We reported the structure peculiarities of nanocrystals formed in Si by means of high-fluence implantation
at 25 and 500 °С followed by rapid thermal annealing (RTA). The structure of implanted samples
has been investigated by means of transmission electron microscopy (TEM). The crystalline nature of the
precipitates is proved by the Moiré fringe patterns presence in the TEM images. The Moiré fringe distance
(Moiré period) is equal of 1.8 nm for small precipitates. This experimental value coincides with the calculated
one for crystalline InAs. It is noted a Moiré period increasing in the case of large precipitates. We
suppose that this feature is a result of surplus As or In atoms embedded in precipitates. One can see an interesting
effect – “glowng” of nanocrystal/Si interfaces at the dark-field images of implanted and annealed
samples. We ascribe this effect to a presence of misfit dislocation networks at the InAs/Si interfaces generated
as a result of strain relaxation in highly mismatched InAs/Si system.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3543

Komarov, F.

Milchanin, O.

Parkhomenko, I.

Vlasukova, L.

Zuk, J.

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 1 No 4, 04RES08(3pp) (2012) 
 
 
2304-1862/2012/1(4)04RES08(3) 04RES08-1  2012 Sumy State University 
Structural Peculiarities of A3B5 Nanocrystals Created in Si by Ion-Beam Synthesis 
 
L.A. Vlasukova1, F.F. Komarov1, O.V. Milchanin1, I.N. Parkhomenko1, J. Zuk2 
 
1 Belarusian State University, 4, Nezavisimosti ave. 4, 220030 Minsk, Belarus 
2 Maria Curie-Skłodowska University, pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland 
 
(Received 22 June 2012; published online 24 August 2012) 
 
We reported the structure peculiarities of nanocrystals formed in Si by means of high-fluence implan-
tation at 25 and 500 °С followed by rapid thermal annealing (RTA). The structure of implanted samples 
has been investigated by means of transmission electron microscopy (TEM). The crystalline nature of the 
precipitates is proved by the Moiré fringe patterns presence in the TEM images. The Moiré fringe distance  
(Moiré period) is equal of 1.8 nm for small precipitates. This experimental value coincides with the calcu-
lated one for crystalline InAs. It is noted a Moiré period increasing in the case of large precipitates. We 
suppose that this feature is a result of surplus As or In atoms embedded in precipitates. One can see an in-
teresting effect – “glowng” of nanocrystal/Si interfaces at the dark-field images of implanted and annealed 
samples. We ascribe this effect to a presence of misfit dislocation networks at the InAs/Si interfaces gener-
ated as a result of strain relaxation in highly mismatched InAs/Si system. 
 
Keywords: Crystalline silicon, InAs nanocrystals, High-fluence implantation, Thermal treatment 
 
 PACS numbers: 61.46._w; 61.72.Tt; 68.37.Lp; 78.67.Bf 
 
 
1. INTRODUCTION 
 
With the increasing of miniaturization current Si 
technology approaches more and more the physical 
limits drawn by the material properties of Si. Cur-
rently used metal interconnections will cause serious 
problems in future such as heat penalty, nonaccepta-
ble delay and complexity, crosstalk. On-chip optical 
interconnections are believed to be able to overcome 
these problems. The quest is for an efficient light 
source operating at room temperature and preferably 
emitting in a narrow wavelength range. Red or near-
infrared light would be very suitable for communica-
tion purposes. A light-emitting source based on silicon 
would be a radical solution. Unfortunately, Si is inap-
plicable to operate as a light emitter due to its indi-
rect band gap of about 1.1 eV. This has motivated an 
intense research for light emitting materials which 
can replace Si but can be integrates well in the cur-
rent Si technology. Light-emitting diodes and lasers 
based on A3B5 semiconductors show excellent tech-
nical qualities, but their integration into a silicon chip 
is problematical. Furthermore, it is impossible to grow 
direct band gap A3B5 materials epitaxially on Si wa-
fers because of the large lattice misfit. A direct crea-
tion of narrow-gap A3B5 quantum dots (QDs) in crys-
talline silicon by ion implantation followed by thermal 
annealing is a promising approach to overcome this 
difficulty. Density and size of nanocrystals can be con-
trolled by varying implantation and annealing condi-
tions [1]. The advantage of ion implantation is its 
compatibility with industrial Si device production 
lines. In this technique, high-fluence ion implantation 
produces a supersaturation of one or more implanted 
species in the near-surface of crystalline or amor-
phous matrix. The embedded impurities then form 
precipitates within the host during thermal pro-
cessing at elevated temperatures. Unfortunately, 
thermal processing of implanted crystals results not 
only in precipitation and radiation damage recovery. 
Negative consequences of thermal processing exist, 
too. High-fluence implantation of heavy ions results in 
a significant damage of Si crystalline lattice. Partly, a 
damaged crystal structure recovers during post-
implantation annealing. At the same time a “second-
ary” defect formation (dislocation loops, microtwins) 
takes place after high temperature treatment. Thus, 
on the one hand complex defect structures are formed 
during implantation and annealing at elevated tem-
peratures, which significantly influence the for-
mation, the size, and the depth distribution of the 
precipitates. On the other hand, the existence of the 
precipitates has also a strong effect on the quality of 
the surrounding crystalline host after the post-
implantation annealing. The aim of this work is to 
present our results on structural characterization of 
“Si - InAs nanocrystals” system. 
 
