The Nanostructure of Hydrogenated Nanocrystalline Silicon Thin Films

Kristin Kiriluk

The environmental, cost, and political aspects of conventional energy sources have increased the interest in renewable energy research. Renewable energy research, especially in photovoltaics, has created a push for new materials and nanotechnology is currently a primary focus. The most familiar of the nanomaterials, hydrogenated nanocrystalline silicon (nc-Si:H) is used in tandem with amorphous silicon (a-Si:H) in multi-junction solar cells. A complicated, heterogeneous material of crystallites suspended in an a-Si matrix, nc-Si:H has less light-induced degradation than a-Si:H and is cheaper to make than crystalline silicon. Structural and electronic characterization of nc-Si:H help to explore its unique opto-electronic properties. Magnetic resonance experiments show that crystallite interfaces play a role in the increased stability of these films by allowing the carriers to reach the crystalline phase from the a-Si matrix before they fully thermalize. X-ray scattering experiments combined with nuclear magnetic resonance experiments show that hydrogen, which plays an important role in the quality of a-Si:H thin films, also serves to passivate these interfaces. Understanding these characteristics in nc-Si:H may lead to a greater understanding of similar characteristics in other nanostructures such as quantum wires or dots.

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