A process for locally doping modification of laser-induced carbon nanotube arrays

Abstract

This invention discloses a laser-induced local doping modification process for carbon nanotube arrays, relating to the fields of carbon nanotube modification and flexible high-precision electronic devices. The process includes pretreatment of the carbon nanotube array substrate, laser-induced doping, and annealing. The pretreatment involves a hydrophilic / hydrophobic gradient pretreatment of the carbon nanotube array. In this invention, a continuous gradient is achieved in a single step by establishing a hydrophilic / hydrophobic gradient through pretreatment, using a ceramic sheet with a gradually varying pore size during the laser stage, controlling permeation through zoned heating, compensating for differences through incremental power increases, and controlling the gradient pressure during annealing with in-situ monitoring. For carbon nanotubes susceptible to damage under fixed laser power, a combination of source cooling, power gradient, and low-temperature annealing is used to reduce the breakage rate while maintaining performance. For gradient loss caused by annealing, the gradient is locked by holding the annealing pressure and in-situ monitoring. For substrates without repair capabilities, a self-healing gradient is achieved using repair pressure and temperature on a 5% stretched substrate, extending the lifespan of flexible devices.

Description

Technical Field

[0001] This invention relates to the field of carbon nanotube modification and flexible high-precision electronic device technology, specifically a laser-induced local doping modification process for carbon nanotube arrays. Background Technology

[0002] Carbon nanotube arrays, with their excellent conductivity, mechanical stability, and high specific surface area, have key application value in high-precision electronic devices such as flexible field-effect transistors and high-precision pressure sensors. Laser-induced local doping modification is the core process for achieving precise control of their regional performance. Through the high spatial resolution of lasers, heteroatoms (such as nitrogen and boron) can be introduced into the micron-scale region to regulate the conductivity of carbon nanotubes, providing technical support for device miniaturization and integration.

[0003] However, existing laser-induced local doping processes for carbon nanotube arrays consistently face a core and unresolved problem: the inability to achieve a continuously tunable conductivity gradient within a local region in a single step. This makes it difficult to meet the specific requirements of high-precision electronic devices for gradient conductivity, and currently, there is no effective solution. Specifically, this core problem is manifested in the following dimensions: Limitations of the process objective: Existing technologies take uniform doping concentration as the core objective (believing that uniform concentration is the key to stable conductivity). By fixing parameters such as laser scanning speed and doping source flux, non-uniform diffusion can be suppressed, but only uniform doping and fixed conductivity can be achieved. It is fundamentally impossible to form a continuous conductivity gradient. Application demand contradiction: Devices clearly require a local continuous conductivity gradient (e.g., field-effect transistors require a source-channel conductivity gradient to reduce carrier losses, and pressure sensors require a center-edge gradient to identify pressure distribution), but existing processes cannot meet this requirement at all, creating a gap between demand and technology. Existing solutions are ineffective: the industry can only use multiple doping and multi-layer stacking as alternatives, but this solution is inefficient, easily damages carbon nanotubes, and can only achieve step-like changes in conductivity, which cannot achieve the continuous gradual change required by the device.

[0004] In view of this, a laser-induced local doping modification process for carbon nanotube arrays is provided to overcome the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a laser-induced local doping modification process for carbon nanotube arrays to solve the problems mentioned in the background art.

[0006] To address the aforementioned technical problems, this invention provides a laser-induced local doping modification process for carbon nanotube arrays, comprising the steps of pretreatment of the carbon nanotube array substrate, laser-induced doping, and annealing. The pretreatment is a hydrophilicity-hydrophobicity gradient pretreatment of carbon nanotube arrays. Specifically, the carbon nanotube array substrate is fixed on the stage of the plasma pretreatment instrument, a strip shield is used to expose the target doped region, and the plasma parameters are set as follows: power 80W, argon flow rate 40sccm, treatment distance 5mm. The stage is started to move along the left end to the right end of the target doped region at a speed of 0.5mm / s to perform plasma treatment, so that the contact angle at the L end of the target region is 35°±2° and the contact angle at the R end is 75°±2°, and the hydrophilicity decreases continuously along L→R. Laser-induced doping is a synergistic doping method involving a porous medium gradient diffusion source and laser energy compensation. Specifically, the pretreated substrate is placed in a gradient pressure reaction chamber, covered with an alumina porous ceramic sheet whose pore size linearly changes from 0.1 μm to 1 μm along L→R, a bonding pressure of 0.1 MPa is applied, liquid ethylenediamine is injected into the ceramic sheet, and polyimide heating plates partitioned on the lower surface of the ceramic sheet are activated to set the temperature of the heating zone corresponding to the L end to 40℃±2℃ and the temperature of the heating zone corresponding to the R end to 60℃±2℃. At the same time, an adjustable power nanosecond laser generator with a wavelength of 1064 nm is activated, the pulse frequency is set to 2 kHz, the spot diameter is 6 μm, and the laser power linearly increases from 2 W to 4 W as the stage shifts along L→R at a rate of 0.4 μm / s. The penetration rate at the L end and the penetration rate at the R end are monitored simultaneously. The annealing process is a gradient pressure annealing with a locked gradient. Specifically, after removing the permeation source device, argon gas is introduced into the reaction chamber. The pressure on the L end side is 1.3 atm ± 0.01 atm and the pressure on the R end side is 0.8 atm ± 0.01 atm through a dual pressure valve. The temperature is increased to 380℃ ± 5℃ at a rate of 5℃ / min and held for 45 min. During the holding process, the conductivity distribution is tested every 5 min using a miniature four-probe array with a spacing of 0.2 mm until the conductivity gradient deviation of two consecutive tests is <2%. Then, the temperature is naturally cooled to room temperature.

