- Email: [email protected]
Photoluminescence in GexAsyS1-x-y glasses by varying the average coordination number
J O U R N A L OF
Journal of Non-Crystalline Solids 137&138 (1991) 959-962 North-Holland
I N-CRNgIII SOLIDS
PHOTOLUMINESCENCE IN GexAsySl-x-y GLASSES BY VARYING THE AVERAGE COORDINATION NUMBER
Vladimir MITSA, Yurij BABINETS, Yurij GVARDIONOV, Irina YERMOLOVlCH Uzhgorod State University, 294017, Uzhgorod, USSR
The results for photoluminescence (PL) (intensity, halfwidth and spectral position of bands) as well as Raman spectroscopy and estimates of sizes 2 Cr for structural correlation zone in GexASySl-x-y glasses by varying the average coordination number (z=2.66 + 2.82) have been discussed. 1.
INTRODUCTION
4.
RESULTS AND DISCUSSION
Over the past years much attention has been paid to
In the PL spectra of a-GeS2 prepared by melt-quenching
ternary glassy alloys of GexAsySl-x-y type 1-3, The study of an
from 900, 1000 and 1100°C the bands with maxima at 1.16,
energy spectrum of localized states in the pseudogap of such
1.23 and 1.12 eV and halfwidths of 0.35, 0.43 and 0.47 eV,
glasses by a photoluminescent method in interrelation with a
r e s p e c t i v e l y (Fig.l) are o b s e r v e d . The increase in the
local coordination of atoms and sizes of structural correlation
halfwidth with increasing Trn is associated with high-and low-
zone may promote the elucidation of PL centres' origin and
energy shoulders to appear at 1.5 and 0,8 eV, respectively. The
the influence of the middle-range order on the radiative
former was observed in the PL spectra of glasses in Ge-As-S system 4 .
recombination processes both in the region of structural phase transition at z = 2.671 and when varying the average coordination number.
The Raman spectrum of a-GeS2 (Tin1 = 900°C) is of a typical shape (Fig.2). When quenched from Tm2 = 1000°C the glass has the Raman spectrum in which beside 5 bands a new less
2.
EXPERIMENTAL PROCEDURE
intensive band near 270 cm -1 appears characteristic for a-Ge 5.
The photoluminescence excitation at 77K was effected by
At Tin3 = 1100°C the intensity of the latter becomes larger and
H)K-100 lamp radiation to be transmitted through a liquid filter
the maximum is shifted to 254 cm -1. I-3 mol.% of As having been added into a GeS2 causes the same transformation of
from CuSO4 solution. He-Ne and Kr-lasers operating at the wavelengths of 0.63 and 0.75/~m,
respectively served as the excitation source
f o r the Raman spectra. The ~ C - 2 4
double monochromator
the Raman spectrum and the appearance of shoulders in the PL spectra as the increase in Trn from 900 to 1100°C for GeS2 d o e s ( F i g s . l , 2). The PL i n t e n s i t y a l r e a d y in the glass
was used as a dispersive instrument. The sound velocity in
at z > 2,66 decreases by an order of magnitude in comparison
glasses was measured by an echo-technique.
with that one in a-GeS2, With increasing z the PL maximum is
3.
direction with the change in the absorption edge. At z > 2.69
shifted from 1.17 eV (z = 2.662) to 1.0 eV (z = 2.73) in one MATERIALS The glasses of Asy(GeS2)l-y and Asy(Ge2S3)l-y sections
in the PL spectra the s h o u l d e r near 1.5 eV practically
were synthesized at a temperature of 1050°C. The melt was
disappears and the band halfwidth decreases up to 0.32 eV.
homogenized within 24 hours at temperatures of 950 and
In the Raman spectrum of such glasses a band at 210 cm -1
1000°C for the compositions rich and depleted in germanium,
appears. T h e latter is also observed in the Raman spectrum
respectively. The melts were quenched in air.
of glasses of Asy(Ge2S3)l-y section (Fig.2).
