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Sample records for 3-d atom probe

  1. A transparent anode array detector for 3D atom probes

    SciTech Connect

    Miller, M.K.

    1998-02-01

    In a three dimensional atom probe, the identity and spatial coordinates of the atoms field evaporated from the specimen are determined. Their identity is calculated from the flight time from the specimen to the single atom detector. The x and y coordinates of the atom in the specimen are determined from the coordinates of its impact position on the position-sensitive detector and the z coordinate is determined from its position in the evaporation sequence. These data may then be reconstructed to visualize and quantify the distribution of all the elements in the specimen. Several types of position-sensitive detectors have been used including a wedge-and-strip detector (position- sensitive atom probe), a 10 by 10 array of anodes (tomographic atom probe), and a gateable CCD camera (optical atom probe). The wedge-and strip and the CCD camera detectors both suffer from the limitation that if more than one atom strikes the detector on a field evaporation pulse then the impact positions cannot be determined in many cases. In order to minimize this limitation, Cerezo et al. have developed a dual detector system (optical position-sensitive atom probe) that uses both an 8 by 10 multianode array and an intensified CCD camera. This dual detector configuration requires a beam splitter which reduces the signal intensity reaching the detectors and two independent detection systems both with image intensifiers. In this paper, an improved version of this detection system that combines these two systems into one is presented.

  2. Standard deviations of composition measurements in atom probe analyses-Part II: 3D atom probe.

    PubMed

    Danoix, F; Grancher, G; Bostel, A; Blavette, D

    2007-09-01

    In a companion paper [F. Danoix, G. Grancher, A. Bostel, D. Blavette, Surf. Interface Anal. this issue (previous paper).], the derivation of variances of the estimates of measured composition, and the underlying hypotheses, have been revisited in the the case of conventional one dimensional (1D) atom probes. In this second paper, we will concentrate on the analytical derivation of the variance when the estimate of composition is obtained from a 3D atom probe. As will be discussed, when the position information is available, compositions can be derived either from constant number of atoms, or from constant volume, blocks. The analytical treatment in the first case is identical to the one developed for conventional 1D instruments, and will not be discussed further in this paper. Conversely, in the second case, the analytical treatment is different, as well as the formula of the variance. In particular, it will be shown that the detection efficiency plays an important role in the determination of the variance.

  3. Ultrafast emission of ions during laser ablation of metal for 3D atom probe

    NASA Astrophysics Data System (ADS)

    Vella, A.; Houard, J.; Vurpillot, F.; Deconihout, B.

    2009-03-01

    The 3D atom probe(3DAP) is an imaging instrument based on the controlled field evaporation of single atoms from a sample having a tip shape with an end radius of 50 nm. In the fs laser assisted 3DAP the evaporation is induced by the laser pulses so that the physical process involved in this 3DAP analysis might correspond to the very early stages of the ablation process. In this paper we present the principle of the 3DAP and we discuss the existing models of the fs assisted evaporation. At last, we test the relevance of these models with pump-probe experiments on tungsten tips in the tomographic atom probe.

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

    PubMed

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

    2015-12-01

    Identifying nanoscale chemical features from atom probe tomography (APT) data routinely involves adjustment of voxel size as an input parameter, through visual supervision, making the final outcome user dependent, reliant on heuristic knowledge and potentially prone to error. This work utilizes Kernel density estimators to select an optimal voxel size in an unsupervised manner to perform feature selection, in particular targeting resolution of interfacial features and chemistries. The capability of this approach is demonstrated through analysis of the γ / γ' interface in a Ni-Al-Cr superalloy. PMID:25825028

  5. Imaging the three orientation variants of the DO22 phase by 3D atom probe microscopy.

    PubMed

    Marteau, L; Pareige, C; Blavette, D

    2001-12-01

    Three-phase NiAlV alloys were investigated using a three-dimensional atom probe. Ageing at 800 degrees C gives rise to the precipitation of two ordered phases within the supersaturated FCC solid solution, namely Ni3Al (L1(2) structure) and Ni3V (DO22 structure). The DO22 phase has three orientation variants which need to be identified in 3DAP images. It is shown that an appropriate choice of analysis site enables us to image the chemical order within both L1(2) and DO22 ordered phases and to distinguish the three orientation variants of the DO22 phase in reconstructed images. The lateral resolution of 3DAP in these experimental conditions was estimated through simple considerations to be less than 0.3 nm.

  6. Three-Dimensional (3-D) Atom Probe Tomography of a Cu-Precipitation-Strengthened, Ultrahigh-Strength Carburized Steel

    NASA Astrophysics Data System (ADS)

    Tiemens, Benjamin L.; Sachdev, Anil K.; Mishra, Raja K.; Olson, Gregory B.

    2012-10-01

    In an effort to reduce material cost, experimental steel alloys were developed that incorporated Cu precipitation in lieu of costly Co alloying additions in secondary hardening carburizing gear steels. This work utilizes three-dimensional atom probe tomography to study one of these prototype alloys and quantify the nanoscale dispersions of body-centered cubic (bcc) Cu and M2C alloy carbides used to strengthen these steels. The temporal evolution of precipitate, size, morphology, and interprecipitate interactions were studied for various tempering times. Findings suggest that Cu precipitation does act as a catalyst for heterogeneous nucleation of M2C carbides at relatively high hardness levels; however, the resultant volume fraction of strengthening carbides was noticeably less than that predicted by thermodynamic equilibrium calculations, indicating a reduced potency compared with Co-assisted precipitation. Microstructural information such as precipitate size and volume fraction was measured at the peak hardness condition and successfully used to recalibrate alloy design models for subsequent alloy design iterations.

  7. Directing Matter: Toward Atomic-Scale 3D Nanofabrication.

    PubMed

    Jesse, Stephen; Borisevich, Albina Y; Fowlkes, Jason D; Lupini, Andrew R; Rack, Philip D; Unocic, Raymond R; Sumpter, Bobby G; Kalinin, Sergei V; Belianinov, Alex; Ovchinnikova, Olga S

    2016-06-28

    Enabling memristive, neuromorphic, and quantum-based computing as well as efficient mainstream energy storage and conversion technologies requires the next generation of materials customized at the atomic scale. This requires full control of atomic arrangement and bonding in three dimensions. The last two decades witnessed substantial industrial, academic, and government research efforts directed toward this goal through various lithographies and scanning-probe-based methods. These technologies emphasize 2D surface structures, with some limited 3D capability. Recently, a range of focused electron- and ion-based methods have demonstrated compelling alternative pathways to achieving atomically precise manufacturing of 3D structures in solids, liquids, and at interfaces. Electron and ion microscopies offer a platform that can simultaneously observe dynamic and static structures at the nano- and atomic scales and also induce structural rearrangements and chemical transformation. The addition of predictive modeling or rapid image analytics and feedback enables guiding these in a controlled manner. Here, we review the recent results that used focused electron and ion beams to create free-standing nanoscale 3D structures, radiolysis, and the fabrication potential with liquid precursors, epitaxial crystallization of amorphous oxides with atomic layer precision, as well as visualization and control of individual dopant motion within a 3D crystal lattice. These works lay the foundation for approaches to directing nanoscale level architectures and offer a potential roadmap to full 3D atomic control in materials. In this paper, we lay out the gaps that currently constrain the processing range of these platforms, reflect on indirect requirements, such as the integration of large-scale data analysis with theory, and discuss future prospects of these technologies.

  8. Directing Matter: Toward Atomic-Scale 3D Nanofabrication.

    PubMed

    Jesse, Stephen; Borisevich, Albina Y; Fowlkes, Jason D; Lupini, Andrew R; Rack, Philip D; Unocic, Raymond R; Sumpter, Bobby G; Kalinin, Sergei V; Belianinov, Alex; Ovchinnikova, Olga S

    2016-06-28

    Enabling memristive, neuromorphic, and quantum-based computing as well as efficient mainstream energy storage and conversion technologies requires the next generation of materials customized at the atomic scale. This requires full control of atomic arrangement and bonding in three dimensions. The last two decades witnessed substantial industrial, academic, and government research efforts directed toward this goal through various lithographies and scanning-probe-based methods. These technologies emphasize 2D surface structures, with some limited 3D capability. Recently, a range of focused electron- and ion-based methods have demonstrated compelling alternative pathways to achieving atomically precise manufacturing of 3D structures in solids, liquids, and at interfaces. Electron and ion microscopies offer a platform that can simultaneously observe dynamic and static structures at the nano- and atomic scales and also induce structural rearrangements and chemical transformation. The addition of predictive modeling or rapid image analytics and feedback enables guiding these in a controlled manner. Here, we review the recent results that used focused electron and ion beams to create free-standing nanoscale 3D structures, radiolysis, and the fabrication potential with liquid precursors, epitaxial crystallization of amorphous oxides with atomic layer precision, as well as visualization and control of individual dopant motion within a 3D crystal lattice. These works lay the foundation for approaches to directing nanoscale level architectures and offer a potential roadmap to full 3D atomic control in materials. In this paper, we lay out the gaps that currently constrain the processing range of these platforms, reflect on indirect requirements, such as the integration of large-scale data analysis with theory, and discuss future prospects of these technologies. PMID:27183171

  9. Directing Matter: Toward Atomic-Scale 3D Nanofabrication

    DOE PAGES

    Jesse, Stephen; Borisevich, Albina Y.; Fowlkes, Jason D.; Lupini, Andrew R.; Rack, Philip D.; Unocic, Raymond R.; Sumpter, Bobby G.; Kalinin, Sergei V.; Belianinov, Alex; Ovchinnikova, Olga S.

    2016-05-16

    Here we report that enabling memristive, neuromorphic, and quantum based computing as well as efficient mainstream energy storage and conversion technologies requires next generation of materials customized at the atomic scale. This requires full control of atomic arrangement and bonding in three dimensions. The last two decades witnessed substantial industrial, academic, and government research efforts directed towards this goal through various lithographies and scanning probe based methods. These technologies emphasize 2D surface structures, with some limited 3D capability. Recently, a range of focused electron and ion based methods have demonstrated compelling alternative pathways to achieving atomically precise manufacturing of 3Dmore » structures in solids, liquids, and at interfaces. Electron and ion microscopies offer a platform that can simultaneously observe dynamic and static structures at the nano and atomic scales, and also induce structural rearrangements and chemical transformation. The addition of predictive modeling or rapid image analytics and feedback enables guiding these in a controlled manner. Here, we review the recent results that used focused electron and ion beams to create free-standing nanoscale 3D structures, radiolysis and the fabrication potential with liquid precursors, epitaxial crystallization of amorphous oxides with atomic layer precision, as well as visualization and control of individual dopant motion within a 3D crystal lattice. These works lay the foundation for new approaches to directing nanoscale level architectures and offer a potential roadmap to full 3D atomic control in materials. Lastly, in this perspective we lay out the gaps that currently constrain the processing range of these platforms, reflect on indirect requirements, such as the integration of large scale data analysis with theory, and discuss future prospects of these technologies.« less

  10. Atom probe tomography

    SciTech Connect

    Miller, M.K.; Forbes, R.G.

    2009-06-15

    This introductory tutorial describes the technique of atom probe tomography for materials characterization at the atomic level. The evolution of the technique from the initial atom probe field ion microscope to today's state-of-the-art three dimensional atom probe is outlined. An introduction is presented on the basic physics behind the technique, the operation of the instrument, and the reconstruction of the three-dimensional data. The common methods for analyzing the three-dimensional atom probe data, including atom maps, isoconcentration surfaces, proximity histograms, maximum separation methods, and concentration frequency distributions, are described.

  11. Microfabrication of 3D neural probes with combined electrical and chemical interfaces

    NASA Astrophysics Data System (ADS)

    John, Jessin; Li, Yuefa; Zhang, Jinsheng; Loeb, Jeffrey A.; Xu, Yong

    2011-10-01

    This paper reports a novel neural probe technology for the manufacture of 3D arrays of electrodes with integrated microchannels. This new technology is based on a silicon island structure and a simple folding procedure. This method simplifies the assembly or packaging process of 3D neural probes, leading to higher yield and lower cost. Prototypes with 3D arrays of electrodes have been successfully developed. Microchannels have been successfully integrated into the 3D neural probes via isotropic XeF2 gas phase etching and a parylene resealing process. The probes have been characterized by scanning electron microscopy imaging, optical imaging, impedance analysis, and atomic force microscopy characterization of the electrode surface. Preliminary animal tests have been carried out to demonstrate the recording functionality of the probes. Flow characteristics of the microchannels were also preliminarily measured.

  12. 3D Parylene sheath neural probe for chronic recordings

    NASA Astrophysics Data System (ADS)

    Kim, B. J.; Kuo, J. T. W.; Hara, S. A.; Lee, C. D.; Yu, L.; Gutierrez, C. A.; Hoang, T. Q.; Pikov, V.; Meng, E.

    2013-08-01

    Objective. Reliable chronic recordings from implanted neural probes remain a significant challenge; current silicon-based and microwire technologies experience a wide range of biotic and abiotic failure modes contributing to loss of signal quality. Approach. A multi-prong alternative strategy with potential to overcome these hurdles is introduced that combines a novel three dimensional (3D), polymer-based probe structure with coatings. Specifically, the Parylene C sheath-based neural probe is coated with neurotrophic and anti-inflammatory factors loaded onto a Matrigel carrier to encourage the ingrowth of neuronal processes for improved recording quality, reduce the immune response, and promote improved probe integration into brain tissue for reliable, long-term implementation compared to its rigid counterparts. Main results. The 3D sheath structure of the probe was formed by thermal molding of a surface micromachined Parylene C microchannel, with electrode sites lining the interior and exterior regions of the lumen. Electrochemical characterization of the probes via cyclic voltammetry and electrochemical impedance spectroscopy was performed and indicated suitable electrode properties for neural recordings (1 kHz electrical impedance of ∼200 kΩ in vitro). A novel introducer tool for the insertion of the compliant polymer probe into neural tissue was developed and validated both in vitro using agarose gel and in vivo in the rat cerebral cortex. In vivo electrical functionality of the Parylene C-based 3D probes and their suitability for recording the neuronal activity over a 28-day period was demonstrated by maintaining the 1 kHz electrical impedance within a functional range (<400 kΩ) and achieving a reasonably high signal-to-noise ratio for detection of resolvable multi-unit neuronal activity on most recording sites in the probe. Immunohistochemical analysis of the implant site indicated strong correlations between the quality of recorded activity and the

  13. Progress in sorting individual atoms in 3D

    NASA Astrophysics Data System (ADS)

    Wu, Tsung-Yao; Kumar, Aishwarya; Wang, Yang; Weiss, David

    2016-05-01

    An exactly unity filled optical lattice is a desirable initial state for a neutral atom quantum computer. We have previously proposed an efficient way to compact a partially filled lattice into a perfectly filled one, by combining site-resolved imaging, site-selective qubit rotations and state-selective motion steps. We have previously demonstrated site-resolved imaging and site-selective rotations in our system of cesium atoms in a 40% filled 5x5x5 3D lattice. We have now demonstrated the final element, state-selective motion steps in 3D produced by rotating the polarizations of one of the lattice beams in each pair. We will present our progress in putting all the elements together to reach perfect unity filling. Supported by NSF.

  14. Atom Probe Tomography 2012

    NASA Astrophysics Data System (ADS)

    Kelly, Thomas F.; Larson, David J.

    2012-08-01

    In the world of tomographic imaging, atom probe tomography (APT) occupies the high-spatial-resolution end of the spectrum. It is highly complementary to electron tomography and is applicable to a wide range of materials. The current state of APT is reviewed. Emphasis is placed on applications and data analysis as they apply to many fields of research and development including metals, semiconductors, ceramics, and organic materials. We also provide a brief review of the history and the instrumentation associated with APT and an assessment of the existing challenges in the field.

  15. Standard deviations of composition measurements in atom probe analyses. Part I conventional 1D atom probe.

    PubMed

    Danoix, F; Grancher, G; Bostel, A; Blavette, D

    2007-09-01

    Atom probe is a very powerful instrument to measure concentrations on a sub nanometric scale [M.K. Miller, G.D.W. Smith, Atom Probe Microanalysis, Principles and Applications to Materials Problems, Materials Research Society, Pittsburgh, 1989]. Atom probe is therefore a unique tool to study and characterise finely decomposed metallic materials. Composition profiles or 3D mapping can be realised by gathering elemental composition measurements. As the detector efficiency is generally not equal to 1, the measured compositions are only estimates of actual values. The variance of the estimates depends on which information is to be estimated. It can be calculated when the detection process is known. These two papers are devoted to give complete analytical derivation and expressions of the variance on composition measurements in several situations encountered when using atom probe. In the first paper, we will concentrate on the analytical derivation of the variance when estimation of compositions obtained from a conventional one dimension (1D) atom probe is considered. In particular, the existing expressions, and the basic hypotheses on which they rely, will be reconsidered, and complete analytical demonstrations established. In the second companion paper, the case of 3D atom probe will be treated, highlighting how the knowledge of the 3D position of detected ions modifies the analytical derivation of the variance of local composition data.

  16. DIII-D Equilibrium Reconstructions with New 3D Magnetic Probes

    NASA Astrophysics Data System (ADS)

    Lao, Lang; Strait, E. J.; Ferraro, N. M.; Ferron, J. R.; King, J. D.; Lee, X.; Meneghini, O.; Turnbull, A. D.; Huang, Y.; Qian, J. G.; Wingen, A.

    2015-11-01

    DIII-D equilibrium reconstructions with the recently installed new 3D magnetic diagnostic are presented. In addition to providing information to allow more accurate 2D reconstructions, the new 3D probes also provide useful information to guide computation of 3D perturbed equilibria. A new more comprehensive magnetic compensation has been implemented. Algorithms are being developed to allow EFIT to reconstruct 3D perturbed equilibria making use of the new 3D probes and plasma responses from 3D MHD codes such as GATO and M3D-C1. To improve the computation efficiency, all inactive probes in one of the toroidal planes in EFIT have been replaced with new probes from other planes. Other 3D efforts include testing of 3D reconstructions using V3FIT and a new 3D variational moment equilibrium code VMOM3D. Other EFIT developments include a GPU EFIT version and new safety factor and MSE-LS constraints. The accuracy and limitation of the new probes for 3D reconstructions will be discussed. Supported by US DOE under DE-FC02-04ER54698 and DE-FG02-95ER54309.

  17. Probing Quantum Capacitance in a 3D Topological Insulator

    NASA Astrophysics Data System (ADS)

    Kozlov, D. A.; Bauer, D.; Ziegler, J.; Fischer, R.; Savchenko, M. L.; Kvon, Z. D.; Mikhailov, N. N.; Dvoretsky, S. A.; Weiss, D.

    2016-04-01

    We measure the quantum capacitance and probe thus directly the electronic density of states of the high mobility, Dirac type two-dimensional electron system, which forms on the surface of strained HgTe. Here we show that observed magnetocapacitance oscillations probe—in contrast to magnetotransport—primarily the top surface. Capacitance measurements constitute thus a powerful tool to probe only one topological surface and to reconstruct its Landau level spectrum for different positions of the Fermi energy.

  18. Atom Probe Tomography of Nanoscale Electronic Materials

    SciTech Connect

    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.

  19. 3D fiber probe for multi sensor coordinate measurement

    NASA Astrophysics Data System (ADS)

    Ettemeyer, A.

    2011-12-01

    Increasing manufacturing accuracy requirements enforce the development of innovative and highly sensitive measuring tools. Especially for measurement with sub micrometer accuracy, the sensor principle has to be chosen appropriately for each measurement surface. Modern multi sensor coordinate measurements systems allow automatic selection of different sensor heads to measure different areas or properties of a sample. As example, different types of optical sensors as well as tactile sensors can be used with the same machine. In this paper we describe different principles of optical sensors used in multi sensor coordinate measurement systems as well as a new approach for tactile measurement with sub micrometer accuracy. A special fiber probe has been developed. The tip of the fiber probe is formed as a sphere. The lateral position of this sphere is observed by a microscope optics and can be determined to a fraction of a micrometer. Additionally, a novel optical set-up now even allows the determination of the z-position of the fiber tip with sub micrometer accuracy. For this purpose we use an interferometric set-up. The light of laser is coupled into the optical fiber. The light, exiting the fiber tip is collected by a microscope optics and superposed with a reference wave, generated directly from the laser. The result is an interferometric signal which is recorded by the camera and processed by a computer. With this set-up, the zdisplacement of the fiber sphere can be measured with an accuracy of a fraction of the used laser wavelength.

  20. Controllable 3D atomic Brownian motor in optical lattices

    NASA Astrophysics Data System (ADS)

    Dion, C. M.; Sjölund, P.; Petra, S. J. H.; Jonsell, S.; Nylén, M.; Sanchez-Palencia, L.; Kastberg, A.

    2008-06-01

    We study a Brownian motor, based on cold atoms in optical lattices, where atomic motion can be induced in a controlled manner in an arbitrary direction, by rectification of isotropic random fluctuations. In contrast with ratchet mechanisms, our Brownian motor operates in a potential that is spatially and temporally symmetric, in apparent contradiction to the Curie principle. Simulations, based on the Fokker-Planck equation, allow us to gain knowledge on the qualitative behaviour of our Brownian motor. Studies of Brownian motors, and in particular ones with unique control properties, are of fundamental interest because of the role they play in protein motors and their potential applications in nanotechnology. In particular, our system opens the way to the study of quantum Brownian motors.

  1. Reading PDB: perception of molecules from 3D atomic coordinates.

    PubMed

    Urbaczek, Sascha; Kolodzik, Adrian; Groth, Inken; Heuser, Stefan; Rarey, Matthias

    2013-01-28

    The analysis of small molecule crystal structures is a common way to gather valuable information for drug development. The necessary structural data is usually provided in specific file formats containing only element identities and three-dimensional atomic coordinates as reliable chemical information. Consequently, the automated perception of molecular structures from atomic coordinates has become a standard task in cheminformatics. The molecules generated by such methods must be both chemically valid and reasonable to provide a reliable basis for subsequent calculations. This can be a difficult task since the provided coordinates may deviate from ideal molecular geometries due to experimental uncertainties or low resolution. Additionally, the quality of the input data often differs significantly thus making it difficult to distinguish between actual structural features and mere geometric distortions. We present a method for the generation of molecular structures from atomic coordinates based on the recently published NAOMI model. By making use of this consistent chemical description, our method is able to generate reliable results even with input data of low quality. Molecules from 363 Protein Data Bank (PDB) entries could be perceived with a success rate of 98%, a result which could not be achieved with previously described methods. The robustness of our approach has been assessed by processing all small molecules from the PDB and comparing them to reference structures. The complete data set can be processed in less than 3 min, thus showing that our approach is suitable for large scale applications.

  2. Repumping of ultracold strontium atoms using the ^3P2 - ^3D2 transition

    NASA Astrophysics Data System (ADS)

    Mickelson, P. G.; Martinez de Escobar, Y. N.; Traverso, A. J.; Killian, T. C.

    2008-05-01

    We discuss recent experiments involving ultracold strontium. Using a commercially-available 3 micron laser, we repump atoms out of the ^3P2 level via the ^3D2 state and gain almost a factor of 10 in the number of atoms in our system. This increase in the signal-to-noise ratio enables improved spectroscopy of strontium in our optical trap.

  3. 3D probe array integrated with a front-end 100-channel neural recording ASIC

    NASA Astrophysics Data System (ADS)

    Cheng, Ming-Yuan; Yao, Lei; Tan, Kwan Ling; Lim, Ruiqi; Li, Peng; Chen, Weiguo

    2014-12-01

    Brain-machine interface technology can improve the lives of spinal cord injury victims and amputees. A neural interface system, consisting of a 3D probe array and a custom low-power (1 mW) 100-channel (100-ch) neural recording application-specific integrated circuit (ASIC), was designed and implemented to monitor neural activity. In this study, a microassembly 3D probe array method using a novel lead transfer technique was proposed to overcome the bonding plane mismatch encountered during orthogonal assembly. The proposed lead transfer technique can be completed using standard micromachining and packaging processes. The ASIC can be stacking-integrated with the probe array, minimizing the form factor of the assembled module. To minimize trauma to brain cells, the profile of the integrated probe array was controlled within 730 μm. The average impedance of the assembled probe was approximately 0.55 MΩ at 1 kHz. To verify the functionality of the integrated neural probe array, bench-top signal acquisitions were performed and discussed.

  4. Imaging of oxygenation in 3D tissue models with multi-modal phosphorescent probes

    NASA Astrophysics Data System (ADS)

    Papkovsky, Dmitri B.; Dmitriev, Ruslan I.; Borisov, Sergei

    2015-03-01

    Cell-penetrating phosphorescence based probes allow real-time, high-resolution imaging of O2 concentration in respiring cells and 3D tissue models. We have developed a panel of such probes, small molecule and nanoparticle structures, which have different spectral characteristics, cell penetrating and tissue staining behavior. The probes are compatible with conventional live cell imaging platforms and can be used in different detection modalities, including ratiometric intensity and PLIM (Phosphorescence Lifetime IMaging) under one- or two-photon excitation. Analytical performance of these probes and utility of the O2 imaging method have been demonstrated with different types of samples: 2D cell cultures, multi-cellular spheroids from cancer cell lines and primary neurons, excised slices from mouse brain, colon and bladder tissue, and live animals. They are particularly useful for hypoxia research, ex-vivo studies of tissue physiology, cell metabolism, cancer, inflammation, and multiplexing with many conventional fluorophors and markers of cellular function.

  5. Ultra precision micro-CMM using a low force 3D touch probe

    NASA Astrophysics Data System (ADS)

    Meli, F.; Kueng, A.; Thalmann, R.

    2005-08-01

    With the continued miniaturisation of mechanical and optical systems there is an increasing demand for high precision dimensional measurements on small parts. METAS combined a new probe head with a recently developed ultra precision CMM stage. The probe head with probing spheres in the diameter range of 0.1 mm to 1 mm has isotropic probing forces below 0.5 mN. Its unique parallel kinematic structure uses exclusively flexure hinges and is manufactured out of a single piece of aluminium. This structure blocks all rotational movements of the probing sphere and separates the 3D movement into three independent 1D displacements which are measured by inductive sensors. The repeatability for a single point probing is in the order of 5 nm. This probe head was combined with an ultra precision micro-CMM, which is based on a development made at Philips CFT [1,2]. The micro-CMM features a 90 mm x 90 mm x 38 mm air bearing stage with interferometric position measurement at zero Abbe offset. At the reached level of precision, the shape deviation of the probing sphere becomes a major contribution to the uncertainty. Therefore a calibration method for spheres based on error separation techniques was implemented. The results of roundness measurements on 3 calibration spheres are presented.

  6. Sandwich-format 3D printed microfluidic mixers: a flexible platform for multi-probe analysis

    NASA Astrophysics Data System (ADS)

    Kise, Drew P.; Reddish, Michael J.; Dyer, R. Brian

    2015-12-01

    We report on a microfluidic mixer fabrication platform that increases the versatility and flexibility of mixers for biomolecular applications. A sandwich-format design allows the application of multiple spectroscopic probes to the same mixer. A polymer spacer is ‘sandwiched’ between two transparent windows, creating a closed microfluidic system. The channels of the mixer are defined by regions in the polymer spacer that lack material and therefore the polymer need not be transparent in the spectral region of interest. Suitable window materials such as CaF2 make the device accessible to a wide range of optical probe wavelengths, from the deep UV to the mid-IR. In this study, we use a commercially available 3D printer to print the polymer spacers to apply three different channel designs into the passive, continuous-flow mixer, and integrated them with three different spectroscopic probes. All three spectroscopic probes are applicable to each mixer without further changes. The sandwich-format mixer coupled with cost-effective 3D printed fabrication techniques could increase the applicability and accessibility of microfluidic mixing to intricate kinetic schemes and monitoring chemical synthesis in cases where only one probe technique proves insufficient.

  7. Sandwich-format 3D printed microfluidic mixers: a flexible platform for multi-probe analysis

    PubMed Central

    Kise, Drew P; Reddish, Michael J; Dyer, R Brian

    2015-01-01

    We report on a microfluidic mixer fabrication platform that increases the versatility and flexibility of mixers for biomolecular applications. A sandwich-format design allows the application of multiple spectroscopic probes to the same mixer. A polymer spacer is ‘sandwiched’ between two transparent windows, creating a closed microfluidic system. The channels of the mixer are defined by regions in the polymer spacer that lack material and therefore the polymer need not be transparent in the spectral region of interest. Suitable window materials such as CaF2 make the device accessible to a wide range of optical probe wavelengths, from the deep UV to the mid-IR. In this study, we use a commercially available 3D printer to print the polymer spacers to apply three different channel designs into the passive, continuous-flow mixer, and integrated them with three different spectroscopic probes. All three spectroscopic probes are applicable to each mixer without further changes. The sandwich-format mixer coupled with cost-effective 3D printed fabrication techniques could increase the applicability and accessibility of microfluidic mixing to intricate kinetic schemes and monitoring chemical synthesis in cases where only one probe technique proves insufficient. PMID:26855478

  8. Template for 3D Printing a Low-Temperature Plasma Probe.

    PubMed

    Martínez-Jarquín, Sandra; Moreno-Pedraza, Abigail; Guillén-Alonso, Héctor; Winkler, Robert

    2016-07-19

    Low-temperature plasma (LTP) ionization represents an emerging technology in ambient mass spectrometry. LTP enables the solvent-free direct detection of a broad range of molecules and mass spectrometry imaging (MSI). The low energy consumption and modest technical requirements of these ion sources favors their employment in mobile applications and as a means to upgrade existing mass analyzers. However, the broad adoption of LTP is hindered by the lack of commercial devices, and constructing personal devices is tricky. Improper setup can result in equipment malfunction or may cause serious damage to instruments due to strong electromagnetic fields or arcing. With this in mind, we developed a reproducible LTP probe, which is designed exclusively from commercial and 3D printed components. The plasma jet generated by the device has a diameter of about 200 μm, which is satisfactory for the ambient imaging of macroscopic samples. We coupled the 3D-LTP probe to an ion trap analyzer and demonstrated the functionality of the ion source by detecting organic and chemical compounds from pure reference standards, biological substances, and pharmaceutical samples. Molecules were primarily detected in their protonated form or as water/ammonium adducts. The identification of compounds was possible by standard collision-induced dissociation (CID) fragmentation spectra. The files necessary to reproduce the 3D parts are available from the project page ( http://lababi.bioprocess.org/index.php/3d-ltp ) under a dual license model, which permits reproduction of the probe and further community-driven development for noncommercial use ("peer production"). Our reproducible probe design thus contributes to a facilitated adaption and evolution of low-temperature plasma technologies in analytical chemistry. PMID:27302654

  9. Template for 3D Printing a Low-Temperature Plasma Probe.

    PubMed

    Martínez-Jarquín, Sandra; Moreno-Pedraza, Abigail; Guillén-Alonso, Héctor; Winkler, Robert

    2016-07-19

    Low-temperature plasma (LTP) ionization represents an emerging technology in ambient mass spectrometry. LTP enables the solvent-free direct detection of a broad range of molecules and mass spectrometry imaging (MSI). The low energy consumption and modest technical requirements of these ion sources favors their employment in mobile applications and as a means to upgrade existing mass analyzers. However, the broad adoption of LTP is hindered by the lack of commercial devices, and constructing personal devices is tricky. Improper setup can result in equipment malfunction or may cause serious damage to instruments due to strong electromagnetic fields or arcing. With this in mind, we developed a reproducible LTP probe, which is designed exclusively from commercial and 3D printed components. The plasma jet generated by the device has a diameter of about 200 μm, which is satisfactory for the ambient imaging of macroscopic samples. We coupled the 3D-LTP probe to an ion trap analyzer and demonstrated the functionality of the ion source by detecting organic and chemical compounds from pure reference standards, biological substances, and pharmaceutical samples. Molecules were primarily detected in their protonated form or as water/ammonium adducts. The identification of compounds was possible by standard collision-induced dissociation (CID) fragmentation spectra. The files necessary to reproduce the 3D parts are available from the project page ( http://lababi.bioprocess.org/index.php/3d-ltp ) under a dual license model, which permits reproduction of the probe and further community-driven development for noncommercial use ("peer production"). Our reproducible probe design thus contributes to a facilitated adaption and evolution of low-temperature plasma technologies in analytical chemistry.

  10. Atom Probe Tomography of Geomaterials

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    From the electron microprobe to the secondary ion microprobe to laser-ablation ICP-MS, steady improvements in the spatial resolution and detection limits of geochemical micro-analysis have been central to generating new discoveries. Atom probe tomography (APT) is a relatively new technology that promises nm-scale spatial resolution (in three dimensions) with ppm level detection limits. The method is substantially different from traditional beam-based (electron, ion, laser) methods. In APT, the sample is shaped (usually with a dual-beam FIB) into a needle with typical dimensions of 1-2 μm height and 100-200 nm diameter. Within the atom probe, the needle is evaporated one atom (ideally) at a time by a high electric field (ten's of V per square nm at the needle tip). A femtosecond laser (12 ps pulse width) is used to assist in evaporating non-conducting samples. The two-dimensional detector locates where the atom was released from the needle's surface and so can reconstruct the positions of all detected atoms in three dimensions. It also records the time of flight of the ion, which is used to calculate the mass/charge ratio of the ion. We will discuss our results analyzing a range of geologic materials. In one case, naturally occurring platinum group alloys (PGA) from the Josephine Ophiolite have been imaged. Such alloys are of interest as recorders of the Os heterogeneity of the mantle [1,2]. Optimal ablation was achieved with a laser power of 120-240 pJ and laser pulse rates 500 kHz. Runs were stopped after 10 million atoms were imaged. An example analysis is: Pt 61(1), Fe 26.1(9), Rh 1.20(4), Ir 7.0(7), Ni 2.65(8), Ru 0.20(9), Cu 1.22(8), Co 0.00029(5). Values are in atomic %; values in parentheses are one-sigma standard deviations on five separate needles from the same FIB lift-out, which was 30 μm long. Assuming the sample is homogenous over the 30 μm from which the needle was extracted, the analyses suggest relative errors for major elements below 5% and for

  11. Combined scanning probe nanotomography and optical microspectroscopy: a correlative technique for 3D characterization of nanomaterials.

    PubMed

    Mochalov, Konstantin E; Efimov, Anton E; Bobrovsky, Alexey; Agapov, Igor I; Chistyakov, Anton A; Oleinikov, Vladimir; Sukhanova, Alyona; Nabiev, Igor

    2013-10-22

    Combination of 3D structural analysis with optical characterization of the same sample area on the nanoscale is a highly demanded approach in nanophotonics, materials science, and quality control of nanomaterial. We have developed a correlative microscopy technique where the 3D structure of the sample is reconstructed on the nanoscale by means of a "slice-and-view" combination of ultramicrotomy and scanning probe microscopy (scanning probe nanotomography, SPNT), and its optical characteristics are analyzed using microspectroscopy. This approach has been used to determine the direct quantitative relationship of the 3D structural characteristics of nanovolumes of materials with their microscopic optical properties. This technique has been applied to 3D structural and optical characterization of a hybrid material consisting of cholesteric liquid crystals doped with fluorescent quantum dots (QDs) that can be used for photochemical patterning and image recording through the changes in the dissymmetry factor of the circular polarization of QD emission. The differences in the polarization images and fluorescent spectra of this hybrid material have proved to be correlated with the arrangement of the areas of homogeneous distribution and heterogeneous clustering of QDs. The reconstruction of the 3D nanostructure of the liquid crystal matrix in the areas of homogeneous QDs distribution has shown that QDs do not perturb the periodic planar texture of the cholesteric liquid crystal matrix, whereas QD clusters do perturb it. The combined microspectroscopy-nanotomography technique will be important for evaluating the effects of nanoparticles on the structural organization of organic and liquid crystal matrices and biomedical materials, as well as quality control of nanotechnology fabrication processes and products.

  12. Combined scanning probe nanotomography and optical microspectroscopy: a correlative technique for 3D characterization of nanomaterials.

    PubMed

    Mochalov, Konstantin E; Efimov, Anton E; Bobrovsky, Alexey; Agapov, Igor I; Chistyakov, Anton A; Oleinikov, Vladimir; Sukhanova, Alyona; Nabiev, Igor

    2013-10-22

    Combination of 3D structural analysis with optical characterization of the same sample area on the nanoscale is a highly demanded approach in nanophotonics, materials science, and quality control of nanomaterial. We have developed a correlative microscopy technique where the 3D structure of the sample is reconstructed on the nanoscale by means of a "slice-and-view" combination of ultramicrotomy and scanning probe microscopy (scanning probe nanotomography, SPNT), and its optical characteristics are analyzed using microspectroscopy. This approach has been used to determine the direct quantitative relationship of the 3D structural characteristics of nanovolumes of materials with their microscopic optical properties. This technique has been applied to 3D structural and optical characterization of a hybrid material consisting of cholesteric liquid crystals doped with fluorescent quantum dots (QDs) that can be used for photochemical patterning and image recording through the changes in the dissymmetry factor of the circular polarization of QD emission. The differences in the polarization images and fluorescent spectra of this hybrid material have proved to be correlated with the arrangement of the areas of homogeneous distribution and heterogeneous clustering of QDs. The reconstruction of the 3D nanostructure of the liquid crystal matrix in the areas of homogeneous QDs distribution has shown that QDs do not perturb the periodic planar texture of the cholesteric liquid crystal matrix, whereas QD clusters do perturb it. The combined microspectroscopy-nanotomography technique will be important for evaluating the effects of nanoparticles on the structural organization of organic and liquid crystal matrices and biomedical materials, as well as quality control of nanotechnology fabrication processes and products. PMID:23991901

  13. Designing and building a permanent magnet Zeeman slower for calcium atoms using a 3D printer

    NASA Astrophysics Data System (ADS)

    Parsagian, Alexandria; Kleinert, Michaela

    2015-10-01

    We present the design of a Zeeman slower for calcium atoms using permanent magnets instead of more traditional electromagnets and the novel technique of 3D printing to create a very robust and flexible structure for these magnets. Zeeman slowers are ideal tools to slow atoms from several hundreds of meters per second to just a few tens of meters per second. These slower atoms can then easily be trapped in a magneto-optical trap, making Zeeman slowers a very valuable tool in many cold atom labs. The use of permanent magnets and 3D printing results in a highly stable and robust slower that is suitable for undergraduate laboratories. In our design, we arranged 28 magnet pairs, 2.0 cm apart along the axis of the slower and at varying radial distances from the axis. We determined the radial position of the magnets by simulating the combined field of all magnet pairs using Mathematica and comparing it to the ideal theoretical field for a Zeeman slower. Finally, we designed a stable, robust, compact, and easy-to-align mounting structure for the magnets in Google Sketchup, which we then printed using a commercially available 3D printer by Solidoodle. The resulting magnetic field is well suited to slow calcium atoms from the 770 m/s rms velocity at a temperature of 950 K, down to the capture velocity of the magneto-optical trap.

  14. Atomically thin layered NiFe double hydroxides assembled 3D microspheres with promoted electrochemical performances

    NASA Astrophysics Data System (ADS)

    Li, Xiaomin; Zai, Jiantao; Liu, Yuanyuan; He, Xiaobo; Xiang, Shijie; Ma, Zifeng; Qian, Xuefeng

    2016-09-01

    LDHs in atomic thickness (mono-/bi-layers) usually exhibit novel physicochemical properties, especially in surface-dependent energy storage and catalysis areas. However, the thickness of the commonly reported 2D LDHs is in nanoscale and the bottom-up synthesis of atomically thin LDHs is rarely reported. Herein, high-quality atomically thin layered NiFe-LDHs assembled 3D microspheres were synthesized via a rational designed reaction system, where the formation of atomically thin building blocks was controlled by the synergetic effects of released carbonate anions and butanol. Furthermore, the complexant and solvents played important effects on the process of coprecipitation and the assembling of LDHs. Due to the nature of atomically thin LDHs nanosheets and unique 3D hierarchical structures, the obtained microspheres exhibited excellent electrocatalytic oxygen evolution reaction (OER) activity in alkaline medium with an onset overpotential (0.435 V, which is lower than that of common LDHs) and good durability. The as-prepared 3D NiFe-LDHs microspheres were also firstly used as supercapacitor materials and displayed a high specific capacitance of 1061 F g-1 at the current density of 1 A g-1.

  15. Universal gates based on targeted phase shifts in a 3D neutral atom array

    NASA Astrophysics Data System (ADS)

    Kumar, Aishwarya; Wang, Yang; Wu, Tsung-Yao; Weiss, David

    2016-05-01

    We demonstrate a new approach to making targeted single qubit gates using Cesium atoms in a 5x5x5 3D neutral atom array. It combines targeted AC Zeeman phase shifts with global microwave pulses to produce arbitrary single qubit gates. Non-targeted atoms are left virtually untouched by the gates. We have addressed 48 sites, targeted individually, in a 40% full array. We have also performed Randomized Benchmarking to characterize the fidelity and crosstalk errors of this gate. These gates are highly insensitive to addressing beam imperfections and can be applied to other systems and geometries. Supported by NSF.

  16. Elucidating the higher-order structure of biopolymers by structural probing and mass spectrometry: MS3D

    PubMed Central

    Fabris, Daniele; Yu, Eizadora T.

    2010-01-01

    Chemical probing represents a very versatile alternative for studying the structure and dynamics of substrates that are intractable by established high-resolution techniques. The implementation of MS-based strategies for the characterization of probing products has not only extended the range of applicability to virtually all types of biopolymers, but has also paved the way for the introduction of new reagents that would not have been viable with traditional analytical platforms. As the availability of probing data is steadily increasing on the wings of the development of dedicated interpretation aids, powerful computational approaches have been explored to enable the effective utilization of such information to generate valid molecular models. This combination of factors has contributed to making the possibility of obtaining actual 3D structures by MS-based technologies (MS3D) a reality. Although approaches for achieving structure determination of unknown substrates or assessing the dynamics of known structures may share similar reagents and development trajectories, they clearly involve distinctive experimental strategies, analytical concerns, and interpretation paradigms. This Perspective offers a commentary on methods aimed at obtaining distance constraints for the modeling of full-fledged structures, while highlighting common elements, salient distinctions, and complementary capabilities exhibited by methods employed in dynamics studies. We discuss critical factors to be addressed for completing effective structural determinations and expose possible pitfalls of chemical methods. We survey programs developed for facilitating the interpretation of experimental data and discuss possible computational strategies for translating sparse spatial constraints into all-atom models. Examples are provided to illustrate how the concerted application of very diverse probing techniques can lead to the solution of actual biological substrates. PMID:20648672

  17. Fully analytical integration over the 3D volume bounded by the β sphere in topological atoms.

    PubMed

    Popelier, Paul L A

    2011-11-17

    Atomic properties of a topological atom are obtained by 3D integration over the volume of its atomic basin. Algorithms that compute atomic properties typically integrate over two subspaces: the volume bounded by the so-called β sphere, which is centered at the nucleus and completely contained within the atomic basin, and the volume of the remaining part of the basin. Here we show how the usual quadrature over the β sphere volume can be replaced by a fully analytical 3D integration leading to the atomic charge (monopole moment) for s, p, and d functions. Spherical tensor multipole moments have also been implemented and tested up to hexadecupole for s functions only, and up to quadrupole for s and p functions. The new algorithm is illustrated by operating on capped glycine (HF/6-31G, 35 molecular orbitals (MOs), 322 Gaussian primitives, 19 nuclei), the protein crambin (HF/3-21G, 1260 MOs, 5922 primitives and 642 nuclei), and tin (Z = 50) in Sn(2)(CH(3))(2) (B3LYP/cc-pVTZ and LANL2DZ, 59 MOs, 1352 primitives).

  18. Ultraprecision micro-CMM using a low force 3D touch probe

    NASA Astrophysics Data System (ADS)

    Küng, A.; Meli, F.; Thalmann, R.

    2007-02-01

    METAS developed a new 3D coordinate measuring machine (CMM) dedicated to traceable measurement for small parts with nanometre accuracy. The innovative design of the touch probe is based on a parallel kinematic structure of flexure hinges in order to minimize the moving mass and ensure an isotropic low stiffness. This head features very weak probing forces, below 0.5 mN, and supports exchangeable probes down to 0.1 mm diameter. It was combined with a highly accurate positioning stage developed at Philips CFT. The machine features a 90 mm × 90 mm × 38 mm air bearing stage with interferometric position measurement with no Abbe offset. The relevant calibration measurements reported here proudly highlight a repeatability of about 5 nm achieved by our micro-CMM. At the reached level of precision, the shape deviation of the probing sphere becomes a major contribution to the uncertainty. Therefore a calibration method for spheres based on error separation techniques was implemented. The result of roundness measurements on three calibration spheres is also presented. In addition, a scanning measurement procedure was implemented without any loss of accuracy, as attested by a comparison using a roundness measuring machine.

  19. The Relationship Between Human Nucleolar Organizer Regions and Nucleoli, Probed by 3D-ImmunoFISH.

    PubMed

    van Sluis, Marjolein; van Vuuren, Chelly; McStay, Brian

    2016-01-01

    3D-immunoFISH is a valuable technique to compare the localization of DNA sequences and proteins in cells where three-dimensional structure has been preserved. As nucleoli contain a multitude of protein factors dedicated to ribosome biogenesis and form around specific chromosomal loci, 3D-immunoFISH is a particularly relevant technique for their study. In human cells, nucleoli form around transcriptionally active ribosomal gene (rDNA) arrays termed nucleolar organizer regions (NORs) positioned on the p-arms of each of the acrocentric chromosomes. Here, we provide a protocol for fixing and permeabilizing human cells grown on microscope slides such that nucleolar proteins can be visualized using antibodies and NORs visualized by DNA FISH. Antibodies against UBF recognize transcriptionally active rDNA/NORs and NOP52 antibodies provide a convenient way of visualizing the nucleolar volume. We describe a probe designed to visualize rDNA and introduce a probe comprised of NOR distal sequences, which can be used to identify or count individual NORs. PMID:27576706

  20. Single qubit gates on neutral atoms in a 3d Optical lattice

    NASA Astrophysics Data System (ADS)

    Kumar, Aishwarya; Wang, Yang; Zhang, Xianli; Corcovilos, Theodore A.; Weiss, David S.

    2015-05-01

    Neutral atoms are especially promising candidates for quantum computing because of their inherent scalability. To realize this scalability requires being able to manipulate the quantum information at target qubits with high fidelity and low crosstalk. We will present two single qubit gate addressing protocols. We have experimentally applied them both to targeted sites in a 5 × 5 × 5 3D array. The two distinct approaches both use crossed MEMS-mirror directed addressing beams along with microwave pulses to target atoms at single sites, while having minimal impact on the quantum information at non-target sites. Supported by DARPA, QUEST and ARO.

  1. All-atom 3D structure prediction of transmembrane β-barrel proteins from sequences

    PubMed Central

    Hayat, Sikander; Sander, Chris; Marks, Debora S.

    2015-01-01

    Transmembrane β-barrels (TMBs) carry out major functions in substrate transport and protein biogenesis but experimental determination of their 3D structure is challenging. Encouraged by successful de novo 3D structure prediction of globular and α-helical membrane proteins from sequence alignments alone, we developed an approach to predict the 3D structure of TMBs. The approach combines the maximum-entropy evolutionary coupling method for predicting residue contacts (EVfold) with a machine-learning approach (boctopus2) for predicting β-strands in the barrel. In a blinded test for 19 TMB proteins of known structure that have a sufficient number of diverse homologous sequences available, this combined method (EVfold_bb) predicts hydrogen-bonded residue pairs between adjacent β-strands at an accuracy of ∼70%. This accuracy is sufficient for the generation of all-atom 3D models. In the transmembrane barrel region, the average 3D structure accuracy [template-modeling (TM) score] of top-ranked models is 0.54 (ranging from 0.36 to 0.85), with a higher (44%) number of residue pairs in correct strand–strand registration than in earlier methods (18%). Although the nonbarrel regions are predicted less accurately overall, the evolutionary couplings identify some highly constrained loop residues and, for FecA protein, the barrel including the structure of a plug domain can be accurately modeled (TM score = 0.68). Lower prediction accuracy tends to be associated with insufficient sequence information and we therefore expect increasing numbers of β-barrel families to become accessible to accurate 3D structure prediction as the number of available sequences increases. PMID:25858953

  2. Development of 3D touch trigger probe with real-time observation

    NASA Astrophysics Data System (ADS)

    Chu, Chih-Liang; Wu, Cheng-Yu

    2010-08-01

    This study aims at inventing a low-price but high-precision 3D touch trigger probe (or a CMM probe). The tip ball of the stylus, with a diameter smaller than 100 μm, is made by a micro electro discharge machine and wire electro discharge grinding. The stylus is mounted at the centre of a stiff cross-form frame, which in turn is suspended on four micro beams. As proven by several experiments, this structure restricts the degrees of freedom on three directions. The displacement sensor and 2D angle sensor is performed using modified commercial DVD pickup heads to measure the three degrees of motional freedom on the suspension structure. As for application, since the tip ball is difficult to identify by naked eye, we use modified commercial webcam and microscope to create a micro imaging system. This imaging system has been tested to have 2.8mmx2.1mm field of view, and 1.5mm depth of field.

  3. Population of the three major exit channels in the 3d resonance region of atomic gallium

    SciTech Connect

    Krause, M.O.; Cerrina, F.; Fahlman, A.

    1983-04-11

    The exit channels in the region of the 3d..-->..4p resonance of atomic gallium were determined in a photoemission experiment. The population of the three major channels involving 4p and 4s electrons was measured by the constant-ionic-state method for twenty resonant states between 18.8 and 21.7 eV, and the angular distribution of the emitted electrons was obtained. As a result, an autoionization case in which many resonances and many continua are coupled has been characterized in the most comprehensive experiment to date.

  4. Atom probe trajectory mapping using experimental tip shape measurements.

    PubMed

    Haley, D; Petersen, T; Ringer, S P; Smith, G D W

    2011-11-01

    Atom probe tomography is an accurate analytical and imaging technique which can reconstruct the complex structure and composition of a specimen in three dimensions. Despite providing locally high spatial resolution, atom probe tomography suffers from global distortions due to a complex projection function between the specimen and detector which is different for each experiment and can change during a single run. To aid characterization of this projection function, this work demonstrates a method for the reverse projection of ions from an arbitrary projection surface in 3D space back to an atom probe tomography specimen surface. Experimental data from transmission electron microscopy tilt tomography are combined with point cloud surface reconstruction algorithms and finite element modelling to generate a mapping back to the original tip surface in a physically and experimentally motivated manner. As a case study, aluminium tips are imaged using transmission electron microscopy before and after atom probe tomography, and the specimen profiles used as input in surface reconstruction methods. This reconstruction method is a general procedure that can be used to generate mappings between a selected surface and a known tip shape using numerical solutions to the electrostatic equation, with quantitative solutions to the projection problem readily achievable in tens of minutes on a contemporary workstation.

  5. Atom probe trajectory mapping using experimental tip shape measurements.

    PubMed

    Haley, D; Petersen, T; Ringer, S P; Smith, G D W

    2011-11-01

    Atom probe tomography is an accurate analytical and imaging technique which can reconstruct the complex structure and composition of a specimen in three dimensions. Despite providing locally high spatial resolution, atom probe tomography suffers from global distortions due to a complex projection function between the specimen and detector which is different for each experiment and can change during a single run. To aid characterization of this projection function, this work demonstrates a method for the reverse projection of ions from an arbitrary projection surface in 3D space back to an atom probe tomography specimen surface. Experimental data from transmission electron microscopy tilt tomography are combined with point cloud surface reconstruction algorithms and finite element modelling to generate a mapping back to the original tip surface in a physically and experimentally motivated manner. As a case study, aluminium tips are imaged using transmission electron microscopy before and after atom probe tomography, and the specimen profiles used as input in surface reconstruction methods. This reconstruction method is a general procedure that can be used to generate mappings between a selected surface and a known tip shape using numerical solutions to the electrostatic equation, with quantitative solutions to the projection problem readily achievable in tens of minutes on a contemporary workstation. PMID:22004277

  6. Interaction of 3d transition metal atoms with charged ion projectiles from Electron Nuclear Dynamics computation

    NASA Astrophysics Data System (ADS)

    Hagelberg, Frank

    2003-03-01

    Computational results on atomic scattering between charged projectiles and transition metal target atoms are presented. This work aims at obtaining detailed information about charge, spin and energy transfer processes that occur between the interacting particles. An in-depth understanding of these phenomena is expected to provide a theoretical basis for the interpretation of various types of ion beam experiments, ranging from gas phase chromatography to spectroscopic observations of fast ions in ferromagnetic media. This contribution focuses on the scattering of light projectiles ranging from He to O, that are prepared in various initial charge states, by 3d transition metal atoms. The presented computations are performed in the framework of Electron Nuclear Dynamics (END)^1 theory which incorporates the coupling between electronic and nuclear degrees of freedom without reliance on the computationally cumbersome and frequently intractable determination of potential energy surfaces. In the present application of END theory to ion - transition metal atom scattering, a supermolecule approach is utilized in conjunction with a spin-unrestricted single determinantal wave function describing the electronic system. Integral scattering, charge and spin exchange cross sections are discussed as functions of the elementary parameters of the problem, such as projectile and target atomic numbers as well as projectile charge and initial kinetic energy. ^1 E.Deumens, A.Diz, R.Longo, Y.Oehrn, Rev.Mod.Phys. 66, 917 (1994)

  7. Reconstructing atom probe data: a review.

    PubMed

    Vurpillot, Francois; Gault, Baptiste; Geiser, Brian P; Larson, D J

    2013-09-01

    Atom probe tomography stands out from other materials characterisation techniques mostly due to its capacity to map individual atoms in three-dimensions with high spatial resolution. The methods used to transform raw detector data into a three-dimensional reconstruction have, comparatively to other aspects of the technique, evolved relatively little since their inception more than 15 years ago. However, due to the importance of the fidelity of the data, this topic is currently attracting a lot of interest within the atom probe community. In this review we cover: (1) the main aspects of the image projection, (2) the methods used to build tomographic reconstructions, (3) the intrinsic limitations of these methods, and (4) future potential directions to improve the integrity of atom probe tomograms.