2. EXPERIMENTAL 
 
(100) Si wafers were implanted at 25 and 500°C 
subsequently with As (170 keV, 3.2×10 16 cm-2) and In 
(250 keV, 2.8×10 16 cm-2). After that, the implanted 
samples were annealed at 950 and 1050°C for 3 
minutes using RTA in an inert ambient. A part of the 
samples implanted at the room temperature was ad-
ditionally exposed to H2+ ions (100 keV, 1.2×1016 cm–2 
in terms of atomic hydrogen). This procedure was per-
formed to obtain an internal getter at a depth of about 
500 nm during post-implantation annealing. A struc-
ture of the implanted samples was studied by means 
of TEM in plan-view geometry. The TEM investiga-
tions were performed using a Hitachi H-800 instru-
ment operating at 200 keV. The samples prepared for 
the TEM measurements have to be transparent for 
probe electron beam. It is possible if this thickness 
does not exceed 150 - 200 nm. For this reason for de-
tailed investigations of more deep regions into crystal 
bulk we combined PV-TEM preparation with the pre-
cise removal of thin layers from the surface of the 
sample. 
 
 L.A. VLASUKOVA, F.F. KOMAROV, O.V. MILCHANIN ET AL. PROC. NAP 1, 04RES08 (2012) 
 
 
04RES08-2 
3. RESULTS AND DISCUSSION  
 
Figure 1 depicts TEM-images of the samples after 
room temperature implantation and RTA.  
 
 
 
Fig. 1 – TEM images of the samples implanted at 25°C and 
annealed at 1050°C for 3 min. The samples with getter layer 
(a, b) and without getter layer (c, d) 
 
On the plan-view images of the subsurface region 
up to depth of about 150 – 200 nm one can see precipi-
tates. The size of ones varies in the range about of (5 – 
40) nm). The crystalline nature of the precipitates is 
proved via the presence of Moiré fringe patterns in the 
nanocluster TEM images (inset in Fig. 1a). The Moiré 
fringes at precipitates are caused by the overlap of two 
crystalline lattices with closed parameters. In our ex-
perimental conditions it is possible a formation of In, 
As, and InAs crystallites. We have calculated Moiré 
fringe distance for the In, As, and InAs crystallites in 
Si matrix. The following equation has been used: 
 
 1 2
1 2
d d
D
d d
,  
 
where D is the distance between the Moiré fringes, and 
d1 and d2 are the first and the second interplanar dis-
tances of the lattice, respectively. 
We have compared the calculated quantities with 
the values measured from the bright-field TEM images. 
The experimental value of 1.8 nm is in a good agree-
ment with the calculated one of 1.818 nm for the {220} 
planes of crystalline InAs.  
The layer of secondary defects is situated at the 
depths of 300 - 400 nm (b, d). The getter layer introduc-
tion does not affect the size and density of the nano-
crystals. Though, the structure of the layer with sec-
ondary defects is different for samples with and with-
out the getter. Thus, for the sample without the getter 
(d) elongated curved defects of dislocation type and the 
disordered region are observed at the depths of 300 - 
400 nm (marked with arrows). The size of the disor-
dered regions gets up to 500 nm. The layer with sec-
ondary defects for the sample with the getter consists 
of densely packed small dislocation loops (b). Figures 2 
and 3 present TEM-images of the samples after “hot” 
implantation and RTA. One can see from Figure 2 that 
the "hot" implantation leads to a significant increase of 
the size and density of clusters in comparison with the 
room temperature one. 
 
