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ELECTRON MICROSCOPY AND MULTISCALE MODELING‐ EMMM‐2007: An International Conference Date: 3–7 September 2007 Location: Moscow (Russia) ISBN: 978-0-7354-0519-6 Editor(s): Anatoly S. Avilov, Sergei L. Dudarev, Laurence D. Marks

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Modeling of the Thermal‐Motion‐Induced Effects in Resonant X‐ray Diffraction Observed for Ge and ZnO

Vladimir E. Dmitrienko, Elena N. Ovchinnikova, Anastasiya M. Kolchinskaya, Aleksey P. Oreshko, Dmitry I. Bazhanov, Jun Kokubun, Kohtaro Ishida, Steve P. Collins, and Enver Kh. Mukhamedzhanov

AIP Conf. Proc. 999, pp. 1-11; doi:http://dx.doi.org/10.1063/1.2918105 (11 pages)

Online Publication Date: 17 April 2008

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Diffraction of X‐rays near absorption edges of atoms (resonant diffraction) is considered theoretically, modeled with modern computer programs, and compared with available experimental data. The process of resonant diffraction includes virtual excitation of an electron from an inner shell to empty electronic states. Therefore this process is very sensitive to atomic environment and to electronic and phonon properties of crystals. In particular, the X‐ray scattering amplitude becomes an anisotropic tensor with the symmetry corresponding to the temporal local symmetry of atomic position. The most spectacular result of this anisotropy is the excitation of additional X‐ray reflections otherwise forbidden by screw‐axis or glide‐plane symmetry of crystals. In comparison with EXAFS, the resonant diffraction is more sensitive to the symmetry of atomic environment. For example, the forbidden reflections can be caused by opposite chirality of atomic positions in centrosymmetric crystals or by phonon displacements of atoms. The presented here modeling of the thermal‐motion‐induced (TMI) reflections observed in Ge and ZnO demonstrates remarkable agreement between simulations and experimental data.
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61.05.cc Theories of x-ray diffraction and scattering
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.
65.40.-b Thermal properties of crystalline solids

Materials Physics Using a Combination of Density‐Functional Theory and Atomic‐Resolution Electron Microscopy

Sokrates T. Pantelides and Stephen J. Pennycook

AIP Conf. Proc. 999, pp. 12-19; doi:http://dx.doi.org/10.1063/1.2918099 (8 pages)

Online Publication Date: 17 April 2008

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Scanning transmission electron microscopes provide atomic‐resolution images and electron‐energy loss spectra of crystalline systems. Density functional theory is a “theoretical microscope” that provides energetically preferred structures and excitation spectra. This paper gives a summary of several applications that demonstrate the breadth and depth of new results that can be obtained from a synergistic application of the experimental and theoretical methods to a wide range of complex materials systems.
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81.05.-t Specific materials: fabrication, treatment, testing, and analysis
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
79.20.Uv Electron energy loss spectroscopy
61.72.S- Impurities in crystals
61.72.Mm Grain and twin boundaries

Protodefect as a Basis of Multilevel Nanoscale Plasticity of Crystal Materials

S. G. Psakhie, K. P. Zolnikov, and D. S. Kryzhevich

AIP Conf. Proc. 999, pp. 20-31; doi:http://dx.doi.org/10.1063/1.2918107 (12 pages)

Online Publication Date: 17 April 2008

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Atomic mechanisms of plastic deformation initiation in materials with crystal structure are investigated. It is shown that thermal fluctuations can be a reason for structural defect generation and there is a threshold strain value at which zones with local structural changes (protodefects) grow almost abruptly. The calculations illustrate that protodefect formation is induced by a local expansion of atomic volume.
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62.20.F- Deformation and plasticity
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling
61.72.-y Defects and impurities in crystals; microstructure
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Theoretical interpretation of electron energy‐loss spectroscopic images

L. J. Allen, A. J. D∕Alfonso, S. D. Findlay, M. P. Oxley, M. Bosman, V. J. Keast, E. C. Cosgriff, G. Behan, P. D. Nellist, and A. I. Kirkland

AIP Conf. Proc. 999, pp. 32-46; doi:http://dx.doi.org/10.1063/1.2918115 (15 pages)

