Method for removing conjugated polymer from surface of carbon nanotube by femtosecond pulsed laser

Abstract

The present application relates to carbon nanotube surface molecule removal technical field, specifically to a kind of method for removing conjugated polymer on carbon nanotube surface by femtosecond pulsed laser, comprising: depositing PCz polymer wrapped single-walled carbon nanotube material on a substrate;Conjugated polymer photolysis removal is carried out in target processing area by scanning target processing area using femtosecond pulsed laser, and the central wavelength of femtosecond pulsed laser is 300 nm-400 nm, and pulse width is 100 fs-350 fs;After laser scanning, soak in organic solvent and soak, remove conjugated polymer photolysis residue, and after drying, the single-walled carbon nanotube finished product of removing conjugated polymer is obtained.The method provided by the present application utilizes the selective absorption and photochemical decomposition of ultraviolet femtosecond laser and polymer, realizes the efficient, lossless and controllable removal of polymer coating layer without high-temperature annealing, strong acid, strong base or special chemical reagent.

Description

Technical Field

[0001] This invention relates to the field of carbon nanotube surface molecular removal technology, specifically to a method for removing conjugated polymers from the surface of carbon nanotubes using femtosecond pulsed laser. Background Technology

[0002] Single-walled carbon nanotubes (SWCNTs) are considered one of the most promising semiconductor channel materials in the post-Moore's Law era due to their excellent electron transport properties, ultra-high aspect ratio, and tunable bandgap. In practical applications of SWCNTs, selective dispersion using conjugated polymers is currently the most mainstream technique for separating semiconductor SWCNTs. However, these polymer residues on the SWCNT surface can severely hinder carrier injection, increase source-drain contact resistance, and reduce the device's on / off ratio and mobility. Furthermore, PCz polymers (such as PCz(poly[9-(1-octylonoyl)-9H-carbazole-2,7-diyl]) can also affect the dispersion and alignment quality of SWCNTs on the substrate. Therefore, effectively removing polymers from the SWCNT surface is crucial for fabricating high-performance carbon nanotube electronic devices.

[0003] Currently, the main methods for removing polymers from the surface of carbon nanotubes (SWCNTs) include thermal annealing and solvent washing. Thermal annealing consumes a large amount of energy, and the high temperature can easily lead to structural defects in SWCNTs. Chemical solvent washing uses strong acids, strong alkalis, or organic solvents, which may leave chemical contaminants and has limited effectiveness in removing some polymers, resulting in high contact resistance between the source / drain electrodes and SWCNTs, affecting the electrical performance of the device. Therefore, there is an urgent need in this field for an efficient, non-destructive, controllable, and environmentally friendly method for removing polymers from the surface of carbon nanotubes. Summary of the Invention

[0004] To develop an efficient, non-destructive, controllable, and environmentally friendly method for removing polymers from the surface of carbon nanotubes, this invention provides a method for removing conjugated polymers from the surface of carbon nanotubes using femtosecond pulsed lasers. The method provided by this invention utilizes the selective interaction and photochemical decomposition of polymers / SWCNTs with ultraviolet femtosecond lasers to achieve efficient, non-destructive, and controllable removal of the polymer coating without the need for high-temperature annealing, strong acids or alkalis, or special chemical reagents.

[0005] This invention provides a method for removing conjugated polymers from the surface of carbon nanotubes using a femtosecond pulsed laser, comprising the following steps: Depositing PCz polymer-encapsulated single-walled carbon nanotubes on a substrate; A femtosecond pulsed laser was used to scan the target processing area of ​​the PCz polymer-encapsulated single-walled carbon nanotube material to photolytically remove the conjugated polymer in the target processing area. The center wavelength of the femtosecond pulsed laser was 300 nm to 400 nm and the pulse width was 100 fs to 350 fs. The single-walled carbon nanotube material encapsulated by PCz polymer after laser scanning is immersed in an organic solvent to remove the photolysis residue of the conjugated polymer. After drying, the finished single-walled carbon nanotube product with the conjugated polymer removed is obtained.

[0006] The method of this invention utilizes the selective interaction and photochemical decomposition of polymers / SWCNTs with ultraviolet femtosecond lasers. By precisely controlling the laser energy, it achieves efficient and selective removal of polymers while preserving the carbon nanotube structure intact. This method enables efficient, non-destructive, and controllable removal of polymer coatings without the need for high-temperature annealing, strong acids or alkalis, or special chemical reagents.

