Tesi sul tema "STM"
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ABREU, FERNANDA DE MELLO. "TIME-DOMAIN OPTICAL MULTIPLEXING IN STM-16, STM-64 AND STM-256 SYSTEMS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2001. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=2361@1.
Testo completoALCATEL TELECOMUNICAÇÕES
Este trabalho tem como foco o up-grade da taxa de bits em enlaces ópticos através da tecnologia OTDM. Os sistemas analisados contemplam os up-grades das taxas de 2,48 Gbps para 10 Gbps e também da taxa de 10 Gbps para 40 Gbps. Para tal, foram introduzidos módulos de transmissão e recepção, capazes de utilizar arquiteturas quase totalmente ópticas. É avaliado então, através de simulações, o comportamento da arquitetura proposta em infra-estruturas de enlaces já instalados no Brasil, destacando os pontos mais críticos. No que se refere ao up-grade de 10 Gbps para 40 Gbps, foi dado enfoque especial para as penalidades relativas à PMD (Polarization Mode Dispersion).
This work aims at up grading the bit rate of optical links through the OTDM technology. The analyzed up-grades change the bit rate of 2,48 Gbps up to 10 Gbps and also from the bit rate of 10 Gbps up to 40 Gbps. To reach these objectives, transmission and reception modules were introduced, using all optical networks topologies. The performance of the proposed architecture was simulated using a infrastructure of links already installed in Brazil. The most critical issues were pointed out. Concerning the up-grade from 10 Gbps to 40 Gbps, a special focus was given to the penalties due to PMD (Polarization Mode Dispersion).
Celis, Retana Arlensiú Eréndira. "Gap en graphène sur des surfaces nanostructurées de SiC et des surfaces vicinales de métaux nobles". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS417/document.
Testo completoThe major challenge for graphene-based electronic applications is the absence of the band-gap necessary to switch between on and off logic states. Graphene nanoribbons provide a route to open a band-gap, though it is challenging to produce atomically precise nanoribbon widths and well-ordered edges. A particularly elegant method to open a band-gap is by electronic confinement, which can in principle be tuned by adjusting the nanoribbon width. This thesis is dedicated to understanding the ways of opening band-gaps by nanostructuration. We have used two approaches: the introduction of a superperiodic potential in graphene on vicinal noble metal substrates and the electronic confinement in artificially patterned nanoribbons on SiC. Superperiodic potentials on graphene have been introduced by two nanostructured substrates, Ir(332) and a multivicinal curved Pt(111) substrate. The growth of graphene modifies the original steps of the pristine substrates and transforms them into an array of (111) terraces and step bunching areas, as observed by STM. This nanostructuration of the underlying substrate induces the superperiodic potential on graphene that opens mini-gaps on the π band as observed by ARPES and consistent with the structural periodicity observed in STM and LEED. The mini-gaps are satisfactorily explained by a Dirac-hamiltonian model, that allows to retrieve the potential strength at the junctions between the (111) terraces and the step bunching. The potential strength depends on the substrate, the surface periodicity and the type of step-edge (A or B type). The surface potential has also been modified by intercalating Cu on Ir(332), that remains preferentially on the step bunching areas, producing there n-doped ribbons, while the non-intercalated areas remain p-doped, giving rise to an array of n- and p- doped nanoribbons on a single continuous layer. In the second approach to control the gap, we have studied the gap opening by electronic confinement in graphene nanoribbons grown on SiC. These ribbons are grown on an array of stabilized sidewalls on SiC. As a band-gap opening with unclear atomic origin had been observed by ARPES, we carried-out a correlated study of the atomic and electronic structure to identify the band gap origin. We performed the first atomically resolved study by STM, demonstrating the smoothness and chirality of the edges, finding the precise location of the metallic graphene nanoribbon on the sidewalls and identifying an unexpected mini-faceting on the substrate. To understand the coupling of graphene to the substrate, we performed a cross-sectional study by STEM/EELS, complementary of our ARPES and STM/STS studies. We observe that the (1-107) SiC sidewall facet is sub-faceted both at its top and bottom edges. The subfacetting consists of a series of (0001) miniterraces and (1-105) minifacets. Graphene is continuous on the whole subfacetting region, but it is coupled to the substrate on top of the (0001) miniterraces, rendering it there semiconducting. On the contrary, graphene is decoupled on top of the (1-105) minifacets but exhibits a bandgap, observed by EELS and compatible with ARPES observations. Such bandgap is originated by electronic confinement in the 1 - 2 nm width graphene nanoribbons that are formed over the (1-105) minifacets
Pavera, Michal. "Konstrukce nízkoteplotních ultravakuových rastrovacích sondových mikroskopů". Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-234579.
Testo completoMüller, Thomas. "Imaging of DNA and DNA-RAP1 assembly by STM, TEM and SFM /". [S.l.] : [s.n.], 1994. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10958.
Testo completoHoll, Christian [Verfasser], Markus [Akademischer Betreuer] Morgenstern e Samir [Akademischer Betreuer] Lounis. "High frequency STM and spin polarized STM on magnetic vortices / Christian Holl ; Markus Morgenstern, Samir Lounis". Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1192217926/34.