 
 
Fig. 2 – Bright-field (a, c, d) and dark-field (b) images of the 
samples implanted at 500 ºC and annealed for 3 minutes at 
1050°C (a, b) and at 950°C (c, d). Right top insets are diffrac-
tion patterns and left top insets are precipitate images taken 
at high magnification (a, c)  
 
The largest precipitates have a size of ~ 100 nm. In 
microdiffraction patterns (insets in a, c) reflections 
from microtwins are clearly visible. The density of pre-
cipitates in the samples after RTA at 950°C is higher in 
comparison with the samples annealed at 1050°C. The 
characteristic Moiré fringes are observed at the precipi-
tates, too. However, for large inclusions the Moiré 
fringe period are larger than for small ones in the sam-
ples implanted at room temperature (Fig.1a, c). A ten-
dency of Moiré period increasing is also observed with 
increasing sizes of incorporations. 
In order to interpret the obtained Moiré patterns let 
us consider the results reported in [2]. In this paper the 
dependence of the Moiré fringe period on the quantum 
dot size, the presence of stress and the atoms of anoth-
er sort was investigated for quantum dots InSb grown 
on a substrate InAs by liquid phase epitaxy. In particu-
lar, it was shown that for small QDs (less than 17 nm) 
the Moiré period corresponded to the calculated value 
for a pure material InSb. For larger ones (30 - 45 nm) 
the Moiré period was significantly larger than for a 
pure material. The authors showed that the increase of 
the Moiré period was observed due to the presence of 
arsenic atoms in QDs. In our case the increase of the 
Moiré fringe distance can also be associated with the 
presence of excessive amounts of As or In inside precip-
itates. In addition, the increase of the Moiré period can 
be caused by a partial loss of coherence and the pres-
ence of stresses inside large inclusions. 
It should be noted that precipitates seem larger on 
the dark-field image because of "glow" of the bounda-
ries between nanocrystals and the silicon matrix 
(Fig. 2b). A large number of small (2 to 5 nm) clusters 
are also present on the dark-field image. A bimodal 
distribution of cluster sizes is observed for samples 
annealed at 950°C, too (d). Figure 3 illustrates a struc-
ture difference for samples implanted in "hot" condi-
tions and annealed at 950 and 1050°C.  
One can see dislocations connected with large precip-
itates in the annealed samples. In addition, there are 
dislocations - precipitates conglomerates in the samples 
annealed at 950°C. Separate dislocations connected with 
precipitates and chains of precipitates connected with 
lines of dislocations form a cellular structure (c, d). 
 STRUCTURAL PECULIARITIES OF A3B5 NANOCRYSTALS… PROC. NAP 1, 04RES08 (2012) 
 
 
04RES08-3 
 
 
Fig. 3 – TEM images of the samples implanted at 500 °C and 
annealed at 1050 °C (a, b) and at 950 °C (c, d)  
 
In order to explain an appearance of cellular struc-
ture let us discuss the data presented at [3]. The au-
thors of [3] have been studied a strain relief of InN 
quantum dots grown on GaN/sapphire wafers. An av-
erage InN island diameter was equal to 73±12 nm, an 
average height - 12±2 nm. This values and large precip-
itate size from our experiment are similar. In highly 
mismatched heterosystems, it is well-known that the 
strain is relieved by the generation of an array of geo-
metrical misfit dislocations at the interface between 
the two materials [4, 5]. The authors of [3] have been 
carried out an analysis of Moiré fringe patterns on InN 
QDs and a computer processing of high-resolution TEM 
images. It has been shown that a strain relief at InN 
QDs is accomplished due to the generation of a 60°-
misfit dislocation network at the InN/GaN interface. 
When they are close to the boundary of the quantum 
dot, the dislocations bend due to the free surface forces, 
thus forming a network of threading dislocations sur-
rounding the QD. Threading dislocations do not appear 
to be present inside the dots. Though, it has been found 
separate dislocations propagated into GaN matrix. 
A lattice mismatch for InAs/Si system is equal of 
11.5%. The formation of large InAs precipitates should 
be result in an appearance of significant mechanical 
strains at «InAs nanocrystal/Si» interfaces. In our case 
the same strain relief mechanism can act as for the 
InN/GaN system that discussed above. Probably, an 
effect of «glowing” nanocrystal/Si interfaces (Fig. 2b) is 
due to dislocation networks formation close the precipi-
tates. It is very likely, the dislocation in silicon matrix 
beside the nanocrystals (Fig. 3c, d) are created because 
of strain relief at InAs/Si interface. If a large precipi-
tate density is high enough the dislocations at high 
temperature can interact and create conglomerates like 
cellular structures.  
 