[0007] Furthermore, the pulse width is 300 fs to 320 fs.

[0008] Furthermore, the conjugated polymer is a polymer containing a carbazole group, a polymer containing a fluorene group, a polythiophene polymer, or other conjugated polymers that absorb the wavelength of the femtosecond pulsed laser and can undergo photochemical degradation.

[0009] Furthermore, the conjugated polymer is a polycarbazole polymer.

[0010] Furthermore, during the femtosecond pulsed laser scanning process, the repetition frequency is 50 kHz to 1 MHz, and the single pulse energy density is 0.1 J / cm² to 10 J / cm².

[0011] Furthermore, the repetition frequency is 500 kHz to 800 kHz, and the single pulse energy density is 2 J / cm² to 5 J / cm². Furthermore, the focused spot diameter of the femtosecond pulsed laser is 0.5 μm to 50 μm, the galvanometer scanning speed is 10 mm / s to 1000 mm / s, the scanning line spacing is 1 μm to 2 μm, and the number of scans is 10 to 20. Furthermore, the focused spot diameter of the femtosecond pulsed laser is 1 μm to 3 μm, and the galvanometer scanning speed is 200 mm / s to 300 mm / s.

[0012] Furthermore, the inert gas is nitrogen or argon, and the gas flow rate is 50 sccm to 1000 sccm.

[0013] Furthermore, the polarization state of the femtosecond pulsed laser is circular polarization, elliptical polarization, or linear polarization.

[0014] Furthermore, the PCz polymer-encapsulated single-walled carbon nanotube material is obtained through the following steps: PCz polymer was dissolved in a solvent and heated until dissolved. Single-walled carbon nanotubes were added, and the mixture was dispersed by ultrasonication and centrifugation to obtain a uniform dispersion of SWCNTs. The substrate is hydrophilized, and the treated substrate is then subjected to liquid phase deposition or interfacial assembly in a uniformly dispersed SWCNTs solution to form a disordered SWCNTs film or an ordered array on the substrate surface. After drying, the polymer-encapsulated single-walled carbon nanotube material is obtained.

[0015] Furthermore, the mass ratio of the PCz polymer to the single-walled carbon nanotubes is 1:1 to 2.

[0016] Further, the liquid phase deposition is as follows: the treated substrate is placed in a uniformly dispersed SWCNTs solution and heated to 45℃~55℃ for 10 h~12 h, and then heated and dried at 140℃~145℃ for 30 min~40 min, thereby obtaining a disordered SWCNTs film on the substrate. The interface assembly is as follows: the treated substrate is immersed in a uniformly dispersed SWCNTs solution, the substrate is pulled up at a speed of 4 μm / s to 6 μm / s to obtain an SWCNTs array, and then heated and dried at 140℃ to 145℃ for 30 min to 40 min to obtain an ordered array of SWCNTs materials.

[0017] Furthermore, the substrate is a SiO2 (100 nm) / Si substrate, a SiO2 (300 nm) / Si substrate, or a SiO2 (500 nm) / Si substrate.

[0018] Furthermore, the ultrasonic dispersion power is 60 W-600 W, the ultrasonic time is 1 second, the interval time is 1 second, and the total ultrasonic time is 30 min; the ultracentrifugation speed is 45000 g-50000 g, and the time is 1.5 h-2 h.

[0019] Furthermore, the power of the ultrasonic dispersion is 120 W to 130 W.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes the strong absorption of polymers in the ultraviolet band and the weak absorption of carbon nanotubes to achieve efficient and selective removal of polymers while perfectly preserving the carbon nanotube structure through precise control of laser energy. This method employs non-contact laser scanning, eliminating the need for strong acids or alkalis, making it environmentally friendly. It boasts sub-micron level high spatial resolution and supports arbitrary patterning. Compared to traditional high-temperature annealing, this process can be performed at room temperature, is compatible with semiconductor processes, and is easily scalable to wafer-level large-area processing. It is suitable for various carbon nanotube materials, including thin films and arrays, making it ideal for high-precision device manufacturing. Details are as follows:

[0021] (1) Highly selective removal of polymers was achieved without damaging the carbon nanotube structure. This invention employs a femtosecond pulsed laser with specific parameters (center wavelength 300 nm–400 nm, pulse width 200 fs–500 fs). The ultrashort pulse duration is much shorter than the thermal diffusion time, precisely limiting the energy within the photolysis threshold range of the PCz polymer. Combined with timely purging and cooling using an auxiliary gas (inert gas or nitrogen), the thermal accumulation effect is effectively avoided. Raman spectroscopy confirms that after removing PCz, the intensity ratio of the D band to the G band of the single-walled carbon nanotube (Ig) is significantly reduced. D / I G The lack of significant increase indicates that the sp² conjugated structure of the carbon nanotube wall has not been significantly damaged, thus maintaining its inherent excellent electrical properties.

