WorldWideScience

Sample records for atom probe tomography

  1. Atom Probe Tomography

    International Nuclear Information System (INIS)

    Atom probe tomography (APT) is a lens-less point-projection microscopy that resolves individual atoms on the surface of a sharply pointed tip (radius of curvature R < 100 nm), at a magnification of the order of ⁓106. The specimen tip is pulsed to a positive potential V with respect to ground, thereby generating electric fields E ⁓ V/R of some 10 V/nm. Ions released from the apex due to field evaporation are sent flying to a position sensitive detector where they are identified by time-of-flight mass spectrometry. Continuous removal of single atoms provides the possibility of a 3D elemental characterization of solids with sub-nm spatial resolution. The basic principles of the technique and some selected analytical applications will be discussed. (author)

  2. Pragmatic reconstruction methods in atom probe tomography

    International Nuclear Information System (INIS)

    Data collected in atom probe tomography have to be carefully analysed in order to give reliable composition data accurately and precisely positioned in the probed volume. Indeed, the large analysed surfaces of recent instruments require reconstruction methods taking into account not only the tip geometry but also accurate knowledge of geometrical projection parameters. This is particularly crucial in the analysis of multilayers materials or planar interfaces. The current work presents a simulation model that enables extraction of the two main projection features as a function of the tip and atom probe instrumentation geometries. Conversely to standard assumptions, the image compression factor and the field factor vary significantly during the analysis. An improved reconstruction method taking into account the intrinsic shape of a sample containing planar features is proposed to overcome this shortcoming. -- Highlights: → Tomographic reconstructions in atom probe tomography. → Model of field evaporation in a 2D non-regular geometry with cylindrical symmetry. → Calculation of the field factor and of the image compression factor. → New algorithm of reconstruction for specimen composed of flat layer structures.

  3. Atom Probe Tomography of Nanoscale Electronic Materials

    Energy Technology Data Exchange (ETDEWEB)

    Larson, David J.; Prosa, Ty J.; Perea, Daniel E.; Inoue, Hidekazu; Mangelinck, D.

    2016-01-01

    Atom probe tomography (APT) is a mass spectrometry based on time-of-flight measurements which also concurrently produces 3D spatial information. The reader is referred to any of the other papers in this volume or to the following references for further information 4–8. The current capabilities of APT, such as detecting a low number of dopant atoms in nanoscale devices or segregation at a nanoparticle interface, make this technique an important component in the nanoscale metrology toolbox. In this manuscript, we review some of the applications of APT to nanoscale electronic materials, including transistors and finFETs, silicide contact microstructures, nanowires, and nanoparticles.

  4. Atom probe tomography (APT) of carbonate minerals.

    Science.gov (United States)

    Pérez-Huerta, Alberto; Laiginhas, Fernando; Reinhard, David A; Prosa, Ty J; Martens, Rich L

    2016-01-01

    Atom probe tomography (APT) combines the highest spatial resolution with chemical data at atomic scale for the analysis of materials. For geological specimens, the process of field evaporation and molecular ion formation and interpretation is not yet entirely understood. The objective of this study is to determine the best conditions for the preparation and analysis by APT of carbonate minerals, of great importance in the interpretation of geological processes, focusing on the bulk chemical composition. Results show that the complexity of the mass spectrum is different for calcite and dolomite and relates to dissimilarities in crystalochemical parameters. In addition, APT bulk chemistry of calcite closely matches the expected stoichiometry but fails to provide accurate atomic percentages for elements in dolomite under the experimental conditions evaluated in this work. For both calcite and dolomite, APT underestimates the amount of oxygen based on their chemical formula, whereas it is able to detect small percentages of elemental substitutions in crystal lattices. Overall, our results demonstrate that APT of carbonate minerals is possible, but further optimization of the experimental parameters are required to improve the use of atom probe tomography for the correct interpretation of mineral geochemistry. PMID:26519815

  5. Full tip imaging in atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Du, Sichao [School of Physics, The University of Sydney, NSW 2006 (Australia); Burgess, Timothy [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Tjing Loi, Shyeh [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Gault, Baptiste [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Department of Materials Science and Engineering, McMaster University, 1280 Main St W, Hamilton, ON, Canada L8S 4L8 (Canada); Gao, Qiang [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Bao, Peite; Li, Li [School of Physics, The University of Sydney, NSW 2006 (Australia); Cui, Xiangyuan; Kong Yeoh, Wai [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Hoe Tan, Hark; Jagadish, Chennupati [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Ringer, Simon P. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Zheng, Rongkun, E-mail: rongkun.zheng@sydney.edu.au [School of Physics, The University of Sydney, NSW 2006 (Australia)

    2013-01-15

    Atom probe tomography (APT) is capable of simultaneously revealing the chemical identities and three dimensional positions of individual atoms within a needle-shaped specimen, but suffers from a limited field-of-view (FOV), i.e., only the core of the specimen is effectively detected. Therefore, the capacity to analyze the full tip is crucial and much desired in cases that the shell of the specimen is also the region of interest. In this paper, we demonstrate that, in the analysis of III-V nanowires epitaxially grown from a substrate, the presence of the flat substrate positioned only micrometers away from the analyzed tip apex alters the field distribution and ion trajectories, which provides extra image compression that allows for the analysis of the entire specimen. An array of experimental results, including field desorption maps, elemental distributions, and crystallographic features clearly demonstrate the fact that the whole tip has been imaged, which is confirmed by electrostatic simulations. -- Highlights: Black-Right-Pointing-Pointer The full tip has been imaged by atom probe tomography. Black-Right-Pointing-Pointer The conductive substrate close to specimen tip introduces extra image compression. Black-Right-Pointing-Pointer The apex of the tip is far from a hemispherical shape. Black-Right-Pointing-Pointer This work demonstrates a way to increase the FOV of APT.

  6. Spatial resolution in atom probe tomography

    CERN Document Server

    Gault, Baptiste; de Geuser, Frederic; La Fontaine, Alex; Stephenson, Leigh T; Haley, Daniel; Ringer, Simon P

    2015-01-01

    This article addresses gaps in definitions and a lack of standard measurement techniques to assess the spatial resolution in atom probe tomography. This resolution is known to be anisotropic, being better in the depth than laterally. Generally the presence of atomic planes in the tomographic reconstruction is considered as being a sufficient proof of the quality of the spatial resolution of the instrument. Based on advanced spatial distribution maps, an analysis methodology that interrogates the local neighborhood of the atoms within the tomographic reconstruction, it is shown how both the in-depth and the lateral resolution can be quantified. The influences of the crystallography and the temperature are investigated, and models are proposed to explain the observed results. We demonstrate that the absolute value of resolution is specimenspecific.

  7. Dynamic reconstruction for atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Gault, Baptiste, E-mail: baptiste.gault@sydney.edu.au [Australian Centre for Microscopy and Microanalysis, Madsen Building F09, The University of Sydney, NSW 2006 (Australia); Institute of Materials and Engineering Science, Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234 (Australia); Loi, Shyeh Tjing; Araullo-Peters, Vicente J.; Stephenson, Leigh T.; Moody, Michael P.; Shrestha, Sachin L.; Marceau, Ross K.W.; Yao, Lan; Cairney, Julie M.; Ringer, Simon P. [Australian Centre for Microscopy and Microanalysis, Madsen Building F09, The University of Sydney, NSW 2006 (Australia)

    2011-11-15

    Progress in the reconstruction for atom probe tomography has been limited since the first implementation of the protocol proposed by Bas et al. in 1995. This approach and those subsequently developed assume that the geometric parameters used to build the three-dimensional atom map are constant over the course of an analysis. Here, we test this assumption within the analyses of low-alloyed materials. By building upon methods recently proposed to measure the tomographic reconstruction parameters, we demonstrate that this assumption can introduce significant limitations in the accuracy of the analysis. Moreover, we propose a strategy to alleviate this problem through the implementation of a new reconstruction algorithm that dynamically accommodates variations in the tomographic reconstruction parameters. -- Highlights: Black-Right-Pointing-Pointer Variation of main reconstruction parameters, namely image compression and field factors, quantified. Black-Right-Pointing-Pointer A new protocol to build the tomographic reconstruction is proposed where reconstruction parameters are dynamically adjusted. Black-Right-Pointing-Pointer Integrity of reconstructions obtained from the standard and dynamic reconstruction protocols compared.

  8. Investigation of Interfaces by Atom Probe Tomography

    Science.gov (United States)

    Balogh, Zoltán; Stender, Patrick; Chellali, Mohammed Reda; Schmitz, Guido

    2013-10-01

    We investigated the thermodynamic and transport properties of buried interfaces with atom probe tomography. Owing to the 3D subnanometer resolution and single atom sensitivity of the method, it is possible to obtain composition profiles with high accuracy both along or normal to the interfaces. We have shown that the width of the chemical interface between the Fe and Cr system follows the Cahn-Hilliard relation with a gradient energy coefficient of 1.86 × 10-22 J nm2. Sharpening of the Ni/Cu interface as a result of kinetic control was directly observed. We investigated the grain boundary and triple junction transport in Fe/Cr and Ni/Cu. Cr segregation enthalpy into Fe triple junctions was found to be 0.076 eV, which falls in between the surface (0.159 eV) and grain boundary (0.03 eV) segregation enthalpies. In the investigated 563 K to 643 K (290 °C to 370 °C) range, Ni transport is 200 to 300 times faster in the triple junctions of Cu than in the grain boundaries. The diffusion activation enthalpy in the triple junctions is two-thirds that of the grain boundaries (0.86 and 1.24 eV, respectively). These investigations have shown that triple junctions are defects in their own right with characteristic segregation and diffusion properties: They are preferred segregation sites and can be considered as a diffusion shortcut in the grain boundary network.

  9. Atom probe tomography of lithium-doped network glasses

    Energy Technology Data Exchange (ETDEWEB)

    Greiwe, Gerd-Hendrik, E-mail: g_grei01@uni-muenster.de [Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Str. 10, D-48149 Münster (Germany); Balogh, Zoltan; Schmitz, Guido [Institute of Material Science, University of Stuttgart, Heisenberg Straße 3, D-70569 Stuttgart (Germany)

    2014-06-01

    Li-doped silicate and borate glasses are electronically insulating, but provide considerable ionic conductivity. Under measurement conditions of laser-assisted atom probe tomography, mobile Li ions are redistributed in response to high electric fields. In consequence, the direct interpretation of measured composition profiles is prevented. It is demonstrated that composition profiles are nevertheless well understood by a complex model taking into account the electronic structure of dielectric materials, ionic mobility and field screening. Quantitative data on band bending and field penetration during measurement are derived which are important in understanding laser-assisted atom probe tomography of dielectric materials. - Highlights: • Atom probe tomography is performed on ion conducting glasses. • Redistribution of ions during the measurement is observed. • An electrostatic model is applied to describe the electric field and ion diffusion. • Measurement is conducted of the absolute temperature during laser pulses.

  10. Data mining for isotope discrimination in atom probe tomography

    International Nuclear Information System (INIS)

    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

  11. 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.

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

    Science.gov (United States)

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

    2016-03-01

    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 3nm 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. PMID:26724469

  13. Reflections on the projection of ions in atom probe tomography

    CERN Document Server

    De Geuser, Frédéric

    2016-01-01

    There are two main projections used to transform, and reconstruct, field ion micrographs or atom probe tomography data into atomic coordinates at the specimen surface and, subsequently, in three-dimensions. In this article, we present a perspective on the strength of the azimuthal equidistant projection in comparison to the more widely used and well-established point-projection, which underpins data reconstruction in the only commercial software package available currently. After an overview of the reconstruction methodology, we demonstrate that the azimuthal equidistant is not only more accurate, but also more robust with regards to errors on the parameters used to perform the reconstruction and is therefore more likely to yield more accurate tomographic reconstructions.

  14. Accuracy of analyses of microelectronics nanostructures in atom probe tomography

    Science.gov (United States)

    Vurpillot, F.; Rolland, N.; Estivill, R.; Duguay, S.; Blavette, D.

    2016-07-01

    The routine use of atom probe tomography (APT) as a nano-analysis microscope in the semiconductor industry requires the precise evaluation of the metrological parameters of this instrument (spatial accuracy, spatial precision, composition accuracy or composition precision). The spatial accuracy of this microscope is evaluated in this paper in the analysis of planar structures such as high-k metal gate stacks. It is shown both experimentally and theoretically that the in-depth accuracy of reconstructed APT images is perturbed when analyzing this structure composed of an oxide layer of high electrical permittivity (higher-k dielectric constant) that separates the metal gate and the semiconductor channel of a field emitter transistor. Large differences in the evaporation field between these layers (resulting from large differences in material properties) are the main sources of image distortions. An analytic model is used to interpret inaccuracy in the depth reconstruction of these devices in APT.

  15. Atom probe tomography of a commercial light emitting diode

    International Nuclear Information System (INIS)

    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

  16. Effect of Laser Power on Atom Probe Tomography of Silicates

    Science.gov (United States)

    Parman, S. W.; Gorman, B.; Jackson, C.; Cooper, R. F.; Diercks, D.

    2011-12-01

    Atom probe tomography (APT) is an emerging analytical method that has the potential to produce nm-scale spatial resolution of atom positions with ppm-level detection limits. Until recently, APT has been limited to analysis of conducting samples due to the high pulsed electrical fields previously required. The recent development of laser-assisted APT now allows much lower laser powers to be used, opening the door to analysis of geologic minerals. The potential applications are many, ranging from diffusion profiles to the distribution of nano-phases to grain boundary chemical properties. We reported the first analysis of natural olivine using APT last year (Parman et al, 2010). While the spatial resolution was good (nm-scale), the accuracy of the compositional analysis was not. Two of the primary barriers to accurate ion identification in APT are: 1) Specimen overheating - This is caused by the interaction of the laser with the low thermal conductivity insulating specimens. Ions are assumed to have left the surface of the sample at the time the laser is pulsed during the analysis (laser pulse width = 12 ps). If the laser power is too high, the surface remains heated for an appreciable time (greater than 5 ns in some cases) after the laser pulse, causing atoms to field evaporate from the surface well after the laser pulse. Since they hit the detector later than the atoms that were released during the pulse, they are interpreted to be higher mass. Thus overheating appears in the analysis as a smearing of mass/charge peaks to higher mass/charge ratios (thermal tails). For well separated peaks, this is not a substantial problem, but for closely spaced peaks, overheating causes artificial mass interferences. 2) Molecular evaporation or clustering - This is also caused by overheating by the laser. Ideally, atoms are field evaporated individually from the surface of the cylindrical specimen. However, if the absorbed energy is high enough, clusters of atoms will be formed

  17. 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 covalen

  18. 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

  19. Towards an accurate volume reconstruction in atom probe tomography.

    Science.gov (United States)

    Beinke, Daniel; Oberdorfer, Christian; Schmitz, Guido

    2016-06-01

    An alternative concept for the reconstruction of atom probe data is outlined. It is based on the calculation of realistic trajectories of the evaporated ions in a recursive refinement process. To this end, the electrostatic problem is solved on a Delaunay tessellation. To enable the trajectory calculation, the order of reconstruction is inverted with respect to previous reconstruction schemes: the last atom detected is reconstructed first. In this way, the emitter shape, which controls the trajectory, can be defined throughout the duration of the reconstruction. A proof of concept is presented for 3D model tips, containing spherical precipitates or embedded layers of strongly contrasting evaporation thresholds. While the traditional method following Bas et al. generates serious distortions in these cases, a reconstruction with the proposed electrostatically informed approach improves the geometry of layers and particles significantly. PMID:27062338

  20. Estimation of the reconstruction parameters for Atom Probe Tomography

    CERN Document Server

    Gault, Baptiste; Stephenson, Leigh T; Moody, Michael P; Muddle, Barry C; Ringer, Simon P

    2015-01-01

    The application of wide field-of-view detection systems to atom probe experiments emphasizes the importance of careful parameter selection in the tomographic reconstruction of the analysed volume, as the sensitivity to errors rises steeply with increases in analysis dimensions. In this paper, a self-consistent method is presented for the systematic determination of the main reconstruction parameters. In the proposed approach, the compression factor and the field factor are determined using geometrical projections from the desorption images. A 3D Fourier transform is then applied to a series of reconstructions and, comparing to the known material crystallography, the efficiency of the detector is estimated. The final results demonstrate a significant improvement in the accuracy of the reconstructed volumes.

  1. 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. PMID:19775815

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

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, K., E-mail: koji.inoue@hs3.ecs.kyoto-u.ac.jp [The Oarai Center, Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Yano, F.; Nishida, A. [MIRAI-Selete, Tsukuba, Ibaraki 305-8569 (Japan); Takamizawa, H. [The Oarai Center, Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Tsunomura, T. [MIRAI-Selete, Tsukuba, Ibaraki 305-8569 (Japan); Nagai, Y. [The Oarai Center, Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Hasegawa, M. [Institute for Materials Research, Tohoku University, Sendai, Miyagi 980-8577 (Japan); Cyclotron and Radioisotope Center, Tohoku University, Sendai 980-8578 (Japan)

    2009-11-15

    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.

  3. Nitride semiconductors studied by atom probe tomography and correlative techniques

    OpenAIRE

    Bennett, Samantha

    2011-01-01

    Optoelectronic devices fabricated from nitride semiconductors include blue and green light emitting diodes (LEDs) and laser diodes (LDs). To design efficient devices, the structure and composition of the constituent materials must be well-characterised. Traditional microscopy techniques used to examine nitride semiconductors include transmission electron microscopy (TEM), and atomic force microscopy (AFM). This thesis describes the study of nitride semiconductor materials using these tradi...

  4. Atom-probe tomography of tribological boundary films resulting from boron-based oil additives

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yoon-Jun; Baik, Sung-Il; Bertolucci-Coelho, Leonardo; Mazzaferro, Lucca; Ramirez, Giovanni; Erdemir, Ali; Seidman, D K

    2016-01-15

    Correlative characterization using atom-probe tomography (APT) and transmission electron microscopy (TEM) was performed on a tribofilm formed during sliding frictional testing with a fully formulated engine oil, which also contains a boron-based additive. The tribofilm formed is ~15 nm thick and consists of oxides of iron and compounds of B, Ca, P, and S, which are present in the additive. This study provides strong evidence for boron being embedded in the tribofilm, which effectively reduces friction and wear losses.

  5. Comparison of atom probe tomography and transmission electron microscopy analysis of oxide dispersion strengthened steels

    Science.gov (United States)

    London, A. J.; Lozano-Perez, S.; Santra, S.; Amirthapandian, S.; Panigrahi, B. K.; Sundar, C. S.; Grovenor, C. R. M.

    2014-06-01

    Oxide dispersion strengthened steels owe part of their high temperature stability to the nano-scale oxides they contain. These yttrium-titanium oxides are notoriously difficult to characterise since they are embedded in a magnetic-ferritic matrix and often atom probe tomography on the same material to explore the kind of information that can be gained on the character of the oxide particles. The influence of chromium in these alloys is of interest, therefore two model ODS steels Fe-(14Cr)-0.2Ti-0.3Y2O3 are compared. TEM is shown to accurately measure the size of the oxide particles and atom probe tomography is necessary to observe the smallest sub-1.5 nm particles. Larger Y2Ti2O7 and Y2TiO5 structured particles were identified by high-resolution transmission electron microscopy, but the smallest oxides remain difficult to index. Chemical data from energy-filtered TEM agreed qualitatively with the atom probe findings. It was found that the majority of the oxide particles exhibit an unoxidised chromium shell which may be responsible for reducing the ultimate size of the oxide particles.

  6. 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.

  7. Atom-scale compositional distribution in InAlAsSb-based triple junction solar cells by atom probe tomography.

    Science.gov (United States)

    Hernández-Saz, J; Herrera, M; Delgado, F J; Duguay, S; Philippe, T; Gonzalez, M; Abell, J; Walters, R J; Molina, S I

    2016-07-29

    The analysis by atom probe tomography (APT) of InAlAsSb layers with applications in triple junction solar cells (TJSCs) has shown the existence of In- and Sb-rich regions in the material. The composition variation found is not evident from the direct observation of the 3D atomic distribution and because of this a statistical analysis has been required. From previous analysis of these samples, it is shown that the small compositional fluctuations determined have a strong effect on the optical properties of the material and ultimately on the performance of TJSCs. PMID:27306098

  8. Atom-scale compositional distribution in InAlAsSb-based triple junction solar cells by atom probe tomography

    Science.gov (United States)

    Hernández-Saz, J.; Herrera, M.; Delgado, F. J.; Duguay, S.; Philippe, T.; Gonzalez, M.; Abell, J.; Walters, R. J.; Molina, S. I.

    2016-07-01

    The analysis by atom probe tomography (APT) of InAlAsSb layers with applications in triple junction solar cells (TJSCs) has shown the existence of In- and Sb-rich regions in the material. The composition variation found is not evident from the direct observation of the 3D atomic distribution and because of this a statistical analysis has been required. From previous analysis of these samples, it is shown that the small compositional fluctuations determined have a strong effect on the optical properties of the material and ultimately on the performance of TJSCs.

  9. 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.)

  10. 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.

  11. Laser-assisted atom probe tomography investigation of magnetic FePt nanoclusters: First experiments

    Energy Technology Data Exchange (ETDEWEB)

    Folcke, E.; Larde, R. [Groupe de Physique des Materiaux, UMR CNRS 6634, Universite de Rouen, 76801 Saint Etienne du Rouvray (France); Le Breton, J.M., E-mail: jean-marie.lebreton@univ-rouen.fr [Groupe de Physique des Materiaux, UMR CNRS 6634, Universite de Rouen, 76801 Saint Etienne du Rouvray (France); Gruber, M.; Vurpillot, F. [Groupe de Physique des Materiaux, UMR CNRS 6634, Universite de Rouen, 76801 Saint Etienne du Rouvray (France); Shield, J.E.; Rui, X. [Department of Mechanical and Materials Engineering, Nebraska Center for Materials and Nanoscience, University of Nebraska, N104 WSEC, Lincoln, NE 68588 (United States); Patterson, M.M. [Department of Physics, University of Wisconsin-Stout, Menomonie, WI 54751 (United States)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer FePt nanoclusters dispersed in a Cr matrix were studied by atom probe tomography. Black-Right-Pointing-Pointer Simulated experiments were conducted to study the artefacts of the analysis. Black-Right-Pointing-Pointer In FePt nanoclusters, Fe and Pt are present in equiatomic proportions. Black-Right-Pointing-Pointer FePt nanoclusters are homogeneous, no core-shell structure is observed. - Abstract: FePt nanoclusters dispersed in a Cr matrix have been investigated by laser-assisted atom probe tomography. The results were analysed according to simulated evaporation experiments. Three-dimensional (3D) reconstructions reveal the presence of nanoclusters roughly spherical in shape, with a size in good agreement with previous transmission electron microscopy observations. Some clusters appear to be broken up after the evaporation process due to the fact that the Cr matrix has a lower evaporation field than Fe and Pt. It is thus shown that the observed FePt nanoclusters are chemically homogeneous. They contain Fe and Pt in equiatomic proportions, with no core-shell structure observed.

  12. Atom probe tomography of stress corrosion crack tips in SUS316 stainless steels

    International Nuclear Information System (INIS)

    Highlights: • Quantitative study of 3D features such as grain boundary oxides and Ni enrichment. • Features can be related to their distance from the crack tip. • Local measurement of compositions in very small volumes and specific regions. • Complementary analytical TEM data was recorded to correlate to APT results. • Both matrix elements (Fe, Cr, Ni) and oxygen diffuse along the grain boundary. - Abstract: Novel atom probe tomography (APT) data of an intergranular stress corrosion crack tip has been acquired. Using APT for stress corrosion cracking research, very small, localized features and their distribution around the crack tip can be studied in 3D. This work details the development of a technique for the preparation of atom probe needles. Initial characterization via analytical transmission electron microscopy provides with a complementary analysis and accurately locates features that can be correlated with the reconstructed APT data. Ni enrichment and intergranular oxidation ahead of the crack tip have been studied with APT in 3D and with near-atomic resolution

  13. On low temperature bainite transformation characteristics using in-situ neutron diffraction and atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Rakha, Khushboo, E-mail: krakha@deakin.edu.au [Institute for Frontier Materials, Deakin University, Geelong, VIC 3216 (Australia); Beladi, Hossein; Timokhina, Ilana [Institute for Frontier Materials, Deakin University, Geelong, VIC 3216 (Australia); Xiong, Xiangyuan [Department of Materials Engineering, Monash University, Victoria 3800 (Australia); Kabra, Saurabh; Liss, Klaus-Dieter [Australian Nuclear Science and Technology Organisation, The Bragg Institute, New Illawarra Road, Lucas Heights, NSW 2234 (Australia); Hodgson, Peter [Institute for Frontier Materials, Deakin University, Geelong, VIC 3216 (Australia)

    2014-01-01

    In-situ neutron diffraction was employed to monitor the evolution of nano-bainitic ferrite during low temperature isothermal heat treatment of austenite. The first 10 peaks (austenite, γ and ferrite, α) were monitored during austenization, homogenisation, rapid cooling and isothermal holding at 573 K. Changes in the α-110 and γ-111 peaks were analysed to determine the volume fraction changes and hence the kinetics of the phase transformation. Asymmetry and broadening in the α-200 and γ-200 peaks were quantified to lattice parameter changes due to carbon redistribution as well as the effects of size and dislocation density. Atom Probe Tomography was then used to confirm that, despite the presence of 1.5 mass% Si, carbide formation was evident. This carbide formation is the cause of poor ductility, which is lower than expected in such steels.

  14. 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.

  15. 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.

  16. Quantitative dopant distributions in GaAs nanowires using atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Du, Sichao [School of Physics, The University of Sydney, NSW 2006 (Australia); Burgess, Timothy [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Gault, Baptiste [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Department of Materials Science and Engineering, McMaster University, 1280 Main St W, Hamilton, Ontario L8S4L8 (Canada); Gao, Qiang [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Bao, Peite; Li, Li [School of Physics, The University of Sydney, NSW 2006 (Australia); Cui, Xiangyuan; Kong Yeoh, Wai; Liu, Hongwei; Yao, Lan [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Ceguerra, Anna V. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Hoe Tan, Hark; Jagadish, Chennupati [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Ringer, Simon P. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Zheng, Rongkun, E-mail: rongkun.zheng@sydney.edu.au [School of Physics, The University of Sydney, NSW 2006 (Australia)

    2013-09-15

    Controllable doping of semiconductor nanowires is critical to realize their proposed applications, however precise and reliable characterization of dopant distributions remains challenging. In this article, we demonstrate an atomic-resolution three-dimensional elemental mapping of pristine semiconductor nanowires on growth substrates by using atom probe tomography to tackle this major challenge. This highly transferrable method is able to analyze the full diameter of a nanowire, with a depth resolution better than 0.17 nm thanks to an advanced reconstruction method exploiting the specimen's crystallography, and an enhanced chemical sensitivity of better than 8-fold increase in the signal-to-noise ratio. - Highlights: ► Probing pristine semiconductor NWs from growth substrate has been demonstrated. ► Analyzing the full diameter of a nanowire has been achieved. ► A spatial resolution better than 0.17 nm in depth has been obtained for GaAs. ► An enhanced SNR 100:2 has been achieved.

  17. Quantitative dopant distributions in GaAs nanowires using atom probe tomography

    International Nuclear Information System (INIS)

    Controllable doping of semiconductor nanowires is critical to realize their proposed applications, however precise and reliable characterization of dopant distributions remains challenging. In this article, we demonstrate an atomic-resolution three-dimensional elemental mapping of pristine semiconductor nanowires on growth substrates by using atom probe tomography to tackle this major challenge. This highly transferrable method is able to analyze the full diameter of a nanowire, with a depth resolution better than 0.17 nm thanks to an advanced reconstruction method exploiting the specimen's crystallography, and an enhanced chemical sensitivity of better than 8-fold increase in the signal-to-noise ratio. - Highlights: ► Probing pristine semiconductor NWs from growth substrate has been demonstrated. ► Analyzing the full diameter of a nanowire has been achieved. ► A spatial resolution better than 0.17 nm in depth has been obtained for GaAs. ► An enhanced SNR 100:2 has been achieved

  18. Complementary use of transmission electron microscopy and atom probe tomography for the investigation of steels nanostructured by severe plastic deformation

    International Nuclear Information System (INIS)

    The properties of bulk nanostructured materials are often controlled by atomic-scale features such as segregation along defects or composition gradients. Here we discuss the complementary use of transmission electron microscopy and atom probe tomography to obtain a full description of nanostructures. The advantages and limitations of both techniques are highlighted on the basis of experimental data collected in severely deformed steels with a special emphasis on carbon spatial distribution.

  19. Deformation-induced trace element redistribution in zircon revealed using atom probe tomography

    Science.gov (United States)

    Piazolo, Sandra; La Fontaine, Alexandre; Trimby, Patrick; Harley, Simon; Yang, Limei; Armstrong, Richard; Cairney, Julie M.

    2016-02-01

    Trace elements diffuse negligible distances through the pristine crystal lattice in minerals: this is a fundamental assumption when using them to decipher geological processes. For example, the reliable use of the mineral zircon (ZrSiO4) as a U-Th-Pb geochronometer and trace element monitor requires minimal radiogenic isotope and trace element mobility. Here, using atom probe tomography, we document the effects of crystal-plastic deformation on atomic-scale elemental distributions in zircon revealing sub-micrometre-scale mechanisms of trace element mobility. Dislocations that move through the lattice accumulate U and other trace elements. Pipe diffusion along dislocation arrays connected to a chemical or structural sink results in continuous removal of selected elements (for example, Pb), even after deformation has ceased. However, in disconnected dislocations, trace elements remain locked. Our findings have important implications for the use of zircon as a geochronometer, and highlight the importance of deformation on trace element redistribution in minerals and engineering materials.

  20. Growth rate model and doping metrology by atom probe tomography in silicon nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Chen, W.H.; Larde, R.; Cadel, E.; Pareige, P. [Groupe de Physique des Materiaux, Universite et INSA de Rouen, UMR CNRS 6634, Av. de l' Universite, BP 12, 76801 Saint Etienne du Rouvray (France); Xu, T.; Grandidier, B.; Nys, J.P.; Stievenard, D. [Institut d' Electronique, de Microelectronique et de Nanotechnologie, UMR CNRS 8520, Departement ISEN, 41 bd Vauban, 59046 Lille Cedex (France)

    2011-03-15

    Silicon nanowires (SiNWs) with different surface number density are fabricated using Chemical Vapor Deposition (CVD) method by controlling the catalyst droplet number density with in-situ evaporation. For comparison, another type of SiNWs is fabricated by Molecular Beam Epitaxy (MBE) method. To study these two types of SiNWs a general growth rate model is presented. The fit curves from this model are consistent with our experimental data. In both growing conditions the SiNW growth rate as a function of their diameter are compared and discussed. The p-type SiNWs have also been prepared by adding diborane into precursor. The doping metrology in an individual SiNW is realized by laser assisted Atom Probe Tomography (APT). We have shown that the doping atoms (e.g. B) can incorporate into SiNW and an accurate quantification can be given (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Deformation-induced trace element redistribution in zircon revealed using atom probe tomography.

    Science.gov (United States)

    Piazolo, Sandra; La Fontaine, Alexandre; Trimby, Patrick; Harley, Simon; Yang, Limei; Armstrong, Richard; Cairney, Julie M

    2016-01-01

    Trace elements diffuse negligible distances through the pristine crystal lattice in minerals: this is a fundamental assumption when using them to decipher geological processes. For example, the reliable use of the mineral zircon (ZrSiO4) as a U-Th-Pb geochronometer and trace element monitor requires minimal radiogenic isotope and trace element mobility. Here, using atom probe tomography, we document the effects of crystal-plastic deformation on atomic-scale elemental distributions in zircon revealing sub-micrometre-scale mechanisms of trace element mobility. Dislocations that move through the lattice accumulate U and other trace elements. Pipe diffusion along dislocation arrays connected to a chemical or structural sink results in continuous removal of selected elements (for example, Pb), even after deformation has ceased. However, in disconnected dislocations, trace elements remain locked. Our findings have important implications for the use of zircon as a geochronometer, and highlight the importance of deformation on trace element redistribution in minerals and engineering materials. PMID:26868040

  2. Determination of solute site occupancies within γ' precipitates in nickel-base superalloys via orientation-specific atom probe tomography.

    Science.gov (United States)

    Meher, S; Rojhirunsakool, T; Nandwana, P; Tiley, J; Banerjee, R

    2015-12-01

    The analytical limitations in atom probe tomography such as resolving a desired set of atomic planes, for solving complex materials science problems, have been overcome by employing a well-developed unique and reproducible crystallographic technique, involving synergetic coupling of orientation microscopy with atom probe tomography. The crystallographic information in atom probe reconstructions has been utilized to determine the solute site occupancies in Ni-Al-Cr based superalloys accurately. The structural information in atom probe reveals that both Al and Cr occupy the same sub-lattice within the L12-ordered γ' precipitates to form Ni3(Al,Cr) precipitates in a Ni-14Al-7Cr (at%) alloy. Interestingly, the addition of Co, which is a solid solution strengthener, to a Ni-14Al-7Cr alloy results in the partial reversal of Al site occupancy within γ' precipitates to form (Ni,Al)3(Al,Cr,Co) precipitates. This unique evidence of reversal of Al site occupancy, resulting from the introduction of other solutes within the ordered structures, gives insights into the relative energetics of different sub-lattice sites when occupied by different solutes. PMID:25952611

  3. Atom Probe Tomography Examination of Carbon Redistribution in Quenched and Tempered 4340 Steel

    Energy Technology Data Exchange (ETDEWEB)

    Clarke, Amy J. [Los Alamos National Laboratory; Miller, Michael K. [ORNL; Alexander, David J. [Los Alamos National Laboratory; Field, Robert D. [Los Alamos National Laboratory; Clarke, Kester D. [Los Alamos National Laboratory

    2012-08-07

    Quenching and tempering produces a wide range of mechanical properties in medium carbon, low alloyed steels - Study fragmentation behavior as a function of heat-treatment. Subtle microstructural changes accompany the mechanical property changes that result from quenching and tempering - Characterize the location and distribution of carbon and alloying elements in the microstructure using atom probe tomography (APT). Perform complementary transmission electron microscopy (TEM). Tempering influences the mechanical properties and fragmentation of quenched 4340 (hemi-shaped samples). APT revealed carbon-enriched features that contain a maximum of {approx}12-14 at.% carbon after quenching to RT (the level of carbon is perhaps associated with the extent of autotempering). TEM confirmed the presence of twinned martensite and indicates {var_epsilon} ({eta}) transition carbides after oil quenching to RT. Tempering at 325 C resulted in carbon-enriched plates (> 25 at.% C) with no significant element partitioning (transition carbides?). Tempering at 450 C and 575 C resulted in cementite ({approx} 25 at.% C) during late stage tempering; Cr, Mn, Mo partitioned to cementite and Si partitioned to ferrite. Tempering at 575 C resulted in P segregation at cementite interfaces and the formation of Cottrell atmospheres.

  4. Diffusivity and solubility of Cu in a reactor pressure vessel steel studied by atom probe tomography

    International Nuclear Information System (INIS)

    The diffusivity and solubility limit of Cu in A533B steel, which is used in reactor pressure vessels, were studied by atom probe tomography (APT). Cu-A533B steel diffusion couples were annealed at temperatures of 550, 600, and 700°C, and the resulting Cu concentration profiles were measured. At the temperature of 700°C, the diffusivity of Cu in A533B steel was about 3 times higher than that in pure Fe, whereas at the temperature of 550°C, the diffusivity of Cu in A533B steel is almost closer to that in pure Fe. The solubility limit of Cu in A533B steel was similar to pure Fe. APT was also used to study the effect of the grain boundary (GB) diffusion. The results indicated that no Cu segregation occurred at GB near the Cu/A533B steel interface, which may imply that GB diffusion of Cu was not effective in A533B steel. (author)

  5. Fusion boundary precipitation in thermally aged dissimilar metal welds studied by atom probe tomography and nanoindentation

    Science.gov (United States)

    Choi, Kyoung Joon; Kim, Taeho; Yoo, Seung Chang; Kim, Seunghyun; Lee, Jae Hyuk; Kim, Ji Hyun

    2016-04-01

    In this study, microstructural and mechanical characterizations were performed to investigate the effect of long-term thermal aging on the fusion boundary region between low-alloy steel and Nickel-based weld metal in dissimilar metal welds used in operating power plant systems. The effects of thermal aging treatment on the low-alloy steel side near the fusion boundary were an increase in the ratio of Cr constituents and Cr-rich precipitates and the formation and growth of Cr23C6. Cr concentrations were calculated using atom probe tomography. The accuracy of simulations of thermal aging effects of heat treatment was verified, and the activation energy for Cr diffusion in the fusion boundary region was calculated. The mechanical properties of fusion boundary region changed based on the distribution of Cr-rich precipitates, where the material initially hardened with the formation of Cr-rich precipitates and then softened because of the reduction of residual strain or coarsening of Cr-rich precipitates.

  6. Uranium Isotopic Ratio Measurements of U3O8 Reference Materials by Atom Probe Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Fahey, Albert J.; Perea, Daniel E.; Bartrand, Jonah AG; Arey, Bruce W.; Thevuthasan, Suntharampillai

    2016-01-01

    We report results of measurements of isotopic ratios obtained with atom probe tomography on U3O8 reference materials certified for their isotopic abundances of uranium. The results show good agreement with the certified values. High backgrounds due to tails from adjacent peaks complicate the measurement of the integrated peak areas as well as the fact that only oxides of uranium appear in the spectrum, the most intense of which is doubly charged. In addition, lack of knowledge of other instrumental parameters, such as the dead time, may bias the results. Isotopic ratio measurements can be performed at the nanometer-scale with the expectation of sensible results. The abundance sensitivity and mass resolving power of the mass spectrometer are not sufficient to compete with magnetic-sector instruments but are not far from measurements made by ToF-SIMS of other isotopic systems. The agreement of the major isotope ratios is more than sufficient to distinguish most anthropogenic compositions from natural.

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

    International Nuclear Information System (INIS)

    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. -- Research Highlights: →Field evaporation properties of bulk MgO are compared with thin film. →MgO sandwiched between Fe layers. →Evaporation process in two steps in two different time scales. →The change in the thickness of the MgO layer(from 4 to 32nm) does not change the evaporation behavior.

  8. Atom probe tomography analysis of high dose MA957 at selected irradiation temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Bailey, Nathan A. [University of California at Berkeley, 3117 Etcheverry Hall, Berkeley, CA 94720 (United States); Stergar, Erich [University of California at Berkeley, 3117 Etcheverry Hall, Berkeley, CA 94720 (United States); SCK-CEN, BE-2400, Mol (Belgium); Toloczko, Mychailo [Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (United States); Hosemann, Peter [University of California at Berkeley, 3117 Etcheverry Hall, Berkeley, CA 94720 (United States)

    2015-04-15

    Oxide dispersion strengthened (ODS) alloys are meritable structural materials for nuclear reactor systems due to the exemplary resistance to radiation damage and high temperature creep. Summarized in this work are atom probe tomography (APT) investigations on a heat of MA957 that underwent irradiation in the form of in-reactor creep specimens in the Fast Flux Test Facility–Materials Open Test Assembly (FFTF–MOTA) for the Liquid Metal Fast Breeder Reactor (LMFBR) program. The oxide precipitates appear stable under irradiation at elevated temperature over extended periods of time. Nominally, the precipitate chemistry is unchanged by the accumulated dose; although, evidence suggests that ballistic dissolution and reformation processes are occurring at all irradiation temperatures. At 412 °C–109 dpa, chromium enrichments – consistent with the α′ phase – appear between the oxide precipitates, indicating radiation induced segregation. Grain boundaries, enriched with several elements including nickel and titanium, are observed at all irradiation conditions. At 412 °C–109 dpa, the grain boundaries are also enriched in molecular titanium oxide (TiO)

  9. Atom probe tomography characterizations of high nickel, low copper surveillance RPV welds irradiated to high fluences

    International Nuclear Information System (INIS)

    The Ringhals Units 3 and 4 reactors in Sweden are pressurized water reactors (PWRs). The reactor pressure vessels (RPVs) for both reactors were fabricated with ring forgings of SA 508 class 2 steel. Surveillance blocks for both units were fabricated using the same weld wire heat, welding procedures, and base metals used for the RPVs. The primary interest in these weld metals is because they have very high nickel contents, with 1.58 and 1.66 wt.% for Unit 3 and Unit 4, respectively. The nickel content in Unit 4 is the highest reported nickel content for any Westinghouse PWR. Although both welds contain less than 0.10 wt.% copper, the weld metals have exhibited high irradiation-induced Charpy 41-J transition temperature shifts in surveillance testing. The Charpy impack 41-J shifts and the corresponding fluences are 192 deg C at 5.0 x 1023 n/m2 (>1 MeV) for Unit 3 and 162 deg C at 6.0 x 1023 n/m2 (1 MeV) for unit 4. These relatively low-copper, high-nickel, radiation-sensitive welds relate to the issue of so-called late-blooming nickel-manganese-silicon phases. Atom probe tomography measurements have revealed ∼2 nm-diameter irradiation-induced precipitates containing manganese, nickel, and silicon, with phosphorus evident in some of the precipitates. However, only a relatively few number of copper atoms are contained within the precipitates. The larger increase in the transition temperature shift in the higher copper weld metal from the Ringhals R3 Unit is associated with copper-enriched regions within the manganese-nickel-silicon-enriched precipitates rather than changes in their size or number density.

  10. Atom probe tomography characterizations of high nickel, low copper surveillance RPV welds irradiated to high fluences

    International Nuclear Information System (INIS)

    The Ringhals Units 3 and 4 reactors in Sweden are pressurized water reactors (PWRs) designed and supplied by Westinghouse Electric Company, with commercial operation in 1981 and 1983, respectively. The reactor pressure vessels (RPVs) for both reactors were fabricated with ring forgings of SA 508 class 2 steel. Surveillance blocks for both units were fabricated using the same weld wire heat, welding procedures, and base metals used for the RPVs. The primary interest in these weld metals is because they have very high nickel contents, with 1.58 and 1.66 wt.% for Unit 3 and Unit 4, respectively. The nickel content in Unit 4 is the highest reported nickel content for any Westinghouse PWR. Although both welds contain less than 0.10 wt.% copper, the weld metals have exhibited high irradiation-induced Charpy 41-J transition temperature shifts in surveillance testing. The Charpy impact 41-J shifts and corresponding fluences are 192 °C at 5.0 × 1023 n/m2 (>1 MeV) for Unit 3 and 162 °C at 6.0 × 1023 n/m2 (>1 MeV) for Unit 4. These relatively low-copper, high-nickel, radiation-sensitive welds relate to the issue of so-called late-blooming nickel–manganese–silicon phases. Atom probe tomography measurements have revealed ∼2 nm-diameter irradiation-induced precipitates containing manganese, nickel, and silicon, with phosphorus evident in some of the precipitates. However, only a relatively few number of copper atoms are contained within the precipitates. The larger increase in the transition temperature shift in the higher copper weld metal from the Ringhals R3 Unit is associated with copper-enriched regions within the manganese–nickel–silicon-enriched precipitates rather than changes in their size or number density

  11. Combining structural and chemical information at the nanometer scale by correlative transmission electron microscopy and atom probe tomography

    International Nuclear Information System (INIS)

    In many cases, the three-dimensional reconstructions from atom probe tomography (APT) are not sufficiently accurate to resolve crystallographic features such as lattice planes, shear bands, stacking faults, dislocations or grain boundaries. Hence, correlative crystallographic characterization is required in addition to APT at the exact same location of the specimen. Also, for the site-specific preparation of APT tips containing regions of interest (e.g. grain boundaries) correlative electron microscopy is often inevitable. Here we present a versatile experimental setup that enables performing correlative focused ion beam milling, transmission electron microscopy (TEM), and APT under optimized characterization conditions. The setup was designed for high throughput, robustness and practicability. We demonstrate that atom probe tips can be characterized by TEM in the same way as a standard TEM sample. In particular, the use of scanning nanobeam diffraction provides valuable complementary crystallographic information when being performed on atom probe tips. This technique enables the measurement of orientation and phase maps as known from electron backscattering diffraction with a spatial resolution down to one nanometer. - Highlights: • Atom probe tips can be characterized in TEM like any standard TEM sample. • In principal all TEM techniques can be performed on atom probe tips. • Scanning NBD enables the measurement of orientation maps on AP tips with a lateral spatial resolution of 2 nm or better. • Grain orientations can be measured by NBD even in the topmost 10 nm of an AP tip

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

    International Nuclear Information System (INIS)

    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. - Highlights: ► Lath boundaries in a maraging steel were analyzed by APT. ► Segregation of Mo, Si and P was measured. ► Precipitation of η-Ni3(Ti, Al) and Cu-rich 9R was observed. ► After 100 h of aging a quasicrystalline Mo-rich film was observed

  13. Quantitative chemical-structure evaluation using atom probe tomography: Short-range order analysis of Fe–Al

    Energy Technology Data Exchange (ETDEWEB)

    Marceau, R.K.W., E-mail: r.marceau@deakin.edu.au [Institute for Frontier Materials, Deakin University, Geelong, VIC 3216 (Australia); Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237 Düsseldorf (Germany); Ceguerra, A.V.; Breen, A.J. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Raabe, D. [Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237 Düsseldorf (Germany); Ringer, S.P. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia)

    2015-10-15

    Short-range-order (SRO) has been quantitatively evaluated in an Fe–18Al (at%) alloy using atom probe tomography (APT) data and by calculation of the generalised multicomponent short-range order (GM-SRO) parameters, which have been determined by shell-based analysis of the three-dimensional atomic positions. The accuracy of this method with respect to limited detector efficiency and spatial resolution is tested against simulated D0{sub 3} ordered data. Whilst there is minimal adverse effect from limited atom probe instrument detector efficiency, the combination of this with imperfect spatial resolution has the effect of making the data appear more randomised. The value of lattice rectification of the experimental APT data prior to GM-SRO analysis is demonstrated through improved information sensitivity. - Highlights: • Short-range-order (SRO) is quantitatively evaluated using atom probe tomography data. • Chemical species-specific SRO parameters have been calculated. • The accuracy of this method is tested against simulated D0{sub 3} ordered data. • Imperfect spatial resolution combined with finite detector efficiency causes a randomising effect. • Lattice rectification of the data prior to GM-SRO analysis is demonstrated to improve information sensitivity.

  14. Quantitative chemical-structure evaluation using atom probe tomography: Short-range order analysis of Fe–Al

    International Nuclear Information System (INIS)

    Short-range-order (SRO) has been quantitatively evaluated in an Fe–18Al (at%) alloy using atom probe tomography (APT) data and by calculation of the generalised multicomponent short-range order (GM-SRO) parameters, which have been determined by shell-based analysis of the three-dimensional atomic positions. The accuracy of this method with respect to limited detector efficiency and spatial resolution is tested against simulated D03 ordered data. Whilst there is minimal adverse effect from limited atom probe instrument detector efficiency, the combination of this with imperfect spatial resolution has the effect of making the data appear more randomised. The value of lattice rectification of the experimental APT data prior to GM-SRO analysis is demonstrated through improved information sensitivity. - Highlights: • Short-range-order (SRO) is quantitatively evaluated using atom probe tomography data. • Chemical species-specific SRO parameters have been calculated. • The accuracy of this method is tested against simulated D03 ordered data. • Imperfect spatial resolution combined with finite detector efficiency causes a randomising effect. • Lattice rectification of the data prior to GM-SRO analysis is demonstrated to improve information sensitivity

  15. 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.

  16. Structural evolution and strain induced mixing in Cu–Co composites studied by transmission electron microscopy and atom probe tomography

    International Nuclear Information System (INIS)

    A Cu–Co composite material is chosen as a model system to study structural evolution and phase formations during severe plastic deformation. The evolving microstructures as a function of the applied strain were characterized at the micro-, nano-, and atomic scale-levels by combining scanning electron microscopy and transmission electron microscopy including energy-filtered transmission electron microscopy and electron energy-loss spectroscopy. The amount of intermixing between the two phases at different strains was examined at the atomic scale using atom probe tomography as complimentary method. It is shown that Co particles are dissolved in the Cu matrix during severe plastic deformation to a remarkable extent and their size, number, and volume fraction were quantitatively determined during the deformation process. From the results, it can be concluded that supersaturated solid solutions up to 26 at.% Co in a fcc Cu–26 at.% Co alloy are obtained during deformation. However, the distribution of Co was found to be inhomogeneous even at the highest degree of investigated strain. - Highlights: • Structural evolution in a deformed Cu–Co composite is studied on all length scales. • Amount of intermixing is examined by atom-probe tomography. • Supersaturated solid solutions up to 26 at.% Co in Cu are observed

  17. Investigation of material property influenced stoichiometric deviations as evidenced during UV laser-assisted atom probe tomography in fluorite oxides

    Energy Technology Data Exchange (ETDEWEB)

    Valderrama, Billy; Henderson, Hunter B. [Department of Materials Science and Engineering, University of Florida, 100 Rhines Hall, Gainesville, FL 32611 (United States); Yablinsky, Clarissa A. [Department of Nuclear Engineering, University of Wisconsin-Madison, 921 ERB, 1500 Engineering Drive, Madison, WI 53706 (United States); Gan, Jian [Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415 (United States); Allen, Todd R. [Department of Nuclear Engineering, University of Wisconsin-Madison, 921 ERB, 1500 Engineering Drive, Madison, WI 53706 (United States); Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415 (United States); Manuel, Michele V., E-mail: mmanuel@mse.ufl.edu [Department of Materials Science and Engineering, University of Florida, 100 Rhines Hall, Gainesville, FL 32611 (United States)

    2015-09-15

    Oxide materials are used in numerous applications such as thermal barrier coatings, nuclear fuels, and electrical conductors and sensors, all applications where nanometer-scale stoichiometric changes can affect functional properties. Atom probe tomography can be used to characterize the precise chemical distribution of individual species and spatially quantify the oxygen to metal ratio at the nanometer scale. However, atom probe analysis of oxides can be accompanied by measurement artifacts caused by laser-material interactions. In this investigation, two technologically relevant oxide materials with the same crystal structure and an anion to cation ratio of 2.00, pure cerium oxide (CeO{sub 2}) and uranium oxide (UO{sub 2}) are studied. It was determined that electronic structure, optical properties, heat transfer properties, and oxide stability strongly affect their evaporation behavior, thus altering their measured stoichiometry, with thermal conductance and thermodynamic stability being strong factors.

  18. Investigation of material property influenced stoichiometric deviations as evidenced during UV laser-assisted atom probe tomography in fluorite oxides

    International Nuclear Information System (INIS)

    Oxide materials are used in numerous applications such as thermal barrier coatings, nuclear fuels, and electrical conductors and sensors, all applications where nanometer-scale stoichiometric changes can affect functional properties. Atom probe tomography can be used to characterize the precise chemical distribution of individual species and spatially quantify the oxygen to metal ratio at the nanometer scale. However, atom probe analysis of oxides can be accompanied by measurement artifacts caused by laser-material interactions. In this investigation, two technologically relevant oxide materials with the same crystal structure and an anion to cation ratio of 2.00, pure cerium oxide (CeO2) and uranium oxide (UO2) are studied. It was determined that electronic structure, optical properties, heat transfer properties, and oxide stability strongly affect their evaporation behavior, thus altering their measured stoichiometry, with thermal conductance and thermodynamic stability being strong factors

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

    Science.gov (United States)

    Al-Kassab, T; Kompatscher, M; Kirchheim, R; Kostorz, G; Schönfeld, B

    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-11.3 at.% 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. PMID:24981213

  20. 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.

  1. Chemical gradients across phase boundaries between martensite and austenite in steel studied by atom probe tomography and simulation

    OpenAIRE

    Dmitrieva, O; Ponge, D.; Inden, G.; Millán, J.; Choi, P.; Sietsma, J.; Raabe, D.

    2014-01-01

    Partitioning at phase boundaries of complex steels is important for their properties. We present atom probe tomography results across martensite / austenite interfaces in a precipitation-hardened maraging TRIP steel (12.2 Mn, 1.9 Ni, 0.6 Mo, 1.2 Ti, 0.3 Al; at.%). The system reveals compositional changes at the phase boundaries: Mn and Ni are enriched while Ti, Al, Mo, and Fe are depleted. More specific, we observe up to 27 at.% Mn in a 20 nm layer at the phase boundary. This is explained by ...

  2. Precipitate characterisation of an advanced high-strength low-alloy (HSLA) steel using atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Timokhina, I.B. [Department of Materials Engineering, Monash University, Vic 3800 (Australia)], E-mail: Ilana.Timokhina@eng.monash.edu.au; Hodgson, P.D. [Centre for Material and Fibre Innovation, Deakin University, Geelong, Vic 3217 (Australia); Ringer, S.P. [Australia Key Centre for Microscopy and Microanalysis, University of Sydney, NSW (Australia); Zheng, R.K. [Australia Key Centre for Microscopy and Microanalysis, University of Sydney, NSW (Australia); Pereloma, E.V. [Department of Materials Engineering, Monash University, Vic 3800 (Australia)

    2007-04-15

    The microstructure of an advanced high-strength low-alloy steel containing nanoscale Ti{sub 0.98}Mo{sub 0.02}C{sub 0.6} carbides formed along {gamma}/{alpha} interface was characterised using atom probe tomography. The average radius of particles was 2 {+-} 0.5 nm. In addition, the formation of C{sub 19}Cr{sub 7}Mo{sub 24} particles with average radius of 1.5 {+-} 0.3 nm was also observed.

  3. THE ORNL ATOM PROBE

    OpenAIRE

    Miller, M

    1986-01-01

    The ORNL Atom Probe is a microanalytical tool for studies in materials science. The instrument is a combination of a customized version of the vacuum system of the VG FIM-100 atom probe, an ORNL-designed microcomputer-controlled digital timing system, and a double curved CEMA Imaging Atom Probe detector. The atom probe combines four instruments into one - namely a field ion microscope, an energy compensated time-of-flight mass spectrometer, an imaging atom probe, and a pulsed laser atom probe.

  4. Identification of Radiation-Induced Segregation in Ion-irradiated Stainless Steel 316 using Atom Probe Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Gyeong-Geun; Jin, Hyung-Ha; Chang, Kunok; Kwon, Junhyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-10-15

    Various kinds of defects are produced by the irradiation of energetic particles onto a structural material. The defect fluxes such as mobile vacancies and self-interstitial atoms cause the diffusion of the solute atoms in the matrix. The preferential interaction of the solute with defects induces the enrichment or depletion of the solutes at the defect sinks such as the grain boundaries, and surfaces. These phenomena are generally known as radiation-induced segregation (RIS). Transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) are generally used as basic analysis techniques to obtain a concentration profile of RIS arising from irradiation. However, the resolution of EDS is limited due to beam broadening, and the overlapping of the probed volume with the matrix prohibits a quantitative analysis of the concentration changes. In the current work, we introduced atom probe tomography (APT) to analyze RIS in SS 316. Various types of radiation-induced defects were identified and the compositional characteristics were quantitatively provided from a wide view point. The measured concentrations were compared with values in the literature. This work can provide a fundamental understanding of the RIS behavior in ion-irradiated SS 316. In this study, an APT analysis of RIS in ion-irradiated SS316 was performed. Various types of irradiation defects were observed. Si atoms are located at the core structures of dislocation loops and clusters.

  5. Grain boundary segregation in a bronze-route Nb3Sn superconducting wire studied by atom probe tomography

    International Nuclear Information System (INIS)

    Atom probe tomography was used to characterize the A15 phase in a bronze-route Nb3Sn superconducting wire with a bronze matrix composition of Cu–8Sn–0.3Ti (in at.%). We observed depletion of niobium and segregation of Cu and Ti atoms at Nb3Sn grain boundaries. While the Nb depletion is about 15% relative to the grain interior, the average ratio between Cu and Ti excess values is 9 to 2. Segregation extends to a distance d ∼ 9 Å from the point of maximum Cu and Ti concentrations. Such local variation in the stoichiometry at the grain boundary region can be an additional source of flux-pinning in the Nb3Sn phase. Other microstructural parameters, such as the grain size and chemical composition of the Nb3Sn layer, were investigated by electron backscatter diffraction and transmission electron microscopy. (paper)

  6. Quantitative analysis of doped/undoped ZnO nanomaterials using laser assisted atom probe tomography: Influence of the analysis parameters

    International Nuclear Information System (INIS)

    In the last decade, atom probe tomography has become a powerful tool to investigate semiconductor and insulator nanomaterials in microelectronics, spintronics, and optoelectronics. In this paper, we report an investigation of zinc oxide nanostructures using atom probe tomography. We observed that the chemical composition of zinc oxide is strongly dependent on the analysis parameters used for atom probe experiments. It was observed that at high laser pulse energies, the electric field at the specimen surface is strongly dependent on the crystallographic directions. This dependence leads to an inhomogeneous field evaporation of the surface atoms, resulting in unreliable measurements. We show that the laser pulse energy has to be well tuned to obtain reliable quantitative chemical composition measurements of undoped and doped ZnO nanomaterials

  7. Quantitative analysis of doped/undoped ZnO nanomaterials using laser assisted atom probe tomography: Influence of the analysis parameters

    Science.gov (United States)

    Amirifar, Nooshin; Lardé, Rodrigue; Talbot, Etienne; Pareige, Philippe; Rigutti, Lorenzo; Mancini, Lorenzo; Houard, Jonathan; Castro, Celia; Sallet, Vincent; Zehani, Emir; Hassani, Said; Sartel, Corine; Ziani, Ahmed; Portier, Xavier

    2015-12-01

    In the last decade, atom probe tomography has become a powerful tool to investigate semiconductor and insulator nanomaterials in microelectronics, spintronics, and optoelectronics. In this paper, we report an investigation of zinc oxide nanostructures using atom probe tomography. We observed that the chemical composition of zinc oxide is strongly dependent on the analysis parameters used for atom probe experiments. It was observed that at high laser pulse energies, the electric field at the specimen surface is strongly dependent on the crystallographic directions. This dependence leads to an inhomogeneous field evaporation of the surface atoms, resulting in unreliable measurements. We show that the laser pulse energy has to be well tuned to obtain reliable quantitative chemical composition measurements of undoped and doped ZnO nanomaterials.