4. CONCLUSIONS 
 
The structural characteristics of the precipitates 
created in silicon matrix by means of (As + In) ion im-
plantation followed by RTA have been studied using 
TEM. 
It has been shown that small inclusions with size 
from 5 to 40 nm are formed in the samples implanted 
at room temperature. The crystalline nature of inclu-
sions is proved by the presence of Moiré fringe patterns 
in the nanocluster TEM images. The precipitates are 
identified as InAs nanocrystals from a comparison of 
calculated and measured Moiré fringe distances. 
A getter introduction by means of an additional im-
plantation of H2+(100 keV, 1,2×1016 cm-2) does not in-
fluence on the precipitate density and size, but results 
in the formation of layer of densely packed small dislo-
cation loops at the depth nearly of 300 – 400 nm.  
“Hot” implantation conditions lead to remarkable 
increasing of size (up to 100 nm) and density of precipi-
tates formed after annealing. It is marked an increas-
ing of Moiré fringe period for large precipitates. We 
ascribe it to a presence of excessive amounts of As or In 
inside precipitates. 
The effect of precipitate interfaces “glowing” was 
observed at the dark-field TEM images of large precipi-
tates. We attribute it to the formation of a dislocation 
network around each precipitate due to relaxation of 
mechanical stresses on the boundaries between the 
nanocrystals and the silicon matrix. The process of 
stress relaxation at the boundaries of precipitates also 
leads to the formation of individual dislocations. In 
case of a high density of precipitates certain disloca-
tions can interact with each other to form larger con-
gestion such as cellular networks. 
 
 
REFERENCES 
 
1. F. Komarov, L.Vlasukova, W. Wesh, et al, Nucl. Instrum. 
Meth. B. 266,  3557 (2008). 
2. K.D. Moiseev, Ya.A. Parkhomenko, E.V. Gushchina at all, 
Semiconductors 43,1102 (2009). 
3. J.G. Lozano, A.M. Sanchez, R. Garcıa, et al., Nanoscale 
Res. Lett. 2, 442 (2007). 
4. V. Lebedev, V. Cimalla, J. Pezoldt et al., J. Appl. Phys. 
100, 094902 (2006). 
5. E. Bellet-Amalric, C. Adelmann, E. Sarigiannidou, et al., 
J. Appl. Phys. 95, 1127 (2004). 
 
а 
d 
 
c 
b 


Structural Peculiarities of A3B5 Nanocrystals Created in Si by Ion-Beam Synthesis