[0022] (2) The removal area can be precisely controlled to achieve micro- and nano-scale patterning processing. This invention employs a high-speed galvanometer scanning system or a spatial light modulator, combined with a three-dimensional precision moving stage, to precisely target a focused light spot (approximately 2 μm in diameter) onto a preset area, achieving selective removal of arbitrary patterns. This advantage is particularly crucial for device fabrication where it is necessary to remove insulating polymers at specific locations in carbon nanotube networks (such as transistor channel regions) to expose clean carbon nanotube surfaces.

[0023] (3) The process is clean and free from liquid phase chemical etching contamination. Compared to traditional methods of polymer removal through strong acid oxidation or liquid-phase chemical reagent immersion, this method directly photolyzes the solid polymer layer using laser, introducing only a small amount of inert auxiliary gas into the processing area. Subsequent solvent immersion is used only to dissolve the photolyzed residues, rather than for direct chemical stripping. This significantly reduces the use of strong acids and oxidants, lowers environmental pollution and process hazards, and avoids potential damage to the carbon nanotube-substrate interface caused by liquid-phase reagent penetration.

[0024] (4) It has wide applicability and can cover various thin film morphologies such as disordered networks and ordered arrays. The method of this invention is applicable to both disordered carbon nanotube network films prepared by conventional deposition methods and highly ordered carbon nanotube arrays prepared by methods such as dimensional self-confined assembly and two-dimensional tangential liquid crystal assembly. By simply adjusting the single-pulse energy density, polymer removal and non-destructive carbon nanotube removal can be achieved under different film morphologies, demonstrating good process window and versatility.

[0025] (5) Provides a key pathway for the fabrication of high-performance carbon nanotube electronic devices Polymers based on carbon nanotubes (PCz) are often used as selective dispersants for semiconducting single-walled carbon nanotubes (SUVs). However, after film deposition, they form an insulating shell encapsulating the surface of the carbon nanotubes, severely limiting device performance. This invention allows for the efficient removal of this insulating layer after carbon nanotube thin film deposition or array assembly, directly clearing the way for the fabrication of high-performance field-effect transistors (FETs). Furthermore, by combining this with a spatial light modulator to achieve multi-focal parallel processing, processing efficiency can be significantly improved, providing a feasible solution for wafer-level, large-scale carbon nanotube integrated circuit manufacturing. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the ultraviolet femtosecond laser system used in an embodiment of the present invention.

[0028] Figure 2 This is a comparison of Raman spectra obtained by femtosecond laser removal of PCz polymer from disordered carbon nanotube films at different times in Example 1 of the present invention.

[0029] Figure 3 This is a comparison of the transfer characteristic curves of carbon nanotube field-effect transistors before and after laser treatment.

[0030] Figure 4 This is a comparison of Raman spectra of different times obtained by femtosecond laser removal of PCz polymer in carbon nanotube array in Example 2 of the present invention.

[0031] Figure 5 This is a comparison of Raman spectra of different times obtained by femtosecond laser removal of PCz polymer in carbon nanotube array in Example 3 of the present invention. Detailed Implementation

[0032] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.

[0033] The material information used in this invention is as follows: N,N-Dimethylformamide, CAS: 68-12-2, Sinopharm Group, Product No.: 81007718.

[0034] The polycarbazole (PCz) polymer was purchased from Shenzhen Ruixun Organic Solar Energy Co., Ltd., CAS: 1093292-01-3, item number: P0567, Mw>50000, PDI<3.

[0035] Single-walled carbon nanotubes (SWCNTs) were purchased from Carbon Solutions, CAS: 1333-86-4, item number: 102906.

[0036] The SiO2 (100 nm) / Si substrate was purchased from Guangzhou Tianhe Crystal Semiconductor E-commerce Firm.

