Low-energy Electron Transmission Research Articles

Structural-order effects in low-energy electron transmission spectra of condensed Ar, Kr, Xe,N2, CO, andO2

Low-energy electron transmission spectroscopy is sensitive to crystal order and electronic band structure. The latter is responsible for minima in transmitted current whenever the incident electron energy coincides with that of a band gap. We propose a quasi-free-electron model to describe the experimental results for Ar, Kr, Xe, ${\mathrm{N}}_{2}$, CO, and ${\mathrm{O}}_{2}$ films deposited on Pt. It contains two parameters: the energy of the bottom of the conduction band ${V}_{0}$ and an average electron effective mass ${m}^{*}$. The onset of inelastic processes is extremely valuable in determining ${V}_{0}$. Further knowledge of the reciprocal-lattice vectors allows a reliable fit to ${m}^{*}$ and ${V}_{0}$. The results for Xe join smoothly to those of higher-energy low-energy electron diffraction experiments. We are also able to correlate the average atomic structure factor to the minima in the elastic mean free path of Xe.

Epitaxial Regrowth of Amorphous Si Deposited on Si(111)

The crystallization of amorphous ultrahigh-vacuum-deposited Si films on Si(111)−7 × 7 is investigated by low energy electron diffraction (LEED) and transmission electron microscopy. The substrate temperature during deposition is 150 °C; the deposition rate is 100 Å/min and the film thickness is 50 to 1200 Å. The films are annealed in the temperature range from 575 to 1000 °C. The crystallization is controlled by LEED observation. The epitaxial regrowth mechanism and the origin of residual disorder in layers annealed at 600 to 800 °C are determined. Epitaxial alignment of the polycrystalline regions of the film is shown to occur at elevated temperatures (900 to 1000 °C). [Russian Text Ignore]

エキソ電子の蒸着膜透過

Exoelectron transmission through thin films is studied by evaporating non-exoelectron materials on exoelectron emission surfaces. The transmission curves through carbon and gold films are separated into two components, the thin film transmission part and the thicker film one. The decay rate in the later part shows almost the same tendency in various films and it is considered as a kind of diffusion process. This isan interesting result from the point of view of low energy electron transmission.

Increasing the optical modulation of low energy electron transmission by the deposition of copper phthalocyanine dye on Si(111)

When films of copper phthalocyanine dye (CuPc) are deposited on etched Si(111) wafers, there is approximately an order of magnitude increase in the optically modulated transmission of low energy electrons. For comparison, the relatively small optically modulated currents obtained for CuPc films on metal contacts have also been measured. This increase in the optically modulated current due to the CuPc deposition occurs for both n- and p-type Si but does not occur when an intervening layer of insulating oxide is present at the Si-phthalocyanine interface. The dependence of this increase in the optically modulated current on both the incident photon and electron energy has been examined. The dependence on photon energy is consistent with photo-generation of electron hole pairs in Si while the complicated electron energy dependence indicates that electronic interactions with the phthalocyanine molecule are probably involved.

Analysis of the Sensitivity of Low Energy Electron Transmission Experiments

Approximate expressions are given for the fraction of scattering events which contribute to the attenuation of the transmitted electron current in cylindrically symmetric electron spectrometers, with and without an imposed axial magnetic field. The sensitivity to scattering is shown to decrease strongly with increasing magnetic field strength owing to the trapping of scattered electrons by the magnetic field and multiple scattering effects due to the path length being a function of the magnetic field strength. The effect of applying a retarding electric field to electrons leaving the interaction region is shown to leave the conclusions substantially the same.

Low Energy Electron Transmission through Ice Films at 77°K

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