Reprint of: Atmospheric scanning electron microscope observes cells and tissues in open medium through silicon nitride film.

PubMed

Nishiyama, Hidetoshi; Suga, Mitsuo; Ogura, Toshihiko; Maruyama, Yuusuke; Koizumi, Mitsuru; Mio, Kazuhiro; Kitamura, Shinichi; Sato, Chikara

2010-11-01

Direct observation of subcellular structures and their characterization is essential for understanding their physiological functions. To observe them in open environment, we have developed an inverted scanning electron microscope with a detachable, open-culture dish, capable of 8 nm resolution, and combined with a fluorescence microscope quasi-simultaneously observing the same area from the top. For scanning electron microscopy from the bottom, a silicon nitride film window in the base of the dish maintains a vacuum between electron gun and open sample dish while allowing electrons to pass through. Electrons are backscattered from the sample and captured by a detector under the dish. Cells cultured on the open dish can be externally manipulated under optical microscopy, fixed, and observed using scanning electron microscopy. Once fine structures have been revealed by scanning electron microscopy, their component proteins may be identified by comparison with separately prepared fluorescence-labeled optical microscopic images of the candidate proteins, with their heavy-metal-labeled or stained ASEM images. Furthermore, cell nuclei in a tissue block stained with platinum-blue were successfully observed without thin-sectioning, which suggests the applicability of this inverted scanning electron microscope to cancer diagnosis. This microscope visualizes mesoscopic-scale structures, and is also applicable to non-bioscience fields including polymer chemistry. Copyright © 2010 Elsevier Inc. All rights reserved.

Fast-scan EM with digital image processing for dynamic experiments

Treesearch

C.W. McMillin; F.C. Billingsley; R.E. Frazer

1974-01-01

The recent introduction of accessory instrumentation capable of display at television scan rates suggests a broadened application for the scanning electron microscope- the direct observation of motion (dynamic events) at magnifications otherwise unattainable. In one illustrative experiment, the transverse surface of southern pine was observed when subjected to large...

Fast-scan em with digital image processing for dynamic experiments

Treesearch

Charles W. McMillin; Fred C. Billingsley; Robert E. Frazer

1973-01-01

The recent introduction of accessory instrumentation capable of display at television scan rates suggests a broadened application for the scanning electron microscope - the direct observation of motion (dynamic events) at magnifactions otherwise unattainable. In one illustrative experiment, the transverse surface of southern pine was observed when subjected to large...

Analysis of improvement in performance and design parameters for enhancing resolution in an atmospheric scanning electron microscope.

PubMed

Yoon, Yeo Hun; Kim, Seung Jae; Kim, Dong Hwan

2015-12-01

The scanning electron microscope is used in various fields to go beyond diffraction limits of the optical microscope. However, the electron pathway should be conducted in a vacuum so as not to scatter electrons. The pretreatment of the sample is needed for use in the vacuum. To directly observe large and fully hydrophilic samples without pretreatment, the atmospheric scanning electron microscope (ASEM) is needed. We developed an electron filter unit and an electron detector unit for implementation of the ASEM. The key of the electron filter unit is that electrons are transmitted while air molecules remain untransmitted through the unit. The electron detector unit collected the backscattered electrons. We conducted experiments using the selected materials with Havar foil, carbon film and SiN film. © The Author 2015. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Direct observation of iron-induced conformational changes of mitochondrial DNA by high-resolution field-emission in-lens scanning electron microscopy.

PubMed Central

Yaffee, M; Walter, P; Richter, C; Müller, M

1996-01-01

When respiring rat liver mitochondria are incubated in the presence of Fe(III) gluconate, their DNA (mtDNA) relaxes from the supercoiled to the open circular form dependent on the iron dose. Anaerobiosis or antioxidants fail to completely inhibit the unwinding. High-resolution field-emission in-lens scanning electron microscopy imaging, in concert with backscattered electron detection, pinpoints nanometer-range iron colloids bound to mtDNA isolated from iron-exposed mitochondria. High-resolution field-emission in-lens scanning electron microscopy with backscattered electron detection imaging permits simultaneous detailed visual analysis of DNA topology, iron dose-dependent mtDNA unwinding, and assessment of iron colloid formation on mtDNA strands. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 PMID:8643576

Precision controlled atomic resolution scanning transmission electron microscopy using spiral scan pathways

NASA Astrophysics Data System (ADS)

Sang, Xiahan; Lupini, Andrew R.; Ding, Jilai; Kalinin, Sergei V.; Jesse, Stephen; Unocic, Raymond R.

2017-03-01

Atomic-resolution imaging in an aberration-corrected scanning transmission electron microscope (STEM) can enable direct correlation between atomic structure and materials functionality. The fast and precise control of the STEM probe is, however, challenging because the true beam location deviates from the assigned location depending on the properties of the deflectors. To reduce these deviations, i.e. image distortions, we use spiral scanning paths, allowing precise control of a sub-Å sized electron probe within an aberration-corrected STEM. Although spiral scanning avoids the sudden changes in the beam location (fly-back distortion) present in conventional raster scans, it is not distortion-free. “Archimedean” spirals, with a constant angular frequency within each scan, are used to determine the characteristic response at different frequencies. We then show that such characteristic functions can be used to correct image distortions present in more complicated constant linear velocity spirals, where the frequency varies within each scan. Through the combined application of constant linear velocity scanning and beam path corrections, spiral scan images are shown to exhibit less scan distortion than conventional raster scan images. The methodology presented here will be useful for in situ STEM imaging at higher temporal resolution and for imaging beam sensitive materials.

Precision controlled atomic resolution scanning transmission electron microscopy using spiral scan pathways.

PubMed

Sang, Xiahan; Lupini, Andrew R; Ding, Jilai; Kalinin, Sergei V; Jesse, Stephen; Unocic, Raymond R

2017-03-08

Atomic-resolution imaging in an aberration-corrected scanning transmission electron microscope (STEM) can enable direct correlation between atomic structure and materials functionality. The fast and precise control of the STEM probe is, however, challenging because the true beam location deviates from the assigned location depending on the properties of the deflectors. To reduce these deviations, i.e. image distortions, we use spiral scanning paths, allowing precise control of a sub-Å sized electron probe within an aberration-corrected STEM. Although spiral scanning avoids the sudden changes in the beam location (fly-back distortion) present in conventional raster scans, it is not distortion-free. "Archimedean" spirals, with a constant angular frequency within each scan, are used to determine the characteristic response at different frequencies. We then show that such characteristic functions can be used to correct image distortions present in more complicated constant linear velocity spirals, where the frequency varies within each scan. Through the combined application of constant linear velocity scanning and beam path corrections, spiral scan images are shown to exhibit less scan distortion than conventional raster scan images. The methodology presented here will be useful for in situ STEM imaging at higher temporal resolution and for imaging beam sensitive materials.

Scanning electron microscopy of a pink inclusion from the Allende meteorite

NASA Technical Reports Server (NTRS)

Grossman, L.; Fruland, R. M.; Mckay, D. S.

1975-01-01

A scanning electron microscope study of a fine-grained, pin, Ca-rich inclusion from the Allende meteorite has revealed strong evidence for direct condensation of its constituent minerals from a vapor. This observation extends to the alkali-bearing phases in addition to the Ca-, Al-silicates and suggests that the feldspathoids as well as the refractory silicates are solar nebular condensates.

Direct visualization of lithium via annular bright field scanning transmission electron microscopy: a review.

PubMed

Findlay, Scott David; Huang, Rong; Ishikawa, Ryo; Shibata, Naoya; Ikuhara, Yuichi

2017-02-08

Annular bright field (ABF) scanning transmission electron microscopy has proven able to directly image lithium columns within crystalline environments, offering much insight into the structure and properties of lithium-ion battery materials. We summarize the image formation mechanisms underpinning ABF imaging, review the experimental application of this technique to imaging lithium in materials and overview the conditions that help maximize the visibility of lithium columns. © The Author 2016. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Direct correlations of structural and optical properties of three-dimensional GaN/InGaN core/shell micro-light emitting diodes

NASA Astrophysics Data System (ADS)

Sadat Mohajerani, Matin; Müller, Marcus; Hartmann, Jana; Zhou, Hao; Wehmann, Hergo-H.; Veit, Peter; Bertram, Frank; Christen, Jürgen; Waag, Andreas

2016-05-01

Three-dimensional (3D) InGaN/GaN quantum-well (QW) core-shell light emitting diodes (LEDs) are a promising candidate for the future solid state lighting. In this contribution, we study direct correlations of structural and optical properties of the core-shell LEDs using highly spatially-resolved cathodoluminescence spectroscopy (CL) in combination with scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM). Temperature-dependent resonant photoluminescence (PL) spectroscopy has been performed to understand recombination mechanisms and to estimate the internal quantum efficiency (IQE).

Expansion of Shockley stacking fault observed by scanning electron microscope and partial dislocation motion in 4H-SiC

NASA Astrophysics Data System (ADS)

Yamashita, Yoshifumi; Nakata, Ryu; Nishikawa, Takeshi; Hada, Masaki; Hayashi, Yasuhiko

2018-04-01

We studied the dynamics of the expansion of a Shockley-type stacking fault (SSF) with 30° Si(g) partial dislocations (PDs) using a scanning electron microscope. We observed SSFs as dark lines (DLs), which formed the contrast at the intersection between the surface and the SSF on the (0001) face inclined by 8° from the surface. We performed experiments at different electron-beam scanning speeds, observing magnifications, and irradiation areas. The results indicated that the elongation of a DL during one-frame scanning depended on the time for which the electron beam irradiated the PD segment in the frame of view. From these results, we derived a formula to express the velocity of the PD using the elongation rate of the corresponding DL during one-frame scanning. We also obtained the result that the elongation velocity of the DL was not influenced by changing the direction in which the electron beam irradiates the PD. From this result, we deduced that the geometrical kink motion of the PD was enhanced by diffusing carriers that were generated by the electron-beam irradiation.

Accurate virus quantitation using a Scanning Transmission Electron Microscopy (STEM) detector in a scanning electron microscope.

PubMed

Blancett, Candace D; Fetterer, David P; Koistinen, Keith A; Morazzani, Elaine M; Monninger, Mitchell K; Piper, Ashley E; Kuehl, Kathleen A; Kearney, Brian J; Norris, Sarah L; Rossi, Cynthia A; Glass, Pamela J; Sun, Mei G

2017-10-01

A method for accurate quantitation of virus particles has long been sought, but a perfect method still eludes the scientific community. Electron Microscopy (EM) quantitation is a valuable technique because it provides direct morphology information and counts of all viral particles, whether or not they are infectious. In the past, EM negative stain quantitation methods have been cited as inaccurate, non-reproducible, and with detection limits that were too high to be useful. To improve accuracy and reproducibility, we have developed a method termed Scanning Transmission Electron Microscopy - Virus Quantitation (STEM-VQ), which simplifies sample preparation and uses a high throughput STEM detector in a Scanning Electron Microscope (SEM) coupled with commercially available software. In this paper, we demonstrate STEM-VQ with an alphavirus stock preparation to present the method's accuracy and reproducibility, including a comparison of STEM-VQ to viral plaque assay and the ViroCyt Virus Counter. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Interfacial scanning tunneling spectroscopy (STS) of chalcogenide/metal hybrid nanostructure

NASA Astrophysics Data System (ADS)

Saad, Mahmoud M.; Abdallah, Tamer; Easawi, Khalid; Negm, Sohair; Talaat, Hassan

2015-05-01

The electronic structure at the interface of chalcogenide/metal hybrid nanostructure (CdSe-Au tipped) had been studied by UHV scanning tunneling spectroscopy (STS) technique at room temperature. This nanostructure was synthesized by a phase transfer chemical method. The optical absorption of this hybrid nanostructure was recorded, and the application of the effective mass approximation (EMA) model gave dimensions that were confirmed by the direct measurements using the scanning tunneling microscopy (STM) as well as the high-resolution transmission electron microscope (HRTEM). The energy band gap obtained by STS agrees with the values obtained from the optical absorption. Moreover, the STS at the interface of CdSe-Au tipped hybrid nanostructure between CdSe of size about 4.1 ± 0.19 nm and Au tip of size about 3.5 ± 0.29 nm shows a band bending about 0.18 ± 0.03 eV in CdSe down in the direction of the interface. Such a result gives a direct observation of the electron accumulation at the interface of CdSe-Au tipped hybrid nanostructure, consistent with its energy band diagram. The presence of the electron accumulation at the interface of chalcogenides with metals has an important implication for hybrid nanoelectronic devices and the newly developed plasmon/chalcogenide photovoltaic solar energy conversion.

Direct-write liquid phase transformations with a scanning transmission electron microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Unocic, Raymond R.; Lupini, Andrew R.; Borisevich, Albina Y.

The highly energetic electron beam from a scanning transmission electron microscope (STEM) can induce local changes in the state of matter, ranging from local knock-out and atomic movement, to amorphization/crystallization, and chemical/electrochemical reactions occuring at localized liquid-solid and gas-solid interfaces. To date, fundamental studies of e-beam induced phenomena and practical applications have been limited by conventional e-beam rastering modes that allow only for uniform e-beam exposures. Here we develop an automated liquid phase nanolithography method that is capable of directly writing nanometer scaled features within silicon nitride encapsulated liquid cells. An external beam control system, connected to the scan coilsmore » of an aberration-corrected STEM, is used to precisely control the position, dwell time, and scan velocity of a sub-nanometer STEM probe. Site-specific locations in a sealed liquid cell containing an aqueous solution of H 2PdCl 4 are irradiated to controllably deposit palladium onto silicon nitride membranes. We determine the threshold electron dose required for the radiolytic deposition of metallic palladium, explore the influence of electron dose on the feature size and morphology of nanolithographically patterned nanostructures, and propose a feedback-controlled monitoring method for active control of the nanofabricated structures through STEM detector signal monitoring. As a result, this approach enables both fundamental studies of electron beam induced interactions with matter, as well as opens a pathway to fabricate nanostructures with tailored architectures and chemistries via shape-controlled nanolithographic patterning from liquid phase precursors.« less

Direct-write liquid phase transformations with a scanning transmission electron microscope

DOE PAGES

Unocic, Raymond R.; Lupini, Andrew R.; Borisevich, Albina Y.; ...

2016-08-03

The highly energetic electron beam from a scanning transmission electron microscope (STEM) can induce local changes in the state of matter, ranging from local knock-out and atomic movement, to amorphization/crystallization, and chemical/electrochemical reactions occuring at localized liquid-solid and gas-solid interfaces. To date, fundamental studies of e-beam induced phenomena and practical applications have been limited by conventional e-beam rastering modes that allow only for uniform e-beam exposures. Here we develop an automated liquid phase nanolithography method that is capable of directly writing nanometer scaled features within silicon nitride encapsulated liquid cells. An external beam control system, connected to the scan coilsmore » of an aberration-corrected STEM, is used to precisely control the position, dwell time, and scan velocity of a sub-nanometer STEM probe. Site-specific locations in a sealed liquid cell containing an aqueous solution of H 2PdCl 4 are irradiated to controllably deposit palladium onto silicon nitride membranes. We determine the threshold electron dose required for the radiolytic deposition of metallic palladium, explore the influence of electron dose on the feature size and morphology of nanolithographically patterned nanostructures, and propose a feedback-controlled monitoring method for active control of the nanofabricated structures through STEM detector signal monitoring. As a result, this approach enables both fundamental studies of electron beam induced interactions with matter, as well as opens a pathway to fabricate nanostructures with tailored architectures and chemistries via shape-controlled nanolithographic patterning from liquid phase precursors.« less

Analytical and numerical analysis of imaging mechanism of dynamic scanning electron microscopy.

PubMed

Schröter, M-A; Holschneider, M; Sturm, H

2012-11-02

The direct observation of small oscillating structures with the help of a scanning electron beam is a new approach to study the vibrational dynamics of cantilevers and microelectromechanical systems. In the scanning electron microscope, the conventional signal of secondary electrons (SE, dc part) is separated from the signal response of the SE detector, which is correlated to the respective excitation frequency for vibration by means of a lock-in amplifier. The dynamic response is separated either into images of amplitude and phase shift or into real and imaginary parts. Spatial resolution is limited to the diameter of the electron beam. The sensitivity limit to vibrational motion is estimated to be sub-nanometer for high integration times. Due to complex imaging mechanisms, a theoretical model was developed for the interpretation of the obtained measurements, relating cantilever shapes to interaction processes consisting of incident electron beam, electron-lever interaction, emitted electrons and detector response. Conclusions drawn from this new model are compared with numerical results based on the Euler-Bernoulli equation.

Use of light, scanning electron microscopy and bioassays to evaluate parasitism by entomopathogenic fungi of the red scale insect of palms (Phoenicococcus marlatti Ckll., 1899).

PubMed

Asensio, L; Lopez-Llorca, L V; López-Jiménez, J A

2005-01-01

We have evaluated the parasitism of the red scale insect of the date palm (Phoenicococcus marlatti) by entomopathogenic fungi, using light microscopy (LM), scanning electron microscopy (SEM) and low temperature scanning electron microscopy (LTSEM). Beauveria bassiana, Lecanicillium dimorphum and Lecanicillium cf. psalliotae, were inoculated directly on the scale insects or on insect infested plant material. We found that L. dimorphum and L. cf. psalliotae developed on plant material and on scale insects, making infection structures. B. bassiana was a bad colonizer of date palm leaves (Phoenix dactylifera L.) and did not parasite the scale insects.

Precision controlled atomic resolution scanning transmission electron microscopy using spiral scan pathways

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sang, Xiahan; Lupini, Andrew R.; Ding, Jilai

Atomic-resolution imaging in an aberration-corrected scanning transmission electron microscope (STEM) can enable direct correlation between atomic structure and materials functionality. The fast and precise control of the STEM probe is, however, challenging because the true beam location deviates from the assigned location depending on the properties of the deflectors. To reduce these deviations, i.e. image distortions, we use spiral scanning paths, allowing precise control of a sub-Å sized electron probe within an aberration-corrected STEM. Although spiral scanning avoids the sudden changes in the beam location (fly-back distortion) present in conventional raster scans, it is not distortion-free. “Archimedean” spirals, with amore » constant angular frequency within each scan, are used to determine the characteristic response at different frequencies. We then show that such characteristic functions can be used to correct image distortions present in more complicated constant linear velocity spirals, where the frequency varies within each scan. Through the combined application of constant linear velocity scanning and beam path corrections, spiral scan images are shown to exhibit less scan distortion than conventional raster scan images. The methodology presented here will be useful for in situ STEM imaging at higher temporal resolution and for imaging beam sensitive materials.« less

Precision controlled atomic resolution scanning transmission electron microscopy using spiral scan pathways

DOE PAGES

Sang, Xiahan; Lupini, Andrew R.; Ding, Jilai; ...

2017-03-08

Atomic-resolution imaging in an aberration-corrected scanning transmission electron microscope (STEM) can enable direct correlation between atomic structure and materials functionality. The fast and precise control of the STEM probe is, however, challenging because the true beam location deviates from the assigned location depending on the properties of the deflectors. To reduce these deviations, i.e. image distortions, we use spiral scanning paths, allowing precise control of a sub-Å sized electron probe within an aberration-corrected STEM. Although spiral scanning avoids the sudden changes in the beam location (fly-back distortion) present in conventional raster scans, it is not distortion-free. “Archimedean” spirals, with amore » constant angular frequency within each scan, are used to determine the characteristic response at different frequencies. We then show that such characteristic functions can be used to correct image distortions present in more complicated constant linear velocity spirals, where the frequency varies within each scan. Through the combined application of constant linear velocity scanning and beam path corrections, spiral scan images are shown to exhibit less scan distortion than conventional raster scan images. The methodology presented here will be useful for in situ STEM imaging at higher temporal resolution and for imaging beam sensitive materials.« less

Special raster scanning for reduction of charging effects in scanning electron microscopy.

PubMed

Suzuki, Kazuhiko; Oho, Eisaku

2014-01-01

A special raster scanning (SRS) method for reduction of charging effects is developed for the field of SEM. Both a conventional fast scan (horizontal direction) and an unusual scan (vertical direction) are adopted for acquiring raw data consisting of many sub-images. These data are converted to a proper SEM image using digital image processing techniques. About sharpness of the image and reduction of charging effects, the SRS is compared with the conventional fast scan (with frame-averaging) and the conventional slow scan. Experimental results show the effectiveness of SRS images. By a successful combination of the proposed scanning method and low accelerating voltage (LV)-SEMs, it is expected that higher-quality SEM images can be more easily acquired by the considerable reduction of charging effects, while maintaining the resolution. © 2013 Wiley Periodicals, Inc.

Scanning transmission electron microscopy: Albert Crewe's vision and beyond.

PubMed

Krivanek, Ondrej L; Chisholm, Matthew F; Murfitt, Matthew F; Dellby, Niklas

2012-12-01

Some four decades were needed to catch up with the vision that Albert Crewe and his group had for the scanning transmission electron microscope (STEM) in the nineteen sixties and seventies: attaining 0.5Å resolution, and identifying single atoms spectroscopically. With these goals now attained, STEM developments are turning toward new directions, such as rapid atomic resolution imaging and exploring atomic bonding and electronic properties of samples at atomic resolution. The accomplishments and the future challenges are reviewed and illustrated with practical examples. Copyright © 2012 Elsevier B.V. All rights reserved.

Nano-scale luminescence characterization of individual InGaN/GaN quantum wells stacked in a microcavity using scanning transmission electron microscope cathodoluminescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmidt, Gordon, E-mail: Gordon.Schmidt@ovgu.de; Müller, Marcus; Veit, Peter

2014-07-21

Using cathodoluminescence spectroscopy directly performed in a scanning transmission electron microscope at liquid helium temperatures, the optical and structural properties of a 62 InGaN/GaN multiple quantum well embedded in an AlInN/GaN based microcavity are investigated at the nanometer scale. We are able to spatially resolve a spectral redshift between the individual quantum wells towards the surface. Cathodoluminescence spectral linescans allow directly visualizing the critical layer thickness in the quantum well stack resulting in the onset of plastic relaxation of the strained InGaN/GaN system.

Neuroanatomy from Mesoscopic to Nanoscopic Scales: An Improved Method for the Observation of Semithin Sections by High-Resolution Scanning Electron Microscopy

PubMed Central

Rodríguez, José-Rodrigo; Turégano-López, Marta; DeFelipe, Javier; Merchán-Pérez, Angel

2018-01-01

Semithin sections are commonly used to examine large areas of tissue with an optical microscope, in order to locate and trim the regions that will later be studied with the electron microscope. Ideally, the observation of semithin sections would be from mesoscopic to nanoscopic scales directly, instead of using light microscopy and then electron microscopy (EM). Here we propose a method that makes it possible to obtain high-resolution scanning EM images of large areas of the brain in the millimeter to nanometer range. Since our method is compatible with light microscopy, it is also feasible to generate hybrid light and electron microscopic maps. Additionally, the same tissue blocks that have been used to obtain semithin sections can later be used, if necessary, for transmission EM, or for focused ion beam milling and scanning electron microscopy (FIB-SEM). PMID:29568263

Neuroanatomy from Mesoscopic to Nanoscopic Scales: An Improved Method for the Observation of Semithin Sections by High-Resolution Scanning Electron Microscopy.

PubMed

Rodríguez, José-Rodrigo; Turégano-López, Marta; DeFelipe, Javier; Merchán-Pérez, Angel

2018-01-01

Semithin sections are commonly used to examine large areas of tissue with an optical microscope, in order to locate and trim the regions that will later be studied with the electron microscope. Ideally, the observation of semithin sections would be from mesoscopic to nanoscopic scales directly, instead of using light microscopy and then electron microscopy (EM). Here we propose a method that makes it possible to obtain high-resolution scanning EM images of large areas of the brain in the millimeter to nanometer range. Since our method is compatible with light microscopy, it is also feasible to generate hybrid light and electron microscopic maps. Additionally, the same tissue blocks that have been used to obtain semithin sections can later be used, if necessary, for transmission EM, or for focused ion beam milling and scanning electron microscopy (FIB-SEM).

Study on the parameters of the scanning system for the 300 keV electron accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leo, K. W.; Chulan, R. M., E-mail: leo@nm.gov.my; Hashim, S. A.

2016-01-22

This paper describes the method to identify the magnetic coil parameters of the scanning system. This locally designed low energy electron accelerator with the present energy of 140 keV will be upgraded to 300 keV. In this accelerator, scanning system is required to deflect the energetic electron beam across a titanium foil in vertical and horizontal direction. The excitation current of the magnetic coil is determined by the energy of the electron beam. Therefore, the magnetic coil parameters must be identified to ensure the matching of the beam energy and excitation coil current. As the result, the essential parameters ofmore » the effective lengths for X-axis and Y-axis have been found as 0.1198 m and 0.1134 m and the required excitation coil currents which is dependenton the electron beam energies have be identified.« less

Solid state optical microscope

DOEpatents

Young, I.T.

1983-08-09

A solid state optical microscope wherein wide-field and high-resolution images of an object are produced at a rapid rate by utilizing conventional optics with a charge-coupled photodiode array. A galvanometer scanning mirror, for scanning in one of two orthogonal directions is provided, while the charge-coupled photodiode array scans in the other orthogonal direction. Illumination light from the object is incident upon the photodiodes, creating packets of electrons (signals) which are representative of the illuminated object. The signals are then processed, stored in a memory, and finally displayed as a video signal. 2 figs.

Solid state optical microscope

DOEpatents

Young, Ian T.

1983-01-01

A solid state optical microscope wherein wide-field and high-resolution images of an object are produced at a rapid rate by utilizing conventional optics with a charge-coupled photodiode array. A galvanometer scanning mirror, for scanning in one of two orthogonal directions is provided, while the charge-coupled photodiode array scans in the other orthogonal direction. Illumination light from the object is incident upon the photodiodes, creating packets of electrons (signals) which are representative of the illuminated object. The signals are then processed, stored in a memory, and finally displayed as a video signal.

Optimization study of direct morphology observation by cold field emission SEM without gold coating.

PubMed

He, Dan; Fu, Cheng; Xue, Zhigang

2018-06-01

Gold coating is a general operation that is generally applied on non-conductive or low conductive materials, during which the morphology of the materials can be examined by scanning electron microscopy (SEM). However, fatal deficiencies in the materials can result in irreversible distortion and damage. The present study directly characterized different low conductive materials such as hydroxyapatite, modified poly(vinylidene fluoride) (PVDF) fiber, and zinc oxide nanopillar by cold field emission scanning electron microscopy (FE-SEM) without a gold coating. According to the characteristics of the low conductive materials, various test conditions, such as different working signal modes, accelerating voltages, electron beam spots, and working distances, were characterized to determine the best morphological observations of each sample. Copyright © 2018 Elsevier Ltd. All rights reserved.

Resolution-enhanced Mapping Spectrometer

NASA Technical Reports Server (NTRS)

Kumer, J. B.; Aubrun, J. N.; Rosenberg, W. J.; Roche, A. E.

1993-01-01

A familiar mapping spectrometer implementation utilizes two dimensional detector arrays with spectral dispersion along one direction and spatial along the other. Spectral images are formed by spatially scanning across the scene (i.e., push-broom scanning). For imaging grating and prism spectrometers, the slit is perpendicular to the spatial scan direction. For spectrometers utilizing linearly variable focal-plane-mounted filters the spatial scan direction is perpendicular to the direction of spectral variation. These spectrometers share the common limitation that the number of spectral resolution elements is given by the number of pixels along the spectral (or dispersive) direction. Resolution enhancement by first passing the light input to the spectrometer through a scanned etalon or Michelson is discussed. Thus, while a detector element is scanned through a spatial resolution element of the scene, it is also temporally sampled. The analysis for all the pixels in the dispersive direction is addressed. Several specific examples are discussed. The alternate use of a Michelson for the same enhancement purpose is also discussed. Suitable for weight constrained deep space missions, hardware systems were developed including actuators, sensor, and electronics such that low-resolution etalons with performance required for implementation would weigh less than one pound.

Cryo-Scanning Electron Microscopy (SEM) and Scanning Transmission Electron Microscopy (STEM)-in-SEM for Bio- and Organo-Mineral Interface Characterization in the Environment.

PubMed

Wille, Guillaume; Hellal, Jennifer; Ollivier, Patrick; Richard, Annie; Burel, Agnes; Jolly, Louis; Crampon, Marc; Michel, Caroline

2017-12-01

Understanding biofilm interactions with surrounding substratum and pollutants/particles can benefit from the application of existing microscopy tools. Using the example of biofilm interactions with zero-valent iron nanoparticles (nZVI), this study aims to apply various approaches in biofilm preparation and labeling for fluorescent or electron microscopy and energy dispersive X-ray spectrometry (EDS) microanalysis for accurate observations. According to the targeted microscopy method, biofilms were sampled as flocs or attached biofilm, submitted to labeling using 4',6-diamidino-2-phenylindol, lectins PNA and ConA coupled to fluorescent dye or gold nanoparticles, and prepared for observation (fixation, cross-section, freezing, ultramicrotomy). Fluorescent microscopy revealed that nZVI were embedded in the biofilm structure as aggregates but the resolution was insufficient to observe individual nZVI. Cryo-scanning electron microscopy (SEM) observations showed nZVI aggregates close to bacteria, but it was not possible to confirm direct interactions between nZVI and cell membranes. Scanning transmission electron microscopy in the SEM (STEM-in-SEM) showed that nZVI aggregates could enter the biofilm to a depth of 7-11 µm. Bacteria were surrounded by a ring of extracellular polymeric substances (EPS) preventing direct nZVI/membrane interactions. STEM/EDS mapping revealed a co-localization of nZVI aggregates with lectins suggesting a potential role of EPS in nZVI embedding. Thus, the combination of divergent microscopy approaches is a good approach to better understand and characterize biofilm/metal interactions.

Tracking the ultrafast motion of a single molecule by femtosecond orbital imaging

NASA Astrophysics Data System (ADS)

Cocker, Tyler L.; Peller, Dominik; Yu, Ping; Repp, Jascha; Huber, Rupert

2016-11-01

Watching a single molecule move on its intrinsic timescale has been one of the central goals of modern nanoscience, and calls for measurements that combine ultrafast temporal resolution with atomic spatial resolution. Steady-state experiments access the requisite spatial scales, as illustrated by direct imaging of individual molecular orbitals using scanning tunnelling microscopy or the acquisition of tip-enhanced Raman and luminescence spectra with sub-molecular resolution. But tracking the intrinsic dynamics of a single molecule directly in the time domain faces the challenge that interactions with the molecule must be confined to a femtosecond time window. For individual nanoparticles, such ultrafast temporal confinement has been demonstrated by combining scanning tunnelling microscopy with so-called lightwave electronics, which uses the oscillating carrier wave of tailored light pulses to directly manipulate electronic motion on timescales faster even than a single cycle of light. Here we build on ultrafast terahertz scanning tunnelling microscopy to access a state-selective tunnelling regime, where the peak of a terahertz electric-field waveform transiently opens an otherwise forbidden tunnelling channel through a single molecular state. It thereby removes a single electron from an individual pentacene molecule’s highest occupied molecular orbital within a time window shorter than one oscillation cycle of the terahertz wave. We exploit this effect to record approximately 100-femtosecond snapshot images of the orbital structure with sub-ångström spatial resolution, and to reveal, through pump/probe measurements, coherent molecular vibrations at terahertz frequencies directly in the time domain. We anticipate that the combination of lightwave electronics and the atomic resolution of our approach will open the door to visualizing ultrafast photochemistry and the operation of molecular electronics on the single-orbital scale.

Direct nanopatterning of polymer/silver nanoblocks under low energy electron beam irradiation.

PubMed

El Mel, Abdel-Aziz; Stephant, Nicolas; Gautier, Romain

2016-10-06

In this communication, we report on the growth, direct writing and nanopatterning of polymer/silver nanoblocks under low energy electron beam irradiation using a scanning electron microscope. The nanoblocks are produced by placing a droplet of an ethylene glycol solution containing silver nitrate and polyvinylpyrrolidone diluted in ethanol directly on a hot substrate heated up to 150 °C. Upon complete evaporation of the droplet, nanospheres, nano- and micro-triangles and nanoblocks made of silver-containing polymers, form over the substrate surface. Considering the nanoblocks as a model system, we demonstrate that such nanostructures are extremely sensitive to the e-beam extracted from the source of a scanning electron microscope operating at low acceleration voltages (between 5 and 7 kV). This sensitivity allows us to efficiently create various nanopatterns (e.g. arrays of holes, oblique slits and nanotrenches) in the material under e-beam irradiation. In addition to the possibility of writing, the nanoblocks revealed a self-healing ability allowing them to recover a relatively smooth surface after etching. Thanks to these properties, such nanomaterials can be used as a support for data writing and erasing on the nanoscale under low energy electron beam irradiation.

SURVIVAL OF SALMONELLA SPECIES IN RIVER WATER.

EPA Science Inventory

The survival of four Salmonella strains in river water microcosms was monitored using culturing techniques, direct counts, whole cell hybridization, scanning electron microscopy, and resuscitation techniques via the direct viable count method and flow cytrometry. Plate counts of...

Growth of single-layer graphene on Ge (1 0 0) by chemical vapor deposition

NASA Astrophysics Data System (ADS)

Mendoza, C. D.; Caldas, P. G.; Freire, F. L.; Maia da Costa, M. E. H.

2018-07-01

The integration of graphene into nanoelectronic devices is dependent on the availability of direct deposition processes, which can provide uniform, large-area and high-quality graphene on semiconductor substrates such as Ge or Si. In this work, we synthesised graphene directly on p-type Ge (1 0 0) substrates by chemical vapour deposition. The influence of the CH4:H2 flow ratio on the graphene growth was investigated. Raman Spectroscopy, Raman mapping, Scanning Electron Microscopy, Atomic Force Microscopy and Scanning Tunnelling Microscopy/Scanning Tunnelling Spectroscopy results showed that good quality and homogeneous monolayer graphene over a large area can be achieved on Ge substrates directly with optimal growth conditions.

Classification of Streptomyces Spore Surfaces into Five Groups

PubMed Central

Dietz, Alma; Mathews, John

1971-01-01

Streptomyces spores surfaces have been classified into five groups, smooth, warty, spiny, hairy, and rugose, by examination of carbon replicas of spores with the transmission electron microscope and by direct examination of spores with the scanning electron microscope. Images PMID:4928607

DNA Binding Peptide Directed Synthesis of Continuous DNA Nanowires for Analysis of Large DNA Molecules by Scanning Electron Microscope.

PubMed

Kim, Kyung-Il; Lee, Seonghyun; Jin, Xuelin; Kim, Su Ji; Jo, Kyubong; Lee, Jung Heon

2017-01-01

Synthesis of smooth and continuous DNA nanowires, preserving the original structure of native DNA, and allowing its analysis by scanning electron microscope (SEM), is demonstrated. Gold nanoparticles densely assembled on the DNA backbone via thiol-tagged DNA binding peptides work as seeds for metallization of DNA. This method allows whole analysis of DNA molecules with entangled 3D features. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

SURVIVAL OF SALMONELLA SPECIES IN RIVER WATER

EPA Science Inventory

The survival of four Salmonella strains in river water microcosms was monitored by culturing techniques, direct counts, whole-cell hybridization, scanning electron microscopy, and resuscitation techniques via the direct viable count method and flow cytometry. Plate counts of bact...

Direct electron-pair production by high energy heavy charged particles

NASA Technical Reports Server (NTRS)

Takahashi, Y.; Gregory, J. C.; Hayashi, T.; Dong, B. L.

1989-01-01

Direct electron pain production via virtual photons by moving charged particles is a unique electro-magnetic process having a substantial dependence on energy. Most electro-magnetic processes, including transition radiation, cease to be sensitive to the incident energy above 10 TeV/AMU. Thus, it is expected, that upon establishment of cross section and detection efficiency of this process, it may provide a new energy measuring technique above 10 TeV/AMU. Three accelerator exposures of emulsion chambers designed for measurements of direct electron-pains were performed. The objectives of the investigation were to provide the fundamental cross-section data in emulsion stacks to find the best-fit theoretical model, and to provide a calibration of measurements of direct electron-pairs in emulsion chamber configurations. This paper reports the design of the emulsion chambers, accelerator experiments, microscope measurements, and related considerations for future improvements of the measurements, and for possible applications to high energy cosmic ray experiments. Also discussed are the results from scanning 56m of emulsion tracks at 1200x magnification so that scanning efficiency is optimized. Measurements of the delta-ray range spectrum were also performed for much shorter track lengths, but with sufficiently large statistics in the number of measured delta-rays.

Establishing an Environmental Scanning System to Augment College and University Planning.

ERIC Educational Resources Information Center

Morrison, James L.

A plan to establish an environmental scanning and forecasting system for colleges and universities is discussed as a way to maximize long-range planning. After proposing a program structure, attention is directed to methods of gaining organizational acceptance, developing a comprehensive taxonomy with an electronic filing system, identifying and…

Scanning electron microscope cathodoluminescence imaging of subgrain boundaries, twins and planar deformation features in quartz

NASA Astrophysics Data System (ADS)

Hamers, M. F.; Pennock, G. M.; Drury, M. R.

2017-04-01

The study of deformation features has been of great importance to determine deformation mechanisms in quartz. Relevant microstructures in both growth and deformation processes include dislocations, subgrains, subgrain boundaries, Brazil and Dauphiné twins and planar deformation features (PDFs). Dislocations and twin boundaries are most commonly imaged using a transmission electron microscope (TEM), because these cannot directly be observed using light microscopy, in contrast to PDFs. Here, we show that red-filtered cathodoluminescence imaging in a scanning electron microscope (SEM) is a useful method to visualise subgrain boundaries, Brazil and Dauphiné twin boundaries. Because standard petrographic thin sections can be studied in the SEM, the observed structures can be directly and easily correlated to light microscopy studies. In contrast to TEM preparation methods, SEM techniques are non-destructive to the area of interest on a petrographic thin section.

Characterization of Discontinuous Coarsening Reaction Products in INCONEL® Alloy 740H® Fusion Welds

NASA Astrophysics Data System (ADS)

Bechetti, Daniel H.; Dupont, John N.; Watanabe, Masashi; de Barbadillo, John J.

2017-04-01

Characterization of γ' coarsened zones (CZs) in alloy 740H fusion welds via a variety of electron microscopy techniques was conducted. The effects of solute partitioning during nonequilibrium solidification on the amount of strengthening precipitates along the grain boundaries were evaluated via electron-probe microanalysis and scanning electron microscopy. Electron backscatter diffraction was used to present evidence for the preferential growth of CZs toward regions of lower γ' content, even if growth in that direction increases grain boundary area. Scanning electron microscopy and image analysis were used to quantify the propensity for CZs to develop along certain segments of the grain boundaries, as governed by the local variations in γ' content. Scanning transmission electron microscopy with X-ray energy-dispersive spectrometry (XEDS) was used to assess the compositions of the matrix and precipitate phases within the CZs and to quantify the segregation of alloying components to the reaction front. Thermodynamic and kinetic modeling were used to compare calculated and experimental compositions. The work presented here provides new insight into the progression of the discontinuous coarsening (DC) reaction in a complex engineering alloy.

Pervasive liquid metal based direct writing electronics with roller-ball pen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Yi; Zhang, Qin; Liu, Jing, E-mail: jliu@mail.ipc.ac.cn

A roller-ball pen enabled direct writing electronics via room temperature liquid metal ink was proposed. With the rolling to print mechanism, the metallic inks were smoothly written on flexible polymer substrate to form conductive tracks and electronic devices. The contact angle analyzer and scanning electron microscope were implemented to disclose several unique inner properties of the obtained electronics. An ever high writing resolution with line width and thickness as 200 μm and 80 μm, respectively was realized. Further, with the administration of external writing pressure, GaIn{sub 24.5} droplets embody increasing wettability on polymer which demonstrates the pervasive adaptability of themore » roller-ball pen electronics.« less

Scanning capacitance microscopy of ErAs nanoparticles embedded in GaAs pn junctions

NASA Astrophysics Data System (ADS)

Park, K. W.; Nair, H. P.; Crook, A. M.; Bank, S. R.; Yu, E. T.

2011-09-01

Scanning capacitance microscopy is used to characterize the electronic properties of ErAs nanoparticles embedded in GaAs pn junctions grown by molecular beam epitaxy. Voltage-dependent capacitance images reveal localized variations in subsurface electronic structure near buried ErAs nanoparticles at lateral length scales of 20-30 nm. Numerical modeling indicates that these variations arise from inhomogeneities in charge modulation due to Fermi level pinning behavior associated with the embedded ErAs nanoparticles. Statistical analysis of image data yields an average particle radius of 6-8 nm—well below the direct resolution limit in scanning capacitance microscopy but discernible via analysis of patterns in nanoscale capacitance images.

Tracking the ultrafast motion of a single molecule by femtosecond orbital imaging

PubMed Central

Yu, Ping; Repp, Jascha; Huber, Rupert

2017-01-01

Watching a single molecule move on its intrinsic time scale—one of the central goals of modern nanoscience—calls for measurements that combine ultrafast temporal resolution1–8 with atomic spatial resolution9–30. Steady-state experiments achieve the requisite spatial resolution, as illustrated by direct imaging of individual molecular orbitals using scanning tunnelling microscopy9–11 or the acquisition of tip-enhanced Raman and luminescence spectra with sub-molecular resolution27–29. But tracking the dynamics of a single molecule directly in the time domain faces the challenge that single-molecule excitations need to be confined to an ultrashort time window. A first step towards overcoming this challenge has combined scanning tunnelling microscopy with so-called ‘lightwave electronics”1–8, which uses the oscillating carrier wave of tailored light pulses to directly manipulate electronic motion on time scales faster even than that of a single cycle of light. Here we use such ultrafast terahertz scanning tunnelling microscopy to access a state-selective tunnelling regime, where the peak of a terahertz electric-field waveform transiently opens an otherwise forbidden tunnelling channel through a single molecular state and thereby removes a single electron from an individual pentacene molecule’s highest occupied molecular orbital within a time window shorter than one oscillation cycle of the terahertz wave. We exploit this effect to record ~100 fs snapshot images of the structure of the orbital involved, and to reveal through pump-probe measurements coherent molecular vibrations at terahertz frequencies directly in the time domain and with sub-angstrom spatial resolution. We anticipate that the combination of lightwave electronics1–8 and atomic resolution of our approach will open the door to controlling electronic motion inside individual molecules at optical clock rates. PMID:27830788

Confined states of individual type-II GaSb/GaAs quantum rings studied by cross-sectional scanning tunneling spectroscopy.

PubMed

Timm, Rainer; Eisele, Holger; Lenz, Andrea; Ivanova, Lena; Vossebürger, Vivien; Warming, Till; Bimberg, Dieter; Farrer, Ian; Ritchie, David A; Dähne, Mario

2010-10-13

Combined cross-sectional scanning tunneling microscopy and spectroscopy results reveal the interplay between the atomic structure of ring-shaped GaSb quantum dots in GaAs and the corresponding electronic properties. Hole confinement energies between 0.2 and 0.3 eV and a type-II conduction band offset of 0.1 eV are directly obtained from the data. Additionally, the hole occupancy of quantum dot states and spatially separated Coulomb-bound electron states are observed in the tunneling spectra.

Environmental scanning electron microscopy of personal and household products.

PubMed

Hoyberg, K

1997-03-01

The ability to forego sample preparation and to make observation directly in the environmental scanning electron microscope has benefited both household and personal product research at Unilever Research. Product efficacy on biological materials such as microcomedones was easily ascertained. Skin biopsies were examined in a moist state with no sample preparation. Effects of relative humidity on detergents were visually determined by recreating the necessary conditions in the microscope. Effects of cooling rates on the morphology of softener sheet actives that remained on polyester fabric were characterized via dynamic experimentation.

Ballistic-Electron-Emission Microscope

NASA Technical Reports Server (NTRS)

Kaiser, William J.; Bell, L. Douglas

1990-01-01

Ballistic-electron-emission microscope (BEEM) employs scanning tunneling-microscopy (STM) methods for nondestructive, direct electrical investigation of buried interfaces, such as interface between semiconductor and thin metal film. In BEEM, there are at least three electrodes: emitting tip, biasing electrode, and collecting electrode, receiving current crossing interface under investigation. Signal-processing device amplifies electrode signals and converts them into form usable by computer. Produces spatial images of surface by scanning tip; in addition, provides high-resolution images of buried interface under investigation. Spectroscopic information extracted by measuring collecting-electrode current as function of one of interelectrode voltages.

High-resolution imaging of living mammalian cells bound by nanobeads-connected antibodies in a medium using scanning electron-assisted dielectric microscopy

NASA Astrophysics Data System (ADS)

Okada, Tomoko; Ogura, Toshihiko

2017-02-01

Nanometre-scale-resolution imaging technologies for liquid-phase specimens are indispensable tools in various scientific fields. In biology, observing untreated living cells in a medium is essential for analysing cellular functions. However, nanoparticles that bind living cells in a medium are hard to detect directly using traditional optical or electron microscopy. Therefore, we previously developed a novel scanning electron-assisted dielectric microscope (SE-ADM) capable of nanoscale observations. This method enables observation of intact cells in aqueous conditions. Here, we use this SE-ADM system to clearly observe antibody-binding nanobeads in liquid-phase. We also report the successful direct detection of streptavidin-conjugated nanobeads binding to untreated cells in a medium via a biotin-conjugated anti-CD44 antibody. Our system is capable of obtaining clear images of cellular organelles and beads on the cells at the same time. The direct observation of living cells with nanoparticles in a medium allowed by our system may contribute the development of carriers for drug delivery systems (DDS).

Combined scanning transmission X-ray and electron microscopy for the characterization of bacterial endospores.

PubMed

Jamroskovic, Jan; Shao, Paul P; Suvorova, Elena; Barak, Imrich; Bernier-Latmani, Rizlan

2014-09-01

Endospores (also referred to as bacterial spores) are bacterial structures formed by several bacterial species of the phylum Firmicutes. Spores form as a response to environmental stress. These structures exhibit remarkable resistance to harsh environmental conditions such as exposure to heat, desiccation, and chemical oxidants. The spores include several layers of protein and peptidoglycan that surround a core harboring DNA as well as high concentrations of calcium and dipicolinic acid (DPA). A combination of scanning transmission X-ray microscopy, scanning transmission electron microscopy, and energy dispersive spectroscopy was used for the direct quantitative characterization of bacterial spores. The concentration and localization of DPA, Ca(2+) , and other elements were determined and compared for the core and cortex of spores from two distinct genera: Bacillus subtilis and Desulfotomaculum reducens. This micro-spectroscopic approach is uniquely suited for the direct study of individual bacterial spores, while classical molecular and biochemical methods access only bulk characteristics. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

Scanning electron microscopy study of adhesion in sea urchin blastulae. M.S. Thesis

NASA Technical Reports Server (NTRS)

Crowther, Susan D.

1988-01-01

The dissociation supernatant (DS) isolated by disaggregating Strongylocentrotus purpuratus blastulae in calcium- and magnesium-free seawater specifically promotes reaggregation of S. purpuratus blastula cells. The purpose of this study was to use scanning electron microscopy to examine the gross morphology of aggregates formed in the presence of DS to see if it resembles adhesion in partially dissociated blastulae. A new reaggregation procedure developed here, using large volumes of cell suspension and a large diameter of rotation, was utilized to obtain sufficient quantities of aggregates for scanning electron microscopy. The results indicate that aggregates formed in the presence of DS resemble partially dissociated intact embryos in terms of the direct cell-cell adhesion observed. DS did not cause aggregation to form as a result of the entrapment of cells in masses of extracellular material. These studies provide the groundwork for further studies using transmission electron microscopy to more precisely define the adhesive contacts made by cells in the presence of the putative adhesion molecules present in DS.

Direct identification of metallic and semiconducting single-walled carbon nanotubes in scanning electron microscopy.

PubMed

Li, Jie; He, Yujun; Han, Yimo; Liu, Kai; Wang, Jiaping; Li, Qunqing; Fan, Shoushan; Jiang, Kaili

2012-08-08

Because of their excellent electrical and optical properties, carbon nanotubes have been regarded as extremely promising candidates for high-performance electronic and optoelectronic applications. However, effective and efficient distinction and separation of metallic and semiconducting single-walled carbon nanotubes are always challenges for their practical applications. Here we show that metallic and semiconducting single-walled carbon nanotubes on SiO(2) can have obviously different contrast in scanning electron microscopy due to their conductivity difference and thus can be effectively and efficiently identified. The correlation between conductivity and contrast difference has been confirmed by using voltage-contrast scanning electron microcopy, peak force tunneling atom force microscopy, and field effect transistor testing. This phenomenon can be understood via a proposed mechanism involving the e-beam-induced surface potential of insulators and the conductivity difference between metallic and semiconducting SWCNTs. This method demonstrates great promise to achieve rapid and large-scale distinguishing between metallic and semiconducting single-walled carbon nanotubes, adding a new function to conventional SEM.

Local nanoscale strain mapping of a metallic glass during in situ testing

NASA Astrophysics Data System (ADS)

Gammer, Christoph; Ophus, Colin; Pekin, Thomas C.; Eckert, Jürgen; Minor, Andrew M.

2018-04-01

The local elastic strains during tensile deformation in a CuZrAlAg metallic glass are obtained by fitting an elliptic shape function to the characteristic amorphous ring in electron diffraction patterns. Scanning nanobeam electron diffraction enables strain mapping with a resolution of a few nanometers. Here, a fast direct electron detector is used to acquire the diffraction patterns at a sufficient speed to map the local transient strain during continuous tensile loading in situ in the transmission electron microscope. The elastic strain in tensile direction was found to increase during loading. After catastrophic fracture, a residual elastic strain that relaxes over time was observed.

Healing of broken multiwalled carbon nanotubes using very low energy electrons in SEM: a route toward complete recovery.

PubMed

Kulshrestha, Neha; Misra, Abhishek; Hazra, Kiran Shankar; Roy, Soumyendu; Bajpai, Reeti; Mohapatra, Dipti Ranjan; Misra, D S

2011-03-22

We report the healing of electrically broken multiwalled carbon nanotubes (MWNTs) using very low energy electrons (3-10 keV) in scanning electron microscopy (SEM). Current-induced breakdown caused by Joule heating has been achieved by applying suitably high voltages. The broken tubes were examined and exposed to electrons of 3-10 keV in situ in SEM with careful maneuvering of the electron beam at the broken site, which results in the mechanical joining of the tube. Electrical recovery of the same tube has been confirmed by performing the current-voltage measurements after joining. This easy approach is directly applicable for the repairing of carbon nanotubes incorporated in ready devices, such as in on-chip horizontal interconnects or on-tip probing applications, such as in scanning tunneling microscopy.

Characterization of the host response to the myxosporean parasite, Ceratomyxa shasta (Noble), by histology, scanning electron microscopy, and immunological techniques

USGS Publications Warehouse

Bartholomew, J.L.; Smith, C.E.; Rohovec, J.S.; Fryer, J.L.

1989-01-01

The tissue response of Salmo gairdneri Richardson, against the myxosporean parasite. Ceratomyxa shasta (Noble), was investigated using histological techniques, scanning electron microscopy and immunological methods. The progress of infection in C. shasta-susceptible and resistant steelhead and rainbow trout was examined by standard histological techniques and by indirect fluorescent antibody methods using monoclonal antibodies directed against C. shasta antigens. Trophozoite stages were first observed in the posterior intestine and there was indication that resistance was due to the inability of the parasite to penetrate this tissue rather than to an inflammatory response. Examination of a severely infected intestine by scanning electron microscopy showed extensive destruction of the mucosal folds of the posterior intestine. Western blotting and indirect fluorescent antibody techniques were used to investigate the immunological component of the host response. No antibodies specific for C. shasta were detected by either method.

Beam distribution reconstruction simulation for electron beam probe

NASA Astrophysics Data System (ADS)

Feng, Yong-Chun; Mao, Rui-Shi; Li, Peng; Kang, Xin-Cai; Yin, Yan; Liu, Tong; You, Yao-Yao; Chen, Yu-Cong; Zhao, Tie-Cheng; Xu, Zhi-Guo; Wang, Yan-Yu; Yuan, You-Jin

2017-07-01

An electron beam probe (EBP) is a detector which makes use of a low-intensity and low-energy electron beam to measure the transverse profile, bunch shape, beam neutralization and beam wake field of an intense beam with small dimensions. While it can be applied to many aspects, we limit our analysis to beam distribution reconstruction. This kind of detector is almost non-interceptive for all of the beam and does not disturb the machine environment. In this paper, we present the theoretical aspects behind this technique for beam distribution measurement and some simulation results of the detector involved. First, a method to obtain a parallel electron beam is introduced and a simulation code is developed. An EBP as a profile monitor for dense beams is then simulated using the fast scan method for various target beam profiles, including KV distribution, waterbag distribution, parabolic distribution, Gaussian distribution and halo distribution. Profile reconstruction from the deflected electron beam trajectory is implemented and compared with the actual profile, and the expected agreement is achieved. Furthermore, as well as fast scan, a slow scan, i.e. step-by-step scan, is considered, which lowers the requirement for hardware, i.e. Radio Frequency deflector. We calculate the three-dimensional electric field of a Gaussian distribution and simulate the electron motion in this field. In addition, a fast scan along the target beam direction and slow scan across the beam are also presented, and can provide a measurement of longitudinal distribution as well as transverse profile simultaneously. As an example, simulation results for the China Accelerator Driven Sub-critical System (CADS) and High Intensity Heavy Ion Accelerator Facility (HIAF) are given. Finally, a potential system design for an EBP is described.

Correlative Fluorescence and Electron Microscopy in 3D-Scanning Electron Microscope Perspective.

PubMed

Franks, Jonathan; Wallace, Callen T; Shibata, Masateru; Suga, Mitsuo; Erdman, Natasha; Stolz, Donna B; Watkins, Simon C

2017-04-03

The ability to correlate fluorescence microscopy (FM) and electron microscopy (EM) data obtained on biological (cell and tissue) specimens is essential to bridge the resolution gap between the data obtained by these different imaging techniques. In the past such correlations were limited to either EM navigation in two dimensions to the locations previously highlighted by fluorescence markers, or subsequent high-resolution acquisition of tomographic information using a TEM. We present a novel approach whereby a sample previously investigated by FM is embedded and subjected to sequential mechanical polishing and backscatter imaging by scanning electron microscope. The resulting three dimensional EM tomogram of the sample can be directly correlated to the FM data. © 2017 by John Wiley & Sons, Inc. Copyright © 2017 John Wiley & Sons, Inc.

Probing Dirac fermion dynamics in topological insulator Bi2Se3 films with a scanning tunneling microscope.

PubMed

Song, Can-Li; Wang, Lili; He, Ke; Ji, Shuai-Hua; Chen, Xi; Ma, Xu-Cun; Xue, Qi-Kun

2015-05-01

Scanning tunneling microscopy and spectroscopy have been used to investigate the femtosecond dynamics of Dirac fermions in the topological insulator Bi2Se3 ultrathin films. At the two-dimensional limit, bulk electrons become quantized and the quantization can be controlled by the film thickness at a single quintuple layer level. By studying the spatial decay of standing waves (quasiparticle interference patterns) off steps, we measure directly the energy and film thickness dependence of the phase relaxation length lϕ and inelastic scattering lifetime τ of topological surface-state electrons. We find that τ exhibits a remarkable (E - EF)(-2) energy dependence and increases with film thickness. We show that the features revealed are typical for electron-electron scattering between surface and bulk states.

Differences between Subjective Balanced Occlusion and Measurements Reported With T-Scan III

PubMed Central

Lila-Krasniqi, Zana; Shala, Kujtim; Krasniqi, Teuta Pustina; Bicaj, Teuta; Ahmedi, Enis; Dula, Linda; Dragusha, Arlinda Tmava; Guguvcevski, Ljuben

2017-01-01

BACKGROUND: The aetiology of Temporomandibular disorder is multifactorial, and numerous studies have addressed that occlusion may be of great importance in the pathogenesis of Temporomandibular disorder. AIM: The aim of this study is to determine if any direct relationship exists between balanced occlusion and Temporomandibular disorder and to evaluate the differences between subjective balanced occlusion and measurements reported with T-scan III electronic system. MATERIAL AND METHODS: A total of 54 subjects were divided into three groups, selection based on anamnesis-responded to a Fonseca questionnaire and clinical measurements analysed with electronic system T-scan III. In the I study group were participants with fixed dentures with prosthetic ceramic restorations. In the II study group were symptomatic participants with TMD. In the third control group were healthy participants with full arch dentition that completed a subjective questionnaire that documented the absence of jaw pain, joint noise, locking and subjects without a history of TMD. The occlusal balance was reported subjectively through Fonseca questionnaire and compared with occlusion analysed with electronic system T-scan III. RESULTS: For attributive data were used percentage of the structure. Differences in P < 0.05 were considered significant. After distributing attributive data of occlusal balance subjectively reported and compared with measurements analysed with electronic system T-scan III were found significant difference P < 0.001 in all three groups. CONCLUSION: In our study, it was concluded that there were statistically significant differences of balanced occlusion in all three groups. Also it was concluded that subjective data are not exact with measurements reported with electronic device T-scan III. PMID:28932311

Acquisition parameters optimization of a transmission electron forward scatter diffraction system in a cold-field emission scanning electron microscope for nanomaterials characterization.

PubMed

Brodusch, Nicolas; Demers, Hendrix; Trudeau, Michel; Gauvin, Raynald

2013-01-01

Transmission electron forward scatter diffraction (t-EFSD) is a new technique providing crystallographic information with high resolution on thin specimens by using a conventional electron backscatter diffraction (EBSD) system in a scanning electron microscope. In this study, the impact of tilt angle, working distance, and detector distance on the Kikuchi pattern quality were investigated in a cold-field emission scanning electron microscope (CFE-SEM). We demonstrated that t-EFSD is applicable for tilt angles ranging from -20° to -40°. Working distance (WD) should be optimized for each material by choosing the WD for which the EBSD camera screen illumination is the highest, as the number of detected electrons on the screen is directly dependent on the scattering angle. To take advantage of the best performances of the CFE-SEM, the EBSD camera should be close to the sample and oriented towards the bottom to increase forward scattered electron collection efficiency. However, specimen chamber cluttering and beam/mechanical drift are important limitations in the CFE-SEM used in this work. Finally, the importance of t-EFSD in materials science characterization was illustrated through three examples of phase identification and orientation mapping. © Wiley Periodicals, Inc.

Design of titania nanotube structures by focused laser beam direct writing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Enachi, Mihai; Stevens-Kalceff, Marion A.; Sarua, Andrei

In this work, we report on electrochemical fabrication of titania films consisting of nanotubes (NTs) and their treatment by focused laser beam. The results of sample characterization by optical and scanning electron microscopy, cathodoluminescence imaging, and Raman scattering scanning spectroscopy are compared to those inherent to specimens subjected to thermal treatment in a furnace. The obtained data demonstrate possibilities for controlling crystallographic structure of TiO{sub 2} NTs by focused laser beam direct writing. These findings open new prospects for the design and fabrication of spatial architectures based on titania nanotubes.

Solid-state optical microscope

DOEpatents

Young, I.T.

1981-01-07

A solid state optical microscope is described wherein wide-field and high-resolution images of an object are produced at a rapid rate by utilizing conventional optics with a charge-coupled photodiode array. Means for scanning in one of two orthogonal directions are provided, while the charge-coupled photodiode array scans in the other orthogonal direction. Illumination light from the object is incident upon the photodiodes, creating packets of electrons (signals) which are representative of the illuminated object. The signals are then processed, stored in a memory, and finally displayed as a video signal.

Direct-detected rapid-scan EPR at 250 MHz

NASA Astrophysics Data System (ADS)

Stoner, James W.; Szymanski, Dennis; Eaton, Sandra S.; Quine, Richard W.; Rinard, George A.; Eaton, Gareth R.

2004-09-01

EPR spectra at 250 MHz for a single crystal of lithium phthalocyanine (LiPc) in the absence of oxygen and for a deoxygenated aqueous solution of a Nycomed triarylmethyl (trityl-CD 3) radical were obtained at scan rates between 1.3 × 10 3 and 3.4 × 10 5 G/s. These scan rates are rapid relative to the reciprocals of the electron spin relaxation times (LiPc: T1=3.5 μs and T2=2.5 μs; trityl: T1=12 μs and T2=11.5 μs) and cause characteristic oscillations in the direct-detected absorption spectra. For a given scan rate, shorter values of T2 and increased inhomogeneous broadening cause less deep oscillations that damp out more quickly than for longer T2. There is excellent agreement between experimental and calculated lineshapes and signal amplitudes as a function of radiofrequency magnetic field ( B1) and scan rate. When B1 is adjusted for maximum signal amplitude as a function of scan rate, signal intensity for constant number of scans is enhanced by up to a factor of three relative to slow scans. The number of scans that can be averaged in a defined period of time is proportional to the scan rate, which further enhances signal amplitude per unit time. Longer relaxation times cause the maximum signal intensity to occur at slower scan rates. These experiments provide the first systematic characterization of direct-detected rapid-scan EPR signals.

New calculations and measurements of the Coulomb cross-section for the production of direct electron pairs by high energy nuclei

NASA Technical Reports Server (NTRS)

Derrickson, J. H.; Dake, S.; Dong, B. L.; Eby, P. B.; Fountain, W. F.; Fuki, M.; Gregory, J. C.; Hayashi, T.; Iyono, A.; King, D. T.

1989-01-01

Recently, new calculations were made of the direct Coulomb pair cross section that rely less in arbitrary parameters. More accurate calculations of the cross section down to low pair energies were made. New measurements of the total direct electron pair yield, and the energy and angular distribution of the electron pairs in emulsion were made for O-16 at 60 and 200 GeV/amu at S-32 at 200 GeV/amu which give satisfactory agreement with the new calculations. These calculations and measurements are presented along with previous accelerator measurements made of this effect during the last 40 years. The microscope scanning criteria used to identify the direct electron pairs is described. Prospects for application of the pair method to cosmic ray energy measurements in the region 10 (exp 13) to 10 (exp 15) eV/amu are discussed.

Scanning electron microscopy of cells and tissues under fully hydrated conditions

PubMed Central

Thiberge, Stephan; Nechushtan, Amotz; Sprinzak, David; Gileadi, Opher; Behar, Vered; Zik, Ory; Chowers, Yehuda; Michaeli, Shulamit; Schlessinger, Joseph; Moses, Elisha

2004-01-01

A capability for scanning electron microscopy of wet biological specimens is presented. A membrane that is transparent to electrons protects the fully hydrated sample from the vacuum. The result is a hybrid technique combining the ease of use and ability to see into cells of optical microscopy with the higher resolution of electron microscopy. The resolution of low-contrast materials is ≈100 nm, whereas in high-contrast materials the resolution can reach 10 nm. Standard immunogold techniques and heavy-metal stains can be applied and viewed in the fluid to improve the contrast. Images present a striking combination of whole-cell morphology with a wealth of internal details. A possibility for direct inspection of tissue slices transpires, imaging only the external layer of cells. Simultaneous imaging with photons excited by the electrons incorporates data on material distribution, indicating a potential for multilabeling and specific scintillating markers. PMID:14988502

Advantages of indium-tin oxide-coated glass slides in correlative scanning electron microscopy applications of uncoated cultured cells.

PubMed

Pluk, H; Stokes, D J; Lich, B; Wieringa, B; Fransen, J

2009-03-01

A method of direct visualization by correlative scanning electron microscopy (SEM) and fluorescence light microscopy of cell structures of tissue cultured cells grown on conductive glass slides is described. We show that by growing cells on indium-tin oxide (ITO)-coated glass slides, secondary electron (SE) and backscatter electron (BSE) images of uncoated cells can be obtained in high-vacuum SEM without charging artefacts. Interestingly, we observed that BSE imaging is influenced by both accelerating voltage and ITO coating thickness. By combining SE and BSE imaging with fluorescence light microscopy imaging, we were able to reveal detailed features of actin cytoskeletal and mitochondrial structures in mouse embryonic fibroblasts. We propose that the application of ITO glass as a substrate for cell culture can easily be extended and offers new opportunities for correlative light and electron microscopy studies of adherently growing cells.

Revelation of graphene-Au for direct write deposition and characterization

NASA Astrophysics Data System (ADS)

Bhandari, Shweta; Deepa, Melepurath; Joshi, Amish G.; Saxena, Aditya P.; Srivastava, Avanish K.

