| Since the discovery of carbon nanotubes(CNTs),researchers have explored its structure and properties to make a lot of achievements.Nowadays,instead of studying the properties of carbon nanotubes themselves,researchers are inclined to use various techniques to regulate the microscopic or macroscopic properties of carbon nanotubes for new structures or improved properties,which is desirable for practical applications and improving production efficiency.In order to explore the effect of excimer lasers on the structure and properties of carbon nanotube films,the preparation of dispersed and uniform CNT films is the key.The preparation of the film by electrophoretic deposition(EPD)is a preferred method.If the dispersant is added directly to the electrophoretic solution,the dispersion effect of the CNTs is improved greatly,but a large number of dispersantsit will be attached to the film to affect the film performance;if no dispersant is added,poor dispersion effect will appear,and long ultrasound time is needed.In this paper,the secondary dispersion method is used to avoid the above problems,and a thin film of about 100 nanometer has been prepared,which provided samples for the experiment of laser irradiation.Laser has the characteristics of high energy,monochchromaticity,well orientation,so it has been widely used in material processing.The CNTs have been modified by fiber lasers and Nd: YAG lasers,which have achieved many great results,such as the connection between CNTs,high current density,superhydrophobic,hydrophobicity and so on.In this paper,248 nm excimer lasers was used to irradiate CNT films under different laser energies,in order to control the conductivity of films and obtain CNTs with variable resistance.The specific research work of this paper is as follows:(1)Introduce the origin,structure and basic properties of CNTs,and the preparation of CNT films;comprehend the principle and method of preparing CNT films by EPD;introduce the present research status of laser modified CNT films at home and abroad.(2)An apparatus and an experimental method for preparing CNT films by electrophoretic deposition were developed,and the optimum conditions for the preparation of CNTs through experiments was explored.The optimum conditions for the preparation of CNT films are as follows: room temperature,the concentration of carbon nanotubes was 0.016 mg/ml,the electrophoresis voltage was 110 V,the electrophoresis time was 6 min.The thickness of the films is 144.9 nm,and the surface resistance of the films is 996.8 Ω/sq.(3)The laser irradiation treatment system was designed.Different energy excimer lasers were used to irradiate CNT films which prepared by EPD,and the films were characterized before and after irradiation.In the SEM image,it was observed that the carbon-carbon bonds of the CNTs were opened and the carbon atoms were dense on the tube wall.The spectral changes of CNTs were analyzed by Raman spectroscopy.It is found that both the D-band and G-band are increased,but the change is small,and the ID/IG increases with the increase of the laser energy.The I-V characteristics of the CNT films before and after irradiation are measured,and the results show that the CNT films after irradiation have performed non-linearity in the varying degrees.When the laser irradiation energy is 450 m J,the nonlinearity is the most obvious.Comparing the resistance of the CNT films before and after irradiation,it can be found that the film resistance after irradiation is reduced by about 1/2 than before,and the film conductivity is improved.This study is of great significance for the application of CNTs in micronanoelectronic devices and other fields. |
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