Zeitschriftenartikel: „Electrons – Diffraction“

1

Qin, L. C., A. J. Garratt-Reed und L. W. Hobbs. „Theory and practice of energy-filtered electron diffraction using the HB5 STEM“. Proceedings, annual meeting, Electron Microscopy Society of America 50, Nr. 1 (August 1992): 350–51. http://dx.doi.org/10.1017/s0424820100122150.

Der volle Inhalt der Quelle

Annotation:

Electron diffraction patterns obtained in TEM have long been an important part of microstructural characterizations. Certain materials, such as crystalline silicas, are amorphized in the fast electron beam of the TEM, and their aperiodic (metamict) structure is of interest. For amorphous materials, both elastically and inelastically scattered electrons contribute to the diffuse diffraction pattern. Analysis of aperiodic structure, however, requires intensity data from only elastically scattered electrons, and it is therefore it is necessary to obtain energy-filtered electron diffraction patterns. With the energy-filtered electron diffraction technique, the background intensity that is mainly due to inelastically scattered electrons is removed. This makes possible the derivation of radial distribution functions (RDFs) from collected electron diffraction intensity data for uniform aperiodic structures.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

2

Lyman, Charles. „Diffraction“. Microscopy Today 20, Nr. 2 (28.02.2012): 7. http://dx.doi.org/10.1017/s1551929512000107.

Der volle Inhalt der Quelle

Annotation:

This year marks the 100th anniversary of the discovery of X-ray diffraction and the 85th anniversary of electron diffraction (see Microscopy Pioneers). For most of the time since their introduction, microscopists have known these two techniques as the primary phase identification methods used in conjunction with various microscopies. However, these two diffraction methods also have played enormous roles in understanding the structure of matter, as well as the nature of both X rays and electrons.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

3

Schröder, Rasmus R., und Christoph Burmester. „Improvements in electron diffraction of frozen hydrated crystals by energy filtering and large-area single-electron detection“. Proceedings, annual meeting, Electron Microscopy Society of America 51 (01.08.1993): 666–67. http://dx.doi.org/10.1017/s0424820100149167.

Der volle Inhalt der Quelle

Annotation:

Diffraction patterns of 3D protein crystals embedded in vitrious ice are critical to record. Inelastically scattered electrons almost completely superimpose the diffraction pattern of crystals if the thickness of the crystal is higher than the mean free path of electrons in the specimen. Figure 1 shows such an example of an unfiltered electron diffraction pattern from a frozen hydrated 3D catalase crystal. However, for thin 2D crystals electron diffraction has been the state of the art method to determine the Fourier amplitudes for reconstructions to atomic level, and in one case the possibility of obtaining Fourier phases from diffraction patterns has been studied. One of the main problems could be the background in the diffraction pattern due to inelastic scattering and the recording characteristics for electrons of conventional negative material.It was pointed out before, that the use of an energy filtered TEM (EFTEM) and of the Image Plate as a large area electron detector gives considerable improvement for detection of diffraction patterns.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

4

Bauer, R., W. Probst und W.I. Miller. „Elemental imaging of thin specimens with an energy filtering electron microscope (EFEM)“. Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988): 524–25. http://dx.doi.org/10.1017/s0424820100104686.

Der volle Inhalt der Quelle

Annotation:

In conventional TEM (CTEM), image contrast is determined by scattering absorption contrast, diffraction contrast and phase contrast. Phase contrast is produced by the interference of unscattered electrons and elastically scattered electrons. Scattering absorption contrast and diffraction contrast are produced by angle selection of the scattered electrons using an objective aperture diaphragm for brightfield, darkfield and diffraction images.In an EFEM, with an integrated imaging electron energy-loss spectrometer, angle selection is used as in CTEM, but, additionally, it is possible to perform energy selection. This is done from the energy-loss spectrum obtained for the specimen area imaged. Energy selection permits the elimination of all inelastically scattered electrons to improve contrast for brightfield, darkfield and diffraction images. This technique also permits imaging of selected, e.g. e1ement-characteristic, ine1astica11y scattered electrons. Images obtained in this way display object- specific or e1ement-specific contrast and are termed electron or element-spectroscopic images (ESI).

APA, Harvard, Vancouver, ISO und andere Zitierweisen

5

Barckhaus, R. H., I. Fromm, H. J. Höhling und L. Reimer. „Advantage of Electron Spectroscopic Diffraction on Calcified Tissue Sections“. Proceedings, annual meeting, Electron Microscopy Society of America 48, Nr. 2 (12.08.1990): 362–63. http://dx.doi.org/10.1017/s0424820100135411.

Der volle Inhalt der Quelle

Annotation:

Different stages in the mineralization of calcified tissues can be investigated by electron diffraction. A disadvantage is the strong background below the Debye—Scherrer rings caused by the large massthickness of calcified products and the high ratio (≃ 3) of the inelastic—to—elastic scattering cross—sections of the embedding material. Therefore, a large fraction of the background consists of inelastically scattered electrons with energy losses. The electron spectroscopic diffraction (ESD) mode of an energy—filtering microscope (ZEISS EM902) allows to record diffraction patterns using only the zero—loss electrons which consist of the primary beam, Bragg diffracted electrons and a smaller fraction of elastically scattered electrons between the Debye—Scherrer rings by thermal—diffuse scattering. Small—area diffraction patterns with different camera lengths are generated at the filter—entrance plane and the zero—loss electrons are selected by a slit in the energy—dispersive plane behind the Castaing—Henry filter lens.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

6

VALERI, SERGIO, und ALESSANDRO di BONA. „MODULATED ELECTRON EMISSION BY SCATTERING-INTERFERENCE OF PRIMARY ELECTRONS“. Surface Review and Letters 04, Nr. 01 (Februar 1997): 141–60. http://dx.doi.org/10.1142/s0218625x9700016x.

Der volle Inhalt der Quelle

Annotation:

We review the effects of scattering-interference of the primary, exciting beam on the electron emission from ordered atomic arrays. The yield of elastically and inelastically backscattered electrons, Auger electrons and secondary electrons shows a marked dependence on the incidence angle of primary electrons. Both the similarity and the relative importance of processes experienced by incident and excident electrons are discussed. We also present recent studies of electron focusing and defocusing along atomic chains. The interplay between these two processes determines the in-depth profile of the primary electron intensity anisotropy. Finally, the potential for surface-structural studies and limits for quantitative analysis are discussed, in comparison with the Auger electron diffraction (AED) and photoelectron diffraction (PD) techniques.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

7

Lynch, D. F., und A. E. Smith. „Electron diffraction phenomena for very low energy electrons“. Acta Crystallographica Section A Foundations of Crystallography 43, a1 (12.08.1987): C246. http://dx.doi.org/10.1107/s0108767387078887.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

8

Yang, Jie, Markus Guehr, Theodore Vecchione, Matthew S. Robinson, Renkai Li, Nick Hartmann, Xiaozhe Shen et al. „Femtosecond gas phase electron diffraction with MeV electrons“. Faraday Discussions 194 (2016): 563–81. http://dx.doi.org/10.1039/c6fd00071a.

