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Thermally induced crystallization of amorphous Ge0.4Se0.6
Journal of Noa-CrystaJline Solids 117/118 (1990) 219-221 North-Holland
219
THERMALLY INDUCED CRYSTALLIZATION OF AMORPHOUSGeo.4Seo. 6 Osamu UEMURA*, Yasuo KAMEDA*, Satomi KOKAI** and Tsuneo SATOW* * Department o f Chemistry, Faculty of Science, Yamagata U niv e r s it y , Yamagata 990, Japan **Graduate School, Yamagata University The Raman scattering measurement in amorphous Geo,4Seo G was carried out at several temperatures below 440°C in order to i n v e s ti g a te the r e l a t i o n in short range order between amorphous and cryst a l l i n e phases. Raman spectra were obtained using 514.5 nm argon-ion laser and a double grating monochrometer. The 175 and 280 cm-1 v i b r a t i o n a l modes in amorphous Ge0 4Se0 G disappear a f t e r the complete c r y s t a l l i z a t i o n , i n d i c a t i n g that the chemical order including Ge-Ge'bonds is characterist i c to the amorphous phase but not to the c r y s t a l l i n e one. This agrees with the r e s u l t by previous radial d i s t r i b u t i o n studies that amorphous GexSe~_x a l l o y s with x > I / 3 have a d i f f e r e n t local order from the c r y s t a l l i n e form. The AI mode peak 6f GeSe~ tetrahedron units a l t e r s i t s position on heating• Therefore, i t may be considered that i n t r a - and inter-molecular i n t e r a c t i o n s of t h i s u n i t change through the c r y s t a l l i z a t i o n process. t i o n pattern.
I . INTRODUCTION Recently a considerable i n t e r e s t concentrates
The Raman spectra were measured at several
on the chemical bonding and the r e s u l t a n t short
temperatures below 440°C by using 514.5 nm ar-
range order in amorphous semiconductors.
gon-ion laser and a double grating monochrometer
Struc-
tural information f o r amorphous GexSel_x i n d i -
(JASCO CT-IOOOD). Powder amorphous sample was
cate that for x ~ I / 3 Ge atoms are f o u r f o l d co-
enclosed into an evacuated quartz c e l l .
ordinated and Se atoms are twofold coordinated as expected from the s i m i l a r i t y to the c r y s t a l l i n e form 1,2
3. RESULTS AND DISCUSSION Figure 1 shows the Raman spectra for amor-
Our i n t e r e s t is stimulated for the amorphous
phous Geo.4Seo. 6 in the range between room tem-
structure o f Ge r i c h a l l o y s above x : I / 3 , because
perature and 380°C, obtained subtracting the
the X-ray anomalous scattering study suggests
cell background i n t e n s i t i e s which are structure-
that the amorphous phase has a d i f f e r e n t ar-
less and monotonic.
rangement of atoms from the corresponding crys-
perature is almost the same as that shown by
t a l l i n e form. 3
Lucovsky et a l . 4
The purpose of t h i s paper is to
The spectrum at room tem-
The dominant(A) and broad(D)
report the c r y s t a l l i z a t i o n process of amorphous
peaks in Fig. 1 may be assigned to the v i b r a -
Geo.4Seo. 6 on heating through the Raman scatter-
t i o n a l modes r e l a t i n g to the structural u n i t
ing measurement and to i n v e s ti g a te the connec-
containing Ge-Ge bonds, such as, e i t h e r the
t i o n of the short range order between amorphous
chemical order; Se3Ge-(GeSe2)n-GeSe3 (n:O,l) or
and c r y s t a l l i n e phases•
the tetrahedron centered about Ge atoms; Ge-
2. EXPERIMENTALS
to the second peak(B) and i t s shoulder(C) is the
GemSe4_m (m=1,2,3,4). 5'6 The p u r i t y of Ge and Se used in t h i s i n v e s t i -
A major c o n t r i b u t i o n
v i b r a t i o n a l modes of GeSe4 tetrahedra and con-
gation was both 99.999%. The amorphous sample
t r i b u t i o n s from the structural units containing
was prepared by quenching the melt into cold wa-
Ge-Ge bonds are p a r t i a l l y added•
ter.