2011-06-01

Graphene nanosheets were prepared using a modified Hummer's method, and Au-graphene nanocomposites were fabricated by in situ reduction of a gold salt. The as-produced graphene was characterized by X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy (HR-TEM). In particular, the HR-TEM demonstrated the layered crystallites of graphene with fringe spacing of about 0.32 nm in individual sheets and the ultrafine facetted structure of about 20 to 50 nm of Au particles in graphene composite. Scanning helium ion microscopy (HIM) technique was employed to demonstrate direct write deposition on graphene by lettering with gaps down to 7 nm within the chamber of the microscope. Bare graphene and graphene-gold nanocomposites were further characterized in terms of their composition and optical and electrical properties.

Direct writing on graphene 'paper' by manipulating electrons as 'invisible ink'.

PubMed

Zhang, Wei; Zhang, Qiang; Zhao, Meng-Qiang; Kuhn, Luise Theil

2013-07-12

The combination of self-assembly (bottom up) and nano-imprint lithography (top down) is an efficient and effective way to record information at the nanoscale by writing. The use of an electron beam for writing is quite a promising strategy; however, the 'paper' on which to save the information is not yet fully realized. Herein, graphene was selected as the thinnest paper for recording information at the nanoscale. In a transmission electron microscope, in situ high precision writing and drawing were achieved on graphene nanosheets by manipulating electrons with a 1 nm probe (probe current ~2 × 10(-9) A m(-2)) in scanning transmission electron microscopy (STEM) mode. Under electron probe irradiation, the carbon atom tends to displace within a crystalline specimen, and dangling bonds are formed from the original sp(2) bonding after local carbon atoms have been kicked off. The absorbed random foreign amorphous carbon assembles along the line of the scanning direction induced by secondary electrons and is immobilized near the edge. With the ultralow secondary electron yield of the graphene, additional foreign atoms determining the accuracy of the pattern have been greatly reduced near the targeting region. Therefore, the electron probe in STEM mode serves as invisible ink for nanoscale writing and drawing. These results not only shed new light on the application of graphene by the interaction of different forms of carbon, but also illuminate the interaction of different carbon forms through electron beams.

Analysis of Scanned Probe Images for Magnetic Focusing in Graphene

DOE PAGES

Bhandari, Sagar; Lee, Gil-Ho; Kim, Philip; ...

2017-02-21

We have used cooled scanning probe microscopy (SPM) to study electron motion in nanoscale devices. The charged tip of the microscope was raster-scanned at constant height above the surface as the conductance of the device was measured. The image charge scatters electrons away, changing the path of electrons through the sample. Using this technique, we imaged cyclotron orbits that flow between two narrow contacts in the magnetic focusing regime for ballistic hBN–graphene–hBN devices. We present herein an analysis of our magnetic focusing imaging results based on the effects of the tip-created charge density dip on the motion of ballistic electrons.more » The density dip locally reduces the Fermi energy, creating a force that pushes electrons away from the tip. When the tip is above the cyclotron orbit, electrons are deflected away from the receiving contact, creating an image by reducing the transmission between contacts. The data and our analysis suggest that the graphene edge is rather rough, and electrons scattering off the edge bounce in random directions. However, when the tip is close to the edge, it can enhance transmission by bouncing electrons away from the edge, toward the receiving contact. Our results demonstrate that cooled SPM is a promising tool to investigate the motion of electrons in ballistic graphene devices.« less

Analysis of Scanned Probe Images for Magnetic Focusing in Graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhandari, Sagar; Lee, Gil-Ho; Kim, Philip

We have used cooled scanning probe microscopy (SPM) to study electron motion in nanoscale devices. The charged tip of the microscope was raster-scanned at constant height above the surface as the conductance of the device was measured. The image charge scatters electrons away, changing the path of electrons through the sample. Using this technique, we imaged cyclotron orbits that flow between two narrow contacts in the magnetic focusing regime for ballistic hBN–graphene–hBN devices. We present herein an analysis of our magnetic focusing imaging results based on the effects of the tip-created charge density dip on the motion of ballistic electrons.more » The density dip locally reduces the Fermi energy, creating a force that pushes electrons away from the tip. When the tip is above the cyclotron orbit, electrons are deflected away from the receiving contact, creating an image by reducing the transmission between contacts. The data and our analysis suggest that the graphene edge is rather rough, and electrons scattering off the edge bounce in random directions. However, when the tip is close to the edge, it can enhance transmission by bouncing electrons away from the edge, toward the receiving contact. Our results demonstrate that cooled SPM is a promising tool to investigate the motion of electrons in ballistic graphene devices.« less

Surface morphology and dislocation characteristics near the surface of 4H-SiC wafer using multi-directional scanning transmission electron microscopy.

PubMed

Sato, Takahiro; Orai, Yoshihisa; Suzuki, Yuya; Ito, Hiroyuki; Isshiki, Toshiyuki; Fukui, Munetoshi; Nakamura, Kuniyasu; Schamp, C T

2017-10-01

To improve the reliability of silicon carbide (SiC) electronic power devices, the characteristics of various kinds of crystal defects should be precisely understood. Of particular importance is understanding the correlation between the surface morphology and the near surface dislocations. In order to analyze the dislocations near the surface of 4H-SiC wafers, a dislocation analysis protocol has been developed. This protocol consists of the following process: (1) inspection of surface defects using low energy scanning electron microscopy (LESEM), (2) identification of small and shallow etch pits using KOH low temperature etching, (3) classification of etch pits using LESEM, (4) specimen preparation of several hundred nanometer thick sample using the in-situ focused ion beam micro-sampling® technique, (5) crystallographic analysis using the selected diffraction mode of the scanning transmission electron microscope (STEM), and (6) determination of the Burgers vector using multi-directional STEM (MD-STEM). The results show a correlation between the triangular terrace shaped surface defects and an hexagonal etch pit arising from threading dislocations, linear shaped surface defects and elliptical shaped etch pits arising from basal plane dislocations. Through the observation of the sample from two orthogonal directions via the MD-STEM technique, a basal plane dislocation is found to dissociate into an extended dislocation bound by two partial dislocations. A protocol developed and presented in this paper enables one to correlate near surface defects of a 4H-SiC wafer with the root cause dislocations giving rise to those surface defects. © The Author 2017. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buck, E.C.; Dietz, N.L.; Bates, J.K.

Uranium contaminated soils from the Fernald Operation Site, Ohio, have been examined by a combination of optical microscopy, scanning electron microscopy with backscattered electron detection (SEM/BSE), and analytical electron microscopy (AEM). A method is described for preparing of transmission electron microscopy (TEM) thin sections by ultramicrotomy. By using these thin sections, SEM and TEM images can be compared directly. Uranium was found in iron oxides, silicates (soddyite), phosphates (autunites), and fluorite. Little uranium was associated with clays. The distribution of uranium phases was found to be inhomogeneous at the microscopic level.

Direct Measurement of Polarization-Induced Fields in GaN/AlN by Nano-Beam Electron Diffraction

NASA Astrophysics Data System (ADS)

Carvalho, Daniel; Müller-Caspary, Knut; Schowalter, Marco; Grieb, Tim; Mehrtens, Thorsten; Rosenauer, Andreas; Ben, Teresa; García, Rafael; Redondo-Cubero, Andrés; Lorenz, Katharina; Daudin, Bruno; Morales, Francisco M.

2016-06-01

The built-in piezoelectric fields in group III-nitrides can act as road blocks on the way to maximizing the efficiency of opto-electronic devices. In order to overcome this limitation, a proper characterization of these fields is necessary. In this work nano-beam electron diffraction in scanning transmission electron microscopy mode has been used to simultaneously measure the strain state and the induced piezoelectric fields in a GaN/AlN multiple quantum well system.

Revolving scanning transmission electron microscopy: correcting sample drift distortion without prior knowledge.

PubMed

Sang, Xiahan; LeBeau, James M

2014-03-01

We report the development of revolving scanning transmission electron microscopy--RevSTEM--a technique that enables characterization and removal of sample drift distortion from atomic resolution images without the need for a priori crystal structure information. To measure and correct the distortion, we acquire an image series while rotating the scan coordinate system between successive frames. Through theory and experiment, we show that the revolving image series captures the information necessary to analyze sample drift rate and direction. At atomic resolution, we quantify the image distortion using the projective standard deviation, a rapid, real-space method to directly measure lattice vector angles. By fitting these angles to a physical model, we show that the refined drift parameters provide the input needed to correct distortion across the series. We demonstrate that RevSTEM simultaneously removes the need for a priori structure information to correct distortion, leads to a dramatically improved signal-to-noise ratio, and enables picometer precision and accuracy regardless of drift rate. Copyright © 2013 Elsevier B.V. All rights reserved.

Graphene templated Directional Growth of an Inorganic Nanowire

DTIC Science & Technology

2015-03-23

ammonium persulphate, (NH4)2S2O8, at room tempera- ture for 17 h (Fig. 1a). Various types of gold precursor, such as gold nanoparticles or gold...directions and grain boundaries in polycrystalline graphene using TEM or even scanning electron microscopy (SEM), as shown in Fig. 1g, h . Because the...directionGraphene Nanowire Grain boundary Nanowire axis directions g h e f i Figure 1 | Directional growth of inorganic nanowires on graphene. a

Synthesis and characterization of bulk metallic glasses prepared by laser direct deposition

NASA Astrophysics Data System (ADS)

Ye, Xiaoyang

Fe-based and Zr-based metallic glasses have attracted extensive interest for structural applications due to their excellent glass forming ability, superior mechanical properties, unique thermal and corrosion properties. In this study, the feasibility of synthesizing metallic glasses with good ductility by laser direct deposition is explored. Both in-situ synthesis with elemental powder mixture and ex-situ synthesis with prealloyed powder are discussed. Microstructure and properties of laser direct deposited metallic glass composites are analyzed. Synthesis of Fe-Cr-Mo-W-Mn-C-Si-B metallic glass composite with a large fraction of amorphous phase was accomplished using laser direct deposition. X-ray diffraction (XRD) and transmission electron microscopy investigations revealed the existence of amorphous structure. Microstructure analyses by optical microscopy and scanning electron microscopy (SEM) indicated the periodically repeated microstructures of amorphous and crystalline phases. Partially crystallized structure brought by laser reheating and remelting during subsequent laser scans aggregated in the overlapping area between each scan. XRD analysis showed that the crystalline particle embedded in the amorphous matrix was Cr 1.07Fe18.93 phase. No significant microstructural differences were found from the first to the last layer. Microhardness of the amorphous phase (HV0.2 1591) showed a much higher value than that of the crystalline phase (HV0.2 947). Macrohardness of the top layer had a value close to the microhardness of the amorphous region. Wear resistance property of deposited layers showed a significant improvement with the increased fraction of amorphous phase. Zr65Al10Ni10Cu15 amorphous composites with a large fraction of amorphous phase were in-situ synthesized by laser direct deposition. X-ray diffraction confirmed the existence of both amorphous and crystalline phases. Laser parameters were optimized in order to increase the fraction of amorphous phase. The microstructure analysis by scanning electron microscopy revealed the deposited structure was composed of periodically repeated amorphous and crystalline phases. Overlapping regions with nanoparticles aggregated were crystallized by laser reheating and remelting processes during subsequent laser scans. Vickers microhardness of the amorphous region showed around 35% higher than that of crystalline region. Average hardness obtained by a Rockwell macrohardness tester was very close to the microhardness of the amorphous region. The compression test showed that the fracture strain of Zr65Al10Ni10Cu15 amorphous composites was enhanced from less than 2% to as high as 5.7%, compared with fully amorphous metallic glass. Differential scanning calorimetry test results further revealed the amorphous structure and glass transition temperature Tg was observed to be around 655K. In 3 mol/L NaCl solution, laser direct deposited amorphous composites exhibited distinctly improved corrosion resistance, compared with fully-crystallized samples.

Evaluating bandgap distributions of carbon nanotubes via scanning electron microscopy imaging of the Schottky barriers.

PubMed

He, Yujun; Zhang, Jin; Li, Dongqi; Wang, Jiangtao; Wu, Qiong; Wei, Yang; Zhang, Lina; Wang, Jiaping; Liu, Peng; Li, Qunqing; Fan, Shoushan; Jiang, Kaili

2013-01-01

We show that the Schottky barrier at the metal-single walled carbon nanotube (SWCNT) contact can be clearly observed in scanning electron microscopy (SEM) images as a bright contrast segment with length up to micrometers due to the space charge distribution in the depletion region. The lengths of the charge depletion increase with the diameters of semiconducting SWCNTs (s-SWCNTs) when connected to one metal electrode, which enables direct and efficient evaluation of the bandgap distributions of s-SWCNTs. Moreover, this approach can also be applied for a wide variety of semiconducting nanomaterials, adding a new function to conventional SEM.

Towards atomic scale engineering of rare-earth-doped SiAlON ceramics through aberration-corrected scanning transmission electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yurdakul, Hilmi; Idrobo Tapia, Juan C; Pennycook, Stephen J

2011-01-01

Direct visualization of rare earths in {alpha}- and {beta}-SiAlON unit-cells is performed through Z-contrast imaging technique in an aberration-corrected scanning transmission electron microscope. The preferential occupation of Yb and Ce atoms in different interstitial locations of {beta}-SiAlON lattice is demonstrated, yielding higher solubility for Yb than Ce. The triangular-like host sites in {alpha}-SiAlON unit cell accommodate more Ce atoms than hexagonal sites in {beta}-SiAlON. We think that our results will be applicable as guidelines for many kinds of rare-earth-doped materials.

Benchmark studies of the gyro-Landau-fluid code and gyro-kinetic codes on kinetic ballooning modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, T. F.; Lawrence Livermore National Laboratory, Livermore, California 94550; Xu, X. Q.

2016-03-15

A Gyro-Landau-Fluid (GLF) 3 + 1 model has been recently implemented in BOUT++ framework, which contains full Finite-Larmor-Radius effects, Landau damping, and toroidal resonance [Ma et al., Phys. Plasmas 22, 055903 (2015)]. A linear global beta scan has been conducted using the JET-like circular equilibria (cbm18 series), showing that the unstable modes are kinetic ballooning modes (KBMs). In this work, we use the GYRO code, which is a gyrokinetic continuum code widely used for simulation of the plasma microturbulence, to benchmark with GLF 3 + 1 code on KBMs. To verify our code on the KBM case, we first perform the beta scan basedmore » on “Cyclone base case parameter set.” We find that the growth rate is almost the same for two codes, and the KBM mode is further destabilized as beta increases. For JET-like global circular equilibria, as the modes localize in peak pressure gradient region, a linear local beta scan using the same set of equilibria has been performed at this position for comparison. With the drift kinetic electron module in the GYRO code by including small electron-electron collision to damp electron modes, GYRO generated mode structures and parity suggest that they are kinetic ballooning modes, and the growth rate is comparable to the GLF results. However, a radial scan of the pedestal for a particular set of cbm18 equilibria, using GYRO code, shows different trends for the low-n and high-n modes. The low-n modes show that the linear growth rate peaks at peak pressure gradient position as GLF results. However, for high-n modes, the growth rate of the most unstable mode shifts outward to the bottom of pedestal and the real frequency of what was originally the KBMs in ion diamagnetic drift direction steadily approaches and crosses over to the electron diamagnetic drift direction.« less

A new FIB fabrication method for micropillar specimens for three-dimensional observation using scanning transmission electron microscopy.

PubMed

Fukuda, Muneyuki; Tomimatsu, Satoshi; Nakamura, Kuniyasu; Koguchi, Masanari; Shichi, Hiroyasu; Umemura, Kaoru

2004-01-01

A new method to prepare micropillar specimens with a high aspect ratio that is suitable for three-dimensional scanning transmission electron microscopy (3D-STEM) was developed. The key features of the micropillar fabrication are: first, microsampling to extract a small piece including the structure of interest in an IC chip, and second, an ion-beam with an incident direction of 60 degrees to the pillar's axis that enables the parallel sidewalls of the pillar to be produced with a high aspect ratio. A memory-cell structure (length: 6 microm; width: 300 x 500 nm) was fabricated in the micropillar and observed from various directions with a 3D-STEM. A planiform capacitor covered with granular surfaces and a solid crossing gate and metal lines was successfully observed threedimensionally at a resolution of approximately 5 nm.

Direct observation of Sr vacancies in SrTiO 3 by quantitative scanning transmission electron microscopy

DOE PAGES

Kim, Honggyu; Zhang, Jack Y.; Raghavan, Santosh; ...

2016-12-22

Unveiling the identity, spatial configuration, and microscopic structure of point defects is one of the key challenges in materials science. Here, we demonstrate that quantitative scanning transmission electron microscopy (STEM) can be used to directly observe Sr vacancies in SrTiO 3 and to determine the atom column relaxations around them. By combining recent advances in quantitative STEM, including variableangle, high-angle annular dark-field imaging and rigid registration methods, with frozen phonon multislice image simulations, we identify which Sr columns contain vacancies and quantify the number of vacancies in them. Here, picometer precision measurements of the surrounding atom column positions show thatmore » the nearest-neighbor Ti atoms are displaced away from the Sr vacancies. The results open up a new methodology for studying the microscopic mechanisms by which point defects control materials properties.« less

Direct observation of Sr vacancies in SrTiO 3 by quantitative scanning transmission electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Honggyu; Zhang, Jack Y.; Raghavan, Santosh

Unveiling the identity, spatial configuration, and microscopic structure of point defects is one of the key challenges in materials science. Here, we demonstrate that quantitative scanning transmission electron microscopy (STEM) can be used to directly observe Sr vacancies in SrTiO 3 and to determine the atom column relaxations around them. By combining recent advances in quantitative STEM, including variableangle, high-angle annular dark-field imaging and rigid registration methods, with frozen phonon multislice image simulations, we identify which Sr columns contain vacancies and quantify the number of vacancies in them. Here, picometer precision measurements of the surrounding atom column positions show thatmore » the nearest-neighbor Ti atoms are displaced away from the Sr vacancies. The results open up a new methodology for studying the microscopic mechanisms by which point defects control materials properties.« less

Imaging of nonlocal hot-electron energy dissipation via shot noise.

PubMed

Weng, Qianchun; Komiyama, Susumu; Yang, Le; An, Zhenghua; Chen, Pingping; Biehs, Svend-Age; Kajihara, Yusuke; Lu, Wei

2018-05-18

In modern microelectronic devices, hot electrons accelerate, scatter, and dissipate energy in nanoscale dimensions. Despite recent progress in nanothermometry, direct real-space mapping of hot-electron energy dissipation is challenging because existing techniques are restricted to probing the lattice rather than the electrons. We realize electronic nanothermometry by measuring local current fluctuations, or shot noise, associated with ultrafast hot-electron kinetic processes (~21 terahertz). Exploiting a scanning and contact-free tungsten tip as a local noise probe, we directly visualize hot-electron distributions before their thermal equilibration with the host gallium arsenide/aluminium gallium arsenide crystal lattice. With nanoconstriction devices, we reveal unexpected nonlocal energy dissipation at room temperature, which is reminiscent of ballistic transport of low-temperature quantum conductors. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gill, Tobias G.; Fleurence, Antoine; Warner, Ben

We observe a new two-dimensional (2D) silicon crystal, using low energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) and it's formed by depositing additional Si atoms onto spontaneously-formed epitaxial silicene on a ZrB 2 thin film. From scanning tunnelling spectroscopy (STS) studies, we find that this atomically-thin layered silicon has distinctly different electronic properties. Angle resolved photoelectron spectroscopy (ARPES) reveals that, in sharp contrast to epitaxial silicene, the layered silicon exhibits significantly enhanced density of states at the Fermi level resulting from newly formed metallic bands. Furthermore, the 2D growth of this material could allow for direct contacting tomore » the silicene surface and demonstrates the dramatic changes in electronic structure that can occur by the addition of even a single monolayer amount of material in 2D systems.« less

Pioneer Venus Orbiter planar retarding potential analyzer plasma experiment

NASA Technical Reports Server (NTRS)

Knudsen, W. C.; Bakke, J.; Spenner, K.; Novak, V.

1980-01-01

The retarding potential analyzer (RPA) on the Pioneer Venus Orbiter Mission measures most of the thermal plasma parameters within and near the Venusian ionosphere. Parameters include total ion concentration, concentrations of the more abundant ions, ion temperatures, ion drift velocity, electron temperature, and low-energy (0-50 eV) electron distribution function. Several functions not previously used in RPA's were developed and incorporated into this instrument to accomplish these measurements on a spinning spacecraft with a small bit rate. The more significant functions include automatic electrometer ranging with background current compensation; digital, quadratic retarding potential step generation for the ion and low-energy electron scans; a current sampling interval of 2 ms throughout all scans; digital logic inflection point detection and data selection; and automatic ram direction detection.

Disparity of secondary electron emission in ferroelectric domains of YMnO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Shaobo; Deng, S. Q.; Yuan, Wenjuan

2015-07-20

The applications of multiferroic materials require our understanding about the behaviors of domains with different polarization directions. Taking advantage of the scanning electron microscope, we investigate the polar surface of single crystal YMnO{sub 3} sample in secondary electron (SE) mode. By slowing down the scanning speed of electron beam, the negative surface potential of YMnO{sub 3} can be realized, and the domain contrast can be correspondingly changed. Under this experimental condition, with the help of a homemade Faraday cup, the difference of intrinsic SE emission coefficients of antiparallel domains is measured to be 0.12 and the downward polarization domains showmore » a larger SE emission ability. Our results indicate that the total SE emission of this material can be altered by changing the ratio of the antiparallel domains, which provide an avenue for device design with this kind of materials.« less

Probing plasmons in three dimensions by combining complementary spectroscopies in a scanning transmission electron microscope

DOE PAGES

Hachtel, Jordan A.; Marvinney, Claire; Mouti, Anas; ...

2016-03-02

The nanoscale optical response of surface plasmons in three-dimensional metallic nanostructures plays an important role in many nanotechnology applications, where precise spatial and spectral characteristics of plasmonic elements control device performance. Electron energy loss spectroscopy (EELS) and cathodoluminescence (CL) within a scanning transmission electron microscope have proven to be valuable tools for studying plasmonics at the nanoscale. Each technique has been used separately, producing three-dimensional reconstructions through tomography, often aided by simulations for complete characterization. Here we demonstrate that the complementary nature of the two techniques, namely that EELS probes beam-induced electronic excitations while CL probes radiative decay, allows usmore » to directly obtain a spatially- and spectrally-resolved picture of the plasmonic characteristics of nanostructures in three dimensions. Furthermore, the approach enables nanoparticle-by-nanoparticle plasmonic analysis in three dimensions to aid in the design of diverse nanoplasmonic applications.« less

Characterizing Surfaces of the Wide Bandgap Semiconductor Ilmenite with Scanning Probe Microcopies

NASA Technical Reports Server (NTRS)

Wilkins, R.; Powell, Kirk St. A.

1997-01-01

Ilmenite (FeTiO3) is a wide bandgap semiconductor with an energy gap of about 2.5eV. Initial radiation studies indicate that ilmenite has properties suited for radiation tolerant applications, as well as a variety of other electronic applications. Two scanning probe microscopy methods have been used to characterize the surface of samples taken from Czochralski grown single crystals. The two methods, atomic force microscopy (AFM) and scanning tunneling microscopy (STM), are based on different physical principles and therefore provide different information about the samples. AFM provides a direct, three-dimensional image of the surface of the samples, while STM give a convolution of topographic and electronic properties of the surface. We will discuss the differences between the methods and present preliminary data of each method for ilmenite samples.

Electronic Bandgap and Edge Reconstruction in Phosphorene Materials

DOE PAGES

Liang, Liangbo; Wang, Jun; Lin, Wenzhi; ...

2014-11-12

Single-layer black phosphorous (BP), or phosphorene, is a highly-anisotropic two-dimensional elemental material possessing promising semiconductor properties for flexible electronics. However, the direct bandgap of single-layer black phosphorus predicted theoretically has not been directly measured, and the properties of its edges have not been considered in detail. Here we report atomic scale electronic variation related to strain-induced anisotropic deformation of the puckered honeycomb structure of freshly cleaved black phosphorus using a highresolved scanning tunneling spectroscopy (STS) survey along the light (x) and heavy (y) effective mass directions. Through a combination of STS measurements and first-principles calculations, a model for edge reconstructionmore » is also determined. The reconstruction is shown to self-passivate any dangling bond by switching the oxidation state of phosphorous from +3 to +5.« less

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.

Mass Determination of Rous Sarcoma Virus Virions by Scanning Transmission Electron Microscopy

PubMed Central

Vogt, Volker M.; Simon, Martha N.

1999-01-01

The internal structural protein of retroviruses, Gag, comprises most of the mass of the virion, and Gag itself can give rise to virus-like particles when expressed in appropriate cells. Previously the stoichiometry of Gag in virions was inferred from indirect measurements carried out 2 decades ago. We now have directly determined the masses of individual particles of the prototypic avian retrovirus, Rous sarcoma virus (RSV), by using scanning transmission electron microscopy. In this technique, the number of scattered electrons in the dark-field image integrated over an individual freeze-dried virus particle on a grid is directly proportional to its mass. The RSV virions had a mean mass of 2.5 × 108 Da, corresponding to about 1,500 Gag molecules per virion. The population of virions was not homogeneous, with about one-third to two-thirds of the virions deviating from the mean by more than 10% of the mass in two respective preparations. The mean masses for virions carrying genomes of 7.4 or 9.3 kb were indistinguishable, suggesting that mass variability is not due to differences in RNA incorporation. PMID:10400808

A glucose biosensor based on direct electrochemistry of glucose oxidase immobilized on nitrogen-doped carbon nanotubes.

PubMed

Deng, Shengyuan; Jian, Guoqiang; Lei, Jianping; Hu, Zheng; Ju, Huangxian

2009-10-15

A novel biosensor for glucose was prepared by immobilizing glucose oxidase (GOx) on nitrogen-doped carbon nanotubes (CNx-MWNTs) modified electrode. The CNx-MWNTs membrane showed an excellent electrocatalytic activity toward the reduction of O(2) due to its diatomic side-on adsorption on CNx-MWNTs. The nitrogen doping accelerated the electron transfer from electrode surface to the immobilized GOx, leading to the direct electrochemistry of GOx. The biofunctional surface showed good biocompatibility, excellent electron-conductive network and large surface-to-volume ratio, which were characterized by scanning electron microscopy, contact angle and electrochemical impedance technique. The direct electron transfer of immobilized GOx led to stable amperometric biosensing for glucose with a linear range from 0.02 to 1.02 mM and a detection limit of 0.01 mM (S/N=3). These results indicated that CNx-MWNTs are good candidate material for construction of the third-generation enzyme biosensors based on the direct electrochemistry of immobilized enzymes.

Direct observation of the actin filament by tip-scan atomic force microscopy

PubMed Central

Narita, Akihiro; Usukura, Eiji; Yagi, Akira; Tateyama, Kiyohiko; Akizuki, Shogo; Kikumoto, Mahito; Matsumoto, Tomoharu; Maéda, Yuichiro; Ito, Shuichi; Usukura, Jiro

2016-01-01

Actin filaments, the actin–myosin complex and the actin–tropomyosin complex were observed by a tip-scan atomic force microscope (AFM), which was recently developed by Olympus as the AFM part of a correlative microscope. This newly developed AFM uses cantilevers of similar size as stage-scan AFMs to improve substantially the spatial and temporal resolution. Such an approach has previously never been possible by a tip-scan system, in which a cantilever moves in the x, y and z directions. We evaluated the performance of this developed tip-scan AFM by observing the molecular structure of actin filaments and the actin–tropomyosin complex. In the image of the actin filament, the molecular interval of the actin subunits (∼5.5 nm) was clearly observed as stripes. From the shape of the stripes, the polarity of the actin filament was directly determined and the results were consistent with the polarity determined by myosin binding. In the image of the actin–tropomyosin complex, each tropomyosin molecule (∼2 nm in diameter) on the actin filament was directly observed without averaging images of different molecules. Each tropomyosin molecule on the actin filament has never been directly observed by AFM or electron microscopy. Thus, our developed tip-scan AFM offers significant potential in observing purified proteins and cellular structures at nanometer resolution. Current results represent an important step in the development of a new correlative microscope to observe nm-order structures at an acceptable frame rate (∼10 s/frame) by AFM at the position indicated by the fluorescent dye observed under a light microscope. PMID:27242058

Virtual scanning tunneling microscopy: A local spectroscopic probe of two-dimensional electron systems

NASA Astrophysics Data System (ADS)

Sciambi, A.; Pelliccione, M.; Bank, S. R.; Gossard, A. C.; Goldhaber-Gordon, D.

2010-09-01

We propose a probe technique capable of performing local low-temperature spectroscopy on a two-dimensional electron system (2DES) in a semiconductor heterostructure. Motivated by predicted spatially-structured electron phases, the probe uses a charged metal tip to induce electrons to tunnel locally, directly below the tip, from a "probe" 2DES to a "subject" 2DES of interest. We test this concept with large-area (nonscanning) tunneling measurements, and predict a high spatial resolution and spectroscopic capability, with minimal influence on the physics in the subject 2DES.

Efficient linear phase contrast in scanning transmission electron microscopy with matched illumination and detector interferometry

DOE PAGES

Ophus, Colin; Ciston, Jim; Pierce, Jordan; ...

2016-02-29

The ability to image light elements in soft matter at atomic resolution enables unprecedented insight into the structure and properties of molecular heterostructures and beam-sensitive nanomaterials. In this study, we introduce a scanning transmission electron microscopy technique combining a pre-specimen phase plate designed to produce a probe with structured phase with a high-speed direct electron detector to generate nearly linear contrast images with high efficiency. We demonstrate this method by using both experiment and simulation to simultaneously image the atomic-scale structure of weakly scattering amorphous carbon and strongly scattering gold nanoparticles. Our method demonstrates strong contrast for both materials, makingmore » it a promising candidate for structural determination of heterogeneous soft/hard matter samples even at low electron doses comparable to traditional phase-contrast transmission electron microscopy. Ultimately, simulated images demonstrate the extension of this technique to the challenging problem of structural determination of biological material at the surface of inorganic crystals.« less

Efficient linear phase contrast in scanning transmission electron microscopy with matched illumination and detector interferometry.

PubMed

Ophus, Colin; Ciston, Jim; Pierce, Jordan; Harvey, Tyler R; Chess, Jordan; McMorran, Benjamin J; Czarnik, Cory; Rose, Harald H; Ercius, Peter

2016-02-29

The ability to image light elements in soft matter at atomic resolution enables unprecedented insight into the structure and properties of molecular heterostructures and beam-sensitive nanomaterials. In this study, we introduce a scanning transmission electron microscopy technique combining a pre-specimen phase plate designed to produce a probe with structured phase with a high-speed direct electron detector to generate nearly linear contrast images with high efficiency. We demonstrate this method by using both experiment and simulation to simultaneously image the atomic-scale structure of weakly scattering amorphous carbon and strongly scattering gold nanoparticles. Our method demonstrates strong contrast for both materials, making it a promising candidate for structural determination of heterogeneous soft/hard matter samples even at low electron doses comparable to traditional phase-contrast transmission electron microscopy. Simulated images demonstrate the extension of this technique to the challenging problem of structural determination of biological material at the surface of inorganic crystals.

Efficient linear phase contrast in scanning transmission electron microscopy with matched illumination and detector interferometry

PubMed Central

Ophus, Colin; Ciston, Jim; Pierce, Jordan; Harvey, Tyler R.; Chess, Jordan; McMorran, Benjamin J.; Czarnik, Cory; Rose, Harald H.; Ercius, Peter

2016-01-01

The ability to image light elements in soft matter at atomic resolution enables unprecedented insight into the structure and properties of molecular heterostructures and beam-sensitive nanomaterials. In this study, we introduce a scanning transmission electron microscopy technique combining a pre-specimen phase plate designed to produce a probe with structured phase with a high-speed direct electron detector to generate nearly linear contrast images with high efficiency. We demonstrate this method by using both experiment and simulation to simultaneously image the atomic-scale structure of weakly scattering amorphous carbon and strongly scattering gold nanoparticles. Our method demonstrates strong contrast for both materials, making it a promising candidate for structural determination of heterogeneous soft/hard matter samples even at low electron doses comparable to traditional phase-contrast transmission electron microscopy. Simulated images demonstrate the extension of this technique to the challenging problem of structural determination of biological material at the surface of inorganic crystals. PMID:26923483

Highlighting material structure with transmission electron diffraction correlation coefficient maps.

PubMed

Kiss, Ákos K; Rauch, Edgar F; Lábár, János L

2016-04-01

Correlation coefficient maps are constructed by computing the differences between neighboring diffraction patterns collected in a transmission electron microscope in scanning mode. The maps are shown to highlight material structural features like grain boundaries, second phase particles or dislocations. The inclination of the inner crystal interfaces are directly deduced from the resulting contrast. Copyright © 2016 Elsevier B.V. All rights reserved.

Symposium LL: Nanowires--Synthesis Properties Assembly and Application

DTIC Science & Technology

2010-09-10

dedicated hard x - ray microscopy beamline is operated in partnership with the Advanced Photon Source to provide fluorescence, diffraction, and...characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X - ray diffraction (XRD) measurements, proving it to be...Investigation of Preferred Growth Direction of GaN Nanorods by Synchrotron X - ray Reciprocal Space Mapping. Yuri Sohn1, Sanghwa Lee1, Chinkyo Kim1 and Dong

Spatially resolving density-dependent screening around a single charged atom in graphene

NASA Astrophysics Data System (ADS)

Wong, Dillon; Corsetti, Fabiano; Wang, Yang; Brar, Victor W.; Tsai, Hsin-Zon; Wu, Qiong; Kawakami, Roland K.; Zettl, Alex; Mostofi, Arash A.; Lischner, Johannes; Crommie, Michael F.

2017-05-01

Electrons in two-dimensional graphene sheets behave as interacting chiral Dirac fermions and have unique screening properties due to their symmetry and reduced dimensionality. By using a combination of scanning tunneling spectroscopy measurements and theoretical modeling we have characterized how graphene's massless charge carriers screen individual charged calcium atoms. A backgated graphene device configuration has allowed us to directly visualize how the screening length for this system can be tuned with carrier density. Our results provide insight into electron-impurity and electron-electron interactions in a relativistic setting with important consequences for other graphene-based electronic devices.

Amoeba proteus displays a walking form of locomotion.

PubMed

Cameron, Ivan; Rinaldi, Robert A; Kirby, Gerald; Davidson, David

2007-08-01

This report deals with observations on the directional locomotion of amoeba before and after fixation and scanning electron microscopy. The study was aimed at visualization of the stepwise events of directional movements. After the analysis of the data it is proposed that the amoeba undergoes a sequence of movement events that can be defined as a walking form of locomotion.

Cryogenic Pressure Calibrator for Wide Temperature Electronically Scanned (ESP) Pressure Modules

NASA Technical Reports Server (NTRS)

Faulcon, Nettie D.

2001-01-01

Electronically scanned pressure (ESP) modules have been developed that can operate in ambient and in cryogenic environments, particularly Langley's National Transonic Facility (NTF). Because they can operate directly in a cryogenic environment, their use eliminates many of the operational problems associated with using conventional modules at low temperatures. To ensure the accuracy of these new instruments, calibration was conducted in a laboratory simulating the environmental conditions of NTF. This paper discusses the calibration process by means of the simulation laboratory, the system inputs and outputs and the analysis of the calibration data. Calibration results of module M4, a wide temperature ESP module with 16 ports and a pressure range of +/- 4 psid are given.

Phase contrast scanning transmission electron microscopy imaging of light and heavy atoms at the limit of contrast and resolution.

PubMed

Yücelen, Emrah; Lazić, Ivan; Bosch, Eric G T

2018-02-08

Using state of the art scanning transmission electron microscopy (STEM) it is nowadays possible to directly image single atomic columns at sub-Å resolution. In standard (high angle) annular dark field STEM ((HA)ADF-STEM), however, light elements are usually invisible when imaged together with heavier elements in one image. Here we demonstrate the capability of the recently introduced Integrated Differential Phase Contrast STEM (iDPC-STEM) technique to image both light and heavy atoms in a thin sample at sub-Å resolution. We use the technique to resolve both the Gallium and Nitrogen dumbbells in a GaN crystal in [[Formula: see text

Molecular charge distribution and dispersion of electronic states in the contact layer between pentacene and Cu(119) and beyond

NASA Astrophysics Data System (ADS)

Annese, E.; Fujii, J.; Baldacchini, C.; Zhou, B.; Viol, C. E.; Vobornik, I.; Betti, M. G.; Rossi, G.

2008-05-01

The interaction of pentacene molecules in contact with the Cu(119) stepped surface has been directly imaged by scanning tunneling microscopy and analyzed by angle resolved photoemission spectroscopy. Interacting molecules, which are in contact with copper, generate dispersive electronic states associated with a perturbed electron charge density distribution of the molecular orbitals. In contrast, the electron charge density of molecules of the pentacene on top of the first layer, which is not in direct contact with the Cu surface, shows an intramolecular structure very similar to that of the free molecule. Our results indicate that the delocalization of the molecular states in the pentacene/Cu system is confined to the very first molecular layer at the interface.

Magnified pseudo-elemental map of atomic column obtained by Moiré method in scanning transmission electron microscopy.

PubMed

Kondo, Yukihito; Okunishi, Eiji

2014-10-01

Moiré method in scanning transmission electron microscopy allows observing a magnified two-dimensional atomic column elemental map of a higher pixel resolution with a lower electron dose unlike conventional atomic column mapping. The magnification of the map is determined by the ratio between the pixel size and the lattice spacing. With proper ratios for the x and y directions, we could observe magnified elemental maps, homothetic to the atomic arrangement in the sample of SrTiO3 [0 0 1]. The map showed peaks at all expected oxygen sites in SrTiO3 [0 0 1]. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

A Shear Strain Route Dependency of Martensite Formation in 316L Stainless Steel.

PubMed

Kang, Suk Hoon; Kim, Tae Kyu; Jang, Jinsung; Oh, Kyu Hwan

2015-06-01

In this study, the effect of simple shearing on microstructure evolution and mechanical properties of 316L austenitic stainless steel were investigated. Two different shear strain routes were obtained by twisting cylindrical specimens in the forward and backward directions. The strain-induced martensite phase was effectively obtained by alteration of the routes. Formation of the martensite phase clearly resulted in significant hardening of the steel. Grain-size reduction and strain-induced martensitic transformation within the deformed structures of the strained specimens were characterized by scanning electron microscopy - electron back-scattered diffraction, X-ray diffraction, and the TEM-ASTAR (transmission electron microscopy - analytical scanning transmission atomic resolution, automatic crystal orientation/phase mapping for TEM) system. Significant numbers of twin networks were formed by alteration of the shear strain routes, and the martensite phases were nucleated at the twin interfaces.

Direct observation for atomically flat and ordered vertical {111} side-surfaces on three-dimensionally figured Si(110) substrate using scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Yang, Haoyu; Hattori, Azusa N.; Ohata, Akinori; Takemoto, Shohei; Hattori, Ken; Daimon, Hiroshi; Tanaka, Hidekazu

2017-11-01

A three-dimensional Si{111} vertical side-surface structure on a Si(110) wafer was fabricated by reactive ion etching (RIE) followed by wet-etching and flash-annealing treatments. The side-surface was studied with scanning tunneling microscopy (STM) in atomic scale for the first time, in addition to atomic force microscopy (AFM), scanning electron microscopy (SEM), and low-energy electron diffraction (LEED). AFM and SEM showed flat and smooth vertical side-surfaces without scallops, and STM proved the realization of an atomically-flat 7 × 7-reconstructed structure, under optimized RIE and wet-etching conditions. STM also showed that a step-bunching occurred on the produced {111} side-surface corresponding to a reversely taped side-surface with a tilt angle of a few degrees, but did not show disordered structures. Characteristic LEED patterns from both side- and top-reconstructed surfaces were also demonstrated.

In situ electronic probing of semiconducting nanowires in an electron microscope.

PubMed

Fauske, V T; Erlbeck, M B; Huh, J; Kim, D C; Munshi, A M; Dheeraj, D L; Weman, H; Fimland, B O; Van Helvoort, A T J

2016-05-01

For the development of electronic nanoscale structures, feedback on its electronic properties is crucial, but challenging. Here, we present a comparison of various in situ methods for electronically probing single, p-doped GaAs nanowires inside a scanning electron microscope. The methods used include (i) directly probing individual as-grown nanowires with a sharp nano-manipulator, (ii) contacting dispersed nanowires with two metal contacts and (iii) contacting dispersed nanowires with four metal contacts. For the last two cases, we compare the results obtained using conventional ex situ litho-graphy contacting techniques and by in situ, direct-write electron beam induced deposition of a metal (Pt). The comparison shows that 2-probe measurements gives consistent results also with contacts made by electron beam induced deposition, but that for 4-probe, stray deposition can be a problem for shorter nanowires. This comparative study demonstrates that the preferred in situ method depends on the required throughput and reliability. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Direct determination of the local Hamaker constant of inorganic surfaces based on scanning force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krajina, Brad A.; Kocherlakota, Lakshmi S.; Overney, René M., E-mail: roverney@u.washington.edu

The energetics involved in the bonding fluctuations between nanometer-sized silicon dioxide (SiO{sub 2}) probes and highly oriented pyrolytic graphite (HOPG) and molybdenum disulfide (MoS{sub 2}) could be quantified directly and locally on the submicron scale via a time-temperature superposition analysis of the lateral forces between scanning force microscopy silicon dioxide probes and inorganic sample surfaces. The so-called “intrinsic friction analysis” (IFA) provided direct access to the Hamaker constants for HOPG and MoS{sub 2}, as well as the control sample, calcium fluoride (CaF{sub 2}). The use of scanning probe enables nanoscopic analysis of bonding fluctuations, thereby overcoming challenges associated with largermore » scale inhomogeneity and surface roughness common to conventional techniques used to determine surface free energies and dielectric properties. A complementary numerical analysis based on optical and electron energy loss spectroscopy and the Lifshitz quantum electrodynamic theory of van der Waals interactions is provided and confirms quantitatively the IFA results.« less

Direct determination of the local Hamaker constant of inorganic surfaces based on scanning force microscopy

NASA Astrophysics Data System (ADS)

Krajina, Brad A.; Kocherlakota, Lakshmi S.; Overney, René M.

2014-10-01

The energetics involved in the bonding fluctuations between nanometer-sized silicon dioxide (SiO2) probes and highly oriented pyrolytic graphite (HOPG) and molybdenum disulfide (MoS2) could be quantified directly and locally on the submicron scale via a time-temperature superposition analysis of the lateral forces between scanning force microscopy silicon dioxide probes and inorganic sample surfaces. The so-called "intrinsic friction analysis" (IFA) provided direct access to the Hamaker constants for HOPG and MoS2, as well as the control sample, calcium fluoride (CaF2). The use of scanning probe enables nanoscopic analysis of bonding fluctuations, thereby overcoming challenges associated with larger scale inhomogeneity and surface roughness common to conventional techniques used to determine surface free energies and dielectric properties. A complementary numerical analysis based on optical and electron energy loss spectroscopy and the Lifshitz quantum electrodynamic theory of van der Waals interactions is provided and confirms quantitatively the IFA results.

Direct determination of the local Hamaker constant of inorganic surfaces based on scanning force microscopy.

PubMed

Krajina, Brad A; Kocherlakota, Lakshmi S; Overney, René M

2014-10-28

The energetics involved in the bonding fluctuations between nanometer-sized silicon dioxide (SiO2) probes and highly oriented pyrolytic graphite (HOPG) and molybdenum disulfide (MoS2) could be quantified directly and locally on the submicron scale via a time-temperature superposition analysis of the lateral forces between scanning force microscopy silicon dioxide probes and inorganic sample surfaces. The so-called "intrinsic friction analysis" (IFA) provided direct access to the Hamaker constants for HOPG and MoS2, as well as the control sample, calcium fluoride (CaF2). The use of scanning probe enables nanoscopic analysis of bonding fluctuations, thereby overcoming challenges associated with larger scale inhomogeneity and surface roughness common to conventional techniques used to determine surface free energies and dielectric properties. A complementary numerical analysis based on optical and electron energy loss spectroscopy and the Lifshitz quantum electrodynamic theory of van der Waals interactions is provided and confirms quantitatively the IFA results.

Facile synthesis of silicon nanowire-nanopillar superhydrophobic structures

NASA Astrophysics Data System (ADS)

Roy, Abhijit; Satpati, Biswarup

2018-04-01

We have used metal assisted chemical etching (MACE) method to produce silicon (Si) nanowire-nanopillar array. Nanowire-nanopillar combined structures show higher degree of hydrophobicity compared to its nanowire (Si-NW) counterparts. The rate of etching is depended on initial metal deposition. The structural analysis was carried out using scanning electron microscopy (SEM) in combination with transmission electron microscopy (TEM) to determine different parameters like etching direction, crystallinity etc.

In-Fiber Magneto-Optic Devices Based on Ultrahigh Verdet Constant Organic Materials and Holey Fibers

DTIC Science & Technology

2009-02-02

protocols and a noise equivalent magnetic field sensitivity of ~ 100 pT/ VHz has been demonstrated. • Magneto-optic properties of magnetite - PMMA composite...nanoparticle - PMMA nanocomposite. We have used both transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) to...we expect to enhance it in our devices by their proper symmetrization as described above. Passive Poking core ^^ direction Magnetic AA

A controlled release of ibuprofen by systematically tailoring the morphology of mesoporous silica materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qu Fengyu; Chemistry and Pharmaceutical College, Jiamusi University, Jiamusi 154007; Zhu Guangshan

2006-07-15

A series of mesoporous silica materials with similar pore sizes, different morphologies and variable pore geometries were prepared systematically. In order to control drug release, ibuprofen was employed as a model drug and the influence of morphology and pore geometry of mesoporous silica on drug release profiles was extensively studied. The mesoporous silica and drug-loaded samples were characterized by X-ray diffraction, Fourier transform IR spectroscopy, N{sub 2} adsorption and desorption, scanning electron microscopy, and transmission electron microscopy. It was found that the drug-loading amount was directly correlated to the Brunauer-Emmett-Teller surface area, pore geometry, and pore volume; while the drugmore » release profiles could be controlled by tailoring the morphologies of mesoporous silica carriers. - Graphical abstract: The release of ibuprofen is controlled by tailoring the morphologies of mesoporous silica. The mesoporous silica and drug-loaded samples are characterized by powder X-ray diffraction, Fourier transform IR spectroscopy, N{sub 2} adsorption and desorption, scanning electron microscopy, and transmission electron microscopy. The drug-loading amount is directly correlated to the Brunauer-Emmett-Teller surface area, pore geometry, and pore volume; while the drug release profiles can be controlled by tailoring the morphologies of mesoporous silica carriers.« less

Physical characterization of a scanning photon counting digital mammography system based on Si-strip detectors.

PubMed

Aslund, Magnus; Cederström, Björn; Lundqvist, Mats; Danielsson, Mats

2007-06-01

The physical performance of a scanning multislit full field digital mammography system was determined using basic image quality parameters. The system employs a direct detection detector comprised of linear silicon strip sensors in an edge-on geometry connected to photon counting electronics. The pixel size is 50 microm and the field of view 24 x 26 cm2. The performance was quantified using the presampled modulation transfer function, the normalized noise power spectrum and the detective quantum efficiency (DQE). Compared to conventional DQE methods, the scanning geometry with its intrinsic scatter rejection poses additional requirements on the measurement setup, which are investigated in this work. The DQE of the photon counting system was found to be independent of the dose level to the detector in the 7.6-206 microGy range. The peak DQE was 72% and 73% in the scan and slit direction, respectively, measured with a 28 kV W-0.5 mm Al anode-filter combination with an added 2 mm Al filtration.

A new fast scanning system for the measurement of large angle tracks in nuclear emulsions

NASA Astrophysics Data System (ADS)

Alexandrov, A.; Buonaura, A.; Consiglio, L.; D'Ambrosio, N.; De Lellis, G.; Di Crescenzo, A.; Di Marco, N.; Galati, G.; Lauria, A.; Montesi, M. C.; Pupilli, F.; Shchedrina, T.; Tioukov, V.; Vladymyrov, M.

2015-11-01

Nuclear emulsions have been widely used in particle physics to identify new particles through the observation of their decays thanks to their unique spatial resolution. Nevertheless, before the advent of automatic scanning systems, the emulsion analysis was very demanding in terms of well trained manpower. Due to this reason, they were gradually replaced by electronic detectors, until the '90s, when automatic microscopes started to be developed in Japan and in Europe. Automatic scanning was essential to conceive large scale emulsion-based neutrino experiments like CHORUS, DONUT and OPERA. Standard scanning systems have been initially designed to recognize tracks within a limited angular acceptance (θ lesssim 30°) where θ is the track angle with respect to a line perpendicular to the emulsion plane. In this paper we describe the implementation of a novel fast automatic scanning system aimed at extending the track recognition to the full angular range and improving the present scanning speed. Indeed, nuclear emulsions do not have any intrinsic limit to detect particle direction. Such improvement opens new perspectives to use nuclear emulsions in several fields in addition to large scale neutrino experiments, like muon radiography, medical applications and dark matter directional detection.

Chemistry at molecular junctions: Rotation and dissociation of O2 on the Ag(110) surface induced by a scanning tunneling microscope.

PubMed

Roy, Sharani; Mujica, Vladimiro; Ratner, Mark A

2013-08-21

The scanning tunneling microscope (STM) is a fascinating tool used to perform chemical processes at the single-molecule level, including bond formation, bond breaking, and even chemical reactions. Hahn and Ho [J. Chem. Phys. 123, 214702 (2005)] performed controlled rotations and dissociations of single O2 molecules chemisorbed on the Ag(110) surface at precise bias voltages using STM. These threshold voltages were dependent on the direction of the bias voltage and the initial orientation of the chemisorbed molecule. They also observed an interesting voltage-direction-dependent and orientation-dependent pathway selectivity suggestive of mode-selective chemistry at molecular junctions, such that in one case the molecule underwent direct dissociation, whereas in the other case it underwent rotation-mediated dissociation. We present a detailed, first-principles-based theoretical study to investigate the mechanism of the tunneling-induced O2 dynamics, including the origin of the observed threshold voltages, the pathway dependence, and the rate of O2 dissociation. Results show a direct correspondence between the observed threshold voltage for a process and the activation energy for that process. The pathway selectivity arises from a competition between the voltage-modified barrier heights for rotation and dissociation, and the coupling strength of the tunneling electrons to the rotational and vibrational modes of the adsorbed molecule. Finally, we explore the "dipole" and "resonance" mechanisms of inelastic electron tunneling to elucidate the energy transfer between the tunneling electrons and chemisorbed O2.

Leaching: use of a thermophilic and chemoautotrophic microbe.

PubMed

Brierley, C L; Murr, L E

1973-02-02

A chemoautotrophic, thermophilic, and acidophilic microorganism capable of oxidizing reduced sulfur and iron compounds and leaching concentrates of molybdenite and chalcopyrite at 60 degrees C has been characterized by transmission and scanning electron microscopy. This constitutes the first direct observations of microorganisms on ore fines.

Column-by-column observation of dislocation motion in CdTe: Dynamic scanning transmission electron microscopy

NASA Astrophysics Data System (ADS)

Li, Chen; Zhang, Yu-Yang; Pennycook, Timothy J.; Wu, Yelong; Lupini, Andrew R.; Paudel, Naba; Pantelides, Sokrates T.; Yan, Yanfa; Pennycook, Stephen J.

2016-10-01

The dynamics of partial dislocations in CdTe have been observed at the atomic scale using aberration-corrected scanning transmission electron microscopy (STEM), allowing the mobility of different dislocations to be directly compared: Cd-core Shockley partial dislocations are more mobile than Te-core partials, and dislocation cores with unpaired columns have higher mobility than those without unpaired columns. The dynamic imaging also provides insight into the process by which the dislocations glide. Dislocations with dangling bonds on unpaired columns are found to be more mobile because the dangling bonds mediate the bond exchanges required for the dislocations to move. Furthermore, a screw dislocation has been resolved to dissociate into a Shockley partial-dislocation pair along two different directions, revealing a way for the screw dislocation to glide in the material. The results show that dynamic STEM imaging has the potential to uncover the details of dislocation motion not easily accessible by other means.

Scanning electron microscopy (SEM) and X-ray dispersive spectrometry evaluation of direct laser metal sintering surface and human bone interface: a case series.

PubMed

Mangano, Carlo; Piattelli, Adriano; Raspanti, Mario; Mangano, Francesco; Cassoni, Alessandra; Iezzi, Giovanna; Shibli, Jamil Awad

2011-01-01

Recent studies have shown that direct laser metal sintering (DLMS) produces structures with complex geometry and consequently that allow better osteoconductive properties. The aim of this patient report was to evaluate the early bone response to DLMS implant surface retrieved from human jaws. Four experimental DLMS implants were inserted in the posterior mandible of four patients during conventional dental implant surgery. After 8 weeks, the micro-implants and the surrounding tissue were removed and prepared for scanning electron microscopy (SEM) and histomorphometric analysis to evaluate the bone-implant interface. The SEM and EDX evaluations showed a newly formed tissue composed of calcium and phosphorus. The bone-to-implant contact presented a mean of 60.5 ± 11.6%. Within the limits of this patient report, data suggest that the DLMS surfaces presented a close contact with the human bone after a healing period of 8 weeks.

The Inventory Of High Objects Applying Laser Scanning, Focus On The Cataloguing A Reinforced Concrete Industrial Chimney

NASA Astrophysics Data System (ADS)

Gawałkiewicz, Rafał

2015-12-01

There are many surveying methods to measure the inclination of a chimney with the use of classical protractor instruments (Theo 010A/B, T2 Wild), electronic theodolites (TC2002 Wild-Leica), electronic total stations, including mirrorless ones, allowing to define indirectly the course of the construction's axis on the selected observation levels. The methods are the following: indentations, direct projection, double-edged method, polar method with the option of mirrorless measurement. At the moment a very practical and quick measurement technology, significantly eliminating the influence of human errors on the observation results, is laser scanning. The article presents the results of the scanning of 120-metres high reinforced concrete industrial chimney of the Cement Plant "Ożarów", with the application of modern scanning total station VX Spatial Station by Trimble, as an alternative to the methods applied so far. The advantage of scanning is the possibility to obtain a point cloud, which, apart from the information on the course of the chimney axis in the space, provides detail information on the real shape and deformations of the coating of the object's core.

Cross-section imaging and p-type doping assessment of ZnO/ZnO:Sb core-shell nanowires by scanning capacitance microscopy and scanning spreading resistance microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Lin, E-mail: lin.wang@insa-lyon.fr; Brémond, Georges; Sallet, Vincent

2016-08-29

ZnO/ZnO:Sb core-shell structured nanowires (NWs) were grown by the metal organic chemical vapor deposition method where the shell was doped with antimony (Sb) in an attempt to achieve ZnO p-type conduction. To directly investigate the Sb doping effect in ZnO, scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM) were performed on the NWs' cross-sections mapping their two dimensional (2D) local electrical properties. Although no direct p-type inversion in ZnO was revealed, a lower net electron concentration was pointed out for the Sb-doped ZnO shell layer with respect to the non-intentionally doped ZnO core, indicating an evident compensating effectmore » as a result of the Sb incorporation, which can be ascribed to the formation of Sb-related acceptors. The results demonstrate SCM/SSRM investigation being a direct and effective approach for characterizing radial semiconductor one-dimensional (1D) structures and, particularly, for the doping study on the ZnO nanomaterial towards its p-type realization.« less

Periodic scarred States in open quantum dots as evidence of quantum Darwinism.

PubMed

Burke, A M; Akis, R; Day, T E; Speyer, Gil; Ferry, D K; Bennett, B R

2010-04-30

Scanning gate microscopy (SGM) is used to image scar structures in an open quantum dot, which is created in an InAs quantum well by electron-beam lithography and wet etching. The scanned images demonstrate periodicities in magnetic field that correlate to those found in the conductance fluctuations. Simulations have shown that these magnetic transform images bear a strong resemblance to actual scars found in the dot that replicate through the modes in direct agreement with quantum Darwinism.

Periodic Scarred States in Open Quantum Dots as Evidence of Quantum Darwinism

NASA Astrophysics Data System (ADS)

Burke, A. M.; Akis, R.; Day, T. E.; Speyer, Gil; Ferry, D. K.; Bennett, B. R.

2010-04-01

Scanning gate microscopy (SGM) is used to image scar structures in an open quantum dot, which is created in an InAs quantum well by electron-beam lithography and wet etching. The scanned images demonstrate periodicities in magnetic field that correlate to those found in the conductance fluctuations. Simulations have shown that these magnetic transform images bear a strong resemblance to actual scars found in the dot that replicate through the modes in direct agreement with quantum Darwinism.

Mapping atomic contact between pentacene and a Au surface using scanning tunneling spectroscopy.

PubMed

Song, Young Jae; Lee, Kyuho; Kim, Seong Heon; Choi, Byoung-Young; Yu, Jaejun; Kuk, Young

2010-03-10

We mapped spatially varying intramolecular electronic structures on a pentacene-gold interface using scanning tunneling spectroscopy. Along with ab initio calculations based on density functional theory, we found that the directional nature of the d orbitals of Au atoms plays an important role in the interaction at the pentacene-gold contact. The gold-induced interface states are broadened and shifted by various pentacene-gold distances determined by the various registries of a pentacene molecule on a gold substrate.

Three-dimensional machining of carbon nanotube forests using water-assisted scanning electron microscope processing

NASA Astrophysics Data System (ADS)

Rajabifar, Bahram; Kim, Sanha; Slinker, Keith; Ehlert, Gregory J.; Hart, A. John; Maschmann, Matthew R.

2015-10-01

We demonstrate that vertically aligned carbon nanotubes (CNTs) can be precisely machined in a low pressure water vapor ambient using the electron beam of an environmental scanning electron microscope. The electron beam locally damages the irradiated regions of the CNT forest and also dissociates the water vapor molecules into reactive species including hydroxyl radicals. These species then locally oxidize the damaged region of the CNTs. The technique offers material removal capabilities ranging from selected CNTs to hundreds of cubic microns. We study how the material removal rate is influenced by the acceleration voltage, beam current, dwell time, operating pressure, and CNT orientation. Milled cuts with depths between 0-100 microns are generated, corresponding to a material removal rate of up to 20.1 μm3/min. The technique produces little carbon residue and does not disturb the native morphology of the CNT network. Finally, we demonstrate direct machining of pyramidal surfaces and re-entrant cuts to create freestanding geometries.

Three-dimensional machining of carbon nanotube forests using water-assisted scanning electron microscope processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajabifar, Bahram; Maschmann, Matthew R., E-mail: MaschmannM@missouri.edu; Kim, Sanha

2015-10-05

We demonstrate that vertically aligned carbon nanotubes (CNTs) can be precisely machined in a low pressure water vapor ambient using the electron beam of an environmental scanning electron microscope. The electron beam locally damages the irradiated regions of the CNT forest and also dissociates the water vapor molecules into reactive species including hydroxyl radicals. These species then locally oxidize the damaged region of the CNTs. The technique offers material removal capabilities ranging from selected CNTs to hundreds of cubic microns. We study how the material removal rate is influenced by the acceleration voltage, beam current, dwell time, operating pressure, andmore » CNT orientation. Milled cuts with depths between 0–100 microns are generated, corresponding to a material removal rate of up to 20.1 μm{sup 3}/min. The technique produces little carbon residue and does not disturb the native morphology of the CNT network. Finally, we demonstrate direct machining of pyramidal surfaces and re-entrant cuts to create freestanding geometries.« less

Detecting element specific electrons from a single cobalt nanocluster with synchrotron x-ray scanning tunneling microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kersell, Heath; Shirato, Nozomi; Cummings, Marvin

We use a nanofabricated scanning tunneling microscope tip as a detector to investigate local X-ray induced tunneling and electron emission from a single cobalt nanocluster on a Au(111) surface. The tip-detector is positioned a few angstroms above the nanocluster, and ramping the incident X-ray energy across the Co photoabsorption K-edge enables the detection of element specific electrons. Atomic-scale spatial dependent changes in the X-ray absorption cross section are directly measured by taking the X-ray induced current as a function of X-ray energy. From the measured sample and tip currents, element specific X-ray induced current components can be separated and therebymore » the corresponding yields for the X-ray induced processes of the single cobalt nanocluster can be determined. The detection of element specific synchrotron X-ray induced electrons of a single nanocluster opens a new avenue for materials characterization on a one particle at-a-time basis.« less

Detecting element specific electrons from a single cobalt nanocluster with synchrotron x-ray scanning tunneling microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kersell, Heath; Shirato, Nozomi; Cummings, Marvin

Here, we use a nanofabricated scanning tunneling microscope tip as a detector to investigate local X-ray induced tunneling and electron emission from a single cobalt nanocluster on a Au(111) surface. The tip-detector is positioned a few angstroms above the nanocluster, and ramping the incident X-ray energy across the Co photoabsorption K-edge enables the detection of element specific electrons. Atomic-scale spatial dependent changes in the X-ray absorption cross section are directly measured by taking the X-ray induced current as a function of X-ray energy. From the measured sample and tip currents, element specific X-ray induced current components can be separated andmore » thereby the corresponding yields for the X-ray induced processes of the single cobalt nanocluster can be determined. The detection of element specific synchrotron X-ray induced electrons of a single nanocluster opens a new avenue for materials characterization on a one particle at-a-time basis.« less

Detecting element specific electrons from a single cobalt nanocluster with synchrotron x-ray scanning tunneling microscopy

DOE PAGES

Kersell, Heath; Shirato, Nozomi; Cummings, Marvin; ...

2017-09-05

Here, we use a nanofabricated scanning tunneling microscope tip as a detector to investigate local X-ray induced tunneling and electron emission from a single cobalt nanocluster on a Au(111) surface. The tip-detector is positioned a few angstroms above the nanocluster, and ramping the incident X-ray energy across the Co photoabsorption K-edge enables the detection of element specific electrons. Atomic-scale spatial dependent changes in the X-ray absorption cross section are directly measured by taking the X-ray induced current as a function of X-ray energy. From the measured sample and tip currents, element specific X-ray induced current components can be separated andmore » thereby the corresponding yields for the X-ray induced processes of the single cobalt nanocluster can be determined. The detection of element specific synchrotron X-ray induced electrons of a single nanocluster opens a new avenue for materials characterization on a one particle at-a-time basis.« less

Atomic scale dynamics of a solid state chemical reaction directly determined by annular dark-field electron microscopy.

PubMed

Pennycook, Timothy J; Jones, Lewys; Pettersson, Henrik; Coelho, João; Canavan, Megan; Mendoza-Sanchez, Beatriz; Nicolosi, Valeria; Nellist, Peter D

2014-12-22

Dynamic processes, such as solid-state chemical reactions and phase changes, are ubiquitous in materials science, and developing a capability to observe the mechanisms of such processes on the atomic scale can offer new insights across a wide range of materials systems. Aberration correction in scanning transmission electron microscopy (STEM) has enabled atomic resolution imaging at significantly reduced beam energies and electron doses. It has also made possible the quantitative determination of the composition and occupancy of atomic columns using the atomic number (Z)-contrast annular dark-field (ADF) imaging available in STEM. Here we combine these benefits to record the motions and quantitative changes in the occupancy of individual atomic columns during a solid-state chemical reaction in manganese oxides. These oxides are of great interest for energy-storage applications such as for electrode materials in pseudocapacitors. We employ rapid scanning in STEM to both drive and directly observe the atomic scale dynamics behind the transformation of Mn3O4 into MnO. The results demonstrate we now have the experimental capability to understand the complex atomic mechanisms involved in phase changes and solid state chemical reactions.