The GeS2 melt was quenched into a cold water beginning from melting temperatures (Tin) of 900, 1000, 1100°C.
At z = 2.8 Em= 1.12 eV and the band halfwidth is close to that one in a-GeS2 quenched from Tin1. At 2,8 < z< 2.808 the
Fresh cleaved glasses were used as the samples to study
PL intensity of glasses decreases by a factor of 1.5-2.5 in
the PL. The samples for Raman spectroscopy and ultrasound
comparison with that one at z = 2.8, The sharpness of an
velocity measurement were prepared by using a conventional technique.
exponential part in the absorption curve increases and the
0022-3093/91/$03.50 © 1991 - Elsevier Science Publishers B.V.
All rights reserved.
960
V. Mitsa et al. / Photoluminescence in GexASySl.x_y glasses
edge itself is somehow shifted to a high-energy region in comparison with the sharpness and edge position at z = 2.8.
342
GeS2(z=2,66) :2 (z=2,66) q=900°C 12=IO00°C 13=llO0°C
y=3% (2,661) 5
(2,671)
7
(2,674)
10
(2,678)
15
(2,687)
:3% (2,661) 5 7 10 15 20 30 40
(2,671) (2,674) (2,678) (2,687) (2,6919) (2,708) (2,727)
20 (2,6919) GezS3 (2,80) 3
(2,802)
5
(2,802)
7
(2,803)
)e2S3 (2,80) =3% 5 7 10
(2,802) (2,802) (2,803) (2,8043)
15 (2,8069) 20 (2,8096) 30 (2,8158) 40 (2,8235) 0,6
0,8 1,0 1,2 1,4 ENERGY, eV
FIGURE 1 PL spectra of a-GeS 2 prepared at different T m and glasses of ASy(GeS2)l.y, ASy(Ge2S3) l_y sections. The respective compositions and average coordination numbers have been indicated in the figure.
10 (2,8043) 15 (2,8069) 20 (2,8096) n
m
400
n
R
200
w
0
RAMAN S H I F T , cm -1 FIGURE 2 Unpolarized Raman spectra of glasses of ASv(GeS2)l_y and Asv(Ge2S3)l_y sections. The respective compositions and average coordination numbers have been indicated in the figure.
The defects which are formed because of breaking of
z > 2.66 or with GeS2 melt to be quenched from Tm3 = 1100°C.
bonds !n structural units (s.u.) are considered to be the source
This transformation is attributed to vibrational bands which
of photoluminescence in chalcogenide glasses 3,6. Following 3.6
appear at 250 cm -1 and are characteristic for the vibration of
the band near 1.2 eV in binary glasses can be attributed to
atoms in Ge2S6/2 s.u, 7,8.The fact that the shoulder disappears
breaking of bonds inclasters built of GeS4/2 s.u., w h o s e
at 1.5 eV and the band appears at 210 cm -1 in the Raman
m a x i m u m o f v i b r a t i o n s 1)1 (A) = 342 cm 1 is o b s e r v e d in
spectrum may testify to the change in the character of G22S6/2
the Raman s p e c t r a ( F i g s . l , 2). The Raman spectra are
s.u. interconnectivity at z>2.69.
O b s e r v e d to be s i m u l t a n e o u s l y t r a n s f o r m e d with the
The disappearance of bands at vl c = 3 7 5 3 n d 110cm 1
shoulders to appear at 0.6 and 1,5 eV in the PL spectra at
according to 9,1o may testify to breaking of O-dimensional
961
V. Mitsa et al. / Photoluminescence in GexASySl_x_y glasses
rings which consist of GeS4/2 tetrahedrons and layered
the PL spectra at z >2.66 the band halfwidth increases which
fragments in Asy(GeS2)l-y glasses. In the light of conception 1
can be attributed to high- and low-energy shoulders to appear
the decrease in the PL intensity when adding As into a-GeS2
at 0.8 and 1.5 eV. The latter disappears at z = 2.69 when in
at z = 2.67 may be explained by the decrease in the number
the
of defects due to the increase in the network connectivity. The
appears.