t i o n of (B) and (C) at room temperature roughly
The check of the amorphization for the
sample was made by obtaining the X-ray d i f f r a c 0022-3093/90/$03.50 (~) Elsevier Science Publishers B.V. (North-Holland)
The peak posiC
agrees with that of A1 and i t s companion A1
O. Uemura et al. / Crystallization of amorphous Geo.4Seo.6
220
annealing amorphous GeSe2 at s l i g h t l y lower tem-
T
peratures than the glass t r a n s i t i o n temperature (390oc).8
U3
I t seems reasonable to measure the
temperature change in Raman spectra for amorphous GeSe2 in order to recognize the above in terpretation.
O
However, in the present i n v e s t i -
gation i t was impossible to detect the clear I-I-,-I ~o Z uJ
s h i f t of the A1 peak position in amorphous GeSe2 since the peak position of the 3D GeSe2 form appeared on heating is extremely close to that of
Z
the amorphous phase at room temperature.
100
200 300 RAIMAN SHI FT/cm-1
400 J,
Then,
we next t r i e d to in v es t ig a t e the Raman spectra of heated amorphous Geo.35Seo.65 ans Geo.37.
FIGURE 1 Raman spectra of Ge0 4Se0 6 glass heated at ( I ) room temperature, (21 200~ (3) 300, (4) 350 and 380°C, re s p e c t i v e l y .
Se0.63, data of which are described in Fig. 2.
modes o f GeSe4 tetrahedra in amorphous GeSe2.
temperature and the A1 peak of 3D c r y s t a l l i n e
Spectra observed in both a l l o y s also e x h i b i t that the peak at 203 cm-I at room temperature shifted toward low frequencies with increasing
The peak position of (B) has a tendency to
-I
phase appears at 199 cm
.
in the range between
s h i f t toward lower energies and to become rather
300 and 380°C.
steeper with increasing temperature ( i . e . , 203 cm-I at room temperature and 199 cm-I at 380°C,
tends to change gradually with increasing tem-
respectively).
The shape of (A), (D) peaks and shoulder (C)
The peak position of the A1 mode
of the GeSe4 unit can be considered to be strongly affected by the d i s t o r t i o n of the unit and by the surrounding atomic c o n f i g u r a t i o n .
T
'(b)
Ca) cTJL
/
._
For example, a sharp A1 l i n e is observed at 210 -I cm in c r y s t a l l i n e GeSe2 consisting of two d i mentional layers in which GeSe4 tetrahedra share each other Se atoms at corners or edges (2D form).7
O
In a d d i t i o n , the low temperature phase
of c r y s t a l l i n e GeSe2 has r e c e n t l y been confirmed by the Raman scattering study, which has the corresponding A1 l i n e around 200 cm-l. 8
The
£b3 Z UJ ~.. Z
structure o f t h i s phase can be assumed to take a three dimensional network with corner-sharing GeSe4 tetrahedra(3D form) from the correspondence of the crystal structure between GeSe2 and GeS2.
120
I 200 240 200 240 RAMAN SHIFT/cm -1
The s h i f t of the peak (B) toward 199 cm"I
seen in the temperature range with 300-,380°C may be interpreted to be due to the appearance of the local order o f 3D form, because t h i s phase has been reported to be p r e f e r e n t i a l l y formed by
FIGURE 2 Raman spectra of Ge0 ~Se 0 65(a) and Geo.37" Se0 G3(b) glasses heated at ( I ) room temperaturG, (2) 200, (3) 390, (4) 350, (5) 380, (6) 410 and (7) 440°C, r e s p e c t i v e l y
O. Uemura et al./Crystallization of amorphous Geo4Seo 6
221
perature but we have no information about t h i s change at present. -I On exceeding 410°C the growth of the 210 cm l i n e of the 2D c r y s t a l l i n e form r a p i d l y promotes e i t h e r by r a i s i n g temperature or by the lapse of
T'
t '
time as shown in Fig. 3, although the spectrum at 300°C in Fig. 1 already gives the i n d i c a t i o n of t h i s l i n e ( n o t e ; an arrow).
