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Anomalous transmission of X-rays in tin single crystals
Volume 27A, number 4
P H Y SIC S L E T T E R S
Table 1 Absorption features in the spectrum of Na-C6H 6 at 70OK. X(~x)*
E(cm -1)
Intensity
5607
17835
2
5585
17905
4
5271
18970
1
5251
19045
2
5179
19310
1
19385
2
5159 o
* all wavelengths ±2A. d u r i n g deposition which i s l a t e r c o n v e r t e d when the t e m p e r a t u r e d e c r e a s e s .
1 July 1968
References 1. C.K.Jen, V.A.Bowers, E.L.Cochran and S.N. Foner, Phys. Rev. 126 (1962) 1749. 2. J. P. Goldsborough and T oR. Koehler, Phys. Rev. 133 (1964) A135. 3. M. MeCarty and G. W. Robinson, Mol. Phys. 2 (1959) 415. 4. W. Weyhmann and F. M. Pipkin, Phys. Rev. 137 (1965) A490. 5. B.Meyer, J. Chem. Phys. 43 (1965) 2986. 6. L.Andrews and G. C. Pimentel, J. Chem. Phys. 47 (1967) 29O5. 7. S.L. Kupfermann and F. M. Pipkin, Phys. Rev. 166 (1968) 207. 8. G.E.Bacon, N.A.Curry and S.A.Wilson, Proc. Roy. Soc. (London) A279 (1964) 98. 9. G.R.Hgbert, private communication. 10. J.L.Hollenberg and D.A.Dows, J. Chem. Phys. 37 (1962) 1300. 11. R.A. Zhitnikov and N. V. Kolesnikov, Soviet Phys. (Solid State) 7 (1965) 927.
T h i s r e s e a r c h was s u p p o r t e d by a g r a n t f r o m the National R e s e a r c h Council.
ANOMALOUS
TRANSMISSION
OF
X-RAYS
IN TIN
SINGLE
CRYSTALS
V. K. VOITOVETSKII, I. L. KORSUNSKII, A . I . NOVIKOV and Yu. F. PAZHIN I. V.Kurchatov Institute of Atomic Energy, Moscow, USSR Received 17 May 1968
An anomalous transmission of X-rays in tin single crystals is found and investigated experimentally.
When X - r a y s p a s s through p e r f e c t o r n e a r l y p e r f e c t c r y s t a l s , s e t of at a B r a g g a n g le to c r y s t a l l o g r a p h i c p l a n e s , the a b s o r p t i o n c o e f f i c i e n t for the t r a n s m i t t e d r a d i a t i o n b e c o m e s a b n o r m a l l y low. It i s a s s u m e d [e.g. 1] that a n o m a l o u s t r a n s m i s s i o n is not e x p e c t e d to take p l a c e in m e t a l c r y s t a l s , b e c a u s e such c r y s t a l s have a g r e a t n u m b e r of d i s l o c a t i o n s and o t h e r d e f e c t s , A n o m a l o u s t r a n s m i s s i o n o b s e r v e d in t h e X r a y d i f f r a c t i o n on the (0002) plane in thick zinc c r y s t a l s was c o n s i d e r e d to be an exception and was a s s u m e d to be c a u s e d by the p e c u l i a r i t i e s of the c h a r a c t e r and a r r a n g e m e n t of d i s l o c a t i o n s , which in this c a s e s did not i n f l u e n c e d i f f r a c t i o n p h e n o m e n a [1] *. H o w e v e r , it was found e x p e r i m e n t a l l y that the r e l a t i o n between the d i s l o c a t i o n n u m b e r and the a n o m a l o u s a b s o r p t i o n c o e f f i c i e n t is non s i n g l e
v a l u e d and depends on the m a t e r i a l of the c r y s t a l
[3].
