Fabrication Of Nanostructures Arrays And Their Applications

With the development of nanofabrication technologies, the integration of the devices continues increasing. The feature size has been pushed toward a smaller scale. Nanopatterning has been playing an important role in the process of device fabrication. Thus, it becomes necessary for us to improve the corresponding nanopatterning methods. For the moment, nanopattern generation methods include:electron beam lithography (EBL), focused ion beam lithography (FIB), interference lithography (IL) and so on. Among them, IL has become a commonly used technology in laboratory because of its easy operation and low cost.Because of its size, nanostructure will maintain some special effects, which will make the materials obtaining corresponding physical and chemical properties. For this reason, nanostructure has been wildly used in optical, magnetic, biomedical electrochemistry and other fields. Metallic nanostructure arrays have attracted more and more attention due to the properties of strong light scattering and absorption and giant enhancement of the local electric fields. Therefore, they have been wildly used as the surface enhanced Raman scattering (SERS) substrates.This paper focuses on these two parts:In the first part of this paper, we have studied the technology of interference lithography. We used a tri-layer resist stack to fabricate the pattern. Firstly, we spin-coated a layer of AZ1500 photoresist, followed by deposition of a layer of 10 nm SiO2, then we spin-coated another layer of AZ 1500 photoresist. By this method, we got steep side wall, which was useful for the coming Lift-off process. We have successfully fabricated gratings and dot arrays with different periods. We discussed the effect of the exposure dose, development time and other parameters on the pattern. We also designed and constructed two different optical path systems, called LLOYD’S-MIRROR method and Mach-Zehnder method. Using the Mach-Zehnder method, we successfully fabricated the grating patterns on 2 inch. At last, we tried to fabricate the dot arrays by exposing the sample twice.In the second part, we have studied the fabrication of SERS substrates based on hybrid nanoimprint lithography. Compared to conventional rigid template, the hybrid mold can have a better conformal contact with the substrate. On the other hand, compared with the traditional soft mold, the hybrid mold can obtain a higher mechanical strength, which will make us achieve high resolution and excellent fidelity during the pattern transfer process. Using the hybrid nanoimprint method, we successfully fabricated different nanostructures, such as dot arrays, rings and dense hexagonal arrays transferred from anodic aluminum oxide (AAO) template. By measuring the Raman spectra, we found the structures from AAO template had the best enhancement. We also studied the influence of the diameters of the nanodots on SERS effect. Finally, we used a software called FDTD for numerical simulations. The absorption, reflection, transmission spectra and local field were performed. Moreover, we found the resonance wavelength could be tuned by changing the diameter of the nanodots.