On the other
hand, both (A) and (D) v i b r a t i o n a l modes in a-
_
(3)c
morphous Geo.4Seo. 6 fade out under the complete c r y s t a l l i z a t i o n , suggesting that there are no chemical orders or no tetrahedron units including Ge-Ge bonds in c r y s t a l l i n e state.
(N.B.,
Main Raman peaks in c r y s t a l l i n e GeSe can be seen at 148, 187 and 211 cm- I , r e s p e c t i v e l y .
The v i -
brational modes in GeSe structure are less
l
100
Raman-active compared with those in c r y s t a l l i n e GeSe2 and, in a d d i t i o n , some of the modes in both crystals f a l l on s i m i l a r frequencies in the spectrum.
Therefore, i t could not be judged
within the present experimental accuracy whether
210 II
I
200 300 RANAN SHIFT/cm-1
&O0
FIGURE 3 Raman spectra of Ge0 4Se0 6 glass heated at ( I ) 410, (2) 420, (3) 436 and'(4) 440°C, respectivel y . Retention times are shown, (3)A-0.5, (3)B1.0, (3)C-I.5 and (3)D-2.0 hr, r e s p e c t i v e l y
the modes in GeSe phase are present or not in the spectrum at 440°C of f u l l y c r y s t a l l i z e d sample.)
After a l l ,
i t can be summarized by the
present Raman scattering measurement of heated amorphous Geo.4Seo. 6 that ( I ) the A1 mode of the GeSe4 tetrahedral unit in the low temperature phase of c r y s t a l l i n e GeSe2 can be observed at r e l a t i v e l y lower temperatures below 400°C and (2) the chemical order containing Ge-Ge bonds evidenced by 175 cm-I and 280 cm-I modes which is c h a r a c t e r i s t i c o f Ge rich a l l o y s exists only in the amorphous state. The Raman scattering measurement can give more d e t a i l e d information about the change in a-
REFERENCES I . O. Uemura, Y. Sagara and T. Satow, phys. star. s o l . ( a ) 26 (1974) 99. 2. R.W. Fawcett, C.N.J. Wagner and G.S. Cargill I I I , J. Non-Cryst. Solids 8 (1972) 369. 3. P.H. Fuoss, W.K. Warburton and A. Bienenstock, J. Non-Cryst. Solids 35&36 (1980) 33. 4. G. Lucovsky, R.J. Nemanich and P.L. Galeener, In Proc. 7th I n t . Conf. Amorphous and Liquid Semiconductors ed. by W.E. Spear (University of Edinburgh, 1977) p.130. 5. A. Feltz, B. Voigt and E. Schlenzig, In Proc. 5th I n t . Conf. Amorphous and Liquid Semiconductors ed. by J. Stuke, W. Brenig (Taylor and Francis, London, 1974) p.261.
tomic c o n f i g u ra t i o n brought about on the cryst a l l i z a t i o n of amorphous materials as compared
6. G. Lucovsky and R.M. Martin, J. Non-Cryst. Solids 8-10 (1972) 185.
with other structural studies such as the d i f f r a c t i o n measurement, but we should keep in mind
7. V.G. Dittmer and H. Schaefer, Acta C r y s t a l l o g. B32 (1976) 2726.
that the l i g h t - i r r a d i a t e d c r y s t a l l i z a t i o n simultaneously goes on at a given temperature during the measurement.