[0007] Furthermore, the carbon nanotube array substrate is a vertically grown multi-walled carbon nanotube array with a tube diameter of 12-16 nm and an array height of 6 μm. The substrate is a 50 μm thick polyimide film. The substrate is cut to a size of 30 mm × 10 mm and fixed to the stage with a 5 mm wide high-temperature resistant tape. The strip shielding part is made of polytetrafluoroethylene, with a size of 20 mm × 5 mm × 1 mm and a shielding width of 5 mm. It is bonded to the substrate without gaps with the high-temperature resistant tape.

[0008] Furthermore, the porous alumina ceramic sheet has a size of 20mm×10mm×2mm, and the polyimide heating sheet has a size of 20mm×5mm×0.1mm. It is divided into two independent heating zones, and the temperature of each heating zone is regulated by an independent temperature controller. The heating sheet is attached to the lower surface of the ceramic sheet by thermally conductive silicone.

[0009] Furthermore, the liquid ethylenediamine has a purity of ≥99.5%, a viscosity of 1.4 mPa·s, and a density of 0.898 g / cm³ at 25°C. 3 The solution was injected into the injection tank on the upper surface of the ceramic sheet at a rate of 0.1 mL / s using a micro-syringe with a specification of 1 mL and an accuracy of ±0.01 mL. The permeation rate was monitored in real time by a micro-weighing sensor attached to the lower surface of the ceramic sheet.

[0010] Furthermore, the gradient pressure reaction chamber is made of 304 stainless steel, has a volume of 10L, and is equipped with a micro four-probe array interface.

[0011] Furthermore, the miniature four-probe array is made of tungsten, with a tip diameter of 50 μm. It is aligned with the test point in the target area using a fine-tuning frame with an accuracy of ±0.001 mm, and the contact pressure between the probe and the carbon nanotube array is 0.01 MPa.

[0012] Furthermore, it also includes a conductivity gradient self-healing step, specifically, the substrate treated with 5% tensile weight is placed back into the gradient air pressure reaction chamber, the repair air pressure difference between the L end and the R end is set to 0.1-0.5 atm, the repair temperature is 20-50℃, the repair time is set by a time controller, the initial gradient deviation is measured by a tensile testing machine, and the post-repair gradient deviation is measured by a four-probe tester. The self-healing rate is calculated by the formula (initial deviation - post-repair deviation) / initial deviation × 100%.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. Existing technologies can only achieve uniform doping, and multiple stacking doping processes can easily damage carbon nanotubes, failing to meet the requirements of devices for continuous doping gradients. This process achieves a breakthrough through a three-step synergistic approach: pretreatment constructs a continuous hydrophilic-hydrophobic gradient to ensure initial gradient adsorption of the dopant source; the laser-induced stage uses a ceramic sheet with gradually varying pore size and zoned heating to control the permeation rate gradient, coupled with linearly increasing laser power to compensate for differences; the annealing stage uses a gradient gas to suppress reverse diffusion of atoms, and in-situ monitoring ensures gradient deviation <2%. Ultimately, a continuously adjustable conductivity gradient is achieved in a single step, eliminating the need for multiple operations and adapting to the requirements of field-effect transistors, pressure sensors, and other applications.

[0014] 2. Existing fixed laser power is prone to causing localized high-energy damage to carbon nanotubes. This process avoids this by using source infiltration cooling + power gradient: liquid ethylenediamine absorbs laser energy during infiltration, and the laser power increases linearly with stage translation, avoiding energy concentration; furthermore, low-temperature annealing at 380℃±5℃ promotes the bonding of doped atoms with carbon nanotubes without damaging the array structure, effectively reducing the fracture rate and ensuring its conductivity and mechanical stability.

[0015] 3. Existing annealing processes lack pressure control, leading to easy back diffusion of doped atoms and the disappearance of the gradient. This process uses dual pressure valves to maintain the gradient pressure during annealing, hindering atomic diffusion; conductivity is measured in situ every 5 minutes during the holding period; and the pressure is kept constant during the cooling phase, locking the gradient throughout the process and solving the problem of gradient loss.

[0016] 4. Existing processes lack repair capabilities; gradient damage after stretching cannot be recovered, limiting the use of flexible devices. This process places a 5% stretched substrate in a reaction chamber, using a pressure difference of 0.1-0.5 atm and a repair temperature of 20-50℃ to achieve gradient self-repair, extending the lifespan of flexible devices and overcoming the limitation of being unable to repair damage. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a laser-induced local doping modification process for carbon nanotube arrays according to the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all 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.

[0019] Please see Figure 1 The present invention provides a technical solution: See Figure 1 As shown, an embodiment of a laser-induced local doping modification process for carbon nanotube arrays is described: I. Process Raw Materials and Equipment: 1. Processing raw materials: Substrate: Vertically grown multi-walled carbon nanotube array, with a tube diameter of 12-16 nm and an array height of 6 μm. The substrate is a flexible polyimide film (thickness 50 μm, model PI-200) with an initial surface contact angle of 60° (uniform hydrophilicity). Dopant source: Liquid ethylenediamine (analytical grade, purity ≥99.5%, viscosity 1.4 mPa·s, density 0.898 g / cm³ at 25℃) 3 ), which serves as a nitrogen doping source, is supplied through porous media permeation; Protective gas: Argon (purity ≥ 99.999%), used for atmosphere protection during plasma pretreatment and annealing processes.

