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Littérature scientifique sur le sujet « Atomic defect »

Auteur : Grafiati

Publié le 9 mars 2023

Mis à jour le 10 mars 2023

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Articles de revues sur le sujet "Atomic defect"

Chu, Liu, Jiajia Shi et Eduardo Souza de Cursi. « The Fingerprints of Resonant Frequency for Atomic Vacancy Defect Identification in Graphene ». Nanomaterials 11, n^o 12 (20 décembre 2021) : 3451. http://dx.doi.org/10.3390/nano11123451.

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The identification of atomic vacancy defects in graphene is an important and challenging issue, which involves inhomogeneous spatial randomness and requires high experimental conditions. In this paper, the fingerprints of resonant frequency for atomic vacancy defect identification are provided, based on the database of massive samples. Every possible atomic vacancy defect in the graphene lattice is considered and computed by the finite element model in sequence. Based on the sample database, the histograms of resonant frequency are provided to compare the probability density distributions and interval ranges. Furthermore, the implicit relationship between the locations of the atomic vacancy defects and the resonant frequencies of graphene is established. The fingerprint patterns are depicted by mapping the locations of atomic vacancy defects to the resonant frequency magnitudes. The geometrical characteristics of computed fingerprints are discussed to explore the feasibility of atomic vacancy defects identification. The work in this paper provides meaningful supplementary information for non-destructive defect detection and identification in nanomaterials.

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Sozykin, Sergey Anatolevich, Valeriy Petrovich Beskachko et G. P. Vyatkin. « Atomic Structure and Mechanical Properties of Defective Carbon Nanotube (7,7) ». Materials Science Forum 843 (février 2016) : 78–84. http://dx.doi.org/10.4028/www.scientific.net/msf.843.78.

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The article presents the results of first-principle modeling of a defectless (7,7) carbon nanotube and (7,7) nanotubes containing single and double vacancy defects, as well as Stone–Wales defects. These types of defects are often found in real nanotubes and affect their properties. We have established that reliable results can be obtained by using models of more than 1.5 nm in length. It turned out that a single vacancy defect has the least influence on Young modulus, and double n type vacancy defect in the most influential. The elongation at break also depends on the defect type and is 30-60% less than for perfect tubes.

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Schuler, Bruno, Katherine A. Cochrane, Christoph Kastl, Edward S. Barnard, Edward Wong, Nicholas J. Borys, Adam M. Schwartzberg, D. Frank Ogletree, F. Javier García de Abajo et Alexander Weber-Bargioni. « Electrically driven photon emission from individual atomic defects in monolayer WS2 ». Science Advances 6, n^o 38 (septembre 2020) : eabb5988. http://dx.doi.org/10.1126/sciadv.abb5988.

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Quantum dot–like single-photon sources in transition metal dichalcogenides (TMDs) exhibit appealing quantum optical properties but lack a well-defined atomic structure and are subject to large spectral variability. Here, we demonstrate electrically stimulated photon emission from individual atomic defects in monolayer WS2 and directly correlate the emission with the local atomic and electronic structure. Radiative transitions are locally excited by sequential inelastic electron tunneling from a metallic tip into selected discrete defect states in the WS2 bandgap. Coupling to the optical far field is mediated by tip plasmons, which transduce the excess energy into a single photon. The applied tip-sample voltage determines the transition energy. Atomically resolved emission maps of individual point defects closely resemble electronic defect orbitals, the final states of the optical transitions. Inelastic charge carrier injection into localized defect states of two-dimensional materials provides a powerful platform for electrically driven, broadly tunable, atomic-scale single-photon sources.

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Kim, Honggyu, Yifei Meng, Ji-Hwan Kwon, Jean-Luc Rouviére et Jian Min Zuo. « Determination of atomic vacancies in InAs/GaSb strained-layer superlattices by atomic strain ». IUCrJ 5, n^o 1 (1 janvier 2018) : 67–72. http://dx.doi.org/10.1107/s2052252517016219.

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Determining vacancy in complex crystals or nanostructures represents an outstanding crystallographic problem that has a large impact on technology, especially for semiconductors, where vacancies introduce defect levels and modify the electronic structure. However, vacancy is hard to locate and its structure is difficult to probe experimentally. Reported here are atomic vacancies in the InAs/GaSb strained-layer superlattice (SLS) determined by atomic-resolution strain mapping at picometre precision. It is shown that cation and anion vacancies in the InAs/GaSb SLS give rise to local lattice relaxations, especially the nearest atoms, which can be detected using a statistical method and confirmed by simulation. The ability to map vacancy defect-induced strain and identify its location represents significant progress in the study of vacancy defects in compound semiconductors.

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Hsu, Julia W. P. « Semiconductor Defect Studies Using Scanning Probes ». Microscopy and Microanalysis 6, S2 (août 2000) : 704–5. http://dx.doi.org/10.1017/s1431927600036011.

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Understanding how defects alter physical properties of materials has lead to improvements in materials growth as well as device performance. Transmission electron microscopy (TEM) provides an invaluable tool for structural characterization of defects. Our current knowledge of crystallographic defects, such as dislocations, would not have been possible without TEM. Recently, scanning tunneling microscopy and scanning force microscopy (SFM) have shown the capability of imaging surface defects with atomic or near-atomic resolution in topographic images. What is more important is to gain knowledge on how the presence of a certain type of defects changes the physical properties of materials. For example, how is the carrier lifetime altered near electrically active defects? How does photoresponse vary near grain boundaries? Where are defect levels in the forbidden bandgap? This talk will discuss several examples of how scanning probe microscopies (SPMs) can contribute to this aspect of defect studies in semiconductors.

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Stemmer, S., G. Duscher, E. M. James, M. Ceh et N. D. Browning. « Atomic Scale Structure-Property Relationships of Defects and Interfaces in Ceramics ». Microscopy and Microanalysis 4, S2 (juillet 1998) : 556–57. http://dx.doi.org/10.1017/s143192760002290x.

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The evaluation of the two dimensional projected atom column positions around a defect or an interface in an electronic ceramic, as it has been performed in numerous examples by (quantitative) conventional high-resolution electron microscopy (HRTEM), is often not sufficient to relate the electronic properties of the material to the structure of the defect. Information about point defects (vacancies, impurity atoms), and chemistry or bonding changes associated with the defect or interface is also required. Such complete characterization is a necessity for atomic scale interfacial or defect engineering to be attained.One instructive example where more than an image is required to understand the structure property relationships, is that of grain boundaries in Fe-doped SrTi03. Here, the different formation energies of point defects cause a charged barrier at the boundary, and a compensating space charge region around it. The sign and magnitude of the barrier depend very sensitively on the atomic scale composition and chemistry of the boundary plane.

