Defect structure of Czochralski silicon co-implanted with helium and hydrogen and treated at high temperature - pressure
Effect of stress created by Ar hydrostatic pressure (HP) up to 1.1 GPa during annealing at the high temperature (HT) 1070 K (HT-HP treatment) on microstructure of Czochralski grown silicon co-implanted with helium and hydrogen Si:(He,H) using the same doses of He+ and H₂+ (DH,He= 5·10¹⁶ cm⁻², at e...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
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irk-123456789-1206542017-06-13T03:06:38Z Defect structure of Czochralski silicon co-implanted with helium and hydrogen and treated at high temperature - pressure Wierzchowski, W. Misiuk, A. Wieteska, K. Bak-Misiuk, J. Jung, W. Shalimov, A. Graeff, W. Prujszczyk, M. Effect of stress created by Ar hydrostatic pressure (HP) up to 1.1 GPa during annealing at the high temperature (HT) 1070 K (HT-HP treatment) on microstructure of Czochralski grown silicon co-implanted with helium and hydrogen Si:(He,H) using the same doses of He+ and H₂+ (DH,He= 5·10¹⁶ cm⁻², at energy 50 and 150 keV, respectively) was investigated by means of X-ray (synchrotron) diffraction, transmission electron microscopy, and electrical measurements. The nanostructured sponge-like buried layers are formed in Si:(He,H) by annealing / high pressure treatment. Decreased interference, diffuse scattering and individual contrast are observed in the synchrotron topograms for HT-HP treated Si:(He,H). The treatment at 723 K and HP results in an additional donor formation as a sequence of the implantation-disturbed layer. The HP-mediated (retarded) out-diffusion of hydrogen and helium is in part responsible for the effects observed. 2005 Article Defect structure of Czochralski silicon co-implanted with helium and hydrogen and treated at high temperature - pressure / W. Wierzchowski, A. Misiuk, K. Wieteska, J. Bak-Misiuk, W. Jung, A. Shalimov, W. Graeff, M. Prujszczyk // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2005. — Т. 8, № 1. — С. 7-11. — Бібліогр.: 14 назв. — англ. 1560-8034 PACS: 61,72Tt, 61,82Fk, 62.50p,73.61.-r, 73.30.+ http://dspace.nbuv.gov.ua/handle/123456789/120654 en Semiconductor Physics Quantum Electronics & Optoelectronics Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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Effect of stress created by Ar hydrostatic pressure (HP) up to 1.1 GPa during annealing at the high temperature (HT) 1070 K (HT-HP treatment) on microstructure of Czochralski grown silicon co-implanted with helium and hydrogen Si:(He,H) using the same doses of He+ and H₂+ (DH,He= 5·10¹⁶ cm⁻², at energy 50 and 150 keV, respectively) was investigated by means of X-ray (synchrotron) diffraction, transmission electron microscopy, and electrical measurements. The nanostructured sponge-like buried layers are formed in Si:(He,H) by annealing / high pressure treatment. Decreased interference, diffuse scattering and individual contrast are observed in the synchrotron topograms for HT-HP treated Si:(He,H). The treatment at 723 K and HP results in an additional donor formation as a sequence of the implantation-disturbed layer. The HP-mediated (retarded) out-diffusion of hydrogen and helium is in part responsible for the effects observed. |
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Wierzchowski, W. Misiuk, A. Wieteska, K. Bak-Misiuk, J. Jung, W. Shalimov, A. Graeff, W. Prujszczyk, M. |
| spellingShingle |
Wierzchowski, W. Misiuk, A. Wieteska, K. Bak-Misiuk, J. Jung, W. Shalimov, A. Graeff, W. Prujszczyk, M. Defect structure of Czochralski silicon co-implanted with helium and hydrogen and treated at high temperature - pressure Semiconductor Physics Quantum Electronics & Optoelectronics |
| author_facet |
Wierzchowski, W. Misiuk, A. Wieteska, K. Bak-Misiuk, J. Jung, W. Shalimov, A. Graeff, W. Prujszczyk, M. |
| author_sort |
Wierzchowski, W. |
| title |
Defect structure of Czochralski silicon co-implanted with helium and hydrogen and treated at high temperature - pressure |
| title_short |
Defect structure of Czochralski silicon co-implanted with helium and hydrogen and treated at high temperature - pressure |