Online Publication Date: 17 April 2008

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We discuss the theory of electron energy‐loss spectroscopic images in scanning transmission electron microscopy. Three case studies are presented which have as common themes issues of inelastic scattering, coherence and image interpretation. The first is a state‐by‐state inelastic transitions analysis of a spectroscopic image which does not admit direct visual interpretation. The second compares theory and experiment for two‐dimensional mapping. The third considers imaging in three dimensions via depth sectioning.
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79.20.Uv Electron energy loss spectroscopy
68.37.Lp Transmission electron microscopy (TEM)
42.30.-d Imaging and optical processing

Ab initio Real Space Calculations of Electron Energy Loss Spectra

A. P. Sorini, J. J. Rehr, and K. Jorissen

AIP Conf. Proc. 999, pp. 47-52; doi:http://dx.doi.org/10.1063/1.2918116 (6 pages)

Online Publication Date: 17 April 2008

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We briefly discuss recent progress in the theory of electron energy loss spectra (EELS) and related spectroscopies such as x‐ray absorption spectra (XAS). In particular we review how the real‐space Green∕s function (RSGF) approach and its extensions described below can provide quantitative ab initio treatments of both XAS and EELS. We also discuss differences in these spectra due to relativistic effects and finite momentum transfer.
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79.20.Uv Electron energy loss spectroscopy
78.70.Dm X-ray absorption spectra
31.15.A- Ab initio calculations
78.70.Ck X-ray scattering
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Cone‐angle Dependence of Ab‐initio Structure Solutions Using Precession Electron Diffraction

James Ciston, Christopher S. Own, and Laurence D. Marks

AIP Conf. Proc. 999, pp. 53-65; doi:http://dx.doi.org/10.1063/1.2918117 (13 pages)

Online Publication Date: 17 April 2008

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Precession electron diffraction (PED) is a technique which is gaining increasing interest due to its ease of use and reduction of the dynamical scattering problem in electron diffraction, leading to more direct structure solutions. We have performed a systematic study of the effect of precession angle for the mineral andalusite on kinematical extinctions and direct methods solutions where the semiangle was varied from 6.5 to 32 mrad in five discrete steps. We show that the intensities of kinematically forbidden reflections decay exponentially as the precession semiangle (φ) is increased and that the amount of information provided by direct methods increases monotonically but non‐systematically as φ increases. We have also investigated the zeolite‐framework mineral mordenite with PED and have found a direct methods solution where the 12‐ring is clearly resolved for the first time.
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61.05.J- Electron diffraction and scattering
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling

In‐Situ Transmission Electron Microscopy of the Dynamics of Point‐Defect Clusters in Metals

Kazuto Arakawa, Kotaro Ono, and Hirotaro Mori

AIP Conf. Proc. 999, pp. 66-78; doi:http://dx.doi.org/10.1063/1.2918118 (13 pages)

Online Publication Date: 17 April 2008

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Point defects and their clusters formed by high energy particle irradiation, plastic deformation, and so on, often affect mechanical and∕or electric properties of materials severely. Therefore, understanding of dynamic processes such as formation, growth, shrinkage, motion, and transformation of these defects is important in materials science. We briefly review our recent results related to the dynamics of point‐defect clusters in metals, which have been obtained by using in‐situ transmission electron microscopy.
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68.37.Lp Transmission electron microscopy (TEM)
62.20.F- Deformation and plasticity
61.72.J- Point defects and defect clusters
61.72.Bb Theories and models of crystal defects

The Behaviour of 1D CuI Crystal@SWNT Nanocomposite under Electron Irradiation

J. L. Hutchison, N. Grobert, R. M. Zakalyukin, A. A. Eliseev, M. V. Chernisheva, A. S. Kumskov, Yu. V. Grigoriev, A. V. Krestinin, B. Freitag, and N. A. Kiselev

AIP Conf. Proc. 999, pp. 79-92; doi:http://dx.doi.org/10.1063/1.2918119 (14 pages)

