Investigation of luminescent properties inherent to SrTiO₃:Pr³⁺ luminophor with Al impurity
The red-emitting SrTiO₃:Pr³⁺,Al luminophors that can be used for the white light emitting diodes (LEDs) were prepared using the sol-gel method. The starting materials were SrCl₂, Ti (O – i – C₃H₇)₄, Al(NO₃)₃·9H₂O and PrCl₃. The reaction between them results in a mixture of compounds that transfor...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2011
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| Цитувати: | Investigation of luminescent properties inherent to SrTiO₃:Pr³⁺ luminophor with Al impurity / O.M. Marchylo, L.V. Zavyalova, Y. Nakanishi, H. Kominami, A.E. Belyaev, G.S. Svechnikov // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2011. — Т. 14, № 4. — С. 461-464. — Бібліогр.:11 назв. — англ. |
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irk-123456789-1177922017-05-27T03:05:03Z Investigation of luminescent properties inherent to SrTiO₃:Pr³⁺ luminophor with Al impurity Marchylo, O.M. Zavyalova, L.V. Nakanishi, Y. Kominami, H. Belyaev, A.E. Svechnikov, G.S. The red-emitting SrTiO₃:Pr³⁺,Al luminophors that can be used for the white light emitting diodes (LEDs) were prepared using the sol-gel method. The starting materials were SrCl₂, Ti (O – i – C₃H₇)₄, Al(NO₃)₃·9H₂O and PrCl₃. The reaction between them results in a mixture of compounds that transform into single-phase SrTiO₃:Pr³⁺,Al after annealing in air. Displacement of Ti out of the SrTiO₃ lattice caused by substitution with Al and formation of individual crystalline TiO₂ phase (rutile) were observed. PL spectra show the high-intense red peak (λ = 617 nm), the same high-intense peak with the full width at half maximum (FWHM) 20 nm was found in cathodoluminescence spectra. The increase of the aluminium concentration from 0 up to 15 mol.% leads to approximately two-fold increase in the luminance. The latter increases from 180 up to 350 cd/m² at the anode voltage 10 kV and current density 30 μA/cm² . 2011 Article Investigation of luminescent properties inherent to SrTiO₃:Pr³⁺ luminophor with Al impurity / O.M. Marchylo, L.V. Zavyalova, Y. Nakanishi, H. Kominami, A.E. Belyaev, G.S. Svechnikov // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2011. — Т. 14, № 4. — С. 461-464. — Бібліогр.:11 назв. — англ. 1560-8034 PACS 61.05.cp, 78.55.-m, 78.60.Hk, 81.20.Fw http://dspace.nbuv.gov.ua/handle/123456789/117792 en Semiconductor Physics Quantum Electronics & Optoelectronics Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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English |
| description |
The red-emitting SrTiO₃:Pr³⁺,Al luminophors that can be used for the white
light emitting diodes (LEDs) were prepared using the sol-gel method. The starting
materials were SrCl₂, Ti (O – i – C₃H₇)₄, Al(NO₃)₃·9H₂O and PrCl₃. The reaction
between them results in a mixture of compounds that transform into single-phase
SrTiO₃:Pr³⁺,Al after annealing in air. Displacement of Ti out of the SrTiO₃ lattice caused
by substitution with Al and formation of individual crystalline TiO₂ phase (rutile) were
observed. PL spectra show the high-intense red peak (λ = 617 nm), the same high-intense
peak with the full width at half maximum (FWHM) 20 nm was found in
cathodoluminescence spectra. The increase of the aluminium concentration from 0 up to
15 mol.% leads to approximately two-fold increase in the luminance. The latter increases
from 180 up to 350 cd/m²
at the anode voltage 10 kV and current density 30 μA/cm²
. |
| format |
Article |
| author |
Marchylo, O.M. Zavyalova, L.V. Nakanishi, Y. Kominami, H. Belyaev, A.E. Svechnikov, G.S. |
| spellingShingle |
