Phase equilibria and diffusion in the Be-Al-Fe
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798-VOLUME 7A, JUNE 1976
1 c (x, t) = o,\,~ - - - - - y Y ( E o ( x , t), t ) . 0-~- Eo(.V, t)
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12 14 Fe AT E(MeW SURFACE Fig. 3 - - E f f e c t of a n n e a l i n g on the b a c k s c a t t e r i n g s p e c t r u m for l r o n - i n a p l a n t e d b e r y l l i u m . The n o m i n a l i r o n fluence is 9• 1016 a t . / c m 2. The v e r t m a I s c a l e is expanded by a f a c t o r of 8 to the left of the b a r at ~ 1 . 4 MeV. O~
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AMPLITUDE MEASUREMENT
a r i s e s f r o m i t s t o t a l p e n e t r a t i o n b e i n g much g r e a t e r than the ~ 2 pm which is p r o b e d by the ion b e a m . Continued a n n e a l i n g at 1073 K c a u s e d f u r t h e r r e d u c t i o n in the a m o u n t of i r o n within the i m p l a n t e d r e g i o n , but the a m p l i t u d e of the d i f f u s e d t a i l r e m a i n e d fixed a s long a s the i m p l a n t e d r e g i o n w a s not fully d e p l e t e d . In fact, throughout all of the i s o t h e r m a l anneal s e q u e n c e s of this e x p e r i m e n t , the a m p l i t u d e of the diffused t a i l w h e r e it i n t e r s e c t e d the i m p l a n t e d r e g i o n d e p e n d e d only on t e m p e r a t u r e . S p e c i f i c a l l y , it was independent of both anneal t i m e and the amount of i m p l a n t e d iron. In the p a r t i c u l a r r u n under c o n s i d e r a t i o n , the peak i r o n c o n c e n t r a t i o n of 20 at. p e t was above the 8.3 at. p c t l e v e l c o r r e s p o n d i n g to F e B e l t . W h i l e this high i m planted concentration permitted a more detailed exa m i n a t i o n of the diffusion k i n e t i c s at 1073 K, it m a y have c a u s e d s o m e FeBe5 to f o r m in a d d i t i o n to the FeBe~l. H o w e v e r , the a m p l i t u d e of the d i f f u s e d i r o n t a i l did not change d u r i n g annealing, even when 75 p e t of the i m p l a n t e d i r o n had diffused f r o m the i m p l a n t e d r e g i o n . In addition, the s a m e t a i l a m p l i t u d e was o b s e r v e d in a n o t h e r run w h e r e the amount of i m p l a n t e d i r o n was s r n a l l e r by a f a c t o r of t h r e e . T h e r e f o r e we conclude that the t a i l a m p h t u d e is unaffected by the higher c o n c e n t r a t i o n l e v e l in the c e n t r a l p o r t i o n of the i m p l a n t e d r e g i o n . Vacuum a n n e a l i n g a l s o i n c r e a s e d the t h i c k n e s s of the s u r f a c e l a y e r of BeO. F o r s h o r t anneal t i m e s such as that of Fig. 3, the oxide depth r e m a i n e d s m a l l in c o m p a r i s o n to the a v e r a g e r a n g e of the i m p l a n t e d a l u m i n u m and i r o n . However, d u r i n g s o m e of the m o r e extended a n n e a l s at l o w e r t e m p e r a t u r e s , the oxide t h i c k n e s s b e c a m e g r e a t e r than the ion r a n g e s : in one e x t r e m e c a s e , a t o t a l a n n e a l t i m e of 20 d a y s a t 873 K p r o d u c e d ~ 0.2 #m of BeO. In s p i t e of t h i s , the i m p
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