#### Versatile fabrication of functional nanostructures using patterning processes and their apprications = 다양한 패터닝 공정을 이용한 기능성 나노구조 제작과 그 응용에 관한 연구

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Fabrication of Metal Oxide Nanotube Array Using Silicon-Containing Block Copoly-mers for Their Applications A novel technique was developed for the fabrication of general-use templates with high-aspect-ratio cylindrical nanopore arrays by combining the self-assembly of a Si-containing block copolymer with a bilayer lithography system. A thin film of self-assembled PS-b-PSSi was used as the top layer to enhance the contrast of etch resistance; a thick, underlying SU-8 film facilitated the pattern transfer. The block copolymer quickly self assembled on the SU-8 during solvent annealing in a mixed solvent, resulting in the generation of a dense and well ordered array of perpendicular cylinders. After simple exposure to an $O_2$ plasma, the top layer of PS-b-PSSi acted as a self-hard etch mask, and patterns were transferred into the underlying organic layer. Cylindrical, high-aspect-ratio nanopore arrays, oriented perpendicular to the substrate surface, were generated over a large area. This technique was also applicable to Au, Pt, Cu, and ITO substrates due to the compatibility of SU-8 onto a wide range of substrates. And we have demonstrated that a novel approach for the fabrication of the highly ordered freestanding $TiO_2$ nanotube arrays with various wall thicknesses by applying ALD process to the nanoporous template with high aspect ratios. The high thermal stability of the cross-linked organic template allowed for high-temperature ALD. The easy removal of organic template by a dry etch process followed by calcination produced vertically aligned and highly crystalline anatase $TiO_2$ nanotube arrays without collapse or bundling. Furthermore, the ultrafine thickness tunability of the ALD process made it possible to develop $TiO_2$ nanorods as well as nanotubes with different wall thicknesses We have demonstrated that a novel approach for the fabrication of the highly ordered freestanding $TiO_2$ nanotube arrays with various wall thicknesses by applying ALD process to the nanoporous template with high aspect ratios. We demonstrated the potential of the $TiO_2$ nanotube arrays in the photovoltaic of a blended P3HT:PCBM material by confining it to nanometer-scale volumes and introducing radial electron-collecting contacts into the device active layer. Our device fabrication scheme allows us to separate the beneficial effects of confining the blend and incorporating radial contacts into the bulk heterojunction architecture. The highest efficiency obtained (3.02 %) is a 21.8% improvement over that of benchmark bilayered devices without the nanotube arrays. Such results are encouraging as they provide important proof-of-concept which can be further explored Finally, we present a novel and simple methodology to obtain one-dimensional (1-D) n-ZnO/p-Si nanotube arrays by using combined techniques of block copolymer (BCP) self-assembly, atomic layer deposition (ALD), and inductive coupled plasma (ICP) dry etching. In order to obtain the highly ordered nanotube pattern, we employed a self-assembled Si-containing poly(styrene-4-(tert-butyldimethylsilyl)oxystyrene) (PS-b-PSSi) BCP on SU-8/p-Si wafer as a template. After n-ZnO formation on the self-assembled BCP template by ALD, ICP etch-back process was performed to produce well-defined n-ZnO/p-Si nanotube arrays with diameters of 52 nm (outer) and 25 nm (inner) using the huge difference of etching rates (1:15) between ZnO and Si in $CF_4/Ar$ plasma. We also successfully obtained an n-ZnO/p-Si nanorod pattern by precisely controlling the ALD cycles and ICP etching time. The electrical property was measured by conductive atomic force microscopy (C-AFM), showing a typical rectifying behavior of diode. This simple and useful approach provides a very convenient route to fabricate high-density nanodiode patterns without using high-cost photolithography. Fabrication of Gold Nanostructures for Surface Enhanced Raman Scattering Substrate Hierarchical cone-shaped nanoporous gold (C-NPG) nanostructure with larger scale cone-shaped gold coupled to smaller scale nanoporous gold have been fabricated via nanosphere lithography and reactive ion etch as a simple and cost-effective method for use as reliable and reproducible surface enhanced Raman scattering (SERS) substrate. Compared to the nanoporous gold film and cone-shaped solid gold array the significantly enhanced SERS signal from C-NPG. The multi-scale C-NPG arrays not only provide surface plasmon resonances at the cone-shaped nanostructures, but an enormous number of ‘hot spots’ in the nanopores (sub 10 nm) within each nanocone. The C-NPG SERS substrate reveal large area uniform enhancement factor about 10x and a detection limit of 10-xx M The finite-difference time-domain simulation provide clearly evidence a electromagnetic field enhancement on the multi-scale C-NPG arrays. Our studies exhibit that the hierarchical nanostructure enhance the SERS effects synergistically by localized Plasmon resonance in the larger scale cone-shaped nanostructures and small scale nanoporous gold. Dendrimer stabilized gold nanoparticles (Au-Den) densely deposited on reduced graphene oxide (rGO) were prepared by a facile solution based method for a highly reliable and robust surface enhanced Raman scattering (SERS) substrate. Au-Den was selectively attached on the surface of rGO by noncovalent interactions between the Au capping dendrimer and $sp^2$ carbon of the graphene surface. Au-Den/rGO exhibits the outstandingly stable and highly magnified Raman signal with an enhancement factor (EF) of $2.5 \times 10^8$ that enables detection of R6G dyes with concentration as low as 10 nM, retaining 93% and 95 % of the Raman signal intensity even for 1 hour of laser exposure and after one and half year, respectively. The remarkable stability and enhancement originated not only from a simple combination of the electromagnetic and chemical mechanism (EM/CM) of SERS but also from intensified packing density of stable Au-Den on the graphene substrate due to the firm binding between the dendrimer capped metal nanoparticles and the rGO substrate. This method is not limited to the gold nanoparticles and G4 dendrimer used herein, but also can be applied to other dendrimers and metal nanoparticles, which makes the material platform suggested here superior to other SERS substrates.
Kim, Jin-Baekresearcher김진백researcher
Description
한국과학기술원 :화학과,
Publisher
한국과학기술원
Issue Date
2016
Identifier
325007
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 화학과, 2016.2,[xii, 107 p. :]

Keywords

Block copolymer; self-assembly; nanoporous template; atomic layer deposition; reactive ion etch; nanotube array; nanosphere lithography; nanoporous gold; surface enhanced Raman scattering; photolithography; 블록공중합체; 자기조립; 나노기공 템플레이트; 원자층 증착; 건식 식각; 나노튜브 배열; 나노구형 리소그래피; 골드 나노기공구조; 표면증강라면산란; 포토리소그래피

URI
http://hdl.handle.net/10203/242143