  8. Barrier-free subsurface incorporation of 3d metal atoms into Bi(111) films

    DOE PAGES

    Klein, C.; Vollmers, N. J.; Gerstmann, U.; Zahl, P.; Lukermann, D.; Jnawali, G.; Pfnur, H.; Sutter, P.; Tegenkamp, C.; Schmidt, W. G.; et al

    2015-05-27

    By combining scanning tunneling microscopy with density functional theory it is shown that the Bi(111) surface provides a well-defined incorporation site in the first bilayer that traps highly coordinating atoms such as transition metals (TMs) or noble metals. All deposited atoms assume exactly the same specific sevenfold coordinated subsurface interstitial site while the surface topography remains nearly unchanged. Notably, 3d TMs show a barrier-free incorporation. The observed surface modification by barrier-free subsorption helps to suppress aggregation in clusters. Thus, it allows a tuning of the electronic properties not only for the pure Bi(111) surface, but may also be observed formore » topological insulators formed by substrate-stabilized Bi bilayers.« less

  9. A 3D fiber probe based on orthogonal micro focal-length collimation and fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Cui, Jiwen; Li, Junying; Feng, Kunpeng; Tan, Jiubin; Zhang, Jian

    2016-07-01

    A 3D fiber probe is proposed for the precision measurement of micro parts with high aspect ratios. The probing system consists of two measuring systems: two mutually orthogonal micro focal-length collimation optical paths for the radial tactile probing measurement, and a matched fiber Bragg grating (FBG) pair interrogation system for the axial tactile probing measurement. The fiber probe consists of a fiber stylus and a probe tip, the fiber stylus works as a micro focal-length cylindrical lens, and the FBG inscribed in the fiber stylus works as a measuring FBG. The radial displacement of the probe tip is transformed into the centroid position shift of the two mutually orthogonal micro focal-length collimation optical paths; the axial displacement of the probe tip is transformed into the power ratio change of the matched FBG pair interrogation system. Experimental results indicate that the probe has a radial sensitivity of 71 pixel μm‑1 in both X and Y directions, and an axial sensitivity of 4.9% μm‑1 in Z direction; the probe can reach a radial resolution of 5 nm, and an axial resolution of 8 nm. The probe has a capability of decoupling the 3D tactility and it can be applied in the measurement of micro parts.

  10. First-principles calculations of the interaction between hydrogen and 3d alloying atom in nickel

    NASA Astrophysics Data System (ADS)

    Liu, Wenguan; Qian, Yuan; Zhang, Dongxun; Liu, Wei; Han, Han

    2015-10-01

    Knowledge of the behavior of hydrogen (H) in Ni-based alloy is essential for the prediction of Tritium behavior in Molten Salt Reactor. First-principles calculations were performed to investigate the interaction between H and 3d transition metal (TM) alloying atom in Ni-based alloy. H prefers the octahedral interstitial site to the tetrahedral interstitial site energetically. Most of the 3d TM elements (except Zn) attract H. The attraction to H in the Ni-TM-H system can be mainly attributed to the differences in electronegativity. With the large electronegativity, H and Ni gain electrons from the other TM elements, resulting in the enhanced Ni-H bonds which are the source of the attraction to H in the Ni-TM-H system. The obviously covalent-like Cr-H and Co-H bindings are also beneficial to the attraction to H. On the other hand, the repulsion to H in the Ni-Zn-H system is due to the stable electronic configuration of Zn. We mainly utilize the results calculated in 32-atom supercell which corresponds to the case of a relatively high concentration of hydrogen. Our results are in good agreement with the experimental ones.

  11. Study of a vibrating fiber probing system for 3-D micro-structures: performance improvement

    NASA Astrophysics Data System (ADS)

    Murakami, H.; Katsuki, A.; Sajima, T.; Suematsu, T.

    2014-09-01

    This paper presents a system for measuring 3D micro-structures that uses an optical fiber probe equipped with a piezo element that causes the probe to vibrate. The optical fiber probe consists of a stylus shaft with a diameter of 3 µm and a glass ball with a diameter of 5 µm attached to the tip. The stylus is vibrated in a circular motion in a single plane. The vibrator mechanism is introduced to prevent adhesion of the stylus tip to the surface being measured. This adhesion, which adversely affects the accuracy and time of the measurement, is caused by intermolecular, electrostatic, and liquid bridge forces. The measuring principle involves monitoring the vibrational amplitude of the stylus shaft that is required to prevent the adhesion of the stylus tip to the surface being measured, this amplitude being measured optically. In our previous report (Murakami et al 2012 Key Eng. Mater. 523-524 907-12), we found that the stylus shaft actually moves in an elliptical motion when it is set to describe a circular motion in the X-Y plane. Therefore, when a measurement is taken, it is necessary to adjust the motion of the piezoelectric tube to compensate for the difference between the diameter of the perfect circle and the actual elliptical motion of the stylus shaft displacement. In this study, the stylus characteristics were examined and the motion of the stylus shaft was then corrected to attain the desired circular motion. Next, the expansion of the measuring area by using a line laser was investigated. Finally, an experiment involving the measurement of a micro-hole was performed to demonstrate the practicality of the vibrating fiber probe. As a result, it was shown that the displacement between the diameter of the perfect circle and the actual elliptical motion of the stylus tip was about 0.034 µm after compensation. In addition, it was confirmed that the measurement area can be expanded by using an optical slit, but the standard deviation of the

  12. Hand-eye calibration of a robot--UltraSound probe system without any 3D localizers.

    PubMed

    Sarrazin, Johan; Promayon, Emmanuel; Baumann, Michael; Troccaz, Jocelyne

    2015-01-01

    3D UltraSound (US) probes are used in clinical applications for their ease of use and ability to obtain intra-operative volumes. In surgical navigation applications a calibration step is needed to localize the probe in a general coordinate system. This paper presents a new hand-eye calibration method using directly the kinematic model of a robot and US volume registration data that does not require any 3D localizers. First results show a targeting error of 2.34 mm on an experimental setup using manual segmentation of five beads in ten US volumes. PMID:26736191

  13. Hand-eye calibration of a robot--UltraSound probe system without any 3D localizers.

    PubMed

    Sarrazin, Johan; Promayon, Emmanuel; Baumann, Michael; Troccaz, Jocelyne

    2015-01-01

    3D UltraSound (US) probes are used in clinical applications for their ease of use and ability to obtain intra-operative volumes. In surgical navigation applications a calibration step is needed to localize the probe in a general coordinate system. This paper presents a new hand-eye calibration method using directly the kinematic model of a robot and US volume registration data that does not require any 3D localizers. First results show a targeting error of 2.34 mm on an experimental setup using manual segmentation of five beads in ten US volumes.

  14. Optical probing of cold trapped atoms

    NASA Technical Reports Server (NTRS)

    Fox, R. W.; Gilbert, S. L.; Hollberg, L.; Marquardt, J. H.; Robinson, H. G.

    1993-01-01

    Transitions between excited states of laser-cooled and laser-trapped rubidium and cesium atoms are probed by use of fiber and diode lasers. High-resolution Doppler-free spectra are detected by observation of the absorption and fluorescence of light from the intermediate level of two-step cascade systems. The optical double-resonance spectra show Autler-Townes splitting in the weak probe limit and more complicated spectra for a strongly coupled three-level system.

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

    PubMed

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

    2015-12-01

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

  16. Room temperature strong light-matter coupling in 3D THz meta-atoms (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Paulillo, Bruno; Manceau, Jean-Michel; Li, Lianhe; Linfield, Edmund; Colombelli, Raffaele

    2016-04-01

    We demonstrate strong light-matter coupling at room temperature in the terahertz (THz) spectral region using 3D meta-atoms with extremely sub-wavelength volumes. Using an air-bridge fabrication scheme, we have implemented sub-wavelength 3D THz micro-resonators that rely on suspended loop antennas connected to semiconductor-filled patch cavities. We have experimentally shown that they possess the functionalities of lumped LC resonators: their frequency response can be adjusted by independently tuning the inductance associated the antenna element or the capacitance provided by the metal-semiconductor-metal cavity. Moreover, the radiation coupling and efficiency can be engineered acting on the design of the loop antenna, similarly to conventional RF antennas. Here we take advantage of this rich playground in the context of cavity electrodynamics/intersubband polaritonics. In the strong light-matter coupling regime, a cavity and a two-level system exchange energy coherently at a characteristic rate called the vacuum Rabi frequency ΩR which is dominant with respect to all other loss mechanisms involved. The signature, in the frequency domain, is the appearance of a splitting between the bare cavity and material system resonances: the new states are called upper and a lower polariton branches. So far, most experimental demonstrations of strong light-matter interaction between an intersubband transition and a deeply sub-wavelength mode in the THz or mid-infrared ranges rely on wavelength-scale or larger resonators such as photonic crystals, diffractive gratings, dielectric micro-cavities or patch cavities. Lately, planar metamaterials have been used to enhance the light-matter interaction and strongly reduce the interaction volume by engineering the electric and magnetic resonances of the individual subwavelength constituents. In this contribution we provide evidence of strong coupling between a THz intersubband transition and an extremely sub-wavelength mode (≈λ/10

  17. Modeling Atom Probe Tomography: A review.

    PubMed

    Vurpillot, F; Oberdorfer, C

    2015-12-01

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

  18. Electron crystallography of ultrathin 3D protein crystals: atomic model with charges.

    PubMed

    Yonekura, Koji; Kato, Kazuyuki; Ogasawara, Mitsuo; Tomita, Masahiro; Toyoshima, Chikashi

    2015-03-17

    Membrane proteins and macromolecular complexes often yield crystals too small or too thin for even the modern synchrotron X-ray beam. Electron crystallography could provide a powerful means for structure determination with such undersized crystals, as protein atoms diffract electrons four to five orders of magnitude more strongly than they do X-rays. Furthermore, as electron crystallography yields Coulomb potential maps rather than electron density maps, it could provide a unique method to visualize the charged states of amino acid residues and metals. Here we describe an attempt to develop a methodology for electron crystallography of ultrathin (only a few layers thick) 3D protein crystals and present the Coulomb potential maps at 3.4-Å and 3.2-Å resolution, respectively, obtained from Ca(2+)-ATPase and catalase crystals. These maps demonstrate that it is indeed possible to build atomic models from such crystals and even to determine the charged states of amino acid residues in the Ca(2+)-binding sites of Ca(2+)-ATPase and that of the iron atom in the heme in catalase.

  19. Gradient-echo 3D imaging of Rb polarization in fiber-coupled atomic magnetometer.

    PubMed

    Savukov, I

    2015-07-01

    The analogy between atomic and nuclear spins is exploited to implement 3D imaging of polarization inside the cell of an atomic magnetometer. The resolution of 0.8mm×1.2mm×1.4mm has been demonstrated with the gradient-echo imaging method. The imaging can be used in many applications. One such an application is the evaluation of active volume of an atomic magnetometer for sensitivity analysis and optimization. It has been found that imaging resolution is limited due to de-phasing from spin-exchange collisions and diffusion in the presence of gradients, and for a given magnetometer operational parameters, the imaging sequence has been optimized. Diffusion decay of the signal in the presence of gradients has been modeled numerically and analytically, and the analytical results, which agreed with numerical simulations, have been used to fit the spin-echo gradient measurements to extract the diffusion coefficient. The diffusion coefficient was found in agreement with previous measurements.

  20. Electron crystallography of ultrathin 3D protein crystals: Atomic model with charges

    PubMed Central

    Yonekura, Koji; Kato, Kazuyuki; Ogasawara, Mitsuo; Tomita, Masahiro; Toyoshima, Chikashi

    2015-01-01

    Membrane proteins and macromolecular complexes often yield crystals too small or too thin for even the modern synchrotron X-ray beam. Electron crystallography could provide a powerful means for structure determination with such undersized crystals, as protein atoms diffract electrons four to five orders of magnitude more strongly than they do X-rays. Furthermore, as electron crystallography yields Coulomb potential maps rather than electron density maps, it could provide a unique method to visualize the charged states of amino acid residues and metals. Here we describe an attempt to develop a methodology for electron crystallography of ultrathin (only a few layers thick) 3D protein crystals and present the Coulomb potential maps at 3.4-Å and 3.2-Å resolution, respectively, obtained from Ca2+-ATPase and catalase crystals. These maps demonstrate that it is indeed possible to build atomic models from such crystals and even to determine the charged states of amino acid residues in the Ca2+-binding sites of Ca2+-ATPase and that of the iron atom in the heme in catalase. PMID:25730881

  1. Closed-loop high-speed 3D thermal probe nanolithography

    NASA Astrophysics Data System (ADS)

    Knoll, A. W.; Zientek, M.; Cheong, L. L.; Rawlings, C.; Paul, P.; Holzner, F.; Hedrick, J. L.; Coady, D. J.; Allen, R.; Dürig, U.

    2014-03-01

    Thermal Scanning Probe Lithography (tSPL) is an AFM based patterning technique, which uses heated tips to locally evaporate organic resists such as molecular glasses [1] or thermally sensitive polymers.[2][3] Organic resists offer the versatility of the lithography process known from the CMOS environment and simultaneously ensure a highly stable and low wear tip-sample contact due to the soft nature of the resists. Patterning quality is excellent up to a resolution of sub 15 nm,[1] at linear speeds of up to 20 mm/s and pixel rates of up to 500 kHz.[4] The patterning depth is proportional to the applied force which allows for the creation of 3-D profiles in a single patterning run.[2] In addition, non-destructive imaging can be done at pixel rates of more than 500 kHz.[4] If the thermal stimulus for writing the pattern is switched off the same tip can be used to record the written topography with Angstrom depth resolution. We utilize this unique feature of SPL to implement an efficient control system for reliable patterning at high speed and high resolution. We combine the writing and imaging process in a single raster scan of the surface. In this closed loop lithography (CLL) approach, we use the acquired data to optimize the writing parameters on the fly. Excellent control is in particular important for an accurate reproduction of complex 3D patterns. These novel patterning capabilities are equally important for a high quality transfer of two-dimensional patterns into the underlying substrate. We utilize an only 3-4 nm thick SiOx hardmask to amplify the 8±0.5 nm deep patterns created by tSPL into a 50 nm thick transfer polymer. The structures in the transfer polymer can be used to create metallic lines by a lift-off process or to further process the pattern into the substrate. Here we demonstrate the fabrication of 27 nm wide lines and trenches 60 nm deep into the Silicon substrate.[5] In addition, the combined read and write approach ensures that the lateral

  2. Billion-atom synchronous parallel kinetic Monte Carlo simulations of critical 3D Ising systems

    SciTech Connect

    Martinez, E.; Monasterio, P.R.; Marian, J.

    2011-02-20

    An extension of the synchronous parallel kinetic Monte Carlo (spkMC) algorithm developed by Martinez et al. [J. Comp. Phys. 227 (2008) 3804] to discrete lattices is presented. The method solves the master equation synchronously by recourse to null events that keep all processors' time clocks current in a global sense. Boundary conflicts are resolved by adopting a chessboard decomposition into non-interacting sublattices. We find that the bias introduced by the spatial correlations attendant to the sublattice decomposition is within the standard deviation of serial calculations, which confirms the statistical validity of our algorithm. We have analyzed the parallel efficiency of spkMC and find that it scales consistently with problem size and sublattice partition. We apply the method to the calculation of scale-dependent critical exponents in billion-atom 3D Ising systems, with very good agreement with state-of-the-art multispin simulations.

  3. The Use of Atomic Force Microscopy for 3D Analysis of Nucleic Acid Hybridization on Microarrays

    PubMed Central

    Dubrovin, E. V.; Presnova, G. V.; Rubtsova, M. Yu.; Egorov, A. M.; Grigorenko, V. G.; Yaminsky, I. V.

    2015-01-01

    Oligonucleotide microarrays are considered today to be one of the most efficient methods of gene diagnostics. The capability of atomic force microscopy (AFM) to characterize the three-dimensional morphology of single molecules on a surface allows one to use it as an effective tool for the 3D analysis of a microarray for the detection of nucleic acids. The high resolution of AFM offers ways to decrease the detection threshold of target DNA and increase the signal-to-noise ratio. In this work, we suggest an approach to the evaluation of the results of hybridization of gold nanoparticle-labeled nucleic acids on silicon microarrays based on an AFM analysis of the surface both in air and in liquid which takes into account of their three-dimensional structure. We suggest a quantitative measure of the hybridization results which is based on the fraction of the surface area occupied by the nanoparticles. PMID:26085952

  4. Comparison of different techniques in optical trap for generating picokelvin 3D atom cloud in microgravity

    NASA Astrophysics Data System (ADS)

    Yao, Hepeng; Luan, Tian; Li, Chen; Zhang, Yin; Ma, Zhaoyuan; Chen, Xuzong

    2016-01-01

    Pursuing ultralow temperature 3D atom gas under microgravity conditions is one of the popular topics in the field of ultracold research. Many groups around the world are using, or are planning to use, delta-kick cooling (DKC) in microgravity. Our group has also proposed a two-stage crossed beam cooling (TSCBC) method that also provides a path to picokelvin temperatures. In this paper, we compare the characteristics of TSCBC and DKC for producing a picokelvin system in microgravity. Using a direct simulation Monte Carlo (DSMC) method, we simulate the cooling process of 87Rb using the two different cooling techniques. Under the same initial conditions, 87Rb can reach 7 pK in 15 s using TSCBC and 75 pK in 5.1 s with DKC. The simulation results show that TSCBC can reach lower temperatures compared with DKC, but needs more time and a more stable laser.

  5. C12/C13-ratio determination in nanodiamonds by atom-probe tomography.

    PubMed

    Lewis, Josiah B; Isheim, Dieter; Floss, Christine; Seidman, David N

    2015-12-01

    The astrophysical origins of ∼ 3 nm-diameter meteoritic nanodiamonds can be inferred from the ratio of C12/C13. It is essential to achieve high spatial and mass resolving power and minimize all sources of signal loss in order to obtain statistically significant measurements. We conducted atom-probe tomography on meteoritic nanodiamonds embedded between layers of Pt. We describe sample preparation, atom-probe tomography analysis, 3D reconstruction, and bias correction. We present new data from meteoritic nanodiamonds and terrestrial standards and discuss methods to correct isotopic measurements made with the atom-probe tomograph.

  6. C12/C13-ratio determination in nanodiamonds by atom-probe tomography.

    PubMed

    Lewis, Josiah B; Isheim, Dieter; Floss, Christine; Seidman, David N

    2015-12-01

    The astrophysical origins of ∼ 3 nm-diameter meteoritic nanodiamonds can be inferred from the ratio of C12/C13. It is essential to achieve high spatial and mass resolving power and minimize all sources of signal loss in order to obtain statistically significant measurements. We conducted atom-probe tomography on meteoritic nanodiamonds embedded between layers of Pt. We describe sample preparation, atom-probe tomography analysis, 3D reconstruction, and bias correction. We present new data from meteoritic nanodiamonds and terrestrial standards and discuss methods to correct isotopic measurements made with the atom-probe tomograph. PMID:26095824

  7. Creating and probing coherent atomic states

    SciTech Connect

    Reinhold, C.O.; Burgdoerfer, J. |; Frey, M.T.; Dunning, F.B.

    1997-06-01

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

  8. Pragmatic reconstruction methods in atom probe tomography.

    PubMed

    Vurpillot, F; Gruber, M; Da Costa, G; Martin, I; Renaud, L; Bostel, A

    2011-07-01

    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.

  9. Accurate nonrelativistic ground-state energies of 3d transition metal atoms

    SciTech Connect

    Scemama, A.; Applencourt, T.; Giner, E.; Caffarel, M.

    2014-12-28

    We present accurate nonrelativistic ground-state energies of the transition metal atoms of the 3d series calculated with Fixed-Node Diffusion Monte Carlo (FN-DMC). Selected multi-determinantal expansions obtained with the CIPSI (Configuration Interaction using a Perturbative Selection made Iteratively) method and including the most prominent determinants of the full configuration interaction expansion are used as trial wavefunctions. Using a maximum of a few tens of thousands determinants, fixed-node errors on total DMC energies are found to be greatly reduced for some atoms with respect to those obtained with Hartree-Fock nodes. To the best of our knowledge, the FN-DMC/(CIPSI nodes) ground-state energies presented here are the lowest variational total energies reported so far. They differ from the recently recommended non-variational values of McCarthy and Thakkar [J. Chem. Phys. 136, 054107 (2012)] only by a few percents of the correlation energy. Thanks to the variational property of FN-DMC total energies, our results provide exact lower bounds for the absolute value of all-electron correlation energies, |E{sub c}|.

  10. An analogue contact probe using a compact 3D optical sensor for micro/nano coordinate measuring machines

    NASA Astrophysics Data System (ADS)

    Li, Rui-Jun; Fan, Kuang-Chao; Miao, Jin-Wei; Huang, Qiang-Xian; Tao, Sheng; Gong, Er-min

    2014-09-01

    This paper presents a new analogue contact probe based on a compact 3D optical sensor with high precision. The sensor comprises an autocollimator and a polarizing Michelson interferometer, which can detect two angles and one displacement of the plane mirror at the same time. In this probe system, a tungsten stylus with a ruby tip-ball is attached to a floating plate, which is supported by four V-shape leaf springs fixed to the outer case. When a contact force is applied to the tip, the leaf springs will experience elastic deformation and the plane mirror mounted on the floating plate will be displaced. The force-motion characteristics of this probe were investigated and optimum parameters were obtained with the constraint of allowable physical size of the probe. Simulation results show that the probe is uniform in 3D and its contacting force gradient is within 1 mN µm - 1. Experimental results indicate that the probe has 1 nm resolution,  ± 10 µm measuring range in X - Y plane, 10 µm measuring range in Z direction and within 30 nm measuring standard deviation. The feasibility of the probe has been preliminarily verified by testing the flatness and step height of high precision gauge blocks.

  11. Modeling STM tips by single absorbed atoms on W(100) films: 3d and 4d transition-metal atoms

    NASA Astrophysics Data System (ADS)

    Hofer, W. A.; Redinger, J.; Podloucky, R.

    2001-09-01

    In order to provide comprehensive data on the electronic structure of realistic STM tips we have studied tungsten (100) films with adsorbed single 3d and 4d transition-metal atoms by ab initio molecular-dynamics and full potential methods. Molecular dynamics using ultrasoft pseudopotentials has been used to determine the relaxation of adsorbate and surface layers. Subsequently the electronic structure of the relaxed model tip has been calculated with an all-electron full potential method. The results suggest that the chemical nature of the tip apex to a high degree determines achievable corrugations and that results for current and corrugation values in a perturbation approach might be considerably improved by including the electronic structure of the tip.

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

    PubMed

    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.

  13. New developments at PTB in 3D-AFM with tapping and torsion AFM mode and vector approach probing strategy

    NASA Astrophysics Data System (ADS)

    Dai, G.; Hässler-Grohne, W.; Hüser, D.; Wolff, H.; Fluegge, J.; Bosse, H.

    2011-06-01

    A new 3D-AFM for true 3D measurements of nano structures has been developed at Physikalisch Technische-Bundesanstalt, the national metrology institute of Germany. In its configuration, two piezo actuators are applied to drive the AFM cantilever near its vertical and torsional resonant frequencies. In such a way, the AFM tip can probe the surface with a vertical and/or a lateral oscillation, offering high 3D probing sensitivity. For enhancing measurement flexibility as well as reducing tip wear, a so called "vector approach probing" (VAP) method has been applied. The sample is measured point by point using this method. At each probing point, the tip is approached towards the surface in its normal direction until the desired tip-sample interaction is detected and then immediately withdrawn from the surface. Preliminary experimental results show promising performance of the developed system. The measurement of a line structure of 800 nm height employing a super sharp AFM tip is performed, showing a repeatability of its 3D profiles of better than 1 nm (p-v). A single crystal critical dimension reference material (SCCDRM) having features with almost vertical sidewall is measured using a flared AFM tip. Results show that the feature has averaged left and right sidewall angles of 88.64° and 88.67deg;, respectively. However, the feature width non-uniformity may reach 10 nm within the measurement range of 1 μm. The standard deviation of the averaged middle CD values of 7 repeated measurements reaches 0.35 nm. In addition, an investigation of long term measurement stability is performed on a PTB photomask. The results shows that the 3D-AFM has a drift rate of about 0.00033 nm per line, which confirms the high measurement stability and the very low tip wear.

  14. 3D Visualization of Solar Data: Preparing for Solar Orbiter and Solar Probe Plus

    NASA Astrophysics Data System (ADS)

    Mueller, D.; Felix, S.; Meier, S.; Csillaghy, A.; Nicula, B.; Verstringe, F.; Bourgoignie, B.; Berghmans, D.; Jiggens, P.

    2014-12-01

    The next generation of ESA/NASA heliophysics missions, Solar Orbiter and Solar Probe Plus, will focus on exploring the linkage between the Sun and the heliosphere. These new missions will collect unique data that will allow us to study, e.g., the coupling between macroscopic physical processes to those on kinetic scales, the generation of solar energetic particles and their propagation into the heliosphere and the origin and acceleration of solar wind plasma. Since 2010, NASA's Solar Dynamics Observatory returns 1.4 TB/day of high-resolution solar images, magnetograms and EUV irradiance data. Within a few years, the scientific community will thus have access to petabytes of multi­dimensional remote­sensing and complex in-situ observations from different vantage points, complemented by petabytes of simulation data. Answering overarching science questions like "How do solar transients drive heliospheric variability and space weather?" will only be possible if the community has the necessary tools at hand. As of today, there is an obvious lack of capability to both visualize these data and assimilate them into sophisticated models to advance our knowledge. A key piece needed to bridge the gap between observables, derived quantities like magnetic field extrapolations and model output is a tool to routinely and intuitively visualize large heterogeneous, multidimensional, time­dependent data sets. As of today, the space science community is lacking the means to do this (i) on a routine basis, (ii) for complex multi­dimensional data sets from various instruments and vantage points and (iii) in an extensible and modular way that is open for future improvements and interdisciplinary usage. In this contribution, we will present recent progress in visualizing the Sun and its magnetic field in 3D using the open-source JHelioviewer framework, which is part of the ESA/NASA Helioviewer Project. Among other features, JHelioviewer offers efficient region-of-interest-based data

  15. Probing 3D Collective Cancer Invasion Using Double-Stranded Locked Nucleic Acid Biosensors.

    PubMed

    Dean, Zachary S; Elias, Paul; Jamilpour, Nima; Utzinger, Urs; Wong, Pak Kin

    2016-09-01

    Cancer is a leading cause of death worldwide and metastases are responsible for over 90% of human cancer deaths. There is an urgent need to develop novel therapeutics for suppressing cancer invasion, the initial step of metastasis. Nevertheless, the regulation of cancer invasion is poorly understood due to a paucity of tools for monitoring the invasion process in 3D microenvironments. Here, we report a double-stranded locked nucleic acid (dsLNA) biosensor for investigating 3D collective cancer invasion. By incorporating multiphoton microscopy and the dsLNA biosensor, we perform dynamic single cell gene expression analysis while simultaneously characterizing the biomechanical interaction between the invading sprouts and the extracellular matrix. Gene profiling of invasive leader cells and detached cells suggest distinctive signaling mechanisms involved in collective and individual invasion in the 3D microenvironment. Our results underscore the involvement of Notch signaling in 3D collective cancer invasion, which warrants further investigation toward antimetastasis therapy in the future.

  16. Is a new high-resolution probe better than the standard probe for 3D anal sphincter and levator ani imaging?

    PubMed

    Rostaminia, Ghazaleh; White, Dena; Quiroz, Lieschen; Shobeiri, S Abbas

    2015-04-01

    The aim of our study was to determine the accuracy of a new three-dimensional (3D) endoluminal ultrasound probe in assessing the levator ani muscle and anal sphincter complex. A total of 85 patients who had undergone concurrent 3D endovaginal (EVUS) and 3D endoanal (EAUS) ultrasound with both the standard BK 2052 probe and the new high-definition BK 8838 probes were included. For EVUS volumes, the levator ani deficiency (LAD) scores were calculated for each probe. For the EAUS volumes, any defects in the external anal sphincter (EAS) and the internal anal sphincter (IAS) visualized with each probe were recorded. The 3D volumes were evaluated in a blinded fashion. Appropriate statistics were utilized to assess absolute agreements between each pair of imaging modalities. The mean age of the patient population was 59 years (SD ± 10.76), the mean body mass index (BMI) was 28.36 (SD ± 5.99), and the median parity was 2 (range 1, 7). In all, 93% of the patients were Caucasian, 31% had stage 0 or 1 prolapse, while 59% had stage 2 prolapse. The mean total LAD score obtained on EVUS with the standard and the new probes were 11.49 (SD ± 4.94) and 11.53 (SD ± 5.01), respectively, p = 0.3778. Among the 53 patients who had EAUS with both probes, exact agreement for visualization of EAS and IAS for the standard and the new probes was 83% and 98%, respectively. Both transducers can be used for endovaginal imaging of the levator ani muscles interchangeably. Both transducers can be used for endoanal imaging of anal sphincter complex interchangeably.

  17. Atom-probe for FinFET dopant characterization.

    PubMed

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

    2011-05-01

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

  18. Predicting the Electronic Properties of 3D, Million-atom Semiconductor nanostructure Architectures

    SciTech Connect

    Jack Dongarra; Stanimire Tomov

    2012-03-15

    This final report describes the work done by Jack Dongarra (University Distinguished Professor) and Stanimire Tomov (Research Scientist) related to the DOE project entitled Predicting the Electronic Properties of 3D, Million-Atom Semiconductor Nanostructure Architectures. In this project we addressed the mathematical methodology required to calculate the electronic and transport properties of large nanostructures with comparable accuracy and reliability to that of current ab initio methods. This capability is critical for further developing the field, yet it is missing in all the existing computational methods. Additionally, quantitative comparisons with experiments are often needed for a qualitative understanding of the physics, and for guiding the design of new nanostructures. We focused on the mathematical challenges of the project, in particular on solvers and preconditioners for large scale eigenvalue problems that occur in the computation of electronic states of large nanosystems. Usually, the states of interest lie in the interior of the spectrum and their computation poses great difficulties for existing algorithms. The electronic properties of a semiconductor nanostructure architecture can be predicted/determined by computing its band structure. Of particular importance are the 'band edge states' (electronic states near the energy gap) which can be computed from a properly defined interior eigenvalue problem. Our primary mathematics and computational challenge here has been to develop an efficient solution methodology for finding these interior states for very large systems. Our work has produced excellent results in terms of developing both new and extending current state-of-the-art techniques.

  19. Probing the heliosphere with energetic hydrogen atoms

    NASA Technical Reports Server (NTRS)

    Hsieh, K. C.; Shih, K. L.; Jokipii, J. R.; Grzedzielski, S.

    1992-01-01

    The idea of using energetic neutral atoms (ENAs), produced by charge exchange between energetic ions and ambient neutral atoms, as a diagnostic tool to investigate planetary magnetospheres from a distance has been extended to the investigation of the heliosphere. The paper explores what one can reasonably expect of the heliospheric ENA (HSENA) and what criteria would be imposed on HSENA instruments by concentrating on 10-10 exp 3 keV protons in quiet-time interplanetary space, solar-flare events, corotating interaction regions, and populations have distinctive signatures and that the detection of these particles can reveal energy spatial and propagation of ions in 3D interplanetary space, including the solar-wind termination shock. Such breadth of information could not be gained by in situ means.

  20. Beyond optical molasses: 3D raman sideband cooling of atomic cesium to high phase-space density

    PubMed

    Kerman; Vuletic; Chin; Chu

    2000-01-17

    We demonstrate a simple, general purpose method to cool neutral atoms. A sample containing 3x10(8) cesium atoms prepared in a magneto-optical trap is cooled and simultaneously spin polarized in 10 ms at a density of 1.1x10(11) cm (-3) to a phase space density nlambda(3)(dB) = 1/500, which is almost 3 orders of magnitude higher than attainable in free space with optical molasses. The technique is based on 3D degenerate Raman sideband cooling in optical lattices and remains efficient even at densities where the mean lattice site occupation is close to unity.

  1. High speed 3D endoscopic optical frequency domain imaging probe for lung cancer diagnosis

    NASA Astrophysics Data System (ADS)

    Li, Jianan; Feroldi, Fabio; Mo, Jianhua; Helderman, Frank; de Groot, Mattijs; de Boer, Johannes F.

    2013-06-01

    We present a miniature motorized endoscopic probe for Optical Frequency Domain Imaging with an outer diameter of 1.65 mm and a rotation speed of 3,000 - 12,500 rpm. The probe has a motorized distal end which provides a significant advantage over proximally driven probes since it does not require a drive shaft to transfer the rotational torque to the distal end of the probe and functions without a fiber rotary junction. The probe has a focal Full Width at Half Maximum of 9.6 μm and a working distance of 0.47 mm. We analyzed the non-uniform rotation distortion and found a location fluctuation of only 1.87° in repeated measurements of the same object. The probe was integrated in a high-speed Optical Frequency Domain Imaging setup at 1310 nm. We demonstrated its performance with imaging ex vivo pig bronchial and in vivo goat lung.

  2. Azo-Based Iridium(III) Complexes as Multicolor Phosphorescent Probes to Detect Hypoxia in 3D Multicellular Tumor Spheroids

    PubMed Central

    Sun, Lingli; Li, Guanying; Chen, Xiang; Chen, Yu; Jin, Chengzhi; Ji, Liangnian; Chao, Hui

    2015-01-01

    Hypoxia is an important characteristic of malignant solid tumors and is considered as a possible causative factor for serious resistance to chemo- and radiotherapy. The exploration of novel fluorescent probes capable of detecting hypoxia in solid tumors will aid tumor diagnosis and treatment. In this study, we reported the design and synthesis of a series of “off-on” phosphorescence probes for hypoxia detection in adherent and three-dimensional multicellular spheroid models. All of the iridium(III) complexes incorporate an azo group as an azo-reductase reactive moiety to detect hypoxia. Reduction of non-phosphorescent probes Ir1-Ir8 by reductases under hypoxic conditions resulted in the generation of highly phosphorescent corresponding amines for detection of hypoxic regions. Moreover, these probes can penetrate into 3D multicellular spheroids over 100 μm and image the hypoxic regions. Most importantly, these probes display a high selectivity for the detection of hypoxia in 2D cells and 3D multicellular spheroids. PMID:26423609

  3. Mining information from atom probe data.

    PubMed

    Cairney, Julie M; Rajan, Krishna; Haley, Daniel; Gault, Baptiste; Bagot, Paul A J; Choi, Pyuck-Pa; Felfer, Peter J; Ringer, Simon P; Marceau, Ross K W; Moody, Michael P

    2015-12-01

    Whilst atom probe tomography (APT) is a powerful technique with the capacity to gather information containing hundreds of millions of atoms from a single specimen, the ability to effectively use this information creates significant challenges. The main technological bottleneck lies in handling the extremely large amounts of data on spatial-chemical correlations, as well as developing new quantitative computational foundations for image reconstruction that target critical and transformative problems in materials science. The power to explore materials at the atomic scale with the extraordinary level of sensitivity of detection offered by atom probe tomography has not been not fully harnessed due to the challenges of dealing with missing, sparse and often noisy data. Hence there is a profound need to couple the analytical tools to deal with the data challenges with the experimental issues associated with this instrument. In this paper we provide a summary of some key issues associated with the challenges, and solutions to extract or "mine" fundamental materials science information from that data.

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

    PubMed

    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. Atom probe tomography (APT) of carbonate minerals.

    PubMed

    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.

  6. Tailored probes for atomic force microscopy fabricated by two-photon polymerization

    NASA Astrophysics Data System (ADS)

    Göring, Gerald; Dietrich, Philipp-Immanuel; Blaicher, Matthias; Sharma, Swati; Korvink, Jan G.; Schimmel, Thomas; Koos, Christian; Hölscher, Hendrik

    2016-08-01

    3D direct laser writing based on two-photon polymerization is considered as a tool to fabricate tailored probes for atomic force microscopy. Tips with radii of 25 nm and arbitrary shape are attached to conventionally shaped micro-machined cantilevers. Long-term scanning measurements reveal low wear rates and demonstrate the reliability of such tips. Furthermore, we show that the resonance spectrum of the probe can be tuned for multi-frequency applications by adding rebar structures to the cantilever.

  7. Probing 3D Collective Cancer Invasion Using Double-Stranded Locked Nucleic Acid Biosensors.

    PubMed

    Dean, Zachary S; Elias, Paul; Jamilpour, Nima; Utzinger, Urs; Wong, Pak Kin

    2016-09-01

    Cancer is a leading cause of death worldwide and metastases are responsible for over 90% of human cancer deaths. There is an urgent need to develop novel therapeutics for suppressing cancer invasion, the initial step of metastasis. Nevertheless, the regulation of cancer invasion is poorly understood due to a paucity of tools for monitoring the invasion process in 3D microenvironments. Here, we report a double-stranded locked nucleic acid (dsLNA) biosensor for investigating 3D collective cancer invasion. By incorporating multiphoton microscopy and the dsLNA biosensor, we perform dynamic single cell gene expression analysis while simultaneously characterizing the biomechanical interaction between the invading sprouts and the extracellular matrix. Gene profiling of invasive leader cells and detached cells suggest distinctive signaling mechanisms involved in collective and individual invasion in the 3D microenvironment. Our results underscore the involvement of Notch signaling in 3D collective cancer invasion, which warrants further investigation toward antimetastasis therapy in the future. PMID:27529634

  8. High speed miniature motorized endoscopic probe for 3D optical frequency domain imaging

    NASA Astrophysics Data System (ADS)

    Li, Jianan; Feroldi, Fabio; Mo, Jianhua; Helderman, Frank; de Groot, Mattijs; de Boer, Johannes F.

    2013-03-01

    We present a miniature motorized endoscopic probe for Optical Frequency Domain Imaging with an outer diameter of 1.65 mm and a rotation speed of 3,000 - 12,500 rpm. This is the smallest motorized high speed OCT probe to our knowledge. The probe has a motorized distal end which provides a significant advantage over proximally driven probes since it does not require a drive shaft to transfer the rotational torque to the distal end of the probe and functions without a fiber rotary junction. The probe has a focal Full Width at Half Maximum of 9.6 μm and a working distance of 0.47 mm. We analyzed the non-uniform rotation distortion and found a location fluctuation of only 1.87° in repeated measurements of the same object. The probe was integrated in a high-speed Optical Frequency Domain Imaging setup at 1310 nm We demonstrated its performance with imaging ex vivo pig bronchial and in vivo goat lung.

  9. Full tip imaging in atom probe tomography.

    PubMed

    Du, Sichao; Burgess, Timothy; Loi, Shyeh Tjing; Gault, Baptiste; Gao, Qiang; Bao, Peite; Li, Li; Cui, Xiangyuan; Kong Yeoh, Wai; Tan, Hark Hoe; Jagadish, Chennupati; Ringer, Simon P; Zheng, Rongkun

    2013-01-01

    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.

  10. Point process statistics in atom probe tomography.

    PubMed

    Philippe, T; Duguay, S; Grancher, G; Blavette, D

    2013-09-01

    We present a review of spatial point processes as statistical models that we have designed for the analysis and treatment of atom probe tomography (APT) data. As a major advantage, these methods do not require sampling. The mean distance to nearest neighbour is an attractive approach to exhibit a non-random atomic distribution. A χ(2) test based on distance distributions to nearest neighbour has been developed to detect deviation from randomness. Best-fit methods based on first nearest neighbour distance (1 NN method) and pair correlation function are presented and compared to assess the chemical composition of tiny clusters. Delaunay tessellation for cluster selection has been also illustrated. These statistical tools have been applied to APT experiments on microelectronics materials.

  11. Optically Trapped Surface-Enhanced Raman Probes Prepared by Silver Photoreduction to 3D Microstructures.

    PubMed

    Vizsnyiczai, Gaszton; Lestyán, Tamás; Joniova, Jaroslava; Aekbote, Badri L; Strejčková, Alena; Ormos, Pál; Miskovsky, Pavol; Kelemen, Lóránd; Bánó, Gregor

    2015-09-15

    3D microstructures partially covered by silver nanoparticles have been developed and tested for surface-enhanced Raman spectroscopy (SERS) in combination with optical tweezers. The microstructures made by two-photon polymerization of SU-8 photoresist were manipulated in a dual beam optical trap. The active area of the structures was covered by a SERS-active silver layer using chemically assisted photoreduction from silver nitrate solutions. Silver layers of different grain size distributions were created by changing the photoreduction parameters and characterized by scanning electron microscopy. The structures were tested by measuring the SERS spectra of emodin and hypericin.

  12. The study of dual camera 3D coordinate vision measurement system using a special probe

    NASA Astrophysics Data System (ADS)

    Liu, Shugui; Peng, Kai; Zhang, Xuefei; Zhang, Haifeng; Huang, Fengshan

    2006-11-01

    Due to high precision and convenient operation, the vision coordinate measurement machine with one probe has become the research focus in visual industry. In general such a visual system can be setup conveniently with just one CCD camera and probe. However, the price of the system will surge up too high to accept while the top performance hardware, such as CCD camera, image captured card and etc, have to be applied in the system to obtain the high axis-oriented measurement precision. In this paper, a new dual CCD camera vision coordinate measurement system based on redundancy principle is proposed to achieve high precision by moderate price. Since two CCD cameras are placed with the angle of camera axis like about 90 degrees to build the system, two sub-systems can be built by each CCD camera and the probe. With the help of the probe the inner and outer parameters of camera are first calibrated, the system by use of redundancy technique is set up now. When axis-oriented error is eliminated within the two sub-systems, which is so large and always exits in the single camera system, the high precision measurement is obtained by the system. The result of experiment compared to that from CMM shows that the system proposed is more excellent in stableness and precision with the uncertainty beyond +/-0.1 mm in xyz orient within the distance of 2m using two common CCD cameras.

  13. Coherent Addressing of Individual Neutral Atoms in a 3D Optical Lattice.

    PubMed

    Wang, Yang; Zhang, Xianli; Corcovilos, Theodore A; Kumar, Aishwarya; Weiss, David S

    2015-07-24

    We demonstrate arbitrary coherent addressing of individual neutral atoms in a 5×5×5 array formed by an optical lattice. Addressing is accomplished using rapidly reconfigurable crossed laser beams to selectively ac Stark shift target atoms, so that only target atoms are resonant with state-changing microwaves. The effect of these targeted single qubit gates on the quantum information stored in nontargeted atoms is smaller than 3×10^{-3} in state fidelity. This is an important step along the path of converting the scalability promise of neutral atoms into reality.

  14. Atomic origin of 3d(9)4 f(1) configuration in La(3+) solids.

    PubMed

    Yu, S-W; Carpenter, M H; Ponce, F; Friedrich, S; Lee, J-S

    2015-10-14

    We have studied the excited electronic structure of LaBr3(Ce) scintillator by soft x-ray spectroscopy such as x-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES). The La 3d XAS and XES spectra of LaBr3(Ce) are compared with those of other La(3+) solids (LaF3, La2O3, and La metal). From this comparison, it turns out that the La 3d XAS and XES spectra from all the La(3+) solids considered here appear at almost the same energy, even though the corresponding binding energies of the 3d core holes determined by XPS (x-ray photoelectron spectroscopy) are very different. As a result, we argue that the atomic nature of the 3d⁹4f¹ configuration created by 3d¹⁰4f⁰ → 3d⁹4f¹ x-ray absorption process in La(3+) solids is maintained via the localized 4 f (1) state, which screens the 3d core holes differently from one La(3+) solid to another.

  15. Extracting chemical information from plane wave calculations by a 3D 'fuzzy atoms' analysis

    NASA Astrophysics Data System (ADS)

    Bakó, I.; Stirling, A.; Seitsonen, A. P.; Mayer, I.

    2013-03-01

    Bond order and valence indices have been calculated by the method of the three-dimensional 'fuzzy atoms' analysis, using the numerical molecular orbitals obtained from plane wave DFT calculations, i.e., without introducing any external atom-centered functions. Weight functions of both Hirshfeld and Becke types have been applied. The results are rather close to the similar 'fuzzy atoms' ones obtained by using atom-centered basis sets and agree well with the chemical expectations, stressing the power of the genuine chemical concepts.

  16. Probing the intrinsic optical Bloch-mode emission from a 3D photonic crystal

    NASA Astrophysics Data System (ADS)

    Hsieh, Mei-Li; Bur, James A.; Du, Qingguo; John, Sajeev; Lin, Shawn-Yu

    2016-10-01

    We report experimental observation of intrinsic Bloch-mode emission from a 3D tungsten photonic crystal at low thermal excitation. After the successful removal of conventional metallic emission (normal emission), it is possible to make an accurate comparison of the Bloch-mode and the normal emission. For all biases, we found that the emission intensity of the Bloch-mode is higher than that of the normal emission. The Bloch-mode emission also exhibits a slower dependence on (\\hslash ω /{k}bT) than that of the normal emission. The observed higher emission intensity and a different T-dependence is attributed to Bloch-mode assisted emission where emitters have been located into a medium having local density of states different than the isotropic case. Furthermore, our finite-difference time-domain (FDTD) simulation shows the presence of localized spots at metal-air boundaries and corners, having intense electric field. The enhanced plasmonic field and local non-equilibrium could induce a strong thermally stimulated emission and may be the cause of our unusual observation.

  17. Probing the intrinsic optical Bloch-mode emission from a 3D photonic crystal.

    PubMed

    Hsieh, Mei-Li; Bur, James A; Du, Qingguo; John, Sajeev; Lin, Shawn-Yu

    2016-10-14

    We report experimental observation of intrinsic Bloch-mode emission from a 3D tungsten photonic crystal at low thermal excitation. After the successful removal of conventional metallic emission (normal emission), it is possible to make an accurate comparison of the Bloch-mode and the normal emission. For all biases, we found that the emission intensity of the Bloch-mode is higher than that of the normal emission. The Bloch-mode emission also exhibits a slower dependence on [Formula: see text] than that of the normal emission. The observed higher emission intensity and a different T-dependence is attributed to Bloch-mode assisted emission where emitters have been located into a medium having local density of states different than the isotropic case. Furthermore, our finite-difference time-domain (FDTD) simulation shows the presence of localized spots at metal-air boundaries and corners, having intense electric field. The enhanced plasmonic field and local non-equilibrium could induce a strong thermally stimulated emission and may be the cause of our unusual observation. PMID:27606574

  18. Probing the intrinsic optical Bloch-mode emission from a 3D photonic crystal.

    PubMed

    Hsieh, Mei-Li; Bur, James A; Du, Qingguo; John, Sajeev; Lin, Shawn-Yu

    2016-10-14

    We report experimental observation of intrinsic Bloch-mode emission from a 3D tungsten photonic crystal at low thermal excitation. After the successful removal of conventional metallic emission (normal emission), it is possible to make an accurate comparison of the Bloch-mode and the normal emission. For all biases, we found that the emission intensity of the Bloch-mode is higher than that of the normal emission. The Bloch-mode emission also exhibits a slower dependence on [Formula: see text] than that of the normal emission. The observed higher emission intensity and a different T-dependence is attributed to Bloch-mode assisted emission where emitters have been located into a medium having local density of states different than the isotropic case. Furthermore, our finite-difference time-domain (FDTD) simulation shows the presence of localized spots at metal-air boundaries and corners, having intense electric field. The enhanced plasmonic field and local non-equilibrium could induce a strong thermally stimulated emission and may be the cause of our unusual observation.

  19. Preparation of Regular Specimens for Atom Probes

    NASA Technical Reports Server (NTRS)

    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

  20. Atom Probe Tomography and Its Application to Refractory Metal Nuggets

    NASA Astrophysics Data System (ADS)

    Daly, L.; Bland, P. A.; Forman, L. V.; Reddy, S. M.; Rickard, W. D. A.; Saxey, D. W.; La Fontaine, A.; Yang, L.; Trimby, P. W.; Cairney, J.; Ringer, S.; Schaefer, B. F.

    2016-08-01

    Atom probe tomography is capable of achieving atomic resolution. This allows us to accurately measure the chemistry of refractory metal nuggets in situ, revealing nanometre scale variations in their chemistry and the presence of sulphur in the alloy.

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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

  4. Probing electronic state at atomic scale on the surface of SrVO3 film

    NASA Astrophysics Data System (ADS)

    Okada, Yoshinori; Shimizu, Ryota; Shiraki, Susumu; Hitosugi, Taro

    2014-03-01

    Probing electronic structure of atomically well controlled surface of Perovskite-type 3d transition-metal oxides have been attracting much interest because of their intriguing emergent physical properties by heterostructure engineering. In this study, we have especially focused on SrVO3, where importance of correlation effects has been considered. We successfully obtained atomically flat surfaces of SrVO3, which gave us the great opportunity to visualize correlated electronic state at atomic scale by means of spectroscopic imaging scanning tunneling spectroscopy. Based on the experimental data, we discuss spectroscopic signature of many body effects on the surface of SrVO3 system.

  5. Two versions of holography vie to show atoms in 3D

    SciTech Connect

    Nadis, S.

    1996-05-03

    In 1948 Dennis Gabor had an idea nearly 50 years ahead of his time, laying the theoretical groundwork for holography, a technique for making three dimensional images from interference patterns created when beams of coherent light or other radiation are shined on the object. Two research groups have developed holography on an atomic scale. One group from Budapest used atoms within a specimen itself as sources of coherent x-rays, a hologram can be made inside a solid - a crystal of the mineral perovskite, and by using atoms to detect rather than generate signals another groups has achieved an atomic-scale hologram. This article discusses the development and progress of the research.

  6. Quantitative binomial distribution analyses of nanoscale like-solute atom clustering and segregation in atom probe tomography data.

    PubMed

    Moody, Michael P; Stephenson, Leigh T; Ceguerra, Anna V; Ringer, Simon P

    2008-07-01

    The applicability of the binomial frequency distribution is outlined for the analysis of the evolution nanoscale atomic clustering of dilute solute in an alloy subject to thermal ageing in 3D atom probe data. The conventional chi(2) statistics and significance testing are demonstrated to be inappropriate for comparison of quantity of solute segregation present in two or more different sized system. Pearson coefficient, mu, is shown to normalize chi(2) with respect to sample size over an order of magnitude. A simple computer simulation is implemented to investigate the binomial analysis and infer meaning in the measured value of mu over a series of systems at different solute concentrations and degree of clustering. The simulations replicate the form of experimental data and demonstrate the effect of detector efficiency to significantly underestimate the measured segregation. The binomial analysis is applied to experimental atom probe data sets and complementary simulations are used to interpret the results.

  7. Efficient Nonlinear Atomization Model for Thin 3D Free Liquid Films

    NASA Astrophysics Data System (ADS)

    Mehring, Carsten

    2007-03-01

    Reviewed is a nonlinear reduced-dimension thin-film model developed by the author and aimed at the prediction of spray formation from thin films such as those found in gas-turbine engines (e.g., prefilming air-blast atomizers), heavy-fuel-oil burners (e.g., rotary-cup atomizers) and in the paint industry (e.g., flat-fan atomizers). Various implementations of the model focusing on different model-aspects, i.e., effect of film geometry, surface tension, liquid viscosity, coupling with surrounding gas-phase flow, influence of long-range intermolecular forces during film rupture are reviewed together with a validation of the nonlinear wave propagation characteristics predicted by the model for inviscid planar films using a two-dimensional vortex- method. An extension and generalization of the current nonlinear film model for implementation into a commercial flow- solver is outlined.

  8. Probe-rotating atomic force microscopy for determining material properties

    SciTech Connect

    Lee, Sang Heon

    2014-03-15

    In this paper, we propose a probe-rotating atomic force microscope that enables scan in an arbitrary direction in the contact imaging mode, which is difficult to achieve using a conventional atomic force microscope owing to the orientation-dependent probe and the inability to rotate the probe head. To enable rotation of the probe about its vertical axis, we employed a compact and light probe head, the sensor of which is made of an optical disk drive pickup unit. Our proposed mechanical configuration, operating principle, and control system enables axial and lateral scan in various directions.

  9. Approximating the 3D Character of a Van Der Waals Atom-Solid Potential

    NASA Astrophysics Data System (ADS)

    Bruch, L. W.

    2016-10-01

    A truncated Fourier decomposition of the atom-substrate potential energy is developed for three-dimensional models of van der Waals systems, specifically for adsorption on the basal plane surface of graphite or the (111) face of a face-centered-cubic lattice. This provides a framework for analysis of a priori calculations of physical adsorption energies.

  10. Numerical simulation in 3D of atomizing coaxial gas-liquid jets

    NASA Astrophysics Data System (ADS)

    Agbaglah, Gilou; Fuster, Daniel; McBain, Geordie; Popinet, Stephane; Zaleski, Stephane

    2012-11-01

    We investigate three-dimensional multiphase flows using the Volume of Fluid method. We are in particular focusing on the problem of jet atomizaton. We use a Volume of Fluid method with oct-tree adaptive finite volume discretization, mostly using the Gerris free code. Surface tension is computed by a balanced-force method. Coaxial, 3D, round and planar air-water jets similar to those investigated experimentally are studied and compared to the equivalent jets in 2D axisymetric and 2D planar setups. A mechanism for large-scale jet disruption is observed. The distribution of droplet sizes is compared to experimental measurements. The effect of grid resolution and of the presence of an explicitly modelled solid separator plate is discussed.

  11. Determination of mass attenuation coefficients and effective atomic numbers for compounds of the 3d transition elements

    NASA Astrophysics Data System (ADS)

    Yılmaz, Demet; Boydaş, Elif; Cömert, Esra

    2016-08-01

    In this study, we aimed to determine mass attenuation coefficient (μm) and effective atomic number (Zeff) for some compounds of the 3d transition elements such as CoO, CoF2, CoF3, Cr2O3, CrF2, CrF3, FeO, Fe2O3, MnO2, TiO2, V2O3, VF3, V2O5, VF4 and ZnO at 19.63 and 22.10 keV photon energies by using an HPGe detector with a resolution of 182 eV at 5.9 keV. The experimental results of μm are compared with the theoretical results. Also, effective atomic numbers of compounds of the 3d transition elements have been determined by using experimental and theoretical mass attenuation coefficients. The agreement of measured values of effective atomic numbers with theoretical calculations is quite satisfactory.

  12. Performance of a Multispectral Optoacoustic Tomography (MSOT) System equipped with 2D vs. 3D Handheld Probes for Potential Clinical Translation

    PubMed Central

    Neuschmelting, Volker; Burton, Neal C.; Lockau, Hannah; Urich, Alexander; Harmsen, Stefan; Ntziachristos, Vasilis; Kircher, Moritz F.

    2015-01-01

    A handheld approach to optoacoustic imaging is essential for the clinical translation. The first 2- and 3-dimensional handheld multispectral optoacoustic tomography (MSOT) probes featuring real-time unmixing have recently been developed. Imaging performance of both probes was determined in vitro and in a brain melanoma metastasis mouse model in vivo. T1-weighted MR images were acquired for anatomical reference. The limit of detection of melanoma cells in vitro was significantly lower using the 2D than the 3D probe. The signal decrease was more profound in relation to depth with the 3D versus the 2D probe. Both approaches were capable of imaging the melanoma tumors qualitatively at all time points. Quantitatively, the 2D approach enabled closer anatomical resemblance of the tumor compared to the 3D probe, particularly at depths beyond 3 mm. The 3D probe was shown to be superior for rapid 3D imaging and, thus, holds promise for more superficial target structures. PMID:27069872

  13. Single-qubit gates based on targeted phase shifts in a 3D neutral atom array

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Kumar, Aishwarya; Wu, Tsung-Yao; Weiss, David S.