Testo completoWiehlmann, Lutz. "Sequenzspezifizierte Transposonmutagenese (STM) in Pseudomonas aeruginosa". [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=96511211X.
Testo completoRuess, Frank Joachim Physics Faculty of Science UNSW. "Atomically controlled device fabrication using STM". Awarded by:University of New South Wales. Physics, 2006. http://handle.unsw.edu.au/1959.4/24855.
Testo completoDeshpande, Aparna. "Atomistic interactions in STM atom manipulation". Ohio : Ohio University, 2007. http://www.ohiolink.edu/etd/view.cgi?ohiou169849272.
Testo completoDixon, Richard. "STM studies of semiconducting metal oxides". Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365728.
Testo completoRevenikiotis, Sackis (Athanasios). "Optimization of STM-tip preparation methods". Thesis, KTH, Materialfysik, MF (Stängd 20120101), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-30873.
Testo completoWilson, Jon H. "Silicon surfaces : STM, theory and experiment". Thesis, University of Oxford, 1991. http://ora.ox.ac.uk/objects/uuid:64998ae3-9316-42b5-967f-da93ff2bfd6c.
Testo completoClarke, A. R. H. "Quantitative STM imaging of metal surfaces". Thesis, University of Oxford, 1996. http://ora.ox.ac.uk/objects/uuid:68cbeba7-d283-498a-9435-b9587e7ef30a.
Testo completoDong, Yi. "Single site surface reactions : STM Studies". Doctoral thesis, Université Laval, 2018. http://hdl.handle.net/20.500.11794/30204.
Testo completoThe demand for enantiopure compounds in the pharmacological sectorsisastrong driving force for research aimed at creating homochiral catalyst surfaces. Heterogeneous catalysts offer potential advantages over homogeneous catalysts including ease of separation of products from the catalyst and greater suitability for operations under continuous ow conditions. One of the most successful examples of a heterogeneous enantioselective reaction is known as the Orito reaction, the hydrogenation of α-ketoesters on cinchona modi ed platinum particles. It is believed that the cinchona modi ers operate chirality transfer by forming bimolecular surface complexes with prochiral reactants. At a fundamental level, heterogeneous asymmetric catalysis is a poorly understood area of surface chemistry. Hence, it is also a fertile area for discovery. Progress in the area can best be made by complementary work in catalysis, surface science and computation. This thesis describes surface science studies that were inspired by reports in the catalysis literature on the Orito reaction. In addition to cinchona alkaloids, which are natural products, a number of synthetic molecules have been shown to be effective chiral modifiers for the Orito reaction. In particular, Baiker and co-workers explored the performance of optically pure 1-(1-naphtyl)-ethylamine (NEA) as a chiral modifier for the enantioselective hydrogenation of ketopantolactone (KPL) to pantolactone on Pt/Al2O3.1 A major part of the work described in this thesis deals with the investigation of surface complexes formed through the interaction of (R)-NEA and KPL on single crystal Pt(111). Scanning tunnelling microscopy (STM) measurements were used to acquire a large number of images of KPL/(R)-NEA complexes. The measurements were performed over a wide ratio KPL to (R)-NEA surface coverage ratios. An algorithm was developed to enable accelerated counting and cataloguing of the large set of STM images of complexes. Therelativeabundancesofmultipledistinctcomplexationstates, allinvolvingNH·· ·O hydrogen bonding, were determined. The prochirality of KPL in these states was assigned by reference to density functional theory (DFT) simulated STM images. The overall prochiral ratio (pr) measured in the surface science experiment was compared to the enantiomeric ratio (er) measured by Baiker and co-workers. An algorithm was developed to investigate uxional events in individual diastereomeric complexes. It was applied to examine state-to-state interconversion occurring during the life times of complexes, as observed using time-lapsed STM measurements. Results are presented for complexes formed by 2,2,2-trifluoroacetophenone (TFAP) interacting with (R)-NEA on Pt(111). The TFAP/(R)-NEA complexes show dynamic events that we describe as decomplexation, on-site prochiral inversion and intracomplex migration. The results are discussed in relation to energy barriers predicted by DFT for hydrogenation and for on-site prochiral inversion. Quantitative data for state-to-state interconversion in single complexes are presented for three systems: TFAP/(R)-NEA, KPL/(R)-NEA and for TFAP interacting with methyl-substituted (R)-NEA. A preliminary analysis of the data is presented. The observations on KPL/(R)-NEA and TFAP/(R)-NEA complexes are reviewed within the context of previously published surface science data from our group. The review emphasizes the role of secondary interactions, CH···O and CF···H bonding, in the stereocontrol of prochiral molecules.
Silva, Neto Francisco Miranda Soares da. "Rewriting Concurrent Haskell programs to STM". Universidade Federal de Pernambuco, 2014. https://repositorio.ufpe.br/handle/123456789/11435.