Marchylo, O.M. Zavyalova, L.V. Nakanishi, Y. Kominami, H. Belyaev, A.E. Svechnikov, G.S. Investigation of luminescent properties inherent to SrTiO₃:Pr³⁺ luminophor with Al impurity Semiconductor Physics Quantum Electronics & Optoelectronics |
| author_facet |
Marchylo, O.M. Zavyalova, L.V. Nakanishi, Y. Kominami, H. Belyaev, A.E. Svechnikov, G.S. |
| author_sort |
Marchylo, O.M. |
| title |
Investigation of luminescent properties inherent to SrTiO₃:Pr³⁺ luminophor with Al impurity |
| title_short |
Investigation of luminescent properties inherent to SrTiO₃:Pr³⁺ luminophor with Al impurity |
| title_full |
Investigation of luminescent properties inherent to SrTiO₃:Pr³⁺ luminophor with Al impurity |
| title_fullStr |
Investigation of luminescent properties inherent to SrTiO₃:Pr³⁺ luminophor with Al impurity |
| title_full_unstemmed |
Investigation of luminescent properties inherent to SrTiO₃:Pr³⁺ luminophor with Al impurity |
| title_sort |
investigation of luminescent properties inherent to srtio₃:pr³⁺ luminophor with al impurity |
| publisher |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| publishDate |
2011 |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/117792 |
| citation_txt |
Investigation of luminescent properties inherent to SrTiO₃:Pr³⁺ luminophor with Al impurity / O.M. Marchylo, L.V. Zavyalova, Y. Nakanishi, H. Kominami, A.E. Belyaev, G.S. Svechnikov // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2011. — Т. 14, № 4. — С. 461-464. — Бібліогр.:11 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
| work_keys_str_mv |
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2025-07-08T12:48:29Z |
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2025-07-08T12:48:29Z |
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Semiconductor Physics, Quantum Electronics & Optoelectronics, 2011. V. 14, N 4. P. 461-464.
PACS 61.05.cp, 78.55.-m, 78.60.Hk, 81.20.Fw
Investigation of luminescent properties inherent
to SrTiO3:Pr3+ luminophor with Al impurity
O.M. Marchylo1, L.V. Zavyalova1, Y. Nakanishi2, H. Kominami2, A.E. Belyaev1, G.S. Svechnikov1
1V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine,
41, prospect Nauky, 03028 Kyiv, Ukraine
2Research Institute of Electronics, Shizuoka University,
3-5-1 Johoku, Naka-ku, Hamamatsu 432-8011, Japan
Abstract. The red-emitting SrTiO3:Pr3+,Al luminophors that can be used for the white
light emitting diodes (LEDs) were prepared using the sol-gel method. The starting
materials were SrCl2, Ti (O – i – C3H7)4, Al(NO3)3·9H2O and PrCl3. The reaction
between them results in a mixture of compounds that transform into single-phase
SrTiO3:Pr3+,Al after annealing in air. Displacement of Ti out of the SrTiO3 lattice caused
by substitution with Al and formation of individual crystalline TiO2 phase (rutile) were
observed. PL spectra show the high-intense red peak (λ = 617 nm), the same high-intense
peak with the full width at half maximum (FWHM) 20 nm was found in
cathodoluminescence spectra. The increase of the aluminium concentration from 0 up to
15 mol.% leads to approximately two-fold increase in the luminance. The latter increases
from 180 up to 350 cd/m2 at the anode voltage 10 kV and current density 30 μA/cm2.
Keywords: luminophor, SrTiO3:Pr3+,Al, photoluminescence, cathodoluminescence, LED.
Manuscript received 21.07.11; revised manuscript received 29.08.11; accepted for
publication 14.09.11; published online 30.11.11.
1. Introduction
In recent years, white light emitting diodes (LED) have
been considered as a next generation of solid-state light
sources and used in many applications related with their
advantages, namely, their long operation lifetime and
low energy consumption [1–2]. A new method to obtain
white light is using near UV InGaN-based LEDs covered
by RGB-tricolor luminophors (red, green and blue).
