Nanofabrication Using High Frequency Laser Ablation and Laser Maskless Lithography

我提出的研究计划将集中在超短激光材料加工及其在微/纳米制造中的应用。纳米结构材料因其独特的光学、生物和力学性能而迅速引起研究人员的兴趣，这些特性与块体材料不同。在纳米结构中观察到的结构纳米迁移率和纳米柔性为开发光伏器件的独特光学性质以及不同分子和细胞之间的物理化学相互作用机制提供了机会。*我的研究将在纳米技术领域开创一个重要的新方向。纳秒激光烧蚀加工传统上用于微纳尺度的材料去除，但由于其效率低，很少用于纳米材料的合成。基于激光的纳米材料合成通常使用高功率连续激光和纳秒激光，并且需要催化剂和受控环境。然而，在兆赫激光脉冲频率下，连续脉冲之间的延迟时间与成核的临界时间相当，这使得在环境条件下无需添加催化剂就可以形成纳米结构。*我之前在激光微/纳米加工方面的研究为利用超短激光加工微/纳米材料奠定了基础。这些研究导致发现了一种与高脉冲频率激光-物质相互作用有关的新现象，由此可以从不同类型的材料产生各种形式的薄膜、亚微型图案和纳米结构。这一发现将带来高频激光材料加工的范式转变，并将为工程师提供一个重要的新工具，用于亚微型图案化和薄膜生成。这项技术也开启了产生纳米结构的可能性，例如纳米纤维结构、纳米复合材料和纳米合金，这些都是很难通过任何其他方法合成的。我的研究表明，通过控制激光特性，可以在硅衬底上生成非晶化或氧化硅薄膜，然后用于太阳能电池制造，也可以用于微电子机械(MEMS)系统和生物医学设备制造。*我提出的工作将向前迈进，展示一种新的纳米杂化材料和基于薄膜的衬底，用于无掩模光刻、生物医学和光伏设备制造。此外，我还将重点演示基于光热理论和有限元模拟的分析方法，这些方法可以描述激光与物质的相互作用、激光等离子体和羽流的产生，以及激光参数可以影响所产生的微/纳米粒子的尺寸和质量的方法。

My proposed research program will focus on ultrashort-laser materials processing and its applications in micro/nano fabrication. Nanostructured materials are rapidly gaining interest among researchers due to their exceptional optical, biological, and mechanical properties, which differ from those of bulk-form materials. The structural nano-mobility and nano-flexibility observed in nanostructures provide opportunities to develop unique optical properties for photovoltaic devices, as well as physico-chemical interactive mechanisms between different molecules and cells.***My research will initiate a major new direction in the field of nanotechnology. Nanosecond-laser ablative machining has traditionally been used for material removal at micro- and nanoscales; due to its low efficiency, however, it is rarely used for nanomaterial synthesis. Laser-based nanomaterial synthesis normally employs high-powered continuous lasers and nanosecond lasers, and requires catalysts and a controlled environment. At megahertz laser-pulse frequency, however, the delay time between successive pulses is comparable to the critical time of nucleation, which enables the formation of nanostructures in ambient conditions without the addition of a catalyst.***My previous research on laser micro/nano fabrication has contributed to establishing the groundwork for micro/nano material processing using ultrashort lasers. These investigations led to the discovery of a new phenomenon associated with high pulse-frequency laser-matter interaction, whereby thin-film, sub-micro patterns and nanostructures of various forms can be generated from different types of materials. This discovery is poised to bring about a paradigm shift in high frequency-laser material processing and will provide engineers with an important new tool for sub-micro patterning, and thin-film generation. This technique also opens up the possibility of generating nanostructures, such as nanofibrous structures, nanocomposites, and nanoalloys, which are difficult to synthesize by any other means. My research has demonstrated that by controlling laser properties, it is possible to generate a thin-film of amorphorized or oxidized silicon on top of a silicon substrate, which can then be used for solar-cell fabrication and also for microelectromechanical (MEMS) systems and biomedical devices fabrication.***My proposed work will take a leap forward by demonstrating a new nano-hybrid material and thin-film-based substrate for maskless photolithography, biomedical and photovoltaic devices fabrication. In addition, I will focus on demonstrating analytical methods - based on photo-thermal theory and finite element simulation - that can describe laser-matter interaction, laser plasma and plume generation, and the method by which laser parameters can affect the size and quality of micro/nano particles that are created.