Template-directed high-pressure growth of single-crystal wires within microstructured optical fibers

Microstructured optical fibers (MOFs) have received considerable recent interest due to their novel optical guiding properties and interesting structural design. The structure of these fibers possess capillary holes extending axially within the fiber cladding, which also presents the opportunity for material infusion and the potential for multifunctional optoelectronic devices. Several devices have been realized using gases and liquids in as-drawn fibers, but there are few examples of solid-state material infusion into the capillaries and only one in as-drawn fibers. The research presented in this thesis represents the first demonstration of template-directed, single-crystal wire growth using high-pressure gas. It is also the first demonstration of this type within an extreme aspect-ratio silica capillary fiber, which could lead to a number of technologically innovative developments.;Single-crystal silicon wires were grown within silica capillary MOFs using the well-known vapor-liquid-solid (VLS) technique. VLS requires the presence of a metal catalyst, which has a low eutectic temperature with silicon. Gold serves this purpose well and was deposited by a technique created in our laboratory called laser-assisted supercritical fluid deposition (LASCFD). The single-crystal wires were analyzed using optical microscopy and Raman spectroscopy while still encased in the MOF. Femtosecond laser micromachining and buffered-oxide etching were used to remove the single-crystal microwire for analysis by scanning electron microscopy and focused-ion-beam (FIB) milling was used to prepare samples for transmission electron microscopy. The FIB thinned microwires exhibited both <111> and <112> growth directions, which is consistent with previous reports. A number of processing and experimental conditions including temperature, pressure, and gold deposition are examined for their impact on growth of long, single-crystal microwires.