Ultrafast Carrier dynamics of InxGa1-xN nanostructures grown directly on Si(111)

NASA Astrophysics Data System (ADS)

Kumar, Praveen; Devi, Pooja; Rodriguez⁠, P. E. D. S.; Kumar, Manish; Shivling, V. D.; Noetzel, Richard; Sharma, Chhavi; Sinha, R. K.; Kumar, Mahesh

2018-05-01

We show a flux dependence changes in structural, optical and electronic properties of InxGa1-xN nanostructures (NSs) namely nanocolumns (NCs), nanoflakes (NFs) and nanowall network (NWN) grown directly on Si(111) surface. Field emission scanning electron microscopy (FESEM) images were recorded to see morphological changes from NFs to NCs and NWNc etc, while high-resolution X-ray diffraction (HRXRD) ω-2θ scans were used to determine In incorporation. The maximum In incorporation was observed to be 20, 33 and 38% for the sharp transition from NFs to NCs and NWNs, respectively. The charge carrier dynamics of these grown NSs were probed using Ultrafast Femtosecond Transient Absorption Spectroscopy (UFTAS) with excitation at 350 nm pump wavelength. The UFTAS studies show the comparative charge carriers dynamics of the NWS, NCs and NFs. The charge carrier studies show a higher lifetime in NWNs as compare to NCs and NFs. Further, to examine electronic structure and level of degeneracy of these NSs, core-level and valence band spectra were analyzed by X-ray photoelectron spectroscopy (XPS), which manifest the upward band bending ranging from 0.2 eV to 0.4 eV.

Interlayer couplings, Moiré patterns, and 2D electronic superlattices in MoS2/WSe2 hetero-bilayers

PubMed Central

Zhang, Chendong; Chuu, Chih-Piao; Ren, Xibiao; Li, Ming-Yang; Li, Lain-Jong; Jin, Chuanhong; Chou, Mei-Yin; Shih, Chih-Kang

2017-01-01

By using direct growth, we create a rotationally aligned MoS2/WSe2 hetero-bilayer as a designer van der Waals heterostructure. With rotational alignment, the lattice mismatch leads to a periodic variation of atomic registry between individual van der Waals layers, exhibiting a Moiré pattern with a well-defined periodicity. By combining scanning tunneling microscopy/spectroscopy, transmission electron microscopy, and first-principles calculations, we investigate interlayer coupling as a function of atomic registry. We quantitatively determine the influence of interlayer coupling on the electronic structure of the hetero-bilayer at different critical points. We show that the direct gap semiconductor concept is retained in the bilayer although the valence and conduction band edges are located at different layers. We further show that the local bandgap is periodically modulated in the X-Y direction with an amplitude of ~0.15 eV, leading to the formation of a two-dimensional electronic superlattice. PMID:28070558

Tailoring Dirac Fermions in Molecular Graphene

NASA Astrophysics Data System (ADS)

Gomes, Kenjiro K.; Mar, Warren; Ko, Wonhee; Camp, Charlie D.; Rastawicki, Dominik K.; Guinea, Francisco; Manoharan, Hari C.

2012-02-01

The dynamics of electrons in solids is tied to the band structure created by a periodic atomic potential. The design of artificial lattices, assembled through atomic manipulation, opens the door to engineer electronic band structure and to create novel quantum states. We present scanning tunneling spectroscopic measurements of a nanoassembled honeycomb lattice displaying a Dirac fermion band structure. The artificial lattice is created by atomic manipulation of single CO molecules with the scanning tunneling microscope on the surface of Cu(111). The periodic potential generated by the assembled CO molecules reshapes the band structure of the two-dimensional electron gas, present as a surface state of Cu(111), into a ``molecular graphene'' system. We create local defects in the lattice to observe the quasiparticle interference patterns that unveil the underlying band structure. We present direct comparison between the tunneling data, first-principles calculations of the band structure, and tight-binding models.

Combined scanning transmission electron microscopy tilt- and focal series.

PubMed

Dahmen, Tim; Baudoin, Jean-Pierre; Lupini, Andrew R; Kübel, Christian; Slusallek, Philipp; de Jonge, Niels

2014-04-01

In this study, a combined tilt- and focal series is proposed as a new recording scheme for high-angle annular dark-field scanning transmission electron microscopy (STEM) tomography. Three-dimensional (3D) data were acquired by mechanically tilting the specimen, and recording a through-focal series at each tilt direction. The sample was a whole-mount macrophage cell with embedded gold nanoparticles. The tilt-focal algebraic reconstruction technique (TF-ART) is introduced as a new algorithm to reconstruct tomograms from such combined tilt- and focal series. The feasibility of TF-ART was demonstrated by 3D reconstruction of the experimental 3D data. The results were compared with a conventional STEM tilt series of a similar sample. The combined tilt- and focal series led to smaller "missing wedge" artifacts, and a higher axial resolution than obtained for the STEM tilt series, thus improving on one of the main issues of tilt series-based electron tomography.

Atomic bonding effects in annular dark field scanning transmission electron microscopy. I. Computational predictions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Odlyzko, Michael L.; Mkhoyan, K. Andre, E-mail: mkhoyan@umn.edu; Himmetoglu, Burak

2016-07-15

Annular dark field scanning transmission electron microscopy (ADF-STEM) image simulations were performed for zone-axis-oriented light-element single crystals, using a multislice method adapted to include charge redistribution due to chemical bonding. Examination of these image simulations alongside calculations of the propagation of the focused electron probe reveal that the evolution of the probe intensity with thickness exhibits significant sensitivity to interatomic charge transfer, accounting for observed thickness-dependent bonding sensitivity of contrast in all ADF-STEM imaging conditions. Because changes in image contrast relative to conventional neutral atom simulations scale directly with the net interatomic charge transfer, the strongest effects are seen inmore » crystals with highly polar bonding, while no effects are seen for nonpolar bonding. Although the bonding dependence of ADF-STEM image contrast varies with detector geometry, imaging parameters, and material temperature, these simulations predict the bonding effects to be experimentally measureable.« less

Metallic atomically-thin layered silicon epitaxially grown on silicene/ZrB 2

DOE PAGES

Gill, Tobias G.; Fleurence, Antoine; Warner, Ben; ...

2017-02-17

We observe a new two-dimensional (2D) silicon crystal, using low energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) and it's formed by depositing additional Si atoms onto spontaneously-formed epitaxial silicene on a ZrB 2 thin film. From scanning tunnelling spectroscopy (STS) studies, we find that this atomically-thin layered silicon has distinctly different electronic properties. Angle resolved photoelectron spectroscopy (ARPES) reveals that, in sharp contrast to epitaxial silicene, the layered silicon exhibits significantly enhanced density of states at the Fermi level resulting from newly formed metallic bands. Furthermore, the 2D growth of this material could allow for direct contacting tomore » the silicene surface and demonstrates the dramatic changes in electronic structure that can occur by the addition of even a single monolayer amount of material in 2D systems.« less

Retarding potential analyzer for the Pioneer-Venus Orbiter Mission

NASA Technical Reports Server (NTRS)

Knudsen, W. C.; Bakke, J.; Spenner, K.; Novak, V.

1979-01-01

The retarding potential analyzer on the Pioneer-Venus Orbiter Mission has been designed to measure most of the thermal plasma parameters within and near the Venusian ionosphere. Parameters include total ion concentration, concentrations of the more abundant ions, ion temperatures, ion drift velocity, electron temperature, and low-energy (0-50 eV) electron distribution function. To accomplish these measurements on a spinning vehicle with a small telemetry bit rate, several functions, including decision functions not previously used in RPA's, have been developed and incorporated into this instrument. The more significant functions include automatic electrometer ranging with background current compensation; digital, quadratic retarding potential step generation for the ion and low-energy electron scans; a current sampling interval of 2 ms throughout all scans; digital logic inflection point detection and data selection; and automatic ram direction detection. Extensive numerical simulation and plasma chamber tests have been conducted to verify adequacy of the design for the Pioneer Mission.

In-situ deformation studies of an aluminum metal-matrix composite in a scanning electron microscope

NASA Technical Reports Server (NTRS)

Manoharan, M.; Lewandowski, J. J.

1989-01-01

Tensile specimens made of a metal-matrix composite (cast and extruded aluminum alloy-based matrix reinforced with Al2O3 particulate) were tested in situ in a scanning electron microscope equipped with a deformation stage, to directly monitor the crack propagation phenomenon. The in situ SEM observations revealed the presence of microcracks both ahead of and near the crack-tip region. The microcracks were primarily associated with cracks in the alumina particles. The results suggest that a region of intense deformation exists ahead of the crack and corresponds to the region of microcracking. As the crack progresses, a region of plastically deformed material and associated microcracks remains in the wake of the crack.

Thermodynamic understanding of Sn whisker growth on the Cu surface in Cu(top)-Sn(bottom) bilayer system upon room temperature aging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Lin; Jian, Wei; Lin, Bing

2015-06-07

Sn whiskers are observed by scanning electron microscope on the Cu surface in Cu(top)-Sn(bottom) bilayer system upon room temperature aging. Only Cu{sub 6}Sn{sub 5} phase appears in the X-ray diffraction patterns and no Sn element is detected in the Cu sublayer by scanning transmission electron microscopy. Based on the interfacial thermodynamics, the intermetallic Cu{sub 6}Sn{sub 5} compound phase may form directly at the Sn grain boundary. Driven by the stress gradient during the formation of Cu{sub 6}Sn{sub 5} compound at Sn grain boundaries, Sn atoms segregate onto the Cu surface and accumulate to form Sn whisker.

Electrostatically focused addressable field emission array chips (AFEA's) for high-speed massively parallel maskless digital E-beam direct write lithography and scanning electron microscopy

DOEpatents

Thomas, Clarence E.; Baylor, Larry R.; Voelkl, Edgar; Simpson, Michael L.; Paulus, Michael J.; Lowndes, Douglas H.; Whealton, John H.; Whitson, John C.; Wilgen, John B.

2002-12-24

Systems and methods are described for addressable field emission array (AFEA) chips. A method of operating an addressable field-emission array, includes: generating a plurality of electron beams from a pluralitly of emitters that compose the addressable field-emission array; and focusing at least one of the plurality of electron beams with an on-chip electrostatic focusing stack. The systems and methods provide advantages including the avoidance of space-charge blow-up.

Atomic-scale mapping of electronic structures across heterointerfaces by cross-sectional scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Chiu, Ya-Ping; Huang, Bo-Chao; Shih, Min-Chuan; Huang, Po-Cheng; Chen, Chun-Wei

2015-09-01

Interfacial science has received much attention recently based on the development of state-of-the-art analytical tools that can create and manipulate the charge, spin, orbital, and lattice degrees of freedom at interfaces. Motivated by the importance of nanoscale interfacial science that governs device operation, we present a technique to probe the electronic characteristics of heterointerfaces with atomic resolution. In this work, the interfacial characteristics of heteroepitaxial structures are investigated and the fundamental mechanisms that pertain in these systems are elucidated through cross-sectional scanning tunneling microscopy (XSTM). The XSTM technique is employed here to directly observe epitaxial interfacial structures and probe local electronic properties with atomic-level capability. Scanning tunneling microscopy and spectroscopy experiments with atomic precision provide insight into the origin and spatial distribution of electronic properties across heterointerfaces. The first part of this report provides a brief description of the cleavage technique and spectroscopy analysis in XSTM measurements. The second part addresses interfacial electronic structures of several model heterostructures in current condensed matter research using XSTM. Topics to be discussed include high-κ‘s/III-V’s semiconductors, polymer heterojunctions, and complex oxide heterostructures, which are all material systems whose investigation using this technique is expected to benefit the research community. Finally, practical aspects and perspectives of using XSTM in interface science are presented.

Scanning tunneling microscopy and spectroscopy of twisted trilayer graphene

NASA Astrophysics Data System (ADS)

Zuo, Wei-Jie; Qiao, Jia-Bin; Ma, Dong-Lin; Yin, Long-Jing; Sun, Gan; Zhang, Jun-Yang; Guan, Li-Yang; He, Lin

2018-01-01

Twist, as a simple and unique degree of freedom, could lead to enormous novel quantum phenomena in bilayer graphene. A small rotation angle introduces low-energy van Hove singularities (VHSs) approaching the Fermi level, which result in unusual correlated states in the bilayer graphene. It is reasonable to expect that the twist could also affect the electronic properties of few-layer graphene dramatically. However, such an issue has remained experimentally elusive. Here, by using scanning tunneling microscopy/spectroscopy (STM/STS), we systematically studied a twisted trilayer graphene (TTG) with two different small twist angles between adjacent layers. Two sets of VHSs, originating from the two twist angles, were observed in the TTG, indicating that the TTG could be simply regarded as a combination of two different twisted bilayers of graphene. By using high-resolution STS, we observed a split of the VHSs and directly imaged the spatial symmetry breaking of electronic states around the VHSs. These results suggest that electron-electron interactions play an important role in affecting the electronic properties of graphene systems with low-energy VHSs.

Solid State Research

DTIC Science & Technology

1985-02-15

Wave Mach-Zehnder Interferometric Modulator with Center-Tapped Electrode. The Two Y Junctions have 2° Full Branching Angles, and the Direction of...and < 110> Directions 20 3-6 Nomarski Micrographs of Seeded 50-/um Ge-on-Insulator Islands After ZMR and Defect Etching 21 3-7 Scanning Electron...achieved to date in this long- wavelength region. A LiNb03 guided-wave interferometric modulator has been demonstrated at A. = 3.39 /um with a

In-situ integrity control of frozen-hydrated, vitreous lamellas prepared by the cryo-focused ion beam-scanning electron microscope.

PubMed

de Winter, D A Matthijs; Mesman, Rob J; Hayles, Michael F; Schneijdenberg, Chris T W M; Mathisen, Cliff; Post, Jan A

2013-07-01

Recently a number of new approaches have been presented with the intention to produce electron beam transparent cryo-sections (lamellas in FIB-SEM terminology) from hydrated vitreously frozen cryo samples with a Focused Ion Beam (FIB) system, suitable for cryo-Transmission Electron Microscopy (cryo-TEM). As the workflow is still challenging and time consuming, it is important to be able to determine the integrity and suitability (cells vs. no cells; vitreous vs. crystalline) of the lamellas. Here we present an in situ method that tests both conditions by using the cryo-Scanning Electron Microscope (cryo-SEM) in transmission mode (TSEM; Transmission Scanning Electron Microscope) once the FIB-made lamella is ready. Cryo-TSEM imaging of unstained cells yields strong contrast, enabling direct imaging of material present in the lamellas. In addition, orientation contrast is shown to be suitable for distinguishing crystalline lamellas from vitreous lamellas. Tilting the stage a few degrees results in changes of contrast between ice grains as a function of the tilt angle, whereas the contrast of areas with vitreous ice remains unchanged as a function of the tilt angle. This orientation contrast has subsequently been validated by cryo-Electron BackScattered Diffraction (EBSD) in transmission mode. Integration of the presented method is discussed and the role it can play in future developments for a new and innovative all-in-one cryo-FIB-SEM life sciences instrument. Copyright © 2013 Elsevier Inc. All rights reserved.

Enhancement of low-energy electron emission in 2D radioactive films

NASA Astrophysics Data System (ADS)

Pronschinske, Alex; Pedevilla, Philipp; Murphy, Colin J.; Lewis, Emily A.; Lucci, Felicia R.; Brown, Garth; Pappas, George; Michaelides, Angelos; Sykes, E. Charles H.

2015-09-01

High-energy radiation has been used for decades; however, the role of low-energy electrons created during irradiation has only recently begun to be appreciated. Low-energy electrons are the most important component of radiation damage in biological environments because they have subcellular ranges, interact destructively with chemical bonds, and are the most abundant product of ionizing particles in tissue. However, methods for generating them locally without external stimulation do not exist. Here, we synthesize one-atom-thick films of the radioactive isotope 125I on gold that are stable under ambient conditions. Scanning tunnelling microscopy, supported by electronic structure simulations, allows us to directly observe nuclear transmutation of individual 125I atoms into 125Te, and explain the surprising stability of the 2D film as it underwent radioactive decay. The metal interface geometry induces a 600% amplification of low-energy electron emission (<10 eV; ref. ) compared with atomic 125I. This enhancement of biologically active low-energy electrons might offer a new direction for highly targeted nanoparticle therapies.

Backscattered electron SEM imaging of resin sections from plant specimens: observation of histological to subcellular structure and CLEM.

PubMed

Rizzo, N W; Duncan, K E; Bourett, T M; Howard, R J

2016-08-01

We have refined methods for biological specimen preparation and low-voltage backscattered electron imaging in the scanning electron microscope that allow for observation at continuous magnifications of ca. 130-70 000 X, and documentation of tissue and subcellular ultrastructure detail. The technique, based upon early work by Ogura & Hasegawa (1980), affords use of significantly larger sections from fixed and resin-embedded specimens than is possible with transmission electron microscopy while providing similar data. After microtomy, the sections, typically ca. 750 nm thick, were dried onto the surface of glass or silicon wafer and stained with heavy metals-the use of grids avoided. The glass/wafer support was then mounted onto standard scanning electron microscopy sample stubs, carbon-coated and imaged directly at an accelerating voltage of 5 kV, using either a yttrium aluminum garnet or ExB backscattered electron detector. Alternatively, the sections could be viewed first by light microscopy, for example to document signal from a fluorescent protein, and then by scanning electron microscopy to provide correlative light/electron microscope (CLEM) data. These methods provide unobstructed access to ultrastructure in the spatial context of a section ca. 7 × 10 mm in size, significantly larger than the typical 0.2 × 0.3 mm section used for conventional transmission electron microscopy imaging. Application of this approach was especially useful when the biology of interest was rare or difficult to find, e.g. a particular cell type, developmental stage, large organ, the interface between cells of interacting organisms, when contextual information within a large tissue was obligatory, or combinations of these factors. In addition, the methods were easily adapted for immunolocalizations. © 2015 The Author. Journal of Microscopy published by John Wiley & Sons, Ltd on behalf of the Royal Microscopical Society.

Controllable spin-charge transport in strained graphene nanoribbon devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diniz, Ginetom S., E-mail: ginetom@gmail.com; Guassi, Marcos R.; Qu, Fanyao

2014-09-21

We theoretically investigate the spin-charge transport in two-terminal device of graphene nanoribbons in the presence of a uniform uniaxial strain, spin-orbit coupling, exchange field, and smooth staggered potential. We show that the direction of applied strain can efficiently tune strain-strength induced oscillation of band-gap of armchair graphene nanoribbon (AGNR). It is also found that electronic conductance in both AGNR and zigzag graphene nanoribbon (ZGNR) oscillates with Rashba spin-orbit coupling akin to the Datta-Das field effect transistor. Two distinct strain response regimes of electronic conductance as function of spin-orbit couplings magnitude are found. In the regime of small strain, conductance ofmore » ZGNR presents stronger strain dependence along the longitudinal direction of strain. Whereas for high values of strain shows larger effect for the transversal direction. Furthermore, the local density of states shows that depending on the smoothness of the staggered potential, the edge states of AGNR can either emerge or be suppressed. These emerging states can be determined experimentally by either spatially scanning tunneling microscope or by scanning tunneling spectroscopy. Our findings open up new paradigms of manipulation and control of strained graphene based nanostructure for application on novel topological quantum devices.« less

Peering into the secrets of food and agricultural co-products

USDA-ARS?s Scientific Manuscript database

Scanning electron microscopy is a valuable tool for understanding food contamination and for directing product development of food and industrial products. The current trend in food research is to produce foods that are fast to prepare and/or ready to eat. At the same time, these processed foods mus...

Peering into the Secrets of Food and Agricultural Co-products

USDA-ARS?s Scientific Manuscript database

Scanning electron microscopy is a useful tool for directing product development and is equally important for developing products from food crops and co-products from the agricultural waste after harvest. The current trend in food research is to produce foods that are fast to prepare and/or ready to ...

Evidence for the suppression of incident beam effects in Auger electron diffraction

NASA Astrophysics Data System (ADS)

Davoli, I.; Gunnella, R.; Bernardini, R.; De Crescenzi, M.

1998-01-01

Auger electron diffraction (AED) of the Cu(100) surface has been studied through the anisotropy of the elastic backdiffused beam electrons, the L 2,3M 4,5M 4,5 (LVV) and the M 2,3M 4,5M 4,5 (MVV) transitions in polar scan along the two main directions [001], [011] and in azimuth scan at normal emission. The intensity anisotropies of the low and high kinetic energy Auger lines are in antiphase to each other as in experiments in which these transitions are excited by X-ray photons. This behaviour has been exploited to single out the origin of the physical mechanisms accompanying the diffraction of the emitted electrons. Incident beam effects appear to be sizeable only when the collection of the AED spectra are made with an angle integrating electron analyser (cylindrical mirror analyser or low electron energy diffraction apparatus), but they appear negligible when electron collection is performed through a small solid-angle detector. The conclusions reached by our measurements are supported by good agreement with experimental and theoretical X-ray photoelectron diffraction data and demonstrate that, when the incident beam energy is sufficiently higher than the kinetic energy of the Auger electron detected, the influence of the incident beam on AED is negligible.

Direct observation and analysis of york-shell materials using low-voltage high-resolution scanning electron microscopy: Nanometal-particles encapsulated in metal-oxide, carbon, and polymer

NASA Astrophysics Data System (ADS)

Asahina, Shunsuke; Suga, Mitsuo; Takahashi, Hideyuki; Young Jeong, Hu; Galeano, Carolina; Schüth, Ferdi; Terasaki, Osamu

2014-11-01

Nanometal particles show characteristic features in chemical and physical properties depending on their sizes and shapes. For keeping and further enhancing their features, the particles should be protected from coalescence or degradation. One approach is to encapsulate the nanometal particles inside pores with chemically inert or functional materials, such as carbon, polymer, and metal oxides, which contain mesopores to allow permeation of only chemicals not the nanometal particles. Recently developed low-voltage high-resolution scanning electron microscopy was applied to the study of structural, chemical, and electron state of both nanometal particles and encapsulating materials in yolk-shell materials of Au@C, Ru/Pt@C, Au@TiO2, and Pt@Polymer. Progresses in the following categories were shown for the yolk-shell materials: (i) resolution of topographic image contrast by secondary electrons, of atomic-number contrast by back-scattered electrons, and of elemental mapping by X-ray energy dispersive spectroscopy; (ii) sample preparation for observing internal structures; and (iii) X-ray spectroscopy such as soft X-ray emission spectroscopy. Transmission electron microscopy was also used for characterization of Au@C.

Towards atomically precise manipulation of 2D nanostructures in the electron microscope

NASA Astrophysics Data System (ADS)

Susi, Toma; Kepaptsoglou, Demie; Lin, Yung-Chang; Ramasse, Quentin M.; Meyer, Jannik C.; Suenaga, Kazu; Kotakoski, Jani

2017-12-01

Despite decades of research, the ultimate goal of nanotechnology—top-down manipulation of individual atoms—has been directly achieved with only one technique: scanning probe microscopy. In this review, we demonstrate that scanning transmission electron microscopy (STEM) is emerging as an alternative method for the direct assembly of nanostructures, with possible applications in plasmonics, quantum technologies, and materials science. Atomically precise manipulation with STEM relies on recent advances in instrumentation that have enabled non-destructive atomic-resolution imaging at lower electron energies. While momentum transfer from highly energetic electrons often leads to atom ejection, interesting dynamics can be induced when the transferable kinetic energies are comparable to bond strengths in the material. Operating in this regime, very recent experiments have revealed the potential for single-atom manipulation using the Ångström-sized electron beam. To truly enable control, however, it is vital to understand the relevant atomic-scale phenomena through accurate dynamical simulations. Although excellent agreement between experiment and theory for the specific case of atomic displacements from graphene has been recently achieved using density functional theory molecular dynamics, in many other cases quantitative accuracy remains a challenge. We provide a comprehensive reanalysis of available experimental data on beam-driven dynamics in light of the state-of-the-art in simulations, and identify important targets for improvement. Overall, the modern electron microscope has great potential to become an atom-scale fabrication platform, especially for covalently bonded 2D nanostructures. We review the developments that have made this possible, argue that graphene is an ideal starting material, and assess the main challenges moving forward.

A direct method of extracting surface recombination velocity from an electron beam induced current line scan

NASA Astrophysics Data System (ADS)

Ong, Vincent K. S.

1998-04-01

The extraction of diffusion length and surface recombination velocity in a semiconductor with the use of an electron beam induced current line scan has traditionally been done by fitting the line scan into complicated theoretical equations. It was recently shown that a much simpler equation is sufficient for the extraction of diffusion length. The linearization coefficient is the only variable that is needed to be adjusted in the curve fitting process. However, complicated equations are still necessary for the extraction of surface recombination velocity. It is shown in this article that it is indeed possible to extract surface recombination velocity with a simple equation, using only one variable, the linearization coefficient. An intuitive feel for the reason behind the method was discussed. The accuracy of the method was verified with the use of three-dimensional computer simulation, and was found to be even slightly better than that of the best existing method.

Direct Observation by Rapid-Scan FT-IR Spectroscopy of Two-Electron-Reduced Intermediate of Tetraaza Catalyst [Co IIN 4H(MeCN)] 2+ Converting CO 2 to CO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheng, Hua; Frei, Heinz

In the search for the two-electron-reduced intermediate of the tetraaza catalyst [Co IIN 4H(MeCN)] 2+ (N 4H = 2,12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),2,11,13,15-pentaene) for CO 2 reduction and elementary steps that result in the formation of CO product, rapid-scan FT-IR spectroscopy of the visible-light-sensitized catalysis, using Ir(ppy) 3 in wet acetonitrile (CD 3CN) solution, led to the observation of two sequential intermediates. The initially formed one-electron-reduced [Co IN 4H] +--CO 2 adduct was converted by the second electron to a transient [Co IN 4H] +--CO 2 - complex that spontaneously converted CO 2 to CO in a rate-limiting step on the second time scalemore » in the dark under regeneration of the catalyst (room temperature). The macrocycle IR spectra of the [Co IN 4H] +--CO 2 - complex and the preceding one-electron [Co IN 4H] +--CO 2 intermediate show close similarity but distinct differences in the carboxylate modes, indicating that the second electron resides mainly on the CO 2 ligand. Vibrational assignments are corroborated by 13C isotopic labeling. The structure and stability of the two-electron-reduced intermediate derived from the time-resolved IR study are in good agreement with recent predictions by DFT electronic structure calculations. This is the first observation of an intermediate of a molecular catalyst for CO 2 reduction during the bond-breaking step producing CO. The reaction pathway for the Co tetraaza catalyst uncovered here suggests that the competition between CO 2 reduction and proton reduction of a macrocyclic multi-electron catalyst is steered toward CO 2 activation if the second electron is directly captured by an adduct of CO 2 and the one-electron-reduced catalyst intermediate.« less

A simplified focusing and astigmatism correction method for a scanning electron microscope

NASA Astrophysics Data System (ADS)

Lu, Yihua; Zhang, Xianmin; Li, Hai

2018-01-01

Defocus and astigmatism can lead to blurred images and poor resolution. This paper presents a simplified method for focusing and astigmatism correction of a scanning electron microscope (SEM). The method consists of two steps. In the first step, the fast Fourier transform (FFT) of the SEM image is performed and the FFT is subsequently processed with a threshold to achieve a suitable result. In the second step, the threshold FFT is used for ellipse fitting to determine the presence of defocus and astigmatism. The proposed method clearly provides the relationships between the defocus, the astigmatism and the direction of stretching of the FFT, and it can determine the astigmatism in a single image. Experimental studies are conducted to demonstrate the validity of the proposed method.

Low-temperature scanning tunneling microscopy of ring-like surface electronic structures around Co islands on InAs(110) surfaces.

PubMed

Muzychenko, D A; Schouteden, K; Savinov, S V; Maslova, N S; Panov, V I; Van Haesendonck, C

2009-08-01

We report on the experimental observation by scanning tunneling microscopy at low temperature of ring-like features that appear around Co metal islands deposited on a clean (110) oriented surface of cleaved p-type InAs crystals. These features are visible in spectroscopic images within a certain range of negative tunneling bias voltages due to the presence of a negative differential conductance in the current-voltage dependence. A theoretical model is introduced, which takes into account non-equilibrium effects in the small tunneling junction area. In the framework of this model the appearance of the ring-like features is explained in terms of interference effects between electrons tunneling directly and indirectly (via a Co island) between the tip and the InAs surface.

Direct Visualization of Local Electromagnetic Field Structures by Scanning Transmission Electron Microscopy.

PubMed

Shibata, Naoya; Findlay, Scott D; Matsumoto, Takao; Kohno, Yuji; Seki, Takehito; Sánchez-Santolino, Gabriel; Ikuhara, Yuichi

2017-07-18

The functional properties of materials and devices are critically determined by the electromagnetic field structures formed inside them, especially at nanointerface and surface regions, because such structures are strongly associated with the dynamics of electrons, holes and ions. To understand the fundamental origin of many exotic properties in modern materials and devices, it is essential to directly characterize local electromagnetic field structures at such defect regions, even down to atomic dimensions. In recent years, rapid progress in the development of high-speed area detectors for aberration-corrected scanning transmission electron microscopy (STEM) with sub-angstrom spatial resolution has opened new possibilities to directly image such electromagnetic field structures at very high-resolution. In this Account, we give an overview of our recent development of differential phase contrast (DPC) microscopy for aberration-corrected STEM and its application to many materials problems. In recent years, we have developed segmented-type STEM detectors which divide the detector plane into 16 segments and enable simultaneous imaging of 16 STEM images which are sensitive to the positions and angles of transmitted/scattered electrons on the detector plane. These detectors also have atomic-resolution imaging capability. Using these segmented-type STEM detectors, we show DPC STEM imaging to be a very powerful tool for directly imaging local electromagnetic field structures in materials and devices in real space. For example, DPC STEM can clearly visualize the local electric field variation due to the abrupt potential change across a p-n junction in a GaAs semiconductor, which cannot be observed by normal in-focus bright-field or annular type dark-field STEM imaging modes. DPC STEM is also very effective for imaging magnetic field structures in magnetic materials, such as magnetic domains and skyrmions. Moreover, real-time imaging of electromagnetic field structures can now be realized through very fast data acquisition, processing, and reconstruction algorithms. If we use DPC STEM for atomic-resolution imaging using a sub-angstrom size electron probe, it has been shown that we can directly observe the atomic electric field inside atoms within crystals and even inside single atoms, the field between the atomic nucleus and the surrounding electron cloud, which possesses information about the atomic species, local chemical bonding and charge redistribution between bonded atoms. This possibility may open an alternative way for directly visualizing atoms and nanostructures, that is, seeing atoms as an entity of electromagnetic fields that reflect the intra- and interatomic electronic structures. In this Account, the current status of aberration-corrected DPC STEM is highlighted, along with some applications in real material and device studies.

An electromagnetic/electrostatic dual cathode system for electron beam instruments

NASA Technical Reports Server (NTRS)

Bradley, J. G.; Conley, J. M.; Wittry, D. B.; Albee, A. L.

1986-01-01

A method of providing cathode redundancy which consists of two fixed cathodes and uses electromagnetic and/or electrostatic fields to direct the electron beam to the electron optical axis is presented, with application to the cathode system of the Scanning Electron Microscope and Particle Analyzer proposed for NASA's Mariner Mark II Comet Rendezvous/Asteroid Flyby projected for the 1990s. The symmetric double deflection system chosen has the optical property that the image of the effective electron source is formed above the magnet assembly near the apparent position of the effective source, and it makes the transverse positions of the electron sources independent of the electron beam energy. Good performance of the system is found, with the sample imaging resolution being the same as for the single-axis cathode.

Electron Microscopy of Living Cells During in Situ Fluorescence Microscopy

PubMed Central

Liv, Nalan; van Oosten Slingeland, Daan S. B.; Baudoin, Jean-Pierre; Kruit, Pieter; Piston, David W.; Hoogenboom, Jacob P.

2016-01-01

We present an approach toward dynamic nanoimaging: live fluorescence of cells encapsulated in a bionanoreactor is complemented with in situ scanning electron microscopy (SEM) on an integrated microscope. This allows us to take SEM snapshots on-demand, that is, at a specific location in time, at a desired region of interest, guided by the dynamic fluorescence imaging. We show that this approach enables direct visualization, with EM resolution, of the distribution of bioconjugated quantum dots on cellular extensions during uptake and internalization. PMID:26580231

Electrolytic Reduction of Titania Slag in Molten Calcium Chloride Bath

NASA Astrophysics Data System (ADS)

Mohanty, Jayashree

2012-05-01

Ferro-titanium is prepared by direct electrolytic reduction of titania-rich slag obtained from plasma smelting of ilmenite in molten CaCl2. The product after electro-reduction is characterized by x-ray diffraction, scanning electron microscopy, and electron probe microanalysis. The electrolysis is carried out at a cell voltage of 3.0 V, taking graphite as the electrolysis cell as well as the anode, and a titania-rich slag piece wrapped by a nichrome wire is used as the cathode.

Cross section TEM characterization of high-energy-Xe-irradiated U-Mo

DOE PAGES

Ye, B.; Jamison, L.; Miao, Y.; ...

2017-03-09

U-Mo alloys irradiated with 84 MeV Xe ions to various doses were characterized with transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) techniques. The TEM thin foils were prepared perpendicular to the irradiated surface to allow a direct observation of the entire region modified by ions. Furthermore, depth-selective microstructural information was revealed. Varied irradiation-induced phenomena such as gas bubble formation, phase reversal, and recrystallization were observed at different ion penetration depths in U-Mo.

Laser-induced selective metallization of polypropylene doped with multiwall carbon nanotubes

NASA Astrophysics Data System (ADS)

Ratautas, Karolis; Gedvilas, Mindaugas; Stankevičiene, Ina; Jagminienė, Aldona; Norkus, Eugenijus; Pira, Nello Li; Sinopoli, Stefano; Račiukaitis, Gediminas

2017-08-01

Moulded interconnect devices (MID) offer the material, weight and cost saving by integration electronic circuits directly into polymeric components used in automotive and other consumer products. Lasers are used to write circuits directly by modifying the surface of polymers followed by an electroless metal plating. A new composite material - the polypropylene doped with multiwall carbon nanotubes was developed for the laser-induced selective metallization. Mechanism of surface activation by laser irradiation was investigated in details utilising pico- and nanoseconds lasers. Deposition of copper was performed in the autocatalytic electroless plating bath. The laser-activated polymer surfaces have been studied using the Raman spectroscopy and scanning electron microscope (SEM). Microscopic images revealed that surface becomes active only after its melting by a laser. Alterations in the Raman spectra of the D and G bands indicated the clustering of carbon additives in the composite material. Optimal laser parameters for the surface activation were found by measuring a sheet resistance of the finally metal-plated samples. A spatially selective copper plating was achieved with the smallest conductor line width of 22 μm at the laser scanning speed of 3 m/s and the pulse repetition rate of 100 kHz. Finally, the technique was validated by making functional electronic circuits by this MID approach.

Development of a novel direct X-ray detector using photoinduced discharge (PID) readout for digital radiography

NASA Astrophysics Data System (ADS)

Heo, D.; Jeon, S.; Kim, J.-S.; Kim, R. K.; Cha, B. K.; Moon, B. J.; Yoon, J.

2013-02-01

We developed a novel direct X-ray detector using photoinduced discharge (PID) readout for digital radiography. The pixel resolution is 512 × 512 with 200 μm pixel and the overall active dimensions of the X-ray imaging panel is 10.24 cm × 10.24 cm. The detector consists of an X-ray absorption layer of amorphous selenium, a charge accumulation layer of metal, and a PID readout layer of amorphous silicon. In particular, the charge accumulation is pixelated because image charges generated by X-ray should be stored pixel by pixel. Here the image charges, or holes, are recombined with electrons generated by the PID method. We used a 405 nm laser diode and cylindrical lens to make a line beam source with a width of 50 μm for PID readout, which generates charges for each pixel lines during the scan. We obtained spatial frequencies of about 1.0 lp/mm for the X-direction (lateral direction) and 0.9 lp/mm for the Y-direction (scanning direction) at 50% modulation transfer function.

Sulfonated reduced graphene oxide as a highly efficient catalyst for direct amidation of carboxylic acids with amines using ultrasonic irradiation.

PubMed

Mirza-Aghayan, Maryam; Tavana, Mahdieh Molaee; Boukherroub, Rabah

2016-03-01

Sulfonated reduced graphene oxide nanosheets (rGO-SO3H) were prepared by grafting sulfonic acid-containing aryl radicals onto chemically reduced graphene oxide (rGO) under sonochemical conditions. rGO-SO3H catalyst was characterized by Fourier-transform infrared (FT-IR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS). rGO-SO3H catalyst was successfully applied as a reusable solid acid catalyst for the direct amidation of carboxylic acids with amines into the corresponding amides under ultrasonic irradiation. The direct sonochemical amidation of carboxylic acid takes place under mild conditions affording in good to high yields (56-95%) the corresponding amides in short reaction times. Copyright © 2015 Elsevier B.V. All rights reserved.

System and method for compressive scanning electron microscopy

DOEpatents

Reed, Bryan W

2015-01-13

A scanning transmission electron microscopy (STEM) system is disclosed. The system may make use of an electron beam scanning system configured to generate a plurality of electron beam scans over substantially an entire sample, with each scan varying in electron-illumination intensity over a course of the scan. A signal acquisition system may be used for obtaining at least one of an image, a diffraction pattern, or a spectrum from the scans, the image, diffraction pattern, or spectrum representing only information from at least one of a select subplurality or linear combination of all pixel locations comprising the image. A dataset may be produced from the information. A subsystem may be used for mathematically analyzing the dataset to predict actual information that would have been produced by each pixel location of the image.

Exceptionally Slow Movement of Gold Nanoparticles at a Solid/Liquid Interface Investigated by Scanning Transmission Electron Microscopy.

PubMed

Verch, Andreas; Pfaff, Marina; de Jonge, Niels

2015-06-30

Gold nanoparticles were observed to move at a liquid/solid interface 3 orders of magnitude slower than expected for the movement in a bulk liquid by Brownian motion. The nanoscale movement was studied with scanning transmission electron microscopy (STEM) using a liquid enclosure consisting of microchips with silicon nitride windows. The experiments involved a variation of the electron dose, the coating of the nanoparticles, the surface charge of the enclosing membrane, the viscosity, and the liquid thickness. The observed slow movement was not a result of hydrodynamic hindrance near a wall but instead explained by the presence of a layer of ordered liquid exhibiting a viscosity 5 orders of magnitude larger than a bulk liquid. The increased viscosity presumably led to a dramatic slowdown of the movement. The layer was formed as a result of the surface charge of the silicon nitride windows. The exceptionally slow motion is a crucial aspect of electron microscopy of specimens in liquid, enabling a direct observation of the movement and agglomeration of nanoscale objects in liquid.

Peering into the secrets of food and agricultural co-products

USDA-ARS?s Scientific Manuscript database

Scanning electron microscopy is a useful tool for understanding food contamination and directing product development of food and industrial products. The current trend in food research is to produce foods that are fast to prepare and/or ready to eat. At the same time, these processed foods must be s...

Direct Observations of the Formation and Redox-Mediator-Assisted Decomposition of Li2 O2 in a Liquid-Cell Li-O2 Microbattery by Scanning Transmission Electron Microscopy.

PubMed

Yang, Chuchu; Han, Jiuhui; Liu, Pan; Hou, Chen; Huang, Gang; Fujita, Takeshi; Hirata, Akihiko; Chen, Mingwei

2017-11-01

Operando scanning transmission electron microscopy observations of cathodic reactions in a liquid-cell Li-O 2 microbattery in the presence of the redox mediator tetrathiafulvalene (TTF) in 1.0 m LiClO 4 dissolved dimethyl sulfoxide electrolyte are reported. It is found that the TTF addition does not obviously affect the discharge reaction for the formation of a solid Li 2 O 2 phase. The coarsening of Li 2 O 2 nanoparticles occurs via both conventional Ostwald ripening and nonclassical crystallization by particle attachment. During charging, the oxidation reaction at significantly reduced charge potentials mainly takes place at Li 2 O 2 /electrolyte interfaces and has obvious correspondence with the oxidized TTF + distributions in the electric fields of the charged electrode. This study provides direct evidence that TTF truly plays a role in promoting the decomposition of Li 2 O 2 as a soluble charge-transfer agent between the electrode and the Li 2 O 2 . © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Few-layered MnO2/SWCNT hybrid in-plane supercapacitor with high energy density

NASA Astrophysics Data System (ADS)

Dutta, Shibsankar; Pal, Shreyasi; De, Sukanta

2018-05-01

In this present work we have synthesized few layered MnO2 nanosheets by mixed solvent exfoliation process for the application as electrode material of in-plane supercapacitor. The Structure and surface morphology of the as prepared samples are characterized by Raman, Transmission electron microscopy and Scanning electron microscopy. The patterns of the hybrids were directly fabricated by (50: 50 wt %) mixture of MnO2 and SWCNT dispersions with the help of a customized mask, and directly transferred onto a flexible PET substrate. Remarkably, the prepared in-plane supercapacitors deliver high energy density of 2.62mWh/cm2. Furthermore, our supercapacitors shows exceptional flexibility and stable performance under bending conditions

Band Alignment and Controllable Electron Migration between Rutile and Anatase TiO2

PubMed Central

Mi, Yang; Weng, Yuxiang

2015-01-01

TiO2 is the most promising semiconductor for photocatalytic splitting of water for hydrogen and degradation of pollutants. The highly photocatalytic active form is its mixed phase of two polymorphs anatase and rutile rather than their pristine compositions. Such a synergetic effect is understood by the staggered band alignment favorable to spatial charge separation. However, electron migration in either direction between the two phases has been reported, the reason of which is still unknown. We determined the band alignment by a novel method, i.e., transient infrared absorption-excitation energy scanning spectra, showing their conduction bands being aligned, thus the electron migration direction is controlled by dynamical factors, such as varying the particle size of anatase, putting electron or hole scavengers on either the surface of anatase or rutile phases, or both. A quantitative criterion capable of predicting the migration direction under various conditions including particle size and surface chemical reactions is proposed, the predictions have been verified experimentally in several typical cases. This would give rise to a great potential in designing more effective titania photocatalysts. PMID:26169699

Measurements and calculations of the Coulomb cross section for the production of direct electron pairs by energetic heavy nuclei in nuclear track emulsion

NASA Technical Reports Server (NTRS)

Derrickson, J. H.; Eby, P. B.; Fountain, W. F.; Parnell, T. A.; Dong, B. L.; Gregory, J. C.; Takahashi, Y.; King, D. T.

1988-01-01

Measurements and theoretical predictions of the Coulomb cross section for the production of direct electron pairs by heavy ions in emulsion have been performed. Nuclear track emulsions were exposed to the 1.8 GeV/amu Fe-56 beam at the Lawrence Berkeley Laboratory bevalac and to the 60 and 200 GeV/amu O-16 and the 200 GeV/amu S-32 beam at the European Center for Nuclear Research Super Proton Synchrotron modified to accelerate heavy ions. The calculations combine the Weizsacker-Williams virtual quanta method applicable to the low-energy transfers and the Kelner-Kotov relativistic treatment for the high-energy transfers. Comparison of the measured total electron pair yield, the energy transfer distribution, and the emission angle distribution with theoretical predictions revealed a discrepancy in the frequency of occurrence of the low-energy pairs (less than or = 10 MeV). The microscope scanning criteria used to identify the direct electron pairs is described and efforts to improve the calculation of the cross section for pair production are also discussed.

Ionospheric electron heating, optical emissions, and striations induced by powerful HF radio waves at high latitudes: Aspect angle dependence

NASA Astrophysics Data System (ADS)

Rietveld, M. T.; Kosch, M. J.; Blagoveshchenskaya, N. F.; Kornienko, V. A.; Leyser, T. B.; Yeoman, T. K.

2003-04-01

In recent years, large electron temperature increases of 300% (3000 K above background) caused by powerful HF-radio wave injection have been observed during nighttime using the EISCAT incoherent scatter radar near Tromsø in northern Norway. In a case study we examine the spatial structure of the modified region. The electron heating is accompanied by ion heating of about 100 degrees and magnetic field-aligned measurements show ion outflows increasing with height up to 300 m s-1 at 582 km. The electron density decreases by up to 20%. When the radar antenna was scanned between three elevations from near field-aligned to vertical, the strongest heating effects were always obtained in the field-aligned position. When the HF-pump beam was scanned between the same three positions, the heating was still almost always strongest in the field-aligned direction. Simultaneous images of the 630 nm O(1D) line in the radio-induced aurora showed that the enhancement caused by the HF radio waves also remained localized near the field-aligned position. Coherent HF radar backscatter also appeared strongest when the pump beam was pointed field-aligned. These results are similar to some Langmuir turbulence phenomena which also show a strong preference for excitation by HF rays launched in the field-aligned direction. The correlation of the position of largest temperature enhancement with the position of the radio-induced aurora suggests that a common mechanism, upper-hybrid wave turbulence, is responsible for both effects. Why the strongest heating effects occur for HF rays directed along the magnetic field is still unclear, but self-focusing on field-aligned striations is a candidate mechanism, and possibly ionospheric tilts may be important.

Opto electronic tweezers based smart sweeper for cells/micro-particles sorting

NASA Astrophysics Data System (ADS)

Verma, R. S.; Kumar, N.

2018-04-01

We report on use of opto-electronic tweezers based sorting approach, termed as smart sweepers, for sorting the microscopic particles by using the Dielectrophoretic (DEP) force response of cells on applied a.c. bias frequency. The applied a.c. bias was kept in negative DEP region, close to the crossover frequency of one of the particles. A line shaped intensity pattern, generated by a cylindrical lens, was scanned across the mixture sample. The particles whose cross over frequency was close to the applied bias frequency, experienced negligible negative DEP(n-DEP) force. On the other hand, the other type of particle experienced large repelling force and were forced to move along the scanning direction of the line shaped intensity profile. We, as a proof of concept, demonstrated the working principle of opto electronic smart sweepers by sweeping out the polystyrene particles from a mixture consisting of polystyrene microspheres (PSM) and red blood cells (RBCs) and leaving RBCs in the region of interest.

Direct electrochemistry and electrocatalysis of glucose oxidase immobilized on reduced graphene oxide and silver nanoparticles nanocomposite modified electrode.

PubMed

Palanisamy, Selvakumar; Karuppiah, Chelladurai; Chen, Shen-Ming

2014-02-01

The direct electrochemistry of glucose oxidase (GOx) was successfully realized on electrochemically reduced graphene oxide and silver nanoparticles (RGO/Ag) nanocomposite modified electrode. The fabricated nanocomposite was characterized by field emission scanning electron microscope and energy dispersive spectroscopy. The GOx immobilized nanocomposite modified electrode showed a pair of well-defined redox peaks with a formal potential (E°) of -0.422 V, indicating that the bioactivity of GOx was retained. The heterogeneous electron transfer rate constant (Ks) of GOx at the nanocomposite was calculated to be 5.27 s(-1), revealing a fast direct electron transfer of GOx. The GOx immobilized RGO/Ag nanocomposite electrode exhibited a good electrocatalytic activity toward glucose over a linear concentration range from 0.5 to 12.5 mM with a detection limit of 0.16 mM. Besides, the fabricated biosensor showed an acceptable sensitivity and selectivity for glucose. Copyright © 2013 Elsevier B.V. All rights reserved.

Synchronized voltage contrast display analysis system

NASA Technical Reports Server (NTRS)

Johnston, M. F.; Shumka, A.; Miller, E.; Evans, K. C. (Inventor)

1982-01-01

An apparatus and method for comparing internal voltage potentials of first and second operating electronic components such as large scale integrated circuits (LSI's) in which voltage differentials are visually identified via an appropriate display means are described. More particularly, in a first embodiment of the invention a first and second scanning electron microscope (SEM) are configured to scan a first and second operating electronic component respectively. The scan pattern of the second SEM is synchronized to that of the first SEM so that both simultaneously scan corresponding portions of the two operating electronic components. Video signals from each SEM corresponding to secondary electron signals generated as a result of a primary electron beam intersecting each operating electronic component in accordance with a predetermined scan pattern are provided to a video mixer and color encoder.

Swept Line Electron Beam Annealing of Ion Implanted Semiconductors.

DTIC Science & Technology

1982-07-01

of my research to the mainstream of technology. The techniques used for beam processing are distinguished by their * ~.* beam source and method by...raster scanned CW lasers (CWL), pulsed ion beams (PI), area pulsed electron beams (PEE), raster scanned (RSEB) or multi - scanned electron beams (MSEB...where high quality or tailored profiles are required. Continuous wave lasers and multi -scanned or swept-line electron beams are the most likely candidates

Focused electron and ion beam systems

DOEpatents

Leung, Ka-Ngo; Reijonen, Jani; Persaud, Arun; Ji, Qing; Jiang, Ximan

2004-07-27

An electron beam system is based on a plasma generator in a plasma ion source with an accelerator column. The electrons are extracted from a plasma cathode in a plasma ion source, e.g. a multicusp plasma ion source. The beam can be scanned in both the x and y directions, and the system can be operated with multiple beamlets. A compact focused ion or electron beam system has a plasma ion source and an all-electrostatic beam acceleration and focusing column. The ion source is a small chamber with the plasma produced by radio-frequency (RF) induction discharge. The RF antenna is wound outside the chamber and connected to an RF supply. Ions or electrons can be extracted from the source. A multi-beam system has several sources of different species and an electron beam source.

Visualizing electron pockets in cuprate superconductors

NASA Astrophysics Data System (ADS)

Das, Tanmoy; Markiewicz, R. S.; Bansil, A.; Balatsky, A. V.

2012-06-01

Fingerprints of the electron pocket in cuprates have been obtained only in numerous magnetotransport measurements, but its absence in spectroscopic observations poses a long-standing mystery. We develop a theoretical tool to provide ways to detect electron pockets via spectroscopies including scanning tunneling microscopy (STM) spectra, inelastic neutron scattering (INS), and angle-resolved photoemission spectroscopy (ARPES). We show that the quasiparticle-interference (QPI) pattern, measured by STM, shows an additional seven q vectors associated with the scattering on the electron pocket than that on the hole pocket. Furthermore, the Bogolyubov quasiparticle scatterings of the electron pocket lead to a second magnetic resonance mode in the INS spectra at a higher resonance energy. Finally, we reanalyze some STM, INS, and ARPES experimental data of several cuprates which dictates the direct fingerprints of electron pockets in these systems.

Scanning Transmission Electron Microscopy | Materials Science | NREL

Science.gov Websites

mode by collecting the EDS and EELS signals point-by-point as one scans the electron probe across the . Examples of Scanning Transmission Electron Microscopy Capabilities Z-contrast image microphoto taken by

Visualization of Nanoplasmonic Coupling to Molecular Orbital in Light Emission Induced by Tunneling Electrons.

PubMed

Yu, Arthur; Li, Shaowei; Wang, Hui; Chen, Siyu; Wu, Ruqian; Ho, W

2018-05-09

The coupling between localized plasmon and molecular orbital in the light emission from a metallic nanocavity has been directly detected and imaged with sub-0.1 nm resolution. The light emission intensity was enhanced when the energy difference between the tunneling electrons and the lowest unoccupied molecular orbital (LUMO) of an azulene molecule matches the energy of a plasmon mode of the nanocavity defined by the Ag-tip and Ag (110) substrate of a scanning tunneling microscope (STM). The spatially resolved image of the light emission intensity matches the spatial distribution of the LUMO obtained by scanning tunneling spectroscopy (STS) and density functional theory (DFT) calculations. Our results highlight the near-field coupling of a molecular orbital to the radiative decay of a plasmonic excitation in a confined nanoscale junction.

Interfacial surfactant competition and its impact on poly(ethylene oxide)/Au and poly(ethylene oxide)/Ag nanocomposite properties

PubMed Central

Seyhan, Merve; Kucharczyk, William; Yarar, U Ecem; Rickard, Katherine; Rende, Deniz; Baysal, Nihat; Bucak, Seyda; Ozisik, Rahmi

2017-01-01

The structure and properties of nanocomposites of poly(ethylene oxide), with Ag and Au nanoparticles, surface modified with a 1:1 (by volume) oleylamine/oleic acid mixture, were investigated via transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), infrared spectroscopy, dynamic mechanical analysis, and static mechanical testing. Results indicated that there was more oleylamine on Ag nanoparticles but more oleic acid on Au nanoparticles. This difference in surfactant populations on each nanoparticle led to different interfacial interactions with poly(ethylene oxide) and drastically influenced the glass transition temperature of these two nanocomposite systems. Almost all other properties were found to correlate strongly with dispersion and distribution state of Au and Ag nanoparticles, such that the property in question changed direction at the onset of agglomeration. PMID:28461744

Application of environmental scanning electron microscopy to determine biological surface structure.

PubMed

Kirk, S E; Skepper, J N; Donald, A M

2009-02-01

The use of environmental scanning electron microscopy in biology is growing as more becomes understood about the advantages and limitations of the technique. These are discussed and we include new evidence about the effect of environmental scanning electron microscopy imaging on the viability of mammalian cells. We show that although specimen preparation for high-vacuum scanning electron microscopy introduces some artefacts, there are also challenges in the use of environmental scanning electron microscopy, particularly at higher resolutions. This suggests the two technologies are best used in combination. We have used human monocyte-derived macrophages as a test sample, imaging their complicated and delicate membrane ruffles and protrusions. We have also explored the possibility of using environmental scanning electron microscopy for dynamic experiments, finding that mammalian cells cannot be imaged and kept alive in the environmental scanning electron microscopy. The dehydration step in which the cell surface is exposed causes irreversible damage, probably via loss of membrane integrity during liquid removal in the specimen chamber. Therefore, mammalian cells should be imaged after fixation where possible to protect against damage as a result of chamber conditions.

Morphological study of fluorescent carbon Nanoparticles (F-CNPs) from ground coffee waste soot oxidation by diluted acid

NASA Astrophysics Data System (ADS)

Gea, S.; Tjandra, S.; Joshua, J.; Wirjosentono, B.

2018-02-01

Coffee ground waste utilization for fluorescent carbon nanoparticles (F-CNPs) through soot oxidation with diluted HNO3 has been conducted. Soot was obtained through three different treatments to coffee ground waste; which was burned in furnaceat 550°C and 650°C and directly burned in a heat-proofcontainer. Then they were analyzed morphologically with Scanning Electron Microscope (SEM) instrument. Soot from direct burning indicated the optimum result where it has denser pores compared to other two soots. Soot obtained from direct burning was refluxed in diluted HNO3 for 12 hours to perform the oxidation. Yellowish brown supernatant was later observed which lead to green fluorescent under the UV light. F-CNPs characterization was done in Transmission Electron Microscopy, which showed that 7.4-23.4 nm of particle size were distributed.

Accurate Virus Quantitation Using a Scanning Transmission Electron Microscopy (STEM) Detector in a Scanning Electron Microscope

DTIC Science & Technology

2017-06-29

Accurate Virus Quantitation Using a Scanning Transmission Electron Microscopy (STEM) Detector in a Scanning Electron Microscope Candace D Blancett1...L Norris2, Cynthia A Rossi4 , Pamela J Glass3, Mei G Sun1,* 1 Pathology Division, United States Army Medical Research Institute of Infectious...Diseases (USAMRIID), 1425 Porter Street, Fort Detrick, Maryland, 21702 2Biostatistics Division, United States Army Medical Research Institute of

Electron probe X-ray microanalysis of cultured myogenic C2C12 cells with scanning and scanning transmission electron microscopy.

PubMed

Tylko, G; Karasiński, J; Wróblewski, R; Roomans, G M; Kilarski, W M

2000-01-01

Heterogeneity of the elemental content of myogenic C2C12 cultured cells was studied by electron probe X-ray microanalysis (EPXMA) with scanning (SEM EPXMA) and scanning transmission electron microscopy (STEM EPXMA). The best plastic substrate for growing cells was Thermanox. For STEM EPXMA, a Formvar film coated with carbon was found to be suitable substrate. The cells examined by scanning transmission electron microscopy showed great heterogeneity in their elemental content in comparison with the cells examined in the scanning electron microscope despite of an almost identical preparation procedure for EPXMA. Nevertheless the K/Na ratios obtained from both methods of EPXMA were very close (4.1 and 4.3). We conclude that the observed discrepancy in the elemental content obtained by the two methods may be due to differences in instrumentation and this must be taken into account when planning a comparative study.

Imaging quality analysis of multi-channel scanning radiometer

NASA Astrophysics Data System (ADS)

Fan, Hong; Xu, Wujun; Wang, Chengliang

2008-03-01

Multi-channel scanning radiometer, on boarding FY-2 geostationary meteorological satellite, plays a key role in remote sensing because of its wide field of view and continuous multi-spectral images acquirements. It is significant to evaluate image quality after performance parameters of the imaging system are validated. Several methods of evaluating imaging quality are discussed. Of these methods, the most fundamental is the MTF. The MTF of photoelectric scanning remote instrument, in the scanning direction, is the multiplication of optics transfer function (OTF), detector transfer function (DTF) and electronics transfer function (ETF). For image motion compensation, moving speed of scanning mirror should be considered. The optical MTF measurement is performed in both the EAST/WEST and NORTH/SOUTH direction, whose values are used for alignment purposes and are used to determine the general health of the instrument during integration and testing. Imaging systems cannot perfectly reproduce what they see and end up "blurring" the image. Many parts of the imaging system can cause blurring. Among these are the optical elements, the sampling of the detector itself, post-processing, or the earth's atmosphere for systems that image through it. Through theory calculation and actual measurement, it is proved that DTF and ETF are the main factors of system MTF and the imaging quality can satisfy the requirement of instrument design.

Three Dimensional Assembly in Directed Self-assembly of Block Copolymers

DOE PAGES

Segal-Peretz, Tamar; Zhou, Chun; Ren, Jiaxing; ...

2016-09-02

The three-dimensional assembly of poly (styrene-b-methyl methacrylate) (PS-b-PMMA) in chemoepitaxy and graphoepitaxy directed self-assembly (DSA) was investigated using scanning transmission electron microscopy (STEM) tomography. The tomographic characterization revealed hidden morphologies and defects at the BCP- chemical pattern interface in lamellar DSA, and probed the formation of cylinders at the bottom of cylindrical DSA for contact hole shrink. Lastly, future work will include control over 3D assembly in sub-10 nm processes.

Peculiarities of the irisation in precious opals in view of their mosaic-cluster (frustumation) inner fabric

NASA Astrophysics Data System (ADS)

Povarennykh, M. Yu.; Knot'ko, A. V.; Matvienko, E. N.; Plechov, P. Yu.; Burmistrov, A. A.; Luksha, V. L.

2016-04-01

A direct correlation was shown for the first time between mosaic irisation patterns in synthetic and natural precious opals (from Australia, Ethiopia, Honduras, Slovakia, and Russia) and their frustumational (lump or mosaic-cluster) inner structure by means of photoluminescence, X-ray phase analysis, IR and Raman spectroscopy, and scanning electron microscopy.

An electron beam linear scanning mode for industrial limited-angle nano-computed tomography.

PubMed

Wang, Chengxiang; Zeng, Li; Yu, Wei; Zhang, Lingli; Guo, Yumeng; Gong, Changcheng

2018-01-01

Nano-computed tomography (nano-CT), which utilizes X-rays to research the inner structure of some small objects and has been widely utilized in biomedical research, electronic technology, geology, material sciences, etc., is a high spatial resolution and non-destructive research technique. A traditional nano-CT scanning model with a very high mechanical precision and stability of object manipulator, which is difficult to reach when the scanned object is continuously rotated, is required for high resolution imaging. To reduce the scanning time and attain a stable and high resolution imaging in industrial non-destructive testing, we study an electron beam linear scanning mode of nano-CT system that can avoid mechanical vibration and object movement caused by the continuously rotated object. Furthermore, to further save the scanning time and study how small the scanning range could be considered with acceptable spatial resolution, an alternating iterative algorithm based on ℓ 0 minimization is utilized to limited-angle nano-CT reconstruction problem with the electron beam linear scanning mode. The experimental results confirm the feasibility of the electron beam linear scanning mode of nano-CT system.

An electron beam linear scanning mode for industrial limited-angle nano-computed tomography

NASA Astrophysics Data System (ADS)

Wang, Chengxiang; Zeng, Li; Yu, Wei; Zhang, Lingli; Guo, Yumeng; Gong, Changcheng

2018-01-01

Nano-computed tomography (nano-CT), which utilizes X-rays to research the inner structure of some small objects and has been widely utilized in biomedical research, electronic technology, geology, material sciences, etc., is a high spatial resolution and non-destructive research technique. A traditional nano-CT scanning model with a very high mechanical precision and stability of object manipulator, which is difficult to reach when the scanned object is continuously rotated, is required for high resolution imaging. To reduce the scanning time and attain a stable and high resolution imaging in industrial non-destructive testing, we study an electron beam linear scanning mode of nano-CT system that can avoid mechanical vibration and object movement caused by the continuously rotated object. Furthermore, to further save the scanning time and study how small the scanning range could be considered with acceptable spatial resolution, an alternating iterative algorithm based on ℓ0 minimization is utilized to limited-angle nano-CT reconstruction problem with the electron beam linear scanning mode. The experimental results confirm the feasibility of the electron beam linear scanning mode of nano-CT system.

Imaging of endodontic biofilms by combined microscopy (FISH/cLSM - SEM).

PubMed

Schaudinn, C; Carr, G; Gorur, A; Jaramillo, D; Costerton, J W; Webster, P

2009-08-01

Scanning electron microscopy is a useful imaging approach for the visualization of bacterial biofilms in their natural environments including their medical and dental habitats, because it allows for the exploration of large surfaces with excellent resolution of topographic features. Most biofilms in nature, however, are embedded in a thick layer of extracellular matrix that prevents a clear identification of individual bacteria by scanning electron microscopy. The use of confocal laser scanning microscopy on the other hand in combination with fluorescence in situ hybridization enables the visualization of matrix embedded bacteria in multi-layered biofilms. In our study, fluorescence in situ hybridization/confocal laser scanning microscopy and scanning electron microscopy were applied to visualize bacterial biofilm in endodontic root canals. The resulting fluorescence in situ hybridization /confocal laser scanning microscopy and scanning electron microscopy and pictures were subsequently combined into one single image to provide high-resolution information on the location of hidden bacteria. The combined use of scanning electron microscopy and fluorescence in situ hybridization / confocal laser scanning microscopy has the potential to overcome the limits of each single technique.

DOE Office of Scientific and Technical Information (OSTI.GOV)

David, M.-L., E-mail: marie-laure.david@univ-poitiers.fr; Pailloux, F.; Canadian Centre for Electron Microscopy, Mc Master University, 1280 Main Street West, Hamilton, Ontario L8S 4M1

We demonstrate that the helium density and corresponding pressure can be modified in single nano-scale bubbles embedded in semiconductors by using the electron beam of a scanning transmission electron microscope as a multifunctional probe: the measurement probe for imaging and chemical analysis and the irradiation source to modify concomitantly the pressure in a controllable way by fine tuning of the electron beam parameters. The control of the detrapping rate is achieved by varying the experimental conditions. The underlying physical mechanisms are discussed; our experimental observations suggest that the helium detrapping from bubbles could be interpreted in terms of direct ballisticmore » collisions, leading to the ejection of the helium atoms from the bubble.« less

Electrochemical Measurement of Electron Transfer Kinetics by Shewanella oneidensis MR-1*

PubMed Central

Baron, Daniel; LaBelle, Edward; Coursolle, Dan; Gralnick, Jeffrey A.; Bond, Daniel R.

2009-01-01

Shewanella oneidensis strain MR-1 can respire using carbon electrodes and metal oxyhydroxides as electron acceptors, requiring mechanisms for transferring electrons from the cell interior to surfaces located beyond the cell. Although purified outer membrane cytochromes will reduce both electrodes and metals, S. oneidensis also secretes flavins, which accelerate electron transfer to metals and electrodes. We developed techniques for detecting direct electron transfer by intact cells, using turnover and single turnover voltammetry. Metabolically active cells attached to graphite electrodes produced thin (submonolayer) films that demonstrated both catalytic and reversible electron transfer in the presence and absence of flavins. In the absence of soluble flavins, electron transfer occurred in a broad potential window centered at ∼0 V (versus standard hydrogen electrode), and was altered in single (ΔomcA, ΔmtrC) and double deletion (ΔomcA/ΔmtrC) mutants of outer membrane cytochromes. The addition of soluble flavins at physiological concentrations significantly accelerated electron transfer and allowed catalytic electron transfer to occur at lower applied potentials (−0.2 V). Scan rate analysis indicated that rate constants for direct electron transfer were slower than those reported for pure cytochromes (∼1 s−1). These observations indicated that anodic current in the higher (>0 V) window is due to activation of a direct transfer mechanism, whereas electron transfer at lower potentials is enabled by flavins. The electrochemical dissection of these activities in living cells into two systems with characteristic midpoint potentials and kinetic behaviors explains prior observations and demonstrates the complementary nature of S. oneidensis electron transfer strategies. PMID:19661057

In Situ Observation of Kinetic Processes of Lath Bainite Nucleation and Growth by Laser Scanning Confocal Microscope in Reheated Weld Metals

NASA Astrophysics Data System (ADS)

Mao, Gaojun; Cao, Rui; Guo, Xili; Jiang, Yong; Chen, Jianhong

2017-12-01

The kinetic processes of nucleation and growth of bainite laths in reheated weld metals are observed and analyzed by a combination of a laser confocal scanning microscope and an electron backscattering diffraction with a field emission scanning electron microscope. The results indicate that the surface relief induced by phase transformation is able to reveal the real microstructural morphologies of bainite laths when viewed from various angles. Five nucleation modes and six types of growth behaviors of bainite laths are revealed. The bainite lath growth rates are measured to vary over a wide range, from 2 μm/s to higher than 2000 μm/s. The orientations of the bainite laths within a prior austenite grain are examined and denoted as different variants. On the basis of variant identification, the reason is analyzed for various growth rates which are demonstrated to be affected by (1) the density of the high-angle misorientation in it, (2) the included angle between habit planes of different variants, and (3) the direction of lath growth with respect to the free (polished) surface.