Commercial red-emitting luminophor for white LEDs is
Y2O2S:Eu3+ that has lower efficiency, shorter operation
lifetime under UV irradiation as compared with blue and
green luminophors. Moreover, it has instability caused
by appearance of sulfide gas [3]. Further, the emission
color of Y2O2S:Eu3+ is inadequate. One of important
tasks in LED technologies is search of luminophors with
high performances. Therefore, many efforts are devoted
to develop new luminophors for white LEDs. Especially,
red emitting luminophors with a high luminance and
good color purity are required. Based on this
background, the red emitting luminophors for LEDs are
currently under investigation. For example, red-emitting
SrTiO3:Pr3+ luminophor has been investigated and
characterized [4–7]. Essential enhancement of the
emission intensity of SrTiO3:Pr3+ can be obtained by Al
addition [8]. Impurity of 23 mol.% Al intesifies emission
by more than 200 times. As shown earlier, the
SrTiO3:Pr3+ luminophor demonstrates high luminescent
characteristics and can be rather promising material for
LEDs. So far, SrTiO3:Pr3+ luminophors have been
synthesized by mixing SrCO3, TiO2, PrCl3 and Al(OH)3
with the subsequent sintering and crushing the prepared
powder.
In this work, to synthesize SrTiO3:Pr3+,Al we used
the sol-gel method with SrCl3, Ti (O – i – C3H7)4, PrCl3
and Al(NO3)3·9H2O as starting materials. By using this
method, we managed to get more complete reactions
between the starting materials and to obtain more
uniform distribution of the doped materials in the host
lattice. In this paper, we report about the influence of Al-
addition to luminophor SrTiO3:Pr3+ on its structural and
luminescent properties.
© 2011, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
461
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2011. V. 14, N 4. P. 461-464.
2. Synthesis of samples
The studied SrTiO3:Pr3+,Al luminophors were
synthesized using the sol-gel method similar to that in
[9] (Fig. 1). Starting materials were strontium chloride
SrCl2, praseodymium chloride PrCl3, aluminium nitrate
9-hydrate Al(NO3)3·9H2O and titanium tetra-i-propoxide
Ti (O – i – C3H7)4. Synthesis was carried out in nitrogen
atmosphere. A ratio of starting materials was Sr/Ti = 1
and concentration of Pr3+ was fixed at 1 mol.%. The
aluminium concentration was varied from 0 to
15 mol.%. The starting materials were dissolved in an
ethanol 96% (with water content of 4%) and stirred for 3
hours. Dissolution was not observed when SrCl2 and
PrCl3 were mixed with the dehydrated ethanol as well as
with dehydrated methanol. Complete dissolution was
observed when SrCl2 and PrCl3 were mixed with ethanol
containing 4% H2O. This suggests that water plays the
primary role in the process of SrCl2 and PrCl3
dissolution despite its small amount. Alcohol is
necessary for uniform distribution of small amounts of
water throughout the reactionary volume. Besides, water
apparently acts as the reagent that interacts with the
titanium tetra-i-propoxide titanium ( )473HCiOTi −− ,
resulting in formation of titanium hydroxide Ti(OH)4.
This is shown in transformation of transparent colorless
solution containing SrCl2 and PrCl3 into the white gel-
like substance. Apparently, it is caused by the reaction:
© 2011, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
Ti(O-i-C3H7)4 + 4 H2O → Ti(OH)4 (gel) + 4 C3H7OH.
Then solvent was evaporated (under the further
stirring) until the gel was obtained. This gel was dried at
the temperature 150 °С and sintered in a muffle furnace
CNOL 6.7/1300. Sintering was carried out in air under
the optimal temperature regime and time of annealing,
1300 ºC and 3 hours, respectively [9]. Finally, the
obtained material was crushed into powder.
3. Results and discussion
3.1. Morphology and XRD-analysis
To measure the size of particles, the alcohol suspension
of SrTiO3:Pr3+,Al powder was dispersed on a glass
substrate. The surface morphology was investigated with
raster microscope by using the method
secondary-emission of electrons. Morphology of
SrTiO
102EREM −
3:Pr3+,Al particles on glass surface is presented in
Fig. 2. In this figure, the arrow shows a single grain of
the most probable size. The crystal sizes mainly varied
within the range 1 to 5 μm and a small amount of
crystals and their conglomerates have sizes up to10 μm.
The structural analysis of the prepared luminophors
was carried out using the X-ray diffractometer
with CuK3MDRON − α radiation (λ = 1.542 Å). The
samples containing various concentrations of aluminium
were annealed at 1300 ºC for 5 hours and investigated.
