HAL Id: jpa-00221755
https://hal.archives-ouvertes.fr/jpa-00221755
Submitted on 1 Jan 1982
HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
GRAIN BOUNDARIES ANALYSIS IN POLYCRYSTALLINE SILICON BY TEM
F. Komninou, Th. Karakostas, G. Bleris, N. Economou
To cite this version:
F. Komninou, Th. Karakostas, G. Bleris, N. Economou. GRAIN BOUNDARIES ANALYSIS IN
POLYCRYSTALLINE SILICON BY TEM. Journal de Physique Colloques, 1982, 43 (C1), pp.C1-9-
C1-14. �10.1051/jphyscol:1982102�. �jpa-00221755�
JOURNAL DE PHYSIQUE
Colloque Cl, supplément au n° 10, Tome 43, octobre 1982 page Cl-9
GRAIN BOUNDARIES ANALYSIS IN POLYCRYSTALLINE SILICON BY TEM
F . Komninou, Th. K a r a k o s t a s , G.L. B l e r i s and N.A. Economou
Physios Department, Aristoteles University, Thessaloniki, Greece
Res.ume.- Des i n t e r f a c e s de Si p o l y c r i s t a l l i n ont ete examinées en u t i l i s a n t l e modèle CSL. La r e l a t i o n de r o t a t i o n de chaque b i c r i s t a l a ete analysée, par l a technique du système instrumental e t l a d e s c r i p t i o n du p e t i t angle a ete a p p l i - que^ pour l a c a r a c t e r i s a t i o n des CSL du S i . L e plus souvent, on observe des £=3 j o i n t s de macles cohérents ou i n c o h é r e n t s , les d e r n i e r s étants cohérents dans l e sens microscopique.Des cas des j o i n t s de grains m u l t i p l e s ont ete
7examinées également e t des r e l a t i o n s entre eux pour CSL avec \>Z ont ete é t a b l i e s . Un exemple i n t é r e s s a n t est l e 7=39 qui se forme par combinaison du Y=13b a^ec
£=3 e t c' e s t un CSL t r i c l i n i q u e sans o p é r a t i o n de r o t a t i o n de 180^. Les r é s u l - t a t s qu'on présente i c i j u s t i f i e n t 1 ' u t i l i s a t i o n du modèle CSL a l a descrip- t i o n des i n t e r f a c e s du Si p o l y c r i s t a l l i n .
A b s t r a c t . - P o l y c r y s t a l l i n e Si i n t e r f a c e s were examined w i t h i n the CSL's appro- ach . The r o t a t i o n r e l a t i o n s h i p o f every b i c r y s t a l has been analyzed w i t h the technique o f the instrumental system and the small angle d e s c r i p t i o n has been used f o r the CSL c h a r a c t e r i z a t i o n . T h e most f r e q u e n t l y occuring d e s c r i p t i o n s are CSL's 1=3 coherent and incoherent t w i n s , the l a t e r being m i c r o s c o p i c a l l y co- h e r e n t . Cases o f m u l t i p l e boundaries were also examined and i n t e r e l a t i o n s we- re found between low or high angle boundaries f o r CSL's w i t h £>3 . A special case o f i n t e r e s t i s a £=39 CSL which i s formed from a combination o f £=13b and 1=3 and i s a t r i c l i n i c CSL l a c k i n g 180° r o t a t i o n a l o p e r a t i o n s . The r e s u l t s presented i n d i c a t e t h a t f o r p o l y c r y s t a l l i n e Si the CSL model could be used i n d e s c r i b i n g the i n t e r f a c e s o c c u r i n g .
