Abstract—The formation of thin-ﬁlm solid solutions of erbium in silicon and synthesis of erbium silicides
were performed using continuous implantation of silicon with erbium ions followed by pulsed ion-beam treat-
ment. Structural and optical properties of formed Si:Er layers were studied by Rutherford backscattering, trans-
mission electron microscopy, and low-temperature photoluminescence. The dependences of erbium redistribu-
tion, the microstructure of Si:Er layers, and their photoluminescence in the near-IR region on the erbium con-
centration and pulsed treatment conditions were determined

Alves, E.

Batalov, R. I.

Bayazitov, R. M.

Gaiduk, P. I.

Kryzhkov, D. I.

Marques, C. P.

Nurutdinov, R. M.

English

Электронная библиотека БГУ

 ISSN 1027-4510, Journal of Surface Investigation. X-ray, Synchrotron and Neutron Techniques, 2009, Vol. 3, No. 4, pp. 604–607. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © R.I. Batalov, R.M. Bayazitov, R.M. Nurutdinov, D.I. Kryzhkov, P.I. Gaiduk, C.P. Marques, E. Alves, 2009, published in Poverkhnost’. Rentgenovskie,
Sinkhrotronnye i Neitronnye Issledovaniya, No. 8, pp. 40–44.
 
604
 
INTRODUCTION
One of the promising directions in the development
of silicon structures emitting in the range of 1.5–1.6 
 
μ
 
m
is Si doping with rare-earth Er atoms. Due to intracenter
optical transitions between 
 
4
 
I
 
13/2
 
  
 
4
 
I
 
15/2
 
 levels in the
Er
 
3+
 
 ion, luminescence at the wavelength 
 
λ
 
 = 1.54 
 
μ
 
m is
characterized by a narrow line and is almost independent
of the temperature and matrix with introduced Er atom
[1]. The method of ion implantation is widely employed
to form light-emitting Si:Er solid solutions [2] and
erbium silicide films on silicon promising for use as
Schottky barriers in microelectronics [3]. A significant
disadvantage of the method of ion implantation is con-
siderable damage of the Si lattice during introduction of
heavy Er
 
+
 
 ions. To eliminate radiation damage and to
optically and electrically activate an impurity, high-tem-
perature annealing (
 
T
 
 > 900°
 
C) is usually performed.
However, along with elimination of simple defects, such
heat treatment can result in the formation of more com-
plex defects (dislocations, dislocation loops) [4] and
erbium silicide precipitates which decrease the effi-
ciency of Er luminescence. Moreover, high-temperature
annealing causes rapid diffusion of Er atoms to the Si
crystal depth, which creates difficulties in the fabrication
of light-emitting diodes due to strongly spread profiles of
introduced atoms.
Pulsed treatment of implanted Si layers by nanose-
cond laser, ion, or electron beams can be an alternative
to thermal annealing. Pulsed treatment allows localiza-
tion of annealing of an amorphous material over its
 
depth (smaller than 1 
 
μ
 
m) and area. Moreover, due to
high melting and crystallization rates, pulsed exposures
result in the formation of epitaxial layers with a low-
ered defect level [5]. It should be noted that the use of
pulsed treatment of Si:Er layers is rarely reflected in the
literature [6], which stimulates studies in this direction.
In this work, we studied the features of pulsed ion-
beam treatment (PIBT) of Si layers implanted with Er
 
+
 
ions.
EXPERIMENTAL
With the purpose of forming thin-film Si:Er solid solu-
tions and erbium silicides, 
 
n
 
-Si(100) wafers grown by the
Czochralski method were implanted with 100-keV
Er
 
+
 
 ions to doses 
 
Φ
 
 = 10
 
16
 
 and 
 
10
 
17
 
 cm
 
–2
 
 at room temper-
ature. To eliminate radiation defects, Si samples were sub-
jected to PIBT. A pulsed accelerator generated nanosec-
ond (
 
τ
 
 = 50 ns) ion beams with energy 
 
E
 
 = 300 keV, con-
sisting of carbon (~80%) and hydrogen (~20%). The
total ion dose per pulse did not exceed 
 
10
 
13
 
 cm
 
–2
 
. The
energy density (
 
W
 
 = 1–2 J/cm
 
2
 
) and the number of pulses
(
 
N
 
 = 1–10) were varied during PIBT. In addition to PIBT,
Si samples were subjected to 20-min thermal annealing
(TA) at 
 
T
 
 = 800°
 
C.
The depth distribution of implanted Er atoms after
ion implantation and PIBT was studied by Rutherford
backscattering (RBS), including ion channeling, using
a 2-MeV helium beam. The microstructure and phase
composition of Si:Er layers was studied by transmis-
 
