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published papers
e r S C H I e N e N e p u B L I K A t I o N e N – p u B L I S H e d p A p e r S
(1) Formation of Vacancy and oxygen
Containing Complexes in Cz-Si by rapid
thermal Annealing
V.D. Akhmetov, G. Kissinger, W. von Ammon
physica B: Condensed Matter 404(23-24),
4572 (2009)
Changes of the oxygen (o) state in Czochralski silicon
(Cz Si) caused by rapid thermal annealing (RtA)
were studied by means of Fourier transform infrared
spectroscopy (FtIR) in a highly sensitive mode. the
formation of vacancy (V) and o containing complexes
Vo 4 , previously known only from radiation experiments
was observed as a result of RtA of Si wafers under clean
room conditions without applying any irradiation.
the use of half wafers during RtA processing and the
use of the second untreated part of the same wafer as
a reference during precise differential FtIR measurements
allowed us to reveal, quite reproducibly, the
small RtA induced changes in the absorbance in the
level of ~10 -5 in absorbance units. Special attention
was paid to separate the real contribution from the
bulk from a possible surface related contribution in
the recorded differential absorbance spectra. As a
result, the quantitatively reproducible vibrational absorption
band 985 cm -1 at room temperature known of
Vo 4 was revealed in each of the examined wafers after
RtA. the concentration of the observed complexes
was approximately 1.4 x 10 13 cm -3 as estimated from
the integrated calibration factor for interstitial oxygen
(oi). no traces of Vo, Vo 2 , Vo 3 , Vo 5 and Vo 6 were
found in a similar level. A moderate decrease, in the
level of 10 13 -10 14 cm -3 , of the content of oxygen dimers
(o 2i , 1012 cm -1 ) and trimers (o 3i , 1005 cm -1 ) in asgrown
Si was observed after RtA. Changes in the concentration
of oi did not exceed approximately 0.5 %.
possible reasons for the preferential formation of Vo 4
by RtA are briefly discussed.
(2) Hydrogen transformations in Si-Based Solar
Structures Studied by precise FtIr
Spectroscopy
V.D. Akhmetov, A.G. ulyashin, A. Holt, M. Kittler
Materials Science and engineering B
159-160, 182 (2009)
In this work, an attempt to clarify the origin of a very
pronounced effect of the minority carrier lifetime
evolution in Sin x :H / a-Si:H / Si / a-Si:H / Sin x :H and
a-Si:H / Si / a-Si:H solar cell structures prepared at
temperatures around 200 °C upon heat treatments
in the temperature interval of 445–550 °C is performed.
For a comparison, heavily hydrogenated Si
substrates were investigated as well. Analysis of all
structures studied was performed by means of precise
FtIR measurements and quasi-steady-state photoconductance
(QsspC) techniques. Annealing-induced
transformations of hydrogen-related states in Si-based
structures upon heat treatments were monitored
by a FtIR system with an enhanced sensitivity. Strong
monotonic decrease of the intensity of various Si–H
and n–H stretching bands was observed in all types
of H-containing layers upon heat treatments applied.
It is concluded that the transformations of H-related
complexes in all structures studied are responsible
for the observed changes in passivation efficiency of
a-Si:H and Sin x :H / a-Si:H layers.
(3) Interaction of oxygen with thermally
Induced Vacancies in Czochralski Silicon
V.D. Akhmetov, G. Kissinger, W. von Ammon
Applied physics letters 94, 092105 (2009)
Complexes consisting of a vacancy and four oxygen
atoms, Vo 4 , were found in oxygen-rich Czochralski
silicon wafers subjected to rapid thermal annealing
(RtA) at 1250 °C for 30 s in Ar / o 2 atmosphere
by means of Fourier transform infrared spectroscopy
with enhanced sensitivity. An absorption band at
985 cm -1 , previously observed only in irradiated Si
and assigned to a local vibration mode of Vo 4 , was
measured reproducibly in all RtA treated wafers examined.
A concentration of about 1.4 x 10 13 cm -3 of
thermally induced Vo 4 was estimated from the inte-
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