Investigations of surface morphology and chemical composition of Ag/ZnS/glassceramic thin-film structure
The surface morphology and chemical composition of Ag/ZnS/glassceramic thin-film system obtained by close-spaced vacuum sublimation technique under different grow conditions were investigated. Examination of surface profile and morphology was performed by scanning electron and optical microscopy....
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2008
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| Цитувати: | Investigations of surface morphology and chemical composition of Ag/ZnS/glassceramic thin-film structure / D. Kurbatov, A. Opanasyuk, V. Denisenko, A. Kramchenkov, M. Zaharets // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2008. — Т. 11, № 3. — С. 252-256. — Бібліогр.: 14 назв. — англ. |
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nasplib_isofts_kiev_ua-123456789-1190592025-06-03T16:25:26Z Investigations of surface morphology and chemical composition of Ag/ZnS/glassceramic thin-film structure Kurbatov, D. Opanasyuk, A. Denisenko, V. Kramchenkov, A. Zaharets, M. The surface morphology and chemical composition of Ag/ZnS/glassceramic thin-film system obtained by close-spaced vacuum sublimation technique under different grow conditions were investigated. Examination of surface profile and morphology was performed by scanning electron and optical microscopy. Chemical composition was studied by Rutherford back scattering method. Results of morphology studies enabled to determine dependence of the growth mechanism, roughness Ra, grain size D of ZnS layers on the growth conditions. The researches of chemical composition allowed to determine the concentration of compound elements and impurities, deviation from stoichiometry and thickness distribution of chemical elements. The authors would like to thank Ph.D. V. Laptev from Institute of Physical Electronics (University of Stuttgart) for optical investigations of film surfaces. 2008 Article Investigations of surface morphology and chemical composition of Ag/ZnS/glassceramic thin-film structure / D. Kurbatov, A. Opanasyuk, V. Denisenko, A. Kramchenkov, M. Zaharets // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2008. — Т. 11, № 3. — С. 252-256. — Бібліогр.: 14 назв. — англ. 1560-8034 PACS 68.35.Ct, 68.55.J, 68.55.Nq https://nasplib.isofts.kiev.ua/handle/123456789/119059 en Semiconductor Physics Quantum Electronics & Optoelectronics application/pdf 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 surface morphology and chemical composition of Ag/ZnS/glassceramic
thin-film system obtained by close-spaced vacuum sublimation technique under different
grow conditions were investigated. Examination of surface profile and morphology was
performed by scanning electron and optical microscopy. Chemical composition was
studied by Rutherford back scattering method. Results of morphology studies enabled to
determine dependence of the growth mechanism, roughness Ra, grain size D of ZnS
layers on the growth conditions. The researches of chemical composition allowed to
determine the concentration of compound elements and impurities, deviation from
stoichiometry and thickness distribution of chemical elements. |
| format |
Article |
| author |
Kurbatov, D. Opanasyuk, A. Denisenko, V. Kramchenkov, A. Zaharets, M. |
| spellingShingle |
Kurbatov, D. Opanasyuk, A. Denisenko, V. Kramchenkov, A. Zaharets, M. Investigations of surface morphology and chemical composition of Ag/ZnS/glassceramic thin-film structure Semiconductor Physics Quantum Electronics & Optoelectronics |
| author_facet |
Kurbatov, D. Opanasyuk, A. Denisenko, V. Kramchenkov, A. Zaharets, M. |
| author_sort |
Kurbatov, D. |
| title |
Investigations of surface morphology and chemical composition of Ag/ZnS/glassceramic thin-film structure |
| title_short |
Investigations of surface morphology and chemical composition of Ag/ZnS/glassceramic thin-film structure |
| title_full |
Investigations of surface morphology and chemical composition of Ag/ZnS/glassceramic thin-film structure |
| title_fullStr |
Investigations of surface morphology and chemical composition of Ag/ZnS/glassceramic thin-film structure |
| title_full_unstemmed |
Investigations of surface morphology and chemical composition of Ag/ZnS/glassceramic thin-film structure |
| title_sort |
investigations of surface morphology and chemical composition of ag/zns/glassceramic thin-film structure |
| publisher |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| publishDate |
2008 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/119059 |
| citation_txt |
Investigations of surface morphology and chemical composition of Ag/ZnS/glassceramic thin-film structure / D. Kurbatov, A. Opanasyuk, V. Denisenko, A. Kramchenkov, M. Zaharets // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2008. — Т. 11, № 3. — С. 252-256. — Бібліогр.: 14 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
| work_keys_str_mv |
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| first_indexed |
2025-11-26T21:25:40Z |
| last_indexed |
2025-11-26T21:25:40Z |
| _version_ |
1849889753668780032 |
| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2008. V. 11, N3. P. 252-256.
