Deposition of iron, nickel and iron-nickel layers from carbonyl vapors
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T h e r a t e of d e p o s i t i o n of i r o n , n i c k e l and i r o n - n i c k e l l a y e r s f r o m c a r b o n y l v a p o r s i s shown to be c o n t r o l l e d by d i f f u s i o n a c r o s s the g a s p h a s e b o u n d a r y l a y e r in c o n t a c t with t h e h e a t e d s u b s t r a t e . A t a c o n s t a n t flow r a t e t h e r a t e of d e p o s i t i o n i s shown to i n c r e a s e with i n c r e a s e i n t e m p e r a t u r e up to a c r i t i c a l v a l u e a b o v e w h i c h t h e r a t e of d e p o s i t i o n e i t h e r r e m a i n s c o n s t a n t (for high flow r a t e s ) o r d e c r e a s e s (for low flow r a t e s ) . T h i s b e h a v i o r i s e x p l a i n e d in t e r m s of t h e t h e r m a l c o n v e c t i o n c o n t r i b u t i o n to m a s s t r a n s f e r in the r e a c t i o n s y s t e m . It i s shown t h a t t h e c o m p o s i t i o n of a l l o y f i l m s p r o d u c e d f r o m c a r b o n y l m i x t u r e s at t e m p e r a t u r e s g r e a t e r than 200~ (473 K) can be p r e d i c t e d to b e a p p r o x i m a t e l y e q u a l to t h e m o l a r r a t i o s of i r o n and n i c k e l i n the v a p o r p h a s e when t h e c a r b o n y l s a l o n e c o n s t i t u t e t h e v a p o r p h a s e . T h e s e p r e d i c t i o n s cannot be e x t e n d e d to s i t u a t i o n s w h e r e high d i l u t i o n of t h e c a r b o n y l s in a n o t h e r g a s i s u s e d , o r to d e p o s i t i o n t e r n p e r a t u r e s of l e s s t h a n 200~ (473 K).
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p r o d u c t i o n of m e t a l l i c l a y e r s by t h e c h e m i c a l d e c o m p o s i t i o n o r r e d u c t i o n of m e t a l - c o n t a i n i n g v a p o r s h a s long b e e n a s u b j e c t of s t u d y . 1"~ A p p l i c a t i o n s r a n g e f r o m the p r o d u c t i o n of r e f r a c t o r y m e t a l t u b e s 3 by the high t e m p e r a t u r e h y d r o g e n r e d u c t i o n of h a l i d e s , to the p r o d u c t i o n of a l u m i n u m f i l m s by the p y r o l y s i s of o r ganometallic compounds such as triisobutyl aluminum. 4 T h e u s e of c a r b o n y l s f o r v a p o r d e p o s i t i o n h a s b e e n i n v e s t i g a t e d p r e v i o u s l y f o r n i c k e l , ~'6 i r o n , 7 c h r o m i u m f '9 and t u n g s t e n and m o l y b d e n u m f A l l of t h e s e s t u d i e s a t t e m p t e d to r e l a t e the t e m p e r a t u r e of d e p o s i t i o n to the r a t e of d e p o s i t i o n o r m o r p h o l o g y of d e p o s i t . T h e d e p o s i t i o n of a l l o y l a y e r s h a s r e c e i v e d a t t e n t i o n only for the c a s e of the i r o n - n i c k e l s y s t e m , and t h e s e s t u d i e s w e r e a i m e d at the p r o d u c t i o n of thin f i l m s f o r c o m p u t e r t e c h n o l o g y , 1~ t h e i n v e s t i g a t i o n of t h e i r o n n i c k e l p h a s e d i a g r a m at low t e m p e r a t u r e xl o r the c o m m e r c i a l p r o d u c t i o n of i r o n - n i c k e l p o w d e r s .12 None of t h e s
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