[0037] Example 1: A method for selectively removing PCz polymer from the surface of SWCNTs using femtosecond pulsed laser.

[0038] 1) Preparation of polymer-encapsulated SWCNTs dispersion: Weigh 50 mg of PCz polymer and add it to 50 mL of toluene. Heat on a hot plate at 90 °C for 20 min to completely dissolve the polymer. Then add 50 mg of SWCNTs and perform angle ultrasonic dispersion. The ultrasonic power is 120 W, the ultrasonic time is 1 s, the interval time is 1 s, and the total ultrasonic time is 30 min to obtain the dispersion. Centrifuge the dispersion at 50000 g for 1.5 h and collect the supernatant to obtain a homogeneous dispersion of polymer selectively encapsulating semiconductor SWCNTs, referred to as SWCNTs homogeneous dispersion.

[0039] 2) Cleaning the substrate: The SiO2 (100 nm) / Si substrate was ultrasonically cleaned sequentially with acetone, isopropanol, and deionized water at 180 W for 10 min each, and then dried with nitrogen. The substrate surface was treated with oxygen plasma for 2 min (power 50 W) to improve the surface hydrophilicity and obtain the original clean substrate.

[0040] 3) Preparation of SWCNTs film by deposition method: The original clean substrate obtained by cleaning in step (2) is placed in a uniform dispersion of SWCNTs diluted 5 times with toluene, heated to 45°C on a hot stage for 12 hours, and then dried at 140°C for 30 min on a hot stage, thus obtaining a disordered SWCNTs film with a thickness of about 3 nm on the substrate.

[0041] 4) Constructing the optical path for femtosecond pulsed laser processing: such as Figure 1 As shown, the optical path system includes: a femtosecond laser (center wavelength 355 nm, pulse width 300 fs, repetition frequency 500 kHz, maximum output power 30 W), which emits light under computer control; after being deflected by a mirror, the laser beam passes sequentially through a λ / 2 waveplate, a polarizing beam splitter, and a beam expander before entering a high-speed galvanometer scanning system and being focused onto the surface of the SWCNTs material to be laser-processed, which is placed on a three-dimensional precision moving stage.

[0042] 5) Femtosecond pulsed laser selective removal of PCz: The SWCNTs material to be laser-processed was fixed on a three-dimensional moving stage. Laser processing parameters were set as follows: focused spot diameter approximately 2 μm, single-pulse energy density 3.18 J / cm², pulse repetition frequency 500 kHz, galvanometer scanning speed 200 mm / s, scanning line spacing 1 μm, and 10 scans. A computer-controlled galvanometer scanning system performed bidirectional scanning of the processing area. The laser polarization was circular. Nitrogen gas was continuously introduced into the processing area as an auxiliary gas at a flow rate of 50 sccm. The SWCNTs material after PCz removal (substrate after laser scanning) was obtained.

[0043] 6) Post-processing: The SWCNTs material (substrate after laser scanning) after PCz removal was immersed in toluene, tetrahydrofuran, and N,N-dimethylformamide for 30 min each to remove polymer photolysis residues. Then it was dried with nitrogen gas. Finally, the dried SWCNTs material was placed on a hot table at 120℃ and dried for 30 min to obtain clean SWCNTs material.

[0044] like Figure 2 As shown, Raman spectral comparison reveals that after removing PCz, the characteristic peak of PCz (carbazole ring respiration vibration) located near 1623 cm⁻¹ is significantly weakened, while the intensity ratio of the D band (near 1340 cm⁻¹) to the G band of SWCNTs is significantly lower. D / I G The lack of significant increase indicates that the SWCNT tube wall structure was not significantly damaged.

[0045] Supplementary device data diagrams are as follows Figure 3As shown, the on-state current was taken as Vg=-5V, and the off-state current was taken as the minimum value within the scanning range. The subthreshold swing was calculated using subthreshold linear region fitting of the original data. Laser removal of PCz significantly improved device performance. The on-state current after processing was approximately 5.01 × 10⁻⁶. -5 A, untreated, is approximately 2.73 × 10⁻⁶. -6 A; The off-state current is 7.36 × 10⁻⁶. -10 A decreased to 1.21 × 10 after treatment. -11 A, decreased by approximately 60.9 times. Therefore, the on / off ratio decreased from approximately 3.7 × 10⁻⁶. 3 Increased to approximately 4.1 × 10 6 Regarding the subthreshold swing, the untreated device has approximately 427 mV / dec, while the laser-treated device has approximately 155 mV / dec. This indicates that removing PCz significantly enhances the gate control capability, resulting in a steeper transition in the subthreshold region, while effectively suppressing off-state leakage current.