Der volle Inhalt der Quelle

Annotation:

We present results on ultrafast gas electron diffraction (UGED) experiments with femtosecond resolution using the MeV electron gun at SLAC National Accelerator Laboratory. UGED is a promising method to investigate molecular dynamics in the gas phase because electron pulses can probe the structure with a high spatial resolution. Until recently, however, it was not possible for UGED to reach the relevant timescale for the motion of the nuclei during a molecular reaction. Using MeV electron pulses has allowed us to overcome the main challenges in reaching femtosecond resolution, namely delivering short electron pulses on a gas target, overcoming the effect of velocity mismatch between pump laser pulses and the probe electron pulses, and maintaining a low timing jitter. At electron kinetic energies above 3 MeV, the velocity mismatch between laser and electron pulses becomes negligible. The relativistic electrons are also less susceptible to temporal broadening due to the Coulomb force. One of the challenges of diffraction with relativistic electrons is that the small de Broglie wavelength results in very small diffraction angles. In this paper we describe the new setup and its characterization, including capturing static diffraction patterns of molecules in the gas phase, finding time-zero with sub-picosecond accuracy and first time-resolved diffraction experiments. The new device can achieve a temporal resolution of 100 fs root-mean-square, and sub-angstrom spatial resolution. The collimation of the beam is sufficient to measure the diffraction pattern, and the transverse coherence is on the order of 2 nm. Currently, the temporal resolution is limited both by the pulse duration of the electron pulse on target and by the timing jitter, while the spatial resolution is limited by the average electron beam current and the signal-to-noise ratio of the detection system. We also discuss plans for improving both the temporal resolution and the spatial resolution.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

9

Vincent, R. „Quantitative energy-filtered electron diffraction“. Proceedings, annual meeting, Electron Microscopy Society of America 52 (1994): 992–93. http://dx.doi.org/10.1017/s0424820100172693.

Der volle Inhalt der Quelle

Annotation:

Microanalysis and diffraction on a sub-nanometre scale have become practical in modern TEMs due to the high brightness of field emission sources combined with the short mean free paths associated with both elastic and inelastic scattering of incident electrons by the specimen. However, development of electron diffraction as a quantitative discipline has been limited by the absence of any generalised theory for dynamical inelastic scattering. These problems have been simplified by recent innovations, principally the introduction of spectrometers such as the Gatan imaging filter (GIF) and the Zeiss omega filter, which remove the inelastic electrons, combined with annual improvements in the speed of computer workstations and the availability of solid-state detectors with high resolution, sensitivity and dynamic range.Comparison of experimental data with dynamical calculations imposes stringent requirements on the specimen and the electron optics, even when the inelastic component has been removed. For example, no experimental CBED pattern ever has perfect symmetry, departures from the ideal being attributable to residual strain, thickness averaging, inclined surfaces, incomplete cells and amorphous surface layers.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

10

Wang, Z. L. „Coupled thermal diffuse-atomic inner shell scattering in electron diffraction“. Proceedings, annual meeting, Electron Microscopy Society of America 52 (1994): 994–95. http://dx.doi.org/10.1017/s042482010017270x.

Der volle Inhalt der Quelle

Annotation:

In electron diffraction patterns, diffuse scattering at high angles is primarily generated by phonon, or thermal diffuse, scattering (TDS). Techniques were introduced to acquire the electron energy-loss spectra (EELS) of high-angle thermal-diffuse-scattered electrons (TDS-EELS) in a transmission electron microscope (TEM). With regards to the scattering mechanism, the TDS-EELS core ionization edge intensity was believed to be generated primarily by TDS - single electron, double-inelastic electron scattering processes. It was concluded from experimental data that the signal from coupled phonon - atomic inner shell excitations is stronger than that from atomic inner shell excitation alone. A formal dynamical theory is presented in this paper to illustrate the theoretical basis of the experimental observations. The theory can be applied to calculate the diffraction patterns of inelastically double-scattered electrons and the signal intensity observed in TDS-EELS.TDS is actually a statistically averaged, quasi-elastic scattering of the electrons by the crystal lattice of different thermal vibration configurations.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

11

Yao, Nan, und J. M. Cowley. „Acceleration voltage effect on electron surface channeling“. Proceedings, annual meeting, Electron Microscopy Society of America 47 (06.08.1989): 530–31. http://dx.doi.org/10.1017/s0424820100154627.

Der volle Inhalt der Quelle

Annotation:

In transmission electron microscopy (TEM), the usable thickness of specimens increases with the incident electron energy. Some Bloch wave calculations of electron channelling along the zone axis in the transmission case show that the energy level for the channelled electrons increases (negatively) with the incident electron energy due to the correction for relativistic effect. Similarly, for reflection electron diffraction geometry, the faster the incident electrons, the deeper they penetrate into the surface. The diffraction patterns are expected to approach steadily to that for a three-dimensional lattice similar to the case of an increase in the angle of the incident electron beam. The potential distribution seen by incident electrons in the reflection geometry for an ideally perfect crystal surface should be similar to that for planes or rows in the transmission of electrons through thin crystal samples although some modifications due to the surface potential barriers have to be taken into account.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

12

Peng, L. M., und J. M. Cowley. „Reflection monolayer scattering and RHEED diffraction conditions“. Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988): 962–63. http://dx.doi.org/10.1017/s0424820100106879.

Der volle Inhalt der Quelle

Annotation:

In an infinite crystal, when the fast electrons are transmitted through the crystal, the effects of the periodic potential distribution on the incident electron wave can be best described by expanding the electron wavefunction in terms of propagating Bloch waves having the same periodicity as that of the crystal. The requirement for a three dimensional translation symmetry excludes the existence of evanescent Bloch waves with imaginary component of wave vector. With the presence of external surfaces, as in the case of reflection high energy electron diffraction (RHEED), the translation symmetry in the surface normal direction is broken. Bloch waves which are confined to the surface region in the form of damping waves in the surface normal direction are then allowed.In an ideal two-beam case, when the Bragg reflection condition is exactly satisfied, the incident electrons are totally reflected back into the vacuum from the surfaces of crystal, giving rise to an evanescent wave in the crystal and a standing wave outside in the vacuum.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

13

Eades, Alwyn. „Insights on Diffraction“. Microscopy Today 10, Nr. 2 (März 2002): 34–35. http://dx.doi.org/10.1017/s1551929500057874.