Testo completoMade available in DSpace on 2015-03-09T13:43:26Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO Francisco Miranda Soares da Silva Neto.pdf: 1968720 bytes, checksum: 60383d7751d95b545cae9a16a83f611c (MD5) Previous issue date: 2014-02-27
In recent years, the diminishing rate with which we can increase the amount of transistors in a processor core has slowed down the increase of computers’ power. Moore’s Law appears to be drawing to an end. With it, the assumption that software written today will be more efficiently executed in the future simply due to processors’ evolution is being challenged. On the other hand, parallel applications can still be made more efficient by distributing work among different processors to be executed at the same time, thus reducing overall execution time. To enable parallelization, we must have multiple processor cores. This has led to the popularization of multicore architectures. However, writing parallel applications is not trivial. A program must be either written from the start to be executed in parallel, or later adapted for parallel execution. The programmer has the error-prone task of parallelizing the application through use of concurrency and parallelism constructs. Locking, the most common concurrency option, presents risks for inexperienced programmers, such as the famous Deadlock and Livelock problems. As we move from single core architectures to multicore, our programming languages need to make it easier for the programmers to use concurrency. Many researchers have pointed at Software Transactional Memory (STM) as an answer to that issue, as it is a lock-free, abstract way to guarantee isolated access to shared resources. But adapting for STM a program that uses lock is not simple. Besides being an error-prone task, technical details of the language might require special attention to preserve the program’s behavior. In this dissertation, we propose a set of program transformations for concurrency constructs in Haskell, a purely functional programming language. They may be used to refactor a program’s existing locks into transactional constructs from Haskell’s STM implementation. This allows a programmer to gain the benefits of working on STM even for programs which were already developed using locks. Each transformation is accompanied by execution examples and a discussion on its ability to preserve program behavior. We also present a supporting study, in which a controlled experiment was used to evaluate the benefits of locks or STM for the development of Haskell programs. Although subjects’ opinions tended to favor lock-based concurrency, those which used STM overall committed significantly fewer mistakes and required on average 12% less time to finish their assignments.
Recentemente, a queda na taxa de crescimento da quantidade de transístores integráveis em processadores tem desacelerado o crescimento de poder computacional. A lei de Moore parece aproximar-se de seu fim. Com isso, é desafiada a premissa de que software escrito hoje terá melhor desempenho no futuro simplesmente devido à evolução dos processadores. Ainda assim, aplicações paralelas ainda podem se tornar mais eficientes ao se distribuir trabalho entre diferentes processadores para execução simultânea. Para permitir a paralelização, são necessários múltiplos núcleos de processamento, o que tem levado à popularização de arquiteturas multinúcleo. Entretanto, a escrita de aplicações paralelas não é trivial. Deve-se escrever um programa para execução paralela desde sua concepção, ou adaptá-lo posteriormente para execução paralela. O programador tem a difícil tarefa de paralelização da aplicação através do uso de construções de concorrência e paralelismo. Travas, a mais comum opção para concorrência, apresentam riscos para programadores inexperientes, tais quais os famosos problemas de Deadlock e Livelock. Ao adaptarem-se de arquiteturas de um único núcleo para as de multinúcleo, as linguagens de programação precisam facilitar o uso de concorrência para os programadores. Muitos pesquisadores têm indicado Memória Transacional em Software (STM, do inglês Software Transactional Memory) como a resposta para esse problema, por ser uma forma abstrata e não bloqueante para garantia de acesso isolado a recursos compartilhados. Mas adaptar para STM programas que usam travas não é simples. Além de ser uma atividade propensa a erros, detalhes técnicos da linguagem podem requerer cuidados para se preservar o comportamento do programa. Nesta dissertação, é proposto um conjunto de transformações de programas para construções de concorrência em Haskell, uma linguagem de programação puramente funcional. Elas podem ser usadas para refatorar travas de um programa para uso de construções transacionais da implementação de STM em Haskell. Isso permite ao programador aproveitar os benefícios do trabalho com STM mesmo para programas já desenvolvidos com uso de travas. Cada transformação é acompanhada de exemplos de execução e uma discussão sobre sua capacidade de preservar o comportamento do programa. Também é apresentado um estudo de apoio, no qual um experimento controlado foi usado para avaliar os benefícios do uso de travas ou STM no desenvolvimento de programas em Haskell. Apesar das opiniões dos participantes terem favorecido o uso de travas, aqueles que usaram STM cometeram em geral menos erros e em média precisaram de 12% a menos de tempo para terminar suas tarefas.
Xue, Jiamin. "Scanning Probe Microscopy of Graphene and Carbon Nanotubes". Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/238911.
Testo completoOlthoff, Silke. "High temperature scanning tunnelling microscopy of adsorbate induced phase transitions". Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264547.
Testo completoLiu, Jun. "Neo--- A new perspective on STM capacity". Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5034.
Testo completoShao, Jianfei. "STM/STS and BEES Study of Nanocrystals". Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10526.
Testo completoLeandro, Silvana Castro [UNESP]. "Batimentos quânticos dependentes do SPIN via STM". Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/91985.
