MÖSSBAUER SPECTROSCOPY OF 57Fe IMPLANTED TO ALUMINIUM AT LIQUID NITROGEN TEMPERATURE

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MÖSSBAUER SPECTROSCOPY OF 57Fe IMPLANTED TO ALUMINIUM AT LIQUID

NITROGEN TEMPERATURE

K. Sassa, Y. Ishida, K. Kaneko

To cite this version:

K. Sassa, Y. Ishida, K. Kaneko. MÖSSBAUER SPECTROSCOPY OF 57Fe IMPLANTED TO

ALUMINIUM AT LIQUID NITROGEN TEMPERATURE. Journal de Physique Colloques, 1979, 40

(C2), pp.C2-556-C2-558. �10.1051/jphyscol:19792193�. �jpa-00218571�

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MOSSBAUER SPECTROSCOPY OF

5 7

Fe IMPLANTED TO ALUMINIUM AT LIQUID NITROGEN TEMPERATURE

K. Sassa, Y. Ishida and K. Kaneko

Institute of Industrial Saienae, University of Tokyo, 7 Roppongi, Minato, Tokyo, Japan

^Institute for Nualear Study, University of Tokyo, 3 Midori, Tanashi, Tokyo, Japan

Abstract.- 5 7F e+ ions were implanted into aluminium in a 38 kV isotope separator at liquid nitrogen temperature. The ageing behavior of the specimen was examined by conversion electron Mossbauer spectroscopy at 77 K. The spectrum change at temperatures below 373 K suggested supersaturation of the lattice vacancies.

1. Introduction.- High energy ions implanted into metals introduce a large amount of lattice defects in addition to the impurity atoms themselves. The resulted defect-impurity structure is currently dra- wing engineering interests l \ l .

Through the implantation of 5 7Fe atoms into aluminium at room temperature, J. Sawicki et al. / 2 , 3/ obtained spectra which were interpreted by two components; a single peak due to Fe atoms in solid solution and a doublet reflecting the electric field gradient caused by randomly distributed neighboring Fe atoms. The interpretation ignores the effect of collision-induced lattice defects.

In the present study 57Fe atoms are implanted at liquid nitrogen temperature to accumulate lattice vacancies in the specimen, and the effect of lattice defects are investigated by comparing the spectra with those obtained at room temperature.

Internal conversion electron Mossbauer spectroscopy is most suitable for the detection of implanted Fe atoms because the electron escape depth is just enough for the range of implanted atoms and low background level improves the spectrum remarka- bly over those taken with usual transmission mode /4/. For the purpose of the investigation, a detector working at 77 K and equipped with a stage to mount the specimen without raising the temperature is necessary.

2. Experimental.- The specimens are 99.999 % aluminium disks of diameter 15mm and thickness Imm which were electrolytically polished and annealed at 873 K in vacuum. For the implantation of 57Fe ions, an isotope separator was used. The acceleration voltage was 38 kV and the beam current was 0.3 uA/cm2. The

specimens are placed in the collector chamber on the surface of a cylindrical copper drum which contains liquid nitrogen. The vacuum of the collector chamber was about 5 x I0-6 torr. To avoid contamination, the copper drum is surrounded by a thermal shield box made of thin stainless steel plates.

A detector for back scattered conversion electron In figure 1, a conversion electron detector used in the present experiment is shown. It is desi- gned to work at 77 K.

Fig. 1 : Detector used to measure back scatted internal conversion electrons at 77 K.

JOURNAL DE PHYSIQUE Colloque C2, supplément au n° 3, Tome 40, mars 1979, page C2-556

Résumé.- Des ions 5 7F e+ ont é t é implantés dans l'aluminium à l ' a i d e d'un s é p a r a t e u r d ' i s o t o p e s de 38 kV à l a température de l ' h é l i u m l i q u i d e . Le comportement du spécimen par v i e i l l i s s e m e n t a é t é examiné par spectrométrie Mossbauer d ' é l e c t r o n s de conversion à 77 K. L ' é v o l u t i o n du s p e c t r e en- dessous de 373 K suggère l ' e x i s t e n c e d'une s u r s a t u r a t i o n de lacunes.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19792193

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Y. Isozumi and M. T a k a f u c h i / 5 / d e v e l o p e d t h e same t y p e of d e t e c t o r which i s i n s e r t e d i n a He g a s con- t a i n e r p l a c e d a t t h e b o t t o m of a l i q u i d n i t r o g e n c r y o s t a t . The a u t h o r s s i m p l i f i e d t h e model i n o r d e r t o mount t h e specimen i n t o t h e d e t e c t o r w i t h o u t r a i - s i n g t e m p e r a t u r e a f t e r t h e i m p l a n t a t i o n . J. S a w i c k i e t a l . / 6 / p u b l i s h e d a l r e a d y a v e r y s i m i l a r one.