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Weber, William J., Fei Gao, Ram Devanathan, Weilin Jiang et Y. Zhang. « Defects and Ion-Solid Interactions in Silicon Carbide ». Materials Science Forum 475-479 (janvier 2005) : 1345–50. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.1345.

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Atomic-level simulations are used to determine defect production, cascade-overlap effects, and defect migration energies in SiC. Energetic C and Si collision cascades primarily produce single interstitials, mono-vacancies, antisite defects, and small defect clusters, while amorphous clusters are produced within 25% of Au cascades. Cascade overlap results in defect stimulated cluster growth that drives the amorphization process. The good agreement of disordering behavior and changes in volume and elastic modulus obtained computationally and experimentally provides atomic-level interpretation of experimentally observed features. Simulations indicate that close-pair recombination activation energies range from 0.24 to 0.38 eV, and long-range migration energies for interstitials and vacancies are determined.

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Wang, Zhen, Hangwen Guo, Shuai Shao, Mohammad Saghayezhian, Jun Li, Rosalba Fittipaldi, Antonio Vecchione et al. « Designing antiphase boundaries by atomic control of heterointerfaces ». Proceedings of the National Academy of Sciences 115, n^o 38 (13 août 2018) : 9485–90. http://dx.doi.org/10.1073/pnas.1808812115.

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Extended defects are known to have critical influences in achieving desired material performance. However, the nature of extended defect generation is highly elusive due to the presence of multiple nucleation mechanisms with close energetics. A strategy to design extended defects in a simple and clean way is thus highly desirable to advance the understanding of their role, improve material quality, and serve as a unique playground to discover new phenomena. In this work, we report an approach to create planar extended defects—antiphase boundaries (APB) —with well-defined origins via the combination of advanced growth, atomic-resolved electron microscopy, first-principals calculations, and defect theory. In La2/3Sr1/3MnO3 thin film grown on Sr2RuO4 substrate, APBs in the film naturally nucleate at the step on the substrate/film interface. For a single step, the generated APBs tend to be nearly perpendicular to the interface and propragate toward the film surface. Interestingly, when two steps are close to each other, two corresponding APBs communicate and merge together, forming a unique triangle-shaped defect domain boundary. Such behavior has been ascribed, in general, to the minimization of the surface energy of the APB. Atomic-resolved electron microscopy shows that these APBs have an intriguing antipolar structure phase, thus having the potential as a general recipe to achieve ferroelectric-like domain walls for high-density nonvolatile memory.

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Cho, Philip, Aihua Wood, Krishnamurthy Mahalingam et Kurt Eyink. « Defect Detection in Atomic Resolution Transmission Electron Microscopy Images Using Machine Learning ». Mathematics 9, n^o 11 (27 mai 2021) : 1209. http://dx.doi.org/10.3390/math9111209.

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Point defects play a fundamental role in the discovery of new materials due to their strong influence on material properties and behavior. At present, imaging techniques based on transmission electron microscopy (TEM) are widely employed for characterizing point defects in materials. However, current methods for defect detection predominantly involve visual inspection of TEM images, which is laborious and poses difficulties in materials where defect related contrast is weak or ambiguous. Recent efforts to develop machine learning methods for the detection of point defects in TEM images have focused on supervised methods that require labeled training data that is generated via simulation. Motivated by a desire for machine learning methods that can be trained on experimental data, we propose two self-supervised machine learning algorithms that are trained solely on images that are defect-free. Our proposed methods use principal components analysis (PCA) and convolutional neural networks (CNN) to analyze a TEM image and predict the location of a defect. Using simulated TEM images, we show that PCA can be used to accurately locate point defects in the case where there is no imaging noise. In the case where there is imaging noise, we show that incorporating a CNN dramatically improves model performance. Our models rely on a novel approach that uses the residual between a TEM image and its PCA reconstruction.

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Ziatdinov, Maxim, Ondrej Dyck, Xin Li, Bobby G. Sumpter, Stephen Jesse, Rama K. Vasudevan et Sergei V. Kalinin. « Building and exploring libraries of atomic defects in graphene : Scanning transmission electron and scanning tunneling microscopy study ». Science Advances 5, n^o 9 (septembre 2019) : eaaw8989. http://dx.doi.org/10.1126/sciadv.aaw8989.

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The presence and configurations of defects are primary components determining materials functionality. Their population and distribution are often nonergodic and dependent on synthesis history, and therefore rarely amenable to direct theoretical prediction. Here, dynamic electron beam–induced transformations in Si deposited on a graphene monolayer are used to create libraries of possible Si and carbon vacancy defects. Deep learning networks are developed for automated image analysis and recognition of the defects, creating a library of (meta) stable defect configurations. Density functional theory is used to estimate atomically resolved scanning tunneling microscopy (STM) signatures of the classified defects from the created library, allowing identification of several defect types across imaging platforms. This approach allows automatic creation of defect libraries in solids, exploring the metastable configurations always present in real materials, and correlative studies with other atomically resolved techniques, providing comprehensive insight into defect functionalities.

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Thèses sur le sujet "Atomic defect"

Siegl, Manuel. « Atomic-scale investigation of point defect interactions in semiconductors ». Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10043636/.

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Miniaturisation of computer hardware has increased the transistor density in silicon devices significantly and is approaching the ultimate physical limit of single atom transistors. A thorough understanding of the nature of materials at the atomic scale is needed in order to increase the transistor density further and exploit more recent technology proposals. Moreover, exploring other materials with more desirable characteristics such as wide band gap semiconductors with a higher dielectric strength and optical addressability are paramount in the effort of moving to a post-silicon era. Scanning Tunnelling Microscopy (STM) has been shown to be a suitable tool for the investigation of the technologically important material surface properties at the atomic scale. In particular, Scanning Tunnelling Spectroscopy (STS) – and its spatial extension Current Imaging Tunnelling Spectroscopy (CITS) – can reveal the electronic properties of single atom point defects as well as quantum effects caused by the confinement of energetic states. Nanoscale device performance is governed by these effects. In order to control and exploit the quantum effects, they firstly need to be understood. In this thesis, three systems have been investigated with STM and STS/CITS to broaden the comprehension of confined quantum states and material surface properties. The first data chapter concentrates on the interaction of confined quantum states of dangling bonds (DB) on the Si(111)-(√ 3 × √ 3)R30◦ surface. The site dependent interaction between neighbouring bound states is investigated by changing the distance and crystallographic direction between two DB point defects, revealing a non-linear constructive interference of the bound states and an antibonding state in resonance with the CB. In the second data chapter we explore subsurface bismuth dopants in silicon, a system relevant to recent information processing proposals. Bismuth was ion-implanted in the Si(001) surface and hydrogen passivated before the STM study. The bismuth dopants form a bismuth-vacancy (Bi+V) complex, which acts as an acceptor and lowers the Fermi level. The Bi+V complex further induces in-band gap states, which appear as square-like protrusions with a round depression in the centre. Interference of these states is energy dependent and the antibonding state is found at a lower energy than the bonding state due to the acceptor-like nature of the Bi+V defect complex. The third investigated system concerns the silicon face of the wide band gap semiconductor Silicon Carbide (SiC(0001)). The influence of atomic hydrogen on the 4HSiC(0001)-3 × 3 surface was investigated and found to result in a surface etching at the lower and upper end of the passivation temperature range. The electronic structure of two different surface defects of the 3 × 3 reconstruction is presented and a new superstructure consisting of silicon atoms on top of the 4H-SiC(0001)-(√ 3 × √ 3)R30◦ surface was discovered. A Schottky barrier height study of different surface reconstructions finds a nearly optimal power device fabrication value for the (√ 3× √ 3)R30◦ prepared surface. In summary, I have found a quantum interference that results in bonding and antibonding states for DB bound states on the Si(111):B surface and Bi+V complex states in the Si(001):H surface. Additionally, a new silicon superstructure on the SiC surface and a silicon reconstruction dependent Schottky barrier height are found.

