My CV includes my honors, awards and memberships in different societies plus history of my research career starting in 1960 after I received my BS degree from New York University's campus in the Bronx.
Direct and visible evidence was obtained for long-range migration of self-interstitial atoms (SIAs) in Stage II of three different ion-irradiated platinum(gold) alloys (Pt/0.1 at% Au, Pt/0.62 at% Au and Pt/4.0 at% Au). Field-ion... more
Direct and visible evidence was obtained for long-range migration of self-interstitial atoms (SIAs) in Stage II of three different ion-irradiated platinum(gold) alloys (Pt/0.1 at% Au, Pt/0.62 at% Au and Pt/4.0 at% Au). Field-ion microscope (FIM) specimens of the alloys were irradiated in-situ with 30 keV W/sup +/ or Pt/sup +/ ions at a tip temperature of 35 to 40 K at approximately 2.10/sup -9/ torr. Direct observation of the surface of the FIM specimens during isochronal warming experiments to 100 K showed that a flux of SIAs crossed the specimen's surfaces between 40 and 100 K. The spectrum for each alloy consisted of two recovery peaks (substages II/sub B/ and II/sub C/). The results are explained on the basis of an impurity delayed diffusion mechanism employing a two-level trapping model.
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A 0-4 kv pulse amplifier has been constructed for field ion microscopy. The circuit employed was a triode amplifier, powered by a 5 kv full-wave voltage doubler, triggered by a General Radio 1217-B pulse generator and capacitively coupled... more
A 0-4 kv pulse amplifier has been constructed for field ion microscopy. The circuit employed was a triode amplifier, powered by a 5 kv full-wave voltage doubler, triggered by a General Radio 1217-B pulse generator and capacitively coupled to the field ion microscope via a 30 kv, 0.01 μF capacitor. The circuit produces either negative or positive field evaporation pulses. The usable minimum pulse time was found to be in the range 10-20 μs for this amplifier design.
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ABSTRACTTernary carbide precipitates improve the high-temperature creep strength of 2-phase TiAl alloys. The perovskite (P-type) Ti3 AlC nucleates at relatively low temperatures (750 deg. C), whereas hexagonal (H-type) Ti2AlC precipitates... more
ABSTRACTTernary carbide precipitates improve the high-temperature creep strength of 2-phase TiAl alloys. The perovskite (P-type) Ti3 AlC nucleates at relatively low temperatures (750 deg. C), whereas hexagonal (H-type) Ti2AlC precipitates occur at somewhat higher temperatures. Calculations are performed, based on first- principles-local-density-functional theory, of the interface structure and energy of these two carbides with a 7-TiAl matrix. Calculations are first done on coherent interfaces, and approximate corrections are then made for the effect of misfit. The perovskite is known to form needle-shaped precipitates oriented along the c-axis of the host. Our calculations yield a relatively low energy for the (100) perovskite-host interface, which is a favorable orientation owing to its low misfit, and because the terminating carbide layer for the coherent interface is pseudomorphic with the host. Predictions are given for the critical thickness for coherence and the critical nucl...
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ABSTRACTThe amorphous(a)-to-crystalline (c) phase transition has been studied in electron(e-) and/or ion irradiated silicon (Si). The irradiations were performed in i n the Argonne High Voltage Microscope-Tandem Facility The irradia ion... more
ABSTRACTThe amorphous(a)-to-crystalline (c) phase transition has been studied in electron(e-) and/or ion irradiated silicon (Si). The irradiations were performed in i n the Argonne High Voltage Microscope-Tandem Facility The irradia ion of Si, at <10 K, with 1-MeV e- to a fluence of 14 dpa failed to induce the c-to-a transition. Whereas an irradiation, at <10 K, with 1.0 or 1.5-MeV Kr+ ions induced the c-to-a transition by a fluence of ≈0.37 dpa. Alternatively a dual irradiation, at 10 K, with 1.0-MeV e and 1.0 or 1.5-MeV Kr+ to a Kr+ fluence of 1.5 dpa -- where the ratio of the displacement rates for e- to ions was ≈0.5--resulted in the Si specimen retaining a degree of crystallinity. These results are discussed in terms of the degree of dispersion of point defects in the primary state of radiation damage and the mobilities of point defects.
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A review is presented of field ion microscope applications in studies of point defect distribution in irradiated metals. FIM results on the primary state of radiation damage in neutron and ion-irradiated iridium and tungsten, at both... more
A review is presented of field ion microscope applications in studies of point defect distribution in irradiated metals. FIM results on the primary state of radiation damage in neutron and ion-irradiated iridium and tungsten, at both room-temperature and 78/sup 0/K, showed that it consists of: (1) isolated vacancies; (2) depleted zones; (3) compact vacancy clusters of voids; and (4) dislocation loops. The fraction of vacancies stored in the dislocation loops represented a small fraction of the total vacancy concentration; in the case of tungsten it was approximately 10 percent. These FIM observations provide a simple explanation of the low yield-factor, determined by transmission electron microscopy, for a number of ion-irradiated metals.
