Ultrafast dynamics of electrons and phonons in graphitic materials

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dc.contributor.author Chatzakis, Ioannis
dc.date.accessioned 2009-09-30T13:25:37Z
dc.date.available 2009-09-30T13:25:37Z
dc.date.issued 2009-09-30T13:25:37Z
dc.identifier.uri http://hdl.handle.net/2097/1728
dc.description.abstract This work focuses on the ultrafast dynamics of electrons and phonons in graphitic materials. In particular, we experimentally investigated the factors which influence the transport properties of graphite and carbon nanotubes. In the first part of this dissertation, we used Time-resolved Two Photon photoemission (TR-TPP) spectroscopy to probe the dynamics of optically excited charge carriers above the Fermi energy of double-wall carbon nanotubes (DWNTs). In the second part of this study, time-resolved anti-Stokes Raman (ASR) spectroscopy is applied to investigating in real time the phonon-phonon interactions, and addressing the way the temperature affects the dynamics of single-wall carbon nanotubes (SWNTs) and graphite. With respect to the first part, we aim to deeply understand the dynamics of the charge carriers and electron-phonon interactions, in order to achieve an as complete as possible knowledge of DWNTs. We measured the energy transfer rate from the electronic system to the lattice, and we observed a strong non-linear increase with the temperature of the electrons. In addition, we determined the electron-phonon coupling parameter, and the mean-free path of the electrons. The TR-TPP technique enables us to measure the above quantities without any electrical contacts, with the advantage of reducing the errors introduced by the metallic electrodes. The second investigation uses time-resolved ASR spectroscopy to probe in real time the G-mode non-equilibrium phonon dynamics and the energy relaxation paths towards the lattice by variation of the temperature in SWNTs and graphite. The lifetime range of the optically excited phonons obtained is 1.23 ps to 0.70 ps in the lowest (cryogenic temperatures) and highest temperature limits, respectively. We have also observed an increase in the energy of the G-mode optical phonons in graphite with the transient temperature. The findings of this study are important since the non-equilibrium phonon population has been invoked to explain the negative differential conductance and current saturation in high biased transport phenomena. en_US
dc.description.sponsorship This work is supported n part by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy. It is also suported in part by the graduate school of Kansas State University and by Columbia University. en_US
dc.language.iso en_US en_US
dc.publisher Kansas State University en
dc.subject Temperature dependence of the anharmonic decay of optical phonons in graphite en_US
dc.subject Temperature dependence of the anharmonic decay of optical phonons in nanotubes en_US
dc.subject Zone center phonon dynamics in graphite en_US
dc.subject Zone center phonon dynamics in carbon nanotubes en_US
dc.subject Time resolved two photon photoemission spectroscopy in carbon nanotubes en_US
dc.subject Time resolved anti stokes Raman spectroscopy in carbon nanotubes en_US
dc.title Ultrafast dynamics of electrons and phonons in graphitic materials en_US
dc.type Dissertation en_US
dc.description.degree Doctor of Philosophy en_US
dc.description.level Doctoral en_US
dc.description.department Department of Physics en_US
dc.description.advisor Itzhak Ben-Itzhak en_US
dc.description.advisor Patrick Richard en_US
dc.subject.umi Physics, Condensed Matter (0611) en_US
dc.date.published 2009 en_US
dc.date.graduationmonth December en_US

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