    2016-06-01

    Although the quality of individual quantum bits (qubits) and quantum gates has been steadily improving, the number of qubits in a single system has increased quite slowly. Here, we demonstrate arbitrary single-qubit gates based on targeted phase shifts, an approach that can be applied to atom, ion, or other atom-like systems. These gates are highly insensitive to addressing beam imperfections and have little cross-talk, allowing for a dramatic scaling up of qubit number. We have performed gates in series on 48 individually targeted sites in a 40% full 5 by 5 by 5 three-dimensional array created by an optical lattice. Using randomized benchmarking, we demonstrate an average gate fidelity of 0.9962(16), with an average cross-talk fidelity of 0.9979(2) (numbers in parentheses indicate the one standard deviation uncertainty in the final digits).

  14. Intraoperative handheld probe for 3D imaging of pediatric benign vocal fold lesions using optical coherence tomography (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Benboujja, Fouzi; Garcia, Jordan; Beaudette, Kathy; Strupler, Mathias; Hartnick, Christopher J.; Boudoux, Caroline

    2016-02-01

    Excessive and repetitive force applied on vocal fold tissue can induce benign vocal fold lesions. Children affected suffer from chronic hoarseness. In this instance, the vibratory ability of the folds, a complex layered microanatomy, becomes impaired. Histological findings have shown that lesions produce a remodeling of sup-epithelial vocal fold layers. However, our understanding of lesion features and development is still limited. Indeed, conventional imaging techniques do not allow a non-invasive assessment of sub-epithelial integrity of the vocal fold. Furthermore, it remains challenging to differentiate these sub-epithelial lesions (such as bilateral nodules, polyps and cysts) from a clinical perspective, as their outer surfaces are relatively similar. As treatment strategy differs for each lesion type, it is critical to efficiently differentiate sub-epithelial alterations involved in benign lesions. In this study, we developed an optical coherence tomography (OCT) based handheld probe suitable for pediatric laryngological imaging. The probe allows for rapid three-dimensional imaging of vocal fold lesions. The system is adapted to allow for high-resolution intra-operative imaging. We imaged 20 patients undergoing direct laryngoscopy during which we looked at different benign pediatric pathologies such as bilateral nodules, cysts and laryngeal papillomatosis and compared them to healthy tissue. We qualitatively and quantitatively characterized laryngeal pathologies and demonstrated the added advantage of using 3D OCT imaging for lesion discrimination and margin assessment. OCT evaluation of the integrity of the vocal cord could yield to a better pediatric management of laryngeal diseases.

  15. The 3D manipulation of a microsphere for nano-CMM probe using single fiber optical trapping

    NASA Astrophysics Data System (ADS)

    Eom, Sang In; Takaya, Yasuhiro; Miyoshi, Takashi; Hayashi, Terutake

    2006-08-01

    We suggest a novel 3-D probing technique for measuring micro parts which have high aspect ratio such as a groove or a deep-hole. This technique uses the optical force exerted on a dielectric microsphere at the tip of optical fiber so called the fiber optical trapping. A microsphere is trapped at the tip of an optical fiber which has micrometer size of the diameter and sub micrometer size of the tapered tip. The optical source is a Nd:YAG laser with the wavelength of 1064 nm. A fiber optical trapping system is quite similar to a conventional CMM. The roll of a microsphere is the same as the probe sphere of a conventional CMM and an optical fiber works as a stylus shaft. The micro optical fiber part is thinner than the diameter of the microsphere and longer than the depth of shapes such as deep holes and grooves, which enable to make an approach to a steep angle surface of a work piece with high aspect ratio.

  16. Adsorption of alkali, alkaline-earth, and 3d transition metal atoms on silicene

    NASA Astrophysics Data System (ADS)

    Sahin, H.; Peeters, F. M.

    2013-02-01

    The adsorption characteristics of alkali, alkaline-earth, and transition metal adatoms on silicene, a graphene-like monolayer structure of silicon are analyzed by means of first-principles calculations. In contrast to graphene, interaction between the metal atoms and the silicene surface is quite strong due to its highly reactive buckled hexagonal structure. In addition to structural properties, we also calculate the electronic band dispersion, net magnetic moment, charge transfer, work function, and dipole moment of the metal adsorbed silicene sheets. Alkali metals, Li, Na, and K, adsorb to hollow sites without any lattice distortion. As a consequence of the significant charge transfer from alkalis to silicene, metalization of silicene takes place. Trends directly related to atomic size, adsorption height, work function, and dipole moment of the silicene/alkali adatom system are also revealed. We found that the adsorption of alkaline-earth metals on silicene is entirely different from their adsorption on graphene. The adsorption of Be, Mg, and Ca turns silicene into a narrow gap semiconductor. Adsorption characteristics of eight transition metals Ti, V, Cr, Mn, Fe, Co, Mo, and W are also investigated. As a result of their partially occupied d orbital, transition metals show diverse structural, electronic, and magnetic properties. Upon the adsorption of transition metals, depending on the adatom type and atomic radius, the system can exhibit metal, half-metal, and semiconducting behavior. For all metal adsorbates, the direction of the charge transfer is from adsorbate to silicene, because of its high surface reactivity. Our results indicate that the reactive crystal structure of silicene provides a rich playground for functionalization at nanoscale.

  17. Atomic-resolution 3D structure of amyloid β fibrils: The Osaka mutation

    DOE PAGES

    Schutz, Anne K.; Wall, Joseph; Vagt, Toni; Huber, Matthias; Ovchinnikova, Oxana Y.; Cadalbert, Riccardo; Guntert, Peter; Bockmann, Anja; Glockshuber, Rudi; Meier, Beat H.

    2014-11-13

    Despite its central importance for understanding the molecular basis of Alzheimer's disease (AD), high-resolution structural information on amyloid β-peptide (Aβ) fibrils, which are intimately linked with AD, is scarce. We report an atomic-resolution fibril structure of the Aβ 1-40 peptide with the Osaka mutation (E22Δ), associated with early-onset AD. The structure, which differs substantially from all previously proposed models, is based on a large number of unambiguous intra- and intermolecular solid-state NMR distance restraints

  18. Embrittlement of RPV steels; An atom probe tomography perspective

    SciTech Connect

    Miller, Michael K; Russell, Kaye F

    2007-01-01

    Atom probe tomography has played a key role in the understanding of the embrittlement of neutron irradiated reactor pressure vessel steels through the atomic level characterization of the microstructure. Atom probe tomography has been used to demonstrate the importance of the post weld stress relief treatment in reducing the matrix copper content in high copper alloys, the formation of {approx}-nm-diameter copper-, nickel-, manganese- and silicon-enriched precipitates during neutron irradiation in copper containing RPV steels, and the coarsening of these precipitates during post irradiation heat treatments. Atom probe tomography has been used to detect {approx}2-nm-diameter nickel-, silicon- and manganese-enriched clusters in neutron irradiated low copper and copper free alloys. Atom probe tomography has also been used to quantify solute segregation to, and precipitation on, dislocations and grain boundaries.

  19. 3D electron tomography of pretreated biomass informs atomic modeling of cellulose microfibrils.

    PubMed

    Ciesielski, Peter N; Matthews, James F; Tucker, Melvin P; Beckham, Gregg T; Crowley, Michael F; Himmel, Michael E; Donohoe, Bryon S

    2013-09-24

    Fundamental insights into the macromolecular architecture of plant cell walls will elucidate new structure-property relationships and facilitate optimization of catalytic processes that produce fuels and chemicals from biomass. Here we introduce computational methodology to extract nanoscale geometry of cellulose microfibrils within thermochemically treated biomass directly from electron tomographic data sets. We quantitatively compare the cell wall nanostructure in corn stover following two leading pretreatment strategies: dilute acid with iron sulfate co-catalyst and ammonia fiber expansion (AFEX). Computational analysis of the tomographic data is used to extract mathematical descriptions for longitudinal axes of cellulose microfibrils from which we calculate their nanoscale curvature. These nanostructural measurements are used to inform the construction of atomistic models that exhibit features of cellulose within real, process-relevant biomass. By computational evaluation of these atomic models, we propose relationships between the crystal structure of cellulose Iβ and the nanoscale geometry of cellulose microfibrils. PMID:23988022

  20. 3D Atomic Arrangement at Functional Interfaces Inside Nanoparticles by Resonant High-Energy X-ray Diffraction.

    PubMed

    Petkov, Valeri; Prasai, Binay; Shastri, Sarvjit; Chen, Tsan-Yao

    2015-10-21

    With current science and technology moving rapidly into smaller scales, nanometer-sized materials, often referred to as NPs, are produced in increasing numbers and explored for numerous useful applications. Evidence is mounting, however, that useful properties of NPs can be improved further and even new NP functionality achieved by not only controlling the NP size and shape but also interfacing chemically or structurally distinct entities into single, so-called "composite" NPs. A typical example is core-shell NPs wherein the synergy of distinct atoms at the core\\shell interface endows the NPs with otherwise unachievable functionality. However, though advantageous, the concept of functional interfaces inside NPs is still pursued largely by trial-and-error. That is because it is difficut to assess the interfaces precisely at the atomic level using traditional experimental techniques and, hence, difficult to take control of. Using the core\\shell interface in less than 10 nm in size Ru core-Pt shells NPs as an example, we demonstrate that precise knowledge of the 3D atomic arrangement at functional interfaces inside NPs can be obtained by resonant high-energy X-ray diffraction (XRD) coupled to element-specific atomic pair distribution function (PDF) analysis. On the basis of the unique structure knowledge obtained, we scrutinize the still-debatable influence of core\\shell interface on the catalytic functionality of Ru core-Pt shell NPs, thus evidencing the usefulness of this nontraditional technique for practical applications.

  1. 3-D Raman Imagery and Atomic Force Microscopy of Ancient Microscopic Fossils

    NASA Astrophysics Data System (ADS)

    Schopf, J.

    2003-12-01

    Investigations of the Precambrian (~540- to ~3,500-Ma-old) fossil record depend critically on identification of authentic microbial fossils. Combined with standard paleontologic studies (e.g., of paleoecologic setting, population structure, cellular morphology, preservational variants), two techniques recently introduced to such studies -- Raman imagery and atomic force microscopy -- can help meet this need. Laser-Raman imagery is a non-intrusive, non-destructive technique that can be used to demonstrate a micron-scale one-to-one correlation between optically discernable morphology and the organic (kerogenous) composition of individual microbial fossils(1,2), a prime indicator of biogencity. Such analyses can be used to characterize the molecular-structural makeup of organic-walled microscopic fossils both in acid-resistant residues and in petrographic thin sections, and whether the fossils analyzed are exposed at the upper surface of, or are embedded within (to depths >65 microns), the section studied. By providing means to map chemically, in three dimensions, whole fossils or parts of such fossils(3), Raman imagery can also show the presence of cell lumina, interior cellular cavities, another prime indicator of biogenicity. Atomic force microscopy (AFM) has been used to visualize the nanometer-scale structure of the kerogenous components of single Precambrian microscopic fossils(4). Capable of analyzing minute fragments of ancient organic matter exposed at the upper surface of thin sections (or of kerogen particles deposited on flat surfaces), such analyses hold promise not only for discriminating between biotic and abiotic micro-objects but for elucidation of the domain size -- and, thus, the degree of graphitization -- of the graphene subunits of the carbonaceous matter analyzed. These techniques -- both new to paleobiology -- can provide useful insight into the biogenicity and geochemical maturity of ancient organic matter. References: (1) Kudryavtsev, A.B. et

  2. Probing Protein 3D Structures and Conformational Changes Using Electrochemistry-Assisted Isotope Labeling Cross-Linking Mass Spectrometry.

    PubMed

    Zheng, Qiuling; Zhang, Hao; Wu, Shiyong; Chen, Hao

    2016-05-01

    This study presents a new chemical cross-linking mass spectrometry (MS) method in combination with electrochemistry and isotope labeling strategy for probing both protein three-dimensional (3D) structures and conformational changes. For the former purpose, the target protein/protein complex is cross-linked with equal mole of premixed light and heavy isotope labeled cross-linkers carrying electrochemically reducible disulfide bonds (i.e., DSP-d0 and DSP-d8 in this study, DSP = dithiobis[succinimidyl propionate]), digested and then electrochemically reduced followed with online MS analysis. Cross-links can be quickly identified because of their reduced intensities upon electrolysis and the presence of doublet isotopic peak characteristics. In addition, electroreduction converts cross-links into linear peptides, facilitating MS/MS analysis to gain increased information about their sequences and modification sites. For the latter purpose of probing protein conformational changes, an altered procedure is adopted, in which the protein in two different conformations is cross-linked using DSP-d0 and DSP-d8 separately, and then the two protein samples are mixed in 1:1 molar ratio. The merged sample is subjected to digestion and electrochemical mass spectrometric analysis. In such a comparative cross-linking experiment, cross-links could still be rapidly recognized based on their responses to electrolysis. More importantly, the ion intensity ratios of light and heavy isotope labeled cross-links reveal the conformational changes of the protein, as exemplified by examining the effect of Ca(2+) on calmodulin conformation alternation. This new cross-linking MS method is fast and would have high value in structural biology. Graphical Abstract ᅟ. PMID:26902947

  3. Probing Protein 3D Structures and Conformational Changes Using Electrochemistry-Assisted Isotope Labeling Cross-Linking Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Zheng, Qiuling; Zhang, Hao; Wu, Shiyong; Chen, Hao

    2016-05-01

    This study presents a new chemical cross-linking mass spectrometry (MS) method in combination with electrochemistry and isotope labeling strategy for probing both protein three-dimensional (3D) structures and conformational changes. For the former purpose, the target protein/protein complex is cross-linked with equal mole of premixed light and heavy isotope labeled cross-linkers carrying electrochemically reducible disulfide bonds (i.e., DSP-d0 and DSP-d8 in this study, DSP = dithiobis[succinimidyl propionate]), digested and then electrochemically reduced followed with online MS analysis. Cross-links can be quickly identified because of their reduced intensities upon electrolysis and the presence of doublet isotopic peak characteristics. In addition, electroreduction converts cross-links into linear peptides, facilitating MS/MS analysis to gain increased information about their sequences and modification sites. For the latter purpose of probing protein conformational changes, an altered procedure is adopted, in which the protein in two different conformations is cross-linked using DSP-d0 and DSP-d8 separately, and then the two protein samples are mixed in 1:1 molar ratio. The merged sample is subjected to digestion and electrochemical mass spectrometric analysis. In such a comparative cross-linking experiment, cross-links could still be rapidly recognized based on their responses to electrolysis. More importantly, the ion intensity ratios of light and heavy isotope labeled cross-links reveal the conformational changes of the protein, as exemplified by examining the effect of Ca2+ on calmodulin conformation alternation. This new cross-linking MS method is fast and would have high value in structural biology.

  4. Probing Protein 3D Structures and Conformational Changes Using Electrochemistry-Assisted Isotope Labeling Cross-Linking Mass Spectrometry.

    PubMed

    Zheng, Qiuling; Zhang, Hao; Wu, Shiyong; Chen, Hao

    2016-05-01

    This study presents a new chemical cross-linking mass spectrometry (MS) method in combination with electrochemistry and isotope labeling strategy for probing both protein three-dimensional (3D) structures and conformational changes. For the former purpose, the target protein/protein complex is cross-linked with equal mole of premixed light and heavy isotope labeled cross-linkers carrying electrochemically reducible disulfide bonds (i.e., DSP-d0 and DSP-d8 in this study, DSP = dithiobis[succinimidyl propionate]), digested and then electrochemically reduced followed with online MS analysis. Cross-links can be quickly identified because of their reduced intensities upon electrolysis and the presence of doublet isotopic peak characteristics. In addition, electroreduction converts cross-links into linear peptides, facilitating MS/MS analysis to gain increased information about their sequences and modification sites. For the latter purpose of probing protein conformational changes, an altered procedure is adopted, in which the protein in two different conformations is cross-linked using DSP-d0 and DSP-d8 separately, and then the two protein samples are mixed in 1:1 molar ratio. The merged sample is subjected to digestion and electrochemical mass spectrometric analysis. In such a comparative cross-linking experiment, cross-links could still be rapidly recognized based on their responses to electrolysis. More importantly, the ion intensity ratios of light and heavy isotope labeled cross-links reveal the conformational changes of the protein, as exemplified by examining the effect of Ca(2+) on calmodulin conformation alternation. This new cross-linking MS method is fast and would have high value in structural biology. Graphical Abstract ᅟ.

  5. Advances in the calibration of atom probe tomographic reconstruction

    SciTech Connect

    Gault, Baptiste; Moody, Michael P.; La Fontaine, Alexandre; Stephenson, Leigh T.; Haley, Daniel; Ringer, Simon P.; Geuser, Frederic de; Tsafnat, Guy

    2009-02-01

    Modern wide field-of-view atom probes permit observation of a wide range of crystallographic features that can be used to calibrate the tomographic reconstruction of the analyzed volume. In this study, methodologies to determine values of the geometric parameters involved in the tomographic reconstruction of atom probe data sets are presented and discussed. The influence of the tip to electrode distance and specimen temperature on these parameters is explored. Significantly, their influence is demonstrated to be very limited, indicating a relatively wide regime of experimental parameters space for sound atom probe tomography (APT) experiments. These methods have been used on several specimens and material types, and the results indicate that the reconstruction parameters are specific to each specimen. Finally, it is shown how an accurate calibration of the reconstruction enables improvements to the quality and reliability of the microscopy and microanalysis capabilities of the atom probe.

  6. Review of atom probe FIB-based specimen preparation methods.

    PubMed

    Miller, Michael K; Russell, Kaye F; Thompson, Keith; Alvis, Roger; Larson, David J

    2007-12-01

    Several FIB-based methods that have been developed to fabricate needle-shaped atom probe specimens from a variety of specimen geometries, and site-specific regions are reviewed. These methods have enabled electronic device structures to be characterized. The atom probe may be used to quantify the level and range of gallium implantation and has demonstrated that the use of low accelerating voltages during the final stages of milling can dramatically reduce the extent of gallium implantation. PMID:18001509

  7. Metastable atom probe for measuring electron beam density profiles

    NASA Technical Reports Server (NTRS)

    Lockhart, J. M.; Zorn, J. C.

    1972-01-01

    Metastable atom probe was developed for measuring current density in electron beam as function of two arbitrary coordinates, with spatial resolution better than 0.5 mm. Probe shows effects of space charge, magnetic fields, and other factors which influence electron current density, but operates with such low beam densities that introduced perturbation is very small.

  8. Atom probe tomography of a commercial light emitting diode

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

  9. Improvements in three-dimensional atom probe design

    NASA Astrophysics Data System (ADS)

    Cerezo, A.; Godfrey, T. J.; Hyde, J. M.; Sijbrandij, S. J.; Smith, G. D. W.

    1994-03-01

    An improved position-sensitive atom probe has been designed which uses a combination of a parallel timing system and a silicon photodiode array camera. The use of two separate data acquisition systems allows the two functions of accurate positioning and flight time determination to be divorced, thus removing the compromises which must be made when these functions are carried out with only a single detector. The resulting instrument is able to determine flight times and positions of impacts straightforwardly, even when multiple ions are evaporated on a single pulse, and should be capable of operating at evaporation rates close to that of a conventional probe-hole atom probe.

  10. Parylene insulated probes for scanning electrochemical-atomic force microscopy.

    PubMed

    Derylo, Maksymilian A; Morton, Kirstin C; Baker, Lane A

    2011-11-15

    Scanning electrochemical-atomic force microscopy (SECM-AFM) is a powerful technique that can be used to obtain in situ information related to electrochemical phenomena at interfaces. Fabrication of probes to perform SECM-AFM experiments remains a challenge. Herein, we describe a method for formation of microelectrodes at the tip of commercial conductive AFM probes and demonstrate application of these probes to SECM-AFM. Probes were first insulated with a thin parylene layer, followed by subsequent exposure of active electrodes at the probe tips by mechanical abrasion of the insulating layer. Characterization of probes was performed by electron microscopy and cyclic voltammetry. In situ measurement of localized electrochemical activity with parylene-coated probes was demonstrated through measurement of the diffusion of Ru(NH)(6)(3+) across a porous membrane.

  11. Characterization of internal interfaces by atom probe field ion microscopy

    SciTech Connect

    Miller, M.K.; Jayaram, R.

    1992-12-31

    The near atomic spatial resolution of the atom probe field ion microscope permits the elemental characterization of internal interfaces, grain boundaries and surfaces to be performed in a wide variety of materials. Information such as the orientation relationship between grains, topology of the interface, and the coherency of small precipitates with the surrounding matrix may be obtained from field ion microscopy. Details of the solute segregation may be obtained at the plane of the interface and as a function of distance from the interface for all elements simultaneously from atom probe compositional analysis. Capabilities and limitations of the atom probe technique in characterization of internal interfaces is illustrated with examples of grain boundaries and interphase interfaces in a wide range of materials including intermetallics, model alloys, and commercial steels.

  12. Characterization of internal interfaces by atom probe field ion microscopy

    SciTech Connect

    Miller, M.K.; Jayaram, R.

    1992-01-01

    The near atomic spatial resolution of the atom probe field ion microscope permits the elemental characterization of internal interfaces, grain boundaries and surfaces to be performed in a wide variety of materials. Information such as the orientation relationship between grains, topology of the interface, and the coherency of small precipitates with the surrounding matrix may be obtained from field ion microscopy. Details of the solute segregation may be obtained at the plane of the interface and as a function of distance from the interface for all elements simultaneously from atom probe compositional analysis. Capabilities and limitations of the atom probe technique in characterization of internal interfaces is illustrated with examples of grain boundaries and interphase interfaces in a wide range of materials including intermetallics, model alloys, and commercial steels.

  13. Probing dark energy with atom interferometry

    SciTech Connect

    Burrage, Clare; Copeland, Edmund J.; Hinds, E.A. E-mail: Edmund.Copeland@nottingham.ac.uk

    2015-03-01

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

  14. In situ geomechanics of crystalline and sedimentary rocks; Part IV, continued field testing of the modified U.S. Geological Survey 3-D borehole stress probe

    USGS Publications Warehouse

    Nichols, Thomas C.

    1983-01-01

    Two modified and calibrated U.S. Geological Survey 3-D borehole probes were successfully tested in the field at a site on South Table Mountain, near Golden, Colo. The probes were installed in separate core holes at depths of 84 and 99 cm in the latite cap rock and subsequently stress relieved with overcoring techniques. The determined stresses from both probes are very low and contain both tensile and compressive components. Magnitudes range from 1196 KPa in tension to 832 KPa in compression. The principal stress orientations are in fair agreement whereas the horizontal secondary principal stress directions are in good agreement; the maximum horizontal compressive stress is oriented N. 76? W.-S. 76? E. for one probe and N. 63? W.-S. 63? E. for the second probe. The greatest determined Young's modulus of the rock is in the N. 89? E. direction, only 15? from the maximum horizontal compressive stress direction.

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

    PubMed

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

    2015-12-01

    The geometry of atom probe tomography tips strongly differs from standard scanning transmission electron microscopy foils. Whereas the later are rather flat and thin (<20 nm), tips display a curved surface and a significantly larger thickness. As far as a correlative approach aims at analysing the same specimen by both techniques, it is mandatory to explore the limits and advantages imposed by the particular geometry of atom probe tomography specimens. Based on simulations (electron probe propagation and image simulations), the possibility to apply quantitative high angle annular dark field scanning transmission electron microscopy to of atom probe tomography specimens has been tested. The influence of electron probe convergence and the benefice of deconvolution of electron probe point spread function electron have been established. Atom counting in atom probe tomography specimens is for the first time reported in this present work. It is demonstrated that, based on single projections of high angle annular dark field imaging, significant quantitative information can be used as additional input for refining the data obtained by correlative analysis of the specimen in APT, therefore opening new perspectives in the field of atomic scale tomography.

  16. Three-Dimensional Atom-Probe Tomographic Analyses of Lead-Telluride Based Thermoelectric Materials

    NASA Astrophysics Data System (ADS)

    Kim, Yoon-Jun; Blum, Ivan D.; He, Jiaqing; Kanatzidis, Mercouri G.; Dravid, Vinayak P.; Seidman, David N.

    2014-11-01

    Precipitates in bulk p-type thermoelectric materials, PbTe-SrTe and PbTe-PbS, are studied using three-dimensional (3-D) atom-probe tomography (APT). APT is capable of characterizing chemically materials in 3-D with subnano-scale spatial resolution on an atom-by-atom basis, which enables us to characterize secondary phases in the PbTe matrix as well as the dopant distributions at different imperfections. We demonstrate that APT provides accurate information about the compositions and morphologies of nanoprecipitates. In the PbTe-SrTe system, different morphology of precipitates is observed and the SrTe composition is confirmed. Also, segregation of Na dopants at mesoscale imperfections, dislocations and grain boundaries, and at matrix/precipitate interfaces is observed. In the PbTe-PbS system, PbS precipitates are observed. The PbS precipitates exhibit faceting, and have a morphology that depends on the bulk Na concentration. A predominance of {100} faceted precipitates is observed for 2 mol.% Na. Using 3-D APT, we demonstrate that Na segregation at matrix/precipitate interfaces is most likely responsible for the change in their morphologies, which occurs by reducing the interfacial free energy of {100} facets.

  17. Three-Dimensional Atom-Probe Tomographic Analyses of Lead-Telluride Based Thermoelectric Materials

    NASA Astrophysics Data System (ADS)

    Kim, Yoon-Jun; Blum, Ivan D.; He, Jiaqing; Kanatzidis, Mercouri G.; Dravid, Vinayak P.; Seidman, David N.

    2014-09-01

    Precipitates in bulk p-type thermoelectric materials, PbTe-SrTe and PbTe-PbS, are studied using three-dimensional (3-D) atom-probe tomography (APT). APT is capable of characterizing chemically materials in 3-D with subnano-scale spatial resolution on an atom-by-atom basis, which enables us to characterize secondary phases in the PbTe matrix as well as the dopant distributions at different imperfections. We demonstrate that APT provides accurate information about the compositions and morphologies of nanoprecipitates. In the PbTe-SrTe system, different morphology of precipitates is observed and the SrTe composition is confirmed. Also, segregation of Na dopants at mesoscale imperfections, dislocations and grain boundaries, and at matrix/precipitate interfaces is observed. In the PbTe-PbS system, PbS precipitates are observed. The PbS precipitates exhibit faceting, and have a morphology that depends on the bulk Na concentration. A predominance of {100} faceted precipitates is observed for 2 mol.% Na. Using 3-D APT, we demonstrate that Na segregation at matrix/precipitate interfaces is most likely responsible for the change in their morphologies, which occurs by reducing the interfacial free energy of {100} facets.

  18. Detecting magnetic ordering with atomic size electron probes

    DOE PAGES

    Idrobo, Juan Carlos; Rusz, Ján; Spiegelberg, Jakob; McGuire, Michael A.; Symons, Christopher T.; Vatsavai, Ranga Raju; Cantoni, Claudia; Lupini, Andrew R.

    2016-05-27

    While magnetism originates at the atomic scale, the existing spectroscopic techniques sensitive to magnetic signals only produce spectra with spatial resolution on a larger scale. However, recently, it has been theoretically argued that atomic size electron probes with customized phase distributions can detect magnetic circular dichroism. Here, we report a direct experimental real-space detection of magnetic circular dichroism in aberration-corrected scanning transmission electron microscopy (STEM). Using an atomic size-aberrated electron probe with a customized phase distribution, we reveal the checkerboard antiferromagnetic ordering of Mn moments in LaMnAsO by observing a dichroic signal in the Mn L-edge. The novel experimental setupmore » presented here, which can easily be implemented in aberration-corrected STEM, opens new paths for probing dichroic signals in materials with unprecedented spatial resolution.« less

  19. Atom pair 2D-fingerprints perceive 3D-molecular shape and pharmacophores for very fast virtual screening of ZINC and GDB-17.

    PubMed

    Awale, Mahendra; Reymond, Jean-Louis

    2014-07-28

    Three-dimensional (3D) molecular shape and pharmacophores are important determinants of the biological activity of organic molecules; however, a precise computation of 3D-shape is generally too slow for virtual screening of very large databases. A reinvestigation of the concept of atom pairs initially reported by Carhart et al. and extended by Schneider et al. showed that a simple atom pair fingerprint (APfp) counting atom pairs at increasing topological distances in 2D-structures without atom property assignment correlates with various representations of molecular shape extracted from the 3D-structures. A related 55-dimensional atom pair fingerprint extended with atom properties (Xfp) provided an efficient pharmacophore fingerprint with good performance for ligand-based virtual screening such as the recovery of active compounds from decoys in DUD, and overlap with the ROCS 3D-pharmacophore scoring function. The APfp and Xfp data were organized for web-based extremely fast nearest-neighbor searching in ZINC (13.5 M compounds) and GDB-17 (50 M random subset) freely accessible at www.gdb.unibe.ch .

  20. 3D-nanoarchitectured Pd/Ni catalysts prepared by atomic layer deposition for the electrooxidation of formic acid.

    PubMed

    Assaud, Loïc; Monyoncho, Evans; Pitzschel, Kristina; Allagui, Anis; Petit, Matthieu; Hanbücken, Margrit; Baranova, Elena A; Santinacci, Lionel

    2014-01-01

    Three-dimensionally (3D) nanoarchitectured palladium/nickel (Pd/Ni) catalysts, which were prepared by atomic layer deposition (ALD) on high-aspect-ratio nanoporous alumina templates are investigated with regard to the electrooxidation of formic acid in an acidic medium (0.5 M H2SO4). Both deposition processes, Ni and Pd, with various mass content ratios have been continuously monitored by using a quartz crystal microbalance. The morphology of the Pd/Ni systems has been studied by electron microscopy and shows a homogeneous deposition of granularly structured Pd onto the Ni substrate. X-ray diffraction analysis performed on Ni and NiO substrates revealed an amorphous structure, while the Pd coating crystallized into a fcc lattice with a preferential orientation along the [220]-direction. Surface chemistry analysis by X-ray photoelectron spectroscopy showed both metallic and oxide contributions for the Ni and Pd deposits. Cyclic voltammetry of the Pd/Ni nanocatalysts revealed that the electrooxidation of HCOOH proceeds through the direct dehydrogenation mechanism with the formation of active intermediates. High catalytic activities are measured for low masses of Pd coatings that were generated by a low number of ALD cycles, probably because of the cluster size effect, electronic interactions between Pd and Ni, or diffusion effects.

  1. 3D-nanoarchitectured Pd/Ni catalysts prepared by atomic layer deposition for the electrooxidation of formic acid

    PubMed Central

    Assaud, Loïc; Monyoncho, Evans; Pitzschel, Kristina; Allagui, Anis; Petit, Matthieu; Hanbücken, Margrit

    2014-01-01

    Summary Three-dimensionally (3D) nanoarchitectured palladium/nickel (Pd/Ni) catalysts, which were prepared by atomic layer deposition (ALD) on high-aspect-ratio nanoporous alumina templates are investigated with regard to the electrooxidation of formic acid in an acidic medium (0.5 M H2SO4). Both deposition processes, Ni and Pd, with various mass content ratios have been continuously monitored by using a quartz crystal microbalance. The morphology of the Pd/Ni systems has been studied by electron microscopy and shows a homogeneous deposition of granularly structured Pd onto the Ni substrate. X-ray diffraction analysis performed on Ni and NiO substrates revealed an amorphous structure, while the Pd coating crystallized into a fcc lattice with a preferential orientation along the [220]-direction. Surface chemistry analysis by X-ray photoelectron spectroscopy showed both metallic and oxide contributions for the Ni and Pd deposits. Cyclic voltammetry of the Pd/Ni nanocatalysts revealed that the electrooxidation of HCOOH proceeds through the direct dehydrogenation mechanism with the formation of active intermediates. High catalytic activities are measured for low masses of Pd coatings that were generated by a low number of ALD cycles, probably because of the cluster size effect, electronic interactions between Pd and Ni, or diffusion effects. PMID:24605281

  2. 3D-nanoarchitectured Pd/Ni catalysts prepared by atomic layer deposition for the electrooxidation of formic acid.

    PubMed

    Assaud, Loïc; Monyoncho, Evans; Pitzschel, Kristina; Allagui, Anis; Petit, Matthieu; Hanbücken, Margrit; Baranova, Elena A; Santinacci, Lionel

    2014-01-01

    Three-dimensionally (3D) nanoarchitectured palladium/nickel (Pd/Ni) catalysts, which were prepared by atomic layer deposition (ALD) on high-aspect-ratio nanoporous alumina templates are investigated with regard to the electrooxidation of formic acid in an acidic medium (0.5 M H2SO4). Both deposition processes, Ni and Pd, with various mass content ratios have been continuously monitored by using a quartz crystal microbalance. The morphology of the Pd/Ni systems has been studied by electron microscopy and shows a homogeneous deposition of granularly structured Pd onto the Ni substrate. X-ray diffraction analysis performed on Ni and NiO substrates revealed an amorphous structure, while the Pd coating crystallized into a fcc lattice with a preferential orientation along the [220]-direction. Surface chemistry analysis by X-ray photoelectron spectroscopy showed both metallic and oxide contributions for the Ni and Pd deposits. Cyclic voltammetry of the Pd/Ni nanocatalysts revealed that the electrooxidation of HCOOH proceeds through the direct dehydrogenation mechanism with the formation of active intermediates. High catalytic activities are measured for low masses of Pd coatings that were generated by a low number of ALD cycles, probably because of the cluster size effect, electronic interactions between Pd and Ni, or diffusion effects. PMID:24605281

  3. Atom probe tomography of lithium-doped network glasses.

    PubMed

    Greiwe, Gerd-Hendrik; Balogh, Zoltan; Schmitz, Guido

    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.

  4. Artemisinin activity-based probes identify multiple molecular targets within the asexual stage of the malaria parasites Plasmodium falciparum 3D7

    PubMed Central

    Ismail, Hanafy M.; Barton, Victoria; Phanchana, Matthew; Charoensutthivarakul, Sitthivut; Wong, Michael H. L.; Hemingway, Janet; Biagini, Giancarlo A.; O’Neill, Paul M.; Ward, Stephen A.

    2016-01-01

    The artemisinin (ART)-based antimalarials have contributed significantly to reducing global malaria deaths over the past decade, but we still do not know how they kill parasites. To gain greater insight into the potential mechanisms of ART drug action, we developed a suite of ART activity-based protein profiling probes to identify parasite protein drug targets in situ. Probes were designed to retain biological activity and alkylate the molecular target(s) of Plasmodium falciparum 3D7 parasites in situ. Proteins tagged with the ART probe can then be isolated using click chemistry before identification by liquid chromatography–MS/MS. Using these probes, we define an ART proteome that shows alkylated targets in the glycolytic, hemoglobin degradation, antioxidant defense, and protein synthesis pathways, processes essential for parasite survival. This work reveals the pleiotropic nature of the biological functions targeted by this important class of antimalarial drugs. PMID:26858419

  5. Artemisinin activity-based probes identify multiple molecular targets within the asexual stage of the malaria parasites Plasmodium falciparum 3D7.

    PubMed

    Ismail, Hanafy M; Barton, Victoria; Phanchana, Matthew; Charoensutthivarakul, Sitthivut; Wong, Michael H L; Hemingway, Janet; Biagini, Giancarlo A; O'Neill, Paul M; Ward, Stephen A

    2016-02-23

    The artemisinin (ART)-based antimalarials have contributed significantly to reducing global malaria deaths over the past decade, but we still do not know how they kill parasites. To gain greater insight into the potential mechanisms of ART drug action, we developed a suite of ART activity-based protein profiling probes to identify parasite protein drug targets in situ. Probes were designed to retain biological activity and alkylate the molecular target(s) of Plasmodium falciparum 3D7 parasites in situ. Proteins tagged with the ART probe can then be isolated using click chemistry before identification by liquid chromatography-MS/MS. Using these probes, we define an ART proteome that shows alkylated targets in the glycolytic, hemoglobin degradation, antioxidant defense, and protein synthesis pathways, processes essential for parasite survival. This work reveals the pleiotropic nature of the biological functions targeted by this important class of antimalarial drugs. PMID:26858419

  6. Design by simulation of the UT array inspection of a nozzle with a flexible probe: Definition of 3D trajectories and focusing parameters

    NASA Astrophysics Data System (ADS)

    Vanhoye, A.; Casula, O.; Moussebois, D.

    2013-01-01

    The inspection of 3D components such as a nozzle weld requires overcoming the difficulties due to the complex geometry. The use of flexible array has been proven to be an efficient solution allowing to compensate the effect of the varying profile and to ensure the quality of the ultrasonic beam transmitted in the material along the probe scanning. The definition of the trajectory of the probe and the focusing parameters (parameters introduced in the delay law calculations) is allowed by using a flexible probe on this evolving 3D geometry (saddle) compared to a solid wedge probe. In this communication we present a study performed in the case of the inspection of a nozzle weld using a flexible array. This study aims at ensuring an efficient coverage of the region of interest around the weld based on software tools. These tools allow calculation of an efficient trajectory and the focusing parameters. A strategy has been implemented in order to minimize the number of delay laws applied to reach this coverage. The probe performances have been assessed by using the CIVA software to detect notch located in the zone of interest.

  7. Atom-Probe Measurements of Meteoritic Nanodiamonds and Terrestrial Standards

    NASA Astrophysics Data System (ADS)

    Lewis, J. B.; Isheim, D.; Floss, C.; Daulton, T. L.; Seidman, D. N.; Heck, P. R.; Davis, A. M.; Pellin, M. J.; Savina, M. R.; Hiller, J.; Mane, A.; Elam, J. W.; Stephan, T.

    2013-09-01

    We present new data from the novel application of atom-probe tomography to the study of nanodiamonds from the meteorite Allende. The mean meteoritic ^12C/^13C peak ratio is higher than that of our standards, but there are instrumental artifacts.

  8. Atom probe tomographic mapping directly reveals the atomic distribution of phosphorus in resin embedded ferritin

    DOE PAGES

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

    2016-02-29

    In this study, 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.

  9. Data mining for isotope discrimination in atom probe tomography.

    PubMed

    Broderick, Scott R; Bryden, Aaron; Suram, Santosh K; Rajan, Krishna

    2013-09-01

    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.

  10. Atomic-scale phase composition through multivariate statistical analysis of atom probe tomography data.

    PubMed

    Keenan, Michael R; Smentkowski, Vincent S; Ulfig, Robert M; Oltman, Edward; Larson, David J; Kelly, Thomas F

    2011-06-01

    We demonstrate for the first time that multivariate statistical analysis techniques can be applied to atom probe tomography data to estimate the chemical composition of a sample at the full spatial resolution of the atom probe in three dimensions. Whereas the raw atom probe data provide the specific identity of an atom at a precise location, the multivariate results can be interpreted in terms of the probabilities that an atom representing a particular chemical phase is situated there. When aggregated to the size scale of a single atom (∼0.2 nm), atom probe spectral-image datasets are huge and extremely sparse. In fact, the average spectrum will have somewhat less than one total count per spectrum due to imperfect detection efficiency. These conditions, under which the variance in the data is completely dominated by counting noise, test the limits of multivariate analysis, and an extensive discussion of how to extract the chemical information is presented. Efficient numerical approaches to performing principal component analysis (PCA) on these datasets, which may number hundreds of millions of individual spectra, are put forward, and it is shown that PCA can be computed in a few seconds on a typical laptop computer.

  11. Extremely sharp carbon nanocone probes for atomic force microscopy imaging

    NASA Astrophysics Data System (ADS)

    Chen, I.-Chen; Chen, Li-Han; Ye, Xiang-Rong; Daraio, Chiara; Jin, Sungho; Orme, Christine A.; Quist, Arjan; Lal, Ratnesh

    2006-04-01

    A simple and reliable catalyst patterning technique combined with electric-field-guided growth is utilized to synthesize a sharp and high-aspect-ratio carbon nanocone probe on a tipless cantilever for atomic force microscopy. A single carbon nanodot produced by an electron-beam-induced deposition serves as a convenient chemical etch mask for catalyst patterning, thus eliminating the need for complicated, resist-based, electron-beam lithography for a nanoprobe fabrication. A gradual, sputtering-induced size reduction and eventual removal of the catalyst particle at the probe tip during electric-field-guided growth creates a sharp probe with a tip radius of only a few nanometers. These fabrication processes are amenable for the wafer-scale synthesis of multiple probes. High resolution imaging of three-dimensional features and deep trenches, and mechanical durability enabling continuous operation for many hours without noticeable image deterioration have been demonstrated.

  12. Atomic Scale Characterization of Compound Semiconductors using Atom Probe Tomography: Preprint

    SciTech Connect

    Gorman, B. P.; Guthrey, H.; Norman, A. G.; Al-Jassim, M.; Lawrence, D.; Prosa, T.

    2011-07-01

    Internal interfaces are critical in determining the performance of III-V multijunction solar cells. Studying these interfaces with atomic resolution using a combination of transmission electron microscopy (TEM), atom probe tomography (APT), and density functional calculations enables a more fundamental understanding of carrier dynamics in photovoltaic (PV) device structures. To achieve full atomic scale spatial and chemical resolution, data acquisition parameters in laser pulsed APT must be carefully studied to eliminate surface diffusion. Atom probe data with minimized group V ion clustering and expected stoichiometry can be achieved by adjusting laser pulse power, pulse repetition rate, and specimen preparation parameters such that heat flow away from the evaporating surface is maximized. Applying these improved analysis conditions to III-V based PV gives an atomic scale understanding of compositional and dopant profiles across interfaces and tunnel junctions and the initial stages of alloy clustering and dopant accumulation. Details on APT experimental methods and future in-situ instrumentation developments are illustrated.

  13. Repumping and spectroscopy of laser-cooled Sr atoms using the (5s5p)3P2-(5s4d)3D2 transition

    NASA Astrophysics Data System (ADS)

    Mickelson, P. G.; Martinez de Escobar, Y. N.; Anzel, P.; De Salvo, B. J.; Nagel, S. B.; Traverso, A. J.; Yan, M.; Killian, T. C.

    2009-12-01

    We describe repumping and spectroscopy of laser-cooled strontium (Sr) atoms using the (5s5p)3P2-(5s4d)3D2 transition. Atom number in a magneto-optical trap is enhanced by driving this transition because Sr atoms that have decayed into the (5s5p)3P2 dark state are repumped back into the (5s2)1S0 ground state. Spectroscopy of 84Sr, 86Sr, 87Sr and 88Sr improves the value of the (5s5p)3P2-(5s4d)3D2 transition frequency and determines the isotope shifts for the transition accurately enough to guide laser-cooling experiments with less abundant isotopes.

  14. Mechanical gate control for atom-by-atom cluster assembly with scanning probe microscopy.

    PubMed

    Sugimoto, Yoshiaki; Yurtsever, Ayhan; Hirayama, Naoki; Abe, Masayuki; Morita, Seizo

    2014-07-11

    Nanoclusters supported on substrates are of great importance in physics and chemistry as well as in technical applications, such as single-electron transistors and nanocatalysts. The properties of nanoclusters differ significantly from those of either the constituent atoms or the bulk solid, and are highly sensitive to size and chemical composition. Here we propose a novel atom gating technique to assemble various atom clusters composed of a defined number of atoms at room temperature. The present gating operation is based on the transfer of single diffusing atoms among nanospaces governed by gates, which can be opened in response to the chemical interaction force with a scanning probe microscope tip. This method provides an alternative way to create pre-designed atom clusters with different chemical compositions and to evaluate their chemical stabilities, thus enabling investigation into the influence that a single dopant atom incorporated into the host clusters has on a given cluster stability.

  15. High-Resolution B Dot Probe for Measuring 3D Magnetic Fields in the MOCHI Labjet Experiment

    NASA Astrophysics Data System (ADS)

    Azuara Rosales, Manuel; von der Linden, Jens; You, Setthivoine

    2014-10-01

    The MOCHI Labjet experiment will use a triple electrode planar plasma gun to explore canonical helicity transport in laboratory astrophysical jets. Canonical helicity transport suggests that destabilizing magnetic energy can be converted into stabilizing shear flows at two-fluid spatial scales li ~c/wpi . A high-resolution . B probe array, capable of measuring magnetic field dynamics at length and time scales important to canonical helicity transport is being built. The probe array consists of three tridents, made of 5 . 13 mm OD and 4 . 32 mm ID stainless steel tubes of 102 cm length, enclosing a total of 1215 commercial inductor chips with a three axis spatial resolution of 11 mm. The average value for the effective NA of each inductor chip is 1 . 21 .10-4 m2. The probe array lays in a plane perpendicular to the jet, and is axially translatable. This work is supported by US DOE Grant DE-SC0010340.

  16. Local Electrode Atom Probe Characterization of Crept CMSX-4 Superalloy

    SciTech Connect

    Miller, Michael K; Reed, R. C.

    2006-01-01

    The solute distributions in crept and annealed single crystal CMSX-4 nickel-based superalloy have been characterized from multi-million atom data sets obtained with the local electrode atom probe. Solute-depleted and solute-enriched regions are evident on both sides of the - interface. Ultrafine (~1 nm diameter) rhenium clusters containing up to ~10-15% Re were evident in the 10-nm wide Reenriched region in the matrix close to the - interface. Re-enriched regions were also detected in asperities in the - interface in the crept conditions.

  17. Combined experimental and theoretical probe of the lifetime of the 3 d 2D5 /2 state in 40Ca+

    NASA Astrophysics Data System (ADS)

    Guan, Hua; Shao, Hu; Qian, Yuan; Huang, Yao; Liu, Pei-Liang; Bian, Wu; Li, Cheng-Bin; Sahoo, B. K.; Gao, Ke-Lin

    2015-02-01

    In light of the diverse range of reported values for the lifetimes of metastable states of 40Ca+ , we have carried out afresh both measurements and theoretical investigation to confirm the lifetime of its 3 d 2D5 /2 state (τ3 d 5 /2) . A high-efficiency quantum state detection method by monitoring the quantum jumps of a laser-cooled single Ca+ ion in a miniature ring Paul trap was employed in the measurement. Also, sophisticated calculations were performed considering higher order nonlinear terms in the relativistic coupled-cluster (RCC) method with all possible single and double excitations, but accounting only for the important triple excitations from both the core and the valence orbitals. Systematic factors affecting measurement, such as collision with background gases, heating effects, the power of the 866-nm laser, and state detection errors were carefully analyzed. Our observational and theoretical values for τ3 d 5 /2 are 1174(10) ms and 1172(3) ms, respectively, which agree well with the experimental results reported by P. A. Barton et al. [Phys. Rev. A 62, 032503 (2000), 10.1103/PhysRevA.62.032503] and A. Kreuter et al. [Phys. Rev. A 71, 032504 (2005), 10.1103/PhysRevA.71.032504]. The present theoretical analysis demonstrates that the contributions from the core triples and Breit interaction are notable, as they improve the theoretical results obtained in the previous RCC calculations [B. K. Sahoo, Phys. Rev. A 74, 062504 (2006), 10.1103/PhysRevA.74.062504].

  18. Using attosecond pulses to probe ultrafast electronic motions inside atoms

    NASA Astrophysics Data System (ADS)

    Collins, L. A.; Hu, S. X.

    2006-05-01

    With using an efficient and accurate parallel solver for the time-dependent Schr"odinger equation, we have performed full-dimensional numerical simulations of the proposed attosecond pump-probe for exploring the extremely fast motion of an electronic wave packet inside atoms. Pumped by a broadband femtosecond UV pulse, one electron of ground-state Helium can be launched into a superposition of low-lying excited states, thus forming a bound wavepacket oscillating relative to the atomic core. A time-delayed attosecond EUV (probe) pulse then ionizes the atom causing three-body breakup. Measuring either the energy sharing of the ionized electrons or the total ionization probability as a function of the time delay traces out the internal motion of the excited electron. Our simulations have shown that an ultrashort oscillating period of 2 fs can be followed for several cylces. This opens the prospect of a wealth of similar pump-probe experiments to examine ultrafast electronic motions.

  19. Generation of a cold pulsed beam of Rb atoms by transfer from a 3D magneto-optic trap

    NASA Astrophysics Data System (ADS)

    Chanu, Sapam Ranjita; Rathod, Ketan D.; Natarajan, Vasant

    2016-08-01

    We demonstrate a technique for producing a cold pulsed beam of atoms by transferring a cloud of atoms trapped in a three dimensional magneto-optic trap (MOT). The MOT is loaded by heating a getter source of Rb atoms. We show that it is advantageous to transfer with two beams (with a small angle between them) compared to a single beam, because the atoms stop interacting with the beams in the two-beam technique, which results in a Gaussian velocity distribution. The atoms are further cooled in optical molasses by turning off the MOT magnetic field before the transfer beams are turned on.

  20. Probing Electronic Transport of Individual Nanostructures with Atomic Precision

    NASA Astrophysics Data System (ADS)

    Qin, Shengyong; Li, An-Ping

    Accessing individual nanostructures with atomic precision is an important process in the bottom-up fabrication and characterization of electronic nanodevices. Local electrical contacts, namely nanoelectrodes, are often fabricated by using top-down lithography and chemical etching techniques. These processes however lack atomic precision and introduce the possibility of contamination. Here, we review recent reports on the application of a field-induced emission process in the fabrication of local contacts onto individual nanowires and nanotubes with atomic spatial precision. In this method, gold nanoislands are deposited onto nanostructures precisely by using a scanning tunneling microscope tip, which provides a clean and controllable process to ensure both electrically conductive and mechanically reliable contacts. The applicability of the technique has been demonstrated in a wide variety of nanostructures, including silicide atomic wires, carbon nanotubes, and copper nanowires. These local contacts bridge the nanostructures and the transport probes, allowing for the measurements of both electrical transport and scanning tunneling microscopy on the same nanostructures in situ. The direct correlation between electronic and transport properties and atomic structures can be explored on individual nanostructures at the unprecedented atomic level.

  1. Probing electronic transport of individual nanostructures with atomic precision

    SciTech Connect

    Qin, Shengyong; Li, An-Ping

    2012-01-01

    Accessing individual nanostructures with atomic precision is an important process in the bottom-up fabrication and characterization of electronic nanodevices. Local electrical contacts, namely nanoelectrodes, are often fabricated by using top-down lithography and chemical etching techniques. These processes however lack atomic precision and introduce the possibility of contamination. Here, we review recent reports on the application of a field-induced emission process in the fabrication of local contacts onto individual nanowires and nanotubes with atomic spatial precision. In this method, gold nanoislands are deposited onto nanostructures precisely by using a scanning tunneling microscope tip, which provides a clean and controllable process to ensure both electrically conductive and mechanically reliable contacts. The applicability of the technique has been demonstrated in a wide variety of nanostructures, including silicide atomic wires, carbon nanotubes, and copper nanowires. These local contacts bridge the nanostructures and the transport probes, allowing for the measurements of both electrical transport and scanning tunneling microscopy on the same nanostructures in situ. The direct correlation between electronic and transport properties and atomic structures can be explored on individual nanostructures at the unprecedented atomic level.

  2. The Interaction of the Solar Wind with Solar Probe Plus - 3D Hybrid Simulation. Report 2: The Study for the Distance 9.5Rs

    NASA Technical Reports Server (NTRS)

    Lipatov, Alexander S.; Sittler, Edward C.; Hartle, Richard E.; Cooper, John F.

    2010-01-01

    Our paper is a 2.5D and 3D numerical plasma models of the interaction of the solar wind (SW) with the Solar Probe Plus spacecraft (SPPSC). These results should be interpreted as a basic plasma model for which the derived SW interaction with spacecraft (SC) could have consequences for both plasma wave and electron plasma measurements on board SC in the inner heliosphere. We observe an excitation of the low frequency Alfven and whistler type wave directed by the magnetic field with an amplitude of the electromagnetic field oscillation about of (0.015-0.06) V/m. The compression waves and the jumps in an electric field with an amplitude of about 1.5 V/m and (12-18) V/m were also observed. The observed strong electromagnetic perturbations may be a crucial point in the electromagnetic measurements, which were planned in future Solar Probe Plus mission.

  3. Analysis of structural correlations in a model binary 3D liquid through the eigenvalues and eigenvectors of the atomic stress tensors.

    PubMed

    Levashov, V A

    2016-03-01

    It is possible to associate with every atom or molecule in a liquid its own atomic stress tensor. These atomic stress tensors can be used to describe liquids' structures and to investigate the connection between structural and dynamic properties. In particular, atomic stresses allow to address atomic scale correlations relevant to the Green-Kubo expression for viscosity. Previously correlations between the atomic stresses of different atoms were studied using the Cartesian representation of the stress tensors or the representation based on spherical harmonics. In this paper we address structural correlations in a 3D model binary liquid using the eigenvalues and eigenvectors of the atomic stress tensors. This approach allows to interpret correlations relevant to the Green-Kubo expression for viscosity in a simple geometric way. On decrease of temperature the changes in the relevant stress correlation function between different atoms are significantly more pronounced than the changes in the pair density function. We demonstrate that this behaviour originates from the orientational correlations between the eigenvectors of the atomic stress tensors. We also found correlations between the eigenvalues of the same atomic stress tensor. For the studied system, with purely repulsive interactions between the particles, the eigenvalues of every atomic stress tensor are positive and they can be ordered: λ1 ≥ λ2 ≥ λ3 ≥ 0. We found that, for the particles of a given type, the probability distributions of the ratios (λ2/λ1) and (λ3/λ2) are essentially identical to each other in the liquids state. We also found that λ2 tends to be equal to the geometric average of λ1 and λ3. In our view, correlations between the eigenvalues may represent "the Poisson ratio effect" at the atomic scale. PMID:26957166

  4. Analysis of structural correlations in a model binary 3D liquid through the eigenvalues and eigenvectors of the atomic stress tensors.

    PubMed

    Levashov, V A

    2016-03-01

    It is possible to associate with every atom or molecule in a liquid its own atomic stress tensor. These atomic stress tensors can be used to describe liquids' structures and to investigate the connection between structural and dynamic properties. In particular, atomic stresses allow to address atomic scale correlations relevant to the Green-Kubo expression for viscosity. Previously correlations between the atomic stresses of different atoms were studied using the Cartesian representation of the stress tensors or the representation based on spherical harmonics. In this paper we address structural correlations in a 3D model binary liquid using the eigenvalues and eigenvectors of the atomic stress tensors. This approach allows to interpret correlations relevant to the Green-Kubo expression for viscosity in a simple geometric way. On decrease of temperature the changes in the relevant stress correlation function between different atoms are significantly more pronounced than the changes in the pair density function. We demonstrate that this behaviour originates from the orientational correlations between the eigenvectors of the atomic stress tensors. We also found correlations between the eigenvalues of the same atomic stress tensor. For the studied system, with purely repulsive interactions between the particles, the eigenvalues of every atomic stress tensor are positive and they can be ordered: λ1 ≥ λ2 ≥ λ3 ≥ 0. We found that, for the particles of a given type, the probability distributions of the ratios (λ2/λ1) and (λ3/λ2) are essentially identical to each other in the liquids state. We also found that λ2 tends to be equal to the geometric average of λ1 and λ3. In our view, correlations between the eigenvalues may represent "the Poisson ratio effect" at the atomic scale.