© 2008, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
252
PACS 68.35.Ct, 68.55.J, 68.55.Nq
Investigations of surface morphology and chemical composition of
Ag/ZnS/glassceramic thin-film structure
D. Kurbatov1, A. Opanasyuk1, V. Denisenko2, A. Kramchenkov2, M. Zaharets2
1Sumy State University, Department of General and Experimental Physics,
2, Rimsky-Korsakov str., 40007 Sumy, Ukraine, e-mail: kurd@ukr.net
2Applied Physics Instiute, 58, Petropavlovskaya str., 40030 Sumy, Ukraine
Abstract. The surface morphology and chemical composition of Ag/ZnS/glassceramic
thin-film system obtained by close-spaced vacuum sublimation technique under different
grow conditions were investigated. Examination of surface profile and morphology was
performed by scanning electron and optical microscopy. Chemical composition was
studied by Rutherford back scattering method. Results of morphology studies enabled to
determine dependence of the growth mechanism, roughness Ra, grain size D of ZnS
layers on the growth conditions. The researches of chemical composition allowed to
determine the concentration of compound elements and impurities, deviation from
stoichiometry and thickness distribution of chemical elements.
Keywords: zinc sulfide, thin films, surface morphology, roughness, Rutherford
backscattering spectroscopy, chemical composition, thickness distribution.
Manuscript received 03.06.08; accepted for publication 20.06.08; published online 15.09.08.
1. Introduction
Thin-film solar cells with Cu(In1-xGax)Se2 (CIGS) and
CuInS2 (CIS) absorbers have achieved high efficiencies in
recent years. Cadmium sulfide (CdS) buffer layers
prepared by chemical bath deposition (CBD) are
commonly used in CIGS or CIS-based cells. Even though
cells with the ZnO/CBD-CdS/CIGS structure have high
efficiencies (η = 19.6 %), manufacturing companies have
sought alternatives to the CBD-CdS buffer layer, which
could eliminate the use of Cd (“Cd-free”) and improve the
collection of carriers generated by shortwave light [1].
One promising alternative material is ZnS. Its bandgap
energy (Eg) of 3.68 eV makes it transparent to practically
all wavelengths of the solar spectrum. In contrast, CdS
with its bandgap of 2.4 eV is highly absorbing for
wavelengths below 520 nm.
There has been a considerable progress in using
CBD-ZnS in CIGS-based thin-film solar cells. The best
efficiency of ZnO/CBD-ZnS/CIGS solar cells increased
to 18.6 % [2] in recent years. As one of the possibilities
of efficiency improving, there is chemically pure growth
of ZnS buffer layer with a high coefficient of optical
transmission. But it is possible only by replacing the
deposition method to receive condensates, since
according the literature CBD-ZnS contains significant
amounts of oxygen in the form of ZnO and/or Zn(OH)2
in its composition.
