Nanofabrication Using High Frequency Laser Ablation and Laser Maskless Lithography

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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.