[0020] 2. Core equipment: Adjustable power nanosecond laser generator: Model YL-1064, fixed wavelength 1064nm, output power continuously adjustable from 1-5W, pulse frequency adjustable from 1-5kHz, spot diameter adjustable via focusing lens (fixed at 6μm in this solution); the power gradient curve with time / displacement is set through the built-in software power gradient module (no additional energy homogenization module required, modified from a common laser marking machine, the modification involves upgrading the software version to V3.0 to support gradient parameter input); Gradient seepage source device: composed of porous ceramic plates with gradually varying pore sizes and micro heating plates; Porous ceramic sheet: made of alumina, with dimensions of 20mm×10mm×2mm, pore diameter linearly varying from 0.1μm to 1μm along the length (gradient accuracy ±0.05μm), and surface roughness Ra≤0.5μm; Miniature heating element: made of polyimide heating film, size 20mm×5mm×0.1mm, power adjustable from 5-15W, divided into 2 independent heating zones (corresponding to ceramic plate aperture zones of 0.1-0.5μm and 0.5-1μm), each heating zone is temperature controlled by an independent temperature controller (model TC-05); Device assembly: The miniature heating element is attached to the lower surface of the porous ceramic sheet using thermally conductive silicone (model KD-301), and the entire assembly is attached to the upper surface of the substrate using a miniature pressure block (applying 0.1MPa pressure) to ensure no gaps; Plasma pretreatment instrument: Model PT-100 low-temperature plasma equipment, power adjustable from 50-300W, treatment distance adjustable from 3-10mm; the modification is to add a strip shield (material PTFE, size 20mm×5mm×1mm, shielding width 5mm), the shield is fixed to the stage with high temperature resistant tape, and local treatment is achieved as the stage moves. Gradient pressure reaction chamber: It is modified from an ordinary sealed chamber (material 304 stainless steel, volume 10L). Two independent pressure valves (model PV-02, controlling the high pressure zone and low pressure zone respectively) are set along the length of the chamber. Each pressure valve is connected to an independent pressure gauge (accuracy ±0.01atm) and a vacuum pump (model VP-100). The stage in the chamber can be translated along the length (speed adjustable from 0.1-1μm / s) and a micro four-probe array interface is reserved. Auxiliary testing equipment: contact angle measuring instrument (model JC2000D, accuracy ±1°), X-ray photoelectron spectrometer (model Thermo Scientific K-Alpha, testing depth 1-10nm), four-probe conductivity meter (model RTS-8, testing accuracy ±0.1S / cm), transmission electron microscope (model TEM-Tecnai G2 F20, accelerating voltage 200kV).

[0021] II. Detailed process steps: Step 1: Pretreatment of carbon nanotube array with hydrophilicity / hydrophobicity gradient: 1.1 Purpose of the operation: By constructing a hydrophilicity-hydrophobicity decreasing gradient along the left end (L end) to the right end (R end), the subsequent doping sources form an initial distribution on the array surface with more adsorption at the L end and less adsorption at the R end, thus solving the problem of no gradient in the initial adsorption of doping sources.

[0022] 1.2 Specific operating procedures: Substrate fixing: The carbon nanotube array substrate (cut to 30mm×10mm size) is fixed to the stage of the plasma pretreatment instrument with high temperature resistant tape (5mm wide), ensuring that the carbon nanotube array face is facing up and without wrinkles; Masking component installation: Cover the substrate surface with a strip-shaped masking component, with only the target doped area exposed (size 1mm×6mm, L end is the left end of the area, R end is the right end). The masking component is fixed with high temperature resistant tape to ensure that it is in close contact with the substrate surface without gaps. Plasma parameter settings: Start the plasma pretreatment instrument and set the parameters as follows: power 80W, argon flow rate 40sccm, treatment distance 5mm, and treatment atmosphere is pure argon (precisely controlled by a flow meter with an error of ±1sccm). Gradient treatment implementation: Activate the stage translation function, set the translation speed to 0.5 mm / s, and the stage moves the substrate along the L-end → R-end direction, with the shielding component moving synchronously with the stage; when the stage reaches the R-end, stop the plasma treatment; at this time, the plasma treatment time for the target area L-end is 30 s (moving distance 6 mm, speed 0.5 mm / s, treatment time = 6 mm / 0.5 mm / s = 12 s; further: the original moving distance should be the target area length 6 mm, speed 0.5 mm / s, treatment time = 6 mm / 0.5 mm / s = 12 s, adjust the L-end treatment time to 12 s, and the R-end treatment time to 2 s to ensure a continuous hydrophilicity gradient; contact angle test results: L-end 35°±2°, R-end 75°±2°, hydrophilicity continuously decreases along L→R). Pre-treatment inspection: Use a contact angle measuring instrument to take 1 test point every 1 mm along the L→R direction in the target area (6 points in total) to confirm that the contact angle difference is ≥5° / mm and there is no sudden change. Otherwise, repeat the pre-treatment.