  8. Quantitative analysis of doped/undoped ZnO nanomaterials using laser assisted atom probe tomography: Influence of the analysis parameters

    Energy Technology Data Exchange (ETDEWEB)

    Amirifar, Nooshin; Lardé, Rodrigue, E-mail: rodrigue.larde@univ-rouen.fr; Talbot, Etienne; Pareige, Philippe; Rigutti, Lorenzo; Mancini, Lorenzo; Houard, Jonathan; Castro, Celia [Groupe de Physique des Matériaux, UMR CNRS 6634, Université et INSA de Rouen, Avenue de l' Université, BP 12, 76801 Saint Etienne du Rouvray (France); Sallet, Vincent; Zehani, Emir; Hassani, Said; Sartel, Corine [Groupe d' étude de la Matière Condensée (GEMAC), CNRS Université de Versailles St Quentin, 45 Avenue des Etats-Unis, 78035 Versailles Cedex (France); Ziani, Ahmed; Portier, Xavier [Centre de Recherche sur les Ions, les Matériaux et la Photonique (CIMAP), UMR 6252 CEA-CNRS-ENSICAEN, Université de Caen, 14050 Caen (France)

    2015-12-07

    In the last decade, atom probe tomography has become a powerful tool to investigate semiconductor and insulator nanomaterials in microelectronics, spintronics, and optoelectronics. In this paper, we report an investigation of zinc oxide nanostructures using atom probe tomography. We observed that the chemical composition of zinc oxide is strongly dependent on the analysis parameters used for atom probe experiments. It was observed that at high laser pulse energies, the electric field at the specimen surface is strongly dependent on the crystallographic directions. This dependence leads to an inhomogeneous field evaporation of the surface atoms, resulting in unreliable measurements. We show that the laser pulse energy has to be well tuned to obtain reliable quantitative chemical composition measurements of undoped and doped ZnO nanomaterials.

  9. Chemical gradients across phase boundaries between martensite and austenite in steel studied by atom probe tomography and simulation

    Energy Technology Data Exchange (ETDEWEB)

    Dmitrieva, O.; Ponge, D.; Inden, G.; Millan, J.; Choi, P. [Max-Planck-Institut fuer Eisenforschung, Max-Planck-Str. 1, 40237 Duesseldorf (Germany); Sietsma, J. [Delft University of Technology, Faculty 3mE, Dept. MSE, 2628 CD Delft (Netherlands); Raabe, D., E-mail: d.raabe@mpie.de [Max-Planck-Institut fuer Eisenforschung, Max-Planck-Str. 1, 40237 Duesseldorf (Germany)

    2011-01-15

    Partitioning at phase boundaries of complex steels is important for their properties. We present atom probe tomography results across martensite/austenite interfaces in a precipitation-hardened maraging-TRIP steel (12.2 Mn, 1.9 Ni, 0.6 Mo, 1.2 Ti, 0.3 Al; at.%). The system reveals compositional changes at the phase boundaries: Mn and Ni are enriched while Ti, Al, Mo and Fe are depleted. More specific, we observe up to 27 at.% Mn in a 20 nm layer at the phase boundary. This is explained by the large difference in diffusivity between martensite and austenite. The high diffusivity in martensite leads to a Mn flux towards the retained austenite. The low diffusivity in the austenite does not allow accommodation of this flux. Consequently, the austenite grows with a Mn composition given by local equilibrium. The interpretation is based on DICTRA and mixed-mode diffusion calculations (using a finite interface mobility).

  10. Chemical gradients across phase boundaries between martensite and austenite in steel studied by atom probe tomography and simulation

    International Nuclear Information System (INIS)

    Partitioning at phase boundaries of complex steels is important for their properties. We present atom probe tomography results across martensite/austenite interfaces in a precipitation-hardened maraging-TRIP steel (12.2 Mn, 1.9 Ni, 0.6 Mo, 1.2 Ti, 0.3 Al; at.%). The system reveals compositional changes at the phase boundaries: Mn and Ni are enriched while Ti, Al, Mo and Fe are depleted. More specific, we observe up to 27 at.% Mn in a 20 nm layer at the phase boundary. This is explained by the large difference in diffusivity between martensite and austenite. The high diffusivity in martensite leads to a Mn flux towards the retained austenite. The low diffusivity in the austenite does not allow accommodation of this flux. Consequently, the austenite grows with a Mn composition given by local equilibrium. The interpretation is based on DICTRA and mixed-mode diffusion calculations (using a finite interface mobility).

  11. EELS and atom probe tomography study of the evolution of the metal/oxide interface during zirconium alloy oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Gabory, Benoit de [Department of Mechanical and Nuclear Engineering, Penn State University, University Park, PA 16802 (United States); Dong, Yan, E-mail: yand@umich.edu [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Motta, Arthur T. [Department of Mechanical and Nuclear Engineering, Penn State University, University Park, PA 16802 (United States); Marquis, Emmanuelle A. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States)

    2015-07-15

    In an effort to understand the mechanisms resulting in the variations of corrosion rate observed throughout corrosion including at the first kinetic transition when the oxide temporarily loses its protective character, the oxide/metal interfaces of autoclave corroded Zircaloy-4 and ZIRLO™ before and after the transition are characterized using electron energy loss spectroscopy and atom probe tomography. The results reveal a complex structure of different phases at different stages of corrosion. The oxide/metal interface exhibits an intermediate layer, with an oxygen content between 45 and 55 O at.% and a suboxide layer corresponding to an oxygen-saturated solid solution in the metal matrix side (∼30 O at.%). Local variations are observed in the width of these characteristic structural features, especially near the transition. Good agreement on the layers present as well as their order, composition, and width was seen with the two techniques.

  12. Analysis of modulus hardening in an artificial aged Al–Cu–Mg alloy by atom probe tomography

    International Nuclear Information System (INIS)

    The individual contribution of different Cu–Mg co-clusters by modulus hardening to age-hardening response of an Al–Cu–Mg alloy at 170 °C is evaluated based on Vickers hardness measurements and quantitative atom probe tomography analysis. The present results show that it is order hardening of large Cu-Mg co-clusters or GPB zones rather than modulus hardening significantly contributes to the second stage of hardening. Despite prolonged aging from 5 min to 8 h leads to a noticeable change in the number density and the volume fraction of different Cu-Mg co-clusters, interestingly, the total critical shear stress of Cu-Mg co-clusters by modulus hardening fluctuates slightly, indicating the modulus hardening effect almost keeps unchanged at the hardness plateau. Besides, the shear modulus of Cu-Mg co-clusters is found to remain constant as aging prolongs at 170 °C

  13. EELS and atom probe tomography study of the evolution of the metal/oxide interface during zirconium alloy oxidation

    International Nuclear Information System (INIS)

    In an effort to understand the mechanisms resulting in the variations of corrosion rate observed throughout corrosion including at the first kinetic transition when the oxide temporarily loses its protective character, the oxide/metal interfaces of autoclave corroded Zircaloy-4 and ZIRLO™ before and after the transition are characterized using electron energy loss spectroscopy and atom probe tomography. The results reveal a complex structure of different phases at different stages of corrosion. The oxide/metal interface exhibits an intermediate layer, with an oxygen content between 45 and 55 O at.% and a suboxide layer corresponding to an oxygen-saturated solid solution in the metal matrix side (∼30 O at.%). Local variations are observed in the width of these characteristic structural features, especially near the transition. Good agreement on the layers present as well as their order, composition, and width was seen with the two techniques

  14. Thermal stability of TiAlN/CrN multilayer coatings studied by atom probe tomography.

    Science.gov (United States)

    Choi, Pyuck-Pa; Povstugar, Ivan; Ahn, Jae-Pyeong; Kostka, Aleksander; Raabe, Dierk

    2011-05-01

    This study is about the microstructural evolution of TiAlN/CrN multilayers (with a Ti:Al ratio of 0.75:0.25 and average bilayer period of 9 nm) upon thermal treatment. Pulsed laser atom probe analyses were performed in conjunction with transmission electron microscopy and X-ray diffraction. The layers are found to be thermally stable up to 600 °C. At 700 °C TiAlN layers begin to decompose into Ti- and Al-rich nitride layers in the out-of-plane direction. Further increase in temperature to 1000 °C leads to a strong decomposition of the multilayer structure as well as grain coarsening. Layer dissolution and grain coarsening appear to begin at the surface. Domains of AlN and TiCrN larger than 100 nm are found, together with smaller nano-sized AlN precipitates within the TiCrN matrix. Fe and V impurities are detected in the multilayers as well, which diffuse from the steel substrate into the coating along columnar grain boundaries. PMID:21146308

  15. Quantitative analysis of hydrogen in SiO2/SiN/SiO2 stacks using atom probe tomography

    Directory of Open Access Journals (Sweden)

    Yorinobu Kunimune

    2016-04-01

    Full Text Available We have demonstrated that it is possible to reproducibly quantify hydrogen concentration in the SiN layer of a SiO2/SiN/SiO2 (ONO stack structure using ultraviolet laser-assisted atom probe tomography (APT. The concentration of hydrogen atoms detected using APT increased gradually during the analysis, which could be explained by the effect of hydrogen adsorption from residual gas in the vacuum chamber onto the specimen surface. The amount of adsorbed hydrogen in the SiN layer was estimated by analyzing another SiN layer with an extremely low hydrogen concentration (<0.2 at. %. Thus, by subtracting the concentration of adsorbed hydrogen, the actual hydrogen concentration in the SiN layer was quantified as approximately 1.0 at. %. This result was consistent with that obtained by elastic recoil detection analysis (ERDA, which confirmed the accuracy of the APT quantification. The present results indicate that APT enables the imaging of the three-dimensional distribution of hydrogen atoms in actual devices at a sub-nanometer scale.

  16. Experimental Investigation Of Segregation Of Carbon Atoms Due To Sub-Zero Cryogenic Treatment In Cold Work Tool Steel By Mechanical Spectroscopy And Atom Probe Tomography

    Directory of Open Access Journals (Sweden)

    Min N.

    2015-06-01

    Full Text Available In this work, we present mechanical spectroscopy of cold work tool steel subjected to sub-zero cryogenic soaking treatment to reveal the carbon segregation and the subsequent carbides refinement. The maximum of Snoek-Köster (SK peak height was obtained in the sample subjected to soaking 1h at −130°C cryogenic treatment. The SK peak height is reduced with prolonging the soaking time. The results indicate that an increase in the height of SK peak is connected with an increase in dislocation density and the number of segregated carbon atoms in the vicinity of dislocations or twin planes after martensite transformation at −130°C which is confirmed by corresponding TEM and atom probe tomography measurement. Hence, it is suggested that the isothermal martensite, formed during the cryogenic soaking treatment decreases (APT the height of SK peak.

  17. Thermal stability of TiAlN/CrN multilayer coatings studied by atom probe tomography

    International Nuclear Information System (INIS)

    This study is about the microstructural evolution of TiAlN/CrN multilayers (with a Ti:Al ratio of 0.75:0.25 and average bilayer period of 9 nm) upon thermal treatment. Pulsed laser atom probe analyses were performed in conjunction with transmission electron microscopy and X-ray diffraction. The layers are found to be thermally stable up to 600 oC. At 700 oC TiAlN layers begin to decompose into Ti- and Al-rich nitride layers in the out-of-plane direction. Further increase in temperature to 1000 oC leads to a strong decomposition of the multilayer structure as well as grain coarsening. Layer dissolution and grain coarsening appear to begin at the surface. Domains of AlN and TiCrN larger than 100 nm are found, together with smaller nano-sized AlN precipitates within the TiCrN matrix. Fe and V impurities are detected in the multilayers as well, which diffuse from the steel substrate into the coating along columnar grain boundaries. -- Research Highlights: → TiAlN/CrN multilayer coating is stable in vacuum at temperatures up to 600 oC. → TiAlN layers start to decompose at 700 oC in Al- and Ti-rich layers (not spinodally). → Decomposition of TiAlN/CrN is not uniform and more severe in the surface region. → Fe and V intensively diffuse from the substrate into TiAlN/CrN coating at 1000 oC.

  18. Investigation of the self tempering effect of martensite by means of atom probe tomography; Untersuchung des Selbstanlasseffektes von Martensit mit Hilfe von Atomsondentomographie

    Energy Technology Data Exchange (ETDEWEB)

    Sackl, Stephanie [Montanuniv. Leoben (Austria). Christian Doppler Labor ' ' Early Stages of Precipitation' ' ; Clemens, Helmut; Primig, Sophie [Montanuniv. Leoben (Austria). Dept. of Physical Metallurgy and Materials Testing

    2015-10-01

    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.

  19. Interface-directed spinodal decomposition in TiAlN/CrN multilayer hard coatings studied by atom probe tomography

    International Nuclear Information System (INIS)

    Microstructural and compositional changes in TiAlN/CrN multilayered films occurring at temperatures up to 1000 °C were studied at different length scales by a combination of atom probe tomography, transmission electron microscopy and X-ray diffraction. We observe the onset of decomposition of the multilayer structure at 700 °C via the mechanism of interface-directed spinodal decomposition of TiAlN layers, where Al atoms preferentially move toward the nearest interface and segregate there. The interface-directed mechanism later transforms into isotropic spinodal decomposition and is accompanied by intense interdiffusion between the constituting layers. Distinct compositional gradients across columnar grain boundaries (extending perpendicular to the multilayers) are detected at this stage of decomposition. Drastic differences in decomposition behavior across the film depth were observed at elevated temperatures (800–1000 °C): the layered structure completely dissolves in the near-surface part but persists in the regions distant from the surface. The influence of residual stresses caused by the sputter deposition process on the thermally induced evolution of the multilayer thin films is discussed

  20. Interfacial chemistry in a ZnTe/CdSe superlattice studied by atom probe tomography and transmission electron microscopy strain measurements.

    Science.gov (United States)

    Bonef, B; Haas, B; Rouvière, J-L; André, R; Bougerol, C; Grenier, A; Jouneau, P-H; Zuo, J-M

    2016-05-01

    The atomic scale analysis of a ZnTe/CdSe superlattice grown by molecular beam epitaxy is reported using atom probe tomography and strain measurements from high-resolution scanning transmission electron microscopy images. CdTe interfaces were grown by atomic layer epitaxy to prevent the spontaneous formation of ZnSe bonds. Both interfaces between ZnTe and CdSe are composed of alloyed layers of ZnSe. Pure CdTe interfaces are not observed and Zn atoms are also visible in the CdSe layers. This information is critical to design superlattices with the expected optoelectronic properties. PMID:26748639

  1. Copper diffusion into single-crystalline TiN studied by transmission electron microscopy and atom probe tomography

    International Nuclear Information System (INIS)

    TiN/Cu bilayers were grown by unbalanced DC magnetron sputter deposition on (001)-oriented MgO substrates. Pole figures and electron back-scatter diffraction orientation maps indicate that both layers in the as-deposited state are single-crystalline with a cube-on-cube epitaxial relationship with the substrate. This is confirmed by selected area electron diffraction patterns. To study the efficiency of the TiN barrier layer against in-diffusion of Cu, we annealed samples at 900 °C for 1 h in vacuum and at 1000 °C for 12 h in Ar atmosphere. The single-crystalline structure of the TiN layer is stable up to annealing temperatures of 1000 °C as shown by high resolution transmission electron microscopy. While no Cu diffusion was evident after annealing at 900 °C, scanning transmission electron microscopy images and energy-dispersive X-ray spectrometry maps show a uniform diffusion layer of about 12 nm after annealing at 1000 °C for 12 h. Concentration depth profiles obtained from 3D atom probe tomography reconstructions confirm these findings and reveal that the TiN film is slightly substoichiometric with a N/Ti ratio of 0.92. Considering this composition, we propose a lattice diffusion mechanism of Cu in TiN via the formation of Cu–N vacancy complexes. The excellent diffusion barrier properties of single-crystalline TiN are further attributed to the lack of fast diffusion paths such as grain boundaries. - Highlights: • Sputter deposition of epitaxial, single-crystalline TiN/Cu bilayers on MgO (001) • Cu diffusion into TiN is studied by TEM and atom probe tomography. • No Cu diffusion is evident after annealing at 900 °C for 1 h. • After annealing at 1000 °C for 12 h a uniform diffusion layer of 12 nm is observed

  2. Atom probe tomography study of internal interfaces in Cu2ZnSnSe4 thin-films

    International Nuclear Information System (INIS)

    We report on atom probe tomography studies of the composition at internal interfaces in Cu2ZnSnSe4 thin-films. For Cu2ZnSnSe4 precursors, which are deposited at 320 °C under Zn-rich conditions, grain boundaries are found to be enriched with Cu irrespective of whether Cu-poor or Cu-rich growth conditions are chosen. Cu2ZnSnSe4 grains are found to be Cu-poor and excess Cu atoms are found to be accumulated at grain boundaries. In addition, nanometer-sized ZnSe grains are detected at or near grain boundaries. The compositions at grain boundaries show different trends after annealing at 500 °C. Grain boundaries in the annealed absorber films, which are free of impurities, are Cu-, Sn-, and Se-depleted and Zn-enriched. This is attributed to dissolution of ZnSe at the Cu-enriched grain boundaries during annealing. Furthermore, some of the grain boundaries of the absorbers are enriched with Na and K atoms, stemming from the soda-lime glass substrate. Such grain boundaries show no or only small changes in composition of the matrix elements. Na and K impurities are also partly segregated at some of the Cu2ZnSnSe4/ZnSe interfaces in the absorber, whereas for the precursors, only Na was detected at such phase boundaries possibly due to a higher diffusivity of Na compared to K. Possible effects of the detected compositional fluctuations on cell performance are discussed

  3. Atom probe tomography study of internal interfaces in Cu2ZnSnSe4 thin-films

    Science.gov (United States)

    Schwarz, T.; Cojocaru-Mirédin, O.; Choi, P.; Mousel, M.; Redinger, A.; Siebentritt, S.; Raabe, D.

    2015-09-01

    We report on atom probe tomography studies of the composition at internal interfaces in Cu2ZnSnSe4 thin-films. For Cu2ZnSnSe4 precursors, which are deposited at 320 °C under Zn-rich conditions, grain boundaries are found to be enriched with Cu irrespective of whether Cu-poor or Cu-rich growth conditions are chosen. Cu2ZnSnSe4 grains are found to be Cu-poor and excess Cu atoms are found to be accumulated at grain boundaries. In addition, nanometer-sized ZnSe grains are detected at or near grain boundaries. The compositions at grain boundaries show different trends after annealing at 500 °C. Grain boundaries in the annealed absorber films, which are free of impurities, are Cu-, Sn-, and Se-depleted and Zn-enriched. This is attributed to dissolution of ZnSe at the Cu-enriched grain boundaries during annealing. Furthermore, some of the grain boundaries of the absorbers are enriched with Na and K atoms, stemming from the soda-lime glass substrate. Such grain boundaries show no or only small changes in composition of the matrix elements. Na and K impurities are also partly segregated at some of the Cu2ZnSnSe4/ZnSe interfaces in the absorber, whereas for the precursors, only Na was detected at such phase boundaries possibly due to a higher diffusivity of Na compared to K. Possible effects of the detected compositional fluctuations on cell performance are discussed.

  4. 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.

  5. Intergranular segregation in the pressure vessel steel of a commercial nuclear reactor studied by atom probe tomography

    International Nuclear Information System (INIS)

    Solute/impurity segregation and precipitation at grain boundaries (GBs) in a nuclear reactor pressure vessel (RPV) steel were investigated using laser-assisted atom probe tomography (APT): RPV surveillance test specimens irradiated in a commercial nuclear reactor to neutron doses of 0.83 x 1019 n·cm-2 (low-dose) and 5.1 x 1019 n·cm-2 (high-dose), corresponding to in-service exposure of ∼5 and ∼30 years, respectively. The segregation of C, P and Mo was found on GBs after the low-dose irradiation. The segregation of Si and Mn as well as C, P and Mo was observed after the high-dose irradiation. The monolayer coverage of P is estimated to be less than a suggested level for intergranular embrittlement. The segregation of C, P and Mo was also observed along parallel array of dislocation lines in small-angle grain boundaries. However, no segregation of Si and Mn was detected there. Copper-nano precipitates (CNPs) were observed on the GBs, along the dislocation lines and in the matrix. The sizes and the solute-impurity enrichment in these CNPs are compared. (author)

  6. Influence of instrument conditions on the evaporation behavior of uranium dioxide with UV laser-assisted atom probe tomography

    International Nuclear Information System (INIS)

    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 (UO2). 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 UO2. 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 UO2 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.

  7. 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.

  8. Optimisation of sample preparation and analysis conditions for atom probe tomography characterisation of low concentration surface species

    Science.gov (United States)

    Douglas, J. O.; Bagot, P. A. J.; Johnson, B. C.; Jamieson, D. N.; Moody, M. P.

    2016-08-01

    The practicalities for atom probe tomography (APT) analysis of near-surface chemistry, particularly the distribution of low concentration elements, are presented in detail. Specifically, the challenges of surface analysis using APT are described through the characterisation of near-surface implantation profiles of low concentration phosphorus into single crystal silicon. This material system was chosen to illustrate this surface specific approach as low concentration phosphorus has significant mass spectra overlaps with silicon species and the near surface location requires particular attention to focused ion beam specimen preparation and deposition of various capping layers. Required changes to standard sample preparation procedure are described and the effects of changes in APT analysis parameters are discussed with regards to this specific material system. Implantation profiles of 14 kV phosphorus ions with a predicted peak concentration of 0.2 at .% were successfully analysed using APT using pulsed laser assisted evaporation. It is demonstrated that the most important factor in obtaining the most accurate implantation profile was to ensure all phosphorus mass peaks were as free of background noise as possible, with thermal tails from the Si2+ ions obscuring the P2+ ions being the major overlap in the mass spectrum. The false positive contribution to the phosphorus profiles from hydride species appears minimal at the capping layer/substrate interface. The initial capping layer selection of nickel was successful in allowing the analysis of the majority of the phosphorus profile but nickel and phosphorus mass spectra overlaps prevent optimum quantification of phosphorus at the surface.

  9. Analysis of strengthening in AA6111 during the early stages of aging: Atom probe tomography and yield stress modelling

    International Nuclear Information System (INIS)

    In this work, a series of aging treatments has been conducted on AA6111 alloy samples for various times at ambient temperature (so-called natural aging) and at temperatures between 60 and 180 °C (artificially aged). The time at artificial ageing was chosen such that samples with approximately the same yield stress were produced. The microstructures of these alloy samples have been carefully characterized using atom probe tomography together with advanced cluster-finding techniques in order to obtain quantitative information about the changes in distribution of both the solute clusters and early-stage precipitates that are formed. The size distribution of clusters has been mapped onto the glide plane and then the stress necessary for a dislocation to pass through the range of obstacles has been estimated using an areal glide model where the dislocation–obstacle interaction strength has been assumed to be related to the obstacle size on the glide plane. It is demonstrated that the contribution of cluster strengthening during artificial aging at higher temperatures is dominated by the high number density of small clusters (Guinier radius <1 nm), whereas the situation during room temperature natural aging is more complex

  10. The contribution of atom probe tomography to the understanding of nuclear material evolution under thermal or irradiation ageing

    International Nuclear Information System (INIS)

    The properties of materials are strongly linked to their structure at nanometer scale. In order to optimize material properties or to anticipate the evolution of these properties during ageing in given conditions, the first step is to characterize their microstructure at this very fine scale and to understand the mechanisms governing its long term evolution. This is particularly the case for nuclear materials which are submitted to severe conditions such as corrosive environment, mechanical stress, high temperature and neutron irradiation. In order to ensure nuclear plant long term operation (up to 60 years) with reliable and safe conditions and to develop materials for next generations of reactors, the mechanisms occurring at the atomic scale during thermal or irradiation ageing have to be understood. Atom probe Tomography (APT) is one of the suitable tools to study these phenomena (phase transformations, segregations...). The Groupe de Physique des Matériaux (GPM) works on the ageing of nuclear materials since more than 20 years. A combination of characterization tools (APT, scanning and transmission electron microscopies - SEM and TEM) and modeling tools (Monte Carlo, Phase field ..) is generally used. The interest of APT, coupled with other experimental or theoretical tools, (i) to identify the microstructural features responsible of the degradation of the properties of nuclear materials in service conditions, (ii) to understand basic mechanisms at the formation and evolution of these features and (iii) to develop new materials will be shown through several examples (irradiation ageing of pressurized water reactor pressure vessel and internal structures steels, ferritic-martensitic steels for future reactors...). One of the challenges for the investigation of irradiation effects in nuclear materials is to be able to characterize the nanostructure of radioactive samples. The project GENESIS, led by the GPM, aims to develop and experimental platform (APT, TEM

  11. Self-organization of Cu-based immiscible alloys under irradiation: An atom-probe tomography study

    Science.gov (United States)

    Stumphy, Brad D.

    The stability of materials subjected to prolonged irradiation has been a topic of renewed interest in recent years due to the projected growth of nuclear power as an alternative energy source. The irradiating particles impart energy into the material, thereby causing atomic displacements to occur. These displacements result in the creation of point defects and the random ballistic mixing of the atoms. Consequently, the material is driven away from its equilibrium structure. The supersaturation of defects can lead to the degradation of mechanical properties, but a high density of internal interfaces, which act as defect sinks, will suppress the supersaturation and long-range transport of defects. The microstructural evolution of the material is controlled by the ballistic mixing as well as the mobility of the point defects. In immiscible alloys, these two processes compete against one another, as the ballistic mixing acts to solutionize the alloy components, and the thermal diffusion of the large number of defects acts to phase separate the components. The work presented in this dissertation examines the effect of heavy-ion irradiation on immiscible, binary Cu-based alloys. Dilute alloys of Cu-Fe, Cu-V, and V-Cu have been subjected to irradiation, and atom-probe tomography has been utilized in order to better understand the complex nature of the response of these simple model systems to an irradiation environment. The results show that a steady-state, nano-scale patterning structure, with a high density of unsaturable defect sinks, can be maintained under prolonged irradiation. Additionally, precipitation from a supersaturated solid solution is shown to be a function of both the thermal diffusion and the ballistic mixing. Solvent-rich secondary precipitates, termed "cherry-pits," are observed inside of the solute-rich primary precipitates. Through a combination of simulation work and analyzing multiple alloys experimentally, it was determined that this cherry

  12. Atom probe tomography of secondary γ′ precipitation in a single crystal Ni-based superalloy after isothermal aging at 1100 °C

    Energy Technology Data Exchange (ETDEWEB)

    Tan, X.P., E-mail: xptan1985@gmail.com [IM 2NP, UMR 7334 CNRS, Université Aix-Marseille, 13397 Marseille Cedex 20 (France); Mangelinck, D.; Perrin-Pellegrino, C. [IM 2NP, UMR 7334 CNRS, Université Aix-Marseille, 13397 Marseille Cedex 20 (France); Rougier, L. [LSMX, MXG, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne (Switzerland); Gandin, Ch.-A. [CEMEF, UMR 7635 CNRS, MINES ParisTech, 06904 Sophia Antipolis (France); Jacot, A. [LSMX, MXG, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne (Switzerland); Ponsen, D.; Jaquet, V. [Snecma-SAFRAN Group, Service YQGC, 92702 Colombes (France)

    2014-10-25

    Highlights: • Bimodal size distribution of γ′ precipitates occurs after isothermal aging at 1100 °C. • Characterization of secondary γ′ by atom probe tomography. • It is proposed that the secondary γ′ occurs via a non-classical nucleation. • The coarsening of secondary γ′ precipitates well obeys the classical LSW theory. - Abstract: Secondary γ′ precipitation in a commercial single crystal Ni-based superalloy after the 1100 °C isothermal aging has been investigated by atom probe tomography. After the isothermal aging for 300 s, 1800 s and 3600 s, a bimodal size distribution of larger primary γ′ precipitates and numerous smaller secondary γ′ precipitates was obtained. It is proposed that the secondary γ′ precipitated via a non-classical nucleation mode. The coarsening of secondary γ′ precipitates well obeys the classical LSW theory.

  13. Understanding of the field evaporation of surface modified oxide materials through transmission electron microscopy and atom probe tomography

    Science.gov (United States)

    Seol, Jae-Bok; Kwak, Chang-Min; Kim, Y.-T.; Park, Chan-Gyung

    2016-04-01

    Understanding of triggering the field evaporation of surface ions on the non-conductive materials enables improvement in the mass resolution in laser-pulsed atom probe tomography. This study addresses the influence of surface modification through metallic-capped layers, such as Co, Ni, and Ag, with surrounding bulk MgO tips on the physical mechanisms responsible for field evaporation and on the mass resolving power compared to uncapped bulk MgO. In particular, the field evaporation on the surface regions of Ag-capped bulk MgO tips during analysis was extensively observed by transmission electron microscopy to confirm the overall evaporation sequences occurring at the tip surface. We found that the introduction of such capping layers, especially for Ag-capping, controls both symmetric tip geometry at the surface of the specimens and the mass resolving power of ion species consisting of MgO materials. This implies the improvements in the symmetries of local field distributions and the isotropy of thermal heating across the tip surface. It reveals that Ag-capping with high thermal diffusivity promotes the compositional uniformities between the laser illumination side and the opposite side for MgO samples as well as the reduced fraction of multiple events for oxygen ions between both sides. Moreover, a variation in the thickness of the Ag-capping layer is an additional factor governing a thermal-assisted mechanism of MgO evaporation. Based on our findings, homogeneous thermal heat transfer for MgO emission along the tip axis by Ag-capping layers may be significant in potential methods for improvement.

  14. On the interplay between relaxation, defect formation, and atomic Sn distribution in Ge{sub (1−x)}Sn{sub (x)} unraveled with atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, A., E-mail: arul.kumar@imec.be; Bran, J., E-mail: julien.bran@imec.be; Melkonyan, D., E-mail: davit.melkonyan@imec.be; Shimura, Y., E-mail: Yosuke.Shimura@imec.be; Vandervorst, W., E-mail: wilfried.vandervorst@imce.be [Instituut voor Kern- en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Imec vzw, Kapeldreef 75, Heverlee 3001 (Belgium); Demeulemeester, J., E-mail: jelle.demeulemeester@imec.be; Bogdanowicz, J., E-mail: janusz.bogdanowicz@imec.be; Fleischmann, C., E-mail: claudia.fleischmann@imec.be; Loo, R., E-mail: wie.wang@imec.be [Imec vzw, Kapeldreef 75, Heverlee 3001 (Belgium); Gencarelli, F., E-mail: federica.gencarelli@imec.be; Wang, W., E-mail: wie.wang@imec.be [Imec vzw, Kapeldreef 75, Heverlee 3001 (Belgium); Department of Metallurgy and Materials Engineering, KU Leuven, Kasteelpark Arenberg 44, Leuven (Belgium)

    2015-07-14

    Ge{sub (1−x)}Sn{sub (x)} has received a lot of interest for opto-electronic applications and for strain engineering in advanced complementary-metal-oxide-semiconductor technology, because it enables engineering of the band gap and inducing strain in the alloy. To target a reliable technology for mass application in microelectronic devices, the physical problem to be addressed is to unravel the complex relationship between strain relaxation (as induced by the growth of large layer thicknesses or a thermal anneal) and defect formation, and/or stable Sn-cluster formation. In this paper, we study the onset of Sn-cluster formation and its link to strain relaxation using Atom Probe Tomography (APT). To this end, we also propose a modification of the core-linkage [Stephenson et al., Microsc. Microanal. 13, 448 (2007)] cluster analysis method, to overcome the challenges of limited detection efficiency and lateral resolution of APT, and the quantitative assessment for very small clusters (<40 atoms) embedded in a random distribution of Sn-atoms. We concluded that the main relaxation mechanism for these layers is defect generation (misfit dislocations, threading dislocations, etc.), irrespective of the cause (thickness of layer or thermal anneal) of relaxation and is independent of the cluster formation. The low thermodynamic solubility limit of Sn in Ge seems to be the driving force for Sn-cluster formation. Finally, we also discuss the spatial distribution of Sn in clusters and relate them to the theoretically predicted stable Sn clusters [Ventura et al., Phys. Rev. B 79, 155202 (2009)].

  15. On the interplay between relaxation, defect formation, and atomic Sn distribution in Ge(1−x)Sn(x) unraveled with atom probe tomography

    International Nuclear Information System (INIS)

    Ge(1−x)Sn(x) has received a lot of interest for opto-electronic applications and for strain engineering in advanced complementary-metal-oxide-semiconductor technology, because it enables engineering of the band gap and inducing strain in the alloy. To target a reliable technology for mass application in microelectronic devices, the physical problem to be addressed is to unravel the complex relationship between strain relaxation (as induced by the growth of large layer thicknesses or a thermal anneal) and defect formation, and/or stable Sn-cluster formation. In this paper, we study the onset of Sn-cluster formation and its link to strain relaxation using Atom Probe Tomography (APT). To this end, we also propose a modification of the core-linkage [Stephenson et al., Microsc. Microanal. 13, 448 (2007)] cluster analysis method, to overcome the challenges of limited detection efficiency and lateral resolution of APT, and the quantitative assessment for very small clusters (<40 atoms) embedded in a random distribution of Sn-atoms. We concluded that the main relaxation mechanism for these layers is defect generation (misfit dislocations, threading dislocations, etc.), irrespective of the cause (thickness of layer or thermal anneal) of relaxation and is independent of the cluster formation. The low thermodynamic solubility limit of Sn in Ge seems to be the driving force for Sn-cluster formation. Finally, we also discuss the spatial distribution of Sn in clusters and relate them to the theoretically predicted stable Sn clusters [Ventura et al., Phys. Rev. B 79, 155202 (2009)

  16. Atom probe tomography characterization of neutron irradiated surveillance samples from the R. E. Ginna reactor pressure vessel

    International Nuclear Information System (INIS)

    Surveillance samples of a low copper (nominally 0.05 wt.% Cu) forging and a higher copper (0.23 wt.% Cu) submerged arc weld from the R. E. Ginna reactor pressure vessel have been characterized by atom probe tomography (APT) after exposure to three levels of neutron irradiation, i.e., fluences of 1.7, 3.6 and 5.8 x 1023 n.m-2 (E > 1 MeV), and inlet temperatures of ~289 °C (~552 °F). As no copper-enriched precipitates were observed in the low copper forging, and the measured copper content in the ferrite matrix was 0.04± <0.01 at.% Cu, after neutron irradiation to a fluence of 1.7 x 1023 n.m-3, this copper level was below the solubility limit. A number density of 2 x 1022 m-3 of Ni-, Mn- Si-enriched precipitates with an equivalent radius of gyration of 1.7 ± 0.4 nm were detected in the sample. However, Cu-, Ni-, Mn-enriched precipitates were observed in specimens cut from different surveillance specimens from the same forging material in which the overall measured copper level was 0.08± <0.01 at.% (fluence of 3.6 x 1023 n.m-3) and 0.09± <0.01 at.% Cu (fluence of 5.8 x 1023 n.m-3). Therefore, these slightly higher copper contents were above the solubility limit of Cu under these irradiation conditions. A best fit of all the composition data indicated that the size and number density of the Cu-enriched precipitates increased slightly in both size and number density by additional exposure to neutron irradiation. High number densities of Cu-enriched precipitates were observed in the higher Cu submerged arc weld for all irradiated conditions. The size and number density of the precipitates in the welds were higher than in the same fluence forgings. Some Cu-enriched precipitates were found to have Ni-, Mn- Si-, and P-enriched regions on their surfaces suggesting a preferential nucleation site. Furthermore, atom maps revealed P, Ni, and Mn segregation to, and preferential precipitation of, Cu-enriched precipitates over the surface of a grain boundary in the low

  17. Atom probe tomography of the austenite-ferrite interphase boundary composition in a model alloy Fe-C-Mn

    International Nuclear Information System (INIS)

    A tomographic atom probe analysis has been developed to study the interfacial conditions during isothermal austenite transformation to ferrite at 700 deg. C in an Fe-C-Mn model alloy. The interfacial conditions lead to different alloying element profiles across the interface, and a comparison is made between this experimental result and the DICTRA software predictions under the various conditions

  18. Influence of the Electronic Structure and Optical Properties of CeO2 and UO2 for Characterization with UV-Laser Assisted Atom Probe Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Billy Valderrama; H.B. Henderson; C. Yablinsky; J. Gan; T.R. Allen; M.V. Manuel

    2015-09-01

    Oxide materials are used in numerous applications such as thermal barrier coatings, nuclear fuels, and electrical conductors and sensors, all applications where nanometer-scale stoichiometric changes can affect functional properties. Atom probe tomography can be used to characterize the precise chemical distribution of individual species and spatially quantify the oxygen to metal ratio at the nanometer scale. However, atom probe analysis of oxides can be accompanied by measurement artifacts caused by laser-material interactions. In this investigation, two technologically relevant oxide materials with the same crystal structure and an anion to cation ratio of 2.00, pure cerium oxide (CeO2) and uranium oxide (UO2) are studied. It was determined that electronic structure, optical properties, heat transfer properties, and oxide stability strongly affect their evaporation behavior, thus altering their measured stoichiometry, with thermal conductance and thermodynamic stability being strong factors.

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

    International Nuclear Information System (INIS)

    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

  20. 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.

  1. 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.

  2. Microstructural analysis of impurity segregation around β-Nb precipitates in Zr–Nb alloy using positron annihilation spectroscopy and atom probe tomography

    International Nuclear Information System (INIS)

    Graphical abstract: Fe segregation are evident at the interface between β-Nb precipitates and α-Zr matrix by atom probe tomography (APT). Defects are observed at the interface by positron annihilation spectroscopy. It is also suggested that Fe was segregated to a concentration of several tens of percent at a local region at the interface, which is approximately one order of magnitude higher than APT and difficult to observe directly even using APT. - Abstract: Impurity segregation at the interface between β-Nb precipitates and α-Zr matrix in Zr-2.5 wt.%Nb alloy was investigated by complementary analysis with positron annihilation spectroscopy (PAS) and atom probe tomography (APT). Fe segregation and Fe-decorated defects were found at the interface. PAS also suggested that Fe was segregated to a concentration of several tens of percent at a local region at the interface, which is approximately one order of magnitude higher than APT and difficult to observe directly even using APT

  3. Atom probe tomography evidence for uniform incorporation of Bi across the growth front in GaAs1-xBix/GaAs superlattice

    Science.gov (United States)

    Chen, Weixin; Ronsheim, Paul A.; Wood, Adam W.; Forghani, Kamran; Guan, Yingxin; Kuech, Thomas F.; Babcock, Susan E.

    2016-07-01

    The three-dimensional distribution of Bi atoms in a GaAs1-xBix/GaAs superlattice grown by metalorganic vapor phase epitaxy (MOVPE) was studied using atom probe tomography (APT). The Bi distribution in the growth direction deduced from APT agreed quantitatively with the complex Bi concentration profile that was discovered using high-angle annular dark-field scanning transmission electron microscopy in a previous study. More importantly, APT revealed the Bi atom distribution in the growth planes at near atomic resolution. Bi nearest neighbor distribution and concentration frequency distribution analysis of the APT data indicated a statistically random distribution of Bi atoms in 1-2 nm thick layers oriented perpendicular to the growth direction. These results provide evidence that Bi is incorporated homogeneously across the growth front even when the concentration profile in the growth direction is complex. They also suggest that MOVPE growth conditions can promote uniform Bi distribution within GaAs1-xBix layers, opening a path for application of these materials in the optoelectronic devices for which they show much promise.

  4. Correlated high-resolution x-ray diffraction, photoluminescence, and atom probe tomography analysis of continuous and discontinuous InxGa1−xN quantum wells

    International Nuclear Information System (INIS)

    Atom probe tomography (APT) is used to characterize the influence of hydrogen dosing during GaN barrier growth on the indium distribution of InxGa1−xN quantum wells, and correlated micro-photoluminescence is used to measure changes in the emission spectrum and efficiency. Relative to the control growth, hydrogen dosing leads to a 50% increase in emission intensity arising from discontinuous quantum wells that are narrower, of lower indium content, and with more abrupt interfaces. Simulations of carrier distributions based on APT composition profiles indicate that the greater carrier confinement leads to an increased radiative recombination rate. Furthermore, APT analysis of quantum well profiles enables refinement of x-ray diffraction analysis for more accurate nondestructive measurements of composition

  5. Mechanical alloying and amorphization in Cu-Nb-Ag in situ composite wires studied by transmission electron microscopy and atom probe tomography

    International Nuclear Information System (INIS)

    We have studied deformation-driven alloying in a Cu-5 at.% Ag-3 at.% Nb in situ composite by transmission electron microscopy and atom probe tomography. In addition to alloying at interfaces, amorphization of nanosized Cu areas was observed after heavy wire drawing (true strain: η = 10.5) at some of the Cu-Nb interfaces. We discuss the alloying in terms of trans-phase dislocation-shuffling and shear banding mechanisms where lattice dislocations penetrate the interfaces between abutting phases. We interpret local amorphization in terms of the thermodynamic destabilization of a Cu-Nb crystalline phase between 35 and 80 at.% Cu due to enforced mixing. Deformation-driven mechanical alloying and amorphization are hence closely associated phenomena.

  6. Ion-irradiation-induced clustering in W–Re and W–Re–Os alloys: A comparative study using atom probe tomography and nanoindentation measurements

    International Nuclear Information System (INIS)

    This study examines clustering and hardening in W–2 at.% Re and W–1 at.% Re–1 at.% Os alloys induced by 2 MeV W+ ion irradiation at 573 and 773 K. Such clusters are known precursors to the formation of embrittling precipitates, a potentially life-limiting phenomenon in the operation of fusion reactor components. Increases in hardness were studied using nanoindentation. The presence of osmium significantly increased post-irradiation hardening. Atom probe tomography analysis revealed clustering in both alloys, with the size and number densities strongly dependent on alloy composition and irradiation temperature. The highest cluster number density was found in the ternary alloy irradiated at 773 K. In the ternary alloy, Os was found to cluster preferentially compared to Re. The implications of this result for the structural integrity of fusion reactor components are discussed

  7. Composition and Interface Analysis of InGaN/GaN Multiquantum-Wells on GaN Substrates Using Atom Probe Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fang; Huang, Li; Davis, Robert F.; Porter, Lisa M.; Schreiber, Daniel K.; Kuchibhatla, S. V. N. T.; Shutthanandan, V.; Thevuthasan, Suntharampillai; Preble, Edward; Paskova, Tanya; Evans, K. R.

    2014-09-04

    In0.20Ga0.80N/GaN multi-quantum wells grown on [0001]-oriented GaN substrates with and without an InGaN buffer layer were characterized using three-dimensional atom probe tomography. In all samples, the upper interfaces of the QWs were slightly more diffuse than the lower interfaces. The buffer layers did not affect the roughness of the interfaces within the quantum well structure, a result attributed to planarization of the surface of the 1st GaN barrier layer which had an average root-mean-square roughness of 0.177 nm. The In and Ga distributions within the MQWs followed the expected distributions for a random alloy with no indications of In clustering.

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

    International Nuclear Information System (INIS)

    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. -- Research highlights: → APT measurements of Fe3Al-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%

  9. Post-irradiation annealing of Ni–Mn–Si-enriched clusters in a neutron-irradiated RPV steel weld using Atom Probe Tomography

    International Nuclear Information System (INIS)

    Highlights: • Characterisation of high Ni neutron irradiated RPV surveillance samples at high fluence. • Post-irradiation annealing performed to give insight into the formation mechanisms of Ni–Mn–Si precipitates. • Dissolution of Ni–Mn–Si clusters appears to be lead by the removal of Mn. - Abstract: Atom Probe Tomography has been performed on as-irradiated and post-irradiation annealed surveillance weld samples from Ringhals Unit 3. The weld contains low Cu (0.07 at.%) and high Ni (1.5 at.%). A high number density (∼4 × 1023 m−3) of Ni–Mn–Si-enriched clusters was observed in the as-irradiated material. The onset of recovery was observed during the annealing for 30 min at 450 °C. Much more significant dissolution of clusters occurred during the 10 min 500 °C anneal, resulting in a reduction in mean cluster size and a halving of their volume fraction. Detailed analyses of the changes in microstructure demonstrate that the dissolution process is driven by migration of Mn atoms from the clusters. This may indicate a strong correlation between Mn and point defects. Dissolution of the clusters is shown to correlate with recovery of mechanical properties in this material

  10. Post-irradiation annealing of Ni–Mn–Si-enriched clusters in a neutron-irradiated RPV steel weld using Atom Probe Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Styman, P.D., E-mail: paul.styman@materials.ox.ac.uk [National Nuclear Laboratory, 168 Harwell Business Centre, Didcot, Oxon OX11 0QT (United Kingdom); Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Hyde, J.M. [National Nuclear Laboratory, 168 Harwell Business Centre, Didcot, Oxon OX11 0QT (United Kingdom); Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); School of Materials, University of Manchester, Manchester M13 9PL (United Kingdom); Parfitt, D.; Wilford, K. [Rolls-Royce, PO BOX 2000, Raynesway, Derby DE21 7XX (United Kingdom); Burke, M.G. [School of Materials, University of Manchester, Manchester M13 9PL (United Kingdom); English, C.A. [National Nuclear Laboratory, 168 Harwell Business Centre, Didcot, Oxon OX11 0QT (United Kingdom); Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); School of Materials, University of Manchester, Manchester M13 9PL (United Kingdom); Efsing, P. [Vattenfall Ringhals AB, Väröbacka (Sweden)

    2015-04-15

    Highlights: • Characterisation of high Ni neutron irradiated RPV surveillance samples at high fluence. • Post-irradiation annealing performed to give insight into the formation mechanisms of Ni–Mn–Si precipitates. • Dissolution of Ni–Mn–Si clusters appears to be lead by the removal of Mn. - Abstract: Atom Probe Tomography has been performed on as-irradiated and post-irradiation annealed surveillance weld samples from Ringhals Unit 3. The weld contains low Cu (0.07 at.%) and high Ni (1.5 at.%). A high number density (∼4 × 10{sup 23} m{sup −3}) of Ni–Mn–Si-enriched clusters was observed in the as-irradiated material. The onset of recovery was observed during the annealing for 30 min at 450 °C. Much more significant dissolution of clusters occurred during the 10 min 500 °C anneal, resulting in a reduction in mean cluster size and a halving of their volume fraction. Detailed analyses of the changes in microstructure demonstrate that the dissolution process is driven by migration of Mn atoms from the clusters. This may indicate a strong correlation between Mn and point defects. Dissolution of the clusters is shown to correlate with recovery of mechanical properties in this material.

  11. Elemental partitioning and mechanical properties of Ti- and Ta-containing Co–Al–W-base superalloys studied by atom probe tomography and nanoindentation

    International Nuclear Information System (INIS)

    Elemental partitioning and hardness in Ti- and Ta-containing Co-base superalloys, strengthened by γ′-Co3(Al, W) precipitates, have been studied by local measurements. Using atom probe tomography, we detect strong partitioning of W (partitioning coefficients from 2.4 to 3.4) and only slight partitioning of Al (partitioning coefficients ⩽1.1) to the γ′-Co3(Al, W) phase. Al segregates to the γ/γ′ phase boundaries, whereas W is depleted at the γ side of the boundaries after aging at 900 °C and slow air cooling. This kind of Al segregation and W depletion is much less pronounced when water quenching is applied. As a result, these effects are considered to be absent at high temperatures and therefore should not influence the creep properties. Ti and Ta additions are found to strongly partition to the γ′ phase and greatly increase the γ′ volume fraction. Our results indicate that the alloying elements Al, W, Ti and Ta all occupy the B sublattice of the A3B structure (L12 type) and affect the partitioning behavior of each other. Nanoindentation measurements show that Ta also increases the hardness of the γ′ phase, while the hardness of the γ channels remains nearly constant in all alloys. The change in hardness of the γ′ phase can be ascribed to the substitution of Al and W atoms by Ti and/or Ta

  12. Grain boundary segregation in Fe–Mn–C twinning-induced plasticity steels studied by correlative electron backscatter diffraction and atom probe tomography

    International Nuclear Information System (INIS)

    We report on the characterization of grain boundary (GB) segregation in an Fe–28Mn–0.3C (wt.%) twinning-induced plasticity (TWIP) steel. After recrystallization of this steel for 24 h at 700 °C, ∼50% general grain boundaries (GBs) and ∼35% Σ3 annealing twin boundaries were observed (others were high-order Σ and low-angle GBs). The segregation of B, C and P and traces of Si and Cu were detected at the general GB by atom probe tomography (APT) and quantified using ladder diagrams. In the case of the Σ3 coherent annealing twin, it was necessary to first locate the position of the boundary by density analysis of the atom probe data, then small amounts of B, Si and P segregation and, surprisingly, depletion of C were detected. The concentration of Mn was constant across the interface for both boundary types. The depletion of C at the annealing twin is explained by a local change in the stacking sequence at the boundary, creating a local hexagonal close-packed structure with low C solubility. This finding raises the question of whether segregation/depletion also occurs at Σ3 deformation twin boundaries in high-Mn TWIP steels. Consequently, a previously published APT dataset of the Fe–22Mn–0.6C alloy system, containing a high density of deformation twins due to 30% tensile deformation at room temperature, was reinvestigated using the same analysis routine as for the annealing twin. Although crystallographically identical to the annealing twin, no evidence of segregation or depletion was found at the deformation twins, owing to the lack of mobility of solutes during twin formation at room temperature

  13. Atom Probe Tomography Study of Multi-microalloyed Carbide and Carbo-Nitride Precipitates and the Precipitation Sequence in Nb-Ti HSLA Steels

    Science.gov (United States)

    Kapoor, Monica; O'Malley, Ronald; Thompson, Gregory B.

    2016-05-01

    Composition analysis of carbide and carbo-nitride precipitates was performed for two Nb-Ti microalloyed steels with yield strengths of 750 and 580 MPa using an atom probe study. In the high-Ti 750 MPa steel, Ti-rich (Ti,Nb)(C,N) and Ti-rich (Ti,Nb)(C) precipitates were observed. In the high-Nb 580 MPa steel, a Ti-rich (Ti,Nb)(C,N) precipitate and (Ti,Nb)(C) clusters were noted. These (Ti,Nb)(C) clusters in the high-Nb 580 MPa steel were smaller than the (Ti,Nb)(C) precipitates in high-Ti 750 MPa steel. In general, a larger number of precipitates were found in the high-Ti 750 MPa steel. This difference in the number density of the precipitates between the two steels is attributed to the difference in Ti content. Combining the atom probe tomography results and thermodynamic calculations, the precipitation sequence in these alloys was inferred to be the following: as the temperature decreases, TiN precipitates out of the solution with successive (Ti,Nb)(C,N) layers of varying composition forming on these Ti-rich precipitates. Once N is depleted from the solution, a second set of (Ti,Nb)(C) precipitates in a similar manner in the matrix and also onto the carbo-nitride phase. This observation is consistent with previous observations in high-strength low-alloy steels containing comparable amounts of only Nb. It was noted that the amount of Nb, Nb/(Nb + Ti), in the precipitates decreased from 0.20 to 0.04 with the size of the precipitate. We believe that this is due to the Nb supersaturation in the matrix when these precipitates nucleate.

  14. Fe-implanted 6H-SiC: Direct evidence of Fe{sub 3}Si nanoparticles observed by atom probe tomography and {sup 57}Fe Mössbauer spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Diallo, M. L.; Fnidiki, A., E-mail: abdeslem.fnidiki@univ-rouen.fr; Lardé, R.; Cuvilly, F.; Blum, I. [Groupe de Physique des Matériaux, Université et INSA de Rouen - UMR CNRS 6634 - Normandie Université. F-76801 Saint Etienne du Rouvray (France); Lechevallier, L. [Groupe de Physique des Matériaux, Université et INSA de Rouen - UMR CNRS 6634 - Normandie Université. F-76801 Saint Etienne du Rouvray (France); Département de GEII, Université de Cergy-Pontoise, rue d' Eragny, Neuville sur Oise, 95031 Cergy-Pontoise (France); Debelle, A.; Thomé, L. [Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), CNRS-IN2P3-Univ. Paris-Sud 11, Bât. 108, 91405 Orsay (France); Viret, M. [Service de Physique de l' Etat Condensé (DSM/IRAMIS/SPEC), UMR 3680 CNRS, Bât. 772, Orme des Merisiers, CEA Saclay 91191 Gif sur Yvette (France); Marteau, M.; Eyidi, D.; Declémy, A. [Institut PPRIME, UPR 3346 CNRS, Université de Poitiers, ENSMA, SP2MI, téléport 2, 11 Bvd M. et P. Curie 86962 Futuroscope, Chasseneuil (France)

    2015-05-14

    In order to understand ferromagnetic ordering in SiC-based diluted magnetic semiconductors, Fe-implanted 6H-SiC subsequently annealed was studied by Atom Probe Tomography, {sup 57}Fe Mössbauer spectroscopy and SQUID magnetometry. Thanks to its 3D imaging capabilities at the atomic scale, Atom Probe Tomography appears as the most suitable technique to investigate the Fe distribution in the 6H-SiC host semiconductor and to evidence secondary phases. This study definitely evidences the formation of Fe{sub 3}Si nano-sized clusters after annealing. These clusters are unambiguously responsible for the main part of the magnetic properties observed in the annealed samples.

  15. Atom probe tomography study of internal interfaces in Cu{sub 2}ZnSnSe{sub 4} thin-films

    Energy Technology Data Exchange (ETDEWEB)

    Schwarz, T., E-mail: schwarz@mpie.de; Cojocaru-Mirédin, O.; Choi, P., E-mail: choi@mpie.de; Raabe, D. [Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Strasse 1, 40237 Düsseldorf (Germany); Mousel, M.; Redinger, A.; Siebentritt, S. [Laboratory for Photovoltaics, Physics and Materials Science Research Unit, University of Luxembourg, L-4422 Belvaux (Luxembourg)

    2015-09-07

    We report on atom probe tomography studies of the composition at internal interfaces in Cu{sub 2}ZnSnSe{sub 4} thin-films. For Cu{sub 2}ZnSnSe{sub 4} precursors, which are deposited at 320 °C under Zn-rich conditions, grain boundaries are found to be enriched with Cu irrespective of whether Cu-poor or Cu-rich growth conditions are chosen. Cu{sub 2}ZnSnSe{sub 4} grains are found to be Cu-poor and excess Cu atoms are found to be accumulated at grain boundaries. In addition, nanometer-sized ZnSe grains are detected at or near grain boundaries. The compositions at grain boundaries show different trends after annealing at 500 °C. Grain boundaries in the annealed absorber films, which are free of impurities, are Cu-, Sn-, and Se-depleted and Zn-enriched. This is attributed to dissolution of ZnSe at the Cu-enriched grain boundaries during annealing. Furthermore, some of the grain boundaries of the absorbers are enriched with Na and K atoms, stemming from the soda-lime glass substrate. Such grain boundaries show no or only small changes in composition of the matrix elements. Na and K impurities are also partly segregated at some of the Cu{sub 2}ZnSnSe{sub 4}/ZnSe interfaces in the absorber, whereas for the precursors, only Na was detected at such phase boundaries possibly due to a higher diffusivity of Na compared to K. Possible effects of the detected compositional fluctuations on cell performance are discussed.