results of work 11
also testify in favour of this fact. The
Raman spectrum
of glasses the band near 210 cm q
Small As additives cause the same transformation of the
decrease in the sizes of structural correlation zone in Martin-
Raman spectrum and appearance of shoulders
Brening model (Fig.3) accompanies this increase in the
spectrum as quenching of GeS2 melt from 1100°C into a cold
connectivity. The latter, probably, causes internal strains in
water does.
glasses at 2.66< z< 2.73 as Vl(A) maximum is shifted from
The decrease in the sizes 2~ of the structural correlation
342
to 352 cm -1 (Fig.2),A similar shift was observed in
zone from 10.5/~ (z = 2.66) up to 7.5 ~ (z = 2.8), disappea-
GexSloo-x glasses when applying external pressure 12. An
rance of v~ and v3(F) = 4 3 5 cm q and the band near 110 cm 1
opposite shift of ~'I(A) is observed when As is added into
reveal an increase in the network connectivity because of
a-Ge2S3
breaking of O-dimensional rings and layered fragments.
and it is accompanied by a slight increase in
in the PL
20" (Fig.3). The PL intensity and ratio of IB/1340at 2.8 < z < 2.803 decrease in comparison with those at z = 2.8. In the PL spectra of glasses at z> 2.69 and 2.808 a weak effect of PL "fatigue" is observed.
REFERENCES 1. K. Tanaka, Phys. Rev. B, 39 (1989) 1270.
26,A .(x,~B,cm-1
13
L
11 4o
E,eV
2. M.F. Thorpe and Y.Cay, J. Non-Cryst. Sol., 114 (1989) 19.
1,2
3. V. Milov and T. Mamontova, Phys. and Chem. Glasses (in Russia), 14 (1988) 246.
//////L
1,0
4. K. Arai, U, hoh, H. Komina and H. Namikava, Photolumieescence in Ge-S glasses, in: Structure and Prop. of Non-Cryst. Semicond., ed B.T. Kolomiets (Leningrad, 1976) pp. 222-226. 5. J.S. Lannin, J. Non-Cryst. Sol., 97-98 (1987) 99.
0,8
0,6 |
I
2,6
2,7
i
AVERAGE COORDINATION NUMBER (Z) FIGURE 3 PL maximum (1), sizes 2o of structural corelation zone (2), and position of Boson maximum LOB (3) of ASy(GeS2)l_y and ASy(Ge2S3)l.y sections as a function of average coordination number. 5.
CONCLUSIONS In the region of structural phase transition (z = 2.67) in
Asy(GeS2)l-y glasses the decrease in the PL intensity is observed in comparison with that one in a-GeS2 (z = 2.66). In
6. R.A. Street, Adv. in Physics, 25 (1976) 397. 7. G. Lucovsky, R.J. Nemanich and F.L Galeener, New chemically-ordered composition in the glass system Gel-xSx and Gel-xSex, in: Proc. Seventh Int. Conf. on Amorphous and Liquid Semiconductors, ed. W.E. Spear (University of Edinburgh, 1977) pp. 130-132. 8. A. Fehz, K. Zickmuller and G. Pfaff, On structure of GeS/GeS2 - and GeSe/GeSe2 - glasses and amorphous compounds Ge2S3 and Ge2Se3, in ref. 7, pp. 125-129. 9. P. Vashishta, R.K. Kalia, I. Ebbsjo, Phys. Rev. 39 (1989) 6034. 10. J.C. Phillips, J. Non-Cryst. Sol., 43 (1981) 37. 11. Yu.Yu. Babinets, Yu.V, Vlasenko, M.P. Lisitsa, V.M. Mitsa et al., Quantum Electron, (in Russia), 15 (1988) 2039. 12. K. Muraze, K. Yakushiji and T. Fukunaga, J. Non-Cryst, Sol., 59-60 (1983) 855.