Der volle Inhalt der Quelle

Annotation:

This article presents ideas on some topics related to electron diffraction in the TEM. These are in regard to topics that I have come to think of as standard parts of what it means to do microscopy. However, they represent insights that not all users share (or even agree with, maybe).Kikuchi lines are of great use in orienting a sample. Unfortunately, in modern microscopes, Kikuchi lines are not seen in selected-area diffraction (SAD). This is because immersion lenses send parallel electrons, from different parts of the sample (like the Kikuchi lines from a flat specimen), to different places in the diffraction pattern.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

14

Moodie, A. F., und J. C. H. Spence. „John Maxwell Cowley 1923 - 2004“. Historical Records of Australian Science 17, Nr. 2 (2006): 227. http://dx.doi.org/10.1071/hr06012.

Der volle Inhalt der Quelle

Annotation:

John Cowley contributed significantly to all of the fields that relate to electron diffraction and electron microscopy, and helped to found not a few of them. His name is associated in particular with n-beam dynamical theory, high-resolution electron microscopy, scanning transmission electron microscopy, instrumental design, and the application of the techniques of electron scattering to structure analysis. His experimental work was not, however, confined to the scattering of electrons: to take but one instance, his seminal work on the theory of short-range order was stimulated initially by his experiments using X-rays, and it was only later that he extended the technique to include electron diffraction. Finally, to all those who practise the techniques of scattering electrons, X-rays, or neutrons in the study of solids, liquids or gases, his book Diffraction Physics remains not only eminently readable but authoritative.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

15

Issanova, M. K., S. K. Kodanova, T. S. Ramazanov, N. Kh Bastykova, Zh A. Moldabekov und C. V. Meister. „Classical scattering and stopping power in dense plasmas: the effect of diffraction and dynamic screening“. Laser and Particle Beams 34, Nr. 3 (27.06.2016): 457–66. http://dx.doi.org/10.1017/s026303461600032x.

Der volle Inhalt der Quelle

Annotation:

AbstractIn the present work, classical electron–ion scattering, Coulomb logarithm, and stopping power are studied taking into account the quantum mechanical diffraction effect and the dynamic screening effect separately and together. The inclusion of the quantum diffraction effect is realized at the same level as the well-known first-order gradient correction in the extended Thomas–Fermi theory. In order to take the effect of dynamic screening into account, the model suggested by Grabowski et al. in 2013 is used. Scattering as well as stopping power of the external electron (ion) beam by plasma ions (electrons) and scattering of the plasma's own electrons (ions) by plasma ions (electrons) are considered differently. In the first case, it is found that in the limit of the non-ideal plasma with a plasma parameter Γ → 1, the effects of quantum diffraction and dynamic screening partially compensate each other. In the second case, the dynamic screening enlarges scattering cross-section, Coulomb logarithm, and stopping power, whereas the quantum diffraction reduces their values. Comparisons with the results of other theoretical methods and computer simulations indicate that the model used in this work gives a good description of the stopping power for projectile velocities $v\,{\rm \lesssim}\, 1.5 v_{{\rm th}}$, where vth is the thermal velocity of the plasma electrons.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

16

Ren, S. X., E. A. Kenik, K. B. Alexander und A. Goyal. „Exploring Spatial Resolution in Electron Back-Scattered Diffraction Experiments via Monte Carlo Simulation“. Microscopy and Microanalysis 4, Nr. 1 (Februar 1998): 15–22. http://dx.doi.org/10.1017/s1431927698980011.

Der volle Inhalt der Quelle

Annotation:

A Monte Carlo model was used to simulate specimen-electron beam interactions relevant to electron back-scattered diffraction (EBSD). Electron trajectories were calculated for a variety of likely experimental conditions to examine the interaction volume of the incident electrons as well as that of the subset of incident electrons that emerge from the specimen, i.e., back-scattered electrons (BSEs). The spatial resolution of EBSD was investigated as functions of both materials properties, such as atomic number, atomic weight, and density, and experimental parameters, such as specimen thickness, tilt, and incident beam accelerating voltage. These simulations reveal that the achievable spatial resolution in EBSD is determined by these intrinsic and extrinsic parameters.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

17

Reimer, L. „Electron Spectroscopic Imaging and Diffraction in TEM“. Proceedings, annual meeting, Electron Microscopy Society of America 48, Nr. 2 (12.08.1990): 66–67. http://dx.doi.org/10.1017/s0424820100133928.

Der volle Inhalt der Quelle

Annotation:

Energy-filtering electron microscopy at 80 keV (ZEISS EM902) offers the combination of electron spectroscopic imaging (ESI) and diffraction (ESD) and electron energy-loss spectroscopy (EELS). For details the reader is referred to a description of the different modes, applications of ESI to biological and crystalline specimens and of ESD. The very important mode of elemental mapping with the difference of ESI below and beyond an edge will not be discussed in this review.The ESI mode increases scattering contrast of stained and unstained biological sections and avoids chromatic aberration by zero-loss filtering. Filtering at ΔE=250 eV below the C edge increases the (structure-sensitive) contrast by non-carbon atoms of unstained sections (Fig.1). Phase contrast is also increased but inelastically scattered electrons show a faint phase contrast which can be explained by treating partial inelastic waves with different q as incoherent. Bragg contrast of crystalline specimens is enhanced due to avoiding chromatic aberration and a blurring by the spectrum of excitation errors of inelastically scattered electrons (Fig.2).

APA, Harvard, Vancouver, ISO und andere Zitierweisen

18

Mayer, J. „Electron spectroscopic imaging and diffraction: applications II materials science“. Proceedings, annual meeting, Electron Microscopy Society of America 50, Nr. 2 (August 1992): 1198–99. http://dx.doi.org/10.1017/s0424820100130626.

Der volle Inhalt der Quelle

Annotation:

With imaging energy filters becoming commercially available in transmission electron microscopy many of the limitations of conventional TEM instruments can be overcome. Energy filtered images of diffraction patterns can now be recorded without scanning using efficient parallel (2-dimensional detection. We have evaluated a prototype of the Zeiss EM 912 Omega, the first commercially available electron microscope with integrated imaging Omega energy filter. Combining the capabilities of the imaging spectrometer with the principal operation modes of a TEM gives access to many new qualitative and quantitative techniques in electron microscopy. The basis for all of them is that the filter selecte electrons within a certain energy loss range ΔE1 <ΔE < ΔE2 and images their contribution to an image (electron spectroscopic imaging, ESI) or a diffraction pattern (electron spectroscopic diffraction, ESD) In many applications the filter is only used to remove the inelastically scattered electrons (elastic or zero loss filtering). Furthermore, the electron energy loss spectrum can be magnified and recorded with serial or parallel detection.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

19

Latychevskaia, Tatiana. „Holography and Coherent Diffraction Imaging with Low-(30–250 eV) and High-(80–300 keV) Energy Electrons: History, Principles, and Recent Trends“. Materials 13, Nr. 14 (10.07.2020): 3089. http://dx.doi.org/10.3390/ma13143089.

