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Preparation and some properties of materials in systems of the type MIMIIIS2MIMIIISe2 where MI = Cu, Ag and MIII = Al, Ga, In
Mat. Res. Bull. Vol. 8, pp. 703-710, 1973. Pergamon Press, Inc. Printed in the United States.
PREPARATION AND SOME PROPERTIES OF MATERIALS IN SYSTEMS OF THE TYPE MIMIIIs2-MIMIIIse2 WHERE M I = Cu, Ag AND MIII = A1, Ga, In M. Robbins and V. G. Lambrecht, Jr. Bell Laboratories Murray Hill, New Jersey 07974
( R e c e i v e d A p r i l 19, 1973; C o m m u n i c a t e d by N. B. Hannay)
ABSTRACT
Complete solid solution between sulfide ~halcopyrites (MIMIIIs2) and se~enide chalcopyrites (MIMIIISe2 where M ~ = Cu, Ag and M ±±~ = A1, Ga, In) has been shown to exist. Single crystals of compositions CuGaS 1 5Seo ~, CuGaSSe, CuGaS 0 5Se I 5' have been grown by vapor tr&~sport techniques~ Th@se materials have a non-centrosymmetric crystal structure and exhibit second harmonic generation. Approximate band gaps of the crystals were obtained from optical transmission measurements.
Materials of the type AIBIIIx VI, where A I = Cu, Ag, BIII = A1, Ga, In and X VI = S, Se, which have the non-centrosymmetric chalcopyrite
(I~2d) structure (1) are of interest with
respect to their optical and semiconducting properties.
The band
gaps and optical properties of many of the ternary sulfur and selenium containing chalcopyrites have been reported (2-4). A study of the mixed sulfide-selenides
(AIBIIIs2-AIBIIIse2)
has been undertaken in order to determine how the properties of these systems vary between the endpoints and if materials with
703
704
CHALCOPYRITES
COMPLEX
useful optical or electrical properties manner.
Vol. 8, No. 6
can be generated in this
In this paper we describe preparation,
properties
crystallographic
and some crystal growth of these systems.
ing systems were studied.
CuAIS2-CuAISe2,
The follow-
CuGaS2-CuGaSe2,
CulnS2-CulnSe 2, AgAIS2-AgAISe 2, AgGaS2-AgGaSe 2, AgInS2-AglnSe 2. Experimental Preparations elements.
- All of the materials were prepared from the
Stoichiometric
evacuated silica tubes.
amounts were mixed and sealed in The tubes were placed in a furnace and
the temperature was raised to 800°C at the rate of lO°C/hr.
The
samples were held at 800°C for ~ 2 days at which time the furnace was shut off and the samples allowed to cool in the furnace to room temperature.
Some approximate melting points were obtained
by sealing samples in silica tubes, placing them in a split furnace, which could be opened,
raising the temperature by 25 °
increments and observing the temperature at which the materials were liquid. Powder materials, off ~ X
gas.
This is especially true when Se is present.
Crystallography
- X-ray patterns
using CuK~ radiation. tetragonal
where MIII = A1, hydrolyze in air giving
of all samples were obtained
All of the compositions
(chalcopyrite)
structure.
formed with the
Unit cell parameters
all of the systems vary linearly with composition,
for
as shown in
Figs. la-lc. Crystal Growth - X-ray measurements
on samples which were air
quenched from the melt indicate that all of the materials melt congruently.
However,
initial attempts to prepare large single
crystals from the melt were not successful because of the presence of small spherical voids within the crystals, due to S or Se vapor evolution.
presumably
Our efforts were then directed
towards vapor transport techniques. The vapor transport technique was first employed for the system CuGaS2-CuGaSe 2.
A furnace with a temperature
between lO00°C and 950°C,
drop of 50 °,
over a distance of 8 inches was used.