Spaceborne electronic imaging systems

NASA Technical Reports Server (NTRS)

1971-01-01

Criteria and recommended practices for the design of the spaceborne elements of electronic imaging systems are presented. A spaceborne electronic imaging system is defined as a device that collects energy in some portion of the electromagnetic spectrum with detector(s) whose direct output is an electrical signal that can be processed (using direct transmission or delayed transmission after recording) to form a pictorial image. This definition encompasses both image tube systems and scanning point-detector systems. The intent was to collect the design experience and recommended practice of the several systems possessing the common denominator of acquiring images from space electronically and to maintain the system viewpoint rather than pursuing specialization in devices. The devices may be markedly different physically, but each was designed to provide a particular type of image within particular limitations. Performance parameters which determine the type of system selected for a given mission and which influence the design include: Sensitivity, Resolution, Dynamic range, Spectral response, Frame rate/bandwidth, Optics compatibility, Image motion, Radiation resistance, Size, Weight, Power, and Reliability.

Visualizing heavy fermion confinement and Pauli-limited superconductivity in layered CeCoIn 5

DOE PAGES

Gyenis, András; Feldman, Benjamin E.; Randeria, Mallika T.; ...

2018-02-07

Layered material structures play a key role in enhancing electron–electron interactions to create correlated metallic phases that can transform into unconventional superconducting states. The quasi-two-dimensional electronic properties of such compounds are often inferred indirectly through examination of bulk properties. Here we use scanning tunneling microscopy to directly probe in cross-section the quasi-two-dimensional electronic states of the heavy fermion superconductor CeCoIn 5. Our measurements reveal the strong confined nature of quasiparticles, anisotropy of tunneling characteristics, and layer-by-layer modulated behavior of the precursor pseudogap gap phase. In the interlayer coupled superconducting state, the orientation of line defects relative to the d-wave ordermore » parameter determines whether in-gap states form due to scattering. Spectroscopic imaging of the anisotropic magnetic vortex cores directly characterizes the short interlayer superconducting coherence length and shows an electronic phase separation near the upper critical in-plane magnetic field, consistent with a Pauli-limited first-order phase transition into a pseudogap phase.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gyenis, András; Feldman, Benjamin E.; Randeria, Mallika T.

Layered material structures play a key role in enhancing electron–electron interactions to create correlated metallic phases that can transform into unconventional superconducting states. The quasi-two-dimensional electronic properties of such compounds are often inferred indirectly through examination of bulk properties. Here we use scanning tunneling microscopy to directly probe in cross-section the quasi-two-dimensional electronic states of the heavy fermion superconductor CeCoIn 5. Our measurements reveal the strong confined nature of quasiparticles, anisotropy of tunneling characteristics, and layer-by-layer modulated behavior of the precursor pseudogap gap phase. In the interlayer coupled superconducting state, the orientation of line defects relative to the d-wave ordermore » parameter determines whether in-gap states form due to scattering. Spectroscopic imaging of the anisotropic magnetic vortex cores directly characterizes the short interlayer superconducting coherence length and shows an electronic phase separation near the upper critical in-plane magnetic field, consistent with a Pauli-limited first-order phase transition into a pseudogap phase.« less

Sparse sampling and reconstruction for electron and scanning probe microscope imaging

DOEpatents

Anderson, Hyrum; Helms, Jovana; Wheeler, Jason W.; Larson, Kurt W.; Rohrer, Brandon R.

2015-07-28

Systems and methods for conducting electron or scanning probe microscopy are provided herein. In a general embodiment, the systems and methods for conducting electron or scanning probe microscopy with an undersampled data set include: driving an electron beam or probe to scan across a sample and visit a subset of pixel locations of the sample that are randomly or pseudo-randomly designated; determining actual pixel locations on the sample that are visited by the electron beam or probe; and processing data collected by detectors from the visits of the electron beam or probe at the actual pixel locations and recovering a reconstructed image of the sample.

The surface topography of the choroid plexus. Environmental, low and high vacuum scanning electron microscopy.

PubMed

Mestres, Pedro; Pütz, Norbert; Garcia Gómez de Las Heras, Soledad; García Poblete, Eduardo; Morguet, Andrea; Laue, Michael

2011-05-01

Environmental scanning electron microscopy (ESEM) allows the examination of hydrated and dried specimens without a conductive metal coating which could be advantageous in the imaging of biological and medical objects. The aim of this study was to assess the performance and benefits of wet-mode and low vacuum ESEM in comparison to high vacuum scanning electron microscopy (SEM) using the choroid plexus of chicken embryos as a model, an organ of the brain involved in the formation of cerebrospinal fluid in vertebrates. Specimens were fixed with or without heavy metals and examined directly or after critical point drying with or without metal coating. For wet mode ESEM freshly excised specimens without any pre-treatment were also examined. Conventional high vacuum SEM revealed the characteristic morphology of the choroid plexus cells at a high resolution and served as reference. With low vacuum ESEM of dried but uncoated samples the structure appeared well preserved but charging was a problem. It could be reduced by a short beam dwell time and averaging of images or by using the backscattered electron detector instead of the gaseous secondary electron detector. However, resolution was lower than with conventional SEM. Wet mode imaging was only possible with tissue that had been stabilized by fixation. Not all surface details (e.g. microvilli) could be visualized and other structures, like the cilia, were deformed. In summary, ESEM is an additional option for the imaging of bio-medical samples but it is problematic with regard to resolution and sample stability during imaging. Copyright © 2011 Elsevier GmbH. All rights reserved.

Morphology- and orientation-controlled gallium arsenide nanowires on silicon substrates.

PubMed

Ihn, Soo-Ghang; Song, Jong-In; Kim, Tae-Wook; Leem, Dong-Seok; Lee, Takhee; Lee, Sang-Geul; Koh, Eui Kwan; Song, Kyung

2007-01-01

GaAs nanowires were epitaxially grown on Si(001) and Si(111) substrates by using Au-catalyzed vapor-liquid-solid (VLS) growth in a solid source molecular beam epitaxy system. Scanning electron microscopy analysis revealed that almost all the GaAs nanowires were grown along <111> directions on both Si substrates for growth conditions investigated. The GaAs nanowires had a very uniform diameter along the growth direction. X-ray diffraction data and transmission electron microscopy analysis revealed that the GaAs<111> nanowires had a mixed crystal structure of the hexagonal wurtzite and the cubic zinc-blende. Current-voltage characteristics of junctions formed by the epitaxially grown GaAs nanowires and the Si substrate were investigated by using a current-sensing atomic force microscopy.

Electronic components embedded in a single graphene nanoribbon.

PubMed

Jacobse, P H; Kimouche, A; Gebraad, T; Ervasti, M M; Thijssen, J M; Liljeroth, P; Swart, I

2017-07-25

The use of graphene in electronic devices requires a band gap, which can be achieved by creating nanostructures such as graphene nanoribbons. A wide variety of atomically precise graphene nanoribbons can be prepared through on-surface synthesis, bringing the concept of graphene nanoribbon electronics closer to reality. For future applications it is beneficial to integrate contacts and more functionality directly into single ribbons by using heterostructures. Here, we use the on-surface synthesis approach to fabricate a metal-semiconductor junction and a tunnel barrier in a single graphene nanoribbon consisting of 5- and 7-atom wide segments. We characterize the atomic scale geometry and electronic structure by combined atomic force microscopy, scanning tunneling microscopy, and conductance measurements complemented by density functional theory and transport calculations. These junctions are relevant for developing contacts in all-graphene nanoribbon devices and creating diodes and transistors, and act as a first step toward complete electronic devices built into a single graphene nanoribbon.Adding functional electronic components to graphene nanoribbons requires precise control over their atomic structure. Here, the authors use a bottom-up approach to build a metal-semiconductor junction and a tunnel barrier directly into a single graphene nanoribbon, an exciting development for graphene-based electronic devices.

Localized to itinerant transition of f electrons in ordered Ce films on W(110)

NASA Astrophysics Data System (ADS)

Chen, Q. Y.; Feng, W.; Xie, D. H.; Lai, X. C.; Zhu, X. G.; Huang, L.

2018-04-01

A key issue to understand the driving force and underlying physics in the isostructural γ -α transition in Cerium is the character of the 4 f states, whether it is localized or itinerant. Here the surface topography and electronic structure of the well-ordered Ce metal films on a W(110) substrate were investigated by using scanning tunneling microscopy, angle-resolved photoemission spectroscopy and density functional theory, and single-site dynamical mean-field theory calculations. Three nearly flat f bands can be observed, and a weakly dispersive quasiparticle band near the Fermi level has been directly observed at low temperature, indicating the hybridization between f electrons and conduction electrons in the low-temperature α phase. The hybridization strength becomes weaker upon increasing temperature, and the f electrons become almost fully localized at 300 K in the high-temperature γ phase. The observed localized-to-itinerant transition of the f electrons with decreasing temperature gives direct experimental proof for the changes of the 4 f character in the isostructural γ -α phase transition. Our results suggest that the character of the f electrons plays a crucial role during the γ -α phase transition.

Investigation of MeV-Cu implantation and channeling effects into porous silicon formation

NASA Astrophysics Data System (ADS)

Ahmad, M.; Naddaf, M.

2011-11-01

P-type (1 1 1) silicon wafers were implanted by copper ions (2.5 MeV) in channeling and random directions using ion beam accelerator of the Atomic Energy Commission of Syria (AECS). The effect of implantation direction on formation process of porous silicon (PS) using electrochemical etching method has been investigated using scanning electron microscope (SEM) and photoluminescence (PL) techniques. SEM observations revealed that the size, shape and density of the formed pores are highly affected by the direction of beam implantation. This in turn is seen to influence the PL behavior of the PS.

Scanning ultrafast electron microscopy.

PubMed

Yang, Ding-Shyue; Mohammed, Omar F; Zewail, Ahmed H

2010-08-24

Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability.

Atom Optics for Bose-Einstein Condensates (BEC)

DTIC Science & Technology

2012-04-25

Electron Micrograph of the Top View of Test Chip A .......................................29 11. A Scanning Electron Micrograph of the Cross...Sectional View of Test Chip A .....................29 12. A Scanning Electron Micrograph of the Top View of Test Chip B...30 13. A Scanning Electron Micrograph of the Cross Sectional View of Test Chip B .....................30 14. Toner Masks for Etching

Oscillatory persistent currents in self-assembled quantum rings.

PubMed

Kleemans, N A J M; Bominaar-Silkens, I M A; Fomin, V M; Gladilin, V N; Granados, D; Taboada, A G; García, J M; Offermans, P; Zeitler, U; Christianen, P C M; Maan, J C; Devreese, J T; Koenraad, P M

2007-10-05

We report the direct measurement of the persistent current carried by a single electron by means of magnetization experiments on self-assembled InAs/GaAs quantum rings. We measured the first Aharonov-Bohm oscillation at a field of 14 T, in perfect agreement with our model based on the structural properties determined by cross-sectional scanning tunneling microscopy measurements. The observed oscillation magnitude of the magnetic moment per electron is remarkably large for the topology of our nanostructures, which are singly connected and exhibit a pronounced shape asymmetry.

Drop-casted self-assembling graphene oxide membranes for scanning electron microscopy on wet and dense gaseous samples.

PubMed

Krueger, Mark; Berg, Shannon; Stone, D'Arcy; Strelcov, Evgheni; Dikin, Dmitriy A; Kim, Jaemyung; Cote, Laura J; Huang, Jiaxing; Kolmakov, Andrei

2011-12-27

Graphene oxide sheets dispersed in water and many other solvents can spontaneously assemble into a surface film covering an evaporating droplet due to their amphiphilicity. Thus, graphene oxide membranes with controllable thickness suspended over an orifice have been directly fabricated using a simple drop-cast approach. Mechanical properties and electron transparency tests of these membranes show their use as electron transparent, but molecularly impenetrable, windows for environmental electron microscopy in liquids and dense gaseous media. The foreseeable, broader application of this drop-cast window methodology is the creation of access spots for electron probes to study isolated microsamples in their natural, undisrupted state within the interior of prefabricated devices (such as microfluidic chips or sealed containers of biological, chemically reactive, toxic, or forensic materials).

Re-evaluation of differential phase contrast (DPC) in a scanning laser microscope using a split detector as an alternative to differential interference contrast (DIC) optics.

PubMed

Amos, W B; Reichelt, S; Cattermole, D M; Laufer, J

2003-05-01

In this paper, differential phase imaging (DPC) with transmitted light is implemented by adding a suitable detection system to a standard commercially available scanning confocal microscope. DPC, a long-established method in scanning optical microscopy, depends on detecting the intensity difference between opposite halves or quadrants of a split photodiode detector placed in an aperture plane. Here, DPC is compared with scanned differential interference contrast (DIC) using a variety of biological specimens and objective lenses of high numerical aperture. While DPC and DIC images are generally similar, DPC seems to have a greater depth of field. DPC has several advantages over DIC. These include low cost (no polarizing or strain-free optics are required), absence of a double scanning spot, electronically variable direction of shading and the ability to image specimens in plastic dishes where birefringence prevents the use of DIC. DPC is also here found to need 20 times less laser power at the specimen than DIC.

Scanning probe microscopy and field emission schemes for studying electron emission from polycrystalline diamond

NASA Astrophysics Data System (ADS)

Chubenko, Oksana; Baturin, Stanislav S.; Baryshev, Sergey V.

2016-09-01

The letter introduces a diagram that rationalizes tunneling atomic force microscopy (TUNA) observations of electron emission from polycrystalline diamonds as described in the recent publications [Chatterjee et al., Appl. Phys. Lett. 104, 171907 (2014); Harniman et al., Carbon 94, 386 (2015)]. The direct observations of electron emission from the grain boundary sites by TUNA could indeed be the evidence of electrons originating from grain boundaries under external electric fields. At the same time, from the diagram, it follows that TUNA and field emission schemes are complimentary rather than equivalent for results interpretation. It is further proposed that TUNA could provide better insights into emission mechanisms by measuring the detailed structure of the potential barrier on the surface of polycrystalline diamonds.

Direct observation of anti-phase boundaries in heteroepitaxy of GaSb thin films grown on Si(001) by transmission electron microscopy

NASA Astrophysics Data System (ADS)

Woo, S. Y.; Hosseini Vajargah, S.; Ghanad-Tavakoli, S.; Kleiman, R. N.; Botton, G. A.

2012-10-01

Unambiguous identification of anti-phase boundaries (APBs) in heteroepitaxial films of GaSb grown on Si has been so far elusive. In this work, we present conventional transmission electron microscopy (TEM) diffraction contrast imaging using superlattice reflections, in conjunction with convergent beam electron diffraction analysis, to determine a change in polarity across APBs in order to confirm the presence of anti-phase disorder. In-depth analysis of anti-phase disorder is further supported with atomic resolution high-angle annular dark-field scanning transmission electron microscopy. The nature of APBs in GaSb is further elucidated by a comparison to previous results for GaAs epilayers grown on Si.

Mechanical Twinning and Microstructures in Experimentally Stressed Quartzite

NASA Astrophysics Data System (ADS)

Minor, A.; Sintubin, M.; Wenk, H. R.; Rybacki, E.

2015-12-01

Since Dauphiné twins in quartz have been identified as a stress-related intracrystalline microstructure, several electron backscatter diffraction (EBSD) studies revealed that Dauphiné twins are present in naturally deformed quartz-bearing rocks in a wide range of tectono-metamorphic conditions. EBSD studies on experimentally stressed quartzite showed that crystals with particular crystallographic orientations contain many Dauphiné twin boundaries, while neighboring crystals with different orientations are largely free of twin boundaries. To understand the relationship between stress direction and orientation of Dauphiné twinned quartz crystals, a detailed EBSD study was performed on experimentally stressed quartzite samples and compared with an undeformed reference sample. We stressed 4 cylindrical samples in triaxial compression in a Paterson type gas deformation apparatus at GFZ Potsdam. Experimental conditions were 300MPa confining pressure, 500°C temperature and axial stresses of 145MPa, 250MPa and 460MPa for about 30 hours, resulting in a minor strain <0.04%. EBSD scans were obtained with a Zeiss Evo scanning electron microscope and TSL software at UC Berkeley. The EBSD maps show that Dauphiné twinning is present in the starting material as well as in experimentally stressed samples. Pole figures of the bulk orientation of the reference sample compared with stressed samples show a significant difference regarding the distribution for the r and z directions. The reference sample shows an indistinct maximum for r and z, whereas the stressed samples show a maximum for r poles and a minimum for z poles in the axial stress direction. EBSD scans of the reference and stressed samples were further analyzed manually to identify the orientations of single grains, which are free of twin boundaries and those, which contain twin boundaries. This analysis aims to quantify the relationship of crystal orientation and stress magnitude to initiate mechanical twinning.

Imaging of surface spin textures on bulk crystals by scanning electron microscopy

NASA Astrophysics Data System (ADS)

Akamine, Hiroshi; Okumura, So; Farjami, Sahar; Murakami, Yasukazu; Nishida, Minoru

2016-11-01

Direct observation of magnetic microstructures is vital for advancing spintronics and other technologies. Here we report a method for imaging surface domain structures on bulk samples by scanning electron microscopy (SEM). Complex magnetic domains, referred to as the maze state in CoPt/FePt alloys, were observed at a spatial resolution of less than 100 nm by using an in-lens annular detector. The method allows for imaging almost all the domain walls in the mazy structure, whereas the visualisation of the domain walls with the classical SEM method was limited. Our method provides a simple way to analyse surface domain structures in the bulk state that can be used in combination with SEM functions such as orientation or composition analysis. Thus, the method extends applications of SEM-based magnetic imaging, and is promising for resolving various problems at the forefront of fields including physics, magnetics, materials science, engineering, and chemistry.

A versatile atomic force microscope integrated with a scanning electron microscope.

PubMed

Kreith, J; Strunz, T; Fantner, E J; Fantner, G E; Cordill, M J

2017-05-01

A versatile atomic force microscope (AFM), which can be installed in a scanning electron microscope (SEM), is introduced. The flexible design of the instrument enables correlated analysis for different experimental configurations, such as AFM imaging directly after nanoindentation in vacuum. In order to demonstrate the capabilities of the specially designed AFM installed inside a SEM, slip steps emanating around nanoindents in single crystalline brass were examined. This example showcases how the combination of AFM and SEM imaging can be utilized for quantitative dislocation analysis through the measurement of the slip step heights without the hindrance of oxide formation. Finally, an in situ nanoindentation technique is introduced, illustrating the use of AFM imaging during indentation experiments to examine plastic deformation occurring under the indenter tip. The mechanical indentation data are correlated to the SEM and AFM images to estimate the number of dislocations emitted to the surface.

Monte Carlo Approach for Estimating Density and Atomic Number From Dual-Energy Computed Tomography Images of Carbonate Rocks

NASA Astrophysics Data System (ADS)

Victor, Rodolfo A.; Prodanović, Maša.; Torres-Verdín, Carlos

2017-12-01

We develop a new Monte Carlo-based inversion method for estimating electron density and effective atomic number from 3-D dual-energy computed tomography (CT) core scans. The method accounts for uncertainties in X-ray attenuation coefficients resulting from the polychromatic nature of X-ray beam sources of medical and industrial scanners, in addition to delivering uncertainty estimates of inversion products. Estimation of electron density and effective atomic number from CT core scans enables direct deterministic or statistical correlations with salient rock properties for improved petrophysical evaluation; this condition is specifically important in media such as vuggy carbonates where CT resolution better captures core heterogeneity that dominates fluid flow properties. Verification tests of the inversion method performed on a set of highly heterogeneous carbonate cores yield very good agreement with in situ borehole measurements of density and photoelectric factor.

Gibbsite Growth History — Revelations of a New Scanning Electron Microscope Technique

NASA Astrophysics Data System (ADS)

Roach, Gerald I. D.; Cornell, John B.; Griffin, Brendan J.

A new scanning electron microscope technique termed charge contrast imaging (CCI), unique to the Environmental SEM, has been developed at the Centre for Microscopy and Microanalysis. The technique enables the growth history of gibbsite particles from the Bayer process to be studied. The technique is used on uncoated polished sections. The seed gibbsite is clearly distinguished from freshly precipitated gibbsite enabling information on agglomeration and growth to be unambiguously obtained. Growth rings associated with each pass through precipitation are readily observed which enables the complete growth history of a particle to be ascertained; for example batch and continuously grown gibbsites can be distinguished. Growth of gibbsite on different crystal faces can be directly measured and the presence of secondary nucleation detected. The data obtained via this technique have been confirmed using specially prepared laboratory samples. The technique is now finding wider application in areas such as medicine (examination of kidney stones), mineralogy and ceramics.

Rose bengal-grafted biodegradable microcapsules: singlet-oxygen generation and cancer-cell incapacitation.

PubMed

Wang, Xiao-Lei; Zeng, Yu; Zheng, Yan-Zhen; Chen, Jian-Feng; Tao, Xia; Wang, Ling-Xuan; Teng, Yan

2011-09-26

Rose bengal-grafted chitosan (RB-CHI), synthesized through dehydration between amino and carboxyl functional groups under mild conditions, was coated onto the outer layer of preformed biodegradable microcapsules consisting of sodium alginate and chitosan. The fabricated photosensitive microcapsules were characterized by optical microscopy, scanning electron microscopy, and confocal laser scanning microscopy. The assembled materials maintained intact spherical morphology and thus showed good ability to form thin films. Electron spin resonance spectroscopy allowed direct observation of the generation of singlet oxygen ((1)O(2)) from photosensitive microcapsules under light excitation at about 545 nm. Furthermore, with increasing light radiation, the content of (1)O(2) increased, as detected by a chemical probe. In vitro cellular toxicity assays showed that RB-CHI-coated photosensitive microcapsules exhibit good biocompatibility in darkness and high cytotoxicity after irradiation, and could provide new photoresponsive drug-delivery vehicles. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Retrieving the Quantitative Chemical Information at Nanoscale from Scanning Electron Microscope Energy Dispersive X-ray Measurements by Machine Learning

NASA Astrophysics Data System (ADS)

Jany, B. R.; Janas, A.; Krok, F.

2017-11-01

The quantitative composition of metal alloy nanowires on InSb(001) semiconductor surface and gold nanostructures on germanium surface is determined by blind source separation (BSS) machine learning (ML) method using non negative matrix factorization (NMF) from energy dispersive X-ray spectroscopy (EDX) spectrum image maps measured in a scanning electron microscope (SEM). The BSS method blindly decomposes the collected EDX spectrum image into three source components, which correspond directly to the X-ray signals coming from the supported metal nanostructures, bulk semiconductor signal and carbon background. The recovered quantitative composition is validated by detailed Monte Carlo simulations and is confirmed by separate cross-sectional TEM EDX measurements of the nanostructures. This shows that SEM EDX measurements together with machine learning blind source separation processing could be successfully used for the nanostructures quantitative chemical composition determination.

Visualising reacting single atoms under controlled conditions: Advances in atomic resolution in situ Environmental (Scanning) Transmission Electron Microscopy (E(S)TEM)

NASA Astrophysics Data System (ADS)

Boyes, Edward D.; Gai, Pratibha L.

2014-02-01

Advances in atomic resolution Environmental (Scanning) Transmission Electron Microscopy (E(S)TEM) for probing gas-solid catalyst reactions in situ at the atomic level under controlled reaction conditions of gas environment and temperature are described. The recent development of the ESTEM extends the capability of the ETEM by providing the direct visualisation of single atoms and the atomic structure of selected solid state heterogeneous catalysts in their working states in real-time. Atomic resolution E(S)TEM provides a deeper understanding of the dynamic atomic processes at the surface of solids and their mechanisms of operation. The benefits of atomic resolution-E(S)TEM to science and technology include new knowledge leading to improved technological processes with substantial economic benefits, improved healthcare, reductions in energy needs and the management of environmental waste generation. xml:lang="fr"

TH-CD-202-02: A Preliminary Study Evaluating Beam-Hardening Artifact Reduction On CT Direct Electron-Density Images

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, H; Dolly, S; Zhao, T

Purpose: A prototype reconstruction algorithm that can provide direct electron density (ED) images from single energy CT scans is being currently developed by Siemens Healthcare GmbH. This feature can eliminate the need for kV specific calibration curve for radiation treatemnt planning. An added benefit is that beam-hardening artifacts are also reduced on direct-ED images due to the underlying material decomposition. This study is to quantitatively analyze the reduction of beam-hardening artifacts on direct-ED images and suggest additional clinical usages. Methods: HU and direct-ED images were reconstructed on a head phantom scanned on a Siemens Definition AS CT scanner at fivemore » tube potentials of 70kV, 80kV, 100kV, 120kV and 140kV respectively. From these images, mean, standard deviation (SD), and local NPS were calculated for regions of interest (ROI) of same locations and sizes. A complete analysis of beam-hardening artifact reduction and image quality improvement was conducted. Results: Along with the increase of tube potentials, ROI means and SDs decrease on both HU and direct-ED images. The mean value differences between HU and direct-ED images are up to 8% with absolute value of 2.9. Compared to that on HU images, the SDs are lower on direct-ED images, and the differences are up to 26%. Interestingly, the local NPS calculated from direct-ED images shows consistent values in the low spatial frequency domain for images acquired from all tube potential settings, while varied dramatically on HU images. This also confirms the beam -hardening artifact reduction on ED images. Conclusions: The low SDs on direct-ED images and relative consistent NPS values in the low spatial frequency domain indicate a reduction of beam-hardening artifacts. The direct-ED image has the potential to assist in more accurate organ contouring, and is a better fit for the desired purpose of CT simulations for radiotherapy.« less

Test strategies for industrial testers for converter controls equipment

NASA Astrophysics Data System (ADS)

Oleniuk, P.; Di Cosmo, M.; Kasampalis, V.; Nisbet, D.; Todd, B.; Uznański, S.

2017-04-01

Power converters and their controls electronics are key elements for the operation of the CERN accelerator complex, having a direct impact on its availability. To prevent early-life failures and provide means to verify electronics, a set of industrial testers is used throughout the converters controls electronics' life cycle. The roles of the testers are to validate mass production during the manufacturing phase and to provide means to diagnose and repair failed modules that are brought back from operation. In the converter controls electronics section of the power converters group in the technology department of CERN (TE/EPC/CCE), two main test platforms have been adopted: a PXI platform for mixed analogue-digital functional tests and a JTAG Boundary-Scan platform for digital interconnection and functional tests. Depending on the functionality of the device under test, the appropriate test platforms are chosen. This paper is a follow-up to results presented at the TWEPP 2015 conference, adding the boundary scan test platform and the first results from exploitation of the test system. This paper reports on the test software, hardware design and test strategy applied for a number of devices that has resulted in maximizing test coverage and minimizing test design effort.

Single turnover studies of oxidative halophenol dehalogenation by horseradish peroxidase reveal a mechanism involving two consecutive one electron steps: toward a functional halophenol bioremediation catalyst.

PubMed

Sumithran, Suganya; Sono, Masanori; Raner, Gregory M; Dawson, John H

2012-12-01

Horseradish peroxidase (HRP) catalyzes the oxidative para-dechlorination of the environmental pollutant/carcinogen 2,4,6-trichlorophenol (2,4,6-TCP). A possible mechanism for this reaction is a direct oxygen atom transfer from HRP compound I (HRP I) to trichlorophenol to generate 2,6-dichloro 1,4-benzoquinone, a two-electron transfer process. An alternative mechanism involves two consecutive one-electron transfer steps in which HRP I is reduced to compound II (HRP II) and then to the ferric enzyme as first proposed by Wiese et al. [F.W. Wiese, H.C. Chang, R.V. Lloyd, J.P. Freeman, V.M. Samokyszyn, Arch. Environ. Contam. Toxicol. 34 (1998) 217-222]. To probe the mechanism of oxidative halophenol dehalogenation, the reactions between 2,4,6-TCP and HRP compounds I or II have been investigated under single turnover conditions (i.e., without excess H(2)O(2)) using rapid scan stopped-flow spectroscopy. Addition of 2,4,6-TCP to HRP I leads rapidly to HRP II and then more slowly to the ferric resting state, consistent with a mechanism involving two consecutive one-electron oxidations of the substrate via a phenoxy radical intermediate. HRP II can also directly dechlorinate 2,4,6-TCP as judged by rapid scan stopped-flow and mass spectrometry. This observation is particularly significant since HRP II can only carry out one-electron oxidations. A more detailed understanding of the mechanism of oxidative halophenol dehalogenation will facilitate the use of HRP as a halophenol bioremediation catalyst. Copyright © 2012 Elsevier Inc. All rights reserved.

Comparison of Microstructures and Mechanical Properties for Solid and Mesh Cobalt-Base Alloy Prototypes Fabricated by Electron Beam Melting

NASA Astrophysics Data System (ADS)

Gaytan, S. M.; Murr, L. E.; Martinez, E.; Martinez, J. L.; Machado, B. I.; Ramirez, D. A.; Medina, F.; Collins, S.; Wicker, R. B.

2010-12-01

The microstructures and mechanical behavior of simple, as-fabricated, solid geometries (with a density of 8.4 g/cm3), as-fabricated and fabricated and annealed femoral (knee) prototypes, and reticulated mesh components (with a density of 1.5 g/cm3) all produced by additive manufacturing (AM) using electron beam melting (EBM) of Co-26Cr-6Mo-0.2C powder are examined and compared in this study. Microstructures and microstructural issues are examined by optical metallography (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDS), and X-ray diffraction (XRD), while mechanical properties included selective specimen tensile testing and Vickers microindentation hardness (HV) and Rockwell C-scale hardness (HRC) measurements. Orthogonal (X-Y) melt scanning of the electron beam during AM produced unique, orthogonal and related Cr23C6 carbide (precipitate) arrays (a controlled microstructural architecture) with dimensions of 2 μm in the build plane perpendicular to the build direction, while connected carbide columns were formed in the vertical plane, parallel to the build direction, with microindentation hardnesses ranging from 4.4 to 5.9 GPa, corresponding to a yield stress and ultimate tensile strength (UTS) of 0.51 and 1.45 GPa with elongations ranging from 1.9 to 5.3 pct. Annealing produced an equiaxed fcc grain structure with some grain boundary carbides, frequent annealing twins, and often a high density of intrinsic {111} stacking faults within the grains. The reticulated mesh strut microstructure consisted of dense carbide arrays producing an average microindentation hardness of 6.2 GPa or roughly 25 pct higher than the fully dense components.

Simultaneous Scanning Electron Microscope Imaging of Topographical and Chemical Contrast Using In-Lens, In-Column, and Everhart-Thornley Detector Systems.

PubMed

Zhang, Xinming; Cen, Xi; Ravichandran, Rijuta; Hughes, Lauren A; van Benthem, Klaus

2016-06-01

The scanning electron microscope provides a platform for subnanometer resolution characterization of material morphology with excellent topographic and chemical contrast dependent on the used detectors. For imaging applications, the predominantly utilized signals are secondary electrons (SEs) and backscattered electrons (BSEs) that are emitted from the sample surface. Recent advances in detector technology beyond the traditional Everhart-Thornley geometry have enabled the simultaneous acquisition and discrimination of SE and BSE signals. This study demonstrates the imaging capabilities of a recently introduced new detector system that consists of the combination of two in-lens (I-L) detectors and one in-column (I-C) detector. Coupled with biasing the sample stage to reduce electron-specimen interaction volumes, this trinity of detector geometry allows simultaneous acquisition of signals to distinguish chemical contrast from topographical changes of the sample, including the identification of surface contamination. The I-C detector provides 4× improved topography, whereas the I-L detector closest to the sample offers excellent simultaneous chemical contrast imaging while not limiting the minimization of working distance to obtain optimal lateral resolution. Imaging capabilities and contrast mechanisms for all three detectors are discussed quantitatively in direct comparison to each other and the conventional Everhart-Thornley detector.

Coupled study by TEM/EELS and STM/STS of electronic properties of C- and CN-nanotubes

NASA Astrophysics Data System (ADS)

Lin, Hong; Lagoute, Jérôme; Repain, Vincent; Chacon, Cyril; Girard, Yann; Lauret, Jean-Sébastien; Arenal, Raul; Ducastelle, François; Rousset, Sylvie; Loiseau, Annick

2011-12-01

Carbon nanotubes are the focus of considerable research efforts due to their fascinating physical properties. They provide an excellent model system for the study of one-dimensional materials and molecular electronics. The chirality of nanotubes can lead to very different electronic behaviour, either metallic or semiconducting. Their electronic spectrum consists of a series of Van Hove singularities defining a bandgap for semiconducting tubes and molecular orbitals at the corresponding energies. A promising way to tune the nanotubes electronic properties for future applications is to use doping by heteroatoms. Here we report on the experimental investigation of the role of many-body interactions in nanotube bandgaps, the visualization in direct space of the molecular orbitals of nanotubes and the properties of nitrogen doped nanotubes using scanning tunneling microscopy and transmission electron microscopy as well as electron energy loss spectroscopy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pantzas, Konstantinos, E-mail: konstantinos.pantzas@lpn.cnrs.fr; Institut P', CNRS-Université de Poitiers - ENSMA - UPR 3346, SP2MI - Téléport 2 Bd Marie Pierre Curie, B.P. 30179, F-86962, Futuroscope Chasseneuil Cedex; Patriarche, Gilles

Direct bonding of yttrium iron garnet (YIG) on silicon without the use of an intermediate bonding layer is demonstrated and characterized using scanning transmission electron microscopy and energy-dispersive x-ray spectroscopy. During the bonding experiment, the garnet is reduced in the presence of oxide-free silicon. As a result, a 5 nm thick SiO{sub 2}/amorphous-YIG bilayer is formed and welds the garnet to silicon.

The Particle inside a Ring: A Two-Dimensional Quantum Problem Visualized by Scanning Tunneling Microscopy

ERIC Educational Resources Information Center

Ellison, Mark D.

2008-01-01

The one-dimensional particle-in-a-box model used to introduce quantum mechanics to students suffers from a tenuous connection to a real physical system. This article presents a two-dimensional model, the particle confined within a ring, that directly corresponds to observations of surface electrons in a metal trapped inside a circular barrier.…

High brightness--multiple beamlets source for patterned X-ray production

DOEpatents

Leung, Ka-Ngo [Hercules, CA; Ji, Qing [Albany, CA; Barletta, William A [Oakland, CA; Jiang, Ximan [El Cerrito, CA; Ji, Lili [Albany, CA

2009-10-27

Techniques for controllably directing beamlets to a target substrate are disclosed. The beamlets may be either positive ions or electrons. It has been shown that beamlets may be produced with a diameter of 1 .mu.m, with inter-aperture spacings of 12 .mu.m. An array of such beamlets, may be used for maskless lithography. By step-wise movement of the beamlets relative to the target substrate, individual devices may be directly e-beam written. Ion beams may be directly written as well. Due to the high brightness of the beamlets from extraction from a multicusp source, exposure times for lithographic exposure are thought to be minimized. Alternatively, the beamlets may be electrons striking a high Z material for X-ray production, thereafter collimated to provide patterned X-ray exposures such as those used in CAT scans. Such a device may be used for remote detection of explosives.

Imaging of zymogen granules in fully wet cells: evidence for restricted mechanism of granule growth.

PubMed

Hammel, Ilan; Anaby, Debbie

2007-09-01

The introduction of wet SEM imaging technology permits electron microscopy of wet samples. Samples are placed in sealed specimen capsules and are insulated from the vacuum in the SEM chamber by an impermeable, electron-transparent membrane. The complete insulation of the sample from the vacuum allows direct imaging of fully hydrated, whole-mount tissue. In the current work, we demonstrate direct inspection of thick pancreatic tissue slices (above 400 mum). In the case of scanning of the pancreatic surface, the boundaries of intracellular features are seen directly. Thus no unfolding is required to ascertain the actual particle size distribution based on the sizes of the sections. This method enabled us to investigate the true granule size distribution and confirm early studies of improved conformity to a Poisson-like distribution, suggesting that the homotypic granule growth results from a mechanism, which favors the addition of a single unit granule to mature granules.

Effect of microstructural anisotropy on fracture toughness of hot rolled 13Cr ODS steel - The role of primary and secondary cracking

NASA Astrophysics Data System (ADS)

Das, A.; Viehrig, H. W.; Bergner, F.; Heintze, C.; Altstadt, E.; Hoffmann, J.

2017-08-01

ODS steels have been known to exhibit anisotropic fracture behaviour and form secondary cracks. In this work, the factors responsible for the anisotropic fracture behaviour have been investigated using scanning electron microscopy and electron backscatter microscopy. Fracture toughness of hot rolled 13Cr ODS steel was determined using unloading compliance method for L-T and T-L orientations at various temperatures. L-T orientation had higher fracture toughness than T-L orientation and also contained more pronounced secondary cracking. Secondary cracks appeared at lower loads than primary cracks in both orientations. Primary crack propagation was found to be preferentially through fine grains in a bimodal microstructure. Grains were aligned and elongated the most towards rolling direction followed by T and S directions resulting in fracture anisotropy. Crystallographic texture and preferential alignment of Ti enriched particles parallel to rolling direction also contributed towards fracture anisotropy.

Atmospheric Gaseous Plasma with Large Dimensions

NASA Astrophysics Data System (ADS)

Korenev, Sergey

2012-10-01

The forming of atmospheric plasma with large dimensions using electrical discharge typically uses the Dielectric Barrier Discharge (DBD). The study of atmospheric DBD was shown some problems related to homogeneous volume plasma. The volume of this plasma determines by cross section and gas gap between electrode and dielectric. The using of electron beam for volume ionization of air molecules by CW relativistic electron beams was shown the high efficiency of this process [1, 2]. The main advantage of this approach consists in the ionization of gas molecules by electrons in longitudinal direction determines by their kinetic energy. A novel method for forming of atmospheric homogeneous plasma with large volume dimensions using ionization of gas molecules by pulsed non-relativistic electron beams is presented in the paper. The results of computer modeling for delivered doses of electron beams in gases and ionization are discussed. The structure of experimental bench with plasma diagnostics is considered. The preliminary results of forming atmospheric plasma with ionization gas molecules by pulsed nanosecond non-relativistic electron beam are given. The analysis of potential applications for atmospheric volume plasma is presented. Reference: [1] S. Korenev. ``The ionization of air by scanning relativistic high power CW electron beam,'' 2002 IEEE International Conference on Plasma Science. May 2002, Alberta, Canada. [2] S. Korenev, I. Korenev. ``The propagation of high power CW scanning electron beam in air.'' BEAMS 2002: 14th International Conference on High-Power Particle Beams, Albuquerque, New Mexico (USA), June 2002, AIP Conference Proceedings Vol. 650(1), pp. 373-376. December 17.

Electronic noise in CT detectors: Impact on image noise and artifacts.

PubMed

Duan, Xinhui; Wang, Jia; Leng, Shuai; Schmidt, Bernhard; Allmendinger, Thomas; Grant, Katharine; Flohr, Thomas; McCollough, Cynthia H

2013-10-01

The objective of our study was to evaluate in phantoms the differences in CT image noise and artifact level between two types of commercial CT detectors: one with distributed electronics (conventional) and one with integrated electronics intended to decrease system electronic noise. Cylindric water phantoms of 20, 30, and 40 cm in diameter were scanned using two CT scanners, one equipped with integrated detector electronics and one with distributed detector electronics. All other scanning parameters were identical. Scans were acquired at four tube potentials and 10 tube currents. Semianthropomorphic phantoms were scanned to mimic the shoulder and abdominal regions. Images of two patients were also selected to show the clinical values of the integrated detector. Reduction of image noise with the integrated detector depended on phantom size, tube potential, and tube current. Scans that had low detected signal had the greatest reductions in noise, up to 40% for a 30-cm phantom scanned using 80 kV. This noise reduction translated into up to 50% in dose reduction to achieve equivalent image noise. Streak artifacts through regions of high attenuation were reduced by up to 45% on scans obtained using the integrated detector. Patient images also showed superior image quality for the integrated detector. For the same applied radiation level, the use of integrated electronics in a CT detector showed a substantially reduced level of electronic noise, resulting in reductions in image noise and artifacts, compared with detectors having distributed electronics.

Additive Manufacturing of AlSi10Mg Alloy Using Direct Energy Deposition: Microstructure and Hardness Characterization

NASA Astrophysics Data System (ADS)

Javidani, M.; Arreguin-Zavala, J.; Danovitch, J.; Tian, Y.; Brochu, M.

2017-04-01

This paper aims to study the manufacturing of the AlSi10Mg alloy with direct energy deposition (DED) process. Following fabrication, the macro- and microstructural evolution of the as-processed specimens was initially investigated using optical microscopy and scanning electron microscopy. Columnar dendritic structure was the dominant solidification feature of the deposit; nevertheless, detailed microstructural analysis revealed cellular morphology near the substrate and equiaxed dendrites at the top end of the deposit. Moreover, the microstructural morphology in the melt pool boundary of the deposit differed from the one in the core of the layers. The remaining porosity of the deposit was evaluated by Archimedes' principle and by image analysis of the polished surface. Crystallographic texture in the deposit was also assessed using electron backscatter diffraction and x-ray diffraction analysis. The dendrites were unidirectionally oriented at an angle of 80° to the substrate. EPMA line scans were performed to evaluate the compositional variation and elemental segregation in different locations. Eventually, microhardness (HV) tests were conducted in order to study the hardness gradient in the as-DED-processed specimen along the deposition direction. The presented results, which exhibited a deposit with an almost defect free structure, indicate that the DED process can suitable for the deposition of Al-Si-based alloys with a highly consolidated structure.

Scanning ultrafast electron microscopy

PubMed Central

Yang, Ding-Shyue; Mohammed, Omar F.; Zewail, Ahmed H.

2010-01-01

Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability. PMID:20696933

Digital direct electron imaging of energy-filtered electron backscatter diffraction patterns

NASA Astrophysics Data System (ADS)

Vespucci, S.; Winkelmann, A.; Naresh-Kumar, G.; Mingard, K. P.; Maneuski, D.; Edwards, P. R.; Day, A. P.; O'Shea, V.; Trager-Cowan, C.

2015-11-01

Electron backscatter diffraction is a scanning electron microscopy technique used to obtain crystallographic information on materials. It allows the nondestructive mapping of crystal structure, texture, and strain with a lateral and depth resolution on the order of tens of nanometers. Electron backscatter diffraction patterns (EBSPs) are presently acquired using a detector comprising a scintillator coupled to a digital camera, and the crystallographic information obtainable is limited by the conversion of electrons to photons and then back to electrons again. In this article we will report the direct acquisition of energy-filtered EBSPs using a digital complementary metal-oxide-semiconductor hybrid pixel detector, Timepix. We show results from a range of samples with different mass and density, namely diamond, silicon, and GaN. Direct electron detection allows the acquisition of EBSPs at lower (≤5 keV) electron beam energies. This results in a reduction in the depth and lateral extension of the volume of the specimen contributing to the pattern and will lead to a significant improvement in lateral and depth resolution. Direct electron detection together with energy filtering (electrons having energy below a specific value are excluded) also leads to an improvement in spatial resolution but in addition provides an unprecedented increase in the detail in the acquired EBSPs. An increase in contrast and higher-order diffraction features are observed. In addition, excess-deficiency effects appear to be suppressed on energy filtering. This allows the fundamental physics of pattern formation to be interrogated and will enable a step change in the use of electron backscatter diffraction (EBSD) for crystal phase identification and the mapping of strain. The enhancement in the contrast in high-pass energy-filtered EBSD patterns is found to be stronger for lighter, less dense materials. The improved contrast for such materials will enable the application of the EBSD technique to be expanded to materials for which conventional EBSD analysis is not presently practicable.

Effect of Welding Heat Input on Microstructure and Texture of Inconel 625 Weld Overlay Studied Using the Electron Backscatter Diffraction Method

NASA Astrophysics Data System (ADS)

Kim, Joon-Suk; Lee, Hae-Woo

2016-12-01

The grain size and the texture of three specimens prepared at different heat inputs were determined using optical microscopy and the electron backscatter diffraction method of scanning electron microscopy. Each specimen was equally divided into fusion line zone (FLZ), columnar dendrite zone (CDZ), and surface zone (SZ), according to the location of the weld. Fine dendrites were observed in the FLZ, coarse dendrites in the CDZ, and dendrites grew perpendicular to the FLZ and CDZ. As the heat input increased, the melted zone in the vicinity of the FLZ widened due to the higher Fe content. A lower image quality value was observed for the FLZ compared to the other zones. The results of grain size measurement in each zone showed that the grain size of the SZ became larger as the heat input increased. From the inverse pole figure (IPF) map in the normal direction (ND) and the rolling direction (RD), as the heat input increased, a specific orientation was formed. However, a dominant [001] direction was observed in the RD IPF map.

Imaging quantum transport using scanning gate microscopy

NASA Astrophysics Data System (ADS)

Hackens, Benoit

2014-03-01

Quantum transport in nanodevices is usually probed thanks to measurements of the electrical resistance or conductance, which lack the spatial resolution necessary to probe electron behaviour inside the devices. In this talk, we will show that scanning gate microscopy (SGM) yields real-space images of quantum transport phenomena inside archetypal mesoscopic devices such as quantum point contacts and quantum rings. We will first discuss the SGM technique, which is based on mapping the electrical conductance of a device as an electrically-biased sharp metallic tip scans in its vicinity. With SGM, we demonstrated low temperature imaging of the electron probability density and interferences in embedded mesoscopic quantum rings [B. Hackens et al., Nat. Phys. 2, 826 (2006)]. At high magnetic field, thanks to the SGM conductance maps, one can decrypt complex transport phenomena such as tunneling between quantum Hall edge state, either direct or through localized states [B. Hackens et al., Nat. Comm. 1, 39 (2010)]. Moreover, the technique also allows to perform local spectroscopy of electron transport through selected localized states [F. Martins et al., New J. of Phys. 15, 013049 (2013); F. Martins et al., Sci. Rep. 3, 1416 (2013)]. Overall, these examples show that scanning gate microscopy is a powerful tool for imaging charge carrier behavior inside devices fabricated from a variety of materials, and opens the way towards a more intimate manipulation of charge and quasiparticle transport. This work was performed in collaboration with F. Martins, S. Faniel, B. Brun, M. Pala, X. Wallart, L. Desplanque, B. Rosenow, T. Ouisse, H. Sellier, S. Huant and V. Bayot.

Phased Array-Fed Reflector (PAFR) Antenna Architectures for Space-Based Sensors

NASA Technical Reports Server (NTRS)

Cooley, Michael E.

2014-01-01

Communication link and target ranges for satellite communications (SATCOM) and space-based sensors (e.g. radars) vary from approximately 1000 km (for LEO satellites) to 35,800 km (for GEO satellites). At these long ranges, large antenna gains are required and legacy payloads have usually employed large reflectors with single beams that are either fixed or mechanically steered. For many applications, there are inherent limitations that are associated with the use of these legacy antennas/payloads. Hybrid antenna designs using Phased Array Fed Reflectors (PAFRs) provide a compromise between reflectors and Direct Radiating phased Arrays (DRAs). PAFRs provide many of the performance benefits of DRAs while utilizing much smaller, lower cost (feed) arrays. The primary limitation associated with hybrid PAFR architectures is electronic scan range; approximately +/-5 to +/- 10 degrees is typical, but this range depends on many factors. For LEO applications, the earth FOV is approximately +/-55 degrees which is well beyond the range of electronic scanning for PAFRs. However, for some LEO missions, limited scanning is sufficient or the CONOPS and space vehicle designs can be developed to incorporate a combination mechanical slewing and electronic scanning. In this paper, we review, compare and contrast various PAFR architectures with a focus on their general applicability to space missions. We compare the RF performance of various PAFR architectures and describe key hardware design and implementation trades. Space-based PAFR designs are highly multi-disciplinary and we briefly address key hardware engineering design areas. Finally, we briefly describe two PAFR antenna architectures that have been developed at Northrop Grumman.

Communication: electronic band gaps of semiconducting zig-zag carbon nanotubes from many-body perturbation theory calculations.

PubMed

Umari, P; Petrenko, O; Taioli, S; De Souza, M M

2012-05-14

Electronic band gaps for optically allowed transitions are calculated for a series of semiconducting single-walled zig-zag carbon nanotubes of increasing diameter within the many-body perturbation theory GW method. The dependence of the evaluated gaps with respect to tube diameters is then compared with those found from previous experimental data for optical gaps combined with theoretical estimations of exciton binding energies. We find that our GW gaps confirm the behavior inferred from experiment. The relationship between the electronic gap and the diameter extrapolated from the GW values is also in excellent agreement with a direct measurement recently performed through scanning tunneling spectroscopy.

Radiation Field Forming for Industrial Electron Accelerators Using Rare-Earth Magnetic Materials

NASA Astrophysics Data System (ADS)

Ermakov, A. N.; Khankin, V. V.; Shvedunov, N. V.; Shvedunov, V. I.; Yurov, D. S.

2016-09-01

The article describes the radiation field forming system for industrial electron accelerators, which would have uniform distribution of linear charge density at the surface of an item being irradiated perpendicular to the direction of its motion. Its main element is non-linear quadrupole lens made with the use of rare-earth magnetic materials. The proposed system has a number of advantages over traditional beam scanning systems that use electromagnets, including easier product irradiation planning, lower instantaneous local dose rate, smaller size, lower cost. Provided are the calculation results for a 10 MeV industrial electron accelerator, as well as measurement results for current distribution in the prototype build based on calculations.

Scanning electron microscopy of hepatic ultrastructure: secondary, backscattered, and transmitted electron imaging.

PubMed

Miyai, K; Abraham, J L; Linthicum, D S; Wagner, R M

1976-10-01

Several methods of tissue preparation and different modes of operation of the scanning electron microscope were used to study the ultrastructure of rat liver. Rat livers were perfusion fixed with buffered 2 per cent paraformaldehyde or a mixture of 1.5 per cent paraformaldehyde and 1 per cent glutaraldehyde and processed as follows. Tissue blocks were postfixed in buffered 2 per cent osmium tetroxide followed sequentially by the ligand-mediated osmium binding technique, dehydration and cryofracture in ethanol, and critical point drying. They were then examined without metal coating in the scanning electron microscope operating in the secondary electron and backscattered electron modes. Fifty-micrometer sections were cut with a tissue sectioner, stained with lead citrate, postfixed with osmium, dehydrated, critical point dried, and examined in the secondary electron and back-scattered electron modes. Frozen sections (0.25 to 0.75 mum. thick) were cut by the method of Tokuyasu (Toluyasu KT: J Cell Biol 57:551, 1973) and their scanning transmission electron microscope images were examined either with a scanning transmission electron microscope detector or with a conversion stub using the secondary electron detector. Secondary electron images of the liver prepared by ligand-mediated osmium binding and subsequent cryofracture revealed such intracellular structures as cisternae of the endoplasmic reticulum, lysosomes, mitochondria, lipid droplets, nucleolus and nuclear chromatin, as well as the usual surface morphology, Lipocytes in the perisinusoidal space were readily identified. Backscattered electron images. Unembedded frozen sections had little drying artifact and were virtually free of freezing damage. The scanning transmission electron microscope image revealed those organelles visualized by the secondary electron mode in the ligand-mediated osmium binding-treated tissue.

Polarization response of RHIC electron lens lattices

DOE PAGES

Ranjbar, V. H.; Méot, F.; Bai, M.; ...

2016-10-10

Depolarization response for a system of two orthogonal snakes at irrational tunes is studied in depth using lattice independent spin integration. Particularly, we consider the effect of overlapping spin resonances in this system, to understand the impact of phase, tune, relative location and threshold strengths of the spin resonances. Furthermore, these results are benchmarked and compared to two dimensional direct tracking results for the RHIC e-lens lattice and the standard lattice. We then consider the effect of longitudinal motion via chromatic scans using direct six dimensional lattice tracking.

A Mobile Nanoscience and Electron Microscopy Outreach Program

NASA Astrophysics Data System (ADS)

Coffey, Tonya; Kelley, Kyle

2013-03-01

We have established a mobile nanoscience laboratory outreach program in Western NC that puts scanning electron microscopy (SEM) directly in the hands of K-12 students and the general public. There has been a recent push to develop new active learning materials to educate students at all levels about nanoscience and nanotechnology. Previous projects, such as Bugscope, nanoManipulator, or SPM Live! allowed remote access to advanced microscopies. However, placing SEM directly in schools has not often been possible because the cost and steep learning curve of these technologies were prohibitive, making this project quite novel. We have developed new learning modules for a microscopy outreach experience with a tabletop SEM (Hitachi TM3000). We present here an overview of our outreach and results of the assessment of our program to date.

Direct synthesis of few-layer graphene supported platinum nanocatalyst for methanol oxidation

NASA Astrophysics Data System (ADS)

Tan, Hong; Ma, Xiaohui; Sheng, Leimei; An, Kang; Yu, Liming; Zhao, Hongbin; Xu, Jiaqiang; Ren, Wei; Zhao, Xinluo

2014-11-01

High-crystalline few-layer graphene supported Pt nanoparticles have been synthesized by arc discharge evaporation of carbon electrodes containing Pt element. A high-temperature treatment under hydrogen atmosphere has been carried out to obtain a new type of Pt/graphene catalyst for methanol oxidation in direct methanol fuel cell. The morphology and structure characterizations of as-grown few-layer graphene supported Pt nanoparticles and Pt/graphene catalysts have been studied by Raman spectroscopy, scanning electron microscopy with energy-dispersive spectroscopy, and high-resolution transmission electron microscopy. Cyclic voltammograms and chronoamperometric curves show that our present Pt/graphene catalysts have larger current density for methanol oxidation, higher tolerance to carbon monoxide poisoning, and better stability during the operating procedure, compared to commercial Pt/C catalysts.

Characterization of two-dimensional hexagonal boron nitride using scanning electron and scanning helium ion microscopy

NASA Astrophysics Data System (ADS)

Guo, Hongxuan; Gao, Jianhua; Ishida, Nobuyuki; Xu, Mingsheng; Fujita, Daisuke

2014-01-01

Characterization of the structural and physical properties of two-dimensional (2D) materials, such as layer number and inelastic mean free path measurements, is very important to optimize their synthesis and application. In this study, we characterize the layer number and morphology of hexagonal boron nitride (h-BN) nanosheets on a metallic substrate using field emission scanning electron microscopy (FE-SEM) and scanning helium ion microscopy (HIM). Using scanning beams of various energies, we could analyze the dependence of the intensities of secondary electrons on the thickness of the h-BN nanosheets. Based on the interaction between the scanning particles (electrons and helium ions) and h-BN nanosheets, we deduced an exponential relationship between the intensities of secondary electrons and number of layers of h-BN. With the attenuation factor of the exponential formula, we calculate the inelastic mean free path of electrons and helium ions in the h-BN nanosheets. Our results show that HIM is more sensitive and consistent than FE-SEM for characterizing the number of layers and morphology of 2D materials.

Electron beams scanning: A novel method

NASA Astrophysics Data System (ADS)

Askarbioki, M.; Zarandi, M. B.; Khakshournia, S.; Shirmardi, S. P.; Sharifian, M.

2018-06-01

In this research, a spatial electron beam scanning is reported. There are various methods for ion and electron beam scanning. The best known of these methods is the wire scanning wherein the parameters of beam are measured by one or more conductive wires. This article suggests a novel method for e-beam scanning without the previous errors of old wire scanning. In this method, the techniques of atomic physics are applied so that a knife edge has a scanner role and the wires have detector roles. It will determine the 2D e-beam profile readily when the positions of the scanner and detectors are specified.

Testing and Comparison of Imaging Detectors for Electrons in the Energy Range 10-20 keV

NASA Astrophysics Data System (ADS)

Matheson, J.; Moldovan, G.; Kirkland, A.; Allinson, N.; Abrahams, J. P.

2017-11-01

Interest in direct detectors for low-energy electrons has increased markedly in recent years. Detection of electrons in the energy range up to low tens of keV is important in techniques such as photoelectron emission microscopy (PEEM) and electron backscatter diffraction (EBSD) on scanning electron microscopes (SEMs). The PEEM technique is used both in the laboratory and on synchrotron light sources worldwide. The ubiquity of SEMs means that there is a very large market for EBSD detectors for materials studies. Currently, the most widely used detectors in these applications are based on indirect detection of incident electrons. Examples include scintillators or microchannel plates (MCPs), coupled to CCD cameras. Such approaches result in blurring in scintillators/phosphors, distortions in optical systems, and inefficiencies due the limited active area of MCPs. In principle, these difficulties can be overcome using direct detection in a semiconductor device. Growing out of a feasibility study into the use of a direct detector for use on an XPEEM, we have built at Rutherford Appleton Laboratory a system to illuminate detectors with an electron beam of energy up to 20 keV . We describe this system in detail. It has been used to measure the performance of a custom back-thinned monolithic active pixel sensor (MAPS), a detector based on the Medipix2 chip, and a commercial detector based on MCPs. We present a selection of the results from these measurements and compare and contrast different detector types.

Biomedical ultrasonoscope

NASA Technical Reports Server (NTRS)

Lee, R. D. (Inventor)

1979-01-01

The combination of a "C" mode scan electronics in a portable, battery powered biomedical ultrasonoscope having "A" and "M" mode scan electronics, the latter including a clock generator for generating clock pulses, a cathode ray tube having X, Y and Z axis inputs, a sweep generator connected between the clock generator and the X axis input of the cathode ray tube for generating a cathode ray sweep signal synchronized by the clock pulses, and a receiver adapted to be connected to the Z axis input of the cathode ray tube. The "C" mode scan electronics comprises a plurality of transducer elements arranged in a row and adapted to be positioned on the skin of the patient's body for converting a pulsed electrical signal to a pulsed ultrasonic signal, radiating the ultrasonic signal into the patient's body, picking up the echoes reflected from interfaces in the patient's body and converting the echoes to electrical signals; a plurality of transmitters, each transmitter being coupled to a respective transducer for transmitting a pulsed electrical signal thereto and for transmitting the converted electrical echo signals directly to the receiver, a sequencer connected between the clock generator and the plurality of transmitters and responsive to the clock pulses for firing the transmitters in cyclic order; and a staircase voltage generator connected between the clock generator and the Y axis input of the cathode ray tube for generating a staircase voltage having steps synchronized by the clock pulses.

Effect of processing on the microstructure of finger millet by X-ray diffraction and scanning electron microscopy.

PubMed

Dharmaraj, Usha; Parameswara, P; Somashekar, R; Malleshi, Nagappa G

2014-03-01

Finger millet is one of the important minor cereals, and carbohydrates form its major chemical constituent. Recently, the millet is processed to prepare hydrothermally treated (HM), decorticated (DM), expanded (EM) and popped (PM) products. The present research aims to study the changes in the microstructure of carbohydrates using X-ray diffraction and scanning electron microscopy. Processing the millet brought in significant changes in the carbohydrates. The native millet exhibited A-type pattern of X-ray diffraction with major peaks at 2θ values of 15.3, 17.86 and 23.15°, whereas, all other products showed V-type pattern with single major peak at 2θ values ranging from 19.39 to 19.81°. The corresponding lattice spacing and the number of unit cells in a particular direction of reflection also reduced revealing that crystallinity of starch has been decreased depending upon the processing conditions. Scanning electron microscopic studies also revealed that the orderly pattern of starch granules changed into a coherent mass due to hydrothermal treatment, while high temperature short time treatment rendered a honey-comb like structure to the product. However, the total carbohydrates and non-starch polysaccharide contents almost remained the same in all the products except for DM and EM, but the individual carbohydrate components changed significantly depending on the type of processing.

Characterization With Scanning Electron Microscopy/Energy-Dispersive X-ray Spectrometry of Microtraces From the Ligature Mean in Hanging Mechanical Asphyxia: A Series of Forensic Cases.

PubMed

Maghin, Francesca; Andreola, Salvatore Ambrogio; Boracchi, Michele; Gentile, Guendalina; Maciocco, Francesca; Zoja, Riccardo

2018-03-01

The authors applied scanning electron microscopy with energy-dispersive x-ray spectrometry to the furrow derived from hanging means. The study was conducted with the purpose to detect possible extraneous microtraces, deriving from the ligature, that could have had an interaction with the cutaneous biological matrix, thanks to a transfert mechanism, in the proximities of the lesion.Fifteen cutaneous samples of the furrow and an equal number of fragments of graphite tape, directly positioned on the lesion produced by the ligature mean and used as a "conductor" of possible traces, were analyzed using scanning electron microscopy with energy-dispersive x-ray spectrometry.The research of microscopic traces on the furrow using this technique highlights extraneous traces leading to 3 main categories: natural fabrics, and synthetic and metallic materials, excluding possible environmental pollutants. The analysis, run on 7 hanging deaths, made available by the judicial authority, found a morphological and compositional compatibility with the traces found on the cutaneous furrow produced during hanging.The technique used in this study is innovative in the pathological-forensic field, and can be considered useful in clarifying and studying this typology of asphyxia leading to a specific ligature material, when missing, or attributing the cause of death to hanging when the furrow is not macroscopically obvious.

Severe head lice infestation in an Andean mummy of Arica, Chile.

PubMed

Arriaza, Bernardo; Orellana, Nancy C; Barbosa, Helene S; Menna-Barreto, Rubem F S; Araújo, Adauto; Standen, Vivien

2012-04-01

Pediculus humanus capitis is an ancient human parasite, probably inherited from pre-hominid times. Infestation appears as a recurrent health problem throughout history, including in pre-Columbian populations. Here, we describe and discuss the occurrence of pre-Columbian pediculosis in the Andean region of the Atacama Desert. Using a light microscope and scanning electron microscopy, we studied a highly infested Maitas Chiribaya mummy from Arica in northern Chile dating to 670-990 calibrated years A.D. The scalp and hair of the mummy were almost completely covered by nits and adult head lice. Low- and high-vacuum scanning electron microscopy revealed a well-preserved morphology of the eggs. In addition, the excellent preservation of the nearly 1,000-yr-old adult head lice allowed us to observe and characterize the head, antennae, thorax, abdomen, and legs. Leg segmentation, abdominal spiracles, and sexual dimorphism also were clearly observed. The preservation of the ectoparasites allowed us to examine the micromorphology using scanning electron microscopy; the opercula, aeropyles, and spiracles were clearly visible. This case study provides strong evidence that head lice were a common nuisance for Andean farmers and herders. Head lice are transmitted by direct head-to-head contact; thus, this ancient farmer and herder was potentially infesting other people. The present study contributes to the body of research focusing on lice in ancient populations.

Comparison of 3D cellular imaging techniques based on scanned electron probes: Serial block face SEM vs. Axial bright-field STEM tomography.

