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PREPARATION AND STRUCTURE OF THIN
Fe1-xBx SPUTTER FILMS
F. Stobiecki, S. Schwarzl, T. Stobiecki, H. Hoffmann
To cite this version:
PREPARATION AND STRUCTURE OF THIN Fel-,
B xSPUTTER FILMS
-I+
F . ~ t o b i e c k i + , S . Schwarzl, T . S t o b i e c k i andH. Hoffmann
I n s t i t u t fur Angewandte Physik, Universitir't Regensburg, 8400 ~ e g e n s b u r g , R.F.A.
+
I n s t i t u t e of MoZeeuZar Physics o f t h e PoZish Academy of Sciences, P o z n d , PoZogne++
iSoZid State Physic Department Academy o f Mining' and MetaZZurgy, Ilrakdw, PoZogneI n t r o d u c t i o n Amorphous m e t a l - m e t a l l o i d /PI-TM/ a l l o y s , i n c l u d i n g Bx a l l o y s , o b t a i - n e d by c h e m i c a l o r r a p i d q u e n c h i n g me- t h o d s h a v e b e e n s u b j e c t e d t o i n t e n s i v e s t u d i e s f o r more t h a n t e n y e a r s C 1 1 . R e c e n t l y , t h i n f i l m s o f t h e s e a l l o y s o b t a i n e d u s u a l l y by t h e s p u t t e r i n g t e c h - n i q u e , h a v e won g r e a t i n t e r e s t [2-41. A s t h e s e a l l o y s i n a n a m o r p h o u s s t a - t e e x h i b i t some i n t e r e s t i n g m a g n e t i c p r o p e r t i e s n u m e r o u s w o r k s a r e c o n c e r n e d w i t h t h e i r s t r u c t u r a l s t u d i e s
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- s h o r t r a n g e o r d e r i n g . F o r Fe B a l l o y s t h e s t u - d i e s a r e p e r f o r m e d by v a r i o u s m e t h o d s : X-Ray d i f f r a c t i o n C5], n e u t r o n d i f f r a c t . i o n [ 6 1 a n d M 6 s s b a u e r t e c h n i q u e C 7 1 T h i s p a p e r i s c o n c e r n e d w i t h some t e c h n o l o g i c a l p r o b l e m s a r i s i n g i n o b t a i - n i h g t h e t . h i n F.el,, B x f i l m s , and, d e l i v e r s a d e s c r i p t i o n o f t h e i r s t r u c t u r e a n d c r y s t a l i z a t i o n p r o c e s s o b t a i n e d by t h e s t u d i e s p e r f o r m e d w i t h t h e u s e o f a n e l e c t r o n m i c r o s c o p e . S a m p l e p r e p a r a t i o n A l l t h e t h i n f i l m s s t u d i e d w e r e ob- c a t h o d e c u r r e n t = 1 0 0 m A c a t h o d e d c b i a s = -7OOV a n o d e d c b i a s =- 6 O V
As s u b s t r a t e s s e r v e d t h e f r e s h l y c l e a v e d NaCl s i n g l e c r y s t a l s , f o r s t u d i e s by a t r a n s m i s s i o n e l e c t r o n m i c r o s c o p e /TEM/, a n d g l a s s e s when t h e c o e r c i v e f i e l d was m e a s u r e d by K e r r e f f e c t . T h e powder p r e s s e d t a r g e t composed o f F e 8 0 i3 20 a t%
was u s e d f o r s p u t t e r i n g . C o m p o s i t i o n o f t h e f i l m s w a s c h a n g e d by a r e g u l a r c o v e r i n g t h e t a r g e t s u r f a c e w i t h p i e c e s o f Fe o r 5 . T h e c o n c e n t r a t i o n o f i n d i v i d u a l e l e m e n t s i n a f i l m was d e t e r m i - n e d by m i c r o a n a l y s i s a n d A u g e r a n a l y s i s , F i g . 1 p r e s e n t s t h e d e p e n d e n c e o f t h e f i l m c o m p o s i t i o n o n t h e d e g r e e o f c o v e r i n g t h e t a r g e t s u r f a c e w i t h t h e p i e c e s o f Fet a i n e d by r f - s p u t t e r i n g u n d e r t h e f o l l o - ~e I% target area) B wo target oreo I w i n g c o n d i t i o n s F i g . 1 . D e p e n d e n c e o f t h e Fel,, Bx t h i n b a c k g r o u n d p r e s s u r e =
lom6
T o r r f i l m c o m p o s i t i o n o n t h e d e g r e e o f a r g o n p r e s s u r e = 2 x 1 0 - ~ T o r r c o v e r e d FeOtSO BO ,20 p o w d e r t a r g e ts u r f a c e w i t h t h e p i e c e s o f Fe o r B.