Approximately 5 gm of prereacted polycrystalline 5 mg 12 per cc of tube was used.
material and
No other iodine concentrations
Vol. 8, No. 6
COMPLEX
CHALCOPYRITES
I 1.0
705
I1.0
M I :Cu
I0.0
MI:Cu
10.9
10,8
10.8
~0.7
~0.7
I0.6
fO.6
CO
CO ~0.5
o~
t0.5 t0.4
I0.3(
<
10.3
~0.2
Z uJ u
10.2
6.0
Z D
b.9
5.8
j.o~
u
6.0
z
5.9
J
5.8
5.7
5.7
A0 5.6
5.6
5.5
5.5
A0 5.4 5.3
MIAI $2
5.4
I
MIAISSe2
I
5.3
MIAISe2
MIGQSSe
MZGQS2
MIAEs2 - MIA|se2
MIGoSe2
MIGOS2 - MZGOSe2
(b)
(a) 11.7
II . 4 CO tt .3
o~
tl.2 tf.1
~
MZ:Cu
t l ,0 j uJ L)
10.9
z
6.0
6.1
~.9 5,8 A 0
5.7 ~.6 5.5
I
M I InS 2
M I InSSe MIInS
2
M I I n Se 2
MI InSe 2
(c) FIG. Unit Cell Parameters
in Systems
i of the Type MIMIIIs2-MIMIIIse2
Where M I - Cu, Ag and M Ill = AI,
Ga,
In
70&
Vol. 8, No. 6
COMPLEX CHALCOPYRITES
were employed in this work.
The end of the tube containing the
feed material was held at 1000°C. this gradient for two weeks.
The tube was maintained in
The compositions grown in this
manner were CuGaS1.5Seo.5, CuGaSSe, CuGaSo.5Sel. ~. Crystals grew in the form of thin, red plates (Figs. 2a-2c) up to 5 mm on an edge.
Optical and x-ray measurements of a number of crystals
(a) CuGaSI. 5Ge0.5
(b) CuGaSSe
(c) FIG. 2
CuGaS0.5Sel.5
Crystals of Compositions From the System CuGaSo-CuGaSe ~, Grown by Vapor Transport in a 50 ° Gradient
V o l . 8, No. 6
C O M P L E X CH.ALCOPYRITES
707
showed that the c-axis was in the plane of the plate. crystals,
however,
These
grew randomly throughout the tube as well as
as on the starting material.
It seemed,
therefore,
that a
relatively large lateral thermal gradient did not enhance crystal growth in this system.
The smaller transverse gradient appeared
to be the most critical. in a quartz tube
A sample of CuGaSSe and 12 was sealed
(~ 3 in long) and held at lO00°C for two weeks.
Crystals grew as plates
(Fig. 3) up to 5 mm on an edge but were
FIG. 3 Crystals of the Compositions CuGaSSe Grown in Sealed Tube With 12 Carrier Using No Laterial Gradient considerably thicker than those grown when a temperature gradient was intentionally employed.
Unit cell parameters
shown in Table 1 along with the parameters
of crystals are
of the preprepared
polycrystalline
material.
It can be seen that the composition
of the crystals
is very close to that of the starting material.
Crystals of CuInSSe were grown in a 50 degree gradient previously described). plates.
We obtained a mixture of needles and
The composition of the crystals
identical to the starting materials in their cell parameters Optical Measurements spectra,
optical cut-offs
appears to be nearly
as shown by the similarity
(Table 1). - Crystals
CuGaSe 2 having the composition transmission
(as
from the system CuGaS 2-
shown in Table 1 were polished and
in the region 0.3~-15~,
are shown in Table 1.
band gap decreases with increasing
obtained.
The
It can be seen that the
Se content.