[0023] 1.3 Key Technical Details: The bonding pressure between the shielding component and the substrate is applied by a micro pressure block of 0.05MPa to prevent plasma from seeping into the gaps and causing uneven processing. Platform translation accuracy: Controlled by the stepper motor built into the equipment, the displacement accuracy is ±0.01mm, ensuring a uniform processing time gradient.

[0024] Step 2: Synergistic doping induced by gradient diffusion source in porous media and laser energy compensation: 2.1 Purpose of the operation: By controlling the permeation rate gradient of the dopant source through the gradual change of the pore size of the porous ceramic sheet and the zoned heating, and by compensating for the permeation rate difference through the linear gradual change of laser power, the synergy of low permeation source-low laser power at the L end and high permeation source-high laser power at the R end is achieved, which solves the problem of damage caused by no permeation rate gradient and uneven laser energy, and forms a continuous doping concentration gradient.

[0025] 2.2 Specific operating procedures: Reaction chamber preparation: Transfer the pretreated substrate from step 1 into the gradient pressure reaction chamber with the carbon nanotube array facing upward; cover the target doping region with the porous ceramic sheet of the gradient diffusion source device, and apply a pressure of 0.1 MPa through a micro-pressurizer to ensure that there are no gaps between the ceramic sheet and the substrate; Dopant source injection: 0.5 mL of liquid ethylenediamine was injected into the injection groove (5 mm × 2 mm × 1 mm) on the upper surface of the porous ceramic sheet using a micro-syringe (1 mL specification, ±0.01 mL accuracy). The injection speed was 0.1 mL / s to avoid the generation of air bubbles. Heating element parameter settings: Start the micro heating element and set the temperature of two heating zones: 0.1-0.5μm pore size zone (corresponding to the L end of the substrate) temperature 40℃±2℃, 0.5-1μm pore size zone (corresponding to the R end of the substrate) temperature 60℃±2℃; monitor the temperature in real time through the temperature controller, and proceed to the next step after stabilizing for 5 minutes; Laser parameter settings: Start the adjustable power nanosecond laser generator and set the parameters as follows: pulse frequency 2kHz, spot diameter 6μm (adjustable via focusing lens, focusing distance 100mm), power gradient curve: initial power (when irradiating end L) 2W, as the stage moves along the L→R direction (speed 0.4μm / s), the power linearly increases to 4W (when irradiating end R), with a power gradient accuracy of ±0.1W; Synergistic induction implementation: The stage inside the reaction chamber is started and translated at a speed of 0.4 μm / s along the L→R direction, while laser irradiation is started simultaneously; when the center of the laser spot moves to the edge of the R end, the translation of the laser and the stage is stopped; the total irradiation time = target area length 6 mm / 0.4 μm / s = 15000 s (i.e. 250 min). Permeation rate monitoring: A micro-weighing sensor (model MS-01, accuracy ±0.001mg) is attached to the lower surface of the ceramic plate to monitor the permeation source volume at the L and R ends in real time, ensuring that the permeation rate at the L end is 0.2μL / (cm²). 2 ·s)±0.02μL / (cm 2 ·s), R-terminus 0.8μL / (cm) 2 ·s)±0.02μL / (cm2 If the deviation exceeds the range, adjust the heating element temperature (for every 5°C increase in temperature, the permeation rate increases by approximately 0.1 μL / (cm²)). 2 ·s)).

[0026] 2.3 Key Technical Details: The bonding pressure between the ceramic sheet and the substrate is 0.1 MPa, achieved by a spring pressure block, with a pressure error of ±0.01 MPa. This avoids leakage due to insufficient pressure and damage to the carbon nanotube array due to excessive pressure. Synchronization of laser power gradient: The laser power is bound to the stage displacement through the equipment software. For every 1mm increase in displacement, the power increases by 0.33W ((4W-2W) / 6mm=0.33W / mm), with a synchronization accuracy of ±0.05W.

[0027] Step 3: Gradient pressure annealing and gradient locking: 3.1 Purpose of the operation: By constructing a pressure gradient along L→R to suppress the back diffusion of doped atoms, combined with low-temperature annealing to promote the bonding of doped atoms with the carbon nanotube lattice, and by ensuring gradient accuracy through in-situ conductivity monitoring, the problem of gradient disappearance caused by back diffusion of doped atoms is solved, and the foundation for subsequent gradient self-repair is laid.

[0028] 3.2 Specific operating procedures: Remove the diffusion source device: Turn off the micro heating element and wait for the ceramic sheet temperature to drop to room temperature (25℃±2℃) before removing the gradient diffusion source device to avoid residual doping sources affecting the annealing. Pressure gradient construction: Argon gas is introduced into the gradient pressure reaction chamber, and two independent pressure valves are activated: the pressure valve on the L end (closer to the L end of the target area) outputs a pressure of 1.3 atm ± 0.01 atm, and the pressure valve on the R end (closer to the R end of the target area) outputs a pressure of 0.8 atm ± 0.01 atm; the pressure is monitored in real time by the pressure gauge in the chamber, and after stabilizing for 10 minutes, proceed to the next step; Annealing parameter settings: Start the reaction chamber heating device, set the heating rate to 5℃ / min, heat to 380℃±5℃, and hold for 45min; during the holding process, the argon flow rate is maintained at 30sccm to avoid atmosphere fluctuations; In-situ conductivity monitoring: A miniature four-probe array (probe spacing 0.2 mm, tungsten material, tip diameter 50 μm) is connected to the target area through the reserved interface of the reaction chamber. The four-probe instrument is set to a test frequency of 1 kHz, and the conductivity distribution along the L→R direction is tested once every 5 minutes (a total of 6 test points, corresponding to the L end to the R end); when the conductivity gradient deviation (the rate of change of the difference between adjacent test points) of two consecutive tests is <2%, heating is stopped; Cooling and removal: Keep the pressure gradient constant and wait for the reaction chamber temperature to cool naturally to room temperature (25℃±2℃). Then, close the pressure valve and argon gas, open the chamber door and remove the substrate to complete the entire local doping modification process.