Testo completoNeste trabalho investigou-se teoricamente a densidade local de estados (LDOS) sondada por uma ponta de STM de metais hospedando um átomo adsorvido e uma impureza subsuperficial. Modelamos o sistema por meio do Hamiltoniano de Anderson de duas impurezas. Utilizando-se do procedimento da equação de movimento nas funções de Green, derivamos expressões analíticas para a LDOS de dois tipos de hospedeiro: uma superfície metálica e um fio quântico. A LDOS revela oscilações de Friedel e interferência Fano como função da posição da ponta. Essas oscilações dependem fortemente da dimensão do hospedeiro. Encontramos que os números de onda de Fermi dependentes do spin dão origem a batimentos quânticos spin-polarizados na LDOS. Embora a LDOS da superfície mostre um padrão de batimentos amortecidos, ela possui um comportamento oposto no fio quântico. Devido a ausência de amortecimento, o fio opera como um filtro de spins espacialmente resolvido com elevada eficiência.
We theoretically investigate the local density of states (LDOS) probed by an STM tip of ferromagnetic metals hosting a single adatom and a subsurface impurity. We model the system via the two-impurity Anderson Hamiltonian. By using the equation of motion with the relevant Green’s functions, we derive analytical expressions for the LDOS of two host types: a surface and a quantum wire. The LDOS reveals Friedel-like oscillations and Fano interference as a function of the STM tip position. These oscillations strongly depend on the host dimension. Interestingly, we find that the spin-dependent Fermi wave numbers of the hosts give rise to spin-polarized quantum beats in the LDOS. Although the LDOS for the metallic surface shows a damped beating pattern, it exhibits the opposite behavior in the quantum wire. Due to this absence of damping, the wire operates as a spatially resolved spin filter with a high efficiency.
Martins, Bruno Vieira da Cunha. "Desenho e construção de um UHV-STM". [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277568.
Testo completoTese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: O estudo da estrutura de nanosistemas individuais requer o uso de equipamentos capazes de gerar imagens de sistemas com poucos átomos. No caso de nanopartículas metálicas produzidas por síntese química, uma questão relevante e ainda pouco estudada é a organização dos passivantes sobre sua superfície e como isso contribui para a definição de sua estrutura de equilíbrio. Para abordar este tema, devemos ser capazes de gerar imagens de resolução atômica em superfícies com alto grau de curvatura: a microscopia de tunelamento (STM) representa o instrumento mais adequado para este tipo de tarefa. Entretanto, o estudo detalhado requer o uso de métodos não-convencionais de microscopia STM (ex. modulação da tensão de bias ou de setpoint), sendo assim desejável que tenhamos total controle sobre a operação do instrumento. Este domínio preciso sobre as características funcionais consiste na principal razão que justifica a construção de um STM no próprio grupo. Este trabalho descreve o desenho, a construção e a caracterização de um STM de Ultra-Alto Vácuo (UHV). Todo o desenho e a construção foram integralmente realizadas no grupo de pesquisa. Apresentamos e justificamos os parâmetros escolhidos para o projeto, os quais definem o perfil do instrumento. O projeto mecânico consiste em um sistema elástico tipo ¿Parallel-Guiding-Spring Table¿(PSM). O sistema de varredura foi desenvolvido utilizando na configuração tipo tripod para os atuadores piezoelétricos. Desenvolvemos dois protótipos da cabeça STM, ambos compatíveis com UHV. Apresentamos o projeto e a construção da câmara de vácuo e do sistema de amortecimento de vibração. Na parte eletrônica, desenvolvemos um projeto que envolve blocos anal'ogicos de precisão e componentes digitais de 16 bits. O sistema funciona com baixa tensão, o que o torna mais estável e menos suscetível ao ruído e a variações térmicas. O sistema de controle embarcado e seu modelo analítico são analisados de modo a se determinar os parâmetros para operação estável. Caracterizamos todo o sistema e obtivemos imagens para superfícies de Grafite e Au como forma de verificar a performance do equipamento construído. Por fim discutimos as dificuldades do projeto e apresentamos soluções para os pontos que requerem certa otimização
Abstract: The study of the structure of individual nanosystems requires the use of equipments capable of generating images of systems containing just a few atoms. In the case of metallic nanoparticles produced by chemical synthesis, a relevant and not much studied question is the organization of the passivant molecules over the surface and how they contribute to the definition of the equilibrium structure. To adress this issue, we must be capable of generating atomic resolution images on surfaces with a high level of curvature: the Scanning Tunneling Microscopy (STM) represents the most adequate instrument for this job. Nevertheless, the detailed study requires the use of non-conventional methods of STM microscopy (ex. bias voltage and setpoint modulation), then it is desirable to have total control over the instrument operation. This precise domain over the functional characteristics consists in the main reason that motivated the construction of a STM in our group. This work describes the design, construction and characterization of an Ultra-High Vacuum (UHV) STM. The design and construction were both integrally done in our research group. We present and justify the chosed project parameters, which define the profile of the instrument. The mechanical project consists of an elastic system of the ¿Parallel-Guiding- Spring-Table Mechanism¿(PSM) type. The scanning system was developed using the tripod configuration for the piezoelectric actuators. We have developed two prototypes for the STM head, both compatible with UHV. We present the project and construction of the vacuum chamber and the vibration isolating system. For the electronics, we have developed a project that involves precision analog blocks and 16 bits digital components. The system works with low voltage, what turns it more stable e less succeptible to noise and thermal variations. The embedded control system and its model are analysed in order to determine the stable operation parameters. We have characterized the system in detail and obtained images for Graphite and Gold surfaces as a way to verify the performance of the constructed equipment. Finally, we discuss the difficulties of the project and present solutions for the points that require optimization
Doutorado
Física da Matéria Condensada
Doutor em Ciências
Leandro, Silvana Castro. "Batimentos quânticos dependentes do SPIN via STM /". Ilha Solteira, 2013. http://hdl.handle.net/11449/91985.
