Ce travail porte sur la réalisation d'un microspectromètre SWIFTS (Stationary Wave Integrated Fourier Transform Spectrometer) incluant des compteurs de photons SNSPD (Superconducting Nanowire Single Photon Detector). Il met en œuvre un interféromètre intégré à guide d'onde en arête bouclé, en SiN, sous lequel sont disposés 24 nanofils supraconducteurs SNSPD en NbN échantillonnant les interférences au pas de 160nm, à une longueur d'onde centrée sur 1.55µm. La conception, l'étude des composantes optique et électronique, la fabrication et la caractérisation à 4.2K sont décrites, jusqu'à la mise en évidence d'une modulation de puissance lumineuse dans le guide conformément à la formation attendue d'interférences. Le SWIFTS-SNSPD constitue le premier dispositif optoélectronique supraconducteur à part entière, doublement intégré. Sa capacité unique d'échantillonnage direct de franges d'interférences ouvre de nombreuses perspectives, pour des applications allant de l'astrophysique aux télécoms.

Ce travail porte sur la fabrication et la mesure de détecteurs quantiques supraconducteurs. Pour nano-structurer ces dispositifs, nous utilisons une technique de lithographie en champ proche : l'anodisation locale sous la pointe d'un microscope à force atomique (AFM). Nous appliquons cette technique à des films ultra-minces (2-10 nm) à base de niobium (Nb, NbN) épitaxiés sur des substrats de saphir. La résolution ultime que nous obtenons est de 10nm. Elle nous permet de réaliser des nanofils cristallins dont la section est nanométrique (100nm2) et homogène sur de grandes distances ( 40µm). Nous caractérisons en amont la qualité cristalline des films et mesurons leurs propriétés électriques jusqu'aux plus basses températures. Ces expertises sont menées en parallèle, sur des films d'épaisseur variable et nous permettent l'analyse de la transition supraconducteur-isolant dans les films ultra-minces en fonction du désordre mesuré dans les couches. Nous déterminons les régimes dissipatifs des nanofils supraconducteurs à très basses températures. Dans le régime de point chaud, nous montrons que les nanofils permettent la détection rapide d'un photon unique. Les détecteurs sont sensibles au photon unique dans le visible et à deux photons dans l'infrarouge. Ces détecteurs supraconducteurs ont une résolution temporelle inégalée par les détecteurs semiconducteurs. Ils peuvent être utilisés comme des compteurs de photons et être utiles à l'implémentation d'une cryptographie classique et quantique pour la transmission d'information sécurisée.

Summary: Background: An increased risk for development of hereditary breast cancer is associated with germline mutations in BRCA1/2 and the influence of NBN mutations is also supposed. The aim of this study is to specify the frequency of recurrent mutations in BRCA1/2 in unselected breast cancer patients and the frequency of most common pathogenic mutations in NBN in Czech republic, to assess current criteria for genetic testing and to consider the addition of NBN to the tested genes. Methods: Screening for recurrent mutations 5382insC and 300T>G in BRCA1 was performed by RFLP, screening for mutations in exon 11 of BRCA1 was performed by PTT, screening for mutations in a selected region of exon 11 of BRCA2 by DHPLC, and screening for mutations in exon 6 of NBN by HRMA. All the mutations were confirmed by direct sequencing. Results: In 679 unselected breast cancer patients 7 carriers of 5382insC, 3 of 300T>G, and 4 of other mutations in BRCA1 were identified. 2 locally prevalent mutations were found in BRCA2. In 730 controls only one 5382insC BRCA1 mutation was identified. Out of 5 NBN mutations found in 600 high-risk patients two were 657del5 and one R215W. A total of 8 NBN mutation carriers were identified among 703 breast cancer patients, 2 of them 657del5 carriers and three R215W carriers. In 915...