The mounting o f a specimen was done i n a l i q u i d n i - t r o g e n b a t h , and t h e d e t e c t o r i s i n s e r t e d t o g e t h e r w i t h a s m a l l amount o f l i q u i d n i t r o g e n i n i t s c a v i t y

i n t o t h e He g a s c o n t a i n e r o f a c r y o s t a t which was c o o l e d b e f o r e h a n d . A f t e r t h e c o n t a i n e r was pumped t o a b o u t 5 x 10

-'

t o r r , h i g h p u r i t y He g a s was p u t i n a t t h e p r e s s u r e of 730 mm Hg a s a c o u n t i n g g a s . The v o l t a g e a p p l i e d t o t h e anode w i r e of t h e d e t e c - t o r was a b o u t 500 V. The r e d u c t i o n of p u l s e h e i g h t w i t h t i m e o c c u r r e d a s was p o i n t e d o u t by Y. Isozumi e t a l . , s o t h a t t h e v o l t a g e was r a i s e d sometimes.

The p r e s s u r e change i n t h e g a s c o n t a i n e r due t o t h e l e v e l change o f l i q u i d n i t r o g e n and t h e o u t g a s from t h e c o n t a i n e r w a l l and t h e d e t e c t o r a r e t h o u g h t t o b e t h e c a u s e s .

3. R e s u l t s and d i s c u s s i o n . - The s p e c t r u m measured a t 77 K w i t h a specimen i m p l a n t e d a t room temperatu- r e a t a d o s e 3 x 10" /cm2 c a n b e f i t t e d by two com- p o n e n t s a s S t a n e k e t a l . 131. One i s a s i n g l e peak component amounting t o 45 % of t h e t o t a l a r e a i s i n agreement w i t h t h a t o f i s o l a t e d Fe atoms ( I S = 0 . 5 7 mm/s w i t h r e s p e c t t o a - i r o n ,

r

⁼0 . 2 4 mmls).

The o t h e r i s a d o u b l e t ( I S = 0.27 mm/s, QS - 0 . 3 5 4 s and

r

= 0.35 mm/s). When measured a t room tempera- t u r e , t h e p a r a m e t e r s a r e I S = 0.46 m / s f o r t h e i s o - l a t e d Fe and I S = 0 . 1 8 m / s , QS = 0 . 3 6 mm/s f o r t h e d o u b l e t component. They a g r e e v e r y w e l l w i t h t h e va- l u e s of S t a n e k e t a l . a f t e r s t a n d a r d i z a t i o n . The d o u b l e t component r e s e m b l e s w e l l t h a t Nasu e t a l . / 7 / o b s e r v e d i n a s p l a t - c o o l e d A1-Fe a l l o y . The s p l i t t i n g was e x p l a i n e d a s t h e f o r m a t i o n of a nea- r e s t n e i g h b o r c o n f i g u r a t i o n between randomly d i s t r i - b u t e d Fe atoms. The s p e c t r u m , however, i s a l s o n e a r t h o s e o f s o c a l l e d AlsFe p h a s e / 8 , 9 / .

A f t e r a g e i n g t h e specimen a t 5 7 3 K f o r IOmin., t h e a r e a o f t h e s i n g l e peak component d e c r e a s e d t o 17 % and t h e d o u b l e t component i n c r e a s e d . But t h e peak p o s i t i o n s and t h e m a g n i t u d e o f s p l i t t i n g d i d n o t change. By a g e i n g a t 673 K , t h e peak o f i s o l a t e d Fe atoms a l m o s t d i s a p p e a r e d and t h e p a r a m e t e r s of t h e d q u b l e t a r e I S = 0.30 mm/s, QS = 0 . 3 5 mm/s and

r

⁼0.33 mm/s. The a g e i n g b e h a v i o r s u g g e s t s t h a t t h e d o u b l e t component e x i s t i n g from t h e b e g i n i n g i s due t o a n o r d e r e d p h a s e s i m i l a r t o AlsFe r a t h e r t h a n t o

a randomly d i s t r i b u t e d Fe atoms.

F i g u r e 2 shows t h e s p e c t r a measured a t 77 K w i t h t h e specimens i m p l a n t e d a t l i q u i d n i t r o g e n tem- p e r a t u r e t o d o s e s ( a ) 1 x 1 0 ' ~ / c m ~ , ( b ) 5 x 10'~/cm:

F i g . 2 : The X s s s b a u e r s p e c t r a measured a t 77 K.