Der volle Inhalt der Quelle

Annotation:

In this paper, we present the theoretical background to electron scattering in an atomic potential and the differences between low- and high-energy electrons interacting with matter. We discuss several interferometric techniques that can be realized with low- and high-energy electrons and which can be applied to the imaging of non-crystalline samples and individual macromolecules, including in-line holography, point projection microscopy, off-axis holography, and coherent diffraction imaging. The advantages of using low- and high-energy electrons for particular experiments are examined, and experimental schemes for holography and coherent diffraction imaging are compared.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

20

Völkl, E., L. F. Allard, B. Frost und T. A. Nolan. „Quanitative aspects of electron diffraction using electron holography“. Proceedings, annual meeting, Electron Microscopy Society of America 53 (13.08.1995): 616–17. http://dx.doi.org/10.1017/s0424820100139457.

Der volle Inhalt der Quelle

Annotation:

Off-axis electron holography has the well known ability to preserve the complex image wave within the final, recorded image. This final image described by I(x,y) = I(r) contains contributions from the image intensity of the elastically scattered electrons IeI (r) = |A(r) exp (iΦ(r)) |, the contributions from the inelastically scattered electrons IineI (r), and the complex image wave Ψ = A(r) exp(iΦ(r)) as:(1) I(r) = IeI (r) + Iinel (r) + μ A(r) cos(2π Δk r + Φ(r))where the constant μ describes the contrast of the interference fringes which are related to the spatial coherence of the electron beam, and Φk is the resulting vector of the difference of the wavefront vectors of the two overlaping beams. Using a software package like HoloWorks, the complex image wave Ψ can be extracted.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

21

March, N. H., und M. P. Tosi. „Diffraction and transport in dense plasmas: Especially liquid metals“. Laser and Particle Beams 16, Nr. 1 (März 1998): 71–81. http://dx.doi.org/10.1017/s0263034600011782.

Der volle Inhalt der Quelle

Annotation:

Recent computer experiments on liquid Mg and Bi (and also on dense hydrogen) have focussed anew on issues involving static and dynamical structure in plasmas. In Mg and Bi, under normal liquid metal conditions, separation of core and valence electrons is valuable both for thermodynamics and in interpreting diffraction experiments. Mg is considered in some detail as a specific example where there is weak electron–ion interaction. Finally, dynamical structure is considered. After a brief summary relating back to the electron–electron pair correlation contribution in X-ray scattering, attention is next focussed on the (longitudinal) viscosity of alkali metals via the Kubo formula. This viscosity is shown to be dominated by ion–ion interactions. Nevertheless, an intimate relation at the melting point is exposed between shear viscosity, thermal conductivity, and electrical resistivity, the latter two transport coefficients being dominated by electrons.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

22

Slouf, Miroslav, Radim Skoupy, Ewa Pavlova und Vladislav Krzyzanek. „Powder Nano-Beam Diffraction in Scanning Electron Microscope: Fast and Simple Method for Analysis of Nanoparticle Crystal Structure“. Nanomaterials 11, Nr. 4 (09.04.2021): 962. http://dx.doi.org/10.3390/nano11040962.

Der volle Inhalt der Quelle

Annotation:

We introduce a novel scanning electron microscopy (SEM) method which yields powder electron diffraction patterns. The only requirement is that the SEM microscope must be equipped with a pixelated detector of transmitted electrons. The pixelated detectors for SEM have been commercialized recently. They can be used routinely to collect a high number of electron diffraction patterns from individual nanocrystals and/or locations (this is called four-dimensional scanning transmission electron microscopy (4D-STEM), as we obtain two-dimensional (2D) information for each pixel of the 2D scanning array). Nevertheless, the individual 4D-STEM diffractograms are difficult to analyze due to the random orientation of nanocrystalline material. In our method, all individual diffractograms (showing randomly oriented diffraction spots from a few nanocrystals) are combined into one composite diffraction pattern (showing diffraction rings typical of polycrystalline/powder materials). The final powder diffraction pattern can be analyzed by means of standard programs for TEM/SAED (Selected-Area Electron Diffraction). We called our new method 4D-STEM/PNBD (Powder NanoBeam Diffraction) and applied it to three different systems: Au nano-islands (well diffracting nanocrystals with size ~20 nm), small TbF3 nanocrystals (size < 5 nm), and large NaYF4 nanocrystals (size > 100 nm). In all three cases, the STEM/PNBD results were comparable to those obtained from TEM/SAED. Therefore, the 4D-STEM/PNBD method enables fast and simple analysis of nanocrystalline materials, which opens quite new possibilities in the field of SEM.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

23

Katsap, Victor. „A novel thermionic crystal electron emission effect similar to Kikuchi lines“. Journal of Vacuum Science & Technology B 41, Nr. 1 (Januar 2023): 010602. http://dx.doi.org/10.1116/6.0002375.

Der volle Inhalt der Quelle

Annotation:

Kikuchi lines, known since 1928 [S. Kikuchi, Jpn. J. Phys. 5, 83 (1928)], are generated by irradiating a crystal with high-energy e-beam in SEM or TEM and observing backscattered electrons diffraction on crystalline planes. The Kikuchi line effect gave rise to several useful tools in electron microscopy of crystalline and nanocrystalline materials [K. Saruwatari, et al., J. Mineral. Petrol. Sci. 103, 16 (2007)]. We have discovered a similar diffraction effect but of the crystal’ own thermally emitted electrons.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

24

Michael, J. R., M. E. Schlienger und R. P. Goehner. „Electron Backscatter Diffraction In The Sem: Is Electron Diffraction In The Tem Obsolete?“ Microscopy and Microanalysis 3, S2 (August 1997): 879–80. http://dx.doi.org/10.1017/s1431927600011284.

Der volle Inhalt der Quelle

Annotation:

The technique of electron backscatter diffraction (EBSD) in the scanning electron microscope is currently finding a large number of important applications in materials science. The patterns formed through EBSD were first studied over 40 years ago. It has only been in the last 10 years that the technique has really begun to have an impact on the study of materials. The introduction of automatic pattern indexing software has enabled the technique to be used for mapping the orientation of a polycrystalline sample. The more exciting and universally interesting application of the technique has been the identification of micron and sub-micron sized crystalline phases based on their chemistry and crystallography determined by EBSD.EBSD is obtained by illuminating a highly tilted sample (>45° from horizontal) with a stationary electron beam. Electrons backscattered from the sample may satisfy the condition for channeling and will produce images that contain bands of increased and decreased intensity that are equivalent to electron channeling patterns.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

25

Beeby, J. L. „Plasmon emission by electrons in reflection high energy electron diffraction“. Surface Science 565, Nr. 2-3 (September 2004): 129–43. http://dx.doi.org/10.1016/j.susc.2004.06.175.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

26

Winkelmann, Aimo, Koceila Aizel und Maarten Vos. „Electron energy loss and diffraction of backscattered electrons from silicon“. New Journal of Physics 12, Nr. 5 (05.05.2010): 053001. http://dx.doi.org/10.1088/1367-2630/12/5/053001.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

27

Reimer, L., und I. Fromm. „Electron spectroscopic diffraction at (111) silicon foils“. Proceedings, annual meeting, Electron Microscopy Society of America 47 (06.08.1989): 382–83. http://dx.doi.org/10.1017/s0424820100153889.