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Valikova, Irina, et Andrei Nazarov. « Pressure effects on point defect diffusion features in cubic metals : atomic simulation ». Diffusion fundamentals 6 (2007) 48, S. 1-2, 2007. https://ul.qucosa.de/id/qucosa%3A14227.

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Lee, Donghun. « Atomic Scale Gate Electrode Formed by a Charged Defect : Scanning Tunneling Microscopy of Single Impurities in GaAs Semiconductors ». The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1274913629.

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Uppal, Hasan Javed. « Nanoscale performance, degradation and defect analysis of mos devices using high-k dielectric materials as gate stacks by atomic force microscopy ». Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509394.

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Gilbert, Mark R. « BCC metals in extreme environments : modelling the structure and evolution of defects ». Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:d972d28d-5d2d-4392-8cf5-fc5728dc74f6.

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Designing materials for fusion applications is a very challenging problem, requiring detailed understanding of the behaviour of materials under the kinds of extreme conditions expected in a fusion environment. During the lifetime of fusion-reactor components, materials will be subjected to high levels of neutron irradiation, but must still perform effectively at high operating temperatures and under significant loading conditions. Body-centred cubic (bcc) transition metals are some of the most promising candidates for structural materials in fusion because of their relatively high density, which allows for effective neutron-shielding with the minimum volume and mass of material. In this work we perform atomistic simulations on two of the most important of these, Fe and W. In this thesis we describe atomic-scale simulations of defects found in bcc systems. In part I we consider the vacancy and interstitial loop defects that are produced and accumulated as a result of irradiation-induced displacement cascades. We show that vacancy dislocation loops have a critical size below which they are highly unstable relative to planar void defects, and thus offer an explanation as to why they are so rarely seen in TEM observations of irradiated bcc metals. Additionally, we compare the diffusion rates of these vacancy loops to their interstitial counterparts and find that, while interstitial loops are more mobile, the difference in mobility is not as significant as might have been expected. In part II we study screw dislocations, which, as the rate limiting carriers of plastic deformation, are significantly responsible for the strength of materials. We present results from large-scale finite temperature molecular dynamics simulations of screw dislocations under stress and observe the thermally-activated kink-pair formation regime at low stress, which appears to be superseded by a frictional regime at higher stresses. The mobility functions fitted to the results are vital components in simulations of dislocation networks and other large-scale phenomena. Lastly, we develop a multi-string Frenkel-Kontorova model that allows us to study the core structure of screw dislocations. Subtle changes in the form of the interaction laws used in this model demonstrate the difference between the non-degenerate and degenerate core structures. We provide simple criteria to guarantee the correct structure when developing interatomic potentials for bcc metals.

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Jin, Xin. « Combining RBS/Channeling, X-ray diffraction and atomic-scale modelling to study irradiation-induced defects and microstructural changes ». Thesis, Limoges, 2021. http://www.theses.fr/2021LIMO0017.

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Les particules énergétiques sont souvent impliquées dans les activités de la société moderne. Ils ont contribué à l'essor de l'industrie des semi-conducteurs et pourront à l'avenir jouer un rôle important dans la mise en forme des matériaux de manière contrôlée. Cependant, leur nature énergétique pose de grands défis. Ainsi, il est essentiel d'avoir une compréhension globale des mécanismes sous-jacents des défauts induits par l'irradiation et des changements microstructuraux associés. Expérimentalement, les effets induits par l'irradiation peuvent être suivis par des techniques de caractérisation telles que la rétrodiffusion de Rutherford en mode canalisé (RBS/C) et la diffraction des rayons X (XRD), pour ne citer que ces deux car elles sont extrêmement sensibles aux perturbations au sein des cristaux. Cependant, il n'est pas aisé d'établir un lien clair entre le résultat de la mesure et la quantité et la nature des défauts, et ce lien est généralement fait à partir de modèles phénoménologiques. Dans ce travail de thèse, afin de faire face à ce problème, nous avons couplé modélisations à l'échelle atomique et simulations de signaux de RBS/C et XRD. La première étape a consisté à améliorer un code de simulation RBS/C récemment développé qui peut générer des signaux à partir de structures atomiques. En modifiant les algorithmes décrivant les interactions ion-solide et en ajoutant de nouvelles fonctionnalités, nous avons amélioré la flexibilité du code et son applicabilité à différents types de matériaux. Par la suite, nous avons utilisé le code RBS/C amélioré avec un code pour la DRX, lui aussi utilisant les données de structures atomiques. Avec ces signaux, nous avons extraits des paramètres de désordre et de déformation élastique et nous avons déterminé les cinétiques d'évolution associées et ce, pour un matériau modèle, à savoir UO2. Les défauts d'irradiation ont été générés par dynamique moléculaire (MD) avec la technique de l'accumulation de paires de Frenkel. Les cinétiques issues des modélisations présentent un accord qualitativement étroit avec celles déterminées expérimentalement, indiquant la validité de la méthodologie utilisée. La décomposition des cinétiques modélisées a permis de décrire de façon quantitative l'évolution des différents de types de défauts. Enfin, nous avons calculé les signaux RBS/C et XRD à partir de cellules modèles de Fe produites par MD et contenant chacune un type de défauts à une concentration donnée, les deux informations étant connues. Une comparaison claire du désordre et de la déformation élastique induits par les différents types de défauts dans Fe a été faite. La relation entre le rendement RBS/C et l'énergie des ions sonde a également été étudiée et la dépendance en énergie, fonction de la nature des défauts, a été établie. L'approche globale utilisée dans ce travail doit désormais être étendue et testée dans d'autres matériaux
Energetic particles are involved in many activities of modern society. They constitute a significant aspect of the semiconductor industry and may play important role in shaping materials in a controllable way in the future. However, their energetic nature also poses grand challenges, especially in the nuclear industry. Thus, it is crucial to have a comprehensive understanding of the underlying mechanisms of irradiation-induced defects and the associated microstructural changes. Experimentally, irradiation-induced effects can be monitored by characterization techniques including, but not limited to, Rutherford backscattering spectrometry in channeling mode (RBS/C) and X-ray diffraction (XRD), because they are extremely sensitive to changes in the crystalline structure. However, it is not straightforward to establish a clear link between the characterization results and the defect quantity and nature, and this connection is usually made according to simple phenomenological models. In this thesis work, in order to cope with this problem, we performed RBS/C and XRD atomic-scale modelling. The first step was to improve a recently developed RBS/C simulation code that can generate RBS/C signals from arbitrary atomic structures. By modifying the algorithms describing ion-solid interactions and adding new features, we enhanced the flexibility of the code and its applicability to different types of materials. Subsequently, we employed the improved RBS/C code with a XRD program to compute disordering and elastic strain kinetics of a model material, namely UO2, as a function of irradiation fluence. Radiation defects in UO2 were simulated by molecular dynamics (MD) calculations. Both the strain and disordering kinetics exhibit qualitatively close agreement with those determined experimentally, indicating the validity of the used methodology. The decomposition of the kinetics was performed in order to study the effect of each defect separately, which enables a quantitative description of the disordering and strain build-up processes. Finally, we computed RBS/C and XRD signals from Fe MD cells, each of which contains one single type of defects. A clear comparison of disorder and elastic strain induced by different types of defects in Fe was made. The relation between RBS/C yield and He energy was also studied using the Fe MD cells, which shows dependency with defect types. The global approach used in this work has the hope to be extended and tested in more materials

