WorldWideScience

Sample records for atom probe methods

  1. Encapsulation method for atom probe tomography analysis of nanoparticles

    International Nuclear Information System (INIS)

    Larson, D.J.; Giddings, A.D.; Wu, Y.; Verheijen, M.A.; Prosa, T.J.; Roozeboom, F.; Rice, K.P.; Kessels, W.M.M.; Geiser, B.P.; Kelly, T.F.

    2015-01-01

    Open-space nanomaterials are a widespread class of technologically important materials that are generally incompatible with analysis by atom probe tomography (APT) due to issues with specimen preparation, field evaporation and data reconstruction. The feasibility of encapsulating such non-compact matter in a matrix to enable APT measurements is investigated using nanoparticles as an example. Simulations of field evaporation of a void, and the resulting artifacts in ion trajectory, underpin the requirement that no voids remain after encapsulation. The approach is demonstrated by encapsulating Pt nanoparticles in an ZnO:Al matrix created by atomic layer deposition, a growth technique which offers very high surface coverage and conformality. APT measurements of the Pt nanoparticles are correlated with transmission electron microscopy images and numerical simulations in order to evaluate the accuracy of the APT reconstruction. - Highlights: • Pt nanoparticles were analyzed using atom probe tomography and TEM. • The particles were prepared by encapsulation using atomic layer deposition. • Simulation of field evaporation near a void results in aberrations in ion trajectories. • Apparent differences between TEM and APT analyses are reconciled through simulation of field evaporation from a low-field matrix containing high-field NPs; ion trajectory aberrations are shown to lead to an apparent mixing of the matrix into the NPs.

  2. A new method for mapping the three-dimensional atomic distribution within nanoparticles by atom probe tomography (APT).

    Science.gov (United States)

    Kim, Se-Ho; Kang, Phil Woong; Park, O Ok; Seol, Jae-Bok; Ahn, Jae-Pyoung; Lee, Ji Yeong; Choi, Pyuck-Pa

    2018-07-01

    We present a new method of preparing needle-shaped specimens for atom probe tomography from freestanding Pd and C-supported Pt nanoparticles. The method consists of two steps, namely electrophoresis of nanoparticles on a flat Cu substrate followed by electrodeposition of a Ni film acting as an embedding matrix for the nanoparticles. Atom probe specimen preparation can be subsequently carried out by means of focused-ion-beam milling. Using this approach, we have been able to perform correlative atom probe tomography and transmission electron microscopy analyses on both nanoparticle systems. Reliable mass spectra and three-dimensional atom maps could be obtained for Pd nanoparticle specimens. In contrast, atom probe samples prepared from C-supported Pt nanoparticles showed uneven field evaporation and hence artifacts in the reconstructed atom maps. Our developed method is a viable means of mapping the three-dimensional atomic distribution within nanoparticles and is expected to contribute to an improved understanding of the structure-composition-property relationships of various nanoparticle systems. Copyright © 2018 Elsevier B.V. All rights reserved.

  3. Detecting and extracting clusters in atom probe data: A simple, automated method using Voronoi cells

    International Nuclear Information System (INIS)

    Felfer, P.; Ceguerra, A.V.; Ringer, S.P.; Cairney, J.M.

    2015-01-01

    The analysis of the formation of clusters in solid solutions is one of the most common uses of atom probe tomography. Here, we present a method where we use the Voronoi tessellation of the solute atoms and its geometric dual, the Delaunay triangulation to test for spatial/chemical randomness of the solid solution as well as extracting the clusters themselves. We show how the parameters necessary for cluster extraction can be determined automatically, i.e. without user interaction, making it an ideal tool for the screening of datasets and the pre-filtering of structures for other spatial analysis techniques. Since the Voronoi volumes are closely related to atomic concentrations, the parameters resulting from this analysis can also be used for other concentration based methods such as iso-surfaces. - Highlights: • Cluster analysis of atom probe data can be significantly simplified by using the Voronoi cell volumes of the atomic distribution. • Concentration fields are defined on a single atomic basis using Voronoi cells. • All parameters for the analysis are determined by optimizing the separation probability of bulk atoms vs clustered atoms

  4. A Filtering Method to Reveal Crystalline Patterns from Atom Probe Microscopy Desorption Maps

    Science.gov (United States)

    2016-03-26

    reveal crystalline patterns from atom probe microscopy desorption maps Lan Yao Department of Materials Science and Engineering, University of Michigan, Ann...reveal the crystallographic information present in Atom Probe Microscopy (APM) data is presented. Themethod filters atoms based on the time difference...between their evaporation and the evaporation of the previous atom . Since this time difference correlates with the location and the local structure of

  5. Atomic beams probe surface vibrations

    International Nuclear Information System (INIS)

    Robinson, A.L.

    1982-01-01

    In the last two years, surface scientist have begun trying to obtain the vibrational frequencies of surface atoms in both insulating and metallic crystals from beams of helium atoms. It is the inelastic scattering that researchers use to probe surface vibrations. Inelastic atomic beam scattering has only been used to obtain vibrational frequency spectra from clean surfaces. Several experiments using helium beams are cited. (SC)

  6. Detecting device of atomic probe

    International Nuclear Information System (INIS)

    Nikonenkov, N.V.

    1979-01-01

    Operation of an atomic-probe recording device is discussed in detail and its flowsheet is given. The basic elements of the atomic-probe recording device intented for microanalysis of metals and alloys in an atomic level are the storage oscillograph with a raster-sweep unit, a two-channel timer using frequency meters, a digital printer, and a control unit. The digital printer records information supplied by four digital devices (two frequency meters and two digital voltmeters) in a four-digit binary-decimal code. The described device provides simultaneous recording of two ions produced per one vaporation event

  7. Lasers probe the atomic nucleus

    International Nuclear Information System (INIS)

    Eastham, D.

    1986-01-01

    The article is contained in a booklet on the Revised Nuffield Advanced Physics Course, and concentrates on two techniques to illustrate how lasers probe the atomic nucleus. Both techniques employ resonance fluorescence spectroscopy for obtaining atomic transition energies. The first uses lasers to determine the change in the nuclear charge radius with isotope, the second concerns the use of lasers for ultrasensitive detection of isotopes and elements. The application of lasers in resonance ionization spectroscopy and proton decay is also described. (UK)

  8. Modeling Atom Probe Tomography: A review

    Energy Technology Data Exchange (ETDEWEB)

    Vurpillot, F., E-mail: francois.vurpillot@univ-rouen.fr [Groupe de Physique des Matériaux, UMR CNRS 6634, Université de Rouen, Saint Etienne du Rouvray 76801 (France); Oberdorfer, C. [Institut für Materialwissenschaft, Lehrstuhl für Materialphysik, Universität Stuttgart, Heisenbergstr. 3, 70569 Stuttgart (Germany)

    2015-12-15

    Improving both the precision and the accuracy of Atom Probe Tomography reconstruction requires a correct understanding of the imaging process. In this aim, numerical modeling approaches have been developed for 15 years. The injected ingredients of these modeling tools are related to the basic physic of the field evaporation mechanism. The interplay between the sample nature and structure of the analyzed sample and the reconstructed image artefacts have pushed to gradually improve and make the model more and more sophisticated. This paper reviews the evolution of the modeling approach in Atom Probe Tomography and presents some future potential directions in order to improve the method. - Highlights: • The basics of field evaporation. • The main aspects of Atom Probe Tomography modeling. • The intrinsic limitations of the current method and future potential directions to improve the understanding of tip to image ion projection.

  9. Atom probe microanalysis: Principles and applications to materials problems

    International Nuclear Information System (INIS)

    Miller, M.K.; Smith, G.D.W.

    1987-01-01

    A historical background and general introduction to field emission and field-ionization, field-ion microscopy, and the atom probe is given. Physical principles of field ion microscopy are explained, followed by interpretation of images. Types of atom probes are discussed, as well as the instrumentation used in atomic probe microanalysis. Methods of atom probe analysis and data representation are covered, along with factors affecting performance and statistical analysis of atom probe data. Finally, some case studies and special types of analyses are presented

  10. The extended wedge method: atomic force microscope friction calibration for improved tolerance to instrument misalignments, tip offset, and blunt probes.

    Science.gov (United States)

    Khare, H S; Burris, D L

    2013-05-01

    One of the major challenges in understanding and controlling friction is the difficulty in bridging the length and time scales of macroscale contacts and those of the single asperity interactions they comprise. While the atomic force microscope (AFM) offers a unique ability to probe tribological surfaces in a wear-free single-asperity contact, instrument calibration challenges have limited the usefulness of this technique for quantitative nanotribological studies. A number of lateral force calibration techniques have been proposed and used, but none has gained universal acceptance due to practical considerations, configuration limitations, or sensitivities to unknowable error sources. This paper describes a simple extension of the classic wedge method of AFM lateral force calibration which: (1) allows simultaneous calibration and measurement on any substrate, thus eliminating prior tip damage and confounding effects of instrument setup adjustments; (2) is insensitive to adhesion, PSD cross-talk, transducer/piezo-tube axis misalignment, and shear-center offset; (3) is applicable to integrated tips and colloidal probes; and (4) is generally applicable to any reciprocating friction coefficient measurement. The method was applied to AFM measurements of polished carbon (99.999% graphite) and single crystal MoS2 to demonstrate the technique. Carbon and single crystal MoS2 had friction coefficients of μ = 0.20 ± 0.04 and μ = 0.006 ± 0.001, respectively, against an integrated Si probe. Against a glass colloidal sphere, MoS2 had a friction coefficient of μ = 0.005 ± 0.001. Generally, the measurement uncertainties ranged from 10%-20% and were driven by the effect of actual frictional variation on the calibration rather than calibration error itself (i.e., due to misalignment, tip-offset, or probe radius).

  11. Investigations of oxide particles in unirradiated ODS-Eurofer by TEM and 3D atom probe methods

    International Nuclear Information System (INIS)

    Aleev, A.A.; Iskandarov, N.A.; Nikitin, A.A.; Rogizhkin, S.V.; Zaluzhny, A.G.; Klimenkov, M.; Lindau, R.; Moeslang, A.; Vladimirov, P.

    2009-01-01

    Oxide dispersion strengthened steels possess better high-temperature creep and radiation resistance than conventionally produced ferritic/martensitic steels. This behavior is mainly caused by the presence of highly dispersed and extremely stable oxide particles with sizes of few nanometers. One of the promising oxides used for dispersion strengthening was yttria (Y 2 O 3 ), which was introduced into EUROFER by mechanical alloying followed by the hot isostatic pressing at temperature around 1000-1200 dg. C and pressure ∼100 MPa. It was found that mechanical properties were strongly depended on size and spatial distribution of the precipitates. Therefore considerable efforts are focused on the investigation of the chemical composition and orientation of precipitates with respect to the steel matrix. Recent studies of Eurofer ODS steel (9%-CrWVTa) by SANS revealed the presence of high number density structural features with a size of approximately one nanometer. At the same time, previous studies by TEM identified only high number of small (6-40 nm) Y 2 O 3 particles. In this work we tried to get a deeper inside into the nanostructure of this material by means of tomographic atom probe and to correlate the results with the picture obtained by TEM. The present investigations revealed fine (∼2 nm) enrichments containing not only yttrium and oxygen but also vanadium and nitrogen. Concentration of vanadium was found to be approximately at the same level as yttrium. Some of the enrichments contained only three or even two elements mentioned above. Estimated number density of enrichments is about (1/5) x 10 23 m -3 . We suppose that these enriched zones might be precursors of the larger precipitates observed by TEM. The thesis seems to be supported by the similarities of the chemical composition and spatial distribution of elements inside enriched zones and nano precipitates studied by atomic probe and analytical TEM methods. (author)

  12. Study of modification methods of probes for critical-dimension atomic-force microscopy by the deposition of carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Ageev, O. A., E-mail: ageev@sfedu.ru [Southern Federal University, Institute for Nanotechnologies, Electronics, and Electronic Equipment Engineering (Russian Federation); Bykov, Al. V. [NT-MDT (Russian Federation); Kolomiitsev, A. S.; Konoplev, B. G.; Rubashkina, M. V.; Smirnov, V. A.; Tsukanova, O. G. [Southern Federal University, Institute for Nanotechnologies, Electronics, and Electronic Equipment Engineering (Russian Federation)

    2015-12-15

    The results of an experimental study of the modification of probes for critical-dimension atomicforce microscopy (CD-AFM) by the deposition of carbon nanotubes (CNTs) to improve the accuracy with which the surface roughness of vertical walls is determined in submicrometer structures are presented. Methods of the deposition of an individual CNT onto the tip of an AFM probe via mechanical and electrostatic interaction between the probe and an array of vertically aligned carbon nanotubes (VACNTs) are studied. It is shown that, when the distance between the AFM tip and a VACNT array is 1 nm and the applied voltage is within the range 20–30 V, an individual carbon nanotube is deposited onto the tip. On the basis of the results obtained in the study, a probe with a carbon nanotube on its tip (CNT probe) with a radius of 7 nm and an aspect ratio of 1:15 is formed. Analysis of the CNT probe demonstrates that its use improves the resolution and accuracy of AFM measurements, compared with the commercial probe, and also makes it possible to determine the roughness of the vertical walls of high-aspect structures by CD-AFM. The results obtained can be used to develop technological processes for the fabrication and reconditioning of special AFM probes, including those for CD-AFM, and procedures for the interoperational express monitoring of technological process parameters in the manufacturing of elements for micro- and nanoelectronics and micro- and nanosystem engineering.

  13. Measurements of H-atom density by a catalytic probe

    International Nuclear Information System (INIS)

    Vesel, A.; Drenik, A.; Mozetic, M.

    2006-01-01

    One of the important plasma parameters in tokamaks is the density of neutral hydrogen atoms which can be measured by catalytic probes. The method is based on the catalytic recombination of H atoms on the metal surface. In order to prevent a substantial drain of atoms by the probe, it should be made as small as possible. But still this effect can not be neglected. Therefore a study of the influence of a catalytic probe on the H-atom density was performed. The source of neutral H-atoms was inductively coupled RF hydrogen plasma. The gas from the discharge vessel was leaked to an experimental chamber through a narrow tube with the diameter of 5 mm and the length of 6 cm. Charged particles created in the discharge vessel were recombined on the walls of the narrow tube, so that the gas entering the experimental chamber was a mixture of hydrogen atoms and molecules only. The density of H-atoms in the experimental chamber was measured with two nickel catalytic probes. One probe was at fixed position and the other one was made movable. A change in the probe signal of the fixed probe was measured versus the position of the movable probe. The measurements were performed at the pressures between 10 Pa and 200 Pa and at two different RF powers 200 W and 300 W. It was found that the density of neutral hydrogen atoms was reduced for about 20% due to the presence of the probe. This result was independent from the pressure in the experimental chamber. (author)

  14. Lasers probe the atomic nucleus

    International Nuclear Information System (INIS)

    Eastham, D.

    1983-01-01

    The role of lasers in nuclear physics research is discussed including nuclear structure experiments involving the measurement of isotope shifts and hyperfine splitting in atomic energy levels in unstable nuclei by resonance fluorescence spectroscopy and the ultra sensitive detection of isotopic element abundances. (U.K.)

  15. Atom-probe tomography the local electrode atom probe

    CERN Document Server

    Miller, Michael K

    2014-01-01

    In this comprehensive introduction to the use of APT in nanocharacterization, readers will find everything they need to get up to speed on the technique, from the core physics to state-of-the-art instrumentation and revised methods of data analysis.

  16. Creating and probing coherent atomic states

    Energy Technology Data Exchange (ETDEWEB)

    Reinhold, C.O.; Burgdoerfer, J. [Oak Ridge National Lab., TN (United States). Physics Div.]|[Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy; Frey, M.T.; Dunning, F.B. [Rice Univ., Houston, TX (United States)

    1997-06-01

    The authors present a brief review of recent experimental and theoretical time resolved studies of the evolution of atomic wavepackets. In particular, wavepackets comprising a superposition of very-high-lying Rydberg states which are created either using a short half-cycle pulse (HCP) or by rapid application of a DC field. The properties of the wavepackets are probed using a second HCP that is applied following a variable time delay and ionizes a fraction of the atoms, much like a passing-by ion in atomic collisions.

  17. Atomic probes of surface structure and dynamics

    International Nuclear Information System (INIS)

    Heller, E.J.; Jonsson, H.

    1992-01-01

    The following were studied: New semiclassical method for scattering calculations, He atom scattering from defective Pt surfaces, He atom scattering from Xe overlayers, thermal dissociation of H 2 on Cu(110), spin flip scattering of atoms from surfaces, and Car-Parrinello simulations of surface processes

  18. Innovation and optimization of a method of pump-probe polarimetry with pulsed laser beams in view of a precise measurement of parity violation in atomic cesium

    International Nuclear Information System (INIS)

    Chauvat, D.

    1997-10-01

    While Parity Violation (PV) experiments on highly forbidden transitions have been using detection of fluorescence signals; our experiment uses a pump-probe scheme to detect the PV signal directly on a transmitted probe beam. A pulsed laser beam of linear polarisation ε 1 excites the atoms on the 6S-7S cesium transition in a colinear electric field E || k(ex). The probe beam (k(pr) || k(ex)) of linear polarisation ε 2 tuned to the transition 7S-6P(3/2) is amplified. The small asymmetry (∼ 10 -6 ) in the gain that depends on the handedness of the tri-hedron (E, ε 1 , ε 2 ) is the manifestation of the PV effect. This is measured as an E-odd apparent rotation of the plane of polarization of the probe beam; using balanced mode polarimetry. New criteria of selection have been devised, that allow us to distinguish the true PV-signal against fake rotations due to electromagnetic interferences, geometrical effects, polarization imperfections, or stray transverse electric and magnetic fields. These selection criteria exploit the symmetry of the PV-rotation - linear dichroism - and the revolution symmetry of the experiment. Using these criteria it is not only possible to reject fake signals, but also to elucidate the underlying physical mechanisms and to measure the relevant defects of the apparatus. The present signal-to-noise ratio allows embarking in PV measurements to reach the 10% statistical accuracy. A 1% measurement still requires improvements. Two methods have been demonstrated. The first one exploits the amplification of the asymmetry at high gain - one major advantage provided by our detection method based on stimulated emission. The second method uses both a much higher incident intensity and a special dichroic component which magnifies tiny polarization rotations. (author)

  19. Atomic probes of surface structure and dynamics

    International Nuclear Information System (INIS)

    Heller, E.J.; Jonsson, H.

    1992-01-01

    Progress for the period Sept. 15, 1992 to Sept. 14, 1993 is discussed. Semiclassical methods that will allow much faster and more accurate three-dimensional atom--surface scattering calculations, both elastic and inelastic, are being developed. The scattering of He atoms from buckyballs is being investigated as a test problem. Somewhat more detail is given on studies of He atom scattering from defective Pt surfaces. Molecular dynamics simulations of He + and Ar + ion sputtering of Pt surfaces are also being done. He atom scattering from Xe overlayers on metal surfaces and the thermalized dissociation of H 2 on Cu(110) are being studied. (R.W.R.) 64 refs

  20. A versatile atomic number correction for electron-probe microanalysis

    International Nuclear Information System (INIS)

    Love, G.; Cox, M.G.; Scott, V.D.

    1978-01-01

    A new atomic number correction is proposed for quantitative electron-probe microanalysis. Analytical expressions for the stopping power S and back-scatter R factors are derived which take into account atomic number of the target, incident electron energy and overvoltage; the latter expression is established using Monte Carlo calculations. The correct procedures for evaluating S and R for multi-element specimens are described. The new method, which overcomes some limitations inherent in earlier atomic number corrections, may readily be used where specimens are inclined to the electron beam. (author)

  1. Data mining for isotope discrimination in atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Broderick, Scott R. [Department of Materials Science and Engineering and Institute for Combinatorial Discovery, Iowa State University, Ames, IA 50011-2230 (United States); Bryden, Aaron [Ames National Laboratory, Ames, IA 50011-2230 (United States); Suram, Santosh K. [Department of Materials Science and Engineering and Institute for Combinatorial Discovery, Iowa State University, Ames, IA 50011-2230 (United States); Rajan, Krishna, E-mail: krajan@iastate.edu [Department of Materials Science and Engineering and Institute for Combinatorial Discovery, Iowa State University, Ames, IA 50011-2230 (United States)

    2013-09-15

    Ions with similar time-of-flights (TOF) can be discriminated by mapping their kinetic energy. While current generation position-sensitive detectors have been considered insufficient for capturing the isotope kinetic energy, we demonstrate in this paper that statistical learning methodologies can be used to capture the kinetic energy from all of the parameters currently measured by mathematically transforming the signal. This approach works because the kinetic energy is sufficiently described by the descriptors on the potential, the material, and the evaporation process within atom probe tomography (APT). We discriminate the isotopes for Mg and Al by capturing the kinetic energy, and then decompose the TOF spectrum into its isotope components and identify the isotope for each individual atom measured. This work demonstrates the value of advanced data mining methods to help enhance the information resolution of the atom probe. - Highlights: ► Atom probe tomography and statistical learning were combined for data enhancement. ► Multiple eigenvalue decompositions decomposed a spectrum with overlapping peaks. ► The isotope of each atom was determined by kinetic energy discrimination. ► Eigenspectra were identified and new chemical information was identified.

  2. In Situ Atom Probe Deintercalation of Lithium-Manganese-Oxide.

    Science.gov (United States)

    Pfeiffer, Björn; Maier, Johannes; Arlt, Jonas; Nowak, Carsten

    2017-04-01

    Atom probe tomography is routinely used for the characterization of materials microstructures, usually assuming that the microstructure is unaltered by the analysis. When analyzing ionic conductors, however, gradients in the chemical potential and the electric field penetrating dielectric atom probe specimens can cause significant ionic mobility. Although ionic mobility is undesirable when aiming for materials characterization, it offers a strategy to manipulate materials directly in situ in the atom probe. Here, we present experimental results on the analysis of the ionic conductor lithium-manganese-oxide with different atom probe techniques. We demonstrate that, at a temperature of 30 K, characterization of the materials microstructure is possible without measurable Li mobility. Also, we show that at 298 K the material can be deintercalated, in situ in the atom probe, without changing the manganese-oxide host structure. Combining in situ atom probe deintercalation and subsequent conventional characterization, we demonstrate a new methodological approach to study ionic conductors even in early stages of deintercalation.

  3. Comparison of the quantitative analysis performance between pulsed voltage atom probe and pulsed laser atom probe

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, J., E-mail: takahashi.3ct.jun@jp.nssmc.com [Advanced Technology Research Laboratories, Nippon Steel & Sumitomo Metal Corporation, 20-1 Shintomi, Futtsu-city, Chiba 293-8511 (Japan); Kawakami, K. [Advanced Technology Research Laboratories, Nippon Steel & Sumitomo Metal Corporation, 20-1 Shintomi, Futtsu-city, Chiba 293-8511 (Japan); Raabe, D. [Max-Planck Institut für Eisenforschung GmbH, Department for Microstructure Physics and Alloy Design, Max-Planck-Str. 1, 40237 Düsseldorf (Germany)

    2017-04-15

    Highlights: • Quantitative analysis in Fe-Cu alloy was investigated in voltage and laser atom probe. • In voltage-mode, apparent Cu concentration exceeded actual concentration at 20–40 K. • In laser-mode, the concentration never exceeded the actual concentration even at 20 K. • Detection loss was prevented due to the rise in tip surface temperature in laser-mode. • Preferential evaporation of solute Cu was reduced in laser-mode. - Abstract: The difference in quantitative analysis performance between the voltage-mode and laser-mode of a local electrode atom probe (LEAP3000X HR) was investigated using a Fe-Cu binary model alloy. Solute copper atoms in ferritic iron preferentially field evaporate because of their significantly lower evaporation field than the matrix iron, and thus, the apparent concentration of solute copper tends to be lower than the actual concentration. However, in voltage-mode, the apparent concentration was higher than the actual concentration at 40 K or less due to a detection loss of matrix iron, and the concentration decreased with increasing specimen temperature due to the preferential evaporation of solute copper. On the other hand, in laser-mode, the apparent concentration never exceeded the actual concentration, even at lower temperatures (20 K), and this mode showed better quantitative performance over a wide range of specimen temperatures. These results indicate that the pulsed laser atom probe prevents both detection loss and preferential evaporation under a wide range of measurement conditions.

  4. Probing stem cell differentiation using atomic force microscopy

    International Nuclear Information System (INIS)

    Liang, Xiaobin; Shi, Xuetao; Ostrovidov, Serge; Wu, Hongkai; Nakajima, Ken

    2016-01-01

    Graphical abstract: - Highlights: • Atomic force microscopy (AFM) was developed to probe stem cell differentiation. • The mechanical properties of stem cells and their ECMs can be used to clearly distinguish specific stem cell-differentiated lineages. • AFM is a facile and useful tool for monitoring stem cell differentiation in a non-invasive manner. - Abstract: A real-time method using atomic force microscopy (AFM) was developed to probe stem cell differentiation by measuring the mechanical properties of cells and the extracellular matrix (ECM). The mechanical properties of stem cells and their ECMs can be used to clearly distinguish specific stem cell-differentiated lineages. It is clear that AFM is a facile and useful tool for monitoring the differentiation of stem cells in a non-invasive manner.

  5. Probing stem cell differentiation using atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Xiaobin [Graduate School of Science and Engineering, Tokyo Institute of Technology, Ookayama 2-12-1, Meguro-ku, Tokyo 152-8550 (Japan); Shi, Xuetao, E-mail: mrshixuetao@gmail.com [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641 (China); Ostrovidov, Serge [WPI-Advanced Institute for Materials Research, Tohoku University, Sendai (Japan); Wu, Hongkai, E-mail: chhkwu@ust.hk [Department of Chemistry & Division of Biomedical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China); Nakajima, Ken [Graduate School of Science and Engineering, Tokyo Institute of Technology, Ookayama 2-12-1, Meguro-ku, Tokyo 152-8550 (Japan)

    2016-03-15

    Graphical abstract: - Highlights: • Atomic force microscopy (AFM) was developed to probe stem cell differentiation. • The mechanical properties of stem cells and their ECMs can be used to clearly distinguish specific stem cell-differentiated lineages. • AFM is a facile and useful tool for monitoring stem cell differentiation in a non-invasive manner. - Abstract: A real-time method using atomic force microscopy (AFM) was developed to probe stem cell differentiation by measuring the mechanical properties of cells and the extracellular matrix (ECM). The mechanical properties of stem cells and their ECMs can be used to clearly distinguish specific stem cell-differentiated lineages. It is clear that AFM is a facile and useful tool for monitoring the differentiation of stem cells in a non-invasive manner.

  6. HAADF-STEM atom counting in atom probe tomography specimens: Towards quantitative correlative microscopy.

    Science.gov (United States)

    Lefebvre, W; Hernandez-Maldonado, D; Moyon, F; Cuvilly, F; Vaudolon, C; Shinde, D; Vurpillot, F

    2015-12-01

    The geometry of atom probe tomography tips strongly differs from standard scanning transmission electron microscopy foils. Whereas the later are rather flat and thin (atom probe tomography specimens. Based on simulations (electron probe propagation and image simulations), the possibility to apply quantitative high angle annular dark field scanning transmission electron microscopy to of atom probe tomography specimens has been tested. The influence of electron probe convergence and the benefice of deconvolution of electron probe point spread function electron have been established. Atom counting in atom probe tomography specimens is for the first time reported in this present work. It is demonstrated that, based on single projections of high angle annular dark field imaging, significant quantitative information can be used as additional input for refining the data obtained by correlative analysis of the specimen in APT, therefore opening new perspectives in the field of atomic scale tomography. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Dynamics of trapped atoms around an optical nanofiber probed through polarimetry.

    Science.gov (United States)

    Solano, Pablo; Fatemi, Fredrik K; Orozco, Luis A; Rolston, S L

    2017-06-15

    The evanescent field outside an optical nanofiber (ONF) can create optical traps for neutral atoms. We present a non-destructive method to characterize such trapping potentials. An off-resonance linearly polarized probe beam that propagates through the ONF experiences a slow axis of polarization produced by trapped atoms on opposite sides along the ONF. The transverse atomic motion is imprinted onto the probe polarization through the changing atomic index of refraction. By applying a transient impulse, we measure a time-dependent polarization rotation of the probe beam that provides both a rapid and non-destructive measurement of the optical trapping frequencies.

  8. Comparison of the quantitative analysis performance between pulsed voltage atom probe and pulsed laser atom probe.

    Science.gov (United States)

    Takahashi, J; Kawakami, K; Raabe, D

    2017-04-01

    The difference in quantitative analysis performance between the voltage-mode and laser-mode of a local electrode atom probe (LEAP3000X HR) was investigated using a Fe-Cu binary model alloy. Solute copper atoms in ferritic iron preferentially field evaporate because of their significantly lower evaporation field than the matrix iron, and thus, the apparent concentration of solute copper tends to be lower than the actual concentration. However, in voltage-mode, the apparent concentration was higher than the actual concentration at 40K or less due to a detection loss of matrix iron, and the concentration decreased with increasing specimen temperature due to the preferential evaporation of solute copper. On the other hand, in laser-mode, the apparent concentration never exceeded the actual concentration, even at lower temperatures (20K), and this mode showed better quantitative performance over a wide range of specimen temperatures. These results indicate that the pulsed laser atom probe prevents both detection loss and preferential evaporation under a wide range of measurement conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. New atom probe approaches to studying segregation in nanocrystalline materials

    International Nuclear Information System (INIS)

    Samudrala, S.K.; Felfer, P.J.; Araullo-Peters, V.J.; Cao, Y.; Liao, X.Z.; Cairney, J.M.

    2013-01-01

    Atom probe is a technique that is highly suited to the study of nanocrystalline materials. It can provide accurate atomic-scale information about the composition of grain boundaries in three dimensions. In this paper we have analysed the microstructure of a nanocrystalline super-duplex stainless steel prepared by high pressure torsion (HPT). Not all of the grain boundaries in this alloy display obvious segregation, making visualisation of the microstructure challenging. In addition, the grain boundaries present in the atom probe data acquired from this alloy have complex shapes that are curved at the scale of the dataset and the interfacial excess varies considerably over the boundaries, making the accurate characterisation of the distribution of solute challenging using existing analysis techniques. In this paper we present two new data treatment methods that allow the visualisation of boundaries with little or no segregation, the delineation of boundaries for further analysis and the quantitative analysis of Gibbsian interfacial excess at boundaries, including the capability of excess mapping. - Highlights: ► New data treatment methods allow delineation of grain boundaries, even without segregation. ► Proxigrams calculated from the surfaces accurately show the extent of segregation. ► Tessellation of the data volume can be used to map the Gibbsian interfacial excess

  10. New atom probe approaches to studying segregation in nanocrystalline materials

    Energy Technology Data Exchange (ETDEWEB)

    Samudrala, S.K.; Felfer, P.J.; Araullo-Peters, V.J. [School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, NSW 2006 (Australia); The Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Cao, Y.; Liao, X.Z. [School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, NSW 2006 (Australia); Cairney, J.M., E-mail: julie.cairney@sydney.edu.au [School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, NSW 2006 (Australia); The Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia)

    2013-09-15

    Atom probe is a technique that is highly suited to the study of nanocrystalline materials. It can provide accurate atomic-scale information about the composition of grain boundaries in three dimensions. In this paper we have analysed the microstructure of a nanocrystalline super-duplex stainless steel prepared by high pressure torsion (HPT). Not all of the grain boundaries in this alloy display obvious segregation, making visualisation of the microstructure challenging. In addition, the grain boundaries present in the atom probe data acquired from this alloy have complex shapes that are curved at the scale of the dataset and the interfacial excess varies considerably over the boundaries, making the accurate characterisation of the distribution of solute challenging using existing analysis techniques. In this paper we present two new data treatment methods that allow the visualisation of boundaries with little or no segregation, the delineation of boundaries for further analysis and the quantitative analysis of Gibbsian interfacial excess at boundaries, including the capability of excess mapping. - Highlights: ► New data treatment methods allow delineation of grain boundaries, even without segregation. ► Proxigrams calculated from the surfaces accurately show the extent of segregation. ► Tessellation of the data volume can be used to map the Gibbsian interfacial excess.

  11. Efficient atom localization via probe absorption in an inverted-Y atomic system

    Science.gov (United States)

    Wu, Jianchun; Wu, Bo; Mao, Jiejian

    2018-06-01

    The behaviour of atom localization in an inverted-Y atomic system is theoretically investigated. For the atoms interacting with a weak probe field and several orthogonal standing-wave fields, their position information can be obtained by measuring the probe absorption. Compared with the traditional scheme, we couple the probe field to the transition between the middle and top levels. It is found that the probe absorption sensitively depends on the detuning and strength of the relevant light fields. Remarkably, the atom can be localized at a particular position in the standing-wave fields by coupling a microwave field to the transition between the two ground levels.

  12. New atom probe approaches to studying segregation in nanocrystalline materials.

    Science.gov (United States)

    Samudrala, S K; Felfer, P J; Araullo-Peters, V J; Cao, Y; Liao, X Z; Cairney, J M

    2013-09-01

    Atom probe is a technique that is highly suited to the study of nanocrystalline materials. It can provide accurate atomic-scale information about the composition of grain boundaries in three dimensions. In this paper we have analysed the microstructure of a nanocrystalline super-duplex stainless steel prepared by high pressure torsion (HPT). Not all of the grain boundaries in this alloy display obvious segregation, making visualisation of the microstructure challenging. In addition, the grain boundaries present in the atom probe data acquired from this alloy have complex shapes that are curved at the scale of the dataset and the interfacial excess varies considerably over the boundaries, making the accurate characterisation of the distribution of solute challenging using existing analysis techniques. In this paper we present two new data treatment methods that allow the visualisation of boundaries with little or no segregation, the delineation of boundaries for further analysis and the quantitative analysis of Gibbsian interfacial excess at boundaries, including the capability of excess mapping. Copyright © 2013 Elsevier B.V. All rights reserved.

  13. Examination of biogenic selenium-containing nanosystems based on polyelectrolyte complexes by atomic force, Kelvin probe force and electron microscopy methods

    Energy Technology Data Exchange (ETDEWEB)

    Sukhanova, T. E., E-mail: tat-sukhanova@mail.ru; Vylegzhanina, M. E.; Valueva, S. V.; Volkov, A. Ya.; Kutin, A. A. [Institute of Macromolecular Compounds RAS, 199004 Bolshoy Pr., 31, St.-Petersburg (Russian Federation); Temiryazeva, M. P.; Temiryazev, A. G. [Kotel’nikov Institute of Radio Engineering and Electronics (Fryazino Branch) Russian Academy of Sciences, Fryazino, Moscow region, 141190 (Russian Federation)

    2016-06-17

    The morphology and electrical properties of biogenic selenium-containing nanosystems based on polyelectrolyte complexes (PECs) were examined using AFM, Kelvin Probe Force and electron microscopy methods. It has been found, that prepared nanostructures significantly differed in their morphological types and parameters. In particular, multilayers capsules can be produced via varying synthesis conditions, especially, the selenium–PEC mass ratio ν. At the “special point” (ν = 0.1), filled and hollow nano- and microcapsules are formed in the system. The multilayer character of the capsules walls is visible in the phase images. Kelvin Probe Force images showed the inhomogeneity of potential distribution in capsules and outside them.

  14. Depletion interaction measured by colloidal probe atomic force microscopy

    NARCIS (Netherlands)

    Wijting, W.K.; Knoben, W.; Besseling, N.A.M.; Leermakers, F.A.M.; Cohen Stuart, M.A.

    2004-01-01

    We investigated the depletion interaction between stearylated silica surfaces in cyclohexane in the presence of dissolved polydimethylsiloxane by means of colloidal probe atomic force microscopy. We found that the range of the depletion interaction decreases with increasing concentration.

  15. Pulsed-laser atom-probe field-ion microscopy

    International Nuclear Information System (INIS)

    Kellogg, G.L.; Tsong, T.T.

    1980-01-01

    A time-of-flight atom-probe field-ion microscope has been developed which uses nanosecond laser pulses to field evaporate surface species. The ability to operate an atom-probe without using high-voltage pulses is advantageous for several reasons. The spread in energy arising from the desorption of surface species prior to the voltage pulse attaining its maximum amplitude is eliminated, resulting in increased mass resolution. Semiconductor and insulator samples, for which the electrical resistivity is too high to transmit a short-duration voltage pulse, can be examined using pulsed-laser assisted field desorption. Since the electric field at the surface can be significantly smaller, the dissociation of molecular adsorbates by the field can be reduced or eliminated, permitting well-defined studies of surface chemical reactions. In addition to atom-probe operation, pulsed-laser heating of field emitters can be used to study surface diffusion of adatoms and vacancies over a wide range of temperatures. Examples demonstrating each of these advantages are presented, including the first pulsed-laser atom-probe (PLAP) mass spectra for both metals (W, Mo, Rh) and semiconductors (Si). Molecular hydrogen, which desorbs exclusively as atomic hydrogen in the conventional atom probe, is shown to desorb undissociatively in the PLAP. Field-ion microscope observations of the diffusion and dissociation of atomic clusters, the migration of adatoms, and the formation of vacancies resulting from heating with a 7-ns laser pulse are also presented

  16. Industrial application of atom probe tomography to semiconductor devices

    NARCIS (Netherlands)

    Giddings, A.D.; Koelling, S.; Shimizu, Y.; Estivill, R.; Inoue, K.; Vandervorst, W.; Yeoh, W.K.

    2018-01-01

    Advanced semiconductor devices offer a metrology challenge due to their small feature size, diverse composition and intricate structure. Atom probe tomography (APT) is an emerging technique that provides 3D compositional analysis at the atomic-scale; as such, it seems uniquely suited to meet these

  17. Atom probe tomography of a commercial light emitting diode

    International Nuclear Information System (INIS)

    Larson, D J; Prosa, T J; Olson, D; Lawrence, D; Clifton, P H; Kelly, T F; Lefebvre, W

    2013-01-01

    The atomic-scale analysis of a commercial light emitting diode device purchased at retail is demonstrated using a local electrode atom probe. Some of the features are correlated with transmission electron microscopy imaging. Subtle details of the structure that are revealed have potential significance for the design and performance of this device

  18. Two-dimensional atom localization via probe absorption in a four-level atomic system

    International Nuclear Information System (INIS)

    Wang Zhi-Ping; Ge Qiang; Ruan Yu-Hua; Yu Ben-Li

    2013-01-01

    We have investigated the two-dimensional (2D) atom localization via probe absorption in a coherently driven four-level atomic system by means of a radio-frequency field driving a hyperfine transition. It is found that the detecting probability and precision of 2D atom localization can be significantly improved via adjusting the system parameters. As a result, our scheme may be helpful in laser cooling or the atom nano-lithography via atom localization

  19. Solid-state electrochemistry on the nanometer and atomic scales: the scanning probe microscopy approach

    Science.gov (United States)

    Strelcov, Evgheni; Yang, Sang Mo; Jesse, Stephen; Balke, Nina; Vasudevan, Rama K.; Kalinin, Sergei V.

    2016-01-01

    Energy technologies of the 21st century require understanding and precise control over ion transport and electrochemistry at all length scales – from single atoms to macroscopic devices. This short review provides a summary of recent works dedicated to methods of advanced scanning probe microscopy for probing electrochemical transformations in solids at the meso-, nano- and atomic scales. Discussion presents advantages and limitations of several techniques and a wealth of examples highlighting peculiarities of nanoscale electrochemistry. PMID:27146961

  20. Multivariate statistical analysis of atom probe tomography data

    International Nuclear Information System (INIS)

    Parish, Chad M.; Miller, Michael K.

    2010-01-01

    The application of spectrum imaging multivariate statistical analysis methods, specifically principal component analysis (PCA), to atom probe tomography (APT) data has been investigated. The mathematical method of analysis is described and the results for two example datasets are analyzed and presented. The first dataset is from the analysis of a PM 2000 Fe-Cr-Al-Ti steel containing two different ultrafine precipitate populations. PCA properly describes the matrix and precipitate phases in a simple and intuitive manner. A second APT example is from the analysis of an irradiated reactor pressure vessel steel. Fine, nm-scale Cu-enriched precipitates having a core-shell structure were identified and qualitatively described by PCA. Advantages, disadvantages, and future prospects for implementing these data analysis methodologies for APT datasets, particularly with regard to quantitative analysis, are also discussed.

  1. Probing dark energy with atom interferometry

    International Nuclear Information System (INIS)

    Burrage, Clare; Copeland, Edmund J.; Hinds, E.A.

    2015-01-01

    Theories of dark energy require a screening mechanism to explain why the associated scalar fields do not mediate observable long range fifth forces. The archetype of this is the chameleon field. Here we show that individual atoms are too small to screen the chameleon field inside a large high-vacuum chamber, and therefore can detect the field with high sensitivity. We derive new limits on the chameleon parameters from existing experiments, and show that most of the remaining chameleon parameter space is readily accessible using atom interferometry

  2. Probing dark energy with atom interferometry

    Energy Technology Data Exchange (ETDEWEB)

    Burrage, Clare; Copeland, Edmund J. [School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD (United Kingdom); Hinds, E.A., E-mail: Clare.Burrage@nottingham.ac.uk, E-mail: Edmund.Copeland@nottingham.ac.uk, E-mail: Ed.Hinds@imperial.ac.uk [Centre for Cold Matter, Blackett Laboratory, Imperial College London, Prince Consort Road, London, SW7 2AZ (United Kingdom)

    2015-03-01

    Theories of dark energy require a screening mechanism to explain why the associated scalar fields do not mediate observable long range fifth forces. The archetype of this is the chameleon field. Here we show that individual atoms are too small to screen the chameleon field inside a large high-vacuum chamber, and therefore can detect the field with high sensitivity. We derive new limits on the chameleon parameters from existing experiments, and show that most of the remaining chameleon parameter space is readily accessible using atom interferometry.

  3. Correlating Atom Probe Crystallographic Measurements with Transmission Kikuchi Diffraction Data.

    Science.gov (United States)

    Breen, Andrew J; Babinsky, Katharina; Day, Alec C; Eder, K; Oakman, Connor J; Trimby, Patrick W; Primig, Sophie; Cairney, Julie M; Ringer, Simon P

    2017-04-01

    Correlative microscopy approaches offer synergistic solutions to many research problems. One such combination, that has been studied in limited detail, is the use of atom probe tomography (APT) and transmission Kikuchi diffraction (TKD) on the same tip specimen. By combining these two powerful microscopy techniques, the microstructure of important engineering alloys can be studied in greater detail. For the first time, the accuracy of crystallographic measurements made using APT will be independently verified using TKD. Experimental data from two atom probe tips, one a nanocrystalline Al-0.5Ag alloy specimen collected on a straight flight-path atom probe and the other a high purity Mo specimen collected on a reflectron-fitted instrument, will be compared. We find that the average minimum misorientation angle, calculated from calibrated atom probe reconstructions with two different pole combinations, deviate 0.7° and 1.4°, respectively, from the TKD results. The type of atom probe and experimental conditions appear to have some impact on this accuracy and the reconstruction and measurement procedures are likely to contribute further to degradation in angular resolution. The challenges and implications of this correlative approach will also be discussed.

  4. Surface Plasmon Polaritons Probed with Cold Atoms

    DEFF Research Database (Denmark)

    Kawalec, Tomasz; Sierant, Aleksandra; Panas, Roman

    2017-01-01

    We report on an optical mirror for cold rubidium atoms based on a repulsive dipole potential created by means of a modified recordable digital versatile disc. Using the mirror, we have determined the absolute value of the surface plasmon polariton (SPP) intensity, reaching 90 times the intensity...

  5. Monitoring of atomic metastable state lifetimes by the laser-enhanced ionization technique--A new method for probing local stoichiometric combustive conditions

    International Nuclear Information System (INIS)

    Ljungberg, Peter; Malmsten, Yvonne; Axner, Ove

    1995-01-01

    The lifetimes of atomic metastable states in an acetylene/air flame have been investigated using the laser-enhanced ionization technique. The lifetimes were found to be several orders of magnitude less than the natural ones, which clearly shows that they are fully determined by the surrounding environment. The lifetime of a specific state has been investigated as a function of flame conditions. It was found that the lifetime is strongly dependent on the local flame composition, with a distinct maximum for stoichiometric conditions. For fuel-lean local conditions, the excess of O2 acts as an effective quencher of the metastable state, while for fuel-rich conditions the quenching is dominated by unburned fuel components. An acetylene/air flame has been probed both as a function of height in the flame, as well as a function of fuel/air composition fed to the burner. The experiments show clearly for which heights and fuel/air compositions that lean, stoichiometric or rich conditions prevail. This makes a monitoring of metastable state lifetimes a useful technique for combustion analysis

  6. Clustered field evaporation of metallic glasses in atom probe tomography

    International Nuclear Information System (INIS)

    Zemp, J.; Gerstl, S.S.A.; Löffler, J.F.; Schönfeld, B.

    2016-01-01

    Field evaporation of metallic glasses is a stochastic process combined with spatially and temporally correlated events, which are referred to as clustered evaporation (CE). This phenomenon is investigated by studying the distance between consecutive detector hits. CE is found to be a strongly localized phenomenon (up to 3 nm in range) which also depends on the type of evaporating ions. While a similar effect in crystals is attributed to the evaporation of crystalline layers, CE of metallic glasses presumably has a different – as yet unknown – physical origin. The present work provides new perspectives on quantification methods for atom probe tomography of metallic glasses. - Highlights: • Field evaporation of metallic glasses is heterogeneous on a scale of up to 3 nm. • Amount of clustered evaporation depends on ion species and temperature. • Length scales of clustered evaporation and correlative evaporation are similar.

  7. Semiconductor studies by radioactive probe atoms

    International Nuclear Information System (INIS)

    Wichert, Thomas

    2003-01-01

    There are a growing number of experimental techniques that have in common the usage of radioactive isotopes for the characterization of semiconductors. These techniques deliver atomistic information about identity, formation, lattice environment, and electronic structure, as well as dynamics of defects and defect complexes. The results obtained by different hyperfine techniques are discussed in context with the study of intrinsic and extrinsic defects, i.e. of vacancies or self-interstitials and dopant or impurity atoms, respectively. In addition, the employment of electrical and optical techniques in combination with radioactive isotopes is presented

  8. Max Auwaerter Price lecture: building and probing atomic structures

    International Nuclear Information System (INIS)

    Ternes, M.

    2008-01-01

    Full text: The control of the geometric, electronic, and magnetic properties of atomic-scale nanostructures is a prerequisite for the understanding and fabrication of new materials and devices. Two routes lead towards this goal: Atomic manipulation of single atoms and molecules by scanning probe microscopy, or patterning using self-assembly. Atomic manipulation has been performed since almost 20 years, but it has been difficult to answer the simple question: how much force does it take to manipulate atoms and molecules on surfaces? To address this question, we used a combined atomic force and scanning tunneling microscope to simultaneously measure the force and the current between an adsorbate and a tip during atomic manipulation. We found that the force it takes to move an atom depends crucially on the binding between adsorbate and surface. Our results indicate that for moving metal atoms on metal surfaces, the lateral force component plays the dominant role. Measuring the forces during manipulation yielded the full potential energy landscape of the tip-sample interaction. Surprisingly, the potential energy barriers are comparable to diffusion barriers, which are obtained in the absence of a probe tip. Furthermore, we used the scanning tunneling microscope to assemble magnetic structures on a thin insulator. We found, that the spin of the atom is influenced by the magnetocrystalline anisotropy of the supporting surface which lifts the spin degeneracy of the ground state and enables the identification of individual atoms. The ground state of atoms with half-integer spin remains always degenerated at zero field due to Kramers theorem. We found that if these states differ by an orbital momentum of m = ±1 the localized spin is screened by the surrounding conducting electrons of the non-magnetic host and form a many-electron spin-singlet at sufficiently low temperature. (author)

  9. Reversible electrochemical modification of the surface of a semiconductor by an atomic-force microscope probe

    Energy Technology Data Exchange (ETDEWEB)

    Kozhukhov, A. S., E-mail: antonkozhukhov@yandex.ru; Sheglov, D. V.; Latyshev, A. V. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

    2017-04-15

    A technique for reversible surface modification with an atomic-force-microscope (AFM) probe is suggested. In this method, no significant mechanical or topographic changes occur upon a local variation in the surface potential of a sample under the AFM probe. The method allows a controlled relative change in the ohmic resistance of a channel in a Hall bridge within the range 20–25%.

  10. Performance and applications of the ORNL local electrode atom probe

    International Nuclear Information System (INIS)

    Miller, M.K.; Russell, K.F.

    2004-01-01

    Full text: The commercial introduction in 2003 of the local electrode atom probe (LEAP) developed by Imago Scientific Instruments has made dramatic, orders of magnitude improvements in the data acquisition rate and the size of the analyzed volume compared to previous types of three-dimensional atom probes and other scanning atom probes. This state-of-the-art instrument may be used for the analysis of traditional needle-shaped specimens and specimens fabricated from 'flat' specimens with focused ion beam (FIB) techniques. The advantage of this local electrode configuration is that significantly lower (∼50 %) standing and pulse voltages are required to produce the field strength required to field evaporate ions from the specimen. New high speed (200 kHz) pulse generators coupled with crossed delay line detectors and faster timing systems also enable significantly faster (up to 300 times) data acquisition rates to be achieved. This new design also permits a significantly larger field of view to be analyzed and results in data sets containing up to 10 8 atoms. In the local electrode atom probe, a ∼10-50 μm diameter aperture is typically positioned approximately one aperture diameter in front of the specimen. In order to accurately align the specimen to the aperture in the funnel-shaped electrode, the specimen is mounted on a three axis nanopositioning stage. An approximate alignment is performed while viewing the relative positions of the specimen and the local electrode with a pair of low magnification video cameras and then a pair of higher magnification video cameras attached to long range microscopes. The final alignment is performed with the use of the field evaporated ions from the specimen. A discussion on the alignment of the specimen with the local electrode, the effects of the fields on the specimen, and the effects of aperture size on aperture lifetime will be presented. The performance of the ORNL local electrode atom probe will be described. The

  11. Attachment of carbon nanotubes to atomic force microscope probes

    International Nuclear Information System (INIS)

    Gibson, Christopher T.; Carnally, Stewart; Roberts, Clive J.

    2007-01-01

    In atomic force microscopy (AFM) the accuracy of data is often limited by the tip geometry and the effect on this geometry of wear. One way to improve the tip geometry is to attach carbon nanotubes (CNT) to AFM tips. CNTs are ideal because they have a small diameter (typically between 1 and 20 nm), high aspect ratio, high strength, good conductivity, and almost no wear. A number of methods for CNT attachment have been proposed and explored including chemical vapour deposition (CVD), dielectrophoresis, arc discharge and mechanical attachment. In this work we will use CVD to deposit nanotubes onto a silicon surface and then investigate improved methods to pick-up and attach CNTs to tapping mode probes. Conventional pick-up methods involve using standard tapping mode or non-contact mode so as to attach only those CNTs that are aligned vertically on the surface. We have developed improved methods to attach CNTs using contact mode and reduced set-point tapping mode imaging. Using these techniques the AFM tip is in contact with a greater number of CNTs and the rate and stability of CNT pick-up is improved. The presence of CNTs on the modified AFM tips was confirmed by high-resolution AFM imaging, analysis of the tips dynamic force curves and scanning electron microscopy (SEM)

  12. Development of atomic beam probe for tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Berta, M., E-mail: bertam@sze.hu [Széchenyi István University, EURATOM Association, Győr (Hungary); Institute of Plasma Physics AS CR, v.v.i., Prague (Czech Republic); Anda, G.; Aradi, M.; Bencze, A.; Buday, Cs.; Kiss, I.G.; Tulipán, Sz.; Veres, G.; Zoletnik, S. [Wigner – RCP, HAS, EURATOM Association, Budapest (Hungary); Havlícek, J.; Háček, P. [Institute of Plasma Physics AS CR, v.v.i., Prague (Czech Republic); Charles University in Prague, Faculty of Mathematics and Physics (Czech Republic)

    2013-11-15

    Highlights: • ABP is newly developed diagnostic. • Unique measurement method for the determination of plasma edge current variations caused by different transient events such as ELMs. • The design process has been fruitfully supported by the physically motivated computer simulations. • Li-BES system has been modified accordingly to the needs of the ABP. -- Abstract: The concept and development of a new detection method for light alkali ions stemming from diagnostic beams installed on medium size tokamak is described. The method allows us the simultaneous measurement of plasma density fluctuations and fast variations in poloidal magnetic field, therefore one can infer the fast changes in edge plasma current. The concept has been worked out and the whole design process has been done at Wigner RCP. The test detector with appropriate mechanics and electronics is already installed on COMPASS tokamak. General ion trajectory calculation code (ABPIons) has also been developed. Detailed calculations show the possibility of reconstruction of edge plasma current density profile changes with high temporal resolution, and the possibility of density profile reconstruction with better spatial resolution compared to standard Li-BES measurement, this is important for pedestal studies.

  13. Development of atomic beam probe for tokamaks

    International Nuclear Information System (INIS)

    Berta, M.; Anda, G.; Aradi, M.; Bencze, A.; Buday, Cs.; Kiss, I.G.; Tulipán, Sz.; Veres, G.; Zoletnik, S.; Havlícek, J.; Háček, P.

    2013-01-01

    Highlights: • ABP is newly developed diagnostic. • Unique measurement method for the determination of plasma edge current variations caused by different transient events such as ELMs. • The design process has been fruitfully supported by the physically motivated computer simulations. • Li-BES system has been modified accordingly to the needs of the ABP. -- Abstract: The concept and development of a new detection method for light alkali ions stemming from diagnostic beams installed on medium size tokamak is described. The method allows us the simultaneous measurement of plasma density fluctuations and fast variations in poloidal magnetic field, therefore one can infer the fast changes in edge plasma current. The concept has been worked out and the whole design process has been done at Wigner RCP. The test detector with appropriate mechanics and electronics is already installed on COMPASS tokamak. General ion trajectory calculation code (ABPIons) has also been developed. Detailed calculations show the possibility of reconstruction of edge plasma current density profile changes with high temporal resolution, and the possibility of density profile reconstruction with better spatial resolution compared to standard Li-BES measurement, this is important for pedestal studies

  14. New approaches to nanoparticle sample fabrication for atom probe tomography

    International Nuclear Information System (INIS)

    Felfer, P.; Li, T.; Eder, K.; Galinski, H.; Magyar, A.P.; Bell, D.C.; Smith, G.D.W.; Kruse, N.; Ringer, S.P.; Cairney, J.M.

    2015-01-01

    Due to their unique properties, nano-sized materials such as nanoparticles and nanowires are receiving considerable attention. However, little data is available about their chemical makeup at the atomic scale, especially in three dimensions (3D). Atom probe tomography is able to answer many important questions about these materials if the challenge of producing a suitable sample can be overcome. In order to achieve this, the nanomaterial needs to be positioned within the end of a tip and fixed there so the sample possesses sufficient structural integrity for analysis. Here we provide a detailed description of various techniques that have been used to position nanoparticles on substrates for atom probe analysis. In some of the approaches, this is combined with deposition techniques to incorporate the particles into a solid matrix, and focused ion beam processing is then used to fabricate atom probe samples from this composite. Using these approaches, data has been achieved from 10–20 nm core–shell nanoparticles that were extracted directly from suspension (i.e. with no chemical modification) with a resolution of better than ±1 nm. - Highlights: • Samples for APT of nanoparticles were fabricated from particle powders and dispersions. • Electrophoresis was suitable for producing samples from dispersions. • Powder lift-out was successfully producing samples from particle agglomerates. • Dispersion application/coating delivered the highest quality results.

  15. New approaches to nanoparticle sample fabrication for atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Felfer, P., E-mail: peter.felfer@sydney.edu.au [School for Aerospace, Mechanical and Mechatronic Engineering/Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Li, T. [School for Aerospace, Mechanical and Mechatronic Engineering/Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Materials Department, The University of Oxford, Oxford (United Kingdom); Eder, K. [School for Aerospace, Mechanical and Mechatronic Engineering/Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Galinski, H. [School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138 (United States); Magyar, A.P.; Bell, D.C. [School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138 (United States); Center for Nanoscale Systems, Harvard University, Cambridge, MA 02138 (United States); Smith, G.D.W. [Materials Department, The University of Oxford, Oxford (United Kingdom); Kruse, N. [Chemical Physics of Materials (Catalysis-Tribology), Université Libre de Bruxelles, Campus Plaine, CP 243, 1050 Brussels (Belgium); Ringer, S.P.; Cairney, J.M. [School for Aerospace, Mechanical and Mechatronic Engineering/Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia)

    2015-12-15

    Due to their unique properties, nano-sized materials such as nanoparticles and nanowires are receiving considerable attention. However, little data is available about their chemical makeup at the atomic scale, especially in three dimensions (3D). Atom probe tomography is able to answer many important questions about these materials if the challenge of producing a suitable sample can be overcome. In order to achieve this, the nanomaterial needs to be positioned within the end of a tip and fixed there so the sample possesses sufficient structural integrity for analysis. Here we provide a detailed description of various techniques that have been used to position nanoparticles on substrates for atom probe analysis. In some of the approaches, this is combined with deposition techniques to incorporate the particles into a solid matrix, and focused ion beam processing is then used to fabricate atom probe samples from this composite. Using these approaches, data has been achieved from 10–20 nm core–shell nanoparticles that were extracted directly from suspension (i.e. with no chemical modification) with a resolution of better than ±1 nm. - Highlights: • Samples for APT of nanoparticles were fabricated from particle powders and dispersions. • Electrophoresis was suitable for producing samples from dispersions. • Powder lift-out was successfully producing samples from particle agglomerates. • Dispersion application/coating delivered the highest quality results.

  16. A computational geometry framework for the optimisation of atom probe reconstructions

    Energy Technology Data Exchange (ETDEWEB)

    Felfer, Peter [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Institute for General Materials Properties, Department of Materials Science, Friedrich-Alexander University Erlangen-Nürnberg, 91058 Erlangen (Germany); Cairney, Julie [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia)

    2016-10-15

    In this paper, we present pathways for improving the reconstruction of atom probe data on a coarse (>10 nm) scale, based on computational geometry. We introduce a way to iteratively improve an atom probe reconstruction by adjusting it, so that certain known shape criteria are fulfilled. This is achieved by creating an implicit approximation of the reconstruction through a barycentric coordinate transform. We demonstrate the application of these techniques to the compensation of trajectory aberrations and the iterative improvement of the reconstruction of a dataset containing a grain boundary. We also present a method for obtaining a hull of the dataset in both detector and reconstruction space. This maximises data utilisation, and can be used to compensate for ion trajectory aberrations caused by residual fields in the ion flight path through a ‘master curve’ and correct for overall shape deviations in the data. - Highlights: • An atom probe reconstruction can be iteratively improved by using shape constraints. • An atom probe reconstruction can be inverted using barycentric coordinate transforms. • Hulls for atom probe datasets can be obtained from 2D detector outlines that are co-reconstructed with the data. • Ion trajectory compressions caused by instrument-specific residual fields in the drift tube can be corrected.

  17. Atom-probe field-ion-microscope mass spectrometer

    International Nuclear Information System (INIS)

    Nishikawa, Osamu

    1983-01-01

    The titled analyzer, called simply atom-probe, has been developed by combining a field ion microscope (FIM) and a mass spectrometer, and is divided into the time-of-flight type, magnetic sector type, and quadrupole type depending on the types of mass spectrometers. In this paper, the author first describes on the principle and construction of a high resolution, time-of-flight atom-probe developed and fabricated in his laboratory. The feature of the atom-probe lies in the analysis of atoms and molecules in hyper-fine structure region one by one utilizing the high resolution of FIM. It also has the advantages of directly determining the composition by a ratio of the numbers of respective ions because of a constant detection sensitivity regardless of mass numbers, of the resolution as high as single atom layer in depth direction, and of detecting the positional relationship among detected ions by the order of detection in a sample. To determine the composition in a hyperfine structure region, the limited small number of atoms and molecules in the region must be identified distinctly one by one. In the analyzed result of Ni-silicide formed by heating Si evaporated on a Ni tip at 1000 K for 5 minutes, each isotope was not only clearly separated, but also their abundance ratio was very close to the natural abundance ratio. The second half of the paper reports on the analysis of TiC promising for a cold cathode material, adsorption of CO and alcohol, and the composition and structure of silicides, as a few application examples. (Wakatsuki, Y.)

  18. Visualization of deuterium dead layer by atom probe tomography

    KAUST Repository

    Gemma, Ryota

    2012-12-01

    The first direct observation, by atom probe tomography, of a deuterium dead layer is reported for Fe/V multilayered film loaded with D solute atoms. The thickness of the dead layers was measured to be 0.4-0.5 nm. The dead layers could be distinguished from chemically intermixed layers. The results suggest that the dead layer effect occurs even near the interface of the mixing layers, supporting an interpretation that the dead layer effect cannot be explained solely by electronic charge transfer but also involves a modulation of rigidity. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  19. Visualization of deuterium dead layer by atom probe tomography

    KAUST Repository

    Gemma, Ryota; Al-Kassab, Talaat; Kirchheim, Reiner; Pundt, Astrid A.

    2012-01-01

    The first direct observation, by atom probe tomography, of a deuterium dead layer is reported for Fe/V multilayered film loaded with D solute atoms. The thickness of the dead layers was measured to be 0.4-0.5 nm. The dead layers could be distinguished from chemically intermixed layers. The results suggest that the dead layer effect occurs even near the interface of the mixing layers, supporting an interpretation that the dead layer effect cannot be explained solely by electronic charge transfer but also involves a modulation of rigidity. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  20. Toward the Atomic-Level Mass Analysis of Biomolecules by the Scanning Atom Probe.

    Science.gov (United States)

    Nishikawa, Osamu; Taniguchi, Masahiro

    2017-04-01

    In 1994, a new type of atom probe instrument, named the scanning atom probe (SAP), was proposed. The unique feature of the SAP is the introduction of a small extraction electrode, which scans over a specimen surface and confines the high field, required for field evaporation of surface atoms in a small space, between the specimen and the electrode. Thus, the SAP does not require a sharp specimen tip. This indicates that the SAP can mass analyze the specimens which are difficult to form in a sharp tip, such as organic materials and biomolecules. Clean single wall carbon nanotubes (CNT), made by high-pressure carbon monoxide process are found to be the best substrates for biomolecules. Various amino acids and dipeptide biomolecules were successfully mass analyzed, revealing characteristic clusters formed by strongly bound atoms in the specimens. The mass analysis indicates that SAP analysis of biomolecules is not only qualitative, but also quantitative.

  1. Fabrication of tungsten probe for hard tapping operation in atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Han, Guebum, E-mail: hanguebum@live.co.kr [Department of Physics and Optical Engineering, Rose-Hulman Institute of Technology, 5500 Wabash Avenue, Terre Haute, Indiana 47803 (United States); Department of Mechanical Design and Robot Engineering, Seoul National University of Science and Technology, 232 Gongneung-ro, Nowon-gu, Seoul 139-743 (Korea, Republic of); Ahn, Hyo-Sok, E-mail: hsahn@seoultech.ac.kr [Manufacturing Systems and Design Engineering Programme, Seoul National University of Science & Technology, 232 Gongneung-ro, Nowon-gu, Seoul 139-743 (Korea, Republic of)

    2016-02-15

    We propose a method of producing a tungsten probe with high stiffness for atomic force microscopy (AFM) in order to acquire enhanced phase contrast images and efficiently perform lithography. A tungsten probe with a tip radius between 20 nm and 50 nm was fabricated using electrochemical etching optimized by applying pulse waves at different voltages. The spring constant of the tungsten probe was determined by finite element analysis (FEA), and its applicability as an AFM probe was evaluated by obtaining topography and phase contrast images of a Si wafer sample partly coated with Au. Enhanced hard tapping performance of the tungsten probe compared with a commercial Si probe was confirmed by conducting hard tapping tests at five different oscillation amplitudes on single layer graphene grown by chemical vapor deposition (CVD). To analyze the damaged graphene sample, the test areas were investigated using tip-enhanced Raman spectroscopy (TERS). The test results demonstrate that the tungsten probe with high stiffness was capable of inducing sufficient elastic and plastic deformation to enable obtaining enhanced phase contrast images and performing lithography, respectively. - Highlights: • We propose a method of producing highly stiff tungsten probes for hard tapping AFM. • Spring constant of tungsten probe is determined by finite element method. • Enhanced hard tapping performance is confirmed. • Tip-enhanced Raman spectroscopy is used to identify damage to graphene.

  2. Fabrication of tungsten probe for hard tapping operation in atomic force microscopy

    International Nuclear Information System (INIS)

    Han, Guebum; Ahn, Hyo-Sok

    2016-01-01

    We propose a method of producing a tungsten probe with high stiffness for atomic force microscopy (AFM) in order to acquire enhanced phase contrast images and efficiently perform lithography. A tungsten probe with a tip radius between 20 nm and 50 nm was fabricated using electrochemical etching optimized by applying pulse waves at different voltages. The spring constant of the tungsten probe was determined by finite element analysis (FEA), and its applicability as an AFM probe was evaluated by obtaining topography and phase contrast images of a Si wafer sample partly coated with Au. Enhanced hard tapping performance of the tungsten probe compared with a commercial Si probe was confirmed by conducting hard tapping tests at five different oscillation amplitudes on single layer graphene grown by chemical vapor deposition (CVD). To analyze the damaged graphene sample, the test areas were investigated using tip-enhanced Raman spectroscopy (TERS). The test results demonstrate that the tungsten probe with high stiffness was capable of inducing sufficient elastic and plastic deformation to enable obtaining enhanced phase contrast images and performing lithography, respectively. - Highlights: • We propose a method of producing highly stiff tungsten probes for hard tapping AFM. • Spring constant of tungsten probe is determined by finite element method. • Enhanced hard tapping performance is confirmed. • Tip-enhanced Raman spectroscopy is used to identify damage to graphene.