Der volle Inhalt der Quelle

Annotation:

An electron diffraction pattern (EDP) consists of an overlap of patterns of all energy losses in the electron energy-loss spectrum (EELS). Electron spectroscopic diffraction (ESD) in an energy filtering electron microscope (EFEM) allows to separate the contributions of different energy losses to the unfiltered diagram observed in conventional TEM. We report about diffraction experiments with a Zeiss EM902 on (111) silicon foils which show how the EDP of single-crystal foils changes with increasing energy loss and foil thickness. An EDP normally contains the Bragg spots, diffuse streaks by electron-phonon scattering, excess and defect Kikuchi lines when the number of electrons striking the lattice planes is different from opposite sites, a system of excess (bright) Kikuchi bands with an intensity proportional to the probability ψψ⋆ of the Bloch wave field at the nuclei, and defect Ki-kuchi bands when the number of diffusely scattered electrons is equal on both sides of the lattice plane and the intensity becomes proportional to ΣIg.EDPs of thin foils show an increase of contrast of the Bragg spots and the thermal diffuse streaks when comparing an unfiltered (Fig.1a) and zero-loss filtered EDP (Fig.1b). Because the streaks are caused by elastic scattering, they can not be ob served with the plasmon loss (Fig.1c). Bragg spots are also observed at higher energy losses because all delocalized inelastic scattering processes with energy losses less a few hundred eV show intraband transitions which preserve the type of excited Bloch waves.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

28

Li, Huawang. „Double-slit interference and single-slit diffraction experiments on electrons“. Physics Essays 35, Nr. 3 (03.09.2022): 313–19. http://dx.doi.org/10.4006/0836-1398-35.3.313.

Der volle Inhalt der Quelle

Annotation:

De Broglie proposed the matter wave in 1924. The de Broglie wave is neither a mechanical wave nor an electromagnetic wave and has a very short wavelength. The Davisson-Germer electron diffraction experiment performed in 1925 involved bombarding the surface of a nickel crystal with a narrow beam of electrons. When the accelerating voltage V was maintained at 54 V, the wavelength of the incident electron was λ=h/ <mml:math display="inline"> <mml:msqrt> <mml:mn>2</mml:mn> <mml:mi mathvariant="normal">m</mml:mi> <mml:mi mathvariant="normal">e</mml:mi> <mml:mi mathvariant="normal">V</mml:mi> </mml:msqrt> </mml:math> = 0.167 nm [Y. S. Chen and Z. Z. Li, College Physics (Tianjin University, Tianjin, 1999)] demonstrating the existence of the matter wave. We introduce a type of electron wave with a very long wavelength in this study that is different from the matter wave. For example, the wavelength of the electron wave can reach 0.43 mm in the double-slit interference of electrons. Experiments demonstrate that this long-wavelength electron wave can produce both double-slit interference and electron diffraction. A comparative analysis of matter and electron waves reveals the physical natures of these waves and wave‐particle duality.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

29

Lehman, J. L., J. Mayer und W. Probst. „Application of the Omega spectrometer TEM“. Proceedings, annual meeting, Electron Microscopy Society of America 50, Nr. 2 (August 1992): 1042–43. http://dx.doi.org/10.1017/s042482010012984x.

Der volle Inhalt der Quelle

Annotation:

The recent development of an analytical TEM with an integrated imaging Omega spectrometer has opened the door to a new world of specimen information. The Omega Spectrometer eliminates some of the information limits which have been imposed by the chromatic aberration effects in thick 3-D specimen imaging, as well as thermal diffuse and inelastic scattering in electron diffraction studies. This benefits both the TEM 3-D imaging and electron diffraction fields.Inelastically scattered electrons are electrons which have lost some of their energy while passing through the specimen. In all conventional TEMs, these inelastically scattered electrons inherently cause the final image to be blurry as the objective lens focuses the different energies into different image planes. The chromatic aberration of the objective lens can be calculated by the simple equation, Δc = Cc .α.ΔE/E, where ΔE is the energy spread of the electrons leaving the specimen, and E is the energy of the electrons entering the specimen. The chromatic aberration of the objective lens can be reduced by increasing the value of E or limiting ΔE.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

30

Wang, Z. L. „Diffraction theory of phonon-scattered electrons“. Proceedings, annual meeting, Electron Microscopy Society of America 49 (August 1991): 788–89. http://dx.doi.org/10.1017/s0424820100088257.

Der volle Inhalt der Quelle

Annotation:

Electron-phonon interactions are inelastic scattering processes in high-energy electron diffraction, and are responsible for thermal diffuse scattering (TDS). The atomic thermal vibrations introduce a small time-dependent perturbation to the crystal potential(1)where is the displacement of the atom (at position within the hth unit cell (position R(h)) from its equilibrium position,(2)

APA, Harvard, Vancouver, ISO und andere Zitierweisen

31

Ascolani, H., R. O. Barrachina, M. M. Guraya und G. Zampieri. „Diffraction of electrons at intermediate energies“. Physical Review B 46, Nr. 8 (15.08.1992): 4899–908. http://dx.doi.org/10.1103/physrevb.46.4899.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

32

Fant, G. Y. „Multislice calculation of Kikuchi patterns“. Proceedings, annual meeting, Electron Microscopy Society of America 47 (06.08.1989): 52–53. http://dx.doi.org/10.1017/s0424820100152239.

Der volle Inhalt der Quelle

Annotation:

The diffraction of the inelastically and pseudo-elastically scattered electrons in a crystal gives rise to the diffuse background in a diffraction pattern, including Kikuchi patterns as they are known, which are very sensitive to the direction of electron incidence relative to the crystal orientation. In the exact zone orientation, i.e., when the electrons are travelling along a major zone axis, a Kikuchi-band pattern is formed which reflects the crystal symmetry about that axis; otherwise, the pattern is known as Kikuchi-line pattern (thereafter collectively referred to as K-patterns).For localized inelastic events, such as interactions of incident electrons with shell electrons and various crystal point defects, in which intra-process coherence is negligible, the K-patterns can be simulated using the method described below.An inelastic event creates a spherical wave which, however, is strongly peaked in the forward direction of electron traveling, as given by the typical form f(θ)e-kr/r, where symbols have their usual meanings.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

33

Tivol, W. F., J. N. Turner und D. L. Dorset. „Ab initio structure analysis of copper perbromophthalocyanine“. Proceedings, annual meeting, Electron Microscopy Society of America 50, Nr. 2 (August 1992): 1446–47. http://dx.doi.org/10.1017/s0424820100131863.