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

    NASA Astrophysics Data System (ADS)

    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.

  6. Nanoscale Cluster Detection in Massive Atom Probe Tomography Data

    SciTech Connect

    Seal, Sudip K; Yoginath, Srikanth B; Miller, Michael K

    2014-01-01

    Recent technological advances in atom probe tomography (APT) have led to unprecedented data acquisition capabilities that routinely generate data sets containing hundreds of millions of atoms. Detecting nanoscale clusters of different atom types present in these enormous amounts of data and analyzing their spatial correlations with one another are fundamental to understanding the structural properties of the material from which the data is derived. Extant algorithms for nanoscale cluster detection do not scale to large data sets. Here, a scalable, CUDA-based implementation of an autocorrelation algorithm is presented. It isolates spatial correlations amongst atomic clusters present in massive APT data sets in linear time using a linear amount of storage. Correctness of the algorithm is demonstrated using large synthetically generated data with known spatial distributions. Benefits and limitations of using GPU-acceleration for autocorrelation-based APT data analyses are presented with supporting performance results on data sets with up to billions of atoms. To our knowledge, this is the first nanoscale cluster detection algorithm that scales to massive APT data sets and executes on commodity hardware.

  7. Pharmacophore modeling and atom-based 3D-QSAR studies on amino derivatives of indole as potent isoprenylcysteine carboxyl methyltransferase (Icmt) inhibitors

    NASA Astrophysics Data System (ADS)

    Bhadoriya, Kamlendra Singh; Sharma, Mukesh C.; Jain, Shailesh V.

    2015-02-01

    Icmt enzymes are of particular importance in the post-translational modification of proteins that are involved in the regulation of cell growth. Thus, effective Icmt inhibitors may be of significant therapeutic importance in oncogenesis. To determine the structural requirements responsible for high affinity of previously reported amino derivatives of indole as Icmt inhibitors, a successful pharmacophore generation and atom-based 3D-QSAR analysis have been carried out. The best four-point pharmacophore model with four features HHRR: two hydrophobic groups (H) and two aromatic rings (R) as pharmacophore features was developed by PHASE module of Schrodinger suite. In this study, highly predictive 3D-QSAR models have been developed for Icmt inhibition using HHRR.191 hypothesis. The pharmacophore hypothesis yielded a 3D-QSAR model with good partial least-square (PLS) statistics results. The validation of the PHASE model was done by dividing the dataset into training and test set. The statistically significant the four-point pharmacophore hypothesis yielded a 3D-QSAR model with good PLS statistics results (R2 = 0.9387, Q2 = 0.8132, F = 114.8, SD = 0.1567, RMSE = 0.2682, Pearson-R = 0.9147). The generated model showed excellent predictive power, with a correlation coefficient of Q2 = 0.8132. The results of ligand-based pharmacophore hypothesis and atom-based 3D-QSAR provide detailed structural insights as well as highlights important binding features of novel amino derivatives of indole as Icmt inhibitors which can afford guidance for the rational drug design of novel, potent and promising Icmt inhibitors with enhanced potencies and may prove helpful for further lead optimization and virtual screening.

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

    PubMed

    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.

  9. 3D-calibration of three- and four-sensor hot-film probes based on collocated sonic using neural networks

    NASA Astrophysics Data System (ADS)

    Kit, Eliezer; Liberzon, Dan

    2016-09-01

    High resolution measurements of turbulence in the atmospheric boundary layer (ABL) are critical to the understanding of physical processes and parameterization of important quantities, such as the turbulent kinetic energy dissipation. Low spatio-temporal resolution of standard atmospheric instruments, sonic anemometers and LIDARs, limits their suitability for fine-scale measurements of ABL. The use of miniature hot-films is an alternative technique, although such probes require frequent calibration, which is logistically untenable in field setups. Accurate and truthful calibration is crucial for the multi-hot-films applications in atmospheric studies, because the ability to conduct calibration in situ ultimately determines the turbulence measurements quality. Kit et al (2010 J. Atmos. Ocean. Technol. 27 23-41) described a novel methodology for calibration of hot-film probes using a collocated sonic anemometer combined with a neural network (NN) approach. An important step in the algorithm is the generation of a calibration set for NN training by an appropriate low-pass filtering of the high resolution voltages, measured by the hot-film-sensors and low resolution velocities acquired by the sonic. In Kit et al (2010 J. Atmos. Ocean. Technol. 27 23-41), Kit and Grits (2011 J. Atmos. Ocean. Technol. 28 104-10) and Vitkin et al (2014 Meas. Sci. Technol. 25 75801), the authors reported on successful use of this approach for in situ calibration, but also on the method’s limitations and restricted range of applicability. In their earlier work, a jet facility and a probe, comprised of two orthogonal x-hot-films, were used for calibration and for full dataset generation. In the current work, a comprehensive laboratory study of 3D-calibration of two multi-hot-film probes (triple- and four-sensor) using a grid flow was conducted. The probes were embedded in a collocated sonic, and their relative pitch and yaw orientation to the mean flow was changed by means of motorized

  10. 3D-calibration of three- and four-sensor hot-film probes based on collocated sonic using neural networks

    NASA Astrophysics Data System (ADS)

    Kit, Eliezer; Liberzon, Dan

    2016-09-01

    High resolution measurements of turbulence in the atmospheric boundary layer (ABL) are critical to the understanding of physical processes and parameterization of important quantities, such as the turbulent kinetic energy dissipation. Low spatio-temporal resolution of standard atmospheric instruments, sonic anemometers and LIDARs, limits their suitability for fine-scale measurements of ABL. The use of miniature hot-films is an alternative technique, although such probes require frequent calibration, which is logistically untenable in field setups. Accurate and truthful calibration is crucial for the multi-hot-films applications in atmospheric studies, because the ability to conduct calibration in situ ultimately determines the turbulence measurements quality. Kit et al (2010 J. Atmos. Ocean. Technol. 27 23–41) described a novel methodology for calibration of hot-film probes using a collocated sonic anemometer combined with a neural network (NN) approach. An important step in the algorithm is the generation of a calibration set for NN training by an appropriate low-pass filtering of the high resolution voltages, measured by the hot-film-sensors and low resolution velocities acquired by the sonic. In Kit et al (2010 J. Atmos. Ocean. Technol. 27 23–41), Kit and Grits (2011 J. Atmos. Ocean. Technol. 28 104–10) and Vitkin et al (2014 Meas. Sci. Technol. 25 75801), the authors reported on successful use of this approach for in situ calibration, but also on the method’s limitations and restricted range of applicability. In their earlier work, a jet facility and a probe, comprised of two orthogonal x-hot-films, were used for calibration and for full dataset generation. In the current work, a comprehensive laboratory study of 3D-calibration of two multi-hot-film probes (triple- and four-sensor) using a grid flow was conducted. The probes were embedded in a collocated sonic, and their relative pitch and yaw orientation to the mean flow was changed by means of

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

    SciTech Connect

    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

  12. Structural analyses in three-dimensional atom probe: a Fourier transform approach.

    PubMed

    Vurpillot, F; Da Costa, G; Menand, A; Blavette, D

    2001-09-01

    The three-dimensional atom probe (3DAP) technique gives the elemental identities and the position of atoms within the small volume analysed (on the order of 10 x 10 x 100 nm(3)). The large number of atoms collected (up to two million) and the excellent spatial resolution of this instrument allows the observation of some crystallographic features of phases chemically identified. This paper shows that the application of a discrete Fourier transform algorithm to a 3DAP dataset provides information that is not easily accessible in real space. The derivation of the mean size of particles from Fourier intensities is an example. Using 3D 'dark-field' imaging, single ordered grains were isolated from the disordered matrix of a ternary alloy. Moreover, the intrinsic spatial resolution of the instrument was evaluated by this method for pure metal; the resolution reaches 0.2 nm laterally and 0.06 nm in depth. This excellent resolution is shown to be sufficient to give access to the crystalline lattice. The use of image filtering in the reciprocal space enables for atomic columns to be imaged the first time from 3DAP data.

  13. Multifunctional hydrogel nano-probes for atomic force microscopy

    NASA Astrophysics Data System (ADS)

    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.

  14. Multifunctional hydrogel nano-probes for atomic force microscopy.

    PubMed

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

    2016-05-20

    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.

  15. Probing Micromechanical Properties of the Extracellular Matrix of Soft Tissues by Atomic Force Microscopy.

    PubMed

    Jorba, Ignasi; Uriarte, Juan J; Campillo, Noelia; Farré, Ramon; Navajas, Daniel

    2017-01-01

    The extracellular matrix (ECM) determines 3D tissue architecture and provides structural support and chemical and mechanical cues to the cells. Atomic force microscopy (AFM) has unique capabilities to measure ECM mechanics at the scale at which cells probe the mechanical features of their microenvironment. Moreover, AFM measurements can be readily combined with bright field and fluorescence microscopy. Performing reliable mechanical measurements with AFM requires accurate calibration of the device and correct computation of the mechanical parameters. A suitable approach to isolate ECM mechanics from cell contribution is removing the cells by means of an effective decellularization process that preserves the composition, structure and mechanical properties of the ECM. AFM measurement of ECM micromechanics provides important insights into organ biofabrication, cell-matrix mechanical crosstalk and disease-induced tissue stiffness alterations. J. Cell. Physiol. 232: 19-26, 2017. © 2016 Wiley Periodicals, Inc. PMID:27163411

  16. Probing Micromechanical Properties of the Extracellular Matrix of Soft Tissues by Atomic Force Microscopy.

    PubMed

    Jorba, Ignasi; Uriarte, Juan J; Campillo, Noelia; Farré, Ramon; Navajas, Daniel

    2017-01-01

    The extracellular matrix (ECM) determines 3D tissue architecture and provides structural support and chemical and mechanical cues to the cells. Atomic force microscopy (AFM) has unique capabilities to measure ECM mechanics at the scale at which cells probe the mechanical features of their microenvironment. Moreover, AFM measurements can be readily combined with bright field and fluorescence microscopy. Performing reliable mechanical measurements with AFM requires accurate calibration of the device and correct computation of the mechanical parameters. A suitable approach to isolate ECM mechanics from cell contribution is removing the cells by means of an effective decellularization process that preserves the composition, structure and mechanical properties of the ECM. AFM measurement of ECM micromechanics provides important insights into organ biofabrication, cell-matrix mechanical crosstalk and disease-induced tissue stiffness alterations. J. Cell. Physiol. 232: 19-26, 2017. © 2016 Wiley Periodicals, Inc.

  17. Laser assisted field evaporation of oxides in atom probe analysis.

    PubMed

    Chen, Y M; Ohkubo, T; Hono, K

    2011-05-01

    We have investigated the laser assisted field evaporation phenomena of ZnO, and MgO to explore the feasibility of quantitative three dimensional atom probe analyses of insulating oxides. To assist the field evaporation of these oxides, the usage of short wavelength 343 nm ultraviolet (UV) laser was found to be more effective than 515 nm green laser. We observed field ion microscopy (FIM) image expansion and mass peak shifting when 343 nm laser was irradiated on MgO. This phenomenon can be attributed to the laser induced electron excitation which causes the reduction of the resistivity of the specimen.

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

    PubMed

    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.

  19. Probing ultrafast electronic motions in atoms with the attosecond pump-probe

    NASA Astrophysics Data System (ADS)

    Collins, Lee; Hu, Suxing; Schneider, Barry

    2006-03-01

    Through full-dimensional numerical simulations with using our recently-developed efficient and accurate parallel solver for the time-dependent Schrödinger equation, we have demonstrated that an attosecond pulse can effectively probe the extremely fast motion of an electronic wave packet in atoms. Pumped by a broadband femtosecond UV pulse, one electron of ground-state Helium can be launched into a superposition of low-lying excited states, thus forming a wavepacket that begins to orbit the atomic core. A time-delayed attosecond EUV pulse (probe) then ionizes the atom causing three-body breakup. Measuring either the energy sharing of the ionized electrons or the total ionization probability as a function of the time delay displays the internal motion of the excited electron. Our simulation has shown that an ultrashort Kepler period of 2 fs can be followed for several cylces. This opens the prospect of a wealth of similar pump-probe experiments to examine electronic motion.

  20. Encapsulation method for atom probe tomography analysis of nanoparticles.

    PubMed

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

    2015-12-01

    Open-space nanomaterials are a widespread class of technologically important materials that are generally incompatible with analysis by atom probe tomography (APT) due to issues with specimen preparation, field evaporation and data reconstruction. The feasibility of encapsulating such non-compact matter in a matrix to enable APT measurements is investigated using nanoparticles as an example. Simulations of field evaporation of a void, and the resulting artifacts in ion trajectory, underpin the requirement that no voids remain after encapsulation. The approach is demonstrated by encapsulating Pt nanoparticles in an ZnO:Al matrix created by atomic layer deposition, a growth technique which offers very high surface coverage and conformality. APT measurements of the Pt nanoparticles are correlated with transmission electron microscopy images and numerical simulations in order to evaluate the accuracy of the APT reconstruction.

  1. Design of a femtosecond laser assisted tomographic atom probe

    SciTech Connect

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

    2006-04-15

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

  2. Probing cell-matrix interactions in RGD-decorated macroporous poly (ethylene glycol) hydrogels for 3D chondrocyte culture.

    PubMed

    Zhang, Jingjing; Mujeeb, Ayeesha; Du, Yanan; Lin, Jianhao; Ge, Zigang

    2015-06-01

    Macroporous hydrogels have shown great promise as scaffolds for cartilage engineering by facilitating nutrition transport and tissue in growth. Cell-matrix adhesion-a fundamental process in tissue engineering-has shown a profound effect on subsequent cell phenotype, extracellular matrix (ECM) accumulation, and tissue reorganization. In this study, arginine-glycine-aspartic acid (RGD) was introduced to macroporous hydrogels of poly (ethylene glycol) (PEG) to fabricate PEG-G400 (with 0.4mM RGD) and PEG-G2000 (2mM RGD) to probe the cell-matrix interactions within hydrogels. Primary chondrocytes demonstrated a slightly stretched morphology with increasing RGD concentration and PEG-G2000 hydrogels boosted cell viability, proliferation, and deposition of collagen II and GAG, in comparison to the PEG-G400 and PEG-RED groups. Results also revealed chondrocytes within the cell aggregates underwent dedifferentiation and hypertrophy within RGD incorporated hydrogels, as evidenced by the high level of gene expression of collagen I on day 14 and strong immunohistological staining of collagen X and collagen I on day 35. Evidently, a high concentration of RGD (2mM RGD) enhanced cell-matrix interactions through elevating the expression of integrin β1 and vinculin. Thus, the integration of RGD in macroporous hydrogels with a concentration of 2 mM may be sufficient for improving cell functionality, with a slight probability of dedifferentiation and hypertrophy of chondrocytes. PMID:26107534

  3. Basis set limit electronic excitation energies, ionization potentials, and electron affinities for the 3d transition metal atoms: Coupled cluster and multireference methods

    NASA Astrophysics Data System (ADS)

    Balabanov, Nikolai B.; Peterson, Kirk A.

    2006-08-01

    Recently developed correlation consistent basis sets for the first row transition metal elements Sc-Zn have been utilized to determine complete basis set (CBS) scalar relativistic electron affinities, ionization potentials, and 4s23dn -2-4s1dn -1 electronic excitation energies with single reference coupled cluster methods [CCSD(T), CCSDT, and CCSDTQ] and multireference configuration interaction with three reference spaces: 3d4s, 3d4s4p, and 3d4s4p3d'. The theoretical values calculated with the highest order coupled cluster techniques at the CBS limit, including extrapolations to full configuration interaction, are well within 1kcal/mol of the corresponding experimental data. For the early transition metal elements (Sc-Mn) the internally contracted multireference averaged coupled pair functional method yielded excellent agreement with experiment; however, the atomic properties for the late transition metals (Mn-Zn) proved to be much more difficult to describe with this level of theory, even with the largest reference function of the present work.

  4. Advance in multi-hit detection and quantization in atom probe tomography

    NASA Astrophysics Data System (ADS)

    Costa, G. Da; Wang, H.; Duguay, S.; Bostel, A.; Blavette, D.; Deconihout, B.

    2012-12-01

    The preferential retention of high evaporation field chemical species at the sample surface in atom-probe tomography (e.g., boron in silicon or in metallic alloys) leads to correlated field evaporation and pronounced pile-up effects on the detector. The latter severely affects the reliability of concentration measurements of current 3D atom probes leading to an under-estimation of the concentrations of the high-field species. The multi-hit capabilities of the position-sensitive time-resolved detector is shown to play a key role. An innovative method based on Fourier space signal processing of signals supplied by an advance delay-line position-sensitive detector is shown to drastically improve the time resolving power of the detector and consequently its capability to detect multiple events. Results show that up to 30 ions on the same evaporation pulse can be detected and properly positioned. The major impact of this new method on the quantization of chemical composition in materials, particularly in highly-doped Si(B) samples is highlighted.

  5. Advance in multi-hit detection and quantization in atom probe tomography.

    PubMed

    Da Costa, G; Wang, H; Duguay, S; Bostel, A; Blavette, D; Deconihout, B

    2012-12-01

    The preferential retention of high evaporation field chemical species at the sample surface in atom-probe tomography (e.g., boron in silicon or in metallic alloys) leads to correlated field evaporation and pronounced pile-up effects on the detector. The latter severely affects the reliability of concentration measurements of current 3D atom probes leading to an under-estimation of the concentrations of the high-field species. The multi-hit capabilities of the position-sensitive time-resolved detector is shown to play a key role. An innovative method based on Fourier space signal processing of signals supplied by an advance delay-line position-sensitive detector is shown to drastically improve the time resolving power of the detector and consequently its capability to detect multiple events. Results show that up to 30 ions on the same evaporation pulse can be detected and properly positioned. The major impact of this new method on the quantization of chemical composition in materials, particularly in highly-doped Si(B) samples is highlighted.

  6. Adsorption of alkali, alkaline-earth, simple and 3d transition metal, and nonmetal atoms on monolayer MoS{sub 2}

    SciTech Connect

    Li, X. D.; Fang, Y. M.; Wu, S. Q. E-mail: wsq@xmu.edu.cn; Zhu, Z. Z. E-mail: wsq@xmu.edu.cn

    2015-05-15

    Single adsorption of different atoms on pristine two-dimensional monolayer MoS{sub 2} have been systematically investigated by using density functional calculations with van der Waals correction. The adatoms cover alkali metals, alkaline earth metals, main group metal, 3d-transition metals, coinage metal and nonmetal atoms. Depending on the adatom type, metallic, semimetallic or semiconducting behavior can be found in direct bandgap monolayer MoS{sub 2}. Additionally, local or long-range magnetic moments of two-dimensional MoS{sub 2} sheet can also attained through the adsorption. The detailed atomic-scale knowledge of single adsorption on MoS{sub 2} monolayer is important not only for the sake of a theoretical understanding, but also device level deposition technological application.

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

    PubMed Central

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

    2016-01-01

    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. PMID:26924804

  8. Development of a 3D-AFM for true 3D measurements of nanostructures

    NASA Astrophysics Data System (ADS)

    Dai, Gaoliang; Häßler-Grohne, Wolfgang; Hüser, Dorothee; Wolff, Helmut; Danzebrink, Hans-Ulrich; Koenders, Ludger; Bosse, Harald

    2011-09-01

    The development of advanced lithography requires highly accurate 3D metrology methods for small line structures of both wafers and photomasks. Development of a new 3D atomic force microscopy (3D-AFM) with vertical and torsional oscillation modes is introduced in this paper. In its configuration, the AFM probe is oscillated using two piezo actuators driven at vertical and torsional resonance frequencies of the cantilever. In such a way, the AFM tip can probe the surface with a vertical and a lateral oscillation, offering high 3D probing sensitivity. In addition, a so-called vector approach probing (VAP) method has been applied. The sample is measured point-by-point using this method. At each probing point, the tip is approached towards the surface until the desired tip-sample interaction is detected and then immediately withdrawn from the surface. Compared to conventional AFMs, where the tip is kept continuously in interaction with the surface, the tip-sample interaction time using the VAP method is greatly reduced and consequently the tip wear is reduced. Preliminary experimental results show promising performance of the developed system. A measurement of a line structure of 800 nm height employing a super sharp AFM tip could be performed with a repeatability of its 3D profiles of better than 1 nm (p-v). A line structure of a Physikalisch-Technische Bundesanstalt photomask with a nominal width of 300 nm has been measured using a flared tip AFM probe. The repeatability of the middle CD values reaches 0.28 nm (1σ). A long-term stability investigation shows that the 3D-AFM has a high stability of better than 1 nm within 197 measurements taken over 30 h, which also confirms the very low tip wear.

  9. Phosphorus doping of Si nanocrystals embedded in silicon oxynitride determined by atom probe tomography

    SciTech Connect

    Gnaser, Hubert Kopnarski, Michael; Gutsch, Sebastian; Hiller, Daniel; Zacharias, Margit; Wahl, Michael; Schiller, Rüdiger

    2014-01-21

    Silicon nanocrystals (SiNCs) embedded in a silicon oxide matrix were studied by 3D atom probe tomography (APT). The distribution of the SiNC diameter was found to have a mean value of 3.7 ± 0.8 nm. The elemental composition of these particles was determined by employing two different approaches: (i) The proximity histogram method and (ii) a cluster identification algorithm based on maximum-atom separations. Both approaches give very similar values in terms of the amount of P, O, and Si within the SiNCs: the mean atomic concentrations are c{sub P} = 0.77% ± 0.4%, c{sub O} = 12.3% ± 2.1%, and c{sub Si} = 85.3% ± 2.1%. A detailed cluster analysis implies that, on average, a 4.5-nm SiNC would contain around 30 P atoms, whereas a 2.0-nm SiNC would contain only around 3 P atoms. Radial concentration profiles obtained for these SiNCs indicate that the P content is inhomogeneous and possibly enhanced at the boundary as compared to the interior of the NCs. About 20% of the P atoms are found to be incorporated into the SiNCs, whereas roughly 30% are trapped within the interfacial layer (with a thickness of ∼ 0.8 nm); the remainder resides in the surrounding matrix. Cluster-size dependent P concentrations support the view of self-purification in the Si nanostructures.

  10. Multifunctional hydrogel nano-probes for atomic force microscopy

    PubMed Central

    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

  11. Mapping magnetism with atomic resolution using aberrated electron probes

    NASA Astrophysics Data System (ADS)

    Idrobo, Juan; Rusz, Ján; McGuire, Michael A.; Symons, Christopher T.; Vatsavai, Ranga Raju; Lupini, Andrew R.

    2015-03-01

    In this talk, we report a direct experimental real-space mapping of magnetic circular dichroism with atomic resolution in aberration-corrected scanning transmission electron microscopy (STEM). Using an aberrated electron probe with customized phase distribution, we reveal with electron energy-loss (EEL) spectroscopy the checkerboard antiferromagnetic ordering of Mn moments in LaMnAsO by observing a dichroic signal in the Mn L-edge. The aberrated probes allow the collection of EEL spectra using the transmitted beam, which results in a magnetic circular dichroic signal with intrinsically larger signal-to-noise ratios than those obtained via nanodiffraction techniques (where most of the transmitted electrons are discarded). The novel experimental setup presented here, which can easily be implemented in aberration-corrected STEM, opens new paths for probing dichroic signals in materials with unprecedented spatial resolution. This research was supported by DOE SUFD MSED, by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the US DOE, and by the Swedish Research Council and Swedish National Infrastructure for Computing (NSC center)

  12. Point-by-point compositional analysis for atom probe tomography.

    PubMed

    Stephenson, Leigh T; Ceguerra, Anna V; Li, Tong; Rojhirunsakool, Tanaporn; Nag, Soumya; Banerjee, Rajarshi; Cairney, Julie M; Ringer, Simon P

    2014-01-01

    This new alternate approach to data processing for analyses that traditionally employed grid-based counting methods is necessary because it removes a user-imposed coordinate system that not only limits an analysis but also may introduce errors. We have modified the widely used "binomial" analysis for APT data by replacing grid-based counting with coordinate-independent nearest neighbour identification, improving the measurements and the statistics obtained, allowing quantitative analysis of smaller datasets, and datasets from non-dilute solid solutions. It also allows better visualisation of compositional fluctuations in the data. Our modifications include:.•using spherical k-atom blocks identified by each detected atom's first k nearest neighbours.•3D data visualisation of block composition and nearest neighbour anisotropy.•using z-statistics to directly compare experimental and expected composition curves. Similar modifications may be made to other grid-based counting analyses (contingency table, Langer-Bar-on-Miller, sinusoidal model) and could be instrumental in developing novel data visualisation options.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  14. Probing modified gravity with atom-interferometry: A numerical approach

    NASA Astrophysics Data System (ADS)

    Schlögel, Sandrine; Clesse, Sébastien; Füzfa, André

    2016-05-01

    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 one 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 1 order of magnitude. In the thin-shell regime, results are found to be in good agreement with the analytical estimations, 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 uncertainties, by doing the experiment at several key positions inside the vacuum chamber. For the chameleon potential V (ϕ )=Λ4 +α/ϕα and a coupling function A (ϕ )=exp (ϕ /M ), one finds M ≳7 ×1016 GeV , independently of the power-law index. For V (ϕ )=Λ4(1 +Λ /ϕ ), one finds M ≳1014 GeV . A sensitivity of a ˜10-11 m /s2 would probe the model up to the Planck scale. Finally, a proposal for a second experimental setup, in a vacuum room, is presented. In this case, Planckian values of M could be probed provided that a ˜10-10 m /s2 , a limit reachable by future experiments. Our method can easily be extended to constrain other models with a screening mechanism, such as symmetron, dilaton and f(R) theories.

  15. The influence of voxel size on atom probe tomography data.

    PubMed

    Torres, K L; Daniil, M; Willard, M A; Thompson, G B

    2011-05-01

    A methodology for determining the optimal voxel size for phase thresholding in nanostructured materials was developed using an atom simulator and a model system of a fixed two-phase composition and volume fraction. The voxel size range was banded by the atom count within each voxel. Some voxel edge lengths were found to be too large, resulting in an averaging of compositional fluctuations; others were too small with concomitant decreases in the signal-to-noise ratio for phase identification. The simulated methodology was then applied to the more complex experimentally determined data set collected from a (Co(0.95)Fe(0.05))(88)Zr(6)Hf(1)B(4)Cu(1) two-phase nanocomposite alloy to validate the approach. In this alloy, Zr and Hf segregated to an intergranular amorphous phase while Fe preferentially segregated to a crystalline phase during the isothermal annealing step that promoted primary crystallization. The atom probe data analysis of the volume fraction was compared to transmission electron microscopy (TEM) dark-field imaging analysis and a lever rule analysis of the volume fraction within the amorphous and crystalline phases of the ribbon.

  16. Atom-probe analysis of cemented carbides and cermets

    NASA Astrophysics Data System (ADS)

    Andrén, H.-O.; Rolander, U.; Lindahl, P.

    1994-03-01

    For many years we have studied the detailed microstructure of cemented carbides (WC-Co and WC-MC-Co) and cermets (TiC-TiN-Mo 2C-Ni/Co and (Ti, W, Ta)(C, N)-(Co, Ni)), using mainly atom-probe field ion microscopy. This paper contains an overview of our experimental methods and results. All investigated materials were found to have a hard-phase skeleton with about half a monolayer of binder metal grain boundary segregation. The binder phase contained metal atoms from hard phases, which dissolve during sintering, but was almost completely free of C and N. Depleted zones existed close to hard phases due to diffusion during cooling after sintering. Cobalt binder phase contains W and Mo but little Ti, nickel binder phase Ti and Mo. The amount of Ti did not vary much with N content in the alloy, whereas the Mo content increased substantially with total N content. Carbide or carbonitride grains in materials containing more than one hard phase formed a core-rim structure. Rims precipitated epitaxially onto cores during sintering, and compositional gradients reflect the sequence of hard-phase dissolution. No diffusion of metal atoms occurred in the hard phases during sintering so the material is far from thermodynamic equilibrium. However, C and N may diffuse so that the system approaches equilibrium with respect to these elements during sintering.

  17. Atomic characterization of Si nanoclusters embedded in SiO2 by atom probe tomography.

    PubMed

    Roussel, Manuel; Talbot, Etienne; Gourbilleau, Fabrice; Pareige, Philippe

    2011-02-23

    Silicon nanoclusters are of prime interest for new generation of optoelectronic and microelectronics components. Physical properties (light emission, carrier storage...) of systems using such nanoclusters are strongly dependent on nanostructural characteristics. These characteristics (size, composition, distribution, and interface nature) are until now obtained using conventional high-resolution analytic methods, such as high-resolution transmission electron microscopy, EFTEM, or EELS. In this article, a complementary technique, the atom probe tomography, was used for studying a multilayer (ML) system containing silicon clusters. Such a technique and its analysis give information on the structure at the atomic level and allow obtaining complementary information with respect to other techniques. A description of the different steps for such analysis: sample preparation, atom probe analysis, and data treatment are detailed. An atomic scale description of the Si nanoclusters/SiO2 ML will be fully described. This system is composed of 3.8-nm-thick SiO layers and 4-nm-thick SiO2 layers annealed 1 h at 900°C.

  18. Atomic characterization of Si nanoclusters embedded in SiO2 by atom probe tomography.

    PubMed

    Roussel, Manuel; Talbot, Etienne; Gourbilleau, Fabrice; Pareige, Philippe

    2011-01-01

    Silicon nanoclusters are of prime interest for new generation of optoelectronic and microelectronics components. Physical properties (light emission, carrier storage...) of systems using such nanoclusters are strongly dependent on nanostructural characteristics. These characteristics (size, composition, distribution, and interface nature) are until now obtained using conventional high-resolution analytic methods, such as high-resolution transmission electron microscopy, EFTEM, or EELS. In this article, a complementary technique, the atom probe tomography, was used for studying a multilayer (ML) system containing silicon clusters. Such a technique and its analysis give information on the structure at the atomic level and allow obtaining complementary information with respect to other techniques. A description of the different steps for such analysis: sample preparation, atom probe analysis, and data treatment are detailed. An atomic scale description of the Si nanoclusters/SiO2 ML will be fully described. This system is composed of 3.8-nm-thick SiO layers and 4-nm-thick SiO2 layers annealed 1 h at 900°C. PMID:21711666

  19. Synthesis-atomic structure-properties relationships in metallic nanoparticles by total scattering experiments and 3D computer simulations: case of Pt-Ru nanoalloy catalysts.

    PubMed

    Prasai, Binay; Ren, Yang; Shan, Shiyao; Zhao, Yinguang; Cronk, Hannah; Luo, Jin; Zhong, Chuan-Jian; Petkov, Valeri

    2015-05-01

    An approach to determining the 3D atomic structure of metallic nanoparticles (NPs) in fine detail and using the unique knowledge obtained for rationalizing their synthesis and properties targeted for optimization is described and exemplified on Pt-Ru alloy NPs of importance to the development of devices for clean energy conversion such as fuel cells. In particular, PtxRu100-x alloy NPs, where x = 31, 49 and 75, are synthesized by wet chemistry and activated catalytically by a post-synthesis treatment involving heating under controlled N2-H2 atmosphere. So-activated NPs are evaluated as catalysts for gas-phase CO oxidation and ethanol electro-oxidation reactions taking place in fuel cells. Both as-synthesized and activated NPs are characterized structurally by total scattering experiments involving high-energy synchrotron X-ray diffraction coupled to atomic pair distribution functions (PDFs) analysis. 3D structure models both for as-synthesized and activated NPs are built by molecular dynamics simulations based on the archetypal for current theoretical modelling Sutton-Chen method. Models are refined against the experimental PDF data by reverse Monte Carlo simulations and analysed in terms of prime structural characteristics such as metal-to-metal bond lengths, bond angles and first coordination numbers for Pt and Ru atoms. Analysis indicates that, though of a similar type, the atomic structure of as-synthesized and respective activated NPs differ in several details of importance to NP catalytic properties. Structural characteristics of activated NPs and data for their catalytic activity are compared side by side and strong evidence found that electronic effects, indicated by significant changes in Pt-Pt and Ru-Ru metal bond lengths at NP surface, and practically unrecognized so far atomic ensemble effects, indicated by distinct stacking of atomic layers near NP surface and prevalence of particular configurations of Pt and Ru atoms in these layers, contribute to the

  20. NiO nanoarrays of a few atoms thickness on 3D nickel network for enhanced pseudocapacitive electrode applications

    NASA Astrophysics Data System (ADS)

    Senthilkumar, Velusamy; Kadumudi, Firoz Babu; Ho, Nhu Thuy; Kim, Ji-Woong; Park, Sungkyun; Bae, Jong-Seong; Choi, Won Mook; Cho, Shinuk; Kim, Yong Soo

    2016-01-01

    The present work focuses on the development of template-free mesoporous NiO nanoarrays with large surface area grown on 3D nickel foam networks by a seed mediated aqueous chemical growth technique and subsequent annealing process. The resultant binder-free, well-aligned and vertically grown NiO nanoarrays exhibits a micron-sized planar structure as well as an ultrathin thickness (˜7 nm). The unique surface and electronic structure facilitates surface-dependent electrochemical reaction processes with no dead volume. They deliver a high capacitance of 2065 F g-1 at a current density of 16 A g-1 as a three electrode system. A specific capacitance of 1247 F g-1 is maintained at a higher current rate of 70 A g-1 with 88.9% retention after 5000 cycles. Finally, in a solid-state asymmetric supercapacitor configuration using NiO//activated carbon, the device delivers an enhanced supercapacitive performance, with an energy density of 43.5 Wh kg-1 and power density of 2.1 kW kg-1. Thus, the current research paves the way for the use of NiO nanoarrays as an electrode material for practical supercapacitor devices with higher cycling retention and rate capacity.

  1. The Interaction of the Solar Wind with Solar Probe Plus - 3D Hybrid Simulation. Report 1; The Study for the Distance 4.5Rs

    NASA Technical Reports Server (NTRS)

    Lipatov, Alexander S.; Sittler, Edward C.; Hartle, Richard E.; Cooper, John F.

    2010-01-01

    Our report devotes a 3D numerical hybrid model of the interaction of the solar wind with the Solar Probe spacecraft. The Solar Probe Plus (SPP) model includes 3 main parts, namely, a non-conducting heat shield, a support system, and cylindrical section or spacecraft bus that contains the particle analysis devices and antenna. One observes an excitation of the low frequency Alfven and whistler type wave directed by the magnetic field with an amplitude of about (0.06-0.6) V/m. The compression waves and the jumps in an electric field with an amplitude of about (0.15-0.7) V/m were also observed. The wave amplitudes are comparable to or greater than previously estimated max wave amplitudes that SPP is expected to measure. The results of our hybrid simulation will be useful for understanding the plasma environment near the SPP spacecraft at the distance 4.5 Rs. Future simulation will take into account the charging of the spacecraft, the charge separation effects, an outgassing from heat shield, a photoionization and an electron impact ionization effects near the spacecraft.

  2. A Bright Fluorescent Probe for H2S Enables Analyte-Responsive, 3D Imaging in Live Zebrafish Using Light Sheet Fluorescence Microscopy

    PubMed Central

    2015-01-01

    Hydrogen sulfide (H2S) is a critical gaseous signaling molecule emerging at the center of a rich field of chemical and biological research. As our understanding of the complexity of physiological H2S in signaling pathways evolves, advanced chemical and technological investigative tools are required to make sense of this interconnectivity. Toward this goal, we have developed an azide-functionalized O-methylrhodol fluorophore, MeRho-Az, which exhibits a rapid >1000-fold fluorescence response when treated with H2S, is selective for H2S over other biological analytes, and has a detection limit of 86 nM. Additionally, the MeRho-Az scaffold is less susceptible to photoactivation than other commonly used azide-based systems, increasing its potential application in imaging experiments. To demonstrate the efficacy of this probe for H2S detection, we demonstrate the ability of MeRho-Az to detect differences in H2S levels in C6 cells and those treated with AOAA, a common inhibitor of enzymatic H2S synthesis. Expanding the use of MeRho-Az to complex and heterogeneous biological settings, we used MeRho-Az in combination with light sheet fluorescence microscopy (LSFM) to visualize H2S in the intestinal tract of live zebrafish. This application provides the first demonstration of analyte-responsive 3D imaging with LSFM, highlighting the utility of combining new probes and live imaging methods for investigating chemical signaling in complex multicellular systems. PMID:26061541

  3. A Bright Fluorescent Probe for H2S Enables Analyte-Responsive, 3D Imaging in Live Zebrafish Using Light Sheet Fluorescence Microscopy.

    PubMed

    Hammers, Matthew D; Taormina, Michael J; Cerda, Matthew M; Montoya, Leticia A; Seidenkranz, Daniel T; Parthasarathy, Raghuveer; Pluth, Michael D

    2015-08-19

    Hydrogen sulfide (H2S) is a critical gaseous signaling molecule emerging at the center of a rich field of chemical and biological research. As our understanding of the complexity of physiological H2S in signaling pathways evolves, advanced chemical and technological investigative tools are required to make sense of this interconnectivity. Toward this goal, we have developed an azide-functionalized O-methylrhodol fluorophore, MeRho-Az, which exhibits a rapid >1000-fold fluorescence response when treated with H2S, is selective for H2S over other biological analytes, and has a detection limit of 86 nM. Additionally, the MeRho-Az scaffold is less susceptible to photoactivation than other commonly used azide-based systems, increasing its potential application in imaging experiments. To demonstrate the efficacy of this probe for H2S detection, we demonstrate the ability of MeRho-Az to detect differences in H2S levels in C6 cells and those treated with AOAA, a common inhibitor of enzymatic H2S synthesis. Expanding the use of MeRho-Az to complex and heterogeneous biological settings, we used MeRho-Az in combination with light sheet fluorescence microscopy (LSFM) to visualize H2S in the intestinal tract of live zebrafish. This application provides the first demonstration of analyte-responsive 3D imaging with LSFM, highlighting the utility of combining new probes and live imaging methods for investigating chemical signaling in complex multicellular systems. PMID:26061541

  4. A Bright Fluorescent Probe for H2S Enables Analyte-Responsive, 3D Imaging in Live Zebrafish Using Light Sheet Fluorescence Microscopy.

    PubMed

    Hammers, Matthew D; Taormina, Michael J; Cerda, Matthew M; Montoya, Leticia A; Seidenkranz, Daniel T; Parthasarathy, Raghuveer; Pluth, Michael D

    2015-08-19

    Hydrogen sulfide (H2S) is a critical gaseous signaling molecule emerging at the center of a rich field of chemical and biological research. As our understanding of the complexity of physiological H2S in signaling pathways evolves, advanced chemical and technological investigative tools are required to make sense of this interconnectivity. Toward this goal, we have developed an azide-functionalized O-methylrhodol fluorophore, MeRho-Az, which exhibits a rapid >1000-fold fluorescence response when treated with H2S, is selective for H2S over other biological analytes, and has a detection limit of 86 nM. Additionally, the MeRho-Az scaffold is less susceptible to photoactivation than other commonly used azide-based systems, increasing its potential application in imaging experiments. To demonstrate the efficacy of this probe for H2S detection, we demonstrate the ability of MeRho-Az to detect differences in H2S levels in C6 cells and those treated with AOAA, a common inhibitor of enzymatic H2S synthesis. Expanding the use of MeRho-Az to complex and heterogeneous biological settings, we used MeRho-Az in combination with light sheet fluorescence microscopy (LSFM) to visualize H2S in the intestinal tract of live zebrafish. This application provides the first demonstration of analyte-responsive 3D imaging with LSFM, highlighting the utility of combining new probes and live imaging methods for investigating chemical signaling in complex multicellular systems.

  5. Coke Formation in a Zeolite Crystal During the Methanol-to-Hydrocarbons Reaction as Studied with Atom Probe Tomography.

    PubMed

    Schmidt, Joel E; Poplawsky, Jonathan D; Mazumder, Baishakhi; Attila, Özgün; Fu, Donglong; de Winter, D A Matthijs; Meirer, Florian; Bare, Simon R; Weckhuysen, Bert M

    2016-09-01

    Understanding the formation of carbon deposits in zeolites is vital to developing new, superior materials for various applications, including oil and gas conversion processes. Herein, atom probe tomography (APT) has been used to spatially resolve the 3D compositional changes at the sub-nm length scale in a single zeolite ZSM-5 crystal, which has been partially deactivated by the methanol-to-hydrocarbons reaction using (13) C-labeled methanol. The results reveal the formation of coke in agglomerates that span length scales from tens of nanometers to atomic clusters with a median size of 30-60 (13) C atoms. These clusters correlate with local increases in Brønsted acid site density, demonstrating that the formation of the first deactivating coke precursor molecules occurs in nanoscopic regions enriched in aluminum. This nanoscale correlation underscores the importance of carefully engineering materials to suppress detrimental coke formation.

  6. Coke formation in a zeolite crystal during the methanol-to-hydrocarbons reaction as studied with atom probe tomography

    DOE PAGES

    Schmidt, Joel E.; Poplawsky, Jonathan D.; Mazumder, Baishakhi; Attila, Özgün; Fu, Donglong; de Winter, D. A. Matthijs; Meirer, Florian; Bare, Simon R.; Weckhuysen, Bert M.

    2016-08-03

    Understanding the formation of carbon deposits in zeolites is vital to developing new, superior materials for various applications, including oil and gas conversion processes. Herein, atom probe tomography (APT) has been used to spatially resolve the 3D compositional changes at the sub-nm length scale in a single zeolite ZSM-5 crystal, which has been partially deactivated by the methanol-to-hydrocarbons reaction using 13C-labeled methanol. The results reveal the formation of coke in agglomerates that span length scales from tens of nanometers to atomic clusters with a median size of 30–60 13C atoms. These clusters correlate with local increases in Brønsted acid sitemore » density, demonstrating that the formation of the first deactivating coke precursor molecules occurs in nanoscopic regions enriched in aluminum. Here, this nanoscale correlation underscores the importance of carefully engineering materials to suppress detrimental coke formation.« less

  7. Coke Formation in a Zeolite Crystal During the Methanol-to-Hydrocarbons Reaction as Studied with Atom Probe Tomography.

    PubMed

    Schmidt, Joel E; Poplawsky, Jonathan D; Mazumder, Baishakhi; Attila, Özgün; Fu, Donglong; de Winter, D A Matthijs; Meirer, Florian; Bare, Simon R; Weckhuysen, Bert M

    2016-09-01

    Understanding the formation of carbon deposits in zeolites is vital to developing new, superior materials for various applications, including oil and gas conversion processes. Herein, atom probe tomography (APT) has been used to spatially resolve the 3D compositional changes at the sub-nm length scale in a single zeolite ZSM-5 crystal, which has been partially deactivated by the methanol-to-hydrocarbons reaction using (13) C-labeled methanol. The results reveal the formation of coke in agglomerates that span length scales from tens of nanometers to atomic clusters with a median size of 30-60 (13) C atoms. These clusters correlate with local increases in Brønsted acid site density, demonstrating that the formation of the first deactivating coke precursor molecules occurs in nanoscopic regions enriched in aluminum. This nanoscale correlation underscores the importance of carefully engineering materials to suppress detrimental coke formation. PMID:27485276

  8. Atom-probe analyses of nanodiamonds from Allende

    NASA Astrophysics Data System (ADS)

    Heck, Philipp R.; Stadermann, Frank J.; Isheim, Dieter; Auciello, Orlando; Daulton, Tyrone L.; Davis, Andrew M.; Elam, Jeffrey W.; Floss, Christine; Hiller, Jon; Larson, David J.; Lewis, Josiah B.; Mane, Anil; Pellin, Michael J.; Savina, Michael R.; Seidman, David N.; Stephan, Thomas

    2014-03-01

    Atom-probe tomography (APT) is currently the only analytical technique that, due to its spatial resolution and detection efficiency, has the potential to measure the carbon isotope ratios of individual nanodiamonds. We describe three different sample preparation protocols that we developed for the APT analysis of meteoritic nanodiamonds at sub-nm resolution and present carbon isotope peak ratios of meteoritic and synthetic nanodiamonds. The results demonstrate an instrumental bias associated with APT that needs to be quantified and corrected to obtain accurate isotope ratios. After this correction is applied, this technique should allow determination of the distribution of 12C/13C ratios in individual diamond grains, solving the decades-old question of the origin of meteoritic nanodiamonds: what fraction, if any, formed in the solar system and in presolar environments? Furthermore, APT could help us identify the stellar sources of any presolar nanodiamonds that are detected.

  9. Interpreting atom probe data from chromium oxide scales.

    PubMed

    La Fontaine, Alexandre; Gault, Baptiste; Breen, Andrew; Stephenson, Leigh; Ceguerra, Anna V; Yang, Limei; Nguyen, Thuan Dinh; Zhang, Jianqiang; Young, David J; Cairney, Julie M

    2015-12-01

    Picosecond-pulsed ultraviolet-laser (UV-355 nm) assisted atom probe tomography (APT) was used to analyze protective, thermally grown chromium oxides formed on stainless steel. The influence of analysis parameters on the thermal tail observed in the mass spectra and the chemical composition is investigated. A new parameter termed "laser sensitivity factor" is introduced in order to quantify the effect of laser energy on the extent of the thermal tail. This parameter is used to compare the effect of increasing laser energy on thermal tails in chromia and chromite samples. Also explored is the effect of increasing laser energy on the measured oxygen content and the effect of specimen base temperature and laser pulse frequency on the mass spectrum. Finally, we report a preliminary analysis of molecular ion dissociations in chromia.

  10. Characterization of Nanoporous Materials with Atom Probe Tomography.

    PubMed

    Pfeiffer, Björn; Erichsen, Torben; Epler, Eike; Volkert, Cynthia A; Trompenaars, Piet; Nowak, Carsten

    2015-06-01

    A method to characterize open-cell nanoporous materials with atom probe tomography (APT) has been developed. For this, open-cell nanoporous gold with pore diameters of around 50 nm was used as a model system, and filled by electron beam-induced deposition (EBID) to obtain a compact material. Two different EBID precursors were successfully tested-dicobalt octacarbonyl [Co2(CO)8] and diiron nonacarbonyl [Fe2(CO)9]. Penetration and filling depth are sufficient for focused ion beam-based APT sample preparation. With this approach, stable APT analysis of the nanoporous material can be performed. Reconstruction reveals the composition of the deposited precursor and the nanoporous material, as well as chemical information of the interfaces between them. Thus, it is shown that, using an appropriate EBID process, local chemical information in three dimensions with sub-nanometer resolution can be obtained from nanoporous materials using APT.

  11. Multivariate statistical analysis of atom probe tomography data.

    PubMed

    Parish, Chad M; Miller, Michael K

    2010-10-01

    The application of spectrum imaging multivariate statistical analysis methods, specifically principal component analysis (PCA), to atom probe tomography (APT) data has been investigated. The mathematical method of analysis is described and the results for two example datasets are analyzed and presented. The first dataset is from the analysis of a PM 2000 Fe-Cr-Al-Ti steel containing two different ultrafine precipitate populations. PCA properly describes the matrix and precipitate phases in a simple and intuitive manner. A second APT example is from the analysis of an irradiated reactor pressure vessel steel. Fine, nm-scale Cu-enriched precipitates having a core-shell structure were identified and qualitatively described by PCA. Advantages, disadvantages, and future prospects for implementing these data analysis methodologies for APT datasets, particularly with regard to quantitative analysis, are also discussed. PMID:20650566

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

    NASA Astrophysics Data System (ADS)

    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.

  13. 3D Micropillars Guide the Mechanobiology of Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes.

    PubMed

    Palankar, Raghavendra; Glaubitz, Michael; Martens, Ulrike; Medvedev, Nikolay; von der Ehe, Marvin; Felix, Stephan B; Münzenberg, Markus; Delcea, Mihaela

    2016-02-01

    3D micropillars generated by photolithography are used as a platform to probe by atomic force microscopy the mechanodynamics of human induced pluripotent stem cell-derived cardiomyocytes. 3D micropillars guide subcellular cytoskeletal modifications of cardiomyocytes and lead to biochemical changes altering beating rate, stiffness, and calcium dynamics of the cells.

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

    NASA Astrophysics Data System (ADS)

    Mittal, Anudha

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

  15. Probe knots and Hopf insulators with ultracold atoms

    NASA Astrophysics Data System (ADS)

    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.

  16. Fingering convection induced by atomic diffusion in stars: 3D numerical computations and applications to stellar models

    SciTech Connect

    Zemskova, Varvara; Garaud, Pascale; Deal, Morgan; Vauclair, Sylvie

    2014-11-10

    Iron-rich layers are known to form in the stellar subsurface through a combination of gravitational settling and radiative levitation. Their presence, nature, and detailed structure can affect the excitation process of various stellar pulsation modes and must therefore be modeled carefully in order to better interpret Kepler asteroseismic data. In this paper, we study the interplay between atomic diffusion and fingering convection in A-type stars, as well as its role in the establishment and evolution of iron accumulation layers. To do so, we use a combination of three-dimensional idealized numerical simulations of fingering convection (which neglect radiative transfer and complex opacity effects) and one-dimensional realistic stellar models. Using the three-dimensional simulations, we first validate the mixing prescription for fingering convection recently proposed by Brown et al. (within the scope of the aforementioned approximation) and identify what system parameters (total mass of iron, iron diffusivity, thermal diffusivity, etc.) play a role in the overall evolution of the layer. We then implement the Brown et al. prescription in the Toulouse-Geneva Evolution Code to study the evolution of the iron abundance profile beneath the stellar surface. We find, as first discussed by Théado et al., that when the concurrent settling of helium is ignored, this accumulation rapidly causes an inversion in the mean molecular weight profile, which then drives fingering convection. The latter mixes iron with the surrounding material very efficiently, and the resulting iron layer is very weak. However, taking helium settling into account partially stabilizes the iron profile against fingering convection, and a large iron overabundance can accumulate. The opacity also increases significantly as a result, and in some cases it ultimately triggers dynamical convection. The direct effects of radiative acceleration on the dynamics of fingering convection (especially in the

  17. Fingering Convection Induced by Atomic Diffusion in Stars: 3D Numerical Computations and Applications to Stellar Models

    NASA Astrophysics Data System (ADS)

    Zemskova, Varvara; Garaud, Pascale; Deal, Morgan; Vauclair, Sylvie

    2014-11-01

    Iron-rich layers are known to form in the stellar subsurface through a combination of gravitational settling and radiative levitation. Their presence, nature, and detailed structure can affect the excitation process of various stellar pulsation modes and must therefore be modeled carefully in order to better interpret Kepler asteroseismic data. In this paper, we study the interplay between atomic diffusion and fingering convection in A-type stars, as well as its role in the establishment and evolution of iron accumulation layers. To do so, we use a combination of three-dimensional idealized numerical simulations of fingering convection (which neglect radiative transfer and complex opacity effects) and one-dimensional realistic stellar models. Using the three-dimensional simulations, we first validate the mixing prescription for fingering convection recently proposed by Brown et al. (within the scope of the aforementioned approximation) and identify what system parameters (total mass of iron, iron diffusivity, thermal diffusivity, etc.) play a role in the overall evolution of the layer. We then implement the Brown et al. prescription in the Toulouse-Geneva Evolution Code to study the evolution of the iron abundance profile beneath the stellar surface. We find, as first discussed by Théado et al., that when the concurrent settling of helium is ignored, this accumulation rapidly causes an inversion in the mean molecular weight profile, which then drives fingering convection. The latter mixes iron with the surrounding material very efficiently, and the resulting iron layer is very weak. However, taking helium settling into account partially stabilizes the iron profile against fingering convection, and a large iron overabundance can accumulate. The opacity also increases significantly as a result, and in some cases it ultimately triggers dynamical convection. The direct effects of radiative acceleration on the dynamics of fingering convection (especially in the

  18. Atom-specific forces and defect identification on surface-oxidized Cu(100) with combined 3D-AFM and STM measurements

    NASA Astrophysics Data System (ADS)

    Baykara, Mehmet Z.; Todorović, Milica; Mönig, Harry; Schwendemann, Todd C.; Ünverdi, Özhan; Rodrigo, Lucia; Altman, Eric I.; Pérez, Rubén; Schwarz, Udo D.

    2013-04-01

    The influence of defects on the local structural, electronic, and chemical properties of a surface oxide on Cu(100) were investigated using atomic resolution three-dimensional force mapping combined with tunneling current measurements and ab initio density functional theory. Results reveal that the maximum attractive force between tip and sample occurs above the oxygen atoms; theory indicates that the tip, in this case, terminates in a Cu atom. Meanwhile, simultaneously acquired tunneling current images emphasize the positions of Cu atoms, thereby, providing species-selective contrast in the two complementary data channels. One immediate outcome is that defects due to the displacement of surface copper are exposed in the current maps, even though force maps only reflect a well-ordered oxygen sublattice. The exact nature of the defects is confirmed by the simulations, which also reveal that the arrangement of the oxygen atoms is not disrupted by the copper displacement. In addition, the experimental force maps uncover a position-dependent modulation of the attractive forces between the surface oxygen and the copper-terminated tips, which is found to reflect the surface's inhomogeneous chemical and structural environment. As a consequence, the demonstrated method has the potential to directly probe how defects affect surface chemical interactions.

