HIGH-PRESSURE MICROFLUIDIC CHEMICAL DEPOSITION: REPLACING THE AIR WITHIN MICROSTRUCTURED OPTICAL FIBERS

Open Access
Author:
Baril, Neil F.
Graduate Program:
Chemistry
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
July 30, 2008
Committee Members:
  • John V Badding, Committee Chair
  • Lasse Jensen, Committee Member
  • Thomas E Mallouk, Committee Member
  • Venkatraman Gopalan, Committee Member
Keywords:
  • optical fiber
  • Silicon
Abstract:
There is currently great interest in advancing both the fundamental technology and underlying science of electronics and photonics. As chemists we can contribute to this area through the synthesis and fabrication of new materials and materials structures with novel or interesting optical and/or electronic properties. Synthesis of materials within templates, in particular, is one powerful tool for realizing this goal. In this work microstructured optical fibers have been employed as templates for the synthesis and organization of materials. High-pressure gas mixtures containing chemical precursors have been configured to flow through the capillaries of MOFs and thermally decomposed depositing materials onto the walls of the capillaries. The deposition of silicon and germanium within the capillaries of various MOF templates has been investigated. The deposition conditions, including temperature, pressure, and concentration, have been refined such that it is possible to deposit solid microwires of silicon and germanium several centimeters in length within the MOFs. Deposition of germanium within a 100 nm capillary over several centimeters has been demonstrated and confirmed by Raman spectra and FESEM cross sections. The thermal annealing conditions to produce high quality crystalline materials without degradation of the MOF integrity have also been investigated. Infiber solid polycrystalline silicon microwire waveguides exhibiting low optical attenuation, 5.8dB/cm at 1.55 μm, and high electron mobilities are demonstrated. This value is the lowest reported for any type of polycrystalline silicon waveguide. Junctions, which are the foundation of semiconductor devices, have been produced within the capillaries of MOFs via sequential deposition of materials. Semiconductorsemiconductor and metal-semiconductor hetero-junctions are demonstrated. Demonstration of such junctions opens the door to the fabrication of many potential in-fiber devices. A traveling furnace platform was constructed for the deposition of uniform layers. Deposition with the traveling furnace is investigated and the formation of a highly uniform layer in a 1 m long 100 μm capillary is presented. The deposition of a silicon-germanium junction with uniform thickness over 1 m in length is demonstrated. The deposition chemistry of silicon carbide and silicon nitride has also been investigated. The ability to tune material composition and optical properties by adjusting the deposition temperature and the concentration of hydrogen gas in the precursor gas mixture is presented. Silicon carbide layers with uniform composition were deposited within a 100 μm capillary using a traveling furnace.