TMDC heterojunction to obtain the photodetector.

[0068] In the present invention, the electrode building method of the source and drain electrodes is preferably by maskless lithography and electron beam evaporation. The present invention does not specifically limit the parameters and methods of the maskless lithography and electron beam evaporation, and the well-known technical means of those skilled in the art can be adopted.

[0069] The following will elaborate on the layered arrayed TMDC heterojunction, photodetector and their preparation methods provided by the present invention in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0070] Example 1

[0071] According to Figure 2 the structural schematic diagram of the photodetector shown, prepare the photodetector:

[0072] Step S1: Prepare a Si / SiO2 substrate with a bottom single-crystalline silicon thickness of 500 μm and an oxide layer thickness of 300 nm.

[0073] Step S2: Mechanically exfoliate the ReS2 single-crystalline wafer and cut a PDMS transparent flexible substrate with a size of about 1.5 cm × 1.5 cm. Then transfer the exfoliated ReS2 layered flake to the PDMS substrate and use a microscope to find the ReS2 with a specific thickness and a long-strip shape.

[0074] Step S3: Under the microscope, place the PDMS substrate with the attached layered ReS2 upside down on the moving platform and transfer it to the Si / SiO2 substrate through the moving stage. Gently press it down and then slowly lift it to attach the layered ReS2 to the Si / SiO2 substrate.

[0075] Figure 3 is the atomic force microscope thickness measurement diagram of the layered ReS2; from Figure 3 it can be seen that the thickness of the layered ReS2 is 110 nm.

[0076] Step S4: Use the Figure 1 shown FIB etching technology to process the layered ReS2 area on the Si / SiO2 substrate. The Ga + ion beam is accelerated by the ion gun and focused on the substrate, which can achieve etching of the substrate, and the etching rate and fineness can be changed by adjusting parameters such as voltage, beam current, and etching time. Etch to form a nano-strip array structure with a groove depth of 100 nm to form a ReS2 nano-array structure.

[0077] The scanning electron microscope image of the obtained ReS2 nano-array structure is as shown in Figure 4 From Figure 4 it can be seen that the surface of the nano-strip array is flat, the size is uniform, the width is 390 nm, and the spacing between adjacent nano-strips is 230 nm.

[0078] The bright-field and dark-field images of the obtained ReS2 nano-array structure are as shown in Figure 5 From Figure 5 it can be seen that in the bright field, the area of the ReS2 nano-array structure shows the same depth color as the substrate, indicating that the ReS2 has been completely etched.

[0079] Step S5: Mechanically exfoliate the WSe2 single-crystalline wafer, then transfer the exfoliated WSe2 to the PDMS substrate, and under the microscope, according to the characteristic that the contrast of different layers is different, find the WSe2 area with the required thickness. The area of the layered WSe2 should be able to cover the entire ReS2 nano-array area. Its thickness should not be too thick, otherwise it may cause damage to the underlying nano-array. Similarly, the area should not be too large, otherwise it will increase the difficulty of subsequent photolithography.

[0080] Step S6: Under a microscope, the PDMS substrate with layered WSe2 attached is placed upside down on the moving platform, and it is transferred to the etched ReS2 nanoarray structure region on the Si / SiO2 substrate through the moving stage. After gently pressing it down and then slowly lifting it, the WSe2 flakes are attached to the ReS2 nanoarray structure region to obtain a ReS2-WSe2 layered heterojunction.

[0081] Figure 6 is the atomic force microscope thickness measurement diagram of layered WSe2. From Figure 6 it can be seen that the thickness of layered WSe2 is 25 nm.

[0082] Figure 7 is the bright-field and dark-field diagram of the ReS2-WSe2 layered heterojunction under an optical microscope. From Figure 7 it can be seen that the basic structure of the photodetector includes gold electrodes, layered WSe2, and layered ReS2. It can be seen that the ReS2-WSe2 layered heterojunction region is mainly composed of nanoarrays.

[0083] Step S7: Use maskless lithography technology to write electrode patterns at specific positions on the ReS2-WSe2 layered heterojunction, and deposit a gold film on the developed substrate by electron beam evaporation to form source and drain electrodes, thus obtaining a photodetector.

[0084] Comparative Example 1

[0085] The difference from Example 1 is that the layered ReS2 is not etched, and the obtained heterojunction is called an unetched ReS2-WSe2 layered heterojunction.

[0086] Test Example 1 Optical Performance Characterization

[0087] The photoluminescence of the unetched ReS2-WSe2 layered heterojunction, etched ReS2-WSe2 layered heterojunction, and pure WSe2 in these three regions under 532 nm laser excitation was tested by a Raman spectrometer. The results of each region were obtained by taking the average value after more than 10 repeated measurements. The obtained photoluminescence spectra are as Figure 8 shown. From Figure 8It can be seen that: due to the very weak photoluminescence of ReS2 with a certain thickness, the luminescence of the heterojunction is mainly dominated by WSe2. Since the ReS2-WSe2 layered heterojunction is a Type-II band structure, this structure promotes the separation of electrons and holes onto two materials respectively, resulting in a lower luminescence intensity of the ReS2-WSe2 layered heterojunction, lower than the photoluminescence of pure WSe2; however, after etching nanowires on the surface of ReS2, more electron-hole pairs can be generated through local optical field enhancement. Although the band structure of the heterojunction cannot be changed by etching, due to the recombination luminescence of the generated more electron-hole pairs, the photoluminescence of the etched ReS2-WSe2 layered heterojunction is much greater than that of the unetched ReS2-WSe2 layered heterojunction.

