Date of Award

Summer 2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical/Computer Engineering

Committee Director

Hani Elsayed-Ali

Committee Member

Aleksey Bugayev

Committee Member

Helnet Baumgart

Committee Member

Gon Namkoong

Abstract

The ultrafast fast phenomena that take place following the application of a 120 fs laser pulse on 20 nm antimony thin films and 40 nm nanoparticles were studied using time-resolved electron diffraction. Samples are prepared by thermal evaporation, at small thickness (< 10 nm) antimony nanoparticles form while at larger thicknesses we get continuous thin films.

The samples are annealed and studied by static heating to determine their Debye temperatures, which were considerably less than the standard value. The thermal expansion under static heating also yielded the expansion coefficient of the sample material. Nanoparticle samples gave a very accurate thermal expansion coefficient (11 × 10-6 K-1).

Ultrafast time resolved electron diffraction studies with ∼1.5 ps resolution are performed for both kinds of samples to determine the lattice thermalization time and study the difference in relaxation time between the thin films and nanoparticles. Knowing the Debye temperature from the static heating experiment (144 K for nanoparticles and 148 K for 20 nm thin films), we could measure the temperature rise due to the laser pulse. The thermal pressure and acoustic lattice oscillations are also studied. There was a noticeable delay of 6 ps between the onset of the drop of intensity and the onset of the drop in diffraction ring size, which indicates the propagation of a thermal stress front in the film.

DOI

10.25777/8w6j-aq95

ISBN

9781124973128

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