[0029] 3.3 Key Technical Details: Stability of air pressure gradient: Through PID feedback control of two air pressure valves, the air pressure fluctuation range is ±0.005atm, avoiding the diffusion of doped atoms caused by sudden changes in air pressure; Installation of the miniature four-probe array: The probes are aligned with the test points in the target area through a fine-tuning bracket (accuracy ±0.001mm). The contact pressure between the probes and the carbon nanotube array is 0.01MPa to avoid damage to the array or poor contact that could lead to test errors.

[0030] IV. Verification of Process Effect: 4.1 Verification of the effectiveness of solving the core problem: 4.1.1 Verification of continuous conductivity gradient: Existing technologies only describe conductivity gradients through test data, failing to quantify the synergistic effect of doping concentration, laser power, and penetration rate on gradient continuity. This process constructs a conductivity gradient synergistic calculation model, which can accurately predict and verify the formation of a continuous gradient. This model is the first to be designed for laser-induced local doping of carbon nanotubes, incorporating key process variables and overcoming the limitations of existing single-variable correlations.

[0031] The continuity of the conductivity gradient is due to the nitrogen atom doping concentration gradient. Laser power gradient Dopant source penetration rate gradient The three factors work together to determine the permeation rate, and the effect of temperature on the permeation rate must also be considered. (Correction factor), which cannot be obtained using existing formulas that only relate to a single variable (such as...) Precise quantification is achieved, therefore the following conductivity gradient is established. The calculation formula, coupled with multivariate effects, enables a quantitative description of gradient continuity: Formula (1): Cooperative calculation formula for conductivity gradient: ; In the formula: (Conductivity gradient): This is the rate of change of conductivity in the target region along the direction from L end to R end, directly reflecting the continuity of the gradient; and the parameter needs to be verified by comparing the calculated results with the measured data of the four-probe tester (RTS-8).

[0032] and (L-end conductivity and R-end conductivity): These are the extreme values ​​of conductivity at both ends of the target region, reflecting the maximum difference in gradient. The parameters need to be measured directly using a four-probe tester (RTS-8) to determine the conductivity values ​​at both ends of the target region.

[0033] (Target region length): This is the length of the doped region along the gradient direction, which is the reference dimension for calculating the gradient change rate. The parameter needs to be measured using precision measuring tools (such as vernier calipers) during substrate cutting and confirmed by optical microscope calibration.

[0034] (Intrinsic conductivity of carbon nanotubes): This is the basic conductivity of the undoped carbon nanotube array and serves as the benchmark reference value for calculating the conductivity after doping. The parameter needs to be obtained by measuring the undoped blank carbon nanotube array using a four-probe tester (RTS-8).

[0035] and (L-terminal nitrogen atom doping concentration and R-terminal nitrogen atom doping concentration): These are the percentages of nitrogen atoms at both ends of the target region, which are the core material basis for forming the conductivity gradient. The parameters need to be obtained by elemental analysis of the regions at both ends using X-ray photoelectron spectroscopy (Thermo Scientific K-Alpha, test depth 1-10nm).

[0036] (Laser power gradient rate): This is the linear variation coefficient of laser power along the direction from L end to R end, reflecting the intensity of power compensation; the parameter needs to be calculated by setting the power gradient curve through the laser generator (model YL-1064, software version V3.0), specifically (4W-2W) / 6mm=0.33W / mm.

[0037] and (L-end permeation rate and R-end permeation rate): These are the permeation rates of the doped source at both ends of the target region, reflecting the difference in permeation gradient. The parameters need to be obtained by real-time monitoring of the permeation source volume using a micro-weighing sensor (model MS-01, accuracy ±0.001mg) attached to the lower surface of the porous ceramic sheet, combined with the permeation area.

[0038] and (Heating temperature at L end and heating temperature at R end): These are the heating temperatures at both ends of the gradient permeation source device, used to correct the effect of temperature on the permeation rate; the parameters need to be monitored and recorded in real time by the independent temperature controller (model TC-05) of the micro heating element.

[0039] (Dynamic compensation coupling coefficient): This is used to quantify the synergistic effect of power, permeability, and concentration, which is different from existing models without synergistic calculation. The parameters need to be obtained by fitting the least squares method based on 10 sets of parallel experimental data to ensure that the deviation between the calculated value and the measured value is minimized.

[0040] This formula facilitates precise quantification of the synergistic effect of power-osmosis-concentration on gradient continuity.

[0041] 4.1.2 Verification of low damage in carbon nanotubes: Existing technologies only statistically analyze fracture rate values, failing to explain the damage suppression mechanism of dynamic compensation based on laser power-penetration rate, nor can they quantify the coupling effect between cooling and power compensation. This process constructs a carbon nanotube fracture rate prediction model, transforming the dynamic compensation effect into a quantifiable damage suppression factor. For the first time, it correlates laser energy density with the cooling effect of the dopant source, enabling quantitative analysis of the damage mechanism.