1 . I n t r o d u c t i o n . P o l y c r y s t a l l i n e Si i s o f p a r t i c u l a r i n t e r e s t due t o i t s vast techno- l o g i c a l a p p l i c a t i o n s mainly f o r s o l a r c e l l s . T h e macroscopic p r o p e r t i e s o f t h i s mate- r i a l are s t r o n g l y a f f e c t e d by the s t r u c t u r e and the o r i e n t a t i o n of i t s g r a i n bounda- r i e s (GB).So f a r , research on the m a t e r i a l i s concerned w i t h the study o f the funda- mental p r o p e r t i e s o f GB's [ 1 - 3 ] o r , the e l e c t r i c a l behaviour i n connection w i t h the GB's [ 4 - 6 ] . The purpose o f t h i s work i s to study and c h a r a c t e r i z e the GB's of p o l y - c r y s t a l l i n e Si i n the frame o f the coincidence s i t e l a t t i c e (CSL) approach which has been used s u c c e s s f u l l y i n semiconducting m a t e r i a l s [ 7 , 8 ] . T h e technique used i s throixh TEM, a p p l y i n g the method o f c h a r a c t e r i z a t i o n which has been r e p o r t e d p r e v i o u s l y [ 9 ] , We have concentrated our e f f o r t t o some special cases o f GB's i n order to understand the behaviour of the material.These r e s u l t s should be combined w i t h a nondestructive study i n order t o have a complete s t a t i s t i c a l a n a l y s i s . Thus we focused our a t t e n t i - on t o analyse coherent and incoherent 1=3 t w i n s , coherent and incoherent GB's w i t h l>3 and GB's w i t h £ which are not c h a r a c t e r i z e d by a 180° r o t a t i o n a l operation.We ha- ve also s t u d i e d combinations o f more than two boundaries i n order t o reveal the gene- r a l behaviour o f the GB's.
2. The CSL's o f p o l y c r y s t a l l i n e Si.Specimens f o r TEM were prepared from p o l y c r y s t a l - l i n e Si wafers used i n commercial a p p l i c a t i o n s of s o l a r c e l l s . C a r e was taken t o i n - clude i n our samples t h r e e or more boundaries congruently j o i n i n g each other.The ex- perimental results showed t h a t the GB's can be c l a s s i f i e d i n t o the f o l l o w i n g catego- r i e s ,
a) C l a s s i c a l 1=3 twins w i t h {111} type boundary plane (BP).These i n t e r f a c e s which are
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1982102
C1-10 JOURNAL DE PHYSIQUE
t h e most f r e q u e n t l y o c c u r i n g f o r m a l s o p a r a l l e l a r r a y s . T h e BP i s c o h e r e n t and i n a l l cases s t u d i e d we d i d n o t observe any r i g i d body t r a n s l a t i o n between t h e two g r a i n s .
The p e r f e c t coherency i s shown i n F i g . 1 where t w i n i n t e r f a c e s a r e presented-The i n - t e r f a c e o f F i g . l ( a ) i s a b r i g h t f i e l d (BF) photograph and has t h e BP i n a v e r t i c a l p o s i t i o n . The BP i s o u t o f c o n t r a s t i n F i g . l ( b ) , w h i c h i s a dark f i e l d (DF) p h o t o - graph, u s i n g a common e f l e c t i o n . I n F i g . l ( c ) we p r e s e n t a common r e f l e c t i o n DF i- mage o f a second case f = 3 i n t e r f a c e i n a t i l t e d p o s i t i o n . The absence o f f r i n g e s , i n t h i s case a l s o , i n d i c a t e s t h e absence o f a r i g i d body t r a n s l a t i o n and t h a t p e r f e c t coherency e x i s t s . N e v e r t h e l e s s i n t h e r e g i o n where an e x t r i n s i c d i s l o c a t i o n e n t e r s , t h e coherency i s d i s r u p t e d b y t h e f i e l d o f t h e d i s l o c a t i o n and f r i n g e s haveappeared.
Fig. 1 (a) BF image o f a 1 = 3 twin boundary in a vertical posi- tion. (b) DF image o f the same region with a reflection common t o both crystals. Coherency is evident. (c) D F image of a 1 = 3 twin in a tilted position from a 220 common reflection.The ab- sence of fringes indicate the absence of a rigid body transla- tion.