| title_full |
Defect structure of Czochralski silicon co-implanted with helium and hydrogen and treated at high temperature - pressure |
| title_fullStr |
Defect structure of Czochralski silicon co-implanted with helium and hydrogen and treated at high temperature - pressure |
| title_full_unstemmed |
Defect structure of Czochralski silicon co-implanted with helium and hydrogen and treated at high temperature - pressure |
| title_sort |
defect structure of czochralski silicon co-implanted with helium and hydrogen and treated at high temperature - pressure |
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| publishDate |
2005 |
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http://dspace.nbuv.gov.ua/handle/123456789/120654 |
| citation_txt |
Defect structure of Czochralski silicon co-implanted with helium and hydrogen and treated at high temperature - pressure / W. Wierzchowski, A. Misiuk, K. Wieteska, J. Bak-Misiuk, W. Jung, A. Shalimov, W. Graeff, M. Prujszczyk // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2005. — Т. 8, № 1. — С. 7-11. — Бібліогр.: 14 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
| work_keys_str_mv |
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2025-07-08T18:17:16Z |
| last_indexed |
2025-07-08T18:17:16Z |
| _version_ |
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| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2005. V. 8, N 2. P. 7-11.
© 2005, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
7
PACS: 61,72Tt, 61,82Fk, 62.50p,73.61.-r, 73.30.+
Defect structure of Czochralski silicon
co-implanted with helium and hydrogen
and treated at high temperature - pressure
W. Wierzchowski1, A. Misiuk 2, K. Wieteska3, J. Bak-Misiuk4, W. Jung2, A. Shalimov4,
W. Graeff 5, and M. Prujszczyk2
1 Institute of Electronic Materials Technology, Wolczynska 133, PL-01-919 Warsaw, Poland
2 Institute of Electron Technology, Al. Lotnikow 46, PL-02-668 Warsaw, Poland
3 Institute of Atomic Energy, PL-05-400 Otwock-Swierk, Poland
4 Institute of Physics, PAS, Al. Lotnikow 32/46, PL-02-668 Warsaw, Poland
5 HASYLAB at DESY, Notkestrasse 85, D-22603 Hamburg, Germany
Corresponding author: Tel. +48-22-548-7792; fax +48-22 847-0631;
E-mail: misiuk@ite.wawpl (A. Misiuk)
Abstract. Effect of stress created by Ar hydrostatic pressure (HP) up to 1.1 GPa during
annealing at the high temperature (HT) 1070 K (HT-HP treatment) on microstructure of
Czochralski grown silicon co-implanted with helium and hydrogen Si:(He,H) using the
same doses of He+ and H2
+ (DH,He= 5·1016 cm–2, at energy 50 and 150 keV, respectively)
was investigated by means of X-ray (synchrotron) diffraction, transmission electron
microscopy, and electrical measurements. The nanostructured sponge-like buried layers
are formed in Si:(He,H) by annealing / high pressure treatment. Decreased interference,
diffuse scattering and individual contrast are observed in the synchrotron topograms for
HT-HP treated Si:(He,H). The treatment at 723 K and HP results in an additional donor
formation as a sequence of the implantation-disturbed layer. The HP-mediated (retarded)
out-diffusion of hydrogen and helium is in part responsible for the effects observed.
Keywords: Cz-Si, hydrogen, helium, implantation, diffusion, high pressure, treatment.
Manuscript received 10.02.05; accepted for publication 18.05.05.
1. Introduction
Hydrogen implantation is used in silicon-on-insulator
(SOI) technology in a smart-cut process [1]. Agarwal et
al. [2] showed that the smart-cut process can be
improved by helium and hydrogen co-implantation to
produce Si:(H,He). Co-implantation of hydrogen and
helium makes also possible to study an interaction of gas
ions implanted into Si and to compare the roles of H and
He in out-splitting of Si:(H,He) on annealing [3]. The
smart-cut effect in Si:(H,He) takes place because of the
build-up of internal pressure in the buried disturbed layer
containing implanted atoms which create H, He-filled
bubbles and platelets on annealing. Some new results
concerning the structural phenomena during the smart-
cut process were published recently by Usenko et al. [4].