Online Publication Date: 17 April 2008

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Nanocomposite 1D CuI crystal@SWNT was obtained by the growth of CuI nanocrystals inside single walled carbon nanotubes (SWNTs) using the capillary technique. High resolution transmission electron microscopy (HRTEM) investigation of the atomic structure of 1D CuI crystals revealed two types of 1D CuI crystals: with growth direction <001> and <1math0> relative to the bulk hexagonal CuI stucture. EM images were recorded and atomic models of the structure were proposed. According to the proposed models and image simulations, the main contrast in the 1D crystal images arises from the iodine atoms. In this paper the 1D CuI crystal@SWNT nanocomposite behavior determined mainly by the influence of the electron beam was investigated and it is shown that the 1D CuI nanocrystals can oscillate and rotate inside the nanotube channel under a 100kV electron beam. The oscillations occur within an exposure time of 25 s. With longer exposure time of ∼ 90 s, the 1D crystal gradually decreases in length, sometimes moving inside the SWNT, CuI begins to evaporate and extruded, probably through defects in the tube wall. Outside the tube iodine is gradually lost but copper atoms are condensed into faceted clusters which grow subsequently into 3D Cu nanocrystals with fcc lattice.
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68.37.Og High-resolution transmission electron microscopy (HRTEM)
61.46.Fg Nanotubes
61.48.De Structure of carbon nanotubes, boron nanotubes, and other related systems
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling
61.46.Hk Nanocrystals

Higher‐order Frenkel‐Kontorova modelling of crowdions

S. P. Fitzgerald and D. Nguyen‐Manh

AIP Conf. Proc. 999, pp. 93-101; doi:http://dx.doi.org/10.1063/1.2918120 (9 pages)

Online Publication Date: 17 April 2008

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In this paper we model 〈111〉 self‐interstitial defects, or crowdions, using an extended version of the analytical Frenkel‐Kontorova model. We use a more general potential than the traditional sinusoidal one, and find that it can better describe the lattice potentials experienced by crowdions in the body‐centred‐cubic transition metals, as calculated in density functional theory. We obtain analytical formulae for the crowdion displacement field and elastic strain energy, as functions of three parameters appearing in the Lagrangian, for the generalized lattice potential. Furthermore, we investigate how the more complex structure of the generalized potential affects the effective potential experienced by the defect centre‐of‐mass, using a collective coordinate approach.
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61.72.Bb Theories and models of crystal defects
61.72.jj Interstitials
71.20.Be Transition metals and alloys

Multilevel Modeling of Phenomena of Irradiation‐induced Swelling and Growth of Materials with Close‐packed Structure

V. E. Panin, V. M. Chernov, D. D. Moiseenko, A. L. Zhevlakov, and P. V. Maksimov

AIP Conf. Proc. 999, pp. 102-117; doi:http://dx.doi.org/10.1063/1.2918097 (16 pages)

Online Publication Date: 17 April 2008

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A thermodynamic method of excited cellular automata is put forward for modeling mass transfer in an open multilevel system “surface layer—interface with chessboard‐like distribution of normal tensile and compressive stresses—substrate with stochastic distribution of atomic nanoclusters having excess atomic volume”. Under excess pressure in the bulk of the irradiated material one can see the formation of nanocluster flows along the conjugate directions of maximum tangential stresses. The outward material extrusion takes place in the local interface zones with normal tensile stresses. Such processes should underlie the swelling and growth of irradiated materials with close‐packed structure.
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81.10.-h Methods of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
62.20.F- Deformation and plasticity
61.80.-x Physical radiation effects, radiation damage
82.60.Qr Thermodynamics of nanoparticles

Strain Fields And Crystallographic Characteristics Of Interstitial Dislocation Loops of Various Geometry In BCC Iron

Alexander B. Sivak, Vladimir A. Romanov, and Viatcheslav M. Chernov

AIP Conf. Proc. 999, pp. 118-133; doi:http://dx.doi.org/10.1063/1.2918098 (16 pages)