1=3 t w i n s can a l s o f o r m BP w i t h random o r i e n t a t i o n . An i n t e r e s t i n g example o f t h i s t y p e i s p r e s e n t e d i n F i g . 2. I n t h i s case t h e i n t e r f a c e i s n o t t h e (111) p l a n e b u t i s s t r o n g l y connected t o t h e c o r r e s p o n d i n g CSL o f t h e - b i c r y s t a l . The b i c r y s t a l has been c h a r a c t e r i z e d as a 1=3 case (a=180° around t h e C1111 a x i s ) . T h e BP has been de- t e r m i n e d t o be t h e (011) p l a n e , w h i c h i s a CSL p l a n e . T h i s i s shown i n F i g . 2 ( a ) whe- r e t h e BP i s i n a v e r t i c a l p o s i t i o n t o g e t h e r w i t h i t s c o r r e s p o n d i n g d i f f r a c t i o n p a t - tern.These r e s u l t s a r e m i s l e a d i n g because a c l o s e r approach r e v e a l e d t h a t t h e i n t e r - f a c e i s composed o f s m a l l f a c e t s i n a s t e p l i k e form, j o i n e d b y a r e g u l a r a r r a y o f p a r a l l e l d i s l o c a t i o n s , F i g . 2(b,c). The p l a n e s o f t h e f a c e t s a r e t h e ( 1 i 2 ) a n d ( 2 1 1 ) , which correspond t o t h e 180° wlanes o f t h e CSL. T h i s means t h a t on these planes t h e l a t t i c e p o i n t s c o i n c i d e . The d i s l o c a t i o n 1 in e s observed i n F i g . 2 ( b ,c) a r e para1 l e l t o t h e C1111 t w i n a x i s o f t h e CSL. The Burqers v e c t o r i s equal t o 6 = 9 [ O l i l ,
S Oi t i s normal t o t h e macroscopic BP t h a t i s DSC l a t t i c e v e c t o r . Burgers v e c t o r d e t e r - m i n a t i o n i s deduced by t h e O F images o f F i g . 2. I n F i g . 2(b,c) t h e d i s l o c a t i o n s a r e i n c o n t r a s t w i t h r e f l e c t i o n s common t o b o t h c r y s t a l s . I n F i g . 2(d,e,f) t h e d i s l o c a - t i o n s a r e o u t o f c o n t r a s t by t h e r e f l e c t i o n s o f t h e [oIT] zone a x i s . From t h e above i t i s concluded t h a t t h i s macroscopic i n c o h e r e n t t w i n i s i n f a c t c o h e r e n t w i t h r e s - p e c t t o i t s CSL model.
b ) GB's w i t h 1>3 w i t h c o h e r e n t BP. The usual case i s 1=9 which i s c h a r a c t e r i z e d by
a a=180° r o t a t i o n around a C2211 o r a C4111 a x i s . I n t h i s case t h e c o h e r e n t BP i s of
t h e (221) t y p e as i t i s i l l u s t r a t e d i n F i g . 3 ( a ) , where t h e BP p l a n e i s i n a v e r t i c a l
p o s i t i o n . The c o r r e s p o n d i n g d i f f r a c t i o n p a t t e r n i s a l s o i n c l u d e d . A r i g i d body t r a n s -
l a t i o n has been observed as i t i s o b v i o u s f r o m F i g . 3 ( b ) w h i c h may be c a l c u l a t e d fol- l o w i n g t h e methods o f 1101 and C111.
F i g . 2 ( a ) BF i m a g e o f t h e i n c o h e r e n t 1 = 3 t w i n i n a v e r t i c a l po-
s i t i o n w i t h t h e c o r r e s p o n d i n g d i f f r a c t i o n p a t t e r n . T h e 0 2 2 common
r e f l e - c t i o n i s n o r m a l t o t h e B P . ( b ) , ( c ) DF i m a g e s o f t h e B P i n a
t i l t e d p o s i t i o n f r o m r e f l e c t i o n s common t o b o t h c r y s t a l s . D i s l o c a -
t i o n s a r e i n c o n t r a s t . ( d ) DF i m a g e w i t h common ( 1 1 1 ) r e f l e c t i o n .
