| Summary: | 碩士 === 國立交通大學 === 材料科學與工程學系奈米科技碩博士班 === 101 === Nanoporous anodic aluminum oxide (AAO), a typically self-ordered nanopore material featuring of ordered high-aspect-ratio channels, has been widely used for the development of various functional nanostructures such as nano-magnetic memories, nanosensors, nanophotonic devices, nano-energe devices and nanoelectronic devices. The conventional fabrication of self-ordered Al2O3 pore arrays so-called mild-anodization (MA) requires several days of processing time and the self-ordering phenomenon occurs only in narrow process windows. Recently, a new attempt for AAO process, hard-anodization (HA), has successfully demonstrated. The HA process offers substantial advantages over conventional anodization processes in terms of processing time, allowing 3000% faster oxide growth with improved long-range ordering of the nanopores. However, compared with H3PO4 HA by us, AAO films obtained in suffer from poor mechanical properties because of structural cracks and defects, while uniformly sized parallel channels and irregular top surface with ‘‘pore in pore’’ structures cannot be exclusive in those using C2H2O4 HA process.
In this work, we report an innovative H3PO4-based HA process for long-range ordered and high growth-rate alumina membranes. The various anodization parameters including applied voltage, electrolyte concentration, and temperature which have significant impact on the morphology of AAO will be discussed deeply. The self-ordering behavior in nanoporous AAO using H3PO4 HA process unlike conventional methods is investigated at applied voltage from 160 to 270 V without pre-anodization step. The applied voltage via the interpore distance is linearly relationship at anodization voltages from 160 to 210 V and presents an interpore distance from 325 to 390 nm. Unexpectedly, the linearly relationship will vanish and saturate from 220 to 270 V, which may result from the jour-heat accumulation supported by the chronoamperic response. By using advantages of H3PO4 HA method to fabricate taper AAO templates, we can obtain highly ordered and high-aspect-ratio taper AAO templates and then the tapered acrylic (PMMA) nanostructure can be obtained by spin coating or hot embossing. Moreover, we find that the PMMA surface with taper nanostructure coating fluoalkysliane display superhydrophobic phenomenon which can be served as a self-cleaning surface. The innovative AAO template fabrication is simple and cost-effective, and is of great value for applications in diverse areas of nanotechnology.
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