4.5
Effective energy loss function of silver derived from reflected electron energy
loss spectra
Z. Zhang a) , Z. Ding a) , H. Li a) , K. Tőkési, D. Varga, and J. Tóth
The inelastic excitations of silver are studied both experimentally and theoretically. The
effective energy loss function of silver was derived from reflected electron energy loss spectra (REELS). The full width at half maximum
of the elastic peak was in the 0.4-0.6 eV region using the ESA-31 home built spectrometer based on a 180◦ hemispherical analyser [1]
with 0.5 % energy resolution but with different
retardation. The electron beam was produced
by LEG 62 VG Microtech electron gun with
tungsten filament. Prior to electron spectroscopic analysis, in-situ cleaning of the sample
surface was performed using 2 keV energy Ar+
ion sputtering.
The effective energy loss functions (EELF)
have been derived from these experiments in
Hefei, China. Inelastic scattering cross sections obtained by the Tougaard’s deconvolution method [2] is similar to the extended Landau approach, but the latter is more sophisticated. Therefore in our numerical simulation
the extended Landau approach was used. The
effective energy loss functions (EELF) have
been derived from differential inverse inelastic
mean free path as described in ref [3].
It has been revealed that the EELF is
very close to the theoretical surface energy loss
function in the lower energy loss region but
gradually approaches the theoretical bulk energy loss function in the higher energy loss region for Ag. The simulated REELS spectra
by Monte Carlo method based on the EELFs
reproduced the experimental REELS spectra
with considerable success.
,QWHQVLW\DUEXQLW
Acknowledgements
This work was partially supported by the
National Natural Science Foundation of China
(Grant No.10025420 and 90206009). The work
was also supported by the Hungarian Scientific Research Found: OTKA No. T038016,
the grant ”Bolyai” from the Hungarian Academy of Sciences, and TéT Grant No. CHN28/2003.
(QHUJ\H9
Figure 1. Reflected electron energy loss spectra
of 1 keV energy primary electrons. solid line: incidence angle of the primary electron beam is 0◦ and
the observation angle is 50◦ , dotted line: incidence
angle of the primary electron beam is 50◦ and the
observation angle is 0◦ .
a) Structure Research Laboratory and Department of
Physics, University of Science and Technology
of China, 96 Jinzhai Road, Hefei, Anhui 230026,
P.R. China
The incidence angle of the primary electron beam were 0◦ and 50◦ while the angle of
analysed beam were measured at 50◦ and 0◦
with respect to the surface normal of the sample, respectively. During measurements the
vacuum was better than 2x10−9 mbar. Fig 1.
shows the typical measured electron spectra.
[1] L. Kövér, D. Varga, I. Cserny, J. Tóth, and K.
Tőkési, Surf. Interface Anal. 19, (1992) 9.
[2] S. Tougaard, J. Kraaer, Phys. Rev. B43, 1651
(1991).
[3] Z. Zhang, T. Koshikawa, T. Iyasu, R. Shimizu, and
K. Goto Surf. Interface Anal. 35, 403 (2003).
42