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A7.09 - Pore Shape Control in Porous Nanocrystalline Silicon Membrane 
April 24, 2014   11:30am - 11:45am

Porous nanocrystalline silicon (pnc-Si) membranes were first reported and used for protein separation by Striemer et al. in 2007 [1]. These nanopores are formed during rapid thermal annealing of ultrathin (~ 15nm) amorphous Si films sandwiched between nm-thick SiO2 layers. Subsequent research has been carried out to study and optimize this novel material for applications in separation and cell culture [2-4]. The pore shape is one of the key parameters for separation applications. We report that the temperature ramp up rate during annealing greatly affects the final pore shape. A fast ramp up rate produces pores with very circular shapes whereas a low ramp up rate results in elongated, irregular pores. The interpretation for this phenomenon is related to the crystallization speed since pore formation is associated with Si nanocrystal formation. At low ramp up rates the amorphous silicon film undergoes slow solid state crystallization. Voids are formed at the interface of silicon nanocrystals and the amorphous silicon matrix. These voids move through the amorphous silicon film, and coalesce with other voids, which produces elongated pores. In contrast, at high ramp up rates, amorphous silicon crystallizes very quickly which prevents the circular pores from moving, coalescing and forming irregular pores. TEM movies of pore creation and evolution taken in-situ during annealing confirm our interpretation.[1] C. C. Striemer, T. R. Gaborski, J. L. McGrath, P. M. Fauchet, Nature 2007, 445, 749.[2] D. Z. Fang, C. C. Striemer, T. R. Gaborski, J. L. McGrath, P. M. Fauchet, J Phys-Condens Mat 2010, 22, 454134.[3] T. R. Gaborski, J. L. Snyder, C. C. Striemer, D. Z. Fang, M. Hoffman, P. M. Fauchet, J. L. McGrath, Acs. Nano. 2010, 4, 6973.[4] A. A. Agrawal, B. J. Nehilla, K. V. Reisig, T. R. Gaborski, D. Z. Fang, C. C. Striemer, P. M. Fauchet, J. L. McGrath, Biomaterials 2010, 31, 5408.

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Keynote Address
Panel Discussion - Different Approaches to Commercializing Materials Research
Business Challenges to Starting a Materials-Based Company
Fred Kavli Distinguished Lectureship in Nanoscience
Application of In-situ X-ray Absorption, Emission and Powder Diffraction Studies in Nanomaterials Research - From the Design of an In-situ Experiment to Data Analysis