Chemistry Reference
In-Depth Information
These singlets are considered to correspond to different charge states of inter-
stitial Fe
i
and substitutional Fe
s
:Fe
i
2+
,Fe
i
1+
,Fe
i
0
,Fe
0
, and Fe
s
-1
are colored by pink,
red, yellow, green and light blue, respectively in Fig.
6.31
b. The isomer shift
values are in good agreement with those of previous absorber experiments
obtained in
57
Fe-diffused mc-Si [
47
]. Notice that the
57
Mn probes were implanted
into the p-type region of mc-Si solar cell, which is the same material as the p-type
mc-Si wafer. The present results indicate that the light illumination changes not
only in the Fermi level (quasi-Fermi level) by the excess carrier injection, but also
in the carrier trapping processes. The latter must be due to the directional excess
carrier flow through the p-n junction, which affects the carrier trapping kinetics
with electrons and holes at the Fe impurities, leading to the different charge states
on both Fe substitutional and interstitial sites in the p-region in mc-Si solar cell.
This is, in fact, the first in situ observation of the carrier trapping processes at Fe
impurities in mc-Si solar cell, which degrades the energy conversion efficiency.
6.6 Conclusions
In this tutorial we have attempted to explain the principles of ion implantation and
of the dedicated Mössbauer techniques that were developed to perform off-line, in-
beam and on-line emission Mössbauer spectroscopy after implantation of radio-
active probe atoms.
We have illustrated these principles with numerous examples, focusing on Fe in
Si, which can be studied by all three techniques.
We hope to have demonstrated the enormous resolving power on atomistic
scale of emission Mössbauer spectroscopy for such studies. For Fe impurities in Si,
with their extremely complex behavior, these techniques have clearly shown their
merits and have substantially contributed to our understanding of the behavior of
Fe impurities in Si.
References
1. E.L. Wolf, Nanophysics and Nanotechnology: An Introduction to Modern Concepts in
Nanoscience (Wiley-VCH, New York, 2006)
2. Electron Microscope
3. C. Kittel, Introduction to Solid State Physics, 8th edn. (Wiley, New York, 2005
4. R.L. Mössbauer, Z. Physik, 151, 124 (1958)
5. R.L. Mössbauer, Naturwissenschaften, 45, 538 (1958)
6. R.L. Mössbauer, Z. Naturforsch. 14a, 211 (1959)
7. Hyperfine Interactions
8. L.C. Feldman,
J.W. Mayer
(eds.),
Fundamentals
of Surface
and Thin
Film Analysis.
(Appleton and Lange, New York, 1986)
9. J.F. Ziegler, J.P. Biersack, U. Littmark, The Stopping and Range of Ions in Solids ed.
(Pergamon Press, New York, 1985);
http://www.srim.org/