8. K. Inoue, K. Kawamoto and K. Murase, J. NonCryst. Solids 95&96 (1987) 517.
219
THERMALLY INDUCED CRYSTALLIZATION OF AMORPHOUSGeo.4Seo. 6 Osamu UEMURA*, Yasuo KAMEDA*, Satomi KOKAI** and Tsuneo SATOW* * Department o f Chemistry, Faculty of Science, Yamagata U niv e r s it y , Yamagata 990, Japan **Graduate School, Yamagata University The Raman scattering measurement in amorphous Geo,4Seo G was carried out at several temperatures below 440°C in order to i n v e s ti g a te the r e l a t i o n in short range order between amorphous and cryst a l l i n e phases. Raman spectra were obtained using 514.5 nm argon-ion laser and a double grating monochrometer. The 175 and 280 cm-1 v i b r a t i o n a l modes in amorphous Ge0 4Se0 G disappear a f t e r the complete c r y s t a l l i z a t i o n , i n d i c a t i n g that the chemical order including Ge-Ge'bonds is characterist i c to the amorphous phase but not to the c r y s t a l l i n e one. This agrees with the r e s u l t by previous radial d i s t r i b u t i o n studies that amorphous GexSe~_x a l l o y s with x > I / 3 have a d i f f e r e n t local order from the c r y s t a l l i n e form. The AI mode peak 6f GeSe~ tetrahedron units a l t e r s i t s position on heating• Therefore, i t may be considered that i n t r a - and inter-molecular i n t e r a c t i o n s of t h i s u n i t change through the c r y s t a l l i z a t i o n process. t i o n pattern.
I . INTRODUCTION Recently a considerable i n t e r e s t concentrates
The Raman spectra were measured at several
on the chemical bonding and the r e s u l t a n t short
temperatures below 440°C by using 514.5 nm ar-
range order in amorphous semiconductors.
gon-ion laser and a double grating monochrometer
Struc-
tural information f o r amorphous GexSel_x i n d i -
(JASCO CT-IOOOD). Powder amorphous sample was
cate that for x ~ I / 3 Ge atoms are f o u r f o l d co-
enclosed into an evacuated quartz c e l l .
ordinated and Se atoms are twofold coordinated as expected from the s i m i l a r i t y to the c r y s t a l l i n e form 1,2
3. RESULTS AND DISCUSSION Figure 1 shows the Raman spectra for amor-
Our i n t e r e s t is stimulated for the amorphous
phous Geo.4Seo. 6 in the range between room tem-
structure o f Ge r i c h a l l o y s above x : I / 3 , because
perature and 380°C, obtained subtracting the
the X-ray anomalous scattering study suggests
cell background i n t e n s i t i e s which are structure-
that the amorphous phase has a d i f f e r e n t ar-
less and monotonic.
rangement of atoms from the corresponding crys-
perature is almost the same as that shown by
t a l l i n e form. 3
Lucovsky et a l . 4
The purpose of t h i s paper is to
The spectrum at room tem-
The dominant(A) and broad(D)
report the c r y s t a l l i z a t i o n process of amorphous
peaks in Fig. 1 may be assigned to the v i b r a -
Geo.4Seo. 6 on heating through the Raman scatter-
t i o n a l modes r e l a t i n g to the structural u n i t
ing measurement and to i n v e s ti g a te the connec-
containing Ge-Ge bonds, such as, e i t h e r the
t i o n of the short range order between amorphous
chemical order; Se3Ge-(GeSe2)n-GeSe3 (n:O,l) or
and c r y s t a l l i n e phases•
the tetrahedron centered about Ge atoms; Ge-
2. EXPERIMENTALS
to the second peak(B) and i t s shoulder(C) is the
GemSe4_m (m=1,2,3,4). 5'6 The p u r i t y of Ge and Se used in t h i s i n v e s t i -
A major c o n t r i b u t i o n
v i b r a t i o n a l modes of GeSe4 tetrahedra and con-
gation was both 99.999%. The amorphous sample
t r i b u t i o n s from the structural units containing
was prepared by quenching the melt into cold wa-
Ge-Ge bonds are p a r t i a l l y added•
ter.
