【作者】 黄永光；

【导师】 刘世炳；

【作者基本信息】 北京工业大学 ， 光学， 2010， 博士

【摘要】 固体表面有序的微纳米结构可以使得材料具有独特的性能,实现诸如超疏水、超黏附、超光学吸收等超性能,在工业、军事、航空、航天、医疗等各个领域都有广阔的应用前景。因此,探索实用高效的表面微纳米结构的制备技术是极其重要的工作。近年来刚刚兴起的飞秒激光直接诱导固体表面有序结构的方法被认为是该领域极具潜力的制备技术之一,但对这种微纳米结构化的物理机制和对该技术的优化控制等还缺乏系统研究。本文开展飞秒激光诱导金属表面有序微纳米结构的研究,在钛金属及钛合金表面获得了多种不同特征的有序微纳米结构,并探讨了它们的形成机制,为进一步开展飞秒激光大面积可控制备固体表面微纳米结构研究打下了基础。全文的主要研究内容、结论与创新性如下:1.通过考察辐照后样品表面的电镜图发现不同脉宽的线偏振激光诱导得到的光栅结构的形貌不同:纳秒激光辐照区域内完全熔化表面得到的光栅结构的轮廓为正弦波形,光栅周期略小于激光波长;而飞秒激光诱导得到的光栅结构周期比激光波长小很多,并且随着辐照激光通量增大,光栅周期增大,光栅的峰-谷的占空比逐渐减小。2.提出了应用表面等离子激元的力学效应来分析光栅结构的形成过程的观点:利用离子声波中离子对液体的碰撞压力效应解释了纳秒激光诱导正弦波形光栅结构的形成机制,利用考虑电子激元的静电场力烧蚀模型解释了飞秒激光诱导金属光栅结构的形成机制。3.利用扫描电镜观察圆偏振飞秒激光诱导金属表面微纳米结构的特征发现:正入射下,除了已经被报告过的光栅矢量一致的规则光栅结构之外,我们还观察到了光栅矢量为圆形的光栅结构和带纳米突起的周期性点状结构;斜入射下,金属表面会出现正交在一起的二维光栅结构;在相同入射角下,左旋光和右旋光得到的表面微结构具有镜面对称性。4.考察多脉冲飞秒激光诱导Ti金属形成的微孔的孔壁,发现了孔壁上可以形成纳米一维光栅结构、二维光栅结构、凹陷结构和凸起结构等四种微纳米结构。利用激光共聚焦显微镜对孔壁二维光栅结构所在位置对应的孔壁倾角进行了测量,利用激光与斜面上表面等离子体波相互作用模型解释了二维光栅结构现象。5.利用扫描方法在钛合金表面大面积制备了光栅结构、光栅结合微凸起结构和周期性微孔结构,这些不同表面结构化的钛合金表面显示出对光谱不同的响应特征。值得一提的是,发现了聚焦光斑直径为70微米的飞秒激光匀速扫描金属表面时会周期性产生数十微米直径的深微孔的新现象,这种深微孔结构使得金属表面实现了对宽带光谱的近全吸收。更多还原

【Abstract】 The ordered micro/nano structure on the solid surface, which can endow materials with unique properties such as super-hydrophobic, super-adhesion, super-light- absorbancy and so on, has comprehensive application foreground in the field of industry, military, aviation, aerospace and medicine. For this reason, the development of efficient and economic techniques for producing surface micro/nano structure is an important work. Recently, femtosecond (fs) laser direct inducing ordered surface structure has been demonstrated to be a promising method for producing of surface micro/nano structure. However, a systematic study of the physical mechanism of the surface micro/nanostructuring as well as the optimal conditions for a controllable micro/nanostructuring using fs laser direct inducing micro/nano structure method are still lack. In this thesis, several kinds of ordered structure on the metal surface have been induced by fs laser irradiation, and the formation mechanism of each type of the micro/nanostructure has been also discussed. All these experimental and theoretical results lay a foundation of fs laser producing wanted micro/nano structure on the solid surface. The main contents, research conclusions and contributions to innovation are summarized as following:1. Under a scanning electron microscope (SEM), different morphology characteristic of grating structure on the metal surface induced by linear-polarized (LP) laser with different pulse widths was identified. The grating on the uniform melted metal surface induced by nanosecond laser shows a regular sine-wave outline, and the period of this grating is just slightly shorter than the laser wavelength. By contrast, the period of the grating induced by fs laser is much shorter than laser wavelength, in addition the period is gradually increase and the duty ratio of crest vs valley is decrease following increasing the laser fluence.2. We proposed that using surface plasmons mechanics effect to explain the formation mechanism of the laser induce grating structure: using the ions collision pressure effect to explain the formation mechanism of sine-waveform grating structure induced by nanosecond laser, using the electrostatic force ablation model which considering the electron plasmons effect to explains the formation mechanism of fs laser induced metallic grating structure.3. The different types of micro/nanostructure on the metal surface induced by a circular-polarized (CP) femtosecond laser were observed under SEM. When laser normal incident, in addition to the grating structure with a linear-grating vector which has been reported, we observed two novel structures, one is grating structure with circular-grating vector, another is spike structure surrounded with nanoprotrusions. When laser oblique incidence, two-dimensional (2D) orthogonal grating structure will appeared on the metal surface. In the same incident angle, the surface structures show exactly mirror symmetry for left and right CP light.4. Four kinds of micro/nano structure, such as one-dimensional grating structure, 2D grating structure, nanocone structure with the size of 200nm and nanohollow structure were formed on the blind-hole wall which induced by multipulses fs laser ablating Ti. In particular, the location elevation angle of two-dimensional grating structure on the hole wall was examined by a confocal laser scanning microscope, and the formation mechanism of this 2D grating structure was successfully interpreted as laser and surface plasmons interaction on a angular surface.5. By the scanning technology, large area micro/nano structures (such as grating structure, microbump structure which covered by grating structure, and periodic microporous structure) on titanium alloy surface have be obtained under single fs laser beam irradiating. These structured surfaces show quite difference on their response characteristics of the reflective spectrum. What is worth mentioning that fs laser with focused spot size of 70μm would periodic producing 30μm hole under scan spot moves in uniform motion, and these microporous structure can realize the metal surface of broad-spectrum nearly all absorption.更多还原