| Nanofabrication has recently attracted much attention because it plays an important role in nanotechnology. The improvement of microelectronic devices and information technologies depends on the development of nanofabrication. Usually, methods used in nanofabrication are characterized as "conventional nanofabrication" and "nonconventional nanofabrication" techniques. The "conventional nanofabrication" techniques include photo lithography, electron beam lithography, focused ion beam etching, etc.; the "nonconventional nanofabrication" techniques inculde molding, embossing, printing, etc.Nanoimprint lithography (NIL) is one of the most important nonconventional lithographic techniques for fabricating nanometer scale pattern. It has been widely used in photonics, biotechnology, electronics, optoelectronics and other related areas due to its advantages such as high efficiency, large area, reproducible, and high resolution. Since it was first invented by Prof. Stephen Chou in 1995, NIL has made great progress. With the development of NIL, many new types of NIL have emerged, such as roller nanoimprint lithography, soft lithography, edge lithography, nanotranfer printing, and reversal nanoimprint technique, which accelerate the industrialization of NIL. However, the cost of high-resolution molds and complex structure patterned molds for NIL is still very high, which seriously limits the development of NIL.In this thesis, we aimed on fabricating the polymer pattern with higher resolution and complex split-ring structure by controlling the defects during nano imprint process and studying the applications of these structures. It can reduce the cost of NIL by transferring the polymer patterns onto Si substrate. Moreover, we try to fabricate bicolour pattern based on traditional NIL.Firstly, the whole nanoimprint process was studied in detail. The critical process of nanoimprint is how the polymer fills the cavity in the molds. The basic theoretical issue is mainly about the filling behavior of polymer rheological properties. The formation of incompletely replicated structures is because the polymer cannot fully fill the spaces between the mold and the substrate. By adjusting the thickness of polymer film, the high-resolution polymer pattern is fabricated using the inexpensive mold with large cavity. We further transfer this pattern onto Si substrate by RIE, and the high-resolution mold was fabricated finally.Secondly, we present a new method to fabricate split-ring structure on polymer surface by controlling the defects of NIL, we called it tilted nanoimprint lithography. These complex structures can be transferred onto glass substrate and form split-ring resonators (SRRs) by using nanotranfer printing. The feature size of SRRs can be further scaled down to 240 nm by scaling down the nanopillars of the original imprinting mold and optimizing the thickness of polymer film. The nature of the elastic molds makes this strategy suitable for creating structures on curved surface. In addition, crescent-shaped nanohole metallic structures, called "hot spots", are also prepared by using this method, which can be used in surface-enhanced Raman spectroscopy, surface-enhanced fluorescence, plasmon resonance energy transfer, etc. This method combines the advantages of NIL and nanotransfer printing. It is a fast, easy-to-implement, and low cost method to fabricate SRRs with high throughput.Thirdly, we study the diffusion behaviour of dye molecules on PMMA film. The state of dye species can be adjusted by controlling the thickness of polymer film. Hence, we can modulate the different color of dye species on the polymer film with different thickness. Finally, the bicolor pattern can be fabricated with a single dye species on the nanoimprinted surface due to the formation of monomers and aggregates at protrusion and recess areas respectively. It is a low cost and high efficiency method to fabricate multicolor pattern over large area, which has potential applications in the field of full color display.
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