[0046] Example 2: A method for selectively removing PCz polymer from the surface of SWCNTs using femtosecond pulsed laser.

[0047] SWCNT arrays obtained by dimension-limited self-alignment (DLSA) or 2D nematic tangential flow interfacial self-assembly (TaFISA) were polymer-removed using a femtosecond laser. The single-pulse energy density was 3.18 J / cm², the pulse repetition frequency was 500 kHz, the galvanometer scanning speed was 200 mm / s, the scan line spacing was 2 μm, and the number of scans was 20. Argon gas was continuously introduced into the processing area as an auxiliary gas at a flow rate of 50 sccm. The laser-scanned SWCNTs material was then immersed in toluene and trichloroethane for 30 min to remove polymer photolysis residues, followed by drying with nitrogen gas. Finally, the SWCNTs material was dried on a hot stage at 120°C for 30 min. Details are as follows:

[0048] 1) Preparation of polymer-encapsulated SWCNTs dispersion: Weigh 50 mg of PCz polymer and add it to 50 mL of toluene. Heat on a hot plate at 90 °C for 20 min to completely dissolve the polymer. Then add 50 mg of SWCNTs and disperse using angle ultrasonication for 30 min. The ultrasonic power is 120 W, the ultrasonic time is 1 s, the interval time is 1 s, and the total ultrasonic time is 30 min to obtain the dispersion. Centrifuge the dispersion at high speed for 1.5 h and finally collect the supernatant to obtain a homogeneous dispersion of polymer selectively encapsulating semiconductor SWCNTs, referred to as SWCNTs homogeneous dispersion.

[0049] 2) Cleaning the substrate: The SiO2 (100 nm) / Si substrate was ultrasonically cleaned sequentially with acetone, isopropanol, and deionized water at 180 W for 10 min each, and then dried with nitrogen. The substrate surface was treated with oxygen plasma for 2 min (power 50 W) to improve the surface hydrophilicity and obtain the original clean substrate.

[0050] 3) Preparation of SWCNT array material: The original clean substrate cleaned in step (2) is assembled into an SWCNT array by dimension-limited self-alignment (DLSA): First, the uniformly dispersed SWCNT liquid is poured into the liquid pool, and then the original clean substrate is vertically immersed in it. The substrate is pulled up at a speed of 4 μm / s to obtain the SWCNT array. Then, the SWCNT array material is placed on a hot table and heated at 140℃ for 30 minutes to dry, thus obtaining the SWCNT array material.

[0051] 4) Constructing the optical path for femtosecond pulsed laser processing: such as... Figure 1 As shown, the optical path system includes: a femtosecond laser (center wavelength 355 nm, pulse width 300 fs, repetition frequency 500 kHz, maximum output power 30 W), which emits light under computer control; after being deflected by a reflector, the laser beam passes sequentially through a λ / 2 waveplate, a polarizing beam splitter, and a beam expander before entering a high-speed galvanometer scanning system and being focused onto the surface of the SWCNTs array material to be laser-processed, which is placed on a three-dimensional precision moving stage.

[0052] 5) Selective removal of PCz by femtosecond pulsed laser: The SWCNTs array material to be laser-processed was fixed on a three-dimensional moving stage, and the laser processing parameters were set as follows: the focused spot diameter was approximately 2 μm, the single pulse energy density was 3.18 J / cm², the pulse repetition frequency was 500 kHz, the galvanometer scanning speed was 200 mm / s, the scanning line spacing was 1 μm, and the number of scans was 10. The galvanometer scanning system controlled by the computer performed a bidirectional scan of the area to be processed, with the laser polarization being circular polarization. Nitrogen gas was continuously introduced into the processing area as an auxiliary gas at a flow rate of 50 sccm, and the SWCNTs array material after PCz removal was obtained (substrate after laser scanning).