Online Publication Date: 17 April 2008

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The formation energy, the relaxation volume, the dipole‐force tensor, the self strain tensor and strain fields of interstitial dislocation loops in bcc iron (clusters of self interstitial atoms) have been calculated by molecular statics. Hexagonal and square dislocation loops of different types with different Burgers vectors, directions of dislocation segments and habit planes containing up to ∼ 2500 self‐interstitials have been considered. Analytical expressions describing size dependence of the formation energy, the relaxation volume and the self strain tensor for the loops stated have been obtained. The most energetically favorable loops are hexagonal loops with Burgers vector a/2〈111〉 and habit plane {11x}, where x takes values in the range from 0 to 1 depending on the loop size. The formation energy of a〈100〉 loops with 〈100〉 and 〈110〉 dislocation segments is ∼ 14% and 23% greater than that of hexagonal a/2〈111〉 loops at N>500, respectively. The analysis of the formation energies of a/2〈111〉 and a〈100〉 loops demonstrated that the nucleation of an a〈100〉 loop by joining of two a/2〈111〉 loops is possible when the total number of constituent self‐interstitials in these loops is larger than 13.
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61.72.jj Interstitials
61.72.Bb Theories and models of crystal defects
61.80.-x Physical radiation effects, radiation damage
82.56.Na Relaxation

Spin‐Lattice Dynamics Simulations of Ferromagnetic Iron

Pui‐Wai Ma, C. H. Woo, and S. L. Dudarev

AIP Conf. Proc. 999, pp. 134-145; doi:http://dx.doi.org/10.1063/1.2918100 (12 pages)

Online Publication Date: 17 April 2008

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We develop a Spin‐Lattice Dynamics (SLD) simulation model for ferromagnetic iron where atoms are treated as classical particles with spins. The atoms interact via many‐body forces as well as via spin‐orientation‐dependent forces of the Heisenberg form. The coupling between the lattice and the spin degrees of freedom is described by a coordinate‐dependent exchange function. An algorithm for integrating the spin‐lattice dynamics equations of motion is based on the 2nd order Suzuki‐Trotter decomposition for the non‐commuting Liouville evolution operators for atomic coordinates and spins. The notions of the spin thermostat and the spin temperature are introduced through a combined application of the Langevin spin dynamics and the fiuctuation‐dissipation theorem. Several applications of the new method described in the paper illustrate the significant effect of the spin degrees of freedom on the dynamics of atomic motion in iron and iron‐based alloys, and confirm that the Spin‐Lattice Dynamics approach provides a viable framework for performing realistic large‐scale simulations of magnetic materials.
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63.10.+a General theory
75.50.Bb Fe and its alloys
75.10.Hk Classical spin models
75.10.Pq Spin chain models
82.56.Na Relaxation

Self‐Point Defects Characteristics and their Dependence on Stress Fields of Edge and Screw Basal Dislocations with Burgers Vector 1/3<11math0> in HCP Zr

D. A. Chulkin, V. M. Chernov, and A. B. Sivak

AIP Conf. Proc. 999, pp. 146-156; doi:http://dx.doi.org/10.1063/1.2918101 (11 pages)

Online Publication Date: 17 April 2008

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In hcp Zr crystal, the characteristics (formation and migration energies, relaxation volume and dipole tensor) of stable and metastable (including saddle point) configurations of self‐point defects (self‐interstitial atoms, vacancies) have been calculated by computer simulation with use of the many‐body interaction potential. The stress fields of the straight edge and screw basal dislocations with Burgers vector 1/3<11math0> and spatial dependence of the interaction energy between these dislocations and self‐point defects (elastic dipoles) have been calculated using the anisotropic theory of elasticity. Stress fields of dislocations significantly affect the point defects characteristics and behaviour in hcp Zr.
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61.72.J- Point defects and defect clusters
61.72.Lk Linear defects: dislocations, disclinations
62.20.D- Elasticity
66.30.-h Diffusion in solids

Asymptotics in discrete dislocation pile‐up modelling

R. E. Voskoboinikov

AIP Conf. Proc. 999, pp. 157-172; doi:http://dx.doi.org/10.1063/1.2918102 (16 pages)

Online Publication Date: 17 April 2008

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An asymptotic methodology for analysing pile‐ups of large numbers of dislocations is proposed. We provide robust proof of the interconnection between continuum and discrete approaches to dislocation description. The practical usefulness of the technique is tested on a pile‐up of screw or edge dislocations in a uniform material stressed against a lock. The approach is extended to the case of a pile‐up of screw dislocations stressed against an interface in a bimetallic solid. The dislocations are located with sufficient accuracy to predict the large but finite stress distribution close the interface. Such a prediction is impossible using a conventional continuum dislocation theory.
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61.72.Lk Linear defects: dislocations, disclinations
02.60.Cb Numerical simulation; solution of equations
81.40.Jj Elasticity and anelasticity, stress-strain relations