  3. Reduction of multiple hits in atom probe tomography

    International Nuclear Information System (INIS)

    Thuvander, Mattias; Kvist, Anders; Johnson, Lars J.S.; Weidow, Jonathan; Andrén, Hans-Olof

    2013-01-01

    The accuracy of compositional measurements using atom probe tomography is often reduced because some ions are not recorded when several ions hit the detector in close proximity to each other and within a very short time span. In some cases, for example in analysis of carbides, the multiple hits result in a preferential loss of certain elements, namely those elements that frequently field evaporate in bursts or as dissociating molecules. In this paper a method of reducing the effect of multiple hits is explored. A fine metal grid was mounted a few millimeters behind the local electrode, effectively functioning as a filter. This resulted in a decrease in the overall detection efficiency, from 37% to about 5%, but also in a decrease in the fraction of multiple hits. In an analysis of tungsten carbide the fraction of ions originating from multiple hits decreased from 46% to 10%. As a result, the measured carbon concentration increased from 48.2 at%to 49.8 at%, very close to the expected 50.0 at%. The characteristics of the multiple hits were compared for analyses with and without the grid filter. - Highlights: ► APT experiments have been performed with a reduced amount of multiple hits. ► The multiple hits were reduced by placing a grid behind the electrode. ► This resulted in improved carbon measurement of WC

  4. Three-dimensional atom localization via probe absorption in a cascade four-level atomic system

    Directory of Open Access Journals (Sweden)

    Zeng Wei

    2018-03-01

    Full Text Available For an atomic system with cascade four-level type, a useful scheme about three-dimensional (3D atom localization is proposed. In our scheme the atomic system is coherently controlled by using a radio-frequency field to couple with two-folded levels under the condition of the existence of probe absorption. Our results show that detecting precision of 3D atom localization may be obviously improved by properly adjusting the frequency detuning and strength of the radio-frequency driving field. So our scheme could be helpful to realize 3D atom localization with high-efficiency and high-precision . In the field of laser cooling or the atom nano-lithography, our studies provide potential applications.

  5. Three-dimensional atom localization via probe absorption in a cascade four-level atomic system

    Science.gov (United States)

    Zeng, Wei; Deng, Li; Chen, Aixi

    2018-03-01

    For an atomic system with cascade four-level type, a useful scheme about three-dimensional (3D) atom localization is proposed. In our scheme the atomic system is coherently controlled by using a radio-frequency field to couple with two-folded levels under the condition of the existence of probe absorption. Our results show that detecting precision of 3D atom localization may be obviously improved by properly adjusting the frequency detuning and strength of the radio-frequency driving field. So our scheme could be helpful to realize 3D atom localization with high-efficiency and high-precision . In the field of laser cooling or the atom nano-lithography, our studies provide potential applications.

  6. The time domain triple probe method

    International Nuclear Information System (INIS)

    Meier, M.A.; Hallock, G.A.; Tsui, H.Y.W.; Bengtson, R.D.

    1994-01-01

    A new Langmuir probe technique based on the triple probe method is being developed to provide simultaneous measurement of plasma temperature, potential, and density with the temporal and spatial resolution required to accurately characterize plasma turbulence. When the conventional triple probe method is used in an inhomogeneous plasma, local differences in the plasma measured at each probe introduce significant error in the estimation of turbulence parameters. The Time Domain Triple Probe method (TDTP) uses high speed switching of Langmuir probe potential, rather than spatially separated probes, to gather the triple probe information thus avoiding these errors. Analysis indicates that plasma response times and recent electronics technology meet the requirements to implement the TDTP method. Data reduction techniques of TDTP data are to include linear and higher order correlation analysis to estimate fluctuation induced particle and thermal transport, as well as energy relationships between temperature, density, and potential fluctuations

  7. Developing detection efficiency standards for atom probe tomography

    Science.gov (United States)

    Prosa, Ty J.; Geiser, Brian P.; Lawrence, Dan; Olson, David; Larson, David J.

    2014-08-01

    Atom Probe Tomography (APT) is a near-atomic-scale analytical technique which, due to recent advances in instrumentation and sample preparation techniques, is being used on a variety of 3D applications. Total system detection efficiency is a key parameter for obtaining accurate spatial reconstruction of atomic coordinates from detected ions, but experimental determination of efficiency can be difficult. This work explores new ways to measure total system detection efficiency as well as the specimen characteristics necessary for such measurements. Composite specimens composed of a nickel/chromium multilayer core, National Institute of Standards and Technology Standard Reference Material 2135c, encapsulated with silver, silicon, or nickel were used to demonstrate the suitability of this approach for providing a direct measurement of APT efficiency. Efficiency measurements based on this multilayer encapsulated in nickel are reported.

  8. Atom probe, AFM and STM study on vacuum fired stainless steel

    International Nuclear Information System (INIS)

    Stupnik, A.; Frank, P.; Leisch, M.

    2008-01-01

    Full text: Stainless steel is one of the most commonly used structural materials for vacuum equipment. An efficient method to reduce the outgassing rate from stainless steel is a high temperature bakeout in vacuum (vacuum firing). This procedure reduces significantly the amount of dissolved hydrogen in the bulk. For the outgassing process the recombination rate of hydrogen atoms to the molecules plays the determining role and recombination is strongly related to the surface structure and composition. To get more detailed information about the surface morphology and composition AFM, STM and atom probe studies were carried out. Experiments on AISI 304L stainless steel samples show that the surface reconstructs completely during vacuum firing and large atomically flat terraces bounded by bunched steps and facets are formed. The large flat terraces can be assigned to (111) planes. The bunched steps and facets are corresponding in orientation almost to (110) planes and (100) planes. Surface inspection after vacuum firing by Auger electron spectroscopy (AES) gives reason for a composition change indicated by a reduction of the chromium signal in relation to the iron and nickel signal. Since the information depth of AES covers several atomic layers not only the top atomic layer of the sample surface is probed. For this reason 3D atom probe was used as well suited tool to investigate the segregation behavior of this alloy with the goal to examine the change in local chemical composition due to the high temperature treatment. As a result of vacuum firing the atom probe experiments show a significant enrichment of nickel at the top surface layer. In the second atomic layer chromium enrichment is detected. After vacuum firing the average composition below the second atomic layer shows certain chromium depletion up to 2 nm in depth. The observed changes in surface chemistry influence recombination and desorption probability from the surface and may contribute to the present

  9. Atomic-scale observation of hydrogen-induced crack growth by atom-probe FIM

    International Nuclear Information System (INIS)

    Kuk, Y.; Pickering, H.W.; Sakurai, T.

    1980-01-01

    Formation and propagation of a microcrack due to hydrogen in a Fe-0.29 wt.% Ti alloy was observed at the atomic scale by field ion microscopy. A microcrack (-20 nm in length) formed and became noticeably large when the tip was heated at 950 0 C in the presence of about 1 torr of Hg. Propagation was reported several times by reheating, until a portion of the tip ruptured and became detached from the tip. Compositional analysis, performed in situ using a high performance atom-probe, identified atomic hydrogen in quantity and some hydrogen molecules and FEH in the crack, but not elsewhere on the surface

  10. Design of a femtosecond laser assisted tomographic atom probe

    International Nuclear Information System (INIS)

    Gault, B.; Vurpillot, F.; Vella, A.; Gilbert, M.; Menand, A.; Blavette, D.; Deconihout, B.

    2006-01-01

    A tomographic atom probe (TAP) in which the atoms are field evaporated by means of femtosecond laser pulses has been designed. It is shown that the field evaporation is assisted by the laser field enhanced by the subwavelength dimensions of the specimen without any significant heating of the specimen. In addition, as compared with the conventional TAP, due to the very short duration of laser pulses, no spread in the energy of emitted ions is observed, leading to a very high mass resolution in a straight TAP in a wide angle configuration. At last, laser pulses can be used to bring the intense electric field required for the field evaporation on poor conductive materials such as intrinsic Si at low temperature. In this article, the performance of the laser TAP is described and illustrated through the investigation of metals, oxides, and silicon materials

  11. Manipulating collective quantum states of ultracold atoms by probing

    DEFF Research Database (Denmark)

    Wade, Andrew Christopher James

    2015-01-01

    The field of cold gases has grown dramatically over the past few decades. The exquisite experimental control of their environment and properties has lead to landmark achievements, and has motivated the pursuit of quantum technologies with ultracold atoms. At the same time, the theory of measureme......The field of cold gases has grown dramatically over the past few decades. The exquisite experimental control of their environment and properties has lead to landmark achievements, and has motivated the pursuit of quantum technologies with ultracold atoms. At the same time, the theory...... of measurements on quantum systems has grown into a well established field. Experimental demonstrations of nondestructive continuous measurements on individual quantum systems now occur in many laboratories. Such experiments with ultracold atoms have shown great progress, but the exploitation of the quantum...... nature of the measurement interaction and backaction is yet to be realised. This dissertation is concerned with ultracold atoms and their control via fully quantum mechanical probes. Nonclassical, squeezed and entangled states of matter and single photon sources are important for fundamental studies...

  12. The Modified Embedded Atom Method

    Energy Technology Data Exchange (ETDEWEB)

    Baskes, M.I.

    1994-08-01

    Recent modifications have been made to generalize the Embedded Atom Method (EAM) to describe bonding in diverse materials. By including angular dependence of the electron density in an empirical way, the Modified Embedded Atom Method (MEAM) has been able to reproduce the basic energetic and structural properties of 45 elements. This method is ideal for examining interfacial behavior of dissimilar materials. This paper explains in detail the derivation of the method, shows how parameters of MEAM are determined directly from experiment or first principles calculations, and examine the quality of the reproduction of the database. Materials with fcc, bcc, hcp, and diamond cubic crystal structure are discussed. A few simple examples of the application of the MEAM to surfaces and interfaces are presented. Calculations of pullout of a SiC fiber in a diamond matrix as a function of applied stress show nonuniform deformation of the fiber.

  13. Effect of laser power and specimen temperature on atom probe analyses of magnesium alloys

    International Nuclear Information System (INIS)

    Oh-ishi, K.; Mendis, C.L.; Ohkubo, T.; Hono, K.

    2011-01-01

    The influence of laser power, wave length, and specimen temperature on laser assisted atom probe analyses for Mg alloys was investigated. Higher laser power and lower specimen temperature led to improved mass and spatial resolutions. Background noise and mass resolutions were degraded with lower laser power and higher specimen temperature. By adjusting the conditions for laser assisted atom probe analyses, atom probe results with atomic layer resolutions were obtained from all the Mg alloys so far investigated. Laser assisted atom probe investigations revealed detailed chemical information on Guinier-Preston zones in Mg alloys. -- Research highlights: → We study performance of UV laser assisted atom probe analysis for Mg alloys. → There is an optimized range of laser power and specimen temperature. → Optimized UV laser enables atom probe data of Mg alloys with high special resolution.

  14. Atom-probe for FinFET dopant characterization

    Energy Technology Data Exchange (ETDEWEB)

    Kambham, A.K., E-mail: kambham@imec.be [K.U.Leuven, Instituut voor Kern-en Stralings fysika, Celestijnenlaan 200D, B-3001, Leuven (Belgium); IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Mody, J.; Gilbert, M.; Koelling, S.; Vandervorst, W. [K.U.Leuven, Instituut voor Kern-en Stralings fysika, Celestijnenlaan 200D, B-3001, Leuven (Belgium); IMEC, Kapeldreef 75, B-3001 Leuven (Belgium)

    2011-05-15

    With the continuous shrinking of transistors and advent of new transistor architectures to keep in pace with Moore's law and ITRS goals, there is a rising interest in multigate 3D-devices like FinFETs where the channel is surrounded by gates on multiple surfaces. The performance of these devices depends on the dimensions and the spatial distribution of dopants in source/drain regions of the device. As a result there is a need for new metrology approach/technique to characterize quantitatively the dopant distribution in these devices with nanometer precision in 3D. In recent years, atom probe tomography (APT) has shown its ability to analyze semiconductor and thin insulator materials effectively with sub-nm resolution in 3D. In this paper we will discuss the methodology used to study FinFET-based structures using APT. Whereas challenges and solutions for sample preparation linked to the limited fin dimensions already have been reported before, we report here an approach to prepare fin structures for APT, which based on their processing history (trenches filled with Si) are in principle invisible in FIB and SEM. Hence alternative solutions in locating and positioning them on the APT-tip are presented. We also report on the use of the atom probe results on FinFETs to understand the role of different dopant implantation angles (10{sup o} and 45{sup o}) when attempting conformal doping of FinFETs and provide a quantitative comparison with alternative approaches such as 1D secondary ion mass spectrometry (SIMS) and theoretical model values. -- Research highlights: {yields} This paper provides the information on how to characterize the FinFET devices using atom probe tomography (APT). {yields} Importance of this work is to assess the performance of these devices at different processing conditions by extracting the compositional profiles. {yields} The performance of these devices depends on the dimensions and the spatial distribution of dopants in source/drain regions

  15. Atom-probe for FinFET dopant characterization

    International Nuclear Information System (INIS)

    Kambham, A.K.; Mody, J.; Gilbert, M.; Koelling, S.; Vandervorst, W.

    2011-01-01

    With the continuous shrinking of transistors and advent of new transistor architectures to keep in pace with Moore's law and ITRS goals, there is a rising interest in multigate 3D-devices like FinFETs where the channel is surrounded by gates on multiple surfaces. The performance of these devices depends on the dimensions and the spatial distribution of dopants in source/drain regions of the device. As a result there is a need for new metrology approach/technique to characterize quantitatively the dopant distribution in these devices with nanometer precision in 3D. In recent years, atom probe tomography (APT) has shown its ability to analyze semiconductor and thin insulator materials effectively with sub-nm resolution in 3D. In this paper we will discuss the methodology used to study FinFET-based structures using APT. Whereas challenges and solutions for sample preparation linked to the limited fin dimensions already have been reported before, we report here an approach to prepare fin structures for APT, which based on their processing history (trenches filled with Si) are in principle invisible in FIB and SEM. Hence alternative solutions in locating and positioning them on the APT-tip are presented. We also report on the use of the atom probe results on FinFETs to understand the role of different dopant implantation angles (10 o and 45 o ) when attempting conformal doping of FinFETs and provide a quantitative comparison with alternative approaches such as 1D secondary ion mass spectrometry (SIMS) and theoretical model values. -- Research highlights: → This paper provides the information on how to characterize the FinFET devices using atom probe tomography (APT). → Importance of this work is to assess the performance of these devices at different processing conditions by extracting the compositional profiles. → The performance of these devices depends on the dimensions and the spatial distribution of dopants in source/drain regions. → In this publication we

  16. Development of Tuning Fork Based Probes for Atomic Force Microscopy

    Science.gov (United States)

    Jalilian, Romaneh; Yazdanpanah, Mehdi M.; Torrez, Neil; Alizadeh, Amirali; Askari, Davood

    2014-03-01

    This article reports on the development of tuning fork-based AFM/STM probes in NaugaNeedles LLC for use in atomic force microscopy. These probes can be mounted on different carriers per customers' request. (e.g., RHK carrier, Omicron carrier, and tuning fork on a Sapphire disk). We are able to design and engineer tuning forks on any type of carrier used in the market. We can attach three types of tips on the edge of a tuning fork prong (i.e., growing Ag2Ga nanoneedles at any arbitrary angle, cantilever of AFM tip, and tungsten wire) with lengths from 100-500 μm. The nanoneedle is located vertical to the fork. Using a suitable insulation and metallic coating, we can make QPlus sensors that can detect tunneling current during the AFM scan. To make Qplus sensors, the entire quartz fork will be coated with an insulating material, before attaching the nanoneedle. Then, the top edge of one prong is coated with a thin layer of conductive metal and the nanoneedle is attached to the fork end of the metal coated prong. The metal coating provides electrical connection to the tip for tunneling current readout and to the electrodes and used to read the QPlus current. Since the amount of mass added to the fork is minimal, the resonance frequency spectrum does not change and still remains around 32.6 KHz and the Q factor is around 1,200 in ambient condition. These probes can enhance the performance of tuning fork based atomic microscopy.

  17. Theoretical study of the effect of probe shape on adhesion force between probe and substrate in atomic force microscope experiment

    OpenAIRE

    Yang, Li; Hu, Junhui; Kong, Lingjiang

    2017-01-01

    The quantitative description of adhesion force dependence on the probe shapes are of importance in many scientific and industrial fields. In order to elucidate how the adhesion force varied with the probe shape in atomic force microscope manipulation experiment, we performed a theoretical study of the influences of the probe shape (the sphere and parabolic probe) on the adhesion force at different humidity. We found that the combined action of the triple point and the Kelvin radius guiding th...

  18. Laser-cooled atomic ions as probes of molecular ions

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Kenneth R.; Viteri, C. Ricardo; Clark, Craig R.; Goeders, James E.; Khanyile, Ncamiso B.; Vittorini, Grahame D. [Schools of Chemistry and Biochemistry, Computational Science and Engineering and Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States)

    2015-01-22

    Trapped laser-cooled atomic ions are a new tool for understanding cold molecular ions. The atomic ions not only sympathetically cool the molecular ions to millikelvin temperatures, but the bright atomic ion fluorescence can also serve as a detector of both molecular reactions and molecular spectra. We are working towards the detection of single molecular ion spectra by sympathetic heating spectroscopy. Sympathetic heating spectroscopy uses the coupled motion of two trapped ions to measure the spectra of one ion by observing changes in the fluorescence of the other ion. Sympathetic heating spectroscopy is a generalization of quantum logic spectroscopy, but does not require ions in the motional ground state or coherent control of the ion internal states. We have recently demonstrated this technique using two isotopes of Ca{sup +} [Phys. Rev. A, 81, 043428 (2010)]. Limits of the method and potential applications for molecular spectroscopy are discussed.

  19. Understanding proton-conducting perovskite interfaces using atom probe tomography

    Science.gov (United States)

    Clark, Daniel R.

    Proton-conducting ceramics are under intense scientific investigation for a number of exciting applications, including fuel cells, electrolyzers, hydrogen separation membranes, membrane reactors, and sensors. However, commercial application requires deeper understanding and improvement of proton conductivity in these materials. It is well-known that proton conductivity in these materials is often limited by highly resistive grain boundaries (GBs). While these conductivity-limiting GBs are still not well understood, it is hypothesized that their blocking nature stems from the formation of a positive (proton-repelling) space-charge zone. Furthermore, it has been observed that the strength of the blocking behavior can change dramatically depending on the fabrication process used to make the ceramic. This thesis applies laser-assisted atom probe tomography (LAAPT) to provide new insights into the GB chemistry and resulting space-charge behavior of BaZr0.9Y0.1O 3--delta (BZY10), a prototypical proton-conducting ceramic. LAAPT is an exciting characterization technique that allows for three-dimensional nm-scale spatial resolution and very high chemical resolution (up to parts-per-million). While it is challenging to quantitatively apply LAAPT to complex, multi-cation oxide materials, this thesis successfully develops a method to accurately quantify the stoichiometry of BZY10 and maintain minimal quantitative cationic deviation at a laser energies of approximately 10--20 pJ. With the analysis technique specifically optimized for BZY10, GB chemistry is then examined for BZY10 samples prepared using four differing processing methods: (1) spark plasma sintering (SPS), (2) conventional sintering using powder prepared by solid-state reaction followed by high-temperature annealing (HT), (3) conventional sintering using powder prepared by solid-state reaction with NiO used as a sintering aid (SSR-Ni), and (4) solid-state reactive sintering directly from BaCO3, ZrO2, and Y2O3

  20. Probing the nanostructural evolution of age-hardenable Al alloys with atom-probe tomography

    International Nuclear Information System (INIS)

    Biswas, Aniruddha

    2010-01-01

    Atom Probe Tomographic (APT) Microscope is a lens-less point-projection 3-D analytical microscope that has the unique capability of (i) three-dimensional imaging at the atomic scale and (ii) compositional analysis with sub-nanometre spatial resolution and single-atom sensitivity. Modern 3-D APT microscope offers the highest the spatial resolution among all the available analytical techniques. It can simultaneously achieve a spatial resolution better than 0.3 nm in all three directions of a three-dimensional analysis-volume. As a result, 3-D APT microscopy, especially as practiced by the high speed, large field of view instruments is the most appropriate tool for studying nano-scale precipitates and their heterophase interfaces. This talk will introduce the technique, discuss its brief historical background and use examples from age-hardenable Al-alloys. The results include a detailed APT study of the compositional evolution of the nano-scale precipitates: θ and Q present in commercial age hardenable aluminium alloy, W319

  1. Application of Delaunay tessellation for the characterization of solute-rich clusters in atom probe tomography

    International Nuclear Information System (INIS)

    Lefebvre, W.; Philippe, T.; Vurpillot, F.

    2011-01-01

    This work presents an original method for cluster selection in Atom Probe Tomography designed to be applied to large datasets. It is based on the calculation of the Delaunay tessellation generated by the distribution of atoms of a selected element. It requires a single input parameter from the user. Furthermore, no prior knowledge of the material is needed. The sensitivity of the proposed Delaunay cluster selection is demonstrated by its application on simulated APT datasets. A strong advantage of the proposed methodology is that it is reinforced by the availability of an analytical model for the distribution of Delaunay cells circumspheres, which is used to control the accuracy of the cluster selection procedure. Another advantage of the Delaunay cluster selection is the direct calculation of a sharp envelope for each identified cluster or precipitate, which leads to the more appropriate morphology of the objects as they are reconstructed in the APT dataset. -- Research Highligthts: →Original method for cluster selection in Atom Probe Tomography. →Delaunay tessellation generated by the distribution of solute atoms. →Direct calculation of a sharp envelope for each identified cluster or precipitate. →Delaunay cluster selection demonstrated by its application on simulated APT datasets.

  2. Atomic quantum superposition state generation via optical probing

    DEFF Research Database (Denmark)

    Nielsen, Anne E. B.; Poulsen, Uffe Vestergaard; Negretti, Antonio

    2009-01-01

    investigate cavity enhanced probing with continuous beams of both coherent and squeezed light. The stochastic master equations used in the analysis are expressed in terms of the Hamiltonian of the probed system and the interaction between the probed system and the probe field and are thus quite generally...

  3. Phase decomposition and ordering in Ni-11.3 at.% Ti studied with atom probe tomography

    KAUST Repository

    Al-Kassab, Talaat; Kompatscher, Michael; Kirchheim, Reiner; Kostorz, Gernot; Schö nfeld, Bernd

    2014-01-01

    The decomposition behavior of Ni-rich Ni-Ti was reassessed using Tomographic Atom Probe (TAP) and Laser Assisted Wide Angle Tomographic Atom Probe. Single crystalline specimens of Ni-11.3at.% Ti were investigated, the states selected from

  4. Guided mass spectrum labelling in atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Haley, D., E-mail: daniel.haley@materials.ox.ac.uk [Max-Planck-Institut für Eisenforschung, Max-Plack Straße 1, Düsseldorf (Germany); Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Choi, P.; Raabe, D. [Max-Planck-Institut für Eisenforschung, Max-Plack Straße 1, Düsseldorf (Germany)

    2015-12-15

    Atom probe tomography (APT) is a valuable near-atomic scale imaging technique, which yields mass spectrographic data. Experimental correctness can often pivot on the identification of peaks within a dataset, this is a manual process where subjectivity and errors can arise. The limitations of manual procedures complicate APT experiments for the operator and furthermore are a barrier to technique standardisation. In this work we explore the capabilities of computer-guided ranging to aid identification and analysis of mass spectra. We propose a fully robust algorithm for enumeration of the possible identities of detected peak positions, which assists labelling. Furthermore, a simple ranking scheme is developed to allow for evaluation of the likelihood of each possible identity being the likely assignment from the enumerated set. We demonstrate a simple, yet complete work-chain that allows for the conversion of mass-spectra to fully identified APT spectra, with the goal of minimising identification errors, and the inter-operator variance within APT experiments. This work chain is compared to current procedures via experimental trials with different APT operators, to determine the relative effectiveness and precision of the two approaches. It is found that there is little loss of precision (and occasionally gain) when participants are given computer assistance. We find that in either case, inter-operator precision for ranging varies between 0 and 2 “significant figures” (2σ confidence in the first n digits of the reported value) when reporting compositions. Intra-operator precision is weakly tested and found to vary between 1 and 3 significant figures, depending upon species composition levels. Finally it is suggested that inconsistencies in inter-operator peak labelling may be the largest source of scatter when reporting composition data in APT. - Highlights: • Demonstration of a complete, but simple, automation chain for APT spectra analysis. • Algorithm for

  5. Guided mass spectrum labelling in atom probe tomography

    International Nuclear Information System (INIS)

    Haley, D.; Choi, P.; Raabe, D.

    2015-01-01

    Atom probe tomography (APT) is a valuable near-atomic scale imaging technique, which yields mass spectrographic data. Experimental correctness can often pivot on the identification of peaks within a dataset, this is a manual process where subjectivity and errors can arise. The limitations of manual procedures complicate APT experiments for the operator and furthermore are a barrier to technique standardisation. In this work we explore the capabilities of computer-guided ranging to aid identification and analysis of mass spectra. We propose a fully robust algorithm for enumeration of the possible identities of detected peak positions, which assists labelling. Furthermore, a simple ranking scheme is developed to allow for evaluation of the likelihood of each possible identity being the likely assignment from the enumerated set. We demonstrate a simple, yet complete work-chain that allows for the conversion of mass-spectra to fully identified APT spectra, with the goal of minimising identification errors, and the inter-operator variance within APT experiments. This work chain is compared to current procedures via experimental trials with different APT operators, to determine the relative effectiveness and precision of the two approaches. It is found that there is little loss of precision (and occasionally gain) when participants are given computer assistance. We find that in either case, inter-operator precision for ranging varies between 0 and 2 “significant figures” (2σ confidence in the first n digits of the reported value) when reporting compositions. Intra-operator precision is weakly tested and found to vary between 1 and 3 significant figures, depending upon species composition levels. Finally it is suggested that inconsistencies in inter-operator peak labelling may be the largest source of scatter when reporting composition data in APT. - Highlights: • Demonstration of a complete, but simple, automation chain for APT spectra analysis. • Algorithm for

  6. Determination of the radial distribution function with the tomographic atom probe

    International Nuclear Information System (INIS)

    Heinrich, A.; Al-Kassab, T.

    2004-01-01

    Full text: An algorithm for the determination of the radial distribution function (RDF) and the partial radial distribution function from tomographic atom probe data is introduced and some examples for its application are discussed. Homogeneous distribution of atoms can easily be determined from measured data. Using our algorithm, the lattice of simple cubic structures may be estimated solely from TAP data. The results for bcc and fcc alloys and metals will be presented. By evaluating the vicinity of each atom, information about order phenomena in multi component alloy can be retrieved including short range order. The advantage of determining the (partial) radial distribution functions for any sample with our algorithm is that all data can be derived by one single experiment whereas all other methods of determining a pRDF require one experiment for each pRDF. (author)

  7. Probe Knots and Hopf Insulators with Ultracold Atoms

    Science.gov (United States)

    Deng, Dong-Ling; Wang, Sheng-Tao; Sun, Kai; Duan, L.-M.

    2018-01-01

    Knots and links are fascinating and intricate topological objects. Their influence spans from DNA and molecular chemistry to vortices in superfluid helium, defects in liquid crystals and cosmic strings in the early universe. Here we find that knotted structures also exist in a peculiar class of three-dimensional topological insulators—the Hopf insulators. In particular, we demonstrate that the momentum-space spin textures of Hopf insulators are twisted in a nontrivial way, which implies the presence of various knot and link structures. We further illustrate that the knots and nontrivial spin textures can be probed via standard time-of-flight images in cold atoms as preimage contours of spin orientations in stereographic coordinates. The extracted Hopf invariants, knots, and links are validated to be robust to typical experimental imperfections. Our work establishes the existence of knotted structures in Hopf insulators, which may have potential applications in spintronics and quantum information processing. D.L.D., S.T.W. and L.M.D. are supported by the ARL, the IARPA LogiQ program, and the AFOSR MURI program, and supported by Tsinghua University for their visits. K.S. acknowledges the support from NSF under Grant No. PHY1402971. D.L.D. is also supported by JQI-NSF-PFC and LPS-MPO-CMTC at the final stage of this paper.

  8. Improvement of sizing methods using focussed probes

    International Nuclear Information System (INIS)

    Birac, A.M.; Saglio, R.; Frappier, J.C.

    1983-05-01

    Three methods are described; these three methods, using the advantages of focussed probes allow, used simultaneously according to the nature of the detected defects, to evaluate with a good accuracy the dimensions and the orientation of the real or artificial defects [fr

  9. Nanometer-scale isotope analysis of bulk diamond by atom probe tomography

    NARCIS (Netherlands)

    Schirhagl, R.; Raatz, N.; Meijer, J.; Markham, M.; Gerstl, S. S. A.; Degen, C. L.

    2015-01-01

    Atom-probe tomography (APT) combines field emission of atoms with mass spectrometry to reconstruct three-dimensional tomograms of materials with atomic resolution and isotope specificity. Despite significant recent progress in APT technology, application to wide-bandgap materials with strong

  10. Probing living bacterial adhesion by single cell force spectroscopy using atomic force microscopy

    DEFF Research Database (Denmark)

    Zeng, Guanghong; Ogaki, Ryosuke; Regina, Viduthalai R.

    be considered. We have therefore developed a simple and versatile method to make single-cell bacterial probes for measuring single cell adhesion with atomic force microscopy (AFM).[1] A single-cell probe was readily made by picking up a bacterial cell from a glass surface using a tipless AFM cantilever coated...... random immobilization is obtained by submerging the cantilever in a bacterial suspension. The reported method provides a general platform for investigating single cell interactions of bacteria with different surfaces and other cells by AFM force spectroscopy, thus improving our understanding....... The strain-dependent susceptibility to bacterial colonization on conventional PLL-g-PEG illustrates how bacterial diversity challenges development of “universal” antifouling coatings, and AFM single-cell force spectroscopy was proven to be a powerful tool to provide insights into the molecular mechanisms...

  11. Applying computational geometry techniques for advanced feature analysis in atom probe data

    International Nuclear Information System (INIS)

    Felfer, Peter; Ceguerra, Anna; Ringer, Simon; Cairney, Julie

    2013-01-01

    In this paper we present new methods for feature analysis in atom probe tomography data that have useful applications in materials characterisation. The analysis works on the principle of Voronoi subvolumes and piecewise linear approximations, and feature delineation based on the distance to the centre of mass of a subvolume (DCOM). Based on the coordinate systems defined by these approximations, two examples are shown of the new types of analyses that can be performed. The first is the analysis of line-like-objects (i.e. dislocations) using both proxigrams and line-excess plots. The second is interfacial excess mapping of an InGaAs quantum dot. - Highlights: • Computational geometry is used to detect and analyse features within atom probe data. • Limitations of conventional feature detection are overcome by using atomic density gradients. • 0D, 1D, 2D and 3D features can be analysed by using Voronoi tessellation for spatial binning. • New, robust analysis methods are demonstrated, including line and interfacial excess mapping

  12. Atom probe characterization of yttria particles in ODS Eurofer steel

    International Nuclear Information System (INIS)

    Aleev, A.A.; Zaluzhny, A.G.; Nikitin, A.A.; Rogozhkin, S.V.; Iskandarov, N.A.; Vladimirov, P.; Moeslang, A.; Lindau, R.; Klimenkov, M.

    2009-01-01

    Oxide dispersion strengthened steels exhibit higher temperature and radiation resistance than conventionally produced ferritic/martensitic steels. Such behaviour, as believed, is mainly caused by presence of highly dispersed and extremely stable oxide particles with sizes of few nanometers. It was shown that the most promising oxide additive was yttria (Y 2 O 3 ) and as mechanical parameters were strongly depended on size and number density of formed peculiarities it is required to reduce their dimensions to few nanometers and drastically increase their number. At present, considerable effort is focused on investigation of behaviour and properties of such particles. Recent studies of Eurofer ODS steel (9%-CrWVTa) by SANS and PoAS revealed the presence of high number density structural peculiarities with size approximately one nanometer. At the same time, previous studies by TEM identified only high number of small (5-10 nm) Y 2 O 3 particles. So, the purpose of this work was to look into this material by means of tomographic atom probe and find out the chemistry and origin of peculiarities with sizes less than 5 nm. These investigations revealed fine (∼ 2 nm) particles that were enriched not only in yttrium and oxygen but also in vanadium and nitrogen. Concentration of vanadium in them is approximately at the same level as yttrium. Moreover, some particles were found to be enriched in only three or even two elements mentioned above. However, total concentration of chemical elements in these particles is considerably less than that of iron. Estimated number density for detected particles is (1 / 5) x 10 23 m -3 . (author)

  13. Blind deconvolution of time-of-flight mass spectra from atom probe tomography

    International Nuclear Information System (INIS)

    Johnson, L.J.S.; Thuvander, M.; Stiller, K.; Odén, M.; Hultman, L.

    2013-01-01

    A major source of uncertainty in compositional measurements in atom probe tomography stems from the uncertainties of assigning peaks or parts of peaks in the mass spectrum to their correct identities. In particular, peak overlap is a limiting factor, whereas an ideal mass spectrum would have peaks at their correct positions with zero broadening. Here, we report a method to deconvolute the experimental mass spectrum into such an ideal spectrum and a system function describing the peak broadening introduced by the field evaporation and detection of each ion. By making the assumption of a linear and time-invariant behavior, a system of equations is derived that describes the peak shape and peak intensities. The model is fitted to the observed spectrum by minimizing the squared residuals, regularized by the maximum entropy method. For synthetic data perfectly obeying the assumptions, the method recovered peak intensities to within ±0.33at%. The application of this model to experimental APT data is exemplified with Fe–Cr data. Knowledge of the peak shape opens up several new possibilities, not just for better overall compositional determination, but, e.g., for the estimation of errors of ranging due to peak overlap or peak separation constrained by isotope abundances. - Highlights: • A method for the deconvolution of atom probe mass spectra is proposed. • Applied to synthetic randomly generated spectra the accuracy was ±0.33 at. • Application of the method to an experimental Fe–Cr spectrum is demonstrated

  14. A theoretical study of dopant atom detection and probe behavior in STEM

    Science.gov (United States)

    Mittal, Anudha

    functional-based tight-binding model revealed that a stress-free single-walled (14,6) MoS2 nanotube has a torsional deformation of 0.87 °/nm. Comparison between simulated electron diffraction patterns and atomic-resolution ADF-STEM images of nanotubes with and without the small twist suggested that these experimental techniques are viable routes for detecting presence of the torsional deformation. 2. Development of theory to cast light on aspects of scattering behavior that affect STEM data.. STEM probe intensity oscillates as the probe transmits through a crystalline sample. The oscillatory behavior of the probe is extremely similar during transmission through 3-D crystals and the hypothetical structure of an isolated column of atoms, a 1-D crystal. This indicates that the physical origin of oscillation in intensity is not due to scattering of electrons away from one atomic column and subsequent scattering back from neighboring columns. It leaves in question what the physical origin or intensity oscillation is. This question was answered here by analysis of electron beam behavior in isolated atomic columns, examined via multislice-based simulations. Two physical origins, changes in angular distribution of the probe and phase shift between the angular components, were shown to cause oscillation in beam intensity. Sensitivity of frequency of oscillation to different probe and sample parameters was used to better understand the influence of the two physical origins on probe oscillation. 3. Acquisition of atomic-scale STEM data to answer specific questions about a material.. Graphene, due to its 2-Dimensionality, and due to its thermal, optical, electrical, and mechanical properties, which are conducive to providing a unique material for incorporation in devices, has gained a lot of interest in the research world and even spurred start-ups. There are several feasible routes of graphene synthesis, among which chemical exfoliation of graphite is a promising method for mass

  15. The mystery of missing species in atom probe tomography of composite materials

    Energy Technology Data Exchange (ETDEWEB)

    Karahka, M.; Xia, Y.; Kreuzer, H. J. [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 3J5 (Canada)

    2015-08-10

    There is a serious problem in atom probe tomography of composite materials such as oxides that even from stoichiometric samples one observes non-stoichiometric ion yields. We present a quantitative model that explains the non-stoichiometry allowing a fit to experimental data of ion yields as a function of applied field to extract activation barriers and prefactors. The numbers are confirmed by density functional theory. We also show that for oxides the missing oxygen is thermally desorbed as neutral O{sub 2}, either directly or associatively. Finally, we suggest methods to improve the experimental setup.

  16. The Model Analysis of a Complex Tuning Fork Probe and Its Application in Bimodal Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Zhichao Wu

    2017-01-01

    Full Text Available A new electromechanical coupling model was built to quantitatively analyze the tuning fork probes, especially the complex ones. A special feature of a novel, soft tuning fork probe, that the second eigenfrequency of the probe was insensitive to the effective force gradient, was found and used in a homemade bimodal atomic force microscopy to measure power dissipation quantitatively. By transforming the mechanical parameters to the electrical parameters, a monotonous and concise method without using phase to calculate the power dissipation was proposed.

  17. Innovation and optimization of a method of pump-probe polarimetry with pulsed laser beams in view of a precise measurement of parity violation in atomic cesium; Innovation et optimisation d'une methode de polarimetrie pompe-sonde avec des faisceaux laser impulsionnels en vue d'une mesure precise de violation de la parite dans l'atome de cesium

    Energy Technology Data Exchange (ETDEWEB)

    Chauvat, D

    1997-10-15

    While Parity Violation (PV) experiments on highly forbidden transitions have been using detection of fluorescence signals; our experiment uses a pump-probe scheme to detect the PV signal directly on a transmitted probe beam. A pulsed laser beam of linear polarisation {epsilon}{sub 1} excites the atoms on the 6S-7S cesium transition in a colinear electric field E || k(ex). The probe beam (k(pr) || k(ex)) of linear polarisation {epsilon}{sub 2} tuned to the transition 7S-6P(3/2) is amplified. The small asymmetry ({approx} 10{sup -6}) in the gain that depends on the handedness of the tri-hedron (E, {epsilon}{sub 1}, {epsilon}{sub 2}) is the manifestation of the PV effect. This is measured as an E-odd apparent rotation of the plane of polarization of the probe beam; using balanced mode polarimetry. New criteria of selection have been devised, that allow us to distinguish the true PV-signal against fake rotations due to electromagnetic interferences, geometrical effects, polarization imperfections, or stray transverse electric and magnetic fields. These selection criteria exploit the symmetry of the PV-rotation - linear dichroism - and the revolution symmetry of the experiment. Using these criteria it is not only possible to reject fake signals, but also to elucidate the underlying physical mechanisms and to measure the relevant defects of the apparatus. The present signal-to-noise ratio allows embarking in PV measurements to reach the 10% statistical accuracy. A 1% measurement still requires improvements. Two methods have been demonstrated. The first one exploits the amplification of the asymmetry at high gain - one major advantage provided by our detection method based on stimulated emission. The second method uses both a much higher incident intensity and a special dichroic component which magnifies tiny polarization rotations. (author)

  18. Atom probe field ion microscopy and related topics: A bibliography 1991

    International Nuclear Information System (INIS)

    Russell, K.F.; Miller, M.K.

    1993-01-01

    This report contains a bibliography for 1991 on the following topics: Atom probe field ion microscopy; field desorption mass spectrometry; field emission; field ion microscopy; and field emission theory

  19. Atom probe tomography simulations and density functional theory calculations of bonding energies in Cu3Au

    KAUST Repository

    Boll, Torben; Zhu, Zhiyong; Al-Kassab, Talaat; Schwingenschlö gl, Udo

    2012-01-01

    In this article the Cu-Au binding energy in Cu3Au is determined by comparing experimental atom probe tomography (APT) results to simulations. The resulting bonding energy is supported by density functional theory calculations. The APT simulations

  20. Broadening the applications of the atom probe technique by ultraviolet femtosecond laser

    Energy Technology Data Exchange (ETDEWEB)

    Hono, K., E-mail: kazuhiro.hono@nims.go.jp [National Institute for Materials Science, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0047 (Japan); CREST, Japan Science and Technology Agency (Japan); Ohkubo, T. [National Institute for Materials Science, Tsukuba 305-0047 (Japan); CREST, Japan Science and Technology Agency (Japan); Chen, Y.M.; Kodzuka, M. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0047 (Japan); Oh-ishi, K. [National Institute for Materials Science, Tsukuba 305-0047 (Japan); CREST, Japan Science and Technology Agency (Japan); Sepehri-Amin, H. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0047 (Japan); Li, F. [National Institute for Materials Science, Tsukuba 305-0047 (Japan); CREST, Japan Science and Technology Agency (Japan); Kinno, T. [Corporate R and D Center, Toshiba Corporation, Saiwai-ku, Kawasaki 212-8582 (Japan); CREST, Japan Science and Technology Agency (Japan); Tomiya, S.; Kanitani, Y. [Advanced Materials Laboratory, Sony Corporation, Atsugi, Kanagawa 243-0021 (Japan)

    2011-05-15

    Laser assisted field evaporation using ultraviolet (UV) wavelength gives rise to better mass resolution and signal-to-noise ratio in atom probe mass spectra of metals, semiconductors and insulators compared to infrared and green lasers. Combined with the site specific specimen preparation techniques using the lift-out and annular Ga ion milling in a focused ion beam machine, a wide variety of materials including insulating oxides can be quantitatively analyzed by the three-dimensional atom probe using UV laser assisted field evaporation. After discussing laser irradiation conditions for optimized atom probe analyses, recent atom probe tomography results on oxides, semiconductor devices and grain boundaries of sintered magnets are presented. -- Research highlights: {yields} Application of ultraviolet (UV) femtosecond pulsed laser in a three dimensional atom probe (3DAP). {yields} Improved mass resolution and signal-to-noise ratio in atom probe mass spectra using UV laser. {yields} UV laser facilitates 3DAP analysis of insulating oxides. {yields} Quantitative analysis of wide variety of materials including insulating oxides using UV femotosecond laser.

  1. Laser-Assisted Atom Probe Tomography of Deformed Minerals: A Zircon Case Study.

    Science.gov (United States)

    La Fontaine, Alexandre; Piazolo, Sandra; Trimby, Patrick; Yang, Limei; Cairney, Julie M

    2017-04-01

    The application of atom probe tomography to the study of minerals is a rapidly growing area. Picosecond-pulsed, ultraviolet laser (UV-355 nm) assisted atom probe tomography has been used to analyze trace element mobility within dislocations and low-angle boundaries in plastically deformed specimens of the nonconductive mineral zircon (ZrSiO4), a key material to date the earth's geological events. Here we discuss important experimental aspects inherent in the atom probe tomography investigation of this important mineral, providing insights into the challenges in atom probe tomography characterization of minerals as a whole. We studied the influence of atom probe tomography analysis parameters on features of the mass spectra, such as the thermal tail, as well as the overall data quality. Three zircon samples with different uranium and lead content were analyzed, and particular attention was paid to ion identification in the mass spectra and detection limits of the key trace elements, lead and uranium. We also discuss the correlative use of electron backscattered diffraction in a scanning electron microscope to map the deformation in the zircon grains, and the combined use of transmission Kikuchi diffraction and focused ion beam sample preparation to assist preparation of the final atom probe tip.

  2. Probing Field Distributions on Waveguide Structures with an Atomic Force/Photon Scanning Tunneling Microscope

    NARCIS (Netherlands)

    Borgonjen, E.G.; Borgonjen, E.G.; Moers, M.H.P.; Moers, M.H.P.; Ruiter, A.G.T.; van Hulst, N.F.

    1995-01-01

    A 'stand-alone' Photon Scanning Tunneling Microscope combined with an Atomic force Microscope, using a micro-fabricated silicon-nitride probe, is applied to the imaging of field distribution in integrated optical ridge waveguides. The electric field on the waveguide is locally probed by coupling to

  3. Wet-chemical etching of atom probe tips for artefact free analyses of nanoscaled semiconductor structures.

    Science.gov (United States)

    Melkonyan, D; Fleischmann, C; Veloso, A; Franquet, A; Bogdanowicz, J; Morris, R J H; Vandervorst, W

    2018-03-01

    We introduce an innovative specimen preparation method employing the selectivity of a wet-chemical etching step to improve data quality and success rates in the atom probe analysis of contemporary semiconductor devices. Firstly, on the example of an SiGe fin embedded in SiO 2 we demonstrate how the selective removal of SiO 2 from the final APT specimen significantly improves accuracy and reliability of the reconstructed data. With the oxide removal, we eliminate the origin of shape artefacts, i.e. the formation of a non-hemispherical tip shape, that are typically observed in the reconstructed volume of complex systems. Secondly, using the same approach, we increase success rates to ∼90% for the damage-free, 3D site-specific localization of short (250 nm), vertical Si nanowires at the specimen apex. The impact of the abrupt emitter radius change that is introduced by this specimen preparation method is evaluated as being minor using field evaporation simulation and comparison of different reconstruction schemes. The Ge content within the SiGe fin as well as the 3D boron distribution in the Si NW as resolved by atom probe analysis are in good agreement with TEM/EDS and ToF-SIMS analysis, respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Probing Local Ionic Dynamics in Functional Oxides: From Nanometer to Atomic Scale

    Science.gov (United States)

    Kalinin, Sergei

    2014-03-01

    Vacancy-mediated electrochemical reactions in oxides underpin multiple applications ranging from electroresistive memories, to chemical sensors to energy conversion systems such as fuel cells. Understanding the functionality in these systems requires probing reversible (oxygen reduction/evolution reaction) and irreversible (cathode degradation and activation, formation of conductive filaments) electrochemical processes. In this talk, I summarize recent advances in probing and controlling these transformations locally on nanometer level using scanning probe microscopy. The localized tip concentrates the electric field in the nanometer scale volume of material, inducing local transition. Measured simultaneously electromechanical response (piezoresponse) or current (conductive AFM) provides the information on the bias-induced changes in material. Here, I illustrate how these methods can be extended to study local electrochemical transformations, including vacancy dynamics in oxides such as titanates, LaxSr1-xCoO3, BiFeO3, and YxZr1-xO2. The formation of electromechanical hysteresis loops and their bias-, temperature- and environment dependences provide insight into local electrochemical mechanisms. In materials such as lanthanum-strontium cobaltite, mapping both reversible vacancy motion and vacancy ordering and static deformation is possible, and can be corroborated by post mortem STEM/EELS studies. In ceria, a broad gamut of electrochemical behaviors is observed as a function of temperature and humidity. The possible strategies for elucidation ionic motion at the electroactive interfaces in oxides using high-resolution electron microscopy and combined ex-situ and in-situ STEM-SPM studies are discussed. In the second part of the talk, probing electrochemical phenomena on in-situ grown surfaces with atomic resolution is illustrated. I present an approach based on the multivariate statistical analysis of the coordination spheres of individual atoms to reveal

  5. Determining the field emitter temperature during laser irradiation in the pulsed laser atom probe

    International Nuclear Information System (INIS)

    Kellogg, G.L.

    1981-01-01

    Three methods are discussed for determining the field emitter temperature during laser irradiation in the recently developed Pulsed Laser Atom Probe. A procedure based on the reduction of the lattice evaporation field with increasing emitter temperature is found to be the most convenient and reliable method between 60 and 500 K. Calibration curves (plots of the evaporation field versus temperature) are presented for dc and pulsed field evaporation of W, Mo, and Rh. These results show directly the important influence of the evaporation rate on the temperature dependence of the evaporation field. The possibility of a temperature calibration based on the ionic charge state distribution of field evaporated lattice atoms is also discussed. The shift in the charge state distributions which occurs when the emitter temperature is increased and the applied field strength is decreased at a constant rate of evaporation is shown to be due to the changing field and not the changing temperature. Nevertheless, the emitter temperature can be deduced from the charge state distribution for a specified evaporation rate. Charge state distributions as a function of field strength and temperature are presented for the same three materials. Finally, a preliminary experiment is reported which shows that the emitter temperature can be determined from field ion microscope observations of single atom surface diffusion over low index crystal planes. This last calibration procedure is shown to be very useful at higher temperatures (>600 K) where the other two methods become unreliable

  6. Laser method of free atom nuclei orientation

    International Nuclear Information System (INIS)

    Barabanov, A.L.

    1987-01-01

    Orientation process of free atom (atoms in beams) nuclei, scattering quanta of circularly polarized laser radiation is considered. A method for the evaluation of nuclei orientation parameters is developed. It is shown that in the process of pumping between the ground and first excited atomic states with electron shell spins J 1 and J 2 , so that J 2 = J 1 + 1, a complete orientation of nuclei can be attained

  7. Dopant distributions in n-MOSFET structure observed by atom probe tomography

    International Nuclear Information System (INIS)

    Inoue, K.; Yano, F.; Nishida, A.; Takamizawa, H.; Tsunomura, T.; Nagai, Y.; Hasegawa, M.

    2009-01-01

    The dopant distributions in an n-type metal-oxide-semiconductor field effect transistor (MOSFET) structure were analyzed by atom probe tomography. The dopant distributions of As, P, and B atoms in a MOSFET structure (gate, gate oxide, channel, source/drain extension, and halo) were obtained. P atoms were segregated at the interface between the poly-Si gate and the gate oxide, and on the grain boundaries of the poly-Si gate, which had an elongated grain structure along the gate height direction. The concentration of B atoms was enriched near the edge of the source/drain extension where the As atoms were implanted.

  8. Dopant distributions in n-MOSFET structure observed by atom probe tomography.

    Science.gov (United States)

    Inoue, K; Yano, F; Nishida, A; Takamizawa, H; Tsunomura, T; Nagai, Y; Hasegawa, M

    2009-11-01

    The dopant distributions in an n-type metal-oxide-semiconductor field effect transistor (MOSFET) structure were analyzed by atom probe tomography. The dopant distributions of As, P, and B atoms in a MOSFET structure (gate, gate oxide, channel, source/drain extension, and halo) were obtained. P atoms were segregated at the interface between the poly-Si gate and the gate oxide, and on the grain boundaries of the poly-Si gate, which had an elongated grain structure along the gate height direction. The concentration of B atoms was enriched near the edge of the source/drain extension where the As atoms were implanted.

  9. Real time drift measurement for colloidal probe atomic force microscope: a visual sensing approach

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yuliang, E-mail: wangyuliang@buaa.edu.cn; Bi, Shusheng [Robotics Institute, School of Mechanical Engineering and Automation, Beihang University, Beijing 100191 (China); Wang, Huimin [Department of Materials Science and Engineering, The Ohio State University, 2041 College Rd., Columbus, OH 43210 (United States)

    2014-05-15

    Drift has long been an issue in atomic force microscope (AFM) systems and limits their ability to make long time period measurements. In this study, a new method is proposed to directly measure and compensate for the drift between AFM cantilevers and sample surfaces in AFM systems. This was achieved by simultaneously measuring z positions for beads at the end of an AFM colloidal probe and on sample surface through an off-focus image processing based visual sensing method. The working principle and system configuration are presented. Experiments were conducted to validate the real time drift measurement and compensation. The implication of the proposed method for regular AFM measurements is discussed. We believe that this technique provides a practical and efficient approach for AFM experiments requiring long time period measurement.

  10. Restoring the lattice of Si-based atom probe reconstructions for enhanced information on dopant positioning.

    Science.gov (United States)

    Breen, Andrew J; Moody, Michael P; Ceguerra, Anna V; Gault, Baptiste; Araullo-Peters, Vicente J; Ringer, Simon P

    2015-12-01

    The following manuscript presents a novel approach for creating lattice based models of Sb-doped Si directly from atom probe reconstructions for the purposes of improving information on dopant positioning and directly informing quantum mechanics based materials modeling approaches. Sophisticated crystallographic analysis techniques are used to detect latent crystal structure within the atom probe reconstructions with unprecedented accuracy. A distortion correction algorithm is then developed to precisely calibrate the detected crystal structure to the theoretically known diamond cubic lattice. The reconstructed atoms are then positioned on their most likely lattice positions. Simulations are then used to determine the accuracy of such an approach and show that improvements to short-range order measurements are possible for noise levels and detector efficiencies comparable with experimentally collected atom probe data. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Atom Probe Analysis of Ex Situ Gas-Charged Stable Hydrides.

    Science.gov (United States)

    Haley, Daniel; Bagot, Paul A J; Moody, Michael P

    2017-04-01

    In this work, we report on the atom probe tomography analysis of two metallic hydrides formed by pressurized charging using an ex situ hydrogen charging cell, in the pressure range of 200-500 kPa (2-5 bar). Specifically we report on the deuterium charging of Pd/Rh and V systems. Using this ex situ system, we demonstrate the successful loading and subsequent atom probe analysis of deuterium within a Pd/Rh alloy, and demonstrate that deuterium is likely present within the oxide-metal interface of a native oxide formed on vanadium. Through these experiments, we demonstrate the feasibility of ex situ hydrogen analysis for hydrides via atom probe tomography, and thus a practical route to three-dimensional imaging of hydrogen in hydrides at the atomic scale.

  12. Customized atomic force microscopy probe by focused-ion-beam-assisted tip transfer

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Andrew; Butte, Manish J., E-mail: manish.butte@stanford.edu [Department of Pediatrics, Division of Immunology, Allergy and Rheumatology, Stanford University, Stanford, California 94305 (United States)

    2014-08-04

    We present a technique for transferring separately fabricated tips onto tipless atomic force microscopy (AFM) cantilevers, performed using focused ion beam-assisted nanomanipulation. This method addresses the need in scanning probe microscopy for certain tip geometries that cannot be achieved by conventional lithography. For example, in probing complex layered materials or tall biological cells using AFM, a tall tip with a high-aspect-ratio is required to avoid artifacts caused by collisions of the tip's sides with the material being probed. We show experimentally that tall (18 μm) cantilever tips fabricated by this approach reduce squeeze-film damping, which fits predictions from hydrodynamic theory, and results in an increased quality factor (Q) of the fundamental flexural mode. We demonstrate that a customized tip's well-defined geometry, tall tip height, and aspect ratio enable improved measurement of elastic moduli by allowing access to low-laying portions of tall cells (T lymphocytes). This technique can be generally used to attach tips to any micromechanical device when conventional lithography of tips cannot be accomplished.

  13. Two-probe atomic-force microscope manipulator and its applications

    Science.gov (United States)

    Zhukov, A. A.; Stolyarov, V. S.; Kononenko, O. V.

    2017-06-01

    We report on a manipulator based on a two-probe atomic force microscope (AFM) with an individual feedback system for each probe. This manipulator works under an upright optical microscope with 3 mm focal distance. The design of the microscope helps us tomanipulate nanowires using the microscope probes as a two-prong fork. The AFM feedback is realized based on the dynamic full-time contact mode. The applications of the manipulator and advantages of its two-probe design are presented.

  14. Two-probe atomic-force microscope manipulator and its applications.

    Science.gov (United States)

    Zhukov, A A; Stolyarov, V S; Kononenko, O V

    2017-06-01

    We report on a manipulator based on a two-probe atomic force microscope (AFM) with an individual feedback system for each probe. This manipulator works under an upright optical microscope with 3 mm focal distance. The design of the microscope helps us tomanipulate nanowires using the microscope probes as a two-prong fork. The AFM feedback is realized based on the dynamic full-time contact mode. The applications of the manipulator and advantages of its two-probe design are presented.

  15. Atomic probe Wigner tomography of a nanomechanical system

    International Nuclear Information System (INIS)

    Singh, Swati; Meystre, Pierre

    2010-01-01

    We propose a scheme to measure the quantum state of a nanomechanical oscillator cooled near its ground state of vibrational motion. This is an extension of the nonlinear atomic homodyning technique scheme first developed to measure the intracavity field in a micromaser. It involves the use of a detector atom that is simultaneously coupled to the resonator via a magnetic interaction and to (classical) optical fields via a Raman transition. We show that the probability for the atom to be found in the ground state is a direct measure of the Wigner characteristic function of the nanomechanical oscillator. We also investigate the back-action effect of this destructive measurement on the state of the resonator.

  16. Photoelectron imaging, probe of the dynamics: from atoms... to clusters

    International Nuclear Information System (INIS)

    Lepine, F.

    2003-06-01

    This thesis concerns the study of the deexcitation of clusters and atoms by photoelectron imaging. The first part is dedicated to thermionic emission of a finite size system. A 3-dimensional imaging setup allows us to measure the time evolution of the kinetic energy spectrum of electrons emitted from different clusters (W n - , C n - , C 60 ). Then we have a direct access to the fundamental quantities which characterize this statistical emission: the temperature of the finite heat bath and the decay rate. The second part concerns the ionization of atomic Rydberg states placed in a static electric field. We performed the first experiment of photoionization microscopy which allows us to obtain a picture which is the macroscopic projection of the electronic wave function. Then we have access to the detail of the photoionization and particularly to the quantum properties of the electron usually confined at the atomic scale. (author)

  17. Cyanine-based probe\\tag-peptide pair fluorescence protein imaging and fluorescence protein imaging methods

    Science.gov (United States)

    Mayer-Cumblidge, M. Uljana; Cao, Haishi

    2013-01-15

    A molecular probe comprises two arsenic atoms and at least one cyanine based moiety. A method of producing a molecular probe includes providing a molecule having a first formula, treating the molecule with HgOAc, and subsequently transmetallizing with AsCl.sub.3. The As is liganded to ethanedithiol to produce a probe having a second formula. A method of labeling a peptide includes providing a peptide comprising a tag sequence and contacting the peptide with a biarsenical molecular probe. A complex is formed comprising the tag sequence and the molecular probe. A method of studying a peptide includes providing a mixture containing a peptide comprising a peptide tag sequence, adding a biarsenical probe to the mixture, and monitoring the fluorescence of the mixture.

  18. Probing new intra-atomic force with isotope shifts

    Energy Technology Data Exchange (ETDEWEB)

    Mikami, Kyoko; Tanaka, Minoru [Osaka University, Department of Physics, Graduate School of Science, Toyonaka, Osaka (Japan); Yamamoto, Yasuhiro [Yonsei University, Department of Physics and IPAP, Seoul (Korea, Republic of)

    2017-12-15

    In the development of atomic clocks, some atomic transition frequencies are measured with remarkable precision. These measured spectra may include the effects of a new force mediated by a weakly interacting boson. Such effects might be distilled out from possible violation of a linear relation in isotope shifts between two transitions, as known as King's linearity, with relatively suppressed theoretical uncertainties. We discuss the experimental sensitivity to a new force in the test of the linearity as well as the linearity violation owing to higher-order effects within the Standard Model. The sensitivity to new physics is limited by such effects. We have found that, for Yb{sup +}, the higher-order effect is in the reach of future experiments. The sensitivity to a heavy mediator is also discussed. It is analytically clarified that the sensitivity becomes weaker than that in the literature. Our numerical results of the sensitivity are compared with other weak force search experiments. (orig.)

  19. Probing Efimov discrete scaling in an atom-molecule collision

    Science.gov (United States)

    Shalchi, M. A.; Yamashita, M. T.; Hadizadeh, M. R.; Garrido, E.; Tomio, Lauro; Frederico, T.

    2018-01-01

    The discrete Efimov scaling behavior, well known in the low-energy spectrum of three-body bound systems for large scattering lengths (unitary limit), is identified in the energy dependence of an atom-molecule elastic cross section in mass-imbalanced systems. That happens in the collision of a heavy atom with mass mH with a weakly bound dimer formed by the heavy atom and a lighter one with mass mL≪mH . Approaching the heavy-light unitary limit, the s -wave elastic cross section σ will present a sequence of zeros or minima at collision energies following closely the Efimov geometrical law. Our results, obtained with Faddeev calculations and supplemented by a Born-Oppenheimer analysis, open a perspective to detecting the discrete scaling behavior from low-energy scattering data, which is timely in view of the ongoing experiments with ultracold binary mixtures having strong mass asymmetries, such as lithium and cesium or lithium and ytterbium.

  20. Probing quantum coherence in single-atom electron spin resonance

    Science.gov (United States)

    Willke, Philip; Paul, William; Natterer, Fabian D.; Yang, Kai; Bae, Yujeong; Choi, Taeyoung; Fernández-Rossier, Joaquin; Heinrich, Andreas J.; Lutz, Christoper P.

    2018-01-01

    Spin resonance of individual spin centers allows applications ranging from quantum information technology to atomic-scale magnetometry. To protect the quantum properties of a spin, control over its local environment, including energy relaxation and decoherence processes, is crucial. However, in most existing architectures, the environment remains fixed by the crystal structure and electrical contacts. Recently, spin-polarized scanning tunneling microscopy (STM), in combination with electron spin resonance (ESR), allowed the study of single adatoms and inter-atomic coupling with an unprecedented combination of spatial and energy resolution. We elucidate and control the interplay of an Fe single spin with its atomic-scale environment by precisely tuning the phase coherence time T2 using the STM tip as a variable electrode. We find that the decoherence rate is the sum of two main contributions. The first scales linearly with tunnel current and shows that, on average, every tunneling electron causes one dephasing event. The second, effective even without current, arises from thermally activated spin-flip processes of tip spins. Understanding these interactions allows us to maximize T2 and improve the energy resolution. It also allows us to maximize the amplitude of the ESR signal, which supports measurements even at elevated temperatures as high as 4 K. Thus, ESR-STM allows control of quantum coherence in individual, electrically accessible spins. PMID:29464211

  1. Pump-probe experiments in atoms involving laser and synchrotron radiation: an overview

    International Nuclear Information System (INIS)

    Wuilleumier, F J; Meyer, M

    2006-01-01

    The combined use of laser and synchrotron radiations for atomic photoionization studies started in the early 1980s. The strong potential of these pump-probe experiments to gain information on excited atomic states is illustrated through some exemplary studies. The first series of experiments carried out with the early synchrotron sources, from 1960 to about 1995, are reviewed, including photoionization of unpolarized and polarized excited atoms, and time-resolved laser-synchrotron studies. With the most advanced generation of synchrotron sources, a whole new class of pump-probe experiments benefiting from the high brightness of the new synchrotron beams has been developed since 1996. A detailed review of these studies as well as possible future applications of pump-probe experiments using third generation synchrotron sources and free electron lasers is presented. (topical review)

  2. Three dimensional atom probe imaging of GaAsSb quantum rings

    International Nuclear Information System (INIS)

    Beltran, A.M.; Marquis, E.A.; Taboada, A.G.; Ripalda, J.M.; Garcia, J.M.; Molina, S.I.

    2011-01-01

    Unambiguous evidence of ring-shaped self-assembled GaSb nanostructures grown by molecular beam epitaxy is presented on the basis of atom-probe tomography reconstructions and dark field transmission electron microscopy imaging. The GaAs capping process causes a strong segregation of Sb out of the center of GaSb quantum dots, leading to the self-assembled GaAs x Sb 1-x quantum rings of 20-30 nm in diameter with x∼0.33. -- Highlights: → Atom-probe tomography resolves QR morphology of GaSb self-assembled GaSb buried nanostructures. → From atom-probe tomography compositional distribution has been obtained. → Strong segregation and morphological changes are observed with respect to uncapped QR.

  3. IMPURITY SEGREGATION OF STAINLESS STEEL STUDIED BY ATOM-PROBE AND AUGER ELECTRON SPECTROSCOPY

    OpenAIRE

    Koguchi , Y.; Takahashi , K.; Ishikawa , Y.

    1987-01-01

    The surface compositions of type 304 stainless steel heated in vacuum at 600-900°C were determined by an atom-probe and Auger electron spectroscopic analysis. In addition to enrichment and depletion of alloying elements in the surface of the stainless steel, segregation of impurity elements such as carbon, nitrogen, phosphorus and sulfur is known to occur. In this paper the atom-probe was used to measure the impurity segregation in the grains as well as in the grain boundary while the AES was...

  4. Investigation of the self tempering effect of martensite by means of atom probe tomography

    International Nuclear Information System (INIS)

    Sackl, Stephanie; Clemens, Helmut; Primig, Sophie

    2015-01-01

    Self-tempering effects can be observed in steels with relatively high martensite start temperatures. After the formation of the first martensitic laths, carbon is able to diffuse in these laths during cooling, which can be attributed to sufficiently high temperatures. This effect cannot be observed in laths formed at lower temperatures. In steels containing up to 0.2 m.-% carbon, up to 90 % of the carbon atoms in the martensite segregate to dislocations during quenching. Due to its atomic resolution and sensitivity with respect to light elements, atom probe tomography is very well suited for the investigation of this phenomenon. In this study, the self-tempering effect in a quenched and tempered steel 42CrMo4 with a martensite start temperature of 310 C is investigated by means of atom probe tomography.

  5. Atomic-scale investigations of grain boundary segregation in astrology with a three dimensional atom-probe

    Energy Technology Data Exchange (ETDEWEB)

    Blavette, D. [Rouen Univ., 76 - Mont-Saint-Aignan (France). Lab. de Microscopie Electronique]|[Institut Universitaire de France (France); Letellier, L. [Rouen Univ., 76 - Mont-Saint-Aignan (France). Lab. de Microscopie Electronique; Duval, P. [Rouen Univ., 76 - Mont-Saint-Aignan (France). Lab. de Microscopie Electronique; Guttmann, M. [Rouen Univ., 76 - Mont-Saint-Aignan (France). Lab. de Microscopie Electronique]|[Institut de Recherches de la Siderurgie Francaise (IRSID), 57 - Maizieres-les-Metz (France)

    1996-08-01

    Both conventional and 3D atom-probes were applied to the investigation of grain-boundary (GB) segregation phenomena in two-phase nickel base superalloys Astroloy. 3D images as provided by the tomographic atom-probe reveal the presence of a strong segregation of both boron and molybdenum at grain-boundaries. Slight carbon enrichment is also detected. Considerable chromium segregation is exhibited at {gamma}`-{gamma}` grain-boundaries. All these segregants are distributed in a continuous manner along the boundary over a width close to 0.5 nm. Experiments show that segregation occurs during cooling and more probably between 1000 C and 800 C. Boron and molybdenum GB enrichments are interpreted as due to an equilibrium type-segregation while chromium segregation is thought to be induced by {gamma}` precipitation at GB`s and stabilised by the presence of boron. No segregation of zirconium is detected. (orig.)

