Semiconductor nanowires have recently emerged as a new class of materials with significant potential for the advancement of understanding of fundamental physics and for new applications in device physics. This research in this project has brought together expertise in state-of-the-art semiconductor nanowire growth, in modeling of these structures, and in experimental efforts that will advance the understanding of semiconductor nanowires which have a core and a shell composed of the same material but grown with two different crystalline symmetries or composed of two different materials with different lattice constants.  Both of these configurations can lead to remarkable phenomena with new technological opportunities, including unique solar cell designs.

Intellectual Merit:

We have designed, grown and then fabricated and characterized devices based on these two configurations of semiconductor nanowires.  We have used both optical techniques, including the new technique of transient Raleigh scattering as well as photocurrent spectroscopy to advance the understanding of the wurtzite crystalline structure of the semiconductor nanowire indium phosphide (InP), a structure not found in nature.  We have explored the energy levels of the valence band as well as a second conduction band, measurements required in order to explore suitable device configurations.  Strained core shell nanowire configurations were found to have a large number of defects and so work was pursued on the two materials GasAsSb/InP which are largely unstrained, have appropriate bandgaps with spatially separated electrons and holes, and which were measured to be coherent and defect-free structures.  Fourteen papers were published on this work providing new information and techniques for utilizing nanowire heterostructures for new technologies.

Broader Impacts:

This research has strong societal impacts because of the potential for designing high-efficiency solar cells for reducing dependence on fossil fuels. The increased fundamental knowledge of electronic structure and transport in these nanowire structures also significantly impacts nanowire electronics and nanowire-based chemical or biological sensors.  As part of this program we have trained both undergraduate and graduate students in advanced theoretical and experimental nanotechnology techniques.   Both graduate and undergraduate students have been involved in outreach to the public as part of the Cincinnati Museum Center, and worked with students in elementary to high schools, providing an introduction to scientific research into nanostructures.

Last Modified: 01/12/2016
Modified by: Leigh M Smith