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CARUSO, FRANCESCO. « Study of electrical conduction and defects in high-permittivity metal oxides : experiments and simulation ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/382298.

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Inizialmente studiati dall’industria elettronica per sostituire lo strato isolante di SiO2, gli ossidi metallici sono ora ampiamente utilizzati come strati attivi o isolanti in una moltitudine di dispositivi elettronici. Le proprietà elettriche sono fortemente correlate ai difetti atomici, che generano stati elettronici localizzati all'interno del band gap che fungono da trappole di carica. La comprensione dei meccanismi fisici e del ruolo dei difetti che regolano il trasporto di carica negli ossidi metallici è pertanto della massima importanza per l'ottimizzazione dei dispositivi nanoelettronici. Tuttavia, il trasporto di carica e il ruolo dei difetti negli ossidi metallici è ancora oggetto di dibattito e non è stata raggiunta una comprensione completa e autoconsistente in ampi regimi di spessore, temperatura e tensione. In questa tesi ho studiato i meccanismi di conduzione in condensatori metallo-isolante-metallo (MIM) che incorporano tre materiali modello Al2O3, HfO2 e HfO2 drogato con Al (AlHfO) depositati mediante deposizione di strati atomici (ALD), in tre diversi spessori 5, 10 e 20nm. Inoltre, sono stati analizzati gli ossidi a base di Hf depositati utilizzando acqua o ozono come fonte di ossigeno ALD, nonché AlHfO a due concentrazioni di Al (5% e 17%). Lo scopo di questo studio è identificare le proprietà delle trappole di carica di ciascun materiale e studiare il percorso che gli elettroni percorrono all'interno dei dielettrici di ossidi metallici sotto l’azione del campo elettrico applicato. Viene inoltre discusso l'impatto dei diversi processi di produzione e dello spessore dei film sulle proprietà del materiale. Le proprietà delle trappole sono estratte dalla caratteristica sperimentale corrente-tensione dei condensatori MIM, in un ampio regime di temperatura e tensione, utilizzando un modello di trasporto di carica completo implementato nel software di simulazione Ginestra (Applied Materials). I difetti del Al2O3 sono caratterizzati da un'energia di ionizzazione termica ET~3.5eV e da un'energia di rilassamento EREL~1eV, in accordo con i calcoli ab-initio per le vacanze di ossigeno riportati in letteratura. In ogni ossido spesso 10 e 20nm a base di Hf sono identificati due tipi di difetti, caratterizzati da ET~1.8eV per le trappole "superficiali" e ET~3eV per le trappole "profonde". L'uso dell'acqua durante la deposizione ALD introduce cariche positive fisse nell'ossido. L'introduzione di atomi di Al nel HfO2 aumenta il band gap dell'ossido, senza influire sulla densità e sulle proprietà dei difetti. L'analisi ha permesso di identificare la posizione delle trappole maggiormente coinvolte nella conduzione e il meccanismo di trasporto dominante in ossidi spessi 20nm, ad ogni campo elettrico applicato. Nonostante le diverse proprietà, in ciascun materiale si verificano correnti di spostamento transitorie a bassi campi elettrici, originate dall'intrappolamento e dall'emissione di elettroni in/da trappole vicine all'interfaccia metallo/ossido. Il trasporto di elettroni attraverso l'ossido avviene solo a campi elettrici più elevati, in due modi diversi. Se una grande densità di trappole è localizzata energeticamente vicino al livello di Fermi degli elettrodi (come nel caso del HfO2), gli elettroni passano da una trappola all'altra fino a raggiungere l'anodo. Altrimenti, quando le trappole sono più vicine alla banda di conduzione (come nel Al2O3 e AlHfO), gli elettroni passano dal catodo in una trappola e poi nella banda di conduzione dell'ossido, interagendo solo con trappole vicino al catodo. Questi risultati potrebbero avere profonde implicazioni per l'ottimizzazione dei futuri dispositivi nanoelettronici. Inoltre, poiché negli ossidi metallici l'intrappolamento, la generazione di difetti e i processi di rottura sono fortemente correlati, i risultati presentati possono fornire nuove indicazioni sul processo di rottura degli ossidi metallici, con un impatto sull'affidabilità dei dispositivi.
Originally investigated in the electronic manufacturing to replace the SiO2 insulating layer, metal oxides are now extensively used as insulating or active layers in a multitude of electronics devices. It is known that the electrical properties are strongly correlated to atomic defects, which generate localized electronic states inside the band gap that act as charge traps. Therefore, the understanding of the physical mechanisms and the role of defects governing the charge transport in metal oxide stacks is of utmost importance for the optimization of nano-electronic devices. However, the charge transport and role of defects in metal oxides is still under debate and a complete and self-consistent understanding over large thickness, temperature and voltage regimes is not reached. In this thesis I investigated the conduction mechanisms in metal-insulator-metal (MIM) capacitors incorporating three model materials Al2O3, HfO2 and Al-doped-HfO2 (AlHfO) deposited by atomic layer deposition (ALD), in three different thicknesses 5, 10, and 20 nm. Furthermore, Hf-based oxides deposited using either water or ozone as ALD oxygen source, as well as AlHfO at two Al concentrations (5% and 17%) were analyzed. The aim of this study is to identify the charge traps properties of each material and investigate the path that electrons take within metal oxide dielectrics under applied electric field. Moreover, the impact of different manufacturing processes and film thicknesses on the material properties is discussed. Traps properties are extracted from experimental current-voltage characteristics of MIM capacitors, over a broad temperature and voltage regime, using a comprehensive charge transport model implemented in the Ginestra® (Applied Materials, Inc.) simulation software. Defects in Al2O3 are characterized by a thermal ionization energy ET≈3.5 eV below the dielectric conduction band minimum (CBM) and a relaxation energy EREL≈1 eV, in agreement with the ab-initio calculations of oxygen vacancies reported in literature. Two kinds of defects are identified in each 10 and 20 nm-thick Hf-based oxide, characterized by ET≈1.8eV for "shallow" traps, and ET≈3eV for "deep" traps. The use of water as oxygen source during the oxide ALD introduces fixed positive charges in the oxide. The introduction of Al atoms in HfO2 increases the oxide energy band gap, without significantly impacting on the density and properties of defects. The analysis allowed to identify the location of traps most involved in the conduction and the dominant transport mechanism in 20 nm-thick oxides, at each applied electric field. Despite the different properties, in each material transient displacement currents occur at low electric fields, originating from electron trapping and emission at traps near the metal/oxide interface. The transport of electrons through the oxide occurs only at higher electric fields, in two different ways. If a large density of traps is energetically located near the electrodes Fermi level (as in HfO2), the electrons tunnel from trap to trap until they reach the anode. Otherwise, when traps are closer to the conduction band (as in Al2O3 and AlHfO), the electrons tunnel from the cathode into one trap and then into the oxide conduction band, interacting only with traps near the cathode. These findings may have profound implications for the functional optimization of future nano-electronics devices. Furthermore, since in metal oxides trapping, defects generation and breakdown processes are strongly related, results can provide new insight in the breakdown process of metal oxides, impacting on device reliability.