Testo completoBanca: Devaney Ribeiro do Carmo
Banca: Guillermo Gerardo Cabrera Oyarzun
Resumo: Neste trabalho investigou-se teoricamente a densidade local de estados (LDOS) sondada por uma ponta de STM de metais hospedando um átomo adsorvido e uma impureza subsuperficial. Modelamos o sistema por meio do Hamiltoniano de Anderson de duas impurezas. Utilizando-se do procedimento da equação de movimento nas funções de Green, derivamos expressões analíticas para a LDOS de dois tipos de hospedeiro: uma superfície metálica e um fio quântico. A LDOS revela oscilações de Friedel e interferência Fano como função da posição da ponta. Essas oscilações dependem fortemente da dimensão do hospedeiro. Encontramos que os números de onda de Fermi dependentes do spin dão origem a batimentos quânticos spin-polarizados na LDOS. Embora a LDOS da superfície mostre um padrão de batimentos amortecidos, ela possui um comportamento oposto no fio quântico. Devido a ausência de amortecimento, o fio opera como um filtro de spins espacialmente resolvido com elevada eficiência.
Abstract: We theoretically investigate the local density of states (LDOS) probed by an STM tip of ferromagnetic metals hosting a single adatom and a subsurface impurity. We model the system via the two-impurity Anderson Hamiltonian. By using the equation of motion with the relevant Green's functions, we derive analytical expressions for the LDOS of two host types: a surface and a quantum wire. The LDOS reveals Friedel-like oscillations and Fano interference as a function of the STM tip position. These oscillations strongly depend on the host dimension. Interestingly, we find that the spin-dependent Fermi wave numbers of the hosts give rise to spin-polarized quantum beats in the LDOS. Although the LDOS for the metallic surface shows a damped beating pattern, it exhibits the opposite behavior in the quantum wire. Due to this absence of damping, the wire operates as a spatially resolved spin filter with a high efficiency.
Mestre
Robertson, Derek. "Variable processing of flavours in rat STM". Thesis, University of St Andrews, 1985. http://hdl.handle.net/10023/14682.
Testo completoPavelec, Jiří. "Vývoj lineárního posuvu pro UHV STM/AFM". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229812.
Testo completoZan, Recep. "Microscopy and spectroscopy of graphene : atomic scale structure and interaction with foreign atom species". Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/microscopy-and-spectroscopy-of-graphene-atomic-scale-structure-and-interaction-with-foreign-atom-species(7ff75244-c81a-414f-88d2-e614297f0390).html.
Testo completoGregoriev, Ross. "DEVELOPMENT OF A SILICON NANOWIRE MASK USING SCANNING PROBE MICROSCOPY". DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1283.
Testo completoCalupitan, Jan Patrick Dela Cruz. "Térarylènes photo réactifs : synthèse et études par microscopie à effet tunnel". Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30016/document.
Testo completoPhotoswitching diarylethenes, and their terarylene derivatives, are promising for the next generation optoelectronic devices because of their excellent photochemical properties. To make them viable for miniaturized electronic devices, it is necessary to study this class of molecules at the single molecular level by scanning tunneling microscopy under ultra-high vacuum (UHV STM). This thesis has three parts: 1) development of terarylenes highly sensitive to switching; (2) their modification for STM studies; and 3) results of STM investigations. To be studied at the single molecular level by STM, terarylenes with high switching sensitivity have been selected. These compounds display high quantum yields of up to 100 %. However, the cycloreversion reaction remains low so an alternative route, through a chain-reaction oxidative mechanism, has been sought. In the first part, we show that the efficiency and speed of this reaction may be controlled by attachment of aromatic groups on the reactive carbons. In the second part, we functionalized these molecules for STM studies by attaching tert-butyl and chloride groups. These substituents preserve their excellent photochemical and switching properties while tert-butyl groups show bright contrast in STM images, minimize aggregation of these molecules on the surface, and slightly decouple the molecule from the surface. The chlorine group has been introduced to direct their surface assembly on insulating substrates composed of crystalline NaCl bilayer previously grown over a metallic substrate. In the third part, results of STM are presented. We developed a new bottom-up approach for forming reproducible nanoassemblies of the unmodified terarylene at 77 K. Meanwhile, at 5 K, the terarylene functionalized with tert-butyl groups present different forms on the Ag(111) surface. From the positioning of the high-contrast tert-butyl groups and with the aid of DFT calculations, we assign different conformations of the molecule on the surface. On NaCl/Ag(111), direct visualization of the occupied and unoccupied states could be achieved. This illustrates that for these applications, molecules with appropriate properties can be interesting candidates for STM studies to obtain information at the single molecular level. Such molecules may be redesigned with a consideration of the surface as its mere presence may induce behavior previously unobserved or neglected if they were studied in solution. This thesis opens terarylenes to future applications which require a solid surface
Zhang, Tianzhen. "Limite d'Anderson et états de bords topologiques". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS240/document.