Afin de mieux comprendre les différents processus qui apparaissent à la transition supraconducteur-isolant (SIT), nous avons sondé simultanément les propriétés électroniques globales et locales de films minces de NbN, élaborés ex-situ sur un substrat de saphir. La transition a été approchée en réduisant l'épaisseur des échantillons, augmentant la résistance par carré de l'état normal à plusieurs kiloOhms. Les Tc correspondant aux films étudiés varient de Tc≈15K qui est proche de TC-bulk à Tc≈3.8K (Tc/TC-bulk≈0.23). Dans la gamme 0.4TC-bulk<Tc<TC-bulk, les mesures de résistances sont en accord avec la loi de Finkelstein pour la réduction de Tc induite par le désordre et les interactions électron-électron. Les mesures de spectroscopie tunnel locale (STS) montrent l'émergence d'une granularité dans les propriétés supraconductrices en réduisant la Tc, ainsi que le développement d'un fort fond Altshuler-Aronov dans les spectres tunnel dI/dV(V), ce qui est en accord avec le scenario de Finkelstein. Pour l'échantillon le plus désordonné (Tc≈3.8K), des mesures de résistance in-situ et de STS en simultané nous ont permis de suivre sur la même zone de l'échantillon, l'évolution des propriétés supraconductrices en fonction de la température et du champ magnétique, qui ont démontré un comportement percolatif de la transition dans l'état normal de mauvais métal. Cette étude locale a été confirmée par le changement de dimensionnalité des fluctuations Aslamasov-Larkin au-dessus de Tc de 2D à 0D. En outre, une telle étude est particulièrement intéressante pour comprendre les différents phénomènes qui limitent le fonctionnement des détecteurs de photon unique basé sur les films de NbN. / In order to better understand the various processes taking place at the superconductor-insulator transition (SIT), we have probed simultaneously the global and local electronic properties of NbN ultrathin films, elaborated ex-situ on sapphire substrate. The transition was approached by reducing the films thickness, increasing the normal state square resistance to several kiloOhms. The corresponding Tc's of the studied films ranged from about Tc≈15K, which is close to TC-bulk, to Tc≈3.8K (Tc/TC-bulk≈0.23). In the range 0.4TC-bulk<Tc<TC-bulk resistivity measurements are consistent with Finkelstein's reduction of Tc induced by disorder and electron-electron repulsion. Local scanning tunneling spectroscopy (STS) measurements show the emergence of granularity in the superconducting properties upon Tc reduction, as well as the progressive development of a strong Altshuler-Aronov background in the dI/dV(V) tunneling spectra, in agreement with Finkelstein scenario. For the most disordered film (Tc≈3.8K), simultaneous in-situ resistivity and STS measurements allowed us to follow at the same sample area the evolution of these emergent granular superconducting properties as a function of temperature and magnetic field, which demonstrate a percolative behavior of the transition to the bad-metal normal state. This local picture finds an interesting signature in the change of the dimensionality of the Aslamasov-Larkin fluctuations above Tc from 2D to 0D. Besides, such a study is particularly interesting to better understand the various phenomena occurring in and limiting the behavior of single-photon detectors patterned out of NbN films.

Summary: Background: An increased risk for development of hereditary breast cancer is associated with germline mutations in BRCA1/2 and the influence of NBN mutations is also supposed. The aim of this study is to specify the frequency of recurrent mutations in BRCA1/2 in unselected breast cancer patients and the frequency of most common pathogenic mutations in NBN in Czech republic, to assess current criteria for genetic testing and to consider the addition of NBN to the tested genes. Methods: Screening for recurrent mutations 5382insC and 300T>G in BRCA1 was performed by RFLP, screening for mutations in exon 11 of BRCA1 was performed by PTT, screening for mutations in a selected region of exon 11 of BRCA2 by DHPLC, and screening for mutations in exon 6 of NBN by HRMA. All the mutations were confirmed by direct sequencing. Results: In 679 unselected breast cancer patients 7 carriers of 5382insC, 3 of 300T>G, and 4 of other mutations in BRCA1 were identified. 2 locally prevalent mutations were found in BRCA2. In 730 controls only one 5382insC BRCA1 mutation was identified. Out of 5 NBN mutations found in 600 high-risk patients two were 657del5 and one R215W. A total of 8 NBN mutation carriers were identified among 703 breast cancer patients, 2 of them 657del5 carriers and three R215W carriers. In 915...