Journal of Non-Crystalline Solids 137&138 (1991) 959-962 North-Holland
I N-CRNgIII SOLIDS
PHOTOLUMINESCENCE IN GexAsySl-x-y GLASSES BY VARYING THE AVERAGE COORDINATION NUMBER
Vladimir MITSA, Yurij BABINETS, Yurij GVARDIONOV, Irina YERMOLOVlCH Uzhgorod State University, 294017, Uzhgorod, USSR
The results for photoluminescence (PL) (intensity, halfwidth and spectral position of bands) as well as Raman spectroscopy and estimates of sizes 2 Cr for structural correlation zone in GexASySl-x-y glasses by varying the average coordination number (z=2.66 + 2.82) have been discussed. 1.
INTRODUCTION
4.
RESULTS AND DISCUSSION
Over the past years much attention has been paid to
In the PL spectra of a-GeS2 prepared by melt-quenching
ternary glassy alloys of GexAsySl-x-y type 1-3, The study of an
from 900, 1000 and 1100°C the bands with maxima at 1.16,
energy spectrum of localized states in the pseudogap of such
1.23 and 1.12 eV and halfwidths of 0.35, 0.43 and 0.47 eV,
glasses by a photoluminescent method in interrelation with a
r e s p e c t i v e l y (Fig.l) are o b s e r v e d . The increase in the
local coordination of atoms and sizes of structural correlation
halfwidth with increasing Trn is associated with high-and low-
zone may promote the elucidation of PL centres' origin and
energy shoulders to appear at 1.5 and 0,8 eV, respectively. The
the influence of the middle-range order on the radiative
former was observed in the PL spectra of glasses in Ge-As-S system 4 .
recombination processes both in the region of structural phase transition at z = 2.671 and when varying the average coordination number.
The Raman spectrum of a-GeS2 (Tin1 = 900°C) is of a typical shape (Fig.2). When quenched from Tm2 = 1000°C the glass has the Raman spectrum in which beside 5 bands a new less
2.
EXPERIMENTAL PROCEDURE
intensive band near 270 cm -1 appears characteristic for a-Ge 5.
The photoluminescence excitation at 77K was effected by
At Tin3 = 1100°C the intensity of the latter becomes larger and
H)K-100 lamp radiation to be transmitted through a liquid filter
the maximum is shifted to 254 cm -1. I-3 mol.% of As having been added into a GeS2 causes the same transformation of
from CuSO4 solution. He-Ne and Kr-lasers operating at the wavelengths of 0.63 and 0.75/~m,
respectively served as the excitation source
f o r the Raman spectra. The ~ C - 2 4
double monochromator
the Raman spectrum and the appearance of shoulders in the PL spectra as the increase in Trn from 900 to 1100°C for GeS2 d o e s ( F i g s . l , 2). The PL i n t e n s i t y a l r e a d y in the glass
was used as a dispersive instrument. The sound velocity in
at z > 2,66 decreases by an order of magnitude in comparison
glasses was measured by an echo-technique.
with that one in a-GeS2, With increasing z the PL maximum is
3.
direction with the change in the absorption edge. At z > 2.69
shifted from 1.17 eV (z = 2.662) to 1.0 eV (z = 2.73) in one MATERIALS The glasses of Asy(GeS2)l-y and Asy(Ge2S3)l-y sections
in the PL spectra the s h o u l d e r near 1.5 eV practically
were synthesized at a temperature of 1050°C. The melt was
disappears and the band halfwidth decreases up to 0.32 eV.
homogenized within 24 hours at temperatures of 950 and
In the Raman spectrum of such glasses a band at 210 cm -1
1000°C for the compositions rich and depleted in germanium,
appears. T h e latter is also observed in the Raman spectrum
respectively. The melts were quenched in air.
of glasses of Asy(Ge2S3)l-y section (Fig.2).