Testo completoThis thesis describes the fabrication of hybrid systems based on the narrow-gap semiconductor InAs and their study through STM spectroscopy and measure of the Josephson characteristics. In the first experiment, I show that high quality superconducting Lead (Pb) nanocrystals can be grown on the (110) surface of InAs. When the lateral size of the Pb nanocrystals is smaller than the Fermi wavelength of the two-dimensional electron gas accumulated at the surface of InAs, the nanocrystals are only weakly coupled to this electron gas and, consequently, are found in the regime of Coulomb blockade. This phenomenon enabled the first study of the superconducting parity effect through STM spectroscopy, which we employed to check the validity of the Anderson limit. In the second experiment, I show that high quality Bismuth (Bi) nanocrystals can also be grown on the (110) surface of InAs. In contrast to Pb nanocrystals, a wetting layer of Bi separates the nanocrystals from the InAs surface, leading to a strong coupling between the Bi nanocrystals and the substrate. From STM spectroscopy, we have identified edge-states on the (111) plane of the nanocrystals with C3 symmetry. Assuming that Bismuth is a 2nd order topological insulator as suggested theoretically, the observed edge-states can be interpreted naturally as the hinge-states predicted in this last topological band-theory. Finally, I will present the methods that I developed for the fabrication of hybrid Josephson junctions on bulk InAs and InAs/GaSb heterostructures, together with preliminary measurements of Josephson characteristics
Le, Sueur Hélène. "Un AFM-STM cryogénique pour la physique mésoscopique". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2007. http://tel.archives-ouvertes.fr/tel-00261434.
Testo completoAu cours de cette thèse, nous avons développé un microscope permettant d'effectuer la spectroscopie tunnel résolue spatialement (10 nm) de nanocircuits individuels, avec une résolution en énergie inégalée (10 µeV). Cet appareil combine les fonctions de Microscopie par Force Atomique (mode AFM) et de spectroscopie Tunnel locale (mode STM), et fonctionne à 30 mK. Dans le mode AFM, la topographie de l'échantillon est imagée grâce à un diapason en quartz piézoélectrique, ce qui permet de repérer les circuits. La spectroscopie tunnel peut ensuite être faite sur les zones conductrices.
Avec ce microscope, nous avons mesuré la DoS locale dans une structure hybride Supraconducteur-métal Normal-Supraconducteur (S-N-S). Dans un tel circuit, les propriétés électroniques de N et de S sont modifiées par l'effet de proximité supraconducteur. Notamment, pour des fils N courts, nous avons pu observer -comme prédit- la présence d'un gap dans sa DoS, indépendant de la position dans la structure : le “minigap”. De plus, en modulant la phase supraconductrice entre les deux S, nous avons mesuré la modification de ce gap, et sa disparition lorsque la différence de phase vaut π.
Nos résultats expérimentaux pour la DoS, ainsi que ses dépendances en phase, en position, et en longueur de N sont en accord quantitatif avec les prédictions de la théorie quasiclassique de la supraconductivité. Certaines de ces prédictions sont observées pour la première fois.
Clark, Kendal W. "STM Study of Molecular and Biomolecular Electronic Systems". Ohio University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1282363151.
Testo completoPham, Van Dong. "STM characterization of functionalized carbon nanotubes and graphene". Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCC245.
Testo completoIn this thesis we studied the interaction between organic molecules and carbon nanomaterials. Using scanning tunneling microscopy (STM) at low temperature and in ultra-high vacuum, we measured the properties of porphyrin molecules at the surface of graphene and single-walled carbon nanotubes. We first studied electron injection in graphene at defect sites (grain boundaries and nitrogen doping atoms). Using image-potential states, we evidenced the variation of local work function in doped graphene. Secondly, we investigated the properties of free-base porphyrin (H2TPP) molecules adsorbed on a Au(111) surface. We performed tip-induced tautomerization and dehydrogenation of the molecules, and revealed how these operations modify the molecular states and molecule-substrate interaction. Following these two preliminary studies, we studied the interaction of graphene with porphyrin molecules. We evidenced a weak electronic coupling between the molecules and graphene. We then showed how a nitrogen dopant on doped graphene can tune the molecule-surface interaction. The comparison between molecules adsorbed on nitrogen doping sites with those adsorbed on carbon sites clearly reveals a downshift of the energy of the molecular states at the doping sites. This downshift reveals a partial electron transfer from the nitrogen sites of graphene to the adsorbed molecules. In the last part of this thesis, we studied the properties of single-walled carbon nanotubes functionalized with a porphyrin polymer. The STM measurements revealed that the polymer is partially covering the nanotubes. Local spectroscopy indicated that the local density of states are modified at the polymer location
Vinet, Maud. "Etude par stm de nanostructures supraconductrices par proximite". Université Joseph Fourier (Grenoble), 2001. http://www.theses.fr/2001GRE10047.