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Bagués, Salguero Núria. « Atomic and electronic structure of self-organized defects in epitaxial films of functional perovskite-type oxides ». Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/405668.

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Les capes fines epitaxials d’òxids funcionals tipus perovskita (ABO3) presenten mecanismes d’acoblament d’intercara i de relaxació del desajust governats per un joc complex de graus de llibertat químics, electrònics i estructurals. Aquests mecanismes poden acomodar defectes, tals com dislocacions de desajust i parets de macla, que presenten una gran tendència a l’auto-organització amb escales característiques de desenes de nanòmetres. L’estructura de la xarxa en el nucli d’aquests defectes és diferent de la major part del material, i per tant pot ser considerat com una nano-fase amb propietats físiques probablement diferents, portant a la formació de nano-estructures funcionals. La correlació entre l’estructura del defecte i la funcionalitat, juntament amb la capacitat d’aquests defectes per auto-organitzar-se, ofereix una oportunitat única per l’elaboració bottom-up de nano-dispositius d’òxids funcionals complexes. Aquesta Tesi es centra en la caracterització de la microestructura, l’intercara i els defectes auto-organitzats de capes epitaxials i nanoestructures funcionals de materials d’òxids mitjançant l’ús de Microscòpia Electrònica de Transmissió. Es presta especial atenció a l’estructura atòmica i electrònica de les intercares i defectes generats, tals com dislocacions, parets de macla i segregacions de fases, així com als camps de deformació i la seva relació amb les homogeneïtats químiques. En aquesta direcció, dos sistemes diferents compostos per manganites de Lantà són considerats: nanocompost de LaMnO3:MnOx crescut sobre substrats de (001)SrTiO3 i de (001)LaAlO3; i capes de La0.7Sr0.3MnO3 amb defectes auto-organitzats crescudes sobre substrats de (001)SrTiO3 i de (001)LaAlO3. Els materials estudiats en aquest treball poden ser considerats com capes nanoestructurades resultants de l’autoorganització de defectes que relaxen el desajust: nanoinclusions de MnOx (defectes de volum) en el LaMnO3; parets de macla entre dominis de macla (defectes planars) en La0.7Sr0.3MnO3/SrTiO3 i dislocacions de desajust (defectes lineals) en La0.7Sr0.3MnO3 /LaAlO3. En el nanocompost de LaMnO3:MnOx, s’analitza la formació regular de nanoinclusions d’òxid de manganès verticalment alienades dins d’una capa de LaMnO3 a través d’una caracterització microestructural. Aquestes anàlisis inclouen la determinació de la microestructura del LaMnO3 respecte el substrat conjuntament amb la identificació de la fase de l’òxid de manganès i d’una fase secundària, una capa rica en La a prop de l’intercara LaMnO3-SrTiO3. En el cas del La0.7Sr0.3MnO3/SrTiO3, es realitza una anàlisi detallada de les parets de macla i de les implicacions d’aquestes en les propietats funcionals. Els canvis locals en les propietats físiques i estructurals de les parets de macla permeten veure una capa amb macles com a una estructura auto-organitzada consistint en nano-lamines verticals de La0.7Sr0.3MnO3 fortament comprimides dins d’una matriu tensionada de La0.7Sr0.3MnO3. En el cas de les capes ultrafines de La0.7Sr0.3MnO3/LaAlO3, s’analitza el mecanisme de relaxament d’aquestes capes, les quals alleugen la tensió de desajust a través de la formació de dislocacions per sobre d’un gruix de crític de capa de 2.5nm. Es realitza un estudi detallat dels canvis estructurals, químics i electrònics associats amb les dislocacions, posant especial atenció a la influència dels camps de deformació en la composició química a la nanoescala. En aquesta direcció, s’observa una reorganització química a la regió del nucli de la dislocació, la qual té lloc per acomodar la deformació. També s’explora la dependència de l’organització de les dislocacions amb el gruix de les capes. Finalment, són analitzades les implicacions del camp de deformació de les dislocacions en la topografia i el transport elèctric a la superfície de les capes, demostrant que la naturalesa multi-escala de les dislocacions és de gran potencial per la creació de nanoestructures funcionals organitzades espontàniament en la superfície de capes fines d’òxids complexes. Els principals resultats i conclusions obtinguts en aquesta Tesis obren una nova perspectiva per al desenvolupament d’estructures funcionals auto-organitzades basades en defectes que relaxen tensions.
The epitaxial thin films of functional perovskite-type oxides (ABO3) present interfacial coupling and misfit relaxation mechanisms governed by a complex interplay of chemical, electronic and structural degrees of freedom. The relaxation mechanisms of strained films may accommodate defects, such as misfit dislocations or twin walls, which exhibit a strong tendency towards self-organization with characteristic length scales of tens of nanometres. The core lattice structure of these defects is different from the bulk of the material and thus may be considered as a nano-phase with likely different physical properties, leading to the formation of functional nanostructures. The correlation between defect structure and functionality, together with the capacity of these defects to self-organize, offers a unique opportunity for the bottom-up elaboration of functional complex oxides nanodevices. This thesis focuses on the characterization of the microstructure, interface and self-organized defects of epitaxial films and functional nanostructures of oxide materials by using advanced transmission electron microscopy. Special emphasis is put on the atomic and chemical structure of the interfaces and generated defects, such as dislocations, twin walls and phase segregations, as well as on the strain fields and their correlation with chemical heterogeneities. In this regard, two different systems composed of lanthanum manganites are considered: LaMnO3:MnOx nanocomposite grown on (001)SrTiO3 and on (001)LaAlO3 substrates; and La0.7Sr0.3MnO3 films with self-organized defects grown on (001)SrTiO3 and on (001)LaAlO3. The materials studied in this work may be regarded as nanostructured films resulting from the self-organization of misfit relieving defects as follows: nanoinclusions of a MnOx phase (volume defects) in LaMnO3; twin walls between twin domains (planar defects) in La0.7Sr0.3MnO3 on SrTiO3; and misfit dislocations (line defects) in La0.7Sr0.3MnO3 on LaAlO3. In the LaMnO3:MnOx nanocomposite, the formation of regular vertically aligned nanoinclusions of a manganese oxide (MnOx) embedded in an LaMnO3 film is analysed via microstructural characterization. This analysis includes the determination of the LaMnO3 matrix microstructure with respect to the substrate together with the identification of the manganese oxide phase and a secondary phase: a La-rich layer close to LaMnO3-substrate interface. In the case of La0.7Sr0.3MnO3 on (001)SrTiO3 substrates, a detailed analysis of twin walls and their implications on the functional properties is performed. Local changes in the physical and structural properties of the TWs lead to the view of a twinned film as a self-organized nanostructure consisting of vertical nano-sheets of strongly compressed La0.7Sr0.3MnO3 embedded in a matrix of tensile strained La0.7Sr0.3MnO3. In the case of La0.7Sr0.3MnO3 ultrathin films grown on (001)LaAlO3, the relaxation mechanism of this films is analysed. These films relieve the misfit strain by the formation of misfit dislocations above a critical film thickness of 2.5 nm. A detailed study of structural, chemical and electronic changes associated with the dislocation is also performed paying particular attention to the influence of strain fields on chemical composition at the nanoscale. A chemical reorganization occurs to accommodate the strain at the dislocations core region. The dependence of the degree of order of the dislocation pattern on film thickness is also explored. Finally, the implications of the dislocation strain field on surface topography and electrical transport are analysed, demonstrating that the multiscale nature of dislocations holds great promise for the creation of spontaneous surface ordered functional nanostructures in complex oxide thin films.The results and main conclusions obtained in this work open new perspectives for the development of functional self-organized nanostructures based on strain relieving defects.