The GeS2 melt was quenched into a cold water beginning from melting temperatures (Tin) of 900, 1000, 1100°C.
At z = 2.8 Em= 1.12 eV and the band halfwidth is close to that one in a-GeS2 quenched from Tin1. At 2,8 < z< 2.808 the
Fresh cleaved glasses were used as the samples to study
PL intensity of glasses decreases by a factor of 1.5-2.5 in
the PL. The samples for Raman spectroscopy and ultrasound
comparison with that one at z = 2.8, The sharpness of an
velocity measurement were prepared by using a conventional technique.
exponential part in the absorption curve increases and the
0022-3093/91/$03.50 © 1991 - Elsevier Science Publishers B.V.
All rights reserved.
960
V. Mitsa et al. / Photoluminescence in GexASySl.x_y glasses
edge itself is somehow shifted to a high-energy region in comparison with the sharpness and edge position at z = 2.8.
342
GeS2(z=2,66) :2 (z=2,66) q=900°C 12=IO00°C 13=llO0°C
y=3% (2,661) 5
(2,671)
7
(2,674)
10
(2,678)
15
(2,687)
:3% (2,661) 5 7 10 15 20 30 40
(2,671) (2,674) (2,678) (2,687) (2,6919) (2,708) (2,727)
20 (2,6919) GezS3 (2,80) 3
(2,802)
5
(2,802)
7
(2,803)
)e2S3 (2,80) =3% 5 7 10
(2,802) (2,802) (2,803) (2,8043)
15 (2,8069) 20 (2,8096) 30 (2,8158) 40 (2,8235) 0,6
0,8 1,0 1,2 1,4 ENERGY, eV
FIGURE 1 PL spectra of a-GeS 2 prepared at different T m and glasses of ASy(GeS2)l.y, ASy(Ge2S3) l_y sections. The respective compositions and average coordination numbers have been indicated in the figure.
10 (2,8043) 15 (2,8069) 20 (2,8096) n
m
400
n
R
200
w
0
RAMAN S H I F T , cm -1 FIGURE 2 Unpolarized Raman spectra of glasses of ASv(GeS2)l_y and Asv(Ge2S3)l_y sections. The respective compositions and average coordination numbers have been indicated in the figure.
The defects which are formed because of breaking of
z > 2.66 or with GeS2 melt to be quenched from Tm3 = 1100°C.
bonds !n structural units (s.u.) are considered to be the source
This transformation is attributed to vibrational bands which
of photoluminescence in chalcogenide glasses 3,6. Following 3.6
appear at 250 cm -1 and are characteristic for the vibration of
the band near 1.2 eV in binary glasses can be attributed to
atoms in Ge2S6/2 s.u, 7,8.The fact that the shoulder disappears
breaking of bonds inclasters built of GeS4/2 s.u., w h o s e
at 1.5 eV and the band appears at 210 cm -1 in the Raman
m a x i m u m o f v i b r a t i o n s 1)1 (A) = 342 cm 1 is o b s e r v e d in
spectrum may testify to the change in the character of G22S6/2
the Raman s p e c t r a ( F i g s . l , 2). The Raman spectra are
s.u. interconnectivity at z>2.69.
O b s e r v e d to be s i m u l t a n e o u s l y t r a n s f o r m e d with the
The disappearance of bands at vl c = 3 7 5 3 n d 110cm 1
shoulders to appear at 0.6 and 1,5 eV in the PL spectra at
according to 9,1o may testify to breaking of O-dimensional
961
V. Mitsa et al. / Photoluminescence in GexASySl_x_y glasses
rings which consist of GeS4/2 tetrahedrons and layered
the PL spectra at z >2.66 the band halfwidth increases which
fragments in Asy(GeS2)l-y glasses. In the light of conception 1
can be attributed to high- and low-energy shoulders to appear
the decrease in the PL intensity when adding As into a-GeS2
at 0.8 and 1.5 eV. The latter disappears at z = 2.69 when in
at z = 2.67 may be explained by the decrease in the number
the
of defects due to the increase in the network connectivity. The
appears.