  6. Standardless quantification methods in electron probe microanalysis

    Energy Technology Data Exchange (ETDEWEB)

    Trincavelli, Jorge, E-mail: trincavelli@famaf.unc.edu.ar [Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba (Argentina); Instituto de Física Enrique Gaviola, Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina, Medina Allende s/n, Ciudad Universitaria, 5000 Córdoba (Argentina); Limandri, Silvina, E-mail: s.limandri@conicet.gov.ar [Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba (Argentina); Instituto de Física Enrique Gaviola, Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina, Medina Allende s/n, Ciudad Universitaria, 5000 Córdoba (Argentina); Bonetto, Rita, E-mail: bonetto@quimica.unlp.edu.ar [Centro de Investigación y Desarrollo en Ciencias Aplicadas Dr. Jorge Ronco, Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina, Facultad de Ciencias Exactas, de la Universidad Nacional de La Plata, Calle 47 N° 257, 1900 La Plata (Argentina)

    2014-11-01

    The elemental composition of a solid sample can be determined by electron probe microanalysis with or without the use of standards. The standardless algorithms are quite faster than the methods that require standards; they are useful when a suitable set of standards is not available or for rough samples, and also they help to solve the problem of current variation, for example, in equipments with cold field emission gun. Due to significant advances in the accuracy achieved during the last years, product of the successive efforts made to improve the description of generation, absorption and detection of X-rays, the standardless methods have increasingly become an interesting option for the user. Nevertheless, up to now, algorithms that use standards are still more precise than standardless methods. It is important to remark, that care must be taken with results provided by standardless methods that normalize the calculated concentration values to 100%, unless an estimate of the errors is reported. In this work, a comprehensive discussion of the key features of the main standardless quantification methods, as well as the level of accuracy achieved by them is presented. - Highlights: • Standardless methods are a good alternative when no suitable standards are available. • Their accuracy reaches 10% for 95% of the analyses when traces are excluded. • Some of them are suitable for the analysis of rough samples.

  7. Interpretation of atom probe tomography data for the intermetallic TiAl+Nb by means of field evaporation simulation

    KAUST Repository

    Boll, Torben; Al-Kassab, Talaat

    2013-01-01

    In this paper simulations of the field evaporation process during field ion microscopy (FIM) and atom probe tomography (APT) are presented and compared with experimental data. The Müller-Schottky-model [1] was extended to include the local atomic

  8. Probing Andreev bound states in one-atom superconducting contacts

    Energy Technology Data Exchange (ETDEWEB)

    Pothier, Hugues; Janvier, Camille; Tosi, Leandro; Girit, Caglar; Goffman, Marcelo; Esteve, Daniel; Urbina, Cristian [Quantronics Group, SPEC, CEA-Saclay (France)

    2015-07-01

    Superconductors are characterized by a dissipationless current. Since the work of Josephson 50 years ago, it is known that a supercurrent can even flow through tunnel junctions between superconductors. This Josephson effect also occurs through any type of ''weak links'' between superconductors: non-superconducting materials, constrictions,.. A unified understanding of the Josephson effect has emerged from a mesoscopic description of weak links. It relies on the existence of doublets of localized states that have energies below the superconducting gap: the Andreev bound states. I will present experiments performed on the simplest conductor possible, a single-atom contact between superconductors, that illustrate these concepts. The most recent work demonstrates time-domain manipulation of quantum superpositions of Andreev bound states.

  9. A method optimization study for atomic absorption ...

    African Journals Online (AJOL)

    A sensitive, reliable and relative fast method has been developed for the determination of total zinc in insulin by atomic absorption spectrophotometer. This designed study was used to optimize the procedures for the existing methods. Spectrograms of both standard and sample solutions of zinc were recorded by measuring ...

  10. Atom probe field ion microscopy and related topics: A bibliography 1992

    Energy Technology Data Exchange (ETDEWEB)

    Russell, K.F.; Godfrey, R.D.; Miller, M.K.

    1993-12-01

    This bibliography contains citations of books, conference proceedings, journals, and patents published in 1992 on the following types of microscopy: atom probe field ion microscopy (108 items); field emission microscopy (101 items); and field ion microscopy (48 items). An addendum of 34 items missed in previous bibliographies is included.

  11. Noncontact atomic force microscopy in liquid environment with quartz tuning fork and carbon nanotube probe

    DEFF Research Database (Denmark)

    Kageshima, M.; Jensenius, Henriette; Dienwiebel, M.

    2002-01-01

    A force sensor for noncontact atomic force microscopy in liquid environment was developed by combining a multiwalled carbon nanotube (MWNT) probe with a quartz tuning fork. Solvation shells of octamethylcyclotetrasiloxane surface were detected both in the frequency shift and dissipation. Due to t...

  12. Probing the stiffness of isolated nucleoli by atomic force microscopy.

    Science.gov (United States)

    Louvet, Emilie; Yoshida, Aiko; Kumeta, Masahiro; Takeyasu, Kunio

    2014-04-01

    In eukaryotic cells, ribosome biogenesis occurs in the nucleolus, a membraneless nuclear compartment. Noticeably, the nucleolus is also involved in several nuclear functions, such as cell cycle regulation, non-ribosomal ribonucleoprotein complex assembly, aggresome formation and some virus assembly. The most intriguing question about the nucleolus is how such dynamics processes can occur in such a compact compartment. We hypothesized that its structure may be rather flexible. To investigate this, we used atomic force microscopy (AFM) on isolated nucleoli. Surface topography imaging revealed the beaded structure of the nucleolar surface. With the AFM's ability to measure forces, we were able to determine the stiffness of isolated nucleoli. We could establish that the nucleolar stiffness varies upon drastic morphological changes induced by transcription and proteasome inhibition. Furthermore, upon ribosomal proteins and LaminB1 knockdowns, the nucleolar stiffness was increased. This led us to propose a model where the nucleolus has steady-state stiffness dependent on ribosome biogenesis activity and requires LaminB1 for its flexibility.

  13. A FIM-atom probe investigation of the bainite transformation in CrMo steel

    International Nuclear Information System (INIS)

    Bach, P.W.

    1981-01-01

    To obtain a better understanding of the role played by Cr and Mo in the bainite transformation a Field-Ion Microscope - Atom Probe was constructed in order to study the distribution of the alloying elements near various types of boundaries on atomic scale. The distribution of alloying elements measured with this instrument is not so smooth on atomic scale as suggested by microprobe analysis. In a coherent twin boundary, formed during the bainite transformation, a depletion of the substitutionals Cr and Mo and an enhancement of the C content is observed, which is in accordance with the atomic model of a B.C.C. twin. In the twin plane the interstitial sites are even larger than the F.C.C. octahedral sites and this plane can act as an effective sink for the carbon atoms from bainitic ferrite. The depletion of Cr and Mo from the twin plane is due to interface coherency. (Auth.)

  14. Study of defects and radiation damage in solids by field-ion and atom-probe microscopy

    International Nuclear Information System (INIS)

    Seidman, D.N.

    1979-06-01

    A brief review is presented of: the basic physical principles of the field-ion and atom-probe microscopes; the many applications of these instruments to the study of defects and radiation damage in solids; and the application of the atom-probe field-ion microscope to the study of the behavior of implanted 3 He and 4 He in tungsten

  15. Probing the accuracy and precision of Hirshfeld atom refinement with HARt interfaced with Olex2

    Directory of Open Access Journals (Sweden)

    Malte Fugel

    2018-01-01

    Full Text Available Hirshfeld atom refinement (HAR is a novel X-ray structure refinement technique that employs aspherical atomic scattering factors obtained from stockholder partitioning of a theoretically determined tailor-made static electron density. HAR overcomes many of the known limitations of independent atom modelling (IAM, such as too short element–hydrogen distances, r(X—H, or too large atomic displacement parameters (ADPs. This study probes the accuracy and precision of anisotropic hydrogen and non-hydrogen ADPs and of r(X—H values obtained from HAR. These quantities are compared and found to agree with those obtained from (i accurate neutron diffraction data measured at the same temperatures as the X-ray data and (ii multipole modelling (MM, an established alternative method for interpreting X-ray diffraction data with the help of aspherical atomic scattering factors. Results are presented for three chemically different systems: the aromatic hydrocarbon rubrene (orthorhombic 5,6,11,12-tetraphenyltetracene, a co-crystal of zwitterionic betaine, imidazolium cations and picrate anions (BIPa, and the salt potassium hydrogen oxalate (KHOx. The non-hydrogen HAR-ADPs are as accurate and precise as the MM-ADPs. Both show excellent agreement with the neutron-based values and are superior to IAM-ADPs. The anisotropic hydrogen HAR-ADPs show a somewhat larger deviation from neutron-based values than the hydrogen SHADE-ADPs used in MM. Element–hydrogen bond lengths from HAR are in excellent agreement with those obtained from neutron diffraction experiments, although they are somewhat less precise. The residual density contour maps after HAR show fewer features than those after MM. Calculating the static electron density with the def2-TZVP basis set instead of the simpler def2-SVP one does not improve the refinement results significantly. All HARs were performed within the recently introduced HARt option implemented in the Olex2 program. They are easily

  16. Probing the accuracy and precision of Hirshfeld atom refinement with HARt interfaced with Olex2.

    Science.gov (United States)

    Fugel, Malte; Jayatilaka, Dylan; Hupf, Emanuel; Overgaard, Jacob; Hathwar, Venkatesha R; Macchi, Piero; Turner, Michael J; Howard, Judith A K; Dolomanov, Oleg V; Puschmann, Horst; Iversen, Bo B; Bürgi, Hans-Beat; Grabowsky, Simon

    2018-01-01

    Hirshfeld atom refinement (HAR) is a novel X-ray structure refinement technique that employs aspherical atomic scattering factors obtained from stockholder partitioning of a theoretically determined tailor-made static electron density. HAR overcomes many of the known limitations of independent atom modelling (IAM), such as too short element-hydrogen distances, r ( X -H), or too large atomic displacement parameters (ADPs). This study probes the accuracy and precision of anisotropic hydrogen and non-hydrogen ADPs and of r ( X -H) values obtained from HAR. These quantities are compared and found to agree with those obtained from (i) accurate neutron diffraction data measured at the same temperatures as the X-ray data and (ii) multipole modelling (MM), an established alternative method for interpreting X-ray diffraction data with the help of aspherical atomic scattering factors. Results are presented for three chemically different systems: the aromatic hydro-carbon rubrene (orthorhombic 5,6,11,12-tetra-phenyl-tetracene), a co-crystal of zwitterionic betaine, imidazolium cations and picrate anions (BIPa), and the salt potassium hydrogen oxalate (KHOx). The non-hydrogen HAR-ADPs are as accurate and precise as the MM-ADPs. Both show excellent agreement with the neutron-based values and are superior to IAM-ADPs. The anisotropic hydrogen HAR-ADPs show a somewhat larger deviation from neutron-based values than the hydrogen SHADE-ADPs used in MM. Element-hydrogen bond lengths from HAR are in excellent agreement with those obtained from neutron diffraction experiments, although they are somewhat less precise. The residual density contour maps after HAR show fewer features than those after MM. Calculating the static electron density with the def2-TZVP basis set instead of the simpler def2-SVP one does not improve the refinement results significantly. All HARs were performed within the recently introduced HARt option implemented in the Olex2 program. They are easily launched

  17. Specialized probes based on hydroxyapatite calcium for heart tissues research by atomic force microscopy

    International Nuclear Information System (INIS)

    Zhukov, Mikhail; Golubok, Alexander; Gulyaev, Nikolai

    2016-01-01

    The new specialized AFM-probes with hydroxyapatite structures for atomic force microscopy of heart tissues calcification were created and studied. A process of probe fabrication is demonstrated. The adhesive forces between specialized hydroxyapatite probe and endothelium/subendothelial layers were investigated. It was found that the adhesion forces are significantly higher for the subendothelial layers. We consider that it is connected with the formation and localization of hydroxyapatite in the area of subendothelial layers of heart tissues. In addition, the roughness analysis and structure visualization of the endothelial surface of the heart tissue were carried out. The results show high efficiency of created specialized probes at study a calcinations process of the aortic heart tissues.

  18. Ion-atom interactions probed by photofragment spectroscopy

    International Nuclear Information System (INIS)

    Helm, H.

    1984-01-01

    Photofragment spectroscopy studies energetic and dynamical properties of molecular states interacting with dissociation continuum. So far, data for eighteen diatomic molecular ions have been gathered by this technique. This paper is a review of these investigations, introduced by a discussion of the experimental methods used. The wealth of information accessible by ion photofragment spectroscopy challenges the experimentalist in the application of innovative techniques and the theoretician for less approximate accounts of the Hamiltonian. (Auth.)

  19. Scanning probe methods applied to molecular electronics

    Energy Technology Data Exchange (ETDEWEB)

    Pavlicek, Niko

    2013-08-01

    Scanning probe methods on insulating films offer a rich toolbox to study electronic, structural and spin properties of individual molecules. This work discusses three issues in the field of molecular and organic electronics. An STM head to be operated in high magnetic fields has been designed and built up. The STM head is very compact and rigid relying on a robust coarse approach mechanism. This will facilitate investigations of the spin properties of individual molecules in the future. Combined STM/AFM studies revealed a reversible molecular switch based on two stable configurations of DBTH molecules on ultrathin NaCl films. AFM experiments visualize the molecular structure in both states. Our experiments allowed to unambiguously determine the pathway of the switch. Finally, tunneling into and out of the frontier molecular orbitals of pentacene molecules has been investigated on different insulating films. These experiments show that the local symmetry of initial and final electron wave function are decisive for the ratio between elastic and vibration-assisted tunneling. The results can be generalized to electron transport in organic materials.

  20. Atomic force microscopy deep trench and sidewall imaging with an optical fiber probe

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Hui, E-mail: xiehui@hit.edu.cn; Hussain, Danish; Yang, Feng [The State Key Laboratory of Robotics and Systems, Harbin Institute of Technology, 2 Yikuang, 150080 Harbin (China); Sun, Lining [The State Key Laboratory of Robotics and Systems, Harbin Institute of Technology, 2 Yikuang, 150080 Harbin (China); Robotics and Microsystems Center, Soochow University, 215021 Suzhou (China)

    2014-12-15

    We report a method to measure critical dimensions of micro- and nanostructures using the atomic force microscope (AFM) with an optical fiber probe (OFP). This method is capable of scanning narrow and deep trenches due to the long and thin OFP tip, as well as imaging of steep sidewalls with unique profiling possibilities by laterally tilting the OFP without any modifications of the optical lever. A switch control scheme is developed to measure the sidewall angle by flexibly transferring feedback control between the Z- and Y-axis, for a serial scan of the horizontal surface (raster scan on XY-plane) and sidewall (raster scan on the YZ-plane), respectively. In experiments, a deep trench with tapered walls (243.5 μm deep) and a microhole (about 14.9 μm deep) have been imaged with the orthogonally aligned OFP, as well as a silicon sidewall (fabricated by deep reactive ion etching) has been characterized with the tilted OFP. Moreover, the sidewall angle of TGZ3 (AFM calibration grating) was accurately measured using the switchable scan method.

  1. Analysis of deuterium in V-Fe5at.% film by atom probe tomography (APT)

    International Nuclear Information System (INIS)

    Gemma, R.; Al-Kassab, T.; Kirchheim, R.; Pundt, A.

    2011-01-01

    Research highlights: → Deuterium distribution in V-Fe thin film was investigated by atom probe tomography. → Correct analysis was possible at analysis temperatures below 30 K. → Inhomogeneous distribution of D atoms was nevertheless observed. → This was interpreted by trapping effect at misfit dislocation. → Atom probe analysis provides detailed information on local chemistry of M-D system. - Abstract: V-Fe5at.% 2 and 10-nm thick single layered films were prepared by ion beam sputtering on W substrate. They were loaded with D from gas phase at 0.2 Pa and at 1 Pa, respectively. Both lateral and depth D distribution of these films was investigated in detail by atom probe tomography. The results of analysis are in good agreement between the average deuterium concentration and the value, expected from electromotive force measurement on a similar flat film. An enrichment of deuterium at the V/W interface was observed for both films. The origin of this D-accumulation was discussed in respect to electron transfer, mechanical stress and misfit dislocations.

  2. Robust operation and performance of integrated carbon nanotubes atomic force microscopy probes

    International Nuclear Information System (INIS)

    Rius, G; Clark, I T; Yoshimura, M

    2013-01-01

    We present a complete characterization of carbon nanotubes-atomic force microscopy (CNT-AFM) probes to evaluate the cantilever operation and advanced properties originating from the CNTs. The fabrication consists of silicon probes tip-functionalized with multiwalled CNTs by microwave plasma enhanced chemical vapor deposition. A dedicated methodology has been defined to evaluate the effect of CNT integration into the Si cantilevers. The presence of the CNTs provides enhanced capability for sensing and durability, as demonstrated using dynamic and static modes, e.g. imaging, indentation and force/current characterization.

  3. Atom probe tomography simulations and density functional theory calculations of bonding energies in Cu3Au

    KAUST Repository

    Boll, Torben

    2012-10-01

    In this article the Cu-Au binding energy in Cu3Au is determined by comparing experimental atom probe tomography (APT) results to simulations. The resulting bonding energy is supported by density functional theory calculations. The APT simulations are based on the Müller-Schottky equation, which is modified to include different atomic neighborhoods and their characteristic bonds. The local environment is considered up to the fifth next nearest neighbors. To compare the experimental with simulated APT data, the AtomVicinity algorithm, which provides statistical information about the positions of the neighboring atoms, is applied. The quality of this information is influenced by the field evaporation behavior of the different species, which is connected to the bonding energies. © Microscopy Society of America 2012.

  4. Probing Single Pt Atoms in Complex Intermetallic Al13Fe4.

    Science.gov (United States)

    Yamada, Tsunetomo; Kojima, Takayuki; Abe, Eiji; Kameoka, Satoshi; Murakami, Yumi; Gille, Peter; Tsai, An Pang

    2018-03-21

    The atomic structure of a 0.2 atom % Pt-doped complex metallic alloy, monoclinic Al 13 Fe 4 , was investigated using a single crystal prepared by the Czochralski method. High-angle annular dark-field scanning transmission electron microscopy showed that the Pt atoms were dispersed as single atoms and substituted at Fe sites in Al 13 Fe 4 . Single-crystal X-ray structural analysis revealed that the Pt atoms preferentially substitute at Fe(1). Unlike those that have been reported, Pt single atoms in the surface layers showed lower activity and selectivity than those of Al 2 Pt and bulk Pt for propyne hydrogenation, indicating that the active state of a given single-atom Pt site is strongly dominated by the bonding to surrounding Al atoms.

  5. The first direct observation of hydrogen trapping sites in TiC precipitation-hardening steel through atom probe tomography

    International Nuclear Information System (INIS)

    Takahashi, Jun; Kawakami, Kazuto; Kobayashi, Yukiko; Tarui, Toshimi

    2010-01-01

    For the first time ever, atomic-scale direct observation of deuterium atoms trapping at nano-sized titanium carbide (TiC) precipitates in steel was successfully achieved using atom probe tomography (APT). Deuterium gas charging into the needle specimen and subsequently quenching were conducted in our designed chamber attached to three-dimensional atom probe (3DAP). The deuterium atoms were definitely observed on the broad surface of TiC platelets, which indicated that the broad interface between the matrix and TiC was the main trapping site.

  6. Atomic wavefunctions probed through strong-field light-matter interaction

    Energy Technology Data Exchange (ETDEWEB)

    Mairesse, Y; Villeneuve, D M; Corkum, P B; Dudovich, N [Natl Res Council Canada, Ottawa, ON K1A 0R6 (Canada); Shafir, D; Dudovich, N [Weizmann Inst Sci, Dept Phys Complex Syst, IL-76100 Rehovot, (Israel); Mairesse, Y [Univ Bordeaux 1, CELIA, CNRS, UMR 5107, CEA, F-33405 Talence (France)

    2009-07-01

    Strong-field light-matter interactions can encode the spatial properties of the electronic wavefunctions that contribute to the process. In particular, the broadband harmonic spectra, measured for a series of molecular alignments, can be used to create a tomographic reconstruction of molecular orbitals. Here, we present an extension of the tomography approach to systems that cannot be naturally aligned. We demonstrate this ability by probing the two-dimensional properties of atomic wavefunctions. By manipulating an electron-ion re-collision process, we are able to resolve the symmetry of the atomic wavefunction with high contrast. (authors)

  7. Momentum distributions of selected rare-gas atoms probed by intense femtosecond laser pulses

    DEFF Research Database (Denmark)

    Abu-Samha, Mahmoud; Madsen, Lars Bojer

    2011-01-01

    We provide a direct comparison between numerical and experimental (Rudenko et al 2004 J. Phys. B: At. Mol. Opt. Phys. 37 L407) photoelectron momentum distributions in strong-field ionization of selected rare-gas atoms (He, Ne and Ar), probed by femtosecond linearly polarized laser pulses. The cal......We provide a direct comparison between numerical and experimental (Rudenko et al 2004 J. Phys. B: At. Mol. Opt. Phys. 37 L407) photoelectron momentum distributions in strong-field ionization of selected rare-gas atoms (He, Ne and Ar), probed by femtosecond linearly polarized laser pulses....... The calculations are performed by solving the time-dependent Schrödinger equation within the single-active-electron approximation, and focal-volume effects are taken into account by appropriately averaging the results. The resulting momentum distributions are in quantitative agreement with the experimental...

  8. Nanomanipulation and nanofabrication with multi-probe scanning tunneling microscope: from individual atoms to nanowires.

    Science.gov (United States)

    Qin, Shengyong; Kim, Tae-Hwan; Wang, Zhouhang; Li, An-Ping

    2012-06-01

    The wide variety of nanoscale structures and devices demands novel tools for handling, assembly, and fabrication at nanoscopic positioning precision. The manipulation tools should allow for in situ characterization and testing of fundamental building blocks, such as nanotubes and nanowires, as they are built into functional devices. In this paper, a bottom-up technique for nanomanipulation and nanofabrication is reported by using a 4-probe scanning tunneling microscope (STM) combined with a scanning electron microscope (SEM). The applications of this technique are demonstrated in a variety of nanosystems, from manipulating individual atoms to bending, cutting, breaking carbon nanofibers, and constructing nanodevices for electrical characterizations. The combination of the wide field of view of SEM, the atomic position resolution of STM, and the flexibility of multiple scanning probes is expected to be a valuable tool for rapid prototyping in the nanoscience and nanotechnology.

  9. Dicke superradiance as nondestructive probe for the state of atoms in optical lattices

    Science.gov (United States)

    ten Brinke, Nicolai; Schützhold, Ralf

    2016-04-01

    We present a proposal for a probing scheme utilizing Dicke superradiance to obtain information about ultracold atoms in optical lattices. A probe photon is absorbed collectively by an ensemble of lattice atoms generating a Dicke state. The lattice dynamics (e.g., tunneling) affects the coherence properties of that Dicke state and thus alters the superradiant emission characteristics - which in turn provides insight into the lattice (dynamics). Comparing the Bose-Hubbard and the Fermi-Hubbard model, we find similar superradiance in the strongly interacting Mott insulator regime, but crucial differences in the weakly interacting (superfluid or metallic) phase. Furthermore, we study the possibility to detect whether a quantum phase transition between the two regimes can be considered adiabatic or a quantum quench.

  10. Phase decomposition and ordering in Ni-11.3 at.% Ti studied with atom probe tomography

    KAUST Repository

    Al-Kassab, Talaat

    2014-09-01

    The decomposition behavior of Ni-rich Ni-Ti was reassessed using Tomographic Atom Probe (TAP) and Laser Assisted Wide Angle Tomographic Atom Probe. Single crystalline specimens of Ni-11.3at.% Ti were investigated, the states selected from the decomposition path were the metastable γ″ and γ\\' states introduced on the basis of small-angle neutron scattering (SANS) and the two-phase model for evaluation. The composition values of the precipitates in these states could not be confirmed by APT data as the interface of the ordered precipitates may not be neglected. The present results rather suggest to apply a three-phase model for the interpretation of SANS measurements, in which the width of the interface remains nearly unchanged and the L12 structure close to 3:1 stoichiometry is maintained in the core of the precipitates from the γ″ to the γ\\' state. © 2014 Elsevier Ltd.

  11. Automated voxelization of 3D atom probe data through kernel density estimation

    International Nuclear Information System (INIS)

    Srinivasan, Srikant; Kaluskar, Kaustubh; Dumpala, Santoshrupa; Broderick, Scott; Rajan, Krishna

    2015-01-01

    Identifying nanoscale chemical features from atom probe tomography (APT) data routinely involves adjustment of voxel size as an input parameter, through visual supervision, making the final outcome user dependent, reliant on heuristic knowledge and potentially prone to error. This work utilizes Kernel density estimators to select an optimal voxel size in an unsupervised manner to perform feature selection, in particular targeting resolution of interfacial features and chemistries. The capability of this approach is demonstrated through analysis of the γ / γ’ interface in a Ni–Al–Cr superalloy. - Highlights: • Develop approach for standardizing aspects of atom probe reconstruction. • Use Kernel density estimators to select optimal voxel sizes in an unsupervised manner. • Perform interfacial analysis of Ni–Al–Cr superalloy, using new automated approach. • Optimize voxel size to preserve the feature of interest and minimizing loss / noise.

  12. Atom probe microscopy of zinc isotopic enrichment in ZnO nanorods

    Directory of Open Access Journals (Sweden)

    C. N. Ironside

    2017-02-01

    Full Text Available We report on atomic probe microscopy (APM of isotopically enriched ZnO nanorods that measures the spatial distribution of zinc isotopes in sections of ZnO nanorods for natural abundance natZnO and 64Zn and 66Zn enriched ZnO nanorods. The results demonstrate that APM can accurately quantify isotopic abundances within these nanoscale structures. Therefore the atom probe microscope is a useful tool for characterizing Zn isotopic heterostructures in ZnO. Isotopic heterostructures have been proposed for controlling thermal conductivity and also, combined with neutron transmutation doping, they could be key to a novel technology for producing p-n junctions in ZnO thin films and nanorods.

  13. Proposal for efficient two-dimensional atom localization using probe absorption in a microwave-driven four-level atomic system

    International Nuclear Information System (INIS)

    Ding Chunling; Li Jiahua; Yang Xiaoxue; Xiong Hao; Zhang Duo

    2011-01-01

    The behavior of two-dimensional (2D) atom localization is explored by monitoring the probe absorption in a microwave-driven four-level atomic medium under the action of two orthogonal standing-wave fields. Because of the position-dependent atom-field interaction, the information about the position of the atom can be obtained via the absorption measurement of the weak probe field. It is found that the localization behavior is significantly improved due to the joint quantum interference induced by the standing-wave and microwave-driven fields. Most importantly, the atom can be localized at a particular position and the maximal probability of finding the atom in one period of the standing-wave fields reaches unity by properly adjusting the system parameters. The proposed scheme may provide a promising way to achieve high-precision and high-resolution 2D atom localization.

  14. Atom probe tomography of Ni-base superalloys Allvac 718Plus and Alloy 718

    Energy Technology Data Exchange (ETDEWEB)

    Viskari, L., E-mail: viskari@chalmers.se [Chalmers University of Technology, Gothenburg (Sweden); Stiller, K. [Chalmers University of Technology, Gothenburg (Sweden)

    2011-05-15

    Atom probe tomography (APT) allows near atomic scale compositional- and morphological studies of, e.g. matrix, precipitates and interfaces in a wide range of materials. In this work two Ni-base superalloys with similar compositions, Alloy 718 and its derivative Allvac 718Plus, are subject for investigation with special emphasis on the latter alloy. The structural and chemical nuances of these alloys are important for their properties. Of special interest are grain boundaries as their structure and chemistry are important for the materials' ability to resist rapid environmentally induced crack propagation. APT has proved to be suitable for analyses of these types of alloys using voltage pulsed APT. However, for investigations of specimens containing grain boundaries and other interfaces the risk for early specimen fracture is high. Analyses using laser pulsing impose lower electrical field on the specimen thereby significantly increasing the success rate of investigations. Here, the effect of laser pulsing was studied and the derived appropriate acquisition parameters were then applied for microstructural studies, from which initial results are shown. Furthermore, the influence of the higher evaporation field experienced by the hardening {gamma}' Ni{sub 3}(Al,Nb) precipitates on the obtained results is discussed. -- Research highlights: {yields} Laser pulsed APT is shown to be a good method for analysis of Ni-based superalloys. {yields} The evaporation field is shown to be different for different phases which affects reconstructions. {yields} B and P are shown to segregate to grain boundaries. {yields} Initial results of {delta}-phase analysed by APT are shown.

  15. First local electrode atom probe analysis of magnetite (Fe3O4)

    International Nuclear Information System (INIS)

    Kuhlman, K.R.; Kelly, T.F.; Miller, M.K.

    2004-01-01

    Full text: We have successfully fabricated atom probe samples of a metamorphic magnetite and performed an analysis of one of these samples using a local electrode atom probe (LEAP). This particular magnetite, previously designated LP204-1, was extracted from a polymetamorphosed, granulite-facies marble and contains grain scale heterogeneity in its oxygen isotope ratios. Crystals of LP204-1 contain a high number density of nanometer-scale, disk-shaped Al-Mn-Fe-spinel precipitates making this magnetite particularly attractive for demonstrating the capabilities of the LEAP with regard to geological materials. Field ion microscope images of these magnetite crystals show precipitate size and morphology that agrees with previous results. A sample of LP-204-1 was analyzed in the LEAP, resulting in a cylindrical analyzed volume approx. 26 nm in diameter and 21 nm high. The mass spectrum contained nearly 106,000 atoms, 97.1 % of which were identified. Peaks for singly, doubly and triply ionized species were fully resolved. The analysis volume appeared to be purely magnetite, i.e. no precipitates were observed. If it is assumed that 77 % of the ions in the peak at 16 are O 2 ++ rather than O+, the stoichiometry measured for this sample using electron probe microanalysis is achieved. The high fraction of O 2 ++ can be explained by lack of a peak for O ++ and significant peaks for FeO x indicating a relatively low field strength, which in turn favors molecular ions. This work is an encouraging beginning for analysis of geological materials in atom probes. Refs. 4 (author)

  16. Atom probe field ion microscopy and related topics: A bibliography 1989

    International Nuclear Information System (INIS)

    Miller, M.K.; Hawkins, A.R.; Russell, K.F.

    1990-12-01

    This bibliography includes references related to the following topics: atom probe field ion microscopy (APFIM), field ion spectroscopy (FIM), field emission microscopy (FEM), liquid metal ion sources (LMIS), scanning tunneling microscopy (STM), and theory. Technique-orientated studies and applications are included. This bibliography covers the period 1989. The references contained in this document were compiled from a variety of sources including computer searches and personal lists of publications

  17. Nonlocal Response of Metallic Nanospheres Probed by Light, Electrons, and Atoms

    DEFF Research Database (Denmark)

    Christensen, Thomas; Yan, Wei; Raza, Søren

    2014-01-01

    Inspired by recent measurements on individual metallic nanospheres that cannot be explained with traditional classical electrodynamics, we theoretically investigate the effects of nonlocal response by metallic nanospheres in three distinct settings: atomic spontaneous emission, electron energy loss...... blueshifted surface plasmon but also an infinite series of bulk plasmons that have no counterpart in a local-response approximation. We show that these increasingly blueshifted multipole plasmons become spectrally more prominent at shorter probe-to-surface separations and for decreasing nanosphere radii...

  18. Pump-probe study of atoms and small molecules with laser driven high order harmonics

    Science.gov (United States)

    Cao, Wei

    A commercially available modern laser can emit over 1015 photons within a time window of a few tens of femtoseconds (10-15second), which can be focused into a spot size of about 10 mum, resulting in a peak intensity above 1014W/cm2. This paves the way for table-top strong field physics studies such as above threshold ionization (ATI), non-sequential double ionization (NSDI), high order harmonic generation (HHG), etc.. Among these strong laser-matter interactions, high order harmonic generation, which combines many photons of the fundamental laser field into a single photon, offers a unique way to generate light sources in the vacuum ultraviolet (VUV) or extreme ultraviolet (EUV) region. High order harmonic photons are emitted within a short time window from a few tens of femtoseconds down to a few hundreds of attoseconds (10 -18second). This highly coherent nature of HHG allows it to be synchronized with an infrared (IR) laser pulse, and the pump-probe technique can be adopted to study ultrafast dynamic processes in a quantum system. The major work of this thesis is to develop a table-top VUV(EUV) light source based on HHG, and use it to study dynamic processes in atoms and small molecules with the VUV(EUV)-pump IR-probe method. A Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) apparatus is used for momentum imaging of the interaction products. Two types of high harmonic pump pulses are generated and applied for pump-probe studies. The first one consists of several harmonics forming a short attosecond pulse train (APT) in the EUV regime (around 40 eV). We demonstrate that, (1) the auto-ionization process triggered by the EUV in cation carbon-monoxide and oxygen molecules can be modified by scanning the EUV-IR delay, (2) the phase information of quantum trajectories in bifurcated high harmonics can be extracted by performing an EUV-IR cross-correlation experiment, thus disclosing the macroscopic quantum control in HHG. The second type of high harmonic source

  19. Variational methods in electron-atom scattering theory

    CERN Document Server

    Nesbet, Robert K

    1980-01-01

    The investigation of scattering phenomena is a major theme of modern physics. A scattered particle provides a dynamical probe of the target system. The practical problem of interest here is the scattering of a low­ energy electron by an N-electron atom. It has been difficult in this area of study to achieve theoretical results that are even qualitatively correct, yet quantitative accuracy is often needed as an adjunct to experiment. The present book describes a quantitative theoretical method, or class of methods, that has been applied effectively to this problem. Quantum mechanical theory relevant to the scattering of an electron by an N-electron atom, which may gain or lose energy in the process, is summarized in Chapter 1. The variational theory itself is presented in Chapter 2, both as currently used and in forms that may facilitate future applications. The theory of multichannel resonance and threshold effects, which provide a rich structure to observed electron-atom scattering data, is presented in Cha...

  20. Nanomechanical properties of lithiated Si nanowires probed with atomic force microscopy

    International Nuclear Information System (INIS)

    Lee, Hyunsoo; Shin, Weonho; Choi, Jang Wook; Park, Jeong Young

    2012-01-01

    The nanomechanical properties of fully lithiated and pristine Si nanowires (NWs) deposited on a Si substrate were studied with atomic force microscopy (AFM). Si NWs were synthesized using the vapour-liquid-solid process on stainless-steel substrates using an Au catalyst. Fully lithiated Si NWs were obtained using the electrochemical method, followed by drop-casting on a Si substrate. The roughness of the Si NWs, which was derived from AFM images, is greater for the lithiated Si NWs than for the pristine Si NWs. Force spectroscopy was used to study the influence of lithiation on the tip-surface adhesion force. The lithiated Si NWs revealed a smaller tip-surface adhesion force than the Si substrate by a factor of two, while the adhesion force of the Si NWs is similar to that of the Si substrate. Young's modulus, obtained from the force-distance curve, also shows that the pristine Si NWs have a relatively higher value than the lithiated Si NWs due to the elastically soft and amorphous structures of the lithiated region. These results suggest that force spectroscopy can be used to probe the degree of lithiation at nanometer scale during the charging and discharging processes. (paper)

  1. Atomic force microscopy. A new method for atom identification and manipulation

    International Nuclear Information System (INIS)

    Abe, Masayuki; Sugimoto, Yoshiaki; Morita, Seizo

    2007-01-01

    Frequency modulation atomic force microscopy (FM-AFM) is a scanning probe technique that detects the interaction forces between the outermost atom of a sharp tip and the atoms at a surface to image the sample surface. It is expected that the FM-AFM can cover the research field which scanning tunneling microscopy does not provide. In this article, we would introduce FM-AFM experiments applied to site-specific force measurements and atom manipulation, including how to solve the problems to achieve precise FM-AFM measurements. (author)

  2. Analysis of atomic distribution in as-fabricated Zircaloy-2 claddings by atom probe tomography under high-energy pulsed laser

    Energy Technology Data Exchange (ETDEWEB)

    Sawabe, T., E-mail: sawabe@criepi.denken.or.jp [Central Research Institute of Electric Power Industry (CRIEPI), Iwado Kita 2-11-1, Komae, Tokyo 201-8511 (Japan); Sonoda, T.; Kitajima, S. [Central Research Institute of Electric Power Industry (CRIEPI), Iwado Kita 2-11-1, Komae, Tokyo 201-8511 (Japan); Kameyama, T. [Tokai University, Department of Nuclear Engineering, Kitakaname 4-1-1, Hiratsuka, Kanagawa 259-1292 (Japan)

    2013-11-15

    The properties of second-phase particles (SPPs) in Zircaloy-2 claddings are key factors influencing the corrosion resistance of the alloy. The chemical compositions of Zr (Fe, Cr){sub 2} and Zr{sub 2}(Fe, Ni) SPPs were investigated by means of pulsed laser atom probe tomography. In order to prevent specimen fracture and to analyse wide regions of the specimen, the pulsed laser energy was increased to 2.0 nJ. This gave a high yield of average of 3 × 10{sup 7} ions per specimen. The Zr (Fe, Cr){sub 2} SPPs contained small amounts of Ni and Si atoms, while in Zr{sub 2}(Fe, Ni) SPPs almost all the Si was concentrated and the ratio of Zr: (Fe + Ni + Si) was 2:1. Atomic concentrations of the Zr-matrix and the SPPs were identified by two approaches: the first by using all the visible peaks of the mass spectrum and the second using the representative peaks with the natural abundance of the corresponding atoms. It was found that the change in the concentration between the Zr-matrix and the SPPs can be estimated more accurately by the second method, although Sn concentration in the Zr{sub 2}(Fe, Ni) SPPs is slightly overestimated.

  3. Influence of laser power on atom probe tomographic analysis of boron distribution in silicon

    Energy Technology Data Exchange (ETDEWEB)

    Tu, Y., E-mail: ytu@imr.tohoku.ac.jp [The Oarai Center, Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Takamizawa, H.; Han, B.; Shimizu, Y.; Inoue, K.; Toyama, T. [The Oarai Center, Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Yano, F. [The Oarai Center, Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Tokyo City University, Setagaya, Tokyo 158-8557 (Japan); Nishida, A. [Renesas Electronics Corporation, Hitachinaka, Ibaraki 312-8504 (Japan); Nagai, Y. [The Oarai Center, Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan)

    2017-02-15

    The relationship between the laser power and the three-dimensional distribution of boron (B) in silicon (Si) measured by laser-assisted atom probe tomography (APT) is investigated. The ultraviolet laser employed in this study has a fixed wavelength of 355 nm. The measured distributions are almost uniform and homogeneous when using low laser power, while clear B accumulation at the low-index pole of single-crystalline Si and segregation along the grain boundaries in polycrystalline Si are observed when using high laser power (100 pJ). These effects are thought to be caused by the surface migration of atoms, which is promoted by high laser power. Therefore, for ensuring a high-fidelity APT measurement of the B distribution in Si, high laser power is not recommended. - Highlights: • Influence of laser power on atom probe tomographic analysis of B distribution in Si is investigated. • When using high laser power, inhomogeneous distributions of B in single-crystalline and polycrystalline Si are observed. • Laser promoted migration of B atoms over the specimen is proposed to explain these effects.

  4. Advancement of Compositional and Microstructural Design of Intermetallic γ-TiAl Based Alloys Determined by Atom Probe Tomography

    Science.gov (United States)

    Klein, Thomas; Clemens, Helmut; Mayer, Svea

    2016-01-01

    Advanced intermetallic alloys based on the γ-TiAl phase have become widely regarded as most promising candidates to replace heavier Ni-base superalloys as materials for high-temperature structural components, due to their facilitating properties of high creep and oxidation resistance in combination with a low density. Particularly, recently developed alloying concepts based on a β-solidification pathway, such as the so-called TNM alloy, which are already incorporated in aircraft engines, have emerged offering the advantage of being processible using near-conventional methods and the option to attain balanced mechanical properties via subsequent heat-treatment. Development trends for the improvement of alloying concepts, especially dealing with issues regarding alloying element distribution, nano-scale phase characterization, phase stability, and phase formation mechanisms demand the utilization of high-resolution techniques, mainly due to the multi-phase nature of advanced TiAl alloys. Atom probe tomography (APT) offers unique possibilities of characterizing chemical compositions with a high spatial resolution and has, therefore, been widely used in recent years with the aim of understanding the materials constitution and appearing basic phenomena on the atomic scale and applying these findings to alloy development. This review, thus, aims at summarizing scientific works regarding the application of atom probe tomography towards the understanding and further development of intermetallic TiAl alloys. PMID:28773880

  5. Irradiation-induced precipitation in a SUS316 stainless steel using three-dimensional atom probe

    International Nuclear Information System (INIS)

    Hatakeyama, M.; Yamagata, I.

    2013-01-01

    Precipitation and segregation were investigated in a compositionally modified 316 austenitic stainless steel, neutron-irradiated at 862 K using a three-dimensional atom probe. In the solution-annealed specimen, Mo, Ti, Nb, C and P enrichment were observed in a silicide, with nominal composition Fe 3 Cr 2 Ni 2 Mo 2 Si 2 . In a Ti-rich carbide, nominaling Fe 5 Cr 8 Ni 10 Mo 2 Ti 11 Si 2 C 6 , enrichment of Mo, Si, O, and Nb was observed. Radiation-induced segregation (RIS) at the precipitate–matrix interface was also investigated at an atomic scale. RIS of Ni and P atoms, which are undersized in Fe, was also analyzed around the interface of the Ti-rich carbide and matrix. Results suggest that the carbide–matrix interface is a sink with an interstitial bias. In the cold-worked specimen, complex-precipitates consisting of silicide and carbide were formed

  6. Grain boundary segregation in neutron-irradiated 304 stainless steel studied by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Toyama, T., E-mail: ttoyama@imr.tohoku.ac.jp [International Research Center for Nuclear Materials Science, Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Nozawa, Y. [International Research Center for Nuclear Materials Science, Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Van Renterghem, W. [SCK Bullet CEN, Nuclear Materials Science Institute, Boeretang 200, 2400 Mol (Belgium); Matsukawa, Y.; Hatakeyama, M.; Nagai, Y. [International Research Center for Nuclear Materials Science, Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Al Mazouzi, A. [EDF R and D, Avenue des Renardieres Ecuelles, 77818 Moret sur Loing Cedex (France); Van Dyck, S. [SCK Bullet CEN, Nuclear Materials Science Institute, Boeretang 200, 2400 Mol (Belgium)

    2012-06-15

    Radiation-induced segregation (RIS) of solute atoms at a grain boundary (GB) in 304 stainless steel (SS), neutron-irradiated to a dose of 24 dpa at 300 Degree-Sign C in the fuel wrapper plates of a commercial pressurized water reactor, was investigated using laser-assisted atom probe tomography (APT). Ni, Si, and P enrichment and Cr and Fe depletion at the GB were evident. The full-width at half-maximum of the RIS region was {approx}3 nm for the concentration profile peaks of Ni and Si. The atomic percentages of Ni, Si, and Cr at the GB were {approx}19%, {approx}7%, and {approx}14%, respectively, in agreement with previously-reported values for neutron-irradiated SS. A high number density of intra-granular Ni-Si rich precipitates formed in the matrix. A precipitate-denuded zone with a width of {approx}10 nm appeared on both sides of the GB.

  7. Atomic species recognition on oxide surfaces using low temperature scanning probe microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Zong Min, E-mail: mzmncit@163.com [National Key Laboratory for Electronic Measurement Technology, North University of China, Taiyuan, 030051 (China); Key Laboratory of Instrumentation Science & Dynamic Measurement, North University of China, Ministry of Education, Taiyuan, 030051 (China); School of Instrument and Electronics, North University of China, Taiyuan, 030051 (China); Shi, Yun Bo; Mu, Ji Liang; Qu, Zhang; Zhang, Xiao Ming; Qin, Li [National Key Laboratory for Electronic Measurement Technology, North University of China, Taiyuan, 030051 (China); Key Laboratory of Instrumentation Science & Dynamic Measurement, North University of China, Ministry of Education, Taiyuan, 030051 (China); School of Instrument and Electronics, North University of China, Taiyuan, 030051 (China); Liu, Jun, E-mail: liuj@nuc.edu.cn [National Key Laboratory for Electronic Measurement Technology, North University of China, Taiyuan, 030051 (China); Key Laboratory of Instrumentation Science & Dynamic Measurement, North University of China, Ministry of Education, Taiyuan, 030051 (China); School of Instrument and Electronics, North University of China, Taiyuan, 030051 (China)

    2017-02-01

    Highlights: • The coexisted phase of p(2 × 1)and c(6 × 2) on Cu(110)-O surface using AFM under UHV at low temperature. • Two different c(6 × 2) phase depending on the status of the tip apex. • Electronic state of tip seriously effect the resolution and stability of the sample surface. - Abstract: In scanning probe microscopy (SPM), the chemical properties and sharpness of the tips of the cantilever greatly influence the scanning of a sample surface. Variation in the chemical properties of the sharp tip apex can induce transformation of the SPM images. In this research, we explore the relationship between the tip and the structure of a sample surface using dynamic atomic force microscopy (AFM) on a Cu(110)-O surface under ultra-high vacuum (UHV) at low temperature (78 K). We observed two different c(6 × 2) phase types in which super-Cu atoms show as a bright spot when the tip apex is of O atoms and O atoms show as a bright spot when the tip apex is of Cu atoms. We also found that the electronic state of the tip has a serious effect on the resolution and stability of the sample surface, and provide an explanation for these phenomena. This technique can be used to identify atom species on sample surfaces, and represents an important development in the SPM technique.

  8. Resolving Iron(II) Sorption and Oxidative Growth on Hematite (001) Using Atom Probe Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, Sandra D. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States; Liu, Jia [Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States; Arey, Bruce W. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States; Schreiber, Daniel K. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States; Perea, Daniel E. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States; Rosso, Kevin M. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States

    2018-02-13

    The distribution of iron resulting from the autocatalytic interaction of aqueous Fe(II) with the hematite (001) surface was directly mapped in three dimensions (3D) for the first time, using iron isotopic labelling and atom probe tomography (APT). Analyses of the mass spectrum showed that natural abundance ratios in 56Fe-dominant hematite are recovered at depth with good accuracy, whereas at the relict interface with 57Fe(II) solution evidence for hematite growth by oxidative adsorption of Fe(II) was found. 3D reconstructions of the isotope positions along the surface normal direction showed a zone enriched in 57Fe, which was consistent with an average net adsorption of 3.2 – 4.3 57Fe atoms nm–2. Statistical analyses utilizing grid-based frequency distribution analyses show a heterogeneous, non-random distribution of oxidized Fe on the (001) surface, consistent with Volmer-Weber-like island growth. The unique 3D nature of the APT data provides an unprecedented means to quantify the atomic-scale distribution of sorbed 57Fe atoms and the extent of segregation on the hematite surface. This new ability to spatially map growth on single crystal faces at the atomic scale will enable resolution to long-standing unanswered questions about the underlying mechanisms for electron and atom exchange involved in a wide variety of redox-catalyzed processes at this archetypal and broadly relevant interface.

  9. Polarized atomic orbitals for linear scaling methods

    Science.gov (United States)

    Berghold, Gerd; Parrinello, Michele; Hutter, Jürg

    2002-02-01

    We present a modified version of the polarized atomic orbital (PAO) method [M. S. Lee and M. Head-Gordon, J. Chem. Phys. 107, 9085 (1997)] to construct minimal basis sets optimized in the molecular environment. The minimal basis set derives its flexibility from the fact that it is formed as a linear combination of a larger set of atomic orbitals. This approach significantly reduces the number of independent variables to be determined during a calculation, while retaining most of the essential chemistry resulting from the admixture of higher angular momentum functions. Furthermore, we combine the PAO method with linear scaling algorithms. We use the Chebyshev polynomial expansion method, the conjugate gradient density matrix search, and the canonical purification of the density matrix. The combined scheme overcomes one of the major drawbacks of standard approaches for large nonorthogonal basis sets, namely numerical instabilities resulting from ill-conditioned overlap matrices. We find that the condition number of the PAO overlap matrix is independent from the condition number of the underlying extended basis set, and consequently no numerical instabilities are encountered. Various applications are shown to confirm this conclusion and to compare the performance of the PAO method with extended basis-set calculations.

  10. Method for producing uranium atomic beam source

    International Nuclear Information System (INIS)

    Krikorian, O.H.

    1976-01-01

    A method is described for producing a beam of neutral uranium atoms by vaporizing uranium from a compound UM/sub x/ heated to produce U vapor from an M boat or from some other suitable refractory container such as a tungsten boat, where M is a metal whose vapor pressure is negligible compared with that of uranium at the vaporization temperature. The compound, for example, may be the uranium-rhenium compound, URe 2 . An evaporation rate in excess of about 10 times that of conventional uranium beam sources is produced

  11. Study of defects, radiation damage and implanted gases in solids by field-ion and atom-probe microscopy

    International Nuclear Information System (INIS)

    Seidman, D.N.; Amano, J.; Wagner, A.

    1980-10-01

    The ability of the field-ion microscope to image individual atoms has been applied, at Cornell University, to the study of fundamental properties of point defects in irradiated or quenched metals. The capability of the atom probe field-ion microscope to determine the chemistry - that is, the mass-to-charge ratio - of a single ion has been used to investigate the behavior of different implanted species in metals. A brief review is presented of: (1) the basic physical principles of the field-ion and atom-probe microscopes; (2) the many applications of these instruments to the study of defects and radiation damage in solids; and (3) the application of the atom-probe field-ion microscope to the study of the behavior of implanted 3 He and 4 He atoms in tungsten. The paper is heavily referenced so that the reader can pursue his specific research interests in detail

  12. Cyanine-based probe\\tag-peptide pair for fluorescence protein imaging and fluorescence protein imaging methods

    Science.gov (United States)

    Mayer-Cumblidge, M Uljana [Richland, WA; Cao, Haishi [Richland, WA

    2010-08-17

    A molecular probe comprises two arsenic atoms and at least one cyanine based moiety. A method of producing a molecular probe includes providing a molecule having a first formula, treating the molecule with HgOAc, and subsequently transmetallizing with AsCl.sub.3. The As is liganded to ethanedithiol to produce a probe having a second formula. A method of labeling a peptide includes providing a peptide comprising a tag sequence and contacting the peptide with a biarsenical molecular probe. A complex is formed comprising the tag sequence and the molecular probe. A method of studying a peptide includes providing a mixture containing a peptide comprising a peptide tag sequence, adding a biarsenical probe to the mixture, and monitoring the fluorescence of the mixture.

  13. Scanning probe microscopy investigation of gold clusters deposited on atomically flat substrates

    International Nuclear Information System (INIS)

    Vandamme, N; Janssens, E; Vanhoutte, F; Lievens, P; Haesendonck, C van

    2003-01-01

    We systematically studied the influence of the substrate on the shape, mobility, and stability of deposited gold clusters. The Au n clusters were produced in a laser vaporization source and deposited with low kinetic energy (∼0.4 eV/atom) on atomically flat substrates (graphite, mica, and gold and silver films on mica) under UHV conditions. Their size distribution is probed with time-of-flight mass spectrometry and ranges from dimers to several hundreds of atoms. Scanning probe microscopy is used to characterize the deposited clusters and the formation of islands by cluster aggregation. On all substrates, Au n islands can be clearly distinguished and the islands are flattened despite the small impact energy. The shape and size of the island configurations are strongly system dependent. Gold clusters deposited on Au(111) and Ag(111) films grown on mica do not aggregate, but deform due to strong cluster-substrate interactions. The clusters tend to grow epitaxially on these surfaces. On graphite and on mica, deposited clusters do diffuse and aggregate. On the graphite surface, large ramified islands are formed by juxtaposition of small islands and trapping of the clusters at the step edges. On the other hand, the diffusion of the clusters on mica results in a total coalescence of the Au n clusters into compact islands

  14. Comparison of NO titration and fiber optics catalytic probes for determination of neutral oxygen atom concentration in plasmas and postglows

    International Nuclear Information System (INIS)

    Mozetic, Miran; Ricard, Andre; Babic, Dusan; Poberaj, Igor; Levaton, Jacque; Monna, Virginie; Cvelbar, Uros

    2003-01-01

    A comparative study of two different absolute methods NO titration and fiber optics catalytic probe (FOCP) for determination of neutral oxygen atom density is presented. Both methods were simultaneously applied for measurements of O density in a postglow of an Ar/O 2 plasma created by a surfatron microwave generator with the frequency of 2.45 GHz an adjustable output power between 30 and 160 W. It was found that the two methods gave similar results. The advantages of FOCP were found to be as follows: it is a nondestructive method, it enables real time measuring of the O density, it does not require any toxic gas, and it is much faster than NO titration. The advantage of NO titration was found to be the ability to measure O density in a large range of dissociation of oxygen molecules

  15. Atom probe field ion microscopy and related topics: A bibliography 1993

    Energy Technology Data Exchange (ETDEWEB)

    Godfrey, R.D.; Miller, M.K.; Russell, K.F.

    1994-10-01

    This bibliography, covering the period 1993, includes references related to the following topics: atom probe field ion microscopy (APFIM), field emission (FE), and field ion microscopy (FIM). Technique-oriented studies and applications are included. The references contained in this document were compiled from a variety of sources including computer searches and personal lists of publications. To reduce the length of this document, the references have been reduced to the minimum necessary to locate the articles. The references are listed alphabetically by authors, an Addendum of references missed in previous bibliographies is included.

  16. Specimen preparation of irradiated materials for examination in the atom probe field ion microscope

    International Nuclear Information System (INIS)

    Russell, K.F.; Miller, M.K.

    1994-01-01

    The atom probe field ion microscope (APFIM) requires specimens in the form of ultrasharp needles. Basic protective measures used to reduce exposure druing specimen preparation are discussed. The low-level radioactive specimen blanks may be made using a two-stage electropolishing process using a thin layer of electrolyte floating on a denser inert liquid; this produces a necked region and eventually two specimens from each single blank. The amount of material handled may also be reduced using a micropolishing technique to repolish blunt or fractured specimens. Control of contamination and possible spills is discussed

  17. Surface adhesion properties of graphene and graphene oxide studied by colloid-probe atomic force microscopy

    International Nuclear Information System (INIS)

    Ding Yanhuai; Zhang Ping; Ren Huming; Zhuo Qin; Yang Zhongmei; Jiang Xu; Jiang Yong

    2011-01-01

    Surface adhesion properties are important to various applications of graphene-based materials. Atomic force microscopy is powerful to study the adhesion properties of samples by measuring the forces on the colloidal sphere tip as it approaches and retracts from the surface. In this paper we have measured the adhesion force between the colloid probe and the surface of graphene (graphene oxide) nanosheet. The results revealed that the adhesion force on graphene and graphene oxide surface were 66.3 and 170.6 nN, respectively. It was found the adhesion force was mainly determined by the water meniscus, which was related to the surface contact angle of samples.

  18. Initial study on Z-phase strengthened 9-12% Cr steels by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fang; Andren, Hans-Olof [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Applied Physics

    2010-07-01

    The microstructure of two different types of Z-phase strengthened experimental steels, CrNbN-based or CrTaN-based, was investigated. Both steels underwent aging at 650 C for relatively short period of time, 24 hours or 1005 hours. Atom probe tomography was used to study the chemical composition of the matrix and precipitates, and the size and number density of the small precipitates. Both steels contain Laves phase at prior austenite grain boundaries and martensitic lath boundaries. The CrTaN-based steel was found more promising due to its finer and more densely distributed precipitates after 1005 hour aging. (orig.)

  19. Atom probe field ion microscopy and related topics: A bibliography 1993

    International Nuclear Information System (INIS)

    Godfrey, R.D.; Miller, M.K.; Russell, K.F.

    1994-10-01

    This bibliography, covering the period 1993, includes references related to the following topics: atom probe field ion microscopy (APFIM), field emission (FE), and field ion microscopy (FIM). Technique-oriented studies and applications are included. The references contained in this document were compiled from a variety of sources including computer searches and personal lists of publications. To reduce the length of this document, the references have been reduced to the minimum necessary to locate the articles. The references are listed alphabetically by authors, an Addendum of references missed in previous bibliographies is included

  20. Thermal diffusivity of diamond nanowires studied by laser assisted atom probe tomography

    Science.gov (United States)

    Arnoldi, L.; Spies, M.; Houard, J.; Blum, I.; Etienne, A.; Ismagilov, R.; Obraztsov, A.; Vella, A.

    2018-04-01

    The thermal properties of single-crystal diamond nanowires (NWs) have been calculated from first principles but have never been measured experimentally. Taking advantage of the sharp geometry of samples analyzed in a laser assisted atom probe, this technique is used to measure the thermal diffusivity of a single NW at low temperature (ab-initio calculations and confirms that thermal diffusivity in nanoscale samples is lower than in bulk samples. The results impact the design and integration of diamond NWs and nanoneedles in nanoscale devices for heat dissipation.

  1. Three dimensional atom probe imaging of GaAsSb quantum rings.

    Science.gov (United States)

    Beltrán, A M; Marquis, E A; Taboada, A G; Ripalda, J M; García, J M; Molina, S I

    2011-07-01

    Unambiguous evidence of ring-shaped self-assembled GaSb nanostructures grown by molecular beam epitaxy is presented on the basis of atom-probe tomography reconstructions and dark field transmission electron microscopy imaging. The GaAs capping process causes a strong segregation of Sb out of the center of GaSb quantum dots, leading to the self-assembled GaAs(x)Sb(1-x) quantum rings of 20-30 nm in diameter with x ∼ 0.33. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Influence of supersaturated carbon on the diffusion of Ni in ferrite determined by atom probe tomography

    KAUST Repository

    Kresse, T.; Li, Yujiao; Boll, Torben; Borchers, Christine; Choi, Pyuckpa; Al-Kassab, Talaat; Raabe, Dierk; Kirchheim, Reiner

    2013-01-01

    In patented and cold-drawn pearlitic steel wires dissociation of cementite occurs during mechanical deformation. In this study the influence of the carbon decomposition on the diffusion of nickel in ferrite is investigated by means of atom probe tomography. In the temperature range 423-523 K we observed a much smaller activation energy of Ni diffusion than for self-diffusion in body-centered cubic iron, indicating an increased vacancy density owing to enhanced formation of vacancy-carbon complexes. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  3. Shot noise as a probe of spin-correlated transport through single atoms

    Science.gov (United States)

    Pradhan, S.; Fransson, J.

    2018-03-01

    We address the shot noise in the tunneling current through a local spin, pertaining to recent experiments on magnetic adatoms and single molecular magnets. We show that both uncorrelated and spin-correlated scattering processes contribute vitally to the noise spectrum. The spin-correlated scattering processes provide an additional contribution to the Landauer-Büttiker shot noise expression, accounting for correlations between the tunneling electrons and the localized spin moment. By calculating the Fano factor, we show that both super- and sub-Poissonian shot noise can be described within our approach. Our theory provides transparent insights into noise spectroscopy, consistent with recent experiments using local probing techniques on magnetic atoms.

  4. Nanoprecipitates in single-crystal molybdenum-alloy nanopillars detected by TEM and atom probe tomography

    International Nuclear Information System (INIS)

    Oveisi, Emad; Bártová, Barbora; Gerstl, Stephan; Zimmermann, Julien; Marichal, Cécile; Van Swygenhoven, Helena; Hébert, Cécile

    2013-01-01

    Transmission electron microscopy (TEM) supported by various chemical analyses techniques as well as atom probe tomography is applied to characterize newly identified nanosized precipitates in Mo-alloy nanopillars that were prepared by directional solidification. It is shown that the α-Mo matrix contains Al-enriched face-centred cubic precipitates which have a 4.12 Å lattice parameter, and exhibit a Kurdjumov–Sachs crystallographic orientation relationship with the matrix. Such precipitates could be responsible for the unusual behaviour of the pillars during compression tests

  5. Influence of supersaturated carbon on the diffusion of Ni in ferrite determined by atom probe tomography

    KAUST Repository

    Kresse, T.

    2013-09-01

    In patented and cold-drawn pearlitic steel wires dissociation of cementite occurs during mechanical deformation. In this study the influence of the carbon decomposition on the diffusion of nickel in ferrite is investigated by means of atom probe tomography. In the temperature range 423-523 K we observed a much smaller activation energy of Ni diffusion than for self-diffusion in body-centered cubic iron, indicating an increased vacancy density owing to enhanced formation of vacancy-carbon complexes. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  6. Microstructural characterization of irradiated PWR steels using the atom probe field-ion microscope

    International Nuclear Information System (INIS)

    Miller, M.K.; Burke, M.G.

    1987-08-01

    Atom probe field-ion microscopy has been used to characterize the microstructure of a neutron-irradiated A533B pressure vessel steel weld. The atomic spatial resolution of this technique permits a complete structural and chemical description of the ultra-fine features that control the mechanical properties to be made. A variety of fine scale features including roughly spherical copper precipitates and clusters, spherical and rod-shaped molybdenum carbide and disc-shaped molybdenum nitride precipitates were observed to be inhomogeneously distributed in the ferrite. The copper content of the ferrite was substantially reduced from the nominal level. A thin film of molybdenum carbides and nitrides was observed on grain boundaries in addition to a coarse copper-manganese precipitate. Substantial enrichment of manganese and nickel were detected at the copper-manganese precipitate-ferrite interface and this enrichment extended into the ferrite. Enrichment of nickel, manganese and phosphorus were also measured at grain boundaries

  7. How can we probe the atom mass currents induced by synthetic gauge fields?

    Science.gov (United States)

    Paramekanti, Arun; Killi, Matthew; Trotzky, Stefan

    2013-05-01

    Ultracold atomic fermions and bosons in an optical lattice can have quantum ground states which support equilibrium currents in the presence of synthetic magnetic fields or spin orbit coupling. As a tool to uncover these mass currents, we propose using an anisotropic quantum quench of the optical lattice which dynamically converts the current patterns into measurable density patterns. Using analytical calculations and numerical simulations, we show that this scheme can probe diverse equilibrium bulk current patterns in Bose superfluids and Fermi fluids induced by synthetic magnetic fields, as well as detect the chiral edge currents in topological states of atomic matter such as quantum Hall and quantum spin Hall insulators. This work is supported by NSERC of Canada and the Canadian Institute for Advanced Research.

  8. Understanding arsenic incorporation in CdTe with atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Burton, G. L.; Diercks, D. R.; Ogedengbe, O. S.; Jayathilaka, P. A. R. D.; Edirisooriya, M.; Myers, T. H.; Zaunbrecher, K. N.; Moseley, J.; Barnes, T. M.; Gorman, B. P.

    2018-08-01

    Overcoming the open circuit voltage deficiency in Cadmium Telluride (CdTe) photovoltaics may be achieved by increasing p-type doping while maintaining or increasing minority carrier lifetimes. Here, routes to higher doping efficiency using arsenic are explored through an atomic scale understanding of dopant incorporation limits and activation in molecular beam epitaxy grown CdTe layers. Atom probe tomography reveals spatial segregation into nanometer scale clusters containing > 60 at% As for samples with arsenic incorporation levels greater than 7-8 x 10^17 cm-3. The presence of arsenic clusters was accompanied by crystal quality degradation, particularly the introduction of arsenic-enriched extended defects. Post-growth annealing treatments are shown to increase the size of the As precipitates and the amount of As within the precipitates.

  9. Study of defects and radiation damage in solids by field-ion and atom-probe microscopy

    International Nuclear Information System (INIS)

    Seidman, D.N.

    1982-01-01

    An attempt is made to introduce the reader to the basic physical ideas involved in the field-ion and atom-probe field-ion microscope techniques, and to the applications of these techniques to the study of defects and radiation damage in solids. The final section discusses, in precise form, the application of the atom-probe field-ion microscope to the study of the behavior of implanted 3 He and 4 He atoms in tungsten. The paper is heavily referenced so that the reader can pursue his specific research interest in detail

  10. Direct comparison of Fe-Cr unmixing characterization by atom probe tomography and small angle scattering

    Energy Technology Data Exchange (ETDEWEB)

    Couturier, Laurent, E-mail: laurent.couturier55@hotmail.fr [Univ. Grenoble Alpes, SIMAP, F-38000 Grenoble (France); CNRS, SIMAP, F-38000 Grenoble (France); Department of Materials Engineering, The University of British Columbia, Vancouver, BC V6T 1Z4 (Canada); De Geuser, Frédéric; Deschamps, Alexis [Univ. Grenoble Alpes, SIMAP, F-38000 Grenoble (France); CNRS, SIMAP, F-38000 Grenoble (France)

    2016-11-15

    The fine microstructure obtained by unmixing of a solid solution either by classical precipitation or spinodal decomposition is often characterized either by small angle scattering or atom probe tomography. This article shows that a common data analysis framework can be used to analyze data obtained from these two techniques. An example of the application of this common analysis is given for characterization of the unmixing of the Fe-Cr matrix of a 15-5 PH stainless steel during long-term ageing at 350 °C and 400 °C. A direct comparison of the Cr composition fluctuations amplitudes and characteristic lengths obtained with both techniques is made showing a quantitative agreement for the fluctuation amplitudes. The origin of the discrepancy remaining for the characteristic lengths is discussed. - Highlights: •Common analysis framework for atom probe tomography and small angle scattering •Comparison of same microstructural characteristics obtained using both techniques •Good correlation of Cr composition fluctuations amplitudes from both techniques •Good correlation of Cr composition fluctuations amplitudes with classic V parameter.

  11. Characterization of Radiation-Induced Clustering using Atom Probe Tomography in Nuclear Structural Materials

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Gyeong Geun; Lim, Sang Yeob; Chang, Kun Ok; Ha, Jin Hyung; Kwon, Jun Hyun [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    The degradations include the change in mechanical properties, which are related to the microstructure evolution caused by irradiation. The most widely used tool for the imaging irradiated microstructure is transmission electron microscopy (TEM). The composition of irradiation defects can be analyzed using X-ray spectroscopy (EDS) equipped in the TEM. However, composition characterization of the nano-sized irradiation defects in the matrix is limited due to the beam broadening of TEM and the overlapping of the probed volume during EDS analysis. Recently, Atom probe tomography (APT) has been introduced to the characterization of irradiation defects. APT provides sub-nano scale position of atoms and the chemical composition of a selected volume. SS316 irradiated with Fe ions at above 300 .deg. C caused significant clustering and segregation of Si and Ni at defect sinks. The neutron irradiated low alloy steel showed similar clustering of Ni and Si. The approach of using APT was demonstrated to be well suited for discovering the structure of irradiation defects and performing quantitative analysis in nuclear materials irradiated at high temperature.

  12. Atom probe field ion microscope study of the range and diffusivity of helium in tungsten

    International Nuclear Information System (INIS)

    Wagner, A.

