Construction of an ELS-LEED: an electron energy-loss spectrometer with electrostatic two-dimensional angular scanning

Nagao, Tadaaki; Hasegawa, Shuji

doi:10.1002/1096-9918(200008)30:1<488::aid-sia755>3.0.co;2-r

Cited by 16 publications

(11 citation statements)

References 17 publications

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“…Electron beams are transferred between these modules through acceleration and deceleration focusing lenses. The whole spectrometer consists of 39 electrodes in total and all the 39 electrode [6]. The spectrometer is installed in a permalloy ultrahigh-vacuum chamber with residual magnetic field below 1mGauss.…”

Section: Methodssupporting

confidence: 87%

Plasmon confinement in atomically thin and flat metallic films

et al. 2007

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We report on the direct measurement of dispersion relations of plasmons confined in atomically thin metal films and wires by electron energy loss spectroscopy in wide energy-momentum range. Ultrathin Ag films are prepared on single crystal Si surfaces by molecular beam epitaxy, and its crystallinity is checked by electron diffraction. For the case of multi-atomic-layer Ag films, two plasmon modes are observed at around 3.9 eV and 1.8 eV which are localized at the top and the bottom surfaces of the films, respectively. For the case of Ag monoatomic layer, a single mode is observed that steeply disperses in the mid-infrared range. Nonlocal and quantum effects are found to be essential in understanding its full plasmon dispersion curve up to the critical wave number of Landau damping. For the case of Au atom chains, an anisotropic sound-wave-like plasmon dispersion is found that clearly shows 1D plasmon confinement in each atom chain.

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Section: Methodssupporting

confidence: 87%

Plasmon confinement in atomically thin and flat metallic films

et al. 2007

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“…However, if the structure of a non-commensurate (i.e., point-on-line, line-on-line, or incommensurate) [4][5][6] overlayer on a known substrate or the structure of a totally unknown sample is to be measured accurately, one has to rely on the visualization of the k-space of the specimen. Owing to the characteristics of the various experimental setups and/or the recording of the diffraction patterns, image distortions will generally occur not only in LEED 2,[7][8][9][10] but also in other diffraction methods. [11][12][13][14] Depending on the purpose of investigation, for example, when measuring lattice parameters and strain or when classifying the coincidence of an epitaxial organic layer, the distortions must be corrected in order to make these measurements meaningful.…”

Section: Introductionmentioning

confidence: 99%

Determination and correction of distortions and systematic errors in low-energy electron diffraction

Helgert

Meißner

Zwick

et al. 2013

Review of Scientific Instruments

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We developed and implemented an algorithm to determine and correct systematic distortions in low-energy electron diffraction (LEED) images. The procedure is in principle independent of the design of the apparatus (spherical or planar phosphorescent screen vs. channeltron detector) and is therefore applicable to all device variants, known as conventional LEED, micro-channel plate LEED, and spot profile analysis LEED. The essential prerequisite is a calibration image of a sample with a well-known structure and a suitably high number of diffraction spots, e.g., a Si(111)-7×7 reconstructed surface. The algorithm provides a formalism which can be used to rectify all further measurements generated with the same device. In detail, one needs to distinguish between radial and asymmetric distortion. Additionally, it is necessary to know the primary energy of the electrons precisely to derive accurate lattice constants. Often, there will be a deviation between the true kinetic energy and the value set in the LEED control. Here, we introduce a method to determine this energy error more accurately than in previous studies. Following the correction of the systematic errors, a relative accuracy of better than 1% can be achieved for the determination of the lattice parameters of unknown samples.

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“…The plasmon measurements were performed in ultrahigh vacuum (6 10 ÿ11 Torr base pressure) by use of EELS with a highly collimated slow electron beam [11]. The spectrometer can also be operated in the energy-filtered low-energy electron diffraction (LEED) mode with a typical resolution of 0:005 A ÿ1 and momentum range of jqj < 2:5 A ÿ1 .…”

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confidence: 99%

One-Dimensional Plasmon in an Atomic-Scale Metal Wire

et al. 2006

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We have measured one-dimensional (1D) plasmons in an atom wire array on the Si(557)-Au surface by inelastic scattering of a highly collimated slow electron beam. The angular dependence of the excitation energy clearly indicates the strong 1D confinement and free propagation of the plasma wave along the wire. The observed plasmon dispersion is explained very well by a quantum-mechanical scheme which takes into account dynamic exchange-correlation effects, interwire interactions, and spin-orbit splitting of the 1D bands. Although the qualitative feature of the plasmon dispersion is reminiscent of that of a highdensity free-electron gas, we detected the substantial influence of electron correlation due to strong 1D confinement. DOI: 10.1103/PhysRevLett.97.116802 PACS numbers: 73.20.Mf, 71.45.Gm, 72.15.Nj, 73.63.Nm One-dimensional electron systems (1DESs) such as metallic atom wires are expected to sustain a unique collective charge-density excitation which can be called onedimensional (1D) plasmon, or wire plasmon. This excitation mode propagates only along the wire and strongly reflects the confined nature of the electron motion. Such a dimensionality effect will show up clearly in the energy dispersion and the linewidth of a plasmon. For example, 3D-type plasmons (bulk and surface plasmons) have finite energies at q 0 (q denotes momentum) [1], but the energies of 1D and 2D plasmons vanish at q 0 [2,3], since the restoring force for charge-density waves in low dimension vanishes in the long-wavelength limit. However, in spite of its broad interest, experimental observation of a plasmon in an atomic-scale metal wire has been lacking so far and its details remain unexplored.Recently, Au-induced 1D chain structures on stepped Si(111) surfaces were found to comprise 1DESs with metallic electron densities [4 -9]. Among them, Au-Si atom wires formed on the Si(557) surface possess two proximal and deep (1 eV) electron pockets [5][6][7][8][9] and can be regarded as an ideal 1D metal. This system has been providing many intriguing topics such as spin-charge separation in a Tomonaga-Luttinger liquid, lattice distortion by Peierls instability, etc., which originate from the restricted 1D motion of electrons [4 -8]. Moreover, a recent theoretical study by ab initio calculation has proposed a large spinorbit (SO) splitting in the 1D electronic band which results from the strong Au 6p character of this 1D band [10].In this Letter, we report the electron-energy-loss spectroscopy (EELS) of the plasmon in such a model 1D system on the Si(557) surface. The measured plasmon clearly shows strong one-dimensional and metallic characteristics which are expected from a 1D electron gas. We analyzed the observed plasmon dispersion by a quantummechanical scheme including the effects of dynamic exchange correlation (XC), interwire interactions, and SO splitting of the 1D bands. These results demonstrate that, although the Fermi velocity of the 1DES is very high, suggesting its free-electron nature, the dynamic electron correlation effect...

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Construction of an ELS-LEED: an electron energy-loss spectrometer with electrostatic two-dimensional angular scanning

Cited by 16 publications

References 17 publications

Plasmon confinement in atomically thin and flat metallic films

Plasmon confinement in atomically thin and flat metallic films

Determination and correction of distortions and systematic errors in low-energy electron diffraction

One-Dimensional Plasmon in an Atomic-Scale Metal Wire

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