All of the
COMPLEX C H A L C O P Y R I T E S
708
Vol. 8, No. 6
TABLE 1 Some Properties of Crystals in the CuGaS2-CuGaSe 2 System and CuInSSe Crystals Composition
ao
Starting Material
co
ao
Approximate M.P.
co
°c
Optical Cut-off
AE
(u)
CuGaS1.5Seo. 5
5.412
10.599
5.408
10.597
1150
0.58
2.14
CuGaSSe
5.478
i0.718
5.483
10.730
1150
0.64
1.92
CuGaSo.5Sel. 5
5.551
10.882
5.547
10.874
ll00
0.74
1.67
CuInSSe
5.653
11.281
5.655
11.283
1200
crystals were essentially transparent and 15~.
between the optical cut-off
Powders and crystals of these materials
CuGaS2-CuGaSe 2 exhibit with materials
second harmonic
generation
having the chalcopyrite
structure.
in the system as expected
Discussion It has been shown that the sulfide and selenide chalcopyrites of the type MIMIIIx2, where M I = Cu, Ag and MIII = A1, Ga, In, are completely miscible compositions
in one another.
Crystals with desired
can be grown by vapor transport
techniques.
Crystals
from the system CuGaS2-CuGaSe 2 transmit well into the infra-red. Optical studies are presently being made to determine non-linear
optical properties
the
of these materials.
Additional experiments in systems of the type AgMIIIx2 CuMIIIxo__ where MIII = A1, Ga, In and X = S, Se and MIAIx2 MIGaX2-MIInx2
where M I = Cu or Ag and X = S or Se are being
carried out in order to study their phase relations,
optical
and electric properties. Acknowledgments The authors wish to thank Drs. Robert C. Miller, Levine, ments.
G. D. Boyd and Miss B. E. Prescott
B. F.
for optical measure-
Vol. 8, No. 6
COMPLEX CHALCOPYRITES
709
References .
A. F. Wells, Structural Inorganic Chemistry, p. 531. University Press (1962).
.
L. I. Berger and V. C. Prochukhan, Ternary Diamond-Like Semiconductors. Consultants Bureau (1969).
e
4.
Oxford
M. V. Hobden, Acta Cryst. A24, 676 (1968). H. Kasper, Crystal Growth and Properties of Some I-III-VI Compounds. 5th Materials Research Symposium, Gaithersburg, Md. Oct. 18-21 (1971).
PREPARATION AND SOME PROPERTIES OF MATERIALS IN SYSTEMS OF THE TYPE MIMIIIs2-MIMIIIse2 WHERE M I = Cu, Ag AND MIII = A1, Ga, In M. Robbins and V. G. Lambrecht, Jr. Bell Laboratories Murray Hill, New Jersey 07974
( R e c e i v e d A p r i l 19, 1973; C o m m u n i c a t e d by N. B. Hannay)
ABSTRACT
Complete solid solution between sulfide ~halcopyrites (MIMIIIs2) and se~enide chalcopyrites (MIMIIISe2 where M ~ = Cu, Ag and M ±±~ = A1, Ga, In) has been shown to exist. Single crystals of compositions CuGaS 1 5Seo ~, CuGaSSe, CuGaS 0 5Se I 5' have been grown by vapor tr&~sport techniques~ Th@se materials have a non-centrosymmetric crystal structure and exhibit second harmonic generation. Approximate band gaps of the crystals were obtained from optical transmission measurements.
Materials of the type AIBIIIx VI, where A I = Cu, Ag, BIII = A1, Ga, In and X VI = S, Se, which have the non-centrosymmetric chalcopyrite
(I~2d) structure (1) are of interest with
respect to their optical and semiconducting properties.
The band
gaps and optical properties of many of the ternary sulfur and selenium containing chalcopyrites have been reported (2-4). A study of the mixed sulfide-selenides
(AIBIIIs2-AIBIIIse2)
has been undertaken in order to determine how the properties of these systems vary between the endpoints and if materials with
703
704
CHALCOPYRITES
COMPLEX
useful optical or electrical properties manner.
Vol. 8, No. 6
can be generated in this
In this paper we describe preparation,
properties
crystallographic
and some crystal growth of these systems.
ing systems were studied.