    1978-08-01

    A time-of-flight (TOF) atom-probe field-ion microscope (FIM) specifically designed for the study of defects in metals is described. With this automated system 600 TOF min -1 can be recorded and analyzed. Performance tests of the instrument demonstrated that (1) the seven isotopes of molybdenum and the five isotopes of tungsten can be clearly resolved; and (2) the concentration and spatial distribution of all constitutents present at levels greater than 0.05 at. % in a W--25 at. % Re, Mo--1.0 at. % Ti, Mo--1.0 at. % Ti--0.08 at. % Zr (TZM), a low swelling stainless steel (LS1A) and a metallic glass (Metglas 2826) can be measured. The effect of the rate of field evaporation on the quantitative atom probe analysis of a Mo--1.0 at. % Ti alloy and a Mo--1.0 at. % Ti--0.08 at. % Zr alloy was investigated. As the field evaporation rate increased the measured Ti concentration was found to also increase. A simple qualitative model was proposed to explain the observation. The spatial distribution of titanium in a fast neutron irradiated Mo--1.0 at. % Ti alloy has been investigated. No evidence of Ti segregation to the voids was detected nor has any evidence of significant resolution of Ti from the TiC precipitates been detected. A small amount of segregation of carbon to a void was detected

  13. Methods for Probing Magnetic Films with Neutrons

    Science.gov (United States)

    Kozhevnikov, S. V.; Ott, F.; Radu, F.

    2018-03-01

    We review various methods in the investigation of magnetic films with neutrons, including those based on the effects of Larmor precession, Zeeman spatial splitting of the beam, neutron spin resonance, and polarized neutron channeling. The underlying principles, examples of the investigated systems, specific features, applications, and perspectives of these methods are discussed.

  14. Atomic hydrogen storage method and apparatus

    Science.gov (United States)

    Woollam, J. A. (Inventor)

    1980-01-01

    Atomic hydrogen, for use as a fuel or as an explosive, is stored in the presence of a strong magnetic field in exfoliated layered compounds such as molybdenum disulfide or an elemental layer material such as graphite. The compounds maintained at liquid helium temperatures and the atomic hydrogen is collected on the surfaces of the layered compound which are exposed during delamination (exfoliation). The strong magnetic field and the low temperature combine to prevent the atoms of hydrogen from recombining to form molecules.

  15. Complex operator method of the hydrogen atom

    International Nuclear Information System (INIS)

    Jiang, X.

    1989-01-01

    Frequently the hydrogen atom eigenvalue problem is analytically solved by solving a radial wave equation for a particle in a Coulomb field. In this article, complex coordinates are introduced, and an expression for the energy levels of the hydrogen atom is obtained by means of the algebraic solution of operators. The form of this solution is in accord with that of the analytical solution

  16. Band excitation method applicable to scanning probe microscopy

    Science.gov (United States)

    Jesse, Stephen [Knoxville, TN; Kalinin, Sergei V [Knoxville, TN

    2010-08-17

    Methods and apparatus are described for scanning probe microscopy. A method includes generating a band excitation (BE) signal having finite and predefined amplitude and phase spectrum in at least a first predefined frequency band; exciting a probe using the band excitation signal; obtaining data by measuring a response of the probe in at least a second predefined frequency band; and extracting at least one relevant dynamic parameter of the response of the probe in a predefined range including analyzing the obtained data. The BE signal can be synthesized prior to imaging (static band excitation), or adjusted at each pixel or spectroscopy step to accommodate changes in sample properties (adaptive band excitation). An apparatus includes a band excitation signal generator; a probe coupled to the band excitation signal generator; a detector coupled to the probe; and a relevant dynamic parameter extractor component coupled to the detector, the relevant dynamic parameter extractor including a processor that performs a mathematical transform selected from the group consisting of an integral transform and a discrete transform.

  17. On the retrieval of crystallographic information from atom probe microscopy data via signal mapping from the detector coordinate space.

    Science.gov (United States)

    Wallace, Nathan D; Ceguerra, Anna V; Breen, Andrew J; Ringer, Simon P

    2018-06-01

    Atom probe tomography is a powerful microscopy technique capable of reconstructing the 3D position and chemical identity of millions of atoms within engineering materials, at the atomic level. Crystallographic information contained within the data is particularly valuable for the purposes of reconstruction calibration and grain boundary analysis. Typically, analysing this data is a manual, time-consuming and error prone process. In many cases, the crystallographic signal is so weak that it is difficult to detect at all. In this study, a new automated signal processing methodology is demonstrated. We use the affine properties of the detector coordinate space, or the 'detector stack', as the basis for our calculations. The methodological framework and the visualisation tools are shown to be superior to the standard method of crystallographic pole visualisation directly from field evaporation images and there is no requirement for iterations between a full real-space initial tomographic reconstruction and the detector stack. The mapping approaches are demonstrated for aluminium, tungsten, magnesium and molybdenum. Implications for reconstruction calibration, accuracy of crystallographic measurements, reliability and repeatability are discussed. Copyright © 2018 Elsevier B.V. All rights reserved.

  18. Probing of multiple magnetic responses in magnetic inductors using atomic force microscopy.

    Science.gov (United States)

    Park, Seongjae; Seo, Hosung; Seol, Daehee; Yoon, Young-Hwan; Kim, Mi Yang; Kim, Yunseok

    2016-02-08

    Even though nanoscale analysis of magnetic properties is of significant interest, probing methods are relatively less developed compared to the significance of the technique, which has multiple potential applications. Here, we demonstrate an approach for probing various magnetic properties associated with eddy current, coil current and magnetic domains in magnetic inductors using multidimensional magnetic force microscopy (MMFM). The MMFM images provide combined magnetic responses from the three different origins, however, each contribution to the MMFM response can be differentiated through analysis based on the bias dependence of the response. In particular, the bias dependent MMFM images show locally different eddy current behavior with values dependent on the type of materials that comprise the MI. This approach for probing magnetic responses can be further extended to the analysis of local physical features.

  19. Irradiation-induced precipitation in a SUS316 stainless steel using three-dimensional atom probe

    Energy Technology Data Exchange (ETDEWEB)

    Hatakeyama, M., E-mail: hatake@imr.tohoku.ac.jp [International Research Center for Nuclear Materials Science, IMR/Tohoku University, Narita, Oarai, Ibaraki 311-1313 (Japan); Yamagata, I. [Japan Atom Energy Agency, Narita, Oarai, Ibaraki 311-1393 (Japan)

    2013-11-15

    Precipitation and segregation were investigated in a compositionally modified 316 austenitic stainless steel, neutron-irradiated at 862 K using a three-dimensional atom probe. In the solution-annealed specimen, Mo, Ti, Nb, C and P enrichment were observed in a silicide, with nominal composition Fe{sub 3}Cr{sub 2}Ni{sub 2}Mo{sub 2}Si{sub 2}. In a Ti-rich carbide, nominaling Fe{sub 5}Cr{sub 8}Ni{sub 10}Mo{sub 2}Ti{sub 11}Si{sub 2}C{sub 6}, enrichment of Mo, Si, O, and Nb was observed. Radiation-induced segregation (RIS) at the precipitate–matrix interface was also investigated at an atomic scale. RIS of Ni and P atoms, which are undersized in Fe, was also analyzed around the interface of the Ti-rich carbide and matrix. Results suggest that the carbide–matrix interface is a sink with an interstitial bias. In the cold-worked specimen, complex-precipitates consisting of silicide and carbide were formed.

  20. Analysis of medical device materials with the local electrode atom probe

    International Nuclear Information System (INIS)

    Goodman, S.L.; Mengelt, T.J.; Ali, M.; Ulfig, R.M.; Martens, R.M.; Kelly, T.F.; Kostrna, S.L.P.; Kostrna, M.S.; Carmichael, W.J.

    2004-01-01

    Full text: As medical technology advances towards microsurgical and minimally invasive techniques, there is a drive to produce ever-smaller devices that demand higher material performance and hence enhanced nano and micro-scale control of material structure. These devices are made from stainless steel alloys, Nitinol, titanium, CoCrMo, and non-metals such as pyrolytic carbon and silicon. These applications are made possible due to suitable physical and mechanical properties, good corrosion resistance in biological environments, reasonable biocompatibility, and good manufacturability. With respect to the metals, the nano-structure and composition of the material surface, typically an oxide, is especially critical since biological responses and corrosion occur at the material-environment interface. Thus, there is an increasing need to understand the 3-D structure and composition of metallic biomaterials at the atomic scale. Three-dimensional atom probe microscopy can uniquely provide such atomic-level structural information. In the present study several of these medical device materials were examined. These include a 316L stainless steel alloy which is widely used in implanted spinal fixation devices, bone screws, cardiovascular and neurological stents, a cast CoCrMo acetabular hip cup of a Cormet metal-on-metal Hip Resurfacing System (Corin Group, Cirencester, England) that was rejected for clinical use, Nitinol wires specimens such as are used for stents and guide wires, and low temperature pyrolytic carbon as used in clinical heart valve prosthetics. (author)

  1. Imaging process in field ion microscopy from the FEM to the atom-probe

    International Nuclear Information System (INIS)

    Mueller, E.W.

    1976-01-01

    The development of the technique and the interpretations of the imaging mechanism, which involve a number of complex phenomena, are traced from the invention of the field emission microscope and the discovery of field desorption to the first field ion microscope. Subsequent introduction of cryogenic operation and utilization of field evaporation led, prior to 1960, to the attainment of high-quality images with full resolution of the atomic lattice and to fundamental applications in the study of lattice defects and other phenomena of physical metallurgy. Extension to the lower-melting metals by imaging with neon was aided by the availability of image intensification technology. The invention of the atom-probe FIM in 1967, permitting surface analysis with ultimate single-atom sensitivity, also brought the discovery of unexpected effects, such as field adsorption of the noble images gases and the abundant formation of metal-noble gas molecular ions. These phenomena, together with recent results of field desorption microcopy, must be included in a refined interpretation of the imaging process. 16 figs., 115 references

  2. Characterization of grain boundaries in Cu(In,Ga)Se{sub 2} by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Schwarz, Torsten; Cojocaru-Miredin, Oana; Choi, Pyuck-Pa; Raabe, Dierk [Max-Planck Institute for Iron Research GmbH, Duesseldorf (Germany); Wuerz, Roland [Zentrum fuer Sonnenenergie- und Wasserstoff-Forschung Baden-Wuerttemberg (ZSW), Stuttgart (Germany)

    2012-07-01

    Solar cells based on the compound semiconductor Cu(In,Ga)Se{sub 2} (CIGS) as absorber material exhibit the highest efficiency among all thin-film solar cells. This is surprising high in view of the polycrystalline defect-rich structure of the CIGS absorber films. The high efficiency has been commonly ascribed to the diffusion of alkali metal atoms from the soda-lime glass substrate into the CIGS layer, which can render the grain boundaries (GB) electrically inactive. However, the exact mechanisms of how these impurities enhance the cell efficiency are yet to be clarified. As a step towards a better understanding of CIGS solar cells, we have analyzed the composition of solar-grade CIGS layers at the atomic-scale by using pulsed laser Atom Probe Tomography (APT). To perform APT analyses on selected GBs site-specific sample preparation was carried out using the Focused Ion Beam lift-out technique. In addition, Electron Back Scattered Diffraction was performed to characterize the structure and misorientation of selected GBs. Using APT, segregation of impurities at the GBs was directly observed. APT data of various types of GBs are presented and discussed with respect to the possible effects on the cell efficiency.

  3. 3D-atom probe analysis of Cr and Cu added nitriding steels

    International Nuclear Information System (INIS)

    Takahashi, J.; Kawakami, K.; Sugiyama, M.; Kawasaki, K.

    2004-01-01

    Full text: Nitriding treatment is a very effective method for hardening the surface of steels and realizing improvement in wear-resistance. Although this technology has been performed for many years, the precipitation and hardening mechanisms are not completely clear. It was not easy to observe very fine precipitates which may be generated in nitriding steels. We performed a three-dimensional atom probe analysis of the nitriding steel plate in which two kinds of precipitates were generated. Hot-rolled steel plates, which mainly contained Cr 1.0wt.% and Cu 1.3wt.%, were nitrided by annealing (550-6000 o ) in a mainly NH 3 atmosphere. The material before the nitriding had a hardness of about 100 Hv. By the nitriding, the surface hardness increased to more than 700 Hv, and the inside hardness also increased to 200 Hv. The specimens were taken from 0.15 mm, 0.3 mm and 0.8 mm depth from the surface, which mostly correspond to the peak, the half and the inside hardness, respectively. In the specimen of 0.8 mm depth, prolate spheroidal Cu precipitates of more than 8 nm in diameter were observed. In the specimen of 0.3 mm depth, plate-shape nitride precipitates of 6-10 nm in diameter were observed in addition to the Cu precipitates. Each Cu precipitate made a pair with the nitride precipitate. In the 0.15 mm depth specimen, Cr nitride precipitates of high volume density in addition to the pairs consisting of a Cu precipitate and a Cr nitride precipitate were observed. The size of the nitride precipitate forming the pair was slightly larger than that of the single Cr nitride precipitates. Furthermore, the denuded zone where the nitride precipitate does not exist was observed around the pairs. From these results, it was concluded that three stages of precipitation arose as follows: By the heat treatment of nitriding processing, Cu precipitates were generated first. Then, Cr nitride nucleated at the surface of the Cu precipitates inhomogeneously, and surrounding solute Cr was

  4. Fabrication of nano-sized magnetic tunnel junctions using lift-off process assisted by atomic force probe tip.

    Science.gov (United States)

    Jung, Ku Youl; Min, Byoung-Chul; Ahn, Chiyui; Choi, Gyung-Min; Shin, Il-Jae; Park, Seung-Young; Rhie, Kungwon; Shin, Kyung-Ho

    2013-09-01

    We present a fabrication method for nano-scale magnetic tunnel junctions (MTJs), employing e-beam lithography and lift-off process assisted by the probe tip of atomic force microscope (AFM). It is challenging to fabricate nano-sized MTJs on small substrates because it is difficult to use chemical mechanical planarization (CMP) process. The AFM-assisted lift-off process enables us to fabricate nano-sized MTJs on small substrates (12.5 mm x 12.5 mm) without CMP process. The e-beam patterning has been done using bi-layer resist, the poly methyl methacrylate (PMMA)/ hydrogen silsesquioxane (HSQ). The PMMA/HSQ resist patterns are used for both the etch mask for ion milling and the self-aligned mask for top contact formation after passivation. The self-aligned mask buried inside a passivation oxide layer, is readily lifted-off by the force exerted by the probe tip. The nano-MTJs (160 nm x 90 nm) fabricated by this method show clear current-induced magnetization switching with a reasonable TMR and critical switching current density.

  5. Status Summary of FY16 Atom Probe Tomography Studies on UCSB ATR-2 Irradiated RPV Steels

    Energy Technology Data Exchange (ETDEWEB)

    Wells, Peter [Idaho National Lab. (INL), Idaho Falls, ID (United States); Odette, G. Robert [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-05-01

    The University of California Santa Barbara-2 RPV Steel Irradiation experiment was awarded in 2010 by the Nuclear Science User Facility (formerly ATR NSUF) through a competitive peer review proposal process. The experiment involved irradiation of nearly 1300 samples distributed over 13 capsules. The major objective of this experiment was to better understand embrittlement behavior of reactor pressure steels at doses beyond which available data exists yet may be achieved if reactor operating licenses are extended beyond 60 years. The experiment was instrumented during irradiation and active temperature control was used to maintain the temperature at the design temperature. Six samples were selected from a large matrix of materials to perform atom probe tomography (APT) to look at formation of high dose phases. The nature and formation behavior of these phases is discussed.

  6. An analytical model accounting for tip shape evolution during atom probe analysis of heterogeneous materials.

    Science.gov (United States)

    Rolland, N; Larson, D J; Geiser, B P; Duguay, S; Vurpillot, F; Blavette, D

    2015-12-01

    An analytical model describing the field evaporation dynamics of a tip made of a thin layer deposited on a substrate is presented in this paper. The difference in evaporation field between the materials is taken into account in this approach in which the tip shape is modeled at a mesoscopic scale. It was found that the non-existence of sharp edge on the surface is a sufficient condition to derive the morphological evolution during successive evaporation of the layers. This modeling gives an instantaneous and smooth analytical representation of the surface that shows good agreement with finite difference simulations results, and a specific regime of evaporation was highlighted when the substrate is a low evaporation field phase. In addition, the model makes it possible to calculate theoretically the tip analyzed volume, potentially opening up new horizons for atom probe tomographic reconstruction. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Evaporation mechanisms of MgO in laser assisted atom probe tomography

    KAUST Repository

    Mazumder, Baishakhi

    2011-05-01

    In this paper the field evaporation properties of bulk MgO and sandwiched MgO layers in Fe are compared using laser assisted Atom Probe Tomography. The comparison of flight time spectra gives an estimate of the evaporation times as a function of the wavelength and the laser energy. It is shown that the evaporation takes place in two steps on two different time scales in MgO. It is also shown that as long as the MgO layer is buried in Fe, the evaporation is dominated by the photon absorption in Fe layer at the tip apex. Eventually the evaporation process of MgO is discussed based on the difference between the bulk materials and the multilayer samples. © 2010 Elsevier B.V.

  8. Atom-probe field-ion-microscopy study of Fe-Ti alloys

    International Nuclear Information System (INIS)

    Pickering, H.W.; Kuk, Y.; Sakurai, T.

    1980-01-01

    A newly developed high-performance atom-probe (field ion microscope) was employed for the composition analysis of Fe-Ti alloys and their interactions with ambient gas, such as H 2 and O 2 . With a mass resolution (m/Δm) better than 2000 and a spatial resolution of a few A, all isotopes of Fe and Ti and their hydrides and other compounds are clearly resolved during the depth profile study. Some of our findings are: (1) Titanium segregated on the surface and grain boundaries upon heating (greater than or equal to 900 0 C), in the form of oxides, and (2) some Ti in the bulk forms clusters of various sizes with C, O, and/or N as nuclei

  9. Analysis of deuterium in V-Fe5at.% film by atom probe tomography (APT)

    KAUST Repository

    Gemma, Ryota

    2011-09-01

    V-Fe5at.% 2 and 10-nm thick single layered films were prepared by ion beam sputtering on W substrate. They were loaded with D from gas phase at 0.2 Pa and at 1 Pa, respectively. Both lateral and depth D distribution of these films was investigated in detail by atom probe tomography. The results of analysis are in good agreement between the average deuterium concentration and the value, expected from electromotive force measurement on a similar flat film. An enrichment of deuterium at the V/W interface was observed for both films. The origin of this D-accumulation was discussed in respect to electron transfer, mechanical stress and misfit dislocations. © 2010 Elsevier B.V. All rights reserved.

  10. Graphene Coatings: Probing the Limits of the One Atom Thick Protection Layer

    DEFF Research Database (Denmark)

    Nilsson, Louis; Andersen, Mie; Balog, Richard

    2012-01-01

    The limitations of graphene as an effective corrosion-inhibiting coating on metal surfaces, here exemplified by the hex-reconstructed Pt(100) surface, are probed by scanning tunneling microscopy measurements and density functional theory calculations. While exposure of small molecules directly onto...... against CO is observed at CO pressures below 106 mbar. However, at higher pressures CO is observed to intercalate under the graphene coating layer, thus lifting the reconstruction. The limitations of the coating effect are further tested by exposure to hot atomic hydrogen. While the coating can withstand...... these extreme conditions for a limited amount of time, after substantial exposure, the Pt(100) reconstruction is lifted. Annealing experiments and density functional theory calculations demonstrate that the basal plane of the graphene stays intact and point to a graphene-mediated mechanism for the H...

  11. Atomic scale properties of magnetic Mn-based alloys probed by emission Mössbauer spectroscopy

    CERN Multimedia

    Mn-based alloys are characterized by a wealth of properties, which are of interest both from fundamental physics point of view and particularly attractive for different applications in modern technology: from magnetic storage to sensing and spin-based electronics. The possibility to tune their magnetic properties through post-growth thermal processes and/or stoichiometry engineering is highly important in order to target different applications (i.e. Mn$_{x}$Ga) or to increase their Curie temperature above room temperature (i.e. off-stoichiometric MnSi). In this project, the Mössbauer effect will be applied at $^{57}$Fe sites following implantation of radioactive $^{57}$Mn, to probe the micro-structure and magnetism of Mn-based alloys on the atomic-scale. The proposed experimental plan is devoted to establish a direct correlation between the local structure and bulk magnetism (and other physical properties) of Mn-based alloys.

  12. Evaporation mechanisms of MgO in laser assisted atom probe tomography

    KAUST Repository

    Mazumder, Baishakhi; Vella, Angela; Dé conihout, Bernard; Al-Kassab, Talaat

    2011-01-01

    In this paper the field evaporation properties of bulk MgO and sandwiched MgO layers in Fe are compared using laser assisted Atom Probe Tomography. The comparison of flight time spectra gives an estimate of the evaporation times as a function of the wavelength and the laser energy. It is shown that the evaporation takes place in two steps on two different time scales in MgO. It is also shown that as long as the MgO layer is buried in Fe, the evaporation is dominated by the photon absorption in Fe layer at the tip apex. Eventually the evaporation process of MgO is discussed based on the difference between the bulk materials and the multilayer samples. © 2010 Elsevier B.V.

  13. Nanogeochronology of discordant zircon measured by atom probe microscopy of Pb-enriched dislocation loops

    Science.gov (United States)

    Peterman, Emily M.; Reddy, Steven M.; Saxey, David W.; Snoeyenbos, David R.; Rickard, William D. A.; Fougerouse, Denis; Kylander-Clark, Andrew R. C.

    2016-01-01

    Isotopic discordance is a common feature in zircon that can lead to an erroneous age determination, and it is attributed to the mobilization and escape of radiogenic Pb during its post-crystallization geological evolution. The degree of isotopic discordance measured at analytical scales of ~10 μm often differs among adjacent analysis locations, indicating heterogeneous distributions of Pb at shorter length scales. We use atom probe microscopy to establish the nature of these sites and the mechanisms by which they form. We show that the nanoscale distribution of Pb in a ~2.1 billion year old discordant zircon that was metamorphosed c. 150 million years ago is defined by two distinct Pb reservoirs. Despite overall Pb loss during peak metamorphic conditions, the atom probe data indicate that a component of radiogenic Pb was trapped in 10-nm dislocation loops that formed during the annealing of radiation damage associated with the metamorphic event. A second Pb component, found outside the dislocation loops, represents homogeneous accumulation of radiogenic Pb in the zircon matrix after metamorphism. The 207Pb/206Pb ratios measured from eight dislocation loops are equivalent within uncertainty and yield an age consistent with the original crystallization age of the zircon, as determined by laser ablation spot analysis. Our results provide a specific mechanism for the trapping and retention of radiogenic Pb during metamorphism and confirm that isotopic discordance in this zircon is characterized by discrete nanoscale reservoirs of Pb that record different isotopic compositions and yield age data consistent with distinct geological events. These data may provide a framework for interpreting discordance in zircon as the heterogeneous distribution of discrete radiogenic Pb populations, each yielding geologically meaningful ages. PMID:27617295

  14. Quantitative atom probe analysis of nanostructure containing clusters and precipitates with multiple length scales

    International Nuclear Information System (INIS)

    Marceau, R.K.W.; Stephenson, L.T.; Hutchinson, C.R.; Ringer, S.P.

    2011-01-01

    A model Al-3Cu-(0.05 Sn) (wt%) alloy containing a bimodal distribution of relatively shear-resistant θ' precipitates and shearable GP zones is considered in this study. It has recently been shown that the addition of the GP zones to such microstructures can lead to significant increases in strength without a decrease in the uniform elongation. In this study, atom probe tomography (APT) has been used to quantitatively characterise the evolution of the GP zones and the solute distribution in the bimodal microstructure as a function of applied plastic strain. Recent nuclear magnetic resonance (NMR) analysis has clearly shown strain-induced dissolution of the GP zones, which is supported by the current APT data with additional spatial information. There is significant repartitioning of Cu from the GP zones into the solid solution during deformation. A new approach for cluster finding in APT data has been used to quantitatively characterise the evolution of the sizes and shapes of the Cu containing features in the solid solution solute as a function of applied strain. -- Research highlights: → A new approach for cluster finding in atom probe tomography (APT) data has been used to quantitatively characterise the evolution of the sizes and shapes of the Cu containing features with multiple length scales. → In this study, a model Al-3Cu-(0.05 Sn) (wt%) alloy containing a bimodal distribution of relatively shear-resistant θ' precipitates and shearable GP zones is considered. → APT has been used to quantitatively characterise the evolution of the GP zones and the solute distribution in the bimodal microstructure as a function of applied plastic strain. → It is clearly shown that there is strain-induced dissolution of the GP zones with significant repartitioning of Cu from the GP zones into the solid solution during deformation.

  15. Experimental facility and void fraction calibration methods for impedance probes

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Fernando L. de; Rocha, Marcelo S., E-mail: floliveira@ipen.br, E-mail: msrocha@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2013-07-01

    An experimental facility was designed and constructed with aims of to calibrate a capacitance probe for gas-liquid flow void fraction measurements. The facility is composed of a metallic hack with a vertical 2,300 mm high glass tube with 38 mm ID with stagnant water and compressed air bubbling system simulating the gas phase (vapor). At the lower part, a mixing section with a porous media element releases the air bubbles into the water, and the compressed air flow is measured by two calibrated rotameters. At the upper part a stagnant water tank separates the liquid and gas. Two pressure taps are located near the lower and upper sides of the glass tube for pressure difference measurement. The pressure difference is used for low void fraction values (0-15%) calibration methods, as described in the work. Two electrically controlled quick closing valves are installed between the porous media element and the upward separation tank for high void fraction values measurement (15-50%) used to calibrate the capacitance probe. The experimental facility design, construction, capacitance probe calibration methods and results, as well as flow pattern visualization, are presented. Finally, the capacitance probe will be installed on a natural circulation circuit mounted at the Nuclear Engineering Center (CEN/IPEN/CNEN-SP) for measurement of the instantaneous bulk void. Instantaneous signals generated by the capacitance probe will allow the determination of natural circulation loop global energy balance. (author)

  16. Experimental facility and void fraction calibration methods for impedance probes

    International Nuclear Information System (INIS)

    Oliveira, Fernando L. de; Rocha, Marcelo S.

    2013-01-01

    An experimental facility was designed and constructed with aims of to calibrate a capacitance probe for gas-liquid flow void fraction measurements. The facility is composed of a metallic hack with a vertical 2,300 mm high glass tube with 38 mm ID with stagnant water and compressed air bubbling system simulating the gas phase (vapor). At the lower part, a mixing section with a porous media element releases the air bubbles into the water, and the compressed air flow is measured by two calibrated rotameters. At the upper part a stagnant water tank separates the liquid and gas. Two pressure taps are located near the lower and upper sides of the glass tube for pressure difference measurement. The pressure difference is used for low void fraction values (0-15%) calibration methods, as described in the work. Two electrically controlled quick closing valves are installed between the porous media element and the upward separation tank for high void fraction values measurement (15-50%) used to calibrate the capacitance probe. The experimental facility design, construction, capacitance probe calibration methods and results, as well as flow pattern visualization, are presented. Finally, the capacitance probe will be installed on a natural circulation circuit mounted at the Nuclear Engineering Center (CEN/IPEN/CNEN-SP) for measurement of the instantaneous bulk void. Instantaneous signals generated by the capacitance probe will allow the determination of natural circulation loop global energy balance. (author)

  17. Analysis conditions of an industrial Al-Mg-Si alloy by conventional and 3D atom probes.

    Science.gov (United States)

    Danoix, F; Miller, M K; Bigot, A

    2001-10-01

    Industrial 6016 Al-Mg-Si(Cu) alloys are presently regarded as attractive candidates for heat treatable sheet materials. Their mechanical properties can be adjusted for a given application by age hardening of the alloys. The resulting microstructural evolution takes place at the nanometer scale, making the atom probe a well suited instrument to study it. Accuracy of atom probe analysis of these aluminium alloys is a key point for the understanding of the fine scale microstructural evolution. It is known to be strongly dependent on the analysis conditions (such as specimen temperature and pulse fraction) which have been widely studied for ID atom probes. The development of the 3D instruments, as well as the increase of the evaporation pulse repetition rate have led to different analysis conditions, in particular evaporation and detection rates. The influence of various experimental parameters on the accuracy of atom probe data, in particular with regard to hydride formation sensitivity, has been reinvestigated. It is shown that hydrogen contamination is strongly dependent on the electric field at the specimen surface, and that high evaporation rates are beneficial. Conversely, detection rate must be limited to smaller than 0.02 atoms/pulse in order to prevent drastic pile-up effect.

  18. Probing individual redox PEGylated gold nanoparticles by electrochemical--atomic force microscopy.

    Science.gov (United States)

    Huang, Kai; Anne, Agnès; Bahri, Mohamed Ali; Demaille, Christophe

    2013-05-28

    Electrochemical-atomic force microscopy (AFM-SECM) was used to simultaneously probe the physical and electrochemical properties of individual ~20 nm sized gold nanoparticles functionalized by redox-labeled PEG chains. The redox PEGylated nanoparticles were assembled onto a gold electrode surface, forming a random nanoarray, and interrogated in situ by a combined AFM-SECM nanoelectrode probe. We show that, in this so-called mediator-tethered (Mt) mode, AFM-SECM affords the nanometer resolution required for resolving the position of individual nanoparticles and measuring their size, while simultaneously electrochemically directly contacting the redox-PEG chains they bear. The dual measurement of the size and current response of single nanoparticles uniquely allows the statistical distribution in grafting density of PEG on the nanoparticles to be determined and correlated to the nanoparticle diameter. Moreover, because of its high spatial resolution, Mt/AFM-SECM allows "visualizing" simultaneously but independently the PEG corona and the gold core of individual nanoparticles. Beyond demonstrating the achievement of single-nanoparticle resolution using an electrochemical microscopy technique, the results reported here also pave the way toward using Mt/AFM-SECM for imaging nano-objects bearing any kind of suitably redox-labeled (bio)macromolecules.

  19. Nanomechanical and topographical imaging of living cells by atomic force microscopy with colloidal probes

    Energy Technology Data Exchange (ETDEWEB)

    Puricelli, Luca; Galluzzi, Massimiliano; Schulte, Carsten; Podestà, Alessandro, E-mail: alessandro.podesta@mi.infn.it; Milani, Paolo [CIMaINa and Department of Physics, Università degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy)

    2015-03-15

    Atomic Force Microscopy (AFM) has a great potential as a tool to characterize mechanical and morphological properties of living cells; these properties have been shown to correlate with cells’ fate and patho-physiological state in view of the development of novel early-diagnostic strategies. Although several reports have described experimental and technical approaches for the characterization of cellular elasticity by means of AFM, a robust and commonly accepted methodology is still lacking. Here, we show that micrometric spherical probes (also known as colloidal probes) are well suited for performing a combined topographic and mechanical analysis of living cells, with spatial resolution suitable for a complete and accurate mapping of cell morphological and elastic properties, and superior reliability and accuracy in the mechanical measurements with respect to conventional and widely used sharp AFM tips. We address a number of issues concerning the nanomechanical analysis, including the applicability of contact mechanical models and the impact of a constrained contact geometry on the measured Young’s modulus (the finite-thickness effect). We have tested our protocol by imaging living PC12 and MDA-MB-231 cells, in order to demonstrate the importance of the correction of the finite-thickness effect and the change in Young’s modulus induced by the action of a cytoskeleton-targeting drug.

  20. High quality-factor quartz tuning fork glass probe used in tapping mode atomic force microscopy for surface profile measurement

    Science.gov (United States)

    Chen, Yuan-Liu; Xu, Yanhao; Shimizu, Yuki; Matsukuma, Hiraku; Gao, Wei

    2018-06-01

    This paper presents a high quality-factor (Q-factor) quartz tuning fork (QTF) with a glass probe attached, used in frequency modulation tapping mode atomic force microscopy (AFM) for the surface profile metrology of micro and nanostructures. Unlike conventionally used QTFs, which have tungsten or platinum probes for tapping mode AFM, and suffer from a low Q-factor influenced by the relatively large mass of the probe, the glass probe, which has a lower density, increases the Q-factor of the QTF probe unit allowing it to obtain better measurement sensitivity. In addition, the process of attaching the probe to the QTF with epoxy resin, which is necessary for tapping mode AFM, is also optimized to further improve the Q-factor of the QTF glass probe. The Q-factor of the optimized QTF glass probe unit is demonstrated to be very close to that of a bare QTF without a probe attached. To verify the effectiveness and the advantages of the optimized QTF glass probe unit, the probe unit is integrated into a home-built tapping mode AFM for conducting surface profile measurements of micro and nanostructures. A blazed grating with fine tool marks of 100 nm, a microprism sheet with a vertical amplitude of 25 µm and a Fresnel lens with a steep slope of 90 degrees are used as measurement specimens. From the measurement results, it is demonstrated that the optimized QTF glass probe unit can achieve higher sensitivity as well as better stability than conventional probes in the measurement of micro and nanostructures.

  1. Investigations of reactions between pure refractory metals and light gases with the field ion microscope and atom probe

    International Nuclear Information System (INIS)

    Krautz, E.; Haiml, G.

    1989-01-01

    The initial stages of selected reactions of the refractory metals tungsten, niobium and tantalum with hydrogen, oxygen, nitrogen and methane have been studied with the field ion microscope in atomic resolution whereby the composition of single net planes converages and surface zones could absolutely be analyzed with the atom probe by using field desorption under defined conditions at low temperatures. 14 refs., 9 figs. (Author)

  2. Probing the interactions between lignin and inorganic oxides using atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jingyu; Qian, Yong, E-mail: qianyong86@163.com; Deng, Yonghong; Liu, Di; Li, Hao; Qiu, Xueqing, E-mail: xueqingqiu66@163.com

    2016-12-30

    Graphical abstract: The interactions between lignin and inorganic oxides are quantitatively probed by atomic force microscopy, which is fundamental but beneficial for understanding and optimizing the absorption-dispersion and catalytic degradation processes of lignin. - Highlights: • The interactions between lignin and inorganic oxides are measured using AFM. • The adhesion forces between lignin and metal oxides are larger than that in nonmetal systems. • Hydrogen bond plays an important role in lignin-inorganic oxides system. - Abstract: Understanding the interactions between lignin and inorganic oxides has both fundamental and practical importance in industrial and energy fields. In this work, the specific interactions between alkali lignin (AL) and three inorganic oxide substrates in aqueous environment are quantitatively measured using atomic force microscopy (AFM). The results show that the average adhesion force between AL and metal oxide such as Al{sub 2}O{sub 3} or MgO is nearly two times bigger than that between AL and nonmetal oxide such as SiO{sub 2} due to the electrostatic difference and cation-π interaction. When 83% hydroxyl groups of AL is blocked by acetylation, the adhesion forces between AL and Al{sub 2}O{sub 3}, MgO and SiO{sub 2} decrease 43, 35 and 75% respectively, which indicate hydrogen bonds play an important role between AL and inorganic oxides, especially in AL-silica system.

  3. Mapping energetics of atom probe evaporation events through first principles calculations.

    Science.gov (United States)

    Peralta, Joaquín; Broderick, Scott R; Rajan, Krishna

    2013-09-01

    The purpose of this work is to use atomistic modeling to determine accurate inputs into the atom probe tomography (APT) reconstruction process. One of these inputs is evaporation field; however, a challenge occurs because single ions and dimers have different evaporation fields. We have calculated the evaporation field of Al and Sc ions and Al-Al and Al-Sc dimers from an L1₂-Al₃Sc surface using ab initio calculations and with a high electric field applied to the surface. The evaporation field is defined as the electric field at which the energy barrier size is calculated as zero, corresponding to the minimum field that atoms from the surface can break their bonds and evaporate from the surface. The evaporation field of the surface atoms are ranked from least to greatest as: Al-Al dimer, Al ion, Sc ion, and Al-Sc dimer. The first principles results were compared with experimental data in the form of an ion evaporation map, which maps multi-ion evaporations. From the ion evaporation map of L1₂-Al₃Sc, we extract relative evaporation fields and identify that an Al-Al dimer has a lower evaporation field than an Al-Sc dimer. Additionally, comparatively an Al-Al surface dimer is more likely to evaporate as a dimer, while an Al-Sc surface dimer is more likely to evaporate as single ions. These conclusions from the experiment agree with the ab initio calculations, validating the use of this approach for modeling APT energetics. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. Charge dynamics of 57Fe probe atoms in La2Li0.5Cu0.5O4

    Science.gov (United States)

    Presniakov, I. A.; Sobolev, A. V.; Rusakov, V. S.; Moskvin, A. S.; Baranov, A. V.

    2018-06-01

    The objective of this study is to characterize the electronic state and local surrounding of 57Fe Mössbauer probe atoms within iron-doped layered perovskite La2Li0.5Cu0.5O4 containing transition metal in unusual formal oxidation states "+3". An approach based on the qualitative energy diagrams analysis and the calculations within the cluster configuration interaction method have been developed. It was shown that a large amount of charge is transferred via Cu-O bonds from the O: 2p bands to the Cu: 3d orbitals and the ground state is dominated by the d9L configuration ("Cu2+-O-" state). The dominant d9L ground state for the (CuO6) sublattice induces in the environment of the 57Fe probe cations a charge transfer Fe3+ + O-(L) → Fe4+ + O2-, which transforms "Fe3+" into "Fe4+" state. The experimental spectra in the entire temperature range 77-300 K were described with the use of the stochastic two-level model based on the assumption of dynamic equilibrium between two Fe3+↔Fe4+ valence states related to the iron atom in the [Fe(1)O4]4- center. The relaxation frequencies and activation energies of the corresponding charge fluctuations were estimated based on Mössbauer data. The results are discussed assuming a temperature-induced change in the electronic state of the [CuO4]5- clusters in the layered perovskite.

  5. A method optimization study for atomic absorption ...

    African Journals Online (AJOL)

    Sadia Ata

    2014-04-24

    Apr 24, 2014 ... Manufacturer brand Win 2.1 software was used for data inte- gration and processing. ... reagents and analyst) is suitable for the intended application. The % relative standard deviation for absorbance ... flame atomic absorption spectrometry. Table 2 Linearity data for analysis of zinc in insulin using AAS.

  6. An integrated high temperature environmental cell for atom probe tomography studies of gas-surface reactions: Instrumentation and results

    International Nuclear Information System (INIS)

    Dumpala, S.; Broderick, S.R.; Bagot, P.A.J.; Rajan, K.

    2014-01-01

    An integrated environmental cell has been designed and developed for the latest generation of Atom Probe Tomography LEAP™ instruments, allowing controlled exposure of samples to gases at high temperatures. Following treatment, samples can be transferred through the LEAP vacuum system for subsequent APT analysis, which provides detailed information on changes to chemical microstructures following the reactions with near-atomic resolution. A full description of the cell is presented, along with some sample results on the oxidation of aluminum and two platinum-group alloys, demonstrating the capability of combining exposure/characterization functionality in a single instrument. - Highlights: • Designed and built atom probe environmental cell for in situ reactions. • Investigated Al oxidation, and demonstrated improvement with new cell. • in situ APT analysis of Pt-alloys showed surface segregation of Rh and Ir

  7. Tetragonal fcc-Fe induced by κ -carbide precipitates: Atomic scale insights from correlative electron microscopy, atom probe tomography, and density functional theory

    Science.gov (United States)

    Liebscher, Christian H.; Yao, Mengji; Dey, Poulumi; Lipińska-Chwalek, Marta; Berkels, Benjamin; Gault, Baptiste; Hickel, Tilmann; Herbig, Michael; Mayer, Joachim; Neugebauer, Jörg; Raabe, Dierk; Dehm, Gerhard; Scheu, Christina

    2018-02-01

    Correlative scanning transmission electron microscopy, atom probe tomography, and density functional theory calculations resolve the correlation between elastic strain fields and local impurity concentrations on the atomic scale. The correlative approach is applied to coherent interfaces in a κ -carbide strengthened low-density steel and establishes a tetragonal distortion of fcc-Fe. An interfacial roughness of ˜1 nm and a localized carbon concentration gradient extending over ˜2 -3 nm is revealed, which originates from the mechano-chemical coupling between local strain and composition.

  8. Monitoring method of an atomic power plant

    International Nuclear Information System (INIS)

    Koba, Akitoshi; Goto, Seiichiro; Ohashi, Hideaki.

    1975-01-01

    Object: To make a monitoring vehicle, which is loaded with various detecting elements, go round along the monorail disposed so as to surround various devices to thereby early discover various abnormal conditions. Structure: The monitoring vehicle is travelled on the monorail disposed so as to surround the periphery of various devices in an atomic power plant so that detection signals from an ITV camera, temperature and radioactive rays and sound detecting elements, and the like are received through a slide contact between the wheel and transmitting and receiving line disposed in the wheel groove to transmit the signals to a central control panel. (Yoshihara, H.)

  9. Perfect/complete scattering experiments. Probing quantum mechanics on atomic and molecular collisions and coincidences

    International Nuclear Information System (INIS)

    Lohmann, Bernd; Grum-Grzhimailo, Alexei N.; Kleinpoppen, Hans

    2013-01-01

    Derives parameters for electrons, photons, atoms, ions, molecules calculated from theory. Delivers the quantum mechanical knowledge of atomic and molecular physics. Presents state-of-the-art experiments in atomic and molecular physics and related theoretical approaches. The main goal of this book is to elucidate what kind of experiment must be performed in order to determine the full set of independent parameters which can be extracted and calculated from theory, where electrons, photons, atoms, ions, molecules, or molecular ions may serve as the interacting constituents of matter. The feasibility of such perfect' and-or 'complete' experiments, providing the complete quantum mechanical knowledge of the process, is associated with the enormous potential of modern research techniques, both, in experiment and theory. It is even difficult to overestimate the role of theory in setting of the complete experiment, starting with the fact that an experiment can be complete only within a certain theoretical framework, and ending with the direct prescription of what, and in what conditions should be measured to make the experiment 'complete'. The language of the related theory is the language of quantum mechanical amplitudes and their relative phases. This book captures the spirit of research in the direction of the complete experiment in atomic and molecular physics, considering some of the basic quantum processes: scattering, Auger decay and photo-ionization. It includes a description of the experimental methods used to realize, step by step, the complete experiment up to the level of the amplitudes and phases. The corresponding arsenal includes, beyond determining the total cross section, the observation of angle and spin resolved quantities, photon polarization and correlation parameters, measurements applying coincidence techniques, preparing initially polarized targets, and even more sophisticated methods. The 'complete' experiment is, until today, hardly to perform

  10. Perfect/complete scattering experiments. Probing quantum mechanics on atomic and molecular collisions and coincidences

    Energy Technology Data Exchange (ETDEWEB)

    Lohmann, Bernd [Muenster Univ. (Germany). Inst. fuer Theoretische Physik 1; Grum-Grzhimailo, Alexei N. [Moscow State Univ. (Russian Federation). Skobeltsyn Inst. of Nuclear Physics; Kleinpoppen, Hans

    2013-07-01

    Derives parameters for electrons, photons, atoms, ions, molecules calculated from theory. Delivers the quantum mechanical knowledge of atomic and molecular physics. Presents state-of-the-art experiments in atomic and molecular physics and related theoretical approaches. The main goal of this book is to elucidate what kind of experiment must be performed in order to determine the full set of independent parameters which can be extracted and calculated from theory, where electrons, photons, atoms, ions, molecules, or molecular ions may serve as the interacting constituents of matter. The feasibility of such perfect' and-or 'complete' experiments, providing the complete quantum mechanical knowledge of the process, is associated with the enormous potential of modern research techniques, both, in experiment and theory. It is even difficult to overestimate the role of theory in setting of the complete experiment, starting with the fact that an experiment can be complete only within a certain theoretical framework, and ending with the direct prescription of what, and in what conditions should be measured to make the experiment 'complete'. The language of the related theory is the language of quantum mechanical amplitudes and their relative phases. This book captures the spirit of research in the direction of the complete experiment in atomic and molecular physics, considering some of the basic quantum processes: scattering, Auger decay and photo-ionization. It includes a description of the experimental methods used to realize, step by step, the complete experiment up to the level of the amplitudes and phases. The corresponding arsenal includes, beyond determining the total cross section, the observation of angle and spin resolved quantities, photon polarization and correlation parameters, measurements applying coincidence techniques, preparing initially polarized targets, and even more sophisticated methods. The 'complete' experiment is

  11. Ordering and site occupancy of D03 ordered Fe3Al-5 at%Cr evaluated by means of atom probe tomography

    KAUST Repository

    Rademacher, Thomas W.

    2011-05-01

    Addition of ternary elements to the D03 ordered Fe3Al intermetallic phase is a general approach to optimise its mechanical properties. To understand the physical influences of such additions the determination of the probability of site occupancies of these additions on the lattice site and ordering parameters is of high interest. Some common experimental techniques such as X-ray diffraction or Atom Location by Channelling Enhanced Microanalysis (ALCHEMI) are usually applied to explore this interplay. Unfortunately, certain published results are partly inconsistent, imprecise or even contradictory. In this study, these aspects are evaluated systematically by atom probe tomography (APT) and a special data analysis method. Additionally, to account for possible field evaporation effects that can falsify the estimation of site occupancy and induce misinterpretations, APT evaporation sequences were also simulated. As a result, chromium occupies most frequently the next nearest neighbour sites of Al atoms and local ordering parameters could be achieved. © 2010 Elsevier B.V.

  12. Ordering and site occupancy of D03 ordered Fe3Al-5 at%Cr evaluated by means of atom probe tomography

    KAUST Repository

    Rademacher, Thomas W.; Al-Kassab, Talaat; Deges, Johannes; Kirchheim, Reiner

    2011-01-01

    Addition of ternary elements to the D03 ordered Fe3Al intermetallic phase is a general approach to optimise its mechanical properties. To understand the physical influences of such additions the determination of the probability of site occupancies of these additions on the lattice site and ordering parameters is of high interest. Some common experimental techniques such as X-ray diffraction or Atom Location by Channelling Enhanced Microanalysis (ALCHEMI) are usually applied to explore this interplay. Unfortunately, certain published results are partly inconsistent, imprecise or even contradictory. In this study, these aspects are evaluated systematically by atom probe tomography (APT) and a special data analysis method. Additionally, to account for possible field evaporation effects that can falsify the estimation of site occupancy and induce misinterpretations, APT evaporation sequences were also simulated. As a result, chromium occupies most frequently the next nearest neighbour sites of Al atoms and local ordering parameters could be achieved. © 2010 Elsevier B.V.

  13. Multielement methods of atomic fluorescence analysis of enviromental samples

    International Nuclear Information System (INIS)

    Rigin, V.I.

    1985-01-01

    A multielement method of atomic fluorescence analysis of environmental samples based on sample decomposition by autoclave fluorination and gas-phase atomization of volatile compounds in inductive araon plasma using a nondispersive polychromator is suggested. Detection limits of some elements (Be, Sr, Cd, V, Mo, Te, Ru etc.) for different sample forms introduced in to an analyzer are given

  14. 2D-PES/XAS method for atomic-layer-resolved magnetic structure analysis

    International Nuclear Information System (INIS)

    Matsui, F.; Daimon, H.; Matsushita, T.; Guo, F.Z.

    2008-01-01

    Photoelectron and Auger electron angular distributions from a localized core level provide information on atomic configurations. Forward-focusing peaks indicate the directions of atoms surrounding the excited atom. X-ray absorption fine structure and X-ray magnetic circular dichroism measurements by Auger electron yield detection on the other hand are excellent methods for studying of the electronic and magnetic structures of surfaces, adsorbates, and thin films. However, all the information from atoms within the electron mean-free-path region is averaged into the obtained spectra. Here, we introduce a new method of X-ray absorption spectroscopy (XAS) combined with measurements of Auger electron angular distribution using a display-type analyzer. Taking advantage of the forward-focusing peak as an excellent element- and site-selective probe, 2D-XAS enables direct access to the individual electronic and magnetic structures of each atomic layer. This method was applied to studying the electronic and magnetic structures of Ni thin film at atomic level. (author)

  15. Atom probe tomography investigation of lath boundary segregation and precipitation in a maraging stainless steel.

    Science.gov (United States)

    Thuvander, Mattias; Andersson, Marcus; Stiller, Krystyna

    2013-09-01

    Lath boundaries in a maraging stainless steel of composition 13Cr-8Ni-2Mo-2Cu-1Ti-0.7Al-0.3Mn-0.2Si-0.03C (at%) have been investigated using atom probe tomography following aging at 475 °C for up to 100 h. Segregation of Mo, Si and P to the lath boundaries was observed already after 5 min of aging, and the amount of segregation increases with aging time. At lath boundaries also precipitation of η-Ni₃(Ti, Al) and Cu-rich 9R, in contact with each other, takes place. These co-precipitates grow with time and because of coarsening the area number density decreases. After 100 h of aging a ∼5 nm thick film-like precipitation of a Mo-rich phase was observed at the lath boundaries. From the composition of the film it is suggested that the phase in question is the quasicrystalline R' phase. The film is perforated with Cu-rich 9R and η-Ni₃(Ti, Al) co-precipitates. Not all precipitate types present in the matrix do precipitate at the lath boundaries; the Si-containing G phase and γ'-Ni₃(Ti, Al, Si) and the Cr-rich α' phase were not observed at the lath boundaries. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. Atom probe characterization of precipitation in an aged Cu-Ni-P alloy

    International Nuclear Information System (INIS)

    Aruga, Yasuhiro; Saxey, David W.; Marquis, Emmanuelle A.; Cerezo, Alfred; Smith, George D.W.

    2011-01-01

    A temporal evolution of clusters associated with age hardening behavior in a Cu-Ni-P alloy during ageing at 250 o C for up to 100 ks after solution treatment has been carried out. A three-dimensional atom probe (3DAP) analysis has showed that Ni-P clusters are present in the as-quenched condition, and that the cluster density increases as the ageing time increases. The clusters have a wide range of Ni/P ratios when they are relatively small, whereas larger clusters exhibit a narrow distribution of the Ni/P ratio, approaching a ratio of approximately two. These results would indicate that the clusters with various Ni/P ratios form at the early stage of precipitation and the ratio approaches a value identical to that of the equilibrium phase at 250 o C as the clusters enlarge during ageing. -- Research highlights: → We characterize the clustering behavior in a Cu-Ni-P alloy during ageing at 250 o C. → The clusters have a wide range of Ni/P ratios when they are relatively small. → Larger clusters exhibit a narrow distribution of the ratio. → Hardness increases almost linearly with the logarithm of ageing time beyond 100s. → We believe increasing density and size of the clusters leads to the age hardening.

  17. Optimisation of mass ranging for atom probe microanalysis and application to the corrosion processes in Zr alloys

    International Nuclear Information System (INIS)

    Hudson, D.; Smith, G.D.W.; Gault, B.

    2011-01-01

    Atom probe tomography uses time-of-flight mass spectrometry to identify the chemical nature of atoms from their mass-to-charge-state ratios. Within a mass spectrum, ranges are defined so as to attribute a chemical identity to each peak. The accuracy of atom probe microanalysis relies on the definition of these ranges. Here we propose and compare several automated ranging techniques, tested against simulated mass spectra. The performance of these metrics compare favourably with a trial of users asked to manually range a simplified simulated dataset. The optimised automated ranging procedure was then used to precisely evaluate the very low iron concentration (0.003-0.018 at%) in a zirconium alloy to reveal its behaviour in the matrix during corrosion; oxygen is injected into solution and has the effect of increasing the local iron concentration near the oxide-metal interface, which in turn affects the corrosion properties of the metal substrate. -- Research Highlights: → Realistic simulated mass spectra were generated so as to reproduce experimental data with a perfectly determined composition. → Several metrics were tested against these simulated mass spectra to determine an optimal methodology for ranging mass peaks in atom probe tomography. Systematic automated ranging provides a significant reduction in the deviation between true and measured concentrations compared to manual ranging by multiple users on the same data. → Experimental datasets were subsequently investigated, and Fe has been shown to be distributed as a random solid solution within the matrix of 'as-received' recrystallised ZIRLO, a zirconium alloy.

  18. Interpretation of atom probe tomography data for the intermetallic TiAl+Nb by means of field evaporation simulation

    KAUST Repository

    Boll, Torben

    2013-01-01

    In this paper simulations of the field evaporation process during field ion microscopy (FIM) and atom probe tomography (APT) are presented and compared with experimental data. The Müller-Schottky-model [1] was extended to include the local atomic arrangement on the evaporation process of atoms. This arrangement was described by the sum of the next-neighbor-binding-energies, which differ for an atom of type A, depending on how many A-A, B-B or A-B bonds are present. Thus simulations of APT-data of intermetallic phases become feasible. In this study simulations of L10-TiAl with additions of Nb are compared with experimental data. Certain artifacts, which appear for experimental data are treated as well. © 2012 Elsevier B.V.

  19. Preparing and probing atomic Majorana fermions and topological order in optical lattices

    International Nuclear Information System (INIS)

    Kraus, C V; Diehl, S; Zoller, P; Baranov, M A

    2012-01-01

    We introduce a one-dimensional system of fermionic atoms in an optical lattice whose phase diagram includes topological states of different symmetry classes with a simple possibility to switch between them. The states and topological phase transitions between them can be identified by looking at their zero-energy edge modes which are Majorana fermions. We propose several universal methods of detecting the Majorana edge states, based on their genuine features: the zero-energy, localized character of the wave functions and the induced non-local fermionic correlations. (paper)

  20. A four-probe thermal transport measurement method for nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jaehyun; Ou, Eric; Sellan, Daniel P.; Shi, Li, E-mail: lishi@mail.utexas.edu [Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States)

    2015-04-15

    Several experimental techniques reported in recent years have enabled the measurement of thermal transport properties of nanostructures. However, eliminating the contact thermal resistance error from the measurement results has remained a critical challenge. Here, we report a different four-probe measurement method that can separately obtain both the intrinsic thermal conductance and the contact thermal resistance of individual nanostructures. The measurement device consists of four microfabricated, suspended metal lines that act as resistive heaters and thermometers, across which the nanostructure sample is assembled. The method takes advantage of the variation in the heat flow along the suspended nanostructure and across its contacts to the four suspended heater and thermometer lines, and uses sixteen sets of temperature and heat flow measurements to obtain nine of the thermal resistances in the measurement device and the nanostructure sample, including the intrinsic thermal resistance and the two contact thermal resistances to the middle suspended segment of the nanostructure. Two single crystalline Si nanowires with different cross sections are measured in this work to demonstrate the effectiveness of the method. This four-probe thermal transport measurement method can lead to future discoveries of unique size-dependent thermal transport phenomena in nanostructures and low-dimensional materials, in addition to providing reliable experimental data for calibrating theoretical models.

  1. A four-probe thermal transport measurement method for nanostructures

    International Nuclear Information System (INIS)

    Kim, Jaehyun; Ou, Eric; Sellan, Daniel P.; Shi, Li

    2015-01-01

    Several experimental techniques reported in recent years have enabled the measurement of thermal transport properties of nanostructures. However, eliminating the contact thermal resistance error from the measurement results has remained a critical challenge. Here, we report a different four-probe measurement method that can separately obtain both the intrinsic thermal conductance and the contact thermal resistance of individual nanostructures. The measurement device consists of four microfabricated, suspended metal lines that act as resistive heaters and thermometers, across which the nanostructure sample is assembled. The method takes advantage of the variation in the heat flow along the suspended nanostructure and across its contacts to the four suspended heater and thermometer lines, and uses sixteen sets of temperature and heat flow measurements to obtain nine of the thermal resistances in the measurement device and the nanostructure sample, including the intrinsic thermal resistance and the two contact thermal resistances to the middle suspended segment of the nanostructure. Two single crystalline Si nanowires with different cross sections are measured in this work to demonstrate the effectiveness of the method. This four-probe thermal transport measurement method can lead to future discoveries of unique size-dependent thermal transport phenomena in nanostructures and low-dimensional materials, in addition to providing reliable experimental data for calibrating theoretical models

  2. Atom probe tomography investigation of lath boundary segregation and precipitation in a maraging stainless steel

    International Nuclear Information System (INIS)

    Thuvander, Mattias; Andersson, Marcus; Stiller, Krystyna

    2013-01-01

    Lath boundaries in a maraging stainless steel of composition 13Cr–8Ni–2Mo–2Cu–1Ti–0.7Al–0.3Mn–0.2Si–0.03C (at%) have been investigated using atom probe tomography following aging at 475 °C for up to 100 h. Segregation of Mo, Si and P to the lath boundaries was observed already after 5 min of aging, and the amount of segregation increases with aging time. At lath boundaries also precipitation of η-Ni 3 (Ti, Al) and Cu-rich 9R, in contact with each other, takes place. These co-precipitates grow with time and because of coarsening the area number density decreases. After 100 h of aging a ∼5 nm thick film-like precipitation of a Mo-rich phase was observed at the lath boundaries. From the composition of the film it is suggested that the phase in question is the quasicrystalline R′ phase. The film is perforated with Cu-rich 9R and η-Ni 3 (Ti, Al) co-precipitates. Not all precipitate types present in the matrix do precipitate at the lath boundaries; the Si-containing G phase and γ′-Ni 3 (Ti, Al, Si) and the Cr-rich α′ phase were not observed at the lath boundaries. - Highlights: ► Lath boundaries in a maraging steel were analyzed by APT. ► Segregation of Mo, Si and P was measured. ► Precipitation of η-Ni 3 (Ti, Al) and Cu-rich 9R was observed. ► After 100 h of aging a quasicrystalline Mo-rich film was observed

  3. Atom probe characterization of nano-scaled features in irradiated Eurofer and ODS Eurofer steel

    International Nuclear Information System (INIS)

    Rogozkin, S.; Aleev, A.; Nikitin, A.; Zaluzhnyi, A.; Vladimirov, P.; Moeslang, A.; Lindau, R.

    2009-01-01

    Outstanding performance of oxide dispersion strengthened (ODS) steels at high temperatures and up to high doses allowed to consider them as potential candidates for fusion and fission power plants. At the same time their mechanical parameters strongly correlate with number density of oxide particles and their size. It is believed that fine particles are formed at the last stage of sophisticated production procedures and play a crucial role in higher heat- and radiation resistance in comparison with conventional materials. However, due to their small size - only few nanometers, characterization of such objects requires considerable efforts. Recent study of ODS steel by tomographic atom probe, the most appropriate technique in this case, shown considerable stability of these particles under high temperatures and ion-irradiation. However, these results were obtained for 12/14% Cr with addition of 0.3% Y 2 O 3 and titanium which is inappropriate in case of ODS Eurofer 97 and possibility to substitute neutron by ion irradiation is still under consideration. In this work effect of neutron irradiation on nanostructure behaviour of ODS Eurofer are investigated. Irradiation was performed on research reactor BOR-60 in SSC RF RIAR (Dimitrovgrad, Russia) up to 30 dpa at 280 deg. C and 580 deg. C. Recent investigation of unirradiated state revealed high number density of nano-scaled features (nano-clusters) even without addition of Ti in steel. It was shown that vanadium played significant role in nucleation process and core of nano-clusters was considerably enriched with it. In irradiated samples solution of vanadium in matrix was observed while the size of particles stayed practically unchanged. Also no nitrogen was detected in these particles in comparison with unirradiated state where bond energy of N with V was considered to be high as VN 2+ ions were detected on mass-spectra. (author)

  4. Fundamental insights into the radium uptake into barite by atom probe tomography and electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Juliane

    2017-10-01

    -of-the-art high-resolution microscopy techniques was used to answer the questions regarding (1) the internal microstructure of the initial barite (2) the role of this internal microstructure during the Ra uptake and (3) t he changes in the Ra distribution within the barite. This study comprises the first characterization of barite by atom probe tomography (APT). By combining APT and transmission electron microscopy (TEM) methods, pores covering the size range from a few nanometers to a few micrometers were identified in the SL barite. The pores were organized in layers parallel to the outer crystal faces. High resolution chemical analysis indicated that the pores contain a solution of water and sodium chloride. By focused ion beam (FIB) tomography, it was revealed that open macropores of several micrometers size are present as well within the SL barite. These partially connected macropores are distributed within the complete barite particles. Therefore, the macropores provide a direct pathway for Ra-containing aqueous fluid to enter the SL barite particles by diffusion within the aqueous solution. In addition, pores were also identified in the AL barite by TEM characterization. The entrapment of solution during mineral precipitation is known for several minerals at high supersaturation. As barite only precipitates at high supersaturation, nanoscale fluid inclusions as well as macropores probably were entrapped during the particle growth by precipitation. A microstructure similar to the one of the barite type used in this study was previously reported for other barites. In Ra-free reference experiment, no microstructural changes were noted over recrystallization times of up to 898 days. In prior studies, three different stages of Ra uptake were described based on macroscopic results. Ra-containing barite samples from all three stages were characterized to understand the role of the internal barite microstructure. At the beginning, the nano-scale fluid inclusions disappeared

  5. Fundamental insights into the radium uptake into barite by atom probe tomography and electron microscopy

    International Nuclear Information System (INIS)

    Weber, Juliane

    2017-01-01

    used to answer the questions regarding (1) the internal microstructure of the initial barite (2) the role of this internal microstructure during the Ra uptake and (3) t he changes in the Ra distribution within the barite. This study comprises the first characterization of barite by atom probe tomography (APT). By combining APT and transmission electron microscopy (TEM) methods, pores covering the size range from a few nanometers to a few micrometers were identified in the SL barite. The pores were organized in layers parallel to the outer crystal faces. High resolution chemical analysis indicated that the pores contain a solution of water and sodium chloride. By focused ion beam (FIB) tomography, it was revealed that open macropores of several micrometers size are present as well within the SL barite. These partially connected macropores are distributed within the complete barite particles. Therefore, the macropores provide a direct pathway for Ra-containing aqueous fluid to enter the SL barite particles by diffusion within the aqueous solution. In addition, pores were also identified in the AL barite by TEM characterization. The entrapment of solution during mineral precipitation is known for several minerals at high supersaturation. As barite only precipitates at high supersaturation, nanoscale fluid inclusions as well as macropores probably were entrapped during the particle growth by precipitation. A microstructure similar to the one of the barite type used in this study was previously reported for other barites. In Ra-free reference experiment, no microstructural changes were noted over recrystallization times of up to 898 days. In prior studies, three different stages of Ra uptake were described based on macroscopic results. Ra-containing barite samples from all three stages were characterized to understand the role of the internal barite microstructure. At the beginning, the nano-scale fluid inclusions disappeared, probably due to coalescing to new macropores

  6. Hidden Markov Model of atomic quantum jump dynamics in an optically probed cavity

    DEFF Research Database (Denmark)

    Gammelmark, S.; Molmer, K.; Alt, W.

    2014-01-01

    We analyze the quantum jumps of an atom interacting with a cavity field. The strong atom- field interaction makes the cavity transmission depend on the time dependent atomic state, and we present a Hidden Markov Model description of the atomic state dynamics which is conditioned in a Bayesian...... manner on the detected signal. We suggest that small variations in the observed signal may be due to spatial motion of the atom within the cavity, and we represent the atomic system by a number of hidden states to account for both the small variations and the internal state jump dynamics. In our theory...

  7. Observation of oscillatory radiation induced segregation profiles at grain boundaries in neutron irradiated 316 stainless steel using atom probe tomography

    Science.gov (United States)

    Barr, Christopher M.; Felfer, Peter J.; Cole, James I.; Taheri, Mitra L.

    2018-06-01

    Radiation induced segregation in austenitic Fe-Ni-Cr stainless steels is a key detrimental microstructural modification experienced in the current generation of light water reactors. In particular, Cr depletion at grain boundaries can be a significant factor in irradiation-assisted stress corrosion cracking. Therefore, having a complete knowledge and mechanistic understanding of radiation induced segregation at high dose and after a long thermal history is desired for continued sustainability of existing reactors. Here, we examine a 12% cold worked AISI 316 stainless steel hexagonal duct exposed in the lower dose, outer blanket region of the EBR-II reactor, by using advanced characterization and analysis techniques including atom probe tomography and analytical scanning transmission electron microscopy. Contrary to existing literature, we observe an oscillatory w-shape Cr and M-shape Ni concentration profile at 31 dpa. The presence and characterization through advanced atom probe tomography analysis of the w-shape Cr RIS profile is discussed in the context of the localized GB plane interfacial excess of the other major and minor alloying elements. The key finding of a co-segregation phenomena coupling Cr, Mo, and C is discussed in the context of the existing solute segregation literature under irradiation with emphasis on improved spatial and chemical resolution of atom probe tomography.

  8. Measuring adhesion on rough surfaces using atomic force microscopy with a liquid probe

    Directory of Open Access Journals (Sweden)

    Juan V. Escobar

    2017-04-01

    Full Text Available We present a procedure to perform and interpret pull-off force measurements during the jump-off-contact process between a liquid drop and rough surfaces using a conventional atomic force microscope. In this method, a micrometric liquid mercury drop is attached to an AFM tipless cantilever to measure the force required to pull this drop off a rough surface. We test the method with two surfaces: a square array of nanometer-sized peaks commonly used for the determination of AFM tip sharpness and a multi-scaled rough diamond surface containing sub-micrometer protrusions. Measurements are carried out in a nitrogen atmosphere to avoid water capillary interactions. We obtain information about the average force of adhesion between a single peak or protrusion and the liquid drop. This procedure could provide useful microscopic information to improve our understanding of wetting phenomena on rough surfaces.

  9. Revolutionary diagnostic method using rotating atomic nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Frese, W.

    1986-01-23

    Nuclear tomography, a newcomer in medical diagnostics, has rapidly gained ground and recently achieved a decisive success: Electronic sectional images of the body which hitherto took measuring times of several minutes now can be obtained within only a few seconds. This jump in time has been earned by experts of the Goettingen Max Planck Institute for biophysical chemistry who puzzled out the significant modification of the method, which offers completely new insight to clinical diagnostics. One advantage is that nuclear magnetic resonance imaging - as the method also is called - allows dynamic processes to be made visible, and not only the movements of anatomic structures such as the heart, but indeed also physiological processes such as renal excretion. The other decisive improvement is that three-dimensional images of tissue and organs can be obtained. And on top of it all, nuclear magnetic resonance imaging does not invade the patient's body with harmful radiation.

  10. Revolutionary diagnostic method using rotating atomic nuclei

    International Nuclear Information System (INIS)

    Frese, W.