Der volle Inhalt der Quelle

Annotation:

The use of high-energy (1200 kV) electrons has been shown to be advantageous in the ab initio structure analysis from electron diffraction of organic compounds. Dynamical scattering from compounds containing heavy atoms may make such an analysis difficult or impossible with data obtained at conventional voltages. In the case that even high-energy electrons do not produce diffraction intensities sufficiently close to the kinematic values, criteria other than the simple minimization of the R-factor must be used to seek the correct structure solution.Copper perbromophthalocyanine (Cu-BrPTCY) was grown epitaxially from the vapor phase onto a clean KCl crystal face. Electron diffraction patterns were obtained from crystals tilted at 26.5° and oriented so that the electron beam was parallel to the c-axis. The AEI EM7 high-voltage electron microscope was used at a voltage of 1200 kV in diffraction mode with a 10 μm selected area aperture. The data were obtained using a minimal electron dose and recorded on DuPont Lo-dose Mammography film (See Fig. 1). Intensities were measured on a Joyce-Loebl MkIIIC flat bed microdensitometer by integrating under the peaks.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

34

Mei, Kaili, Kejia Zhang, Jungu Xu und Zhengyang Zhou. „The Application of 3D-ED to Distinguish the Superstructure of Sr1.2Ca0.8Nb2O7 Ignored in SC-XRD“. Crystals 13, Nr. 6 (08.06.2023): 924. http://dx.doi.org/10.3390/cryst13060924.

Der volle Inhalt der Quelle

Annotation:

Compared to X-rays, electrons have stronger interactions with matter. In electron diffraction, the low-order structure factors are sensitive to subtle changes in the arrangement of valence electrons around atoms when the scattering vector is smaller than the critical scattering vector. Therefore, electron diffraction is more advantageous for studying the distribution of atoms in the structure with atomic numbers smaller than that of sulfur. In this work, the crystal structure of Sr1.2Ca0.8Nb2O7 (SCNO-0.8) was analyzed using single-crystal X-ray diffraction (SC-XRD) and three-dimensional electron diffraction (3D-ED) techniques, respectively. Interestingly, the superstructure could only be identified by the 3D-ED technique, while no signal corresponding to the superstructure was detected from the SC-XRD data. The superstructure in SCNO-0.8 was disclosed to be caused by different tilting of NbO6 octahedra and the displacements of Sr/Ca atoms in the different atomic layers perpendicular to the a-axis. Therefore, the application of 3D-ED provides an effective method for studying superstructures caused by ordered arrangements of light atoms.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

35

Sakakura, Terutoshi, Takahiro Nakano, Hiroyuki Kimura, Yukio Noda, Yoshihisa Ishikawa, Yasuyuki Takenaka, Kiyoaki Tanaka, Shunji Kishimoto, Yoshinori Tokura und Shigeki Miyasaka. „Importance of multiple diffraction avoidance for charge density observation“. Acta Crystallographica Section A Foundations and Advances 70, a1 (05.08.2014): C280. http://dx.doi.org/10.1107/s2053273314097198.

Der volle Inhalt der Quelle

Annotation:

It might not be well recognized, most reflections are contaminated by multiple diffractions (MD). Therefore high redundancy data could not coincide with high accuracy data when MDs are not avoided. We collected both data set of MD-avoided and no MD-avoided ones and investigated its effectiveness in electron density measurement. For data collection, four-circle diffractometer at KEK-PF BL14A (Tsukuba, Japan) was used. In MD-avoided measurement, each reflection is collected at angle setting of least of MD contamination which calculated by psi-scan simulation software MDC [1]. In no MD-avoided measurement, usual bisect setting were used. In no MD-avoided measurement, intensities of forbidden reflections of YMn2O5 are more than 10 times largely observed than for MD-avoided one, and resulting residual density map is also highly contaminated reflecting the tendency of Fo>>Fc which is typical for reflections of weak intensity. Figure 1 shows this situation. Figure 2 is the deformation density of YTiO3 for MD-avoided data. Where model density of without Ti-3d1 valence electrons is subtracted from experimentally observed electron density. In the figure, quenching of angular momentum of Ti-3d1 electron is clearly observed. Although Rint could not be an ideal indicator of data accuracy since it cannot perceive Fo>>Fc, Rint(F) of MD-avoided measurement for YTiO3 is significantly reduced to ~0.5%. For no MD-avoided one, Rint(F) is ~1.2%. Since accuracy of MD-avoidance technique is confirmed, the next step is to exploit informations of only a few numbers of valence electrons among F(000) electrons. To accomplish this, wave function based refinement such as XAO [2] should be applied and studied.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

36

Qin, L. C., und L. D. Marks. „Electron diffraction contrast of fluxons“. Proceedings, annual meeting, Electron Microscopy Society of America 49 (August 1991): 1102–3. http://dx.doi.org/10.1017/s0424820100089822.

Der volle Inhalt der Quelle

Annotation:

Partial penetration of an applied external magnetic field occurs in type-II superconductors. The properties of magnetic fluxons are important in determining the critical current density of type-II superconductors as it is the mobility of the fluxon lattice that limits the high value of critical current density of superconductors. There have been various experimental techniques in use to study the fluxons, e.g. the decoration technique, neutron diffraction, electron holography and scanning tunneling microscopy.Noting that in the thin crystal case the magnetic fluxes have a tangential component which deflects incident electrons, we explore the possibility of using conventional electron diffraction contrast technique to observe the fluxons. This is accomplished by using the London model for the vortex in thin crystals and the classical electromagnetic theory based on Maxwell equations to construct the magnetic field of a fluxon.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

37

Vincent, R. „Analysis of multiple diffraction contrast“. Proceedings, annual meeting, Electron Microscopy Society of America 45 (August 1987): 48–51. http://dx.doi.org/10.1017/s0424820100125270.

Der volle Inhalt der Quelle

Annotation:

Transmission microscopy of modern alloys, ceramics and semiconductor/metal contact/insulator assemblies often discloses unfamiliar crystalline compounds, either uncharted on the relevant phase diagrams (if available) or metastable. Although the standard technigues of convergent beam electron diffraction (CBED) are sufficient to establish the space group, further progress towards defining the contents of the unit cell requires at least some qualitative estimate of the structure factors F, which are obscured by the varieties of multiple diffraction paths followed by electrons. However, modern analytical microscopes contain condenser-objective optics which focus the electron beam into a probe with a large convergence angle (∼0.1 rad). Although the bright- and dark-field (BF and DF) discs in these CBED patterns inevitably overlap, suitable aperturing is sufficient to transmit only the large-angle pattern from the direct or from any diffracted beam.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

38

Mancuso, James F., Leo A. Fama, William B. Maxwell, Jerry L. Lehman, Hasso Weiland und Ronald R. Biederman. „Effect of energy filtering on micro-diffraction in the SEM“. Proceedings, annual meeting, Electron Microscopy Society of America 52 (1994): 604–5. http://dx.doi.org/10.1017/s042482010017075x.