PubMed

McBride, E L; Rao, A; Zhang, G; Hoyne, J D; Calco, G N; Kuo, B C; He, Q; Prince, A A; Pokrovskaya, I D; Storrie, B; Sousa, A A; Aronova, M A; Leapman, R D

2018-06-01

Microscopies based on focused electron probes allow the cell biologist to image the 3D ultrastructure of eukaryotic cells and tissues extending over large volumes, thus providing new insight into the relationship between cellular architecture and function of organelles. Here we compare two such techniques: electron tomography in conjunction with axial bright-field scanning transmission electron microscopy (BF-STEM), and serial block face scanning electron microscopy (SBF-SEM). The advantages and limitations of each technique are illustrated by their application to determining the 3D ultrastructure of human blood platelets, by considering specimen geometry, specimen preparation, beam damage and image processing methods. Many features of the complex membranes composing the platelet organelles can be determined from both approaches, although STEM tomography offers a higher ∼3 nm isotropic pixel size, compared with ∼5 nm for SBF-SEM in the plane of the block face and ∼30 nm in the perpendicular direction. In this regard, we demonstrate that STEM tomography is advantageous for visualizing the platelet canalicular system, which consists of an interconnected network of narrow (∼50-100 nm) membranous cisternae. In contrast, SBF-SEM enables visualization of complete platelets, each of which extends ∼2 µm in minimum dimension, whereas BF-STEM tomography can typically only visualize approximately half of the platelet volume due to a rapid non-linear loss of signal in specimens of thickness greater than ∼1.5 µm. We also show that the limitations of each approach can be ameliorated by combining 3D and 2D measurements using a stereological approach. Copyright © 2018. Published by Elsevier Inc.

Creating and Steering Highly Directional Electron Beams in Graphene.

PubMed

Liu, Ming-Hao; Gorini, Cosimo; Richter, Klaus

2017-02-10

We put forward a concept to create highly collimated, nondispersive electron beams in pseudorelativistic Dirac materials such as graphene or topological insulator surfaces. Combining negative refraction and Klein collimation at a parabolic pn junction, the proposed lens generates beams, as narrow as the focal length, that stay focused over scales of several microns and can be steered by a magnetic field without losing collimation. We demonstrate the lens capabilities by applying it to two paradigmatic settings of graphene electron optics: We propose a setup for observing high-resolution angle-dependent Klein tunneling, and, exploiting the intimate quantum-to-classical correspondence of these focused electron waves, we consider high-fidelity transverse magnetic focusing accompanied by simulations for current mapping through scanning gate microscopy. Our proposal opens up new perspectives for next-generation graphene electron optics experiments.

Creating and Steering Highly Directional Electron Beams in Graphene

NASA Astrophysics Data System (ADS)

Liu, Ming-Hao; Gorini, Cosimo; Richter, Klaus

2017-02-01

We put forward a concept to create highly collimated, nondispersive electron beams in pseudorelativistic Dirac materials such as graphene or topological insulator surfaces. Combining negative refraction and Klein collimation at a parabolic p n junction, the proposed lens generates beams, as narrow as the focal length, that stay focused over scales of several microns and can be steered by a magnetic field without losing collimation. We demonstrate the lens capabilities by applying it to two paradigmatic settings of graphene electron optics: We propose a setup for observing high-resolution angle-dependent Klein tunneling, and, exploiting the intimate quantum-to-classical correspondence of these focused electron waves, we consider high-fidelity transverse magnetic focusing accompanied by simulations for current mapping through scanning gate microscopy. Our proposal opens up new perspectives for next-generation graphene electron optics experiments.

New method for characterizing paper coating structures using argon ion beam milling and field emission scanning electron microscopy.

PubMed

Dahlström, C; Allem, R; Uesaka, T

2011-02-01

We have developed a new method for characterizing microstructures of paper coating using argon ion beam milling technique and field emission scanning electron microscopy. The combination of these two techniques produces extremely high-quality images with very few artefacts, which are particularly suited for quantitative analyses of coating structures. A new evaluation method has been developed by using marker-controlled watershed segmentation technique of the secondary electron images. The high-quality secondary electron images with well-defined pores makes it possible to use this semi-automatic segmentation method. One advantage of using secondary electron images instead of backscattered electron images is being able to avoid possible overestimation of the porosity because of the signal depth. A comparison was made between the new method and the conventional method using greyscale histogram thresholding of backscattered electron images. The results showed that the conventional method overestimated the pore area by 20% and detected around 5% more pores than the new method. As examples of the application of the new method, we have investigated the distributions of coating binders, and the relationship between local coating porosity and base sheet structures. The technique revealed, for the first time with direct evidence, the long-suspected coating non-uniformity, i.e. binder migration, and the correlation between coating porosity versus base sheet mass density, in a straightforward way. © 2010 The Authors Journal compilation © 2010 The Royal Microscopical Society.

Direct measurement of the Goos-Hänchen shift using a scanning quadrant detector and a polarization maintaining fiber.

PubMed

Yallapragada, Venkata Jayasurya; Mulay, Gajendra L; Rao, Ch N; Ravishankar, Ajith P; Achanta, Venu Gopal

2016-10-01

High precision measurements of optical beam shifts are important in various fields including sensing, atomic force microscopy, and measuring beam shifts at interfaces. Sub-micron shifts are generally measured by indirect techniques such as weak measurements. We demonstrate a straightforward and robust measurement scheme for the shift, based on a scanning quadrant photodiode (QPD) that is biased using a low noise electronic circuit. The shift is measured with respect to a reference beam that is co-propagating with the signal beam. Thus, the shift of the signal beam is readout directly as the difference between the x-intercepts of the QPD scan plot of the signal and reference beams versus the position of the detector. To measure the beam shift, we use polarization multiplexing scheme where the p-polarized signal and s-polarized reference beams are modulated at two different frequencies and co-launched into a polarization-maintaining fiber. Both the signal and reference beam positions are readout by two lock-in amplifiers simultaneously. In order to demonstrate the utility of this method, we perform a direct measurement of Goos-Hänchen shift of a beam that is reflected from a plane gold surface. Accuracy of 150 nm is achieved using this technique.

Direct measurement of the Goos-Hänchen shift using a scanning quadrant detector and a polarization maintaining fiber

NASA Astrophysics Data System (ADS)

Yallapragada, Venkata Jayasurya; Mulay, Gajendra L.; Rao, Ch. N.; Ravishankar, Ajith P.; Achanta, Venu Gopal

2016-10-01

High precision measurements of optical beam shifts are important in various fields including sensing, atomic force microscopy, and measuring beam shifts at interfaces. Sub-micron shifts are generally measured by indirect techniques such as weak measurements. We demonstrate a straightforward and robust measurement scheme for the shift, based on a scanning quadrant photodiode (QPD) that is biased using a low noise electronic circuit. The shift is measured with respect to a reference beam that is co-propagating with the signal beam. Thus, the shift of the signal beam is readout directly as the difference between the x-intercepts of the QPD scan plot of the signal and reference beams versus the position of the detector. To measure the beam shift, we use polarization multiplexing scheme where the p-polarized signal and s-polarized reference beams are modulated at two different frequencies and co-launched into a polarization-maintaining fiber. Both the signal and reference beam positions are readout by two lock-in amplifiers simultaneously. In order to demonstrate the utility of this method, we perform a direct measurement of Goos-Hänchen shift of a beam that is reflected from a plane gold surface. Accuracy of 150 nm is achieved using this technique.

Synthesis and structural characterization of CZTS nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lydia, R.; Reddy, P. Sreedhara

2013-06-03

The CZTS nanoparticles were successfully synthesized by Chemical co-precipitation method with different pH values in the range of 6 to 8. The synthesized nanoparticles were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. XRD studies revealed that the CZTS nanoparticles exhibited Kesterite Structure with preferential orientation along the (112) direction. Sample at pH value of 7 reached the nearly stoichiometric ratio.

Bordered pit structure and function determine spatial patterns of air-seeding thresholds in xylem of Douglas-fir (Pseudotsuga menziesii; Pinaceae) trees.

Treesearch

J.C. Domec; B. Lachenbruch; F.C. Meinzer

2006-01-01

The air-seeding hypothesis predicts that xylem embolism resistance is linked directly to bordered pit functioning. We tested this prediction in trunks, roots, and branches at different vertical and radial locations in young and old trees of Pseudotsuga menziesii. Dimensions of bordered pits were measured from light and scanning electron micrographs...

Lithium Self-Discharge and Its Prevention: Direct Visualization through In Situ Electrochemical Scanning Transmission Electron Microscopy

DOE PAGES

Harrison, Katharine L.; Zavadil, Kevin R.; Hahn, Nathan T.; ...

2017-11-07

To understand the mechanism that controls low-aspect-ratio lithium deposition morphologies for Li-metal anodes in batteries, we conducted direct visualization of Li-metal deposition and stripping behavior through nanoscale in situ electrochemical scanning transmission electron microscopy (EC-STEM) and macroscale-cell electrochemistry experiments in a recently developed and promising solvate electrolyte, 4 M lithium bis(fluorosulfonyl)imide in 1,2-dimethoxyethane. In contrast to published coin cell studies in the same electrolyte, our experiments revealed low Coulombic efficiencies and inhomogeneous Li morphology during in situ observation. In addition, we conclude that this discrepancy in Coulombic efficiency and morphology of the Li deposits was dependent on the presence ofmore » a compressed lithium separator interface, as we have confirmed through macroscale (not in the transmission electron microscope) electrochemical experiments. Our data suggests that cell compression changed how the solid-electrolyte interphase formed, which is likely responsible for improved morphology and Coulombic efficiency with compression. Furthermore, during the in situ EC-STEM experiments, we observed direct evidence of nanoscale self-discharge in the solvate electrolyte (in the state of electrical isolation). This self-discharge was duplicated in the macroscale, but it was less severe with electrode compression, likely due to a more passivating and corrosion-resistant solid-electrolyte interphase formed in the presence of compression. By combining the solvate electrolyte with a protective LiAl 0.3S coating, we show that the Li nucleation density increased during deposition, leading to improved morphological uniformity. In conclusion, self-discharge was suppressed during rest periods in the cycling profile with coatings present, as evidenced through EC-STEM and confirmed with coin cell data.« less

Lithium Self-Discharge and Its Prevention: Direct Visualization through In Situ Electrochemical Scanning Transmission Electron Microscopy.

PubMed

Harrison, Katharine L; Zavadil, Kevin R; Hahn, Nathan T; Meng, Xiangbo; Elam, Jeffrey W; Leenheer, Andrew; Zhang, Ji-Guang; Jungjohann, Katherine L

2017-11-28

To understand the mechanism that controls low-aspect-ratio lithium deposition morphologies for Li-metal anodes in batteries, we conducted direct visualization of Li-metal deposition and stripping behavior through nanoscale in situ electrochemical scanning transmission electron microscopy (EC-STEM) and macroscale-cell electrochemistry experiments in a recently developed and promising solvate electrolyte, 4 M lithium bis(fluorosulfonyl)imide in 1,2-dimethoxyethane. In contrast to published coin cell studies in the same electrolyte, our experiments revealed low Coulombic efficiencies and inhomogeneous Li morphology during in situ observation. We conclude that this discrepancy in Coulombic efficiency and morphology of the Li deposits was dependent on the presence of a compressed lithium separator interface, as we have confirmed through macroscale (not in the transmission electron microscope) electrochemical experiments. Our data suggests that cell compression changed how the solid-electrolyte interphase formed, which is likely responsible for improved morphology and Coulombic efficiency with compression. Furthermore, during the in situ EC-STEM experiments, we observed direct evidence of nanoscale self-discharge in the solvate electrolyte (in the state of electrical isolation). This self-discharge was duplicated in the macroscale, but it was less severe with electrode compression, likely due to a more passivating and corrosion-resistant solid-electrolyte interphase formed in the presence of compression. By combining the solvate electrolyte with a protective LiAl 0.3 S coating, we show that the Li nucleation density increased during deposition, leading to improved morphological uniformity. Furthermore, self-discharge was suppressed during rest periods in the cycling profile with coatings present, as evidenced through EC-STEM and confirmed with coin cell data.

Lithium Self-Discharge and Its Prevention: Direct Visualization through In Situ Electrochemical Scanning Transmission Electron Microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harrison, Katharine L.; Zavadil, Kevin R.; Hahn, Nathan T.

To understand the mechanism that controls low-aspect-ratio lithium deposition morphologies for Li-metal anodes in batteries, we conducted direct visualization of Li-metal deposition and stripping behavior through nanoscale in situ electrochemical scanning transmission electron microscopy (EC-STEM) and macroscale-cell electrochemistry experiments in a recently developed and promising solvate electrolyte, 4 M lithium bis(fluorosulfonyl)imide in 1,2-dimethoxyethane. In contrast to published coin cell studies in the same electrolyte, our experiments revealed low Coulombic efficiencies and inhomogeneous Li morphology during in situ observation. In addition, we conclude that this discrepancy in Coulombic efficiency and morphology of the Li deposits was dependent on the presence ofmore » a compressed lithium separator interface, as we have confirmed through macroscale (not in the transmission electron microscope) electrochemical experiments. Our data suggests that cell compression changed how the solid-electrolyte interphase formed, which is likely responsible for improved morphology and Coulombic efficiency with compression. Furthermore, during the in situ EC-STEM experiments, we observed direct evidence of nanoscale self-discharge in the solvate electrolyte (in the state of electrical isolation). This self-discharge was duplicated in the macroscale, but it was less severe with electrode compression, likely due to a more passivating and corrosion-resistant solid-electrolyte interphase formed in the presence of compression. By combining the solvate electrolyte with a protective LiAl 0.3S coating, we show that the Li nucleation density increased during deposition, leading to improved morphological uniformity. In conclusion, self-discharge was suppressed during rest periods in the cycling profile with coatings present, as evidenced through EC-STEM and confirmed with coin cell data.« less

Origin of coloration in beetle scales: An optical and structural investigation

NASA Astrophysics Data System (ADS)

Nagi, Ramneet Kaur

In this thesis the origin of angle-independent yellowish-green coloration of the exoskeleton of a beetle was studied. The beetle chosen was a weevil with the Latin name Eupholus chevrolati. The origin of this weevil's coloration was investigated by optical and structural characterization techniques, including optical microscopy, scanning electron microscopy imaging and focused ion beam milling, combined with three-dimensional modeling and photonic band structure calculations. Furthermore, using color theory the pixel-like coloring of the weevil's exoskeleton was investigated and an interesting additive color mixing scheme was discovered. For optical studies, a microreflectance microscopy/spectroscopy set-up was optimized. This set-up allowed not only for imaging of individual colored exoskeleton domains with sizes ˜2-10 μm, but also for obtaining reflection spectra of these micrometer-sized domains. Spectra were analyzed in terms of reflection intensity and wavelength position and shape of the reflection features. To find the origin of these colored exoskeleton spots, a combination of focused ion beam milling and scanning electron microscopy imaging was employed. A three-dimensional photonic crystal in the form of a face-centered cubic lattice of ABC-stacked air cylinders in a biopolymeric cuticle matrix was discovered. Our photonic band structure calculations revealed the existence of different sets of stop-gaps for the lattice constant of 360, 380 and 400 nm in the main lattice directions, Gamma-L, Gamma-X, Gamma-U, Gamma-W and Gamma-K. In addition, scanning electron microscopy images were compared to the specific directional-cuts through the constructed face-centered cubic lattice-based model and the optical micrographs of individual domains to determine the photonic structure corresponding to the different lattice directions. The three-dimensional model revealed stop-gaps in the Gamma-L, Gamma-W and Gamma-K directions. Finally, the coloration of the weevil as perceived by an unaided human eye was represented (mathematically) on the xy-chromaticity diagram, based on XYZ color space developed by CIE (Commission Internationale de l'Eclairage), using the micro-reflectance spectroscopy measurements. The results confirmed the additive mixing of various colors produced by differently oriented photonic crystal domains present in the weevil's exoskeleton scales, as a reason for the angle-independent dull yellowish-green coloration of the weevil E. chevrolati.

A new apparatus for electron tomography in the scanning electron microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morandi, V., E-mail: morandi@bo.imm.cnr.it; Maccagnani, P.; Masini, L.

2015-06-23

The three-dimensional reconstruction of a microscopic specimen has been obtained by applying the tomographic algorithm to a set of images acquired in a Scanning Electron Microscope. This result was achieved starting from a series of projections obtained by stepwise rotating the sample under the beam raster. The Scanning Electron Microscope was operated in the scanning-transmission imaging mode, where the intensity of the transmitted electron beam is a monotonic function of the local mass-density and thickness of the specimen. The detection strategy has been implemented and tailored in order to maintain the projection requirement over the large tilt range, as requiredmore » by the tomographic workflow. A Si-based electron detector and an eucentric-rotation specimen holder have been specifically developed for the purpose.« less

The STAR Detector Upgrades and Electromagnetic Probes in Beam Energy Scan Phase II

NASA Astrophysics Data System (ADS)

Yang, Chi

The Beam Energy Scan Phase II at RHIC, BES-II, is scheduled from year 2019 to 2020 and will explore the high baryon density region of the QCD phase diagram with high precision. The program will focus on the interesting energy region determined from the results of BES-I. Some of the key measurements anticipated are the chiral symmetry restoration and QGP thermal radiation in the dilepton and direct photon channels. The measurements will be possible with an order of magnitude better statistics provided by the electron cooling upgrade of RHIC and with the detector upgrades planned to extend STAR experimental reach. The upgrades are: the inner Time Projection Chamber sectors (iTPC), the Event Plane Detector (EPD), and the end-cap Time of Flight (eTOF). We present the BES-II program details and the physics opportunities in the dilepton and direct photon channels enabled by the upgrades.

On the structural origins of ferroelectricity in HfO{sub 2} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sang, Xiahan; Grimley, Everett D.; LeBeau, James M.

2015-04-20

Here, we present a structural study on the origin of ferroelectricity in Gd doped HfO{sub 2} thin films. We apply aberration corrected high-angle annular dark-field scanning transmission electron microscopy to directly determine the underlying lattice type using projected atom positions and measured lattice parameters. Furthermore, we apply nanoscale electron diffraction methods to visualize the crystal symmetry elements. Combined, the experimental results provide unambiguous evidence for the existence of a non-centrosymmetric orthorhombic phase that can support spontaneous polarization, resolving the origin of ferroelectricity in HfO{sub 2} thin films.

Auger spectroscopy of fracture surfaces of ceramics

NASA Technical Reports Server (NTRS)

Marcus, H. L.; Harris, J. M.; Szalkowski, F. J.

1974-01-01

Results of Auger electron spectroscopy (AES) studies of fracture surfaces in a series of ceramic materials, including Al2O3, MgO, and Si3N4, which were formed using different processing techniques. AES on the fractured surface of a lunar sample is also discussed. Scanning electron micrograph fractography is used to relate the surface chemistry to the failure mode. Combined argon ion sputtering and AES studies demonstrate the local variations in chemistry near the fracture surface. The problems associated with doing AES in insulators are also discussed, and the experimental techniques directed toward solving them are described.

Preparation of polymeric Janus particles by directional UV-induced reactions.

PubMed

Liu, Lianying; Ren, Mingwei; Yang, Wantai

2009-09-15

Polymeric Janus particles are obtained by UV-induced selective surface grafting polymerizations and coupling reactions, in virtue of the light-absorption of photoreactive materials such as the immobilized photoinitiator and spread photoinitiator solution on the surfaces exposed to UV light and the sheltering of densely arrayed immovable particles from light. Varying the monomers or macromolecules applied in photografting polymerization or coupling reaction, and choosing diverse polymeric particles of various size, bicolor and amphiphilic Janus particles could be successfully achieved. Observations by fluorescence microscope, scanning electron microscope ,and transmission electron microscope confirmed the asymmetrical morphology of the resultant Janus particles.

Inter-Layer Coupling Induced Valence Band Edge Shift in Mono- to Few-Layer MoS2

PubMed Central

Trainer, Daniel J.; Putilov, Aleksei V.; Di Giorgio, Cinzia; Saari, Timo; Wang, Baokai; Wolak, Mattheus; Chandrasena, Ravini U.; Lane, Christopher; Chang, Tay-Rong; Jeng, Horng-Tay; Lin, Hsin; Kronast, Florian; Gray, Alexander X.; Xi, Xiaoxing X.; Nieminen, Jouko; Bansil, Arun; Iavarone, Maria

2017-01-01

Recent progress in the synthesis of monolayer MoS2, a two-dimensional direct band-gap semiconductor, is paving new pathways toward atomically thin electronics. Despite the large amount of literature, fundamental gaps remain in understanding electronic properties at the nanoscale. Here, we report a study of highly crystalline islands of MoS2 grown via a refined chemical vapor deposition synthesis technique. Using high resolution scanning tunneling microscopy and spectroscopy (STM/STS), photoemission electron microscopy/spectroscopy (PEEM) and μ-ARPES we investigate the electronic properties of MoS2 as a function of the number of layers at the nanoscale and show in-depth how the band gap is affected by a shift of the valence band edge as a function of the layer number. Green’s function based electronic structure calculations were carried out in order to shed light on the mechanism underlying the observed bandgap reduction with increasing thickness, and the role of the interfacial Sulphur atoms is clarified. Our study, which gives new insight into the variation of electronic properties of MoS2 films with thickness bears directly on junction properties of MoS2, and thus impacts electronics application of MoS2. PMID:28084465

Inter-layer coupling induced valence band edge shift in mono- to few-layer MoS 2

DOE PAGES

Trainer, Daniel J.; Putilov, Aleksei V.; Di Giorgio, Cinzia; ...

2017-01-13

In this study, recent progress in the synthesis of monolayer MoS 2, a two-dimensional direct band-gap semiconductor, is paving new pathways toward atomically thin electronics. Despite the large amount of literature, fundamental gaps remain in understanding electronic properties at the nanoscale. Here,we report a study of highly crystalline islands of MoS 2 grown via a refined chemical vapor deposition synthesis technique. Using high resolution scanning tunneling microscopy and spectroscopy (STM/STS), photoemission electron microscopy/spectroscopy (PEEM) and μ-ARPES we investigate the electronic properties of MoS 2 as a function of the number of layers at the nanoscale and show in-depth how themore » band gap is affected by a shift of the valence band edge as a function of the layer number. Green’s function based electronic structure calculations were carried out in order to shed light on the mechanism underlying the observed bandgap reduction with increasing thickness, and the role of the interfacial Sulphur atoms is clarified. Our study, which gives new insight into the variation of electronic properties of MoS 2 films with thickness bears directly on junction properties of MoS2, and thus impacts electronics application of MoS 2.« less

Subsurface examination of a foliar biofilm using scanning electron- and focused-ion-beam microscopy

USDA-ARS?s Scientific Manuscript database

The dual beam scanning electron microscope, equipped with both a focused ion- and scanning electron- beam (FIB SEM) is a novel tool for the exploration of the subsurface structure of biological tissues. The FIB is capable of removing small cross sections to view the subsurface features and may be s...

Design of a fast multileaf collimator for radiobiological optimized IMRT with scanned beams of photons, electrons, and light ions.

PubMed

Svensson, Roger; Larsson, Susanne; Gudowska, Irena; Holmberg, Rickard; Brahme, Anders

2007-03-01

Intensity modulated radiation therapy is rapidly becoming the treatment of choice for most tumors with respect to minimizing damage to the normal tissues and maximizing tumor control. Today, intensity modulated beams are most commonly delivered using segmental multileaf collimation, although an increasing number of radiation therapy departments are employing dynamic multileaf collimation. The irradiation time using dynamic multileaf collimation depends strongly on the nature of the desired dose distribution, and it is difficult to reduce this time to less than the sum of the irradiation times for all individual peak heights using dynamic leaf collimation [Svensson et al., Phys. Med. Biol. 39, 37-61 (1994)]. Therefore, the intensity modulation will considerably increase the total treatment time. A more cost-effective procedure for rapid intensity modulation is using narrow scanned photon, electron, and light ion beams in combination with fast multileaf collimator penumbra trimming. With this approach, the irradiation time is largely independent of the complexity of the desired intensity distribution and, in the case of photon beams, may even be shorter than with uniform beams. The intensity modulation is achieved primarily by scanning of a narrow elementary photon pencil beam generated by directing a narrow well focused high energy electron beam onto a thin bremsstrahlung target. In the present study, the design of a fast low-weight multileaf collimator that is capable of further sharpening the penumbra at the edge of the elementary scanned beam has been simulated, in order to minimize the dose or radiation response of healthy tissues. In the case of photon beams, such a multileaf collimator can be placed relatively close to the bremsstrahlung target to minimize its size. It can also be flat and thin, i.e., only 15-25 mm thick in the direction of the beam with edges made of tungsten or preferably osmium to optimize the sharpening of the penumbra. The low height of the collimator will minimize edge scatter from glancing incidence. The major portions of the collimator leafs can then be made of steel or even aluminum, so that the total weight of the multileaf collimator will be as low as 10 kg, which may even allow high-speed collimation in real time in synchrony with organ movements. To demonstrate the efficiency of this collimator design in combination with pencil beam scanning, optimal radiobiological treatments of an advanced cervix cancer were simulated. Different geometrical collimator designs were tested for bremsstrahlung, electron, and light ion beams. With a 10 mm half-width elementary scanned photon beam and a steel collimator with tungsten edges, it was possible to make as effective treatments as obtained with intensity modulated beams of full resolution, i.e., here 5 mm resolution in the fluence map. In combination with narrow pencil beam scanning, such a collimator may provide ideal delivery of photons, electrons, or light ions for radiation therapy synchronized to breathing and other organ motions. These high-energy photon and light ion beams may allow three-dimensional in vivo verification of delivery and thereby clinical implementation of the BioArt approach using Biologically Optimized three-dimensional in vivo predictive Assay based adaptive Radiation Therapy [Brahme, Acta Oncol. 42, 123-126 (2003)].

Spatial Resolution in Scanning Electron Microscopy and Scanning Transmission Electron Microscopy Without a Specimen Vacuum Chamber.

PubMed

Nguyen, Kayla X; Holtz, Megan E; Richmond-Decker, Justin; Muller, David A

2016-08-01

A long-standing goal of electron microscopy has been the high-resolution characterization of specimens in their native environment. However, electron optics require high vacuum to maintain an unscattered and focused probe, a challenge for specimens requiring atmospheric or liquid environments. Here, we use an electron-transparent window at the base of a scanning electron microscope's objective lens to separate column vacuum from the specimen, enabling imaging under ambient conditions, without a specimen vacuum chamber. We demonstrate in-air imaging of specimens at nanoscale resolution using backscattered scanning electron microscopy (airSEM) and scanning transmission electron microscopy. We explore resolution and contrast using Monte Carlo simulations and analytical models. We find that nanometer-scale resolution can be obtained at gas path lengths up to 400 μm, although contrast drops with increasing gas path length. As the electron-transparent window scatters considerably more than gas at our operating conditions, we observe that the densities and thicknesses of the electron-transparent window are the dominant limiting factors for image contrast at lower operating voltages. By enabling a variety of detector configurations, the airSEM is applicable to a wide range of environmental experiments including the imaging of hydrated biological specimens and in situ chemical and electrochemical processes.

Spatial Resolution in Scanning Electron Microscopy and Scanning Transmission Electron Microscopy Without a Specimen Vacuum Chamber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Kayla X.; Holtz, Megan E.; Richmond-Decker, Justin

2016-07-25

Abstract A long-standing goal of electron microscopy has been the high-resolution characterization of specimens in their native environment. However, electron optics require high vacuum to maintain an unscattered and focused probe, a challenge for specimens requiring atmospheric or liquid environments. Here, we use an electron-transparent window at the base of a scanning electron microscope’s objective lens to separate column vacuum from the specimen, enabling imaging under ambient conditions, without a specimen vacuum chamber. We demonstrate in-air imaging of specimens at nanoscale resolution using backscattered scanning electron microscopy (airSEM) and scanning transmission electron microscopy. We explore resolution and contrast using Montemore » Carlo simulations and analytical models. We find that nanometer-scale resolution can be obtained at gas path lengths up to 400μm, although contrast drops with increasing gas path length. As the electron-transparent window scatters considerably more than gas at our operating conditions, we observe that the densities and thicknesses of the electron-transparent window are the dominant limiting factors for image contrast at lower operating voltages. By enabling a variety of detector configurations, the airSEM is applicable to a wide range of environmental experiments including the imaging of hydrated biological specimens andin situchemical and electrochemical processes.« less

Secretory glands and microvascular systems imaged in aqueous solution by atmospheric scanning electron microscopy (ASEM).

PubMed

Yamazawa, Toshiko; Nakamura, Naotoshi; Sato, Mari; Sato, Chikara

2016-12-01

Exocrine glands, e.g., salivary and pancreatic glands, play an important role in digestive enzyme secretion, while endocrine glands, e.g., pancreatic islets, secrete hormones that regulate blood glucose levels. The dysfunction of these secretory organs immediately leads to various diseases, such as diabetes or Sjögren's syndrome, by poorly understood mechanisms. Gland-related diseases have been studied by optical microscopy (OM), and at higher resolution by transmission electron microscopy (TEM) of Epon embedded samples, which necessitates hydrophobic sample pretreatment. Here, we report the direct observation of tissue in aqueous solution by atmospheric scanning electron microscopy (ASEM). Salivary glands, lacrimal glands, and pancreas were fixed, sectioned into slabs, stained with phosphotungstic acid (PTA), and inspected in radical scavenger d-glucose solution from below by an inverted scanning electron microscopy (SEM), guided by optical microscopy from above to target the tissue substructures. A 2- to 3-µm specimen thickness was visualized by the SEM. In secretory cells, cytoplasmic vesicles and other organelles were clearly imaged at high resolution, and the former could be classified according to the degree of PTA staining. In islets of Langerhans, the microvascular system used as an outlet by the secretory cells was also clearly observed. Microvascular system is also critically involved in the onset of diabetic complications and was clearly visible in subcutaneous tissue imaged by ASEM. The results suggest the use of in-solution ASEM for histology and to study vesicle secretion systems. Further, the high-throughput of ASEM makes it a potential tool for the diagnosis of exocrine and endocrine-related diseases. © 2016 Wiley Periodicals, Inc.

Imaging surface acoustic wave dynamics in semiconducting polymers by scanning ultrafast electron microscopy.

PubMed

Najafi, Ebrahim; Liao, Bolin; Scarborough, Timothy; Zewail, Ahmed

2018-01-01

Understanding the mechanical properties of organic semiconductors is essential to their electronic and photovoltaic applications. Despite a large volume of research directed toward elucidating the chemical, physical and electronic properties of these materials, little attention has been directed toward understanding their thermo-mechanical behavior. Here, we report the ultrafast imaging of surface acoustic waves (SAWs) on the surface of the Poly(3-hexylthiophene-2,5-diyl) (P3HT) thin film at the picosecond and nanosecond timescales. We then use these images to measure the propagation velocity of SAWs, which we then employ to determine the Young's modulus of P3HT. We further validate our experimental observation by performing a semi-empirical transient thermoelastic finite element analysis. Our findings demonstrate the potential of ultrafast electron microscopy to not only probe charge carrier dynamics in materials as previously reported, but also to measure their mechanical properties with great accuracy. This is particularly important when in situ characterization of stiffness for thin devices and nanomaterials is required. Copyright © 2017 Elsevier B.V. All rights reserved.

Modeling of profilometry with laser focus sensors

NASA Astrophysics Data System (ADS)

Bischoff, Jörg; Manske, Eberhard; Baitinger, Henner

2011-05-01

Metrology is of paramount importance in submicron patterning. Particularly, line width and overlay have to be measured very accurately. Appropriated metrology techniques are scanning electron microscopy and optical scatterometry. The latter is non-invasive, highly accurate and enables optical cross sections of layer stacks but it requires periodic patterns. Scanning laser focus sensors are a viable alternative enabling the measurement of non-periodic features. Severe limitations are imposed by the diffraction limit determining the edge location accuracy. It will be shown that the accuracy can be greatly improved by means of rigorous modeling. To this end, a fully vectorial 2.5-dimensional model has been developed based on rigorous Maxwell solvers and combined with models for the scanning and various autofocus principles. The simulations are compared with experimental results. Moreover, the simulations are directly utilized to improve the edge location accuracy.

Cellular lining of the sheep pineal recess studied by light-, transmission-, and scanning electron microscopy: morphologic indications for a direct secretion of melatonin from the pineal gland to the cerebrospinal fluid.

PubMed

Tricoire, Hélène; Malpaux, Benoit; Møller, Morten

2003-01-27

In the sheep, the pineal hormone melatonin displays nocturnal levels 20 times as high in the cerebrospinal fluid of the third ventricle as in the jugular blood. Moreover, in the pineal recess, the evagination of the third ventricle into the pineal stalk, the levels of melatonin in the cerebrospinal fluid are even higher than in the ventral part of the third ventricle. This finding suggests melatonin to be secreted directly from the pineal gland to the ventricular lumen of the pineal recess of this species. We have, therefore, studied the interface between the sheep pineal gland and the cerebrospinal fluid by light-, scanning-, and electron microscopy of the pineal recess, as well as the permeability of the interface by tracer injections into the third ventricle. First, we show that the classic ependymal lining of the third ventricle disappears in the superior part of the recess. In this area, bulging pinealocytes, displaying immunoreactivity for serotonin, directly appose the cerebrospinal fluid. This pineal-cerebrospinal fluid interface of the sheep is large compared with other species, especially rodent species. Intraventricular injections of horseradish peroxidase and fluorescein isothiocyanate showed that both these tracers could permeate from the pineal recess into the sheep pineal parenchyma. This permeation was due to the presence of gap and intermediate junctions connecting the pinealocytes apposing the ventricular lumen. Thus, our results show that endocrine cells in this specialized area of the ventricular system are in direct contact with the cerebrospinal fluid. This finding supports the physiological concept of a direct secretion of melatonin into the cerebrospinal fluid of the sheep pineal recess. Copyright 2002 Wiley-Liss, Inc.

Electron Acceleration from the Interaction of VULCAN 100TW Laser with Au Foils and its Dependence on Laser Polarisation

NASA Astrophysics Data System (ADS)

Nagel, S. R.; Bellei, C.; Kneip, S.; Mangles, S. P. D.; Palmer, C.; Willingale, L.; Dangor, A. E.; Najmudin, Z.; Clarke, R. J.; Heathcote, R.; Henig, A.; Schreiber, J.; Saevert, A.; Kaluza, M.

2008-11-01

Electrons as well as ions can be accelerated to high energies (MeV) by high intensity laser interactions with solid targets. An overview of an experiment on the Vulcan laser (pulse length cτ˜150μm, energy on target ˜60 J), will be presented. In this experiment electron acceleration from thick overdense plasmas is investigated by conducting thickness scans using Au foil targets ranging from 10 to 100 μm. The electron spectra, of the most energetic electrons produced in the interaction, are measured along the laser direction and extend up to 40MeV. Surprisingly the electron acceleration depends on target thickness. Simultaneously rear surface proton beam profiles show a dependence of target thickness. Both effects are attributed to electron recirculation. In addition the effects of polarisation was investigated. A decrease in number and effective temperature of energetic electrons is observed for circular polarisation as compared to linear polarisation.

A scanning electron microscopy study of the macro-crystalline structure of 2-(2,4-dinitrobenzyl) pyridine

NASA Technical Reports Server (NTRS)

Ware, Jacqueline; Hammond, Ernest C., Jr.

1989-01-01

The compound, 2-(2,4-dinitrobenzyl) pyridine, was synthesized in the laboratory; an introductory level electron microscopy study of the macro-crystalline structure was conducted using the scanning electron microscope (SEM). The structure of these crystals was compared with the macrostructure of the crystal of 2-(2,4-dinitrobenzyl) pyridinium bromide, the hydrobromic salt of the compound which was also synthesized in the laboratory. A scanning electron microscopy crystal study was combined with a study of the principle of the electron microscope.

High throughput optical scanner

DOEpatents

Basiji, David A.; van den Engh, Gerrit J.

2001-01-01

A scanning apparatus is provided to obtain automated, rapid and sensitive scanning of substrate fluorescence, optical density or phosphorescence. The scanner uses a constant path length optical train, which enables the combination of a moving beam for high speed scanning with phase-sensitive detection for noise reduction, comprising a light source, a scanning mirror to receive light from the light source and sweep it across a steering mirror, a steering mirror to receive light from the scanning mirror and reflect it to the substrate, whereby it is swept across the substrate along a scan arc, and a photodetector to receive emitted or scattered light from the substrate, wherein the optical path length from the light source to the photodetector is substantially constant throughout the sweep across the substrate. The optical train can further include a waveguide or mirror to collect emitted or scattered light from the substrate and direct it to the photodetector. For phase-sensitive detection the light source is intensity modulated and the detector is connected to phase-sensitive detection electronics. A scanner using a substrate translator is also provided. For two dimensional imaging the substrate is translated in one dimension while the scanning mirror scans the beam in a second dimension. For a high throughput scanner, stacks of substrates are loaded onto a conveyor belt from a tray feeder.

Exploring transmission Kikuchi diffraction using a Timepix detector

NASA Astrophysics Data System (ADS)

Vespucci, S.; Winkelmann, A.; Mingard, K.; Maneuski, D.; O'Shea, V.; Trager-Cowan, C.

2017-02-01

Electron backscatter diffraction (EBSD) is a well-established scanning electron microscope (SEM)-based technique [1]. It allows the non-destructive mapping of the crystal structure, texture, crystal phase and strain with a spatial resolution of tens of nanometers. Conventionally this is performed by placing an electron sensitive screen, typically consisting of a phosphor screen combined with a charge coupled device (CCD) camera, in front of a specimen, usually tilted 70° to the normal of the exciting electron beam. Recently, a number of authors have shown that a significant increase in spatial resolution is achievable when Kikuchi diffraction patterns are acquired in transmission geometry; that is when diffraction patterns are generated by electrons transmitted through an electron-transparent, usually thinned, specimen. The resolution of this technique, called transmission Kikuchi diffraction (TKD), has been demonstrated to be better than 10 nm [2,3]. We have recently demonstrated the advantages of a direct electron detector, Timepix [4,5], for the acquisition of standard EBSD patterns [5]. In this article we will discuss the advantages of Timepix to perform TKD and for acquiring spot diffraction patterns and more generally for acquiring scanning transmission electron microscopy micrographs in the SEM. Particularly relevant for TKD, is its very compact size, which allows much more flexibility in the positioning of the detector in the SEM chamber. We will furthermore show recent results using Timepix as a virtual forward scatter detector, and will illustrate the information derivable on producing images through processing of data acquired from different areas of the detector. We will show results from samples ranging from gold nanoparticles to nitride semiconductor nanorods.

Localized melt-scan strategy for site specific control of grain size and primary dendrite arm spacing in electron beam additive manufacturing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raghavan, Narendran; Simunovic, Srdjan; Dehoff, Ryan

In addition to design geometry, surface roughness, and solid-state phase transformation, solidification microstructure plays a crucial role in controlling the performance of additively manufactured components. Crystallographic texture, primary dendrite arm spacing (PDAS), and grain size are directly correlated to local solidification conditions. We have developed a new melt-scan strategy for inducing site specific, on-demand control of solidification microstructure. We were able to induce variations in grain size (30 μm–150 μm) and PDAS (4 μm - 10 μm) in Inconel 718 parts produced by the electron beam additive manufacturing system (Arcam®). A conventional raster melt-scan resulted in a grain size ofmore » about 600 μm. The observed variations in grain size with different melt-scan strategies are rationalized using a numerical thermal and solidification model which accounts for the transient curvature of the melt pool and associated thermal gradients and liquid-solid interface velocities. The refinement in grain size at high cooling rates (>104 K/s) is also attributed to the potential heterogeneous nucleation of grains ahead of the epitaxially growing solidification front. The variation in PDAS is rationalized using a coupled numerical-theoretical model as a function of local solidification conditions (thermal gradient and liquid-solid interface velocity) of the melt pool.« less

U-10Mo Sample Preparation and Examination using Optical and Scanning Electron Microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prabhakaran, Ramprashad; Joshi, Vineet V.; Rhodes, Mark A.

2016-10-01

The purpose of this document is to provide guidelines to prepare specimens of uranium alloyed with 10 weight percent molybdenum (U-10Mo) for optical metallography and scanning electron microscopy. This document also provides instructions to set up an optical microscope and a scanning electron microscope to analyze U-10Mo specimens and to obtain the required information.

U-10Mo Sample Preparation and Examination using Optical and Scanning Electron Microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prabhakaran, Ramprashad; Joshi, Vineet V.; Rhodes, Mark A.

2016-03-30

The purpose of this document is to provide guidelines to prepare specimens of uranium alloyed with 10 weight percent molybdenum (U-10Mo) for optical metallography and scanning electron microscopy. This document also provides instructions to set up an optical microscope and a scanning electron microscope to analyze U-10Mo specimens and to obtain the required information.

STM on Gate-Tunable Graphene

NASA Astrophysics Data System (ADS)

Zhang, Yuanbo

2009-03-01

We have successfully performed atomically-resolved scanning tunneling microscopy and spectroscopy (STS) on mechanically exfoliated graphene samples having tunable back-gates. We have discovered that the tunneling spectra of graphene flakes display an unexpected gap-like feature that is pinned to the Fermi level for different gate voltages, and which coexists with another depression in density-of-states that moves with gate voltage. Extensive tests and careful analysis show that the gap-feature is due to phonon-assisted inelastic tunneling, and the depression directly marks the location of the graphene Dirac point. Using tunneling spectroscopy as a new tool, we further probe the local energetic variations of the graphene charge neutral point (Dirac point) to map out spatial electron density inhomogeneities in graphene. Such measurements are two orders of magnitude higher in resolution than previous experiments, and they can be directly correlated with nanometer scale topographic features. Based on our observation of energy-dependent periodic electronic interference patterns, our measurements also reveal the nature of impurity scattering of Dirac fermions in graphene. These results are significant for understanding the sources of electron density inhomogeneity and electron scattering in graphene, and the microscopic causes of graphene electron mobility.

Electronic Structure, Surface Doping, and Optical Response in Epitaxial WSe2 Thin Films.

PubMed

Zhang, Yi; Ugeda, Miguel M; Jin, Chenhao; Shi, Su-Fei; Bradley, Aaron J; Martín-Recio, Ana; Ryu, Hyejin; Kim, Jonghwan; Tang, Shujie; Kim, Yeongkwan; Zhou, Bo; Hwang, Choongyu; Chen, Yulin; Wang, Feng; Crommie, Michael F; Hussain, Zahid; Shen, Zhi-Xun; Mo, Sung-Kwan

2016-04-13

High quality WSe2 films have been grown on bilayer graphene (BLG) with layer-by-layer control of thickness using molecular beam epitaxy. The combination of angle-resolved photoemission, scanning tunneling microscopy/spectroscopy, and optical absorption measurements reveal the atomic and electronic structures evolution and optical response of WSe2/BLG. We observe that a bilayer of WSe2 is a direct bandgap semiconductor, when integrated in a BLG-based heterostructure, thus shifting the direct-indirect band gap crossover to trilayer WSe2. In the monolayer limit, WSe2 shows a spin-splitting of 475 meV in the valence band at the K point, the largest value observed among all the MX2 (M = Mo, W; X = S, Se) materials. The exciton binding energy of monolayer-WSe2/BLG is found to be 0.21 eV, a value that is orders of magnitude larger than that of conventional three-dimensional semiconductors, yet small as compared to other two-dimensional transition metal dichalcogennides (TMDCs) semiconductors. Finally, our finding regarding the overall modification of the electronic structure by an alkali metal surface electron doping opens a route to further control the electronic properties of TMDCs.

Properties of Rolled AZ31 Magnesium Alloy Sheet Fabricated by Continuous Variable Cross-Section Direct Extrusion

NASA Astrophysics Data System (ADS)

Liu, Yang; Li, Feng; Li, Xue Wen; Shi, Wen Yong

2018-03-01

Rolling is currently a widely used method for manufacturing and processing high-performance magnesium alloy sheets and has received widespread attention in recent years. Here, we combined continuous variable cross-section direct extrusion (CVCDE) and rolling processes. The microstructure and mechanical properties of the resulting sheets rolled at different temperatures from CVCDE extrudate were investigated by optical microscopy, scanning electron microscope, transmission electron microscopy and electron backscatter diffraction. The results showed that a fine-grained microstructure was present with an average grain size of 3.62 μm in sheets rolled from CVCDE extrudate at 623 K. Dynamic recrystallization and a large strain were induced by the multi-pass rolling, which resulted in grain refinement. In the 573-673 K range, the yield strength, tensile strength and elongation initially increased and then declined as the CVCDE temperature increased. The above results provide an important scientific basis of processing, manufacturing and the active control on microstructure and property for high-performance magnesium alloy sheet.

Direct imaging of Cl- and Cu-induced short-circuit efficiency changes in CdTe solar cells

DOE PAGES

Poplawsky, Jonathan D.; Parish, Chad M.; Leonard, Donovan N.; ...

2014-05-30

To achieve high-efficiency polycrystalline CdTe-based thin-film solar cells, the CdTe absorbers must go through a post-deposition CdCl 2 heat treatment followed by a Cu diffusion step. To better understand the roles of each treatment with regard to improving grains, grain boundaries, and interfaces, CdTe solar cells with and without Cu diffusion and CdCl 2 heat treatments are investigated using cross-sectional electron beam induced current, electron backscatter diffraction, and scanning transmission electron microscope techniques. The evolution of the cross-sectional carrier collection profile due to these treatments that cause an increase in short-circuit current and higher open-circuit voltage are identified. Additionally, anmore » increased carrier collection in grain boundaries after either/both of these treatments is revealed. The increased current at the grain boundaries is shown to be due to the presence of a space charge region with an intrinsic carrier collection profile width of ≈350 nm. Scanning transmission electron microscope electron-energy loss spectroscopy shows a decreased Te and increased Cl concentration in grain boundaries after treatment, which causes the inversion. Furthermore, each treatment improves the overall carrier collection efficiency of the cell separately, and, therefore, the benefits realized by each treatment are shown to be independent of each other.« less

Modeling a Miniaturized Scanning Electron Microscope Focusing Column - Lessons Learned in Electron Optics Simulation

NASA Technical Reports Server (NTRS)

Loyd, Jody; Gregory, Don; Gaskin, Jessica

2016-01-01

This presentation discusses work done to assess the design of a focusing column in a miniaturized Scanning Electron Microscope (SEM) developed at the NASA Marshall Space Flight Center (MSFC) for use in-situ on the Moon-in particular for mineralogical analysis. The MSFC beam column design uses purely electrostatic fields for focusing, because of the severe constraints on mass and electrical power consumption imposed by the goals of lunar exploration and of spaceflight in general. The resolution of an SEM ultimately depends on the size of the focused spot of the scanning beam probe, for which the stated goal here is a diameter of 10 nanometers. Optical aberrations are the main challenge to this performance goal, because they blur the ideal geometrical optical image of the electron source, effectively widening the ideal spot size of the beam probe. In the present work the optical aberrations of the mini SEM focusing column were assessed using direct tracing of non-paraxial rays, as opposed to mathematical estimates of aberrations based on paraxial ray-traces. The geometrical ray-tracing employed here is completely analogous to ray-tracing as conventionally understood in the realm of photon optics, with the major difference being that in electron optics the lens is simply a smoothly varying electric field in vacuum, formed by precisely machined electrodes. Ray-tracing in this context, therefore, relies upon a model of the electrostatic field inside the focusing column to provide the mathematical description of the "lens" being traced. This work relied fundamentally on the boundary element method (BEM) for this electric field model. In carrying out this research the authors discovered that higher accuracy in the field model was essential if aberrations were to be reliably assessed using direct ray-tracing. This led to some work in testing alternative techniques for modeling the electrostatic field. Ultimately, the necessary accuracy was attained using a BEM/Fourier series hybrid approach. The presentation will give background remarks about the MSFC mini Lunar SEM concept and electron optics modeling, followed by a description of the alternate field modeling techniques that were tried, along with their incorporation into a ray-trace simulation. Next, the validation of this simulation against commercially available software will be discussed using an example lens as a test case. Then, the efficacy of aberration assessment using direct ray-tracing will be demonstrated, using this same validation case. The discussion will include practical error checks of the field solution. Finally, the ray-trace assessment of the MSFC mini Lunar SEM concept will be shown and discussed. The authors believe this presentation will be of general interest to practitioners of modeling and simulation, as well as those with a general optics background. Because electron optics and photon optics share many basic concepts (e.g., lenses, images, aberrations, etc.), the appeal of this presentation need not be restricted to just those interested in charged particle optics.

Nanoscale contact resistance of V2O5 xerogel films developed by nanostructured powder

NASA Astrophysics Data System (ADS)

Bera, Biswajit; Sekhar Das, Pradip; Bhattacharya, Manjima; Ghosh, Swapankumar; Mukhopadhyay, Anoop Kumar; Dey, Arjun

2016-03-01

Here we report the synthesis of V2O5 nanostructures by a fast, simple, cost-effective, low-temperature chemical process; followed by the deposition of V2O5 xerogel thin films on a glass substrate by a sol-gel route. Phase analysis, phase transition, microstructural and electronic characterization studies are carried out by x-ray diffraction, texture coefficient analysis, field emission scanning electron microscopy, transmission electron microscopy (TEM), related selected area electron diffraction pattern (SAED) analysis, Fourier transform infrared spectroscopy, thermogravimetry and differential thermal analysis, differential scanning calorimetry, and x-ray photoelectron spectroscopy techniques. Confirmatory TEM and SAED data analysis prove further that in this polycrystalline powder there is a unique localized existence of purely single crystalline V2O5 powder with a preferred orientation in the (0 1 0) direction. The most interesting result obtained in the present work is that the xerogel thin films exhibit an inherent capability to enhance the intrinsic resistance against contact induced deformations as more external load is applied during the nanoindentation experiments. In addition, both the nanohardness and Young’s modulus of the films are found to be insensitive to load variations (e.g. 1 to 7 mN). These results are explained in terms of microstructural parameters, e.g. porosity and structural configuration.

On mapping subangstrom electron clouds with force microscopy.

PubMed

Wright, C Alan; Solares, Santiago D

2011-11-09

In 2004 Hembacher et al. (Science 2004, 305, 380-383) reported simultaneous higher-harmonics atomic force mocroscopy (AFM)/scanning tunneling microscopy (STM) images acquired while scanning a graphite surface with a tungsten tip. They interpreted the observed subatomic features in the AFM images as the signature of lobes of increased electron density at the tungsten tip apex. Although these intriguing images have stirred controversy, an in-depth theoretical feasibility study has not yet been produced. Here we report on the development of a method for simulating higher harmonics AFM images and its application to the same system. Our calculations suggest that four lobes of increased electron density are expected to be present at a W(001) tip apex atom and that the corresponding higher harmonics AFM images of graphite can exhibit 4-fold symmetry features. Despite these promising results, open questions remain since the calculated amplitudes of the higher harmonics generated by the short-range forces are on the order of hundredths of picometers, leading to very small corrugations in the theoretical images. Additionally, the complex, intermittent nature of the tip-sample interaction, which causes constant readjustment of the tip and sample orbitals as the tip approaches and retracts from the surface, prevents a direct quantitative connection between the electron density and the AFM image features.

Rational design of Ag/TiO2 nanosystems by a combined RF-sputtering/sol-gel approach.

PubMed

Armelao, Lidia; Barreca, Davide; Bottaro, Gregorio; Gasparotto, Alberto; Maccato, Chiara; Tondello, Eugenio; Lebedev, Oleg I; Turner, Stuart; Van Tendeloo, Gustaaf; Sada, Cinzia; Stangar, Urska Lavrencic

2009-12-21

The present work is devoted to the preparation of Ag/TiO(2) nanosystems by an original synthetic strategy, based on the radio-frequency (RF) sputtering of silver particles on titania-based xerogels prepared by the sol-gel (SG) route. This approach takes advantage of the synergy between the microporous xerogel structure and the infiltration power characterizing RF-sputtering, whose combination enables the obtainment of a tailored dispersion of Ag-containing particles into the titania matrix. In addition, the system's chemico-physical features can be tuned further through proper ex situ thermal treatments in air at 400 and 600 degrees C. The synthesized composites are extensively characterized by the joint use of complementary techniques, that is, X-ray photoelectron and X-ray excited Auger electron spectroscopies (XPS, XE-AES), secondary ion mass spectrometry (SIMS), glancing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), electron diffraction (ED), high-angle annular dark field scanning TEM (HAADF-STEM), energy-filtered TEM (EF-TEM) and optical absorption spectroscopy. Finally, the photocatalytic performances of selected samples in the decomposition of the azo-dye Plasmocorinth B are preliminarily investigated. The obtained results highlight the possibility of tailoring the system characteristics over a broad range, directly influencing their eventual functional properties.

Direct imaging of defect formation in strained organic flexible electronics by Scanning Kelvin Probe Microscopy

PubMed Central

Cramer, Tobias; Travaglini, Lorenzo; Lai, Stefano; Patruno, Luca; de Miranda, Stefano; Bonfiglio, Annalisa; Cosseddu, Piero; Fraboni, Beatrice

2016-01-01

The development of new materials and devices for flexible electronics depends crucially on the understanding of how strain affects electronic material properties at the nano-scale. Scanning Kelvin-Probe Microscopy (SKPM) is a unique technique for nanoelectronic investigations as it combines non-invasive measurement of surface topography and surface electrical potential. Here we show that SKPM in non-contact mode is feasible on deformed flexible samples and allows to identify strain induced electronic defects. As an example we apply the technique to investigate the strain response of organic thin film transistors containing TIPS-pentacene patterned on polymer foils. Controlled surface strain is induced in the semiconducting layer by bending the transistor substrate. The amount of local strain is quantified by a mathematical model describing the bending mechanics. We find that the step-wise reduction of device performance at critical bending radii is caused by the formation of nano-cracks in the microcrystal morphology of the TIPS-pentacene film. The cracks are easily identified due to the abrupt variation in SKPM surface potential caused by a local increase in resistance. Importantly, the strong surface adhesion of microcrystals to the elastic dielectric allows to maintain a conductive path also after fracture thus providing the opportunity to attenuate strain effects. PMID:27910889

Positive effects of bio-nano Pd (0) toward direct electron transfer in Pseudomona putida and phenol biodegradation.

PubMed

Niu, Zhuyu; Jia, Yating; Chen, Yuancai; Hu, Yongyou; Chen, Junfeng; Lv, Yuancai

2018-06-08

This study constructed a biological-inorganic hybrid system including Pseudomonas putida (P. putida) and bioreduced Pd (0) nanoparticles (NPs), and inspected the influence of bio-nano Pd (0) on the direct electron transfer and phenol biodegradation. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDX) showed that bio-nano Pd (0) (~10 nm) were evenly dispersed on the surface and in the periplasm of P. putida. With the incorporation of bio-nano Pd (0), the redox currents of bacteria in the cyclic voltammetry (CV) became higher and the oxidation current increased as the addition of lactate, while the highest increase rates of two electron transfer system (ETS) rates were 63.97% and 33.79%, respectively. These results indicated that bio-nano Pd (0) could directly promote the electron transfer of P. putida. In phenol biodegradation process, P. putida-Pd (0)- 2 showed the highest k (0.2992 h -1 ), μ m (0.035 h -1 ) and K i (714.29 mg/L) and the lowest apparent K s (76.39 mg/L). The results of kinetic analysis indicated that bio-nano Pd (0) markedly enhanced the biocatalytic efficiency, substrate affinity and the growth of cells compared to native P. putida. The positive effects of bio-nano Pd (0) to the electron transfer of P. putida would promote the biodegradation of phenol. Copyright © 2018 Elsevier Inc. All rights reserved.

Portable Handheld Optical Window Inspection Device

NASA Technical Reports Server (NTRS)

Ihlefeld, Curtis; Dokos, Adam; Burns, Bradley

2010-01-01

The Portable Handheld Optical Window Inspection Device (PHOWID) is a measurement system for imaging small defects (scratches, pits, micrometeor impacts, and the like) in the field. Designed primarily for window inspection, PHOWID attaches to a smooth surface with suction cups, and raster scans a small area with an optical pen in order to provide a three-dimensional image of the defect. PHOWID consists of a graphical user interface, motor control subsystem, scanning head, and interface electronics, as well as an integrated camera and user display that allows a user to locate minute defects before scanning. Noise levels are on the order of 60 in. (1.5 m). PHOWID allows field measurement of defects that are usually done in the lab. It is small, light, and attaches directly to the test article in any orientation up to vertical. An operator can scan a defect and get useful engineering data in a matter of minutes. There is no need to make a mold impression for later lab analysis.

Research and application on imaging technology of line structure light based on confocal microscopy

NASA Astrophysics Data System (ADS)

Han, Wenfeng; Xiao, Zexin; Wang, Xiaofen

2009-11-01

In 2005, the theory of line structure light confocal microscopy was put forward firstly in China by Xingyu Gao and Zexin Xiao in the Institute of Opt-mechatronics of Guilin University of Electronic Technology. Though the lateral resolution of line confocal microscopy can only reach or approach the level of the traditional dot confocal microscopy. But compared with traditional dot confocal microscopy, it has two advantages: first, by substituting line scanning for dot scanning, plane imaging only performs one-dimensional scanning, with imaging velocity greatly improved and scanning mechanism simplified, second, transfer quantity of light is greatly improved by substituting detection hairline for detection pinhole, and low illumination CCD is used directly to collect images instead of photoelectric intensifier. In order to apply the line confocal microscopy to practical system, based on the further research on the theory of the line confocal microscopy, imaging technology of line structure light is put forward on condition of implementation of confocal microscopy. Its validity and reliability are also verified by experiments.

Deep data mining in a real space: Separation of intertwined electronic responses in a lightly doped BaFe 2As 2

DOE PAGES

Ziatdinov, Maxim; Maksov, Artem; Li, Li; ...

2016-10-25

Electronic interactions present in material compositions close to the superconducting dome play a key role in the manifestation of high-T c superconductivity. In many correlated electron systems, however, the parent or underdoped states exhibit strongly inhomogeneous electronic landscape at the nanoscale that may be associated with competing, coexisting, or intertwined chemical disorder, strain, magnetic, and structural order parameters. Here we demonstrate an approach based on a combination of scanning tunneling microscopy/spectroscopy and advanced statistical learning for an automatic separation and extraction of statistically significant electronic behaviors in the spin density wave regime of a lightly (~1%) gold-doped BaFe 2As 2.more » Lastly, we show that the decomposed STS spectral features have a direct relevance to fundamental physical properties of the system, such as SDW-induced gap, pseudogap-like state, and impurity resonance states.« less

Deep data mining in a real space: Separation of intertwined electronic responses in a lightly doped BaFe 2As 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ziatdinov, Maxim; Maksov, Artem; Li, Li

Electronic interactions present in material compositions close to the superconducting dome play a key role in the manifestation of high-T c superconductivity. In many correlated electron systems, however, the parent or underdoped states exhibit strongly inhomogeneous electronic landscape at the nanoscale that may be associated with competing, coexisting, or intertwined chemical disorder, strain, magnetic, and structural order parameters. Here we demonstrate an approach based on a combination of scanning tunneling microscopy/spectroscopy and advanced statistical learning for an automatic separation and extraction of statistically significant electronic behaviors in the spin density wave regime of a lightly (~1%) gold-doped BaFe 2As 2.more » Lastly, we show that the decomposed STS spectral features have a direct relevance to fundamental physical properties of the system, such as SDW-induced gap, pseudogap-like state, and impurity resonance states.« less

Imaging the dynamics of free-electron Landau states

PubMed Central

Schattschneider, P.; Schachinger, Th.; Stöger-Pollach, M.; Löffler, S.; Steiger-Thirsfeld, A.; Bliokh, K. Y.; Nori, Franco

2014-01-01

Landau levels and states of electrons in a magnetic field are fundamental quantum entities underlying the quantum Hall and related effects in condensed matter physics. However, the real-space properties and observation of Landau wave functions remain elusive. Here we report the real-space observation of Landau states and the internal rotational dynamics of free electrons. States with different quantum numbers are produced using nanometre-sized electron vortex beams, with a radius chosen to match the waist of the Landau states, in a quasi-uniform magnetic field. Scanning the beams along the propagation direction, we reconstruct the rotational dynamics of the Landau wave functions with angular frequency ~100 GHz. We observe that Landau modes with different azimuthal quantum numbers belong to three classes, which are characterized by rotations with zero, Larmor and cyclotron frequencies, respectively. This is in sharp contrast to the uniform cyclotron rotation of classical electrons, and in perfect agreement with recent theoretical predictions. PMID:25105563

Electron beam induced damage in ITO coated Kapton. [Indium Tin Oxide

NASA Technical Reports Server (NTRS)

Krainsky, I.; Gordon, W. L.; Hoffman, R. W.

1981-01-01

Data for the stability of thin conductive indium tin oxide films on 0.003 inch thick Kapton substrates during exposure of the surface to electron beams are reported. The electron beam energy was 3 keV and the diameter was about 0.8 mm. Thermal effects and surface modifications are considered. For primary current greater than 0.6 microamperes, an obvious dark discoloration with diameter approximately that of the beam was produced. The structure of the discolored region was studied with the scanning electron microscope, and the findings are stated. Surface modifications were explored by AES, obtaining spectra and secondary emission coefficient as a function of time for different beam intensities. In all cases beam exposure results in a decrease of the secondary yield but because of thermal effects this change, as well as composition changes, cannot be directly interpreted in terms of electron beam dosage.

Pulsed Laser-Assisted Focused Electron-Beam-Induced Etching of Titanium with XeF 2 : Enhanced Reaction Rate and Precursor Transport

DOE PAGES

Noh, J. H.; Fowlkes, J. D.; Timilsina, R.; ...

2015-01-28

We introduce a laser-assisted focused electron-beam-induced etching (LA-FEBIE) process which is a versatile, direct write nanofabrication method that allows nanoscale patterning and editing; we do this in order to enhance the etch rate of electron-beam-induced etching. The results demonstrate that the titanium electron stimulated etch rate via the XeF2 precursor can be enhanced up to a factor of 6 times with an intermittent pulsed laser assist. Moreover, the evolution of the etching process is correlated to in situ stage current measurements and scanning electron micrographs as a function of time. Finally, the increased etch rate is attributed to photothermally enhancedmore » Ti–F reaction and TiF4 desorption and in some regimes enhanced XeF2 surface diffusion to the reaction zone.« less

Analysis of FIB-induced damage by electron channelling contrast imaging in the SEM.

PubMed

Gutierrez-Urrutia, Ivan

2017-01-01

We have investigated the Ga + ion-damage effect induced by focused ion beam (FIB) milling in a [001] single crystal of a 316 L stainless steel by the electron channelling contrast imaging (ECCI) technique. The influence of FIB milling on the characteristic electron channelling contrast of surface dislocations was analysed. The ECCI approach provides sound estimation of the damage depth produced by FIB milling. For comparison purposes, we have also studied the same milled surface by a conventional electron backscatter diffraction (EBSD) approach. We observe that the ECCI approach provides further insight into the Ga + ion-damage phenomenon than the EBSD technique by direct imaging of FIB artefacts in the scanning electron microscope. We envisage that the ECCI technique may be a convenient tool to optimize the FIB milling settings in applications where the surface crystal defect content is relevant. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

Directional budding of human immunodeficiency virus from monocytes.

PubMed Central

Perotti, M E; Tan, X; Phillips, D M

1996-01-01

Time-lapse cinematography revealed that activated human immunodeficiency virus (HIV)-infected monocytes crawl along surfaces, putting forward a leading pseudopod. Scanning electron micrographs showed monocyte pseudopods associated with spherical structures the size of HIV virions, and transmission electron micrographs revealed HIV virions budding from pseudopods. Filamentous actin (F-actin) was localized by electron microscopy in the pseudopod by heavy meromyosin decoration. Colocalization of F-actin and p24 viral antigen by light microscopy immunofluorescence indicated that F-actin and virus were present on the same pseudopod. These observations indicate that monocytes produce virus from a leading pseudopod. We suggest that HIV secretion at the leading edges of donor monocytes/macrophages may be an efficient way for HIV to infect target cells. PMID:8709212

Direct evidence of single quantum dot emission from GaN islands formed at threading dislocations using nanoscale cathodoluminescence: A source of single photons in the ultraviolet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmidt, Gordon, E-mail: Gordon.Schmidt@ovgu.de; Berger, Christoph; Veit, Peter

2015-06-22

Intense emission from GaN islands embedded in AlN resulting from GaN/AlN quantum well growth is directly resolved by performing cathodoluminescence spectroscopy in a scanning transmission electron microscope. Line widths down to 440 μeV are measured in a wavelength region between 220 and 310 nm confirming quantum dot like electronic properties in the islands. These quantum dot states can be structurally correlated to islands of slightly enlarged thicknesses of the GaN/AlN quantum well layer preferentially formed in vicinity to dislocations. The quantum dot states exhibit single photon emission in Hanbury Brown-Twiss experiments with a clear antibunching in the second order correlation function atmore » zero time delay.« less

Structural and optical properties of WTe2 single crystals synthesized by DVT technique

NASA Astrophysics Data System (ADS)

Dixit, Vijay; Vyas, Chirag; Pathak, V. M.; Soalanki, G. K.; Patel, K. D.

