Oriented Nanochannels for Nanowire Synthesis

Abstract

This thesis aims at the synthesis of oriented nanochannel systems for the synthesis of metallic or semiconducting nanowires. Three different synthesis strategies have been developed. First, horizontal macro- to mesoporous anodic aluminum oxide (AAO) structures with individually addressable channel systems were fabricated in collaboration with the group of Dr. Anna Fontcuberta at TU München. For this purpose, a multi-contact design of aluminum finger structures on silicon wafers was developed. Each finger structure can be individually contacted and between 2 - 5 contacts were generated on a single silicon wafer. The aluminum contacts were electrically isolated from each other, thus each contact can be individually anodized. This way it is possible to synthesize different pore diameters, pore densities, and channel lengths on a single chip. After the anodization, these channels were successfully filled by electro-deposition and thermal chemical vapor deposition. The resulting metal (Au, Cu, Ni, Co) and semiconductor (Te, Si) nanowires embedded within the AAO mold were characterized by SEM and EDX measurements. The second strategy deals with hierarchical channel structures formed from columnar silica mesophases inside AAO membranes. These channels were then used for the fabrication of high-aspect ratio copper, silver, and tellurium nanowires. The resulting wires were structurally and spectroscopically characterized within the host matrix, in the partially dissolved matrix, and completely removed from the matrix with electron microscopy methods. Plan-view images of wires featuring 10 nm diameter within the intact matrix showed the successful replication of the hexagonal arrangement of the columnar mesoporous system. The concept of hierarchical structures within PAA templates was again utilized for the third strategy, where the structural behavior of periodic mesoporous organosilica (PMO) mesophases within the AAO pores was studied. PMO mesophases with different orientations with respect to the alumina pores were obtained; one of the observed mesophases (cubic Im-3m) has not been reported before. After successful template removal, the hexagonal circular mesophase could be used for the synthesis of nanowires by electrodeposition.

• Item Type: Thesis (Dissertation, LMU Munich)
• Keywords: mesoporous silica, nanowires, anodic alumina,
• Dewey Decimal Classification: 600 Natural sciences and mathematics; 600 Natural sciences and mathematics > 540 Chemistry and allied sciences
• Faculties: Faculty of Chemistry and Pharmacy
• Language: English
• Date Accepted: 10. June 2010
• 1. Referee: Bein, Thomas
• Persistent Identifier (URN): urn:nbn:de:bvb:19-117691
• Signature of the printed copy: 0001/UMC 18714