    1986-01-01

    Nuclear tomography, a newcomer in medical diagnostics, has rapidly gained ground and recently achieved a decisive success: Electronic sectional images of the body which hitherto took measuring times of several minutes now can be obtained within only a few seconds. This jump in time has been earned by experts of the Goettingen Max Planck Institute for biophysical chemistry who puzzled out the significant modification of the method, which offers completely new insight to clinical diagnostics. One advantage is that nuclear magnetic resonance imaging - as the method also is called - allows dynamic processes to be made visible, and not only the movements of anatomic structures such as the heart, but indeed also physiological processes such as renal excretion. The other decisive improvement is that three-dimensional images of tissue and organs can be obtained. And on top of it all, nuclear magnetic resonance imaging does not invade the patient's body with harmful radiation. (orig./MG) [de

  11. Impact of dynamic specimen shape evolution on the atom probe tomography results of doped epitaxial oxide multilayers: Comparison of experiment and simulation

    Energy Technology Data Exchange (ETDEWEB)

    Madaan, Nitesh; Nandasiri, Manjula; Devaraj, Arun, E-mail: arun.devaraj@pnnl.gov [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 3335 Innovation Boulevard, Richland, Washington 99354 (United States); Bao, Jie [Energy and Environment Directorate, Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99354 (United States); Xu, Zhijie [Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99354 (United States); Thevuthasan, Suntharampillai [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 3335 Innovation Boulevard, Richland, Washington 99354 (United States); Qatar Environment and Energy Research Institute, Qatar Foundation, PO Box 5825, Doha (Qatar)

    2015-08-31

    The experimental atom probe tomography (APT) results from two different specimen orientations (top-down and sideways) of a high oxygen ion conducting Samaria-doped-ceria/Scandia-stabilized-zirconia multilayer thin film solid oxide fuel cell electrolyte was compared with level-set method based field evaporation simulations for the same specimen orientations. This experiment-simulation comparison explains the dynamic specimen shape evolution and ion trajectory aberrations that can induce density artifacts in final reconstruction, leading to inaccurate estimation of interfacial intermixing. This study highlights the importance of comparing experimental results with field evaporation simulations when using APT to study oxide heterostructure interfaces.

  12. Development of laser excited atomic fluorescence and ionization methods

    International Nuclear Information System (INIS)

    Winefordner, J.D.

    1991-01-01

    Progress report: May 1, 1988 to December 31, 1991. The research supported by DE-FG05-88ER13881 during the past (nearly) 3 years can be divided into the following four categories: (1) theoretical considerations of the ultimate detection powers of laser fluorescence and laser ionization methods; (2) experimental evaluation of laser excited atomic fluorescence; (3) fundamental studies of atomic and molecular parameters in flames and plasmas; (4) other studies

  13. Probing atomic-size defects and free volumes with positron and positronium

    International Nuclear Information System (INIS)

    Dolveck, J.Y.; Moser, P.; Guo-Huan Dai

    1992-01-01

    The lifetime measurement of positrons injected in a metal allows to investigate defects of atomic dimension. Many crucial problems in metallurgy have found their solutions by the positron annihilation (PA) techniques for about three decades. Application to semiconductors research has been developed in recent years. Specific theory and analysing method can be used in the studies of the free-volume hole in polymers, the size of the empty spaces being between 0.3 and 1.5 nanometers. In many insulating materials, the diffusing positron can trap an electron and form a metastable positronium (Ps). Like a gas bubble, the Ps atom may diffuse and get trapped by the free-volume hole. When this mechanism is governing, lifetimes over the range of 1-10 ns are well observable and a correspondence exists between the positronium lifetime and minimum diameter of the trapping open space. Example of application is given in a study of polyimide membranes used for gas separation. A good correlation is revealed between the Ps lifetime and H 2 and/or CH 4 permeabilities. Recent progress in polymers research is also reviewed

  14. Atomic power plant and its operation method

    International Nuclear Information System (INIS)

    Yamamoto, Fumiaki; Higashio, Satoru.

    1986-01-01

    Purpose: To improve operation performance by partially restraining local over power in the axial power distribution of the reactor core by properly controlling the reactor pressure and furthermore by smoothly and properly performing reactor start-up operation in a short time while maintaining fuel integrity. Method: With the reactor pressure input to the pressure controller from the pressure detector, the valve opening of the main steam adjusting valve is adjusted so that the pressure will decrease when the reactor is started up. Also the adjusting valve is controlled so that the pressure will be lower than the set value of rated pressure, thus changing the axial distribution of void. In the meantime, with the stored state of xenon stored along with the increase of reactor power taken into consideration, the reactor pressure is increased as high as the rated value until the reactor power reaches to the rated power, thereby alleviating the local increase of reactor power without changing the whole reactor power and also enabling substantial reduction of reactor start-up time while maintaining reactor integrity. (Horiuchi, T.)

  15. Inhomogeneous distribution of manganese atoms in ferromagnetic ZnSnAs{sub 2}:Mn thin films on InP revealed by three-dimensional atom probe investigation

    Energy Technology Data Exchange (ETDEWEB)

    Uchitomi, Naotaka, E-mail: uchitomi@nagaokaut.ac.jp; Inoue, Hiroaki; Kato, Takahiro; Toyota, Hideyuki [Nagaoka University of Technology, 1603-1 Kamitomioka-cho, Nagaoka 940-2188 (Japan); Uchida, Hiroshi [Toshiba Nanoanalysis Corporation, 8 Shinsugita-cho, Isogo-ku, Yokohama 235-8522 (Japan)

    2015-05-07

    Atomic-scale Mn distributions in ferromagnetic ZnSnAs{sub 2}:Mn thin films grown on InP substrates have been studied by applying three-dimensional atom probe (3DAP) microscopy. It is found that Mn atoms in cross-sectional 3DAP maps show the presence of inhomogeneities in Mn distribution, which is characteristic patterns of a spinoidal decomposition phase with slightly high and low concentration regions. The high Mn concentration regions are expected to be coherently clustered MnAs in the zinc-blende structure, resulting in the formation of Mn-As random connecting patterns. The origin of room-temperature ferromagnetism in ZnSnAs{sub 2}:Mn on InP can be well explained by the formation of atomic-scale magnetic clustering by spinoidal decomposition without breaking the continuity of the zinc-blende structure, which has been suggested by previous theoretical works. The lattice-matching between magnetic epi-layers and substrates should be one of the most important factors to avoid the formation of secondary hexagonal MnAs phase precipitates in preparing ferromagnetic semiconductor thin films.

  16. Characterization of local hydrophobicity on sapphire (0001) surfaces in aqueous environment by colloidal probe atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wada, Tomoya; Yamazaki, Kenji; Isono, Toshinari; Ogino, Toshio, E-mail: ogino-toshio-rx@ynu.ac.jp

    2017-02-28

    Highlights: • Local hydrophobicity of phase-separated sapphire (0001) surfaces was investigated. • These surfaces are featured by coexistence of hydrophilic and hydrophobic domains. • Each domain was characterized by colloidal probe atomic force microscopy in water. • Both domains can be distinguished by adhesive forces of the probe to the surfaces. • Characterization in aqueous environment is important in bio-applications of sapphire. - Abstract: Sapphire (0001) surfaces exhibit a phase-separation into hydrophobic and hydrophilic domains upon high-temperature annealing, which were previously distinguished by the thickness of adsorbed water layers in air using atomic force microscopy (AFM). To characterize their local surface hydrophobicity in aqueous environment, we used AFM equipped with a colloidal probe and measured the local adhesive force between each sapphire domain and a hydrophilic SiO{sub 2} probe surface, or a hydrophobic polystyrene one. Two data acquisition modes for statistical analyses were used: one is force measurements at different positions of the surface and the other repeated measurement at a fixed position. We found that adhesive force measurements using the polystyrene probe allow us to distinctly separate the hydrophilic and hydrophobic domains. The dispersion in the force measurement data at different positions of the surface is larger than that in the repeated measurements at a fixed position. It indicates that the adhesive force measurement is repeatable although their data dispersion for the measurement positions is relatively large. From these results, we can conclude that the hydrophilic and hydrophobic domains on the sapphire (0001) surfaces are distinguished by a difference in their hydration degrees.

  17. The effect orientation of features in reconstructed atom probe data on the resolution and measured composition of T1 plates in an A2198 aluminium alloy.

    Science.gov (United States)

    Mullin, Maria A; Araullo-Peters, Vicente J; Gault, Baptiste; Cairney, Julie M

    2015-12-01

    Artefacts in atom probe tomography can impact the compositional analysis of microstructure in atom probe studies. To determine the integrity of information obtained, it is essential to understand how the positioning of features influences compositional analysis. By investigating the influence of feature orientation within atom probe data on measured composition in microstructural features within an AA2198 Al alloy, this study shows differences in the composition of T1 (Al2CuLi) plates that indicates imperfections in atom probe reconstructions. The data fits a model of an exponentially-modified Gaussian that scales with the difference in evaporation field between solutes and matrix. This information provides a guide for obtaining the most accurate information possible. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. MPAI (mass probes aided ionization) method for total analysis of biomolecules by mass spectrometry.

    Science.gov (United States)

    Honda, Aki; Hayashi, Shinichiro; Hifumi, Hiroki; Honma, Yuya; Tanji, Noriyuki; Iwasawa, Naoko; Suzuki, Yoshio; Suzuki, Koji

    2007-01-01

    We have designed and synthesized various mass probes, which enable us to effectively ionize various molecules to be detected with mass spectrometry. We call the ionization method using mass probes the "MPAI (mass probes aided ionization)" method. We aim at the sensitive detection of various biological molecules, and also the detection of bio-molecules by a single mass spectrometry serially without changing the mechanical settings. Here, we review mass probes for small molecules with various functional groups and mass probes for proteins. Further, we introduce newly developed mass probes for proteins for highly sensitive detection.

  19. Measuring the homogeneity of Bi(2223)/Ag tapes by four-probe method and a Hall probe array

    International Nuclear Information System (INIS)

    Kovac, P.

    1999-01-01

    The nature of the BSCCO compound and application of the powder-in-tube technique usually lead to non-uniform quality across and/or along the ceramic fibres and finally to variations in the critical current and its irregular distribution in the Bi(2223)/Ag tape. Therefore, the gliding four-probe method and contactless field monitoring measurements have been used for homogeneity studies. The gliding potential contacts moved along the tape surface and a sensitive system based on an integrated Hall probe array containing 16 or 19 in-line probes supported by PC-compatible electronics with software allowed us to make a comparison of contact and contactless measurements at any elements of Bi(2223)/Ag sample. The results of both methods show very good correlation and the possibility of using a sensitive Hall probe array for monitoring the final quality of Bi(2223)/Ag tapes. (author)

  20. Atomic-scale investigation of ε and θ precipitates in bainite in 100Cr6 bearing steel by atom probe tomography and ab initio calculations

    International Nuclear Information System (INIS)

    Song, W.; Appen, J. von; Choi, P.; Dronskowski, R.; Raabe, D.; Bleck, W.

    2013-01-01

    Carbide precipitation during upper and lower bainite formation in high-carbon bearing steel 100Cr6 is characterized using transmission electron microscopy and atom probe tomography. The results reveal that both ε and θ carbides precipitate in lower bainite isothermally held at 260 °C and only θ precipitates form in upper bainite isothermally held at 500 °C. ε and θ precipitate under paraequilibrium condition at 260 °C in lower bainite and θ precipitates under negligible partitioning local equilibrium condition in upper bainite at 500 °C. In order to theoretically study ε and θ precipitation and the ε → θ transition in bainite, thermodynamic calculations have been carried out using ab initio techniques. We find that ε and θ carbides in ferrite have almost identical thermodynamic stability, and hence have similar formation probability. In austenite, however, cementite formation is clearly preferred: it is favored by 5 kJ mol −1 at room temperature and still by 4 kJ mol −1 at 500 °C. Hence, the thermodynamic predictions agree well with the atom probe tomography results

  1. Atom-probe field-ion microscope for the study of the interaction of impurity atoms or alloying elements with defects

    International Nuclear Information System (INIS)

    Wagner, A.; Hall, T.M.; Seidman, D.N.

    1976-10-01

    A time-of-flight (TOF) atom-probe field-ion microscope (FIM) designed for the study of defects is described. This atom probe features: (1) a variable magnification internal-image-intensification system; (2) a liquid-helium goniometer stage; (3) a low-energy (less than or equal 3 keV) gas-ion gun for in-situ irradiations; (4) an ultra-high vacuum (approximately 3.10 -10 torr) chamber; (5) a high vacuum (approximately 10 -6 torr) specimen-exchange device; (6) a Chevron ion detector; and (7) an eight-channel digital timer with a +-10 nsec resolution for measuring the TOFs. The entire process of applying the evaporation pulse to the specimen, measuring the voltages, and analyzing the TOF data is controlled by a computer. With this system we can record and analyze 600 TOFmin. Results on unirradiated specimens of molybdenum, tungsten, W/25 at. % Re, Mo/1.0 at. % Ti, Mo/1.0 at. % Ti/0.08 at. % Zr and a special low swelling stainless steel alloy (LS1A) demonstrate the instrument's ability to quantitatively determine concentrations at the 5.10 -4 at fr level and to determine their spatial distribution with a resolution of a few angstroms

  2. Method of producing excited states of atomic nuclei

    International Nuclear Information System (INIS)

    Morita, M.; Morita, R.

    1976-01-01

    A method is claimed of producing excited states of atomic nuclei which comprises bombarding atoms with x rays or electrons, characterized in that (1) in the atoms selected to be produced in the excited state of their nuclei, (a) the difference between the nuclear excitation energy and the difference between the binding energies of adequately selected two electron orbits is small enough to introduce the nuclear excitation by electron transition, and (b) the system of the nucleus and the electrons in the case of ionizing an orbital electron in said atoms should satisfy the spin and parity conservation laws; and (2) the energy of the bombarding x rays or electrons should be larger than the binding energy of one of the said two electron orbits which is located at shorter distance from the atomic nucleus. According to the present invention, atomic nuclei can be excited in a relatively simple manner without requiring the use of large scale apparatus, equipment and production facilities, e.g., factories. It is also possible to produce radioactive substances or separate a particular isotope with an extremely high purity from a mixture of isotopes by utilizing nuclear excitation

  3. Parameter sensitivity analysis of nonlinear piezoelectric probe in tapping mode atomic force microscopy for measurement improvement

    Energy Technology Data Exchange (ETDEWEB)

    McCarty, Rachael; Nima Mahmoodi, S., E-mail: nmahmoodi@eng.ua.edu [Department of Mechanical Engineering, The University of Alabama, Box 870276, Tuscaloosa, Alabama 35487 (United States)

    2014-02-21

    The equations of motion for a piezoelectric microcantilever are derived for a nonlinear contact force. The analytical expressions for natural frequencies and mode shapes are obtained. Then, the method of multiple scales is used to analyze the analytical frequency response of the piezoelectric probe. The effects of nonlinear excitation force on the microcantilever beam's frequency and amplitude are analytically studied. The results show a frequency shift in the response resulting from the force nonlinearities. This frequency shift during contact mode is an important consideration in the modeling of AFM mechanics for generation of more accurate imaging. Also, a sensitivity analysis of the system parameters on the nonlinearity effect is performed. The results of a sensitivity analysis show that it is possible to choose parameters such that the frequency shift minimizes. Certain parameters such as tip radius, microcantilever beam dimensions, and modulus of elasticity have more influence on the nonlinearity of the system than other parameters. By changing only three parameters—tip radius, thickness, and modulus of elasticity of the microbeam—a more than 70% reduction in nonlinearity effect was achieved.

  4. Irradiation-induced precipitates in a neutron irradiated 304 stainless steel studied by three-dimensional atom probe

    Energy Technology Data Exchange (ETDEWEB)

    Toyama, T., E-mail: ttoyama@imr.tohoku.ac.jp [International Research Center for Nuclear Materials Science, Institute for Materials Research, Tohoku University, Narita-cho 2145-2, Oarai, Ibaraki 311-1313 (Japan); Nozawa, Y. [International Research Center for Nuclear Materials Science, Institute for Materials Research, Tohoku University, Narita-cho 2145-2, Oarai, Ibaraki 311-1313 (Japan); Van Renterghem, W. [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, 2400 Mol (Belgium); Matsukawa, Y.; Hatakeyama, M.; Nagai, Y. [International Research Center for Nuclear Materials Science, Institute for Materials Research, Tohoku University, Narita-cho 2145-2, Oarai, Ibaraki 311-1313 (Japan); Al Mazouzi, A. [EDF R and D, Avenue des Renardieres Ecuelles, 77818 Moret sur Loing Cedex (France); Van Dyck, S. [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, 2400 Mol (Belgium)

    2011-11-15

    Highlights: > Irradiation-induced precipitates in a 304 stainless steel were investigated by three-dimensional atom probe. > The precipitates were found to be {gamma}' precipitates (Ni{sub 3}Si). > Post-irradiation annealing was performed to discuss the contribution of the precipitates to irradiation-hardening. - Abstract: Irradiation-induced precipitates in a 304 stainless steel, neutron-irradiated to a dose of 24 dpa at 300 deg. C in the fuel wrapper plates of a commercial pressurized water reactor, were investigated by laser-assisted three-dimensional atom probe. A high number density of 4 x 10{sup 23} m{sup -3} of Ni-Si rich precipitates was observed, which is one order of magnitude higher than that of Frank loops. The average diameter was {approx}10 nm and the average chemical composition was 40% Ni, 14% Si, 11% Cr and 32% Fe in atomic percent. Over a range of Si concentrations, the ratio of Ni to Si was {approx}3, close to that of {gamma}' precipitate (Ni{sub 3}Si). In some precipitates, Mn enrichment inside the precipitate and P segregation at the interface were observed. Post-irradiation annealing was performed to discuss the contribution of the precipitates to irradiation-hardening.

  5. Pump-probe study of the formation of rubidium molecules by ultrafast photoassociation of ultracold atoms

    Science.gov (United States)

    McCabe, David J.; England, Duncan G.; Martay, Hugo E. L.; Friedman, Melissa E.; Petrovic, Jovana; Dimova, Emiliya; Chatel, Béatrice; Walmsley, Ian A.

    2009-09-01

    An experimental pump-probe study of the photoassociative creation of translationally ultracold rubidium molecules is presented together with numerical simulations of the process. The formation of loosely bound excited-state dimers is observed as a first step toward a fully coherent pump-dump approach to the stabilization of Rb2 into its lowest ground vibrational states. The population that contributes to the pump-probe process is characterized and found to be distinct from a background population of preassociated molecules.

  6. An analytical method for computing atomic contact areas in biomolecules.

    Science.gov (United States)

    Mach, Paul; Koehl, Patrice

    2013-01-15

    We propose a new analytical method for detecting and computing contacts between atoms in biomolecules. It is based on the alpha shape theory and proceeds in three steps. First, we compute the weighted Delaunay triangulation of the union of spheres representing the molecule. In the second step, the Delaunay complex is filtered to derive the dual complex. Finally, contacts between spheres are collected. In this approach, two atoms i and j are defined to be in contact if their centers are connected by an edge in the dual complex. The contact areas between atom i and its neighbors are computed based on the caps formed by these neighbors on the surface of i; the total area of all these caps is partitioned according to their spherical Laguerre Voronoi diagram on the surface of i. This method is analytical and its implementation in a new program BallContact is fast and robust. We have used BallContact to study contacts in a database of 1551 high resolution protein structures. We show that with this new definition of atomic contacts, we generate realistic representations of the environments of atoms and residues within a protein. In particular, we establish the importance of nonpolar contact areas that complement the information represented by the accessible surface areas. This new method bears similarity to the tessellation methods used to quantify atomic volumes and contacts, with the advantage that it does not require the presence of explicit solvent molecules if the surface of the protein is to be considered. © 2012 Wiley Periodicals, Inc. Copyright © 2012 Wiley Periodicals, Inc.

  7. Numerical modeling of probe velocity effects for electromagnetic NDE methods

    Science.gov (United States)

    Shin, Y. K.; Lord, W.

    The present discussion of magnetic flux (MLF) leakage inspection introduces the behavior of motion-induced currents. The results obtained indicate that velocity effects exist at even low probe speeds for magnetic materials, compelling the inclusion of velocity effects in MLF testing of oil pipelines, where the excitation level and pig speed are much higher than those used in the present work. Probe velocity effect studies should influence probe design, defining suitable probe speed limits and establishing training guidelines for defect-characterization schemes.

  8. Atomic and magnetic configurational energetics by the generalized perturbation method

    DEFF Research Database (Denmark)

    Ruban, Andrei V.; Shallcross, Sam; Simak, S.I.

    2004-01-01

    in the framework of the Korringa-Kohn-Rostoker method within the atomic sphere and coherent potential approximations. This is demonstrated with calculations of ordering energies, short-range order parameters, and transition temperatures in the CuZn, CuAu, CuPd, and PtCo systems. Furthermore, we show that the GPM...

  9. Using muonium to probe the kinetics of the reaction between the H atom and OH"- in superheated water

    International Nuclear Information System (INIS)

    Ghandi, K.; Alcorn, C.; Brodovitch, J.-C.; Driedger, E.; Mozafari, M.; Percival, P.W.

    2011-01-01

    Operation of a supercritical-water-cooled nuclear reactor requires knowledge of water chemistry over a wide range of conditions. The considerable knowledge gap for conditions above the operating temperature of current-generation CANDU reactors is the target of this study. Since the H atom is difficult to probe at the desired temperatures and pressures, muonium is used as an alternative. In the current CANDU reactors, coolant pH is controlled using LiOH. We are studying how the rate constants for the reaction of muonium with LiOH and NaOH change with temperature and pressure. (author)

  10. Using muonium to probe the kinetics of the reaction between the H atom and OH{sup -} in superheated water

    Energy Technology Data Exchange (ETDEWEB)

    Ghandi, K.; Alcorn, C. [Mount Allison Univ., Sackville, NB (Canada); Brodovitch, J.-C. [Simon Fraser Univ., Burnaby, BC (Canada); Driedger, E. [Mount Allison Univ., Sackville, NB (Canada); Mozafari, M. [Simon Fraser Univ., Burnaby, BC (Canada); Percival, P.W. [Simon Fraser Univ., Burnaby, BC (Canada); TRIUMF, Vancouver, BC (Canada)

    2011-07-01

    Operation of a supercritical-water-cooled nuclear reactor requires knowledge of water chemistry over a wide range of conditions. The considerable knowledge gap for conditions above the operating temperature of current-generation CANDU reactors is the target of this study. Since the H atom is difficult to probe at the desired temperatures and pressures, muonium is used as an alternative. In the current CANDU reactors, coolant pH is controlled using LiOH. We are studying how the rate constants for the reaction of muonium with LiOH and NaOH change with temperature and pressure. (author)

  11. Long-term thermal stability of nanoclusters in ODS-Eurofer steel: An atom probe tomography study

    Science.gov (United States)

    Zilnyk, K. D.; Pradeep, K. G.; Choi, P.; Sandim, H. R. Z.; Raabe, D.

    2017-08-01

    Oxide-dispersion strengthened materials are important candidates for several high-temperature structural applications in advanced nuclear power plants. Most of the desirable mechanical properties presented by these materials are due to the dispersion of stable nanoparticles in the matrix. Samples of ODS-Eurofer steel were annealed for 4320 h (6 months) at 800 °C. The material was characterized using atom probe tomography in both conditions (prior and after heat treatment). The particles number density, size distribution, and chemical compositions were determined. No significant changes were observed between the two conditions indicating a high thermal stability of the Y-rich nanoparticles at 800 °C.

  12. Atom probe microscopy investigation of Mg site occupancy within δ′ precipitates in an Al–Mg–Li alloy

    International Nuclear Information System (INIS)

    Gault, Baptiste; Cui, Xiang Yuan; Moody, Michael P.; De Geuser, Frederic; Sigli, Christophe; Ringer, Simon P.; Deschamps, Alexis

    2012-01-01

    The composition and site occupancy of Mg within ordered δ′ precipitates in a model Al–Mg–Li alloy have been characterized by atom probe microscopy and first-principles simulations. The concentration in the precipitates is found to be almost the same as that of the matrix; however, we show evidence that Mg partitions to the sites normally occupied by Li in the L1 2 structure. Density functional calculations demonstrate that this partitioning is energetically favorable, in agreement with experimental results.

  13. CD2 probe infrared method for determining polymethylene chain conformation

    International Nuclear Information System (INIS)

    Maroncelli, M.; Strauss, H.L.; Snyder, R.G.

    1985-01-01

    The rocking mode frequency of a CD 2 group substituted in a polymethylene chain is sensitive to conformation in the immediate vicinity of the CD 2 group. This sensitivity forms the basis of a commonly used infrared method for determining site-specific conformation in polymethylene systems. In the present work, the CD 2 probe method has been extended and quantified with the use of infrared data on model CD 2 -substituted n-alkanes. The frequency of the CD 2 rocking band is determined primarily by the conformation of adjoining CC bonds, i.e., by tt, gt, and gg pairs. However, we have found that there are significant frequency shifts associated with other factors. These include the conformation of the next nearest CC bonds, both with the CD 2 positioned at the end and in the interior of the chain, and chain length. In addition, the ratio of the absorptivities of the tt to gt bands has been established. These results enable the method to provide new details about the conformation of the chains in polymethylene systems and reliable estimates of the concentrations of specific kinds of short conformational sequences. 14 references, 6 figures, 2 tables

  14. Monolayer dispersion of CoO on Al2O3 probed by positronium atom

    International Nuclear Information System (INIS)

    Liu, Z.W.; Zhang, H.J.; Chen, Z.Q.

    2014-01-01

    CoO/Al 2 O 3 catalysts were prepared by wet impregnation method with CoO contents ranging from 0 wt% to 24 wt%. X-ray diffraction and X-ray photoelectron spectroscopy measurements suggest formation of CoO after calcined in N 2 . Quantitative X-ray diffraction analysis indicates monolayer dispersion capacity of CoO in CoO/Al 2 O 3 catalysts to be about 3 wt%. Positron annihilation lifetime and coincidence Doppler broadening measurements were performed to study the dispersion state of CoO on Al 2 O 3 . The positron lifetime measurements reveal two long lifetime components τ 3 and τ 4 , which correspond to ortho-positronium annihilation lifetime in microvoids and large pores, respectively. It was found that the positronium atom is very sensitive to the dispersion state of CoO on Al 2 O 3 . The presence of CoO significantly decreases both the lifetime and the intensity of τ 4 . Detailed analysis of the coincidence Doppler broadening measurements suggests that with the CoO content lower than the monolayer dispersion, spin conversion reaction of positronium is induced by CoO. When the cobalt content is higher than the monolayer dispersion capacity, inhibition of positronium formation becomes the dominate effect.

  15. The all-too-flexible abductive method: ATOM's normative status.

    Science.gov (United States)

    Romeijn, Jan-Willem

    2008-09-01

    The author discusses the abductive theory of method (ATOM) by Brian Haig from a philosophical perspective, connecting his theory with a number of issues and trends in contemporary philosophy of science. It is argued that as it stands, the methodology presented by Haig is too permissive. Both the use of analogical reasoning and the application of exploratory factor analysis leave us with too many candidate theories to choose from, and explanatory coherence cannot be expected to save the day. The author ends with some suggestions to remedy the permissiveness and lack of normative force in ATOM, deriving from the experimental practice within which psychological data are produced.

  16. Characterization of microstructural evolution in Fe-C(-Mn) alloys during early stages of ageing using atom probe

    International Nuclear Information System (INIS)

    Xiong, X.Y.; Tran, P.; Pereloma, E.; Ringer, S.P.

    2004-01-01

    Full text: Extensive studies on the effect of ageing treatment on the micro structure and mechanical properties of most commercial ferritic (a) Fe-C(-X) alloys reveal age-hardening characteristics that involve a monotonic increase towards a peak hardness after several hours of ageing. Peak hardness is always associated with the formation of precipitate particles (e.g: MnC 3 ). However, there is relatively little systematic work on the very early stages of ageing using direct nanostructural analysis and many questions remain on the potential for clustering of interstitial C atoms prior to the precipitation reaction. In this experimental work, we report a small but significant hardness peak within 300 sec during ageing at 550 deg C. High resolution transmission electron microscopy (HRTEM) observations did not show any microstructural change during this early stage of ageing. In order to understand the microstructural evolution in ultra-low carbon a-Fe-C(-Mn) alloys during these early stages of ageing, 3-dimensional atom probe (3DAP) has been used to examine the C atom distribution and possible segregation of C and Mn atoms in these alloys. In this report, the 3DAP analyses and HRTEM observations of Fe-C and Fe-C-Mn alloys are correlated with age hardening measurements and possible mechanisms of the initial hardening phenomenon will be discussed

  17. Atom probe tomographic studies of precipitation in Al-0.1Zr-0.1Ti (at.%) alloys.

    Science.gov (United States)

    Knipling, Keith E; Dunand, David C; Seidman, David N

    2007-12-01

    Atom probe tomography was utilized to measure directly the chemical compositions of Al(3)(Zr(1)-(x)Ti(x)) precipitates with a metastable L1(2) structure formed in Al-0.1Zr-0.1Ti (at.%) alloys upon aging at 375 degrees C or 425 degrees C. The alloys exhibit an inhomogeneous distribution of Al(3)(Zr(1)-(x)Ti(x)) precipitates, as a result of a nonuniform dendritic distribution of solute atoms after casting. At these aging temperatures, the Zr:Ti atomic ratio in the precipitates is about 10 and 5, respectively, indicating that Ti remains mainly in solid solution rather than partitioning to the Al(3)(Zr(1)-(x)Ti(x)) precipitates. This is interpreted as being due to the very small diffusivity of Ti in alpha-Al, consistent with prior studies on Al-Sc-Ti and Al-Sc-Zr alloys, where the slower diffusing Zr and Ti atoms make up a small fraction of the Al(3)(Zr(1)-(x)Ti(x)) precipitates. Unlike those alloys, however, the present Al-Zr-Ti alloys exhibit no interfacial segregation of Ti at the matrix/precipitate heterophase interface, a result that may be affected by a significant disparity in the evaporation fields of the alpha-Al matrix and Al(3)(Zr(1)-(x)Ti(x)) precipitates and/or a lack of local thermodynamic equilibrium at the interface.

  18. NMR Chemical Shift of a Helium Atom as a Probe for Electronic Structure of FH, F-, (FHF)-, and FH2.

    Science.gov (United States)

    Tupikina, E Yu; Efimova, A A; Denisov, G S; Tolstoy, P M

    2017-12-21

    In this work, we present the first results of outer electronic shell visualization by using a 3 He atom as a probe particle. As model objects we have chosen F - , FH, and FH 2 + species, as well as the hydrogen-bonded complex FH···F - at various H···F - distances (3.0, 2.5, 2.0, and 1.5 Å and equilibrium at ca. 1.14 Å). The interaction energy of investigated objects with helium atom (CCSD/aug-cc-pVTZ) and helium atom chemical shift (B3LYP/pcS-2) surfaces were calculated, and their topological analysis was performed. For comparison, the results of standard quantum mechanical approaches to electronic shell visualization were presented (ESP, ELF, ED, ∇ 2 ED). We show that the Laplacian of helium chemical shift, ∇ 2 δ He , is sensitive to fluorine atom lone pair localization regions, and it can be used for the visualization of the outer electronic shell, which could be used to evaluate the proton accepting ability. The sensitivity of ∇ 2 δ He to lone pairs is preserved at distances as large as 2.0-2.5 Å from the fluorine nucleus (in comparison with the distance to ESP minima, located at 1.0-1.5 Å or maxima of ELF, which are as close as 0.6 Å to the fluorine nucleus).

  19. Coaxial atomic force microscope probes for dielectrophoresis of DNA under different buffer conditions

    Science.gov (United States)

    Tao, Yinglei; Kumar Wickramasinghe, H.

    2017-02-01

    We demonstrate a coaxial AFM nanoprobe device for dielectrophoretic (DEP) trapping of DNA molecules in Tris-EDTA (TE) and phosphate-buffered saline (PBS) buffers. The DEP properties of 20 nm polystyrene beads were studied with coaxial probes in media with different conductivities. Due to the special geometry of our DEP probe device, sufficiently high electric fields were generated at the probe end to focus DNA molecules with positive DEP. DEP trapping for both polystyrene beads and DNA molecules was quantitatively analyzed over the frequency range from 100 kHz to 50 MHz and compared with the Clausius-Mossotti theory. Finally, we discussed the negative effect of medium salinity during DEP trapping.

  20. Probing the quantum analog of chaos with atoms in external fields

    Energy Technology Data Exchange (ETDEWEB)

    Gay, J C; Delande, D

    1987-01-01

    For a few years, considerable interest arose in the problem of the quantum analog of classical chaos for hamiltonian system. Among several other simple atomic physics systems, the atom in a magnetic field turns out to be the most promising prototype for tackling such questions. The classical and quantum motions are now well understood. The experimental study is possible in high Rydberg states of atoms. Throughout the study of some aspects of this problem, the authors demonstrate that the quantum analog of chaos presents a two-fold aspect. While the spectral properties at short range are conveniently described by Random matrix theories, a long-range order still exist in the quantum dynamics which indicates the existence of scars of symmetries. This in turn is quite clearly exhibited in the experimental data on Rydberg atoms. Finally the authors indicate how to generalize the notions to any situation involving the Coulomb field and perturbing potentials. 21 refs.; 8 figs.

  1. Method and apparatus for quantum information processing using entangled neutral-atom qubits

    Science.gov (United States)

    Jau, Yuan Yu; Biedermann, Grant; Deutsch, Ivan

    2018-04-03

    A method for preparing an entangled quantum state of an atomic ensemble is provided. The method includes loading each atom of the atomic ensemble into a respective optical trap; placing each atom of the atomic ensemble into a same first atomic quantum state by impingement of pump radiation; approaching the atoms of the atomic ensemble to within a dipole-dipole interaction length of each other; Rydberg-dressing the atomic ensemble; during the Rydberg-dressing operation, exciting the atomic ensemble with a Raman pulse tuned to stimulate a ground-state hyperfine transition from the first atomic quantum state to a second atomic quantum state; and separating the atoms of the atomic ensemble by more than a dipole-dipole interaction length.

  2. Direct measurement of surface-state conductance by microscopic four-point probe method

    DEFF Research Database (Denmark)

    Hasegawa, S.; Shiraki, I.; Tanikawa, T.

    2002-01-01

    For in situ measurements of local electrical conductivity of well defined crystal surfaces in ultrahigh vacuum, we have developed microscopic four-point probes with a probe spacing of several micrometres, installed in a scanning-electron - microscope/electron-diffraction chamber. The probe...... is precisely positioned on targeted areas of the sample surface by using piezoactuators. This apparatus enables conductivity measurement with extremely high surface sensitivity, resulting in direct access to surface-state conductivity of the surface superstructures, and clarifying the influence of atomic steps...

  3. Atoms

    International Nuclear Information System (INIS)

    Fuchs, Alain; Villani, Cedric; Guthleben, Denis; Leduc, Michele; Brenner, Anastasios; Pouthas, Joel; Perrin, Jean

    2014-01-01

    Completed by recent contributions on various topics (atoms and the Brownian motion, the career of Jean Perrin, the evolution of atomic physics since Jean Perrin, relationship between scientific atomism and philosophical atomism), this book is a reprint of a book published at the beginning of the twentieth century in which the author addressed the relationship between atomic theory and chemistry (molecules, atoms, the Avogadro hypothesis, molecule structures, solutes, upper limits of molecular quantities), molecular agitation (molecule velocity, molecule rotation or vibration, molecular free range), the Brownian motion and emulsions (history and general features, statistical equilibrium of emulsions), the laws of the Brownian motion (Einstein's theory, experimental control), fluctuations (the theory of Smoluchowski), light and quanta (black body, extension of quantum theory), the electricity atom, the atom genesis and destruction (transmutations, atom counting)

  4. Atom Probe Tomography Characterization of the Solute Distributions in a Neutron-Irradiated and Annealed Pressure Vessel Steel Weld

    Energy Technology Data Exchange (ETDEWEB)

    Miller, M.K.

    2001-01-30

    A combined atom probe tomography and atom probe field ion microscopy study has been performed on a submerged arc weld irradiated to high fluence in the Heavy-Section Steel irradiation (HSSI) fifth irradiation series (Weld 73W). The composition of this weld is Fe - 0.27 at. % Cu, 1.58% Mn, 0.57% Ni, 0.34% MO, 0.27% Cr, 0.58% Si, 0.003% V, 0.45% C, 0.009% P, and 0.009% S. The material was examined after five conditions: after a typical stress relief treatment of 40 h at 607 C, after neutron irradiation to a fluence of 2 x 10{sup 23} n m{sup {minus}2} (E > 1 MeV), and after irradiation and isothermal anneals of 0.5, 1, and 168 h at 454 C. This report describes the matrix composition and the size, composition, and number density of the ultrafine copper-enriched precipitates that formed under neutron irradiation and the change in these parameters with post-irradiation annealing treatments.

  5. Methods for Probing New Physics at High Energies

    Science.gov (United States)

    Denton, Peter B.

    This dissertation covers two broad topics. The title, " Methods for Probing New Physics at High Energies," hopefully encompasses both of them. The first topic is located in part I of this work and is about integral dispersion relations. This is a technique to probe for new physics at energy scales near to the machine energy of a collider. For example, a hadron collider taking data at a given energy is typically only sensitive to new physics occurring at energy scales about a factor of five to ten beneath the actual machine energy due to parton distribution functions. This technique is sensitive to physics happening directly beneath the machine energy in addition to the even more interesting case: directly above. Precisely where this technique is sensitive is one of the main topics of this area of research. The other topic is located in part II and is about cosmic ray anisotropy at the highest energies. The unanswered questions about cosmic rays at the highest energies are numerous and interconnected in complicated ways. What may be the first piece of the puzzle to fall into place is determining their sources. This work looks to determine if and when the use of spherical harmonics becomes sensitive enough to determine these sources. The completed papers for this work can be found online. For part I on integral dispersion relations see reference published in Physical Review D. For part II on cosmic ray anisotropy, there are conference proceedings published in the Journal of Physics: Conference Series. The analysis of the location of an experiment on anisotropy reconstruction is, and the comparison of different experiments' abilities to reconstruct anisotropies is published in The Astrophysical Journal and the Journal of High Energy Astrophysics respectively. While this dissertation is focused on three papers completed with Tom Weiler at Vanderbilt University, other papers were completed at the same time. The first was with Nicusor Arsene, Lauretiu Caramete, and

  6. Probing the atomic structure of metallic nanoclusters with the tip of a scanning tunneling microscope.

    Science.gov (United States)

    Schouteden, Koen; Lauwaet, Koen; Janssens, Ewald; Barcaro, Giovanni; Fortunelli, Alessandro; Van Haesendonck, Chris; Lievens, Peter

    2014-02-21

    Preformed Co clusters with an average diameter of 2.5 nm are produced in the gas phase and are deposited under controlled ultra-high vacuum conditions onto a thin insulating NaCl film on Au(111). Relying on a combined experimental and theoretical investigation, we demonstrate visualization of the three-dimensional atomic structure of the Co clusters by high-resolution scanning tunneling microscopy (STM) using a Cl functionalized STM tip that can be obtained on the NaCl surface. More generally, use of a functionalized STM tip may allow for systematic atomic structure determination with STM of nanoparticles that are deposited on metal surfaces.

  7. Reversal of atomic contrast in scanning probe microscopy on (111) metal surfaces

    Czech Academy of Sciences Publication Activity Database

    Ondráček, Martin; González, C.; Jelínek, Pavel

    2012-01-01

    Roč. 24, 08 (2012), 084003/1-084003/7 ISSN 0953-8984 R&D Projects: GA ČR(CZ) GPP204/11/P578; GA ČR GAP204/10/0952; GA ČR GA202/09/0545; GA MŠk(CZ) ME10076 Grant - others:AVČR(CZ) M100100904 Institutional research plan: CEZ:AV0Z10100521 Keywords : atomic force microscopy * metallic surfaces * atomic contrast * scanning tunneling microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.355, year: 2012 http://iopscience.iop.org/0953-8984/24/8/084003

  8. The variational method in the atomic structure calcularion

    International Nuclear Information System (INIS)

    Tomimura, A.

    1970-01-01

    The importance and limitations of variational methods on the atomic structure calculations is set into relevance. Comparisons are made to the Perturbation Theory. Ilustrating it, the method is applied to the H - , H + and H + 2 simple atomic structure systems, and the results are analysed with basis on the study of the associated essential eigenvalue spectrum. Hydrogenic functions (where the screening constants are replaced by variational parameters) are combined to construct the wave function with proper symmetry for each one of the systems. This shows the existence of a bound state for H - , but no conclusions can be made for the others, where it may or may not be necessary to use more flexible wave functions, i.e., with greater number of terms and parameters. (author) [pt

  9. Field ion microscopy and imaging atom-probe mass spectroscopy of superconducting YBa2Cu3O7/sub -//sub x/

    International Nuclear Information System (INIS)

    Kellogg, G.L.; Brenner, S.S.

    1987-01-01

    The structure and composition of the superconducting oxide YBa 2 Cu 3 O/sub 7-//sub x/ have been examined in atomic detail by field ion microscopy and imaging atom-probe mass spectroscopy. The field ion samples were prepared from hot-pressed disks of the oxide powders. Atomic resolution images were obtained with either argon or hydrogen as the imaging gas. Individual layers of atoms were observed which could be field evaporated in a uniform, layer-by-layer manner. Imaging atom-probe analysis of the field ion tips indicated a metal composition which varied noticeably from sample to sample and an oxygen concentration which was consistently much too low

  10. Dependence of EIA spectra on mutual coherence between coupling and probe fields in Cs atomic vapors

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Mi Rang; Kim, Kyoung Dae; Park, Hyun Deok; Kim, Jung Bog [Korea National University of Education, Chungwon (Korea, Republic of); Moon, Han Seb [Korea Research Institute of the Standards and Science, Taejon (Korea, Republic of)

    2002-03-01

    We observed the dependence of EIA spectra on the mutual coherence between the coupling and the probe fields in the D{sub 2}F{sub 9} = 4 {r_reversible} F{sub e} = 5 transition of Cs vapors at room temperature where the coupling and the probe fields were made from one laser source or two independent laser sources. By using one source having a high mutual coherence, we found EIA spectra linewidths much narrower than 0.1 {gamma} on the weak coupling field and the transparent spectra with linewidths narrower than 1 MHz within subnatural absorption on the strong coupling field. On the other hand, where the two sources which were nearly incoherent with each other were used, the absorption profiles showed the same dependence on the coupling power as the spectra for the one source, but their linewidths were broad, on the order of the natural linewidth.

  11. Variable scaling method and Stark effect in hydrogen atom

    International Nuclear Information System (INIS)

    Choudhury, R.K.R.; Ghosh, B.

    1983-09-01

    By relating the Stark effect problem in hydrogen-like atoms to that of the spherical anharmonic oscillator we have found simple formulas for energy eigenvalues for the Stark effect. Matrix elements have been calculated using 0(2,1) algebra technique after Armstrong and then the variable scaling method has been used to find optimal solutions. Our numerical results are compared with those of Hioe and Yoo and also with the results obtained by Lanczos. (author)

  12. Shot noise as a probe of spin-polarized transport through single atoms

    DEFF Research Database (Denmark)

    Burtzlaff, Andreas; Weismann, Alexander; Brandbyge, Mads

    2015-01-01

    Single atoms on Au(111) surfaces have been contacted with the Au tip of a low temperature scanning tunneling microscope. The shot noise of the current through these contacts has been measured up to frequencies of 120 kHz and Fano factors have been determined to characterize the transport channels...

  13. Ordering and site occupancy of D03 ordered Fe3Al-5 at%Cr evaluated by means of atom probe tomography

    International Nuclear Information System (INIS)

    Rademacher, Thomas; Al-Kassab, Talaat; Deges, Johannes; Kirchheim, Reiner

    2011-01-01

    Addition of ternary elements to the D0 3 ordered Fe 3 Al intermetallic phase is a general approach to optimise its mechanical properties. To understand the physical influences of such additions the determination of the probability of site occupancies of these additions on the lattice site and ordering parameters is of high interest. Some common experimental techniques such as X-ray diffraction or Atom Location by Channelling Enhanced Microanalysis (ALCHEMI) are usually applied to explore this interplay. Unfortunately, certain published results are partly inconsistent, imprecise or even contradictory. In this study, these aspects are evaluated systematically by atom probe tomography (APT) and a special data analysis method. Additionally, to account for possible field evaporation effects that can falsify the estimation of site occupancy and induce misinterpretations, APT evaporation sequences were also simulated. As a result, chromium occupies most frequently the next nearest neighbour sites of Al atoms and local ordering parameters could be achieved. -- Research highlights: → APT measurements of Fe 3 Al-Cr are systematically analysed to study ordering. → APT measurements are simulated using EAM to calculate binding energies. → Cr occupies next nearest neighbour sites of aluminium with at least 83% ordering. → Aluminium ordering is at least 92%

  14. Multiconfiguration Dirac-Fock method for atomic structure

    International Nuclear Information System (INIS)

    Sasaki, Ken

    1982-02-01

    The multiconfiguration Dirac-Fock method for calculating the atomic structure is reviewed in some detail. Being more comprehensive than the ones introduced in Desclaux's paper, the mathematical formulae derived in this review are more helpful to trace the thread of ideas and understand the algorithm in Desclaux's computer program which embodied the method. A detailed analysis is made on the restrictions on how the program is used, that is, on the fact that it does not apply to the problem where the configuration mixing occurs via the one-electron Hamiltonian. Finally, in conclusion, a way to overcome the difficulty is suggested. (author)

  15. Photoelectron spectra as a probe of double-core resonsance in two-electron atoms

    International Nuclear Information System (INIS)

    Grobe, R.; Haan, S.L.; Eberly, J.H.

    1996-01-01

    The authors calculate photoelectron spectra for a two-electron atom under the influence of two external driving fields, using an essential states formalism. They focus on the regime of so-called coherence transfer, in which electron-electron correlation transfers field-induced photo-coherence from one electron to the other. In the case studied here, two laser fields are resonant with coupled atomic transitions, in the manner familiar from three-level dark-state spectroscopy. Dynamical two electron effects are monitored via the photoelectron energy spectrum. The authors show that the distribution of the photoelectron energies can be singly, doubly or triply peaked depending on the relative laser intensities. The electron spectra are independent of the turn-on sequence of the fields

  16. Theoretical atomic-force-microscopy study of a stepped surface: Nonlocal effects in the probe

    International Nuclear Information System (INIS)

    Girard, C.

    1991-01-01

    The interaction force between a metallic tip and a nonplanar dielectric surface is derived from a nonlocal formalism. A general formulation is given for the case of a spherical tip of nanometer size and for surfaces of arbitrary shapes (stepped surfaces and single crystals adsorbed on a planar surface). The dispersion part of the attractive force is obtained from a nonlocal theory expressed in terms of generalized electric susceptibilities of the two constituents. Implications for atomic force microscopy in attractive modes are discussed. In this context, the present model indicates two different forms of corrugation: those due to the protuberance present on the tip leading to atomic corrugations; nanometer-sized corrugations detected in the attractive region by the spherical part of the tip

  17. Note: A scanning electron microscope sample holder for bidirectional characterization of atomic force microscope probe tips

    Energy Technology Data Exchange (ETDEWEB)

    Eisenstein, Alon; Goh, M. Cynthia [Department of Chemistry and Institute for Optical Sciences, University of Toronto, 80 St. George Street, Toronto M5S 3H6 (Canada)

    2012-03-15

    A novel sample holder that enables atomic force microscopy (AFM) tips to be mounted inside a scanning electron microscopy (SEM) for the purpose of characterizing the AFM tips is described. The holder provides quick and easy handling of tips by using a spring clip to hold them in place. The holder can accommodate two tips simultaneously in two perpendicular orientations, allowing both top and side view imaging of the tips by the SEM.

  18. Reaction (γ,2e) and (e,3e) as probe of electron correlation in atoms

    International Nuclear Information System (INIS)

    Amusia, M.Y.

    1995-01-01

    Cross sections of the (γ,2e) and (e,3e) reactions contain information about the two vacancy-energy spectrum and electron-pair correlations in initial and final states of the target atom. Physical pictures of these processes are presented for two- and many-electron atoms. The simplest mechanisms are discussed, demonstrating some features which await experimental confirmation. Attention is given to high photon energy and the relativistic energy region of these reactions. The energy distribution of outgoing relativistic electrons is qualitatively different from the nonrelativistic case. The origin and types of corrections to the simplest mechanisms, and possible means of their detection, are discussed. In addition, the role of different resonances: shape, giant, autoionizational, and Feshbach-type are considered. Results of calculations are compared with experimental data, mainly on double photoionization cross sections. Different possible objects as targets for the reactions are considered, including negative ions, excited atoms, molecules, and clusters. The modification of these reactions due to photon emission is discussed. The future of the domain is outlined

  19. Reactions (γ,2e) and (e,3e) as probes of electronic correlations in atoms

    International Nuclear Information System (INIS)

    Amusia, M.Ya.

    1993-01-01

    Cross sections of the (γ,2e) and (e,3e) reactions carry information on two vacancy energy spectrum and on electron pair correlations in initial and final states of the target atom. Physical pictures of these processes are presented for two- and many-electron atoms. Simplest mechanisms of them are discussed, demonstrating some features which are waiting for experimental confirmation. Attention is given to high photon energy and even to relativistic energy region of these reactions. The energy distribution of outgoing relativistic electrons is qualitatively different from what it is for the nonrelativistic case. Origin and types of corrections to the simplest mechanisms and possible means of their detection are discussed. Role of different resonances: shape, giant, autoionizational, and Feschbach-type are considered. Results of calculations are compared with experimental data, mainly on double photoionization cross sections. Different possible objects as targets for the reactions are mentioned, including negative ions, excited atoms, molecules and clusters. Modification of the type of these reactions due to rather probable emission of the photon is discussed. Future of the domain is outlined. (orig.)

  20. Large-scale atomic calculations using variational methods

    Energy Technology Data Exchange (ETDEWEB)

    Joensson, Per

    1995-01-01

    Atomic properties, such as radiative lifetimes, hyperfine structures and isotope shift, have been studied both theoretically and experimentally. Computer programs which calculate these properties from multiconfiguration Hartree-Fock (MCHF) and configuration interaction (CI) wave functions have been developed and tested. To study relativistic effects, a program which calculates hyperfine structures from multiconfiguration Dirac-Fock (MCDF) wave functions has also been written. A new method of dealing with radial non-orthogonalities in transition matrix elements has been investigated. This method allows two separate orbital sets to be used for the initial and final states, respectively. It is shown that, once the usual orthogonality restrictions have been overcome, systematic MCHF calculations are able to predict oscillator strengths in light atoms with high accuracy. In connection with recent high-power laser experiments, time-dependent calculations of the atomic response to intense laser fields have been performed. Using the frozen-core approximation, where the atom is modeled as an active electron moving in the average field of the core electrons and the nucleus, the active electron has been propagated in time under the influence of the laser field. Radiative lifetimes and hyperfine structures of excited states in sodium and silver have been experimentally determined using time-resolved laser spectroscopy. By recording the fluorescence light decay following laser excitation in the vacuum ultraviolet spectral region, the radiative lifetimes and hyperfine structures of the 7p{sup 2}P states in silver have been measured. The delayed-coincidence technique has been used to make very accurate measurements of the radiative lifetimes and hyperfine structures of the lowest 2P states in sodium and silver. 77 refs, 2 figs, 14 tabs.

  1. Large-scale atomic calculations using variational methods

    International Nuclear Information System (INIS)

    Joensson, Per.

    1995-01-01

    Atomic properties, such as radiative lifetimes, hyperfine structures and isotope shift, have been studied both theoretically and experimentally. Computer programs which calculate these properties from multiconfiguration Hartree-Fock (MCHF) and configuration interaction (CI) wave functions have been developed and tested. To study relativistic effects, a program which calculates hyperfine structures from multiconfiguration Dirac-Fock (MCDF) wave functions has also been written. A new method of dealing with radial non-orthogonalities in transition matrix elements has been investigated. This method allows two separate orbital sets to be used for the initial and final states, respectively. It is shown that, once the usual orthogonality restrictions have been overcome, systematic MCHF calculations are able to predict oscillator strengths in light atoms with high accuracy. In connection with recent high-power laser experiments, time-dependent calculations of the atomic response to intense laser fields have been performed. Using the frozen-core approximation, where the atom is modeled as an active electron moving in the average field of the core electrons and the nucleus, the active electron has been propagated in time under the influence of the laser field. Radiative lifetimes and hyperfine structures of excited states in sodium and silver have been experimentally determined using time-resolved laser spectroscopy. By recording the fluorescence light decay following laser excitation in the vacuum ultraviolet spectral region, the radiative lifetimes and hyperfine structures of the 7p 2 P states in silver have been measured. The delayed-coincidence technique has been used to make very accurate measurements of the radiative lifetimes and hyperfine structures of the lowest 2P states in sodium and silver. 77 refs, 2 figs, 14 tabs

  2. New Isotope Analysis Method: Atom Trap Mass Spectrometry

    International Nuclear Information System (INIS)

    Ko, Kwang Hoon; Park, Hyun Min; Han, Jae Min; Kim, Taek Soo; Cha, Yong Ho; Lim, Gwon; Jeong, Do Young

    2011-01-01

    Trace isotope analysis has been an important role in science, archaeological dating, geology, biology and nuclear industry. Some fission products such as Sr-90, Cs-135 and Kr-85 can be released to the environment when nuclear accident occurs and the reprocessing factory operates. Thus, the analysis of artificially produced radioactive isotopes has been of interest in nuclear industry. But it is difficult to detect them due to low natural abundance less then 10 -10 . In general, radio-chemical method has been applied to detect ultra-trace radio isotopes. But this method has disadvantages of long measurement time for long lived radioisotopes and toxic chemical process for the purification. The Accelerator Mass Spectrometer has high isotope selectivity, but the system is huge and its selectivity is affected by isobars. The laser based method, such as RIMS (Resonance Ionization Mass Spectrometry) has the advantage of isobar-effect free characteristics. But the system size is still huge for high isotope selective system. Recently, ATTA (Atom Trap Trace Analysis) has been successfully applied to detect ultra-trace isotope, Kr-81 and Kr-85. ATTA is the isobar-effect free detection with high isotope selectivity and the system size is small. However, it requires steady atomic beam source during detection, and is not allowed simultaneous detection of several isotopes. In this presentation, we introduce new isotope detection method which is a coupled method of Atom Trap Mass Spectrometry (ATMS). We expect that it can overcome the disadvantage of ATTA while it has both advantages of ATTA and mass spectrometer. The basic concept and the system design will be presented. In addition, the experimental status of ATMS will also be presented

  3. A New Method for Calibrating the Time Delay of a Piezoelectric Probe

    DEFF Research Database (Denmark)

    Hansen, Bengt Hurup

    1974-01-01

    A simple method for calibrating the time delay of a piezoelectric probe of the type often used in plasma physics is described.......A simple method for calibrating the time delay of a piezoelectric probe of the type often used in plasma physics is described....

  4. Charge Transport in Metal-Molecule-Metal Junctions Probed by Conducting Atomic Force Microscopy

    International Nuclear Information System (INIS)

    Lee, Min Hyung; Song, Hyunwook

    2013-01-01

    We have demonstrated a proof of intrinsic charge transport properties in alkanedithiol molecular junctions using a multiprobe approach combining a variety of transport techniques. The temperature-independent I(V) behavior and the correct exponential decay of conductance with respect to molecular length shows that the dominant charge transport mechanism is off-resonant tunneling. Length-dependent TVS measurements for the saturated alkane-dithiol series indicate that we did indeed probe a molecular system with CAFM. These results can provide stringent criteria to establish a valid molecular transport junction via a probabilistic measurement technique. In this study, we report a study of charge transport in alkanedithiol SAMs formed in metal-molecule-metal junctions using CAFM in combination with a variety of molecular transport techniques including temperature-and length-variable transport measurements and transition voltage spectroscopy. The main goal of this study is to probe the intrinsic transport properties of component molecules using CAFM, but not parasitic or defect-related effects

  5. Atom-probe field-ion microscopy investigation of CMSX-4 Ni-base superalloy laser beam welds

    International Nuclear Information System (INIS)

    Babu, S.S.; David, S.A.; Vitek, J.M.; Miller, M.K.

    1996-01-01

    CMSX-4 superalloy laser beam welds were investigated by transmission electron microscopy and atom probe field-ion microscopy (APFIM). The weld microstructure consisted of fine (10- to 50-nm) irregularly shaped γ' precipitates (0.65 to 0.75 volume fraction) within the γ matrix. APFIM compositions of the γ and γ' phases were found to be different from those in the base metal. Concentration profiles across the γ and γ' phases showed extensive variations of Cr, Co and Al concentrations as a function of distance within the γ phase. Calculated lattice misfits near the γ/γ' interface in the welds are positive values compared to the negative values for base metal. (orig.)

  6. Three dimensional atom probe study of Ni-base alloy/low alloy steel dissimilar metal weld interfaces

    International Nuclear Information System (INIS)

    Choi, Kyoung Joon; Shin, Sang Hun; Kim, Jong Jin; Jung, Ju Ang; Kim, Ji Hyun

    2012-01-01

    Three dimensional atom probe tomography (3D APT) is applied to characterize the dissimilar metal joint which was welded between the Ni-based alloy, Alloy 690 and the low alloy steel, A533 Gr. B, with Alloy 152 filler metal. While there is some difficulty in preparing the specimen for the analysis, the 3D APT has a truly quantitative analytical capability to characterize nanometer scale particles in metallic materials, thus its application to the microstructural analysis in multicomponent metallic materials provides critical information on the mechanism of nanoscale microstructural evolution. In this study, the procedure for 3D APT specimen preparation was established, and those for dissimilar metal weld interface were prepared near the fusion boundary by a focused ion beam. The result of the analysis in this study showed the precipitation of chromium carbides near the fusion boundary between A533 Gr. B and Alloy 152.

  7. Three dimensional atom probe study of Ni-base alloy/low alloy steel dissimilar metal weld interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Kyoung Joon; Shin, Sang Hun; Kim, Jong Jin; Jung, Ju Ang; Kim, Ji Hyun [Interdisciplinary School of Green Energy, Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)

    2012-08-15

    Three dimensional atom probe tomography (3D APT) is applied to characterize the dissimilar metal joint which was welded between the Ni-based alloy, Alloy 690 and the low alloy steel, A533 Gr. B, with Alloy 152 filler metal. While there is some difficulty in preparing the specimen for the analysis, the 3D APT has a truly quantitative analytical capability to characterize nanometer scale particles in metallic materials, thus its application to the microstructural analysis in multicomponent metallic materials provides critical information on the mechanism of nanoscale microstructural evolution. In this study, the procedure for 3D APT specimen preparation was established, and those for dissimilar metal weld interface were prepared near the fusion boundary by a focused ion beam. The result of the analysis in this study showed the precipitation of chromium carbides near the fusion boundary between A533 Gr. B and Alloy 152.

  8. Atomic Layer Deposition Alumina-Passivated Silicon Nanowires: Probing the Transition from Electrochemical Double-Layer Capacitor to Electrolytic Capacitor.

    Science.gov (United States)

    Gaboriau, Dorian; Boniface, Maxime; Valero, Anthony; Aldakov, Dmitry; Brousse, Thierry; Gentile, Pascal; Sadki, Said

    2017-04-19

    Silicon nanowires were coated by a 1-5 nm thin alumina layer by atomic layer deposition (ALD) in order to replace poorly reproducible and unstable native silicon oxide by a highly conformal passivating alumina layer. The surface coating enabled probing the behavior of symmetric devices using such electrodes in the EMI-TFSI electrolyte, allowing us to attain a large cell voltage up to 6 V in ionic liquid, together with very high cyclability with less than 4% capacitance fade after 10 6 charge/discharge cycles. These results yielded fruitful insights into the transition between an electrochemical double-layer capacitor behavior and an electrolytic capacitor behavior. Ultimately, thin ALD dielectric coatings can be used to obtain hybrid devices exhibiting large cell voltage and excellent cycle life of dielectric capacitors, while retaining energy and power densities close to the ones displayed by supercapacitors.

  9. Atom probe tomography of the evolution of the nanostructure of oxide dispersion strengthened steels under ion irradiation

    Science.gov (United States)

    Orlov, N. N.; Rogozhkin, S. V.; Bogachev, A. A.; Korchuganova, O. A.; Nikitin, A. A.; Zaluzhnyi, A. G.; Kozodaev, M. A.; Kulevoy, T. V.; Kuibeda, R. P.; Fedin, P. A.; Chalykh, B. B.; Lindau, R.; Hoffmann, Ya.; Möslang, A.; Vladimirov, P.

    2017-09-01

    The atom probe tomography of the nanostructure evolution in ODS1 Eurofer, ODS 13.5Cr, and ODS 13.5Cr-0.3Ti steels under heavy ion irradiation at 300 and 573 K is performed. The samples were irradiated by 5.6 MeV Fe2+ ions and 4.8 MeV Ti2+ ions to a fluence of 1015 cm-2. It is shown that the number of nanoclusters increases by a factor of 2-3 after irradiation. The chemical composition of the clusters in the steels changes after irradiation at 300 K, whereas the chemical composition of the clusters in the 13.5Cr-0.3Ti ODS steel remains the same after irradiation at 573 K.

  10. Atom-probe tomographic study of interfaces of Cu{sub 2}ZnSnS{sub 4} photovoltaic cells

    Energy Technology Data Exchange (ETDEWEB)

    Tajima, S., E-mail: e0954@mosk.tytlabs.co.jp; Asahi, R.; Itoh, T.; Hasegawa, M.; Ohishi, K. [Toyota Central R and D Labs., Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192 (Japan); Isheim, D.; Seidman, D. N. [Northwestern University, Evanston, Illinois 60208-3108 (United States)

    2014-09-01

    The heterophase interfaces between the CdS buffer layer and the Cu{sub 2}ZnSnS{sub 4} (CZTS) absorption layers are one of the main factors affecting photovoltaic performance of CZTS cells. We have studied the compositional distributions at heterophase interfaces in CZTS cells using three-dimensional atom-probe tomography. The results demonstrate: (a) diffusion of Cd into the CZTS layer; (b) segregation of Zn at the CdS/CZTS interface; and (c) a change of oxygen and hydrogen concentrations in the CdS layer depending on the heat treatment. Annealing at 573 K after deposition of CdS improves the photovoltaic properties of CZTS cells probably because of the formation of a heterophase epitaxial junction at the CdS/CZTS interface. Conversely, segregation of Zn at the CdS/CZTS interface after annealing at a higher temperature deteriorates the photovoltaic properties.

  11. Structure and orbital ordering of ultrathin LaVO{sub 3} probed by atomic resolution electron microscopy and Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lindfors-Vrejoiu, Ionela; Engelmayer, Johannes; Loosdrecht, Paul H.M. van [II. Physikalisches Institut, Koeln Univ. (Germany); Jin, Lei; Jia, Chun-Lin [Peter Gruenberg Institut (PGI-5) and Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C), Forschungszentrum Juelich GmbH (Germany); Himcinschi, Cameliu [Institut fuer Theoretische Physik, TU Bergakademie Freiberg (Germany); Hensling, Felix; Waser, Rainer; Dittmann, Regina [Peter Gruenberg Institut (PGI-7), Forschungszentrum Juelich GmbH (Germany)

    2017-03-15

    Orbital ordering has been less investigated in epitaxial thin films, due to the difficulty to evidence directly the occurrence of this phenomenon in thin film samples. Atomic resolution electron microscopy enabled us to observe the structural details of the ultrathin LaVO{sub 3} films. The transition to orbital ordering of epitaxial layers as thin as ∼4 nm was probed by temperature-dependent Raman scattering spectroscopy of multilayer samples. From the occurrence and temperature dependence of the 700 cm{sup -1} Raman active mode it can be inferred that the structural phase transition associated with orbital ordering takes place in ultrathin LaVO{sub 3} films at about 130 K. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Atom probe tomography of intermetallic phases and interfaces formed in dissimilar joining between Al alloys and steel

    International Nuclear Information System (INIS)

    Lemmens, B.; Springer, H.; Duarte, M.J.; De Graeve, I.; De Strycker, J.; Raabe, D.; Verbeken, K.

    2016-01-01

    While Si additions to Al are widely used to reduce the thickness of the brittle intermetallic seam formed at the interface during joining of Al alloys to steel, the underlying mechanisms are not clarified yet. The developed approach for the site specific atom probe tomography analysis revealed Si enrichments at grain and phase boundaries between the θ (Fe 4 Al 13 ) and η (Fe 2 Al 5 ) phase, up to about ten times that of the concentration in Al. The increase in Si concentration could play an important role for the growth kinetics of the intermetallic phases formed for example in hot-dip aluminizing of steel. - Highlights: •Si additions to Al reduce thickness of intermetallic seam in joining with steel. •Approach developed for the site specific APT analysis of the intermetallic seam •Si enrichment at grain and phase boundaries possibly affects growth of intermetallics.

  13. Flux-focusing eddy current probe and rotating probe method for flaw detection

    Science.gov (United States)

    Wincheski, Buzz A.; Fulton, James P.; Nath, Shridhar C.; Simpson, John W.; Namkung, Min

    1994-11-01

    A flux-focusing electromagnetic sensor which uses a ferromagnetic flux-focusing lens simplifies inspections and increases detectability of fatigue cracks about circular fasteners and other circular inhomogeneities in high conductivity material. The unique feature of the device is the ferrous shield isolating a high-turn pick-up coil from an excitation coil. The use of the magnetic shield is shown to produce a null voltage output across the receiving coil in the presence of an unflawed sample. A redistribution of the current flow in the sample caused by the presence of flaws, however, eliminates the shielding condition and a large output voltage is produced, yielding a clear unambiguous flaw signal. By rotating the probe in a path around a circular fastener such as a rivet while maintaining a constant distance between the probe and the center of a rivet, the signal due to current flow about the rivet can be held constant. Any further changes in the current distribution, such as due to a fatigue crack at the rivet joint, can be detected as an increase in the output voltage above that due to the flow about the rivet head.

