A&S Graduate Studies
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A&S Graduate Studies
[PAST EVENT] Elizabeth Lee Radue, Physics - Oral Exam for the Ph.D.
June 28, 2016
10am - 1pm
Abstract:
Vanadium dioxide is an intensely studied material, since it goes through an insulator-metal transition at a critical temperature just above room temperature at 340~K. The dramatic change in conductivity and the easily accessible transition temperature makes it an attractive material for novel technologies. Thin films of VO2 have a reversible transition without any significant degradation in contrast, and depending on the microstructure of the films, the properties of the transition are tunable. In this work, I study the dynamics of the insulator-transition in thin films grown on different substrates using a pump-probe configuration. The energy needed to trigger the transition, as well as the time constants of the change in reflectivity are affected by the strain in the VO2 films. I also characterized the samples using Raman spectroscopy and XRD measurements in order to identify what underlies the differences in behavior. Finally, in collaboration with Dr. Yamaguchi's group at RPI, I show that it is possible to trigger the transition using a THz pulse that directly pumps energy into the lattice, and at lower energies than needed to pump films by photoinducing the electrons across the band gap.
Bio:
Elizabeth Radue was born in 1987 in the District of Columbia, and grew up in Mount Airy, MD. As a young girl she dreamed of being a writer/astronaut/ballerina/scientist/dolphin trainer; she figures one out of five isn't bad. She attended Sandy Spring Friends School from 1992-2005. She graduated from Mount Holyoke College cum laude in 2009 with a B.A. in physics. She entered William & Mary in Williamsburg, Virginia in Fall 2010 and joined Irina Novikova's research group in the summer of 2011. She has been working on the vanadium dioxide project in collaboration with Ale Lukaszew's research group.
Vanadium dioxide is an intensely studied material, since it goes through an insulator-metal transition at a critical temperature just above room temperature at 340~K. The dramatic change in conductivity and the easily accessible transition temperature makes it an attractive material for novel technologies. Thin films of VO2 have a reversible transition without any significant degradation in contrast, and depending on the microstructure of the films, the properties of the transition are tunable. In this work, I study the dynamics of the insulator-transition in thin films grown on different substrates using a pump-probe configuration. The energy needed to trigger the transition, as well as the time constants of the change in reflectivity are affected by the strain in the VO2 films. I also characterized the samples using Raman spectroscopy and XRD measurements in order to identify what underlies the differences in behavior. Finally, in collaboration with Dr. Yamaguchi's group at RPI, I show that it is possible to trigger the transition using a THz pulse that directly pumps energy into the lattice, and at lower energies than needed to pump films by photoinducing the electrons across the band gap.
Bio:
Elizabeth Radue was born in 1987 in the District of Columbia, and grew up in Mount Airy, MD. As a young girl she dreamed of being a writer/astronaut/ballerina/scientist/dolphin trainer; she figures one out of five isn't bad. She attended Sandy Spring Friends School from 1992-2005. She graduated from Mount Holyoke College cum laude in 2009 with a B.A. in physics. She entered William & Mary in Williamsburg, Virginia in Fall 2010 and joined Irina Novikova's research group in the summer of 2011. She has been working on the vanadium dioxide project in collaboration with Ale Lukaszew's research group.