t i o n of (B) and (C) at room temperature roughly
The check of the amorphization for the
sample was made by obtaining the X-ray d i f f r a c 0022-3093/90/$03.50 (~) Elsevier Science Publishers B.V. (North-Holland)
The peak posiC
agrees with that of A1 and i t s companion A1
O. Uemura et al. / Crystallization of amorphous Geo.4Seo.6
220
annealing amorphous GeSe2 at s l i g h t l y lower tem-
T
peratures than the glass t r a n s i t i o n temperature (390oc).8
U3
I t seems reasonable to measure the
temperature change in Raman spectra for amorphous GeSe2 in order to recognize the above in terpretation.
O
However, in the present i n v e s t i -
gation i t was impossible to detect the clear I-I-,-I ~o Z uJ
s h i f t of the A1 peak position in amorphous GeSe2 since the peak position of the 3D GeSe2 form appeared on heating is extremely close to that of
Z
the amorphous phase at room temperature.
100
200 300 RAIMAN SHI FT/cm-1
400 J,
Then,
we next t r i e d to in v es t ig a t e the Raman spectra of heated amorphous Geo.35Seo.65 ans Geo.37.
FIGURE 1 Raman spectra of Ge0 4Se0 6 glass heated at ( I ) room temperature, (21 200~ (3) 300, (4) 350 and 380°C, re s p e c t i v e l y .
Se0.63, data of which are described in Fig. 2.
modes o f GeSe4 tetrahedra in amorphous GeSe2.
temperature and the A1 peak of 3D c r y s t a l l i n e
Spectra observed in both a l l o y s also e x h i b i t that the peak at 203 cm-I at room temperature shifted toward low frequencies with increasing
The peak position of (B) has a tendency to
-I
phase appears at 199 cm
.
in the range between
s h i f t toward lower energies and to become rather
300 and 380°C.
steeper with increasing temperature ( i . e . , 203 cm-I at room temperature and 199 cm-I at 380°C,
tends to change gradually with increasing tem-
respectively).
The shape of (A), (D) peaks and shoulder (C)
The peak position of the A1 mode
of the GeSe4 unit can be considered to be strongly affected by the d i s t o r t i o n of the unit and by the surrounding atomic c o n f i g u r a t i o n .
T
'(b)
Ca) cTJL
/
._
For example, a sharp A1 l i n e is observed at 210 -I cm in c r y s t a l l i n e GeSe2 consisting of two d i mentional layers in which GeSe4 tetrahedra share each other Se atoms at corners or edges (2D form).7
O
In a d d i t i o n , the low temperature phase
of c r y s t a l l i n e GeSe2 has r e c e n t l y been confirmed by the Raman scattering study, which has the corresponding A1 l i n e around 200 cm-l. 8
The
£b3 Z UJ ~.. Z
structure o f t h i s phase can be assumed to take a three dimensional network with corner-sharing GeSe4 tetrahedra(3D form) from the correspondence of the crystal structure between GeSe2 and GeS2.
120
I 200 240 200 240 RAMAN SHIFT/cm -1
The s h i f t of the peak (B) toward 199 cm"I
seen in the temperature range with 300-,380°C may be interpreted to be due to the appearance of the local order o f 3D form, because t h i s phase has been reported to be p r e f e r e n t i a l l y formed by
FIGURE 2 Raman spectra of Ge0 ~Se 0 65(a) and Geo.37" Se0 G3(b) glasses heated at ( I ) room temperaturG, (2) 200, (3) 390, (4) 350, (5) 380, (6) 410 and (7) 440°C, r e s p e c t i v e l y
O. Uemura et al./Crystallization of amorphous Geo4Seo 6
221
perature but we have no information about t h i s change at present. -I On exceeding 410°C the growth of the 210 cm l i n e of the 2D c r y s t a l l i n e form r a p i d l y promotes e i t h e r by r a i s i n g temperature or by the lapse of
T'
t '
time as shown in Fig. 3, although the spectrum at 300°C in Fig. 1 already gives the i n d i c a t i o n of t h i s l i n e ( n o t e ; an arrow).
