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Kyropoulos-growth of low-dislocation-density KC1-crystals
Volume 20, number 3
PHYSICS LETTERS
/~/
si n ce p l a s m o n e x c i t a t i o n does not c o n t r i b u t e to ~h. About 50% of ~h can be a t t r i b u t e d to t h e r m a l diffuse s c a t t e r i n g and the r e m a i n i n g p a r t a p p e a r s to be due to e l e c t r o n i c e x c i t a t i o n s l o c a l i z e d n e a r the a t o m i c s i t e s . 4) An i n c r e a s e of ~o and ~h b e t w e e n 520 and 680°K has been o b s e r v e d which is c l e a r l y out of e x p e r i m e n t a l e r r o r s . T h i s m e a n s that t h e r m a l diffuse s c a t t e r i n g c o n t r i b u t e s to n o r m a l as well as to a n o m a l o u s ab so r p t i o n . A ~ o and A ~ h a r e of the s a m e o r d e r as the c o r r e s p o n d i n g t h e o r e t i c a l values.
V
~
15February 1966
w
T h i s w o r k was s u p p o r t e d by a p e r s o n a l g r a n t of the D e u t s c h e F o r s c h u n g s g e m e i n s c h a f t .
Fig. 1. I000 and I2~0 measured with 69 keV electrons using a Si single crystal (D = 2100 .~) at 680°K ( ) and a theoretical curve (~h D = 0.85) neglecting the oscillating part (. . . . . -).
References
1) The e x p e r i m e n t a l v a l u e s Vh c o r r e c t e d by the r e l a t i v i s t i c f a c t o r [11] a r e in a g r e e m e n t with the t h e o r e t i c a l v a l u e s V~e -M [12]. T h i s m e a n s that the e l a s t i c s c a t t e r i n g i s d e t e r m i n e d by the t h e r m a l l y r e d u c e d F o u r i e r c o e f f i c i e n t s of the c r y s t a l p o t e n t i a l [13]. 2) A l a r g e p a r t (60%) of the m e a n a b s o r p t i o n (~o) c a n be a s c r i b e d to p l a s m o n e x c i t a t i o n s , w h e r e a s only 12% is due to t h e r m a l diffuse s c a t t e r i n g . The r e m a i n i n g p a r t p r o b a b l y c o m e s f r o m o t h e r e l e c t r o n i c e x c i t a t i o n s a s e.g. band-band transitions. 3) ~h is c o n s i d e r a b l y s m a l l e r than ~o which m e a n s that only a s m a l l f r a c t i o n of the t o t a l a b s o r p t i o n p r o c e s s e s i s r e s t r i c t e d to the r e g i o n s n e a r the a t o m i c s i t e s . T h i s r e s u l t i s u n d e r s t o o d
1. H. Hashimoto, J. App. Phys. 35 (1964) 277. 2. e . g . H . Watanabe et al., J. Phys. Soc. Japan 17, Suppl. BH (1962) 195. 3. P. Goodman and G. Lehmpfuhl, Z. Naturforsch. 20a (1965) 110. 4. C. R. Hall and P. B. Hirsch, Proc. Roy. Soc. A 286 (1965) 158. 5. M.Horstmann, Z. Physik 188 (1965) 124. J. Hansen-Schmidt and M. Horstmann, Z. Naturforsch. 20a((1965) 1239; H.Watanabe, Japan. J.Appl. Phys.4 (1965) 384. 6. K.Brack, Z.Naturforsch. 17a (1962) 1066. 7. I. Grambow, Z. Physik 187 (1965) 197. 8. H. Hashimoto et al., Proc. Roy. Soc. A 269 (1962) 80. 9. R. A. F e r r e l l , Phys. Rev. 101 (1956) 554. 10. H. Raether, Springer Tracts in Mod. Phys. 38 (1965) 84. 11. K.Fujiwara, J.Phys.Soc.Japan 16 (1961) 2226. 12. Int. Tab. f. X-ray Crystallogr. HI (1962). 13. M.Horstmann, Z.Physik 183 (1965) 375.
KYROPOULOS-GROWTH
OF
LOW-DISLOCATION-DENSITY
KCI-CRYSTALS
E. SCHONHERR
Physikalisches Institut der Universit~it Frankfurt~Main Received 26 November 1965
A method of growing KCl-crystals of low dislocation density in [111]-direction is described. The crystals are examined for dislocation density using etch-pit techniques on (lll)-faces. The density is less than 3 x 103 cm -2.
The c r y s t a l s a r e g r o w n by t h e K y r o p o u l o s t e c hni q u e d e s c r i b e d in ref. 1. The a m b i e n t atmo-
s p h e r e u s e d during growth i s n i t r o g e n at a p r e s s u r e of about I00 T o r r . 241
Volume 20, number 3
-J- . . . .
