ZnO:Al wide zone “windows” deposited by magnetron sputtering on unheated substrate
Electrical and optical properties of ZnO:Al films deposited on unheated glass substrate by non-reactive RF magnetron sputtering of target ZnO:Al₂O₃ (98/2 wt.%) were studied. It was shown that Zno:Al films with the thickness of 0.75 µm deposited at the magnetron power 130 W and 4 µbar argon pressure...
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| Опубліковано в: : | Вопросы атомной науки и техники |
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| Дата: | 2000 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2000
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| Цитувати: | ZnO:Al wide zone “windows” deposited by magnetron sputtering on unheated substrate / B.Т. Boyko, G.S. Khrypunov, G.V. Yurchenko // Вопросы атомной науки и техники. — 2000. — № 5. — С. 91-93. — Бібліогр.: 10 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859953270958587904 |
|---|---|
| author | Boyko, B.Т. Khrypunov, G.S. Yurchenko, G.V. |
| author_facet | Boyko, B.Т. Khrypunov, G.S. Yurchenko, G.V. |
| citation_txt | ZnO:Al wide zone “windows” deposited by magnetron sputtering on unheated substrate / B.Т. Boyko, G.S. Khrypunov, G.V. Yurchenko // Вопросы атомной науки и техники. — 2000. — № 5. — С. 91-93. — Бібліогр.: 10 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | Electrical and optical properties of ZnO:Al films deposited on unheated glass substrate by non-reactive RF magnetron sputtering of target ZnO:Al₂O₃ (98/2 wt.%) were studied. It was shown that Zno:Al films with the thickness of 0.75 µm deposited at the magnetron power 130 W and 4 µbar argon pressure with adding of 4·10⁻³ µbar oxygen pressure during the first minute of condensation has the following electrical and optical characteristics: surface, resistance 6 Ω/ and transmittance in visible spectral range about 88%. The ZnO:Al films with such optical and electrical parameters are suitable for substrate configuration highly efficiency thin film solar cells on CuInSe₂ base.
|
| first_indexed | 2025-12-07T16:17:47Z |
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УДК: 537. 221:537.221
ZnO:Al WIDE ZONE «WINDOWS» DEPOSITED BY
MAGNETRON SPUTTERING ON UNHEATED SUBSTRATE
B.Т.Boyko, G.S. Khrypunov , G.V. Yurchenko
Kharkov State Polytechnic University, Kharkov, Ukraine
Electrical and optical properties of ZnO:Al films deposited on unheated glass substrate by non-reactive RF
magnetron sputtering of target ZnO:Al2O3 (98/2 wt.%) were studied. It was shown that Zno:Al films with the
thickness of 0.75 µm deposited at the magnetron power 130 W and 4 µbar argon pressure with adding of 4·10-3 µ
bar oxygen pressure during the first minute of condensation has the following electrical and optical characteristics:
surface, resistance 6 Ω/� and transmittance in visible spectral range about 88%. The ZnO:Al films with such
optical and electrical parameters are suitable for substrate configuration highly efficiency thin film solar cells on
CuInSe2 base.
1. INTRODUCTION
One of the most perspective materials for wide-
zone «windows» for the solar cell are ZnO:Al films ,
obtained by magnetron sputtering method [1]. Up to
now [1…3] the optimal electrical and optical
properties of ZnO:Al layers were prepared by
magnetron sputtering at the substrate temperature
only in the range 200-450oC.
In process of preparation of Cu-In-Se thin film solar
cells in substrate configuration and with CdS buffer
layer it is desirable to deposit ZnO:Al layers at
possible low temperature to minimise mutual diffusion
of atoms Zn, Al, Cd, In, Cu in conjunction layers of
solar cells [2].
So, the definition of optimal conditions of
magnetron sputtering for formation high quality
ZnO:Al films without special heating of substrate is the
important problem for further increase of efficiency of
thin film solar cells on the base Cu-In-Se system
compounds.
