| Functional nano-and microscale structures of biological materials in nature are a source of inspiration for scientists and engineers. One of those areas is the fabrication of functional nano-and microscale structures by using femtosecond laser on various material surfaces including metal and semiconductor for improving characteristic of the materials. The development of the technology for achieving new functions on solid surface can serve daily life and production efficiently. For example, such structures can carry out the properties regulation for optical absorption, wetting, etc. The preparation technique of the functional micro-and nanoscale structures on solids has a far-reaching significance for the application in many fields, such as solar energy utilization, metal lubrication, anticorrosive, self-cleaning, military stealth and so on.In our work, in order to develop insights in functional structures formation and its functional characteristics on solid surface produced by femtosecond laser, the corresponding research on the hot spots and the key problems in physics involved are carried out. The main contents include as follows:femtosecond laser induced sub-wavelength periodic ripples on metal surface, femtosecond laser induced nano-and microscale structures on semiconductor surface and their optical characteristics research, femtosecond laser induces nano-and microscale structures on metal surface and optical characteristics research. Furthermore, the absorption mechanism of "Black Metal" with broad-band optical absorptivity produced by a femtosecond laser is analyzed by numerical simulations. The wetting properties of the Black Metal and structured silicon are studied. Moreover, the preparation of multifunctional integration (with broad-band optical absorptivity and lubrication at the same time) are developed. Furthermore, fabrication of functional nano-and microscale structures on non-planar surface produced by femtosecond laser filament is also studied.In this thesis, we experimentally investigate the sub-wavelength periodic structures induced by femtosecond laser pulse on metal surface. On account of two temperature model (TTM) and Maxwell theory, we numerically study the phenomena observed in the experiments. Subsequently, we carry out the fabrication of nano-and microscale structures on silicon surface, and research on the effects of the different experimental conditions such as gas environment, laser pulse width, laser pulse energy density and others on the micro-spike structure on silicon surface. The mechanism of formation and optical absorption are researched by consulting experimental data in this work. Moreover, the new black silicon with micropore structure is created by scaning the focused laser beam through further exploration. The testing results show that it has a well anti-reflection property for the light wave band from0.35to1μm.In the matter of the study on the metal surface covered with nano-and microscale structures and its optical characteristics, various colored aluminum (Al) are achieved by changing the experimental conditions (laser pulse energy density, scanning velocity, and scanning interval). Such colors include white, gold, brown, gray, black, etc and the color change mechanism is analyzed. We also make the detailed experimental research on the black metal surface, and fabricate kinds of typical nano-and microscale structures in various metal surfaces (Al, Ti, Ni and Mo). The typical structures include as follow:1) microscale groove covered nanostructures;2) microcolumn covered nanostructures;3) sub-micron structure. The measured reflectivity is less than10%from ultraviolet to infrared band (0.2-2.5μm) and it is indeed less than1%in some wave bands.In order to study the optical absorption of traditional nanostructures (e.g. grating, hemisphere and tetrahedron) influenced by their period, gap distance and array, finite difference time domain (FDTD) numerically simulating method was used. Especially for the character of broad spectral absorbing which had not been clearly explained in physics had been studied systematically in this work. The hybridized layer consists of air and nanostructure induces the absorbing spectral broadening as the dielectric environment changing.In this thesis, we also research on the wettability of the Black Metal and find that metal surfaces with the micro groove structure shows a superhydrophilic property. The wick effect enhances its water transport function. Similarly, silicon surfaces with this structure also has the same wettability. However, the metal surface equipped the microcolumn structure is superhydrophobic (contact angle>155°) and has a small rolling angle with contact angle hysteresis. The hydrophobic performance shows that the metal surface achieves functions including anticorrosion and self-cleaning. More importantly, general superhydrophobic surface need a coating organic film on a micro-nano structure surface in order to reduce the surface energy. It is different from the superhydrophobic surface we created. We realized, for the first time, a technique about one-step formation of multifunctional (together with broadband spectrum absorption and super hydrophobic) nano-and microscale structures on metals by using femtosecond laser without other auxiliary process mentioned above. The metal surface with multi-functional structure could be directly applied to natural enviroments without any protection measures. The striking feature of multi-functional surface drives us to apply it to the field of solar thermal power generation. We take Al foil with the multi-functional microcolumns structure as solar absorber to study the solar thermoelectric generation efficiency. The generated output of manufactured multi-functional Al foil surface is increased by17.4and33.7times, compared with normal Al foil without micro structure and no metal foil.For a long time, it has been hard technical problem for scientists and engineers to fabricate functional structures on curved surface. In this research, for the first time, filament structuring technology extends the fabrication of functional nano-and microscale structures from a planar surface to a complex one without the complexity of5-axis sample control. An effect to the microcolumn under different experimental conditions (incident angle and polarization direction of the illuminating laser) was studied. An appropriate numerical simulation was used to explain the formational mechanism of microcolumn and the new phenomenon in this experiment.Through the investigation of the fabricating nano-and microscale structures and their functional characteristics, the formation mechanics of micro-and nanoscale structures induced by femtosecond laser on solid surface and the physical essence of function are revealed, and the existing technology is expanded. Therefore this work will play an important role in the fields of research and application of the functional nano-and microscale structures. |
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