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 1 No 4, 04RES08(3pp) (2012)   2304-1862/2012/1(4)04RES08(3) 04RES08-1  2012 Sumy State University Structural Peculiarities of A3B5 Nanocrystals Created in Si by Ion-Beam Synthesis  L.A. Vlasukova1, F.F. Komarov1, O.V. Milchanin1, I.N. Parkhomenko1, J. Zuk2  1 Belarusian State University, 4, Nezavisimosti ave. 4, 220030 Minsk, Belarus 2 Maria Curie-Skłodowska University, pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland  (Received 22 June 2012; published online 24 August 2012)  We reported the structure peculiarities of nanocrystals formed in Si by means of high-fluence implan-tation at 25 and 500 °С followed by rapid thermal annealing (RTA). The structure of implanted samples has been investigated by means of transmission electron microscopy (TEM). The crystalline nature of the precipitates is proved by the Moiré fringe patterns presence in the TEM images. The Moiré fringe distance  (Moiré period) is equal of 1.8 nm for small precipitates. This experimental value coincides with the calcu-lated one for crystalline InAs. It is noted a Moiré period increasing in the case of large precipitates. We suppose that this feature is a result of surplus As or In atoms embedded in precipitates. One can see an in-teresting effect – “glowng” of nanocrystal/Si interfaces at the dark-field images of implanted and annealed samples. We ascribe this effect to a presence of misﬁt dislocation networks at the InAs/Si interfaces gener-ated as a result of strain relaxation in highly mismatched InAs/Si system.  Keywords: Crystalline silicon, InAs nanocrystals, High-fluence implantation, Thermal treatment   PACS numbers: 61.46._w; 61.72.Tt; 68.37.Lp; 78.67.Bf   1. INTRODUCTION  With the increasing of miniaturization current Si technology approaches more and more the physical limits drawn by the material properties of Si. Cur-rently used metal interconnections will cause serious problems in future such as heat penalty, nonaccepta-ble delay and complexity, crosstalk. On-chip optical interconnections are believed to be able to overcome these problems. The quest is for an efficient light source operating at room temperature and preferably emitting in a narrow wavelength range. Red or near-infrared light would be very suitable for communica-tion purposes. A light-emitting source based on silicon would be a radical solution. Unfortunately, Si is inap-plicable to operate as a light emitter due to its indi-rect band gap of about 1.1 eV. This has motivated an intense research for light emitting materials which can replace Si but can be integrates well in the cur-rent Si technology. Light-emitting diodes and lasers based on A3B5 semiconductors show excellent tech-nical qualities, but their integration into a silicon chip is problematical. Furthermore, it is impossible to grow direct band gap A3B5 materials epitaxially on Si wa-fers because of the large lattice misfit. A direct crea-tion of narrow-gap A3B5 quantum dots (QDs) in crys-talline silicon by ion implantation followed by thermal annealing is a promising approach to overcome this difficulty. Density and size of nanocrystals can be con-trolled by varying implantation and annealing condi-tions [1]. The advantage of ion implantation is its compatibility with industrial Si device production lines. In this technique, high-fluence ion implantation produces a supersaturation of one or more implanted species in the near-surface of crystalline or amor-phous matrix. The embedded impurities then form precipitates within the host during thermal pro-cessing at elevated temperatures. Unfortunately, thermal processing of implanted crystals results not only in precipitation and radiation damage recovery. Negative consequences of thermal processing exist, too. High-fluence implantation of heavy ions results in a significant damage of Si crystalline lattice. Partly, a damaged crystal structure recovers during post-implantation annealing. At the same time a “second-ary” defect formation (dislocation loops, microtwins) takes place after high temperature treatment. Thus, on the one hand complex defect structures are formed during implantation and annealing at elevated tem-peratures, which significantly influence the for-mation, the size, and the depth distribution of the precipitates. On the other hand, the existence of the precipitates has also a strong effect on the quality of the surrounding crystalline host after the post-implantation annealing. The aim of this work is to present our results on structural characterization of “Si - InAs nanocrystals” system.  