' ~ e was i m p l a n t e d a t l i q u i d n i t r o g e n t e m p e r a t u r e t o d o s e s ( a ) 1 x 1 0 ' ~ / c m ~ , ( b ) 5 x 1 0 ' ~ / c m ~ . S p e c t r a ( c ) t o ( f ) a r e t h o s e of t h e specimen ( b ) aged f o r 10 min. a t ( c ) 2 7 3 K , ( d ) 373 K, ( e ) 473 K and ( f ) 773 K , r e s p e c t i v e l y .

The s p e c t r u m ( a ) may be r e s o l v e d i n t o two components a s above w i t h s i m i l a r p a r a m e t e r s e x c e p t i n g t h e w i d t h which i n c r e a s e d . The s p e c t r u m ( b ) , on t h e o t h e r hand.

l o o k s l i k e a d o u b l e t . F i g u r e 2 ( c ) % ( f ) shows t h e change of s p e c t r a w i t h t h e specimen ( b ) by a g e i n g a t s p e c i f i e d t e m p e r a t u r e s f o r 10 min. A s m a l l change o c c u r r e d by t h e a g e i n g a t from 2 7 3 K t o 373 K. Up t o t h e a g e i n g a t 333 K, t h e peak p o s i t i o n s remained c o n s t a n t a t 0 . 0 6 and 0.57 m / s . But by a g e i n g a t 373 K t h e y s h i f t e d t o 0.07 and 0 . 5 2 mmfs. A t t h e same t i m e t h e r a t i o between two p e a k ' s a r e a s c h a n g e d :

t h e a r e a of t h e l e f t peak r e d u c e d from 4 9 . 7 % t o 45.9 % of t h e t o t a l a r e a . I t seems t h a t two p e a k s a r e n o t t h o s e of a s i m p l e d o u b l e t b u t s e v e r a l compw n e n t s . The change i n t h e low t e m p e r a t u r e a g e i n g i s i n t e r p r e t e d a s t h e i n c r e a s e of t h e components e x i s - t i n g between two main p e a k s and t h e d e c r e a s e o f t h e component a t t h e h i g h e n e r g y s i d e of t h e r i g h t peak.

Simple s t r u c t u r e s of Fe atom w i t h i n t e r s t i -

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C2-558 JOURNAL DE PHYSIQUE

t i a l s / l o / , o r v a c a n c i e s / I l l do n o t seem t o have By a g e i n g a t 473-673 K , peak p o s i t i o n s d i d n ' t o c c u r r e d s i n c e t h e y s h o u l d be a n n e a l e d by a g e i n g be- c h a n g e , b u t t h e peak a t 0 . 0 7 mm/s i n c r e a s e d . It sug- low 273 K. The g r a d u a l change below 373 K , a b s e n t g e s t s t h e i n c r e a s e of t h e same d o u b l e t component a s w i t h t h e s p e c i m e n i m p l a n t e d a t room t e m p e r a t u r e may b e f o r e . By 773 K and 873 K a g e i n g , m e t a s t a b l e o r b e d u e t o t h e o r d e r i n g of Fe atoms enhanced by s u p e r s t a b l e compounds seem t o e x i s t p r i m a r i l y .

s a t u r a t e d v a c a n c i e s .

R e f e r e n c e s

--

N e l s o n , R.S.. P r o c . R. Soc. A .

311

(1969) 53.

S a w i c k i , J . . S a w i c k a , B . , L a z a r s k i , S. and Maydell-Ondrusz, E . , Phys. S t a t u s S o l i d i ( b ) 5 7 (1973) K143.

-

S t a n e k , J . , S a w i c k i , J . , S a w i c k a , B. and D ~ w i e g a , M . , "Proc. I n t . Conf. Mossbauer S p e c t r o s c o p y "

Poland-Cracow (1 975) 2D-6.

S t a n e k , J . , S a w i c k i , J. and S a w i c k a , B . , i b i d . IB-10.

I s o z u m i , Y. and T a k a f u c h i , Y . , B u l l . I n s t . Chem.

R e s . , Kyoto U n i v . ,

53

(1975) 1 , 63.

S a w i c k i , J . , Sawicka, B. and S t a n e k , J . , Nucl.

I n s t r u m . Methods

138

(1976) 565.

Nasu, S . , G o n s e r , U.. S h i n g u , P.H. and Murakami, Y . . J. P h y s . F: M e t a l Phys.

4

(1974) L24.

S t i c k e l s , C.A. and Bush, R.H., Met. T r a n s .

1

(1971) 2031.

P r e s t o n , R.S., Yet. T r a n s .

2

(1972) 1831.

M a n s e l , W . , Vogl, G . , J. P h y s . F:Metal Phys.

2

(1977) 253.

S a s s a , K . , Goto, H . , I s h i d a , Y . and K a t o , M., S c r . Met.

11

(1977) 1029.