Features of the Pulsed Treatment of Silicon Layers 
Implanted with Erbium Ions
 
R. I. Batalov
 
a
 
,
 
 
 
*
 
, R. M. Bayazitov
 
a
 
, R. M. Nurutdinov
 
a, D. I. Kryzhkov
 
b
 
, P. I. Gaiduk
 
c
 
, 
C. P. Marques
 
d
 
, and E. Alves
 
d
 
a
 
Kazan Physical-Technical Institute, Russian Academy of Sciences, Sibirskii trakt 107, Kazan, 420029 Russia
*e-mail: batalov@kfti.knc.ru
 
b
 
Institute for Physics of Microstructures, Russian Academy of Sciences, ul. Ul’yanova 46, Nizhni Novgorod, 603950 Russia
 
c
 
Belarusian State University, pr. Nezavisimosti 4, Minsk, 220030 Belarus
 
d
 
Nuclear and Technological Institute, Estrada Nacional 10, Sacavem PT-2686-953, Portugal
 
Received August 14, 2008
 
Abstract
 
—The formation of thin-film solid solutions of erbium in silicon and synthesis of erbium silicides
were performed using continuous implantation of silicon with erbium ions followed by pulsed ion-beam treat-
ment. Structural and optical properties of formed Si:Er layers were studied by Rutherford backscattering, trans-
mission electron microscopy, and low-temperature photoluminescence. The dependences of erbium redistribu-
tion, the microstructure of Si:Er layers, and their photoluminescence in the near-IR region on the erbium con-
centration and pulsed treatment conditions were determined.
 
DOI: 
 
10.1134/S102745100904020X
 JOURNAL OF SURFACE INVESTIGATION. X-RAY, SYNCHROTRON AND NEUTRON TECHNIQUES Vol. 3
 
 
 
 No. 4 2009
 
FEATURES OF THE PULSED TREATMENT OF SILICON LAYERS 605
 
sion electron microscopy (TEM). Photoluminescence
(PL) of Si:Er layers was studied in the near-IR range
(1–1.7 
 
μ
 
m) at 
 
T
 
 = 77 K. The PL signal was excited by
continuous radiation of an argon laser (
 
λ
 
 = 514.5 nm)
with power 
 
P
 
 = 200 mW. PL was recorded using a
BOMEM Fourier spectrometer with a cooled germa-
nium detector.
RESULTS AND DISCUSSION
Figure 1 shows unoriented and oriented (Si
 
〈
 
100
 
〉
 
)
RBS spectra of Si samples after ion implantation with
various doses and PIBT. We can see that, due to the low
implantation energy, Er atoms are concentrated in a
narrow range corresponding to the Gaussian peak near
the surface. Spectrum processing shows that the Er
peak halfwidth and amorphous Si layer thickness
increase with the dose from 55 and 110 nm for 
 
Φ
 
 =
10
 
16
 
 cm
 
–2
 
 to 80 and 130 nm for 
 
Φ
 
 
 
=
 
 
 
10
 
17
 
 cm
 
–2
 
, respec-
tively. We can see from Fig. 1a that PIBT results in epi-
taxial recrystallization of the amorphous Si layer
(helium ion beam channeling in the range of channels
450–500) and in displacement of an Er atom fraction to
the surface (the narrow peak ~30 nm thick (segrega-
tion)) and to the Si crystal depth (diffusion). The segre-
gation effect is caused by low Er solubility in Si
(
 
~10
 
16
 
 cm
 
–3
 
); the small width of the Er peak is caused
by the high velocity (~1 m/s) of the crystallization front
during hardening of the silicon melt. This effect is more
pronounced at lower implantation doses (
 
Φ
 
 < 10
 
16
 
 cm
 
–2
 
),
where almost all impurity atoms are displaced into a
thin surface peak to 30 nm thick. In contrast to Si, chan-
neling in the Er peak (channels 750–800) is absent after
PIBT, which indicates interstitial Er atom positions in
the Si lattice.
In the case of high-dose implantation (Fig. 1b), PIBT
results in significant suppression of Er segregation to the
surface, since the Er concentration in the implanted layer
reaches the eutectic point (
 
~10
 
22
 
 cm
 
–3
 
), and the coeffi-
cient of the impurity distribution approaches unity. In
this case, Er atoms mostly diffuse to the Si crystal depth,
and the diffusion tail becomes wider as the number of
pulses increases. Rapid diffusion of Er atoms in the Si
melt with diffusivity 
 
