Title: Experimental study of electron and phonon dynamics in nanoscale materials by ultrafast laser time-domain spectroscopy,
Abstract: With the rapid advances in the development of nanotechnology, nowadays, the
sizes of elementary unit, i.e. transistor, of micro- and nanoelectronic devices
are well deep into nanoscale. For the pursuit of cheaper and faster nanoscale
electronic devices, the size of transistors keeps scaling down. As the
miniaturization of the nanoelectronic devices, the electrical resistivity
increases dramatically, resulting rapid growth in the heat generation. The heat
generation and limited thermal dissipation in nanoscale materials have become a
critical problem in the development of the next generation nanoelectronic
devices. Copper (Cu) is widely used conducting material in nanoelectronic
devices, and the electron-phonon scattering is the dominant contributor to the
resistivity in Cu nanowires at room temperature. Meanwhile, phonons are the
main carriers of heat in insulators, intrinsic and lightly doped
semiconductors. The thermal transport is an ensemble of phonon transport, which
strongly depends on the phonon frequency. In addition, the phonon transport in
nanoscale materials can behave fundamentally different than in bulk materials,
because of the spatial confinement. However, the size effect on electron-phonon
scattering and frequency dependent phonon transport in nanoscale materials
remain largely unexplored, due to the lack of suitable experimental techniques.
This thesis is mainly focusing on the study of carrier dynamics and acoustic
phonon transport in nanoscale materials.