It was reported [3, 5-8] that enhanced hydrostatic
pressure (HP) of ambient gas on annealing (HT (high
temperature)-HP treatment) Czochralski silicon (Cz-Si)
implanted with hydrogen and helium exerts pronounced
effect on microstructure as well as on gettering processes
within the implantation damaged areas. Also recently it
was determined that, by changing the external
(hydrostatic) pressure on annealing of Si:(H,He) and the
sequence of the H- and He-enriched layers, it is possible
to tune some properties of the Si:(H,He) structures [5, 6].
It is well known that oxygen-related centres formed
in oxygen containing Cz-Si are responsible for thermal
donor (TD) formation at about 720 K. An application of
increased HP of argon atmosphere during a heat
treatment of Cz-Si samples results in the strain-induced
creation of TDs [9, 10]. Similar effects of that treatment
on hydrogen-enriched Cz-Si:H was also reported [11].
As it follows from rather preliminary data, a similar HP-
stimulated creation of TDs can be expected also for
Si:(H,He) [12].
The aim of this work is to determine the structural
and electrical effects of the HT-HP treatment on defect
structure of Si:(He,H) with the reversed (in comparison
to the previously investigated case of Si:(H,He) [5, 13])
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2005. V. 8, N 2. P. 7-11.
© 2005, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
8
sequence of the layers enriched with helium and
hydrogen (RpHe < RpH, where Rp means the projected
range of implanted ions).
2. Experimental
Boron doped (resistivity 4…6 Ohm·cm) p-type (100)
oriented Cz-Si wafers with the initial interstitial oxygen
concentration cO ≈ 6·1017 cm–3 were used as initial
crystals. Hydrogen, H2
+, and helium, He+, ions were co-
implanted with the same doses DH,He= 5·1016 cm–2 at
Ti ≤ 350 K, He+ were implanted into Cz-Si wafers at
energy EHe = 50 keV ( RpHe ≈ 420 nm), and H2
+ at
EH = 135 keV (RpH ≈ 580 nm). In what follows, the
samples with RpHe < RpH are referred to as Si:(He,H).
The Si:(He,H) samples were annealed/HT-HP
treated at the temperatures up to 1070 K in argon
atmosphere under the hydrostatic pressure up to 1.1 GPa
for 10 h. The samples were studied using X-ray
diffraction methods, transmission electron microscopy
(TEM), and electrical measurements. The sample
structure was checked by TEM.
The X-ray measurements were performed using
X-ray high resolution diffractometry (HRXRD) and
synchrotron methods. In the HRXRD measurements we
used Philips X’Pert equipment in symmetrical 004
reflection of Cu Kα1 radiation.
The synchrotron investigations at the monochro-
matic beam station E2 in HASYLAB included taking the
rocking curves using 400 symmetrical and 511
asymmetrical reflections for 0.117 nm radiation with a
beam limited to the sizes 50x100 μm2 and the
monochromatic beam topograms.
Electrical properties of the as-implanted and
annealed/treated Si:(He,H) samples were studied by the
measurements and numerical analysis of current-voltage
(I-V) and capacitance-voltage (C-V) characteristics of
the Schottky barrier junction Hg-Si (mercury probe).
The measurement system was controlled via GPIB bus
by PC with TestPoint environment and consisted of
QuadTech 7600 admittance meter and Keithley 237 and
238 source measurements units. The QuadTech
7600 Precision LCR meter can measure the capacitance
in a wide band of test signal frequencies from 10 Hz to
2 MHz. Keithley 237 and 238 source measurement units
provided bias voltage during measurements of the I-V
and C-V characteristics. Electrical measurements of
Si:(He,H) samples were performed both on the top (im-
planted) surface and on the back (non-implanted) one.
The carrier concentration profiles were calculated
from C-V characteristics of the Schottky Hg-Si barrier
measured for test signal frequencies 1 kHz and 1 MHz.