[0042] The fracture of carbon nanotubes is essentially caused by the breaking of lattice bonds due to excessively high laser energy density. During the doping process, the dopant source absorbs some laser energy (cooling effect), and the gradual change in laser power avoids localized energy concentration. Existing formulas (such as...) Since these two key inhibitory factors were not considered, the following fracture rate was established. Predictive formula, which couples the competition between energy input and damage suppression: Formula (2): Prediction formula for carbon nanotube fracture rate: ; In the formula: (Carbon nanotube fracture rate): The percentage of fractured carbon nanotubes in the target area, directly reflecting the degree of damage; the parameter is obtained by observing five random regions of 1μm×1μm using a transmission electron microscope (model TecnaiG2F20, accelerating voltage 200kV) and counting the percentage of fractured tubes (defined as tubes with obvious cracks or length < 50% of the original length).

[0043] (Reference fracture rate): This is the fracture rate under undoped source cooling (i.e., ...) The laser-induced fracture rate is a benchmark reference value for the degree of damage; the parameter needs to be obtained by blank experiment (laser irradiation only on carbon nanotube arrays without source penetration).

[0044] (Laser energy density): This refers to the energy distribution of the laser on the surface of the carbon nanotube, and is the main cause of lattice damage; the parameter needs to be calculated from the laser generator parameters, and the formula is: , in For laser power, The pulse frequency, The area is the spot size.

[0045] (Permeation Cooling Coefficient): This parameter is a unique damage suppression parameter of this process, used to quantify the absorption efficiency of laser energy by the doping source. The parameter needs to be determined by calorimetry, i.e., by monitoring the temperature change of the carbon nanotube array during the permeation process and calculating the ratio of the energy absorbed by the permeation source to the amount of permeation.

[0046] (Average penetration rate): This is the average penetration rate of the doped source within the target region, reflecting the strength of the cooling effect. The parameter needs to be obtained by monitoring the penetration rates at the L and R ends using a micro-weighing sensor (model MS-01) and taking the average of the two values.

[0047] (Power-compensated damage suppression coefficient): To quantify the suppression effect of laser power gradient on local high energy, and to distinguish it from the existing fixed power damage model, the parameter needs to be obtained by fitting the relationship between the fracture rate and the power gradient rate through multiple sets of experiments with different power gradient rates (0.1-0.5W / mm).

[0048] (Laser power gradient): Consistent with the definition in formula (1), its physical meaning is the linear change coefficient of laser power from L end to R end, which is used here to correct the suppression effect of power compensation on damage; the parameter source is the same as formula (1).

[0049] (Total processing time): Physically, this refers to the total duration of laser irradiation, reflecting the strength of the energy accumulation effect. This parameter needs to be calculated using the stage translation time; the formula is: , in The length of the target region. The translation speed of the platform.

[0050] (Gradient-Coordinated Damage Correction Coefficient): To quantify the synergistic inhibitory effect of the permeation gradient and temperature gradient on damage; the parameter needs to be fitted to the fracture rate and temperature gradient through 10 sets of experiments with different combinations of permeation rate differences and temperature differences. The relationship was obtained.

[0051] (Permeability Rate Difference): This is the difference between the permeability rates at end L and end R, reflecting the magnitude of the permeability gradient; the parameter is derived from... Obtained through calculation.

[0052] (Temperature Difference): This is the difference in heating temperature between end L and end R, reflecting the magnitude of the temperature gradient; the parameter is obtained through... Obtained through calculation.

[0053] This formula facilitates precise quantification of the damage suppression mechanism of dynamic compensation.

[0054] 4.1.3 Gradient stability verification: Existing technologies describe stability solely through numerical values ​​of gradient deviation after bending, failing to quantify the effect of gradient pressure-annealing temperature on gradient locking and explaining the suppression mechanism of atomic back diffusion. This process constructs a gradient stability evaluation formula, transforming the gradient locking effect of the pressure gradient into a quantifiable stability coefficient. For the first time, it correlates pressure with atomic diffusion suppression, enabling quantitative analysis of the stability mechanism.

[0055] The core of gradient stability is to suppress the reverse diffusion of doped atoms (diffusion from high-concentration regions to low-concentration regions). Gradient gas pressure can hinder atomic diffusion through pressure difference, while annealing temperature can fix atoms by strengthening lattice bonding. Existing formulas... Since these two key locking factors were not considered, the following stability bias was established. The calculation formula utilizes the synergistic effect of coupling diffusion suppression and structural reinforcement: Formula (3): Evaluation formula for conductivity gradient stability: ; In the formula: (Conductivity gradient deviation after bending): This is the percentage difference between the conductivity gradient after bending and the initial gradient, directly reflecting the stability of the gradient. The parameter needs to be obtained by measuring the conductivity gradient before and after bending using a four-probe tester (RTS-8) and calculating the deviation value (gradient difference after bending / gradient difference before bending × 100%).

[0056] (Reference gradient deviation): When there is no gradient pressure (i.e.) The gradient deviation after bending is the benchmark reference value for stability; the parameter needs to be obtained by blank experiment (using conventional annealing process without air pressure).

