Investigations Of Different Patterns Of Metal Nanostructures Fabricated By Nanoimprint Lithography

Surface patterns of noble metal arrays play an important role in diverse applications such assurface-enhanced Raman scattering (SERS) sensors, solar cells, and other optical devices. By combiningnanoimprint lithography with metal deposition method, large scale hemisphere gold nanostructures arefabricated for plasmonic applications. Most interestingly, an inverted gold nanowell structures aresuccessfully transfer printed on flexible plastic substrate by nanoimprint techniques. The nanoimprintlithography shown in this paper is a general fabrication process in achieving not only metallic arrays，butalso arrays of semiconductors and metallic oxides. The main research contents are as follows:1、Using the PS microspheres prepared by our group, PDMS stamp with nanobowl array which has anarea of2cm*2cm(diameter426nm) are obtained by self-assembly technique. Then by combiningnanoimprinting technologie with evaporation magnetron sputtering deposition method, the silver and goldnanohemisphere arrays were fabricated. Reactive ion etch (RIE) treatments were used to control thestructural parameters, including the diameter, the surface roughness, and the spacing between theneighboring hemispheres. Meanwhile, different intershell spacing of the Au hemisphere arrays showndifferent water contact angles. Most interestingly, an inverted gold nanowell structures with size of2cm*2cm are successfully fabricated on flexible plastic substrate by nanoimprint techniques.2、 Tunable localized surface plasmon resonance and SERS properties of silver nanohemisphere arraysare investigated. The result showed that new signals compared with conventional Raman spectrum wereobserved. Transmission spectra of the gold hemisphere arrays prepared under the different RIE time whichclearly illustrates that the spacing and surface roughness has prominent influence on the LSPR properties.The LSPR peaks red-shift from672to775nm compared with those of the close packed gold hemispherearrays. The gaps spacing with40nm and more surface roughness have the highest SERS enhancementsignals. Meanwhile an inverted gold nanowell structures are successfully transfer printed on flexible plasticsubstrate by nanoimprint techniques, which show good SERS applications also.3、Composite ZnO nanorod arrays with Au hemisphere arrays are fabricated by hydrothermal growthmethod through sputtering ZnO seed layer on the surface of Au nanoparticle hemisphere. FESEM results show that the length of ZnO nanorod increased with increasing the reaction time in the hydrothermalprocess. XRD characterization indicate that the ZnO nanorod arrays fabricated by this method are highlyorientation along the (002) direction. Photoluminescence spectra shows oxygen defects are on the surfaceof the ZnO nanorod arrays. The following I-V test shows there is a Schottky contact between Au and ZnOnanorods. Finally, the photocatalytic efficiency indicated that the ZnO nanorods obviously increased thedegradation of methylene blue, but the photocatalytic efficiency did not improve after the introduction ofgold nanostructures which is due to the much longer of ZnO nanorods and patterned structure isdisappeared.