Study on Fabrication of Metal Nanostructures by Electrochemical Methods &Their Plasmonic Coupling

• Main Authors: Sajal Biring, 畢少強
• Other Authors: Prof. Yuh-Lin Wang
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/43995569233047856324

博士 === 國立清華大學 === 化學系 === 96 === A rapid electrochemical replication technique is developed to fabricate ultra-smooth aluminum foils by exploiting readily available large-scale smooth silicon wafer as the master. Since the adhesion of aluminum on silicon depends on the time of surface pretreatment in water, it is possible to either detach the replicated aluminum from the silicon master without damaging the replicated aluminum and master or integrate the aluminum film to the silicon substrate. Replicated ultra-smooth aluminum foils are used for the growth of both self-organized and lithographically guided long-range ordered arrays of anodic alumina nanochannels without any polishing pre-treatment. An electrochemical nanomolding technique for the large-scale and rapid fabrication of metallic nanostructures has been demonstrated taking advantage of the above method. Here, Nanostructures with features down to 10 nm has been fabricated by fast electrochemical deposition of aluminum on nanopatterned silicon mold followed by mechanical peeling off the aluminum foil from the mold. This high fidelity, non-destructive technique can exploit the mold for repeated use in mass production of nanostructures and also opens up new possibilities in the field of nano-scale design and fabrication. Finally, a large-scale guiding technique has been presented to fabricate long-range order anodic alumina nanochannel arrays based on electrochemical nanomolding. Optical properties of metal nanostructures grown inside the anodic alumina nanochannels have been studied thoroughly. Electromagnetic interactions of the near-, intermediate- and far-zone in an array of metallic nanoparticles are responsible for many of its anomalous plasmonic properties. While this so-called plasmonic coupling has become a focus of many researches lately, its interaction mechanisms still remain concealed, mainly due to the lack of spectroscopic observations from precisely fabricated samples as well as analytical interpretations. Here, I present light scattering spectra of arrays of silver nanoparticles with gaps of sub-10 nm precision, which are fabricated based on the unique self-organizing property of porous alumina templates. I show that their near- and immediate-zone interactions are manifested in the spectra through analytical formulae derived from first principle. The findings provide a profound base to predict unexplored plasmonic properties such as the relationship between the Q factor of the arrays and their structural characteristics. The results are instrumental in the development of extended plasmonic nanostructures, such as surface-enhanced Raman substrates. In a very lucid way, I have also studied the particle plasmon resonace behavior using light scattering spectroscopy in a binary dielectric media where silver nano-rods are embedded partially in Anodic Aluminum Oxide (AAO) matrix and in air. Here I did a systematic experimental study under a controlled variation of the degree of embedding of nano-rods in AAO matrix. I used Finite Difference Time Domain (FDTD) method to calculate the nature of the silver nano-rod resonance at the experimental conditions. The results have been interpreted based on the Drude model.