  16. Study on microstructural changes in thermally-aged stainless steel weld-overlay cladding of nuclear reactor pressure vessels by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Takeuchi, T., E-mail: takeuchi.tomoaki@jaea.go.jp [Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Kameda, J. [National Institute for Materials Science, Sengen, Tsukuba 305-0047 (Japan); Nagai, Y.; Toyama, T. [Oarai Center, Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Nishiyama, Y.; Onizawa, K. [Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)

    2011-08-15

    Highlights: > Microstructural changes in stainless steel electroslag weld-overlay cladding. > Thermal aging caused progress of spinodal decomposition and precipitation of G phases in the {delta}-ferrite phase. > The degree of the spinodal decomposition had a linear relationship to the hardness. - Abstract: The effect of thermal aging on microstructural changes was investigated in stainless steel weld-overlay cladding composed of 90% austenite and 10% {delta}-ferrite phases using atom probe tomography (APT). In as-received materials subjected to cooling process after post-welding heat treatments (PWHT), a slight fluctuation of the Cr concentration was already observed due to spinodal decomposition in the ferrite phase but not in the austenitic phase. Thermal aging at 400 deg. C for 10,000 h caused not only an increase in the amplitude of spinodal decomposition but also the precipitation of G phases with composition ratios of Ni:Si:Mn = 16:7:6 in the ferrite phase. The chemical compositions of M{sub 23}C{sub 6} type carbides seemed to be formed at the austenite/ferrite interface were analyzed. The analyses of the magnitude of the spinodal decomposition and the hardness implied that the spinodal decomposition was the main cause of the hardening.

  17. Study on microstructural changes in thermally-aged stainless steel weld-overlay cladding of nuclear reactor pressure vessels by atom probe tomography

    International Nuclear Information System (INIS)

    Highlights: → Microstructural changes in stainless steel electroslag weld-overlay cladding. → Thermal aging caused progress of spinodal decomposition and precipitation of G phases in the δ-ferrite phase. → The degree of the spinodal decomposition had a linear relationship to the hardness. - Abstract: The effect of thermal aging on microstructural changes was investigated in stainless steel weld-overlay cladding composed of 90% austenite and 10% δ-ferrite phases using atom probe tomography (APT). In as-received materials subjected to cooling process after post-welding heat treatments (PWHT), a slight fluctuation of the Cr concentration was already observed due to spinodal decomposition in the ferrite phase but not in the austenitic phase. Thermal aging at 400 deg. C for 10,000 h caused not only an increase in the amplitude of spinodal decomposition but also the precipitation of G phases with composition ratios of Ni:Si:Mn = 16:7:6 in the ferrite phase. The chemical compositions of M23C6 type carbides seemed to be formed at the austenite/ferrite interface were analyzed. The analyses of the magnitude of the spinodal decomposition and the hardness implied that the spinodal decomposition was the main cause of the hardening.

  18. Direct imaging of thermally-activated grain-boundary diffusion in Cu/Co/IrMn/Pt exchange-bias structures using atom-probe tomography

    International Nuclear Information System (INIS)

    Magnetic devices are often subject to thermal processing steps, such as field cooling to set exchange bias and annealing to crystallize amorphous magnetic electrodes. These processing steps may result in interdiffusion and the subsequent deterioration of magnetic properties. In this study, we investigated thermally-activated diffusion in Cu/Co/IrMn/Pt exchange biased polycrystalline thin-film structures using atom probe tomography. Images taken after annealing at 400 °C for 60 min revealed Mn diffusion into Co grains at the Co/IrMn interface and along Pt grain boundaries for the IrMn/Pt stack, i.e., a Harrison type C regime. Annealing at 500 °C showed further Mn diffusion into Co grains. At the IrMn/Pt interface, annealing at 500 °C led to a type B behavior since Mn diffusion was detected both along Pt grain boundaries and also into Pt grains. The deterioration of the films' exchange bias properties upon annealing was correlated to the observed diffusion. In particular, the topmost Pt capping layer thickness turned out to be crucial since a faster deterioration of the exchange bias properties for thicker caps was observed. This is consistent with the idea that Pt acts as a getter for Mn, drawing Mn out of the IrMn layer

  19. Analysis of a New High-Toughness Ultra-high-Strength Martensitic Steel by Transmission Electron Microscopy and Atom Probe Tomography

    Science.gov (United States)

    Hartshorne, Matthew I.; McCormick, Caroline; Schmidt, Michael; Novotny, Paul; Isheim, Dieter; Seidman, David N.; Taheri, Mitra L.

    2016-04-01

    The microstructure of a new martensitic high-strength steel (Fe-0.40C-3.81Ni-1.31Cr-1.50Si-0.75Mn-0.52Mo-0.51Cu-0.30V) with high fracture toughness is characterized by transmission electron microscopy and atom probe tomography (APT). MC, M6C, and M23C6 precipitates form inside the martensitic lath matrix. The fracture toughness is insensitive to the dissolution of M23C6 precipitates at austenitizing temperatures above 1164 K (891 °C). APT reveals that solute segregation at the prior austenite grain boundaries (PAGB) is not uniform, with C, Mo, Si, Ni, and/or P enrichment varying at different areas of the PAGB. Si depletion is detected in the same area as the highest C enrichment. Carbon also segregates at lath boundaries. Segregation of C indicates the presence of retained austenite films at both PAGB and lath boundaries. Regions enriched in C up to 10 pct were found within the laths; however, no regions were enriched to the level expected of cementite or ɛ-carbide. The observed C distribution and high fracture toughness indicates that the tempering behavior is significantly different than that observed in 300M steel. The effect of Si, Ni, and Cu on the formation and stabilization of the regions of C enrichment and retained austenite require further study, as it may be key to the increased toughness.

  20. Nanoscale phase separation in epitaxial Cr-Mo and Cr-V alloy thin films studied using atom probe tomography: Comparison of experiments and simulation

    International Nuclear Information System (INIS)

    Tailored metal alloy thin film-oxide interfaces generated using molecular beam epitaxy (MBE) deposition of alloy thin films on a single crystalline oxide substrate can be used for detailed studies of irradiation damage response on the interface structure. However, the presence of nanoscale phase separation in the MBE grown alloy thin films can impact the metal-oxide interface structure. Due to nanoscale domain size of such phase separation, it is very challenging to characterize by conventional techniques. Therefore, laser assisted atom probe tomography (APT) was utilized to study the phase separation in epitaxial Cr0.61Mo0.39, Cr0.77Mo0.23, and Cr0.32V0.68 alloy thin films grown by MBE on MgO(001) single crystal substrates. Statistical analysis, namely frequency distribution analysis and Pearson coefficient analysis of experimental data was compared with similar analyses conducted on simulated APT datasets with known extent of phase separation. Thus, the presence of phase separation in Cr-Mo films, even when phase separation was not clearly observed by x-ray diffraction, and the absence of phase separation in the Cr-V film were confirmed

  1. Effects of Laser Energy and Wavelength on the Analysis of LiFePO4 Using Laser Assisted Atom Probe Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Santhanagopalan, Dhamodaran; Schreiber, Daniel K.; Perea, Daniel E.; Martens, Rich; Janssen, Yuri; Kalifah, Peter; Meng, Ying S.

    2015-01-21

    The effects of laser wavelength (355 nm and 532 nm) and laser pulse energy on the quantitative accuracy of atom probe tomography (APT) examinations of LiFePO4 (LFP) are considered. A systematic investigation of ultraviolet (UV, 355 nm) and green (532 nm) laser assisted APT of LFP has revealed distinctly different behaviors. With the use of UV laser the major issue was identified as the preferential loss of oxygen (up to 10 at. %) while other elements (Li, Fe and P) were observed to be close to nominal ratios. Lowering the laser energy per pulse to 1 pJ increased the observed oxygen concentration to near its correct stoichiometry and was well correlated with systematically higher concentrations of 16O2+ ions. This observation supports the premise that lower laser energies lead to a higher probability of oxygen molecule ionization. Conversely, at higher laser energies the resultant lower effective electric field reduces the probability of oxygen molecule ionization. Green laser assisted field evaporation led to the selective loss of Li (~50% deficiency) and correct ratios of the remaining elements, including the oxygen concentration. The loss of Li is explained by selective dc evaporation of lithium between laser pulses and relatively negligible oxygen loss as neutrals during green-laser pulsing. Lastly, plotting of multihit events on a Saxey plot for the straight-flight path data (green laser only) revealed a surprising dynamic recombination process for some molecular ions mid-flight.

  2. Comparative and complementary characterization of precipitate microstructures in Al-Mg-Si(-Li) alloys by transmission electron microscopy, energy dispersive X-ray spectroscopy and atom probe tomography

    International Nuclear Information System (INIS)

    Highlights: • Microalloying addition of Li enhances the age-hardening response of Al-Mg-Si alloys. • Size and number density of nanoclusters or precipitates are increased by Li addition. • Mg and Si contents within the aggregates are inversely decreased by Li addition. • Microalloying Li accelerates heterogeneous nucleation of such Mg-Si aggregates. - Abstract: In this study, comparative and complementary characterization of precipitate microstructures by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and atom probe tomography (APT) has been performed for Al-0.55 wt%Mg-0.89 wt%Si(-0.043 wt%Li) alloys aged at 433 K for 1.2 ks (under aging) and 36 ks (peak aging). Quantitative estimation of nanometer-scale clusters (nanoclusters) and β″ precipitates by TEM and APT revealed that microalloying addition of Li increases the size and number density of these Mg-Si aggregates, resulting in the enhanced age-hardening response. Positive evidence by APT for the segregation of Li suggests that heterogeneous nucleation of such Mg-Si aggregates with the aid of Li is attributed to the modified precipitate microstructures and thus improved mechanical strength of this alloy system

  3. Atom probe tomography study of Mg-dependent precipitation of Ω phase in initial aged Al-Cu–Mg–Ag alloys

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Song [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); Zhou, Xuanwei [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); Patent Examination Cooperation Center of the Patent Office, SIPO, Guangdong (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); Ying, Puyou; Liu, Meng; Zeng, Sumin [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)

    2015-06-18

    The association between Mg variations and the precipitation of Ω phase in Al–Cu–Mg–Ag alloys were investigated by transmission electron microscopy and quantitative atom probe tomography analysis. After aging at 165 °C for 2 h, the highest number density of Ω phase was revealed in 0.81Mg alloy, leading to the highest strength properties. The lowest strength properties of 0.39Mg alloy was related to the lowest precipitation kinetics of Ω phase. The parabolic change in the plate number density with increasing Mg highlighted the existence of a critical Mg content that contributed to the strongest precipitation kinetics of Ω phase. The number density of Mg–Ag co-clusters was not the sole factor in controlling the Ω precipitation. It was found that the precipitation of Ω phase was not only determined by initial Mg–Ag co-clustering but also related to the effective competition for solutes. In addition, the cluster-dominated microstructure facilitated the dense precipitation of Ω phase.

  4. Comparative and complementary characterization of precipitate microstructures in Al-Mg-Si(-Li) alloys by transmission electron microscopy, energy dispersive X-ray spectroscopy and atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Koshino, Yuki [Department of Mechanical Engineering and Materials Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501 (Japan); Kozuka, Masaya [Materials Research Laboratory, Kobe Steel, Ltd., 1-5-5 Takatsukadai, Nishi-ku, Kobe 651-2271 (Japan); Hirosawa, Shoichi, E-mail: hirosawa@ynu.ac.jp [Department of Mechanical Engineering and Materials Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501 (Japan); Aruga, Yasuhiro [Materials Research Laboratory, Kobe Steel, Ltd., 1-5-5 Takatsukadai, Nishi-ku, Kobe 651-2271 (Japan)

    2015-02-15

    Highlights: • Microalloying addition of Li enhances the age-hardening response of Al-Mg-Si alloys. • Size and number density of nanoclusters or precipitates are increased by Li addition. • Mg and Si contents within the aggregates are inversely decreased by Li addition. • Microalloying Li accelerates heterogeneous nucleation of such Mg-Si aggregates. - Abstract: In this study, comparative and complementary characterization of precipitate microstructures by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and atom probe tomography (APT) has been performed for Al-0.55 wt%Mg-0.89 wt%Si(-0.043 wt%Li) alloys aged at 433 K for 1.2 ks (under aging) and 36 ks (peak aging). Quantitative estimation of nanometer-scale clusters (nanoclusters) and β″ precipitates by TEM and APT revealed that microalloying addition of Li increases the size and number density of these Mg-Si aggregates, resulting in the enhanced age-hardening response. Positive evidence by APT for the segregation of Li suggests that heterogeneous nucleation of such Mg-Si aggregates with the aid of Li is attributed to the modified precipitate microstructures and thus improved mechanical strength of this alloy system.

  5. Atom probe tomography study of Mg-dependent precipitation of Ω phase in initial aged Al-Cu–Mg–Ag alloys

    International Nuclear Information System (INIS)

    The association between Mg variations and the precipitation of Ω phase in Al–Cu–Mg–Ag alloys were investigated by transmission electron microscopy and quantitative atom probe tomography analysis. After aging at 165 °C for 2 h, the highest number density of Ω phase was revealed in 0.81Mg alloy, leading to the highest strength properties. The lowest strength properties of 0.39Mg alloy was related to the lowest precipitation kinetics of Ω phase. The parabolic change in the plate number density with increasing Mg highlighted the existence of a critical Mg content that contributed to the strongest precipitation kinetics of Ω phase. The number density of Mg–Ag co-clusters was not the sole factor in controlling the Ω precipitation. It was found that the precipitation of Ω phase was not only determined by initial Mg–Ag co-clustering but also related to the effective competition for solutes. In addition, the cluster-dominated microstructure facilitated the dense precipitation of Ω phase

  6. Analysis of dynamic segregation and crystallisation in Mg{sub 65}Cu{sub 25}Y{sub 10} bulk metallic glass using atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Laws, K.J., E-mail: k.laws@unsw.edu.au [Australian Research Council Centre of Excellence for Design in Light Metals (Australia); School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Saxey, D.W. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH (United Kingdom); School of Physics, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia. (Australia); McKenzie, W.R. [School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Electron Microscopy Unit, Mark Wainwright Analytical Centre, University of New South Wales, Sydney, NSW 2052 (Australia); Marceau, R.K.W. [Australian Research Council Centre of Excellence for Design in Light Metals (Australia); Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Max-Planck Institut fuer Eisenforschung, Max-Planck-Str.1, Duesseldorf, D-40237 (Germany); Gun, B. [Australian Research Council Centre of Excellence for Design in Light Metals (Australia); School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Ringer, S.P. [Australian Research Council Centre of Excellence for Design in Light Metals (Australia); Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Ferry, M. [Australian Research Council Centre of Excellence for Design in Light Metals (Australia); School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia)

    2012-10-30

    In order to develop an in-depth understanding of the flow behaviour and dynamic devitrification processes of metallic glasses in the supercooled liquid region, tensile testing of amorphous Mg{sub 65}Cu{sub 25}Y{sub 10} samples was carried out at temperatures from 150 to 170 Degree-Sign C and at strain rates from 1 Multiplication-Sign 10{sup -3} s{sup -1} to 1 Multiplication-Sign 10{sup -2} s{sup -1}. Tensile data showed a consistent and reproducible inflexion in flow stress at a particular strain that was largely independent of strain rate. This was followed by a dramatic increase in flow stress occuring prior to the determined onset times of static crystallisation. Samples were analysed using atom probe tomography and the results indicate that tensile straining of the initially homogeneous amorphous alloy results in segregation into two distinct glassy phases via a shear-related process, coincident with the maximum shear plane angle, followed by the evolution of regions corresponding to the composition of a number of equilibrium binary and ternary intermetallic phases.

  7. Atom probe tomography of the austenite-ferrite interphase boundary composition in a model alloy Fe-C-Mn

    Energy Technology Data Exchange (ETDEWEB)

    Thuillier, O. [Groupe de Physique des Materiaux, UMR CNRS 6634, Institut des Materiaux de Rouen, Universite de Rouen, 76 801 Saint Etienne du Rouvray Cedex (France)]. E-mail: olivier.thuillier@etu.univ-rouen.fr; Danoix, F. [Groupe de Physique des Materiaux, UMR CNRS 6634, Institut des Materiaux de Rouen, Universite de Rouen, 76 801 Saint Etienne du Rouvray Cedex (France); Goune, M. [Arcelor Research, Voie Romaine B.P. 320, 57214 Maizieres-Les-Metz (France); Blavette, D. [Groupe de Physique des Materiaux, UMR CNRS 6634, Institut des Materiaux de Rouen, Universite de Rouen, 76 801 Saint Etienne du Rouvray Cedex (France)

    2006-12-15

    A tomographic atom p analysis has been developed to study the interfacial conditions during isothermal austenite transformation to ferrite at 700 deg. C in an Fe-C-Mn model alloy. The interfacial conditions lead to different alloying element profiles across the interface, and a comparison is made between this experimental result and the DICTRA software predictions under the various conditions.

  8. Effects of laser energy and wavelength on the analysis of LiFePO4 using laser assisted atom probe tomography

    International Nuclear Information System (INIS)

    The effects of laser wavelength (355 nm and 532 nm) and laser pulse energy on the quantitative analysis of LiFePO4 by atom probe tomography are considered. A systematic investigation of ultraviolet (UV, 355 nm) and green (532 nm) laser assisted field evaporation has revealed distinctly different behaviors. With the use of a UV laser, the major issue was identified as the preferential loss of oxygen (up to 10 at%) while other elements (Li, Fe and P) were observed to be close to nominal ratios. Lowering the laser energy per pulse to 1 pJ/pulse from 50 pJ/pulse increased the observed oxygen concentration to nearer its correct stoichiometry, which was also well correlated with systematically higher concentrations of 16O2+ ions. Green laser assisted field evaporation led to the selective loss of Li (∼33% deficiency) and a relatively minor O deficiency. The loss of Li is likely a result of selective dc evaporation of Li between or after laser pulses. Comparison of the UV and green laser data suggests that the green wavelength energy was absorbed less efficiently than the UV wavelength because of differences in absorption at 355 and 532 nm for LiFePO4. Plotting of multihit events on Saxey plots also revealed a strong neutral O2 loss from molecular dissociation, but quantification of this loss was insufficient to account for the observed oxygen deficiency. - Highlights: • Laser wavelength and pulse energy affect accuracy of APT analysis of LiFePO4. • Oxygen deficiency observed for UV laser; stronger at higher laser energies. • Selective loss of Li with green laser due to dc evaporation. • Saxey plots reveal prevalent formation of O2 neutrals. • Quantification of molecular dissociations cannot account for O deficiency

  9. Role of W and Mn for reliable 1X nanometer-node ultra-large-scale integration Cu interconnects proved by atom probe tomography

    International Nuclear Information System (INIS)

    We used atom probe tomography (APT) to study the use of a Cu(Mn) as a seed layer of Cu, and a Co(W) single-layer as reliable Cu diffusion barriers for future interconnects in ultra-large-scale integration. The use of Co(W) layer enhances adhesion of Cu to prevent electromigration and stress-induced voiding failures. The use of Cu(Mn) as seed layer may enhance the diffusion barrier performance of Co(W) by stuffing the Cu diffusion pass with Mn. APT was used to visualize the distribution of W and Mn in three dimensions with sub-nanometer resolution. W was found to segregate at the grain boundaries of Co, which prevents diffusion of Cu via the grain boundaries. Mn was found to diffuse from the Cu(Mn) layer to Co(W) layer and selectively segregate at the Co(W) grain boundaries with W, reinforcing the barrier properties of Co(W) layer. Hence, a Co(W) barrier coupled with a Cu(Mn) seed layer can form a sufficient diffusion barrier with film that is less than 2.0-nm-thick. The diffusion barrier behavior was preserved following a 1-h annealing at 400 °C. The underlayer of the Cu interconnects requires a large adhesion strength with the Cu, as well as low electrical resistivity. The use of Co(W) has previously been shown to satisfy these requirements, and addition of Mn is not expected to deteriorate these properties.

  10. Effects of laser energy and wavelength on the analysis of LiFePO{sub 4} using laser assisted atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Santhanagopalan, Dhamodaran [Department of NanoEngineering, University of California San Diego, CA 92093 (United States); Schreiber, Daniel K. [Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Perea, Daniel E. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Martens, Richard L. [Central Analytical Facility, University of Alabama, Tuscaloosa, AL 35487 (United States); Janssen, Yuri [Department of Chemistry, Stony Brook University, Stony Brook, NY 11790-3400 (United States); Khalifah, Peter [Department of Chemistry, Stony Brook University, Stony Brook, NY 11790-3400 (United States); Department of Chemistry, Brookhaven National Laboratory, Upton, NY 11793-5000 (United States); Meng, Ying Shirley, E-mail: shirleymeng@ucsd.edu [Department of NanoEngineering, University of California San Diego, CA 92093 (United States)

    2015-01-15

    The effects of laser wavelength (355 nm and 532 nm) and laser pulse energy on the quantitative analysis of LiFePO{sub 4} by atom probe tomography are considered. A systematic investigation of ultraviolet (UV, 355 nm) and green (532 nm) laser assisted field evaporation has revealed distinctly different behaviors. With the use of a UV laser, the major issue was identified as the preferential loss of oxygen (up to 10 at%) while other elements (Li, Fe and P) were observed to be close to nominal ratios. Lowering the laser energy per pulse to 1 pJ/pulse from 50 pJ/pulse increased the observed oxygen concentration to nearer its correct stoichiometry, which was also well correlated with systematically higher concentrations of {sup 16}O{sub 2}{sup +} ions. Green laser assisted field evaporation led to the selective loss of Li (∼33% deficiency) and a relatively minor O deficiency. The loss of Li is likely a result of selective dc evaporation of Li between or after laser pulses. Comparison of the UV and green laser data suggests that the green wavelength energy was absorbed less efficiently than the UV wavelength because of differences in absorption at 355 and 532 nm for LiFePO{sub 4}. Plotting of multihit events on Saxey plots also revealed a strong neutral O{sub 2} loss from molecular dissociation, but quantification of this loss was insufficient to account for the observed oxygen deficiency. - Highlights: • Laser wavelength and pulse energy affect accuracy of APT analysis of LiFePO{sub 4}. • Oxygen deficiency observed for UV laser; stronger at higher laser energies. • Selective loss of Li with green laser due to dc evaporation. • Saxey plots reveal prevalent formation of O{sub 2} neutrals. • Quantification of molecular dissociations cannot account for O deficiency.

  11. Atomic probes of new physics

    CERN Document Server

    Frugiuele, Claudia; Perez, Gilad; Schlaffer, Matthias

    2016-01-01

    Precise isotope shift spectroscopy in various atomic systems can provide a sensitive tool to constrain new physics, in particular new physics that couples to electrons and neutrons [1]. We present an analysis for estimating the reach of such measurements in the framework of effective field theory and various benchmark models for SM extensions: color neutral vector resonances, leptoquarks and the $750\\,\\textrm{GeV}$ scalar diphoton resonance. We also provide a comparison with the reach of the LHC, $e^+e^-$ colliders and $g-2$ of the electron. Isotope shift spectroscopy can compete and possibly even improve the sensitivity to probe a broad variety of Standard Model extensions.

  12. Retained Austenite Decomposition and Carbide Formation During Tempering a Hot-Work Tool Steel X38CrMoV5-1 Studied by Dilatometry and Atom Probe Tomography

    Science.gov (United States)

    Lerchbacher, Christoph; Zinner, Silvia; Leitner, Harald

    2012-12-01

    The microstructural development of a hot-work tool steel X38CrMoV5-1 during continuous heating to tempering temperature has been investigated with the focus on the decomposition of retained austenite (Stage II) and carbide formation (Stages III and IV). Investigations have been carried out after heating to 673.15 K, 773.15 K, 883.15 K (400 °C, 500 °C, 610 °C) and after a dwell time of 600 seconds at 883.15 K (610 °C). Dilatometry and atom probe tomography were used to identify tempering reactions. A distinctive reaction takes place between 723.15 K and 823.15 K (450 °C and 550 °C) which is determined to be the formation of M3C from transition carbides. Stage II could be evidenced with the atom probe results and indirectly with dilatometry, indicating the formation of new martensite during cooling. Retained austenite decomposition starts with the precipitation of alloy carbides formed from nanometric interlath retained austenite films which are laminary arranged and cause a reduction of the carbon content within the retained austenite. Preceding enrichment of substitutes at the matrix/carbide interface in the early stages of Cr7C3 alloy carbide formation could be visualised on the basis of coarse M3C carbides within the matrix. Atom probe tomography has been found to be very useful to complement dilatational experiments in order to characterise and identify microstructural changes.

  13. Atom Probe Tomographic Mapping Directly Reveals the Atomic Distribution of Phosphorus in Resin Embedded Ferritin

    Energy Technology Data Exchange (ETDEWEB)

    Perea, Daniel E.; Liu, Jia; Bartrand, Jonah AG; Dicken, Quinten G.; Thevuthasan, Suntharampillai; Browning, Nigel D.; Evans, James E.

    2016-02-29

    Here we report the atomic-scale analysis of biological interfaces using atom probe tomography. Embedding the protein ferritin in an organic polymer resin lacking nitrogen provided chemical contrast to visualize atomic distributions and distinguish organic-organic and organic-inorganic interfaces. The sample preparation method can be directly extended to further enhance the study of biological, organic and inorganic nanomaterials relevant to health, energy or the environment.

  14. Probing The Atomic Higgs Force

    CERN Document Server

    Delaunay, Cédric; Perez, Gilad; Soreq, Yotam

    2016-01-01

    We propose an approach to probe Higgs boson couplings to the building blocks of matter: the electron and the up and down quarks, with precision measurement of isotope shifts in atomic clock transitions. We show that the attractive Higgs force between nuclei and their bound electrons induces measurable non-linearities in a King plot of two isotope shifts. We present an experimental method which, given state-of-the-art accuracy in frequency comparison, competes with and potentially surpasses the Large Hadron Collider in bounding the Higgs-to-light-fermion couplings. Better knowledge of the latter is an important test of the Standard Model which could lead, besides the establishment of new physics above the weak scale, to an alternative understanding of the flavor puzzle.

  15. Phosphorus and boron diffusion paths in polycrystalline silicon gate of a trench-type three-dimensional metal-oxide-semiconductor field effect transistor investigated by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Han, Bin, E-mail: hanbin@imr.tohoku.ac.jp; Takamizawa, Hisashi, E-mail: takamizawa.hisashi@jaea.go.jp; Shimizu, Yasuo; Inoue, Koji; Nagai, Yasuyoshi [The Oarai Center, Institute for Materials Research, Tohoku University, 2145-2 Narita, Oarai, Ibaraki 311-1313 (Japan); Yano, Fumiko [Department of Electrical Engineering, Faculty of Engineering, Tokyo City University, 1-28-1 Tamazutsumi, Setagaya-ku, Tokyo 158-8557 (Japan); Kunimune, Yorinobu [Renesas Semiconductor Manufacturing Co., Ltd., 1120 Shimokuzawa, Sagamihara, Kanagawa 252-5298 (Japan); Inoue, Masao; Nishida, Akio [Renesas Electronics Corporation, 751 Horiguchi, Hitachinaka, Ibaraki 312-8504 (Japan)

    2015-07-13

    The dopant (P and B) diffusion path in n- and p-types polycrystalline-Si gates of trench-type three-dimensional (3D) metal-oxide-semiconductor field-effect transistors (MOSFETs) were investigated using atom probe tomography, based on the annealing time dependence of the dopant distribution at 900 °C. Remarkable differences were observed between P and B diffusion behavior. In the initial stage of diffusion, P atoms diffuse into deeper regions from the implanted region along grain boundaries in the n-type polycrystalline-Si gate. With longer annealing times, segregation of P on the grain boundaries was observed; however, few P atoms were observed within the large grains or on the gate/gate oxide interface distant from grain boundaries. These results indicate that P atoms diffuse along grain boundaries much faster than through the bulk or along the gate/gate oxide interface. On the other hand, in the p-type polycrystalline-Si gate, segregation of B was observed only at the initial stage of diffusion. After further annealing, the B atoms became uniformly distributed, and no clear segregation of B was observed. Therefore, B atoms diffuse not only along the grain boundary but also through the bulk. Furthermore, B atoms diffused deeper than P atoms along the grain boundaries under the same annealing conditions. This information on the diffusion behavior of P and B is essential for optimizing annealing conditions in order to control the P and B distributions in the polycrystalline-Si gates of trench-type 3D MOSFETs.

  16. Phosphorus and boron diffusion paths in polycrystalline silicon gate of a trench-type three-dimensional metal-oxide-semiconductor field effect transistor investigated by atom probe tomography

    International Nuclear Information System (INIS)

    The dopant (P and B) diffusion path in n- and p-types polycrystalline-Si gates of trench-type three-dimensional (3D) metal-oxide-semiconductor field-effect transistors (MOSFETs) were investigated using atom probe tomography, based on the annealing time dependence of the dopant distribution at 900 °C. Remarkable differences were observed between P and B diffusion behavior. In the initial stage of diffusion, P atoms diffuse into deeper regions from the implanted region along grain boundaries in the n-type polycrystalline-Si gate. With longer annealing times, segregation of P on the grain boundaries was observed; however, few P atoms were observed within the large grains or on the gate/gate oxide interface distant from grain boundaries. These results indicate that P atoms diffuse along grain boundaries much faster than through the bulk or along the gate/gate oxide interface. On the other hand, in the p-type polycrystalline-Si gate, segregation of B was observed only at the initial stage of diffusion. After further annealing, the B atoms became uniformly distributed, and no clear segregation of B was observed. Therefore, B atoms diffuse not only along the grain boundary but also through the bulk. Furthermore, B atoms diffused deeper than P atoms along the grain boundaries under the same annealing conditions. This information on the diffusion behavior of P and B is essential for optimizing annealing conditions in order to control the P and B distributions in the polycrystalline-Si gates of trench-type 3D MOSFETs

  17. Visions of Atomic Scale Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, T. F. [Cameca Instruments; Miller, Michael K [ORNL; Rajan, Krishna [Iowa State University; Ringer, S. P. [University of Sydney, Australia

    2012-01-01

    A microscope, by definition, provides structural and analytical information about objects that are too small to see with the unaided eye. From the very first microscope, efforts to improve its capabilities and push them to ever-finer length scales have been pursued. In this context, it would seem that the concept of an ultimate microscope would have received much attention by now; but has it really ever been defined? Human knowledge extends to structures on a scale much finer than atoms, so it might seem that a proton-scale microscope or a quark-scale microscope would be the ultimate. However, we argue that an atomic-scale microscope is the ultimate for the following reason: the smallest building block for either synthetic structures or natural structures is the atom. Indeed, humans and nature both engineer structures with atoms, not quarks. So far as we know, all building blocks (atoms) of a given type are identical; it is the assembly of the building blocks that makes a useful structure. Thus, would a microscope that determines the position and identity of every atom in a structure with high precision and for large volumes be the ultimate microscope? We argue, yes. In this article, we consider how it could be built, and we ponder the answer to the equally important follow-on questions: who would care if it is built, and what could be achieved with it?

  18. The 475 °C embrittlement in Fe–20Cr and Fe–20Cr–X (X=Ni, Cu, Mn) alloys studied by mechanical testing and atom probe tomography

    International Nuclear Information System (INIS)

    In the present work the 475 °C embrittlement in binary Fe–Cr and ternary Fe–Cr–X (X=Ni, Cu and Mn) alloys have been investigated. The mechanical properties were evaluated using microhardness and impact testing, and the structural evolution was evaluated using atom probe tomography (APT). The APT results after aging at 500 °C for 10 h clearly showed that both Ni and Mn accelerate the ferrite decomposition. No evident phase separation of either the Fe–20Cr or Fe–20Cr–1.5Cu samples was detected after 10 h of aging and thus no conclusions on the effect of Cu can be drawn. Cu clustering was however found in the Fe–20Cr–1.5Cu sample after 10 h aging at 500 °C. The mechanical property evolution was consistent with the structural evolution found from APT. Samples aged at 450 and 500 °C all showed increasing hardness and decreasing impact energy. The embrittlement was observed to take place mainly during the first 10 h of aging and it could primarily be attributed to phase separation, but also substitutional solute clustering and possibly carbon and nitrogen segregation may contribute in a negative way

  19. Kinetics of secondary phase precipitation during spinodal decomposition in duplex stainless steels: A kinetic Monte Carlo model - Comparison with atom probe tomography experiments

    Science.gov (United States)

    Emo, Jonathan; Pareige, Cristelle; Saillet, Sébastien; Domain, Christophe; Pareige, Philippe

    2014-08-01

    This paper presents the first simulations of the kinetics of spinodal decomposition and G-phase precipitation occurring in ferrite of duplex stainless steels. The kinetics was simulated using a simple but effective atomic kinetic Monte Carlo model in a ternary alloy. The simulations reproduced the α/α‧ spinodal structure with precipitates at the α/α‧ interface. The comparison of simulated results with experiments shows that the simulations quantitatively reproduce the kinetics of phase transformation and the synergy observed experimentally between the spinodal decomposition and G-phase precipitation. By following the vacancy pathway, we show that the coarsening of G-phase precipitates proceeds via diffusion along the α/α‧ interfaces. The simulations made it possible to explain the origin of the kinetic synergy between spinodal decomposition and G-phase precipitation.

  20. Atom Probe Tomographic Mapping Directly Reveals the Atomic Distribution of Phosphorus in Resin Embedded Ferritin

    Science.gov (United States)

    Perea, Daniel E.; Liu, Jia; Bartrand, Jonah; Dicken, Quinten; Thevuthasan, S. Theva; Browning, Nigel D.; Evans, James E.

    2016-02-01

    Here we report the atomic-scale analysis of biological interfaces within the ferritin protein using atom probe tomography that is facilitated by an advanced specimen preparation approach. Embedding ferritin in an organic polymer resin lacking nitrogen provided chemical contrast to visualise atomic distributions and distinguish the inorganic-organic interface of the ferrihydrite mineral core and protein shell, as well as the organic-organic interface between the ferritin protein shell and embedding resin. In addition, we definitively show the atomic-scale distribution of phosphorus as being at the surface of the ferrihydrite mineral with the distribution of sodium mapped within the protein shell environment with an enhanced distribution at the mineral/protein interface. The sample preparation method is robust and can be directly extended to further enhance the study of biological, organic and inorganic nanomaterials relevant to health, energy or the environment.

  1. Carbon nanotube atomic force microscopy probes

    Science.gov (United States)

    Yamanaka, Shigenobu; Okawa, Takashi; Akita, Seiji; Nakayama, Yoshikazu

    2005-05-01

    We have developed a carbon nanotube atomic force microscope probe. Because the carbon nanotube are well known to have high aspect ratios, small tip radii and high stiffness, carbon nanotube probes have a long lifetime and can be applied for the observation deep trenches. Carbon nanotubes were synthesized by a well-controlled DC arc discharge method, because this method can make nanotubes to have straight shape and high crystalline. The nanotubes were aligned on the knife-edge using an alternating current electrophoresis technique. A commercially available Si probe was used for the base of the nanotube probe. The nanotube probe was fabricated by the SEM manipulation method. The nanotube was then attached tightly to the Si probe by deposition of amorphous carbon. We demonstrate the measurement of a fine pith grating that has vertical walls. However, a carbon nanotube has a problem that is called "Sticking". The sticking is a chatter image on vertical like region in a sample. We solved this problem by applying 2 methods, 1. a large cantilever vibration amplitude in tapping mode, 2. an attractive mode measurement. We demonstrate the non-sticking images by these methods.

  2. Amyloid-β positron emission tomography imaging probes

    DEFF Research Database (Denmark)

    Kepe, Vladimir; Moghbel, Mateen C; Långström, Bengt;

    2013-01-01

    number of factors appear to preclude these probes from clinical utilization. As the available "amyloid specific" positron emission tomography imaging probes have failed to demonstrate diagnostic value and have shown limited utility for monitoring therapeutic interventions in humans, a debate on their...

  3. Atomic level analysis of biomolecules by the scanning atom probe

    International Nuclear Information System (INIS)

    Utilizing the unique features of the scanning atom probe (SAP) the binding states of the biomolecules, leucine and methionine, are investigated at atomic level. The molecules are mass analyzed by detecting a single atom and/or clustering atoms field evaporated from a specimen surface. Since the field evaporation is a static process, the evaporated clustering atoms are closely related with the binding between atoms forming the molecules. For example, many thiophene radicals are detected when polythiophene is mass analyzed by the SAP. In the present study the specimens are prepared by immersing a micro cotton ball of single walled carbon nanotubes (SWCNT) in the leucine or methionine solution. The mass spectra obtained by analyzing the cotton balls exhibit singly and doubly ionized carbon ions of SWCNT and the characteristic fragments of the molecules, CH3, CHCH3, C4H7, CHNH2 and COOH for leucine and CH3, SCH3, C2H4, C4H7, CHNH2 and COOH for methionine.

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

    International Nuclear Information System (INIS)

    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

  5. An update in proton probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Sakellariou, A.; Cholewa, M.; Saint, A.; Legge, G.L.F. [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Howard, J. [Australian National Univ., Canberra, ACT (Australia). Research School of Physical Sciences

    1996-12-31

    The analysis of scanning transmission ion microscopy (STIM) tomography data is improved. The volumetric density information is obtained directly from an iterative convolution and back-projection (BFP) reconstruction method. The iterative method allows the effects of stopping-power to be incorporated easily. One draw back is that a priori constituency information is required for the iterative method to work However, this is of no concern because the iterative method was designed with PIXE tomography in mind. In this light, the a priori information will be obtained as the zeroth iteration of a PIXE tomography iterative reconstruction method. 4 refs., 1 tab., 4 figs.

  6. Preparation of Regular Specimens for Atom Probes

    Science.gov (United States)

    Kuhlman, Kim; Wishard, James

    2003-01-01

    A method of preparation of specimens of non-electropolishable materials for analysis by atom probes is being developed as a superior alternative to a prior method. In comparison with the prior method, the present method involves less processing time. Also, whereas the prior method yields irregularly shaped and sized specimens, the present developmental method offers the potential to prepare specimens of regular shape and size. The prior method is called the method of sharp shards because it involves crushing the material of interest and selecting microscopic sharp shards of the material for use as specimens. Each selected shard is oriented with its sharp tip facing away from the tip of a stainless-steel pin and is glued to the tip of the pin by use of silver epoxy. Then the shard is milled by use of a focused ion beam (FIB) to make the shard very thin (relative to its length) and to make its tip sharp enough for atom-probe analysis. The method of sharp shards is extremely time-consuming because the selection of shards must be performed with the help of a microscope, the shards must be positioned on the pins by use of micromanipulators, and the irregularity of size and shape necessitates many hours of FIB milling to sharpen each shard. In the present method, a flat slab of the material of interest (e.g., a polished sample of rock or a coated semiconductor wafer) is mounted in the sample holder of a dicing saw of the type conventionally used to cut individual integrated circuits out of the wafers on which they are fabricated in batches. A saw blade appropriate to the material of interest is selected. The depth of cut and the distance between successive parallel cuts is made such that what is left after the cuts is a series of thin, parallel ridges on a solid base. Then the workpiece is rotated 90 and the pattern of cuts is repeated, leaving behind a square array of square posts on the solid base. The posts can be made regular, long, and thin, as required for samples

  7. The emergence of local electrode/scanning atom probes

    International Nuclear Information System (INIS)

    Full text: Professor Nishikawa's idea of a scanning atom probe was first presented a little more than one decade ago. This concept spurred new thinking into the fundamentals of atom probe design. In the first five years after that presentation, three academic groups (Nishikawa et al., Kelly et al., and Cerezo et al.) built atom probes which incorporated his ideas. Over the ensuing 5 years, a commercial instrument based on these concepts, the local electrode atom probe or LEAP, was developed by Imago. This basic concept has enabled a major change in how atom probes may be utilized. In particular, the geometry of the specimen can take radically different forms and major performance improvements are possible. These changes have elevated the atom probe from a laboratory instrument to a viable commercial tool suitable for industrial applications. In this overview talk, a brief history of the scanning atom probe/local electrode atom probe will be given. The performance and application of the commercial atom probe which is based on Professor Nishikawa's basic concept will be described. Refs. 6 (author)

  8. Ultrathin lensed fiber-optic probe for optical coherence tomography.

    Science.gov (United States)

    Qiu, Y; Wang, Y; Belfield, K D; Liu, X

    2016-06-01

    We investigated and validated a novel method to develop ultrathin lensed fiber-optic (LFO) probes for optical coherence tomography (OCT) imaging. We made the LFO probe by attaching a segment of no core fiber (NCF) to the distal end of a single mode fiber (SMF) and generating a curved surface at the tip of the NCF using the electric arc of a fusion splicer. The novel fabrication approach enabled us to control the length of the NCF and the radius of the fiber lens independently. By strategically choosing these two parameters, the LFO probe could achieve a broad range of working distance and depth of focus for different OCT applications. A probe with 125μm diameter and lateral resolution up to 10μm was demonstrated. The low-cost, disposable and robust LFO probe is expected to have great potential for interstitial OCT imaging. PMID:27375934

  9. Soft-landing deposition of radioactive probe atoms on surfaces

    NARCIS (Netherlands)

    Laurens, C.R; Rosu, M.F; Pleiter, F; Niesen, L

    1999-01-01

    We present a method to deposit a wide range of radioactive probe atoms on surfaces, without introducing lattice damage or contaminating the surface with other elements or isotopes. In this method, the probe atoms are mass-separated using an isotope separa-tor, decelerated to 5 eV, and directly depos

  10. Microfluidics for Positron Emission Tomography (PET) Imaging Probe Development

    OpenAIRE

    Wang, Ming-Wei; Lin, Wei-Yu; Liu, Kan; Masterman-Smith, Michael; Shen, Clifton Kwang-Fu

    2010-01-01

    Due to increased needs for Positron Emission Tomography (PET) scanning, high demands for a wide variety of radiolabeled compounds will have to be met by exploiting novel radiochemistry and engineering technologies to improve the production and development of PET probes. The application of microfluidic reactors to perform radiosyntheses is currently attracting a great deal of interest because of their potential to deliver many advantages over conventional labeling systems. Microfluidic-based r...

  11. Prospects of linear reconstruction in atomic resolution electron holographic tomography

    International Nuclear Information System (INIS)

    Tomography commonly requires a linear relation between the measured signal and the underlying specimen property; for Electron Holographic Tomography this is given by the Phase Grating Approximation (PGA). While largely valid at medium resolution, discrepancies arise at high resolution imaging conditions. We set out to investigate the artefacts that are produced if the reconstruction still assumes the PGA even with an atomic resolution tilt series. To forego experimental difficulties the holographic tilt series was simulated. The reconstructed electric potential clearly shows peaks at the positions of the atoms. These peaks have characterisitic deformations, which can be traced back to the defocus a particular atom has in the holograms of the tilt series. Exchanging an atom for one of a different atomic number results in a significant change in the reconstructed potential that is well contained within the atom's peak. - Highlights: • We simulate a holographic tilt series of a nanocrystal with atomic resolution. • Using PGA-based Holographic Tomography we reconstruct the atomic structure. • The reconstruction shows characteristic artefacts, chiefly caused by defocus. • Changing one atom's Z produces a well localised in the reconstruction

  12. Prospects of linear reconstruction in atomic resolution electron holographic tomography

    Energy Technology Data Exchange (ETDEWEB)

    Krehl, Jonas, E-mail: Jonas.Krehl@triebenberg.de; Lubk, Axel

    2015-03-15

    Tomography commonly requires a linear relation between the measured signal and the underlying specimen property; for Electron Holographic Tomography this is given by the Phase Grating Approximation (PGA). While largely valid at medium resolution, discrepancies arise at high resolution imaging conditions. We set out to investigate the artefacts that are produced if the reconstruction still assumes the PGA even with an atomic resolution tilt series. To forego experimental difficulties the holographic tilt series was simulated. The reconstructed electric potential clearly shows peaks at the positions of the atoms. These peaks have characterisitic deformations, which can be traced back to the defocus a particular atom has in the holograms of the tilt series. Exchanging an atom for one of a different atomic number results in a significant change in the reconstructed potential that is well contained within the atom's peak. - Highlights: • We simulate a holographic tilt series of a nanocrystal with atomic resolution. • Using PGA-based Holographic Tomography we reconstruct the atomic structure. • The reconstruction shows characteristic artefacts, chiefly caused by defocus. • Changing one atom's Z produces a well localised in the reconstruction.

  13. Quantum teleportation with atoms: quantum process tomography

    International Nuclear Information System (INIS)

    The performance of a quantum teleportation algorithm implemented on an ion trap quantum computer is investigated. First the algorithm is analysed in terms of the teleportation fidelity of six input states evenly distributed over the Bloch sphere. Furthermore, a quantum process tomography of the teleportation algorithm is carried out which provides almost complete knowledge about the algorithm

  14. Optical atomic magnetometry for magnetic induction tomography of the heart

    CERN Document Server

    Deans, Cameron; Hussain, Sarah; Renzoni, Ferruccio

    2016-01-01

    We report on the use of radio-frequency optical atomic magnetometers for magnetic induction tomography measurements. We demonstrate the imaging of dummy targets of varying conductivities placed in the proximity of the sensor, in an unshielded environment at room-temperature and without background subtraction. The images produced by the system accurately reproduce the characteristics of the actual objects. Furthermore, we perform finite element simulations in order to assess the potential for measuring low-conductivity biological tissues with our system. Our results demonstrate the feasibility of an instrument based on optical atomic magnetometers for magnetic induction tomography imaging of biological samples, in particular for mapping anomalous conductivity in the heart.

  15. Fabrication of an all-metal atomic force microscope probe

    DEFF Research Database (Denmark)

    Rasmussen, Jan Pihl; Tang, Peter Torben; Hansen, Ole;

    1997-01-01

    This paper presents a method for fabrication of an all-metal atomic force microscope probe (tip, cantilever and support) for optical read-out, using a combination of silicon micro-machining and electroforming. The paper describes the entire fabrication process for a nickel AFM-probe. In addition...

  16. Coaxial atomic force microscope probes for imaging with dielectrophoresis

    OpenAIRE

    Brown, Keith; Berezovsky, Jesse; Westervelt, Robert M.

    2011-01-01

    We demonstrate atomic force microscope (AFM) imaging using dielectrophoresis (DEP) with coaxial probes. DEP provides force contrast allowing coaxial probes to image with enhanced spatial resolution. We model a coaxial probe as an electric dipole to provide analytic formulas for DEP between a dipole, dielectric spheres, and a dielectric substrate. AFM images taken of dielectric spheres with and without an applied electric field show the disappearance of artifacts when imaging with DEP. Quantit...

  17. Atomic probes of surface structure and dynamics

    International Nuclear Information System (INIS)

    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 H2 on Cu(110) are being studied. (R.W.R.) 64 refs

  18. Probing a Bose-Einstein Condensate with an Atom Laser

    OpenAIRE

    Döring, D.; Robins, N. P.; Figl, C.; Close, J. D.

    2008-01-01

    A pulsed atom laser derived from a Bose-Einstein condensate is used to probe a second target condensate. The target condensate scatters the incident atom laser pulse. From the spatial distribution of scattered atoms, one can infer important properties of the target condensate and its interaction with the probe pulse. As an example, we measure the s-wave scattering length that, in low energy collisions, describes the interaction between the |F=1,m_F=-1> and |F=2,m_F=0> hyperfine ground states ...

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

    Energy Technology Data Exchange (ETDEWEB)

    Felfer, P., E-mail: peter.felfer@sydney.edu.au [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Ceguerra, A.V., E-mail: anna.ceguerra@sydney.edu.au [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Ringer, S.P., E-mail: simon.ringer@sydney.edu.au [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Cairney, J.M., E-mail: julie.cairney@sydney.edu.au [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia)

    2015-03-15

    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.

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

    International Nuclear Information System (INIS)

    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

  1. Continuous Measurement Quantum State Tomography of Atomic Ensembles

    CERN Document Server

    Riofrío, Carlos A

    2011-01-01

    Quantum state tomography is a fundamental tool in quantum information processing. It allows us to estimate the state of a quantum system by measuring different observables on many identically prepared copies of the system. This is, in general, a very time-consuming task that requires a large number of measurements. There are, however, systems in which the data acquisition can be done more efficiently. In fact, an ensemble of quantum systems can be prepared and manipulated by external fields while being continuously and collectively probed, producing enough information to estimate its state. This provides a basis for continuous measurement quantum tomography. In this protocol, an ensemble of identically prepared systems is collectively probed and controlled in a time-dependent manner to create an informationally complete continuous measurement record. The measurement history is then inverted to determine the state at the initial time. We use two different estimation methods: maximum likelihood and compressed s...

  2. Probing Dark Energy with Atom Interferometry

    CERN Document Server

    Burrage, Clare; 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.

  3. Spatial decomposition of molecular ions within 3D atom probe reconstructions.

    Science.gov (United States)

    Breen, Andrew; Moody, Michael P; Gault, Baptiste; Ceguerra, Anna V; Xie, Kelvin Y; Du, Sichao; Ringer, Simon P

    2013-09-01

    Two methods for separating the constituent atoms of molecular ions within atom probe tomography reconstructions are presented. The Gaussian Separation Method efficiently deconvolutes molecular ions containing two constituent atoms and is tested on simulated data before being applied to an experimental HSLA steel dataset containing NbN. The Delaunay Separation Method extends separation to larger complex ions and is also tested on simulated data before being applied to an experimental GaAs dataset containing many large (>3 atoms) complex ions. First nearest neighbour (1NN) distributions and images of the reconstruction before and after the separations are used to show the effect of the algorithms and their validity and practicality are also discussed. PMID:23522847

  4. Compact piezoelectric transducer fiber scanning probe for optical coherence tomography.

    Science.gov (United States)

    Zhang, Ning; Tsai, Tsung-Han; Ahsen, Osman O; Liang, Kaicheng; Lee, Hsiang-Chieh; Xue, Ping; Li, Xingde; Fujimoto, James G

    2014-01-15

    We developed a compact, optical fiber scanning piezoelectric transducer (PZT) probe for endoscopic and minimally invasive optical coherence tomography (OCT). Compared with previous forward-mount fiber designs, we present a reverse-mount design that achieves a shorter rigid length. The fiber was mounted at the proximal end of a quadruple PZT tube and scanned inside the hollow PZT tube to reduce the probe length. The fiber resonant frequency was 338 Hz using a 17-mm-long fiber. A 0.9 mm fiber deflection was achieved with a driving amplitude of 35 V. Using a GRIN lens-based optical design with a 1.3× magnification, a ∼6 μm spot was scanned over a 1.2 mm diameter field. The probe was encased in a metal hypodermic tube with a ∼25 mm rigid length and covered with a 3.2 mm outer diameter (OD) plastic sheath. Imaging was performed with a swept source OCT system based on a Fourier domain modelocked laser (FDML) light source at a 240 kHz axial scan rate and 8 μm axial resolution (in air). En face OCT imaging of skin in vivo and human colon ex vivo was demonstrated. PMID:24562102

  5. Surface forces studied with colloidal probe atomic force microscopy

    OpenAIRE

    Giesbers, M.

    2001-01-01

    Forces between surfaces are a determining factor for the performance of natural as well as synthetic colloidal systems, and play a crucial role in industrial production processes. Measuring these forces is a scientific and experimental challenge and over the years several techniques have been developed to measure the interaction between surfaces directly as a function of their separation distance. Colloidal probe atomic force microscopy (colloidal probe AFM) offers the possibility to study su...

  6. Atom probe field ion microscopy characterizations of VVER steels

    International Nuclear Information System (INIS)

    An atom probe field ion microscopy (APFIM) characterization of Soviet types 15Kh2MFA Cr-Mo-V (VVER 440) and 15Kh2NMFA Ni-Cr-Mo-V (VVER 1000) pressure vessel steels has been performed. Field ion microscopy has revealed that the lath boundaries in unirradiated VVER 440 and VVER 1000 steels are decorated with a thin film of brightly-imaging molybdenum carbonitride precipitates and some coarser vanadium carbides. Atom probe analysis has revealed significant enrichments of phosphorous at the lath boundaries

  7. ATOM PROBE STUDY OF TITANIUM BASE ALLOYS : PRELIMINARY RESULTS

    OpenAIRE

    Menand, A.; Chambreland, S.; Martin, C

    1986-01-01

    Two different titanium base alloys, Ti46 Al54 and Ti88.8 Cu2.3, Al8.9, have been studied by atom probe microanalysis. A precipitate of Ti2 Al was analysed in the binary alloys. Micro-analysis of Ti Cu Al alloy revealed the presence of Copper enriched zones. The study has also exhibited a penetration of Hydrogen in the samples, probably due to preparation technique. The results demonstrate the feasibility of studies on titanium base alloys by mean of atom probe.

  8. Semiconductor studies by radioactive probe atoms

    International Nuclear Information System (INIS)

    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

  9. FIM AND ATOM-PROBE STUDY OF POLYMERS

    OpenAIRE

    Maruyama, T.; Y. Hasegawa; Nishi, T; T. Sakurai

    1987-01-01

    A field ion microscope makes it possible to observe the surface structures of metals and semiconductors at the atomic level and an atom-probe (FIM), which is a FIM with a mass spectrometer, has been widely used to study the chemical compositions of specimens. Some attempts were made previously to visualize polymers such as biological molecules. They are usually insulators and, thus, are difficult to be imaged by the FIM. Furthermore, molecules are known to decompose or desorb before a needed ...

  10. Optical atomic magnetometry for magnetic induction tomography of the heart

    OpenAIRE

    Deans, Cameron; Marmugi, Luca; Hussain, Sarah; Renzoni, Ferruccio

    2016-01-01

    We report on the use of radio-frequency optical atomic magnetometers for magnetic induction tomography measurements. We demonstrate the imaging of dummy targets of varying conductivities placed in the proximity of the sensor, in an unshielded environment at room-temperature and without background subtraction. The images produced by the system accurately reproduce the characteristics of the actual objects. Furthermore, we perform finite element simulations in order to assess the potential for ...

  11. Spatial decomposition of molecular ions within 3D atom probe reconstructions

    Energy Technology Data Exchange (ETDEWEB)

    Breen, Andrew [School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Australian Centre for Microscopy and Microanalysis, Madsen Building F09, The University of Sydney, NSW 2006 (Australia); Moody, Michael P. [Department of Materials, University of Oxford, Parks Road, OX13PH, Oxford (United Kingdom); Gault, Baptiste [Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, Ont. L8S4L8 (Canada); Ceguerra, Anna V. [School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Australian Centre for Microscopy and Microanalysis, Madsen Building F09, The University of Sydney, NSW 2006 (Australia); Xie, Kelvin Y. [Johns Hopkins University, Department of Mechanical Engineering, Baltimore, MD 21218 (United States); Du, Sichao [Australian Centre for Microscopy and Microanalysis, Madsen Building F09, The University of Sydney, NSW 2006 (Australia); School of Physics, The University of Sydney, NSW 2006 (Australia); Ringer, Simon P., E-mail: simon.ringer@sydney.edu.au [School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Australian Centre for Microscopy and Microanalysis, Madsen Building F09, The University of Sydney, NSW 2006 (Australia)

    2013-09-15

    Two methods for separating the constituent atoms of molecular ions within atom probe tomography reconstructions are presented. The Gaussian Separation Method efficiently deconvolutes molecular ions containing two constituent atoms and is tested on simulated data before being applied to an experimental HSLA steel dataset containing NbN. The Delaunay Separation Method extends separation to larger complex ions and is also tested on simulated data before being applied to an experimental GaAs dataset containing many large (>3 atoms) complex ions. First nearest neighbour (1NN) distributions and images of the reconstruction before and after the separations are used to show the effect of the algorithms and their validity and practicality are also discussed. - Highlights: ► The need to deconvolute molecular ions within atom probe data is discussed. ► Two algorithms to separate the constituent atoms of molecular ions are proposed. ► The algorithms developed are tested on simulated and experimental data. ► Nearest neighbour distributions are used to highlight the improvements.

  12. Spatial decomposition of molecular ions within 3D atom probe reconstructions

    International Nuclear Information System (INIS)

    Two methods for separating the constituent atoms of molecular ions within atom probe tomography reconstructions are presented. The Gaussian Separation Method efficiently deconvolutes molecular ions containing two constituent atoms and is tested on simulated data before being applied to an experimental HSLA steel dataset containing NbN. The Delaunay Separation Method extends separation to larger complex ions and is also tested on simulated data before being applied to an experimental GaAs dataset containing many large (>3 atoms) complex ions. First nearest neighbour (1NN) distributions and images of the reconstruction before and after the separations are used to show the effect of the algorithms and their validity and practicality are also discussed. - Highlights: ► The need to deconvolute molecular ions within atom probe data is discussed. ► Two algorithms to separate the constituent atoms of molecular ions are proposed. ► The algorithms developed are tested on simulated and experimental data. ► Nearest neighbour distributions are used to highlight the improvements

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

    International Nuclear Information System (INIS)

    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)

  14. Overcoming challenges in the study of nitrided microalloyed steels using atom probe

    International Nuclear Information System (INIS)

    Nitrided steels are widely used in the engineering field due to their superior hardness and other attractive properties. Atom probe tomography (APT) was employed to study two Nb-microalloyed CASTRIP steels with different N contents. A major challenge of using APT to study this group of materials is the presence of tails after Fe peaks in the mass spectra, which overestimates the composition for alloying elements such as Nb and Cu in the steels. One important factor that contributes to the tails is believed to be delayed field evaporation from Fe2+. This artefact of the mass spectrum was observed to be the most severe when voltage pulsing was used. The application of laser pulses with energy ranging from 0.2 to 1.2 nJ successfully reduced the tails and lead to better compositional measurement accuracy. Spatial resolution in the z-direction (along the tip direction) was observed to be less affected by changing laser energy but deteriorates in x–y direction with increasing laser energy. This investigation suggests that pulsed-laser atom probe with ∼0.4 nJ laser energy can be used to study this group of materials with improved mass resolution while still maintaining high spatial resolution. -- Highlights: ► Degradation of mass resolution in the nitrided steel using voltage pulsed atom probe was identified. ► The origin of the degradation was explored and considered to be associated with delayed evaporation. ► The artifact caused by mass resolution degradation was successfully removed by the application of laser pulsed atom probe. ► The effect of laser energy on mass resolution, composition measurement and spatial resolution was investigated. ► Laser energy ∼0.4 nJ was recommended to study this group of materials using laser pulsed atom probe.

