A 1D GaN nanopillar array / 2D MoS2 / Pedot:Pss self-powered flexible UV detector and its preparation

Abstract

The present invention discloses a 1D GaN nanopillar array / 2D MoS2 film / Pedot:Pss self-powered flexible ultraviolet detector and its preparation; the device includes a PET substrate, an ITO film, a metal electrode, a MoS2 film, and a GaN nanopillar array. The inventors used a wet transfer technique to non-destructively transfer the 1D GaN nanopillar array / 2D MoS2 film onto a Pedot:Pss / ITO / PET flexible substrate to construct a flexible heterojunction, thereby achieving the preparation of a self-powered flexible detector. Because the 2D MoS2 film serves as a transfer template, the 1D GaN nanopillar array does not collapse or break. The device utilizes the large specific surface area of ​​the GaN nanopillar array to enhance light absorption and the two-dimensional quantum confinement of 2D MoS2 to improve carrier mobility. As a result, the flexible detector exhibits high responsiveness and fast response speed as an ultraviolet detector. The preparation process does not involve complex operations or the generation of harmful pollutants, providing an effective strategy for next-generation photoelectric detection.

Description

Technical Field

[0001] The present invention relates to an ultraviolet detection device, in particular to a 1D GaN nanocolumn array / 2D MoS2 / Pedot:Pss self-powered flexible ultraviolet detector and its preparation. Background Art

[0002] Self-powered UV detectors, which require no external power source for photodetection, are compact and lightweight, offering promising applications in military and civilian fields such as aerospace, broadband communications, and flexible wearables. One effective strategy for realizing this type of device is to construct a heterojunction and introduce a built-in electric field to separate photogenerated carriers. However, common heterojunction detectors are mostly thin-film devices, which suffer from slow response speed and low responsivity due to low light capture efficiency and severe defect scattering. Furthermore, these devices suffer from severe performance degradation in the flexible state due to electrode slippage. Against this backdrop, the inventors have proposed a novel heterostructure of 1D GaN nanopillar arrays / 2D MoS2 thin film / Pedot:Pss thin film and realized flexible, self-powered UV detection. This structure achieves multiple reflection absorption of incident UV light, improving the light capture efficiency, while confining carriers in a low-dimensional space for rapid separation. Flexible UV detectors based on this structure exhibit high responsivity and fast response speed in the absence of an operating voltage, demonstrating promising applications. At the same time, during the preparation process, no complex operations and other harmful by-products are produced, providing an effective strategy for the preparation of flexible photoelectric detection devices. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings and deficiencies of the above-mentioned prior art and provide a 1D GaN nanorod array / 2D MoS2 / Pedot:Pss self-powered flexible ultraviolet detector and its preparation.

[0004] The present invention uses wet transfer technology to losslessly transfer 1D GaN nanocolumn arrays / 2D MoS2 thin films to Pedot:Pss / ITO / PET flexible substrates, realizing the preparation of high-performance, self-powered flexible ultraviolet photodetectors.

[0005] The present invention overcomes the problems of low responsiveness, slow response speed, and poor performance in the bent state of traditional thin-film flexible detectors. The preparation process does not require complex operations and does not produce harmful pollutants, providing an effective strategy for the next generation of photoelectric detection.

[0006] The 1D GaN nanopillar array of the present invention is fabricated via molecular beam epitaxy; the MoS2 thin film is prepared via chemical vapor deposition. A flexible heterojunction is achieved by losslessly transferring the 1D GaN nanopillar array / 2D MoS2 thin film onto a Pedot:Pss / ITO / PET flexible substrate using a wet transfer technique. Because the 2D MoS2 thin film serves as the transfer template, the 1D GaN nanopillar array is protected from collapse and damage. Furthermore, type II band alignment is achieved at the GaN / MoS2 / Pedot:Pss heterointerface, effectively enhancing the separation of photogenerated carriers and improving device performance.

[0007] The present invention is achieved through the following technical solutions:

[0008] A 1D GaN nanopillar array / 2D MoS2 / Pedot:Pss self-powered flexible ultraviolet detector, comprising a GaN nanopillar vertical array 6, a MoS2 film 5, a Pedot:Pss film, an ITO film 2, a PET flexible substrate 1, a first metal electrode 3, and a second metal electrode 4;

[0009] The ITO film 2 is located on the PET flexible substrate 1;

[0010] The MoS2 film 5 is located on the ITO film 2;

[0011] The GaN nanocolumn vertical array 6 is located on the MoS2 film 5;

[0012] The first metal electrode 3 is located on the ITO film 2 to form an ohmic contact;

[0013] The second metal electrode 4 is located on the GaN nanorod vertical array 6 to form an ohmic contact.