The recent advancement of superconducting nano devices has allowed for making a Superconducting Nanowire Single Photon Detector (SNSPD), whose extraordinary features have strongly motivated the research community to exploit it in many practical applications. In this thesis, an experimental setup for testing the SNSPD has been established. It contains an in-house packaging that meets the requirements of RF/microwave and optoelectronic characterizations. The quantum efficiency and detection efficiency measurements have confirmed that our approach is satisfactory. The dark count performance has reached the anticipated level. The factors affecting rise and fall times of the photoresponses are addressed. Based on the successful setup, the characterizations including dc, small signal ac measurements have been undertaken. The measurements are aimed at quantitatively investigating Cooper pair density in the superconducting nanowire. The experimental method involves a two-step, small signal S-parameter measurement either in the presence or absence of optical powers. The subsequent measurements by varying the temperature and dc bias current have achieved remarkable understanding on the physical properties of SNSPD nanowires. Then, the electrically induced nonlinearity is studied via the large signal RF and Microwave measurements. The experiments are a set of one-tone and two-tone measurements, in which either the RF driving power is varied at a fixed frequency, or vice versa. Two major nonlinear microwave circuit analysis methods, i.e. time-domain transient and hybrid-domain harmonic balance analysis, are employed. The simulation result reveals the optimized conditions of reaching the desired nonlinearity. Finally, we have successfully measured the optoelectronic mixing products in an electrically pumped optoelectronic mixer, which has identical structures as that of the SNSPD. The experiments confirm that this mixer is not only sensitive to the classical light intensities, but also to that of the single photon level. Meanwhile, the quantum conversion matrices is derived to interpret the quantum optoelectronic mixing effects.

The recent advancement of superconducting nano devices has allowed for making a Superconducting Nanowire Single Photon Detector (SNSPD), whose extraordinary features have strongly motivated the research community to exploit it in many practical applications. In this thesis, an experimental setup for testing the SNSPD has been established. It contains an in-house packaging that meets the requirements of RF/microwave and optoelectronic characterizations. The quantum efficiency and detection efficiency measurements have confirmed that our approach is satisfactory. The dark count performance has reached the anticipated level. The factors affecting rise and fall times of the photoresponses are addressed. Based on the successful setup, the characterizations including dc, small signal ac measurements have been undertaken. The measurements are aimed at quantitatively investigating Cooper pair density in the superconducting nanowire. The experimental method involves a two-step, small signal S-parameter measurement either in the presence or absence of optical powers. The subsequent measurements by varying the temperature and dc bias current have achieved remarkable understanding on the physical properties of SNSPD nanowires. Then, the electrically induced nonlinearity is studied via the large signal RF and Microwave measurements. The experiments are a set of one-tone and two-tone measurements, in which either the RF driving power is varied at a fixed frequency, or vice versa. Two major nonlinear microwave circuit analysis methods, i.e. time-domain transient and hybrid-domain harmonic balance analysis, are employed. The simulation result reveals the optimized conditions of reaching the desired nonlinearity. Finally, we have successfully measured the optoelectronic mixing products in an electrically pumped optoelectronic mixer, which has identical structures as that of the SNSPD. The experiments confirm that this mixer is not only sensitive to the classical light intensities, but also to that of the single photon level. Meanwhile, the quantum conversion matrices is derived to interpret the quantum optoelectronic mixing effects.

No description available.