2018-05-01

Layered transition metal di-chalcogenide (LTMDCs) crystals have attracted much attention due to their potential in optoelectronic device applications recently due to realization of their monolayer based structures. In the present investigation we report growth of WTe2 single crystals by direct vapor transport (DVT) technique. These crystals are then characterized by energy dispersive analysis of x-rays (EDAX) to study stoichiometric composition after growth. The structural properties are studied by x-ray diffraction (XRD) and selected area electron diffraction (SAED) is used to confirm orthorhombic structure of grown WTe2 crystal. Surface morphological properties of the crystals are also studied by scanning electron microscope (SEM). The optical properties of the grown crystals are studied by UV-Visible spectroscopy which gives direct band gap of 1.44 eV for grown WTe2 single crystals.

Direct imaging of electron transfer and its influence on superconducting pairing at FeSe/SrTiO3 interface

PubMed Central

Zhao, Weiwei; Li, Mingda; Chang, Cui-Zu; Jiang, Jue; Wu, Lijun; Liu, Chaoxing; Moodera, Jagadeesh S.; Zhu, Yimei; Chan, Moses H. W.

2018-01-01

The exact mechanism responsible for the significant enhancement of the superconducting transition temperature (Tc) of monolayer iron selenide (FeSe) films on SrTiO3 (STO) over that of bulk FeSe is an open issue. We present the results of a coordinated study of electrical transport, low temperature electron energy-loss spectroscopy (EELS), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) measurements on FeSe/STO films of different thicknesses. HAADF-STEM imaging together with EELS mapping across the FeSe/STO interface shows direct evidence of electrons transferred from STO to the FeSe layer. The transferred electrons were found to accumulate within the first two atomic layers of the FeSe films near the STO substrate. An additional Se layer is also resolved to reside between the FeSe film and the TiOx-terminated STO substrate. Our transport results found that a positive backgate applied from STO is particularly effective in enhancing Tc of the films while minimally changing the carrier density. This increase in Tc is due to the positive backgate that “pulls” the transferred electrons in FeSe films closer to the interface and thus enhances their coupling to interfacial phonons and also the electron-electron interaction within FeSe films. PMID:29556528

Direct imaging of electron transfer and its influence on superconducting pairing at FeSe/SrTiO 3 interface

DOE PAGES

Zhao, Weiwei; Li, Mingda; Chang, Cui -Zu; ...

2018-03-16

The exact mechanism responsible for the significant enhancement of the superconducting transition temperature (T c) of monolayer iron selenide (FeSe) films on SrTiO 3 (STO) over that of bulk FeSe is an open issue. We present the results of a coordinated study of electrical transport, low temperature electron energy-loss spectroscopy (EELS), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) measurements on FeSe/STO films of different thicknesses. HAADF-STEM imaging together with EELS mapping across the FeSe/STO interface shows direct evidence of electrons transferred from STO to the FeSe layer. The transferred electrons were found to accumulate within the first twomore » atomic layers of the FeSe films near the STO substrate. An additional Se layer is also resolved to reside between the FeSe film and the TiO x-terminated STO substrate. Our transport results found that a positive backgate applied from STO is particularly effective in enhancing T c of the films while minimally changing the carrier density. Furthermore, this increase in T c is due to the positive backgate that “pulls” the transferred electrons in FeSe films closer to the interface and thus enhances their coupling to interfacial phonons and also the electron-electron interaction within FeSe films.« less

Ultrasound – A new approach for non-woven scaffolds investigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khramtsova, E. A.; Morokov, E. S.; Levin, V. M.

2016-05-18

In this study we verified the method of impulse acoustic microscopy as a tool for scaffold evaluation in tissue engineering investigation. Cellulose diacetate (CDA) non-woven 3D scaffold was used as a model object. Scanning electron microscopy and optical microscopy were used as reference methods in order to realize feasibility of acoustic microscopy method in a regenerative medicine field. Direct comparison of the different methods was carried out.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Segal-Peretz, Tamar; Zhou, Chun; Ren, Jiaxing

The three-dimensional assembly of poly (styrene-b-methyl methacrylate) (PS-b-PMMA) in chemoepitaxy and graphoepitaxy directed self-assembly (DSA) was investigated using scanning transmission electron microscopy (STEM) tomography. The tomographic characterization revealed hidden morphologies and defects at the BCP- chemical pattern interface in lamellar DSA, and probed the formation of cylinders at the bottom of cylindrical DSA for contact hole shrink. Lastly, future work will include control over 3D assembly in sub-10 nm processes.

Directed Biosynthesis of Oriented Crystalline Cellulose for Advanced Composite Fibers

DTIC Science & Technology

2012-05-03

8 growth rate Table 2. An optimized minimal salts high conductivity growth medium (named 9 Son-Matsuoka- Fructose , SMF) based on the optimized...basis for a high -conductivity medium for Acetobacter that also contained corn steep liquor. List of Figures Figure 1. Scanning electron micrographs of...bacterial cellulose production include corn steep liquor (Matsuoka et al., 1996) apples, beer wort (Brown, 1886; Herrmann, 1928), corn syrup , kale (black

[The morphology of the peripheral blood erythrocytes in patients with tetralogy of Fallot before and after its surgical correction].

PubMed

Guliamov, D S; Vorozheĭkin, V M; Ikmatov, A A; Abdumadzhidov, Kh A

1995-01-01

Quantitative changes in red cells were studied by dark field scanning electron microscopy of native preparations obtained from patients with Fallot's tetralogy of varying severity and duration. Mainly echinocytic transformation of red cells was revealed that directly depended on the disease duration. Morphologic findings have confirmed the efficacy of surgical correction and drug therapy of Fallot's tetralogy.

High-resolution, high-throughput imaging with a multibeam scanning electron microscope

PubMed Central

EBERLE, AL; MIKULA, S; SCHALEK, R; LICHTMAN, J; TATE, ML KNOTHE; ZEIDLER, D

2015-01-01

Electron–electron interactions and detector bandwidth limit the maximal imaging speed of single-beam scanning electron microscopes. We use multiple electron beams in a single column and detect secondary electrons in parallel to increase the imaging speed by close to two orders of magnitude and demonstrate imaging for a variety of samples ranging from biological brain tissue to semiconductor wafers. Lay Description The composition of our world and our bodies on the very small scale has always fascinated people, making them search for ways to make this visible to the human eye. Where light microscopes reach their resolution limit at a certain magnification, electron microscopes can go beyond. But their capability of visualizing extremely small features comes at the cost of a very small field of view. Some of the questions researchers seek to answer today deal with the ultrafine structure of brains, bones or computer chips. Capturing these objects with electron microscopes takes a lot of time – maybe even exceeding the time span of a human being – or new tools that do the job much faster. A new type of scanning electron microscope scans with 61 electron beams in parallel, acquiring 61 adjacent images of the sample at the same time a conventional scanning electron microscope captures one of these images. In principle, the multibeam scanning electron microscope’s field of view is 61 times larger and therefore coverage of the sample surface can be accomplished in less time. This enables researchers to think about large-scale projects, for example in the rather new field of connectomics. A very good introduction to imaging a brain at nanometre resolution can be found within course material from Harvard University on http://www.mcb80x.org/# as featured media entitled ‘connectomics’. PMID:25627873

Direct Comparison of Phosphate Uptake by Adnate and Loosely Attached Microalgae within an Intact Biofilm Matrix

PubMed Central

Burkholder, JoAnn M.; Wetzel, Robert G.; Klomparens, Karen L.

1990-01-01

We report a direct comparison of phosphate uptake by adnate and loosely attached microalgae in an intact biofilm matrix, with resolution at the level of individual cells. Track scanning electron microscope autoradiography enabled assay of [33P]phosphate uptake from the overlying water by adnate algae left undisturbed on mature leaves of the macrophyte Potamogeton illinoensis or on artificial plant mimics. The epiphyte communities developed in either phosphate-poor or moderately phosphate-enriched water, and they were assayed on both natural and artificial plants. All adnate taxa examined from both natural and artificial plants in both habitats took up significantly less radiolabel when assayed beneath the overlying matrix than when they were exposed to the water upon removal of the overstory material. Track scanning electron microscope autoradiography and track light microscope autoradiography were intercalibrated to enable comparison of [33P]phosphate uptake by adnate and loosely attached components of the epiphyte matrix. Loosely attached cells on substrata from both habitats took up significantly more radiolabel than did underlying adnate cells, indicating that access to phosphate supplies from the water depended on the position of microbial cells in the matrix. In this short-term assay, the adnate microalgae were relatively isolated from the water column nutrient source. Images PMID:16348296

Effect of the nanosized TiO2 particles in Pd/C catalysts as cathode materials in direct methanol fuel cells.

PubMed

Choi, Mahnsoo; Han, Choonsoo; Kim, In-Tae; Lee, Ji-Jung; Lee, Hong-Ki; Shim, Joongpyo

2011-07-01

Pd-TiO2/C catalysts were prepared by impregnating titanium dioxide (TiO2) on carbon-supported Pd (Pd/C) for use as the catalyst for the oxygen reduction reaction (ORR) in direct methanol fuel cells (DMFCs). Transmission electron microscope (TEM), scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses were carried to confirm the distribution, morphology and structure of Pd and TiO2 on the carbon support. In fuel cell test, we confirmed that the addition of TiO2 nanoparticles make the improved catalytic activity of oxygen reduction. The electrochemical characterization of the Pd-TiO2/C catalyst for the ORR was carried out by cyclic voltammetry (CV) in the voltage window of 0.04 V to 1.2 V with scan rate of 25 mV/s. With the increase in the crystallite size of TiO2, the peak potential for OH(ads) desorption on the surface of Pd particle shifted to higher potential. This implies that TiO2 might affect the adsorption and desorption of oxygen molecules on Pd catalyst. The performance of Pd-TiO2/C as a cathode material was found to be similar to or better performance than that of Pt/C.

Construction and characterization of the fringe field monochromator for a field emission gun

PubMed

Mook; Kruit

2000-04-01

Although some microscopes have shown stabilities sufficient to attain below 0.1 eV spectral resolution in high-resolution electron energy loss spectroscopy, the intrinsic energy width of the high brightness source (0.3-0.6 eV) has been limiting the resolution. To lower the energy width of the source to 50 meV without unnecessary loss of brightness, a monochromator has been designed consisting of a short (4 mm) fringe field Wien filter and a 150 nm energy selection slit (nanoslit) both to be incorporated in the gun area of the microscope. A prototype has been built and tested in an ultra-high-vacuum setup (10(-9) mbar). The monochromator, operating on a Schottky field emission gun, showed stable and reproducible operation. The nanoslits did not contaminate and the structure remained stable. By measuring the current through the slit structure a direct image of the beam in the monochromator could be attained and the monochromator could be aligned without the use of a microscope. Good dispersed imaging conditions were found indicating an ultimate resolution of 55 meV. A Mark II fringe field monochromator (FFM) was designed and constructed compatible with the cold tungsten field emitter of the VG scanning transmission microscope. The monochromator was incorporated in the gun area of the microscope at IBM T.J. Watson research center, New York. The monochromator was aligned on 100 kV and the energy distribution measured using the monochromator displayed a below 50 meV filtering capability. The retarding Wien filter spectrometer was used to show a 61 meV EELS system resolution. The FFM is shown to be a monochromator which can be aligned without the use of the electron microscope. This makes it directly applicable for scanning transmission microscopy and low-voltage scanning electron microscopy, where it can lower the resolution loss which is caused by chromatic blur of the spot.

Development of an emittance meter and off-line measurements for the SPES project

NASA Astrophysics Data System (ADS)

Montano, Jacobo; Vasquez, Jesus; Andrighetto, Aberto; Poggi, Marco; Bassato, Giorgio; Boscagli, Lucia; Prete, Gianfranco; Conforto, Nicola

2012-02-01

In the framework of the Selective Production of Exotic Species (SPES) project, an emittance meter has been designed and constructed to determine the ion sources operational characteristics. This instrument allows scanning the beam in two orthogonal planes establishing the distribution of the beam spatial density as well as the particles directions. The controls of the scanning sequence and the data collection during the measurements are performed by an appropriated electronic unit. The collected data is then analyzed and the twiss parameters are determined including the emittance for both planes under scrutiny. Finally a user friendly interface is developed that allows a general user to perform the mentioned tasks.

Charge ordering in stoichiometric FeTe: Scanning tunneling microscopy and spectroscopy

DOE PAGES

Li, Wei; Yin, Wei -Guo; Wang, Lili; ...

2016-01-04

In this study, we use scanning tunneling microscopy and spectroscopy to reveal a unique stripy charge order in a parent phase of iron-based superconductors in stoichiometric FeTe epitaxy films. The charge order has unusually the same—usually half—period as the spin order. We also found highly anisotropic electron band dispersions being large and little along the ferromagnetic (crystallographic b) and antiferromagnetic (a) directions, respectively. Our data suggest that the microscopic mechanism is likely of the Stoner type driven by interatomic Coulomb repulsion V ij, and that V ij and charge fluctuations, so far much neglected, are important to the understanding ofmore » iron-based superconductors.« less

A photon-counting photodiode array detector for far ultraviolet (FUV) astronomy

NASA Technical Reports Server (NTRS)

Hartig, G. F.; Moos, H. W.; Pembroke, R.; Bowers, C.

1982-01-01

A compact, stable, single-stage intensified photodiode array detector designed for photon-counting, far ultraviolet astronomy applications employs a saturable, 'C'-type MCP (Galileo S. MCP 25-25) to produce high gain pulses with a narrowly peaked pulse height distribution. The P-20 output phosphor exhibits a very short decay time, due to the high current density of the electron pulses. This intensifier is being coupled to a self-scanning linear photodiode array which has a fiber optic input window which allows direct, rigid mechanical coupling with minimal light loss. The array was scanned at a 250 KHz pixel rate. The detector exhibits more than adequate signal-to-noise ratio for pulse counting and event location.

Scanning tunneling microscope with two-dimensional translator.

PubMed

Nichols, J; Ng, K-W

2011-01-01

Since the invention of the scanning tunneling microscope (STM), it has been a powerful tool for probing the electronic properties of materials. Typically STM designs capable of obtaining resolution on the atomic scale are limited to a small area which can be probed. We have built an STM capable of coarse motion in two dimensions, the z- and x-directions which are, respectively, parallel and perpendicular to the tip. This allows us to image samples with very high resolution at sites separated by macroscopic distances. This device is a single unit with a compact design making it very stable. It can operate in either a horizontal or vertical configuration and at cryogenic temperatures.

Towards native-state imaging in biological context in the electron microscope

PubMed Central

Weston, Anne E.; Armer, Hannah E. J.

2009-01-01

Modern cell biology is reliant on light and fluorescence microscopy for analysis of cells, tissues and protein localisation. However, these powerful techniques are ultimately limited in resolution by the wavelength of light. Electron microscopes offer much greater resolution due to the shorter effective wavelength of electrons, allowing direct imaging of sub-cellular architecture. The harsh environment of the electron microscope chamber and the properties of the electron beam have led to complex chemical and mechanical preparation techniques, which distance biological samples from their native state and complicate data interpretation. Here we describe recent advances in sample preparation and instrumentation, which push the boundaries of high-resolution imaging. Cryopreparation, cryoelectron microscopy and environmental scanning electron microscopy strive to image samples in near native state. Advances in correlative microscopy and markers enable high-resolution localisation of proteins. Innovation in microscope design has pushed the boundaries of resolution to atomic scale, whilst automatic acquisition of high-resolution electron microscopy data through large volumes is finally able to place ultrastructure in biological context. PMID:19916039

Visualizing spatial correlation: structural and electronic orders in iron-based superconductors on atomic scale

NASA Astrophysics Data System (ADS)

Maksov, Artem; Ziatdinov, Maxim; Li, Li; Sefat, Athena; Maksymovych, Petro; Kalinin, Sergei

Crystalline matter on the nanoscale level often exhibits strongly inhomogeneous structural and electronic orders, which have a profound effect on macroscopic properties. This may be caused by subtle interplay between chemical disorder, strain, magnetic, and structural order parameters. We present a novel approach based on combination of high resolution scanning tunneling microscopy/spectroscopy (STM/S) and deep data style analysis for automatic separation, extraction, and correlation of structural and electronic behavior which might lead us to uncovering the underlying sources of inhomogeneity in in iron-based family of superconductors (FeSe, BaFe2As2) . We identify STS spectral features using physically robust Bayesian linear unmixing, and show their direct relevance to the fundamental physical properties of the system, including electronic states associated with individual defects and impurities. We collect structural data from individual unit cells on the crystalline lattice, and calculate both global and local indicators of spatial correlation with electronic features, demonstrating, for the first time, a direct quantifiable connection between observed structural order parameters extracted from the STM data and electronic order parameters identified within the STS data. This research was sponsored by the Division of Materials Sciences and Engineering, Office of Science, Basic Energy Sciences, US DOE.

A simple way to higher speed atomic force microscopy by retrofitting with a novel high-speed flexure-guided scanner

NASA Astrophysics Data System (ADS)

Ouma Alunda, Bernard; Lee, Yong Joong; Park, Soyeun

2018-06-01

A typical line-scan rate for a commercial atomic force microscope (AFM) is about 1 Hz. At such a rate, more than four minutes of scanning time is required to obtain an image of 256 × 256 pixels. Despite control electronics of most commercial AFMs permit faster scan rates, default piezoelectric X–Y scanners limit the overall speed of the system. This is a direct consequence of manufacturers choosing a large scan range over the maximum operating speed for a X–Y scanner. Although some AFM manufacturers offer reduced-scan area scanners as an option, the speed improvement is not significant because such scanners do not have large enough reduction in the scan range and are mainly targeted to reducing the overall cost of the AFM systems. In this article, we present a simple parallel-kinematic substitute scanner for a commercial atomic force microscope to afford a higher scanning speed with no other hardware or software upgrade to the original system. Although the scan area reduction is unavoidable, our modified commercial XE-70 AFM from Park Systems has achieved a line scan rate of over 50 Hz, more than 10 times faster than the original, unmodified system. Our flexure-guided X–Y scanner can be a simple drop-in replacement option for enhancing the speed of various aging atomic force microscopes.

High-resolution scanning precession electron diffraction: Alignment and spatial resolution.

PubMed

Barnard, Jonathan S; Johnstone, Duncan N; Midgley, Paul A

2017-03-01

Methods are presented for aligning the pivot point of a precessing electron probe in the scanning transmission electron microscope (STEM) and for assessing the spatial resolution in scanning precession electron diffraction (SPED) experiments. The alignment procedure is performed entirely in diffraction mode, minimising probe wander within the bright-field (BF) convergent beam electron diffraction (CBED) disk and is used to obtain high spatial resolution SPED maps. Through analysis of the power spectra of virtual bright-field images extracted from the SPED data, the precession-induced blur was measured as a function of precession angle. At low precession angles, SPED spatial resolution was limited by electronic noise in the scan coils; whereas at high precession angles SPED spatial resolution was limited by tilt-induced two-fold astigmatism caused by the positive spherical aberration of the probe-forming lens. Copyright © 2016 Elsevier B.V. All rights reserved.

The application of scanning electron microscopy to fractography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brooks, C.R.; McGill, B.L.

1994-10-01

Many failures involve fracture, and determination of the fracture process is a key factor in understanding the failure. This is frequently accomplished by characterizing the topography of the fracture surface. Scanning electron microscopy has a prominent role in fractography due to three features of the scanning electron microscope (SEM): high resolution, great depth of field, and the ability to obtain chemical information via analysis of the X-rays generated by the electrons. A qualitative treatment is presented of the interaction of electrons with a sample and the effect of the SEM operating parameters on image formation, quality, and X-ray analysis. Fractographsmore » are presented to illustrate these features of scanning electron microscopy and to illustrate the limitations and precautions in obtaining fractographs and x-ray analyses. The review is concluded with examples of fracture surface features of metallic, ceramic, and polymeric materials.« less

Evidence of sharp and diffuse domain walls in BiFeO3 by means of unit-cell-wise strain and polarization maps obtained with high resolution scanning transmission electron microscopy.

PubMed

Lubk, A; Rossell, M D; Seidel, J; He, Q; Yang, S Y; Chu, Y H; Ramesh, R; Hÿtch, M J; Snoeck, E

2012-07-27

Domain walls (DWs) substantially influence a large number of applications involving ferroelectric materials due to their limited mobility when shifted during polarization switching. The discovery of greatly enhanced conduction at BiFeO(3) DWs has highlighted yet another role of DWs as a local material state with unique properties. However, the lack of precise information on the local atomic structure is still hampering microscopical understanding of DW properties. Here, we examine the atomic structure of BiFeO(3) 109° DWs with pm precision by a combination of high-angle annular dark-field scanning transmission electron microscopy and a dedicated structural analysis. By measuring simultaneously local polarization and strain, we provide direct experimental proof for the straight DW structure predicted by ab initio calculations as well as the recently proposed theory of diffuse DWs, thus resolving a long-standing discrepancy between experimentally measured and theoretically predicted DW mobilities.

Contact detection for nanomanipulation in a scanning electron microscope.

PubMed

Ru, Changhai; To, Steve

2012-07-01

Nanomanipulation systems require accurate knowledge of the end-effector position in all three spatial coordinates, XYZ, for reliable manipulation of nanostructures. Although the images acquired by a scanning electron microscope (SEM) provide high resolution XY information, the lack of depth information in the Z-direction makes 3D nanomanipulation time-consuming. Existing approaches for contact detection of end-effectors inside SEM typically utilize fragile touch sensors that are difficult to integrate into a nanomanipulation system. This paper presents a method for determining the contact between an end-effector and a target surface during nanomanipulation inside SEM, purely based on the processing of SEM images. A depth-from-focus method is used in the fast approach of the end-effector to the substrate, followed by fine contact detection. Experimental results demonstrate that the contact detection approach is capable of achieving an accuracy of 21.5 nm at 50,000× magnification while inducing little end-effector damage. Copyright © 2012 Elsevier B.V. All rights reserved.

Domain characterization of Pb(Zn1/3Nb2/3)O3-(6%-7%)PbTiO3 single crystals using scanning electron acoustic microscopy

NASA Astrophysics Data System (ADS)

Wong, Meng Fei; Heng, Xiangxin; Zeng, Kaiyang

2008-10-01

Domain structures of [001]T and [011]T-cut Pb(Zn1/3Nb2/3)O3-(6%-7%)PbTiO3 (PZN-PT) single crystals are studied using scanning electron acoustic microscope (SEAM) technique. The observation of the orientation of domain walls agree reasonably well with the trigonometric projection of rhombohedral and orthorhombic dipoles on the (001) and (011) surfaces, respectively. After mechanical loading with microindentation, domain switching is also observed to form a hyperbolic butterfly shape and extend preferentially along four diagonal directions, i.e., ⟨110⟩ on (001) surface and ⟨111¯⟩ on (011) surface. The critical shear stress to cause domain switching for PZN-PT crystal is estimated to be approximately 49 MPa for both {110} and {111¯} planes based on theoretical analysis. Generally, the SEAM technique has been successfully demonstrated to be a valid technique for observation of domain structures in single crystal PZN-PTs.

Scanning retarding field analyzer for plasma profile measurements in the boundary of the Alcator C-Mod tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brunner, D.; LaBombard, B.; Ochoukov, R.

2013-03-15

A new Retarding Field Analyzer (RFA) head has been created for the outer-midplane scanning probe system on the Alcator C-Mod tokamak. The new probe head contains back-to-back retarding field analyzers aligned with the local magnetic field. One faces 'upstream' into the field-aligned plasma flow and the other faces 'downstream' away from the flow. The RFA was created primarily to benchmark ion temperature measurements of an ion sensitive probe; it may also be used to interrogate electrons. However, its construction is robust enough to be used to measure ion and electron temperatures up to the last-closed flux surface in C-Mod. Amore » RFA probe of identical design has been attached to the side of a limiter to explore direct changes to the boundary plasma due to lower hybrid heating and current drive. Design of the high heat flux (>100 MW/m{sup 2}) handling probe and initial results are presented.« less

Self-assembled growth of MnSi~1.7 nanowires with a single orientation and a large aspect ratio on Si(110) surfaces

PubMed Central

2013-01-01

MnSi~1.7 nanowires (NWs) with a single orientation and a large aspect ratio have been formed on a Si(110) surface with the molecular beam epitaxy method by a delicate control of growth parameters, such as temperature, deposition rate, and deposition time. Scanning tunneling microscopy (STM) was employed to study the influence of these parameters on the growth of NWs. The supply of free Si atoms per unit time during the silicide reaction plays a critical role in the growth kinetics of the NWs. High growth temperature and low deposition rate are favorable for the formation of NWs with a large aspect ratio. The orientation relationship between the NWs and the reconstruction rows of the Si(110) surface suggests that the NWs grow along the 11¯0 direction of the silicon substrate. High-resolution STM and backscattered electron scanning electron microscopy images indicate that the NWs are composed of MnSi~1.7. PMID:23339353

Understanding the crack formation of graphite particles in cycled commercial lithium-ion batteries by focused ion beam - scanning electron microscopy

NASA Astrophysics Data System (ADS)

Lin, Na; Jia, Zhe; Wang, Zhihui; Zhao, Hui; Ai, Guo; Song, Xiangyun; Bai, Ying; Battaglia, Vincent; Sun, Chengdong; Qiao, Juan; Wu, Kai; Liu, Gao

2017-10-01

The structure degradation of commercial Lithium-ion battery (LIB) graphite anodes with different cycling numbers and charge rates was investigated by focused ion beam (FIB) and scanning electron microscopy (SEM). The cross-section image of graphite anode by FIB milling shows that cracks, resulted in the volume expansion of graphite electrode during long-term cycling, were formed in parallel with the current collector. The crack occurs in the bulk of graphite particles near the lithium insertion surface, which might derive from the stress induced during lithiation and de-lithiation cycles. Subsequently, crack takes place along grain boundaries of the polycrystalline graphite, but only in the direction parallel with the current collector. Furthermore, fast charge graphite electrodes are more prone to form cracks since the tensile strength of graphite is more likely to be surpassed at higher charge rates. Therefore, for LIBs long-term or high charge rate applications, the tensile strength of graphite anode should be taken into account.

On the Progress of Scanning Transmission Electron Microscopy (STEM) Imaging in a Scanning Electron Microscope.

PubMed

Sun, Cheng; Müller, Erich; Meffert, Matthias; Gerthsen, Dagmar

2018-04-01

Transmission electron microscopy (TEM) with low-energy electrons has been recognized as an important addition to the family of electron microscopies as it may avoid knock-on damage and increase the contrast of weakly scattering objects. Scanning electron microscopes (SEMs) are well suited for low-energy electron microscopy with maximum electron energies of 30 keV, but they are mainly used for topography imaging of bulk samples. Implementation of a scanning transmission electron microscopy (STEM) detector and a charge-coupled-device camera for the acquisition of on-axis transmission electron diffraction (TED) patterns, in combination with recent resolution improvements, make SEMs highly interesting for structure analysis of some electron-transparent specimens which are traditionally investigated by TEM. A new aspect is correlative SEM, STEM, and TED imaging from the same specimen region in a SEM which leads to a wealth of information. Simultaneous image acquisition gives information on surface topography, inner structure including crystal defects and qualitative material contrast. Lattice-fringe resolution is obtained in bright-field STEM imaging. The benefits of correlative SEM/STEM/TED imaging in a SEM are exemplified by structure analyses from representative sample classes such as nanoparticulates and bulk materials.

Imaging of Norway spruce early somatic embryos with the ESEM, Cryo-SEM and laser scanning microscope.

PubMed

Neděla, Vilém; Hřib, Jiří; Havel, Ladislav; Hudec, Jiří; Runštuk, Jiří

2016-05-01

This article describes the surface structure of Norway spruce early somatic embryos (ESEs) as a typical culture with asynchronous development. The microstructure of extracellular matrix covering ESEs were observed using the environmental scanning electron microscope as a primary tool and using the scanning electron microscope with cryo attachment and laser electron microscope as a complementary tool allowing our results to be proven independently. The fresh samples were observed in conditions of the air environment of the environmental scanning electron microscope (ESEM) with the pressure from 550Pa to 690Pa and the low temperature of the sample from -18°C to -22°C. The samples were studied using two different types of detector to allow studying either the thin surface structure or material composition. The scanning electron microscope with cryo attachment was used for imaging frozen extracellular matrix microstructure with higher resolution. The combination of both electron microscopy methods was suitable for observation of "native" plant samples, allowing correct evaluation of our results, free of error and artifacts. Copyright © 2016 Elsevier Ltd. All rights reserved.

A correlative optical microscopy and scanning electron microscopy approach to locating nanoparticles in brain tumors.

PubMed

Kempen, Paul J; Kircher, Moritz F; de la Zerda, Adam; Zavaleta, Cristina L; Jokerst, Jesse V; Mellinghoff, Ingo K; Gambhir, Sanjiv S; Sinclair, Robert

2015-01-01

The growing use of nanoparticles in biomedical applications, including cancer diagnosis and treatment, demands the capability to exactly locate them within complex biological systems. In this work a correlative optical and scanning electron microscopy technique was developed to locate and observe multi-modal gold core nanoparticle accumulation in brain tumor models. Entire brain sections from mice containing orthotopic brain tumors injected intravenously with nanoparticles were imaged using both optical microscopy to identify the brain tumor, and scanning electron microscopy to identify the individual nanoparticles. Gold-based nanoparticles were readily identified in the scanning electron microscope using backscattered electron imaging as bright spots against a darker background. This information was then correlated to determine the exact location of the nanoparticles within the brain tissue. The nanoparticles were located only in areas that contained tumor cells, and not in the surrounding healthy brain tissue. This correlative technique provides a powerful method to relate the macro- and micro-scale features visible in light microscopy with the nanoscale features resolvable in scanning electron microscopy. Copyright © 2014 Elsevier Ltd. All rights reserved.

Detecting magnetic ordering with atomic size electron probes

DOE PAGES

Idrobo, Juan Carlos; Rusz, Ján; Spiegelberg, Jakob; ...

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

Opal shell structures: direct assembly versus inversion approach.

PubMed

Deng, Tian-Song; Sharifi, Parvin; Marlow, Frank

2013-09-16

Opal shell structures can be fabricated in two ways: By direct assembly from hollow spheres (hs-opal) or by infiltration of precursors into opal templates and inversion. The resulting lattice disturbances were characterized by scanning electron microscopy (SEM), optical microscopy, and transmission spectra. The hs-opal system shows much lower disturbances, for example, a lower number of cracks and lattice deformations. The strong suppression of crack formation in one of these inverse opal structures can be considered as promising candidates for the fabrication of more perfect photonic crystals. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rapid-scan EPR imaging.

PubMed

Eaton, Sandra S; Shi, Yilin; Woodcock, Lukas; Buchanan, Laura A; McPeak, Joseph; Quine, Richard W; Rinard, George A; Epel, Boris; Halpern, Howard J; Eaton, Gareth R

2017-07-01

In rapid-scan EPR the magnetic field or frequency is repeatedly scanned through the spectrum at rates that are much faster than in conventional continuous wave EPR. The signal is directly-detected with a mixer at the source frequency. Rapid-scan EPR is particularly advantageous when the scan rate through resonance is fast relative to electron spin relaxation rates. In such scans, there may be oscillations on the trailing edge of the spectrum. These oscillations can be removed by mathematical deconvolution to recover the slow-scan absorption spectrum. In cases of inhomogeneous broadening, the oscillations may interfere destructively to the extent that they are not visible. The deconvolution can be used even when it is not required, so spectra can be obtained in which some portions of the spectrum are in the rapid-scan regime and some are not. The technology developed for rapid-scan EPR can be applied generally so long as spectra are obtained in the linear response region. The detection of the full spectrum in each scan, the ability to use higher microwave power without saturation, and the noise filtering inherent in coherent averaging results in substantial improvement in signal-to-noise relative to conventional continuous wave spectroscopy, which is particularly advantageous for low-frequency EPR imaging. This overview describes the principles of rapid-scan EPR and the hardware used to generate the spectra. Examples are provided of its application to imaging of nitroxide radicals, diradicals, and spin-trapped radicals at a Larmor frequency of ca. 250MHz. Copyright © 2017 Elsevier Inc. All rights reserved.

Experimental demonstration of a single-molecule electric motor.

PubMed

Tierney, Heather L; Murphy, Colin J; Jewell, April D; Baber, Ashleigh E; Iski, Erin V; Khodaverdian, Harout Y; McGuire, Allister F; Klebanov, Nikolai; Sykes, E Charles H

2011-09-04

For molecules to be used as components in molecular machines, methods that couple individual molecules to external energy sources and that selectively excite motion in a given direction are required. Significant progress has been made in the construction of molecular motors powered by light and by chemical reactions, but electrically driven motors have not yet been built, despite several theoretical proposals for such motors. Here we report that a butyl methyl sulphide molecule adsorbed on a copper surface can be operated as a single-molecule electric motor. Electrons from a scanning tunnelling microscope are used to drive the directional motion of the molecule in a two-terminal setup. Moreover, the temperature and electron flux can be adjusted to allow each rotational event to be monitored at the molecular scale in real time. The direction and rate of the rotation are related to the chiralities of both the molecule and the tip of the microscope (which serves as the electrode), illustrating the importance of the symmetry of the metal contacts in atomic-scale electrical devices.

Autoionizing resonances in electron-impact ionization of O5+ ions

NASA Astrophysics Data System (ADS)

Müller, A.; Teng, H.; Hofmann, G.; Phaneuf, R. A.; Salzborn, E.

2000-12-01

We report on a detailed experimental and theoretical study of electron-impact ionization of O5+ ions. A high-resolution scan measurement of the K-shell excitation threshold region has been performed with statistical uncertainties as low as 0.03%. At this level of precision a wealth of features in the cross section arising from indirect ionization processes becomes visible, and even interference of direct ionization with resonant-excitation/auto-double-ionization (READI) is clearly observed. The experimental results are compared with R-matrix calculations that include both direct and indirect processes in a unified way. Radiative damping of autoionizing Li-like states is found to be about 10-15 %. The calculations almost perfectly reproduce most of the experimental resonance features found in the present measurement including READI. They also agree with the direct-ionization converged close-coupling results of I. Bray [J. Phys. B 28, L247 (1995)] and the absolute total ionization cross section measurement of K. Rinn et al. [Phys. Rev. A 36, 595 (1987)].

Comparative morphology analysis of live blood platelets using scanning ion conductance and robotic dark-field microscopy.

PubMed

Kraus, Max-Joseph; Seifert, Jan; Strasser, Erwin F; Gawaz, Meinrad; Schäffer, Tilman E; Rheinlaender, Johannes

2016-09-01

Many conventional microscopy techniques for investigating platelet morphology such as electron or fluorescence microscopy require highly invasive treatment of the platelets such as fixation, drying and metal coating or staining. Here, we present two unique but entirely different microscopy techniques for direct morphology analysis of live, unstained platelets: scanning ion conductance microscopy (SICM) and robotic dark-field microscopy (RDM). We demonstrate that both techniques allow for a quantitative evaluation of the morphological features of live adherent platelets. We show that their morphology can be quantified by both techniques using the same geometric parameters and therefore can be directly compared. By imaging the same identical platelets subsequently with SICM and RDM, we found that area, perimeter and circularity of the platelets are directly correlated between SICM and dark-field microscopy (DM), while the fractal dimension (FD) differed between the two microscopy techniques. We show that SICM and RDM are both valuable tools for the ex vivo investigation of the morphology of live platelets, which might contribute to new insights into the physiological and pathophysiological role of platelet spreading.

A setup for combined multiphoton laser scanning microscopic and multi-electrode patch clamp experiments on brain slices

NASA Astrophysics Data System (ADS)

Helm, P. Johannes; Reppen, Trond; Heggelund, Paul

2009-02-01

Multi Photon Laser Scanning Microscopy (MPLSM) appears today as one of the most powerful experimental tools in cellular neurophysiology, notably in studies of the functional dynamics of signal processing in single neurons. Simultaneous recording of fluorescence signals at high spatial and temporal resolution and electric signals by means of multi electrode patch clamp techniques have provided new paths for the systematic investigation of neuronal mechanisms. In particular, this approach has opened for direct studies of dendritic signal processing in neurons. We report about a setup optimized for simultaneous electrophysiological multi electrode patch clamp and multi photon laser scanning fluorescence microscopic experiments on brain slices. The microscopic system is based on a modified commercially available confocal scanning laser microscope (CLSM). From a technical and operational point of view, two developments are important: Firstly, in order to reduce the workload for the experimentalist, who in general is forced to concentrate on controlling the electrophysiological parameters during the recordings, a system of shutters has been installed together with dedicated electronic modules protecting the photo detectors against destructive light levels caused by erroneous opening or closing of microscopic light paths by the experimentalist. Secondly, the standard detection unit has been improved by installing the photomultiplier tubes (PMT) in a Peltier cooled thermal box shielding the detector from both room temperature and distortions caused by external electromagnetic fields. The electrophysiological system is based on an industrial standard multi patch clamp unit ergonomically arranged around the microscope stage. The electrophysiological and scanning processes can be time coordinated by standard trigger electronics.

Enhanced Electro-Kinetics of C-C Bond-Splitting during Ethanol Oxidation Reaction using Pt/Rh/Sn Catalyst with a Partially Oxidized Pt and Rh Core and a SnO2 Shell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, G.; Su, D.; Frenkel, A. I.

Direct ethanol fuel cell (DEFC) is a promising technology for generating electricity via the electro-oxidation of liquid ethanol. Its implementation requires the development of anode catalysts capable of producing CO 2 and yielding 12-electron transfer through breaking C-C bond of ethanol. Here we presented comprehensive studies of electro-kinetics of the CO 2 generation on Pt/Rh/Sn ternary catalysts. Our studies showed that, for the first time, the tri–phase PtRhOx- SnO 2 catalysts with a partially oxidized Pt and Rh core and a SnO 2 shell, validated by X-ray absorption analyses and scanning transmission electron microscope-electron energy loss spectroscopy line scan, coincidedmore » with a 2.5-fold increase in the CO 2 generation rate towards ethanol oxidation reaction, compared with the bi-phase PtRh-SnO 2 catalysts with a metallic PtRh alloy core and commercial Pt. These studies provided insight on the design of a new genre of electro-catalysts with a partially oxidized noble metal.« less

Compact antenna for two-dimensional beam scan in the JT-60U electron cyclotron heating/current drive system

NASA Astrophysics Data System (ADS)

Moriyama, S.; Kajiwara, K.; Takahashi, K.; Kasugai, A.; Seki, M.; Ikeda, Y.; Fujii, T.

2005-11-01

A compact antenna system was designed and fabricated to enable millimeter-wave beam scanning in the toroidal and poloidal directions of the JT-60U tokamak for electron cyclotron heating (ECH) and electron cyclotron current drive (ECCD) experiments. The antenna consists of a fast movable flat mirror mounted on the tokamak vacuum vessel and a rotary focusing mirror attached at the end of the waveguide that is supported from outside the vacuum vessel. This separate support concept enables a compact structure inside a shallow port (0.68×0.54×0.2m) that is shared with a subport for an independent diagnostic system. During a plasma shot, the flat mirror is driven by a servomotor with a 3-m-long drive shaft to reduce the influence of the high magnetic field on the motor. The focusing mirror is rotated by a simple mechanism utilizing a push rod and an air cylinder. The antenna has been operated reliably for 3 years after a small improvement to the rotary drive mechanism. It has made significant contributions to ECH and ECCD experiments, especially the current profile control in JT-60U.

Field modeling and ray-tracing of a miniature scanning electron microscope beam column.

PubMed

Loyd, Jody S; Gregory, Don A; Gaskin, Jessica A

2017-08-01

A miniature scanning electron microscope (SEM) focusing column design is introduced and its potential performance assessed through an estimation of parameters that affect the probe radius, to include source size, spherical and chromatic aberration, diffraction and space charge broadening. The focusing column, a critical component of any SEM capable of operating on the lunar surface, was developed by the NASA Marshall Space Flight Center and Advanced Research Systems. The ray-trace analysis presented uses a model of the electrostatic field (within the focusing column) that is first calculated using the boundary element method (BEM). This method provides flexibility in modeling the complex electrode shapes of practical electron lens systems. A Fourier series solution of the lens field is then derived within a cylindrical domain whose boundary potential is provided by the BEM. Used in this way, the Fourier series solution is an accuracy enhancement to the BEM solution, allowing sufficient precision to assess geometric aberrations through direct ray-tracing. Two modes of operation with distinct lens field solutions are described. © The Author 2017. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Amyloid Structure and Assembly: Insights from Scanning Transmission Electron Microscopy

PubMed Central

Goldsbury, Claire; Baxa, Ulrich; Simon, Martha N.; Steven, Alasdair C.; Engel, Andreas; Wall, Joseph S.; Aebi, Ueli; Müller, Shirley A.

2010-01-01

Amyloid fibrils are filamentous protein aggregates implicated in several common diseases like Alzheimer’s disease and type II diabetes. Similar structures are also the molecular principle of the infectious spongiform encephalopathies like Creutzfeldt-Jakob disease in humans, scrapie in sheep, and of the so-called yeast prions, inherited non-chromosomal elements found in yeast and fungi. Scanning transmission electron microscopy (STEM) is often used to delineate the assembly mechanism and structural properties of amyloid aggregates. In this review we consider specifically contributions and limitations of STEM for the investigation of amyloid assembly pathways, fibril polymorphisms and structural models of amyloid fibrils. This type of microscopy provides the only method to directly measure the mass-per-length (MPL) of individual filaments. Made on both in vitro assembled and ex vivo samples, STEM mass measurements have illuminated the hierarchical relationships between amyloid fibrils and revealed that polymorphic fibrils and various globular oligomers can assemble simultaneously from a single polypeptide. The MPLs also impose strong constraints on possible packing schemes, assisting in molecular model building when combined with high-resolution methods like solid-state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR). PMID:20868754

Self-supported supercapacitor membrane through incorporating MnO2 nanowires into carbon nanotube networks.

PubMed

Fang, Yueping; Liu, Jianwei; Li, Jun

2010-08-01

We report on a study on the development of a self-supported membrane of carbon nanotube (CNT) mixed with MnO2 nanowires as supercapacitors. Both single-walled CNTs (SWCNTs) and multiwalled CNTs (MWCNTs) have been explored to serve as the electrically conductive networks to connect redox active MnO2 nanowires. High-quality alpha-MnO2 nanowires were synthesized using bulk alpha-MnO2 crystals as the precursor by a facile hydrothermal method. The morphology and structure of the as-prepared alpha-MnO2 nanowires were characterized by X-ray and electron diffraction, transmission electron microscopy, and scanning electron microscopy. Supercapacitor membranes were prepared by filtration of mixture solutions of MnO2 nanowires and CNTs at various ratios, forming entangled networks which are self-supported and directly used as supercapacitor electrodes without binders or backing metals. Cyclic voltammetry at various scan rates and charge--discharging measurements are used to characterize the supercapacitance of the CNT-MnO2 nanowire membranes. The specific capacitance has been found to be increased by several times over that of pure CNT membranes after incorporation of MnO2 nanowires.

Enhanced Electro-Kinetics of C-C Bond-Splitting during Ethanol Oxidation Reaction using Pt/Rh/Sn Catalyst with a Partially Oxidized Pt and Rh Core and a SnO2 Shell

DOE PAGES

Yang, G.; Su, D.; Frenkel, A. I.; ...

2016-09-04

Direct ethanol fuel cell (DEFC) is a promising technology for generating electricity via the electro-oxidation of liquid ethanol. Its implementation requires the development of anode catalysts capable of producing CO 2 and yielding 12-electron transfer through breaking C-C bond of ethanol. Here we presented comprehensive studies of electro-kinetics of the CO 2 generation on Pt/Rh/Sn ternary catalysts. Our studies showed that, for the first time, the tri–phase PtRhOx- SnO 2 catalysts with a partially oxidized Pt and Rh core and a SnO 2 shell, validated by X-ray absorption analyses and scanning transmission electron microscope-electron energy loss spectroscopy line scan, coincidedmore » with a 2.5-fold increase in the CO 2 generation rate towards ethanol oxidation reaction, compared with the bi-phase PtRh-SnO 2 catalysts with a metallic PtRh alloy core and commercial Pt. These studies provided insight on the design of a new genre of electro-catalysts with a partially oxidized noble metal.« less

Bacterial Biofilms in Jones Tubes.

PubMed

Ahn, Eric S; Hauck, Matthew J; Kirk Harris, Jonathan; Robertson, Charles E; Dailey, Roger A

To investigate the presence and microbiology of bacterial biofilms on Jones tubes (JTs) by direct visualization with scanning electron microscopy and polymerase chain reaction (PCR) of representative JTs, and to correlate these findings with inflammation and/or infection related to the JT. In this study, prospective case series were performed. JTs were recovered from consecutive patients presenting to clinic for routine cleaning or recurrent irritation/infection. Four tubes were processed for scanning electron microscopy alone to visualize evidence of biofilms. Two tubes underwent PCR alone for bacterial quantification. One tube was divided in half and sent for scanning electron microscopy and PCR. Symptoms related to the JTs were recorded at the time of recovery. Seven tubes were obtained. Five underwent SEM, and 3 out of 5 showed evidence of biofilms (60%). Two of the 3 biofilms demonstrated cocci and the third revealed rods. Three tubes underwent PCR. The predominant bacteria identified were Pseudomonadales (39%), Pseudomonas (16%), and Staphylococcus (14%). Three of the 7 patients (43%) reported irritation and discharge at presentation. Two symptomatic patients, whose tubes were imaged only, revealed biofilms. The third symptomatic patient's tube underwent PCR only, showing predominantly Staphylococcus (56%) and Haemophilus (36%) species. Two of the 4 asymptomatic patients also showed biofilms. All symptomatic patients improved rapidly after tube exchange and steroid antibiotic drops. Bacterial biofilms were variably present on JTs, and did not always correlate with patients' symptoms. Nevertheless, routine JT cleaning is recommended to treat and possibly prevent inflammation caused by biofilms.

Processing and characterization of Zr-based metallic glass by laser direct deposition

NASA Astrophysics Data System (ADS)

Bae, Heehun

Bulk Metallic Glass has become famous for its exceptional mechanical and corrosion properties. Especially, Zirconium has been the prominent constituent in Bulk Metallic Glass due to its superior glass forming ability, the ability to form amorphous phase with low cooling rate, thereby giving advantages in structural applications. In this study, Zirconium powder was alloyed with Aluminum, Nickel and Copper powder at an atomic ratio of 65:10:10:15, respectively. Using the ball milling process to mix the powders, Zr65Al10Ni 10Cu15 amorphous structure was manufactured by laser direct deposition. Laser power and laser scanning speed were optimized to increase the fraction of amorphous phase. X-ray Diffraction confirmed the existence of both amorphous and crystalline phase by having a wide halo peak and sharp intense peak in the spectrum. Differential Scanning Calorimetry proved the presence of amorphous phase and glass transition was observed to be around 655 K. Scanning electron microscopy showed the microstructure of the deposited sample to have repetitive amorphous and crystalline phase as XRD examined. Crystalline phase resulted from the laser reheating and remelting process due to subsequent laser scan. Laser direct deposited amorphous/crystalline composite showed Vickers Hardness of 670 Hv and exhibited improved corrosion resistance in comparison to fully-crystallized sample. The compression test showed that, due to the existence of crystalline phase, fracture strain of Zr65Al10Ni10Cu 15 amorphous composites was enhanced from less than 2% to as high as 5.7%, compared with fully amorphous metallic glass.

New developments in electron microscopy for serial image acquisition of neuronal profiles.

PubMed

Kubota, Yoshiyuki

2015-02-01

Recent developments in electron microscopy largely automate the continuous acquisition of serial electron micrographs (EMGs), previously achieved by laborious manual serial ultrathin sectioning using an ultramicrotome and ultrastructural image capture process with transmission electron microscopy. The new systems cut thin sections and capture serial EMGs automatically, allowing for acquisition of large data sets in a reasonably short time. The new methods are focused ion beam/scanning electron microscopy, ultramicrotome/serial block-face scanning electron microscopy, automated tape-collection ultramicrotome/scanning electron microscopy and transmission electron microscope camera array. In this review, their positive and negative aspects are discussed. © The Author 2015. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Integration of scanned document management with the anatomic pathology laboratory information system: analysis of benefits.

PubMed

Schmidt, Rodney A; Simmons, Kim; Grimm, Erin E; Middlebrooks, Michael; Changchien, Rosy

2006-11-01

Electronic document management systems (EDMSs) have the potential to improve the efficiency of anatomic pathology laboratories. We implemented a novel but simple EDMS for scanned documents as part of our laboratory information system (AP-LIS) and collected cost-benefit data with the intention of discerning the value of such a system in general and whether integration with the AP-LIS is advantageous. We found that the direct financial benefits are modest but the indirect and intangible benefits are large. Benefits of time savings and access to data particularly accrued to pathologists and residents (3.8 h/d saved for 26 pathologists and residents). Integrating the scanned document management system (SDMS) into the AP-LIS has major advantages in terms of workflow and overall simplicity. This simple, integrated SDMS is an excellent value in a practice like ours, and many of the benefits likely apply in other practice settings.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Chang W.; Iddir, Hakim; Uzun, Alper

To address the challenge of fast, direct atomic-scale visualization of the diffusion of atoms and clusters on surfaces, we used aberration-corrected scanning transmission electron microscopy (STEM) with high scan speeds (as little as ~0.1 s per frame) to visualize the diffusion of (1) a heavy atom (Ir) on the surface of a support consisting of light atoms, MgO(100), and (2) an Ir 3 cluster on MgO(110). Sequential Z-contrast images elucidate the diffusion mechanisms, including the hopping of Ir1 and the rotational migration of Ir 3 as two Ir atoms remain anchored to the surface. Density functional theory (DFT) calculations providedmore » estimates of the diffusion energy barriers and binding energies of the iridium species to the surfaces. The results show how the combination of fast-scan STEM and DFT calculations allow real-time visualization and fundamental understanding of surface diffusion phenomena pertaining to supported catalysts and other materials.« less

Systematic analyses of vibration noise of a vibration isolation system for high-resolution scanning tunneling microscopes.

PubMed

Iwaya, Katsuya; Shimizu, Ryota; Hashizume, Tomihiro; Hitosugi, Taro

2011-08-01

We designed and constructed an effective vibration isolation system for stable scanning tunneling microscopy measurements using a separate foundation and two vibration isolation stages (i.e., a combination of passive and active vibration isolation dampers). Systematic analyses of vibration data along the horizontal and vertical directions are present, including the vibration transfer functions of each stage and the overall vibration isolation system. To demonstrate the performance of the system, tunneling current noise measurements are conducted with and without the vibration isolation. Combining passive and active vibration isolation dampers successfully removes most of the vibration noise in the tunneling current up to 100 Hz. These comprehensive vibration noise data, along with details of the entire system, can be used to establish a clear guideline for building an effective vibration isolation system for various scanning probe microscopes and electron microscopes.

Direct imaging of coexisting ordered and frustrated sublattices in artificial ferromagnetic quasicrystals

DOE PAGES

Farmer, B.; Bhat, V. S.; Balk, A.; ...

2016-04-25

Here, we have used scanning electron microscopy with polarization analysis and photoemission electron microscopy to image the two-dimensional magnetization of permalloy films patterned into Penrose P2 tilings (P2T). The interplay of exchange interactions in asymmetrically coordinated vertices and short-range dipole interactions among connected film segments stabilize magnetically ordered, spatially distinct sublattices that coexist with frustrated sublattices at room temperature. Numerical simulations that include long-range dipole interactions between sublattices agree with images of as-grown P2T samples and predict a magnetically ordered ground state for a two-dimensional quasicrystal lattice of classical Ising spins.

Hydrothermal synthesis of uniform WO{sub 3} submicrospheres using thiourea as an assistant agent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, X.T.; Xiao, F.; Lin, J.L.

2010-08-15

Nearly monodisperse tungsten trioxide submicrospheres have been synthesized with tungsten acid and HCl as the starting materials and thiourea as a structure-directing agent through a facile hydrothermal method. The obtained products were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy and energy dispersive X-ray, respectively. The results show that the WO{sub 3} submicrospheres are monodisperse with a diameter of about 800-1000 nm. The morphology of the products gradually evolutes from rods to spheres with increase of the reaction time. The formation mechanism of the WO{sub 3} submicrospheres is primarily discussed.

Laser Fabrication of Two-Dimensional Rotating-Lattice Single Crystal

DOE PAGES

Savytskii, Dmytro; Au-Yeung, Courtney; Dierolf, Volkmar; ...

2017-03-09

A rotating lattice single (RLS) crystal is a unique form of solid, which was fabricated recently as one-dimensional architecture in glass via solid state transformation induced by laser irradiation. In these objects, the lattice rotates gradually and predictably about an axis that lies in the plane of the crystal and is normal to the laser scanning direction. This paper reports on the fabrication of Sb 2S 3 two-dimensional (2D) RLS crystals on the surface of 16SbI 3-84Sb 2S 3 glass, as a model example: individual RLS crystal lines are joined together using "stitching" or "rastering" as two successful protocols. Themore » electron back scattered diffraction mapping and scanning Laue X-ray microdiffraction of the 2D RLS crystals show gradual rotation of lattice comprising of two components, one along the length of each line and another normal to this direction. The former component is determined by the rotation of the first line of the 2D pattern, but the relative contribution of the last component depends on the extent of overlap between two successive lines. By the appropriate choice of initial seed orientation and the direction of scanning, it is possible to control the lattice rotation, and even to reduce it down to 5 for a 50 × 50 μm 2 2D pattern of Sb 2S 3 crystal.« less

The Scanning Electron Microscope and the Archaeologist

ERIC Educational Resources Information Center

Ponting, Matthew

2004-01-01

Images from scanning electron microscopy are now quite common and they can be of great value in archaeology. Techniques such as secondary electron imaging, backscattered electron imaging and energy-dispersive x-ray analysis can reveal information such as the presence of weevils in grain in Roman Britain, the composition of Roman coins and the…

Measurement of atomic electric fields and charge densities from average momentum transfers using scanning transmission electron microscopy.

PubMed

Müller-Caspary, Knut; Krause, Florian F; Grieb, Tim; Löffler, Stefan; Schowalter, Marco; Béché, Armand; Galioit, Vincent; Marquardt, Dennis; Zweck, Josef; Schattschneider, Peter; Verbeeck, Johan; Rosenauer, Andreas

2017-07-01

This study sheds light on the prerequisites, possibilities, limitations and interpretation of high-resolution differential phase contrast (DPC) imaging in scanning transmission electron microscopy (STEM). We draw particular attention to the well-established DPC technique based on segmented annular detectors and its relation to recent developments based on pixelated detectors. These employ the expectation value of the momentum transfer as a reliable measure of the angular deflection of the STEM beam induced by an electric field in the specimen. The influence of scattering and propagation of electrons within the specimen is initially discussed separately and then treated in terms of a two-state channeling theory. A detailed simulation study of GaN is presented as a function of specimen thickness and bonding. It is found that bonding effects are rather detectable implicitly, e.g., by characteristics of the momentum flux in areas between the atoms than by directly mapping electric fields and charge densities. For strontium titanate, experimental charge densities are compared with simulations and discussed with respect to experimental artifacts such as scan noise. Finally, we consider practical issues such as figures of merit for spatial and momentum resolution, minimum electron dose, and the mapping of larger-scale, built-in electric fields by virtue of data averaged over a crystal unit cell. We find that the latter is possible for crystals with an inversion center. Concerning the optimal detector design, this study indicates that a sampling of 5mrad per pixel is sufficient in typical applications, corresponding to approximately 10×10 available pixels. Copyright © 2016 Elsevier B.V. All rights reserved.

Scanning Electron Microscopy (SEM) Procedure for HE Powders on a Zeiss Sigma HD VP SEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zaka, F.

This method describes the characterization of inert and HE materials by the Zeiss Sigma HD VP field emission Scanning Electron Microscope (SEM). The SEM uses an accelerated electron beam to generate high-magnification images of explosives and other materials. It is fitted with five detectors (SE, Inlens, STEM, VPSE, HDBSD) to enable imaging of the sample via different secondary electron signatures, angles, and energies. In addition to imaging through electron detection, the microscope is also fitted with two Oxford Instrument Energy Dispersive Spectrometer (EDS) 80 mm detectors to generate elemental constituent spectra and two-dimensional maps of the material being scanned.

Comparative study of image contrast in scanning electron microscope and helium ion microscope.

PubMed

O'Connell, R; Chen, Y; Zhang, H; Zhou, Y; Fox, D; Maguire, P; Wang, J J; Rodenburg, C

2017-12-01

Images of Ga + -implanted amorphous silicon layers in a 110 n-type silicon substrate have been collected by a range of detectors in a scanning electron microscope and a helium ion microscope. The effects of the implantation dose and imaging parameters (beam energy, dwell time, etc.) on the image contrast were investigated. We demonstrate a similar relationship for both the helium ion microscope Everhart-Thornley and scanning electron microscope Inlens detectors between the contrast of the images and the Ga + density and imaging parameters. These results also show that dynamic charging effects have a significant impact on the quantification of the helium ion microscope and scanning electron microscope contrast. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Distributed Beam Former for Distributed-Aperture Electronically Steered Antennas

DTIC Science & Technology

2006-11-01

of planar or conformal aperture, it will be replaced by a distributed aperture configuration with a base-band digital network that is used to combine...beam forming network that can be designed with pre-set scanning directions. The beam former for this stage can be realized using a printed Butler...matrix (Bona et al, 2002; Neron and Delisle, 2005), a printed Rotman lens (Kilic and Dahlstrom, 2005) or other switched time delay system. The

Inverse opal with an ultraviolet photonic gap

NASA Astrophysics Data System (ADS)

Ni, Peigen; Cheng, Bingying; Zhang, Daozhong

2002-03-01

Photonic crystals composed of TiO2 and air voids fabricated by the template method exhibit an ultraviolet photonic stop band (˜380 nm) in the Γ-L direction. Scanning electron microscopy images show that the inverse opal possesses face-centered-cubic symmetry with a lattice constant of 240 nm. The transmission spectra show that the change in transmittance is one order of magnitude in the gap, which is in accord with the reflection spectrum.

High-resolution analytical imaging and electron holography of magnetite particles in amyloid cores of Alzheimer’s disease

PubMed Central

Plascencia-Villa, Germán; Ponce, Arturo; Collingwood, Joanna F.; Arellano-Jiménez, M. Josefina; Zhu, Xiongwei; Rogers, Jack T.; Betancourt, Israel; José-Yacamán, Miguel; Perry, George

2016-01-01

Abnormal accumulation of brain metals is a key feature of Alzheimer’s disease (AD). Formation of amyloid-β plaque cores (APC) is related to interactions with biometals, especially Fe, Cu and Zn, but their particular structural associations and roles remain unclear. Using an integrative set of advanced transmission electron microscopy (TEM) techniques, including spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM), nano-beam electron diffraction, electron holography and analytical spectroscopy techniques (EDX and EELS), we demonstrate that Fe in APC is present as iron oxide (Fe3O4) magnetite nanoparticles. Here we show that Fe was accumulated primarily as nanostructured particles within APC, whereas Cu and Zn were distributed through the amyloid fibers. Remarkably, these highly organized crystalline magnetite nanostructures directly bound into fibrillar Aβ showed characteristic superparamagnetic responses with saturated magnetization with circular contours, as observed for the first time by off-axis electron holography of nanometer scale particles. PMID:27121137

High-resolution analytical imaging and electron holography of magnetite particles in amyloid cores of Alzheimer’s disease

NASA Astrophysics Data System (ADS)

Plascencia-Villa, Germán; Ponce, Arturo; Collingwood, Joanna F.; Arellano-Jiménez, M. Josefina; Zhu, Xiongwei; Rogers, Jack T.; Betancourt, Israel; José-Yacamán, Miguel; Perry, George

2016-04-01

Abnormal accumulation of brain metals is a key feature of Alzheimer’s disease (AD). Formation of amyloid-β plaque cores (APC) is related to interactions with biometals, especially Fe, Cu and Zn, but their particular structural associations and roles remain unclear. Using an integrative set of advanced transmission electron microscopy (TEM) techniques, including spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM), nano-beam electron diffraction, electron holography and analytical spectroscopy techniques (EDX and EELS), we demonstrate that Fe in APC is present as iron oxide (Fe3O4) magnetite nanoparticles. Here we show that Fe was accumulated primarily as nanostructured particles within APC, whereas Cu and Zn were distributed through the amyloid fibers. Remarkably, these highly organized crystalline magnetite nanostructures directly bound into fibrillar Aβ showed characteristic superparamagnetic responses with saturated magnetization with circular contours, as observed for the first time by off-axis electron holography of nanometer scale particles.

Communication: Visualization and spectroscopy of defects induced by dehydrogenation in individual silicon nanocrystals

NASA Astrophysics Data System (ADS)

Kislitsyn, Dmitry A.; Mills, Jon M.; Kocevski, Vancho; Chiu, Sheng-Kuei; DeBenedetti, William J. I.; Gervasi, Christian F.; Taber, Benjamen N.; Rosenfield, Ariel E.; Eriksson, Olle; Rusz, Ján; Goforth, Andrea M.; Nazin, George V.

2016-06-01

We present results of a scanning tunneling spectroscopy (STS) study of the impact of dehydrogenation on the electronic structures of hydrogen-passivated silicon nanocrystals (SiNCs) supported on the Au(111) surface. Gradual dehydrogenation is achieved by injecting high-energy electrons into individual SiNCs, which results, initially, in reduction of the electronic bandgap, and eventually produces midgap electronic states. We use theoretical calculations to show that the STS spectra of midgap states are consistent with the presence of silicon dangling bonds, which are found in different charge states. Our calculations also suggest that the observed initial reduction of the electronic bandgap is attributable to the SiNC surface reconstruction induced by conversion of surface dihydrides to monohydrides due to hydrogen desorption. Our results thus provide the first visualization of the SiNC electronic structure evolution induced by dehydrogenation and provide direct evidence for the existence of diverse dangling bond states on the SiNC surfaces.

Scanning transmission electron microscopy methods for the analysis of nanoparticles.

PubMed

Ponce, Arturo; Mejía-Rosales, Sergio; José-Yacamán, Miguel

2012-01-01

Here we review the scanning transmission electron microscopy (STEM) characterization technique and STEM imaging methods. We describe applications of STEM for studying inorganic nanoparticles, and other uses of STEM in biological and health sciences and discuss how to interpret STEM results. The STEM imaging mode has certain benefits compared with the broad-beam illumination mode; the main advantage is the collection of the information about the specimen using a high angular annular dark field (HAADF) detector, in which the images registered have different levels of contrast related to the chemical composition of the sample. Another advantage of its use in the analysis of biological samples is its contrast for thick stained sections, since HAADF images of samples with thickness of 100-120 nm have notoriously better contrast than those obtained by other techniques. Combining the HAADF-STEM imaging with the new aberration correction era, the STEM technique reaches a direct way to imaging the atomistic structure and composition of nanostructures at a sub-angstrom resolution. Thus, alloying in metallic nanoparticles is directly resolved at atomic scale by the HAADF-STEM imaging, and the comparison of the STEM images with results from simulations gives a very powerful way of analysis of structure and composition. The use of X-ray energy dispersive spectroscopy attached to the electron microscope for STEM mode is also described. In issues where characterization at the atomic scale of the interaction between metallic nanoparticles and biological systems is needed, all the associated techniques to STEM become powerful tools for the best understanding on how to use these particles in biomedical applications.

Low vacuum scanning electron microscopy for paraffin sections utilizing the differential stainability of cells and tissues with platinum blue.