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Khazaka, Rami. « From atomic level investigations to membrane architecture : an in-depth study of the innovative 3C-SiC/Si/3C-SiC/Si heterostructure ». Thesis, Tours, 2016. http://www.theses.fr/2016TOUR4023/document.

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Le polytype cubique du carbure de silicium (3C-SiC) est un matériau très prometteur pour les applications MEMS. En plus de sa tenue mécanique et chimique, il peut être épitaxié sur des substrats Si de faible coût. De plus, l'hétéroépitaxie multiple, c’est-à-dire quand on empile plusieurs couches Si et 3C-SiC peut ouvrir des pistes pour de nouveaux dispositifs à base de 3C-SiC. Vue la complexité de développer de telles hétérostructures, nous avons procédé à l'amélioration de la qualité de chaque couche séparément. De plus, nous avons mené une étude approfondie sur la nature des défauts dans chaque couche. Après le développement de l'hétérostructure complète, nous avons procédé à la fabrication de microstructures à base de cet empilement. Nous présentons une méthode inédite pour former des membranes de 3C-SiC auto-supportées. Cette technique simplifie considérablement le procédé de fabrication de membranes tout en réduisant le temps de fabrication et le coût. En outre, elle aide à surmonter plusieurs problèmes techniques
Due to its outstanding physico-chemical properties, the cubic polytype of silicon carbide (3C-SiC) gained significant interest in several fields. In particular, this material emerged as a potential candidate to replace Si in MEMS devices operating in harsh environment. The development of 3C-SiC/Si/3C-SiC heterostructures on top of Si substrate can pave the road towards original and novel MEMS devices profiting from the properties of the 3C-SiC. However, such epitaxial system suffers from wide range of defects characterizing each layer. Thus, we first tried to improve the quality of each layer in this heterostructure. This was achieved relying on two levers; (i) the optimization of the growth parameters of each layer and (ii) the understanding of the nature of defects present in each layer. These two key points combined together allowed an in-depth understanding of the limit of improvement of the overall quality of this heterostructure. After the development of the complete heterostructure, the fabrication of 3C-SiC microstructures was performed. Furthermore, we presented an unprecedented method to form free-standing 3C-SiC membranes in-situ during its growth stage. This novel technique is expected to markedly simplify the fabrication process of suspended membranes by reducing the fabrication time and cost

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Drain, John Frederick. « Development of magnetic bond-order potentials for Mn and Fe-Mn ». Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:68a01493-4a20-4d78-ad4a-6c3c2fe072d6.

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While group VII 4d Tc and 5d Re have hexagonally close-packed (hcp) ground states, 3d Mn adopts the complex chi-phase which exhibits non-collinear magnetism. Density functional theory (DFT) calculations have shown that without magnetism the chi-phase remains the ground state of Mn implying that magnetism is not the critical factor, as is commonly believed, in driving the anomalous stability of the chi-phase over hcp. Using a tight-binding (TB) model it is found that while harder potentials stabilise close-packed hcp, a softer potential stabilises the more open chi-phase. By analogy with the structural trend from open to close-packed phases down the group IV elements, the anomalous stability of the chi-phase in Mn is shown to be due to 3d valent Mn lacking d states in the core which leads to an effectively softer atomic repulsion between the atoms than in 4d Tc and 5d Re. Subsequently an analytic Bond-Order Potential (BOP) is developed to investigate the structural and magnetic properties of elemental Mn at 0 K. It is derived within BOP theory directly from a new short-ranged orthogonal d-valent TB model of Mn, the parameters of which are fitted to reproduce the DFT binding energy curves of the five experimentally observed phases of Mn, alpha, beta, gamma, delta, and epsilon-Mn. Not only does the BOP reproduce qualitatively DFT binding energy curves of the five different structure types, it also predicts the complex collinear antiferromagnetic (AFM) ordering in alpha-Mn, the ferrimagnetic (FiM) ordering in beta-Mn and the AFM ordering in the other phases that are found by DFT. A BOP expansion including 14 moments is sufficiently converged to reproduce most of the properties of the TB model with the exception of the elastic shear constants which require further moments. Magnetic analytic BOPs are also developed for Fe and Fe-Mn. The Fe model correctly reproduces trends in the structural stabilities of the common metallic structures except that AFM hcp is overstabilised. Reproduction of the elastic constants with a 9-moment BOP is reasonable although as is found for the Mn BOP the elastic shear constants require more moments to converge. Vacancy formation energies are close to those determined by experiment and DFT and the relative stabilities of self-interstitial atom (SIA) defects in ferromagnetic bcc Fe are correctly reproduced. The SIA formation energies are found to be better than those calculated with existing BOP models. The Fe-Mn TB and BOP models were challenging to fit and nonmagnetic face-centred cubic (fcc) structures are overstabilised. Furthermore within BOP an incorrect magnetic solution is predicted for one fcc structure resulting in poor reproduction of the DFT stacking fault energies. Refitting the bond integrals might help to better reproduce the nonmagnetic hcp-fcc energy differences while an environment-dependent Stoner parameter could help provide the flexibility needed to correctly capture the magnetic energy differences.

