| Summary: | 博士 === 國立清華大學 === 奈米工程與微系統研究所 === 99 === Nanotechnology has been developed as a reliable technology for producing minimal components to perform more precise functions. In particular, the availability of nanolithography and nanostructure fabricating processes is important in the fields of photonics, electronics, biotechnology, and metamaterial. In our research, we present a generic and efficient chemical patterning method, compared with conventional photolithography this approach is without diffraction limit. Base on this approach, we expand a method for synthesizing three-dimensional (3D) gold and silver nanoparticle supercrystal films. Since nanoparticles have unique properties of surface plasmon, this technology will offer a pathway to designer plasmonic metamaterials.
We fabricate chemical pattern based on local plasma-induced conversion of surface functional groups on self-assembled monolayers. Here, spatially controlled plasma exposure is realized by elastomeric poly(dimethylsiloxane) (PDMS) contact masks or channel stamps with feature sizes ranging from nanometer, micrometer, to centimeter, and an achievable resolution is down to the 50 nm range. This chemical conversion method has been comprehensively characterized by a set of techniques, including contact angle measurements, X-ray photoelectron spectroscopy (XPS), scanning photoelectron microscopy (SPEM), scanning electron microscopy (SEM), and scanning Kelvin probe microscopy (SKPM). In particular, XPS and SPEM can be used to distinguish regions of different surface functionalities and elucidate the mechanism of plasma-induced chemical conversion.
Based on plasma-induced conversion, we expand a simple and efficient method for synthesizing large-area (>cm2), three-dimensional (3D) gold and silver nanoparticle supercrystal films. In this approach, Janus nanoparticle (top face solvent-phobic and bottom face solvent-philic) films with an arbitrary number of close-packed nanoparticle monolayers can be formed by using layer-by-layer (LbL) assembly from suspensions of thiolate-passivated gold or silver colloids. Furthermore, we demonstrate that these films can act as true 3D plasmonic crystals with strong transverse (intralayer) and longitudinal (interlayer) near-field coupling. In contrast to conventional polyelectrolyte-mediated LbL assembly processes, this approach allows multiple longitudinal coupling modes with a conspicuous spectral dependence on the layer number. We have found a universal scaling relation between the spectral position of the reflectance dips related to the longitudinal modes and the layer number. This relation can be understood by the presence of a plasmonic Fabry-Pérot nanocavity along the longitudinal direction, allowing the formation of standing plasmon waves under plasmon resonance conditions. The realization of 3D plasmonic coupling enables broadband tuning of collective plasmon response in a wide spectral range (visible and near-infrared) and a key pathway to designer plasmonic metamaterials.
|
|---|