results of work 11
also testify in favour of this fact. The
Raman spectrum
of glasses the band near 210 cm q
Small As additives cause the same transformation of the
decrease in the sizes of structural correlation zone in Martin-
Raman spectrum and appearance of shoulders
Brening model (Fig.3) accompanies this increase in the
spectrum as quenching of GeS2 melt from 1100°C into a cold
connectivity. The latter, probably, causes internal strains in
water does.
glasses at 2.66< z< 2.73 as Vl(A) maximum is shifted from
The decrease in the sizes 2~ of the structural correlation
342
to 352 cm -1 (Fig.2),A similar shift was observed in
zone from 10.5/~ (z = 2.66) up to 7.5 ~ (z = 2.8), disappea-
GexSloo-x glasses when applying external pressure 12. An
rance of v~ and v3(F) = 4 3 5 cm q and the band near 110 cm 1
opposite shift of ~'I(A) is observed when As is added into
reveal an increase in the network connectivity because of
a-Ge2S3
breaking of O-dimensional rings and layered fragments.
and it is accompanied by a slight increase in
in the PL
20" (Fig.3). The PL intensity and ratio of IB/1340at 2.8 < z < 2.803 decrease in comparison with those at z = 2.8. In the PL spectra of glasses at z> 2.69 and 2.808 a weak effect of PL "fatigue" is observed.
REFERENCES 1. K. Tanaka, Phys. Rev. B, 39 (1989) 1270.
26,A .(x,~B,cm-1
13
L
11 4o
E,eV
2. M.F. Thorpe and Y.Cay, J. Non-Cryst. Sol., 114 (1989) 19.
1,2
3. V. Milov and T. Mamontova, Phys. and Chem. Glasses (in Russia), 14 (1988) 246.
//////L
1,0
4. K. Arai, U, hoh, H. Komina and H. Namikava, Photolumieescence in Ge-S glasses, in: Structure and Prop. of Non-Cryst. Semicond., ed B.T. Kolomiets (Leningrad, 1976) pp. 222-226. 5. J.S. Lannin, J. Non-Cryst. Sol., 97-98 (1987) 99.
0,8
0,6 |
I
2,6
2,7
i
AVERAGE COORDINATION NUMBER (Z) FIGURE 3 PL maximum (1), sizes 2o of structural corelation zone (2), and position of Boson maximum LOB (3) of ASy(GeS2)l_y and ASy(Ge2S3)l.y sections as a function of average coordination number. 5.
CONCLUSIONS In the region of structural phase transition (z = 2.67) in
Asy(GeS2)l-y glasses the decrease in the PL intensity is observed in comparison with that one in a-GeS2 (z = 2.66). In
6. R.A. Street, Adv. in Physics, 25 (1976) 397. 7. G. Lucovsky, R.J. Nemanich and F.L Galeener, New chemically-ordered composition in the glass system Gel-xSx and Gel-xSex, in: Proc. Seventh Int. Conf. on Amorphous and Liquid Semiconductors, ed. W.E. Spear (University of Edinburgh, 1977) pp. 130-132. 8. A. Fehz, K. Zickmuller and G. Pfaff, On structure of GeS/GeS2 - and GeSe/GeSe2 - glasses and amorphous compounds Ge2S3 and Ge2Se3, in ref. 7, pp. 125-129. 9. P. Vashishta, R.K. Kalia, I. Ebbsjo, Phys. Rev. 39 (1989) 6034. 10. J.C. Phillips, J. Non-Cryst. Sol., 43 (1981) 37. 11. Yu.Yu. Babinets, Yu.V, Vlasenko, M.P. Lisitsa, V.M. Mitsa et al., Quantum Electron, (in Russia), 15 (1988) 2039. 12. K. Muraze, K. Yakushiji and T. Fukunaga, J. Non-Cryst, Sol., 59-60 (1983) 855.