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The steady state surfaces of ion bombarded 3C-, 4H- and 6H-SiC samples were studied by means of reflected electron energy loss spectroscopy (REELS). The REELS exhibit a well-defined loss peak in the region of about 20 eV. The position of the maximum of the loss peak depends on the bombarding ion energy (decreasing with increasing ion energy), and on the primary electron beam energy (increasing with increasing primary energy). This behavior can be explained if we suppose that the plasmon energy in the altered layer (produced by ion bombardment) is different from that of the unaltered bulk. In this case the measured loss peak is the sum of two overlapping plasmon peaks. With modeling the system as a homogeneous altered layer and a homogeneous unaltered substrate the plasmon energy in the altered layer was derived to be 19.8 eV. The large change of the plasmon energy with respect to the bulk value of 23 eV is explained by a thin low density overlayer on the surface of the sample produced by the ion bombardment. 相似文献
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M. Beuve M. Caron B. Gervais H. Rothard A. Clouvas C. Potiriadis 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(3):293-300
It is usually well accepted that for swift protons, the induced backward and forward electron emission yield is proportional
to the projectile electronic stopping power. This was observed in particular for thin amorphous carbon foils. However, this
law was established from a non extensive set of experimental data and somewhat confirmed by rough macroscopic theories. We
then developed a standard Monte Carlo simulation to predict the yield dependence on proton energy [0.5–10 MeV] and for a wide
range of foil thickness. After evaluating the reliability of this simulation, we showed and explained why the law of proportionality
cannot generally hold for forward electron emission. In particular, the ratio between forward yield and stopping power generally
depends on foil thickness and proton energy. We performed a new experiment that confirmed our theoretical predictions.
Received 9 March 2001 相似文献
4.
J.H. Xu F. Mango G. Alzetta R.A. Bernheim 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(2):243-246
Alkali metals adsorbed to surface films of the polymer poydimethylsiloxane (PDMS) have been shown to exhibit a unique photodesorption
behavior, characterized by a frequency threshold and high efficiency. In this work, the temperature dependence of the photodesorption
yields of Na and Na
2
from PDMS surfaces were measured between room temperature and 183 K. Over most of the temperature range, the yields exhibited
an Arrhenius behavior characterized by thermal activation energies of 0.36 eV and 0.34 eV for Na and Na
2
, respectively. These values are suggestive of a surface diffusion as one of the elementary steps in the photodesorption mechanism.
Moreover, the similarity of the two values indicates that the same elementary step applies to the desorption of both Na and
Na
2
.
Received 23 April 1999 and Received in final form 15 July 1999 相似文献
5.
N. Grewe T. Jabben S. Schmitt 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(1):23-32
The low energy region of certain transition metal compounds reveals dramatic correlation effects between electrons, which
can be studied by photoelectron spectroscopy. Theoretical investigations are often based on multi-orbital impurity models,
which exhibit modified versions of the Kondo effect. We present a systematic study of a multi-orbital Anderson-like model,
based on a new semi-analytical impurity solver which goes beyond simple modifications of the well known NCA. We discuss one-particle
excitation spectra and in particular the role of level positions and Coulomb-matrix elements. It is shown that the low-energy
region as well as the overall features of spectra critically depend on the model parameters and on the quality of the approximations
used. Recent photoelectron experiments and corresponding existing calculations are put into perspective. An interesting crossover
scenario between different regimes of ground states with characteristically different local correlations is uncovered. 相似文献