D i s l o c a t i o n s a r e o u t o f c o n t r a s t . ( e . f ) DF i m a g e s w i t h noncommon
r e f l e c t i o n s . D i s l o c a t i o n s a r e o u t o f - c o n t r a s t . The ( d , e , f ) h a v e
b e e n - t a k e n b y r e f l e c t i o n s o f t h e [ O l l l z o n e a x i s t h a t i s , ( d ) b y
t h e 111 common r e f l e c t i o n , ( e ) t h e 220 o f c r y s t a l 1 a n d ( f ) t h e
220 o f c r y s t a l 2 . The e x t i n c t i o n o f d i s l o c a t i o n s b y c o p l a n a r r e -
f l e c t i o n s i n d i c a t e s t h a t t h e B u r g e r s v e c t o r i s p a r a l l e l t o t h e
z o n e a x i s o f t h i s p l a n e . T h u s b = 5 [ O l i l .
JOURNAL DE PHYSIQUE
F i g . 3 T h e 1=9 C S L w i t h t h e BP i n a v e r t i c a l p o s i t i o n a n d t h e c o r r e s p o n d i n g d i f f r a c t i o n p a t t e r n . ( b ) B F o f t h e !=9 i n a t i l t e d p o s i t i o n s h o w i n g a - t y p e f r i n g e s i n d i c a t i n g t h e e x i s t e n c e o f a r i g i d b o d y t r a n s l a t i o n .
c ) GB's which a r e n o t described by an 1800 r o t a t i o n a l o p e r a t i o n have a l s o been obser- ved. An example o f t h i s i s 1=39 and w i l l become c l e a r l a t e r .
d) As mentioned above we s t u d i e d a l s o the r e l a t i o n between more than two boundaries.
Three examples a r e presented.
The f i r s t example concerns the case o f t h r e e g r a i n s A,B and C j o i n i n g a t a common p o i n t , i n such an o r i e n t a t i o n t h a t the El111 a x i s i s common t o a l l o f them. The AB boundary forms a 1=13b CSL (a=27.780 around the C1111 a x i s ) and the AC forms a 1=21b (a=21.7g0 around t h e C l l l l a x i s ) . Due t o the f a c t t h a t the C l l l l a x i s i s common i n a l l t h r e e g r a i n s and i t i s a CSL v e c t o r t h e t h i r d i n t e r f a c e i s a low angle boundary.
The second example i s the case o f a s e t o f p a r a l l e l t w i n s crossed by an i n t e r f a c e ( F i g . 4 ) . The p a r a l l e l g r a i n s A,B,A1 form i n t e r f a c e s AB and BA' which a r e described by t h e operations r e s p e c t i v e l y , : R , R;~, , symnetrical l y e q u i v a l e n t . The i n t e r f a c e s BC are described by IE;~ and both AC o r A'C by ~i~ o r R:,~, symmetrically e q u i v a l e n t .
A \
R~~=R;~*c;~.A(I=~!J
= - A ~ ~ = R ; ~ - C ~ ~ ~ R ( I = 3 )
le F i g . 4 ( a ) T h e s e t o f p a r a l l e l t w i n i n t e r f a c e s c r o s s e d b y a
B h i g h s y m m e t r y i n t e r f a c e .
R ~ ~ = R ~ ~ * R ( E = ~ ~ ~
Between them e x i s t s t h e obvious r e l a t i o n ?SB . R ; ~ = R:~, o r u s i n g t h e corresponding e x p e r i m e n t a l e x o l i c i t n u m e r i c a l expression$:
- .341 .292 -.865 .502 -.a38
(:%; 6 7 6 ::? x (:::I -:. -:3 = 1 . 3 3 3 6 2 8 ( 1 )
.343 .653 .674 ,, -.218 - .281 ,, ,377 .595 -.708 ,c
E q u a t i o n ( 1 ) i s d i r e c t l y t r a n s f o r m e d t o t h e t h e o r e t i c a l r e l a t i o n o f t h e correspon- d i n g CSL ' s . I n f a c t , by u s i n g t h e e q u a t i o n R ' = R ~ ( R ~ ) - ~ [91 e v e r y e x p e r i m e n t a l descrip- t i o n i s expressed as a f u n c t i o n o f t h e c o r r e s p o n d i n g CSL t h e o r e t i c a l d e s c r i p t i o n
~ ( [ u , v , w l , m, n, a ) o f t h e l=(n3+dn2)/a [ I 2 1 p l u s a s m a l l a n g l e . Thus i n t h i s case:
where RiB , P& , R : ~ a r e s m a l l a n g l e r w i t h v a l u e s 1.17' , 1.96' and 3.16' r e s p e c t i - v e l y , w h i l e t h e m, n, a d a t a a r e e a s i l y deduced [121. U s i n g t h e t h e o r e t i c a l expres- s i o n s from eq. ( 2 ) t h e d i r e c t CSL r e l a t i o n i m p l i e d f r o m (1) i s :
T h i s e x p e r i m e n t a l evidence o f t h e r e l a t i o n between t h e t h r e e CSL's l e a d s t o an im- p o r t a n t c o n c l u s i o n f o r t h e c o n s t r u c t i o n o f t h e y.39. ( w h i c h i s n o t a t y p i c a l t w i n ca- se, s i n c e i t l a c k s a 180° o p e r a t i o n ) t h a t i s , t h e 1:39 i s t h e r e s u l t o f p a s s i n g f i r s t f r o m t h e 1.13 CSL and then f r o m CSL 1.3.