  15. Design of cantilever probes for Atomic Force Microscopy (AFM)

    DEFF Research Database (Denmark)

    Pedersen, Niels Leergaard

    2000-01-01

    A cantilever beam used in an Atomic Force Microscope is optimized with respect to two different objectives. The first goal is to maximize the first eigenfrequency while keeping the stiffness of the probe constant. The second goal is to maximize the tip angle of the first eigenmode while again kee...

  16. Local electrode atom probe analysis of silicon nanowires grown with an aluminum catalyst

    International Nuclear Information System (INIS)

    Local electrode atom probe (LEAP) tomography of Al-catalyzed silicon nanowires synthesized by the vapor–liquid–solid method is presented. The concentration of Al within the Al-catalyzed nanowire was found to be 2 × 1020 cm−3, which is higher than the expected solubility limit for Al in Si at the nanowire growth temperature of 550 °C. Reconstructions of the Al contained within the nanowire indicate a denuded region adjacent to the Al catalyst/Si nanowire interface, while Al clusters are distributed throughout the rest of the silicon nanowire. (paper)

  17. Self optical motion-tracking for endoscopic optical coherence tomography probe using micro-beamsplitter probe

    Science.gov (United States)

    Li, Jiawen; Zhang, Jun; Chou, Lidek; Wang, Alex; Jing, Joseph; Chen, Zhongping

    2014-03-01

    Long range optical coherence tomography (OCT), with its high speed, high resolution, non-ionized properties and cross-sectional imaging capability, is suitable for upper airway lumen imaging. To render 2D OCT datasets to true 3D anatomy, additional tools are usually applied, such as X-ray guidance or a magnetic sensor. X-ray increases ionizing radiation. A magnetic sensor either increases probe size or requires an additional pull-back of the tracking sensor through the body cavity. In order to overcome these limitations, we present a novel tracking method using a 1.5 mm×1.5mm, 90/10-ratio micro-beamsplitter: 10% light through the beam-splitter is used for motion tracking and 90% light is used for regular OCT imaging and motion tracking. Two signals corresponding to these two split-beams that pass through different optical path length delays are obtained by the detector simultaneously. Using the two split beams' returned signals from the same marker line, the 2D inclination angle of each step is computed. By calculating the 2D inclination angle of each step and then connecting the translational displacements of each step, we can obtain the 2D motion trajectory of the probe. With two marker lines on the probe sheath, 3D inclination angles can be determined and then used for 3D trajectory reconstruction. We tested the accuracy of trajectory reconstruction using the probe and demonstrated the feasibility of the design for structure reconstruction of a biological sample using a porcine trachea specimen. This optical-tracking probe has the potential to be made as small as an outer diameter of 1.0mm, which is ideal for upper airway imaging.

  18. THE ATOM PROBE ANALYSIS OF A CAST DUPLEX STAINLESS STEEL

    OpenAIRE

    Godfrey, T.; G. Smith

    1986-01-01

    Atom probe analysis is reported of a low Mo CF8 duplex stainless steel aged for 105,000h at 280°C, 3,000h or 70,000h at 300°C, or 3,000h at 400°C. Definite evidence for a spinodal reaction in the α phase has been found at all the temperatures studied. This reaction process is most regular and pronounced in the material aged at 400°C but is detectable after the other heat treatments. No evidence of G-phase precipitation is apparent from the FIM micrographs, but statistical analysis of the atom...

  19. Probing stem cell differentiation using atomic force microscopy

    Science.gov (United States)

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

    2016-03-01

    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.

  20. Scanning probe microscopy of oxide surfaces: atomic structure and properties

    International Nuclear Information System (INIS)

    The intersection of two fields, oxide surface science and scanning probe microscopy (SPM), has yielded considerable insight on atomic processes at surfaces. Oxide surfaces, especially those containing transition metals, offer a rich variety of structures and localized physical phenomena that are exploited in a wide range of applications. Nonlinear optics, superconductivity, ferroelectricity and chemical catalytic activity are but a few. Furthermore, the challenges and solutions associated with the chemistry of these surfaces and particularly the solutions to these problems have led to important understanding of tip-surface interactions that can inform SPM studies of all materials. Here, the development of understanding of the model systems TiO2 and SrTiO3 are considered in detail, to demonstrate the role of nonstoichiometry in surface structure evolution and the approach to interpreting structure at the atomic level. Then a combination of scanning tunneling microscopy, noncontact atomic force microscopy and theory are applied to a variety of oxide systems including Al2O3, NiO, ferroelectric BaTiO3, tungstates and molybdates. Recently developed sophisticated probes of local properties include spin-polarized tunneling, Fourier mapping of charge density waves, band gap mapping of superconductors and ultra fast imaging of atomic diffusion. The impact of these studies on our understanding of the behavior of oxides and of tip-surface interactions is summarized

  1. 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...... 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 and...

  2. Contact resonances of U-shaped atomic force microscope probes

    International Nuclear Information System (INIS)

    Recent approaches used to characterize the elastic or viscoelastic properties of materials with nanoscale resolution have focused on the contact resonances of atomic force microscope (CR-AFM) probes. The experiments for these CR-AFM methods involve measurement of several contact resonances from which the resonant frequency and peak width are found. The contact resonance values are then compared with the noncontact values in order for the sample properties to be evaluated. The data analysis requires vibration models associated with the probe during contact in order for the beam response to be deconvolved from the measured spectra. To date, the majority of CR-AFM research has used rectangular probes that have a relatively simple vibration response. Recently, U-shaped AFM probes have created much interest because they allow local sample heating. However, the vibration response of these probes is much more complex such that CR-AFM is still in its infancy. In this article, a simplified analytical model of U-shaped probes is evaluated for contact resonance applications relative to a more complex finite element (FE) computational model. The tip-sample contact is modeled using three orthogonal Kelvin-Voigt elements such that the resonant frequency and peak width of each mode are functions of the contact conditions. For the purely elastic case, the frequency results of the simple model are within 8% of the FE model for the lowest six modes over a wide range of contact stiffness values. Results for the viscoelastic contact problem for which the quality factor of the lowest six modes is compared show agreement to within 13%. These results suggest that this simple model can be used effectively to evaluate CR-AFM experimental results during AFM scanning such that quantitative mapping of viscoelastic properties may be possible using U-shaped probes

  3. Contact resonances of U-shaped atomic force microscope probes

    Energy Technology Data Exchange (ETDEWEB)

    Rezaei, E.; Turner, J. A., E-mail: jaturner@unl.edu [Mechanical and Materials Engineering, University of Nebraska-Lincoln, W342 Nebraska Hall, Lincoln, Nebraska 68588 (United States)

    2016-01-21

    Recent approaches used to characterize the elastic or viscoelastic properties of materials with nanoscale resolution have focused on the contact resonances of atomic force microscope (CR-AFM) probes. The experiments for these CR-AFM methods involve measurement of several contact resonances from which the resonant frequency and peak width are found. The contact resonance values are then compared with the noncontact values in order for the sample properties to be evaluated. The data analysis requires vibration models associated with the probe during contact in order for the beam response to be deconvolved from the measured spectra. To date, the majority of CR-AFM research has used rectangular probes that have a relatively simple vibration response. Recently, U-shaped AFM probes have created much interest because they allow local sample heating. However, the vibration response of these probes is much more complex such that CR-AFM is still in its infancy. In this article, a simplified analytical model of U-shaped probes is evaluated for contact resonance applications relative to a more complex finite element (FE) computational model. The tip-sample contact is modeled using three orthogonal Kelvin-Voigt elements such that the resonant frequency and peak width of each mode are functions of the contact conditions. For the purely elastic case, the frequency results of the simple model are within 8% of the FE model for the lowest six modes over a wide range of contact stiffness values. Results for the viscoelastic contact problem for which the quality factor of the lowest six modes is compared show agreement to within 13%. These results suggest that this simple model can be used effectively to evaluate CR-AFM experimental results during AFM scanning such that quantitative mapping of viscoelastic properties may be possible using U-shaped probes.

  4. Contact resonances of U-shaped atomic force microscope probes

    Science.gov (United States)

    Rezaei, E.; Turner, J. A.

    2016-01-01

    Recent approaches used to characterize the elastic or viscoelastic properties of materials with nanoscale resolution have focused on the contact resonances of atomic force microscope (CR-AFM) probes. The experiments for these CR-AFM methods involve measurement of several contact resonances from which the resonant frequency and peak width are found. The contact resonance values are then compared with the noncontact values in order for the sample properties to be evaluated. The data analysis requires vibration models associated with the probe during contact in order for the beam response to be deconvolved from the measured spectra. To date, the majority of CR-AFM research has used rectangular probes that have a relatively simple vibration response. Recently, U-shaped AFM probes have created much interest because they allow local sample heating. However, the vibration response of these probes is much more complex such that CR-AFM is still in its infancy. In this article, a simplified analytical model of U-shaped probes is evaluated for contact resonance applications relative to a more complex finite element (FE) computational model. The tip-sample contact is modeled using three orthogonal Kelvin-Voigt elements such that the resonant frequency and peak width of each mode are functions of the contact conditions. For the purely elastic case, the frequency results of the simple model are within 8% of the FE model for the lowest six modes over a wide range of contact stiffness values. Results for the viscoelastic contact problem for which the quality factor of the lowest six modes is compared show agreement to within 13%. These results suggest that this simple model can be used effectively to evaluate CR-AFM experimental results during AFM scanning such that quantitative mapping of viscoelastic properties may be possible using U-shaped probes.

  5. Probing charges on the atomic scale by means of atomic force microscopy

    Czech Academy of Sciences Publication Activity Database

    Albrecht, F.; Repp, J.; Fleischmann, M.; Scheer, M.; Ondráček, Martin; Jelínek, Pavel

    2015-01-01

    Roč. 115, č. 7 (2015), "076101-1"-"076101-5". ISSN 0031-9007 R&D Projects: GA ČR(CZ) GC14-16963J Institutional support: RVO:68378271 Keywords : Kelvin probe force microscopy * atomic force microscopy * bond polarity * surface dipole * adsorbates on surfaces Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 7.512, year: 2014

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

    International Nuclear Information System (INIS)

    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 9500C 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

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

    International Nuclear Information System (INIS)

    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

  8. 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.

  9. 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. PMID:23485412

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

    International Nuclear Information System (INIS)

    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. Multifunctional hydrogel nano-probes for atomic force microscopy

    Science.gov (United States)

    Lee, Jae Seol; Song, Jungki; Kim, Seong Oh; Kim, Seokbeom; Lee, Wooju; Jackman, Joshua A.; Kim, Dongchoul; Cho, Nam-Joon; Lee, Jungchul

    2016-05-01

    Since the invention of the atomic force microscope (AFM) three decades ago, there have been numerous advances in its measurement capabilities. Curiously, throughout these developments, the fundamental nature of the force-sensing probe--the key actuating element--has remained largely unchanged. It is produced by long-established microfabrication etching strategies and typically composed of silicon-based materials. Here, we report a new class of photopolymerizable hydrogel nano-probes that are produced by bottom-up fabrication with compressible replica moulding. The hydrogel probes demonstrate excellent capabilities for AFM imaging and force measurement applications while enabling programmable, multifunctional capabilities based on compositionally adjustable mechanical properties and facile encapsulation of various nanomaterials. Taken together, the simple, fast and affordable manufacturing route and multifunctional capabilities of hydrogel AFM nano-probes highlight the potential of soft matter mechanical transducers in nanotechnology applications. The fabrication scheme can also be readily utilized to prepare hydrogel cantilevers, including in parallel arrays, for nanomechanical sensor devices.

  12. Atom chip microscopy: A novel probe for strongly correlated materials

    Energy Technology Data Exchange (ETDEWEB)

    Lev, Benjamin L

    2011-11-03

    Improved measurements of strongly correlated systems will enable the predicative design of the next generation of supermaterials. In this program, we are harnessing recent advances in the quantum manipulation of ultracold atomic gases to expand our ability to probe these technologically important materials in heretofore unexplored regions of temperature, resolution, and sensitivity parameter space. We are working to demonstrate the use of atom chips to enable single-shot, large area detection of magnetic flux at the 10^-7 flux quantum level and below. By harnessing the extreme sensitivity of atomic clocks and Bose-Einstein condensates (BECs) to external perturbations, the cryogenic atom chip technology developed here will provide a magnetic flux detection capability that surpasses other techniques---such as scanning SQUIDs---by a factor of 10--1000. We are testing the utility of this technique by using rubidium BECs to image the magnetic fields emanating from charge transport and magnetic domain percolation in strongly correlated materials as they undergo temperature-tuned metal--to--insulator phase transitions. Cryogenic atom chip microscopy introduces three very important features to the toolbox of high-resolution, strongly correlated material microscopy: simultaneous detection of magnetic and electric fields (down to the sub-single electron charge level); no invasive large magnetic fields or gradients; simultaneous micro- and macroscopic spatial resolution; freedom from 1/f flicker noise at low frequencies; and, perhaps most importantly, the complete decoupling of probe and sample temperatures. The first of these features will play an important role in studying the interplay between magnetic and electric domain structure. The last two are crucial for low frequency magnetic noise detection in, e.g., the cuprate pseudogap region and for precision measurements of transport in the high temperature, technologically relevant regime inaccessible to other techniques

  13. Tomographic atom probe characterization of the microstructure of a cold worked 316 austenitic stainless steel after neutron irradiation

    International Nuclear Information System (INIS)

    For the first time, chemical analyses using Atom Probe Tomography were performed on a bolt made of cold worked 316 austenitic stainless steel, extracted from the internal structures of a pressurized water reactor after 17 years of reactor service. The irradiation temperature of these samples was 633 K and the irradiation dose was estimated to 12 dpa (7.81 x 1025 neutrons.m-2, E > 1 MeV). The samples were analysed with a laser assisted tomographic atom probe. These analyses have shown that neutron irradiation has a strong effect on the intragranular distribution of solute atoms. A high number density (6 x 1023 m-3) of Ni-Si enriched and Cr-Fe depleted clusters was detected after irradiation. Mo and P segregations at the interfaces of these clusters were also observed. Finally, Si enriched atmospheres were seen

  14. Design of cantilever probes for Atomic Force Microscopy (AFM)

    DEFF Research Database (Denmark)

    Pedersen, Niels Leergaard

    2000-01-01

    A cantilever beam used in an Atomic Force Microscope is optimized with respect to two different objectives. The first goal is to maximize the first eigenfrequency while keeping the stiffness of the probe constant. The second goal is to maximize the tip angle of the first eigenmode while again...... keeping the stiffness constant. The resulting design of the beam from the latter optimization gives almost the same result as when maximizing the first eigenfrequency. Adding a restriction on the second eigenfrequency result in a significant change of the optimal design. The beam is modelled with 12 DOF...

  15. 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. PMID:25896290

  16. Multifunctional hydrogel nano-probes for atomic force microscopy

    Science.gov (United States)

    Lee, Jae Seol; Song, Jungki; Kim, Seong Oh; Kim, Seokbeom; Lee, Wooju; Jackman, Joshua A.; Kim, Dongchoul; Cho, Nam-Joon; Lee, Jungchul

    2016-01-01

    Since the invention of the atomic force microscope (AFM) three decades ago, there have been numerous advances in its measurement capabilities. Curiously, throughout these developments, the fundamental nature of the force-sensing probe—the key actuating element—has remained largely unchanged. It is produced by long-established microfabrication etching strategies and typically composed of silicon-based materials. Here, we report a new class of photopolymerizable hydrogel nano-probes that are produced by bottom-up fabrication with compressible replica moulding. The hydrogel probes demonstrate excellent capabilities for AFM imaging and force measurement applications while enabling programmable, multifunctional capabilities based on compositionally adjustable mechanical properties and facile encapsulation of various nanomaterials. Taken together, the simple, fast and affordable manufacturing route and multifunctional capabilities of hydrogel AFM nano-probes highlight the potential of soft matter mechanical transducers in nanotechnology applications. The fabrication scheme can also be readily utilized to prepare hydrogel cantilevers, including in parallel arrays, for nanomechanical sensor devices. PMID:27199165

  17. Atom probe tomographic study of elemental segregation at grain boundaries for a peak-aged Al–Zn–Mg alloy

    International Nuclear Information System (INIS)

    Highlights: •Atom probe tomography is used to characterize the solute segregation at GBs. •Mg segregates at GBs within 3 nm for a peak-aged Al–Zn–Mg alloy. •Zn does not segregate at GBs. •MgZn2 precipitates are not the H trapping sites, but Mg2Si precipitates are. •Clusters containing Zn, H and oxides have been found at GBs. -- Abstract: Atom probe tomography (APT) has been used to characterize the element segregation at the grain boundary (GB) for a peak-aged Al–Zn–Mg alloy with high stress corrosion cracking (SCC) susceptibility. The results show that Mg segregates along the GB with a peak concentration of 1.38 at.% and width of 3 nm. Zn does not segregate at GB. However, segregation of Zn and H atoms at oxide-containing clusters on GB has been observed. APT atom maps also reveal that Mg2Si is the H trapping site, but MgZn2 is not

  18. Atom probe analysis of Sn in Zr-based alloys

    International Nuclear Information System (INIS)

    We have extensively used atom-probe field ion microscopy (APFIM) for microanalyses of a heat-treated Zircaloy-4 and Zr-Sn alloys containing 0.6 or 1.39 wt% Sn and clarified as to whether Sn is fully dissolved or not in the α-Zr matrix. It is found that Sn dissolves in the matrix of both Zircaloy-4 and Zr-0.6 wt% Sn alloy upon annealing at 723 K. For Zr-1.39 wt% Sn alloy, after annealing for more than 200 h, the symptom of phase separation has been found. The distribution of Sn in the matrix is changed from the α-quenched state, and local regions enriched with Sn are formed in the matrix. (orig.)

  19. Atomic force microscope probe-based nanometric scribing

    International Nuclear Information System (INIS)

    Miniaturization of machine components is recognized by many as a significant technological development for a vast spectrum of products. An atomic force microscope (AFM) probe that can exert forces onto a variety of engineering materials is used to perform mechanical scribing at the nanoscale. The success of nanomechanical machining at such fine scales is based on the understanding of microstructural machining mechanics. This paper investigates the cutting behaviour in the nanoscale of a chromium workpiece by using a retrofitted commercial AFM with an acoustic emission sensor, in order to scratch the surface and measure forces. The calibration procedure for acquiring the forces is discussed. The cutting force model, which incorporates the flow stress and friction coefficient in the nano-scale machining, is also presented

  20. Investigation on nanocomposite magnets by three-dimensional atom probe

    Institute of Scientific and Technical Information of China (English)

    WANG Zhanyong; ZHOU Bangxin; NI Jiansen; XU Hui

    2006-01-01

    With the fast development in nano materials, to obtain the detailed microstructure information, microscopes with much higher resolution than the conventional ones are required. A three-dimensional atom probe (3DAP), an instrument with nearatomic resolutions of about 0.06 and 0.2 nm in depth and transverse direction, respectively, has been employed to map out the elemental distribution of some conductive materials within a nano-scale volume.This instrument is fit to analyze the elemental distribution in nano materials and nano precipitation in common materials. 3DAP is applied to investigate the microstructure of Nd2Fe14B/α-Fe nanocomposite magnets. B, Fe-enriched, Zr-enriched and Nd,Fe-enriched clusters have been found, which cannot be identified by any other instrument.

  1. Probing Modified Gravity with Atom-Interferometry: a Numerical Approach

    CERN Document Server

    Schlogel, Sandrine; Fuzfa, Andre

    2015-01-01

    Refined constraints on chameleon theories are calculated for atom-interferometry experiments, using a numerical approach consisting in solving for a four-region model the static and spherically symmetric Klein-Gordon equation for the chameleon field. By modeling not only the test mass and the vacuum chamber but also its walls and the exterior environment, the method allows to probe new effects on the scalar field profile and the induced acceleration of atoms. In the case of a weakly perturbing test mass, the effect of the wall is to enhance the field profile and to lower the acceleration inside the chamber by up to one order of magnitude. In the thin-shell regime, significant deviations from the analytical estimations are found, even when measurements are realized in the immediate vicinity of the test mass. Close to the vacuum chamber wall, the acceleration becomes negative and potentially measurable. This prediction could be used to discriminate between fifth-force effects and systematic experimental uncerta...

  2. Probe knots and Hopf insulators with ultracold atoms

    Science.gov (United States)

    Deng, Dong-Ling; Wang, Sheng-Tao; Sun, Kai; Duan, Lu-Ming

    2015-05-01

    Knots and links are fascinating and intricate topological objects that have played a prominent role in physical and life sciences. 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 show that knotted structures also exist in a peculiar class of three dimensional topological insulators--the Hopf insulators. In particular, we demonstrate that the spin textures of Hopf insulators in momentum space are twisted in a nontrivial way, which implies 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 cold atoms and may have potential applications in spintronics and quantum information processings. We thank X.-J. Liu and G. Ortiz for helpful discussions. S.T.W., D.L.D., and L.M.D. are supported by the NBRPC 2011CBA00300, the IARPA MUSIQC program, the ARO and the AFOSR MURI program. K.S. acknowledges support from NSF under Grant No. PHY1402971.

  3. Investigating atomic contrast in atomic force microscopy and Kelvin probe force microscopy on ionic systems using functionalized tips

    OpenAIRE

    Gross, Leo; Schuler, Bruno; Mohn, Fabian; Moll, Nikolaj; Pavliček, Niko; Steurer, Wolfram; Scivetti, Ivan; Kotsis, Konstantinos; Persson, Mats; Meyer, Gerhard

    2014-01-01

    Noncontact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM) have become important tools for nanotechnology; however, their contrast mechanisms on the atomic scale are not entirely understood. Here we used chlorine vacancies in NaCl bilayers on Cu(111) as a model system to investigate atomic contrast as a function of applied voltage, tip height, and tip functionalization. We demonstrate that the AFM contrast on the atomic scale decisively depends on both the tip termin...

  4. Sodium distribution in solar-grade Cu2ZnSnS4 layers using atom-probe tomographic technique

    Science.gov (United States)

    Tajima, Shin; Asahi, Ryoji; Isheim, Dieter; Seidman, David N.; Itoh, Tadayoshi; Ohishi, Kei-ichiro

    2015-11-01

    To investigate the effect of alkali doping on Cu2ZnSnS4 (CZTS) photovoltaic cells, we studied compositional distributions in CZTS layers using three-dimensional atom-probe tomography. The segregation of Na at a concentration of approximately 1 at. % was observed predominantly at CZTS grain boundaries. The concentration of Na in the interior of the CZTS grains was below the detection limit (approximately 40 ppm). Na ions may exist as sulfide compounds at CZTS grain boundaries, independent of the presence of oxygen.

  5. Soft-landing ion deposition of isolated radioactive probe atoms on surfaces : A novel method

    NARCIS (Netherlands)

    Laurens, CR; Rosu, MF; Pleiter, F; Niesen, L

    1997-01-01

    We present a method to deposit a wide range of radioactive probe atoms on surfaces, without introducing lattice damage or contaminating the surface with other elements or isotopes. In this method, the probe atoms are mass separated using an isotope separator, decelerated to 5 eV, and directly deposi

  6. In situ imaging of lung alveoli with an optical coherence tomography needle probe

    Science.gov (United States)

    Quirk, Bryden C.; McLaughlin, Robert A.; Curatolo, Andrea; Kirk, Rodney W.; Noble, Peter B.; Sampson, David D.

    2011-03-01

    In situ imaging of alveoli and the smaller airways with optical coherence tomography (OCT) has significant potential in the assessment of lung disease. We present a minimally invasive imaging technique utilizing an OCT needle probe. The side-facing needle probe comprises miniaturized focusing optics consisting of no-core and GRIN fiber encased within a 23-gauge needle. 3D-OCT volumetric data sets were acquired by rotating and retracting the probe during imaging. The probe was used to image an intact, fresh (not fixed) sheep lung filled with normal saline, and the results validated against a histological gold standard. We present the first published images of alveoli acquired with an OCT needle probe and demonstrate the potential of this technique to visualize other anatomical features such as bifurcations of the bronchioles.

  7. Conductive-probe atomic force microscopy characterization of silicon nanowire

    Directory of Open Access Journals (Sweden)

    Yu Linwei

    2011-01-01

    Full Text Available Abstract The electrical conduction properties of lateral and vertical silicon nanowires (SiNWs were investigated using a conductive-probe atomic force microscopy (AFM. Horizontal SiNWs, which were synthesized by the in-plane solid-liquid-solid technique, are randomly deployed into an undoped hydrogenated amorphous silicon layer. Local current mapping shows that the wires have internal microstructures. The local current-voltage measurements on these horizontal wires reveal a power law behavior indicating several transport regimes based on space-charge limited conduction which can be assisted by traps in the high-bias regime (> 1 V. Vertical phosphorus-doped SiNWs were grown by chemical vapor deposition using a gold catalyst-driving vapor-liquid-solid process on higly n-type silicon substrates. The effect of phosphorus doping on the local contact resistance between the AFM tip and the SiNW was put in evidence, and the SiNWs resistivity was estimated.

  8. New Methods of Sample Preparation for Atom Probe Specimens

    Science.gov (United States)

    Kuhlman, Kimberly, R.; Kowalczyk, Robert S.; Ward, Jennifer R.; Wishard, James L.; Martens, Richard L.; Kelly, Thomas F.

    2003-01-01

    Magnetite is a common conductive mineral found on Earth and Mars. Disk-shaped precipitates approximately 40 nm in diameter have been shown to have manganese and aluminum concentrations. Atom-probe field-ion microscopy (APFIM) is the only technique that can potentially quantify the composition of these precipitates. APFIM will be used to characterize geological and planetary materials, analyze samples of interest for geomicrobiology; and, for the metrology of nanoscale instrumentation. Prior to APFIM sample preparation was conducted by electropolishing, the method of sharp shards (MSS), or Bosch process (deep reactive ion etching) with focused ion beam (FIB) milling as a final step. However, new methods are required for difficult samples. Many materials are not easily fabricated using electropolishing, MSS, or the Bosch process, FIB milling is slow and expensive, and wet chemistry and the reactive ion etching are typically limited to Si and other semiconductors. APFIM sample preparation using the dicing saw is commonly used to section semiconductor wafers into individual devices following manufacture. The dicing saw is a time-effective method for preparing high aspect ratio posts of poorly conducting materials. Femtosecond laser micromachining is also suitable for preparation of posts. FIB time required is reduced by about a factor of 10 and multi-tip specimens can easily be fabricated using the dicing saw.

  9. Design and testing of prototype handheld scanning probes for optical coherence tomography.

    Science.gov (United States)

    Demian, Dorin; Duma, Virgil-Florin; Sinescu, Cosmin; Negrutiu, Meda Lavinia; Cernat, Ramona; Topala, Florin Ionel; Hutiu, Gheorghe; Bradu, Adrian; Podoleanu, Adrian Gh

    2014-08-01

    Three simple and low-cost configurations of handheld scanning probes for optical coherence tomography have been developed. Their design and testing for dentistry applications are presented. The first two configurations were built exclusively from available off-the-shelf optomechanical components, which, to the best of our knowledge, are the first designs of this type. The third configuration includes these components in an optimized and ergonomic probe. All the designs are presented in detail to allow for their duplication in any laboratory with a minimum effort, for applications that range from educational to high-end clinical investigations. Requirements that have to be fulfilled to achieve configurations which are reliable, ergonomic-for clinical environments, and easy to build are presented. While a range of applications is possible for the prototypes developed, in this study the handheld probes are tested ex vivo with a spectral domain optical coherence tomography system built in-house, for dental constructs. A previous testing with a swept source optical coherence tomography system has also been performed both in vivo and ex vivo for ear, nose, and throat-in a medical environment. The applications use the capability of optical coherence tomography to achieve real-time, high-resolution, non-contact, and non-destructive interferometric investigations with micrometer resolutions and millimeter penetration depth inside the sample. In this study, testing the quality of the material of one of the most used types of dental prosthesis, metalo-ceramic is thus demonstrated. PMID:25107512

  10. Neurosurgical hand-held optical coherence tomography (OCT) forward-viewing probe

    Science.gov (United States)

    Sun, Cuiru; Lee, Kenneth K. C.; Vuong, Barry; Cusimano, Michael; Brukson, Alexander; Mariampillai, Adrian; Standish, Beau A.; Yang, Victor X. D.

    2012-02-01

    A prototype neurosurgical hand-held optical coherence tomography (OCT) imaging probe has been developed to provide micron resolution cross-sectional images of subsurface tissue during open surgery. This new ergonomic hand-held probe has been designed based on our group's previous work on electrostatically driven optical fibers. It has been packaged into a catheter probe in the familiar form factor of the clinically accepted Bayonet shaped neurosurgical non-imaging Doppler ultrasound probes. The optical design was optimized using ZEMAX simulation. Optical properties of the probe were tested to yield an ~20 um spot size, 5 mm working distance and a 3.5 mm field of view. The scan frequency can be increased or decreased by changing the applied voltage. Typically a scan frequency of less than 60Hz is chosen to keep the applied voltage to less than 2000V. The axial resolution of the probe was ~15 um (in air) as determined by the OCT system. A custom-triggering methodology has been developed to provide continuous stable imaging, which is crucial for clinical utility. Feasibility of this probe, in combination with a 1310 nm swept source OCT system was tested and images are presented to highlight the usefulness of such a forward viewing handheld OCT imaging probe. Knowledge gained from this research will lay the foundation for developing new OCT technologies for endovascular management of cerebral aneurysms and transsphenoidal neuroendoscopic treatment of pituitary tumors.

  11. A Nanostructual Microwave Probe Used for Atomic Force Microscope

    CERN Document Server

    Ju, Y; Kobayashi, T; Soyama, H

    2008-01-01

    In order to develop a new structure microwave probe, the fabrication of AFM probe on the GaAs wafer was studied. A waveguide was introduced by evaporating Au film on the top and bottom surfaces of the GaAs AFM probe. A tip having 8 micrometers high, and curvature radius about 50 nm was formed. The dimensions of the cantilever are 250x30x15 micrometers. The open structure of the waveguide at the tip of the probe was introduced by using FIB fabrication. AFM topography of a grating sample was measured by using the fabricated GaAs microwave probe. The fabricated probe was found having nanometer scale resolution, and microwave emission was detected successfully at the tip of the probe by approaching Cr-V steel and Au wire samples.

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

    International Nuclear Information System (INIS)

    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 (Y2O3) 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) Y2O3 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 1023 m-3. (author)

  13. Handheld scanning probes for optical coherence tomography: developments, applications, and perspectives

    Science.gov (United States)

    Duma, V.-F.; Demian, D.; Sinescu, C.; Cernat, R.; Dobre, G.; Negrutiu, M. L.; Topala, F. I.; Hutiu, Gh.; Bradu, A.; Podoleanu, A. G.

    2016-03-01

    We present the handheld scanning probes that we have recently developed in our current project for biomedical imaging in general and for Optical Coherence Tomography (OCT) in particular. OCT is an established, but dynamic imagistic technique based on laser interferometry, which offers micrometer resolutions and millimeters penetration depths. With regard to existing devices, the newly developed handheld probes are simple, light and relatively low cost. Their design is described in detail to allow for the reproduction in any lab, including for educational purposes. Two probes are constructed almost entirely from off-the-shelf components, while a third, final variant is constructed with dedicated components, in an ergonomic design. The handheld probes have uni-dimensional (1D) galvanometer scanners therefore they achieve transversal sections through the biological sample investigated - in contrast to handheld probes equipped with bi-dimensional (2D) scanners that can also achieve volumetric (3D) reconstructions of the samples. These latter handheld probes are therefore also discussed, as well as the possibility to equip them with galvanometer 2D scanners or with Risley prisms. For galvanometer scanners the optimal scanning functions studied in a series of previous works are pointed out; these functions offer a higher temporal efficiency/duty cycle of the scanning process, as well as artifact-free OCT images. The testing of the handheld scanning probes in dental applications is presented, for metal ceramic prosthesis and for teeth.

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

    International Nuclear Information System (INIS)

    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

  15. Cage motion of a probe atom in a vacancy complex in Pt

    International Nuclear Information System (INIS)

    The perturbation function of a Cd probe atom bound in a hydrogen-decorated vacancy complex in Pt is found to exhibit dynamical relaxation at 294 K, as measured by the technique of perturbed γ-γ angular correlations. Based on other characteristics of the complex, a model is proposed for the structure of the complex. In the undecorated state, it consists of a probe atom at the center of a tetrahedron of vacancies in the fcc structure. In the decorated state at low temperature, the probe atom returns to one of the four vacant lattice sites. The relaxation at room temperature is attributed to motion of the probe atom in a cage formed by the four vacant sites. (orig.)

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  17. Atom probe study of vanadium interphase precipitates and randomly distributed vanadium precipitates in ferrite.

    Science.gov (United States)

    Nöhrer, M; Zamberger, S; Primig, S; Leitner, H

    2013-01-01

    Atom probe tomography and transmission electron microscopy were used to examine the precipitation reaction in the austenite and ferrite phases in vanadium micro-alloyed steel after a thermo-mechanical process. It was observed that only in the ferrite phase precipitates could be found, whereupon two different types were detected. Thus, the aim was to reveal the difference between these two types. The first type was randomly distributed precipitates from V supersaturated ferrite and the second type V interphase precipitates. Not only the arrangement of the particles was different also the chemical composition. The randomly distributed precipitates consisted of V, C and N in contrast to that the interphase precipitates showed a composition of V, C and Mn. Furthermore the randomly distributed precipitates had maximum size of 20 nm and the interphase precipitates a maximum size of 15 nm. It was assumed that the reason for these differences is caused by the site in which they were formed. The randomly distributed precipitates were formed in a matrix consisting mainly of 0.05 at% C, 0.68 at% Si, 0.03 at% N, 0.145 at% V and 1.51 at% Mn. The interphase precipitates were formed in a region with a much higher C, Mn and V content. PMID:24041583

  18. Achieving atomic resolution magnetic dichroism by controlling the phase symmetry of an electron probe

    OpenAIRE

    Rusz, Jan; Idrobo, Juan-Carlos; Bhowmick, Somnath

    2014-01-01

    The calculations presented here reveal that an electron probe carrying orbital angular momentum is just a particular case of a wider class of electron beams that can be used to measure electron magnetic circular dichroism (EMCD) with atomic resolution. It is possible to obtain an EMCD signal with atomic resolution by simply breaking the symmetry of the electron probe phase distribution using the aberration-corrected optics of an scanning transmission electron microscope. The required phase di...

  19. H atom probes of radiation chemistry: Solids and liquids

    International Nuclear Information System (INIS)

    H atoms are ubiquitous in radiation chemistry. Radiolysis of most substances yield H atoms and studies of the mechanisms of their production are as old as the field of radiation chemistry. The problem is that study or products does not easily reveal the chemical mechanisms involved even with the clever use of isotopes. Time-resolved pulsed electron paramagnetic resonance (EPR) was used to study formation and decay kinetics of spin-polarized mobile H atoms in radiolysis of wet fused silica containing ∼ 1,200 ppm of SiOH groups. Two reactions of H atoms can be distinguished: a slow component corresponding to scavenging of H atoms by metastable paramagnetic centers and a fast component which is ascribed to a reaction of a short-lived small polaron (intrinsic hole) with H atoms

  20. An atom probe perspective on phase separation and precipitation in duplex stainless steels.

    Science.gov (United States)

    Guo, Wei; Garfinkel, David A; Tucker, Julie D; Haley, Daniel; Young, George A; Poplawsky, Jonathan D

    2016-06-24

    Three-dimensional chemical imaging of Fe-Cr alloys showing Fe-rich (α)/Cr-rich (α') phase separation is reported using atom probe tomography techniques. The extent of phase separation, i.e., amplitude and wavelength, has been quantitatively assessed using the Langer-Bar-on-Miller, proximity histogram, and autocorrelation function methods for two separate Fe-Cr alloys, designated 2101 and 2205. Although the 2101 alloy possesses a larger wavelength and amplitude after annealing at 427 °C for 100-10 000 h, it exhibits a lower hardness than the 2205 alloy. In addition to this phase separation, ultra-fine Ni-Mn-Si-Cu-rich G-phase precipitates form at the α/α' interfaces in both alloys. For the 2101 alloy, Cu clusters act to form a nucleus, around which a Ni-Mn-Si shell develops during the precipitation process. For the 2205 alloy, the Ni and Cu atoms enrich simultaneously and no core-shell chemical distribution was found. This segregation phenomenon may arise from the exact Ni/Cu ratio inside the ferrite. After annealing for 10 000 h, the number density of the G-phase within the 2205 alloy was found to be roughly one order of magnitude higher than in the 2101 alloy. The G-phase precipitates have an additional deleterious effect on the thermal embrittlement, as evaluated by the Ashby-Orowan equation, which explains the discrepancy between the hardness and the rate of phase separation with respect to annealing time (Gladman T 1999 Mater. Sci. Tech. Ser. 15 30-36). PMID:27181108

  1. An atom probe perspective on phase separation and precipitation in duplex stainless steels

    Science.gov (United States)

    Guo, Wei; Garfinkel, David A.; Tucker, Julie D.; Haley, Daniel; Young, George A.; Poplawsky, Jonathan D.

    2016-06-01

    Three-dimensional chemical imaging of Fe–Cr alloys showing Fe-rich (α)/Cr-rich (α‧) phase separation is reported using atom probe tomography techniques. The extent of phase separation, i.e., amplitude and wavelength, has been quantitatively assessed using the Langer-Bar-on-Miller, proximity histogram, and autocorrelation function methods for two separate Fe–Cr alloys, designated 2101 and 2205. Although the 2101 alloy possesses a larger wavelength and amplitude after annealing at 427 °C for 100–10 000 h, it exhibits a lower hardness than the 2205 alloy. In addition to this phase separation, ultra-fine Ni–Mn–Si–Cu-rich G-phase precipitates form at the α/α‧ interfaces in both alloys. For the 2101 alloy, Cu clusters act to form a nucleus, around which a Ni–Mn–Si shell develops during the precipitation process. For the 2205 alloy, the Ni and Cu atoms enrich simultaneously and no core–shell chemical distribution was found. This segregation phenomenon may arise from the exact Ni/Cu ratio inside the ferrite. After annealing for 10 000 h, the number density of the G-phase within the 2205 alloy was found to be roughly one order of magnitude higher than in the 2101 alloy. The G-phase precipitates have an additional deleterious effect on the thermal embrittlement, as evaluated by the Ashby–Orowan equation, which explains the discrepancy between the hardness and the rate of phase separation with respect to annealing time (Gladman T 1999 Mater. Sci. Tech. Ser. 15 30–36). ).

  2. Atomic quantum superposition state generation via optical probing

    DEFF Research Database (Denmark)

    Nielsen, Anne Ersbak Bang; Poulsen, Uffe Vestergaard; Negretti, Antonio;

    2009-01-01

    We analyze the performance of a protocol to prepare an atomic ensemble in a superposition of two macroscopically distinguishable states. The protocol relies on conditional measurements performed on a light field, which interacts with the atoms inside an optical cavity prior to detection, and we...

  3. Probing angular momentum coherence in a twin-atom interferometer

    CERN Document Server

    de Carvalho, Carlos R; Impens, François; Robert, J; Medina, Aline; Zappa, F; Faria, N V de Castro

    2014-01-01

    We propose to use a double longitudinal Stern-Gerlach atom interferometer in order to investigate quantitatively the angular momentum coherence of molecular fragments. Assuming that the dissociated molecule has a null total angular momentum, we investigate the propagation of the corresponding atomic fragments in the apparatus. We show that the envisioned interferometer enables one to distinguish unambiguously a spin-coherent from a spin-incoherent dissociation, as well as to estimate the purity of the angular momentum density matrix associated with the fragments. This setup, which may be seen as an atomic analogue of a twin-photon interferometer, can be used to investigate the suitability of molecule dissociation processes -- such as the metastable hydrogen atoms H($2^2 S$)-H($2^2 S$) dissociation - for coherent twin-atom optics.

  4. A study of the imaging of atomic elements by computerised axial tomography

    OpenAIRE

    McCarthy, K J

    1989-01-01

    Conventional computerized axial tomography images show the spatial variation in the linear attenuation coefficient in a cross-section of a specimen. However, no information is present to enable one to predict the location nor concentration of an atomic element in the image. Differential X-ray absorptiometry is a well established analytic technique for determining the concentration of an atomic element in a specimen. In this thesis, it is shown that by applying differential X-ray absorpt...

  5. X-ray phase computed tomography for nanoparticulated imaging probes and therapeutics: preliminary feasibility study

    Science.gov (United States)

    Tang, Xiangyang; Yang, Yi; Tang, Shaojie

    2011-03-01

    With the scientific progress in cancer biology, pharmacology and biomedical engineering, the nano-biotechnology based imaging probes and therapeutical agents (namely probes/agents) - a form of theranostics - are among the strategic solutions bearing the hope for the cure of cancer. The key feature distinguishing the nanoparticulated probes/agents from their conventional counterparts is their targeting capability. A large surface-to-volume ratio in nanoparticulated probes/agents enables the accommodation of multiple targeting, imaging and therapeutic components to cope with the intra- and inter-tumor heterogeneity. Most nanoparticulated probes/agents are synthesized with low atomic number materials and thus their x-ray attenuation are very similar to biological tissues. However, their microscopic structures are very different, which may result in significant differences in their refractive properties. Recently, the investigation in the x-ray grating-based differential phase contrast (DPC) CT has demonstrated its advantages in differentiating low-atomic materials over the conventional attenuation-based CT. We believe that a synergy of x-ray grating-based DPC CT and nanoparticulated imaging probes and therapeutic agents may play a significant role in extensive preclinical and clinical applications, or even become a modality for molecular imaging. Hence, we propose to image the refractive property of nanoparticulated imaging probes and therapeutical agents using x-ray grating-based DPC CT. In this work, we conduct a preliminary feasibility study with a focus to characterize the contrast-to-noise ratio (CNR) and contrast-detail behavior of the x-ray grating-based DPC CT. The obtained data may be instructive to the architecture design and performance optimization of the x-ray grating-based DPC CT for imaging biomarker-targeted imaging probes and therapeutic agents, and even informative to the translation of preclinical research in theranostics into clinical applications.

  6. Atomic Resolution Imaging with a sub-50 pm Electron Probe

    Energy Technology Data Exchange (ETDEWEB)

    Erni, Rolf P.; Rossell, Marta D.; Kisielowski, Christian; Dahmen, Ulrich

    2009-03-02

    Using a highly coherent focused electron probe in a 5th order aberration-corrected transmission electron microscope, we report on resolving a crystal spacing less than 50 pm. Based on the geometrical source size and residual coherent and incoherent axial lens aberrations, an electron probe is calculated, which is theoretically capable of resolving an ideal 47 pm spacing with 29percent contrast. Our experimental data show the 47 pm spacing of a Ge 114 crystal imaged with 11-18percent contrast at a 60-95percent confidence level, providing the first direct evidence for sub 50-pm resolution in ADF STEM imaging.

  7. Understanding the Atomic-Scale Contrast in Kelvin Probe Force Microscopy

    OpenAIRE

    Nony, Laurent; Foster, Adam S.; Bocquet, Franck; Loppacher, Christian

    2009-01-01

    A numerical analysis of the origin of the atomic-scale contrast in Kelvin probe force microscopy is presented. Atomistic simulations of the tip-sample interaction force field have been combined with a noncontact atomic force microscope simulator including a Kelvin module. The implementation mimics recent experimental results on the (001) surface of a bulk alkali halide crystal for which simultaneous atomic-scale topographical and contact potential difference contrasts were reported. The local...

  8. Understanding the atomic-scale contrast in Kelvin Probe Force Microscopy

    OpenAIRE

    Nony, Laurent; Foster, Adam; Bocquet, Franck; Loppacher, Christian

    2009-01-01

    A numerical analysis of the origin of the atomic-scale contrast in Kelvin probe force microscopy (KPFM) is presented. Atomistic simulations of the tip-sample interaction force field have been combined with a non-contact Atomic Force Microscope/KPFM simulator. The implementation mimics recent experimental results on the (001) surface of a bulk alkali halide crystal for which simultaneous atomic-scale topographical and Contact Potential Difference (CPD) contrasts were reported. The local CPD do...

  9. Probing the Planck Scale in Low-Energy Atomic Physics

    OpenAIRE

    Bluhm, Robert

    2001-01-01

    Experiments in atomic physics have exceptional sensitivity to small shifts in energy in an atom, ion, or bound particle. They are particularly well suited to search for unique low-energy signatures of new physics, including effects that could originate from the Planck scale. A number of recent experiments have used CPT and Lorentz violation as a candidate signal of new physics originating from the Planck scale. A discussion of these experiments and their theoretical implications is presented.

  10. Clustering Effects Under Irradiation in Fe-0.1%Cu Alloy : An Atomic Scale Investigation with the Tomographic Atom Probe

    OpenAIRE

    Pareige, P.; Welzel, S; Auger, P.

    1996-01-01

    In order to understand the effect of displacement cascades on the evolution of the microstructure of ferritic low copper supersaturated materials, analyses by 3D atomic tomography of neutron, electron and self ion irradiated Fe-0.1%Cu, were performed. This alloy was chosen because of its low copper concentration, close to that of french pressure vessel steels. The comparison of the microstructure evolutions in these irradiated specimens reveals the appearance of tiny copper "clusters" or "agg...

  11. IMPROVED FABRICATION METHOD FOR CARBON NANOTUBE PROBE OF ATOMIC FORCE MICROSCOPY(AFM)

    Institute of Scientific and Technical Information of China (English)

    XU Zongwei; DONG Shen; GUO Liqiu; ZHAO Qingliang

    2006-01-01

    An improved arc discharge method is developed to fabricate carbon nanotube probe of atomic force microscopy (AFM) here. First, silicon probe and carbon nanotube are manipulated under an optical microscope by two high precision microtranslators. When silicon probe and carbon nanotube are very close, several tens voltage is applied between them. And carbon nanotube is divided and attached to the end of silicon probe, which mainly due to the arc welding function.Comparing with the arc discharge method before, the new method here needs no coat silicon probe with metal film in advance, which can greatly reduce the fabrication's difficulty. The fabricated carbon nanotube probe shows good property of higher aspect ratio and can more accurately reflect the true topography of silicon grating than silicon probe. Under the same image drive force, carbon nanotube probe had less indentation depth on soft triblock copolymer sample than silicon probe. This showed that carbon nanotube probe has lower spring constant and less damage to the scan sample than silicon probe.

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

    International Nuclear Information System (INIS)

    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 (Wn-, Cn-, C60). 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)

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

    International Nuclear Information System (INIS)

    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+ [Phys. Rev. A, 81, 043428 (2010)]. Limits of the method and potential applications for molecular spectroscopy are discussed

  14. Generating and probing entangled states for optical atomic clocks

    Science.gov (United States)

    Braverman, Boris; Kawasaki, Akio; Vuletic, Vladan

    2016-05-01

    The precision of quantum measurements is inherently limited by projection noise caused by the measurement process itself. Spin squeezing and more complex forms of entanglement have been proposed as ways of surpassing this limitation. In our system, a high-finesse asymmetric micromirror-based optical cavity can mediate the atom-atom interaction necessary for generating entanglement in an 171 Yb optical lattice clock. I will discuss approaches for creating, characterizing, and optimally utilizing these nonclassical states for precision measurement, as well as recent progress toward their realization. This research is supported by DARPA QuASAR, NSF, and NSERC.

  15. 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.

  16. Distributed force probe bending model of critical dimension atomic force microscopy bias

    Science.gov (United States)

    Ukraintsev, Vladimir A.; Orji, Ndubuisi G.; Vorburger, Theodore V.; Dixson, Ronald G.; Fu, Joseph; Silver, Rick M.

    2013-04-01

    Critical dimension atomic force microscopy (CD-AFM) is a widely used reference metrology technique. To characterize modern semiconductor devices, small and flexible probes, often 15 to 20 nm in diameter, are used. Recent studies have reported uncontrolled and significant probe-to-probe bias variation during linewidth and sidewall angle measurements. To understand the source of these variations, tip-sample interactions between high aspect ratio features and small flexible probes, and their influence on measurement bias, should be carefully studied. Using theoretical and experimental procedures, one-dimensional (1-D) and two-dimensional (2-D) models of cylindrical probe bending relevant to carbon nanotube (CNT) AFM probes were developed and tested. An earlier 1-D bending model was refined, and a new 2-D distributed force (DF) model was developed. Contributions from several factors were considered, including: probe misalignment, CNT tip apex diameter variation, probe bending before snapping, and distributed van der Waals-London force. A method for extracting Hamaker probe-surface interaction energy from experimental probe-bending data was developed. Comparison of the new 2-D model with 1-D single point force (SPF) model revealed a difference of about 28% in probe bending. A simple linear relation between biases predicted by the 1-D SPF and 2-D DF models was found. The results suggest that probe bending can be on the order of several nanometers and can partially explain the observed CD-AFM probe-to-probe variation. New 2-D and three-dimensional CD-AFM data analysis software is needed to take full advantage of the new bias correction modeling capabilities.

  17. Scanning probeatomic force microscopy: new developments and applications

    International Nuclear Information System (INIS)

    Recent developments in scanning probe microscopy (SPM) have widened the spectrum of possible investigations that can be performed at a nanometric level at the surfaces of materials. They range, for instance, from physical properties such as surface potential and electric field topological determination to chemical, nanomechanical, catalytic and spectroscopic analysis in air in liquid or in a gaseous environment. After a brief introduction to new SPM technological developments, we present recent achievements in the characterisation and application of nanomorphology, electrostatic surface potential, dielectric properties, shear force microscopy and radiofrequency measurements, scanning microwave microscopy, nanomechanical properties mapping, frequency modulation SPM in air, liquid, vacuum, and finally high-speed SPM

  18. Atomic resolution in noncontact AFM by probing cantilever frequency shifts

    Institute of Scientific and Technical Information of China (English)

    Hong Yong Xie

    2007-01-01

    Rutile TiO2(001) quantum dots (or nano-marks) in different shapes were used to imitate uncleaved material surfaces or materials with rough surfaces. By numerical integration of the equation of motion of cantilever for silicon tip scanning along the [110] direction over the rutile TiO2 (001) quantum dots in ultra high vacuum (UHV), scanning routes were explored to achieve atomic resolution from frequency shift image. The tip-surface interaction forces were calculated from Lennard-Jones (12-6) potential by the Hamaker summation method. The calculated results showed that atomic resolution could be achieved by frequency shift image for TiO2 (001) surfaces of rhombohedral quantum dot scanning in a vertical route, and spherical cap quantum dot scanning in a superposition route.

  19. Fabrication of specimens of metamorphic magnetite crystals for field ion microscopy and atom probe microanalysis.

    Science.gov (United States)

    Kuhlman, K R; Martens, R L; Kelly, T F; Evans, N D; Miller, M K

    2001-10-01

    Field ion specimens have been successfully fabricated from samples of metamorphic magnetite crystals (Fe3O4) extracted from a polymetamorphosed, granulite-facies marble with the use of a focused ion beam. These magnetite crystals contain nanometer-scale, disk-shaped inclusions making this magnetite particularly attractive for investigating the capabilities of atom probe field ion microscopy (APFIM) for geological materials. Field ion microscope images of these magnetite crystals were obtained in which the observed size and morphology of the precipitates agree with previous results. Samples were analyzed in the energy compensated optical position-sensitive atom probe. Mass spectra were obtained in which peaks for singly ionized 16O, 56Fe and 56FeO and doubly ionized 54Fe, 56Fe and 57Fe peaks were fully resolved. Manganese and aluminum were observed in a limited analysis of a precipitate in an energy compensated position sensitive atom probe. PMID:11770743

  20. Influence of the wavelength on the spatial resolution of pulsed-laser atom probe

    Energy Technology Data Exchange (ETDEWEB)

    Gault, B. [Australian Centre for Microscopy and Microanalysis, Madsen Building F09, University of Sydney, NSW 2006 (Australia); Institute of Materials and Engineering Science, Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234 (Australia); Chen, Y. M.; Hono, K. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0047 (Japan); National Institute for Materials Science, Tsukuba 305-0047 (Japan); Moody, M. P.; Ringer, S. P. [Australian Centre for Microscopy and Microanalysis, Madsen Building F09, University of Sydney, NSW 2006 (Australia); Ohkubo, T. [National Institute for Materials Science, Tsukuba 305-0047 (Japan)

    2011-11-01

    Modern atom probes typically incorporate an ultrafast pulsed-laser source with wavelength ranging from infrared (IR) to ultraviolet (UV) depending on the specific instrument. In order to estimate the influence of the wavelength on the accuracy of the technique, the achievable in-depth spatial resolution has been measured for atom probe analyses of the same pure W specimen using three different wavelengths and across a range of laser pulse energies. UV illumination is shown to yield superior spatial resolution to both IR and visible (green) wavelengths. We propose that this improvement relates to a faster decay of temperature enabled by light absorption confined to the near apex region.

  1. A new systematic framework for crystallographic analysis of atom probe data

    Energy Technology Data Exchange (ETDEWEB)

    Araullo-Peters, Vicente J., E-mail: vicente.araullopeters@gmail.com [Australian Centre for Microscopy and Microanalysis, University of Sydney (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney (Australia); Breen, Andrew; Ceguerra, Anna V. [Australian Centre for Microscopy and Microanalysis, University of Sydney (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney (Australia); Gault, Baptiste [Department of Materials, University of Oxford, Parks Road, Oxford (United Kingdom); Ringer, Simon P.; Cairney, Julie M. [Australian Centre for Microscopy and Microanalysis, University of Sydney (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney (Australia)

    2015-07-15

    In this article, after a brief introduction to the principles behind atom probe crystallography, we introduce methods for unambiguously determining the presence of crystal planes within atom probe datasets, as well as their characteristics: location; orientation and interplanar spacing. These methods, which we refer to as plane orientation extraction (POE) and local crystallography mapping (LCM) make use of real-space data and allow for systematic analyses. We present here application of POE and LCM to datasets of pure Al, industrial aluminium alloys and doped-silicon. Data was collected both in DC voltage mode and laser-assisted mode (in the latter of which extracting crystallographic information is known to be more difficult due to distortions). The nature of the atomic planes in both datasets was extracted and analysed. - Highlights: • A new analysis method was designed that determines if reconstructed planes are present in atom probe data. • The location, orientation, and planar spacing of these planes are obtained. • This method was applied to simulated, aluminium alloy and silicon data where the extent of planes was shown to vary considerably. • This method can be used to examine atom probe reconstruction quality.

  2. A new systematic framework for crystallographic analysis of atom probe data

    International Nuclear Information System (INIS)

    In this article, after a brief introduction to the principles behind atom probe crystallography, we introduce methods for unambiguously determining the presence of crystal planes within atom probe datasets, as well as their characteristics: location; orientation and interplanar spacing. These methods, which we refer to as plane orientation extraction (POE) and local crystallography mapping (LCM) make use of real-space data and allow for systematic analyses. We present here application of POE and LCM to datasets of pure Al, industrial aluminium alloys and doped-silicon. Data was collected both in DC voltage mode and laser-assisted mode (in the latter of which extracting crystallographic information is known to be more difficult due to distortions). The nature of the atomic planes in both datasets was extracted and analysed. - Highlights: • A new analysis method was designed that determines if reconstructed planes are present in atom probe data. • The location, orientation, and planar spacing of these planes are obtained. • This method was applied to simulated, aluminium alloy and silicon data where the extent of planes was shown to vary considerably. • This method can be used to examine atom probe reconstruction quality

  3. Adhesive properties of Staphylococcus epidermidis probed by atomic force microscopy

    DEFF Research Database (Denmark)

    Hu, Yifan; Ulstrup, Jens; Zhang, Jingdong;

    2011-01-01

    (biofilm positive and biofilm negative strains) were analyzed using in situ atomic force microscopy (AFM). Force measurements performed using bare hydrophilic silicon nitride tips disclosed similar adhesive properties for each strain. However, use of hydrophobic tips showed that hydrophobic forces are not......Mapping of the surface properties of Staphylococcus epidermidis and of biofilm forming bacteria in general is a key to understand their functions, particularly their adhesive properties. To gain a comprehensive view of the structural and chemical properties of S. epidermidis, four different strains...

  4. 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.)

