In this dissertation, I developed a Pd seeding method in association with electroless plating, to successfully metallize both lambda DNA and DNA origami templates on different surfaces. On mica surfaces, this method offered a fast, simple process, and the ability to obtain a relatively high yield of metallized DNA nanostructures. When using lambda DNA as the templates, I studied the effect of Pd(II) activation time on the seed height and density, and an optimal activation time between 10 and 30 min was obtained. Based on the Pd seeds formed on DNA, as well as a Pd electroless plating solution, continuous Pd nanowires that had an average diameter of ~28 nm were formed with good selectivity on lambda DNA. The selected Pd activation time was also applied to metallize "T"-shape DNA origami, and Au coated branched nanostructures with a length between 200-250 nm, and wire diameters of ~40 nm were also fabricated. In addition, I found that the addition of Mg2+ ion into the reducing agent and electroless plating solution could benefit the surface retention of Pd seeded DNA and Au plated DNA structures. This work indicated that DNA molecules were promising templates to fabricate metal nanostructures; moreover, the formation of Au metallized branched nanostructures showed progress towards nanodevice fabrication using DNA origami. Silicon surfaces were also used as the substrates for DNA metallization. More complex circular circuit DNA origami templates were used. To obtain high enough seed density, multiple Pd seeding steps were applied which showed good selectivity and the seeded DNA origami remained on the surface after seeding steps. I used distribution analysis of seed height to study the effect of seeding steps on both average height and the uniformity of the Pd seeds. Four-repeated palladium seedings were confirmed to be optimal by the AFM images, seed height distribution analysis, and Au electroless plating results. Both Au and Cu metallized circular circuit design DNA origami were successfully obtained with high yield and good selectivity. The structures were maintained well after metallization, and the average diameters of Au and Cu samples were ~32 nm and 40 nm, respectively. Electrical conductivity measurements were done on these Au and Cu samples, both of which showed ohmic behavior. This is the first work to demonstrate the conductivity of Cu metallized DNA templates. In addition, the resistivities were calculated based on the measured resistance and the size of the metallized structures. My work shows promising progress with metallized DNA and DNA origami templates. The resulting metal nanostructures may find use as conducting interconnects for nanoscale objects as well as in surface enhanced Raman scattering analysis.

Nous avons étudié l'action à l'échelle mésoscopique de la présence d'un supraconducteur sur la conductance d'un circuit de métal normal. Après une discussion de différentes théories concernant ce sujet, nous présentons des mesures à très basse température (20 mK) mettant en évidence l'action non locale de la supraconductivité sur la conductance métallique. Nous montrons que la conductance du métal normal est alors fortement dépendante de l'énergie des électrons, l'énergie caractéristique étant l'énergie de Thouless. Une expérience d'interférence effectuée dans la configuration Aharonov-Bohm met en évidence la portée de la cohérence quantique de paires d'électrons dans le métal normal. Nous effectuons une comparaison détaillée avec la théorie des fonctions de Green quasiclassiques. Cette comparaison met en évidence le rôle important joué par les parties extérieures de l'échantillon qui constituent les réservoirs. Nous présentons une technique originale de fabrication d'échantillons mésoscopiques hybrides de Niobium et de Cuivre. De plus, afin de pouvoir contrôler la formation des barrières tunnel, nous avons développé une vanne permettant de maîtriser l'entrée, dans un enceinte à Ultra-Vide, d'oxygène pur à partir de l'air. Nous décrivons un programme écrit en langage C++, qui permet de calculer la conductance d'un circuit hybride quelconque composé de métal normal et de supraconducteur. Dans le cas où deux supraconducteurs sont présents à des tensions différentes, l'effet Josephson alternatif module la densité d'états dans le métal normal. Nous présentons une expérience, en cours de développement, visant à mesurer les effets de ces variations de la densité d'états sur le transport.

This work examines the selective deposition of metallic and semiconductor materials onto DNA templates for the fabrication of nanodevices. DNA origami provides a simple and robust method for folding DNA into a variety of shapes and patterns and makes it possible to create the complex templates needed for nanodevices, such as nanoelectronic circuits, plasmonics, and nanosensors. Metallization of DNA origami templates is essential for the fabrication of such nanodevices. In addition, selective deposition of semiconductor materials onto the DNA template is of importance for making many nanodevices such as nanocircuits. Metallization of DNA origami presents several challenges beyond those associated with the metallization of other DNA templates such as λ-DNA. All of these challenges were addressed in this study. DNA origami templates were seeded with Ag and then plated with Au via electroless deposition. Selective continuous metal deposition was achieved, with an average metallized height as small as 32 nm. The structure of T-shaped DNA origami was also retained after metallization. Following the metallization of complete origami, site-specific metallization of branched DNA origami was also demonstrated. To achieve this, staple strands at select locations on origami were replaced with staple strands modified with binding sites at the end. These binding sites then attached to thiolated DNA coated Au nanoparticles through base pairing. The continuous Au nanowires formed at designated sites on DNA origami after Au plating had an average width of 33 nm, with the smallest ones ~20 nm wide. The continuity of nanowires was verified by conductivity tests- the only tests of this nature of which I am aware. Moreover, predesigned sites on "circuit-shaped" DNA origami were successfully metallized. The selective deposition of a variety of materials onto DNA templates for the formation of continuous DNA-templated nanowires was also demonstrated. Specifically, an electroless Ni plating solution was developed to enable the fabrication of uniform and continuous DNA-templated Ni nanowires. Tests showed that these DNA-templated Ni nanowires were conductive. Moreover, continuous DNA-templated Bi2Te3 and/or Te nanowires have been fabricated through galvanic displacement of DNA-templated Ni and Cu nanowires. Altogether, these results represent important progress toward the realization of DNA-templated nanofabrication.