F i n a l l y as a t h i r d example we have i n v e s t i g a t e d t h e case o f t h r e e a d j a c e n t g r a i n s , w i t h mutual h i g h a n g l e boundaries. I n F i g . 5 we p r e s e n t t h e d i f f r a c t i o n p a t t e r n s o f
r i g . 5 D i f f r a c t i o n p a t t e r r l s f r o m t h r o e a d j a c e n t g r a i n s in t h e
s s m c i n s t r u m e n t a l o r r e n t a t i o n . ( a ) g r a i n A , ( b ) g r a i n B , ( c )
g r a i n C . T h e conlrron r e f l c c t i o n s a r e e n c i r c l e d .
JOURNAL DE PHYSIQUE
t h r e e g r a i n s taken i n the same instrumental o r i e n t a t i o n . I n t h i s case t h r e e CSL's ha- ve been i d e n t i f i e d , taken by two, C=9, 1=13b and 1=19a. F i g . 5(a) ,(b) show t h e C1311 a x i s o f 1=9, Fig. 5 ( b ) , ( c ) show t h e C l I l l a x i s o f 1=13b and f i n a l l y Fig. 5 ( c ) , ( a ) t h e C O l T l a x i s o f 1=19a. This assignement i s n o t the d e f i n i t e case and needs f u r t h e r e l a b o r a t i o n .
I t should be n o t i c e d t h a t a l l t h e GB's which have been s t u d i e d i n t h i s work have been c h a r a c t e r i z e d according t o t h e small angle c r i t e r i o n C91 and have been approa- ched by t h e CSL's o f t h e s m a l l e s t angles.
3. Conclusion. The r e s u l t s presented above i n d i c a t e t h a t t h e CSL model, can be i s e d t o describe the i n t e r f a c e s i n p o l y c r y s t a l Si . The most f r e q u e n t l y observed twins 1=3, which macroscopically a r e coherent o r incoherent, m i c r o s c o p i c a l l y viewed form cohe- r e n t c o n f i g u r a t i o n s , w i t h t h e absence o f r i g i d body t r a n s l a t i o n s . Other coherent BP are connected w i t h 1=9 , 1=13b . 1=19a and 1=21b CSL. I n t e r f a c e s which a r e n o t des- c r i b e d by a 180° symnetry operations i . e 1=39 have been a l s o found. I n these c o n f i - g u r a t i o n s r i g i d body t r a n s l a t i o n s a r e necessary t o preserve semi coherency. The i n t e r - faces formed by t h r e e o r more g r a i n s are found t o have a c e r t a i n r e l a t i o n s h i p between them, r e s u l t i n g combinations o f h i g h and low angle boundaries.
References
[I] MOLLER J . H . , C r y s t a l R e s e a r c h a n d T e c h n o l o g y 1 6 , ( 1 9 8 1 ) 259.
C21 CARTER B.C., ROSE J . , a n d AST G.D., I n s t . Phys. Conf. S e r . No 6 0 : S e c t i o n 3 ,
( 1 9 8 1 ) 153.
C31 FONTAINE C., a n d ROCHER A . , J . Microscopy 1 1 8 , ( 1 9 8 0 ) 1 0 5 .
[ 4 ]