2. EXPERIMENTAL  (100) Si wafers were implanted at 25 and 500°C subsequently with As (170 keV, 3.2×10 16 cm-2) and In (250 keV, 2.8×10 16 cm-2). After that, the implanted samples were annealed at 950 and 1050°C for 3 minutes using RTA in an inert ambient. A part of the samples implanted at the room temperature was ad-ditionally exposed to H2+ ions (100 keV, 1.2×1016 cm–2 in terms of atomic hydrogen). This procedure was per-formed to obtain an internal getter at a depth of about 500 nm during post-implantation annealing. A struc-ture of the implanted samples was studied by means of TEM in plan-view geometry. The TEM investiga-tions were performed using a Hitachi H-800 instru-ment operating at 200 keV. The samples prepared for the TEM measurements have to be transparent for probe electron beam. It is possible if this thickness does not exceed 150 - 200 nm. For this reason for de-tailed investigations of more deep regions into crystal bulk we combined PV-TEM preparation with the pre-cise removal of thin layers from the surface of the sample.   L.A. VLASUKOVA, F.F. KOMAROV, O.V. MILCHANIN ET AL. PROC. NAP 1, 04RES08 (2012)   04RES08-2 3. RESULTS AND DISCUSSION   Figure 1 depicts TEM-images of the samples after room temperature implantation and RTA.     Fig. 1 – TEM images of the samples implanted at 25°C and annealed at 1050°C for 3 min. The samples with getter layer (a, b) and without getter layer (c, d)  On the plan-view images of the subsurface region up to depth of about 150 – 200 nm one can see precipi-tates. The size of ones varies in the range about of (5 – 40) nm). The crystalline nature of the precipitates is proved via the presence of Moiré fringe patterns in the nanocluster TEM images (inset in Fig. 1a). The Moiré fringes at precipitates are caused by the overlap of two crystalline lattices with closed parameters. In our ex-perimental conditions it is possible a formation of In, As, and InAs crystallites. We have calculated Moiré fringe distance for the In, As, and InAs crystallites in Si matrix. The following equation has been used:   1 21 2d dDd d,   where D is the distance between the Moiré fringes, and d1 and d2 are the first and the second interplanar dis-tances of the lattice, respectively. We have compared the calculated quantities with the values measured from the bright-field TEM images. The experimental value of 1.8 nm is in a good agree-ment with the calculated one of 1.818 nm for the {220} planes of crystalline InAs.  The layer of secondary defects is situated at the depths of 300 - 400 nm (b, d). The getter layer introduc-tion does not affect the size and density of the nano-crystals. Though, the structure of the layer with sec-ondary defects is different for samples with and with-out the getter. Thus, for the sample without the getter (d) elongated curved defects of dislocation type and the disordered region are observed at the depths of 300 - 400 nm (marked with arrows). The size of the disor-dered regions gets up to 500 nm. The layer with sec-ondary defects for the sample with the getter consists of densely packed small dislocation loops (b). Figures 2 and 3 present TEM-images of the samples after “hot” implantation and RTA. One can see from Figure 2 that the "hot" implantation leads to a significant increase of the size and density of clusters in comparison with the room temperature one.    Fig. 2 – Bright-field (a, c, d) and dark-field (b) images of the samples implanted at 500 ºC and annealed for 3 minutes at 1050°C (a, b) and at 950°C (c, d). Right top insets are diffrac-tion patterns and left top insets are precipitate images taken at high magnification (a, c)   The largest precipitates have a size of ~ 100 nm. In microdiffraction patterns (insets in a, c) reflections from microtwins are clearly visible. The density of pre-cipitates in the samples after RTA at 950°C is higher in comparison with the samples annealed at 1050°C. The characteristic Moiré fringes are observed at the precipi-tates, too. However, for large inclusions the Moiré fringe period are larger than for small ones in the sam-ples implanted at room temperature (Fig.1a, c). A ten-dency of Moiré period increasing is also observed with increasing sizes of incorporations. In order to interpret the obtained Moiré patterns let us consider the results reported in [2]. In this paper the dependence of the Moiré fringe period on the quantum dot size, the presence of stress and the atoms of anoth-er sort was investigated for quantum dots InSb grown on a substrate InAs by liquid phase epitaxy. In particu-lar, it was shown that for small QDs (less than 17 nm) the Moiré period corresponded to the calculated value for a pure material InSb. For larger ones (30 - 45 nm) the Moiré period was significantly larger than for a pure material. The authors showed that the increase of the Moiré period was observed due to the presence of arsenic atoms in QDs. In our case the increase of the Moiré fringe distance can also be associated with the presence of excessive amounts of As or In inside precip-itates. In addition, the increase of the Moiré period can be caused by a partial loss of coherence and the pres-ence of stresses inside large inclusions. It should be noted that precipitates seem larger on the dark-field image because of "glow" of the bounda-ries between nanocrystals and the silicon matrix (Fig. 2b). A large number of small (2 to 5 nm) clusters are also present on the dark-field image. A bimodal distribution of cluster sizes is observed for samples annealed at 950°C, too (d). Figure 3 illustrates a struc-ture difference for samples implanted in "hot" condi-tions and annealed at 950 and 1050°C.  