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Identifier	uch.physics.phd//2002loukakos
Title	The influence of structure on ultrafast electron dynamics in non-stoichiometric III-V semiconductors and metallic nano-composites
Alternative Title	Η επίδραση της δομής στην υπερταχεία ηλεκτρονιακή δυναμική σε μη-στοιχειομετρικούς III-V ημιαγωγούς και μεταλλικές νανο-συνθέσεις
Creator	Λουκάκος, Παναγιώτης Α
Thesis advisor	Φωτάκης, Κωνσταντίνος
Abstract	Ultrafast pump and probe spectroscopy has been utilized in order to study the electronic trapping behavior in nonstoichiometric GaAs and AlGaAs and to study the effect of the size reduction of nanometer sized Au particles on the kinetics of the confined electron population. The dynamics of conduction band electrons of Low-Temperature-Grown GaAs and AlGaAs is studied by exciting electrons in the vicinity of the conduction band bottom and by probing the induced transient changes in the absorption from the top of the valence to the bottom of the conduction band of the semiconductor. The nonstoichiometric semiconductors, that we examine, contain As precipitates. The electron trapping behavior is found to depend on both the average As precipitate radius α and spacing R. The interplay of these parameters is for the first time experimentally determined to be governed by the law ατ3R∝ which can be predicted theoretically by assuming diffusion mediated trapping of electrons on the surfaces of the As precipitates. The kinetics of the confined electrons in Au nanoparticles is studied by perturbing the electron population in the vicinity of the Fermi energy and by probing the transient interband transition from the d-bands to the Fermi surface. The mechanism of the internal electron energy re-distribution is experimentally found to accelerate with the reduction (enhancement) of the nanoparticle size (confinement). The results show an independency of the surrounding dielectric host and are in good agreement with a numerical model based on the reduction of the Coulomb screening interaction. The mechanism of the cooling of the thermalized electron population to the lattice is also found to accelerate with size reduction.
Language	English
Issue date	2002-05-01
Date available	2002-05-16
Collection	School/Department--School of Sciences and Engineering--Department of Physics--Doctoral theses
	Type of Work--Doctoral theses
Permanent Link	https://elocus.lib.uoc.gr//dlib/7/8/1/metadata-dlib-2002loukakos.tkl
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