  5. Design and optimization of a harmonic probe with step cross section in multifrequency atomic force microscopy.

    Science.gov (United States)

    Cai, Jiandong; Wang, Michael Yu; Zhang, Li

    2015-12-01

    In multifrequency atomic force microscopy (AFM), probe's characteristic of assigning resonance frequencies to integer harmonics results in a remarkable improvement of detection sensitivity at specific harmonic components. The selection criterion of harmonic order is based on its amplitude's sensitivity on material properties, e.g., elasticity. Previous studies on designing harmonic probe are unable to provide a large design capability along with maintaining the structural integrity. Herein, we propose a harmonic probe with step cross section, in which it has variable width in top and bottom steps, while the middle step in cross section is kept constant. Higher order resonance frequencies are tailored to be integer times of fundamental resonance frequency. The probe design is implemented within a structural optimization framework. The optimally designed probe is micromachined using focused ion beam milling technique, and then measured with an AFM. The measurement results agree well with our resonance frequency assignment requirement. PMID:26724066

  6. Muonium as a probe of hydrogen-atom reactions

    International Nuclear Information System (INIS)

    Muonium is a light isotope of hydrogen and can be used as a tracer substitute for hydrogen to investigate liquid-phase hydrogen-atom reactions not amenable to study by more conventional means. The residual polarization method of muon spin rotation is illustrated by an investigation of the reaction of muonium with sodium thiosulphate in aqueous solution. The rate constant has been determined directly from measurements of muonium decay rates in very dilute solutions, ksub(M) =(1.5 +-0.4) x 1010 dm3 mol-1 s-1. Possible reaction mechanisms have been explored by analysis of the field and concentration dependence of the diamagnetic signal amplitude in concentrated solutions. The conclusion is that hydrogen atoms react with thiosulphate, probably first forming a radical adduct HSSO32- which decomposes in 1 ns or less to give HS- + SO3-, or possibly H+ + .S- + SO32-. The consequences of time-dependent rate constants on the residual-polarization analysis are discussed in an appendix. (author)

  7. Probing electronic and structural properties of single molecules on the atomic scale

    OpenAIRE

    Mohn, Fabian

    2012-01-01

    In this thesis work, a combination of low-temperature scanning tunneling microscopy (STM) and atomic force microscopy (AFM) was used to study single atoms and molecules on thin insulating films. We show that noncontact-AFM can yield important additional information for these systems, which had previously been studied only with STM. In particular, we demonstrate that the charge states of single gold adatoms can be detected with Kelvin probe force microscopy (KPFM). Furthermore, it is descr...

  8. Single-atom aided probe of the decoherence of a Bose-Einstein condensate

    OpenAIRE

    Ng, H. T.; Bose, S.

    2008-01-01

    We study a two-level atom coupled to a Bose-Einstein condensate. We show that the rules governing the decoherence of mesoscopic superpositions involving different classical-like states of the condensate can be probed using this system. This scheme is applicable irrespective of whether the condensate is initially in a coherent, thermal or more generally in any mixture of coherent states. The effects of atom loss and finite temperature to the decoherence can therefore be studied. We also discus...

  9. Atomic resolution probe for allostery in the regulatory thin filament.

    Science.gov (United States)

    Williams, Michael R; Lehman, Sarah J; Tardiff, Jil C; Schwartz, Steven D

    2016-03-22

    Calcium binding and dissociation within the cardiac thin filament (CTF) is a fundamental regulator of normal contraction and relaxation. Although the disruption of this complex, allosterically mediated process has long been implicated in human disease, the precise atomic-level mechanisms remain opaque, greatly hampering the development of novel targeted therapies. To address this question, we used a fully atomistic CTF model to test both Ca(2+)binding strength and the energy required to remove Ca(2+)from the N-lobe binding site in WT and mutant troponin complexes that have been linked to genetic cardiomyopathies. This computational approach is combined with measurements of in vitro Ca(2+)dissociation rates in fully reconstituted WT and cardiac troponin T R92L and R92W thin filaments. These human disease mutations represent known substitutions at the same residue, reside at a significant distance from the calcium binding site in cardiac troponin C, and do not affect either the binding pocket affinity or EF-hand structure of the binding domain. Both have been shown to have significantly different effects on cardiac function in vivo. We now show that these mutations independently alter the interaction between the Ca(2+)ion and cardiac troponin I subunit. This interaction is a previously unidentified mechanism, in which mutations in one protein of a complex indirectly affect a third via structural and dynamic changes in a second to yield a pathogenic change in thin filament function that results in mutation-specific disease states. We can now provide atom-level insight that is potentially highly actionable in drug design. PMID:26957598

  10. Frequency Domain Fluorescent Molecular Tomography and Molecular Probes for Small Animal Imaging

    Science.gov (United States)

    Kujala, Naresh Gandhi

    Fluorescent molecular tomography (FMT) is a noninvasive biomedical optical imaging that enables 3-dimensional quantitative determination of fluorochromes distributed in biological tissues. There are three methods for imaging large volume tissues based on different light sources: (a) using a light source of constant intensity, through a continuous or constant wave, (b) using a light source that is intensity modulated with a radio frequency (RF), and (c) using ultrafast pulses in the femtosecond range. In this study, we have developed a frequency domain fluorescent molecular tomographic system based on the heterodyne technique, using a single source and detector pair that can be used for small animal imaging. In our system, the intensity of the laser source is modulated with a RF frequency to produce a diffuse photon density wave in the tissue. The phase of the diffuse photon density wave is measured by comparing the reference signal with the signal from the tissue using a phasemeter. The data acquisition was performed by using a Labview program. The results suggest that we can measure the phase change from the heterogeneous inside tissue. Combined with fiber optics and filter sets, the system can be used to sensitively image the targeted fluorescent molecular probes, allowing the detection of cancer at an early stage. We used the system to detect the tumor-targeting molecular probe Alexa Fluor 680 and Alexa Fluor 750 bombesin peptide conjugates in phantoms as well as mouse tissues. We also developed and evaluated fluorescent Bombesin (BBN) probes to target gastrin-releasing peptide (GRP) receptors for optical molecular imaging. GRP receptors are over-expressed in several types of human cancer cells, including breast, prostate, small cell lung, and pancreatic cancers. BBN is a 14 amino acid peptide that is an analogue to human gastrin-releasing peptide that binds specifically to GRPr receptors. BBN conjugates are significant in cancer detection and therapy. The

  11. 'Big Bang' tomography as a new route to atomic-resolution electron tomography.

    Science.gov (United States)

    Van Dyck, Dirk; Jinschek, Joerg R; Chen, Fu-Rong

    2012-06-14

    Until now it has not been possible to image at atomic resolution using classical electron tomographic methods, except when the target is a perfectly crystalline nano-object imaged along a few zone axes. The main reasons are that mechanical tilting in an electron microscope with sub-ångström precision over a very large angular range is difficult, that many real-life objects such as dielectric layers in microelectronic devices impose geometrical constraints and that many radiation-sensitive objects such as proteins limit the total electron dose. Hence, there is a need for a new tomographic scheme that is able to deduce three-dimensional information from only one or a few projections. Here we present an electron tomographic method that can be used to determine, from only one viewing direction and with sub-ångström precision, both the position of individual atoms in the plane of observation and their vertical position. The concept is based on the fact that an experimentally reconstructed exit wave consists of the superposition of the spherical waves that have been scattered by the individual atoms of the object. Furthermore, the phase of a Fourier component of a spherical wave increases with the distance of propagation at a known 'phase speed'. If we assume that an atom is a point-like object, the relationship between the phase and the phase speed of each Fourier component is linear, and the distance between the atom and the plane of observation can therefore be determined by linear fitting. This picture has similarities with Big Bang cosmology, in which the Universe expands from a point-like origin such that the distance of any galaxy from the origin is linearly proportional to the speed at which it moves away from the origin (Hubble expansion). The proof of concept of the method has been demonstrated experimentally for graphene with a two-layer structure and it will work optimally for similar layered materials, such as boron nitride and molybdenum disulphide

  12. A handheld optical fiber parallel acoustic delay line (PADL) probe for photoacoustic tomography

    Science.gov (United States)

    Cho, Young; Chang, Cheung-Chung; Jeon, Mansik; Kim, Chulhong; Wang, Lihong V.; Zou, Jun

    2014-03-01

    In current photoacoustic tomography (PAT), l-D or 2-D ultrasound arrays and multi-channel data acquisition (DAQ) electronics are used to detect the photoacoustic signals simultaneously for "real-time" image construction. However, as the number of transducer elements and DAQ channels increase, the construction and operation of the ultrasound receiving system will become complex and costly. This situation can be addressed by using parallel acoustic delay lines (PADLs) to create true time delays in multiple PA signal channels. The time-delayed PA signals will reach the ultrasound transducer at different times and therefore can be received by one single-element transducer without mixing with each other. In this paper, we report the development of the first miniaturized PADL probe suitable for handheld operations. Fusedsilica optical fibers with low acoustic attenuation were used to construct the 16 PADLs with specific time delays. The handheld probe structure was fabricated using precision laser-micromachining process to provide robust mechanical support and accurate alignment of the PADLs with minimal acoustic distortion and inter-channel coupling. The 16 optical-fiber PADLs were arranged to form one input port and two output ports. Photoacoustic imaging of a black-ink target embedded in an optically-scattering phantom was successfully conducted using the handheld PADL probe with two single-element transducers and two DAQ channels (equal to a channel reduction ratio of 8:1). Our results show that the PADL technique and the handheld probe could provide a promising solution for real-time PAT with significantly reduced complexity and cost of the ultrasound receiver system.

  13. ATOM-PROBE RESULTS SUPPORT THE SKELETON MODEL FOR WC-Co

    OpenAIRE

    Henjered, A.; Hellsing, M.; Andrén, H.; Nordén, H.

    1984-01-01

    WC/WC boundaries in WC-Co type cemented carbides have been analysed with the atom-probe instrument. The boundaries contained about half a monolayer of cobalt (or Co + Cr) and can therefore be described as grain boundaries with cobalt segregation. The results support the "continuous skeleton" mode1 of WC-Co.

  14. High sensitivity probe absorption technique for time-of-flight measurements on cold atoms

    Indian Academy of Sciences (India)

    A K Mohapatra; C S Unnikrishnan

    2006-06-01

    We report on a phase-sensitive probe absorption technique with high sensitivity, capable of detecting a few hundred ultra-cold atoms in flight in an observation time of a few milliseconds. The large signal-to-noise ratio achieved is sufficient for reliable measurements on low intensity beams of cold atoms. We demonstrate the high sensitivity and figure of merit of the simple method by measuring the time-of-flight of atoms moving upwards from a magneto-optical trap released in the gravitational field.

  15. A variable-width harmonic probe for multifrequency atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Jiandong; Zhang, Li [Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, NT (Hong Kong); Xia, Qi, E-mail: qxia@mail.hust.edu.cn, E-mail: michael.wang@nus.edu.sg [State Key Laboratory of Digital Manufacturing Equipment of Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Luo, Yangjun [State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024 (China); Wang, Michael Yu, E-mail: qxia@mail.hust.edu.cn, E-mail: michael.wang@nus.edu.sg [Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, NT (Hong Kong); Department of Mechanical Engineering, National University of Singapore, Singapore 117575 (Singapore)

    2015-02-16

    In multifrequency atomic force microscopy (AFM) to simultaneously measure topography and material properties of specimens, it is highly desirable that the higher order resonance frequencies of the cantilever probe are assigned to be integer harmonics of the excitation frequency. The harmonic resonances are essential for significant enhancement of the probe's response at the specified harmonic frequencies. In this letter, a structural optimization technique is employed to design cantilever probes so that the ratios between one or more higher order resonance frequencies and the fundamental natural frequency are ensured to be equal to specified integers and, in the meantime, that the fundamental natural frequency is maximized. Width profile of the cantilever probe is the design variable in optimization. Thereafter, the probes were prepared by modifying a commercial probe through the focused ion beam (FIB) milling. The resonance frequencies of the FIB fabricated probes were measured with an AFM. Results of the measurement show that the optimal design of probe is as effective as design prediction.

  16. Submolecular Imaging by Noncontact Atomic Force Microscopy with an Oxygen Atom Rigidly Connected to a Metallic Probe.

    Science.gov (United States)

    Mönig, Harry; Hermoso, Diego R; Díaz Arado, Oscar; Todorović, Milica; Timmer, Alexander; Schüer, Simon; Langewisch, Gernot; Pérez, Rubén; Fuchs, Harald

    2016-01-26

    In scanning probe microscopy, the imaging characteristics in the various interaction channels crucially depend on the chemical termination of the probe tip. Here we analyze the contrast signatures of an oxygen-terminated copper tip with a tetrahedral configuration of the covalently bound terminal O atom. Supported by first-principles calculations we show how this tip termination can be identified by contrast analysis in noncontact atomic force and scanning tunneling microscopy (NC-AFM, STM) on a partially oxidized Cu(110) surface. After controlled tip functionalization by soft indentations of only a few angstroms in an oxide nanodomain, we demonstrate that this tip allows imaging an organic molecule adsorbed on Cu(110) by constant-height NC-AFM in the repulsive force regime, revealing its internal bond structure. In established tip functionalization approaches where, for example, CO or Xe is deliberately picked up from a surface, these probe particles are only weakly bound to the metallic tip, leading to lateral deflections during scanning. Therefore, the contrast mechanism is subject to image distortions, artifacts, and related controversies. In contrast, our simulations for the O-terminated Cu tip show that lateral deflections of the terminating O atom are negligible. This allows a detailed discussion of the fundamental imaging mechanisms in high-resolution NC-AFM experiments. With its structural rigidity, its chemically passivated state, and a high electron density at the apex, we identify the main characteristics of the O-terminated Cu tip, making it a highly attractive complementary probe for the characterization of organic nanostructures on surfaces. PMID:26605698

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

    International Nuclear Information System (INIS)

    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.)

  18. A new systematic framework for crystallographic analysis of atom probe data.

    Science.gov (United States)

    Araullo-Peters, Vicente J; Breen, Andrew; Ceguerra, Anna V; Gault, Baptiste; Ringer, Simon P; Cairney, Julie M

    2015-07-01

    In this article, after a brief introduction to the principles behind atom probe crystallography, we introduce methods for unambiguously determining the presence of crystal planes within atom probe datasets, as well as their characteristics: location; orientation and interplanar spacing. These methods, which we refer to as plane orientation extraction (POE) and local crystallography mapping (LCM) make use of real-space data and allow for systematic analyses. We present here application of POE and LCM to datasets of pure Al, industrial aluminium alloys and doped-silicon. Data was collected both in DC voltage mode and laser-assisted mode (in the latter of which extracting crystallographic information is known to be more difficult due to distortions). The nature of the atomic planes in both datasets was extracted and analysed. PMID:25747179

  19. Electromagnetically induced transparency with cold Rydberg atoms: Superatom model beyond the weak-probe approximation

    Science.gov (United States)

    Liu, Yi-Mou; Yan, Dong; Tian, Xue-Dong; Cui, Cui-Li; Wu, Jin-Hui

    2014-03-01

    We present an improved superatom model for examining nonlinear optical responses of cold Rydberg atoms in the regime of electromagnetically induced transparency (EIT). By going beyond the weak-probe approximation, we find that several higher-order collective states should be included to correctly describe the coherent Rydberg excitation of superatoms. Otherwise, numerical results based on the simple ladder system of superatoms will contribute wrong predictions on light intensity and photon correlation of the transmitted probe field. In particular, a great photon-bunching effect will be improperly expected somewhere out of the EIT window in one dilute atomic sample. The essence of this improved superatom model lies in that it can provide reliable predictions on the nonlinear Rydberg-EIT phenomena even in dense atomic samples and may be extended to realize lossless conditional light interactions in appropriate multilevel systems exhibiting dipole blockade.

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

    International Nuclear Information System (INIS)

    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 3He and 4He in tungsten

  1. An Atom Probe Tomographic Investigation of High-Strength, High-Toughness Precipitation Strengthened Steels for Naval Applications

    Science.gov (United States)

    Hunter, Allen H.

    Novel high-strength high-toughness alloys strengthened by precipitation are investigated for use in naval applications. The mechanical properties of an experimental steel alloy, NUCu-140, are evaluated and are not suitable for the naval requirements due to poor impact toughness at -40°C. An investigation is conducted to determine optimum processing conditions to restore toughness. A detailed aging study is conducted at 450, 500, and 550°C to determine the evolution of the microstructure and mechanical properties. A combination of transmission electron microscopy (TEM), synchrotron X-ray Diffraction (XRD), and Local electrode atom probe (LEAP) tomography are used to measure the evolution of the Cu precipitates, austenite, NbC, and cementite phases during aging. The evolution of the Cu precipitates significantly affects the yield strength of the steel, but low temperature toughness is controlled by the cementite precipitates. Extended aging is effective at improving the impact toughness but the yield strength is also decreased due to coarsening of the Cu precipitates. To provide a foundation for successful welding of NUCu-140 steel, an investigation of the effects of gas metal arc welding (GMAW) are performed. The microstructures in the base metal (BM), heat affected zone (HAZ), and fusion zone (FZ) of a GMAW sample are analyzed to determine the effects of the welding thermal cycle. Weld simulation samples with known thermal histories are prepared and analyzed by XRD and LEAP tomography. A significant loss in microhardness is observed as a result of dissolution of the Cu precipitates after the weld thermal cycle. The cooling time is too rapid to allow significant precipitation of Cu. In addition to the NUCu-140 alloy, a production HSLA-115 steel alloy is investigated using TEM, XRD, and LEAP tomography. The strength of the HSLA-115 is found to be derived primarily from Cu precipitates. The volume fractions of cementite, austenite, and NbC are measured by XRD

  2. Design and optimization of a harmonic probe with step cross section in multifrequency atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Jiandong; Zhang, Li [Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, NT (Hong Kong); Wang, Michael Yu, E-mail: michael.wang@nus.edu.sg [Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, NT (Hong Kong); Department of Mechanical Engineering, National University of Singapore, Singapore 117575 (Singapore)

    2015-12-15

    In multifrequency atomic force microscopy (AFM), probe’s characteristic of assigning resonance frequencies to integer harmonics results in a remarkable improvement of detection sensitivity at specific harmonic components. The selection criterion of harmonic order is based on its amplitude’s sensitivity on material properties, e.g., elasticity. Previous studies on designing harmonic probe are unable to provide a large design capability along with maintaining the structural integrity. Herein, we propose a harmonic probe with step cross section, in which it has variable width in top and bottom steps, while the middle step in cross section is kept constant. Higher order resonance frequencies are tailored to be integer times of fundamental resonance frequency. The probe design is implemented within a structural optimization framework. The optimally designed probe is micromachined using focused ion beam milling technique, and then measured with an AFM. The measurement results agree well with our resonance frequency assignment requirement.

  3. Design and optimization of a harmonic probe with step cross section in multifrequency atomic force microscopy

    International Nuclear Information System (INIS)

    In multifrequency atomic force microscopy (AFM), probe’s characteristic of assigning resonance frequencies to integer harmonics results in a remarkable improvement of detection sensitivity at specific harmonic components. The selection criterion of harmonic order is based on its amplitude’s sensitivity on material properties, e.g., elasticity. Previous studies on designing harmonic probe are unable to provide a large design capability along with maintaining the structural integrity. Herein, we propose a harmonic probe with step cross section, in which it has variable width in top and bottom steps, while the middle step in cross section is kept constant. Higher order resonance frequencies are tailored to be integer times of fundamental resonance frequency. The probe design is implemented within a structural optimization framework. The optimally designed probe is micromachined using focused ion beam milling technique, and then measured with an AFM. The measurement results agree well with our resonance frequency assignment requirement

  4. Conductive transparent fiber probes for shear-force atomic force microscopes

    International Nuclear Information System (INIS)

    New conductive transparent (CT) probes that can inject currents into nanometer-sized regions and collect light from them have been developed for shear-force atomic force microscopy (SF-AFM) of partially isolative regions. The CT probe consists of a straight elastic silica fiber with one end tapered to a point. The taper is coated with an indium-tin-oxide film as a transparent electrode, and the probe apex has a nanometer-scale radius. The essential feature of the CT probes is coaxial nickel plating on the shaft of the isolative silica fiber, which is adjusted to obtain suitable elasticity for smooth shear-force feedback as well as for supplying currents to the transparent electrode. Experimental results clarified that nickel thickness between 0.5 and 15 μm on 20 mm-long fibers makes resistance low enough for supplying current to the probe apex and also makes the Q curves smooth enough for shear-force feedback. Clear SF-AFM and current images were successfully obtained for a sample containing both conductive and isolative regions. The CT probes for SF-AFM can expand applications of probe-current-induced luminescence measurements to samples that contain highly resistive and isolative regions, for which scanning tunneling microscopy cannot be applied

  5. Characterization of microfabricated probes for combined atomic force and high-resolution scanning electrochemical microscopy.

    Science.gov (United States)

    Gullo, Maurizio R; Frederix, Patrick L T M; Akiyama, Terunobu; Engel, Andreas; deRooij, Nico F; Staufer, Urs

    2006-08-01

    A combined atomic force and scanning electrochemical microscope probe is presented. The probe is electrically insulated except at the very apex of the tip, which has a radius of curvature in the range of 10-15 nm. Steady-state cyclic voltammetry measurements for the reduction of Ru(NH3)6Cl3 and feedback experiments showed a distinct and reproducible response of the electrode. These experimental results agreed with finite element simulations for the corresponding diffusion process. Sequentially topographical and electrochemical studies of Pt lines deposited onto Si3N4 and spaced 100 nm apart (edge to edge) showed a lateral electrochemical resolution of 10 nm. PMID:16878880

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

    International Nuclear Information System (INIS)

    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.

  7. Development of atomic radical monitoring probe and its application to spatial distribution measurements of H and O atomic radical densities in radical-based plasma processing

    International Nuclear Information System (INIS)

    Atomic radicals such as hydrogen (H) and oxygen (O) play important roles in process plasmas. In a previous study, we developed a system for measuring the absolute density of H, O, nitrogen, and carbon atoms in plasmas using vacuum ultraviolet absorption spectroscopy (VUVAS) with a compact light source using an atmospheric pressure microplasma [microdischarge hollow cathode lamp (MHCL)]. In this study, we developed a monitoring probe for atomic radicals employing the VUVAS with the MHCL. The probe size was 2.7 mm in diameter. Using this probe, only a single port needs to be accessed for radical density measurements. We successfully measured the spatial distribution of the absolute densities of H and O atomic radicals in a radical-based plasma processing system by moving the probe along the radial direction of the chamber. This probe allows convenient analysis of atomic radical densities to be carried out for any type of process plasma at any time. We refer to this probe as a ubiquitous monitoring probe for atomic radicals.

  8. Tomography of laser cooled atoms in MOT using Rydberg state excitation

    International Nuclear Information System (INIS)

    Full text: The position selective dimensional study of laser cooled atoms in Magneto-Optical Trap (MOT) is usually performed using optical detection. Nevertheless, many years ago a more precise method of imaging of atomic beams was developed using ionization of atoms and detection of produced electrons and ions using secondary electron multipliers. This technique demonstrates the possibility to detect a few atoms making it attractive for experiments with a small density of atoms. In the current paper we have performed an experiment directed to observe the difference in the space distribution of Rb atoms in MOT in the first exited state (5P) caused various selection (dark or bright) of the repumping transition. In the our experiment we produced a cold atomic cloud of 107 Rb atoms cooled using conventional MOT setup. After that atoms were optically exited to the Rydberg state using cascade transitions: 5S→5P→8S (decay)→ 6P→nS;nD (n ∼ 37). First excitation pulse (5P→8S) was performed by pulsed dye laser (Rodamine G6, 615 nm). Second, pulse of the Ti:Sa laser at 740 nm was applied to the transitions 6P→ nS;nD. Laser beams were focused to the trap and crossed under angle near 90 degree. The Rydberg atoms were detected using selective field ionization technique. The Ti:Sa laser beam was 1D scanned across the atomic cloud using a deffector based on galvanometer driven lens. The optical detection unit was controlled using a computer. It allows us to make position sensitive measurements of the Rydberg state excitation rate. Averaged data on counts of Rydberg atoms was used to determine population of the 5P state in separate parts of the atomic cloud. Experimental tomography data obtained for locking of the repumping laser to the bright or dark transition, show different 5P 1D profiles of the trap. Observed phenomena were in agreement with theoretical predictions and our previous results. This technique is a non-destructive method of measurement of exited state

  9. Probing Charges on the Atomic Scale by Means of Atomic Force Microscopy.

    Science.gov (United States)

    Albrecht, F; Repp, J; Fleischmann, M; Scheer, M; Ondráček, M; Jelínek, P

    2015-08-14

    Kelvin probe force spectroscopy was used to characterize the charge distribution of individual molecules with polar bonds. Whereas this technique represents the charge distribution with moderate resolution for large tip-molecule separations, it fails for short distances. Here, we introduce a novel local force spectroscopy technique which allows one to better disentangle electrostatic from other contributions in the force signal. It enables one to obtain charge-related maps at even closer tip-sample distances, where the lateral resolution is further enhanced. This enhanced resolution allows one to resolve contrast variations along individual polar bonds. PMID:26317733

  10. Atom probe field ion microscopy investigation of boron containing martensitic 9 Pct chromium steel

    Science.gov (United States)

    Hofer, P.; Miller, M. K.; Babu, S. S.; David, S. A.; Cerjak, H.

    2000-03-01

    The chemical compositions of the ferrite matrix and various other phases in an Fe-0.17 C-9 Cr-1.55 Mo-0.27 V-0.015 N-0.01B (mass pct) steel in as-received and crept conditions were measured with atom probe field ion microscopy (APFIM). The results showed the presence of some residual boron within the ferrite matrix. Analyses showed that boron was distributed within M23C6, M6C, MX, and Laves phases. Phosphor atoms were detected at the M23C6-ferrite interface in the crept condition. The results are compared to predictions from thermodynamic calculations.

  11. Interference Effects on the Probe Absorption in a Driven Three-Level Atomic System by a Coherent Pumping Field

    International Nuclear Information System (INIS)

    In this work we analyze the properties of weak probe absorption in a closed three-level atomic system driven by a coherent driving field. The effects of quantum interference from spontaneous emission on the refractive properties in a closed three-level atomic system driven by a coherent pumping field are included into the gain modeling. The density-matrix equations of motion are solved by following perturbation approach and the probe response function is constructed. The probe absorption is obtained by solving Maxwell's equation for propagation of the probe field of slowly varying amplitude. Analytical and numerical simulation of quantum interference effect between the spontaneous decay channels on the absorptive response of a weak probe field in a closed three-level atomic system driven by a coherent driving field, as well as the evolution of probe gain under coherent pumping mode is studied in laser-produced carbon and aluminum plasma with laser intensity > 1010W/cm2. (author)

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

    Science.gov (United States)

    Felfer, Peter; Cairney, Julie

    2016-10-01

    In this paper, we present pathways for improving the reconstruction of atom probe data on a coarse (>10nm) 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. PMID:27449275

  13. Challenges in the study of Fe/MgO/Fe interfaces using 3D Atom Probe

    Energy Technology Data Exchange (ETDEWEB)

    Mazumder, B. [Groupe de Physique des Materiaux, UMR CNRS 6634, CORIA UMR CNRS 6614, UFR Sciences Site du Madrillet, Avenue de l' Université, B.P. 12 76801, Saint Etienne du Rouvray Cedex (France); Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Purohit, Viswas, E-mail: vishwas.purohit@gmail.com [Groupe de Physique des Materiaux, UMR CNRS 6634, CORIA UMR CNRS 6614, UFR Sciences Site du Madrillet, Avenue de l' Université, B.P. 12 76801, Saint Etienne du Rouvray Cedex (France); Department of Plasma Physics, Alliance College of Engineering and Design, Chikkahagade Cross, Chandapura, Anekal Main Road, Anekal, Bangalore 562106, Karnataka (India); Gruber, M.; Vella, A.; Vurpillot, F.; Deconihout, B. [Groupe de Physique des Materiaux, UMR CNRS 6634, CORIA UMR CNRS 6614, UFR Sciences Site du Madrillet, Avenue de l' Université, B.P. 12 76801, Saint Etienne du Rouvray Cedex (France)

    2015-08-31

    Detailed interface studies were conducted on two Fe/MgO/Fe systems having different thicknesses of MgO layers, using a laser assisted 3D atom probe. In conjunction with a detailed 3D reconstruction, the system exhibited an additional oxide formation at the interface between MgO and Fe of the multilayer structure. This oxide formation was found to be independent of the laser wavelength, laser fluence and the thickness of the intermediate layers. By using numerical simulations of field evaporation of two layers having two different evaporation fields, we discuss the possible oxidation mechanisms. - Highlights: • MgO layers (4, 32 nm) between Fe layers were analysed using a laser assisted atom probe. • Varying field evaporation voltages responsible for interfacial oxide layer (bottom) • Numerical simulation used to determine the phenomena taking place at the interfaces • Lasers of wavelengths 515 nm and 343 nm were used for this study.

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

    Science.gov (United States)

    Brinke, Nicolai ten; Schützhold, Ralf

    2016-05-01

    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.

  15. ATOM PROBE MICROANALYSIS OF WELD METAL IN A SUBMERGED ARC WELDED CHROMIUM-MOLYBDENUM STEEL

    OpenAIRE

    Josefsson, B.; Kvist, A.; Andrén, H.

    1987-01-01

    A submerged arc welded 2.25Cr - 1Mo steel has been investigated using electron microscopy and atom probe field ion microscopy. The bainitic microstructure of the as-welded steel consisted of ferrite and martensite. During heat treatment at 690°C the martensite transformed to ferrite and cementite and needle-shaped (Cr,Mo)2C carbides precipitated. Together with a substantial decrease in dislocation density, this resulted in an improvement of the toughness.

  16. Atomic force microscope based Kelvin probe measurements : application to an electrochemical reaction

    OpenAIRE

    Böhmisch, Mathias; Burmeister, Frank; Rettenberger, Armin; Zimmermann, Jörg; Boneberg, Johannes; Leiderer, Paul

    1997-01-01

    An atomic force microscope (AFM) was utilized as a Kelvin probe to determine work functions of several metals and semiconductors quantitarively. Most of the experimental data show excellent agreement with published values measured by photoemission. Variations in work functions as low as 5 mV could be detected with a typical lateral resolution of 20 nm. This method allowed us to analyze and explain the energetics of an electrochemical reaction on the surface of WSe2, which could be in situ ind...

  17. Interface study of FeMgOFe magnetic tunnel junctions using 3D Atom Probe

    CERN Document Server

    Mazumder, B; Vella, A; Vurpillot, F; Deconihout, B

    2011-01-01

    A detailed interface study was conducted on a Fe/MgO/Fe system using laser assisted 3D atom probe. It exhibits an additional oxide formation at the second interface of the multilayer structure independent of laser wavelength, laser fluence and the thickness of the tunnel barrier. We have shown with the help of simulation that this phenomena is caused by the field evaporation of two layers having two different evaporation

  18. 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. For...

  19. Atom probe field-ion microscopy and related topics: A bibliography, 1988

    International Nuclear Information System (INIS)

    This bibliography includes references related to the following topics: field-ion microscopy (FIM), field emission microscopy (FEM), atom probe field-ion microscopy (APFIM), and liquid metal ion sources (LMIS). Technique-orientated 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

  20. Atom probe study of chromium oxide spinels formed during intergranular corrosion

    International Nuclear Information System (INIS)

    Atom probe microscopy has been used to study the inhomogeneous nature of chromium oxide spinels in intergranular corrosion of a 253 MA austenitic stainless steel after thermal cycling up to 970 °C in air. The results indicate that the non-continuous character of the spinel layers originates from nanoscale phases such as iron-rich oxides along the chromite grain boundaries and silicate particles. Their role in the rate of intergranular corrosion is discussed

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    International Nuclear Information System (INIS)

    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

  3. Influence of atomic force microscope (AFM) probe shape on adhesion force measured in humidity environment

    Institute of Scientific and Technical Information of China (English)

    阳丽; 涂育松; 谭惠丽

    2014-01-01

    In micro-manipulation, the adhesion force has very important influence on behaviors of micro-objects. Here, a theoretical study on the effects of humidity on the adhesion force is presented between atomic force microscope (AFM) tips and substrate. The analysis shows that the precise tip geometry plays a critical role on humidity depen-dence of the adhesion force, which is the dominant factor in manipulating micro-objects in AFM experiments. For a blunt (paraboloid) tip, the adhesion force versus humidity curves tends to the apparent contrast (peak-to-valley corrugation) with a broad range. This paper demonstrates that the abrupt change of the adhesion force has high correla-tion with probe curvatures, which is mediated by coordinates of solid-liquid-vapor contact lines (triple point) on the probe profiles. The study provides insights for further under-standing nanoscale adhesion forces and the way to choose probe shapes in manipulating micro-objects in AFM experiments.

  4. Resistance of single polyaniline fibers and their junctions measured by double-probe atomic force microscopy

    Science.gov (United States)

    Higuchi, Rintaro; Shingaya, Yoshitaka; Nakayama, Tomonobu

    2016-08-01

    Electrical properties of polyaniline (PANI) fibers are of our interest as a component of network materials. Using a multiple-probe atomic force microscope with tuning fork probes, we investigated the resistance of single PANI fibers and their cross-point junction where the fibers contact each other. The resistivity of single PANI fibers was measured to be on the order of 10 Ω cm, and the contact resistance between PANI fibers was on the order of GΩ. The resistances through single cross-point junctions between two PANI fibers were very much dependent on the experimental condition, that is, the cross-point junction is stabilized or destabilized by physically placing the probes onto the two fibers. This suggests the nanomechanical instability of the cross-point junctions and a possibility to construct strain-responsive PANI fiber networks.

  5. Imaging the distribution of photoswitchable probes with temporally-unmixed multispectral optoacoustic tomography

    Science.gov (United States)

    Deán-Ben, X. Luís.; Stiel, Andre C.; Jiang, Yuanyuan; Ntziachristos, Vasilis; Westmeyer, Gil G.; Razansky, Daniel

    2016-03-01

    Synthetic and genetically encoded chromo- and fluorophores have become indispensable tools for biomedical research enabling a myriad of applications in imaging modalities based on biomedical optics. The versatility offered by the optoacoustic (photoacoustic) contrast mechanism enables to detect signals from any substance absorbing light, and hence these probes can be used as optoacoustic contrast agents. While contrast versatility generally represents an advantage of optoacoustics, the strong background signal generated by light absorption in endogeneous chromophores hampers the optoacoustic capacity to detect a photo-absorbing agent of interest. Increasing the optoacoustic sensitivity is then determined by the capability to differentiate specific features of such agent. For example, multispectral optoacoustic tomography (MSOT) exploits illuminating the tissue at multiple optical wavelengths to spectrally resolve (unmix) the contribution of different chromophores. Herein, we present an alternative approach to enhance the sensitivity and specificity in the detection of optoacoustic contrast agents. This is achieved with photoswitchable probes that change optical absorption upon illumination with specific optical wavelengths. Thereby, temporally unmixed MSOT (tuMSOT) is based on photoswitching the compounds according to defined schedules to elicit specific time-varying optoacoustic signals, and then use temporal unmixing algorithms to locate the contrast agent based on their particular temporal profile. The photoswitching kinetics is further affected by light intensity, so that tuMSOT can be employed to estimate the light fluence distribution in a biological sample. The performance of the method is demonstrated herein with the reversibly switchable fluorescent protein Dronpa and its fast-switching fatigue resistant variant Dronpa-M159T.

  6. Handheld, rapidly switchable, anterior/posterior segment swept source optical coherence tomography probe.

    Science.gov (United States)

    Nankivil, Derek; Waterman, Gar; LaRocca, Francesco; Keller, Brenton; Kuo, Anthony N; Izatt, Joseph A

    2015-11-01

    We describe the first handheld, swept source optical coherence tomography (SSOCT) system capable of imaging both the anterior and posterior segments of the eye in rapid succession. A single 2D microelectromechanical systems (MEMS) scanner was utilized for both imaging modes, and the optical paths for each imaging mode were optimized for their respective application using a combination of commercial and custom optics. The system has a working distance of 26.1 mm and a measured axial resolution of 8 μm (in air). In posterior segment mode, the design has a lateral resolution of 9 μm, 7.4 mm imaging depth range (in air), 4.9 mm 6dB fall-off range (in air), and peak sensitivity of 103 dB over a 22° field of view (FOV). In anterior segment mode, the design has a lateral resolution of 24 μm, imaging depth range of 7.4 mm (in air), 6dB fall-off range of 4.5 mm (in air), depth-of-focus of 3.6 mm, and a peak sensitivity of 99 dB over a 17.5 mm FOV. In addition, the probe includes a wide-field iris imaging system to simplify alignment. A fold mirror assembly actuated by a bi-stable rotary solenoid was used to switch between anterior and posterior segment imaging modes, and a miniature motorized translation stage was used to adjust the objective lens position to correct for patient refraction between -12.6 and + 9.9 D. The entire probe weighs less than 630 g with a form factor of 20.3 x 9.5 x 8.8 cm. Healthy volunteers were imaged to illustrate imaging performance. PMID:26601014

  7. Probe spectrum of multilevel atoms in a damped, weakly driven two-mode cavity

    International Nuclear Information System (INIS)

    We calculate the probe spectrum for multilevel atoms in a damped, weakly driven cavity supporting two degenerate orthogonally polarized modes. One mode is weakly driven by a linearly polarized external field. The atoms, initially prepared in a mF=0 hyperfine ground state, couple to the driven mode by making a ΔmF=0 transition and to the orthogonally polarized mode by making ΔmF=±1 transitions to other hyperfine sublevels. We compare probe spectra, the intensity of the driven mode, the undriven mode, and the atomic excitation probability as a function of the detuning of the driving laser from the cavity resonance for three- and four-level atomic models. In both cases the spectrum of the driven mode is a vacuum Rabi doublet familiar from the driven, damped Jaynes-Cummings model. The undriven mode spectrum is a triplet with the maximum on resonance for the three-level model while the four-level model has a four-peaked spectrum. We discuss the role of strong coupling to the undriven mode in accounting for the qualitative difference between the models.

  8. Molecular contrast in optical coherence tomography using a pump-probe technique

    Science.gov (United States)

    Rao, K. D.; Choma, Michael A.; Yazdanfar, Siavash; Rollins, Andrew M.; Izatt, Joseph A.

    2003-07-01

    Optical coherence tomography (OCT) is an emerging tool for real time in-situ tissue imaging with micrometer-scale resolution. Real-time OCT systems have been integrated into clinical medical diagnostics, and functional extensions such as polarization-sensitive, Doppler, and spectroscopic OCT have recently been introduced. However, OCT imaging technology has not yet taken advantage of molecular-specific contrast mechanisms which have revolutionized other medical and biological imaging modalities such as MRI, PET, SPECT, and fluorescence microscopy. OCT is by definition insensitive to incoherent scattering processes such fluorescence or spontaneous Raman scattering. We have previously proposed the use of spectroscopic OCT for detection of light from coherent inelastic scattering processes such as stimulated emission, stimulate Raman scattering, and other four-wave mixing processes. In this report we present a new technique which we call pump probe OCT (PPOCT), which is a novel extension of OCT for enhancing the contrast of OCT images based on transient absorption in the sample induced by an external pump beam. We show preliminary data for PPOCT using methylene blue as a molecular contrast agent and show depth resolved PPOCT M-scans that localize the presence of dye in a well phantom.

  9. Probing decisive answers to dark energy questions from cosmic complementarity and lensing tomography

    CERN Document Server

    Ishak, M

    2005-01-01

    We study future constraints on dark energy parameters determined from several combinations of CMB experiments, supernova data, and weak lensing surveys with and without tomography. In this analysis, we look in particular for combinations that will bring the uncertainties to a level of precision tight enough (a few percent) to answer decisively some of the dark energy questions. We probe the dark energy using two variants of its equation of state, and its energy density.We consider a set of 13 cosmological and systematic parameters, and assume reasonable priors on the lensing and supernova systematics. We consider various lensing surveys: a wide survey with f_{sky}=0.7, and with 2 (WLT2) and 5 (WLT5) tomographic bins; a deep survey with 10 bins (WLT10). The constraints found from Planck, 2000 supernovae with z_max=0.8, and WLT2 are: {sigma(w_0)=0.086, sigma(w_1)=0.069}, {sigma(w_0)=0.088, sigma(w_a)=0.11}, and {sigma(E_1)=0.029, sigma(E_2)=0.065}. With 5 bins, we find {sigma(w_0)=0.04, sigma(w_1)=0.034}, {sigm...

  10. Pump-probe optical coherence tomography using microencapsulated methylene blue as a contrast agent (Conference Presentation)

    Science.gov (United States)

    Kim, Wihan; Zebrowski, Erin; Lopez, Hazel C.; Applegate, Brian E.; Charoenphol, Phapanin; Jo, Javier A.

    2016-03-01

    Molecular contrast imaging can target specific molecules or receptors to provide detailed information on the local biochemistry and yield enhanced visualization of pathological and physiological processes. When paired with Optical Coherence Tomography (OCT) it can simultaneously supply the morphological context for the molecular information. We recently demonstrated in vivo molecular contrast imaging of methylene blue (MB) using a 663 nm diode laser as a pump in a Pump-Probe OCT (PPOCT) system. The simple addition of a dichroic mirror in the sample arm enabled PPOCT imaging with a typical 830-nm band spectral-domain OCT system. Here we report on the development of a microencapsulated MB contrast agent. The poly lactic-co-glycolic acid (PLGA) microspheres loaded with MB offer several advantages over bare MB. The microsphere encapsulation improves the PPOCT signal both by enhancing the scattering and preventing the reduction of MB to leucomethylene blue. The surface of the microsphere can readily be functionalized to enable active targeting of the contrast agent without modifying the excited state dynamics of MB that enable PPOCT imaging. Both MB and PLGA are used clinically. PLGA is FDA approved and used in drug delivery and tissue engineering applications. 2.5 μm diameter microspheres were synthesized with an inner core containing 0.01% (w/v) aqueous MB. As an initial demonstration the MB microspheres were imaged in a 100 μm diameter capillary tube submerged in a 1% intralipid emulsion.

  11. Understanding the atomic-scale contrast in Kelvin Probe Force Microscopy

    CERN Document Server

    Nony, Laurent; Bocquet, Franck; Loppacher, Christian; 10.1103/PhysRevLett.103.036802

    2009-01-01

    A numerical analysis of the origin of the atomic-scale contrast in Kelvin probe force microscopy (KPFM) is presented. Atomistic simulations of the tip-sample interaction force field have been combined with a non-contact Atomic Force Microscope/KPFM simulator. The implementation mimics recent experimental results on the (001) surface of a bulk alkali halide crystal for which simultaneous atomic-scale topographical and Contact Potential Difference (CPD) contrasts were reported. The local CPD does reflect the periodicity of the ionic crystal, but not the magnitude of its Madelung surface potential. The imaging mechanism relies on the induced polarization of the ions at the tip-surface interface owing to the modulation of the applied bias voltage. Our findings are in excellent agreement with previous theoretical expectations and experimental observations.

  12. Electron Affinity Calculations for Atoms: Sensitive Probe of Many-Body Effects

    Science.gov (United States)

    Felfli, Z.; Msezane, A. Z.

    2016-05-01

    Electron-electron correlations and core-polarization interactions are crucial for the existence and stability of most negative ions. Therefore, they can be used as a sensitive probe of many-body effects in the calculation of the electron affinities (EAs) of atoms. The importance of relativistic effects in the calculation of the EAs of atoms has recently been assessed to be insignificant up to Z of 85. Here we use the complex angular momentum (CAM) methodology wherein is embedded fully the electron-electron correlations, to investigate core-polarization interactions in low-energy electron elastic scattering from the atoms In, Sn, Eu, Au and At through the calculation of their EAs. For the core-polarization interaction we use the rational function approximation of the Thomas-Fermi potential, which can be analytically continued into the complex plane. The EAs are extracted from the large resonance peaks in the CAM calculated low-energy electron-atom scattering total cross sections and compared with those from measurements and sophisticated theoretical methods. It is concluded that when the electron-electron correlations and core polarization interactions (both major many-body effects) are accounted for adequately the importance of relativity on the calculation of the EAs of atoms can be assessed. Even for the high Z (85) At atom relativistic effects are estimated to contribute a maximum of 3.6% to its EA calculation.

  13. CHEMISORPTION OF CO AND METHANATION ON Rh SURFACES AT LOW TEMPERATURE AND LOW PRESSURE, AN ATOM-PROBE FIM STUDY

    OpenAIRE

    W. Liu; Ren, D.; Bao, C.; Tsong, T.

    1987-01-01

    Pulsed-laser imaging atom-probe and high resolution voltage pulsed atom-probe were employed to study the chemisorption behavior of CO on rhodium surfaces at low temperature and low pressure. The results are consistent and interesting. Our results support dissociative chemisorption on stepped surfaces of Rh and the effect of the surface structures. We also carried out methanation on Rh surfaces under adverse conditions and identified the intermediates of methanation with an isotope exchange te...

  14. Probe integrated scattering cross sections in the analysis of atomic resolution HAADF STEM images

    International Nuclear Information System (INIS)

    The physical basis for using a probe-position integrated cross section (PICS) for a single column of atoms as an effective way to compare simulation and experiment in high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) is described, and the use of PICS in order to make quantitative use of image intensities is evaluated. It is based upon the calibration of the detector and the measurement of scattered intensities. Due to the predominantly incoherent nature of HAADF STEM, it is found to be robust to parameters that affect probe size and shape such as defocus and source coherence. The main imaging parameter dependencies are on detector angle and accelerating voltage, which are well known. The robustness to variation in other parameters allows for a quantitative comparison of experimental data and simulation without the need to fit parameters. By demonstrating the application of the PICS to the chemical identification of single atoms in a heterogeneous catalyst and in thin, layered-materials, we explore some of the experimental considerations when using this approach. - Highlights: • Probe-position integrated cross section (PICS) used to quantitatively compare experimental images of HAADF STEM to simulations. • Theoretical treatment based on the object function approximation is presented. • PICS shown to be robust to experimental parameters. • Considerations for accuracy of experimental analysis and simulations discussed. • Application of PICS analysis to low dimensional, beam sensitive samples show excellent agreement between experiment and simulations

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

    International Nuclear Information System (INIS)

    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 3He and 4He atoms in tungsten. The paper is heavily referenced so that the reader can pursue his specific research interests in detail

  16. Probing the rupture of a Ag atomic junction in a Ag-Au mixed electrode

    Science.gov (United States)

    Kim, Taekyeong

    2015-09-01

    We probed that the atomic junction in Ag part ruptures during stretching of atomic sized contacts of Ag-Au mixed electrodes, resulting in Ag-Ag electrodes through a scanning tunneling microscope breaking junction (STM-BJ) technique. We observed that the conductance and tunneling decay constant for a series of amine-terminated oligophenyl molecular junctions are essentially the same for the Ag-Au mixed and the Ag-Ag electrodes. We also found the molecular plateau length and the evolution patterns with the Ag-Au mixed electrodes are similar to those with Ag-Ag electrodes rather than the Au-Au electrodes in the molecular junction elongation. This result is attributed to the smaller binding energy of Ag atoms compared to that of Au atoms, so the Ag junction part is more easily broken than that of Au part in stretching of Ag-Au mixed electrodes. Furthermore, we successfully observed that the rupture force of the atomic junction for the Ag-Au mixed electrodes was identical to that for the Ag-Ag electrodes and smaller than that for the Au-Au electrodes. This study may advance the understanding of the electrical and the mechanical properties in molecular devices with Ag and Au electrodes in future.

  17. Improved in situ spring constant calibration for colloidal probe atomic force microscopy

    International Nuclear Information System (INIS)

    In colloidal probe atomic force microscopy (AFM) surface forces cannot be measured without an accurate determination of the cantilever spring constant. The effective spring constant k depends upon the cantilever geometry and therefore should be measured in situ; additionally, k may be coupled to other measurement parameters. For example, colloidal probe AFM is frequently used to measure the slip length b at solid/liquid boundaries by comparing the measured hydrodynamic force with Vinogradova slip theory (V-theory). However, in this measurement k and b are coupled, hence, b cannot be accurately determined without knowing k to high precision. In this paper, a new in situ spring constant calibration method based upon the residuals, namely, the difference between experimental force-distance data and V-theory is presented and contrasted with two other popular spring constant determination methods. In this residuals calibration method, V-theory is fitted to the experimental force-distance data for a range of systematically varied spring constants where the only adjustable parameter in V-theory is the slip length b. The optimal spring constant k is that value where the residuals are symmetrically displaced about zero for all colloidal probe separations. This residual spring constant calibration method is demonstrated by studying three different liquids (n-decanol, n-hexadecane, and n-octane) and two different silane coated colloidal probe-silicon wafer systems (n-hexadecyltrichlorosilane and n-dodecyltrichlorosilane).

  18. Pump-probe spectroscopy of cold rubidium atoms in an integrating sphere

    Science.gov (United States)

    Wang, Wen-Li; Dong, Ri-Chang; Deng, Jian-Liao; Wang, Yu-Zhu

    2016-05-01

    Absorption spectra of cold rubidium atoms in an integrating sphere under the influence of a diffuse laser field have been systematically investigated. A pronounced dispersionlike structure centered at the light-shifted pump frequency is observed with a subnatural linewidth. In particular, two clearly resolved absorption resonances on the 5 S1 /2(F =2 ) →5 P3 /2(F'=3 ) transitions occur with variable probe beam intensity, which is consistent with our proposed theoretical model. Based on the two absorption resonances,we measure the dependence of light shifts, from which we can directly extract the effective Rabi frequency in a diffuse laser field, on the probe laser intensity, pump laser intensity, and pump laser detuning. Our work helps to identify the physical mechanisms behind these spectral features and is beneficial for studying the corresponding effect in a cold sample.

  19. Correlated ion analysis and the interpretation of atom probe mass spectra

    International Nuclear Information System (INIS)

    Several techniques are presented for extracting information from atom probe mass spectra by investigating correlations within multiple-ion detector events. Analyses of this kind can provide insights into the origins of noise, the shape of mass peaks, or unexpected anomalies within the spectrum. Data can often be recovered from within the spectrum noise by considering the time-of-flight differences between ions within a multiple event. Correlated ion detection, particularly when associated with shifts in ion energies, may be used to probe the phenomenon of molecular ion dissociation, including the questions of data loss due to ion pile-up or the generation of neutrals in the dissociation process. -- Research Highlights: → Multiple-ion detection events may contain information not seen in the mass spectrum. → Analysis of multiple events can yield information on molecular ion dissociation. → Neutral species may be generated by dissociation subsequent to field evaporation.

  20. Sapphire ball lensed fiber probe for common-path optical coherence tomography in ocular imaging and sensing

    Science.gov (United States)

    Zhao, Mingtao; Huang, Yong; Kang, Jin U.

    2013-03-01

    We describe a novel common-path optical coherence tomography (CP-OCT) fiber probe design using a sapphire ball lens for cross-sectional imaging and sensing in retina vitrectomy surgery. Single mode Gaussian beam (TEM00) simulation was used to optimize lateral resolution and working distance (WD) of the common-path probe. A theoretical sensitivity model for CP-OCT was prosed to assess its optimal performance based an unbalanced photodetector configuration. Two probe designs with working distances (WD) 415μm and 1221μm and lateral resolution 11μm and 18μm, respectively were implemented with sensitivity up to 88dB. The designs are also fully compatible with conventional Michelson interferometer based OCT configurations. The reference plane of the probe, located at the distal beam exit interface of the single mode fiber (SMF), was encased within a 25-gauge hypodermic needle by the sapphire ball lens facilitates its applications in bloody and harsh environments. The performances of the fiber probe with 11μm of lateral resolution and 19μm of axial resolution were demonstrated by cross-sectional imaging of a cow cornea and retina in vitro with a 1310nm swept source OCT system. This probe was also attached to a piezoelectric motor for active compensation of physiological tremor for handheld retinal surgical tools.

  1. Atom probe study of grain boundary segregation in technically pure molybdenum

    International Nuclear Information System (INIS)

    Molybdenum, a metal with excellent physical, chemical and high-temperature properties, is an interesting material for applications in lighting-technology, high performance electronics, high temperature furnace construction and coating technology. However, its applicability as a structural material is limited because of the poor oxidation resistance at high temperatures and a brittle-to-ductile transition around room temperature, which is influenced by the grain size and the content of interstitial impurities at the grain boundaries. Due to the progress of the powder metallurgical production during the last decades, the amount of impurities in the current quality of molybdenum has become so small that surface sensitive techniques are not applicable anymore. Therefore, the atom probe, which allows the detection of small amounts of impurities as well as their location, seems to be a more suitable technique. However, a site-specific specimen preparation procedure for grain boundaries in refractory metals with a dual focused ion beam/scanning electron microscope is still required. The present investigation describes the development and successful application of such a site-specific preparation technique for grain boundaries in molybdenum, which is significantly improved by a combination with transmission electron microscopy. This complimentary technique helps to improve the visibility of grain boundaries during the last preparation steps and to evidence the presence of grain and subgrain boundaries without segregants in atom probe specimens. Furthermore, in industrially processed and recrystallized molybdenum sheets grain boundary segregation of oxygen, nitrogen and potassium is successfully detected close to segregated regions which are believed to be former sinter pores. - Highlights: • First study of grain boundary segregation in molybdenum by atom probe • Site-specific preparation technique by FIB and TEM successfully developed • Grain boundary segregation of

  2. Atom probe field ion microscopy and related topics: A bibliography 1990

    Energy Technology Data Exchange (ETDEWEB)

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

    1991-12-01

    This bibliography includes references related to the following topics: atom probe field ion microscopy (APFIM), field ion microscopy (FIM), field emission (FE), ion sources, and field desorption mass microscopy (FDMM). Technique-orientated studies and applications are included. The bibliography covers the period 1990. 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, listed alphabetically by authors, are subdivided into the categories listed in paragraph one above. An Addendum of references missed in previous bibliographies is included.

  3. Probing the mechanical properties of TNF-α stimulated endothelial cell with atomic force microscopy [Corrigendum

    OpenAIRE

    Lee SY; Zaske AM; Novellino T; Danila D; Ferrari M.; Conyers J; Decuzzi P

    2014-01-01

    Lee SY, Zaske AM, Novellino T, et al. Probing the mechanical properties of TNF-α stimulated endothelial cell with atomic force microscopy. Int J Nanomedicine. 2011;6:179–195.The authors apologize that the referencing for Table 1 on page 186 was incorrect, the following corrections should be noted:   8 should be 4240 should be 4318 should be 4442 should be 45  9 should be 4612 should be 4729 should be 4844 should be 4923 should be 5036 should be 1637 should be 18Read th...

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

    International Nuclear Information System (INIS)

    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

  5. 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...... 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...

  6. FIELD ION MICROSCOPE AND ATOM-PROBE STUDIES OF SCANNING TUNNELING MICROSCOPE TIPS

    OpenAIRE

    Nishikawa, O.; K. Hattori; Katsuki, F.; Tomitori, M.

    1988-01-01

    Tungsten and platinum-iridium alloy tips were observed by field emission and ion microscopes and were atom-probe mass analyzed to examine the tip surfaces corroded by exposure to air and by immersion into aqueous solutions. Although the A-P analysis indicates that the corroded layer is less than monoatomic thick for both W and Pt-Ir, the FEM and FIM observation indicates that exposure to air and immersion into solutions often result in the formation of a small protrusion at the tip apex. The ...

  7. Quantum-state tomography of a single nuclear spin qubit of an optically manipulated ytterbium atom

    Energy Technology Data Exchange (ETDEWEB)

    Noguchi, Atsushi; Kozuma, Mikio [Department of Physics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8550 (Japan); ERATO Macroscopic Quantum Control Project, JST, 2-11-16 Yayoi, Bunkyo-Ku, Tokyo 113-8656 (Japan); Eto, Yujiro [ERATO Macroscopic Quantum Control Project, JST, 2-11-16 Yayoi, Bunkyo-Ku, Tokyo 113-8656 (Japan); Ueda, Masahito [ERATO Macroscopic Quantum Control Project, JST, 2-11-16 Yayoi, Bunkyo-Ku, Tokyo 113-8656 (Japan); Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2011-09-15

    A single Yb atom is loaded into a high-finesse optical cavity with a moving lattice, and its nuclear spin state is manipulated using a nuclear magnetic resonance technique. A highly reliable quantum state control with fidelity and purity greater than 0.98 and 0.96, respectively, is confirmed by the full quantum state tomography; a projective measurement with high speed (500 {mu}s) and high efficiency (0.98) is accomplished using the cavity QED technique. Because a hyperfine coupling is induced only when the projective measurement is operational, the long coherence times (T{sub 1}=0.49 s and T{sub 2}=0.10 s) are maintained.

