Fabrication and application of self-assembled functional nanostructures

Abstract

Fabrication of structures at nanometer scale is a key factor for the investigation of nanoscience and nanotechnology that requires delicate and sophisticated techniques to build nanostructures, especially 2-dimensional (2D) thin film systems. Photolithography is a conventional, but powerful tool in the area; it is, however, limited owing to its high-cost and complication. As a result, there is an evolution of lithography technique, with the appearance of new lithography methods used for typical purposes. Colloidal lithography is recently employed thanks to its facility in producing 2D functional nanostructures on large scale substrates. In this work, we apply the colloidal lithography to fabricate and study two types of nanostructures: noble metal triangle array and titania nanocone array. Self-assembled silica nanosphere monolayer built by Langmuir-Blodgett trough is combined with electron beam evaporation to produce the noble metal triangle arrays, or with dry etching to shape the TiO2 nanocone structures. The system of platinum triangles on SrTiO3 or TiO2 layer was characterized by Atomic Force Microscopy (AFM), indicating a potential model in study of metal-oxide interfaces at nanoscale, whereas the UV-VIS-NIR spectra of gold triangles show surface plasmon resonance phenomenon. Meanwhile, the TiO2 nanocone arrays were investigated by Scanning Electron Microscopy (SEM) and AFM to observe the morphology variation of the nanopatterned samples, or by X-ray Diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) to study the change in crystal structure and chemical composition of the samples after the dry etching process. In addition, static contact angle measurements on the modified TiO2 layers exhibit a tunability of hydrophilicity or hydrophobicity, which results from the change in roughness and geometry of the samples. Self-assembled nanopatterning may bring the advanced scheme of multifunctional transparent layers with photocatalytic and self-cleaning...