We o b s e r v e d a n o m a l o u s t r a n s m i s s i o n of X r a y s in s i n g l e c r y s t a l s KCI having 6 × 103 - 104 d i s l o c a t i o n s p e r c m 2. At a d i s l o c a t i o n density of 1 0 5 / c m 2 the B o r r m a n n effect in KC1 c r y s t a l s d i s a p p e a r s [4], while the c r i t i c a l d i s l o c a t i o n d e n sity of Ge c r y s t a l is 1.7 × 1 0 0 / c m 2 [5,6]. It s e e m s that it is c o n n e c t e d with the type of c o u p l ing in the l a t t i c e and that f o r c r y s t a l s , whose e l e c t r i c a l and optical p r o p e r t i e s a r e a f f e c t e d l e s s by s t r u c t u r e d e f e c t s , the r e q u i r e m e n t s to the d e g r e e of p e r f e c t i o n f o r the p o s s i b i l i t y of obs e r v a t i o n of a n o m a l o u s t r a n s m i s s i o n will be l e s s * The Borrmann effect was also observed in the X-ray diffraction on the (111) plane in very perfect copper crygstals, which had less than 103 dislocations per c m - [2]. 207
Volume27A, number 4
PHYSICS LETTERS
s e v e r e . In ref. 3 a n o t a b l e d i f f e r e n c e i n the d e pendence of a n o m a l o u s t r a n s m i s s i o n coefficients on dislocation d e n s i t y i s found even for c r y s t a l s of the s a m e t y p e - G e and GaAs. In m e t a l s the e l e c t r o n gas s c r e e n s g r e a t l y p r e s e n t i m p e r f e c t i o n s and so it could be s u g g e s ted that the B o r r m a n n effect can be o b s e r v e d in m e t a l c r y s t a l s with r e l a t i v e l y l a r g e n u m b e r of defects c o m p a r e d to the c r y s t a l s of other types. We have e x p e r i m e n t a l l y found a n o m a l o u s t r a n s m i s s i o n in one of the most "delicate" c r y s t a l s - i n tin single c r y s t a l s d u r i n g the diffraction on the p l a n e s (020) and (220). In spite of the cons i d e r a b l e d i v e r g e n c e of the b e a m (~ 40") the effect is displayed v e r y s h a r p l y . The t r a n s m i s s i o n of c h a r a c t e r i s t i c X - r a y r a d i a t i o n of m o l y b d e n i u m was i n v e s t i g a t e d ; the q u a r t z m o n o c h r o m a t o r d i s plays the line K~3 (19.6 keV). The L a u e - s c a t t e r e d b e a m and that t r a n s m i t t e d through the tin single c r y s t a l w e r e detected by a s c i n t i l l a t i o n counter with a r e c o r d i n g device. The tin s i n g l e c r y s t a l s w e r e p r e p a r e d by the method of growing o r i e n t e d single c r y s t a l s in optically polished moulds [7]. Fig. 1 shows r e l a t i v e i n t e n s i t i e s of s c a t t e r e d and t r a n s m i t t e d r a d i a t i o n at Laue diffraction on (020) p l a n e s in tin s i n g l e c r y s t a l with 0.6 m m t h i c k n e s s . The B o r r m a n n effect at Laue d i f f r a c tion on (220) planes was also detected. T i n single c r y s t a l s studied a r e inhomogeneous in the d e g r e e of p e r f e c t i o n and the i n t e n s i t y and half-width of diffraction peaks is changed s i g n i f i cantly depending on region of c r y s t a l , w h e r e the b e a m falls. X - r a y topographs a c c o r d i n g to the B o r r m a n n and to the Lang show that s o m e c r y s t a l s have cell s t r u c t u r e , and a r o u n d some of the c e l l s t h e r e is a dense n e t of d i s l o c a t i o n s . In other c r y s t a l s l a r g e t r a n s p a r e n t r e g i o n s a r e seen. In t h e s e s c r y s t a l s the dislocation density is > 1 0 6 / c m 2. At the s a m e c r y s t a l t h i c k n e s s the i n c r e a s i n g of the a m o u n t of defects t e l l s differently on the a n o m a l o u s t r a n s m i s s i o n in tin and KCI s i n g l e c r y s t a l s studied. In the case of tin at the i n c r e a s i n g of the amount of defects showing the b r o a d e n i n g of the diffraction peak the shape of the r e l a t i v e i n t e n s i t y c u r v e of the t r a n s m i t t e d b e a m does not change; it i s only the a b s o l u t e i n t e n s i t y of the a n o m a l o u s ly t r a n s m i t t e d r a d i a t i o n that changes.