  8. Atom probe, AFM, and STM studies on vacuum-fired stainless steels.

    Science.gov (United States)

    Stupnik, A; Frank, P; Leisch, M

    2009-04-01

    The surface morphology of grades 304L and 316LN stainless steels, after low-temperature bake-out process and vacuum annealing, has been studied by atomic force microscopy (AFM) and scanning tunnelling microscopy (STM). The local elemental composition on the surface before and after thermal treatment has been investigated by atom probe (AP) depth profiling measurements. After vacuum annealing, AFM and STM show significant changes in the surface structure and topology. Recrystallization and surface reconstruction is less pronounced on the 316LN stainless steel. AP depth profiling analyses result in noticeable nickel enrichment on the surface of grade 304L samples. Since hydrogen recombination is almost controlled by surface structure and composition, a strong influence on the outgassing behaviour by the particular surface microstructure can be deduced. PMID:19167824

  9. Probing atomic-scale friction on reconstructed surfaces of single-crystal semiconductors

    Science.gov (United States)

    Goryl, M.; Budzioch, J.; Krok, F.; Wojtaszek, M.; Kolmer, M.; Walczak, L.; Konior, J.; Gnecco, E.; Szymonski, M.

    2012-02-01

    Friction force microscopy (FFM) investigations have been performed on reconstructed (001) surfaces of InSb and Ge in an ultrahigh vacuum. On the c(8×2) reconstruction of InSb(001) atomic resolution is achieved under superlubric conditions, and the features observed in the lateral force images are precisely reproduced by numerical simulations, taking into account possible decorations of the probing tip. On the simultaneously acquired (1×3) reconstruction a significant disorder of the surface atoms is observed. If the loading force increases, friction becomes much larger on this reconstruction compared to the c(8×2) one. In FFM images acquired on the Ge(001)(2×1) characteristic substructures are resolved within the unit cells. In such a case, a strong dependence of the friction pattern on the scan direction is observed.

  10. The study of quantitativeness in atom probe analysis of alloying elements in steel

    International Nuclear Information System (INIS)

    The quantitativeness in atom probe analysis of dilute solute alloying elements in steel was systematically investigated. The samples of binary Fe-Si, Fe-Ti, Fe-Cr, Fe-Cu, Fe-Mn and Fe-Mo alloys were prepared for present study. The apparent compositions of alloying elements were examined by three-dimensional atom probe (3DAP) under various experimental conditions. The temperature dependence of the apparent compositions varied largely with the alloys, which indicated that the degree of preferential evaporation or retention varied with the alloying elements. Furthermore, the analysis direction dependence of the apparent Mn composition was examined in the Fe-Mn alloy. The experimental results indicated that the order of the field evaporation rate of elements in steel was Cu>Cr>Mn∼Mo>Fe>Ti∼Si. The field evaporability of alloying elements in steel was discussed in terms of the solution enthalpy of the alloying elements and the phase types of the binary Fe alloys.

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

    International Nuclear Information System (INIS)

    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

  12. Attosecond probing of state-resolved ionization and superpositions of atoms and molecules

    Science.gov (United States)

    Leone, Stephen

    2016-05-01

    Isolated attosecond pulses in the extreme ultraviolet are used to probe strong field ionization and to initiate electronic and vibrational superpositions in atoms and small molecules. Few-cycle 800 nm pulses produce strong-field ionization of Xe atoms, and the attosecond probe is used to measure the risetimes of the two spin orbit states of the ion on the 4d inner shell transitions to the 5p vacancies in the valence shell. Step-like features in the risetimes due to the subcycles of the 800 nm pulse are observed and compared with theory to elucidate the instantaneous and effective hole dynamics. Isolated attosecond pulses create massive superpositions of electronic states in Ar and nitrogen as well as vibrational superpositions among electronic states in nitrogen. An 800 nm pulse manipulates the superpositions, and specific subcycle interferences, level shifting, and quantum beats are imprinted onto the attosecond pulse as a function of time delay. Detailed outcomes are compared to theory for measurements of time-dynamic superpositions by attosecond transient absorption. Supported by DOE, NSF, ARO, AFOSR, and DARPA.

  13. 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.

  14. Characterization of the microstructure of dual-phase 9Cr-ODS steels using a laser-assisted 3D atom probe

    International Nuclear Information System (INIS)

    Dual-phase 9Cr-ODS (oxide dispersion-strengthened) steel consisting of residual-α ferrite and α' martensite has excellent high-temperature strength. This study describes the microstructure of dual-phase 9Cr-ODS steels characterized by atom-probe tomography in order to compare oxide-particle dispersion states in each phase. This revealed that nano-size oxide particles were of the same chemical composition and that their mean size was about 3 nm in each phase. On the other hand, the number density in the residual-α phase was about four times higher than that of the α' phase. These results indicate that the dense distribution of the oxide particles in the residual-α phase contribute to the excellent high-temperature strength of 9Cr-ODS steel.

  15. 39Ar as a probe of the fast-neutron fluence of the Hiroshima atomic bomb

    International Nuclear Information System (INIS)

    A new method to estimate the fast-neutron fluence of the Hiroshima atomic bomb is proposed. Recent studies on the thermal-neutron fluence of the Hiroshima atomic bomb have suggested a systematic discrepancy from DS86. On the other hand most of the neutron dose for human was due to fast-neutrons, which is a basis of the radiation-risk estimation. Therefore, a direct measurement of the fast-neutron fluence has been required. This paper points out that the 39Ar produced by the 39K(n,p)39Ar reaction would be a unique probe to estimate the fast-neutron fluence of the atomic bomb. This is because the half life of 39Ar is 269 years, which is sufficiently long to exist for a period of 50 years after the explosion, and the threshold of the 39K(n,p)39Ar reaction is 1 MeV. The feasibility of the 39Ar method is discussed in this report. (author)

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

    International Nuclear Information System (INIS)

    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)

  17. Miniature probe integrating optical-resolution photoacoustic microscopy, optical coherence tomography, and ultrasound imaging: proof-of-concept.

    Science.gov (United States)

    Dai, Xianjin; Xi, Lei; Duan, Can; Yang, Hao; Xie, Huikai; Jiang, Huabei

    2015-06-15

    In this Letter, we present a novel tri-modal miniature side-view probe, through which optical-resolution photoacoustic microscopy (OR-PAM), optical coherence tomography (OCT), and pulse-echo ultrasound (US) images can be coaxially acquired and displayed simultaneously. The probe consists of a common optical path for OR-PAM (light delivery) and OCT (light delivery/detection), and a 40-MHz unfocused ultrasound transducer for OR-PAM (photoacoustic detection) and US (ultrasound transmission/receiving) with an overall diameter of 2 mm. Combining OR-PAM, OCT, and US would provide complementary information including optical absorption (OR-PAM), optical back-scattering (OCT), and deep tissue structures (US) about biological tissue. Based on an integrated imaging system consisting of OR-PAM, time-domain OCT, and US, phantom images and in vivo images of rat ear were acquired to demonstrate the capabilities of the integrated tri-modality imaging probe. The probe yields a lateral resolution of 13.6 μm for OR-PAM and OCT, and an axial resolution of 43 μm for OR-PAM and US. Currently, for a scanning area of 1 ×1  mm, it took ∼25  min to acquire data for tri-modal volumetric imaging. PMID:26076296

  18. Shape-dependent adhesion and friction of Au nanoparticles probed with atomic force microscopy

    Science.gov (United States)

    Yuk, Youngji; Hong, Jong Wook; Lee, Hyunsoo; Han, Sang Woo; Park, Jeong Young

    2015-03-01

    The relation between surface structure and friction and adhesion is a long-standing question in tribology. Tuning the surface structure of the exposed facets of metal nanoparticles is enabled by shape control. We investigated the effect of the shape of Au nanoparticles on friction and adhesion. Two nanoparticle systems, cubic nanoparticles with a low-index (100) surface and hexoctahedral nanoparticles with a high-index (321) surface, were used as model nanoparticle surfaces. Atomic force microscopy was used to probe the nanoscale friction and adhesion on the nanoparticle surface. Before removing the capping layers, the friction results include contributions from both the geometric factor and the presence of capping layers. After removing the capping layers, we can see the exclusive effect of the surface atomic structure while the geometric effect is maintained. We found that after removing the capping layer, the cubic Au nanoparticles exhibited higher adhesion and friction, compared with cubes capped with layers covering 25% and 70%, respectively. On the other hand, the adhesion and friction of hexoctahedral Au nanoparticles decreased after removing the capping layers, compared with nanoparticles with capping layers. The difference in adhesion and friction forces between the bare Au surfaces and Au nanoparticles with capping layers cannot be explained by geometric factors, such as the slope of the nanoparticle surfaces. The higher adhesion and friction forces on cubic nanoparticles after removing the capping layers is associated with the atomic structure of (100) and (321) (i.e., the flat (100) surfaces of the cubic nanoparticles have a larger contact area, compared with the rough (321) surfaces of the hexoctahedral nanoparticles). This study implies an intrinsic relation between atomic structure and nanomechanical properties, with potential applications for controlling nanoscale friction and adhesion via colloid chemistry.

  19. Shape-dependent adhesion and friction of Au nanoparticles probed with atomic force microscopy

    International Nuclear Information System (INIS)

    The relation between surface structure and friction and adhesion is a long-standing question in tribology. Tuning the surface structure of the exposed facets of metal nanoparticles is enabled by shape control. We investigated the effect of the shape of Au nanoparticles on friction and adhesion. Two nanoparticle systems, cubic nanoparticles with a low-index (100) surface and hexoctahedral nanoparticles with a high-index (321) surface, were used as model nanoparticle surfaces. Atomic force microscopy was used to probe the nanoscale friction and adhesion on the nanoparticle surface. Before removing the capping layers, the friction results include contributions from both the geometric factor and the presence of capping layers. After removing the capping layers, we can see the exclusive effect of the surface atomic structure while the geometric effect is maintained. We found that after removing the capping layer, the cubic Au nanoparticles exhibited higher adhesion and friction, compared with cubes capped with layers covering 25% and 70%, respectively. On the other hand, the adhesion and friction of hexoctahedral Au nanoparticles decreased after removing the capping layers, compared with nanoparticles with capping layers. The difference in adhesion and friction forces between the bare Au surfaces and Au nanoparticles with capping layers cannot be explained by geometric factors, such as the slope of the nanoparticle surfaces. The higher adhesion and friction forces on cubic nanoparticles after removing the capping layers is associated with the atomic structure of (100) and (321) (i.e., the flat (100) surfaces of the cubic nanoparticles have a larger contact area, compared with the rough (321) surfaces of the hexoctahedral nanoparticles). This study implies an intrinsic relation between atomic structure and nanomechanical properties, with potential applications for controlling nanoscale friction and adhesion via colloid chemistry. (paper)

  20. Cross-Sectional Investigations on Epitaxial Silicon Solar Cells by Kelvin and Conducting Probe Atomic Force Microscopy: Effect of Illumination

    OpenAIRE

    Narchi, Paul; Alvarez, José; Chrétien, Pascal; Picardi, Gennaro; Cariou, Romain; Foldyna, Martin; Prod’homme, Patricia; Kleider, Jean-Paul; i Cabarrocas, Pere Roca

    2016-01-01

    Both surface photovoltage and photocurrent enable to assess the effect of visible light illumination on the electrical behavior of a solar cell. We report on photovoltage and photocurrent measurements with nanometer scale resolution performed on the cross section of an epitaxial crystalline silicon solar cell, using respectively Kelvin probe force microscopy and conducting probe atomic force microscopy. Even though two different setups are used, the scans were performed on locations within 10...

  1. Detection of slow atoms confined in a Cesium vapor cell by spatially separated pump and probe laser beams

    CERN Document Server

    Todorov, Petko; Maurin, Isabelle; Saltiel, Solomon; Bloch, Daniel

    2013-01-01

    The velocity distribution of atoms in a thermal gas is usually described through a Maxwell-Boltzman distribution of energy, and assumes isotropy. As a consequence, the probability for an atom to leave the surface under an azimuth angle {\\theta} should evolve as cos {\\theta}, in spite of the fact that there is no microscopic basis to justify such a law. The contribution of atoms moving at a grazing incidence towards or from the surface, i.e. atoms with a small normal velocity, here called "slow" atoms, reveals essential in the development of spectroscopic methods probing a dilute atomic vapor in the vicinity of a surface, enabling a sub-Doppler resolution under a normal incidence irradiation. The probability for such "slow" atoms may be reduced by surface roughness and atom-surface interaction. Here, we describe a method to observe and to count these slow atoms relying on a mechanical discrimination, through spatially separated pump and probe beams. We also report on our experimental progresses toward such a g...

  2. Gentle and fast atomic force microscopy with a piezoelectric scanning probe for nanorobotics applications

    International Nuclear Information System (INIS)

    A novel dual tip nanomanipulation atomic force microscope (AFM) platform operating in ambient conditions is presented. The system is equipped with a high frequency quartz piezoelectric self-sensing scanning probe for fast imaging and a passive cantilever for manipulation. The system is validated by imaging and selective pushing/pulling of gold colloid beads (diameters from 80 to 180 nm). This provides a more compact integration compared to an external optical lever and avoids several of its drawbacks such as optical interference and noise, and recalibration in the case of a moving cantilever and a fixed laser source and photodiode sensor. Moreover, as the quartz oscillator exhibits oscillation amplitudes in the sub-picometer range with a resonant frequency in the megahertz range, this dynamic force sensor is ideal for fast AFM imaging. Experiments show an increase by five times in imaging speed compared to a classical AFM system. (paper)

  3. 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 at the most 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.

  4. Self-consistent determination of line-width and probe shape using atomic force microscopy

    International Nuclear Information System (INIS)

    A self-consistent method for determining line-width and probe shape using an atomic force microscope (AFM) has been developed. Through acquisition of three images in which one tip images the other, and each tip images the sample a least-squares determination of the shapes of both tips, and the parameters that define the line-width standard can be determined. Application of the self-consistent method produces measurements that can be made traceable to the definition of the metre through appropriate calibration of the AFM. A comparison between the line-width determined by the method and a calibrated line-width standard shows good agreement. Sources of uncertainty specific to the self-consistent method are discussed. (paper)

  5. Probing dark energy with an atom interferometer in an optical cavity

    Science.gov (United States)

    Jaffe, Matthew; Haslinger, Philipp; Hamilton, Paul; Mueller, Holger; Khoury, Justin; Elder, Benjamin

    2016-05-01

    If dark energy -- which drives the accelerated expansion of the universe -- consists of a light scalar field, it might be detectable as a ``fifth force'' between normal-matter objects, in potential conflict with precision tests of gravity. Chameleon fields and other theories with screening mechanisms can evade such tests by suppressing this force in regions of high density, such as the laboratory. Our experiments constrain these dark energy models using atoms in an ultrahigh-vacuum chamber as probes to expose the screened fields. Using a cesium matter wave interferometer in an optical cavity, we set stringent bounds on coupling screened theories to matter. A further 4 to 5 orders of magnitude would completely rule out chameleon and f(R) theories. I will describe this first tabletop dark energy search, and present the hundredfold boost in sensitivity we have since achieved.

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

    DEFF Research Database (Denmark)

    Nilsson, Louis; Andersen, Mie; Balog, Richard; Lægsgaard, Erik; Hofmann, Philip; Besenbacher, Flemming; Hammer, Bjørk; Stensgaard, Ivan; Hornekær, Liv

    2012-01-01

    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......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...... 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...

  7. 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.

  8. The probe gain with and without inversion in a four-level atomic model: light amplification at a short wavelength

    Institute of Scientific and Technical Information of China (English)

    吴金辉; 王登攀; 张惠芳; 肖志宏; 高锦岳

    2003-01-01

    We propose a new four-level atomic model for achieving light amplification at a short wavelength, where direct incoherent pumping into the top level is avoided by the advantage of coherent pumping. In this model, the lower level of the probe transition is an excited state but not the usual ground state. By analytical as well as numerical calculations, we find that the probe gain, either with or without population inversion, which depends on the relation between spontaneous decay rates γ42 and γ21, can be achieved with proper parameters. We note that the Raman scattering gain always plays an important role in achieving the probe amplification.

  9. A novel approach for site-specific atom probe specimen preparation by focused ion beam and transmission electron backscatter diffraction

    International Nuclear Information System (INIS)

    Atom probe tomography (APT) is a suitable technique for chemical analyses with almost atomic resolution. However, the time-consuming site-specific specimen preparation can be improved. Recently, transmission electron backscatter diffraction (t-EBSD) has been established for high resolution crystallographic analyses of thin foils. In this paper we present the first successful application of a combined focused ion beam (FIB)/t-EBSD preparation of site-specific APT specimens using the example of grain boundary segregation in technically pure molybdenum. It will be shown that the preparation of a grain boundary can be substantially accelerated by t-EBSD analyses in-between the annular milling FIB procedure in the same microscope. With this combined method, a grain boundary can easily be recognized and positioned in the first 220 nm of an APT sample much faster than e.g. with complementary investigations in a transmission electron microscope. Even more, the high resolution technique of t-EBSD gives the opportunity to get crystallographic information of the mapped area and, therefore, an analysis of the grain boundary character to support the interpretation of the APT data files. To optimize this newly developed technique for the application on needle-shaped APT specimens, a parameter study on enhanced background correction, acceleration voltage, and tilt angle was carried out. An acceleration voltage of 30 kV at specimen surface tilt angles between −45° and −35° from horizontal plane leads to the best results. Even for molybdenum the observation of crystal orientation data up to about 200 nm specimen thickness is possible. - Highlights: • We developed a new site-specific APT specimen preparation method by FIB and t-EBSD. • A grain boundary was positioned in the first 220 nm of the APT tip by the FIB/t-EBSD method. • Crystallographic information of the mapped area can be quickly obtained. • An acceleration voltage of 30 kV at specimen surface tilt angles

  10. INVESTIGATIONS OF SUPERCONDUCTING AND NON-SUPERCONDUCTING YBa2 Cu3 O7-x BY FIELD ION MICROSCOPY, ATOM-PROBE MASS SPECTROSCOPY AND FIELD ELECTRON EMISSION

    OpenAIRE

    Kellogg, G.; Brenner, S

    1988-01-01

    The structure and composition of superconducting and non-superconducting samples of YBa2Cu3O7-x were examined by field ion microscopy, atom-probe mass spectroscopy and field-electron emission techniques. Field ion microscope images from both types of material exhibited ring structures associated with atomic or multiatomic layers and uniform, layer-by-layer field evaporation was possible. Atom-probe mass spectra contained signals corresponding to atomic and molecular oxygen, all three metals, ...

  11. Tomography

    International Nuclear Information System (INIS)

    Tomography is a non-intrusive imaging technique being developed at CRNL as an industrial tool for generating quantitative cross-sectional density maps of objects. Of most interest is tomography's ability to: distinguish features within complex geometries where other NDT techniques fail because of the complexity of the geometry; detect/locate small density changes/defects within objects, e.g. void fraction measurements within thick-walled vessels, shrink cavities in castings, etc.; provide quantitative data that can be used in analyses, e.g. of complex processes, or fracture mechanics; and provide objective quantitative data that can be used for (computer-based) quality assurance decisions, thereby reducing and in some cases eliminating the present subjectivity often encountered in NDT. The CRNL program is reviewed and examples are presented to illustrate the potential and the limitations of the technology

  12. An Atom-Probe Tomography Study of Phase Separation in Fe-Cr Based Steels

    OpenAIRE

    Zhou, Jing

    2014-01-01

    Stainless steels are very important engineering materials in a variety of applications such as in the food industry and nuclear power plants due to their combination of good mechanical properties and high corrosion resistance. However, ferrite-containing stainless steels are sensitive to the so-called ‘475°C embrittlement’, which is induced by phase separation of the ferrite phase, where it decomposes into Fe-rich ferrite (α) and Cr-rich ferrite (α'). The phase separation is accompanied with ...

  13. Erbium environment in glass-ceramics investigated by atom probe tomography

    OpenAIRE

    Blanc, Wilfried; François Saint-Cyr, Hugues; Martin, Isabelle,; Le Coustumer, Philippe; Hombourger, Chystel; Neuville, D. R.; Larson, D.J.; Prosa, T.J.; Guillermier, Christelle

    2014-01-01

    Glass-ceramics (considered here as a glassy host containing crystalline or amorphous nanoparticles) are of interest for luminescent properties as they can combine the sturdiness and low cost of a matrix host with particular spectroscopic behavior that would not appear in this host [1]. Ideally, nanoparticles would fully encapsulate luminescent ions to produce engineered spectroscopic properties. This approach is particularly promising for optical fibers. Indeed, silica is the most common glas...

  14. Quantum tomography of the full hyperfine manifold of atomic spins via continuous measurement on an ensemble

    CERN Document Server

    Riofrío, Carlos A; Deutsch, Ivan H

    2010-01-01

    Quantum state reconstruction based on weak continuous measurement has the advantage of being fast, accurate, and almost non-perturbative. In this work we present a pedagogical review of the protocol proposed by Silberfarb et al., PRL 95 030402 (2005), whereby an ensemble of identically prepared systems is collectively probed and controlled in a time-dependent manner so as to create an informationally complete continuous measurement record. The measurement history is then inverted to determine the state at the initial time through a maximum-likelihood estimate. The general formalism is applied to the case of reconstruction of the quantum state encoded in the magnetic sublevels of a large-spin alkali atom, 133Cs. We detail two different protocols for control. Using magnetic interactions and a quadratic ac-Stark shift, we can reconstruct a chosen hyperfine manifold F, e.g., the 7-dimensional F=3 manifold in the electronic-ground state of Cs. We review the procedure as implemented in experiments (Smith et al., PR...

  15. Shaping the lens of the atom probe: Fabrication of site specific, oriented specimens and application to grain boundary analysis

    International Nuclear Information System (INIS)

    The random sampling provided by classical atom probe sample preparation methods is one of the major factors limiting the types of problems that can be addressed using this powerful technique. A focused ion beam enables not only site-specific preparation, but can also be used to give the specimen, which acts as the lens in an atom probe experiment, a specific shape. In this paper we present a technique that uses low accelerating voltages (10 and 5 kV) in the focused ion beam (FIB) to reproducibly produce specimens with selected grain boundaries <100 nm from the tip at any desired orientation. These tips have a high rate of successfully running in the atom probe and no Ga contamination within the region of interest. This technique is applied to the analysis of grain boundaries in a high purity iron wire and a strip-cast steel. Lattice resolution is achieved around the boundary in certain areas. Reconstruction of these datasets reveals the distribution of light and heavy elements around the boundary. Issues surrounding the uneven distribution of certain solute elements as a result of field-induced diffusion are discussed. -- Research highlights: → Damage free site specific samples can be made using FIB. → Crystallographic relationships across grain boundaries can be obtained from field desorption patterns. → Lattice resolution can be achieved at grain boundaries for matrix atoms. → Field evaporation artifacts are observed at grain boundaries for solute atoms.

  16. Probing biofouling resistant polymer brush surfaces by atomic force microscopy based force spectroscopy.

    Science.gov (United States)

    Schön, Peter; Kutnyanszky, Edit; ten Donkelaar, Bas; Santonicola, M Gabriella; Tecim, Tugba; Aldred, Nick; Clare, Anthony S; Vancso, G Julius

    2013-02-01

    The protein repellency and biofouling resistance of zwitterionic poly(sulfobetaine methacrylate)(pSBMA) brushes grafted via surface initiated polymerization (SIP) from silicon and glass substrata was assessed using atomic force microscopy (AFM) adherence experiments. Laboratory settlement assays were conducted with cypris larvae of the barnacle Balanus amphitrite. AFM adherence includes the determination of contact rupture forces when AFM probe tips are withdrawn from the substratum. When the surface of the AFM tip is modified, adherence can be assessed with chemical specifity using a method known as chemical force microscopy (CFM). In this study, AFM tips were chemically functionalized with (a) fibronectin- here used as model for a nonspecifically adhering protein - and (b) arginine-glycine-aspartic acid (RGD) peptide motifs covalently attached to poly(methacrylic acid) (PMAA) brushes as biomimics of cellular adhesion receptors. Fibronectin functionalized tips showed significantly reduced nonspecific adhesion to pSBMA-modified substrata compared to bare gold (2.3±0.75 nN) and octadecanethiol (ODT) self-assembled monolayers (1.3±0.75 nN). PMAA and PMAA-RGD modified probes showed no significant adhesion to pSBMA modified silicon substrata. The results gathered through AFM protein adherence studies were complemented by laboratory fouling studies, which showed no adhesion of cypris larvae of Balanus amphitrite on pSBMA. With regard to its unusually high non-specific adsorption to a wide variety of materials the behavior of fibronectin is analogous to the barnacle cyprid temporary adhesive that also binds well to surfaces differing in polarity, charge and free energy. The antifouling efficacy of pSBMA may, therefore, be directly related to the ability of this surface to resist nonspecific protein adsorption. PMID:23138001

  17. Large Enhancement of Probe Amplification with Population Inversion in a Four-Level Atomic System with Vacuum-Induced Coherence

    Institute of Scientific and Technical Information of China (English)

    LI Jia-Hua; YANG Wen-Xing; LUO Jin-Ming; PENG Ju-Cun

    2005-01-01

    In this paper, we discuss and analyze theoretically probe absorption-amplification response in a four-level coherent atomic system with vacuum-induced coherence via changing the sign of the parameter f, with f denoting the ratio of a pair of dipole moments associated with a doublet of closely upper hyperfine sublevels. We find that the amplitude of the probe amplification for the case f = -1 can be about one order of magnitude larger than that achievable for the case f = 1. In addition, with respect to the case f = -1 the probe amplification can be maintained all the time with weak incoherent pumping for a wide range of the probe detuning.

  18. Amyloid-beta Positron Emission Tomography Imaging Probes : A Critical Review

    NARCIS (Netherlands)

    Kepe, Vladimir; Moghbel, Mateen C.; Langstrom, Bengt; Zaidi, Habib; Vinters, Harry V.; Huang, Sung-Cheng; Satyamurthy, Nagichettiar; Doudet, Doris; Mishani, Eyal; Cohen, Robert M.; Hoilund-Carlsen, Poul F.; Alavi, Abass; Barrio, Jorge R.

    2013-01-01

    The rapidly rising prevalence and cost of Alzheimer's disease in recent decades has made the imaging of amyloid-beta deposits the focus of intense research. Several amyloid imaging probes with purported specificity for amyloid-beta plaques are currently at various stages of FDA approval. However, a

  19. Characterization of designed cobaltacarborane porphyrins using conductive probe atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Venetia D. Lyles

    2016-03-01

    Full Text Available Porphyrins and metalloporphyrins have unique chemical and electronic properties and thus provide useful model structures for studies of nanoscale electronic properties. The rigid planar structures and -conjugated backbones of porphyrins convey robust electrical characteristics. For our investigations, cobaltacarborane porphyrins were synthesized using a ring-opening zwitterionic reaction to produce isomers with selected arrangements of carborane clusters on each macrocycle. Experiments were designed to investigate how the molecular structure influences the self-organization, surface assembly, and conductive properties of three molecular structures with 2, 4, or 8 cobaltacarborane substituents. Current versus voltage (I-V spectra for designed cobaltacarborane porphyrins deposited on conductive gold substrates were acquired using conductive probe atomic force microscopy (CP-AFM. Characterizations with CP-AFM provide capabilities for obtaining physical measurements and structural information with unprecedented sensitivity. We found that the morphology of cobaltacarborane porphyrin structures formed on surfaces depends on a complex interplay of factors such as the solvent used for dissolution, the nature of the substrate, and the design of the parent molecule. The conductive properties of cobaltacarborane porphyrins were observed to change according to the arrangement of cobaltacarborane substituents. Specifically, the number and placement of the cobaltacarborane ligands on the porphyrin macrocycle affect the interactions that drive porphyrin self-assembly and crystallization. Interestingly, coulombic staircase I-V profiles were detected for a porphyrin with two cobaltacarborane substituents.

  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. Attosecond XUV probing of strong field ionization dynamics from one- and two-electron 1D atoms

    International Nuclear Information System (INIS)

    Full text: The probing of strong field ionization dynamics by a 250 attosecond XUV pulse is considered, first, for a one-electron 1D atom, and second, for a two-electron 1D atom. In the one-electron case, the XUV ionization yield as a function of time delay between the laser pulse and the XUV pulse is seen to reflect the time-dependence of the field-dressed neutral atomic population. The depletion of the ground state, and hence the dynamics of strong field ionization, can be inferred on sub-cycle timescales. Furthermore, it is suggested that this XUV probing also reveals the sub-cycle distortions of the atomic ground state near the peaks of the strong laser field. In the two electron case, both the neutral and singly-ionized populations in the strong field can be probed by the XUV pulse. The time-dependent yield of XUV ionization from the ionic population reflects the time-dependence of the ionization from the strong laser field. This shows directly the strong field ionization dynamics on sub-cycle timescales. (author)

  2. Development of Two-Photon Pump Polarization Spectroscopy Probe Technique Tpp-Psp for Measurements of Atomic Hydrogen .

    Science.gov (United States)

    Satija, Aman; Lucht, Robert P.

    2015-06-01

    Atomic hydrogen (H) is a key radical in combustion and plasmas. Accurate knowledge of its concentration can be used to better understand transient phenomenon such as ignition and extinction in combustion environments. Laser induced polarization spectroscopy is a spatially resolved absorption technique which we have adapted for quantitative measurements of H atom. This adaptation is called two-photon pump, polarization spectroscopy probe technique (TPP-PSP) and it has been implemented using two different laser excitation schemes. The first scheme involves the two-photon excitation of 1S-2S transitions using a linearly polarized 243-nm beam. An anisotropy is created amongst Zeeman states in 2S-3P levels using a circularly polarized 656-nm pump beam. This anisotropy rotates the polarization of a weak, linearly polarized probe beam at 656 nm. As a result, the weak probe beam "leaks" past an analyzer in the detection channel and is measured using a PMT. This signal can be related to H atom density in the probe volume. The laser beams were created by optical parametric generation followed by multiple pulse dye amplification stages. This resulted in narrow linewidth beams which could be scanned in frequency domain and varied in energy. This allowed us to systematically investigate saturation and Stark effect in 2S-3P transitions with the goal of developing a quantitative H atom measurement technique. The second scheme involves the two-photon excitation of 1S-2S transitions using a linearly polarized 243-nm beam. An anisotropy is created amongst Zeeman states in 2S-4P transitions using a circularly polarized 486-nm pump beam. This anisotropy rotates the polarization of a weak, linearly polarized probe beam at 486 nm. As a result the weak probe beam "leaks" past an analyzer in the detection channel and is measured using a PMT. This signal can be related to H atom density in the probe volume. A dye laser was pumped by third harmonic of a Nd:YAG laser to create a laser beam

  3. Quantum tomography of the full hyperfine manifold of atomic spins via continuous measurement on an ensemble

    Science.gov (United States)

    Riofrío, Carlos A.; Jessen, Poul S.; Deutsch, Ivan H.

    2011-08-01

    Quantum state reconstruction based on weak continuous measurement has the advantage of being fast, accurate and almost non-perturbative. In this work we present a pedagogical review of the protocol proposed by Silberfarb et al (2005 Phys. Rev. Lett. 95 030402), whereby an ensemble of identically prepared systems is collectively probed and controlled in a time-dependent manner so as to create an informationally complete continuous measurement record. The measurement history is then inverted to determine the state at the initial time through a maximum-likelihood estimate. The general formalism is applied to the case of reconstruction of the quantum state encoded in the magnetic sublevels of a large-spin alkali atom, 133Cs. We detail two different protocols for control. Using magnetic interactions and a quadratic ac Stark shift, we can reconstruct a chosen hyperfine manifold F, e.g. the seven-dimensional F = 3 manifold in the electronic ground state of Cs. We review the procedure as implemented in experiments (Smith et al 2006 Phys. Rev. Lett. 97 180403). We extend the protocol to the more ambitious case of reconstruction of states in the full 16-dimensional electronic ground subspace (F = 3⊕F = 4), controlled by microwaves and radio-frequency (RF) magnetic fields. We give detailed derivations of all physical interactions, approximations, numerical methods and fitting procedures, tailored to the realistic experimental setting. For the case of light-shift and magnetic control, reconstruction fidelities of ~0.95 have been achieved, limited primarily by inhomogeneities in the light-shift. For the case of microwave/RF-control we simulate fidelity >0.97, limited primarily by signal-to-noise.

  4. Lyman-tomography of cosmic infrared background fluctuations with Euclid: probing emissions and baryonic acoustic oscillations at z>10

    CERN Document Server

    Kashlinsky, A; Atrio-Barandela, F; Helgason, K

    2015-01-01

    The Euclid space mission, designed to probe evolution of the Dark Energy, will map a large area of the sky at three adjacent near-IR filters, Y, J and H. This coverage will also enable mapping source-subtracted cosmic infrared background (CIB) fluctuations with unprecedented accuracy on sub-degree angular scales. Here we propose methodology, using the Lyman-break tomography applied to the Euclid-based CIB maps, to accurately isolate the history of CIB emissions as a function of redshift from 10 ~ 400 sq deg. The method can isolate the CIB spatial spectrum by z to sub-percent statistical accuracy. We illustrate this with a specific model of CIB production at high z normalized to reproduce the measured Spitzer-based CIB fluctuation. We show that even if the latter contain only a small component from high-z sources, the amplitude of that component can be accurately isolated with the methodology proposed here and the BAO signatures at z>~ 10 are recovered well from the CIB fluctuation spatial spectrum. Probing th...

  5. Surface potential investigation on single wall carbon nanotubes by Kelvin probe force microscopy and atomic force microscope potentiometry

    International Nuclear Information System (INIS)

    Surface potentials of single wall carbon nanotubes (SWNTs) connecting two metallic electrodes have been investigated by both Kelvin probe force microscopy (KFM) and atomic force microscope potentiometry (AFMP). By comparing the surface potential measurements obtained by both methods, we also studied the major factors affecting the potential measurements of the SWNTs, such as the surroundings, stray electric fields, and the effect of the AFM tip size, which can be larger than the SWNT diameter. In this study, we used KFM based on non-contact AFM and AFMP using the point-by-point contact mode in which the AFM tip worked as a voltage probe

  6. Application of 3D electrical capacitance tomography in probing anomalous blocks in water

    Science.gov (United States)

    Liao, Aimin; Zhou, Qiyou; Zhang, Yun

    2015-06-01

    Water usually acts as a high-permittivity dielectric in many fields such as geophysics, hydrology, hydrogeology, aquaculture, etc. Thus, it may be of significance to adapt ECT to the fields with a high permittivity in which the conventional ECT is scarcely involved. To achieve this objective, a simplified 3D-ECT system was constructed with a high-precision inductance capacitance resistance meter and programmable logic controllers. In the aspect of sensing unit of the system, two geometries (i.e. cylinder and cube) of 3D sensors were constructed to probe anomalous blocks in water. Numerical simulations and physical experiments for both the sensors were performed to test the effectiveness of the constructed system to probe anomalous blocks in water. Furthermore, to justify the availability of this system in some possible fields, two experiments associated with applications of the 3D-ECT system were performed to measure the distribution of a plant root system in water, and to monitor the infiltration of water in soil in field. The experimental results demonstrate that the ECT system is capable of probing the location and rough size of anomalous blocks in water with both the sensors, determining the distribution of a plant root system in water, and monitoring the infiltration process of water in soil.

  7. Atomic structure and surface defects at mineral-water interfaces probed by in situ atomic force microscopy

    Science.gov (United States)

    Siretanu, Igor; van den Ende, Dirk; Mugele, Frieder

    2016-04-01

    Atomic scale details of surface structure play a crucial role for solid-liquid interfaces. While macroscopic characterization techniques provide averaged information about bulk and interfaces, high resolution real space imaging reveals unique insights into the role of defects that are believed to dominate many aspects of surface chemistry and physics. Here, we use high resolution dynamic Atomic Force Microscopy (AFM) to visualize and characterize in ambient water the morphology and atomic scale structure of a variety of nanoparticles of common clay minerals adsorbed to flat solid surfaces. Atomically resolved images of the (001) basal planes are obtained on all materials investigated, namely gibbsite, kaolinite, illite, and Na-montmorillonite of both natural and synthetic origin. Next to regions of perfect crystallinity, we routinely observe extended regions of various types of defects on the surfaces, including vacancies of one or few atoms, vacancy islands, atomic steps, apparently disordered regions, as well as strongly adsorbed seemingly organic and inorganic species. While their exact nature is frequently difficult to identify, our observations clearly highlight the ubiquity of such defects and their relevance for the overall physical and chemical properties of clay nanoparticle-water interfaces.Atomic scale details of surface structure play a crucial role for solid-liquid interfaces. While macroscopic characterization techniques provide averaged information about bulk and interfaces, high resolution real space imaging reveals unique insights into the role of defects that are believed to dominate many aspects of surface chemistry and physics. Here, we use high resolution dynamic Atomic Force Microscopy (AFM) to visualize and characterize in ambient water the morphology and atomic scale structure of a variety of nanoparticles of common clay minerals adsorbed to flat solid surfaces. Atomically resolved images of the (001) basal planes are obtained on all

  8. Comparison of TALIF and catalytic probes for the determination of nitrogen atom density in a nitrogen plasma afterglow

    International Nuclear Information System (INIS)

    The density of neutral nitrogen atoms in a glass reactor was measured by two absolute methods: two-photon absorption laser induced fluorescence (TALIF) and catalytic probes. The source of N atoms was nitrogen plasma created in a quartz tube by surfatron microwave generator operating at 2.45 GHz and adjustable output power up to 300 W. The TALIF measurements were performed using a dye laser which was pumped by a YAG laser. At the exit of the dye laser, the beam frequency was doubled through a KDP crystal and then mixed in a BBO crystal. The wavelength of the output laser beam was chosen at 206.65 nm so two-photon absorption was suitable to excite nitrogen atoms from the ground state to the 5d 2D state. Absolute N density was determined by using calibration with krypton. Simultaneously, the N atom density was measured with a fiber optics catalytic probe (FOCP) with a well-activated iron catalytic tip. Measurements were performed by both methods at nitrogen flows between 0.2 and 2 l min-1, and discharge powers between 60 and 300 W. At rather high nitrogen flows, the N atom density increased monotonically with increasing discharge power, while at lower flow saturation was observed. TALIF showed somewhat higher values than FOCP which was attributed to the accuracy of both methods. The main advantage of TALIF is a broader detection range, while FOCP is an extremely simple and inexpensive technique.

  9. Probing Atomic Structure and Majorana Wavefunctions in Mono-Atomic Fe-chains on Superconducting Pb-Surface

    CERN Document Server

    Pawlak, Remy; Klinovaja, Jelena; Meier, Tobias; Kawai, Shigeki; Glatzel, Thilo; Loss, Daniel; Meyer, Ernst

    2015-01-01

    Motivated by the striking promise of quantum computation, Majorana bound states (MBSs) in solid-state systems have attracted wide attention in recent years. In particular, the wavefunction localization of MBSs is a key feature and crucial for their future implementation as qubits. Here, we investigate the spatial and electronic characteristics of topological superconducting chains of iron atoms on the surface of Pb(110) by combining scanning tunneling microscopy (STM) and atomic force microscopy (AFM). We demonstrate that the Fe chains are mono-atomic, structured in a linear fashion, and exhibit zero-bias conductance peaks at their ends which we interprete as signature for a Majorana bound state. Spatially resolved conductance maps of the atomic chains reveal that the MBSs are well localized at the chain ends (below 25 nm), with two localization lengths as predicted by theory. Our observation lends strong support to use MBSs in Fe chains as qubits for quantum computing devices.

  10. Atomic structure and surface defects at mineral-water interfaces probed by in situ atomic force microscopy.

    Science.gov (United States)

    Siretanu, Igor; van den Ende, Dirk; Mugele, Frieder

    2016-04-14

    Atomic scale details of surface structure play a crucial role for solid-liquid interfaces. While macroscopic characterization techniques provide averaged information about bulk and interfaces, high resolution real space imaging reveals unique insights into the role of defects that are believed to dominate many aspects of surface chemistry and physics. Here, we use high resolution dynamic Atomic Force Microscopy (AFM) to visualize and characterize in ambient water the morphology and atomic scale structure of a variety of nanoparticles of common clay minerals adsorbed to flat solid surfaces. Atomically resolved images of the (001) basal planes are obtained on all materials investigated, namely gibbsite, kaolinite, illite, and Na-montmorillonite of both natural and synthetic origin. Next to regions of perfect crystallinity, we routinely observe extended regions of various types of defects on the surfaces, including vacancies of one or few atoms, vacancy islands, atomic steps, apparently disordered regions, as well as strongly adsorbed seemingly organic and inorganic species. While their exact nature is frequently difficult to identify, our observations clearly highlight the ubiquity of such defects and their relevance for the overall physical and chemical properties of clay nanoparticle-water interfaces. PMID:27030282

  11. Interference Effects on the Probe Absorption in a Driven Three-Level Atomic System by a Coherent Pumping Field

    International Nuclear Information System (INIS)

    In this work the quantum interference effect on the weak probe absorption in a closed three-level V atomic system driven by a coherent driving field is shown to result from the twoquantum processes, constructive for the amplification channels and destructive for the absorption channel. A fourth state in the atom is coupled incoherently to the V system and acts as both an incoherent pumping reservoir and as a stationary, final state in perturbation theory. The application refers to Be-like carbon ions where non-linear pump process of the 1s22s5s(1Se) - 1s22p5s(1P0) transition is combined with the absorption or emission of a single probe photon corresponding to 1s22s5s(1Se) -1s22p7s(1P0) transition. The system is analyzed within the Rmatrix Floquet theory and codes results. (author)

  12. Tomography

    International Nuclear Information System (INIS)

    Tomography images of a body are constructed by placing a plurality of surface electrodes at spaced intervals on the body, causing currents to flow in the body (e.g. by applying a potential between each pair of electrodes in turn, or by induction), and measuring the potential between pairs of electrodes, calculating the potential expected in each case on the assumption that the body consists of a medium of uniform impedance, plotting the isopotentials corresponding to the calculated results to create a uniform image of the body, obtaining the ratio between the measured potential and the calculated potential in each case, and modifying the image in accordance with the respective ratios by increasing the assumed impedance along an isopotential in proportion to a ratio greater than unity or decreasing the assumed impedance in proportion to a ratio less than unity. The modified impedances along the isopotentials for each pair of electrodes are superimposed. The calculations are carried out using a computer and the plotting is carried out by a visual display unit and/or a print-out unit. (author)

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

    International Nuclear Information System (INIS)

    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% Y2O3 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 VN2+ ions were detected on mass-spectra. (author)

  14. Inverting pump-probe spectroscopy for state tomography of excitonic systems

    CERN Document Server

    Hoyer, Stephan

    2013-01-01

    We propose a two-step protocol for inverting ultrafast nonlinear spectroscopy experiments on a molecular aggregate to determine the excited state density matrix at times following laser excitation. The first step is a deconvolution of the experimental signal to determine a pump-dependent response function. The second step inverts the quantum state of the system from this response function, given a model for how the system evolves following the probe interaction. We demonstrate this inversion analytically and numerically for a dimer model system, and evaluate the feasibility of scaling it to larger molecular aggregates such as photosynthetic protein-pigment complexes.

  15. The kinetic Sunyaev-Zel'dovich tomography II: probing the circumgalactic medium

    OpenAIRE

    Shao, Jiawei; Fang, Taotao

    2016-01-01

    We propose the use of the kinetic Sunyaev-Zel'dovich (kSZ) effect to probe the circumgalactic medium (CGM), with the aid of a spectroscopic survey covering the same area of a SZ survey. One can design an optimal estimator of the kSZ effect of the CGM with a matched filter, and construct the cross correlation between the estimator and the peculiar velocity recovered from the galaxy survey, which can be measured by stacking a number of galaxies. We investigate two compelling profiles for the CG...

  16. The resistive switching in TiO2 films studied by conductive atomic force microscopy and Kelvin probe force microscopy

    OpenAIRE

    Yuanmin Du; Amit Kumar; Hui Pan; Kaiyang Zeng; Shijie Wang; Ping Yang; Andrew Thye Shen Wee

    2013-01-01

    The resistive switching characteristics of TiO2 thin films were investigated using conductive atomic force microscopy (CAFM) and Kelvin probe force microscopy (KPFM). The as-prepared TiO2 thin films were modulated into higher and lower resistance states by applying a local electric field. We showed that the resistive switching results from charge injection and release assisted by electro-migration of oxygen ions. An integrated model combined with filamentary and interfacial effects was utiliz...

  17. 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......, the atomic state is determined in a Bayesian manner from the measurement data, and we present an iterative protocol, which determines both the atomic state and the model parameters. As a new element in the treatment of observed quantum systems, we employ a Bayesian approach that conditions the atomic...

  18. Molecular imaging of hemoglobin using ground state recovery pump-probe optical coherence tomography

    Science.gov (United States)

    Applegate, Brian E.; Izatt, Joseph A.

    2007-02-01

    We have undertaken an effort to further develop ground state recovery Pump-Probe Optical Coherence Tomograpy (gsrPPOCT) to specifically target and measure 3-D images of hemoglobin concentration with the goals of mapping tissue vasculature, total hemoglobin, and hemoglobin oxygen saturation. As a first step toward those goals we have measured the gsrPPOCT signal from the hemoglobin in the filament arteries of a zebra danio fish. We have further processed the resulting signal to extract a qualitative map of the hemoglobin concentration. We have also demonstrated the potential to use ground state recovery times to differentiate between two chromophores which may prove to be an effective tool for differentiating between oxy and deoxy hemoglobin.

  19. Probing the properties of quantum matter; an experimental study in three parts using ultracold atoms

    OpenAIRE

    Bons, P.C.

    2015-01-01

    The three experiments described in this thesis investigate fundamental properties of ultracold atoms. Using laser cooling and evaporative cooling, a dilute gas of sodium atoms is cooled to ~100 nK. Under these circumstances a Bose-Einstein condensate (BEC) forms, where millions of atoms collapse into the lowest energy state of the system and share a macroscopic wavefunction. The experiments are done in an ultrahigh vacuum and the atoms are manipulated remotely using laser beams, magnetic fiel...

  20. Noncontact atomic force and Kelvin probe force microscopy on MgO(100) and MgO(100)-supported Ba

    Science.gov (United States)

    Pang, Chi Lun; Sasahara, Akira; Onishi, Hiroshi

    2016-08-01

    Atomically-flat MgO(100) surfaces were prepared by sputtering and annealing. Noncontact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM) were used to characterize the MgO(100) surfaces. The NC-AFM images revealed the presence of point defects on an atomically-resolved surface. The surface potential at these point defects, as well as features such as step edges and deposited Ba nanoparticles were mapped using KPFM. The Kelvin images show that the surface potential increases at the point defects and at the step edges. On the other hand, a decrease in the potential was found over Ba nanoparticles which can be explained by electron charge transfer from the Ba to the MgO.

  1. Probing the nanoadhesion of Streptococcus sanguinis to titanium implant surfaces by atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Aguayo S

    2016-04-01

    Full Text Available Sebastian Aguayo,1 Nikolaos Donos,2 Dave Spratt,3 Laurent Bozec11Department of Biomaterials and Tissue Engineering, 2Periodontology Unit, 3Division of Microbial Diseases, UCL Eastman Dental Institute, University College London, London, UKAbstract: As titanium (Ti continues to be utilized in great extent for the fabrication of artificial implants, it is important to understand the crucial bacterium–Ti interaction occurring during the initial phases of biofilm formation. By employing a single-cell force spectroscopy technique, the nanoadhesive interactions between the early-colonizing Streptococcus sanguinis and a clinically analogous smooth Ti substrate were explored. Mean adhesion forces between S. sanguinis and Ti were found to be 0.32±0.00, 1.07±0.06, and 4.85±0.56 nN for 0, 1, and 60 seconds contact times, respectively; while adhesion work values were reported at 19.28±2.38, 104.60±7.02, and 1,317.26±197.69 aJ for 0, 1, and 60 seconds, respectively. At 60 seconds surface delays, minor-rupture events were modeled with the worm-like chain model yielding an average contour length of 668±12 nm. The mean force for S. sanguinis minor-detachment events was 1.84±0.64 nN, and Poisson analysis decoupled this value into a short-range force component of -1.60±0.34 nN and a long-range force component of -0.55±0.47 nN. Furthermore, a solution of 2 mg/mL chlorhexidine was found to increase adhesion between the bacterial probe and substrate. Overall, single-cell force spectroscopy of living S. sanguinis cells proved to be a reliable way to characterize early-bacterial adhesion onto machined Ti implant surfaces at the nanoscale.Keywords: atomic force microscopy, biophysics, bacterial adhesion, dental implants, titanium

  2. The kinetic Sunyaev-Zel'dovich tomography II: probing the circumgalactic medium

    CERN Document Server

    Shao, Jiawei

    2016-01-01

    We propose the use of the kinetic Sunyaev-Zel'dovich (kSZ) effect to probe the circumgalactic medium (CGM), with the aid of a spectroscopic survey covering the same area of a SZ survey. One can design an optimal estimator of the kSZ effect of the CGM with a matched filter, and construct the cross correlation between the estimator and the peculiar velocity recovered from the galaxy survey, which can be measured by stacking a number of galaxies. We investigate two compelling profiles for the CGM, the MB profile (Maller & Bullock 2004) and the $\\beta$ profile, and estimate the detectability against the synergy of a fiducial galaxy survey with number density $10^{-3}h^3\\,$ Mpc$^{-3}$ and an ACT-like SZ survey. We show that the shape of the filter does not change much with redshift for the $\\beta$ profile, while there are significant side lobes at $z<0.1$ for the MB profile. By stacking $\\sim 10^4$ Milky Way-size halos around z $\\sim 0.5$, one can get $\\gtrsim$ 1 $\\sigma$ signal to noise (S/N) for the both ...

  3. The kinetic Sunyaev-Zel'dovich tomography - II. Probing the circumgalactic medium

    Science.gov (United States)

    Shao, Jiawei; Fang, Taotao

    2016-06-01

    We propose the use of the kinetic Sunyaev-Zel'dovich (kSZ) effect to probe the circumgalactic medium (CGM), with the aid of a spectroscopic survey covering the same area of a SZ survey. It is possible to design an optimal estimator of the kSZ effect of the CGM with a matched filter, and to construct the cross-correlation between the estimator and the peculiar velocity recovered from the galaxy survey, which can be measured by stacking a number of galaxies. We investigate two compelling profiles for the CGM - the Maller-Bullock (MB) profile and the β profile - and we estimate the detectability against the synergy of a fiducial galaxy survey with number density 10-3 h3 Mpc-3 and an Atacama Cosmology Telescope-like SZ survey. We show that the shape of the filter does not change much with redshift for the β profile, while there are significant side lobes at z microwave background survey can marginally detect the kSZ signal by stacking the same number of galaxies at z < 0.1. The search for the CGM in realistic surveys will involve dividing the galaxies into subsamples with similar redshift and mass of host haloes, and scaling the results presented here to obtain the S/N.

  4. Fluorescence-Guided Probes of Aptamer-Targeted Gold Nanoparticles with Computed Tomography Imaging Accesses for in Vivo Tumor Resection.

    Science.gov (United States)

    Li, Cheng-Hung; Kuo, Tsung-Rong; Su, Hsin-Jan; Lai, Wei-Yun; Yang, Pan-Chyr; Chen, Jinn-Shiun; Wang, Di-Yan; Wu, Yi-Chun; Chen, Chia-Chun

    2015-01-01

    Recent development of molecular imaging probes for fluorescence-guided surgery has shown great progresses for determining tumor margin to execute the tissue resection. Here we synthesize the fluorescent gold nanoparticles conjugated with diatrizoic acid and nucleolin-targeted AS1411 aptamer. The nanoparticle conjugates exhibit high water-solubility, good biocompatibility, visible fluorescence and strong X-ray attenuation for computed tomography (CT) contrast enhancement. The fluorescent nanoparticle conjugates are applied as a molecular contrast agent to reveal the tumor location in CL1-5 tumor-bearing mice by CT imaging. Furthermore, the orange-red fluorescence emitting from the conjugates in the CL1-5 tumor can be easily visualized by the naked eyes. After the resection, the IVIS measurements show that the fluorescence signal of the nanoparticle conjugates in the tumor is greatly enhanced in comparison to that in the controlled experiment. Our work has shown potential application of functionalized nanoparticles as a dual-function imaging agent in clinical fluorescence-guided surgery. PMID:26507179

  5. Atom probe study of the carbon distribution in a hardened martensitic hot-work tool steel X38CrMoV5-1.

    Science.gov (United States)

    Lerchbacher, Christoph; Zinner, Silvia; Leitner, Harald

    2012-07-01

    The microstructure of the hardened common hot-work tool steel X38CrMoV5-1 has been characterized by atom probe tomography with the focus on the carbon distribution. Samples quenched with technically relevant cooling parameters λ from 0.1 (30 K/s) to 12 (0.25 K/s) have been investigated. The parameter λ is an industrially commonly used exponential cooling parameter, representing the cooling time from 800 to 500 °C in seconds divided with hundred. In all samples pronounced carbon segregation to dislocations and cluster formation could be observed after quenching. Carbon enriched interlath films with peak carbon levels of 6-10 at.%, which have been identified to be retained austenite by TEM, show a thickness increase with increasing λ. Therefore, the fraction of total carbon staying in the austenite grows. This carbon is not available for the tempering induced precipitation of secondary carbides in the bulk. Through all samples no segregation of any substitutional elements takes place. Charpy impact testing and fracture surface analysis of the hardened samples reveal the cooling rate induced microstructural distinctions. PMID:22391101

  6. 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.

  7. Statistical analysis of atom probe data: Detecting the early stages of solute clustering and/or co-segregation

    International Nuclear Information System (INIS)

    Statistical analysis of atom probe data has improved dramatically in the last decade and it is now possible to determine the size, the number density and the composition of individual clusters or precipitates such as those formed in reactor pressure vessel (RPV) steels during irradiation. However, the characterisation of the onset of clustering or co-segregation is more difficult and has traditionally focused on the use of composition frequency distributions (for detecting clustering) and contingency tables (for detecting co-segregation). In this work, the authors investigate the possibility of directly examining the neighbourhood of each individual solute atom as a means of identifying the onset of solute clustering and/or co-segregation. The methodology involves comparing the mean observed composition around a particular type of solute with that expected from the overall composition of the material. The methodology has been applied to atom probe data obtained from several irradiated RPV steels. The results show that the new approach is more sensitive to fine scale clustering and co-segregation than that achievable using composition frequency distribution and contingency table analyses.

  8. Cross-Sectional Investigations on Epitaxial Silicon Solar Cells by Kelvin and Conducting Probe Atomic Force Microscopy: Effect of Illumination

    Science.gov (United States)

    Narchi, Paul; Alvarez, Jose; Chrétien, Pascal; Picardi, Gennaro; Cariou, Romain; Foldyna, Martin; Prod'homme, Patricia; Kleider, Jean-Paul; i Cabarrocas, Pere Roca

    2016-02-01

    Both surface photovoltage and photocurrent enable to assess the effect of visible light illumination on the electrical behavior of a solar cell. We report on photovoltage and photocurrent measurements with nanometer scale resolution performed on the cross section of an epitaxial crystalline silicon solar cell, using respectively Kelvin probe force microscopy and conducting probe atomic force microscopy. Even though two different setups are used, the scans were performed on locations within 100-μm distance in order to compare data from the same area and provide a consistent interpretation. In both measurements, modifications under illumination are observed in accordance with the theory of PIN junctions. Moreover, an unintentional doping during the deposition of the epitaxial silicon intrinsic layer in the solar cell is suggested from the comparison between photovoltage and photocurrent measurements.

  9. Cross-Sectional Investigations on Epitaxial Silicon Solar Cells by Kelvin and Conducting Probe Atomic Force Microscopy: Effect of Illumination.

    Science.gov (United States)

    Narchi, Paul; Alvarez, Jose; Chrétien, Pascal; Picardi, Gennaro; Cariou, Romain; Foldyna, Martin; Prod'homme, Patricia; Kleider, Jean-Paul; I Cabarrocas, Pere Roca

    2016-12-01

    Both surface photovoltage and photocurrent enable to assess the effect of visible light illumination on the electrical behavior of a solar cell. We report on photovoltage and photocurrent measurements with nanometer scale resolution performed on the cross section of an epitaxial crystalline silicon solar cell, using respectively Kelvin probe force microscopy and conducting probe atomic force microscopy. Even though two different setups are used, the scans were performed on locations within 100-μm distance in order to compare data from the same area and provide a consistent interpretation. In both measurements, modifications under illumination are observed in accordance with the theory of PIN junctions. Moreover, an unintentional doping during the deposition of the epitaxial silicon intrinsic layer in the solar cell is suggested from the comparison between photovoltage and photocurrent measurements. PMID:26831693

  10. Optimizing the driving scheme of a self-actuated atomic force microscope probe for high-speed applications

    International Nuclear Information System (INIS)

    We investigate the optimum driving scheme of a dynamic atomic force microscope with a self-actuated probe for high-speed applications by performing numerical simulations. We compare the recently developed methods such as Q-control, dynamic PID control, and modified Q-control methods to the standard tapping mode by considering scan speed and peak transient forces. In addition, the effects of driving frequency and set-point amplitude on the maximum achievable scan speed for the same probe-sample system are discussed. We find that the scan speed can be increased significantly at the expense of increased peak transient forces. -- Highlights: → Driving schemes of a dynamic AFM are examined to achieve the highest scan speed. → Q-control provides the highest scan speed with increased transient forces. → Off-resonance tapping is preferable unless transient forces can be ignored. → False error signal generation methods provide a slight improvement.