PHYSICS LETTERS
15 February 1966
A
(I00)-~ (001) Fig. 1. Schematic diagramm of the seed with the crystal. The c r y s t a l s a r e pulled in [ l l l ] - d i r e c t i o n . T h e r e f o r e the d i s l o c a t i o n s can be d e t e c t e d conv e n i e n t l y by etch p i t s f o r m e d on ( l l l ) - p l a n e s . The m e t h o d is d e s c r i b e d in ref. 2. At f i r s t a c r y s t a l of about 50 m m in d i a m e t e r and 80 m m in length is pulled in a i r in J i l l ] d i r e c t i o n in the usual way. T h i s c r y s t a l is p o l i s h e d into a s e e d of about 4 × 8 × 80 mm3 and thinned to 1 m m 2 at the l o w e r end. T h i s c r y s t a l is mounted i m m e d i a t e l y above the s u r f a c e of the KC1 salt during the slow h e a t ing of both salt and s e e d c r y s t a l . As soon as the salt m e l t s the s e e d is l o w e r e d into the m e l t at a r a t e of about 10 m m / h . The t e m p e r a t u r e has to be c o n t r o l l e d to b e t t e r than one d e g r e e , and the c r y s t a l h as to be withdrawn at a r a t e l o w e r than 4 m m / h . A f t e r w a r d s the c r y s t a l is slowly cooled down at a r a t e of 10°/h. Fig. 1 shows s c h e m a t i c a l l y the s e e d with the c r y s t a l . F i g s . 2 A - C a r e p h o t o g r a p h s of e t c h e d p l a n e s n o r m a l to the growth a x i s at c r o s s s e c t i ons A - C in fig. 1 r e s p e c t i v e l y . A shows no g r a i n b o u n d a r i e s and the d i s l o c a t i o n d e n s i t y is l e s s than 3 x 103 c m - 2 . In plane B t h e r e a r e s u b g r a l n s of low e t c h - p i t density. In the l o w e r plane C of the c r y s t a l the d i s l o c a t i o n s a r e p r e s e n t m a i n l y along slip p l a n e s . They w e r e obviously p r o d u c e d by the t h e r m a l shock when the c r y s t a l was pulled out of the m e l t. D e t a i l e d r e s u l t s and d i s c u s s i o n s will be r e p o r t e d soon. The author is g r a t e f u l f o r helpful d i s c u s s i o n s with Dr. H. J. Q u e i s s e r , P r o f . Dr. W. M a r t i e n s s e n and P r o f . Dr. H. A. Miiser.
References 1. H. Grt~ndig, Z. Physik 176 (1963) 451. 2. H . J . Q u e i s s e r and E. SchSnherr, Z. Ang. Phys. 18 (1964) 123. 242
Fig. 2. (111)-planes A-C normal to the growth direction at A-C of fig. 1 respectively. Etched with one part CH3COOH and one part CH3OH.
PHYSICS LETTERS
/~/
si n ce p l a s m o n e x c i t a t i o n does not c o n t r i b u t e to ~h. About 50% of ~h can be a t t r i b u t e d to t h e r m a l diffuse s c a t t e r i n g and the r e m a i n i n g p a r t a p p e a r s to be due to e l e c t r o n i c e x c i t a t i o n s l o c a l i z e d n e a r the a t o m i c s i t e s . 4) An i n c r e a s e of ~o and ~h b e t w e e n 520 and 680°K has been o b s e r v e d which is c l e a r l y out of e x p e r i m e n t a l e r r o r s . T h i s m e a n s that t h e r m a l diffuse s c a t t e r i n g c o n t r i b u t e s to n o r m a l as well as to a n o m a l o u s ab so r p t i o n . A ~ o and A ~ h a r e of the s a m e o r d e r as the c o r r e s p o n d i n g t h e o r e t i c a l values.
V
~
15February 1966
w
T h i s w o r k was s u p p o r t e d by a p e r s o n a l g r a n t of the D e u t s c h e F o r s c h u n g s g e m e i n s c h a f t .
Fig. 1. I000 and I2~0 measured with 69 keV electrons using a Si single crystal (D = 2100 .~) at 680°K ( ) and a theoretical curve (~h D = 0.85) neglecting the oscillating part (. . . . . -).