Der volle Inhalt der Quelle

Annotation:

Micro-diffraction based crystallography is essential to the design and development of many classes of ‘crafted materials’. Although the scanning electron microscope can provide crystallographic information with high spatial resolution, its current utility is severely limited by the low sensitivity of existing diffraction techniques (ref: Dingley). Previously, Joy showed that energy filtering increased contrast and pattern visibility in electron channelling. This present paper discribes the effect of energy filtering on EBSP sensitivity and backscattered SEM imaging.The EBSP detector consisted of an electron energy filter, a microchannel plate detector, a phosphor screen, optical coupler, and a slow scan CCD camera. The electrostatic energy filter used in this experiment was constructed as a cone with 5 coaxial electrodes. The angular field-of-view of the filter was approximately 38°. The microchannel plate, which was the initial sensing component, had high gain and had 50% to 80% detection efficiency for the low energy electrons that passed through the retarding field filter.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

39

Lee, M. R. „Transmission electron microscopy (TEM) of Earth and planetary materials: A review“. Mineralogical Magazine 74, Nr. 1 (Februar 2010): 1–27. http://dx.doi.org/10.1180/minmag.2010.074.1.1.

Der volle Inhalt der Quelle

Annotation:

AbstractUsing high intensity beams of fast electrons, the transmission electron microscope (TEM) and scanning transmission electron microscope (STEM) enable comprehensive characterization of rocks and minerals at micrometre to sub-nanometre scales. This review outlines the ways in which samples of Earth and planetary materials can be rendered sufficiently thin for TEM and STEM work, and highlights the significant advances in site-specific preparation enabled by the focused ion beam (FIB) technique. Descriptions of the various modes of TEM and STEM imaging, electron diffraction and X-ray and electron spectroscopy are outlined, with an emphasis on new technologies that are of particular relevance to geoscientists. These include atomic-resolution Z-contrast imaging by high-angle annular dark-field STEM, electron crystallography by precession electron diffraction, spectrum mapping using X-rays and electrons, chemical imaging by energy-filtered TEM and true atomic-resolution imaging with the new generation of aberration-corrected microscopes. Despite the sophistication of modern instruments, the spatial resolution of imaging, diffraction and X-ray and electron spectroscopy work on many natural materials is likely to remain limited by structural and chemical damage to the thin samples during TEM and STEM.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

40

ZHANG, S. Y., Y. K. HO, Z. CHEN, Y. J. XIE, Z. YAN und J. J. XU. „DYNAMIC TRAJECTORIES OF RELATIVISTIC ELECTRONS INJECTED INTO TIGHTLY-FOCUSED INTENSE LASER FIELDS“. Journal of Nonlinear Optical Physics & Materials 13, Nr. 01 (März 2004): 103–12. http://dx.doi.org/10.1142/s0218863504001785.

Der volle Inhalt der Quelle

Annotation:

Dynamic trajectories of relativistic electrons injected into tightly focused ultra-intense laser field have been investigated. In addition to the previously-reported CAS (Capture and Acceleration Scenario) and IS (Inelastic Scattering) trajectories, a new kind of nonlinear electron trajectory is found when the beam waist radius w0 is small enough (kw0≤30, k is the wave number) and incident angle is small. We shall call it PARM (Penetrate into Axial Region and Move). The basic feature of PARM trajectory shows the strong diffraction effect of a tightly-focused laser field. Part of the incident electrons that experience the strong transversal force from the diffraction edge field as they travel toward the beam waist will follow the PARM trajectory. This force can push the electrons toward the beam center. Thus unlike the CAS and IS electrons, the PARM electrons will move along the region near the beam axis. We also found some of the PARM electrons can gain energy from the field. The conditions for PARM electrons to appear were examined and are presented here. The implication of the presence of PARM to the planned experimental test of the CAS scheme is addressed.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

41

Wang, Z. L. „Towards quantitative simulations of inelastic electron diffraction patterns and images“. Proceedings, annual meeting, Electron Microscopy Society of America 50, Nr. 2 (August 1992): 1170–71. http://dx.doi.org/10.1017/s0424820100130481.

Der volle Inhalt der Quelle

Annotation:

A new dynamical theory has been developed based on Yoshioka's coupled equations for describing inelastic electron scattering in thin crystals. Compared to existing theories, the primary advantage of this theory is that the incoherent summation of the diffracted intensities contributed by electrons after exciting vast numbers of different excited states has been evaluated before any numerical calculation. An additional advantage is that the phase correlations of atomic vibrations are considered, so that full lattice dynamics can be combined in the phonon scattering calculation. The new theory has been proven to be equivalent to the inelastic multislice theory, and has been applied to calculate energy-filtered diffraction patterns and images formed by phonon, single electron and valence scattered electrons.A calculated diffraction pattern of elastic and phonon scattered electrons for a parallel incident beam case is in agreement with the one observed (Fig. 1), showing thermal diffuse scattering (TDS) streaks and Kikuchi pattern.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

42

He, Y., L. M. Yu, P. A. Thiry und R. Caudano. „Negative Ion Resonance Evidenced by Vibrationally Resolved Electron Diffraction On the H/Si(111) Surface“. Surface Review and Letters 05, Nr. 01 (Februar 1998): 63–67. http://dx.doi.org/10.1142/s0218625x98000141.

Der volle Inhalt der Quelle

Annotation:

The surface vibrations of H-terminated Si(111) are investigated by high resolution electron energy loss spectroscopy (HREELS). Clear evidence is obtained for reassigning the electron resonant scattering from a surface resonance to a negative ion resonance mechanism. Since the electrons emitted from the trapping states show characteristic angular diffraction patterns realated with the geometric and vibrational symmetries of the surface, we suggest the possibility of using this system to investigate vibrationally resolved electron diffraction processes.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

43

Zou, Xiaodong, und Sven Hovmöller. „Structure Determination at Atomic Resolution by Electron Crystallography“. Proceedings, annual meeting, Electron Microscopy Society of America 48, Nr. 1 (12.08.1990): 44–45. http://dx.doi.org/10.1017/s0424820100178975.

