共查询到20条相似文献,搜索用时 750 毫秒
1.
A single-atom-sized gold wire was successfully observed in real time by a newly developed defocus-image modulation processing electron microscope. Because of phase retrieval processing with spherical aberration correction, the single-atom strand wire was observed with high contrast and without contrast blurring. By carefully looking at the atomic distance, the contrast, and the dynamic behavior of the wire, we recognized that there are two stages of the wire. In the first stage the wire maintained the atomic distance in the bulk crystal, but in the second stage the wire showed the atomic distance of the nearest-neighbor atoms with weaker contrast. The gold wire was rather stable for a few seconds under strong electron beam illumination. 相似文献
2.
In the framework of the many-body theory, the differential and total cross sections of elastic scattering of slow electrons
by the negative lithium ion Li− are obtained. Calculations are performed both in the Hartree-Fock single-particle approximation and with regard to many-electron
correlations, which take into account the dynamic polarization of the core. Features observed in the behavior of the phases
and cross sections for p and d partial waves are associated with resonance scattering of electron waves. Considering the dynamic polarization of the core
by an incident electron heightens the diffraction character of the scattering. The real process is compared with particle
scattering in models with a repulsive potential. 相似文献
3.
In order to investigate dynamic change in surface structure, we tried to measure the rocking curve of reflection high-energy electron diffraction (RHEED) by using a quasi-1D convergent beam method, which means a superposition of a hundred RHEED patterns at different glancing angles on one image. After we have checked the experimental accuracy, it is confirmed that the measurement time is shortened to 0.3 s by using this method. We also show an application of this method to a real time observation of surface segregation of B atoms while a highly B-doped Si is annealed. 相似文献
4.
5.
The EIGER detector for low‐energy electron microscopy and photoemission electron microscopy 下载免费PDF全文
G. Tinti H. Marchetto C. A. F. Vaz A. Kleibert M. Andrä R. Barten A. Bergamaschi M. Brückner S. Cartier R. Dinapoli T. Franz E. Fröjdh D. Greiffenberg C. Lopez-Cuenca D. Mezza A. Mozzanica F. Nolting M. Ramilli S. Redford M. Ruat Ch. Ruder L. Schädler Th. Schmidt B. Schmitt F. Schütz X. Shi D. Thattil S. Vetter J. Zhang 《Journal of synchrotron radiation》2017,24(5):963-974
EIGER is a single‐photon‐counting hybrid pixel detector developed at the Paul Scherrer Institut, Switzerland. It is designed for applications at synchrotron light sources with photon energies above 5 keV. Features of EIGER include a small pixel size (75 µm × 75 µm), a high frame rate (up to 23 kHz), a small dead‐time between frames (down to 3 µs) and a dynamic range up to 32‐bit. In this article, the use of EIGER as a detector for electrons in low‐energy electron microscopy (LEEM) and photoemission electron microscopy (PEEM) is reported. It is demonstrated that, with only a minimal modification to the sensitive part of the detector, EIGER is able to detect electrons emitted or reflected by the sample and accelerated to 8–20 keV. The imaging capabilities are shown to be superior to the standard microchannel plate detector for these types of applications. This is due to the much higher signal‐to‐noise ratio, better homogeneity and improved dynamic range. In addition, the operation of the EIGER detector is not affected by radiation damage from electrons in the present energy range and guarantees more stable performance over time. To benchmark the detector capabilities, LEEM experiments are performed on selected surfaces and the magnetic and electronic properties of individual iron nanoparticles with sizes ranging from 8 to 22 nm are detected using the PEEM endstation at the Surface/Interface Microscopy (SIM) beamline of the Swiss Light Source. 相似文献
6.
A new coaxial detection system for backscattered electrons in SEM is described. This coaxial detection system allows us to collect only the backscattered electrons that have lost a small percentage of the primary energy, emerging from the sample surface with a take-off angle defined by the objective lens. This new configuration reinforces the atomic-number contrast and suppresses effectively the topographic contrast. The simulation and experimental results confirm these expectations: this new type of SEM is very suitable for observing differences in atomic number. Moreover, by associating the obtained image with a conventional secondary electron image, we build a third (color) image that allows us to give finally at the same time, in a single image, both of the chemical and topographic information. 相似文献
7.
Nongelatin dichromated holographic film(NGD) is a new holographic recordingmaterial.Holograms recorded on this material have better environmental stability, higherdiffraction efficiency and stronger real time effect, etc..An experimental study to ascertainthe influence of two electron donors, namely,N,N-dimethylformamide(DMF) and dimethyl-sulfoxide(DMSO),on the real time diffraction efficiency(RTDE) of NGD holograms is car-ried out.The pressence of electron donors not only improves the sensitivity,but also enhancesthe real time effect greatly.RTDE of above 60% at±1 orders of NGD plane transimissiongrating is achieved by introducing electron donors. 相似文献
8.