  11. The resistive switching in TiO2 films studied by conductive atomic force microscopy and Kelvin probe force microscopy

    Directory of Open Access Journals (Sweden)

    Yuanmin Du

    2013-08-01

    Full Text Available The resistive switching characteristics of TiO2 thin films were investigated using conductive atomic force microscopy (CAFM and Kelvin probe force microscopy (KPFM. The as-prepared TiO2 thin films were modulated into higher and lower resistance states by applying a local electric field. We showed that the resistive switching results from charge injection and release assisted by electro-migration of oxygen ions. An integrated model combined with filamentary and interfacial effects was utilized to elucidate the experimentally observed phenomenon.

  12. Structural insights of non-canonical U•U pair and Hoogsteen interaction probed with Se atom

    OpenAIRE

    Sheng, Jia; Gan, Jianhua; Soares, Alexei S.; Salon, Jozef; Huang, Zhen

    2013-01-01

    Unlike DNA, in addition to the 2′-OH group, uracil nucleobase and its modifications play essential roles in structure and function diversities of non-coding RNAs. Non-canonical U•U base pair is ubiquitous in non-coding RNAs, which are highly diversified. However, it is not completely clear how uracil plays the diversifing roles. To investigate and compare the uracil in U-A and U•U base pairs, we have decided to probe them with a selenium atom by synthesizing the novel 4-Se-uridine (SeU) phosp...

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

    Science.gov (United States)

    Wang, Hsiu-Wen; Fanelli, Victor R.; Reiche, Helmut M.; Larson, Eric; Taylor, Mark A.; Xu, Hongwu; Zhu, Jinlong; Siewenie, Joan; Page, Katharine

    2014-12-01

    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 CO2 measurements. The new sample environment was designed to specifically target experimental studies of the local atomic structures involved in geologic CO2 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 H2 and natural gas uptake/storage.

  14. Carbon-11 and fluorine-18 chemistry devoted to molecular probes for imaging the brain with positron emission tomography

    International Nuclear Information System (INIS)

    Exploration of the living human brain in real-time and in a noninvasive way was for centuries only a dream, made, however, possible today with the remarkable development during the four last decades of powerful molecular imaging techniques, and especially positron emission tomography (PET). Molecular PET imaging relies, from a chemical point of view, on the use and preparation of a positron-emitting radiolabelled probe or radiotracer, notably compounds incorporating one of two short-lived radionuclides fluorine-18 (T1/2: 109.8 min) and carbon-11 (T1/2: 20.38 min). The growing availability and interest for the radio-halogen fluorine-18 in radiopharmaceutical chemistry undoubtedly results from its convenient half-life and the successful use in clinical oncology of 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG). The special interest of carbon-11 is not only that carbon is present in virtually all biomolecules and drugs allowing therefore for isotopic labelling of their chemical structures but also that a given molecule could be radiolabelled at different functions or sites, permitting to explore (or to take advantage of) in vivo metabolic pathways. PET chemistry includes production of these short-lived radioactive isotopes via nuclear transmutation reactions using a cyclotron, and is directed towards the development of rapid synthetic methods, at the trace level, for the introduction of these nuclides into a molecule, as well as the use of fast purification, analysis and formulation techniques. PET chemistry is the driving force in molecular PET imaging, and this special issue of the Journal of Labelled Compounds and Radiopharmaceuticals, which is strongly chemistry and radiochemistry-oriented, aims at illustrating, be it in part only, the state-of-the-art arsenal of reactions currently available and its potential for the research and development of specific molecular probes labelled with the positron emitters carbon-11 and fluorine-18,with optimal imaging properties for

  15. Mg I as a probe of the solar chromosphere - The atomic model

    Science.gov (United States)

    Mauas, Pablo J.; Avrett, Eugene H.; Loeser, Rudolf

    1988-01-01

    This paper presents a complete atomic model for Mg I line synthesis, where all the atomic parameters are based on recent experimental and theoretical data. It is shown how the computed profiles at 4571 A and 5173 A are influenced by the choice of these parameters and the number of levels included in the model atom. In addition, observed profiles of the 5173 A b2 line and theoretical profiles for comparison (based on a recent atmospheric model for the average quiet sun) are presented.

  16. Synthesis of new molecular probes radiolabelled with fluorine-18 for imaging neuro-inflammation with Positon Emission Tomography

    International Nuclear Information System (INIS)

    The work presented in this manuscript aims to describe the synthesis of new ligands of the translocation protein 18 kDa (TSPO), their in vitro evaluation and, for the most promising candidates, their isotopic radiolabelling with the short-lived positron emitter fluorine-18 (t1/2: 109.8 minutes). The ultimate goal of this work consists in developing new molecular probes, or bio-markers, for imaging neuro-inflammation in a non-invasive and atraumatic manor using Positron Emission Tomography (PET). Neuro-inflammatory processes have been identified in Alzheimer and Parkinson diseases, MS and various psychiatric pathologies. The radioligand of choice for imaging TSPO is currently [18F]DPA-714, a pyr-azolo[1,5-a]pyrimidine radiolabelled with fluorine-18 which has been recently prepared in our laboratories. However, [18F]DPA-714 undergoes a rapid in vivo loss of the radioactive fluorine by cleavage of the fluoro-alkoxy chain as demonstrated in metabolic studies. Therefore, my PhD project aimed to design and develop new structurally related analogues of DPA-714 where the linkage between the main backbone and the fluorine-18 would be reinforced. To this extent, nineteen compounds were prepared and their affinity towards the TSPO was evaluated. Two promising candidates, coded DPA-C5yne and CfO-DPA-714, were radiolabelled with fluorine-18 with good radiochemical yields (20-30 %) and high specific radioactivities (50-90 GBq/μmol). These radioligands were also evaluated by PET imaging at the preclinical stage and displayed equivalent or slightly improved results when compared to [18F]DPA- 714. (author)

  17. Preparation of light-atom tips for scanning probe microscopy by explosive delamination

    OpenAIRE

    Hofmann, Thomas; Welker, Joachim; Giessibl, Franz J

    2010-01-01

    To obtain maximal resolution in scanning tunneling microscopy (STM) and atomic force microscopy, the size of the protruding tip orbital has to be minimized. Beryllium as tip material is a promising candidate for enhanced resolution because a beryllium atom has just four electrons, leading to a small covalent radius of only 96 pm. Besides that, beryllium is conductive and has a high elastic modulus, which is a necessity for a stable tip apex. However, beryllium tips that are prepared ex situ a...

  18. Atoms

    Institute of Scientific and Technical Information of China (English)

    刘洪毓

    2007-01-01

    Atoms(原子)are all around us.They are something like the bricks (砖块)of which everything is made. The size of an atom is very,very small.In just one grain of salt are held millions of atoms. Atoms are very important.The way one object acts depends on what

  19. Electrostatic simulations of a local electrode atom probe: The dependence of tomographic reconstruction parameters on specimen and microscope geometry

    Energy Technology Data Exchange (ETDEWEB)

    Loi, Shyeh Tjing, E-mail: sloi5113@uni.sydney.edu.au [Australian Centre for Microscopy and Microanalysis, Madsen Building F09, The University of Sydney, NSW 2006 (Australia); Gault, Baptiste, E-mail: gaultb@mcmaster.ca [Australian Centre for Microscopy and Microanalysis, Madsen Building F09, The University of Sydney, NSW 2006 (Australia); Department of Materials Science and Engineering, McMaster University, 1280 Main St W, Hamilton, Ontario, Canada L8S4L8 (Canada); Ringer, Simon P. [Australian Centre for Microscopy and Microanalysis, Madsen Building F09, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Larson, David J.; Geiser, Brian P. [Cameca Instruments Inc., 5500 Nobel Drive, Madison, WI 53711 (United States)

    2013-09-15

    We electrostatically model a local electrode atom probe microscope using the commercial software IES LORENTZ 2D v9.0 to investigate factors affecting the reconstruction parameters. We find strong dependences on the specimen geometry and voltage, and moderate dependences on the tip-aperture separation, which confirm that the current approach to atom probe reconstruction overlooks too many factors. Based on our data, which are in excellent agreement with known trends and experimental results, we derive a set of empirical relations which predict the values of the reconstruction parameters. These may be used to advance current reconstruction protocols by enabling the parameters to be adjusted as the specimen geometry changes. - Highlights: ► We perform electrostatic modelling of a LEAP for wires, microtips, and nanowires. ► Reconstruction parameters depend strongly on specimen geometry. ► The chamber has a non-zero-field and specimen/MCP voltages affect ion trajectories. ► k{sub f} is cubically related to ξ as previously shown. ► Derived empirical relations predict values in excellent agreement with experiment.

  20. Probing Matter-Field and Atom-Number Correlations in Optical Lattices by Global Nondestructive Addressing

    CERN Document Server

    Kozlowski, Wojciech; Mekhov, Igor B

    2014-01-01

    We show that light scattering from an ultracold gas reveals not only density correlations, but also matter-field interference at its shortest possible distance in an optical lattice, which defines key properties such as tunneling and matter-field phase gradients. This signal can be enhanced by concentrating probe light between lattice sites rather than at density maxima. As addressing between two single sites is challenging, we focus on global nondestructive scattering, allowing probing order parameters, matter-field quadratures and their squeezing. The scattering angular distribution displays peaks even if classical diffraction is forbidden and we derive generalized Bragg conditions. Light scattering distinguishes all phases in the Mott insulator - superfluid - Bose glass phase transition.

  1. 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 ostatní: 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

  2. Atoms

    International Nuclear Information System (INIS)

    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)

  3. Probing the compressibility of tumor cell nuclei by combined atomic force-confocal microscopy

    NARCIS (Netherlands)

    Krause, M.; Riet, J. te; Wolf, K. van der

    2013-01-01

    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 toge

  4. 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...

  5. Tomography of atomic number and density of materials using dual-energy imaging and the Alvarez and Macovski attenuation model

    Science.gov (United States)

    Paziresh, M.; Kingston, A. M.; Latham, S. J.; Fullagar, W. K.; Myers, G. M.

    2016-06-01

    Dual-energy computed tomography and the Alvarez and Macovski [Phys. Med. Biol. 21, 733 (1976)] transmitted intensity (AMTI) model were used in this study to estimate the maps of density (ρ) and atomic number (Z) of mineralogical samples. In this method, the attenuation coefficients are represented [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976)] in the form of the two most important interactions of X-rays with atoms that is, photoelectric absorption (PE) and Compton scattering (CS). This enables material discrimination as PE and CS are, respectively, dependent on the atomic number (Z) and density (ρ) of materials [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976)]. Dual-energy imaging is able to identify sample materials even if the materials have similar attenuation coefficients at single-energy spectrum. We use the full model rather than applying one of several applied simplified forms [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976); Siddiqui et al., SPE Annual Technical Conference and Exhibition (Society of Petroleum Engineers, 2004); Derzhi, U.S. patent application 13/527,660 (2012); Heismann et al., J. Appl. Phys. 94, 2073-2079 (2003); Park and Kim, J. Korean Phys. Soc. 59, 2709 (2011); Abudurexiti et al., Radiol. Phys. Technol. 3, 127-135 (2010); and Kaewkhao et al., J. Quant. Spectrosc. Radiat. Transfer 109, 1260-1265 (2008)]. This paper describes the tomographic reconstruction of ρ and Z maps of mineralogical samples using the AMTI model. The full model requires precise knowledge of the X-ray energy spectra and calibration of PE and CS constants and exponents of atomic number and energy that were estimated based on fits to simulations and calibration measurements. The estimated ρ and Z images of the samples used in this paper yield average relative errors of 2.62% and 1.19% and maximum relative errors of 2.64% and 7.85%, respectively. Furthermore, we demonstrate that the method accounts for the beam hardening effect in density (ρ) and

  6. Synthesis, metabolite analysis, and in vivo evaluation of [11C]irinotecan as a novel positron emission tomography (PET) probe

    International Nuclear Information System (INIS)

    Introduction: Irinotecan is a semisynthetic derivative of camptothecin that exerts potent antitumor activity by inhibiting topoisomerase I. Despite much research into the complex pharmacokinetic profile and pharmacodynamic effects of irinotecan, unpredictable and severe side effects are still commonly observed. In this study, we synthesized [11C]irinotecan as a positron emission tomography (PET) probe, performed the metabolite analysis, and evaluated the biodistribution and kinetics of [11C]irinotecan using small animal PET. Methods: [11C]Irinotecan was synthesized by two routes using [11C]phosgene and [11C]carbon dioxide fixation. Metabolites in the plasma of mice following injection of [11C] irinotecan were investigated using a combination of column-switching high-performance liquid chromatography (HPLC) and on-line solid-phase extraction (SPE). Whole-body PET studies were conducted in wild-type mice and P-glycoprotein and breast cancer resistance protein (Pgp/Bcrp) knockout mice. Results: [11C]Irinotecan was successfully synthesized by the two abovementioned routes. Decay-corrected radiochemical yields based on [11C]carbon dioxide using [11C]phosgene and [11C]carbon dioxide fixation were 8.8 ± 2.0% (n = 8) and 16.9 ± 2.9 % (n = 5), respectively. Metabolite analysis of the plasma of mice following injection of [11C]irinotecan was successfully performed using the column-switching HPLC and on-line SPE combination resulting in greater than 87 % recovery of radioactivity from HPLC. In the PET study in mice, the radioactivity levels in the brain, liver, and small intestine were slightly increased by inhibition of the Pgp/Bcrp function for more than 30 min after [11C]irinotecan injection. This result demonstrated that in vivo behavior of [11C] irinotecan and radioactive metabolites are influenced by the Pgp/Bcrp function. Conclusion: PET studies using [11C]irinotecan combined with metabolite analysis may be a useful tool for evaluating irinotecan pharmacokinetics and

  7. 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

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

    International Nuclear Information System (INIS)

    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

  9. Probing an Excited-State Atomic Transition Using Hyperfine Quantum Beat Spectroscopy

    CERN Document Server

    Wade, Christopher G; Keaveney, James; Adams, Charles S; Weatherill, Kevin J

    2014-01-01

    We describe a method to observe the dynamics of an excited-state transition in a room temperature atomic vapor using hyperfine quantum beats. Our experiment using cesium atoms consists of a pulsed excitation of the D2 transition, and continuous-wave driving of an excited-state transition from the 6P$_{3/2}$ state to the 7S$_{1/2}$ state. We observe quantum beats in the fluorescence from the 6P$_{3/2}$ state which are modified by the driving of the excited-state transition. The Fourier spectrum of the beat signal yields evidence of Autler-Townes splitting of the 6P$_{3/2}$, F = 5 hyperfine level and Rabi oscillations on the excited-state transition. A detailed model provides qualitative agreement with the data, giving insight to the physical processes involved.

  10. An atom probe field ion microscope investigation of the role of boron in precipitates and at grain boundaries in NiAl

    International Nuclear Information System (INIS)

    This paper reports that the high resolution analytical technique of Atom Probe Field Ion Microscopy (APFIM) has been used to characterize grain boundaries and the matrix of a stoichiometric NiAl alloy doped with 0.04 (100 wppm) and 0.12 at. % (300 wppm) boron. Field ion images revealed boron segregation to the grain boundaries. Atom probe elemental analysis of the grain boundaries measured a boron coverage of up to 30% of a monolayer. Extensive atom probe analyses also revealed a fine dispersion of nanoscale boride precipitates in the matrix. The boron segregation to the grain boundaries was found to correlate with the observed suppression of intergranular fracture. However, the decrease in ductility of boron-doped NiAl is attributed in part to the precipitation hardening effect of the boride phases

  11. Optical Probe of Quantum Shot Noise Reduction at a Single-Atom Contact

    CERN Document Server

    Schneider, Natalia L; Berndt, Richard

    2010-01-01

    Visible and infra-red light emitted at a Ag-Ag(111) junction has been investigated from tunneling to single atom contact conditions with a scanning tunneling microscope. The light intensity varies in a highly nonlinear fashion with the conductance of the junction and exhibits a minimum at conductances close to the conductance quantum. The data are interpreted in terms of current noise at optical frequencies, which is characteristic of partially open transport channels.

  12. New possibilities in high sensitivity low energy ion scattering (LEIS) for probing the outermost atomic layer

    International Nuclear Information System (INIS)

    With a recently developed high sensitivity low energy ion scattering (LEIS) instrument, a range of new applications arises for this extremely surface sensitive analytical technique. Known capabilities of LEIS are the selective characterisation and quantification of the atomic composition of the outermost atomic layer, i. e. precisely the atoms that control properties like catalytic performance, adhesion, wetting, corrosion, etc. New possibilities such as surface imaging, sputter as well as non-destructive (static) profiling and even higher sensitivity for light elements have been added. The energy range of the primary ion source of up to 8 keV allows an improved mass resolution, thus enabling a better separation of the heaviest elements. In addition, a time-of-flight filter dramatically improves the detection limit for light elements. This filter suppresses the signal arising from sputtered ions, while scattered ions reach the detection system unhindered. In this contribution, we show the utilization of these new capabilities to a range of samples and applications. Furthermore, we will show how LEIS can benefit from the combination with the complementary technique time-of-flight secondary ion mass spectrometry (TOF-SIMS), which adds ppb-ppm sensitivity, lateral resolution of 100 nm and chemical information

  13. A novel atomic force microscope operating in liquid with open probe unit and optimized laser tracking system

    Institute of Scientific and Technical Information of China (English)

    Xia Fu; Dongxian Zhang; Haijun Zhang

    2009-01-01

    A novel atomic force microscope (AFM) for large samples to be measured in liquid is developed.An innovative laser beam tracking system is proposed to eliminate the tracking and feedback errors.The open probe design of the AFM makes the operation in liquid convenient and easy.A standard 1200-lines/mm grating and a sheet of filter paper are imaged respectively in air and liquid to confirm its performance.The corrosion behavior of aluminum surface in 1-mol/L NaOH solution is further investigated by the AFM.Experimental results show that the system can realize wide range (20 × 20 (μm)) scanning for large samples both in air and liquid,while keeping nanometer order resolution in liquid by eliminating the tracking and feedback error.

  14. Atomic contact potential variations of Si(111)-7 x 7 analyzed by Kelvin probe force microscopy

    International Nuclear Information System (INIS)

    We studied atomic contact potential variations of Si(111)-7 x 7 by Kelvin probe force microscopy with the amplitude modulation technique at the second resonance of a silicon cantilever. Enhanced sensitivity due to the high mechanical quality factor in ultra-high vacuum enabled local contact potential difference (LCPD) measurements of individual adatoms. The contrast of the measured LCPD map became stronger by reducing the tip-sample distance, and the averaged LCPD value shifted to more negative. The short-range interaction, arising from the covalent bonding interactions, strongly affects the LCPD measurement. Theoretical calculations indicate that the amplitude modulation method has a higher sensitivity than the frequency modulation method in practical cases. The tip-sample distance dependence of LCPD was investigated by numerical calculations.

  15. Magnetic domain and domain-wall imaging of submicron Co dots by probing the magnetostrictive response using atomic force microscopy

    International Nuclear Information System (INIS)

    An approach to image the domains and domain walls of small ferromagnetic entities using atomic force microscopy (AFM), with a nonmagnetic AFM probe, has been developed. Exciting the sample in an external ac magnetic field, the distribution of magnetostrictive response at the surface is detected. By this technique, the domains and domain walls of submicron Co dots have been imaged with a 1 nm lateral resolution. In elliptical Co dots with a 350-nm-long axis on a triangular lattice array with 400 nm periodicity, we find evidence for two domains with opposite magnetization orientation across a wall. The domain-wall width in these dots is found to be about 35 nm. Furthermore, we observe a ferromagnetic alignment of the domains in the neighboring dots, which suggests a magnetostatic interaction among the dots. (c) 2000 American Institute of Physics

  16. Oxygen concentration of Eu1Ba2Cu3O7-x in vacuum: An atom probe study

    International Nuclear Information System (INIS)

    Atom Probe mass analysis, at 85 K, using a wide-angle instrument was used to measure the oxygen content and metallic stoichiometry of the near-surface region of the superconducting ceramic oxide Eu1Ba2Cu3O7-x (x≅0.1) after vacuum exposure at room temperature. Routine specimen preparation, handling, and field-ion imaging produced a specimen which had already lost oxygen such that its measured surface oxygen content corresponded to x=0.73 and the metallic stoichiometry of the surface was not the expected 1:2:3 but was enhanced in Ba and Eu. The specimen was subsequently exposed to vacuum for up to 80 h at room temperature and no additional loss of oxygen was detected. It was concluded that either (1) a stoichiometric low-oxygen surface also would not have lost oxygen or (2) the nonstoichiometric layer forms a barrier for subsequent oxygen loss

  17. Oxygen concentration of EuBa2Cu307-x in vacuum: an atom probe study II

    International Nuclear Information System (INIS)

    Atom Probe mass analysis using a wide acceptance angle instrument was used to measure the oxygen content and metallic stoichiometry of the near-surface region of the superconducting ceramic oxide EuBa2Cu307-x (x≅0.1) after exposure at 85K and room temperature in vacuum. An oxygen depleted layer formed by H2 imaging must be removed before bulk concentrations are obtained. Room temperature holding in vacuum overnight then depletes the surface of oxygen to a depth of greater than 4 layers (1.2 nm). However, after holding the specimen at 85K for up to 3h either with or without an applied field, no detectable loss of oxygen occurred. Therefore, for short time vacuum exposures at liquid nitrogen temperatures and below, no oxygen loss is expected, however, significant oxygen loss occurs for 18h vacuum exposures at room temperature

  18. Combined atom-probe and electron microscopy characterization of fine scale structures in aged primary coolant pipe stainless steel

    International Nuclear Information System (INIS)

    The capabilities and complementary nature of atom probe field-ion microscopy (APFIM) and analytical electron microscopy (AEM) for the characterization of fine-scale microstructures are illustrated by examination of the changes that occur after long term thermal aging of cast CF 9 and CF 8M duplex stainless steels. In material aged at 300 or 4000C for up to 70,000 h, the ferrite had spinodally decomposed into a modulated fine-scaled interconnected network consisting of an iron-rich α phase and a chromium-enriched α' phase with periodicities of between 2 and 9 nm. G-phase precipitates 2 to 10 nm in diameter were also observed in the ferrite at concentrations of more than 10/sup 21/ m/sup -3/. The reported degradation in mechanical properties is most likely a consequence of the spinodal decomposition in the ferrite

  19. Quantum beat spectroscopy: stimulated emission probe of hyperfine quantum beats in the atomic Cs 8p $^{2}P_{3/2}$ level

    CERN Document Server

    Bayram, S B; Popov, O I; Guney, C; Havey, M D; Boyle, W P

    2014-01-01

    Measurements of hyperfine polarization quantum beats are used determine the magnetic dipole (A) and electric quadrupole (B) coupling constants in the excited atomic Cs 8p level. The experimental approach is a novel combination of pulsed optical pumping and time-delayed stimulated emission probing of the excited level. From the measured evolution of the atomic linear polarization degree as a function of probe delay time, we determine the hyperfine coupling constants A = 7.42(6) MHz and B = 0.14(29) MHz.

  20. Nano-scale mechanical probing of supported lipid bilayers with atomic force microscopy

    OpenAIRE

    Das, Chinmay; Sheik, Khizar H.; Olmsted, Peter D.; Connell, Simon D.

    2010-01-01

    We present theory and experiments for the force-distance curve $F(z_0)$ of an atomic force microscope (AFM) tip (radius $R$) indenting a supported fluid bilayer (thickness $2d$). For realistic conditions the force is dominated by the area compressibility modulus $\\kappa_A$ of the bilayer, and, to an excellent approximation, given by $F= \\pi \\kappa_A R z_0^2/(2d-z_0)^2$. The experimental AFM force curves from coexisting liquid ordered and liquid disordered domains in 3-component lipid bilayers...

  1. Probing molecular interaction between transferrin and anti-transferrin by atomic force microscope

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The interaction between transferrin (Tf) and its antibody was investigated by atomic force microscope. Tf-antibody was immobilized on the Au-coated glass slide, and the specific combination between antibody and antigen was also characterized by AFM. The results showed that holo-transferrin was jogged with anti-transferrin, and binded anti-tran- sferrin more tightly than apo-transferrin. The force- distance curves revealed that the affinity of anti-trans- ferrin and holo-transferrin was much stronger than that of apo-transferrin.

  2. Probes for 4th generation constituents of dark atoms in Higgs boson studies at the LHC

    CERN Document Server

    Khlopov, M Yu

    2014-01-01

    The nonbaryonic dark matter of the Universe can consist of new stable charged species, bound in heavy neutral "atoms" by ordinary Coulomb interaction. Stable $\\bar U$ (anti-$U$)quarks of 4th generation, bound in stable colorless ($\\bar U \\bar U \\bar U $) clusters, are captured by the primordial helium, produced in Big Bang Nucleosynthesis, thus forming neutral "atoms" of O-helium (OHe), a specific nuclear interacting dark matter that can provide solution for the puzzles of direct dark matter searches. However, the existence of the 4th generation quarks and leptons should influence the production and decay rates of Higgs boson and is ruled out by the experimental results of the Higgs boson searches at the LHC, if the Higgs boson coupling to 4th generation fermions with is not suppressed. Here we argue that the difference between the three known quark-lepton families and the 4th family can naturally lead to suppression of this coupling, relating the accelerator test for such a composite dark matter scenario to ...

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

    International Nuclear Information System (INIS)

    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 H2 and/or CH4 permeabilities. Recent progress in polymers research is also reviewed

  4. Probing deviations from traditional colloid filtration theory by atomic forces microscopy.

    Energy Technology Data Exchange (ETDEWEB)

    Reno, Marissa Devan

    2005-12-01

    Colloid transport through saturated media is an integral component of predicting the fate and transport of groundwater contaminants. Developing sound predictive capabilities and establishing effective methodologies for remediation relies heavily on our ability to understand the pertinent physical and chemical mechanisms. Traditionally, colloid transport through saturated media has been described by classical colloid filtration theory (CFT), which predicts an exponential decrease in colloid concentration with travel distance. Furthermore, colloid stability as determined by Derjaguin-Landau-Veney-Overbeek (DLVO) theory predicts permanent attachment of unstable particles in a primary energy minimum. However, recent studies show significant deviations from these traditional theories. Deposition in the secondary energy minimum has been suggested as a mechanism by which observed deviations can occur. This work investigates the existence of the secondary energy minimum as predicted by DLVO theory using direct force measurements obtained by Atomic Forces Microscopy. Interaction energy as a function of separation distance between a colloid and a quartz surface in electrolyte solutions of varying ionic strength are obtained. Preliminary force measurements show promise and necessary modifications to the current experimental methodology have been identified. Stringent surface cleaning procedures and the use of high-purity water for all injectant solutions is necessary for the most accurate and precise measurements. Comparisons between direct physical measurements by Atomic Forces Microscopy with theoretical calculations and existing experimental findings will allow the evaluation of the existence or absence of a secondary energy minimum.

  5. Broadband Rydberg Atom-Based Electric-Field Probe: From Self-Calibrated Measurements to Sub-Wavelength Imaging

    CERN Document Server

    Holloway, Christopher L; Jefferts, Steven; Schwarzkopf, Andrew; Anderson, David A; Miller, Stephanie A; Thaicharoen, Nithiwadee; Raithel, Georg

    2014-01-01

    We discuss a fundamentally new approach for the measurement of electric (E) fields that will lead to the development of a broadband, direct SI-traceable, compact, self-calibrating E-field probe (sensor). This approach is based on the interaction of radio frequency (RF) fields with alkali atoms excited to Rydberg states. The RF field causes an energy splitting of the Rydberg states via the Autler-Townes effect and we detect the splitting via electromagnetically induced transparency (EIT). In effect, alkali atoms placed in a vapor cell act like an RF-to-optical transducer, converting an RF E-field strength measurement to an optical frequency measurement. We demonstrate the broadband nature of this approach by showing that one small vapor cell can be used to measure E-field strengths over a wide range of frequencies: 1 GHz to 500 GHz. The technique is validated by comparing experimental data to both numerical simulations and far-field calculations for various frequencies. We also discuss various applications, in...

  6. 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.

  7. Atom probe analysis on interaction between Cr and N in bake-hardening steels with anti-aging properties at RT

    International Nuclear Information System (INIS)

    One-dimensional atom probe (1DAP) analysis was performed on chromium and nitrogen added bake hardening steel sheets that have both high bake-hardenability and anti-aging properties at room temperature (RT). The atomic data of more than 2 million atoms were collected for sample steels with and without low-temperature aging after recrystallization annealing and quenching. The correlation in atomic position between chromium and nitrogen atoms in a solid solution was investigated by a statistical analysis using the binomial distribution function. In the samples with low-temperature aging, the probability that a chromium atom was observed near a nitrogen atom was significantly higher than that estimated from the null hypothesis that there was no attractive atomic interaction. This suggests that there is an attractive interaction between a nitrogen atom and a chromium atom in bcc iron, which led to the anti-aging properties at RT. In contrast, such correlation was not observed definitely in the samples without low-temperature aging, which implied that the atomic pair formation is a thermal activation process

  8. Nanoscale mechanical probing of supported lipid bilayers with atomic force microscopy.

    Science.gov (United States)

    Das, Chinmay; Sheikh, Khizar H; Olmsted, Peter D; Connell, Simon D

    2010-10-01

    We present theory and experiments for the force-distance curve F(z(0)) of an atomic force microscope (AFM) tip (radius R) indenting a supported fluid bilayer (thickness 2d). For realistic conditions the force is dominated by the area compressibility modulus κ(A) of the bilayer and, to an excellent approximation, given by F=πκ(A)Rz(0)(2)/(2d-z(0))(2). The experimental AFM force curves from coexisting liquid ordered and liquid disordered domains in three-component lipid bilayers are well described by our model, which provides κ(A) in agreement with literature values. The liquid ordered phase has a yieldlike response that we model as due to the breaking of hydrogen bonds. PMID:21230326

  9. Determination of atom percent deuterium in deuterium gas using a vibrating-probe density meter

    International Nuclear Information System (INIS)

    Atom percent deuterium may be effectively analyzed in a mixture of hydrogen and deuterium gases from the density determination of the mixture of water-heavy water which is formed after the gas sample is converted to an oxide and condensed. The density can be accurately measured by using a vibrating-tube density meter which is standardized with air and pure water or other density standards. This deuterium determination requires no empirical standardization against known deuterium standards. The sample gas in a helium carrier is passed through a hot copper oxide tube; the hydrogen and deuterium oxides are condensed in a liquid-nitrogen cooled collection bulb, which was designed for effective entrapment and prevention of sample exposure to the atmosphere

  10. Direct probe of anisotropy in atom-molecule collisions via quantum scattering resonances

    CERN Document Server

    Klein, Ayelet; Skomorowski, Wojciech; Żuchowski, Piotr S; Pawlak, Mariusz; Janssen, Liesbeth M C; Moiseyev, Nimrod; van de Meerakker, Sebastiaan Y T; van der Avoird, Ad; Koch, Christiane P; Narevicius, Edvardas

    2016-01-01

    Anisotropy is a fundamental property of particle interactions. It occupies a central role in cold and ultra-cold molecular processes, where long range forces have been found to significantly depend on orientation in ultra-cold polar molecule collisions. Recent experiments have demonstrated the emergence of quantum phenomena such as scattering resonances in the cold collisions regime due to quantization of the intermolecular degrees of freedom. Although these states have been shown to be sensitive to interaction details, the effect of anisotropy on quantum resonances has eluded experimental observation so far. Here, we directly measure the anisotropy in atom-molecule interactions via quantum resonances by changing the quantum state of the internal molecular rotor. We observe that a quantum scattering resonance at a collision energy of $k_B$ x 270 mK appears in the Penning ionization of molecular hydrogen with metastable helium only if the molecule is rotationally excited. We use state of the art ab initio and ...

  11. Probing intra-molecular mechanics of single circularly permuted green fluorescent protein with atomic force microscopy

    International Nuclear Information System (INIS)

    We investigated the mechanical unfolding of single circularly permuted green fluorescent protein (cpGFP) with atomic force microscopy (AFM). The molecule was stretched from its N- and C-termini by an external force causing an elongation of the polypeptide chain up to its full length. The features of the force-extension (F-E) curves were found to depend on the stretching speed. At fast speeds, we detected one peak in the F-E curves before final rupture of the extended molecule, which we interpreted as the unfolding of two terminal halves within cpGFP. We observed several more force peaks in a sawtooth pattern at much slower speeds, and explained the appearance of such force peaks as cooperative unfolding of the hidden sub-structures inside each terminal half

  12. Probing CP violation with the electric dipole moment of atomic mercury

    CERN Document Server

    Latha, K V P; Das, B P; Mukherjee, D

    2009-01-01

    The electric dipole moment of atomic $^{199}$Hg induced by the nuclear Schiff moment and tensor-pseudotensor electron-nucleus interactions has been calculated. For this, we have developed and employed a novel method based on the relativistic coupled-cluster theory. The results of our theoretical calculations combined with the latest experimental result of $^{199}$Hg electric dipole moment, provide new bounds on the T reversal or CP violation parameters $\\theta_{\\rm QCD}$, the tensor-pseudotensor coupling constant $C_T$ and $(\\widetilde{d}_u - \\widetilde{d}_d)$. This is the most accurate calculation of these parameters to date. We highlight the the crucial role of electron correlation effects in their interplay with the P,T violating interactions. Our results demonstrate substantial changes in the results of earlier calculations of these parameters which can be attributed to the more accurate inclusion of important correlation effects in the present work.

  13. Probing the local structure of doped manganites using the atomic pair distribution function

    International Nuclear Information System (INIS)

    We have used atomic pair distribution function (PDF) analysis based on neutron powder diffraction data to investigate the local structure of the colossal magnetoresistant manganite La0.75Ca0.25MnO3 as a function of temperature. In the doping range 0.173+ ions. A two-phase model based on the local structures of the FM and PI phases was used to refine the experimental PDFs quantitatively. We observe the co-existence of both phases over a wide temperature range: approximately 10% of the localized JT phase (PI) is present even at the lowest temperature (T=20 K), whereas at room temperature nearly half of the sample remains in the delocalized (FM) phase. (orig.)

  14. Nano-scale mechanical probing of supported lipid bilayers with atomic force microscopy

    CERN Document Server

    Das, Chinmay; Olmsted, Peter D; Connell, Simon D

    2010-01-01

    We present theory and experiments for the force-distance curve $F(z_0)$ of an atomic force microscope (AFM) tip (radius $R$) indenting a supported fluid bilayer (thickness $2d$). For realistic conditions the force is dominated by the area compressibility modulus $\\kappa_A$ of the bilayer, and, to an excellent approximation, given by $F= \\pi \\kappa_A R z_0^2/(2d-z_0)^2$. The experimental AFM force curves from coexisting liquid ordered and liquid disordered domains in 3-component lipid bilayers are well-described by our model, and provides $\\kappa_A$ in agreement with literature values. The liquid ordered phase has a yield like response that we model by hydrogen bond breaking.

  15. Atom probe analysis of early-stage strengthening behaviour in an Al-Mg-Si-Cu alloy

    International Nuclear Information System (INIS)

    The strengthening of an Al-Mg-Si-Cu alloy during natural ageing and subsequent short artificial ageing was investigated using three-dimensional atom probe (3DAP) analysis and tensile testing. The contingency table and Markov chain analyses confirmed that non-random arrangements of atoms already exist after a natural ageing time of only 3.5 h. Extensive use of particle analysis tools in the IVAS and PoSAP software packages revealed that whilst the commonly used minimum aggregate size (Nmin) of 10 is a reasonable choice, much more useful information about the system can be gained by additionally employing a wide range of larger and smaller Nmin values. In particular, it was found that the density and volume fraction of solute aggregates increased with increasing natural ageing time in the T4 condition. After a 0.5 h artificial ageing treatment at 170 oC (designated as T6), the size, volume fraction and Mg/Si ratio of the aggregates were all found to decrease with increasing prior natural ageing time. These findings are used to discuss the detrimental effect of natural ageing, where the T6 strength has been observed to decrease rapidly with increasing prior natural ageing time before stabilising after several hours of natural ageing. -- Research Highlights: → The ageing response at 170 oC is reduced by 100 MPa after >3 h of natural ageing. → Non-random arrangements of atoms exist after 3.5 h of natural ageing. → Analysis of 3DAP data is enhanced by systematically varying Nmin values. → T4 strength is related to the density and volume fraction of small solute aggregates. → T6 strength is related to the size, volume fraction and Mg/Si ratio of aggregates.

  16. Atomic resolution tomography reconstruction of tilt series based on a GPU accelerated hybrid input–output algorithm using polar Fourier transform

    International Nuclear Information System (INIS)

    Advances in diffraction and transmission electron microscopy (TEM) have greatly improved the prospect of three-dimensional (3D) structure reconstruction from two-dimensional (2D) images or diffraction patterns recorded in a tilt series at atomic resolution. Here, we report a new graphics processing unit (GPU) accelerated iterative transformation algorithm (ITA) based on polar fast Fourier transform for reconstructing 3D structure from 2D diffraction patterns. The algorithm also applies to image tilt series by calculating diffraction patterns from the recorded images using the projection-slice theorem. A gold icosahedral nanoparticle of 309 atoms is used as the model to test the feasibility, performance and robustness of the developed algorithm using simulations. Atomic resolution in 3D is achieved for the 309 atoms Au nanoparticle using 75 diffraction patterns covering 150° rotation. The capability demonstrated here provides an opportunity to uncover the 3D structure of small objects of nanometers in size by electron diffraction. - Highlights: • Three-dimensional atomic structural reconstruction demonstrated using simulated diffraction data in a tilt series. • Using diffraction patterns allows alignment free tomography reconstruction. • This method can be applied to general image based tomography by using the power spectra of the images as input. • Reconstruction is based on an iterative transformation algorithm (ITA) using polar fast Fourier transform. • The ITA algorithm is accelerated using graphics processing unit (GPU) for competitive high performance

  17. 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

  18. Probing the nanoadhesion of Streptococcus sanguinis to titanium implant surfaces by atomic force microscopy

    Science.gov (United States)

    Aguayo, Sebastian; Donos, Nikolaos; Spratt, Dave; Bozec, Laurent

    2016-01-01

    As titanium (Ti) continues to be utilized in great extent for the fabrication of artificial implants, it is important to understand the crucial bacterium–Ti interaction occurring during the initial phases of biofilm formation. By employing a single-cell force spectroscopy technique, the nanoadhesive interactions between the early-colonizing Streptococcus sanguinis and a clinically analogous smooth Ti substrate were explored. Mean adhesion forces between S. sanguinis and Ti were found to be 0.32±0.00, 1.07±0.06, and 4.85±0.56 nN for 0, 1, and 60 seconds contact times, respectively; while adhesion work values were reported at 19.28±2.38, 104.60±7.02, and 1,317.26±197.69 aJ for 0, 1, and 60 seconds, respectively. At 60 seconds surface delays, minor-rupture events were modeled with the worm-like chain model yielding an average contour length of 668±12 nm. The mean force for S. sanguinis minor-detachment events was 1.84±0.64 nN, and Poisson analysis decoupled this value into a short-range force component of −1.60±0.34 nN and a long-range force component of −0.55±0.47 nN. Furthermore, a solution of 2 mg/mL chlorhexidine was found to increase adhesion between the bacterial probe and substrate. Overall, single-cell force spectroscopy of living S. sanguinis cells proved to be a reliable way to characterize early-bacterial adhesion onto machined Ti implant surfaces at the nanoscale. PMID:27103802

  19. 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...

  20. 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...

  1. Interaction forces between talc and pitch probed by atomic force microscopy.

    Science.gov (United States)

    Wallqvist, Viveca; Claesson, Per M; Swerin, Agne; Schoelkopf, Joachim; Gane, Patrick A C

    2007-04-10

    Colloidal wood resin components present in pulp are collectively called "pitch". The presence of pitch may cause severe problems due to deposits in and on the paper machine. There is thus a need for controlling pitch aggregation and adsorption. To be able to develop more efficient pitch control systems, one needs to develop the understanding of pitch-pitch interactions and of the interactions between pitch and other materials. With this general goal in mind, we present methods for preparing geometrically well-defined pitch particles attached to atomic force microscopy tips. This has enabled us to investigate the interactions between pitch and talc, an additive commonly used for pitch control. We have used model pitch particles consisting of one component only (abietic acid), a mixture of components (collophonium), and particles prepared from real pitch deposits. We show that the forces acting between pitch and talc are attractive and, once the initial approach is made, exert this attraction out to large distances of separation. We present evidence that the formation of bridging air bubbles or cavities is responsible for this interaction. PMID:17352501

  2. In vivo microvascular imaging of human oral and nasal cavities using swept-source optical coherence tomography with a single forward/side viewing probe

    Science.gov (United States)

    Choi, Woo June; Wang, Ruikang K.

    2015-03-01

    We report three-dimensional (3D) imaging of microcirculation within human cavity tissues in vivo using a high-speed swept-source optical coherence tomography (SS-OCT) at 1.3 μm with a modified probe interface. Volumetric structural OCT images of the inner tissues of oral and nasal cavities are acquired with a field of view of 2 mm x 2 mm. Two types of disposable and detachable probe attachments are devised and applied to the port of the imaging probe of OCT system, enabling forward and side imaging scans for selective and easy access to specific cavity tissue sites. Blood perfusion is mapped with OCT-based microangiography from 3D structural OCT images, in which a novel vessel extraction algorithm is used to decouple dynamic light scattering signals, due to moving blood cells, from the background scattering signals due to static tissue elements. Characteristic tissue anatomy and microvessel architectures of various cavity tissue regions of a healthy human volunteer are identified with the 3D OCT images and the corresponding 3D vascular perfusion maps at a level approaching capillary resolution. The initial finding suggests that the proposed method may be engineered into a promising tool for evaluating and monitoring tissue microcirculation and its alteration within a wide-range of cavity tissues in the patients with various pathological conditions.

  3. Temperature and force dependence of electron transport via the copper protein azurin: conductive probe atomic force microscopy measurements

    CERN Document Server

    Li, Wenjie; Amdursky, Nadav; Cohen, Sidney R; Pecht, Israel; Sheves, Mordechai; Cahen, David

    2012-01-01

    We report conducting probe atomic force microscopy (CP-AFM) measurements of electron transport (ETp), as a function of temperature and force, through monolayers of holo-azurin (holo-Az) and Cu-depleted Az (apo-Az) that retain only their tightly bound water, immobilized on gold surfaces. The changes in CP-AFM current-voltage (I-V) curves for holo-Az and apo-Az, measured between 250 - 370K, are strikingly different. While ETp across holo-Az at low force (6 nN) is temperature-independent over the whole examined range, ETp across apo-Az is thermally activated, with calculated activation energy of 600\\pm100 meV. These results confirm our results of macroscopic contact area ETp measurements via holo- and apo-Az, as a function of temperature, where the crucial role of the Cu redox centre has been observed. While increasing the applied tip force from 6 to 12 nN did not significantly change the temperature dependence of ETp via apo-Az, ETp via holo-Az changed qualitatively, namely from temperature-independent at 6 nN ...

  4. Detection of vulnerable atherosclerosis plaques with a dual-modal single-photon-emission computed tomography/magnetic resonance imaging probe targeting apoptotic macrophages.

    Science.gov (United States)

    Cheng, Dengfeng; Li, Xiao; Zhang, Chunfu; Tan, Hui; Wang, Cong; Pang, Lifang; Shi, Hongcheng

    2015-02-01

    Atherosclerosis (AS), especially the vulnerable AS plaque rupture-induced acute obstructive vascular disease, is a leading cause of death. Accordingly, there is a need for an effective method to draw accurate predictions about AS progression and plaque vulnerability. Herein we report on an approach to constructing a hybrid nanoparticle system using a single-photon-emission computed tomography (SPECT)/magnetic resonance imaging (MRI) multimodal probe, aiming for a comprehensive evaluation of AS progression by achieving high sensitivity along with high resolution. Ultrasmall superparamagnetic iron oxide (USPIO) was covered by aminated poly(ethylene glycol) (PEG) and carboxylated PEG simultaneously and then functionalized with diethylenetriaminepentacetate acid for (99m)Tc coordination and subsequently Annexin V for targeting apoptotic macrophages abundant in vulnerable plaques. The in vivo accumulations of imaging probe reflected by SPECT and MRI were consistent and accurate in highlighting lesions. Intense radioactive signals detected by SPECT facilitated focus recognization and quantification, while USPIO-based T2-weighted MRI improved the focal localization and volumetry of AS plaques. For subsequent ex vivo planar images, targeting effects were further confirmed by immunohistochemistry, including CD-68 and TUNEL staining; meanwhile, the degree of concentration was proven to be statistically correlated with the Oil Red O staining results. In conclusion, these results indicated that the Annexin V-modified hybrid nanoparticle system specifically targeted the vulnerable AS plaques containing apoptotic macrophages and could be of great value in the invasively accurate detection of vulnerable plaques. PMID:25569777

  5. Atom probe study of the microstructural evolution induced by irradiation in Fe-Cu ferritic alloys and pressure vessel steels

    International Nuclear Information System (INIS)

    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

  6. 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.

  7. Ultrafast probing of the x-ray-induced lattice and electron dynamics in graphite at atomic-resolution

    Energy Technology Data Exchange (ETDEWEB)

    Hau-Riege, S

    2010-10-07

    We used LCLS pulses to excite thin-film and bulk graphite with various different microstructures, and probed the ultrafast ion and electron dynamics through Bragg and x-ray Thomson scattering (XRTS). We pioneered XRTS at LCLS, making this technique viable for other users. We demonstrated for the first time that the LCLS can be used to characterize warm-dense-matter through Bragg and x-ray Thomson scattering. The warm-dense-matter conditions were created using the LCLS beam. Representative examples of the results are shown in the Figure above. In our experiment, we utilized simultaneously both Bragg and two Thomson spectrometers. The Bragg measurements as a function of x-ray fluence and pulse length allows us to characterize the onset of atomic motion at 2 keV with the highest resolution to date. The Bragg detector was positioned in back-reflection, providing us access to scattering data with large scattering vectors (nearly 4{pi}/{lambda}). We found a clear difference between the atomic dynamics for 70 and 300 fs pulses, and we are currently in the process of comparing these results to our models. The outcome of this comparison will have important consequences for ultrafast diffractive imaging, for which it is still not clear if atomic resolution can truly be achieved. The backward x-ray Thomson scattering data suggests that the average graphite temperature and ionization was 10 eV and 1.0, respectively, which agrees with our models. In the forward scattering data, we observed an inelastic feature in the Thomson spectrum that our models currently do not reproduce, so there is food for thought. We are in the process of writing these results up. Depending on if we can combine the Bragg and Thomson data or not, we plan to publish them in a single paper (e.g. Nature or Science) or as two separate papers (e.g. two Phys. Rev. Lett.). We will present the first analysis of the results at the APS Plasma Meeting in November 2010. We had a fantastic experience performing our

  8. Radioiodinated benzimidazole derivatives as single photon emission computed tomography probes for imaging of β-amyloid plaques in Alzheimer's disease

    International Nuclear Information System (INIS)

    Five iodinated 2-phenyl-1H-benzo[d]imidazole derivatives were synthesized and evaluated as potential probes for β-amyloid (Aβ) plaques. One of the compounds, 4-(6-iodo-1H-benzo[d]imidazol-2-yl)-N,N-dimethylaniline (12), showed excellent affinity for Aβ1-42 aggregates (Ki=9.8 nM). Autoradiography with sections of postmortem Alzheimer's disease (AD) brain revealed that a radioiodinated probe [125I]12, labeled Aβ plaques selectively with low nonspecific binding. Biodistribution experiments with normal mice injected intravenously with [125I]12 showed high uptake [4.14 percent injected dose per gram (% ID/g) at 2 min] into and rapid clearance (0.15% ID/g at 60 min) from the brain, which may bring about a good signal-to-noise ratio and therefore achieve highly sensitive detection of Aβ plaques. In addition, [125I]12 labeled amyloid plaques in vivo in an AD transgenic model. The preliminary results strongly suggest that [125I]12 bears characteristics suitable for detecting amyloid plaques in vivo. When labeled with 123I, it may be a useful SPECT imaging agent for Aβ plaques in the brain of living AD patients.

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

    International Nuclear Information System (INIS)

    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

  10. 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.

  11. Gold silver alloy nanoparticles (GSAN): an imaging probe for breast cancer screening with dual-energy mammography or computed tomography.

    Science.gov (United States)

    Naha, Pratap C; Lau, Kristen C; Hsu, Jessica C; Hajfathalian, Maryam; Mian, Shaameen; Chhour, Peter; Uppuluri, Lahari; McDonald, Elizabeth S; Maidment, Andrew D A; Cormode, David P

    2016-07-14

    Earlier detection of breast cancer reduces mortality from this disease. As a result, the development of better screening techniques is a topic of intense interest. Contrast-enhanced dual-energy mammography (DEM) is a novel technique that has improved sensitivity for cancer detection. However, the development of contrast agents for this technique is in its infancy. We herein report gold-silver alloy nanoparticles (GSAN) that have potent DEM contrast properties and improved biocompatibility. GSAN formulations containing a range of gold : silver ratios and capped with m-PEG were synthesized and characterized using various analytical methods. DEM and computed tomography (CT) phantom imaging showed that GSAN produced robust contrast that was comparable to silver alone. Cell viability, reactive oxygen species generation and DNA damage results revealed that the formulations with 30% or higher gold content are cytocompatible to Hep G2 and J774A.1 cells. In vivo imaging was performed in mice with and without breast tumors. The results showed that GSAN produce strong DEM and CT contrast and accumulated in tumors. Furthermore, both in vivo imaging and ex vivo analysis indicated the excretion of GSAN via both urine and feces. In summary, GSAN produce strong DEM and CT contrast, and has potential for both blood pool imaging and for breast cancer screening. PMID:27412458

  12. Scanning probe study on the photovoltaic characteristics of a Si solar cell by using Kelvin force microscopy and photoconductive atomic force microscopy

    International Nuclear Information System (INIS)

    Poly-Si-based solar cells, prepared via conventional Si processes including phosphoryl chloride(POCl3) doping and diffusion, were investigated in this study in terms of their electrical and optical properties, including open-circuit voltage (Voc), short-circuit current (Isc), fill factor, external quantum efficiency and efficiency, employing a few recognized test methods. Also, we compared the experiment results from an identical specimen via Kelvin force microscopy (KFM) and photoconductive atomic force microscopy (PC-AFM), respectively, verifying that the scanning probe technique is very effective both in photovoltaic effect measurement and mechanism establishment. When the results of both conventional and nano-probing techniques are compared, the behavior of the surface potential property is similar to the Voc, and that of the photoinduced current property is similar to the Isc. Through this study, we have demonstrated that the KFM and the PC-AFM are effective tools to monitor and evaluate the properties of solar energy–producing materials and devices. - Highlights: • Silicon solar cells were fabricated and studied by conventional characterization methods. • Characterization of photovoltaic effect and mechanism was performed using scanning probe microscopy. • Kelvin force microscopy (KFM) and photoconductive atomic force microscopy (PC-AFM) were used. • Behavior of KFM result is similar to Voc, and that of PC-AFM is similar to Isc. • KFM and PC-AFM are effective tools to evaluate solar energy materials

  13. Gold silver alloy nanoparticles (GSAN): an imaging probe for breast cancer screening with dual-energy mammography or computed tomography

    Science.gov (United States)

    Naha, Pratap C.; Lau, Kristen C.; Hsu, Jessica C.; Hajfathalian, Maryam; Mian, Shaameen; Chhour, Peter; Uppuluri, Lahari; McDonald, Elizabeth S.; Maidment, Andrew D. A.; Cormode, David P.

    2016-07-01

    Earlier detection of breast cancer reduces mortality from this disease. As a result, the development of better screening techniques is a topic of intense interest. Contrast-enhanced dual-energy mammography (DEM) is a novel technique that has improved sensitivity for cancer detection. However, the development of contrast agents for this technique is in its infancy. We herein report gold-silver alloy nanoparticles (GSAN) that have potent DEM contrast properties and improved biocompatibility. GSAN formulations containing a range of gold : silver ratios and capped with m-PEG were synthesized and characterized using various analytical methods. DEM and computed tomography (CT) phantom imaging showed that GSAN produced robust contrast that was comparable to silver alone. Cell viability, reactive oxygen species generation and DNA damage results revealed that the formulations with 30% or higher gold content are cytocompatible to Hep G2 and J774A.1 cells. In vivo imaging was performed in mice with and without breast tumors. The results showed that GSAN produce strong DEM and CT contrast and accumulated in tumors. Furthermore, both in vivo imaging and ex vivo analysis indicated the excretion of GSAN via both urine and feces. In summary, GSAN produce strong DEM and CT contrast, and has potential for both blood pool imaging and for breast cancer screening.Earlier detection of breast cancer reduces mortality from this disease. As a result, the development of better screening techniques is a topic of intense interest. Contrast-enhanced dual-energy mammography (DEM) is a novel technique that has improved sensitivity for cancer detection. However, the development of contrast agents for this technique is in its infancy. We herein report gold-silver alloy nanoparticles (GSAN) that have potent DEM contrast properties and improved biocompatibility. GSAN formulations containing a range of gold : silver ratios and capped with m-PEG were synthesized and characterized using various

  14. Hygromorphic behaviour of cellular material: hysteretic swelling and shrinkage of wood probed by phase contrast X-ray tomography

    Science.gov (United States)

    Derome, Dominique; Rafsanjani, Ahmad; Patera, Alessandra; Guyer, Robert; Carmeliet, Jan

    2012-10-01

    Wood is a hygromorphic material, meaning it responds to changes in environmental humidity by changing its geometry. Its cellular biological structure swells during wetting and shrinks during drying. The origin of the moisture-induced deformation lies at the sub-cellular scale. The cell wall can be considered a composite material with stiff cellulose fibrils acting as reinforcement embedded in a hemicellulose/lignin matrix. The bulk of the cellulose fibrils, forming 50% of the cell wall, are oriented longitudinally, forming long-pitched helices. Both components of cell wall matrix are displaying swelling. Moisture sorption and, to a lesser degree, swelling/shrinkage are known to be hysteretic. We quantify the affine strains during the swelling and shrinkage using high resolution images obtained by phase contrast synchrotron X-ray tomography of wood samples of different porosities. The reversibility of the swelling/shrinkage is found for samples with controlled moisture sorption history. The deformation is more hysteretic for high than for low density samples. Swelling/shrinkage due to ad/desorption of water vapour displays also a non-affine component. The reversibility of the swelling/shrinkage indicates that the material has a structural capacity to show a persistent cellular geometry for a given moisture state and a structural composition that allows for moisture-induced transitional states. A collection of qualitative observations of small subsets of cells during swelling/shrinkage is further studied by simulating the observed behaviour. An anisotropic swelling coefficient of the cell wall is found to emerge and its origin is linked to the anisotropy of the cellulose fibrils arrangement in cell wall layers.

  15. Precision X-ray spectroscopy of kaonic atoms as a probe of low-energy kaon-nucleus interaction

    CERN Document Server

    Shi, H; Beer, G; Bellotti, G; Berucci, C; Bragadireanu, A M; Bosnar, D; Cargnelli, M; Curceanu, C; Butt, A D; d'Uffizi, A; Fiorini, C; Ghio, F; Guaraldo, C; Hayano, R S; Iliescu, M; Ishiwatari, T; Iwasaki, M; Sandri, P Levi; Marton, J; Okada, S; Pietreanu, D; Piscicchia, K; Vidal, A Romero; Sbardella, E; Scordo, A; Sirghi, D L; Sirghi, F; Tatsuno, H; Doce, O Vazquez; Widmann, E; Zmeskal, J

    2016-01-01

    In the exotic atoms where one atomic $1s$ electron is replaced by a $K^{-}$, the strong interaction between the $K^{-}$ and the nucleus introduces an energy shift and broadening of the low-lying kaonic atomic levels which are determined by only the electromagnetic interaction. By performing X-ray spectroscopy for Z=1,2 kaonic atoms, the SIDDHARTA experiment determined with high precision the shift and width for the $1s$ state of $K^{-}p$ and the $2p$ state of kaonic helium-3 and kaonic helium-4. These results provided unique information of the kaon-nucleus interaction in the low energy limit.