3. Results and discussion
As may be followed from Figs 1a, b, the rocking curves
of as-implanted samples revealed a tail of irregular
interferential peaks in the low-angle side of the peak
originating from the substrate with an increased
periodicity towards lower angles. These fringes are
caused by a peak of the strain profiles and formed only
in the samples with a small defect concentration.
The HT-HP treatment results in formation of
strained buried nanostructured layers composed of
partially amorphous silicon (a-Si) containing
hydrogen/helium filled cavities/platelets and numerous
point and extended defects.
For the treated/annealed samples, an effect of defect
agglomeration leads to the fast vanishing the
interferential peaks in the rocking curves and to
increased X-ray diffuse scattering. In this case, it was
possible to detect the formation of gaseous inclusions by
means of X-ray topography. The representative pictures
of gaseous inclusions obtained by synchrotron plane-
wave topography are shown in Fig. 2.
The samples annealed under atmospheric pressure
(105 Pa) provided some point-like contrast that is more
dense for the samples annealed at 723 K. Contrasts
became less dense but more distinct for the samples
treated at higher temperatures. In this case, we observe
also some individual larger round-shaped contrasts. This
contrast may be most probably attributed to larger
gaseous inclusion or small bubbles connected with a
local exfoliation. The samples become relatively flat.
The samples annealed under HP 1.1 GPa do not reveal
any individual resolved contrast similarly to the as-
implanted samples and those significantly bent. Also, a
small part of diffuse scattering is detectable in the tails
of rocking curves, but the diffuse scattering can be much
better followed in the reciprocal space maps (XRRSM’s)
obtained using a high resolution diffractometer. No
significant increase in the full width at half maximum
(FWHM) was observed in the synchrotron rocking
curves shown in Fig. 1, which were recorded using a
very narrow probe beam.
As seen in Fig. 3a, the level of diffuse scattering is
low for the as-implanted sample, and we may observe a
tail along the reciprocal lattice vector, corresponding to
the interferential peaks in the rocking curves in Figs 1a,
b. This tail vanished in the curves of the annealed/treated
samples. The treatments of Si:(He,H) at 723 K – HP for
1 …10 h resulted in the gradually worsened (with HP)
structural perfection, as evidenced by the enhanced X-
ray diffuse scattering intensity (Figs 3 b, c).
Electrical measurements of Si:(He,H) with under-
laying sponge-like layer as well as of the sample back
sides are tabulated in Table for the samples as-implanted
and annealed/treated at 723 K. As detected from I-V
and C-V characteristics of the Schottky barrier for
Si:(He,H) samples, the type of conductivity in the
surface layer of the as-implanted sample was changed
from the initial p-type (still detected on the sample back
side) to the n-type. Because the helium projected range
is smaller than that of hydrogen, one can assume that the
helium implantation results in the increased generation
of donor-like defect centres even for the low initial
oxygen concentration in Cz-Si (cO ≈ 6·1017 cm–3).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2005. V. 8, N 2. P. 7-11.
© 2005, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
9
Fig. 2. 004 X-ray plane wave topograms for Si:(He,H)
samples: a – annealed at 723 K, 105 Pa for 1 h, and b – treated
at 923 K, 1.1 GPa for 1 h.
The calculations of the carrier concentration for the
Si:(He,H) sample result that the concentration of donor-
like defects is rather high (about 2·1017 cm-3) for the
as-implanted sample and decreases to the level of
3·1016 cm-3 after sample annealing at 723 K for 10 h
under the atmospheric pressure. This fact means that
some implantation induced donor defects, not related to
the presence of oxygen, are annihilated on annealing.
The H2/He filled bubbles are detectable by TEM in
the Si:(He,H) samples annealed/treated in a wide
temperature range [14]. TEM image of Si:(He,H) treated
at 923 K – 1.1 GPa for 1 h is presented in Fig. 4. The
presence of similar H2 filled cavities and bubbles was
obtained also for the HT-HP treated Si:H samples [3].
As it follows from XRRSM’s of the Si:(He,H)
samples annealed/treated at 923 K (Fig. 5), no marked
effect of HP on the resulting sample microstructure is
detectable by this X-ray method.