D 
 
~ 10
 
–4
 
 cm
 
2
 
/s results in an almost
twofold increase in the initial Er peak width; its initial
height approximately corresponding to 40 at % Er also
decreases almost twice. At such a high impurity concen-
tration, erbium silicides are formed, which is seen by an
RBS signal drop near the Si surface (channels 460–500).
We note that channeling in the Si region after PIBT is
less pronounced in this case; this indicates a certain dis-
order in the implanted layer, which can be associated
with the polycrystalline structure of Si and erbium sili-
cides. The prevalence of diffusion processes over segre-
gation ones and silicide formation at high concentra-
tions of a poorly soluble impurity was also observed in
the Si–Fe system during pulsed treatments [7].
The microstructure and phase composition of Si lay-
ers implanted withEr
 
+
 
 ions and subjected to PIBT were
studied by TEM and microdiffraction methods. Figure 2
shows the bright-field TEM images of implanted Si lay-
ers after PIBT. We can see that PIBT results in the forma-
tion of a cellular structure of the implanted layer in the
case of low-dose implantation (
 
Φ
 
 = 10
 
16
 
 cm
 
–2
 
) (Fig. 2a).
This structure represents large (to 0.2 
 
μ
 
m in size) Si cells
(columns) threading to the surface. Erbium (dark areas)
is concentrated in walls of these columns in the form of
erbium silicide precipitates up to 20 nm in size. Microd-
iffraction measurements of the cellular structure show
the presence of point reflexes associated with silicon and
erbium monosilicide (Si:Er), which indicates epitaxial
recrystallization of the implanted layer due to PIBT. This
result is in agreement with the RBS data (Fig. 1a) where
channeling is observed in the implanted layer region
after PIBT. The study of the microstructure of implanted
 
(b)
450 500 700 750 800
 
Channels
 
400
0
0.5
1.0
1.5
2.0
2.5
3.5
3.0
4.0
 
Y
ie
ld
 (c
ou
nts
/10
00
)
 
Φ
 
(Er) = 10
 
17
 
 ÒÏ
 
–2
 
Er
Si
 
unoriented
 
, 
 
W
 
 = 0
<100>, 
 
W
 
 = 0
<100>, 
 
W
 
 = 1.7,
 
 N
 
 = 2
<100>, 
 
W
 
 = 1.7, 
 
N
 
 = 10
(‡)
450 500 700 750 800
 
Channels
 
400
0
0.2
0.4
0.6
0.8
1.0
1.2
 
Y
ie
ld
 (c
ou
nts
/10
00
)
 
Φ
 
(Er) = 10
 
16
 
 ÒÏ
 
–2
 
Er
Si
 
unoriented
 
, 
 
W
 
 = 0
<100>, 
 
W
 
 = 0
<100>, 
 
W
 
 = 2,
 
 N
 
 = 2
 
unoriented
 
, 
 
W
 
 = 2, 
 
N
 
 = 2
 
Fig. 1.
 
 RBS and channeled ion spectra of Si(100) samples
after ion implantation and PIBT (
 
W
 
 = 1.7–2 J/cm
 
2
 
, 
 
N
 
 = 2–
10). Implantation doses are 
 
Φ
 
 = (a) 10
 
16
 
 and (b) 10
 
17
 
 cm
 
–2
 
.
Vertical arrows indicate the surface position for Si and Er.
 606
 
JOURNAL OF SURFACE INVESTIGATION. X-RAY, SYNCHROTRON AND NEUTRON TECHNIQUES Vol. 3
 
 
 
 No. 4 2009
 
BATALOV et al.
 
Si layers after PIBT and additional TA at temperatures
below 
 
900°ë
 
 showed that the cellular structure is highly
thermally stable and does not endure significant changes.
In the case of high-dose implantation of Er
 
+
 
 ions
 
(
 
Φ
 
 = 10
 
17
 
 cm
 
–2
 
), the formation of fine grains of silicon
and erbium silicides to 40 nm in size is observed
(Fig. 2b). The microdiffraction pattern shows the pres-
ence of a large number of rings (up to 20) caused by the
formation of polycrystalline Si and erbium disilicide
ErSi
 