PubMed

Inaga, Sumire; Hirashima, Sayuri; Tanaka, Keiichi; Katsumoto, Tetsuo; Kameie, Toshio; Nakane, Hironobu; Naguro, Tomonori

2009-07-01

The present study introduces a novel method for the direct observation of histological paraffin sections by low vacuum scanning electron microscopy (LVSEM) with platinum blue (Pt-blue) treatment. Pt-blue was applied not only as a backscattered electron (BSE) signal enhancer but also as a histologically specific stain. In this method, paraffin sections of the rat tongue prepared for conventional light microscopy (LM) were stained on glass slides with a Pt-blue staining solution (pH 9) and observed in a LVSEM using BSE detector. Under LVSEM, overviews of whole sections as well as three-dimensional detailed observations of individual cells and tissues could be easily made at magnifications from x40 to x10,000. Each kind of cell and tissue observed in the section could be clearly distinguished due to the different yields of BSE signals, which depended on the surface structures and different affinities to Pt-blue. Thus, we roughly classified cellular and tissue components into three groups according to the staining intensity of Pt-blue observed by LM and LVSEM: 1) a strongly stained (deep blue by LM and brightest by LVSEM) group which included epithelial tissue, endothelium and mast cells; 2) a moderately stained (light blue and bright) group which included muscular tissue and nervous tissue; 3) an unstained or weakly stained (colorless and dark) group which included elastic fibers and collagen fibers. We expect that this method will prove useful for the three-dimensional direct observation of histological paraffin sections of various tissues by LVSEM with higher resolutions than LM.

Correction of image drift and distortion in a scanning electron microscopy.

PubMed

Jin, P; Li, X

2015-12-01

Continuous research on small-scale mechanical structures and systems has attracted strong demand for ultrafine deformation and strain measurements. Conventional optical microscope cannot meet such requirements owing to its lower spatial resolution. Therefore, high-resolution scanning electron microscope has become the preferred system for high spatial resolution imaging and measurements. However, scanning electron microscope usually is contaminated by distortion and drift aberrations which cause serious errors to precise imaging and measurements of tiny structures. This paper develops a new method to correct drift and distortion aberrations of scanning electron microscope images, and evaluates the effect of correction by comparing corrected images with scanning electron microscope image of a standard sample. The drift correction is based on the interpolation scheme, where a series of images are captured at one location of the sample and perform image correlation between the first image and the consequent images to interpolate the drift-time relationship of scanning electron microscope images. The distortion correction employs the axial symmetry model of charged particle imaging theory to two images sharing with the same location of one object under different imaging fields of view. The difference apart from rigid displacement between the mentioned two images will give distortion parameters. Three-order precision is considered in the model and experiment shows that one pixel maximum correction is obtained for the employed high-resolution electron microscopic system. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

High-resolution, high-throughput imaging with a multibeam scanning electron microscope.

PubMed

Eberle, A L; Mikula, S; Schalek, R; Lichtman, J; Knothe Tate, M L; Zeidler, D

2015-08-01

Electron-electron interactions and detector bandwidth limit the maximal imaging speed of single-beam scanning electron microscopes. We use multiple electron beams in a single column and detect secondary electrons in parallel to increase the imaging speed by close to two orders of magnitude and demonstrate imaging for a variety of samples ranging from biological brain tissue to semiconductor wafers. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Osteoblast-like cell response to macro- and micro-patterned carbon scaffolds obtained from the sea rush Juncus maritimus.

PubMed

López-Álvarez, M; Pereiro, I; Serra, J; de Carlos, A; González, P

2011-08-01

Carbon scaffolds with a directional patterned surface were obtained by pyrolysis of the sea rush Juncus maritimus. The structure of the scaffolds was investigated using scanning electron microscopy, mercury porosimetry and interferometric profilometry. X-ray diffraction and x-ray fluorescence were the techniques used for their chemical characterization. The alignment and differentiation of pre-osteoblasts (MC3T3-E1 cell line) incubated on the patterned scaffolds were evaluated by scanning electron microscopy, confocal laser scanning microscopy and by the quantification of the phosphatase alkaline activity and the osteocalcin synthesis. It was found that pyrolysis at 500 °C preserved and even enhanced the natural macro- and micro-patterning of the plant. The results obtained for porosity and chemical composition validated these structures as viable scaffolds for tissue engineering applications. Finally, the patterned surface was confirmed to promote the oriented growth of the pre-osteoblasts MC3T3-E1, not only after short periods of incubation (hours) but also after longer ones (several weeks). The quantification of the cell differentiation markers together with the evaluation of the cell layer morphology up to 28 days of incubation confirmed the differentiation of MC3T3-E1 cells to osteoblasts. © 2011 IOP Publishing Ltd

Investigation on Electrochemical Properties of Polythiophene Nanocomposite with Graphite Derivatives as Supercapacitor Material on Breath Figure-Decorated PMMA Electrode

NASA Astrophysics Data System (ADS)

Azimi, Mona; Abbaspour, Mohsen; Fazli, Ali; Setoodeh, Hamideh; Pourabbas, Behzad

2018-03-01

Breath figures have been formed by the direct breath figure method on polymethyl methacrylate electrode sand hexagonal oriented holes with 0.5- to 10- μm2 surface area have been created. Deposition of materials on the electrodes has been performed by the spray-coating method. polythiophene (PTh) nanoparticles, polythiophene-graphene oxide (PTh-GO) and polythiophene-reduced graphene oxide (PTh-G) nanocomposites were synthesized by emulsion polymerization, while characterization of synthetic materials have been carried out by Fourier transform infrared, Χ-ray diffraction, transmission electron microscopy, UV-Vis spectroscopy and field emission scanning electron microscopy techniques. Also, the electrochemical properties of the designed electrodes were investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy techniques. Specific capacitance of porous electrodes coated by PTh nanoparticles, PTh-GO and PTh-G nanocomposites were calculated from cyclic voltammetry curves at 5 mV/s scan rate, andthe values are 3.5 F/g, 16.39 F/g, and 28.68 F/g, respectively. Also, the energy density of each electrode at 5 mV/s scan rate has been calculated and the results show that incorporation of GO and G nanolayers with PTh nanoparticles enhances the electrochemical properties of electrodes.

Sample mounting and transfer for coupling an ultrahigh vacuum variable temperature beetle scanning tunneling microscope with conventional surface probes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nafisi, Kourosh; Ranau, Werner; Hemminger, John C.

2001-01-01

We present a new ultrahigh vacuum (UHV) chamber for surface analysis and microscopy at controlled, variable temperatures. The new instrument allows surface analysis with Auger electron spectroscopy, low energy electron diffraction, quadrupole mass spectrometer, argon ion sputtering gun, and a variable temperature scanning tunneling microscope (VT-STM). In this system, we introduce a novel procedure for transferring a sample off a conventional UHV manipulator and onto a scanning tunneling microscope in the conventional ''beetle'' geometry, without disconnecting the heating or thermocouple wires. The microscope, a modified version of the Besocke beetle microscope, is mounted on a 2.75 in. outer diameter UHVmore » flange and is directly attached to the base of the chamber. The sample is attached to a tripod sample holder that is held by the main manipulator. Under UHV conditions the tripod sample holder can be removed from the main manipulator and placed onto the STM. The VT-STM has the capability of acquiring images between the temperature range of 180--500 K. The performance of the chamber is demonstrated here by producing an ordered array of island vacancy defects on a Pt(111) surface and obtaining STM images of these defects.« less

Electrical transport and structural characterization of epitaxial monolayer MoS2 /n- and p-doped GaN vertical lattice-matched heterojunctions

NASA Astrophysics Data System (ADS)

Ruzmetov, D.; O'Regan, T.; Zhang, K.; Herzing, A.; Mazzoni, A.; Chin, M.; Huang, S.; Zhang, Z.; Burke, R.; Neupane, M.; Birdwell, Ag; Shah, P.; Crowne, F.; Kolmakov, A.; Leroy, B.; Robinson, J.; Davydov, A.; Ivanov, T.

We investigate vertical semiconductor junctions consisting of monolayer MoS2 that is epitaxially grown on n- and p-doped GaN crystals. Such a junction represents a building block for 2D/3D vertical semiconductor heterostructures. Epitaxial, lattice-matched growth of MoS2 on GaN is important to ensure high quality interfaces that are crucial for the efficient vertical transport. The MoS2/GaN junctions were characterized with cross-sectional and planar scanning transmission electron microscopy (STEM), scanning tunneling microscopy, and atomic force microscopy. The MoS2/GaN lattice mismatch is measured to be near 1% using STEM. The electrical transport in the out-of-plane direction across the MoS2/GaN junctions was measured using conductive atomic force microscopy and mechanical nano-probes inside a scanning electron microscope. Nano-disc metal contacts to MoS2 were fabricated by e-beam lithography and evaporation. The current-voltage curves of the vertical MoS2/GaN junctions exhibit rectification with opposite polarities for n-doped and p-doped GaN. The metal contact determines the general features of the current-voltage curves, and the MoS2 monolayer modifies the electrical transport across the contact/GaN interface.

Dynamic scan control in STEM: Spiral scans

DOE PAGES

Lupini, Andrew R.; Borisevich, Albina Y.; Kalinin, Sergei V.; ...

2016-06-13

Here, scanning transmission electron microscopy (STEM) has emerged as one of the foremost techniques to analyze materials at atomic resolution. However, two practical difficulties inherent to STEM imaging are: radiation damage imparted by the electron beam, which can potentially damage or otherwise modify the specimen and slow-scan image acquisition, which limits the ability to capture dynamic changes at high temporal resolution. Furthermore, due in part to scan flyback corrections, typical raster scan methods result in an uneven distribution of dose across the scanned area. A method to allow extremely fast scanning with a uniform residence time would enable imaging atmore » low electron doses, ameliorating radiation damage and at the same time permitting image acquisition at higher frame-rates while maintaining atomic resolution. The practical complication is that rastering the STEM probe at higher speeds causes significant image distortions. Non-square scan patterns provide a solution to this dilemma and can be tailored for low dose imaging conditions. Here, we develop a method for imaging with alternative scan patterns and investigate their performance at very high scan speeds. A general analysis for spiral scanning is presented here for the following spiral scan functions: Archimedean, Fermat, and constant linear velocity spirals, which were tested for STEM imaging. The quality of spiral scan STEM images is generally comparable with STEM images from conventional raster scans, and the dose uniformity can be improved.« less

Dynamic scan control in STEM: Spiral scans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lupini, Andrew R.; Borisevich, Albina Y.; Kalinin, Sergei V.

Here, scanning transmission electron microscopy (STEM) has emerged as one of the foremost techniques to analyze materials at atomic resolution. However, two practical difficulties inherent to STEM imaging are: radiation damage imparted by the electron beam, which can potentially damage or otherwise modify the specimen and slow-scan image acquisition, which limits the ability to capture dynamic changes at high temporal resolution. Furthermore, due in part to scan flyback corrections, typical raster scan methods result in an uneven distribution of dose across the scanned area. A method to allow extremely fast scanning with a uniform residence time would enable imaging atmore » low electron doses, ameliorating radiation damage and at the same time permitting image acquisition at higher frame-rates while maintaining atomic resolution. The practical complication is that rastering the STEM probe at higher speeds causes significant image distortions. Non-square scan patterns provide a solution to this dilemma and can be tailored for low dose imaging conditions. Here, we develop a method for imaging with alternative scan patterns and investigate their performance at very high scan speeds. A general analysis for spiral scanning is presented here for the following spiral scan functions: Archimedean, Fermat, and constant linear velocity spirals, which were tested for STEM imaging. The quality of spiral scan STEM images is generally comparable with STEM images from conventional raster scans, and the dose uniformity can be improved.« less

Chemical lift-off and direct wafer bonding of GaN/InGaN P-I-N structures grown on ZnO

NASA Astrophysics Data System (ADS)

Pantzas, K.; Rogers, D. J.; Bove, P.; Sandana, V. E.; Teherani, F. H.; El Gmili, Y.; Molinari, M.; Patriarche, G.; Largeau, L.; Mauguin, O.; Suresh, S.; Voss, P. L.; Razeghi, M.; Ougazzaden, A.

2016-02-01

p-GaN/i-InGaN/n-GaN (PIN) structures were grown epitaxially on ZnO-buffered c-sapphire substrates by metal organic vapor phase epitaxy using the industry standard ammonia precursor for nitrogen. Scanning electron microscopy revealed continuous layers with a smooth interface between GaN and ZnO and no evidence of ZnO back-etching. Energy Dispersive X-ray Spectroscopy revealed a peak indium content of just under 5 at% in the active layers. The PIN structure was lifted off the sapphire by selectively etching away the ZnO buffer in an acid and then direct bonded onto a glass substrate. Detailed high resolution transmission electron microscoy and grazing incidence X-ray diffraction studies revealed that the structural quality of the PIN structures was preserved during the transfer process.

Angle-resolved PED and AED calculations for different structures of the diamond C(111) surface

NASA Astrophysics Data System (ADS)

Niebergall, L.; Rennert, P.; Chassé, A.; Kucherenko, Yu

1998-05-01

Angle-resolved (AR) photoelectron diffraction (PED) spectra for electrons excited from the C 1s core state and angle-resolved KVV Auger electron diffraction (AED) spectra are calculated for the Pandey and the Tsai stucture models of diamond C(111) which extend previous investigations of the ideal structure. It is shown how to decide on the structure model by comparing PE spectra for different directions and by comparing PED and AED spectra. Calculations have been performed by evaluating the scattering path operator for a finite cluster in a curved-wave approximation. The different matrix elements for the photoelectron excitation and for the Auger process, respectively, are included. It is shown that the PED intensities are very sensitive to the surface reconstruction for polar angles in the range of 80°. In the AED intensities, polar scans in the plane perpendicular to the chain direction can be considered.

Metallurgical and Mechanical Evaluation of 4340 Steel Produced by Direct Metal Laser Sintering

NASA Astrophysics Data System (ADS)

Jelis, Elias; Clemente, Matthew; Kerwien, Stacey; Ravindra, Nuggehalli M.; Hespos, Michael R.

2015-03-01

Direct metal laser sintering (DMLS) was used to produce high-strength low-alloy 4340 steel specimens. Mechanical and metallurgical analyses were performed on the specimens to determine the samples with the highest strengths and the least porosity. The optimal process parameters were thus defined based on the corresponding experimental conditions. Additionally, the effects of fabricating specimens with both virgin and recycled powders were studied. Scanning electron microscopy and electron-dispersive spectroscopy were performed on both types of powders to determine the starting morphology and composition. The initial tensile results are promising, suggesting that DMLS can produce specimens equal in strength to wrought materials. However, there is evidence of cracking on several of the heat-treated tensile specimens that is unexplained. Several theories point to disturbances in the build chamber environment that went undetected while the specimens were being fabricated.

GePb Alloy Growth Using Layer Inversion Method

NASA Astrophysics Data System (ADS)

Alahmad, Hakimah; Mosleh, Aboozar; Alher, Murtadha; Banihashemian, Seyedeh Fahimeh; Ghetmiri, Seyed Amir; Al-Kabi, Sattar; Du, Wei; Li, Bauhoa; Yu, Shui-Qing; Naseem, Hameed A.

2018-04-01

Germanium-lead films have been investigated as a new direct-bandgap group IV alloy. GePb films were deposited on Si via thermal evaporation of Ge and Pb solid sources using the layer inversion metal-induced crystallization method for comparison with the current laser-induced recrystallization method. Material characterization of the films using x-ray diffraction analysis revealed highly oriented crystallinity and Pb incorporation as high as 13.5% before and 5.2% after annealing. Transmission electron microscopy, scanning electron microscopy, and energy-dispersive x-ray mapping of the samples revealed uniform incorporation of elements and complete layer inversion. Optical characterization of the GePb films by Raman spectroscopy and photoluminescence techniques showed that annealing the samples resulted in higher crystalline quality as well as bandgap reduction. The bandgap reduction from 0.67 eV to 0.547 eV observed for the highest-quality material confirms the achievement of a direct-bandgap material.

Facile approach to prepare Pt decorated SWNT/graphene hybrid catalytic ink

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayavan, Sundar, E-mail: sundarmayavan@cecri.res.in; Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon, 305-701; Mandalam, Aditya

Highlights: • Pt NPs were in situ synthesized onto CNT–graphene support in aqueous solution. • The as-prepared material was used directly as a catalyst ink without further treatment. • Catalyst ink is active toward methanol oxidation. • This approach realizes both scalable and greener production of hybrid catalysts. - Abstract: Platinum nanoparticles were in situ synthesized onto hybrid support involving graphene and single walled carbon nanotube in aqueous solution. We investigate the reduction of graphene oxide, and platinum nanoparticle functionalization on hybrid support by X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The as-preparedmore » platinum on hybrid support was used directly as a catalyst ink without further treatment and is active toward methanol oxidation. This work realizes both scalable and greener production of highly efficient hybrid catalysts, and would be valuable for practical applications of graphene based fuel cell catalysts.« less

A self-assembled synthesis of carbon nanotubes for interconnects.

PubMed

Chen, Zexiang; Cao, Guichuan; Lin, Zulun; Koehler, Irmgard; Bachmann, Peter K

2006-02-28

We report a novel approach to grow highly oriented, freestanding and structured carbon nanotubes (CNTs) between two substrates, using microwave plasma chemical vapour deposition. Sandwiched, multi-layered catalyst structures are employed to generate such structures. The as-grown CNTs adhere well to both the substrate and the top contact, and provide a low-resistance electric contact between the two. High-resolution scanning electron microscope (SEM) images show that the CNTs grow perpendicular to these surfaces. This presents a simple way to grow CNTs in different, predetermined directions in a single growth step. The overall resistance of a CNT bundle and two CNT-terminal contacts is measured to be about 14.7 k Ω. The corresponding conductance is close to the quantum limit conductance G(0). This illustrates that our new approach is promising for the direct assembly of CNT-based interconnects in integrated circuits (ICs) or other micro-electronic devices.

Analysis of Ti valence states in resistive switching regions of a rutile TiO2‑ x four-terminal memristive device

NASA Astrophysics Data System (ADS)

Yamaguchi, Kengo; Takeuchi, Shotaro; Tohei, Tetsuya; Ikarashi, Nobuyuki; Sakai, Akira

2018-06-01

We have performed Ti valence state analysis of our four-terminal rutile TiO2‑ x single-crystal memristors using scanning transmission electron microscopy–electron energy loss spectroscopy (STEM–EELS). Analysis of Ti-L2,3 edge EELS spectra revealed that the electrocolored region formed by the application of voltage includes a valence state reflecting highly reduced TiO2‑ x due to the accumulation of oxygen vacancies. Such a valence state mainly exists within ∼50 nm from the crystal surface and extends along specific crystal directions. These electrically reduced surface layers are considered to directly contribute to the resistive switching (RS) in the four-terminal device. The present results add new insights into the microscopic mechanisms of the RS phenomena and should contribute to further development and improvements of TiO2‑ x based memristive devices.

GePb Alloy Growth Using Layer Inversion Method

NASA Astrophysics Data System (ADS)

Alahmad, Hakimah; Mosleh, Aboozar; Alher, Murtadha; Banihashemian, Seyedeh Fahimeh; Ghetmiri, Seyed Amir; Al-Kabi, Sattar; Du, Wei; Li, Bauhoa; Yu, Shui-Qing; Naseem, Hameed A.

2018-07-01

Germanium-lead films have been investigated as a new direct-bandgap group IV alloy. GePb films were deposited on Si via thermal evaporation of Ge and Pb solid sources using the layer inversion metal-induced crystallization method for comparison with the current laser-induced recrystallization method. Material characterization of the films using x-ray diffraction analysis revealed highly oriented crystallinity and Pb incorporation as high as 13.5% before and 5.2% after annealing. Transmission electron microscopy, scanning electron microscopy, and energy-dispersive x-ray mapping of the samples revealed uniform incorporation of elements and complete layer inversion. Optical characterization of the GePb films by Raman spectroscopy and photoluminescence techniques showed that annealing the samples resulted in higher crystalline quality as well as bandgap reduction. The bandgap reduction from 0.67 eV to 0.547 eV observed for the highest-quality material confirms the achievement of a direct-bandgap material.

Electrochemical detection of uric acid using ruthenium-dioxide-coated carbon nanotube directly grown onto Si wafer

NASA Astrophysics Data System (ADS)

Shih, Yi-Ting; Lee, Kuei-Yi; Lin, Chung-Kuang

2015-12-01

Carbon nanotubes (CNTs) directly grown onto a Si substrate by thermal chemical vapor deposition were used in uric acid (UA) detection. The process is simple and formation is easy without the need for additional chemical treatments. However, CNTs lack selectivity and sensitivity to UA. To enhance the electrochemical analysis, ruthenium oxide was used as a catalytic mediator in the modification of electrodes. The electrochemical results show that RuO2 nanostructures coated onto CNTs can strengthen the UA signal. The peak currents of RuO2 nanostructures coated onto CNTs linearly increase with increasing UA concentration, meaning that they can work as electrodes for UA detection. The lowest detection limit and highest sensitivity were 55 nM and 4.36 µA/µM, respectively. Moreover, the characteristics of RuO2 nanostructures coated onto CNTs were examined by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy.

Direct versus indirect ACL femoral attachment fibres and their implications on ACL graft placement.

PubMed

Moulton, Samuel G; Steineman, Brett D; Haut Donahue, Tammy L; Fontboté, Cristián A; Cram, Tyler R; LaPrade, Robert F

2017-01-01

To further elucidate the direct and indirect fibre insertion morphology within the human ACL femoral attachment using scanning electron microscopy and determine where in the footprint each fibre type predominates. The hypothesis was that direct fibre attachment would be found centrally in the insertion site, while indirect fibre attachment would be found posteriorly adjacent to the posterior articular cartilage. Ten cadaveric knees were dissected to preserve and isolate the entirety of the femoral insertion of the ACL. Specimens were then prepared and evaluated with scanning electron microscopy to determine insertional fibre morphology and location. The entirety of the fan-like projection of the ACL attachment site lay posterior to the lateral intercondylar ridge. In all specimens, a four-phase architecture, consistent with previous descriptions of direct fibres, was found in the centre of the femoral attachment site. The posterior margin of the ACL attachment attached directly adjacent to the posterior articular cartilage with some fibres coursing into it. The posterior portion of the ACL insertion had a two-phase insertion, consistent with previous descriptions of indirect fibres. The transition from the ligament fibres to bone had less interdigitations, and the interdigitations were significantly smaller (p < 0.001) compared to the transition in the direct fibre area. The interdigitations of the direct fibres were 387 ± 81 μm (range 282-515 μm) wide, while the interdigitations of indirect fibres measured 228 ± 75 μm (range 89-331 μm). The centre of the ACL femoral attachment consisted of a direct fibre structure, while the posterior portion had an indirect fibre structure. These results support previous animal studies reporting that the centre of the ACL femoral insertion was comprised of the strongest reported fibre type. Clinically, the femoral ACL reconstruction tunnel should be oriented to cover the entirety of the central direct ACL fibres and may need to be customized based on graft type and the fixation device used during surgery.

Three-dimensional imaging of adherent cells using FIB/SEM and STEM.

PubMed

Villinger, Clarissa; Schauflinger, Martin; Gregorius, Heiko; Kranz, Christine; Höhn, Katharina; Nafeey, Soufi; Walther, Paul

2014-01-01

In this chapter we describe three different approaches for three-dimensional imaging of electron microscopic samples: serial sectioning transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) tomography, and focused ion beam/scanning electron microscopy (FIB/SEM) tomography. With these methods, relatively large volumes of resin-embedded biological structures can be analyzed at resolutions of a few nm within a reasonable expenditure of time. The traditional method is serial sectioning and imaging the same area in all sections. Another method is TEM tomography that involves tilting a section in the electron beam and then reconstruction of the volume by back projection of the images. When the scanning transmission (STEM) mode is used, thicker sections (up to 1 μm) can be analyzed. The third approach presented here is focused ion beam/scanning electron microscopy (FIB/SEM) tomography, in which a sample is repeatedly milled with a focused ion beam (FIB) and each newly produced block face is imaged with the scanning electron microscope (SEM). This process can be repeated ad libitum in arbitrary small increments allowing 3D analysis of relatively large volumes such as eukaryotic cells. We show that resolution of this approach is considerably improved when the secondary electron signal is used. However, the most important prerequisite for three-dimensional imaging is good specimen preparation. For all three imaging methods, cryo-fixed (high-pressure frozen) and freeze-substituted samples have been used.

Microstructure and Sn crystal orientation evolution in Sn-3.5Ag lead-free solders in high temperature packaging applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Bite; Muralidharan, Govindarajan; Kurumaddali, Nalini Kanth

2014-01-01

Understanding the reliability of eutectic Sn-3.5Ag lead-free solders in high temperature packaging applications is of significant interest in power electronics for the next generation electric grid. Large area (2.5mm 2.5mm) Sn-3.5Ag solder joints between silicon dies and direct bonded copper substrates were thermally cycled between 5 C and 200 C. Sn crystal orientation and microstructure evolution during thermal cycling were characterized by electron backscatter diffraction (EBSD) in scanning electron microscope (SEM). Comparisons are made between observed initial texture and microstructure and its evolution during thermal cycling. Gradual lattice rotation and grain boundary misorientation evolution suggested the continuous recrystallization mechanism. Recrystallizationmore » behavior was correlated with dislocation slip activities.« less

Understanding luminescence properties of grain boundaries in GaN thin films and their atomistic origin

NASA Astrophysics Data System (ADS)

Yoo, Hyobin; Yoon, Sangmoon; Chung, Kunook; Kang, Seoung-Hun; Kwon, Young-Kyun; Yi, Gyu-Chul; Kim, Miyoung

2018-03-01

We report our findings on the optical properties of grain boundaries in GaN films grown on graphene layers and discuss their atomistic origin. We combine electron backscatter diffraction with cathodoluminescence to directly correlate the structural defects with their optical properties, enabling the high-precision local luminescence measurement of the grain boundaries in GaN films. To further understand the atomistic origin of the luminescence properties, we carefully probed atomic core structures of the grain boundaries by exploiting aberration-corrected scanning transmission electron microscopy. The atomic core structures of grain boundaries show different ordering behaviors compared with those observed previously in threading dislocations. Energetics of the grain boundary core structures and their correlation with electronic structures were studied by first principles calculation.

The trapping and distribution of charge in polarized polymethylmethacrylate under electron-beam irradiation

NASA Astrophysics Data System (ADS)

Song, Z. G.; Gong, H.; Ong, C. K.

1997-06-01

A scanning electron microscope (SEM) mirror-image method (MIM) is employed to investigate the charging behaviour of polarized polymethylmethacrylate (PMMA) under electron-beam irradiation. An ellipsoid is used to model the trapped charge distribution and a fitting method is employed to calculate the total amount of the trapped charge and its distribution parameters. The experimental results reveal that the charging ability decreases with increasing applied electric field, which polarizes the PMMA sample, whereas the trapped charge distribution is elongated along the direction of the applied electric field and increases with increasing applied electric field. The charges are believed to be trapped in some localization states, of activation energy and radius estimated to be about 19.6 meV and 0022-3727/30/11/004/img6, respectively.

Switching behaviour of individual Ag-TCNQ nanowires: an in situ transmission electron microscopy study

NASA Astrophysics Data System (ADS)

Ran, Ke; Rösner, Benedikt; Butz, Benjamin; Fink, Rainer H.; Spiecker, Erdmann

2016-10-01

The organic semiconductor silver-tetracyanoquinodimethane (Ag-TCNQ) exhibits electrical switching and memory characteristics. Employing a scanning tunnelling microscopy setup inside a transmission electron microscope, the switching behaviour of individual Ag-TCNQ nanowires (NWs) is investigated in detail. For a large number of NWs, the switching between a high (OFF) and a low (ON) resistance state was successfully stimulated by negative bias sweeps. Fitting the experimental I-V curves with a Schottky emission function makes the switching features prominent and thus enables a direct evaluation of the switching process. A memory cycle including writing, reading and erasing features is demonstrated at an individual NW. Moreover, electronic failure mechanisms due to Joule heating are discussed. These findings have a significant impact on our understanding of the switching behaviour of Ag-TCNQ.

Coverage evolution of the unoccupied Density of States in sulfur superstructures on Ru(0001)

NASA Astrophysics Data System (ADS)

Pisarra, M.; Bernardo-Gavito, R.; Navarro, J. J.; Black, A.; Díaz, C.; Calleja, F.; Granados, D.; Miranda, R.; Martín, F.; Vázquez de Parga, A. L.

2018-03-01

Sulfur adsorbed on Ru(0001) presents a large number of ordered structures. This characteristic makes S/Ru(0001) the ideal system to investigate the effect of different periodicities on the electronic properties of interfaces. We have performed scanning tunneling microscopy/spectroscopy experiments and density functional theory calculations showing that a sulfur adlayer generates interface states inside the Γ directional gap of Ru(0001) and that the position of such states varies monotonically with sulfur coverage. This is the result of the interplay between band folding effects arising from the new periodicity of the system and electron localization on the sulfur monolayer. As a consequence, by varying the amount of sulfur in S/Ru(0001) one can control the electronic properties of these interfacial materials.

A next generation positron microscope and a survey of candidate samples for future positron studies

NASA Astrophysics Data System (ADS)

Dull, Terry Lou

A positron microscope has been constructed and is nearing the conclusion of its assembly and testing. The instrument is designed to perform positron and electron microscopy in both scanning and magnifying modes. In scanning mode, a small beam of particles is rastered across the target and the amplitude of a positron or electron related signal is recorded as a function of position. For positrons this signal may come from Doppler Broadening Spectroscopy, Reemitted Positron Spectroscopy or Positron Annihilation Lifetime Spectroscopy. For electrons this signal may come from the number of secondary electrons or Auger Electron Spectroscopy. In magnifying mode an incident beam of particles is directed onto the target and emitted particles, either secondary electrons or reemitted positrons, are magnified to form an image. As a positron microscope the instrument will primarily operate in magnifying mode, as a positron reemission microscope. As an electron microscope the instrument will be able to operate in both magnifying and scanning modes. Depth-profiled Doppler Broadening Spectroscopy studies using a non-microscopic low-energy positron beam have also been performed on a series of samples to ascertain the applicability of positron spectroscopies and/or microscopy to their study. All samples have sub-micron film and/or feature size and thus are only susceptible to positron study with low-energy beams. Several stoichiometries and crystallinities of chalcogenide thin films (which can be optically reversibly switched between crystalline states) were studied and a correlation was found to exist between the amorphous/FCC S-parameter difference and the amorphous/FCC switching time. Amorphous silicon films were studied in an attempt to observe the well-established Staebler-Wronski effect as well as the more controversial photodilatation effect. However, DBS was not able to detect either effect. The passive oxide films on titanium and aluminum were studied in an attempt to verify the Point Defect Model, a detailed, but as yet microscopically unconfirmed, theory of the corrosive breakdown of passive films. DBS results supportive of the PDM were observed. Graphitic carbon fibers were also studied and DBS indicated the presence of a 200 nm thick outer fiber skin possibly characterized by a high degree of graphitic crystallite alignment.

Electronic and mechanical properties of graphene-germanium interfaces grown by chemical vapor deposition

DOE PAGES

Kiraly, Brian T.; Jacobberger, Robert M.; Mannix, Andrew J.; ...

2015-10-27

Epitaxially oriented wafer-scale graphene grown directly on semiconducting Ge substrates is of high interest for both fundamental science and electronic device applications. To date, however, this material system remains relatively unexplored structurally and electronically, particularly at the atomic scale. To further understand the nature of the interface between graphene and Ge, we utilize ultrahigh vacuum scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) along with Raman and X-ray photoelectron spectroscopy to probe interfacial atomic structure and chemistry. STS reveals significant differences in electronic interactions between graphene and Ge(110)/Ge(111), which is consistent with a model of stronger interaction on Ge(110)more » leading to epitaxial growth. Raman spectra indicate that the graphene is considerably strained after growth, with more point-to-point variation on Ge(111). Furthermore, this native strain influences the atomic structure of the interface by inducing metastable and previously unobserved Ge surface reconstructions following annealing. These nonequilibrium reconstructions cover >90% of the surface and, in turn, modify both the electronic and mechanical properties of the graphene overlayer. Finally, graphene on Ge(001) represents the extreme strain case, where graphene drives the reorganization of the Ge surface into [107] facets. From this study, it is clear that the interaction between graphene and the underlying Ge is not only dependent on the substrate crystallographic orientation, but is also tunable and strongly related to the atomic reconfiguration of the graphene–Ge interface.« less

Real-Space Imaging of Carrier Dynamics of Materials Surfaces by Second-Generation Four-Dimensional Scanning Ultrafast Electron Microscopy.

PubMed

Sun, Jingya; Melnikov, Vasily A; Khan, Jafar I; Mohammed, Omar F

2015-10-01

In the fields of photocatalysis and photovoltaics, ultrafast dynamical processes, including carrier trapping and recombination on material surfaces, are among the key factors that determine the overall energy conversion efficiency. A precise knowledge of these dynamical events on the nanometer (nm) and femtosecond (fs) scales was not accessible until recently. The only way to access such fundamental processes fully is to map the surface dynamics selectively in real space and time. In this study, we establish a second generation of four-dimensional scanning ultrafast electron microscopy (4D S-UEM) and demonstrate the ability to record time-resolved images (snapshots) of material surfaces with 650 fs and ∼5 nm temporal and spatial resolutions, respectively. In this method, the surface of a specimen is excited by a clocking optical pulse and imaged using a pulsed primary electron beam as a probe pulse, generating secondary electrons (SEs), which are emitted from the surface of the specimen in a manner that is sensitive to the local electron/hole density. This method provides direct and controllable information regarding surface dynamics. We clearly demonstrate how the surface morphology, grains, defects, and nanostructured features can significantly impact the overall dynamical processes on the surface of photoactive-materials. In addition, the ability to access two regimes of dynamical probing in a single experiment and the energy loss of SEs in semiconductor-nanoscale materials will also be discussed.

Atomic layer-by-layer thermoelectric conversion in topological insulator bismuth/antimony tellurides.

PubMed

Sung, Ji Ho; Heo, Hoseok; Hwang, Inchan; Lim, Myungsoo; Lee, Donghun; Kang, Kibum; Choi, Hee Cheul; Park, Jae-Hoon; Jhi, Seung-Hoon; Jo, Moon-Ho

2014-07-09

Material design for direct heat-to-electricity conversion with substantial efficiency essentially requires cooperative control of electrical and thermal transport. Bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3), displaying the highest thermoelectric power at room temperature, are also known as topological insulators (TIs) whose electronic structures are modified by electronic confinements and strong spin-orbit interaction in a-few-monolayers thickness regime, thus possibly providing another degree of freedom for electron and phonon transport at surfaces. Here, we explore novel thermoelectric conversion in the atomic monolayer steps of a-few-layer topological insulating Bi2Te3 (n-type) and Sb2Te3 (p-type). Specifically, by scanning photoinduced thermoelectric current imaging at the monolayer steps, we show that efficient thermoelectric conversion is accomplished by optothermal motion of hot electrons (Bi2Te3) and holes (Sb2Te3) through 2D subbands and topologically protected surface states in a geometrically deterministic manner. Our discovery suggests that the thermoelectric conversion can be interiorly achieved at the atomic steps of a homogeneous medium by direct exploiting of quantum nature of TIs, thus providing a new design rule for the compact thermoelectric circuitry at the ultimate size limit.

Direct electron transfer of glucose oxidase and biosensing for glucose based on PDDA-capped gold nanoparticle modified graphene/multi-walled carbon nanotubes electrode.

PubMed

Yu, Yanyan; Chen, Zuanguang; He, Sijing; Zhang, Beibei; Li, Xinchun; Yao, Meicun

2014-02-15

In this work, poly (diallyldimethylammonium chloride) (PDDA)-capped gold nanoparticles (AuNPs) functionalized graphene (G)/multi-walled carbon nanotubes (MWCNTs) nanocomposites were fabricated. Based on the electrostatic attraction, the G/MWCNTs hybrid material can be decorated with AuNPs uniformly and densely. The new hierarchical nanostructure can provide a larger surface area and a more favorable microenvironment for electron transfer. The AuNPs/G/MWCNTs nanocomposite was used as a novel immobilization platform for glucose oxidase (GOD). Direct electron transfer (DET) was achieved between GOD and the electrode. Field emission scanning electron microscopy (FESEM), UV-vis spectroscopy and cyclic voltammetry (CV) were used to characterize the electrochemical biosensor. The glucose biosensor fabricated based on GOD electrode modified with AuNPs/G/MWCNTs demonstrated satisfactory analytical performance with high sensitivity (29.72mAM(-1)cm(-2)) and low limit of detection (4.8 µM). The heterogeneous electron transfer rate constant (ΚS) and the apparent Michaelis-Menten constant (Km) of GOD were calculated to be 11.18s(-1) and 2.09 mM, respectively. With satisfactory selectivity, reproducibility, and stability, the nanostructure we proposed offered an alternative for electrode fabricating and glucose biosensing. © 2013 Elsevier B.V. All rights reserved.

Energetic-particle drift motions in the outer dayside magnetosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buck, R.C.

1987-01-01

Models of the geomagnetic field predict that within a distance of approximately one earth radius inside the dayside magnetopause, magnetic fields produced by the Chapman-Ferraro magnetopause currents create high-latitude minimum-B pockets in the geomagnetic field. These pockets are theoretically capable of temporarily trapping azimuthally-drifting electrons and modifying electron directional distributions. The Lawrence Livermore National Laboratory's scanning electron spectrometer aboard the OGO-5 satellite provided detailed energetic (E > 70 keV) electron pitch-angle distributions throughout the magnetosphere. Distributions obtained in the outer dayside magnetosphere over a wide range of longitudes show unusual flux features. This study analyzes drift-shell branching caused by themore » minimum-B pockets, and interprets the observed flux features in terms of an adiabatic-shell branching and rejoining process. The author examines the shell-branching process for a static field in detail, using the Choe-Beard 1974 magnetospheric magnetic field mode. He finds that shell branching and rejoining conserves the particle mirror field B/sub M/, the fieldline integral invariant I, and the directional electron flux j. He also finds a good correlation between the itch angles that mark the transition from branched to unbranched shells in the model and the distinctive features of the OGO-5 distributions.« less

Immobilization of glucose oxidase into a nanoporous TiO₂ film layered on metallophthalocyanine modified vertically-aligned carbon nanotubes for efficient direct electron transfer.

PubMed

Cui, Hui-Fang; Zhang, Kuan; Zhang, Yong-Fang; Sun, Yu-Long; Wang, Jia; Zhang, Wei-De; Luong, John H T

2013-08-15

Glucose oxidase (GOD) was adsorbed into a nanoporous TiO₂ film layered on the surface of an iron phthalocyanine (FePc) vertically-aligned carbon nanotube (CNT) modified electrode. A Nafion film was then dropcast on the electrode's surface to improve operational and storage stabilities of the GOD-based electrode. Scanning electron microscopy (SEM) micrographs revealed the formation of FePc and nanoporous TiO₂ nanoparticles along the sidewall and the tip of CNTs. Cyclic voltammograms of the GOD electrode in neutral PBS exhibited a pair of well-defined redox peaks, attesting the direct electron transfer of GOD (FAD/FADH₂) with the underlying electrode. The potential of glucose electro-oxidation under nitrogen was ∼+0.12 V with an oxidation current density of 65.3 μA cm(-2) at +0.77 V. Voltammetric and amperometric responses were virtually unaffected by oxygen, illustrating an efficient and fast direct electron transfer. The modification of the CNT surface with FePc resulted in a biosensor with remarkable detection sensitivity with an oxygen-independent bioelectrocatalysis. In deaerated PBS, the biosensor displayed average response time of 12 s, linearity from 50 μM to 4 mM, and a detection limit of 30 μM (S/N=3) for glucose. Copyright © 2013 Elsevier B.V. All rights reserved.

Direct observation of antisite defects in LiCoPO4 cathode materials by annular dark- and bright-field electron microscopy.

PubMed

Truong, Quang Duc; Devaraju, Murukanahally Kempaiah; Tomai, Takaaki; Honma, Itaru

2013-10-23

LiCoPO4 cathode materials have been synthesized by a sol-gel route. X-ray diffraction analysis confirmed that LiCoPO4 was well-crystallized in an orthorhombic structure in the Pmna space group. From the high-resolution transmission electron microscopy (HR-TEM) image, the lattice fringes of {001} and {100} are well-resolved. The HR-TEM image and selected area electron diffraction pattern reveal the highly crystalline nature of LiCoPO4 having an ordered olivine structure. The atom-by-atom structure of LiCoPO4 olivine has been observed, for the first time, using high-angle annular dark-field (HAADF) and annual bright-field scanning transmission electron microscopy. We observed the bright contrast in Li columns in the HAADF images and strong contrast in the ABF images, directly indicating the antisite exchange defects in which Co atoms partly occupy the Li sites. The LiCoPO4 cathode materials delivered an initial discharge capacity of 117 mAh/g at a C/10 rate with moderate cyclic performance. The discharge profile of LiCoPO4 shows a plateau at 4.75 V, revealing its importance as a potentially high-voltage cathode. The direct visualization of atom-by-atom structure in this work represents important information for the understanding of the structure of the active cathode materials for Li-ion batteries.

Electric field imaging of single atoms

PubMed Central

Shibata, Naoya; Seki, Takehito; Sánchez-Santolino, Gabriel; Findlay, Scott D.; Kohno, Yuji; Matsumoto, Takao; Ishikawa, Ryo; Ikuhara, Yuichi

2017-01-01

In scanning transmission electron microscopy (STEM), single atoms can be imaged by detecting electrons scattered through high angles using post-specimen, annular-type detectors. Recently, it has been shown that the atomic-scale electric field of both the positive atomic nuclei and the surrounding negative electrons within crystalline materials can be probed by atomic-resolution differential phase contrast STEM. Here we demonstrate the real-space imaging of the (projected) atomic electric field distribution inside single Au atoms, using sub-Å spatial resolution STEM combined with a high-speed segmented detector. We directly visualize that the electric field distribution (blurred by the sub-Å size electron probe) drastically changes within the single Au atom in a shape that relates to the spatial variation of total charge density within the atom. Atomic-resolution electric field mapping with single-atom sensitivity enables us to examine their detailed internal and boundary structures. PMID:28555629

Self-catalytic branch growth of SnO 2 nanowire junctions

NASA Astrophysics Data System (ADS)

Chen, Y. X.; Campbell, L. J.; Zhou, W. L.

2004-10-01

Multiple branched SnO2 nanowire junctions have been synthesized by thermal evaporation of SnO powder. Their nanostructures were studied by transmission electron microscopy and field emission scanning electron microcopy. It was observed that Sn nanoparticles generated from decomposition of the SnO powder acted as self-catalysts to control the SnO2 nanojunction growth. Orthorhombic SnO2 was found as a dominate phase in nanojunction growth instead of rutile structure. The branches and stems of nanojunctions were found to be an epitaxial growth by electron diffraction analysis and high-resolution electron microscopy observation. The growth directions of the branched SnO2 nanojunctions were along the orthorhombic [1 1 0] and [ 1 1 bar 0 ] . A self-catalytic vapor-liquid-solid growth mechanism is proposed to describe the growth process of the branched SnO2 nanowire junctions.

Segregation Phenomena on the Crystal Surface of Chemical Compounds

NASA Astrophysics Data System (ADS)

Tomashpol'skii, Yu. Ya.

2018-06-01

The current state of the theoretical and experimental studies of changes in the chemical structure and composition caused by segregation phenomena on the surface of chemical compounds was reviewed. The review considers the experimental data obtained exclusively on single crystals, which were studied by modern instrumental methods, including in situ Auger electron spectrometry, X-ray spectral microanalysis, high-resolution scanning and transmission electron microscopy, secondary electron emission, and atomic force microscopy. The models that suggest the crystal-chemical diffusion and liquid-phase mechanisms of segregation were described. The parameters of the theory include the type of chemical bond, elastic constants, and crystal-chemical characteristics of substances. The models make it possible to predict the nature of changes in the surface composition: segregation tendency, segregant type, and degree of nonstoichiometry. A new direction in surface segregation was considered, which is promising for nanoelectronics and emission electronics.

Non-spectroscopic composition measurements of SrTiO 3-La 0.7Sr 0.3MnO 3 multilayers using scanning convergent beam electron diffraction

DOE PAGES

Ophus, Colin; Ercius, Peter; Huijben, Mark; ...

2017-02-08

The local atomic structure of a crystalline sample aligned along a zone axis can be probed with a focused electron probe, which produces a convergent beam electron diffraction pattern. The introduction of high speed direct electron detectors has allowed for experiments that can record a full diffraction pattern image at thousands of probe positions on a sample. By incoherently summing these patterns over crystalline unit cells, we demonstrate in this paper that in addition to crystal structure and thickness, we can also estimate the local composition of a perovskite superlattice sample. This is achieved by matching the summed patterns tomore » a library of simulated diffraction patterns. Finally, this technique allows for atomic-scale chemical measurements without requiring a spectrometer or hardware aberration correction.« less

High performance membrane-electrode assembly based on a surface-modified membrane

NASA Astrophysics Data System (ADS)

Han, Sangil; Lee, Jang Woo; Kwak, Chan; Chai, Geun Seok; Son, In Hyuk; Jang, Moon Yup; An, Sung Guk; Cho, Sung Yong; Kim, Jun Young; Kim, Hyung Wook; Serov, Alexey Alexandrovych; Yoo, Youngtai; Nam, Kie Hyun

A surface-modified membrane is prepared using a sputtering technique that deposits gold directly on a Nafion ® 115 membrane surface that is roughened with silicon carbide paper. The surface-modified membranes are characterized by means of a scanning electron microscope (SEM), differential scanning calorimetry (DSC), and water contact-angle analysis. A single direct methanol fuel cell (DMFC) with a surface-modified membrane exhibits enhanced performance (160 mW cm -2), while a bare Nafion ® 115 cell yields 113 mW cm -2 at 0.4 V and an operating temperature of 70 °C. From FE-SEM images and CO ad stripping voltammograms, it is also found that the gold layer is composed of clusters of porous nodule-like particles, which indicates that an anode with nodule-like gold leads to the preferential oxidation of carbon monoxide. These results suggest that the topology of gold in the interfacial area and its electrocatalytic nature may be the critical factors that affect DMFC performance.

Directed Assembly of Molecules on Graphene/Ru(0001)

NASA Astrophysics Data System (ADS)

Zhang, L. Z.; Zhang, H. G.; Sun, J. T.; Pan, Y.; Liu, Q.; Mao, J. H.; Zhou, H. T.; Low, T.; Guo, H. M.; Du, S. X.; Gao, H.-J.

2012-02-01

Recently, the graphene monolayers have been seen to adopt a superstructure - moir'e pattern - on Ru(0001). By using low temperature scanning tunneling spectroscopy, we identified the laterally localized electronic states on this system. The individual states are separated by 3 nm and comprise regions of about 90 carbon atoms. This constitutes a highly regular quantum dot-array with molecular precision. It is evidenced by quantum well resonances with energies that relate to the corrugation of the graphene layer. By using scanning tunneling microscopy/spectroscopy, we demonstrate the selective adsorption and formation of ordered molecular arrays of FePc and pentacene molecules on the graphene/Ru(0001) templates. With in-depth investigations of the molecular adsorption and assembly processes we reveal the existence lateral electric dipoles in the epitaxial graphene monolayers and the capability of the dipoles in directing and driving the molecular adsorption and assembly. When increasing the molecular coverage, we observed the formation of regular Kagome lattices that duplicate the lattice of the moir'e pattern of monolayer graphene.

Photon counting photodiode array detector for far ultraviolet (FUV) astronomy

NASA Technical Reports Server (NTRS)

Hartig, G. F.; Moos, H. W.; Pembroke, R.; Bowers, C.

1982-01-01

A compact, stable, single-stage intensified photodiode array detector designed for photon-counting, far ultraviolet astronomy applications employs a saturable, 'C'-type MCP (Galileo S. MCP 25-25) to produce high gain pulses with a narrowly peaked pulse height distribution. The P-20 output phosphor exhibits a very short decay time, due to the high current density of the electron pulses. This intensifier is being coupled to a self-scanning linear photodiode array which has a fiber optic input window which allows direct, rigid mechanical coupling with minimal light loss. The array was scanned at a 250 KHz pixel rate. The detector exhibits more than adequate signal-to-noise ratio for pulse counting and event location. Previously announced in STAR as N82-19118

Large area fabrication of plasmonic nanoparticle grating structure by conventional scanning electron microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sudheer,, E-mail: sudheer@rrcat.gov.in; Tiwari, P.; Rai, V. N.

Plasmonic nanoparticle grating (PNG) structure of different periods has been fabricated by electron beam lithography using silver halide based transmission electron microscope film as a substrate. Conventional scanning electron microscope is used as a fabrication tool for electron beam lithography. Optical microscope and energy dispersive spectroscopy (EDS) have been used for its morphological and elemental characterization. Optical characterization is performed by UV-Vis absorption spectroscopic technique.

Investigating the use of in situ liquid cell scanning transmission electron microscopy to explore DNA-mediated gold nanoparticle growth

NASA Astrophysics Data System (ADS)

Nguy, Amanda

Engineering nanoparticles with desired shape-dependent properties is the key to many applications in nanotechnology. Although many synthetic procedures exist to produce anisotropic gold nanoparticles, the dynamics of growth are typically unknown or hypothetical. In the case of seed-mediated growth in the presence of DNA into anisotropic nanoparticles, it is not known exactly how DNA directs growth into specific morphologies. A series of preliminary experiments were carried out to contribute to the investigation of the possible mechanism of DNA-mediated growth of gold nanoprisms into gold nanostars using liquid cell scanning transmission electron microscopy (STEM). Imaging in the liquid phase was achieved through the use of a liquid cell platform and liquid cell holder that allow the sample to be contained within a “chip sandwich” between two electron transparent windows. Ex situ growth experiments were performed using Au-T30 NPrisms (30-base thymine oligonucleotide-coated gold nanoprisms) that are expected to grow into gold nanostars. Growth to form these nanostars were imaged using TEM (transmission electron microscopy) and liquid cell STEM (scanning transmission electron microscopy). An attempt to perform in situ growth experiments with the same Au-T30 nanoprisms revealed challenges in obtaining desired morphology results due to the environmental differences within the liquid cell compared to the ex situ environment. Different parameters in the experimental method were explored including fluid line set up, simultaneous and alternating reagent addition, and the effect of different liquid cell volumes to ensure adequate flow of reagents into the liquid cell. Lastly, the binding affinities were compared for T30 and A30 DNA incubated with gold nanoparticles using zeta potential measurements, absorption spectroscopy, and isothermal titration calorimetry (ITC). It was previously reported thymine bases have a lower binding affinity to gold surfaces than adenine bases. However, the results reported here contradict the previously reported data. Future prospectives on this work are outlined.

Investigating the use of in situ liquid cell scanning transmission electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguy, Amanda

2016-02-19

Engineering nanoparticles with desired shape-dependent properties is the key to many applications in nanotechnology. Although many synthetic procedures exist to produce anisotropic gold nanoparticles, the dynamics of growth are typically unknown or hypothetical. In the case of seed-mediated growth in the presence of DNA into anisotropic nanoparticles, it is not known exactly how DNA directs growth into specific morphologies. A series of preliminary experiments were carried out to contribute to the investigation of the possible mechanism of DNA-mediated growth of gold nanoprisms into gold nanostars using liquid cell scanning transmission electron microscopy (STEM). Imaging in the liquid phase was achievedmore » through the use of a liquid cell platform and liquid cell holder that allow the sample to be contained within a “chip sandwich” between two electron transparent windows. Ex situ growth experiments were performed using Au-T30 NPrisms (30-base thymine oligonucleotide-coated gold nanoprisms) that are expected to grow into gold nanostars. Growth to form these nanostars were imaged using TEM (transmission electron microscopy) and liquid cell STEM (scanning transmission electron microscopy). An attempt to perform in situ growth experiments with the same Au-T30 nanoprisms revealed challenges in obtaining desired morphology results due to the environmental differences within the liquid cell compared to the ex situ environment. Different parameters in the experimental method were explored including fluid line set up, simultaneous and alternating reagent addition, and the effect of different liquid cell volumes to ensure adequate flow of reagents into the liquid cell. Lastly, the binding affinities were compared for T30 and A30 DNA incubated with gold nanoparticles using zeta potential measurements, absorption spectroscopy, and isothermal titration calorimetry (ITC). It was previously reported thymine bases have a lower binding affinity to gold surfaces than adenine bases. However, the results reported here contradict the previously reported data. Future prospectives on this work are outlined.« less

Note: Electron energy spectroscopy mapping of surface with scanning tunneling microscope.

PubMed

Li, Meng; Xu, Chunkai; Zhang, Panke; Li, Zhean; Chen, Xiangjun

2016-08-01

We report a novel scanning probe electron energy spectrometer (SPEES) which combines a double toroidal analyzer with a scanning tunneling microscope to achieve both topography imaging and electron energy spectroscopy mapping of surface in situ. The spatial resolution of spectroscopy mapping is determined to be better than 0.7 ± 0.2 μm at a tip sample distance of 7 μm. Meanwhile, the size of the field emission electron beam spot on the surface is also measured, and is about 3.6 ± 0.8 μm in diameter. This unambiguously demonstrates that the spatial resolution of SPEES technique can be much better than the size of the incident electron beam.

Development of scanning holographic display using MEMS SLM

NASA Astrophysics Data System (ADS)

Takaki, Yasuhiro

2016-10-01

Holography is an ideal three-dimensional (3D) display technique, because it produces 3D images that naturally satisfy human 3D perception including physiological and psychological factors. However, its electronic implementation is quite challenging because ultra-high resolution is required for display devices to provide sufficient screen size and viewing zone. We have developed holographic display techniques to enlarge the screen size and the viewing zone by use of microelectromechanical systems spatial light modulators (MEMS-SLMs). Because MEMS-SLMs can generate hologram patterns at a high frame rate, the time-multiplexing technique is utilized to virtually increase the resolution. Three kinds of scanning systems have been combined with MEMS-SLMs; the screen scanning system, the viewing-zone scanning system, and the 360-degree scanning system. The screen scanning system reduces the hologram size to enlarge the viewing zone and the reduced hologram patterns are scanned on the screen to increase the screen size: the color display system with a screen size of 6.2 in. and a viewing zone angle of 11° was demonstrated. The viewing-zone scanning system increases the screen size and the reduced viewing zone is scanned to enlarge the viewing zone: a screen size of 2.0 in. and a viewing zone angle of 40° were achieved. The two-channel system increased the screen size to 7.4 in. The 360-degree scanning increases the screen size and the reduced viewing zone is scanned circularly: the display system having a flat screen with a diameter of 100 mm was demonstrated, which generates 3D images viewed from any direction around the flat screen.

Analysis of the EBT3 Gafchromic film irradiated with 6 MV photons and 6 MeV electrons using reflective mode scanners.

PubMed

Farah, Nicolas; Francis, Ziad; Abboud, Marie

2014-09-01

We explore in our study the effects of electrons and X-rays irradiations on the newest version of the Gafchromic EBT3 film. Experiments are performed using the Varian "TrueBeam 1.6" medical accelerator delivering 6 MV X-ray photons and 6 MeV electron beams as desired. The main interest is to compare the responses of EBT3 films exposed to two separate beams of electrons and photons, for radiation doses ranging up to 500 cGy. The analysis is done on a flatbed EPSON 10000 XL scanner and cross checked on a HP Scanjet 4850 scanner. Both scanners are used in reflection mode taking into account landscape and portrait scanning positions. After thorough verifications, the reflective scanning method can be used on EBT3 as an economic alternative to the transmission method which was also one of the goals of this study. A comparison is also done between single scan configuration including all samples in a single A4 (HP) or A3 (EPSON) format area and multiple scan procedure where each sample is scanned separately on its own. The images analyses are done using the ImageJ software. Results show significant influence of the scanning configuration but no significant differences between electron and photon irradiations for both single and multiple scan configurations. In conclusion, the film provides a reliable relative dose measurement method for electrons and photons irradiations in the medical field applications. Copyright © 2014 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Writing silica structures in liquid with scanning transmission electron microscopy.

PubMed

van de Put, Marcel W P; Carcouët, Camille C M C; Bomans, Paul H H; Friedrich, Heiner; de Jonge, Niels; Sommerdijk, Nico A J M

2015-02-04

Silica nanoparticles are imaged in solution with scanning transmission electron microscopy (STEM) using a liquid cell with silicon nitride (SiN) membrane windows. The STEM images reveal that silica structures are deposited in well-defined patches on the upper SiN membranes upon electron beam irradiation. The thickness of the deposits is linear with the applied electron dose. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) demonstrate that the deposited patches are a result of the merging of the original 20 nm-diameter nanoparticles, and that the related surface roughness depends on the electron dose rate used. Using this approach, sub-micrometer scale structures are written on the SiN in liquid by controlling the electron exposure as function of the lateral position. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Examination of Surveyor 3 parts with the scanning electron microscope and electron microprobe

NASA Technical Reports Server (NTRS)

Chodos, A. A.; Devaney, J. R.; Evens, K. C.

1972-01-01

Two screws and two washers, several small chips of tubing, and a fiber removed from a third screw were examined with the scanning electron microscope and the electron microprobe. The purpose of the examination was to determine the nature of the material on the surface of these samples and to search for the presence of meteoritic material.

Observations on the Role of Hydrogen in Facet Formation in Near-alpha Titanium (Preprint)

DTIC Science & Technology

2011-05-01

using quantitative tilt fractography and electron backscatter diffraction while facet topography was examined using ultra high resolution scanning...quantitative tilt fractography and electron backscatter diffraction while facet topography was examined using ultra high resolution scanning electron...tilt fractography / electron backscatter diffraction (EBSD) technique in which both the crystallographic orientation of the fractured grain and the

Development of online lines-scan imaging system for chicken inspection and differentiation

NASA Astrophysics Data System (ADS)

Yang, Chun-Chieh; Chan, Diane E.; Chao, Kuanglin; Chen, Yud-Ren; Kim, Moon S.

2006-10-01

An online line-scan imaging system was developed for differentiation of wholesome and systemically diseased chickens. The hyperspectral imaging system used in this research can be directly converted to multispectral operation and would provide the ideal implementation of essential features for data-efficient high-speed multispectral classification algorithms. The imaging system consisted of an electron-multiplying charge-coupled-device (EMCCD) camera and an imaging spectrograph for line-scan images. The system scanned the surfaces of chicken carcasses on an eviscerating line at a poultry processing plant in December 2005. A method was created to recognize birds entering and exiting the field of view, and to locate a Region of Interest on the chicken images from which useful spectra were extracted for analysis. From analysis of the difference spectra between wholesome and systemically diseased chickens, four wavelengths of 468 nm, 501 nm, 582 nm and 629 nm were selected as key wavelengths for differentiation. The method of locating the Region of Interest will also have practical application in multispectral operation of the line-scan imaging system for online chicken inspection. This line-scan imaging system makes possible the implementation of multispectral inspection using the key wavelengths determined in this study with minimal software adaptations and without the need for cross-system calibration.

Integration of Ion Implantation with Scanning ProbeAlignment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Persaud, A.; Rangelow, I.W.; Schenkel, T.

We describe a scanning probe instrument which integrates ion beams with imaging and alignment functions of a piezo resistive scanning probe in high vacuum. Energetic ions (1 to a few hundred keV) are transported through holes in scanning probe tips [1]. Holes and imaging tips are formed by Focused Ion Beam (FIB) drilling and ion beam assisted thin film deposition. Transport of single ions can be monitored through detection of secondary electrons from highly charged dopant ions (e. g., Bi{sup 45+}) enabling single atom device formation. Fig. 1 shows SEM images of a scanning probe tip formed by ion beammore » assisted Pt deposition in a dual beam FIB. Ion beam collimating apertures are drilled through the silicon cantilever with a thickness of 5 {micro}m. Aspect ratio limitations preclude the direct drilling of holes with diameters well below 1 {micro}m, and smaller hole diameters are achieved through local thin film deposition [2]. The hole in Fig. 1 was reduced from 2 {micro}m to a residual opening of about 300 nm. Fig. 2 shows an in situ scanning probe image of an alignment dot pattern taken with the tip from Fig. 1. Transport of energetic ions through the aperture in the scanning probe tip allows formation of arbitrary implant patterns. In the example shown in Fig. 2 (right), a 30 nm thick PMMA resist layer on silicon was exposed to 7 keV Ar{sup 2+} ions with an equivalent dose of 10{sup 14} ions/cm{sup 2} to form the LBL logo. An exciting goal of this approach is the placement of single dopant ions into precise locations for integration of single atom devices, such as donor spin based quantum computers [3, 4]. In Fig. 3, we show a section of a micron size dot area exposed to a low dose (10{sup 11}/cm{sup 2}) of high charge state dopant ions. The Bi{sup 45+} ions (200 keV) were extracted from a low emittance highly charged ions source [5]. The potential energy of B{sup 45+}, i. e., the sum of the binding energies required to remove the electrons, amounts to 36 keV. This energy is deposited within {approx}10 fs when an ion impinges on a target. The highly localized energy deposition results in efficient resist exposure, and is associated with strongly enhanced secondary electron emission, which allows monitoring of single ion impacts [4]. The ex situ scanning probe image with line scan in Fig. 3 shows a single ion impact site in PMMA (after standard development). In our presentation, we will discuss resolution requirements for ion placement in prototype quantum computer structures [3] with respect to resolution limiting factors in ion implantation with scanning probe alignment.« less

Nondestructive determination of the depth of planar p-n junctions by scanning electron microscopy

NASA Technical Reports Server (NTRS)

Chi, J.-Y.; Gatos, H. C.

1977-01-01

A method was developed for measuring nondestructively the depth of planar p-n junctions in simple devices as well as in integrated-circuit structures with the electron-beam induced current (EBIC) by scanning parallel to the junction in a scanning electron microscope (SEM). The results were found to be in good agreement with those obtained by the commonly used destructive method of lapping at an angle to the junction and staining to reveal the junction.

Use of scanning electron microscopy and microanalysis to determine chloride content of concrete and raw materials.

DOT National Transportation Integrated Search

2013-02-01

Standard sample sets of cement and mortar formulations with known levels of Cl as well as concrete samples subject to Cl diffusion were all prepared for and analyzed with scanning electron microscopy (SEM) and electron microprobe (EPMA). Using x-ray ...

Electronically-Scanned Pressure Sensors

NASA Technical Reports Server (NTRS)

Coe, C. F.; Parra, G. T.; Kauffman, R. C.

1984-01-01

Sensors not pneumatically switched. Electronic pressure-transducer scanning system constructed in modular form. Pressure transducer modules and analog to digital converter module small enough to fit within cavities of average-sized wind-tunnel models. All switching done electronically. Temperature controlled environment maintained within sensor modules so accuracy maintained while ambient temperature varies.

41 CFR 301-71.201 - What are the reviewing official's responsibilities?

Code of Federal Regulations, 2013 CFR

2013-07-01

... 41 Public Contracts and Property Management 4 2013-07-01 2012-07-01 true What are the reviewing official's responsibilities? 301-71.201 Section 301-71.201 Public Contracts and Property Management Federal... implements electronic scanning, the electronic travel claim includes scanned electronic images of such...

41 CFR 301-71.201 - What are the reviewing official's responsibilities?

Code of Federal Regulations, 2014 CFR

2014-07-01

... 41 Public Contracts and Property Management 4 2014-07-01 2014-07-01 false What are the reviewing official's responsibilities? 301-71.201 Section 301-71.201 Public Contracts and Property Management Federal... implements electronic scanning, the electronic travel claim includes scanned electronic images of such...

41 CFR 301-71.201 - What are the reviewing official's responsibilities?

Code of Federal Regulations, 2012 CFR

2012-07-01

... 41 Public Contracts and Property Management 4 2012-07-01 2012-07-01 false What are the reviewing official's responsibilities? 301-71.201 Section 301-71.201 Public Contracts and Property Management Federal... implements electronic scanning, the electronic travel claim includes scanned electronic images of such...

41 CFR 301-71.201 - What are the reviewing official's responsibilities?

Code of Federal Regulations, 2011 CFR

2011-07-01

... 41 Public Contracts and Property Management 4 2011-07-01 2011-07-01 false What are the reviewing official's responsibilities? 301-71.201 Section 301-71.201 Public Contracts and Property Management Federal... implements electronic scanning, the electronic travel claim includes scanned electronic images of such...

Janus monolayers of transition metal dichalcogenides.