This work is devoted to chemical composition and
morphology studies of ZnS thin films obtained by close-
spaced vacuum sublimation technique (CSVS) under
different grow conditions. It is considered that the close-
spaced vacuum evaporation method (CSVE) may
become successful alternative to CBD method for
producing the ZnS-based window layer of solar cells
with improved characteristics [3].
Under the deposition of ZnS films exercisable as
basic layers of solar cells, the optimization of film
characteristics is very important. These condensates on
cheap glass substrates must have monophase columned
structure with low level of non-controlled impurities and
composition close to stoichiometric. It stipulated the aim
of this paper.
2. Experimental details
Thin ZnS films were obtained by CSVE method [4]. The
refined glassceramic plates were used as substrates. The
evaporation of two-phase stoichiometric ZnS powder
was carried out. The temperature Te of the evaporator
was 1373 K. The temperature Ts of substrate was varied
within the range 373 to 973 К. The time t of layer
condensation was 300 s. The thickness of films L was
varied within the range 0.2 to 7 µm. Geometry of our
samples was determined by the mask in-use. Usually
they had a shape of a circle with a diameter 10 mm. The
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2008. V. 11, N3. P. 252-256.
© 2008, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
253
thin Ag layer was applied on the ZnS film to support
gathering the charge from the film surface during
measurements using charge particles. Under these
conditions, the temperature of the ZnS surface was
373 K.
The morphology of ZnS films surface was
investigated by scanning electron (SEM 103-01) and
optical microscopy. The average grain size D inside the
layers was determined by the Jeffries method by using
the formula nMSkD 2−= , where k is the coefficient
of grain shape, S – the area of the section in a
micrograph; M – magnification; n – the number of grains
in a chosen plot. The calculation of surface roughness
was performed according to the standard ISO/R 468 [5],
while the average arithmetic deviation Ra of profile was
defined by formula ∑
=
=
n
i
ia y
n
R
1
1 , where iy – profile
deviation of film surface from the mean line, n – the
number of profile peaks.
To determine elemental composition of
Ag/ZnS/glassceramic, the Rutherford backscattering
method (RBS) of protons was used [6]. As the source of
charged particles, the electrostatic accelerator on 1 MeV
(Institute of Applied Physics, NAS of Ukraine) was
utilized. The primary beam of protons bombarded the
target normally, scattering angle was 135°. As the
detecting system, the magnetic spectrometer and Si-
detector of charged particles were used. This magnetic
spectrometer allowed to enhance the energy resolution to
3.2 keV.
The RBS spectra processing was performed by the
SIMNRA program. Determination of the impurity
concentration and component depth profiles for this
compound was fulfilled by means of standard
technique [7].
3. Results and discussion
As a result of pursued researches of ZnS films in
Ag/ZnS/glassceramic structure surface morphology, it
was determined that these films are polycrystalline,
homogeneous along the samples area and they have
good adhesion to substrate for deposition temperatures
Ts > 300 K (Fig. 1). At low temperatures the film
substrates were fine-crystalline (D < 0.1 µm). Through
intensive secondary nucleation, at the same time growth
of crystallite dimensions with increasing of film
thicknesses almost didn’t take place.
With increasing Ts, the growth mechanism varied,
and the films began to grow according to the column-
like mechanism. While increasing Ts from 323 to 993 K,
the average size D of crystallite in the film plane grew
from 0.1 µm to 1-2 µm at L ~3 µm. D increase occurred
also while L increasing. Under conditions close to
thermodynamic equilibrium, the films were practically
monoblock along the layer thickness.
Fig. 1. Microstructure of ZnS films: surface morphology of the
films grown under various substrate temperatures: Ts =
393 К (a); 573 (b); 993 (c); and their cross-section (d).
The investigation of optical characteristics of
condensates [8] demonstrated that for the wavelength λ
greater than 350-360 nm the significant enhancement of
the transmission coefficient occurred and for λ greater
than 450-500 nm all the films had a very high
transmission coefficient that ran up to 85-95 %. This
argues about availability to use vacuum ZnS condensates
as a high-energy gap window of thin-film solar cells.