Der volle Inhalt der Quelle

Annotation:

Structure determination by electron microscopy is emerging as a serious competitor to the classical methods of X-ray diffraction. The main advantage of EM is that the phase information is restored in the image, whereas with X-ray diffraction it is lost.The structure determination of an inorganic crystal by electron microscopy would be trivial if the micrograph was just a magnified image of the electron density in the crystal. Unfortunately it is not. A limited number of non-linear effects distort the image. These effects can be divided into two parts; those arising already in the crystal and those that are due to optical distortions. For a crystal one unit cell thick the wave front at the exit surface of the crystal is a linear function of the electron density within the unit cell. As the crystals become thicker more and more of the diffracted electrons will have been doubly diffracted, making the image no longer a linear function of the electron density. For crystals thinner than half the mean free path for electrons most of the scattered electrons are still scattered only once, making the image interpretable.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

44

Takubo, Kou, Samiran Banu, Sichen Jin, Misaki Kaneko, Wataru Yajima, Makoto Kuwahara, Yasuhiko Hayashi et al. „Generation of sub-100 fs electron pulses for time-resolved electron diffraction using a direct synchronization method“. Review of Scientific Instruments 93, Nr. 5 (01.05.2022): 053005. http://dx.doi.org/10.1063/5.0086008.

Der volle Inhalt der Quelle

Annotation:

To investigate photoinduced phenomena in various materials and molecules, ultrashort pulsed x-ray and electron sources with high brightness and high repetition rates are required. The x-ray and electron’s typical and de Broglie wavelengths are shorter than lattice constants of materials and molecules. Therefore, photoinduced structural dynamics on the femtosecond to picosecond timescales can be directly observed in a diffraction manner by using these pulses. This research created a tabletop ultrashort pulsed electron diffraction setup that used a femtosecond laser and electron pulse compression cavity that was directly synchronized to the microwave master oscillator (∼3 GHz). A compressed electron pulse with a 1 kHz repetition rate contained 228 000 electrons. The electron pulse duration was estimated to be less than 100 fs at the sample position by using photoinduced immediate lattice changes in an ultrathin silicon film (50 nm). The newly developed time-resolved electron diffraction setup has a pulse duration that is comparable to femtosecond laser pulse widths (35–100 fs). The pulse duration, in particular, fits within the timescale of photoinduced phenomena in quantum materials. Our developed ultrafast time-resolved electron diffraction setup with a sub-100 fs temporal resolution would be a powerful tool in material science with a combination of optical pump–probe, time-resolved photoemission spectroscopic, and pulsed x-ray measurements.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

45

BONDARCHUCK, O., S. GOYSA, I. KOVAL, P. MEL'NIK und M. NAKHODKIN. „SHORT-RANGE ORDER OF DISORDERED SOLID SURFACES FROM ELASTICALLY SCATTERED ELECTRON SPECTRA“. Surface Review and Letters 04, Nr. 05 (Oktober 1997): 965–67. http://dx.doi.org/10.1142/s0218625x97001139.

Der volle Inhalt der Quelle

Annotation:

The diffraction phenomenon of low- and middle-energy electrons for disordered solid surfaces was experimentally studied and a new electron spectroscopy technique for surface short-range order parameter determination proposed.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

46

Li, Pen-Xin, Ai-Yun Yang, Lang Xin, Biao Xue und Chun-Hao Yin. „Photocatalytic Activity and Mechanism of Cu²⁺ Doped ZnO Nanomaterials“. Science of Advanced Materials 14, Nr. 10 (01.10.2022): 1599–604. http://dx.doi.org/10.1166/sam.2022.4363.

Der volle Inhalt der Quelle

Annotation:

The photocatalytic activity and mechanism of photocatalysts made of ZnO nanoparticles before and after doping with different Cu2+ concentrations were studied by electron paramagnetic resonance and X-ray diffraction. The nanoparticles were prepared using sol–gel method. UV-vis spectrometers characterized the photocatalytic degradation effect of the composite samples on methyl orange solution. The results of X-ray diffraction showed that the hexagonal wurtzite structure of ZnO changed little by Cu2+ doping. With the increase in doping concentration, the CuO and Cu2O diffraction peaks were detected successively in the crystal. The results of the electron paramagnetic resonance test for all samples indicated three kinds of unpaired electrons with g factors of 2.07, 1.997, and 1.954. Further analysis confirmed them to be Cu2+, V+O, and Zn–H complexes. Photocatalytic degradation results of methyl orange showed that proper doping (c(Cu2+) = 2%) could improve the photocatalytic activity of ZnO. The main reason for the increase was that the substitution of Cu2+ for Zn2+ in the crystal lattice produced Zni, and the Zn atom could act as the donor to release electrons, so that the number of electrons in the material increased, which indirectly increased the superoxide radical content in the solution and improves the photocatalytic activity of ZnO.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

47

Yang, Jinfeng, Kazuki Gen, Nobuyasu Naruse, Shouichi Sakakihara und Yoichi Yoshida. „A Compact Ultrafast Electron Diffractometer with Relativistic Femtosecond Electron Pulses“. Quantum Beam Science 4, Nr. 1 (20.01.2020): 4. http://dx.doi.org/10.3390/qubs4010004.

Der volle Inhalt der Quelle

Annotation:

We have developed a compact relativistic femtosecond electron diffractometer with a radio-frequency photocathode electron gun and an electron lens system. The electron gun generated 2.5-MeV-energy electron pulses with a duration of 55 ± 5 fs containing 6.3 × 104 electrons per pulse. Using these pulses, we successfully detected high-contrast electron diffraction images of single crystalline, polycrystalline, and amorphous materials. An excellent spatial resolution of diffraction images was obtained as 0.027 ± 0.001 Å−1. In the time-resolved electron diffraction measurement, a laser-excited ultrafast electronically driven phase transition in single-crystalline silicon was observed with a temporal resolution of 100 fs. The results demonstrate the advantages of the compact relativistic femtosecond electron diffractometer, including access to high-order Bragg reflections, single shot imaging with the relativistic femtosecond electron pulse, and the feasibility of time-resolved electron diffraction to study ultrafast structural dynamics.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

48

Gerchikov, Leonid G., Peotr V. Efimov, Valerii M. Mikoushkin und Andrey V. Solov'yov. „Diffraction of Fast Electrons on the FullereneC60Molecule“. Physical Review Letters 81, Nr. 13 (28.09.1998): 2707–10. http://dx.doi.org/10.1103/physrevlett.81.2707.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

49

Ran, Ke, Jian-Min Zuo, Qing Chen und Zujin Shi. „Electrons for single molecule diffraction and imaging“. Ultramicroscopy 119 (August 2012): 72–77. http://dx.doi.org/10.1016/j.ultramic.2011.11.007.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

50

Pierce, Jordan, Cameron Johnson und Benjamin McMorran. „Corrected Off-axis Diffraction Holograms for Electrons“. Microscopy and Microanalysis 26, S2 (30.07.2020): 426–27. http://dx.doi.org/10.1017/s1431927620014634.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Zeitschriftenartikel zum Thema „Electrons – Diffraction“

Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an