Dislocation Aging Caused By Absorbed Impurities

Boris V. Petukhov

AIP Conf. Proc. 999, pp. 173-185; doi:http://dx.doi.org/10.1063/1.2918103 (13 pages)

Online Publication Date: 17 April 2008

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Impurities absorption at dislocations manifests itself at different scales from single dislocation kinetics to macroscopic plasticity, and it is a tool to control dislocation motion and multiplication in semiconductor devices. Critical review of existing models of the phenomenon is given, and a new model consistent with the basic mechanism of dislocation dynamics in a high crystalline relief (the kink mode) is presented, which allows for a new interpretation of experimental observations. A random inhomogeneity of the absorbed impurities distribution along dislocations creates barriers of large amplitude against the kink motion, which require thermal activation to be overcome. As is shown, this leads to the existence of a dislocation‐mobility threshold at a stress σth dependent on temperature and interaction between impurities within the dislocation core. In the low‐temperature region, σth can significantly exceed the pinning stress σpin determined by the average concentration of absorbed impurities. This means extending of the load range for safe treatment of materials in semiconductor technology.
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61.72.Lk Linear defects: dislocations, disclinations
61.72.Yx Interaction between different crystal defects; gettering effect
85.30.-z Semiconductor devices
61.72.S- Impurities in crystals

Thermodynamic modelling of glasses at atomistic scale

Gilles Adjanor and Manuel Athènes

AIP Conf. Proc. 999, pp. 186-201; doi:http://dx.doi.org/10.1063/1.2918104 (16 pages)

Online Publication Date: 17 April 2008

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Establishing the conditions of phase equilibria involves measuring the relative free energies of the various phases appearing in a given multi‐component system. Equilibrium free energy differences are traditionally computed by thermodynamic integration : one may integrate, for instance with respect to inverse temperature, the mean internal energy that has been previously estimated using a Monte Carlo sampling method. Such an approach can not be applied to a glassy system because it slowly relaxes with time. To palliate this difficulty, we focus on the glass thermodynamic properties that can be described by restricting the phase space to a relevant portion of the energy landscape. Assuming that the glassy system gets trapped into a single metabasin after it is driven out of equilibrium, the thermodynamical potential is shown to correspond to a Landau free energy that can be computed by implementing a path‐sampling Monte Carlo scheme. The present method is applied to the calculation of the Gibbs free energies of binary amorphous alloys. We correlate the computed Gibbs free energies to the atomic structures and to the glass‐forming ability of metallic glasses. We finally compute the driving force to phase separation in a simplified three‐oxide nuclear glass modeled by a Born‐Mayer‐Huggins potential that includes a three‐body term, and we compare the simulated quantities and microstructures to the available experimental observations.
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64.10.+h General theory of equations of state and phase equilibria
65.40.-b Thermal properties of crystalline solids
64.70.P- Glass transitions of specific systems
64.60.My Metastable phases

Cluster Mechanism of Liquid Metals Crystallization at Great Supercooling: Liquid Silver

D. K. Belashchenko and E. S. Lobanov

AIP Conf. Proc. 999, pp. 202-212; doi:http://dx.doi.org/10.1063/1.2918106 (11 pages)

Online Publication Date: 17 April 2008

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The process of homogeneous crystallization is investigated using molecular dynamics method. The models consisted of 2048 atoms in the basic cube with periodical boundary conditions. Many‐particle inter‐atomic potential of Embedded Atom Model (EAM) was applied for Ag. The models were constructed at zero pressure. The structure of the models was inspected using the local order parameter, structure factor value, the number of solid‐like atoms and the energy. At the temperatures lower than 802 K the crystallization via cluster mechanism was observed in isothermal conditions with the creation of solid phase having fcc crystal structure. The crystallization mechanism differs from commonly applied classic nucleation mechanism. It consists of the steady growth of crystal‐like atoms number, creation of clusters from these atoms and the growth of these clusters. The clusters have very loose structure at the initial step of the process and the linear size of the clusters approaches very quickly the basic cube size. Crystal‐like atoms play the leading role in the cluster solidification. The bottom limit of supercooling is discovered and calculated for Ag ( ∼ 803 K). This is the temperature above which the cluster mechanism can′t work.
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61.20.Ja Computer simulation of liquid structure
61.25.Mv Liquid metals and alloys
64.10.+h General theory of equations of state and phase equilibria

