Self-Assembling Of Polymer Film On Patterned Substrates And Its Applications

Thin film is widely used in both technological applications and scientific investigations,the study of its rupture mechanism would enable us to predict stability conditions for practical use,and to develop peculiar microstructures simultaneously.While 3D arrays of metallic nanocavities exhibit their remarkable and unique optical properties due to the excitation and coupling of localized and delocalized surface plasmons,fabrication techniques that are capable of forming large area micro-nano structures rapidly and economically have been the focus of recent researches,for the incompatibility between controllability and efficiency in traditional micro processing technologies.In this thesis,we investigate the self-assembling process of PS and PMMA/PS films on physically patterned substrates to repeatedly prepare large area arrays of polymer microstructures,which are used as masks to fabricate arrays of 3D mushroom-like metallic microcavies with subsequent pattern transfer techniques.The main parts of this thesis are included as follows:1.We investigate the influence of physically patterned micro holes on the self-assembling process of PMMA/PS blend films spin-coated on silicon substrates.PS/PMMA blend films with weight ratio 1:1 are ruptured through spinodal dewetting on a flat silicon substrate,as for blend films on patterned substrates,the holes change local surface energy and serve as artificial initial nuclei leading to the nucleation process,whose influence is confined.When the lattice distance between holes is large,the PS/PMMA blend film is ruptured mainly through spinodal dewetting,during which the distribution of polymer droplets is affected by adjacent holes.However,nucleation hollows originated from boundary of holes dominate the self-assembling process,quickly encounter each other,and confine the polymer in the center of interstice between micro holes,when the lattice distance is small.2.The self-assembling process of PS monolayer films on periodically excavated silicon substrates is studied,the role of micro holes during the annealing progress is further confirmed comparing with PS/PMMA blend film system.PS monolayer film on silicon substrates basically rupture through nucleation,and the distribution of microstructure after annealing is affected by the initial nuclei,which can be efficiently controlled by the patterned holes.In contradiction to the bilayer system for blend film,PS film is dewetting on SiOx substrates,the nucleation hollows can spread over a very large area.It develops into arrays of PS microspheres as long as the lattice distance is smaller than the average distance between spontaneous nuclei,which is more suitable for the preparation of a perfectly ordered array of droplets over a large scale.And the interaction between polymer droplets and holes during the annealing process requires further investigation.3.We report a unique procedure for fabricating arrays of 3D mushroom-like metallic microcavies.It utilizes the self-assembling structure of the polymer films as templates and involves pattern transfer techniques like reactive ion etching(RIE)and metal evaporation.Such a cavity significantly enhances the light transmission through arrays of holes despite the opaque disk of the metal cavity blocks the direct transmission of electromagnetic wave.4.We demonstrate the influence of structure parameters on the optical properties of 3D metal microcavities,which are prepared by electron beam lithography(EBL).Height and diameter of the cavity change the morphology of silicon conical between the metal disk and hole,which determines the effective dielectric constant,and eventually tailors the localized resonance,respectively.The coupling of localized resonance with delocalized surface plasmons greatly enhances light transmission.However,it makes the transmission peak significantly redshift,when the localized resonance frequency approaches the delocalized surface plasmons.And the transmission of electromagnetic waves with higher frequency than the localized resonance is restrained.