dc.contributor.advisor | Sood, Ajay K | |
dc.contributor.author | Prakash, Gyan | |
dc.date.accessioned | 2021-03-29T05:32:38Z | |
dc.date.available | 2021-03-29T05:32:38Z | |
dc.date.submitted | 2019 | |
dc.identifier.uri | https://etd.iisc.ac.in/handle/2005/5011 | |
dc.description.abstract | In a typical time-resolved pump-probe spectroscopy, ultrafast laser pulses (pulse width ~ 100
fs) are utilized to induce a perturbation in the material of study within a time much shorter
than the characterisitic lifetime of its constituents such as charge carriers, phonons and other
excitations. Using a probe pulse much weaker in intensity, the temporal evolution of the
nonequilibrium state of the material and the different relaxation pathways through which it
restores are studied. In this thesis, time-resolved studies of layered three-dimensional (3D)
topological insulators, graphene-gold hybrid nanostructure and ultrathin gold nanowires is
reported.
we have investigated the carrier dynamics in high aspect ratio ultrathin
gold nanowires (Au-UNWs) of average diameter 2 nm using pump (3.1 eV) and coherent
white light continuum as probe in the spectral range of 1.15 eV to 2.75 eV. The dynamics
in the Au-UNWs is systematically probed in weak to strong excitation regime. The results
show that under extreme excitation regime, the cooling dynamics of thermalized hot conduction
electrons at elevated electronic temperature is slower than that predicted by the
well established two-temperature model (TTM). Surface e ects in the carrier dynamics are
found to play important role. We show that the screened electron-electron interactions due
to spilling of conduction band and localization of core (d band) electrons at the surface
promotes many-body interaction leading to nonequilibrium carrier density dependent Auger
heating which slows the carrier cooling dynamics. In a quest to understand the e ect of size
on carrier dynamics in metals, previous reports on femtosecond pump-probe study of metals
have only focused on thin metal lms of varying thickness [14] and metal nanoparticles
(MNs) of varying size [15{21]. Our study of electron dynamics in ultrathin metal nanowires
which con ne the conduction electrons only in two dimensions instead of three dimensions
like in MNs lls the missing and yet unexplored gap in this quest. Our results are of potential
importance for devices and sensors based on Au-UNWs whose performance depends on the
electron dynamics in gold at reduced dimensions. | en_US |
dc.language.iso | en_US | en_US |
dc.relation.ispartofseries | ;G29811 | |
dc.rights | I grant Indian Institute of Science the right to archive and to make available my thesis or dissertation in whole or in part in all forms of media, now hereafter known. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part
of this thesis or dissertation | en_US |
dc.subject | Nanowire | en_US |
dc.subject | Gold nanowire | en_US |
dc.subject | Au-UNW | en_US |
dc.subject | cooling dynamics | en_US |
dc.subject.classification | Research Subject Categories::NATURAL SCIENCES::Physics | en_US |
dc.title | Ultrafast Study of Layered 3D Topological Insulators, Graphene-Gold Hybrid Plasmonic Nanostructure and Ultrathin Gold Nanowires | en_US |
dc.type | Thesis | en_US |
dc.degree.name | PhD | en_US |
dc.degree.level | Doctoral | en_US |
dc.degree.grantor | Indian Institute of Science | en_US |
dc.degree.discipline | Faculty of Science | en_US |