Electron Microscopy Investigation of Amorphous Alloys

B. N. Grudin, S. V. Dolzhikov, E. V. Pustovalov, V. S. Plotnikov, and E. S. Slabzhennikov

AIP Conf. Proc. 999, pp. 213-227; doi:http://dx.doi.org/10.1063/1.2918108 (15 pages)

Online Publication Date: 17 April 2008

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The structure hierarchy of amorphous metallic alloys (AMA) was investigated by means of electron microscopy. Different kinds of microstructure with sizes from 0.2 nm to 3 mm were visualized in AMA. Microstructure image has a quasi‐stochastic nature. The two dimensional correlation function used for multi‐scale modeling consisted of Gauss and quasi‐periodic components. The Gauss component describes the stochastic structure of the amorphous matrix. The quasi‐periodic component describes any kind of structure ordering, for example, the atomic clusters in the amorphous matrix. An image modeling method was developed for atomic clusters and long wave AMA structure inhomogeneities. High resolution electron microscopy images of one‐ and two‐dimensional atomic clusters and electron microscopy images of long wave inhomogeneities in AMA structure (for example, “network” structures) were modeled using this method. The type of the correlation function and its parameters, and the estimation of electron potential distribution in the atomic structure were determined for different types of AMA structures. In this way the correlation characteristics of structure hierarchy in real AMA were experimentally determined.
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68.37.Og High-resolution transmission electron microscopy (HRTEM)
36.40.-c Atomic and molecular clusters
61.43.Dq Amorphous semiconductors, metals, and alloys

A Revisitation of Some Problems of Dislocations in Silicon

J. L. Demenet, V. Eremenko, D. Eyidi, and J. Rabier

AIP Conf. Proc. 999, pp. 228-237; doi:http://dx.doi.org/10.1063/1.2918109 (10 pages)

Online Publication Date: 17 April 2008

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Dislocation microstructures obtained following plastic deformation close to the Brittle to Ductile Transition temperature have been investigated using multiscale imaging techniques. TEM investigations show a multiplicity in the dislocation core configurations which can appear as dissociated of as perfect segments. The evidence, after etching, of trails of point defect behind dislocations is also characteristic of these deformation conditions. These observations are discussed in the light of the possible core structures of dislocation proposed in silicon.
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61.72.Lk Linear defects: dislocations, disclinations
61.72.J- Point defects and defect clusters
62.20.F- Deformation and plasticity
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Monte‐Carlo simulations of electronic excitations in swift heavy ion tracks in SiO2

N. A. Medvedev and A. E. Volkov

AIP Conf. Proc. 999, pp. 238-244; doi:http://dx.doi.org/10.1063/1.2918110 (7 pages)

Online Publication Date: 17 April 2008

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Monte‐Carlo simulations were applied for investigation of the initial electronic kinetics ( ⩽ 10−14 s) in tracks of Ca+19 (11.4 MeV∕u) in SiO2. The spatial and temporal distributions of the volume and excess energy densities of free electrons, electronic vacancies in different atomic shells and the lattice were obtained. It was demonstrated that at 10−14 s an essential part ( ∼ 55%) of the energy deposited by the ion is trapped in electronic vacancies. The energy transferred to the lattice at times shorter than the characteristic time of electron‐phonon coupling was determined. It was found that only ∼ 6% of the excess energy of delocalized electrons near the projectile trajectory ( ∼ 6 nm) may be thermalized on the time 10−14 s from the projectile passage. Ballistic spatial propagation of excess energy cannot be described by thermal diffusion.
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02.70.Uu Applications of Monte Carlo methods
34.50.Fa Electronic excitation and ionization of atoms (including beam-foil excitation and ionization)
61.80.Az Theory and models of radiation effects
61.80.Jh Ion radiation effects

Crystalline and Amorphous Frameworks with Giant Pores: What Information Can We Expect from Advanced TEM?