References
1) The e x p e r i m e n t a l v a l u e s Vh c o r r e c t e d by the r e l a t i v i s t i c f a c t o r [11] a r e in a g r e e m e n t with the t h e o r e t i c a l v a l u e s V~e -M [12]. T h i s m e a n s that the e l a s t i c s c a t t e r i n g i s d e t e r m i n e d by the t h e r m a l l y r e d u c e d F o u r i e r c o e f f i c i e n t s of the c r y s t a l p o t e n t i a l [13]. 2) A l a r g e p a r t (60%) of the m e a n a b s o r p t i o n (~o) c a n be a s c r i b e d to p l a s m o n e x c i t a t i o n s , w h e r e a s only 12% is due to t h e r m a l diffuse s c a t t e r i n g . The r e m a i n i n g p a r t p r o b a b l y c o m e s f r o m o t h e r e l e c t r o n i c e x c i t a t i o n s a s e.g. band-band transitions. 3) ~h is c o n s i d e r a b l y s m a l l e r than ~o which m e a n s that only a s m a l l f r a c t i o n of the t o t a l a b s o r p t i o n p r o c e s s e s i s r e s t r i c t e d to the r e g i o n s n e a r the a t o m i c s i t e s . T h i s r e s u l t i s u n d e r s t o o d
1. H. Hashimoto, J. App. Phys. 35 (1964) 277. 2. e . g . H . Watanabe et al., J. Phys. Soc. Japan 17, Suppl. BH (1962) 195. 3. P. Goodman and G. Lehmpfuhl, Z. Naturforsch. 20a (1965) 110. 4. C. R. Hall and P. B. Hirsch, Proc. Roy. Soc. A 286 (1965) 158. 5. M.Horstmann, Z. Physik 188 (1965) 124. J. Hansen-Schmidt and M. Horstmann, Z. Naturforsch. 20a((1965) 1239; H.Watanabe, Japan. J.Appl. Phys.4 (1965) 384. 6. K.Brack, Z.Naturforsch. 17a (1962) 1066. 7. I. Grambow, Z. Physik 187 (1965) 197. 8. H. Hashimoto et al., Proc. Roy. Soc. A 269 (1962) 80. 9. R. A. F e r r e l l , Phys. Rev. 101 (1956) 554. 10. H. Raether, Springer Tracts in Mod. Phys. 38 (1965) 84. 11. K.Fujiwara, J.Phys.Soc.Japan 16 (1961) 2226. 12. Int. Tab. f. X-ray Crystallogr. HI (1962). 13. M.Horstmann, Z.Physik 183 (1965) 375.
KYROPOULOS-GROWTH
OF
LOW-DISLOCATION-DENSITY
KCI-CRYSTALS
E. SCHONHERR
Physikalisches Institut der Universit~it Frankfurt~Main Received 26 November 1965
A method of growing KCl-crystals of low dislocation density in [111]-direction is described. The crystals are examined for dislocation density using etch-pit techniques on (lll)-faces. The density is less than 3 x 103 cm -2.
The c r y s t a l s a r e g r o w n by t h e K y r o p o u l o s t e c hni q u e d e s c r i b e d in ref. 1. The a m b i e n t atmo-
s p h e r e u s e d during growth i s n i t r o g e n at a p r e s s u r e of about I00 T o r r . 241
Volume 20, number 3
-J- . . . .
PHYSICS LETTERS
15 February 1966
A
(I00)-~ (001) Fig. 1. Schematic diagramm of the seed with the crystal. The c r y s t a l s a r e pulled in [ l l l ] - d i r e c t i o n . T h e r e f o r e the d i s l o c a t i o n s can be d e t e c t e d conv e n i e n t l y by etch p i t s f o r m e d on ( l l l ) - p l a n e s . The m e t h o d is d e s c r i b e d in ref. 2. At f i r s t a c r y s t a l of about 50 m m in d i a m e t e r and 80 m m in length is pulled in a i r in J i l l ] d i r e c t i o n in the usual way. T h i s c r y s t a l is p o l i s h e d into a s e e d of about 4 × 8 × 80 mm3 and thinned to 1 m m 2 at the l o w e r end. T h i s c r y s t a l is mounted i m m e d i a t e l y above the s u r f a c e of the KC1 salt during the slow h e a t ing of both salt and s e e d c r y s t a l . As soon as the salt m e l t s the s e e d is l o w e r e d into the m e l t at a r a t e of about 10 m m / h . The t e m p e r a t u r e has to be c o n t r o l l e d to b e t t e r than one d e g r e e , and the c r y s t a l h as to be withdrawn at a r a t e l o w e r than 4 m m / h . A f t e r w a r d s the c r y s t a l is slowly cooled down at a r a t e of 10°/h. Fig. 1 shows s c h e m a t i c a l l y the s e e d with the c r y s t a l . F i g s . 2 A - C a r e p h o t o g r a p h s of e t c h e d p l a n e s n o r m a l to the growth a x i s at c r o s s s e c t i ons A - C in fig. 1 r e s p e c t i v e l y . A shows no g r a i n b o u n d a r i e s and the d i s l o c a t i o n d e n s i t y is l e s s than 3 x 103 c m - 2 . In plane B t h e r e a r e s u b g r a l n s of low e t c h - p i t density. In the l o w e r plane C of the c r y s t a l the d i s l o c a t i o n s a r e p r e s e n t m a i n l y along slip p l a n e s . They w e r e obviously p r o d u c e d by the t h e r m a l shock when the c r y s t a l was pulled out of the m e l t. D e t a i l e d r e s u l t s and d i s c u s s i o n s will be r e p o r t e d soon. The author is g r a t e f u l f o r helpful d i s c u s s i o n s with Dr. H. J. Q u e i s s e r , P r o f . Dr. W. M a r t i e n s s e n and P r o f . Dr. H. A. Miiser.
References 1. H. Grt~ndig, Z. Physik 176 (1963) 451. 2. H . J . Q u e i s s e r and E. SchSnherr, Z. Ang. Phys. 18 (1964) 123. 242
Fig. 2. (111)-planes A-C normal to the growth direction at A-C of fig. 1 respectively. Etched with one part CH3COOH and one part CH3OH.