Dislocation nodes observed in ge single crystals recovery annealed after dual slip deformation

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p r e v i o u s p a p e r 1 d e a l t with the d e f o r m a t i o n of s i n g l e c r y s t a l s of g e r m a n i u m in dual s l i p , which is s l i p in two glide d i r e c t i o n s on a s i n g l e s e t of p a r a l l e l glide p l a n e s . M a c r o s c o p i c d e f o r m a t i o n p a r a m e t e r s and e l e c t r o n m i c r o s c o p e o b s e r v a t i o n s of the a t t e n d a n t d i s l o c a t i o n s t r u c t u r e w e r e p r e s e n t e d and d i s c u s s e d . In the p r e s e n t work, d i s l o c a t i o n a r r a n g e m e n t s f o r m e d b y a n n e a l i n g the d e formed crystals are considered. In a d d i t i o n to p r o v i d i n g i n f o r m a t i o n c o n c e r n i n g the d e f o r m a t i o n c h a r a c t e r i s t i c s in dual s l i p , of d i r e c t i n t e r e s t f o r r e a s o n s d i s c u s s e d b e f o r e , 1 the r e s e a r c h was d e s i g n e d to p e r m i t s u b s e q u e n t r e c o v e r y and p o l y g o n i z a t i o n e x p e r i m e n t s to t e s t g r a i n b o u n d a r y t h e o r i e s . 2'3 T h r e e fold nodes in n e t w o r k s f o r m e d in d i a m o n d - c u b i c c r y s t a l s a r e i d e n t i c a l in f o r m to t h o s e in fcc c r y s t a l s and should f o r m with node a n g l e s of 120 d e g and with each a r m of the node having s c r e w c h a r a c t e r if the n e t w o r k i s to b e s t r e s s f r e e . N u m e r o u s o b s e r v a t i o n s of 120 d e g nodes have b e e n m a d e . However in the two m o s t e x t e n s i v e s t u d i e s of node c h a r a c t e r , t h o s e b y G a l l a g h e r 4 on s i l v e r - i n d i u m a l l o y p o l y c r y s t a l s and b y E r i c s s o n s on c o b a l t - n i c k e l a l l o y p o l y c r y s t a l s , the node d i s l o c a t i o n s w e r e found to have a p r e f e r r e d o r i e n t a t i o n which was r o t a t e d b y 30 deg f r o m s c r e w o r i e n t a t i o n : h e n c e the n e t w o r k s had l o n g - r a n g e s t r e s s f i e l d s and w e r e not t r u e g r a i n b o u n d a r i e s . The i n t e r a c t i o n of the two s y s t e m s o p e r a t i v e in dual s l i p is p r e c i s e l y that f a v o r i n g the f o r m a t i o n of a h e x a g o n a l b o u n d a r y . Hence the s t u d y of the n e t w o r k s in g e r m a n i u m was of i n t e r e s t in d e t e r m i n i n g w h e t h e r the 30 deg r o t a t i o n effect was p r e s e n t in a s i n g l e c r y s t a l , in a d i f f e r e n t c r y s t a l s y s t e m and in a p u r e e l e m e n t , s o l u t e i n t e r a c t i o n having b e e n s u g g e s t e d a s a c a u s e f o r the effect o b s e r v e d e a r l i e r in the a l l o y s . 4 In a d d i t i o n the dual s l i p i n t e r a c t i o n s could l e a d to the f o r m a t i o n of s o - c a l l e d u n s y m m e t r i c a l n o d e s . 6 O b s e r v a t i o n s of t h e s e nodes w e r e of i n t e r e s t b e c a u s e t h e i r t h e o r e t i c a l p r o p e r t i e s had b e e n d i s c u s s e d e x t e n s

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