а)
b)
Fig. 2. Typical optical migrograph of the ZnS film (a) grown
under Ts = 863 K and profile of the surface part (b).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2008. V. 11, N3. P. 252-256.
© 2008, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
254
The surface morphology investigation of ZnS films,
fulfilled in this work, revealed that the rise of the
condensation temperature is going with increase in height
of layers relief and therefore its surface roughness. The
typical micrographs of condensate surfaces and surface
profilograms are presented in Fig. 2. For quantitative
estimation of films roughness by using the profilograms,
the calculation of average arithmetic deviations of profiles
Ra from the average line was performed.
Determination of the parameter Ra shows that
under rising temperature from Ts = 423 K to 863 K the
surface roughness is increased from Ra ≈ 0.062 µm to
0.147 µm at L ~ 3 µm. The dependence of the profile
average arithmetic deviation for ZnS films versus Ts is
shown in Fig. 3.
In Fig. 3, two regions of temperature with different
Ra – dependences on the temperature Ts might be
indicated. Their presence may be explained by changing
the mechanism of ZnS films growth under Ts > 650-
700 K. The sharper arising of average arithmetic
deviation Ra of films surface profile occurs in the range
of deposition temperature, where the column mechanism
of film growth is realized.
It is known that solar cells with heterojunctions are
fabricated in two configurations: back- and frontal-
barriered. The maximal efficiency is inherent to back-
barriered structures, where the electrically conductive
transparent layer of ZnO (SnO2) or its analogue is initially
deposited on the glass substrates, then ZnS buffer layer
follows and finally the basic light-absorbing layer (CIGS or
CdTe) with current-collecting contact completes the block.
Using ZnS films with the columned structure and
comprehensive surface relief must promote improving the
efficiency of corresponding solar cells through reduction of
reflectivity factor from basic layer surface and series
connected resistance relating to presence of grain boundary.
The typical proton-scattering spectra obtained from
films deposited under various physical and technological
conditions are represented in Fig. 4a. In Fig. 4b, the
simulated with program package SIMNRA [9] RBS
spectra accompanied with the measured ones are
represented. The reconstruction degree of experimental
spectra is very high. As shown in Fig. 4, the elements
that belong to substrate and current-collecting contact
contribute to RBS spectra besides ZnS compound.
Fig. 3. The average arithmetic film profile deviation Ra vs Ts.
After processing RBS spectra of ZnS, silicon was
found near the substrate (we assume that Si atoms
diffused from glassceramic to halcogenide under high
temperatures of condensation). The small amount of W
(~1-2 %) is also on film surface, and it is obviously
caused by tungsten evaporator. It is known that the RBS
method has a high sensitivity to elements with large
atomic number, therefore W is registered despite very
small concentration. The oxygen is found only close to
the substrate and in the near-surface film layer where
oxide phases (ZnO for example) may be formed in the
air. It is necessary to mark that in ZnS films obtained by
the pyrolitic method and from chemical solutions the
oxygen amount dissolved in halcogenide may run up to
3-8 % and such films can be rather considered to be a
solid solution x1xOZnS − or mixture ZnS, Zn(OH)2 and
ZnO [10]. In vacuum condensates, the oxygen amount
don’t exceed 1-2 % (usually). That is registered
experimentally. Although the carbon trace (<1 %) is
detected on examined films surface but, as the additional
investigation argues, this element penetrates into the
sample from vacuum oil.
а)
b)
Fig. 4. RBS spectra of 1 MeV protons, scattered from
Ag/ZnS/glassceramic (a) and example of simulation pattern at
Ts = 573 K (b).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2008. V. 11, N3. P. 252-256.
© 2008, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
255
RBS spectra analysis enabled to calculate the layer
thickness and component concentrations of compound.