Testo completoWillis, Mary L. "STM Studies of Oxygen Etching of Silicon Surfaces". VCU Scholars Compass, 2005. http://scholarscompass.vcu.edu/etd/1008.
Testo completoVoňka, Jakub. "Návrh a ověření nízkoteplotní části UHV - STM mikroskopu". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230611.
Testo completoDao, Tomáš. "Návrh nosné platformy pro nízkoteplotní UHV STM mikroskop". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231317.
Testo completoMcHardy, Robert John. "Surface diffusion of electrodes investigated by scanning tunnelling microscopy". Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366719.
Testo completoZheng, Husong. "STM Study of Interfaces and Defects in 2D Materials". Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/97440.
Testo completoDoctor of Philosophy
Since the discovery of graphene in 2004, two-dimensional (2D) materials have attracted more and more attentions. When the thickness of a layered material thinned to one or few atoms, it shows interesting properties different from its bulk phase. Due to the reduced dimensionality, interfaces and defects in 2D materials will significantly affect the electronic property and chemical activity. However, such nanometer scale features are several orders of magnitude smaller than the wavelength of visible light, which is the limit of resolution for optical microscope. Scanning tunneling microscope (STM) is widely used in study of 2D materials not only because it can provide the topography and local electronic information at atomic scale, but also because of the possibility of directly fabricate atomic scale structure on the surface. The first part of the thesis focuses on the synthesis of 2D TiSe2 with chemical vapor transport (CVT). TiSe2 belongs to the transition metal dichalcogenides (TMDCs) family, showing a sandwiched layered structure. When the temperature goes down to 200K, a 2 × 2 superlattice called charge density wave (CDW) will show up, which is clearly observed in our STM images. The second part of the thesis focuses on monolayer vacancy islands growing on TiSe2 surface controlled by electrical stressing. During continuous STM scanning, we have observed nonlinear area growth of the vacancy islands. The shape of those islands transfers from triangular to hexagonal. We successfully simulated such growth using phase-field modeling and first-principles calculations. The results could be potentially important for device reliability in systems containing ultrathin TMDCs and related 2D materials subject to electrical stressing. The third part of the thesis focuses on defects in 2D PtSe2. We observed five types of distinct defects in our STM topography images. By comparing them with DFT-calculated simulation images, we identified the types and characteristics of these defects. Our findings would provide critical insight into tuning of carrier mobility, charge carrier relaxation, and electron-hole recombination rates by defect engineering in few-layer 1T-PtSe2 and other related 2D materials.
Ericsson, Leif KE. "Growth and Characterization of ZnO Nanocrystals". Doctoral thesis, Karlstads universitet, Institutionen för ingenjörsvetenskap och fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-27156.
Testo completoBaksidestext The understanding of the surfaces of materials is of crucial importance to all of us. Considering nanocrystals (NCs), that have a large surface to bulk ratio, the surfaces become even more important. In the work in this thesis ZnO NCs were studied. The fundamental properties of ZnO surfaces were studied using distributions of ZnO NCs on SiO2/Si surfaces. Annealing at 650 °C in UHV cleaned the surfaces of the ZnO NCs enough for sharp LEEM imaging and chemical characterization while no sign of de-composition was found. A flat energy band structure for the ZnO/SiO2/Si system was proposed after 650 °C. Increasing the annealing temperature to 700 °C causes a de-composition of the ZnO that induce a downward band bending on the surfaces of ZnO NCs. Flat ZnO NCs with predominantly polar surfaces were grown using a microwave assisted process. Tuning the chemistry in the growth solution the growth was restricted to only plate-shaped crystals, i.e. a very uniform growth. The surfaces of the NCs were characterized using AFM, revealing a triangular reconstruction of the ZnO(0001) surface not seen without surface treatment at ambient conditions before. Following cycles of sputtering and annealing in UHV, we observe by STM a surface reconstruction interpreted as 2x2 with 1/4 missing Zn atoms.
Ccori, Pablo César Calcina. "Avaliação de desempenho do sistema de memória transacional de Clojure como biblioteca de sincronização na linguagem Java". Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/45/45134/tde-18082011-134122/.
Testo completoIn this work a performance evaluation of Clojure transactional memory implementation is presented, using it as a synchronization library to work together with other applications on Java virtual machine. It is implemented an interface layer between Clojure data structures and STMBench7 benchmark, and issues about overhead in performance are discussed.
Juteräng, David. "STM Study of PTCDA on Pb/Si(111) 1×1". Thesis, Karlstads universitet, Fakulteten för teknik- och naturvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-16179.
Testo completoFerlauto, Andre Santarosa. "Construção e aplicações de um microscópio de tunelamento (STM)". Universidade de São Paulo, 1996. http://www.teses.usp.br/teses/disponiveis/43/43133/tde-02082013-144215/.
Testo completoThe aim of this work was the construction of a scanning tunneling microscope (STM) and its application to some interesting physical systems. All its parts- measurement head, antivibration system, electronic feedback circuit and control software were developed and mounted in our laboratory. The instrument was tested and calibrated by optical interferometry and using images of the atomic structure of graphite obtained with the microscope itself. A systematic study of thin sputtered Au films was carried out in order to optimize the sputtering process for its use in the coverage of insulating samples to be investigated by scanning electron microscopy (SEM) and STM. We also proposed a new method to prepare semiconducting surfaces for STM measurements in air, which was used to study InAs quantum dots grown by molecular beam epitaxy (MBE).