  14. Digital phase-shifting atomic force microscope Moire method

    International Nuclear Information System (INIS)

    Liu Chiaming; Chen Lienwen

    2005-01-01

    In this study, the digital atomic force microscope (AFM) Moire method with phase-shifting technology is established to measure the in-plane displacement and strain fields. The Moire pattern is generated by the interference between the specimen grating and the virtual reference grating formed by digital image processes. The overlapped image is filtered by two-dimensional wavelet transformation to obtain the clear interference Moire patterns. The four-step phase-shifting method is realized by translating the phase of the virtual reference grating from 0 to 2π. The principle of the digital AFM Moire method and the phase-shifting technology are described in detail. Experimental results show that this method is convenient to use and efficient in realizing the microscale measurement

  15. Calibration of reconstruction parameters in atom probe tomography using a single crystallographic orientation

    International Nuclear Information System (INIS)

    Suram, Santosh K.; Rajan, Krishna

    2013-01-01

    The purpose of this work is to develop a methodology to estimate the APT reconstruction parameters when limited crystallographic information is available. Reliable spatial scaling of APT data currently requires identification of multiple crystallographic poles from the field desorption image for estimating the reconstruction parameters. This requirement limits the capacity of accurately reconstructing APT data for certain complex systems, such as highly alloyed systems and nanostructured materials wherein more than one pole is usually not observed within one grain. To overcome this limitation, we develop a quantitative methodology for calibrating the reconstruction parameters in an APT dataset by ensuring accurate inter-planar spacing and optimizing the curvature correction for the atomic planes corresponding to a single crystallographic orientation. We validate our approach on an aluminum dataset and further illustrate its capabilities by computing geometric reconstruction parameters for W and Al–Mg–Sc datasets. - Highlights: ► Quantitative approach is developed to accurately reconstruct APT data. ► Curvature of atomic planes in APT data is used to calibrate the reconstruction. ► APT reconstruction parameters are determined from a single crystallographic axis. ► Quantitative approach is demonstrated on W, Al and Al–Mg–Sc systems. ► Accurate APT reconstruction of complex materials is now possible

  16. Method And Apparatus For Atomizing And Vaporizing Liquid

    KAUST Repository

    Lal, Amit

    2014-09-18

    A method and apparatus for atomizing and vaporizing liquid is described. An apparatus having an ejector configured to eject one or more droplets of liquid may be inserted into a reservoir containing liquid. The ejector may have a vibrating device that vibrates the ejector and causes liquid to move from the reservoir up through the ejector and out through an orifice located on the top of the ejector. The one or more droplets of liquid ejected from the ejector may be heated and vaporized into the air.

  17. Detection methods for atoms and radicals in the gas phase

    Science.gov (United States)

    Hack, W.

    This report lists atoms and free radicals in the gas phase which are of interest for environmental and flame chemistry and have been detected directly. The detection methods which have been used are discussed with respect to their range of application, specificity and sensitivity. In table 1, detection methods for the five atoms of group IV (C, Si, Ge, Sn, Pb) and about 60 radicals containing at least one atom of group IV are summarized (CH, Cd, Cf, CC1, CBr, Cn, Cs, CSe, CH2, CD2, Chf, Cdf, CHC1, CHBr, CF2, CC12, CBr2, CFC1, CFBr, CH3, CD3, CF3, CH2F, CH2C1, CH2Br, CHF2, CHC12, CHBr2, Hco, Fco, CH30, CD30, CH2OH, CH3S, Nco, CH4N, CH302, CF302; C2, C2N, C2H, C20, C2HO, C2H3, C2F3, C2H5, C2HsO, C2H4OH, CH3CO, CD3CO, C2H3O, C2H502, CH3COO2, C2H4N, C2H6N, C3; Si, SiF, SiF2, SiO, SiC, Si2; Ge, GeC, GeO, GeF, GeF2, GeCl2, Sn, SnF, SnO, SnF2, Pb, PbF, PbF2, PbO, PbS). In table 2 detection methods for about 25 other atoms and 60 radicals are listed: (H, D, O, O2, Oh, Od, HO2, DO2, F, Ci, Br, I, Fo, Cio, BrO, Io, FO2, C1O2, Li, Na, K, Rb, Cs, N, N3, Nh, Nd, Nf, Nci, NBr, NH2, ND2, Nhd, Nhf, NF2, NC12, N2H3, No, NO2, NO3, Hno, Dno, P, Ph, Pd, Pf, Pci, PH2, PD2, PF2, Po, As, AsO, AsS, Sb, Bi, S, S2, Sh, Sd, Sf, SF2, So, Hso, Dso, Sn, Se, Te, Se2, SeH, SeD, SeF, SeO, SeS, SeN, TeH, TeO, Bh, BH2, Bo, Bn, B02, Cd, Hg, UF5). The tables also cite some recent kinetic applications of the various methods.

  18. Method And Apparatus For Atomizing And Vaporizing Liquid

    KAUST Repository

    Lal, Amit; Mayet, Abdulilah M.

    2014-01-01

    A method and apparatus for atomizing and vaporizing liquid is described. An apparatus having an ejector configured to eject one or more droplets of liquid may be inserted into a reservoir containing liquid. The ejector may have a vibrating device that vibrates the ejector and causes liquid to move from the reservoir up through the ejector and out through an orifice located on the top of the ejector. The one or more droplets of liquid ejected from the ejector may be heated and vaporized into the air.

  19. Atom

    International Nuclear Information System (INIS)

    Auffray, J.P.

    1997-01-01

    The atom through centuries, has been imagined, described, explored, then accelerated, combined...But what happens truly inside the atom? And what are mechanisms who allow its stability? Physicist and historian of sciences, Jean-Paul Auffray explains that these questions are to the heart of the modern physics and it brings them a new lighting. (N.C.)

  20. Pressure/temperature fluid cell apparatus for the neutron powder diffractometer instrument: Probing atomic structure in situ

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hsiu-Wen; Fanelli, Victor R.; Reiche, Helmut M.; Larson, Eric; Taylor, Mark A.; Siewenie, Joan [Lujan Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Xu, Hongwu [Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Zhu, Jinlong [High Pressure Science and Engineering Center, Department of Physics and Astronomy, The University of Nevada, Las Vegas, Nevada 89154, USA and National Lab for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Page, Katharine, E-mail: pagekl@ornl.gov [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2014-12-15

    This contribution describes a new local structure compatible gas/liquid cell apparatus for probing disordered materials at high pressures and variable temperatures in the Neutron Powder Diffraction instrument at the Lujan Neutron Scattering Center, Los Alamos National Laboratory. The new sample environment offers choices for sample canister thickness and canister material type. Finite element modeling is utilized to establish maximum allowable working pressures of 414 MPa at 15 K and 121 MPa at 600 K. High quality atomic pair distribution function data extraction and modeling have been demonstrated for a calibration standard (Si powder) and for supercritical and subcritical CO{sub 2} measurements. The new sample environment was designed to specifically target experimental studies of the local atomic structures involved in geologic CO{sub 2} sequestration, but will be equally applicable to a wide variety of energy applications, including sorption of fluids on nano/meso-porous solids, clathrate hydrate formation, catalysis, carbon capture, and H{sub 2} and natural gas uptake/storage.

  1. Indium clustering in a-plane InGaN quantum wells as evidenced by atom probe tomography

    International Nuclear Information System (INIS)

    Tang, Fengzai; Zhu, Tongtong; Oehler, Fabrice; Fu, Wai Yuen; Griffiths, James T.; Massabuau, Fabien C.-P.; Kappers, Menno J.; Oliver, Rachel A.; Martin, Tomas L.; Bagot, Paul A. J.; Moody, Michael P.

    2015-01-01

    Atom probe tomography (APT) has been used to characterize the distribution of In atoms within non-polar a-plane InGaN quantum wells (QWs) grown on a GaN pseudo-substrate produced using epitaxial lateral overgrowth. Application of the focused ion beam microscope enabled APT needles to be prepared from the low defect density regions of the grown sample. A complementary analysis was also undertaken on QWs having comparable In contents grown on polar c-plane sample pseudo-substrates. Both frequency distribution and modified nearest neighbor analyses indicate a statistically non-randomized In distribution in the a-plane QWs, but a random distribution in the c-plane QWs. This work not only provides insights into the structure of non-polar a-plane QWs but also shows that APT is capable of detecting as-grown nanoscale clustering in InGaN and thus validates the reliability of earlier APT analyses of the In distribution in c-plane InGaN QWs which show no such clustering

  2. Indium clustering in a-plane InGaN quantum wells as evidenced by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Fengzai; Zhu, Tongtong; Oehler, Fabrice; Fu, Wai Yuen; Griffiths, James T.; Massabuau, Fabien C.-P.; Kappers, Menno J.; Oliver, Rachel A., E-mail: rao28@cam.ac.uk [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Martin, Tomas L.; Bagot, Paul A. J.; Moody, Michael P., E-mail: michael.moody@materials.ox.ac.uk [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom)

    2015-02-16

    Atom probe tomography (APT) has been used to characterize the distribution of In atoms within non-polar a-plane InGaN quantum wells (QWs) grown on a GaN pseudo-substrate produced using epitaxial lateral overgrowth. Application of the focused ion beam microscope enabled APT needles to be prepared from the low defect density regions of the grown sample. A complementary analysis was also undertaken on QWs having comparable In contents grown on polar c-plane sample pseudo-substrates. Both frequency distribution and modified nearest neighbor analyses indicate a statistically non-randomized In distribution in the a-plane QWs, but a random distribution in the c-plane QWs. This work not only provides insights into the structure of non-polar a-plane QWs but also shows that APT is capable of detecting as-grown nanoscale clustering in InGaN and thus validates the reliability of earlier APT analyses of the In distribution in c-plane InGaN QWs which show no such clustering.

  3. Probing and Manipulating the Interfacial Defects of InGaAs Dual-Layer Metal Oxides at the Atomic Scale.

    Science.gov (United States)

    Wu, Xing; Luo, Chen; Hao, Peng; Sun, Tao; Wang, Runsheng; Wang, Chaolun; Hu, Zhigao; Li, Yawei; Zhang, Jian; Bersuker, Gennadi; Sun, Litao; Pey, Kinleong

    2018-01-01

    The interface between III-V and metal-oxide-semiconductor materials plays a central role in the operation of high-speed electronic devices, such as transistors and light-emitting diodes. The high-speed property gives the light-emitting diodes a high response speed and low dark current, and they are widely used in communications, infrared remote sensing, optical detection, and other fields. The rational design of high-performance devices requires a detailed understanding of the electronic structure at this interface; however, this understanding remains a challenge, given the complex nature of surface interactions and the dynamic relationship between the morphology evolution and electronic structures. Herein, in situ transmission electron microscopy is used to probe and manipulate the structural and electrical properties of ZrO 2 films on Al 2 O 3 and InGaAs substrate at the atomic scale. Interfacial defects resulting from the spillover of the oxygen-atom conduction-band wavefunctions are resolved. This study unearths the fundamental defect-driven interfacial electric structure of III-V semiconductor materials and paves the way to future high-speed and high-reliability devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Development of the interfacial area concentration measurement method using a five sensor conductivity probe

    International Nuclear Information System (INIS)

    Euh, Dong Jin; Yun, Byong Jo; Song, Chul Hwa; Kwon, Tae Soon; Chung, Moon Ki; Lee, Un Chul

    2000-01-01

    The interfacial area concentration(IAC) is one of the most important parameters in the two-fluid model for two-phase flow analysis. The IAE can be measured by a local conductivity probe method that uses the difference of conductivity between water and air/steam. The number of sensors in the conductivity probe may be differently chosen by considering the flow regime of two-phase flow. The four sensor conductivity probe method predicts the IAC without any assumptions of the bubble shape. The local IAC can be obtained by measuring the three dimensional velocity vector elements at the measuring point, and the directional cosines of the sensors. The five sensor conductivity probe method proposed in this study is based on the four sensor probe method. With the five sensor probe, the local IAC for a given referred measuring area of the probe can be predicted more exactly than the four sensor prober. In this paper, the mathematical approach of the five sensor probe method for measuring the IAC is described, and a numerical simulation is carried out for ideal cap bubbles of which the sizes and locations are determined by a random number generator

  5. Eddy current probe and method for flaw detection in metals

    Science.gov (United States)

    Watjen, John P.

    1987-06-23

    A flaw detecting system is shown which includes a probe having a pair of ferrite cores with in-line gaps in close proximity to each other. An insulating, non-magnetic, non-conducting holder fills the gaps and supports the ferrite cores in a manner such that the cores form a generally V-shape. Each core is provided with an excitation winding and a detection winding. The excitation windings are connected in series or parallel with an rf port for connection thereof to a radio frequency source. The detection windings, which are differentially wound, are connected in series circuit to a detector port for connection to a voltage measuring instrument. The ferrite cores at the in-line gaps directly engage the metal surface of a test piece, and the probe is scanned along the test piece. In the presence of a flaw in the metal surface the detection winding voltages are unbalanced, and the unbalance is detected by the voltage measuring instrument. The insulating holder is provided with a profile which conforms to that of a prominent feature of the test piece to facilitate movement of the probe along the feature, typically an edge or a corner.

  6. Heavy atoms as molecular probes in studying the solvent dependence of the dynamics of triplet exciplexes

    International Nuclear Information System (INIS)

    Steiner, U.; Winter, G.

    1981-01-01

    Electron transfer reactions between thiopyronine triplet (acceptor 3 A + ) and the electron donors (D), aniline, p-Br-aniline and p-I-aniline, are investigated by flash spectroscopy in solvents of different viscosity and polarity. Due to the heavy-atom effect the radical yield becomes very sensitive to the solvent influence, which can be explained by the dynamic properties of a triplet exciplex ( 3 (AD + )) formed as a primary product in the reaction between acceptor triplet and donor. Whereas on variation of solvent viscosity the solvent cage effect on the dissociation of 3 (AD + ) is observed, a change in solvent polarity is suggested to affect the radiationless deactivation of 3 (AD + ) to the ground state of the components. (author)

  7. Atomic force microscopy and spectroscopy to probe single membrane proteins in lipid bilayers.

    Science.gov (United States)

    Sapra, K Tanuj

    2013-01-01

    The atomic force microscope (AFM) has opened vast avenues hitherto inaccessible to the biological scientist. The high temporal (millisecond) and spatial (nanometer) resolutions of the AFM are suited for studying many biological processes in their native conditions. The AFM cantilever stylus is aptly termed as a "lab on a tip" owing to its versatility as an imaging tool as well as a handle to manipulate single bonds and proteins. Recent examples assert that the AFM can be used to study the mechanical properties and monitor processes of single proteins and single cells, thus affording insight into important mechanistic details. This chapter specifically focuses on practical and analytical protocols of single-molecule AFM methodologies related to high-resolution imaging and single-molecule force spectroscopy of membrane proteins. Both these techniques are operator oriented, and require specialized working knowledge of the instrument, theoretical, and practical skills.

  8. Characterization of ion-irradiation-induced nanodot structures on InP surfaces by atom probe tomography.

    Science.gov (United States)

    Gnaser, Hubert; Radny, Tobias

    2015-12-01

    Surfaces of InP were bombarded by 1.9 keV Ar(+) ions under normal incidence. The total accumulated ion fluence the samples were exposed to was varied from 1 × 10(17) cm(-2) to 3 × 10(18)cm(-2) and ion flux densities f of (0.4-2) × 10(14) cm(-2) s(-1) were used. Nanodot structures were found to evolve on the surface from these ion irradiations, their dimensions however, depend on the specific bombardment conditions. The resulting surface morphology was examined by atomic force microscopy (AFM). As a function of ion fluence, the mean radius, height, and spacing of the dots can be fitted by power-law dependences. In order to determine possible local compositional changes in these nanostructures induced by ion impact, selected samples were prepared for atom probe tomography (APT). The results indicate that by APT the composition of individual InP nanodots evolving under ion bombardment could be examined with atomic spatial resolution. At the InP surface, the values of the In/P concentration ratio are distinctly higher over a distance of ~1 nm and amount to 1.3-1.8. However, several aspects critical for the analyses were identified: (i) because of the small dimensions of these nanostructures a successful tip preparation proved very challenging. (ii) The elemental compositions obtained from APT were found to be influenced pronouncedly by the laser pulse energy; typically, low energies result in the correct stoichiometry whereas high ones lead to an inhomogeneous evaporation from the tips and deviations from the nominal composition. (iii) Depending again on the laser energy, a prolific emission of Pn cluster ions was observed, with n ≤ 11. Copyright © 2015. Published by Elsevier B.V.

  9. Atomization in graphite-furnace atomic absorption spectrometry. Peak-height method vs. integration method of measuring absorbance: carbon rod atomizer 63

    International Nuclear Information System (INIS)

    Sturgeon, R.E.; Chakrabarti, C.L.; Maines, I.S.; Bertels, P.C.

    1975-01-01

    Oscilloscopic traces of transient atomic absorption signals generated during continuous heating of a Carbon Rod Atomizer model 63 show features which are characteristic of the element being atomized. This research was undertaken to determine the significance and usefulness of the two analytically significant parameters, absorbance maximum and integrated absorbance. For measuring integrated absorbance, an electronic integrating control unit consisting of a timing circuit, a lock-in amplifier, and a digital voltmeter, which functions as a direct absorbance x second readout, has been designed, developed, and successfully tested. Oscilloscopic and recorder traces of the absorbance maximum and digital display of the integrated absorbance are simultaneously obtained. For the elements studied, Cd, Zn, Cu, Al, Sn, Mo, and V, the detection limits and the precision obtained are practically identical for both methods of measurements. The sensitivities by the integration method are about the same as, or less than, those obtained by the peak-height method, whereas the calibration curves by the former are generally linear over wider ranges of concentrations. (U.S.)

  10. Understanding Atom Probe Tomography of Oxide-Supported Metal Nanoparticles by Correlation with Atomic-Resolution Electron Microscopy and Field Evaporation Simulation.

    Science.gov (United States)

    Devaraj, Arun; Colby, Robert; Vurpillot, François; Thevuthasan, Suntharampillai

    2014-04-17

    Oxide-supported metal nanoparticles are widely used in heterogeneous catalysis. The increasingly detailed design of such catalysts necessitates three-dimensional characterization with high spatial resolution and elemental selectivity. Laser-assisted atom probe tomography (APT) is uniquely suited to the task but faces challenges with the evaporation of metal/insulator systems. Correlation of APT with aberration-corrected scanning transmission electron microscopy (STEM), for Au nanoparticles embedded in MgO, reveals preferential evaporation of the MgO and an inaccurate assessment of nanoparticle composition. Finite element field evaporation modeling is used to illustrate the evolution of the evaporation front. Nanoparticle composition is most accurately predicted when the MgO is treated as having a locally variable evaporation field, indicating the importance of considering laser-oxide interactions and the evaporation of various molecular oxide ions. These results demonstrate the viability of APT for analysis of oxide-supported metal nanoparticles, highlighting the need for developing a theoretical framework for the evaporation of heterogeneous materials.

  11. Methods for measurement of electron emission yield under low energy electron-irradiation by collector method and Kelvin probe method

    Energy Technology Data Exchange (ETDEWEB)

    Tondu, Thomas; Belhaj, Mohamed; Inguimbert, Virginie [Onera, DESP, 2 Avenue Edouard Belin, 31400 Toulouse (France); Onera, DESP, 2 Avenue Edouard Belin, 31400 Toulouse, France and Fondation STAE, 4 allee Emile Monso, BP 84234-31432, Toulouse Cedex 4 (France); Onera, DESP, 2 Avenue Edouard Belin, 31400 Toulouse (France)

    2010-09-15

    Secondary electron emission yield of gold under electron impact at normal incidence below 50 eV was investigated by the classical collector method and by the Kelvin probe method. The authors show that biasing a collector to ensure secondary electron collection while keeping the target grounded can lead to primary electron beam perturbations. Thus reliable secondary electron emission yield at low primary electron energy cannot be obtained with a biased collector. The authors present two collector-free methods based on current measurement and on electron pulse surface potential buildup (Kelvin probe method). These methods are consistent, but at very low energy, measurements become sensitive to the earth magnetic field (below 10 eV). For gold, the authors can extrapolate total emission yield at 0 eV to 0.5, while a total electron emission yield of 1 is obtained at 40{+-}1 eV.

  12. Methods for measurement of electron emission yield under low energy electron-irradiation by collector method and Kelvin probe method

    International Nuclear Information System (INIS)

    Tondu, Thomas; Belhaj, Mohamed; Inguimbert, Virginie

    2010-01-01

    Secondary electron emission yield of gold under electron impact at normal incidence below 50 eV was investigated by the classical collector method and by the Kelvin probe method. The authors show that biasing a collector to ensure secondary electron collection while keeping the target grounded can lead to primary electron beam perturbations. Thus reliable secondary electron emission yield at low primary electron energy cannot be obtained with a biased collector. The authors present two collector-free methods based on current measurement and on electron pulse surface potential buildup (Kelvin probe method). These methods are consistent, but at very low energy, measurements become sensitive to the earth magnetic field (below 10 eV). For gold, the authors can extrapolate total emission yield at 0 eV to 0.5, while a total electron emission yield of 1 is obtained at 40±1 eV.

  13. On the quantification of the dissolved hydroxyl radicals in the plasma-liquid system using the molecular probe method

    Science.gov (United States)

    Ma, Yupengxue; Gong, Xinning; He, Bangbang; Li, Xiaofei; Cao, Dianyu; Li, Junshuai; Xiong, Qing; Chen, Qiang; Chen, Bing Hui; Huo Liu, Qing

    2018-04-01

    Hydroxyl (OH) radical is one of the most important reactive species produced by plasma-liquid interactions, and the OH in liquid phase (dissolved OH radical, OHdis) takes effect in many plasma-based applications due to its high reactivity. Therefore, the quantification of the OHdis in a plasma-liquid system is of great importance, and a molecular probe method usually used for the OHdis detection might be applied. Herein, we investigate the validity of using the molecular probe method to estimate the [OHdis] in the plasma-liquid system. Dimethyl sulfoxide is used as the molecular probe to estimate the [OHdis] in an air plasma-liquid system, and usually the estimation of [OHdis] is deduced by quantifying the OHdis-induced derivative, the formaldehyde (HCHO). The analysis indicates that the true concentration of the OHdis should be estimated from the sum of three terms: the formed HCHO, the existing OH scavengers, and the H2O2 formed from the OHdis. The results show that the measured [HCHO] needs to be corrected since the HCHO consumption is not negligible in the plasma-liquid system. We conclude from the results and the analysis that the molecular probe method generally underestimates the [OHdis] in the plasma-liquid system. If one wants to obtain the true concentration of the OHdis in the plasma-liquid system, one needs to know the consumption behavior of the OHdis-induced derivatives, the information of the OH scavengers (such as hydrated electron, atomic hydrogen besides the molecular probe), and also the knowledge of the H2O2 formed from the OHdis.

  14. The design method for the electric field probe based on PSpice

    International Nuclear Information System (INIS)

    Wu Wei; Cheng Yinhui; Ma Liang; Zhou Hui

    2006-01-01

    The equivalent circuit for E-filed probe with or without cable, which connected the antenna to the load, was simulated by PSpice. The AC and transient analyses were performed on the equivalent circuit. As a result of AC sweep analysis, (a) the sensitivity and practice bandwidth of the probe without the cable are increased along with the capacitance of antenna as long as the capacitance under a certain value, (b) in the case of the probe with cable the sensitivity and practice bandwidth can't be improved by adjusting the capacitance of antenna simultaneously. A novel approach was proposed for increasing the practice bandwidth of the probe with short cable and was simulated. The PPD (Parallel Plate Dipole) E-Filed probe was designed. It is proved that the design method for the E-Field probe based on PSpice can be used in the measurement of EMP (Electromagnetic Pulse). (authors)

  15. A new image correction method for live cell atomic force microscopy

    International Nuclear Information System (INIS)

    Shen, Y; Sun, J L; Zhang, A; Hu, J; Xu, L X

    2007-01-01

    During live cell imaging via atomic force microscopy (AFM), the interactions between the AFM probe and the membrane yield distorted cell images. In this work, an image correction method was developed based on the force-distance curve and the modified Hertzian model. The normal loading and lateral forces exerted on the cell membrane by the AFM tip were both accounted for during the scanning. Two assumptions were made in modelling based on the experimental measurements: (1) the lateral force on the endothelial cells was linear to the height; (2) the cell membrane Young's modulus could be derived from the displacement measurement of a normal force curve. Results have shown that the model could be used to recover up to 30% of the actual cell height depending on the loading force. The accuracy of the model was also investigated with respect to the loading force and mechanical property of the cell membrane

  16. A new image correction method for live cell atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Y; Sun, J L; Zhang, A; Hu, J; Xu, L X [College of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai 200030 (China)

    2007-04-21

    During live cell imaging via atomic force microscopy (AFM), the interactions between the AFM probe and the membrane yield distorted cell images. In this work, an image correction method was developed based on the force-distance curve and the modified Hertzian model. The normal loading and lateral forces exerted on the cell membrane by the AFM tip were both accounted for during the scanning. Two assumptions were made in modelling based on the experimental measurements: (1) the lateral force on the endothelial cells was linear to the height; (2) the cell membrane Young's modulus could be derived from the displacement measurement of a normal force curve. Results have shown that the model could be used to recover up to 30% of the actual cell height depending on the loading force. The accuracy of the model was also investigated with respect to the loading force and mechanical property of the cell membrane.

  17. Ultrafast atomic process in X-ray emission by using inner-shell ionization method for sodium and carbon atoms

    Energy Technology Data Exchange (ETDEWEB)

    Moribayashi, Kengo; Sasaki, Akira; Tajima, Toshiki [Japan Atomic Energy Research Inst., Neyagawa, Osaka (Japan). Kansai Research Establishment

    1998-07-01

    An ultrafast inner-shell ionization process with X-ray emission stimulated by high-intensity short-pulse X-ray is studied. Carbon and sodium atoms are treated as target matter. It is shown that atomic processes of the target determine the necessary X-ray intensity for X-ray laser emission as well as the features of X-ray laser such as wavelength and duration time. The intensity also depends on the density of initial atoms. Furthermore, we show that as the intensity of X-ray source becomes high, the multi-inner-shell ionization predominates, leading to the formation of hollow atoms. As the density of hollow atoms is increased by the pumping X-ray power, the emission of X-rays is not only of significance for high brightness X-ray measurement but also is good for X-ray lasing. New classes of experiments of pump X-ray probe and X-ray laser are suggested. (author)

  18. Probing the mechanical properties of TNF-α stimulated endothelial cell with atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Sei-Young Lee

    2011-01-01

    Full Text Available Sei-Young Lee1,2, Ana-Maria Zaske3, Tommaso Novellino1,4*, Delia Danila3, Mauro Ferrari1,5*, Jodie Conyers3, Paolo Decuzzi1,6*1Department of Nanomedicine and Biomedical Engineering, The University of Texas Medical School at Houston, Houston, TX, USA; 2Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX, USA; 3CeTIR – Center for Translational Injury Research, The University of Texas Health Science Center at Houston, Houston, TX, USA; 4Department of Biomedical Engineering, Biomedical Campus University of Rome, Italy; 5MD Anderson Cancer Center, Houston, TX, USA; 6BioNEM – Center of Bio-Nanotechnology and Engineering for Medicine, University of Magna Graecia, Catanzaro, Italy; *Currently at Department of Nanomedicine and Biomedical Engineering, The Methodist Hospital Research Institute, Houston, TX, USAAbstract: TNF-α (tumor necrosis factor-α is a potent pro-inflammatory cytokine that regulates the permeability of blood and lymphatic vessels. The plasma concentration of TNF-α is elevated (> 1 pg/mL in several pathologies, including rheumatoid arthritis, atherosclerosis, cancer, pre-eclampsia; in obese individuals; and in trauma patients. To test whether circulating TNF-α could induce similar alterations in different districts along the vascular system, three endothelial cell lines, namely HUVEC, HPMEC, and HCAEC, were characterized in terms of 1 mechanical properties, employing atomic force microscopy; 2 cytoskeletal organization, through fluorescence microscopy; and 3 membrane overexpression of adhesion molecules, employing ELISA and immunostaining. Upon stimulation with TNF-α (10 ng/mL for 20 h, for all three endothelial cells, the mechanical stiffness increased by about 50% with a mean apparent elastic modulus of E ~5 ± 0.5 kPa (~3.3 ± 0.35 kPa for the control cells; the density of F-actin filaments increased in the apical and median planes; and the ICAM-1 receptors were overexpressed compared with

  19. Topographic and electronic contrast of the graphene moir´e on Ir(111) probed by scanning tunneling microscopy and noncontact atomic force microscopy

    NARCIS (Netherlands)

    Sun, Z.; Hämäläinen, K.; Sainio, K.; Lahtinen, J.; Vanmaekelbergh, D.A.M.; Liljeroth, P.

    2011-01-01

    Epitaxial graphene grown on transition-metal surfaces typically exhibits a moir´e pattern due to the lattice mismatch between graphene and the underlying metal surface. We use both scanning tunneling microscopy (STM) and atomic force microscopy (AFM) to probe the electronic and topographic contrast

  20. Nanostructural evolution of Cr-rich precipitates in a Cu-Cr-Zr alloy during heat treatment studied by 3 dimensional atom probe

    DEFF Research Database (Denmark)

    Hatakeyama, Masahiko; Toyama, Takeshi; Nagai, Yasuyoshi

    2008-01-01

    Nanostructural evolution of Cr (Cr-rich) precipitates in a Cu-0.78%Cr-0.13%Zr alloy has been studied after aging and overaging (reaging) by laser assisted local electrode 3 dimensional atom probe (Laser-LEAP). This material is a candidate for the first wall and divertor components of future fusion...

  1. Electromechanical Characterization of Single GaN Nanobelt Probed with Conductive Atomic Force Microscope

    Science.gov (United States)

    Yan, X. Y.; Peng, J. F.; Yan, S. A.; Zheng, X. J.

    2018-04-01

    The electromechanical characterization of the field effect transistor based on a single GaN nanobelt was performed under different loading forces by using a conductive atomic force microscope (C-AFM), and the effective Schottky barrier height (SBH) and ideality factor are simulated by the thermionic emission model. From 2-D current image, the high value of the current always appears on the nanobelt edge with the increase of the loading force less than 15 nN. The localized (I-V) characteristic reveals a typical rectifying property, and the current significantly increases with the loading force at the range of 10-190 nN. The ideality factor is simulated as 9.8 within the scope of GaN nano-Schottky diode unity (6.5-18), therefore the thermionic emission current is dominant in the electrical transport of the GaN-tip Schottky junction. The SBH is changed through the piezoelectric effect induced by the loading force, and it is attributed to the enhanced current. Furthermore, a single GaN nanobelt has a high mechanical-induced current ratio that could be made use of in a nanoelectromechanical switch.

  2. Morphology and current-voltage characteristics of nanostructured pentacene thin films probed by atomic force microscopy.

    Science.gov (United States)

    Zorba, S; Le, Q T; Watkins, N J; Yan, L; Gao, Y

    2001-09-01

    Atomic force microscopy was used to study the growth modes (on SiO2, MoS2, and Au substrates) and the current-voltage (I-V) characteristics of organic semiconductor pentacene. Pentacene films grow on SiO2 substrate in a layer-by-layer manner with full coverage at an average thickness of 20 A and have the highest degree of molecular ordering with large dendritic grains among the pentacene films deposited on the three different substrates. Films grown on MoS2 substrate reveal two different growth modes, snowflake-like growth and granular growth, both of which seem to compete with each other. On the other hand, films deposited on Au substrate show granular structure for thinner coverages (no crystal structure) and dendritic growth for higher coverages (crystal structure). I-V measurements were performed with a platinum tip on a pentacene film deposited on a Au substrate. The I-V curves on pentacene film reveal symmetric tunneling type character. The field dependence of the current indicates that the main transport mechanism at high field intensities is hopping (Poole-Frenkel effect). From these measurements, we have estimated a field lowering coefficient of 9.77 x 10(-6) V-1/2 m1/2 and an ideality factor of 18 for pentacene.

  3. Schottky nanocontact of one-dimensional semiconductor nanostructures probed by using conductive atomic force microscopy

    Science.gov (United States)

    Lee, Jung Ah; Rok Lim, Young; Jung, Chan Su; Choi, Jun Hee; Im, Hyung Soon; Park, Kidong; Park, Jeunghee; Kim, Gyu Tae

    2016-10-01

    To develop the advanced electronic devices, the surface/interface of each component must be carefully considered. Here, we investigate the electrical properties of metal-semiconductor nanoscale junction using conductive atomic force microscopy (C-AFM). Single-crystalline CdS, CdSe, and ZnO one-dimensional nanostructures are synthesized via chemical vapor transport, and individual nanobelts (or nanowires) are used to fabricate nanojunction electrodes. The current-voltage (I -V) curves are obtained by placing a C-AFM metal (PtIr) tip as a movable contact on the nanobelt (or nanowire), and often exhibit a resistive switching behavior that is rationalized by the Schottky (high resistance state) and ohmic (low resistance state) contacts between the metal and semiconductor. We obtain the Schottky barrier height and the ideality factor through fitting analysis of the I-V curves. The present nanojunction devices exhibit a lower Schottky barrier height and a higher ideality factor than those of the bulk materials, which is consistent with the findings of previous works on nanostructures. It is shown that C-AFM is a powerful tool for characterization of the Schottky contact of conducting channels between semiconductor nanostructures and metal electrodes.

  4. Perfect/complete scattering experiments probing quantum mechanics on atomic and molecular collisions and coincidences

    CERN Document Server

    Kleinpoppen, Hans; Grum-Grzhimailo, Alexei N

    2013-01-01

    The main goal of this book is to elucidate what kind of experiment must be performed in order to determine the full set of independent parameters which can be extracted and calculated from theory, where electrons, photons, atoms, ions, molecules, or molecular ions may serve as the interacting constituents of matter.  The feasibility of such perfect' and-or `complete' experiments, providing the complete quantum mechanical knowledge of the process, is associated with the enormous potential of modern research techniques, both, in experiment and theory.  It is even difficult to overestimate the role of theory in setting of the complete experiment, starting with the fact that an experiment can be complete only within a certain theoretical framework, and ending with the direct prescription of what, and in what conditions should be measured to make the experiment `complete'.  The language of the related theory is the language of quantum mechanical amplitudes and their relative phases.  This book captures the spi...

  5. Probing the compressibility of tumor cell nuclei by combined atomic force-confocal microscopy

    Science.gov (United States)

    Krause, Marina; te Riet, Joost; Wolf, Katarina

    2013-12-01

    The cell nucleus is the largest and stiffest organelle rendering it the limiting compartment during migration of invasive tumor cells through dense connective tissue. We here describe a combined atomic force microscopy (AFM)-confocal microscopy approach for measurement of bulk nuclear stiffness together with simultaneous visualization of the cantilever-nucleus contact and the fate of the cell. Using cantilevers functionalized with either tips or beads and spring constants ranging from 0.06-10 N m-1, force-deformation curves were generated from nuclear positions of adherent HT1080 fibrosarcoma cell populations at unchallenged integrity, and a nuclear stiffness range of 0.2 to 2.5 kPa was identified depending on cantilever type and the use of extended fitting models. Chromatin-decondensating agent trichostatin A (TSA) induced nuclear softening of up to 50%, demonstrating the feasibility of our approach. Finally, using a stiff bead-functionalized cantilever pushing at maximal system-intrinsic force, the nucleus was deformed to 20% of its original height which after TSA treatment reduced further to 5% remaining height confirming chromatin organization as an important determinant of nuclear stiffness. Thus, combined AFM-confocal microscopy is a feasible approach to study nuclear compressibility to complement concepts of limiting nuclear deformation in cancer cell invasion and other biological processes.

  6. Advances in Probes and Methods for Clinical EPR Oximetry

    Science.gov (United States)

    Hou, Huagang; Khan, Nadeem; Jarvis, Lesley A.; Chen, Eunice Y.; Williams, Benjamin B.; Kuppusamy, Periannan

    2015-01-01

    EPR oximetry, which enables reliable, accurate, and repeated measurements of the partial pressure of oxygen in tissues, provides a unique opportunity to investigate the role of oxygen in the pathogenesis and treatment of several diseases including cancer, stroke, and heart failure. Building on significant advances in the in vivo application of EPR oximetry for small animal models of disease, we are developing suitable probes and instrumentation required for use in human subjects. Our laboratory has established the feasibility of clinical EPR oximetry in cancer patients using India ink, the only material presently approved for clinical use. We now are developing the next generation of probes, which are both superior in terms of oxygen sensitivity and biocompatibility including an excellent safety profile for use in humans. Further advances include the development of implantable oxygen sensors linked to an external coupling loop for measurements of deep-tissue oxygenations at any depth, overcoming the current limitation of 10 mm. This paper presents an overview of recent developments in our ability to make meaningful measurements of oxygen partial pressures in human subjects under clinical settings. PMID:24729217

  7. A new method for building an atomic matter-wave interferometry

    International Nuclear Information System (INIS)

    Gao Hongyi; Chen Jianwen; Xie Honglan; Chen Min; Xu Zhizhan; Xiao Tiqiao; Zhu Peiping

    2002-01-01

    A new method for building an atomic matter-wave interferometry is proposed. A Fresnel zone-plate is used for restricting the linewidth of atomic beams, then a quasi-monochromatic atomic beam is obtained to illuminate four slits on a copper foil. The phenomenon of atomic interference and holograph can be observed, which is used to measure the coherent length of atomic beams

  8. Study of borehole probing methods to improve the ground characterization

    Science.gov (United States)

    Naeimipour, Ali

    Collecting geological information allows for optimizing ground control measures in underground structures. This includes understanding of the joints and discontinuities and rock strength to develop rock mass classifications. An ideal approach to collect such information is through correlating the drilling data from the roofbolters to assess rock strength and void location and properties. The current instrumented roofbolters are capable of providing some information on these properties but not fully developed for accurate ground characterization. To enhance existing systems additional instrumentation and testing was conducted in laboratory and field conditions. However, to define the geology along the boreholes, the use of probing was deemed to be most efficient approach for locating joints and structures in the ground and evaluation of rock strength. Therefore, this research focuses on selection and evaluation of proper borehole probes that can offer a reliable assessment of rock mass structure and rock strength. In particular, attention was paid to borehole televiewer to characterize rock mass structures and joints and development of mechanical rock scratcher for determination of rock strength. Rock bolt boreholes are commonly drilled in the ribs and the roof of underground environments. They are often small (about 1.5 inches) and short (mostly 2-3 meter). Most of them are oriented upward and thus, mostly dry or perhaps wet but not filled with water. No suitable system is available for probing in such conditions to identify the voids/joints and specifically to measure rock strength for evaluation of rock mass and related optimization of ground support design. A preliminary scan of available borehole probes proved that the best options for evaluation of rock structure is through analysis of borehole images, captured by optical televiewers. Laboratory and field trials with showed that these systems can be used to facilitate measurement of the location, frequency and

  9. Atom Probe Tomography of Phase and Grain Boundaries in Experimentally-Deformed and Hot-Pressed Wehrlite

    Science.gov (United States)

    Cukjati, J.; Parman, S. W.; Cooper, R. F.; Zhao, N.

    2017-12-01

    Atom probe tomography (APT) was used to characterize the chemistry of three grain boundaries: an olivine-olivine (ol-ol) and olivine-clinopyroxene (ol-cpx) boundary in fine-grained experimentally-deformed wehrlite and an ol-cpx boundary in a fine-grained, hot-pressed wehrlite. Grain boundaries were extracted and formed into APT tips using a focused ion beam (FIB). The tips were analyzed in a reflectron-equipped LEAP4000HR (Harvard University) at 1% or 0.5% detection rate, 5pJ laser energy and 100kHz pulse rate. Total ion counts are between 40 and 100 million per tip. Examination of grain and phase boundaries in wehrlite are of interest since slow-diffusing and olivine-incompatible cations present in cpx (e.g. Ca and Al) may control diffusion-accommodated grain boundary sliding and affect mantle rheology (Sundberg & Cooper, 2008). At steady state, ol-cpx aggregates are weaker than either ol or cpx end member, the results of which are not currently well-explained. We investigate grain boundary widths to understand the transport of olivine-incompatible elements. Widths of grain/phase boundary chemical segregation are between 3nm and 6nm for deformed ol-ol and ol-cpx samples; minimally-deformed (hot-pressed) samples having slightly wider chemical segregation widths. Chemical segregation widths were determined from profiles of Na, Al, P, Cl, K, Ca, or Ni, although not all listed elements can be used for all samples (e.g. Na, K segregation profiles can only be observed for ol-ol sample). These estimates are consistent with prior estimates of grain boundary segregation by atom probe tomography on ol-ol and opx-opx samples (Bachhav et al., 2015) and are less than ol-ol interface widths analyzed by STEM/EDX (Hiraga, Anderson, & Kohlstedt, 2007). STEM/EDX will be performed on deformed wehrlite to investigate chemical profile as a function of applied stress orientation and at length scales between those observable by APT and EPMA. Determination of phase boundary chemistry and

  10. Blinded Comparison between an In-Air Reverberation Method and an Electronic Probe Tester in the Detection of Ultrasound Probe Faults.

    Science.gov (United States)

    Dudley, Nicholas J; Woolley, Darren J

    2017-12-01

    The aim of this study was to perform a blinded trial, comparing the results of a visual inspection of the in-air reverberation pattern with the results of an electronic probe tester in detecting ultrasound probe faults. Sixty-two probes were tested. A total of 28 faults were found, 3 only by in-air reverberation assessment and 2 only by the electronic probe tester. The electronic probe tester provided additional information regarding the location of the fault in 74% of the cases in which both methods detected a fault. It is possible to detect the majority of probe faults by visual inspection and in-air reverberation assessment. The latter provides an excellent first-line test, easily performed on a daily basis by equipment users. An electronic probe tester is required if detailed evaluation of faults is necessary. Copyright © 2017 World Federation for Ultrasound in Medicine and Biology. All rights reserved.

  11. Prototyping method for Bragg-type atom interferometers

    Energy Technology Data Exchange (ETDEWEB)

    Benton, Brandon; Krygier, Michael; Heward, Jeffrey; Edwards, Mark [Department of Physics, Georgia Southern University, Statesboro, Georgia 30460-8031 (United States); Clark, Charles W. [Joint Quantum Insitute, National Institute of Standards and Technology and the University of Maryland, Gaithersburg, Maryland 20899 (United States)

    2011-10-15

    We present a method for rapid modeling of new Bragg ultracold atom-interferometer (AI) designs useful for assessing the performance of such interferometers. The method simulates the overall effect on the condensate wave function in a given AI design using two separate elements. These are (1) modeling the effect of a Bragg pulse on the wave function and (2) approximating the evolution of the wave function during the intervals between the pulses. The actual sequence of these pulses and intervals is then followed to determine the approximate final wave function from which the interference pattern can be calculated. The exact evolution between pulses is assumed to be governed by the Gross-Pitaevskii (GP) equation whose solution is approximated using a Lagrangian variational method to facilitate rapid estimation of performance. The method presented here is an extension of an earlier one that was used to analyze the results of an experiment [J. E. Simsarian et al., Phys. Rev. Lett. 85, 2040 (2000)], where the phase of a Bose-Einstein condensate was measured using a Mach-Zehnder-type Bragg AI. We have developed both 1D and 3D versions of this method and we have determined their validity by comparing their predicted interference patterns with those obtained by numerical integration of the 1D GP equation and with the results of the above experiment. We find excellent agreement between the 1D interference patterns predicted by this method and those found by the GP equation. We show that we can reproduce all of the results of that experiment without recourse to an ad hoc velocity-kick correction needed by the earlier method, including some experimental results that the earlier model did not predict. We also found that this method provides estimates of 1D interference patterns at least four orders-of-magnitude faster than direct numerical solution of the 1D GP equation.

  12. Method and apparatus for probing relative volume fractions

    Science.gov (United States)

    Jandrasits, Walter G.; Kikta, Thomas J.

    1998-01-01

    A relative volume fraction probe particularly for use in a multiphase fluid system includes two parallel conductive paths defining therebetween a sample zone within the system. A generating unit generates time varying electrical signals which are inserted into one of the two parallel conductive paths. A time domain reflectometer receives the time varying electrical signals returned by the second of the two parallel conductive paths and, responsive thereto, outputs a curve of impedance versus distance. An analysis unit then calculates the area under the curve, subtracts the calculated area from an area produced when the sample zone consists entirely of material of a first fluid phase, and divides this calculated difference by the difference between an area produced when the sample zone consists entirely of material of the first fluid phase and an area produced when the sample zone consists entirely of material of a second fluid phase. The result is the volume fraction.

  13. Generalized Hartree-Fock method for electron-atom scattering

    International Nuclear Information System (INIS)

    Rosenberg, L.

    1997-01-01

    In the widely used Hartree-Fock procedure for atomic structure calculations, trial functions in the form of linear combinations of Slater determinants are constructed and the Rayleigh-Ritz minimum principle is applied to determine the best in that class. A generalization of this approach, applicable to low-energy electron-atom scattering, is developed here. The method is based on a unique decomposition of the scattering wave function into open- and closed-channel components, so chosen that an approximation to the closed-channel component may be obtained by adopting it as a trial function in a minimum principle, whose rigor can be maintained even when the target wave functions are imprecisely known. Given a closed-channel trial function, the full scattering function may be determined from the solution of an effective one-body Schroedinger equation. Alternatively, in a generalized Hartree-Fock approach, the minimum principle leads to coupled integrodifferential equations to be satisfied by the basis functions appearing in a Slater-determinant representation of the closed-channel wave function; it also provides a procedure for optimizing the choice of nonlinear parameters in a variational determination of these basis functions. Inclusion of additional Slater determinants in the closed-channel trial function allows for systematic improvement of that function, as well as the calculated scattering parameters, with the possibility of spurious singularities avoided. Electron-electron correlations can be important in accounting for long-range forces and resonances. These correlation effects can be included explicitly by suitable choice of one component of the closed-channel wave function; the remaining component may then be determined by the generalized Hartree-Fock procedure. As a simple test, the method is applied to s-wave scattering of positrons by hydrogen. copyright 1997 The American Physical Society

  14. RCP: a novel probe design bias correction method for Illumina Methylation BeadChip.

    Science.gov (United States)

    Niu, Liang; Xu, Zongli; Taylor, Jack A

    2016-09-01

    The Illumina HumanMethylation450 BeadChip has been extensively utilized in epigenome-wide association studies. This array and its successor, the MethylationEPIC array, use two types of probes-Infinium I (type I) and Infinium II (type II)-in order to increase genome coverage but differences in probe chemistries result in different type I and II distributions of methylation values. Ignoring the difference in distributions between the two probe types may bias downstream analysis. Here, we developed a novel method, called Regression on Correlated Probes (RCP), which uses the existing correlation between pairs of nearby type I and II probes to adjust the beta values of all type II probes. We evaluate the effect of this adjustment on reducing probe design type bias, reducing technical variation in duplicate samples, improving accuracy of measurements against known standards, and retention of biological signal. We find that RCP is statistically significantly better than unadjusted data or adjustment with alternative methods including SWAN and BMIQ. We incorporated the method into the R package ENmix, which is freely available from the Bioconductor website (https://www.bioconductor.org/packages/release/bioc/html/ENmix.html). niulg@ucmail.uc.edu Supplementary data are available at Bioinformatics online. Published by Oxford University Press 2016. This work is written by US Government employees and is in the public domain in the US.

  15. Study of precipitation in Al–Mg–Si Alloys by atom probe tomography II. Influence of Cu additions

    International Nuclear Information System (INIS)

    Zandbergen, M.W.; Cerezo, A.; Smith, G.D.W.

    2015-01-01

    Atom probe tomography (APT) analysis and hardness measurements have been used to characterise the early stages of precipitation in three Al–Mg–Si alloys with different Cu contents (Al–0.51 at.%Mg–0.94 at.%Si, with 0.01 at.%, 0.06 at.%, or 0.34 at.% Cu). A range of single and multi- stage heat treatments were chosen to evaluate the changes in precipitation processes. Three ageing temperatures were investigated, 298 K (natural ageing), 353 K (pre-ageing) and 453 K (automotive paint-bake conditions). The Cu content had significant effects on the microstructural evolution within the alloy. Formation of clusters which can act as precursors of elongated precipitates during paint-baking was found to be enhanced with increasing Cu content. This improved the paint-bake hardening response and mitigated the deleterious effects of natural ageing. Cu was present in all precipitates in the highest Cu-containing alloy. These precipitates were believed to be precursors to the Q′ phase. Mechanisms for the effects of Cu on precipitation kinetics are proposed.

  16. Microstructural evolution of Fe−22%Cr model alloy under thermal ageing and ion irradiation conditions studied by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Korchuganova, Olesya A., E-mail: KorchuganovaOA@gmail.com [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 115409, Moscow (Russian Federation); State Scientific Center of the Russian Federation, Institute for Theoretical and Experimental Physics of National Research Centre “Kurchatov Institute”, 117218, Moscow (Russian Federation); Thuvander, Mattias [Chalmers University of Technology, SE-412 96, Göteborg (Sweden); Aleev, Andrey A.; Rogozhkin, Sergey V. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 115409, Moscow (Russian Federation); State Scientific Center of the Russian Federation, Institute for Theoretical and Experimental Physics of National Research Centre “Kurchatov Institute”, 117218, Moscow (Russian Federation); Boll, Torben [Chalmers University of Technology, SE-412 96, Göteborg (Sweden); Kulevoy, Timur V. [State Scientific Center of the Russian Federation, Institute for Theoretical and Experimental Physics of National Research Centre “Kurchatov Institute”, 117218, Moscow (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 115409, Moscow (Russian Federation)

    2016-08-15

    Nanostructure evolution during ion irradiation of two thermally aged binary Fee22Cr alloys has been investigated using atom probe tomography. Specimens aged at 500 °C for 50 and 200 h were irradiated by 5.6 MeV Fe ions at room temperature up to fluences of 0.3 × 10{sup 15} ions/cm{sup 2} and 1 × 10{sup 15} ions/cm{sup 2}. The effect of irradiation on the material nanostructure was examined at a depth of 1 μm from the irradiated surface. The analysis of Cr radial concentration functions reveals that dense α′-phase precipitates in the 200 h aged alloy become diffuse and thereby larger when subjected to irradiation. On the other hand, less Cr-enriched precipitates in the alloy aged for 50 h are less affected. The CreCr pair correlation function analysis shows that matrix inhomogeneity decreases under irradiation. Irradiation leads to a decrease in the number density of diffuse clusters, whereas in the case of well-developed precipitates it remains unchanged.

  17. Microstructural evolution of Fe−22%Cr model alloy under thermal ageing and ion irradiation conditions studied by atom probe tomography

    International Nuclear Information System (INIS)

    Korchuganova, Olesya A.; Thuvander, Mattias; Aleev, Andrey A.; Rogozhkin, Sergey V.; Boll, Torben; Kulevoy, Timur V.

    2016-01-01

    Nanostructure evolution during ion irradiation of two thermally aged binary Fee22Cr alloys has been investigated using atom probe tomography. Specimens aged at 500 °C for 50 and 200 h were irradiated by 5.6 MeV Fe ions at room temperature up to fluences of 0.3 × 10 15 ions/cm 2 and 1 × 10 15 ions/cm 2 . The effect of irradiation on the material nanostructure was examined at a depth of 1 μm from the irradiated surface. The analysis of Cr radial concentration functions reveals that dense α′-phase precipitates in the 200 h aged alloy become diffuse and thereby larger when subjected to irradiation. On the other hand, less Cr-enriched precipitates in the alloy aged for 50 h are less affected. The CreCr pair correlation function analysis shows that matrix inhomogeneity decreases under irradiation. Irradiation leads to a decrease in the number density of diffuse clusters, whereas in the case of well-developed precipitates it remains unchanged.

  18. Microstructural evolution of Fesbnd 22%Cr model alloy under thermal ageing and ion irradiation conditions studied by atom probe tomography

    Science.gov (United States)

    Korchuganova, Olesya A.; Thuvander, Mattias; Aleev, Andrey A.; Rogozhkin, Sergey V.; Boll, Torben; Kulevoy, Timur V.

    2016-08-01

    Nanostructure evolution during ion irradiation of two thermally aged binary Fee22Cr alloys has been investigated using atom probe tomography. Specimens aged at 500 °C for 50 and 200 h were irradiated by 5.6 MeV Fe ions at room temperature up to fluences of 0.3 × 1015 ions/cm2 and 1 × 1015 ions/cm2. The effect of irradiation on the material nanostructure was examined at a depth of 1 μm from the irradiated surface. The analysis of Cr radial concentration functions reveals that dense α‧-phase precipitates in the 200 h aged alloy become diffuse and thereby larger when subjected to irradiation. On the other hand, less Cr-enriched precipitates in the alloy aged for 50 h are less affected. The CreCr pair correlation function analysis shows that matrix inhomogeneity decreases under irradiation. Irradiation leads to a decrease in the number density of diffuse clusters, whereas in the case of well-developed precipitates it remains unchanged.

  19. Atomic Force Microscopy Probing of Receptor–Nanoparticle Interactions for Riboflavin Receptor Targeted Gold–Dendrimer Nanocomposites

    Science.gov (United States)

    2015-01-01

    Riboflavin receptors are overexpressed in malignant cells from certain human breast and prostate cancers, and they constitute a group of potential surface markers important for cancer targeted delivery of therapeutic agents and imaging molecules. Here we report on the fabrication and atomic force microscopy (AFM) characterization of a core–shell nanocomposite consisting of a gold nanoparticle (AuNP) coated with riboflavin receptor-targeting poly(amido amine) dendrimer. We designed this nanocomposite for potential applications such as a cancer targeted imaging material based on its surface plasmon resonance properties conferred by AuNP. We employed AFM as a technique for probing the binding interaction between the nanocomposite and riboflavin binding protein (RfBP) in solution. AFM enabled precise measurement of the AuNP height distribution before (13.5 nm) and after chemisorption of riboflavin-conjugated dendrimer (AuNP–dendrimer; 20.5 nm). Binding of RfBP to the AuNP–dendrimer caused a height increase to 26.7 nm, which decreased to 22.8 nm when coincubated with riboflavin as a competitive ligand, supporting interaction of AuNP–dendrimer and its target protein. In summary, physical determination of size distribution by AFM imaging can serve as a quantitative approach to monitor and characterize the nanoscale interaction between a dendrimer-covered AuNP and target protein molecules in vitro. PMID:24571134

  20. Characterization of Precipitation in Al-Li Alloy AA2195 by means of Atom Probe Tomography and Transmission Electron Microscopy

    KAUST Repository

    Khushaim, Muna

    2015-05-19

    The microstructure of the commercial alloy AA2195 was investigated on the nanoscale after conducting T8 tempering. This particular thermomechanical treatment of the specimen resulted in the formation of platelet-shaped T 1 Al 2 CuLi / θ ′ Al 2 Cu precipitates within the Al matrix. The electrochemically prepared samples were analyzed by scanning transmission electron microscopy and atom probe tomography for chemical mapping. The θ ′ platelets, which are less than 2 nm thick, have the stoichiometric composition consistent with the expected Al 2 Cu equilibrium composition. Additionally, the Li distribution inside the θ ′ platelets was found to equal the same value as in the matrix. The equally thin T 1 platelet deviates from the formula (Al 2 CuLi) in its stoichiometry and shows Mg enrichment inside the platelet without any indication of a higher segregation level at the precipitate/matrix interface. The deviation from the (Al 2 CuLi) stoichiometry cannot be simply interpreted as a consequence of artifacts when measuring the Cu and Li concentrations inside the T 1 platelet. The results show rather a strong hint for a true lower Li and Cu contents, hence supporting reasonably the hypothesis that the real chemical composition for the thin T 1 platelet in the T8 tempering condition differs from the equilibrium composition of the thermodynamic stable bulk phase.

  1. Characterization of Precipitation in Al-Li Alloy AA2195 by means of Atom Probe Tomography and Transmission Electron Microscopy

    KAUST Repository

    Khushaim, Muna; Boll, Torben; Seibert, Judith; Haider, Ferdinand; Al-Kassab, Talaat

    2015-01-01

    The microstructure of the commercial alloy AA2195 was investigated on the nanoscale after conducting T8 tempering. This particular thermomechanical treatment of the specimen resulted in the formation of platelet-shaped T 1 Al 2 CuLi / θ ′ Al 2 Cu precipitates within the Al matrix. The electrochemically prepared samples were analyzed by scanning transmission electron microscopy and atom probe tomography for chemical mapping. The θ ′ platelets, which are less than 2 nm thick, have the stoichiometric composition consistent with the expected Al 2 Cu equilibrium composition. Additionally, the Li distribution inside the θ ′ platelets was found to equal the same value as in the matrix. The equally thin T 1 platelet deviates from the formula (Al 2 CuLi) in its stoichiometry and shows Mg enrichment inside the platelet without any indication of a higher segregation level at the precipitate/matrix interface. The deviation from the (Al 2 CuLi) stoichiometry cannot be simply interpreted as a consequence of artifacts when measuring the Cu and Li concentrations inside the T 1 platelet. The results show rather a strong hint for a true lower Li and Cu contents, hence supporting reasonably the hypothesis that the real chemical composition for the thin T 1 platelet in the T8 tempering condition differs from the equilibrium composition of the thermodynamic stable bulk phase.

  2. Influence of instrument conditions on the evaporation behavior of uranium dioxide with UV laser-assisted atom probe tomography

    International Nuclear Information System (INIS)

    2015-01-01

    Atom probe tomography (APT) provides the ability to detect subnanometer chemical variations spatially with high accuracy. Due to its ability to spatially characterize chemistry in non-conducting materials, such as oxides, provides the opportunity to characterize stoichiometry, which strongly is tied to material performance. However, accuracy has been correlated with instrument run parameters. A systematic study of the effect of laser energy, temperature, and detection rate is performed on the evaporation behavior of a model oxide, uranium dioxide (UO 2 ). Modifying the detection rate and temperature did not affect its evaporation behavior as laser energy. It was discovered that three laser evaporation regimes are present in UO 2 . Very low laser energy produces a behavior similar to DC-field evaporation, moderate laser energy produces the desired laser assisted field evaporation and high laser energy produces thermal effects in the evaporation behavior. Laser energy had the greatest impact on evaporation and the optimal instrument condition for UO 2 was determined to be 50K, 10 pJ laser energy, 0.3% detection rate, and a 100 kHz repetition rate. These conditions provide the best combination of mass resolution, accurate stoichiometry, and evaporation behavior.

  3. Characterization of Precipitation in Al-Li Alloy AA2195 by means of Atom Probe Tomography and Transmission Electron Microscopy

    Directory of Open Access Journals (Sweden)

    Muna Khushaim

    2015-01-01

    Full Text Available The microstructure of the commercial alloy AA2195 was investigated on the nanoscale after conducting T8 tempering. This particular thermomechanical treatment of the specimen resulted in the formation of platelet-shaped T1Al2CuLi/θ′Al2Cu precipitates within the Al matrix. The electrochemically prepared samples were analyzed by scanning transmission electron microscopy and atom probe tomography for chemical mapping. The θ′ platelets, which are less than 2 nm thick, have the stoichiometric composition consistent with the expected Al2Cu equilibrium composition. Additionally, the Li distribution inside the θ′ platelets was found to equal the same value as in the matrix. The equally thin T1 platelet deviates from the formula (Al2CuLi in its stoichiometry and shows Mg enrichment inside the platelet without any indication of a higher segregation level at the precipitate/matrix interface. The deviation from the (Al2CuLi stoichiometry cannot be simply interpreted as a consequence of artifacts when measuring the Cu and Li concentrations inside the T1 platelet. The results show rather a strong hint for a true lower Li and Cu contents, hence supporting reasonably the hypothesis that the real chemical composition for the thin T1 platelet in the T8 tempering condition differs from the equilibrium composition of the thermodynamic stable bulk phase.

  4. 3D site specific sample preparation and analysis of 3D devices (FinFETs) by atom probe tomography.

    Science.gov (United States)

    Kambham, Ajay Kumar; Kumar, Arul; Gilbert, Matthieu; Vandervorst, Wilfried

    2013-09-01

    With the transition from planar to three-dimensional device architectures such as Fin field-effect-transistors (FinFETs), new metrology approaches are required to meet the needs of semiconductor technology. It is important to characterize the 3D-dopant distributions precisely as their extent, positioning relative to gate edges and absolute concentration determine the device performance in great detail. At present the atom probe has shown its ability to analyze dopant distributions in semiconductor and thin insulating materials with sub-nm 3D-resolution and good dopant sensitivity. However, so far most reports have dealt with planar devices or restricted the measurements to 2D test structures which represent only limited challenges in terms of localization and site specific sample preparation. In this paper we will discuss the methodology to extract the dopant distribution from real 3D-devices such as a 3D-FinFET device, requiring the sample preparation to be carried out at a site specific location with a positioning accuracy ∼50 nm. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. Sources of polarized ions and atoms

    International Nuclear Information System (INIS)

    Cornelius, W.D.

    1988-01-01

    In this presentation we discuss methods of producing large quantities of polarized atoms and ions (Stern-Gerlach separation, optical pumping, and spin-exchange) as well as experimental methods of measuring the degree of polarization of atomic systems. The usefulness of polarized atoms in probing the microscopic magnetic surface properties of materials will also be discussed. 39 refs., 5 figs., 2 tabs

  6. Method and apparatus for synthesis of arrays of DNA probes

    Science.gov (United States)

    Cerrina, Francesco; Sussman, Michael R.; Blattner, Frederick R.; Singh-Gasson, Sangeet; Green, Roland

    2002-04-23

    The synthesis of arrays of DNA probes sequences, polypeptides, and the like is carried out using a patterning process on an active surface of a substrate. An image is projected onto the active surface of the substrate utilizing an image former that includes a light source that provides light to a micromirror device comprising an array of electronically addressable micromirrors, each of which can be selectively tilted between one of at least two positions. Projection optics receives the light reflected from the micromirrors along an optical axis and precisely images the micromirrors onto the active surface of the substrate, which may be used to activate the surface of the substrate. The first level of bases may then be applied to the substrate, followed by development steps, and subsequent exposure of the substrate utilizing a different pattern of micromirrors, with further repeats until the elements of a two dimensional array on the substrate surface have an appropriate base bound thereto. The micromirror array can be controlled in conjunction with a DNA synthesizer supplying appropriate reagents to a flow cell containing the active substrate to control the sequencing of images presented by the micromirror array in coordination of the reagents provided to the substrate.

  7. Influence of multi-hit capability on quantitative measurement of NiPtSi thin film with laser-assisted atom probe tomography

    International Nuclear Information System (INIS)

    Kinno, T.; Akutsu, H.; Tomita, M.; Kawanaka, S.; Sonehara, T.; Hokazono, A.; Renaud, L.; Martin, I.; Benbalagh, R.; Sallé, B.; Takeno, S.

    2012-01-01

    Highlights: ► Laser-assisted atom probe tomography was applied to NiPtSi films on Si substrates. ► Comparison of depth profiles of single-hit events and those of multi-hit events. ► ∼80% of Pt atoms were detected in multi-hit events. ► Multiple-ion detection is important for Laser-assisted atom probe tomography. - Abstract: Laser-assisted atom probe tomography (LA-APT) was applied to NiPtSi (0, 30, and 50% Pt contents) thin films on Si substrates. Consistent results with those of high-resolution Rutherford backscattering spectrometry (HR-RBS) were obtained. Based on the obtained data sets, the composition profiles from only the signals of single-hit events, meaning detection of one ion by one laser pulse, were compiled. The profiles from only the signals of multi-hit events, meaning detection of multiple ions by one laser pulse, were also compiled. There were large discrepancies with respect to Ni and Pt concentrations among the compiled profiles and the original profiles including the signals of both types of detection events. Additionally, the profiles compiled from single-hit events showed that Si concentration in NiPtSi layer became smaller toward the surface, differing from the original profiles and the multi-hit profiles. These results suggest that capability of simultaneous multiple-ion detection is important for appropriate LA-APT analyses.

  8. Study of confined many electron atoms by means of the POEP method

    International Nuclear Information System (INIS)

    Sarsa, A; Buendía, E; Gálvez, F J

    2014-01-01

    The electronic structure of confined atoms under impenetrable spherical walls is studied by means of the parameterized optimized effective potential method. A cut-off factor is employed to account for Dirichlet boundary conditions. Two atomic basis sets commonly used for describing free atoms have been analyzed within this scheme. The accuracy of the method is similar to that achieved for the free atoms. The ground state electrostatic multiplet of the carbon atom as well as the ground state and both the [Ar]4s3d 7 5 F and [Ar]3d 8 3 F excited states of the iron atom are studied. The behaviour of the energy levels with the confinement has been analyzed in terms of the different contributions to the total energy of the atom. For the iron atom, the effect of confinement on the outermost orbitals is studied. (paper)

  9. A single-probe heat pulse method for estimating sap velocity in trees.

    Science.gov (United States)

    López-Bernal, Álvaro; Testi, Luca; Villalobos, Francisco J

    2017-10-01

    Available sap flow methods are still far from being simple, cheap and reliable enough to be used beyond very specific research purposes. This study presents and tests a new single-probe heat pulse (SPHP) method for monitoring sap velocity in trees using a single-probe sensor, rather than the multi-probe arrangements used up to now. Based on the fundamental conduction-convection principles of heat transport in sapwood, convective velocity (V h ) is estimated from the temperature increase in the heater after the application of a heat pulse (ΔT). The method was validated against measurements performed with the compensation heat pulse (CHP) technique in field trees of six different species. To do so, a dedicated three-probe sensor capable of simultaneously applying both methods was produced and used. Experimental measurements in the six species showed an excellent agreement between SPHP and CHP outputs for moderate to high flow rates, confirming the applicability of the method. In relation to other sap flow methods, SPHP presents several significant advantages: it requires low power inputs, it uses technically simpler and potentially cheaper instrumentation, the physical damage to the tree is minimal and artefacts caused by incorrect probe spacing and alignment are removed. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

  10. A New Method for Analyzing Near-Field Faraday Probe Data in Hall Thrusters

    Science.gov (United States)

    Huang, Wensheng; Shastry, Rohit; Herman, Daniel A.; Soulas, George C.; Kamhawi, Hani

    2013-01-01

    This paper presents a new method for analyzing near-field Faraday probe data obtained from Hall thrusters. Traditional methods spawned from far-field Faraday probe analysis rely on assumptions that are not applicable to near-field Faraday probe data. In particular, arbitrary choices for the point of origin and limits of integration have made interpretation of the results difficult. The new method, called iterative pathfinding, uses the evolution of the near-field plume with distance to provide feedback for determining the location of the point of origin. Although still susceptible to the choice of integration limits, this method presents a systematic approach to determining the origin point for calculating the divergence angle. The iterative pathfinding method is applied to near-field Faraday probe data taken in a previous study from the NASA-300M and NASA-457Mv2 Hall thrusters. Since these two thrusters use centrally mounted cathodes the current density associated with the cathode plume is removed before applying iterative pathfinding. A procedure is presented for removing the cathode plume. The results of the analysis are compared to far-field probe analysis results. This paper ends with checks on the validity of the new method and discussions on the implications of the results.

