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Résumé Ce travail de thèse en cotutelle a été réalisé à l’Institut de Chimie Moléculaire de l’Université de Bourgogne (France) ainsi qu’au département de Chimie de l’Université de Sherbrooke (Québec). Ces travaux sont consacrés à la modification de la structure des BODIPY en vue d'une application in vivo pour l'imagerie bimodale optique/TEP ou TEMP. Ces modifications concernent l'hydrosolubilisation des fluorophores, mais aussi le décalage des domaines d’absorption et d’émission vers la fenêtre thérapeutique, zone dans laquelle la lumière est moins atténuée par les tissus biologiques. Des solutions permettant la bioconjugaison des fluorophores sur un dérivé de la bombésine, peptide permettant de cibler des récepteurs membranaires surexprimés dans certains types de cellules cancéreuses, sont également présentées. Enfin, une stratégie d’introduction d’un radioélément sur le BODIPY est décrite. Elle implique l’introduction sur l’atome de bore d’un groupe partant permettant sa radiofluoration. Différents dérivés de BODIPY ont également été utilisés pour la construction d’édifices multichromophoriques à transfert d’énergie. Ces travaux sont décrits dans la seconde partie de cette thèse. Ils comprennent notamment des études photophysiques permettant de mettre en évidence le transfert d’énergie photoinduit donneur-accepteur entre différents chromophores Dans les différents système élaborés, de type BODIPY-pophyrine et BODIPY-corolle, le BODIPY est alternativement donneur, ou accepteur d’énergie.

The conduction band of InAs lies lower in energy than the GaSb valence band. In order to preserve continuity of the Fermi level across the interface, charge transfer takes place resulting in a confined quasi two dimensional electron gas (2DEG) in the InAs and a confined quasi two dimensional hole gas (2DHG) in the GaSb. This study is an investigation into the vertical transport in an n-InAs/p-GaSb single heterojunction (SHET). Application of a forward bias (InAs negative with respect to GaSb) increases the 2DEG and 2DHG concentrations and, therefore, their confinement energies. Eventually a critical bias is reached where the electron confinement energy moves above the hole confinement energy (the theoretical voltage induced semimetal/semiconductor transition V_c). Any subsequent increase in voltage is expected to result in a current decrease, and a region of negative differential resistance (NDR) should occur. The SHET can be grown with two distinct interface types, 'InSb-like' and 'GaAs-like'. This in turn affects the vertical transport characteristics of each type. Experimental IV traces at various pressures are compared with the corresponding results from sophisticated self-consistent band profile calculations taking into account band mixing effects for the first time through a k.p theory framework. Experimental IV traces of the SHETs under a magnetic field parallel to the interface are also compared with results from calculations that take into account the coupling of the growth and in-plane electron and heavy hole motions. Both sets of analysis support earlier conclusions that NDR occurs after V_c for both interfaces, and that each interface supports a different conduction mechanism. Evidence of multiple phonon processes occurring in both sample types is observed for the first time and is proposed to reconcile the above experimental observations with theory. This data is found to offer explanations for a number of other observations. Field perpendicular to the interface leads to the observation of features beyond the NDR region in both sample types. In samples with an 'InSb-like' interface, applying additional hydrostatic pressure leads to very strong features beyond the main NDR. Through a complex self-consistent decoupled model taking into account electrons and heavy holes, all these features are proposed to be due to a filling of an integer number of Landau levels. The band profile is predicted to alter dramatically at this point. The same model explains the observation of weaker features at 1 bar at high fields (~ 40T). A variation of NDR position is found with a rotation of an-plane field.

[Truncated abstract] Over the past decade, the group III-nitride semiconducting compounds (GaN, AlN, InN, and their alloys) have attracted tremendous research efforts due to their unique electronic and optical properties. Their low thermal carrier generation rates and large breakdown fields make them attractive for the development of robust electronic devices capable of reliable operation in extreme conditions, i.e. at high power/voltage levels, high temperatures and in radiation environments. For device applications in radiation environments, such as space electronics, GaN-based devices are expected to manifest superior radiation hardness and reliability without the need for cumber- some and expensive cooling systems and/or radiation shielding. The principle aim of this Thesis is to ascertain the level of susceptibility of current GaN-based elec- tron devices to radiation-induced degradation, by undertaking a detailed study of 60Co gamma-irradiation-induced defects and defect-related effects on the electrical characteristics of n-type GaN-based materials and devices . . . While the irradiation-induced effects on device threshold voltage could be regarded as relatively benign (taking into account that the irradiation levels employed in this study are equivalent to more than 60 years exposure at the average ionising dose rate levels present in space missions), the observed device instabilities and the degradation of gate current characteristics are deleterious effects which will have a significant impact on the performance of AlGaN/GaN HEMTs operating in radiation environments at low temperatures, a combination of conditions which are found in spaceborne electronic systems.

Thesis (Ph. D.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xvi, 145 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 142-145).

Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: Daniel Cassidy. Includes bibliographical references (p. 199-211).