The ZnS film thickness is determined from the
relationship:
[ ] ZnSZnSε n
EL
⋅
∆
= , (1)
were E∆ is the energy width of a peak; ZnSn -
concentration of ZnS compound; [ ] ZnSε – “stopping”
cross-section of ZnS calculated from Bragg’s rule
through “stopping” cross-sections of the different
compound elements:
[ ] ZnSε = [ ] Znε c1 + [ ] Sε c2, (2)
AN
sAcA
ccn
2S1Zn
2S1Zn
ZnS
ρρ
+
+
= , (3)
here Znρ , Sρ are the densities of individual elements,
respectively; ZnA , SA are their atomic masses; c1 and
c2 – weighting factors.
The film thicknesses average ratio of atomic
concentrations of compound components was
determined using the formulae
SSZn
ZnZnS
S
Zn
∆σ
∆σ
γ
EH
EH
C
C
== ,
γ+
γ
=
11c ,
γ+
γ
=
12c , (4)
where ZnC , SC are atomic percentage of Zn and S,
respectively; Znσ , Sσ – cross-sections of protons
scattered by Zn and S; ZnE∆ , SE∆ – energetic width
(FWHM) of a peak for Zn and S, respectively; ZnH ,
SH – the magnitudes of a signal for Zn and S,
respectively.
For the RBS data, the thicknesses of ZnS films
were determined. The spectra of these films are shown in
Fig. 4. The thicknesses L are 194±5, 178±5, and
450±5 nm for the samples deposited under temperatures
Ts equal to 393, 573, and 993 К, respectively.
The investigations show that for L > 300 nm and
proton energies E0 = 1 MeV overlapping of partial
peaks takes place that complicates the data processing.
In fact, Fig. 4a shows that peaks are separated for
L = 178 nm and 194 nm, but for L = 450 nm peaks are
overlapped.
RBS method also allows determining the depth
profile of layer components. For the case when partial
peaks are separated on RBS spectra, the component
concentrations of compound, ratio γ and stoichiometry
changes with the layer thickness were calculated. With
this, it was considered that the condensates are area
homogeneous.
In Fig. 5, the Zn-to-S ratios of ZnS compound as a
function of depth for temperatures Ts = 393 K and 573 K
are represented.
Fig. 5. Dependence of ZnS films stoichiometry on depth for
Ag/ZnS/glassceramic structure.
As seen from Fig. 5, layer stoichiometry is lightly
varying with depth, and the S concentration is increased in
the interlayer that adjoins the substrate. It is the evidence
of evaporation incongruence of ZnS compound under
deposition process. It appears also that condensate
stoichiometry is determined by the substrate temperature
Ts and depends on the film thickness. The stoichiometry
depending on these parameters was varying from 0.72 to
1.07. The obtained ratios of the component concentrations
for ZnS films (γ ~ 0.72) are somewhat unexpected and
require refinement using other methods. The analogous
data are published only in the paper [11]. It will be
possible in the case of RBS data that ZnS films must be
two-phase and contain inclusions of S. But this contradicts
results of X-ray diffraction study and scanning electron
and optical microscopy. By means of these methods the S
precipitates are not detected in films. But it is necessary to
point out that our X-ray diffraction and electron
microscopy investigations were fulfilled using more thick
films (L ~ 3-5 µm). The concentration ratios γ = 1.07
found for these films (L = 450 nm) correspond to
published data. As a rule, ZnS films obtained by various
methods reveal the Zn excess [12-14].
The interdiffusion of elements was observed in the
interface between Ag and ZnS that is related with
applying the metal contact over heated substrate. While
the calculation results of “spreading” magnitudes of Zn
and S distribution profiles in this transition layer are
quantitatively and qualitatively harmonized with the data
of film surface roughness measurements.