[0057] (Gradient pressure difference): This is the pressure difference between the L end and the R end, reflecting the strength of the inhibition of atomic back diffusion by the pressure. The parameter needs to be obtained by real-time monitoring of the pressure at both ends by an independent pressure gauge (accuracy ±0.01 atm) in the gradient pressure reaction chamber and calculating the difference.

[0058] (Gas pressure lock gradient coefficient): This is a stability parameter unique to this process, used to quantify the suppression efficiency of the gas pressure gradient on the diffusion of doped atoms. The parameter needs to be obtained by fitting the relationship between the stability deviation and the gas pressure difference through multiple sets of experiments with different gas pressure differences (0.1-0.8 atm).

[0059] (Annealing temperature): This is the holding temperature for gradient pressure annealing, used to strengthen the lattice bonding between doped atoms and carbon nanotubes; the parameter needs to be monitored in real time by the temperature controller of the reaction chamber heating device.

[0060] (Number of bending cycles): This refers to the number of bending cycles of the flexible substrate, reflecting the degree of structural damage in actual applications. The parameter needs to be obtained by setting the bending parameters (bending radius 5mm, bending angle 180°) on a bending tester (model ZW-01).

[0061] (Annealing holding time): This refers to the holding time during the annealing process, reflecting the degree of lattice bonding. The parameter needs to be set and recorded by the time controller of the reaction chamber heating device.

[0062] (Annealing enhancement coefficient): To quantify the enhancement effect of annealing time on gradient stability, and to distinguish it from the existing pressureless annealing model, the parameter needs to be obtained by fitting the relationship between stability deviation and annealing time through multiple sets of experiments with different annealing times (20-60 min).

[0063] This formula facilitates precise quantification of the gradient locking effect of gradient pressure annealing.

[0064] 4.2. Effect Verification: Existing technologies lack quantitative models for the self-healing effect of conductivity gradients, failing to explain the mechanism of pressure gradient-driven free nitrogen atom replacement and predicting self-healing efficiency. This process constructs a formula for predicting the self-healing rate based on conductivity gradients, for the first time linking pressure gradients with the migration and replacement effect of free nitrogen atoms, achieving quantitative prediction and mechanism analysis of the self-healing effect.

[0065] The core of self-repair is that gradient gas pressure drives free nitrogen atoms to migrate and fill the gradient gap (the low-concentration region caused by stretching), while the repair temperature activates the atomic migration ability. Current technology lacks a relevant quantitative model; therefore, the following self-repair rate is established. Predictive methods, leveraging the synergistic effect of coupled pressure-driven and temperature-activated approaches, enable a quantitative description of self-healing efficiency. Formula (4): Prediction formula for self-healing rate of conductivity gradient: ; In the formula: (Self-repair rate): This is the percentage reduction in gradient deviation after self-repair, directly reflecting the effectiveness of self-repair. The parameter needs to be verified by comparing the calculated result with the measured data of the four-probe tester (RTS-8). The calculation logic is (initial deviation - post-repair deviation) / initial deviation × 100%.

[0066] (Post-repair gradient deviation): This refers to the conductivity gradient deviation after self-repair treatment, reflecting the accuracy of the gradient after repair. The parameter needs to be obtained by measuring the conductivity gradient after self-repair using a four-probe tester (RTS-8) and calculating the deviation value.

[0067] (Initial gradient deviation): This is the unrepaired conductivity gradient deviation after stretching, reflecting the degree of damage to be repaired. The parameter needs to be obtained by measuring the gradient deviation using a four-probe tester after processing with a tensile testing machine (model WDW-02, stretching rate 1mm / min, 5% stretching amount).

[0068] (Repair pressure difference): This is the pressure difference between the L end and the R end during the self-repair process, which drives free nitrogen atoms to migrate towards the gradient gap. The parameter needs to be obtained by real-time monitoring of the pressure at both ends by an independent pressure gauge (accuracy ±0.01 atm) in the gradient pressure reaction chamber and calculating the difference.

[0069] (Pressure-driven replacement coefficient): To quantify the driving efficiency of pressure gradient on the migration of free nitrogen atoms, the parameter needs to be obtained by fitting the relationship between self-repair rate and pressure difference through multiple sets of experiments with different repair pressure differences (0.1-0.5 atm).

[0070] (Repair Time): This refers to the heat preservation time of the self-repair process, reflecting the cumulative effect of the replacement process; the parameter needs to be set and recorded through the time controller of the gradient air pressure reaction chamber.

[0071] (Repair Temperature): This is the holding temperature for the self-repair process, which activates the migration ability of free nitrogen atoms; the parameter needs to be monitored in real time by the temperature controller of the reaction chamber heating device.

[0072] (Atom migration activation coefficient): To quantify the activation effect of temperature on the migration ability of free nitrogen atoms, and to distinguish it from the existing temperature-free repair model, the parameter needs to be obtained by fitting the relationship between self-repair rate and temperature through multiple sets of experiments at different repair temperatures (20-50℃).

[0073] This formula allows for convenient and accurate quantification of self-healing effects.

[0074] Summarize: Pretreatment steps: Existing technologies only perform overall plasma cleaning, while this solution constructs a treatment time gradient by using a strip-shaped shielding component and stage translation, thereby forming a hydrophilicity-hydrophobicity gradient; Synergistic induction steps: Existing technologies use drop-on / spray coating for source supply (uniform rate) + fixed laser power. This solution controls the permeation rate gradient through a ceramic sheet with gradually varying pore size + zoned heating, combined with linearly varying laser power to compensate for permeation differences. Annealing process: Existing technology uses constant temperature and no pressure annealing. This solution uses dual pressure valves to build a gradient pressure + in-situ conductivity monitoring to achieve pressure gradient suppression of back diffusion + real-time correction of gradient accuracy.

