Irene Goldthorpe
Department of Materials Science and Engineering
Advisor: Prof. Paul McIntyre
Thursday, August 13th, 10:00 am (refreshments at 9:45 am)
Location: McCullough 115
ABSTRACT:
Because semiconductor nanowires possess a variety of technologically useful properties and can be synthesized with relative ease, they are attractive candidates for a wide range of electronic, optical, sensing, and energy applications. The first part of this talk will focus on germanium nanowires, because of germanium's compatibility with standard integrated circuit fabrication processes, its high electron and hole mobilities, and the low temperature required for germanium nanowire growth. The chemical vapor deposition of epitaxially-aligned germanium nanowires with uniform diameters between 5 and 50 nm will be discussed. Next, I will demonstrate the synthesis of a radial heterostructure, where silicon is heteroepitaxially deposited around a germanium nanowire. This silicon shell passivates the germanium nanowire surface, creates an electronic band offset to confine holes away the surface where they can scatter or recombine, and induces strain which could allow for the engineering of properties such as carrier mobilities and band gap. Detailed transmission electron microscopy and x-ray diffraction characterization of various Ge-core/Si-shell nanowire samples show that, analogous to planar heteroepitaxy, surface roughening and misfit dislocations relax misfit strain. Lessons learned generated strategies to avoid the strain-induced surface roughening that promotes dislocation nucleation, resulting in the fabrication of metastably strained, dislocation-free core-shell nanowires.
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