  19. Mechanics of interaction and atomic-scale wear of amplitude modulation atomic force microscopy probes.

    PubMed

    Vahdat, Vahid; Grierson, David S; Turner, Kevin T; Carpick, Robert W

    2013-04-23

    Wear is one of the main factors that hinders the performance of probes for atomic force microscopy (AFM), including for the widely used amplitude modulation (AM-AFM) mode. Unfortunately, a comprehensive scientific understanding of nanoscale wear is lacking. We have developed a protocol for conducting consistent and quantitative AM-AFM wear experiments. The protocol involves controlling the tip-sample interaction regime during AM-AFM scanning, determining the tip-sample contact geometry, calculating the peak repulsive force and normal stress over the course of the wear test, and quantifying the wear volume using high-resolution transmission electron microscopy imaging. The peak repulsive tip-sample interaction force is estimated from a closed-form equation accompanied by an effective tip radius measurement procedure, which combines transmission electron microscopy and blind tip reconstruction. The contact stress is estimated by applying Derjaguin-Müller-Toporov contact mechanics model and also numerically solving a general contact mechanics model recently developed for the adhesive contact of arbitrary axisymmetric punch shapes. We discuss the important role that the assumed tip shape geometry plays in calculating both the interaction forces and the contact stresses. Contact stresses are significantly affected by the tip geometry while the peak repulsive force is mainly determined by experimentally controlled parameters, specifically, the free oscillation amplitude and amplitude ratio. The applicability of this protocol is demonstrated experimentally by assessing the performance of diamond-like carbon-coated and silicon-nitride-coated silicon probes scanned over ultrananocrystalline diamond substrates in repulsive mode AM-AFM. There is no sign of fracture or plastic deformation in the case of diamond-like carbon; wear could be characterized as a gradual atom-by-atom process. In contrast, silicon nitride wears through removal of the cluster of atoms and plastic

  20. Synthesis-atomic structure-properties relationships in metallic nanoparticles by total scattering experiments and 3D computer simulations: case of Pt-Ru nanoalloy catalysts

    NASA Astrophysics Data System (ADS)

    Prasai, Binay; Ren, Yang; Shan, Shiyao; Zhao, Yinguang; Cronk, Hannah; Luo, Jin; Zhong, Chuan-Jian; Petkov, Valeri

    2015-04-01

    An approach to determining the 3D atomic structure of metallic nanoparticles (NPs) in fine detail and using the unique knowledge obtained for rationalizing their synthesis and properties targeted for optimization is described and exemplified on Pt-Ru alloy NPs of importance to the development of devices for clean energy conversion such as fuel cells. In particular, PtxRu100-x alloy NPs, where x = 31, 49 and 75, are synthesized by wet chemistry and activated catalytically by a post-synthesis treatment involving heating under controlled N2-H2 atmosphere. So-activated NPs are evaluated as catalysts for gas-phase CO oxidation and ethanol electro-oxidation reactions taking place in fuel cells. Both as-synthesized and activated NPs are characterized structurally by total scattering experiments involving high-energy synchrotron X-ray diffraction coupled to atomic pair distribution functions (PDFs) analysis. 3D structure models both for as-synthesized and activated NPs are built by molecular dynamics simulations based on the archetypal for current theoretical modelling Sutton-Chen method. Models are refined against the experimental PDF data by reverse Monte Carlo simulations and analysed in terms of prime structural characteristics such as metal-to-metal bond lengths, bond angles and first coordination numbers for Pt and Ru atoms. Analysis indicates that, though of a similar type, the atomic structure of as-synthesized and respective activated NPs differ in several details of importance to NP catalytic properties. Structural characteristics of activated NPs and data for their catalytic activity are compared side by side and strong evidence found that electronic effects, indicated by significant changes in Pt-Pt and Ru-Ru metal bond lengths at NP surface, and practically unrecognized so far atomic ensemble effects, indicated by distinct stacking of atomic layers near NP surface and prevalence of particular configurations of Pt and Ru atoms in these layers, contribute to the

  1. First-principles modeling of 3d-transition-metal-atom adsorption on silicene: a linear-response DFT + U approach.

    PubMed

    Le, Hung M; Pham, Tan-Tien; Dinh, Thach S; Kawazoe, Yoshiyuki; Nguyen-Manh, Duc

    2016-04-01

    By employing DFT  +  U calculations with the linear response method, we investigate the interactions between various 3d transition-metal atoms (Cr, Mn, Fe, Co) and silicene. In the cases of two-dimensional (2D) FeSi2 and CoSi2, the metal atoms tend to penetrate into the silicene layer. While CoSi2 is non-magnetic, FeSi2 exhibits a total magnetic moment of 2.21 μ(B)/cell. Upon the examination of 2D MSi6, a trend in anti-ferromagnetic (AFM) favorability in the z-direction is observed according to our DFT  +  U calculations. In the ferromagnetic (FM) states (less stable), each primary unit cell of CrSi6, MnSi6, and FeSi6 possesses different levels of total magnetization (4.01, 5.18, and 2.00 μ B/cell, respectively). The absolute magnetization given by AFM MSi6 structures varies in the range of 5.33-5.84 μ(B)/cell. A direct band gap in AFM MnSi6 (0.2 eV) is predicted, while the metastable FM FeSi6 structure has a wider band gap (0.85 eV). Interestingly, there are superexchange interactions between metal atoms in the MSi6 systems, which result in the AFM alignments. PMID:26940978

  2. Ethanol Electro-Oxidation on Ternary Platinum–Rhodium–Tin Nanocatalysts: Insights in the Atomic 3D Structure of the Active Catalytic Phase

    SciTech Connect

    Erini, Nina; Loukrakpam, Rameshwori; Petkov, Valeri; Baranova, Elena A.; Yang, Ruizhi; Teschner, Detre; Huang, Yunhui; Brankovic, Stanko R.; Strasser, Peter

    2014-04-25

    Novel insights in the synthesis–structure–catalytic activity relationships of nanostructured trimetallic Pt–Rh–Sn electrocatalysts for the electrocatalytic oxidation of ethanol are reported. In particular, we identify a novel single-phase Rh-doped Pt–Sn Niggliite mineral phase as the source of catalytically active sites for ethanol oxidation; we discuss its morphology, composition, chemical surface state, and the detailed 3D atomic arrangement using high-energy (HE-XRD), atomic pair distribution function (PDF) analysis, and X-ray photoelectron spectroscopy (XPS). The intrinsic ethanol oxidation activity of the active Niggliite phase exceeded those of earlier reports, lending support to the notion that the atomic-scale neighborhood of Pt, Rh, and Sn is conducive to the emergence of active surface catalytic sites under reaction conditions. In situ mechanistic Fourier transform infrared (in situ FTIR) analysis confirms an active 12 electron oxidation reaction channel to CO2 at electrode potentials as low as 450 mV/RHE, demonstrating the favorable efficiency of the PtRhSn Niggliite phase for C–C bond splitting.

  3. Oxidized carbon nitrides: water-dispersible, atomically thin carbon nitride-based nanodots and their performances as bioimaging probes.

    PubMed

    Oh, Junghoon; Yoo, Ran Ji; Kim, Seung Yeon; Lee, Yong Jin; Kim, Dong Wook; Park, Sungjin

    2015-04-13

    Three-dimensional (3D) carbon nitride (C3 N4 )-based materials show excellent performance in a wide range of applications because of their suitable band structures. To realize the great promise of two-dimensional (2D) allotropes of various 3D materials, it is highly important to develop routes for the production of 2D C3 N4 materials, which are one-atom thick, in order to understand their intrinsic properties and identify their possible applications. In this work, water-dispersible, atomically thin, and small carbon nitride nanodots were produced using the chemical oxidation of graphitic C3 N4 . Various analyses, including X-ray diffraction, X-ray photoelectron, Fourier-transform infrared spectroscopy, and combustion-based elemental analysis, and thermogravimetric analysis, confirmed the production of 3D oxidized C3 N4 materials. The 2D C3 N4 nanodots were successfully exfoliated as individual single layers; their lateral dimension was several tens of nanometers. They showed strong photoluminescence in the visible region as well as excellent performances as cell-imaging probes in an in vitro study using confocal fluorescence microscopy.

  4. The Interaction of the Solar Wind with Solar Probe Plus - 3D Hybrid Simulation. Report 1; The Study for the Distance 4.5Rs

    NASA Technical Reports Server (NTRS)

    Lipatov, Alexander S.; Sittler, Edward C.; Hartle, Richard E.; Cooper, John F.

    2010-01-01

    Our report devotes a 3D numerical hybrid model of the interaction of the solar wind with the Solar Probe spacecraft. The SPP model includes 3 main parts, namely, a non-conducting heat shield, a support system, and cylindrical section or spacecraft bus that contains the particle analysis devices and antenna. One observes an excitation of the low frequency Alfven and whistler type wave directed by the magnetic field with an amplitude of about (0.06-0.6) V/m. The compression waves and the jumps in an electric field with an amplitude of about (0.15-0.7) V/m were also observed. The wave amplitudes are comparable to or greater than previously estimated max wave amplitudes that SPP is expected to measure. The results of our hybrid simulation will be useful for understanding the plasma environment near the SPP spacecraft at the distance 4.5 Rs. Future simulation will take into account the charging of the spacecraft, the charge separation effects, an outgassing from heat shield, a photoionization and an electron impact ionization effects near the spacecraft.

  5. A combination of pharmacophore modeling, atom-based 3D-QSAR, molecular docking and molecular dynamics simulation studies on PDE4 enzyme inhibitors.

    PubMed

    Tripuraneni, Naga Srinivas; Azam, Mohammed Afzal

    2016-11-01

    Phosphodiesterases 4 enzyme is an attractive target for the design of anti-inflammatory and bronchodilator agents. In the present study, pharmacophore and atom-based 3D-QSAR studies were carried out for pyrazolopyridine and quinoline derivatives using Schrödinger suite 2014-3. A four-point pharmacophore model was developed using 74 molecules having pIC50 ranging from 10.1 to 4.5. The best four feature model consists of one hydrogen bond acceptor, two aromatic rings, and one hydrophobic group. The pharmacophore hypothesis yielded a statistically significant 3D-QSAR model, with a high correlation coefficient (R(2 )= .9949), cross validation coefficient (Q(2 )= .7291), and Pearson-r (.9107) at six component partial least square factor. The external validation indicated that our QSAR model possessed high predictive power with R(2) value of .88. The generated model was further validated by enrichment studies using the decoy test. Molecular docking, free energy calculation, and molecular dynamics (MD) simulation studies have been performed to explore the putative binding modes of these ligands. A 10-ns MD simulation confirmed the docking results of both stability of the 1XMU-ligand complex and the presumed active conformation. Outcomes of the present study provide insight in designing novel molecules with better PDE4 inhibitory activity.

  6. Dopant-induced 2D-3D transition in small Au-containing clusters: DFT-global optimisation of 8-atom Au-Ag nanoalloys.

    PubMed

    Heiles, Sven; Logsdail, Andrew J; Schäfer, Rolf; Johnston, Roy L

    2012-02-21

    A genetic algorithm (GA) coupled with density functional theory (DFT) calculations is used to perform global optimisations for all compositions of 8-atom Au-Ag bimetallic clusters. The performance of this novel GA-DFT approach for bimetallic nanoparticles is tested for structures reported in the literature. New global minimum structures for various compositions are predicted and the 2D-3D transition is located. Results are explained with the aid of an analysis of the electronic density of states. The chemical ordering of the predicted lowest energy isomers are explained via a detailed analysis of the charge separation and mixing energies of the bimetallic clusters. Finally, dielectric properties are computed and the composition and dimensionality dependence of the electronic polarizability and dipole moment is discussed, enabling predictions to be made for future electric beam deflection experiments.

  7. Guided mass spectrum labelling in atom probe tomography.

    PubMed

    Haley, D; Choi, P; Raabe, D

    2015-12-01

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

  8. Contingency table techniques for three dimensional atom probe tomography.

    PubMed

    Moody, Michael P; Stephenson, Leigh T; Liddicoat, Peter V; Ringer, Simon P

    2007-03-01

    A contingency table analysis procedure is developed and applied to three dimensional atom probe data sets for the investigation of fine-scale solute co-/anti-segregation effects in multicomponent alloys. Potential sources of error and inaccuracy are identified and eliminated from the technique. The conventional P value testing techniques associated with chi(2) are shown to be unsatisfactory and can become ambiguous in cases of large block numbers or high solute concentrations. The coefficient of contingency is demonstrated to be an acceptable and useful basis of comparison for contingency table analyses of differently-conditioned materials. However, care must be taken in choice of block size and to maintain a consistent overall composition between experiments. The coefficient is dependent upon block size and solute composition, and cannot be used to compare analyses with significantly different solute compositions or to assess the extent of clustering without reference to that of the randomly ordered case. It is shown that as clustering evolves into larger precipitates and phases, contingency table analysis becomes inappropriate. Random labeling techniques are introduced to infer further meaning from the coefficient of contingency. We propose the comparison of experimental result, mu(exp), to the randomized value, micro(rand), as a new method by which to interpret the quantity of solute clustering present in a material. It is demonstrated that how this method may be utilized to identify an appropriate size of contingency table analysis blocks into which the data set is partitioned to optimize the significance of the results.

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

    PubMed Central

    2011-01-01

    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. PMID:21711623

  10. New Methods of Sample Preparation for Atom Probe Specimens

    NASA Technical Reports Server (NTRS)

    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.

  11. Antiferromagnetic half metallicity in codoped chalcopyrite semiconductors Cu(Al 1 - 2 xAxBx)Se2 (A and B are 3d transition-metal atoms)

    NASA Astrophysics Data System (ADS)

    Shahjahan, M.; Oguchi, T.

    2016-06-01

    Electronic structures and magnetic properties of group I-III-VI2 chalcopyrite-type compounds Cu(Al 1 - 2 xAxBx)Se2 are calculated using the Korringa-Kohn-Rostoker Green's function method, where A (Ti, V, Cr, Mn) and B (Fe, Co, Ni) are 3d transition metal atoms, and x is atomic concentration. We found that codoping of Cr-Co and V-Ni pairs at Al site of host CuAlSe2 exhibit antiferromagnetic (AF) half metallicity with low Curie temperature (TC). The AF half metallic property is supported by nullified net magnetic moment and compensated density of states in the minority spin direction. On the other hand, codoping of Cr-Ni, Mn-Co, V-Co, and Ti-Co pairs at Al site of host CuAlSe2 manifest ferrimagnetic half metallicity with a small net magnetization and keeping antiparallel local spin moments. In Mn-Co case TC is close to room temperature. Besides, Cr-Fe, V-Fe, and Ti-Ni codoping cases lead to an instable magnetic ordering and therefore obtain a disordered local moment (spin-glass like) state.

  12. Atomic-scale characterization of germanium isotopic multilayers by atom probe tomography

    SciTech Connect

    Shimizu, Y.; Takamizawa, H.; Toyama, T.; Inoue, K.; Nagai, Y.; Kawamura, Y.; Uematsu, M.; Itoh, K. M.; Haller, E. E.

    2013-01-14

    We report comparison of the interfacial sharpness characterization of germanium (Ge) isotopic multilayers between laser-assisted atom probe tomography (APT) and secondary ion mass spectrometry (SIMS). An alternating stack of 8-nm-thick naturally available Ge layers and 8-nm-thick isotopically enriched {sup 70}Ge layers was prepared on a Ge(100) substrate by molecular beam epitaxy. The APT mass spectra consist of clearly resolved peaks of five stable Ge isotopes ({sup 70}Ge, {sup 72}Ge, {sup 73}Ge, {sup 74}Ge, and {sup 76}Ge). The degree of intermixing at the interfaces between adjacent layers was determined by APT to be around 0.8 {+-} 0.1 nm which was much sharper than that obtained by SIMS.

  13. Geochemical Proxy Distribution at the Atomic-Scale: Atom Probe Tomography of Foraminiferal Calcite

    NASA Astrophysics Data System (ADS)

    Branson, O.; Perea, D. E.; Winters, M. A.; Fehrenbacher, J. S.; Russell, A. D.; Spero, H. J.; Gagnon, A. C.

    2014-12-01

    Biomineral composition reflects a complex interplay between minute-scale biological control, mineral growth processes, and the influence of environmental conditions. For this reason, the mechanisms responsible for the formation of these minerals, as well as the incorporation of trace elements during biomineral growth, are poorly understood. Potential mechanisms governing the production and composition of biominerals can be organized into two distinct groups: a) biological mechanisms controlling the calcifying environment and b) mineral growth processes from this controlled environment. Despite significant advances in both these areas, critical gaps remain in our understanding of biomineral production and geochemical tracer incorporation. We are adapting Atom Probe Tomography (APT), a technique that maps the arrangement and identity of individual atoms within a bulk material, to analyze foraminiferal calcite for the first time. These data-rich atom-scale chemical maps provide a unique opportunity to deconvolve the effects of biological and crystal growth processes in the incorporation of geochemical tracers. Our first experiments have examined the influence of the biological-mineral interface on geochemical proxy element incorporation. Preliminary measurements show that (1) we can successfully map impurities in calcite biominerals, while also distinguishing between mineral and organic zones, overcoming a major technical hurdle; and (2) that elements like sodium appear to be recruited to the organic-mineral interface. The high-resolution chemical data from the APT will further allow us to investigate the fundamental basis for geochemical proxy behavior. For example, we can determine for a certain set of conditions whether the substitution of trace elements into the calcite follows ideal solid-solution behavior, as tacitly assumed in many geochemical proxy systems, or is modulated by intra-shell organics, or coupled-substitution interactions. Collectively, the

  14. Probing Atomic Dynamics and Structures Using Optical Patterns

    NASA Astrophysics Data System (ADS)

    Schmittberger, Bonnie L.; Gauthier, Daniel J.

    2015-05-01

    Pattern formation is a widely studied phenomenon that can provide fundamental insights into nonlinear systems. Emergent patterns in cold atoms are of particular interest in condensed matter physics and quantum information science because one can relate optical patterns to spatial structures in the atoms. In our experimental system, we study multimode optical patterns generated from a sample of cold, thermal atoms. We observe this nonlinear optical phenomenon at record low input powers due to the highly nonlinear nature of the spatial bunching of atoms in an optical lattice. We present a detailed study of the dynamics of these bunched atoms during optical pattern formation. We show how small changes in the atomic density distribution affect the symmetry of the generated patterns as well as the nature of the nonlinearity that describes the light-atom interaction. We gratefully acknowledge the financial support of the National Science Foundation through Grant #PHY-1206040.

  15. Sharp microwave frequency dependence in {open_quotes}ionization{close_quotes} of 3d H atoms and the effect of additive noise

    SciTech Connect

    Sirko, L.; Bellermann, M.; Haffmans, A.; Koch, P.M.

    1993-05-01

    For weak broadband (26-40 GHz) added shot noise (rms amplitude F{sub n} {approx_equal} 0.5 V/cm, <5% of the coherent amplitude F), we saw sharp variations around {nu}=30 GHz in e.g., F(10%) for 10%-{open_quotes}ionization{close_quotes} probability (n-cutoff {approx_equal} 89) of n{sub 0}=57 3d H atoms. Sharp means varying {nu} {approx_lt} 1/3 of the Fourier bandwidth 0.35 GHz of the 4.3 ns long half-sinewave pulseshape. Increased noise lowered (raised) F(10%) near sharp maxima (minima). (For some other cases noise did very little.) F{sub n} {approx_equal} 2.2 V/cm. suppressed the sharp {nu}-variation of F(10%). Our bound-basis integration of the 1d Schrodinger equation reproduces the results well, including influence of noise. Leopold, Richards, and Jensen are developing theory for a perturbed pendulum effective Hamiltonian H{sub eff} locally describing the dynamics at the classical nonlinear resonance island centered near n{sub 0}{sup 3}{omega}=1. Our data may be the first spectroscopic glimpse of novel quantal states of H{sub eff}.

  16. Standardization and Correction of Artifacts in Atom-Probe Tomographic Analysis of Allende Nanodiamonds

    NASA Astrophysics Data System (ADS)

    Lewis, J. B.; Isheim, D.; Moutanabbir, O.; Floss, C.; Seidman, D. N.

    2015-07-01

    We use complementary atom-probe tomography and secondary ion mass spectrometry to measure the 12C/13C isotopic ratios of meteoritic nanodiamonds and thus determine their origins. We are investigating and quantifying instrumental artifacts.

  17. Atom Probe Insights into U-Pb Age Resetting in Baddeleyite

    NASA Astrophysics Data System (ADS)

    White, L. F.; Reinhard, D.; Moser, D.; Darling, J. R.; Bullen, D.; Prosa, T. J.; Olson, D.; Larson, D. J.; Clifton, P. H.; Lawrence, D.; Martin, I.

    2016-08-01

    Atom probe analysis of highly shocked baddeleyite suggests that igneous crystallisation ages can be isolated from 'partially reset' grains through careful segregation and rejection of planar features known to induce post-impact Pb-diffusion.

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

    DOE PAGES

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

    2016-04-21

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

  19. Strategies for fabricating atom probe specimens with a dual beam FIB.

    PubMed

    Miller, M K; Russell, K F; Thompson, G B

    2005-03-01

    A FIB-based lift-out method for preparing atom probe specimens at site specific locations such as coarse precipitates, grain boundaries, interphase interfaces, denuded zones, heat affected zones, implanted, near surface and subsurface regions, shear bands, etc. has been developed. FIB-based methods for the fabrication of atom probe specimens from thin ribbons, sheet stock, and powders have been developed. PMID:15694675

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

    PubMed

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

    2016-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  2. Aberrated electron probes for magnetic spectroscopy with atomic resolution: Theory and practical aspects

    DOE PAGES

    Rusz, Ján; Idrobo, Juan Carlos

    2016-03-24

    It was recently proposed that electron magnetic circular dichroism (EMCD) can be measured in scanning transmission electron microscopy (STEM) with atomic resolution by tuning the phase distribution of a electron beam. Here, we describe the theoretical and practical aspects for the detection of out-of-plane and in-plane magnetization utilizing atomic size electron probes. Here we present the calculated optimized astigmatic probes and discuss how to achieve them experimentally.

  3. Preparation of nanowire specimens for laser-assisted atom probe tomography

    NASA Astrophysics Data System (ADS)

    Blumtritt, H.; Isheim, D.; Senz, S.; Seidman, D. N.; Moutanabbir, O.

    2014-10-01

    The availability of reliable and well-engineered commercial instruments and data analysis software has led to development in recent years of robust and ergonomic atom-probe tomographs. Indeed, atom-probe tomography (APT) is now being applied to a broader range of materials classes that involve highly important scientific and technological problems in materials science and engineering. Dual-beam focused-ion beam microscopy and its application to the fabrication of APT microtip specimens have dramatically improved the ability to probe a variety of systems. However, the sample preparation is still challenging especially for emerging nanomaterials such as epitaxial nanowires which typically grow vertically on a substrate through metal-catalyzed vapor phase epitaxy. The size, morphology, density, and sensitivity to radiation damage are the most influential parameters in the preparation of nanowire specimens for APT. In this paper, we describe a step-by-step process methodology to allow a precisely controlled, damage-free transfer of individual, short silicon nanowires onto atom probe microposts. Starting with a dense array of tiny nanowires and using focused ion beam, we employed a sequence of protective layers and markers to identify the nanowire to be transferred and probed while protecting it against Ga ions during lift-off processing and tip sharpening. Based on this approach, high-quality three-dimensional atom-by-atom maps of single aluminum-catalyzed silicon nanowires are obtained using a highly focused ultraviolet laser-assisted local electrode atom probe tomograph.

  4. Preparation of nanowire specimens for laser-assisted atom probe tomography.

    PubMed

    Blumtritt, H; Isheim, D; Senz, S; Seidman, D N; Moutanabbir, O

    2014-10-31

    The availability of reliable and well-engineered commercial instruments and data analysis software has led to development in recent years of robust and ergonomic atom-probe tomographs. Indeed, atom-probe tomography (APT) is now being applied to a broader range of materials classes that involve highly important scientific and technological problems in materials science and engineering. Dual-beam focused-ion beam microscopy and its application to the fabrication of APT microtip specimens have dramatically improved the ability to probe a variety of systems. However, the sample preparation is still challenging especially for emerging nanomaterials such as epitaxial nanowires which typically grow vertically on a substrate through metal-catalyzed vapor phase epitaxy. The size, morphology, density, and sensitivity to radiation damage are the most influential parameters in the preparation of nanowire specimens for APT. In this paper, we describe a step-by-step process methodology to allow a precisely controlled, damage-free transfer of individual, short silicon nanowires onto atom probe microposts. Starting with a dense array of tiny nanowires and using focused ion beam, we employed a sequence of protective layers and markers to identify the nanowire to be transferred and probed while protecting it against Ga ions during lift-off processing and tip sharpening. Based on this approach, high-quality three-dimensional atom-by-atom maps of single aluminum-catalyzed silicon nanowires are obtained using a highly focused ultraviolet laser-assisted local electrode atom probe tomograph.

  5. Temperature measurement of cold atoms using transient absorption of a resonant probe through an optical nanofibre

    NASA Astrophysics Data System (ADS)

    Kumar, Ravi; Gokhroo, Vandna; Bhushan Tiwari, Vibhuti; Chormaic, Síle Nic

    2016-11-01

    Optical nanofibres are ultrathin optical fibres with a waist diameter typically less than the wavelength of light being guided through them. Cold atoms can couple to the evanescent field of the nanofibre-guided modes and such systems are emerging as promising technologies for the development of atom-photon hybrid quantum devices. Atoms within the evanescent field region of an optical nanofibre can be probed by sending near or on-resonant light through the fibre; however, the probe light can detrimentally affect the properties of the atoms. In this paper, we report on the modification of the local temperature of laser-cooled 87Rb atoms in a magneto-optical trap centred around an optical nanofibre when near-resonant probe light propagates through it. A transient absorption technique has been used to measure the temperature of the affected atoms and temperature variations from 160 μk to 850 μk, for a probe power ranging from 0 to 50 nW, have been observed. This effect could have implications in relation to using optical nanofibres for probing and manipulating cold or ultracold atoms.

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

    NASA Astrophysics Data System (ADS)

    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

  7. Atomic-scale observation of hydrogen-induced crack growth by atom-probe FIM. [Fe-0. 29% Ti

    SciTech Connect

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

    1980-01-01

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

  8. Bragg scattering as a probe of atomic wave functions and quantum phase transitions in optical lattices.

    PubMed

    Miyake, Hirokazu; Siviloglou, Georgios A; Puentes, Graciana; Pritchard, David E; Ketterle, Wolfgang; Weld, David M

    2011-10-21

    We have observed Bragg scattering of photons from quantum degenerate ^{87}Rb atoms in a three-dimensional optical lattice. Bragg scattered light directly probes the microscopic crystal structure and atomic wave function whose position and momentum width is Heisenberg limited. The spatial coherence of the wave function leads to revivals in the Bragg scattered light due to the atomic Talbot effect. The decay of revivals across the superfluid to Mott insulator transition indicates the loss of superfluid coherence.

  9. Bragg scattering as a probe of atomic wave functions and quantum phase transitions in optical lattices.

    PubMed

    Miyake, Hirokazu; Siviloglou, Georgios A; Puentes, Graciana; Pritchard, David E; Ketterle, Wolfgang; Weld, David M

    2011-10-21

    We have observed Bragg scattering of photons from quantum degenerate ^{87}Rb atoms in a three-dimensional optical lattice. Bragg scattered light directly probes the microscopic crystal structure and atomic wave function whose position and momentum width is Heisenberg limited. The spatial coherence of the wave function leads to revivals in the Bragg scattered light due to the atomic Talbot effect. The decay of revivals across the superfluid to Mott insulator transition indicates the loss of superfluid coherence. PMID:22107532

  10. Interaction of a probe pulse with a 'dressed' Bose-Einstein condensate of rarefied atomic gases

    SciTech Connect

    Shamrov, N I

    2008-01-31

    Semiclassical equations describing the interaction of a probe pulse with a 'dressed' Bose-Einstein condensate of a rarefied atomic gas are proposed. The analytic solution of these equations is obtained for low-intensity pulses. The conditions of the appearance of a diffraction grating from recoil atoms are found. The existence of induced superradiance at the probe-beam frequency is predicted. The pulse propagation velocity in the condensate is determined as a function of its energy. The limits of the applicability of the two-level model of a 'dressed' atom are estimated. (nonlinear optical phenomena)

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

    PubMed

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

    2015-12-01

    The following manuscript presents a novel approach for creating lattice based models of Sb-doped Si directly from atom probe reconstructions for the purposes of improving information on dopant positioning and directly informing quantum mechanics based materials modeling approaches. Sophisticated crystallographic analysis techniques are used to detect latent crystal structure within the atom probe reconstructions with unprecedented accuracy. A distortion correction algorithm is then developed to precisely calibrate the detected crystal structure to the theoretically known diamond cubic lattice. The reconstructed atoms are then positioned on their most likely lattice positions. Simulations are then used to determine the accuracy of such an approach and show that improvements to short-range order measurements are possible for noise levels and detector efficiencies comparable with experimentally collected atom probe data. PMID:26190007

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

    PubMed

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

    2015-12-01

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

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

    SciTech Connect

    Brown, Kenneth R.; Viteri, C. Ricardo; Clark, Craig R.; Goeders, James E.; Khanyile, Ncamiso B.; Vittorini, Grahame D.

    2015-01-22

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

  14. Generating and probing entangled states for optical atomic clocks

    NASA Astrophysics Data System (ADS)

    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. Development of a 3D touch trigger probe using micro spherical stylus machining by micro-EDM for micro-CMM

    NASA Astrophysics Data System (ADS)

    Chu, Chih-Liang; Chen, Yi-Lin; Tai, Tzu-Yao; Liu, Yun-Hui; Chuang, Cheng-Hsin; Lu, Chin-Tu

    2011-12-01

    This study develops a low-cost three-dimensional touch trigger probe for micro-CMM using micro spherical stylus machining by micro-EDM. The tip ball of the stylus, with a diameter smaller than 100 µm, is made by a micro electro discharge machine with the method of wire electro discharge grinding (WEDG). The current study uses tungsten carbide (WC) as the material for the stylus. Experimental results show that, the tip ball roundness could amount to 2 µm. Since the tip ball is not easily observable by naked eyes, we designed a micro imaging system to observe the probing in real time. This system is created with modified commercial webcam and microscope. The general design of the touch trigger probe is combined the stylus and suspension structure. When the stylus touches workpiece, it can be determined the time of probe trigger by measuring the motion of suspension structure. The stylus machined by micro-EDM was very fragile and the stylus handle of the tip ball was very thin. Therefore, the stylus handle bends easily that would result in the large measurement error or stylus break when the stylus touched workpiece. In this study we designed a measuring probe using a small chuck and an electrical circuit to measure the probe trigger. When the stylus touches the workpiece, the parallel circuit will switch on immediately and pick up the voltage variation of the resistor. Because the transistor always turns ON, it can avoid the problems of excessive energy and electrical noise.

  16. Singlet-triplet energy splitting between 1D and 3D (1s2 2s nd), n = 3, 4, 5, and 6, Rydberg states of the beryllium atom (9Be) calculated with all-electron explicitly correlated Gaussian functions

    NASA Astrophysics Data System (ADS)

    Sharkey, Keeper L.; Bubin, Sergiy; Adamowicz, Ludwik

    2014-11-01

    Accurate variational nonrelativistic quantum-mechanical calculations are performed for the five lowest 1D and four lowest 3D states of the 9Be isotope of the beryllium atom. All-electron explicitly correlated Gaussian (ECG) functions are used in the calculations and their nonlinear parameters are optimized with the aid of the analytical energy gradient determined with respect to these parameters. The effect of the finite nuclear mass is directly included in the Hamiltonian used in the calculations. The singlet-triplet energy gaps between the corresponding 1D and 3D states, are reported.

  17. Preparation and Analysis of Atom Probe Tips by Xenon Focused Ion Beam Milling.

    PubMed

    Estivill, Robert; Audoit, Guillaume; Barnes, Jean-Paul; Grenier, Adeline; Blavette, Didier

    2016-06-01

    The damage and ion distribution induced in Si by an inductively coupled plasma Xe focused ion beam was investigated by atom probe tomography. By using predefined patterns it was possible to prepare the atom probe tips with a sub 50 nm end radius in the ion beam microscope. The atom probe reconstruction shows good agreement with simulated implantation profiles and interplanar distances extracted from spatial distribution maps. The elemental profiles of O and C indicate co-implantation during the milling process. The presence of small disc-shaped Xe clusters are also found in the three-dimensional reconstruction. These are attributed to the presence of Xe nanocrystals or bubbles that open during the evaporation process. The expected accumulated dose points to a loss of >95% of the Xe during analysis, which escapes undetected. PMID:27056544

  18. Preparation and Analysis of Atom Probe Tips by Xenon Focused Ion Beam Milling.

    PubMed

    Estivill, Robert; Audoit, Guillaume; Barnes, Jean-Paul; Grenier, Adeline; Blavette, Didier

    2016-06-01

    The damage and ion distribution induced in Si by an inductively coupled plasma Xe focused ion beam was investigated by atom probe tomography. By using predefined patterns it was possible to prepare the atom probe tips with a sub 50 nm end radius in the ion beam microscope. The atom probe reconstruction shows good agreement with simulated implantation profiles and interplanar distances extracted from spatial distribution maps. The elemental profiles of O and C indicate co-implantation during the milling process. The presence of small disc-shaped Xe clusters are also found in the three-dimensional reconstruction. These are attributed to the presence of Xe nanocrystals or bubbles that open during the evaporation process. The expected accumulated dose points to a loss of >95% of the Xe during analysis, which escapes undetected.

  19. A model to predict image formation in Atom probe Tomography.

    PubMed

    Vurpillot, F; Gaillard, A; Da Costa, G; Deconihout, B

    2013-09-01

    A model devoted to the modelling of the field evaporation of a tip is presented in this paper. The influence of length scales from the atomic scale to the macroscopic scale is taken into account in this approach. The evolution of the tip shape is modelled at the atomic scale in a three dimensional geometry with cylindrical symmetry. The projection law of ions is determined using a realistic representation of the tip geometry including the presence of electrodes in the surrounding area of the specimen. This realistic modelling gives a direct access to the voltage required to field evaporate, to the evolving magnification in the microscope and to the understanding of reconstruction artefacts when the presence of phases with different evaporation fields and/or different dielectric permittivity constants are modelled. This model has been applied to understand the field evaporation behaviour in bulk dielectric materials. In particular the role of the residual conductivity of dielectric materials is addressed.

  20. Preventing nanoscale wear of atomic force microscopy tips through the use of monolithic ultrananocrystalline diamond probes.

    PubMed

    Liu, J; Grierson, D S; Moldovan, N; Notbohm, J; Li, S; Jaroenapibal, P; O'Connor, S D; Sumant, A V; Neelakantan, N; Carlisle, J A; Turner, K T; Carpick, R W

    2010-05-21

    Nanoscale wear is a key limitation of conventional atomic force microscopy (AFM) probes that results in decreased resolution, accuracy, and reproducibility in probe-based imaging, writing, measurement, and nanomanufacturing applications. Diamond is potentially an ideal probe material due to its unrivaled hardness and stiffness, its low friction and wear, and its chemical inertness. However, the manufacture of monolithic diamond probes with consistently shaped small-radius tips has not been previously achieved. The first wafer-level fabrication of monolithic ultrananocrystalline diamond (UNCD) probes with <5-nm grain sizes and smooth tips with radii of 30-40 nm is reported, which are obtained through a combination of microfabrication and hot-filament chemical vapor deposition. Their nanoscale wear resistance under contact-mode scanning conditions is compared with that of conventional silicon nitride (SiN(x)) probes of similar geometry at two different relative humidity levels (approximately 15 and approximately 70%). While SiN(x) probes exhibit significant wear that further increases with humidity, UNCD probes show little measurable wear. The only significant degradation of the UNCD probes observed in one case is associated with removal of the initial seed layer of the UNCD film. The results show the potential of a new material for AFM probes and demonstrate a systematic approach to studying wear at the nanoscale.

  1. Probing starch-iodine interaction by atomic force microscopy.

    PubMed

    Du, Xiongwei; An, Hongjie; Liu, Zhongdong; Yang, Hongshun; Wei, Lijuan

    2014-01-01

    We explored the interaction of iodine with three crystalline type starches, corn, potato, and sweet potato starches using atomic force microscopy. Results revealed that starch molecules aggregated through interaction with iodine solution as well as iodine vapor. Detailed fine structures such as networks, chains, and super-helical structures were found in iodide solution tests. The nanostructures formed due to iodine adsorption could help to understand the formation and properties of the starch-iodine complex.

  2. Probing starch-iodine interaction by atomic force microscopy.

    PubMed

    Du, Xiongwei; An, Hongjie; Liu, Zhongdong; Yang, Hongshun; Wei, Lijuan

    2014-01-01

    We explored the interaction of iodine with three crystalline type starches, corn, potato, and sweet potato starches using atomic force microscopy. Results revealed that starch molecules aggregated through interaction with iodine solution as well as iodine vapor. Detailed fine structures such as networks, chains, and super-helical structures were found in iodide solution tests. The nanostructures formed due to iodine adsorption could help to understand the formation and properties of the starch-iodine complex. PMID:24338992

  3. Laser assisted atom probe analysis of thin film on insulating substrate.

    PubMed

    Kodzuka, M; Ohkubo, T; Hono, K

    2011-05-01

    We demonstrate that the atom probe analyses of metallic thin films on insulating substrates are possible using laser assisted field evaporation. The tips with metallic thin film and insulating substrate (0.6-3 μm in thickness) were prepared by the lift-out and annular ion beam milling techniques on tungsten supports. In spite of the existence of thick insulating layer between the metallic film and the tungsten support, atom probe tomography with practical mass resolution, signal-to-noise ratio and spatial resolution was found to be possible using laser assisted field evaporation. PMID:21172729

  4. Design of a laser-assisted tomographic atom probe at Muenster University

    SciTech Connect

    Schlesiger, Ralf; Oberdorfer, Christian; Greiwe, Gerd; Stender, Patrick; Artmeier, Michael; Pelka, Patrick; Spaleck, Frank; Schmitz, Guido; Wuerz, Roland

    2010-04-15

    To benefit from the latest technical improvements in atom probe analysis, a new tomographic atom probe has been built at the University of Muenster, Germany. The instrument utilizes a femtosecond laser system with a high repetition rate combined with the ability of using a micrometer-sized extraction electrode and a wide angle configuration. Since field evaporation is triggered by laser pulses instead of high-voltage pulses, the instrument offers the ability to expand the range of analyzed materials to poorly conducting or insulating materials such as oxides, glasses, ceramics, and polymeric materials. The article describes the design of the instrument and presents characterizing measurements on metals, semiconductors, and oxide ceramic.

  5. Understanding the detection of carbon in austenitic high-Mn steel using atom probe tomography.

    PubMed

    Marceau, R K W; Choi, P; Raabe, D

    2013-09-01

    A high-Mn TWIP steel having composition Fe-22Mn-0.6C (wt%) is considered in this study, where the need for accurate and quantitative analysis of clustering and short-range ordering by atom probe analysis requires a better understanding of the detection of carbon in this system. Experimental measurements reveal that a high percentage of carbon atoms are detected as molecular ion species and on multiple hit events, which is discussed with respect to issues such as optimal experimental parameters, correlated field evaporation and directional walk/migration of carbon atoms at the surface of the specimen tip during analysis. These phenomena impact the compositional and spatial accuracy of the atom probe measurement and thus require careful consideration for further cluster-finding analysis.

  6. Europeana and 3D

    NASA Astrophysics Data System (ADS)

    Pletinckx, D.

    2011-09-01

    The current 3D hype creates a lot of interest in 3D. People go to 3D movies, but are we ready to use 3D in our homes, in our offices, in our communication? Are we ready to deliver real 3D to a general public and use interactive 3D in a meaningful way to enjoy, learn, communicate? The CARARE project is realising this for the moment in the domain of monuments and archaeology, so that real 3D of archaeological sites and European monuments will be available to the general public by 2012. There are several aspects to this endeavour. First of all is the technical aspect of flawlessly delivering 3D content over all platforms and operating systems, without installing software. We have currently a working solution in PDF, but HTML5 will probably be the future. Secondly, there is still little knowledge on how to create 3D learning objects, 3D tourist information or 3D scholarly communication. We are still in a prototype phase when it comes to integrate 3D objects in physical or virtual museums. Nevertheless, Europeana has a tremendous potential as a multi-facetted virtual museum. Finally, 3D has a large potential to act as a hub of information, linking to related 2D imagery, texts, video, sound. We describe how to create such rich, explorable 3D objects that can be used intuitively by the generic Europeana user and what metadata is needed to support the semantic linking.

  7. Probing Persistence in DNA Curvature Properties with Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Moukhtar, J.; Fontaine, E.; Faivre-Moskalenko, C.; Arneodo, A.

    2007-04-01

    We elaborate on a mean-field extension of the wormlike chain model that accounts for the presence of long-range correlations (LRC) in the intrinsic curvature disorder of genomic DNA, the stronger the LRC, the smaller the persistence length. The comparison of atomic force microscopy imaging of straight, uncorrelated virus and correlated human DNA fragments with DNA simulations confirms that the observed decrease in persistence length for human DNA more likely results from a sequence-induced large-scale intrinsic curvature than from some increased flexibility.

  8. Magnetoencephalography with a two-color pump probe atomic magnetometer.

    SciTech Connect

    Johnson, Cort N.

    2010-07-01

    The authors have detected magnetic fields from the human brain with a compact, fiber-coupled rubidium spin-exchange-relaxation-free magnetometer. Optical pumping is performed on the D1 transition and Faraday rotation is measured on the D2 transition. The beams share an optical axis, with dichroic optics preparing beam polarizations appropriately. A sensitivity of <5 fT/{radical}Hz is achieved. Evoked responses resulting from median nerve and auditory stimulation were recorded with the atomic magnetometer. Recordings were validated by comparison with those taken by a commercial magnetoencephalography system. The design is amenable to arraying sensors around the head, providing a framework for noncryogenic, whole-head magnetoencephalography.

  9. A detailed guideline for the fabrication of single bacterial probes used for atomic force spectroscopy.

    PubMed

    Thewes, Nicolas; Loskill, Peter; Spengler, Christian; Hümbert, Sebastian; Bischoff, Markus; Jacobs, Karin

    2015-12-01

    The atomic force microscope (AFM) evolved as a standard device in modern microbiological research. However, its capability as a sophisticated force sensor is not used to its full capacity. The AFM turns into a unique tool for quantitative adhesion research in bacteriology by using "bacterial probes". Thereby, bacterial probes are AFM cantilevers that provide a single bacterium or a cluster of bacteria as the contact-forming object. We present a step-by-step protocol for preparing bacterial probes, performing force spectroscopy experiments and processing force spectroscopy data. Additionally, we provide a general insight into the field of bacterial cell force spectroscopy.

  10. A detailed guideline for the fabrication of single bacterial probes used for atomic force spectroscopy.

    PubMed

    Thewes, Nicolas; Loskill, Peter; Spengler, Christian; Hümbert, Sebastian; Bischoff, Markus; Jacobs, Karin

    2015-12-01

    The atomic force microscope (AFM) evolved as a standard device in modern microbiological research. However, its capability as a sophisticated force sensor is not used to its full capacity. The AFM turns into a unique tool for quantitative adhesion research in bacteriology by using "bacterial probes". Thereby, bacterial probes are AFM cantilevers that provide a single bacterium or a cluster of bacteria as the contact-forming object. We present a step-by-step protocol for preparing bacterial probes, performing force spectroscopy experiments and processing force spectroscopy data. Additionally, we provide a general insight into the field of bacterial cell force spectroscopy. PMID:26701715

  11. Probing mechanical quantum coherence with an ultracold-atom meter

    SciTech Connect

    Lo Gullo, N.; Busch, Th.; Palma, G. M.; Paternostro, M.

    2011-12-15

    We propose a scheme to probe quantum coherence in the state of a nanocantilever based on its magnetic coupling (mediated by a magnetic tip) with a spinor Bose Einstein condensate (BEC). By mapping the BEC into a rotor, its coupling with the cantilever results in a gyroscopic motion whose properties depend on the state of the cantilever: the dynamics of one of the components of the rotor angular momentum turns out to be strictly related to the presence of quantum coherence in the state of the cantilever. We also suggest a detection scheme relying on Faraday rotation, which produces only a very small back-action on the BEC and is thus suitable for a continuous detection of the cantilever's dynamics.

  12. Probing Individual Atoms and Molecules on Pt(111)

    NASA Astrophysics Data System (ADS)

    Liang, Zhu; Surface; Interface Science Laboratory, Riken, JAPAN Collaboration

    2015-03-01

    A low-temperature scanning tunneling microscopy (LT-STM) is used to investigate the structure and reactivity of atomic nitrogen on Pt surfaces, which is important to a variety of catalytic processes. The adsorption of ammonia on an oxygen covered Pt surface leads to the formation of an NH3-O2 complex. Such a complex serves as a precursor to ammonia oxydehydrogenation, which produces an ordered atomic N layer on the surface when annealed to temperatures above 300 K. (√{ 3} ×√{ 3})R30°-N and p(2 × 2)-N phases are found to coexist at temperatures between 360 and 400 K. After exposing the N-covered surface to hydrogen gas at 300 K, NH molecules are present as scattered molecules, as well as in dense islands. Mechanisms of dissociation of NH and lateral movement of H have been explored by examining the threshold energies and reaction rates. Measuring the response of the motion against applied bias voltage reveals the threshold energy, which is the energy of the vibrational mode that is responsible for activating a given motion. A theoretical model is used to fit the spectra, from which an estimate of reaction rate is obtained. ND dissociation and D hopping have also been investigated to examine the role of tunneling in these reactions. Hyowon Kim, Hyun Jin Yang, and Junepyo Oh are acknowledged for their contributions to this work. Support and supervision by professor Yousoo Kim and professor Michael Trenary are gratefully acknowledged.

  13. Probing non-Hermitian physics with flying atoms

    NASA Astrophysics Data System (ADS)

    Wen, Jianming; Xiao, Yanhong; Peng, Peng; Cao, Wanxia; Shen, Ce; Qu, Weizhi; Jiang, Liang

    2016-05-01

    Non-Hermtian optical systems with parity-time (PT) symmetry provide new means for light manipulation and control. To date, most of experimental demonstrations on PT symmetry rely on advanced nanotechnologies and sophisticated fabrication techniques to manmade solid-state materials. Here, we report the first experimental realization of optical anti-PT symmetry, a counterpart of conventional PT symmetry, in a warm atomic-vapor cell. By exploiting rapid coherence transport via flying atoms, we observe essential features of anti-PT symmetry with an unprecedented precision on phase-transition threshold. Moreover, our system allows nonlocal interference of two spatially-separated fields as well as anti-PT assisted four-wave mixing. Besides, another intriguing feature offered by the system is refractionless (or unit-refraction) light propagation. Our results thus represent a significant advance in non-Hermitian physics by bridging a firm connection with the AMO field, where novel phenomena and applications in quantum and nonlinear optics aided by (anti-)PT symmetry can be anticipated.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    Hu, Yifan; Ulstrup, Jens; Zhang, Jingdong; Molin, Søren; Dupres, Vincent

    2011-06-01

    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 (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 the driving forces for adhesion of the four strains. Rather, the observation of sawtooth force-distance patterns on the surface of biofilm positive strains documents the presence of modular proteins such as Aap that may mediate cell adhesion. Treatment of two biofilm positive strains with two chemical inhibitor compounds leads to a loss of adhesion, suggesting that AFM could be a valuable tool to screen for anti-adhesion molecules.

  16. Creating and Using Interactive, 3D-Printed Models to Improve Student Comprehension of the Bohr Model of the Atom, Bond Polarity, and Hybridization

    ERIC Educational Resources Information Center

    Smiar, Karen; Mendez, J. D.

    2016-01-01

    Molecular model kits have been used in chemistry classrooms for decades but have seen very little recent innovation. Using 3D printing, three sets of physical models were created for a first semester, introductory chemistry course. Students manipulated these interactive models during class activities as a supplement to existing teaching tools for…

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

    SciTech Connect

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

    1993-12-01

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

  18. Field Ion Microscopy and Atom Probe Tomography of Metamorphic Magnetite Crystals

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    Magnetite has been analysed using Field Ion Microscopy (FIM) and Atom Probe Tomography (APT), highly attractive techniques for the nanoanalysis of geological materials despite the difficulties inherent in analyzing semiconducting and insulating materials. Additional information is contained in the original extended abstract.

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

    SciTech Connect

    Cai, Jiandong; Zhang, Li; Xia, Qi E-mail: michael.wang@nus.edu.sg; Luo, Yangjun; Wang, Michael Yu E-mail: michael.wang@nus.edu.sg

    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.

  20. 3d-3d correspondence revisited

    NASA Astrophysics Data System (ADS)

    Chung, Hee-Joong; Dimofte, Tudor; Gukov, Sergei; Sułkowski, Piotr

    2016-04-01

    In fivebrane compactifications on 3-manifolds, we point out the importance of all flat connections in the proper definition of the effective 3d {N}=2 theory. The Lagrangians of some theories with the desired properties can be constructed with the help of homological knot invariants that categorify colored Jones polynomials. Higgsing the full 3d theories constructed this way recovers theories found previously by Dimofte-Gaiotto-Gukov. We also consider the cutting and gluing of 3-manifolds along smooth boundaries and the role played by all flat connections in this operation.

  1. 3d-3d correspondence revisited

    DOE PAGES

    Chung, Hee -Joong; Dimofte, Tudor; Gukov, Sergei; Sułkowski, Piotr

    2016-04-21

    In fivebrane compactifications on 3-manifolds, we point out the importance of all flat connections in the proper definition of the effective 3d N = 2 theory. The Lagrangians of some theories with the desired properties can be constructed with the help of homological knot invariants that categorify colored Jones polynomials. Higgsing the full 3d theories constructed this way recovers theories found previously by Dimofte-Gaiotto-Gukov. As a result, we also consider the cutting and gluing of 3-manifolds along smooth boundaries and the role played by all flat connections in this operation.

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

    PubMed

    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.

  3. Characterization of Probe Dynamic Behaviors in Critical Dimension Atomic Force Microscopy

    PubMed Central

    Feng, Shaw C.; Joung, Che Bong; Vorburger, Theodore V.

    2009-01-01

    This paper describes a detailed computational model of the interaction between an atomic force microscope probe tip and a sample surface. The model provides analyses of dynamic behaviors of the tip to estimate the probe deflections due to surface intermittent contact and the resulting dimensional biases and uncertainties. Probe tip and cantilever beam responses to intermittent contact between the probe tip and sample surface are computed using the finite element method. Intermittent contacts with a wall and a horizontal surface are computed and modeled, respectively. Using a 75 nm Critical Dimension (CD) tip as an example, the responses of the probe to interaction forces between the sample surface and the probe tip are shown in both time and frequency domains. In particular, interaction forces between the tip and both a vertical wall and a horizontal surface of a silicon sample are modeled using Lennard-Jones theory. The Snap-in and Snap-out of the probe tip in surface scanning are calculated and shown in the time domain. Based on the given tip-sample interaction force model, the calculation includes the compliance of the probe and dynamic forces generated by an excitation. Cantilever and probe tip deflections versus interaction forces in the time domain can be derived for both vertical contact with a plateau and horizontal contact with a side wall. Dynamic analysis using the finite element method and Lennard-Jones model provide a unique means to analyze the interaction of the probe and sample, including calculation of the deflection and the gap between the probe tip and the measured sample surface. PMID:27504222

  4. Differential and integrated cross sections for excitation to the 3s, 3p, and 3d states of atomic hydrogen by electron impact below the n=4 threshold

    SciTech Connect

    Bartlett, Philip L.; Bray, Igor; Stelbovics, Andris T.; Williams, J. F.; Mikosza, A. G.

    2006-08-15

    Integrated cross sections for the electron-impact excitation of ground-state hydrogen to the 3s, 3p, and 3d final states have been calculated using propagating exterior complex scaling and convergent close-coupling methods at energies between the n=3 and 4 excitation thresholds. The calculations are in excellent agreement and demonstrate that exterior complex scaling methods can accurately reproduce the resonance structure and magnitude of the excitation cross sections below the ionization threshold. Measurements of the separate 3s, 3p, and 3d differential cross sections were made at 12.24 eV, and are consistent with both calculations within a total experimental uncertainty of about 35%.

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

    PubMed

    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.

  6. Application of Fourier transform and autocorrelation to cluster identification in the three-dimensional atom probe.

    PubMed

    Vurpillot, F; De Geuser, F; Da Costa, G; Blavette, D

    2004-12-01

    Because of the increasing number of collected atoms (up to millions) in the three-dimensional atom probe, derivation of chemical or structural information from the direct observation of three-dimensional images is becoming more and more difficult. New data analysis tools are thus required. Application of a discrete Fourier transform algorithm to three-dimensional atom probe datasets provides information that is not easily accessible in real space. Derivation of mean particle size from Fourier intensities or from three-dimensional autocorrelation is an example. These powerful methods can be used to detect and image nano-segregations. Using three-dimensional 'bright-field' imaging, single nano-segregations were isolated from the surrounding matrix of an iron-copper alloy. Measurement of the inner concentration within clusters is, therefore, straightforward. Theoretical aspects related to filtering in reciprocal space are developed.

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

    PubMed

    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

  8. Three-dimensional atom probe tomography of oxide, anion, and alkanethiolate coatings on gold.

    PubMed

    Zhang, Yi; Hillier, Andrew C

    2010-07-15

    We have used three-dimensional atom probe tomography to analyze several nanometer-thick and monomolecular films on gold surfaces. High-purity gold wire was etched by electropolishing to create a sharp tip suitable for field evaporation with a radius of curvature of <100 nm. The near-surface region of a freshly etched gold tip was examined with the atom probe at subnanometer spatial resolution and with atom-level composition accuracy. A thin contaminant layer, primarily consisting of water and atmospheric gases, was observed on a fresh tip. This sample exhibited crystalline lattice spacings consistent with the interlayer spacing of {200} lattice planes of bulk gold. A thin oxide layer was created on the gold surface via plasma oxidation, and the thickness and composition of this layer was measured. Clear evidence of a nanometer-thick oxide layer was seen coating the gold tip, and the atomic composition of the oxide layer was consistent with the expected stoichiometry for gold oxide. Monomolecular anions layers of Br(-) and I(-) were created via adsorption from aqueous solutions onto the gold. Atom probe data verified the presence of the monomolecular anion layers on the gold surface, with ion density values consistent with literature values. A hexanethiolate monolayer was coated onto the gold tip, and atom probe analysis revealed a thin film whose ion fragments were consistent with the molecular composition of the monolayer and a surface coverage similar to that expected from literature. Details of the various coating compositions and structures are presented, along with discussion of the reconstruction issues associated with properly analyzing these thin-film systems.

  9. Switching surface polarization of atomic force microscopy probe utilizing photoisomerization of photochromic molecules

    SciTech Connect

    Aburaya, Yoshihiro; Nomura, Hikaru; Kageshima, Masami; Naitoh, Yoshitaka; Li, Yan Jun; Sugawara, Yasuhiro

    2011-03-15

    An attempt to develop an atomic force microscopy (AFM) probe with optically switchable polarization is described. Modification with a single molecular layer of photochromic molecules was attempted onto a Si substrate that is a prototype for a probe surface. Polarization switching caused by alternate irradiation of UV and visible lights were detected using the electrostatic force?>spectroscopy (EFS) technique. Si substrates modified with spiropyran and azobenzene exhibited reversible polarization switching that caused changes in CPD of about 100 and 50 mV, respectively. Modification with spiropyran was also attempted onto a Si probe and resulted in a CPD change of about 100 mV. It was confirmed that modification of an AFM probe or substrate with a single molecular layer of photochromic molecules can generate surface polarization switching of a mechanically detectable level.

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

    SciTech Connect

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

    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.

  11. Optical probes of atomic and molecular decay processes.

    SciTech Connect

    Pratt, S. T.