  11. Studying nearest neighbor correlations by atom probe tomography (APT) in metallic glasses as exemplified for Fe40Ni40B20 glassy ribbons

    KAUST Repository

    Shariq, Ahmed

    2012-01-01

    A next nearest neighbor evaluation procedure of atom probe tomography data provides distributions of the distances between atoms. The width of these distributions for metallic glasses studied so far is a few Angstrom reflecting the spatial resolution of the analytical technique. However, fitting Gaussian distributions to the distribution of atomic distances yields average distances with statistical uncertainties of 2 to 3 hundredth of an Angstrom. Fe 40Ni40B20 metallic glass ribbons are characterized this way in the as quenched state and for a state heat treated at 350 °C for 1 h revealing a change in the structure on the sub-nanometer scale. By applying the statistical tool of the χ2 test a slight deviation from a random distribution of B-atoms in the as quenched sample is perceived, whereas a pronounced elemental inhomogeneity of boron is detected for the annealed state. In addition, the distance distribution of the first fifteen atomic neighbors is determined by using this algorithm for both annealed and as quenched states. The next neighbor evaluation algorithm evinces a steric periodicity of the atoms when the next neighbor distances are normalized by the first next neighbor distance. A comparison of the nearest neighbor atomic distribution for as quenched and annealed state shows accumulation of Ni and B. Moreover, it also reveals the tendency of Fe and B to move slightly away from each other, an incipient step to Ni rich boride formation. © 2011 Elsevier B.V.

  12. Atom probe study of the microstructural evolution induced by irradiation in Fe-Cu ferritic alloys and pressure vessel steels

    International Nuclear Information System (INIS)

    Pareige, P.

    1996-04-01

    Pressure vessel steels used in pressurized water reactors are low alloyed ferritic steels. They may be prone to hardening and embrittlement under neutron irradiation. The changes in mechanical properties are generally supposed to result from the formation of point defects, dislocation loops, voids and/or copper rich clusters. However, the real nature of the irradiation induced-damage in these steels has not been clearly identified yet. In order to improve our vision of this damage, we have characterized the microstructure of several steels and model alloys irradiated with electrons and neutrons. The study was performed with conventional and tomographic atom probes. The well known importance of the effects of copper upon pressure vessel steel embrittlement has led us to study Fe-Cu binary alloys. We have considered chemical aging as well as aging under electron and neutron irradiations. The resulting effects depend on whether electron or neutron irradiations ar used for thus. We carried out both kinds of irradiation concurrently so as to compare their effects. We have more particularly considered alloys with a low copper supersaturation representative of that met with the French vessel alloys (0.1% Cu). Then, we have examined steels used on French nuclear reactor pressure vessels. To characterize the microstructure of CHOOZ A steel and its evolution when exposed to neutrons, we have studied samples from the reactor surveillance program. The results achieved, especially the characterization of neutron-induced defects have been compared with those for another steel from the surveillance program of Dampierre 2. All the experiment results obtained on model and industrial steels have allowed us to consider an explanation of the way how the defects appear and grow, and to propose reasons for their influence upon steel embrittlement. (author). 3 appends

  13. Quantitative compositional analysis and field-evaporation behavior of ordered Ni4Mo on an atomic plane-by-plane basis: an atom-probe field-ion microscope study. MSC report No. 4802

    International Nuclear Information System (INIS)

    Yamamoto, M.; Seidman, D.N.

    1982-10-01

    The (211) fundamental and (101) superlattice planes, of the bct lattice, were analysed chemically on an atomic plane-by-plane basis. It was demonstrated that the composition of each individual plane can be determined as a function of depth without any ambiguity. The overall average Mo concentration was measured to be 17.1 at. % for the (211) fundamental plane. Details of the field evaporation behavior of the (211) fundamental and (101) superlattice planes were studied. The field-evaporation behavior is described in terms of the field-evaporation rate, the order of the field evaporated ions, etc. Each individual atomic plane field evaporated on an atomic plane-by-plane basis for the (211) fundamental plane. While for (101) superlattice plane a group of planes consisting of one plane of Mo atoms and four planes of Ni atoms field-evaporated as a unit. An abnormal increase in the number of Mo atoms was found in the central portion of the (211) fundamental plane. Possible mechanisms for the abnormal field evaporation rate are discussed. It is concluded that the atom probe technique can be used to follow the physics and chemistry of the field-evaporation process and the chemistry of the alloy as a function of position, on a subnanometer scale, throughout the specimen. 13 figures

  14. Direct observation of the leakage current in epitaxial diamond Schottky barrier devices by conductive-probe atomic force microscopy and Raman imaging

    OpenAIRE

    Alvarez, Jose; Boutchich, M.; Kleider, J. P.; Teraji, T.; Koide, Y.

    2014-01-01

    The origin of the high leakage current measured in several vertical-type diamond Schottky devices is conjointly investigated by conducting probe atomic force microscopy (CP-AFM) and confocal micro-Raman/Photoluminescence (PL) imaging analysis. Local areas characterized by a strong decrease of the local resistance (5-6 orders of magnitude drop) with respect to their close surrounding have been identified in several different regions of the sample surface. The same local areas, also referenced ...

  15. Invited Review Article: Tip modification methods for tip-enhanced Raman spectroscopy (TERS) and colloidal probe technique: A 10 year update (2006-2016) review

    Science.gov (United States)

    Yuan, C. C.; Zhang, D.; Gan, Y.

    2017-03-01

    Engineering atomic force microscopy tips for reliable tip enhanced Raman spectroscopy (TERS) and colloidal probe technique are becoming routine practices in many labs. In this 10 year update review, various new tip modification methods developed over the past decade are briefly reviewed to help researchers select the appropriate method. The perspective is put in a large context to discuss the opportunities and challenges in this area, including novel combinations of seemingly different methods, potential applications of some methods which were not originally intended for TERS tip fabrication, and the problems of high cost and poor reproducibility of tip fabrication.

  16. Control of electrolytic refinement of silver by atomic absorption method

    International Nuclear Information System (INIS)

    Kulish, N.G.; Burylev, B.P.

    1983-01-01

    Results of atomic absorption determination of 18 elements: Fe, Cu, Zn, Cd, Bi, Ga, In, Ca, Mg, K, Na, Sb, Te, Ni, Co, Cr, Mn, Pb in silver and electrolytes are presented. When determining impurities in silver the basis has been separated by the extraction of O-isopropyl-N-ethyl thiocarbamate in the 1M HN0 3 medium. Optimum measuring conditions and the range of linear dependence between concentration and atomic absorption value are given

  17. Effect of the interaction conditions of the probe of an atomic-force microscope with the n-GaAs surface on the triboelectrization phenomenon

    Energy Technology Data Exchange (ETDEWEB)

    Baklanov, A. V., E-mail: baklanov@mail.ioffe.ru [St. Petersburg State Polytechnical University, Institute of Physics, Nanotechnology, and Telecommunications (Russian Federation); Gutkin, A. A.; Kalyuzhnyy, N. A. [Russian Academy of Sciences, Ioffe Institute (Russian Federation); Brunkov, P. N. [St. Petersburg State Polytechnical University, Institute of Physics, Nanotechnology, and Telecommunications (Russian Federation)

    2015-08-15

    Triboelectrization as a result of the scanning of an atomic-force-microscope probe over an n-GaAs surface in the contact mode is investigated. The dependences of the local potential variation on the scanning rate and the pressing force of the probe are obtained. The results are explained by point-defect formation in the surface layers of samples under the effect of deformation of these layers during probe scanning. The charge localized at these defects in the case of equilibrium changes the potential of surface, which is subject to triboelectrization. It is shown that, for qualitative explanation of the observed dependences, it is necessary to take into account both the generation and annihilation of defects in the region experiencing deformation.

  18. Rapid detection and identification of pathogenic mycobacteria by combining radiometric and nucleic acid probe methods

    International Nuclear Information System (INIS)

    Ellner, P.D.; Kiehn, T.E.; Cammarata, R.; Hosmer, M.

    1988-01-01

    The combination of radiometric methodology (BACTEC 12B) and probe technology for recovery and identification of mycobacteria was studied in two large hospital laboratories. The sediment from vials with positive growth indices was tested with DNA probes specific for Mycobacterium tuberculosis, Mycobacterium avium, and Mycobacterium intracellulare. The sensitivity of the radiometric method and the specificity of the probes resulted in a marked reduction in the time to the final report. Biochemical testing could be eliminated on isolates giving a positive reaction with one of the probes. Some 176 isolates of M. tuberculosis, 110 of M. avium, and 5 of M. intracellulare were recovered. Two-thirds of these isolates were detected and identified within 2 weeks of inoculation and the remainder was detected by 4 weeks, a reduction of 5 to 7 weeks to the final report

  19. A new method for intraoperative localization of epilepsy focus by means of a gamma probe

    International Nuclear Information System (INIS)

    Carneiro Filho, Omar; Vilela Filho, Osvaldo; Ragazzo, Paulo Cesar; Fonseca, Lea Mirian Barbosa da

    2014-01-01

    Objective: to evaluate the utility of a new multimodal image-guided intervention technique to detect epileptogenic areas with a gamma probe as compared with intraoperative electrocorticography. Materials and methods: two symptomatic patients with refractory epilepsy underwent magnetic resonance imaging, videoelectroencephalography, brain SPECT scan, neuropsychological evaluation and were submitted to gamma probe-assisted surgery. Results: in patient 1, maximum radioactive count was initially observed on the temporal gyrus at about 3.5 cm posteriorly to the tip of the left temporal lobe. After corticotomy, the gamma probe indicated maximum count at the head of the hippocampus, in agreement with the findings of intraoperative electrocorticography. In patient 2, maximum count was observed in the occipital region at the transition between the temporal and parietal lobes (right hemisphere). During the surgery, the area of epileptogenic activity mapped at electrocorticography was also delimited, demarcated, and compared with the gamma probe findings. After lesionectomy, new radioactive counts were performed both in the patients and on the surgical specimens (ex-vivo). Conclusion: the comparison between intraoperative electrocorticography and gamma probe-assisted surgery showed similarity of both methods. The advantages of gamma probe include: noninvasiveness, low cost and capacity to demonstrate decrease in the radioactive activity at the site of excision after lesionectomy. (author)

  20. Scanning tunneling microscopy III theory of STM and related scanning probe methods

    CERN Document Server

    Güntherodt, Hans-Joachim

    1996-01-01

    Scanning Tunneling Microscopy III provides a unique introduction to the theoretical foundations of scanning tunneling microscopy and related scanning probe methods. The different theoretical concepts developed in the past are outlined, and the implications of the theoretical results for the interpretation of experimental data are discussed in detail. Therefore, this book serves as a most useful guide for experimentalists as well as for theoreticians working in the filed of local probe methods. In this second edition the text has been updated and new methods are discussed.

  1. Mg dopant distribution in an AlGaN/GaN p-type superlattice assessed using atom probe tomography, TEM and SIMS

    International Nuclear Information System (INIS)

    Bennett, S E; Kappers, M J; Barnard, J S; Humphreys, C J; Oliver, R A; Clifton, P H; Ulfig, R M

    2010-01-01

    P-type conducting layers are critical in GaN-based devices such as LEDs and laser diodes. Such layers are often produced by doping GaN with Mg, but the hole concentration can be enhanced using AlGaN/GaN p-type superlattices by exploiting the built-in polarisation fields. A Mg-doped AlGaN/GaN superlattice was studied using SIMS. Although the AlGaN and GaN were nominally doped to the same level, the SIMS data suggested a difference in doping density between the two materials. Atom probe tomography was then used to investigate the Mg distribution. The superlattice repeats were clearly visible, as expected and, in addition, significant Mg clustering was observed in both the GaN and AlGaN layers. There were many more Mg clusters in the AlGaN layers than the GaN layers, accounting for the difference in doping density suggested by SIMS. To evaluate the structural accuracy of the atom probe reconstruction, layer thicknesses from the atom probe were compared with STEM images. Finally, future work is proposed to investigate the Mg clusters in the TEM.

  2. Pulsed-voltage atom probe tomography of low conductivity and insulator materials by application of ultrathin metallic coating on nanoscale specimen geometry.

    Science.gov (United States)

    Adineh, Vahid R; Marceau, Ross K W; Chen, Yu; Si, Kae J; Velkov, Tony; Cheng, Wenlong; Li, Jian; Fu, Jing

    2017-10-01

    We present a novel approach for analysis of low-conductivity and insulating materials with conventional pulsed-voltage atom probe tomography (APT), by incorporating an ultrathin metallic coating on focused ion beam prepared needle-shaped specimens. Finite element electrostatic simulations of coated atom probe specimens were performed, which suggest remarkable improvement in uniform voltage distribution and subsequent field evaporation of the insulated samples with a metallic coating of approximately 10nm thickness. Using design of experiment technique, an experimental investigation was performed to study physical vapor deposition coating of needle specimens with end tip radii less than 100nm. The final geometries of the coated APT specimens were characterized with high-resolution scanning electron microscopy and transmission electron microscopy, and an empirical model was proposed to determine the optimal coating thickness for a given specimen size. The optimal coating strategy was applied to APT specimens of resin embedded Au nanospheres. Results demonstrate that the optimal coating strategy allows unique pulsed-voltage atom probe analysis and 3D imaging of biological and insulated samples. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Nucleic acid extraction, oligonucleotide probes and PCR methods

    International Nuclear Information System (INIS)

    Zhongtang Yu; Forster, R.J.

    2005-01-01

    Complex microbiomes of rumen and gastrointestinal tracts. Bacteria, fungi and protozoa, present in rumen and gastrointestinal (GI) tracts, interact with feed, with each other, and with their host animals, resulting in a complex symbiotic microbiota of distinctive composition and structure. Such microbiota is dynamic and highly responsive to a variety of biotic and abiotic factors, such as diet, feed additives, age, health and physiological status of the host animal, geographical locations, season and feeding regimen (reviewed in Ref. [39]). This symbiotic microbiota has been the focus of microbial research for over half a century in search for improved ruminant nutrition. Before the advent of molecular biology techniques, microorganisms in rumen and GI tracts, as in other habitats, were studied with cultivation-based techniques, which only allows for the isolation and characterization of a limited number of readily culturable species. As estimated, there are more than 400 species of bacteria and up to 100 species of protozoa and fungi inhabiting rumen and GI tracts. In human GI tracts, as much as 60% of these members cannot be isolated on agar plates and, thus, remain unknown. In ruminants, although it is not known, the culturable species of the microbiota are probably in the same range. Even among the culturable species, probably only some of them have been isolated and described. The application of cultivation-independent, more sensitive and accurate molecular techniques to the study of ruminal and GI microorganisms provided an alternative to directly examining the diversity and the community structure of ruminal and GI microbiota on the basis of genotypes, instead of phenotypes. Both polymerase chain reaction (PCR)-based methods, such as denaturing gradient gel electrophoresis (DGGE), ribosomal intergenic spacer analysis, terminal restriction fragment length polymorphism, cloning and sequencing of PCR amplicons and amplified 16S ribosomal DNA restriction

  4. Multi-point probe for testing electrical properties and a method of producing a multi-point probe

    DEFF Research Database (Denmark)

    2011-01-01

    A multi-point probe for testing electrical properties of a number of specific locations of a test sample comprises a supporting body defining a first surface, a first multitude of conductive probe arms (101-101'''), each of the probe arms defining a proximal end and a distal end. The probe arms...... of contact with the supporting body, and a maximum thickness perpendicular to its perpendicular bisector and its line of contact with the supporting body. Each of the probe arms has a specific area or point of contact (111-111''') at its distal end for contacting a specific location among the number...... of specific locations of the test sample. At least one of the probe arms has an extension defining a pointing distal end providing its specific area or point of contact located offset relative to its perpendicular bisector....

  5. Complementary Characterization of Cu(In,Ga)Se₂ Thin-Film Photovoltaic Cells Using Secondary Ion Mass Spectrometry, Auger Electron Spectroscopy, and Atom Probe Tomography.

    Science.gov (United States)

    Jang, Yun Jung; Lee, Jihye; Jeong, Jeung-Hyun; Lee, Kang-Bong; Kim, Donghwan; Lee, Yeonhee

    2018-05-01

    To enhance the conversion performance of solar cells, a quantitative and depth-resolved elemental analysis of photovoltaic thin films is required. In this study, we determined the average concentration of the major elements (Cu, In, Ga, and Se) in fabricated Cu(In,Ga)Se2 (CIGS) thin films, using inductively coupled plasma atomic emission spectroscopy, X-ray fluorescence, and wavelengthdispersive electron probe microanalysis. Depth profiling results for CIGS thin films with different cell efficiencies were obtained using secondary ion mass spectrometry and Auger electron spectroscopy to compare the atomic concentrations. Atom probe tomography, a characterization technique with sub-nanometer resolution, was used to obtain three-dimensional elemental mapping and the compositional distribution at the grain boundaries (GBs). GBs are identified by Na increment accompanied by Cu depletion and In enrichment. Segregation of Na atoms along the GB had a beneficial effect on cell performance. Comparative analyses of different CIGS absorber layers using various analytical techniques provide us with understanding of the compositional distributions and structures of high efficiency CIGS thin films in solar cells.

  6. Mobile Probing and Probes

    DEFF Research Database (Denmark)

    Duvaa, Uffe; Ørngreen, Rikke; Weinkouff Mathiasen, Anne-Gitte

    2013-01-01

    Mobile probing is a method, developed for learning about digital work situations, as an approach to discover new grounds. The method can be used when there is a need to know more about users and their work with certain tasks, but where users at the same time are distributed (in time and space......). Mobile probing was inspired by the cultural probe method, and was influenced by qualitative interview and inquiry approaches. The method has been used in two subsequent projects, involving school children (young adults at 15-17 years old) and employees (adults) in a consultancy company. Findings point...... to mobile probing being a flexible method for uncovering the unknowns, as a way of getting rich data to the analysis and design phases. On the other hand it is difficult to engage users to give in depth explanations, which seem easier in synchronous dialogs (whether online or face2face). The development...

  7. Mobile Probing and Probes

    DEFF Research Database (Denmark)

    Duvaa, Uffe; Ørngreen, Rikke; Weinkouff, Anne-Gitte

    2012-01-01

    Mobile probing is a method, which has been developed for learning about digital work situations, as an approach to discover new grounds. The method can be used when there is a need to know more about users and their work with certain tasks, but where users at the same time are distributed (in time...... and space). Mobile probing was inspired by the cultural probe method, and was influenced by qualitative interview and inquiry approaches. The method has been used in two subsequent projects, involving school children (young adults at 15-17 years old) and employees (adults) in a consultancy company. Findings...... point to mobile probing being a flexible method for uncovering the unknowns, as a way of getting rich data to the analysis and design phases. On the other hand it is difficult to engage users to give in depth explanations, which seem easier in synchronous dialogs (whether online or face2face...

  8. A method for probing the mutational landscape of amyloid structure.

    Science.gov (United States)

    O'Donnell, Charles W; Waldispühl, Jérôme; Lis, Mieszko; Halfmann, Randal; Devadas, Srinivas; Lindquist, Susan; Berger, Bonnie

    2011-07-01

    Proteins of all kinds can self-assemble into highly ordered β-sheet aggregates known as amyloid fibrils, important both biologically and clinically. However, the specific molecular structure of a fibril can vary dramatically depending on sequence and environmental conditions, and mutations can drastically alter amyloid function and pathogenicity. Experimental structure determination has proven extremely difficult with only a handful of NMR-based models proposed, suggesting a need for computational methods. We present AmyloidMutants, a statistical mechanics approach for de novo prediction and analysis of wild-type and mutant amyloid structures. Based on the premise of protein mutational landscapes, AmyloidMutants energetically quantifies the effects of sequence mutation on fibril conformation and stability. Tested on non-mutant, full-length amyloid structures with known chemical shift data, AmyloidMutants offers roughly 2-fold improvement in prediction accuracy over existing tools. Moreover, AmyloidMutants is the only method to predict complete super-secondary structures, enabling accurate discrimination of topologically dissimilar amyloid conformations that correspond to the same sequence locations. Applied to mutant prediction, AmyloidMutants identifies a global conformational switch between Aβ and its highly-toxic 'Iowa' mutant in agreement with a recent experimental model based on partial chemical shift data. Predictions on mutant, yeast-toxic strains of HET-s suggest similar alternate folds. When applied to HET-s and a HET-s mutant with core asparagines replaced by glutamines (both highly amyloidogenic chemically similar residues abundant in many amyloids), AmyloidMutants surprisingly predicts a greatly reduced capacity of the glutamine mutant to form amyloid. We confirm this finding by conducting mutagenesis experiments. Our tool is publically available on the web at http://amyloid.csail.mit.edu/. lindquist_admin@wi.mit.edu; bab@csail.mit.edu.

  9. Numerical simulations for quantitative analysis of electrostatic interaction between atomic force microscopy probe and an embedded electrode within a thin dielectric: meshing optimization, sensitivity to potential distribution and impact of cantilever contribution

    Science.gov (United States)

    Azib, M.; Baudoin, F.; Binaud, N.; Villeneuve-Faure, C.; Bugarin, F.; Segonds, S.; Teyssedre, G.

    2018-04-01

    Recent experimental results demonstrated that an electrostatic force distance curve (EFDC) can be used for space charge probing in thin dielectric layers. A main advantage of the method is claimed to be its sensitivity to charge localization, which, however, needs to be substantiated by numerical simulations. In this paper, we have developed a model which permits us to compute an EFDC accurately by using the most sophisticated and accurate geometry for the atomic force microscopy probe. To avoid simplifications and in order to reproduce experimental conditions, the EFDC has been simulated for a system constituted of a polarized electrode embedded in a thin dielectric layer (SiN x ). The individual contributions of forces on the tip and on the cantilever have been analyzed separately to account for possible artefacts. The EFDC sensitivity to potential distribution is studied through the change in electrode shape, namely the width and the depth. Finally, the numerical results have been compared with experimental data.

  10. Establishment of screening method for effective vaccination using radiolabelled probe

    International Nuclear Information System (INIS)

    Nomaguchi, Hiroko; Yogi, Yasuko

    1998-01-01

    Aiming to develop a screening method for effective vaccination, an investigation was made to establish basic techniques for evaluating cytokine producing abilities of host cells after immunization to mycobacterium leprae. In this study, proliferation of the bacterium was investigated with immunodeficient mice such as BALB/cA-nu/nu, CB-scid, aly/ + and aly/aly and the respective normal mice. When the splenic cells from BALB/cA mouse sensitized with M. leprae (ip, 5 days) was challenged with its cell lysate, γ-IFN was produced, whereas its production was not observed in those from sensitive mouse BALB/cA-nu/nu. In addition, it was suggested that cells which could induce γ-IFN in response to IL-12 were extremely limited in the nude mouse. On the contrary, for IL-18, γ-IFN was inducible in the nude mouse when anti-CD3 was previously coated, indicating that it is difficult to evaluate the efficacy of vaccination only by measuring the productions of IL-12 and IL-18. Therefore, it seems better to determine the amount of γ-IFN protein induced by resensitization with the antigen in the splenic cells. (M.N.)

  11. Establishment of screening method for effective vaccination using radiolabelled probe

    Energy Technology Data Exchange (ETDEWEB)

    Nomaguchi, Hiroko; Yogi, Yasuko [National Inst. of Infectious Deseases, Tokyo (Japan)

    1998-02-01

    Aiming to develop a screening method for effective vaccination, an investigation was made to establish basic techniques for evaluating cytokine producing abilities of host cells after immunization to mycobacterium leprae. In this study, proliferation of the bacterium was investigated with immunodeficient mice such as BALB/cA-nu/nu, CB-scid, aly/{sup +} and aly/aly and the respective normal mice. When the splenic cells from BALB/cA mouse sensitized with M. leprae (ip, 5 days) was challenged with its cell lysate, {gamma}-IFN was produced, whereas its production was not observed in those from sensitive mouse BALB/cA-nu/nu. In addition, it was suggested that cells which could induce {gamma}-IFN in response to IL-12 were extremely limited in the nude mouse. On the contray, for IL-18, {gamma}-IFN was inducible in the nude mouse when anti-CD3 was previously coated, indicating that it is difficult to evaluate the efficacy of vaccination only by measuring the productions of IL-12 and IL-18. Therefore, it seems better to determine the amount of {gamma}-IFN protein induced by resensitization with the antigen in the splenic cells. (M.N.)

  12. Method and means for a spatial and temporal probe for laser-generated plumes based on density gradients

    Science.gov (United States)

    Yeung, E.S.; Chen, G.

    1990-05-01

    A method and means are disclosed for a spatial and temporal probe for laser generated plumes based on density gradients includes generation of a plume of vaporized material from a surface by an energy source. The probe laser beam is positioned so that the plume passes through the probe laser beam. Movement of the probe laser beam caused by refraction from the density gradient of the plume is monitored. Spatial and temporal information, correlated to one another, is then derived. 15 figs.

  13. CHARACTERIZATION OF THE ELECTROPHYSICAL PROPERTIES OF SILICON-SILICON DIOXIDE INTERFACE USING PROBE ELECTROMETRY METHODS

    Directory of Open Access Journals (Sweden)

    V. А. Pilipenko

    2017-01-01

    Full Text Available Introduction of submicron design standards into microelectronic industry and a decrease of the gate dielectric thickness raise the importance of the analysis of microinhomogeneities in the silicon-silicon dioxide system. However, there is very little to no information on practical implementation of probe electrometry methods, and particularly scanning Kelvin probe method, in the interoperational control of real semiconductor manufacturing process. The purpose of the study was the development of methods for nondestructive testing of semiconductor wafers based on the determination of electrophysical properties of the silicon-silicon dioxide interface and their spatial distribution over wafer’s surface using non-contact probe electrometry methods.Traditional C-V curve analysis and scanning Kelvin probe method were used to characterize silicon- silicon dioxide interface. The samples under testing were silicon wafers of KEF 4.5 and KDB 12 type (orientation <100>, diameter 100 mm.Probe electrometry results revealed uniform spatial distribution of wafer’s surface potential after its preliminary rapid thermal treatment. Silicon-silicon dioxide electric potential values were also higher after treatment than before it. This potential growth correlates with the drop in interface charge density. At the same time local changes in surface potential indicate changes in surface layer structure.Probe electrometry results qualitatively reflect changes of interface charge density in silicon-silicon dioxide structure during its technological treatment. Inhomogeneities of surface potential distribution reflect inhomogeneity of damaged layer thickness and can be used as a means for localization of interface treatment defects.

  14. Production of pulsed atomic oxygen beams via laser vaporization methods

    International Nuclear Information System (INIS)

    Brinza, D.E.; Coulter, D.R.; Liang, R.H.; Gupta, A.

    1987-01-01

    Energetic pulsed atomic oxygen beams were generated by laser-driven evaporation of cryogenically frozen ozone/oxygen films and thin films of indium-tin oxide (ITO). Mass and energy characterization of beams from the ozone/oxygen films were carried out by mass spectrometry. The peak flux, found to occur at 10 eV, is estimated from this data to be 3 x 10(20) m(-2) s(-1). Analysis of the time-of-flight data indicates a number of processes contribute to the formation of the atomic oxygen beam. The absence of metastable states such as the 2p(3) 3s(1) (5S) level of atomic oxygen blown off from ITO films is supported by the failure to observe emission at 777.3 nm from the 2p(3) 3p(1) (5P/sub J/) levels. Reactive scattering experiments with polymer film targets for atomic oxygen bombardment are planned using a universal crossed molecular beam apparatus

  15. Localized atomic basis set in the projector augmented wave method

    DEFF Research Database (Denmark)

    Larsen, Ask Hjorth; Vanin, Marco; Mortensen, Jens Jørgen

    2009-01-01

    We present an implementation of localized atomic-orbital basis sets in the projector augmented wave (PAW) formalism within the density-functional theory. The implementation in the real-space GPAW code provides a complementary basis set to the accurate but computationally more demanding grid...

  16. A method to control the fabrication of etched optical fiber probes with nanometric tips

    International Nuclear Information System (INIS)

    Tao, Miaomiao; Gu, Ning; Huang, Lan; Jin, Yonglong

    2010-01-01

    Optical fiber probes with small size tips have attracted much interest in the areas of biosensor and near-field scanning optical microscopy. Chemical etching is a common useful method to fabricate such probes. But it is difficult to study or determine the etching time and control the shape of the fiber during the etching. In this work, a new method combining a fiber optic spectrometer with static chemical etching has been developed to fabricate optical fiber probe nanotips, where the fiber optic spectrometer is used to measure the optical signal during the etching. By calculating and analyzing the testing data, the relationship between the apex angle and the optical signal can be obtained. Accordingly, the process of fabricating optical fibers based on the optical signal can be controlled

  17. A Method for Measuring Fast Time Evolutions of the Plasma Potential by Means of a Simple Emissive Probe

    DEFF Research Database (Denmark)

    Iizuka, S.; Michelsen, Poul; Juul Rasmussen, Jens

    1981-01-01

    potential is measured across a high resistance. During each sweep of the probe voltage, the changing of the sign of the probe current, which is sampled at a specific time, gives rise to a negative pulse, driving the pen-lift of an X-Y recorder. Since the real floating potential is measured where the probe......A method is presented for obtaining the temporal evolution of the plasma potential, which is assumed to be given by the floating potential of a simple emissive probe. The construction of the probe is also described. The method avoids the slow time response of the usual technique where the floating...

  18. Ultrasound surface probe as a screening method for evaluating the patients with blunt abdominal trauma

    Directory of Open Access Journals (Sweden)

    Mohammad Nasr-Esfahani

    2014-01-01

    Full Text Available Background: Blunt abdominal trauma is one of the causes of mortality in emergency department. Free fluid in the abdomen due to intra-abdominal blunt trauma can be determined by the surface probe of ultrasound. Since the importance of this free fluid in hemodynamic stable patients with blunt trauma is associated with the unknown outcome for surgeons, this study was performed to evaluate the role of ultrasound surface probe as a screening method in evaluating the patients with blunt abdominal trauma. Materials and Methods: A descriptive-analytical study was done on 45 patients with blunt abdominal trauma and hemodynamic stability. The patients were evaluated twice during the three-hours, including repeated ultrasound surface probe and clinical examinations. Computerized tomography was also performed. The patients were divided based on the amount of the free fluid in the abdomen during the evaluations into two groups: Fixed or increased, and decreased free fluid. The results of the different evaluated methods were compared using the sensitivity and specificity. Results: From 17 patients with CT abnormalities, free fluid increased in 14 patients (82.4%. Free fluid was decreased in three patients who were discharged well from the surgery service without any complication. Surface probe in prognosis detection had a sensitivity of 82.4% and specificity of 92.9%. The percentage of false positive and negative ultrasound compared with CT scan was 7.1% and 17.6%. Also, positive and negative predictive value of the ultrasound with surface probe was 87.5% and 89.7% respectively. Conclusion: The use of the ultrasound with surface probe in the diagnosis of free fluid in blunt abdominal trauma in hemodynamic stable patients can be considered as a useful screening method.

  19. A novel analysis strategy for HLA typing using a sequence-specific oligonucleotide probe method.

    Science.gov (United States)

    Won, D I

    2017-11-01

    The technique of reverse sequence-specific oligonucleotide probes (SSOPs) is commonly used in human leukocyte antigen (HLA) typing. In the conventional method for data analysis (exact pattern matching, EPM), the larger is the number of mismatched probes, the longer the time for final typing assignment. A novel strategy, filtering and scoring (FnS), has been developed to easily assign the best-fit allele pair. In the FnS method, candidate alleles and allele pairs were filtered based on (1) subject's ethnicity, and (2) the measured partial reaction pattern with only definitely negative or positive probes. Then, the complete reaction pattern for all probes (CRPoAPs) were compared between the raw sample and expected residual allele pairs to obtain mismatch scores. To compare the FnS and EPM methods, each analysis time (minutes:seconds) for reverse SSOP HLA typing with intermediate resolution (n = 507) was measured. The analysis time with FnS method was shorter than that of the EPM method [00:21 (00:08-01:47) and 01:04 (00:15-23:45), respectively, P typing in a comprehensive and quantitative comparison between measured and expected CRPoAPs of candidate allele pairs. Therefore, this analysis strategy might be useful in a clinical setting. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  20. Effective atomic numbers of some tissue substitutes by different methods: A comparative study

    Directory of Open Access Journals (Sweden)

    Vishwanath P Singh

    2014-01-01

    Full Text Available Effective atomic numbers of some human organ tissue substitutes such as polyethylene terephthalate, red articulation wax, paraffin 1, paraffin 2, bolus, pitch, polyphenylene sulfide, polysulfone, polyvinylchloride, and modeling clay have been calculated by four different methods like Auto-Z eff, direct, interpolation, and power law. It was found that the effective atomic numbers computed by Auto-Z eff , direct and interpolation methods were in good agreement for intermediate energy region (0.1 MeV < E < 5 MeV where the Compton interaction dominates. A large difference in effective atomic numbers by direct method and Auto-Z eff was observed in photo-electric and pair-production regions. Effective atomic numbers computed by power law were found to be close to direct method in photo-electric absorption region. The Auto-Z eff , direct and interpolation methods were found to be in good agreement for computation of effective atomic numbers in intermediate energy region (100 keV < E < 10 MeV. The direct method was found to be appropriate method for computation of effective atomic numbers in photo-electric region (10 keV < E < 100 keV. The tissue equivalence of the tissue substitutes is possible to represent by any method for computation of effective atomic number mentioned in the present study. An accurate estimation of Rayleigh scattering is required to eliminate effect of molecular, chemical, or crystalline environment of the atom for estimation of gamma interaction parameters.

  1. Research on the Method of Noise Error Estimation of Atomic Clocks

    Science.gov (United States)

    Song, H. J.; Dong, S. W.; Li, W.; Zhang, J. H.; Jing, Y. J.

    2017-05-01

    The simulation methods of different noises of atomic clocks are given. The frequency flicker noise of atomic clock is studied by using the Markov process theory. The method for estimating the maximum interval error of the frequency white noise is studied by using the Wiener process theory. Based on the operation of 9 cesium atomic clocks in the time frequency reference laboratory of NTSC (National Time Service Center), the noise coefficients of the power-law spectrum model are estimated, and the simulations are carried out according to the noise models. Finally, the maximum interval error estimates of the frequency white noises generated by the 9 cesium atomic clocks have been acquired.

  2. Influences in Thermal Conductivity Evaluation Using the Thermal Probe Method; some Practical Aspects

    OpenAIRE

    Strâmbu, Vasile

    2012-01-01

    The thermal probe is a device used for measuring the thermal conductivity of materials in the food industry, plastics industry, geotechnical engineering and studies of soft soils and rocks. The method also started being utilized in the field of construction materials with particularities that take into account their composition and the state they are in.

  3. A robust method for processing scanning probe microscopy images and determining nanoobject position and dimensions

    NARCIS (Netherlands)

    Silly, F.

    2009-01-01

    P>Processing of scanning probe microscopy (SPM) images is essential to explore nanoscale phenomena. Image processing and pattern recognition techniques are developed to improve the accuracy and consistency of nanoobject and surface characterization. We present a robust and versatile method to

  4. Omics methods for probing the mode of action of natural phytotoxins

    Science.gov (United States)

    For a little over a decade, omics methods (transcriptomics, proteomics, metabolomics, and physionomics) have been used to discover and probe the mode of action of both synthetic and natural phytotoxins. For mode of action discovery, the strategy for each of these approaches is to generate an omics...

  5. Resistivity Correction Factor for the Four-Probe Method: Experiment I

    Science.gov (United States)

    Yamashita, Masato; Yamaguchi, Shoji; Enjoji, Hideo

    1988-05-01

    Experimental verification of the theoretically derived resistivity correction factor (RCF) is presented. Resistivity and sheet resistance measurements by the four-probe method are made on three samples: isotropic graphite, ITO film and Au film. It is indicated that the RCF can correct the apparent variations of experimental data to yield reasonable resistivities and sheet resistances.

  6. Method and apparatus for remote tube crevice detection by current and voltage probe resistance measurement

    Science.gov (United States)

    Kikta, Thomas J.; Mitchell, Ronald D.

    1992-01-01

    A method and apparatus for determining the extent of contact between an electrically conducting tube and an electrically conductive tubesheet surrounding the tube, based upon the electrical resistance of the tube and tubesheet. A constant current source is applied to the interior of the electrically conducting tube by probes and a voltmeter is connected between other probes to measure the voltage at the point of current injection, which is inversely proportional to the amount of contact between the tube and tubesheet. Namely, the higher the voltage measured by the voltmeter, the less contact between the tube and tubesheet.

  7. Methods for radiation detection and characterization using a multiple detector probe

    Science.gov (United States)

    Akers, Douglas William; Roybal, Lyle Gene

    2014-11-04

    Apparatuses, methods, and systems relating to radiological characterization of environments are disclosed. Multi-detector probes with a plurality of detectors in a common housing may be used to substantially concurrently detect a plurality of different radiation activities and types. Multiple multi-detector probes may be used in a down-hole environment to substantially concurrently detect radioactive activity and contents of a buried waste container. Software may process, analyze, and integrate the data from the different multi-detector probes and the different detector types therein to provide source location and integrated analysis as to the source types and activity in the measured environment. Further, the integrated data may be used to compensate for differential density effects and the effects of radiation shielding materials within the volume being measured.

  8. Self-probing spectroscopy of XUV photo-ionization dynamics in atoms subjected to a strong-field environment.

    Science.gov (United States)

    Azoury, Doron; Krüger, Michael; Orenstein, Gal; Larsson, Henrik R; Bauch, Sebastian; Bruner, Barry D; Dudovich, Nirit

    2017-11-13

    Single-photon ionization is one of the most fundamental light matter interactions in nature, serving as a universal probe of the quantum state of matter. By probing the emitted electron, one can decode the full dynamics of the interaction. When photo-ionization is evolving in the presence of a strong laser field, the fundamental properties of the mechanism can be signicantly altered. Here we demonstrate how the liberated electron can perform a self-probing measurement of such interaction with attosecond precision. Extreme ultraviolet attosecond pulses initiate an electron wavepacket by photo-ionization, a strong infrared field controls its motion, and finally electron-ion collision maps it into re-emission of attosecond radiation bursts. Our measurements resolve the internal clock provided by the self-probing mechanism, obtaining a direct insight into the build-up of photo-ionization in the presence of the strong laser field.

  9. Photoelectron imaging, probe of the dynamics: from atoms... to clusters; Imagerie de photoelectrons, sonde de la dynamique: des atomes... aux agregats

    Energy Technology Data Exchange (ETDEWEB)

    Lepine, F

    2003-06-15

    This thesis concerns the study of the deexcitation of clusters and atoms by photoelectron imaging. The first part is dedicated to thermionic emission of a finite size system. A 3-dimensional imaging setup allows us to measure the time evolution of the kinetic energy spectrum of electrons emitted from different clusters (W{sub n}{sup -}, C{sub n}{sup -}, C{sub 60}). Then we have a direct access to the fundamental quantities which characterize this statistical emission: the temperature of the finite heat bath and the decay rate. The second part concerns the ionization of atomic Rydberg states placed in a static electric field. We performed the first experiment of photoionization microscopy which allows us to obtain a picture which is the macroscopic projection of the electronic wave function. Then we have access to the detail of the photoionization and particularly to the quantum properties of the electron usually confined at the atomic scale. (author)

  10. Application of the Ursell-Mayer method in the theory of spin-polarized atomic hydrogen

    International Nuclear Information System (INIS)

    Kilic, S.; Radelja, T.

    1981-01-01

    Employing the Ursell-Mayer method and Ljolje semi-free gas model analytic relations describing ground state properties (energy, pressure, compressibility, sound velocity, radial distribution function and one-particle density matrix) of spin-polarized atomic hydrogen were derived. The expressions are valid up to density 2 10 26 atoms/m 3 . It was found out that at density of 2 10 26 atoms/m 3 the condensation of particle in momentum space is 88% (at absolute zero). (orig.)

  11. Polarization-dependent pump-probe studies in atomic fine-structure levels: towards the production of spin-polarized electrons

    International Nuclear Information System (INIS)

    Sokell, E.; Zamith, S.; Bouchene, M.A.; Girard, B.

    2000-01-01

    The precession of orbital and spin angular momentum vectors has been observed in a pump-probe study of the 4P fine-structure states of atomic potassium. A femtosecond pump pulse prepared a coherent superposition of the two fine-structure components. A time-delayed probe pulse then ionized the system after it had been allowed to evolve freely. Oscillations recorded in the ion signal reflect the evolution of the orientation of the orbital and spin angular momentum due to spin-orbit coupling. This interpretation gives physical insight into the cause of the half-period phase shift observed when the relative polarizations of the laser pulses were changed from parallel to perpendicular. Finally, it is shown that these changes in the orientation of the spin momentum vector of the system can be utilized to produce highly spin-polarized free electrons on the femtosecond scale. (author)

  12. The method of intersecting spheres for determination of coordination numbers of atoms in crystal structures

    International Nuclear Information System (INIS)

    Serezhkin, V.N.; Buslaev, Yu.A.; Mikhajlov, Yu.N.

    1997-01-01

    New method for determination of coordination numbers (CN) of atoms in crystal structures, based on the model of interatomic interaction, within the frames whereof each atom is approximated by two spheres with the common center in the atom nuclei, is proposed. One of the spheres specifies conditionally isolated (chemically unbound) atom and its radius is a constant, which for atoms of the given chemical sort in the structure of any compound is equal to quasi-orbital Sleiter radius. The sphere of the other radius specifies chemically bound atom and coincides with the sphere, the volume whereof is equal to the volume of the Voronoj-Dirichlet polyhedron of the corresponding atom in the structure of the concrete crystal. Using a series of examples, workability of the given method for CN determination of atoms in structures of both simple substances and chemical compounds (alkali, transition metals, U, Th). Good agreement of the obtained results with the generally accepted CN s of atoms for the considered crystals is noted and a number of principal advantages of the new method, as compared to classical one of the CNs evaluation, is demonstrated

  13. A method for automatically extracting infectious disease-related primers and probes from the literature

    Directory of Open Access Journals (Sweden)

    Pérez-Rey David

    2010-08-01

    Full Text Available Abstract Background Primer and probe sequences are the main components of nucleic acid-based detection systems. Biologists use primers and probes for different tasks, some related to the diagnosis and prescription of infectious diseases. The biological literature is the main information source for empirically validated primer and probe sequences. Therefore, it is becoming increasingly important for researchers to navigate this important information. In this paper, we present a four-phase method for extracting and annotating primer/probe sequences from the literature. These phases are: (1 convert each document into a tree of paper sections, (2 detect the candidate sequences using a set of finite state machine-based recognizers, (3 refine problem sequences using a rule-based expert system, and (4 annotate the extracted sequences with their related organism/gene information. Results We tested our approach using a test set composed of 297 manuscripts. The extracted sequences and their organism/gene annotations were manually evaluated by a panel of molecular biologists. The results of the evaluation show that our approach is suitable for automatically extracting DNA sequences, achieving precision/recall rates of 97.98% and 95.77%, respectively. In addition, 76.66% of the detected sequences were correctly annotated with their organism name. The system also provided correct gene-related information for 46.18% of the sequences assigned a correct organism name. Conclusions We believe that the proposed method can facilitate routine tasks for biomedical researchers using molecular methods to diagnose and prescribe different infectious diseases. In addition, the proposed method can be expanded to detect and extract other biological sequences from the literature. The extracted information can also be used to readily update available primer/probe databases or to create new databases from scratch.

  14. 1-D Metal Nanobead Arrays within Encapsulated Nanowires via a Red-Ox-Induced Dewetting: Mechanism Study by Atom-Probe Tomography.

    Science.gov (United States)

    Sun, Zhiyuan; Tzaguy, Avra; Hazut, Ori; Lauhon, Lincoln J; Yerushalmi, Roie; Seidman, David N

    2017-12-13

    Metal nanoparticle arrays are excellent candidates for a variety of applications due to the versatility of their morphology and structure at the nanoscale. Bottom-up self-assembly of metal nanoparticles provides an important complementary alternative to the traditional top-down lithography method and makes it possible to assemble structures with higher-order complexity, for example, nanospheres, nanocubes, and core-shell nanostructures. Here we present a mechanism study of the self-assembly process of 1-D noble metal nanoparticles arrays, composed of Au, Ag, and AuAg alloy nanoparticles. These are prepared within an encapsulated germanium nanowire, obtained by the oxidation of a metal-germanium nanowire hybrid structure. The resulting structure is a 1-D array of equidistant metal nanoparticles with the same diameter, the so-called nanobead (NB) array structure. Atom-probe tomography and transmission electron microscopy were utilized to investigate the details of the morphological and chemical evolution during the oxidation of the encapsulated metal-germanium nanowire hybrid-structures. The self-assembly of nanoparticles relies on the formation of a metal-germanium liquid alloy and the migration of the liquid alloy into the nanowire, followed by dewetting of the liquid during shape-confined oxidation where the liquid column breaks-up into nanoparticles due to the Plateau-Rayleigh instability. Our results demonstrate that the encapsulating oxide layer serves as a structural scaffold, retaining the overall shape during the eutectic liquid formation and demonstrates the relationship between the oxide mechanical properties and the final structural characteristics of the 1-D arrays. The mechanistic details revealed here provide a versatile tool-box for the bottom-up fabrication of 1-D arrays nanopatterning that can be modified for multiple applications according to the RedOx properties of the material system components.

  15. Characterization of duplex stainless steels by TEM [transmission electron microscopy], SANS [small-angle neutron scattering], and APFIM [atom-probe field ion microscopy] techniques

    International Nuclear Information System (INIS)

    Chung, H.M.; Chopra, O.K.

    1987-06-01

    Results are presented of complementary characterization of aged duplex stainless steels by advanced metallographic techniques, including transmission and high-voltage electron microscopies; small-angle neutron scattering; and atom-probe field ion microscopy. On the basis of the characterization, the mechanisms of aging embrittlement have been shown to be associated with the precipitation of Ni- and Si-rich G phase and Cr-rich α' in the ferrite, and M 23 C 6 carbides on the austenite-ferrite phase boundaries. 19 refs., 19 figs., 1 tab

  16. Combined frequency modulated atomic force microscopy and scanning tunneling microscopy detection for multi-tip scanning probe microscopy applications

    International Nuclear Information System (INIS)

    Morawski, Ireneusz; Spiegelberg, Richard; Korte, Stefan; Voigtländer, Bert

    2015-01-01

    A method which allows scanning tunneling microscopy (STM) tip biasing independent of the sample bias during frequency modulated atomic force microscopy (AFM) operation is presented. The AFM sensor is supplied by an electronic circuit combining both a frequency shift signal and a tunneling current signal by means of an inductive coupling. This solution enables a control of the tip potential independent of the sample potential. Individual tip biasing is specifically important in order to implement multi-tip STM/AFM applications. An extensional quartz sensor (needle sensor) with a conductive tip is applied to record simultaneously topography and conductivity of the sample. The high resonance frequency of the needle sensor (1 MHz) allows scanning of a large area of the surface being investigated in a reasonably short time. A recipe for the amplitude calibration which is based only on the frequency shift signal and does not require the tip being in contact is presented. Additionally, we show spectral measurements of the mechanical vibration noise of the scanning system used in the investigations

  17. Combined frequency modulated atomic force microscopy and scanning tunneling microscopy detection for multi-tip scanning probe microscopy applications

    Energy Technology Data Exchange (ETDEWEB)

    Morawski, Ireneusz [Peter Grünberg Institut (PGI-3) and JARA-Fundamentals of Future Information Technology, Forschungszentrum Jülich, 52425 Jülich (Germany); Institute of Experimental Physics, University of Wrocław, pl. M. Borna 9, 50-204 Wrocław (Poland); Spiegelberg, Richard; Korte, Stefan; Voigtländer, Bert [Peter Grünberg Institut (PGI-3) and JARA-Fundamentals of Future Information Technology, Forschungszentrum Jülich, 52425 Jülich (Germany)

    2015-12-15

    A method which allows scanning tunneling microscopy (STM) tip biasing independent of the sample bias during frequency modulated atomic force microscopy (AFM) operation is presented. The AFM sensor is supplied by an electronic circuit combining both a frequency shift signal and a tunneling current signal by means of an inductive coupling. This solution enables a control of the tip potential independent of the sample potential. Individual tip biasing is specifically important in order to implement multi-tip STM/AFM applications. An extensional quartz sensor (needle sensor) with a conductive tip is applied to record simultaneously topography and conductivity of the sample. The high resonance frequency of the needle sensor (1 MHz) allows scanning of a large area of the surface being investigated in a reasonably short time. A recipe for the amplitude calibration which is based only on the frequency shift signal and does not require the tip being in contact is presented. Additionally, we show spectral measurements of the mechanical vibration noise of the scanning system used in the investigations.

  18. Development of atomic-beam resonance method to measure the nuclear moments of unstable nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Sugimoto, T., E-mail: sugimoto@ribf.riken.jp [SPring-8 (Japan); Asahi, K. [Tokyo Institute of Technology, Department of Physics (Japan); Kawamura, H.; Murata, J. [Rikkyo University, Department of Physics (Japan); Nagae, D.; Shimada, K. [Tokyo Institute of Technology, Department of Physics (Japan); Ueno, H.; Yoshimi, A. [RIKEN Nishina Center (Japan)

    2008-01-15

    We have been working on the development of a new technique of atomic-beam resonance method to measure the nuclear moments of unstable nuclei. In the present study, an ion-guiding system to be used as an atomic-beam source have been developed.

  19. Numerical evaluation for a five-sensor probe method to measure the interfacial area concentration under the bubble fluctuation condition

    International Nuclear Information System (INIS)

    Euh, D. J.; Yun, B. J.; Song, C. H.

    2003-01-01

    Interfacial area concentration is an important parameter in the two phase flow models. Currently, two types of probe methods, double-sensor and four-sensor, are widely used to measure the interfacial area concentration. In this study, a configuration of five-sensor probe sensor tips and a measuring method for the interfacial area concentration by using the probe are proposed to improve the performance of the previous probe methods. The five-sensor probe method proposed in this study is essentially based on the four-sensor probe method but improves it by adapting one more sensor. The passing types of the interfaces through the sensors are categorized into four and independent methods are applied to the interfaces belonging to each category. This method has an advantage such that a more systematic approach for missing bubbles can be made when compared with the classical four sensor probe method. To verify the applicability of the five-sensor probe method, numerical tests are performed with consideration of the bubble lateral movement. The effects of bubble size and intensity of the bubble lateral motion on the measurement of the interfacial area concentration are also investigated. The bubble parameters related to the bubble fluctuation and interface geometry are determined by the Monte Carlo approach

  20. Hybrid statistics-simulations based method for atom-counting from ADF STEM images

    Energy Technology Data Exchange (ETDEWEB)

    De wael, Annelies, E-mail: annelies.dewael@uantwerpen.be [Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp (Belgium); De Backer, Annick [Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp (Belgium); Jones, Lewys; Nellist, Peter D. [Department of Materials, University of Oxford, Parks Road, OX1 3PH Oxford (United Kingdom); Van Aert, Sandra, E-mail: sandra.vanaert@uantwerpen.be [Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp (Belgium)

    2017-06-15

    A hybrid statistics-simulations based method for atom-counting from annular dark field scanning transmission electron microscopy (ADF STEM) images of monotype crystalline nanostructures is presented. Different atom-counting methods already exist for model-like systems. However, the increasing relevance of radiation damage in the study of nanostructures demands a method that allows atom-counting from low dose images with a low signal-to-noise ratio. Therefore, the hybrid method directly includes prior knowledge from image simulations into the existing statistics-based method for atom-counting, and accounts in this manner for possible discrepancies between actual and simulated experimental conditions. It is shown by means of simulations and experiments that this hybrid method outperforms the statistics-based method, especially for low electron doses and small nanoparticles. The analysis of a simulated low dose image of a small nanoparticle suggests that this method allows for far more reliable quantitative analysis of beam-sensitive materials. - Highlights: • A hybrid method for atom-counting from ADF STEM images is introduced. • Image simulations are incorporated into a statistical framework in a reliable manner. • Limits of the existing methods for atom-counting are far exceeded. • Reliable counting results from an experimental low dose image are obtained. • Progress towards reliable quantitative analysis of beam-sensitive materials is made.

  1. Parametrization of Combined Quantum Mechanical and Molecular Mechanical Methods: Bond-Tuned Link Atoms.

    Science.gov (United States)

    Wu, Xin-Ping; Gagliardi, Laura; Truhlar, Donald G

    2018-05-30

    Combined quantum mechanical and molecular mechanical (QM/MM) methods are the most powerful available methods for high-level treatments of subsystems of very large systems. The treatment of the QM-MM boundary strongly affects the accuracy of QM/MM calculations. For QM/MM calculations having covalent bonds cut by the QM-MM boundary, it has been proposed previously to use a scheme with system-specific tuned fluorine link atoms. Here, we propose a broadly parametrized scheme where the parameters of the tuned F link atoms depend only on the type of bond being cut. In the proposed new scheme, the F link atom is tuned for systems with a certain type of cut bond at the QM-MM boundary instead of for a specific target system, and the resulting link atoms are call bond-tuned link atoms. In principle, the bond-tuned link atoms can be as convenient as the popular H link atoms, and they are especially well adapted for high-throughput and accurate QM/MM calculations. Here, we present the parameters for several kinds of cut bonds along with a set of validation calculations that confirm that the proposed bond-tuned link-atom scheme can be as accurate as the system-specific tuned F link-atom scheme.

  2. Parametrization of Combined Quantum Mechanical and Molecular Mechanical Methods: Bond-Tuned Link Atoms

    Directory of Open Access Journals (Sweden)

    Xin-Ping Wu

    2018-05-01

    Full Text Available Combined quantum mechanical and molecular mechanical (QM/MM methods are the most powerful available methods for high-level treatments of subsystems of very large systems. The treatment of the QM−MM boundary strongly affects the accuracy of QM/MM calculations. For QM/MM calculations having covalent bonds cut by the QM−MM boundary, it has been proposed previously to use a scheme with system-specific tuned fluorine link atoms. Here, we propose a broadly parametrized scheme where the parameters of the tuned F link atoms depend only on the type of bond being cut. In the proposed new scheme, the F link atom is tuned for systems with a certain type of cut bond at the QM−MM boundary instead of for a specific target system, and the resulting link atoms are call bond-tuned link atoms. In principle, the bond-tuned link atoms can be as convenient as the popular H link atoms, and they are especially well adapted for high-throughput and accurate QM/MM calculations. Here, we present the parameters for several kinds of cut bonds along with a set of validation calculations that confirm that the proposed bond-tuned link-atom scheme can be as accurate as the system-specific tuned F link-atom scheme.

  3. Atomic diffusion theory challenging the Cahn-Hilliard method

    International Nuclear Information System (INIS)

    Nastar, M.

    2014-01-01

    Our development of the self-consistent mean-field (SCMF) kinetic theory for nonuniform alloys leads to the statement that kinetic correlations induced by the vacancy diffusion mechanism have a dramatic effect on nano-scale diffusion phenomena, leading to nonlinear features of the interdiffusion coefficients. Lattice rate equations of alloys including nonuniform gradients of chemical potential are derived within the Bragg-Williams statistical approximation and the third shell kinetic approximation of the SCMF theory. General driving forces including deviations of the free energy from a local equilibrium thermodynamic formulation are introduced. These deviations are related to the variation of vacancy motion due to the spatial variation of the alloy composition. During the characteristic time of atomic diffusion, multiple exchanges of the vacancy with the same atoms may happen, inducing atomic kinetic correlations that depend as well on the spatial variation of the alloy composition. As long as the diffusion driving forces are uniform, the rate equations are shown to obey in this form the Onsager formalism of thermodynamics of irreversible processes (TIP) and the TIP-based Cahn-Hilliard diffusion equation. If now the chemical potential gradients are not uniform, the continuous limit of the present SCMF kinetic equations does not coincide with the Cahn-Hilliard (CH) equation. In particular, the composition gradient and higher derivative terms depending on kinetic parameters add to the CH thermodynamic-based composition gradient term. Indeed, a diffusion equation written as a mobility multiplied by a thermodynamic formulation of the driving forces is shown to be inadequate. In the reciprocal space, the thermodynamic driving force has to be multiplied by a nonlinear function of the wave vector accounting for the variation of kinetic correlations with composition inhomogeneities. Analytical expressions of the effective interdiffusion coefficient are given for two limit

  4. Atomization in a graphite furnace with ballast - a method of improvement of reliability of atomic absorption analysis

    International Nuclear Information System (INIS)

    Katskov, D.A.; Grinshtejn, I.L.

    1978-01-01

    For the purpose of improving the reliability with which elements are determined in atomic absorption analysis with atomization in a graphite furnace, a method is proposed based on the use of a furnace with an extra ballast body. A small cylinder of graphite or refractory metal (Ta) placed in the central part of the furnace, is used as ballast. When in poor heat contact with the wall the ballast is heated by ray emission at a somewhat slower rate than the furnace. It is shown that the kinetics of evaporation of the substance being analysed in the ballast furnace is determined by the rate of change of temperature of the ballast body. As a result of the lag in evaporation, vapour from the analysed substance reaches a zone of a much higher temperature than with evaporation in the usual type furnace, leading to an increase in the degree of atomization. Theoretical analysis establishes the temperature of the ballast, and conditions for the determination of elements (Cd) are optimized. The experiments conducted indicate a considerable decrease in the effect of the composition of the sample on the results of the analysis and a lower molecular interference in the ballast furnace. With high evaporation lag the vapours of the sample reach the zone of practically constant temperature, thus making it possible to use the integral method of absorption registration with absolute accuracy. With fractionated distillation of volatile components of the sample, fractionation is considerably more accurate in a ballast furnace than in the usual type furnace

  5. Heavy Atom Substituents as Molecular Probes for Solvent Effects on the Dynamics of Short-lived Triplet Exciplexes

    OpenAIRE

    Winter, Gerhard; Steiner, Ulrich

    1980-01-01

    The influence of heavy atom substituents (Br, I) in the electron donor aniline on the electron transfer reaction with thiopyronine triplet is investigated by flash spectroscopy in solvents of different viscosity and polarity. Triplet quenching constants and radical yields are determined. The results are analysed in terms of decay constants of an intermediate triplet exciplex where the heavy atom substituents significantly enhance the intersystem crossing process leading to singlet ground stat...

  6. Determination of paraquat in water samples using a sensitive fluorescent probe titration method.

    Science.gov (United States)

    Yao, Feihu; Liu, Hailong; Wang, Guangquan; Du, Liming; Yin, Xiaofen; Fu, Yunlong

    2013-06-01

    Paraquat (PQ), a nonselective herbicide, is non-fluorescent in aqueous solutions. Thus, its determination through direct fluorescent methods is not feasible. The supramolecular inclusion interaction of PQ with cucurbit[7]uril was studied by a fluorescent probe titration method. Significant quenching of the fluorescence intensity of the cucurbit[7]uril-coptisine fluorescent probe was observed with the addition of PQ. A new fluorescent probe titration method with high selectivity and sensitivity at the ng/mL level was developed to determine PQ in aqueous solutions with good precision and accuracy based on the significant quenching of the supramolecular complex fluorescence intensity. The proposed method was successfully used in the determination of PQ in lake water, tap water, well water, and ditch water in an agricultural area, with recoveries of 96.73% to 105.77%. The fluorescence quenching values (deltaF) showed a good linear relationship with PQ concentrations from 1.0 x 10(-8) to 1.2 x 10(-5) mol/L with a detection limit of 3.35 x 10(-9) mol/L. In addition, the interaction models of the supramolecular complexes formed between the host and the guest were established using theoretical calculations. The interaction mechanism between the cucurbit[7]uril and PQ was confirmed by 1H NMR spectroscopy.

  7. Omics Methods for Probing the Mode of Action of Natural and Synthetic Phytotoxins

    OpenAIRE

    Duke, Stephen O.; Bajsa, Joanna; Pan, Zhiqiang

    2013-01-01

    For a little over a decade, omics methods (transcriptomics, proteomics, metabolomics, and physionomics) have been used to discover and probe the mode of action of both synthetic and natural phytotoxins. For mode of action discovery, the strategy for each of these approaches is to generate an omics profile for phytotoxins with known molecular targets and to compare this library of responses to the responses of compounds with unknown modes of action. Using more than one omics approach enhances ...

  8. A new capacitive/resistive probe method for studying magnetic surfaces

    International Nuclear Information System (INIS)

    Kitajima, Sumio; Takayama, Masakazu; Zama, Tatsuya; Takaya, Kazuhiro; Takeuchi, Nobunao; Watanabe, Hiroshige

    1991-01-01

    A new capacitive/resistive probe method for mapping the magnetic surfaces from resistance or capacitance between a magnetic surface and a vacuum vessel was developed and tested. Those resistances and capacitances can be regarded as components of a simple electrical bridge circuit. This method exploits electrical transient response of the bridge circuit for a square pulse. From equiresistance or equicapacitance points, the magnetic surface structure can be deduced. Measurements on the Tohoku University Heliac, which is a small-size standard heliac, show good agreement with numerical calculations. This method is particularly useful for pulse-operated machines. (author)

  9. A touch probe method of operating an implantable RFID tag for orthopedic implant identification.

    Science.gov (United States)

    Liu, Xiaoyu; Berger, J Lee; Ogirala, Ajay; Mickle, Marlin H

    2013-06-01

    The major problem in operating an implantable radio-frequency identification (RFID) tag embedded on an orthopedic implant is low efficiency because of metallic interference. To improve the efficiency, this paper proposes a method of operating an implantable passive RFID tag using a touch probe at 13.56 MHz. This technology relies on the electric field interaction between two pairs of electrodes, one being a part of the touch probe placed on the surface of tissue and the other being a part of the tag installed under the tissue. Compared with using a conventional RFID antenna such as a loop antenna, this method has a better performance in the near field operation range to reduce interference with the orthopedic implant. Properly matching the touch probe and the tag to the tissue and the implant reduces signal attenuation and increases the overall system efficiency. The experiments have shown that this method has a great performance in the near field transcutaneous operation and can be used for orthopedic implant identification.

  10. Virial-statistic method for calculation of atom and molecule energies

    International Nuclear Information System (INIS)

    Borisov, Yu.A.

    1977-01-01

    A virial-statistical method has been applied to the calculation of the atomization energies of the following molecules: Mo(CO) 6 , Cr(CO) 6 , Fe(CO) 5 , MnH(CO) 5 , CoH(CO) 4 , Ni(CO) 4 . The principles of this method are briefly presented. Calculation results are given for the individual contributions to the atomization energies together with the calculated and experimental atomization energies (D). For the Mo(CO) 6 complex Dsub(calc) = 1759 and Dsub(exp) = 1763 kcal/mole. Calculated and experimental combination heat values for carbonyl complexes are presented. These values are shown to be adequately consistent [ru

  11. Evaluation of a method for the determination of chromium in urine by atomic absorption spectrometry

    International Nuclear Information System (INIS)

    Garcia, M.; Sardinas, O.; Castaneda, I.; Sanchez, R.

    1990-01-01

    A method for the determination of chromium in urine by atomic absorption spectrometry, using electrothermic atomization with pyrolytic graphite tubes, is proposed. The determinations are performed by standard addition. The method is applicable to biologic monitoring of populations with different degrees of exposition. It is also used in the analysis of chromium in sediments. Results of chromium in urine of a population group non-exposed to the metal are presented. 11 refs

  12. nuclear and atomic methods applied in the determination of some

    African Journals Online (AJOL)

    NAA is a quantitative and qualitative method for the precise determination of a number of major, minor and trace elements in different types of geological, environmental and biological samples. It is based on nuclear reaction between neutron and target nuclei of a sample material. It is a useful method for the simultaneous.

  13. Numerical evaluation of the five sensor probe method for measurement of local interfacial area concentration of cap bubbles

    International Nuclear Information System (INIS)

    Euh, D.J.; Yun, B.J.; Song, C.H.; Kwon, T.S.; Chung, M.K.; Lee, U.C.

    2000-01-01

    The interfacial area concentration (IAC) is one of the most important parameters in the two-fluid model for two-phase flow analysis. The IAC can be measured by a local conductivity probe method that uses the difference of conductivity between water and air/steam. The number of sensors in the conductivity probe may be differently chosen by considering the flow regime of two-phase flow. The four sensor conductivity probe method predicts the IAC without any assumptions of the bubble shape. The local IAC can be obtained by measuring the three dimensional velocity vector elements at the measuring point, and the directional cosines of the sensors. The five sensor conductivity probe method proposed in this study is based on the four sensor probe method. With the five sensor probe, the local IAC for a given referred measuring area of the probe can be predicted more exactly. In this paper, the mathematical approach of the five sensor probe method for measuring the IAC is described, and a numerical simulation is carried out for ideal cap bubbles of which the sizes and locations are determined by a random number generator. (author)

  14. Atom-by-atom assembly

    International Nuclear Information System (INIS)

    Hla, Saw Wai

    2014-01-01

    Atomic manipulation using a scanning tunneling microscope (STM) tip enables the construction of quantum structures on an atom-by-atom basis, as well as the investigation of the electronic and dynamical properties of individual atoms on a one-atom-at-a-time basis. An STM is not only an instrument that is used to ‘see’ individual atoms by means of imaging, but is also a tool that is used to ‘touch’ and ‘take’ the atoms, or to ‘hear’ their movements. Therefore, the STM can be considered as the ‘eyes’, ‘hands’ and ‘ears’ of the scientists, connecting our macroscopic world to the exciting atomic world. In this article, various STM atom manipulation schemes and their example applications are described. The future directions of atomic level assembly on surfaces using scanning probe tips are also discussed. (review article)

  15. Clustering methods for the optimization of atomic cluster structure

    Science.gov (United States)

    Bagattini, Francesco; Schoen, Fabio; Tigli, Luca

    2018-04-01

    In this paper, we propose a revised global optimization method and apply it to large scale cluster conformation problems. In the 1990s, the so-called clustering methods were considered among the most efficient general purpose global optimization techniques; however, their usage has quickly declined in recent years, mainly due to the inherent difficulties of clustering approaches in large dimensional spaces. Inspired from the machine learning literature, we redesigned clustering methods in order to deal with molecular structures in a reduced feature space. Our aim is to show that by suitably choosing a good set of geometrical features coupled with a very efficient descent method, an effective optimization tool is obtained which is capable of finding, with a very high success rate, all known putative optima for medium size clusters without any prior information, both for Lennard-Jones and Morse potentials. The main result is that, beyond being a reliable approach, the proposed method, based on the idea of starting a computationally expensive deep local search only when it seems worth doing so, is capable of saving a huge amount of searches with respect to an analogous algorithm which does not employ a clustering phase. In this paper, we are not claiming the superiority of the proposed method compared to specific, refined, state-of-the-art procedures, but rather indicating a quite straightforward way to save local searches by means of a clustering scheme working in a reduced variable space, which might prove useful when included in many modern methods.