CuAIS2-CuAISe2,
The follow-
CuGaS2-CuGaSe2,
CulnS2-CulnSe 2, AgAIS2-AgAISe 2, AgGaS2-AgGaSe 2, AgInS2-AglnSe 2. Experimental Preparations elements.
- All of the materials were prepared from the
Stoichiometric
evacuated silica tubes.
amounts were mixed and sealed in The tubes were placed in a furnace and
the temperature was raised to 800°C at the rate of lO°C/hr.
The
samples were held at 800°C for ~ 2 days at which time the furnace was shut off and the samples allowed to cool in the furnace to room temperature.
Some approximate melting points were obtained
by sealing samples in silica tubes, placing them in a split furnace, which could be opened,
raising the temperature by 25 °
increments and observing the temperature at which the materials were liquid. Powder materials, off ~ X
gas.
This is especially true when Se is present.
Crystallography
- X-ray patterns
using CuK~ radiation. tetragonal
where MIII = A1, hydrolyze in air giving
of all samples were obtained
All of the compositions
(chalcopyrite)
structure.
formed with the
Unit cell parameters
all of the systems vary linearly with composition,
for
as shown in
Figs. la-lc. Crystal Growth - X-ray measurements
on samples which were air
quenched from the melt indicate that all of the materials melt congruently.
However,
initial attempts to prepare large single
crystals from the melt were not successful because of the presence of small spherical voids within the crystals, due to S or Se vapor evolution.
presumably
Our efforts were then directed
towards vapor transport techniques. The vapor transport technique was first employed for the system CuGaS2-CuGaSe 2.
A furnace with a temperature
between lO00°C and 950°C,
drop of 50 °,
over a distance of 8 inches was used.
Approximately 5 gm of prereacted polycrystalline 5 mg 12 per cc of tube was used.
material and
No other iodine concentrations
Vol. 8, No. 6
COMPLEX
CHALCOPYRITES
I 1.0
705
I1.0
M I :Cu
I0.0
MI:Cu
10.9
10,8
10.8
~0.7
~0.7
I0.6
fO.6
CO
CO ~0.5
o~
t0.5 t0.4
I0.3(
<
10.3
~0.2
Z uJ u
10.2
6.0
Z D
b.9
5.8
j.o~
u
6.0
z
5.9
J
5.8
5.7
5.7
A0 5.6
5.6
5.5
5.5
A0 5.4 5.3
MIAI $2
5.4
I
MIAISSe2
I
5.3
MIAISe2
MIGQSSe
MZGQS2
MIAEs2 - MIA|se2
MIGoSe2
MIGOS2 - MZGOSe2
(b)
(a) 11.7
II . 4 CO tt .3
o~
tl.2 tf.1
~
MZ:Cu
t l ,0 j uJ L)
10.9
z
6.0
6.1
~.9 5,8 A 0
5.7 ~.6 5.5
I
M I InS 2
M I InSSe MIInS
2
M I I n Se 2
MI InSe 2
(c) FIG. Unit Cell Parameters
in Systems
i of the Type MIMIIIs2-MIMIIIse2
Where M I - Cu, Ag and M Ill = AI,
Ga,
In
70&
Vol. 8, No. 6
COMPLEX CHALCOPYRITES
were employed in this work.
The end of the tube containing the
feed material was held at 1000°C. this gradient for two weeks.
The tube was maintained in
The compositions grown in this
manner were CuGaS1.5Seo.5, CuGaSSe, CuGaSo.5Sel. ~. Crystals grew in the form of thin, red plates (Figs. 2a-2c) up to 5 mm on an edge.
Optical and x-ray measurements of a number of crystals
(a) CuGaSI. 5Ge0.5
(b) CuGaSSe
(c) FIG. 2
CuGaS0.5Sel.5
Crystals of Compositions From the System CuGaSo-CuGaSe ~, Grown by Vapor Transport in a 50 ° Gradient
V o l . 8, No. 6
C O M P L E X CH.ALCOPYRITES
707
showed that the c-axis was in the plane of the plate. crystals,
however,
These
grew randomly throughout the tube as well as
as on the starting material.