吳誼暉 e Yee-fai Ng. "Optimization of etching parameters for STM tips and an STM study of SiC (0001) [square root]3 x [square root]3 reconstruction". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B29797834.
Testo completoNg, Yee-fai. "Optimization of etching parameters for STM tips and an STM study of SiC (0001) [square root]3 x [square root]3 reconstruction /". Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20567583.
Testo completoWalton, John Moorcroft. "The acquisition, analysis and processing of Scanning Auger Microscopy (SAM) and Scanning Tunneling Microscopy (STM) data". Thesis, University of York, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387184.
Testo completoIshii, Masaru. "Nanofabrication and STM/XPS Studies of Automotive Model Catalysts". Thesis, University of Reading, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485372.
Testo completoJemander, Thorbjörn. "STM studies of overlayers on semiconductor or insulator surfaces /". Linköping : Univ, 2001. http://www.bibl.liu.se/liupubl/disp/disp2001/tek686s.pdf.
Testo completoZotti, Linda Angela. "Molecular ordering and STM imaging of functionalized organic molecules". Thesis, University of Liverpool, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.479082.
Testo completoRokni, Fard Mahroo. "Study of fullerenes on Au (111) surfaces using STM". Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/7974/.
Testo completoOvramenko, Tamara. "STM studies of single organic molecules on silicon carbide". Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112315.
Testo completoThe interaction of organic molecules with a semiconductor surface enables the physical properties of the surface to be controlled, from a local modification using individual isolated molecules to passivation using a complete monolayer. Controlling the molecular interaction also allows us to modify the intrinsic properties of the molecules by partial or complete electronic decoupling between the molecular orbitals and the surface. To this end, this thesis presents experimental studies of the adsorption of molecules on the wide band gap 6H-SiC(0001)-3×3 substrate. The experiments were performed using Ultra-High Vacuum Room Temperature Scanning Tunneling Microscopy (UHV RT STM) and the results were compared with comprehensive theoretical Density Functional Theory (DFT) calculations. Three different molecules were studied in this thesis: C60, Caltrop and Trima. The STM and DFT studies show that individual C60 fullerene molecules are chemisorbed on the silicon carbide SiC(0001)-3×3 surface through the formation of a single Si-C bond to one silicon adatom, in contrast to multiple bond formation on other semiconducting surfaces. We observed three stable adsorption sites with respect to the Si adatoms of the surface unit cell. To explain the STM observations, Van der Waals forces between the C60 molecule and the neighboring surface atoms had to be included in the DFT calculations. The C60 molecules are also observed to form small clusters even at low coverage indicating the presence of a mobile molecular precursor state and non negligible intermolecular interactions. The second newly designed Caltrop molecule was studied on both the Si and SiC surfaces. Intact adsorption of this complex organic molecule cannot be realized using classical adsorption methods and requires the use of specific evaporation techniques. Our experimental results show remarkable behavior: The STM tip efficiently deposits single molecules one at a time, demonstrating the concept of single molecule printing. After adsorption on the Si surface through one bond, the Caltrop operates as a thermally activated molecular rotor. The third molecule to be studied is the Trima molecule. This molecule was chosen because it is commensurable in size with the surface Si adatom distance. The chemical termination of the molecule with a ketone group enables the successful functionalization of the SiC surface. The Trima molecule provides a rare and clear-cut example of the formation of two dative bonds between the oxygen atoms of the carbonyl groups and the Si adatoms of the SiC surface. This is revealed by the DFT calculations of the charge density. The charge distribution shows that there is no sharing of electrons between the oxygen atoms of the molecule and the surface which is clear evidence for the formation of a dative bond
Губкіна, Євгенія Олександрівна. "Дизайн веб-сайту для сфери послуг компанії «STM services»". Бакалаврська робота, ЗНУ, 2021. https://dspace.znu.edu.ua/jspui/handle/12345/5231.
Testo completoEN : The work is presented on 68 pages of printed text. The list of links includes 39 sources. The object of research is the development of the web-site "STM services. The subject of research – methods and technologies of web-site development. The purpose of the study is a theoretical analysis of web-site design. The following software was used in the work: Adobe Illustrator; Adobe Photoshop; Figma; Microsoft Word; Microsoft PowerPoint. Additional tools: Adobe Color; Content watch; Languagetool.
UA : Робота викладена на 68 сторінках друкованого тексту. Перелік посилань включає 39 джерел. Об'єктом дослідження є розробка web-сайту «STM services. Предмет дослідження – методи й технології розробки web-сайту. Мета дослідження – теоретичний аналіз проєктування web-сайтів. В роботі було використане наступне програмне забезпечення: Adobe Illustrator; Adobe Photoshop; Figma; Microsoft Word; Microsoft PowerPoint. Додаткові інструменти: Adobe Color; Сontent-watch; Languagetool.
Perera, Uduwanage Gayani E. "STM Investigation of Charge-Transfer and Spintronic Molecular Systems". Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1300141817.
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