Fig. 3 shows that Pr- and Al-containing starting
materials do not form individual crystalline compounds
in the final product, but incorporate into the crystal
lattice of SrTiO3 and replace Sr and Ti, respectively.
This substitution occurs because of the proximity values
of ionic radii of Pr and Sr, Al and Ti, respectively, which
is consistent with the results reported in [4, 6]. Thus, Al
replaces Ti in the lattice SrTiO3, which leads to
deterioration of the crystallinity. Moreover, Ti is
displaced from the lattice SrTiO3 and forms the
individual crystalline phase of TiO2-rutile.
We assume that formation of SrTiO3 can be
represented by the following processes:
1. Gel formation:
Ti(O-i-C3H7)4 + 4 H2O → Ti(OH)4 + 4 C3H7OH.
2. Annealing:
а) Ti(OH)4 → (600 – 800 °С) → TiO2 + 2 H2O;
b) 2SrCl2 + O2 → (1000 – 1250 °С) → 2SrO + 2Cl2.
Al(NO3)3•9H2O C2H5(OH)
H2O SrCl2
Ti(O-i-C3H7)4
Mixing at room
temperature
in N2 atmosphere
Mixing and
evaporation
o
Gel
Drying at 150 oC
Powder
Heat treatment
at 1300 °C
PrCl3
Fig. 1. Preparation of SrTiO3:Pr3+,Al luminophor.
Fig. 2. Microrelief of a glass surface with crystals of
SrTiO3:Pr3+,Al luminophor.
462
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2011. V. 14, N 4. P. 461-464.
20 25 30 35 40 45 50 55 60
0
200
400
600
800
1000
1200
1400SrTiO3(110)
Al = 0 mol.%
Al = 5 mol.%
(211)(111)
(200)
TiO2
(100)
Al = 15 mo
In
te
ns
ity
(a
rb
.u
ni
ts
)
Fig. 3. XRD spectra of the samples with various Al
concentrations.
3. Structuring:
TiO2 +SrO → (1000 – 1250 °С) → SrTiO3.
Thus, decomposition of titanium hydroxide and
formation of strontium oxide occur at different
temperatures, so they could not take place
simultaneously.
3.2. Photoluminescence spectra
Photoluminescence (PL) spectra were measured within
the wavelength range 450 to 750 nm under nitrogen laser
(wavelength 337 nm, pulse duration 8 ns) excitation at
the width of measuring strobe of 75 μs. Fig. 4 shows the
typical PL spectrum of the sample SrTiO3:Pr3+ with no
additional Al annealed at 1300 °C for 5 h. The PL
spectrum has three peaks, the highest intensity is
observed for the peak at λ = 617 nm. Blue emission with
its maximum at λmax1 = 488 nm corresponds to the intra-
4f transition from the excited state 3P0 to the ground state
3H4 of Pr3+, green emission with the maximum at λmax2 =
530 nm corresponds to the intra-4f transition from the
excited state 3P1 to the state 3H5, and red emission with
the maximum at λmax3 = 617 nm corresponds to the intra-
4f transition from the excited state 1D2 to the ground
state 3H4 [8, 10, 11].
450 500 550 600 650 700 750
0
20
40
60
80
100
3H5
3P1
3H4
In
te
ns
ity
, a
rb
.u
ni
ts
Wavelength, nm
3P0
3H
4
1D2
Fig. 4. PL spectrum of the sample SrTiO3:Pr3+.
The used increase in aluminium concentration from
0 up to 15 mol.% results in a slight growth of the
intensity of the main peak λmax3 = 617 nm (Fig. 5). Thus,
when the aluminum concentration is changed from 0 up
to 5 mol.%, an increase in the photoluminescence
intensity by 20% is observed. However, the further
increase in concentration from 5 to 15 mol.% leads to
insignificant decrease in the peak intensity λmax3 (Fig. 5,
insert).