Two technologies, namely Laser Technology and Surface Modification Technology, have made rapid strides in the last few decades. The lasers have evolved from a simple laboratory curiosity to a matured industrial tool and its applications are limited only by imagination. Intense, coherent and monochromatic laser sources with power outputs ranging over several orders of magnitude have found innumerable applications in the realm of materials engineering. Reactive Pulsed Laser Deposition (PLD) is a powerful technique that utilises the power of a nanosecond pulsed laser for materials synthesis. Unlike conventional PLD, which require high density targets that are difficult to synthesize at a reasonable cost, the RPLD circumvents the need for one such ceramic target. This thesis presents a detailed and judicious use of this technique for synthesis of hard ceramic multilayer coatings using elemental metal targets. Transition metal nitrides having rock salt structure are known to exhibit superior properties such as hardness and wear resistance and hence formed the basis for the development of first generation coatings. Further improvements through alloying of these binary compounds with metal or metalloid components lead to the development of second generation coatings. As the demand for functional materials increased, surface modification technology alias surface engineering, grew in leaps and bounds. As the large number of coating requirements for optimal performance could not be fulfilled by a single homogeneous material, third generation coatings, comprising multilayer coatings, were developed. It is this aspect of combining the advantages of RPLD process to synthesize ceramic multilayer coatings, provides the main motivation for the present research work. In this thesis, a systematic study presented for synthesis of nanocrystalline and stoichiometric TiN and NbN thin films using RPLD through ablation of high purity titanium and niobium targets, in the presence of low pressure nitrogen gas. A novel Secondary Ion Mass Spectrometry (SIMS) based analysis was developed to effectively deduce the important process parameters in minimum trials to arrive at desired composition. The validity of this SIMS based method, for optimization of process parameters to get stoichiometric nitride films, was proved beyond any speculation by corroborative Proton Elastic Backscattering Spectrometric (PEBS) analysis. SIMS was also used to characterize the [NbN/TiN] multilayers. The feasibility of growing nanocrystalline multilayers with varying thicknesses has been demonstrated. Nanomechanical properties including hardness and adhesion strength of monolithic TiN and NbN films and multilayers were evaluated. The thesis is organised into six chapters. The first chapter gives a brief account on the history and development of ‘surface engineering’. The second chapter provides a comprehensive description of the experimental facility developed in-house to pursue research on PLD grown ceramic thin films and multilayers. Thin film synthesis procedure for ex-situ SIMS and TEM analyses is described. Brief introduction is also presented on the characterization techniques used in this study to investigate the surface, interface and microstructural aspects of PLD grown films with underlying basic principles. The third and fourth chapter describes the synthesis and characterization of titanium nitride and niobium nitride thin films using RPLD technique, respectively. SIMS was used in depth profiling mode, for optimization of three important process parameters, viz., nitrogen gas pressure, substrate temperature and laser pulse energy, to get stoichiometric nitride films. Further, films were characterized using GIXRD, TEM, XPS and PEBS for their structure and composition. AFM measurements were made to elucidate the surface morphological features. PEBS was effectively used to estimate the nitrogen concentration in a quantitative manner and the results corroborate well with the SIMS measurements. Having succeeded in synthesizing stoichiometric TiN and NbN films, further studies on the nanomechanical properties of monolithic TiN and NbN films and their multilayers were carried out and these results form the contents of the fifth chapter. The findings of the work reported in this thesis are concluded in Chapter 6 and few possible suggestions were presented as future directions. Both the monolithic TiN and NbN coatings showed a deposition pressure dependent hardness variation. The hardness of these monolithic films was found to be around 30 GPa, higher than the hardness values obtained by other conventional techniques. Keeping total thickness of the multilayers constant at 1 μm, [NbN/TiN] multilayers having bilayer periods ranging from 50 nm to 1000 nm, were synthesized. A systematic enhancement in hardness upto ~ 40 GPa was observed for [NbN/TiN]10 with the modulus of the multilayer remaining almost constant. The pileup observed around the indentation edge is indicative of toughening in multilayers. The tribological properties of multilayer films showed a better performance in terms of low coefficient of friction and regeneration of coating surfaces as revealed from the nanotribological studies. Overall, the multilayer coatings exhibited better performance in terms of hardness, toughness and adhesion with the substrate material.