[0014] The thickness of the PET flexible substrate 1 is 300-400 μm, and the resistance of the ITO film 2 is 10 -4 ~10 -3 Ω·cm.

[0015] The length of the GaN nanopillar vertical array 6 is 200-600 nm, and the diameter is 30-70 nm. The density of the GaN nanopillars is 5.0×10 9 ~10.0×10 9 / cm 2 .

[0016] The thickness of the MoS2 film 5 is 2 to 7 nm.

[0017] The first metal electrode 3 and the second metal electrode 4 are both formed by sequentially stacking an 80-100 nm Ti metal layer and a 100-120 nm Au metal layer; wherein the Au metal layer is above the Ti metal layer.

[0018] The preparation method of the 1D GaN nanorod array / 2D MoS2 / Pedot:Pss self-powered flexible ultraviolet detector of the present invention comprises the following steps:

[0019] S1: 2D MoS2 thin films were prepared on SiO2 / Si substrates by chemical vapor deposition.

[0020] S2: placing the MoS2 / SiO2 / Si prepared in step S1 in a radio frequency assisted molecular beam epitaxy (PA-MBE) apparatus to grow GaN nanorods on the MoS2 / SiO2 / Si;

[0021] S3: Spin-coat the GaN nanorods / MoS2 / SiO2 / Si in step S2 with PMMA solution and heat to cure;

[0022] S4: placing the PMMA / GaN nanorods / MoS2 / SiO2 / Si in step S3 in a dilute HF solution to remove the SiO2 film to obtain PMMA / GaN nanorods / MoS2;

[0023] S5, transferring the PMMA / GaN nanorods / MoS2 in step S4 to a Pedot:Pss / ITO / PET flexible substrate, and removing the surface PMMA by reactive ion etching;

[0024] S6. Prepare Ti / Au electrodes on the GaN nanorod / MoS2 / Pedot:Pss / ITO / PET flexible substrate obtained in step S5 by electron beam evaporation to obtain a self-powered flexible ultraviolet photodetector.

[0025] The PA-MBE chamber pressure, substrate temperature, beam source temperature, gas flow rate, RF plasma power, and growth time in step S2 are the main factors in achieving a vertical array of GaN nanorods. Therefore, the process conditions for the RF-assisted molecular beam epitaxy device growth of the present invention are set as follows:

[0026] Annealing treatment at a temperature range of 900-950°C for 40-60 minutes;

[0027] The N2 gas flow rate is 1.5 to 2 sccm;

[0028] The cavity pressure is 1×10 -8 ~5×10 -8 Torr;

[0029] Growth temperature is 920-940°C;

[0030] RF plasma power is 380-400W;

[0031] Ga source temperature is 920-950°C;

[0032] The total growth time is 2.6 to 2.8 hours.

[0033] The PMMA spin coating speed and curing temperature in step S3 are key factors affecting the adhesion between PMMA and GaN nanopillars. Therefore, the PMMA spin coating speed in the present invention is 4000-6000 rpm for 50-60 seconds, and the curing temperature is 100-110°C for 3-5 minutes.

[0034] The concentration of the HF solution in step S4 determines the SiO2 etching rate. If the concentration is too high, the GaN nanopillars may collapse, while if the concentration is too low, SiO2 may remain. Therefore, the volume concentration of the HF solution in the present invention is 7-10%, and the immersion time is 25-30 minutes.

[0035] In the S5 process, excessive reactive ion etching time and power can easily damage the underlying MoS2 film. If the reactive ion etching time and power are too low, PMMA residue will remain. Therefore, the reactive ion etching process of the present invention uses Ar gas, an etching time of 15 to 20 minutes, and an etching power of 20 to 25 W.