208
1 July 1968
40"-" -
~a/UV
h.lO'J -
8.#0"$-
0 Fig. 1. Laue diffraction of the X-ray radiation of Mokfl in tin. The crystal thickness is 0.6 ram, reflection planes are (020). The solid line shows the transmitted part of the radiation; the dashed line shows the reflected part of the radiation.
The increase of the dislocation density in KCI crystals (the diffraction peak broadening as well) results in a substantial changing of the relative intensity curve of the transmRted beam; in spite of the constant crystal thickness the peak of the anomalous transmission is replaced even by an extinction dip; the "effective" value of ~t decreasing. This effect seems to be due to the difference in the types of structure distortions or due to the different type of coupling in the lattice.
References 1. A.Merlini and S. Pace, Nuovo Cimento 35 (1965) 377. 2. M.C. Wittels, F.A. 8herill and F. W. Young Jr., Appl. Phys. Letters 2 (1963) 127. 3. S.Maruyama, J. Phys. Soc. Japan 21 (1966) 2092. 4. E.F. Tchaikovskii and L. B. Sagarii, Fiz. Tverd. Tel., to be published. 5. O.N. Ephimov, Thesis, Leningrad (1964). 6. S. Maruyama, J. Phys. Soc. Japan 20 (1965) 1399.
7. Y.W. Sharwin and W. Ph. Gantmacher, Prib. i Teehn. Exp. 6 (1963) 165.
P H Y SIC S L E T T E R S
Table 1 Absorption features in the spectrum of Na-C6H 6 at 70OK. X(~x)*
E(cm -1)
Intensity
5607
17835
2
5585
17905
4
5271
18970
1
5251
19045
2
5179
19310
1
19385
2
5159 o
* all wavelengths ±2A. d u r i n g deposition which i s l a t e r c o n v e r t e d when the t e m p e r a t u r e d e c r e a s e s .
1 July 1968
References 1. C.K.Jen, V.A.Bowers, E.L.Cochran and S.N. Foner, Phys. Rev. 126 (1962) 1749. 2. J. P. Goldsborough and T oR. Koehler, Phys. Rev. 133 (1964) A135. 3. M. MeCarty and G. W. Robinson, Mol. Phys. 2 (1959) 415. 4. W. Weyhmann and F. M. Pipkin, Phys. Rev. 137 (1965) A490. 5. B.Meyer, J. Chem. Phys. 43 (1965) 2986. 6. L.Andrews and G. C. Pimentel, J. Chem. Phys. 47 (1967) 29O5. 7. S.L. Kupfermann and F. M. Pipkin, Phys. Rev. 166 (1968) 207. 8. G.E.Bacon, N.A.Curry and S.A.Wilson, Proc. Roy. Soc. (London) A279 (1964) 98. 9. G.R.Hgbert, private communication. 10. J.L.Hollenberg and D.A.Dows, J. Chem. Phys. 37 (1962) 1300. 11. R.A. Zhitnikov and N. V. Kolesnikov, Soviet Phys. (Solid State) 7 (1965) 927.
T h i s r e s e a r c h was s u p p o r t e d by a g r a n t f r o m the National R e s e a r c h Council.
