Date Awarded

2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Physics

Advisor

Gunter Lüpke

Abstract

The microscopic motion of hydrogen in solid oxides plays an important role in defect migration and reaction processes. Understanding the vibrational dynamics associated with both hydrogen-oxygen (O-H) bonds and the surrounding ionic environment allows one to better characterize these fundamental interactions. This thesis presents a comprehensive investigation into the vibrational decay dynamics of O-H and O-D stretch modes in crystalline oxides using time-resolved infrared pump-probe spectroscopy.;Measurements of the vibrational lifetimes of hydrogen related local modes in potassium tantalate (KTaO3) and titanium dioxide (TiO2 ) show that the localized O-H vibration is very closely tied to proton transport. In KTaO3 we find the lifetimes to be on the order of a few hundred picoseconds and determine that the vibrational decay is due to a lattice-assisted tunneling process. Furthermore, we identify the assisting phonon and extract the excited-state tunneling rate. In TiO2 we measure the lifetimes at only a few picoseconds. Here, the decay can be described by a classical hopping process. In both cases the absorption-stimulated transfer rate is found to be dramatically larger than spontaneous or thermally activated proton transfer.;These studies provide valuable information regarding the details and fundamentals of hydrogen-lattice interactions in solid oxides. Such insight is valuable for better understanding the role of hydrogen in materials important for a variety of applications ranging from optoelectronics to alternative energy technologies.

DOI

https://dx.doi.org/doi:10.21220/s2-xhww-1m84

Rights

© The Author

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