Preparation Of New Structure Anodic Aluminum Oxide And Research On Template Effects For Channel Growth

Anodic aluminum oxide (AAO) is a porous membrane, which can be obtainedvia the anodic oxidation of aluminum in the suitable acidic or alkaline electrolyte. Anideal AAO template is supposed to be a membrane with close-packed highly orderedhexagonal nanochannels like a honeycomb. In the anodic oxidation process, thevarious structure parameters can be adjustable and controlled with change of theanodic oxidation conditions, and channel is straight, aperture uniform. Owing to theseadvantages, AAO is at present one of the most widely used templates. Currently arelatively mature two-step anodization method can realize such an organized structurein nanoscale. One of the most fascinating properties of AAO is attributed to its specialhexagonally arrayed channel structures. The pre-patterning of periodicnanoindentations on aluminum substrates is supposed to be an effective strategy,discrepancies in period will disappear at the micrometer scale. Lithography methodsfor pre-patterning aluminum substrates include hard stamping method, focused ionbeam, nanosphere lithography (NSL).A highly ordered and hierarchically structuredanodic aluminum oxide (AAO) template was prepared by pre-patterning an aluminumsubstrate surface with a nanoindentation array via the nanosphere lithography (NSL)and following an anodization treatment by our group. Then the novel structure willextend the development and application on new field. How to achieve the newstructure AAO via the anodization of pre-patterned aluminum substrate remains unresolved.In this thesis, adopting NSL method, building templates, new structure of theAAO templates ate prepared, and the influence of the pre-template structure for itsforming is studied. In addition, by choosing the alkaline electrolyte, the AAOmembranes with small pore interval is obtained, to broad the AAO pore intervalcontrol range. Specific content is as follows:Sodium hydroxide is selected as electrolyte for preparation of AAO with smallpore interval, to broad the AAO pore interval control range. First,0.3M sodiumhydroxide solution was as reaction liquid electrolyte, in order to prevent the excessivecorrosion of AAO in the process of anodization, Volume ratio of50%ethanol wasdoped with in the electrolyte, optimized voltage,20V was chosen for anodicoxidation preparation of AAO. The AAO with10-20nm pore interval is obtained, tobroad the regulating scope of AAO pore interval.Adopting NSL method, nanosphere array template is built-in under the surface ofaluminum for the preparation of AAO to obtain a new type of structure, triangularprism shape pore of hierarchically structured AAO. First a polystyrene (PS)nanosphere monolayer was formed on the aluminum surface. Then, the PSnanosphere monolayer was etched with oxygen reactive ion etching (RIE) in order toreduce the diameter of the PS spheres. A fully thick aluminum film was deposited onthe etched PS nanosphere monolayer by way of vacuum evaporation. After theseprocesses, the nanosphere array was encased under aluminum surface. A built-intemplate was made before the process of anodization. A new hierarchically structureAAO was obtained. Its surface was preserved periodic structure of the originalnanosphere array, and a triangular prism shape pore array was formed according to thehexagonal arrangement to form a new periodic structure. In addition, the built-intemplate not only changed the AAO pore distribution but also have the role to expandpore interval of the AAO.Combining NSL method with oblique angle deposition (OAD), banded structure is constructed in the aluminum surface for the preparation of AAO.A kind of AAOmembrane with banded pore distribution and a kind of AAO membrane with diamondpore distribution. First, a PS nanosphere monolayer was formed on the aluminumsurface. Then, the PS nanosphere monolayer was etched with oxygen RIE in order toreduce the diameter of the PS spheres. An aluminum film was deposited on the etchedPS nanosphere monolayer by way of OAD. The aluminum substrate underwentultrasonic treatment in an ethanol/water solution to remove PS nanospheres. Afterthese processes, a pre-patterned nanoband structure was obtained. The new structureAAO membranes were obtained after the process of anodization. According todifferent directions of vacuum evaporation, the pore distributions of AAO werebanded or diamond. And the template structure would induce channel priority form atthe concave of the structure and inhibit the formation of channels in the regionalbetween template structures.