L-L, \ \ L 2 4
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F i g . 4 . M i c r o d e n s i t o g r a m s o f a Fe 1-x d i f f r a c t i o n p a t t e r n s , /a/ 0 . 1 2 G x 5 0 . 7 5 a s - d e p o s i r e d /amorphous s t a t e / , /b/ 0 . 1 2 S x L 0 . 7 5 a f t e r a n n e a l i n g and x-0-06. x=O a s - d e p o s i t e d / c r y s t a l l i n e s t a t e / , /c/ x=0.32 f o r v a r i o u s a n n e a l i n g t e m p e r a t u r e s . a n n e a l i n g r u n s i n s t e p s , as i t shown F i g . 4c. F o r example i n t h e case o f Fe0-68B0,32 t h i n f i l m t h e p r o c e s s o f a n n e a l i n g does n o t p r o d d c e any a p p a r e n t change i n t h e I ( s l dependence. A t t h e t e m p e r a t u r e o f - 7 3 0 K t h e c r y - s t a l l i z a t i o n s t a r t s what i s e v i d e n c e d b y t h e $ 0 - r m a t i o n o f c r y s t a l l i t i e s witfh a d i a m e t e r between 100 and 200k
/see F i g . 3b/ and b y t h e changes i n t h e I ( s ) c o u r s e /see Fig.4c/. The t e m p e r a t u r e a t w h i c h t h e c r y s t a l l i - z a t i o n s t a r t s depends o n t h e c o m p o s i t i o n o f t h e t h i n f i l m s i n t h e f o l l o w i n g way: and d e c r e a s e s f o r b o t h s m a l l e r and g r e a t e r x v a l u e s /see T a b l e / . T a b l e-
increases during annealing [K] S t u d y i n g t h e dependence o f t h e c o e r - c i v e f i e l d .on t h e a n n e a l i n g t e m p e r a t u r e i t was f o u n d t h a t f o r t h e amorphous f i l m s t h e f i e l d i s l o w /Hc L 0.5 Oe/ and i n c r e a s e s s t r o n g l y a t a t e m p e r a t u r e c l o s e t o t h a t a t w h i c h t h e f i l m c r y s t a l l i z a t i o n s t a r t s . The I ( s ) dependences o b t a i n e d f o r a l l t h e amorphous t h i n f i l m s a l l o w t o e s t a - b l i s h d e f i n i t e l y t h e o c c u r e n c e o f t h e a - F e phase. F o r t h e s y s t e m s o f B con- c e n t r a t i o n a b o u t 3 0 a t%
t h e Fe2B phase c a n a l s o be d i s t i n g u i s h e d . However, i t i s n o t p o , s s i b l e t o p r o v e t h e e x i s t e n c e o f o t h e r phases as f o r example a m e t a s t a b l e phase Fe3B o b s e r v e d i n r i b b o n s [7,81.R a d i a l d i s t r i b u t i o n f u n c t i o n
-
RDFFollowing the method as described by H. Hoffmann and R. Winkler [9] we corrected the measured i n t e n s i t i e s
from the background due t o i n e l a s t i c scattering, whereas small angle scattering due t o inhomogeneities was neglected. With t h i s correction i t was possible t o obtain an interference function i (s) which gives
dy
Fourier transformation, a rather good estimate o f the interatomic distances, we have :c8-174 JOURNAL DE PHYSIQUE
L .
.
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Fi.g.5. Reduced RDF's f o r Fel,x Bx f i l m s , a/ 0 . 1 2 6 x L 0 - 7 5 a s - d e p o s i t e d
,
b/ 0 . 1 2 ~ x r o ,75 a f t e r a n n e a l i n g and x=0.06, x-0 a s - d e p o s i t e d . t h e d e p e n d e n c i e s shown i n F i g . 5 t h e nearest n e i g h b o u r d i s t a n c e f o r i r o n t h i n f i l m s i s 2.7A
and d e c r e a s e s o n l y o f a b o u t 5% w i t h t h e B c o n t e n t i n c r e a s i n g u p t o 6 0 a t g . F o r g r e a t e r B c o n t e n t s t h e n e a r e s t n e i g h - b o u r d i s t a n c e c o n s i d e r a b l y d e c r e a s e s and r e a c h e s 2.2A
i n case o f 7 5 a t % B, T h i s e f f e c t may be due t o t h e f a c t t h a t as t h e s c a t t e r i n g a m p l i t u d e o f B atoms i s s m a l l , f o r t h e l o w e r B c o n c e n t r a t i o n s t h e f i r s t peak may c o r r e s p o n d t o Fe-Fe p a i r s . F o r h i g h B c o n c e n t r a t i o n x=0.75 t h e n e a r e s t n e i g h b o u r d i s t a n c e may c o r r e s p o n d t o Fe-B p a i r s , i n s p i t e o f a c o n s i d e r a b l e d i t t e - r e n c e i n t h e s c a t t e r i n g - a m p l i t u d e s o f B and Fe. 2. The t e m p e r a r u r e a t w h i c h c r y s t a l l i z a t i o n o f t h i n f i l m s s t a r t s depends o n t h e i r c o m p o s i t i o n s . I t r e a c h e s t h e g r e a t e s t v a l u e f o r f i l m s c o n t a i n i n g a b o u t 3 0 a t % B a n d d e c r e a s e s b o t h f o r s m a l l e r and g r e a t e r B c o n c e n t r a t i o n s . 3. The n e a r e s t n e i g h b o u r d i s t a n c e i s a b o u t 2.6 f o r f i l m s o f B c o n c e n t r a t i o n de- f i n e d b y 0 . 1 2 ~ ~ L 0 . 6 0 , c o r r e s p o n d i n g t o Fe-Fe p a i r s , and f o r x = 0.75 t h i s d i s t a n c e i s 2.2fi
c o r r e s p o n d i n g t o Fe-B p a i r s . 4. ,A r a p i d i n c r e a s e i n c o e r c i v e f i e l d oc- c u r s d u r i n g a n n e a l i n g o f f i l m s a t a t e m p e r a t u r e c l o s e t o t h a t a t w h i c h t h e c r y s t a l l i z a t i o n s t a r t s . reference^ 1 G . S . C a r g i i 1 L I I , I B M R e s e a r c h RC 5 7 9 1 /1975/ 2 Y.Shimada, H , l < o j i n a , J.Appl.Phys, 50, 1 5 4 1 /197'9/3 J.A.Aboaf, E.Klokholm, J.Magn.Mat. 15-18, 1585 /1980/
4 A.G.Dirks, J.R.M.Gijsbers, 3.Phys.D: Appl.Phys., 1 2 , 1 4 9 /1479/
