飞秒激光双脉冲乙醇辅助加工及硅纳米粒子的制备

发布时间：2018-05-04 11:37

本文选题：飞秒激光 + 脉冲序列　；参考：《北京理工大学》2015年硕士论文

【摘要】：近年来，基于飞秒激光的微/纳制造技术已经成为了科研热点之一。在传统飞秒脉冲激光的基础上发展而来的时域整形的脉冲序列技术，为实现材料加工中的高质量、高效率、高精度加工提供了可能性。通过设计脉冲序列，不仅可以控制固体材料加工中的电子激发/电离过程，而且甚至可以在飞秒尺度上控制化学反应过程。本人在前人的研究基础上，结合飞秒激光控制化学反应过程的原理，从理论和实验上对基于脉冲序列设计的飞秒激光与物质材料的相互作用机理作出了探索研究。同时，将时域整形的双脉冲用于液相烧蚀制备纳米粒子的方法，高效率制备出了小粒径、均匀分布的硅纳米粒子。本论文主要研究工作和创新点概括如下：（1）采用时域整形的飞秒双脉冲在空气和乙醇环境中加工半导体和金属材料。在空气环境中，延时小于1ps双脉冲加工半导体材料硅和锗时，烧蚀面积呈现振荡减小；而在乙醇环境中，相同实验条件下，当激光通量高于0.4J/cm2时加工半导体时，，当延时大于200fs时会呈现烧蚀增强的现象。而在使用飞秒双脉冲加工金属材料铝时，乙醇环境中的实验结果与空气环境类似，并没有存在烧蚀增强的现象。（2）飞秒激光在电离乙醇分子时由于乙醇分子中H-O键的断裂会产生自由电子。泵浦探测技术表明，飞秒激光电离乙醇分子这一反应完成时间约200fs，而电子-空穴的结合往往在半导体材料中更容易发生。通过时域整形的脉冲激光，两束脉冲延时超200fs后，第二束子脉冲到达时由于自由电子密度的升高而对光子能量的吸收增强，成功的提高了烧蚀效率。同时，通过设计的脉冲序列，还可以有效改善材料的加工质量和效率。（3）使用液相烧蚀方法成功制备出硅纳米粒子。传统飞秒激光在低能量下能够制备小粒径的纳米粒子，但是制备效率却降低。本课题通过采用飞秒激光脉冲序列技术，当脉冲延时超过200fs，与传统单脉冲激光相比，高效率制备出了小粒径、均匀分布的硅纳米粒子。本方法可以广泛的加工多种基底材料，实验过程简单易操作。
[Abstract]:In recent years, micro / nano fabrication technology based on femtosecond laser has become one of the hotspots in scientific research. Based on the traditional femtosecond pulse laser, the pulse sequence technology of time domain shaping provides the possibility for the realization of high quality, high efficiency and high precision in material processing. By designing the pulse sequence, not only the electron excitation / ionization process can be controlled, but also the chemical reaction process can be controlled on the femtosecond scale. On the basis of previous studies and the principle of femtosecond laser controlling chemical reaction, the interaction mechanism between femtosecond laser and material based on pulse sequence design is studied theoretically and experimentally. At the same time, the double pulse shaping in time domain was used to prepare nano-particles by liquid phase ablation, and the small particle size and uniform distribution of silicon nanoparticles were prepared with high efficiency. The main research work and innovation of this paper are summarized as follows: Femtosecond pulse shaping in time domain is used to process semiconductors and metal materials in air and ethanol environment. In the air environment, when the delay time is less than 1ps double pulse processing semiconductor materials silicon and germanium, the ablation area decreases, but in ethanol environment, when the laser flux is higher than 0.4J/cm2, the laser flux is higher than that of 0.4J/cm2, while in ethanol environment, when the laser flux is higher than 0.4J/cm2, the ablation area decreases. When the delay is longer than 200fs, it will appear the phenomenon of ablation enhancement. However, the experimental results in ethanol environment are similar to those in air environment, and there is no phenomenon of ablation enhancement when aluminum is processed by femtosecond double pulses. When the femtosecond laser ionizes the ethanol molecule, free electrons will be produced due to the breaking of H-O bond in the ethanol molecule. Pump detection technique shows that the reaction time of femtosecond laser ionization of ethanol molecule is about 200fs, and the combination of electron-hole is more likely to occur in semiconductor materials. With the pulse laser of time domain shaping, after two pulses delay over 200fs, the absorption of photon energy is enhanced due to the increase of free electron density when the second sub-pulse arrives, and the ablation efficiency is improved successfully. At the same time, the quality and efficiency of material processing can be improved effectively by the designed pulse sequence. The silicon nanoparticles were successfully prepared by liquid phase ablation. The traditional femtosecond laser can produce small nanoparticles at low energy, but the preparation efficiency is decreased. By using femtosecond laser pulse sequence technology, when the pulse delay exceeds 200fs, compared with the traditional monopulse laser, the silicon nanoparticles with small particle size and uniform distribution have been prepared with high efficiency. This method can be widely used to process a variety of substrate materials, and the experimental process is simple and easy to operate.
【学位授予单位】：北京理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN249;TB383.1

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