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Livres sur le sujet "Atomic defect"

K, De Groh Kim, et NASA Glenn Research Center, dir. The dependence of atomic oxygen undercutting of protected polyimide Kapton® H upon defect size. [Cleveland, Ohio] : National Aeronautics and Space Administration, Glenn Research Center, 2001.

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Snyder, Aaron. The dependence of atomic oxygen undercutting of protected polyimide Kapton® H upon defect size. [Cleveland, Ohio] : National Aeronautics and Space Administration, Glenn Research Center, 2001.

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Ullmaier, H., dir. Atomic Defects in Metals. Berlin/Heidelberg : Springer-Verlag, 1991. http://dx.doi.org/10.1007/b37800.

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Frank-Kamenetskaya, O. V. Atomic defects and crystal structure of minerals. Sous la direction de Rozhdestvenskaya, I. V. (Ira V.) et Frank-Kamenet︠s︡kiĭ V. A. 2^e éd. Saint Petersburg : Yanus, 2004.

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Dongchuan, Wu, Old Dominion University. Research Foundation. et Langley Research Center, dir. Hyperthermal atomic oxygen generator. Norfolk, Va : Old Dominion University Research Foundation, 1990.

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Janot, Christian, Winfried Petry, Dieter Richter et Tasso Springer, dir. Atomic Transport and Defects in Metals by Neutron Scattering. Berlin, Heidelberg : Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-71007-0.

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The most controversial decision : Truman, the atomic bombs, and the defeat of Japan. Cambridge : Cambridge University Press, 2011.

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Great Britain. Advisory Committee on the Safety of Nuclear Installations. An examination of the CEGB's R6 procedure for the assessment of the integrity of structures containing defects. London : H.M.S.O., 1989.

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Defects and diffusion studied using PAC spectroscopy : Special topic volume with invited peer reviewed papers only. Zurich-Durnten, Switzerland : Trans Tech Publications, 2011.

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Rutledge, Sharon K. Undercutting of defects in thin film protective coatings on polymer surfaces exposed to atomic oxygen. [Washington, DC : National Aeronautics and Space Administration, 1989.

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Chapitres de livres sur le sujet "Atomic defect"

Weik, Martin H. « atomic defect absorption ». Dans Computer Science and Communications Dictionary, 72. Boston, MA : Springer US, 2000. http://dx.doi.org/10.1007/1-4020-0613-6_954.

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Baskes, M. I. « Defect and Atomic Process Simulations ». Dans Intermetallic Compounds - Principles and Practice, 765–78. Chichester, UK : John Wiley & Sons, Ltd, 2002. http://dx.doi.org/10.1002/0470845856.ch36.

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Kozubski, Rafał, Andrzej Biborski, Mirosław Kozłowski, Christine Goyhenex, Veronique Pierron-Bohnes, Mebarek Alouani, Marcus Rennhofer et Savko Malinov. « Atomic-Migration-Controlled Processes in Intermetallics ». Dans Defect and Diffusion Forum, 113–18. Stafa : Trans Tech Publications Ltd., 2008. http://dx.doi.org/10.4028/3-908451-55-8.113.

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Greene, Chris H. « Quantum Defect Theory ». Dans Springer Handbook of Atomic, Molecular, and Optical Physics, 751–59. Cham : Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-030-73893-8_50.

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Evteev, Alexander V., Elena V. Levchenko, Irina V. Belova et Graeme E. Murch. « Atomic Mechanism of Carbon Diffusion in Cementite ». Dans Defect and Diffusion Forum, 101–6. Stafa : Trans Tech Publications Ltd., 2008. http://dx.doi.org/10.4028/3-908451-55-8.101.

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Li, Jun Hui, Si Zong Min, Ji An Duan, Lei Han et Jue Zhong. « Atomic Diffusion Features in Au/Al & ; Al/Ni Bonding Interface ». Dans Defect and Diffusion Forum, 29–0. Stafa : Trans Tech Publications Ltd., 2005. http://dx.doi.org/10.4028/3-908451-20-5.29.

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Pierron-Bohnes, Veronique, R. V. P. Montsouka, Christine Goyhenex, T. Mehaddene, Leila Messad, H. Bouzar, Hiroshi Numakura, Katsushi Tanaka et B. Hennion. « Atomic Migration in Bulk and Thin Film L1₀ Alloys : Experiments and Molecular Dynamics Simulations ». Dans Defect and Diffusion Forum, 41–50. Stafa : Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/3-908451-35-3.41.

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Gruber, W., Günter Borchardt et Harald Schmidt. « Atomic Motion and Diffusion Mechanism of Hydrogen in Amorphous Ceramics of the System Si-B-C-N ». Dans Defect and Diffusion Forum, 63–68. Stafa : Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/3-908451-35-3.63.

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Shimokawa, Tomotsugu. « Atomistic Study of Disclinations in Nanostructured Metals ». Dans The Plaston Concept, 57–78. Singapore : Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-7715-1_3.

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AbstractDisclination is a line defect in which rotational symmetry is broken. Recently, such defects have been observed in nanostructured metals. Hence, disclinations can bring out the unique properties of nanostructured metals. This chapter shows two examples of disclination-mediated plastic phenomena observed in atomic simulations. The first one is the grain subdivision mechanism, which is related to the mobility of partial disclination under severe plastic deformation processes. The second one is a mechanism that improves the fracture toughness using the disclination shielding effect, which appears at grain boundaries after dislocation emission. These atomic simulations with the geometrical restrictions of boundary conditions showed the possibility of selecting a plastic deformation mode by designing structures, elements, and environments to obtain materials with excellent mechanical properties.

