Resonant frequencies and their impact on the optical properties materials are investigated. It is shown that the optical response of solids to photo-stimulus can be described predominantly by the vibrational responses of the atomic lattice, bound charge carriers, and free charge carriers within the material. These vibrations are also coupled to electronic and physical properties such as band gap energy and crystal structure. As such, they are an important aspect of material characterization. First, the ultrafast response of GaAs to a 3.1 eV, 10 fs light pulse is examined. The time and density dependence of the coupled phonon and plasmon responses are observed and explained through combined experimental and theoretical methods. Next, infrared through visible light spectroscopy of the transition metal dichalcogenides MoS2, MoSe2 is performed. Niobium and rhenium doped samples of MoSe 2 are also characterized for the first time. The optically thin samples motivate development of a new method for obtaining the single-bounce reflectance from measured reflection and transmission. The broad spectrum reflectance and permittivity of a new material, Bi2Ti2O7 is found for temperatures between 20 K and 300 K. A displacement of the Bi and O’ atoms from the typical pyrochlore structure is supported by the infrared phonons displayed in these optical measurements. Finally the compositional dependence of the optical properties of the pyrochlore Gd2(Mo 1-xTix)2O7 are explored via optical spectroscopy and Kramers-Krönig analysis.
|Advisor:||Stanton, Christopher, Tanner, David|
|School:||University of Florida|
|School Location:||United States -- Florida|
|Source:||DAI-B 78/05(E), Dissertation Abstracts International|
|Keywords:||Bismuth titanate, Coupled phonon-plasmon, Infrared spectroscopy, Molybdenum dichalcogenide, Pyrochlore, Ultrafast|
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