[0053] 6) Post-processing: The SWCNTs array material (substrate after laser scanning) after PCz removal was immersed in toluene (CAS: 108-88-3), tetrahydrofuran (CAS: 109-99-9), and N,N-dimethylformamide (CAS: 68-12-2) for 30 min each to remove polymer photolysis residues. Then it was dried with nitrogen gas. Finally, the laser-scanned SWCNTs array material was placed on a hot stage at 120℃ and dried for 30 min to obtain clean SWCNTs array material.

[0054] like Figure 4 As shown, Raman spectral comparison reveals that after removing PCz, the characteristic peak of PCz (carbazole ring respiration vibration) located near 1623 cm⁻¹ is significantly weakened, while the intensity ratio of the D band (near 1340 cm⁻¹) to the G band of SWCNTs is significantly lower. D / I G The lack of significant increase indicates that the SWCNT tube wall structure was not significantly damaged.

[0055] Example 3: A method for selectively removing PCz polymer from the surface of SWCNTs using femtosecond pulsed laser.

[0056] Using a spatial light modulator, the laser was adjusted to a flat-top beam. A hologram of the active region of the transistor was calculated to achieve multi-focal processing, improving processing efficiency. The single-pulse energy density was 3.18 J / cm², the pulse repetition frequency was 800 kHz, the galvanometer scanning speed was 300 mm / s, the scanning line spacing was 2 μm, and the number of scans was 10. Argon gas was continuously introduced into the processing area as an auxiliary gas at a flow rate of 50 sccm. The laser-scanned SWCNTs material was immersed in tetrahydrofuran and toluene for 30 min to remove polymer photolysis residues, then dried with nitrogen gas, and finally dried on a hot stage at 120℃ for 30 min. Details are as follows:

[0057] 1) Preparation of polymer-encapsulated SWCNTs dispersion: Weigh 50 mg of polymer and add it to 50 mL of toluene. Heat the mixture on a hot plate at 90 degrees Celsius for 20 min to completely dissolve the polymer. Then add 50 mg of SWCNTs and disperse the mixture using angle ultrasonication for 30 min. The ultrasonic power is 120 W, the ultrasonic time is 1 s, the interval time is 1 s, and the total ultrasonic time is 30 min. Centrifuge the resulting dispersion at high speed and finally take the supernatant to obtain a uniform dispersion of polymer selectively encapsulating semiconductor SWCNTs.

[0058] 2) Cleaning the substrate: The SiO2 (100 nm) / Si substrate was ultrasonically cleaned sequentially with acetone, isopropanol, and deionized water at 180 W for 10 min each, and then dried with nitrogen. The substrate surface was treated with oxygen plasma for 2 min (power 50 W) to improve the surface hydrophilicity and obtain the original clean substrate.

[0059] 3) Preparation of SWCNT array material: The original clean substrate obtained after cleaning in step (2) is assembled into an SWCNT array using dimension-limited self-alignment (DLSA) method: First, the uniformly dispersed SWCNTs is poured into a liquid pool, and then the original clean substrate is vertically immersed in it. The substrate is pulled up at a speed of 4 μm / s to obtain the SWCNT array. Then, the SWCNT array material is placed on a hot table and heated at 140℃ for 30 min to dry, thus obtaining the SWCNT array material. 4) Constructing the optical path for femtosecond pulsed laser processing: The optical path system includes a femtosecond laser (center wavelength 355 nm, pulse width 300 fs, repetition frequency 500 kHz, maximum output power 30 W), with light output controlled by a computer; after being redirected by a reflector, the laser beam passes sequentially through a λ / 2 waveplate, a polarizing beam splitter, and a beam expander before entering a spatial light modulator, where the laser is adjusted to a flat-top beam, and the hologram of the active region of the transistor is calculated to achieve multi-focal processing and improve processing efficiency.

[0060] 5) Selective removal of PCz by femtosecond pulsed laser: The SWCNTs array material to be laser-processed is fixed on a three-dimensional moving stage, and the laser processing parameters are set as follows: the focused spot diameter is about 2 μm, the single pulse energy density is 3.18 J / cm², the pulse repetition frequency is 500 kHz, the galvanometer scanning speed is 200 mm / s, the scanning line spacing is 1 μm, and the number of scans is 10. The galvanometer scanning system is controlled by a computer to perform bidirectional scanning of the area to be processed, with the laser polarization being one of the circular polarizations. Nitrogen gas is continuously introduced into the processing area as an auxiliary gas at a flow rate of 50 sccm, and the SWCNTs array material after PCz removal is obtained (substrate after laser scanning).