On the other
hand, both (A) and (D) v i b r a t i o n a l modes in a-
_
(3)c
morphous Geo.4Seo. 6 fade out under the complete c r y s t a l l i z a t i o n , suggesting that there are no chemical orders or no tetrahedron units including Ge-Ge bonds in c r y s t a l l i n e state.
(N.B.,
Main Raman peaks in c r y s t a l l i n e GeSe can be seen at 148, 187 and 211 cm- I , r e s p e c t i v e l y .
The v i -
brational modes in GeSe structure are less
l
100
Raman-active compared with those in c r y s t a l l i n e GeSe2 and, in a d d i t i o n , some of the modes in both crystals f a l l on s i m i l a r frequencies in the spectrum.
Therefore, i t could not be judged
within the present experimental accuracy whether
210 II
I
200 300 RANAN SHIFT/cm-1
&O0
FIGURE 3 Raman spectra of Ge0 4Se0 6 glass heated at ( I ) 410, (2) 420, (3) 436 and'(4) 440°C, respectivel y . Retention times are shown, (3)A-0.5, (3)B1.0, (3)C-I.5 and (3)D-2.0 hr, r e s p e c t i v e l y
the modes in GeSe phase are present or not in the spectrum at 440°C of f u l l y c r y s t a l l i z e d sample.)
After a l l ,
i t can be summarized by the
present Raman scattering measurement of heated amorphous Geo.4Seo. 6 that ( I ) the A1 mode of the GeSe4 tetrahedral unit in the low temperature phase of c r y s t a l l i n e GeSe2 can be observed at r e l a t i v e l y lower temperatures below 400°C and (2) the chemical order containing Ge-Ge bonds evidenced by 175 cm-I and 280 cm-I modes which is c h a r a c t e r i s t i c o f Ge rich a l l o y s exists only in the amorphous state. The Raman scattering measurement can give more d e t a i l e d information about the change in a-
REFERENCES I . O. Uemura, Y. Sagara and T. Satow, phys. star. s o l . ( a ) 26 (1974) 99. 2. R.W. Fawcett, C.N.J. Wagner and G.S. Cargill I I I , J. Non-Cryst. Solids 8 (1972) 369. 3. P.H. Fuoss, W.K. Warburton and A. Bienenstock, J. Non-Cryst. Solids 35&36 (1980) 33. 4. G. Lucovsky, R.J. Nemanich and P.L. Galeener, In Proc. 7th I n t . Conf. Amorphous and Liquid Semiconductors ed. by W.E. Spear (University of Edinburgh, 1977) p.130. 5. A. Feltz, B. Voigt and E. Schlenzig, In Proc. 5th I n t . Conf. Amorphous and Liquid Semiconductors ed. by J. Stuke, W. Brenig (Taylor and Francis, London, 1974) p.261.
tomic c o n f i g u ra t i o n brought about on the cryst a l l i z a t i o n of amorphous materials as compared
6. G. Lucovsky and R.M. Martin, J. Non-Cryst. Solids 8-10 (1972) 185.
with other structural studies such as the d i f f r a c t i o n measurement, but we should keep in mind
7. V.G. Dittmer and H. Schaefer, Acta C r y s t a l l o g. B32 (1976) 2726.
that the l i g h t - i r r a d i a t e d c r y s t a l l i z a t i o n simultaneously goes on at a given temperature during the measurement.
8. K. Inoue, K. Kawamoto and K. Murase, J. NonCryst. Solids 95&96 (1987) 517.