2
 
 in the implanted layer. The formation of polycrys-
talline ErSi
 
2 is in agreement with the data of [3], where
high-dose and high-current-density implantation also
resulted in the formation of the polycrystalline ErSi2
phase. This is also confirmed by the RBS data (Fig. 1b),
according to which, the maximum concentration of the
Er atoms decreased from ~40 to ~20 at % due to PIBT.
To study the PL properties in a near-IR region, the
Si:Er layers obtained by ion implantation and PIBT
were additionally annealed in a furnace at T = 800°C for
20 min to eliminate point defects which are nonradia-
tive recombination centers. Figure 3 shows the PL spec-
tra (T = 77 K) of Si samples in which concentrations of
(a)
(b)
200 nm
20 nm
Fig. 2. Bright-field TEM images of the implanted Si layer
after PIBT (W = 2 J/cm2, N = 2). Implantation doses are
Φ = (a) 1016 and (b) 1017 cm–2.
T = 77 K
0
0.8 0.9 1.0 1.1 1.20.7
2000
4000
6000
8000
10000
Φ(Er) = 1017 cm–2 Si
1.098
Er
0.806
Photon energy, eV
PL
 in
te
ns
ity
,
 
ar
b.
 
u
n
.
T = 77 K
0
0.8 0.9 1.0 1.1 1.20.7
4000
8000
12000
16000
Φ(Er) = 1016 cm–2 Si1.098
Er
0.806
Photon energy, eV
PL
 in
te
ns
ity
,
 
ar
b.
 
u
n
.
(a)
(b)
Fig. 3. PL spectra of the implanted Si layer after PIBT (W =
1.4 J/cm2, N = 2) and additional TA (800°C, 20 min), mea-
sured at T = 77 K. Implantation doses are Φ = (a) 1016 and
(b) 1017 cm–2.
JOURNAL OF SURFACE INVESTIGATION. X-RAY, SYNCHROTRON AND NEUTRON TECHNIQUES Vol. 3  No. 4 2009
FEATURES OF THE PULSED TREATMENT OF SILICON LAYERS 607
Er atoms (~1021 and ~1022 cm–3) significantly exceed
their precipitation threshold (~1019 cm–3). Both spectra
contain two strong peaks at 0.806 and ~1.1 eV, and the
intensity of the latter peak is about one and a half times
higher. This peak is caused by Si band-edge lumines-
cence emitted from a depth of ~1 μm, i.e., the penetra-
tion depth of radiation of the Ar laser (λ = 514.5 nm). It
should be noted that, despite the high concentration of
the Er atoms in Si (N > 1021 cm–3) and erbium precipita-
tion in the form of optically inactive silicides, the PL
peak at 0.806 eV, caused by optical transitions between
the 4I13/2  4I15/2 levels of the Er3+ ion, exists in the
spectra of both samples. In our opinion, the light-emit-
ting region responsible for erbium PL at 0.806 eV is
mostly localized in the extended tail regions of the pro-
file of the impurity distribution, in which an Er solid
solution in Si is formed. The Er concentration in these
regions is 1018–1020 cm–3 which is significantly lower
than near the surface. We also note that the Er peak at
0.806 eV is overlapped with a broad peak in the energy
range of 0.75–0.9 eV in the PL spectrum of the second
sample. The latter peak is probably associated with the
formation of dislocation structures in the layer due to
high-dose implantation and thermal annealing. Thus,
despite the high concentration of erbium and its precip-
itation in the form of silicides, the obtained layers
exhibit photoluminescence properties in the near-IR
region, which allows the development of efficient light-
emitting diodes on their basis.
CONCLUSIONS
The formation of Er solid solutions in Si and synthe-
sis of erbium silicides using highly nonequilibrium
methods, i.e., continuous ion implantation and pulsed
treatment, were studied. The following results were
obtained.
Pulsed treatment of Si layers implanted with a rather
low dose of Er+ ion (Φ = 1016 cm–2) results in epitaxial
crystallization of the amorphous implanted layer with
the formation of cellular structures with Si cell sizes to
0.2 μm and preferential displacement of Er atoms to the
surface layer to 30 nm thick (segregation).
Pulsed treatment of Si layers implanted with a high
dose of Er+ ion (Φ = 1017 cm–2) results in unoriented
crystallization of the amorphous layer with the forma-
tion of polycrystalline erbium disilicide ErSi2 with
grain sizes up to 40 nm and diffusion redistribution of
Er impurity to the Si crystal depth.
High-dose ion implantation and nanosecond pulsed
treatments allow the formation of layers emitting in the
near-IR region with erbium impurity concentration sig-
nificantly exceeding the precipitation threshold.
ACKNOWLEDGMENTS
This study was supported in part by the Russian Foun-
dation for Basic Research, project no. 08-02-01280, pro-
gram “New Materials and Structures” of the Physical Sci-
ence Division of the Russian Academy of Sciences, and
the Russian Science Support Foundation.
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4. N. A. Sobolev, A. M. Emel’yanov, E. I. Shek, et al.,
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Features of the Pulsed Treatment of Silicon Layers  Implanted with Erbium Ions

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