PubMed

Lu, Ang-Yu; Zhu, Hanyu; Xiao, Jun; Chuu, Chih-Piao; Han, Yimo; Chiu, Ming-Hui; Cheng, Chia-Chin; Yang, Chih-Wen; Wei, Kung-Hwa; Yang, Yiming; Wang, Yuan; Sokaras, Dimosthenis; Nordlund, Dennis; Yang, Peidong; Muller, David A; Chou, Mei-Yin; Zhang, Xiang; Li, Lain-Jong

2017-08-01

Structural symmetry-breaking plays a crucial role in determining the electronic band structures of two-dimensional materials. Tremendous efforts have been devoted to breaking the in-plane symmetry of graphene with electric fields on AB-stacked bilayers or stacked van der Waals heterostructures. In contrast, transition metal dichalcogenide monolayers are semiconductors with intrinsic in-plane asymmetry, leading to direct electronic bandgaps, distinctive optical properties and great potential in optoelectronics. Apart from their in-plane inversion asymmetry, an additional degree of freedom allowing spin manipulation can be induced by breaking the out-of-plane mirror symmetry with external electric fields or, as theoretically proposed, with an asymmetric out-of-plane structural configuration. Here, we report a synthetic strategy to grow Janus monolayers of transition metal dichalcogenides breaking the out-of-plane structural symmetry. In particular, based on a MoS 2 monolayer, we fully replace the top-layer S with Se atoms. We confirm the Janus structure of MoSSe directly by means of scanning transmission electron microscopy and energy-dependent X-ray photoelectron spectroscopy, and prove the existence of vertical dipoles by second harmonic generation and piezoresponse force microscopy measurements.

Direct observation of CD4 T cell morphologies and their cross-sectional traction force derivation on quartz nanopillar substrates using focused ion beam technique

NASA Astrophysics Data System (ADS)

Kim, Dong-Joo; Kim, Gil-Sung; Hyung, Jung-Hwan; Lee, Won-Yong; Hong, Chang-Hee; Lee, Sang-Kwon

2013-07-01

Direct observations of the primary mouse CD4 T cell morphologies, e.g., cell adhesion and cell spreading by culturing CD4 T cells in a short period of incubation (e.g., 20 min) on streptavidin-functionalized quartz nanopillar arrays (QNPA) using a high-content scanning electron microscopy method were reported. Furthermore, we first demonstrated cross-sectional cell traction force distribution of surface-bound CD4 T cells on QNPA substrates by culturing the cells on top of the QNPA and further analysis in deflection of underlying QNPA via focused ion beam-assisted technique.

Removal of Micrometer Size Morphological Defects and Enhancement of Ultraviolet Emission by Thermal Treatment of Ga-Doped ZnO Nanostructures

PubMed Central

Manzoor, Umair; Kim, Do K.; Islam, Mohammad; Bhatti, Arshad S.

2014-01-01

Mixed morphologies of Ga-doped Zinc Oxide (ZnO) nanostructures are synthesized by vapor transport method. Systematic scanning electron microscope (SEM) studies of different morphologies, after periodic heat treatments, gives direct evidence of sublimation. SEM micrographs give direct evidence that morphological defects of nanostructures can be removed by annealing. Ultra Violet (UV) and visible emission depends strongly on the annealing temperatures and luminescent efficiency of UV emission is enhanced significantly with each subsequent heat treatment. X-Ray diffraction (XRD) results suggest that crystal quality improved by annealing and phase separation may occur at high temperatures. PMID:24489725

Removal of micrometer size morphological defects and enhancement of ultraviolet emission by thermal treatment of Ga-doped ZnO nanostructures.

PubMed

Manzoor, Umair; Kim, Do K; Islam, Mohammad; Bhatti, Arshad S

2014-01-01

Mixed morphologies of Ga-doped Zinc Oxide (ZnO) nanostructures are synthesized by vapor transport method. Systematic scanning electron microscope (SEM) studies of different morphologies, after periodic heat treatments, gives direct evidence of sublimation. SEM micrographs give direct evidence that morphological defects of nanostructures can be removed by annealing. Ultra Violet (UV) and visible emission depends strongly on the annealing temperatures and luminescent efficiency of UV emission is enhanced significantly with each subsequent heat treatment. X-Ray diffraction (XRD) results suggest that crystal quality improved by annealing and phase separation may occur at high temperatures.

Scanning tunneling microscopy studies of diamond films and optoelectronic materials

NASA Technical Reports Server (NTRS)

Perez, Jose M.

1993-01-01

In this report, we report on progress achieved from 12/1/92 to 10/1/93 under the grant entitled 'Scanning Tunneling Microscopy Studies of Diamond Films and Optoelectronic Materials'. We have set-up a chemical vapor deposition (CVD) diamond film growth system and a Raman spectroscopy system to study the nucleation and growth of diamond films with atomic resolution using scanning tunneling microscopy (STM). A unique feature of the diamond film growth system is that diamond films can be transferred directly to the ultrahigh vacuum (UHV) chamber of a scanning tunneling microscope without contaminating the films by exposure to air. The University of North Texas (UNT) provided $20,000 this year as matching funds for the NASA grant to purchase the diamond growth system. In addition, UNT provided a Coherent Innova 90S Argon ion laser, a Spex 1404 double spectrometer, and a Newport optical table costing $90,000 to set-up the Raman spectroscopy system. The CVD diamond growth system and Raman spectroscopy system will be used to grow and characterize diamond films with atomic resolution using STM as described in our proposal. One full-time graduate student and one full-time undergraduate student are supported under this grant. In addition, several graduate and undergraduate students were supported during the summer to assist in setting-up the diamond growth and Raman spectroscopy systems. We have obtained research results concerning STM of the structural and electronic properties of CVD grown diamond films, and STM and scanning tunneling spectroscopy of carbon nanotubes. In collaboration with the transmission electron microscopy (TEM) group at UNT, we have also obtained results concerning the optoelectronic material siloxene. These results were published in refereed scientific journals, submitted for publication, and presented as invited and contributed talks at scientific conferences.

Direct and continuous synthesis of VO2 nanoparticles

NASA Astrophysics Data System (ADS)

Powell, M. J.; Marchand, P.; Denis, C. J.; Bear, J. C.; Darr, J. A.; Parkin, I. P.

2015-11-01

Monoclinic VO2 nanoparticles are of interest due to the material's thermochromic properties, however, direct synthesis routes to VO2 nanoparticles are often inaccessible due to the high synthesis temperatures or long reaction times required. Herein, we present a two-step synthesis route for the preparation of monoclinic VO2 nanoparticles using Continuous Hydrothermal Flow Synthesis (CHFS) followed by a short post heat treatment step. A range of particle sizes, dependent on synthesis conditions, were produced from 50 to 200 nm by varying reaction temperatures and the residence times in the process. The nanoparticles were characterised by powder X-ray diffraction, Raman and UV/Vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The nanoparticles were highly crystalline with rod and sphere-like morphologies present in TEM micrographs, with the size of both the rod and spherical particles being highly dependent on both reaction temperature and residence time. SEM micrographs showed the surface of the powders produced from the CHFS process to be highly uniform. The samples were given a short post synthesis heat treatment to ensure that they were phase pure monoclinic VO2, which led to them exhibiting a large and reversible switch in optical properties (at near-IR wavelengths), which suggests that if such materials can be incorporated into coatings or in composites, they could be used for fenestration in architectural applications.

Direct and continuous synthesis of VO2 nanoparticles.

PubMed

Powell, M J; Marchand, P; Denis, C J; Bear, J C; Darr, J A; Parkin, I P

2015-11-28

Monoclinic VO2 nanoparticles are of interest due to the material's thermochromic properties, however, direct synthesis routes to VO2 nanoparticles are often inaccessible due to the high synthesis temperatures or long reaction times required. Herein, we present a two-step synthesis route for the preparation of monoclinic VO2 nanoparticles using Continuous Hydrothermal Flow Synthesis (CHFS) followed by a short post heat treatment step. A range of particle sizes, dependent on synthesis conditions, were produced from 50 to 200 nm by varying reaction temperatures and the residence times in the process. The nanoparticles were characterised by powder X-ray diffraction, Raman and UV/Vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The nanoparticles were highly crystalline with rod and sphere-like morphologies present in TEM micrographs, with the size of both the rod and spherical particles being highly dependent on both reaction temperature and residence time. SEM micrographs showed the surface of the powders produced from the CHFS process to be highly uniform. The samples were given a short post synthesis heat treatment to ensure that they were phase pure monoclinic VO2, which led to them exhibiting a large and reversible switch in optical properties (at near-IR wavelengths), which suggests that if such materials can be incorporated into coatings or in composites, they could be used for fenestration in architectural applications.

Flatness metrology based on small-angle deflectometric procedures with electronic tiltmeters

NASA Astrophysics Data System (ADS)

Ehret, G.; Laubach, S.; Schulz, M.

2017-06-01

The measurement of optical flats, e. g. synchrotron or XFEL mirrors, with single nanometer topography uncertainty is still challenging. At PTB, we apply for this task small-angle deflectometry in which the angle between the direction of the beam sent to the surface and the beam detected is small. Conventional deflectometric systems measure the surface angle with autocollimators whose light beam also represents the straightness reference. An advanced flatness metrology system was recently implemented at PTB that separates the straightness reference task from the angle detection task. We call it `Exact Autocollimation Deflectometric Scanning' because the specimen is slightly tilted in such a way that at every scanning position the specimen is `exactly' perpendicular to the reference light beam directed by a pentaprism to the surface under test. The tilt angle of the surface is then measured with an additional autocollimator. The advantage of the EADS method is that the two tasks (straightness reference and measurement of surface slope) are separated and each of these can be optimized independently. The idea presented in this paper is to replace this additional autocollimator by one or more electro-mechanical tiltmeters, which are typically faster and have a higher resolution than highly accurate commercially available autocollimators. We investigate the point stability and the linearity of a highly accurate electronic tiltmeter. The pros and cons of using tiltmeters in flatness metrology are discussed.

Laser direct writing of carbon/Au composite electrodes for high-performance micro-supercapacitors

NASA Astrophysics Data System (ADS)

Cai, Jinguang; Watanabe, Akira; Lv, Chao

2017-02-01

Micro-supercapacitors with small size, light weight, flexibility while maintaining high energy and power output are required for portable miniaturized electronics. The fabrication methods and materials should be cost-effective, scalable, and easily integrated to current electronic industry. Carbon materials have required properties for high-performance flexible supercapacitors, including high specific surface areas, electrochemical stability, and high electrical conductivity, as well as the high mechanical tolerance. Laser direct writing method is a non-contact, efficient, single-step fabrication technique without requirements of masks, post-processing, and complex clean room, which is a useful patterning technique, and can be easily integrated with current electronic product lines for commercial use. Previously we have reported micro-supercapacitors fabricated by laser direct writing on polyimide films in air or Ar, which showed highcapacitive performance. However, the conductivity of the carbon materials is still low for fast charge-discharge use. Here, we demonstrated the fabrication of flexible carbon/Au composite high-performance MSCs by first laser direct writing on commercial polyimide films followed by spin-coating Au nanoparticles ink and second in-situ laser direct writing using the low-cost semiconductor laser. As-prepared micro-supercapacitors show an improved conductivity and capacitance of 1.17 mF/cm2 at a high scanning rate of 10,000 mV/s, which is comparable to the reported capacitance of carbon-based micro-supercapacitors. In addition, the micro-supercapacitors have high bend tolerance and long-cycle stability.

Scanning Microscopes Using X Rays and Microchannels

NASA Technical Reports Server (NTRS)

Wang, Yu

2003-01-01

Scanning microscopes that would be based on microchannel filters and advanced electronic image sensors and that utilize x-ray illumination have been proposed. Because the finest resolution attainable in a microscope is determined by the wavelength of the illumination, the xray illumination in the proposed microscopes would make it possible, in principle, to achieve resolutions of the order of nanometers about a thousand times as fine as the resolution of a visible-light microscope. Heretofore, it has been necessary to use scanning electron microscopes to obtain such fine resolution. In comparison with scanning electron microscopes, the proposed microscopes would likely be smaller, less massive, and less expensive. Moreover, unlike in scanning electron microscopes, it would not be necessary to place specimens under vacuum. The proposed microscopes are closely related to the ones described in several prior NASA Tech Briefs articles; namely, Miniature Microscope Without Lenses (NPO-20218), NASA Tech Briefs, Vol. 22, No. 8 (August 1998), page 43; and Reflective Variants of Miniature Microscope Without Lenses (NPO-20610), NASA Tech Briefs, Vol. 26, No. 9 (September 2002) page 6a. In all of these microscopes, the basic principle of design and operation is the same: The focusing optics of a conventional visible-light microscope are replaced by a combination of a microchannel filter and a charge-coupled-device (CCD) image detector. A microchannel plate containing parallel, microscopic-cross-section holes much longer than they are wide is placed between a specimen and an image sensor, which is typically the CCD. The microchannel plate must be made of a material that absorbs the illuminating radiation reflected or scattered from the specimen. The microchannels must be positioned and dimensioned so that each one is registered with a pixel on the image sensor. Because most of the radiation incident on the microchannel walls becomes absorbed, the radiation that reaches the image sensor consists predominantly of radiation that was launched along the longitudinal direction of the microchannels. Therefore, most of the radiation arriving at each pixel on the sensor must have traveled along a straight line from a corresponding location on the specimen. Thus, there is a one-to-one mapping from a point on a specimen to a pixel in the image sensor, so that the output of the image sensor contains image information equivalent to that from a microscope.

Chemical mapping and quantification at the atomic scale by scanning transmission electron microscopy.

PubMed

Chu, Ming-Wen; Chen, Cheng Hsuan

2013-06-25

With innovative modern material-growth methods, a broad spectrum of fascinating materials with reduced dimensions-ranging from single-atom catalysts, nanoplasmonic and nanophotonic materials to two-dimensional heterostructural interfaces-is continually emerging and extending the new frontiers of materials research. A persistent central challenge in this grand scientific context has been the detailed characterization of the individual objects in these materials with the highest spatial resolution, a problem prompting the need for experimental techniques that integrate both microscopic and spectroscopic capabilities. To date, several representative microscopy-spectroscopy combinations have become available, such as scanning tunneling microscopy, tip-enhanced scanning optical microscopy, atom probe tomography, scanning transmission X-ray microscopy, and scanning transmission electron microscopy (STEM). Among these tools, STEM boasts unique chemical and electronic sensitivity at unparalleled resolution. In this Perspective, we elucidate the advances in STEM and chemical mapping applications at the atomic scale by energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy with a focus on the ultimate challenge of chemical quantification with atomic accuracy.

Publications - GMC 357 | Alaska Division of Geological & Geophysical

Science.gov Websites

DGGS GMC 357 Publication Details Title: Thin Section and Scanning Electron Microscopy summary Laboratories, Inc., 2008, Thin Section and Scanning Electron Microscopy summary photographs from plugs taken

Laser-induced selective copper plating of polypropylene surface

NASA Astrophysics Data System (ADS)

Ratautas, K.; Gedvilas, M.; Stankevičiene, I.; JagminienÄ--, A.; Norkus, E.; Li Pira, N.; Sinopoli, S.; Emanuele, U.; Račiukaitis, G.

2016-03-01

Laser writing for selective plating of electro-conductive lines for electronics has several significant advantages, compared to conventional printed circuit board technology. Firstly, this method is faster and cheaper at the prototyping stage. Secondly, material consumption is reduced, because it works selectively. However, the biggest merit of this method is potentiality to produce moulded interconnect device, enabling to create electronics on complex 3D surfaces, thus saving space, materials and cost of production. There are two basic techniques of laser writing for selective plating on plastics: the laser-induced selective activation (LISA) and laser direct structuring (LDS). In the LISA method, pure plastics without any dopant (filler) can be used. In the LDS method, special fillers are mixed in the polymer matrix. These fillers are activated during laser writing process, and, in the next processing step, the laser modified area can be selectively plated with metals. In this work, both methods of the laser writing for the selective plating of polymers were investigated and compared. For LDS approach, new material: polypropylene with carbon-based additives was tested using picosecond and nanosecond laser pulses. Different laser processing parameters (laser pulse energy, scanning speed, the number of scans, pulse durations, wavelength and overlapping of scanned lines) were applied in order to find out the optimal regime of activation. Areal selectivity tests showed a high plating resolution. The narrowest width of a copper-plated line was less than 23 μm. Finally, our material was applied to the prototype of the electronic circuit board on a 2D surface.

Current-Driven Hydrogen Desorption from Graphene: Experiment and Theory.

PubMed

Gao, Li; Pal, Partha Pratim; Seideman, Tamar; Guisinger, Nathan P; Guest, Jeffrey R

2016-02-04

Electron-stimulated desorption of hydrogen from the graphene/SiC(0001) surface at room temperature was investigated with ultrahigh vacuum scanning tunneling microscopy and ab initio calculations in order to elucidate the desorption mechanisms and pathways. Two different desorption processes were observed. In the high electron energy regime (4-8 eV), the desorption yield is independent of both voltage and current, which is attributed to the direct electronic excitation of the C-H bond. In the low electron energy regime (2-4 eV), however, the desorption yield exhibits a threshold dependence on voltage, which is explained by the vibrational excitation of the C-H bond via transient ionization induced by inelastic tunneling electrons. The observed current independence of the desorption yield suggests that the vibrational excitation is a single-electron process. We also observed that the curvature of graphene dramatically affects hydrogen desorption. Desorption from concave regions was measured to be much more probable than desorption from convex regions in the low electron energy regime (∼2 eV), as would be expected from the identified desorption mechanism.

Hot Electrons Regain Coherence in Semiconducting Nanowires

NASA Astrophysics Data System (ADS)

Reiner, Jonathan; Nayak, Abhay Kumar; Avraham, Nurit; Norris, Andrew; Yan, Binghai; Fulga, Ion Cosma; Kang, Jung-Hyun; Karzig, Toesten; Shtrikman, Hadas; Beidenkopf, Haim

2017-04-01

The higher the energy of a particle is above equilibrium, the faster it relaxes because of the growing phase space of available electronic states it can interact with. In the relaxation process, phase coherence is lost, thus limiting high-energy quantum control and manipulation. In one-dimensional systems, high relaxation rates are expected to destabilize electronic quasiparticles. Here, we show that the decoherence induced by relaxation of hot electrons in one-dimensional semiconducting nanowires evolves nonmonotonically with energy such that above a certain threshold hot electrons regain stability with increasing energy. We directly observe this phenomenon by visualizing, for the first time, the interference patterns of the quasi-one-dimensional electrons using scanning tunneling microscopy. We visualize the phase coherence length of the one-dimensional electrons, as well as their phase coherence time, captured by crystallographic Fabry-Pèrot resonators. A remarkable agreement with a theoretical model reveals that the nonmonotonic behavior is driven by the unique manner in which one-dimensional hot electrons interact with the cold electrons occupying the Fermi sea. This newly discovered relaxation profile suggests a high-energy regime for operating quantum applications that necessitate extended coherence or long thermalization times, and may stabilize electronic quasiparticles in one dimension.

Superconducting parity effect across the Anderson limit

PubMed Central

Vlaic, Sergio; Pons, Stéphane; Zhang, Tianzhen; Assouline, Alexandre; Zimmers, Alexandre; David, Christophe; Rodary, Guillemin; Girard, Jean-Christophe; Roditchev, Dimitri; Aubin, Hervé

2017-01-01

How small can superconductors be? For isolated nanoparticles subject to quantum size effects, P.W. Anderson in 1959 conjectured that superconductivity could only exist when the electronic level spacing δ is smaller than the superconducting gap energy Δ. Here we report a scanning tunnelling spectroscopy study of superconducting lead (Pb) nanocrystals grown on the (110) surface of InAs. We find that for nanocrystals of lateral size smaller than the Fermi wavelength of the 2D electron gas at the surface of InAs, the electronic transmission of the interface is weak; this leads to Coulomb blockade and enables the extraction of electron addition energy of the nanocrystals. For large nanocrystals, the addition energy displays superconducting parity effect, a direct consequence of Cooper pairing. Studying this parity effect as a function of nanocrystal volume, we find the suppression of Cooper pairing when the mean electronic level spacing overcomes the superconducting gap energy, thus demonstrating unambiguously the validity of the Anderson criterion. PMID:28240294

Ripple-modulated electronic structure of a 3D topological insulator.

PubMed

Okada, Yoshinori; Zhou, Wenwen; Walkup, D; Dhital, Chetan; Wilson, Stephen D; Madhavan, V

2012-01-01

Three-dimensional topological insulators host linearly dispersing states with unique properties and a strong potential for applications. An important ingredient in realizing some of the more exotic states in topological insulators is the ability to manipulate local electronic properties. Direct analogy to the Dirac material graphene suggests that a possible avenue for controlling local properties is via a controlled structural deformation such as the formation of ripples. However, the influence of such ripples on topological insulators is yet to be explored. Here we use scanning tunnelling microscopy to determine the effects of one-dimensional buckling on the electronic properties of Bi(2)Te(3.) By tracking spatial variations of the interference patterns generated by the Dirac electrons we show that buckling imposes a periodic potential, which locally modulates the surface-state dispersion. This suggests that forming one- and two-dimensional ripples is a viable method for creating nanoscale potential landscapes that can be used to control the properties of Dirac electrons in topological insulators.

Direct ultrasonic-assisted synthesis of sphere-like nanocrystals of spinel Co3O4 and Mn3O4.

PubMed

Askarinejad, Azadeh; Morsali, Ali

2009-01-01

A simple sonochemical method was developed to synthesize uniform sphere-like or cubic Co(3)O(4) and Mn(3)O(4) nanocrystals by using acetate salts and sodium hydroxide or tetramethylammonium hydroxide (TMAH) as precursors. Influence of some parameters such as time of reaction, alkali salts, and power of the ultrasound and the molar ratio of the starting materials on the size, morphology and degree of crystallinity of the products was studied. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), FTIR spectroscopy, Thermal gravimetry analysis and differential thermal analysis (TGA/DTA) were used to characterize the nanocrystals.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, D.F.; Zhang, X.M.; Gautier, E.

The morphology and crystallography of deformation-induced martensites formed during isothermal tensile tests in Fe-30Ni-0.34C and Fe-25Ni-0.66C alloys were investigated by means of optical, transmission electron and scanning electron microscopy. Transitions in morphology from thin plate to coupled plate, to lenticular coupled-plate martensite and from thin plate to lenticular to compact martensite have been observed with increasing deformation. Stress favors the growth of martensite when concurrent plastic strain allows accommodation of macroscopic transformation strains and the change of the Bain strain accommodation mechanism. Mobile dislocations and emission dislocations are directly related to the change of the Bain strain accommodation mechanism frommore » twinning to slip.« less

Otoconial formation in the fetal rat

NASA Technical Reports Server (NTRS)

Salamat, M. S.; Ross, M. D.; Peacor, D. R.

1980-01-01

Otoconial formation in the fetal rat is examined by scanning and transmission electron microscopy, and by X-ray elemental analysis. The primitive otoconia appear highly organic, but are trigonal in cross section, indicating that they already possess a three-fold axis of symmetry and a complement of calcite. These otoconia develop into spindle-shaped and, subsequently, dumbbell-shaped units. Transmission electron microscopy of dumbbell-shaped otoconia not exposed to fluids during embedment showed that calcite deposits mimicked the arrangement of the organic material. X-ray elemental analysis demonstrated that calcium was present in lower quantities in the central core than peripherally. It is concluded that organic material is essential to otoconial seeding and directs otoconial growth.

Mapping the magnetic and crystal structure in cobalt nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cantu-Valle, Jesus; Betancourt, Israel; Sanchez, John E.

2015-07-14

Using off-axis electron holography under Lorentz microscopy conditions to experimentally determine the magnetization distribution in individual cobalt (Co) nanowires, and scanning precession-electron diffraction to obtain their crystalline orientation phase map, allowed us to directly visualize with high accuracy the effect of crystallographic texture on the magnetization of nanowires. The influence of grain boundaries and disorientations on the magnetic structure is correlated on the basis of micromagnetic analysis in order to establish the detailed relationship between magnetic and crystalline structure. This approach demonstrates the applicability of the method employed and provides further understanding on the effect of crystalline structure on magneticmore » properties at the nanometric scale.« less

Correlation of doping, structure, and carrier dynamics in a single GaN nanorod

NASA Astrophysics Data System (ADS)

Zhou, Xiang; Lu, Ming-Yen; Lu, Yu-Jung; Gwo, Shangjr; Gradečak, Silvija

2013-06-01

We report the nanoscale optical investigation of a single GaN p-n junction nanorod by cathodoluminescence (CL) in a scanning transmission electron microscope. CL emission characteristic of dopant-related transitions was correlated to doping and structural defect in the nanorod, and used to determine p-n junction position and minority carrier diffusion lengths of 650 nm and 165 nm for electrons and holes, respectively. Temperature-dependent CL study reveals an activation energy of 19 meV for non-radiative recombination in Mg-doped GaN nanorods. These results directly correlate doping, structure, carrier dynamics, and optical properties of GaN nanostructure, and provide insights for device design and fabrication.

Microcircuit testing and fabrication, using scanning electron microscopes

NASA Technical Reports Server (NTRS)

Nicolas, D. P.

1975-01-01

Scanning electron microscopes are used to determine both user-induced damages and manufacturing defects subtle enough to be missed by conventional light microscopy. Method offers greater depth of field and increased working distances.

Towards the low-dose characterization of beam sensitive nanostructures via implementation of sparse image acquisition in scanning transmission electron microscopy

NASA Astrophysics Data System (ADS)

Hwang, Sunghwan; Han, Chang Wan; Venkatakrishnan, Singanallur V.; Bouman, Charles A.; Ortalan, Volkan

2017-04-01

Scanning transmission electron microscopy (STEM) has been successfully utilized to investigate atomic structure and chemistry of materials with atomic resolution. However, STEM’s focused electron probe with a high current density causes the electron beam damages including radiolysis and knock-on damage when the focused probe is exposed onto the electron-beam sensitive materials. Therefore, it is highly desirable to decrease the electron dose used in STEM for the investigation of biological/organic molecules, soft materials and nanomaterials in general. With the recent emergence of novel sparse signal processing theories, such as compressive sensing and model-based iterative reconstruction, possibilities of operating STEM under a sparse acquisition scheme to reduce the electron dose have been opened up. In this paper, we report our recent approach to implement a sparse acquisition in STEM mode executed by a random sparse-scan and a signal processing algorithm called model-based iterative reconstruction (MBIR). In this method, a small portion, such as 5% of randomly chosen unit sampling areas (i.e. electron probe positions), which corresponds to pixels of a STEM image, within the region of interest (ROI) of the specimen are scanned with an electron probe to obtain a sparse image. Sparse images are then reconstructed using the MBIR inpainting algorithm to produce an image of the specimen at the original resolution that is consistent with an image obtained using conventional scanning methods. Experimental results for down to 5% sampling show consistency with the full STEM image acquired by the conventional scanning method. Although, practical limitations of the conventional STEM instruments, such as internal delays of the STEM control electronics and the continuous electron gun emission, currently hinder to achieve the full potential of the sparse acquisition STEM in realizing the low dose imaging condition required for the investigation of beam-sensitive materials, the results obtained in our experiments demonstrate the sparse acquisition STEM imaging is potentially capable of reducing the electron dose by at least 20 times expanding the frontiers of our characterization capabilities for investigation of biological/organic molecules, polymers, soft materials and nanostructures in general.

Imaging of high-angle annular dark-field scanning transmission electron microscopy and observations of GaN-based violet laser diodes.

PubMed

Shiojiri, M; Saijo, H

2006-09-01

The first part of this paper is devoted to physics, to explain high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging and to interpret why HAADF-STEM imaging is incoherent, instructing a strict definition of interference and coherence of electron waves. Next, we present our recent investigations of InGaN/GaN multiple quantum wells and AlGaN/GaN strained-layer superlattice claddings in GaN-based violet laser diodes, which have been performed by HAADF-STEM and high-resolution field-emission gun scanning electron microscopy.

Scanning electron microscope observation of dislocations in semiconductor and metal materials.

PubMed

Kuwano, Noriyuki; Itakura, Masaru; Nagatomo, Yoshiyuki; Tachibana, Shigeaki

2010-08-01

Scanning electron microscope (SEM) image contrasts have been investigated for dislocations in semiconductor and metal materials. It is revealed that single dislocations can be observed in a high contrast in SEM images formed by backscattered electrons (BSE) under the condition of a normal configuration of SEM. The BSE images of dislocations were compared with those of the transmission electron microscope and scanning transmission electron microscope (STEM) and the dependence of BSE image contrast on the tilting of specimen was examined to discuss the origin of image contrast. From the experimental results, it is concluded that the BSE images of single dislocations are attributed to the diffraction effect and related with high-angle dark-field images of STEM.

Note: Electron energy spectroscopy mapping of surface with scanning tunneling microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Meng; Xu, Chunkai, E-mail: xuck@ustc.edu.cn, E-mail: xjun@ustc.edu.cn; Zhang, Panke

We report a novel scanning probe electron energy spectrometer (SPEES) which combines a double toroidal analyzer with a scanning tunneling microscope to achieve both topography imaging and electron energy spectroscopy mapping of surface in situ. The spatial resolution of spectroscopy mapping is determined to be better than 0.7 ± 0.2 μm at a tip sample distance of 7 μm. Meanwhile, the size of the field emission electron beam spot on the surface is also measured, and is about 3.6 ± 0.8 μm in diameter. This unambiguously demonstrates that the spatial resolution of SPEES technique can be much better than themore » size of the incident electron beam.« less

Measurement of Strain and Stress Distributions in Structural Materials by Electron Moiré Method

NASA Astrophysics Data System (ADS)

Kishimoto, Satoshi; Xing, Yougming; Tanaka, Yoshihisa; Kagawa, Yutaka

A method for measuring the strain and stress distributions in structural materials has been introduced. Fine model grids were fabricated by electron beam lithography, and an electron beam scan by a scanning electron microscope (SEM) was used as the master grid. Exposure of the electron beam scan onto the model grid in an SEM produced the electron beam moiré fringes of bright and dark parts caused by the different amounts of the secondary electrons per a primary electron. For demonstration, the micro-creep deformation of pure copper was observed. The creep strain distribution and the grain boundary sliding were analyzed. The residual strain and stress at the interface between a fiber and a matrix of a fiber reinforced plastic (FRP) were measured using the pushing-out test and this electron moiré method. Also, a non-uniform deformation around the boundary of 3-point bended laminated steel was observed and the strain distribution analyzed.

Electron nanoprobe induced oxidation: A simulation of direct-write purification

DOE PAGES

Fowlkes, J. D.; Geier, B.; Lewis, B. B.; ...

2015-06-01

Electron beam direct-write has recently taken a large step forward with the advent of methods to purify deposits. This development has opened the door for future direct-write device prototyping and editing. In one such approach, an additional beam scanning procedure removes carbonaceous impurities via oxidation from metal–carbon deposits (e.g., PtC 5) in the presence of H 2O or O 2 after deposition. So far, critical aspects of the oxidation reaction remain unclear; experiments reveal clearly that electron stimulated oxidation drives the process yet it is not understood why H 2O purifies by a bottom-up mechanism while O 2 purifies frommore » the top-down. The simulation results presented here suggest that the chemisorption of dissolved O 2 at buried Pt nanoparticle surfaces controls purification in the top-down case while both the high relative solubility coupled with weak physisorption of H 2O explains the bottom-up process. Crucial too is the role that the carbonaceous contaminant itself has on the dissolution and diffusion of O 2 and H 2O. The results pave the way for simulation driven experiments where (1) the transient densification of the deposit can be accounted for in the initial deposit design stage and (2) the deposition and purification steps can be combined.« less

Electron nanoprobe induced oxidation: A simulation of direct-write purification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fowlkes, J. D.; Geier, B.; Lewis, B. B.

Electron beam direct-write has recently taken a large step forward with the advent of methods to purify deposits. This development has opened the door for future direct-write device prototyping and editing. In one such approach, an additional beam scanning procedure removes carbonaceous impurities via oxidation from metal–carbon deposits (e.g., PtC 5) in the presence of H 2O or O 2 after deposition. So far, critical aspects of the oxidation reaction remain unclear; experiments reveal clearly that electron stimulated oxidation drives the process yet it is not understood why H 2O purifies by a bottom-up mechanism while O 2 purifies frommore » the top-down. The simulation results presented here suggest that the chemisorption of dissolved O 2 at buried Pt nanoparticle surfaces controls purification in the top-down case while both the high relative solubility coupled with weak physisorption of H 2O explains the bottom-up process. Crucial too is the role that the carbonaceous contaminant itself has on the dissolution and diffusion of O 2 and H 2O. The results pave the way for simulation driven experiments where (1) the transient densification of the deposit can be accounted for in the initial deposit design stage and (2) the deposition and purification steps can be combined.« less

Imaging of bacterial multicellular behaviour in biofilms in liquid by atmospheric scanning electron microscopy

PubMed Central

Sugimoto, Shinya; Okuda, Ken-ichi; Miyakawa, Reina; Sato, Mari; Arita-Morioka, Ken-ichi; Chiba, Akio; Yamanaka, Kunitoshi; Ogura, Teru; Mizunoe, Yoshimitsu; Sato, Chikara

2016-01-01

Biofilms are complex communities of microbes that attach to biotic or abiotic surfaces causing chronic infectious diseases. Within a biofilm, microbes are embedded in a self-produced soft extracellular matrix (ECM), which protects them from the host immune system and antibiotics. The nanoscale visualisation of delicate biofilms in liquid is challenging. Here, we develop atmospheric scanning electron microscopy (ASEM) to visualise Gram-positive and -negative bacterial biofilms immersed in aqueous solution. Biofilms cultured on electron-transparent film were directly imaged from below using the inverted SEM, allowing the formation of the region near the substrate to be studied at high resolution. We visualised intercellular nanostructures and the exocytosis of membrane vesicles, and linked the latter to the trafficking of cargos, including cytoplasmic proteins and the toxins hemolysin and coagulase. A thick dendritic nanotube network was observed between microbes, suggesting multicellular communication in biofilms. A universal immuno-labelling system was developed for biofilms and tested on various examples, including S. aureus biofilms. In the ECM, fine DNA and protein networks were visualised and the precise distribution of protein complexes was determined (e.g., straight curli, flagella, and excreted cytoplasmic molecular chaperones). Our observations provide structural insights into bacteria-substratum interactions, biofilm development and the internal microbe community. PMID:27180609

Flexible all-solid-state supercapacitors based on polyaniline orderly nanotubes array.

PubMed

Li, Huihua; Song, Juan; Wang, Linlin; Feng, Xiaomiao; Liu, Ruiqing; Zeng, Wenjin; Huang, Zhendong; Ma, Yanwen; Wang, Lianhui

2017-01-07

Flexible all-solid-state supercapacitors are crucial to meet the growing needs for portable electronic devices such as foldable phones and wearable electronics. As promising candidates for pseudocapacitor electrode materials, polyaniline (PANI) orderly nanotube arrays are prepared via a simple template electrodeposition method. The structures of the final product were characterized using various characterization techniques, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The obtained PANI nanotube film could be directly used as a flexible all-solid-state supercapacitor electrode. Electrochemical results show that the areal capacitance of a PANI nanotube-based supercapacitor with the deposition cycle number of 100 can achieve a maximum areal capacitance of 237.5 mF cm -2 at a scan rate of 10 mV s -1 and maximum energy density of 24.31 mW h cm -2 at a power density of 2.74 mW cm -2 . In addition, the prepared supercapacitor exhibits excellent flexibility under different bending conditions. It retains 95.2% of its initial capacitance value after 2000 cycles at a current density of 1.0 mA cm -1 , which displays its superior cycling stability. Moreover, the prepared flexible all-solid-state supercapacitor can power a light-emitting-diode (LED), which meets the practical applications of micropower supplies.

Focussed Ion Beam Milling and Scanning Electron Microscopy of Brain Tissue

PubMed Central

Knott, Graham; Rosset, Stéphanie; Cantoni, Marco

2011-01-01

This protocol describes how biological samples, like brain tissue, can be imaged in three dimensions using the focussed ion beam/scanning electron microscope (FIB/SEM). The samples are fixed with aldehydes, heavy metal stained using osmium tetroxide and uranyl acetate. They are then dehydrated with alcohol and infiltrated with resin, which is then hardened. Using a light microscope and ultramicrotome with glass knives, a small block containing the region interest close to the surface is made. The block is then placed inside the FIB/SEM, and the ion beam used to roughly mill a vertical face along one side of the block, close to this region. Using backscattered electrons to image the underlying structures, a smaller face is then milled with a finer ion beam and the surface scrutinised more closely to determine the exact area of the face to be imaged and milled. The parameters of the microscope are then set so that the face is repeatedly milled and imaged so that serial images are collected through a volume of the block. The image stack will typically contain isotropic voxels with dimenions as small a 4 nm in each direction. This image quality in any imaging plane enables the user to analyse cell ultrastructure at any viewing angle within the image stack. PMID:21775953

Characterization of Graphene Grown Directly on Crystalline Substrates

NASA Astrophysics Data System (ADS)

Rothwell, Sara L.

Graphene has become one of the most popular materials under research, particularly since the 2010 Nobel Prize in Physics. Many visions posit that graphene electronics will be some of the fastest and smallest circuitry physically feasible, however before this becomes reality the scientific community must gain a firm handle on the creation of semiconducting varieties of graphene. In addition, well understood epitaxial growth of graphene on insulating materials will add to the facility of fabricating all-carbon electronics. This thesis presents experimental work detailing the growth of pristine graphene grown on sapphire (GOS) through the thermal decomposition of acetylene, and the electronic characterization of graphene grown on nitrogen-seeded silicon carbide (NG), a semiconducting variety of graphene grown in collaboration with researchers at Georgia Institute of Technology and Rutgers University. GOS displays turbostratic stacking and characteristics of monolayer graphene as analyzed by Raman spectroscopy and atomic force microscopy. Scanning tunneling microscopy characterization of NG illustrates a topography of pleats from 0.5-2 nm tall, 1-4 nm thick, and 1-20 nm long, as well as atomically flat plateaus and other areas of intermixed features. Scanning tunneling spectroscopy measurements across NG features show peaks interpreted as Landau levels induced by strain. Analysis of these Landau levels in coordination with previous characterization concludes that a model employing a bandgap fits best.

Distinction between amorphous and healed planar deformation features in shocked quartz using composite color scanning electron microscope cathodoluminescence (SEM-CL) imaging

NASA Astrophysics Data System (ADS)

Hamers, Maartje F.; Pennock, Gill M.; Herwegh, Marco; Drury, Martyn R.

2016-10-01

Planar deformation features (PDFs) in quartz are one of the most reliable and most widely used forms of evidence for hypervelocity impact. PDFs can be identified in scanning electron microscope cathodoluminescence (SEM-CL) images, but not all PDFs show the same CL behavior: there are nonluminescent and red luminescent PDFs. This study aims to explain the origin of the different CL emissions in PDFs. Focused ion beam (FIB) thin foils were prepared of specific sample locations selected in composite color SEM-CL images and were analyzed in a transmission electron microscope (TEM). The FIB preparation technique allowed a direct, often one-to-one correlation between the CL images and the defect structure observed in TEM. This correlation shows that composite color SEM-CL imaging allows distinction between amorphous PDFs on one hand and healed PDFs and basal Brazil twins on the other: nonluminescent PDFs are amorphous, while healed PDFs and basal Brazil twins are red luminescent, with a dominant emission peak at 650 nm. We suggest that the red luminescence is the result of preferential beam damage along dislocations, fluid inclusions, and twin boundaries. Furthermore, a high-pressure phase (possibly stishovite) in PDFs can be detected in color SEM-CL images by its blue luminescence.

Insights into radiation damage from atomic resolution scanning transmission electron microscopy imaging of mono-layer CuPcCl16 films on graphene.

PubMed

Mittelberger, Andreas; Kramberger, Christian; Meyer, Jannik C

2018-03-19

Atomically resolved images of monolayer organic crystals have only been obtained with scanning probe methods so far. On the one hand, they are usually prepared on surfaces of bulk materials, which are not accessible by (scanning) transmission electron microscopy. On the other hand, the critical electron dose of a monolayer organic crystal is orders of magnitudes lower than the one for bulk crystals, making (scanning) transmission electron microscopy characterization very challenging. In this work we present an atomically resolved study on the dynamics of a monolayer CuPcCl 16 crystal under the electron beam as well as an image of the undamaged molecules obtained by low-dose electron microscopy. The results show the dynamics and the radiation damage mechanisms in the 2D layer of this material, complementing what has been found for bulk crystals in earlier studies. Furthermore, being able to image the undamaged molecular crystal allows the characterization of new composites consisting of 2D materials and organic molecules.

Direct Reduction of Ferrous Oxides to form an Iron-Rich Alternative Charge Material

NASA Astrophysics Data System (ADS)

Ünal, H. İbrahim; Turgut, Enes; Atapek, Ş. H.; Alkan, Attila

2015-12-01

In this study, production of sponge iron by direct reduction of oxides and the effect of reductant on metallization were investigated. In the first stage of the study, scale formed during hot rolling of slabs was reduced in a rotating furnace using solid and gas reductants. Coal was used as solid reductant and hydrogen released from the combustion reaction of LNG was used as the gas one. The sponge iron produced by direct reduction was melted and solidified. In the second stage, Hematite ore in the form of pellets was reduced using solid carbon in a furnace heated up to 1,100°C for 60 and 120 minutes. Reduction degree of process was evaluated as a function of time and the ratio of Cfix/Fetotal. In the third stage, final products were examined using scanning electron microscope and microanalysis was carried out by energy dispersive x-ray spectrometer attached to the electron microscope. It is concluded that (i) direct reduction using both solid and gas reductants caused higher metallization compared to using only solid reductant, (ii) as the reduction time and ratio of Cfix/Fetotal increased %-reduction of ore increased.

Far-field optical imaging with subdiffraction resolution enabled by nonlinear saturation absorption

NASA Astrophysics Data System (ADS)

Ding, Chenliang; Wei, Jingsong

2016-01-01

The resolution of far-field optical imaging is required to improve beyond the Abbe limit to the subdiffraction or even the nanoscale. In this work, inspired by scanning electronic microscopy (SEM) imaging, in which carbon (or Au) thin films are usually required to be coated on the sample surface before imaging to remove the charging effect while imaging by electrons. We propose a saturation-absorption-induced far-field super-resolution optical imaging method (SAI-SRIM). In the SAI-SRIM, the carbon (or Au) layers in SEM imaging are replaced by nonlinear-saturation-absorption (NSA) thin films, which are directly coated onto the sample surfaces using advanced thin film deposition techniques. The surface fluctuant morphologies are replicated to the NSA thin films, accordingly. The coated sample surfaces are then imaged using conventional laser scanning microscopy. Consequently, the imaging resolution is greatly improved, and subdiffraction-resolved optical images are obtained theoretically and experimentally. The SAI-SRIM provides an effective and easy way to achieve far-field super-resolution optical imaging for sample surfaces with geometric fluctuant morphology characteristics.

The relationship between morphological changes of lens epithelial cells and intraocular lens optic material.

PubMed

Majima, K

1998-01-01

To examine the morphological changes of lens epithelial cells (LECs) occurring directly beneath and at regions contacting various intraocular lens (IOL) optic materials, human LECs were cultured on human anterior lens capsules and were further incubated upon placing above the cells lens optics made of polymethylmethacrylate, silicone, and soft acrylic material. Observations as to the morphological changes of LECs under phase-contrast microscope and scanning electron microscope were performed on the 14th day of incubation. Gatherings of LECs were observed at regions contacting the soft acrylic material under phase-contrast microscope, and gatherings of LECs were observed accurately at the same regions mentioned above under scanning electron microscope. On the other hand, LECs in contact with two other optic materials did not show morphological changes. The results suggest that LECs attached to and proliferated on not only the anterior lens capsules but also the soft acrylic IOL optics. The model used in this study may be useful in studying the relationship between cellular movement of LECs and IOL optic material.

Scanning electron microscope analysis of gunshot defects to bone: an underutilized source of information on ballistic trauma.

PubMed

Rickman, John M; Smith, Martin J

2014-11-01

Recent years have seen increasing involvement by forensic anthropologists in the interpretation of skeletal trauma. With regard to ballistic injuries, there is now a large literature detailing gross features of such trauma; however, less attention has been given to microscopic characteristics. This article presents analysis of experimentally induced gunshot trauma in animal bone (Bos taurus scapulae) using full metal jacket (FMJ), soft point (SP), and captive bolt projectiles. The results were examined using scanning electron microscopy (SEM). Additional analysis was conducted on a purported parietal gunshot lesion in a human cranial specimen. A range of features was observed in these samples suggesting that fibrolamellar bone response to projectile impact is analogous to that observed in synthetic composite laminates. The results indicate that direction of bullet travel can be discerned microscopically even when it is ambiguous on gross examination. It was also possible to distinguish SP from FMJ lesions. SEM analysis is therefore recommended as a previously underexploited tool in the analysis of ballistic trauma. © 2014 American Academy of Forensic Sciences.

Operando characterization of cathodic reactions in a liquid-state lithium-oxygen micro-battery by scanning transmission electron microscopy.

PubMed

Liu, Pan; Han, Jiuhui; Guo, Xianwei; Ito, Yoshikazu; Yang, Chuchu; Ning, Shoucong; Fujita, Takeshi; Hirata, Akihiko; Chen, Mingwei

2018-02-16

Rechargeable non-aqueous lithium-oxygen batteries with a large theoretical capacity are emerging as a high-energy electrochemical device for sustainable energy strategy. Despite many efforts made to understand the fundamental Li-O 2 electrochemistry, the kinetic process of cathodic reactions, associated with the formation and decomposition of a solid Li 2 O 2 phase during charging and discharging, remains debate. Here we report direct visualization of the charge/discharge reactions on a gold cathode in a non-aqueous lithium-oxygen micro-battery using liquid-cell aberration-corrected scanning transmission electron microscopy (STEM) combining with synchronized electrochemical measurements. The real-time and real-space characterization by time-resolved STEM reveals the electrochemical correspondence of discharge/charge overpotentials to the nucleation, growth and decomposition of Li 2 O 2 at a constant current density. The nano-scale operando observations would enrich our knowledge on the underlying reaction mechanisms of lithium-oxygen batteries during round-trip discharging and charging and shed lights on the strategies in improving the performances of lithium-oxygen batteries by tailoring the cathodic reactions.

Charge collection microscopy of in-situ switchable PRAM line cells in a scanning electron microscope: Technique development and unique observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oosthoek, J. L. M.; Schuitema, R. W.; Brink, G. H. ten

2015-03-15

An imaging method has been developed based on charge collection in a scanning electron microscope (SEM) that allows discrimination between the amorphous and crystalline states of Phase-change Random Access Memory (PRAM) line cells. During imaging, the cells are electrically connected and can be switched between the states and the resistance can be measured. This allows for electrical characterization of the line cells in-situ in the SEM. Details on sample and measurement system requirements are provided which turned out to be crucial for the successful development of this method. Results show that the amorphous or crystalline state of the line cellsmore » can be readily discerned, but the spatial resolution is relatively poor. Nevertheless, it is still possible to estimate the length of the amorphous mark, and also for the first time, we could directly observe the shift of the amorphous mark from one side of the line cell to the other side when the polarity of the applied (50 ns) RESET pulse was reversed.« less

Understanding the crack formation of graphite particles in cycled commercial lithium-ion batteries by focused ion beam - scanning electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Na; Jia, Zhe; Wang, Zhihui

Here in this paper, the structure degradation of commercial Lithium-ion battery (LIB) graphite anodes with different cycling numbers and charge rates was investigated by focused ion beam (FIB) and scanning electron microscopy (SEM). The cross-section image of graphite anode by FIB milling shows that cracks, resulted in the volume expansion of graphite electrode during long-term cycling, were formed in parallel with the current collector. The crack occurs in the bulk of graphite particles near the lithium insertion surface, which might derive from the stress induced during lithiation and de-lithiation cycles. Subsequently, crack takes place along grain boundaries of the polycrystallinemore » graphite, but only in the direction parallel with the current collector. Furthermore, fast charge graphite electrodes are more prone to form cracks since the tensile strength of graphite is more likely to be surpassed at higher charge rates. Therefore, for LIBs long-term or high charge rate applications, the tensile strength of graphite anode should be taken into account.« less

Understanding the crack formation of graphite particles in cycled commercial lithium-ion batteries by focused ion beam - scanning electron microscopy

DOE PAGES

Lin, Na; Jia, Zhe; Wang, Zhihui; ...

2017-10-01

Here in this paper, the structure degradation of commercial Lithium-ion battery (LIB) graphite anodes with different cycling numbers and charge rates was investigated by focused ion beam (FIB) and scanning electron microscopy (SEM). The cross-section image of graphite anode by FIB milling shows that cracks, resulted in the volume expansion of graphite electrode during long-term cycling, were formed in parallel with the current collector. The crack occurs in the bulk of graphite particles near the lithium insertion surface, which might derive from the stress induced during lithiation and de-lithiation cycles. Subsequently, crack takes place along grain boundaries of the polycrystallinemore » graphite, but only in the direction parallel with the current collector. Furthermore, fast charge graphite electrodes are more prone to form cracks since the tensile strength of graphite is more likely to be surpassed at higher charge rates. Therefore, for LIBs long-term or high charge rate applications, the tensile strength of graphite anode should be taken into account.« less

Biocompatibility enhancement of rare earth magnesium alloy by laser surface processing

NASA Astrophysics Data System (ADS)

Nie, Shilin; Wang, Yuqing; Liu, Haifeng; Guan, Yingchun

2018-01-01

Although magnesium and magnesium alloys are considered biocompatible and biodegradable, insufficient biocompatibility in body fluid environment is still the major drawback of magnesium alloys for their successful applications as biodegradable orthopaedic implants. In this work, magnesium alloy surface with both enhanced corrosion resistance and better cell adhesion property was directly fabricated by laser surface processing. Laser surface melting was used to improve corrosion resistance of Mg-6Gd-0.6Ca alloy. After laser surface melting, laser surface texturing was utilized on melted surface for better cell adhesion property. The corrosion resistance of laser-treated and as-received samples were evaluated using electrochemical technique. The effect of laser surface treatment on phase and microstructure evolution was evaluated using scanning electron microscopy, optical microscopy and X-ray diffraction. This work investigated the effect of laser treatment on cell distribution across the surface of magnesium alloy substrates. Osteoblast was cultured on the laser-treated surface and as-received surface. Cell morphology was observed with a scanning electron microscopy, and cell viability was evaluated by optical density measurement.

Histological preparation of developing vestibular otoconia for scanning electron microscopy

NASA Technical Reports Server (NTRS)

Huss, D.; Dickman, J. D.

2003-01-01

The unique nature of vestibular otoconia as calcium carbonate biominerals makes them particularly susceptible to chemical deformation during histological processing. We fixed and stored otoconia from all three otolith endorgans of embryonic, hatchling and adult Japanese quail in glutaraldehyde containing either phosphate or non-phosphate buffers for varying lengths of time and processed them for scanning electron microscopy. Otoconia from all age groups and otolith endorgans processed in 0.1 M phosphate buffer (pH 7.4) showed abnormal surface morphology when compared to acetone fixed controls. Otoconia processed in 0.1 M sodium cacodylate or HEPES buffered artificial endolymph (pH 7.4) showed normal morphology that was similar to controls. The degree of otoconial deformation was directly related to the time exposed to phosphate buffer. Short duration exposure produced particulate deformations while longer exposures resulted in fused otoconia that formed solid sheets. Otoconial surface deformation and fusing was independent of the glutaraldehyde component of the histological processing. These findings should help vestibular researchers to develop appropriate histological processing protocols in future studies of otoconia.

Morphology and Viability of Pleistocene Microbiota from the CRREL Permafrost Tunnel Near Fox, Alaska

NASA Technical Reports Server (NTRS)

Hoover, Richard B.

2000-01-01

The U. S. Army Cold Regions Research and Engineering Laboratory maintains the CRREL Permafrost Tunnel at Fox, Alaska (-10 miles north of Fairbanks.) The active microbial ecosystems and the cryopreserved anabiotic viable microorganisms and dead microbial remains and biomarkers frozen within the permafrost and ice of the CRREL Permafrost Tunnel are of direct relevance to Astrobiology. Microbial extremophiles from permafrost and ice provide information concerning where and how should we search for evidence of life elsewhere in the Cosmos. The permafrost and ice wedges of the Fox tunnel preserves a magnificent of record of Pliocene, Pleistocene and Holocene life on Earth spanning more than 2.5 million years. This record includes frozen fossil bacteria, archaea, algae, mosses, higher plants, insects and mammals. In this paper we present the preliminary results of studies of the morphology, ultramicrostructure and elemental distributions of Fox tunnel microbiota as determined in-situ by the Environmental Scanning Electron Microscope (ESEM) and the Field Emission Scanning Electron Microscope (FESEM) investigations. The long-term viability of cryopreserved microbiota and potential implications to Astrobiology will be discussed.

Silicide induced ion beam patterning of Si(001).

PubMed

Engler, Martin; Frost, Frank; Müller, Sven; Macko, Sven; Will, Moritz; Feder, René; Spemann, Daniel; Hübner, René; Facsko, Stefan; Michely, Thomas

2014-03-21

Low energy ion beam pattern formation on Si with simultaneous co-deposition of Ag, Pd, Pb, Ir, Fe or C impurities was investigated by in situ scanning tunneling microscopy as well as ex situ atomic force microscopy, scanning electron microscopy, transmission electron microscopy and Rutherford backscattering spectrometry. The impurities were supplied by sputter deposition. Additional insight into the mechanism of pattern formation was obtained by more controlled supply through e-beam evaporation. For the situations investigated, the ability of the impurity to react with Si, i.e. to form a silicide, appears to be a necessary, but not a sufficient condition for pattern formation. Comparing the effects of impurities with similar mass and nuclear charge, the collision kinetics is shown to be not of primary importance for pattern formation. To understand the observed phenomena, it is necessary to assume a bi-directional coupling of composition and height fluctuations. This coupling gives rise to a sensitive dependence of the final morphology on the conditions of impurity supply. Because of this history dependence, the final morphology cannot be uniquely characterized by a steady state impurity concentration.

Effect of black clay soil moisture on the electrochemical behavior of API X70 pipeline steel

NASA Astrophysics Data System (ADS)

Hendi, R.; Saifi, H.; Belmokre, K.; Ouadah, M.; Smili, B.; Talhi, B.

2018-03-01

The effect of moisture content variation (20–100 wt.%) on the electrochemical behavior of API X70 pipeline steel buried in the soil of Skikda (East of Algeria) was studied using electrochemical techniques, scanning electron microscopy (SEM), X ray diffraction analysis (XRD) and weight loss measurement. The electrochemical measurements showed that the corrosion current Icorr is directly proportional to the moisture content up to 50 wt.%, beyond this content, this value becomes almost constant. The result were confirmed by electrochemical impedance spectroscopy; the capacitance of the double layer formed on the surface is the highest at 50 wt.%. A single time constant was detected by plotting the Bode diagrams. The steel surface degradation has been appreciated using the scanning electron microscopy observations. A few pitting corrosion at 20 wt.% moisture, followed by more degradation at 50 wt.% have been revealed. However, when the moisture amount exceeded 50 wt.%, the surface became entirely covered by a corrosion product. XRD analysis revealed the dominance of FeOOH and Fe3O4 phases on steel surface for a moisture content of 50 wt.%.

Polymer based nanocomposites with nanofibers and exfoliated clay

NASA Technical Reports Server (NTRS)

Meador, Michael A.; Reneker, Darrell H.

2005-01-01

Polymer solutions, containing clay sheets, were electrospun into nanofibers and microfibers that contained clay sheets inside. Controllable removal of polymer by plasma etching from the surface of fibers revealed the arrangement of clay. The shape, flexibility, size distribution and arrangement of clay sheets were observed by transmission and scanning electron microscopy. The clay sheets were partially aligned in big fibers with normal direction of clay sheets perpendicular to fiber axis. Crumpling of clay sheets inside fibers was observed when the fiber diameter was comparable to the lateral size of clay sheets. Single sheets of clay were observed both by catching clay sheets dispersed in water with electrospun nanofiber mats and by the deliberate removal of most of the polymer in the fibers. Thin, flexible gas barrier films, that are reasonably strong, were assembled from clay sheets and polymer nanofibers. Structure of composite films was characterized with scanning electron microscopy. Continuous film of clay sheets were physically attached to the surface of fiber mats. Spincoating film of polymer and clay sheets was reinforced by electrospun fiber scaffold. Certain alignment of clay sheets was observed in the vicinity of fibers.

Correlation of live-cell imaging with volume scanning electron microscopy.

PubMed

Lucas, Miriam S; Günthert, Maja; Bittermann, Anne Greet; de Marco, Alex; Wepf, Roger

2017-01-01

Live-cell imaging is one of the most widely applied methods in live science. Here we describe two setups for live-cell imaging, which can easily be combined with volume SEM for correlative studies. The first procedure applies cell culture dishes with a gridded glass support, which can be used for any light microscopy modality. The second approach is a flow-chamber setup based on Ibidi μ-slides. Both live-cell imaging strategies can be followed up with serial blockface- or focused ion beam-scanning electron microscopy. Two types of resin embedding after heavy metal staining and dehydration are presented making best use of the particular advantages of each imaging modality: classical en-bloc embedding and thin-layer plastification. The latter can be used only for focused ion beam-scanning electron microscopy, but is advantageous for studying cell-interactions with specific substrates, or when the substrate cannot be removed. En-bloc embedding has diverse applications and can be applied for both described volume scanning electron microscopy techniques. Finally, strategies for relocating the cell of interest are discussed for both embedding approaches and in respect to the applied light and scanning electron microscopy methods. Copyright © 2017 Elsevier Inc. All rights reserved.

Scanning electron microscope fractography in failure analysis of steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wouters, R.; Froyen, L.

1996-04-01

For many failure cases, macroscopic examination of the fracture surface permits discrimination of fatigue fractures from overload fractures. For clarifying fatigue fractures, the practical significance of microfractography is limited to an investigation of the crack initiation areas. Scanning electron microscopy is successfully used in tracing local material abnormalities that act as fatigue crack initiators. The task for the scanning electron microscope, however, is much more substantial in failure analysis of overload fractures, especially for steels. By revealing specific fractographic characteristics, complemented by information about the material and the loading conditions, scanning electron microscopy provides a strong indication of the probablemore » cause of failure. A complete dimple fracture is indicative of acceptable bulk material properties; overloading, by subdimensioning or excessive external loading, has to be verified. The presence of cleavage fracture makes the material properties questionable if external conditions causing embrittlement are absent. Intergranular brittle fracture requires verification of grain-boundary weakening conditions--a sensitized structure, whether or not combined with a local stress state or a specific environment. The role of scanning electron microscopy in failure analysis is illustrated by case histories of the aforementioned fracture types.« less

Controlled clockwise and anticlockwise rotational switching of a molecular motor.

PubMed

Perera, U G E; Ample, F; Kersell, H; Zhang, Y; Vives, G; Echeverria, J; Grisolia, M; Rapenne, G; Joachim, C; Hla, S-W

2013-01-01

The design of artificial molecular machines often takes inspiration from macroscopic machines. However, the parallels between the two systems are often only superficial, because most molecular machines are governed by quantum processes. Previously, rotary molecular motors powered by light and chemical energy have been developed. In electrically driven motors, tunnelling electrons from the tip of a scanning tunnelling microscope have been used to drive the rotation of a simple rotor in a single direction and to move a four-wheeled molecule across a surface. Here, we show that a stand-alone molecular motor adsorbed on a gold surface can be made to rotate in a clockwise or anticlockwise direction by selective inelastic electron tunnelling through different subunits of the motor. Our motor is composed of a tripodal stator for vertical positioning, a five-arm rotor for controlled rotations, and a ruthenium atomic ball bearing connecting the static and rotational parts. The directional rotation arises from sawtooth-like rotational potentials, which are solely determined by the internal molecular structure and are independent of the surface adsorption site.

Atomic resolution study of the interfacial bonding at Si3N4/CeO2-δ grain boundaries

NASA Astrophysics Data System (ADS)

Walkosz, W.; Klie, R. F.; Öǧüt, S.; Borisevich, A.; Becher, P. F.; Pennycook, S. J.; Idrobo, J. C.

2008-08-01

Using a combination of atomic-resolution Z-contrast imaging and electron energy-loss spectroscopy (EELS) in the scanning transmission electron microscope, we examine the atomic and electronic structures at the interface between Si3N4 (101¯0) and CeO2-d intergranular film (IGF). Ce atoms are observed to segregate to the interface in a two-layer periodic arrangement, which is significantly different from the structure observed in a previous study. Our EELS experiments show (i) oxygen in direct contact with the terminating Si3N4 open-ring structures, (ii) a change in the Ce valence from a nominal oxidation state of +3 to almost +4 moving from the interface into the IGF, and (iii) a uniform concentration of Si in the film.

Field Emission Auger Electron Spectroscopy with Scanning Auger Microscopy |

Science.gov Websites

0.5 at.% for elements from lithium to uranium. Depth Profiling Removes successive layers by using size (> ~25 nm). Imaging Obtains SEM micrographs with up to 20,000x magnification by using raster scanning with a highly focused electron beam ≥25 nm in diameter. Using the same raster scan, SAM can

Plasmon 3D Electron Tomography and Local Electric-Field Enhancement of Engineered Plasmonic Nanoantennas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Archanjo, B. S.; Vasconcelos, T. L.; Oliveira, B. S.

Plasmonic nano-antennas are pushing the limits of optical imaging resolution capabilities in near-field scanning optical microscopy (NSOM). Accordingly, these techniques are driving the basic understanding of photonic and optoelectronic nanoscale devices with applications in sensing, energy conversion, solid-state lighting and information technology. Imaging the localized surface plasmon resonance (LSPR) at the nanoscale is a key to understanding the optical responses of a given tip geometry in order to engineer better plasmonic nano-antennas for near-field experiments. In recent years the advancement of focused ion beam technology provides the ability to directly modify plasmonic structures with nanometer resolution. Also, scanning transmission electronmore » microscopy (STEM) with electron energy loss spectroscopy (EELS) is an established technique allowing imaging of LSPR. Specifically, the combination of these two techniques provides spectrally sensitive two-dimensional (2D) imaging information to better visualize and understand LSPR on the nanometer scale. This can be combined with electron tomography to provide the three-dimensional LSPR distribution. Here in this paper we demonstrate the fabrication of Au nano-pyramids using helium ion microscopy, and analyze the LSPR in 3D reconstructions produced by total variation (TV)-norm minimization of a set of 2D STEM-EELS maps. Additionally, a boundary element simulation method was used to verify the experimentally observed nanopyramid LSPR modes. Finally, we show that the point-spread-functions (PSF) of LSPR mode hot spots in nanopyramids differ to local electric-field enhancement under optical excitation making direct comparison to NSOM experimental resolution difficult. However, the STEM-EELS results show how LSPR modes are influenced by the tip characteristics, which can inform the development of new nano-antenna designs.« less

Plasmon 3D Electron Tomography and Local Electric-Field Enhancement of Engineered Plasmonic Nanoantennas

DOE PAGES

Archanjo, B. S.; Vasconcelos, T. L.; Oliveira, B. S.; ...

2018-06-01

Plasmonic nano-antennas are pushing the limits of optical imaging resolution capabilities in near-field scanning optical microscopy (NSOM). Accordingly, these techniques are driving the basic understanding of photonic and optoelectronic nanoscale devices with applications in sensing, energy conversion, solid-state lighting and information technology. Imaging the localized surface plasmon resonance (LSPR) at the nanoscale is a key to understanding the optical responses of a given tip geometry in order to engineer better plasmonic nano-antennas for near-field experiments. In recent years the advancement of focused ion beam technology provides the ability to directly modify plasmonic structures with nanometer resolution. Also, scanning transmission electronmore » microscopy (STEM) with electron energy loss spectroscopy (EELS) is an established technique allowing imaging of LSPR. Specifically, the combination of these two techniques provides spectrally sensitive two-dimensional (2D) imaging information to better visualize and understand LSPR on the nanometer scale. This can be combined with electron tomography to provide the three-dimensional LSPR distribution. Here in this paper we demonstrate the fabrication of Au nano-pyramids using helium ion microscopy, and analyze the LSPR in 3D reconstructions produced by total variation (TV)-norm minimization of a set of 2D STEM-EELS maps. Additionally, a boundary element simulation method was used to verify the experimentally observed nanopyramid LSPR modes. Finally, we show that the point-spread-functions (PSF) of LSPR mode hot spots in nanopyramids differ to local electric-field enhancement under optical excitation making direct comparison to NSOM experimental resolution difficult. However, the STEM-EELS results show how LSPR modes are influenced by the tip characteristics, which can inform the development of new nano-antenna designs.« less