One can see dislocations connected with large precip-itates in the annealed samples. In addition, there are dislocations - precipitates conglomerates in the samples annealed at 950°C. Separate dislocations connected with precipitates and chains of precipitates connected with lines of dislocations form a cellular structure (c, d).  STRUCTURAL PECULIARITIES OF A3B5 NANOCRYSTALS… PROC. NAP 1, 04RES08 (2012)   04RES08-3   Fig. 3 – TEM images of the samples implanted at 500 °C and annealed at 1050 °C (a, b) and at 950 °C (c, d)   In order to explain an appearance of cellular struc-ture let us discuss the data presented at [3]. The au-thors of [3] have been studied a strain relief of InN quantum dots grown on GaN/sapphire wafers. An av-erage InN island diameter was equal to 73±12 nm, an average height - 12±2 nm. This values and large precip-itate size from our experiment are similar. In highly mismatched heterosystems, it is well-known that the strain is relieved by the generation of an array of geo-metrical misfit dislocations at the interface between the two materials [4, 5]. The authors of [3] have been carried out an analysis of Moiré fringe patterns on InN QDs and a computer processing of high-resolution TEM images. It has been shown that a strain relief at InN QDs is accomplished due to the generation of a 60°-misfit dislocation network at the InN/GaN interface. When they are close to the boundary of the quantum dot, the dislocations bend due to the free surface forces, thus forming a network of threading dislocations sur-rounding the QD. Threading dislocations do not appear to be present inside the dots. Though, it has been found separate dislocations propagated into GaN matrix. A lattice mismatch for InAs/Si system is equal of 11.5%. The formation of large InAs precipitates should be result in an appearance of significant mechanical strains at «InAs nanocrystal/Si» interfaces. In our case the same strain relief mechanism can act as for the InN/GaN system that discussed above. Probably, an effect of «glowing” nanocrystal/Si interfaces (Fig. 2b) is due to dislocation networks formation close the precipi-tates. It is very likely, the dislocation in silicon matrix beside the nanocrystals (Fig. 3c, d) are created because of strain relief at InAs/Si interface. If a large precipi-tate density is high enough the dislocations at high temperature can interact and create conglomerates like cellular structures.   4. CONCLUSIONS  The structural characteristics of the precipitates created in silicon matrix by means of (As + In) ion im-plantation followed by RTA have been studied using TEM. It has been shown that small inclusions with size from 5 to 40 nm are formed in the samples implanted at room temperature. The crystalline nature of inclu-sions is proved by the presence of Moiré fringe patterns in the nanocluster TEM images. The precipitates are identified as InAs nanocrystals from a comparison of calculated and measured Moiré fringe distances. A getter introduction by means of an additional im-plantation of H2+(100 keV, 1,2×1016 cm-2) does not in-fluence on the precipitate density and size, but results in the formation of layer of densely packed small dislo-cation loops at the depth nearly of 300 – 400 nm.  “Hot” implantation conditions lead to remarkable increasing of size (up to 100 nm) and density of precipi-tates formed after annealing. It is marked an increas-ing of Moiré fringe period for large precipitates. We ascribe it to a presence of excessive amounts of As or In inside precipitates. The effect of precipitate interfaces “glowing” was observed at the dark-field TEM images of large precipi-tates. We attribute it to the formation of a dislocation network around each precipitate due to relaxation of mechanical stresses on the boundaries between the nanocrystals and the silicon matrix. The process of stress relaxation at the boundaries of precipitates also leads to the formation of individual dislocations. In case of a high density of precipitates certain disloca-tions can interact with each other to form larger con-gestion such as cellular networks.   REFERENCES  1. F. Komarov, L.Vlasukova, W. Wesh, et al, Nucl. Instrum. Meth. B. 266,  3557 (2008). 2. K.D. Moiseev, Ya.A. Parkhomenko, E.V. Gushchina at all, Semiconductors 43,1102 (2009). 3. J.G. Lozano, A.M. Sanchez, R. Garcıa, et al., Nanoscale Res. Lett. 2, 442 (2007). 4. V. Lebedev, V. Cimalla, J. Pezoldt et al., J. Appl. Phys. 100, 094902 (2006). 5. E. Bellet-Amalric, C. Adelmann, E. Sarigiannidou, et al., J. Appl. Phys. 95, 1127 (2004).  а d  c b 

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Structural Peculiarities of A3B5 Nanocrystals Created in Si by Ion-Beam Synthesis

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