Nanofabrication based on self-ordered porous anodic alumina

Self-ordered porous nanostructures have attracted a lot of attention because they can be used as starting materials in both the top-down and bottom-up approaches. The typical dimension of pores can be varied from a few nanometers to many micrometers. The highly-ordered patterns can be transferred to desired materials by the top-down method. In the bottom-up approaches, the porous substrates can be used as a template to fabricate nanomaterials with narrow size distribution.;One of the most widely used porous substrates is self-ordered porous anodic alumina (PAA). This dissertation describes the control over the morphology of PAAs and their applications in both top-down and bottom-up approaches for preparing nanostructures such as the template synthesis and the pattern transfer, respectively.;First, a highly self-ordered porous anodic alumina has been fabricated by the anodization of Al in appropriate acidic solutions. It exhibits narrow distributions in pore size, pore density, porosity and pore depth. Different types of PAAs were prepared for the template synthesis and the pattern transfer, respectively. For the former, PAA was attached on Al and the pore size was controlled by the post etching treatment. For the latter, free standing PAA's were prepared and used as a mask. Two different pore sizes (∼80 nm and ∼50 nm) were prepared under the different anodization voltages. The thickness of PAA showed a good linear relationship with the anodization time.;In the template synthesis study, the channel shape of PAA was tuned from straight-through type to branched one. Bifurcated silica nano tubes with a control over the length of each segment were fabricated from the template. In addition, straight-through silica nano test tubes were filled with gold by using the gold electroless plating. The aspect ratio of gold cores was controlled by the inner space of silica test tubes. The optical properties of gold-filled silica nano test tubes were investigated.;In the pattern transfer study, the PAA pattern was successively transferred onto silicon via an Ar plasma etch method. The pore depth linearly increased as the etch time increased. The porous silicon substrates were used as platforms in Laser Desorption/Ionization Mass Spectrometry. The effect of pore depth on the ionization efficiency was investigated. Significant improvement in the ionization was observed by increasing the pore depth from 10 nm to 30 nm.