2. EXPERIMENT
The ZnO:Al films were deposited on soda lime
glass substrates by non-reactive RF magnetron
sputtering of ZnO:Al2O3 (98/2 wt.%) target in
atmosphere of clean argon (99,999 %) . The initial
pressure in the vacuum chamber was 3·10-7 mbar. The
ZnO:Al film have been prepared without substrate
heating . The distance between the target and substrate
was 35 mm. The thickness of films t were determined
by Dektat 3030 profilometer. Surface resistance Rs
and electrical resistivity ρ of ZnO:Al films were
measured by four-probe method. The value of charge
carriers concentration n and mobility µ were determined
in constant magnetic field 0,2 Tesla at room temperature
using van der Pauw method [4]. Optical transmittance
T measurements have been carried out in the visible
spectral range (300…900 nm) on the double beam
spectrophotometer (type Perkin) by two-channel method
[5].
3.RESULTS AND DISCUSSION
3.1 THE INFLUENCE OF THE MAGNETRON
POWER AND ARGON PARTIAL PRESSURE ON
THE ELECTRICAL AND OPTICAL
PROPERTIES OF ZNO:AL FILMS
The ZnO:Al films were prepared at the
following magnetron powers P: 80W, 100W, 130
W, 150W, 200W and argon partial pressures pAr: 4 , 8
and 12 µbars. The results of the ZnO:Al films optical
and electrical properties are shown in the table 1.
Table 1
The influence of magnetron power and argon partial pressure
on the ZnO:Al films optical and electrical properties
P, W 200 200 200 150 130 100 80
par,µbar 12 8 4 4 4 4 4
t, µm 0,80 0,55 0,55 0,68 0,24 0,25 0,15
ρ,10-4, Ω
cm
7,8 8,9 11,4 9,5 5,2 5,3 148
µ,
cm2/V*s
8 10 11 11 12 13 6
n,
1020cm-3
10 7 5 6 10 9 0,7
T, % 30 60 90 80 60 65 90
As it is seen from the table 1 the increase of argon
partial pressure from 4 µbar up to 12 µbar at the
constant 200W magnetron power results in decrease
electrical resistivity from ρ=1,14·10-3 Ωсm up to ρ
=7,8·10-4 Ωсm as the result of substantial increase of
charge carriers concentration from n=5·1020 сm -3 up to
n=1·1021 см-3 with the small decrease of the mobility.
At the same time the optical transmittance of ZnO:Al
films decreases from T=90 % up to T=30 %. As we can
see from the table 1 the films which were prepared at
the 200W magnetron power and 4 µbar argon partial
pressure have the maximum transparent. Therefore in
our experiments (samples 5…8) we did not change the
argon partial pressure (par =4µbar).
At constant partial argon pressure 4 µbar - the
reduction of magnetron power from 200 up to 130W
results in decrease of electrical resistivity (ρ) from
1,14·10-3 up to 5,2·10-4 Ωсm . In this case the charge
carriers concentration (n) in the ZnO:Al films
increases from 5·1020 up to 10·1020 см-3 at minor
increase of the mobility. The transmission of ZnO:Al
films in visible spectral range (T) decreases from 90
up to 60 %. The further reduction of magnetron power
up to 80W was accompanied by increase of ρ as
the result of the decrease of charge carriers
concentration (n) from 10·1020 up to 7·1019 см-3 with
increase of the transmission up to 90 %.
Thus, minimum electrical resistivity ρ
=(5,2… 5,3)·10-4 Ωсm was observed in ZnO:Al films
prepared at magnetron power of P=(130…100)W and
argon partial pressure par=4µbar. The transmittance
of these films was 60…65%. In the solar cells
ZnO:Al films usually have the thicknesses 0,5…
0,7 µm. At such thickness and above ρ the surface
resistance Rs are 8…10 Ω/� . It is well known [6],
that at Rs = 12 Ω/� the surface resistance of ZnO:Al
does not influence on the characteristics of solar cells.
