Show simple item record

dc.contributor.advisorSood, Ajay K
dc.contributor.authorPrakash, Gyan
dc.date.accessioned2021-03-29T05:32:38Z
dc.date.available2021-03-29T05:32:38Z
dc.date.submitted2019
dc.identifier.urihttps://etd.iisc.ac.in/handle/2005/5011
dc.description.abstractIn 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.isoen_USen_US
dc.relation.ispartofseries;G29811
dc.rightsI 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 dissertationen_US
dc.subjectNanowireen_US
dc.subjectGold nanowireen_US
dc.subjectAu-UNWen_US
dc.subjectcooling dynamicsen_US
dc.subject.classificationResearch Subject Categories::NATURAL SCIENCES::Physicsen_US
dc.titleUltrafast Study of Layered 3D Topological Insulators, Graphene-Gold Hybrid Plasmonic Nanostructure and Ultrathin Gold Nanowiresen_US
dc.typeThesisen_US
dc.degree.namePhDen_US
dc.degree.levelDoctoralen_US
dc.degree.grantorIndian Institute of Scienceen_US
dc.degree.disciplineFaculty of Scienceen_US


Files in this item

This item appears in the following Collection(s)

Show simple item record