4. Conclusions
The surface morphology investigation and
nondestructive elemental analysis of many-layer
Ag/ZnS/glassceramic structure obtained by close-spaced
vacuum sublimation technique under different grow
temperatures were carried out. Two temperature ranges
where the film growth is realized by different
mechanisms were determined. It was established that the
layer surface roughness was significantly increased in
the region of columned growth.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2008. V. 11, N3. P. 252-256.
© 2008, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
256
By means of the RBS method, the elemental
composition of condensates was determined, and
component distribution of compound as a function of
many-layer system depth was obtained. The impurities
including oxygen are revealed only near the film surface
and in layer contacting with substrate. It was shown that
thickness averaged stoichiometry of ZnS films were
determined by deposition regimes and were varying in
Zn-to-S ratio range 0.72-1.07.
The fulfilled studies indicate the CSVS method
availability of deposition of ZnS films, suitable for using
as high-bandgap window of solar cells.
Acknowledgement
The authors would like to thank Ph.D. V. Laptev from
Institute of Physical Electronics (University of Stuttgart)
for optical investigations of film surfaces.
References
1. K. Ramanathan, M.A. Contreras, C.L. Perkins et al.,
Properties of 19.2 % efficiency ZnO/CdS/CuInGaSe2
thin-film solar cell // Progr. Photovolt.: Res. Appl.
11, p. 225 (2003).
2. M.A. Contreras, T. Nakada, M. Hongo et al. // Proc.
3rd World Conference of Photovoltaic Energy
Conversion, Osaka, Japan, p. 570 (2003).
3. D. Hariskos, S. Spiering, M. Powalla, Buffer layers
in Cu(In,Ga)Se2 solar cells and modules // Thin
Solid Films 480-481, p. 99-109 (2005).
4. Y.P.V. Subbaiah, P. Prathap, M. Devika, K.T.R.
Reddy, Close-spaced evaporated ZnSe films:
preparation and characterization // Physica B 365,
p. 240 (2005).
5. ISO Recommendations on Roughness Measure-
ments. ISO/R 468, 1878, 1880, ТC 57.
6. J.R. Tesma, M. Nastasi, J.C. Barbow et al.,
Handbook of Modern Ion Beam Materials Analysis.
Materials Research Society, Pittsburgh, 1995.
7. L.C. Feldman, J.W. Mayer, Fundamentals of
Surface and Thin Film Analysis. North Holland-
Elsevier, New York, 1986.
8. D.I. Kurbatov, A.S. Opanasyuk, Оptical properties
ZnS thin films for the antireflection coating of solar
cells // Visnyk Sumskogo Derzhav. Universitetu 2,
p. 60-66 (2008) (in Ukrainian).
9. H.H. Andersen, J.F. Ziegler, Hydrogen Stopping
Powers and Ranges in All Elements. Pergamon
Press, New York, 1977.
10. A.O. Pudov, J.R. Sites, T. Nakada, Performance and
loss analyses of high-efficiency chemical bath
deposition (CBD)-ZnS/Cu(In1-xGax)Se2 thin-film
solar cells // Jpn J. Appl. Phys. 41(Part 2), p. 672-
674 (2002).
11. R. Kobayashi, N. Sato, M. Ichimura, E. Arai,
Photochemical deposition of ZnS thin films from
C4H4KNaO6-added solutions // J. Opt. and Adv.
Mat. 5(4), p. 893-898 (2003).
12. H. Kashani, Production and evaluation of ZnS thin
films by the MOCVD technique as alpha-particle
detectors // Thin Solid Films 288, p. 50-56 (1996).
13. I.O. Oladeji, L. Chow, Synthesis and processing of
CdS/ZnS multilayer films for solar cell application
// Thin Solid Films 474, р. 77-83 (2005).
14. S.J. Yun, S. Dey, K.S. Nam, Zinc sulfide and
terbium doped zinc sulfide films grown by
traveling wave reactor atomic layer epitaxy // J.
Korean Phys. Soc. 33, p. 454-457 (1998).
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