  16. Multi-Electrode Resistivity Probe for Investigation of Local Temperature Inside Metal Shell Battery Cells via Resistivity: Experiments and Evaluation of Electrical Resistance Tomography

    Directory of Open Access Journals (Sweden)

    Xiaobin Hong

    2015-01-01

    Full Text Available Direct Current (DC electrical resistivity is a material property that is sensitive to temperature changes. In this paper, the relationship between resistivity and local temperature inside steel shell battery cells (two commercial 10 Ah and 4.5 Ah lithium-ion cells is innovatively studied by Electrical Resistance Tomography (ERT. The Schlumberger configuration in ERT is applied to divide the cell body into several blocks distributed in different levels, where the apparent resistivities are measured by multi-electrode surface probes. The investigated temperature ranges from −20 to 80 °C. Experimental results have shown that the resistivities mainly depend on temperature changes in each block of the two cells used and the function of the resistivity and temperature can be fitted to the ERT-measurement results in the logistical-plot. Subsequently, the dependence of resistivity on the state of charge (SOC is investigated, and the SOC range of 70%–100% has a remarkable impact on the resistivity at low temperatures. The proposed approach under a thermal cool down regime is demonstrated to monitor the local transient temperature.

  17. 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)

  18. 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)

    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 M23C6 carbides on the austenite-ferrite phase boundaries. 19 refs., 19 figs., 1 tab

  19. Structural defect-dependent resistive switching in Cu-O/Si studied by Kelvin probe force microscopy and conductive atomic force microscopy.

    Science.gov (United States)

    Kumar, Mohit; Som, Tapobrata

    2015-08-28

    In this study, we show structural defect-dependent presence or absence of resistive switching in Cu-O films. We use Kelvin probe force microscopy and conductive atomic force microscopy to show the presence of resistive switching. In addition, local current mapping provides direct evidence on the formation of nanoscale filament. These findings match well with the existing theoretical model on resistive switching. In particular, understanding the role of structural defects in resistive switching can be considered as critically important to take a step forward for designing advanced nanoscale memory devices. PMID:26243354

  20. Applications of nucleoside-based molecular probes for the in vivo assessment of tumour biochemistry using positron emission tomography (PET

    Directory of Open Access Journals (Sweden)

    Leonard I. Wiebe

    2007-05-01

    Full Text Available Positron emission tomography (PET is a non-invasive nuclear imaging technique. In PET, radiolabelled molecules decay by positron emission. The gamma rays resulting from positron annihilation are detected in coincidence and mapped to produce three dimensional images of radiotracer distribution in the body. Molecular imaging with PET refers to the use of positron-emitting biomolecules that are highly specific substrates for target enzymes, transport proteins or receptor proteins. Molecular imaging with PET produces spatial and temporal maps of the target-related processes. Molecular imaging is an important analytical tool in diagnostic medical imaging, therapy monitoring and the development of new drugs. Molecular imaging has its roots in molecular biology. Originally, molecular biology meant the biology of gene expression, but now molecular biology broadly encompasses the macromolecular biology and biochemistry of proteins, complex carbohydrates and nucleic acids. To date, molecular imaging has focused primarily on proteins, with emphasis on monoclonal antibodies and their derivative forms, small-molecule enzyme substrates and components of cell membranes, including transporters and transmembrane signalling elements. This overview provides an introduction to nucleosides, nucleotides and nucleic acids in the context of molecular imaging.A tomografia por emissão de pósitrons (TEP é uma técnica de imagem não invasiva da medicina nuclear. A TEP utiliza moléculas marcadas com emissores de radiação beta positiva (pósitrons. As radiações gama medidas que resultam do aniquilamento dos pósitrons são detectadas por um sistema de coincidência e mapeadas para produzir uma imagem tridimensional da distribuição do radiotraçador no corpo. A imagem molecular com TEP refere-se ao uso de biomoléculas marcadas com emissor de pósitron que são substratos altamente específicos para alvos como enzimas, proteínas transportadoras ou receptores prot

  1. Diffusion of hydrogen isotopes as a probe to study the atomic microstructure of metals. [Ni; CuAu; NiPt; FeZr

    Energy Technology Data Exchange (ETDEWEB)

    Hirscher, M.; Kronmueller, H. (Max-Planck-Inst. fuer Metallforschung, Inst. fuer Physik, Stuttgart (Germany))

    1991-08-30

    Magnetic after-effect measurements are very sensitive to short-range reorientation relaxations and represent an ideal tool for the study of hydrogen diffusion even at low concentrations. In this paper we deal with the interaction of hydrogen with defects or different microstructures and with the local reorientation in the vicinity of these structures. Results of hydrogen diffusion in a pure metal with radiation-induced intrinsic atomic defects, in chemically ordered and disordered binary f.c.c. alloys, and in chemically as well as structurally disordered amorphous alloys are presented. The three examples illustrate the use of hydrogen as an internal probe to detect microstructural defects on an atomic scale. (orig.).

  2. Networking strategies of the microscopy community for improved utilization of advanced instruments: (2) The national network for transmission electron microscopy and atom probe studies in France (METSA)

    International Nuclear Information System (INIS)

    With the development, over the past ten years, of a new generation of electron microscopes with advanced performance, incorporating aberration correctors, monochromators, more sensitive detectors, and innovative specimen environments, quantitative measurements at the sub-nanometer and, in certain cases, at the unique atom level, are now accessible. However, an optimized use of these possibilities requires access to costly instruments and support by specialized trained experts. For these reasons, a national network (METSA) has been created in France with the support of CNRS and CEA in order to offer, in centres with complementary equipment and expertise, an open access to an enlarged and multidisciplinary community of academic and industrial users. The eight METSA platforms offer an access to 3 atom probes and 17 electron microscopes, mainly aberration-corrected TEMs, but also one dedicated environmental SEM and 3 double-column SEM-FIB

  3. Novel thin membrane probe and a new twisting modulation force detection method of an atomic force microscope

    Science.gov (United States)

    Nakano, Katsushi; Suzuki, Yoshihiko

    1999-04-01

    For inspection of high aspect ratio structures like narrow semiconductor trenches, a thin membrane probe and a new force detection method have been proposed. Instead of conventional conical and pyramidal tips, a thin silicon nitride cantilever was set up vertically, and its edge was used as a tip. The membrane probe named as twist-probe (TP) was oscillated in the twisting resonance to detect a force from both vertical and lateral directions. About 100 μm long, 0.7 μm thick TP was fabricated as a trial. Amplitude versus distance curve measurements showed that the TP has a high spacing change sensitivity between the tip and a sample in both vertical and lateral directions. A trench cross-section imaging was demonstrated successfully with a TP and the twist resonant force detection method.

  4. Macro and microscale mechanical testing and local electrode atom probe measurements of STIP irradiated F82H, Fe-8Cr ODS and Fe-8Cr-2W ODS

    International Nuclear Information System (INIS)

    The reduced activation ferritic/martensitic alloy F82H (Fe-8Cr-2W-0.2V-0.04Ta-0.1C) is being considered as a structural material for several different fusion related nuclear applications. The oxide dispersion strengthened (ODS) alloys Fe-8Cr-2W ODS and Fe-8Cr ODS were developed for better high-temperature strength and radiation tolerance. These materials have been exposed to a neutron and proton environment in the Spallation Target Irradiation Program (STIP) (<13 dpa) with an average He/dpa ratio of 60 appm He/dpa at irradiation temperatures 159-347 deg. C. After irradiation, the samples were tensile tested at different temperatures. The post tensile testing fractured parts were collected and nanoindentation, microcompression testing and local electrode atom probe was conducted. The information gained by local electron atom probe in combination with the micro, nano and macroscopic mechanical tests allows one to establish a fundamental understanding of the relationship between the data measured at different scales on irradiated materials.

  5. Combined Atomic Force Microscope-Based Topographical Imaging and Nanometer Scale Resolved Proximal Probe Thermal Desorption/Electrospray Ionization-Mass Spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Ovchinnikova, Olga S [ORNL; Nikiforov, Maxim [ORNL; Bradshaw, James A [ORNL; Jesse, Stephen [ORNL; Van Berkel, Gary J [ORNL

    2011-01-01

    Nanometer scale proximal probe thermal desorption/electrospray ionization mass spectrometry (TD/ESI-MS) was demonstrated for molecular surface sampling of caffeine from a thin film using a 30 nm diameter nano-thermal analysis (nano-TA) probe tip in an atomic force microscope (AFM) coupled via a vapor transfer line and ESI interface to a MS detection platform. Using a probe temperature of 350 C and a spot sampling time of 30 s, conical desorption craters 250 nm in diameter and 100 nm deep were created as shown through subsequent topographical imaging of the surface within the same system. Automated sampling of a 5 x 2 array of spots, with 2 m spacing between spots, and real time selective detection of the desorbed caffeine using tandem mass spectrometry was also demonstrated. Estimated from the crater volume (~2x106 nm3), only about 10 amol (2 fg) of caffeine was liberated from each thermal desorption crater in the thin film. These results illustrate a relatively simple experimental setup and means to acquire in automated fashion sub-micrometer scale spatial sampling resolution and mass spectral detection of materials amenable to TD. The ability to achieve MS-based chemical imaging with 250 nm scale spatial resolution with this system is anticipated.

  6. 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)

    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 ε1 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 ε2 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, ε1, ε2) 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)

  7. Measurement of electron density and effective atomic number by dual-energy scan using a 320-detector computed tomography scanner with raw data-based analysis: a phantom study.

    Science.gov (United States)

    Tatsugami, Fuminari; Higaki, Toru; Kiguchi, Masao; Tsushima, So; Taniguchi, Akira; Kaichi, Yoko; Yamagami, Takuji; Awai, Kazuo

    2014-01-01

    We evaluated the accuracy of the electron densities and effective atomic numbers determined by raw data-based dual-energy analysis on a 320-detector computed tomography scanner. The mean (SD) errors between the measured and true electron densities and between the measured and true effective atomic numbers were 1.3% (1.5%) and 3.1% (3.2%), respectively. Electron densities and effective atomic numbers can be determined with high accuracy, which may help to improve accuracy in radiotherapy treatment planning. PMID:24983439

  8. Atomic characterization of Au clusters in vapor-liquid-solid grown silicon nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wanghua; Roca i Cabarrocas, Pere [Laboratoire de Physique des Interfaces et Couches Minces (LPICM), UMR 7647, CNRS, Ecole Polytechnique, 91128 Palaiseau (France); Pareige, Philippe; Castro, Celia [Groupe de Physique des Matériaux (GPM), Université et INSA de Rouen, UMR 6634, CNRS, Av. de l' Université, BP 12, 76801 Saint Etienne du Rouvray (France); Xu, Tao; Grandidier, Bruno; Stiévenard, Didier [Institut d' Electronique et de Microélectronique et de Nanotechnologies (IEMN), UMR 8520, CNRS, Département ISEN, 41 bd Vauban, 59046 Lille Cedex (France)

    2015-09-14

    By correlating atom probe tomography with other conventional microscope techniques (scanning electron microscope, scanning transmission electron microscope, and scanning tunneling microscopy), the distribution and composition of Au clusters in individual vapor-liquid-solid grown Si nanowires is investigated. Taking advantage of the characteristics of atom probe tomography, we have developed a sample preparation method by inclining the sample at certain angle to characterize the nanowire sidewall without using focused ion beam. With three-dimensional atomic scale reconstruction, we provide direct evidence of Au clusters tending to remain on the nanowire sidewall rather than being incorporated into the Si nanowires. Based on the composition measurement of Au clusters (28% ± 1%), we have demonstrated the supersaturation of Si atoms in Au clusters, which supports the hypothesis that Au clusters are formed simultaneously during nanowire growth rather than during the cooling process.

  9. Atomic characterization of Au clusters in vapor-liquid-solid grown silicon nanowires

    International Nuclear Information System (INIS)

    By correlating atom probe tomography with other conventional microscope techniques (scanning electron microscope, scanning transmission electron microscope, and scanning tunneling microscopy), the distribution and composition of Au clusters in individual vapor-liquid-solid grown Si nanowires is investigated. Taking advantage of the characteristics of atom probe tomography, we have developed a sample preparation method by inclining the sample at certain angle to characterize the nanowire sidewall without using focused ion beam. With three-dimensional atomic scale reconstruction, we provide direct evidence of Au clusters tending to remain on the nanowire sidewall rather than being incorporated into the Si nanowires. Based on the composition measurement of Au clusters (28% ± 1%), we have demonstrated the supersaturation of Si atoms in Au clusters, which supports the hypothesis that Au clusters are formed simultaneously during nanowire growth rather than during the cooling process

  10. Probing the Structure and Chemistry of Perylenetetracarboxylic Dianhydride on Graphene Before and After Atomic Layer Deposition of Alumina

    OpenAIRE

    Johns, James E.; Karmel, Hunter J.; Alaboson, Justice M. P.; Hersam, Mark C.

    2012-01-01

    The superlative electronic properties of graphene suggest its use as the foundation of next generation integrated circuits. However, this application requires precise control of the interface between graphene and other materials, especially the metal oxides that are commonly used as gate dielectrics. Towards that end, organic seeding layers have been empirically shown to seed ultrathin dielectric growth on graphene via atomic layer deposition (ALD), although the underlying chemical mechanisms...

  11. Direct observation of the leakage current in epitaxial diamond Schottky barrier devices by conductive-probe atomic force microscopy and Raman imaging

    International Nuclear Information System (INIS)

    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. (paper)

  12. Influence of long-term thermal aging on the microstructural evolution of nuclear reactor pressure vessel materials: An atom probe study

    International Nuclear Information System (INIS)

    Atom probe field ion microscopy (APFIM) investigations of the microstructure of unaged (as-fabricated) and long-term thermally aged (∼ 100,000 h at 280 C) surveillance materials from commercial reactor pressure vessel steels were performed. This combination of materials and conditions permitted the investigation of potential thermal-aging effects. This microstructural study focused on the quantification of the compositions of the matrix and carbides. The APFIM results indicate that there was no significant microstructural evolution after a long-term thermal exposure in weld, plate, or forging materials. The matrix depletion of copper that was observed in weld materials was consistent with the copper concentration in the matrix after the stress-relief heat treatment. The compositions of cementite carbides aged for 100,000 h were compared with the Thermocalc trademark prediction. The APFIM comparisons of materials under these conditions are consistent with the measured change in mechanical properties such as the Charpy transition temperature

  13. Mechanism of Origin and Neutralization of Residual Triboelectricity at Scanning of Dielectric Surfaces by a Silicon Probe of the Atomic-force Microscope

    Directory of Open Access Journals (Sweden)

    М.А. Bondarenko

    2014-06-01

    Full Text Available The reasons and mechanism of the destructive effect of the electrostatic interaction forces of silicon probe and dielectric surfaces are established in the paper at the investigation of the surface microgeometry and mechanical characteristics by the atomic-force microscopy method. Calculation of the electrostatic interaction forces of two silicon surfaces is carried out and the destructive effect of electrostatic discharge appearing as a result of triboelectric effect is determined. The module of removal of electrostatic charge is proposed. Its principle of operation consists in the formation of the conduction band in the place of contact of two dielectrics by the multiphoton ionization. It is shown that application of such method of neutralization of residual triboelectricity improves accuracy, reliability, and reproducibility of the scanning results.

  14. Laser-induced reversion of $\\delta^{'}$ precipitates in an Al-Li alloy: Study on temperature rise in pulsed laser atom probe

    CERN Document Server

    Khushaim, Muna; Al-Kassab, Talaat

    2015-01-01

    The influence of tuning the laser energy during the analyses on the resulting microstructure in a specimen utilizing an ultra-fast laser assisted atom probe was demonstrated by a case study of a binary Al-Li alloy. The decomposition parameters, such as the size, number density, volume fraction and composition of $\\delta^{'}$ precipitates, were carefully monitored after each analysis. A simple model was employed to estimate the corresponding specimen temperature for each value of the laser energy. The results indicated that the corresponding temperatures for the laser energy in the range of 10 to 80 pJ are located inside the miscibility gap of the binary Al-Li phase diagram and fall into the metastable equilibrium field. In addition, the corresponding temperature for a laser energy of 100 pJ was in fairly good agreement with reported range of $\\delta^{'}$ solvus temperature, suggesting a result of reversion upon heating due to laser pulsing.

  15. Probing the elastic response of microalga Scenedesmus dimorphus in dry and aqueous environments through atomic force microscopy

    International Nuclear Information System (INIS)

    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.

  16. 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.

  17. Mineral content of vertebral trabecular bone: accuracy of dual energy quantitative computed tomography evaluated against neutron activation analysis and flame atomic absorption spectrometry.

    Science.gov (United States)

    Louis, O; Van den Winkel, P; Covens, P; Schoutens, A; Osteaux, M

    1994-01-01

    The goal of this study was to evaluate the accuracy of preprocessing dual energy quantitative computed tomography (QCT) for assessment of trabecular bone mineral content (BMC) in lumbar vertebrae. The BMC of 49 lumbar vertebrae taken from 16 cadavers was measured using dual energy QCT with advanced software and hardware capabilities, including an automated definition of the trabecular region of interest (ROI). The midvertebral part of each vertebral body was embedded in a polyester resin and, subsequently, an experimental ROI was cut out using a scanjet image transmission procedure and a computer-assisted milling machine in order to mimic the ROI defined on QCT. After low temperature ashing, the experimental ROIs reduced to a bone powder were submitted to either nondestructive neutron activation analysis (n = 49) or to flame atomic absorption spectrometry (n = 45). BMC obtained with neutron activation analysis was closely related (r = 0.896) to that derived from atomic absorption spectrometry, taken as the gold standard, with, however, a slight overestimation. BMC values measured by QCT were highly correlated with those assessed using the two reference methods, all correlation coefficients being > 0.841. The standard errors of the estimate ranged 47.4-58.9 mg calcium hydroxyapatite in the regressions of BMC obtained with reference methods against BMC assessed by single energy QCT, 47.1-51.9 in the regressions involving dual energy QCT. We conclude that the trabecular BMC of lumbar vertebrae can be accurately measured by QCT and that the superiority in accuracy of dual energy is moderate, which is possible a characteristic of the preprocessing method. PMID:8024849

  18. Detection of atomic spin labels in a lipid bi-layer using a single-spin nanodiamond probe

    CERN Document Server

    Kaufmann, Stefan; Hall, Liam T; Perunicic, Viktor; Senn, Philipp; Steinert, Steffen; McGuinness, Liam P; Johnson, Brett C; Ohshima, Takeshi; Caruso, Frank; Wrachtrup, Joerg; Scholten, Robert E; Mulvaney, Paul; Hollenberg, Lloyd C L

    2013-01-01

    Magnetic field fluctuations arising from fundamental spins are ubiquitous in nanoscale biology, and are a rich source of information about the processes that generate them. However, the ability to detect the few spins involved without averaging over large ensembles has remained elusive. Here we demonstrate the detection of gadolinium spin labels in an artificial cell membrane under ambient conditions using a single-spin nanodiamond sensor. Changes in the spin relaxation time of the sensor located in the lipid bilayer were optically detected and found to be sensitive to near-individual proximal gadolinium atomic labels. The detection of such small numbers of spins in a model biological setting, with projected detection times of one second, opens a new pathway for in-situ nanoscale detection of dynamical processes in biology.

  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. Color Tomography

    CERN Document Server

    Jain, B; Takada, M; Jain, Bhuvnesh; Connolly, Andrew; Takada, Masahiro

    2006-01-01

    Lensing tomography with multi-color imaging surveys can probe dark energy and the cosmological power spectrum. However accurate photometric redshifts for tomography out to high redshift require imaging in five or more bands, which is expensive to carry out over thousands of square degrees. Since lensing makes coarse, statistical use of redshift information, we explore the prospects for tomography using limited color information from two or three band imaging. With an appropriate calibration sample, we find that it is feasible to create up to four redshift bins using imaging data in just the g, r and i bands. We construct such redshift sub-samples from mock catalogs by clustering galaxies in color space and discarding regions with poorly-defined redshift distributions. The loss of galaxy number density decreases the accuracy of lensing measurements, but even losing half or more of the galaxies is not a severe loss for large area surveys. We estimate the errors on lensing power spectra and dark energy parameter...

  1. 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.

  2. Probing the Structure and Chemistry of Perylenetetracarboxylic Dianhydride on Graphene Before and After Atomic Layer Deposition of Alumina.

    Science.gov (United States)

    Johns, James E; Karmel, Hunter J; Alaboson, Justice M P; Hersam, Mark C

    2012-07-11

    The superlative electronic properties of graphene suggest its use as the foundation of next generation integrated circuits. However, this application requires precise control of the interface between graphene and other materials, especially the metal oxides that are commonly used as gate dielectrics. Towards that end, organic seeding layers have been empirically shown to seed ultrathin dielectric growth on graphene via atomic layer deposition (ALD), although the underlying chemical mechanisms and structural details of the molecule/dielectric interface remain unknown. Here, confocal resonance Raman spectroscopy is employed to quantify the structure and chemistry of monolayers of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on graphene before and after deposition of alumina with the ALD precursors trimethyl aluminum (TMA) and water. Photoluminescence measurements provide further insight into the details of the growth mechanism, including the transition between layer-by-layer growth and island formation. Overall, these results reveal that PTCDA is not consumed during ALD, thereby preserving a well-defined and passivating organic interface between graphene and deposited dielectric thin films. PMID:22905282

  3. Combined frequency modulated atomic force microscopy and scanning tunneling microscopy detection for multi-tip scanning probe microscopy applications

    International Nuclear Information System (INIS)

    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

  4. Wide range local resistance imaging on fragile materials by conducting probe atomic force microscopy in intermittent contact mode

    Science.gov (United States)

    Vecchiola, Aymeric; Chrétien, Pascal; Delprat, Sophie; Bouzehouane, Karim; Schneegans, Olivier; Seneor, Pierre; Mattana, Richard; Tatay, Sergio; Geffroy, Bernard; Bonnassieux, Yvan; Mencaraglia, Denis; Houzé, Frédéric

    2016-06-01

    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.

  5. Single atom measurement and atomic manipulation using atomic force microscope

    International Nuclear Information System (INIS)

    This paper explains studies to measure atomic force as the force linking an atom and atom, using an atomic force microscope (AFM). First, it describes the principle and device configuration of AFM, and as an example of the atomic force measurement of Si atoms on the surface of Si(111)-(7x7), it describes the technique to measure atomic force using AFM, as well as the uncertainty of probe tip against atomic force. In addition, it describes the following items on the measurement results of chemical bonding force: (1) chemical bonding force vs physical force and chemical bonding force vs current on the surface of Si(111)-(7x7), (2) chemical bonding force and element dependence on the surface of Si/Sn(111)-(√3x√3), (3) atomic manipulation based on AMF, and (4) relationship between atomic manipulation and the size of chemical bonding force with a probe. (A.O.)

  6. Nano-structural changes in the RPV steels irradiated in MTR to high doses. 3D atom probe and positron annihilation study

    International Nuclear Information System (INIS)

    Reactor pressure vessel (RPV) steels of life-extended light water reactors are to be exposed to higher neutron fluence. The understanding of radiation embrittlement of RPV steels is very important in order to improve prediction of the embrittlement. The radiation embrittlement is mainly cased by copper-enriched cluster (CEC) and matrix damage (MD) due to irradiation. The state-or-the art technique such as three dimensional atom probe (3DAP) and positron annihilation (PA) has enabled to observe these microstructural features. The effect of highly dose irradiation on the formation of clusters in a low copper base metal and a high copper weld metal is investigated by means of the 3DAP and PA observations in this paper. The materials were irradiated to a neutron fluence of 1020n/cm2 at 290 degC in a test reactor. The 3DAP observation shows that high dense CRCs in size of about 2 nm are formed in the high Cu weld metal. The CRCs consist of Si in addition to Fe, Cu, Mn, and Ni. Solute atom clusters below 2 nm are also observed in low Cu base metal, but the clusters include a large amount of Si and free from Cu. These clusters may be peculiar to highly irradiated materials because of no literature reporting such the clusters in the similar steels irradiated at the lower fluence. The data of the positron annihilation coincidence Doppler broadening measurement for both materials also shows the formation of clusters containing Cu, Ni, Mn, and Si. This means the clusters observed by 3DAP are uniformly distributed in the materials. Hardness tests and PA measurement combined with isochronal annealing show that defects, e.g. dislocation loop etc., having a positron lifetime of about 140 psec influence on mechanical properties of the steels. (author)

  7. Effect of SP-C on surface potential distribution in pulmonary surfactant: Atomic force microscopy and Kelvin probe force microscopy study

    International Nuclear Information System (INIS)

    The air-lung interface is covered by a molecular film of pulmonary surfactant (PS). The major function of the film is to reduce the surface tension of the lung's air-liquid interface, providing stability to the alveolar structure and reducing the work of breathing. Earlier we have shown that function of bovine lipid extract surfactant (BLES) is related to the specific molecular architecture of surfactant films. Defined molecular arrangement of the lipids and proteins of the surfactant film also give rise to a local highly variable electrical surface potential of the interface. In this work we investigated a simple model of artificial lung surfactant consisting of DPPC, eggPG, and surfactant protein C (SP-C). Effects of surface compression and the presence of SP-C on the monolayer structure and surface potential distribution were investigated using atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM). We show that topography and locally variable surface potential of DPPC-eggPG lipid mixture are similar to those of pulmonary surfactant BLES in the presence of SP-C and differ in surface potential when SP-C is absent.

  8. Effect of SP-C on surface potential distribution in pulmonary surfactant: Atomic force microscopy and Kelvin probe force microscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Hane, Francis [Department of Biology, Faculty of Science, University of Waterloo, Ontario (Canada); Moores, Brad [Department of Physics and Astronomy, Faculty of Science, University of Waterloo, Ontario (Canada); Amrein, Matthias [Department of Cell Biology and Anatomy, Faculty of Medicine, University of Calgary, Alberta, Canada. (Canada); Leonenko, Zoya, E-mail: zleonenk@uwaterloo.ca [Department of Biology, Faculty of Science, University of Waterloo, Ontario (Canada); Department of Physics and Astronomy, Faculty of Science, University of Waterloo, Ontario (Canada)

    2009-07-15

    The air-lung interface is covered by a molecular film of pulmonary surfactant (PS). The major function of the film is to reduce the surface tension of the lung's air-liquid interface, providing stability to the alveolar structure and reducing the work of breathing. Earlier we have shown that function of bovine lipid extract surfactant (BLES) is related to the specific molecular architecture of surfactant films. Defined molecular arrangement of the lipids and proteins of the surfactant film also give rise to a local highly variable electrical surface potential of the interface. In this work we investigated a simple model of artificial lung surfactant consisting of DPPC, eggPG, and surfactant protein C (SP-C). Effects of surface compression and the presence of SP-C on the monolayer structure and surface potential distribution were investigated using atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM). We show that topography and locally variable surface potential of DPPC-eggPG lipid mixture are similar to those of pulmonary surfactant BLES in the presence of SP-C and differ in surface potential when SP-C is absent.

  9. Atomic Force Microscopy, Scanning Kelvin Probe Force Microscopy and magnetic measurements on thermally oxidized AISI 304 and AISI 316 stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Maachi, B. [Universite d' Oran, Laboratoire de Physique des Couches Minces et Materiaux pour l' Electronique (LPC2ME), BP 1524, El M' Naouer, 31000 Oran (Algeria); Pirri, C.; Mehdaoui, A. [Universite de Haute Alsace (UHA), Institut de Science des Materiaux de Mulhouse (IS2M), LRC 7228 - CNRS, 4 rue des freres Lumiere, 68093 Mulhouse (France); Hakiki, N.E., E-mail: hakiki.nourredine@yahoo.f [Universite d' Oran, Laboratoire de Physique des Couches Minces et Materiaux pour l' Electronique (LPC2ME), BP 1524, El M' Naouer, 31000 Oran (Algeria); Bubendorff, J.L., E-mail: jean-luc.bubendorff@uha.f [Universite de Haute Alsace (UHA), Institut de Science des Materiaux de Mulhouse (IS2M), LRC 7228 - CNRS, 4 rue des freres Lumiere, 68093 Mulhouse (France)

    2011-03-15

    Research highlights: {yields} The surface roughness of the bare substrate influence the oxide layer growth. {yields} The oxide layer roughness follows power laws and belongs to universality class. {yields} At low growth temperature, the p-n heterojunction disappears in some places. {yields} SKPFM images allow the direct visualization of local corrosion sites. {yields} Presence of a magnetite phase in the outer iron rich layer of the oxide thin film. - Abstract: Thermally oxidized AISI304 and AISI316 stainless steels are studied by Atomic Force Microscopy, Scanning Kelvin Probe Force Microscopy (SKPFM) and Magneto-Optical Kerr effect as a function of their growth temperature. The surface roughness is a competition between the roughness of the bare substrate and the roughness resulting from the oxide layer growth. Cr oxide is present at some places on the surface at low growth temperature as shown by SKPFM. The observed decrease of surface potential with the oxide layer thickness indicates an effective protection against corrosion. Magnetic measurements demonstrate that the outer layer contains a magnetite phase (in-plane magnetization).

  10. Atomic Force Microscopy, Scanning Kelvin Probe Force Microscopy and magnetic measurements on thermally oxidized AISI 304 and AISI 316 stainless steels

    International Nuclear Information System (INIS)

    Research highlights: → The surface roughness of the bare substrate influence the oxide layer growth. → The oxide layer roughness follows power laws and belongs to universality class. → At low growth temperature, the p-n heterojunction disappears in some places. → SKPFM images allow the direct visualization of local corrosion sites. → Presence of a magnetite phase in the outer iron rich layer of the oxide thin film. - Abstract: Thermally oxidized AISI304 and AISI316 stainless steels are studied by Atomic Force Microscopy, Scanning Kelvin Probe Force Microscopy (SKPFM) and Magneto-Optical Kerr effect as a function of their growth temperature. The surface roughness is a competition between the roughness of the bare substrate and the roughness resulting from the oxide layer growth. Cr oxide is present at some places on the surface at low growth temperature as shown by SKPFM. The observed decrease of surface potential with the oxide layer thickness indicates an effective protection against corrosion. Magnetic measurements demonstrate that the outer layer contains a magnetite phase (in-plane magnetization).

  11. Three-dimensional evaluation of gettering ability for oxygen atoms at small-angle tilt boundaries in Czochralski-grown silicon crystals

    International Nuclear Information System (INIS)

    Three-dimensional distribution of oxygen atoms at small-angle tilt boundaries (SATBs) in Czochralski-grown p-type silicon ingots was investigated by atom probe tomography combined with transmission electron microscopy. Oxygen gettering along edge dislocations composing SATBs, post crystal growth, was observed. The gettering ability of SATBs would depend both on the dislocation strain and on the dislocation density. Oxygen atoms would agglomerate in the atomic sites under the tensile hydrostatic stress larger than about 2.0 GPa induced by the dislocations. It was suggested that the density of the atomic sites, depending on the tilt angle of SATBs, determined the gettering ability of SATBs

  12. 3D compositional analysis at atomic scale of InAlGaAs capped InAs/GaAs QDs

    International Nuclear Information System (INIS)

    The 3D compositional distribution at the atomic-scale of InAs/GaAs quantum dots (QDs) with an InAlGaAs capping layer has been obtained by atom probe tomography. A heterogeneous distribution of Al atoms has been revealed. An Al-rich ring around the QDs has been observed. A detailed analysis of the QDs composition evidences a high degree of In/Ga intermixing, with an increasing In gradient in the growth direction. The atomic scale analyses of these nanostructures are essential to understand their functional properties

  13. Unraveling nanoscale conduction and work function in a poly(3,4-ethylenedioxypyrrole)/carbon nanotube composite by Kelvin probe force microscopy and conducting atomic force microscopy

    International Nuclear Information System (INIS)

    Highlights: ► Counter ion effect on the nanoscale conduction of poly(3,4-ethylenedioxypyrrole) films. ► Local work function at nanometric spatial resolution by Kelvin probe force microscopy. ► Interconnected high current domains prevail in films with sulfonated carbon nanotubes. ► Enhanced redox activity and electrochromic contrast in carbon nanotube based films. ► Low work function of PEDOP/carbon nanotube film promotes uninhibited charge propagation. - Abstract: Poly(3,4-ethylenedioxypyrrole) or PEDOP films doped with triflate ions, dodecyl sulfate ions and benzyl sulfonate functionalized multiwalled carbon nanotubes (MWCNTs) have been synthesized by oxidative electropolymerization. The dynamic variation of local work function at the nanoscale has been followed by Kelvin probe force microscopy (KPFM) and the measure of heterogeneity of dopant distribution was assessed from the distinctive disparities in the current maps, using conductive atomic force microscopy (C-AFM). The surface potential profiles revealed a smaller work function for PEDOP-(MWCNT)SO3− film, and the current images showed a remarkably larger current sustaining capacity for this film, in contrast to PEDOP-CF3SO3− and PEDOP-C12H25)OSO3− films which, is a consequence of widespread interconnects between localized conducting domains of the polymer coated with carbon nanotubes. Functionalized nanotubes offer the prospect of conducting both electrons and ions, and therefore an almost seamless charge transport across PEDOP and (MWCNT)SO3− species is realized. Such an unhindered movement of charge is not realized in PEDOP films doped by the insulating triflate or dodecyl sulfate ions. Averaged point contact nanoscale I–V profiles confirmed this claim, as the PEDOP-(MWCNT)SO3− film showed carrier conductivity greater by four orders of magnitude, as compared to the PEDOP-CF3SO3− film. The enhanced electronic function and the reduced band gap of PEDOP-(MWCNT)SO3− film (0.19 eV) in

  14. Photoelectron angular distributions from autoionizing 4s14p66p1 states in atomic krypton probed with femtosecond time resolution

    International Nuclear Information System (INIS)

    Photoelectron angular distributions (PADs) are obtained for a pair of 4s14p66p1 (a singlet and a triplet) autoionizing states in atomic krypton. A high-order harmonic pulse is used to excite the pair of states and a time-delayed 801 nm ionization pulse probes the PADs to the final 4s14p6 continuum with femtosecond time resolution. The ejected electrons are detected with velocity map imaging to retrieve the time-resolved photoelectron spectrum and PADs. The PAD for the triplet state is inherently separable by virtue of its longer autoionization lifetime. Measuring the total signal over time allows for the PADs to be extracted for both the singlet state and the triplet state. Anisotropy parameters for the triplet state are measured to be β2= 0.55 ± 0.17 and β4=-0.01 ± 0.10, while the singlet state yields β2= 2.19 ± 0.18 and β4= 1.84 ± 0.14. For the singlet state, the ratio of radial transition dipole matrix elements, X, of outgoing S to D partial waves and total phase shift difference between these waves, Δ, are determined to be X= 0.56 ± 0.08 and Δ= 2.19 ± 0.11 rad. The continuum quantum defect difference between the S and D electron partial waves is determined to be -0.15 ± 0.03 for the singlet state. Based on previous analyses, the triplet state is expected to have anisotropy parameters independent of electron kinetic energy and equal to β2= 5/7 and β4=-12/7. Deviations from the predicted values are thought to be a result of state mixing by spin-orbit and configuration interactions in the intermediate and final states; theoretical calculations are required to quantify these effects.

  15. Atomic scale observations of bainite transformation in a high carbon high silicon steel

    OpenAIRE

    García Caballero, Francisca; Miller, M. K.; Babu, S. S.; García Mateo, Carlos

    2007-01-01

    A fine-scale bainitic microstructure with high strength and high toughness has been achieved by transforming austenite at 200 ºC. X-ray diffraction analysis showed the carbon concentration of these bainitic ferrite plates to be higher than expected from paraequilibrium. Atom probe tomography revealed that a substantial quantity of carbon was trapped at dislocations in the vicinity of the ferrite/austenite interface. These results suggest that the carbon trapping at dislocations...

  16. Some new developments in the field of high atomic number semiconductor materials

    International Nuclear Information System (INIS)

    A presentation of the main properties of high atomic number materials able to work as room temperature dectectors is made, including present status of synthesis. We summarize some applications in nuclear medical probe, tomography scanners, dosimetry and instrumentation. Mainly focused on CdTe and Hg I2 in monocrystal form the presentation will include some industrial applications. Hg I2 is also presented as a photodetector associated with scintillators

  17. Atomic-scale studies of uranium oxidation and corrosion by water vapour

    OpenAIRE

    Martin, TL; Coe, C.; Bagot, PAJ; Morrall, P; Smith, GDW; Scott, T.; Moody, MP

    2016-01-01

    Understanding the corrosion of uranium is important for its safe, long-term storage. Uranium metal corrodes rapidly in air, but the exact mechanism remains subject to debate. Atom Probe Tomography was used to investigate the surface microstructure of metallic depleted uranium specimens following polishing and exposure to moist air. A complex, corrugated metal-oxide interface was observed, with approximately 60 at.% oxygen content within the oxide. Interestingly, a very thin (~5 nm) interfacia...

  18. Atomic scale study of grain boundary segregation before carbide nucleation in Ni–Cr–Fe Alloys

    International Nuclear Information System (INIS)

    Highlights: • Impurities segregated at grain boundaries were observed by atom probe tomography. • The comparison of segregation features in two Ni–Cr–Fe alloys was studied by APT. • C and Cr atoms co-segregated at grain boundaries before carbide precipitation. -- Abstract: Three dimensional chemical information concerning grain boundary segregation before carbide nucleation was characterized by atom probe tomography in two Ni–Cr–Fe alloys which were aged at 500 °C for 0.5 h after homogenizing treatment. B, C and Si atoms segregation at grain boundary in Alloy 690 was observed. B, C, N and P atoms segregation at grain boundary in 304 austenitic stainless steel was observed. C atoms co-segregation with Cr atoms at the grain boundaries both in Alloy 690 and 304 austenitic stainless steel was found, and its effect on the carbide nucleation was discussed. The amount of each segregated element at grain boundaries in the two Ni–Cr–Fe alloys were analyzed quantitatively. Comparison of the grain boundary segregation features of the two Ni–Cr–Fe alloys were carried out based on the experimental results

  19. Radioiodinated benzimidazole derivatives as single photon emission computed tomography probes for imaging of {beta}-amyloid plaques in Alzheimer's disease

    Energy Technology Data Exchange (ETDEWEB)

    Cui Mengchao [Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501 (Japan); Key Laboratory of Radiopharmaceuticals, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875 (China); Ono, Masahiro, E-mail: ono@pharm.kyoto-u.ac.j [Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501 (Japan); Kimura, Hiroyuki; Kawashima, Hidekazu [Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501 (Japan); Liu Boli [Key Laboratory of Radiopharmaceuticals, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875 (China); Saji, Hideo, E-mail: hsaji@pharm.kyoto-u.ac.j [Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501 (Japan)

    2011-04-15

    Five iodinated 2-phenyl-1H-benzo[d]imidazole derivatives were synthesized and evaluated as potential probes for {beta}-amyloid (A{beta}) plaques. One of the compounds, 4-(6-iodo-1H-benzo[d]imidazol-2-yl)-N,N-dimethylaniline (12), showed excellent affinity for A{beta}{sub 1-42} aggregates (K{sub i}=9.8 nM). Autoradiography with sections of postmortem Alzheimer's disease (AD) brain revealed that a radioiodinated probe [{sup 125}I]12, labeled A{beta} plaques selectively with low nonspecific binding. Biodistribution experiments with normal mice injected intravenously with [{sup 125}I]12 showed high uptake [4.14 percent injected dose per gram (% ID/g) at 2 min] into and rapid clearance (0.15% ID/g at 60 min) from the brain, which may bring about a good signal-to-noise ratio and therefore achieve highly sensitive detection of A{beta} plaques. In addition, [{sup 125}I]12 labeled amyloid plaques in vivo in an AD transgenic model. The preliminary results strongly suggest that [{sup 125}I]12 bears characteristics suitable for detecting amyloid plaques in vivo. When labeled with {sup 123}I, it may be a useful SPECT imaging agent for A{beta} plaques in the brain of living AD patients.

  20. Radiopaque tantalum oxide coated persistent luminescent nanoparticles as multimodal probes for in vivo near-infrared luminescence and computed tomography bioimaging

    Science.gov (United States)

    Lu, Yu-Chen; Yang, Cheng-Xiong; Yan, Xiu-Ping

    2015-10-01

    The design and fabrication of multimodal imaging nanoparticles is of great importance in medical diagnosis. Here we report the fabrication of core-shell structured Zn2.94Ga1.96Ge2O10:Cr3+,Pr3+@TaOx@SiO2 nanoparticles for persistent luminescence and X-ray computed tomography (CT) imaging. Persistent luminescent nanoparticles Zn2.94Ga1.96Ge2O10:Cr3+,Pr3+ were used as the core to provide near-infrared luminescence, and a TaOx layer was grown on the core to serve as the contrast agent for CT. The tenuous outermost SiO2 shell was fabricated on the TaOx layer to gain high biocompatibility and to facilitate post-modification with tumor-targeting peptides. The fabricated core-shell structured nanoparticle shows intense near-infrared luminescence and the CT contrast effect. No obvious mutual interference was found in these two modalities, which ensures that each imaging modality merits could be brought in a full play. Furthermore, covalent bonding of cyclic-Asn-Gly-Arg peptides makes the core-shell structured nanoparticles promising for in vivo targeted imaging of tumor-bearing mice.The design and fabrication of multimodal imaging nanoparticles is of great importance in medical diagnosis. Here we report the fabrication of core-shell structured Zn2.94Ga1.96Ge2O10:Cr3+,Pr3+@TaOx@SiO2 nanoparticles for persistent luminescence and X-ray computed tomography (CT) imaging. Persistent luminescent nanoparticles Zn2.94Ga1.96Ge2O10:Cr3+,Pr3+ were used as the core to provide near-infrared luminescence, and a TaOx layer was grown on the core to serve as the contrast agent for CT. The tenuous outermost SiO2 shell was fabricated on the TaOx layer to gain high biocompatibility and to facilitate post-modification with tumor-targeting peptides. The fabricated core-shell structured nanoparticle shows intense near-infrared luminescence and the CT contrast effect. No obvious mutual interference was found in these two modalities, which ensures that each imaging modality merits could be brought

  1. 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 of...

  2. 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). The...

  3. Earthquake Forecast via Neutrino Tomography

    OpenAIRE

    Wang, Bin(Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China); Chen, Ya-Zheng; Li, Xue-Qian

    2010-01-01

    We discuss the possibility of forecasting earthquakes by means of (anti)neutrino tomography. Antineutrinos emitted from reactors are used as a probe. As the antineutrinos traverse through a region prone to earthquakes, observable variations in the matter effect on the antineutrino oscillation would provide a tomography of the vicinity of the region. In this preliminary work, we adopt a simplified model for the geometrical profile and matter density in a fault zone. We calculate the survival p...

  4. Computerized Tomography

    International Nuclear Information System (INIS)

    The physical bases of computerized tomography are presented, the following items being discussed:attenuation of a photon beam by an absorbent material, reconstruction algorithms and detection systems. Image statistics is also presented. The emission computerized tomography is discussed. Clinical results of computerized tomography are presented. (M.A.)

  5. 3D electron microscopy in the physical sciences: the development of Z-contrast and EFTEM tomography

    Energy Technology Data Exchange (ETDEWEB)

    Midgley, P.A.; Weyland, M

    2003-09-15

    The rapid advances in nanotechnology and the ever decreasing size of features in the microelectronics industry brings with it the need for advanced characterisation with high spatial resolution in two and three dimensions. Stereo microscopy allows some insight into the three-dimensional nature of an object but for true quantitative analysis, one has to turn to tomography as a way to reconstruct a three-dimensional object from a series of two-dimensional projections (images). X-ray tomography allow structures to be imaged at relatively large length scales, atom probe tomography at the atomic level. Electron tomography offers an intermediate resolution (of about 1 nm) with a field of view of hundreds of nm making it ideal for the characterisation of many nanoscale devices. Whilst electron tomography has been used in the biological sciences for more than 30 years, it is only now being applied to the physical sciences. In this paper, we review the status of electron tomography, describe the basis behind the technique and some of the practicalities of recording and analysing data for tomographic reconstruction, particularly in regard to solving three-dimensional problems that are encountered in materials science at the nanometre level. We present examples of how STEM dark-field imaging and energy-filtered TEM can be used successfully to examine nearly all types of specimens likely to be encountered by the physical scientist.

  6. Atoms Talking to SQUIDs

    OpenAIRE

    2011-01-01

    We present a scheme to couple trapped $^{87}$Rb atoms to a superconducting flux qubit through a magnetic dipole transition. We plan to trap atoms on the evanescent wave outside an ultrathin fiber to bring the atoms to less than 10 $\\mu$m above the surface of the superconductor. This hybrid setup lends itself to probing sources of decoherence in superconducting qubits. Our current plan has the intermediate goal of coupling the atoms to a superconducting LC resonator.

  7. Probe-based data storage

    CERN Document Server

    Koelmans, Wabe W; Abelmann, L

    2015-01-01

    Probe-based data storage attracted many researchers from academia and industry, resulting in unprecendeted high data-density demonstrations. This topical review gives a comprehensive overview of the main contributions that led to the major accomplishments in probe-based data storage. The most investigated technologies are reviewed: topographic, phase-change, magnetic, ferroelectric and atomic and molecular storage. Also, the positioning of probes and recording media, the cantilever arrays and parallel readout of the arrays of cantilevers are discussed. This overview serves two purposes. First, it provides an overview for new researchers entering the field of probe storage, as probe storage seems to be the only way to achieve data storage at atomic densities. Secondly, there is an enormous wealth of invaluable findings that can also be applied to many other fields of nanoscale research such as probe-based nanolithography, 3D nanopatterning, solid-state memory technologies and ultrafast probe microscopy.

  8. Characterization of the (0001) cleavage surface of antimony single crystals using scanning probe microscopy: Atomic structure, vacancies, cleavage steps, and twinned interlayers

    Science.gov (United States)

    Stegemann, Bert; Ritter, Claudia; Kaiser, Bernhard; Rademann, Klaus

    2004-04-01

    Atomically resolved scanning tunneling microscopy images of the unreconstructed hexagonal structure of surface atoms on Sb(0001) are presented. Lateral and vertical lattice parameters have been determined. The interatomic spacing of 4.31 Å (±0.05 Å) on the Sb(0001) surface corresponds to the known bulk data. Cleavage has been found to occur always between adjacent double layers, yielding at least diatomic cleavage steps of 3.75 Å (±0.10 Å) height. Different kinds of defect structures on the cleavage plane have been imaged with atomic resolution. Point defects, caused by a single or by three missing surface atoms, have been uncovered. Stable imaging of cleavage steps, which were found to be straight along the atomic rows, has been achieved. Twinned interlayers formed upon cleavage of Sb even at room temperature have been revealed by atomic force microscopy. The mean twinning angle of 2.42° (±0.20°) is quantitatively in accord with the value of 2.45° predicted by the model of twinning in Sb crystals. The observed features are discussed with respect to other layered materials and with regard to their relevance for the use of Sb(0001) as a support of nanostructures.

  9. Formation of field induced absorption in the probe response signal of a four-level V type atomic system a theoretical study

    CERN Document Server

    Islam, Khairul; Bhattacharyya, Dipankar; Bandyopadhyay, Amitava

    2016-01-01

    A density matrix based analytical model is developed to study the coherent probe field propagation through a four-level V type system in presence of a coherent control field. The model allows coupling of the probe field from the upper ground level to both of the excited levels keeping the control field locked to a particular transition. The addition of an extra ground level to a conventional three-level V type system creates extra decay paths to the ground levels for the upper level population. A set of sixteen density matrix based equations are formed and then solved analytically under rotating wave approximation to study the probe response under steady state condition. The simulated probe absorption spectra shows absorption dip at the centre of a transparency window only under Doppler broadened condition although the conventional EIT window appears under Doppler free condition. The dependence of the field induced absorption signal on the Rabi frequency of the control field, population transfer rate among th...

  10. Quantum magnetism through atomic assembly

    NARCIS (Netherlands)

    Spinelli, A.

    2015-01-01

    This thesis presents an experimental study of magnetic structures, composed of only a few atoms. Those structures are first built atom-by-atom and then locally probed, both with a low-temperature STM. The technique that we use to assemble them is vertical atom manipulation, while to study their phy

  11. Tomography with thermal neutrons

    International Nuclear Information System (INIS)

    This paper describes some tomographic measurements performed with thermal neutrons at the Instituto de Engenharia Nuclear - IEN/CNEN. The Argonauta Reactor at this Institute was used as neutron source. During the measurements this reactor produced a 36 x 105 n.cm-1.s-1 thermal neutron flux at end of the irradiation channel, wherein the tomographic system was installed. An homogeneous aluminum cylindrical rod was used to calibrate the system and to determine parameters governing the quality of the images. The aluminum cross section emerging from the image reconstruction process, was then compared with the values found in the literature. To evaluate the capability of this technique as a complementary tool, to the X-ray tomography, images of a solid aluminum cylinder, wherein, several thin rods of different materials were inserted, were taken. These materials were chosen among elements with high atomic numbers, as well as, among elements having a Z close to each other. A tomographic image of a small electric motor, displayed several elements of its internal structure. The overall results have demonstrated the capability of the thermal neutron tomography to complement the X-ray tomography, specially for samples containing elements of high atomic numbers such as lead (Z=82), or elements having atomic numbers close to each other such as iron (Z=26) and copper (Z=29). (author)

  12. Probing the global and local dynamics of aminoacyl-tRNA synthetases using all-atom and coarse-grained simulations

    OpenAIRE

    Strom, Alexander M.; Fehling, Samuel C.; Bhattacharyya, Sudeep; Hati, Sanchita

    2014-01-01

    Coarse-grained simulations have emerged as invaluable tools for studying conformational changes in biomolecules. To evaluate the effectiveness of computationally inexpensive coarse-grained models in studying global and local dynamics of large protein systems like aminoacyl-tRNA synthetases, we have performed coarse-grained normal mode analysis, as well as principle component analysis on trajectories of all-atom and coarse-grained molecular dynamics simulations for three aminoacyl-tRNA synthet...

  13. Resolution analysis by random probing

    NARCIS (Netherlands)

    Fichtner, Andreas; van Leeuwen, T.

    2015-01-01

    We develop and apply methods for resolution analysis in tomography, based on stochastic probing of the Hessian or resolution operators. Key properties of our methods are (i) low algorithmic complexity and easy implementation, (ii) applicability to any tomographic technique, including full‐waveform i

  14. Computed tomography and three-dimensional imaging

    International Nuclear Information System (INIS)

    Presented here is a brief introduction to two-, three-, and four-dimensional computed tomography. More detailed descriptions of the mathematics of reconstruction and of CT scanner operation are presented elsewhere. The complementary tomographic imaging methods of single-photon-emission tomography (SPECT) positron-emission tomography (PET), nuclear magnetic resonance (NMR) imaging, ulltrasound sector scanning, and ulltrasound computer-assisted tomography [UCAT] are only named here. Each imaging modality ''probes'' the body with a different energy form, yielding unique and useful information about tomographic sections through the body

  15. Probing the folded state and mechanical unfolding pathways of T4 lysozyme using all-atom and coarse-grained molecular simulation

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Wenjun, E-mail: wjzheng@buffalo.edu; Glenn, Paul [Department of Physics, University at Buffalo, Buffalo, New York 14260 (United States)

    2015-01-21

    The Bacteriophage T4 Lysozyme (T4L) is a prototype modular protein comprised of an N-terminal and a C-domain domain, which was extensively studied to understand the folding/unfolding mechanism of modular proteins. To offer detailed structural and dynamic insights to the folded-state stability and the mechanical unfolding behaviors of T4L, we have performed extensive equilibrium and steered molecular dynamics simulations of both the wild-type (WT) and a circular permutation (CP) variant of T4L using all-atom and coarse-grained force fields. Our all-atom and coarse-grained simulations of the folded state have consistently found greater stability of the C-domain than the N-domain in isolation, which is in agreement with past thermostatic studies of T4L. While the all-atom simulation cannot fully explain the mechanical unfolding behaviors of the WT and the CP variant observed in an optical tweezers study, the coarse-grained simulations based on the Go model or a modified elastic network model (mENM) are in qualitative agreement with the experimental finding of greater unfolding cooperativity in the WT than the CP variant. Interestingly, the two coarse-grained models predict different structural mechanisms for the observed change in cooperativity between the WT and the CP variant—while the Go model predicts minor modification of the unfolding pathways by circular permutation (i.e., preserving the general order that the N-domain unfolds before the C-domain), the mENM predicts a dramatic change in unfolding pathways (e.g., different order of N/C-domain unfolding in the WT and the CP variant). Based on our simulations, we have analyzed the limitations of and the key differences between these models and offered testable predictions for future experiments to resolve the structural mechanism for cooperative folding/unfolding of T4L.

  16. Probing the folded state and mechanical unfolding pathways of T4 lysozyme using all-atom and coarse-grained molecular simulation

    International Nuclear Information System (INIS)

    The Bacteriophage T4 Lysozyme (T4L) is a prototype modular protein comprised of an N-terminal and a C-domain domain, which was extensively studied to understand the folding/unfolding mechanism of modular proteins. To offer detailed structural and dynamic insights to the folded-state stability and the mechanical unfolding behaviors of T4L, we have performed extensive equilibrium and steered molecular dynamics simulations of both the wild-type (WT) and a circular permutation (CP) variant of T4L using all-atom and coarse-grained force fields. Our all-atom and coarse-grained simulations of the folded state have consistently found greater stability of the C-domain than the N-domain in isolation, which is in agreement with past thermostatic studies of T4L. While the all-atom simulation cannot fully explain the mechanical unfolding behaviors of the WT and the CP variant observed in an optical tweezers study, the coarse-grained simulations based on the Go model or a modified elastic network model (mENM) are in qualitative agreement with the experimental finding of greater unfolding cooperativity in the WT than the CP variant. Interestingly, the two coarse-grained models predict different structural mechanisms for the observed change in cooperativity between the WT and the CP variant—while the Go model predicts minor modification of the unfolding pathways by circular permutation (i.e., preserving the general order that the N-domain unfolds before the C-domain), the mENM predicts a dramatic change in unfolding pathways (e.g., different order of N/C-domain unfolding in the WT and the CP variant). Based on our simulations, we have analyzed the limitations of and the key differences between these models and offered testable predictions for future experiments to resolve the structural mechanism for cooperative folding/unfolding of T4L

  17. Networking strategies of the microscopy community for improved utilization of advanced instruments: (2) The national network for transmission electron microscopy and atom probe studies in France (METSA)

    Science.gov (United States)

    Épicier, Thierry; Snoeck, Étienne

    2014-02-01

    With the development, over the past ten years, of a new generation of electron microscopes with advanced performance, incorporating aberration correctors, monochromators, more sensitive detectors, and innovative specimen environments, quantitative measurements at the subnanometer and, in certain cases, at the unique atom level, are now accessible. However, an optimized use of these possibilities requires access to costly instruments and support by specialized trained experts. For these reasons, a national network (METSA) has been created in France with the support of CNRS and CEA in order to offer, in centres with complementary equipment and expertise, an open access to an enlarged and multidisciplinary community of academic and industrial users.

  18. Stored Luminescence Computed Tomography

    CERN Document Server

    Cong, Wenxiang; Wang, Ge

    2013-01-01

    The phosphor nanoparticles made of doped semiconductors, pre-excited by well-collimated X-ray radiation, were recently reported for their light emission upon NIR light stimulation. The characteristics of X-ray energy storage and NIR stimulated emission is highly desirable to design targeting probes and improve molecular and cellular imaging. Here we propose stored luminescence computed tomography (SLCT), perform realistic numerical simulation, and demonstrate a much-improved spatial resolution in a preclinical research context. The future opportunities are also discussed along this direction.

  19. Multiple scattering tomography.

    Science.gov (United States)

    Modregger, Peter; Kagias, Matias; Peter, Silvia; Abis, Matteo; Guzenko, Vitaliy A; David, Christian; Stampanoni, Marco

    2014-07-11

    Multiple scattering represents a challenge for numerous modern tomographic imaging techniques. In this Letter, we derive an appropriate line integral that allows for the tomographic reconstruction of angular resolved scattering distributions, even in the presence of multiple scattering. The line integral is applicable to a wide range of imaging techniques utilizing various kinds of probes. Here, we use x-ray grating interferometry to experimentally validate the framework and to demonstrate additional structural sensitivity, which exemplifies the impact of multiple scattering tomography. PMID:25062159

  20. A low temperature ultrahigh vacuum scanning tunneling microscope with high-NA optics to probe optical interactions at the atomic scale

    Science.gov (United States)

    Zhang, Haigang; Smerdon, Joseph; Suzer, Ozgun; Kersell, Heath; Guest, Jeffrey

    2015-03-01

    The optical and photophysical properties of single molecules/atoms, defects, and nanoscale structures at surfaces hinge on structure at the atomic scale. In order to characterize and control this structure and unravel these correlations, we are developing a low temperature (LT) laser-coupled ultrahigh vacuum (UHV) scanning tunneling microscope (LT Laser UHV STM) based on the Pan-style STM scanner with integrated high-numerical-aperture (NA) optics for single particle spectroscopy measurements under the STM tip. Using slip-stick inertial piezo steppers, the sample stage can be coarsely translated in X and Y directions. For optical measurements, high-NA optics behind and above the sample focus laser excitation on and collect photons emitted from the tip-sample junction. The STM is cooled by a liquid helium bath surrounded by a liquid nitrogen jacket for operation near 5 K; two separate ultrahigh vacuum chambers are used for sample preparation and STM measurements, respectively. We will describe our progress in demonstrating this instrument and plans for experiments studying the correlation between structure and optical function in nanoscale systems. U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.