Nanostructure Designs Derived from Oxide-based Sacrificial Materials

Materials with various nanostructures exhibit distinct electrical, magnetic, and optical properties compared to their bulk counterparts. Despite significant progress in developing diverse nanomaterials synthesized either by solution or vapor-based deposition method. Challenges persist in fabricating nanostructured materials for integration on chips and flexible substrates. The goal of this dissertation is to design and fabricate nanostructured thin films by introducing sacrificial oxide materials either as a phase in the vertically aligned nanocomposites (VANs) or as a buffer layer for the transfer of VANs. Two different sacrificial oxide materials are selected here, i.e., La₀.₇Sr₀.₃MnO₃ (LSMO) and Sr₃Al₂O₆ (SAO), since they can be dissolved in water or etched in mild acid solution. Using pulsed laser deposition (PLD), both sacrificial oxide materials can self-assemble into a pillar-in-matrix form in VAN structures, where highly textured nanomaterials can remain on the desired substrate and flexible materials.

This dissertation consists of a general review of relevant background and experimental approaches, followed by four research chapters to present the results of various nanostructures achieved by the sacrificial oxides in VANs. The first chapter involves synthesizing SAO-Au VAN, where metal can be either in nanoparticle form or nanopillar form, depending on the laser frequency for the deposition. In the second chapter, SAO-CeO₂ VAN was synthesized, where the concentration of CeO₂ varies from low to high. Different CeO₂ nanostructures, ranging from rounded nanopillars and faceted nanopillars to nanomaze structures, were synthesized by dissolving the SAO phase in the films. Next, to investigate the multi-sensing capabilities of the VAN thin film, SAO was deposited as a buffer layer for BTO-Au VAN layer. After integrating BTO-Au VAN into a flexible polymer, the mechanical properties of the VAN thin film and its potential applications in multi-functional sensors are demonstrated. Lastly, to expand the possibilities of other sacrificial oxide materials and nanostructures, LSMO-Au was synthesized using oblique angle deposition to obtain zig-zag shape of Au nanostructure after acid etching of LSMO.