    2008-01-01

    characterize both the photoexcitation and subsequent decay processes. These techniques include mass spectrometry, dispersive and threshold photoelectron spectroscopy, laser-induced fluorescence, fluorescence-dip spectroscopy, and laser-induced grating spectroscopy. While the instrumentation is currently available for each of these techniques, two instruments deserve special mention. First, a high-resolution magnetic-bottle electron spectrometer has been developed that is equipped with a pulsed, skimmed molecular beam source. This instrument is capable of {approx}3-4 meV resolution in the electron kinetic energy while providing a collection efficiency of {approx}50%. Second, a time-of-flight mass spectrometer has been constructed with a similar molecular beam source. This instrument is currently being adapted to allow both ion- and electron-imaging studies. A typical experimental study is performed in three steps. First, resonant one-color multiphoton ionization is used to map out the transition between the ground state of the molecule of interest and the low-lying excited state to be used as an intermediate in the double-resonance process. The lasers used in these studies are Nd:YAG-pumped dye lasers with {approx}5 ns pulse durations. In general, this pump transition corresponds to a one- or two-photon process, and the laser output is frequency doubled, tripled, or mixed to generate light in the region of interest. In molecules such as ammonia and aniline, the pump transitions of interest are well characterized, allowing the unambiguous choice of pump transitions that access levels with the rovibronic character of interest. In other cases, the spectroscopy of the pump transition must be analyzed before it can be useful for the double-resonance experiments. In the second step, the pump laser is fixed on the pump transition of interest and a second laser is used to probe transitions from the upper state of the pump transition to the autoionizing or predissociating resonances in

  12. Probing tumor-stroma interactions and response to photodynamic therapy in a 3D pancreatic cancer-fibroblast co-culture model

    NASA Astrophysics Data System (ADS)

    Glidden, Michael D.; Massodi, Iqbal; Rizvi, Imran; Celli, Jonathan P.; Hasan, Tayyaba

    2012-02-01

    Pancreatic ductal adenocarcinoma is a lethal disease that is often unresectable by the time of diagnosis and is typically non-responsive to chemo- and radiotherapy, resulting in a five year survival of only 3%. Tumors of the pancreas are characterized by a dense fibrous stroma rich in extracellular matrix proteins, which is implicated in poor therapeutic response, though its precise roles remain poorly understood. Indeed, while the use of therapeutics that target the stroma is an emerging paradigm in the clinical management of this disease, the primary focus of such efforts is to enhance drug penetration through dense fibrous stroma and it is unclear to what extent the characteristically rigid stroma of pancreatic tumors imparts drug resistance by acting as a complex signaling partner, or merely as a physical barrier for drug delivery. Here we use 3D in vitro co-cultures of pancreatic cancer cells and normal human fibroblasts as a model system to study heterotypic interactions between these populations. Leveraging this in vitro model along with image-based methods for quantification of growth and therapeutic endpoints, we characterize these co-cultures and examine the role of verteporfin-based photodynamic therapy (PDT) for targeting tumor-fibroblast interactions in pancreatic tumors.

  13. Field evaporation behaviour in the gamma phase in Ti-Al during analysis in the tomographic atom probe.

    PubMed

    Lefebvre, W; Loiseau, A; Menand, A

    2002-07-01

    A Ti-48 at% Al alloy has been successfully investigated, using atom probe field ion microscopy and transmission electron microscopy. After a specific heat treatment, this alloy has a (alpha2 + gamma) lamellar microstructure. Using the tomographic atom probe (TAP), it has been possible to image the stacking of superlattice planes of gamma and to identify titanium as the highest evaporation field element. In addition, the influence of analysis site on atom probe measurements has been estimated for this phase. A TAP analysis has also made it possible to observe an extremely thin step along a gamma/gamma interface at a near atomic scale.

  14. 3D and Education

    NASA Astrophysics Data System (ADS)

    Meulien Ohlmann, Odile

    2013-02-01

    Today the industry offers a chain of 3D products. Learning to "read" and to "create in 3D" becomes an issue of education of primary importance. 25 years professional experience in France, the United States and Germany, Odile Meulien set up a personal method of initiation to 3D creation that entails the spatial/temporal experience of the holographic visual. She will present some different tools and techniques used for this learning, their advantages and disadvantages, programs and issues of educational policies, constraints and expectations related to the development of new techniques for 3D imaging. Although the creation of display holograms is very much reduced compared to the creation of the 90ies, the holographic concept is spreading in all scientific, social, and artistic activities of our present time. She will also raise many questions: What means 3D? Is it communication? Is it perception? How the seeing and none seeing is interferes? What else has to be taken in consideration to communicate in 3D? How to handle the non visible relations of moving objects with subjects? Does this transform our model of exchange with others? What kind of interaction this has with our everyday life? Then come more practical questions: How to learn creating 3D visualization, to learn 3D grammar, 3D language, 3D thinking? What for? At what level? In which matter? for whom?

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

    PubMed

    Han, Guebum; Ahn, Hyo-Sok

    2016-02-01

    We propose a method of producing a tungsten probe with high stiffness for atomic force microscopy (AFM) in order to acquire enhanced phase contrast images and efficiently perform lithography. A tungsten probe with a tip radius between 20nm and 50nm was fabricated using electrochemical etching optimized by applying pulse waves at different voltages. The spring constant of the tungsten probe was determined by finite element analysis (FEA), and its applicability as an AFM probe was evaluated by obtaining topography and phase contrast images of a Si wafer sample partly coated with Au. Enhanced hard tapping performance of the tungsten probe compared with a commercial Si probe was confirmed by conducting hard tapping tests at five different oscillation amplitudes on single layer graphene grown by chemical vapor deposition (CVD). To analyze the damaged graphene sample, the test areas were investigated using tip-enhanced Raman spectroscopy (TERS). The test results demonstrate that the tungsten probe with high stiffness was capable of inducing sufficient elastic and plastic deformation to enable obtaining enhanced phase contrast images and performing lithography, respectively. PMID:26630069

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

    PubMed

    Han, Guebum; Ahn, Hyo-Sok

    2016-02-01

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

  17. Development of Insulated Conductive Probes with Platinum Silicide Tips for Atomic Force Microscopy in Cell Biology

    NASA Astrophysics Data System (ADS)

    Akiyama, Terunobu; Gullo, Maurizio R.; Rooij, Nicolaas F. de; Tonin, Andreas; Hidber, Hans-Rudolf; Frederix, Patrick L. T. M.; Engel, Andreas; Staufer, Urs

    2004-06-01

    A microfabrication process of a multifunctional probe is introduced for atomic force microscopy and various electrochemical measurements on biological samples in buffer solution. The silicon nitride probes have a spring constant lower than 0.1 N/m and a conductive tip, which is tightly insulated except at the apex. The conductive core of the tip consists of PtxSiy and shows a typical radius of curvature of 15 nm. A simultaneous measurement of topography and electrical current on graphite in air was demonstrated.

  18. A filtering method to reveal crystalline patterns from atom probe microscopy desorption maps

    PubMed Central

    Yao, Lan

    2016-01-01

    A filtering method to reveal the crystallographic information present in Atom Probe Microscopy (APM) data is presented. The method filters atoms based on the time difference between their evaporation and the evaporation of the previous atom. Since this time difference correlates with the location and the local structure of the evaporating atoms on the surface, it can be used to reveal any crystallographic information contained within APM data. The demonstration of this method is illustrated on: • A pure Al specimen for which crystallographic poles are clearly visible on the desorption patterns easily indexed. • Three Fe-15at.% Cr datasets where crystallographic patterns are less obvious and require this filtering method. PMID:27104149

  19. A filtering method to reveal crystalline patterns from atom probe microscopy desorption maps.

    PubMed

    Yao, Lan

    2016-01-01

    A filtering method to reveal the crystallographic information present in Atom Probe Microscopy (APM) data is presented. The method filters atoms based on the time difference between their evaporation and the evaporation of the previous atom. Since this time difference correlates with the location and the local structure of the evaporating atoms on the surface, it can be used to reveal any crystallographic information contained within APM data. The demonstration of this method is illustrated on: •A pure Al specimen for which crystallographic poles are clearly visible on the desorption patterns easily indexed.•Three Fe-15at.% Cr datasets where crystallographic patterns are less obvious and require this filtering method.

  20. Dynamics of Hollow Atom Formation in Intense X-Ray Pulses Probed by Partial Covariance Mapping

    NASA Astrophysics Data System (ADS)

    Frasinski, L. J.; Zhaunerchyk, V.; Mucke, M.; Squibb, R. J.; Siano, M.; Eland, J. H. D.; Linusson, P.; v. d. Meulen, P.; Salén, P.; Thomas, R. D.; Larsson, M.; Foucar, L.; Ullrich, J.; Motomura, K.; Mondal, S.; Ueda, K.; Osipov, T.; Fang, L.; Murphy, B. F.; Berrah, N.; Bostedt, C.; Bozek, J. D.; Schorb, S.; Messerschmidt, M.; Glownia, J. M.; Cryan, J. P.; Coffee, R. N.; Takahashi, O.; Wada, S.; Piancastelli, M. N.; Richter, R.; Prince, K. C.; Feifel, R.

    2013-08-01

    When exposed to ultraintense x-radiation sources such as free electron lasers (FELs) the innermost electronic shell can efficiently be emptied, creating a transient hollow atom or molecule. Understanding the femtosecond dynamics of such systems is fundamental to achieving atomic resolution in flash diffraction imaging of noncrystallized complex biological samples. We demonstrate the capacity of a correlation method called “partial covariance mapping” to probe the electron dynamics of neon atoms exposed to intense 8 fs pulses of 1062 eV photons. A complete picture of ionization processes competing in hollow atom formation and decay is visualized with unprecedented ease and the map reveals hitherto unobserved nonlinear sequences of photoionization and Auger events. The technique is particularly well suited to the high counting rate inherent in FEL experiments.

  1. Probing primordial non-Gaussianity: the 3D Bispectrum of Ly-α forest and the redshifted 21-cm signal from the post reionization epoch

    SciTech Connect

    Sarkar, Tapomoy Guha; Hazra, Dhiraj Kumar E-mail: dhiraj@apctp.org

    2013-04-01

    We explore possibility of using the three dimensional bispectra of the Ly-α forest and the redshifted 21-cm signal from the post-reionization epoch to constrain primordial non-Gaussianity. Both these fields map out the large scale distribution of neutral hydrogen and maybe treated as tracers of the underlying dark matter field. We first present the general formalism for the auto and cross bispectrum of two arbitrary three dimensional biased tracers and then apply it to the specific case. We have modeled the 3D Ly-α transmitted flux field as a continuous tracer sampled along 1D skewers which corresponds to quasars sight lines. For the post reionization 21-cm signal we have used a linear bias model. We use a Fisher matrix analysis to present the first prediction for bounds on f{sub NL} and the other bias parameters using the three dimensional 21-cm bispectrum and other cross bispectra. The bounds on f{sub NL} depend on the survey volume, and the various observational noises. We have considered a BOSS like Ly-α survey where the average number density of quasars n-bar = 10{sup −3}Mpc{sup −2} and the spectra are measured at a 2-σ level. For the 21-cm signal we have considered a 4000 hrs observation with a futuristic SKA like radio array. We find that bounds on f{sub NL} obtained in our analysis (6 ≤ Δf{sub NL} ≤ 65) is competitive with CMBR and galaxy surveys and may prove to be an important alternative approach towards constraining primordial physics using future data sets. Further, we have presented a hierarchy of power of the bispectrum-estimators towards detecting the f{sub NL}. Given the quality of the data sets, one may use this method to optimally choose the right estimator and thereby provide better constraints on f{sub NL}. We also find that by combining the various cross-bispectrum estimators it is possible to constrain f{sub NL} at a level Δf{sub NL} ∼ 4.7. For the equilateral and orthogonal template we obtain Δf{sub NL}{sup equ} ∼ 17 and

  2. Probing Rotational Motion in 4-tert-Butylcatechol through H Atom Photofragmentation: Deviations from Axial Recoil.

    PubMed

    Staniforth, M; Young, J D; Stavros, V G

    2015-12-17

    The time-resolved photofragmentation dynamics of 4-tert-butylcatechol were studied following one photon excitation to the S1 (1(1)ππ*) state with ultraviolet radiation in the range 260 ≤ λ ≤ 286 nm. The preparation of an aligned molecular ensemble via photoexcitation leads to anisotropy in the H atom photofragments. These H atoms originate from the decay of the S1 state through coupling onto the S2 ((1)πσ*) state, which is dissociative along the nonintramolecular hydrogen bonded "free" O-H bond. The degree of anisotropy of these photogenerated H atoms decreases with increasing pump-probe time delay. This is attributed to rotational dephasing of the initially aligned molecular ensemble. The measured dephasing occurs on a time scale akin to the appearance time of these H atoms, which likely places an intrinsic lower bound on the dephasing lifetime. The present work demonstrates how a careful balance between the appearance time of the H atoms, determined by the S1 lifetime, and the rotational dephasing in 4-tert-butylcatechol provides an opportune window to probe rotational motion in real time.

  3. Acoustic Attenuation Probe for Fermion Superfluidity in Ultracold-Atom Gases

    SciTech Connect

    Gaudio, Sergio; Mihaila, Bogdan; Blagoev, Krastan B.; Timmermans, Eddy; Bedell, Kevin S.

    2007-03-16

    Dilute gas Bose-Einstein condensates (BEC's), currently used to cool fermionic atoms in atom traps, can also probe the superfluidity of these fermions. The damping rate of BEC-acoustic excitations (phonon modes), measured in the middle of the trap as a function of the phonon momentum, yields an unambiguous signature of BCS-like superfluidity, provides a measurement of the superfluid gap parameter, and gives an estimate of the size of the Cooper pairs in the BEC-BCS crossover regime. We also predict kinks in the momentum dependence of the damping rate which can reveal detailed information about the fermion quasiparticle dispersion relation.

  4. Characterization of a dielectric/GaN system using atom probe tomography

    NASA Astrophysics Data System (ADS)

    Mazumder, Baishakhi; Esposto, Michele; Hung, Ting H.; Mates, Tom; Rajan, Siddharth; Speck, James S.

    2013-10-01

    Characterization of Al2O3 gate dielectric on GaN using pulsed laser Atom Probe Tomography is reported. Atomic layer deposition was used to grow 5 nm of aluminum oxide on Ga-polar GaN. No oxidation of the surface of the semiconductor was observed and the interface was found to be non-abrupt. A significant amount of carbon impurities (1019/cm3) were detected in the dielectric film that matches well with the estimated bulk trap density from C-V measurements. Our experiments suggest possible correlation between trap-related electrical hysteresis and the observed impurity concentration in these films.

  5. Probing the 3-D Structure, Dynamics, and Stability of Bacterial Collagenase Collagen Binding Domain (apo- versus holo-) by Limited Proteolysis MALDI-TOF MS

    NASA Astrophysics Data System (ADS)

    Sides, Cynthia R.; Liyanage, Rohana; Lay, Jackson O.; Philominathan, Sagaya Theresa Leena; Matsushita, Osamu; Sakon, Joshua

    2012-03-01

    Pairing limited proteolysis and matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) to probe clostridial collagenase collagen binding domain (CBD) reveals the solution dynamics and stability of the protein, as these factors are crucial to CBD effectiveness as a drug-delivery vehicle. MS analysis of proteolytic digests indicates initial cleavage sites, thereby specifying the less stable and highly accessible regions of CBD. Modulation of protein structure and stability upon metal binding is shown through MS analysis of calcium-bound and cobalt-bound CBD proteolytic digests. Previously determined X-ray crystal structures illustrate that calcium binding induces secondary structure transformation in the highly mobile N-terminal arm and increases protein stability. MS-based detection of exposed residues confirms protein flexibility, accentuates N-terminal dynamics, and demonstrates increased global protein stability exported by calcium binding. Additionally, apo- and calcium-bound CBD proteolysis sites correlate well with crystallographic B-factors, accessibility, and enzyme specificity. MS-observed cleavage sites with no clear correlations are explained either by crystal contacts of the X-ray crystal structures or by observed differences between Molecules A and B in the X-ray crystal structures. The study newly reveals the absence of the βA strand and thus the very dynamic N-terminal linker, as corroborated by the solution X-ray scattering results. Cobalt binding has a regional effect on the solution phase stability of CBD, as limited proteolysis data implies the capture of an intermediate-CBD solution structure when cobalt is bound.

  6. 3D Imaging.

    ERIC Educational Resources Information Center

    Hastings, S. K.

    2002-01-01

    Discusses 3 D imaging as it relates to digital representations in virtual library collections. Highlights include X-ray computed tomography (X-ray CT); the National Science Foundation (NSF) Digital Library Initiatives; output peripherals; image retrieval systems, including metadata; and applications of 3 D imaging for libraries and museums. (LRW)

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

    SciTech Connect

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

    2014-09-30

    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 front using the aberration-corrected optics of a scanning transmission electron microscope. The probe’s required phase distribution depends on the sample’s magnetic symmetry and crystal structure. The calculations indicate that EMCD signals that use the electron probe’s phase are as strong as those obtained by nanodiffraction methods.

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

    PubMed

    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.

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

    PubMed

    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.

  10. Methods for atom probe analysis of microgradients in functionally graded cemented carbides.

    PubMed

    Frykholm, R; Jansson, B; Andrén, H-O

    2002-01-01

    Methods to prepare needle-shaped specimens for atom probe field ion microscopy from near surface regions have been developed. The material used was a cemented carbide with a composition gradient towards the surface, but the method is equally applicable for other materials. The preparation technique involves dimple grinding, electropolishing and focused ion beam (FIB) milling. The use of FIB milling allows for specimen preparation of materials which due to the preferential etching of different phases are difficult to electropolish. The technique also allows for preparation of specimens at well defined depth from the sample surface, selection of phase to be analysed, and to sharpen and re-use already analysed specimens. Atom probe analyses of the near surface zone region in a gradient sintered WC-Ti(C,N)-TaC-Co cemented carbide are presented.

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

    PubMed

    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

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

    DOE PAGES

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

    2014-09-30

    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 front using the aberration-corrected optics of a scanning transmission electron microscope. The probe’s required phase distribution depends on the sample’s magnetic symmetry and crystal structure. The calculations indicate that EMCD signals that use the electron probe’s phase are as strongmore » as those obtained by nanodiffraction methods.« less

  13. Pulsed-laser atom probe studies of a precipitation hardened maraging TRIP steel.

    PubMed

    Dmitrieva, O; Choi, P; Gerstl, S S A; Ponge, D; Raabe, D

    2011-05-01

    A precipitation hardened maraging TRIP steel was analyzed using a pulsed laser atom probe. The laser pulse energy was varied from 0.3 to 1.9 nJ to study its effect on the measured chemical compositions and spatial resolution. Compositional analyses using proximity histograms did not show any significant variations in the average matrix and precipitate compositions. The only remarkable change in the atom probe data was a decrease in the ++/+ charge state ratios of the elements. The values of the evaporation field used for the reconstructions exhibit a linear dependence on the laser pulse energy. The adjustment of the evaporation fields used in the reconstructions for different laser pulse energies was based on the correlation of the obtained cluster shapes to the TEM observations. No influence of laser pulse energy on chemical composition of the precipitates and on the chemical sharpness of their interfaces was detected.

  14. Nanomanipulation and nanofabrication with multi-probe STM: From individual atoms to nanowires

    SciTech Connect

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

    2012-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

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

    SciTech Connect

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

    1990-12-01

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

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

    SciTech Connect

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

    1989-10-01

    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.

  18. Probing the Kondo lattice model with alkaline-earth-metal atoms

    SciTech Connect

    Foss-Feig, Michael; Hermele, Michael; Rey, Ana Maria

    2010-05-15

    We study transport properties of alkaline-earth-metal atoms governed by the Kondo lattice Hamiltonian plus a harmonic confining potential, and suggest simple dynamical probes of several different regimes of the phase diagram that can be implemented with current experimental techniques. In particular, we show how Kondo physics at strong coupling, at low density, and in the heavy fermion phase is manifest in the dipole oscillations of the conduction band upon displacement of the trap center.

  19. Pump-probe spectroscopy in degenerate two-level atoms with arbitrarily strong fields

    NASA Astrophysics Data System (ADS)

    Zigdon, T.; Wilson-Gordon, A. D.; Goren, C.; Rosenbluh, M.; Friedmann, H.

    2007-03-01

    We review our previous work on pump-probe spectroscopy in realistic degenerate two-level systems and model systems. In particular, we discuss the role of transfer of coherence (TOC) between the ground and excited hyperfine states in producing electromagnetically-induced transparency (EIA) peaks in the probe spectrum, when an F g goes to F e = F g +1 transition in an alkali-metal atom interacts with a strong pump and weak probe that have perpendicular polarizations. When the pump is rho + polarized and the probe pi polarized, this system can be modelled by an N system. We also discuss the role of transfer of population (TOP) between the Zeeman levels of the ground hyperfine state in producing EIA peaks when the pump and probe have the same polarization. This system can be modelled using a double two-level system. The role of Doppler broadening and phase-changing collisions in modifying the EIA-TOC and EIA-TOP absorption and refraction spectra is also discussed. All these spectra were calculated using MATLAB programs that both construct and solve the relevant Bloch equations. In our recent work, we consider the effect of a strong probe on the pump absorption and refraction spectra when the pump and probe polarizations are linear and perpendicular. It is difficult to solve this problem numerically due to the large number frequencies involved. In order to simplify the problem, we considered two cases: (i) rho + polarized pump and pi polarized probe, and (ii) rho + polarized pump and rho - polarized probe, and investigated a series of transitions in both Rb and Cs, using modified versions of the MATLAB programs devised for the weakprobe case. A number of interesting differences from the weak-probe case were found. For example, when the probe is sufficiently strong, we found the pump and probe spectra to show complementary behavior. In addition, as the number of Zeeman levels increase, the EIA peaks become progressively sharper, and are accompanied by steeper dispersion.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Accurate noncontact calibration of colloidal probe sensitivities in atomic force microscopy.

    PubMed

    Chung, Koo-Hyun; Shaw, Gordon A; Pratt, Jon R

    2009-06-01

    The absolute force sensitivities of colloidal probes comprised of atomic force microscope, or AFM, cantilevers with microspheres attached to their distal ends are measured. The force sensitivities are calibrated through reference to accurate electrostatic forces, the realizations of which are described in detail. Furthermore, the absolute accuracy of a common AFM force calibration scheme, known as the thermal noise method, is evaluated. It is demonstrated that the thermal noise method can be applied with great success to colloidal probe calibration in air and in liquid to yield force measurements with relative standard uncertainties below 5%. Techniques to combine the electrostatics-based determination of the AFM force sensitivity with measurements of the colloidal probe's thermal noise spectrum to compute noncontact estimates of the displacement sensitivity and spring constant are also developed.

  2. Accurate noncontact calibration of colloidal probe sensitivities in atomic force microscopy

    SciTech Connect

    Chung, Koo-Hyun; Shaw, Gordon A.; Pratt, Jon R.

    2009-06-15

    The absolute force sensitivities of colloidal probes comprised of atomic force microscope, or AFM, cantilevers with microspheres attached to their distal ends are measured. The force sensitivities are calibrated through reference to accurate electrostatic forces, the realizations of which are described in detail. Furthermore, the absolute accuracy of a common AFM force calibration scheme, known as the thermal noise method, is evaluated. It is demonstrated that the thermal noise method can be applied with great success to colloidal probe calibration in air and in liquid to yield force measurements with relative standard uncertainties below 5%. Techniques to combine the electrostatics-based determination of the AFM force sensitivity with measurements of the colloidal probe's thermal noise spectrum to compute noncontact estimates of the displacement sensitivity and spring constant are also developed.

  3. Template-Free 3D Microprinting of Metals Using a Force-Controlled Nanopipette for Layer-by-Layer Electrodeposition.

    PubMed

    Hirt, Luca; Ihle, Stephan; Pan, Zhijian; Dorwling-Carter, Livie; Reiser, Alain; Wheeler, Jeffrey M; Spolenak, Ralph; Vörös, János; Zambelli, Tomaso

    2016-03-23

    A novel 3D printing method for voxel-by-voxel metal printing is presented. Hollow atomic force microscopy (AFM) cantilevers are used to locally supply metal ions in an electrochemical cell, enabling a localized electroplating reaction. By exploiting the deflection feedback of these probes, electrochemical 3D metal printing is, for the first time, demonstrated in a layer-by-layer fashion, enabling the fabrication of arbitrary-shaped geometries.

  4. Template-Free 3D Microprinting of Metals Using a Force-Controlled Nanopipette for Layer-by-Layer Electrodeposition.

    PubMed

    Hirt, Luca; Ihle, Stephan; Pan, Zhijian; Dorwling-Carter, Livie; Reiser, Alain; Wheeler, Jeffrey M; Spolenak, Ralph; Vörös, János; Zambelli, Tomaso

    2016-03-23

    A novel 3D printing method for voxel-by-voxel metal printing is presented. Hollow atomic force microscopy (AFM) cantilevers are used to locally supply metal ions in an electrochemical cell, enabling a localized electroplating reaction. By exploiting the deflection feedback of these probes, electrochemical 3D metal printing is, for the first time, demonstrated in a layer-by-layer fashion, enabling the fabrication of arbitrary-shaped geometries. PMID:26783090

  5. Polarisation response of delay dependent absorption modulation in strong field dressed helium atoms probed near threshold

    NASA Astrophysics Data System (ADS)

    Simpson, E. R.; Sanchez-Gonzalez, A.; Austin, D. R.; Diveki, Z.; Hutchinson, S. E. E.; Siegel, T.; Ruberti, M.; Averbukh, V.; Miseikis, L.; Strüber, C. S.; Chipperfield, L.; Marangos, J. P.

    2016-08-01

    We present the first measurement of the vectorial response of strongly dressed helium atoms probed by an attosecond pulse train (APT) polarised either parallel or perpendicular to the dressing field polarisation. The transient absorption is probed as a function of delay between the APT and the linearly polarised 800 nm field of peak intensity 1.3× {10}14 {{W}} {{cm}}-2. The APT spans the photon energy range 16-42 eV, covering the first ionisation energy of helium (24.59 eV). With parallel polarised dressing and probing fields, we observe modulations with periods of one half and one quarter of the dressing field period. When the polarisation of the dressing field is altered from parallel to perpendicular with respect to the APT polarisation we observe a large suppression in the modulation depth of the above ionisation threshold absorption. In addition to this we present the intensity dependence of the harmonic modulation depth as a function of delay between the dressing and probe fields, with dressing field peak intensities ranging from 2 × 1012 to 2 × 1014 {{W}} {{cm}}-2. We compare our experimental results with a full-dimensional solution of the single-atom time-dependent (TD) Schrödinger equation obtained using the recently developed abinitio TD B-spline ADC method and find good qualitative agreement for the above threshold harmonics.

  6. Polarisation response of delay dependent absorption modulation in strong field dressed helium atoms probed near threshold

    NASA Astrophysics Data System (ADS)

    Simpson, E. R.; Sanchez-Gonzalez, A.; Austin, D. R.; Diveki, Z.; Hutchinson, S. E. E.; Siegel, T.; Ruberti, M.; Averbukh, V.; Miseikis, L.; Strüber, C. S.; Chipperfield, L.; Marangos, J. P.

    2016-08-01

    We present the first measurement of the vectorial response of strongly dressed helium atoms probed by an attosecond pulse train (APT) polarised either parallel or perpendicular to the dressing field polarisation. The transient absorption is probed as a function of delay between the APT and the linearly polarised 800 nm field of peak intensity 1.3× {10}14 {{W}} {{cm}}-2. The APT spans the photon energy range 16–42 eV, covering the first ionisation energy of helium (24.59 eV). With parallel polarised dressing and probing fields, we observe modulations with periods of one half and one quarter of the dressing field period. When the polarisation of the dressing field is altered from parallel to perpendicular with respect to the APT polarisation we observe a large suppression in the modulation depth of the above ionisation threshold absorption. In addition to this we present the intensity dependence of the harmonic modulation depth as a function of delay between the dressing and probe fields, with dressing field peak intensities ranging from 2 × 1012 to 2 × 1014 {{W}} {{cm}}-2. We compare our experimental results with a full-dimensional solution of the single-atom time-dependent (TD) Schrödinger equation obtained using the recently developed abinitio TD B-spline ADC method and find good qualitative agreement for the above threshold harmonics.

  7. Microstructural characterization of an Al-li-mg-cu alloy by correlative electron tomography and atom probe tomography.

    PubMed

    Xiong, Xiangyuan; Weyland, Matthew

    2014-08-01

    Correlative electron tomography and atom probe tomography have been carried out successfully on the same region of a commercial 8090 aluminum alloy (Al-Li-Mg-Cu). The combination of the two techniques allows accurate geometric reconstruction of the atom probe tomography data verified by crystallographic information retrieved from the reconstruction. Quantitative analysis of the precipitate phase compositions and volume fractions of each phase have been obtained from the atom probe tomography and electron tomography at various scales, showing strong agreement between both techniques.

  8. The Rossiter-McLaughlin effect reloaded: Probing the 3D spin-orbit geometry, differential stellar rotation, and the spatially-resolved stellar spectrum of star-planet systems

    NASA Astrophysics Data System (ADS)

    Cegla, H. M.; Lovis, C.; Bourrier, V.; Beeck, B.; Watson, C. A.; Pepe, F.

    2016-04-01

    When a planet transits its host star, it blocks regions of the stellar surface from view; this causes a distortion of the spectral lines and a change in the line-of-sight (LOS) velocities, known as the Rossiter-McLaughlin (RM) effect. Since the LOS velocities depend, in part, on the stellar rotation, the RM waveform is sensitive to the star-planet alignment (which provides information on the system's dynamical history). We present a new RM modelling technique that directly measures the spatially-resolved stellar spectrum behind the planet. This is done by scaling the continuum flux of the (HARPS) spectra by the transit light curve, and then subtracting the in- from the out-of-transit spectra to isolate the starlight behind the planet. This technique does not assume any shape for the intrinsic local profiles. In it, we also allow for differential stellar rotation and centre-to-limb variations in the convective blueshift. We apply this technique to HD 189733 and compare to 3D magnetohydrodynamic (MHD) simulations. We reject rigid body rotation with high confidence (>99% probability), which allows us to determine the occulted stellar latitudes and measure the stellar inclination. In turn, we determine both the sky-projected (λ ≈ -0.4 ± 0.2°) and true 3D obliquity (ψ ≈ 7+12-4°). We also find good agreement with the MHD simulations, with no significant centre-to-limb variations detectable in the local profiles. Hence, this technique provides a new powerful tool that can probe stellar photospheres, differential rotation, determine 3D obliquities, and remove sky-projection biases in planet migration theories. This technique can be implemented with existing instrumentation, but will become even more powerful with the next generation of high-precision radial velocity spectrographs.

  9. The role of amino acid electron-donor/acceptor atoms in host-cell binding peptides is associated with their 3D structure and HLA-binding capacity in sterile malarial immunity induction

    SciTech Connect

    Patarroyo, Manuel E.; Almonacid, Hannia; Moreno-Vranich, Armando

    2012-01-20

    Highlights: Black-Right-Pointing-Pointer Fundamental residues located in some HABPs are associated with their 3D structure. Black-Right-Pointing-Pointer Electron-donor atoms present in {beta}-turn, random, distorted {alpha}-helix structures. Black-Right-Pointing-Pointer Electron-donor atoms bound to HLA-DR53. Black-Right-Pointing-Pointer Electron-acceptor atoms present in regular {alpha}-helix structure bound to HLA-DR52. -- Abstract: Plasmodium falciparum malaria continues being one of the parasitic diseases causing the highest worldwide mortality due to the parasite's multiple evasion mechanisms, such as immunological silence. Membrane and organelle proteins are used during invasion for interactions mediated by high binding ability peptides (HABPs); these have amino acids which establish hydrogen bonds between them in some of their critical binding residues. Immunisation assays in the Aotus model using HABPs whose critical residues had been modified have revealed a conformational change thereby enabling a protection-inducing response. This has improved fitting within HLA-DR{beta}1{sup Asterisk-Operator} molecules where amino acid electron-donor atoms present in {beta}-turn, random or distorted {alpha}-helix structures preferentially bound to HLA-DR53 molecules, whilst HABPs having amino acid electron-acceptor atoms present in regular {alpha}-helix structure bound to HLA-DR52. This data has great implications for vaccine development.

  10. Probing three-dimensional surface force fields with atomic resolution: Measurement strategies, limitations, and artifact reduction.

    PubMed

    Baykara, Mehmet Z; Dagdeviren, Omur E; Schwendemann, Todd C; Mönig, Harry; Altman, Eric I; Schwarz, Udo D

    2012-01-01

    Noncontact atomic force microscopy (NC-AFM) is being increasingly used to measure the interaction force between an atomically sharp probe tip and surfaces of interest, as a function of the three spatial dimensions, with picometer and piconewton accuracy. Since the results of such measurements may be affected by piezo nonlinearities, thermal and electronic drift, tip asymmetries, and elastic deformation of the tip apex, these effects need to be considered during image interpretation.In this paper, we analyze their impact on the acquired data, compare different methods to record atomic-resolution surface force fields, and determine the approaches that suffer the least from the associated artifacts. The related discussion underscores the idea that since force fields recorded by using NC-AFM always reflect the properties of both the sample and the probe tip, efforts to reduce unwanted effects of the tip on recorded data are indispensable for the extraction of detailed information about the atomic-scale properties of the surface.

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

    SciTech Connect

    Diallo, M. L.; Fnidiki, A. Lardé, R.; Cuvilly, F.; Blum, I.; Lechevallier, L.; Debelle, A.; Thomé, L.; Viret, M.; Marteau, M.; Eyidi, D.; Declémy, A.

    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.

  12. Probing the energy flow in Bessel light beams using atomic photoionization

    NASA Astrophysics Data System (ADS)

    Surzhykov, A.; Seipt, D.; Fritzsche, S.

    2016-09-01

    The growing interest in twisted light beams also requires a better understanding of their complex internal structure. Particular attention is currently being given to the energy circulation in these beams as usually described by the Poynting vector field. In the present study we propose to use the photoionization of alkali-metal atoms as a probe process to measure (and visualize) the energy flow in twisted light fields. Such measurements are possible since the angular distribution of photoelectrons, emitted from a small atomic target, appears sensitive to and is determined by the local direction of the Poynting vector. To illustrate the feasibility of the proposed method, detailed calculations were performed for the ionization of sodium atoms by nondiffractive Bessel beams.

  13. Probing dissociative electron attachment through heavy-Rydberg ion-pair production in Rydberg atom collisions

    NASA Astrophysics Data System (ADS)

    Buathong, S.; Kelley, M.; Dunning, F. B.

    2016-10-01

    Electron transfer in collisions between low-n, n = 12, Rydberg atoms and targets that attach low-energy electrons can lead to the formation of heavy-Rydberg ion-pair states comprising a weakly-bound positive-negative ion pair that orbit each other at large separations. Measurements of the velocity and angular distribution of ion-pair states produced in collisions with 1,1,1-C2Cl3F3, CBrCl3, BrCN, and Fe(CO)5 are used to show that electron transfer reactions furnish a new technique with which to examine the lifetime and decay energetics of the excited intermediates formed during dissociative electron capture. The results are analyzed with the aid of Monte Carlo simulations based on the free electron model of Rydberg atom collisions. The data further highlight the capabilities of Rydberg atoms as a microscale laboratory in which to probe the dynamics of electron attachment reactions.

  14. Measuring excited state lifetime of Rb atoms with pump-probe technique

    SciTech Connect

    Zeng, X.; Boiko, D. L.

    2015-08-31

    A technique for measuring the excited state lifetime τ{sub ex} of optical transitions in alkali atoms is presented. It is a form of pump-probe technique based on time-resolved optical transmission through the atomic vapor cell. This technique can serve as an alternative to the traditionally used time-resolved photofluorescence methods when measuring alkali vapor cells with heavily quenched fluorescence, where the τ{sub ex} is expected to be on the order of a few nanoseconds, and the highly sensitive fluorescence detectors with sub-nanosecond temporal resolution that are required may not be available. We use this technique to measure the τ{sub ex} of Rb atoms in vapor cells with different buffer gas pressures.

  15. Atom-column distinction by Kikuchi pattern observed by an aberration-corrected convergent electron probe.

    PubMed

    Saitoh, Koh; Tatara, Yoshihide; Tanaka, Nobuo

    2010-01-01

    Kikuchi patterns of an MgO crystal at the [110] incidence have been taken by a sub-angstrom electron beam focused on the single atom-column. A significant change in intensity has been observed in the 111 band; that is, the contrast in the central and side bands is reversed depending on the illuminated atom-column. The contrast reversal in the 111 band has been reproduced by multislice simulation using the frozen-phonon approach. The beam-position dependence of the 111 band intensity can be interpreted by electron channelling and the reciprocity theorem. The anomalous Kikuchi pattern can be a probe for identifying the illuminated atom-column, which is useful for column-by-column electron energy-loss spectroscopy and X-ray emission spectroscopy.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. 3-D Technology Approaches for Biological Ecologies

    NASA Astrophysics Data System (ADS)

    Liu, Liyu; Austin, Robert; U. S-China Physical-Oncology Sciences Alliance (PS-OA) Team

    Constructing three dimensional (3-D) landscapes is an inevitable issue in deep study of biological ecologies, because in whatever scales in nature, all of the ecosystems are composed by complex 3-D environments and biological behaviors. Just imagine if a 3-D technology could help complex ecosystems be built easily and mimic in vivo microenvironment realistically with flexible environmental controls, it will be a fantastic and powerful thrust to assist researchers for explorations. For years, we have been utilizing and developing different technologies for constructing 3-D micro landscapes for biophysics studies in in vitro. Here, I will review our past efforts, including probing cancer cell invasiveness with 3-D silicon based Tepuis, constructing 3-D microenvironment for cell invasion and metastasis through polydimethylsiloxane (PDMS) soft lithography, as well as explorations of optimized stenting positions for coronary bifurcation disease with 3-D wax printing and the latest home designed 3-D bio-printer. Although 3-D technologies is currently considered not mature enough for arbitrary 3-D micro-ecological models with easy design and fabrication, I hope through my talk, the audiences will be able to sense its significance and predictable breakthroughs in the near future. This work was supported by the State Key Development Program for Basic Research of China (Grant No. 2013CB837200), the National Natural Science Foundation of China (Grant No. 11474345) and the Beijing Natural Science Foundation (Grant No. 7154221).

  18. Three-dimensional atom localization via electromagnetically induced transparency in a three-level atomic system.

    PubMed

    Wang, Zhiping; Cao, Dewei; Yu, Benli

    2016-05-01

    We present a new scheme for three-dimensional (3D) atom localization in a three-level atomic system via measuring the absorption of a weak probe field. Owing to the space-dependent atom-field interaction, the position probability distribution of the atom can be directly determined by measuring the probe absorption. It is found that, by properly varying the parameters of the system, the probability of finding the atom in 3D space can be almost 100%. Our scheme opens a promising way to achieve high-precision and high-efficiency 3D atom localization, which provides some potential applications in laser cooling or atom nano-lithography via atom localization.

  19. Large-Scale Fabrication of Carbon Nanotube Probe Tips For Atomic Force Microscopy Critical Dimension Imaging Applications

    NASA Technical Reports Server (NTRS)

    Ye, Qi Laura; Cassell, Alan M.; Stevens, Ramsey M.; Meyyappan, Meyya; Li, Jun; Han, Jie; Liu, Hongbing; Chao, Gordon

    2004-01-01

    Carbon nanotube (CNT) probe tips for atomic force microscopy (AFM) offer several advantages over Si/Si3N4 probe tips, including improved resolution, shape, and mechanical properties. This viewgraph presentation discusses these advantages, and the drawbacks of existing methods for fabricating CNT probe tips for AFM. The presentation introduces a bottom up wafer scale fabrication method for CNT probe tips which integrates catalyst nanopatterning and nanomaterials synthesis with traditional silicon cantilever microfabrication technology. This method makes mass production of CNT AFM probe tips feasible, and can be applied to the fabrication of other nanodevices with CNT elements.

  20. 3D ultrafast ultrasound imaging in vivo.

    PubMed

    Provost, Jean; Papadacci, Clement; Arango, Juan Esteban; Imbault, Marion; Fink, Mathias; Gennisson, Jean-Luc; Tanter, Mickael; Pernot, Mathieu

    2014-10-01

    Very high frame rate ultrasound imaging has recently allowed for the extension of the applications of echography to new fields of study such as the functional imaging of the brain, cardiac electrophysiology, and the quantitative imaging of the intrinsic mechanical properties of tumors, to name a few, non-invasively and in real time. In this study, we present the first implementation of Ultrafast Ultrasound Imaging in 3D based on the use of either diverging or plane waves emanating from a sparse virtual array located behind the probe. It achieves high contrast and resolution while maintaining imaging rates of thousands of volumes per second. A customized portable ultrasound system was developed to sample 1024 independent channels and to drive a 32  ×  32 matrix-array probe. Its ability to track in 3D transient phenomena occurring in the millisecond range within a single ultrafast acquisition was demonstrated for 3D Shear-Wave Imaging, 3D Ultrafast Doppler Imaging, and, finally, 3D Ultrafast combined Tissue and Flow Doppler Imaging. The propagation of shear waves was tracked in a phantom and used to characterize its stiffness. 3D Ultrafast Doppler was used to obtain 3D maps of Pulsed Doppler, Color Doppler, and Power Doppler quantities in a single acquisition and revealed, at thousands of volumes per second, the complex 3D flow patterns occurring in the ventricles of the human heart during an entire cardiac cycle, as well as the 3D in vivo interaction of blood flow and wall motion during the pulse wave in the carotid at the bifurcation. This study demonstrates the potential of 3D Ultrafast Ultrasound Imaging for the 3D mapping of stiffness, tissue motion, and flow in humans in vivo and promises new clinical applications of ultrasound with reduced intra--and inter-observer variability.

  1. 3D ultrafast ultrasound imaging in vivo

    NASA Astrophysics Data System (ADS)

    Provost, Jean; Papadacci, Clement; Esteban Arango, Juan; Imbault, Marion; Fink, Mathias; Gennisson, Jean-Luc; Tanter, Mickael; Pernot, Mathieu

    2014-10-01

    Very high frame rate ultrasound imaging has recently allowed for the extension of the applications of echography to new fields of study such as the functional imaging of the brain, cardiac electrophysiology, and the quantitative imaging of the intrinsic mechanical properties of tumors, to name a few, non-invasively and in real time. In this study, we present the first implementation of Ultrafast Ultrasound Imaging in 3D based on the use of either diverging or plane waves emanating from a sparse virtual array located behind the probe. It achieves high contrast and resolution while maintaining imaging rates of thousands of volumes per second. A customized portable ultrasound system was developed to sample 1024 independent channels and to drive a 32  ×  32 matrix-array probe. Its ability to track in 3D transient phenomena occurring in the millisecond range within a single ultrafast acquisition was demonstrated for 3D Shear-Wave Imaging, 3D Ultrafast Doppler Imaging, and, finally, 3D Ultrafast combined Tissue and Flow Doppler Imaging. The propagation of shear waves was tracked in a phantom and used to characterize its stiffness. 3D Ultrafast Doppler was used to obtain 3D maps of Pulsed Doppler, Color Doppler, and Power Doppler quantities in a single acquisition and revealed, at thousands of volumes per second, the complex 3D flow patterns occurring in the ventricles of the human heart during an entire cardiac cycle, as well as the 3D in vivo interaction of blood flow and wall motion during the pulse wave in the carotid at the bifurcation. This study demonstrates the potential of 3D Ultrafast Ultrasound Imaging for the 3D mapping of stiffness, tissue motion, and flow in humans in vivo and promises new clinical applications of ultrasound with reduced intra—and inter-observer variability.

  2. 3D ultrafast ultrasound imaging in vivo.

    PubMed

    Provost, Jean; Papadacci, Clement; Arango, Juan Esteban; Imbault, Marion; Fink, Mathias; Gennisson, Jean-Luc; Tanter, Mickael; Pernot, Mathieu

    2014-10-01

    Very high frame rate ultrasound imaging has recently allowed for the extension of the applications of echography to new fields of study such as the functional imaging of the brain, cardiac electrophysiology, and the quantitative imaging of the intrinsic mechanical properties of tumors, to name a few, non-invasively and in real time. In this study, we present the first implementation of Ultrafast Ultrasound Imaging in 3D based on the use of either diverging or plane waves emanating from a sparse virtual array located behind the probe. It achieves high contrast and resolution while maintaining imaging rates of thousands of volumes per second. A customized portable ultrasound system was developed to sample 1024 independent channels and to drive a 32  ×  32 matrix-array probe. Its ability to track in 3D transient phenomena occurring in the millisecond range within a single ultrafast acquisition was demonstrated for 3D Shear-Wave Imaging, 3D Ultrafast Doppler Imaging, and, finally, 3D Ultrafast combined Tissue and Flow Doppler Imaging. The propagation of shear waves was tracked in a phantom and used to characterize its stiffness. 3D Ultrafast Doppler was used to obtain 3D maps of Pulsed Doppler, Color Doppler, and Power Doppler quantities in a single acquisition and revealed, at thousands of volumes per second, the complex 3D flow patterns occurring in the ventricles of the human heart during an entire cardiac cycle, as well as the 3D in vivo interaction of blood flow and wall motion during the pulse wave in the carotid at the bifurcation. This study demonstrates the potential of 3D Ultrafast Ultrasound Imaging for the 3D mapping of stiffness, tissue motion, and flow in humans in vivo and promises new clinical applications of ultrasound with reduced intra--and inter-observer variability. PMID:25207828

  3. Robust Electrografting on Self-Organized 3D Graphene Electrodes.

    PubMed

    Fortgang, Philippe; Tite, Teddy; Barnier, Vincent; Zehani, Nedjla; Maddi, Chiranjeevi; Lagarde, Florence; Loir, Anne-Sophie; Jaffrezic-Renault, Nicole; Donnet, Christophe; Garrelie, Florence; Chaix, Carole

    2016-01-20

    Improving graphene-based electrode fabrication processes and developing robust methods for its functionalization are two key research routes to develop new high-performance electrodes for electrochemical applications. Here, a self-organized three-dimensional (3D) graphene electrode processed by pulsed laser deposition with thermal annealing is reported. This substrate shows great performance in electron transfer kinetics regarding ferrocene redox probes in solution. A robust electrografting strategy for covalently attaching a redox probe onto these graphene electrodes is also reported. The modification protocol consists of a combination of diazonium salt electrografting and click chemistry. An alkyne-terminated phenyl ring is first electrografted onto the self-organized 3D graphene electrode by in situ electrochemical reduction of 4-ethynylphenyl diazonium. Then the ethynylphenyl-modified surface efficiently reacts with the redox probe bearing a terminal azide moiety (2-azidoethyl ferrocene) by means of Cu(I)-catalyzed alkyne-azide cycloaddition. Our modification strategy applied to 3D graphene electrodes was analyzed by means of atomic force microscopy, scanning electron microscopy, Raman spectroscopy, cyclic voltammetry, and X-ray photoelectron spectroscopy (XPS). For XPS chemical surface analysis, special attention was paid to the distribution and chemical state of iron and nitrogen in order to highlight the functionalization of the graphene-based substrate by electrochemically grafting a ferrocene derivative. Dense grafting was observed, offering 4.9 × 10(-10) mol cm(-2) surface coverage and showing a stable signal over 22 days. The electrografting was performed in the form of multilayers, which offers higher ferrocene loading than a dense monolayer on a flat surface. This work opens highly promising perspectives for the development of self-organized 3D graphene electrodes with various sensing functionalities. PMID:26710829

  4. [Real time 3D echocardiography

    NASA Technical Reports Server (NTRS)

    Bauer, F.; Shiota, T.; Thomas, J. D.

    2001-01-01

    Three-dimensional representation of the heart is an old concern. Usually, 3D reconstruction of the cardiac mass is made by successive acquisition of 2D sections, the spatial localisation and orientation of which require complex guiding systems. More recently, the concept of volumetric acquisition has been introduced. A matricial emitter-receiver probe complex with parallel data processing provides instantaneous of a pyramidal 64 degrees x 64 degrees volume. The image is restituted in real time and is composed of 3 planes (planes B and C) which can be displaced in all spatial directions at any time during acquisition. The flexibility of this system of acquisition allows volume and mass measurement with greater accuracy and reproducibility, limiting inter-observer variability. Free navigation of the planes of investigation allows reconstruction for qualitative and quantitative analysis of valvular heart disease and other pathologies. Although real time 3D echocardiography is ready for clinical usage, some improvements are still necessary to improve its conviviality. Then real time 3D echocardiography could be the essential tool for understanding, diagnosis and management of patients.

  5. [Real time 3D echocardiography].

    PubMed

    Bauer, F; Shiota, T; Thomas, J D

    2001-07-01

    Three-dimensional representation of the heart is an old concern. Usually, 3D reconstruction of the cardiac mass is made by successive acquisition of 2D sections, the spatial localisation and orientation of which require complex guiding systems. More recently, the concept of volumetric acquisition has been introduced. A matricial emitter-receiver probe complex with parallel data processing provides instantaneous of a pyramidal 64 degrees x 64 degrees volume. The image is restituted in real time and is composed of 3 planes (planes B and C) which can be displaced in all spatial directions at any time during acquisition. The flexibility of this system of acquisition allows volume and mass measurement with greater accuracy and reproducibility, limiting inter-observer variability. Free navigation of the planes of investigation allows reconstruction for qualitative and quantitative analysis of valvular heart disease and other pathologies. Although real time 3D echocardiography is ready for clinical usage, some improvements are still necessary to improve its conviviality. Then real time 3D echocardiography could be the essential tool for understanding, diagnosis and management of patients. PMID:11494630

  6. Atomic Force Microscope Controlled Topographical Imaging and Proximal Probe Thermal Desorption/Ionization Mass Spectrometry Imaging

    SciTech Connect

    Ovchinnikova, Olga S; Kjoller, Kevin; Hurst, Gregory {Greg} B; Pelletier, Dale A; Van Berkel, Gary J

    2014-01-01

    This paper reports on the development of a hybrid atmospheric pressure atomic force microscopy/mass spectrometry imaging system utilizing nano-thermal analysis probes for thermal desorption surface sampling with subsequent atmospheric pressure chemical ionization and mass analysis. The basic instrumental setup and the general operation of the system were discussed and optimized performance metrics were presented. The ability to correlate topographic images of a surface with atomic force microscopy and a mass spectral chemical image of the same surface, utilizing the same probe without moving the sample from the system, was demonstrated. Co-registered mass spectral chemical images and atomic force microscopy topographical images were obtained from inked patterns on paper as well as from a living bacterial colony on an agar gel. Spatial resolution of the topography images based on pixel size (0.2 m x 0.8 m) was better than the resolution of the mass spectral images (2.5 m x 2.0 m), which were limited by current mass spectral data acquisition rate and system detection levels.

  7. Atom probe tomography studies of Al₂O₃ gate dielectrics on GaN

    SciTech Connect

    Mazumder, Baishakhi Wu, Feng; Speck, James S.; Liu, Xiang; Yeluri, Ramya; Mishra, Umesh K.

    2014-10-07

    Atom probe tomography was used to achieve three-dimensional characterization of in situ Al₂O₃/GaN structures grown by metal organic chemical vapor deposition (MOCVD). Al₂O₃ dielectrics grown at three different temperatures of 700, 900, and 1000 °C were analyzed and compared. A low temperature GaN cap layer grown atop Al₂O₃ enabled a high success rate in the atom probe experiments. The Al₂O₃/GaN interfaces were found to be intermixed with Ga, N, and O over the distance of a few nm. Impurity measurements data showed that the 1000 °C sample contains higher amounts of C (4 × 10¹⁹/cm³) and lower amounts of H (7 × 10¹⁹/cm³), whereas the 700 °C sample exhibits lower C impurities (<10¹⁷/cm³) and higher H incorporation (2.2 × 10²⁰/cm³). On comparing with Al₂O₃ grown by atomic layer deposition (ALD), it was found that the MOCVD Al₂O₃/GaN interface is comparatively abrupt. Scanning transmission electron microscopy data showed that the 900 °C and 1000 °C MOCVD films exhibit polycrystalline nature, while the ALD films were found to be amorphous.

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

    PubMed

    McBride, Sean P; Law, Bruce M

    2010-11-01

    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).

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

    SciTech Connect

    McBride, Sean P.; Law, Bruce M.

    2010-11-15

    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).

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

    NASA Astrophysics Data System (ADS)

    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.

  11. Radiochromic 3D Detectors

    NASA Astrophysics Data System (ADS)

    Oldham, Mark

    2015-01-01

    Radiochromic materials exhibit a colour change when exposed to ionising radiation. Radiochromic film has been used for clinical dosimetry for many years and increasingly so recently, as films of higher sensitivities have become available. The two principle advantages of radiochromic dosimetry include greater tissue equivalence (radiologically) and the lack of requirement for development of the colour change. In a radiochromic material, the colour change arises direct from ionising interactions affecting dye molecules, without requiring any latent chemical, optical or thermal development, with important implications for increased accuracy and convenience. It is only relatively recently however, that 3D radiochromic dosimetry has become possible. In this article we review recent developments and the current state-of-the-art of 3D radiochromic dosimetry, and the potential for a more comprehensive solution for the verification of complex radiation therapy treatments, and 3D dose measurement in general.

  12. 3-D Seismic Interpretation

    NASA Astrophysics Data System (ADS)

    Moore, Gregory F.

    2009-05-01

    This volume is a brief introduction aimed at those who wish to gain a basic and relatively quick understanding of the interpretation of three-dimensional (3-D) seismic reflection data. The book is well written, clearly illustrated, and easy to follow. Enough elementary mathematics are presented for a basic understanding of seismic methods, but more complex mathematical derivations are avoided. References are listed for readers interested in more advanced explanations. After a brief introduction, the book logically begins with a succinct chapter on modern 3-D seismic data acquisition and processing. Standard 3-D acquisition methods are presented, and an appendix expands on more recent acquisition techniques, such as multiple-azimuth and wide-azimuth acquisition. Although this chapter covers the basics of standard time processing quite well, there is only a single sentence about prestack depth imaging, and anisotropic processing is not mentioned at all, even though both techniques are now becoming standard.

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

    SciTech Connect

    Babinsky, K.; Weidow, J.; Knabl, W.; Lorich, A.; Leitner, H.; Primig, S.

    2014-01-15

    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

  14. Bootstrapping 3D fermions

    DOE PAGES

    Iliesiu, Luca; Kos, Filip; Poland, David; Pufu, Silviu S.; Simmons-Duffin, David; Yacoby, Ran

    2016-03-17

    We study the conformal bootstrap for a 4-point function of fermions <ψψψψ> in 3D. We first introduce an embedding formalism for 3D spinors and compute the conformal blocks appearing in fermion 4-point functions. Using these results, we find general bounds on the dimensions of operators appearing in the ψ × ψ OPE, and also on the central charge CT. We observe features in our bounds that coincide with scaling dimensions in the GrossNeveu models at large N. Finally, we also speculate that other features could coincide with a fermionic CFT containing no relevant scalar operators.

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

    NASA Astrophysics Data System (ADS)

    Kalinin, Sergei

    2014-03-01

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

  16. Note: Seesaw actuation of atomic force microscope probes for improved imaging bandwidth and displacement range

    SciTech Connect

    Torun, H.; Torello, D.; Degertekin, F. L.