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Atomistic Monte Carlo simulations utilizing many-body embedded atom method (EAM) potentials have been carried out for a series of symmetrical [001] twist boundaries in Pt-3 at.% Ni and Ni-3 at.% Pt alloy bicrystals at 850 K throughout the... more
Atomistic Monte Carlo simulations utilizing many-body embedded atom method (EAM) potentials have been carried out for a series of symmetrical [001] twist boundaries in Pt-3 at.% Ni and Ni-3 at.% Pt alloy bicrystals at 850 K throughout the misorientation range 0° to 45°. The results demonstrate enhancement of the solute-atom concentration at twist boundaries for both alloys; the interfacial Gibbsian excess is a factor of two greater on the Ni-rich side of the phase diagram. The spatial distributions of solute atoms in the vicinity of the interfaces are found to be markedly different on the two sides of the Ni-Pt phase diagram. For low-angle boundaries on the Pt-rich side solute atoms tend to segregate in hourglass-like regions along the cores of the primary grain boundary screw dislocations, while in the case of Ni-3 at.% Pt they occupy bipyramidal regions centered on the cells of the dislocation grid. The former behavior explains the oscillatory solute-atom concentration profiles no...
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The precise knowledge of the atomic order in monocrystalline alloys is fundamental to understand and predict their physical properties. With this perspective, we utilized laser-assisted atom probe tomography to investigate the... more
The precise knowledge of the atomic order in monocrystalline alloys is fundamental to understand and predict their physical properties. With this perspective, we utilized laser-assisted atom probe tomography to investigate the three-dimensional distribution of atoms in non-equilibrium epitaxial Sn-rich group IV SiGeSn ternary semiconductors. Different atom probe statistical analysis tools including frequency distribution analysis, partial radial distribution functions, and nearest neighbor analysis were employed in order to evaluate and compare the behavior of the three elements to their spatial distributions in an ideal solid solution. This atomistic-level analysis provided clear evidence of an unexpected repulsive interaction between Sn and Si leading to the deviation of Si atoms from the theoretical random distribution. This departure from an ideal solid solution is supported by first principal calculations and attributed to the tendency of the system to reduce its mixing enthalp...
Atom-probe field-ion microscope (FIM) analyses were performed on specimens of fully ordered Pt/sub 3/Co. The purpose of the investigation was to study the effects of different important experimental variables on the composition measured... more
Atom-probe field-ion microscope (FIM) analyses were performed on specimens of fully ordered Pt/sub 3/Co. The purpose of the investigation was to study the effects of different important experimental variables on the composition measured by the atom probe technique. The dependence of the alloy's composition on the following variables was determined: (1) pulse fraction (f); (2) specimen temperature; (3) crystal plane; and (4) field-evaporation rate. It was demonstrated that the composition determined by atom probe analyses of Pt/sub 3/Co was very sensitive to the above four variables. The observations were discussed in terms of possible field-evaporation mechanisms.
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Research Interests: Materials Science, Microscopy, Crystal structure, Platinum, Long Range, and 13 moreDiffusion Coefficient, Spectrum, Radiation Effect, Ion, Irradiation, Low Temperature, Diffusion Model, Electric Field, Physical Properties, Field Ion Microscopy, Ion Irradiation, self-interstitial atom, and Charged Particles
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Abstract The voids forming a three-dimensional lattice in a molybdenum specimen irradiated at 550°C to a fast neutron fluence of approximately 1 × 1022 n cm−2 have been investigated for the fist time by the field ion microscope (FIM)... more
Abstract The voids forming a three-dimensional lattice in a molybdenum specimen irradiated at 550°C to a fast neutron fluence of approximately 1 × 1022 n cm−2 have been investigated for the fist time by the field ion microscope (FIM) technique. The numerical values obtained for the mean void diameter, the number density, and mean spacing are in approximate agreement with transmission electron microscope observations. Controlled field evaporation sequences through sixteen voids revealed complex atomic displacements around each void much of which is a result of the void intersecting the surface. The advantages of the FIM technique for the study of high number densities (< 5 × 1017 cm−3) of voids are discussed and the potentialities of the FIM atom probe for the solution of problems concerning the nucleation and stabilization of voids is also considered.
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A versatile system has been designed and fabricated to prepare atom-probe field-ion-microscope (APFIM) specimens in a systematic manner, such that internal interfaces can be positioned in the tips of these wire specimens for subsequent... more
A versatile system has been designed and fabricated to prepare atom-probe field-ion-microscope (APFIM) specimens in a systematic manner, such that internal interfaces can be positioned in the tips of these wire specimens for subsequent analysis of their chemical composition. This system incorporates both beaker electrolytic and zone electrolytic cell configurations, a specially constructed power supply, and a special transmission electron
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... of the discrepancy between the present and previous pulse-duration measurements may be due to different electronic instrumentation, we feel that improvement in ion laser construction leading ... 3R.M. Scanlan, DL Styris, and DN... more
... of the discrepancy between the present and previous pulse-duration measurements may be due to different electronic instrumentation, we feel that improvement in ion laser construction leading ... 3R.M. Scanlan, DL Styris, and DN Seidman, Phil ... 4M.K. SinhaandE.W. Müller, J. Appi ...