3.3. Cathodoluminescence spectra
Cathodoluminescence (CL) was also investigated under
the electron beam excitation (current density 30 μA/cm2,
anode voltage 2 to 10 kV). The same samples of
SrTiO3:Pr3+,Al were investigated. The typical CL
spectrum of the sample SrTiO3:Pr3+,Al and its
comparison with PL spectra are shown in Fig. 6. It is
appeared that the shape of these spectra is completely
identical, and no shifts of the main peaks or
redistribution of their intensities is not observed. Both,
PL and CL spectra have the same intensity of red peak
with 20-nm FWHM.
500 600 700
0
20
40
60
80
100
610 615 620
75
90
105
PL
in
te
ns
ity
a
rb
.u
n.
Wavelength, nm
0% Al
5% Al
10% Al
15% Al
P
L
in
te
ns
ity
, a
rb
.u
ni
ts
Wavelength, nm
Fig. 5. PL spectra of the samples with various Al
concentrations.
450 500 550 600 650 700 750
0
20
40
60
80
100
CL
PL
3H5
3P1
3H4
In
te
ns
ity
, a
rb
.u
ni
ts
Wavelength, nm
3P0
3H4
1D2
Fig. 6. CL and PL spectra of luminophor SrTiO3:Pr3+,Al (Al =
15 mol.%), the former being measured at Va = 2 kV,
Js = 30 μA/cm2, P = 7.8×10–9 Torr, adduced together for
comparison.
© 2011, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
463
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2011. V. 14, N 4. P. 461-464.
2 4 6 8
0
100
200
300
400
10
0% Al
5% Al
10% Al
15% Al
C
L
lu
m
in
an
ce
, c
d/
m
2
Voltage, kV
Fig. 7. Dependence of CL luminance on the anode voltage for
various Al concentrations. Js = 30 μA/cm2; P = 7.8×10–9 Torr.
The CL intensity measurements with increasing the
anode voltage show that the samples with no aluminium
addition have the luminance 177 cd/m2. The increase in
aluminium concentration from 0 up to 5 mol.% leads to
the 2-fold increase in luminance, and the latter reaches
333 cd/m2 at the anode voltage close to 10 kV (Fig. 7). A
further increase in aluminum concentration from 5 to
15 mol.% does not lead to any significant enhance in
luminance as it was reported in [8]. The maximum CL
luminance is observed at the concentration of aluminium
15 mol.%, and it reaches 354 cd/m2.
Thus, for the samples SrTiO3:Pr3+ the high
luminance 177 cd/m2 was obtained. The Al-addition of
15 mol.% leads to increase in luminance by 2 times, and
it reaches 354 cd/m2. These results are not consistent
with the data reported in the paper [8]. It was reported
earlier that initially SrTiO3:Pr3+ has an extreme low
luminance of the luminescence and only aluminium
addition can increase it by more than 200 times.
Therefore, such a discrepancy between the results
requires further researches.
4. Conclusions
It has been shown that mixture of compounds SrCl2,
Ti (O – i – C3H7)4, PrCl3 and Al(NO3)3·9H2O can be
transformed to SrTiO3:Pr3+,Al under definite
technological conditions. Herewith, displacement of Ti
out of SrTiO3 lattice due to substitution with Al and
formation of the individual crystalline TiO2-rutile phase
take place.
The increase in aluminium concentration from 0 up
to 15 mol.% results in a slight growth of the intensity of
the main peak λmax3 = 617 nm. Simultaneously, the
increase in aluminium concentration from 0 up to
15 mol.% leads to the 2-fold increase in luminance, and
the latter reaches 354 cd/m2 at the anode voltage value
10 kV and current density 30 μA/cm2 (Fig. 7).
A further increase in aluminum concentration from 5 to
15 mol.% does not lead to significant enhance in
luminance, as it was reported in [8]. The maximum CL
luminance is observed at the concentration of aluminum
15 mol.%, and its value reaches 354 cd/m2.
It has been found a significant difference between
the PL and CL data reported in this paper as compared
with the data reported earlier. This discrepancy between
the results requires further researches.
Thus, it has been shown that luminophor
SrTiO3:Pr3+,Al prepared using the sol-gel method is
promising material for further researches and
applications as the red-emitting one for white light
emitting diodes.
Acknowledgements
We are grateful to Dr. E. Manoilov for the PL
measurements, Dr. A. A. Korchevoi for XRD
measurements and V.I. Poludin for microrelief
measurements.
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© 2011, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
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