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Tatarenko, Valentin A., S. M. Bokoch, V. M. Nadutov, Taras M. Radchenko et Yong Bum Park. « Semi-Empirical Parameterization of Interatomic Interactions and Kinetics of the Atomic Ordering in Ni-Fe-C Permalloys and Elinvars ». Dans Defect and Diffusion Forum, 29–78. Stafa : Trans Tech Publications Ltd., 2008. http://dx.doi.org/10.4028/3-908451-62-0.29.

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Actes de conférences sur le sujet "Atomic defect"

Campbell, J. P., P. M. Lenahan, A. T. Krishnan et S. Krishnan. « NBTI : An Atomic-Scale Defect Perspective ». Dans 2006 IEEE International Reliability Physics Symposium Proceedings. IEEE, 2006. http://dx.doi.org/10.1109/relphy.2006.251259.

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Yudin, Valeriy I., et Alexey V. Taichenachev. « Mass defect effects in atomic clocks ». Dans 2017 Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium ((EFTF/IFC). IEEE, 2017. http://dx.doi.org/10.1109/fcs.2017.8088813.

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Gao, F. « Atomic Modeling of Defects, Defect Generation and Multiple Ion-Solid Interactions ». Dans APPLICATION OF ACCELERATORS IN RESEARCH AND INDUSTRY : 17TH International Conference on the Application of Accelerators in Research and Industry. AIP, 2003. http://dx.doi.org/10.1063/1.1619782.

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Mazevet, S. « Using Quantum Defect Theory in the (e,2e) Ionization of Argon ». Dans ATOMIC PROCESSES AND PLASMAS : 13th APS Topical Conference on Atomic Processes in Plasmas. AIP, 2002. http://dx.doi.org/10.1063/1.1516306.

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Osborne, Jason, Shuiqing Hu, Haiming Wang, Yan Hu, Jian Shi, Sean Hand et Chanmin Su. « High-speed atomic force microscopy for patterned defect review ». Dans SPIE Advanced Lithography, sous la direction de Alexander Starikov et Jason P. Cain. SPIE, 2013. http://dx.doi.org/10.1117/12.2011665.

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Murthy, Aravind N., Karl A. Flechsig, Wes Hillman, Keith Conard et Remmelt Pit. « Thermal Fly-Height Controlled Glide for Disk Defect Detection and In-Situ Defect Size Estimation for Disk Drives ». Dans ASME 2013 Conference on Information Storage and Processing Systems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/isps2013-2805.

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Current hard disk drives (HDD’s) use thermal fly-height control (TFC) during read/write operations. In this study, we use TFC technology during the disk glide process to determine sub-5nm height defects. We also utilize TFC to measure the height of the defect during glide operation. Addtionally, we magnetically mark the disk locations where defects are detected for further post-processing of the defects using optical surface analysis (OSA), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The defect height estimation during the glide was confirmed to be accurate by AFM and SEM analysis. Finally, we will present the TFC glide sensitivity showing capability of detecting smaller defects than conventional non-TFC glide technologies.

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Harmin, David A. « Multichannel quantum-defect theory of the Stark effect ». Dans International conference on the physics of electronic and atomic collisions. AIP, 1990. http://dx.doi.org/10.1063/1.39192.

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Lee, Z. H., C. J. Lin, S. W. Lai et J. H. Chou. « Gate Oxide Defect Localization and Analysis by Using Conductive Atomic Force Microscopy ». Dans ISTFA 2005. ASM International, 2005. http://dx.doi.org/10.31399/asm.cp.istfa2005p0235.

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Abstract This paper describes gate oxide defect localization and analysis using passive voltage contrast (PVC) and conductive atomic force microscopy (C-AFM) in a real product through two case studies. In this paper, 10% wt KOH was used to etch poly-Si and expose gate oxide. In the case studies, different types of gate oxide defects will cause different leakage paths. According to the I-V curve measured by C-AFM, we can distinguish between short mode and gate oxide related leakage. For gate oxide leakage, KOH wet etching was successfully used to identify the gate oxide pinholes.

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Krainov, V. P. « Barrier-Suppression Ionization of Complex Atoms and Diatomic Molecules ». Dans Applications of High Field and Short Wavelength Sources. Washington, D.C. : Optica Publishing Group, 1997. http://dx.doi.org/10.1364/hfsw.1997.the8.

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Theory of tunneling ionization of atoms and atomic ions by strong low- frequency laser radiation was developed in Ref.[1] (so called ADK- approach). This theory is based on the conception of the quasi-stationary electromagnetoc field producing tunneling ejection of valence electrons. A complex atom or an atomic ion is considered in the frames of quantum defect method; its wave function is an asymptotic wave function at the large distances from the atomic core. In Ref.[2] the angular and energy distributions of ejected electrons in tunneling ionization were obtained.

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Pan, Li, Don R. Metzger et Marek Niewczas. « The Meshless Dynamic Relaxation Techniques for Simulating Atomic Structures of Materials ». Dans ASME 2002 Pressure Vessels and Piping Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/pvp2002-1284.

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Traditionally, Molecular Dynamics combined with pair potential functions or the Embedded Atom Method (EAM) is applied to simulate the motion of atoms. When a defect is generated in the crystalline lattice, the equilibrium of atoms around it is destroyed. The atoms move to find a new place where the potential energy in the system is minimum, which could result in a change of the local atomic structure. The present paper introduces new Dynamic Relaxation algorithm, which is based on explicit Finite Element Analysis, and pair or EAM potential function, to find equilibrium positions of the block of atoms containing different structural defects. The internal force and stiffness at the atoms (nodes) are obtained by the first and second derivatives of the potential energy functions. The convergence criterion is based on the Euclidean norm of internal force being close to zero when the potential energy is minimum. The damping ratio affects the solution path so that different damping ratios could lead to different minimum potential energy and equilibrium shapes. The numerical responses and results by applying free boundary conditions and certain periodic boundary conditions are presented. The choice of scaled mass of atoms, proper time step and damping appropriate for the efficient and stable simulation is studied.

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Rapports d'organisations sur le sujet "Atomic defect"

Diaz de la Rubia, T., N. Soneda et Y. Shimomura. Atomic scale modeling of defect production and microstructure evolution in irradiated metals. Office of Scientific and Technical Information (OSTI), avril 1997. http://dx.doi.org/10.2172/543299.

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Xin, Y., S. J. Pennycook, N. D. Browning, S. Sivananthan, P. D. Nellist, J. P. Faurie et P. Gibart. Direct observations of atomic structures of defects in GaN by high-resolution Z-contrast STEM. Office of Scientific and Technical Information (OSTI), décembre 1997. http://dx.doi.org/10.2172/564252.

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Wolf, R. J., et K. A. Mansour. Molecular modeling of metal hydrides : 2. Calculation of lattice defect structures and energies utilizing the Embedded Atom Method. Office of Scientific and Technical Information (OSTI), décembre 1990. http://dx.doi.org/10.2172/6335193.

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