[0088] Test Example 2: Optoelectronic Performance Characterization

[0089] The probes connecting the source and drain are respectively pressed on the large rectangular electrode area extending from the back end of the gold electrode, and the optoelectronic characteristics of different regions are tested by connecting the electrodes on different materials.

[0090] Figure 9 is the photocurrent curve of the ReS2-WSe2 layered heterojunction region under forward and reverse biases of 1 V at an excitation wavelength of 405 nm. From Figure 9 it can be seen that: the laser spot is focused on the ReS2-WSe2 layered heterojunction region, and the photocurrent of the ReS2-WSe2 layered heterojunction from the dark condition to a laser power of 305.31 mW / cm 2 is measured. Whether a forward or reverse voltage is applied, the photocurrent of the ReS2-WSe2 layered heterojunction increases with the increase of the laser power, and the photocurrent reaches the -10 order of magnitude. The photocurrent is slightly larger when a reverse voltage is applied than when a forward voltage is applied, and the generated open-circuit voltage is about 0.25 V.

[0091] The optical response time is also an important performance index for evaluating a photodetector. A photodetector with better performance generally has a larger on-off ratio or a faster response time. Figure 10 is the photocurrent-time relationship curve of the ReS2-WSe2 layered heterojunction region under an excitation wavelength of 405 nm, a laser power of 305.31 mw / cm 2 , and a 3 V bias voltage, showing the rise and fall times of a switching cycle; Figure 10 In, the picture on the right is a partial enlarged view of the picture on the left. From Figure 10 it can be seen that: the on-off ratio of the ReS2-WSe2 layered heterojunction can reach 10 4and has good stability under multiple cycles. The rise and fall times are 38.3 ms and 42.5 ms respectively, indicating that the carriers of this photodetector have the ability to quickly separate.

[0092] Test Example 3: Characterization of Photodetection Performance

[0093] Figure 12 In order to focus the laser into a 10-μm-sized spot through collimation and objective lens focusing, and then hit the spot on different regions to test the corresponding photocurrent. The tested positions include the ReS2-WSe2 layered heterojunction nanorod array region and the individual regions of ReS2 and WSe2. The labels of the tested regions are as Figure 11 shown, and the corresponding photocurrents of different regions are as Figure 12 shown. It can be seen from Figure 12 that: after normalizing the measured photocurrent, it can be found that the photocurrent at point 1 in the ReS2 region is the lowest. When the spot moves towards the heterojunction region, the photocurrent gradually increases and reaches the maximum in the nanorod array heterojunction region, indicating that after nano-etching, the photocurrent of the device can be increased, and the photocurrent at the center is the largest.

[0094] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A layered arrayed TMDC heterojunction, characterized in that, It includes a first-layered TMDC and a second-layered TMDC which are stacked; The first-layered TMDC has a nanoarray structure; The materials of the first-layered TMDC and the second-layered TMDC are different; The nanoarray structure includes a nanobar array structure or a nanopore array structure; The parameters of the nanobar array structure include: the width of the nanobar is 200 - 400 nm, the depth of the groove is 20 - N nm, and the spacing between adjacent nanobars is 200 - 500 nm; N in the depth of the groove is the thickness of the first-layered TMDC; The parameters of the nanopore array structure include: the diameter of the nanopore is 200 - 400 nm, the depth of the nanopore is 20 - N nm, and the spacing between nanopores is 200 - 500 nm; N in the depth of the nanopore is the thickness of the first-layered TMDC; The materials of the first-layered TMDC and the second-layered TMDC are independently ReS2, WSe2, WS2, MoSe2 or MoS2; The thickness of the first-layered TMDC is 20 nm - 150 nm; the thickness of the second-layered TMDC is 5 nm - 100 nm; The preparation method of the layered arrayed TMDC heterojunction includes the following steps: Transfer the first-layered TMDC material onto a substrate and perform etching to obtain the first-layered TMDC; Transfer the second-layered TMDC material onto the first-layered TMDC to obtain the layered arrayed TMDC heterojunction.

2. A photodetector, characterized in that, It includes a substrate, a layered arrayed TMDC heterojunction and source-drain electrodes which are stacked; The layered arrayed TMDC heterojunction is the layered arrayed TMDC heterojunction as claimed in claim 1; The first-layered TMDC of the layered arrayed TMDC heterojunction is in contact with the substrate.

3. The photodetector according to claim 2, characterized in that, The substrate is a Si / SiO2 substrate; the source-drain electrodes are gold films.

4. The method for preparing the photodetector according to claim 2 or 3, characterized in that, It includes the following steps: Transfer the first-layered TMDC material onto a substrate and perform etching to obtain the first-layered TMDC; Transfer the second-layered TMDC material onto the first-layered TMDC to obtain the layered arrayed TMDC heterojunction; Deposit source-drain electrodes on a specific area of the layered arrayed TMDC heterojunction to obtain the photodetector.

5. The preparation method according to claim 4, characterized in that, The etching is FIB etching; the FIB etching uses a FIB-SEM dual-beam workstation; the etching beam current of the FIB etching is 10 - 50 pA.

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