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Quantitative Prediction of Elastic and Anelastic Phenomena on the Nanometer Scale

Author
Ustunel, Hande
Abstract
In the past two decades, nanometer scale devices have become increasingly
important in various scientific and technological applications such as
sensors, actuators and storage devices. This thesis presents
a theoretical exploration of some of the vibrational properties of such
devices, with an emphasis on quality factor, the fraction
of energy lost per period of oscillation in a vibrating system.
The thesis introduces a new method for obtaining the ground state structure
of defects by looking at their mechanical response. This method involves
calculation of the activation volume tensor of the defect using
reliable ab initio techniques. As an application, results are
presented for the activation volume tensor of a divacancy in
silicon, a defect commonly introduced in the fabrication stages of silicon
actuators. Comparison of the activation volume tensor to experimental
values leads to an unambigious identification of the ground state of this
defect, which has proved elusive in the literature to date. Finally, the
calculation of the mechanical energy loss caused by divacancies in a silicon
oscillator is given.
The thesis then turns to the calculation of the electronic mean-free path
in carbon nanotubes under high-bias. Electron-phonon interactions have been
found to have a considerable effect in the determination of the electron
mean-free path. We determine the mean-free path of the nanotubes in the
presence of various phonon modes that cause scattering of electrons. The
thesis concludes with a consideration of the vibrations of suspended
nanotubes, exploring first the dependence of the vibration frequencies on
such factors as downward force and built-in slack in the nanotube and then
turning to a fundamental loss mechanism intrinsic to any system, namely
loss due to phonon-phonon interactions.
Sponsorship
MRSEC program of the NSF(No. DMR-0079992)
NSF NIRT program
Cornell Center for Materials Research
Date Issued
2005-10-10Subject
anharmonic; harmonic; NEMS; MEMS; oscillator; quality factor; nanotube; divacancy; Green's function; phonon-phonon interaction; electron mean-free path
Has other format(s)
bibid: 6475823
Type
dissertation or thesis