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Nanoorganization and device fabrication (carbon nanotubes) by vertical Porous Anodic Alumina Templates

Bernd Marquardt
Abstract : This thesis is devoted to the study of vertical Pourous Anodic Alumina templates (PAA) and the application thereof for nanoorganization and device fabrication. Our principle objective was to develop an anodization method of Al that allows a reproducible fabrication of PAA offering the possibility to create complex porous nanostructures as well as the organization of nanomaterials. The PAA fabrication, i.e. the anodization process, has been studied in detail on various substrates on which initially an Al layer has been deposited. We have been able to control the fabrication rate of PAA precisely. PAAs have been fabricated using highly acidic anodization acids at low temperature, by which pore diameters down to 4.2 nm and pore densities up to 7.2*1011cm-² could be obtained. Further, we have developed a unique approach to control the barrier layer at the pore bottom of PAA applying an exponential anodization voltage decrease. This allows to vary and to control precisely the thickness of the barrier layer including the possibility to control the uniformity and distribution of the barrier layer thickness. Based on the fundamental control of PAA fabrication, we have been able to develop an electrodeposition technique inside PAA that allowed us to deposit Ni-particles of adjustable size (from about 10 nm to 2.5 μm) at predetermined deposition densities in the range of 2.3 109 cm-2 to 7.1 x 1010 cm-2 inside PAA with a pore diameter of 40 nm. The CNT growth was studied inside PAA and on PAA patterned surfaces. The variability of the deposited growth catalyst particles allowed us to vary the density of grown CNTs. This was the basis for the fabrication of CNT field emission samples, by which field emission of 1 mA/cm² has been realized. Last but not least, we have demonstrated that PAA can be used as etching mask for multilayer structures allowing to create nanoporous multilayers by anisotropic etching. This might open the way for new bottom-up devices like a vertical transistor based on CNTs or Si-nanowires.
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Submitted on : Thursday, April 1, 2010 - 8:00:00 AM
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Bernd Marquardt. Nanoorganization and device fabrication (carbon nanotubes) by vertical Porous Anodic Alumina Templates. Physics [physics]. Ecole Polytechnique X, 2009. English. ⟨pastel-00005877⟩

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