[0061] 6) Post-processing: The scanned SWCNTs array material (substrate after laser scanning) was immersed in toluene (CAS: 108-88-3), tetrahydrofuran (CAS: 109-99-9), and N,N-dimethylformamide (CAS: 68-12-2) for 30 min each to remove polymer photolysis residues. Then it was dried with nitrogen gas. Finally, the laser-scanned SWCNTs array material was placed on a hot stage at 120℃ and dried for 30 min to obtain clean SWCNTs array material.

[0062] like Figure 5 As shown, Raman spectral comparison reveals that after removing PCz, the characteristic peak of PCz (carbazole ring respiration vibration) located near 1623 cm⁻¹ is significantly weakened, while the intensity ratio of the D band (near 1340 cm⁻¹) to the G band of SWCNTs is significantly lower. D / I G The lack of significant increase indicates that the SWCNT tube wall structure was not significantly damaged.

[0063] Although preferred embodiments of the invention have been described, those skilled in the art, once they have learned the basic inventive concept, can make other changes and modifications to these embodiments.

[0064] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for removing conjugated polymers from the surface of carbon nanotubes using a femtosecond pulsed laser, characterized in that, Includes the following steps: Depositing PCz polymer-encapsulated single-walled carbon nanotubes on a substrate; A femtosecond pulsed laser was used to scan the target processing area of ​​PCz polymer-encapsulated single-walled carbon nanotube material to photolytically remove the conjugated polymer in the target processing area. The center wavelength of the femtosecond pulsed laser was 300 nm to 400 nm and the pulse width was 100 fs to 350 fs. The single-walled carbon nanotube material encapsulated by PCz polymer after laser scanning is immersed in an organic solvent to remove the photolysis residue of the conjugated polymer. After drying, the finished single-walled carbon nanotube product with the conjugated polymer removed is obtained.

2. The method according to claim 1, characterized in that, The conjugated polymer is a polymer containing a carbazole group, a polymer containing a fluorene group, or a polythiophene polymer.

3. The method according to claim 1, characterized in that, During femtosecond pulsed laser scanning, the repetition frequency is 50 kHz to 1 MHz, and the single pulse energy density is 0.1 J / cm² to 10 J / cm².

4. The method according to claim 1, characterized in that, The femtosecond pulsed laser has a focused spot diameter of 0.5 μm to 50 μm, a galvanometer scanning speed of 10 mm / s to 1000 mm / s, a scanning line spacing of 1 μm to 2 μm, and a scanning number of 10 to 20 times.

5. The method according to claim 1, characterized in that, The laser scanning is performed in an inert gas atmosphere, wherein the inert gas is nitrogen or argon, and the gas flow rate is 50 sccm to 1000 sccm.

6. The method according to claim 1, characterized in that, The polarization state of the femtosecond pulsed laser is circular polarization, elliptical polarization, or linear polarization.

7. The method according to claim 1, characterized in that, The PCz polymer-encapsulated single-walled carbon nanotube material is obtained through the following steps: PCz polymer was dissolved in a solvent and heated until dissolved. Single-walled carbon nanotubes were added, and the mixture was dispersed by ultrasonication and centrifugation to obtain a uniform dispersion of SWCNTs. The substrate is hydrophilized, and the treated substrate is then subjected to liquid phase deposition or interfacial assembly in a uniformly dispersed SWCNTs solution to form a disordered SWCNTs film or an ordered array on the substrate surface. After drying, the polymer-encapsulated single-walled carbon nanotube material is obtained.

8. The method according to claim 8, characterized in that, The mass ratio of the PCz polymer to the single-walled carbon nanotubes is 1:1 to 2.

9. The method according to claim 9, characterized in that, The liquid phase deposition is as follows: the treated substrate is placed in a uniformly dispersed SWCNTs solution and heated to 45℃~55℃ for 10 h~12 h for deposition, and then heated to 140℃~145℃ for drying for 30 min~40 min, thereby obtaining a disordered SWCNTs film on the substrate. The interface assembly is as follows: the treated substrate is immersed in a uniformly dispersed SWCNTs solution, the substrate is pulled up at a speed of 4 μm / s to 6 μm / s to obtain an SWCNTs array, and then heated and dried at 140℃ to 145℃ for 30 min to 40 min to obtain an ordered array of SWCNTs materials.

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