  16. Description of the atomic disorder (local order) in crystals by the mixed-symmetry method

    Science.gov (United States)

    Dudka, A. P.; Novikova, N. E.

    2017-11-01

    An approach to the description of local atomic disorder (short-range order) in single crystals by the mixed-symmetry method based on Bragg scattering data is proposed, and the corresponding software is developed. In defect-containing crystals, each atom in the unit cell can be described by its own symmetry space group. The expression for the calculated structural factor includes summation over different sets of symmetry operations for different atoms. To facilitate the search for new symmetry elements, an "atomic disorder expert" was developed, which estimates the significance of tested models. It is shown that the symmetry lowering for some atoms correlates with the existence of phase transitions (in langasite family crystals) and the anisotropy of physical properties (in rare-earth dodecaborides RB12).

  17. Holographic method for site-resolved detection of a 2D array of ultracold atoms

    Science.gov (United States)

    Hoffmann, Daniel Kai; Deissler, Benjamin; Limmer, Wolfgang; Hecker Denschlag, Johannes

    2016-08-01

    We propose a novel approach to site-resolved detection of a 2D gas of ultracold atoms in an optical lattice. A near-resonant laser beam is coherently scattered by the atomic array, and after passing a lens its interference pattern is holographically recorded by superimposing it with a reference laser beam on a CCD chip. Fourier transformation of the recorded intensity pattern reconstructs the atomic distribution in the lattice with single-site resolution. The holographic detection method requires only about two hundred scattered photons per atom in order to achieve a high reconstruction fidelity of 99.9 %. Therefore, additional cooling during detection might not be necessary even for light atomic elements such as lithium. Furthermore, first investigations suggest that small aberrations of the lens can be post-corrected in imaging processing.

  18. The Definition Method and Optimization of Atomic Strain Tensors for Nuclear Power Engineering Materials

    Directory of Open Access Journals (Sweden)

    Xiangguo Zeng

    2016-01-01

    Full Text Available A common measure of deformation between atomic scale simulations and the continuum framework is provided and the strain tensors for multiscale simulations are defined in this paper. In order to compute the deformation gradient of any atom m, the weight function is proposed to eliminate the different contributions within the neighbor atoms which have different distances to atom m, and the weighted least squares error optimization model is established to seek the optimal coefficients of the weight function and the optimal local deformation gradient of each atom. The optimization model involves more than 9 parameters. To guarantee the reliability of subsequent parameters identification result and lighten the calculation workload of parameters identification, an overall analysis method of parameter sensitivity and an advanced genetic algorithm are also developed.

  19. Generalized series method in the theory of atomic nucleus

    International Nuclear Information System (INIS)

    Gorbatov, A.M.

    1991-01-01

    On a hypersphere of a prescribed radius the so-called genealogical basis has been constructed. By making use of this basis, the many-body Schroedinger equation has been obtained for bound states of various physical systems. The genealogical series method, being in general outline the extension of the angular potential functions method, deals with the potential harmonics of any generation needed. The new approach provides an exact numerical description of the hadron systems with two-body higher interaction

  20. Diode laser probe of CO2 vibrational excitation produced by collisions with hot deuterium atoms from the 193 nm excimer laser photolysis D2S

    International Nuclear Information System (INIS)

    O'Neill, J.A.; Cai, J.Y.; Flynn, G.W.; Weston, R.E. Jr.

    1986-01-01

    The 193 nm excimer laser photolysis of D 2 S in D 2 S/CO 2 mixtures produces fast deuterium atoms (E/sub TR/approx.2.2 eV) which vibrationally excite CO 2 molecules via inelastic translation--vibration/rotation (T--V/R) energy exchange processes. A high resolution (10 -3 cm -1 ) cw diode laser probe was used to monitor the excitation of ν 3 (antisymmetric stretch) and ν 2 (bend) vibrations in CO 2 . The present results are compared with previous experiments involving hot hydrogen atom excitation of CO 2 in H 2 S/CO 2 mixtures as well as with theoretical calculations of the excitation probability. The probability for excitation of a ν 3 quantum in CO 2 is about 1%--2% per gas kinetic D/CO 2 collision. Bending (ν 2 ) quanta are produced about eight times more efficiently than antisymmetric stretching (ν 3 ) quanta. The thermalization rate for cooling hot D atoms below the threshold for production of a ν 3 vibrational quantum corresponds to less than 2 D*/D 2 S collisions or 15 D*/CO 2 collisions

  1. A COMPARISON OF A SPECTROPHOTOMETRIC (QUERCETIN) METHOD AND AN ATOMIC-ABSORPTION METHOD FOR DETERMINATION OF TIN IN FOOD

    DEFF Research Database (Denmark)

    Engberg, Å

    1973-01-01

    Procedures for the determination of tin in food, which involve a spectrophotometric method (with the quercetin-tin complex) and an atomic-absorption method, are described. The precision of the complete methods and of the individual analytical steps required is evaluated, and the parameters...

  2. z calibration of the atomic force microscope by means of a pyramidal tip

    DEFF Research Database (Denmark)

    Jensen, Flemming

    1993-01-01

    A new method for imaging the probe tip of an atomic force microscope cantilever by the atomic force microscope itself (self-imaging) is presented. The self-imaging is accomplished by scanning the probe tip across a sharper tip on the surface. By using a pyramidal probe tip with a very well......-defined aspect ratio, this technique provides an excellent z-calibration standard for the atomic force microscope....

  3. An Efficient Method for Electron-Atom Scattering Using Ab-initio Calculations

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yuan; Yang, Yonggang; Xiao, Liantuan; Jia, Suotang [Shanxi University, Taiyuan (China)

    2017-02-15

    We present an efficient method based on ab-initio calculations to investigate electron-atom scatterings. Those calculations profit from methods implemented in standard quantum chemistry programs. The new approach is applied to electron-helium scattering. The results are compared with experimental and other theoretical references to demonstrate the efficiency of our method.

  4. The effective atomic numbers of some biomolecules calculated by two methods: A comparative study

    DEFF Research Database (Denmark)

    Manohara, S.R.; Hanagodimath, S.M.; Gerward, Leif

    2009-01-01

    The effective atomic numbers Z(eff) of some fatty acids and amino acids have been calculated by two numerical methods, a direct method and an interpolation method, in the energy range of 1 keV-20 MeV. The notion of Z(eff) is given a new meaning by using a modern database of photon interaction cro...

  5. Reaction mechanism of oxygen atoms with unsaturated hydrocarbons by the crossed molecular beams method

    Energy Technology Data Exchange (ETDEWEB)

    Buss, R.J.; Baseman, R.J.; Guozhong, H.; Lee, Y.T.

    1982-04-01

    From a series of studies of the reaction of oxygen atoms with unsaturated hydrocarbons using the crossed molecular beam method, the dominant reaction mechanisms were found to be the simple substitution reactions with oxygen atoms replacing H, Cl, Br atom or alkyl groups. Complication due to secondary reaction was avoided by carrying out experiments under single collisions and observing primary products directly. Primary products were identified by measuring the angular and velocity distributions of products at all the mass numbers which could be detected by the mass spectrometer, and from comparison of these distributions, applying the requirement of energy and momentum conservation.

  6. The generalized sturmian method for calculating spectra of atoms and ions

    DEFF Research Database (Denmark)

    Avery, James Emil; Avery, John Scales

    2003-01-01

    The properties of generalized Sturmian basis sets are reviewed, and functions of this type are used to perform direct configuration interaction calculations on the spectra of atoms and ions. Singlet excited states calculated in this way show good agreement with experimentally measured spectra. When...... the generalized Sturmian method is applied to atoms, the configurations are constructed from hydrogenlike atomic orbitals with an effective charge which is characteristic of the configuration. Thus, orthonormality between the orbitals of different configurations cannot be assumed, and the generalized Slater...

  7. Reaction Mechanism of Oxygen Atoms with Unsaturated Hydrocarbons by the Crossed-Molecular-Beams Method

    Science.gov (United States)

    Buss, R. J.; Baseman, R. J.; Guozhong, H.; Lee, Y. T.

    1982-04-01

    From a series of studies of the reaction of oxygen atoms with unsaturated hydrocarbons using the crossed molecular beam method, the dominant reaction mechanisms were found to be the simple substitution reactions with oxygen atoms replacing H, Cl, Br atom or alkyl groups. Complication due to secondary reaction was avoided by carrying out experiments under single collisions and observing primary products directly. Primary products were identified by measuring the angular and velocity distributions of products at all the mass numbers which could be detected by the mass spectrometer, and from comparison of these distributions, applying the requirement of energy and momentum conservation.

  8. Reflection and diffraction of atomic de Broglie waves by evanescent laser waves. Bare-state method

    International Nuclear Information System (INIS)

    Feng, Xiaoping; Witte, N.S.; Hollenberg, C.L.; Opat, G.

    1994-01-01

    Two methods are presented for the investigation of the reflection and diffraction of atoms by gratings formed either by standing or travelling evanescent laser waves. Both methods use the bare-state rather than dressed-state picture. One method is based on the Born series, whereas the other is based on the Laplace transformation of the coupled differential equations. The two methods yield the same theoretical expressions for the reflected and diffracted atomic waves in the whole space including the interaction and the asymptotic regions. 1 ref., 1 fig

  9. Nucleic acid hybridization assays employing dA-tailed capture probes. II. Advanced multiple capture methods

    International Nuclear Information System (INIS)

    Hunsaker, W.R.; Badri, H.; Lombardo, M.; Collins, M.L.

    1989-01-01

    A fourth capture is added to the reversible target capture procedure. This results in an improved radioisotopic detection limit of 7.3 x 10(-21) mol of target. In addition, the standard triple capture method is converted into a nonradioactive format with a detection limit of under 1 amol of target. The principal advantage of nonradioactive detection is that the entire assay can be performed in about 1 h. Nucleic acids are released from cells in the presence of the (capture probe) which contains a 3'-poly(dA) sequence and the (labeled probe) which contains a detectable nonradioactive moiety such as biotin. After a brief hybridization in solution, the target is captured on oligo(dT) magnetic particles. The target is further purified from sample impurities and excess labeled probe by recapture either once or twice more on fresh magnetic particles. The highly purified target is then concentrated to 200 nl by recapture onto a poly(dT) nitrocellulose filter and rapidly detected with streptavidin-alkaline phosphatase using bromochloroindolyl phosphate and nitroblue tetrazolium. Using this procedure, as little as 0.25 amol of a target plasmid has been detected nonradioactively in crude samples in just 1 h without prior purification of the DNA and RNA. Finally, a new procedure called background capture is introduced to complement the background-reducing power of RTC

  10. Three-dimensional atom-probe microscopy investigation of the temporal evolution of the nanostructure of a model Ni-Al-Cr alloy

    International Nuclear Information System (INIS)

    Sudbrack, C.K.; Noebe, R.D.; Seidman, D.N.

    2004-01-01

    Full text: Due to complex interactions in multi-component multi-phase metallic alloys, as well as experimental limitations, insight into the decomposition pathways of isothermal precipitation from a supersaturated solid-solution is limited. Experimentally, the direct, spatial characterization of the chemical composition on a sub-nano- and nanometer scale of small features is challenging, but necessary to understand solid-solid phase-transformation phenomena. The power and capacity of three-dimensional atom-probe (3DAP) microscopy to characterize an ordering precipitation reaction, gamma (fcc) → gamma (fcc) + gamma-prime (L1 2 structure) in Ni-5.2 Al-14.2 Cr at. % aged isothermally at 600 o C, was first demonstrated by Schmuck et al., and is examined in great detail here. Complementary transmission electron microscopy experiments are utilized to study the temporal evolution. For the decomposition stages investigated (2 minutes to 1024 hours aging), this alloy exhibits a high number density (3.2 x 10 24 m -3 maximum) of spheroidal precipitates, 0.5-10 nm in radius. The average composition of the γ'-precipitates is shown to evolve temporally, such that solute concentrations decrease toward their equilibrium values. Sub-nanometer scale compositional profiles across the interface are obtained by the proximity histogram method, or 'proxigram' for short. In agreement with the theory of diffusion-limited growth, chemical gradients of the Al (depletion) and Cr (enrichment) that extend approximately 3 nm from the interface into the matrix are observed in the 0.25 h aging state. As the alloy is aged, these gradients decay, and completely disappear between 4 and 16 h of aging. The interfacial widths of the proxigram composition profiles are found to be component dependent, such that, the widths of the Ni, Al, and Cr profiles are 0.78 ± 0.09, 1.24 ± 0.11, and 1.84 ± 0.13 nm, respectively. Precipitates interconnected by necks are observed, and their implication on the

  11. A new digitized reverse correction method for hypoid gears based on a one-dimensional probe

    Science.gov (United States)

    Li, Tianxing; Li, Jubo; Deng, Xiaozhong; Yang, Jianjun; Li, Genggeng; Ma, Wensuo

    2017-12-01

    In order to improve the tooth surface geometric accuracy and transmission quality of hypoid gears, a new digitized reverse correction method is proposed based on the measurement data from a one-dimensional probe. The minimization of tooth surface geometrical deviations is realized from the perspective of mathematical analysis and reverse engineering. Combining the analysis of complex tooth surface generation principles and the measurement mechanism of one-dimensional probes, the mathematical relationship between the theoretical designed tooth surface, the actual machined tooth surface and the deviation tooth surface is established, the mapping relation between machine-tool settings and tooth surface deviations is derived, and the essential connection between the accurate calculation of tooth surface deviations and the reverse correction method of machine-tool settings is revealed. Furthermore, a reverse correction model of machine-tool settings is built, a reverse correction strategy is planned, and the minimization of tooth surface deviations is achieved by means of the method of numerical iterative reverse solution. On this basis, a digitized reverse correction system for hypoid gears is developed by the organic combination of numerical control generation, accurate measurement, computer numerical processing, and digitized correction. Finally, the correctness and practicability of the digitized reverse correction method are proved through a reverse correction experiment. The experimental results show that the tooth surface geometric deviations meet the engineering requirements after two trial cuts and one correction.

  12. Atomic and nuclear methods in fossil energy research

    International Nuclear Information System (INIS)

    Filby, R.H.; Carpenter, B.S.; Ragaini, R.C.

    1982-01-01

    This book presents information on the following topics: analysis of oil shale products and effluents using a multitechnique approach; nuclear methods for trace elements in petroleum and petroleum products; uranium content of petroleum by fission; fast neutron activation analysis of fossil fuels and liquefaction products; determination of trace element forms in solvent refined coal products; an automated multidetector system for instrumental neutron activation analysis of geological and environmental materials; on-line nuclear analysis of coal and its uses; investigation of coal hydrogenation using deuterium as an isotopic tracer; the natural permeability reduction in porous media due to the presence of kaolinite; the application of photon induced x-ray fluorescence for the simultaneous determinations of cobalt, nickel and molybdenum in hydrodesulfurization catalysts; and applications of nuclear magnetic resonance of oil shale evaluation and processing

  13. Cultural probes

    DEFF Research Database (Denmark)

    Madsen, Jacob Østergaard

    The aim of this study was thus to explore cultural probes (Gaver, Boucher et al. 2004), as a possible methodical approach, supporting knowledge production on situated and contextual aspects of occupation.......The aim of this study was thus to explore cultural probes (Gaver, Boucher et al. 2004), as a possible methodical approach, supporting knowledge production on situated and contextual aspects of occupation....

  14. Quantitative transmission electron microscopy and atom probe tomography study of Ag-dependent precipitation of Ω phase in Al-Cu-Mg alloys

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Song; Ying, Puyou [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Liu, Zhiyi, E-mail: liuzhiyi@csu.edu.cn [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Wang, Jian; Li, Junlin [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China)

    2017-02-27

    The close association between the Ω precipitation and various Ag additions is systematically investigated by quantitative transmission electron microscopy and atom probe tomography analysis. Our results suggest that the precipitation of Ω phase is strongly dependent on Ag variations. Increasing the bulk Ag content favors a denser Ω precipitation and hence leads to a greater age-hardening response of Al-Cu-Mg-Ag alloy. This phenomenon, as proposed by proximity histograms, is directly related to the greater abundance of Ag solutes within Ω precursors. This feature lowers its nucleation barrier and increases the nucleation rate of Ω phase, finally contributes to the enhanced Ω precipitation. Also, it is noted that increasing Ag remarkably restricts the precipitation of θ' phase.

  15. Nanostructural evolution in surveillance test specimens of a commercial nuclear reactor pressure vessel studied by three-dimensional atom probe and positron annihilation

    International Nuclear Information System (INIS)

    Toyama, T.; Nagai, Y.; Tang, Z.; Hasegawa, M.; Almazouzi, A.; Walle, E. van; Gerard, R.

    2007-01-01

    The nanostructural evolution of irradiation-induced Cu-rich nanoprecipitates (CRNPs) and vacancy clusters in surveillance test specimens of in-service commercial nuclear reactor pressure vessel steel welds of Doel-1 and Doel-2 are revealed by combining the three-dimensional local electrode atom probe and positron annihilation techniques. In both medium (0.13 wt.%) and high (0.30 wt.%) Cu welds, the CRNPs are found to form readily at the very beginning of the reactor lifetime. Thereafter, during the subsequent 30 years of operation, the residual Cu concentration in the matrix shows a slight decrease while the CRNPs coarsen. On the other hand, small vacancy clusters of V 3 -V 4 start appearing after the initial Cu precipitation and accumulate steadily with increasing neutron dose. The observed nanostructural evolution is shown to provide unique and fundamental information about the mechanisms of the irradiation-induced embrittlement of these specific materials

  16. Direct observation of the leakage current in epitaxial diamond Schottky barrier devices by conductive-probe atomic force microscopy and Raman imaging

    Science.gov (United States)

    Alvarez, J.; Boutchich, M.; Kleider, J. P.; Teraji, T.; Koide, Y.

    2014-09-01

    The origin of the high leakage current measured in several vertical-type diamond Schottky devices is conjointly investigated by conducting probe atomic force microscopy and confocal micro-Raman/photoluminescence imaging analysis. Local areas characterized by a strong decrease of the local resistance (5-6 orders of magnitude drop) with respect to their close surrounding have been identified in several different regions of the sample surface. The same local areas, also referenced as electrical hot-spots, reveal a slightly constrained diamond lattice and three dominant Raman bands in the low-wavenumber region (590, 914 and 1040 cm-1). These latter bands are usually assigned to the vibrational modes involving boron impurities and its possible complexes that can electrically act as traps for charge carriers. Local current-voltage measurements performed at the hot-spots point out a trap-filled-limited current as the main conduction mechanism favouring the leakage current in the Schottky devices.

  17. A quantitative atom probe study of the Nb excess at prior austenite grain boundaries in a Nb microalloyed strip-cast steel

    International Nuclear Information System (INIS)

    Felfer, Peter J.; Killmore, Chris R.; Williams, Jim G.; Carpenter, Kristin R.; Ringer, Simon P.; Cairney, Julie M.

    2012-01-01

    Most modern HSLA steels rely on the effect of Nb in steels to achieve the properties desired for a specific application. While the role of Nb in forming precipitates has been well characterized, its role in a solid solution is less well understood due to the difficulty of obtaining quantitative experimental data. In the current work, site-specific atom probe tomography was used to quantify the amount of Nb present at prior austenite grain boundaries in a commercial strip-cast steel, produced via the Castrip ® process. This was compared to the amount of Nb found at ferrite–ferrite grain boundaries that had formed during the transformation from austenite to ferrite. With the interfacial excess Nb measured, thermodynamic calculations were carried out and compared to the change in transformation temperature obtained by dilatometry, with reference to a comparable Nb free, strip-cast steel.

  18. Ultrafast Photodissociation Dynamics of the F State of Sulfur Dioxide by Femtosecond Time-Resolved Pump-Probe Method

    International Nuclear Information System (INIS)

    Zhang Dong-Dong; Ni Qiang; Luo Si-Zuo; Zhang Jing; Liu Hang; Xu Hai-Feng; Jin Ming-Xing; Ding Da-Jun

    2011-01-01

    A femtosecond pump-probe method is employed to study the dissociation dynamics of sulfur dioxide. SO 2 molecules are excited to the F state by absorbing two photons of 267 nm femtosecond laser pulses, and ionized by 400 nm laser pulses at different delay times between the two lasers. Transients of both parent ions (SO + 2 ) and the fragment ions (SO + , S + and O + ) are observed. The SO + 2 transient can be well fitted to a biexponential decay comprising a fast and a slow component of 280 fs and 2.97 ps lifetimes, respectively. The SO + transient consists of two growth components of 270 fs and 2.50 ps. The results clearly show that the F state of SO 2 dissociates along an S-O bond. The transients of S + and O + , however, have different behavior, which consist of a fast growth and a long decay component. A possible mechanism of the fragment formation is discussed to understand the dissociation dynamics of the F state of SO 2 . (atomic and molecular physics)

  19. Injection locking method for Raman beams in atom interferometer

    Science.gov (United States)

    Zi, Fei; Deng, Jianing; Zeng, Daji; Li, Tong; Sun, Mingli; Zhang, Xian; Huang, Kaikai; Lu, Xuanhui

    2018-03-01

    We present a novel method to generate two phase-locked beams with a frequency offset of 6.834 GHz. The output of the master laser is firstly modulated by an electric optical modulator (EOM), and then further injected into an Extended Cavity Diode Lasers (ECDL) which is used to filter out the unwanted mode and amplify the laser power. By locking to the first-order lower sideband of the modulated master laser, the average variance of the phase fluctuations is 5.6 x 10-3 rad2 , which implies phase coherence of 99.44% between the master laser and the slave ECDL. The line width of the beat notes is less than 1Hz. For the long term stability, with the delicate design of the electronic controller in ECDL, the phase coherence of the two laser beams can be stabilized over 200 hours without any adjustment. The Raman system is applicable for gravity detection with a preliminary sensitivity Δg/g of 4.5 x 10-7 for interrogation time of 1500 s.

  20. Method of shaping of direction-characterization of sensitivity of ionizing radiation detection probe

    International Nuclear Information System (INIS)

    Czarnecki, J.; Jaszczuk, J.; Kruczyk, M.; Slapa, M.; Wroblewski, T.

    1986-01-01

    A method of shaping of direction-characterization of sensitivity of the ionizing radiation detection probe, especially equipped with small gamma detectors is described. Two detectors are placed coaxially in the bases of the cylindrical shield. One of them is uncovered in the highest degree and the second is not covered to a maximum. The signals from them are processed on the standarized sequences of electrical impulses (taking into account the heights and the widths of the amplitude). 2 figs., 1 tab. (A.S.)

  1. Time-of-flight atom-probe field-ion microscope for the study of defects in metals. Report No. 2357

    International Nuclear Information System (INIS)

    Hall, T.M.; Wagner, A.; Berger, A.S.; Seidman, D.N.

    1975-06-01

    An ultra-high vacuum time-of-flight (TOF) atom-probe field ion microscope (FIM) specifically designed for the study of defects in metals is described. The variable magnification FIM image is viewed with the aid of an internal image intensification system based on a channel electron-multiplier array. The specimen is held in a liquid-helium-cooled goniometer stage, and the specimen is exchanged by means of a high-vacuum (less than 10 -6 torr) specimen exchange device. This stage allows the specimen to be maintained at a tip temperature anywhere in the range from 13 to 450 0 K. Specimens can also be irradiated in-situ with any low-energy (less than 1 keV) gas ion employing a specially constructed ion gun. The pulse-field evaporated ions are detected by a Chevron ion-detector located 2.22 m from the FIM specimen. The TOF of the ions are measured by a specially constructed eight-channel digital timer with a resolution of +-10 ns. The entire process of applying the evaporation pulse to the specimen, measuring the dc and pulse voltages, and analyzing the TOF data is controlled by a NOVA 1220 computer. The computer is also interfaced to a Tektronix graphics terminal which displays the data in the form of a histogram of the number of events versus the mass-to-charge ratio. An extensive set of computer programs to test and operate the atom-probe FIM have been developed. With this automated system we can presently record and analyze 10 TOF s -1 . In the performance tests reported here the instrument has resolved the seven stable isotopes of molybdenum, the five stable isotopes of tungsten, and the two stable isotopes of rhenium in a tungsten--25 at. percent rhenium alloy

  2. Probing the elastic response of microalga Scenedesmus dimorphus in dry and aqueous environments through atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Warren, K. M.; Mpagazehe, J. N.; Higgs, C. F., E-mail: prl@andrew.cmu.edu, E-mail: higgs@andrew.cmu.edu [Department of Mechanical Engineering, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, Pennsylvania 15213 (United States); LeDuc, P. R., E-mail: prl@andrew.cmu.edu, E-mail: higgs@andrew.cmu.edu [Department of Mechanical Engineering, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, Pennsylvania 15213 (United States); Departments of Biomedical Engineering and Biological Sciences, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213 (United States)

    2014-10-20

    With the re-emergence of microalgae as a replacement feedstock for petroleum-derived oils, researchers are working to understand its chemical and mechanical behavior. In this work, the mechanical properties of microalgae, Scenedesmus dimorphus, were investigated at the subcellular level to determine the elastic response of cells that were in an aqueous and dried state using nano-scale indentation through atomic force microscopy. The elastic modulus of single-celled S. dimorphus cells increased over tenfold from an aqueous state to a dried state, which allows us to better understand the biophysical response of microalgae to stress.

  3. Probing the elastic response of microalga Scenedesmus dimorphus in dry and aqueous environments through atomic force microscopy

    International Nuclear Information System (INIS)

    Warren, K. M.; Mpagazehe, J. N.; Higgs, C. F.; LeDuc, P. R.

    2014-01-01

    With the re-emergence of microalgae as a replacement feedstock for petroleum-derived oils, researchers are working to understand its chemical and mechanical behavior. In this work, the mechanical properties of microalgae, Scenedesmus dimorphus, were investigated at the subcellular level to determine the elastic response of cells that were in an aqueous and dried state using nano-scale indentation through atomic force microscopy. The elastic modulus of single-celled S. dimorphus cells increased over tenfold from an aqueous state to a dried state, which allows us to better understand the biophysical response of microalgae to stress.

  4. Possibility to Probe Negative Values of a Wigner Function in Scattering of a Coherent Superposition of Electronic Wave Packets by Atoms.

    Science.gov (United States)

    Karlovets, Dmitry V; Serbo, Valeriy G

    2017-10-27

    Within a plane-wave approximation in scattering, an incoming wave packet's Wigner function stays positive everywhere, which obscures such purely quantum phenomena as nonlocality and entanglement. With the advent of the electron microscopes with subnanometer-sized beams, one can enter a genuinely quantum regime where the latter effects become only moderately attenuated. Here we show how to probe negative values of the Wigner function in scattering of a coherent superposition of two Gaussian packets with a nonvanishing impact parameter between them (a Schrödinger's cat state) by atomic targets. For hydrogen in the ground 1s state, a small parameter of the problem, a ratio a/σ_{⊥} of the Bohr radius a to the beam width σ_{⊥}, is no longer vanishing. We predict an azimuthal asymmetry of the scattered electrons, which is found to be up to 10%, and argue that it can be reliably detected. The production of beams with the not-everywhere-positive Wigner functions and the probing of such quantum effects can open new perspectives for noninvasive electron microscopy, quantum tomography, particle physics, and so forth.

  5. Determination of trace amounts of cadmium in sea water by a flameless atomic absorption method

    International Nuclear Information System (INIS)

    Yamazoe, Seigo; Oshima, Shozo

    1975-01-01

    Determination of trace amounts of cadmium in sea water has been developed by a flameless atomic absorption method using a carbon rod atomizer. Sea water is diluted with isopropyl alcohol and the white salt formed is removed by filtration, then the filtrate is fed to the instrument as a sample for measurement. A complete separation of the salt is not needed in this pre-treatment. The effect of the residual salt can be avoided by separating the atomic absorption of cadmium and the molecular absorption of the residual salt by means of controlling the temperature and the time of ashing and atomization of the sample in the carbon rod. The repeatability and the accuracy are 2.0--8.5% in the coefficient of variation and 0.8--5.3% respectively. (auth.)

  6. Energetic Analysis of Conjugated Hydrocarbons Using the Interacting Quantum Atoms Method.

    Science.gov (United States)

    Jara-Cortés, Jesús; Hernández-Trujillo, Jesús

    2018-07-05

    A number of aromatic, antiaromatic, and nonaromatic organic molecules was analyzed in terms of the contributions to the electronic energy defined in the quantum theory of atoms in molecules and the interacting quantum atoms method. Regularities were found in the exchange and electrostatic interatomic energies showing trends that are closely related to those of the delocalization indices defined in the theory. In particular, the CC interaction energies between bonded atoms allow to rationalize the energetic stabilization associated with the bond length alternation in conjugated polyenes. This approach also provides support to Clar's sextet rules devised for aromatic systems. In addition, the H⋯H bonding found in some of the aromatic molecules studied was of an attractive nature, according to the stabilizing exchange interaction between the bonded H atoms. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  7. Optimization of parameters for the extended Hueckel method starting from ab-initio atomic calculations

    International Nuclear Information System (INIS)

    Branda, M.M.; Ferullo, R.; Castellani, N.J.

    1990-01-01

    The application of an atomic Hartree-Fock-Slater method is exposed in the present work for the simultaneous obtainment of all parameters used in the extended Hueckel method with charge interaction (IEH): The diagonal elements of the Hamiltonian, the constants of the quadratic relation between. (Author). 16 refs., 3 tabs

  8. Effective linear two-body method for many-body problems in atomic and nuclear physics

    International Nuclear Information System (INIS)

    Kim, Y.E.; Zubarev, A.L.

    2000-01-01

    We present an equivalent linear two-body method for the many body problem, which is based on an approximate reduction of the many-body Schroedinger equation by the use of a variational principle. The method is applied to several problems in atomic and nuclear physics. (author)

  9. Hybrid statistics-simulations based method for atom-counting from ADF STEM images.

    Science.gov (United States)

    De Wael, Annelies; De Backer, Annick; Jones, Lewys; Nellist, Peter D; Van Aert, Sandra

    2017-06-01

    A hybrid statistics-simulations based method for atom-counting from annular dark field scanning transmission electron microscopy (ADF STEM) images of monotype crystalline nanostructures is presented. Different atom-counting methods already exist for model-like systems. However, the increasing relevance of radiation damage in the study of nanostructures demands a method that allows atom-counting from low dose images with a low signal-to-noise ratio. Therefore, the hybrid method directly includes prior knowledge from image simulations into the existing statistics-based method for atom-counting, and accounts in this manner for possible discrepancies between actual and simulated experimental conditions. It is shown by means of simulations and experiments that this hybrid method outperforms the statistics-based method, especially for low electron doses and small nanoparticles. The analysis of a simulated low dose image of a small nanoparticle suggests that this method allows for far more reliable quantitative analysis of beam-sensitive materials. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Radiotracer investigation of the cold-vapour atomic absorption method of analysis for trace mercury

    International Nuclear Information System (INIS)

    Stuart, D.C.

    1978-01-01

    Because of certain problems found in application of the atomic absorption method for trace analysis of mercury, a careful check of the procedures used was undertaken, with radiotracer mercury to facilitate the investigation. The results obtained, in conjunction with those of sample ashing procedures, indicate that the method is less straightforward than its simplicity suggests. (Auth.)

  11. Investigation of RNA Structure by High-Throughput SHAPE-Based Probing Methods

    DEFF Research Database (Denmark)

    Poulsen, Line Dahl

    of highthroughput SHAPE-based approaches to investigate RNA structure based on novel SHAPE reagents that permit selection of full-length cDNAs. The SHAPE Selection (SHAPES) method is applied to the foot-and-mouth disease virus (FMDV) plus strand RNA genome, and the data is used to construct a genome-wide structural...... that they are functional. The SHAPES method is further applied to the hepatitis C virus (HCV), where the data is used to refine known and predicted structures. Over the past years, the interest of studying RNA structure in their native environment has been increased, and to allow studying RNA structure inside living cells...... using the SHAPE Selection approach, I introduce a biotinylated probing reagent. This chemical can cross cell membranes and reacts with RNA inside the cells, allowing the structural conformations to be studied in the context of physiological relevant conditions in living cells. The methods and results...

  12. Methods for the numerical calculation of the plasma potential from measured Langmuir probe characteristics

    International Nuclear Information System (INIS)

    Seifert, W.; Johanning, D.; Bankov, N.

    1986-01-01

    In a previous paper the results of the Langmuir probe experiment carried out on board of two INTERKOSMOS satellites have been described. The experiences have shown that the usage of high quality algorithms for analyzing the current-voltage-characteristics is necessary to yield real physical parameters. The key problem is the determination of the plasma potential. This paper reviews the different methods to determine the plasma potential especially under the circumstances of computer application. The test of the well developed methods shows, that for the evaluation of the applied methods a number of different factors, discussed in the following sections of this paper, has to be taken into account. The used test data are model values or real measurements obtained by the satellite missions IK-10, IK-18 and BULGARIA-1300. The computer procedures have been realized as FORTRAN-subroutines for the BESM 6 and ES 1040. (author)

  13. The calculation of surface free energy based on embedded atom method for solid nickel

    International Nuclear Information System (INIS)

    Luo Wenhua; Hu Wangyu; Su Kalin; Liu Fusheng

    2013-01-01

    Highlights: ► A new solution for accurate prediction of surface free energy based on embedded atom method was proposed. ► The temperature dependent anisotropic surface energy of solid nickel was obtained. ► In isotropic environment, the approach does not change most predictions of bulk material properties. - Abstract: Accurate prediction of surface free energy of crystalline metals is a challenging task. The theory calculations based on embedded atom method potentials often underestimate surface free energy of metals. With an analytical charge density correction to the argument of the embedding energy of embedded atom method, an approach to improve the prediction for surface free energy is presented. This approach is applied to calculate the temperature dependent anisotropic surface energy of bulk nickel and surface energies of nickel nanoparticles, and the obtained results are in good agreement with available experimental data.

  14. Atom probe study on the bulk nanocomposite SmCo/Fe permanent magnet produced by ball-milling and warm compaction

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, X.Y., E-mail: xiangyuan.xiong@mcem.monash.edu.au [Monash Centre for Electron Microscopy, Monash University, Vic. 3800 (Australia); Department of Materials Engineering, Monash University, Vic. 3800 (Australia); Rong, C.B. [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States); Rubanov, S. [Electron Microscopy Unit, Bio21 Institute, University of Melbourne, Vic. 3052 (Australia); Zhang, Y. [Division of Materials Science and Engineering, Ames Laboratory, Iowa State University, Ames, IA 50011 (United States); Liu, J.P. [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States)

    2011-11-15

    The microstructure and compositions of the bulk nanocomposite SmCo/Fe permanent magnet were studied using transmission electron microscopy and 3-dimensional atom probe techniques. The excellent magnetic properties were related to the uniform nanocomposite structure with nanometer {alpha}-Fe particles uniformly distributed in the SmCo phase matrix. The {alpha}-Fe phase contained {approx}26 at% Co, and the SmCo phase contained {approx}19 at% Fe, confirming that the interdiffusion of Fe and Co atoms between the two phases occurred. The formation of the {alpha}-Fe(Co) phase explained why the saturation magnetization of the nanocomposite permanent magnet was higher than that expected from the original pure {alpha}-Fe and SmCo{sub 5} powders, which enhanced further the maximum energy product of the nanocomposite permanent magnet. - Highlights: > A uniform nanocomposite SmCo/{alpha}-Fe permanent magnet with high performance obtained. > The first quantitative analyses of interdiffusion of Fe and Co between the two phases presented. > The saturation magnetization of the nanocomposite enhanced by the resulting {alpha}-Fe(Co) phase.

  15. Design of a scanning probe microscope with advanced sample treatment capabilities: An atomic force microscope combined with a miniaturized inductively coupled plasma source

    International Nuclear Information System (INIS)

    Hund, Markus; Herold, Hans

    2007-01-01

    We describe the design and performance of an atomic force microscope (AFM) combined with a miniaturized inductively coupled plasma source working at a radio frequency of 27.12 MHz. State-of-the-art scanning probe microscopes (SPMs) have limited in situ sample treatment capabilities. Aggressive treatments such as plasma etching or harsh treatments such as etching in aggressive liquids typically require the removal of the sample from the microscope. Consequently, time consuming procedures are required if the same sample spot has to be imaged after successive processing steps. We have developed a first prototype of a SPM which features a quasi in situ sample treatment using a modified commercial atomic force microscope. A sample holder is positioned in a special reactor chamber; the AFM tip can be retracted by several millimeters so that the chamber can be closed for a treatment procedure. Most importantly, after the treatment, the tip is moved back to the sample with a lateral drift per process step in the 20 nm regime. The performance of the prototype is characterized by consecutive plasma etching of a nanostructured polymer film

  16. The effective atomic numbers of some biomolecules calculated by two methods: A comparative study

    Energy Technology Data Exchange (ETDEWEB)

    Manohara, S. R.; Hanagodimath, S. M.; Gerward, L. [Department of Physics, Gulbarga University, Gulbarga, Karnataka 585 106 (India); Department of Physics, Technical University of Denmark, Lyngby DK-2800 (Denmark)

    2009-01-15

    The effective atomic numbers Z{sub eff} of some fatty acids and amino acids have been calculated by two numerical methods, a direct method and an interpolation method, in the energy range of 1 keV-20 MeV. The notion of Z{sub eff} is given a new meaning by using a modern database of photon interaction cross sections (WinXCom). The results of the two methods are compared and discussed. It is shown that for all biomolecules the direct method gives larger values of Z{sub eff} than the interpolation method, in particular at low energies (1-100 keV) At medium energies (0.1-5 MeV), Z{sub eff} for both methods is about constant and equal to the mean atomic number of the material. Wherever possible, the calculated values of Z{sub eff} are compared with experimental data.

  17. The effective atomic numbers of some biomolecules calculated by two methods: A comparative study

    International Nuclear Information System (INIS)

    Manohara, S. R.; Hanagodimath, S. M.; Gerward, L.

    2009-01-01

    The effective atomic numbers Z eff of some fatty acids and amino acids have been calculated by two numerical methods, a direct method and an interpolation method, in the energy range of 1 keV-20 MeV. The notion of Z eff is given a new meaning by using a modern database of photon interaction cross sections (WinXCom). The results of the two methods are compared and discussed. It is shown that for all biomolecules the direct method gives larger values of Z eff than the interpolation method, in particular at low energies (1-100 keV) At medium energies (0.1-5 MeV), Z eff for both methods is about constant and equal to the mean atomic number of the material. Wherever possible, the calculated values of Z eff are compared with experimental data.

  18. Improving method of real-time offset tuning for arterial signal coordination using probe trajectory data

    Directory of Open Access Journals (Sweden)

    Jian Zhang

    2016-12-01

    Full Text Available In the environment of intelligent transportation systems, traffic condition data would have higher resolution in time and space, which is especially valuable for managing the interrupted traffic at signalized intersections. There exist a lot of algorithms for offset tuning, but few of them take the advantage of modern traffic detection methods such as probe vehicle data. This study proposes a method using probe trajectory data to optimize and adjust offsets in real time. The critical point, representing the changing vehicle dynamics, is first defined as the basis of this approach. Using the critical points related to different states of traffic conditions, such as free flow, queue formation, and dissipation, various traffic status parameters can be estimated, including actual travel speed, queue dissipation rate, and standing queue length. The offset can then be adjusted on a cycle-by-cycle basis. The performance of this approach is evaluated using a simulation network. The results show that the trajectory-based approach can reduce travel time of the coordinated traffic flow when compared with using well-defined offline offset.

  19. Note: A silicon-on-insulator microelectromechanical systems probe scanner for on-chip atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Fowler, Anthony G.; Maroufi, Mohammad; Moheimani, S. O. Reza, E-mail: Reza.Moheimani@newcastle.edu.au [School of Electrical Engineering and Computer Science, University of Newcastle, Callaghan, NSW 2308 (Australia)

    2015-04-15

    A new microelectromechanical systems-based 2-degree-of-freedom (DoF) scanner with an integrated cantilever for on-chip atomic force microscopy (AFM) is presented. The silicon cantilever features a layer of piezoelectric material to facilitate its use for tapping mode AFM and enable simultaneous deflection sensing. Electrostatic actuators and electrothermal sensors are used to accurately position the cantilever within the x-y plane. Experimental testing shows that the cantilever is able to be scanned over a 10 μm × 10 μm window and that the cantilever achieves a peak-to-peak deflection greater than 400 nm when excited at its resonance frequency of approximately 62 kHz.

  20. PIEZO channel protein naturally expressed in human breast cancer cell MDA-MB-231 as probed by atomic force microscopy

    Science.gov (United States)

    Weng, Yuanqi; Yan, Fei; Chen, Runkang; Qian, Ming; Ou, Yun; Xie, Shuhong; Zheng, Hairong; Li, Jiangyu

    2018-05-01

    Mechanical stimuli drives many physiological processes through mechanically activated channels, and the recent discovery of PIEZO channel has generated great interests in its mechanotransduction. Many previous researches investigated PIEZO proteins by transcribing them in cells that originally have no response to mechanical stimulation, or by forming PIEZO-combined complexes in vitro, and few studied PIEZO protein's natural characteristics in cells. In this study we show that MDA-MB-231, a malignant cell in human breast cancer cell line, expresses the mechanosensitive behavior of PIEZO in nature without extra treatment, and we report its characteristics in response to localized mechanical stimulation under an atomic force microscope, wherein a correlation between the force magnitude applied and the channel opening probability is observed. The results on PIEZO of MDA-MB-231 can help establish a basis of preventing and controlling of human breast cancer cell via mechanical forces.

  1. Probing the Surface Charge on the Basal Planes of Kaolinite Particles with High-Resolution Atomic Force Microscopy.

    Science.gov (United States)

    Kumar, N; Andersson, M P; van den Ende, D; Mugele, F; Siretanu, I

    2017-12-19

    High-resolution atomic force microscopy is used to map the surface charge on the basal planes of kaolinite nanoparticles in an ambient solution of variable pH and NaCl or CaCl 2 concentration. Using DLVO theory with charge regulation, we determine from the measured force-distance curves the surface charge distribution on both the silica-like and the gibbsite-like basal plane of the kaolinite particles. We observe that both basal planes do carry charge that varies with pH and salt concentration. The silica facet was found to be negatively charged at pH 4 and above, whereas the gibbsite facet is positively charged at pH below 7 and negatively charged at pH above 7. Investigations in CaCl 2 at pH 6 show that the surface charge on the gibbsite facet increases for concentration up to 10 mM CaCl 2 and starts to decrease upon further increasing the salt concentration to 50 mM. The increase of surface charge at low concentration is explained by Ca 2+ ion adsorption, while Cl - adsorption at higher CaCl 2 concentrations partially neutralizes the surface charge. Atomic resolution imaging and density functional theory calculations corroborate these observations. They show that hydrated Ca 2+ ions can spontaneously adsorb on the gibbsite facet of the kaolinite particle and form ordered surface structures, while at higher concentrations Cl - ions will co-adsorb, thereby changing the observed ordered surface structure.

  2. Time-Dependent Close-Coupling Methods for Electron-Atom/Molecule Scattering

    International Nuclear Information System (INIS)

    Colgan, James

    2014-01-01

    The time-dependent close-coupling (TDCC) method centers on an accurate representation of the interaction between two outgoing electrons moving in the presence of a Coulomb field. It has been extensively applied to many problems of electrons, photons, and ions scattering from light atomic targets. Theoretical Description: The TDCC method centers on a solution of the time-dependent Schrödinger equation for two interacting electrons. The advantages of a time-dependent approach are two-fold; one treats the electron-electron interaction essentially in an exact manner (within numerical accuracy) and a time-dependent approach avoids the difficult boundary condition encountered when two free electrons move in a Coulomb field (the classic three-body Coulomb problem). The TDCC method has been applied to many fundamental atomic collision processes, including photon-, electron- and ion-impact ionization of light atoms. For application to electron-impact ionization of atomic systems, one decomposes the two-electron wavefunction in a partial wave expansion and represents the subsequent two-electron radial wavefunctions on a numerical lattice. The number of partial waves required to converge the ionization process depends on the energy of the incoming electron wavepacket and on the ionization threshold of the target atom or ion.

  3. Atom-to-continuum methods for gaining a fundamental understanding of fracture.

    Energy Technology Data Exchange (ETDEWEB)

    McDowell, David Lynn (Georgia Institute of Technology, Atlanta, GA); Reedy, Earl David, Jr.; Templeton, Jeremy Alan; Jones, Reese E.; Moody, Neville Reid; Zimmerman, Jonathan A.; Belytschko, Ted. (Northwestern University, Evanston, IL); Zhou, Xiao Wang; Lloyd, Jeffrey T. (Georgia Institute of Technology, Atlanta, GA); Oswald, Jay (Northwestern University, Evanston, IL); Delph, Terry J. (Lehigh University, Bethlehem, PA); Kimmer, Christopher J. (Indiana University Southeast, New Albany, IN)

    2011-08-01

    This report describes an Engineering Sciences Research Foundation (ESRF) project to characterize and understand fracture processes via molecular dynamics modeling and atom-to-continuum methods. Under this aegis we developed new theory and a number of novel techniques to describe the fracture process at the atomic scale. These developments ranged from a material-frame connection between molecular dynamics and continuum mechanics to an atomic level J integral. Each of the developments build upon each other and culminated in a cohesive zone model derived from atomic information and verified at the continuum scale. This report describes an Engineering Sciences Research Foundation (ESRF) project to characterize and understand fracture processes via molecular dynamics modeling and atom-to-continuum methods. The effort is predicated on the idea that processes and information at the atomic level are missing in engineering scale simulations of fracture, and, moreover, are necessary for these simulations to be predictive. In this project we developed considerable new theory and a number of novel techniques in order to describe the fracture process at the atomic scale. Chapter 2 gives a detailed account of the material-frame connection between molecular dynamics and continuum mechanics we constructed in order to best use atomic information from solid systems. With this framework, in Chapter 3, we were able to make a direct and elegant extension of the classical J down to simulations on the scale of nanometers with a discrete atomic lattice. The technique was applied to cracks and dislocations with equal success and displayed high fidelity with expectations from continuum theory. Then, as a prelude to extension of the atomic J to finite temperatures, we explored the quasi-harmonic models as efficient and accurate surrogates of atomic lattices undergoing thermo-elastic processes (Chapter 4). With this in hand, in Chapter 5 we provide evidence that, by using the appropriate

  4. The study of the irradiation-induced embrittlement of reactor pressure vessels. Analysis of surveillance test specimens of a commercial nuclear reactor pressure vessel studied by three-dimensional atom probe and positron annihilation

    International Nuclear Information System (INIS)

    Nagai, Yasuyoshi; Toyama, Takeshi; Hasegawa, Masayuki

    2007-01-01

    The study of embrittlement of nuclear power reactor pressure vessels (RPVs) is of critical importance for the safety assessment in the nuclear industry. Some origins of embrittlement are attributed to fine Cu precipitates, matrix defects, grain boundary segregation of P and late blooming phase. This review article described nanostructural observation by three-dimensional atom probe (3DAP) and positron annihilation spectroscopy (PAS). The density and sizes of Cu-rich nanoprecipitates and grain boundary segregation are sensitively detected by 3DAP, and vacancies are probed by PAS. Element analysis around vacancies and fine microstructural Cu precipitates not containing vacancies are successfully observed by a coincidence doppler broadening method. The nanostructural evolution of irradiation-induced Cu-rich nanoprecipitates (CRNPs) and vacancy clusters in surveillance test specimens of commercial nuclear reactor pressure vessel steel welds of Doel-2 in Belgium were revealed by combining 3DAP and PAS. In both medium (0.13 wt%) and high (0.30 wt%) Cu welds, the CRNPs were found to form readily at the very beginning of the reactor lifetime. On the other hand, small vacancy clusters start appearing after the initial Cu precipitates and accumulate steadily with increasing neutron dose. The CRNPs were also observed at very low dose rate of neutrons in the test specimen of Calder Hall Reactor of Japan Atomic Power Company. The significant enhancement of these Cu precipitates results in the embrittlement in practical RPVs. At very high dose of 2.2x10 18 n/cm 2 by JMTR, the Cu precipitates were scarcely observed, and the irradiation-induced embrittlement was primarily caused from vacancy-impurity complexes and dislocation loops. (author)

  5. Electromagnetic methods for measuring materials properties of cylindrical rods and array probes for rapid flaw inspection

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Haiyan [Iowa State Univ., Ames, IA (United States)

    2005-01-01

    The case-hardening process modifies the near-surface permeability and conductivity of steel, as can be observed through changes in alternating current potential drop (ACPD) along a rod. In order to evaluate case depth of case hardened steel rods, analytical expressions are derived for the alternating current potential drop on the surface of a homogeneous rod, a two-layered and a three-layered rod. The case-hardened rod is first modeled by a two-layer rod that has a homogeneous substrate with a single, uniformly thick, homogeneous surface layer, in which the conductivity and permeability values differ from those in the substrate. By fitting model results to multi-frequency ACPD experimental data, estimates of conductivity, permeability and case depth are found. Although the estimated case depth by the two-layer model is in reasonable agreement with the effective case depth from the hardness profile, it is consistently higher than the effective case depth. This led to the development of the three-layer model. It is anticipated that the new three-layered model will improve the results and thus makes the ACPD method a novel technique in nondestructive measurement of case depth. Another way to evaluate case depth of a case hardened steel rod is to use induction coils. Integral form solutions for an infinite rod encircled by a coaxial coil are well known, but for a finite length conductor, additional boundary conditions must be satisfied at the ends. In this work, calculations of eddy currents are performed for a two-layer conducting rod of finite length excited by a coaxial circular coil carrying an alternating current. The solution is found using the truncated region eigenfunction expansion (TREE) method. By truncating the solution region to a finite length in the axial direction, the magnetic vector potential can be expressed as a series expansion of orthogonal eigenfunctions instead of as a Fourier integral. Closed-form expressions are derived for the electromagnetic

  6. The development of high-resolution spectroscopic methods and their use in atomic structure studies

    International Nuclear Information System (INIS)

    Poulsen, O.

    1984-01-01

    This thesis discusses work performed during the last nine years in the field of atomic spectroscopy. Several high-resolution techniques, ranging from quantum beats, level crossings, rf-laser double resonances to nonlinear field atom interactions, have been employed. In particular, these methods have been adopted and developed to deal with fast accelerated atomic or ionic beams, allowing studies of problems in atomic-structure theory. Fine- and hyperfine-structure determinations in the He I and Li I isoelectronic sequences, in 51 V I, and in 235 U I, II have permitted a detailed comparison with ab initio calculations, demonstrating the change in problems when going towards heavier elements or higher ionization stage. The last part of the thesis is concerned with the fundamental question of obtaining very high optical resolution in the interaction between a fast accelerated atom or ion beam and a laser field, this problem being the core in the continuing development of atomic spectroscopy necessary to challenge the more precise and sophisticated theories advanced. (Auth.)

  7. Matrix Methods for Solving Hartree-Fock Equations in Atomic Structure Calculations and Line Broadening

    Directory of Open Access Journals (Sweden)

    Thomas Gomez

    2018-04-01

    Full Text Available Atomic structure of N-electron atoms is often determined by solving the Hartree-Fock equations, which are a set of integro-differential equations. The integral part of the Hartree-Fock equations treats electron exchange, but the Hartree-Fock equations are not often treated as an integro-differential equation. The exchange term is often approximated as an inhomogeneous or an effective potential so that the Hartree-Fock equations become a set of ordinary differential equations (which can be solved using the usual shooting methods. Because the Hartree-Fock equations are an iterative-refinement method, the inhomogeneous term relies on the previous guess of the wavefunction. In addition, there are numerical complications associated with solving inhomogeneous differential equations. This work uses matrix methods to solve the Hartree-Fock equations as an integro-differential equation. It is well known that a derivative operator can be expressed as a matrix made of finite-difference coefficients; energy eigenvalues and eigenvectors can be obtained by using linear-algebra packages. The integral (exchange part of the Hartree-Fock equation can be approximated as a sum and written as a matrix. The Hartree-Fock equations can be solved as a matrix that is the sum of the differential and integral matrices. We compare calculations using this method against experiment and standard atomic structure calculations. This matrix method can also be used to solve for free-electron wavefunctions, thus improving how the atoms and free electrons interact. This technique is important for spectral line broadening in two ways: it improves the atomic structure calculations, and it improves the motion of the plasma electrons that collide with the atom.

  8. Electrochemical preconcentration and hydride generation methods for trace determination of selenium by atomic absorption spectrometry

    International Nuclear Information System (INIS)

    Bye, R.

    1986-01-01

    The use of atomic absorption spectrometry in combination with two different preconcentration/separation techniques for the determination of trace concentrations of selenium is described. Electrochemical preconcentration onto a platinum electrode with a subsequent atomization of selenium is discussed briefly. Several parameters are considered such as the presence of depolarizers, and the temperature of the electrolyzed solutions. Special attention is payed to the efficiency of the atomization step, and a method to improve this is proposed. Applications of the technique to real samples are also reported. Secondly, the separation of the selenium as the volatile selenium hydride from the sample solution is considered. Several papers in this thesis deal with commonly occurring interferants as nickel and copper and with ways of minimizing or avoiding the interferring effects, whereas other papers relate to more theoretical aspects of the hydride generation process. New methods for the determination of selenium in technical samples with high contents of nickel and copper are also presented

  9. Applications of the semiclassical spectral method to nuclear, atomic, molecular, and polymeric dynamics

    International Nuclear Information System (INIS)

    Koszykowski, M.L.; Pfeffer, G.A.; Noid, D.W.

    1987-01-01

    Nonlinear dynamics plays a dominant role in a variety of important problems in chemical physics. Examples are unimolecular reactions, infrared multiphoton decomposition of molecules, the pumping process of the gamma ray laser, dissociation of vibrationally excited state-selected van der Waals's complexes, and many other chemical and atomic processes. The present article discusses recent theoretical studies on the quasi-periodic and chaotic dynamic aspects of vibrational-rotational states of atomic, nuclear, and molecular systems using the semiclassical spectral method (SSM). The authors note that the coordinates, momenta, and so on, are found using classical mechanics in the studies included in this review. They outline the semiclassical spectral method and a wide variety of applications. Although this technique was first developed ten years ago, it has proved to be tremendously successful as a tool used in dynamics problems. Applications include problems in nonlinear dynamics, molecular and atomic spectra, surface science, astronomy and stellar dynamics, nuclear physics, and polymer physics

  10. Method to determine the sticking coefficient of precursor molecules in atomic layer deposition

    International Nuclear Information System (INIS)

    Rose, M.; Bartha, J.W.

    2009-01-01

    A method to determine the sticking coefficient of precursor molecules used in atomic layer deposition (ALD) will be introduced. The sticking coefficient is an interesting quantity for comparing different ALD processes and reactors but it cannot be observed easily. The method relies on free molecular flow in nanoscale cylindrical holes. The sticking coefficient is determined for tetrakis(dimethylamino)titanium in combination with ozone. The proposed method can be applied independent of the type of reactor, precursor delivery system and precursors.

  11. Wide range local resistance imaging on fragile materials by conducting probe atomic force microscopy in intermittent contact mode

    Energy Technology Data Exchange (ETDEWEB)

    Vecchiola, Aymeric [Laboratoire de Génie électrique et électronique de Paris (GeePs), UMR 8507 CNRS-CentraleSupélec, Paris-Sud and UPMC Universities, 11 rue Joliot-Curie, Plateau de Moulon, 91192 Gif-sur-Yvette (France); Concept Scientific Instruments, ZA de Courtaboeuf, 2 rue de la Terre de Feu, 91940 Les Ulis (France); Unité Mixte de Physique CNRS-Thales UMR 137, 1 avenue Augustin Fresnel, 91767 Palaiseau (France); Chrétien, Pascal; Schneegans, Olivier; Mencaraglia, Denis; Houzé, Frédéric, E-mail: frederic.houze@geeps.centralesupelec.fr [Laboratoire de Génie électrique et électronique de Paris (GeePs), UMR 8507 CNRS-CentraleSupélec, Paris-Sud and UPMC Universities, 11 rue Joliot-Curie, Plateau de Moulon, 91192 Gif-sur-Yvette (France); Delprat, Sophie [Unité Mixte de Physique CNRS-Thales UMR 137, 1 avenue Augustin Fresnel, 91767 Palaiseau (France); UPMC, Université Paris 06, 4 place Jussieu, 75005 Paris (France); Bouzehouane, Karim; Seneor, Pierre; Mattana, Richard [Unité Mixte de Physique CNRS-Thales UMR 137, 1 avenue Augustin Fresnel, 91767 Palaiseau (France); Tatay, Sergio [Molecular Science Institute, University of Valencia, 46980 Paterna (Spain); Geffroy, Bernard [Lab. Physique des Interfaces et Couches minces (PICM), UMR 7647 CNRS-École polytechnique, 91128 Palaiseau (France); Lab. d' Innovation en Chimie des Surfaces et Nanosciences (LICSEN), NIMBE UMR 3685 CNRS-CEA Saclay, 91191 Gif-sur-Yvette (France); and others

    2016-06-13

    An imaging technique associating a slowly intermittent contact mode of atomic force microscopy (AFM) with a home-made multi-purpose resistance sensing device is presented. It aims at extending the widespread resistance measurements classically operated in contact mode AFM to broaden their application fields to soft materials (molecular electronics, biology) and fragile or weakly anchored nano-objects, for which nanoscale electrical characterization is highly demanded and often proves to be a challenging task in contact mode. Compared with the state of the art concerning less aggressive solutions for AFM electrical imaging, our technique brings a significantly wider range of resistance measurement (over 10 decades) without any manual switching, which is a major advantage for the characterization of materials with large on-sample resistance variations. After describing the basics of the set-up, we report on preliminary investigations focused on academic samples of self-assembled monolayers with various thicknesses as a demonstrator of the imaging capabilities of our instrument, from qualitative and semi-quantitative viewpoints. Then two application examples are presented, regarding an organic photovoltaic thin film and an array of individual vertical carbon nanotubes. Both attest the relevance of the technique for the control and optimization of technological processes.

  12. Probing surface magnetism with ion beams

    International Nuclear Information System (INIS)

    Winter, H.

    2007-01-01

    Ion beams can be used to probe magnetic properties of surfaces by a variety of different methods. Important features of these methods are related to trajectories of atomic projectiles scattered from the surface of a solid target and to the electronic interaction mechanisms in the surface region. Both items provide under specific conditions a high sensitivity for the detection of magnetic properties in the region at the topmost layer of surface atoms. This holds in particular for scattering under planar surface channeling conditions, where under grazing impact atoms or ions are reflected specularly from the surface without penetration into the subsurface region. Two different types of methods are employed based on the detection of the spin polarization of emitted or captured electrons and on spin blocking effects for capture into atomic terms. These techniques allow one to probe the long range and short range magnetic order in the surface region

  13. Quenching methods for background reduction in luminescence-based probe-target binding assays

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Hong [Los Alamos, NM; Goodwin, Peter M [Los Alamos, NM; Keller, Richard A [Los Alamos, NM; Nolan, Rhiannon L [Santa Fe, NM

    2007-04-10

    Background luminescence is reduced from a solution containing unbound luminescent probes, each having a first molecule that attaches to a target molecule and having an attached luminescent moiety, and luminescent probe/target adducts. Quenching capture reagent molecules are formed that are capable of forming an adduct with the unbound luminescent probes and having an attached quencher material effective to quench luminescence of the luminescent moiety. The quencher material of the capture reagent molecules is added to a solution of the luminescent probe/target adducts and binds in a proximity to the luminescent moiety of the unbound luminescent probes to quench luminescence from the luminescent moiety when the luminescent moiety is exposed to exciting illumination. The quencher capture reagent does not bind to probe molecules that are bound to target molecules and the probe/target adduct emission is not quenched.

  14. Long-range dispersion interactions. III: Method for two homonuclear atoms

    International Nuclear Information System (INIS)

    Mitroy, J.; Zhang, J.-Y.

    2007-01-01

    A procedure for systematically evaluating the long-range dispersion interaction between two homonuclear atoms in arbitrary LS coupled states is outlined. The method is then used to generate dispersion coefficients for a number of the low-lying states of the Na and Mg dimers

  15. Primary Student Teachers' Ideas of Atoms and Molecules: Using Drawings as a Research Method

    Science.gov (United States)

    Ozden, Mustafa

    2009-01-01

    The purpose of this study is to reveal the primary student teachers' basic knowledge and misconceptions about atoms and molecules by use of a drawing method. Data collected from drawings of 92 primary student teachers at the second term of 2007-2008 educational period in Faculty of Education in Adiyaman University. The analysis of their drawings…

  16. Tungsten determination in heat resistant nickel-base-alloys by the method of atomic absorption

    International Nuclear Information System (INIS)

    Gregorczyk, S.; Wycislik, A.

    1980-01-01

    A method of atomic absorption was developed. It allows for the tungsten to be determined in heatresistant nickel-base-alloys within the range 0.01 to 7%. It consists in precipitating tungsten acid in the presence of alkaloids with its following decomposition by hydrofluoric acid in the teflon bomb. (author)

  17. Calculating Relativistic Transition Matrix Elements for Hydrogenic Atoms Using Monte Carlo Methods

    Science.gov (United States)

    Alexander, Steven; Coldwell, R. L.

    2015-03-01

    The nonrelativistic transition matrix elements for hydrogen atoms can be computed exactly and these expressions are given in a number of classic textbooks. The relativistic counterparts of these equations can also be computed exactly but these expressions have been described in only a few places in the literature. In part, this is because the relativistic equations lack the elegant simplicity of the nonrelativistic equations. In this poster I will describe how variational Monte Carlo methods can be used to calculate the energy and properties of relativistic hydrogen atoms and how the wavefunctions for these systems can be used to calculate transition matrix elements.

  18. An indirect method for determining phosphorus in aluminium alloys by atomic-absorption spectrometry.

    Science.gov (United States)

    Bernal, J L; Del Nozal, M A; Deban, L; Aller, A J

    1981-07-01

    An indirect method is described for the determination of phosphorus in aluminium alloys. Ammonium molybdate is added to a solution of the aluminium alloy and the molybdophosphoric acid formed is selectively extracted into n-butyl acetate. The twelve molybdenum atoms associated with each phosphate ion are determined by direct atomic-absorption spectrometry with the n-butyl acetate phase in a nitrous oxide-acetylene flame, with measurement at 313.2 nm. The most suitable conditions have been established and the effect of other ions has been studied.

  19. Probe-based real-time PCR method for multilocus melt typing of Xylella fastidiosa strains.

    Science.gov (United States)

    Brady, Jeff A; Faske, Jennifer B; Ator, Rebecca A; Castañeda-Gill, Jessica M; Mitchell, Forrest L

    2012-04-01

    Epidemiological studies of Pierce's disease (PD) can be confounded by a lack of taxonomic detail on the bacterial causative agent, Xylella fastidiosa (Xf). PD in grape is caused by strains of Xylella fastidiosa subsp. fastidiosa, but is not caused by other subspecies of Xf that typically colonize plants other than grape. Detection assays using ELISA and qPCR are effective at detecting and quantifying Xf presence or absence, but offer no information on Xf subspecies or strain identity. Surveying insects or host plants for Xf by current ELISA or qPCR methods provides only presence/absence and quantity information for any and all Xf subspecies, potentially leading to false assessments of disease threat. This study uses a series of adjacent-hybridizing DNA melt analysis probes that are capable of efficiently discriminating Xf subspecies and strain relationships in rapid real-time PCR reactions. Copyright © 2012 Elsevier B.V. All rights reserved.

  20. Study on modulation amplitude stabilization method for PEM based on FPGA in atomic magnetometer

    Science.gov (United States)

    Wang, Qinghua; Quan, Wei; Duan, Lihong

    2017-10-01

    Atomic magnetometer which uses atoms as sensitive elements have ultra-high precision and has wide applications in scientific researches. The photoelastic modulation method based on photoelastic modulator (PEM) is used in the atomic magnetometer to detect the small optical rotation angle of a linearly polarized light. However, the modulation amplitude of the PEM will drift due to the environmental factors, which reduces the precision and long-term stability of the atomic magnetometer. Consequently, stabilizing the PEM's modulation amplitude is essential to precision measurement. In this paper, a modulation amplitude stabilization method for PEM based on Field Programmable Gate Array (FPGA) is proposed. The designed control system contains an optical setup and an electrical part. The optical setup is used to measure the PEM's modulation amplitude. The FPGA chip, with the PID control algorithm implemented in it, is used as the electrical part's micro controller. The closed loop control method based on the photoelastic modulation detection system can directly measure the PEM's modulation amplitude in real time, without increasing the additional optical devices. In addition, the operating speed of the modulation amplitude stabilization control system can be greatly improved because of the FPGA's parallel computing feature, and the PID control algorithm ensures flexibility to meet different needs of the PEM's modulation amplitude set values. The Modelsim simulation results show the correctness of the PID control algorithm, and the long-term stability of the PEM's modulation amplitude reaches 0.35% in a 3-hour continuous measurement.