    2011-08-15

    The authors describe a method of actuation for atomic force microscope (AFM) probes to improve imaging speed and displacement range simultaneously. Unlike conventional piezoelectric tube actuation, the proposed method involves a lever and fulcrum ''seesaw'' like actuation mechanism that uses a small, fast piezoelectric transducer. The lever arm of the seesaw mechanism increases the apparent displacement range by an adjustable gain factor, overcoming the standard tradeoff between imaging speed and displacement range. Experimental characterization of a cantilever holder implementing the method is provided together with comparative line scans obtained with contact mode imaging. An imaging bandwidth of 30 kHz in air with the current setup was demonstrated.

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

    SciTech Connect

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

    1994-10-01

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

  18. Probing Non-Abelian Statistics of Majorana Fermions in Ultracold Atomic Superfluid

    SciTech Connect

    Zhu Shiliang; Shao, L.-B.; Wang, Z. D.; Duan, L.-M.

    2011-03-11

    We propose an experiment to directly probe the non-Abelian statistics of Majorana fermions by braiding them in an s-wave superfluid of ultracold atoms. We show that different orders of braiding operations give orthogonal output states that can be distinguished through Raman spectroscopy. Realization of Majorana states in an s-wave superfluid requires strong spin-orbital coupling and a controllable Zeeman field in the perpendicular direction. We present a simple laser configuration to generate the artificial spin-orbital coupling and the required Zeeman field in the dark-state subspace.

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

    SciTech Connect

    Karahka, M.; Xia, Y.; Kreuzer, H. J.

    2015-08-10

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

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

    SciTech Connect

    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.

  1. Understanding the Behavior of Advanced High-Strength Steels Using Atom Probe Tomography

    NASA Astrophysics Data System (ADS)

    Pereloma, Elena; Beladi, Hossein; Zhang, Laichang; Timokhina, Ilana

    2012-11-01

    The key evidence for understanding the mechanical behavior of advanced high strength steels was provided by atom probe tomography (APT). Chemical overstabilization of retained austenite (RA) leading to the limited transformation-induced plasticity (TRIP) effect was deemed to be the main factor responsible for the low ductility of nanostructured bainitic steel. Appearance of the yield point on the stress-strain curve of prestrained and bake-hardened transformation-induced plasticity steel is due to the unlocking from weak carbon atmospheres of newly formed during prestraining dislocations.

  2. 3D Ultrafast Ultrasound Imaging In Vivo

    PubMed Central

    Provost, Jean; Papadacci, Clement; Arango, Juan Esteban; Imbault, Marion; Gennisson, Jean-Luc; Tanter, Mickael; Pernot, Mathieu

    2014-01-01

    Very high frame rate ultrasound imaging has recently allowed for the extension of the applications of echography to new fields of study such as the functional imaging of the brain, cardiac electrophysiology, and the quantitative real-time imaging of the intrinsic mechanical properties of tumors, to name a few, non-invasively and in real time. In this study, we present the first implementation of Ultrafast Ultrasound Imaging in three dimensions based on the use of either diverging or plane waves emanating from a sparse virtual array located behind the probe. It achieves high contrast and resolution while maintaining imaging rates of thousands of volumes per second. A customized portable ultrasound system was developed to sample 1024 independent channels and to drive a 32×32 matrix-array probe. Its capability to track in 3D transient phenomena occurring in the millisecond range within a single ultrafast acquisition was demonstrated for 3-D Shear-Wave Imaging, 3-D Ultrafast Doppler Imaging and finally 3D Ultrafast combined Tissue and Flow Doppler. The propagation of shear waves was tracked in a phantom and used to characterize its stiffness. 3-D Ultrafast Doppler was used to obtain 3-D maps of Pulsed Doppler, Color Doppler, and Power Doppler quantities in a single acquisition and revealed, for the first time, the complex 3-D flow patterns occurring in the ventricles of the human heart during an entire cardiac cycle, and the 3-D in vivo interaction of blood flow and wall motion during the pulse wave in the carotid at the bifurcation. This study demonstrates the potential of 3-D Ultrafast Ultrasound Imaging for the 3-D real-time mapping of stiffness, tissue motion, and flow in humans in vivo and promises new clinical applications of ultrasound with reduced intra- and inter-observer variability. PMID:25207828

  3. Resolving the morphology of niobium carbonitride nano-precipitates in steel using atom probe tomography.

    PubMed

    Breen, Andrew J; Xie, Kelvin Y; Moody, Michael P; Gault, Baptiste; Yen, Hung-Wei; Wong, Christopher C; Cairney, Julie M; Ringer, Simon P

    2014-08-01

    Atom probe is a powerful technique for studying the composition of nano-precipitates, but their morphology within the reconstructed data is distorted due to the so-called local magnification effect. A new technique has been developed to mitigate this limitation by characterizing the distribution of the surrounding matrix atoms, rather than those contained within the nano-precipitates themselves. A comprehensive chemical analysis enables further information on size and chemistry to be obtained. The method enables new insight into the morphology and chemistry of niobium carbonitride nano-precipitates within ferrite for a series of Nb-microalloyed ultra-thin cast strip steels. The results are supported by complementary high-resolution transmission electron microscopy.

  4. Extracting features buried within high density atom probe point cloud data through simplicial homology.

    PubMed

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

    2015-12-01

    Feature extraction from Atom Probe Tomography (APT) data is usually performed by repeatedly delineating iso-concentration surfaces of a chemical component of the sample material at different values of concentration threshold, until the user visually determines a satisfactory result in line with prior knowledge. However, this approach allows for important features, buried within the sample, to be visually obscured by the high density and volume (~10(7) atoms) of APT data. This work provides a data driven methodology to objectively determine the appropriate concentration threshold for classifying different phases, such as precipitates, by mapping the topology of the APT data set using a concept from algebraic topology termed persistent simplicial homology. A case study of Sc precipitates in an Al-Mg-Sc alloy is presented demonstrating the power of this technique to capture features, such as precise demarcation of Sc clusters and Al segregation at the cluster boundaries, not easily available by routine visual adjustment.

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

    SciTech Connect

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

    1987-08-01

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

  6. Venus in 3D

    NASA Astrophysics Data System (ADS)

    Plaut, J. J.

    1993-08-01

    Stereographic images of the surface of Venus which enable geologists to reconstruct the details of the planet's evolution are discussed. The 120-meter resolution of these 3D images make it possible to construct digital topographic maps from which precise measurements can be made of the heights, depths, slopes, and volumes of geologic structures.

  7. 3D reservoir visualization

    SciTech Connect

    Van, B.T.; Pajon, J.L.; Joseph, P. )

    1991-11-01

    This paper shows how some simple 3D computer graphics tools can be combined to provide efficient software for visualizing and analyzing data obtained from reservoir simulators and geological simulations. The animation and interactive capabilities of the software quickly provide a deep understanding of the fluid-flow behavior and an accurate idea of the internal architecture of a reservoir.

  8. Impact of Atomic Corrugation on Sliding Friction as Probed by QCM

    NASA Astrophysics Data System (ADS)

    Coffey, Tonya; Lee, Sang; Krim, Jacqueline

    2004-03-01

    At the atomic scale, friction is believed to originate primarily via sliding induced excitation of phonons. [1] Theoretical predictions of the magnitude of phononic dissipation have been related to the atomic corrugation of the adsorbate/substrate potential. [2] Braun and colleagues [3] measured a corrugation of 1.9 meV for xenon on a copper(111) surface using helium atom scattering. Using the Quartz Crystal Microbalance (QCM), we have measured the sliding friction of Xe/Cu(111) adsorbed at 77 K. The QCM probe of sliding friction is the sliptime, which measures the slippage of the adsorbate atop the oscillating surface of the QCM. For monolayer coverages, we observed a sliptime of 10 ns for Xe/Cu(111). We also discuss theoretical predictions for the impact of atomic corrugation on sliding friction. [1] Fundamentals of Friction; Macroscopic and Microscopic Processes, ed. I.L. Singer and H.M. Pollock, Kluwer, Dordrecht (1992). [2] M. Cieplak, E.D. Smith, and M.O. Robbins, Science 265 (1994) 1209. [3] J. Braun et al., PRL 80 (1998) 125.

  9. A new approach to the interpretation of atom probe field-ion microscopy images.

    PubMed

    Vurpillot, F; Bostel, A; Blavette, D

    2001-10-01

    The field distribution and the ion trajectories close to the tip surface are known to mainly control the contrast of field-ion microscopy and the resolution of the three-dimensional atom probe. The proper interpretation of images provided by these techniques requires the electric field and the ion trajectories to be determined accurately. A model has been developed in order to compute the ion trajectories close to a curved emitting surface modelled at the atomic scale. In this model, both the gradual change of the tip surface and the chemical nature of atoms were taken into account. Predictions and results given by this approach are shown to be in excellent agreement with experiments. The calculated electric field at the tip surface is consistent with field-ion microscopy contrasts. The preferential retention of surface atoms and the order of evaporation were correctly simulated. The ion trajectories were successfully described. In this way, the crucial problem of trajectory overlap and local magnification could be investigated. These simulations not only lead to a new understanding of the physical basis of image formation, but also have a predictive value.

  10. BEAMS3D Neutral Beam Injection Model

    SciTech Connect

    Lazerson, Samuel

    2014-04-14

    With the advent of applied 3D fi elds in Tokamaks and modern high performance stellarators, a need has arisen to address non-axisymmetric effects on neutral beam heating and fueling. We report on the development of a fully 3D neutral beam injection (NBI) model, BEAMS3D, which addresses this need by coupling 3D equilibria to a guiding center code capable of modeling neutral and charged particle trajectories across the separatrix and into the plasma core. Ionization, neutralization, charge-exchange, viscous velocity reduction, and pitch angle scattering are modeled with the ADAS atomic physics database [1]. Benchmark calculations are presented to validate the collisionless particle orbits, neutral beam injection model, frictional drag, and pitch angle scattering effects. A calculation of neutral beam heating in the NCSX device is performed, highlighting the capability of the code to handle 3D magnetic fields.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    Xie, Kelvin Y; Breen, Andrew J; Yao, Lan; Moody, Michael P; Gault, Baptiste; Cairney, Julie M; Ringer, Simon P

    2012-01-01

    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.

  13. Coupling atom probe tomography and photoluminescence spectroscopy: exploratory results and perspectives.

    PubMed

    Rigutti, Lorenzo; Vella, Angela; Vurpillot, François; Gaillard, Aurore; Sevelin-Radiguet, Nicolas; Houard, Jonathan; Hideur, Ammar; Martel, Gilles; Jacopin, Gwénolé; De Luna Bugallo, Andrés; Deconihout, Bernard

    2013-09-01

    The development of laser-assisted atom probes makes it possible, in principle, to exploit the femtosecond laser pulse not only for triggering ion evaporation from a nanometric field emission tip, but also for generating photons via the radiative recombination of electron-hole pairs in tips made of dielectric materials. In this article we demonstrate a first step towards a correlation of micro-photoluminescence (μ-PL) and laser-assisted tomographic atom probe (LA-TAP) analysis applied separately on the same objects, namely on ZnO microwires. In particular, we assess that the use of the focused ion beam (FIB) tip preparation method significantly degrades the radiative recombination yield of the analyzed microwires. We discuss the strategies to avoid the FIB-induced damage on the optical properties of the sample and how to get beyond the correlated μ-PL and LA-TAP analysis with a coupled approach allowing to perform the two analyses within the same instrument. PMID:23489908

  14. Probing poly(N-isopropylacrylamide-co-butylacrylate)/cell interactions by atomic force microscopy.

    PubMed

    Natalia, Becerra; Henry, Andrade; Betty, López; Marina, Restrepo Luz; Roberto, Raiteri

    2015-01-01

    Poly(N-isopropylacrylamide) based hydrogels have been proposed as cell culture supports in cell sheet engineering. Toward this goal, we characterized the poly(N-isopropylacrylamide-co-butylacrylate) copolymer thermo-sensitivity and the cell/copolymer interactions above and below the copolymer lower critical solution temperature. We did that by direct force measurements at different temperatures using an atomic force microscope with either a polystyrene or a glass microbead as probes. We used a copolymer-coated microbead to measure adhesion after a short contact time with a single fibroblast in culture. Statistical analysis of the maximum adhesion force and the mechanical work necessary to separate the probe from the cell surface confirmed the hydrophilic/hydrophobic behavior of poly(N-isopropylacrylamide-co-butylacrylate) as a function of temperature in the range 20-37°C and, consequently, a reversible increase/decrease in cell adhesion with the copolymer. As control experiments we measured interactions between uncoated microbeads with the copolymer hydrogel or cells as well as interaction of the Poly(N-isopropylacrylamide) homopolymer with cells. These results show the potential of an assay based on atomic force microscopy for an in situ and quantitative assessment of cell/substrate interactions and support the use of poly(N-isopropylacrylamide-co-butylacrylate) copolymer as an efficient culture substrate in cell sheet engineering.

  15. Probing poly(N-isopropylacrylamide-co-butylacrylate)/cell interactions by atomic force microscopy.

    PubMed

    Natalia, Becerra; Henry, Andrade; Betty, López; Marina, Restrepo Luz; Roberto, Raiteri

    2015-01-01

    Poly(N-isopropylacrylamide) based hydrogels have been proposed as cell culture supports in cell sheet engineering. Toward this goal, we characterized the poly(N-isopropylacrylamide-co-butylacrylate) copolymer thermo-sensitivity and the cell/copolymer interactions above and below the copolymer lower critical solution temperature. We did that by direct force measurements at different temperatures using an atomic force microscope with either a polystyrene or a glass microbead as probes. We used a copolymer-coated microbead to measure adhesion after a short contact time with a single fibroblast in culture. Statistical analysis of the maximum adhesion force and the mechanical work necessary to separate the probe from the cell surface confirmed the hydrophilic/hydrophobic behavior of poly(N-isopropylacrylamide-co-butylacrylate) as a function of temperature in the range 20-37°C and, consequently, a reversible increase/decrease in cell adhesion with the copolymer. As control experiments we measured interactions between uncoated microbeads with the copolymer hydrogel or cells as well as interaction of the Poly(N-isopropylacrylamide) homopolymer with cells. These results show the potential of an assay based on atomic force microscopy for an in situ and quantitative assessment of cell/substrate interactions and support the use of poly(N-isopropylacrylamide-co-butylacrylate) copolymer as an efficient culture substrate in cell sheet engineering. PMID:24619976

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

    SciTech Connect

    Lev, Benjamin L.

    2014-05-31

    Microscopy techniques co-opted from nonlinear optics and high energy physics have complemented solid-state probes in elucidating the order manifest in condensed matter materials. Up until now, however, no attempts have been made to use modern techniques of ultracold atomic physics to directly explore properties of strongly correlated or topologically protected materials. Our current program is focused on introducing a novel magnetic field microscopy technique into the toolbox of imaging probes. Our prior DOE ESPM program funded the development of a novel instrument using a dilute gas Bose-Einstein condensate (BEC) as a scanning probe capable of measuring tiny magnetic (and electric) DC and AC fields above materials. We successfully built the world's first “scanning cryogenic atom chip microscope” [1], and we now are in the process of characterizing its performance before using the instrument to take the first wide-area images of transport flow within unconventional superconductors, pnictides and oxide interfaces (LAO/STO), topological insulators, and colossal magnetoresistive manganites. We will do so at temperatures outside the capability of scanning SQUIDs, with ~10x better resolution and without 1/f-noise. A notable goal will be to measure the surface-to-bulk conductivity ratio in topological insulators in a relatively model-independent fashion [2]. We have completed the construction of this magnetic microscope, shown in Figure 1. The instrument uses atom chips—substrates supporting micron-sized current-carrying wires that create magnetic microtraps near surfaces for ultracold thermal gases and BECs—to enable single-shot and raster-scanned large-field-of-view detection of magnetic fields. The fields emanating from electronic transport may be detected at the 10-7 flux quantum (Φ0) level and below (see Fig. 2); that is, few to sub-micron resolution of sub-nanotesla fields over single-shot, millimeter-long detection lengths. By harnessing the extreme

  17. NUBEAM developments and 3d halo modeling

    NASA Astrophysics Data System (ADS)

    Gorelenkova, M. V.; Medley, S. S.; Kaye, S. M.

    2012-10-01

    Recent developments related to the 3D halo model in NUBEAM code are described. To have a reliable halo neutral source for diagnostic simulation, the TRANSP/NUBEAM code has been enhanced with full implementation of ADAS atomic physic ground state and excited state data for hydrogenic beams and mixed species plasma targets. The ADAS codes and database provide the density and temperature dependence of the atomic data, and the collective nature of the state excitation process. To be able to populate 3D halo output with sufficient statistical resolution, the capability to control the statistics of fast ion CX modeling and for thermal halo launch has been added to NUBEAM. The 3D halo neutral model is based on modification and extension of the ``beam in box'' aligned 3d Cartesian grid that includes the neutral beam itself, 3D fast neutral densities due to CX of partially slowed down fast ions in the beam halo region, 3D thermal neutral densities due to CX deposition and fast neutral recapture source. More details on the 3D halo simulation design will be presented.

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

    PubMed

    Wang, Andrew; Butte, Manish J

    2014-08-01

    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. PMID:25161320

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

    NASA Astrophysics Data System (ADS)

    Wang, Andrew; Butte, Manish J.

    2014-08-01

    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.

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

    SciTech Connect

    Wang, Andrew; Butte, Manish J.

    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.

  1. Fabrication of a polymer-metal combined atomic force microscopy probe for coarse food surface imaging.

    PubMed

    Kang, Hyen-Wook; Muramatsu, Hiroshi; Kwon, Young-Soo

    2013-05-01

    We fabricated a polymer-metal combined atomic force microscopy (AFM) probe by two steps; a polymeric resin was used at first step, and a metal-ion was used at second step which needs more fabricating time than the resin. At first step, we fabricated a cylindrical base on to a commercial cantilever. At second step, we fabricated a conical probe on to the fabricated cylindrical base. To make the conical probe composed with silver, a 0.2 M aqueous solution of silver nitrate (AgNO3) was used. A 50 microm length polymeric-metallic hybrid tip has been fabricated to observe large bio and food samples. Generally, the AFM images of bio/food samples show cliff-like sharp patters in vertical. However, the AFM image by fabricated long tip shows clear structure of each brown rice flours. As most of commercial tips have three-angular pyramidal, the scanned results should be influenced by the lateral face of the three-angular pyramid, which results in cliff-like images. Because the sample size is large, the side area of the sample was adversely affected by the pyramidal structure during imaging. This problem may be resolved by designing conical structure tips. As the conical structure has no edge, the AFM image becomes clear. The fabricated tip has conical structure, and a clear AFM image was achieved. PMID:23858900

  2. Measurement of atomic oxygen in the middle atmosphere using solid electrolyte sensors and catalytic probes

    NASA Astrophysics Data System (ADS)

    Eberhart, M.; Löhle, S.; Steinbeck, A.; Binder, T.; Fasoulas, S.

    2015-09-01

    The middle- and upper-atmospheric energy budget is largely dominated by reactions involving atomic oxygen (O). Modeling of these processes requires detailed knowledge about the distribution of this oxygen species. Understanding the mutual contributions of atomic oxygen and wave motions to the atmospheric heating is the main goal of the rocket project WADIS (WAve propagation and DISsipation in the middle atmosphere). It includes, amongst others, our instruments for the measurement of atomic oxygen that have both been developed with the aim of resolving density variations on small vertical scales along the trajectory. In this paper the instrument based on catalytic effects (PHLUX: Pyrometric Heat Flux Experiment) is introduced briefly. The experiment employing solid electrolyte sensors (FIPEX: Flux φ(Phi) Probe Experiment) is presented in detail. These sensors were laboratory calibrated using a microwave plasma as a source of atomic oxygen in combination with mass spectrometer reference measurements. The spectrometer was in turn calibrated for O with a method based on methane. In order to get insight into the horizontal variability, the rocket payload had instrument decks at both ends. Each housed several sensor heads measuring during both the up- and downleg of the trajectory. The WADIS project comprises two rocket flights during different geophysical conditions. Results from WADIS-1 are presented, which was successfully launched in June 2013 from the Andøya Space Center, Norway. FIPEX data were sampled at 100 Hz and yield atomic oxygen density profiles with a vertical resolution better than 9 m. This allows density variations to be studied on very small spatial scales. Numerical simulations of the flow field around the rocket were done at several points of the trajectory to assess the influence of aerodynamic effects on the measurement results. Density profiles peak at 3 × 1010 cm-3 at altitudes of 93.6 and 96 km for the up- and downleg, respectively.

  3. 3D rapid mapping

    NASA Astrophysics Data System (ADS)

    Isaksson, Folke; Borg, Johan; Haglund, Leif

    2008-04-01

    In this paper the performance of passive range measurement imaging using stereo technique in real time applications is described. Stereo vision uses multiple images to get depth resolution in a similar way as Synthetic Aperture Radar (SAR) uses multiple measurements to obtain better spatial resolution. This technique has been used in photogrammetry for a long time but it will be shown that it is now possible to do the calculations, with carefully designed image processing algorithms, in e.g. a PC in real time. In order to get high resolution and quantitative data in the stereo estimation a mathematical camera model is used. The parameters to the camera model are settled in a calibration rig or in the case of a moving camera the scene itself can be used for calibration of most of the parameters. After calibration an ordinary TV camera has an angular resolution like a theodolite, but to a much lower price. The paper will present results from high resolution 3D imagery from air to ground. The 3D-results from stereo calculation of image pairs are stitched together into a large database to form a 3D-model of the area covered.

  4. Determining the location and nearest neighbours of aluminium in zeolites with atom probe tomography

    DOE PAGES

    Perea, Daniel E.; Arslan, Ilke; Liu, Jia; Ristanović, Zoran; Kovarik, Libor; Arey, Bruce W.; Lercher, Johannes A.; Bare, Simon R.; Weckhuysen, Bert M.

    2015-07-02

    Zeolite catalysis is determined by a combination of pore architecture and Brønsted acidity. As Brønsted acid sites are formed by the substitution of AlO4 for SiO4 tetrahedra, it is of utmost importance to have information on the number as well as the location and neighbouring sites of framework aluminium. Unfortunately, such detailed information has not yet been obtained, mainly due to the lack of suitable characterization methods. Here we report, using the powerful atomic-scale analysis technique known as atom probe tomography, the quantitative spatial distribution of individual aluminium atoms, including their three-dimensional extent of segregation. Ultimately, using a nearest-neighbour statisticalmore » analysis, we precisely determine the short-range distribution of aluminium over the different T-sites and determine the most probable Al–Al neighbouring distance within parent and steamed ZSM-5 crystals, as well as assess the long-range redistribution of aluminium upon zeolite steaming.« less

  5. Determining the location and nearest neighbours of aluminium in zeolites with atom probe tomography

    SciTech Connect

    Perea, Daniel E.; Arslan, Ilke; Liu, Jia; Ristanović, Zoran; Kovarik, Libor; Arey, Bruce W.; Lercher, Johannes A.; Bare, Simon R.; Weckhuysen, Bert M.

    2015-07-02

    Zeolite catalysis is determined by a combination of pore architecture and Brønsted acidity. As Brønsted acid sites are formed by the substitution of AlO4 for SiO4 tetrahedra, it is of utmost importance to have information on the number as well as the location and neighbouring sites of framework aluminium. Unfortunately, such detailed information has not yet been obtained, mainly due to the lack of suitable characterization methods. Here we report, using the powerful atomic-scale analysis technique known as atom probe tomography, the quantitative spatial distribution of individual aluminium atoms, including their three-dimensional extent of segregation. Ultimately, using a nearest-neighbour statistical analysis, we precisely determine the short-range distribution of aluminium over the different T-sites and determine the most probable Al–Al neighbouring distance within parent and steamed ZSM-5 crystals, as well as assess the long-range redistribution of aluminium upon zeolite steaming.

  6. Determining the location and nearest neighbours of aluminium in zeolites with atom probe tomography

    PubMed Central

    Perea, Daniel E.; Arslan, Ilke; Liu, Jia; Ristanović, Zoran; Kovarik, Libor; Arey, Bruce W.; Lercher, Johannes A.; Bare, Simon R.; Weckhuysen, Bert M.

    2015-01-01

    Zeolite catalysis is determined by a combination of pore architecture and Brønsted acidity. As Brønsted acid sites are formed by the substitution of AlO4 for SiO4 tetrahedra, it is of utmost importance to have information on the number as well as the location and neighbouring sites of framework aluminium. Unfortunately, such detailed information has not yet been obtained, mainly due to the lack of suitable characterization methods. Here we report, using the powerful atomic-scale analysis technique known as atom probe tomography, the quantitative spatial distribution of individual aluminium atoms, including their three-dimensional extent of segregation. Using a nearest-neighbour statistical analysis, we precisely determine the short-range distribution of aluminium over the different T-sites and determine the most probable Al–Al neighbouring distance within parent and steamed ZSM-5 crystals, as well as assess the long-range redistribution of aluminium upon zeolite steaming. PMID:26133270

  7. Determining the location and nearest neighbours of aluminium in zeolites with atom probe tomography.

    PubMed

    Perea, Daniel E; Arslan, Ilke; Liu, Jia; Ristanović, Zoran; Kovarik, Libor; Arey, Bruce W; Lercher, Johannes A; Bare, Simon R; Weckhuysen, Bert M

    2015-01-01

    Zeolite catalysis is determined by a combination of pore architecture and Brønsted acidity. As Brønsted acid sites are formed by the substitution of AlO4 for SiO4 tetrahedra, it is of utmost importance to have information on the number as well as the location and neighbouring sites of framework aluminium. Unfortunately, such detailed information has not yet been obtained, mainly due to the lack of suitable characterization methods. Here we report, using the powerful atomic-scale analysis technique known as atom probe tomography, the quantitative spatial distribution of individual aluminium atoms, including their three-dimensional extent of segregation. Using a nearest-neighbour statistical analysis, we precisely determine the short-range distribution of aluminium over the different T-sites and determine the most probable Al-Al neighbouring distance within parent and steamed ZSM-5 crystals, as well as assess the long-range redistribution of aluminium upon zeolite steaming.

  8. Determining the location and nearest neighbours of aluminium in zeolites with atom probe tomography.

    PubMed

    Perea, Daniel E; Arslan, Ilke; Liu, Jia; Ristanović, Zoran; Kovarik, Libor; Arey, Bruce W; Lercher, Johannes A; Bare, Simon R; Weckhuysen, Bert M

    2015-01-01

    Zeolite catalysis is determined by a combination of pore architecture and Brønsted acidity. As Brønsted acid sites are formed by the substitution of AlO4 for SiO4 tetrahedra, it is of utmost importance to have information on the number as well as the location and neighbouring sites of framework aluminium. Unfortunately, such detailed information has not yet been obtained, mainly due to the lack of suitable characterization methods. Here we report, using the powerful atomic-scale analysis technique known as atom probe tomography, the quantitative spatial distribution of individual aluminium atoms, including their three-dimensional extent of segregation. Using a nearest-neighbour statistical analysis, we precisely determine the short-range distribution of aluminium over the different T-sites and determine the most probable Al-Al neighbouring distance within parent and steamed ZSM-5 crystals, as well as assess the long-range redistribution of aluminium upon zeolite steaming. PMID:26133270

  9. Determining the location and nearest neighbours of aluminium in zeolites with atom probe tomography

    NASA Astrophysics Data System (ADS)

    Perea, Daniel E.; Arslan, Ilke; Liu, Jia; Ristanović, Zoran; Kovarik, Libor; Arey, Bruce W.; Lercher, Johannes A.; Bare, Simon R.; Weckhuysen, Bert M.

    2015-07-01

    Zeolite catalysis is determined by a combination of pore architecture and Brønsted acidity. As Brønsted acid sites are formed by the substitution of AlO4 for SiO4 tetrahedra, it is of utmost importance to have information on the number as well as the location and neighbouring sites of framework aluminium. Unfortunately, such detailed information has not yet been obtained, mainly due to the lack of suitable characterization methods. Here we report, using the powerful atomic-scale analysis technique known as atom probe tomography, the quantitative spatial distribution of individual aluminium atoms, including their three-dimensional extent of segregation. Using a nearest-neighbour statistical analysis, we precisely determine the short-range distribution of aluminium over the different T-sites and determine the most probable Al-Al neighbouring distance within parent and steamed ZSM-5 crystals, as well as assess the long-range redistribution of aluminium upon zeolite steaming.

  10. Improving the calculation of rovibrational spectra of five-atom molecules with three identical atoms by using a C3upsilonG6 symmetry-adapted grid: applied to CH3D and CHD3.

    PubMed

    Wang, Xiao-Gang; Carrington, Tucker

    2005-10-15

    In this paper we report two improvements on the approach we have used to compute rovibrational levels of methane and apply the new ideas to calculate rovibrational levels of two methane isotopomers CH3D and CHD3. Both improvements make the bend calculation better. The first improvement is a G6-invariant (or C3upsilon-invariant) grid which is designed such that each point on the grid is mapped to another point on the grid by any of the G6 operations. The second improvement is the use of fast Fourier transform (FFT) to compute the bend potential matrix-vector products. The FFT matrix-vector product is about three and ten times faster than the previous sequential summation method for the J=0 and J>0 cases, respectively. The calculated J=1 rovibrational levels of CH3D and CHD3 on the Schwenke and Partridge [Spectrochim. Acta, Part A 57, 887 (2001)] ab initio potential are in good agreement (within 6 cm(-1) for the levels up to 3000 cm(-1)) with the experimental data. The agreement is even better (within 0.1 cm(-1) for the levels up to 6000 cm(-1)) if the associated J=0 energies are subtracted. PMID:16252944

  11. Taming supersymmetric defects in 3d-3d correspondence

    NASA Astrophysics Data System (ADS)

    Gang, Dongmin; Kim, Nakwoo; Romo, Mauricio; Yamazaki, Masahito

    2016-07-01

    We study knots in 3d Chern-Simons theory with complex gauge group {SL}(N,{{C}}), in the context of its relation with 3d { N }=2 theory (the so-called 3d-3d correspondence). The defect has either co-dimension 2 or co-dimension 4 inside the 6d (2,0) theory, which is compactified on a 3-manifold \\hat{M}. We identify such defects in various corners of the 3d-3d correspondence, namely in 3d {SL}(N,{{C}}) CS theory, in 3d { N }=2 theory, in 5d { N }=2 super Yang-Mills theory, and in the M-theory holographic dual. We can make quantitative checks of the 3d-3d correspondence by computing partition functions at each of these theories. This Letter is a companion to a longer paper [1], which contains more details and more results.

  12. 3D Audio System

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Ames Research Center research into virtual reality led to the development of the Convolvotron, a high speed digital audio processing system that delivers three-dimensional sound over headphones. It consists of a two-card set designed for use with a personal computer. The Convolvotron's primary application is presentation of 3D audio signals over headphones. Four independent sound sources are filtered with large time-varying filters that compensate for motion. The perceived location of the sound remains constant. Possible applications are in air traffic control towers or airplane cockpits, hearing and perception research and virtual reality development.

  13. Characterization of Minerals of Geochronological Interest by EPMA and Atom Probe Tomography

    NASA Astrophysics Data System (ADS)

    Snoeyenbos, D.; Jercinovic, M. J.; Reinhard, D. A.; Hombourger, C.

    2012-12-01

    Isotopic and chemical dating techniques for zircon and monazite rely on several assumptions: that initial common Pb is low to nonexistent, that the analyzed domain is chronologically homogeneous, and that any relative migration of radiogenic Pb and its parent isotopes has not exceeded the analyzed domain. Yet, both zircon and monazite commonly contain significant submicron heterogeneities that may challenge these assumptions and can complicate the interpretation of chemical and isotopic data. Compositional mapping and submicron quantitative analysis by EPMA and FE-EPMA have been found to be useful techniques both for the characterization of these heterogeneities, and for quantitative geochronological determinations within the analytical limits of these techniques and the statistics of submicron sampling. Complementary to high-resolution EPMA techniques is Atom Probe Tomography (APT), wherein a specimen with dimensions of a few hundreds of nanometers is field evaporated atom by atom. The original position of each atom is identified, along with its atomic species and isotope. The result is a reconstruction allowing quantitative three-dimensional study of the specimen at the atomic scale, with low detection limits and high mass resolution. With the introduction of laser-induced thermal pulsing to achieve field evaporation, the technique is no longer limited to conductive specimens. There exists the capability to explore the compositional and isotopic structure of insulating materials at sub-nanometer resolution. Minerals of geochronological interest have been studied by an analytical method involving first compositional mapping and submicron quantitative analysis by EPMA and FE-EPMA, and subsequent use of these data to select specific sites for APT specimen extraction by FIB. Examples presented include 1) zircon from the Taconian of New England, USA, containing a fossil resorption front included between an unmodified igneous core, and a subsequent metamorphic

  14. Conducting Probe Atomic Force Microscope as a Relevant Tool for Studying Some Phenomena in MEMS Switches

    NASA Astrophysics Data System (ADS)

    Peschot, A.; Vincent, M.; Poulain, C.; Mariolle, D.; Houzé, F.; Delamare, J.

    2015-12-01

    As the reliability of electrical microcontacts has proved to be the main limitation to a fast-growing production of ultraminiaturized switches, a thorough understanding of their failure mechanisms is an all-important purpose. This paper aims at showing that conducting-probe Atomic Force Microscopy (cp-AFM) is an adequate tool to actuate and study electrical contacts. By choosing relevant cantilevers and operating mode of the cp-AFM, dimensions, gap and force level representative of existing microelectromechanical switches (MEMS switches) are obtained. With two examples, the advantages of using a cp-AFM in force mode for studying physical phenomena at very low scale are highlighted. The reported investigations concern material transfer between contact parts and contact bounces. Those two undesirable phenomena induce surface damages and impinge reliability of MEMS switches. In both cases an explanatory scenario of phenomena occurring at nanoscale is proposed and preventive recommendations for improving the lifetime of such devices are suggested.

  15. THERMAL EFFECTS ON MASS AND SPATIAL RESOLUTION DURING LASER PULSE ATOM PROBE TOMOGRAPHY OF CERIUM OXIDE

    SciTech Connect

    Rita Kirchhofer; Melissa C. Teague; Brian P. Gorman

    2013-05-01

    Cerium oxide (CeO2) is an ideal surrogate material for trans-uranic elements and fission products found in nuclear fuels due to similarities in their thermal properties; therefore, cerium oxide was used to determine the best run condition for atom probe tomography (APT). Laser pulse APT is a technique that allows for spatial resolution in the nm scale and isotopic/elemental chemical identification. A systematic study of the impact of laser pulse energy and specimen base temperature on the mass resolution, measurement of stoichiometry, multiples, and evaporation mechanisms are reported in this paper. It was demonstrated that using laser pulse APT stoichiometric field evaporation of cerium oxide was achieved at 1 pJ laser pulse energy and 20 K specimen base temperature.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. An atom probe study of phase decomposition in three iron meteorites

    SciTech Connect

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

    1989-01-01

    An atom probe field-ion microscopy characterization of the Cape York, Twin City and Santa Catharina iron-nickel meteorites has been performed. This investigation has revealed that the taenite, corresponding to an interface region between the cloudy zone and the clear taenite 2 (CT2) region in the Cape York meteorite and the matrix of the Twin City and Santa Catharina meteorites, has phase separated to form an ultra-fine scale duplex microstructure. The composition of these two phases was determined to be 50 at. % Ni and approximately 15 at. % Ni. These compositions correspond to the equiatomic FeNi L1/sub 0/-ordered phase and a disordered face centered cubic phase. 38 refs., 16 figs., 3 tabs.

  18. Three-dimensional chemical imaging of embedded nanoparticles using atom probe tomography.

    PubMed

    Kuchibhatla, Satyanarayana V N T; Shutthanandan, V; Prosa, T J; Adusumilli, P; Arey, B; Buxbaum, A; Wang, Y C; Tessner, T; Ulfig, R; Wang, C M; Thevuthasan, S

    2012-06-01

    Analysis of nanoparticles is often challenging especially when they are embedded in a matrix. Hence, we have used laser-assisted atom probe tomography (APT) to analyze the Au nanoclusters synthesized in situ using ion-beam implantation in a single crystal MgO matrix. APT analysis along with scanning transmission electron microscopy and energy dispersive spectroscopy (STEM-EDX) indicated that the nanoparticles have an average size ~8-12 nm. While it is difficult to analyze the composition of individual nanoparticles using STEM, APT analysis can give three-dimensional compositions of the same. It was shown that the maximum Au concentration in the nanoparticles increases with increasing particle size, with a maximum Au concentration of up to 50%.

  19. RF Pulse Signal Integrity Analysis for Nonlinear Ended Microstrip Line Atom-Probe Tomography

    NASA Astrophysics Data System (ADS)

    Zhao, L.; Delamare, A.; Normand, A.; Delaroche, F.; Latry, O.; Vurpillot, F.; Ravelo, B.

    2016-03-01

    A signal integrity (SI) analysis of high voltage rectangular short pulses for the atom- probe system is explored in this paper. The operated RF transient pulse is considered for exciting on material sample inside an ultra-high vacuum (UHV) cryogenic chamber. The ns- duration pulse signal is injected into the cryogenic analysis chamber through the transmitting system mainly constituted by a microstrip interconnect line ended by optical controlled nonlinear load. The whole system frequency characterization is performed based on the S- parameter measurements. As expected, a challenging ultra-short rectangular shape pulse is exhibited by the pulser. Promising experimental results with the improvement of ion mass spectrum is demonstrated with the designed RF pulser.

  20. Atom Probe Tomography Analysis of Precipitation during Tempering of a Nanostructured Bainitic Steel

    SciTech Connect

    Caballero, Francesca G.; Miller, Michael K; Garcia-Mateo, C.

    2011-01-01

    Carbon distribution during tempering of a nanostructured bainitic steel was analyzed by atom probe tomography (APT). Three different types of particles are detected on samples tempered at 673 K (400 C) for 30 minutes: lower bainite cementite with a carbon content of {approx}25 at. pct, {var_epsilon}-carbides with a carbon content close to 30 at. pct, and carbon clusters, small features with a carbon content of {approx}14 at. pct indicative of a stage of tempering prior to precipitation of {var_epsilon}-carbide. After tempering at 773 K (500 C) for 30 minutes, the {var_epsilon}-carbide-to-cementite transition was observed. Solute concentration profiles across carbide/ferrite interfaces showed the distribution of substitutional elements in {var_epsilon}-carbide and cementite for all the tempering conditions.

  1. Three-dimensional Chemical Imaging of Embedded Nanoparticles using Atom Probe Tomography

    SciTech Connect

    Kuchibhatla, Satyanarayana V N T; Shutthanandan, V.; Prosa, Ty J.; Adusumilli, Praneet; Arey, Bruce W.; Buxbaum, Alex; Wang, Y. C.; Tessner, Ted; Ulfig, Robert M.; Wang, Chong M.; Thevuthasan, Suntharampillai

    2012-05-03

    Analysis of nanoparticles is often challenging especially when they are embedded in a matrix. Hence, we have used laser-assisted atom probe tomography (APT) to analyze the Au-nanoclusters synthesized in situ using ion beam implantation in single crystal MgO matrix. APT analysis along with scanning transmission electron microscopy and energy dispersive spectroscopy (STEM-EDS) indicated that the nanoparticles have an average size ~ 8 - 12 nm. While it is difficult to analyze the composition of individual nanoparticles using STEM, APT analysis can give three dimensional compositions of the same. It was shown that the maximum Au-concentration in the nanoparticles increases with increasing particle size, with a maximum Au-concentration of up to 50%.

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

    SciTech Connect

    Wang, Yuliang Bi, Shusheng; Wang, Huimin

    2014-05-15

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

  3. Simulating compact quantum electrodynamics with ultracold atoms: probing confinement and nonperturbative effects.

    PubMed

    Zohar, Erez; Cirac, J Ignacio; Reznik, Benni

    2012-09-21

    Recently, there has been much interest in simulating quantum field theory effects of matter and gauge fields. In a recent work, a method for simulating compact quantum electrodynamics (CQED) using Bose-Einstein condensates has been suggested. We suggest an alternative approach, which relies on single atoms in an optical lattice, carrying 2l + 1 internal levels, which converges rapidly to CQED as l increases. That enables the simulation of CQED in 2 + 1 dimensions in both the weak and the strong coupling regimes, hence, allowing us to probe confinement as well as other nonperturbative effects of the theory. We provide an explicit construction for the case l = 1 which is sufficient for simulating the effect of confinement between two external static charges.

  4. Atom Probe Tomography Analysis of the Distribution of Rhenium in Nickel Alloys

    SciTech Connect

    Mottura, A.; Warnken, N; Miller, Michael K; Reed, R. C.; Finnis, M.

    2010-01-01

    Atom probe tomography (APT) is used to characterise the distributions of rhenium in a binary Ni-Re alloy and the nickel-based single-crystal CMSX-4 superalloy. A purpose-built algorithm is developed to quantify the size distribution of solute clusters, and applied to the APT datasets to critique the hypothesis that rhenium is prone to the formation of clusters in these systems. No evidence is found to indicate that rhenium forms solute clusters above the level expected from random fluctuations. In CMSX-4, enrichment of Re is detected in the matrix phase close to the matrix/precipitate ({gamma}/{gamma}{prime}) phase boundaries. Phase field modelling indicates that this is due to the migration of the {gamma}/{gamma}{prime} interface during cooling from the temperature of operation. Thus, neither clustering of rhenium nor interface enrichments can be the cause of the enhancement in high temperature mechanical properties conferred by rhenium alloying.

  5. Quantitative imaging of electrospun fibers by PeakForce Quantitative NanoMechanics atomic force microscopy using etched scanning probes.

    PubMed

    Chlanda, Adrian; Rebis, Janusz; Kijeńska, Ewa; Wozniak, Michal J; Rozniatowski, Krzysztof; Swieszkowski, Wojciech; Kurzydlowski, Krzysztof J

    2015-05-01

    Electrospun polymeric submicron and nanofibers can be used as tissue engineering scaffolds in regenerative medicine. In physiological conditions fibers are subjected to stresses and strains from the surrounding biological environment. Such stresses can cause permanent deformation or even failure to their structure. Therefore, there is a growing necessity to characterize their mechanical properties, especially at the nanoscale. Atomic force microscopy is a powerful tool for the visualization and probing of selected mechanical properties of materials in biomedical sciences. Image resolution of atomic force microscopy techniques depends on the equipment quality and shape of the scanning probe. The probe radius and aspect ratio has huge impact on the quality of measurement. In the presented work the nanomechanical properties of four different polymer based electrospun fibers were tested using PeakForce Quantitative NanoMechanics atomic force microscopy, with standard and modified scanning probes. Standard, commercially available probes have been modified by etching using focused ion beam (FIB). Results have shown that modified probes can be used for mechanical properties mapping of biomaterial in the nanoscale, and generate nanomechanical information where conventional tips fail.

  6. Probing interlayer interactions between graphene and metal substrates by supersonic rare-gas atom scattering

    NASA Astrophysics Data System (ADS)

    Shichibe, H.; Satake, Y.; Watanabe, K.; Kinjyo, A.; Kunihara, A.; Yamada, Y.; Sasaki, M.; Hayes, W. W.; Manson, J. R.

    2015-04-01

    We demonstrate that highly surface-sensitive supersonic rare-gas (He, Ar, and Xe) atom scattering, in both the quantum and classical regimes, can probe and quantify the interlayer interactions between graphene monolayers and metal substrates in terms of the Debye temperature corresponding to the surface normal vibration, and the surface effective mass. As models of the strongly and weakly interacting graphene, we investigated two systems, graphene on Ru(0001) and Pt(111), respectively. The experimental data for Ar and Xe are compared with the results from theoretical simulations based on the classical smooth surface model. For gr/Pt(111) we find that the scattering pattern of the rare-gas beam, including the Debye-Waller attenuation of the He beam, are quite similar to that from highly oriented pyrolytic graphite (HOPG); this suggests that the graphene-Pt(111) interaction is much like a van der Waals interaction. On the contrary, for the gr/Ru(0001) system, we find a smaller Debye-Waller attenuation and a larger surface effective mass, indicating that graphene on Ru(0001) is tightly bonded to the substrate. Furthermore, asymmetrical spectral shapes in the Ar and Xe scattering spectra from gr/Ru(0001) are interpreted as a result of the lateral distribution of the interlayer interaction corresponding to the moiré pattern. It is found that the "valley" region of the moiré pattern has high effective mass reflecting stronger bonding to the substrate, contributing to the high reflectivity of the He beam reported for this system. On the other hand, the effective mass of the "hill" region is found to be similar to that of HOPG, indicating that this region is well decoupled from the substrate. These results demonstrate a unique capability of atom scattering to probe and evaluate the molecule-substrate interaction and its spatial distributions.

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-09-01

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

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-09-01

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

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

    SciTech Connect

    Meher, Subhashish; Rojhirunsakool, Tanaporn; Nandwana, Peeyush; Tiley, Jamie; Banerjee, Rajarshi

    2015-04-28

    In this study, 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 g 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 g 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.

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

    DOE PAGES

    Meher, Subhashish; Rojhirunsakool, Tanaporn; Nandwana, Peeyush; Tiley, Jamie; Banerjee, Rajarshi

    2015-04-28

    In this study, 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 g precipitates to form Ni3(Al,Cr) precipitates in a Ni-14Al-7Cr(at.%) alloy. Interestingly, the additionmore » of Co, which is a solid solution strengthener, to a Ni-14Al-7Cr alloy results in the partial reversal of Al site occupancy within g 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.« less

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

    PubMed

    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.

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

    SciTech Connect

    Puricelli, Luca; Galluzzi, Massimiliano; Schulte, Carsten; Podestà, Alessandro Milani, Paolo

    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.

  15. Probing mechanical properties of living cells by atomic force microscopy with blunted pyramidal cantilever tips.

    PubMed

    Rico, Félix; Roca-Cusachs, Pere; Gavara, Núria; Farré, Ramon; Rotger, Mar; Navajas, Daniel

    2005-08-01

    Atomic force microscopy (AFM) allows the acquisition of high-resolution images and the measurement of mechanical properties of living cells under physiological conditions. AFM cantilevers with blunted pyramidal tips are commonly used to obtain images of living cells. Measurement of mechanical properties with these tips requires a contact model that takes into account their blunted geometry. The aim of this work was to develop a contact model of a blunted pyramidal tip and to assess the suitability of pyramidal tips for probing mechanical properties of soft gels and living cells. We developed a contact model of a blunted pyramidal tip indenting an elastic half-space. We measured Young's modulus (E) and the complex shear modulus (G*= G' +i G" ) of agarose gels and A549 alveolar epithelial cells with pyramidal tips and compared them with those obtained with spherical tips. The gels exhibited an elastic behavior with almost coincident loading and unloading force curves and negligible values of G". E fell sharply with indentation up to approximately 300 nm , showing a linear regime for deeper indentations. A similar indentation dependence of E with twofold lower values at the linear regime was obtained with the spherical tip fitted with Hertz's model. The dependence of E on indentation in cells paralleled that found in gels. Cells exhibited viscoelastic behavior with G"/G' approximately 1/4 . Pyramidal tips commonly used for AFM imaging are suitable for probing mechanical properties of soft gels and living cells. PMID:16196611

  16. Reliable measurements of interfacial slip by colloid probe atomic force microscopy. II. Hydrodynamic force measurements.

    PubMed

    Zhu, Liwen; Attard, Phil; Neto, Chiara

    2011-06-01

    Here we report a new study on the boundary conditions for the flow of a simple liquid in a confined geometry obtained by measuring hydrodynamic drainage forces with colloid probe atomic force microscopy (AFM). In this work, we provide experimental data obtained using a best practice experimental protocol and fitted with a new theoretical calculation (Zhu, L.; Attard, P.; Neto, C. Langmuir 2010, submitted for publication, preceding paper). We investigated the hydrodynamic forces acting on a silica colloid probe approaching a hydrophobized silicon surface in a single-component viscous Newtonian liquid (di-n-octylphthalate), a partially wetting system. The measured average slip lengths were in the range of 24-31 nm at approach velocities of between 10 and 80 μm/s. Using our experimental approach, the presence of nanoparticle contaminants in the system can be indentified, which is important because it has been shown that nanoparticles lead to a large apparent slip length. Under our stringent control of experimental conditions, the measurement of the slip length is reproducible and independent of the spring constant of the cantilever.

  17. Probing the interaction between air bubble and sphalerite mineral surface using atomic force microscope.

    PubMed

    Xie, Lei; Shi, Chen; Wang, Jingyi; Huang, Jun; Lu, Qiuyi; Liu, Qingxia; Zeng, Hongbo

    2015-03-01

    The interaction between air bubbles and solid surfaces plays important roles in many engineering processes, such as mineral froth flotation. In this work, an atomic force microscope (AFM) bubble probe technique was employed, for the first time, to directly measure the interaction forces between an air bubble and sphalerite mineral surfaces of different hydrophobicity (i.e., sphalerite before/after conditioning treatment) under various hydrodynamic conditions. The direct force measurements demonstrate the critical role of the hydrodynamic force and surface forces in bubble-mineral interaction and attachment, which agree well with the theoretical calculations based on Reynolds lubrication theory and augmented Young-Laplace equation by including the effect of disjoining pressure. The hydrophobic disjoining pressure was found to be stronger for the bubble-water-conditioned sphalerite interaction with a larger hydrophobic decay length, which enables the bubble attachment on conditioned sphalerite at relatively higher bubble approaching velocities than that of unconditioned sphalerite. Increasing the salt concentration (i.e., NaCl, CaCl2) leads to weakened electrical double layer force and thereby facilitates the bubble-mineral attachment, which follows the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory by including the effects of hydrophobic interaction. The results provide insights into the basic understanding of the interaction mechanism between bubbles and minerals at nanoscale in froth flotation processes, and the methodology on probing the interaction forces of air bubble and sphalerite surfaces in this work can be extended to many other mineral and particle systems.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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

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

    PubMed Central

    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

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

    PubMed

    Viskari, L; Stiller, K

    2011-05-01

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

  2. Reduced-density-matrix description for pump-probe optical phenomena in moving atomic systems

    NASA Astrophysics Data System (ADS)

    Jacobs, V. L.

    2014-09-01

    Linear and nonlinear (especially coherent) electromagnetic interactions of moving many-electron atoms are investigated using a reduced-density-matrix description, which is applied to electromagnetically induced transparency and related resonant pump-probe optical phenomena. External magnetic fields are included on an equal footing with the electromagnetic fields and spin-Zeeman interactions are taken into account. Complimentary time-domain (equation-of-motion) and frequency-domain (resolvent-operator) formulations of the reduced-density-matrix description are self-consistently developed. The general nonperturbative and non-Markovian formulations provide a fundamental framework for systematic evaluations of corrections to the standard Born (lowest-order-perturbation) and Markov (short-memory-time) approximations. The macroscopic electromagnetic response is described semiclassically, employing a perturbation expansion of the reduced-density operator in powers of the classical electromagnetic field. Our primary results are compact Liouville-space operator expressions for the linear and general (nth-order) nonlinear macroscopic electromagnetic-response tensors, which can be evaluated for nonlocal and nonstationary optical media described by multilevel atomic-system representations. Interactions among atoms and with environmental photons are treated as line-broadening effects by means of a general Liouville-space self-energy operator, for which the tetradic-matrix elements are explicitly evaluated in the diagonal, lowest-order, and Markov approximations. The compact Liouville-space operator expressions that are derived for the macroscopic electromagnetic-response tensors are introduced into the dynamical description of the electromagnetic-field propagation. It is pointed out that a quantized-electromagnetic-field approach will be required for a fully self-consistent quantum-mechanical treatment of local-field effects and radiative corrections.

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

    PubMed

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

    2013-09-01

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

  4. 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

    SciTech Connect

    Han, Bin Takamizawa, Hisashi Shimizu, Yasuo; Inoue, Koji; Nagai, Yasuyoshi; Yano, Fumiko; Kunimune, Yorinobu; Inoue, Masao; Nishida, Akio

    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.

  5. Fabrication of 3D core-shell multiwalled carbon nanotube@RuO2 lithium-ion battery electrodes through a RuO2 atomic layer deposition process.

    PubMed

    Gregorczyk, Keith E; Kozen, Alexander C; Chen, Xinyi; Schroeder, Marshall A; Noked, Malachi; Cao, Anyuan; Hu, Liangbing; Rubloff, Gary W

    2015-01-27

    Pushing lithium-ion battery (LIB) technology forward to its fundamental scaling limits requires the ability to create designer heterostructured materials and architectures. Atomic layer deposition (ALD) has recently been applied to advanced nanostructured energy storage devices due to the wide range of available materials, angstrom thickness control, and extreme conformality over high aspect ratio nanostructures. A class of materials referred to as conversion electrodes has recently been proposed as high capacity electrodes. RuO2 is considered an ideal conversion material due to its high combined electronic and ionic conductivity and high gravimetric capacity, and as such is an excellent material to explore the behavior of conversion electrodes at nanoscale thicknesses. We report here a fully characterized atomic layer deposition process for RuO2, electrochemical cycling data for ALD RuO2, and the application of the RuO2 to a composite carbon nanotube electrode scaffold with nucleation-controlled RuO2 growth. A growth rate of 0.4 Å/cycle is found between ∼ 210-240 °C. In a planar configuration, the resulting RuO2 films show high first cycle electrochemical capacities of ∼ 1400 mAh/g, but the capacity rapidly degrades with charge/discharge cycling. We also fabricated core/shell MWCNT/RuO2 heterostructured 3D electrodes, which show a 50× increase in the areal capacity over their planar counterparts, with an areal lithium capacity of 1.6 mAh/cm(2).

  6. Prominent rocks - 3D

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Many prominent rocks near the Sagan Memorial Station are featured in this image, taken in stereo by the Imager for Mars Pathfinder (IMP) on Sol 3. 3D glasses are necessary to identify surface detail. Wedge is at lower left; Shark, Half-Dome, and Pumpkin are at center. Flat Top, about four inches high, is at lower right. The horizon in the distance is one to two kilometers away.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is an operating division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

    Click below to see the left and right views individually. [figure removed for brevity, see original site] Left [figure removed for brevity, see original site] Right

  7. 'Diamond' in 3-D

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This 3-D, microscopic imager mosaic of a target area on a rock called 'Diamond Jenness' was taken after NASA's Mars Exploration Rover Opportunity ground into the surface with its rock abrasion tool for a second time.

    Opportunity has bored nearly a dozen holes into the inner walls of 'Endurance Crater.' On sols 177 and 178 (July 23 and July 24, 2004), the rover worked double-duty on Diamond Jenness. Surface debris and the bumpy shape of the rock resulted in a shallow and irregular hole, only about 2 millimeters (0.08 inch) deep. The final depth was not enough to remove all the bumps and leave a neat hole with a smooth floor. This extremely shallow depression was then examined by the rover's alpha particle X-ray spectrometer.