《Composite Interfaces》2013,20(2-3):231-247
Henequen natural fiber-reinforced poly(butylene succinate) biocomposites were prepared through a resin microdroplet formation on a single fiber and also fabricated by a compression molding technique using chopped henequen fibers, surface-treated with electron beam irradiation (EBI) at various dosages. The effect of EBI treatment on the surface characteristics and dynamic mechanical properties of henequen fibers was investigated using SEM, XPS and DMA methods, respectively. Also, the interfacial behavior of biocomposites was explored through a single fiber microbonding test and fracture surface observations. The result indicates that the interfacial shear strength (IFSS) of biocomposites greatly depends on the EBI treatment level on the henequen fiber surface. This study also suggests that appropriate modification of natural fiber surfaces at an optimum EBI dosage significantly contributes to improving the interfacial properties of biocomposites. 相似文献
9.
A. A. Sidorkin S. D. Milovidova O. V. Rogazinskaya A. S. Sidorkin 《Physics of the Solid State》2000,42(4):743-744
A study is reported on the behavior in time of the electron emission current density from a triglycine sulfate ferroelectric crystal measured at fixed temperatures. This relation is shown to have an exponential nature. The characteristic emission relaxation time depends on temperature and decreases as one approaches the phase-transition point. The magnitude of the relaxation time and its temperature dependence can be accounted for both within a mechanism in which the emission decay is associated with the emptying of surface electron states, and in terms of the Maxwellian relaxation process. 相似文献
10.
A. Krasyuk A. Oelsner S.A. Nepijko A. Kuksov C.M. Schneider G. Schönhense 《Applied Physics A: Materials Science & Processing》2003,76(6):863-868
Owing to its parallel image acquisition, photoemission electron microscopy is well suited for real-time observation of fast
processes on surfaces. Pulsed excitation sources like synchrotron radiation or lasers, fast electric pulsers for the study
of magnetic switching, and/or time-resolved detection can be utilised. A standard approach also being used in light optical
imaging is stroboscopic illumination of a periodic (or quasi-periodic) process. Using this technique, the time dependence
of the magnetic field in a pulsed microstrip line has been imaged in real time exploiting Lorentz-type contrast. Similarly,
the corresponding field-induced changes in the magnetisation of cobalt microstructures deposited on the microstrip line have
been observed exploiting magnetic X-ray circular dichroism as a contrast mechanism. The experiment has been performed at the
UE 56/1-PGM at BESSY II (Berlin) in the single-bunch mode.
Received: 2 September 2002 / Accepted: 2 September 2002 / Published online: 5 March 2003
RID="*"
ID="*"Corresponding author. Fax: +49-6131/392-3807, E-mail: krasyuk@mail.uni-mainz.de 相似文献
11.
K.?K.?Satarin E.?P.?Amanbaev I.?K.?Gainullin 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(2):149-152
The problem of electron transfer along a linear chain of atoms is discussed. The process under study occurs after the electron has transited from a hydrogen ion to an atomic chain. The wave packet propagation method not involving the perturbation theory was used for the calculations. Conclusions on the electron transfer behavior and necessary conditions are drawn. The approach can be applied to real physical systems where electron transition from a charged particle takes place. 相似文献
12.
根据原电子射程表达式和金属的有效真二次电子发射系数表达式,推导出金属的高能有效真二次电子发射系数与入射能量、能量幂次的关系式;并根据金属的高能有效真二次电子发射系数与金属的高能二次电子发射系数的关系,推导出金属的高能二次电子发射系数与入射能量、能量幂次的关系式。用实验数据计算出高能原电子轰击在金或银上时原电子入射能量幂次n,采用实验数据证实高能二次电子发射系数与原电子入射能量和能量幂次三者的关系,对结果进行讨论并得出结论:当高能原电子轰击在同一块金属上时,高能二次电子发射系数与原电子入射能量的n-1次幂之积近似为一常数。 相似文献
13.
Dynamics of a pair of electron and hole in semiconductor superlattice under an intense electric field 下载免费PDF全文
This paper investigates the behavior of a pair of electron and hole
in semiconductor superlattice under an external electric field with
the consideration of Coulomb interaction. By numerically calculating
the corresponding probability in the nearest neighbor tight binding
approximation, we find that the single electron (or the hole) can
not be dynamically localized due to the Coulomb interaction, while
the dynamic localization of exciton (the pair of the electron and
hole) still exists. Moreover we find that with the increase of the
intensity of electric field, the exciton can be dynamically
localized more completely. 相似文献
14.