ANOMALOUS
TRANSMISSION
OF
X-RAYS
IN TIN
SINGLE
CRYSTALS
V. K. VOITOVETSKII, I. L. KORSUNSKII, A . I . NOVIKOV and Yu. F. PAZHIN I. V.Kurchatov Institute of Atomic Energy, Moscow, USSR Received 17 May 1968
An anomalous transmission of X-rays in tin single crystals is found and investigated experimentally.
When X - r a y s p a s s through p e r f e c t o r n e a r l y p e r f e c t c r y s t a l s , s e t of at a B r a g g a n g le to c r y s t a l l o g r a p h i c p l a n e s , the a b s o r p t i o n c o e f f i c i e n t for the t r a n s m i t t e d r a d i a t i o n b e c o m e s a b n o r m a l l y low. It i s a s s u m e d [e.g. 1] that a n o m a l o u s t r a n s m i s s i o n is not e x p e c t e d to take p l a c e in m e t a l c r y s t a l s , b e c a u s e such c r y s t a l s have a g r e a t n u m b e r of d i s l o c a t i o n s and o t h e r d e f e c t s , A n o m a l o u s t r a n s m i s s i o n o b s e r v e d in t h e X r a y d i f f r a c t i o n on the (0002) plane in thick zinc c r y s t a l s was c o n s i d e r e d to be an exception and was a s s u m e d to be c a u s e d by the p e c u l i a r i t i e s of the c h a r a c t e r and a r r a n g e m e n t of d i s l o c a t i o n s , which in this c a s e s did not i n f l u e n c e d i f f r a c t i o n p h e n o m e n a [1] *. H o w e v e r , it was found e x p e r i m e n t a l l y that the r e l a t i o n between the d i s l o c a t i o n n u m b e r and the a n o m a l o u s a b s o r p t i o n c o e f f i c i e n t is non s i n g l e
v a l u e d and depends on the m a t e r i a l of the c r y s t a l
[3].
We o b s e r v e d a n o m a l o u s t r a n s m i s s i o n of X r a y s in s i n g l e c r y s t a l s KCI having 6 × 103 - 104 d i s l o c a t i o n s p e r c m 2. At a d i s l o c a t i o n density of 1 0 5 / c m 2 the B o r r m a n n effect in KC1 c r y s t a l s d i s a p p e a r s [4], while the c r i t i c a l d i s l o c a t i o n d e n sity of Ge c r y s t a l is 1.7 × 1 0 0 / c m 2 [5,6]. It s e e m s that it is c o n n e c t e d with the type of c o u p l ing in the l a t t i c e and that f o r c r y s t a l s , whose e l e c t r i c a l and optical p r o p e r t i e s a r e a f f e c t e d l e s s by s t r u c t u r e d e f e c t s , the r e q u i r e m e n t s to the d e g r e e of p e r f e c t i o n f o r the p o s s i b i l i t y of obs e r v a t i o n of a n o m a l o u s t r a n s m i s s i o n will be l e s s * The Borrmann effect was also observed in the X-ray diffraction on the (111) plane in very perfect copper crygstals, which had less than 103 dislocations per c m - [2]. 207
Volume27A, number 4
PHYSICS LETTERS
s e v e r e . In ref. 3 a n o t a b l e d i f f e r e n c e i n the d e pendence of a n o m a l o u s t r a n s m i s s i o n coefficients on dislocation d e n s i t y i s found even for c r y s t a l s of the s a m e t y p e - G e and GaAs. In m e t a l s the e l e c t r o n gas s c r e e n s g r e a t l y p r e s e n t i m p e r f e c t i o n s and so it could be s u g g e s ted that the B o r r m a n n effect can be o b s e r v e d in m e t a l c r y s t a l s with r e l a t i v e l y l a r g e n u m b e r of defects c o m p a r e d to the c r y s t a l s of other types. We have e x p e r i m e n t a l l y found a n o m a l o u s t r a n s m i s s i o n in one of the most "delicate" c r y s t a l s - i n tin single c r y s t a l s d u r i n g the diffraction on the p l a n e s (020) and (220). In spite of