Therefore the ZnO:Al films prepared in our
experiments at magnetron power 100W and 130W and
argon partial pressure 4 µbar have electrical
parameters which permit to use it for creation of highly
effective film solar cells . However their optical
transmission should be increased up to 90 % [1].
3.2 INFLUENCE OF THE OXYGEN ADDITIVE TO
ARGON SPUTTER GAS ON ELECTRICAL AND
OPTICAL PROPERTIES OF ZNO:AL FILMS
For the increase of the optical transmission of
ZnO:Al films prepared by non-reactive magnetron
sputtering, but without the change their electrical
properties it is necessary to add small quantity of
oxygen to argon sputter gas [1]. As it is known [7], the
presence of oxygen vacancies in grains reduces the
transmission of ZnO:Al polycrystalline films . The
additive of oxygen in the argon sputter gas allows to
reduce nonstoichiometry and thus to increase the
transmission of ZnO:Al films. However, the excess of
oxygen atoms in ZnO:Al film results in formation
Al2O3 on the grain boundaries [8]. In this case the
concentration of aluminium atoms in volume of the
grain decreases and therefore the charge carriers
concentration reduces .
Thus, from our point of view, the quantity of
oxygen additive to argon sputter gas is the critical
value for non-reactive RF magnetron sputtering
method of preparation ZnO:Al films with good optical
and electrical properties. Therefore we started to add to
argon sputter gas the possible minimum value of oxygen
(on the level 0.1% from argon partial pressure). The
magnetron power were 100 and 130W, argon partial
pressure was 4 µbar and the partial oxygen pressure in
our case was 4·10-3 µbar. The results of optical and
electrical properties of ZnO:Al films prepared in such
conditions are presented in the table 2, where τ -
admission time of oxygen additive to argon sputter gas.
As one can see from the table 2, under magnetron
power 100 W and argon partial pressure 4 µbar the
addition of oxygen to argon sputter gas during the all
process of film condensation (i.e. 35 min) results in
increase of transmission ZnO:Al film in a visible
spectrum range from 65 up to 92 % (compare sample 7
in table1 and sample 9 in table 2). However, the
electrical resistivity of sample 9 in comparison with
the sample 5 was increased on five orders. It testifies
that in such ZnO:Al film there is an excess of oxygen,
which formats oxides Al2O3 on the grain boundaries. To
decrease the amount of oxygen in argon sputter gas
during ZnO:Al film preparation we reduced admission
time τ of oxygen additive. So, under admission time of
oxygen to argon during 3 minutes in the beginning and
during the last 3 minutes ( 3/3 ) of 35 minute process of
ZnO:Al film condensation we prepared sample No.10.
In this case the decrease τ did not reduce the
transmission of film, but results in decrease of electrical
resistivity up to ρ=1,7·10-2 Ωcm.
Table2
Influence of the oxygen additive to argon sputter gas on
electrical and optical properties of ZnO:Al films
Samples 9 10 11 12 15
P, W 100 100 100 130 130
Par, µbar 4 4 4 4 4
τ , min 35 3/3 1 1 1
t, µm 0,13 0,15 0,15 0,30 0,75
Rs, Ω/ð 1,8· 106 1,2·103 470 22 6
ρ,10-4 Ωсм 2,3·105 1,7·102 65 7,0 4,2
n,1020
cm-3
--- 0,3 0,8 7 10
µ,
cm2/V*s
--- 12 13 13 15
T, % 92 92 92 92 88
The minimization of τ up to 1 minute in the
beginning of process of condensation was stipulated the
further decrease of resistivity up to 6,5·10-3 Ωсм
(sample No.11, table 2) The transmission of such films
did not change (T=92%) . The increase of magnetron
power up to 130W (sample No.12, table 2) results in
reduction of electrical resistivity up to ρ=7,0·10-4 Ωcm.