    On Sol 178, Opportunity's 'robotic rodent' dined on Diamond Jenness once again, grinding almost an additional 5 millimeters (about 0.2 inch). The rover then applied its Moessbauer spectrometer to the deepened hole. This double dose of Diamond Jenness enabled the science team to examine the rock at varying layers. Results from those grindings are currently being analyzed.

    The image mosaic is about 6 centimeters (2.4 inches) across.

  8. Martian terrain - 3D

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This area of terrain near the Sagan Memorial Station was taken on Sol 3 by the Imager for Mars Pathfinder (IMP). 3D glasses are necessary to identify surface detail.

    The IMP is a stereo imaging system with color capability provided by 24 selectable filters -- twelve filters per 'eye.' It stands 1.8 meters above the Martian surface, and has a resolution of two millimeters at a range of two meters.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is an operating division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

    Click below to see the left and right views individually. [figure removed for brevity, see original site] Left [figure removed for brevity, see original site] Right

  9. 3D optical measuring technologies and systems

    NASA Astrophysics Data System (ADS)

    Chugui, Yuri V.

    2005-02-01

    The results of the R & D activity of TDI SIE SB RAS in the field of the 3D optical measuring technologies and systems for noncontact 3D optical dimensional inspection applied to atomic and railway industry safety problems are presented. This activity includes investigations of diffraction phenomena on some 3D objects, using the original constructive calculation method. The efficient algorithms for precise determining the transverse and longitudinal sizes of 3D objects of constant thickness by diffraction method, peculiarities on formation of the shadow and images of the typical elements of the extended objects were suggested. Ensuring the safety of nuclear reactors and running trains as well as their high exploitation reliability requires a 100% noncontact precise inspection of geometrical parameters of their components. To solve this problem we have developed methods and produced the technical vision measuring systems LMM, CONTROL, PROFIL, and technologies for noncontact 3D dimensional inspection of grid spacers and fuel elements for the nuclear reactor VVER-1000 and VVER-440, as well as automatic laser diagnostic COMPLEX for noncontact inspection of geometric parameters of running freight car wheel pairs. The performances of these systems and the results of industrial testing are presented and discussed. The created devices are in pilot operation at Atomic and Railway Companies.

  10. Direct atomic-scale imaging of hydrogen and oxygen interstitials in pure niobium using atom-probe tomography and aberration-corrected scanning transmission electron microscopy.

    PubMed

    Kim, Yoon-Jun; Tao, Runzhe; Klie, Robert F; Seidman, David N

    2013-01-22

    Imaging the three-dimensional atomic-scale structure of complex interfaces has been the goal of many recent studies, due to its importance to technologically relevant areas. Combining atom-probe tomography and aberration-corrected scanning transmission electron microscopy (STEM), we present an atomic-scale study of ultrathin (~5 nm) native oxide layers on niobium (Nb) and the formation of ordered niobium hydride phases near the oxide/Nb interface. Nb, an elemental type-II superconductor with the highest critical temperature (T(c) = 9.2 K), is the preferred material for superconducting radio frequency (SRF) cavities in next-generation particle accelerators. Nb exhibits high solubilities for oxygen and hydrogen, especially within the RF-field penetration depth, which is believed to result in SRF quality factor losses. STEM imaging and electron energy-loss spectroscopy followed by ultraviolet laser-assisted local-electrode atom-probe tomography on the same needle-like sample reveals the NbO(2), Nb(2)O(5), NbO, Nb stacking sequence; annular bright-field imaging is used to visualize directly hydrogen atoms in bulk β-NbH.

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

    PubMed

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

    2011-05-01

    Atom probe tomography uses time-of-flight mass spectrometry to identify the chemical nature of atoms from their mass-to-charge-state ratios. Within a mass spectrum, ranges are defined so as to attribute a chemical identity to each peak. The accuracy of atom probe microanalysis relies on the definition of these ranges. Here we propose and compare several automated ranging techniques, tested against simulated mass spectra. The performance of these metrics compare favourably with a trial of users asked to manually range a simplified simulated dataset. The optimised automated ranging procedure was then used to precisely evaluate the very low iron concentration (0.003-0.018 at%) in a zirconium alloy to reveal its behaviour in the matrix during corrosion; oxygen is injected into solution and has the effect of increasing the local iron concentration near the oxide-metal interface, which in turn affects the corrosion properties of the metal substrate.

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

    PubMed

    Marceau, R K W; Ceguerra, A V; Breen, A J; Raabe, D; Ringer, S P

    2015-10-01

    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.

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

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

    Miller, M. K.; Powers, K. A.; Nanstad, R. K.; Efsing, P.

    2013-06-01

    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.

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

    PubMed

    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

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

    DOE PAGES

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

    2016-05-16

    Here, 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 2101more » 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).« less

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

    NASA Astrophysics Data System (ADS)

    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). ).

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

    NASA Astrophysics Data System (ADS)

    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). ).

  19. Atom probe microscopy of three-dimensional distribution of silicon isotopes in {sup 28}Si/{sup 30}Si isotope superlattices with sub-nanometer spatial resolution

    SciTech Connect

    Shimizu, Yasuo; Kawamura, Yoko; Uematsu, Masashi; Itoh, Kohei M.; Tomita, Mitsuhiro; Sasaki, Mikio; Uchida, Hiroshi; Takahashi, Mamoru

    2009-10-01

    Laser-assisted atom probe microscopy of 2 nm period {sup 28}Si/{sup 30}Si isotope superlattices (SLs) is reported. Three-dimensional distributions of {sup 28}Si and {sup 30}Si stable isotopes are obtained with sub-nanometer spatial resolution. The depth resolution of the present atom probe analysis is much higher than that of secondary ion mass spectrometry (SIMS) even when SIMS is performed with a great care to reduce the artifact due to atomic mixing. Outlook of Si isotope SLs as ideal depth scales for SIMS and three-dimensional position standards for atom probe microscopy is discussed.

  20. R3D-2-MSA: the RNA 3D structure-to-multiple sequence alignment server

    PubMed Central

    Cannone, Jamie J.; Sweeney, Blake A.; Petrov, Anton I.; Gutell, Robin R.; Zirbel, Craig L.; Leontis, Neocles

    2015-01-01

    The RNA 3D Structure-to-Multiple Sequence Alignment Server (R3D-2-MSA) is a new web service that seamlessly links RNA three-dimensional (3D) structures to high-quality RNA multiple sequence alignments (MSAs) from diverse biological sources. In this first release, R3D-2-MSA provides manual and programmatic access to curated, representative ribosomal RNA sequence alignments from bacterial, archaeal, eukaryal and organellar ribosomes, using nucleotide numbers from representative atomic-resolution 3D structures. A web-based front end is available for manual entry and an Application Program Interface for programmatic access. Users can specify up to five ranges of nucleotides and 50 nucleotide positions per range. The R3D-2-MSA server maps these ranges to the appropriate columns of the corresponding MSA and returns the contents of the columns, either for display in a web browser or in JSON format for subsequent programmatic use. The browser output page provides a 3D interactive display of the query, a full list of sequence variants with taxonomic information and a statistical summary of distinct sequence variants found. The output can be filtered and sorted in the browser. Previous user queries can be viewed at any time by resubmitting the output URL, which encodes the search and re-generates the results. The service is freely available with no login requirement at http://rna.bgsu.edu/r3d-2-msa. PMID:26048960

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

    PubMed

    Thuvander, Mattias; Andersson, Marcus; Stiller, Krystyna

    2013-09-01

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

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

    PubMed

    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.

  3. Practical Issues for Atom Probe Tomography Analysis of III-Nitride Semiconductor Materials.

    PubMed

    Tang, Fengzai; Moody, Michael P; Martin, Tomas L; Bagot, Paul A J; Kappers, Menno J; Oliver, Rachel A

    2015-06-01

    Various practical issues affecting atom probe tomography (APT) analysis of III-nitride semiconductors have been studied as part of an investigation using a c-plane InAlN/GaN heterostructure. Specimen preparation was undertaken using a focused ion beam microscope with a mono-isotopic Ga source. This enabled the unambiguous observation of implantation damage induced by sample preparation. In the reconstructed InAlN layer Ga implantation was demonstrated for the standard "clean-up" voltage (5 kV), but this was significantly reduced by using a lower voltage (e.g., 1 kV). The characteristics of APT data from the desorption maps to the mass spectra and measured chemical compositions were examined within the GaN buffer layer underlying the InAlN layer in both pulsed laser and pulsed voltage modes. The measured Ga content increased monotonically with increasing laser pulse energy and voltage pulse fraction within the examined ranges. The best results were obtained at very low laser energy, with the Ga content close to the expected stoichiometric value for GaN and the associated desorption map showing a clear crystallographic pole structure. PMID:25926083

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

    SciTech Connect

    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.

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

    NASA Astrophysics Data System (ADS)

    Bailey, Nathan A.; Stergar, Erich; Toloczko, Mychailo; Hosemann, Peter

    2015-04-01

    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).

  6. Uranium isotopic ratio measurements of U3O8 reference materials by atom probe tomography.

    PubMed

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

    2016-03-01

    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. PMID:26774651

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

    PubMed

    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

  8. Atom probe field-ion microscopy investigation of nickel base superalloy welds

    SciTech Connect

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

    1998-11-01

    Microstructure development and elemental partitioning between {gamma} and {gamma}{prime} were measured in PWA-1480 electron beam welds and CMSX-4 pulsed-laser welds. In PWA-1480 EB welds, eutectic {gamma}{prime} phases were observed along the dendritic boundaries. The elemental partitioning between {gamma} and {gamma}{prime} was found to be similar to that in PWA-1480 base metal. In CMSX-4 pulsed laser welds, negligible eutectic {gamma}{prime} was observed. In addition, fine and irregularly shaped {gamma}{prime} precipitates were observed. The elemental partitioning between {gamma} and {gamma}{prime} was found to be different from that measured in the base metal. Large concentration gradients were observed in the {gamma} phase. The {gamma}{prime} precipitation kinetics in CM247DS alloy was measured using dilatometry and showed differences with different cooling rates. The microstructural investigations showed that at large undercoolings the number density of {gamma}{prime} precipitates increased and led to a finer size. This supports the microstructure development observations in PWA-1480 and CMSX-4 welds. Thermodynamic and kinetic calculations for the Ni-Al-Cr alloy system showed that as the cooling rate increases, the {gamma}{prime} growth leads to large concentration gradients in the {gamma} phase. The calculations agree with the atom probe results from PWA-1480 and CMSX-4 welds.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

    Xie, Hui Hussain, Danish; Yang, Feng; Sun, Lining

    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.

  11. Nonlocal response of metallic nanospheres probed by light, electrons, and atoms.

    PubMed

    Christensen, Thomas; Yan, Wei; Raza, Søren; Jauho, Antti-Pekka; Mortensen, N Asger; Wubs, Martijn

    2014-02-25

    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 spectroscopy, and light scattering. These constitute two near-field and one far-field measurements, with zero-, one-, and two-dimensional excitation sources, respectively. We search for the clearest signatures of hydrodynamic pressure waves in nanospheres. We employ a linearized hydrodynamic model, and Mie-Lorenz theory is applied for each case. Nonlocal response shows its mark in all three configurations, but for the two near-field measurements, we predict especially pronounced nonlocal effects that are not exhibited in far-field measurements. Associated with every multipole order is not only a single 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 selected metals, we predict hydrodynamic multipolar plasmons to be measurable on single nanospheres.

  12. Compact metal probes: a solution for atomic force microscopy based tip-enhanced Raman spectroscopy.

    PubMed

    Rodriguez, R D; Sheremet, E; Müller, S; Gordan, O D; Villabona, A; Schulze, S; Hietschold, M; Zahn, D R T

    2012-12-01

    There are many challenges in accomplishing tip-enhanced Raman spectroscopy (TERS) and obtaining a proper tip is probably the greatest one. Since tip size, composition, and geometry are the ultimate parameters that determine enhancement of intensity and lateral resolution, the tip becomes the most critical component in a TERS experiment. However, since the discovery of TERS the cantilevers used in atomic force microscopy (AFM) have remained basically the same: commercial silicon (or silicon nitride) tips covered by a metallic coating. The main issues of using metal-coated silicon cantilevers, such as wearing off of the metal layer or increased tip radius, can be completely overcome by using all-metal cantilevers. Until now in TERS experiments such probes have only been used in a scanning tunneling microscope or in a tuning fork-based shear force microscope but not in AFM. In this work for the first time, we show the use of compact silver cantilevers that are fully compatible with contact and tapping modes in AFM demonstrating their superb performance in TERS experiments.

  13. Compact metal probes: A solution for atomic force microscopy based tip-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Rodriguez, R. D.; Sheremet, E.; Müller, S.; Gordan, O. D.; Villabona, A.; Schulze, S.; Hietschold, M.; Zahn, D. R. T.

    2012-12-01

    There are many challenges in accomplishing tip-enhanced Raman spectroscopy (TERS) and obtaining a proper tip is probably the greatest one. Since tip size, composition, and geometry are the ultimate parameters that determine enhancement of intensity and lateral resolution, the tip becomes the most critical component in a TERS experiment. However, since the discovery of TERS the cantilevers used in atomic force microscopy (AFM) have remained basically the same: commercial silicon (or silicon nitride) tips covered by a metallic coating. The main issues of using metal-coated silicon cantilevers, such as wearing off of the metal layer or increased tip radius, can be completely overcome by using all-metal cantilevers. Until now in TERS experiments such probes have only been used in a scanning tunneling microscope or in a tuning fork-based shear force microscope but not in AFM. In this work for the first time, we show the use of compact silver cantilevers that are fully compatible with contact and tapping modes in AFM demonstrating their superb performance in TERS experiments.

  14. Atomic arrangement at ZnTe/CdSe interfaces determined by high resolution scanning transmission electron microscopy and atom probe tomography

    SciTech Connect

    Bonef, Bastien; Rouvière, Jean-Luc; Jouneau, Pierre-Henri; Bellet-Amalric, Edith; Gérard, Lionel; Mariette, Henri; André, Régis; Bougerol, Catherine; Grenier, Adeline

    2015-02-02

    High resolution scanning transmission electron microscopy and atom probe tomography experiments reveal the presence of an intermediate layer at the interface between two binary compounds with no common atom, namely, ZnTe and CdSe for samples grown by Molecular Beam Epitaxy under standard conditions. This thin transition layer, of the order of 1 to 3 atomic planes, contains typically one monolayer of ZnSe. Even if it occurs at each interface, the direct interface, i.e., ZnTe on CdSe, is sharper than the reverse one, where the ZnSe layer is likely surrounded by alloyed layers. On the other hand, a CdTe-like interface was never observed. This interface knowledge is crucial to properly design superlattices for optoelectronic applications and to master band-gap engineering.

  15. Measuring Young's modulus of biological objects in a liquid medium using an atomic force microscope with a special probe

    NASA Astrophysics Data System (ADS)

    Lebedev, D. V.; Chuklanov, A. P.; Bukharaev, A. A.; Druzhinina, O. S.

    2009-04-01

    A special probe with a 5-μm-diameter ball fixed at the end is developed for an atomic force microscope (AFM), with the use of which it is possible to obtain more correct values of the Young’s moduli of biological objects in liquid media and eliminate the risk of damaging the sample surface. In particular, the AFM measurements with this probe in situ revealed an increase in the Young’s modulus of rat blood vessel under the action of chlorhexidine.

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

    NASA Astrophysics Data System (ADS)

    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

  17. Voltage-pulsed and laser-pulsed atom probe tomography of a multiphase high-strength low-carbon steel.

    PubMed

    Mulholland, Michael D; Seidman, David N

    2011-12-01

    The differences in artifacts associated with voltage-pulsed and laser-pulsed (wavelength = 532 or 355 nm) atom-probe tomographic (APT) analyses of nanoscale precipitation in a high-strength low-carbon steel are assessed using a local-electrode atom-probe tomograph. It is found that the interfacial width of nanoscale Cu precipitates increases with increasing specimen apex temperatures induced by higher laser pulse energies (0.6-2 nJ pulse(-1) at a wavelength of 532 nm). This effect is probably due to surface diffusion of Cu atoms. Increasing the specimen apex temperature by using pulse energies up to 2 nJ pulse(-1) at a wavelength of 532 nm is also found to increase the severity of the local magnification effect for nanoscale M2C metal carbide precipitates, which is indicated by a decrease of the local atomic density inside the carbides from 68 ± 6 nm(-3) (voltage pulsing) to as small as 3.5 ± 0.8 nm(-3). Methods are proposed to solve these problems based on comparisons with the results obtained from voltage-pulsed APT experiments. Essentially, application of the Cu precipitate compositions and local atomic density of M2C metal carbide precipitates measured by voltage-pulsed APT to 532 or 355 nm wavelength laser-pulsed data permits correct quantification of precipitation.

  18. Dopant characterization in self-regulatory plasma doped fin field-effect transistors by atom probe tomography

    SciTech Connect

    Takamizawa, H.; Shimizu, Y.; Nozawa, Y.; Toyama, T.; Nagai, Y.; Morita, H.; Yabuuchi, Y.; Ogura, M.

    2012-02-27

    Fin field-effect transistors are promising next-generation electronic devices, and the identification of dopant positions is important for their accurate characterization. We report atom probe tomography (APT) of silicon fin structures prepared by a recently developed self-regulatory plasma doping (SRPD) technique. Trenches between fin-arrays were filled using a low-energy focused ion beam to directly deposit silicon, which allowed the analysis of dopant distribution by APT near the surface of an actual fin transistor exposed to air. We directly demonstrate that SRPD can achieve a boron concentration above 1 x 10{sup 20} atoms/cm{sup 3} at the fin sidewall.

  19. High-purity 3D nano-objects grown by focused-electron-beam induced deposition

    NASA Astrophysics Data System (ADS)

    Córdoba, Rosa; Sharma, Nidhi; Kölling, Sebastian; Koenraad, Paul M.; Koopmans, Bert

    2016-09-01

    To increase the efficiency of current electronics, a specific challenge for the next generation of memory, sensing and logic devices is to find suitable strategies to move from two- to three-dimensional (3D) architectures. However, the creation of real 3D nano-objects is not trivial. Emerging non-conventional nanofabrication tools are required for this purpose. One attractive method is focused-electron-beam induced deposition (FEBID), a direct-write process of 3D nano-objects. Here, we grow 3D iron and cobalt nanopillars by FEBID using diiron nonacarbonyl Fe2(CO)9, and dicobalt octacarbonyl Co2(CO)8, respectively, as starting materials. In addition, we systematically study the composition of these nanopillars at the sub-nanometer scale by atom probe tomography, explicitly mapping the homogeneity of the radial and longitudinal composition distributions. We show a way of fabricating high-purity 3D vertical nanostructures of ∼50 nm in diameter and a few micrometers in length. Our results suggest that the purity of such 3D nanoelements (above 90 at% Fe and above 95 at% Co) is directly linked to their growth regime, in which the selected deposition conditions are crucial for the final quality of the nanostructure. Moreover, we demonstrate that FEBID and the proposed characterization technique not only allow for growth and chemical analysis of single-element structures, but also offers a new way to directly study 3D core–shell architectures. This straightforward concept could establish a promising route to the design of 3D elements for future nano-electronic devices.

  20. High-purity 3D nano-objects grown by focused-electron-beam induced deposition

    NASA Astrophysics Data System (ADS)

    Córdoba, Rosa; Sharma, Nidhi; Kölling, Sebastian; Koenraad, Paul M.; Koopmans, Bert

    2016-09-01

    To increase the efficiency of current electronics, a specific challenge for the next generation of memory, sensing and logic devices is to find suitable strategies to move from two- to three-dimensional (3D) architectures. However, the creation of real 3D nano-objects is not trivial. Emerging non-conventional nanofabrication tools are required for this purpose. One attractive method is focused-electron-beam induced deposition (FEBID), a direct-write process of 3D nano-objects. Here, we grow 3D iron and cobalt nanopillars by FEBID using diiron nonacarbonyl Fe2(CO)9, and dicobalt octacarbonyl Co2(CO)8, respectively, as starting materials. In addition, we systematically study the composition of these nanopillars at the sub-nanometer scale by atom probe tomography, explicitly mapping the homogeneity of the radial and longitudinal composition distributions. We show a way of fabricating high-purity 3D vertical nanostructures of ˜50 nm in diameter and a few micrometers in length. Our results suggest that the purity of such 3D nanoelements (above 90 at% Fe and above 95 at% Co) is directly linked to their growth regime, in which the selected deposition conditions are crucial for the final quality of the nanostructure. Moreover, we demonstrate that FEBID and the proposed characterization technique not only allow for growth and chemical analysis of single-element structures, but also offers a new way to directly study 3D core-shell architectures. This straightforward concept could establish a promising route to the design of 3D elements for future nano-electronic devices.

  1. BEAMS3D Neutral Beam Injection Model

    NASA Astrophysics Data System (ADS)

    McMillan, Matthew; Lazerson, Samuel A.

    2014-09-01

    With the advent of applied 3D fields in Tokamaks and modern high performance stellarators, a need has arisen to address non-axisymmetric effects on neutral beam heating and fueling. We report on the development of a fully 3D neutral beam injection (NBI) model, BEAMS3D, which addresses this need by coupling 3D equilibria to a guiding center code capable of modeling neutral and charged particle trajectories across the separatrix and into the plasma core. Ionization, neutralization, charge-exchange, viscous slowing down, and pitch angle scattering are modeled with the ADAS atomic physics database. Elementary benchmark calculations are presented to verify the collisionless particle orbits, NBI model, frictional drag, and pitch angle scattering effects. A calculation of neutral beam heating in the NCSX device is performed, highlighting the capability of the code to handle 3D magnetic fields. Notice: this manuscript has been authored by Princeton University under Contract Number DE-AC02-09CH11466 with the US Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.

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

    PubMed

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

    2016-04-21

    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.

  3. Imaging of a soft, weakly adsorbing, living cell with a colloid probe tapping atomic force microscope technique.

    PubMed

    McNamee, Cathy E; Pyo, Nayoung; Tanaka, Saaya; Kanda, Yoichi; Higashitani, Ko

    2006-01-15

    Here, we propose a new method to improve the atomic force microscopy (AFM) image resolution of soft samples, such as cells, in liquid. Attaching a colloid probe to a cantilever was seen improve the image resolution of a living cell in a physiological buffer solution, obtained by the normal tapping mode, when compared to an image obtained using a regular cantilever tip. This may be due to the averaging out of the cantilever tip swinging caused by the visco-elasticity of the cell. The resolution was best, when silica spheres with a 3.3 microm diameter were attached. Although larger spheres gave a resolution better than a bare cantilever tip, their resolution was less than that obtained for the 3.3 microm diameter silica colloid. This dependency of the image resolution on the colloid probe size may be a result of the increased macroscopic van der Waals attraction between the cell and probe, the decreased repulsive force dependence on the cantilever probe radius, and the decrease in resolution due to the increased probe size. The size of the colloid probe, which should be attached to the cantilever to give the best image resolution, would be the one that optimises the combined result of these facts. PMID:16406494

  4. Using Atom-Probe Tomography to Understand Zn O ∶Al /SiO 2/Si Schottky Diodes

    NASA Astrophysics Data System (ADS)

    Jaramillo, R.; Youssef, Amanda; Akey, Austin; Schoofs, Frank; Ramanathan, Shriram; Buonassisi, Tonio

    2016-09-01

    We use electronic transport and atom-probe tomography to study Zn O ∶Al /SiO 2/Si Schottky diodes on lightly doped n - and p -type Si. We vary the carrier concentration in the ZnO ∶Al films by 2 orders of magnitude, but the Schottky barrier height remains nearly constant. Atom-probe tomography shows that Al segregates to the interface, so that the ZnO ∶Al at the junction is likely to be metallic even when the bulk of the ZnO ∶Al film is semiconducting. We hypothesize that the observed Fermi-level pinning is connected to the insulator-metal transition in doped ZnO. This implies that tuning the band alignment at oxide/Si interfaces may be achieved by controlling the transition between localized and extended states in the oxide, thereby changing the orbital hybridization across the interface.

  5. Three-dimensional sub-half-wavelength atom localization via interacting double-dark resonances

    NASA Astrophysics Data System (ADS)

    Yang, Lei; Cao, Dewei; Wang, Yu; Wang, Zhiping; Yu, Benli

    2016-11-01

    We present a new scheme for three-dimensional (3D) atom localization in a four-level atomic system based on the interference of double-dark resonances. Owing to the space-dependent atom-field interaction, the position probability distribution of the atom can be directly determined by measuring the probe absorption. It is found that, by properly varying the parameters of the system, the probability of finding the atom in 3D space can be 1/2. Our scheme opens a promising way to achieve high-precision and high-efficiency 3D atom localization, which provides some potential applications in the atom nanolithography via 3D atom localization.

  6. Probing Deviations From Traditional Colloid Filtration Theory by Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Bowman, R. S.; Reno, M. D.; Altman, S. J.

    2006-12-01

    Understanding 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 physical and chemical mechanisms controlling colloid attachment and detachment. Colloid filtration theory (CFT) has been ubiquitously employed to describe particle advection, dispersion, and deposition in saturated media and predicts an exponential decrease in colloid concentration with travel distance from the source. Colloid depositional behavior can be further understood through consideration of Derjaguin Landau Verwey Overbeek (DLVO) interactions. Recent studies give evidence for significant deviations from traditional CFT in the presence of repulsive DLVO interactions. Deposition in the secondary energy minimum has been suggested as a mechanism to explain the observed deviations. This work reports on attempts to quantify the secondary energy minimum as predicted by DLVO theory using direct measurements obtained by atomic force microscopy. The colloid probe technique is used to directly measure the force of interaction between a single carboxylate modified polystyrene latex microsphere and a model collector surface in electrolyte solutions of varying ionic strength. Systematic variations in the size of the microsphere and the ionic strength of the electrolyte solutions yield force measurements that are compared to theoretical predictions and the experimental results of others. The importance of proper sample characterization and cleaning in obtaining meaningful measurements is emphasized. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04- 94AL85000.

  7. Microstructural development in PWA-1480 electron beam welds: An atom probe field ion microscopy study

    SciTech Connect

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

    1995-12-31

    The microstructure development in PWA-1480 superalloy electron beam weld (Ni-11.0 at. % Al-11.5% Cr-1.9% Ti-5.1% Co-4.0% Ta-1.3% W) was characterized. Optical microscopy revealed a branched dendritic structure in the weld metal. Transmission electron microscopy of these welds, in the as-welded condition, showed fine cuboidal (0.05--0.5 {mu}m) L1{sub 2}-ordered {gamma}{prime} precipitates within the y grains. The average volume percentage of {gamma}{prime} precipitates was found to be {approx}5%. Atom probe analyses revealed that the composition of {gamma} matrix was Ni-4.6 at. % Al-25.5% Cr-0.4% Ti-9.4% Co-0.8% Ta-2.9% W and that of {gamma}{prime} precipitates was Ni-17.3 at. % Al-2.6% Cr-2.4% Ti-3.0% Co-7.4% Ta-1.3% W. These compositions were compared with the previous APFIM analyses of commercial PWA-1480 single crystals that had received conventional heat treatments. Small differences were found in the chromium and aluminum levels and these may be due to the nonequilibrium nature of phase transformations that occur during weld cooling. No solute segregation was detected at the {gamma}-{gamma}{prime}interface. The APFIM results were also compared with the thermodynamic calculations of alloying element partitioning between {gamma} and {gamma}{prime} using the ThermoCalc{trademark} software.

  8. Atom probe tomography investigation of assisted precipitation of secondary hardening carbides in a medium carbon martensitic steels.

    PubMed

    Danoix, F; Danoix, R; Akre, J; Grellier, A; Delagnes, D

    2011-12-01

    A medium carbon martensitic steel containing nanometer scale secondary hardening carbides and intermetallic particles is investigated by field ion microscopy and atom probe tomography. The interaction between the concomitant precipitations of both types of particles is investigated. It is shown that the presence of the intermetallic phase affects the nucleation mechanism and the spatial distribution of the secondary hardening carbides, which shifts from heterogeneous on dislocations to heterogeneous on the intermetallic particles.

  9. 3D Elevation Program—Virtual USA in 3D

    USGS Publications Warehouse

    Lukas, Vicki; Stoker, J.M.

    2016-01-01

    The U.S. Geological Survey (USGS) 3D Elevation Program (3DEP) uses a laser system called ‘lidar’ (light detection and ranging) to create a virtual reality map of the Nation that is very accurate. 3D maps have many uses with new uses being discovered all the time.  

  10. 3D Elevation Program—Virtual USA in 3D

    USGS Publications Warehouse

    Lukas, Vicki; Stoker, J.M.

    2016-04-14

    The U.S. Geological Survey (USGS) 3D Elevation Program (3DEP) uses a laser system called ‘lidar’ (light detection and ranging) to create a virtual reality map of the Nation that is very accurate. 3D maps have many uses with new uses being discovered all the time.  

  11. Combining colloidal probe atomic force and reflection interference contrast microscopy to study the compressive mechanics of hyaluronan brushes.

    PubMed

    Attili, Seetharamaiah; Richter, Ralf P

    2012-02-14

    We describe a method that combines colloidal probe atomic force microscopy (AFM) and reflection interference contrast microscopy (RICM) to characterize the mechanical properties of thin and solvated polymer films. When analyzing polymer films, a fundamental problem in colloidal probe AFM experiments is to determine the distance at closest approach between the probe and the substrate on which the film is deposited. By combining AFM and RICM in situ, forces and absolute distances can be measured simultaneously. Using the combined setup, we quantify the compressive mechanics of films of the polysaccharide hyaluronan that is end-grafted to a supported lipid bilayer. The experimental data, and comparison with polymer theory, show that hyaluronan films are well-described as elastic, very soft and highly solvated polymer brushes. The data on these well-defined films should be a useful reference for the investigation of the more complex hyaluronan-rich coats that surround many living cells.

  12. Diamond-modified AFM probes: from diamond nanowires to atomic force microscopy-integrated boron-doped diamond electrodes.

    PubMed

    Smirnov, Waldemar; Kriele, Armin; Hoffmann, René; Sillero, Eugenio; Hees, Jakob; Williams, Oliver A; Yang, Nianjun; Kranz, Christine; Nebel, Christoph E

    2011-06-15

    In atomic force microscopy (AFM), sharp and wear-resistant tips are a critical issue. Regarding scanning electrochemical microscopy (SECM), electrodes are required to be mechanically and chemically stable. Diamond is the perfect candidate for both AFM probes as well as for electrode materials if doped, due to diamond's unrivaled mechanical, chemical, and electrochemical properties. In this study, standard AFM tips were overgrown with typically 300 nm thick nanocrystalline diamond (NCD) layers and modified to obtain ultra sharp diamond nanowire-based AFM probes and probes that were used for combined AFM-SECM measurements based on integrated boron-doped conductive diamond electrodes. Analysis of the resonance properties of the diamond overgrown AFM cantilevers showed increasing resonance frequencies with increasing diamond coating thicknesses (i.e., from 160 to 260 kHz). The measured data were compared to performed simulations and show excellent correlation. A strong enhancement of the quality factor upon overgrowth was also observed (120 to 710). AFM tips with integrated diamond nanowires are shown to have apex radii as small as 5 nm and where fabricated by selectively etching diamond in a plasma etching process using self-organized metal nanomasks. These scanning tips showed superior imaging performance as compared to standard Si-tips or commercially available diamond-coated tips. The high imaging resolution and low tip wear are demonstrated using tapping and contact mode AFM measurements by imaging ultra hard substrates and DNA. Furthermore, AFM probes were coated with conductive boron-doped and insulating diamond layers to achieve bifunctional AFM-SECM probes. For this, focused ion beam (FIB) technology was used to expose the boron-doped diamond as a recessed electrode near the apex of the scanning tip. Such a modified probe was used to perform proof-of-concept AFM-SECM measurements. The results show that high-quality diamond probes can be fabricated, which are

  13. Quantitative atomic resolution force imaging on epitaxial graphene with reactive and nonreactive AFM probes.

    PubMed

    Boneschanscher, Mark P; van der Lit, Joost; Sun, Zhixiang; Swart, Ingmar; Liljeroth, Peter; Vanmaekelbergh, Daniël

    2012-11-27

    Atomic force microscopy (AFM) images of graphene and graphite show contrast with atomic periodicity. However, the contrast patterns vary depending on the atomic termination of the AFM tip apex and the tip-sample distance, hampering the identification of the atomic positions. Here, we report quantitative AFM imaging of epitaxial graphene using inert (carbon-monoxide-terminated) and reactive (iridium-terminated) tips. The atomic image contrast is markedly different with these tip terminations. With a reactive tip, we observe an inversion from attractive to repulsive atomic contrast with decreasing tip-sample distance, while a nonreactive tip only yields repulsive atomic contrast. We are able to identify the atoms with both tips at any tip-sample distance. This is a prerequisite for future structural and chemical analysis of adatoms, defects, and the edges of graphene nanostructures, crucial for understanding nanoscale graphene devices.

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

    SciTech Connect

    Bachmaier, A.; Aboulfadl, H.; Pfaff, M.; Mücklich, F.; Motz, C.

    2015-02-15

    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.

  15. Market study: 3-D eyetracker

    NASA Technical Reports Server (NTRS)

    1977-01-01

    A market study of a proposed version of a 3-D eyetracker for initial use at NASA's Ames Research Center was made. The commercialization potential of a simplified, less expensive 3-D eyetracker was ascertained. Primary focus on present and potential users of eyetrackers, as well as present and potential manufacturers has provided an effective means of analyzing the prospects for commercialization.

  16. 3D World Building System

    ScienceCinema

    None

    2016-07-12

    This video provides an overview of the Sandia National Laboratories developed 3-D World Model Building capability that provides users with an immersive, texture rich 3-D model of their environment in minutes using a laptop and color and depth camera.

  17. 3D World Building System

    SciTech Connect

    2013-10-30

    This video provides an overview of the Sandia National Laboratories developed 3-D World Model Building capability that provides users with an immersive, texture rich 3-D model of their environment in minutes using a laptop and color and depth camera.

  18. LLNL-Earth3D

    SciTech Connect

    2013-10-01

    Earth3D is a computer code designed to allow fast calculation of seismic rays and travel times through a 3D model of the Earth. LLNL is using this for earthquake location and global tomography efforts and such codes are of great interest to the Earth Science community.

  19. [3-D ultrasound in gastroenterology].

    PubMed

    Zoller, W G; Liess, H

    1994-06-01

    Three-dimensional (3D) sonography represents a development of noninvasive diagnostic imaging by real-time two-dimensional (2D) sonography. The use of transparent rotating scans, comparable to a block of glass, generates a 3D effect. The objective of the present study was to optimate 3D presentation of abdominal findings. Additional investigations were made with a new volumetric program to determine the volume of selected findings of the liver. The results were compared with the estimated volumes of 2D sonography and 2D computer tomography (CT). For the processing of 3D images, typical parameter constellations were found for the different findings, which facilitated processing of 3D images. In more than 75% of the cases examined we found an optimal 3D presentation of sonographic findings with respect to the evaluation criteria developed by us for the 3D imaging of processed data. Great differences were found for the estimated volumes of the findings of the liver concerning the three different techniques applied. 3D ultrasound represents a valuable method to judge morphological appearance in abdominal findings. The possibility of volumetric measurements enlarges its potential diagnostic significance. Further clinical investigations are necessary to find out if definite differentiation between benign and malign findings is possible.

  20. Atomic probes of surface structure and dynamics. Technical progress report, September 15, 1991--September 14, 1992

    SciTech Connect

    Heller, E.J.; Jonsson, H.

    1992-12-31

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

  1. Atom probe tomography and transmission electron microscopy of a Mg-doped AlGaN/GaN superlattice.

    PubMed

    Bennett, S E; Ulfig, R M; Clifton, P H; Kappers, M J; Barnard, J S; Humphreys, C J; Oliver, R A

    2011-02-01

    The electronic characteristics of semiconductor-based devices are greatly affected by the local dopant atom distribution. In Mg-doped GaN, the clustering of dopants at structural defects has been widely reported, and can significantly affect p-type conductivity. We have studied a Mg-doped AlGaN/GaN superlattice using transmission electron microscopy (TEM) and atom probe tomography (APT). Pyramidal inversion domains were observed in the TEM and the compositional variations of the dopant atoms associated with those defects have been studied using APT. Rarely has APT been used to assess the compositional variations present due to structural defects in semiconductors. Here, TEM and APT are used in a complementary fashion, and the strengths and weaknesses of the two techniques are compared.

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

    NASA Astrophysics Data System (ADS)

    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.

  3. Determination of matrix composition based on solute-solute nearest-neighbor distances in atom probe tomography.

    PubMed

    De Geuser, F; Lefebvre, W

    2011-03-01

    In this study, we propose a fast automatic method providing the matrix concentration in an atom probe tomography (APT) data set containing two phases or more. The principle of this method relies on the calculation of the relative amount of isolated solute atoms (i.e., not surrounded by a similar solute atom) as a function of a distance d in the APT reconstruction. Simulated data sets have been generated to test the robustness of this new tool and demonstrate that rapid and reproducible results can be obtained without the need of any user input parameter. The method has then been successfully applied to a ternary Al-Zn-Mg alloy containing a fine dispersion of hardening precipitates. The relevance of this method for direct estimation of matrix concentration is discussed and compared with the existing methodologies.

  4. Euro3D Science Conference

    NASA Astrophysics Data System (ADS)

    Walsh, J. R.

    2004-02-01

    The Euro3D RTN is an EU funded Research Training Network to foster the exploitation of 3D spectroscopy in Europe. 3D spectroscopy is a general term for spectroscopy of an area of the sky and derives its name from its two spatial + one spectral dimensions. There are an increasing number of instruments which use integral field devices to achieve spectroscopy of an area of the sky, either using lens arrays, optical fibres or image slicers, to pack spectra of multiple pixels on the sky (``spaxels'') onto a 2D detector. On account of the large volume of data and the special methods required to reduce and analyse 3D data, there are only a few centres of expertise and these are mostly involved with instrument developments. There is a perceived lack of expertise in 3D spectroscopy spread though the astronomical community and its use in the armoury of the observational astronomer is viewed as being highly specialised. For precisely this reason the Euro3D RTN was proposed to train young researchers in this area and develop user tools to widen the experience with this particular type of data in Europe. The Euro3D RTN is coordinated by Martin M. Roth (Astrophysikalisches Institut Potsdam) and has been running since July 2002. The first Euro3D science conference was held in Cambridge, UK from 22 to 23 May 2003. The main emphasis of the conference was, in keeping with the RTN, to expose the work of the young post-docs who are funded by the RTN. In addition the team members from the eleven European institutes involved in Euro3D also presented instrumental and observational developments. The conference was organized by Andy Bunker and held at the Institute of Astronomy. There were over thirty participants and 26 talks covered the whole range of application of 3D techniques. The science ranged from Galactic planetary nebulae and globular clusters to kinematics of nearby galaxies out to objects at high redshift. Several talks were devoted to reporting recent observations with newly

  5. 3D printing in dentistry.

    PubMed

    Dawood, A; Marti Marti, B; Sauret-Jackson, V; Darwood, A

    2015-12-01

    3D printing has been hailed as a disruptive technology which will change manufacturing. Used in aerospace, defence, art and design, 3D printing is becoming a subject of great interest in surgery. The technology has a particular resonance with dentistry, and with advances in 3D imaging and modelling technologies such as cone beam computed tomography and intraoral scanning, and with the relatively long history of the use of CAD CAM technologies in dentistry, it will become of increasing importance. Uses of 3D printing include the production of drill guides for dental implants, the production of physical models for prosthodontics, orthodontics and surgery, the manufacture of dental, craniomaxillofacial and orthopaedic implants, and the fabrication of copings and frameworks for implant and dental restorations. This paper reviews the types of 3D printing technologies available and their various applications in dentistry and in maxillofacial surgery. PMID:26657435

  6. PLOT3D user's manual

    NASA Technical Reports Server (NTRS)

    Walatka, Pamela P.; Buning, Pieter G.; Pierce, Larry; Elson, Patricia A.

    1990-01-01

    PLOT3D is a computer graphics program designed to visualize the grids and solutions of computational fluid dynamics. Seventy-four functions are available. Versions are available for many systems. PLOT3D can handle multiple grids with a million or more grid points, and can produce varieties of model renderings, such as wireframe or flat shaded. Output from PLOT3D can be used in animation programs. The first part of this manual is a tutorial that takes the reader, keystroke by keystroke, through a PLOT3D session. The second part of the manual contains reference chapters, including the helpfile, data file formats, advice on changing PLOT3D, and sample command files.

  7. 3D printing in dentistry.

    PubMed

    Dawood, A; Marti Marti, B; Sauret-Jackson, V; Darwood, A

    2015-12-01

    3D printing has been hailed as a disruptive technology which will change manufacturing. Used in aerospace, defence, art and design, 3D printing is becoming a subject of great interest in surgery. The technology has a particular resonance with dentistry, and with advances in 3D imaging and modelling technologies such as cone beam computed tomography and intraoral scanning, and with the relatively long history of the use of CAD CAM technologies in dentistry, it will become of increasing importance. Uses of 3D printing include the production of drill guides for dental implants, the production of physical models for prosthodontics, orthodontics and surgery, the manufacture of dental, craniomaxillofacial and orthopaedic implants, and the fabrication of copings and frameworks for implant and dental restorations. This paper reviews the types of 3D printing technologies available and their various applications in dentistry and in maxillofacial surgery.

  8. Three-dimensional atom localization from spatial interference in a double two-level atomic system

    NASA Astrophysics Data System (ADS)

    Zhu, Zhonghu; Yang, Wen-Xing; Xie, Xiao-Tao; Liu, Shasha; Liu, Shaopeng; Lee, Ray-Kuang

    2016-07-01

    We propose a efficient scheme for high-precision three-dimensional (3D) atom localization via spatial interference in a generic double two-level atomic system driven by a weak probe field and three mutually perpendicular standing-wave fields. Because the spatial interference originates from the position-dependent atom-field interaction, the position information of the atom can be obtained by the measurement of the atom population. We find that the precision of 3D atom localization in volumes depends sensitively on the frequency detuning and the phase shifts associated with the standing-wave fields. Interestingly enough, we show that adjusting the frequency detuning and phase shifts can lead to a redistribution of the atoms and a significant change in the visibility of the interference pattern. As a result, the atom can be localized in volumes that are substantially smaller than a cubic optical wavelength.

  9. PLOT3D/AMES, APOLLO UNIX VERSION USING GMR3D (WITHOUT TURB3D)

    NASA Technical Reports Server (NTRS)

    Buning, P.

    1994-01-01

    PLOT3D is an interactive graphics program designed to help scientists visualize computational fluid dynamics (CFD) grids and solutions. Today, supercomputers and CFD algorithms can provide scientists with simulations of such highly complex phenomena that obtaining an understanding of the simulations has become a major problem. Tools which help the scientist visualize the simulations can be of tremendous aid. PLOT3D/AMES offers more functions and features, and has been adapted for more types of computers than any other CFD graphics program. Version 3.6b+ is supported for five computers and graphic libraries. Using PLOT3D, CFD physicists can view their computational models from any angle, observing the physics of problems and the quality of solutions. As an aid in designing aircraft, for example, PLOT3D's interactive computer graphics can show vortices, temperature, reverse flow, pressure, and dozens of other characteristics of air flow during flight. As critical areas become obvious, they can easily be studied more closely using a finer grid. PLOT3D is part of a computational fluid dynamics software cycle. First, a program such as 3DGRAPE (ARC-12620) helps the scientist generate computational grids to model an object and its surrounding space. Once the grids have been designed and parameters such as the angle of attack, Mach number, and Reynolds number have been specified, a "flow-solver" program such as INS3D (ARC-11794 or COS-10019) solves the system of equations governing fluid flow, usually on a supercomputer. Grids sometimes have as many as two million points, and the "flow-solver" produces a solution file which contains density, x- y- and z-momentum, and stagnation energy for each grid point. With such a solution file and a grid file containing up to 50 grids as input, PLOT3D can calculate and graphically display any one of 74 functions, including shock waves, surface pressure, velocity vectors, and particle traces. PLOT3D's 74 functions are organized into

  10. PLOT3D/AMES, APOLLO UNIX VERSION USING GMR3D (WITH TURB3D)

    NASA Technical Reports Server (NTRS)

    Buning, P.

    1994-01-01

    PLOT3D is an interactive graphics program designed to help scientists visualize computational fluid dynamics (CFD) grids and solutions. Today, supercomputers and CFD algorithms can provide scientists with simulations of such highly complex phenomena that obtaining an understanding of the simulations has become a major problem. Tools which help the scientist visualize the simulations can be of tremendous aid. PLOT3D/AMES offers more functions and features, and has been adapted for more types of computers than any other CFD graphics program. Version 3.6b+ is supported for five computers and graphic libraries. Using PLOT3D, CFD physicists can view their computational models from any angle, observing the physics of problems and the quality of solutions. As an aid in designing aircraft, for example, PLOT3D's interactive computer graphics can show vortices, temperature, reverse flow, pressure, and dozens of other characteristics of air flow during flight. As critical areas become obvious, they can easily be studied more closely using a finer grid. PLOT3D is part of a computational fluid dynamics software cycle. First, a program such as 3DGRAPE (ARC-12620) helps the scientist generate computational grids to model an object and its surrounding space. Once the grids have been designed and parameters such as the angle of attack, Mach number, and Reynolds number have been specified, a "flow-solver" program such as INS3D (ARC-11794 or COS-10019) solves the system of equations governing fluid flow, usually on a supercomputer. Grids sometimes have as many as two million points, and the "flow-solver" produces a solution file which contains density, x- y- and z-momentum, and stagnation energy for each grid point. With such a solution file and a grid file containing up to 50 grids as input, PLOT3D can calculate and graphically display any one of 74 functions, including shock waves, surface pressure, velocity vectors, and particle traces. PLOT3D's 74 functions are organized into

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

    SciTech Connect

    Uchitomi, Naotaka Inoue, Hiroaki; Kato, Takahiro; Toyota, Hideyuki; Uchida, Hiroshi

    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.

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

    PubMed

    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

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

    PubMed

    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.

  14. Multistep atomic reaction enhanced by an atomic force microscope probe on Si(111) and Ge(111) surfaces

    NASA Astrophysics Data System (ADS)

    Enkhtaivan, Batnyam; Oshiyama, Atsushi

    2016-08-01

    We present first-principles total-energy electronic-structure calculations that provide the microscopic mechanism of the adatom interchange reaction on the Sn- and Pb-covered Ge(111)-(2 ×8 ) and the Sb-covered Si(111)-(7 ×7 ) surfaces with and without the tip of the atomic force microscope (AFM). We find that, without the presence of the AFM tip on the Ge surface, the adatom interchange occurs through the migration of the adatom, the spontaneous formation of the dimer structures of the two adatoms, the dimer-dimer structural transitions that induce the exchange of the positions of the two adatoms, and then the backward migration of the adatom. We also find that the dimer structure is unfeasible at room temperature on the Si surface and the adatom interchange are hereby unlikely. With the presence of the tip, we find that the reaction pathways are essentially the same for the Ge surface but that the energy barriers of the migration and the exchange processes are substantially reduced by the AFM tip. We further find that the AFM tip induces the spontaneous formation of the dimer structure even on the Si surface, hereby opening a channel of the interchange of the adatoms. Our calculations show that the bond formation between the AFM tip atom and the surface adatom is essential for the atom manipulation using the AFM tip.

  15. 3D Band Diagram and Photoexcitation of 2D–3D Semiconductor Heterojunctions

    DOE PAGES

    Li, Bo; Shi, Gang; Lei, Sidong; He, Yongmin; Gao, Weilu; Gong, Yongji; Ye, Gonglan; Zhou, Wu; Keyshar, Kunttal; Hao, Ji; et al

    2015-08-17

    The emergence of a rich variety of two-dimensional (2D) layered semiconductor materials has enabled the creation of atomically thin heterojunction devices. Junctions between atomically thin 2D layers and 3D bulk semiconductors can lead to junctions that are fundamentally electronically different from the covalently bonded conventional semiconductor junctions. In this paper, we propose a new 3D band diagram for the heterojunction formed between n-type monolayer MoS2 and p-type Si, in which the conduction and valence band-edges of the MoS2 monolayer are drawn for both stacked and in-plane directions. This new band diagram helps visualize the flow of charge carriers inside themore » device in a 3D manner. Our detailed wavelength-dependent photocurrent measurements fully support the diagrams and unambiguously show that the band alignment is type I for this 2D-3D heterojunction. Photogenerated electron–hole pairs in the atomically thin monolayer are separated and driven by an external bias and control the “on/off” states of the junction photodetector device. Finally, two photoresponse regimes with fast and slow relaxation are also revealed in time-resolved photocurrent measurements, suggesting the important role played by charge trap states.« less

  16. 3D Band Diagram and Photoexcitation of 2D–3D Semiconductor Heterojunctions

    SciTech Connect

    Li, Bo; Shi, Gang; Lei, Sidong; He, Yongmin; Gao, Weilu; Gong, Yongji; Ye, Gonglan; Zhou, Wu; Keyshar, Kunttal; Hao, Ji; Dong, Pei; Ge, Liehui; Lou, Jun; Kono, Junichiro; Vajtai, Robert; Ajayan, Pulickel M.

    2015-08-17

    The emergence of a rich variety of two-dimensional (2D) layered semiconductor materials has enabled the creation of atomically thin heterojunction devices. Junctions between atomically thin 2D layers and 3D bulk semiconductors can lead to junctions that are fundamentally electronically different from the covalently bonded conventional semiconductor junctions. In this paper, we propose a new 3D band diagram for the heterojunction formed between n-type monolayer MoS2 and p-type Si, in which the conduction and valence band-edges of the MoS2 monolayer are drawn for both stacked and in-plane directions. This new band diagram helps visualize the flow of charge carriers inside the device in a 3D manner. Our detailed wavelength-dependent photocurrent measurements fully support the diagrams and unambiguously show that the band alignment is type I for this 2D-3D heterojunction. Photogenerated electron–hole pairs in the atomically thin monolayer are separated and driven by an external bias and control the “on/off” states of the junction photodetector device. Finally, two photoresponse regimes with fast and slow relaxation are also revealed in time-resolved photocurrent measurements, suggesting the important role played by charge trap states.

  17. Unassisted 3D camera calibration

    NASA Astrophysics Data System (ADS)

    Atanassov, Kalin; Ramachandra, Vikas; Nash, James; Goma, Sergio R.

    2012-03-01

    With the rapid growth of 3D technology, 3D image capture has become a critical part of the 3D feature set on mobile phones. 3D image quality is affected by the scene geometry as well as on-the-device processing. An automatic 3D system usually assumes known camera poses accomplished by factory calibration using a special chart. In real life settings, pose parameters estimated by factory calibration can be negatively impacted by movements of the lens barrel due to shaking, focusing, or camera drop. If any of these factors displaces the optical axes of either or both cameras, vertical disparity might exceed the maximum tolerable margin and the 3D user may experience eye strain or headaches. To make 3D capture more practical, one needs to consider unassisted (on arbitrary scenes) calibration. In this paper, we propose an algorithm that relies on detection and matching of keypoints between left and right images. Frames containing erroneous matches, along with frames with insufficiently rich keypoint constellations, are detected and discarded. Roll, pitch yaw , and scale differences between left and right frames are then estimated. The algorithm performance is evaluated in terms of the remaining vertical disparity as compared to the maximum tolerable vertical disparity.

  18. Tactile-optical 3D sensor applying image processing

    NASA Astrophysics Data System (ADS)

    Neuschaefer-Rube, Ulrich; Wissmann, Mark

    2009-01-01

    The tactile-optical probe (so-called fiber probe) is a well-known probe in micro-coordinate metrology. It consists of an optical fiber with a probing element at its end. This probing element is adjusted in the imaging plane of the optical system of an optical coordinate measuring machine (CMM). It can be illuminated through the fiber by a LED. The position of the probe is directly detected by image processing algorithms available in every modern optical CMM and not by deflections at the fixation of the probing shaft. Therefore, the probing shaft can be very thin and flexible. This facilitates the measurement with very small probing forces and the realization of very small probing elements (diameter: down to 10 μm). A limitation of this method is that at present the probe does not have full 3D measurement capability. At the Physikalisch-Technische Bundesanstalt (PTB), several arrangements and measurement principles for a full 3D tactile-optical probe have been implemented and tested successfully in cooperation with Werth-Messtechnik, Giessen, Germany. This contribution provides an overview of the results of these activities.

  19. Local Probes of Strain Texture and Individual Atomic Dopant Sites in Monolayer MoS2

    NASA Astrophysics Data System (ADS)

    Fragapane, Alex H.; Contryman, Alex W.; Li, Hong; Qian, Xiaofeng; Ardakani, Sina Moeini; Gong, Yongji; Wang, Xingli; Weisse, Jeffrey M.; Lee, Chi Hwan; Zhao, Jiheng; Ajayan, Pulickel M.; Li, Ju; Zheng, Xiaolin; Manoharan, Hari C.

    The 2D semiconductor MoS2 is an optically active material uniquely responsive to local perturbations. As an atomically thin membrane with exceptional strength, it can embed wide band gap variations overlapping the visible light spectrum when subjected to biaxial strain, where the modified electronic potential emanating from point-induced tensile strain perturbations mimics the Coulomb potential in a mesoscopic atom. We have realized this ``artificial atom'' concept via monolayer nanoindentation, and demonstrate that a synthetic superlattice of these building blocks forms an optoelectronic crystal capable of broadband light absorption and efficient funneling of photogenerated excitons to points of maximum strain at the artificial-atom nuclei. We also investigate the effects of individual atomic dopant sites through STM/STS, and visualize the atomic-scale local band structure changes. The modification of 2D semiconductors through methods such as strain texturing and doping connects to applications in next generation optoelectronics and photovoltaics.

  20. Application of colloid probe atomic force microscopy to the adhesion of thin films of viscous and viscoelastic silicone fluids.

    PubMed

    Bowen, James; Cheneler, David; Andrews, James W; Avery, Andrew R; Zhang, Zhibing; Ward, Michael C L; Adams, Michael J

    2011-09-20

    The adhesive characteristics of thin films (0.2-2 μm) of linear poly(dimethylsiloxane) (PDMS) liquids with a wide range of molecular weights have been measured using an atomic force microscope with a colloid probe (diameters 5 and 12 μm) for different separation velocities. The data were consistent with a residual film in the contact region having a thickness of ∼6 nm following an extended dwell time before separation of the probe. It was possible to estimate the maximum adhesive force as a function of the capillary number, Ca, by applying existing theoretical models based on capillary interactions and viscous flow except at large values of Ca in the case of viscoelastic fluids, for which it was necessary to develop a nonlinear viscoelastic model. The compliance of the atomic force microscope colloid beam was an important factor in governing the retraction velocity of the probe and therefore the value of the adhesive force, but the inertia of the beam and viscoelastic stress overshoot effects were not significant in the range of separation velocities investigated.