[0036] The thickness of the MoS2 in the S1 is one of the key factors affecting the growth of the GaN nanopillar array. If the MoS2 is too thin, the GaN nanopillar array is prone to merging; if the MoS2 is too thick, the density of the GaN nanopillars is too low, and the light absorption capacity decreases. The thickness of the MoS2 film is mainly determined by the growth temperature, growth pressure, growth time and source. Therefore, the present invention adopts chemical vapor deposition, using 0.04-0.07g of molybdenum trioxide (MoO3) and 0.1-0.15g of sulfur (S) powder as the Mo and S sources, and growing at a temperature of 650-700°C and atmospheric pressure for 10-15 minutes.

[0037] Compared with the prior art, the present invention has the following advantages and effects:

[0038] The present invention overcomes the problems of low responsiveness, slow response speed, and poor performance in a bent state of traditional thin-film flexible detectors. Type II band alignment can be formed at the heterojunction of GaN / MoS2 / Pedot:Pss, effectively enhancing the separation of photogenerated carriers. The device exhibits high light responsiveness and extremely fast response speed during ultraviolet light detection.

[0039] The flexible heterojunction is created by losslessly transferring a 1D GaN nanopillar array / 2D MoS2 film onto a Pedot:Pss / ITO / PET flexible substrate using a wet transfer technique. Because the 2D MoS2 film serves as the transfer template, the 1D GaN nanopillar array remains intact and undamaged. Consequently, the device leverages the large surface area of ​​the GaN nanopillar array to enhance light absorption and the two-dimensional quantum confinement of 2D MoS2 to improve carrier mobility. The fabrication process is painless and produces no hazardous contaminants, providing an effective strategy for next-generation photodetection. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the 1D GaN / 2D MoS2 / Pedot:Pss self-powered flexible ultraviolet photodetector of the present invention.

[0041] Figure 2 This is a SEM cross-sectional image of the GaN nanorod array / MoS2 film / SiO2 / Si prepared in Example 1 of the present invention.

[0042] Figure 3 This is an SEM top view of the GaN nanorod array / MoS2 film / Pedot:pss / ITO / PET flexible heterojunction prepared in Example 1 of the present invention.

[0043] Figure 4 This is an enlarged SEM top view of the GaN nanorod array / MoS2 film / Pedot:pss / ITO / PET flexible heterojunction prepared in Example 1 of the present invention.

[0044] Figure 5 IT curves of 1D GaN / 2D MoS2 / Pedot:Pss self-powered flexible ultraviolet photodetector in different flexible states. DETAILED DESCRIPTION

[0045] The present invention is described in further detail below with reference to specific embodiments.

[0046] The present invention discloses a 1D GaN nanopillar array / 2D MoS2 / Pedot:Pss self-powered flexible ultraviolet detector, comprising a GaN nanopillar vertical array 6, a MoS2 film 5, a Pedot:Pss film, an ITO film 2, a PET flexible substrate 1, a first metal electrode 3, and a second metal electrode 4;

[0047] The ITO film 2 is located on the PET flexible substrate 1;

[0048] The MoS2 film 5 is located on the ITO film 2;

[0049] The GaN nanocolumn vertical array 6 is located on the MoS2 film 5;

[0050] The first metal electrode 3 is located on the ITO film 2 to form an ohmic contact;

[0051] The second metal electrode 4 is located on the GaN nanorod vertical array 6 to form an ohmic contact.

[0052] The thickness of the PET flexible substrate 1 is 300-400 μm, and the resistance of the ITO film 2 is 10 -4 ~10 -3 Ω·cm.

[0053] The length of the GaN nanopillar vertical array 6 is 200-600 nm, and the diameter is 30-70 nm. The density of the GaN nanopillars is 5.0×10 9 ~10.0×10 9 / cm 2 .

[0054] The thickness of the MoS2 film 5 is 2 to 7 nm.

[0055] The first metal electrode 3 and the second metal electrode 4 are both formed by sequentially stacking an 80-100 nm Ti metal layer and a 100-120 nm Au metal layer; wherein the Au metal layer is above the Ti metal layer.

[0056] The preparation method of the 1D GaN nanorod array / 2D MoS2 / Pedot:Pss self-powered flexible UV detector of the present invention is further illustrated by the following examples.

[0057] Example 1:

[0058] S1. MoS2 thin film was prepared on SiO2 / Si by the general process of chemical vapor deposition, using 0.04g molybdenum trioxide (MoO3) and 0.1g sulfur (S) powder as Mo and S sources, growing at 650℃ and atmospheric pressure for 10 minutes.