Fig. 3. XRRSM’s recorded near 004 reciprocal lattice point for
Si:(He,H) samples, as-implanted (a) and annealed/treated for 1 h
at 723 K under 105 Pa (b), 1.1 GPa (c), and for 10 h at 723 K
under 1.1 GPa (d). Axes are marked in λ/2d units (λ is the
wavelength, d is the distance between crystallographic planes).
Fig. 1. Synchrotron rocking curves of Cz-Si:(He,H): a, b – as-implanted, for asymmetric 400 and 511 reflections, c – annealed
for 1 h, 105 Pa, 723 K, d – treated for 6 h, 1.1 GPa , 723 K.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2005. V. 8, N 2. P. 7-11.
© 2005, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
10
Fig. 4. XTEM image of Si:(He,H) sample treated for 1 h at
923 K under 1.1 GPa.
Annealing Si:(He,H) at 923 K for 10 h under
atmospheric pressure results in annihilating all donor
centres not related to the presence of oxygen, and the
surface layer recovers its initial p-type of conductivity,
but with a much higher level of the hole concentration
which means that the acceptor-like defect centres are
also generated during the implantation process (Table).
The concentration of these defects is increased after the
heat treatment at 923 K under 1.1 GPa for 10 h.
We have observed that the application of an
increased hydrostatic pressure of argon atmosphere
during the heat treatment of Si:(He,H) resulted in rather
small stress-induced creation of TDs because of the low
oxygen concentration. It is particularly evident for the
sample back side as shown in Table.
The XRRSM data of the Si:(He,H) samples treated
at 1070 K are indicative of some improvement of their
crystallographic perfection with increasing HP
manifested by smaller diffuse scattering (Fig. 6).
Our investigations concerned Cz-Si Si:(He,H)
samples: prepared by sequential helium and hydrogen
implantation at T ≤ 370 K with the same H and He
Fig. 5. XRRSM’s recorded near 004 reciprocal lattice point for
Si:(He,H) samples, annealed/treated for 1 h at 923 K under 105
Pa (a) and 1.1 GPa (b). Axes are marked as in Fig. 3.
Table 1. Carrier concentration and conductivity type of
Si:(He,H) samples. Electrical measurements were performed
on the sample surface taking into account the existence of
buried sponge-like layer as well as the sample back contact.
Carrier concentration [cm–3],
type of conductivity Samples Si:(He,H)
Implanted side Back side
1. As-implanted 2⋅1017, n 1⋅1015, p
2. 723 K, 105 Pa, 1 h 1⋅1017, n 1⋅1015, p
3. 723 K, 0.1 GPa, 1 h 1.7⋅1017, n 1⋅1015, p
4. 723 K, 0.6 GPa, 1 h 2⋅1017, n 1⋅1015, p
5. 723 K, 1.1 GPa, 1 h 1.5⋅1017, n 1⋅1015, p
6. 723 K, 105 Pa, 10 h 3⋅1016, n 1⋅1015, p
7. 723 K, 1.1 GPa, 10 h 1⋅1017, n 1⋅1015, p
8. 923 K, 105 Pa, 10 h 6⋅1016 , p 1⋅1015, p
9. 920 K, 1.1 GPa, 10 h 8⋅1016, p 1⋅1015, p
doses (D = 5·1016 cm-2) and with maximum He concent-
rations lower in respect to that of hydrogen (RpH ≈
580 nm). The H- and He-containing areas were almost
overlapping owing to extended tails of the distributions
of the implanted species. The presently discussed X-ray
and electric measurements correspond with the photo-
luminescence (PL) and SIMS measurements in similar
samples [5, 13]. Some specific HT-HP induced
phenomena were determined, among them:
- the increased hydrogen out-diffusion and so the
lowered H concentration in the samples treated at HT –
(1…1.1) GPa, in comparison to those treated under the
lower pressures 105…107 Pa.
- HP-mediated suppression of oxygen accumulation,
especially at 720 K, and general improvement with HP
of the crystallographic perfection of Cz-Si:(H,He) and
Cz-Si:(He,H) samples.
