Third Day Poster Session, 17 June 2010 - NanoTR-VI

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Poster Session, Thursday, June 17
Theme F686 - N1123
Characterization of Sputtering Deposited AgGaSe2 Thin Films
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UHakan KaraaaçUP P*, Mehmet ParlakP Pand Çidem ErçelebiP
1
PDepartment of Physics, Middle East Technical University, Ankara 06531, Turkey
Abstract- The single phase of AgGaSeR2R thin films were deposited onto soda-lime glass substrate by sequentially deposition of Ag and GaSe
using DC and RF sputtering. Physical properties were investigated by carrying out several type of measurements and the convenience of this
material to be used in the solar cell structure was determined.
Nowadays, I-III-VIR2R ternary compounds have been
attracting considerable attention due to their interesting
physical properties. These compounds are regarded to be the
ternary analog of the II-VI binary materials. I-III-VIR2R
semiconductors crystallize with the structure called
chalcopyrite being a super lattice of II-VI binary’s (zinc
blende) structure [1]. I-III-VIR2R ternary compounds are
potential candidates for photovoltaic applications [2], nonlinear
optics [3], light-emitting diodes [4], and frequency
conversation applications [5].
AgGaSeR2R is a well-known ternary semiconductor. It’s of
particular interest due to owing optical non-linear properties
used in many applications like the generation of second and
third harmonic frequencies of COR2R laser output [6-8]. It is also
found that AgGaSeR2R is a good candidate for the preparation of
schottky diodes [9], X- and Gamma-ray detector [10], and
solar cells [11].
AgGaSeR2R thin films were deposited onto soda-lime glass
substrates by a combination of DC and RF sputtering. The
optimization of single layers of Ag and GaSe was performed
by conducting several deposition cycles with the same
parameters before the sequentially deposition of
GaSe/Ag/GaSe/Ag/GaSe/Ag/GaSe/Ag/GaSe thin film layers
onto soda-lime glass substrates kept at constant temperature
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around 250 P PC to form AgGaSeR2R thin film.
Results of energy dispersive analysis of X-rays (EDXA)
indicated a Ga-rich composition and that there is a
considerable effect of annealing temperature on variation in
amount of constituent elements in AgGaSeR2R thin film. The
structural analysis of the as-grown and films annealed between
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350 P PC and 600 P PC has been carried out by X-ray diffraction
(XRD) measurements. Results revealed that all films are
polycrystalline in nature and Ag metallic phase exists in the
amorphous AgGaSeR2R structure up to annealing temperature
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450 P PC. When the annealing temperature raised to 600 P PC it
was observed that the Ag phase disappears perfectly and the
structure is consisting of single phase AgGaSeR2R with (112)
preferred orientation. The crystalline sizes of the annealed film
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between 350 P PC and 600 P PC were calculated from the XRD
measurements and compared with grain sizes measured from
the recorded scanning electron microscopy (SEM)
micrographs. In addition, from the lattice parameters found for
AgGaSeR2R thin film, some structural anomalies parameters
related to chalcopyrite compounds like anion displacement
and tetragonal distortion parameters have been calculated and
compared with previously reported values.
Optical properties of AgGaSeR2R thin films were studied by
carrying out transmittance and reflectance measurements in
the wavelength range of 325-1100 nm at room temperature.
By using the obtained spectral data for transmittance and
reflection, the absorption coefficient and optic band gap values
for as-grown and annealed samples were calculated. The
found energy values indicated that AgGaSeR2R thin film shows
the characteristic optical structure related to I-III-VIR2R
chalcopyrite compounds. That’s the crystal-field and spinorbit
splitting levels were resolved by observing band to band,
the crystal-field to conduction band minimum, and spin-orbit
level to conduction band minimum transitions with
characteristic energy values reported previously. The
calculated energy values for these transitions were found to be
1.77 eV, 2.00 eV, and 2.25 eV, respectively for film annealed
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at 550 P PC and there is a fair agreement with previously
reported data. The levels originating from the crystal-field and
spin-orbit interaction were also observed from the
photospectral response measurements with the almost same
energy values obtained from the absorption measurements
(1.77 eV, 2.00 eV, and 2.25 eV respectively for sample
o
annealed at 550 P PC).
Finally, the temperature dependent conductivity and Hall
effect measurements were carried out in the temperature range
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of 100-430 K for as-grown and film annealed at 450 P PC and
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550 P PC. The electrical resistivity of the films was in the range
of 30-1000 -cm and indicated n-type conduction confirmed
from the hot-probe and Hall effect measurements. Based on
Hall effect measurement results it is found that there is
decrease in mobility and increase in carrier concentration
following to increasing annealing temperature. The room
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temperature carrier concentration calculated to be 9.6x10P
-3
15 -3
16 -3
cmP
P, 1.7x10P
P cmP
P, and 6.6x10P
P cmP as-grown, films
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annealed at 450 P PC and 550 P PC, respectively. The room
2 -1
temperature mobility values were found to be 6.4 cmP P (Vs)P
P,
2 -1
2 -1
3.7 cmP P (Vs)P
P, and 3 cmP P (Vs)P as-grown and films
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o
annealed at 450 P PC and 550 P PC, respectively.
*Corresponding author: karaagac@metu.edu.tr
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Growth, Electronic Properties and Applications, Pergamon, Oxford,
1975
[2] L. L. Kazmerski, Nuovo Cimento D 2 (1983) 2013
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Phys. 43 (1972) 2805
[5] F. K. Hopkius, Laser Focus World 31 (1995) 87
[6] P. G. Schunemann, S. D. Setzler, T. M. Pollak, J. Cryst. Growth
211 (2000) 257
[7] G. C. Bhar, S. Das, D. V. Satyanarayan, P. K. Datta, U. Nundy,
Y. N. Andreev, Opt. Lett. 15 (1995) 2057
[8] E. Takaoka, K. Kato, Opt. Lett. 24 (1999) 902
[9] P. Ribinson, J. I. B. Wilson, Inst. Phys. Conf. Ser. 35 (1977) 229
rd
[10] G. F. Knoll, Radiation detection and Measurement 3P
(New-York; Willey), (1999)
[11] Y. Satyanarayana Murty, O. M. Hussain, B. S. Naidu, P. J.
Reddy, Mater. Lett. 10 (1987) 504
6th Nanoscience and Nanotechnology Conference, zmir, 2010 754