Thesis (M.Sc.)--University of Wollongong, 2005. / Typescript. Includes bibliographical references: leaf 146-148.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 115-119).

Tübingen, Universiẗat, Diss., 2003.

Tübingen, Univ., Diss., 2005.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 153-159).

Techn. Hochsch., Diss., 2002--Aachen.

Thesis (MIng)--University of Stellenbosch, 2006. / Bibliography. Also available via the Internet.

Made available in DSpace on 2014-06-11T19:25:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-05-28Bitstream added on 2014-06-13T19:53:26Z : No. of bitstreams: 1 solano_rav_me_ilha.pdf: 1596702 bytes, checksum: 57065466a13a3d33408ee670525cd7f2 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho foram estudados os filmes supercondutores do sistema BPSCCO ( (2-X) X 2 2 3 10 Bi Pb Sr Ca Cu O ), depositados em dois substratos diferentes (lâmina de prata e cristal de aluminato de lantânio). Estas deposições foram feitas pelo método de Dip coating, e foram feitas 3 deposições para cada substrato em seguida foi submetido a um tratamento térmico. Os resultados da medida elétrica do filme depositado nos substratos confirmaram o estado supercondutor a uma temperatura crítica (Tc) de 80K. Para determinar a temperatura crítica Tc foram efetuadas as medidas de resistência em função da temperatura. A Junção foi montada no Laboratório de Vidros e Cerâmica do Departamento de Física e Química da UNESP. As Junções Josephson usadas neste trabalho foram: Junções SIS (supercondutor – isolante – supercondutor) e SNS (supercondutor – metal normal – supercondutor), sobre as quais se mediu a corrente (I) em função da voltagem (V) obtendo-se as curvas característica da junção. As barreiras usadas nas junções foram de dois tipos: óxido de alumínio e a prata (metal). O alumínio foi depositado utilizando-se uma evaporadora em alto vácuo e posteriormente oxidado em um forno a uma temperatura de 400ºC durante uma hora; e a prata, depositada com a técnica de Sputtering. O efeito túnel ou tunelamento é característico em Junções Josephson. No entanto, para que esse efeito ocorra é necessário que a espessura do isolante seja da ordem de 10 Å. Portanto, trabalhamos de tal forma que a deposição fosse feita para que obtivessemos isolantes com essa espessura. Os resultados obtidos com as medidas de corrente e voltagem mostraram que a curva característica de tunelamento apresentou a forma prevista pela teoria. / In this work, we have studied the superconducting thin films of the system BPSCCO ( (2-X) X 2 2 3 10 Bi Pb Sr Ca Cu O ) with critical temperature around 110 K. The films were deposited in two different substrates (thin foil of silver and lanthanum aluminate polished crystal). These depositions have been made by the method called Dip coating, and it has been made 3 depositions for each substrate after that they were submitted to a thermal treatment. Electrical measurements of the films have confirmed the superconducting state to a critical temperature (Tc) around 80K. Critical temperature has been determined by measures temperature dependence of the resistance. The Junction was mounted in the Laboratory of Glasses and Ceramics of the Department of Physics and Chemistry of the FEIS-UNESP. The proposal of this work was to study two types of Josephson Junctions: SIS (Superconducting - Isolating - Superconducting) and SNS (Superconducting - Normal metal - Superconducting). Josephson junctions Characteristic Curves were done measuring dc electrical current (I) as a function of the voltage (V). It was used two kinds of barriers: aluminum oxide and silver. Aluminum was deposited using a high vacuum evaporator after this it was oxidized by thermal process using an oven, it was applied a thermal treatment around 400ºC during one hour. Silver was deposited using Sputtering technique. The tunnel effect or tunneling is characteristic property of the Josephson Junctions, although, this effect occurs just for barriers with thickness below tenth of nm. In this way, we have tried to get insolated barriers with the same order thickness as described above. Our results have shown that it is possible to observe the characteristic tunneling curve predicted by the theory.

