Baril, N.F., Gopalan, V., Badding, J.V., Krishnamurthi, M., Temnykh, I., Sazio, P.J.A., Sparks, J. and He, R.
High pressure thermal chemical deposition of a Si-H from Silane within microstructural optical fibers
At 2009 MRS (Materials Research Society) Fall Meeting.
30 Nov - 04 Dec 2009.
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We report a simple high pressure thermal chemical deposition technique capable of infiltrating high aspect ratio structures such as microstructured optical fibers with a-Si:H tubes and wires. High quality films and structures of a-Si:H are generally produced via PECVD, or hot wire CVD. However, because these techniques rely on remote generation of reactive radicals for deposition they are not suitable for the infiltration of deep high aspect ratio structures.
Template organization of materials is a powerful tool for developing new and exciting functionalities and light matter interactions. We show that thermal deposition from silane at temperatures as low as 400°C is possible when using high pressures. Raman and IR spectroscopy give confirmation to the presence of hydrogen in the deposited material. Without optimization of the deposition process we have already achieved optical loss values at 1.55 µm that are greater than a 20 fold improvement as a result of the hydrogenation. The best non-hydrogenated microwires deposited under similar pressure conditions have losses of 17dB/cm, we have already achieved loss values as low as 3dB/cm. Generally high pressure pyrolysis of silane leads to the formation of Si fines that are a result of gas phase homogeneous reactions.
We have found that the increased surface area to volume ratio within high aspect ratio templates such as the capillaries of microstructures optical fibers favors heterogeneous surface deposition allowing the formation of highly conformal structures and solid micro wires centimeters in length. We have investigated the deposition within fused silica microstructured optical as well as polyimide and PTFE substrates. Infiltration of a-Si:H into high aspect ratio structures would enable the production of waveguides capable of long, intense light matter interactions. Such interactions could be exploited for the production of new in-fiber photonic, photovoltaic, and optoelectronic devices that would, for example, allow manipulation of light in transmission.
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