The charge carriers concentration in such layers was
increased up to n=7·1020 см-3, the charge carriers
mobility was µ=13 cm2/V·s. From our point of view,
the optimization of optical and electrical properties was
stipulated by increasing the film speed deposition due
to the increasing of magnetron power from 100 up to
130W. The increasing of film speed deposition under
minimum τ =1 min, results in reduction of relative
quantity of oxygen, that stipulated only doping
process of ZnO by Al. Besides, the increasing of
speed deposition under the constants time condensation
was resulted in essential increasing of film thickness
(compare samples 11 and samples 12, table 2).
According to [9] the grain sizes are increased with
the increase of ZnO:Al film thickness. The increase of
the grain sizes reduces the quantity of aluminium atoms
located on the grain boundaries in electrical non-active
condition (as Al2O3), that also increases charge carriers
concentration [9]. Under above condition we prepared
ZnO:Al film with thickness t=0,3µm, the
transmission T= 92 % and the surface resistance Rs =22
Ω/ � . In order to decrease the surface resistance of
ZnO:Al film up to a best value (Rs = 12 Ω/� ) it is
necessary to increase the film thickness. By increasing
the time of condensation up to 80 minutes we
prepared ZnO:Al film with thickness t=0,75µm
(sample 15, table2). The surface resistance of such
film was decreased up to Rs =6 Ω/� . The transmission
of ZnO:Al film was acceptable (T= 88 %). It was
shown that the surface resistance was decreased not
only due to the geometric increase of film thickness,
but also as a result of decreasing the resistivity (ρ) from
7,0·10-4 Ωсм up to 4,2·10-4 Ωсм. The decrease of
electrical resistivity is stipulated by further increase of
charge carriers concentration (n) from 7·1020 up to
1·1021 см-3 and due to the growth of their mobility (µ)
from 13 cm2/V·s up to 15 cm2/V·s.
4. CONCLUSION
The optical and electrical properties of ZnO:Al
films prepared by non-reactive RF magnetron
sputtering without special heating of the substrate were
investigated. It was shown, that the film ZnO:Al
obtained at the magnetron power 130W, partial pressure
of argon 4 µbar with adding of 4·10-3 µbar oxygen
pressure during the first minute of condensation has
transmission in visible spectral range 88 % and surface
resistance 6 Ω/� . The ZnO:Al films with such optical
and electrical parameters are suitable for substrate
configuration of thin film solar cells on
CuInSe2/OVC/CdS base.
ACKNOWLEGMENT
This work has been supported by the INTAS-96-
0206 Project of European Commission and 7IP 050129
Project of Swiss National Science Foundation.
REFERENCES
1. A.Loff, S. Wieder, D. Rech, O. Kluth, C. Beneking
and H. Wagner Al-doped ZnO films for thin-films solar
cells with very low sheet resistance and controlled
texture // 14th European Photovoltaic Solar Energy
Conference and Exibition, Barselona, Spain, 1997,
p. 2089-2093.
2. T. Minami, H. Sonohara, S. Takata, I. Fukuda. Low
temperature formation of textured ZnO electrodes //
J. Vac. Sci. Technol, 1995, A, Vol. 13(3), p. 1053-1057.
3. R. Schaffler and H.W. Schock. High mobility
ZnO:Al thin films grown by reactive magnetron
sputtering // 14th European Photovoltaic Solar Energy
Conference and Exibition , Barselona , Spain, 1997,
p. 995-998.
4. B.L. Sharma, R..K. Puroxit. Semiconducting
heterojunctions // M.: Soviet radio, 1979, 320 p.
5. V.V. Lebedeva. Engineering optical spectroscopy //
M.: MGU,1986, 219 c.
6. R.C. Powell, R.A. Sasala, G. Doper, McMaster.
Development of thin-film CdTe Photovoltaics //
Technical Digest of International PVSEC-9, Miyazaki,
Japan, 1996, p. 117-120
7. M.A. Martinez, J. Herero and M.T. Gutierrez .
Properties of RF sputtered zinc oxide based thin films
made from different targets // Solar Energy Materials
and Solar Cells,1994, p. 489-498.