It seemed,
therefore,
that a
relatively large lateral thermal gradient did not enhance crystal growth in this system.
The smaller transverse gradient appeared
to be the most critical. in a quartz tube
A sample of CuGaSSe and 12 was sealed
(~ 3 in long) and held at lO00°C for two weeks.
Crystals grew as plates
(Fig. 3) up to 5 mm on an edge but were
FIG. 3 Crystals of the Compositions CuGaSSe Grown in Sealed Tube With 12 Carrier Using No Laterial Gradient considerably thicker than those grown when a temperature gradient was intentionally employed.
Unit cell parameters
shown in Table 1 along with the parameters
of crystals are
of the preprepared
polycrystalline
material.
It can be seen that the composition
of the crystals
is very close to that of the starting material.
Crystals of CuInSSe were grown in a 50 degree gradient previously described). plates.
We obtained a mixture of needles and
The composition of the crystals
identical to the starting materials in their cell parameters Optical Measurements spectra,
optical cut-offs
appears to be nearly
as shown by the similarity
(Table 1). - Crystals
CuGaSe 2 having the composition transmission
(as
from the system CuGaS 2-
shown in Table 1 were polished and
in the region 0.3~-15~,
are shown in Table 1.
band gap decreases with increasing
obtained.
The
It can be seen that the
Se content.
All of the
COMPLEX C H A L C O P Y R I T E S
708
Vol. 8, No. 6
TABLE 1 Some Properties of Crystals in the CuGaS2-CuGaSe 2 System and CuInSSe Crystals Composition
ao
Starting Material
co
ao
Approximate M.P.
co
°c
Optical Cut-off
AE
(u)
CuGaS1.5Seo. 5
5.412
10.599
5.408
10.597
1150
0.58
2.14
CuGaSSe
5.478
i0.718
5.483
10.730
1150
0.64
1.92
CuGaSo.5Sel. 5
5.551
10.882
5.547
10.874
ll00
0.74
1.67
CuInSSe
5.653
11.281
5.655
11.283
1200
crystals were essentially transparent and 15~.
between the optical cut-off
Powders and crystals of these materials
CuGaS2-CuGaSe 2 exhibit with materials
second harmonic
generation
having the chalcopyrite
structure.
in the system as expected
Discussion It has been shown that the sulfide and selenide chalcopyrites of the type MIMIIIx2, where M I = Cu, Ag and MIII = A1, Ga, In, are completely miscible compositions
in one another.
Crystals with desired
can be grown by vapor transport
techniques.
Crystals
from the system CuGaS2-CuGaSe 2 transmit well into the infra-red. Optical studies are presently being made to determine non-linear
optical properties
the
of these materials.
Additional experiments in systems of the type AgMIIIx2 CuMIIIxo__ where MIII = A1, Ga, In and X = S, Se and MIAIx2 MIGaX2-MIInx2
where M I = Cu or Ag and X = S or Se are being
carried out in order to study their phase relations,
optical
and electric properties. Acknowledgments The authors wish to thank Drs. Robert C. Miller, Levine, ments.
G. D. Boyd and Miss B. E. Prescott
B. F.
for optical measure-
Vol. 8, No. 6
COMPLEX CHALCOPYRITES
709
References .
A. F. Wells, Structural Inorganic Chemistry, p. 531. University Press (1962).
.
L. I. Berger and V. C. Prochukhan, Ternary Diamond-Like Semiconductors. Consultants Bureau (1969).
e
4.
Oxford
M. V. Hobden, Acta Cryst. A24, 676 (1968). H. Kasper, Crystal Growth and Properties of Some I-III-VI Compounds. 5th Materials Research Symposium, Gaithersburg, Md. Oct. 18-21 (1971).