《Nuclear Physics B》2006,744(3):277-294
We investigate the interplay between the electron–electron and the electron–phonon interaction in the Hubbard–Holstein model. We implement the flow-equation method to investigate within this model the effect of correlation on the electron–phonon effective coupling and, conversely, the effect of phonons in the effective electron–electron interaction. Using this technique we obtain analytical momentum-dependent expressions for the effective couplings and we study their behavior for different physical regimes. In agreement with other works on this subject, we find that the electron–electron attraction mediated by phonons in the presence of Hubbard repulsion is peaked at low transferred momenta. The role of the characteristic energies involved is also analyzed. 相似文献
15.
Structure characterisation of interfaces is a field of widespread application of high resolution transmission electron microscopy for its very high spatial resolution. Specimen thickness and electron optical condition have a deep influence on the high resolution electron transmission microscopy image contrast. Hence, in many cases, the real structure of the sample can be understood from experimental images only by comparison with the relevant simulation. Moreover, the understanding of the contrast variation of a few A at an interface is a task in which even the use of simulation could not produce an unequivocal solution of the experimental result. In this paper high resolution transmission electron microscopy image simulations show that two monolayers of crystalline material buried at an amorphous-crystalline interface can be successfully revealed and interpreted. The simulated images reproduce the experimental results as obtained from the Al/Si-As/n-GaAs (001) heterostructure. 相似文献
16.
L. Wang 《Physics letters. A》2008,372(16):2925-2929
The partition function of the single electron box (SEB), a small metallic island connected by a tunnel junction to the source lead and by a gate capacitor to the gate, can be expressed in path-integral form, which contains the effective action of the collective variable, phase, after integrating out the background electron degrees of freedom. The cluster transfer matrix method (CTM) is applied to the SEB. By using an improved numerical algorithm and more intensive calculations with larger cluster size, we obtained a highly accurate result for the effective charging energy of SEB up to a large barrier conductance. With a clear converging tendency and the fact that we do not use any approximation in calculation of the partition function, our CTM calculation is systematic and exact. The result is in excellent agreement with the real time renormalization group method of König and Schoeller. 相似文献
17.
《中国物理C(英文版)》2016,(8)
In order to study the dynamic response of the material and the physical mechanism of fluid dynamics,an accelerator scenario which can be applied to both hard X-ray free electron laser and high energy electron radiography is proposed.This accelerator is mainly composed of a 12 GeV linac,an undulator branch and an eRad beamline.In order to characterize a sample's dynamic behavior in situ and real-time with XFEL and eRad simultaneously,the linac should be capable of accelerating the two kinds of beam within the same operation mode.Combining in-vacuum and tapering techniques,the undulator branch can produce more than 1011 photons per pulse in 0.1%bandwidth at42 keV.Finally,an eRad amplifying beamline with 1:10 ratio is proposed as an important complementary tool for the wider view field and density identification ability. 相似文献
18.
Angel Alastuey 《Journal of statistical physics》1987,48(3-4):839-871
We study the static and dynamic behavior of a classical electron gas in the periodic potential created by an ionic lattice. Using the well-known Vlasov approximation, we derive a mean-field kinetic equation for the density-response function of the electrons. This equation is formally solved in terms of the trajectories of one electron in the mean-field equilibrium potential which determines the local electronic density. The mean-field expressions of the static and dynamic structure factors are then obtained through the fluctuation-dissipation theorem. These expressions are used to show that within the mean-field approximation the system is a conductor at all temperatures and for all dimensions. 相似文献
19.
B. Lang 《Surface science》1977,66(2):527-541
The surfaces of platinum single crystals, of carbon deposits on platinum and of pyrographite are examined by secondary electron spectroscopy under 100 eV electron excitation. The spectra contain characteristic peaks in the range 0–30 eV, which are interpreted as band-like in origin. The effects of gas adsorption, of the reconstruction at Pt(100), of the temperature and of ion bombardment induced disorder are reported. The secondary electron spectrum provides a criterion for distinguishing between amorphous and graphitic carbon surfaces. By contrast with the Auger spectrum, it is sensitive to the degree of crystalline order at the surface over distances of 10–100Å. 相似文献
20.
S. V. Blazhevich A. V. Noskov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(2):315-321
Parametric X-ray radiation and parametric X-ray radiation at a small angle with respect to the velocity of a relativistic
electron crossing a single crystal plate in Laue scattering geometry are studied based on the dynamic X-ray diffraction theory.
Analytical expressions for the spectral-angular density of radiations are derived in the general case of asymmetric reflection.
The ratio of the contributions of these radiation mechanisms is considered. 相似文献