8. C. Privato, A. Antonaia, A. Di Nocera, S. Loreci , E.
Terzini. Enhancement in the properties of large area Rf
sputtered ZnO layers by H2 process gas dilation // 14th
European Photovoltaic Solar Energy Conference and
Exibition, Barselona, 1997, p. 1623-1626.
9. Y. Qu, T.A. Gessert, K. Ramanathan, R,.G. Dhere,
R. Noufi, T.J. Coutts. Electrical and optical properties
of ion beam sputtered ZnO:Al films as a function of
film thickness // J. Vac. Sci. Technol. 1993, A, Vol.
11(4), p. 996-1000.
10. O. Kluth, B. Beneking, W. Appenzeller, H.
Wagner, R. Waser, S. Hoffmann. Nucleation and
growth of textured Al-doped ZnO films for aSi:H -
Solar Cells Analysed by High resolution SEM films for
thin-films solar cells with very low sheet resistance and
controlled texture // 14th European Photovoltaic Solar
Energy Conference and Exibition, Barselona, Spain,
1997, p. 2089-2093.
MAGNETRON SPUTTERING ON UNHEATED SUBSTRATE
ACKNOWLEGMENT
|
| id | nasplib_isofts_kiev_ua-123456789-78239 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T16:17:47Z |
| publishDate | 2000 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Boyko, B.Т. Khrypunov, G.S. Yurchenko, G.V. 2015-03-13T06:42:36Z 2015-03-13T06:42:36Z 2000 ZnO:Al wide zone “windows” deposited by magnetron sputtering on unheated substrate / B.Т. Boyko, G.S. Khrypunov, G.V. Yurchenko // Вопросы атомной науки и техники. — 2000. — № 5. — С. 91-93. — Бібліогр.: 10 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/78239 537. 221:537.221 Electrical and optical properties of ZnO:Al films deposited on unheated glass substrate by non-reactive RF magnetron sputtering of target ZnO:Al₂O₃ (98/2 wt.%) were studied. It was shown that Zno:Al films with the thickness of 0.75 µm deposited at the magnetron power 130 W and 4 µbar argon pressure with adding of 4·10⁻³ µbar oxygen pressure during the first minute of condensation has the following electrical and optical characteristics: surface, resistance 6 Ω/ and transmittance in visible spectral range about 88%. The ZnO:Al films with such optical and electrical parameters are suitable for substrate configuration highly efficiency thin film solar cells on CuInSe₂ base. This work has been supported by the INTAS-96-0206 Project of European Commission and 7IP 050129 Project of Swiss National Science Foundation. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Пленочные материалы и покрытия ZnO:Al wide zone “windows” deposited by magnetron sputtering on unheated substrate Article published earlier |
| spellingShingle | ZnO:Al wide zone “windows” deposited by magnetron sputtering on unheated substrate Boyko, B.Т. Khrypunov, G.S. Yurchenko, G.V. Пленочные материалы и покрытия |
| title | ZnO:Al wide zone “windows” deposited by magnetron sputtering on unheated substrate |
| title_full | ZnO:Al wide zone “windows” deposited by magnetron sputtering on unheated substrate |
| title_fullStr | ZnO:Al wide zone “windows” deposited by magnetron sputtering on unheated substrate |
| title_full_unstemmed | ZnO:Al wide zone “windows” deposited by magnetron sputtering on unheated substrate |
| title_short | ZnO:Al wide zone “windows” deposited by magnetron sputtering on unheated substrate |
| title_sort | zno:al wide zone “windows” deposited by magnetron sputtering on unheated substrate |
| topic | Пленочные материалы и покрытия |
| topic_facet | Пленочные материалы и покрытия |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/78239 |
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