the cons i d e r a b l e d i v e r g e n c e of the b e a m (~ 40") the effect is displayed v e r y s h a r p l y . The t r a n s m i s s i o n of c h a r a c t e r i s t i c X - r a y r a d i a t i o n of m o l y b d e n i u m was i n v e s t i g a t e d ; the q u a r t z m o n o c h r o m a t o r d i s plays the line K~3 (19.6 keV). The L a u e - s c a t t e r e d b e a m and that t r a n s m i t t e d through the tin single c r y s t a l w e r e detected by a s c i n t i l l a t i o n counter with a r e c o r d i n g device. The tin s i n g l e c r y s t a l s w e r e p r e p a r e d by the method of growing o r i e n t e d single c r y s t a l s in optically polished moulds [7]. Fig. 1 shows r e l a t i v e i n t e n s i t i e s of s c a t t e r e d and t r a n s m i t t e d r a d i a t i o n at Laue diffraction on (020) p l a n e s in tin s i n g l e c r y s t a l with 0.6 m m t h i c k n e s s . The B o r r m a n n effect at Laue d i f f r a c tion on (220) planes was also detected. T i n single c r y s t a l s studied a r e inhomogeneous in the d e g r e e of p e r f e c t i o n and the i n t e n s i t y and half-width of diffraction peaks is changed s i g n i f i cantly depending on region of c r y s t a l , w h e r e the b e a m falls. X - r a y topographs a c c o r d i n g to the B o r r m a n n and to the Lang show that s o m e c r y s t a l s have cell s t r u c t u r e , and a r o u n d some of the c e l l s t h e r e is a dense n e t of d i s l o c a t i o n s . In other c r y s t a l s l a r g e t r a n s p a r e n t r e g i o n s a r e seen. In t h e s e s c r y s t a l s the dislocation density is > 1 0 6 / c m 2. At the s a m e c r y s t a l t h i c k n e s s the i n c r e a s i n g of the a m o u n t of defects t e l l s differently on the a n o m a l o u s t r a n s m i s s i o n in tin and KCI s i n g l e c r y s t a l s studied. In the case of tin at the i n c r e a s i n g of the amount of defects showing the b r o a d e n i n g of the diffraction peak the shape of the r e l a t i v e i n t e n s i t y c u r v e of the t r a n s m i t t e d b e a m does not change; it i s only the a b s o l u t e i n t e n s i t y of the a n o m a l o u s ly t r a n s m i t t e d r a d i a t i o n that changes.
208
1 July 1968
40"-" -
~a/UV
h.lO'J -
8.#0"$-
0 Fig. 1. Laue diffraction of the X-ray radiation of Mokfl in tin. The crystal thickness is 0.6 ram, reflection planes are (020). The solid line shows the transmitted part of the radiation; the dashed line shows the reflected part of the radiation.
The increase of the dislocation density in KCI crystals (the diffraction peak broadening as well) results in a substantial changing of the relative intensity curve of the transmRted beam; in spite of the constant crystal thickness the peak of the anomalous transmission is replaced even by an extinction dip; the "effective" value of ~t decreasing. This effect seems to be due to the difference in the types of structure distortions or due to the different type of coupling in the lattice.
References 1. A.Merlini and S. Pace, Nuovo Cimento 35 (1965) 377. 2. M.C. Wittels, F.A. 8herill and F. W. Young Jr., Appl. Phys. Letters 2 (1963) 127. 3. S.Maruyama, J. Phys. Soc. Japan 21 (1966) 2092. 4. E.F. Tchaikovskii and L. B. Sagarii, Fiz. Tverd. Tel., to be published. 5. O.N. Ephimov, Thesis, Leningrad (1964). 6. S. Maruyama, J. Phys. Soc. Japan 20 (1965) 1399.
7. Y.W. Sharwin and W. Ph. Gantmacher, Prib. i Teehn. Exp. 6 (1963) 165.