[0059] S2. The MoS2 / SiO2 / Si prepared in step 1 was placed in a radio frequency assisted molecular beam epitaxy (PA-MBE) apparatus and annealed at 900°C for 40 min; the N2 gas flow rate was 1.5 sccm, and the chamber pressure was 1×10 -8 The growth temperature was 920°C, the RF plasma power was 380W, the Ga source temperature was 920°C, and the total growth time was 2.6 hours. GaN nanorod arrays were grown on MoS2 / SiO2 / Si.

[0060] S3. Spin-coat the PMMA solution on the GaN nanorods / MoS2 / SiO2 / Si prepared in step 2 at a spin speed of 4000 r for 50 s, and heat-cure at 100°C for 3 min.

[0061] S4. Place the PMMA / GaN nanorods / MoS2 / SiO2 / Si prepared in step 3 in a 7% volume concentration HF solution for 25 minutes to remove SiO2.

[0062] S5. Transfer the PMMA / GaN nanorods / MoS2 in step 4 to the Pedot:Pss / ITO / PET flexible substrate, and use reactive ion etching to remove the surface PMMA. The gas used is Ar gas, the etching time is 15 minutes, and the etching power is 20W.

[0063] S6. Using the general process of electron beam evaporation, 80nm Ti / 100nm Au electrodes were prepared on the GaN nanorod / MoS2 / Pedot:Pss / ITO / PET flexible substrate obtained in step 5 to obtain a self-powered flexible UV photodetector.

[0064] Example 2:

[0065] S1. MoS2 thin film was prepared on SiO2 / Si by the general process of chemical vapor deposition, using 0.06g molybdenum trioxide (MoO3) and 0.12g sulfur (S) powder as Mo and S sources, growing at 680℃ and atmospheric pressure for 12 minutes.

[0066] S2. The MoS2 / SiO2 / Si prepared in step 1 was placed in a radio frequency assisted molecular beam epitaxy (PA-MBE) apparatus and annealed at 920°C for 50 min. The N2 gas flow rate was 1.8 sccm and the chamber pressure was 3×10 -8 The growth temperature was 930°C, the RF plasma power was 390W, the Ga source temperature was 940°C, and the total growth time was 2.7h. GaN nanorod arrays were grown on MoS2 / SiO2 / Si.

[0067] S3. Spin-coat the PMMA solution on the GaN nanorods / MoS2 / SiO2 / Si prepared in step 2 at a spin speed of 5000 r for 55 s, and heat-cure at 105°C for 4 min.

[0068] S4. Place the PMMA / GaN nanorods / MoS2 / SiO2 / Si prepared in step 3 in an 8% volume concentration HF solution for 28 minutes to remove SiO2.

[0069] S5. Transfer the PMMA / GaN nanorods / MoS2 in step 4 to the Pedot:Pss / ITO / PET flexible substrate, and use reactive ion etching to remove the surface PMMA. The gas used is Ar gas, the etching time is 18 minutes, and the etching power is 22W.

[0070] S6. Using the general process of electron beam evaporation, a 90nm Ti / 110nm Au electrode was prepared on the GaN nanorod / MoS2 / Pedot:Pss / ITO / PET flexible substrate obtained in step 5 to obtain a self-powered flexible UV photodetector.

[0071] Example 3:

[0072] S1. MoS2 thin film was prepared on SiO2 / Si by the general process of chemical vapor deposition, using 0.07g molybdenum trioxide (MoO3) and 0.15g sulfur (S) powder as Mo and S sources, growing at 700℃ and atmospheric pressure for 15 minutes.

[0073] S2. The MoS2 / SiO2 / Si prepared in step 1 was placed in a radio frequency assisted molecular beam epitaxy (PA-MBE) apparatus and annealed at 950°C for 60 min. The N2 gas flow rate was 2 sccm and the chamber pressure was 5×10 -8 The growth temperature was 940°C, the RF plasma power was 400W, the Ga source temperature was 950°C, and the total growth time was 2.8h. GaN nanorod arrays were grown on MoS2 / SiO2 / Si.

[0074] S3. Spin-coat the PMMA solution on the GaN nanorods / MoS2 / SiO2 / Si prepared in step 2 at a spin speed of 6000 r for 60 s, and heat-cure at 110°C for 5 min.

[0075] S4. Place the PMMA / GaN nanorods / MoS2 / SiO2 / Si prepared in step 3 in a 10% volume concentration HF solution for 30 minutes to remove SiO2.