Claims

1. A laser-induced local doping modification process for carbon nanotube arrays, comprising the steps of pretreatment of the carbon nanotube array substrate, laser-induced doping, and annealing, characterized in that: The pretreatment is a hydrophilicity-hydrophobicity gradient pretreatment of carbon nanotube arrays. Specifically, the carbon nanotube array substrate is fixed on the stage of the plasma pretreatment instrument, a strip shield is used to expose the target doped region, and the plasma parameters are set as follows: power 80W, argon flow rate 40sccm, treatment distance 5mm. The stage is started to move along the left end to the right end of the target doped region at a speed of 0.5mm / s to perform plasma treatment, so that the contact angle at the L end of the target region is 35°±2° and the contact angle at the R end is 75°±2°, and the hydrophilicity decreases continuously along L→R. Laser-induced doping is a synergistic doping method involving a porous medium gradient diffusion source and laser energy compensation. Specifically, the pretreated substrate is placed in a gradient pressure reaction chamber, covered with an alumina porous ceramic sheet whose pore size linearly changes from 0.1 μm to 1 μm along L→R, a bonding pressure of 0.1 MPa is applied, liquid ethylenediamine is injected into the ceramic sheet, and polyimide heating plates partitioned on the lower surface of the ceramic sheet are activated to set the temperature of the heating zone corresponding to the L end to 40℃±2℃ and the temperature of the heating zone corresponding to the R end to 60℃±2℃. At the same time, an adjustable power nanosecond laser generator with a wavelength of 1064 nm is activated, the pulse frequency is set to 2 kHz, the spot diameter is 6 μm, and the laser power linearly increases from 2 W to 4 W as the stage shifts along L→R at a rate of 0.4 μm / s. The penetration rate at the L end and the penetration rate at the R end are monitored simultaneously. The annealing process is a gradient pressure annealing with a locked gradient. Specifically, after removing the permeation source device, argon gas is introduced into the reaction chamber. The pressure on the L end side is 1.3 atm ± 0.01 atm and the pressure on the R end side is 0.8 atm ± 0.01 atm through a dual pressure valve. The temperature is increased to 380℃ ± 5℃ at a rate of 5℃ / min and held for 45 min. During the holding process, the conductivity distribution is tested every 5 min using a miniature four-probe array with a spacing of 0.2 mm until the conductivity gradient deviation of two consecutive tests is <2%. Then, the temperature is naturally cooled to room temperature.

2. The local doping modification process for laser-induced carbon nanotube arrays as described in claim 1, characterized in that: The carbon nanotube array substrate is a vertically grown multi-walled carbon nanotube array with a diameter of 12-16 nm and an array height of 6 μm. The substrate is a 50 μm thick polyimide film. The substrate is cut to a size of 30 mm × 10 mm and fixed to the stage with a 5 mm wide high-temperature resistant tape. The strip shielding part is made of polytetrafluoroethylene, with a size of 20 mm × 5 mm × 1 mm and a shielding width of 5 mm. It is bonded to the substrate without gaps with the high-temperature resistant tape.

3. The local doping modification process for laser-induced carbon nanotube arrays as described in claim 1, characterized in that: The porous alumina ceramic sheet measures 20mm×10mm×2mm, and the polyimide heating element measures 20mm×5mm×0.1mm. It is divided into two independent heating zones, each with its own temperature controller. The heating element is attached to the lower surface of the ceramic sheet using thermally conductive silicone.

4. The local doping modification process for laser-induced carbon nanotube arrays as described in claim 1, characterized in that: Liquid ethylenediamine with a purity ≥99.5%, a viscosity of 1.4 mPa・s, and a density of 0.898 g / cm³ at 25℃ was injected into the injection tank on the upper surface of the ceramic sheet at a rate of 0.1 mL / s using a micro-syringe with a specification of 1 mL and an accuracy of ±0.01 mL. The permeation rate was monitored in real time by a micro-weighing sensor attached to the lower surface of the ceramic sheet.

5. The local doping modification process for laser-induced carbon nanotube arrays as described in claim 1, characterized in that: The gradient pressure reaction chamber is made of 304 stainless steel, has a volume of 10L, and is equipped with a micro four-probe array interface.

6. The local doping modification process for laser-induced carbon nanotube arrays as described in claim 1, characterized in that: The miniature four-probe array is made of tungsten, with a probe tip diameter of 50 μm. It is aligned with the test point in the target area using a fine-tuning frame with an accuracy of ±0.001 mm. The contact pressure between the probe and the carbon nanotube array is 0.01 MPa.

7. The local doping modification process for laser-induced carbon nanotube arrays as described in claim 1, characterized in that: It also includes a conductivity gradient self-healing step, specifically, the substrate treated with 5% tensile weight is placed back into the gradient air pressure reaction chamber, the repair air pressure difference between the L end and the R end is set to 0.1-0.5 atm, the repair temperature is 20-50℃, the repair time is set by a time controller, the initial gradient deviation is measured by a tensile testing machine, and the post-repair gradient deviation is measured by a four-probe tester. The self-healing rate is calculated by the formula (initial deviation - post-repair deviation) / initial deviation × 100%.

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