Orientador: Cláudio Luiz Carvalho / Banca: Hermes Adolfo de Aquino / Banca: Edson Sardella / Resumo: Neste trabalho foram estudados os filmes supercondutores do sistema BPSCCO ( (2-X) X 2 2 3 10 Bi Pb Sr Ca Cu O ), depositados em dois substratos diferentes (lâmina de prata e cristal de aluminato de lantânio). Estas deposições foram feitas pelo método de Dip coating, e foram feitas 3 deposições para cada substrato em seguida foi submetido a um tratamento térmico. Os resultados da medida elétrica do filme depositado nos substratos confirmaram o estado supercondutor a uma temperatura crítica (Tc) de 80K. Para determinar a temperatura crítica Tc foram efetuadas as medidas de resistência em função da temperatura. A Junção foi montada no Laboratório de Vidros e Cerâmica do Departamento de Física e Química da UNESP. As Junções Josephson usadas neste trabalho foram: Junções SIS (supercondutor - isolante - supercondutor) e SNS (supercondutor - metal normal - supercondutor), sobre as quais se mediu a corrente (I) em função da voltagem (V) obtendo-se as curvas característica da junção. As barreiras usadas nas junções foram de dois tipos: óxido de alumínio e a prata (metal). O alumínio foi depositado utilizando-se uma evaporadora em alto vácuo e posteriormente oxidado em um forno a uma temperatura de 400ºC durante uma hora; e a prata, depositada com a técnica de Sputtering. O efeito túnel ou tunelamento é característico em Junções Josephson. No entanto, para que esse efeito ocorra é necessário que a espessura do isolante seja da ordem de 10 Å. Portanto, trabalhamos de tal forma que a deposição fosse feita para que obtivessemos isolantes com essa espessura. Os resultados obtidos com as medidas de corrente e voltagem mostraram que a curva característica de tunelamento apresentou a forma prevista pela teoria. / Abstract: In this work, we have studied the superconducting thin films of the system BPSCCO ( (2-X) X 2 2 3 10 Bi Pb Sr Ca Cu O ) with critical temperature around 110 K. The films were deposited in two different substrates (thin foil of silver and lanthanum aluminate polished crystal). These depositions have been made by the method called Dip coating, and it has been made 3 depositions for each substrate after that they were submitted to a thermal treatment. Electrical measurements of the films have confirmed the superconducting state to a critical temperature (Tc) around 80K. Critical temperature has been determined by measures temperature dependence of the resistance. The Junction was mounted in the Laboratory of Glasses and Ceramics of the Department of Physics and Chemistry of the FEIS-UNESP. The proposal of this work was to study two types of Josephson Junctions: SIS (Superconducting - Isolating - Superconducting) and SNS (Superconducting - Normal metal - Superconducting). Josephson junctions Characteristic Curves were done measuring dc electrical current (I) as a function of the voltage (V). It was used two kinds of barriers: aluminum oxide and silver. Aluminum was deposited using a high vacuum evaporator after this it was oxidized by thermal process using an oven, it was applied a thermal treatment around 400ºC during one hour. Silver was deposited using Sputtering technique. The tunnel effect or tunneling is characteristic property of the Josephson Junctions, although, this effect occurs just for barriers with thickness below tenth of nm. In this way, we have tried to get insolated barriers with the same order thickness as described above. Our results have shown that it is possible to observe the characteristic tunneling curve predicted by the theory. / Mestre

Abstract The quantum-mechanical effects typical for single atoms or molecules can be reproduced in micrometer-scale electric devices. In these systems the essential component is a small Josephson junction (JJ) consisting of two superconductors separated by a thin insulator. The quantum phenomena can be controlled in real time by external signals and have a great potential for novel applications. However, their fragility on uncontrolled disturbance caused by typical nearby environments is a drawback for quantum information science, but a virtue for detector technology. Motivated by this we have theoretically studied transistor kind of devices based on single-charge tunneling through small JJs. A common factor of the research is the analysis of the interplay between the coherent Cooper-pair (charge carriers in the superconducting state) tunneling and incoherent environmental processes. In the first work we calculate the current due to incoherent Cooper-pair tunneling through a voltage-biased small JJ in series with large JJs and compare the results with recent experiments. We are able to reproduce the main experimental features and interpret these as traces of energy levels and energy bands of the mesoscopic device. In the second work we analyze a similar circuit (asymmetric single-Cooper-pair transistor) but under the assumption that the Cooper-pair tunneling is mainly coherent. This predicts new resonant transport voltages in the circuit due to higher-order processes. However, no clear traces of most of them are seen in the experiments, and similar discrepancy is present also in the case of the symmetric circuit. We continue to study this problem by modeling the interplay between the coherent and incoherent processes more accurately using a density-matrix approach. By this we are able to demonstrate that in typical conditions most of these resonances are indeed washed out by strong decoherence caused by the environment. We also analyze the contribution of three typical weakly interacting dissipative environments: electromagnetic environment, spurious charge fluctuators in the nearby insulating materials, and quasiparticles. In the last work we model the dynamics of a current-biased JJ perturbed by a smaller JJ using a similar density-matrix approach. We demonstrate that the small JJ can be used also as a detector of the energy-band dynamics in a current biased JJ. The method is also used for modeling the charge transport in the Bloch-oscillating transistor.