The first mentioned effect is unexpected, and, as it
concerns our knowledge, the first of this kind reported.
The lowered hydrogen concentration in Cz-Si:(He,H)
samples treated at the temperature up to (at least) 1070 K
under HP up to (at least) 1.1 GPa is evidently related to
Fig. 6. XRRSM’s recorded near 004 reciprocal lattice point for
Si:(He,H) samples, treated for 5 h at 1070 K under 105 Pa (a)
and 1.1 GPa (b). Axes are marked as in Fig. 3.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2005. V. 8, N 2. P. 7-11.
© 2005, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
11
the more rapid hydrogen out-diffusion from Cz-
Si:(H,He) at 720…1070 K and so to the HP-mediated
enhancement of the effective hydrogen atom mobility.
No unique explanation of the lowered hydrogen
storage in silicon co-implanted with helium and hydrogen
can be given at present. It is obvious that the considered
phenomenon is related to the presence of He (or to
creation of some specific He-induced defects), because
implantation of the only hydrogen leads to a much more
obvious effect of the enhanced hydrogen concentration in
HT-HP treated Si:H. The effect seems to be related to the
influence of He atoms on the behaviour of hydrogen in
silicon – most probably the He-filled microca-
vities/bubbles in Si:(H,He) affects creation of the H–Si
bonds. It was reported in [14] that, after filling, the
vacancy-like defect created at implantation and at the
beginning of annealing/treatment step, some hydrogen
molecules in Si:H react with dangling or strained Si–Si
bonds creating Si–H silanic terminations. Under
atmospheric pressure hydrogen out-diffuses appreciably
from Si:H at T ≥ 720 K. The lowered hydrogen out-
diffusion rate was obtained for Si:(H,He) annealed at
570…720 K [14]. It was explained by the He presence,
owing to the increased number of H–Si bonds.
In the case of Si:(He,H), with RpH > RpHe at HT
hydrogen, out-diffuses from the sample reaching the
originally He-filled cavities and bubbles. Probably, also
some (not so numerous) He atoms would reach the
originally H-filled cavities and bubbles in the vicinity of
RpH (> RpHe) by the in-sample diffusion. Consequently,
part of hydrogen would become immobilized in those
cavities and bubbles (in respect of its further diffusion)
because of creation of the mentioned H–Si bonds.
The observed effect of enhanced hydrostatic pressure
during annealing on the suppression of oxygen
accumulation/gettering and on the creation/annihilation of
crystallographic defects [13] is related to decreased
diffusivity of oxygen interstitials during HP. The oxygen
accumulation in Cz-Si:(H,He) is affected also by the above
discussed indirect interaction between hydrogen and helium
difficult for understanding at the present stage of
investigations. Explanation of other observed structural
transformations during HT-HP is even more difficult, and
so further investigation is also needed to solve this problem.
4. Conclusions
Using the rocking curves and XRRSM’s of Cz-
Si:(He,H), we revealed characteristic interferential peaks
with increased periodicity on low-angle side of the
substrate related peak, which may be attributed to strains
reaching their maximum under the surface. After
annealing and the HT-HP treatment, the interferential
effects vanish, and the increased X-ray diffuse scattering
was observed; still some individual contrast was
recognizable by the monochromatic beam topography,
which may be caused by formation of larger gaseous
inclusions. A certain improvement of the structure was
observed in case of HT-HP treatment performed for the
highest values of the temperature and pressure.
Formation of the sponge-like layers in Cz-Si
exposed to implantation with helium and oxygen and to
high temperature-pressure treatment is accompanied
with the creation of the structural and electrically active
defects such as oxygen related TDs both donor-like and
acceptor-like. Electrical properties of sponge-like silicon
surface structures formed by the high pressure annealing
of silicon co-implanted with hydrogen and helium are
dependent on the implantation and treatment conditions.
There was determined the possibility to form the p-n
junctions with various carrier concentration levels
influencing on the semiconductor device properties by
changing the projected range of implanted ions and the
conditions of the high temperature-pressure treatment.
Acknowledgements
The authors are grateful to Dr J. Ratajczak (Institute
of Electron Technology, Warsaw) for some TEM data.
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