[0076] S5. Transfer the PMMA / GaN nanorods / MoS2 in step 4 to the Pedot:Pss / ITO / PET flexible substrate, and use reactive ion etching to remove the surface PMMA. The gas used is Ar gas, the etching time is 20 minutes, and the etching power is 25W.

[0077] S6. Using the general process of electron beam evaporation, a 100nm Ti / 120nm Au electrode was prepared on the GaN nanorod / MoS2 / Pedot:Pss / ITO / PET flexible substrate obtained in step 5 to obtain a self-powered flexible UV photodetector.

[0078] As described above, the present invention can be better implemented. The present invention uses a wet transfer technology to losslessly transfer the 1D GaN nanopillar array / 2D MoS2 film to a Pedot:Pss / ITO / PET flexible substrate to construct a flexible heterojunction, thereby realizing the preparation of a self-powered flexible detector. Since the 2D MoS2 film is used as a transfer template, the 1D GaN nanopillar array will not collapse or be damaged. The device utilizes the huge specific surface area of ​​the GaN nanopillar array to enhance light absorption and utilizes the two-dimensional quantum confinement of 2D MoS2 to improve carrier mobility. Therefore, the flexible detector exhibits high responsiveness and fast response speed as an ultraviolet detector. The preparation process does not involve complex operations and the generation of harmful pollutants, providing an effective strategy for the next generation of photoelectric detection.

[0079] The implementation methods of the present invention are not limited to the above-mentioned embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing 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 preparing a 1D GaN nanorod array / 2D MoS2 / Pedot:Pss self-powered flexible UV detector, characterized in that: The following steps are involved: S1: 2D MoS2 thin films were prepared on SiO2 / Si substrates by chemical vapor deposition. S2: placing the MoS2 / SiO2 / Si prepared in step S1 in a radio frequency assisted molecular beam epitaxy device to grow GaN nanorods on the MoS2 / SiO2 / Si; S3: Spin-coat the GaN nanorods / MoS2 / SiO2 / Si in step S2 with PMMA solution and heat to cure; S4: placing the PMMA / GaN nanorods / MoS2 / SiO2 / Si in step S3 in a dilute HF solution to remove the SiO2 film to obtain PMMA / GaN nanorods / MoS2; S5, transferring the PMMA / GaN nanorods / MoS2 in step S4 to a Pedot:Pss / ITO / PET flexible substrate, and removing the surface PMMA by reactive ion etching; S6. Prepare a Ti / Au electrode on the GaN nanorod / MoS2 / Pedot:Pss / ITO / PET flexible substrate obtained in step S5 by electron beam evaporation to obtain a self-powered flexible UV photodetector; The length of the vertical array of GaN nanopillars is 200~600 nm, and the diameter is 30~70 nm. The density of GaN nanopillars is 5.0×10 9 ~10.0×10 9 / cm 2 ; The thickness of MoS2 film is 2~7nm.

2. The method for preparing the 1D GaN nanorod array / 2D MoS2 / Pedot:Pss self-powered flexible UV detector according to claim 1, characterized in that: The process conditions for the growth of the RF-assisted molecular beam epitaxy device in step S2 are as follows: Annealing treatment at 900-950 °C for 40-60 min; The N2 gas flow rate is 1.5~2 sccm; The cavity pressure is 1×10 -8 ~5×10 -8 Torr; Growth temperature is 920~940℃; RF plasma power is 380~400W; Ga source temperature is 920~950℃; The total growth time is 2.6~2.8h.

3. The method for preparing the 1D GaN nanorod array / 2D MoS2 / Pedot:Pss self-powered flexible UV detector according to claim 1, characterized in that: The PMMA spin coating in step S3 is performed at a speed of 4000-6000 r and a time of 50-60 s; The curing temperature is 100~110℃ and the curing time is 3~5min.

4. The method for preparing the 1D GaN nanorod array / 2D MoS2 / Pedot:Pss self-powered flexible UV detector according to claim 1, characterized in that: In step S4, the volume concentration ratio of the HF solution is 7-10%, and the soaking time is 25-30 minutes.

5. The method for preparing the 1D GaN nanorod array / 2D MoS2 / Pedot:Pss self-powered flexible UV detector according to claim 1, characterized in that: In the S5 , the reactive ion etching adopts Ar gas, the etching time is 15-20 minutes, and the etching power is 20-25W.

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