Formation of High Aspect-Ratio Solid Silicon Wires within Optical Fibers Using High Pressure Chemical Fluidic Deposition

High-pressure chemical fluidic deposition is used for the formation of semiconductor micro and nanowires within the capillary spaces of highly-ordered microstructured optical fibers. We consider deposition of silicon under high pressure flow of a silane/helium mixture within extreme aspect-ratio microcapillaries. Although a complete filling of the microcapillary is ideally desired, experimental observations show that the thickness of the deposited silicon layer varies with axial position. It is shown that, in the case of flowing deposition, the temperature and concentration profiles along the capillary length during deposition lead to the formation of two separate nodes in the deposition profile. The formation of the initial node is shown to be due to an instability resulting from the coupling between flow and reaction. A complete filling of the region between these nodes, several centimeters in length, was achieved by optimizing the deposition conditions. Deposition within sealed capillaries also demonstrated a filling profile possessing a completely filled region centimeters in length.