Thesis (Ph. D.)--University of Rochester. Dept. of Electrical and Computer Engineering, 2012.
Membranes made of an ultrathin porous nanocrystalline silicon (pnc-Si) film are well suited for many applications due to their key attributes, including thinness (15-30 nm), pore diameters (5-80 nm) and porosity (0.5-15 %). This thesis in an investigation into the unique properties of pnc-Si material in the context of gas transport, sensing and nanofluidics. The first part of the thesis investigates the flow properties of the material, and shows that membranes based on pnc-Si exhibit gas permeances that are several orders of magnitude higher than in other similar membranes. The components of the flow due to ballistic transport and transport after collision with the pore walls are quantified as a function of pore diameter. In addition, we demonstrate that changing the pore interior from silicon to carbon leads to flow enhancement resulting from a change in the nature of the molecule-pore wall interactions. Integrating the pnc-Si material into nanoscale devices is considered next. A novel approach to the fabrication of a capacitive sensor for organic vapor detection using a pnc-Si membrane metallized with gold as a porous electrode is presented. We show that the ultrathin nature of the pnc-Si allows for fast analyte vapor permeation to the receptor material. Finally, we describe a technique for effectively depositing gold electrodes on different sides of the membrane that is used to fabricate an ultrathin electroosmotic pump. These metallized pumps are shown to achieve significantly higher flow rates compared to bare pnc-Si membranes when low voltages are applied directly across the membrane.