Research Interests: Engineering, Chemistry, Evaporation, Diffusion, Physical sciences, and 3 morePlatinum, Ion, and Irradiation
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ISOTOPIC ANALYSES OF PRESOLAR SILICON CARBIDE BY ATOM-PROBE TOMOGRAPHY. J. B. Lewis 1 C. Floss 1 , D. Isheim 2 , and D. N. Seidman 2 1 Laboratory for Space Sciences, Physics Department, Washington University in St. Louis, St. Louis, MO,... more
ISOTOPIC ANALYSES OF PRESOLAR SILICON CARBIDE BY ATOM-PROBE TOMOGRAPHY. J. B. Lewis 1 C. Floss 1 , D. Isheim 2 , and D. N. Seidman 2 1 Laboratory for Space Sciences, Physics Department, Washington University in St. Louis, St. Louis, MO, USA. jlewis@physics.wustl.edu, 2 Northwestern University Center for Atom-Probe Tomography (NUCAPT), and Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA.
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Nb3Sn is a promising advanced material under development for superconducting radiofrequency cavities. Past efforts have been focused primarily on small development-scale cavities, but large, often multi-celled cavities, are needed for... more
Nb3Sn is a promising advanced material under development for superconducting radiofrequency cavities. Past efforts have been focused primarily on small development-scale cavities, but large, often multi-celled cavities, are needed for particle accelerator applications. In this work, we report on successful Nb3Sn coatings on Nb in a 1 m-long 9-cell Nb sample-host cavity at Fermilab. The geometry of the first coating with only one Sn source made it possible to study the influence of Sn flux on the microstructure. Based on these results, we postulate a connection between recently observed anomalously large thin grains and uncovered niobium spots observed in the past by other authors (Trenikhina et al 2018 Supercond. Sci. Technol. 32 015004). A phenomenological model to explain how these anomalously large grains could form is proposed. This model is invoked to provide possible explanations for literature results from several groups and to guide key process parameters to achieve uniform ...
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J. Greer, D. Isheim, D. N. Seidman, and P. R. Heck, Chicago Center for Cosmochemistry, Dept. of the Geophysical Sciences, Univ. of Chicago, Chicago IL, USA (*E-mail: jennika@uchicago.edu). Robert A. Pritzker Center for Meteoritics and... more
J. Greer, D. Isheim, D. N. Seidman, and P. R. Heck, Chicago Center for Cosmochemistry, Dept. of the Geophysical Sciences, Univ. of Chicago, Chicago IL, USA (*E-mail: jennika@uchicago.edu). Robert A. Pritzker Center for Meteoritics and Polar Studies, The Field Museum of Natural History, Chicago, IL, USA. Northwestern Univ. Center for Atom-Probe Tomography, Dept. of Materials Science & Engineering, Northwestern Univ., Evanston, IL, USA.
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Adhesion at ceramic/metal (C/M) interfaces often controls the macroscopic behavior of materials containing metallic and ceramic phases, and experimental studies of bonding at C/M interfaces have recently been reported. Electron energy... more
Adhesion at ceramic/metal (C/M) interfaces often controls the macroscopic behavior of materials containing metallic and ceramic phases, and experimental studies of bonding at C/M interfaces have recently been reported. Electron energy loss spectroscopy (EELS) offers unique opportunities to examine bonding at interfaces on an atomic scale. The EELS near edge fine structure is sensitive to local atomic arrangements and thus can be used as a coordination fingerprint. Much more can be done, however, by analyzing the connection between the EELS fine structure, the underlying local electronic structure and the cohesive energy of an interface to gain a deeper understanding of the nature of the adhesion at the interface.In this work, we apply high spatial-resolution EELS instrument to study {222} MgO/Cu interfaces produced by internal oxidation. We determine interfacial chemistry of this interface with subnanometer resolution (Fig. 1) and use EELS to directly measure the electronic states p...
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ABSTRACTA novel in situ sample cleavage technique has been developed for fabricating specimens for cross-sectional scanning tunneling microscopy (XSTM) applications. This technique can be easily adapted to any ultrahigh vacuum (UHV) STM... more
ABSTRACTA novel in situ sample cleavage technique has been developed for fabricating specimens for cross-sectional scanning tunneling microscopy (XSTM) applications. This technique can be easily adapted to any ultrahigh vacuum (UHV) STM that has a coarse motion capability. A conducting diamond STM tip is used to create micron long scratches on Ge/GaAs or GaAs {001 }-type surfaces. These {001} surfaces are imaged with STM to observe scratch characteristics, and GaAs samples are cleaved to reveal {110}-type faces. Atomic resolution images of {110}-type GaAs surfaces are readily and reproducibly obtained.