O. I. Lebedev and G. Van Tendeloo

AIP Conf. Proc. 999, pp. 245-256; doi:http://dx.doi.org/10.1063/1.2918111 (12 pages)

Online Publication Date: 17 April 2008

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The current intense research on new porous materials (nano‐∕micro‐ and mesoporous) is motivated by their numerous applications in catalysis, gas separation and gas storage or in nanosciences. Since several years, TEM is playing an important role as a structure characterization tool. Recently, a general approach for direct structure determination of some mesoporous materials by TEM has been reported. However, this method does not work for a number of porous materials because of the much lower stability under the e‐beam inside of electron microscope. We report here our latest results on numerous “TEM‐unstable” porous materials, such as nanoporous metal‐organic frameworks, and complex mesoporous materials, such as silica spherical particles. TEM results on new Zeolite‐type materials (Zeotile) and SBA‐15 material with impregnated VS nanoparticles are reported as well.
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68.37.Lp Transmission electron microscopy (TEM)
61.43.Gt Powders, porous materials
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Devitrification of Al‐Y‐Ni Glasses

A. L. Vasiliev and M. Aindow

AIP Conf. Proc. 999, pp. 257-267; doi:http://dx.doi.org/10.1063/1.2918112 (11 pages)

Online Publication Date: 17 April 2008

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Crystallization of gas‐atomized Al‐4.3Y‐3.8Ni alloy powder during consolidation has been studied ex‐situ in a transmission electron microscope using high‐resolution lattice imaging together with the image simulations, selected‐area diffraction and energy‐dispersive X‐ray spectrometry experiments. The as‐atomized powder is predominantly amorphous but some particles others show evidence of decomposition. On the application of heat and pressure two types of decomposition product are formed initially; equiaxed nanoscale α‐Al grains embedded in an amorphous matrix, and dendritic aluminum grains containing complex ordered structures. The ordered structures in the α‐Al were identified as Guinier‐Preston like zones: thin sheets of solute rich material parallel to {100} and {110} aluminum planes with ordered cubic symmetry. Amorphous and micro‐crystalline phases are in between the aluminum‐rich regions. The second and third stages of crystallization involve the conversion of these ordered phases and embryonic precipitates to the better‐known binary and ternary compounds.
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68.37.Lp Transmission electron microscopy (TEM)
64.70.P- Glass transitions of specific systems
61.72.Dd Experimental determination of defects by diffraction and scattering
61.05.cc Theories of x-ray diffraction and scattering
61.66.Dk Alloys

Metal Microstructure After Large Plastic Deformations: Models and TEM Possibilities

Alexander N. Tyumentsev

AIP Conf. Proc. 999, pp. 268-285; doi:http://dx.doi.org/10.1063/1.2918113 (18 pages)

Online Publication Date: 17 April 2008

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The results of electron microscopy examination of high‐energy structure states formed in metallic materials under different mechanical forcing conditions, including the formation of nanostructured states by the method of severe plastic deformation, are generalized. A structural model of these states as the states with high continual density of defects (dislocations and disclinations) in the bulk and at grain boundaries is proposed. New techniques for electron microscopy validation of these states and investigation of internal stresses and gradients (moments) of these stresses localized at the submicron scale level are reported. An analysis of cooperative (nondislocational) mechanisms of large plastic deformations is performed. The results of experimental validation of the new mechanism and crystal lattice re‐orientation—the mechanisms of direct plus reverse martensitic transformations (MT) in the fields of high local stresses are presented. Using these mechanisms, new (atomic) models of origination of dislocations, localization bands and deformation twins are developed.
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68.37.Lp Transmission electron microscopy (TEM)
62.20.F- Deformation and plasticity
61.72.Lk Linear defects: dislocations, disclinations
81.30.Kf Martensitic transformations

Metrology And Standardization For Nanotechnologies

V. P. Gavrilenko, Yu. A. Novikov, A. V. Rakov, and P. A. Todua

AIP Conf. Proc. 999, pp. 286-297; doi:http://dx.doi.org/10.1063/1.2918114 (12 pages)

Online Publication Date: 17 April 2008

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Metrology and standardization have a crucial role in the development of nanotechnologies. First Russian standards for nanotechnologies are considered. These standards are based on the use of silicon test objects–measures of small length at the nanoscale level. Characteristics of these test objects are presented.
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62.23.St Complex nanostructures, including patterned or assembled structures
06.20.fb Standards and calibration
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Ps Atomic force microscopy (AFM)
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Postdoc in Experimental CM Physics

University of Rochester
US - NY - Rochester
Biomedical Optics

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